JP2004111940A - Polishing pad, polishing apparatus and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad having electrical conductivity for reducing a dishing and recesses after polishing in chemical-mechanical polishing, to which electrolytic polishing of a device wafer having a metal wiring film is added, and to provide a polishing apparatus and a polishing method using the polishing pad. <P>SOLUTION: The polishing pad 12 possessing electrical conductivity is obtained by uniformly dispersing an electrically conductive paste material in a resin material for a polishing-pad base member, and molding the resultant material to make a unified body. The polishing apparatus and the method of polishing using the polishing pad perform polishing by setting the electrically conductive polishing pad 12 in the polishing apparatus 10, applying a voltage between the wafer W and the polishing pad 12, and forming a narrow electrode-gap between the wafer W and the polishing pad 12 to work an electrolytic action selectively even to convex parts having extremely small steps on the wafer surface. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a polishing pad, a polishing apparatus and a polishing method using the same, and more particularly to a polishing pad having conductivity and a wafer polishing apparatus and a polishing method by chemical mechanical polishing (CMP) added with an electrolytic action.

In recent years, with the development of semiconductor technology, finer design rules and multi-layer wiring have been developed, and wafers have become larger in diameter in order to reduce costs. Due to such miniaturization of the design rule, the depth of focus of the stepper in the lithography process is becoming increasingly shallow, and a prescribed wiring width cannot be accurately obtained due to fine irregularities on the wafer surface.

Therefore, a surface flattening process has been performed for each wiring layer. A chemical mechanical polishing (CMP) apparatus is used for the planarization. This is a method of polishing a wafer by a combined action of chemical action and mechanical action by pressing the surface of the wafer to be flattened against a rotating polishing cloth while applying slurry mixed with fine abrasive grains and chemicals, especially In recent years, flattening of metal films such as Cu wiring and Al wiring has been studied.

Conventionally, in the case of CMP for flattening a wiring material such as a Cu wiring or an Al wiring, a phenomenon such as dishing or recess in which a metal wiring portion is excessively polished with respect to an insulating portion occurs, which has been a problem. The occurrence of the dishing or the recess significantly reduces the wiring cross-sectional area at the time of device fabrication, thereby increasing the resistance of the portion and causing a failure. It is considered that the dishing or the recess is caused by deformation of the polishing pad.

(5) In the Cu damascene process in which Cu is buried in a contact hole or a trench of a wiring, the state of the film thickness distribution of Cu before CMP is as shown in FIG. Since the Cu film is formed uniformly with respect to the shape of the groove previously formed on the oxide film, the surface of the Cu film is not a completely flat surface, but the unevenness of the initial step corresponds to the groove shape of the base. Exists. In the conventional polishing method, the initial step cannot be completely flattened due to minute deformation of the polishing pad, and as a result, it is considered that dishing or a recess remains as shown in FIG.

Further, in CMP for removing a conductive material film such as Cu, a voltage is applied between a polishing film-forming wafer and a polishing platen in order to improve polishing removal efficiency and reduce surface roughness. An electrolytic CMP apparatus has been proposed in which an electrolytic action is performed by applying an electric field.

Here, the electrolytic action will be described. By applying a voltage between the wafer and the polishing pad, a potential difference occurs between the two. This potential difference induces the transfer of electrons between the wafer as the sample and the slurry as the electrolyte, and Cu on the surface of the wafer as the anode becomes Cu → Cu ²⁺ + 2e ⁻ , and is ionized and dissolved into the slurry. Here, this is defined as an electrolytic action. Generally, it is also called electrolytic elution.

In this case, since the polishing pad is an insulating material such as a resin, an electrode gap for electrolytic polishing is formed between the polishing platen and the sample, and usually has an electrode equivalent to the thickness of a polishing pad having a thickness of 1 mm to 3 mm. There is always a gap between them. Usually, the initial step of the wafer for flattening the Cu film is on the order of 0.1 μm, so that an electric field difference that eliminates the unevenness of the initial step may be generated in the gap between the electrodes of the order of several mm. It was difficult, and the protrusions could not be selectively polished.

Further, as compared with a conventional polishing pad made of an insulating material, a polishing pad having a polishing layer made of a syntactic foam containing conductive fine particles is disclosed as a polishing pad containing a conductive material (for example, Patent Reference 1).
JP 2000-216121 A

However, since the polishing pad described in Patent Document 1 aims to prevent clogging during polishing and stabilize the polishing rate, the amount of the conductive material added is small, and the conductivity is low. However, even when used in the above-described electrolytic polishing, the convex portions could not be selectively polished.

The present invention has been made in view of such circumstances, and a chemical mechanical polishing of a device wafer having a metal wiring film to which an electrolytic action is added (hereinafter, chemical mechanical polishing to which an electrolytic action is added is referred to as electrolytic CMP). In the above, the gap between the electrodes for electrolytic polishing is extremely narrowed so that the convex portion on the sample surface has an extremely large electric field difference as compared with the concave portion. In this way, by giving a difference in the degree of electric field concentration of the convex portion compared to the concave portion, selective polishing is advanced to the convex portion to eliminate a step on the sample surface and reduce dishing and recess after polishing is completed. The purpose is to let them. Another object of the present invention is to provide a polishing pad having conductivity for that purpose, a polishing apparatus and a polishing method using the same.

In order to achieve the above object, an invention according to claim 1 is a polishing pad of a polishing apparatus that presses a wafer against a polishing pad while supplying a slurry to flatten the surface of the wafer. It is characterized in that a material having conductivity is used as a material, and the material is formed to have conductivity.

According to a second aspect of the present invention, there is provided a polishing pad of a polishing apparatus for pressing a wafer against a polishing pad while supplying a slurry to flatten the surface of the wafer, wherein the polishing pad is formed using conductive fibers. This is characterized by having conductivity.

Further, the invention according to claim 3 is a polishing pad of a polishing apparatus for flattening the surface of the wafer by pressing the wafer against the polishing pad while supplying the slurry, the cloth containing conductive fibers. It is characterized by having conductivity by being composed of a bonding base material.

According to the first, second or third aspect of the present invention, a polishing pad having a uniform conductivity can be obtained. These polishing pads can be suitably used especially in electrolytic CMP.

The invention according to claim 4 is a polishing apparatus that presses a wafer against a polishing pad while supplying a slurry, and planarizes the surface of the wafer. Voltage applying means for applying a voltage therebetween, wherein the wafer is polished while performing an electrolytic action on the surface of the wafer.

According to the fourth aspect of the present invention, since a narrow inter-electrode gap is formed between the wafer and the polishing pad having conductivity, an electric field is selectively applied to the very small step on the surface of the wafer. It is possible to concentrate and eliminate a step.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the conductive polishing pad is attached to a polishing platen using a conductive double-sided tape.

According to the fifth aspect of the present invention, the polishing pad can be easily replaced while maintaining the conduction between the polishing pad and the polishing platen.

According to a sixth aspect of the present invention, there is provided a polishing method for flattening a surface of a wafer by pressing a wafer against a polishing pad while supplying a slurry. The method is characterized in that a pad is used and a voltage is applied between the wafer and the polishing pad to polish the wafer while performing an electrolytic action.

According to the invention of claim 6, a narrow inter-electrode gap is formed between the wafer and the polishing pad having conductivity, and an electrolytic action is selectively performed on a very small stepped portion on the wafer surface. As a result, the step on the wafer surface can be eliminated.

According to a seventh aspect of the present invention, in the sixth aspect, the polishing rate is controlled by controlling the applied voltage.

According to the seventh aspect of the present invention, since the polishing rate is controlled by controlling the voltage applied between the wafer and the conductive polishing pad, it is easy to control the polishing rate.

The invention according to claim 8 is characterized in that, in polishing the surface of the wafer having the conductive material film on the surface according to the invention according to claim 6 or 7, until the irregularities on the surface of the conductive material film are removed. The wafer is polished by a first step of selectively polishing the projections and a second step of polishing the conductive material film until the polishing is completed after the irregularities are removed. .

According to the invention of claim 8, since the protrusions on the surface of the conductive material film are selectively polished in the first step to remove irregularities and then polished in the second step until the polishing is completed, Dishing and recess on the wafer surface after polishing is reduced.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, the voltage applied in the first step is set to be higher than the voltage applied in the second step, so that the protrusion is formed so as to remove the unevenness. Is selectively polished.

According to the ninth aspect of the present invention, the convex portions are selectively electropolished at a high voltage, and then the surface roughness and defects are reduced at a low voltage, so that the unevenness of the wafer can be efficiently removed and the surface scratches can be reduced. And a smooth surface can be obtained.

As described above, the polishing pad of the present invention has a uniform electrical conductivity, and the control of the physical property values is easy. Therefore, according to the polishing pad of the present invention and the polishing apparatus and the polishing method using the same, In electrolytic CMP of a device wafer having a metal wiring film, the polishing pad is made conductive and a narrow inter-electrode gap is formed between the wafer and the polishing pad. In contrast, a step can be eliminated by selectively performing an electrolytic action, and dishing and recess after polishing is completed can be greatly reduced. In addition, since the convexities are selectively electropolished at high voltage and then the surface roughness and defects are reduced at low voltage, the unevenness of the wafer can be efficiently removed, and a smooth surface can be obtained without scratching the surface. Can be.

According to the polishing method of the present invention, an extremely large electric field is applied only to the convex portion by making the polishing pad and the material to be polished such as Cu or the like substantially contact each other at the step convex portion and making the gap between the electrodes almost equal. The polishing pad according to the present invention is required to have conductivity since the polishing pad is generated and the polishing is selectively advanced to improve the step-elimination property.

  First, a polishing pad having conductivity and a method for manufacturing the polishing pad will be described. The polishing pad having conductivity is not particularly limited as long as it contains a material having conductivity, and specifically, a polishing pad having a resin itself using a material having conductivity, a resin, etc. Examples thereof include a material obtained by dispersing a conductive material in a material, and a material formed by using a conductive fiber.

Examples of the resin having conductivity include resins having conductivity such as polypyrrole and polyacetylene.

When the conductive material is dispersed in the resin, a resin or elastomer such as polyurethane, nylon, polyester, polycarbonate, polyvinyl alcohol, polyimide, epoxy, natural rubber, or synthetic rubber can be used as the resin, Examples of the conductive material include carbon black, metal powder, metal oxide powder, carbon nanotube, and the like, and among them, inexpensive carbon black with less metal contamination is preferable. Examples of the polishing pad include those in which a resin in which such a conductive material is dispersed is formed into a sheet, foam, or the like by injection molding, casting, or the like.

The amount of the conductive material in the resin is preferably 1% by mass or more, more preferably 10% by mass or more. If it is less than 1% by mass, the conductivity is low, and it tends to be difficult to obtain sufficient polishing characteristics when used as a polishing pad.

In the case of a polishing pad composed of conductive fibers, the conductive fibers are obtained by melting or wet spinning a fiber-forming resin in which the above-described conductive material is dispersed. And the like. The polishing pad is formed using conductive fibers. However, it is preferable that the polishing pad be a cloth formed using at least a part of the conductive fibers. It is also preferable to use a molded article dispersed in the form.

First, the conductive fiber will be described. As the conductive fiber used in the present invention, the entire fiber may be a fiber-forming resin in which a conductive material is dispersed, or may have a structure such as a core-sheath structure or a sea-island structure, Either the core or the sheath, the sea or the island may be made of a conductive resin. The shape may be a hollow structure or an irregular cross-sectional shape. The fineness and cross-sectional shape of the conductive fiber are not particularly limited, and may be appropriately changed according to the intended use of the polishing pad to be obtained.

Particularly in the case of a hollow shape, it is easy to control the porosity and the like in the pad, and it is also easy to control physical properties such as hardness of the obtained polishing pad, which is preferable. Furthermore, not only does the electric current flow through the conductive fibers, but also when the slurry is supplied, the slurry fills the hollow holes of each single yarn, so that the electric current flows through the slurry. It is preferable because it is possible. Further, the hollow hole is preferable because dust generated by polishing can be removed and retained, and thus effective polishing can be performed.

Here, the hollow ratio of the hollow conductive fiber (refers to the ratio of the area of the hollow portion to the cross-sectional area of the fiber) depends on the single-fiber fineness of the conductive fiber used, but is preferably 5 to 60%. It is preferably from 10 to 40%, and more preferably from 15 to 30%. If the hollow ratio exceeds 60%, the hollow shape may be crushed in the pad making process. If the hollow ratio is less than 5%, the filling of the conductive slurry and the elimination and holding of the polishing debris become insufficient. Not preferred.

Next, as a cloth formed using conductive fibers suitable as the polishing pad of the present invention, a cloth such as a woven or knitted cloth, a nonwoven cloth, or a pile is preferable. In addition, in such a cloth, conductive fibers are used at least in part, and other fibers may be contained as long as the conductive performance is not deteriorated.

Furthermore, it is preferable that the polishing pad of the present invention is composed of a cloth composed of conductive fibers and a bonding substrate. Specifically, the cloth obtained by using the conductive fiber as described above, using a resin or an adhesive as a binding base material, impregnated into the cloth, surface-coated, interlayer-bonded, and the like. No. Examples of resins and adhesives used as the bonding substrate include polyurethane, epoxy, acrylic, phenol, polyester, polyamide, melamine, polyimide, polyvinyl alcohol, polyvinyl chloride, polystyrene, silicone, polycarbonate, polyethylene, polypropylene, and fluorine compounds. Resins and adhesives can be used. Alternatively, a binder fiber may be used as the binding substrate, and a nonwoven fabric or a polishing pad in which the nonwoven fabric is interlayer-bonded together with the conductive fiber and the binder fiber of the binding substrate may be used.

The above-described conductive material may be dispersed in the bonding base material, and the electric resistance value of the polishing pad may be controlled by using the conductive fiber and the conductive material in the bonding base material together.

Also, the polishing pad of the present invention may be a polishing pad in which the conductive fibers are short fibers having a length of several millimeters to several centimeters, and the resulting fibers are floppy-processed pile fabrics. Further, a pile fabric impregnated with a resin or an adhesive such as polyurethane or epoxy as a bonding base material as a binding base material, a surface-coated fabric, and an interlayer-bonded fabric are also preferable. In flocking processing, general electrostatic processing is preferable.Fibers to be implanted are supplied and charged to one side of an electric field where a high voltage is applied, and the other side of the electric field is accelerated and bonded in the direction of a base cloth coated with an adhesive. Hair is implanted on the base cloth by anchoring into the agent. As the adhesive, those similar to those used as the above-mentioned bonding base material are preferable, and as the base cloth, it is preferable to use the above-mentioned nonwoven fabric or woven fabric.

Further, as the polishing pad of the present invention, after impregnating the resin of the binding base material into such a flocky processed pile cloth, the base cloth and unnecessary impregnated resin are removed by polishing or slicing processing, and the short fiber form is contained in the resin. It is preferable that the conductive fiber of the above is present upright. As a result, there are a plurality of upstanding conductive fibers penetrating both the front and back surfaces of the polishing pad, and the conductivity is improved through the conductive fibers.

In such a case, the area ratio of the conductive fiber occupying the pad surface (the ratio of the area of the end of the upstanding conductive fiber appearing on the pad surface to the surface area of the pad) is determined by the electric resistance value of the conductive fiber used. However, from the viewpoint of increasing the amount of electricity, it is preferably 1% or more, more preferably 3% or more, more preferably 7% or more, and suitably 10% or more. When the base fabric and the unnecessary impregnated resin are removed by polishing or slicing, the base fabric to be used may not include conductive fibers.

In order to keep the electric resistance of the entire polishing pad in the range described below, the electric resistance of the conductive fiber used is preferably in the range of 10 ^-10 to 10 ¹⁰ Ωcm, more preferably 10 ^-8 to ¹⁰ Ωcm. ⁸ [Omega] cm, more preferably 10 ^-4 ~10 ⁷ Ωcm, preferably a 10 ^-4 ~10 ² Ωcm.

As the polishing pad of the present invention, by using the conductive fiber as described above, the porosity in the pad is smaller than that when the polishing pad is formed by molding or the like using a conductive resin. This is preferable because it is easy to control the physical properties such as hardness of the obtained polishing pad.

Furthermore, since a polishing pad having a lower electric resistance can be obtained as compared with a conductive polishing pad obtained by dispersing a conductive material in a resin, it is more preferable.

This is because, in the case of a polishing pad formed by molding a resin in which a conductive material is dispersed, since the conductive material in the pad is randomly dispersed, the connection between the conductive materials is low. Only those having a relatively high electric resistance value with respect to the amount of the conductive material added can be obtained. On the other hand, in a polishing pad composed of conductive fibers, the conductive materials are oriented and arranged in the fiber forming step, so that the conductive fibers have very good connection between the conductive materials. For this reason, a polishing pad formed using conductive fibers has an electrical resistance value of two digits or more when obtained under appropriate spinning and stretching conditions, compared to a pad molded from a resin with the same amount of conductive material added. May be better.

In the polishing pad of the present invention having the conductivity described in detail above, since the polishing efficiency is higher when a certain amount of electricity is supplied to the polishing pad, the electric resistance value of the polishing pad is in the range of 10 ⁻¹⁰ to 10 ¹⁰ Ωcm. preferably, more preferably 10 ^-8 to 10 ⁸ [Omega] cm, more preferably 10 ^-4 to 10 ⁷ [Omega] cm, and preferably from 10 ^-4 ~10 ² Ωcm.

The thickness of the polishing pad is preferably 10 mm or less, more preferably 5 mm or less, because if the thickness of the polishing pad is too large, heat and deformation are generated due to electrical loss in the polishing pad. Considering the efficient supply and holding of slurry and chemical liquid to the polishing surface, the surface of the polishing pad should be moderately submicron-level with grooves such as grids and concentric circles, diamond abrasive grains, etc. Irregularities may be provided.

Extruder-type melt extrusion of a nylon 6 master chip in which 35% by mass of carbon black is uniformly dispersed in a nylon 6 resin (a relative viscosity of 1.8 (using 96% sulfuric acid as a solvent, at a concentration of 1 g / dl at a temperature of 25 ° C.)) The undrawn yarn was melted at a spinning temperature of 255 ° C., discharged from a spinneret having 48 spinning holes having a hole diameter of 0.35 mm, and the undrawn yarn was wound at a winding speed of 600 m / min.

Next, the obtained undrawn yarn was supplied to a heat drawing / relaxation heat treatment machine 20 shown in FIG. 6, where drawing and heat treatment were performed. First, the undrawn yarn 21 is drawn by the tension roller 25 through the guide roller 22. Then, heat treatment at the time of stretching is performed by a box-shaped heater 24 provided below the guide roller 22. The stretching is performed between the guide roller 22 and the tension roller 25. The heat treatment device 26 is a device having a saddle type heater 28 and a heating roller 29, and performs a relaxation heat treatment on the drawn yarn. Then, the multifilament yarn that has passed through the heat treatment device 26 is wound by the traveler 27.

At this time, a heat treatment time of 0.12 seconds at a 150 ° C. box heater 24, a stretching tension of 0.39 g / dtex and a relaxation heat treatment time of 170 ° C. at a heat treatment device 26 of 3.8 seconds, a tension of 0.02 g / dtex, The film was drawn at 60% of the maximum draw ratio to obtain a 220 dtex / 48f nylon conductive yarn.

A core-sheath composite fiber obtained by cutting the obtained nylon conductive yarn 220 dtex / 48f to a fiber length of 5 mm and a binder fiber comprising a core of nylon 6 and a sheath of a nylon 6 / nylon 12 copolymer (melting point 140 ° C.) (Core / sheath ratio; core: sheath = 2: 1), using a fiber with a single yarn fineness of 2.2 dtex and a fiber length of 38 mm, mixed at a conductive yarn / binder (mass ratio) = 70/30, and with a dispersant The suspension was dispersed in water, and the suspension was made by wet papermaking to obtain a conductive nonwoven fabric having a basis weight of 250 g / ^{m 2} and a thickness of 800 μm. Further, the obtained conductive nonwoven fabric was heated and pressed between a heated roller at 170 ° C. and a non-heated roller at a pressing pressure of 0.7 kg / cm and a roller speed of 0.5 m / min to obtain a conductive pad. The volume resistivity of the conductive pads was 10 ^3.0 [Omega] cm.

Extruder-type melt extrusion of a nylon 6 master chip in which 35% by mass of carbon black is uniformly dispersed in a nylon 6 resin (a relative viscosity of 1.8 (using 96% sulfuric acid as a solvent, at a concentration of 1 g / dl at a temperature of 25 ° C.)) The undrawn yarn was melted at a spinning temperature of 255 ° C., discharged from a spinneret having 96 spinning holes having a hole diameter of 0.20 mm, and an undrawn yarn was wound at a winding speed of 600 m / min.

  Next, the obtained undrawn yarn is supplied to the hot drawing / relaxation heat treatment machine 20 shown in FIG. 6 described in the first embodiment, and is subjected to a heat treatment time of 0.12 sec. The film was stretched at a relaxation heat treatment time of 3.8 seconds in a heat treatment apparatus 26 of 39 g / dtex and 170 ° C., a tension of 0.02 g / dtex, and 60% of the maximum draw ratio to obtain a 220 dtex / 96f nylon conductive yarn.

The obtained nylon conductive yarn 220dtex / 96f was woven as a pile tape having a pile density of 1,000 yarns / 2.54 cm, a pile length of 7 mm, and a cloth width of 350 mm, and was taken with 500 parts by mass of methyl ethyl ketone and Takenate L-2695 (polyurethane prepolymer, 100 parts by mass of Mitsui Takeda Chemical Co., Ltd.) and 18 parts by mass of iharacuamine (MOCA, manufactured by Ihara Chemical Co.) are dipped in a solution and dried at 120 ° C. for 24 hours to obtain a polyurethane resin / conductive fiber composite material. Got. This was sliced with a diamond knife to produce a polishing pad having a thickness of 1 mm. The volume resistance value of the obtained conductive pad was 10 ^7.0 Ωcm.

A polishing pad having a thickness of 1 mm was produced by injection molding 35 mass% of carbon black uniformly dispersed in 100 mass parts of Elastran S90A (thermoplastic polyurethane elastomer, manufactured by BASF Polyurethane Elastomers). The volume resistivity of the obtained conductive pads was 10 ^4.0 [Omega] cm.

A polishing pad having a thickness of 1 mm was produced by injection-molding 48 parts by mass of carbon black uniformly dispersed in 100 parts by mass of Elastran S90A (thermoplastic polyurethane elastomer, manufactured by BASF Polyurethane Elastomers). The volume resistivity of the obtained conductive pads was 10 ^2.0 [Omega] cm.

Extruder-type melt extrusion of nylon 6 master chips in which 40% by mass of carbon black is uniformly dispersed in nylon 6 resin (relative viscosity: 1.8 (concentration: 1 g / dl using 96% sulfuric acid as a solvent, temperature: 25 ° C.)) The undrawn yarn was melted at a spinning temperature of 255 ° C., discharged from a spinneret having 48 spinning holes having a hole diameter of 0.35 mm, and an undrawn yarn was wound at a winding speed of 400 m / min.

  Next, the obtained undrawn yarn is supplied to the heat drawing / relaxation heat treatment machine 20 shown in FIG. 6 described above, and the heat treatment time is 0.12 seconds in the box-shaped heater 24 at 150 ° C., the drawing tension is 0.39 g / dtex and 170. The film was stretched with a relaxation heat treatment time of 3.8 seconds in a heat treatment device 26 ° C., a tension of 0.02 g / dtex, and 60% of the maximum draw ratio to obtain a 1000 dtex / 48f nylon conductive yarn.

The obtained nylon conductive yarn 1000dtex / 48f cut into a fiber length of 2 mm was subjected to electrostatic floppy processing to obtain a pile fabric. At this time, a plain woven polyester fabric was used as a base fabric. The pile fabric was impregnated and cured with a polyurethane resin (HICAST 3400, manufactured by H & K) under reduced pressure, and then heat-treated at 120 ° C. for 1 hour to obtain a polyurethane-impregnated fabric having a thickness of 4 mm. Next, both sides of the polyurethane-impregnated cloth are polished (a sander polisher manufactured by Amitec) to remove unnecessary portions of the base cloth and the polyurethane resin, and the thickness is set to 1 mm so that conductive fibers appear on both front and back surfaces. Conductivity between both sides of the pad was secured. The area occupied by the conductive fibers in the obtained conductive pad was 7%, and the volume resistivity was 10 ^−2.0 Ωcm.

Extruder-type melt extrusion of nylon 6 master chips in which 40% by mass of carbon black is uniformly dispersed in nylon 6 resin (relative viscosity: 1.8 (concentration: 1 g / dl using 96% sulfuric acid as a solvent, temperature: 25 ° C.)) Melted at a spinning temperature of 255 ° C., discharged from a spinneret having 48 spinning holes with a hole diameter of 0.35 mm, and wound up at 400 m / min. A hollow nylon conductive yarn (having a hollow ratio of 20%) having a circular cross section was obtained.

  Next, the obtained undrawn yarn is supplied to the heat drawing / relaxation heat treatment machine 20 shown in FIG. 6 described above, and the heat treatment time is 0.12 seconds in the box-shaped heater 24 at 150 ° C., the drawing tension is 0.39 g / dtex and 170. The film was stretched with a relaxation heat treatment time of 3.8 seconds in a heat treatment device 26 ° C., a tension of 0.02 g / dtex, and 60% of the maximum draw ratio to obtain a 1000 dtex / 48f nylon conductive yarn.

The obtained nylon conductive yarn 1000dtex / 48f cut into a fiber length of 2 mm was subjected to electrostatic floppy processing to obtain a pile fabric. At this time, a plain woven polyester fabric was used as a base fabric. The pile fabric was impregnated and cured with a polyurethane resin (HICAST 3400, manufactured by H & K) under reduced pressure, and then heat-treated at 120 ° C. for 1 hour to obtain a polyurethane-impregnated fabric having a thickness of 4 mm. Next, both sides of the polyurethane-impregnated cloth are polished (a sander polisher manufactured by Amitec) to remove unnecessary portions of the base cloth and the polyurethane resin, and the thickness is set to 1 mm so that conductive fibers appear on both front and back surfaces. Conductivity between both sides of the pad was secured. The area occupied by the conductive fibers in the obtained conductive pad was 7%, and the volume resistivity was 10 ^−1.5 Ωcm.

Comparative Example 1

A multifilament yarn was obtained and a polishing pad was produced in the same manner as in Example 1 except that a nylon 6 resin containing no carbon black was used. The volume resistivity of the obtained polishing pad was 10 ¹¹ Ωcm.

Comparative Example 2

A polishing pad was produced in the same manner as in Example 3 except that a thermoplastic polyurethane elastomer containing no carbon black was used. The volume resistivity of the obtained polishing pad was 10 ¹¹ Ωcm.

The volume resistance was measured by applying a voltage of 100 V to almost all of the front and back surfaces of the pad in an environment of 20 ° C. and 45% RH to measure the electric resistance. The relative viscosity of the nylon resin was measured at a concentration of 1 g / dl and a temperature of 25 ° C. using 96% sulfuric acid as a solvent.

Next, preferred embodiments of the polishing apparatus and the polishing method according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same members are given the same numbers or symbols.

FIG. 1 is a front view of the polishing apparatus according to the present invention. As shown in FIG. 1, the polishing apparatus 10 includes a polishing platen 11, a polishing pad 12, a polishing head 13, a voltage applying unit 14, a slurry supply pipe 16, and the like. The polishing platen 11 is configured to rotate on its own by driving means (not shown), and a polishing pad 12 is attached to the upper surface thereof via a conductive double-sided tape 15 having an adhesive on both surfaces.

As the polishing pad 12, the conductive pads obtained in [Example 1] to [Example 6] and [Comparative Example 1] and [Comparative Example 2] and pads having poor conductivity were used. The polishing head 13 is for holding the wafer W to be polished and pressing the surface of the wafer W against the polishing pad 12 while rotating, and is rotated by driving means (not shown). A polishing pressure is applied by an airbag (not shown) provided on the polishing pad 12. The wafer W is held on the polishing head 13 by a conductive double-sided tape 15. The metal wiring film formed on the surface of the wafer W extends to the side surface of the wafer W, and is electrically connected to the double-sided tape 15 on the side surface.

The voltage applying means 14 applies a positive potential to the metal wiring film of the wafer W via the double-sided tape 15, and applies the polishing pad 12 from the polishing platen 11 to the negative potential via the double-sided tape 15.

(4) The slurry supply pipe 16 supplies a polishing slurry 17 containing an electrolytic solution to the upper surface of the polishing pad 12. This slurry is interposed between the metal wiring film of the wafer W and the polishing pad 12, so that even when the gap between the electrodes between the metal wiring film and the polishing pad 12 is extremely narrow, both are electrically connected. Has been blocked.

In the present embodiment, the voltage is applied to each of the wafer W and the polishing pad 12 via the conductive double-sided tape. However, the present invention is not limited to this, and other known conductive means may be used. .

Next, the operation of the polishing apparatus 10 configured as described above will be described. First, the surface of the wafer W on which the metal wiring film to be polished is formed is turned down, and the back surface is held by the polishing head 13 via the conductive double-sided tape 15. The voltage applying means 14 applies a negative potential to the conductive polishing pad 12 via the polishing platen 11 and the conductive double-sided tape 15, and applies a wafer via the conductive double-sided tape 15 of the polishing head 13. A positive potential is applied to the metal wiring film formed on W.

In this state, the polishing platen 11 is rotated, and the slurry 17 containing the electrolytic solution is supplied from the slurry supply pipe 16 to the upper surface of the conductive polishing pad 12 attached to the upper surface of the polishing platen 11.

On the other hand, the wafer W held by the polishing head 13 is rotated and pressed against the polishing pad 12 by an air bag provided in the polishing head 13. The metal wiring film formed on the surface of the pressed wafer and the upper surface of the polishing pad 12 have an extremely narrow interval with only a slurry interposed therebetween. Electrolysis acts in the narrow gap between the electrodes, and the metal wiring film is electrolytically eluted and polishing proceeds.

FIG. 2 schematically shows the structure of the surface of a wafer W having a Cu damascene structure, and the situation where the surface is polished. In FIG. 2, the surface to be processed is shown facing upward so that it can be easily perceived. As shown in FIG. 2, in the wafer W, a Ta film as a barrier film is formed in a uniform thickness in a groove formed in an oxide film on a Si substrate, and a Cu of a wiring film is uniformly formed thereon. It is formed with a thickness. Therefore, the surface of the Cu film is not flat, and there is an initial step of about 0.05 to 0.1 μm corresponding to the groove shape of the base.

(4) At the projection of the initial step, the gap between the electrodes and the surface of the polishing pad 12 is very small, and a high electric field is generated. On the other hand, since the gap between the electrodes is larger in the concave portion of the initial step than in the convex portion, the electric field is reduced. Therefore, the polishing rate in this portion is small, and the portion other than the concave portion is selectively polished.

When polishing other than the concave portion is selectively polished and the polishing until the initial step is eliminated is a first step, and when the polishing is completed after the initial step is eliminated is a second step, the first step is as follows. The voltage applied in the step is higher than the voltage applied in the second step, and the convex portion is selectively polished efficiently, and the second step is polished with a low applied voltage to obtain a good surface-free scratch. The voltage applying means 14 is controlled so as to obtain the surface roughness.

FIGS. 3 and 4 show examples of chemical mechanical polishing performed by using the conductive polishing pad 12 and adding an electrolytic action to the wafer W. The table in FIG. 3 shows polishing conditions, and the table in FIG. 4 shows polishing results.

As shown in the table of FIG. 3, a Cu / Ta / Oxide wafer (Cu film thickness 0.2 μm) was subjected to a polishing pressure of 3 psi, a polishing pad rotation speed of 60 rpm, a polishing head rotation speed of 60 rpm, and a slurry flow rate of 150 ml / min. Polishing was performed with a first step applied voltage of 15 V polishing time of 40 sec and a second step applied voltage of 5 V polishing time of 20 sec.

As shown in the table of FIG. 4, the polishing results are shown in Table 1. In Example 1, the surface roughness of the polished surface was determined by using an atomic force microscope (AFM: Atomic Force Microscope) to have a least square surface roughness (Rms) of 0. Least square surface roughness (Rms) was 0.2 nm to 0.3 nm as measured by WYKO TOP03D. The dishing was 200 ° or less, and the polishing rate was 5000 ° / min.

Also, in Example 2, the surface roughness was (Rms) 0.4 nm to 0.5 nm by AFM, (Rms) 0.55 nm to 0.6 nm by WYKO, dishing was 500 ° or less, and the polishing rate was 4500 ° / min. Was.

In Example 3, the surface roughness was (Rms) 0.35 nm to 0.4 nm by AFM, (Rms) 0.4 nm by WYKO, dishing was 300 ° or less, and the polishing rate was 4800 ° / min. In Example 4, the surface roughness was Was 0.1 nm to 0.2 nm for AFM (Rms), 0.2 nm to 0.25 nm for WYKO, dishing was 200 ° or less, and polishing rate was 4600 ° / min.

In Example 5, the surface roughness was (Rms) 0.05 nm to 0.1 nm by AFM, (Rms) 0.2 nm to 0.3 nm by WYKO, the dishing was 150 ° or less, and the polishing rate was 5000 ° / min. The surface roughness was (Rms) 0.1 nm to 0.2 nm by AFM, (Rms) 0.2 nm to 0.3 nm by WYKO, dishing was 100 ° or less, and the polishing rate was 5000 ° / min.

測定 AFM measurement is an evaluation of a 1 μm square area at 500 × 500 measurement points. Further, the measurement by WYKO TOP03D is obtained by magnifying with a 40 × lens, and 250 × 250 points (each point is obtained by averaging a 1 μm square area) of a 250 μm square area by differential interference. .

As shown in the table of FIG. 4, the polishing pad using the polishing pad of the present invention was polished by the conventional electromechanical chemical mechanical polishing using the poorly conductive polishing pad shown in Comparative Examples 1 and 2. In comparison with the results, in the case of Example 1, the surface roughness measured by AFM was about 15 to 40%, and the measurement by WYKO TOP03D was about 22 to 38%. The dishing was also reduced to about 17 to 20%. The polishing rate was about 83-100%.

Also, in the case of Example 2, the surface roughness measured by AFM was about 62 to 100%, and the surface roughness was about 61 to 75% measured by WYKO TOP03D. The dishing was also reduced to 44 to 50%. The polishing rate was 75-90%.

In the case of Example 3, the surface roughness is about 54 to 80% by AFM, about 44 to 50% by TOP03D of WYKO, dishing is reduced to 26 to 30%, and the polishing rate is 80 to 96%. In the case of Example 4, the surface roughness was about 15 to 40% by AFM, about 22 to 31% by TOP03D manufactured by WYKO, the dishing was reduced to 17 to 40%, and the polishing rate was 77 to 92%. %Met.

In the case of Example 5, the surface roughness measured by AFM was about 7.5 to 20%, and the measurement by WYKO TOP03D was about 22 to 38%. The dishing was also reduced to about 13 to 15%. The polishing rate was about 83-100%. Also in the case of Example 6, the surface roughness measured by AFM was about 15 to 40%, and the measurement by WYKO TOP03D was about 22 to 38%. The dishing was also reduced to about 10 to 11.5%. The polishing rate was about 83-100%.

As described above, in the polishing with the electrolytic action using the conductive polishing pad 12 of the present invention, the polishing rate is lower than that of the prior art, but a remarkable effect is exhibited in the surface roughness and dishing. ing.

FIG. 1 is a front view of an electrolytic CMP apparatus according to an embodiment of the present invention. FIG. 4 is a cross-sectional view schematically illustrating a wafer polishing state by the polishing method of the present invention. Table showing polishing conditions of processing examples by the polishing method of the present invention. Table showing polishing results of processing examples by the polishing method of the present invention Sectional view schematically showing a wafer polishing state by a conventional polishing method. Block diagram showing thermal stretching / relaxation heat treatment machine

Explanation of reference numerals

W: wafer, 10: polishing apparatus, 11: polishing table, 12: polishing pad, 13: polishing head, 14: voltage applying means, 15: double-sided tape, 16: slurry supply pipe, 17: slurry

Claims (9)

(4) A polishing pad of a polishing apparatus for flattening the surface of a wafer by pressing a wafer against the polishing pad while supplying slurry, wherein the polishing pad has conductivity. <4> The polishing pad according to claim 1, wherein the polishing pad is formed using conductive fibers. (4) The polishing pad according to (1) or (2), comprising a cloth containing conductive fibers and a bonding substrate. A polishing apparatus for pressing a wafer against a polishing pad while supplying a slurry to flatten the surface of the wafer, wherein a voltage is applied between the polishing pad according to claim 1 and the wafer and the polishing pad. And a voltage applying means for applying a voltage, and polishing the wafer while performing an electrolytic action on the surface of the wafer. The polishing apparatus according to claim 4, wherein the conductive polishing pad is attached to a polishing platen using a conductive double-sided tape. In a polishing method of pressing a wafer against a polishing pad while supplying a slurry, and flattening the surface of the wafer, using the conductive polishing pad according to any one of claims 1 to 3, the wafer and the wafer A polishing method, wherein a voltage is applied between the substrate and a polishing pad to polish the wafer while performing an electrolytic action. 7. The polishing method according to claim 6, wherein the polishing rate is controlled by controlling the applied voltage. In polishing the surface of the wafer having the conductive material film on the surface, a first step of selectively polishing the protrusions until the unevenness on the surface of the conductive material film is removed; 8. The polishing method according to claim 6, wherein the wafer is polished by a second step of polishing until the polishing of the conductive material film is completed after the polishing. 9. The method according to claim 8, wherein the voltage applied in the first step is higher than the voltage applied in the second step to selectively polish the protrusion so as to remove the unevenness. The polishing method as described above.

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