Method for polishing a silicon wafer and method for producing an epitaxial wafer

Abstract

A method of polishing a silicon wafer, comprising performing a mirror polishing process on the silicon wafer, the mirror polishing process including: Performing pre-polishing on the silicon wafer; then Removing metallic impurities adhering to a surface of the silicon wafer by performing both an oxidation process with ozone water and an oxide layer removal process with hydrofluoric acid vapor or hydrofluoric acid solution on an entire surface of the silicon wafer; and then Carrying out re-polishing.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for polishing a silicon wafer and a method for producing an epitaxial wafer. STATE OF THE ART

[0002] It is known that unevenness of an epitaxial layer resulting from an epitaxial growth process of a semiconductor silicon wafer is due to scratches or polishing-induced defects (PIDs) that arise in a previous mirror polishing process.

[0003] Scratches on a wafer surface after mirror polishing are associated with displacements, which are crystal defects. When epitaxial growth is performed on this wafer with scratches, the displacements propagate to the epitaxial layer, causing displacements within the epitaxial layer and resulting in deteriorated epitaxial layer quality. Therefore, it is important that the wafer be scratch-free before epitaxial growth after mirror polishing.

[0004] Fig. Figure 7 shows detected epitaxial defects in an epitaxial layer generated during epitaxial growth on a wafer (a polished wafer) after mirror polishing with a defect such as a scratch. A magnified view at the bottom left shows a defect near the interface between the epitaxial layer and a substrate.

[0005] When epitaxial growth is performed on a PID, a protruding portion (a projection) influenced by the shape of the PID can be observed on the outermost surface of the epitaxial layer. It can also be observed that there is no defect, such as displacement, in the interior of the epitaxial layer just below this protruding portion, and the crystallinity of the epitaxial layer is not disturbed.

[0006] Fig. Figure 8(A) shows an image of a PID observed on a polished wafer using a laser microscope (MAGICS from Lasertec Corporation). Fig. Figure 8(B) shows an image of an observation at the same coordinates as the PID after epitaxial growth was performed on it. As can be seen in the image after epitaxial growth, a protrusion is visible due to the PID.

[0007] Fig. Figure 9 shows the cross-section of an epitaxial layer with a convex shape, observed through a transmission electron microscope (TEM) at the same coordinates as the PID after epitaxial growth on a wafer using the PID. This result shows that although the epitaxial layer has no defects, the outermost layer of the epitaxial layer is convex upwards over a width of 200 nm and its height is approximately 2 to 3 nm.

[0008] In conventional processes, defects such as scratches can be reduced if high-gloss polishing material removal is sufficiently ensured.

[0009] On the other hand, PIDs are usually reduced under conditions where a polishing apparatus and a polishing pad are well handled by various methods, such as those disclosed in Patent Document 1. Exemplary techniques applied to PIDs also include cleaning just before epitaxial growth and after mirror polishing, as disclosed in Patent Document 2.

[0010] Furthermore, Patent Document 3 discloses a method in which a silicon wafer, after mirror polishing but before forming an epitaxial layer thereon, is subjected to an ozone gas treatment that oxidizes a surface of the silicon wafer using ozone gas, a hydrofluoric acid gas treatment that dissolves and removes the oxidized surface of the silicon wafer using hydrofluoric acid gas, and a washing treatment that removes the impurities remaining on the surface of the silicon wafer, thereby forcibly oxidizing, dissolving, and removing PIDs (Polishing Induced Defects) generated by mirror polishing. By performing a subsequent epitaxial treatment, the formation of PID-induced convex defects on the surface of the epitaxial wafer can be prevented.

[0011] Patent Document 4 discloses a method in which the flatness of the wafer surface is measured in a flatness measurement step before final polishing. After concentrically distributed protrusions are determined on the surface, a cup member is arranged to cover the protrusions in the radial direction of the wafer in a protrusion removal step. A mixed gas of an ozone gas and hydrogen fluoride vapor is introduced into the cup member while the wafer is rotated around the wafer center, and the protrusion portions are etched away by a chemical reaction with the mixed gas.

[0012] Patent Document 5 discloses a method for cleaning the silicon wafer, in which an oxide film is formed and removed on a surface of the silicon wafer to remove impurities on the surface after final polishing performed after rough polishing of the silicon wafer, wherein the removal of the oxide film is performed until a processing-altered layer formed on a polished surface of the silicon wafer during final polishing is removed in an oxide film removal process. LIST OF CITING PATENTS LITERATURE Patent document 1: JP 2008 - 205 147 A Patent document 2: WO 2010 / 150 547 A1 Patent document 3: US 2012 / 0 100 701 A1 Patent document 4: JP 2011 - 101 930 A Patent document 5: JP 2010 - 165 960 A SUMMARY OF THE INVENTIONTECHNICAL PROBLEM

[0013] As described above, countermeasures such as those disclosed in Patent Documents 1 and 2 are conventionally used against PID. However, these are not sufficient to prevent deterioration of the surface quality of a polished wafer and an epitaxial wafer having an epitaxial layer formed on the polished wafer.

[0014] Against this background, the inventor of the present invention investigated PID.

[0015] A PID on the surface of a silicon wafer, which was cut from a silicon ingot, ground, and then mirror-polished, was first directly observed by scanning electron microscopy (SEM) and analyzed by energy-dispersive X-ray spectroscopy (EDX). A peak of a generated X-ray beam indicating metal was consequently detected in a section of the PID.

[0016] In a Fig. In the example shown in Figure 3(A), metallic impurities were detected with Zr (2.042 keV) in addition to silicon. In an example shown in Fig. In the example shown in Figure 3(B), metallic impurities were detected with Ni (0.851 keV).

[0017] It should be noted that when the same analysis was performed on shallow torn and scratched sections, peaks indicating metal were equally obtained.

[0018] Metallic impurities with Ni were found in the Fig. 4 scratches shown.

[0019] The cross-sectional structure of the PID was subsequently examined by TEM to further investigate the PID. EDX analysis revealed that approximately 2 nm of an upper layer portion within the PID, with a height of 3 to 6 nm, was an adherent metallic substance.

[0020] Fig. 5(A) shows an image of a PID by SEM; Fig. Figure 5(B) shows a cross-sectional image of this PID by TEM observation; Fig. 5(C) shows an enlarged view thereof. Fig. Figure 5(D) shows the result of an EDX analysis of the outermost surface layer of the PID. As shown in this EDX analysis result, Zr was detected in a surface layer section of the PID.

[0021] It should be noted that other metals detected in this study were Fe, Ni and Zr.

[0022] These results correspond to the analysis results of grinding media and the components of a grindstone. Table 1 shows the analysis of the grindstone components. [Table 1] ELEMENT ANALYSIERTER WERT (PPM) A1 880 Cr 64 Fe 430 Ni 5.7 Cu 100 Zr 98

[0023] A hypothesized mechanism by which the aforementioned metallic impurities adhere to the PID is described below. The outline of this mechanism is shown in Fig. 6 shown.

[0024] A silicon single crystal is first cut into wafers using a wire saw. During this process, the wafer is damaged by a wire wheel, grinding media, and the appropriate pressure.

[0025] After cleaning, an etching process is performed to remove damage caused by processing using an acid or alkali solution, so that this damage is forcibly removed. At this time, some damage may remain, or a propagating crack generated during slicing may remain.

[0026] A grinding process with a grindstone or abrasives, or a lapping process, or both, is then performed to remove the remaining damage. This process removes some of the remaining damage, but also creates new damage. Therefore, the remaining damage created during the wheel cutting process and the damage created by grinding or lapping remain as mixed damage. A subsequent process follows cleaning.

[0027] In these mixed damages, the metallic impurities are present in a gap. When the remaining damage is removed in a subsequent polishing process, the metallic impurities appear in a surface layer. Accordingly, the polishing material removal varies, partly due to a difference in hardness between the metal and the silicon, resulting in the occurrence of PID. These are the inventor's assumptions.

[0028] The present inventor predicted that although metallic contaminants can normally be removed by various cleaning methods, not all metallic contaminants are necessarily removed, as sufficient convection of a cleaning liquid may not occur depending on a tiny gap in a generated damage or the structure. This is also assumed from the fact that Ni was detected in a scratch on a wafer surface in an exemplary SEM-EDS analysis in the past.

[0029] For example, the cleaning method following the mirror polishing method disclosed in Patent Document 2 can remove PID by itself, but then forms the wafer surface in a concave shape. Depending on the concave shape, an epitaxial failure followed by displacement may be triggered during subsequent epitaxial growth. Therefore, the cleaning method in Patent Document 2 is not sufficient as a countermeasure against PID.

[0030] The present invention was accomplished in consideration of the above-described problems. It is an object of the present invention to provide a method for polishing a silicon wafer and a method for producing an epitaxial wafer that prevent the occurrence of PID in the silicon wafer due to a mirror polishing process and the deterioration of the surface quality of the silicon wafer after the mirror polishing process, and wherein an epitaxial layer is deposited on the epitaxial wafer in a subsequent process. SOLUTION TO THE PROBLEM

[0031] To achieve this object, the present invention provides a method for polishing a silicon wafer, which comprises performing a mirror polishing process on the silicon wafer, wherein the mirror polishing process includes: Performing pre-polishing on the silicon wafer; then Removing metallic impurities adhering to a surface of the silicon wafer by performing both an oxidation process with ozone water and an oxide layer removal process with hydrofluoric acid vapor or hydrofluoric acid solution on an entire surface of the silicon wafer; and then Carrying out re-polishing.

[0032] This polishing method according to the invention can forcibly remove the metallic impurities adhering to the surface of the silicon wafer after pre-polishing by the forced oxidation with ozone water and the removal together with the oxide layer with hydrofluoric acid vapor or solution on an entire surface of the silicon wafer.

[0033] During subsequent repolishing, there is no difference in hardness, which is a factor in the occurrence of PID, across the entire surface of the silicon wafer due to the difference between silicon and metal. Repolishing can therefore be performed with great uniformity. This allows for a flat, polished wafer of high quality and free of PID.

[0034] In addition, an epitaxial wafer having excellent surface quality and no protrusion due to PID on its entire surface can be obtained because such a polished wafer of high quality can be obtained when an epitaxial layer is deposited thereon in a subsequent process.

[0035] Furthermore, after removing the metallic contaminants, the silicon wafer can be subjected to an RCA cleaning process.

[0036] In this way, organic particles and metallic particles on the wafer surface can be removed.

[0037] Furthermore, the silicon wafer can be subjected to a final cleaning process after repolishing.

[0038] In this way, various types of particles on the wafer surface can be removed after repolishing.

[0039] Furthermore, the present invention provides a method for producing an epitaxial wafer, comprising: performing the mirror polishing process by the aforementioned polishing process on a surface of a silicon wafer; and forming an epitaxial layer on the surface of the silicon wafer.

[0040] Such a method for producing an epitaxial wafer can form the epitaxial layer on a polished wafer in which the occurrence of PID is inhibited, thereby obtaining an epitaxial wafer having excellent surface quality and in which the occurrence of a protrusion due to PID is inhibited. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0041] According to the aforementioned present invention, the mirror polishing process can remove metallic impurities adhering to an entire surface of a silicon wafer, and a flat, polished wafer of high quality can be obtained after post-polishing, in which the occurrence of PID is inhibited. In addition, the invention can obtain an epitaxial wafer having excellent surface quality and in which the occurrence of protrusion due to PID is inhibited. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exemplary flowchart of processes of the inventive method for polishing a silicon wafer and the inventive method for producing an epitaxial wafer; Fig. 2 shows the result of a surface inspection of a silicon wafer after pre-polishing, a polished wafer, and an epitaxial wafer in an example and a comparative example; Fig. 3 are measurement diagrams of examples of generated X-ray peaks indicating metal from PID, where (A) is an example of detection of Zr, and (B) is an example of detection of Ni; Fig. 4 shows an observation diagram of a scratch and a measurement diagram of an example of a generated X-ray peak indicating metal (Ni) from the scratch; Fig. 5 shows an SEM image of PID at (A), an image of the cross section of PID by TEM observation at (B), an enlarged view thereof at (C), and the result of EDX analysis of the outermost surface of PID at (D); Fig. 6 is an exemplary outline view of a mechanism by which metallic impurities adhere to PID; Fig. 7 is an observation diagram of exemplary epitaxial defects in an epitaxial layer; Fig. 8 shows an observation diagram of PID on a polished wafer at (A), and an observation diagram of a protrusion at the same coordinates as PID after epitaxial growth has been performed at (B); and Fig. 9 is an observation diagram of the cross section of an epitaxial layer having a convex shape observed at the same coordinates as PID after epitaxial growth was performed on a silicon wafer with the PID. DESCRIPTION OF EMBODIMENTS

[0042] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to this embodiment.

[0043] The present inventor has carefully investigated PID on a silicon wafer surface and, as a result, discovered the following: Metallic impurities are present in mixed damages generated during cutting, grinding, and lapping processes. During a mirror polishing process to remove these mixed damages, PID is generated because the polishing stock removal varies, partly due to the difference in hardness between metal and silicon.

[0044] The cleaning method disclosed in, for example, Patent Document 2 imparts a concave shape to a polished wafer after cleaning, thereby causing an epitaxial defect followed by displacement during subsequent epitaxial growth. Therefore, this method is insufficient as a countermeasure against PID.

[0045] The inventor also considered removing metallic impurities by ozone water and other methods before post-polishing and after pre-polishing. This method can inhibit the occurrence of PID, thereby enabling the acquisition of a polished wafer and an epitaxial wafer with high surface quality and no concave shape as mentioned above. The inventor discovered this effect and thereby completed the invention.

[0046] Fig. 1 is an exemplary flowchart of operations of the method for polishing a silicon wafer and the method for producing an epitaxial wafer according to the invention. (Disc cutting process)

[0047] A silicon ingot produced by the Czochralski process or another process is cut into wafers using a wire saw. (grinding and lapping processes)

[0048] The resulting sliced ​​wafer is etched to remove damage from the process and is then subjected to a grinding process or a lapping process or both.

[0049] It should be noted that cleaning, as required, can be performed before and after these procedures. As in Fig. For example, as shown in Figure 1, RCA cleaning can be performed after the grinding and lapping process. This can remove organic particles, metallic particles, and other particles on the wafer surface. (High-gloss polishing process) <vorpolieren>

[0050] A high-gloss polishing process is then carried out. In this high-gloss polishing process, a pre-polishing step is performed first.

[0051] In pre-polishing, for example, the silicon wafer, supported by a wafer support plate of a polishing head, is brought into contact with a polishing pad mounted on a rotating turntable at an appropriate pressure to polish the silicon wafer. This polishing process uses an alkali solution (also called a polishing slurry or polishing agent) containing colloidal silica. Directing this polishing agent to a contact surface between the polishing pad and the silicon wafer induces a mechanochemical reaction between the polishing slurry and the silicon wafer, thus initiating the polishing process.

[0052] Either a double-sided polisher or a single-sided polisher can be used as the polishing device. Various conditions, such as the composition and temperature of the polishing slurry, polishing pressure, polishing material removal rate, and polishing rate, are not particularly limited.

[0053] Pre-polishing can be a single-step polishing or a multi-step polishing. Pre-polishing can be performed in stages, e.g., in two stages, so that a second polishing uses a finer polishing compound and a smoother polishing pad than the first polishing. <RCA-Reinigen und Reinwasser-Reinigen>

[0054] After pre-polishing, organic particles, metallic particles, etc., on the wafer surface are removed by RCA cleaning. Subsequently, a pure water rinse (pure water cleaning) is performed. This rinsing process can be performed either by an overflow method, which involves batch-wise immersion in running water, or by a spray method. <Flusssäure-Verfahren und Reinwasser-Reinigen>

[0055] A silicon oxide on the wafer surface is removed by immersing it in hydrofluoric acid solution or spraying it. This hydrofluoric acid solution can be used at a concentration of, for example, approximately 1 to 5%; however, it is not particularly limited to this concentration. This concentration is preferably 5% or less to effectively prevent the adhesion of new particles from being promoted due to a higher than necessary hydrofluoric acid concentration. The time for immersing it in hydrofluoric acid solution and the time for spraying it can be changed depending on the concentration. An exemplary estimated time can be determined so that the surface of the silicon wafer has water repellency.The time for immersion and spraying is preferably determined to be a minimum required to exhibit water repellency, since a longer time for immersion and spraying may promote the adhesion of particles.

[0056] Rinsing is then performed with pure water. The silicon wafer is dried by spin drying, IPA drying, or another method. <Entfernungsverfahren für metallische Verunreinigungen>

[0057] The metallic contaminants adhering to an entire surface of the silicon wafer are then removed.

[0058] The process described here includes an oxidation process with ozone water and an oxide layer removal process with hydrofluoric acid solution or hydrofluoric acid vapor.

[0059] After pre-polishing, the entire surface of the cleaned silicon wafer is first oxidized with ozone water. At this time, silicon is forcedly oxidized on the entire surface of the silicon wafer, including the portion where metallic impurities embedded in mixed damage, scratches, and microcracks are adhered, to form a silicon oxide layer. The growth rate of the silicon oxide layer is designed to be larger, especially around these adhesions. This silicon oxide layer is formed to bind these adhesions.

[0060] The time for forced oxidation by ozone water is not particularly limited; if the time is one minute or longer, then a more sufficient silicon oxide layer can be formed; the time is preferably three minutes or longer.

[0061] Forced oxidation by ozone water is preferably carried out in a sealed container while continuously supplying ozone water, but is not limited to this. Using a method of directly spraying ozone gas over the entire surface of the silicon wafer in an open container can also achieve the same effect.

[0062] The adhesions of the metallic impurities, together with the silicon oxide grown on an entire surface layer of the silicon wafer by forced oxidation, are then removed by immersion in hydrofluoric acid solution or spraying of hydrofluoric acid solution.

[0063] This effect can be achieved not only by hydrofluoric acid solution, but also by hydrofluoric acid vapor.

[0064] Although either hydrofluoric acid solution or hydrofluoric acid vapor can be used, spraying the hydrofluoric acid solution onto the entire surface of the silicon wafer is more preferred considering that the metallic contaminants are removed from the wafer surface to the exterior of a system. <RCA-Reinigen und Reinwasser-Reinigen>

[0065] After the metallic contaminants have been removed, the surface is rinsed with pure water. Subsequent polishing is preferably carried out under immersion conditions to prevent the adhesion of ambient airborne particles.

[0066] After removing metallic contaminants, pure water rinsing can alternatively be performed after RCA cleaning. This allows the subsequent post-polishing step to be performed after the particles have been more effectively removed from an entire silicon wafer surface. <nachpolieren>

[0067] Subsequently, repolishing is performed. This repolishing process maintains a material removal rate sufficient to remove a section, including the path of scratches and the depth of microcracks, etc. This material removal rate is not particularly limited and varies depending on the previous processes and other factors; the material removal rate is preferably 10 nm or more.

[0068] Different conditions, such as the polishing machine to be used, the composition and temperature of the polishing slurry, the polishing pressure, the polishing material removal rate, and the polishing rate, are not particularly limited. These conditions can be the same as the conventional conditions and can be changed each time. <Abschließendes Reinigen>

[0069] After post-polishing, a final cleaning step is performed. The method for this final cleaning step is not particularly limited and can be determined by the user. This embodiment uses RCA cleaning and pure water cleaning. The cleaning method only needs to be able to remove various particles on the wafer surface after post-polishing.

[0070] In this invention, the metallic impurities on an entire silicon wafer surface are removed before repolishing. Accordingly, during repolishing, there is no difference in the hardness of the silicon wafer surface, which is a factor in the occurrence of PID. A flat, high-quality polished wafer with a uniformly repolished surface can be obtained. In this wafer, the number of PIDs is greatly reduced after repolishing.

[0071] The polishing method of the present invention has no need for cleaning after the mirror polishing method as disclosed in Patent Document 2, and can obtain a polished wafer with excellent surface quality and no concave surface. (Epitaxy growth process)

[0072] An epitaxial layer is then formed on the silicon wafer, which has undergone the aforementioned mirror polishing process.

[0073] The method for forming the epitaxial layer itself is not particularly limited and may be a conventional method.

[0074] For example, the silicon wafer is placed on an epitaxial growth device, and the epitaxial layer can be grown at temperatures in the range of 1000 to 1300°C at a H 2 atmosphere, while a silicide gas, such as SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , and SiH 4 , and a doping gas, such as B 2 H 6 or PH 3 , is fed into this atmosphere.

[0075] In the present invention, the entire surface of the silicon wafer on which the epitaxial layer is to be formed is free of PID because the aforementioned mirror polishing process is performed. This greatly inhibits the generation of protrusions due to PID on the entire surface of the epitaxial layer during formation of the epitaxial layer, which conventionally occurs. Therefore, an epitaxial wafer with excellent surface quality can be obtained. EXAMPLE

[0076] The present invention will be described below in more detail with reference to an example and a comparative example, but the present invention is not limited to this example. (Example)

[0077] The inventive method for polishing a silicon wafer and the inventive method for producing an epitaxial wafer were implemented.

[0078] As from Fig. As shown in Figure 1, a CZ silicon ingot was sliced ​​into wafers using a wire saw. Three silicon wafers from the sliced ​​wafers were subjected to grinding and RCA cleaning. Then, the mirror polishing process was performed. It should be noted that silicon wafers with a diameter of 300 mm and a crystal orientation of <100> were used.

[0079] In the mirror polishing process, pre-polishing was performed first, and then RCA cleaning, pure water cleaning, a hydrofluoric acid process, and pure water cleaning were performed in this order to obtain a pre-polished silicon wafer.

[0080] The conditions of pre-polishing (a first polishing and a second polishing) are as follows: A silicon wafer after grinding and lapping was first etched by 20 µm with NaOH as a pretreatment.

[0081] Both surfaces of this silicon wafer were then polished using the first polishing process, using a double-sided polisher and a polishing agent consisting of an alkali solution whose main component was colloidal silica. Since a polishing material removal of at least 10 µm was sufficient, the polishing material removal was set to 10 µm for this polishing step. Urethane foam was used as the polishing pad.

[0082] Subsequently, the second polishing step was performed with a polishing material removal of approximately 1 µm similarly using a single-sided polisher with a non-woven textile polishing pad made of polyurethane and a NaOH-based polishing agent made of colloidal silica.

[0083] After pre-polishing, the silicon wafer was subjected to a metal impurity removal process. In this process, the silicon wafer was first placed in a container, and ozone gas was continuously supplied to the container to oxidize a surface of the silicon wafer. This forced oxidation by the ozone gas was carried out for three minutes.

[0084] A 1% concentration of hydrofluoric acid solution was then prepared. This solution was sprayed onto the surface of the silicon wafer for one minute to remove the metallic contaminants that had adhered to the surface of the silicon wafer along with a silicon oxide layer.

[0085] This spraying process over one minute was repeated twice as an oxide layer removal process.

[0086] The pure water cleaning was then carried out.

[0087] Subsequently, post-polishing was performed. During post-polishing, the polishing material removal was considered the management criterion, so the polishing amount was sufficient to ensure a material removal of 80 nm or more. After post-polishing, RCA cleaning and pure water cleaning were performed to obtain a polished wafer.

[0088] It should be noted that other conditions of repolishing are as follows.

[0089] The polishing was carried out using a single-sided polishing device with a polyurethane suede polishing pad and a NH 4 OH based polishing agent made of colloidal silica.

[0090] It should be noted that the polishing rate was 10 nm / min or less; the polishing time was 2.5 minutes.

[0091] An epitaxial layer was formed on the surface of the resulting polished wafer. The polished wafer was placed on an epitaxial growth device. The epitaxial layer with a thickness of 3 µm was grown in the gas phase at 1130°C in a H 2 atmosphere, while a silicide gas of SiCl 4 was introduced into this atmosphere.

[0092] This resulted in an epitaxial wafer. (Comparison example)

[0093] A conventional method for polishing a silicon wafer and methods for producing an epitaxial wafer were implemented. Specifically, a silicon wafer was polished in the same manner as in the aforementioned example, except that the removal process for metallic impurities was not performed, so that a polished wafer with a diameter of 300 mm and a crystal orientation of <100> was achieved.

[0094] An epitaxial layer was grown in the gas phase on the polished wafer under the same conditions as in the example, so that an epitaxial wafer was obtained.

[0095] The surface of the silicon wafers after pre-polishing, the polished wafers, and the epitaxial wafers obtained in the example and the comparative example were observed using a laser microscope (MAGICS from Lasertec Corporation) to compare the degree to which the number of defects controlled after each polishing was reduced.

[0096] Fig. Figure 2 shows the result of this surface analysis. Points in the silicon wafers that Fig. 2 indicate errors (PIDs, etc.). As shown in Fig. 2, the number of defects of the silicon wafers after pre-polishing, the polished wafers, and the epitaxial wafers in the example were 1080, 26, and 7, respectively. The number of defects in the comparative example was 1279, 585, and 225.

[0097] In the comparative example, the number of defects in the polished wafer after post-polishing was reduced by up to approximately 45% compared to after pre-polishing. In contrast, the example implementing the invention showed a reduction of up to approximately 3%.

[0098] When comparing the number of defects after epitaxial growth, the comparative example showed a reduction of up to approximately 18%, while the example showed a reduction of up to approximately 0.65%. The example was 27 times or more more effective than the comparative example.

[0099] Therefore, the present invention can significantly reduce the number of errors including PID, compared with the conventional method.< / nachpolieren> < / vorpolieren>

Claims

[1] A method of polishing a silicon wafer, comprising performing a mirror polishing process on the silicon wafer, the mirror polishing process including: Performing pre-polishing on the silicon wafer; then Removing metallic impurities adhering to a surface of the silicon wafer by performing both an oxidation process with ozone water and an oxide layer removal process with hydrofluoric acid vapor or hydrofluoric acid solution on an entire surface of the silicon wafer; and then Carrying out re-polishing. [2] The method of claim 1, wherein the silicon wafer is subjected to an RCA cleaning process after removing the metallic impurities. [3] A method according to claim 1 or claim 2, wherein the silicon wafer is subjected to a final cleaning process after the post-polishing. [4] A method of producing an epitaxial wafer, comprising: Performing the mirror polishing process by the method according to any one of claims 1 to 3 on a surface of a silicon wafer; and Forming an epitaxial layer on the surface of the silicon wafer.

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