A method for testing the cutting damage depth of group III-V single crystals

Abstract

The present invention provides a method for testing the cutting damage depth of a III-V group single crystal, which is characterized by comprising the following steps: S1, cleaning the wafer surface, S2, measuring the initial thickness of the wafer, S3, applying a protective film, S4, etching in steps to obtain a stepped terrace, S5, selecting a preferred etching solution to make the cutting damage visible, S6, observing and testing the wafer step surface, and S7, obtaining the cutting damage depth of the III-V group single crystal. The method of the present invention has high testing accuracy and can detect sub-damage defects that cannot be detected by existing testing methods. Sample preparation and operation are simple, time-saving, and the testing efficiency is high. By adopting the method of the present invention, the damage caused by the cutting process of the III-V group single crystal can be quantitatively evaluated to guide the improvement of the cutting process. At the same time, quantitative guidance can be provided for the removal amount of the surface treatment process of the III-V group wafer.

Description

Technical Field

[0001] The invention provides a testing method, in particular a method for testing the cutting damage depth of a III-V group single crystal, belonging to the technical field of semiconductor crystal material testing. Background Art

[0002] Group III-V compound crystal materials are a key branch of the semiconductor materials field. Narrow-bandgap materials such as gallium antimonide (GaSb) and indium arsenide (InAs) offer advantages such as low effective electron mass, high electron mobility, and long carrier lifetime, making them suitable for the fabrication of high-performance optoelectronic devices such as infrared detectors, lasers, and thermophotovoltaic cells. The development of high-performance Group III-V semiconductor optoelectronic devices also creates a demand for high-quality GaSb and InAs single crystals.

[0003] However, the process of cutting III-V single crystals inevitably introduces surface damage, such as cracks, dislocations, phase transitions, and amorphous layers. The surface quality of single crystals directly impacts both the performance of the crystal and the quality of the epitaxial thin films. For example, surface lattice incompleteness can affect the resistivity uniformity of the ion-implanted layer; surface damage can increase the potential for leakage current; and dislocation defects in the single crystal substrate can extend into the epitaxial thin film, reducing carrier mobility. Therefore, after cutting, the crystals must undergo surface treatments such as grinding and polishing to achieve a damage-free, low-roughness, and clean single crystal surface. Detecting and analyzing the thickness of the damaged layer on the crystal surface is crucial to accurately guide the removal amount in subsequent surface treatment steps and achieve efficient processing of crystal materials.

[0004] At present, surface damage depth detection methods have been developed for a variety of single crystal materials (such as silicon, silicon carbide, cadmium zinc telluride, and lithium niobate), but there is still a blank in the cutting damage depth testing method for III-V group single crystals including GaSb and InAs. Summary of the Invention

[0005] In order to solve the technical gap problem existing in the cutting damage depth testing method of III-V single crystal materials, and at the same time, to further optimize the cutting process of III-V single crystal materials such as gallium antimonide (GaSb) and indium arsenide (InAs) and provide quantitative guidance for the surface treatment of III-V single crystal wafers, the present invention provides a cutting damage depth testing method for III-V single crystal materials.

[0006] The present invention is accomplished by the following technical solutions: a method for testing the cutting damage depth of a III-V group single crystal material, characterized by comprising the following steps:

[0007] S1, wafer surface cleaning:

[0008] Take a (100) wafer cut from a III-V group single crystal material, rinse it with acetone three times and ethanol three times in sequence, and blow it dry with nitrogen for later use;

[0009] S2, initial wafer thickness measurement:

[0010] Use a thickness gauge to measure the thickness of the wafer at multiple points and record the data as: D1, D2, D3,…, D n ,The purpose is to eliminate the impact of the thickness difference of the wafer itself on the test accuracy;

[0011] S3, apply protective film:

[0012] A full sheet of protective film is applied to the back of the wafer to protect it from corrosion throughout the experiment. N strips of protective film of equal width and arranged in parallel are applied to the front of the wafer to control the etching time at different locations of the wafer during the step-by-step etching process.

[0013] S4, step-by-step etching to obtain stepped terraces:

[0014] The nth protective film on the front of the wafer is peeled off, and the wafer is immersed in a non-preferential etching solution for a soaking time of Δt. After removal, it is rinsed with ultrapure water. Then, the n-1th protective film on the front of the wafer is peeled off, and it is soaked in the non-preferential etching solution for a soaking time of Δt. After removal, it is rinsed with ultrapure water. This process is repeated until only one protective film is left on the front of the wafer. The above distributed etching method can obtain a stepped wafer table.

[0015] S5, select the best corrosive liquid to make the cutting damage visible:

[0016] After removing the last protective film on the front of the wafer, soak the wafer in the selective etching solution for 3 to 5 minutes, remove the wafer and rinse it with a large amount of ultrapure water, and then blow dry with nitrogen;

[0017] S6, observe and test the wafer step surface:

[0018] The thickness of the stepped wafer table was measured and the surface morphology was photographed using a non-contact measuring microscope. The final thickness of the crystal covered by the first to nth protective films was obtained as follows: d1, d2, d3,…, d n ;

[0019] S7, obtain the cutting damage depth of III-V group single crystal:

[0020] According to the surface morphology photos obtained by S6, the following phenomena can be observed: as the etching time increases, the wafer thickness decreases and the density of the etching pits also gradually decreases. However, when the density of the etching pits drops to a certain level, it will no longer change with the wafer thinning. The density of the etching pits at this time is the density of dislocation defects inside the crystal, indicating that the cutting damage layer on the wafer surface has been completely removed. The minimum wafer thickness difference Δd corresponding to the minimum value of the etching pit density is i That is the cutting damage depth (Δd i =D i -d i ).

[0021] The III-V group single crystals include but are not limited to gallium antimonide (GaSb) and indium arsenide (InAs).

[0022] The single crystal cutting methods of S1 include but are not limited to multi-wire cutting and inner circle cutting.

[0023] The non-preferential etching solution of S4 includes but is not limited to:

[0024] A mixture of bromine and methanol, with a bromine concentration of 1% to 5% by volume;

[0025] Alternatively, a mixture of bromine + methanol + ethylene glycol, with the volume ratio of the three being 1:6:18;

[0026] Alternatively, a mixture of phosphoric acid and hydrogen peroxide, with the volume ratio of the two being 1:1.

[0027] In the stepwise etching of S4, the immersion time Δt is controlled within a range of 3 to 10 minutes. Due to the difference in total etching time at positions covered by different protective films, a stepped wafer table can be obtained.

[0028] The step-by-step etching of S4 can obtain a stepped wafer table without introducing new surface damage. Different table tops have different etching depths and therefore fall on different areas of the wafer surface: damaged areas (including crack areas, amorphous areas, deformed areas, etc.) and non-damaged areas.

[0029] The preferred etching solution of S5 is as follows:

[0030] For GaSb (100) wafers, the preferred etching solution is a mixture of hydrochloric acid, hydrogen peroxide, and water, with a volume ratio of 2:2:1.

[0031] For InAs (100) wafers, the preferred etching solution is a mixture of hydrochloric acid and sulfuric acid, with a volume ratio of 1:1.

[0032] The preferential etching solution used in S5 has a faster etching rate on crystal defects. Therefore, the defect state of the crystal surface can be evaluated by observing the size and density of the etching pits. Combined with the stepped wafer table obtained by the step-by-step etching method, damage defects at different depths on the wafer surface can be simultaneously revealed.

[0033] The thickness gauge, protective film, non-contact measuring microscope, etc. used in the present invention are all conventional equipment and commercially available products.

[0034] The present invention has the following advantages: 1. High test accuracy, capable of detecting sub-damage defects, which are undetectable by other existing testing methods, including double-crystal diffraction half-width method and cross-sectional microscopy; 2. High test efficiency, simple sample preparation and operation, saving time. The present invention can quantitatively assess the damage caused by the cutting process of III-V single crystals, thereby guiding cutting process improvements. It also provides quantitative guidance on the amount of material removed during surface treatment of III-V wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of the testing method of the present invention;

[0036] Figure 2 Schematic diagram of the wafer structure obtained through steps S1-S5 of the present invention;

[0037] Figure 3 Surface optical microscope photographs of GaSb single crystal slices according to Example 1 of the present invention, including: (a) step-terrace morphology after step-by-step etching with a non-preferential etching solution; (b) step-terrace morphology after etching with a preferential etching solution;

[0038] Figure 4 Surface optical microscope photos of the InAs single crystal slice of Example 2 of the present invention, including: (a) the step terrace morphology after step-by-step etching with a non-preferential etching solution; (b) the step terrace morphology after etching with a preferential etching solution. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention. Example

[0040] The present invention provides a method for testing the cutting damage depth of GaSb single crystal slices, comprising the following steps:

[0041] S1, GaSb wafer surface cleaning:

[0042] A (100) wafer obtained by inner circle cutting of a GaSb single crystal was taken. The feed rate of the inner circle cutting was 1.5 mm / h. The wafer size was 40 mm × 50 mm. The wafer was rinsed with acetone three times and ethanol three times in sequence, and then dried with nitrogen for later use.

[0043] S2, GaSb wafer initial thickness measurement:

[0044] The thickness of the GaSb (100) wafer was measured using a thickness gauge, with a point measured every 10 mm along the long side, and the data were recorded: D1, D2, D3, D4, D5. The specific data are shown in Table 1.

[0045] S3, apply protective film:

[0046] A whole protective film was attached to the back of the GaSb (100) wafer to protect the back from corrosion during the whole experiment. Five protective films were attached to the front of the wafer in parallel with the short edge (each protective film was 15 mm wide and pressed 5 mm above the previous one) to control the etching time at different positions of the wafer during the step-by-step etching process.

[0047] S4, step-by-step etching to obtain stepped terraces:

[0048] After peeling off the fifth protective film on the front of the GaSb (100) wafer, the wafer was immersed in a mixture of bromine and methanol (the volume concentration of bromine was 3%) for 5 minutes, and then rinsed with ultrapure water. Then, the fourth protective film on the front of the wafer was peeled off and the above operation was repeated until only one protective film remained on the front of the wafer. Since the total etching time at different positions covered by the protective film was different, namely: t1 = 0, t2 = 5 minutes, t3 = 10 minutes, t4 = 15 minutes, and t5 = 20 minutes, a stepped wafer surface was obtained.

[0049] S5, select the best corrosive liquid to make the cutting damage visible:

[0050] Remove the last protective film on the front of the GaSb (100) wafer, soak the wafer in a mixture of hydrochloric acid + hydrogen peroxide + water (volume ratio of 2:2:1) for 3 minutes, take it out, rinse it with a large amount of ultrapure water, and then blow it dry with nitrogen to obtain the following: Figure 2 The step-shaped GaSb wafer with defective etch pits shown completes sample preparation;

[0051] S6, observe and test the wafer step surface:

[0052] The thickness of the step surface of the GaSb wafer was measured and the surface morphology was photographed using a non-contact measurement microscope. Figure 3), the final thickness of the crystal covered by the 1st to 5th protective films are: d1, d2, d3, d4, d5, and the specific data are shown in Table 1;

[0053] S7, obtain the cutting damage depth of GaSb single crystal:

[0054] Observe the surface morphology of GaSb wafer obtained by S6 ( Figure 3 ), it can be seen that when the non-preferential etching time is 20 min, the etching pits on the wafer surface basically disappear, and the wafer thickness difference corresponding to this position Δd5 = 45 μm is the cutting damage depth of the GaSb single crystal.

[0055] Table 1

[0056]

[0057] Based on the test method of Example 1 of the present invention, it was found that the thickness of the damaged layer introduced on the GaSb wafer surface during internal circular dicing at a feed rate of 1.5 mm / h was 45 μm. This means that the subsequent surface treatment of the GaSb wafer must remove no less than 45 μm. The damaged layer thickness can be further reduced by further reducing the feed rate, but this should be balanced with slicing efficiency. Example

[0058] The present invention provides a method for testing the cutting damage depth of InAs single crystal slices, comprising the following steps:

[0059] S1, InAs wafer surface cleaning:

[0060] A (100) wafer obtained by inner circle cutting of an InAs single crystal was taken. The feed rate of the inner circle cutting was 1.0 mm / h. The wafer size was 30 mm × 40 mm. The wafer was rinsed with acetone three times and ethanol three times in sequence, and then dried with nitrogen gas for later use.

[0061] S2, InAs wafer initial thickness measurement:

[0062] The thickness of the InAs (100) wafer was measured using a thickness gauge. A point was measured every 10 mm along the long side, and the data were recorded: D1, D2, D3, and D4. The specific data are shown in Table 2.

[0063] S3, apply protective film:

[0064] A whole protective film was attached to the back of the InAs (100) wafer to protect the back from corrosion during the whole experiment. Four protective films were attached to the front of the wafer in parallel with the short edge (each protective film was 15 mm wide and pressed 5 mm above the previous one) to control the etching time at different positions of the wafer during the step-by-step etching process.

[0065] S4, step-by-step etching to obtain stepped terraces:

[0066] After removing the fourth protective film from the front of the InAs (100) wafer, the wafer was immersed in a mixture of bromine and methanol (bromine concentration of 2% by volume) for 10 minutes, removed, and rinsed with ultrapure water. The fourth protective film was then removed and the above steps were repeated until only one protective film remained on the front of the wafer. Because the total etching time for each protective film-covered position was different (t1 = 0, t2 = 10 minutes, t3 = 20 minutes, and t4 = 30 minutes), a stepped wafer surface was obtained.

[0067] S5, select the best corrosive liquid to make the cutting damage visible:

[0068] Remove the last protective film on the front of the InAs (100) wafer, soak the wafer in a mixture of hydrochloric acid and sulfuric acid (volume ratio of 1:1) for 4 minutes, then take it out, rinse it with a large amount of ultrapure water, and then blow it dry with nitrogen. Figure 2 The step-shaped InAs wafer with defective etch pits is shown, completing the sample preparation;

[0069] S6, observe and test the wafer step surface:

[0070] The thickness of the step surface of the InAs wafer was measured and the surface morphology was photographed using a non-contact measurement microscope. Figure 4 The final thickness of the crystal covered by the first to fourth protective films are d1, d2, d3, and d4, respectively. The specific data are shown in Table 2.

[0071] S7, obtain the cutting damage depth of InAs single crystal:

[0072] Observe the surface morphology of the InAs wafer obtained by S6 ( Figure 4 ), it can be seen that when the non-preferential etching time is 30 min, the etching pits on the wafer surface basically disappear, and the wafer thickness difference corresponding to this position Δd4 = 27 μm is the cutting damage depth of the InAs single crystal.

[0073] Table 2

[0074]

[0075] Based on the test method of Example 2 of the present invention, it was found that the thickness of the damaged layer introduced on the InAs wafer surface during internal circular dicing at a feed rate of 1.0 mm / h was 27 μm. This means that the amount of material removed during subsequent surface treatment of the InAs wafer must be no less than 27 μm. The thickness of the damaged layer can be further reduced by further reducing the feed rate, but this should be balanced with slicing efficiency.

Claims

1. A method for testing the cutting damage depth of a III-V group single crystal, characterized in that The following steps are involved: S1, wafer surface cleaning: Take a (100) wafer cut from a III-V group single crystal material, rinse it with acetone three times and ethanol three times in sequence, and blow it dry with nitrogen for later use; S2, initial wafer thickness measurement: Use a thickness gauge to measure the thickness of the wafer in step S1 at multiple points and record the data as: D1, D2, D3,…, D n ; S3, apply protective film: In step S2, a full sheet of protective film is applied to the back of the wafer to protect the back from corrosion throughout the experiment, and n strips of protective film of equal width and arranged in parallel are applied to the front of the wafer one by one; S4, step-by-step etching to obtain stepped terraces: The nth protective film on the front side of the wafer in step S3 is removed, and the wafer is immersed in a non-preferential etching solution for a soaking time of Δt, and then rinsed with ultrapure water. Then, the n-1th protective film on the front side of the wafer is removed, and the wafer is immersed in the non-preferential etching solution for a soaking time of Δt, and then rinsed with ultrapure water. This process is repeated until only one protective film is left on the front side of the wafer. The non-preferential etching solution includes but is not limited to: A mixture of bromine and methanol, with a bromine concentration of 1% to 5% by volume; Alternatively, a mixture of bromine + methanol + ethylene glycol, with the volume ratio of the three being 1:6:18; Alternatively, a mixture of phosphoric acid and hydrogen peroxide, with a volume ratio of 1:1; S5, select the best corrosive liquid to make the cutting damage visible: After removing the last protective film on the front of the wafer in step S4, soak the wafer in the selective etching solution for 3-5 minutes, remove the wafer and rinse it with a large amount of ultrapure water, and then blow dry with nitrogen; The preferred etching solution is as follows: For GaSb (100) wafers, the preferred etching solution is a mixture of hydrochloric acid, hydrogen peroxide, and water, with a volume ratio of 2:2:

1. For InAs (100) wafers, the preferred etching solution is a mixture of hydrochloric acid and sulfuric acid, with a volume ratio of 1:

1. S6, observe and test the wafer step surface: The thickness of the stepped wafer table in step S5 was measured and the surface morphology was photographed using a non-contact measuring microscope. The final thickness of the crystal covered by the protective film from the 1st to the nth line was obtained as follows: d1, d2, d3,…, d n ; S7, obtain the cutting damage depth of III-V group single crystal: According to the surface morphology photos obtained in step S6, the following phenomena are observed: as the non-preferential etching time increases, the wafer thickness decreases and the etch pit density also gradually decreases. However, when the etch pit density drops to a certain level, it no longer changes with wafer thinning. The etch pit density at this time is the dislocation defect density inside the crystal, indicating that the cutting damage layer on the wafer surface has been completely removed. The minimum wafer thickness difference Δd corresponding to the etch pit density dropping to the minimum value is i That is the cutting damage depth (Δd i =D i -d i ).

2. A method for testing the cutting damage depth of a III-V group single crystal according to claim 1, characterized in that The III-V group single crystals include but are not limited to gallium antimonide (GaSb) and indium arsenide (InAs).

3. The method for testing the cutting damage depth of a III-V group single crystal according to claim 1, characterized in that The single crystal cutting methods of S1 include but are not limited to multi-wire cutting and inner circle cutting.

4. The method for testing the cutting damage depth of a III-V group single crystal according to claim 1, characterized in that In the step-by-step corrosion of S4, the immersion time Δt is controlled within 3 to 10 minutes.

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