A low-damage surface polishing process method for soft and brittle material cadmium zinc telluride wafer

Abstract

The present application relates to a kind of polishing techniques, specifically, a kind of surface low damage grinding and polishing tellurium zinc cadmium wafer grinding and polishing method.The method is: after the tellurium zinc cadmium wafer to be polished is fixed, first horizontal vibration polishing is carried out;Then horizontal vibration chemical polishing is carried out;Vibration polishing is controlled vibration frequency 1000-5000Hz, time is 2-8 hours;Vibration chemical polishing is controlled frequency 1000-5000Hz, time is 2-8 hours;Horizontal vibration polishing is used polishing liquid by particle size 40-65nm aluminium oxide polishing powder and deionized water according to volume ratio 1:15-25;Horizontal vibration chemical polishing is used polishing liquid for silicic acid concentration 3-8wt% silicic acid solution.The present application is simple and controllable, and the surface roughness of the obtained product is 7.9-9.65nm;It is easy for industrial application.

Description

TECHNICAL FIELD

[0001] The application relates to a polishing technology, in particular to a surface low-damage grinding and polishing method for a CdZnTe wafer. BACKGROUND

[0002] Cadmium zinc telluride (Cd 1-x Zn x Te, CZT) as an important II-VI compound semiconductor material can convert radiation energy into electrical signals through photoelectric effect. It belongs to the sphalerite structure, 43m point group, space group, the interatomic bond is mainly covalent bond, the average atomic number is large, the band gap Eg at room temperature is about 1.57 eV, the resistivity p at room temperature is greater than 10 9 Ω·cm, the electron mobility mue is greater than 1000 cm 2 / (V·s), the lifetime te is greater than 10 -5 s, and excellent carrier transport characteristics. At present, CZT crystal is widely used in medical treatment, nuclear industry, national security, aerospace and the like as an X-ray and gamma-ray detector material. In addition, the lattice constant of the CZT crystal can be continuously regulated according to the content of Zn, and the CZT crystal is the most ideal substrate material for HgCdTe infrared detectors.

[0003] The CZT crystal material has low hardness and high plasticity, is different from hard and brittle functional crystal materials such as monocrystalline silicon and sapphire, and is a typical soft and brittle functional crystal material. After the traditional suspended abrasive material grinding and polishing method is used to grind the hard and brittle material, the roughness Ra can reach 23 nm, while the roughness Ra of the soft and brittle material can only reach 268 nm, and there is still deep subsurface damage after polishing. Therefore, for the soft and brittle material such as CZT, at present, a multiple process of physical grinding-rotary mechanical polishing-chemical etching is mainly used in China. Although the CZT wafer processed by the process can also reach a relatively low roughness, the quality is unstable, and subsurface damage caused by the combination of two-body wear and three-body wear due to the embedding of hard particles such as impurities is still prone to occur. Even some laboratories still use manual polishing, and manual processing has the disadvantages of low efficiency, poor repeatability and low processing precision. The high-precision processing technology of the CZT wafer is a key technology for producing and detecting nuclear radiation detectors and manufacturing substrates. SUMMARY

[0004] Based on the requirements of surface flatness and low damage of the surface layer in current industrial and scientific research applications, a surface polishing process method for a CdZnTe wafer is provided. The CdZnTe wafer is subjected to surface treatment, is ground by using sandpaper in sequence, is subjected to mechanical vibration polishing by using Al2O3 polishing powder, and finally is subjected to vibration and chemical etching polishing by using a silicic acid solution.

[0005] The application aims to provide a horizontal vibration polishing process, which maximizes the time of sample contact with polishing cloth, avoids the binary and ternary friction damage of hard particles caused by long distance sliding to the surface of a CZT wafer, and obtains a wafer with high flatness and smoothness and low subsurface damage, which can be used for further processing etching or high-end characterization research.

[0006] The application discloses a low-damage surface polishing process of a soft and brittle material cadmium zinc telluride wafer.

[0007] The polishing liquid used in the horizontal vibration polishing is composed of alumina polishing powder with a particle size of 40-65 nm and deionized water in a volume ratio of 1:15-25.

[0008] The polishing liquid used in the horizontal vibration chemical polishing is a silicic acid solution with a silicic acid concentration of 3-8 wt%.

[0009] The application discloses a low-damage surface polishing process of a soft and brittle material cadmium zinc telluride wafer.

[0010] The application discloses a low-damage surface polishing process of a soft and brittle material cadmium zinc telluride wafer.

[0011] The application discloses a low-damage surface polishing process of a soft and brittle material cadmium zinc telluride wafer.

[0012] The application discloses a low-damage surface polishing process method for soft and brittle material cadmium zinc telluride wafers.

[0013] The application discloses a low-damage surface polishing process method for soft and brittle material cadmium zinc telluride wafers.

[0014] The application discloses a low-damage surface polishing process method for soft and brittle material cadmium zinc telluride wafers.

[0015] In the test process, it is found that if high-frequency short-time horizontal polishing and / or horizontal vibration chemical polishing are adopted within the technical scheme of the application, the surface roughness of the product will increase.

[0016] The cadmium zinc telluride wafer after the horizontal vibration chemical polishing treatment is cleaned by deionized water and anhydrous ethanol for 3-10 minutes, taken out and dried by high-pressure nitrogen, so that the CZT wafer with a mirror polishing effect of a smooth and bright surface can be obtained.

[0017] The surface roughness of the product obtained by the application is 7.9-9.65 nm; and after optimization, the surface roughness can be 7.9-7.92 nm.

[0018] Principle and advantage

[0019] The application firstly proposes the process of horizontal vibration polishing + horizontal vibration chemical polishing for processing the CZT wafer, and the principle is that through the high-frequency horizontal friction between the sample and the polishing cloth, the physical abrasive is firstly adopted to wear the damage layer on the wafer surface to the greatest extent, and then through the composite mode of chemical corrosion and vibration friction, the wafer surface is further flattened, so that the highly flat and low-damage surface is obtained.

[0020] The advantages are that it does not require frequent replacement of polishing slurry; high-frequency horizontal vibration maximizes the sample's contact time with the polishing cloth while avoiding secondary damage to the CZT wafer surface caused by hard particles sliding over long distances, resulting in less subsurface damage; no wafer fixing device is required, simplifying the loading and unloading process, and each wafer can be loaded and unloaded at any time during polishing, ensuring the continuity of the polishing process and maximizing the utilization efficiency of the grinding disc; the pressure can be adjusted by using different counterweights on the clamps, and this invention also provides the necessary conditions for industrial production. Furthermore, the surface roughness of the product obtained by this invention, after optimization, can reach 7.9-7.92 nm, far superior to existing technologies. Attached Figure Description

[0021] Appendix Figure 1 The AFM diagram of the product obtained in Example 1;

[0022] Appendix Figure 2 Here is a SEM image of the product obtained in Example 1;

[0023] Appendix Figure 3 The AFM diagram of the product obtained in Example 2;

[0024] Appendix Figure 4 SEM image of the product obtained in Example 2;

[0025] Appendix Figure 5 AFM diagram of the product obtained in Comparative Example 1;

[0026] Appendix Figure 6 Here is the SEM image of the product obtained in Comparative Example 1;

[0027] Appendix Figure 7 AFM diagram of the product obtained in Comparative Example 2;

[0028] Appendix Figure 8 The image shown is a SEM image of the product obtained in Comparative Example 2. Detailed Implementation

[0029] The present invention will be further illustrated below with specific examples. However, the preferred embodiments provided are merely illustrative and do not limit the scope of the invention in any way. Any modifications and variations that can be easily implemented by those skilled in the art are included within the scope of the present invention and the appended claims. The polishing equipment used in the following examples is the Vibromet2 vibratory polisher manufactured by Buehler, Inc., USA.

[0030] Example 1:

[0031] (1) Mechanical grinding: first, the wafer after slicing, wafer thickness of 1 mm, length and width of 10 mm, in the grinding machine grinding disc near the edge, in turn using 1000 mesh grinding: grinding machine speed of 20 rpm / min, time for 2 min, after the wafer surface stripe direction is consistent, rotate 90° repeat the above steps; ensure that the wafer surface only one direction grinding mark, then use 3000 mesh grinding disc, repeat the above steps. After the wafer surface only one direction of grinding mark, washed with deionized water or anhydrous ethanol and dried with high pressure nitrogen.

[0032] (2) Inlay sample: in order to install the special fixture of vibration polishing, using hot / cold inlay material to inlay CZT wafer into a sample block with a diameter of about 25 mm, the height of the sample block is 25 mm.

[0033] (3) Install the fixture: first, turn the fixture over, unscrew the fixing screw on the side, then put the sample block into the fixture from the bottom, and keep the wafer surface on the outside of the fixture, screw the fixing screw into the side of the fixture, and then turn another circle when you meet resistance.

[0034] (4) Vibration polishing: mix alumina polishing powder with a particle size of 50 nm and deionized water in a volume ratio of about 1:20 to prepare alumina polishing solution, and stir until use. Install the polishing cloth to the vibration polisher No. 1, pour the prepared polishing solution onto the grinding disc of the polisher until the polishing solution is evenly distributed on the entire grinding disc. Place the sample block on the grinding disc for horizontal vibration polishing, set the vibration frequency to 2100 Hz, and the time to 4 hours.

[0035] (5) Vibration chemical polishing: after vibration polishing, clean the surface of the CZT wafer with deionized water or anhydrous ethanol and dry it with high pressure nitrogen. Install another new polishing cloth to the vibration polisher No. 2, pour 5% silicic acid solution onto it until it covers the entire grinding disc. Place the sample block on the grinding disc for horizontal vibration chemical polishing, set the vibration frequency to 2100 Hz, and the time to 4 hours.

[0036] (6) Cleaning: clean the treated CZT wafer with deionized water and anhydrous ethanol for 5 minutes each, then take it out and dry it with high pressure nitrogen. The CZT wafer with smooth and bright surface can be obtained.

[0037] Detection:

[0038] The CZT wafer prepared in this example was used as a sample for experimental testing. Using a scanning electron microscope and an atomic force microscope, the CZT wafer prepared in this example was observed under SEM at a magnification of 500 times at room temperature. The wafer surface was smooth and had no obvious scratches. The wafer surface roughness was measured by AFM to be 7.91 nm.

[0039] Example 2

[0040] The process is the same, the vibration frequency is changed to 3600 Hz, and the time is 2 hours each time. The surface is observed under SEM at 500 times magnification. The surface is flat, and the surface roughness measured by AFM is 9.62 nm.

[0041] Comparative Example 1

[0042] Only the first step of vibration polishing is performed. The surface is observed under SEM at 500 times magnification. There are many pits on the surface, and the surface roughness measured by AFM is 22.0 nm.

[0043] Comparative Example 2

[0044] Only the second step of chemical vibration polishing is performed. The surface is observed under SEM at 500 times magnification. The surface is relatively flat, but there are still a small number of deep scratches. The surface roughness measured by AFM is 14.2 nm.

Claims

1. A low damage surface polishing process method for soft brittle material CdZnTe wafer; characterized in that: The teledium zinc cadmium wafer to be polished is fixed and then subjected to horizontal vibration polishing; then horizontal vibration chemical polishing is performed; during vibration polishing, a suede polishing cloth is installed on a vibration polisher No. 1, and a polishing liquid is poured into the polishing disc of the polisher until the polishing liquid is uniformly distributed on the entire polishing disc; the sample block is placed on the polishing disc to perform horizontal vibration polishing, and the frequency of the horizontal vibration polishing is set to 2000-3600 Hz, and the time is 4-6 hours; during vibration chemical polishing, after the horizontal vibration polishing is completed, the surface of the CZT wafer is cleaned with deionized water or anhydrous ethanol, and then high-pressure nitrogen is used for drying, and then horizontal vibration chemical polishing is performed; another new suede polishing cloth is installed on a vibration polisher No. 2, and a silicic acid solution with a silicic acid concentration of 3-8 wt% is poured until the entire polishing disc is covered; the sample block is placed on the polishing disc to perform horizontal vibration chemical polishing, and the vibration frequency is set to 2000-3600 Hz, and the time is 4-6 hours. The polishing liquid used during horizontal vibration polishing is composed of alumina polishing powder with a particle size of 40-65 nm and deionized water in a volume ratio of 1:15-25. The surface roughness of the obtained product is 7.9-9.65 nm.

2. The process of claim 1, wherein the soft and brittle material is CdZnTe wafer; and wherein the process further comprises: The polished teledium zinc cadmium wafer is prepared by the following arrangement: first, the wafer after slicing, with a wafer thickness of 1-3 mm and a length and width of 5-15 mm, is ground on the polishing disc of a grinder near the edge, and 1000 mesh is used for grinding in sequence: the grinding machine speed is 20-50 rpm / min, and the time is 1-2 min; after the surface stripe direction of the wafer is consistent, the above steps are repeated after rotating 90°; after ensuring that the wafer surface has only one direction of grinding marks, a 3000 mesh polishing disc is used, and the above steps are repeated; after the wafer surface has only one direction of grinding marks, the wafer is cleaned with deionized water or anhydrous ethanol and dried with high-pressure nitrogen. ​ 3. The process of claim 2, wherein the process is characterized in that: The teledium zinc cadmium wafer to be polished is fixed and then subjected to horizontal vibration polishing; then horizontal vibration chemical polishing is performed; during vibration polishing, a suede polishing cloth is installed on a vibration polisher No. 1, and a polishing liquid is poured into the polishing disc of the polisher until the polishing liquid is uniformly distributed on the entire polishing disc; the sample block is placed on the polishing disc to perform horizontal vibration polishing, and the frequency of the horizontal vibration polishing is set to 2000-3600 Hz, and the time is 4-6 hours; during vibration chemical polishing, after the horizontal vibration polishing is completed, the surface of the CZT wafer is cleaned with deionized water or anhydrous ethanol, and then high-pressure nitrogen is used for drying, and then horizontal vibration chemical polishing is performed; another new suede polishing cloth is installed on a vibration polisher No. 2, and a silicic acid solution with a silicic acid concentration of 3-8 wt% is poured until the entire polishing disc is covered; the sample block is placed on the polishing disc to perform horizontal vibration chemical polishing, and the vibration frequency is set to 2000-3600 Hz, and the time is 4-6 hours.

4. The process of claim 1, wherein the soft and brittle material is CdZnTe wafer; and wherein the process further comprises: The polishing liquid used during horizontal vibration polishing is composed of alumina polishing powder with a particle size of 40-65 nm and deionized water in a volume ratio of 1:15-25. ​ 5. The process of claim 1, wherein the soft and brittle material is CdZnTe wafer; and wherein the process further comprises: The surface roughness of the obtained product is 7.9-9.65 nm. ​ 6. The process of claim 1, wherein the soft and brittle material is CdZnTe wafer; and wherein the process further comprises: The polished teledium zinc cadmium wafer is prepared by the following arrangement: first, the wafer after slicing, with a wafer thickness of 1-3 mm and a length and width of 5-15 mm, is ground on the polishing disc of a grinder near the edge, and 1000 mesh is used for grinding in sequence: the grinding machine speed is 20-50 rpm / min, and the time is 1-2 min; after the surface stripe direction of the wafer is consistent, the above steps are repeated after rotating 90°; after ensuring that the wafer surface has only one direction of grinding marks, a 3000 mesh polishing disc is used, and the above steps are repeated; after the wafer surface has only one direction of grinding marks, the wafer is cleaned with deionized water or anhydrous ethanol and dried with high-pressure nitrogen. ​ 7. The process of claim 6, wherein the process is characterized in that: The teledium zinc cadmium wafer to be polished is fixed and then subjected to horizontal vibration polishing; then horizontal vibration chemical polishing is performed; during vibration polishing, a suede polishing cloth is installed on a vibration polisher No. 1, and a polishing liquid is poured into the polishing disc of the polisher until the polishing liquid is uniformly distributed on the entire polishing disc; the sample block is placed on the polishing disc to perform horizontal vibration polishing, and the frequency of the horizontal vibration polishing is set to 2000-3600 Hz, and the time is 4-6 hours; during vibration chemical polishing, after the horizontal vibration polishing is completed, the surface of the CZT wafer is cleaned with deionized water or anhydrous ethanol, and then high-pressure nitrogen is used for drying, and then horizontal vibration chemical polishing is performed; another new suede polishing cloth is installed on a vibration polisher No. 2, and a silicic acid solution with a silicic acid concentration of 3-8 wt% is poured until the entire polishing disc is covered; the sample block is placed on the polishing disc to perform horizontal vibration chemical polishing, and the vibration frequency is set to 2000-3600 Hz, and the time is 4-6 hours.

8. The process of claim 7, wherein the process is characterized in that: The polishing liquid used during horizontal vibration polishing is composed of alumina polishing powder with a particle size of 40-65 nm and deionized water in a volume ratio of 1:15-25. The surface roughness of the obtained product is 7.9-9.65 nm.

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