Processing method of tellurium-zinc-cadmium wafer with high surface shape quality

Abstract

The invention discloses a processing method of a tellurium-zinc-cadmium wafer with high surface shape quality, which is characterized in that adverse factors in the processing process of the tellurium-zinc-cadmium wafer are neutralized by adjusting process steps, so that the purpose of preparing the tellurium-zinc-cadmium wafer with high surface shape quality is achieved. That is, the edge collapse phenomenon of the wafer in the chemical polishing process is neutralized by using the deformation of the wafer caused by the stress of the damaged layer generated in the polishing process of the tellurium-zinc-cadmium wafer. According to the method, firstly, a wafer needs to be subjected to chemical corrosion to remove damage layer stress on the two faces of the wafer, secondly, a diamond grinding wheel is used for grinding the growth face of the wafer, after grinding, the wafer is fixed again and then polished, and finally chemical polishing is conducted. The method has the advantages of being simple in process, good in repeatability, high in realizability and the like, and the surface shape control level in the tellurium-zinc-cadmium wafer production process can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectric detection, and in particular relates to a method for processing a cadmium zinc telluride wafer with high surface quality. Background Art

[0002] Cadmium zinc telluride (CdZnTe) wafers are widely used in the fields of photoelectric detection technology such as nuclear safety, astrophysics, environmental monitoring and medical imaging. Such uses place high demands on the surface processing of CdZnTe wafers, requiring high flatness and low surface damage. At the same time, due to the requirements of transmittance for photoelectric detection, CdZnTe must be processed on both sides; double-sided grinding and polishing has been widely used in silicon technology, but due to the irregularity of CdZnTe process wafers and the high edge damage rate of double-sided grinding and polishing, most CdZnTe wafer processing processes still use single-sided grinding and single-sided polishing processes.

[0003] The single-sided grinding and polishing technology, on the one hand, will introduce repeated changes in residual stress and cause warping deformation, which has strong randomness and irregularity. On the other hand, the requirement of low surface damage also requires chemical polishing of CdZnTe in the last step, and the chemical polishing process will introduce chip edge collapse due to the "edge effect". Under the traditional process, the purpose of controlling the surface shape in the chemical polishing process is mainly achieved by adjusting the chemical polishing liquid components, adjusting the chemical polishing parameters, optimizing the previous fine polishing process to shorten the chemical polishing time, etc. However, due to the inevitable "edge effect" and the strong randomness of the shape after the previous process, the stability and repeatability of the effect of using chemical polishing to control the surface shape are poor, and it is impossible to stably obtain CdZnTe wafers with high surface quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for processing cadmium zinc telluride wafers with high surface quality in view of the above-mentioned deficiencies in the prior art. The method has simple process, good repeatability and feasibility, is suitable for industrial production, and can effectively improve the surface control level in the production process of cadmium zinc telluride wafers.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A method for processing CdZnTe wafers with high surface quality is disclosed. The unfavorable factors in the processing of CdZnTe wafers are neutralized by adjusting the process steps, so as to achieve the purpose of preparing CdZnTe wafers with high surface quality. That is, the deformation of the wafer caused by the stress of the damaged layer generated during the grinding and polishing of the CdZnTe wafer is utilized to "neutralize" the edge collapse phenomenon of the wafer during the chemical polishing process. The method includes the following four steps:

[0007] Step 1: chemically corrode the CdZnTe wafer to remove the stress of the damaged layer on both sides of the wafer, ensuring that the wafer is not deformed before proceeding to step 2;

[0008] Step 2: fix the cadmium zinc telluride wafer and grind it with a grinding wheel, remove the wafer after grinding, and make the wafer warp and deform toward the damaged layer under the action of the damaged layer stress;

[0009] Step 3: Remove the CdZnTe wafer and re-fix it for polishing to remove the stress of the damaged layer. After polishing, remove the wafer to obtain a "concave" wafer with a low center and high surroundings.

[0010] Step 4: Chemically polish the CdZnTe wafer, so that the wafer collapses under the chemical action and the removal rate around it is higher than that in the center, and the "concave" wafer becomes flat.

[0011] According to the above scheme, the chemical etching solution used in step 1 is a bromine-based solution with a concentration of 0.1% to 10.0%.

[0012] According to the above scheme, the corrosion time in step 1 is 2 to 15 minutes.

[0013] According to the above scheme, the fixing methods in step 2 and step 3 include any one of adsorption, wax adhesion and membrane adhesion.

[0014] According to the above scheme, in step 2, a diamond grinding wheel is used for grinding, and the mesh number of the grinding wheel is 8000 to 15000.

[0015] According to the above scheme, the grinding speed in step 2 is 1500-2500 rpm, and the feed speed is 0.03-0.05 μm / s.

[0016] According to the above scheme, the polishing speed in step three is 50-70 rpm.

[0017] According to the above scheme, the polishing time in step three is 10 to 20 minutes.

[0018] According to the above scheme, the chemical polishing solution used in step 4 is a bromine-based solution with a concentration of 0.1 to 10.0%.

[0019] According to the above scheme, the chemical polishing time in step 4 is 1 to 8 minutes.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] like Figure 1The figure shows the schematic diagram of step 2 and step 3 in the CdZnTe wafer processing method of the present invention. After step 3, the surface shape of the wafer is "concave". The subsequent step 4 chemical polishing will make the surface shape of the wafer "convex" due to the edge collapse effect. Therefore, after steps 1 to 4 of the present invention, the surface shape of the wafer will tend to be flat. The present invention is improved based on the existing actual process, and the two unfavorable and irreconcilable factors of the damaged layer stress and the edge collapse of chemical polishing are mutually neutralized to process CdZnTe wafers with high surface quality. The process has the advantages of simplicity, good repeatability, strong feasibility, etc., and can effectively improve the surface shape control level in the production process of CdZnTe wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the principle of the cadmium zinc telluride wafer processing method of the present invention.

[0023] Figure 2 The surface images of Example 1 and Example 2 before and after chemical polishing are shown. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to embodiments, but the present invention is not limited to the following embodiments.

[0025] A method for processing a cadmium zinc telluride wafer with high surface quality comprises the following steps:

[0026] 1) chemically etching the cadmium zinc telluride wafers cut from the cadmium zinc telluride single crystal, wherein the chemical etching solution is 1.5% bromine methanol, and the etching time is 6 minutes;

[0027] 2) The etched CdZnTe wafer was fixed on a silicon wafer with paraffin wax, and the B side (the front and back sides of the CdZnTe wafer are represented by B side and A side, respectively) was ground with a diamond grinding wheel, the rotation speed of the diamond grinding wheel was 2500 rpm, the feed speed was 0.04 μm / s, the mesh number of the diamond grinding wheel used in Example 1 was 15000 mesh, and the mesh number of the diamond grinding wheel used in Example 2 was 8000 mesh;

[0028] 3) Remove the CdZnTe wafer after grinding with the diamond wheel, remove the paraffin, fix it on the silicon wafer again with paraffin, and polish the B surface at a speed of 60 rpm for 12 minutes. After processing, cut it into wafers of the required size and clean it;

[0029] 4) The cleaned wafer is subjected to chemical polishing on the B side. The chemical polishing liquid is bromomethanol. The concentration used in Example 1 is 0.2%, and the chemical polishing time is 2 minutes. The concentration used in Example 2 is 0.4%, and the chemical polishing time is 8 minutes.

[0030] Through the above steps 1) to 4), Example 1 and Example 2 were prepared respectively. Figure 2The surface shapes of Example 1 and Example 2 before and after chemical polishing.

[0031] The parameters in step 1 and step 3 of the present invention are empirical parameters related to the actual process. The parameters in step 2 and step 4 are the main determining factors for the present invention. The parameters in step 2 of the present invention mainly control the residual stress of the chip damage layer. Figure 1 The residual stress of the damaged layer determines the degree of concavity of the B surface of the wafer after step 3. Therefore, compared with embodiment 1, embodiment 2 has a lower mesh count, a higher residual stress of the damaged layer, and a higher degree of concavity of the B surface. Figure 2 The chemical polishing parameters in step 4 of the present invention mainly control the convexity trend of the wafer B surface after chemical polishing, that is, the greater the concentration of the chemical polishing solution and the longer the chemical polishing time, the more serious the edge collapse and the greater the convexity trend. Figure 2 As shown, before chemical polishing, the concavity of Example 2 is greater than that of Example 1, so the concentration of chemical polishing liquid and the chemical polishing time required for Example 2 are also greater than those required for Example 1 to ensure flattening after chemical polishing. In summary, the method for preparing a high-planarity cadmium zinc telluride wafer material provided by the present invention is feasible.

[0032] The above examples are only some examples of the present invention and are not intended to limit the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent alternatives to the technical features in the technical solutions recorded in the claims. That is, equivalent replacement and improvement within this scope are also within the protection scope of the present invention.

Claims

1. A method for processing a cadmium zinc telluride wafer with high surface quality, characterized in that: The following steps are involved: Step 1: chemically corrode the CdZnTe wafer to remove the stress of the damaged layer on both sides of the wafer, ensuring that the wafer is not deformed before proceeding to step 2; Step 2: fix the cadmium zinc telluride wafer and grind it with a grinding wheel, remove the wafer after grinding, and make the wafer warp and deform toward the damaged layer under the action of the damaged layer stress; Step 3: Remove the CdZnTe wafer and re-fix it for polishing to remove the stress of the damaged layer. After polishing, remove the wafer to obtain a "concave" wafer with a low center and high surroundings. Step 4: Chemically polish the CdZnTe wafer so that the wafer collapses under chemical action and the removal rate around it is higher than that in the center, and the "concave" wafer becomes flat.

2. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The chemical etching solution used in step 1 is a bromine-based solution with a concentration of 0.1% to 10.0%.

3. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The corrosion time in step 1 is 2 to 15 minutes.

4. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The fixing methods in step 2 and step 3 include any one of adsorption, wax adhesion and membrane adhesion.

5. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: In step 2, a diamond grinding wheel is used for grinding, and the mesh number of the grinding wheel is 8000 to 15000.

6. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The grinding speed in step 2 is 1500-2500 rpm, and the feed speed is 0.03-0.05 μm / s.

7. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The polishing speed in step 3 is 50-70 rpm.

8. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The polishing time in step 3 is 10 to 20 minutes.

9. The method for processing a CdZnTe wafer with high surface quality according to claim 1, characterized in that: The chemical polishing solution used in step 4 is a bromine-based solution with a concentration of 0.1 to 10.0%.

10. A method for processing a cadmium zinc telluride wafer with high surface quality according to any one of claims 1 to 9, characterized in that: The chemical polishing time in step 4 is 1 to 8 minutes.

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