In-situ real-time monitoring and regulating method for molecular beam epitaxy tellurium-cadmium-mercury surface temperature

Abstract

The invention provides an in-situ real-time monitoring and regulating method for the surface temperature of molecular beam epitaxy tellurium-cadmium-mercury. The method comprises the following steps: correcting the heating uniformity of the molecular beam epitaxy tellurium-cadmium-mercury before growth; the surface temperature during growth of molecular beam epitaxy mercury cadmium telluride is monitored in real time. According to the method provided by the invention, aiming at the molecular beam epitaxial growth of the tellurium-cadmium-mercury material, the implementation mode of switching the spectrograph is designed, and the consistent effect of spectrum temperature measurement before the tellurium-cadmium-mercury material grows and after the tellurium-cadmium-mercury material grows to a certain thickness is realized; furthermore, a simple and efficient surface scanning mode is combined, and the substrate molybdenum support is improved, so that comprehensive scanning of material surface temperature distribution is realized, molecular beam epitaxy process parameters are optimized, the process development efficiency is improved, quantitative control of defect density is realized, and the consistency and repeatability of the epitaxial material are improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor material growth technology, and in particular to a method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride (MCT) via molecular beam epitaxy. Background Technology

[0002] Large-area, high-performance, multi-color integrated infrared focal plane array detectors have broad application prospects, and mercury cadmium telluride (HCdT) thin films are the preferred material for fabricating such detectors. During the molecular beam epitaxy (MBE) growth of HCdT materials, the substrate surface temperature is a key factor affecting the film material composition, thickness uniformity, and defect control. To obtain high-quality HCdT thin films via MBE, the epitaxial surface temperature needs to be controlled within ±5℃ of the optimal temperature.

[0003] Against this backdrop, achieving real-time and accurate characterization of surface temperature is crucial. Traditional temperature monitoring methods primarily rely on thermocouples placed on the back side of the substrate, which suffer from limitations such as single-point temperature measurement, inaccurate readings, and response lag. Especially when using CdZnTe substrates with low thermal conductivity, the temperature difference between the back and front sides is significant, and the temperature response between the two surfaces is even slower, making it difficult to monitor surface temperature changes accurately in real time. This results in poor temperature control accuracy and directly leads to low efficiency in the development of molecular beam epitaxy (MBE) mercury cadmium telluride (HCdTe) thin film growth processes. Therefore, there is an urgent need for an in-situ real-time surface temperature monitoring system to achieve real-time monitoring and control of the surface temperature of HCdTe materials. To address this issue, other research institutions in China mostly use infrared thermometers to detect the surface temperature of HCdTe. This method has advantages such as being non-contact and highly adaptable, but it suffers from significant disadvantages in terms of measurement accuracy.

[0004] Establishing an in-situ real-time surface temperature monitoring system based on the light absorption effect of semiconductor materials promises to be an effective solution. This method leverages the characteristic that the bandgap of semiconductor materials changes with temperature, measuring temperature by detecting changes in the absorption characteristics of light signals within the semiconductor. The spectral temperature measurement system used mainly includes a light source, a receiver, and a spectrometer, such as... Figure 1 As shown, the system employs a transmission / reflection absorption edge mode. By analyzing the spectral absorption edges of the transmitted / reflected light from the sample, it calculates the bandgap width and then deduces the sample surface temperature in real time based on the relationship between the bandgap width and temperature. This system offers high temperature measurement accuracy and is suitable for materials with different crystal orientations, substrate types, and polishing methods.

[0005] Molecular beam epitaxy (MBE) of mercury cadmium telluride (HCdT) thin films requires extremely high real-time and precise monitoring of surface temperature. Currently, MBE temperature monitoring primarily relies on thermocouples placed on the back side of the substrate, which can only monitor the temperature at a single point on the back side. This lack of comprehensive monitoring of the substrate surface temperature results in poor temperature control accuracy, affecting material quality and directly leading to low efficiency in the development of MBE HCdT thin film growth processes. Furthermore, regarding the spectroscopic temperature measurement technology designed in this patent, because HCdT is an infrared absorbing material, its absorption spectrum differs from that of the substrate (such as silicon or cadmium zinc telluride). As HCdT grows to a certain thickness, its spectral absorption edge red-shifts beyond the detection limit of visible light (silicon) or near-infrared (cadmium zinc telluride) spectrometers, rendering temperature measurement ineffective. Summary of the Invention

[0006] The technical solution adopted in this invention is to achieve real-time and accurate monitoring of the substrate surface temperature during molecular beam epitaxy of mercury cadmium telluride (HCDT) materials. Therefore, this invention provides an in-situ real-time monitoring and control method for the surface temperature of HCDT materials grown via molecular beam epitaxy.

[0007] This invention proposes an in-situ real-time monitoring and control method for the surface temperature of mercury cadmium telluride (HCdT) via molecular beam epitaxy, comprising: Step S1: Correct the heating uniformity before the growth of cadmium cadmium telluride by molecular beam epitaxy. Step S2 involves real-time monitoring of the surface temperature during the growth of mercury cadmium telluride via molecular beam epitaxy.

[0008] In one embodiment, step S1 includes: Perform system calibration on the molecular beam epitaxy system; The substrate for molecular beam epitaxy is placed on a hollowed-out molybdenum support, covered with a cover plate on the back, and then transferred into the molecular beam epitaxy system. After being degassed in the degassing chamber, it is transferred into the growth chamber. The transmissive light source of the in-situ real-time surface temperature monitoring system is turned on to begin temperature measurement and calibration.

[0009] In one embodiment, the temperature measurement and calibration process includes: Measure the temperature at the center (0,0) of the substrate and record it in the system; The driving light spot moves from the center of the substrate (0,0) to (x1-1,0), where 0 corresponds to the point 1-1 of the opening on the cover plate; After recording the temperature at that point, the substrate is made to rotate at a constant speed, that is, the light spot starts to rotate along a circle with the center as the center. When it reaches the hole position x1-2, x1-3...x1-n, the corresponding temperature is recorded until it returns to (x1-1,0), completing the measurement of one circle. The light spot continues to move along the x-direction to (x2-1,0), and rotates again to complete a measurement of one circumference. This process is repeated to achieve the measurement of the temperature distribution across the entire surface. When the measurement reveals that the substrate edge temperature is too low, the power of the external heating wire is corrected, and the above measurement and calibration are repeated until the uniformity meets the standard.

[0010] In one embodiment, step S2 includes: Using a near-infrared / visible spectrometer, the substrate is placed on a hollowed-out molybdenum support, and a cover plate is placed on the back. The substrate is then transferred to the molecular beam epitaxy system. After being degassed by water in the degassing chamber, the substrate is transferred to the growth chamber. The in-situ real-time surface temperature monitoring system with a transmission light source is turned on to begin temperature measurement and control.

[0011] In one embodiment, the temperature measurement and control process includes: Once the target temperature is set and growth begins, the surface temperature is monitored in situ in real time. The detected values ​​are then communicated with the control system for real-time feedback and adjustment of the output power. After growing a mercury cadmium telluride film of a predetermined thickness, the spectrometer was switched from a near-infrared / visible spectrometer to the infrared band to continue monitoring and adjusting the growth temperature in order to maintain a stable surface temperature. After growing the specified cadmium cadmium telluride (CdMt) thin film to the specified thickness, the growth process is terminated, the temperature is lowered to the growth temperature, and the cadmium telluride layer is passivated in situ. After growth is complete, lower the temperature to room temperature.

[0012] In one embodiment, during the temperature measurement and control process, the surface morphology is monitored in real time using a reflective high-energy electron diffractometer to ensure the single crystal growth state.

[0013] In one embodiment, the cover plate has a plurality of through-hole structures evenly distributed thereon.

[0014] By adopting the above technical solution, the present invention has at least the following advantages: The method provided by this invention, for the molecular beam epitaxy (MBE) growth of mercury cadmium telluride (MDT) materials, designs an implementation method for switching spectrometers, achieving consistent spectral temperature measurement results before and after MDT growth to a certain thickness. Furthermore, by combining a simple and efficient surface scanning method with an improved design of the molybdenum substrate support, a comprehensive scan of the material surface temperature distribution is achieved, thereby optimizing the MBE process parameters, improving process development efficiency, achieving quantitative control of defect density, and enhancing the consistency and repeatability of the epitaxial material. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1This is a schematic diagram of a surface temperature in-situ real-time monitoring system. Figure 2 This is a schematic diagram of the in-situ real-time monitoring and control method for the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to an embodiment of the present invention. Figure 3 This is a schematic diagram of optical path switching according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the detector surface scanning mechanism according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a perforated molybdenum support and cover plate designed for transmissivity according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the molecular beam epitaxy growth mechanism of mercury cadmium telluride according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the growth structure of a molecular beam epitaxy system according to an embodiment of the present invention. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0017] While exemplary embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey its scope to those skilled in the art. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] This invention provides an in-situ real-time monitoring and control method and apparatus for the surface temperature of mercury cadmium telluride (MCH) via molecular beam epitaxy, such as... Figure 2 As shown, it includes the following steps: Step S1: Correct the heating uniformity before the growth of cadmium cadmium telluride by molecular beam epitaxy. Step S2 involves real-time monitoring of the surface temperature during the growth of mercury cadmium telluride via molecular beam epitaxy.

[0019] In this embodiment, step S1 includes: Perform system calibration on the molecular beam epitaxy system; The substrate for molecular beam epitaxy is placed on a hollowed-out molybdenum support, covered with a cover plate on the back, and then transferred into the molecular beam epitaxy system. After being degassed in the degassing chamber, it is transferred into the growth chamber. The transmissive light source of the in-situ real-time surface temperature monitoring system is turned on to begin temperature measurement and calibration.

[0020] Specifically, the temperature measurement and calibration process includes: Measure the temperature at the center (0,0) of the substrate and record it in the system; The driving light spot moves from the center of the substrate (0,0) to (x1-1,0), where 0 corresponds to the point 1-1 of the opening on the cover plate; After recording the temperature at that point, the substrate is made to rotate at a constant speed, that is, the light spot starts to rotate along a circle with the center as the center. When it reaches the hole position x1-2, x1-3...x1-n, the corresponding temperature is recorded until it returns to (x1-1,0), completing the measurement of one circle. The light spot continues to move along the x-direction to (x2-1,0), and rotates again to complete a measurement of one circumference. This process is repeated to achieve the measurement of the temperature distribution across the entire surface. When the measurement reveals that the substrate edge temperature is too low, the power of the external heating wire is corrected, and the above measurement and calibration are repeated until the uniformity meets the standard.

[0021] In this embodiment, step S2 includes: Using a near-infrared / visible spectrometer, the substrate is placed on a hollowed-out molybdenum support, and a cover plate is placed on the back. The substrate is then transferred to the molecular beam epitaxy system. After being degassed by water in the degassing chamber, the substrate is transferred to the growth chamber. The in-situ real-time surface temperature monitoring system with a transmission light source is turned on to begin temperature measurement and control.

[0022] Specifically, the temperature measurement and control process includes: Once the target temperature is set and growth begins, the surface temperature is monitored in situ in real time. The detected values ​​are then communicated with the control system for real-time feedback and adjustment of the output power. After growing a mercury cadmium telluride film of a predetermined thickness, the spectrometer was switched from a near-infrared / visible spectrometer to the infrared band to continue monitoring and adjusting the growth temperature in order to maintain a stable surface temperature. After growing the specified cadmium cadmium telluride (CdMt) thin film to the specified thickness, the growth process is terminated, the temperature is lowered to the growth temperature, and the cadmium telluride layer is passivated in situ. After growth is complete, lower the temperature to room temperature.

[0023] Specifically, in the temperature measurement and control process, the surface morphology is monitored in real time using a reflective high-energy electron diffractometer to ensure the single crystal growth state.

[0024] In this embodiment, the cover plate has a plurality of through holes evenly distributed thereon.

[0025] The method provided in this embodiment will be described in detail step by step below.

[0026] Specifically, this embodiment provides a surface temperature precision monitoring system and method based on spectral analysis, enabling real-time and accurate monitoring of substrate surface temperature. For molecular beam epitaxy (MBE) of mercury cadmium telluride (HCdT), an automatic spectrometer switching method is designed, achieving consistent spectral temperature measurement results before and after HCdT growth to a certain thickness. Combined with a simple and efficient surface scanning method and an improved design of the molybdenum substrate holder, comprehensive scanning of the material surface temperature distribution is achieved, thereby optimizing MBE process parameters, improving process development efficiency, enabling quantitative control of defect density, and enhancing the consistency and repeatability of epitaxial materials.

[0027] a. Automatic switching spectrometer device To match the mercury cadmium telluride (HCd) molecular beam epitaxy process, the system is equipped with three spectrometers: near-infrared (for silicon substrates), visible (for cadmium zinc telluride substrates), and infrared (for HCd) spectrometers, along with an automatic switching device to sequentially detect the substrate temperature before growth and the epitaxial temperature of the HCd material during growth. Figure 3 As shown, according to the light intensity detection device, a near-infrared / visible spectrometer is used in the substrate pretreatment stage. After a certain thickness of mercury cadmium telluride material is grown, when the light intensity is detected to be reduced to about 1 / 10 of the original, the automatic switching device switches the light path to an infrared spectrometer to realize the temperature detection of mercury cadmium telluride.

[0028] b. Surface scanning drive module and matching molybdenum support design An improved detector structure enables temperature distribution scanning at multiple points on the substrate surface. This approach can be directly applied to diffuse reflection structures. Figure 4 This diagram illustrates a surface scanning drive. A motor drives a detector spot to deflect along the x-axis from the center of the substrate and stop at a specific position, while the substrate rotates one full revolution, recording data at each point. The spot then continues to move along the x-axis, repeating the process to achieve a distributed scan of the material surface. This method requires no complex structural design and can achieve full-surface scanning simply and efficiently. In contrast, the transmission-type operation requires balancing growth temperature uniformity and light transmittance; therefore, improvements were made to the transmission-type molybdenum support. For example... Figure 5 As shown, the design consists of two parts: a hollow molybdenum support and a cover plate. The cover plate has multiple through-hole structures evenly distributed, which can achieve transmissive surface scanning while ensuring temperature uniformity.

[0029] Based on the above system design, a specific application embodiment of this example, namely, using in-situ monitoring technology to monitor the molecular beam epitaxial growth process of mercury cadmium telluride, can be combined with... Figure 6 as well as Figure 7 The details are as follows: Step S1, Heating uniformity correction before growth First, the system is calibrated by using a blackbody source with a known temperature to calibrate the bandgap-temperature relationship curve. The system readings are then communicated with the PID temperature control system, and the response sensitivity of the heating plate power regulator is adjusted to ensure that the temperature regulation range is controllable.

[0030] The substrate is placed on a perforated molybdenum support, covered with a back cover, and then transferred into the molecular beam epitaxy system. After degassing in the degassing chamber, it is transferred into the growth chamber. The transmission light source of the in-situ real-time surface temperature monitoring system is turned on to begin temperature measurement. The specific temperature measurement process is as follows: Before preprocessing the substrate, a surface scanning module was used to acquire the temperature distribution on the substrate surface. First, the temperature at the center of the substrate (xy coordinate (0,0)) was measured and recorded in the system. Then, a motor drove the light spot to move from (0,0) to (x1-1,0), where 0 corresponds to point 1-1 of the opening on the cover plate. After recording the temperature at this point, the substrate began to rotate at a constant speed, that is, the light spot began to rotate along a circle centered on the center. When it reached the openings 1-2, 1-3…1-n, the temperature was recorded again, and this process was repeated until it returned to (x1-1,0), completing one circumference measurement. Then, the light spot continued to move along the x-axis to (x2-1,0) and rotated again to complete one circumference measurement. This process was repeated to measure the temperature distribution of the entire surface. The measurement revealed that the temperature at the substrate edge was too low, so the power of the external heating wire was corrected, and the calibration was repeated until uniformity was achieved.

[0031] Step S2: Real-time monitoring of surface temperature during growth Substrate pretreatment stage control: The substrate is placed on a hollowed-out molybdenum support, covered with a back cover, and then transferred to the molecular beam epitaxy system. After degassing in the degassing chamber, it is transferred to the growth chamber. The in-situ real-time surface temperature monitoring system with a transmission light source is turned on to begin temperature measurement. Temperature uniformity is corrected according to the method provided in section a.

[0032] Growth stage control of mercury cadmium telluride (HCdT): After setting the target temperature and starting growth, the surface temperature is monitored in situ in real time. The detected values ​​are communicated with the control system for real-time feedback and output power adjustment, significantly reducing surface temperature fluctuations. Surface morphology is monitored in real time using a reflective high-energy electron diffractometer (RHEED) to ensure single-crystal growth. After growing a HCdT film of a certain thickness, the system automatically switches the spectrometer to the infrared band to continue monitoring and adjusting the growth temperature, maintaining a stable surface temperature. Growth ends when the specified HCdT film thickness is reached, and the temperature is lowered to the growth temperature for in-situ passivation of the cadmium telluride layer.

[0033] After growth is complete, the temperature monitoring system monitors the temperature as it drops to room temperature, and the sample is then removed for subsequent testing and micro / nano fabrication steps.

[0034] Compared with the prior art, this embodiment has at least the following advantages: 1) This invention employs an in-situ real-time surface temperature monitoring system to achieve real-time monitoring of the surface temperature. It can obtain the true temperature of the substrate surface in real time, eliminating the need to deduce the growth temperature from the growth state, thus significantly improving the efficiency and success rate of mercury cadmium telluride thin film epitaxial growth process development.

[0035] 2) In this embodiment of the invention, the surface temperature distribution is monitored and scanned using a surface scanning module. The temperature distribution on the surface of mercury cadmium telluride (MDT) during the epitaxial process is obtained. By adjusting the heating power in different regions of the heater, the composition and thickness uniformity of the MDT material are significantly improved.

[0036] 3) The automatic switching spectrometer device in this embodiment of the invention enables temperature monitoring throughout the entire process from pretreatment to growth. Automated temperature monitoring is achieved in both the pretreatment process and the mercury cadmium telluride thin film growth stage, thus achieving precise control over the entire material growth process.

[0037] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims. All of these forms are within the protection scope of this application.

Claims

1. A method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride (HCdT) via molecular beam epitaxy, characterized in that, include: Step S1: Correct the heating uniformity before the growth of cadmium cadmium telluride by molecular beam epitaxy. Step S2 involves real-time monitoring of the surface temperature during the growth of mercury cadmium telluride via molecular beam epitaxy.

2. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to claim 1, characterized in that, Step S1 includes: Perform system calibration on the molecular beam epitaxy system; The substrate for molecular beam epitaxy is placed on a hollowed-out molybdenum support, covered with a cover plate on the back, and then transferred into the molecular beam epitaxy system. After being degassed in the degassing chamber, it is transferred into the growth chamber. The transmissive light source of the in-situ real-time surface temperature monitoring system is turned on to begin temperature measurement and calibration.

3. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to claim 2, characterized in that, The temperature measurement and calibration process includes: Measure the temperature at the center (0,0) of the substrate and record it in the system; The driving light spot moves from the center of the substrate (0,0) to (x1-1,0), where 0 corresponds to the point 1-1 of the opening on the cover plate; After recording the temperature at that point, the substrate is made to rotate at a constant speed, that is, the light spot starts to rotate along a circle with the center as the center. When it reaches the hole position x1-2, x1-3...x1-n, the corresponding temperature is recorded until it returns to (x1-1,0), completing the measurement of one circle. The light spot continues to move along the x-direction to (x2-1,0), and rotates again to complete a measurement of one circumference. This process is repeated to achieve the measurement of the temperature distribution across the entire surface. When the measurement reveals that the substrate edge temperature is too low, the power of the external heating wire is corrected, and the above measurement and calibration are repeated until the uniformity meets the standard.

4. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to claim 3, characterized in that, Step S2 includes: Using a near-infrared / visible spectrometer, the substrate is placed on a hollowed-out molybdenum support, and a cover plate is placed on the back. The substrate is then transferred to the molecular beam epitaxy system. After being degassed by water in the degassing chamber, the substrate is transferred to the growth chamber. The in-situ real-time surface temperature monitoring system with a transmission light source is turned on to begin temperature measurement and control.

5. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride (MCH) via molecular beam epitaxy according to claim 4, characterized in that, The temperature measurement and control process includes: Once the target temperature is set and growth begins, the surface temperature is monitored in situ in real time. The detected values ​​are then communicated with the control system for real-time feedback and adjustment of the output power. After growing a mercury cadmium telluride film of a predetermined thickness, the spectrometer was switched from a near-infrared / visible spectrometer to the infrared band to continue monitoring and adjusting the growth temperature in order to maintain a stable surface temperature. After growing the specified cadmium cadmium telluride (CdMt) thin film to the specified thickness, the growth process is terminated, the temperature is lowered to the growth temperature, and the cadmium telluride layer is passivated in situ. After growth is complete, lower the temperature to room temperature.

6. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to claim 5, characterized in that, During the temperature measurement and control process, the surface morphology is monitored in real time using a reflective high-energy electron diffractometer to ensure the single crystal growth state.

7. The method for in-situ real-time monitoring and control of the surface temperature of mercury cadmium telluride via molecular beam epitaxy according to claim 2, characterized in that, The cover plate has multiple through holes evenly distributed on it.

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