Polishing pad and wafer polishing method
The polishing pad with a polyimide resin and three-dimensional network structure addresses the challenges of managing polishing solutions, simplifying cleaning and disposal, and ensuring high polish retention and wear resistance, thus reducing costs and environmental impact.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NORITAKE MACHINE TECHNO CO LTD
- Filing Date
- 2022-03-29
- Publication Date
- 2026-07-03
Smart Images
Figure 0007884351000006 
Figure 0007884351000007 
Figure 0007884351000008
Abstract
Description
Technical Field
[0001] The present invention relates to a polishing pad and a wafer polishing method.
Background Art
[0002] A wafer polishing apparatus including a platen and a carrier is known. The platen has a fixed surface extending in a direction orthogonal to the axis, and is rotated around the axis. The carrier holds a flat wafer relative to the platen so as to be rotatable.
[0003] When polishing a flat wafer such as Si, SiC, GaN, etc. with this wafer polishing apparatus, a polishing pad is fixed to the fixed surface of the platen. Then, while the polishing pad and the wafer are brought into contact with each other under a predetermined surface pressure in the presence of a polishing liquid, the platen and the carrier are relatively rotated. When the polishing liquid contains a chemical such as an alkali, the wafer is polished in a CMP (Chemical Mechanical Polishing) process.
[0004] When the polishing pad does not have polishing particles such as a general non-woven fabric or hard urethane, the polishing liquid contains polishing particles. In this case, it is necessary to manage the polishing liquid and to wash the polished wafer. Also, since the polishing liquid becomes expensive, it is necessary to recover the polished polishing liquid, readjust it to a predetermined state, and then reuse it. Further, when disposing of the polished polishing liquid and cleaning liquid, complicated treatment must be performed so as not to damage the environment. Therefore, in this case, the manufacturing cost of semiconductor devices increases and the environmental load is large.
[0005] On the other hand, if the polishing pad is made of a base resin, as disclosed in Patent Documents 1 to 3, and has a base material with multiple pores formed therein, and polishing particles held in the base material or pores, then a polishing liquid that does not contain polishing particles can be used. In this case, the polishing liquid is inexpensive, so it is not always necessary to recover and reuse the polishing liquid after polishing. Furthermore, even when disposing of the polishing liquid after polishing, not much treatment is required. Therefore, in this case, it is possible to reduce the manufacturing cost of semiconductor devices and reduce the environmental burden. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Patent No. 4266579 [Patent Document 2] Patent No. 5511266 [Patent Document 3] Patent No. 6636634 [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] However, the wafer polishing process may also require high polish retention, high heat resistance, and excellent wear resistance.
[0008] The present invention has been made in view of the above-mentioned conventional circumstances, and aims to solve the problem of providing a polishing pad that allows for easy management of the polishing solution, omits or simplifies the cleaning process of the wafer after polishing, does not require troublesome disposal of the polishing solution after polishing, and achieves high polish retention, high heat resistance, and excellent wear resistance. Furthermore, the present invention aims to solve the problem of providing such a wafer polishing method. [Means for solving the problem]
[0009] The polishing pad of the present invention is A polishing pad for polishing a wafer, which, in the presence of a polishing liquid that does not contain abrasive particles, contacts a flat wafer under a predetermined surface pressure and rotates relative to the wafer around an axis extending in the thickness direction of the wafer, A base material consisting of a resin, having multiple pores formed therein, and a base material or a pore held within the base material The aforementioned Abrasive particles death, The abrasive particles include first abrasive particles which are diamond, and second abrasive particles which are at least one of alumina, silica, talc, calcium carbonate, mica, and kaolin, which have a lower hardness than the first abrasive particles and enhance abrasive retention. The aforementioned base resin is a polyimide resin. The aforementioned base resin is given as 150% by volume. The abrasive particles are contained in an amount of 75 to 360 by volume. The aforementioned base material has a porosity of 50-80%. 、 The aforementioned base material is The aforementioned pores are formed by a three-dimensional network structure. Having a network that The aforementioned network is The aforementioned adjacent to each other Stomata In between, the base material resin is made and has a thickness of 10 μm or less. here It is characterized by the following.
[0010] The polishing pad of the present invention is made of a base material resin and has a base material in which a plurality of pores are formed, and polishing particles held in the base material or within the pores. Therefore, a polishing liquid that does not contain polishing particles can be used. As a result, the management of the polishing liquid is easy, and the cleaning process of the wafer after polishing can be omitted or simplified. Furthermore, since the polishing liquid is inexpensive, it is not always necessary to collect and reuse the polishing liquid after polishing. Moreover, even when disposing of the polishing liquid after polishing, not much processing is required.
[0011] Furthermore, according to the inventors' test results, if the base material resin is a polyimide resin, the base material can achieve high strength, high heat resistance, and excellent wear resistance. In addition, because the base material has a three-dimensional network structure of pores, the abrasive particles are easily exposed as the base material wears down, resulting in high polishing retention.
[0012] In particular, according to the inventors' test results, if the porosity of the base material is 50-80%, the abrasive particles are more easily exposed from the base material, making it easier to achieve a high polishing rate and high polishing retention.
[0013] Also, the base materials are adjacent to each other. StomataIn between, if it is made of a base resin and has a network with a thickness of 10 μm or less, the network can preferably hold abrasive particles, and the base material is moderately worn to easily expose the abrasive particles, achieving high polishing maintainability. According to the test results of the inventors, when the abrasive particles are less than 75% by volume, the wear of the base material in the polishing pad does not progress and there is no polishing maintainability. When the abrasive particles exceed 360% by volume, the wear of the base material progresses too much and is not suitable for processing. Furthermore, as the ratio of the abrasive particles increases, the processing load is dispersed and the necessary load for processing cannot be applied, and there are cases where the processing does not progress at all.
[0014] The wafer polishing method of the present invention is a wafer polishing method in which a flat wafer and a flat polishing pad are brought into contact with each other under a predetermined surface pressure in the presence of a polishing liquid, and the wafer and the polishing pad are relatively rotated around an axis extending in the thickness direction of the wafer to polish the wafer, and is characterized by using the polishing pad of the present invention.
Effect of the Invention
[0015] By using the polishing pad of the present invention, the management of the polishing liquid is easy, the cleaning process of the wafer after polishing can be omitted or simplified, and the treatment of the polishing liquid after polishing is not troublesome, and high polishing maintainability, high heat resistance and excellent wear resistance can be realized. In addition, since the wafer polishing method of the present invention uses the polishing pad of the present invention, the management of the polishing liquid is easy, the cleaning process of the wafer after polishing can be omitted or simplified, and the treatment of the polishing liquid after polishing is not troublesome, and high polishing maintainability, high heat resistance and excellent wear resistance can be realized.
Brief Description of the Drawings
[0016] [Figure 1] FIG. 1 is a SEM photograph at 200 times of the polishing surface of the polishing pad of Example 2. [Figure 2] FIG. 2 is a SEM photograph at 2000 times of the polishing surface of the polishing pad of Example 2. [Figure 3] FIG. 3 is a SEM photograph at 1000 times of the polishing surface of the polishing pad of Example 24. [Figure 4]Figure 4 is a 100x magnification SEM image of the polished surface of the polishing pad in Comparative Example 2. [Figure 5] Figure 5 is a schematic cross-sectional view of the wafer polishing apparatus used in the wafer polishing method. [Modes for carrying out the invention]
[0017] The polyimide resin, which is the base resin, is a resin polymerized with imide (-CO-NR-CO-) bonds. In order to form the base material made of polyimide resin, an imide composition or an amide-imide composition can be used. As solvents that can be mixed with the imide composition or amide-imide composition, amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide, and ether solvents such as triglyceride (triethylene glycol dimethyl ether) and tripropylene glycol can be used. One of these may be used, but a mixture of two or more is preferable.
[0018] The following manufacturing method can be used to form a three-dimensional network structure using polyimide resin. First, an imide composition or amide-imide composition is mixed with a solvent and abrasive particles to form a paste. In this case, the solvent used is N,N-dimethylformamide or the like, which undergoes phase separation during heat treatment. The paste is then molded into a sheet-like first molded body. After this, the solvent is removed from the first molded body to obtain a second molded body. The second molded body is then polymerized.
[0019] As abrasive particles, diamond, cubic boron nitride, silica, ceria, alumina, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, iron oxide, etc. can be used. As the first abrasive particle described later, at least one of diamond and cubic boron nitride can be used. As the second abrasive particle described later, at least one of inorganic particles such as alumina and silica can be used.
[0020] According to the inventors' tests, it is preferable that the abrasive particles include first abrasive particles and second abrasive particles that have lower hardness than the first abrasive particles and enhance abrasive retention. In this case, it is presumed that the second abrasive particles reduce the toughness of the base material or mitigate the impact force acting on the first abrasive particles. If the toughness of the base material is reduced by the second abrasive particles, the base material becomes more likely to expose the first abrasive particles, thereby achieving high abrasive retention. If the second abrasive particles mitigate the impact force acting on the first abrasive particles, the first abrasive particles become less likely to break, thereby achieving high abrasive retention.
[0021] The first abrasive particles preferably have an average particle size of 100 μm or less, more preferably 50 μm or less. In this case, the network effectively holds the first abrasive particles, and the abrasive particles are easily exposed as the base material wears down, thereby achieving high abrasive retention.
[0022] The second abrasive particles preferably have an average particle size of 30 μm or less, more preferably 20 μm or less. In this case, the second abrasive particles are more likely to reduce the toughness of the base material or mitigate the impact force acting on the first abrasive particles.
[0023] According to the inventors' test results, the first abrasive particles are preferably at least one of diamond and cubic boron nitride, and the second abrasive particles are preferably at least one of inorganic particles that do not change easily when heated during polymerization, such as alumina, silica, talc, calcium carbonate, mica, kaolin, and glass frit. In this case, diamond and cubic boron nitride achieve a high polishing rate. Furthermore, it is presumed that the second abrasive particles reduce the toughness of the base material and have the effect of making the resin more easily abraded to improve processing durability.
[0024] According to the inventors' test results, it is preferable that the base material has air pores with a larger diameter than the mesh. In this case, the distance between abrasive particles is appropriately maintained, the processing pressure is dispersed, and the cutting performance is improved. As a result, a high polishing rate can be achieved and the processing durability is also increased.
[0025] The air vents can be formed by hollow particles. Examples of hollow particles include ceramic hollow particles, glass balloons, and foamed resins. These hollow particles can be mixed into the paste.
[0026] (Examples and comparative examples) Examples 1 to 27 and Comparative Examples 1 to 6 that embody the present invention will be described.
[0027] First, the following base resin, solvent, abrasive particles, and hollow particles were prepared. (Base resin) Imide compositions (Examples 1-27, Comparative Examples 3-6: Imide varnish (BP-BM, manufactured by Unitika Ltd.), Comparative Examples 1 and 2: Imide varnish (CR, manufactured by Unitika Ltd.)) (solvent) Examples 1-27: Triethylene glycol dimethyl ether Comparative Examples 1-6: NMP (N-methyl-2-pyrrolidone) (abrasive particles) First polishing particle (diamond particle (average particle size: 1-100 μm)) Second-stage polishing particles (alumina particles (average particle size: 1 μm), silica particles (average particle size: 1 μm), talc particles (average particle size: 15 μm), calcium carbonate particles (average particle size: 7 μm), mica particles (average particle size: 27 μm), kaolin particles (average particle size: 10 μm)) (hollow particles) Microplastic spheres (Sekisui Chemical Co., Ltd.'s "Advancell")
[0028] These were mixed in the volume percentages shown in Tables 1-3 to obtain each paste. At this time, the volume percentage of the base resin was calculated from the solid content of the imide varnish, and the solvent, first abrasive particles, second abrasive particles, and hollow particles were mixed in predetermined volume percentages. Each paste was used to form a sheet-like first molded body using a molding device such as a T-die. This molding method is not limited to this as long as the thickness can be made uniform to some extent. The first molded body was heated to 120°C in air to evaporate the solvent and obtain a second molded body. Then, the second molded body was heated to 350°C to polymerize. In this way, each solidified body was obtained. The surface of each solidified body was ground to a predetermined thickness to obtain each abrasive pad 10 with a diameter of 30 cm.
[0029] [Table 1]
[0030] [Table 2]
[0031] [Table 3]
[0032] Tables 4 and 5 show the porosity (%) and pore ratio (volume %) for each polishing pad 10. Porosity was measured by the Archimedes method, including pores caused by hollow particles. The pore ratio was calculated from the area ratio of the SEM image of the polished surface of each polishing pad 10.
[0033] Furthermore, in Examples 1 to 27, the thickness (μm) of the network made of the base material resin between adjacent pores in the three-dimensional network structure was measured using SEM images of each polishing pad 10. On the other hand, in Comparative Examples 1 and 2, the three-dimensional network structure as in Examples 1 to 27 does not exist. However, considering the case where the three-dimensional network structure is replaced by air pores of hollow particles, the thickness (μm) of the space between adjacent pores (including air pores) made of the base material resin was measured using SEM images of each polishing pad 10. The network thickness or the space between pores is also shown in Tables 4 and 5.
[0034] [Table 4]
[0035] [Table 5]
[0036] Figure 1 shows a 200x magnification SEM image of the polished surface of the polishing pad 10 of Example 2, and Figure 2 shows a 2000x magnification SEM image. Figure 3 shows a 1000x magnification SEM image of the polishing surface of the polishing pad of Example 24. On the other hand, Figure 4 shows a 100x magnification SEM image of the polishing surface of the polishing pad of Comparative Example 2.
[0037] As shown in Figures 1-3, each polishing pad 10 in Examples 1-27 is made of a base resin and has a base material with multiple pores formed therein, and first polishing particles held within the base material or pores. Each polishing pad 10 in Examples 3-9, 13, and 16-27 also has second polishing particles held within the base material or pores. The base resin is a polyimide resin, and the base material has pores formed by a three-dimensional network structure. Each polishing pad 10 in Examples 2 and 11-19 also includes air pores.
[0038] On the other hand, as shown in Figure 4, although the base material resin of the polishing pads 10 in Comparative Examples 1 and 2 is a polyimide resin, the base material does not constitute a three-dimensional network structure. This is presumed to be because the solvent did not undergo phase separation during the heat treatment process. The polishing pads 10 in Comparative Examples 2 to 6 have air pores made of hollow particles in the base material, and the first polishing particles are retained in the base material. The polishing pad 10 in Comparative Example 3 has too many air pores and is too brittle to be suitable for processing. The polishing pad 10 in Comparative Example 5 has too high a ratio of polishing particles to base material resin, causing excessive wear of the base material and making it unsuitable for processing. The polishing pad in Comparative Example 4 has an even higher ratio of polishing particles to base material resin than in Comparative Example 5, which disperses the processing load, making it impossible to apply the load necessary for processing, resulting in no progress at all. The polishing pad in Comparative Example 6 has too low a ratio of polishing particles to base material resin, so the base material does not wear down and polishing is not maintained.
[0039] As shown in Figure 5, a wafer polishing apparatus (Engis EJW-380) was prepared with a wafer 1 as the object to be polished, and the wafer 1 was polished using the polishing pads 10 of Examples 1 to 27 and Comparative Examples 1 to 6. The wafer polishing apparatus comprises a plurality of carriers 5, a base plate 7, a drive unit 9, and a polishing fluid supply device 11. Although only a single carrier 5 is shown in Figure 5, the wafer polishing apparatus has a plurality of carriers 5. Each carrier 5 is a horizontal disc shape. A second fixing surface 5a is recessed on the lower surface of each carrier 5, and the wafer 1 is fixed to the second fixing surface 5a. A carrier rotation shaft 5b is vertically projected from the upper surface of each carrier 5. Each wafer 1 is a 4H-SiC single crystal with a diameter of 4 inches. The polishing surface 1a, which is the Si surface of each wafer 1, faces downward.
[0040] The surface plate 7 is a horizontal disc shape that encloses all the carriers 5. A surface plate rotation shaft 7a is provided protruding vertically from the bottom surface of the surface plate 7. The top surface of the surface plate 7 is the first fixed surface 7b. Disc-shaped polishing pads 10 are fixed to the first fixed surface 7b with adhesive so as to face each wafer 1. The center line O of the polishing pad 10 coincides with the first axis O1.
[0041] The drive unit 9 comprises a main drive unit 9a, a sub-drive unit 9b, and a pressurizing device 9c. The main drive unit 9a rotates the platen rotation shaft 7a around the first axis O1 at a predetermined speed. The sub-drive unit 9b rotates each carrier rotation shaft 5b around the second axis O2 at a predetermined speed. The pressurizing device 9c applies a predetermined load to each carrier rotation shaft 5b and the sub-drive unit 9b toward the platen 7.
[0042] The polishing liquid supply device 11 is located above the surface platen 7. The polishing liquid supply device 11 interposes the polishing liquid 11a between each wafer 1 and the polishing pad 41. In the polishing methods of Examples 1 to 27 and Comparative Examples 1 to 6, a polishing liquid 11a consisting of water and not containing polishing particles was used.
[0043] In this wafer polishing apparatus, each wafer 1 was polished under the following conditions. Flow rate of polishing solution 11a: 10 mL / min Load: 20kPa Rotation speed of surface plate 7: 10 rpm Carrier 5 rotation speed: 0 rpm (Intentionally kept from rotating, allowed to rotate along with the other components.)
[0044] For each polishing pad 10, the polishing rate and wear rate were determined, and the polishing retention and wear resistance were evaluated.
[0045] For the polishing rate, a rate of 0.05 μm / min or higher was marked with ◎, a rate of 0.01 μm / min or higher but less than 0.05 μm / min was marked with ○, and a rate of less than 0.01 μm / min was marked with ×.
[0046] Polishing retention was evaluated by the ratio of the polishing rate 60 minutes after the start of processing to the polishing rate at the start of processing. A ratio of 0.5 or higher was marked with ◎, a ratio of 0.1 or higher but less than 0.5 was marked with ○, and a ratio less than 0.1 was marked with ×.
[0047] Abrasion resistance was assessed as follows: a wear rate of less than 0.01 μm / min for each polishing pad 10 was marked ◎, 0.01 μm / min or more but less than 0.5 μm / min was marked ○, and 0.5 μm / min or more was marked ×. These results are also shown in Tables 4 and 5.
[0048] Tables 4 and 5 show that the polishing pads 10 of Examples 1 to 27 exhibit a higher polishing rate, higher polishing retention, and superior wear resistance compared to the polishing pads 10 of Comparative Examples 1 to 6. On the other hand, the polishing pads 10 of Comparative Examples 1 to 6 are insufficient in one or more of the following areas compared to the polishing pads 10 of Examples 1 to 27: polishing rate, polishing retention, and wear resistance.
[0049] The polishing pads 10 in Examples 1 to 27 are made of a polyimide resin, and the base material achieves high strength and high heat resistance. In addition, the polishing pads 10 in Examples 1 to 27 have a base material in which the pores are formed by a three-dimensional network structure, and adjacent to each other Stomata In between, there is a network made of the base resin with a thickness of 10 μm or less, so the first and second abrasive particles are easily exposed as the base material wears down, thus achieving high abrasive retention. Comparative Examples 3 and 6 show that this three-dimensional network structure cannot be replaced by air pores in hollow particles.
[0050] Furthermore, since the polishing pads of Examples 1 to 27 are made of a base resin and have a base material with multiple pores formed therein, and first and second polishing particles held in the base material or pores, a polishing liquid 11a that does not contain polishing particles can be used.
[0051] Therefore, by using the polishing pads 10 of Examples 1 to 27, the management of the polishing solution 11a is easy, the cleaning step of the wafer 1 after polishing can be omitted or simplified, and the disposal of the polishing solution 11a after polishing is not troublesome. Furthermore, high polish retention, high heat resistance, and excellent wear resistance can be achieved. As a result, the manufacturing cost of semiconductor devices can be further reduced, and the environmental impact can be minimized.
[0052] Furthermore, if the base material has a porosity of 50-80%, the abrasive particles are more easily exposed from the base material, making it easier to achieve a high polishing rate and high polishing retention.
[0053] If the abrasive particles include a second type of abrasive particle in addition to the first type, high polishing retention can be achieved. This is presumed to be because the second type of abrasive particle reduces the toughness of the base material and mitigates the impact force acting on the first type of abrasive particle.
[0054] Furthermore, as shown in Tables 1 and 2, high polishing retention can be achieved by including diamond particles with an average particle size of 100 μm or less, more preferably 50 μm or less. This is presumed to be because the network suitably holds the diamond particles, and the first and second polishing particles are easily exposed as the base material wears down.
[0055] Furthermore, from the viewpoint of polishing rate and polishing retention, it is preferable that the base material has air pores that are larger in diameter than the mesh.
[0056] Although the present invention has been described above in reference to Examples 1 to 27, it goes without saying that the present invention is not limited to Examples 1 to 27 and can be applied with appropriate modifications without departing from its spirit.
[0057] For example, instead of diamond particles, cubic boron nitride can be used as the first polishing particle. Furthermore, the base material can be made of polyamide-imide instead of polyimide. [Industrial applicability]
[0058] This invention can be used in semiconductor manufacturing equipment. [Explanation of Symbols]
[0059] O1…Axis center 7b…Fixed surface 7… Surface plate 5…Carrier 1… Wafer 10… Polishing pad 11a...polishing liquid
Claims
1. A polishing pad for polishing a wafer, in the presence of a polishing liquid that does not contain abrasive particles, in contact with a flat wafer under a predetermined surface pressure, and rotating relative to the wafer about an axis extending in the thickness direction of the wafer, The material comprises a base material made of a resin, having a plurality of pores formed therein, and abrasive particles held within the base material or the pores, The abrasive particles include first abrasive particles which are diamond, and second abrasive particles which are at least one of alumina, silica, talc, calcium carbonate, mica, and kaolin, which have a lower hardness than the first abrasive particles and enhance abrasive retention. The aforementioned base resin is a polyimide resin. The aforementioned base resin is 150% by volume, and the abrasive particles are contained in an amount of 75 to 360% by volume. The aforementioned base material has a porosity of 50-80%. The base material has a network that forms the pores by a three-dimensional mesh structure. The aforementioned network is characterized in that, between adjacent pores, it is made of the base resin and has a thickness of 10 μm or less, forming a polishing pad.
2. The polishing pad according to Claim 1, wherein the first polishing particles are contained in an amount of 65 to 350% by volume, with the base material resin being 150% by volume, and the second polishing particles are contained in an amount of 1 to 60% by volume, with the base material resin being 150% by volume.
3. The polishing pad according to claim 1 or 2, wherein the base material has air pores that are larger in diameter than the mesh.
4. The polishing pad according to claim 3, wherein the air vents are formed by hollow particles.
5. The polishing pad according to claim 4, wherein the hollow particles are contained in an amount of 1.6 to 28.0% by volume, with the base resin being 150% by volume.
6. It is used in a wafer polishing apparatus comprising a platen having a fixed surface extending in a direction perpendicular to the axis and rotating around the axis, and a carrier that holds a flat wafer so as to be rotatable relative to the platen, A polishing pad according to any one of claims 1 to 5, which is fixed to the fixed surface and polishes the wafer in the presence of the polishing liquid under a predetermined surface pressure.
7. In a wafer polishing method in which a flat wafer and a flat polishing pad are brought into contact with each other under a predetermined surface pressure in the presence of the polishing liquid, and the wafer and the polishing pad are rotated relative to each other around an axis extending in the thickness direction of the wafer, the wafer is polished. A wafer polishing method characterized by using a polishing pad according to any one of claims 1 to 5.