Substrate surface microstructure for efficiently depositing Hg and preparation method thereof

Abstract

The invention discloses a substrate surface microstructure for efficiently depositing Hg and a preparation method of the substrate surface microstructure, which are used for solving the problems of low Hg adhesion coefficient and non-uniform beam intensity in an MBE growth tellurium-cadmium-mercury nucleation stage so as to improve the quality of an epitaxial growth tellurium-cadmium-mercury material. The structure is a specially-distributed concentric nanometer circular ring groove structure, and the distances between the concentric circular ring grooves are different and are mainly determined according to beam intensity distribution on the surface of a substrate. The preparation method of the substrate surface microstructure mainly comprises the steps of substrate surface treatment, photoetching and dry etching, and finally the concentric nanometer circular ring groove type substrate surface microstructure is obtained.

Description

Technical Field

[0001] The invention relates to a substrate surface microstructure and a preparation method thereof, in particular to a preparation method of a concentric nano-ring microstructure, in which photolithography technology is utilized, and the method belongs to the technical field of surface microstructure preparation. Background Art

[0002] Mercury cadmium telluride material has many ideal properties, including low intrinsic carrier concentration, high electron mobility, long carrier lifetime, and large absorption coefficient. In addition, the bandgap width of mercury cadmium telluride material can change continuously with the composition to achieve coverage of the entire infrared band. Therefore, mercury cadmium telluride has become the most widely used third-generation focal plane detector material.

[0003] Commonly used substrate materials for epitaxial growth of HgCdTe materials include CdTe, GaAs, Ge, Si, etc. The selection of substrate is crucial for MBE epitaxial growth of HgCdTe. The structure, thermal expansion coefficient and chemical stability of the substrate material greatly affect the quality of epitaxially grown HgCdTe materials.

[0004] In the nucleation stage of MBE growth of HgCdTe, most of the Hg molecular flow cannot be effectively adsorbed on the substrate surface due to the low adhesion coefficient of Hg on the substrate surface, and the Hg beam intensity is unevenly distributed on the substrate surface, which will affect the growth quality of the HgCdTe epitaxial film. Usually, we use a high-density Hg molecular flow to prepare a HgCdTe epitaxial film that meets the requirements, but an overly high-density Hg molecular flow will cause more defects in the growth of HgCdTe, reducing the quality of the material. The present invention prepares a concentric nano-ring surface microstructure on the substrate, improves the adhesion coefficient of Hg on the substrate surface during the nucleation stage, and improves the problem of uneven beam intensity distribution, ultimately effectively improving the quality of MBE epitaxially grown HgCdTe materials. Summary of the invention

[0005] The present invention aims to provide a substrate surface microstructure for efficiently depositing Hg and a preparation method thereof, so as to improve the problem of low Hg adhesion coefficient in the nucleation stage of MBE growth of HgCdTe, thereby improving the quality of epitaxially grown HgCdTe materials.

[0006] The purpose of the present invention is, on the one hand, to provide a substrate with a concentric nano-ring microstructure, wherein the surface structure is a concentric nano-ring with a specific distribution, the rings are grooves of the same width, the depth of the grooves is much smaller than the thickness of the substrate, and the density distribution of the concentric ring grooves is sparse to dense from the inside to the outside. In order to improve the problem of uneven beam intensity, the surface microstructure presents a sparse and dense change to change the roughness of the substrate surface so as to balance the beam intensity distribution, and the density distribution of the concentric ring grooves is relatively sparse at locations with high beam intensity compared to locations with low intensity.

[0007] The present invention has the following characteristics: the depth of the concentric circular groove is 10-20 nm. The thickness of the general HgCdTe epitaxial film is about 5 μm, and the 10-20 nm only accounts for a few tenths of a percent, which has little effect on the growth of the epitaxial HgCdTe material. The width W of the concentric circular groove and the distance l between two adjacent circular rings along the radial direction of the edge are N It is artificially determined based on the size of the substrate, the lithography capability of the existing lithography equipment, the expected precision and the production cost. The concentric ring grooves have a specific distribution and arrangement, and their density D is determined according to the beam intensity I, and the relationship is: I×D=A (1) The beam intensity distribution relationship on the substrate surface can be expressed as I = I0 (cosθ) 4 , I0 is the beam intensity at the center of the substrate, and θ is the angle between the line from the center of the source furnace mouth to any point on the substrate surface and the line from the center of the source furnace mouth to the center of the substrate. Due to the uneven distribution of beam intensity, according to the compensation principle, the problem of uneven distribution of beam intensity is improved by increasing the surface roughness of the position with weaker beam intensity.

[0008] The relationship between the density distribution of the concentric nano-rings of the present invention and the distance from the position to the center of the circle is: make (k is a constant), then we have L is the distance from the center of the substrate to the source furnace mouth, and r is the distance from any point on the substrate surface to the center of the circle. Since I is objectively unevenly distributed, it is intuitively reflected in the relationship between I and θ. According to the trigonometric formula and the relationship between D and I, it is transformed into the relationship between D, L and r.

[0009] The relationship between the density distribution of the concentric nano-rings of the present invention and the distance from the position to the center of the circle can be further expressed as: Where r n is the outer diameter of the nth ring from the center of the circle, where n is the radius r n The number of rings in a circle, where n is an integer greater than 0. Assume r N If the radius of the substrate is equal to R, then the substrate surface microstructure has N concentric circular grooves, r N is the outer diameter of the largest ring. Assume r N -r N-1 =W+l N , from formula (4) we can get r N 、r N-1satisfy Where r N -r N-1 is the distance between the outer diameters of two adjacent circular rings along the radial direction from the edge, l N The distance between two adjacent rings. According to equation (3) and engineering requirements, the integral equation (4) model is established to transform the difficult-to-calculate relationship between I and θ into the relationship between L, r and n. To facilitate data calculation, the integral equation is further expressed as equation (5).

[0010] Another aspect of the present invention is to provide a method for preparing a substrate having the above structure, comprising the steps of:

[0011] Determine the material and size of the substrate and the distance L from the substrate to the source furnace port;

[0012] According to formula (2), the multiple relationship between the density of the concentric circular grooves at the center and the edge of the substrate is calculated, and W and l are determined in combination with the accuracy requirements of the structure. N ;

[0013] Then, the constant k is calculated according to formula (5), and then the outer diameters of all concentric circular grooves are calculated according to formula (4);

[0014] The mask plate is produced according to the data obtained in the above steps;

[0015] Substrate pretreatment including substrate degreasing, substrate wet chemical etching, deionized water cleaning, nitrogen drying and baking according to substrate material;

[0016] The photolithography process includes steps such as coating, pre-baking, alignment and exposure, post-baking, development and rinsing, hardening, dry etching, and degumming to obtain the concentric nano-ring surface microstructure.

[0017] The present invention has the following advantages:

[0018] The present invention proposes a novel substrate surface microstructure based on MBE growth of HgCdTe, which greatly increases the substrate specific surface area, improves the adhesion coefficient of Hg on the substrate surface during the nucleation stage, and improves the problem of uneven Hg beam intensity distribution, thereby achieving the purpose of improving the quality of epitaxially grown HgCdTe materials.

[0019] The present invention provides a substrate surface microstructure for efficiently depositing Hg and a preparation method thereof. The surface microstructure is universal and applicable to commonly used substrate materials for epitaxial growth of mercury cadmium telluride, such as CZT, CdTe, GaAs, Ge, Si, etc., and differs only in the substrate pretreatment process according to the selection of the substrate material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the concentric ring groove structure.

[0021] Figure 2 This is a cross-sectional diagram of the concentric ring groove structure.

[0022] Figure 3 Schematic diagram of beam and substrate

[0023] Figure 4 Schematic diagram of beam intensity distribution

[0024] Figure 5 This is a schematic diagram of the density of concentric ring grooves.

[0025] Explanation of the numbers in the figure: 1, concentric ring groove; 2, substrate; 3, center of the source furnace mouth; DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with specific implementation methods. This example is only used to illustrate the present invention and does not limit the scope of the present invention.

[0027] Embodiment 1

[0028] A substrate surface microstructure for efficiently depositing Hg and a preparation method thereof. The substrate material is cadmium zinc telluride, and the surface is a concentric ring groove type microstructure.

[0029] A 3-inch substrate is selected, and the center of the substrate is 100 mm away from the source furnace port. According to formula (2), the multiple of the density of the concentric circular grooves at the center of the substrate and the edge of the substrate is calculated to be 1.311393715921;

[0030] The depth of the concentric circular grooves is set to 20nm, the width is set to 90nm, and the spacing between two adjacent circular rings at the edge of the substrate is 60nm;

[0031] Substituting the known data into equation (5), the value of the constant k is calculated to be 5083.655076251571. Then according to equation (4), it is calculated that a total of 213247 concentric circular grooves need to be etched on the substrate surface, and the outer diameters of all the concentric circular grooves are calculated.

[0032] According to the above data, a mask plate that meets the requirements is made;

[0033] The preparation method of the cadmium zinc telluride substrate having a substrate surface microstructure is as follows:

[0034] The cut, ground and polished CdZnTe substrate was rinsed several times with acetone and ethanol solution to remove the oil stains on the surface;

[0035] The substrate was chemically etched with 0.01% bromine methanol solution for 45 seconds to convert cadmium ions and zinc ions into aqueous solution and simultaneously oxidized and reduced to generate tellurium;

[0036] Rinse twice with methanol solution, wash with deionized water, blow dry with nitrogen, and bake in an oven;

[0037] Use Shanghai Microelectronics' 600 series photolithography machine for photolithography exposure;

[0038] The baked substrate is dry-etched using ECR Ar / H2 plasma treatment;

[0039] The photoresist is removed by wet stripping and then cleaned with deionized water to obtain a cadmium zinc telluride substrate with a concentric nano-ring microstructure.

[0040] Embodiment 2

[0041] A substrate surface microstructure for efficiently depositing Hg and a preparation method thereof. The substrate material is Si, and the surface is a concentric ring groove type microstructure.

[0042] A 3-inch substrate is selected, and the center of the substrate is 120 mm away from the source furnace port. According to formula (2), the multiple of the density of the concentric circular grooves at the center of the substrate and the edge of the substrate is calculated to be 1.311393715921;

[0043] The depth of the concentric ring groove is 15nm, the specified width is 90nm, and the distance between two adjacent rings along the radial direction of the edge is 60nm;

[0044] Substituting the known data into equation (5), the value of the constant k is calculated to be 6107.174422759183. Then, according to equation (4), a total of 159817 concentric circular grooves need to be etched on the substrate surface, and the outer diameters of all the concentric circular grooves are calculated.

[0045] According to the above data, a mask plate that meets the requirements is made;

[0046] The preparation method of the Si substrate with substrate surface microstructure is as follows:

[0047] The Si substrate was cleaned using the RCA cleaning method, cleaned with deionized water, and dehydrated and baked at 200°C under nitrogen protection for 1 to 2 minutes;

[0048] Use Shanghai Microelectronics' 600 series photolithography machine for photolithography exposure;

[0049] The baked substrate is dry-etched using an RIE method;

[0050] The photoresist was removed by wet stripping and then washed with deionized water to obtain a Si substrate with a concentric nano-ring microstructure.

Claims

1. A substrate surface microstructure for improving Hg deposition efficiency, characterized in that: Its surface structure is concentric nano-circular grooves with a specific distribution, and the density distribution of the concentric circular grooves is from sparse to dense from the inside to the outside.

2. A substrate surface microstructure for improving Hg deposition efficiency according to claim 1, characterized in that: The depth of the concentric circular grooves is 10 to 20 nm.

3. A substrate surface microstructure for improving Hg deposition efficiency according to claim 1, characterized in that: The width of the concentric ring groove is W, l N is the distance between two adjacent rings, and W, l N These two values ​​are determined by a comprehensive consideration of the size of the substrate, the lithography capabilities of existing lithography equipment, the desired level of precision, and production costs.

4. A substrate surface microstructure for improving Hg deposition efficiency according to claim 1, characterized in that: The concentric annular grooves have a specific distribution and arrangement, and their density D and the beam intensity I on the substrate surface conform to the relationship: I×D=A (1) Where A is a constant. The beam intensity I on the substrate surface can be expressed as I = I0 (cosθ) 4 , I0 is the beam intensity at the center of the substrate, and θ is the angle between the line between the center of the source furnace mouth and any point on the substrate surface and the line between the center of the source furnace mouth and the center of the substrate.

5. A substrate surface microstructure for improving Hg deposition efficiency according to claim 1, characterized in that: The relationship between the density D of the concentric circular grooves and the distance r from the position to the center of the circle is: Where L is the distance from the center of the substrate to the source furnace mouth, r is the distance from any point on the substrate surface to the center of the substrate circle, let (k is a constant), then we have 6. The relationship between the density distribution D of the concentric annular grooves and the distance r from the position to the center of the circle according to claim 5 is characterized in that: The relationship can be further expressed as Where r n is the outer diameter of the nth ring from the center of the circle, where n is the radius r n The number of concentric nano-rings within the circle is n, and n is an integer greater than 0.

7. The integral relationship between the density distribution D of the concentric annular grooves and the distance r from the position to the center of the circle according to claim 6 is characterized in that: Assume r N If the radius of the substrate is equal to R, then the substrate surface microstructure has N concentric circular grooves, r N is the outer diameter of the largest ring. Assume r N -r N-1 =W+l N , from formula (4) we can get r N 、r N-1 satisfy Where r N -r N-1 It is the distance between the outer diameters of two adjacent circular rings along the radial direction from the edge.

8. A method for preparing a substrate surface structure for improving Hg deposition efficiency, characterized in that: include Follow these steps: (1) Determine the material and size of the substrate and the distance L from the substrate to the source furnace mouth; (2) According to formula (2), the multiple relationship between the density of the concentric circular grooves at the center and the edge of the substrate is calculated, and W and l are determined in combination with the required accuracy of the structure. N ; (3) Calculate the constant k according to equation (5), and then calculate the outer diameters of all concentric circular grooves according to equation (4); (4) Making a mask plate based on the data obtained above; (5) Pre-treating the substrate according to the substrate material; (6) Using the prepared mask plate, the concentric nano-ring surface microstructure is obtained by photolithography.

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