The present invention refers to a method for blood purification by means of hemodialysis and/or hemofiltration, wherein to the blood in the extra-corporeal circuit of the hemodialysis and/or hemofiltration device a substitution solution is added upstream as well as downstream of the hemodialyser and/or hemofilter. A purification effect remaining constant with a high purification performance is achieved in that one or several of the operational and/or blood parameters are controlled and that the control is carried out using at least one of the infusion rates of the substitution solutions supplied upstream or downstream of the hemodialyser and/or hemofilter. The present invention also refers to a hemodialysis and/or hemofiltration apparatus for the performance of the inventive method.

1. Field of the Invention
The present invention refers to a method for blood purification by means of hemodialysis and/or hemofiltration, wherein to the blood in the extra-corporeal circuit of the hemodialysis and/or hemofiltration device a substitution solution is added upstream as well as downstream of the hemodialyser and/or hemofilter.
2. Description of the Related Art
In xe2x80x9cReplacement of Renal Function by Dialysisxe2x80x9d (Drukker, Parsons and Maher; Kluwer Academic Publishers, 4th edition 1996; xe2x80x9cHemodialysis Machines and Monitorsxe2x80x9d by H.-D. Polaschegg and N. W. Levin)xe2x80x94to the disclosure of which is explicitly referred herebyxe2x80x94a summary of most important hemodialysis procedures and machines is given:
In hemodialysis the blood of a patient is fed through an arterial blood line into the blood chamber of a dialyser. The blood is usually transported by means of a rotary peristalic pump arranged in the arterial blood line. After passing the pump blood is fed through the blood chamber of the dialyser and finally through a venous drip chamber and a venous blood line connected thereto back to the patient. A venous pressure monitor is connected to the venous drip chamber as a protective system for immediate detection of blood loss to the environment. If necessary two needles required for the arterial and venous cannula may be replaced by a single needle in the so-called single-needle-dialysis. In this mode of dialysis, the extra-corporal circuit consists of a single needle cannula with connected Y-piece. From the dialyser the venous line leads back to the Y-piece. The arterial and venous line are occluded alternately by clamps. One or more blood pumps run to manage the alternate flow to and from the Y-piece.
In hemodialysis the solute removal from the blood is driven by diffusion through the dialyser membrane. Though in addition a small transmembrane pressure is applied in order to ultrafiltrate excessive water of a patient, this filtration hardly plays a role for the purification of the blood from specific substances.
Solute removal in hemofiltration is driven by convection rather than by diffusion. At the same time ultrafiltrate is almost entirely replaced by a substitution fluid of a composition similar to dialysate in dialysis. This method emphasizes the similarity to the natural kidney and the more effective removal of larger molecules. On the other hand removal of low molecular substances is reduced as compared to hemodialysis because at best 45% of blood can be ultrafiltrated in the so-called post-dilution hemofiltration. Today, hemofiltration is only used in a small number of patients because of the high cost of commercial replacement fluid and the high blood flow required to perform the treatment in a reasonable time.
Hemofiltration machines for chronic treatment comprise the same extracorporal pumping and monitoring systems as hemodialysis machines. The dialysate circuit is replaced by a fluid balancing and warming system. In the so-called pre-dilution mode substitution fluid is added to blood upstream of the dialyser and the filtrate is produced by the corresponding transmembrane pressure. To be clinically effective a very large amount of substitution fluid is required. Because of the high cost of commercial substitution fluid this method never became widely accepted. More common is the post-dilution mode because less substitution fluid is required. In this mode the substitution fluid is added to the blood downstream of a dialyser. In the post-dilution mode good purification coefficients are obtained. During a 4 hour treatment normally approximately 20 to 24 liters of substitution fluid are added. The efficiency of the method is, however, limited by a critical transmembrane pressure above which blood damage will occur.
Various systems have been proposed for fluid balancing. In the gravimetric balancing method ultrafiltrate may be withdrawn by the ultrafiltrate pump into a bag or container hanging or standing on a balancing platform. Substitution fluid from a bag or container on the same platform is pumped by another pump to the venous drip chamber. Net fluid removal is achieved either by an additional ultrafiltration pump or by a programming unit that controls the substitution pump to deliver less fluid than removed by the filtration pump.
Hemodiafiltration, a combination of hemodialysis and hemofiltration, can be performed by combining the extracorporal circuits of a hemofiltration and a hemodialysis machine. Hemodialysis machines with volumetrically controlled ultrafiltration can be adapted easily for hemodiafiltration which is more cost-effective. This is particularly cost-effective if the substitution fluid is prepared online from the dialysis fluid.
Treatment parameters such as dialysate contents (sodium concentration), ultrafiltration rate, blood and dialysate flow are varied intradialytically in an attempt to increase or maintain efficacy and/or reduce intradialytic symtoms. The variation either follows a kinetic model or, more often, xe2x80x9cclinical judgementxe2x80x9d. Intradialytic symptoms, especially hypotension, are closely related to ultrafiltration. In dialysis machines having ultrafiltration pumps independent of dialysate pumps, profiling is performed by variation of the ultrafiltration speed.
To summarize in hemodialysis the blood of the patient is purified in that the substances of the blood which have to be removed diffuse through the membrane due to a concentration gradient across the membrane of the dialyser and thereby reach the dialysis fluid. The driving force in hemofiltration is substantially a pressure difference across the membrane which effects a convective transport of substances through the membrane and in doing so cleans the blood above all also from higher-molecular substances. In hemofiltration as well as in the combined method of hemodiafiltration, fluid is removed from the patient blood which has to be substituted except a small difference amount for the control of the fluid balance.
The relatively low efficiency of the pre-dilution mode, especially for low-molecular substances, results from the low concentration gradient across the membrane caused by the dilution and the fact that a purification of the blood as well as of the added substitution liquid is carried out. For the pre-dilution mode, the amounts of substitution fluid added during a 4 hour treatment lie in a range between 40 to 50 liters.
Pre-dilution is used preferably for patients who have a higher risk of coagulation or clotting of the blood. Said risk is reduced by the dilution of the blood prior to blood treatment wherein the cited disadvantages are accepted.
As mentioned above disadvantages occur in post-dilution as it has to be worked with high hemoconcentrations. With respect thereto the hemoconcentrations in predilution are low at least in the entrance section of the hemodialyser and/or hemofilter. Low hematocrit concentrations result in correspondingly large amounts of free water, i.e. unbound water, which renders possible a distinct convective substance transport through the membrane. Correspondingly, the purification effect for middle- and high-molecular substances may be higher in the pre-dilution mode than in the post-dilution mode.
To couple the advantages of the pre- and post-dilution mode it has also been proposed to apply both modes simultaneously with a fixed ratio of pre- and post-dilution substitution fluid flow (L. Pedrini and V. De Cristofaro, Abstract at the EDTA/ERA Congress in Madrid, 1999).
A further disadvantage of the post-dilution mode is that during the blood purification a limiting membrane is built up at the membrane of the hemodialyser and/or hemofilter. The thickness of this membrane increases with increasing duration of treatment, which reduces the permeability of the membrane. Therebyxe2x80x94if the transmembrane pressure remains constantxe2x80x94the purification effect is deteriorated. If a constant purification effect was to be achieved, an increasing trans-membrane pressure would be required which can lead to a damaging of the membrane.
U.S. Pat. No. 5,578,223 discloses an artificial kidney working in the post-dilution mode and being adaptable for use in hemofiltration, hemodialysis and hemodiafiltration treatment. For maintaining a desired concentration of bicarbonate in the blood of a patient the apparatus comprises means for perfusing a liquid containing bicarbonate into the extracorporal blood circuit after passing the exchanger and dosage means for adjusting the bicarbonate concentration in the blood of a patient to a desired level. An extraction pump which is connected to the outlet of the exchanger is controlled by a control unit to obtain a desired level of weight loss during the treatment session. The flow rate of bicarbonate solution is controlled by the control unit as a function of the flow rate of the extraction pump, the desired bicarbonate concentration in the blood of a patient and of the concentration of the bicarbonate solution before perfusion into the extracorporal circuit.
It is the object of the present invention to provide a method for the blood purification by means of hemodialysis and/or hemofiltration by means of which the advantages of the post-dilution mode and pre-dilution mode can be combined and at the same time the purification effect of the hemodialyser and/or hemofilter remains constant.
Proceeding from a method of the generic type, said object is solved in that one or several of the operational and/or blood parameters are controlled and that the control is carried out using at least one of the infusion rates of the substitution solutions supplied upstream or downstream of the hemodialyser and/or hemofilter.
By adding substitution solutions to the extra-corporeal circuit upstream and downstream of the hemodialyser and/or hemofilter, on the one hand the advantages of the post-dilution and pre-dilution can be combined, i.e. satisfying purification results are obtained for low-molecular substances as well as for middle- and high-molecular substances. On the other hand, according to the invention the infusion rates of one or both of the substitution fluids supplied upstream and downstream are used for the control of operational and/or blood parameters.
Thus, for instance in case of a high trans-membrane pressure or a high hematocrit value of the blood, the infusion rate of the substitution solution added upstream of the dialyser can be increased until the desired values for the values to be controlled are achieved or the values fall below given limiting values. Correspondingly, in case of a low trans-membrane pressure or a low hematocrit value, the infusion rate of the substitution fluid supplied downstream of the dialyser can be increased which, due to the then resulting larger concentration gradient across the membrane leads to an improvement of the diffusive substance transport, i.e. to an improved purification effect for low-molecular substances.
According to a preferred embodiment of the present invention the operational and/or blood parameters are the trans-membrane pressure and/or the blood density and/or the hematocrit value of the blood.
The infusion rate of the substitution solutions supplied upstream of the hemodialyser and/or the hemofilter is preferably increased relative to the infusion rate supplied downstream of the hemodialyser and/or the hemofilter with increasing trans-membrane pressure and/or increasing blood density and/or increasing hematocrit value of the blood.
According to a preferred embodiment of the present invention the operational and/or blood parameters are detected continuously.
It is particularly advantageous when the infusion rates of the substitution solutions are chosen such that a substantially stationary limiting membrane is formed on the side of the membrane of the hemodialyser and/or hemofilter facing the chamber through which the blood flows. Therefrom results the advantage that the efficiency and the sieving-coefficient spectrum of the hemodialyser and/or hemofilter remain constant during the time of treatment.
In a further embodiment of the present invention the relation of the infusion rates of the substitution solutions in the blood stream is changed after termination of the treatment in order to dissolve the limiting membrane. Thereby a major part of the proteins forming the limiting membrane can be supplied back to the patient after finishing the blood treatment.
The present invention also refers to a hemodialysis and/or hemofiltration apparatus with an extra-corporeal circuit for receiving the blood to be purified as well as with a hemodialyser and/or hemofilter communicating with the blood circuit, wherein, upstream and downstream of the hemodialyser and/or hemofilter, the blood circuit has at least one supply line, respectively, for supplying substitution fluid. According to the invention, a control unit for controlling one or several operational and/or blood parameters is provided, wherein the control unit is designed such that the control is carried out by means of at least one of the infusion rates of the substitution solution.
In a preferred embodiment of the present invention measuring devices connected to the control unit are provided for recording the operational and/or blood parameters. Therein said measuring devices can comprise pressure sensors arranged in the extra-corporeal circuit and/or in the dialysis-fluid circuit upstream and/or downstream of the hemodialyser and/or hemofilter, respectively.
In a further embodiment of the present invention the measuring devices comprise sensors in the extra-corporeal circuit upstream and/or downstream of the hemodialyser and/or hemofilter for the detection of the hematocrit value.
In accordance to a further embodiment of the present invention the measuring devices comprise sensors in the extra-corporeal circuit upstream and/or downstream of the hemodialyser and/or hemofilter for the detection of the blood density. According to these preferred embodiments the operational and/or blood parameters are the transmembran pressure and/or the blood density and/or the hematocrit value of the blood.
According to a preferred embodiment means for controlling the at least one of the infusion rates (Qspre, Qspost) are pumps in the supply lines.
In a further embodiment means for controlling the at least one of the infusion rates (Qspre, Qspost) are valves 16, 17 in the supply lines.

Method for the purification of blood by means of hemodialysis and/or hemofiltration and apparatus for performing said method


An apparatus for insufflating a treating gas into a patient and for measuring a carbon dioxide content exhaled by the patient includes a hollow body with a partitioning wall separating the body into inhalation and exhalation manifolds. Two hollow prongs have coaxial openings close to the body which allow gas exchange for breathing and carbon dioxide measuring purposes. The holes are of a size such that suction drawn through the holes is limited while still allowing accurate gas analysis.

The practice of measuring end-tidal carbon dioxide during the administration of anesthesia, particularly regional anesthesia, has grown markedly in the past several years. The reasons that anesthesiologists have embraced this technique are described more fully in U.S. Pat. No. 5,335,656 which is incorporated herein by reference in its entirety.
The preferred nasal cannula used in this procedure is a cannula which insufflates the patient with oxygen through one nare of a cannula and separately samples the exhaled gases by drawing the exhaled gas from the other nare into a conventional carbon dioxide analyzer. The cannula is preferably provided with an internal wall or system in the face piece to keep the conduits separate for insufflation and sampling, however, separate lines can be used or even multiple nares for insufflation and sampling, though the latter device substantially increases the risk of gases mixing which can distort the readings for end-tidal carbon dioxide. It is preferred that two nares only are employed and that each nare performs only one function, i.e., insufflation or sampling into or from separate nostrils. Likewise, insufflation has normally been continuous, however, it could advantageously be intermittent which would further improve the end-tidal carbon dioxide measurement by insuring that gases being sampled were representative of exhaled gases undiluted by the other gases being insufflated. Most preferably, the intermittent insufflation is accomplished by the apparatus and method described in U.S. Pat. No. 5,626,131 which is incorporated herein by reference in its entirety. Other so-called demand insufflation devices which begin insufflation upon the start of inhalation can also be employed.
Normal nasal cannulae are designed with the nares having a slight inward curvature as they extend upward from the face piece. This is anatomically desirable and important for imparting the proper direction of insufflating gas into the nasal cavities. When the patient is in the upright sitting position or ambulatory, this is the most satisfactory design configuration. Conversely, problems can be encountered if the patient is horizontal or prone and tends to accumulate secretions in the nasal cavities. It can be a particularly vexing problem if either the insufflation or sampling nare becomes occluded during the use of the cannula for sampling and monitoring end-tidal carbon dioxide during the administration of anesthesia.
It is therefore an object of the present invention to provide a nasal cannula structure for sampling carbon dioxide which reduces or eliminates the incidence of occlusion of the tip of the carbon dioxide sampling nare during the removal of carbon dioxide by the sampling line connected to a monitoring device and/or a source of suction or vacuum.
It is also an object of the present invention to provide a nasal cannula for insufflating a patient with oxygen while accurately monitoring end-tidal carbon dioxide, that will continue to function properly for its intended purpose when either or both nares become occluded for any reason.
It is a further object to accomplish the foregoing objects with a minimum risk of distorting the end-tidal carbon dioxide readings from the sampled exhalation gases during the administration of anesthesia.
The foregoing objects and advantages are obtained by providing a nasal cannula structure that is adapted for insufflation and sampling, with additional holes or vents on the nares of the nasal cannula, preferably both anterior and posterior of one or both nares at a location proximate the entrance of the nasal passageways when the cannula is in use.


A polishing pad comprising a polishing pad substrate and at least one solid catalyst, the polishing pad being useful to remove metal layers from a substrate.

1. Field of the Invention
This invention concerns a chemical mechanical polishing slurry including at least one oxidizer and a solid catalyst. The chemical mechanical polishing slurry is useful alone or in combination with other chemicals and abrasives for polishing metal layers and thin-films associated with semiconductor manufacturing. More particularly this invention concerns a chemical mechanical polishing slurry that is especially adapted for polishing multiple metal layers and thin-films where one of the layers or films is comprised of aluminum, copper, copper-aluminum alloy, and tungsten and another layer or thin film is comprised of titanium, tantalum or a titanium or tantalum containing alloy such as titanium nitride or tantalum nitride. This invention also concerns a method for using the polishing slurry that includes exposing the slurry to an energy source in order to activate the solid catalyst. This invention further concerns polishing pads including a polishing pad substrate and at least one solid catalyst as well as a method for polishing a metal feature with solid catalyst containing polishing pads.
2. Description of the Related Art
Integrated circuits are made up of millions of active devices formed in or on a silicon substrate. The active devices, which are initially isolated from one another, are united to form functional circuits and components. The devices are interconnected through the use of well-known multilevel interconnections. Interconnection structures normally have a first layer of metallization, an interconnection layer, a second level of metallization, and sometimes a third and subsequent levels of metallization. Interlevel dielectrics such as doped and undoped silicon dioxide (SiO2), are used to electrically isolate the different levels of metallization in a silicon substrate or well. The electrical connections between different interconnection levels are made through the use of metallized vias. U.S. Pat. No. 4,789,648, which is incorporated herein by reference, describes a method for preparing multiple metallized layers and metallized vias in insulator films. In a similar manner, metal contacts are used to form electrical connections between interconnection levels and devices formed in a well. The metal vias and contacts are generally filled with tungsten and generally employ an adhesion layer such as titanium nitride (TiN) and/or titanium to adhere a metal layer such as a tungsten metal layer to SiO2. At the contact level, the adhesion layer acts as a diffusion barrier to prevent tungsten and SiO2 from reacting.
In one semiconductor manufacturing process, metallized vias or contacts are formed by a blanket tungsten deposition followed by a chemical mechanical polish (CMP) step. In a typical process, via holes are etched through an interlevel dielectric (ILD) to interconnection lines or to a semiconductor substrate. Next, a thin adhesion layer such as titanium nitride and/or titanium is generally formed over the ILD and is directed into the etched via hole. Then, a tungsten film is blanket deposited over the adhesion layer and into the via. The deposition is continued until the via hole is filled with tungsten. Finally, the excess metal is removed by chemical mechanical polishing (CMP) to form metal vias. Processes for manufacturing and/or CMP of ILD""s are disclosed in U.S. Pat. Nos. 4,671,851, 4,910,155 and 4,944,836.
In a typical chemical mechanical polishing process, the substrate is placed in direct contact with a rotating polishing pad. A carrier applies pressure against the backside of the substrate. During the polishing process, the pad and table are rotated while a downward force is maintained against the substrate back. An abrasive and chemically reactive solution, commonly referred to as a xe2x80x9cslurryxe2x80x9d is deposited onto the pad during polishing. The slurry initiates the polishing process by chemically reacting with the film being polished. The polishing process is facilitated by the rotational movement of the pad relative to the substrate as slurry is provided to the wafer/pad interface. Polishing is continued in this manner until the desired film on the insulator is removed.
The slurry composition is an important factor in the CMP step. Depending on the choice of the oxidizing agent, the abrasive, and other useful additives, the polishing slurry can be tailored to provide effective polishing to metal layers at desired polishing rates while minimizing surface imperfections, defects, corrosion, and erosion. Furthermore, the polishing slurry may be used to provide controlled polishing selectivities to other thin-film materials used in current integrated circuit technology such as titanium, titanium nitride and the like.
Typically CMP polishing slurries contain an abrasive material, such as silica or alumina, suspended in an oxidizing, aqueous medium. For example, U.S. Pat. No. 5,244,534 to Yu et al. reports a slurry containing alumina, hydrogen peroxide, and either potassium or ammonium hydroxide that is useful to remove tungsten at predictable rates with little removal of the underlying insulating layer. U.S. Pat. No. 5,209,816 to Yu et al. discloses a slurry comprising perchloric acid, hydrogen peroxide and a solid abrasive material in an aqueous medium. U.S. Pat. No. 5,340,370 to Cadien and Feller discloses a tungsten polishing slurry comprising approximately 0.1M potassium ferricyanide, approximately 5 weight percent silica and potassium acetate. Acetic acid is added to buffer the pH at approximately 3.5.
Most of the currently available CMP slurries contain large concentrations of dissolved, ionic metallic components. As a result, the polished substrates can become contaminated by the adsorption of charged species into the interlayers. These species can migrate and change the electrical properties of the devices at gates and contacts and change the dielectric properties of the SiO2 layers. These changes may reduce the reliability of the integrated circuits with time. Therefore, it is desirable to expose the wafer only to high purity chemicals with very low concentrations of mobile metallic ions.
Many well known, compositions will polish films such as copper at a low rate. In addition, the binder layers such as titanium and tantalum are very inert towards the chemistries. Because it can be difficult to polish these layers at a high rate, the polishing step must be lengthened to remove the last traces of the deposited metal. Lengthening the polishing step exposes layers, such as aluminum layers and SiO2 layers, to overpolishing and to undesireable erosion. This erosion makes it more difficult to print high resolution lines during subsequent photolithography steps increasing the number of wafer failures. In addition, lengthened polishing steps reduce the throughput of an IC fabrication plant and increase the cost of the resulting IC.
Despite these advances, improvements to polishing compositions, polishing pads and polishing methods are still needed that will allow for the polishing of multiple metal layers such as aluminum and titanium, copper and tantalum, tungsten and titanium, and copper and titanium at high rates and in a single step.
The present invention is directed to chemical mechanical polishing composition that includes a heterogeneous solid metal oxide catalyst and an oxidizing agent.
The present invention is also directed to chemical mechanical polishing compositions in which the heterogeneous solid catalyst activity can be enhanced by activation with an energy source such as UV radiation.
In addition, this invention is a state-of-the art chemical mechanical polishing composition that is a xe2x80x9csmart compositionxe2x80x9d because the heterogeneous solid catalyst can be selected to enhance the polishing of a specific metal or metal alloy by enhancing the catalytic activity of the heterogeneous solid catalyst using an energy source separated from the polishing composition and separated from the surface being polished.
Furthermore, this invention also includes methods for using the chemical polishing compositions of this invention to polish a plurality of metal layers in an integrated circuit in a controlled and efficient manner.
In one embodiment, this invention is an aqueous chemical mechanical polishing composition comprising at least one oxidizing agent and at least one solid catalyst.
In another embodiment, this invention is a chemical mechanical polishing slurry. The chemical mechanical polishing slurry comprises from about 0.1 to about 7.0 weight percent of an abrasive selected from silica, alumina, and mixtures thereof. The polishing slurry also includes at least one photoactivated solid catalyst, and an oxidizing agent selected from the group including monopersulfate, di-persulfate, peracetic acid, urea hydrogen peroxide, hydrogen peroxide, acids thereof, salts thereof, adducts thereof, or mixtures thereof wherein the solid catalyst is not silica and not alumina.
In still another embodiment, this invention is a method for polishing a substrate including at least one metal layer. The method comprises the steps of; (a) admixing at least one oxidizing agent, at least one solid catalyst, and deionized water to give an aqueous chemical mechanical polishing composition; (b) applying the chemical mechanical polishing composition to the substrate; and (c) removing at least a portion of the metal layer from the substrate by bringing a pad into contact with the substrate and moving the pad in relation to the substrate. The metal layers that can be removed from the substrate include, but are not limited to titanium, titanium nitride, tungsten, tantalum, tantalum nitride, aluminum and copper.
In yet another embodiment, this invention is a polishing pad including a polishing pad substrate and at least one heterogeneous solid catalyst.
In a further embodiment, this invention is a method for polishing a substrate surface including at least one metal portion. The method includes the steps of preparing a polishing pad by incorporating at least one heterogeneous solid catalyst into a polishing pad substrate. Once prepared, the polishing pad is then, in the presence of a solution including an oxidizing agent, brought into contact with the substrate surface after which at least a portion of the substrate surface metal portion is removed by moving the polishing pad in relation to the substrate.
The present invention relates to chemical mechanical polishing compositions and polishing pads that comprise at least one solid catalyst that controllably promotes a chemical reaction between an oxidizing agent and a substrate layer. The chemical mechanical polishing compositions and polishing pads are used to polish at least one layer associated with a substrate selected from the group including, but not limited to, silicon substrates, TFT-LCD glass substrates, GaAs substrates, and other substrates associated with integrated circuits, thin films, multiple level semiconductors, and wafers. In particular, the solid catalyst containing chemical mechanical polishing compositions and polishing pads of this invention have been found to exhibit excellent polishing performance when used to polish substrates including one or more layers of aluminum, copper, copper-aluminum alloy, tungsten, titanium, tantalum, titanium and tantalum containing alloys such as titanium nitride or tantalum nitride one or more nobel metals and combinations thereof in a single step, multiple metal layer chemical mechanical polishing process.
Before describing the details of the various preferred embodiments of this invention, some of the terms that are used herein will be defined. The xe2x80x9cchemical mechanical compositionxe2x80x9d refers to the combination comprising of at least one oxidizing agent and at least one solid catalyst that may be used in conjunction with an abrasive pad to remove one or more layers of metal from a multiple layer metallization.
The term chemical mechanical polishing slurry, (xe2x80x9cCMP slurryxe2x80x9d), refers to a useful product of this invention that comprises the chemical mechanical composition of this invention and at least one abrasive. The CMP slurry is useful for polishing a multiple level metallization which may include but are not limited to semi-conductor thin-films, integrated circuit thin-films, and for polishing any other films, surfaces and substrates where CMP processes are useful.
The term xe2x80x9cnon-metallicxe2x80x9d refers to compounds that are not at their zero oxidation state. For purposes of this invention, the term xe2x80x9cnon-metallic solid catalystxe2x80x9d refers to catalysts wherein at least 50 wt % and preferably at least 80 wt % of the catalyst is non-metallic.
One aspect of this invention is a chemical mechanical composition comprising an oxidizing agent and solid catalyst that is useful in oxidizing metal layers in polishing applications. This chemical mechanical composition is useful when incorporated in a chemical mechanical polishing slurry or when used in conjunction with an abrasive polishing pad to oxidize a metal layer to its corresponding oxide or ions. For example, the combination can be used to oxidize tungsten to tungsten oxide, aluminum to aluminum oxide and copper to copper oxide. The oxidizing agentxe2x80x94solid catalyst combinations disclosed herein are useful when incorporated into a CMP slurry or when used alone in conjunction with an abrasive pad to polish metals and metal based components including copper, aluminum, copper-aluminum alloy, tungsten, titanium, titanium nitride, tantalum, tantalum nitride and various mixtures and combinations thereof.
The chemical mechanical composition of this invention includes at least one oxidizing agent. The oxidizing agent is preferably an inorganic or organic per-compound. A per-compound as defined by Hawley""s Condensed Chemical Dictionary is a compound containing at least one peroxy group (xe2x80x94Oxe2x80x94Oxe2x80x94) or a compound containing an element in its highest oxidation state. Examples of compounds containing at least one peroxy group include but are not limited to hydrogen peroxide, urea hydrogen peroxide, monopersulfates (SO5=), dipersulfates (S2O8=), peracetic acid, percarbonates, organic peroxides such as benzoyl peroxide, and di-t-butyl peroxide. These oxidizers are useful in their listed form or in the form of their respective acid, salts, adducts, and mixtures thereof. Other, non-peroxy compounds which can be useful in compositions of this invention are periodic acid, periodiate salts, perbromic acid, perbromate salts, perchloric acid, perchloric salts, perboric acid, perborate salts, permanganates, and permanganate salts.
Monopersulfates are compounds which include the oxidizing SO5= group as shown below.
where X1 and X2 are each individually H1, Si(Rxe2x80x2)3, xe2x80x94NH3, N(Rxe2x80x3)3 and alkali earth metals such as Li, Na, K, and so forth; where Rxe2x80x2 is an alkyl group having from 1 to 10 or more carbon atoms, and wherein Rxe2x80x3 is H, an alkyl group, an aryl group, or mixtures thereof including, for example, xe2x80x94Nme3, Nbu3, NPh3, NmeBu2, NHEt2 and so forth. One well known and preferred class of monopersulfates are combinations of KHSO5, KHSO4 and K2SO4. This combination is known as a triple salt. A most preferred monopersulfate oxidizing agent is ammonium persulfate.
Most preferred oxidizing agents are xe2x80x9cperxe2x80x9d compounds or a compound possessing a (xe2x80x94Oxe2x80x94Oxe2x80x94) reactive functional group such as monopersulftate, di-persulfate, peracetic acid, urea hydrogen peroxide, hydrogen peroxide, and acids, salts, adducts and mixtures thereof.
The oxidizing agent may be present in the overall chemical mechanical polishing slurry in an amount ranging from about 0.1 to about 20.0 weight percent. It is preferred that the oxidizer is present in the slurry in an amount ranging from about 0.2 to about 10.0 weight percent.
The chemical mechanical composition of this invention includes at least one heterogeneous solid catalyst. The purpose of the solid catalyst is to act as a catalyst and increase the kinetic rate of the oxidation reaction on the surface of a metal feature.
The term xe2x80x9cheterogeneous solid catalystxe2x80x9d is used herein to refer to compositions in which the solid catalyst is distinct from the liquid phase and not significantly soluble (essentially insoluble) in the chemical mechanical composition liquid phase. In other words, the xe2x80x9cactivexe2x80x9d insoluble solid catalyst can be mechanically or physically separated from the liquid phase. For example, the solid catalyst can be removed by a mechanical process such as centrifugation or filtration. This is distinct from a homogeneous catalyst system where the soluble catalyst exists in the liquid phase.
The heterogeneous solid catalyst can be a homogeneous composition of the active catalyst, or the active heterogeneous solid catalyst can be chemically or physically associated with the surface of the preferred abrasive as molecular species, as a small particle or as a monolayer. The solid catalysts are preferably small particles with high surface areas. The solid catalysts should have a mean particle diameter less than about 1 micron and a surface area greater that about 10 m2/g and less than about 250 m2/g. It is more preferred that the solid catalysts have a mean particle diameter that is less than about 0.5 microns and most preferably less than about 0.25 microns.
The heterogeneous solid catalyst of this invention may also act as an abrasive when present in large enough amounts in the compositions of this invention. Since the useful catalytically active sites on the solid catalyst are restricted to the catalyst particle surface, the active catalyst will always be present even if portions of the abrasive surface is removed. This invention includes compositions and method for using a heterogeneous solid which has a catalytically active surface in any concentration up to 25 weight percent of the composition as both an abrasive and as a catalyst.
However, it is preferred that the solid catalyst is present in a small amount in the chemical mechanical compositions and slurries of this invention. The concentration of solid catalyst can be minimized in several ways. The pure abrasive particles can be physically dispersed or mixed with the solid catalyst. The abrasive can be a co-formed abrasive in which the solid catalyst is homogeneously mixed with another oxide to form solid particles containing an intimate mixture of the catalyst supported on metal oxide. In addition the solid catalyst can be supported on the abrasive particles. By xe2x80x9csupportedxe2x80x9d we mean that the solid catalyst can be chemically or physically adsorbed on the surface of the abrasive as molecular species, small particles or as a monolayer.
The solid catalyst may be present in compositions of this invention in an amount of solid catalyst ranging from about 0.001 to about 25.0 weight percent. More preferably, the solid catalyst will be present in the compositions of this invention in an amount ranging from about 0.1 to about 10 wt %. When present in large amounts, greater than about 5.0 wt %, the solid catalyst may also have significant abrasive activity. It is preferred that the solid catalyst is present in a catalytic amount in the chemical mechanical compositions and slurries of this invention. By xe2x80x9ccatalytic amountxe2x80x9d it is meant that the solid catalyst is present in an amount that is sufficient to promote the desired reaction without being consumed in the catalyzed process. Therefore, compositions of this invention may also include only a small amount, from about 0.005 to about 5.0 wt %, and more preferably from about 0.1 to about 3.0 wt % solid catalyst. It is also preferred that the solid catalyst is a composition other than the selected abrasive.
The solid catalyst of this invention is preferably an energy activated or photoactivated solid catalyst. By xe2x80x9cphotoactivexe2x80x9d it is meant that the solid catalyst catalytic activity is enhanced by bombarding the solid catalyst with photons of light or electromagnetic radiation. It is preferred that catalytic activity of a photoactive solid catalyst of this invention is enhanced by exposing the catalyst to a source that emits light at wavelengths in the UV range of from about 1 to about 800 nm. It is most preferred that the activity of the photoactive solid catalyst is enhanced by a UV light source having a wavelength of from 200-400 nm and most preferably a UV wavelength less than about 390 nm.
The wattage of the UV light used to activate the photoactive solid catalyst is also important. The UV light used should have a wattage greater than 1 xcexcw/cm2. More preferably, the UV light used should have a wattage greater than about 20,000 xcexcw/cm2.
UV light wavelength and wattage are useful parameters for controlling the activation of the photoactive solid catalysts. For example, the UV light wattage can be kept constant while the wavelength is varied in order to increase or decrease the photoactivation rate of the photoactive solid catalyst. It is more preferred, however, to keep the wavelength of the UV light used constant while varying the UV light wattage in order to increase or decrease photoactive solid catalyst activity.
Solid catalysts useful in the compositions of this invention include all solid materials where photoelectric stimulation causes electrons in the solid material to be excited to a conducting band. Non-limiting examples of useful solid catalysts are semiconducting solid oxides having the formula MxOy wherein M is selected from Ti, Ta, W, V, Nb, Mn, Zr. and mixtures thereof, where x and y are each the same or different numbers and wherein x and y are both greater than 0. Preferably, x and y are each individually greater than 0 and less than about 5.
Preferred photoactive solid catalysts are oxides of titanium including TiO2, Ti2O3, and mixtures thereof. A most preferred photoacive solid catalyst is Ti2O3 because it is photoactivated with a greater efficiency than other more highly oxidized forms of titania
The concentration ranges of solid catalyst in the chemical mechanical polishing slurry of this invention are generally reported as a weight percent of the entire compound. The use of high molecular weight metal containing compounds that comprise only a small percentage by weight of catalyst is well within the scope of catalysts in this invention.
As noted above, the solid catalysts useful in the compositions of this invention may be abrasive in nature. The solid catalysts may be present in compositions of this invention as discrete solid particles or they may be associated with the surface of metal oxide abrasive particles. For example, a titania photoactive solid catalyst can be chemically or physically absorbed on the surface of a silica abrasive particle or agglomerate and thereafter used in compositions of this invention.
The chemical mechanical composition of this invention may be combined with at least one abrasive to produce a CMP slurry. The abrasive is typically a metal oxide abrasive. The metal oxide abrasive may be selected from the group including alumina, titania, zirconia, germania, silica, ceria and mixtures thereof. The CMP slurry of this invention preferably includes from about 0.1 to about 20.0 weight percent or more of an abrasive. It is more preferred, however, that the CMP slurry of this invention includes from about 0.5 to about 7.0 weight percent abrasive.
The metal oxide abrasive may be produced by any techniques known to those skilled in the art. Metal oxide abrasives can be produced using any high temperature process such as sol-gel, hydrothermal or, plasma process, or by processes for manufacturing fumed or precipitated metal oxides. Preferably, the metal oxide is a fumed or precipitated abrasive and, more preferably it is a fumed abrasive such as fumed silica or fumed alumina. For example, the production of fumed metal oxides is a well-known process which involves the hydrolysis of suitable feedstock vapor (such as aluminum chloride for an alumina abrasive) in a flame of hydrogen and oxygen. Molten particles of roughly spherical shapes are formed in the combustion process, the diameters of which are varied through process parameters. These molten spheres of alumina or similar oxide, typically referred to as primary particles, fuse with one another by undergoing collisions at their contact points to form branched, three dimensional chain-like aggregates. The force necessary to break aggregates is considerable and often considered irreversible. During cooling and collecting, the aggregates undergo further collision that may result in some mechanical entanglement to form agglomerates. Agglomerates are thought to be loosely held together by van der Waals forces and can be reversed, i.e., de-agglomerated, by proper dispersion in a suitable media.
Precipitated abrasives may be manufactured by conventional techniques such as by coagulation of the desired particles from an aqueous medium under the influence of high salt concentrations, acids or other coagulants. The particles are filtered, washed, dried and separated from residues of other reaction products by conventional techniques known to those skilled in the art.
A preferred metal oxide will have a surface area, as calculated from the method of S. Brunauer, P. H. Emmet, and I. Teller, J. Am. Chemical Society, Volume 60, Page 309 (1938) and commonly referred to as BET, ranging from about 5 m2/g to about 430 m2/g and preferably from about 30 m2/g to about 260 m2/g. Due to stringent purity requirements in the IC industry the preferred metal oxide should be of a high purity. High purity means that the total impurity content, from sources such as raw material impurities and trace processing contaminants, is typically less than 1% and preferably less than 0.01% (i.e., 100 ppm).
In this preferred embodiment, the metal oxide abrasive consists of metal oxide aggregates having a size distribution less than about 1.0 micron, a mean aggregate diameter less than about 0.4 micron and a force sufficient to repel and overcome the van der Waals forces between abrasive aggregates themselves. Such metal oxide abrasive has been found to be effective in minimizing or avoiding scratching, pit marks, divots and other surface imperfections during polishing. The aggregate size distribution in the present invention may be determined utilizing known techniques such as transmission electron microscopy (TEM). The mean aggregate diameter refers to the average equivalent spherical diameter when using TEM image analysis, i.e., based on the cross-sectional area of the aggregate. By force is meant that either the surface potential or the hydration force of the metal oxide aggregates must be sufficient to repel and overcome the van der Waals attractive forces between the aggregates.
In another preferred embodiment, the metal oxide abrasive may consist of discrete, individual metal oxide particles having a primary particle diameter less than 0.4 micron (400 nm) and a surface area ranging from about 10 m2/g to about 250 m2/g.
It is preferred that the metal oxide abrasive is silica having a surface area of from about 120 m2/g to about 200 m2/g.
Preferably, the metal oxide abrasive is incorporated into the aqueous medium of the polishing slurry as a concentrated aqueous dispersion of metal oxides, which concentrated aqueous dispersion of metal oxide abrasives typically ranges from about 3% to about 45% solids, and preferably between 10% and 20% solids. The aqueous dispersion of metal oxides may be produced utilizing conventional techniques, such as slowly adding the metal oxide abrasive to an appropriate media, for example, deionized water, to form a colloidal dispersion. The dispersion is typically completed by subjecting it to high shear mixing conditions known to those skilled in the art and optionally filtering the dispersion to remove unwanted impurities including large particles. The pH of the slurry may be adjusted away from the isoelectric point to maximize colloidal stability.
The chemical mechanical compositions and slurries of this invention may also include a film forming agent. The film forming agent may be any compound or mixtures of compounds that are capable of facilitating the formation of a passivation layer of metal oxides and dissolution inhibiting layers on the surface of the metal layer. Passivation of the substrate surface layer is important to prevent wet etching of the substrate surface. An example of useful film-forming agent is BTA, (benzotriazole).
Once a passivation layer has formed on the substrate surface it becomes useful to be able to disturb the passivation layer in order to abrade metal oxides from the substrate surface with abrasive components of CMP slurries of this invention. One class of compounds that is useful in disturbing the passivation layer is complexing agents. Useful complexing agents include but are not limited to acids such as inorganic acids, citric, lactic, tartaric, succinic, acetic, oxalic and other acids, as well as amino acid and amino sulfuric acids and their salts.
The complexing agents serve at least two useful functions in the CMP slurry of this invention. The complexing agent disturbs the passivation layer during the mechanical abrasion step without destroying the layer or inhibiting its formation during the abrasion step and especially after the abrasion step is complete. Secondly, the complexing agent is believed to form a complex with the oxidized metal and not the underlying unoxidized metal thereby limiting the depth of the oxidized layer. Complexing agents, if used in the compositions of this invention, should be present in the compositions in an amount ranging from about 0.5 to about 5.0 weight present.
The chemical mechanical composition of this invention may include at least one soluble catalyst. The purpose of the soluble catalyst is to transfer electrons from the metal being oxidized to the oxidizing agent (or analogously to transfer electrochemical current from the oxidizer to the metal). The soluble catalyst or soluble catalysts chosen may be metallic, non-metallic, or a combination thereof and the soluble catalyst must be able to shuffle electrons efficiently and rapidly between the oxidizer and metal substrate surface. Preferably, the soluble catalyst is chosen from soluble compounds including metal ions that have multiple oxidation states, such as but not limited to Ag, Co, Cr, Cu, Fe, Mo, Mn, Nb, Ni, Os, Pd, Ru, Sn, Ti and V. The term xe2x80x9cmultiple oxidation statesxe2x80x9d refers to an atom and/or compound that has a valence number that is capable of being augmented as the result of a loss of one or more negative charges in the form of electrons. Most preferred soluble metal catalysts are compounds of Ag, Cu and Fe and mixtures thereof. Especially preferred are soluble iron catalysts such as but not limited to inorganic salts of iron, such as iron (II or III) nitrate, iron (II or III) sulfate, iron (II or III) halides, including fluorides, chlorides, bromides, and iodides, as well as perchlorates, perbromates and periodates, and ferric organic iron (II or III) compounds such as but not limited to acetates, acetylacetonates, citrates, gluconates, malonates, oxalates, phthalates, and succinates, and mixtures thereof. The soluble catalyst may be present in the chemical mechanical polishing composition in an amount ranging from about 0.001 to about 2.0 weight percent. A most preferred soluble metal catalyst is ferric nitrate.
Other well known polishing slurry additives may be incorporated into the chemical mechanical polishing slurry of this invention. One class of optional additives are inorganic acids and/or salts thereof which may be added to the polishing slurry to further improve or enhance the polishing rate of the barrier layers in the wafer, such as titanium and tantalum. Useful inorganic additives include sulfuric acid, phosphoric acid, nitric acid, HF acid, ammonium fluoride, ammonium salts, potassium salts, sodium salts or other cationic salts of sulfates, phosphates and fluorides.
In order to promote stabilization of a CMP slurry of this invention against settling, flocculation, and decomposition, a variety of optional CMP slurry additives, such as surfactants, stabilizers, or dispersing agents, can be used. In general, the amount of additive such as a surfactant that may be used in the present invention should be sufficient to achieve effective stabilization of the slurry and will typically vary depending on the particular surfactant selected and the nature of the surface of the metal oxide abrasive. For example, if not enough of a selected surfactant is used, it will have little or no effect on CMP slurry stabilization. On the other hand, too much surfactant in the CMP slurry may result in undesirable foaming and/or flocculation in the slurry. Stabilizers such as surfactants should generally be present in the slurry of this invention in an amount ranging from about 0.001% to about 0.2% by weight, and preferably from about 0.001 to about 0.1 weight percent. Furthermore, the additive may be added directly to the slurry or treated onto the surface of the metal oxide abrasive utilizing known techniques. In either case, the amount of additive is adjusted to achieve the desired concentration in the polishing slurry. Preferred surfactants include dodecyl sulfate sodium salt, sodium lauryl sulfate, dodecyl sulfate ammonium salt, and mixtures thereof. Examples of useful surfactants include TRITON(copyright) DF-16 manufactured by Union Carbide, and SURFYNOL(copyright) manufactured by Air Products and Chemicals.
An additive which may be useful with this invention is one which stabilizes the oxidizer in the presence of the metal complex. It is well known that hydrogen peroxide is not stable in the presence of many metal ions without the use of stabilizers. For this reason, the CMP composition and slurries of this invention may include a stabilizer. Without the stabilizer, the catalyst and the oxidizing agent may react in a manner that degrades the oxidizing agent rapidly over time. The addition of a stabilizer to compositions of this invention reduces the effectiveness of the catalyst. Therefore the choice of the type and amount of stabilizer added to the composition is important and has a significant impact on CMP performance.
Useful stabilizers include phosphoric acid, organic acids (e.g., adipic, citric, malonic, orthophthalic, and EDTA), phosphonate compounds, nitriles and other ligands which bind to the metal and reduce its reactivity toward hydrogen peroxide decomposition and mixture thereof. The acid stabilizers may be used in their conjugate form, e.g., the carboxylate can be used instead of the carboxylic acid. For purposes of this application the term xe2x80x9cacidxe2x80x9d as it is used to describe useful stabilizers also means the conjugate base of the acid stabilizer. For example the term xe2x80x9cadipic acidxe2x80x9d means adipic acid and its conjugate base. Stabilizers can be used alone or in combination and significantly decrease the rate at which oxidizing agents such as hydrogen peroxide decomposes.
It is desirable to maintain the pH of the CMP slurry of this invention within a range of from about 2 to about 11, and preferably between from about 2 to about 8 in order to facilitate control of the CMP process. Slurry handling problems and substrate polishing quality problems are encountered when the pH of the CMP slurry of this invention is too low, e.g., less than 2. The pH of the CMP slurry of this invention may be adjusted using any known acid, base, or amine. However, the use of an acid or base that contains no metal ions, such as ammonium hydroxide and amines, or nitric, phosphoric, sulfuric, or organic acids is preferred to avoid introducing undesirable metal components into the CMP slurry of this invention.
The composition of this invention may be produced using any techniques known to those skilled in the art. In one method, the oxidizing agent and solid catalyst are mixed into an aqueous medium, such as deionized or distilled water, at pre-determined concentrations under low shear conditions until the oxidizer is completely dissolved and the solid catalyst is dispensed in the medium. A concentrated liquid dispersion of the metal oxide abrasive, such as fumed silica or alumina, is added to the chemical mechanical composition and diluted to the desired loading level of abrasive in the final CMP slurry. In addition, the solid catalyst and any additives such as one or more stabilizers, may be added to the slurry by any method that is able to incorporate solid catalyst compounds of this invention in an aqueous solution.
The compositions of the present invention may be supplied as one package system (at least one oxidizing agent, at least one solid catalyst, optional abrasive, and optional additives in a stable aqueous medium). To avoid possible composition degradation, however, it is preferred that at least a two package system is used where the first package comprises at least one oxidizing agent, and the second package comprises at least one solid catalyst. Optional components, such as an abrasive and any other optional additives may be placed in either the first container, the second container or in a third container. Furthermore, the components in the first container or second container may be in dry form while the components in the corresponding container are in the form of an aqueous dispersion.
A multi-package chemical mechanical composition or CMP slurry may be used with any standard polishing equipment appropriate for use on the desired metal layer of the wafer. The multi-package system includes one or more CMP components in aqueous or dry form in two or more containers. The multi-package system is used by combining the components from the various containers in the desired amounts to give CMP slurries comprising at least one oxidizing agent, at least one solid catalyst, and an optional abrasive in amounts described above.
Another aspect of this invention are catalyst containing polishing pads including a polishing pad substrate and at least one heterogeneous solid catalyst, preferably a non-metallic solid catalyst. The polishing pad substrate may be any type of polishing pad substrate that is useful for CMP. Typical polishing pad substrates available for polishing applications, such as CMP, are manufactured using both soft and/or rigid materials and may be divided into at least four groups: (1) polymer-impregnated fabrics; (2) microporous films; (3) cellular polymer foams and (4) porous sintered substrates. For example, a pad substrate containing a polyurethane resin impregnated into a polyester non-woven fabric is illustrative of the first group. Polishing pad substrates of the second group consist of microporous urethane films coated onto a base material which is often an impregnated fabric of the first group. These porous films are composed of a series of vertically oriented closed end cylindrical pores. Polishing pad substrates of the third group are closed cell polymer foams having a bulk porosity which is randomly and uniformly distributed in all three dimensions. Polishing pad substrates of the fourth group are open-celled, porous substrates having sintered particles of synthetic resin. Representative examples of polishing pad substrates useful, in the present invention, are described in U.S. Pat. Nos. 4,728,552, 4,841,680, 4,927,432, 4,954,141, 5,020,283, 5,197,999, 5,212,910, 5,297,364, 5,394,655, 5,489,233, and 6,062,968 each of the specifications of which are incorporated herein in their entirety by reference.
The polishing pad of this invention includes at least one non-metallic solid catalyst, as described above. The non-metallic solid catalyst should be present in the polishing pad in an amount ranging from 0.005-20.0 wt. %. Preferably, the non-metallic solid catalyst is present in the polishing pad in an amount ranging from about 1.0-10.0 wt. %.
Non-metallic solid catalysts may be incorporated into a polishing pad substrate by any method known in the art for incorporating a material into or onto a polymeric substrate. Examples of methods for incorporating the non-metallic solid catalysts into a polishing pad substrate include encapsulation, incorporation of time release catalyst particles into the polishing pad substrate, impregnation, creating a polymer/catalyst complex, incorporating the catalyst as a small molecule into the polishing pad substrate polymer matrix, or any combinations of these methods.
In one method for incorporating the catalyst into a polishing pad substrate, the catalyst maybe encapsulated within void spaces created during the manufacture of the pad substrate polymer matrix as an insoluble, semi-soluble or soluble material. Alternatively, the catalyst may be incorporated into the polymer precursor before it is polymerized into a matrix thereby allowing the pad substrate polymer to integrate and secure the catalyst in the polymer matrix.
In another alternative, the catalyst can be incorporated into a pad substrate after the pad substrate has been manufactured. One method for incorporating the catalyst into a premanufactured pad substrate is by impregnating the pad with a catalyst using conventional impregnation techniques. Impregnation can be accomplished by preparing a catalyst solution and applying the catalyst solution to the polishing pad and thereafter drying the polishing pad. One advantage of the impregnation technique is that the pads can be reimpregnated with catalyst once the catalyst in the catalyst containing polishing pad has been depleted to the point where it is no longer effective. This way, the polishing pad can be reused until the polishing pad substrate fails.
Catalyst containing polishing pads of this invention are used to planarize metal, semicontuctor or insulator layers during the manufacture of integrated circuits. The catalyst containing polishing pads are associated with a polishing machine and then brought into contact with the surface being polished. Typically, an aqueous polishing solution or composition comprising an oxidizing agent will be applied to the pad or directly to the metal layer where its reaction with the metal surface is catalyzed by the catalyst in the catalyst containing polishing pad. As mentioned above, an abrasive may optionally be incorporated into the oxidizing agent solution or an abrasive may be incorporated into the catalyst containing polishing pad. In addition, other polishing composition additives such as film forming agents, complexing agents, corrosion inhibitors, surfactants and the like may be incorporated into the polishing composition. Once the aqueous polishing composition is directed to the interface between the polishing pad and the substrate being polished, the catalyst containing polishing pad is moved in relationship to the substrate layer to planarize the substrate layer. When the planarization is complete the catalyst containing polishing pad is removed from contact with the substrate surface.
The solid catalysts used in the polishing pads and polishing compositions of this invention are generally most effective when used in chemical mechanical polishing processes. However, it has been determined that the preferred photoactive solid catalysts exhibit improved metal polishing properties and specifically improved titanium polishing rates when the solid catalyst used is photoactive. The photoactive solid catalysts typically are activated by light energy in the UV wavelength (from about 1-800 nm) at a wattage greater than 1 xcexcw/cm2 which causes the photoactive solid catalyst to be excited to a conducting band of the selected photoactive solid catalyst. This reaction will create more reactive sites on the surface on the catalyst to facilitate the formation of activated oxidizing species on surface on in solution.
When using the preferred photoactive solid titania catalysts, the UV light used to excite the solid catalyst emits in a wavelength from about 200-400 nm at a wattage greater than about 20,000 xcexcw/cm2. An Example of useful UV light source is an UVP high intensity long wave lamp manufactured by Black-Ray having a wattage of 27,100 xcexcw/cm2. The wavelengths useful for activating the preferred energy activated solid catalysts lie within the range of the wavelength of light emitted by ultraviolet light sources. Therefore, when the preferred energy activated solid catalyst are used in compositions of this invention, they may be activated with an ultraviolet light source. The photoreaction of the photoactivated catalyst is essentially instantaneous. When on, UV light will enhance the activity of the photoactivated catalyst and when the UV light is off, the catalyst will return quickly to its previous level of reactivity. It is preferred that the UV light is on continuously when enhanced catalyst activity is desired. In addition, the level of xe2x80x9cenhancementxe2x80x9d catalyst activity is influenced by the intensity or power output which is typically measured in watts. The UV light wattage can be adjusted to control the level of catalyst activity enhancement desired at the preferred wavelengths. Changing the UV light wavelength will also influence the efficiency of the catalyst photoactivation.
The ability to activate the photoactive solid catalyst containing compositions of this invention allows the compositions and polishing pads of this invention to be used to polish substrates including multiple layers or portions of metallization. For example, polishing compositions and polishing pads including photoactivated solid catalyst of this invention are useful for polishing substrates including both titanium and aluminum metal portions. The photoactive solid catalyst containing composition is applied to a substrate in order to polish the aluminum portion prior to activating the photoactivated solid catalyst. Prior to activation, the polishing compositions of this invention exhibit a high aluminum polishing rate. Once the polishing of the aluminum substrate portion is complete, the preferred photoactivated solid catalysts are activated with an ultraviolet light source and the titanium layer is polished. Upon activation, the preferred catalysts activates to help convert the oxidizing agent into activated form. This activated form of the oxidizing agent may be peroxy-type complexes on the surface of the solid catalyst or it may be hydroxy radicals in solution. What form the activated oxidizing agent takes is not well understood. However, what is known is that the activated oxidizing agent species are more aggressive towards certain metal layers such as titanium which improves titanium polishing rates.
When the preferred photoactivated non-metallic solid catalyst is incorporated into a polishing pad, the catalyst containing polishing pad may be activated with UV light before, and/or during and/or after polishing a semiconductor substrate with the polishing pad. The catalyst containing polishing pad of this invention may be activated with UV light intermittently, or continuously. Furthermore, the photoactivated non-metallic solid catalyst may also be useful in pad reconditioning. Pad reconditioning becomes necessary after multiple polishing pad uses. Reconditioning is typically a mechanical procedure in which the surface of the polishing pad is roughened to restore polishing pad polishing efficiency. The polishing pads of this invention can be reconditioned by exposing the catalyst containing polishing pads to UV light for a period of time sufficient to allow the catalyst to alter the surface characteristics of the polishing pad in order to improve the polishing pad polishing efficiencey. Catalysts useful for reconditioning the polishing pad surface not limited to non-metallic solid catalyst but may be any photoactivated solid catalyst that can be incorporated into the polishing pad polymer matrix.

CMP polishing pad including a solid catalyst