A refrigerated intercooler for an air conditioning, refrigeration or similar cooling system. The intercooler provides a thermal interface between colder refrigerant gas leaving the air conditioning system""s evaporator and the hotter refrigerant liquid leaving the system""s condenser. The thermal interface occurs between the gas in the accumulator portion of the intercooler and the liquid in an interior container of the intercooler. In the preferred embodiment, the interior container is coiled tubing, to promote better heat exchange. The system""s oil/refrigerant emulsion is metered and returned from the intercooler to the compressor through an oil return line that is external to the accumulator portion of the intercooler.

Not applicable.
Not applicable.
1. Field of Invention
This invention is directed toward improved performance of stationary and mobile air conditioning systems and other similar cooling systems by reducing the amount of saturated heat during the gas-to-liquid phase change in the condenser. To accomplish this objective, an intercooler device is placed between the condenser and evaporator, which enables more complete refrigerant condensation by improving the efficiency of the phase change. Such liquid refrigerant delivered to the evaporator, typically after passing through an expansion valve, arrives further below the critical temperature than before, with less saturated heat, and is thereby enabled to absorb more new heat during the evaporation phase than would be possible without the device. The intercooler is suitable for mobile and stationary air conditioning and refrigeration applications because of its ability to capture and recycle the otherwise wasted heat absorption capacity of the cold return gas. The operational improvement that is most immediately noticed by the user of the invention is the faster cool-down time and lower duct temperature achieved on a hot day compared with systems that are not fitted with the disclosed device. The differences are easier to identify when there is a high ambient heat load because systems not equipped with the device are not able to keep up in such hot weather. Systems with the device achieve faster cool-down times and lower temperatures, therefore greater comfort levels. Government, military, public and private sectors of the economy will benefit from the use of this invention.
In high heat and humidity areas, such as along the U.S. Gulf Coast, where the summer is long and intense, air conditioners and refrigeration systems frequently cannot keep up with the demands placed upon them. Hot and humid climates subject an air conditioning or refrigeration system to greater heat loads than such systems found in cooler climates. For example, in cities along the Gulf of Mexico, an air conditioner must perform efficiently during six to eight months of hot weather during the year, often having many weeks when daily temperatures range between 90-103xc2x0 F.
Aftermarket enhancements are frequently needed to overcome built-in engineering deficiencies in factory systems. Manufacturers frequently do not produce systems, which are able to function well in hot climates, and many condensers do a poor job of giving up heat because of their inefficient designs and/or poor airflow through them. For example, the lack of airflow produced by fan clutches is a common reason for the inability of condensers to give up heat. Automobile engine fan clutches have notoriously poor engineering, and frequently won""t do an adequate job in high heat load climates. Technicians are often not taught how to properly test fan clutches, thus high head pressures are ignored and continue to reduce condenser efficiency affecting the entire system like a low grade fever, e.g., the compressor works harder and fails prematurely, the engine consumes more fuel, etc. The problem of condenser fan inefficiency is not as prevalent on commercial heating, ventilation and air conditioning (HVAC) systems because they are electrically driven, and are generally not of the slip type viscous engagement design. However, by lowering the saturated heat levels and higher head pressures, the present invention can provide lower fuel costs, lower temperatures, and faster cool-down on both mobile and stationary applications. The second issue of condenser efficiencies can be summarized by stating that the new generation of high efficiency condensers has become a necessity because of the more problematic R134a, which is now the refrigerant of choice by manufacturers.
To obtain a better understanding of why systems not equipped with the present invention do not perform up to their potential, two basic principles of the a/c-refrigeration system heat transfer process must be understood. Technically, air conditioning and refrigeration systems do not make cold air; they remove heat (evaporation cycle); then they give up heat (condensation cycle). After the evaporator picks up heat from the air inside the compartment to be cooled, the condenser has to return that heat (usually back to the atmosphere). If the condenser cannot effectively give up the heat absorbed by the evaporator, then the heat soaked liquid leaving the condenser reenters the evaporator unable to accept as much new heat as it should. The result is occupant discomfort, longer cool-down time and unacceptably high head pressures. Vehicle a/c systems are not able to remove enough heat from the passenger compartment to provide a sufficient comfort level when driving on short trips, or only provide a marginal level of cooling on longer trips for passengers in the rear of the vehicle. In the case of homes and commercial buildings, the same inefficiencies, high pressures, and creature discomfort problems occur. Systems not equipped with the invention exhibit greater high side pressures, which cause the compressor to work harder, reducing its life and increasing fuel consumption and operating costs. Condensers are unable to fully condense that overheated liquid before feeding it to the evaporator. Condenser manufacturers now have the burden of providing designs that are 25-40% more efficient than were required with the more efficient, but almost depleted supply of, R12 refrigerant. Condensers must now be designed to compensate for the inefficiency of the new R134a, and other refrigerants having similar characteristics such as higher critical temperatures and working pressures than R12. Regardless of which refrigerant is used, because evaporators are rendered less efficient by being fed heat-saturated liquid, they lack the ability to effectively absorb new heat. Systems equipped with a refrigerated intercooler provide better heat dissipation during the condensation cycle so that better heat acceptance can be achieved during the evaporation cycle.
The term critical temperature is defined as the temperature above which a gas cannot be liquefied, regardless of how much pressure is applied. This is important because refrigerants resist staying liquid when acted upon by heat. Heat is absorbed into an a/c or refrigeration system, not just from air passing across the evaporator, but also from the very hot under-hood engine temperatures. One such example is the problem of xe2x80x9cheat soakxe2x80x9d from the engine radiator to the a/c condenser due to their near proximity. For the expansion valve to do its job effectively, it needs to meter a fully condensed, non heat-saturated liquid refrigerant into the evaporator.
The solution to the problem of excessive saturated heat within the condenser and its downstream liquid line is to reduce that heat load well below the critical temperature of prevailing refrigerants used in modern air conditioning and refrigeration systems. This is achieved by precooling the liquid going to the evaporator, making all refrigerant in the closed system cooler.
The theory of why better performance is achieved when using this invention is confirmed by field testing. After observing improved cool-down time, and lower duct temperatures on systems equipped with the apparatus, it has been concluded that the heat absorption capacity of evaporators, and the heat rejection capacity of condensers are underutilized. By intercooling the liquid stream between condenser outlet and evaporator inlet, the following results occurred: (a) Maximum cooling was achieved prior to reaching the factory specified charge level, and adding more refrigerant resulted in an overcharge with diminished cooling. (b) Faster cool-down time occurred. (c) Lower head pressures resulted because the cooler and lesser volume of refrigerant being compressed by the compressor resulted in more efficient condensation, creating greater expansion space in the condenser. Comparative readings were taken before and after the apparatus was installed. The field observations confirm that when equipped with the apparatus, almost any original equipment manufactured (OEM) condenser and evaporator combination exhibited these improved performance characteristics compared to those previously attained when not equipped with the apparatus.
As noted above, insufficient airflow across the condenser because of poorly designed mechanical fan clutches on automobile a/c systems is one of the most overlooked service items by technicians. The only way to properly check a fan clutch is to do a performance test on the a/c system. A cold engine should be run at fast idle (1500-2000 rpm) with the evaporator fan on high speed and passenger doors open, while watching the high side pressure gage. If the fan is working correctly, even on a 95-100xc2x0 F. day, the reading should correct back to 250-275 psi (without the intercooler) prior to exceeding 350 psi and before the elapse of 30 seconds. On systems with defective fans, but without the intercooler, the system will exhibit high side pressure readings of 300-430 psi, yet the engine temperatures will be normal. Thus, normal engine temperatures do not indicate that the fan clutch is working. The point is that an a/c condenser requires much more airflow than an engine radiator. Manufacturers have yet to adequately address this problem with a meaningful solution. No air conditioning system can function properly under those conditions. It is understood, however, that the present invention is not to be used to mask latent system defects (defective condenser fan, etc.), but that the system would be restored to good operating condition prior to installing the apparatus.
After installing the intercooler, the above head pressures dropped to readings of 225-250 psi, under the same operating conditions that previously produced 300-425 psi (without the intercooler). Outlet air temperatures were colder and the cool-down time was shorter. While field tests show that performance results will vary from vehicle to vehicle, based on system design and repair status, all achieved improved cool-down time using the present invention.
A question may arise as to xe2x80x9cwhy wouldn""t introducing a greater heat load back into the condenser result in worsening system inefficiency?xe2x80x9d One reason is that a system equipped with the preferred device requires less refrigerant than before, thus making it easier for complete vaporization to occur within the evaporator because of the lower saturated heat in the liquid stream as it enters the expansion valve. Less heat-saturated liquid entering the evaporator means that as vaporization occurs, more heat can be absorbed without exceeding an efficient superheat level, unlike systems not equipped with the device. A lower superheat is achieved during vaporization (evaporation cycle) because the total system has first become more efficient at processing refrigerant during liquefication (condensation cycle.) The phase changes from liquid to gas, then from gas back to liquid are now complimentary instead of struggling against each other. To accomplish this, however, the condenser must be more efficient. Most systems contain more refrigerant than is required to achieve best efficiencies, but without refrigerated intercooling their charge levels cannot be lowered and they cannot perform up to their potential.
To further understand why condenser efficiency is one of the keys to total system efficiency, the following field observations and conclusions are also submitted. The greatest amount of saturated heat is found in liquid within the lower third of the condenser. Condensers have a limited amount of expansion space. When liquid backs up in the condenser above approximately one third of its vertical height, the result is inadequate vaporization within the evaporator due to the saturated heat still in the refrigerant. This unbalanced ratio between the evaporation phase and condensation phase also means inefficient refrigerant circulation, system-wide.
Refrigerant is supposed to be changed from a hot gas to a cooler liquid within the condenser as ambient air passes through its exterior fins, releasing heat back to atmosphere. That is not done very efficiently in many applications. After installing a refrigerated intercooler, the condenser is no longer totally responsible for condensing hot gas back to a liquid. Using the invention""s interface allows heat transfer from the hot liquid section to the cold gas section of the interaction device. The cooled liquid is able to release additional heat to the cold return gas, which results in beneficial lower head pressures, duct temperatures, and faster cool-down time. Again, the system is no longer totally dependant on the condenser for complete condensation.
In summary, when prior art uses single components that are individually similar to the three base components of the invention, they are less efficient because of the differences in the way that they interface with each other. Prior art systems, especially receivers, are generally non-serviceable without system disassembly, due to their physical construction. In cases when they have serviceable features, or have the same intent and purpose, they differ from the present invention in other ways that negate the benefit of such similarities. The advantages of the invention shall become apparent in the disclosure and claims hereof.
2. Related Art
Prior art includes that described by Davis (U.S. Pat. No. 4,341,092). As shown in FIG. 2, Davis teaches a liquid modulator receiver/dryer having an interfacing of the hot liquid refrigerant from the condenser with the cold gas refrigerant from the evaporator to lower the latent heat in the liquid refrigerant. However, the present invention is able to perform this function more efficiently without the use of a receiver or drier, due to the improved accumulator and oil return design.
Cool refrigerant coming from the evaporator contains inherent amounts of oil, primarily from compressor pump lubrication. The oil/refrigerant mixture must not return in liquid form to the compressor, else it will damage the gas compressor. To vaporize this mixture in the return line to the compressor from the accumulator, Davis depends solely on the phase change from liquid to gas of this mixture in the accumulator, aided by the heat transfer from the receiver canister inside the accumulator. System oil/refrigerant is screen filtered within the receiver at the bottom of the pick-up tube, which leads to the evaporator. Servicing the screen requires complete disassembly of the receiver.
Davis"" oil/refrigerant return orifice is fixed and not interchangeable. Thus, there is no selective orifice replacement or sizing to accommodate the variety of manufacturer""s equipment btu-ratings that affect oil/refrigerant return flow rate requirements. Because of the configuration of the receiver, Davis requires the use of a drier within or associated with the interaction device (gas and liquid chambers interface), to reduce the potential for acid and moisture encroachment systemwide. Unfortunately, desiccant deteriorization and resultant system contamination has long been a worse problem. With the preferred device, system acids and moisture removal is accomplished by periodic flushing and service, thus eliminating the need for desiccant as an embodiment of its function.
Other prior art falls short of addressing the need to use a colder than ambient medium to subcool condenser liquid. Yamanaka et al (U.S. Pat. No. Re. 36,408) teaches a method of recirculating refrigerant with the condenser to create a boundary between the liquid phase and the gas phase, but does not use the cold return gas (from the evaporator) in the method.
It would therefore be useful improvement of the prior art for a mobile air conditioning system to not have the limitations of the prior art, including those described above.
The intercooler consists of three xe2x80x9cbasexe2x80x9d components which can be configured in various ways to provide the results described above in the stated invention objects. These cooperative components are:
the cold gas chamber component,
the hot liquid chamber component inside the cold gas chamber component, and
the oil return line assembly component outside the cold gas chamber component, consisting of a cleanable screen and a replaceable metering orifice within a housing. The oil return line assembly and its internal oil movement extend in the direction of the gas flow.
The inventive intercooler can be described as a xe2x80x9crefrigerated intercoolerxe2x80x9d, xe2x80x9cheat exchanger,xe2x80x9d xe2x80x9ccondenser intercooler,xe2x80x9d or xe2x80x9crefrigerant liquefierxe2x80x9d which uses the cold refrigerant return gas to subcool hot liquid refrigerant after it leaves the condenser, preparing it for delivery to the expansion valve. The invention contains two sections of the heat exchange device (gas and liquid sections). They are separate pressure vessels that interact with each other by their physical proximity to one another. The result of their interaction is that a coalescing interface is created which provides efficient heat transfer between them. These co-dependent heat exchange devices may be designed of any convenient shape and/or size to achieve the best transfer of heat from the higher pressure liquid to the adjacent lower pressure cold return gas. A cold return gas accumulator may be used to house the hot higher pressure liquid section, while the hot higher pressure liquid section may be used to house the cold return gas accumulator. They must coalesce to effect heat transfer without commingling, mixing or to otherwise compromise the separateness of the pressure vessels that confine the gas and liquid paths.
The preceding paragraph describes the heat transfer from the liquid section to the gas section. It must also be pointed out that the heat absorbed into the compressor return gas stream also is a function of the invention, i.e., it carries the heat for disposition at the condenser. This results in two phenomenons. First, the condenser""s heat rejection capacity is more filly utilized, resulting in an improved phase change. Second, the evaporative phase change improves because the evaporator is now fed a cooler, better condensed liquid. Third, the refrigerant charge level is now lower while the total system efficiency is higher.
Accordingly, this invention provides, inter alia, a new and improved method of and device for intercooling air conditioning refrigerant according to the following objectives.
An object of the invention is to shorten the cool-down time between air conditioning system start-up and maximum cooling.
A further object of the invention is to lower the maximum outlet air temperature to achieve improved comfort.
A still further object of the invention is to lessen the negative impact on consumer comfort because of the EPA-mandated phaseout of R12, which has resulted in less cooling after retrofitting or conversion of a/c systems from their original refrigerant to an alternate refrigerant.
An object of the invention is to provide lower fuel costs as a result of lowering the power consumption required to operate the system.
A further object of the invention is to reduce the refrigerant charge level required to service the system, while achieving the above objectives. Benefits would be the reduced refrigerant costs to the manufacturer and/or consumer, and less ozone depletion potential to the atmosphere.
A still further object of the invention is to provide a method of gas flow through the accumulator so that a better interface between the gas and liquid sections would enhance heat absorption by the gas, and heat removal from the liquid.
An object of the invention is not only to make the gas and liquid interface more efficient but also to make it less subject to desiccant contamination by eliminating the presence of a drier as a feature of its design.
A further object of the invention is to eliminate the need for a receiver on air conditioning systems. Until about 1976, receivers were a requirement on virtually all OEM and aftermarket systems to insure that liquid was fed to the expansion valve, even if such liquid was saturated with heat. Starting in 1977 when clutch cycling orifice tube systems (CCOT) became popular among vehicle manufacturers, accumulators replaced receivers, but the same heat-saturated liquid problem remained. Today, some prior art aftermarket products require the use of both an accumulator plus a receiver and drier, such as the Liquid Modulator (Davis).
A still further object of the invention is to intercool liquid refrigerant leaving the condenser using the evaporative return gas to substantially reduce the saturated heat in the liquid; thus, upon such prepared liquid being metered into the evaporator by the expansion valve, the resultant vaporized gas is able to absorb new heat more efficiently.
An object of the invention is to provide a means to selectively install, clean and/or replace an oil metering orifice, in order to satisfy the oil return requirements based on the manufacturer""s btu rating and other operating criteria.
A further object of the invention is to provide an external means to clean the oil return screen of various system residues and debris that may build up and block the flow of lubrication necessary to the longevity of the compressor.
A still further object of the invention is to provide a means to flush the interior surfaces of the accumulator, liquid chamber, and screen, to allow the entire intercooler to be flushed, reassembled, then reinstalled, rather than to be replaced.
An object of the invention is to refrigerate the condenser""s downstream hot liquid in order to provide a supplement for the lower volume and higher temperature of ambient airflow across the condenser. The low volume air is caused by (a) insufficient ram air due to slow vehicle speed or when idling in traffic, (b) air restrictions caused by objects in front of the condenser such as the grill, or transmission oil cooler, etc., (c) an inefficient mechanical or electrical fan.
A further object of the invention is to improve the efficiency of internally and externally equalized type expansion valves by reducing the temperature of the incoming liquid stream. When the temperature of the incoming liquid stream is too high, the pilot valve""s metering action is adversely affected. The result is that the wrong amount of refrigerant is fed into the evaporator, and the evaporator is unable to digest the refrigerant as evidenced by an incomplete phase change. The effectiveness of a fixed orifice tube type expansion valve would likewise be enhanced.
A still further object of the invention is to address a basic problem that now plagues prevailing mobile and stationary HVAC systems, that of inefficient phase change during condensation which defeats phase change in the evaporator. Part of the problem is based on the chemistry differences in refrigerants. Refrigerants with a lower critical temperature are less efficient because they resist changing back to a gas more than those with a higher critical temperature. In the case of R134a, its comparatively low critical temperature results in the need for a more efficient condenser than R12, just to achieve the equivalent heat rejection capacity of the older R12.
A still further objective and advantage of the invention is that the external oil return filtering and metering features, along with the absence of an internal drier, means that the invention""s internal parts are also totally cleanable, unlike prevailing accumulators, receivers and other such components which must be discarded when their desiccant is adsorbed with moisture, acid and/or system contaminations when they have formed a residue on interior surfaces.
A further object of the present invention is to re-vaporize refrigerant oil that has dropped out of solution with its carrier (liquid refrigerant), as well as liquid refrigerant itself, during the evaporative phase change. Liquid refrigerant enters the expansion valve and immediately undergoes a simultaneous rapid expansion and pressure drop. The abrupt transition causes some of the oil to temporarily drop out of solution because it cannot vaporize as readily as the refrigerant. This phenomenon indicates that it is more difficult for oil to stay in solution with refrigerant during the evaporative phase because of the scrubbing effect, which mechanically separates some of the oil as it passes through the expansion valve orifice. After falling out of solution, the oil must go back into solution with the evaporative refrigerant gas quickly in order to reach the correct oil-to-refrigerant blend ratio, otherwise it will arrive at the compressor without the proper lubricity. Total dependence on the evaporator for re-vaporization can result in oil starvation of the compressor, especially when chemical imbalances and/or contaminants cause oil dilution and the subsequent reduction of viscosity. The invention improves the efficiency of such oil vaporization by providing a secondary heat exchange interface as the final stage in the conversion of liquid into gas. It has been previously stated that whatever liquid is not vaporized is collected as a puddle and returned to the compressor through the accumulator outlet. The invention also helps maintain healthy oil chemistry by (a) reducing overall system stress as the result of achieving lower head pressures, and (b) providing better phase change efficiencies based on lower system charge level.
The problem for oil manufacturers has been to produce oils that have the following qualities:
(a) During the Evaporation Phase Change: The ability to convert from a hot oily liquid into a cold oily vapor rapidly enough to prevent unvaporized liquid oil ingestion (xe2x80x9csluggingxe2x80x9d) damage to the compressor and/or to arrive at the compressor as a gas with a diluted oil-to-refrigerant ratio.
(b) During the Condensation Phase Change: The ability to rapidly convert from a hot, oily gas into a hot, oily, liquid.
(c) Dilution Resistance: The ability for oil to maintain its viscosity, lubricity, and the correct oil-to-refrigerant blend ratio during both of the above phase changes.
(d) CST Stability. Critical Solubility Temperature (CST) is the temperature at which the viscosity of oil will change enough to make it drop out of solution with the refrigerant. Synthetic oils such as PAG oil (polylkylene glycol) have superior lubricity qualities, but their viscosity is affected greatly by temperature. So, it is important that PAGS would be designed for use within the minimum and maximum temperature boundaries of a/c systems. The CST of oils varies by type and manufacturer, so the rate of oil vaporization and liquefication will also vary.
Furthermore, even if good oil solubility issues are addressed, system contamination factors which result in viscosity dilution and solubility reduction are additional reasons why compressor damage can occur in systems not equipped with the present invention. Attention is again drawn to the hot/cold interface by and between the oily vapor and the hot liquid container within the accumulator""s interior region. The oily vapor and refrigerant droplets from the evaporator (drawn by the compressor suction pressure) are carried by the refrigerant gas into the accumulator inlet. The present invention, located downstream of the evaporator, accelerates and finalizes the vaporization phase change for any remaining liquids, and if oil solubility is diminished, the present invention helps to alleviate the problem.
A further object of the invention is that it serves as a compressor high pressure spike buffer. The scroll compressor has become popular among automobile manufacturers because of its high efficiency, smooth-running qualities. But, it has a tendency to cause more severe transient pressure spikes during rapid acceleration than piston compressors. The byproduct of its greater efficiency is that during 5 to 15-second, high rpm acceleration bursts, it is able to pump a greater mass of refrigerant into the condenser than the condenser can process. An advantage of systems equipped with the invention is that their improved condensation phase change efficiencies also provide greater expansion space because the liquid level within the condenser is lower than systems not so equipped. Thus the condenser can accept more new refrigerant into the top portion and act as an accumulator or shock absorber, reducing the magnitude of the high pressure spikes much better than systems not equipped with the device. Other strategies for handling these spikes include, but are not limited to installing: (a) a variable orifice tube which senses the spike and acts as a relief valve, dumping liquid refrigerant into the evaporator, (b) a hot gas bypass valve which senses the spike and dumps hot compressor discharge gas into the cold evaporative return line, (c) a variable-output compressor, able to sense and make sudden pressure reductions, and (d) methods of compressor clutch disengagement such as a wide-open throttle cutout relay which causes the compressor to quit pumping, thus it quits building up pressure. These alternate strategies all essentially prevent the compressor from pumping, whereas the present invention does not disrupt the volumetric advantages of any compressor, but makes provision for its extra needs.
These objectives are addressed by the structure and use of the inventive process. Other objectives of the invention will become apparent from time to time throughout the specification hereinafter disclosed.


Antireflective compositions characterized by the presence of an SiO-containing polymer having chromophore moieties and transparent moieties are useful antireflective hardmask compositions in lithographic processes. These compositions provide outstanding optical, mechanical and etch selectivity properties while being applicable using spin-on application techniques. The compositions of the invention are advantageously useful with shorter wavelength lithographic processes and/or have minimal residual acid content.

In the microelectronics industry as well as in other industries involving construction of microscopic structures (e.g. micromachines, magnetoresistive heads, etc.), there is a continued desire to reduce the size of structural features. In the microelectronics industry, the desire is to reduce the size of microelectronic devices and/or to provide greater amount of circuitry for a given chip size.
Effective lithographic techniques are essential to achieving reduction of feature sizes. Lithography impacts the manufacture of microscopic structures not only in terms of directly imaging patterns on the desired substrate, but also in terms of making masks typically used in such imaging. Typical lithographic processes involve formation of a patterned resist layer by patternwise exposing the radiation-sensitive resist to an imaging radiation. The image is subsequently developed by contacting the exposed resist layer with a material (typically an aqueous alkaline developer) to selectively remove portions of the resist layer to reveal the desired pattern. The pattern is subsequently transferred to an underlying material by etching the material in openings of the patterned resist layer. After the transfer is complete, the remaining resist layer is then removed.
For some lithographic imaging processes, the resist used does not provide sufficient resistance to subsequent etching steps to enable effective transfer of the desired pattern to a layer underlying the resist. In many instances (e.g., where an ultrathin resist layer is desired, where the underlying material to be etched is thick, where a substantial etching depth is required, and/or where it is desired to use certain etchants for a given underlying material), a so-called hardmask layer is used intermediate between the resist layer and the underlying material to be patterned by transfer from the patterned resist. The hardmask layer receives the pattern from the patterned resist layer and should be able withstand the etching processes needed to transfer the pattern to the underlying material.
While many hardmask materials exist in the prior art, there is a continued desire for improved hardmask compositions. Many of the prior art materials are difficult to apply to the substrate, e.g., they may require use of chemical or physical vapor deposition, special solvents, and/or high temperature baking. It would be desirable to have hardmask compositions which could be applied by spin-coating techniques without need for a high temperature bake. Additionally, it is desirable to have hardmask compositions which can be easily etched selective to the overlying photoresist while being resistant to the etch process needed to pattern the underlying layer, especially where the underlying layer is a metal layer. It is also desired to provide adequate shelf-life and to avoid adverse interaction with the imaging resist layer (e.g., by acid contamination from the hardmask). Additionally, it is desired to have hardmask compositions which possess the desired optical characteristics relative to shorter wavelength (e.g.,  less than 200 nm) imaging radiation.
The invention encompasses novel antireflective hardmask compositions which are useful in lithographic processes. These compositions provide outstanding optical, mechanical and etch selectivity properties while being applicable using spin-on application techniques. The compositions also have good shelf-life and minimal or no acid contaminant content. The antireflective hardmask compositions are characterized by the presence of an SiO-containing polymer having chromophore moieties and transparent moieties. The invention also encompasses methods of using the hardmask compositions of the invention to pattern underlying material layers on a substrate. The invention also encompasses lithographic structures such as a patterned combination of resist layer and hardmask layer.
In one aspect, the invention encompasses a composition suitable for formation of a spin-on antireflective hardmask layer, the composition comprising:
(a) an SiO-containing polymer having chromophore moieties and transparent moieties,
(b) a crosslinking component, and
(c) an acid generator.
The SiO moieties are preferably selected from the group consisting of siloxane moieties and silsesquioxane moieties. The SiO moieties are preferably in a backbone portion of the polymer. The SiO-containing polymer also preferably contains a plurality of reactive sites distributed along the polymer for reaction with the crosslinking component. The acid generator is preferably a thermally activated acid generator. The transparent moieties are preferably bulky (C2 or higher) or fluorine-containing moieties which are substantially transparent to the desired imaging radiation.
In another aspect, the invention encompasses method of forming a patterned material feature on a substrate, the method comprising:
(a) providing a material layer on a substrate,
(b) forming an antireflective hardmask layer of the invention over the material layer,
(c) forming a radiation-sensitive imaging layer over the antireflective layer,
(d) patternwise exposing the imaging layer to radiation thereby creating a pattern of radiation-exposed regions in the imaging layer,
(e) selectively removing portions of the imaging layer and the antireflective layer to expose portions of the material layer, and
(f) etching the exposed portions of the material layer, thereby forming the patterned material feature.
The material to be patterned is preferably a conductive, semiconductive, magnetic or insulative material, more preferably a metal. The SiO moieties are preferably in a backbone portion of the polymer. The SiO-containing polymer also preferably contains a plurality of reactive sites distributed along the polymer for reaction with the crosslinking component.
These and other aspects of the invention are discussed in further detail below.
The invention encompasses novel antireflective hardmask compositions which are useful in lithographic processes. These antireflective hardmask compositions are characterized by the presence of an SiO-containing polymer having chromophore moieties and transparent moieties. The invention also encompasses methods of using the antireflective hardmask compositions of the invention to pattern underlying material layers on a substrate. The invention also encompasses lithographic structures such as a patterned combination of resist layer and hardmask layer.
The antireflective hardmask compositions of the invention generally comprise:
(a) an SiO-containing polymer having chromophore moieties and transparent moieties,
(b) a crosslinking component, and
(c) an acid generator.
The SiO-containing polymer preferably contains SiO moieties in its backbone. The polymer is preferably an organosiloxane, more preferably organosilsesquioxane. The polymer should have solution and film-forming characteristics conducive to forming a layer by conventional spin-coating.
In general, the polymer preferably contains one or more monomers having structures selected from (I)-(III) below:
where x is from about 1 to about 1.5. R1 comprises a chromophore moiety; R2 comprises a transparent moiety; R3 comprises a reactive site for reaction with the crosslinking component. For linear organosiloxane polymers, x would equal about 1. For silsesquioxane polymers, x would equal about 1.5. In some instances, multiple functional moieties may be present on the same monomer (e.g., a reactive group and a chromophore). Generally, silsesquioxane polymers are preferred on the basis of superior etch resistance. If the ordinary organosiloxane polymers are used, then preferably, the degree of crosslinking is increased compared to formulations based on silsesquioxanes.
The chromophore-containing groups R1 may contain any suitable chromophore which (i) can be grafted onto the SiO-containing polymer (ii) has suitable radiation absorption characteristics, and (iii) does not adversely affect the performance of the layer or any overlying photoresist layers. Preferred chromophore moieties include phenyl, chrysenes, pyrenes, fluoranthrenes, anthrones, benzophenones, thioxanthones, and anthracenes. Anthracene derivatives, such as those described in U.S. Pat. No. 4,371,605 may also be used; the disclosure of this patent is incorporated herein by reference. 9-anthracene methanol is a preferred chromophore. The chromophore moiety preferably does not contain nitrogen, except for possibly deactivated amino nitrogen such as in phenol thiazine. For 193 nm radiation, non-aromatic compounds containing unsaturated carbon bonds (e.g., carbonxe2x80x94carbon double bonds) are also suitable chromophores. For 157 nm radiation, compounds containing saturated carbonxe2x80x94carbon bonds can act as chromophores.
The chromophore moieties may be chemically attached to the SiO containing polymer by acid-catalyzed O-alkylation or C-alkylation such as by Friedel-Crafts alkylation. Alternatively, the chromophore moiety may be attached by an esterification mechanism. A preferred acid for Friedel-Crafts catalysis is HCl. Preferably, about 15 to 40% of the monomers contain chromophore moieties. In some instances, it may be possible to bond the chromophore to the monomer before formation of the SiO-containing polymer, however this is generally not preferred. The site for attachment of the chromophore is preferably an aromatic group such as a hydroxybenzyl or hydroxymethylbenzyl group. Alternatively, the chromophore may be attached by reaction with other moieties such as cyclohexanol or other alcohols. The reaction to attach the chromophore is preferably an esterification of the alcoholic OH group.
R2 transparent moieties may vary depending on the wavelength or character of the imaging radiation. In the case of 193 nm imaging radiation, the transparent moieties are preferably a bulky (C2 or higher) organic moieties substantially free of unsaturated carbonxe2x80x94carbon bonds. A preferred transparent moiety for 193 nm applications in an alcohol derived from an epoxy-functionalized silsesquioxane monomer. In the case of 157 nm imaging radiation, the transparent moieties are preferably fluorine-containing moieties such as a trifluoromethyl group or perfluoroalkyl. The amount of transparent moieties is preferably balanced with the amount of chromophore to provide a desired combination of energy absorption and antireflection.
R3 comprises a reactive site for reaction with the crosslinking component. Preferred reactive moieties contained in R2 are alcohols, more preferably aromatic alcohols (e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) or cycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclic alcohols such as fluorocarbon alcohols, aliphatic alcohols, amino groups, vinyl ethers, and epoxides may be used.
Examples of SiO containing polymers include:
poly(3-propanoloxypropyl)silsesquioxane, copolymer of 3-propanoloxypropylsilsesquioxane and phenylsilsesquioxane, blend of poly(hydroxybenzyl)silsesquioxane and poly(1-hydroxy-1-trifluoromethylethyl) silsesquioxane, copolymer of 1-hydroxy-1-trifluoromethylethylsilsesquioxane and p-Hydroxymethylbenzylsilsesquioxane.
The SiO-containing polymers of the invention preferably have a weight average molecular weight, before reaction with the crosslinking component, of at least about 1000, more preferably a weight average molecular weight of about 1000-10000.
The crosslinking component is preferably a crosslinker that can be reacted with the SiO-containing polymer in a manner which is catalyzed by generated acid and/or by heating. Generally, the crosslinking component used in the antireflective hardmask compositions of the invention may be any suitable crosslinking agent known in the negative photoresist art which is otherwise compatible with the other selected components of the composition. The crosslinking agents preferably act to crosslink the polymer component in the presence of a generated acid. Preferred crosslinking agents are glycoluril compounds such as tetramethoxymethyl glycoluril, methylpropyltetramethoxymethyl glycoluril, and methylphenyltetramethoxymethyl glycoluril, available under the POWDERLINK trademark from Cytec Industries. Other possible crosslinking agents include: 2,6-bis(hydroxymethyl)-p-cresol compounds such as those found in Japanese Laid-Open Patent Application (Kokai) No. 1-293339, etherified amino resins, for example methylated or butylated melamine resins (N-methoxymethyl- or N-butoxymethyl-melamine respectively), and methylated/butylated glycolurils, for example as can be found in Canadian Patent No. 1 204 547. Other crosslinking agents such as bis-epoxies or bis-phenols (e.g., bisphenol-A) may also be used. Combinations of crosslinking agents may be used.
The acid generator is preferably an acid generator compound is employed that liberates acid upon thermal treatment. A variety of known thermal acid generators are suitably employed such as e.g. 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate and other alkyl esters of organic sulfonic acids. Compounds that generate a sulfonic acid upon activation are generally suitable. Other suitable thermally activated acid generators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236; the disclosures of these two patents are incorporated herein by reference. If desired, a radiation-sensitive acid generator may be employed as an alternative to a thermally activated acid generator or in combination with a thermally activated acid generator. Examples of suitable radiation-sensitive acid generators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236. Other radiation-sensitive acid generators known in the resist art may also be used as long as they are compatible with the other components of the antireflective composition. Where a radiation-sensitive acid generator is used, the cure (crosslinking) temperature of the composition may be reduced by application of appropriate radiation to induce acid generation which in turn catalyzes the crosslinking reaction. Even if a radiation-sensitive acid generator is used, it is preferred to thermally treat the composition to accelerate the crosslinking process (e.g., for wafers in a production line).
The antireflective hardmask compositions of the invention preferably contain (on a solids basis) (i) about 50-98 wt. % of the SiO-containing polymer, more preferably about 70-80 wt. %, (ii) about 1-50 wt. % of crosslinking component, more preferably about 3-25%, and (iii) about 1-20 wt. % acid generator, more preferably about 1-15 wt. %.
The antireflective hardmask compositions of the invention may be used in combination with any desired resist material in the forming of a lithographic structure. Preferably, the resist is imageable with shorter wavelength ultraviolet radiation (e.g.  less than 200 nm wavelength) or with electron beam radiation. Examples of suitable resist materials are described in U.S. Pat. No. 6,037,097, the disclosure of which is incorporated herein by reference.
The antireflective hardmask compositions of the invention will typically contain a solvent prior to their application to the desired substrate. The solvent may be any solvent conventionally used with resists which otherwise does not have any excessively adverse impact on the performance of the antireflective composition. Preferred solvents are propylene glycol monomethyl ether acetate, cyclohexanone, and ethyl lactate. The amount of solvent in the composition for application to a substrate is preferably sufficient to achieve a solids content of about 8-20 wt. %. Higher solids content formulations will generally yield thicker coating layers. The compositions of the invention may further contain minor amounts of auxiliary components (e.g., base additives, etc.) as may be known in the art.
The antireflective hardmask compositions of the invention can be prepared by combining the polymer, crosslinking component and acid generator, and any other desired ingredients using conventional methods. The compositions of the invention advantageously may be formed into antireflective hardmask layers on a substrate by spin-coating followed by baking to achieve crosslinking and solvent removal. The baking is preferably conducted at about 250xc2x0 C. or less, more preferably about 150xc2x0-220xc2x0 C. The baking time may be varied depending on the layer thickness and bake temperature.
The thickness of the antireflective hardmask composition of the invention may be varied depending on the desired function. For typical applications, the thickness of the composition is preferably about 0.02-5.0 xcexcm, more preferably about 0.1-5.0 xcexcm. If desired, the compositions of the invention may also be used as dielectric materials in a similar manner to conventional spin-on glass materials. The compositions of the invention advantageously resist lateral etch such that they may act as hard masks even at thin film thickness traditionally associated with organic antireflective layers.
The hardmask compositions of the invention are especially useful for lithographic processes used in the manufacture of integrated circuits on semiconductor substrates. The compositions are especially useful for lithographic processes using 193 nm, 157 nm, EUV, x-ray, e-beam or other imaging radiation.
Semiconductor lithographic applications generally involve transfer of a pattern to a layer of material on the semiconductor substrate. The material layer of the semiconductor substrate may be a metal conductor layer, a ceramic insulator layer, a semiconductor layer or other material depending on the stage of the manufacture process and the desired material set for the end product. The composition of the invention is preferably applied directly over the material layer to be patterned, preferably by spin-coating. The composition is then baked to remove solvent and cure (crosslink) the composition. A radiation-sensitive resist layer can then be applied (directly or indirectly) over the cured antireflective composition of the invention.
Typically, the solvent-containing resist composition is applied using spin coating or other technique. The substrate with the resist coating is then preferably heated (pre-exposure baked) to remove the solvent and improve the coherence of the resist layer. The thickness of the applied layer is preferably as thin as possible with the provisos that the thickness is preferably substantially uniform and that the resist layer be sufficient to withstand subsequent processing (typically reactive ion etching) to transfer the lithographic pattern to the underlying substrate material layer. The pre-exposure bake step is preferably conducted for about 10 seconds to 15 minutes, more preferably about 15 seconds to one minute. The pre-exposure bake temperature may vary depending on the glass transition temperature of the photoresist.
After solvent removal, the resist layer is then patternwise-exposed to the desired radiation (e.g. 193 nm ultraviolet radiation). Where scanning particle beams such as electron beam are used, patternwise exposure may be achieved by scanning the beam across the substrate and selectively applying the beam in the desired pattern. More typically, where wavelike radiation forms such as 193 nm ultraviolet radiation, the patternwise exposure is conducted through a mask which is placed over the resist layer. For 193 nm UV radiation, the total exposure energy is preferably about 100 millijoules/cm2 or less, more preferably about 50 millijoules/cm2 or less (e.g. 15-30 millijoules/cm2).
After the desired patternwise exposure, the resist layer is typically baked to further complete the acid-catalyzed reaction and to enhance the contrast of the exposed pattern. The post-exposure bake is preferably conducted at about 60-175xc2x0 C., more preferably about 90-160xc2x0 C. The post-exposure bake is preferably conducted for about 30 seconds to 5 minutes.
After post-exposure bake, the resist structure with the desired pattern is obtained (developed) by contacting the resist layer with an alkaline solution which selectively dissolves the areas of the resist which were exposed to radiation. Preferred alkaline solutions (developers) are aqueous solutions of tetramethyl ammonium hydroxide. The resulting lithographic structure on the substrate is then typically dried to remove any remaining developer solvent.
The pattern from the resist structure may then be transferred to the exposed portions of the layer of antireflective material of the invention by etching with CF4 or other suitable etchant using techniques known in the art.
After the opening of the layer of antireflective hardmask of the invention, the underlying material layer to be patterned may then be etched using an etchant appropriate to the material layer composition. Where the material layer is a metal (e.g., Cr) a combination of Cl2/O2 may be used as a dry etchant.
Once the desired pattern transfer has taken place, any remaining resist may be removed using conventional stripping techniques. If the composition of the invention is being used strictly as a hardmask, the composition of the invention may be removed by contacting with a CF4/O2 plasma.
Thus, the compositions of the invention and resulting lithographic structures can be used to create patterned material layer structures such as metal wiring lines, holes for contacts or vias, insulation sections (e.g., damascene trenches or shallow trench isolation), trenches for capacitor structures, etc. as might be used in the design of integrated circuit devices. The compositions are especially useful in the context of creating patterned layers of oxides, nitrides or polysilicon.
Examples of general lithographic processes where the composition of the invention may be useful are disclosed in U.S. Pat. Nos. 4,855,017; 5,362,663; 5,429,710; 5,562,801; 5,618,751; 5,744,376; 5,801,094; 5,821,469 and 5,948,570, the disclosures of which patents are incorporated herein by reference. Other examples of pattern transfer processes are described in Chapters 12 and 13 of xe2x80x9cSemiconductor Lithography, Principles, Practices, and Materialsxe2x80x9d by Wayne Moreau, Plenum Press, (1988), the disclosure of which is incorporated herein by reference. It should be understood that the invention is not limited to any specific lithographic technique or device structure.

Antireflective SiO-containing compositions for hardmask layer

International Business Machines Corporation


A single entity product is provided for administration to persons being treated for nutritional deficiencies associated with addiction to alcohol, wherein the product is an extended-release multivitamin with minerals and trace elements in beneficial dose ranges and specifically contains thiamine and folic acid in the desired amounts of about 100 mg and 1 mg, respectively. The product may also contain riboflavin in an amount between about 1 mg and about 3 mg, pyridoxine in an amount between about 1 mg and about 3 mg, cyanocobalamin in an amount between about 6 mg and about 12 mg, biotin in an amount between about 10 mcg and about 50 mcg, niacin in an amount between about 10 mg and about 50 mg, vitamin D in an amount between about 200 IU and about 500 IU, vitamin E in an amount between about 10 IU and about 50 IU, selenium in an amount between about 5 mcg and about 50 mcg, and/or magnesium in an amount between about 100 mg and about 400 mg.

Each year, approximately 1.5 million Americans seek medical/psychiatric treatment for alcoholism. Alcoholism remains one of the major causes of nutritional deficiency syndromes in the United States. Alcohol (ethanol) is directly toxic to many tissues and can affect almost every cell and organ system in the human body. Additionally, chronic use leads to impaired absorption, transport, and storage of numerous vitamins and minerals (Persson J., Scandinavian Journal of Gastroenterology, 1991;26: pp. 3-15.). Further, the nutritional content of ethanol is very poor and is often consumed in the context of inadequate dietary intake. For example, on average Americans consume about 4.5% of total calories as alcohol while alcoholics may consume 50% of their daily calories as ethanol (Feinman L., Lieber C. S. in: Medical and Nutritional Complications of Alcoholism: Mechanisms of Management. (Ed. Lieber, C. S.), 1992 Plenum Medical Book Company, New York, pp. 515-530.). The exact reasons for poor food intake among alcoholics are unknown but may include depressed consciousness during intoxication, hangover, and gastrointestinal problems induced by ethanol consumption.
Vitamins
Serious medical complications may occur as a result of uncorrected malnutrition. Most notably, as a result of thiamine (Vitamin B.sub.1) deficiency, Wernicke's syndrome, an encephalopathy marked by gait disturbance, acute confusion, memory loss and disorientation may develop in chronic users of ethanol. If untreated with thiamine supplementation, this condition may progress to the more serious Korsakoffs syndrome, a permanent disorder leading to brain damage in which patients manifest symptoms such as psychosis, severe memory loss, delirium, insomnia, and painful extremities. These patients frequently require long-term institutionalization. Additionally, beriberi heart disease and possibly polyneuropathy may result from thiamine deficiency. Alcoholics have demonstrated impaired abilities to absorb thiamine (Holzbach E. Journal of Studies on Alcohol, 1996;57: pp. 581-584.). However, it is clinically impractical to measure thiamine blood concentrations. Thiamine corrects early Wernicke signs rapidly and may prevent development of an irreversible Korsakoff dementia. Once the dementia is established, thiamine usually does not help. Therefore, due to the relative safety and ease of administering thiamine, 50-100 mg is generally given orally as a separate drug entity to [all] alcoholics daily while in treatment.
A significant number of alcoholics suffer from anemia, a general term for describing a reduction in the number of circulating red blood cells (erythrocytes). The clinical expression of anemia results from tissue hypoxia or oxygen starvation and the resulting cardiovascular pulmonary compensatory responses. Severe anemia is associated with weakness, vertigo, headache, tinnitus, fatigue, drowsiness, irritability, and in some cases bizarre behavior. Additionally, amenorrhea, loss of libido, GI complaints, and splenomegaly can result. Finally, heart failure and shock may result in some patients. Specifically, megaloblastic anemia, a disorder in the body's ability to manufacture functional red blood cells (erythropoiesis) may occur in a large number of alcoholics as a result of depleted B-complex vitamins such as folic acid and/or cyanocobalamin (Vitamin B.sub.12). Alcoholics tend to have low folic acid status when they are drinking. Ethanol is also known to accelerate the production of megaloblastic anemia in patients with depleted folic acid stores. In addition to folic acid deficiency, the direct effect of ethanol on bone marrow, liver disease, bleeding, iron deficiency, and infection may exert additive influences on the hematological status of the alcoholic. For this reason, chronic ethanol users are commonly administered 1 mg of folic acid by mouth daily as a separate drug entity while in treatment to replete folic acid stores.
When there is a general poor intake of B-vitamins, riboflavin (Vitamin B.sub.2) deficiency may result, and this has been found to be the case with alcoholics (Cook C. C. H, Thomson A. D. British Journal of Hospital Medicine, 1997;57: pp.461-465.). Clinical consequences of riboflavin deficiency include behavioral changes and peripheral neuropathy. For this reason, riboflavin is commonly administered to alcoholics daily as a component (1-3 mg) of a multivitamin as long as they are in treatment.
Behavioral changes, neurological disorders, peripheral neuropathy and dermatological disorders can result in part due to pyridoxine (Vitamin B.sub.6) deficiency disorders. This is most important with regard to alcoholics since up to 50% may have pyridoxine deficiencies as measured in plasma. It is unknown if inadequate dietary intake alone accounts for the deficiency, but increased destruction and reduced formation of pyridoxine may be related to ethanol use. Whatever the cause, clinical management usually involves provision of pyridoxine (1-3 mg) as part of a daily multivitamin administered as long as the patient is in treatment.
The absorption of cyanocobalamin (Vitamin B.sub.12) has also been shown to be decreased when coadministered with ethanol. Deficiencies may result in hematological as well as neurological disorders. Cyanocobalamin (6-12 mg) is commonly administered as part of a multivitamin supplement on a daily basis to alcoholics in treatment.
Biotin is a coenzyme that is essential to the metabolism of both fatty acids and carbohydrates. Deficiency states may result in dermatological disorders. Biotin 10-50 mcg is commonly included in multivitamin supplements used in the treatment of malnourished individuals.
Niacin (Nicotinic acid) deficiency may develop as a result of poor dietary intake among alcoholics. This water soluble vitamin is found in many of the same foods which contain thiamine. Severe niacin deficiency may result in the clinical condition of Pellagra which is characterized by dermatologic, central nervous system, and gastrointestinal symptoms. Niacin is generally included as part of a multivitamin preparation in doses of 10-50 mg given daily.
Clearly, alcoholics have illness related to abnormalities of vitamin D (cholecalciferol) and calcium. They have decreases in bone density and bone mass and increased susceptibility to bone fractures. Decreased blood calcium, phosphorous, magnesium and 25-OH-vitamin D have been reported. Changes in vitamin D metabolism may result from the inability of the alcoholic to hydroxylate vitamin D3 at the 25 position to its more active form. This condition may be in part due to poor liver function, decreased exposure to sunlight, a diet deficient in vitamin D, and malabsorption of fat. The end result may be osteomalacia leading to bone pain and fractures. Since poor dietary intake is common in alcoholics, vitamin D 200-500 IU administered as part of a multivitamin on a daily basis may be prudent.
Vitamin E and selenium serve protective roles as antioxidants and function synergistically in the human body. For instance, vitamin E reduces selenium requirements, prevents its loss from the body, and maintains it in its active form. Conversely, selenium spares vitamin E and reduces the requirement for the vitamin. Alcoholic patients and patients with poor fat absorption may become deficient in vitamin E. Clinical manifestations of vitamin E deficiency include decreased erythrocyte survival, and neurological disturbances including visual problems. Vitamin E 10-50 IU as a component of multivitamin supplements should be administered daily.
Trace Elements
There are 13 trace elements presently recognized as necessary for normal biological functioning of the human body. They are referred to as trace elements as they occur in concentrations <0.005% body weight. In order of demonstrated need they are iron, iodine, copper, manganese, zinc, cobalt, molybdenum, selenium, chromium, fluorine, silicon, nickel, and arsenic (The Merck Manual, 15th Edition (1987) pp. 894-1013). Importantly, a variety of essential trace elements such as magnesium, zinc, and selenium are often found in inadequate amounts in chronic alcoholics (Cook C. C. H., Walden R. J., Graham B. R., Gillham C., Davies S., Prichard B. N. C. Alcohol & Alcoholism, 1991;26: pp. 541-548.).
Serum selenium levels have been found to be decreased in the alcoholic, especially in the presence of liver disease. Selenium should be supplemented if patients are suspected to be deficient in this element. Muscle pain and tenderness have been reported to result from deficiency states. Selenium may be administered at doses from 5-50 mcg daily. However, at present, no U.S. Recommended Daily Allowance (RDA) has been established.
Chronic alcoholism is clearly associated with magnesium deficiency as measured by serum levels of the element. Alcohol ingestion is known to cause magnesium excretion. Magnesium deficiency may lead to hypocalcemia and hypoparathyroidism and clinical manifestations may include lethargy, weakness, anorexia nausea. If magnesium deficiency is suspected or confirmed, repletion is indicated. This may be done by giving the element intramuscularly or by oral supplementation. Magnesiun 100-400 mg may be given orally as a supplement daily.
As a consequence of the known risk of malnutrition in this patient population, most physicians who treat alcoholic patients in the inpatient hospital settings tend to treat alcoholics with three (3) immediate release oral supplement products, a multivitamin, thiamine 100 mg, and folic acid 1 mg. Additionally, some patients are also treated with thiamine and magnesium sulfate intramuscularly on admission.
At present there is no existing single entity product to administer to patients which is an extended-release multivitamin with minerals and trace elements in the aforementioned dose ranges and which specifically contains thiamine and folic acid in the desired amounts of 100 mg and 1 mg, respectively. Umbdenstock (U.S. Pat. No. 5,308,627) described a nutritional product to assist persons recovering from addictions to various health damaging substances. The product did not have folic acid in the appropriate amount (1 mg), and 3 tablets would have to be administered to approach 100 mg of thiamine. Additionally, the Umbdenstock product contains valerian, an herbal product of questionable utility, sedating effects, and unlikely to be recommended by most physicians treating alcoholic patients. Lastly, the product was not an extended release formulation.