CN115608694A - Method for cleaning gallium arsenide wafer with deflection angle of 15 degrees for laser - Google Patents

Method for cleaning gallium arsenide wafer with deflection angle of 15 degrees for laser Download PDF

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Publication number
CN115608694A
CN115608694A CN202211310523.7A CN202211310523A CN115608694A CN 115608694 A CN115608694 A CN 115608694A CN 202211310523 A CN202211310523 A CN 202211310523A CN 115608694 A CN115608694 A CN 115608694A
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wafer
cleaning
deionized water
hydrogen peroxide
mixed solution
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CN202211310523.7A
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Chinese (zh)
Inventor
杨春柳
鲁闻华
李有云
刘汉保
韦华
牛应硕
杨杰
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Kunming Yunzhe High Tech Co ltd
Yunnan Zhongke Xinyuan Crystalline Material Co ltd
Yunnan Xinyao Semiconductor Material Co ltd
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Kunming Yunzhe High Tech Co ltd
Yunnan Zhongke Xinyuan Crystalline Material Co ltd
Yunnan Xinyao Semiconductor Material Co ltd
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Priority to CN202211310523.7A priority Critical patent/CN115608694A/en
Publication of CN115608694A publication Critical patent/CN115608694A/en
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    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Cleaning Or Drying Semiconductors (AREA)

Abstract

A method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser relates to a method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser, and belongs to the technical field of semiconductor processing. The method of the present invention includes cleaning with an alkaline solution followed by cleaning with an acidic solution to reduce the ratio of arsenic oxide to gallium oxide on the wafer surface. The method of the invention can improve the cleanliness, the micro roughness, the uniformity and the thickness of the oxide layer of the wafer surface and the proportion of arsenic oxide and gallium oxide on the wafer surface.

Description

Method for cleaning gallium arsenide wafer with deflection angle of 15 degrees for laser
Technical Field
The invention relates to a method for cleaning a compound semiconductor wafer, in particular to a method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser.
Background
Gallium arsenide is an important semiconductor material and belongs to III-V compound semiconductors. Due to the unique electrical properties, the material has wide application in the fields of satellite communication, microwave devices, laser devices, light emitting diodes and the like. Gallium arsenide can be made into semi-insulating high-resistance materials with resistivity higher than that of silicon and germanium by more than 3 orders of magnitude, and is used for manufacturing integrated circuit substrates, infrared detectors, gamma photon detectors and the like. The electronic mobility of the gallium arsenide semiconductor device is 5-6 times higher than that of silicon, so that the gallium arsenide semiconductor device is important in the aspect of manufacturing microwave devices and high-speed digital circuits, and the gallium arsenide semiconductor device has the advantages of good high-frequency, high-temperature and low-temperature performances, low noise, strong radiation resistance and the like.
The cleaning is the last procedure in the wafer processing process and is also the key for obtaining a high-quality surface, and the purpose is to remove various residual substances in the previous procedure and obtain a fresh and clean surface, thereby providing a foundation for subsequent production. The lack of a high quality substrate surface can affect the epitaxial results and ultimately the device performance.
The gallium arsenide surface cleaning has the cleaning requirements for the similar semiconductors such as silicon, germanium and the like, not only can effectively remove organic and inorganic pollutants on the surface, but also can not cause the roughness of the surface, and also has an important requirement that the ideal chemical proportion of the gallium arsenide is not damaged. The mismatching can form a large amount of defects which cause Fermi level pinning and seriously affect the performance of the device. In addition, different cleaning methods may cause different surface chemical ratios, which may cause different annealing requirements during epitaxial layer growth, resulting in unstable growth quality.
Gallium arsenide wafer surfaces are composed of Ga and As atoms, which differ in number due to differences in the chemical properties of arsenic and gallium, as well As wafer deflection angles. For wafers with large off angles, the surface is made gallium rich, i.e., there are more gallium atoms than arsenic atoms on the surface. In this case, the wafer of 15 ° still adopts the existing cleaning method, alkaline cleaning solution, i.e. ammonia water, hydrogen peroxide and deionized water solution, cleans the wafer, and it will not make too large difference to the removal efficiency of gallium and arsenic atoms, and the wafer surface after cleaning is still in gallium-rich state, and the gallium-rich state wafer will generate some vacancies on the surface in the subsequent epitaxial process, thus leading to epitaxial failure.
Disclosure of Invention
The invention aims to provide a method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser, which improves the cleanliness, the microroughness and the uniformity of the surface of the wafer, the thickness of an oxide layer and the proportion of arsenic oxide and gallium oxide on the surface of the wafer.
The method for cleaning the wafer with the gallium arsenide deflection angle of 15 degrees for the laser is characterized by comprising the following steps of:
step 1, cleaning a wafer by using potassium hydroxide, acetone or alcohol, wherein the potassium hydroxide, the acetone or the alcohol is selected from one, two or three of the potassium hydroxide, the acetone or the alcohol; and rinsing the wafer with deionized water;
step 2, cleaning the wafer by using a mixed solution of ammonia water, deionized water and hydrogen peroxide; the temperature of the mixed solution is 5-10 ℃, according to the volume, NH 3 5-15% of H 2 O 2 15 to 25 percent; and rinsing the wafer with deionized water;
step 3, cleaning the wafer by using a mixed solution of hydrochloric acid, deionized water and hydrogen peroxide; the temperature of the mixed solution is 5-10 ℃, HCl accounts for 15-30% and H by volume 2 O 2 1-10% of the total; and rinsing the wafer with deionized water;
steps 1-3, are carried out at ambient temperature 15-25 ℃.
And after the wafer is cleaned, drying the cleaned wafer by throwing and drying in air or inert gas or vacuum.
The deionized water is used for washing the wafer, the resistivity of the deionized water is 18.25 megaohm-cm, and the temperature is 14 +/-2 ℃; the washing time is 1 to 5 minutes, preferably 3 minutes.
In the step 1, the step 2 and the step 3, megasonic waves are adopted in the cleaning process except for deionized water flushing, and the wavelength range of the megasonic waves is 700-900KHz, preferably 700-800KHz. The megasonic wave action time can be the same as the time for processing the wafer by using diluted ammonia water, hydrogen peroxide and a water system, and can also be longer or shorter than the time for processing the wafer by using the diluted ammonia water, the hydrogen peroxide and the water system. The megasonic technology is used to further improve the removal capability of foreign particles, so as to achieve the purpose of making the surface of the wafer uniform and clean.
The time for cleaning the wafer by the potassium hydroxide, acetone or alcohol is 2 to 10 minutes, preferably 3 to 6 minutes. Acetone or alcohol is selected to clean the wafer, first removing a hydrophobic organic residue layer covering the surface because it has a barrier effect to remove atomic and ionic impurities. And thus can be removed with acetone or alcohol, which are chemical reagents capable of dissolving oil impurities and organic residues.
The content of the ammonia water is preferably 8-13%, and the content of the hydrogen peroxide is preferably 17-22%; the cleaning time of the mixed solution of ammonia water, deionized water and hydrogen peroxide is 15-40 seconds, preferably 15-30 seconds.
In the process of treating the wafer by using ammonia water, deionized water and hydrogen peroxide solution at low temperature, the corrosion speed to the surface of the wafer is favorably reduced by selecting the proportion of the ammonia water to the hydrogen peroxide solution. The ammonia water has strong dissolving capacity after being added with hydrogen peroxide, and can oxidize the insoluble arsenic pentoxide into soluble arsenate. In addition, the corrosion of the solution to the surface can be further reduced by using low temperature, and the micro roughness of the surface of the wafer can be improved.
The content of the hydrochloric acid is preferably 20-25%, and the content of the hydrogen peroxide is preferably 4-8%; the cleaning time of the mixed solution of the hydrochloric acid, the deionized water and the hydrogen peroxide is 15 to 40 seconds, preferably 15 to 30 seconds.
Based on the characteristic that the gallium arsenide surface oxide can be dissolved in acid or alkali solution, the oxide layer generated before is dissolved by using dilute acid or dilute alkali solution, and a fresh gallium arsenide surface can be exposed.
The contents of the solvent, acetone, alcohol, ammonia water, hydrogen peroxide and hydrochloric acid are calculated according to pure substances.
The method of the invention is suitable for cleaning gallium arsenide semiconductor wafers, in particular to a method for cleaning gallium arsenide wafers with special deflection angles for lasers. The method of the invention can improve the cleanness, the micro roughness, the uniformity, the thickness of the oxide layer and the proportion of arsenic oxide and gallium oxide on the surface of the wafer.
Drawings
FIG. 1 is an As 3d XPS spectra for three samples;
fig. 2 is Ga 3d XPS spectra of three samples.
Detailed Description
Example 1:
roughly and finely polished 150mm (6 inch) GaAs wafers are inclined at an angle of 15 degrees and have a thickness of 675 mu m, and the surfaces of the wafers are inspected by a powerful lamp to have visible particles; the number of particles larger than 0.3 micrometer is larger than 1000 particles by CS20 inspection; and the surface micro roughness Ra = 0.25-0.35 nm by atomic force microscope inspection.
The following cleaning method is used for the wafer, and the method comprises the following steps:
step 1, clamping a wafer by using a wafer clamp, sequentially cleaning acetone and alcohol megasonic waves for 5 minutes respectively, and then washing the surface of the wafer for 2 minutes by using a deionized water quick-discharge spraying mode.
Step 2, cleaning the wafer washed by the deionized water in the step 1 for 30 seconds in the mixed liquid of ammonia water, the deionized water and hydrogen peroxide at the temperature of 6 ℃, and then washing the surface of the wafer for 2 minutes in a deionized water fast-discharging spraying mode, wherein NH is added into the mixed solution according to volume 3 10% of H 2 O 2 Accounting for 18 percent.
Step 3, the wafer washed by the deionized water in the step 2 is deionized by hydrochloric acid at the temperature of 6 DEG CMegasonic cleaning with water and hydrogen peroxide mixed solution for 30S, and then washing the surface of the wafer for 3 minutes in a deionized water quick-discharge spraying mode, wherein HCl accounts for 20% and H in the mixed solution by volume 2 O 2 Accounting for 6 percent.
And 4, putting the washed wafer into a wafer rotary dryer for spin-drying, wherein the spin-drying time is generally 120S.
In this example, the resistivity of deionized water was 18.25 megohm-cm at a temperature of 14. + -. 2 ℃.
In the embodiment, the power of the megasonic generator is 780KHz.
In this embodiment, the contents of acetone, alcohol, ammonia water, hydrogen peroxide, and hydrochloric acid are calculated as pure substances.
In this example, the ambient temperature was 20 ℃.
The dried wafer was examined for surface with a powerful lamp, CS20, atomic force microscope.
The wafer surface was inspected with a high intensity light to confirm that there were no visible particles, no white haze, and uniform surface. The number of particles larger than 0.3 μm was 50 as checked by CS 20. And the surface micro roughness Ra =0.2-0.3nm by atomic force microscope inspection.
XPS test analysis is carried out on the cleaned wafer, and XPS spectra of As 3d and Ga 3d of GaAs silicon-doped 15 degrees, including conventional cleaning 15 degrees, cleaning II 15 degrees by adding acid solution and 2-degree deviation angle wafer are shown in figure 1, and Ga of the wafer after adding acid cleaning solution can be seen in the XPS spectra 2 O 3 And As 2 O 3 The difference from the 2 ° sample was reduced. From Table 1, ga can be seen 2 O 3 And As 2 O 3 The ratio of (d) has decreased, indicating that the gallium oxide content of the wafer surface has decreased. From the data of the oxide ratio, the thickness of the oxide layer on the surface of the wafer cleaned by the cleaning process is increased, the surface of the wafer can be well protected, the deoxidation temperature of external delay is not increased, and the formation of the thickness of the oxide layer has a larger relation with the content of hydrogen peroxide in the step 3. The oxide layer acts as a passivation surface and protects the wafer, and the epitaxy has a high temperature stage, namely the wafer surface is removedThe oxide layer on the surface is too thick and difficult to remove, and the protective effect on the wafer is not good when the oxide layer is too thin.
TABLE 1
Sample (I) Ga(As)% Ga 2 O 3 % As(Ga) % As% As 2 O 3 % Ga/As Ga 2 O 3 /As 2 O 3 Oxide content in%
15° 37.79 5.54 46.68 3.40 6.59 0.81 0.84 12.13
Ⅱ15° 35.87 4.34 46.02 4.47 9.31 0.78 0.47 13.65
2° 33.55 9.39 37.61 2.90 16.54 0.89 0.57 25.93
In this embodiment, the wafer quality inspection apparatus has a Yamada high-intensity lamp with a light intensity of more than 25 ten thousand Lux, a wafer surface analyzer of CS20, KLA-TENCOR, usa, and a lateral resolution of an Atomic Force Microscope (AFM): 0.2nm, longitudinal resolution 0.01nm, analysis zone 5 μm × 5 μm.
Example 2:
after rough polishing and finish polishing, the thickness of a 100mm (4 inch) GaAs wafer is 625 μm at a deflection angle of 15 degrees; inspecting the surface of the wafer with a powerful light lamp to obtain visible particles; the number of particles larger than 0.3 micrometer is larger than 1000 particles by CS20 inspection; and the surface micro roughness Ra =0.25-0.3nm by atomic force microscope inspection.
The following cleaning method is used for the wafer, and the method comprises the following steps:
step 1, clamping a wafer by using a wafer clamp, sequentially cleaning acetone and alcohol megasonic waves for 5 minutes respectively, and then washing the surface of the wafer for 2 minutes by using a deionized water fast-discharging spraying mode.
Step 2, cleaning the wafer washed by the deionized water in the step 1 for 30 seconds in the mixed liquid of ammonia water, the deionized water and hydrogen peroxide at the temperature of 6 ℃, and then washing the surface of the wafer for 2 minutes in a deionized water fast-discharging spraying mode, wherein NH is added into the mixed solution according to volume 3 13% of H 2 O 2 Accounting for 22 percent.
And 3, cleaning the wafer washed by the deionized water in the step 2 by megasonic cleaning with a mixed solution of hydrochloric acid, deionized water and hydrogen peroxide at 6 ℃ for 30 seconds, and then washing the surface of the wafer for 3 minutes in a mode of quick-discharge spraying of the deionized water, wherein the HCl accounts for 25% by volume and H in the mixed solution 2 O 2 6 percent of the total weight.
And 4, putting the washed wafer into a wafer rotary dryer for spin-drying, wherein the spin-drying time is generally 120S.
In this example, the resistivity of deionized water was 18.25 megohm-cm at a temperature of 14. + -. 2 ℃.
In the embodiment, the power of the megasonic generator is 800KHz.
In this embodiment, the contents of acetone, alcohol, ammonia water, hydrogen peroxide, and hydrochloric acid are calculated as pure substances.
The dried wafer was examined for surface with a powerful lamp, CS20, atomic force microscope.
The wafer surface was inspected with a high intensity light to verify that there were no visible particles, no white haze, and uniform surface. The number of particles larger than 0.3 micron is within 40 by CS20 inspection. And the surface micro roughness Ra =0.2-0.3nm by atomic force microscope inspection.
Example 3:
a roughly polished and finely polished 76mm (3 inch) GaAs wafer having a thickness of 625 μm; the wafer surface was inspected with a powerful light and visible particles were present. The number of particles larger than 0.3 micrometer is larger than 1000 particles by CS20 inspection; surface microroughness Ra =0.25-0.30nm as checked by atomic force microscope;
the following cleaning method is used for the wafer, and the method comprises the following steps:
step 1, a whole box of wafers is packed by a card plug and is immersed in a potassium hydroxide solution for 5 minutes; then the wafer is put into a rinsing tank, and the surface of the wafer is rinsed for 2 minutes by using a deionized water quick-discharge spraying mode.
Step 2, cleaning the wafer washed by the deionized water in the step 1 for 30 seconds in a mixed solution of ammonia water, deionized water and hydrogen peroxide at the temperature of 6 ℃, and then washing the surface of the wafer for 2 minutes in a deionized water fast-discharging spraying mode, wherein NH is added into the mixed solution according to volume 3 Accounting for 12%, H 2 O 2 Accounting for 20 percent.
And 3, cleaning the wafer washed by the deionized water in the step 2 for 30 seconds in a mixed solution of hydrochloric acid, deionized water and hydrogen peroxide at the temperature of 6 ℃, and then washing the surface of the wafer for 3 minutes in a mode of quick-discharge spraying of the deionized water, wherein HCl accounts for 22% and H accounts for the mixed solution by volume 2 O 2 Accounting for 5 percent.
And 4, putting the washed wafer into a wafer rotary dryer for spin-drying, wherein the spin-drying time is generally 120S.
In this example, the resistivity of the deionized water is 18.25 megaohm-cm, and the temperature is 14 +/-2 ℃.
In this embodiment, the contents of the potassium hydroxide, the alcohol, the ammonia water, the hydrogen peroxide and the hydrochloric acid are calculated according to pure substances.
The dried wafer was examined for surface with a powerful lamp, CS20, atomic force microscope.
The wafer surface was inspected with a high intensity light to verify that there were no visible particles, no white haze, and uniform surface. The number of particles larger than 0.3 micron is within 40 by CS20 inspection. And the surface micro roughness Ra =0.18-0.25nm by atomic force microscope inspection.

Claims (6)

1. The method for cleaning the wafer with the gallium arsenide deflection angle of 15 degrees for the laser is characterized by comprising the following steps of:
step 1, cleaning a wafer by using potassium hydroxide, acetone or alcohol, wherein the potassium hydroxide, the acetone or the alcohol is selected from one, two or three of the potassium hydroxide, the acetone or the alcohol; and rinsing the wafer with deionized water;
step 2, cleaning the wafer by using a mixed solution of ammonia water, deionized water and hydrogen peroxide; the temperature of the mixed solution is 5-10 ℃, according to volume, NH 3 5-15% of H 2 O 2 15 to 25 percent;and rinsing the wafer with deionized water;
step 3, cleaning the wafer by using a mixed solution of hydrochloric acid, deionized water and hydrogen peroxide; the temperature of the mixed solution is 5-10 ℃, the HCl accounts for 15-30% by volume and H 2 O 2 1-10% of the total; and rinsing the wafer with deionized water;
steps 1-3, are carried out at ambient temperature 15-25 ℃.
2. The method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser as claimed in claim 1, wherein the ammonia water content is 8-13%, the hydrogen peroxide content is 17-22%; the cleaning time of the mixed solution of ammonia water, deionized water and hydrogen peroxide is 15-40 seconds.
3. The method for cleaning a wafer with a gallium arsenide deflection angle of 15 degrees for a laser as claimed in claim 1, wherein said hydrochloric acid content is 20-25%, hydrogen peroxide content is 4-8%; the cleaning time of the mixed solution of hydrochloric acid, deionized water and hydrogen peroxide is 15-40 seconds.
4. The method of claim 1, wherein the wafer is rinsed with deionized water having a resistivity of 18.25 mega ohm-cm and a temperature of 14 ± 2 ℃; the cleaning time is 1-5 minutes.
5. The method according to claim 1, wherein the cleaning process except the deionized water rinsing in step 1, step 2 and step 3 is performed by megasonic waves having a wavelength of 700-900KHz.
6. The method for cleaning a 15 ° GaAs wafer for a laser as set forth in claim 1, wherein the wafer is cleaned, and the cleaned wafer is spun and dried, and the drying is performed in air, an inert gas, or a vacuum.
CN202211310523.7A 2022-10-25 2022-10-25 Method for cleaning gallium arsenide wafer with deflection angle of 15 degrees for laser Pending CN115608694A (en)

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