CN101381893A - CdGeAs2 crystal etching agent and etching method - Google Patents

Abstract

A kind of etchant for CdGeAs ₂ crystals, prepared by hydrochloric acid, nitric acid and pure water, the volume ratio of hydrochloric acid, nitric acid, pure water is hydrochloric acid: nitric acid: pure water=1: 1: 1, the mass concentration of described hydrochloric acid is 35 ~38%, the mass concentration of the nitric acid is 65~68%. A method for etching _CdGeAs2 crystals, using the above-mentioned etchant, the process steps are as follows: (1) etching, immersing the ground and polished _CdGeAs2 wafers in the etchant, under normal pressure, 15°C to 30°C under swinging Corrode for 15 seconds to 40 seconds and take it out; (2) Clean, immerse the CdGeAs ₂ wafer taken out of the etchant into an alkaline cleaning agent to terminate the corrosion reaction, and then clean it with pure water until neutral; (3) Dry, wash the CdGeAs 2 wafer CdGeAs ₂ wafers are naturally dried or baked under normal pressure.

Description

Etchant and Etching Method of CdGeAs2 Crystal

technical field

The invention belongs to the field of corrosion of ternary compound semiconductor materials, in particular to a _CdGeAs2 crystal etchant and corrosion method.

Background technique

Chalcopyrite crystal CdGeAs ₂ (CGA for short), which belongs to tetragonal structure, point group I42d, is a kind of infrared nonlinear optical material. The CdGeAs ₂ crystal thermal expansion coefficient differs by more than 15 times along the a-axis and c-axis, which makes it extremely difficult to grow a complete crystal without cracks, and the grown crystal has many defects. The occurrence and number of various defects are not only related to the crystal preparation process, but also have an important impact on the performance of the prepared device.

There are many methods for experimental observation of crystal defects, such as transmission electron microscope, scanning electron microscope, infrared microscope and metallographic corrosion display. Among them, the metallographic corrosion display method and the scanning electron microscope are one of the most commonly used methods for observing and studying crystal defects. They are not only simple in equipment and easy to operate, but also can display the crystallographic direction more intuitively. They are used in determining the crystal plane index and crystal orientation. Wide range of applications. Metallographic corrosion display can also reveal the number and distribution of defects, find out the relationship between defect formation, proliferation, crystal preparation process and device process, and provide clues for improving process, reducing defects, increasing device qualification rate and improving device performance.

The metallographic corrosion of CdGeAs ₂ crystal, especially the preferential corrosion is a technical problem. At present, the corrosion of CdGeAs ₂ crystals is only reported by the Robert S. Feigelson group of Stanford University in the United States. The etchant used is: HNO ₃ :HF:H ₂ O=1:1:2 (volume ratio), and the corrosion time is 10 minutes to 14 minutes. However, the pattern of the observed pits is not clear enough, and no regular-shaped three-dimensional pits can be seen. In addition, there is no report on the corrosion research of _CdGeAs2 crystals.

Contents of the invention

The object of the present invention is to overcome the deficiencies of the prior art, and provide a preferred etchant and etching method for _CdGeAs2 crystals, so as to perform preferential etching of _CdGeAs2 crystals and obtain the morphology of corrosion pits of the crystals.

The corrosive agent of _CdGeAs2 crystal of the present invention is formulated by hydrochloric acid, nitric acid and pure water, and the volume ratio of hydrochloric acid, nitric acid, pure water is hydrochloric acid: nitric acid: pure water=1:1:1, and the mass concentration of described hydrochloric acid is 35-38%, the mass concentration of the nitric acid is 65-68%.

The used pure water of above-mentioned corrosive agent is deionized water or distilled water.

The etching method of _CdGeAs2 crystal of the present invention uses above-mentioned etchant, and its process step is as follows successively:

(1) corrosion

Immerse the ground and polished CdGeAs ₂ wafer in the etchant, etch it under normal pressure at 15°C to 30°C for 15 seconds to 40 seconds and take it out;

(2) cleaning

Immerse the _CdGeAs2 wafer taken out of the etchant into an alkaline cleaning agent to terminate the corrosion reaction (for 5 seconds to 10 seconds), and then wash it with pure water until neutral;

(3) dry

The cleaned CdGeAs ₂ wafers are naturally dried or baked under normal pressure.

In the above method, the alkaline cleaning agent is a NaOH solution with a mass concentration of 5-10%, or a _NaCO solution with a mass concentration of 10-20%, or a KOH solution with a mass concentration of 5-10%. Pure water is deionized water or distilled water. If drying is adopted, the drying temperature is preferably 40°C-60°C, and the drying time is at least 2 hours.

The present invention has the following beneficial effects:

1. Experiments show that the etchant and etching method of the present invention have good preferential corrosion to _CdGeAs2 crystals, and the corroded _CdGeAs2 wafer can clearly show the corrosion pit shape of a certain crystal plane under a metallographic microscope. appearance.

2. The raw materials of the corrosive agent in the present invention are conventional chemical reagents, which are low in cost and easy to obtain.

3. The etching method of the present invention is carried out under normal pressure and room temperature, and the time is short and the operation is convenient.

4. Through the metallographic micrograph of the CdGeAs2 wafer corroded by the etching method of the present invention, _the dislocation density of the growing crystal can be calculated, which provides a simple and easy method for preliminary evaluation of _CdGeAs2 crystal quality and wafer screening .

Description of drawings

Fig. 1 is to use etchant and etching method of the present invention obtained CdGeAs _2Crystal (101) crystal plane's etch pit appearance figure;

Fig. 2 is the multilevel X-ray diffraction spectrum of _CdGeAs2 crystal (101) crystal plane;

Fig. 3 is to use etchant and etching method of the present invention obtained _{CdGeAs2Crystal} (312) crystal plane's etch pit appearance figure;

Fig. 4 is the X-ray diffraction spectrum of the (312) crystal plane of CdGeAs ₂ crystal.

Detailed ways

Example 1

In this embodiment, the etchant for the CdGeAs ₂ crystal is prepared from hydrochloric acid, nitric acid and deionized water, the mass concentration of the hydrochloric acid is 35-38%, and the mass concentration of the nitric acid is 65-68%. The volume ratio of hydrochloric acid, nitric acid, deionized water is hydrochloric acid: nitric acid: deionized water=1:1:1, measure hydrochloric acid, nitric acid and deionized water respectively by described volume ratio, then hydrochloric acid, nitric acid are added deionized water and Stir evenly to form a corrosive agent.

Example 2

In this embodiment, the (101) crystal plane of the CdGeAs ₂ crystal is etched, and the etchant used is the etchant prepared in Example 1, and the process steps are as follows:

(1) Grinding and polishing

The CdGeAs ₂ crystal (101) wafer is roughly ground and finely ground with 0#-02#-04#-06# metallographic sandpaper with an average particle size distribution of 50 μm to 5 μm, and then white corundum powder (average particle size 0.5 μm) and deionized water suspension (the mass ratio of white corundum powder to deionized water is 1:10) was mechanically polished on silk cloth for 20 minutes, and then rinsed with deionized water to obtain a _CdGeAs2 wafer with a flat surface Then place the mechanically polished wafer in a bromomethanol solution with a mass concentration of 3%, soak it at room temperature for about 1 minute to carry out chemical polishing, and clean it with methanol, acetone, ethanol and deionized water successively after taking it out;

(2) Corrosion

Immerse the ground and polished _CdGeAs2 crystal (101) wafer in the etchant, and take it out under normal pressure and 15°C for 40 seconds under swing;

(3) cleaning

Immerse the CdGeAs ₂ wafer taken out of the etchant in a NaOH solution with a mass concentration of 5% and shake it to stop the corrosion reaction for about 5 seconds, and then wash it with deionized water until it is neutral;

(4) dry

Put the cleaned CdGeAs ₂ wafer into an oven, and dry it at normal pressure and 40°C for 4 hours.

Observing the dried _CdGeAs2 wafer with a metallographic microscope, the appearance of the corrosion pits is shown in Figure 1. From Figure 1, it can be seen that the appearance of the etch pits is an isosceles triangle with consistent orientation, with clear boundaries and three-dimensional feel.

Example 3

In this embodiment, the etchant for the CdGeAs ₂ crystal is prepared from hydrochloric acid, nitric acid and distilled water, the mass concentration of the hydrochloric acid is 35-38%, and the mass concentration of the nitric acid is 65-68%. The volume ratio of hydrochloric acid, nitric acid, distilled water is hydrochloric acid: nitric acid: distilled water=1:1:1, measure hydrochloric acid, nitric acid and distilled water respectively by said volume ratio, then add hydrochloric acid, nitric acid to distilled water and stir to form corrosive agent.

Example 4

In this embodiment, the (312) crystal plane of CdGeAs ₂ crystal is etched, and the etchant used is the etchant prepared in Example 3, and the process steps are as follows:

(1) Grinding and polishing

The CdGeAs ₂ crystal (312) wafer is roughly ground and finely ground with 0#-02#-04#-06# metallographic sandpaper with an average particle size distribution of 50 μm to 5 μm, and then white corundum powder prepared with distilled water (average Particle size 0.5μm) suspension (mass ratio of white corundum powder and deionized water is 1:10) was mechanically polished on silk cloth for 20 minutes, and then rinsed with distilled water to obtain a CdGeAs ₂ wafer with a smooth surface; The polished wafer is placed in bromomethanol solution with a mass concentration of 3%, soaked at room temperature for about 1 minute for chemical polishing, and then cleaned with methanol, acetone, ethanol and distilled water in sequence after taking it out;

(2) Corrosion

Immerse the (312) wafer of the ground and polished _CdGeAs2 crystal in the etchant, and take it out under swinging at normal pressure and 30°C for 15 seconds;

(3) cleaning

Immerse the CdGeAs ₂ wafer taken out of the etchant in a NaCO ₃ solution with a mass concentration of 20% and shake it to stop the corrosion reaction for about 10 seconds, and then wash it with distilled water until it is neutral;

(4) dry

Put the cleaned CdGeAs ₂ wafer into an oven, and dry it under normal pressure at 60°C for 2 hours.

Observing the dried CdGeAs ₂ wafer with a metallographic microscope, the appearance of the corrosion pits is shown in Figure 3. From Figure 3, it can be seen that the etch pits are square with uniform orientation, with clear boundaries and a three-dimensional effect.

Claims (7)

1, a kind of etchant of _CdGeAs2 crystal, it is characterized in that being formulated by hydrochloric acid, nitric acid and pure water, the volume ratio of hydrochloric acid, nitric acid, pure water is hydrochloric acid: nitric acid: pure water=1:1:1, described hydrochloric acid The mass concentration of the nitric acid is 35-38%, and the mass concentration of the nitric acid is 65-68%. 2. The etchant for CdGeAs ₂ crystals according to claim 1, characterized in that the pure water is deionized water or distilled water. 3. A method for etching _CdGeAs2 crystals, characterized in that the process steps are as follows: (1) corrosion Immerse the ground and polished CdGeAs ₂ wafer in the etchant, etch it under normal pressure at 15°C to 30°C for 15 seconds to 40 seconds and take it out. (2) cleaning Immerse the _CdGeAs2 wafer taken out of the etchant into an alkaline cleaning agent to terminate the corrosion reaction, and then clean it with pure water until neutral; (3) dry The cleaned CdGeAs ₂ wafer is naturally dried or dried under normal pressure; Described corrosive agent is formulated by hydrochloric acid, nitric acid and pure water, and the volume ratio of hydrochloric acid, nitric acid, pure water is hydrochloric acid: nitric acid: pure water=1:1:1, and the mass concentration of described hydrochloric acid is 35～38%, so The mass concentration of said nitric acid is 65～68%. 4. The method for etching CdGeAs ₂ crystals according to claim 3, characterized in that the alkaline cleaning agent is NaOH solution with a mass concentration of 5-10% or NaCO ₃ solution with a mass concentration of 10-20% or a mass concentration of 5-10% % KOH solution. 5. The method for etching CdGeAs ₂ crystals according to claim 3 or 4, characterized in that the pure water is deionized water or distilled water. 6. The method for etching _CdGeAs2 crystals according to claim 3 or 4, characterized in that the drying temperature in the drying step is 40°C-60°C, and the drying time is at least 2 hours. 7. The method for etching _CdGeAs2 crystals according to claim 5, characterized in that the drying temperature in the drying step is 40°C-60°C, and the drying time is at least 2 hours.

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