Silicon wafer polishing method

Abstract

To provide a silicon wafer polishing method capable of obtaining a silicon wafer of high LPD quality as a whole surface of the silicon wafer.SOLUTION: In succession to a polishing step, a rinse step performs rinse treatment by pressing a silicon wafer held by a polishing head against a polishing cloth with prescribed weight, dropping rinse agent on the polishing cloth and sliding the silicon wafer. The number of rotations of the polishing head and a polishing turn table in the rinse step is smaller than that of the polishing head and the polishing turn table in the polishing step performed prior to the rinse step, and is 10 rpm or less, and pressing weight of the silicon wafer against the polishing cloth during the rinse treatment is smaller than that of the silicon wafer against the polishing cloth in the polishing step performed prior to the rinse step, and is 3kPa or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for polishing a silicon wafer. [Background technology]

[0002] Silicon wafer polishing is usually performed in multiple stages using different types of polishing cloth and abrasives (multi-stage polishing).The most common method of polishing silicon wafers is chemical mechanical polishing (CMP), which combines chemical and mechanical polishing, and uses an abrasive (slurry) in which minute silica particles are dispersed in an alkaline-based aqueous solution to achieve an excellent smoothness and mirror finish. In particular, in the final polishing process of silicon wafer manufacturing, silicon wafers with a defect-free surface and high smoothness are required, and efforts are being made to optimize the combination of polishing consumable materials such as slurries and polishing cloths, as well as the polishing conditions.

[0003] Incidentally, the polishing process for silicon wafers generally involves multiple polishing steps, such as a rough polishing step, an intermediate polishing step, and a finish polishing step. For example, the rinsing step is performed after each polishing step among the multiple polishing steps, or after the finish polishing step.

[0004] In this rinsing step, for example, a polishing composition as disclosed in Patent Document 1 or a rinsing composition as disclosed in Patent Document 2 (hereinafter, these are referred to as rinse agents) is used. The rinsing step is performed by pressing the silicon wafer held by the polishing head against a polishing cloth attached to a polishing platen, dripping a predetermined rinse agent onto the polishing cloth, and rotating the polishing platen and the polishing head relative to each other to slide the silicon wafer.

[0005] The rinsing step removes abrasive particles and the like adhering to the surface of the silicon wafer, cleaning the surface of the silicon wafer and making the surface of the silicon wafer highly smooth and mirror-finish. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-57467 [Patent Document 2] Japanese Patent Publication No. 2020-167237 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, it is desirable that the surface of the silicon wafer that has undergone the rinsing process be free of defects such as PID (Polishing Induced Defects) that occur in the polishing process, as well as foreign matter, in the first place. However, when the silicon wafer surface is observed using a laser surface inspection device, foreign matter and defects are detected as LPD (Light Point Defects). Furthermore, the LPDs (Light Point Defects) were not uniform across the entire surface of the silicon wafer, and there were more LPDs on the outer periphery of the silicon wafer than on the inner periphery of the silicon wafer, resulting in poor LPD quality on the outer periphery of the silicon wafer.

[0008] The present inventors have conducted extensive research into the causes of deterioration in LPD quality in the outer periphery of a silicon wafer. As a result, it was found that the reason why there are more foreign matter and defects in the outer periphery of the silicon wafer is that the outer periphery of the silicon wafer is likely to become hydrophobic in the rinsing step, causing the adhering abrasives and foreign matter to aggregate and become difficult to remove. Specifically, the present inventors have found that the rinse agent coating on the outer periphery of the silicon wafer is likely to be removed by shear stress caused by friction between the silicon wafer and the polishing cloth in the rinsing step after polishing, and that as a result, the outer periphery of the silicon wafer is likely to become hydrophobic. The inventors then conceived that by performing a rinsing step under specified conditions, the outer periphery of the silicon wafer is less likely to become hydrophobic, and the adhering abrasives and foreign matter can be easily removed without agglomerating, thereby reducing the number of LPDs (light point defects).

[0009] The present invention has been made in view of the above-mentioned problems, and has an object to provide a method for polishing silicon wafers that can improve the LPD (Light Point Defect) quality of the outer periphery of a silicon wafer, thereby obtaining a silicon wafer with higher LPD quality over the entire surface of the silicon wafer. [Means for solving the problem]

[0010] The method for polishing silicon wafers according to the present invention, which has been made to solve the above technical problems, comprises a polishing step in which a silicon wafer held by a polishing head is pressed against a polishing cloth attached to a polishing platen with a predetermined load, an abrasive is dropped onto the polishing cloth, and the silicon wafer is slid over the polishing step to perform polishing, and a rinsing step is performed after the polishing step, in which the rinsing step is performed continuously following the polishing step by pressing the silicon wafer held by the polishing head against a polishing cloth with a predetermined load, and dropping a rinsing agent onto the polishing cloth. The rinse process is a process in which a polishing cloth is dropped onto the polishing cloth and the silicon wafer is slid across the polishing cloth, and the rinse process is performed such that the rotation speed of the polishing head and the polishing platen during the rinse process is set to 10 rpm or less, which is lower than the rotation speed of the polishing head and the polishing platen in the polishing step performed before the rinse process, and the pressing load of the silicon wafer against the polishing cloth during the rinse process is set to 3 kPa or less, which is lower than the pressing load of the silicon wafer against the polishing cloth in the polishing step performed before the rinse process.

[0011] According to the present invention, the surface of the silicon wafer is prevented from becoming hydrophobic by performing a rinsing step under predetermined conditions immediately after the polishing step. The rinsing step is performed by setting the rotation speed of the polishing head and the polishing platen during the rinsing process to 10 rpm or less, which is smaller than the rotation speed of the polishing head and the polishing platen in the polishing step performed before the rinsing step, and by setting the pressing load of the silicon wafer against the polishing cloth during the rinsing process to 3 kPa or less, which is smaller than the pressing load of the silicon wafer against the polishing cloth in the polishing step performed before the rinsing step. As a result, the rinse agent film is maintained on the outer periphery of the silicon wafer, and wettability is maintained (the rinse agent coverage rate is maintained high), which makes it possible to efficiently remove particles such as abrasives and foreign matter adhering to the outer periphery of the silicon wafer, thereby improving LPD quality.

[0012] The rinse agent coverage rate is calculated by dividing the hydrophilic area of ​​the wafer surface by the area of ​​the wafer surface and multiplying the result by 100. In other words, a rinse agent coverage rate of 100% means that the entire wafer surface is hydrophilic. Furthermore, if the rotation speed of the polishing head and the polishing platen exceeds 10 rpm and the pressing load of the silicon wafer against the polishing cloth exceeds 3 kPa, the rinse agent coating on the outer periphery of the silicon wafer W is likely to be removed and become hydrophobic, which is undesirable.

[0013] Here, it is desirable that the rotational speeds of the polishing head and the polishing platen during the rinsing process are gradually reduced, and that the rinsing process is ultimately performed at 5 rpm or more and 10 rpm or less. It is not preferable that the rotation speed of the polishing head and polishing platen during the rinsing process is less than 5 rpm, since it is not possible to maintain the wettability of the outer periphery of the silicon wafer (to maintain a high coverage rate with the rinse agent).

[0014] Furthermore, it is desirable that the pressing load of the silicon wafer against the polishing cloth during the rinsing process be 1 kPa or more and 3 kPa or less. It is not preferable that the load on the surface of the silicon wafer is less than 1 kPa, since it is not possible to maintain the wettability of the outer periphery of the silicon wafer (to maintain a high coverage rate of the rinse agent).

[0015] Furthermore, it is desirable that the rinse treatment time be between 2 seconds and 20 seconds. It is not preferable that the rinse treatment time is less than 2 seconds, because the rinse agent does not spread over the entire silicon wafer, and the wettability (high rinse agent coverage) of the outer periphery of the silicon wafer W cannot be maintained. Also, it is not preferable that the rinse treatment time is more than 20 seconds, because the rinse agent coating on the outer periphery of the silicon wafer W is easily removed and the silicon wafer W becomes hydrophobic. [Effects of the Invention]

[0016] According to the present invention, by improving the LPD (Light Point Defect) quality in the outer periphery of a silicon wafer, it is possible to obtain higher LPD quality over the entire surface of the silicon wafer. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a polishing apparatus for polishing silicon wafers. [Figure 2] FIG. 2 is a flowchart showing an example of a method for polishing a silicon wafer according to the present invention. [Figure 3] FIG. 3 is a diagram showing another example of the method for polishing a silicon wafer according to the present invention. [Figure 4] FIG. 4 is a diagram showing the rotation speed of the polishing platen and polishing head, the load on the silicon wafer, and the polishing time in the polishing step and the rinsing step in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the method for polishing a silicon wafer according to the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0019] The method for polishing silicon wafers according to the present invention includes a polishing step in which a silicon wafer held by a polishing head is pressed against a polishing cloth attached to a polishing platen with a predetermined load, an abrasive is dropped onto the polishing cloth, and the silicon wafer is slid across the polishing cloth to polish it, and a rinsing step is performed continuously following the polishing step after the polishing step is completed.

[0020] In particular, the rinsing step is a step of performing a rinse process by continuously pressing the silicon wafer held by the polishing head against the polishing cloth with a predetermined load, dropping a rinse agent onto the polishing cloth, and sliding the silicon wafer over the polishing cloth, and is characterized in that the rotation speed of the polishing head and the polishing platen during the rinsing process in the rinsing step is lower than the rotation speed of the polishing head and the polishing platen in the polishing step performed before the rinsing step, that is, 10 rpm or less, and the pressing load of the silicon wafer against the polishing cloth during the rinsing process is lower than the pressing load of the silicon wafer against the polishing cloth in the polishing step performed before the rinsing step, that is, 3 kPa or less.

[0021] First, the schematic configuration of the polishing apparatus used in this silicon wafer polishing method is shown in FIG. In FIG. 1, a polishing apparatus (single-side polishing apparatus) 100 includes a polishing head 1 having a retainer ring 2 and a membrane 3 as a silicon wafer holder, a polishing platen 4, and a polishing cloth 5 attached to the polishing platen 4. The polishing head 1 includes an annular retainer ring 2 that surrounds the silicon wafer W, and a membrane 3 that abuts against the upper surface of the silicon wafer W to apply a pressing force, and the retainer ring 2 and the membrane 3 hold one silicon wafer W.

[0022] Then, the silicon wafer W held by the polishing head 1 is pressed against the polishing cloth 5 attached to the polishing platen 4 with a predetermined load, a predetermined alkali-based polishing agent is dropped onto the polishing cloth 5 from the polishing agent supply pipe 6, and the polishing platen 4 and the polishing head 1 are rotated relative to each other to slide the silicon wafer (see FIG. 1). As a result, as shown in FIG. 2, a polishing step (polishing treatment) S1 of the silicon wafer W is carried out for a predetermined time.

[0023] After the polishing step S1 of the silicon wafer W is completed, a rinsing step S2 is performed as shown in FIG. This rinsing step S2 is performed on the same polishing cloth immediately after polishing, and is performed by pressing the silicon wafer W held by the polishing head 1 against the polishing cloth 5 with a predetermined load, dropping a rinse agent from the rinse agent supply pipe 7 onto the polishing cloth 5, and sliding the silicon wafer W. The polishing agent supply pipe 6 and the rinse agent supply pipe 7 may be a single pipe that can be switched by a valve (not shown) to drip the polishing agent or rinse agent.

[0024] The polishing agent is an alkaline-based polishing agent, and the pH is adjusted by adding a KOH solution. The abrasive may be any abrasive that contains abrasive grains and can polish the silicon wafer W. For example, an abrasive containing a water-soluble polymer and free abrasive grains can be suitably used. As the water-soluble polymer, it is preferable to use hydroxyethyl cellulose (HEC) in order to efficiently protect the silicon wafer W and improve the surface roughness. The water-soluble polymer is not limited to these, and may be a cellulose derivative such as hydroxypropyl cellulose or methyl cellulose, or a polymer containing an N-vinyl type monomer unit such as an N-vinyl chain amide.

[0025] The free abrasive grains contained in the abrasive are preferably colloidal silica, but are not limited to this and may be fumed silica, alumina particles, chromium oxide particles, etc.

[0026] The rinse agent is preferably one containing a polymer surfactant, but is not limited to this and may be an organic alkaline or inorganic alkaline rinse agent.

[0027] The polishing cloth 5 is not particularly limited, but can be appropriately determined (hardness, softness, etc.) from the viewpoints of protecting the silicon wafer W and the removal allowance of the silicon wafer W. As the polishing cloth, general nonwoven fabric types, polyurethane types, suede types, etc. can be used without any particular limitations.

[0028] As described above, the rotation speed of the polishing head and the polishing platen during the rinsing process is lower than the rotation speed of the polishing head and the polishing platen during polishing, and the rinsing process is performed at 10 rpm or less. Furthermore, the pressure load of the silicon wafer against the polishing cloth during the rinsing process is smaller than the pressure load of the silicon wafer against the polishing cloth during polishing, and the rinsing process is performed at 3 kPa or less.

[0029] In this way, the rotation speed of the polishing head and the polishing platen during the rinsing process is lower than that during the polishing process, being 10 rpm or less, and the pressing load of the silicon wafer against the polishing cloth is lower than that during the polishing process, being 3 kPa or less during the rinsing process. Therefore, the shear stress due to friction between the silicon wafer and the polishing cloth can be reduced, and the rinse coating on the outer periphery of the silicon wafer is difficult to remove and remains.

[0030] As a result, the surface of the silicon wafer can be covered (coated) with the rinse liquid, that is, the surface of the silicon wafer becomes hydrophilic, so that the adhering abrasives and foreign matter are less likely to aggregate, and the abrasives and foreign matter can be easily removed. In particular, the wettability of the outer periphery of the silicon wafer W can be maintained (the rinse agent coverage rate can be maintained high), the outer periphery of the silicon wafer W is less likely to become hydrophobic, and adhering abrasives and foreign matter are less likely to aggregate and are easier to remove.

[0031] Specifically, in the polishing step performed before the rinsing step, the rotation speed of the polishing head 1 and the polishing platen 4 during the polishing process is 20 rpm or more and 70 rpm or less, and the load on the surface of the silicon wafer W is in the range of 3 kPa or more and 20 kPa or less. The load on the silicon wafer W is mainly due to the pressure of the polishing head 1. If the pressure is in the range of 3 kPa or more and 20 kPa or less, polishing can be performed with a sufficient removal amount, good flatness quality, and minimal introduction of defects.

[0032] On the other hand, in the rinsing step performed after the polishing step, the rotation speed of the polishing head 1 and polishing platen 4 during the rinsing process is lower than the rotation speed during the polishing process, for example, 5 rpm or more and 10 rpm or less. Furthermore, the load on the surface of the silicon wafer W during the rinsing process is smaller than the polishing load during the polishing process, and is, for example, 1 kPa or more and 3 kPa or less.

[0033] If the rotation speed of the polishing head 1 and the polishing platen 4 during the rinsing process is less than 5 rpm, the wettability of the outer periphery of the silicon wafer W cannot be maintained (the coverage rate of the rinsing agent cannot be maintained high), which is not preferable. Furthermore, if the rotation speed of the polishing head 1 and polishing platen 4 during the rinsing process exceeds 10 rpm, the rinse film on the outer periphery of the silicon wafer W is likely to be removed and become hydrophobic, which is undesirable.

[0034] Furthermore, if the load on the surface of the silicon wafer W during the rinsing process is less than 1 kPa, the wettability of the outer periphery of the silicon wafer W cannot be maintained (the coverage rate of the rinsing agent cannot be maintained high), which is not preferable. Furthermore, if the load on the surface of the silicon wafer W during the rinsing process exceeds 3 kPa, the rinse film on the outer periphery of the silicon wafer W is likely to be removed and become hydrophobic, which is undesirable.

[0035] In addition, in the rinsing step, the rotation speed of the polishing head and polishing platen is reduced to 10 rpm or less, and the pressing load on the silicon wafer is reduced to 3 kPa or less, and the rinsing process time is preferably set to 2 seconds or more and 20 seconds or less. If the time for the rinse treatment step is less than 2 seconds, the rinse agent will not be distributed over the entire silicon wafer W, and the wettability of the outer periphery of the silicon wafer W cannot be maintained (the rinse agent coverage rate cannot be maintained high), which is not preferable. Furthermore, if the time for the rinse treatment step exceeds 20 seconds, the rinse coating on the outer periphery of the silicon wafer W is likely to be removed and become hydrophobic, which is undesirable.

[0036] In the rinsing step, the rotation speed of the polishing head 1 and the polishing platen 4 and the load on the surface of the silicon wafer W may be reduced, for example, in two stages. Specifically, at the start of the rinsing process, the rotation speed of the polishing head 1 and the polishing platen 4 and the load on the surface of the silicon wafer W may be reduced to be lower than the rotation speed and load during polishing, and further, the rotation speed and load may be reduced by another step during the rinsing process. In the present invention, it is sufficient that the rotation speed of the polishing head 1 and the polishing platen 4 is 5 rpm or more and 10 rpm or less, and the load on the surface of the silicon wafer W is 1 kPa or more and 3 kPa or less, for at least 2 seconds or more before the end of rinsing in the rinsing step, and the number of stages in which the rotation speed and the load are reduced may be one stage or three or more stages.

[0037] In the rinsing step, the surface temperature of the polishing pad 5 is preferably set to 10°C or higher and 40°C or lower. If the surface temperature of the polishing cloth 5 is less than 10°C, the wettability of the silicon wafer surface may deteriorate, which is not preferable. Also, if the surface temperature of the polishing cloth 5 exceeds 40°C, the haze on the silicon wafer surface may worsen, which may worsen the wettability of the outer periphery of the silicon wafer, which is not preferable.

[0038] Furthermore, although the case of one polishing step has been described in FIG. 2, multiple polishing steps may be provided as shown in FIG. In this case, only the third rinsing step (S2-3) after the final third polishing step (finish polishing (S1-3)) may be performed. Preferably, as shown in FIG. 3, for example, an abrasive containing a water-soluble polymer and free abrasive grains is dropped onto the surface, and after each of the three polishing steps, namely the first polishing step (rough polishing (S1-1)), the second polishing step (intermediate polishing (S1-2)), and the third polishing step (finish polishing (S1-3)), a first rinsing step (S2-1) is carried out after the first polishing step (rough polishing (S1-1)), a second rinsing step (S2-2) is carried out after the second polishing step (intermediate polishing (S1-2)), and a third rinsing step (S2-3) is carried out after the third polishing step (finish polishing (S1-3)).

[0039] At this time, the rotation speed of the polishing head and the polishing platen during the rinsing process in the first rinsing step (S2-1) is lower than the rotation speed of the polishing head and the polishing platen in the first polishing step (rough polishing step (S1-1)) carried out before the first rinsing step (S2-1), and the rinsing process is carried out at 5 rpm or more and 10 rpm or less, and the pressing load of the silicon wafer against the polishing cloth during the rinsing process is lower than the pressing load of the silicon wafer against the polishing cloth in the first polishing step (rough polishing step (S1-1)) carried out before the first rinsing step (S2-1), and the rinsing process is carried out at 1 kPa or more and 3 kPa or less.

[0040] Similarly, the rotation speed of the polishing head and the polishing table during the rinsing process in the second rinsing step (S2-2) is lower than the rotation speed of the polishing head and the polishing table during the second polishing step (intermediate polishing step (S1-2)), and the rinsing process is carried out at a speed of 5 rpm or more and 10 rpm or less. The pressure of the silicon wafer against the polishing cloth during the rinsing process is smaller than the pressure of the silicon wafer against the polishing cloth in the second polishing step (intermediate polishing step (S1-2)), and is carried out at 1 kPa or more and 3 kPa or less.

[0041] Similarly, the rotation speed of the polishing head and the polishing table during the rinsing process in the third rinsing step (S2-3) is lower than the rotation speed of the polishing head and the polishing table during the third polishing step (finish polishing step (S1-3)), and the rinsing process is carried out at a speed of 5 rpm or more and 10 rpm or less. The pressing load of the silicon wafer against the polishing cloth during the rinsing process is smaller than the pressing load of the silicon wafer against the polishing cloth in the third polishing step (finish polishing step (S1-3)), and is carried out at 1 kPa or more and 3 kPa or less.

[0042] In this way, since a rinse step is performed in each of the plurality of polishing steps, the entire surface of the silicon wafer W is covered with a rinse agent film in each step, and wettability is maintained (the rinse agent coverage is maintained high), so that particles can be efficiently removed from the entire silicon wafer W.

[0043] As described above, the entire surface of the silicon wafer W is covered with a rinse agent film, and wettability is maintained (the rinse agent coverage is maintained high), so that particles can be efficiently removed from the entire silicon wafer W, and the LPD quality can be significantly improved. In particular, particles on the outer periphery of the silicon wafer W can be removed efficiently, and the LPD quality can be significantly improved. [Example]

[0044] Example 1 In Example 1, an alkali-based polishing agent containing hydroxyethyl cellulose with an average molecular weight of 30,000 and colloidal silica with an average particle size of 35 nm was used, and a foamed urethane resin was used as the polishing cloth. Polishing was performed for 100 seconds at a rotation speed of the polishing platen of 55 rpm, a rotation speed of the polishing head of 56 rpm, and a polishing load of 10 kPa. The surface temperature of the polishing cloth was 25°C. A rinse step was then carried out. A rinse agent containing a polymer surfactant was used, and the rinse time was 10 seconds. The polishing platen rotation speed was 8 rpm. The polishing head rotation speed was 10 rpm. The load on the silicon wafer was 3 kPa. The surface temperature of the polishing cloth was 25°C. After the rinsing step was completed, the LPD was measured using a laser surface inspection device. The results are shown in Table 1.

[0045] Example 2 In Example 2, an alkali-based abrasive containing hydroxyethyl cellulose with an average molecular weight of 30,000 and colloidal silica with an average particle size of 35 nm was used, and a foamed urethane resin was used as the polishing cloth. Polishing was performed for 100 seconds with the polishing platen rotation speed set to 55 rpm, the polishing head rotation speed set to 56 rpm, and the polishing load set to 10 kPa. Thereafter, a rinsing step was carried out. The same rinsing agent as in Example 1 was used as the rinsing agent, and the rinsing time was 10 seconds. The rotation speed of the polishing platen was 5 rpm. The rotation speed of the polishing head was 7 rpm. The load on the silicon wafer was 1 kPa, and the rinsing time was 10 seconds. The surface temperature of the polishing cloth was 25°C. After the rinsing step was completed, the LPD was measured using a laser surface inspection device. The results are shown in Table 1.

[0046] Example 3 In Example 3, an alkali-based abrasive containing hydroxyethyl cellulose with an average molecular weight of 30,000 and colloidal silica with an average particle size of 35 nm was used, and a foamed urethane resin was used as the polishing cloth. As shown in FIG. 4, polishing was performed for 100 seconds with the polishing platen rotation speed set to 55 rpm, the polishing head rotation speed set to 56 rpm, and the polishing load set to 10 kPa. Thereafter, a rinsing step was carried out. The same rinsing agent as in Example 1 was used as this rinsing agent, and the rinsing time for the rinsing step carried out 100 seconds later (after polishing) was set to 10 seconds (first 5 seconds → last 5 seconds) as shown in Figure 4. The rotation speed of the polishing platen was 44 rpm for the first 5 seconds and 8 rpm for the last 5 seconds. The rotation speed of the polishing head was 45 rpm for the first 5 seconds and 10 rpm for the last 5 seconds.

[0047] The load on the silicon wafer was 5 kPa for the first 5 seconds and 3 kPa for the last 5 seconds. The surface temperature of the polishing pad was 25°C. FIG. 4 is a diagram showing the rotation speed (rpm) of the polishing platen and polishing head, the load (kPa) on the silicon wafer, and the polishing time (seconds) in the polishing step and the rinsing step that is performed continuously following the polishing step. After the rinsing step was completed, the LPD was measured using a laser surface inspection device. The results are shown in Table 1.

[0048] (Comparative Example) In the comparative example, under the same conditions as in Example 1, an alkali-based abrasive containing hydroxyethyl cellulose with an average molecular weight of 30,000 and colloidal silica with an average particle size of 35 nm was used, and a foamed urethane resin was used as the polishing cloth. Polishing was performed for 100 seconds with the polishing platen rotation speed set to 55 rpm, the polishing head rotation speed set to 56 rpm, and the polishing load set to 10 kPa. Thereafter, a rinsing step was carried out. The same rinsing agent as in Example 1 was used as the rinsing agent, and the rinsing time was 10 seconds. The rotation speeds of the polishing platen and polishing head were not slowed down from the polishing step, and the rotation speed of the polishing platen was 55 rpm, and the rotation speed of the polishing head was 56 rpm. The load on the silicon wafer was 10 kPa. The surface temperature of the polishing cloth was 25°C. After the rinsing step was completed, the LPD was measured using a laser surface inspection device. The results are shown in Table 1.

[0049] [Table 1]

[0050] <Evaluation> It was confirmed that the wettability (rinse agent coverage) of the outer periphery of the silicon wafer was improved in the Examples compared to the Comparative Examples, allowing for more efficient particle removal and improved LPD quality. More specifically, it was confirmed that the number of LPDs on the surface of the silicon wafer was reduced to 75% in Example 1, 80% in Example 2, and 70% in Example 3 compared to the Comparative Examples. Similarly, it was confirmed that the number of LPDs on the outer periphery of the silicon wafer was reduced to 62% in Example 1, 68% in Example 2, and 50% in Example 3 compared to the Comparative Examples. [Explanation of symbols]

[0051] 1 polishing head 2 retainer ring 3. Membrane 4 Polishing plate 5 Polishing cloth 100 Single side polishing equipment

Claims

1. A method for polishing a silicon wafer, comprising: a polishing step in which a silicon wafer held by a polishing head is pressed against a polishing cloth attached to a polishing platen with a predetermined load, an abrasive is dropped onto the polishing cloth, and the silicon wafer is slid over the polishing cloth to polish the silicon wafer; and a rinsing step is performed after the polishing step is completed, the rinsing step is a step of performing a rinsing treatment by pressing the silicon wafer held by the polishing head against a polishing cloth with a predetermined load, dropping a rinse agent onto the polishing cloth, and sliding the silicon wafer over the polishing cloth, continuously following the polishing step; In the rinsing step, the rotation speed of the polishing head and the polishing platen during the rinsing process is set to be 10 rpm or less, which is smaller than the rotation speed of the polishing head and the polishing platen during the polishing process performed before the rinsing process; and performing a rinse process in which the pressing load of the silicon wafer against the polishing cloth during the rinse process is set to 3 kPa or less, which is smaller than the pressing load of the silicon wafer against the polishing cloth in the polishing process performed before the rinse process.

2. 2. The method for polishing a silicon wafer according to claim 1, wherein the rotation speeds of the polishing head and the polishing platen during the rinsing process are gradually reduced, and the rinsing process is finally performed at a speed of 5 rpm or more and 10 rpm or less.

3. 2. The method for polishing a silicon wafer according to claim 1, wherein a pressing load of the silicon wafer against the polishing cloth during the rinsing process is 1 kPa or more and 3 kPa or less.

4. 2. The method for polishing a silicon wafer according to claim 1, wherein the rinse treatment time is from 2 seconds to 20 seconds.

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