CN117253778A - Wafer cleaning method - Google Patents
Wafer cleaning method Download PDFInfo
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- CN117253778A CN117253778A CN202311427581.2A CN202311427581A CN117253778A CN 117253778 A CN117253778 A CN 117253778A CN 202311427581 A CN202311427581 A CN 202311427581A CN 117253778 A CN117253778 A CN 117253778A
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- 238000004140 cleaning Methods 0.000 title claims abstract description 236
- 238000000034 method Methods 0.000 title claims abstract description 50
- 239000012530 fluid Substances 0.000 claims abstract description 39
- 239000007800 oxidant agent Substances 0.000 claims abstract description 34
- 230000001590 oxidative effect Effects 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000002253 acid Substances 0.000 claims abstract description 10
- 239000003513 alkali Substances 0.000 claims abstract description 8
- 238000010926 purge Methods 0.000 claims description 5
- 239000002585 base Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 abstract description 26
- 230000003647 oxidation Effects 0.000 abstract description 6
- 238000007254 oxidation reaction Methods 0.000 abstract description 6
- 230000003749 cleanliness Effects 0.000 abstract description 3
- 230000003068 static effect Effects 0.000 abstract 1
- 235000012431 wafers Nutrition 0.000 description 90
- 239000000243 solution Substances 0.000 description 65
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 16
- 229910010271 silicon carbide Inorganic materials 0.000 description 16
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 14
- 229910021642 ultra pure water Inorganic materials 0.000 description 14
- 239000012498 ultrapure water Substances 0.000 description 14
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 12
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000002156 adsorbate Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000011010 flushing procedure Methods 0.000 description 3
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000011109 contamination Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
- B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Cleaning Or Drying Semiconductors (AREA)
Abstract
The application discloses a wafer cleaning method, which comprises the following steps: performing a first cleaning step: the first cleaning step comprises cleaning at least one side of the wafer with a fluid and a first megasonic wave; the fluid comprises water and N 2 The method comprises the steps of carrying out a first treatment on the surface of the Performing a second cleaning step: the second cleaning step comprises: cleaning at least one surface of the wafer with a first solution; the first solution comprises alkali and first oxidant; performing a third cleaning step: the third cleaning step includes: cleaning at least one surface of the wafer with a second solution; the second solution includes a second oxidant; performing a fourth cleaning step, the fourth cleaning step comprising: cleaning at least one surface of the wafer with a third solution; the third solution includes an acid. The application employs fluid and megasonic cleaning of the wafer, the fluid cleaning removes dirt from the wafer, the megasonic cleaning removes small particles from the wafer, and then oxidation andthe static repulsion removes tiny particles and organic matters, and the surface cleanliness of the cleaned wafer is high.
Description
Technical Field
The application relates to the technical field of semiconductors, in particular to a wafer cleaning method.
Background
Silicon carbide is a potential semiconductor material because of the characteristics of wide band gap, high electric breakdown field, high thermal conductivity, high carrier saturation velocity and the like, can be used under extreme conditions of high power, high temperature, high frequency and the like, and has been widely studied in recent years because of its excellent performance. However, since silicon carbide materials have many processes yet to be solved, such as a silicon carbide cleaning process, the most currently used RCA process is a cleaning process for silicon, but the physicochemical properties of silicon carbide and silicon are different, and the RCA cleaning process uses a large amount of chemical reagents, which has a problem in terms of safety, so that a cleaning process with high efficiency, safety and less pollution needs to be developed.
Disclosure of Invention
The present application is directed to a wafer cleaning method, which can solve the above technical problems.
The embodiment of the application provides a wafer cleaning method, which comprises the following steps:
performing a first cleaning step, the first cleaning step comprising: cleaning at least one surface of the wafer by adopting fluid cleaning and first megasonic waves; the fluid comprises water and N 2 ；
Performing a second cleaning step, the second cleaning step comprising: cleaning at least one surface of the wafer with a first solution; the first solution comprises alkali and first oxidant;
performing a third cleaning step, the third cleaning step comprising: cleaning at least one surface of the wafer with a second solution; the second solution includes a second oxidant;
performing a fourth cleaning step, the fourth cleaning step comprising: cleaning at least one surface of the wafer by adopting a third solution; the third solution includes an acid.
In some embodiments, the fluid has a pressure of 0.1MPa to 0.5MPa and a temperature of 25 ℃ to 50 ℃.
In some embodiments, the first megasonic cleaning has a frequency of 400kHz to 2000kHz.
In some embodiments, the mass ratio of the base to the first oxidant is (0.5-1): (0.5-1).
In some embodiments, the temperature of the first solution is from 25 ℃ to 80 ℃.
In some embodiments, the second cleaning step further comprises: and after the first solution is adopted for cleaning, performing second megasonic cleaning on the wafer.
In some embodiments, the third cleaning step further comprises: and after the second solution is adopted for cleaning, third megasonic cleaning is carried out on the wafer.
In some embodiments, the concentration of the second oxidant is from 5ppm to 60ppm.
In some embodiments, the mass percent concentration of the acid in the third solution is 0.1% to 5%.
In some embodiments, the fourth cleaning step further comprises: and after the third solution is adopted for cleaning, the wafer is subjected to fourth megasonic cleaning.
In some embodiments, after performing the fourth cleaning step, a fifth cleaning step is performed, the fifth cleaning step comprising: cleaning at least one surface of the wafer with a fourth solution; the fourth solution includes a third oxidizing agent.
In some embodiments, the third oxidant is present at a mass concentration of 5ppm to 60ppm.
In some embodiments, after performing the fifth cleaning step, further comprising performing a sixth cleaning step comprising: and cleaning at least one surface of the wafer by water.
In some embodiments, after performing the sixth cleaning step, a purging step is performed.
The beneficial effects of this application lie in: the application provides a wafer cleaning method, which comprises the following steps: performing a first cleaning step: the first cleaning step comprises cleaning at least one side of the wafer with a fluid and a first megasonic wave; the fluid comprises water and N 2 The method comprises the steps of carrying out a first treatment on the surface of the Performing a second cleaning step: the second cleaning step comprises: cleaning at least one surface of the wafer with a first solution; the first solution comprises alkali and first oxidant; performing a third cleaning step: the third cleaning step includes: cleaning at least one surface of the wafer with a second solution; the second solution includes a second oxidant; performing a fourth cleaning step, the fourth cleaning step comprising: cleaning at least one surface of the wafer with a third solution; the third solution includes an acid. The wafer is cleaned by adopting fluid and megasonic, dirt on the wafer can be removed by fluid cleaning, and small particles on the wafer are further removed by megasonic cleaning; and in combination with the first solution, tiny particles and organic matters are removed through oxidation and electrostatic repulsion, and the surface cleanliness of the cleaned wafer is high.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a wafer cleaning process in some embodiments of the present application;
FIG. 2 shows the results of KLA-8520 testing of SiC wafers not processed by the cleaning method of example 1 of this application;
FIG. 3 shows the result of testing KLA-8520 of the SiC wafer processed by the cleaning method of example 1 of this application;
FIG. 4 is a graph showing the ICP-MS test results of an SiC epitaxial wafer after being subjected to the cleaning method of example 1 of the present application;
FIG. 5 is a schematic view of the first cleaning step of the present application;
in the figure, 1-wafer, 2-showerhead.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings and examples of the present application, in which it is evident that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be 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 used merely as labels, and do not impose numerical requirements or on the order of construction. Various embodiments of the present application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range 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, etc., as well as single numbers within the ranges, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.
The embodiment of the application provides a wafer cleaning method, which comprises the following steps:
performing a first cleaning step: the first cleaning step comprises the steps of cleaning at least one surface of the wafer 1 by using fluid and first megasonic waves; the fluid comprises water and N 2 ；
Performing a second cleaning step: the second cleaning step comprises: cleaning at least one surface of the wafer 1 by adopting a first solution; the first solution comprises alkali and first oxidant;
performing a third cleaning step: the third cleaning step includes: cleaning at least one surface of the wafer 1 by adopting a second solution; the second solution includes a second oxidant;
performing a fourth cleaning step, the fourth cleaning step comprising: cleaning at least one surface of the wafer 1 by adopting a third solution; the third solution includes an acid.
In some embodiments, the fluid is at a pressure of 0.1MPa to 0.5MPa and a temperature of 25 ℃ to 50 ℃. As in some embodiments, the pressure of the fluid is any value or range of values from any two values of 0.1, 0.2, 0.3, 0.4, 0.5. As in some embodiments, the temperature of the fluid is any value or range of values from any two values 25, 30, 35, 40, 45, 50. The wafer 1 is cleaned by the fluid, dirt on the wafer 1 can be removed, and particularly particles with the surface of the wafer 1 being more than or equal to 1 mu m can be removed.
In the first purge step, as shown in FIG. 5, the fluid is a mixture of nitrogen and water, and the fluid is passed through a nitrogen (N 2 ) As high-pressure gaseous fluid and water are used as liquid fluid to be mixed to obtain two fluids, the two fluids adopt a spray head 2 to spray mixed liquid comprising nitrogen and water at supersonic speed, the pressure range of the two fluids is 0.1Mpa-0.5Mpa, the range of the spraying angle alpha is 60-80 degrees, and the flow rate of the fluids is 0.5L/min-2L/min.
In some embodiments, the volume ratio of nitrogen to water is 1: (2-5). For example, the mixing volume of nitrogen and water is any value or range of any two values of 1:2, 1:3, 1:4 and 1:5.
In the present application, the wafer 1 has a first direction X and a second direction Y, and the ejection angle α in the present application refers to an angle at which the fluid is ejected from the head 2 (the angle at which the fluid is ejected is the fluid center line O 1 As a reference) and the first direction X of the wafer 1. The angle of the fluid jet cleaning is in this range, and the wafer 1 can be cleaned better while avoiding damage to the wafer 1 by direct vertical jet.
In some embodiments, in the first cleaning step, the first megasonic cleaning has a frequency of 400kHz to 2000kHz. Such as megasonic frequencies ranging from any one or two of 400, 500, 1000, 1500, 2000. In some embodiments, the solution used for the first megasonic cleaning is ultrapure water. The wafer 1 is cleaned by the first megasonic wave, so that dirt of the wafer 1 can be removed, and particularly particles with the particle size of more than or equal to 0.5 mu m on the wafer 1 can be removed.
In some embodiments, the first cleaning step is performed for a period of time ranging from 30 seconds to 120 seconds, such as cleaning the wafer 1 with a fluid for a period of time ranging from 30 seconds to 60 seconds, followed by cleaning the wafer 1 with a first megasonic wave for a period of time ranging from 30 seconds to 60 seconds. In some embodiments, the time of the first cleaning step is any or a range of values from 30, 40, 50, 60, 70, 80, 90, 100, 110, 120. In some embodiments, the time for fluid cleaning the wafer 1 is any one or a range of any two of 30, 40, 50, 60; the time of the first megasonic cleaning is any value or any range of values consisting of 30, 40, 50 and 60.
In some embodiments, the mass ratio of base to first oxidant is (0.5-1): (0.5-1). In some embodiments, the base comprises aqueous ammonia and the first oxidant comprises hydrogen peroxide. In some implementations, the first solution includes a mass ratio of (0.5-1): (0.5-1): the alkali, hydrogen peroxide and water in the steps (4-5). In some embodiments, the first solution comprises a mass ratio of 1:1:5, alkali, hydrogen peroxide and water. In some embodiments, the solvent water of the first solution refers to ultrapure water.
In some embodiments, the temperature of the first solution is 25 ℃ to 80 ℃. For example, the temperature of the first solution is any one or a range of any two of 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.
The wafer 1 is processed by adopting a first solution, and alkali and a first oxidant in the first solution can remove tiny particles and organic matters through oxidation and electrostatic repulsion.
In some embodiments, the second cleaning step further comprises: after the cleaning with the first solution, the wafer 1 is subjected to a second megasonic cleaning. After the wafer 1 is processed by the first solution, tiny particles are timely taken away from the wafer 1 through second megasonic cleaning.
In some embodiments, in the second cleaning step, the second megasonic cleaning has a frequency of 400kHz to 2000kHz and the solution used for the second megasonic cleaning is ultrapure water. For example, the second megasonic frequency may be any one of 400, 500, 1000, 1500, and 2000 or a range of any two values.
In some embodiments, the time of the second cleaning step is 30s to 120s, e.g., the time of the second cleaning step is 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, or any value or range of values.
In some embodiments, the third cleaning step further comprises: after the second solution is used for cleaning, the wafer 1 is subjected to third megasonic cleaning. The organic matters and some metals on the surface are removed through the second solution, a layer of oxide film is formed, tiny particles and metal pollution which are difficult to remove are fixed, and the third megasonic cleaning is combined, so that the particles on the wafer 1 are further removed.
In some embodiments, in the third cleaning step, the third megasonic cleaning has a frequency of 400kHz to 2000kHz and the solution used for the third megasonic cleaning is ultrapure water. For example, the third megasonic frequency can be any value or a range of values of any two values of 400, 500, 1000, 1500 and 2000.
In some embodiments, the second oxidizing agent comprises ozone, and in other embodiments, the second solution is an aqueous solution in which ozone is dissolved.
In some embodiments, the concentration of the second oxidant is from 5ppm to 60ppm, such as the concentration of the second oxidant (ppm) is any value or range of values from any two values of 5, 10, 15, 20, 25, 30, 25, 40, 45, 50, 55, 60.
In some embodiments, the time of the third cleaning step ranges from 30s to 120s, e.g., the time of the third cleaning step ranges from any one or two of 30, 40, 50, 60, 70, 80, 90, 100, 110, 120; in some embodiments, the second solution has a cleaning time of 30s to 60s, e.g., the second solution has a cleaning time ranging from any one or two of 30, 40, 50, 60; the third megasonic cleaning time is 30 s-60 s, for example, the third megasonic cleaning time is any value or any two values of 30, 40, 50 and 60.
The method etches away the pollution which is difficult to remove in the oxide film in the third cleaning step through the fourth cleaning step, and thoroughly removes the strong adsorbate on the wafer 1.
In some embodiments, the acid in the third solution comprises hydrofluoric acid and the third solution is an aqueous solution of hydrofluoric acid.
In some embodiments, the mass percent concentration of the acid in the third solution is 0.1% to 5%, e.g., the mass percent (%) of the acid in the third solution has a value of any value or a range of any two values of 0.1, 0.5, 1, 2, 3, 4, 5.
In some embodiments, the fourth cleaning step further comprises: after the third solution is used for cleaning, the wafer 1 is subjected to the fourth megasonic cleaning.
In some embodiments, the fourth megasonic cleaning has a frequency of 400kHz to 2000kHz and the solution used for the fourth megasonic cleaning is ultrapure water. For example, the fourth megasonic frequency can be any value or a range of values of any two values of 400, 500, 1000, 1500 and 2000.
In some embodiments, the time of the fourth cleaning step ranges from 30s to 120s, such as the time of the fourth cleaning step ranges from 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, or any two, such as in the fourth cleaning step, the time of the third solution cleaning ranges from 30s to 60s, such as the time of the third solution cleaning ranges from 30, 40, 50, 60, or any two; the fourth megasonic cleaning time is 30 s-60 s, for example, the fourth megasonic cleaning time is any value or any two value ranges of 30, 40, 50 and 60.
In some embodiments, after performing the fourth cleaning step, performing a fifth cleaning step comprising: cleaning at least one surface of the wafer 1 by adopting a fourth solution; the fourth solution includes a third oxidant; the mass concentration of the third oxidant is 5ppm to 60ppm. The fourth solution is used for cleaning the wafer 1 again, and an oxide film is formed on at least one surface of the wafer 1 to prevent the wafer 1 from being polluted by secondary adsorption.
In some embodiments, the time of the fifth cleaning step ranges from 30s to 120s, e.g., the time of the fifth cleaning step ranges from any one or two of 30, 40, 50, 60, 70, 80, 90, 100, 110, 120.
In some embodiments, the third oxidizing agent comprises ozone.
In some embodiments, the fourth solution is an aqueous solution in which ozone is dissolved. In some embodiments, the concentration of the third oxidizing agent takes on a value of any or a range of any two values of 5, 10, 15, 20, 25, 30, 25, 40, 45, 50, 55, 60.
In some embodiments, the third oxidant is the same as or different from the second oxidant.
In some embodiments, the concentration of the third oxidizing agent is the same as that of the second oxidizing agent, that is, the concentration of the ozone water used in both steps is the same, and in both steps, the same concentration of the oxidizing agent is used for cleaning, so that the consistency of the cleaning process can be ensured, and meanwhile, the damage of the wafer 1 caused by different concentrations of the oxidizing agents can be avoided.
The method removes strong adsorbates and metal pollution on the wafer 1 through an ozone and hydrofluoric acid cleaning process, and finally prevents electrostatic adsorption from polluting again through ozone oxidation in a fifth cleaning step. The application designs a cleaning flow from the dirt removal principle, uses mechanical cleaning for multiple times, and reduces the use of chemical reagents.
In some embodiments, after performing the fifth cleaning step, further comprising performing a sixth cleaning step comprising: at least one side of the wafer 1 is rinsed with water.
In some embodiments, the time of the sixth cleaning step ranges from 30s to 120s, e.g., the time of the sixth cleaning step ranges from any one or two of 30, 40, 50, 60, 70, 80, 90, 100, 110, 120.
In some embodiments, the purging step is performed after the sixth cleaning step is performed.
In some embodiments, the purging step comprises: using N 2 The wafer 1 is purged and finally spin-dried at high speed.
In some embodiments, in the first cleaning step, the second cleaning step, the third cleaning step, the fourth cleaning step, the fifth cleaning step, and the sixth cleaning step of the present application, the wafer 1 has a first rotation speed, where the first rotation speed is 400rpm to 2000rpm, and the first rotation speed is any value or a range of any two values of 400, 500, 600, 700, 800, 900, 1000, 1500, and 2000.
In some embodiments, as shown in fig. 5, the wafer 1 has a first side 101 and a second side 102 disposed away from each other, and each cleaning step in the present application cleans both sides of the wafer 1 at the same time, and in each step, the megasonic cleaning frequency is the same.
The SiC wafer is cleaned by adopting a method of combining fluid, megasonic and ozone with an RCA process, wherein the fluid process can be used for preliminarily removing dirt on the wafer, and megasonic cleaning is used for further removing small particles on the wafer 1; the mixed solution of ammonia water, hydrogen peroxide and ultrapure water is washed to remove tiny particles and organic matters through oxidation and electrostatic repulsion, then tiny particles are timely taken away from the surface of the wafer 1 through megasonic technology, then strong adsorbates and metal pollution on the wafer 1 are removed through an ozone and hydrofluoric acid cleaning technology, and finally ozone oxidation is used for preventing electrostatic adsorption from being polluted again. The cleaning flow is designed from the dirt removal principle, mechanical cleaning is used for multiple times, the use of chemical reagents is reduced, and the cleanliness of the cleaned wafer 1 is high.
Example 1:
a wafer 1 is provided, the wafer 1 being a SiC die.
Performing a first cleaning step: the SiC wafer is rinsed with a fluid and a first megasonic wave in sequence, wherein the fluid is ultrapure water and N in a volume ratio of 1:3 2 The water temperature is 25 ℃, the pressure is 0.3-0.4 MPa, the fluid injection angle alpha is 80 degrees, the cleaning time is 30s, the first megasonic wave is megasonic and ultrapure water cleaning, the megasonic frequency is 1000kHz, and the megasonic cleaning time is 30s.
Performing a second cleaning step: the SiC wafer is rinsed by a first solution comprising ammonia water, hydrogen peroxide and ultrapure water for 30s, then is rinsed by second megasonic wave by the ultrapure water, the megasonic frequency is 1000kHz, the megasonic rinsing time is 30s, wherein the mass ratio of the mixed solution of the ammonia water, the hydrogen peroxide and the ultrapure water is 1:1:5, and the temperature of the first solution is 50 ℃.
Performing a third cleaning step: the SiC wafer was rinsed with a second solution comprising ozone water at a concentration of 30ppm for 60 seconds, then with ultra-pure water for a third megasonic rinse at a megasonic frequency of 1000kHz for 30 seconds.
Performing a fourth cleaning step: and (3) flushing the SiC wafer by using a third solution containing hydrofluoric acid, wherein the mass percentage concentration of the hydrofluoric acid solution is 2%, the flushing time of the third solution is 60s, after the hydrofluoric acid treatment, the third solution is flushed by using ultrapure water in a fourth megasonic mode, the megasonic frequency is 1000kHz, and the megasonic flushing time is 30s.
A fifth cleaning step is performed: the SiC wafer was rinsed with a fourth solution comprising ozone water at a concentration of 30ppm for a rinsing time of 60 seconds.
A sixth cleaning step is performed: washing with ultrapure water for 30-120 s, N 2 The SiC wafer is purged and then spin-dried at high speed.
Example 2: the cleaning method is the same as in example 1, except that the fifth cleaning step is not performed.
Comparative example 1: the cleaning method is the same as in example 1, except that the first cleaning step is not performed.
Comparative example 2: the cleaning method is the same as in example 1, except that the second cleaning step is not performed.
Comparative example 3: the cleaning method is the same as in example 1, except that the third cleaning step and the fourth cleaning step are not performed.
The testing method comprises the following steps: and detecting by using a KLA-8520 surface defect detector, detecting metal element residues by using ICP-MS, and taking 30 wafers as detection samples processed in the same batch.
Table 1 test results of the cleaning method of the present application
From the results in table 1, it can be seen that:
in example 2, compared with example 1, the fifth cleaning step was not performed, no oxide film was formed on the wafer surface, and the electrostatic effect on the wafer surface increased the residue of particles on the wafer.
Compared with example 1, the capability of removing large particles is significantly weakened without performing the first cleaning step, and the residual amount of particles of 1 μm or more on the wafer surface is large.
Compared with example 1, the residual amount of particles of 0.5 μm or more on the wafer surface was increased, and especially small particles of 0.5 to 3 μm were more evident without performing the second cleaning step.
Comparative example 3 compared with example 1, the wafer surface metal residual amount was maximized without performing the third cleaning step and the fourth cleaning step.
As shown in fig. 2, particles with a particle size of > 0.5 μm on the wafer surface before cleaning are 2403 particles/sheet, and as shown in fig. 3, particles with a particle size of > 0.5 μm on the wafer after the above cleaning treatment are controlled to 36 particles/sheet; as shown in FIG. 4, the ICP-MS detection results after cleaning in the present application show that the residual content of the detected metal elements is less than 5E+10atom/cm 2 Meets the actual production requirement.
The solution of embodiment 1 of the present application was adopted to test the metal residue on the surface of the wafer 1, wherein the first test is performed after the first cleaning step is performed, the second test is performed after the second cleaning step is performed, and the third test is performed after the third and fourth cleaning steps are performed, and the test results are shown in table 2 and fig. 4.
TABLE 2 wafer surface Metal detection results (atoms/cm) 2 )
From the above results, the cleaning method of the present application can remove contaminants introduced into the silicon carbide epitaxial wafer during the epitaxy and measurement processes, such as dust particles, graphite, organic contamination, metal contamination or residues, etc. attached to the surface.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.
The foregoing has described in detail a method for cleaning a wafer provided by the embodiments of the present application, and specific examples have been applied herein to illustrate the principles and embodiments of the present application, where the foregoing examples are provided to assist in understanding the method and core ideas of the present application; meanwhile, those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present application, and the present description should not be construed as limiting the present application in view of the above.
Claims (14)
1. The wafer cleaning method is characterized by comprising the following steps of:
performing a first cleaning step, the first cleaning step comprising: cleaning at least one surface of the wafer (1) by using fluid and first megasonic waves; the fluid comprises water and N 2 ；
Performing a second cleaning step, the second cleaning step comprising: cleaning at least one side of the wafer (1) with a first solution; the first solution comprises alkali and first oxidant;
performing a third cleaning step, the third cleaning step comprising: cleaning at least one side of the wafer (1) with a second solution; the second solution includes a second oxidant;
performing a fourth cleaning step, the fourth cleaning step comprising: cleaning at least one side of the wafer (1) with a third solution; the third solution includes an acid.
2. The method for cleaning a wafer according to claim 1, wherein the pressure of the fluid is 0.1MPa to 0.5MPa and the temperature of the fluid is 25 ℃ to 50 ℃.
3. The method of claim 1, wherein the first megasonic cleaning has a frequency of 400kHz to 2000kHz.
4. The method for cleaning a wafer according to claim 1, wherein a mass ratio of the base to the first oxidizing agent is (0.5 to 1): (0.5-1).
5. The method of claim 1, wherein the first solution has a temperature of 25 ℃ to 80 ℃.
6. The method of cleaning a wafer according to claim 1, wherein the second cleaning step further comprises: and after the first solution is adopted for cleaning, performing second megasonic cleaning on the wafer (1).
7. The method of cleaning a wafer according to claim 1, wherein the third cleaning step further comprises: and after the second solution is adopted for cleaning, third megasonic cleaning is carried out on the wafer (1).
8. The method for cleaning a wafer according to claim 1, wherein the concentration of the second oxidizing agent is 5ppm to 60ppm.
9. The method of claim 1, wherein the third solution has a concentration of 0.1% to 5% by mass of the acid.
10. The method of cleaning a wafer according to claim 1, wherein the fourth cleaning step further comprises: and after the third solution is adopted for cleaning, the wafer (1) is subjected to fourth megasonic cleaning.
11. The method of cleaning a wafer according to claim 1, wherein a fifth cleaning step is performed after the fourth cleaning step is performed, the fifth cleaning step comprising: cleaning at least one side of the wafer (1) with a fourth solution; the fourth solution includes a third oxidizing agent.
12. The method for cleaning a wafer according to claim 11, wherein the mass concentration of the third oxidizing agent is 5ppm to 60ppm.
13. The method of claim 12, further comprising performing a sixth cleaning step after performing the fifth cleaning step, the sixth cleaning step comprising: and cleaning at least one surface of the wafer (1) by water.
14. The method of claim 13, wherein the purging step is performed after the sixth cleaning step is performed.
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