Wafer-holding ring member

Abstract

A wafer-holding ring member (10) for use in a polishing device is characterized by being provided with a polishing surface (12) and by being 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.

Description

Wafer holding ring member

[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. This application claims priority to Japanese Patent Application No. 2024-027157 filed on February 27, 2024, and Japanese Patent Application No. 2025-019842 filed on February 10, 2025, the contents of which are incorporated herein by reference.

[0002] With the development 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. In particular, with semiconductor wafers, as their integration density increases, nano-order surface finishes are required. To meet this high precision surface finish, semiconductor wafers are generally polished using a CMP (chemical mechanical polishing) device that uses a porous CMP pad.

[0003] In the above-mentioned CMP apparatus, 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] Conventionally, the above-mentioned wafer holding ring member has been made of a resin material such as polyether ether kent (PEEK). In addition, Patent Document 1 proposes a wafer holding ring member having a structure in which a ceramic member and a resin member are laminated.

[0005] Japanese Patent Application Publication No. 2002-355753 (A)

[0006] However, resin wafer holding ring members have a much lower hardness than the substrate being polished (e.g., silicon, sapphire, diamond, etc.), so they are subject to rapid wear during polishing, which can make it difficult to ensure the flatness of the wafer's outer periphery. Furthermore, resin wafer holding ring members have low thermal conductivity, which means that heat during polishing does not spread sufficiently, resulting in temperature distribution, which can cause cracks in the wafer due to thermal expansion when polishing wafers made of GaAs, LN, LT, GaN, InP, etc.

[0007] Furthermore, resin wafer holding rings have insufficient acid resistance and are prone 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. Resin material degradation is particularly pronounced when slurries containing oxidizing agents (potassium permanganate, nitric acid, hypochlorous acid, hydrogen peroxide, etc.) are used. Such resin material degradation can lead to the inability to maintain the flatness of the wafer's peripheral edge. Furthermore, resin wafer holding rings are subject to static charge and particle adhesion during high-pressure injection molding. Furthermore, the rings are subject to surface contamination by metal impurities due to contact with the mold. Metal contamination during planarization of insulating films used in semiconductor devices can diffuse and deteriorate the insulating properties. High-purity components free of 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 is capable of stably performing surface polishing by CMP on various types of wafers.

[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 aspect 1 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 aspect 2 of the present invention is characterized in that it is made of a silicon material having a purity of 99.9999 mass% or more in the wafer holding ring member according to aspect 1. Since the wafer holding ring member according to aspect 2 of the present invention is made of a high-purity silicon material having a purity of 99.9999 mass% or more, it has few impurities and stable characteristics, allowing for more stable surface polishing of wafers.

[0012] The wafer holding ring member of Aspect 3 of the present invention is characterized in that, in the wafer holding ring member of Aspect 1 or Aspect 2, the contact angle of water 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 has sufficient hydrophilicity, which allows slurry to easily adhere to the ring, and enables stable polishing.

[0013] A wafer holding ring member according to Aspect 4 of the present invention is characterized in that an oxide film is formed on the polishing surface of the wafer holding ring member according to any one of Aspects 1 to 3. According to the wafer holding ring member according to 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 polishing surface has sufficient hydrophilicity, and slurry easily adheres to the surface, allowing stable polishing.

[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, which allows slurry to easily adhere to the surface, and enables stable polishing.

[0015] A wafer holding ring member of Aspect 6 of the present invention is characterized in that the flatness of the polishing surface is 0.05 mm or less in the wafer holding ring member of any one of Aspects 1 to 5. 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 periphery of the wafer can be sufficiently ensured by surface polishing.

[0016] A wafer holding ring member according to aspect 7 of the present invention is characterized in that it is made of columnar crystal silicon in the wafer holding ring member according to any one of aspects 1 to 6. The wafer holding ring member according to aspect 7 of the present invention is made of columnar crystal silicon, and therefore is very hard and has excellent wear resistance.

[0017] A wafer holding ring member of Aspect 8 of the present invention is characterized in that it is the wafer holding ring member of any one of Aspects 1 to 7, in that it is formed with screw insertion holes through which fixing screws are inserted. According to the wafer holding ring member of Aspect 8 of the present invention, since screw insertion holes through which screws are inserted are formed, the wafer holding ring member can be fixed to the fixing member with screws 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 suppressed, allowing for stable polishing.

[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 is capable of stably polishing the surfaces of various wafers by CMP.

[0019] 1 is a top view showing an example of a wafer holding ring member according to an embodiment of the present invention; 2 is a cross-sectional view showing an example of a wafer holding ring member according to an embodiment of the present invention; 3 is a flow chart showing an example of a method for manufacturing a wafer holding ring member according to an embodiment of the present invention; 4 is an explanatory diagram showing a thickness measurement position when evaluating the flatness of a wafer holding ring member according to an embodiment of the present invention; and 5 is a diagram showing a thickness measurement position when evaluating the flatness of a wafer holding ring member according to an embodiment of the present invention.

[0020] 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. Here, the wafer holding ring member 10 is also referred to as a retainer ring for a polishing apparatus.

[0021] The wafer holding ring member 10 of this embodiment is used to hold a wafer in a CMP (chemical mechanical polishing) device that polishes the surface of a wafer made of, for example, silicon, SiC, diamond, sapphire, GaAs, LN, LT, GaN, InP, etc. The wafer holding ring member 10 of this embodiment 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] 1A and 1B, the wafer-holding ring member 10 of this embodiment is disk-shaped and has an inner peripheral hole 11 into which a wafer is attached. This wafer-holding ring member 10 is configured to hold the outer periphery of a wafer and 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 serves as a polishing surface 12 that is polished together with the wafer. This polishing surface 12 has a plurality of discharge grooves (groove portions) 13 formed at predetermined positions for discharging polishing slurry.

[0023] The wafer-holding ring member 10 of this embodiment has a polishing surface 12 and a groove formed in the polishing surface 12, and is made of a silicon material. 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. The wafer-holding ring member 10 preferably contains a high-purity (99.99999 mass% or higher) silicon material, with the remainder consisting of inevitable impurities. In this embodiment, the wafer-holding ring member 10 is preferably made from a columnar silicon ingot.

[0024] In this embodiment, the silicon material constituting the wafer holding ring member 10 preferably has a purity of 99.9999% by mass or more (so-called solar cell grade of 6N or more), more preferably 99.99999% by mass or more, and even more preferably 99.999999% by mass or more. In this embodiment, the wafer holding ring member 10 is preferably made of a silicon material with a purity of 99.999999999% by mass or more (so-called 11N or more). Although not particularly limited, the silicon material constituting the wafer holding ring member 10 may have a purity of 99.9999999999% by mass or less (so-called 12N or less).

[0025] Furthermore, in the wafer-holding ring member 10 of this embodiment, the polishing surface 12, which is polished together with the wafer, is preferably imparted with hydrophilicity. Specifically, the contact angle of water on the polishing surface 12 is preferably 30° or less. By imparting hydrophilicity to the polishing surface 12, the polishing slurry can be more easily spread in the surface direction, enabling uniform polishing. 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 polishing surface 12 is preferably 1 nm or more, and more preferably 5 nm or more. The thickness of the oxide film formed on the polishing surface 12 is preferably 50 nm or less, and more preferably 10 nm or less.

[0027] Furthermore, in the wafer holding ring member 10 of this embodiment, in order to impart hydrophilicity to the polishing surface 12, a hydrophilic functional group may be imparted to the polishing surface 12. Examples of hydrophilic functional groups imparted to the polishing surface 12 include OH (hydroxyl group), NH (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, as shown in FIGS. 1A and 1B , the wafer holding ring member 10 of this embodiment preferably has screw insertion holes 15 through which screws can be inserted. 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 fixing screws inserted through the screw insertion holes 15. The wafer holding ring member 10 of this embodiment is used in a CMP apparatus while fixed to the fixing member. The wafer holding ring member 10 may also 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, e.g., anodized aluminum) and stainless steel, 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. 2. As shown in Fig. 2, the method for manufacturing 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 step S07.

[0031] (Cutting step S01) First, a silicon ingot that will be the raw 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 obtain a silicon disk material having columnar crystals extending in the thickness direction.

[0032] (Heat Treatment Step S02) Next, the silicon disk material is subjected to heat treatment. By performing the heat treatment, strain accumulated in the silicon disk material is removed. Here, the heat treatment conditions are preferably, for example, an argon atmosphere, a heat treatment temperature of 200°C to 800°C, a holding time at the heat treatment temperature of 0.2 hours to 2 hours, and a cooling rate of 100°C / min to 180 min / min.

[0033] (Ring Machining Step S03) Next, the above-mentioned silicon disk material is machined to form a silicon ring material of a predetermined size.

[0034] (Shape Machining Step S04) Next, the silicon ring material is machined to form the discharge grooves 13 on the polished surface 12 and also form the screw insertion holes 15. When the silicon ring material is made of columnar crystal silicon, the grain boundaries may become groove-shaped 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 step S05) Next, a planarization process is performed 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 machine (a surface grinder or a rotary grinder) is used to perform a grinding process on the polished surface 12 and the back surface to achieve flatness. After the grinding process, additional processing may be performed using a polishing device to improve flatness.

[0036] Table 1 shows the results of measuring the flatness of the polished surface 12 after the planarization step S05. 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 measurement method may be, for example, a method using a laser white light interferometer. The locations (16 locations in total) where the thickness was measured are described in detail below. As shown in FIG. 3, a predetermined point on the outer side of the surface of the silicon ring material (e.g., a portion from the outer periphery of the silicon ring material to the inner periphery of the silicon ring material, 10% to 40%, when the length from the outer periphery to the inner periphery 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. This process is repeated, and eight equally spaced clockwise points on the surface of the silicon ring material are designated as A1 to H1, respectively. Furthermore, a point on the line connecting A1 and the center of the circle that forms the outer periphery of the silicon ring material, and inside the silicon ring material (for example, a portion that is 60% to 90% from the outer periphery edge of the silicon ring material toward the inner periphery edge, when the length from the outer periphery edge to the inner periphery edge of the silicon ring material is 100%) is designated as A2. Similarly, a predetermined point on the line connecting B1 and the center of the circle that forms the outer periphery of the silicon ring material, and inside the silicon ring material, is designated as B2. Repeating this, 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]

[0038] (Cleaning step S06) Next, at least the polished surface 12 of the silicon ring material is cleaned. Cleaning is preferably performed 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 performed to impart hydrophilicity to the polished surface 12 of the silicon ring material. When forming an oxide film on the polished surface 12 to impart hydrophilicity, it is preferable to perform oxidation heat treatment under the following conditions: an atmosphere of air, oxygen, or water vapor, a heat treatment temperature of 40°C or higher and 800°C or lower, and a holding time at the heat treatment temperature of 5 minutes or higher and 60 minutes or lower. When imparting hydrophilicity to the polished surface 12 by imparting hydrophilic functional groups, it is preferable to activate the polished surface 12 (e.g., with a surfactant or plasma surface activation) and then contact (e.g., by spraying or immersion) a functional group imparting agent (e.g., a silane coupling agent or an amino coupling agent).

[0040] Here, the water wettability 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 water contact angle was 6°, and when a hydrophilic functional group was imparted to the polished surface 12, the water contact angle was 9°. It was confirmed that the hydrophilic treatment sufficiently reduced the water contact angle.

[0041]

[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, its excellent thermal conductivity allows for uniform dispersion of heat generated during polishing, reducing temperature distribution and suppressing cracking of the substrate during polishing. Furthermore, the wafer holding ring member 10 of this embodiment is highly acid-resistant, free from particle and metal contamination, and highly clean. Therefore, the wafer surface can be reliably polished using a CMP apparatus.

[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, if 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 the polishing surface that is polished together with the wafer is given hydrophilic functional groups, the polishing surface 12 can be given sufficient hydrophilicity, 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, the fixing member and the wafer holding ring member can be prevented from peeling off, 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.

[0052] The results of experiments conducted to confirm the effectiveness of the present invention are described below. First, as shown in Table 3, 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. The solvent, pH, abrasive grains, and abrasive grain concentration in each polishing slurry are shown in Table 3. The sodium hydroxide concentration, oxalic acid concentration, and potassium permanganate concentration in each prepared slurry were adjusted to the corresponding pH as shown in Table 3. Ring members (ring members having the shapes shown in FIGS. 1A and 1B) made of silicone, PEEK (polyether ether ketone) resin, PTFE (polytetrafluoroethylene) resin, and PPS (polyphenylene sulfide) resin were also prepared. By appropriately subjecting these ring members to hydrophilic treatment, the water contact angles of the surfaces of these ring members were adjusted to 60° or more, 29°, and 9°, respectively.

[0053] A polishing experiment was conducted using an AR681MSII manufactured by Machine Application Tools. Chemical mechanical polishing was performed 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 rpm, and polishing time: 300 min, and the amount of thickness reduction of the various ring members described above was investigated. The evaluation results, which show the amount of thickness reduction (μm), are shown in Tables 4 to 6.

[0054]

[0055]

[0056]

[0057]

[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, when an oxidizer slurry containing potassium permanganate is used, the thickness loss of various resin materials is very large, but the thickness loss of the ring member made of a silicone material is sufficiently suppressed. 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 ring member has excellent hydrophilicity, the thickness loss is even smaller and deterioration due to the slurry is 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.

[0061] According to the present invention, it is possible to provide a wafer holding ring member that is excellent in wear resistance, thermal conductivity, acid resistance and cleanliness, and that is capable of stably polishing the surfaces of various wafers by CMP.

[0062] 10 Wafer holding ring member 12 Polished surface 15 Screw insertion hole

Claims

1. A wafer holding ring member for use in a polishing apparatus, characterized in that it has a polishing surface and is made of a silicon material.

2. The wafer holding ring member according to claim 1, characterized in that it is made of a silicon material with a purity of 99.9999 mass% or more.

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

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

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

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

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

8. The wafer holding ring member according to claim 1, wherein screw insertion holes for inserting screws are formed.

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