A method for controlling surface temperature of mercury cadmium telluride epitaxy by molecular beam epitaxy

Abstract

This application discloses a method for controlling the surface temperature of HgCdTe epitaxy using molecular beam epitaxy, comprising: fixing a substrate; controlling the epitaxial surface temperature using a thermocouple, growing HgCdTe material on the substrate using a temperature-compensated growth method, and performing As doping; determining the variation in As doping concentration at different depths during the growth of the HgCdTe material; predicting the degree to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at corresponding depths; and, based on the determined degree of epitaxial surface temperature deviation, modifying the temperature-compensated growth method and repeatedly growing the HgCdTe material on the substrate until the As concentration does not change with HgCdTe depth. This embodiment of the application designs a method for characterizing temperature deviation, modifies the growth temperature reduction curve, and addresses the issue of poor quality HgCdTe material resulting from the inability to accurately characterize the HgCdTe epitaxial surface temperature.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for controlling the surface temperature of a molecular beam epitaxial mercury cadmium telluride (HgCdTe) epitaxial layer. Background Art

[0002] Currently, infrared focal plane detectors are developing towards third-generation focal plane detectors with large arrays and dual multi-color technology. These detectors are not only gaining widespread military use but are also finding widespread civilian application as their costs continue to decline. Among the various focal plane detectors, those based on mercury cadmium telluride (HgCdTe) materials dominate the market due to their high quantum efficiency and full-spectrum tunability.

[0003] During the molecular beam epitaxy (MBE) process of HgCdTe (HgCdTe) growth, changes in epitaxial surface temperature significantly impact crystal quality: excessively high or low epitaxial surface temperatures can easily lead to the formation of polycrystalline or twin structures, impacting device performance. Furthermore, changes in epitaxial surface temperature significantly alter the atomic adhesion coefficient, particularly that of mercury atoms, which inevitably alters the material's chemical composition. As growth proceeds, the HgCdTe composition fluctuates, resulting in a non-uniform composition. Therefore, the epitaxial surface temperature during HgCdTe growth is a critical parameter affecting material growth and must be controlled within a range of 190°C ± 2°C. Minimizing temperature fluctuations improves material quality.

[0004] In the HgCdTe epitaxial growth process, indium-free bonding is typically used to secure the substrate. The epitaxial surface temperature is controlled via a thermocouple on the back of the substrate. As the HgCdTe material grows, the epitaxial heat absorption capacity increases, necessitating a lower set temperature to keep the epitaxial surface temperature within the HgCdTe growth temperature window of 190°C ± 2°C. This technique, which compensates for the increase in HgCdTe epitaxial surface temperature due to the increased heat absorption coefficient of the HgCdTe material and thus keeps the epitaxial surface temperature within the HgCdTe growth temperature window, is called temperature-compensated growth. It presents the following two main issues:

[0005] Low precision in measuring epitaxial surface temperature: Whether it is a thermocouple on the back of the substrate, a pyrometer on the front of the substrate, or an optical measurement device, an ellipsometer, none of them can accurately characterize the epitaxial surface temperature. The thermocouple on the back of the substrate has high stability and strong controllability, but because the thermocouple is some distance away from the substrate, the epitaxial surface temperature change cannot be directly characterized by the thermocouple. Pyrometers and ellipsometers are easily affected by external factors such as measurement window contamination and equipment vibration, making it difficult to directly characterize the epitaxial surface temperature.

[0006] The temperature-compensated growth method uses an empirical curve to determine the temperature drop as HgCdTe grows. Existing methods for verifying this growth temperature drop curve use online characterization techniques, such as reflection high-energy electron diffractometers, to characterize the surface temperature of the HgCdTe epitaxial growth by observing changes in the mass of the HgCdTe crystals. This verification method has very low temperature characterization accuracy, typically requiring a temperature deviation of more than 5°C from the optimal growth temperature to be clearly characterized. This deviation is significant from the HgCdTe growth temperature window of ±2°C. Summary of the Invention

[0007] The embodiment of the present application provides a method for controlling the surface temperature of HgCdTe epitaxial growth by molecular beam epitaxy, designs a method for characterizing temperature deviation, corrects the growth temperature reduction curve, and solves the problem of poor quality of HgCdTe material caused by the inability to accurately characterize the surface temperature of HgCdTe epitaxial growth.

[0008] The present application provides a method for controlling the surface temperature of a mercury cadmium telluride (HgCdTe) epitaxial layer by molecular beam epitaxy, comprising:

[0009] fixing the substrate;

[0010] Using a thermocouple to control the epitaxial surface temperature, adopting a temperature compensation growth method, growing a mercury cadmium telluride material based on the substrate, and performing As doping;

[0011] Determine the variation of As doping concentration at different depths during the growth of HgCdTe material;

[0012] According to the changes of As doping concentration at different depths, the extent to which the surface temperature of the HgCdTe epitaxial layer deviates from the HgCdTe growth temperature window at the corresponding depth is predicted;

[0013] Based on the determined degree of temperature deviation of the epitaxial surface, the temperature compensation growth mode is modified, and the HgCdTe material is repeatedly grown based on the substrate until the As concentration does not change with the depth of the HgCdTe.

[0014] Optionally, growing the mercury cadmium telluride material based on the substrate using a temperature compensation growth method includes:

[0015] As the HgCdTe material grows, the set temperature is lowered based on the thermocouple to control the epitaxial surface temperature within a specified HgCdTe growth temperature window.

[0016] Optionally, the growth temperature reduction curve adopted by the temperature compensation growth method is determined based on an empirical curve.

[0017] Optionally, predicting, based on the determined changes in As doping concentrations at different depths, the extent to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at the corresponding depths includes:

[0018] During the As doping process of HgCdTe by molecular beam epitaxy, the As doping amount is kept constant while the temperature is changed;

[0019] Measure the As doping concentration at different doping temperatures to obtain the growth relationship between growth temperature and As doping concentration;

[0020] Based on the growth temperature reduction curve of the original As-doped HgCdTe material and the growth relationship obtained by measurement, the degree of deviation from the optimal growth temperature of HgCdTe when growing to different depths was calculated.

[0021] Optionally, based on the determined degree of temperature deviation of the epitaxial surface, modifying the temperature compensation growth mode includes:

[0022] Based on the estimated degree of deviation from the optimal growth temperature of mercury cadmium telluride when growing to different depths, the growth temperature reduction curve is modified;

[0023] The growth temperature reduction curve is fine-tuned and corrected overall, and the optimal growth temperature reduction curve is determined according to the quality of HgCdTe.

[0024] Optionally, determining an optimal growth temperature reduction curve based on HgCdTe mass includes:

[0025] The quality of HgCdTe is characterized by its surface defects, double crystal diffraction half-peak width, and dislocations to obtain an accurate optimal growth temperature reduction curve.

[0026] An embodiment of the present application also proposes a molecular beam epitaxy mercury cadmium telluride epitaxial surface temperature control device, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the aforementioned molecular beam epitaxy mercury cadmium telluride epitaxial surface temperature control method are implemented.

[0027] The embodiment of the present application designs a method for characterizing temperature deviation, corrects the growth temperature reduction curve, and solves the problem of poor quality of HgCdTe material caused by the inability to accurately characterize the surface temperature of HgCdTe epitaxy.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0030] Figure 1 This is an example of the process of the epitaxial mercury cadmium telluride surface temperature control method according to an embodiment of the present application;

[0031] Figure 2 An example of the position of a thermocouple in the epitaxial HgCdTe surface temperature control method according to an embodiment of the present application;

[0032] Figure 3 This is an example of a growth temperature cooling curve according to an embodiment of the present application;

[0033] Figure 4 This is an example of calibration of the correlation between As doping concentration and temperature in an embodiment of the present application;

[0034] Figure 5 This is an example of correction after calibration of the correlation between As doping concentration and temperature in an embodiment of the present application;

[0035] Figure 6 This is an example of secondary ion mass spectrometry result analysis and temperature curve correction in an embodiment of the present application;

[0036] Figure 7 This is an example of determining the optimal growth temperature curve in an embodiment of the present application. DETAILED DESCRIPTION

[0037] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0038] The present application provides a method for controlling the surface temperature of HgCdTe epitaxy by molecular beam epitaxy. Figure 1 As shown, including:

[0039] In step S101, the substrate is fixed. Specifically, the equipment used in this example includes: a molecular beam epitaxy system (including a sample operation stage) and a secondary ion mass spectrometer (SIMS). The substrate can be fixed by indium-free bonding.

[0040] In step S102, the epitaxial surface temperature is controlled by a thermocouple, a temperature-compensated growth method is adopted, and HgCdTe material is grown on the substrate, and As doping is performed. In some embodiments, the temperature-compensated growth method is adopted to grow HgCdTe material on the substrate, including: as the HgCdTe material grows, the set temperature is lowered based on the thermocouple to control the epitaxial surface temperature within a specified HgCdTe growth temperature window. Specifically, Figure 2As shown, the epitaxial surface temperature can be controlled by a thermocouple on the back side of the substrate. As the HgCdTe material grows, the material's heat absorption capacity increases, and the set temperature needs to be lowered to control the epitaxial surface temperature within the HgCdTe growth temperature window, for example, a temperature window range of 190°C ± 2°C. Specific implementation steps will be described later.

[0041] In some embodiments, the growth temperature reduction curve used in the temperature compensation growth method is determined based on an empirical curve. Figure 3 As shown, the temperature-compensated growth method uses an empirical curve for the temperature drop curve as HgCdTe grows. Existing methods for verifying this growth temperature drop curve use online characterization methods such as reflection high-energy electron diffraction, which characterizes the surface temperature changes of HgCdTe epitaxy by observing changes in HgCdTe crystal mass.

[0042] In step S103 , during the growth of the HgCdTe material, the variation of the As doping concentration at different depths is determined.

[0043] In step S104 , the extent to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at the corresponding depth is predicted based on the determined variation of the As doping concentration at different depths.

[0044] Specifically, this example utilizes the principle that the arsenic adhesion coefficient is sensitive to the growth temperature during the growth of HgCdTe material. As is doped during the growth of HgCdTe material, and then a secondary ion mass spectrometer is used to measure the arsenic concentration at different depths of the As-doped HgCdTe material. The variation in the As doping concentration at different depths is then used to predict the degree to which the HgCdTe epitaxial surface temperature at the corresponding depth deviates from the HgCdTe growth temperature window.

[0045] In step S105, the temperature-compensated growth method is modified based on the determined degree of epitaxial surface temperature deviation, and HgCdTe material is repeatedly grown on the substrate until the As concentration does not change with HgCdTe depth. Specifically, the degree to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at different depths can be inferred based on the As concentration variation, and the growth temperature reduction curve in the temperature-compensated growth method can be modified accordingly.

[0046] The embodiment of the present application designs a method for characterizing temperature deviation, corrects the growth temperature reduction curve, and solves the problem of poor quality of HgCdTe material caused by the inability to accurately characterize the surface temperature of HgCdTe epitaxy.

[0047] In some embodiments, predicting the extent to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at the corresponding depth based on the determined As doping concentration variation at different depths includes:

[0048] During the As doping process of HgCdTe by molecular beam epitaxy, the As doping amount is kept constant while the temperature is changed.

[0049] Measure the As doping concentration at different doping temperatures to obtain the growth relationship between growth temperature and As doping concentration. The measurement can be completed by SIMS. Figure 4 The data given in the paper show that for every 0.5°C decrease in temperature, the As doping concentration increases by about 100%.

[0050] Based on the growth temperature reduction curve of the original As-doped HgCdTe material and the measured growth relationship, the degree of deviation from the optimal growth temperature of HgCdTe when growing to different depths is calculated. Then the growth temperature reduction curve is corrected as follows: Figure 5 As shown, the process is repeated until the As concentration in the HgCdTe material does not change with depth. At this time, the growth temperature cooling curve can control the surface temperature of the HgCdTe epitaxial layer within the HgCdTe growth temperature window, as shown in FIG. Figure 6 shown.

[0051] In some embodiments, based on the determined degree of temperature deviation of the epitaxial surface, modifying the temperature-compensated growth method includes:

[0052] Based on the estimated degree of deviation from the optimal growth temperature of mercury cadmium telluride when growing to different depths, the growth temperature reduction curve is modified;

[0053] The overall fine-tuned and corrected growth temperature reduction curve is then used to determine an optimal growth temperature reduction curve based on the quality of the HgCdTe. In some embodiments, determining the optimal growth temperature reduction curve based on the quality of the HgCdTe includes characterizing the quality of the HgCdTe using surface defects, double crystal diffraction half-maximum width, and dislocations to obtain an accurate optimal growth temperature reduction curve.

[0054] Specifically, after the growth temperature reduction curve is determined, the overall growth temperature reduction curve is further slightly increased or decreased in this embodiment. The quality of HgCdTe is characterized by surface defects, double crystal diffraction half-peak width, and dislocation of HgCdTe to determine the optimal growth temperature reduction curve. Figure 7 The method of the present application can be used to obtain a bonded substrate for molecular beam epitaxy.

[0055] The temperature control method in this application adopts a highly stable and controllable substrate backside thermocouple method. This application designs a method for characterizing temperature deviation. Utilizing the principle that the arsenic adhesion coefficient is very sensitive to the growth temperature during the growth of HgCdTe materials, a secondary ion mass spectrometer is used to measure the arsenic concentration at different depths of As-doped HgCdTe materials. Based on the degree of As concentration change measured by the secondary ion mass spectrometer, the degree of deviation from the optimal growth temperature of HgCdTe when growing to different depths is inferred, and the growth temperature reduction curve is corrected. The process is then repeated until the As concentration in the HgCdTe material does not change with depth. Thus, the growth temperature cooling curve at this time can control the HgCdTe epitaxial surface temperature within the HgCdTe growth temperature window, solving the problem of poor quality of HgCdTe materials caused by the inability to accurately characterize the HgCdTe epitaxial surface temperature, thereby improving the crystal quality of the HgCdTe material.

[0056] An embodiment of the present application also proposes a molecular beam epitaxy mercury cadmium telluride epitaxial surface temperature control device, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the aforementioned molecular beam epitaxy mercury cadmium telluride epitaxial surface temperature control method are implemented.

[0057] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0058] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0059] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server or network device, etc.) to execute the methods described in each embodiment of the present application.

[0060] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are protected by this application.

Claims

1. A method for controlling the surface temperature of mercury cadmium telluride epitaxy by molecular beam epitaxy, characterized in that: include: fixing the substrate; Using a thermocouple to control the epitaxial surface temperature, adopting a temperature compensation growth method, growing a mercury cadmium telluride material based on the substrate, and performing As doping; Determine the variation of As doping concentration at different depths during the growth of HgCdTe material; According to the changes of As doping concentration at different depths, the extent to which the surface temperature of the HgCdTe epitaxial layer deviates from the HgCdTe growth temperature window at the corresponding depth is predicted; Based on the determined degree of temperature deviation of the epitaxial surface, the temperature compensation growth mode is modified, and the HgCdTe material is repeatedly grown based on the substrate until the As concentration does not change with the depth of the HgCdTe.

2. The method for controlling the surface temperature of HgCdTe epitaxial grown by molecular beam epitaxy according to claim 1, wherein: Growing a mercury cadmium telluride material based on the substrate using a temperature compensation growth method includes: As the HgCdTe material grows, the set temperature is lowered based on the thermocouple to control the epitaxial surface temperature within a specified HgCdTe growth temperature window.

3. The method for controlling the surface temperature of HgCdTe epitaxial grown by molecular beam epitaxy according to claim 1, wherein: The growth temperature reduction curve adopted by the temperature compensation growth method is determined based on an empirical curve.

4. The method for controlling the surface temperature of HgCdTe epitaxial grown by molecular beam epitaxy according to claim 1, wherein: The degree to which the HgCdTe epitaxial surface temperature deviates from the HgCdTe growth temperature window at the corresponding depth is predicted based on the determined As doping concentration variation at different depths. During the As doping process of HgCdTe by molecular beam epitaxy, the As doping amount is kept constant while the temperature is changed; Measure the As doping concentration at different doping temperatures to obtain the growth relationship between growth temperature and As doping concentration; Based on the growth temperature reduction curve of the original As-doped HgCdTe material and the growth relationship obtained by measurement, the degree of deviation from the optimal growth temperature of HgCdTe when growing to different depths was calculated.

5. The method for controlling the surface temperature of HgCdTe epitaxial grown by molecular beam epitaxy according to claim 4, wherein: Based on the determined degree of temperature deviation of the epitaxial surface, modifying the temperature compensation growth mode includes: Based on the estimated degree of deviation from the optimal growth temperature of mercury cadmium telluride when growing to different depths, the growth temperature reduction curve is modified; The growth temperature reduction curve is fine-tuned and corrected overall, and the optimal growth temperature reduction curve is determined according to the quality of HgCdTe.

6. The method for controlling the surface temperature of HgCdTe epitaxial grown by molecular beam epitaxy according to claim 5, wherein: The optimal growth temperature reduction curve determined based on the quality of HgCdTe includes: The quality of HgCdTe is characterized by its surface defects, double crystal diffraction half-peak width, and dislocations to obtain an accurate optimal growth temperature reduction curve.

7. A molecular beam epitaxy mercury cadmium telluride epitaxial surface temperature control device, characterized in that: The method comprises a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the molecular beam epitaxial mercury cadmium telluride epitaxial surface temperature control method according to any one of claims 1 to 6 are implemented.

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