Silicon polishing method and composition for silicon polishing

Abstract

Provided is a silicon polishing method and a polishing fluid 26 with which polishing efficiency is achieved. When a polishing pad 18 that is a polishing abrasive grain-including polishing pad including polishing abrasive grains 36 is used to polish a workpiece (silicon wafer) 16 while a polishing fluid (composition for silicon polishing) 26 that does not include polishing abrasive grains is supplied, due to the polishing fluid 26 including an organic amine and water and the pH of the polishing fluid 26 being 10.6-12.8, the reactivity of the silicon is increased under the strong alkalinity from the organic amine, and thus a high polishing efficiency is achieved.

Description

Silicon polishing method and silicon polishing composition

[0001] The present invention relates to a silicon polishing method and a silicon wafer polishing composition used to polish one side of a silicon wafer known as a substrate for semiconductor devices, and relates to a technology for improving polishing efficiency while reducing the environmental load.

[0002] Conventionally, for mirror polishing of silicon wafers, a slurry-like polishing composition containing silica abrasive grains as polishing grains, a polishing accelerator containing a basic compound, and water has been used, such as the polishing composition described in Japanese Patent No. 6960341.

[0003] When a silicon wafer is polished using a polishing pad (polishing cloth) supplied with such a polishing composition, a large amount of used silica abrasive grains is discharged from the polishing apparatus, which places a heavy burden on the environment. Furthermore, the polishing accelerator added to such a polishing composition contains an amine compound, and the amine compound may contain tetramethylammonium hydroxide (TMAH), which is known to be a toxic substance, deteriorating the working environment.

[0004] Patent No. 6960341

[0005] In response to this, attempts have been made to polish silicon wafers using a polishing pad containing abrasive grains with a small amount of discharged abrasive grains, while supplying a polishing liquid (water), using only the abrasive grains contained in the polishing pad. However, although the amount of used silica abrasive grains discharged from the polishing apparatus is reduced, the polishing efficiency (polishing rate) is low and scratches caused by polishing debris occur, making it impossible to obtain polishing quality.

[0006] The present invention has been made against the background of the above circumstances, and its object is to provide a silicon polishing method and a silicon polishing composition for use in the silicon polishing method, which increase the polishing efficiency of a polishing pad containing abrasive grains while maintaining polishing quality, on the premise that a polishing pad containing abrasive grains that emits fewer abrasive grains is used in silicon polishing to reduce the environmental burden.

[0007] The inventors of the present invention have conducted extensive research in light of the above circumstances and have found that mirror polishing of silicon wafers can be performed with high efficiency by providing a silicon wafer polishing composition supplied to a polishing pad containing abrasive grains, the polishing composition containing abrasive grains, with a substance that improves chemical reactivity with silicon without using any toxic or deleterious substances, as described below. Specifically, an alkaline agent was added to the silicon polishing composition to make it alkaline so that it would react more easily with the silicon wafer, and an organic amine was added as needed as a substance that reacts with silicon. The organic amine can be added alone to water to maintain alkalinity. Alternatively, to improve the stability of alkalinity, an alkaline agent was added to water together with the organic amine. In this way, in the polishing composition for silicon polishing, which is a mixture of organic amine and water or organic amine and alkaline agent and water, piperazine, ethylenediamine, or diethylenetriamine was used as the organic amine, and a quaternary amine similar to tetramethylammonium hydroxide or aqueous ammonia, which is not a deleterious substance at low concentrations, was used as the alkaline agent.

[0008] The gist of the first invention is a method for polishing silicon wafers using a polishing pad containing abrasive grains, while supplying a silicon polishing composition that does not contain abrasive grains, wherein the silicon polishing composition contains an organic amine and water, and the pH of the silicon polishing composition is 10.6 to 12.8.

[0009] The gist of the second invention is that in the first invention, the silicon polishing composition contains an inorganic alkaline agent in addition to the organic amine and water, and the inorganic alkaline agent is ammonium hydroxide at a concentration of 2.82 mol / L or less or potassium hydroxide at a concentration of 0.93 mol / L or less.

[0010] The gist of the third invention is that in the second invention, the concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / l.

[0011] The gist of a fourth invention is that in any one of the first to third inventions, the organic amine has a concentration of 0.025 to 0.100 mol / l.

[0012] The gist of the fifth invention is that in any one of the first to fourth inventions, the organic amine is a primary amine, a secondary amine, or a substance having a primary amine and a secondary amine.

[0013] The gist of the sixth invention is that in the fifth invention, the organic amine is ethylenediamine, piperazine, or diethylenetriamine.

[0014] The gist of the seventh invention is that in any one of the first to sixth inventions, the abrasive grains contained in the polishing pad containing abrasive grains are at least one of silica, ceria, zirconia, alumina, and silicon carbide.

[0015] The gist of the eighth invention is a silicon polishing composition that is supplied onto a polishing pad containing abrasive grains when polishing a silicon wafer with the polishing pad containing abrasive grains, the silicon polishing composition containing an organic amine and water, and having a pH of 10.6 to 12.8.

[0016] The gist of the ninth invention is that, in the eighth invention, the silicon polishing composition contains, in addition to the organic amine and water, an inorganic alkaline agent, and the inorganic alkaline agent is ammonium hydroxide having a concentration of 2.82 mol / L or less or potassium hydroxide having a concentration of 0.93 mol / L or less.

[0017] The gist of a tenth aspect of the present invention is that in the ninth aspect, the concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / L.

[0018] The gist of an eleventh aspect of the present invention is that, in any one of the eighth to tenth aspects of the present invention, the organic amine has a concentration of 0.025 to 0.100 mol / l.

[0019] The gist of the twelfth invention is that in any one of the eighth to eleventh inventions, the organic amine is a primary amine, a secondary amine, or a substance having a primary amine and a secondary amine.

[0020] The gist of a thirteenth aspect of the present invention is that, in the twelfth aspect of the present invention, the organic amine is ethylenediamine, piperazine, or diethylenetriamine.

[0021] According to the silicon polishing method of the first invention, a silicon wafer is polished using a polishing pad containing abrasive grains, while a silicon polishing composition not containing abrasive grains is supplied, and the silicon polishing composition contains an organic amine and water, and the pH of the silicon polishing composition is 10.6 to 12.8. This increases the reactivity of silicon under the strong alkalinity caused by the organic amine, thereby achieving high polishing efficiency.

[0022] According to the silicon polishing method of the second invention, the silicon polishing composition contains, in addition to the organic amine and water, an inorganic alkaline agent, the inorganic alkaline agent being ammonium hydroxide at a concentration of 2.82 mol / L or less or potassium hydroxide at a concentration of 0.93 mol / L or less. This maintains a stable, strong alkalinity, further enhancing the reactivity of silicon and achieving a higher polishing efficiency. At the same time, the inorganic alkaline agent is ammonium hydroxide at a concentration of 2.82 mol / L (10%) or less or potassium hydroxide at a concentration of 0.93 mol / L (5%) or less, which is below the concentration range of deleterious substances, thereby reducing the risk of the polishing work environment.

[0023] According to the silicon polishing method of the third invention, the concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / L, so that a stable and strong alkalinity is maintained, which further enhances the reactivity of silicon, thereby achieving a higher polishing efficiency and reducing the risk of the polishing work environment.

[0024] According to the silicon polishing method of the fourth invention, the organic amine has a concentration of 0.025 to 0.100 mol / l, and therefore the reactivity of silicon is enhanced under the strong alkalinity caused by the organic amine, thereby achieving a high polishing efficiency.

[0025] According to the silicon polishing method of the fifth invention, the organic amine is a substance containing a primary amine, a secondary amine, or a primary amine and a secondary amine, and therefore, when dissolved in water, it becomes strongly alkaline.

[0026] According to the silicon polishing method of the sixth aspect of the present invention, the organic amine is ethylenediamine, piperazine, or diethylenetriamine, and therefore, when dissolved in water, it becomes strongly alkaline.

[0027] According to the silicon polishing method of the seventh invention, the abrasive grains contained in the polishing pad containing the abrasive grains are at least one of silica, ceria, zirconia, alumina, and silicon carbide, thereby achieving suitable polishing efficiency.

[0028] According to the silicon polishing composition of the eighth invention, the silicon polishing composition is supplied onto a polishing pad containing abrasive grains when polishing a silicon wafer using the polishing pad containing abrasive grains, and contains an organic amine and water. The pH of the silicon polishing composition is 10.6 to 12.8, and therefore the reactivity of silicon is enhanced under the strong alkalinity caused by the organic amine, thereby achieving high polishing efficiency.

[0029] According to the ninth invention, the silicon polishing composition contains an inorganic alkaline agent in addition to the organic amine and water, and the inorganic alkaline agent contains ammonium hydroxide at a concentration of 2.82 mol / L or less or potassium hydroxide at a concentration of 0.93 mol / L or less, thereby improving the polishing efficiency of silicon. This maintains a stable, strong alkalinity, further enhancing the reactivity of silicon and achieving a higher polishing efficiency. At the same time, the inorganic alkaline agent is ammonium hydroxide at a concentration of 2.82 mol / L (10%) or less or potassium hydroxide at a concentration of 0.93 mol / L (5%) or less, which is below the concentration range of deleterious substances, thereby reducing the risk of the polishing work environment.

[0030] According to the silicon polishing composition of the tenth invention, the concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / L, so that a stable strong alkalinity is maintained, which further enhances the reactivity of silicon, thereby achieving a higher polishing efficiency and reducing the risk of the polishing work environment.

[0031] According to the silicon polishing composition of the eleventh invention, the organic amine is 0.025 to 0.100 mol / l, so that the reactivity of silicon is enhanced under strong alkalinity due to the organic amine, thereby achieving high polishing efficiency.

[0032] According to the silicon polishing composition of the twelfth invention, the organic amine is a substance having a primary amine, a secondary amine, or a primary amine and a secondary amine, and therefore, when dissolved in water, it becomes strongly alkaline.

[0033] According to the silicon polishing composition of the thirteenth invention, the organic amine is ethylenediamine, piperazine, or diethylenetriamine, and therefore, when dissolved in water, strong alkalinity is obtained.

[0034] 1 is a perspective view conceptually illustrating the configuration of a polishing apparatus for carrying out a polishing method according to an application example of the present invention; FIG. 2 is a plan view schematically illustrating the rotation mechanism of the attachment disk of the polishing apparatus of FIG. 1; FIG. 3 is a schematic view illustrating an enlarged view of the surface structure of the polishing pad of FIG. 1; FIG. 4 is a diagram illustrating the chemical structure of a primary amine (ethylenediamine), which is an example of an organic amine contained in the polishing liquid used in the polishing method of FIG. 1; FIG. 5 is a diagram illustrating the chemical structure of a secondary amine (piperazine), which is an example of an organic amine contained in the polishing liquid used in the polishing method of FIG. 1; FIG. 6 is a diagram illustrating the chemical structure of a substance (diethylenetriamine) having a primary amine and a secondary amine, which is an example of an organic amine contained in the polishing liquid used in the polishing method of FIG. 1; FIG. 7 is a diagram illustrating the chemical structure of ammonium hydroxide, which is an example of an inorganic alkaline agent contained in the polishing liquid used in the polishing method of FIG. 1; 1 is a table showing the type of polishing pad, the composition of the polishing liquid, and the hydrogen ion concentration pH, as well as the polishing test results (removal rate PR (nm / min) and surface roughness Sa (nm) of the polished surface) for each of Comparative Example Methods 01 to 08 and Example Methods 01 to 13 in the polishing tests conducted by the inventors. FIG. 1 is a bar graph showing the relationship between the difference in the concentration (mol / L) of the organic amine contained in the grinding liquid and the polishing rate PR, using the data of FIG. 9. FIG. 1 is a bar graph showing the relationship between the difference in the concentration (mol / L) of the organic amine contained in the grinding liquid and the surface roughness Sa (nm) of the polished surface, using the data of FIG. 9. FIG. 1 is a line graph showing the relationship between the difference in the concentration (mol / L) of the organic amine contained in the grinding liquid and the polishing rate, using the data of FIG. 9. FIG. 1 is a line graph showing the relationship between the difference in the concentration (mol / L) of the organic amine contained in the grinding liquid and the surface roughness Sa (nm) of the polished surface, using the data of FIG. 9. 10 is a line graph showing the relationship between the concentration (mol / L) of piperazine, an organic amine contained in the grinding fluid, and the polishing rate, using the data of FIG. 9. 11 is a line graph showing the relationship between the concentration (mol / L) of piperazine, an organic amine contained in the grinding fluid, and the surface roughness Sa, using the data of FIG. 9. 12 is a diagram showing the change in the polishing rate PR due to differences in the concentration (mol / L) of the inorganic alkaline agent in the polishing fluid, using the data of FIG. 9.10 is a diagram showing, using the data of FIG. 9, the change in surface roughness Sa of the polished surface due to differences in the concentration (mol / l) of the inorganic alkaline agent in the polishing liquid. It is a bar graph showing, for each silica and ceria, the effect of differences in the concentrations (mol / l) of the organic amine and inorganic alkaline agent contained in the grinding liquid on the polishing rate PR from the data of FIG. 9. It is a bar graph showing, for each silica and ceria, the effect of differences in the concentrations (mol / l) of the organic amine and inorganic alkaline agent contained in the grinding liquid on the surface roughness Sa of the polished surface from the data of FIG. 9. It is a diagram showing the relationship between the pH of the polishing liquid and the polishing rate PR from the data of FIG. 9. It is a diagram showing the relationship between the pH of the polishing liquid and the surface roughness Sa from the data of FIG. 9. It is a schematic diagram explaining the polishing mechanism when a workpiece is polished on a polishing table using a slurry containing abrasive grains. It is a schematic diagram explaining the polishing mechanism when a workpiece is polished on a fixed-abrasive polishing pad with fixed abrasive grains. It is a schematic diagram explaining the polishing mechanism when a workpiece is polished on a nonwoven fabric polishing pad. 2 is a micrograph showing an example of the polishing pad of FIG. 1. FIG. 3 is a schematic diagram illustrating the polishing mechanism when a workpiece is polished on the polishing pad.

[0035] An application example of the present invention will be described in detail below with reference to the drawings.

[0036] Figure 1 conceptually shows the main components of a surface polishing apparatus 10 for carrying out a silicon polishing method according to one embodiment of the present invention, with the guide roller stationary member removed. In Figure 1, the surface polishing apparatus 10 includes a polishing platen 12 rotatably supported about a vertical axis of rotation C1, and the polishing platen 12 is driven by a platen drive motor 14 to rotate at a constant speed in one direction indicated by the arrow in the figure. A polishing pad 18 is attached to the upper surface of the polishing platen 12, i.e., the surface against which a workpiece (silicon wafer) 16 is pressed.

[0037] The workpiece 16 is held on the underside of the application disc 20, i.e., the surface facing the polishing pad 18, and the application disc 20 presses the workpiece 16 against the polishing pad 18 with a predetermined load. In addition, a drip nozzle 22 and a spray nozzle 24 are provided near the application disc 20 of the surface polishing device 10, and a polishing liquid (lubricant) 26, which is an alkaline aqueous solution, is supplied from a tank (not shown) onto the polishing surface plate 12.

[0038] The surface polishing apparatus 10 is optionally provided with an adjustment tool holder (not shown) that is rotatable about a rotation axis parallel to the rotation axis C1 of the polishing table 12 and that is movable in the direction of the rotation axis and in the radial direction of the polishing table 12, and an abrasive body adjustment tool (dresser or conditioner) such as a diamond wheel (not shown) that is attached to the underside of the adjustment tool holder, i.e., the surface facing the polishing pad 18. The adjustment tool holder and the abrasive body adjustment tool attached thereto are pressed against the polishing pad 18 while being rotated by an adjustment tool drive motor (not shown), and are moved back and forth in the radial direction of the polishing table 12, thereby adjusting the polishing surface of the polishing pad 18 and constantly maintaining the surface condition of the polishing pad 18 in a state suitable for polishing.

[0039] 2, at a position eccentric from the rotation axis C1 on the polishing table 12, a short cylindrical application disk 20 holds the workpiece 16, which is the object to be polished, on its underside by suction, adhesion, or using a holding frame or the like. The outer peripheral surface of the application disk 20 is supported by a pair of free-rotating guide rollers 30 and a drive guide roller 32 provided on a guide roller fixing base 28, which is fixed in a position fixed to a frame (not shown), so that the application disk 20 can rotate about the rotation axis C2. The application disk 20 is rotated about the rotation axis C2 by the rotational force based on the difference in peripheral speed of the polishing table or polishing pad 18, and the application disk 20 is pressed against the polishing pad 18 on the polishing table 12 by the load of, for example, a weight 34, thereby polishing the workpiece 16.

[0040] The surface polishing apparatus 10 may optionally be provided with an adjustment tool holder (not shown) that is rotatable about a rotation axis parallel to the rotation axis C1 of the polishing table 12 and that is movable in the direction of the rotation axis and in the radial direction of the polishing table 12, and an abrasive body adjustment tool (conditioner) such as a diamond wheel (not shown) that is attached to the underside of the adjustment tool holder, i.e., the surface facing the polishing pad 18. The adjustment tool holder and the abrasive body adjustment tool attached thereto are pressed against the polishing pad 18 while being rotated by an adjustment tool drive motor (not shown), and are moved back and forth in the radial direction of the polishing table 12, thereby adjusting the polishing surface of the polishing pad 18 and constantly maintaining the surface condition of the polishing pad 18 in a state suitable for polishing.

[0041] The polishing apparatus 10 uses the following polishing method. The polishing platen 12 and the polishing pad 18 attached thereto, and the attachment disk 20 and the workpiece (silicon wafer) 16 held on its underside are rotated about their respective rotation axes C1 and C2 by the platen drive motor 14 and drive guide roller 32. While the polishing liquid 26, which does not contain abrasive grains, is supplied onto the surface of the polishing pad 18 from the drip nozzle 22 and spray nozzle 24, the workpiece 16 held on the attachment disk 20 is pressed against the polishing pad 18. As a result, the polished surface of the workpiece 16, i.e., the surface facing the polishing pad 18, is polished flat by the chemical polishing action of the polishing liquid 26 and the mechanical polishing action of the abrasive grains 36 contained within and self-supplied from the polishing pad 18. The abrasive grains 36 are, for example, silica having an average particle size of about 80 nm.

[0042] The polishing pad 18 attached to the polishing platen 12 is an abrasive grain-containing polishing pad (LHA pad) made of epoxy resin or PES resin having independent pores or interconnected pores 38 containing abrasive grains 36, as shown in FIG. 3, and has dimensions of, for example, an outer diameter of about 300 mm and a thickness of about 5 mm.

[0043] The polishing pad 18 is formed in a disk shape and includes a matrix resin 40 made of epoxy resin or PES resin, which has either closed or interconnected pores 38 formed therein, and numerous abrasive grains 36 that are filled into the interconnected pores 38 of the matrix resin 40, some of which adhere to the matrix resin 40, and some of which detach from the matrix resin 40 during polishing. For this reason, the polishing pad 18 is referred to as a semi-fixed abrasive-containing polishing pad containing the abrasive grains 36, and polishing using this abrasive-containing polishing pad is referred to as semi-fixed abrasive polishing. The polishing pad 18 is composed of, for example, approximately 32% by volume of the abrasive grains 36 and approximately 33% by volume of the matrix resin 40, with the remaining volume being occupied by interconnected pores 38. The interconnected pores 38 of the matrix resin 40, which is formed in a sponge or mesh-like shape, are formed to be equal to or larger than the abrasive grains 36, and numerous abrasive grains 36 are retained within the interconnected pores 38. The base resin 40 and the abrasive grains 36 are fixed to each other by a necessary and sufficient bonding force. The polishing pad 18 of this embodiment is capable of polishing the workpiece (silicon wafer) 16 by a mechanical polishing action by the abrasive grains 36 supplied by the polishing pad 18 itself, without using a slurry containing, for example, colloidal silica, and a chemical polishing action by supplying a highly alkaline polishing liquid 26 that does not contain abrasive grains.

[0044] The abrasive grains 36 are preferably silica, but other abrasive grains containing at least one of ceria, alumina, zirconia, silicon carbide, titania, manganese compounds, barium carbonate, chromium oxide, and iron oxide may also be used. Examples of silica include fumed silica (fine silica particles obtained by burning silicon tetrachloride, chlorosilane, etc. at high temperatures in the presence of hydrogen and oxygen). The average particle size of the abrasive grains 26 is preferably 0.005 to 3.0 μm, more preferably 0.005 to 1.0 μm, more preferably 0.02 to 0.6 μm, more preferably 0.08 to 0.5 μm, and even more preferably 0.08 to 0.3 μm. For example, if the average particle size of the abrasive grains 36 exceeds 3.0 μm, abrasive grains 26 released from the matrix resin 40 during the polishing process described below are more likely to cause scratches on the workpiece 16. Furthermore, if the average particle size of the polishing grains 36 is less than 0.005 (μm), the polishing grains 36 tend to aggregate, which makes it easier for polishing scratches to occur on the object being polished during polishing.

[0045] The particle size of the abrasive grains 36 is measured by a laser diffraction / scattering method, for example, using a particle size / particle size distribution measuring device, Microtrac MT3300, manufactured by Nikkiso Co., Ltd., and the average particle size is the arithmetic mean of the particle size. Particle sizes below the measurement limit of the laser diffraction / scattering method are measured by a dynamic light scattering method using, for example, a particle size / particle size distribution measuring device, Nanotrac UPA-EX250, manufactured by Nikkiso Co., Ltd.

[0046] The polishing liquid 26 corresponds to a silicon polishing composition, contains an organic amine and water to increase alkalinity, is highly alkaline (pH=10.6 to 12.8) to enhance reactivity with the workpiece (silicon wafer) 16 and promote chemical polishing, and does not contain (free) polishing abrasive grains. The organic amine preferably has a concentration of 0.025 to 0.100 mol / L.

[0047] As the organic amine, a primary amine such as ethylenediamine having the chemical structure shown in Figure 4, a secondary amine such as piperazine having the chemical structure shown in Figure 5, or a substance having a primary amine and a secondary amine such as diethylenetriamine having the chemical structure shown in Figure 6 are preferably used. In Figures 4, 5, and 6, the portions surrounded by dashed lines indicate amino groups.

[0048] In addition to the organic amine and water, the polishing liquid 26 also contains an inorganic alkaline agent to achieve a more stable, highly alkaline solution. The inorganic alkaline agent is ammonium hydroxide at a concentration of 2.82 mol / L (10%) or less, or potassium hydroxide at a concentration of 0.93 mol / L (50%) or less, so that the concentration is below the range of deleterious substances. Preferably, the concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / L.

[0049] As the inorganic alkaline agent, for example, ammonium hydroxide shown in FIG. 7 and potassium hydroxide shown in FIG. 8 are preferably used.

[0050] [Experimental Example] The following describes an experimental example conducted by the present inventors. First, using an apparatus configured similarly to the polishing apparatus 10 shown in Figure 1, free abrasive polishing using a nonwoven fabric pad and a silica-containing (40 wt%) slurry, and semi-fixed abrasive polishing using a silica abrasive grain-containing polishing pad or a ceria abrasive grain-containing pad and 21 types of polishing solutions adjusted to have different components and pH were performed under the polishing conditions shown below to polish a common sample of a silicon single crystal plate having a diameter of 4 inches and a thickness of 350 μm. The polishing rate PR and surface roughness Sa of the silicon wafer after the polishing test were measured using the following polishing rate measurement method and surface roughness measurement method.

[0051] [Polishing processing test conditions] Surface polishing device: Lapmaster LP15 modified machine (3-axis polishing machine) Work: 4-inch φ silicon wafer <100> Work rotation speed: 60 rpm Polishing pad / polishing liquid: Nonwoven pad / silica slurry (40 wt%) Polishing pad / polishing liquid: Silica abrasive grain-containing pad / polishing liquid Polishing pad / polishing liquid: Ceria abrasive grain-containing pad / polishing liquid Polishing pad diameter: 300 mm φ Polishing pad rotation speed: 60 rpm Polishing pressure: 10.1 kPa Center distance between polishing pad / work: 85 mm Polishing liquid flow rate: 10 ml / min Dressing pressure, rotation speed, time: 25 kPa, 60 rpm, 120 sec

[0052] [Method for Measuring Polishing Rate] The difference in mass of the silicon wafer before and after the polishing test was determined using an analytical balance, and the polishing amount (wear thickness) was determined from the known density of the silicon wafer and the surface area of ​​the polished surface. The polishing amount was divided by the polishing time to calculate the polishing rate PR (nm / min).

[0053] [Surface Roughness Measurement Method] The surface roughness of the surface profile of the polished surface of the silicon wafer after the polishing test was measured using a white light interference microscope (Hitachi High-Tech VS-1330), and the arithmetic mean roughness Sa specified in ISO 25178 was calculated.

[0054] 9 shows the type of polishing pad, the composition of the polishing liquid, and the hydrogen ion concentration pH, as well as the polishing test results (removal rate PR (nm / min) and surface roughness Sa (nm) of the polished surface) for each of eight polishing methods (Comparative Examples 01 to 08) and thirteen polishing methods (Example Methods 01 to 13). The polishing rates PR (nm / min) and surface roughness Sa (nm) of the polished surface for each of Comparative Examples 01 to 08 and Example Methods 01 to 13 shown in FIG. 9 are analyzed below. Comparative Examples 01 to 02 and 04 to 08 are in a failing polishing group with a low polishing rate PR of, for example, less than 120, while Example Methods 01 to 13 are in a passing polishing group with a high polishing rate PR of, for example, 120 or more. It should be noted that the comparative example method 03 has a high polishing rate PR of, for example, 120 or more, but since the inorganic alkaline agent contained in the polishing agent used therein is tetramethylammonium hydroxide (TMAH), which is a hazardous substance, it is classified as a non-qualified polishing processing group.

[0055] The concentration of the organic amine in the polishing solution in the example methods 01 to 13 in FIG. 9 is set to 0.025 to 0.100 mol / l, and the solution is highly alkaline (pH=10.6 to 12.8).

[0056] 9, the maximum polishing rate PR obtained by Comparative Methods 01-02 and 04-08 was 118 nm / min, while the minimum polishing rate PR obtained by Example Methods 01-13 was 131 nm / min. This indicates that, if the organic amine concentration is 0.025-0.100 mol / L, a polishing solution composed of an organic amine and water, or an organic amine, an inorganic alkaline agent, and water, can achieve a higher polishing rate PR than the Comparative Method. Comparative Method 03 achieved a high polishing rate PR, but was excluded from consideration because the inorganic alkaline agent contained therein is tetramethylammonium hydroxide (TMAH), a deleterious substance.

[0057] Fig. 10 is a bar graph showing the relationship between the difference in concentration (mol / L) of the organic amine contained in the grinding fluid and the removal rate PR, using data from, for example, Comparative Example Method 02, Example Method 02, Example Method 11, and Example Method 12. As is clear from Fig. 10, compared to Comparative Example Method 02, in which the difference in concentration of the organic amine contained in the grinding fluid (pure water) was 0 mol / L and the pH was 7.0, Example Methods 02, 11, and 12, in which the difference in concentration of the organic amine contained in the grinding fluid was 0.50 mol / L and the pH was 11 or more, achieved a removal rate PR of about four times or more.

[0058] Fig. 11 is a bar graph showing the relationship between the difference in concentration (mol / L) of the organic amine contained in the grinding fluid and the surface roughness Sa (nm) of the polished surface, using data from, for example, Comparative Example Method 02, Example Method 02, Example Method 11, and Example Method 12. As is clear from Fig. 11, compared to Comparative Example Method 02, in which the difference in concentration of the organic amine contained in the grinding fluid (pure water) was 0 mol / L and the pH was 7.0, Example Methods 02, 11, and 12, in which the difference in concentration of the organic amine contained in the grinding fluid was 0.50 mol / L and the pH was 11 or more, a surface roughness Sa of about 1 / 3.6 or less was obtained.

[0059] As is clear from FIGS. 10 and 11, in Example Method 01 to Example Method 13, all of the organic amines have the effect of improving the polishing rate PR and the effect of reducing (smaller) the surface roughness Sa of the polished surface.

[0060] 12 and 13 show that even if the grinding fluid does not contain an organic alkaline agent, piperazine alone can improve the polishing rate PR if the piperazine content is 0.025 mol / L or more, and piperazine alone can reduce the surface roughness Sa of the polished surface if the piperazine content is 0.050 mol / L or more.

[0061] Fig. 12 shows the relationship between the difference in concentration (mol / L) of the organic amine contained in the grinding fluid and the removal rate, using data from, for example, Comparative Example Method 02, Example Method 01, Example Method 02, and Example Method 03. As is clear from Fig. 12, in Comparative Example Method 02, in which the difference in concentration of the organic amine contained in the grinding fluid (pure water) is 0 mol / L and the pH is 7.0, when the grinding fluid does not contain an inorganic alkaline agent but contains an organic amine alone, Example Method 01, Example Method 02, and Example Method 03, in which the difference in concentration of the organic amine is 0.250 mol / L or more and the pH is 10.6 or more, a removal rate PR of about four times or more was obtained.

[0062] Fig. 13 shows the relationship between the difference in concentration (mol / L) of organic amine contained in the grinding fluid and the surface roughness Sa (nm) of the polished surface, using data from, for example, Comparative Example Method 02, Example Method 01, Example Method 02, and Example Method 03. As is clear from Fig. 13, in Comparative Example Method 02, in which the difference in concentration of organic amine contained in the grinding fluid (pure water) is 0 mol / L and the pH is 7.0, Example Methods 01, 02, and 03, in which the grinding fluid does not contain an inorganic alkaline agent but contains an organic amine alone, have a difference in concentration of organic amine of 0.250 mol / L or more and a pH of 10.6 or more, and a surface roughness Sa of about 1 / 1.9 or less was obtained.

[0063] 14 and 15 show that the polishing rate can be improved as the concentration (mol / l) of piperazine, which is an organic amine contained in the grinding fluid, increases, and the surface roughness Sa can be reduced and the polishing rate PR can be increased as the amount of ammonia water, which is an inorganic alkaline agent, is added to the polishing fluid.

[0064] The relationship between the concentration (mol / l) of piperazine, an organic amine contained in the grinding fluid, and the polishing rate in Figure 14, and the relationship between the concentration (mol / l) of piperazine, an organic amine contained in the grinding fluid, and the surface roughness Sa in Figure 15 are shown using data from Comparative Example Method 02, Comparative Example Method 08, Example Method 01, Example Method 02, Example Method 03, Example Method 05, Example Method 07, Example Method 08, Example Method 09, and Example Method 10.

[0065] In Fig. 14, as the concentration (mol / L) of piperazine contained in the polishing solution increases, the polishing rate PR increases and reaches saturation. Also, as the concentration (mol / L) of ammonia contained in the polishing solution increases, the polishing rate PR also increases. In Fig. 15, as the concentration (mol / L) of piperazine contained in the polishing solution increases, the surface roughness Sa of the polished surface decreases and reaches saturation. Also, as the concentration (mol / L) of ammonia contained in the polishing solution increases, the surface roughness Sa of the polished surface also decreases.

[0066] Fig. 16 shows the change in the polishing rate PR due to the difference in the concentration (mol / L) of the inorganic alkaline agent in the polishing solution, and Fig. 17 shows the change in the surface roughness Sa of the polished surface due to the difference in the concentration (mol / L) of the inorganic alkaline agent in the polishing solution. In Fig. 16 and Fig. 17, ammonia water and tetramethylene ammonium hydroxide have the effect of improving the polishing rate PR. In contrast, tetraethylammonium hydroxide significantly reduces the polishing rate PR, and while kalium hydroxide also reduces the polishing rate PR, it has the effect of improving the surface roughness Sa.

[0067] Fig. 18 is a bar graph showing the effect of differences in the concentrations (mol / L) of organic amines and inorganic alkaline agents contained in the grinding fluid on the polishing rate PR for silica and ceria. Fig. 19 is a bar graph showing the effect of differences in the concentrations (mol / L) of organic amines and inorganic alkaline agents contained in the grinding fluid on the surface roughness Sa of the polished surface for silica and ceria. As is clear from Figs. 18 and 19, whether the polishing abrasive grains are silica or ceria, the increase in the concentration of piperazine in the polishing fluid increases the polishing rate PR and decreases the surface roughness Sa in the same way.

[0068] FIG. 20 shows the relationship between the pH of the polishing liquid and the polishing rate PR based on the data in FIG. 9 , and FIG. 21 shows the relationship between the pH of the polishing liquid and the surface roughness Sa of the polished surface based on the data in FIG. 20 and FIG. 21 . In FIGS. 20 and 21 , Example Methods 01 to 13, which have polishing rates PR of 120 or more, are indicated by ●, Comparative Examples 01 to 02 and 04 to 08, which have polishing rates PR of less than 120, are indicated by △, and Comparative Example Method 03 is indicated by ▲. FIG. 20 shows that the polishing rate PR peaks around pH 11 to 12. FIG. 21 shows that Example Methods 01 to 13 have pH values ​​in the range of 10.6 to 12.8, and that the higher the pH, the lower the surface roughness Sa of the polished surface.

[0069] 22 is a schematic diagram illustrating the polishing mechanism in the case of free-abrasive polishing, in which a workpiece 16 is polished on a hard polishing pad or polishing platen 12 using a slurry containing abrasive grains 36. In this case, the number of active abrasive grains (shown as ●) is greater than the number of inactive abrasive grains (shown as ○), and the abrasive grains 36 rotate and act on the entire surface, resulting in a high polishing rate PR. However, the uneven distribution of the active abrasive grains makes it difficult to achieve high flatness. In addition, many of the abrasive grains 36 (shown as ○) do not contribute to polishing, resulting in a large amount of abrasive grain 36 being discharged, which places a heavy burden on the environment.

[0070] 23 is a schematic diagram illustrating the polishing mechanism when a workpiece 16 is polished on a fixed-abrasive polishing pad 18a in which abrasive grains 36 are directly fixed in a non-foaming matrix resin 40. In this case, the amount of abrasive grains 36 supplied from the fixed-abrasive polishing pad 18a is small, and the number of abrasive grains active in polishing, indicated by ●, is small, resulting in a low environmental impact. However, because the active abrasive grains 36, indicated by ●, that contribute to polishing, do not rotate, they only act on one point on the surface of the abrasive grains 36, resulting in a low polishing rate PR due to the small number of points of action. Furthermore, because the abrasive grains 36 do not rotate, scratches are likely to appear on the workpiece 16.

[0071] 24 is a schematic diagram illustrating the polishing mechanism when a workpiece 16 is polished on a polishing pad 18b made of nonwoven fabric in which relatively rigid resin fibers F are bonded together in a meandering manner. In this case, the polishing grains 36, indicated by ●, which are active abrasive grains that contribute to polishing and are contained in the spaces between the resin fibers, can move in all directions, including vertical movement (perpendicular to the polishing surface). When the polishing grains 36 present on the surface of the polishing pad 18b overcome the protrusions of the polishing pad 18b, a large load is applied to the workpiece 16, making it prone to scratches.

[0072] FIG. 25 is a micrograph of a semi-fixed polishing pad 18 according to the aforementioned embodiment, and FIG. 26 is a schematic diagram illustrating the polishing mechanism when a workpiece 16 is polished on the polishing pad 18. In FIG. 26, the polishing grains 36 are relatively loosely accommodated in the interconnected pores 38 formed in the matrix resin 40, and a moderate amount of polishing grains 36 is supplied from the polishing pad 18a. The active abrasive grains 36, indicated by a black circle, that contribute to polishing primarily move laterally (parallel to the polishing surface) and rotate, with little vertical movement (perpendicular to the polishing surface). During polishing, the polishing process progresses as the polishing grains 36 rotate, and the vertical movement of the polishing grains 36 (perpendicular to the polishing surface) is minimal. Therefore, the polishing grains 36 remain within the interconnected pores 38 until the workpiece 16 passes. This prevents a large load from being applied to the workpiece 16, making it less likely to scratch the workpiece 16.

[0073] As described above, according to the polishing method of this embodiment and the polishing liquid 26 used therein, when the workpiece (silicon wafer) 16 is polished using the polishing pad 18, which is an abrasive grain-containing polishing pad containing abrasive grains 36, while supplying the polishing liquid (silicon polishing composition) 26 that does not contain abrasive grains, the polishing liquid 26 contains an organic amine and water, and the pH of the polishing liquid 26 is 10.6 to 12.8. Therefore, the reactivity of silicon is enhanced under the strong alkalinity caused by the organic amine, and high polishing efficiency can be obtained.

[0074] Furthermore, according to the polishing method and polishing solution 26 used therein, the polishing solution 26 contains, in addition to the organic amine and water, an inorganic alkaline agent, which is ammonium hydroxide at a concentration of 2.82 mol / L or less, or potassium hydroxide at a concentration of 0.93 mol / L or less. This maintains a stable, strong alkalinity, further enhancing the reactivity of the workpiece (silicon wafer) 16 and achieving a higher polishing efficiency. At the same time, the inorganic alkaline agent used is ammonium hydroxide at a concentration of 2.82 mol / L (10%) or less, or potassium hydroxide at a concentration of 0.93 mol / L (5%) or less, which is below the concentration range of deleterious substances, thereby reducing the risk of hazardous substances in the polishing work environment.

[0075] Furthermore, according to the polishing method of this embodiment and the polishing solution 26 used therein, the concentration of the inorganic alkaline agent contained in the polishing solution 26 is 0.030 to 0.100 mol / L, and therefore a stable, strong alkalinity is maintained. This further enhances the reactivity of the workpiece (silicon wafer) 16, thereby achieving a higher polishing efficiency and reducing the risk of the polishing work environment.

[0076] Furthermore, according to the polishing method of this embodiment and the polishing solution 26 used therein, the organic amine contained in the polishing solution 26 is 0.025 to 0.100 mol / L, and therefore the reactivity of the workpiece (silicon wafer) 16 is enhanced under the strong alkalinity caused by the organic amine, thereby achieving high polishing efficiency.

[0077] Furthermore, according to the polishing method of this embodiment and the polishing liquid 26 used therein, the organic amine contained in the polishing liquid 26 is a substance that is a primary amine, a secondary amine, or a substance that has a primary amine and a secondary amine, and therefore, when dissolved in water, it becomes strongly alkaline.

[0078] Furthermore, according to the polishing method of this embodiment and the polishing liquid 26 used therein, the organic amine contained in the polishing liquid 26 is ethylenediamine, piperazine, or diethylenetriamine, and therefore, when dissolved in water, it becomes strongly alkaline.

[0079] Furthermore, according to the polishing method of this embodiment and the polishing liquid 26 used therein, the abrasive grains 36 contained in the polishing pad 18, which is a polishing pad containing abrasive grains, are at least one of silica, ceria, zirconia, alumina, silicon carbide, titania, manganese compounds, barium carbonate, chromium oxide, and iron oxide, thereby achieving favorable polishing efficiency.

[0080] Although one embodiment of the present invention has been described above, the present invention can also be applied in other aspects.

[0081] For example, in the surface polishing apparatus 10 of the above-mentioned embodiment, the workpiece 16 on the polishing pad 18, which is driven to rotate around the rotation axis C1, is rotated around the rotation axis C2 parallel to the rotation axis C1, but the workpiece 16 may be polished while rotating and revolving by revolving the rotation axis C2 of the workpiece 16 along an orbit around the revolution axis parallel to the rotation axis C1.

[0082] Furthermore, although epoxy resin or PES resin is used for the base resin 40, other resins may be used, such as at least one of rigid foamed polyurethane resin, polyamide, polyamideimide, polyimide, polyacrylonitrile, polyvinylidene fluoride, cellulose acetate, polyvinyl alcohol, polyester, polyolefin resin, and non-foamed polyurethane.

[0083] The silica used for the abrasive grains 26 is preferably, for example, fumed silica (fine silica particles obtained by burning silicon tetrachloride, chlorosilane, etc. at high temperatures in the presence of hydrogen and oxygen).

[0084] Although not specifically exemplified, the present invention can be used with various modifications within the scope of the invention.

[0085] 10: Polishing device 12: Polishing platen 16: Work (silicon wafer) 18: Polishing pad 20: Adhesive disc 26: Polishing liquid (silicon polishing composition) 36: Polishing abrasive grains

Claims

1. A method for polishing silicon wafers using a polishing pad containing abrasive grains while supplying a silicon polishing composition not containing abrasive grains, comprising: The silicon polishing composition contains an organic amine and water, The pH of the silicon polishing composition is 10.6 to 12.

8. A method for polishing silicon comprising the steps of:

2. The silicon polishing composition contains an inorganic alkaline agent in addition to the organic amine and water, The inorganic alkaline agent is ammonium hydroxide having a concentration of 2.82 mol / l or less, or potassium hydroxide having a concentration of 0.93 mol / l or less.

2. The silicon polishing method according to claim 1.

3. The concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / l.

3. The silicon polishing method according to claim 2.

4. The organic amine is 0.025 to 0.100 mol / l.

4. The method for polishing silicon according to claim 1,

5. The organic amine is a primary amine, a secondary amine, or a material having a primary amine and a secondary amine.

4. The method for polishing silicon according to claim 1,

6. The organic amine is ethylenediamine, piperazine, or diethylenetriamine.

6. The silicon polishing method according to claim 5.

7. The abrasive grains contained in the polishing pad containing the abrasive grains are at least one of silica, ceria, zirconia, alumina, and silicon carbide.

4. The method for polishing silicon according to claim 1,

8. A silicon polishing composition that is supplied onto a polishing pad containing abrasive grains when polishing a silicon wafer using the polishing pad containing abrasive grains, comprising: Contains an organic amine and water, The pH is 10.6 to 12.

8. A composition for polishing silicon, comprising:

9. The silicon polishing composition contains an inorganic alkaline agent in addition to the organic amine and water, The inorganic alkaline agent is ammonium hydroxide having a concentration of 2.82 mol / l or less or potassium hydroxide having a concentration of 0.93 mol / l or less. The silicon polishing composition according to claim 8.

10. The concentration of the inorganic alkaline agent is 0.030 to 0.100 mol / l. The silicon polishing composition according to claim 9 .

11. The organic amine is 0.025 to 0.100 mol / l. The silicon polishing composition according to any one of claims 8 to 10.

12. The organic amine is a primary amine, a secondary amine, or a material having a primary amine and a secondary amine. The silicon polishing composition according to any one of claims 8 to 10.

13. The organic amine is ethylenediamine, piperazine, or diethylenetriamine. The silicon polishing composition according to any one of claims 8 to 10.