Before forming a trench in a silicon substrate through a patterned silicon nitride film serving as a mask, etching is executed until the main surface of the silicon substrate is exposed. Thereafter exposed side walls of a silicon dioxide film and a polysilicon film and the exposed surface of the silicon substrate are oxynitrided thereby forming an silicon oxynitride film. Thereafter the trench is formed, then a silicon dioxide film is formed on its inner wall, and thereafter the trench is filled with an insulation. In the process of forming the silicon dioxide film on the inner wall, a bird""s beak is formed on the side walls of the silicon dioxide film and the polysilicon film. The silicon oxynitride film suppresses excessive growth of the bird""s beak and prevents the bird""s beak from formation of a depressed part. Thus, reduction of the area of an active region caused by the bird""s beak is suppressed without no depression part formed on the upper end of an STI structure.

1. Field of the Invention
The present invention relates to a semiconductor device having an element isolation structure in the main surface of a semiconductor substrate and a method of manufacturing the same, and more particularly, it relates to a semiconductor device whose element isolation structure is an STI structure having a bird""s beak on its upper end and a method of manufacturing the same.
2. Description of the Background Art
In a semiconductor device structured as an integrated circuit, a number of semiconductor elements are formed in active regions of a semiconductor substrate. An element isolation structure electrically isolates these semiconductor elements from each other, for preventing unnecessary interference thereamong. At the same time, in order to implement prescribed functions for which the integrated circuit is designed, an electrical conductor (wire) formed on the element isolation structure selectively connects these semiconductor elements with each other.
When element isolation is incomplete, a leakage current flows between the semiconductor elements. When still another semiconductor element recognizes the leakage current as a signal, it follows that the integrated circuit malfunctions. Therefore, element isolation must be completely performed in order to keep operations of the integrated circuit normal, and hence it can be said that element isolation is an important technique.
In a semiconductor device of such a generation that the minimum line width on a silicon substrate is set to not more than 0.2 xcexcm, its element isolation structure changes from a conventional LOCOS (local oxidation of silicon) structure to an STI (shallow trench isolation) structure. The conventional element isolation structure formed by a LOCOS method has such disadvantages that (1) a large bird""s beak remarkably corrodes and narrows active regions, (2) a channel stop impurity layer formed in a substrate region located under the LOCOS structure is re-distributed in a later heat treatment step, (3) the thickness of a LOCOS oxide film changes between a narrow pitch (width of the element isolation structure or the active regions) and a wide pitch, and (4) a lithography process becomes difficult due to large steps between the active regions and the element isolation structure.
Element isolation by the STI structure has been proposed as a method of solving these problems. Steps of forming the same are briefly described. First, a trench of about 0.1 to 0.5 xcexcm in depth is formed on the main surface of a silicon substrate by anisotropic etching, and thereafter filled with an insulator. This insulator is flattened by CMP (chemical mechanical polishing) or the like, thereby completing an STI element isolation structure. Since such flattening is performed, the step between the main surface of the semiconductor substrate and the surface of the element isolation structure is smaller as compared with that in an element isolation structure formed by the LOCOS method.
The STI element isolation structure is formed in an initial stage among a series of steps for forming an integrated circuit. In other words, the STI element isolation structure is formed in a step before source and drain regions of a MOS (metal oxide semiconductor) transistor are formed by ion implantation in the vicinity of surfaces of active regions holding the element isolation structure. The STI element isolation structure suppresses such a disadvantage that a channel of a parasitic MOSFET (MOS field-effect transistor) is formed in a field region (region of the element isolation structure: element isolation region) between the active regions. Consequently, an integrated circuit having a small leakage current between active regions holding an element isolation structure is implemented regardless of presence/absence of operations of a MOSFET.
The STI structure is an element isolation structure essentially free from a bird""s beak, i.e., involving no bird""s beak. In the STI structure free from a bird""s beak, however, stress resulting from the shape of a trench forming the STI structure concentrates to a corner part (part between the bottom and the side wall) on the bottom of the trench or the upper end (i.e., opening end) of the trench, to result in formation of a defect in a silicon substrate. When a defect is formed around the trench, a leakage current is increased when the MOSFET is turned off, to remarkably increase power consumption of the semiconductor device.
It is known as a conventional technique that the inner wall of the trench is oxidized thereby the shape of the corner part on the bottom of the trench is rounded while simultaneously a small bird""s beak is formed on the upper end of the trench thereby the shape of the trench is rounded so that the stress is relaxed. In this technique, however, it follows that a small bird""s beak is formed from the element isolation structure toward the active regions despite the STI structure.
A series of steps of forming an STI structure including a step of forming a bird""s beak are now described in detail. FIGS. 48 to 58 are step diagrams showing a conventional method of forming an STI structure. In order to form the STI structure, a silicon dioxide film 102, a polysilicon film 103 and a silicon nitride film 104 are formed in this order on a silicon substrate 101, as shown in FIG. 48. The silicon dioxide film 102 is also referred to as an underlayer oxide film.
The step shown in FIG. 49 is then carried out. In the step shown in FIG. 49, resist is applied onto the silicon nitride film 104 and thereafter patterned through a transfer step, for forming a resist mask 105. Thereafter the resist mask 105 is employed as a mask (screen) for executing anisotropic etching, thereby selectively removing the silicon nitride film 104. Since the ratio of the etching rates for the silicon nitride film 104 and the polysilicon film 103 is sufficiently large, the anisotropic etching stops on the upper surface of the polysilicon film 103. In this step, the resist mask 105 is also partially removed by the etching. If the quantity of this overetching is large, the resist mask 105 may be entirely removed.
In the subsequent step shown in FIG. 50, the resist mask 105 is removed and thereafter anisotropic etching is executed through the patterned silicon nitride film 104 employed as a hard mask, thereby selectively removing the polysilicon film 103, the silicon dioxide film 102 and the silicon substrate 101 in this order. Needless to say, etchants employed for the anisotropic etching are properly changed following stepwise change of the films to be removed in this step. Through this step, a trench 106 of about 300 nm in depth, for example, is formed in the silicon substrate 101. In the anisotropic etching performed on the silicon substrate 101, the etching rate for polysilicon is larger than that for single-crystalline silicon. Therefore, the inner wall of the polysilicon film 103 slightly retreats through the step shown in FIG. 50.
Then, as shown in FIG. 51, an inner wall silicon dioxide film 107 of about 50 nm in thickness is formed on the inner wall of the trench 106 by thermal oxidation. This treatment is referred to as inner wall oxidation. The inner wall oxidation is performed in order to round the shape of a corner part on the bottom of the trench 106 or that of the upper end of the trench 106 for attaining an effect of relaxing stress, as described above. In addition to this effect, an effect of introducing an etching damage layer formed on the surface part of the inner wall of the trench 106 by the anisotropic etching into the inner wall silicon dioxide film 107 for reducing defects (point defects, dislocations etc.) in the silicon substrate 101 and an effect of reducing interface state density between the STI structure and the silicon substrate 101 are also attained by performing the inner wall oxidation.
In the step shown in FIG. 51, the inner wall of the polysilicon film 103 and part of the silicon substrate 101 coming into contact with the silicon dioxide film 102 are simultaneously oxidized to form a bird""s beak 108 on the upper end of the trench 106. A thermal oxide film of polysilicon grows at a higher rate than that of single-crystalline silicon, and hence the thickness of a silicon dioxide film formed on the polysilicon film 103 is larger than that of a silicon dioxide film formed on the silicon substrate 101. Consequently, the bird""s beak length (the thickness of the bird""s beak 108 along the main surface of the silicon substrate 101) is larger than the thickness of the remaining part of the inner wall silicon dioxide film 107. Needless to say, active regions are reduced as the thickness of the inner wall silicon dioxide film 107 is increased. When the active regions are reduced, the gate width of a MOS transistor is reduced, for example, and hence a drain current disadvantageously falls below a designed value.
It is possible to assume a method of omitting the step of depositing the polysilicon film 103 and directly depositing the silicon nitride film 104 on the silicon dioxide film 102 in order to reduce the bird""s beak length. In this case, however, stress caused on the upper end of the trench 108 is disadvantageously increased as compared with the case of providing the polysilicon film 103, depending on the conditions.
Then, the trench 106 covered with the inner wall silicon dioxide film 107 is filled with silicon dioxide 109, for example, as shown in FIG. 52. This step is carried out by depositing the silicon dioxide 109 to cover the upper surface of the silicon nitride film 104, the side surfaces of the silicon nitride film 104 and the polysilicon film 103, the side surface of the underlayer dioxide film 102 and the inner wall of the silicon substrate 101 by a film formation method such as HDP (high density plasma)-CVD (chemical vapor deposition), for example, simultaneously performing etching and film formation. The trench 107 may be basically filled with any insulation such as silicon dioxide, silicon oxynitride or TEOS, for example.
Then, CMP (chemical mechanical polishing) is performed through the silicon nitride film 104 serving as a stopper thereby flattening the upper end of the silicon dioxide 109, as shown in FIG. 53. After this flattening step, the silicon dioxide 109 remains in the trench 106.
Then, the silicon nitride film 104 and the polysilicon film 103 are removed by etching, as shown in FIG. 54.
Then, as FIG. 55 shows, the upper portion of the silicon dioxide 109 is removed by etching, for leaving silicon dioxide 120 as a principal component of the STI structure. At this time, part of the bird""s beak 108 and the silicon dioxide film 102 are simultaneously removed by etching. If the inner wall silicon dioxide film 107 is thick and hence the bird""s beak 108 is also thick, the upper end of the STI structure is not depressed toward the silicon substrate 101, as shown by symbol F in FIG. 55. If the bird""s beak 108 is thin or the etching is overetching, however, a depressed part 110 is caused as shown by symbol G in FIG. 56.
Then, the following step is carried out for forming a structure shown in FIG. 57 or 58 for the structure of FIG. 55 or FIG. 56. In this step, an underlayer oxide film is first formed in a thickness of 10 nm to 20 nm to cover the main surface of the silicon substrate 101 and heat-treated at a temperature of 800xc2x0 C. to 1100xc2x0 C. This treatment, performed for densifying the silicon dioxide 120 filled into the trench 106, is referred to as thermal shrinking. After the thermal shrinking step, well implantation (ion implantation for forming a well in the silicon substrate 101), channel stopper implantation (ion implantation for forming a channel stopper in the silicon substrate 101) and channel implantation (ion implantation for forming a channel in the silicon substrate 101) are performed and thereafter the aforementioned underlayer oxide film is removed by etching. Then, the main surface of the silicon substrate 101 is thermally oxidized thereby forming a gate insulator film 111, and then a gate electrode 112 is deposited. Consequently, the structure shown in FIG. 57 or 58 is completed.
When the depressed part 110 is formed as shown in FIG. 58, the gate electrode 112 is formed to partially fill up the depressed part 110. Therefore, even if the thickness of the gate insulator film 111 and a voltage applied to the gate electrode 112 are uniform between a plurality of semiconductor elements, electric field strength on the upper end of the STI structure is greater in the region G shown in FIG. 58 having the depressed part 110 as compared with the region F shown in FIG. 57 having no depressed part 110. This results from the difference in the thickness (bird""s beak length) of the bird""s beak 108. In the structure shown in FIG. 58 having the depressed part 110, therefore, a potential is bent larger in the vicinity of the upper end of the STI structure in the silicon substrate 101, to reduce the threshold voltage in this region. In the vicinity of the center of the active region separate from the upper end of the STI structure, on the other hand, the threshold voltage remains substantially identical between the structures shown in FIGS. 57 and 58 due to the same structure.
The ratio of an end of the STI structure to the gate width (width of the active regions) is increased when the gate width is reduced, and hence, as shown in a graph of FIG. 59, the threshold voltage is reduced in the structure shown in FIG. 58 having the depressed part 110 (curve C11). While the threshold voltage is reduced when the gate width is reduced also in the structure shown in FIG. 57 having no depressed part 110 (curve C10), the degree of this reduction is small.
The threshold voltage is reduced also in the structure shown in FIG. 57 since the amount of a channel dopant introduced into the silicon substrate 101 is reduced as compared with the center of the active region when channel implantation is performed through the thick bird""s beak 108 with low energy. Although the threshold voltage must be increased when the bird""s beak 108 is thick since an effective gate insulator film thickness on the upper end of the STI structure is increased as compared with the centers of the active region, an effect of reducing the amount (dose) of ions introduced into the silicon substrate 101 is large if the energy for channel implantation is low and hence the threshold voltage tends to slightly lower as the gate width is reduced as a whole. If the channel implantation is performed with high energy and therefore the ions are implanted into the silicon substrate 101 by about 100% through the thick bird""s beak 108 in the channel implantation, the threshold voltage tends to increase as the gate width is reduced. The effect of thus increasing the threshold voltage as the gate width is reduced is referred to as xe2x80x9cnarrow channel effectxe2x80x9d and an effect of reducing the threshold voltage as the gate width is reduced is referred to as xe2x80x9cinverse narrow channel effectxe2x80x9d.
Therefore, it is disadvantageous that the inverse narrow channel effect becomes remarkable when the depressed part 110 is present on the upper end of the STI structure, as shown in FIG. 59. This is because the threshold voltage is remarkably dispersed as the inverse narrow channel effect becomes remarkable when the finished gate width fluctuates, to cause a malfunction of the semiconductor device or reduction of the yield.
FIG. 60 is a graph showing a gate voltage-to-drain current characteristic of a MOSFET employing the aforementioned STI structure for element isolation. As shown on a curve C13, a hump HP appears when the depressed part 110 is present on the upper end of the STI structure. This is because the potential is bent more largely on the gate end as compared with the center of the active region to reduce the threshold voltage on the gate end due to concentration of an electric field in the vicinity of the depressed part 110 in the silicon substrate 101 and hence a drain current flows as a leakage current at a gate voltage lower than the threshold voltage at the center of the active region. This characteristic is also a sign of the inverse narrow channel effect. Thus, the drain current flows in a standby state of the MOSFET when the inverse narrow channel effect results from the depressed part 110, to disadvantageously increase power consumption of the semiconductor device.
While it is effective to increase the thickness of the bird""s beak 108 in order to prevent formation of the depressed part 110 on the end of the STI structure, the area of the active region is disadvantageously reduced in this case. When the width of the active regions is reduced, the effective gate width is also reduced to disadvantageously reduce the drain current of the MOSFET.
The trench 106 is formed by anisotropically etching the silicon substrate 101, and hence dangling bonds (unsaturated bonds of silicon atoms) or irregular grain structures are formed in the vicinity of the side wall and the bottom surface of the trench 106 in the silicon substrate 101. After formation of the STI structure, source/drain regions (a set of source and drain regions formed in one MOSFET are generically referred to as xe2x80x9csource/drain regionsxe2x80x9d) are formed on the active regions of the silicon substrate 101 by ion implantation, and thereafter high-temperature heat treatment is performed. Thus, ions implanted into the active regions are electrically activated and crystal defects present in the silicon substrate 101 disappear to recover the crystallographic order of the silicon substrate 101. In this high-temperature heat treatment, an impurity such as boron having a relatively high impurity diffusion coefficient diffuses to reach the STI structure. When irregular grain structures are present, the impurity acceleratingly diffuses along the grain boundaries thereof to reach the STI structure. Further, the dangling bonds provide proper bond sites for the diffusing impurity species, and hence it follows that the impurity is accumulated on the interface of the STI structure or in the vicinity thereof.
It is known that, when impurity species are present in an STI structure, defects follow in relatively high density. In relation to this, the following phenomena are observed: (1) Dislocations are formed in the vicinity of the STI structure in the silicon substrate 101 due to clusters of the impurity species. (2) A voltage necessary for dielectric breakdown of the STI structure is reduced as the defect density (or the dopant concentration) in the STI structure is increased. Consequently, dielectric breakdown takes place on a portion of the STI structure having high defect density (dopant concentration) when a voltage is applied to the source/drain regions formed adjacently to the STI structure. Further, a leakage current resulting from defects flows in or around the STI structure, and hence the threshold voltage is reduced in the vicinity of the side wall of the STI structure.
The chip area of the semiconductor device must be reduced in order to save the cost for manufacturing the same, and hence the isolation width of the STI structure tends to reduce. Therefore, the parasitic capacitance between active regions must be reduced in order to guarantee element isolability among semiconductor elements formed on the active regions. This parasitic capacitance depends on the element isolation width and the relative dielectric constant of the insulator filled into the STI structure. More specifically, the parasitic capacitance between two active regions isolated by the STI structure is proportional to the dielectric constant of the insulator filled into the STI structure and substantially inverse proportional to the element isolation width. The relative dielectric constant is that of a substance normalized with a vacuum dielectric constant. SiO2 is known as a representative insulator filled into the STI structure. The relative dielectric constant of SiO2, which is about 3.7 to 3.9 is by no means small. When the element isolation width is reduced, therefore, the parasitic capacitance is problematically increased. Following this, an isolation breakdown voltage is also reduced. Further, a leakage current flows between source/drain regions of one MOSFET and those of another MOSFET, to result in a malfunction of the integrated circuit.
A semiconductor device according to a first aspect of the present invention has an element isolation structure separating a main surface of a semiconductor substrate into a plurality of regions selectively formed on the main surface and a semiconductor element formed on each of the plurality of regions, and the element isolation structure comprises an inner wall insulator film formed on an inner wall of a trench selectively formed in the main surface to include an oxide semiconductor film coming into contact with the inner wall and having a bird""s beak, increased in thickness on an opening end of the trench, containing an oxynitride semiconductor, and an insulation filled into the trench through the inner wall insulator film.
In the device according to the first aspect, the bird""s beak contains the oxynitride semiconductor, whereby excessive growth of the bird""s beak following formation of the inner wall insulator film is suppressed in a manufacturing step for suppressing reduction of an active region. At the same time, the part of the oxynitride semiconductor in the bird""s beak is left unremoved, whereby no depressed part is formed despite the small thickness of the bird""s beak.
According to a second aspect of the present invention, the inner wall insulator film contains an oxynitride semiconductor over a range from the bird""s beak to a portion, shallower than the trench, under the bird""s beak in the semiconductor device according to the first aspect.
In the device according to the second aspect, the inner wall insulator film contains the oxynitride semiconductor up to the portion under the bird""s beak, whereby segregation of impurities contained in an active region of the semiconductor element is suppressed in a manufacturing step.
According to a third aspect of the present invention, another insulator film including a nitride semiconductor film is interposed between the insulator film and the insulation in the semiconductor device according to the first or second aspect.
In the device according to the third aspect, the nitride semiconductor film is interposed between the insulator film and the insulation, whereby diffusion of an oxidant following thermal oxidation is suppressed in a manufacturing step to suppress oxidation on the interface between the semiconductor substrate and the element isolation structure. Therefore, the density of oxidation-induced defects is suppressed.
According to a fourth aspect of the present invention, another insulator film including an oxynitride semiconductor film is interposed between the insulator film and the insulation in the semiconductor device according to the first or second aspect.
In the device according to the fourth aspect, the oxynitride semiconductor film is interposed between the insulator film and the insulation, whereby diffusion of an oxidant following thermal oxidation is suppressed in a manufacturing step to suppress oxidation on the interface between the semiconductor substrate and the element isolation structure. Therefore, the density of oxidation-induced defects is suppressed. Further, the coefficient of volumetric expansion of the oxynitride semiconductor is approximate to that of the semiconductor, whereby stress is further effectively relaxed.
A semiconductor device according to a fifth aspect of the present invention has an element isolation structure separating a main surface of a semiconductor substrate into a plurality of regions selectively formed on the main surface and a semiconductor element formed on each of the plurality of regions, and the element isolation structure comprises an inner wall insulator film formed on an inner wall of a trench selectively formed in the main surface to include an oxide semiconductor film coming into contact with the inner wall and a nitride semiconductor film covering the same and having a bird""s beak increased in thickness on an opening end of the trench and a fluorine-containing insulation filled into the trench through the inner wall insulator film.
In the device according to the fifth aspect, the trench is filled with the fluorine-containing insulation, whereby the parasitic capacitance between the semiconductor elements isolated by the element isolation structure is reduced. Further, the nitride semiconductor film suppresses diffusion of an oxidant, thereby suppressing oxidation on the interface between the semiconductor substrate and the element isolation structure in thermal oxidation performed in a manufacturing step. Therefore, the density of oxidation-induced defects is suppressed.
A method of manufacturing a semiconductor device according to a sixth aspect of the present invention comprises steps of (a) preparing a semiconductor substrate having a main surface, (b) forming a multilayer film including an oxide semiconductor film and a nitride semiconductor film located thereon on the main surface of the semiconductor substrate, (c) patterning the nitride semiconductor film thereby selectively forming an opening having a shape separating the main surface into a plurality of regions in the nitride semiconductor film, (d) executing etching through the patterned nitride semiconductor film employed as a mask thereby selectively removing a portion immediately under the opening at least until the main surface of the semiconductor substrate is exposed, (e) oxynitriding a surface located under the nitride semiconductor film and exposed in a cavity formed immediately under the opening, (f) executing etching through the patterned nitride semiconductor film employed as a mask thereby forming a trench in a portion of the semiconductor substrate immediately under the opening, (g) forming an inner wall insulator film including an oxide semiconductor film coming into contact with an inner wall of the trench on the inner wall, (h) filling the trench with an insulation after the step (g), (i) removing the multilayer film at least after the step (g), and (j) forming a component of a semiconductor element in each of the plurality of regions separated from each other by the trench in the main surface of the semiconductor substrate.
In the manufacturing method according to the sixth aspect, an oxynitride semiconductor film is formed on the side wall of a portion under the nitride semiconductor film of the multilayer film through the oxynitriding step, thereby suppressing diffusion of an oxidant on the side wall of the portion under the nitride semiconductor film of the multilayer film in the step of forming the inner wall insulator film. Thus, excessive growth of a bird""s beak following formation of the inner wall insulator film can be suppressed, for suppressing reduction of an active region. At the same time, an oxynitride semiconductor part in the bird""s beak is left unremoved in the step of removing the multilayer film, whereby no depressed part is formed despite the small thickness of the bird""s beak.
According to a seventh aspect of the present invention, the multilayer film further includes a polycrystalline semiconductor film held between the oxide semiconductor film and the nitride semiconductor film in the method of manufacturing a semiconductor device according to the sixth aspect.
In the manufacturing method according to the seventh aspect, a bird""s beak largely grows due to the polycrystalline semiconductor film included in the multilayer film, whereby stress is further effectively relaxed.
According to an eighth aspect of the present invention, the step (d) further includes a step (d-1) of executing etching through the patterned nitride semiconductor film employed as a mask thereby selectively removing a portion immediately under the opening until a groove shallower than the trench is formed in the semiconductor substrate in the method of manufacturing a semiconductor device according to the sixth or seventh aspect.
In the manufacturing method according to the eighth aspect, an oxynitride film is formed also on the side wall of the groove formed in the semiconductor substrate, thereby suppressing segregation of impurities contained in an active region of the semiconductor element.
According to a ninth aspect of the present invention, the step (e) includes steps of (e-1) oxidizing the surface exposed in the cavity in an oxygen atmosphere and (e-2) oxynitriding the surface exposed in the cavity in a nitric oxide atmosphere after the step (e-1), and the step (j) includes a step (j-1) of forming a component of an N-channel MOSFET as the component of the semiconductor element in each of the plurality of regions in the method of manufacturing a semiconductor device according to any of the sixth to eighth aspects.
In the manufacturing method according to the ninth aspect, the oxynitriding step is carried out by performing oxidation in the oxygen atmosphere and thereafter performing oxynitridation in the nitric oxide atmosphere, thereby increasing the nitrogen concentration in the semiconductor substrate. Thus, the mobility of an inversion layer of the N-channel MOSFET is increased.
According to a tenth aspect of the present invention, the step (e) comprises steps of (e-1) oxynitriding the surface exposed in the cavity in a nitric oxide atmosphere and (e-2) oxidizing the surface exposed in the cavity in an oxygen atmosphere after the step (e-1), and the step (j) comprises a step (j-1) of forming a component of a P-channel MOSFET as the component of the semiconductor element in each of the plurality of regions in the method of manufacturing a semiconductor device according to any of the sixth to eighth aspects.
In the manufacturing method according to the tenth aspect, the oxynitriding step is carried out by performing oxynitridation in the nitric acid atmosphere and thereafter performing oxidation in the oxygen atmosphere, thereby reducing the nitrogen concentration in the semiconductor substrate. Thus, reduction of mobility of an inversion layer of the P-channel MOSFET is suppressed.
A method of manufacturing a semiconductor device according to an eleventh aspect of the present invention comprises steps of (a) preparing a semiconductor substrate having a main surface, (b) forming a multilayer film including an oxide semiconductor film, an oxynitride semiconductor film or an oxyhalide semiconductor film coming into contact therewith and a nitride semiconductor film located thereon on the main surface of the semiconductor substrate, (c) patterning the nitride semiconductor film thereby selectively forming an opening having a shape separating the main surface into a plurality of regions in the nitride semiconductor film, (d) executing etching through the patterned nitride semiconductor film employed as a mask for selectively removing a portion immediately under the opening thereby forming a trench in a portion of the semiconductor substrate immediately under the opening, (e) forming an inner wall insulator film including an oxide semiconductor film coming into contact with an inner wall of the trench on the inner wall, (f) filling the trench with an insulation after the step (e), (g) removing the multilayer film at least after the step (e), and (h) forming a component of a semiconductor element in each of the plurality of regions separated from each other by the trench in the main surface of the semiconductor substrate.
In the manufacturing method according to the eleventh aspect, the multilayer film includes the oxynitride semiconductor film or the oxyhalide semiconductor film coming into contact with the oxide semiconductor film, whereby diffusion of an oxidant is suppressed on the side wall of a portion under the nitride semiconductor film of the multilayer film in the step of forming the inner wall insulator film. Thus, it is possible to suppress excessive growth of a bird""s beak following formation of the inner wall insulator film, for suppressing reduction of an active region. Further, an oxynitride semiconductor part in the bird""s beak is left unremoved in the step of removing the multilayer film, whereby no depressed part is formed despite the small thickness of the bird""s beak.
According to a twelfth aspect of the present invention, the step (g) includes a step (g-1) of removing the nitride semiconductor film included in the multilayer film between the steps (e) and (f), and the method further comprises a step (i) of forming an insulator film including a nitride semiconductor film on an exposed surface between the steps (g-1) and (f) in the method of manufacturing a semiconductor device according to the eleventh aspect.
In the manufacturing method according to the twelfth aspect, the nitride semiconductor film has a function of suppressing diffusion of an oxidant, thereby suppressing oxidation on the interface between the semiconductor substrate and the element isolation structure in thermal oxidation performed in the step of forming the element of the semiconductor element or the like. Thus, occurrence of oxidation-inductive defects is suppressed.
According to a thirteenth aspect of the present invention, the insulator film further includes a nitride semiconductor film in the method of manufacturing a semiconductor device according to the twelfth aspect.
According to a fourteenth aspect of the present invention, the step (g) includes a step (g-1) of removing the nitride semiconductor film included in the multilayer film between the steps (e) and (f), and the method further comprising a step (i) of forming an insulator film including an oxynitride semiconductor film on an exposed surface between the steps (g-1) and (f) in the method of manufacturing a semiconductor device according to the eleventh aspect.
In the manufacturing method according to the fourteenth aspect, the oxynitride semiconductor film has a function of suppressing diffusion of an oxidant, thereby suppressing oxidation on the interface between the semiconductor substrate and the element isolation structure in thermal oxidation performed in the step of forming the element of the semiconductor element or the like. Thus, occurrence of oxidation-inductive defects is suppressed. Further, the coefficient of volume expansion of the oxynitride semiconductor is approximate to that of the semiconductor, whereby stress is further effective relaxed.
A method of manufacturing a semiconductor device according to a fifteenth aspect of the present invention comprises steps of (a) preparing a semiconductor substrate having a main surface, (b) forming a multilayer film including an oxide semiconductor film and a nitride semiconductor film located thereon on the main surface of the semiconductor substrate, (c) patterning the nitride semiconductor film thereby selectively forming an opening having a shape separating the main surface into a plurality of regions in the nitride semiconductor film, (d) executing etching through the patterned nitride semiconductor film employed as a mask for selectively removing a portion immediately under the opening thereby forming a trench in a portion of the semiconductor substrate immediately under the opening, (e) forming an inner wall insulator film including an oxide semiconductor film coming into contact with an inner wall of the trench on the inner wall, (f) filling the trench with an insulation after the step (e), (g) removing the multilayer film at least after the step (e), (h) forming a component of a semiconductor element in each of the plurality of regions separated from each other by the trench in the main surface of the semiconductor substrate, and (i) implanting nitrogen, halogen or nitrogen halide into at least part of the multilayer film at least after the step (a).
In the manufacturing method according to the fifteenth aspect, nitrogen, halogen or nitrogen halide is implanted into at least part of the multilayer film, so that the implanted element thermally diffuses due to heat treatment performed in some later step, to reach a portion close to a bird""s beak on the upper end of the element isolation structure or the interface between the oxide semiconductor film and the semiconductor substrate. Consequently, the interface state density is reduced in this region, to reduce dispersion of the characteristics of the semiconductor element.
According to a sixteenth aspect of the present invention, the step (d) comprises steps of (d-1) executing the etching until the oxide semiconductor film included in the multilayer film is exposed and (d-2) executing the etching until the trench is formed after the step (d-1), and the step (i) includes a step (i-1) of oblique-rotationally implanting nitrogen, halogen or nitrogen halide into at least part of the multilayer film between the steps (d-1) and (d-2) in the method of manufacturing a semiconductor device according to the fifteenth aspect.
In the manufacturing method according to the sixteenth aspect, ions of nitrogen or the like are directly implanted into a portion where a bird""s beak is formed by oblique rotational implantation, whereby the interface state density can be further effectively reduced.
According to a seventeenth aspect of the present invention, at least part in the step (i) includes the nitride semiconductor film in the method of manufacturing a semiconductor device according to the fifteenth or sixteenth aspect.
According to an eighteenth aspect of the present invention, the multilayer film further includes a polycrystalline semiconductor film held between the oxide semiconductor film and the nitride semiconductor film, and at least part in the step (i) includes the polycrystalline semiconductor film in the method of manufacturing a semiconductor device according to any of the fifteenth to seventeenth aspects.
According to a nineteenth aspect of the present invention, the multilayer film further includes a polycrystalline semiconductor film held between the oxide semiconductor film and the nitride semiconductor film, and the step (i) includes a step (i-1) of implanting nitrogen, halogen or nitrogen halide into the polycrystalline semiconductor film before the nitride semiconductor film included in the multilayer film is formed in the step (b) in the method of manufacturing a semiconductor device according to the fifteenth aspect.
A method of manufacturing a semiconductor device according to a twentieth aspect of the present invention comprises steps of (a) preparing a semiconductor substrate having a main surface, (b) forming a multilayer film including an oxide semiconductor film and a nitride semiconductor film located thereon on the main surface of the semiconductor substrate, (c) patterning the nitride semiconductor film thereby selectively forming an opening having a shape separating the main surface into a plurality of regions in the nitride semiconductor film, (d) executing etching through the patterned nitride semiconductor film employed as a mask for selectively removing a portion immediately under the opening thereby forming a trench in a portion of the semiconductor substrate immediately under the opening, (e) forming an inner wall insulator film including an oxide semiconductor film coming into contact with an inner wall of the trench on the inner wall, (f) filling the trench with an insulation after the step (e), (g) removing the multilayer film at least after the step (e), (h) implanting nitrogen, halogen or nitrogen halide into the insulation at least after the step (f), and (i) forming a component of a semiconductor element on each of the plurality of regions separated from each other by the trench in the main surface of the semiconductor substrate.
In the manufacturing method according to the twentieth aspect, nitrogen, halogen or nitrogen halide is implanted into the insulation charged into the trench, so that the implanted element thermally diffuses due to heat treatment performed in some later step, to reach a portion close to a bird""s beak on the upper end of the element isolation structure or the interface between the oxide semiconductor film and the semiconductor substrate. Consequently, the interface state density is reduced in this region, to reduce dispersion of the characteristics of the semiconductor element.
A method of manufacturing a semiconductor device according to a twenty-first aspect of the present invention comprises steps of (a) preparing a semiconductor substrate having a main surface, (b) forming a multilayer film including an oxide semiconductor film and a nitride semiconductor film located thereon on the main surface of the semiconductor substrate, (c) patterning the nitride semiconductor film thereby selectively forming an opening having a shape separating the main surface into a plurality of regions in the nitride semiconductor film, (d) executing etching through the patterned nitride semiconductor film employed as a mask for selectively removing a portion immediately under the opening thereby forming a trench in a portion of the semiconductor substrate immediately under the opening, (e) forming an oxide semiconductor film on an inner wall of the trench, (f) forming a nitride semiconductor film on the oxide semiconductor film formed on the inner wall, (g) filling the trench with a fluorine-containing insulation after the step (f), (h) removing the multilayer film at least after the step (f), and (i) forming a component of a semiconductor element on each of the plurality of regions separated from each other by the trench in the main surface of the semiconductor substrate.
In the manufacturing method according to the twenty-first aspect, the trench is filled with the fluorine-containing insulation, thereby reducing the parasitic capacitance between the semiconductor elements isolated by the element isolation structure. Further, the nitride semiconductor film suppresses diffusion of an oxidant, thereby suppressing oxidation on the interface between the semiconductor substrate and the element isolation structure in thermal oxidation performed in the step of forming the element of the semiconductor element or the like. Thus, occurrence of oxidation-induced defects is suppressed.
A first object of the present invention is to provide a semiconductor device having no depression part on an end of an STI structure with small reduction of the area of an active region caused by a bird""s beak and a method of manufacturing the same. A second object of the present invention is to provide a semiconductor device capable of reducing an interface state on the interface between an STI structure and a semiconductor substrate thereby improving reliability (hot carrier resistance etc.) of a gate insulator film on a gate end of a MOSFET in the gate width direction, for example, and a method of manufacturing the same. A third object of the present invention is to provide a semiconductor device capable of reducing the density of defects introduced into the interface between an STI structure and a semiconductor substrate and a method of manufacturing the same. A fourth object of the present invention is to provide a semiconductor device capable of reducing parasitic capacitance between active regions holding an STI structure therebetween and a method of manufacturing the same.
Japanese Patent Laying-Open Gazette No. 9-82794 (1997) (hereinafter referred to as literature 1), Japanese Patent Laying-Open Gazette No. 8-213382 (1996) (hereinafter referred to as literature 2), xe2x80x9cSymposium on VLSI Technology, Digest of Technical Papersxe2x80x9d (1999) pp. 159-160 (hereinafter referred to as literature 3), Japanese Patent Laying-Open Gazette No. 11-186378 (1999) (hereinafter referred to as literature 4) and U.S. Pat. No. 5,447,884 (hereinafter referred to as literature 5) are known as literature disclosing techniques related to the present invention. Superiority of the present invention over the prior art is described in detail with reference to embodiments.


The present invention provides a composition of matter having a harmonized form (Φ/φ) of a hydroxyl modified fullerene having a molecular formula of C60(OH)xHy∀z (where x is from 10 to 36, and y is from 0 to 24 and z is from 0 to 12) the composition of matter having substantially the same 13C NMR spectra shown in FIG. 8 having a dominant peak at 170.2 ppm. This peak shows that each carbon atom of C60 is equally covered by OH groups and that the system [C60(OH)xHy∀z](Φ/φ is one body entity.

1. Technical Field
The present invention provides harmonized hydroxyl-modified fullerenes, hydroxyl-modified fullerenes in a suitable carrier, and hydroxyl-modified fullerene formulations including a suitable carrier with optional additives. These compositions of matter and formulations have numerous applications including, for example, the cosmetic and healthcare fields. What is meant by the term "harmonized" is that ratio of two quantities obeys the golden mean ratio. Examples include the energy states of atoms or molecules; the length of covalent, ionic, hydrogen or other type of bonds; electrical field strengths, and magnetic field strengths to name a few.
2. Background Art
Schrödinger's book What is Life? has had an enormous influence on the development of molecular biology, stimulating scientists such as Crick and Watson to explore the double helix structure of DNA as the basis of life (Schrödinger 1943, Watson and Crick, 1953). One of the central points in the book is statement "that the most essential part of a living cell—the chromosome fiber—may suitably be called an aperiodic crystal" as opposed to a periodic crystal in classical physics. It has been found that DNA works as a classical information system based on a double helix structure and a ternary coding system with 43=64 coding words [Crick, 1963]. Many years later it was recognized that that the genetic ternary code, which codes for amino and imino acids in proteins, also, may be represented as a classical binary code 26=64 [Swanson, 1984, Doolittle, 1981, Rakocević, 1998].
The importance of hydrogen bonding in the structure and function of biological macromolecules was predicted by the earliest investigators (Pauling, Corey, and Branson, 1951). According to Linus Pauling, the first prediction of the existence of a hydrogen bond should be attributed to M. L. Huggins in 1919 and independently to W. M. Latimir and W. H. Rodebush in 1920. Bearing in mind that most biological systems contain water from 60% to 80%, the importance of hydrogen bonds has become most relevant for understanding how biomolecular machinery, as a complex system, works. Within a collection of water molecules, the hydrogen atom is covalently bound to an oxygen atom in the water molecule and hydrogen bonds with oxygen atoms on separate water molecules. It is well known that covalent bond may only be described by quantum mechanics, because each electron does not really belong to a single atom—it belongs to both simultaneously. For a long period of time, scientists believed that the hydrogen bond could be perfectly understood by the principles of electrostatic interactions using Coulomb's law (pre-20th century classical physics), based on the attraction and repulsion between charged particles separated from each other by a distance. However, recent experimental data indicate that a hydrogen bond has double identity: classical and quantum (Isaacs, 1999, Barbiellini, and Shukla, 2003). This is the key point for understanding a new approach to explaining bow DNA and proteins function in water. It is believed that water itself may be a coding structure, via its hydrogen bonds, if some water molecules are organized in clusters and some of them are ordered in interconnected chains between water clusters by Fibonacci law. Some local domains of water, under the influence of DNA and microtubules, may be responsible for organizing water molecules into clusters as complementary coding forms. In a human, 40% of it is water is free water, while 60% is captured by biomolecules. Estimates predict that only 5% of free water is in clusters organized by a sphere packing law of coding number 12. The remaining 95% of free water is in the form of "chaos" with local polymerized islands.
According to a coding approach based on sphere packing analysis, the optimal molecular organization of water molecules should be as a hydrogen-bonded (H2O)n polyhedra 5126n (n=0,2,4 . . . ), where 512 represents 12 pentagons and n different number of hexagons (Jeffrey, 1997). Through hydrogen bonds dynamics, this polyhedra-shaped structure of water molecules posses a spherical coding system 25=32. The arrangement of water molecules, based on number 12, may represent a coding system which is part of an optimal information peak of sphere packing (Sloane 1984, Koruga, 1986). Accordingly, water hydrogen-bonded polyhedra is both compatible and complementary with the coding system of the genetic code (DNA and proteins).
An understanding of the hydrogen bonding dynamic on quantum chemical scales is useful in the study of biological systems, including the study of diseases such as cancer and medical and cosmetic conditions related to the human skin. By way of background with regard to the human skin, the epidermis is a dynamic renewing structure that provides life-sustaining protection from the environment. Keratinocytes and melanocytes are the major cells types responsible for the structure of the epidermis. They begin as stem cells in the basal epidermal layer. As keratinocytes move to the epidermal surface, the cells cease cell division and undergo morphological changes to form the prickle or spinous cells, granular cells, transition cells, keratinized squames and surface squames. One melanocyte cell may overlap a few keratinocytes giving them melanin (mechanism is yet unknown), which is responsible for protection of the environmental electromagnetic radiation (UV radiation) and neutralization of free radicals (Varni et al, 2004 van den Bossche, at al. 2006).
It is also well known that vitamin C (L-ascorbic acid) can be used in the treatment of conditions related to the skin. One of the major roles of vitamin C is its stimulation effects on collagen synthesis without affecting other protein synthesis. Vitamin C is a desired component of cosmetic products for both praline and lysine hydroxylase which stabilize the collagen molecule. This reaction is necessary for skin to maintain its strength.
Also, collagen distortion below the base level membrane (lamina fibroreticularis) occurs when cancer penetrates through the epidermis into the dermis, and "opens the door" for metastases. From a classical communication channels point of view, gene expression is responsible for it: normal collagen, type I [α1(I)2α2(I)], comprises two procollagen chains, the first α1(I) (gene located on chromosome 17 (q21-q22)), and the second procollagen chain α2(I) (gene located on chromosome 7(q21-q22)). According to quantum theory, quantum communication channels exists among keratinocyte or melanocyte and fibroblast cells (entanglement) based on hydrogen bonding in the DNA. When symmetry-breaking of hydrogen bonds happens in DNA, then automatically, through DNA-microtubule-water coding entanglement, synergy of classical and quantum communication is broken. There is experimental evidence that fibroblast cells and human melanoma cells interact with tumour cell growth as a function of tumour progression (Coinil, at.al. 1991). If UV radiation damages DNA on chromosome 7, in keratinocyte or melanocyte cells, then through non-classical quantum channels this information will transfer to both centriole (damaged cell) and fibroblast cells in the region. The centriole will become "wild" (from bipolar mitosis change to three polar or multipolar mitosis) and will start to divide chromosomes irregularly. The nucleus of an initial cancer cell will grow faster than normal cells. The "wild" cell will be duplicated and rapidly increase in number because positive feedback control mechanism water-centriole will change perpendicularly to centriole pairs (Koruga, et.al. 1992). From another side, fibroblast cells will cease synthesizing collagen α2(I). In the absence of α2(I), procollagen chains during assembly into procollagen molecules, will incorporate an additional α1(I) procollagen chain. This will give collagen type I-trimer with a structure [α1(I)3]. The I-trimer links between procollagen chains do not fit well, and OH groups will be removed from collagen to make free water molecules. The volume of free water will increase from 20% in tissue (Foster and Schwan, 1986). A similar occurrence is observed in skin aging an accounts for the reason for people of advancing age frequently having cancer (Richard, at.al., 2004).
When this type of collagen becomes dominant in a given tissue, the lamina fibroreticularis (as "a woof" of basal lamina) becomes weak, because the interconnection between procollagen chains in procollagen molecules, based on hydrogen bonds, is not adequate (the electromagnetic shield of a basal membrane has holes). Then, a mass of skin cancer or melanoma, can penetrate the basal lamina and reach the superficial arteriovenous plexus (Brinkley, 2001).
Hydrogen bonding in biomolecule networks in cell and tissue, as well as their complex intermolecular connections, resemble spider webs. It is a link between classical and quantum behaviour of matter on molecular level, and it is a basic element of synergy between mass-energy and information in living matter.
DNA is coded by 4th perfect number code 2n(2n+1−1) with 8128 code words, which is responsible for protein coding (classical) and system complexity coding (quantum) by entanglement (Koruga, 2005, Koruga, et al. 2006). There is mapping one-to-one from genetic code to proteins by synergetic code. There is synergetic code (classical/quantum) in protein chain based on amino acids and peptide plains. Hydrogen bonds are links between classical and quantum behaviours of matter on a molecular level, and it is a basic element for synergy of mass-energy-information in living matter.
Understanding DNA as synergetic classical/quantum device, based on golden mean and the forth prefect number, may help us not only for better understanding of the origin of life, but also for finding methods for prevention and healing the most illnesses. Bearing in mind that proteins are the second side of DNA code, interaction and communication DNA-protein may be both through separate classical and quantum communications channels, and through synergetic one. However, synergetic approach, which we proposed open a new possibilities for therapy of many skin illnesses including cancer.
DNA and water exist in a very delicate relationship. In normal situations, DNA operates in accordance with the forth perfect number law, while water operates in accordance with the third perfect number law. In normal situations, the DNA-water system works harmonically. However, when, for some reason, DNA collapses from operating in accordance with the fourth perfect number law to the third perfect number law, then information about the disharmonic state of DNA travels more smoothly through water than its harmonic one.
These and other aspects and attributes of the present invention will be discussed with reference to the following drawings and accompanying specification

Composition of matter containing harmonized hydroxyl modified fullerene substance


A network analysis system and methods facilitate a match-corrected signal power measurement using a vector network analyzer (VNA). The network analysis system includes the VNA and a computer program stored in memory and executed by a controller. The computer program has instructions that implement one or both of calibrating a test port of the VNA to determine the match-corrected signal power measurement and correcting a power measured for a signal received at the test port of the VNA using corrected error terms of a port calibration of the test port to yield a corrected measured power. The corrected error terms are determined from error terms of the port calibration using a switch term and an incident power calibration, both of the test port. A method 100 determines the match-corrected signal power measurement and a method 300 calibrates the VNA test port to determine the measurement.

Signal power measurement is a commonly performed test in radio frequency (RF) test and measurement. A variety of measurement systems provide some form of power measurement including, but not limited to, power meters, spectrum analyzers, scalar network analyzers, and vector network analyzers. Power meters are generally considered a preferred measurement tool for performing precise and accurate power measurements. A vector network analyzer (VNA) can also provide accurate power measurements of a signal emitted by a device under test (DUT) provided the VNA is properly calibrated. In particular, error coefficients from a full two-port calibration of the VNA may be used to compute a correction of raw power measurements taken using the VNA to yield accurate power measurements. See for example, Shoulders et al., U.S. Pat. No. 7,061,254, incorporated herein by reference.
However, in some situations a full two-port calibration is either difficult to perform or is not needed for other reasons and therefore is not performed. For example, when making waveguide mixer scalar conversion gain measurements, performing a full two-port calibration of a VNA can be problematic due to the frequency conversion inherent in the operation of the mixer. In other situations, a full two-port calibration of the VNA (or multiport calibration of a multiport VNA) is simply too complicated to be practical. In such situations where a full two-port or full multiport calibration is not desirable or is simply not performed, the accuracy of the VNA-based power measurement will suffer from a presence of systematic errors associated with the measurement process.

Match-corrected power measurements with a vector network analyzer


Compositions containing cyclophilin B, mutants of cyclophilin B or inhibitors of cyclophilin B and methods of using these compositions to modulate somatolactogenic function are provided.

The somatolactogenic hormones prolactin (PRL) and growth hormone (GH) are necessary for the full growth and maturation of vertebrate species.
Prolactin (PRL) was originally identified as a neuroendocrine hormone of pituitary origin. PRL expression has also been detected in the decidua, breast and T-lymphocytes (Clevenger, C. V. and Plank, T. L. J. Mammary Gland Biol. Neoplasia 1997 2:59–68; Mershon et al. Endocrinology 1995 136:3619–3623; DiMattia et al. Endocrinology 1986 122:2508–2517; Ginsburg, E. and Vonderhaar, B. K. Cancer Res. 1995 55:2591–2595; Gellersen et al. Mol. Endocrinol. 1994 8:356–373; Clevenger et al. Proc. Natl. Acad. Sci. USA 1990 87:6460–6464; Montogomery et al. Biochem. Biophys. Res. Commun. 1987 145:692–698). A primary function of this hormone lies within the breast. However, functional pleiotropism of this peptide with regard to reproduction, osmoregulation and behavior has also been recognized (Nicoll, C. S. Handbook of Physiology; Section 7: Endocrinology, pp. 253–292, Washington, D.C.: American Physiology Society. 1974). Several lines of evidence have also indicated an immunoregulatory role for this peptide (Clevenger et al. Journal of Endocrinology 1998 157:187–197; Weigent, D. A. Pharmacol. Ther. 1996 69:237–257). Structural analysis of PRL has revealed it to be related to members of the cytokine/hematopoietin family which also includes growth hormone, erythropoietin, granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukins 2–7 (Bazan, J. F. Immunol. Today 1990 11:350–354)
The pleiotropic actions of PRL are mediated through its receptor (PRLr), a member of the superfamily of type I cytokine receptors. PRLr is present on numerous tissues including mammary epithelia, T and B lymphocytes and macrophages (Dardenne et al. Endocrinology 1994 134:2108–2114; Pellegrini et al. Mol, Endocrinol. 1992 6:1023–1031). Acting through its receptor, PRL signaling stimulates cell proliferation, survival and cellular differentiation in a tissue- and microenvironment-dependent manner. In the mammary and immune systems, PRL is believed to act at the endocrine, paracrine, and autocrine levels in regulating T-lymphocyte proliferation and survival (Gala, R. R. PSEBM 1991 198:513–527; Yu-Lee, L. Y. Proceedings of the Society for Experimental Biology and Medicine 1997 215:35–52; Kooijman et al. Adv. Immunol. 1996 63:377–454; Prystowski, M. B. and Clevenger, C. V. Immunomethods 1994 5:49–55) and the terminal maturation of mammary tissues (Kelly et al. Rec. Prog. Horm. Res. 1993 48:123–164; Shiu et al. Rec. Prog. Horm. res. 1987 43:277–289). PRL is also believed to act as both an endocrine and autocrine/paracrine progression factor for mammary carcinoma in both rodents and humans (Welsch, C. W. Cancer Res. 1985 45:3415–3443; Welsch, C. W. and Nagasawa, H. Cancer Res. 1977 37:951–963; Manni et al. Cancer Res. 1986 37:951–963; Malarkey et al. J. Clin. Endocrinol. Metab. 1983 56:673–677; Clevenger et al. Am. J. Pathol. 1995 146:1–11; Fields et al. Lab. Invest. 1993 68:354–360; Ormandy et al. J. Clin. Endocrinol. Metab. 1997 82:3692–3699; and Mertani et al. Int. J. Cancer 1998 79:202–22).
Pleiotropic actions of GH are also largely mediated through a type I cytokine receptor, GHr.
Ligand-induced dimerization of PRLr and GHr activates several associated signaling cascades including the Jak-Stat, Ras-Raf, and Fyn-Vav pathways (Campbell et al. Proc. Natl. Acad. Sci. USA 1994 91:5232; Clevenger et al. J. Biol. Chem. 1994 269:5559; Clevenger et al. Mol. Endocrinol. 1994 8:674; Clevenger et al. J. Biol. Chem. 1995 270:13246). However, studies indicate that both PRL and GH are internalized via an endosomal-like pathway and transported across the endoplasmic reticulum (ER) and nuclear envelopes (Clevenger et al. Endocrinology 1990 127:3151; Rao et al. J. Cell Physiol. 1995 163:266). This process is referred to as nuclear retrotranslocation. The mechanism of this retrotranslocation, and the nuclear action of these somatolactogenic hormones, however, is not well understood.
Both PRL and GH lack enzymatic activity. These hormones also contain no nuclear translocation signal. Thus, for PRL and GH to act within the nucleus, they must do so through a binding partner or chaperone.
CypB is a member of the cyclophilin family of cistrans peptidyl prolyl isomerases (PPI) (Price et al. Proc. Natl. Acad. Sci. USA 1991 88:1903; Ruhlmann, A. and Nordheim, A. Immunobiol. 1997 198:192; Resch, K. and Szamel, M. Int. J. Immunopharmac. 1997 19:579). This family of proteins was initially identified as the binding partners for the immunosuppressive agent cyclosporine (CsA). CsA interacts with the cyclophilin with high affinity, inhibiting their PPI activity and the action of the phosphatase calcineurin, necessary for NF/AT-transactivated expression of IL-2 (Kronke et al. Proc. Natl. Acad. Sci. USA 1984 81:5214; Liu et al. Cell 1991 55:807; Friedman, J. and Weissman, I. Cell 1991 66:799; McCaffrey et al. J. Biol. Chem. 1993 268:3747; Bram, R. J. and Crabtree, G. R. Nature 1994 371:355; Bram et al. Mol. Cell Biol. 1993 13:4760). Structurally CypB is a β-barrel protein containing both N-terminal ER-leader and putative nuclear translocation signal sequences and C-terminal ER-retention sequences (Allain et al. J. Immunol. Meth. 1995 178:113; Mariller et al. Biochem. Biophys. Acta 1996 1293:31). CypB has been observed in the ER and nucleus, and can be found in appreciable levels in blood (150 ng/ml) and breast milk (Hirada et al. Cell 1990 63:303; Price et al. Proc. Natl. Acad. Sci. USA 1994 91:3931). Cyclophilins, via their PPI activity, facilitate protein folding and have been shown to contribute to the maturation of several proteins, including carbonic anhydrase and the HIV glycoprotein Gag (Taylor et al. Prog. Biophys. Molec. Biol. 1997 67:155; Streblow et al. Virology 1998 245:197). Despite these insights, the physiologic function of CypB has remained uncertain.
It has now been found that cyclophilin B (CypB) interacts specifically with somatolactogenic hormones, PRL and GH, as a chaperone mediating the transport, maturation and/or function of these proteins.

Methods and compositions for modulating somatolactogenic functions

Trustees of the University of Pennsylvania


Ultrasonic processing apparatus and methods are disclosed, which includes multiple transducers of at least two different resonant frequencies supplying ultrasonic energy to a liquid filled tank containing components to be cleaned or processed ultrasonically. The transducers are arranged in equilateral triangular patterns along diagonal lines on a wall of the tank so that each transducer has an adjacent transducer of a different frequency. Alternatively, the apparatus includes one or more rod transducers having different resonant frequencies so that the apparatus provides a mixture of various frequencies of ultrasonic energy to the tank. Another aspect of the invention involves selecting transducers with different resonant frequencies that are outside an excluded subrange, and powering the transducers by a driving signal that sweeps through the resonant frequencies of the transducers and the excluded subrange.

1. Field of the Invention
This invention relates generally to ultrasonic cleaning and liquid processing methods and apparatus and other uses involving two or more piezoelectric transducers, and relates more particularly to improving performance by using ultrasonic energy at multiple frequencies.
2. Description of the Relevant Art
Ultrasonic devices are used in a variety of processes, including cleaning, emulsifying, and dispersing components or parts in a liquid medium, and other applications such as metal welding, plastic joining, and wire bonding. All these devices and processes use ultrasonic transducers to supply ultrasonic frequency sound waves to a liquid or solid medium.
Cleaning parts in a liquid medium is one common use of ultrasonics. Cleaning with ultrasonics uses ultrasonic waves to generate and distribute cavitation implosions in a liquid medium. The released energies reach and penetrate deep into crevices, blind holes and areas that are inaccessible to other cleaning methods.
Ultrasonic waves are -pressure waves formed by actuating the ultrasonic transducers with high frequency, high voltage current generated by electronic oscillators (typically referred to as power supplies or generators). A typical industrial high power generator produces ultrasonic frequencies ranging from 20 to 300 kHz or more. Ultrasonic transducers typically include piezoelectric (PZT) devices that expand and contract when subjected to the oscillating driving signals supplied by generators. The transducers are normally mounted on the bottom and/or the sides of the cleaning tanks or immersed in the liquid. The generated ultrasonic waves propagate perpendicularly to the resonating surface. The waves interact with liquid media to generate cavitation implosions. High intensity ultrasonic waves create micro vapor/vacuum bubbles in the liquid medium, which grow to maximum sizes proportional to the applied ultrasonic frequency and then implode, releasing their energies. The higher the frequency, the smaller the cavitation size.
The energy released from an implosion in close vicinity to the surface collides with and fragments or disintegrates the contaminants, allowing the detergent or the cleaning solvent to displace it. The implosion also produces dynamic pressure waves which carry the fragments away from the surface. The cumulative effect of millions of continuous tiny implosions in a liquid medium is what provides the necessary mechanical energy to break physically bonded contaminants, speed up the hydrolysis of chemically bonded ones and enhance the solubilization of ionic contaminants.
In general, at low frequencies (20–30 kHz), a relatively smaller number of cavitations with larger sizes and more energy are generated. At higher frequencies, much denser cavitations with moderate or lower energies are formed. Low frequencies are more appropriate for cleaning heavy and large-size components, while higher frequency (60–80 kHz) ultrasonics is recommended for cleaning delicate surfaces and for the rinsing step.
In some applications it is advantageous to use multiple transducers operating at different frequencies in combination. See, for example, U.S. Pat. No. 6,019,852 and U.K. Patent 1,488,252. These patents disclose cleaning apparatus with rectangular grids of two different frequency transducers, separately driven by two power supplies or generators.

Ultrasonic processing method and apparatus with multiple frequency transducers


A breather structure for internal combustion engine, the structure making a breather chamber smaller and thus making an internal combustion engine as a whole smaller. A breather chamber and a small chamber are formed. The breather chamber includes a first side face cover. The first side face cover is joined to a case to cover a first one of the right and left side faces of the case. Inside the first side face cover, an auxiliary apparatus chamber is formed. The auxiliary apparatus chamber houses a clutch mechanism connecting or disconnecting the power transmission route. Additionally, formed inside a housing are an external communication port communicating to the outside of the housing, and the small chamber communicating to a crank chamber and to the auxiliary apparatus chamber. Moreover, the auxiliary apparatus chamber communicates to the breather chamber.

1. Field of the Invention
The present invention relates to a breather structure for an internal combustion engine with a cylinder block and a case joined to the cylinder block. The cylinder block has a cylinder bore formed therein, and a piston, which is disposed in the cylinder bore by being inserted thereinto, and which can reciprocally travel freely in the cylinder bore. Meanwhile, the case has a crank chamber communicating to the cylinder bore. A crankshaft is housed in the crank chamber, while the crankshaft rotates in conjunction with the piston.
2. Description of Background Art
In such an internal combustion engine, the internal pressure of the crank chamber, which communicates to the cylinder bore, fluctuates with the reciprocating travels of the piston. To reduce the fluctuation in the internal pressure, a breather chamber is formed to allow the inside of the housing where the internal combustion engine is housed to communicate to the outside. The mitigation of the fluctuation in the internal pressure of the crank chamber is thus pursued.
In the breather structure disclosed in Japanese Utility Model Application Laid-Open Publication No. Hei 2-22451, the crank chamber communicates to a clutch chamber housing a clutch while the clutch chamber communicates to a breather chamber. Such a breather structure, however, makes the impact of the fluctuation in the pressure in the crank chamber great because the clutch chamber directly communicates to the crank chamber. For this reason, use of a breather chamber with a larger capacity is required for mitigating the fluctuation in the pressure in the crank chamber, but this makes the capacity in total of the housing larger.

Breather structure for internal combustion engine


A first enhanced Node B (eNB) and method for contention-free handoff return in a wireless network are provided. The first eNB in one example embodiment includes a transceiver system configured to communicate with a User Equipment (UE) and a processing system coupled to the transceiver system and configured to receive signal strength information from the UE, with the processing system being further configured to obtain a pre-handoff CF preamble for handoff of the UE from the first eNB to the second eNB, provide the pre-handoff CF preamble to the UE, generate a post-handoff CF preamble for the UE where the UE can use the post-handoff CF preamble to return from the second eNB to the first eNB, and provide the post-handoff CF preamble to the UE.

Wireless communication systems, such as cellular voice and data networks, typically include multiple wireless access nodes spread over a geographic area. As a result, wireless communication devices can register at various wireless access nodes and access communication services. In many examples, the wireless communication devices are mobile, and can move between wireless coverage areas of the wireless access nodes. As a result, people can use cellular telephones in a wide variety of locations and can make calls while moving or traveling.
Continuous cellular telephone service is available through handoffs, wherein an active cellular telephone can move from cell to cell in a cellular network. The cellular network hands off the cellular telephone from one base station to the next. As a result, a user receives continuous and uninterrupted service.
A handoff may occur where the cellular telephone is moving from one cell to the next and a handoff must be performed for the cellular telephone to maintain communications. Alternately, a handoff may occur where a cellular telephone is in a region overlapped by another cell and the cellular telephone is handed off to provide more capacity in the cell. In another alternative, a handoff may occur where a cellular telephone is experiencing interference in a current cell and is handed off to a neighboring cell to reduce interference.
In a handoff, an adjacent cell will be using a different set of frequencies in order to avoid interference. Consequently, during a handoff process, the cellular telephone must negotiate with both a current cell and a next cell over the transfer of service. Issues that must be addressed are the identity of the cellular telephone and the traffic load/capacity of the next cell, for example.
Overview
Systems and methods for contention-free handoff return in a wireless network are provided herein. In one example, a first enhanced Node B (eNB) for contention-free handoff return in a wireless network includes a transceiver system configured to communicate with a User Equipment (UE) and a processing system coupled to the transceiver system and configured to receive a signal strength and an interference information from the UE via the transceiver system, with the processing system being configured to obtain a pre-handoff CF preamble for handoff of the UE from the first eNB to a second eNB, provide the pre-handoff CF preamble to the UE, generate a post-handoff CF preamble for the UE, and provide the post-handoff CF preamble to the UE.
In an example of a contention-free handoff return method for a wireless network having a first enhanced Node B (eNB), the method includes in the first eNB, obtaining a pre-handoff contention-free (CF) preamble for handoff of the UE from the first eNB to a second eNB, in the first eNB, providing the pre-handoff CF preamble to the UE, in the first eNB, generating a post-handoff CF preamble for the UE, and in the first eNB, providing the post-handoff CF preamble to the UE.
In another example of a contention-free handoff return method for a wireless network having a first enhanced Node B (eNB), the method includes in the first eNB, obtaining a pre-handoff contention-free (CF) preamble for handoff of the UE from the first eNB to a second eNB, in the first eNB, providing the pre-handoff CF preamble to the UE, in the first eNB, comparing a first eNB signal strength of a signal received in the UE from the first eNB to a second eNB signal strength of a signal received in the UE from the second eNB, in the first eNB, generating a post-handoff CF preamble if a signal strength difference between the first eNB signal strength and the second eNB signal strength does not exceed a predetermined strength similarity range, and in the first eNB, providing the post-handoff CF preamble to the UE.

Contention-free handoff return in a wireless network


The present invention relates to a reducer of an electric power steering apparatus. According to the exemplary embodiments of the present invention, a damping member is provided on an outer circumference surface of a bearing bush so that impact between a worm shaft bearing and a bearing bush can be dampened, and noise generated at the time of impact can be reduced.

1. Field of the Invention
The present invention relates to a reducer of an electric power steering apparatus, and more particularly, a reducer of electric power steering apparatus in which a damping member is provided on an outer circumference surface of a bearing bush so that impact between a worm shaft bearing and the bearing bush is dampened, and noise generated at a time of impact is reduced.
2. Description of the Prior Art
FIG. 1 is a cross-sectional view illustrating a conventional reducer of an electric power steering apparatus.
As illustrated in FIG. 1, a conventional reducer 100 of an electric power steering apparatus is provided with a worm shaft 103 which is formed with a worm 101 on an outer circumference surface thereof. Worm shaft bearings 105a and 105b are installed on both ends of the worm shaft 103, respectively, so as to support the worm shaft 103. A plug bolt 107 is fastened between a damping coupler 109 and the worm shaft bearing 105b so as to prevent the worm shaft bearing 105b from being moved in an axial direction of the worm shaft 103. The plug bolt 107 is anchored by a plug nut 111.
The worm shaft 103 is connected with a motor shaft 115 of a motor 113 via a damping coupler 109 such that the worm shaft 103 is rotated when the motor 113 is driven.
In addition, a worm wheel 117 is provided on one diametric side of the worm 101 to be tooth-engaged with a worm 101 formed on the worm shaft 103. The worm wheel 117 is mounted on a steering shaft 119 configured to transmit a rotation force of a steering wheel (not illustrated) operated by a driver, so that a rotation force of the worm shaft 103 generated by driving the motor 113 is transmitted to the steering shaft 119.
The worm shaft 103, the worm wheel 117 etc. are disposed within a gear housing 121 and the motor 113 configured to provide a driving force to the worm shaft 103 is provided on a side of the gear housing 121, in which a motor cover 123 is coupled to the gear housing 121 through a bolt 125.
Balls 131 are interposed between an inner wheel 127 and an outer wheel 129 of the worm shaft bearing 105b so as to support the rotation of the worm shaft 103 connected with the motor shaft 115 of the motor 113.
The reducer of the electric power steering apparatus configured as described above controls the driving of the motor 113 by an electronic control unit provided in a vehicle according to a vehicle driving condition, the rotation force of the worm shaft 103 generated by driving the motor 113 is added to the rotation force of the steering wheel operated by the driver and transmitted to the steering shaft 119 so that the driver's steering operation state can be smoothly and stably maintained.
However, such a conventional reducer of an electric power steering apparatus causes problems in that when the endurance of the worm shaft, which is rotated by driving the motor, and the worm, which is wheel tooth-engaged with the worm formed on the worm shaft, is consumed, a clearance is increased, which not only causes occurrence of noise, but also causes a steering-assist force assisting in the driver's steering wheel operating force to be incorrectly provided.

Reducer of electric power steering apparatus


The invention includes a method of mounting a component to the skin of an aircraft. The component can include a drain valve, a gas cap, other external fuel instrumentation such as sensors, and antennae. One aspect of the invention includes a new method of mounting a drain valve to an aircraft fuel tank. The drain valve in the method includes any conventional drain valve having a stem and a flange that surrounds the stem. The method includes applying a material around a drain opening of the fuel tank; the material directs an electric charge away from the drain valve.

Drain valves are often provided on aircraft fuel tanks so that liquid within the tank, such as water formed from condensated moisture, may be readily removed or drained. Such drain valves typically include a drain port or opening through which the liquid in the tank is drained and a valve member or poppet that moves in relation to the port to open and close the port. In operation, a preferred form of drain valve has a poppet which is biased to close the port and can be simply pushed inwardly of the fuel tank by use of a screwdriver or other simple tool to open the port. Upon release, the poppet automatically returns to its part-closing position under spring tension. Examples of such drain valves are shown in commonly owned Koller, U.S. Pat. No. 3,703,189 and Koller, U.S. Pat. No. 4,351,355. Another and improved construction is disclosed in, commonly owned Koller, U.S. Pat. No. 4,880,029, the disclosure of which is hereby incorporated by reference herein. These valves have proved reliable and have been commercially successful for a number of years.
A known method of mounting a drain valve to the frame of an aircraft includes the following steps in the order recited. First, the frame or skin of the aircraft is primed with a conventional paint primer. Second, the valve is installed. Third, the valve is masked with a conventional tape, or the like. Finally, the frame of the aircraft is painted.
Part of the design of drain valves used in aircraft is to withstand a wide variety of environmental conditions while maintaining the desired, normally closed position of the poppet. For example, valve components formed of dielectric or non-conductive materials are widely used to improve the capabilities of withstanding and/or avoiding lightning strikes. Likewise, the known devices employ special locking devices and complex constructions to address lightning strike issues. Drain valves are subject to involuntary opening as a result of a lightning strike. During a lightning strike the electric charge from the lightning seeks the least resistant path in order to dissipate the charge. It is believed that the electric charge or arc finds the metal that surrounds the drain valve opening in the aircraft even though careful attention is provided to ensure that the surface is primed and painted, and that no bare metal is exposed. It is also believed that the electric charge or arc results in a very large force concentrated in a relatively small area, i.e., the cracks in the paint. This arc results in a concussion, of sorts, that can crack or even destroy the flange that surrounds the stem of the drain valve. Furthermore, the arc can bypass the valve completely en route to the drain opening.
Accordingly, it is desirable to provide a drain valve and method of mounting the drain valve that encourages diffusion of electric arc into the frame or skin of the aircraft away from the drain opening, and prevents the potential for the energy from a lightning strike from reaching the drain valve opening, thus avoiding the resultant concussion.


A method of detecting defects in membranes such as ion exchange membranes of electrochemical cells. The electrochemical cell includes an assembly having an anode side and a cathode side with the ion exchange membrane in between. In a configuration step a chemochromic sensor is placed above the cathode and flow isolation hardware lateral to the ion exchange membrane which prevents a flow of hydrogen (H2) between the cathode and anode side. The anode side is exposed to a first reactant fluid including hydrogen. The chemochromic sensor is examined after the exposing for a color change. A color change evidences the ion exchange membrane has at least one defect that permits H2 transmission therethrough.

Although fuel cells show promise as future energy delivery devices, they are limited in their ability to be commercialized due to several reasons. Such reasons include the cost of the catalyst, cost of the balance of plant (e.g., saturators, flow controllers, etc.) and the limited durability of the fuel cell ion exchange membrane (hereafter referred to as the "membrane").
Membrane durability is limited by the development of membrane defects during testing and device operation. Examples of membrane defects include, 1) pinholes, where a small hole can develop in the membrane which can allow bulk hydrogen gas (H2) to flow easily from the anode to the cathode, 2) crack formation where a crack develops through the membrane again permitting H2 to flow to the cathode, and 3) membrane thinning, where diffusion of H2 from the anode to the cathode is increased due to a reduction in thickness of the membrane material.
For each case, the unintended presence of H2 at the cathode reduces fuel cell performance significantly, and may even lead to hazardous situations. Increasing the durability of the membrane will make the fuel cells more commercially feasible since they would last longer in the field. However, identifying the factors that affect those failures remains difficult. The ability to locate the specific points of failures in membrane has had limited progress, as typical diagnostic techniques are only able to determine bulk hydrogen crossover. Identifying the location(s) of membrane failures would assist greatly in developing more durable fuel cell membranes.
One known method for identifying the location of membrane failures involves infrared imaging. At membrane defect locations, the respective reactant fluids (H2 and O2) are both present and will exothermically react in the presence of a catalyst generating heat, which is then detected using an infrared thermal detector, thermal imaging device, or a layer of thermally sensitive film positioned in proximity with the membrane.
The infrared method has some significant limitations. These limitations include a requirement that a platinum electrode (or other catalyst) be present over the ion exchange membrane during testing to produce heat. There are also safety concerns because the top of the membrane electrode assembly (MEA) is exposed to the ambient conditions allowing the potential for H2 to enter the ambient environment. Moreover, the localized generation of heat may cause further damage to the membrane.

Method of detecting defects in ion exchange membranes of electrochemical cells by chemochromic sensors

University of Central Florida Research Foundation, Inc.


A hydrostatic seal configured to be disposed between relatively rotatable components includes a base. The seal also includes a seal housing. The seal further includes a shoe operatively coupled to the base and extending axially from a forward end to an aft end. The seal yet further includes a plurality of teeth extending radially from a sealing surface of the shoe, one of the teeth being a longest tooth that extends furthest radially from the sealing surface, the axial distance from the forward end of the shoe to the longest tooth being greater than a radial distance from a radial tooth tip to the sealing surface.

Exemplary embodiments pertain to the art of gas turbine engines and, more particularly, to a hydrostatic seal with enhanced maneuver response.
Hydrostatic seals exhibit less leakage compared to traditional knife edge seals while exhibiting a longer life than brush seals. Some hydrostatic seals may be used between a stator and a rotor within a gas turbine engine. The hydrostatic seal is mounted to the stator to maintain a desired gap dimension between the hydrostatic seal and the rotor. The hydrostatic seal has the ability to 'track' the relative movement between the stator and the rotor throughout the engine operating profile when a pressure differential is developed across the seal.
Hydrostatic seals involve motion of a spring-attached shoe whose response is based on aerodynamic forces developed between the seal shoe and a rotor surface during operation. When properly designed, the hydrostatic seal will maintain tight clearances across the operating range of the engine. The portion of the hydrostatic seal that moves is in contact with the static seal housing in order to prevent air from circumventing the primary flowpath. When the seal is in motion, a friction force develops which is proportional to the geometry of the seal (piston area) and the aerodynamic forces acting on the seal. There is potential for the seal to become "stuck" in a certain position if the friction force is higher than the aerodynamic and mechanical forces acting on the seal shoe. In maneuver conditions, the seal gap can change rapidly and the seal is expected to respond quickly to such changes. If the friction force is too high, though, the seal may not respond to gap changes and there is potential for the seal to come into undesirable contact with the rotor.

Hydrostatic seal with enhanced maneuver response