Liquid phase epitaxy method of HgCdTe material based on patterned sapphire substrate

Abstract

The present invention belongs to the field of infrared detector manufacturing technology and specifically provides a method for liquid phase epitaxy of HgCdTe material based on a patterned sapphire substrate. The method comprises: providing a sapphire substrate having a polished surface on one side and a nanoimprinted surface on the other, the nanoimprinted surface being imprinted with a regular hexagonal pyramid convex lattice structure; growing a CdZnTe transition layer on the surface of the regular hexagonal pyramid convex lattice structure using metal organic chemical vapor deposition (MOCVD); performing in-situ annealing after growth, and then placing the substrate in a liquid phase epitaxy system for liquid phase epitaxy of HgCdTe material on the CdZnTe transition layer. The sapphire substrate has high strength and will not crack during device fabrication or when subjected to high and low temperature shock during device operation. This method can reduce the defect density of the epitaxial material, improve material uniformity, and enable the production of large-area HgCdTe epitaxial materials, thereby meeting the requirements of third-generation infrared focal plane arrays for low-cost, large-area detectors.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared detector manufacturing and relates to a liquid phase epitaxy method of mercury cadmium telluride material based on a patterned sapphire substrate. Background Art

[0002] Mercury cadmium telluride (HgCdTe) infrared detectors, due to their high sensitivity, wide-band response, and fast response time, have important applications in industrial testing, environmental monitoring, medical and biological research, spectral analysis, astronomical observation, and other fields. They are particularly prominent in the military and aerospace sectors. With technological advancements, their application range will further expand.

[0003] The preparation methods for mercury cadmium telluride (HgCdTe) infrared detector materials have undergone several stages of development, primarily including bulk growth, liquid phase epitaxy (LPE), molecular beam epitaxy (MBE), and metal-organic chemical vapor deposition (MOCVD). Early methods primarily employed bulk growth, using the Bridgman method or vertical gradient solidification, offered advantages such as high material uniformity and low cost, but struggled to achieve uniform growth over large areas and exhibited high defect densities. Molecular beam epitaxy, which emerged in the 1980s, enabled atomic-level control of composition and thickness, making it suitable for the fabrication of superlattice and quantum well structures. However, this approach was associated with high equipment costs and slow growth rates. Metal-organic chemical vapor deposition, which gradually developed after the 1990s, offers advantages such as uniform growth over large areas and high growth rates, making it suitable for industrial production. However, it suffers from low material purity and complex processes. In the 1960s and 1970s, LPE, due to its inherent advantages, occupied a prominent position in the preparation of HgCdTe materials. The LPE growth process involves saturating the constituent elements of HgCdTe in the liquid phase at a certain temperature, then growing the HgCdTe thin film layer by layer on the substrate surface. This technique offers significant advantages, including precise control of the chemical composition of the HgCdTe material, enabling precise regulation of the bandgap, which is crucial for the performance of infrared detectors. Furthermore, the HgCdTe crystals grown using LPE are of high quality and have a relatively low defect density, which enabled infrared detectors fabricated using LPE to exhibit superior detection performance at the time.

[0004] In general, the development of HgCdTe infrared detector material preparation methods is a process of continuous pursuit of higher performance, lower cost and easier large-scale production.

[0005] The development of liquid-phase epitaxy (LPE) substrate technology for mercury cadmium telluride (HgCdTe) has undergone decades of evolution. Early substrates used CdTe single crystals, but their poor lattice matching with HgCdTe resulted in a high dislocation density in the epitaxial layer, limiting infrared detector performance. CdZnTe (cadmium zinc telluride) substrates, by adjusting the Zn content to achieve lattice matching with HgCdTe, significantly reduced the defect density and became the mainstream choice. However, CdZnTe substrates have inherent drawbacks, such as high single crystal growth costs, low mechanical strength, brittleness, and difficulty exceeding 100mm in maximum size, which severely hinder large-scale production.

[0006] Current improvements focus on alternative substrates and process optimization: 1) Developing low-cost substrates such as Si and GaAs, and using buffer layer technologies such as CdTe / ZnTe multilayer structures to mitigate lattice mismatch, although interface defects still need to be suppressed; 2) Using flexible substrates such as graphene to improve thermal compatibility; and 3) Combining molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD) to achieve heteroepitaxial growth, thus overcoming the substrate size limitations of traditional LPE. Future breakthroughs are needed to reduce defect density, improve substrate uniformity, and achieve 200mm wafer compatibility to meet the demand for low-cost, large-area detectors in third-generation infrared focal plane arrays. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a liquid phase epitaxial growth method of mercury cadmium telluride material based on a patterned sapphire substrate, comprising the following steps:

[0008] A sapphire substrate is provided, one side of which is a polished surface and the other side of which is a nanoimprinted surface. A regular hexagonal pyramid convex lattice structure is imprinted on the nanoimprinted surface. The sapphire substrate is a nanoimprinted patterned sapphire (Al2O3) substrate, the sapphire substrate is an R-plane (1102) oriented substrate, the diameter of the sapphire is 2-10 inches, and the thickness of the sapphire substrate is 0.3-2.0 mm excluding the height of the patterned regular hexagonal pyramid convex lattice structure. The height of the regular hexagonal pyramid convex lattice structure is 150 nm-350 nm, and the length of a single base side is 35 nm-50 nm.

[0009] A cadmium zinc telluride transition layer is grown on the surface of a regular hexagonal pyramid convex lattice structure using a metal organic chemical vapor deposition system. The growth temperature is controlled between 350-420°C, and the temperature uniformity is controlled within ±0.6°C. The organic gas sources use dimethyl cadmium, dimethyl zinc, and dimethyl telluride gases, and the carrier gas is nitrogen with a purity of ≥99.99999%. The flow ratio of each gas source is controlled by a mass flow meter, and the component control of the mass flow meter controller is ±0.9%. The purity of the metal organic compound gas source for growing the cadmium zinc telluride transition layer is ≥99.9999%.

[0010] In a metal organic chemical vapor deposition system, a low pressure mode with a vacuum degree of 50-200 Torr is adopted in the reaction chamber to control the growth rate of the cadmium zinc telluride transition layer to 1-2 μm / h.

[0011] After the CdZnTe transition layer is grown, the in-situ annealing step is to increase the temperature by 80°C based on the growth temperature, hold it for 2 hours, and then cool it down to room temperature at a rate of 2-4°C / min. This completes the growth of the CdZnTe transition layer.

[0012] A sapphire substrate with a cadmium zinc telluride transition layer is placed in a mercury cadmium telluride liquid phase epitaxy system.

[0013] The liquid phase epitaxy system uses an independent three-temperature zone sliding graphite boat growth furnace. The three temperature zones include melting zone, growth zone and cooling zone. The temperature control accuracy of the three temperature zones is within ±0.6°C; the melting zone temperature is set between 550-580°C, the growth zone temperature is set between 480-530°C, and the cooling zone temperature is set between 350-430°C.

[0014] HgCdTe material liquid phase epitaxial layer 1-x Cd x The Te component is x = 0.3-0.4 ± 0.02, which is suitable for infrared detectors with a cutoff wavelength between 3 and 5 microns. Sapphire has high transmittance in this wavelength range. The purity of Hg, Cd, and Te elements is ≥ 99.99999%. The aforementioned HgCdTe material is a mercury-cadmium-telluride alloy synthesized in a vacuum quartz tube with a Te:(Hg+Cd) ratio of 1.08-1.12, ensuring that the Te liquid phase serves as the solvent during the growth of the liquid phase epitaxial layer of the HgCdTe material.

[0015] First, the liquid phase epitaxial system with three temperature zones was evacuated to 10 -6 After 10000 ft (10000 ft) of 10000 ft (12000 ft) of 10000 ft (24 ...

[0016] The temperature was then raised to 350°C at a rate of 5°C / min, and after in-situ annealing at 350°C for 5 hours, the temperature was then lowered to room temperature at a rate of 5°C / min.

[0017] The HgCdTe liquid phase epitaxial growth is completed, and the material with the HgCdTe epitaxial layer is taken out from the liquid phase epitaxial system.

[0018] The technical solution of the present invention has the following advantages over the prior art:

[0019] This invention proposes a liquid-phase epitaxy method for HgCdTe materials based on patterned sapphire substrates. Using nanoimprint technology to create a large-area hexagonal pyramidal patterned sapphire substrate, the problem of dislocation defects penetrating the surface of the growing material is minimized. Sapphire's high strength eliminates the need for substrate thinning during device fabrication, as sapphire has high infrared transmittance between 1 and 5 microns. Furthermore, the sapphire substrate's high mechanical strength prevents cracking under high and low temperature impacts. Furthermore, the use of sapphire substrates offers a certain degree of radiation resistance in aerospace applications.

[0020] The method provided by the present invention grows cadmium zinc telluride material in a metal organic chemical vapor deposition (MOCVD) system. Compared with the previous growth of the above material in a molecular beam epitaxy (MBE) system, the MOCVD system heating method is conducive to heating the sapphire substrate. At the same time, the MOCVD system material growth method is also conducive to the lateral growth of the material on the hexagonal pyramid patterned substrate.

[0021] Since a CdZnTe transition layer and a HgCdTe liquid phase epitaxial layer are grown in sequence on a sapphire substrate and in-situ annealing is performed, the defect density of the HgCdTe epitaxial layer is significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 This is a schematic diagram of the layered structure of epitaxial material of a detector according to an embodiment of the present invention.

[0024] Figure 2 The present invention is a flowchart of a method for liquid phase epitaxy of HgCdTe material based on a patterned sapphire substrate according to an embodiment of the present invention.

[0025] Explanation of the accompanying symbols: 1. Sapphire substrate with a regular hexagonal pyramid convex lattice structure prepared by nanoimprint technology; 2. Cadmium zinc telluride transition layer; 3. Mercury cadmium telluride liquid phase epitaxial layer. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0027] In the present invention, unless otherwise defined, technical and scientific terms used herein have the same meanings as commonly understood by one skilled in the art to which the present invention belongs.

[0028] In the present invention, unless otherwise stated, the experimental methods used in the examples of the present invention are conventional methods unless otherwise stated, and the materials, gases, etc. used are all commercially available unless otherwise stated.

[0029] The embodiment of the present application provides a liquid phase epitaxy method of mercury cadmium telluride material based on a patterned sapphire substrate, which can prepare a reference Figure 1 The detector epitaxial material layered structure is shown.

[0030] Please refer to Figure 2 As shown, the above method provided in this embodiment includes steps S1 to S9.

[0031] S1: providing a sapphire substrate having a polished surface on one side and a nanoimprinted surface on the other side, wherein a regular hexagonal pyramid convex lattice structure is imprinted on the nanoimprinted surface.

[0032] The sapphire substrate is a nanoimprint patterned sapphire (Al2O3) substrate with an R-plane (1102) orientation. The height of the regular hexagonal pyramidal lattice structure is 300 nm, and the length of a single base is 40 nm. The sapphire diameter is 4 inches, and the thickness of the sapphire substrate, excluding the height of the patterned regular hexagonal pyramidal lattice structure, is 1.0 mm.

[0033] S2: A cadmium zinc telluride transition layer is grown on the surface of the regular hexagonal pyramid convex lattice structure using a metal organic chemical vapor deposition system.

[0034] In the metal-organic chemical vapor deposition system, the growth temperature was controlled at 390°C, with a temperature uniformity of ±0.6°C. The organic gas sources used dimethylcadmium, dimethylzinc, and dimethyltellurium, and the carrier gas was nitrogen with a purity of ≥99.99999%. The flow ratio of each gas source was controlled by a mass flow meter, and the mass flow meter controller controlled the composition to ±0.9%. The purity of the metal-organic compound gas sources used in the CdZnTe growth was ≥99.999%. A low-pressure vacuum of 100 Torr was used in the reaction chamber of the metal-organic chemical vapor deposition system, and the growth rate of the CdZnTe transition layer was controlled to 1.5 μm / h.

[0035] S3: In-situ annealing is performed after the CdZnTe transition layer growth is completed.

[0036] After the CdZnTe transition layer is grown, in-situ annealing is performed in a metal organic chemical vapor deposition system. The temperature is increased by 80°C above the growth temperature, held for 2 hours, and then cooled to room temperature at a rate of 3°C / min. This completes the CdZnTe transition layer growth.

[0037] S4: placing the sapphire substrate with the CdZnTe transition layer obtained after annealing in a HgCdTe liquid phase epitaxy system.

[0038] S5: Setting the temperatures of the three temperature zones of the HgCdTe liquid phase epitaxy system.

[0039] The HgCdTe liquid phase epitaxy system utilizes an independent three-zone sliding graphite boat growth furnace. The three zones consist of a melting zone, a growth zone, and a cooling zone. All three zones are controlled to an accuracy of ±0.6°C. The melting zone is set at 560±0.6°C, the growth zone at 490±0.6°C, and the cooling zone at 360±0.6°C.

[0040] S6: Component configuration and solvent selection for HgCdTe materials.

[0041] HgCdTe material liquid phase epitaxial layer 1-x Cd x The composition of Te is x=0.35±0.02, and the purity of Hg, Cd, and Te elements is ≥99.99999%. The above-mentioned mercury cadmium telluride material is a mercury cadmium telluride alloy synthesized in a vacuum quartz tube with a ratio of Te:(Hg+Cd)=1.1, ensuring that the Te liquid phase is used as a solvent during the growth of the liquid phase epitaxial layer of the above-mentioned mercury cadmium telluride material.

[0042] S7: Evacuate the liquid phase epitaxial system with three temperature zones to 10 -6 After 3000 Torr, nitrogen with a purity of ≥99.99999% is filled as a protective gas, and the substrate with the cadmium zinc telluride transition layer is placed in the growth area of ​​the liquid phase epitaxy system. After reaching the required growth temperature, the mercury cadmium telluride epitaxial material is grown until the required thickness is reached.

[0043] The growth process of the HgCdTe epitaxial material is the growth process of the liquid phase epitaxial layer of the HgCdTe material.

[0044] Nitrogen was chosen as the shielding gas because it is safer than the commonly used hydrogen.

[0045] By adjusting the moving speed and temperature gradient of the substrate, the growth rate of the liquid phase epitaxial layer of the mercury cadmium telluride material is controlled to be 0.3 mm / h.

[0046] A liquid phase epitaxial layer of mercury cadmium telluride material is grown in a liquid phase epitaxial system to a thickness of 1 mm.

[0047] Step S8 is performed in the liquid phase epitaxy system to perform in-situ annealing.

[0048] S8: Cool down to 100°C±3°C at a rate of 5°C / min, then heat up to 350°C at a rate of 5°C / min, anneal in situ at 350°C for 5 hours, and then cool down to room temperature at a rate of 5°C / min.

[0049] S9: The HgCdTe liquid phase epitaxial growth is completed, and the material with the HgCdTe epitaxial layer is removed from the liquid phase epitaxial system.

[0050] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A liquid phase epitaxial growth method of mercury cadmium telluride material based on a patterned sapphire substrate, characterized in that: The following steps are involved: A sapphire substrate having a polished surface on one side and a nanoimprinted surface on the other side is provided, wherein a regular hexagonal pyramid convex lattice structure is imprinted on the nanoimprinted surface; a cadmium zinc telluride transition layer is grown on the surface of the regular hexagonal pyramid convex lattice structure using a metal organic chemical vapor deposition technique, and an in-situ annealing is performed after the growth is completed. After the annealing, the following steps are performed: first, a liquid phase epitaxial system with three temperature zones is evacuated to 10 -6 Torr, then fill with nitrogen with a purity of ≥99.99999% as a protective gas, place the substrate with the cadmium zinc telluride transition layer in the growth area of ​​the liquid phase epitaxy system, grow the mercury cadmium telluride epitaxial material after reaching the required growth temperature, cool down to 100℃±3℃ at a rate of 5℃ / min after reaching the required thickness, then increase the temperature to 350℃ at a rate of 5℃ / min, anneal in situ at 350℃ for 5 hours, and then cool down to room temperature at a rate of 5℃ / min.

2. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1, characterized in that: The sapphire substrate is a nano-imprint patterned sapphire substrate, the sapphire substrate is an R-plane (1102) direction substrate, the height of the regular hexagonal pyramid convex lattice structure is 150nm-350nm, and the length of a single bottom side is 35nm-50nm.

3. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1, characterized in that: The cadmium zinc telluride transition layer is grown using a metal organic chemical vapor deposition system, with the growth temperature controlled between 350-420°C and the temperature uniformity controlled within ±0.6°C. The organic gas sources use dimethyl cadmium, dimethyl zinc, and dimethyl telluride gases, and the carrier gas is high-purity nitrogen. The flow ratio of each gas source is controlled by a mass flow meter, and the component control of the mass flow meter controller is ±0.9%.

4. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 3, characterized in that: The purity of the organic gas source is ≥99.999%, and the purity of the high-purity nitrogen is ≥99.99999%.

5. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1 or claim 3, characterized in that: A low pressure mode of 50-200 Torr is adopted in the reaction chamber to control the growth rate of the CdZnTe transition layer to 1-2 μm / h.

6. The method for liquid phase epitaxy of HgCdTe material based on a patterned sapphire substrate according to claim 1 or claim 3, characterized in that: The in-situ annealing after the CdZnTe transition layer is grown is to increase the growth temperature by 80°C, maintain it for 2 hours, and then cool it down to room temperature at a rate of 2-4°C / min.

7. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1, characterized in that: The liquid phase epitaxy system adopts an independent three-temperature zone sliding graphite boat growth furnace, the three temperature zones include a melting zone, a growth zone and a cooling zone, and the temperature control accuracy of the three temperature zones is within ±0.6°C.

8. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 7, characterized in that: The temperature of the melting zone is set between 550-580°C, the temperature of the growth zone is set between 480-530°C, and the temperature of the cooling zone is set between 350-430°C.

9. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1, characterized in that: HgCdTe material liquid phase epitaxial layer 1-x Cd x The composition of Te is x=0.3-0.4±0.02, and the purity of Hg, Cd, and Te elements is ≥99.99999%. The mercury cadmium telluride material is a mercury cadmium telluride alloy synthesized in a vacuum quartz tube, with a ratio of Te:(Hg+Cd)=1.08-1.12, ensuring that the Te liquid phase is used as a solvent during the growth of the liquid phase epitaxial layer of the mercury cadmium telluride material.

10. The liquid phase epitaxy method of HgCdTe material based on a patterned sapphire substrate according to claim 1, characterized in that: By adjusting the moving speed and temperature gradient of the substrate, the growth rate of the liquid phase epitaxial layer of the mercury cadmium telluride material is controlled between 0.001-0.5 mm / h.

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