JP2020094257A - Conductive member for electrochemical polishing and sliding ring - Google Patents

Abstract

To provide a conductive member for electrochemical polishing that can be used for a long period of time.SOLUTION: A conductive member for electrochemical polishing of the present invention comprises a ceramic including: an aluminum oxide as a primary component; and at least one of the carbide, nitride, carbonitride, boride, and oxide of titanium as an accessory component.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electropolishing conductive member and a sliding ring.

Conventionally, a Cu film formed on a wafer is made into wiring by polishing (planarizing) using an electrolytic polishing apparatus.

This electrolytic polishing apparatus is an apparatus for flattening a Cu film formed on a wafer and supplied with electricity as an anode by electrolytic action and mechanical polishing.

4A and 4B show an example of a schematic configuration of an electropolishing apparatus provided with a conventional electropolishing conductive member. FIG. 4A is a schematic view, and FIG. 4B is a cross-sectional view taken along line XX'.

Patent Document 1 proposes the following polishing method using the electrolytic polishing apparatus 21 shown in FIG.

First, in the electrolytic bath 22 containing the electrolytic polishing liquid E, the polishing pad 24 attached to the surface plate 23 is rotated to rotate in the same direction, and a wafer W provided with a film made of copper (not shown). Is brought into sliding contact with the polishing pad 24 while being pressed. The wafer W is previously fixed to the wafer chuck 25 from above. The polishing pad 24 rotates together with a surface plate rotating shaft 26 that supports the surface plate 23, and the wafer W rotates together with a wafer rotation shaft 27 that supports the wafer chuck 25.

At this time, a part of the anode current-carrying ring 28 located on the inner circumference side of the polishing pad 24, a part of the anode current-carrying ring 29 located on the outer circumference side of the polishing pad 24, and the outer circumference of the Cu film formed on the wafer W. It is always in sliding contact with a part of the section. Further, the polishing pad 24 has a through hole 24a that allows the electrolytic polishing solution E to pass through along the thickness direction, and a net-like spacer 30 that supports the polishing pad 24 from the film side to the cathode plate 31 through the surface plate 23 to the electrolytic polishing solution. E is arranged to intervene.

Then, by applying a voltage from a power source (not shown), the film is energized through the anode energizing rings 28 and 29, and the electrolytic polishing liquid E passes through the through holes 24a, so that a current required for electrolytic polishing is generated. It flows to the cathode plate 31. Then, the surface of the film subjected to the electrolytic action is oxidized.

Deteriorated layers such as a high electric resistance layer, an insoluble complex coating, and a passivation coating are generated along with the oxidation of the surface of the film. Therefore, when the polishing pad 24 is slidably contacted (wiped) on the surface of the film, the altered layer is removed. As a result, the underlying copper or copper alloy is exposed. When the altered layer is removed, the exposed copper or copper alloy is again subjected to electrolytic action. As described above, by repeating the electrolytic polishing and the wiping, the film formed on the wafer W is flattened and becomes wiring.

It is described that the anode current-carrying rings 28, 29 are made of, for example, graphite, a carbon-based alloy such as a sintered copper alloy, a sintered silver alloy, platinum, copper or the like.

JP, 2003-311540, A

When the anode current-carrying ring is made of these materials, there is a problem that it is not worn for a long period of time due to the significant wear due to electrolytic polishing.

The present invention has been devised to solve the above problems, and an object thereof is to provide a conductive member for electrolytic polishing and a sliding ring that can be used for a long period of time.

The electropolishing conductive member of the present disclosure is made of ceramics containing aluminum oxide as a main component and at least one of titanium carbide, nitride, carbonitride, boride and oxide as a subcomponent.

The electropolishing conductive member of the present disclosure can be used for a long period of time.

FIG. 2A is a schematic view showing an example of a schematic configuration of an electrolytic polishing apparatus provided with a conductive member for electrolytic polishing of the present disclosure, and FIG. FIG. 2 is a schematic view showing a state in which a portion B of the electrolytic polishing apparatus shown in FIG. 1 is enlarged and the object to be polished is in contact with the electrolytic polishing conductive member. FIG. 4 is a cross-sectional view showing an example of an arrangement state of a molded body that is a precursor of the electropolishing conductive member of the present disclosure in the pressure sintering device. FIG. 2A is a schematic view showing an example of a schematic configuration of an electropolishing apparatus including a conventional electropolishing conductive member, and FIG. 3B is a cross-sectional view taken along line XX′.

Hereinafter, the electropolishing conductive member of the present disclosure will be described in detail with reference to the drawings.

1A and 1B show an example of a schematic configuration of an electropolishing apparatus including an electropolishing conductive member of the present disclosure. FIG. 1A is a schematic view, and FIG. 1B is a cross-sectional view taken along line AA′.

FIG. 2 is an enlarged view of a portion B of the electropolishing apparatus shown in FIG. 1, and is a schematic view showing a state where the object to be polished is in contact with the electropolishing conductive member.

The electropolishing apparatus 1 shown in FIG. 1 planarizes a circular film 2 made of copper or copper alloy shown in FIG. 2 formed on a wafer W and energized as an anode by electrolytic action and mechanical polishing. The film 2 is an object to be polished.

The electropolishing apparatus 1 includes a wafer chuck 3 for fixing the film 2 formed on the wafer W downward, a wafer rotation shaft 4 for rotating the wafer chuck 3 in the direction of arrow C, and a vertical movement of the wafer chuck 3. And a pressing means (not shown) for pressing downward.

Further, the electropolishing apparatus 1 is provided with an electrolytic bath 5 for containing the electropolishing liquid E at a position facing the wafer chuck 3. Inside the electrolytic bath 5, a polishing pad 6 for polishing the surface of the film 2 while being immersed in the electrolytic polishing liquid E is installed. The electropolishing liquid E also functions as a slurry containing abrasive grains that mechanically remove the surface of the film 2 that has been altered by oxidation, complex formation, or the like by electrolytic action, for example, abrasive grains made of aluminum oxide.

The polishing pad 6 rotates in the direction of arrow D together with the surface plate rotating shaft 9 that supports the surface plate 8 while being placed on the surface plate 8 via the mesh-shaped spacer 7.

The polishing pad 6 is made of expanded polyurethane, expanded polypropylene, polyvinyl acetal, or the like, and has a through hole 6a through which the electrolytic polishing liquid E is interposed in the thickness direction. Further, the outer peripheral edge of the film 2 contacts and slides on the inner peripheral edge and the outer peripheral edge of the polishing pad 6, and energizes the wafer W as an anode. The anode energizing rings 10a and 10b are elastic members 11 installed on the surface plate 8. (Partially shown in FIG. 2) so as to press the membranes 2 respectively. The side surface and the bottom surface of each of the anode conduction rings 10a and 10b are covered with an insulator 12. The distance between the anode current-carrying rings 10a and 10b is set so that the anode current-carrying rings 10a and 10b contact the outer periphery of the membrane 2.

A cathode plate 13 is provided below the polishing pad 6 so as to face the wafer W via the surface plate 8. The cathode plate 13 is energized via the electropolishing liquid E. The cathode plate 13 has a disk shape and is made of, for example, copper or platinum.

Then, by applying a voltage from a power source (not shown), the film 2 is energized through the anode energization rings 9 and 10, and the electrolytic polishing liquid E passes through the through holes 6a, so that a current required for electrolytic polishing is obtained. Flow into the cathode plate 13. Then, the surface of the film 2 that is subjected to the electrolytic action is oxidized.

Deteriorated layers such as a high electric resistance layer, an insoluble complex coating, and a passivation coating are generated along with the oxidation of the surface of the film 2. Therefore, when the polishing pad 6 is slid on the surface of the film 2, the altered layer is formed. It is removed to expose the underlying copper or copper alloy. When the altered layer is removed, the exposed copper or copper alloy is again subjected to electrolytic action. As described above, by repeating the electrolytic polishing and the wiping, the film 2 formed on the wafer W is flattened and becomes a wiring.

The electrolytic bath 5 is provided with a waste liquid pipe 14 for discharging the used electrolytic polishing liquid E to the outside of the electrolytic bath 5.

The anode current-carrying rings 10a and 10b are an example of the electropolishing conductive member of the present disclosure, and the electropolishing conductive member of the present disclosure contains aluminum oxide as a main component and contains titanium carbide, nitride, or carbonitride. , Ceramics containing at least one of a boride and an oxide as an accessory component. Since such ceramics have high hardness, rigidity, and mechanical strength among the ceramics, wear and shedding due to the sliding contact can be suppressed even in a portion in sliding contact with the film 2, so that such ceramics should be used for a long period of time. You can

Therefore, the frequency of replacement is low when it is repeatedly used over a long period of time. When the anode energization rings 10a and 10b are replaced, it is necessary to adjust the relative positions of these parts. However, since the replacement frequency is low, the frequency of this operation is low and the replacement work when used for a long period of time. The time required for can also be reduced.

Further, when the electropolishing conductive member is made of the above-mentioned ceramics, it is non-magnetic. Therefore, even if the electropolishing liquid E is discharged from the electrolytic bath 6 through the waste liquid pipe 14 and then washed and dried, it remains in the atmosphere. Since it becomes difficult to adsorb the floating magnetic dust, the dust is unlikely to be damaged by the dust. Moreover, since such ceramics have high hardness and are unlikely to be shed during sliding, damage to the film due to shedding can be suppressed.

Further, since the above-mentioned ceramics have higher conductivity than, for example, silicon carbide-based ceramics known to exhibit semiconductivity, they can be easily processed into a complicated shape by electric discharge machining.

Here, the main component in the ceramics means a component having a content of 50% by mass or more among the components constituting the ceramics. In the electropolishing conductive member of the present disclosure, the content of aluminum oxide is, for example, 50% by mass or more and 80% by mass or less, and at least any of titanium carbide, nitride, carbonitride, boride, and oxide. (Hereinafter, these are referred to as titanium compounds), the total content is more than 20% by mass and less than 50% by mass.

Further, in the ceramic constituting the electropolishing conductive member of the present disclosure, the total content of titanium compounds may be 30% by mass or more and 40% by mass or less. When the total content of titanium compounds is 30% by mass or more, a ceramic having high conductivity can be obtained, and electric discharge machining such as wire electric discharge machining or single-sided electric discharge machining can be facilitated. A shaped electropolishing conductive member can be manufactured with less labor. On the other hand, when the total content of titanium compounds is 40 mass% or less, generation of minute pores (for example, pores having a diameter of 100 nm to 500 nm) inside the ceramic can be suppressed in the sintering step. .. Therefore, graining is less likely to occur during processing after sintering, such as cutting, grinding, and polishing. When the total content of titanium compounds is within the above range, it is possible to obtain a conductive member for electropolishing which is difficult to shed and has high fracture resistance.

Here, the composition of the components contained in the ceramics can be identified by using an X-ray diffractometer. Moreover, the amount of each element contained in the ceramics can be determined by a fluorescent X-ray analyzer or an ICP (Inductively Coupled Plasma) emission spectroscopy analyzer. When the components identified by the X-ray diffractometer are aluminum oxide and titanium carbide, the aluminum obtained by a fluorescent X-ray analyzer or an ICP (Inductively Coupled Plasma) emission spectrometer is an oxide (Al ₂ O ₃ ). In addition, titanium may be converted into carbide (TiC).

When the components identified by the X-ray diffractometer are aluminum oxide and titanium nitride, aluminum may be converted into oxide (Al ₂ O ₃ ) and titanium may be converted into nitride (TiN). When the identified component is titanium carbonitride (TiCN) or titanium oxide (TiO ₂ ), the conversion may be performed by the same method.

Further, when the ceramic constituting the electropolishing conductive member of the present disclosure contains titanium carbide as an accessory component, the titanium carbide has a composition formula of TiCx (where x=0.95 to 0.99). May be When the number of atoms x is in this range, the bond between Ti and C becomes a covalent bond having a metal-bonding property, and the toughness is increased, so that the wear becomes more difficult.

The number of atoms x may be determined by energy dispersive X-ray spectroscopy (EDS) using a transmission electron microscope (TEM).

Further, the ceramic constituting the electropolishing conductive member of the present disclosure may contain at least one of ytterbium, yttrium, and dysprosium as an oxide. When the oxide of at least one of ytterbium, yttrium, and dysprosium (hereinafter, these oxides are referred to as rare earth element oxides) is included, the rare earth element oxide has a high sintering promoting action, and Since it is high, the mechanical strength can be increased.

In particular, the total content of rare earth element oxides may be 0.01% by mass or more and 1% by mass or less, and particularly preferably 0.06% by mass or more and 0.2% by mass or less. Rare earth oxides
Since the sintering promoting action is high, if the total content of rare earth element oxides is 0.06 mass% or more, the density becomes higher, and therefore the mechanical strength can be made higher. On the other hand, when the total content of the rare earth element oxides is 0.2% by mass or less, the rare earth elements are less likely to segregate, so that the risk of shedding due to this segregation is suppressed, and for electrolytic polishing with higher defect resistance. A conductive member can be obtained.

The ceramic constituting the electro-polishing conductive member of the present disclosure may contain at least one of nickel, cobalt, and molybdenum.

These elements can firmly bond the crystal particles of the titanium compound, and when a part of these elements is oxidized, the wettability between the element and aluminum oxide is improved, so that the mechanical strength is increased. It is possible to suppress the chipping caused by grinding.

In the ceramic constituting the electropolishing conductive member of the present disclosure, the surface layer portion may have a higher density than the central portion in the thickness direction. With such a configuration, the surface layer portion has a relatively higher density, so that the progress of wear is suppressed. Further, since the central portion having a larger volume than the surface layer portion has a lower density, the whole ceramic becomes lighter, and the rigidity of the surface plate 8 can be maintained for a long period of time.

The surface layer portion is a region in the vicinity of the sliding contact surface with the object to be polished. It should be noted that the area in the vicinity of the surface located on the side opposite to the sliding contact surface may have a higher density than the central portion. If both the area near the sliding contact surface and the area near the opposite surface have a higher density than the central portion, the warp of the electropolishing conductive member can be reduced. The difference in density between the central portion and the surface layer portion is preferably 0.004 g/cm ³ or more, for example.

When the electropolishing conductive member has a substrate shape or an annular shape, the surface layer portion is, for example, a region within 2 mm from the main surface on the sliding contact surface side with the object to be polished, and the central portion is electropolishing conductive material. It is a region excluding a region within 2 mm from both main surfaces of the member.

Here, the density may be obtained in accordance with JIS R 1634-1996, and the apparent density may be compared.

The sliding ring of the present disclosure may be made of the electropolishing conductive member described above.

When the sliding ring of the present disclosure is made of such a conductive member for electrolytic polishing, it has high durability and can be used for a long period of time.

Further, in the sliding ring of the present disclosure, one of the main surfaces is a sliding contact surface with the object to be polished, and a cutting level at a load length ratio of 25% in the roughness curve of the sliding contact surface, The cutting level difference (Rδc) in the roughness curve, which represents the difference from the cutting level at the load length ratio of 75% in the roughness curve, may be 1 μm or less.

The load length rate Rmr is, as shown in the following formula (1), extracted from the roughness curve specified in JIS B0601:2001 by the reference length L in the direction of the average line, and the extracted portion The ratio of the sum of the cutting lengths η1, η2,..., ηn (load length ηp) obtained when the roughness curve of No. 1 is cut at a cutting level parallel to the peak line to the reference length L in percentage. These are the values shown, and show the surface texture in the height direction and in the direction perpendicular to this height direction.

Rmr=ηp/L×100 (1)
ηp: η1 + η2 +... + ηn
The cutting level C (Rrmr) corresponding to each of the two types of load length ratios corresponding to the load length ratio Rmr, and the cutting level difference (Rδc) representing the difference between these cutting levels C (Rrmr) are also included. , The surface height direction and the surface texture in the direction perpendicular to this height direction. When the cutting level difference (Rδc) is large, the unevenness of the surface to be measured is large, but when it is small, it can be said that the unevenness of the surface is small and relatively flat.

When the cutting level difference (Rδc) is 1 μm or less, even when the sliding ring makes sliding contact with the object to be polished such as the film 2, the initial wear of the sliding surface can be reduced.

In particular, the cutting level difference (Rδc) may be 0.5 μm or more and 0.9 μm or less.

When the cutting level difference (Rδc) is in this range, it is possible to reduce the initial wear of the sliding contact surface and suppress the adhesion that is likely to occur in the initial movement of the sliding contact.

Next, an example of a method for manufacturing the electropolishing conductive member of the present disclosure will be described.

First, the case where the accessory component is a carbide of titanium will be described.

Powders of aluminum oxide, titanium dioxide, and titanium carbide are prepared, and the ratio of each powder in the total 100 mass% of these powders is 55 mass% or more and 75 mass% or less of aluminum oxide, and 0.2 mass% or more of titanium dioxide. The balance is 10% by mass or less, and the balance is titanium carbide. In order to obtain ceramics having a titanium carbide content of 30% by mass or more and 40% by mass or less, aluminum oxide is 60% by mass or more and 70% by mass or less, titanium dioxide is 0.2% by mass or more and 10% by mass or less, and the balance is May be titanium carbide. Here, titanium dioxide (TiO ₂ ) functions as a sintering aid, and the reaction formula is changed by a trace amount of carbon monoxide (CO) contained in the firing atmosphere such as argon, helium, neon, nitrogen, or vacuum in the firing step. As shown in (1), it is reduced to titanium monoxide (TiO). Titanium monoxide (TiO) forms a solid solution with titanium carbide (TiC) to newly generate TiC _x O _y (x+y<1 and x>>y) as shown in the reaction formula (2). In addition, x=0.85-0.9 and y=0.1-0.15.

TiO ₂ +CO → TiO+CO ₂ (1)
TiO+TiC→TiC _x O _y (x+y<1 and x>>y) (2)
The density of the produced TiC _x O _y varies depending on the solid solution amount y of titanium oxide, and when the solid solution amount y is 0.15, the density of the ceramics becomes maximum.

Most of titanium dioxide added as a sintering aid changes to TiC _x O _y . In the range of x=0.85 to 0.9 and y=0.1 to 0.15, minute pores generated inside due to solid solution of titanium oxide in titanium carbide, for example, the diameter is 100 to 500 nm. Generation of pores can be reduced, and aggregation of these pores can also be suppressed.

Next, the case where the accessory component is at least one of titanium nitride, carbonitride, and boride will be described.

An aluminum oxide powder and a titanium compound powder selected from at least one of titanium nitride, carbonitride and boride are prepared, and the ratio of each powder in the total 100% by mass of these powders is aluminum oxide. 50 mass% or more and 86 mass% or less and the balance titanium compound. Instead of the titanium carbonitride powder, titanium carbide powder and titanium nitride powder may be used. Titanium nitrides, carbides, carbonitrides and borides are
For example, titanium nitride, titanium carbide, titanium carbonitride, and titanium boride.

These powders are wet-mixed using a barrel mill, a rotary mill, a vibration mill, a colloid mill, a bead mill, an attritor, a high speed mixer or the like, and pulverized into a slurry. In order to obtain a ceramic containing a rare earth element oxide, the total content of the rare earth element oxide powders may be added, for example, from 0.06% by mass to 0.2% by mass. For the wet mixing and pulverization of the powder, for example, beads for pulverization having a diameter of 2 mm or less may be put into a bead mill.

A molding aid such as a binder or a dispersant is added to the crushed powder and mixed, and then granulated by using, for example, a tumbling granulator, a spray dryer or a compression granulator to obtain granules. ..

Then, the obtained granules are molded by a molding means such as dry pressure molding, cold isostatic pressing, etc. to obtain, for example, a ring-shaped molded body, which is then placed in a pressure sintering apparatus.

FIG. 3 is a cross-sectional view showing an example of an arrangement state of a molded body, which is a precursor of the electropolishing conductive member of the present disclosure, in the pressure sintering device.

A dense carbon sheet 16 is placed on both sides of the molded body 15, and a graphite spacer 17 is placed on both sides of the carbon sheet 16 so as to be in a stacked state. By disposing the dense carbon sheet 16 in contact with both main surfaces of the molded body 15, carbon dioxide (CO ₂ ) generated by reduction of TiO ₂ in the firing step does not easily flow from the inside of the ceramic toward the surface layer portion. Therefore, it is possible to obtain a ceramic having a higher density in the surface layer portion than in the central portion in the thickness direction, and the difference in density can be 0.004 g/cm ³ or more, for example.

On the other hand, in order to suppress the difference in density between the central portion and the surface layer portion of the ceramics, a porous carbon sheet 16 is contacted with both sides of the molded body 15 and a graphite spacer 17 is contacted with both sides of the carbon sheet 16. Place them in a stack. By placing the porous carbon sheets 16 in contact with both main surfaces of the molded body 14, carbon dioxide (CO ₂ ) generated by reducing TiO ₂ in the firing step is easily discharged, and the surface layer portion and the inside of the ceramics are discharged. It is possible to control the difference in the density at 0.004 g/cm ³ or less.

After such arrangement, ring-shaped firing is performed by pressure sintering in an atmosphere of argon, helium, neon, nitrogen, vacuum or the like at a sintering temperature of 1400° C. or more and 1700° C. or less and a pressing force of 30 MPa or more. It is possible to obtain a ceramic that is a united body.

Here, by setting the temperature to 1400 to 1700° C., it is possible to suppress the abnormal grain growth of the titanium compound crystal particles while appropriately dispersing the titanium compound crystal particles without causing insufficient sintering. You can Further, when the pressure applied in the pressure sintering is 30 MPa or more, the densification of the ceramics can be promoted and the mechanical strength required for the electropolishing conductive member can be obtained.

Further, when the shielding material 18 containing a carbonaceous material is arranged around the molded body and pressure-sintered, it is possible to obtain a ceramic having excellent mechanical properties.

After the pressure sintering, hot isotropic pressure sintering (HIP) may be performed if necessary. By performing hot isostatic pressing (HIP), the three-point bending strength of ceramics can be increased to 800 MPa or more.

The ceramics obtained in this manner can be ground to both the main surface, the inner peripheral surface, and the outer peripheral surface to obtain the electropolishing conductive member of the present disclosure.

Here, the cutting in the roughness curve, which represents the difference between the cutting level at the 25% load length rate in the roughness curve of the sliding contact surface and the cutting level at the 75% load length rate in the roughness curve In order to obtain a sliding ring having a level difference (Rδc) of 1 μm or less, a diamond abrasive grain having a grain size number of 270 or more described in ASTM E11-61, that is, a grain size of 53 μm or less with a resin is used. It suffices to grind using a bonded grinding wheel.

If the required electropolishing conductive member has a complicated shape, wire-discharge machining, electric discharge machining such as single-sided erosion machining, etc. can be used to shape the ceramic into a desired shape and buff the surface with diamond powder or the like. Good.

1: Electropolishing device 2: Membrane 3: Wafer chuck 4: Wafer rotating shaft 5: Electrolytic bath 6: Polishing pad 7: Spacer 8: Surface plate 9: Surface plate rotating shaft 10a: Anode current ring 10b: Anode current ring 11: Elastic member 12: Insulator 13: Cathode plate 14: Waste liquid pipe 15: Molded body 16: Carbon sheet 17: Graphite spacer 18: Shielding material

Claims (7)

A conductive member for electropolishing, which comprises aluminum oxide as a main component and ceramics containing titanium carbide, nitride, carbonitride, boride and/or oxide as an accessory component. The conductive member for electrolytic polishing according to claim 1, wherein the composition of the titanium carbide is TiCx (where x=0.95 to 0.99). 3. The electropolishing conductive member according to claim 1, wherein the ceramic contains at least one of ytterbium, yttrium, and dysprosium. 4. The electropolishing conductive member according to claim 1, wherein the ceramic contains at least one of nickel, cobalt, and molybdenum. The electropolishing conductive member according to any one of claims 1 to 4, wherein the ceramic has a higher density in the surface layer portion than in the central portion in the thickness direction. A sliding ring comprising the electro-polishing conductive member according to claim 1. One of the main surfaces is a sliding contact surface with the object to be polished, a cutting level at a load length ratio of 25% in the roughness curve of the sliding contact surface, and a load of 75% in the roughness curve. A sliding ring having a cutting level difference (Rδc) in the roughness curve of 1 μm or less, which represents a difference from the cutting level in length ratio.

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