Polishing liquid and polishing method for semiconductor substrate

Abstract

To provide a polishing liquid and polishing method that enable polishing in the low polishing rate region without changing the mechanical polishing conditions, thereby obtaining a high-quality polished surface.SOLUTION: The polishing liquid for a semiconductor substrate including permanganate ions and water contains at least one type of phosphate or phosphoric acid. The phosphate concentration (total content) is 0.005 mol / L or more and less than 0.02 mol / L. This facilitates polishing in the low polishing rate range without changing the mechanical polishing conditions, thereby obtaining a high-quality polished surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a polishing liquid and a polishing method used to polish one surface of a semiconductor substrate used in a semiconductor device, and relates to a technology that enables polishing at a low polishing rate that is not possible by changing mechanical conditions, and that obtains a high-quality polished surface. [Background technology]

[0002] Regarding the polishing of semiconductor substrates (semiconductor wafers) such as SiC, for example, there is a surface polishing method described in Patent Document 1. According to this surface polishing method, an acidic polishing liquid containing permanganate ions, a weak acid, and a soluble salt thereof, and having a pH adjusted to 0.5 to 6 before the start of polishing, is circulated and repeatedly supplied to the polishing surface.

[0003] According to this polishing method, the inclusion of a weak acid and its soluble salt in the polishing liquid suppresses a rapid decrease in the polishing rate caused by a sudden increase in the pH of the polishing liquid due to oxidation of the material to be polished by permanganate ions in the polishing liquid, thereby improving the polishing efficiency of the polished surface of the semiconductor substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6301571 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, in flat surface polishing of semiconductor substrates, there is a strong correlation between the polishing rate of the semiconductor substrate and the surface roughness of the polished surface, such that the lower the polishing rate, the higher the surface roughness (the smaller the surface roughness Ra).

[0006] However, in the conventional surface polishing method for semiconductor substrates described above, even if mechanical conditions such as the rotation speed of the polishing platen and the pressure on the polishing surface were changed in order to obtain a high-quality polished surface, it was impossible to obtain a low polishing rate of, for example, 500 nm / h or less.

[0007] The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a polishing liquid and a polishing method that enable polishing in a low polishing rate range without changing the mechanical polishing conditions, thereby obtaining a high-quality polished surface.

[0008] The present inventors have conducted extensive research in light of the above circumstances and have found that adding a phosphate or phosphoric acid to an acidic polishing solution containing permanganate ions can easily reduce the polishing rate and improve the quality of the polished surface. The present invention was made based on this finding. [Means for solving the problem]

[0009] That is, the gist of the first invention is (a) a polishing liquid for semiconductor substrates containing permanganate ions and water, (b) containing at least one type of phosphate or phosphoric acid, and (c) the concentration (total content) of the phosphate is 0.005 mol / L or more and less than 0.02 mol / L.

[0010] The gist of the second invention is that, in the first invention, the phosphate is at least one of disodium hydrogen phosphate (Na2HPO4), dipotassium hydrogen phosphate (K2HPO4), and potassium dihydrogen phosphate (KH2PO4).

[0011] The gist of the third invention is that, in the second invention, the phosphate is disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO), and the concentration (total content) of the phosphate is 0.005 mol / L or more and 0.01 mol / L or less.

[0012] The gist of the fourth invention is that in the third invention, in a two-dimensional coordinate system consisting of an x-axis representing the content of disodium hydrogen phosphate and a y-axis representing the content of potassium dihydrogen phosphate, the concentrations of the disodium hydrogen phosphate and the potassium dihydrogen phosphate are within a region that satisfies formula (1) and formula (2). 0≦y<0.01 (1) -(5 / 12)(y-0.0114)≦x<0.01 ···(2)

[0013] The gist of the fifth invention is that in the first invention, the concentration of the phosphoric acid is 0.0011 mol / L or more and less than 0.015 mol / L.

[0014] The gist of the sixth invention is (a) a polishing method for wet-polishing a semiconductor substrate on a polishing pad using the polishing liquid of any one of the first to fifth inventions, (b) the polishing liquid does not contain abrasive grains, and (c) the polishing pad is an abrasive grain-containing polishing pad having a base resin having independent pores or interconnected pores that accommodate the abrasive grains, and the abrasive grains filled in the independent pores or interconnected pores. [Effects of the Invention]

[0015] The polishing solution of the first invention is a polishing solution for semiconductor substrates that contains permanganate ions and water, and contains at least one type of phosphate or phosphoric acid, with the phosphate concentration (total content) being 0.005 mol / L or more and less than 0.02 mol / L. This makes it possible to easily perform polishing in a low polishing rate range without changing the mechanical polishing conditions, and to obtain a high-quality polished surface.

[0016] According to the polishing liquid of the second invention, the phosphate is at least one of disodium hydrogen phosphate (NaHPO), dipotassium hydrogen phosphate (KHPO), and potassium dihydrogen phosphate (KHPO), so polishing in a low polishing rate range is easily possible without changing the mechanical polishing conditions, and a high-quality polished surface can be obtained.

[0017] According to the polishing liquid of the third invention, the phosphate is disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO), and the phosphate concentration (total content) is 0.005 mol / L or more and 0.01 mol / L or less. This makes it possible to easily perform polishing in a low polishing rate range without changing the mechanical polishing conditions, and to obtain a high-quality polished surface.

[0018] According to the polishing liquid of the fourth invention, in a two-dimensional coordinate system consisting of an x-axis representing the content of disodium hydrogen phosphate and a y-axis representing the content of potassium dihydrogen phosphate, the concentrations of disodium hydrogen phosphate and potassium dihydrogen phosphate are within the region that satisfies formulas (1) and (2). Therefore, polishing in a low polishing rate region is easily possible without changing the mechanical polishing conditions, and a high-quality polished surface can be obtained. 0≦y<0.01 (1) -(5 / 12)(y-0.0114)≦x<0.01 ···(2)

[0019] In the polishing solution of the fifth invention, the concentration of phosphoric acid is 0.0011 mol / L or more and less than 0.015 mol / L, which makes it possible to easily perform polishing in a low polishing rate range without changing the mechanical polishing conditions, and to obtain a high-quality polished surface.

[0020] According to the sixth aspect of the present invention, a polishing method is provided in which a semiconductor substrate is wet-polished on a polishing pad using the polishing liquid of any one of the first to fifth aspects of the present invention. The polishing liquid does not contain abrasive grains, and the polishing pad is an abrasive-containing polishing pad having a base resin having closed or interconnected pores containing the abrasive grains, and the closed or interconnected pores are filled with the abrasive grains. This facilitates polishing in a low polishing rate range without changing the mechanical polishing conditions, resulting in a high-quality polished surface. Furthermore, since expensive abrasive grains are not consumed in large quantities, the polishing process can be performed inexpensively without increasing the burden on the environment. [Brief explanation of the drawings]

[0021] [Figure 1] 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; [Figure 2] 2 is an enlarged schematic view illustrating the surface structure of the polishing pad of FIG. 1. FIG. [Figure 3] 1 is a table showing the composition of the polishing liquid used in polishing test 1 by the present inventors. [Figure 4] 4 is a table showing the polishing rate, surface roughness, and scratches obtained for each polishing liquid in the polishing test 1 shown in FIG. 3. [Figure 5] FIG. 5 is a correlation diagram showing the relationship between the polishing rate and the surface roughness obtained for each polishing liquid in FIG. [Figure 6] 5 is an evaluation table for evaluating, by scores, the polishing rate and surface quality (surface roughness and scratches) obtained for each polishing liquid in FIG. [Figure 7] 5 is a table showing the total evaluation score of the polishing results using the polishing liquid shown in FIG. 4, which contains disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO) as phosphate. [Figure 8] FIG. 8 is a diagram showing the concentration ranges of disodium hydrogen phosphate (Na 2 HPO 4 ) and / or potassium dihydrogen phosphate (KH 2 PO 4 ) in the polishing liquids of FIG. 7 that have a total evaluation score of 5 or more. [Figure 9] 1 is a table showing the composition of the polishing liquid used in Polishing Test 1 by the present inventors, the polishing rate for each polishing liquid, the surface roughness value and scratches, and their evaluation points. [Figure 10] 10 is a line graph showing the relationship between the concentration of phosphoric acid at each level shown in FIG. 9 and the total evaluation score. DETAILED DESCRIPTION OF THE INVENTION

[0022] An application example of the present invention will be described in detail below with reference to the drawings. Note that in the following embodiment, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0023] The polishing liquid 26 of this embodiment is used in a surface polishing apparatus 10 for carrying out a surface polishing method for a workpiece (semiconductor substrate) 16 such as SiC. FIG. 1 conceptually shows the main components of the surface polishing apparatus 10 with the guide roller fixing base removed. In FIG. 1, the surface polishing apparatus 10 is provided with a polishing platen 12 rotatably supported about its vertical rotation axis C1, and the polishing platen 12 is rotated at a constant speed in one rotation direction indicated by the arrow in FIG. 1 by a platen drive motor 14. A polishing pad 18 is attached to the upper surface of the polishing platen 12, i.e., the surface against which the workpiece (e.g., a SiC wafer) 16 is pressed.

[0024] The workpiece 16 is held on the lower surface 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. A drip nozzle 22 is provided near the application disc 20 of the surface polishing device 10, and a polishing liquid (lubricant) 26, which is a polishing composition, is delivered from a polishing liquid supply device 24 and supplied onto the polishing surface plate 12.

[0025] 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 surface of the application disk 20 is supported by a pair of free-rotating guide rollers and a drive guide roller provided on a fixed guide roller fixing base fixed to a frame (not shown), allowing the application disk 20 to rotate about the rotation axis C2. The application disk 20 is rotated about the rotation axis C2 by a rotational force based on the difference in peripheral speed between the polishing table 12 and the 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.

[0026] The following polishing method is applied during polishing using the surface polishing apparatus 10. Specifically, 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 rollers. While a polishing liquid 26 that does not contain abrasive grains 36 is supplied onto the surface of the polishing pad 18 from the drip nozzle 22 and a spray nozzle (not shown), the workpiece 16 held on the attachment disk 20 is pressed against the polishing pad 18. As a result, the surface of the workpiece 16 to be polished, 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 in and self-supplied from the polishing pad 18.

[0027] The polishing pad 18 attached to the polishing table 12 is formed in a disk shape and includes a matrix resin 40 made of epoxy resin or PES resin, which has either closed pores or interconnected pores 38, 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 an LHA pad, which contains the abrasive grains 36. 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 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 bonded to each other by a necessary and sufficient bonding force. The polishing pad 18 of this embodiment is capable of polishing the workpiece 16 by a mechanical polishing action of 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 of the supplied polishing liquid 26 that does not contain the abrasive grains 36.

[0028] The abrasive grains 36 are preferably silica, but other abrasive grains 36 containing at least one of ceria, alumina, zirconia, silicon carbide, titania, manganese compounds, barium carbonate, chromium oxide, and iron oxide may also be used. As the silica, for example, fumed silica (fine silica particles obtained by burning silicon tetrachloride, chlorosilane, etc. at high temperatures in the presence of hydrogen and oxygen) is preferably used. The average particle size of the abrasive grains 36 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, polishing scratches on the workpiece 16 are more likely to occur. Furthermore, if the average particle size of the polishing grains 36 is below 0.005 (μm), the polishing grains 36 tend to aggregate, which makes it easier for polishing scratches to occur on the workpiece 16 during polishing. Note that the particle size of the polishing 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.

[0029] The polishing solution 26 is an aqueous solution containing permanganate ions and phosphoric acid and / or a phosphate. The polishing solution 26 is, for example, an aqueous solution containing potassium permanganate (KMnO), phosphoric acid (HPO), and / or a phosphate. The phosphate is at least one of disodium hydrogen phosphate (NaHPO), dipotassium hydrogen phosphate (KHPO), and potassium dihydrogen phosphate (KHPO). The concentration (total content) of the phosphate in the polishing solution 26 is preferably 0.005 mol / L or more and less than 0.02 mol / L. Preferably, the phosphate contained in the polishing solution 26 is disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO), and the concentration (total content) of the phosphate is 0.005 mol / L or more and 0.01 mol / L or less. More preferably, in a two-dimensional coordinate system consisting of an x-axis representing the content of disodium hydrogen phosphate contained in the polishing liquid 26 and a y-axis representing the content of potassium dihydrogen phosphate, the concentrations of disodium hydrogen phosphate and potassium dihydrogen phosphate contained in the polishing liquid 26 are within a region that satisfies the above-mentioned formulas (1) and (2).

[0030] (Explanation of Polishing Test 1) Next, the inventors will describe the polishing test and test results performed under the following conditions: Polishing Test 1 (shown below). This polishing test was performed using 19 types of polishing solutions 26, including single-pass polishing (Levels 12, 19, 21, 23, 38, 39, 40, 41, 42, 43, 44, 47, 48, 51, 52, 53, and 54) and double-pass polishing (Levels 45 and 46), as shown in FIG. 3 . The polishing rate PR (nm / h), surface roughness Ra (nm), and number of scratches on the polished substrates polished using each of the 19 types of polishing solutions 26 were measured using the following measurement methods. The above levels refer to sample numbers of polishing solutions 26 with different compositions.

[0031] (Polishing test conditions) Polishing equipment: SPEEDFAM 36SPAW Polishing pad rotation speed: 35 rpm Polished object: Si surface of single crystal SiC wafer (6 inch) Polishing pad: Abrasive grain-containing (LHA) pad Type of contained abrasive: Silica Polishing solution: 19 types of aqueous solutions containing KMnO4 polishing solution, or KMnO4 polishing solution and potassium permanganate (KMnO4), or CH3COOH, CH3COONa, H3PO4, Na2HPO4, K2HPO4, or KH2PO4 Polishing liquid capacity: 2L Polishing liquid flow rate: 100ml / min Polishing time: 120 mins, 1-stage polishing Levels 45 and 46 are polished in two stages: 100 min + 20 min

[0032] (Method for measuring polishing rate PR) The difference in thickness of the SiC single crystal plate before and after the polishing test was measured using a spectroscopic interference laser displacement meter, and the polishing rate PR (nm / h) was calculated by dividing the difference in thickness before and after the polishing test by the polishing time. (Surface roughness Ra measurement method) The surface profile of the Si face ((001) face) of the SiC single crystal plate after the polishing test was measured using a white light interference microscope (Hitachi High-Tech VS-1330), and the arithmetic mean surface roughness Ra specified in ISO 25178 was calculated from the surface profile. (Method for measuring scratches) The surface differential interference contrast image of the Si face ((001) face) of the SiC single crystal plate after the polishing test was measured using a laser microscope (Lasertec Opterics Hybrid), and the number of scratches was counted.

[0033] Figure 4 shows the polishing test results for each of the 19 types of polishing liquid 26. Figure 5 is a plot of points showing the polishing rate PR and surface roughness Ra in the polishing test obtained for each of the 17 types of polishing liquid 26 for one polishing in Figure 4. Figure 5 shows the relationship between the polishing rate PR in the polishing test and the surface roughness Ra, where the lower the polishing rate PR in the polishing test, the lower the surface roughness Ra.

[0034] Next, the evaluation criteria set out in Figure 6 were applied to the test results in Figure 4 to determine individual evaluation points for each measurement value, and a total evaluation point for each polishing liquid 26 was determined and added to Figure 4. Then, if level 19, where polishing was performed using only potassium permanganate without any phosphate, is used as a benchmark, a level with a higher total evaluation point than level 19, i.e., a total evaluation point of 6 or more, can be evaluated as having a high effect.

[0035] Level 12 is an example using an acetate buffer solution, which is a buffer solution other than phosphate. Levels 38, 39, 47, and 48 are examples in which the concentrations of phosphoric acid and phosphate were changed. Level 38, which was polished at a low polishing rate, achieved the highest rating of "8" for surface roughness Ra and scratches. Levels 39, 47, and 48 have decreasing total ratings. Level 41 is an example in which a low-concentration potassium permanganate polishing solution was used to lower the polishing rate PR, and received a total rating of "7." Based on these facts, it is desirable to include 0.20 mol / L of potassium permanganate and a total of approximately 0.01 mol / L of phosphate.

[0036] The second polishing involves polishing for 100 minutes using polishing solution 26 containing KMnO4 (0.250 mol / L), followed by polishing for 20 minutes using polishing solution 26 of level 45 or polishing solution 26 of level 46. Compared to the use of polishing solution 26 of level 46, which does not contain potassium permanganate and contains only phosphate, polishing solution 26 of level 45 contains phosphate at the concentration of level 38, which is the highest rating for a single polishing, and so received a total rating of "8", the highest rating.

[0037] FIG. 7 is a table showing the total evaluation scores of polishing solutions 26 in descending order when the phosphate contained therein is disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO). These polishing solutions 26 have low removal rates PR and low evaluation scores, but high evaluation scores for surface roughness Ra and scratches. When the concentrations (mol / L) of disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO) in polishing solution 26 shown in FIG. 7 are plotted on an xy two-dimensional Cartesian coordinate system, with x representing the concentration of disodium hydrogen phosphate and y representing the concentration of potassium dihydrogen phosphate, it becomes clear that a polished surface of high surface quality can be obtained in a specific region, as shown in FIG. 8.

[0038] In Figure 8, plots marked with ● indicate levels where the total evaluation score is 6 or more, and plots marked with △ indicate levels where the total evaluation score is 5 or less. The numbers near the ● and △ marks in Figure 8 indicate the level numbers in Figure 7, for example. The specific region is a region that includes levels where the total evaluation score is 6 or more. The y-direction range of this specific region is between the line L1 at y = 0 and the line L2 at y = 0.01, and the x-direction range of this specific region is between the line L3 at x = 0.01 and the line L4 at y = -(12 / 5)x + 0.0114. In other words, the specific region is a region that satisfies the following equations (1) and (2).

[0039] 0≦y<0.01 (1) -(5 / 12)(y-0.0114)≦x<0.01 ···(2)

[0040] (Explanation of polishing test 2) Next, the inventors conducted Polishing Test 2 described below under the same conditions as those for Polishing Test 1. In Polishing Test 2, polishing tests and test results for four polishing solutions, Levels 56, 57, 58, and 59, are described. As shown in FIG. 9 , these four levels share the commonality of containing potassium permanganate, but differ in the concentration of phosphoric acid contained instead of phosphate. Polishing was performed using polishing solutions 26 of Levels 56, 57, 58, and 59 under the same conditions as those for Polishing Test 1. The polishing rate PR (nm / h), surface roughness Ra (nm), and number of scratches for the polished substrates polished in the polishing test for each polishing solution 26 were measured using the aforementioned measurement methods, and the results were evaluated in the same manner as for Polishing Test 1. Figure 9 shows the evaluation results for a total of six levels with different phosphoric acid concentrations, including the four levels 56, 57, 58, and 59 mentioned above, as well as levels 19 and 43 evaluated in Polishing Test 1. Figure 10 shows the change in the total evaluation score for surface quality versus the phosphoric acid concentration.

[0041] 9 and 10, when level 19, which does not contain phosphoric acid, is used as a benchmark, the total evaluation score for level 57 is lower than level 19, while levels 43, 56, 58, and 59 exhibited effects equal to or greater than level 19. As shown in FIG. 10, the total evaluation score increases as the phosphoric acid concentration increases, decreases when the phosphoric acid concentration exceeds 0.01 (mol / L), and falls below level 19 when the phosphoric acid concentration exceeds 0.015 (mol / L). In other words, polishing solution 26, which uses phosphoric acid instead of phosphate, can obtain a total evaluation score higher than that of the benchmark level 19 when the phosphoric acid concentration is in the range of 0.0011 (mol / L) or more and less than 0.015 (mol / L).

[0042] As described above, the polishing solution 26 of this embodiment is a polishing solution 26 for a semiconductor substrate (workpiece 16) that contains permanganate ions and water, and contains at least one type of phosphate or phosphoric acid, with the phosphate concentration (total content) being 0.005 mol / L or more and less than 0.02 mol / L. This makes it possible to easily perform polishing in a low polishing rate range without changing the mechanical polishing conditions, and to obtain a high-quality polished surface.

[0043] Furthermore, the phosphate contained in the polishing solution 26 of this embodiment is at least one of disodium hydrogen phosphate (NaHPO), dipotassium hydrogen phosphate (KHPO), and potassium dihydrogen phosphate (KHPO). This makes it possible to easily perform polishing in a low polishing rate range without changing the mechanical polishing conditions, and to obtain a high-quality polished surface.

[0044] Furthermore, the phosphate contained in the polishing solution 26 of this embodiment is disodium hydrogen phosphate (NaHPO) and / or potassium dihydrogen phosphate (KHPO), and the concentration (total content) of the phosphate is 0.005 mol / L or more and 0.01 mol / L or less. Therefore, polishing in a low polishing rate range is easily possible without changing the mechanical polishing conditions, and a high-quality polished surface can be obtained.

[0045] Furthermore, in this embodiment, in an xy two-dimensional Cartesian coordinate system consisting of an x-axis representing the content of disodium hydrogen phosphate and a y-axis representing the content of potassium dihydrogen phosphate, the concentrations of disodium hydrogen phosphate and potassium dihydrogen phosphate contained in the polishing liquid 26 are within the region that satisfies the above-mentioned formulas (1) and (2). Therefore, polishing in a low polishing rate region is easily possible without changing the mechanical polishing conditions, and a high-quality polished surface can be obtained.

[0046] Furthermore, in the polishing solution 26 of this embodiment, in which phosphoric acid is used instead of phosphate, when the concentration of phosphoric acid is 0.0011 mol / L or more and less than 0.015 mol / L, polishing in a low polishing rate range is easily possible without changing the mechanical polishing conditions, and a high-quality polished surface can be obtained.

[0047] The polishing method using the polishing liquid 26 of this embodiment is a polishing method in which a semiconductor substrate (workpiece 16) is wet-polished on a polishing pad 18, where the polishing liquid 26 does not contain abrasive grains 36, and the polishing pad 18 is an abrasive-grain-containing polishing pad having a base resin 40 with closed or interconnected pores 38 containing the abrasive grains 36, and the closed or interconnected pores 38 filled with the abrasive grains 36. This makes it possible to easily polish in a low polishing rate range without changing the mechanical polishing conditions, resulting in a high-quality polished surface. Furthermore, since expensive abrasive grains 36 are not consumed in large quantities, polishing can be performed inexpensively without increasing the burden on the environment.

[0048] Although one embodiment of the present invention has been described above, the present invention can also be applied in other aspects.

[0049] For example, in the surface polishing apparatus 10 of the above-described embodiment, SiC is polished as the semiconductor substrate (workpiece 16). Instead of SiC, other semiconductors such as Si may be polished, or other compound semiconductors such as GaN, GaP, and AlGaAs may be polished.

[0050] Furthermore, the polishing solution 26 in the above-described embodiment contains permanganate ions by dissolving potassium permanganate (KMnO4), but it may contain permanganate ions by dissolving other permanganate compounds, such as sodium permanganate. In short, the polishing solution 26 may be any solution that contains permanganate ions.

[0051] Furthermore, the polishing solution 26 in the above-described embodiment contains potassium permanganate (KMnO4) and a phosphate such as phosphoric acid (H3PO4) and / or a phosphate salt, but a weak acid such as acetic acid may also be added.

[0052] Although not specifically exemplified, the present invention can be used with various modifications within the scope of the invention. [Explanation of symbols]

[0053] 16: Work (semiconductor substrate) 18: Polishing pad 26: Polishing liquid 36: Polishing grain 38:Communicating pores 40: Base resin

Claims

1. A polishing solution for a semiconductor substrate, comprising permanganate ions and water, containing at least one phosphate or phosphoric acid; The concentration (total content) of the phosphate is 0.005 mol / L or more and less than 0.02 mol / L. A polishing solution for semiconductor substrates characterized in that:

2. The phosphate salt is disodium hydrogen phosphate (Na ２ HPO ４ ), dipotassium hydrogen phosphate (K ２ HPO ４ ), potassium dihydrogen phosphate (KH ２ P.O. ４ ) is at least one of 2. The polishing liquid for semiconductor substrates according to claim 1.

3. The phosphate salt is disodium hydrogen phosphate (Na ２ HPO ４ ) and / or the potassium dihydrogen phosphate (KH ２ P.O. ４ ) and The concentration (total content) of the phosphate is 0.005 mol / L or more and 0.01 mol / L or less.

3. The polishing liquid for semiconductor substrates according to claim 2.

4. In a two-dimensional coordinate system consisting of an x-axis representing the content of disodium hydrogen phosphate and a y-axis representing the content of potassium dihydrogen phosphate, the concentrations of the disodium hydrogen phosphate and the potassium dihydrogen phosphate are within a region satisfying formula (1) and formula (2).

4. The polishing liquid for semiconductor substrates according to claim 3. 0≦y<0.01 (1) -(5 / 12)(y-0.0114)≦x<0.01...(2)

5. The concentration of the phosphoric acid is 0.0011 mol / L or more and less than 0.015 mol / L.

2. The polishing liquid for semiconductor substrates according to claim 1.

6. 6. A polishing method for wet-polishing a semiconductor substrate on a polishing pad using the polishing liquid according to claim 1, comprising: The polishing liquid does not contain abrasive grains, The polishing pad is an abrasive grain-containing polishing pad having a base resin having independent pores or interconnected pores containing the abrasive grains, and the abrasive grains filled in the independent pores or interconnected pores.

1. A method for polishing a semiconductor substrate.

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