Wafer-holding ring member

Abstract

To provide a wafer-holding ring member that is excellent in wear resistance, thermal conductivity, acid resistance, and cleanliness and can stably polish surfaces of various wafers with CMP.SOLUTION: A wafer-holding ring member 10 for use in a polishing device is provided with a polishing surface 12 and is made from a silicon material. The wafer-holding ring member is preferably made from a silicon material having a purity of 99.9999 mass% or more. The contact angle of water on the polishing surface 12 is preferably 30° or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wafer holding ring member used in a polishing apparatus such as a CMP (Chemical Mechanical Polishing) apparatus for polishing wafers. [Background technology]

[0002] With the advancement of the semiconductor industry, there is an increasing need for processing methods that can finish the surfaces of metals, semiconductors, ceramics, etc. with high precision, and in particular, with semiconductor wafers, the increase in their integration density has led to a demand for nano-order surface finishes. To meet this high-precision surface finish, semiconductor wafers are generally polished using CMP (chemical mechanical polishing) equipment that uses porous CMP pads.

[0003] In the CMP apparatus described above, the surface of the wafer is polished while being held by a wafer holding ring member disposed on the outer periphery of the wafer. At this time, in order to ensure the polishing flatness of the outer periphery of the wafer, the wafer holding ring member disposed on the outer periphery of the wafer itself is polished together with the wafer.

[0004] Here, as the above-mentioned wafer holding ring member, one made of a resin material such as polyether ether kent (PEEK) has been conventionally provided. Furthermore, Patent Document 1 proposes a wafer holding ring member having a structure in which a ceramic member and a resin member are laminated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-355753 Summary of the Invention [Problem to be solved by the invention]

[0006] However, wafer holding ring members made of resin material have a much lower hardness than the substrate to be polished (e.g., silicon, sapphire, diamond, etc.), so they are subject to rapid wear during polishing, and there is a risk that the flatness of the outer periphery of the wafer cannot be ensured. Furthermore, in wafer holding ring members made of resin material, the heat generated during polishing does not spread sufficiently due to low thermal conductivity, resulting in temperature distribution. Therefore, when polishing wafers made of GaAs, LN, LT, GaN, InP, etc., there is a risk of the wafer cracking due to thermal expansion.

[0007] Furthermore, resin wafer holding ring members have insufficient acid resistance and may be subject to early deterioration when acidic slurries (organic acid slurries such as carboxylic acids, sulfonic acids, sulfinic acids, phenols, thiols, acid imides, oximes, and sulfonamides) are used. Deterioration of the resin material is particularly pronounced when using slurries containing oxidizing agents (potassium permanganate, nitric acid, hypochlorous acid, hydrogen peroxide, etc.). Such deterioration of the resin material may result in the resin wafer holding ring members being unable to ensure flatness around the periphery of the wafer. Furthermore, wafer holding ring components made of resin material become charged when extruded under high pressure during injection molding, which causes particles to adhere to them. Furthermore, the ring components come into contact with the mold, resulting in surface contamination by metal impurities. Metal contamination during the planarization of insulating films used in semiconductor devices can spread and deteriorate the insulating properties. Highly clean components that are free from metal contamination and particle adhesion are required.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a wafer holding ring member that has excellent wear resistance, thermal conductivity, acid resistance, and cleanliness, and that is capable of stably performing surface polishing of various wafers by CMP. [Means for solving the problem]

[0009] In order to solve the above problem, the wafer holding ring member of aspect 1 of the present invention is a wafer holding ring member used in a polishing apparatus, characterized in that it has a polishing surface and is made of a silicon material.

[0010] The wafer holding ring member of the first aspect of the present invention is made of a silicon material, which is sufficiently hard and has excellent wear resistance compared to resin materials. It also has excellent thermal conductivity, which allows the heat generated during polishing to be uniformly dispersed, reducing the risk of temperature distribution. Furthermore, it has excellent acid resistance, is free from particle and metal contamination, and has a high level of cleanliness. Therefore, the surface of the wafer can be stably polished using a polishing device such as a CMP device.

[0011] A wafer holding ring member according to a second aspect of the present invention is the wafer holding ring member according to the first aspect, characterized in that it is made of a silicon material with a purity of 99.9999 mass % or more. According to the wafer holding ring member of aspect 2 of the present invention, it is made of a high-purity silicon material with a purity of 99.9999 mass% or more, so it has few impurities and stable characteristics, allowing for more stable surface polishing of wafers.

[0012] A third aspect of the present invention provides a ring wafer holding member according to the first or second aspect, characterized in that the water contact angle on the polishing surface is 30° or less. According to the wafer holding ring member of aspect 3 of the present invention, the contact angle of water on the polishing surface that is polished together with the wafer is 30° or less, so that the ring member has sufficient hydrophilicity, the slurry is easily absorbed, and stable polishing can be performed.

[0013] A fourth aspect of the present invention is a ring wafer holding member according to any one of the first to third aspects, characterized in that an oxide film is formed on the polishing surface. According to the wafer holding ring member of aspect 4 of the present invention, an oxide film is formed on the polishing surface that is polished together with the wafer, so that the surface has sufficient hydrophilicity, slurry is easily absorbed, and stable polishing can be performed.

[0014] A wafer holding ring member of aspect 5 of the present invention is characterized in that, in the wafer holding ring member of any one of aspects 1 to 4, hydrophilic functional groups are imparted to the polishing surface. According to the wafer holding ring member of aspect 5 of the present invention, hydrophilic functional groups are imparted to the polishing surface that is polished together with the wafer, so that the polishing surface has sufficient hydrophilicity, and the slurry easily adheres to the surface, allowing for stable polishing.

[0015] A sixth aspect of the present invention provides a wafer holding ring member according to any one of the first to fifth aspects, characterized in that the flatness of the polished surface is 0.05 mm or less. According to the wafer holding ring member of aspect 6 of the present invention, the flatness of the polishing surface that is polished together with the wafer is 0.05 mm or less, so that the flatness of the outer peripheral portion of the wafer can be sufficiently ensured by surface polishing.

[0016] A seventh aspect of the present invention is a ring wafer holding member according to any one of the first to sixth aspects, characterized in that it is made of columnar crystal silicon. According to the wafer holding ring member of the seventh aspect of the present invention, since it is made of columnar crystal silicon, it is very hard and has excellent wear resistance.

[0017] The wafer holding ring member of aspect 8 of the present invention is characterized in that, in the wafer holding ring member of any one of aspects 1 to 7, a screw insertion hole is formed through which a fixing screw is inserted. According to the wafer holding ring member of aspect 8 of the present invention, a screw insertion hole through which a screw is inserted is formed, so that the wafer holding ring member can be fixed to the fixing member with a screw without using adhesive or the like, and even if heat is generated during polishing, separation between the fixing member and the wafer holding ring member can be prevented, allowing for stable polishing. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a wafer holding ring member that has excellent wear resistance, thermal conductivity, acid resistance, and cleanliness, and that allows stable surface polishing of various wafers by CMP. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are explanatory views showing an example of a wafer holding ring member according to an embodiment of the present invention, in which (a) is a top view and (b) is a cross-sectional view. [Figure 2] FIG. 2 is a flow diagram showing an example of a method for manufacturing a wafer holding ring member according to an embodiment of the present invention. [Figure 3] 1 is an explanatory diagram showing thickness measurement positions when evaluating the flatness of a wafer holding ring member according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wafer holding ring member according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The wafer holding ring member 10 of this embodiment is used in a polishing apparatus such as a CMP apparatus, etc. Here, the wafer holding ring member 10 is also called a retainer ring for a polishing apparatus.

[0021] The wafer holding ring member 10 of this embodiment is used to hold wafers in a CMP (chemical mechanical polishing) device that polishes the surfaces of wafers made of, for example, silicon, SiC, diamond, sapphire, GaAs, LN, LT, GaN, InP, etc. The wafer holding ring member 10 of this embodiment is a wafer holding ring member 10 that is arranged on the outer periphery of a wafer in a polishing device that polishes the wafer (e.g., the front or back surface of the wafer), holds the wafer, and is polished together with the wafer, and is made of a silicon material.

[0022] As shown in FIG. 1, the wafer holding ring member 10 of this embodiment is disk-shaped and has an inner peripheral hole 11 in which a wafer is mounted. This wafer holding ring member 10 is configured to hold the outer periphery of the wafer and to be polished together with the wafer in a polishing device such as a CMP device. In this way, the wafer holding ring member 10 located on the outer periphery of the wafer is polished together with the wafer, thereby ensuring polishing flatness of the outer periphery of the wafer. That is, one surface of the wafer holding ring member 10 is made to be a polishing surface 12 that is polished together with the wafer. Note that this polishing surface 12 has a plurality of discharge grooves (groove portions) 13 formed at predetermined positions for discharging the polishing slurry.

[0023] The wafer-holding ring member 10 of this embodiment is made of a silicon material and includes a polishing surface 12 and grooves formed in the polishing surface 12. The silicon material used to make the wafer-holding ring member 10 may be, for example, silicon cut from a single-crystal silicon ingot, a mono-like silicon ingot, a columnar silicon ingot, or a polycrystalline silicon ingot. Preferably, the wafer-holding ring member 10 contains a high-purity (99.99999 mass% or higher) silicon material, with the remainder consisting of inevitable impurities. In this embodiment, it is preferable that the silicon substrate is made from a columnar crystal silicon ingot.

[0024] In this embodiment, the silicon material constituting the wafer holding ring member 10 preferably has a purity of 99.9999 mass% or more (so-called solar cell grade of 6N or more), more preferably 99.99999 mass% or more, and even more preferably 99.999999 mass% or more. In this embodiment, the wafer holding ring member 10 is preferably made of a silicon material with a silicon content of 99.999999999 mass % or more (so-called 11N or more). Although not particularly limited, the purity of the silicon material constituting the wafer holding ring member 10 may be 99.9999 mass% or more, 99.99999999 mass% or more, or 99.99999999999 mass% or more.

[0025] Furthermore, in the wafer holding ring member 10 of this embodiment, it is preferable that the polishing surface 12, which is polished together with the wafer, is made hydrophilic, and specifically, it is preferable that the contact angle of water on the polishing surface 12 is 30° or less. By providing hydrophilicity to the polishing surface 12, the polishing slurry spreads more easily in the surface direction, and polishing can be performed uniformly. The contact angle of water on the polishing surface 12 is more preferably 20° or less, and even more preferably 10° or less. For example, in the wafer holding ring member 10 of this embodiment, the polishing surface 12 is a hydrophilic surface having hydrophilic properties, and the contact angle of water on the polishing surface 12 is preferably 20° or less or 10° or less. Although not particularly limited, the contact angle of water on the polishing surface 12 may be 0° or more, 1° or more, or 5° or more.

[0026] In the wafer holding ring member 10 of this embodiment, an oxide film may be formed on the polishing surface 12 to impart hydrophilicity to the polishing surface 12. The thickness of the oxide film formed on the polished surface 12 is preferably 1 nm or more, more preferably 5 nm or more, and is preferably 50 nm or less, more preferably 10 nm or less.

[0027] In addition, in the wafer holding ring member 10 of this embodiment, the polishing surface 12 may be provided with a hydrophilic functional group in order to impart hydrophilic properties to the polishing surface 12. Examples of hydrophilic functional groups imparted to the polishing surface 12 include OH (hydroxyl group), NH3 (amino group), COOH (carbonyl group), and CO (carboxyl group).

[0028] In addition, in the wafer holding ring member 10 of this embodiment, the flatness of the polishing surface 12 is preferably 0.05 mm or less. The flatness of the polishing surface 12 is more preferably 0.03 mm or less, and even more preferably 0.01 mm or more. There is no particular lower limit to the flatness of the polishing surface 12, and it is preferably 0 mm.

[0029] Furthermore, in the wafer holding ring member 10 of this embodiment, as shown in FIG. 1, it is preferable that screw insertion holes 15 through which screws are inserted are formed. The wafer holding ring member 10 of this embodiment is configured to be fixed to a fixing member (not shown) disposed on the opposite side of the polishing surface 12 by means of fixing screws inserted into the screw insertion holes 15. The wafer holding ring member 10 of this embodiment is used in a CMP apparatus while being fixed to the fixing member. The wafer holding ring member 10 may have a structure in which a substrate is bonded as a support member to the surface (other surface) opposite the polishing surface 12. For example, the support member is a substrate made of a material other than silicon. Examples of substrates include metal materials such as aluminum (coated products such as anodized aluminum) and SUS, ceramic materials such as alumina and SiC, and resin materials such as PEEK, polyimide, and polyimide.

[0030] Next, an example of a method for manufacturing the wafer holding ring member 10 according to this embodiment will be described with reference to FIG. As shown in FIG. 2, the manufacturing method of the wafer-holding ring member 10 according to this embodiment includes a cutting step S01, a heat treatment step S02, a ring processing step S03, a shape processing step S04, a planarization step S05, a cleaning step S06, and a hydrophilization treatment step S07.

[0031] (Cutting process S01) First, a silicon ingot, which is the material for the wafer holding ring member 10, is cut to obtain a silicon disk material of a predetermined thickness. In this embodiment, a directionally solidified columnar crystal silicon ingot is cut perpendicular to the solidification direction to form a silicon disk material having columnar crystals extending in the thickness direction.

[0032] (Heat treatment process S02) Next, the silicon disk material is subjected to a heat treatment, which removes the strain accumulated in the silicon disk material. Here, the heat treatment conditions are preferably, for example, argon atmosphere, heat treatment temperature: 200°C or higher and 800°C or lower, holding time at the heat treatment temperature: 0.2 hours or higher and 2 hours or lower, and cooling rate: 100°C / min or higher and 180 min / min or lower.

[0033] (Ring processing process S03) Next, the silicon disk material is machined to form a silicon ring material of a predetermined size.

[0034] (Shape processing process S04) Next, the silicon ring material is machined to form the discharge groove 13 on the polished surface 12 and the screw insertion hole 15 . When the silicon ring material is made of columnar crystal silicon, the grain boundaries may have groove shapes and form the discharge grooves 13 . Furthermore, since the silicon ring material (silicon material) is a brittle material, care must be taken when forming the screw insertion holes 15.

[0035] (Planarization process S05) Next, a planarization process is carried out so that at least the polished surface 12 of the silicon ring material becomes a flat surface. In the planarization step S05, for example, a machining device (a surface grinder or a rotary grinder) is used to perform grinding on the polished surface 12 and the back surface to flatten them. After the grinding, additional processing may be performed using a polishing device to improve the flatness.

[0036] Here, the results of measuring the flatness of the polished surface 12 after the planarization step S05 are shown in Table 1. The flatness was calculated by measuring the thickness at the locations shown in FIG. 3 (16 locations in total). The flatness was 0.008 mm. Although not particularly limited, the thickness can be measured by, for example, a method using a laser white light interferometer. Details of the locations where thickness was measured (16 locations in total) are given below. As shown in FIG. 3, a predetermined point on the outer side of the surface of the silicon ring material (for example, a portion 10% to 40% from the outer circumferential edge of the silicon ring material toward the inner circumferential edge when the length from the outer circumferential edge to the inner circumferential edge of the silicon ring material is 100%) is designated as A1. Furthermore, a point 45 degrees clockwise from A1 is designated as B1, and a point 45 degrees clockwise from B1 is designated as C1. Repeating this process, eight equally spaced clockwise points on the surface of the silicon ring material are designated as A1 to H1. Furthermore, a point A2 is designated on the line connecting A1 and the center of the circle that forms the outer periphery of the silicon ring material and on the inside of the silicon ring material (for example, a portion 60% to 90% from the outer circumferential edge of the silicon ring material toward the inner circumferential edge when the length from the outer circumferential edge to the inner circumferential edge of the silicon ring material is 100%). Similarly, a predetermined point B2 is designated on the line connecting B1 and the center of the circle that forms the outer periphery of the silicon ring material and on the inside of the silicon ring material. This process is repeated, and the eight points on the silicon ring material inside A1 to H1 are designated as A2 to H2. The above 16 points A1 to H1 and A2 to H2 are the points at which the thickness is measured.

[0037] [Table 1]

[0038] (Cleaning process S06) Next, at least the polished surface 12 of the silicon ring material is washed. The washing is preferably carried out using ultrapure water at a temperature of 20° C. or higher and 80° C. or lower, for example.

[0039] (Hydrophilic treatment step S07) Next, a hydrophilic treatment is carried out to impart hydrophilicity to the polished surface 12 of the silicon ring material. When forming an oxide film on the polishing surface 12 to impart hydrophilicity, it is preferable to perform the oxidation heat treatment under the following conditions: atmosphere: air, oxygen, or water vapor; heat treatment temperature: 40°C or higher and 800°C or lower; and holding time at the heat treatment temperature: 5 minutes or higher and 60 minutes or lower. When imparting hydrophilicity to the polishing surface 12 by imparting hydrophilic functional groups, it is preferable to activate the polishing surface 12 (e.g., with a surfactant or plasma surface activation) and then contact (e.g., spray or immerse) it with a functional group imparting agent (e.g., a silane coupling agent or an amino coupling agent).

[0040] Here, the wettability with water due to the hydrophilic treatment step S07 was evaluated. The contact angle was measured using pure water before and after the hydrophilic treatment. The measurement results are shown in Table 2. As shown in Table 2, when an oxide film was formed on the polished surface 12, the contact angle of water was 6°, and when a hydrophilic functional group was imparted to the polished surface 12, the contact angle of water was 9°. It was confirmed that the contact angle of water was sufficiently reduced by performing the hydrophilization treatment.

[0041] [Table 2]

[0042] Through the above steps, the wafer holding ring member 10 of this embodiment is manufactured.

[0043] The wafer holding ring member 10 of this embodiment configured as described above is made of a silicon material, which is sufficiently hard and has excellent wear resistance compared to resin materials. Furthermore, since it has excellent thermal conductivity, it can uniformly disperse the heat generated during polishing, making it difficult for temperature distribution to occur and suppressing cracks in the substrate during polishing. Furthermore, the wafer holding ring member 10 of this embodiment is also excellent in acid resistance, is free from particle and metal contamination, and has a high degree of cleanliness. Therefore, the surface of the wafer can be stably polished by the CMP device.

[0044] In the wafer holding ring member 10 of this embodiment, when it is made of a silicon material with a purity of 99.9999 mass% or more (6N or more), the impurities are few and the characteristics are stable, allowing for even more stable surface polishing of wafers. In particular, when it is made of a silicon material with a purity of 99.999999999 mass% or more (11N or more), as in this embodiment, the impurities are few and the characteristics are stable, allowing for even more stable surface polishing of wafers.

[0045] In the wafer holding ring member 10 of this embodiment, when the contact angle of water on the polishing surface 12 that is polished together with the wafer is 30° or less, the surface is sufficiently hydrophilic, the polishing slurry easily adheres to the surface, and stable polishing can be performed.

[0046] In the wafer holding ring member 10 of this embodiment, if an oxide film is formed on the polishing surface 12 that is polished together with the wafer, the polishing surface 12 can be made sufficiently hydrophilic, making it easy for the polishing slurry to adhere to it and allowing for stable polishing.

[0047] In the wafer holding ring member 10 of this embodiment, if hydrophilic functional groups are imparted to the polishing surface that is polished together with the wafer, sufficient hydrophilicity can be imparted to the polishing surface 12, making it easy for the polishing slurry to adhere to it and allowing for stable polishing.

[0048] In the wafer holding ring member 10 of this embodiment, if the flatness of the polishing surface 12 that is polished together with the wafer is 0.05 mm or less, the flatness of the outer peripheral portion of the wafer can be sufficiently ensured by surface polishing using a CMP device.

[0049] When the wafer holding ring member 10 of this embodiment is made of columnar crystal silicon, it is very hard and has excellent wear resistance.

[0050] In the wafer holding ring member 10 of this embodiment, if a screw insertion hole through which a fixing screw is inserted is formed, the wafer holding ring member 10 can be fixed to the fixing member with a screw without using adhesive or the like, and even if heat is generated during polishing, separation between the fixing member and the wafer holding ring member can be prevented, allowing for stable polishing.

[0051] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. [Example]

[0052] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below. First, three types of polishing slurries were prepared: an alkaline slurry containing sodium hydroxide, an acidic slurry containing oxalic acid, and an oxidizing agent slurry containing potassium permanganate, as shown in Table 3. The solvent, pH, abrasive grains, and abrasive grain concentration in the solution of each polishing slurry are shown in Table 3. The concentrations of sodium hydroxide, oxalic acid, and potassium permanganate in each prepared slurry were adjusted to the corresponding pH as shown in Table 3. Additionally, ring members (with the shapes shown in Figure 1) made of silicone, PEEK (polyether ether ketone) resin, PTFE (polytetrafluoroethylene) resin, and PPS (polyphenylene sulfide) resin were prepared. By appropriately treating these ring members with hydrophilic agents, the water contact angles of the surfaces of these ring members were adjusted to 60° or more, 29°, and 9°, respectively.

[0053] Polishing experiments were carried out using an AR681MS II manufactured by Machine Application Tools. Chemical mechanical polishing was carried out using the various slurries shown in Table 3 under the following conditions: ring pressure: 80 kPa, ring rotation speed: 72 rpm, polishing platen rotation speed: 80 pm, and polishing time: 300 min, and the amount of thickness reduction of the various ring components mentioned above was investigated. The evaluation results, which show the amount of thickness reduction (μm), are shown in Tables 4 to 6.

[0054] [Table 3]

[0055] [Table 4]

[0056] [Table 5]

[0057] [Table 6]

[0058] As shown in Tables 4 to 6, in all cases of alkaline slurry, acidic slurry, and oxidizing agent slurry, the ring members made of silicone material showed less thickness loss than the various resin materials, confirming that deterioration due to the slurry was suppressed. Whether the water contact angle on the surface of the ring member was 60° or more, 29°, or 9°, the ring members made of silicone material showed less thickness loss.

[0059] In particular, in the case of an oxidizer slurry containing potassium permanganate, the thickness reduction of various resin materials is very large, but it can be seen that the thickness reduction is sufficiently suppressed in the ring member made of a silicon material. Furthermore, comparing Table 4 with Tables 5 and 6, when the water contact angle on the surface of the ring member is small and the surface is highly hydrophilic, the thickness loss is further reduced and deterioration due to the slurry is further suppressed.

[0060] As a result of the above confirmation experiments, it was confirmed that the present invention can provide a wafer holding ring member that has excellent wear resistance, thermal conductivity, acid resistance, and cleanliness, and is capable of stably performing surface polishing by CMP on various types of wafers. [Explanation of symbols]

[0061] 10 Wafer holding ring member 12 Polished surface 15 Screw insertion hole

Claims

1. A wafer holding ring member used in a polishing apparatus, comprising: A wafer holding ring member having a polished surface and made of a silicon material.

2. 2. The wafer holding ring member according to claim 1, which is made of a silicon material having a purity of 99.9999 mass % or more.

3. 2. The wafer holding ring member according to claim 1, wherein the contact angle of water on said polishing surface is 30 degrees or less.

4. 2. The wafer holding ring member according to claim 1, wherein an oxide film is formed on the polished surface.

5. 2. The wafer holding ring member according to claim 1, wherein the polishing surface is provided with a hydrophilic functional group.

6. 2. The wafer holding ring member according to claim 1, wherein the flatness of the polished surface is 0.05 mm or less.

7. 2. The wafer holding ring member according to claim 1, which is made of columnar crystal silicon.

8. 2. The wafer holding ring member according to claim 1, further comprising screw insertion holes formed therein for inserting screws.

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