A silicon wafer external gettering method

Abstract

The present disclosure provides a method for external gettering of silicon wafers, the method comprising: obtaining a first silicon wafer, the first silicon wafer being obtained by performing a first pretreatment operation on an initial silicon wafer; depositing a predetermined material on the back side of the first silicon wafer to form a thin film on the back side of the first silicon wafer; performing a second pretreatment operation on the first silicon wafer with the thin film formed on the back side to obtain a second silicon wafer, wherein the second pretreatment operation includes a heat treatment, the heat treatment being used to induce stacking faults in the first silicon wafer to form gettering centers through film stress; removing the thin film from the second silicon wafer; and polishing the second silicon wafer after the thin film is removed. This method is applied to introduce an external gettering process after the silicon wafer is pretreated, so that the silicon wafer has external gettering capability while achieving high flatness, and after the gettering centers are introduced, the thin film is removed to release stress, thereby reducing warping of the silicon wafer.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and in particular to a silicon wafer external doping method. Background Art

[0002] The growth of silicon single crystals and the manufacturing of silicon wafers in device factories inevitably introduce metallic impurities. If these impurities are introduced into the active area of a chip made from silicon wafers, they can affect chip performance or even cause it to fail. Therefore, to mitigate the adverse effects of these impurities, a gettering process is necessary. This process involves creating crystal defects within or on the backside of the silicon wafer to attract metallic impurities and precipitate there. It is an effective method for reducing impurity levels within the wafer. Gettering processes can be categorized as internal or external, depending on the location of the gettering. Internal gettering involves heat treatment to form large oxygen precipitates within the silicon wafer, using these oxygen precipitates as gettering centers to trap metallic impurities. External gettering involves introducing numerous defects, such as dislocations, on the backside of the silicon wafer, causing metallic impurities to precipitate there, thereby ensuring that the active area of the silicon device is free of defects and metallic impurities.

[0003] Currently, the most common gettering processes are back-side sandblasting and polycrystalline deposition. However, as semiconductor feature sizes continue to shrink, the flatness requirements for silicon substrates are becoming increasingly stringent. Therefore, double-sided polishing is being used to process silicon wafers instead of the traditional single-sided polishing process. However, double-sided polishing can affect the damage layer introduced by the gettering process, causing the silicon wafer to lose its gettering ability. Therefore, the ability to achieve double-sided polishing of silicon wafers is of great significance to the integrated circuit industry and the solar photovoltaic industry. Summary of the Invention

[0004] The present disclosure provides a silicon wafer external gettering method to at least solve the above technical problems existing in the prior art.

[0005] According to a first aspect of the present disclosure, a method for silicon wafer external doping is provided, the method comprising: obtaining a first silicon wafer, the first silicon wafer being obtained by performing a first pretreatment operation on an initial silicon wafer; depositing a preset material on the back side of the first silicon wafer to produce a thin film on the back side of the first silicon wafer; performing a second pretreatment operation on the first silicon wafer with the thin film produced on the back side to obtain a second silicon wafer, wherein the second pretreatment operation comprises a heat treatment, the heat treatment being used to induce stacking faults in the first silicon wafer to form doping centers through thin film stress; removing the thin film from the second silicon wafer; and polishing the second silicon wafer after the thin film is removed.

[0006] In one embodiment, the first pre-processing operation on the initial silicon wafer includes: performing a first chamfering process on the initial silicon wafer; performing a double-sided grinding process on the initial silicon wafer that has undergone the first chamfering process; performing a second chamfering process on the initial silicon wafer that has undergone the double-sided grinding process; performing an etching process on the initial silicon wafer that has undergone the second chamfering process; and performing a double-sided polishing process on the initial silicon wafer that has undergone the etching process.

[0007] In one embodiment, the second pretreatment operation is performed on the first silicon wafer with a thin film formed on the back side to obtain a second silicon wafer, including: cleaning the first silicon wafer with a thin film formed on the back side; heating the first silicon wafer after cleaning within a preset temperature range to obtain a second silicon wafer, and the preset temperature range is 900°C-1200°C.

[0008] In one embodiment, the preset material is silicon nitride. Accordingly, depositing the preset material on the back of the first silicon wafer to produce a thin film on the back of the first silicon wafer includes: depositing silicon nitride on the back of the first silicon wafer by sputtering or chemical vapor deposition to produce a silicon nitride film on the back of the first silicon wafer; wherein the deposition temperature of the silicon nitride is 650°C-800°C, and the thickness of the produced silicon nitride film is 500 angstroms-4000 angstroms.

[0009] In one embodiment, the first silicon wafer after cleaning is subjected to heat treatment within a preset temperature range to obtain a second silicon wafer, comprising: placing the first silicon wafer after cleaning in a nitrogen gas atmosphere or an argon gas atmosphere and heating it for 1-4 hours to obtain the second silicon wafer.

[0010] In one embodiment, the preset material is polysilicon. Accordingly, depositing the preset material on the back of the first silicon wafer to produce a thin film on the back of the first silicon wafer includes: depositing polysilicon on the back of the first silicon wafer by chemical vapor deposition to produce a polysilicon film on the back of the first silicon wafer; wherein the thickness of the produced polysilicon film is 100 angstroms to 600 angstroms.

[0011] In one embodiment, the first silicon wafer after cleaning is subjected to heat treatment within a preset temperature range to obtain a second silicon wafer, comprising: placing the first silicon wafer after cleaning in an oxygen gas atmosphere for heat treatment to convert the polysilicon film into a silicon dioxide film to obtain a second silicon wafer, wherein the thickness of the silicon dioxide film is 200 angstroms to 1000 angstroms.

[0012] In one embodiment, removing the thin film of the second silicon wafer includes removing the thin film of the second silicon wafer by wet etching.

[0013] In one embodiment, the etching treatment performed on the initial silicon wafer after the second chamfering treatment is an alkali etching treatment, an acid etching treatment or a mixed acid etching treatment.

[0014] In one embodiment, polishing the second silicon wafer from which the thin film is removed includes: polishing an edge portion of the second silicon wafer from which the thin film is removed; and polishing a front surface of the second silicon wafer from which the thin film is removed.

[0015] The present invention discloses a silicon wafer external gettering method. A first silicon wafer is obtained by subjecting an initial silicon wafer to a first pretreatment. A predetermined material is deposited on the backside of the first silicon wafer to form a thin film on the backside of the first silicon wafer. The first silicon wafer with the thin film on the backside undergoes a second pretreatment operation to induce stacking faults in the first silicon wafer through film stress, thereby generating gettering centers in the first silicon wafer. The thin film is then removed and the second silicon wafer with the thin film removed is polished. This method introduces an external gettering process after the initial silicon wafer has been subjected to the first pretreatment to obtain the first silicon wafer. This avoids particle deposition, achieves high flatness on the silicon wafer, and simultaneously provides the silicon wafer with external gettering capability. After the gettering centers are introduced, the deposited thin film is removed to release stress, thereby reducing warping of the silicon wafer.

[0016] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings, in which several embodiments of the present disclosure are shown by way of example and not limitation, wherein:

[0018] In the drawings, the same or corresponding reference numerals denote the same or corresponding parts.

[0019] Figure 1 A first flow chart of a silicon wafer external gettering method according to an embodiment of the present disclosure is shown;

[0020] Figure 2 A second flow chart of a silicon wafer external gettering method according to an embodiment of the present disclosure is shown;

[0021] Figure 3 A schematic diagram of a first implementation scenario of a silicon wafer external gettering method according to an embodiment of the present disclosure is shown;

[0022] Figure 4 A schematic diagram of a second implementation scenario of a silicon wafer external doping method according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0023] To make the purposes, features, and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative work shall fall within the scope of protection of the present disclosure.

[0024] Figure 1 A first flow chart of a silicon wafer external gettering method according to an embodiment of the present disclosure is shown.

[0025] See also Figure 1 The present disclosure provides a method for silicon wafer external impurity gettering, comprising: operation 101, obtaining a first silicon wafer, wherein the first silicon wafer is obtained by performing a first pretreatment operation on an initial silicon wafer; operation 102, depositing a predetermined material on the back side of the first silicon wafer to form a thin film on the back side of the first silicon wafer; operation 103, performing a second pretreatment operation on the first silicon wafer with the thin film formed on the back side to obtain a second silicon wafer, wherein the second pretreatment operation includes a heat treatment, wherein the heat treatment is used to induce stacking faults in the first silicon wafer to form impurity gettering centers through thin film stress; operation 104, removing the thin film from the second silicon wafer; and operation 105, polishing the second silicon wafer after the thin film is removed.

[0026] The disclosed embodiment provides a method for external gettering of silicon wafers. A first silicon wafer is obtained by performing a first pretreatment on an initial silicon wafer. A predetermined material is deposited on the back of the first silicon wafer to produce a thin film on the back of the first silicon wafer. The first silicon wafer with the thin film on the back is subjected to a second pretreatment operation. The thin film stress induces stacking faults in the first silicon wafer to produce gettering centers in the first silicon wafer to obtain a second silicon wafer. The thin film is then removed and the second silicon wafer with the thin film removed is polished. This method introduces an external gettering process after the initial silicon wafer is subjected to the first pretreatment to obtain the first silicon wafer, thereby avoiding particle deposition and achieving both high flatness and external gettering capability for the silicon wafer. After the gettering centers are introduced, the deposited thin film is removed to release stress, thereby reducing warping of the silicon wafer.

[0027] In operation 101 of the present method, the initial silicon wafer is a silicon wafer that has not been processed in any way. The initial silicon wafer is formed by cutting a single crystal silicon rod. Specifically, the single crystal silicon rod can be cut into thin slices with precise geometric dimensions by wire cutting to obtain the initial silicon wafer. The single crystal silicon rod can be obtained by a Czochralski method or a zone melting method. After the initial silicon wafer is subjected to a first pretreatment operation, a first silicon wafer is obtained. The first pretreatment operation is a series of processing operations on the initial silicon wafer to obtain a first silicon wafer that meets the requirements, that is, a silicon wafer with a smooth cutting surface, no chipping edges, and no surface slides. The first pretreatment operation may include: sorting, chamfering, grinding, polishing and other operations.

[0028] After the monocrystalline silicon rod is cut to obtain initial silicon wafers, the initial silicon wafers may be subjected to a wafer inspection process to confirm whether the initial silicon wafers are qualified.

[0029] In operation 102 of this method, the predetermined material is a material capable of inducing stacking faults in the first silicon wafer, thereby generating gettering centers in the first silicon wafer and exhibiting external gettering capability. By depositing the predetermined material on the backside of the first silicon wafer, a thin film corresponding to the predetermined material is formed on the backside of the first silicon wafer.

[0030] In operation 103 of this method, the second pretreatment operation includes a cleaning operation on the first silicon wafer with the thin film formed on the back side and an operation capable of generating gettering centers in the first silicon wafer. The second pretreatment operation on the first silicon wafer with the thin film formed on the back side produces a second silicon wafer. The second pretreatment operation includes a heat treatment. During the heat treatment of the first silicon wafer with the thin film formed on the back side, the thin film generates high stress on the first silicon wafer. The high stress induces stacking faults in the first silicon wafer. The heat treatment causes the stacking faults to expand into the interior of the first silicon wafer, forming gettering centers. The second silicon wafer, thus having gettering centers, has external gettering capability.

[0031] In operation 104 of this method, the thin film on the back side of the second silicon wafer is removed. Since the stress of the thin film on the silicon wafer can cause the silicon wafer to warp, the deposited thin film can be removed after the gettering centers are generated to release the stress and reduce the warping of the silicon wafer. Specifically, the thin film can be removed by etching.

[0032] In operation 105 of the present method, the removal of the thin film will cause the morphology of the silicon wafer to deteriorate and the roughness of the silicon wafer to increase. Therefore, the second silicon wafer after the thin film is removed needs to be polished to further improve the flatness and morphology of the second silicon wafer.

[0033] Figure 2 A second flow chart of a silicon wafer external gettering method according to an embodiment of the present disclosure is shown.

[0034] See also Figure 2, performing a first pretreatment operation on the initial silicon wafer, including: operation 1011, performing a first chamfering treatment on the initial silicon wafer; operation 1012, performing a double-sided grinding treatment on the initial silicon wafer that has undergone the first chamfering treatment; operation 1013, performing a second chamfering treatment on the initial silicon wafer that has undergone the double-sided grinding treatment; operation 1014, performing an etching treatment on the initial silicon wafer that has undergone the second chamfering treatment; operation 1015, performing a double-sided polishing treatment on the initial silicon wafer that has undergone the etching treatment.

[0035] Specifically, chamfering is to grind off the sharp edges around the cut initial silicon wafer to prevent cracks, edge collapse and lattice defects on the edge of the initial silicon wafer during subsequent processing, so as to improve the mechanical strength and machinability of the silicon wafer; the specific process is to fix the initial silicon wafer on a bracket that can rotate at high speed, and there is a high-speed rotating diamond chamfering grinding wheel in the direction of its edge. The relative rotation between the two and the addition of appropriate grinding fluid are used to complete the grinding of the edge of the initial silicon wafer to achieve the required diameter size tolerance and edge profile shape.

[0036] The purpose of grinding is to remove knife marks and damage from the surface of the initial silicon wafer, improve flatness, make the initial silicon wafer thickness uniform, and increase the flatness of the initial silicon wafer surface. Double-sided grinding refers to grinding both the front and back sides of the initial silicon wafer. The initial silicon wafer is placed between the upper and lower grinding discs of the double-sided grinder, and the corresponding liquid grinding fluid is added. The initial silicon wafer moves relative to the grinding discs, and the initial silicon wafer is pressurized in sections to achieve double-sided grinding.

[0037] After mechanical processing such as chamfering and grinding, the surface of the initial silicon wafer will form a mechanical stress damage layer of a certain depth due to the stress generated by the mechanical processing, and there will be metal ion contamination on the surface. These effects need to be eliminated through corrosion treatment. The commonly used corrosion treatment method is chemical corrosion treatment.

[0038] Polishing is the process of removing microscopic damage from the silicon wafer surface to achieve a highly flat and smooth surface. Polishing methods include mechanical polishing and chemical polishing. To ensure surface precision, wafers may be polished multiple times depending on process requirements. Specific polishing methods include coarse polishing and fine polishing.

[0039] Therefore, the initial silicon wafer is sequentially subjected to the first chamfering treatment, double-sided grinding treatment, second chamfering treatment, etching treatment and double-sided polishing treatment to obtain the first silicon wafer with a smooth cutting surface, no chipping, and no surface slip.

[0040] In one embodiment, the etching treatment performed on the initial silicon wafer after the second chamfering treatment is an alkaline etching treatment, an acid etching treatment, or a mixed acid etching treatment.

[0041] Specifically, an acid or alkaline solution at a certain concentration and temperature reacts chemically with the silicon wafer to form a uniform chemical film on the surface of the silicon wafer. For example, a mixture of nitric acid, hydrofluoric acid, and glacial acetic acid is used as the etching solution to etch the silicon wafer.

[0042] In one embodiment, a second pretreatment operation is performed on the first silicon wafer with a thin film formed on the back side to obtain a second silicon wafer, including: cleaning the first silicon wafer with a thin film formed on the back side; heating the first silicon wafer after cleaning within a preset temperature range to obtain a second silicon wafer, and the preset temperature range is 900°C-1200°C.

[0043] Specifically, during the first pre-treatment operation on the initial silicon wafer and the process of depositing a predetermined material on the back of the first silicon wafer to form a thin film, certain contaminants will be generated. Therefore, after the thin film is formed on the back of the first silicon wafer, a cleaning process is required to eliminate as much of the contaminants generated in the previous processing stage as possible. In one embodiment, the contaminants can be removed by standard cleaning, which is the RAC cleaning method. Afterwards, the first silicon wafer after the cleaning process is heated at a temperature range of 900°C to 1200°C. The heating process can cause the thin film to generate high stress on the silicon wafer, induce stacking faults in the silicon wafer, and form impurity centers, thereby achieving external impurity gettering of the silicon wafer.

[0044] At the same time, since heat treatment is required when depositing the preset material on the back of the first silicon wafer to produce a thin film, the oxygen precipitates nucleated inside the first silicon wafer will further grow during the heating process, forming high-density oxygen precipitates and their induced defects, further enhancing the ability of the silicon wafer to absorb impurities.

[0045] In one embodiment, wet etching can be used to remove the thin film of the second silicon wafer, which only etches the thin film to remove it without damaging the first silicon wafer.

[0046] In one embodiment, polishing the second silicon wafer from which the thin film is removed includes: polishing an edge portion of the second silicon wafer from which the thin film is removed; and polishing a front surface of the second silicon wafer from which the thin film is removed.

[0047] Specifically, the second silicon wafer is edge-polished to improve the quality of the chamfered surface. Because thin film removal deteriorates the topography and increases roughness of the front surface of the second silicon wafer, the front surface of the second silicon wafer is single-sided polished to repair the deteriorated surface topography caused by etching and reduce the surface roughness of the second silicon wafer.

[0048] In addition, the silicon wafer external gettering method disclosed in the present invention can be applied to solar silicon wafers, lightly doped silicon wafers and heavily doped silicon wafers.

[0049] Figure 3 A schematic diagram of a first implementation scenario of a silicon wafer external doping method according to an embodiment of the present disclosure is shown.

[0050] See also Figure 3 The present disclosure provides a first implementation scenario of a silicon wafer gettering method, including: operation 301, obtaining a first silicon wafer, the first silicon wafer being obtained by performing a first pretreatment operation on an initial silicon wafer; operation 302, depositing silicon nitride on the back side of the first silicon wafer by sputtering or chemical vapor deposition, so that a silicon nitride film is formed on the back side of the first silicon wafer; wherein the deposition temperature of the silicon nitride is 650°C-800°C, and the thickness of the produced silicon nitride film is 500 angstroms-4000 angstroms; operation 303, cleaning the first silicon wafer with the silicon nitride film formed on the back side; operation 304, placing the cleaned first silicon wafer in a nitrogen gas atmosphere or an argon gas atmosphere, and heating it within a preset temperature range of 900°C-1200°C for 1-4 hours to obtain a second silicon wafer; operation 305, removing the silicon nitride film from the second silicon wafer; and operation 306, polishing the second silicon wafer after the silicon nitride film is removed.

[0051] After performing a first pretreatment operation on an initial silicon wafer to obtain a first silicon wafer, a preset material is deposited on the back side of the first silicon wafer, which is silicon nitride, so that a silicon nitride film is formed on the back side of the first silicon wafer.

[0052] Specifically, silicon nitride is deposited on the back side of the first silicon wafer using a thin film deposition technique to form a silicon nitride film on the back side of the first silicon wafer. Preferably, the thin film deposition technique employed may be chemical vapor deposition or sputtering. In one embodiment, the thickness of the silicon nitride film formed after the deposition of the silicon nitride is 500-4000 angstroms.

[0053] In one embodiment, the thickness of the silicon nitride film produced after depositing silicon nitride on the back side of the first silicon wafer is preferably 2000-3000 angstroms.

[0054] Specifically, the deposition temperature for producing the silicon nitride film is 650°C to 800°C. Silicon nitride films are amorphous and can serve as good gettering centers. Furthermore, this temperature range coincides with the nucleation temperature for bulk micro-defects, which also allows the first silicon wafer to possess a certain degree of internal gettering capability.

[0055] Afterwards, the first silicon wafer with the silicon nitride film on the back is subjected to standard cleaning, and the first silicon wafer after the standard cleaning treatment is placed in a nitrogen or argon gas atmosphere for heat treatment for 1-4 hours to obtain a second silicon wafer. This process causes the silicon nitride film to produce high stress on the first silicon wafer, and the high stress induces stacking faults in the first silicon wafer, which expand into the interior of the first silicon wafer, thereby forming an impurity center to obtain the second silicon wafer. The second silicon wafer has external impurity gettering ability.

[0056] In one embodiment, the first silicon wafer after the standard cleaning process is placed in a nitrogen or argon atmosphere for heating at a temperature of 1000° C. to 1200° C.

[0057] In addition, the oxygen precipitates nucleated in the silicon wafer further grow under the action of the heating temperature, forming high-density oxygen precipitates and their induced defects, which can further enhance the impurity gettering ability of the silicon wafer.

[0058] Because the high stress of the silicon nitride film can cause the warpage of the silicon wafer to worsen, the deposited silicon nitride film needs to be removed after the gettering center is generated to reduce the warpage of the silicon wafer while retaining the gettering ability of the silicon wafer. In one embodiment, the silicon nitride film is preferably removed by wet etching. The etching solution used in the wet etching is phosphoric acid. Since the silicon wafer is single crystal silicon, phosphoric acid does not corrode the silicon wafer. Therefore, removing the silicon nitride film by phosphoric acid does not cause over-etching of the silicon wafer and the disappearance of dislocations, thereby preserving the gettering ability of the silicon wafer.

[0059] Finally, the edge and front sides of the silicon wafer are polished to improve the quality of the chamfered surface of the silicon wafer and repair the surface morphology deterioration caused by etching, and the second silicon wafer after polishing is finally cleaned.

[0060] Figure 4 A schematic diagram of a second implementation scenario of a silicon wafer external doping method according to an embodiment of the present disclosure is shown.

[0061] See also Figure 4 The present disclosure provides a silicon wafer gettering method, comprising: operation 401, obtaining a first silicon wafer, the first silicon wafer being obtained by performing a first pretreatment operation on an initial silicon wafer; operation 402, depositing polycrystalline silicon on the back side of the first silicon wafer by chemical vapor deposition, thereby forming a polycrystalline silicon film on the back side of the first silicon wafer; wherein the thickness of the polycrystalline silicon film formed is 100 angstroms to 600 angstroms; operation 403, cleaning the first silicon wafer with the polycrystalline silicon film formed on the back side; operation 404, placing the cleaned first silicon wafer in an oxygen atmosphere, and heating it within a preset temperature range to convert the polycrystalline silicon film into a silicon dioxide film, thereby obtaining a second silicon wafer; the preset temperature range is 900° C. to 1200° C., and the thickness of the silicon dioxide film is 200 angstroms to 1000 angstroms; operation 405, removing the silicon dioxide film from the second silicon wafer; and operation 406, polishing the second silicon wafer with the silicon dioxide film removed.

[0062] In another implementation scenario of the method, after performing a first pretreatment operation on an initial silicon wafer to obtain a first silicon wafer, the preset material deposited on the back side of the first silicon wafer is polysilicon, so that a polysilicon film is formed on the back side of the first silicon wafer.

[0063] Specifically, polysilicon is deposited on the back side of the first silicon wafer using a thin film deposition technique to form a polysilicon film on the back side of the first silicon wafer. Since the polysilicon film has many grain boundaries, these interfaces can serve as gettering centers. Preferably, the thin film deposition technique used is chemical vapor deposition.

[0064] In one embodiment, preferably, the thickness of the polysilicon film produced after the polysilicon is deposited is 100 angstroms to 600 angstroms.

[0065] The first silicon wafer, with the polysilicon film formed on its backside, then undergoes a standard clean. After the standard clean, the first silicon wafer is placed in an oxygen atmosphere for high-temperature oxidation to produce a second silicon wafer. The purpose of high-temperature oxidation of the first silicon wafer with the polysilicon film deposited on it is to consume the deposited polysilicon film and completely oxidize it to form a silicon dioxide film. The silicon dioxide film induces stacking faults in the first silicon wafer, forming gettering centers and achieving external gettering of the silicon wafer.

[0066] In one embodiment, the oxidation temperature is preferably 900°C to 1200°C.

[0067] In one embodiment, the silicon dioxide film is formed to a thickness of 200-1000 angstroms.

[0068] Since the high stress of the silicon dioxide film will also cause the warping of the silicon wafer to worsen, it is necessary to remove the silicon dioxide film to reduce the warping of the silicon wafer while retaining the impurity gettering ability of the silicon wafer. During the high-temperature oxidation of the polysilicon film, the front of the silicon wafer will also produce a silicon dioxide film due to the high-temperature oxidation. Therefore, it is necessary to remove the silicon dioxide film on the front and back of the silicon wafer so that the back of the silicon wafer has the impurity gettering ability while remaining polished. In one embodiment, the silicon dioxide film is preferably removed by wet etching. The etching solution used for wet etching is a hydrogen fluoride solution, which only corrodes silicon dioxide and does not corrode the silicon wafer. Therefore, the silicon wafer still retains the impurity gettering ability after removing the silicon dioxide film.

[0069] It is understandable that the thickness of the oxide layer can be precisely controlled by oxidizing the polysilicon film into a silicon dioxide film. Oxidation consumes the polysilicon on the surface of the silicon wafer, and the thickness of the consumed polysilicon accounts for approximately 44% of the total thickness of the oxide film.

[0070] Finally, the edge and front sides of the silicon wafer are polished to improve the quality of the chamfered surface of the silicon wafer and repair the surface morphology deterioration caused by etching, and the second silicon wafer after polishing is finally cleaned.

[0071] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0072] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A silicon wafer external gettering method, characterized in that: The method comprises: Obtaining a first silicon wafer, wherein the first silicon wafer is obtained by performing a first pretreatment operation on an initial silicon wafer; depositing a predetermined material on the back surface of the first silicon wafer to form a thin film on the back surface of the first silicon wafer; performing a second pretreatment operation on the first silicon wafer with a thin film on the back side thereof to obtain a second silicon wafer, wherein the second pretreatment operation includes a heat treatment, wherein the heat treatment is used to induce stacking faults in the first silicon wafer to form gettering centers through film stress; removing the thin film of the second silicon wafer; The second silicon wafer with the thin film removed is polished.

2. The method according to claim 1, characterized in that The first pre-processing operation on the initial silicon wafer includes: performing a first chamfering process on the initial silicon wafer; performing double-sided grinding on the initial silicon wafer that has undergone the first chamfering process; performing a second chamfering process on the initial silicon wafer that has undergone the double-sided grinding process; performing an etching process on the initial silicon wafer that has undergone the second chamfering process; The initial silicon wafer that has undergone the etching treatment is subjected to double-side polishing.

3. The method according to claim 1, characterized in that The step of performing a second pretreatment operation on the first silicon wafer with a thin film on the back side to obtain a second silicon wafer comprises: Cleaning the first silicon wafer with a thin film formed on the back side; The first silicon wafer after the cleaning treatment is heated within a preset temperature range to obtain a second silicon wafer, wherein the preset temperature range is 900° C.-1200° C.

4. The method according to claim 3, characterized in that The preset material is silicon nitride, Accordingly, depositing a preset material on the back side of the first silicon wafer to form a thin film on the back side of the first silicon wafer includes: depositing silicon nitride on the back surface of the first silicon wafer by sputtering or chemical vapor deposition to form a silicon nitride film on the back surface of the first silicon wafer; The deposition temperature of silicon nitride is 650° C.-800° C., and the thickness of the silicon nitride film is 500 angstroms-4000 angstroms.

5. The method according to claim 4, characterized in that The step of heating the cleaned first silicon wafer within a preset temperature range to obtain a second silicon wafer comprises: The first silicon wafer after the cleaning process is placed in a nitrogen gas atmosphere or an argon gas atmosphere and heated for 1-4 hours to obtain a second silicon wafer.

6. The method according to claim 3, characterized in that The preset material is polysilicon, Accordingly, depositing a preset material on the back side of the first silicon wafer to form a thin film on the back side of the first silicon wafer includes: Depositing polysilicon on the back side of the first silicon wafer by chemical vapor deposition to form a polysilicon film on the back side of the first silicon wafer; The thickness of the generated polysilicon film is 100 angstroms to 600 angstroms.

7. The method according to claim 6, characterized in that The step of heating the cleaned first silicon wafer within a preset temperature range to obtain a second silicon wafer comprises: The first silicon wafer after cleaning is placed in an oxygen gas atmosphere for heating treatment to convert the polysilicon film into a silicon dioxide film to obtain a second silicon wafer. The thickness of the silicon dioxide film is 200 angstroms to 1000 angstroms.

8. The method according to claim 1, characterized in that The removing the thin film of the second silicon wafer comprises: The thin film of the second silicon wafer is removed by a wet etching method.

9. The method according to claim 2, characterized in that The etching treatment method for etching the initial silicon wafer after the second chamfering treatment is alkaline etching treatment, acid etching treatment or mixed acid etching treatment.

10. The method according to claim 1, characterized in that The polishing process of the second silicon wafer after the thin film is removed comprises: The edge portion of the second silicon wafer from which the thin film is removed is polished; and the front side of the second silicon wafer from which the thin film is removed is polished.

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