Silicon wafer and processing method thereof

Abstract

The invention discloses a silicon wafer and a processing method thereof, and belongs to the technical field of semiconductor manufacturing. The silicon wafer is a silicon wafer after electron injection. The processing method comprises the following steps: thinning the silicon wafer; carrying out acid pickling on the thinned silicon wafer; performing heat treatment on the silicon wafer after acid pickling to obtain a treated silicon wafer; wherein the resistivity of the silicon wafer after electron injection is greater than or equal to 300 omega.cm. The silicon wafer after electron injection is subjected to pre-cleaning, thinning, acid pickling, heat treatment and cleaning, the long-term stability of the resistivity is effectively improved, and the surface state of the silicon wafer is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a silicon wafer and a processing method thereof. BACKGROUND

[0002] In the field of semiconductor metrology, specific high resistivity silicon wafers are used as reference carriers for instrument calibration and high-precision experiments, because their extremely low carrier concentration can minimize test background interference. To meet this demand, the existing technology generally controls the resistivity of silicon wafers through electron injection process - by introducing electrons into the lattice through external energy, and using carrier concentration compensation to increase the resistivity. However, the resistivity of the silicon wafer after electron injection shows significant aging drift, and the resistivity change rate is high after long-term storage, which makes it unable to serve as a long-term reliable metrology reference. SUMMARY

[0003] The purpose of the present application is to provide a silicon wafer processing method for processing the silicon wafer after electron injection.

[0004] A silicon wafer processing method, the silicon wafer being a silicon wafer after electron injection, the processing method comprising:

[0005] thinning the silicon wafer;

[0006] acid washing the thinned silicon wafer;

[0007] heat treating the acid washed silicon wafer to obtain a processed silicon wafer;

[0008] wherein the resistivity of the silicon wafer after electron injection is greater than or equal to 300 Ω·cm.

[0009] In some embodiments, the silicon wafer is an N-type single crystal silicon wafer.

[0010] In some embodiments, the silicon wafer has a first face and a second face arranged opposite to each other;

[0011] wherein the original thickness of the silicon wafer is H, the thickness of the first face after thinning is H1, the thickness of the second face after thinning is H2, the thickness of the first face after thinning H1 ranges from 2.5 μm to 20 μm; the thickness of the second face after thinning H2 ranges from 2.5 μm to 20 μm; the sum of the thickness of the first face after thinning H1 and the thickness of the second face after thinning H2 ranges from 5 μm to 40 μm.

[0012] In some embodiments, before thinning the silicon wafer, the silicon wafer is pre-cleaned, the pre-cleaning method comprising: contacting the silicon wafer with a first cleaning solution for 15 minutes to 25 minutes, the first cleaning solution comprising an aqueous acid solution.

[0013] In some embodiments, the aqueous acid solution comprises an aqueous acetic acid solution, the mass fraction of acetic acid in the aqueous acetic acid solution being 1wt% to 3wt%.

[0014] In some embodiments, the aqueous acid solution comprises an aqueous nitric acid solution, and the mass fraction of the nitric acid in the aqueous nitric acid solution is 1wt% to 3wt%.

[0015] In some embodiments, the method of acid washing comprises: contacting the thinned silicon wafer with an acid washing solution for 25 minutes to 35 minutes, the acid washing solution comprising a mixture of an aqueous acetic acid solution and an aqueous inorganic acid solution, and the volume ratio of the aqueous acetic acid solution to the aqueous inorganic acid solution being 5:1 to 2:1.

[0016] In some embodiments, the mass fraction of the acetic acid in the aqueous acetic acid solution in the acid washing solution is greater than or equal to 98wt%.

[0017] In some embodiments, the aqueous inorganic acid solution is an aqueous hydrochloric acid solution, and the mass fraction of the hydrochloric acid in the aqueous hydrochloric acid solution is greater than or equal to 30wt%.

[0018] In some embodiments, the aqueous inorganic acid solution is an aqueous nitric acid solution, and the mass fraction of the nitric acid in the aqueous nitric acid solution is greater than or equal to 60wt%.

[0019] In some embodiments, the aqueous inorganic acid solution is an aqueous hydrofluoric acid solution, and the mass fraction of the hydrofluoric acid in the aqueous hydrofluoric acid solution is greater than or equal to 50wt%.

[0020] In some embodiments, the method of heat treatment comprises: annealing the silicon wafer after acid washing; the temperature of annealing is 200℃ to 500℃, and the time of annealing is 2 to 5 hours.

[0021] In some embodiments, the silicon wafer after heat treatment is cleaned after the silicon wafer after acid washing is subjected to heat treatment.

[0022] In some embodiments, the method of cleaning comprises: contacting the silicon wafer after heat treatment with a second cleaning solution for 15 minutes to 25 minutes, the second cleaning solution comprising an aqueous hydrofluoric acid solution, wherein the volume ratio of the hydrofluoric acid to water is 1:3 to 1:11.

[0023] A silicon wafer is prepared by the method of silicon wafer processing described above, and the resistivity change rate of the silicon wafer is controlled within ±3% after a storage period of 240 days.

[0024] The present application provides a silicon wafer and a processing method thereof, which pre-clean, thin, acid wash, heat treat and clean the silicon wafer after electron injection, effectively improve the long-term stability of resistivity, and improve the surface state of the silicon wafer. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms "first", "second", "third" and the like are only used as labels, and do not impose numerical requirements or establish sequences. Various embodiments of the present application can exist in a range of forms; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, and single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) within the indicated range.

[0026] The inventors found that the resistivity of the silicon wafer after electron injection presents a significant aging drift, and the resistivity change rate is higher after long-term storage, which leads to its inability to serve as a long-term reliable metrology reference. In addition, the surface state of the silicon wafer after electron injection has degradation problems, such as residual metal impurities, heat treatment oxide films and surface contamination, which not only increase the total thickness deviation and roughness, but also introduce test random errors, making the resistivity repeatability test results fluctuate greatly and reducing the metrology reliability.

[0027] The inventors propose a processing method for the silicon wafer after electron injection, which maintains the target high resistivity, solves the problems of aging drift and surface interference, ensures the long-term stability of the resistivity, and reduces the test repeatability fluctuation.

[0028] In one aspect, the present application provides a silicon wafer processing method, the silicon wafer being a silicon wafer after electron injection, and the processing method comprising:

[0029] Thinning the silicon wafer after electron injection;

[0030] Acid washing the thinned silicon wafer;

[0031] Heat treating the acid washed silicon wafer to obtain a processed silicon wafer;

[0032] The resistivity of the silicon wafer after electron injection is greater than or equal to 300 Ω·cm.

[0033] Specifically, the resistivity of the silicon wafer is increased to 300 Ω·cm or above after the electron injection process, for internal experimental research and precision instrument calibration applications. The silicon wafer after electron injection is an N-type monocrystalline silicon wafer, and the main crystal direction is <111> or <100>.

[0034] In some embodiments, the silicon wafer is a monocrystalline silicon wafer prepared by the zone melting method (FZ) or the Czochralski method (CZ). Specifically, the silicon wafer is a monocrystalline silicon wafer prepared by the zone melting method (FZ), which has no crucible contamination, low crystal defect density, and relatively low oxygen content, and can ensure radial resistivity uniformity.

[0035] It should be noted that the electron injection process can use existing processes, and specific process parameters such as electron injection amount and injection time are not limited herein, as long as the resistivity of the silicon wafer after electron injection is greater than or equal to 300 Ω·cm.

[0036] The resistivity change rate of the silicon wafer treated by the treatment method of the present application is controlled within ±3% after 240 days of storage.

[0037] In some embodiments, the step of thinning the silicon wafer after electron injection can use grinding or other grinding methods to thin the silicon wafer after electron injection. The silicon wafer has a first surface and a second surface arranged opposite to each other; wherein the original thickness of the silicon wafer is H, the thinning thickness of the first surface is H1, and the thinning thickness of the second surface is H2.

[0038] In some embodiments, the original thickness H of the silicon wafer after electron injection is in the range of 700-900 μm. The thinning thickness H1 of the first surface is greater than or equal to 2.5 μm, the thinning thickness H2 of the second surface is greater than or equal to 2.5 μm, and the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface is greater than or equal to 5 μm.

[0039] Specifically, the thinning thickness H1 of the first surface is in the range of 2.5 μm to 20 μm, the thinning thickness H2 of the second surface is in the range of 2.5 μm to 20 μm, and the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface is in the range of 5 μm to 40 μm, to ensure the strength of the thinned silicon wafer.

[0040] More specifically, the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface can be any one or any value in the range of any two of 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, and 40 μm.

[0041] It should be noted that in the silicon wafer thinning process, due to the influence of equipment precision and stress deformation, the actual single-side thinning thickness has a deviation from the preset thinning thickness, and the deviation is usually not greater than 0.5 μm. Within the deviation range, the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface is any case between 4 μm and 41 μm, which should be regarded as having the same technical effect as the case where the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface is between 5 μm and 40 μm in the present embodiment.

[0042] It can be understood that the thinning thickness is the thickness removed by the thinning step. The thinning step can remove large particles on the surface of the silicon wafer and contaminants that cannot be removed by the cleaning process, etc. By physically thinning the silicon wafer, the surface of the silicon wafer is made more flat, the geometric parameters of the surface are repaired, and parameters such as total indicated reading (TIR) and total thickness variation (TTV) are reduced. By physical thinning, the thickness of the silicon wafer is removed by 5 μm to 40 μm, the surface contaminants and impurities of the silicon wafer are removed, and the influence of the particles on the surface of the silicon wafer on the measuring machine is avoided. After the thinning treatment, the total indicated reading (TIR) of the silicon wafer is not greater than 8 μm; and the total thickness variation (TTV) is not greater than 12 μm.

[0043] In some embodiments, before the electron-implanted silicon wafer is thinned, the electron-implanted silicon wafer is pre-cleaned. The pre-cleaning method comprises: contacting the electron-implanted silicon wafer with a first cleaning solution for 15 minutes to 25 minutes, and the first cleaning solution comprises an aqueous acid solution. Specifically, the electron-implanted silicon wafer is immersed in the first cleaning solution for any one or any two of 15 min, 16 min, 18 min, 20 min, 22 min, 25 min or any value within the range formed by any two of them.

[0044] In some embodiments, in the pre-cleaning step, the aqueous acid solution comprises an aqueous acetic acid solution, and the mass fraction of acetic acid in the aqueous acetic acid solution is 1wt% to 3wt%. Specifically, the mass fraction of acetic acid is any one or any two of 1wt%, 2wt%, 3wt% or any value within the range formed by any two of them.

[0045] In some embodiments, in the pre-cleaning step, the aqueous acid solution comprises an aqueous nitric acid solution, and the mass fraction of nitric acid in the aqueous nitric acid solution is 1wt% to 3wt%. Specifically, the mass fraction of nitric acid is any one or any two of 1wt%, 2wt%, 3wt% or any value within the range formed by any two of them.

[0046] In some embodiments, the method of pickling the thinned silicon wafer comprises: contacting the thinned silicon wafer with an acid pickling solution for 25-35 minutes, the acid pickling solution comprising a mixture of an aqueous acetic acid solution and an aqueous inorganic acid solution, and the volume ratio of the aqueous acetic acid solution to the aqueous inorganic acid solution being 5-2:1. Specifically, the thinned silicon wafer is immersed in the acid pickling solution for any one or any value in the range of any two of 25 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, and 35 minutes.

[0047] The acid pickling step is performed after the thinning step, and further removes the contamination on the surface of the silicon wafer on the basis of the thinning, ensures the cleanliness of the surface, and prepares for the subsequent heat treatment step. The acid pickling step can also remove the bulk metal on the surface of the silicon wafer, so as to avoid the metal from entering the interior of the silicon wafer to form impurity atoms during annealing, and affect the stability of the resistivity.

[0048] The thinning and pickling processes eliminate the surface interference sources through synergistic effects: first, the physical thinning removes the surface layer of 5-40 μm in thickness, directly peels off the surface contamination layer and microcrack defects embedded due to cutting and grinding; and then, the acid pickling selectively dissolves the residual metal impurities. If the residual contamination is not removed, the impurities will diffuse to the interior of the silicon wafer along the grain boundaries in the subsequent heat treatment process, form local conductive channels or carrier recombination centers, and cause abnormal fluctuations in the resistivity.

[0049] In some embodiments, in the acid pickling step, the acid pickling solution comprises a mixture of an aqueous acetic acid solution and an aqueous hydrochloric acid solution, the mass fraction of acetic acid in the aqueous acetic acid solution is greater than or equal to 98 wt%, the mass fraction of hydrochloric acid in the aqueous hydrochloric acid solution is greater than or equal to 30 wt%, and the volume ratio of the aqueous acetic acid solution to the aqueous hydrochloric acid solution is 5-2:1.

[0050] In some embodiments, in the acid pickling step, the acid pickling solution comprises a mixture of an aqueous acetic acid solution and an aqueous nitric acid solution, the mass fraction of acetic acid in the aqueous acetic acid solution is greater than or equal to 98 wt%, the mass fraction of nitric acid in the aqueous nitric acid solution is greater than or equal to 60 wt%, and the volume ratio of the aqueous acetic acid solution to the aqueous nitric acid solution is 5-2:1.

[0051] In some embodiments, in the acid pickling step, the acid pickling solution comprises a mixture of an aqueous acetic acid solution and an aqueous hydrofluoric acid solution, the mass fraction of acetic acid in the aqueous acetic acid solution is greater than or equal to 98 wt%, the mass fraction of hydrofluoric acid in the aqueous hydrofluoric acid solution is greater than or equal to 50 wt%, and the volume ratio of the aqueous acetic acid solution to the aqueous hydrofluoric acid solution is 5-2:1.

[0052] In some embodiments, the method of heat treating the acid-washed silicon wafer comprises annealing the acid-washed silicon wafer at a temperature of 200-500°C for a time period of 2-5 hours. Specifically, the annealing temperature can be any one of 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, or any value within a range defined by any two of them. The annealing time period can be any one of 2 hours, 3 hours, 4 hours, 4.5 hours, 5 hours, or any value within a range defined by any two of them.

[0053] By controlling the annealing temperature and time period, the long-term stability of the resistivity of the single-crystal silicon wafer after electron injection is achieved, effectively solving the problem of resistivity drift over time caused by the migration of injected electrons. After the electron injection process, the injected electrons in the silicon wafer have a migratory property in the initial state. By implementing annealing treatment under specific conditions, the injected electrons can be prompted to occupy specific stable positions in the silicon lattice and be fixed, significantly reducing their migration ability. This fixation process enables the injected electrons to remain stable for months or even years, ensuring that the resistivity of the silicon wafer remains at the target value within this time range, thereby guaranteeing the stability of the resistivity.

[0054] In some embodiments, after heat treating the acid-washed silicon wafer, the heat-treated silicon wafer is cleaned. The specific cleaning method comprises contacting the heat-treated silicon wafer with a second cleaning solution for 15-25 minutes, the second cleaning solution comprising an aqueous solution of hydrofluoric acid, wherein the volume ratio of hydrofluoric acid to water is 1:3-11. Specifically, the contact time of the silicon wafer with the second cleaning solution can be any one of 15 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, or any value within a range defined by any two of them. The volume ratio of hydrofluoric acid to water can be any one of 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, or any value within a range defined by any two of them.

[0055] The annealed silicon wafer is cleaned to remove the thin layer of oxide film formed on the surface of the silicon wafer during the annealing step, reducing the impact on the stability of the resistivity test.

[0056] The silicon wafer after electron injection is pre-cleaned, thinned, pickled, heat treated and cleaned, which effectively improves the test stability of resistivity, improves the total thickness deviation (TTV) and surface roughness of the silicon wafer. By physical thinning, the thickness of 5um to 40um of the silicon wafer is removed, the surface contamination and impurities of the silicon wafer are removed, and the influence of visible particles on the measuring machine is avoided. The pickling step can remove the bulk metal on the surface of the silicon wafer, so that the metal does not enter the interior of the silicon wafer during annealing to form impurity atoms, thereby affecting the stability of the resistivity. After annealing, a layer of oxide film is formed on the surface of the silicon wafer, which affects the actual test results. The cleaning step can effectively remove the oxide film to ensure the test stability. By controlling the annealing temperature and time, the resistivity of the electron-injected single crystal silicon wafer is stable within a certain time range, and the internal injected electrons of the silicon wafer do not fail with time. The resistivity change rate of the treated silicon wafer is stable within ±3% after 240 days of storage period.

[0057] In another aspect, the application provides a silicon wafer prepared by the above-mentioned silicon wafer processing method, and the resistivity change rate of the silicon wafer is controlled within ±3% after 240 days of storage period. The silicon wafer of the embodiment is an N-type single crystal silicon wafer, and the main crystal direction is <111> or <100>. The silicon wafer is processed by the above-mentioned processing method, so it has all the technical effects corresponding to the above-mentioned processing method, which will not be repeated here.

[0058] The application will be described below in conjunction with specific embodiments.

[0059] Embodiment 1

[0060] The silicon wafer with a resistivity of 500.1Ω·cm after electron injection is pre-cleaned, and the pre-cleaning time is 20min. An aqueous acetic acid solution is used as the first cleaning liquid, wherein the mass fraction of acetic acid is 1wt%;

[0061] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700um, the first surface thinning thickness H1 and the second surface thinning thickness H2 of the grinding equipment are both 2.5um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 5um;

[0062] The thinned silicon wafer is pickled, and the pickling time is 30min. A mixture of an aqueous acetic acid solution and an aqueous hydrochloric acid solution is used as the pickling liquid, wherein the mass fraction of acetic acid in the aqueous acetic acid solution is 98wt%, the mass fraction of hydrochloric acid in the aqueous hydrochloric acid solution is 30wt%, and the volume ratio of the aqueous acetic acid solution to the aqueous hydrochloric acid solution is 5:1;

[0063] The pickled silicon wafer is annealed, and the annealing time is 3h and the annealing temperature is 200℃;

[0064] The annealed silicon wafer is cleaned for 20 minutes, and a hydrofluoric acid aqueous solution is used as a second cleaning liquid, wherein the volume ratio of hydrofluoric acid to water is 1:10.

[0065] The processed silicon wafer is obtained.

[0066] Example 2

[0067] The silicon wafer with a resistivity of 500.2 Ω·cm after electron injection is pre-cleaned for 20 minutes, and an acetic acid aqueous solution is used as a first cleaning liquid, wherein the mass fraction of acetic acid is 1wt%;

[0068] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700um, the preset first surface thinning thickness H1 and the second surface thinning thickness H2 of the grinding equipment are both 20.0um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0um.

[0069] The thinned silicon wafer is pickled for 30 minutes, and a mixture of an acetic acid aqueous solution and a hydrochloric acid aqueous solution is used as a pickling liquid, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 5:1.

[0070] The pickled silicon wafer is annealed for 3 hours at an annealing temperature of 200℃.

[0071] The annealed silicon wafer is cleaned for 20 minutes, and a hydrofluoric acid aqueous solution is used as a second cleaning liquid, wherein the volume ratio of hydrofluoric acid to water is 1:10.

[0072] The processed silicon wafer is obtained.

[0073] Example 3

[0074] The silicon wafer with a resistivity of 500.1 Ω·cm after electron injection is pre-cleaned for 20 minutes, and an acetic acid aqueous solution is used as a first cleaning liquid, wherein the mass fraction of acetic acid is 3wt%;

[0075] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700um, the preset first surface thinning thickness H1 and the second surface thinning thickness H2 of the grinding equipment are both 20.0um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0um.

[0076] The thinned silicon wafer is subjected to acid pickling for 30 minutes, and a mixture of acetic acid aqueous solution and hydrochloric acid aqueous solution is used as the acid pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98 wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30 wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 5:1;

[0077] The silicon wafer after acid pickling is subjected to annealing for 3 hours at a temperature of 200 DEG C.

[0078] The silicon wafer after annealing is subjected to cleaning for 20 minutes, and a hydrofluoric acid aqueous solution is used as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water is 1:10.

[0079] The treated silicon wafer is obtained.

[0080] Example 4

[0081] The silicon wafer with a resistivity of 499.8 ohm-cm after electron injection is subjected to pre-cleaning for 20 minutes, and an acetic acid aqueous solution is used as the first cleaning solution, wherein the mass fraction of acetic acid is 3 wt%.

[0082] The silicon wafer after pre-cleaning is subjected to lapping and thinning, wherein the original thickness H of the silicon wafer is 700 um, the first surface thinning thickness H1 and the second surface thinning thickness H2 of the lapping equipment are both 20.0 um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0 um.

[0083] The thinned silicon wafer is subjected to acid pickling for 30 minutes, and a mixture of acetic acid aqueous solution and hydrochloric acid aqueous solution is used as the acid pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98 wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30 wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 2:1;

[0084] The silicon wafer after acid pickling is subjected to annealing for 3 hours at a temperature of 200 DEG C.

[0085] The silicon wafer after annealing is subjected to cleaning for 20 minutes, and a hydrofluoric acid aqueous solution is used as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water is 1:10.

[0086] The treated silicon wafer is obtained.

[0087] Example 5

[0088] The silicon wafer with a resistivity of 499.6 ohm-cm and an RRV of 100.3% after electron injection is subjected to pre-cleaning for 20 minutes, and an acetic acid aqueous solution is used as the first cleaning solution, wherein the mass fraction of acetic acid is 3 wt%.

[0089] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700 um, the first surface thinning thickness H1 and the second surface thinning thickness H2 preset by the grinding equipment are both 20.0 um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0 um;

[0090] The thinned silicon wafer is pickled for 30 min, and a mixed solution of acetic acid aqueous solution and hydrochloric acid aqueous solution is used as the pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 2:1;

[0091] The pickled silicon wafer is annealed for 3h at a temperature of 500℃;

[0092] The annealed silicon wafer is cleaned for 20 min, and a hydrofluoric acid aqueous solution is used as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water is 1:10;

[0093] The treated silicon wafer is obtained.

[0094] Example 6

[0095] The silicon wafer with a resistivity of 803.2Ω·cm after electron injection is pre-cleaned for 20 min, and an acetic acid aqueous solution is used as the first cleaning solution, wherein the mass fraction of acetic acid is 3wt%;

[0096] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700 um, the first surface thinning thickness H1 and the second surface thinning thickness H2 preset by the grinding equipment are both 20.0 um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0 um;

[0097] The thinned silicon wafer is pickled for 30 min, and a mixed solution of acetic acid aqueous solution and hydrochloric acid aqueous solution is used as the pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 2:1;

[0098] The pickled silicon wafer is annealed for 3h at a temperature of 200℃;

[0099] The annealed silicon wafer is cleaned for 20 min, and a hydrofluoric acid aqueous solution is used as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water is 1:5;

[0100] The treated silicon wafer is obtained.

[0101] Example 7

[0102] The silicon wafer with a resistivity of 500.2 Ω·cm after electron injection was pre-cleaned for 20 min using an acetic acid aqueous solution as the first cleaning solution, wherein the mass fraction of acetic acid was 3 wt%;

[0103] The pre-cleaned silicon wafer was ground and thinned, wherein the original thickness H of the silicon wafer was 700 um, the first surface thinning thickness H1 and the second surface thinning thickness H2 of the grinding equipment were both 20.0 um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 was 40.0 um;

[0104] The thinned silicon wafer was pickled for 30 min using a mixture of an acetic acid aqueous solution and a hydrochloric acid aqueous solution as the pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution was 98 wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution was 30 wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution was 2:1;

[0105] The pickled silicon wafer was annealed for 3 h at a temperature of 200℃;

[0106] The annealed silicon wafer was cleaned for 20 min using a hydrofluoric acid aqueous solution as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water was 1:11;

[0107] The treated silicon wafer was obtained.

[0108] Example 8

[0109] Compared with Example 7, the difference between Example 8 and Example 7 is that the resistivity of the silicon wafer after electron injection is 500.6 Ω·cm, and the first surface thinning thickness H1 and the second surface thinning thickness H2 are both 25 um.

[0110] Example 9

[0111] Compared with Example 7, the difference between Example 9 and Example 7 is that the resistivity of the silicon wafer after electron injection is 500.1 Ω·cm, and the first surface thinning thickness H1 and the second surface thinning thickness H2 are both 30 um.

[0112] Comparative Example 1

[0113] The silicon wafer with a resistivity of 500.1 Ω·cm after electron injection was pre-cleaned for 20 min using an acetic acid aqueous solution as the first cleaning solution, wherein the mass fraction of acetic acid was 3 wt%;

[0114] The pre-cleaned silicon wafer is ground and thinned, wherein the original thickness H of the silicon wafer is 700 um, the first surface thinning thickness H1 and the second surface thinning thickness H2 of the grinding equipment are both 20.0 um, and the sum of the first surface thinning thickness H1 and the second surface thinning thickness H2 is 40.0 um;

[0115] The thinned silicon wafer is pickled for 30 min, and a mixture of acetic acid aqueous solution and hydrochloric acid aqueous solution is used as the pickling solution, wherein the mass fraction of acetic acid in the acetic acid aqueous solution is 98 wt%, the mass fraction of hydrochloric acid in the hydrochloric acid aqueous solution is 30 wt%, and the volume ratio of the acetic acid aqueous solution to the hydrochloric acid aqueous solution is 2:1.

[0116] The pickled silicon wafer is annealed for 3 h at 350℃.

[0117] The annealed silicon wafer is cleaned for 20 min, and a hydrofluoric acid aqueous solution is used as the second cleaning solution, wherein the volume ratio of hydrofluoric acid to water is 1:2.

[0118] The treated silicon wafer is obtained.

[0119] Comparative Example 2

[0120] The silicon wafer with the same electronic injection resistivity of 500.1 Ω·cm as in Example 1 is taken, and no subsequent treatment is performed.

[0121] Comparative Example 3

[0122] The silicon wafer with the same electronic injection resistivity of 500.2 Ω·cm as in Example 2 is taken, and no subsequent treatment is performed.

[0123] Comparative Example 4

[0124] The silicon wafer with the same electronic injection resistivity of 500.1 Ω·cm as in Example 3 is taken, and no subsequent treatment is performed.

[0125] The resistivity of the silicon wafer prepared in Examples 1-9 and Comparative Example 1 is measured, and the evaluation radial resistivity variation (RRV), the three measurement result deviations, and the RRV improvement rate of each silicon wafer are calculated, and the test results are shown in Table 1.

[0126] The measurement method of the resistivity is as follows: the resistivity of 9 positioning points (9 positioning points are distributed on a straight line, 2 points at 3 mm from the edge, 2 points at R / 2, 2 points at 3 / 4R between R / 2 and the edge, 2 points at 16 mm from the center, and 1 point at the center) of the silicon wafer is measured at 25℃ constant temperature environment by using CRESBOX (four-probe resistivity tester), the maximum value of all positioning points is taken as the maximum resistivity, and the minimum value of all positioning points is taken as the minimum resistivity.

[0127] The calculation formula of radial resistivity variation (RRV) is: RRV=(resistivity maximum-resistivity minimum) / resistivity minimum*100%;

[0128] The calculation method of three test result deviations is: according to the above-mentioned resistivity measurement method, repeatedly measuring 3 times, and respectively calculating radial resistivity variation (RRV) A1, A2, A3 of each measurement, defining the maximum value of the three radial resistivity variations (RRV) as MaxA, and defining the minimum value of the three radial resistivity variations (RRV) as MinA;

[0129] Three test result deviations=(MaxA / MinA-1)*100%;

[0130] Average radial resistivity variation (RRV)=(A1+A2+A3) / 3;

[0131] RRV / % improvement rate=(average RRV after injection-average RRV after treatment) / average RRV after injection*100%.

[0132] It can be understood that the greater the RRV / % improvement rate value, the better the improvement effect on the RRV of the silicon wafer.

[0133] Resistivity, average RRV and three test result deviations of the silicon wafer prepared in examples 1-9 and comparative example 1

[0134]

[0135] As shown in Table 1, by comparing example 1 and example 2, when the total thickness reduction is 40.0 um, the three test result deviations of resistivity is 4.3%, which is significantly lower than 5.7% when the total thickness reduction is 5.0 um.

[0136] By comparing example 2 and example 3, when the mass fraction of acetic acid in the first cleaning solution is 3wt%, the three test result deviations of resistivity is 4.1%, which is lower than 4.3% when the mass fraction of acetic acid in the first cleaning solution is 1wt%.

[0137] By comparing example 3 and example 4, when the volume ratio of acetic acid to hydrochloric acid in the pickling solution is 2:1, the three test result deviations of resistivity is 3.4%, which is lower than 4.1% when the volume ratio of acetic acid to hydrochloric acid is 5:1.

[0138] By comparing example 4 and example 5, when the annealing temperature is 500℃, the three test result deviations of resistivity is 2.6%, which is lower than 3.4% when the annealing temperature is 200℃.

[0139] As can be seen from Examples 1-9, the resistivity of the silicon wafer after electron injection is reduced and relatively stable at a certain value, and the RRV is also improved to a certain extent.

[0140] The resistivity of the silicon wafer prepared in Examples 1-3 and Comparative Examples 2-4 was measured on the day of electron injection, 30 days, 60 days, 120 days and 240 days after injection under the same storage conditions, and the resistivity measurement method was the same as described above. The test results are shown in Table 2.

[0141] Table 2: Resistivity measurement results at different days

[0142]

[0143] As can be seen from the comparison of Comparative Example 2 and Example 1, the resistivity change rate of the silicon wafer prepared by the treatment method of the present application after 240 days is 1.3%, while the resistivity change rate of the silicon wafer after electron injection without the treatment method of the present application is 4.1%. As can be seen from the comparison of Comparative Example 3 and Example 2, or the comparison of Comparative Example 4 and Example 3, the resistivity change of the silicon wafer after 240 days treated by the treatment method is significantly smaller than that of the silicon wafer without the treatment.

[0144] The resistivity change rate after 240 days = (the maximum resistivity on the day of injection - the maximum resistivity after 240 days of injection) / the maximum resistivity on the day of injection * 100%.

[0145] After the thinning step, the global flatness (TIR) and total thickness variation (TTV) of the silicon wafer after thinning in Examples 1-9 and Comparative Example 1 were measured, and the measurement results are shown in Table 3.

[0146] The measurement method of global flatness (TIR) and total thickness variation (TTV) is as follows: TIR measurement is performed using an ADE-9600 detector, surface topography scanning is performed on the silicon wafer, and TIR value and TTV value are obtained.

[0147] Table 3: TIR and TTV of the silicon wafer after the thinning step in Examples 1-9 and Comparative Example 1

[0148]

[0149]

[0150] As shown in Table 3, comparing Example 1 and Example 2, as the removal amount of the thinning thickness increases, the global flatness (TIR) and total thickness variation (TTV) of the silicon wafer surface are significantly improved. This change makes the contact state between the measuring instrument and the silicon wafer surface better, thereby ensuring that the stability and accuracy of the test results are improved.

[0151] From comparative example 7, example 8 and example 9, it can be seen that after the total thickness of the silicon wafer is removed on both sides by more than 40 um, further increasing the thinning thickness has little effect on the global flatness (TIR) and total thickness variation (TTV).

[0152] In the above examples, the description of each example has its own focus, and the parts not described in detail in a certain example can be referred to the relevant description of other examples.

[0153] The principles and implementation manners of the present application are described by applying specific examples herein, and the above example descriptions are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will have changes according to the idea of the present application, and the above description should not be understood as a limitation on the present application.

Claims

1. A method of processing a silicon wafer, characterized by, The silicon wafer is an electron-injected silicon wafer, and the processing method comprises: thinning the silicon wafer; acid washing the thinned silicon wafer; heat treating the acid washed silicon wafer to obtain a processed silicon wafer; wherein the resistivity of the electron-injected silicon wafer is greater than or equal to 300 Ω·cm.

2. The method of claim 1, wherein the step of applying a photoresist to the surface of the silicon wafer is performed by spin coating. The electron-injected silicon wafer is an N-type single crystal silicon wafer.

3. The method of claim 1, wherein the step of applying a photoresist to the silicon wafer is performed by spin coating the photoresist onto the silicon wafer. The silicon wafer has a first surface and a second surface arranged opposite to each other; the first surface has a thinning thickness H1, and the second surface has a thinning thickness H2; wherein the thinning thickness H1 of the first surface ranges from 2.5 μm to 20 μm; the thinning thickness H2 of the second surface ranges from 2.5 μm to 20 μm; and the sum of the thinning thickness H1 of the first surface and the thinning thickness H2 of the second surface ranges from 5 μm to 40 μm.

4. The method of claim 1, wherein the step of applying a photoresist to the silicon wafer is performed by spin coating. Before thinning the silicon wafer, the silicon wafer is pre-cleaned, and the pre-cleaning method comprises: contacting the silicon wafer with a first cleaning solution for 15 minutes to 25 minutes, the first cleaning solution comprising an aqueous acid solution.

5. The method of claim 4, wherein the step of applying a photoresist to the surface of the silicon wafer is performed by spin coating. The aqueous acid solution comprises an aqueous acetic acid solution, and the mass fraction of acetic acid in the aqueous acetic acid solution is 1wt%-3wt%; or The aqueous acid solution comprises an aqueous nitric acid solution, and the mass fraction of nitric acid in the aqueous nitric acid solution is 1wt%-3wt%.

6. The method of claim 1, wherein the step of applying a photoresist to the silicon wafer is performed by spin coating. The acid washing method comprises: contacting the thinned silicon wafer with an acid washing solution for 25 minutes to 35 minutes, the acid washing solution comprising a mixture of an aqueous acetic acid solution and an aqueous inorganic acid solution, and the volume ratio of the aqueous acetic acid solution to the aqueous inorganic acid solution being 5-2:

1.

7. The method of claim 6, wherein the step of applying a layer of photoresist to the surface of the silicon wafer is performed by spin coating. The mass fraction of acetic acid in the aqueous acetic acid solution in the acid washing solution is greater than or equal to 98wt%.

8. The silicon wafer processing method of claim 6, wherein the aqueous inorganic acid solution is an aqueous hydrochloric acid solution, and the mass fraction of hydrochloric acid in the aqueous hydrochloric acid solution is greater than or equal to 30wt%; or the aqueous inorganic acid solution is an aqueous nitric acid solution, and the mass fraction of nitric acid in the aqueous nitric acid solution is greater than or equal to 60wt%; or the aqueous inorganic acid solution is an aqueous hydrofluoric acid solution, and the mass fraction of hydrofluoric acid in the aqueous hydrofluoric acid solution is greater than or equal to 50wt%.

9. A silicon wafer processing method according to claim 1, characterized in that, The heat treating method comprises: annealing the acid washed silicon wafer; the annealing temperature is 200°C-500°C, and the annealing time is 2-5 hours.

10. The method of claim 1, wherein the step of providing a silicon wafer comprises providing a silicon wafer having a thickness of less than 100 microns. After heat treating the acid washed silicon wafer, the heat treated silicon wafer is cleaned.

11. The method of claim 10, wherein the step of applying a photoresist to the surface of the silicon wafer is performed by spin coating the photoresist onto the surface of the silicon wafer. The cleaning method comprises: contacting the heat treated silicon wafer with a second cleaning solution for 15 minutes to 25 minutes, the second cleaning solution comprising an aqueous hydrofluoric acid solution, wherein the volume ratio of the hydrofluoric acid to water is 1:3-11.

12. A silicon wafer, characterized by, The silicon wafer is prepared by the silicon wafer processing method of any one of claims 1-11, and the resistivity change rate of the silicon wafer is controlled within ±3% after a 240-day storage period.

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