Epitaxial growth control method and device, computer device and storage medium

Abstract

The application provides an epitaxial growth control method and device, computer equipment and a storage medium. The application uses a supercontinuum laser light source to irradiate the surface of a wafer to be measured and a reference irradiation surface to obtain a reflected light signal; the reflected light signal is synchronously scanned and filtered to output two narrow-band lights; the two narrow-band lights are converted into electrical signals and then subjected to differential operation, and the reflectivity of the wafer to be measured is calculated according to the differential result; the growth parameters of the epitaxial layer are determined based on the reflectivity, and the process parameters of the reaction cavity are adjusted according to the growth parameters to control the epitaxial growth of the wafer to be measured. The supercontinuum laser light source can scan multiple characteristic wavelengths in one process step, realizes the synchronous monitoring of multiple growth parameters, meets the monitoring requirements of complex epitaxial structures; in addition, the common-mode noise in the measurement process is eliminated in real time by using the double-beam differential measurement technology, the signal-to-noise ratio is greatly improved, the measurement accuracy is improved, and the precise control of epitaxial growth is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor detection, and in particular to an epitaxial growth control method and device, a computer device and a storage medium. BACKGROUND

[0002] In the epitaxial growth process of a VCSEL (Vertical Cavity Surface Emitting Laser), a DBR (Distributed Bragg Reflector) structure and a quantum well active region with as many as hundreds of layers need to be prepared, and the thickness, composition and interface quality of each layer directly affect the performance of the final device. Therefore, it is crucial to monitor the film thickness, temperature, reflectivity and growth rate in real time during the epitaxial process.

[0003] In the traditional technology, a single-beam wide-spectrum light source is usually used in combination with a spectrometer for monitoring. With this monitoring method, the detection signal is easily submerged by the strong high-temperature background radiation, plasma light and air flow disturbance in the reaction chamber, resulting in low signal-to-noise ratio (SNR) and large data fluctuation, and the measurement accuracy and reliability sharply decrease in a complex process environment, which cannot effectively control the epitaxial growth of the wafer. SUMMARY

[0004] The present application aims to provide an epitaxial growth control method and device, a computer device and a storage medium to overcome the problem that the single-beam wide-spectrum detection technology used in the traditional technology sharply decreases the measurement accuracy and reliability in a complex process environment, and cannot effectively control the epitaxial growth of the wafer.

[0005] In a first aspect, the present application provides an epitaxial growth control method, comprising: obtaining a reflected light signal, wherein the reflected light signal comprises a measurement light signal and a reference light signal, the measurement light signal is generated by reflecting a preset light source on the surface of a wafer to be measured in an epitaxial growth process, the reference light signal is generated by reflecting the preset light source on a reference irradiation surface, and the preset light source is an ultra-continuous spectrum laser light source; synchronously scanning and filtering the measurement light signal and the reference light signal to output first narrowband light and second narrowband light with the same center wavelength at any time; converting the first narrowband light and the second narrowband light into electrical signals and then performing differential operation to suppress common-mode noise, and calculating the reflectivity of the wafer to be measured according to the differential operation result; determining the growth parameters of the epitaxial layer based on the reflectivity, and adjusting the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer to be measured.

[0006] In one of the embodiments, the differential operation after the conversion of the first narrowband light and the second narrowband light into electrical signals comprises: converting the first narrowband light and the second narrowband light into corresponding first electrical signals and second electrical signals respectively; performing synchronous demodulation on the first electrical signals and the second electrical signals to obtain first and second lock-in signals; performing differential operation on the first lock-in signal and the second lock-in signal after the second lock-in signal is leveled based on pre-calibrated channel matching parameters to obtain a differential operation result.

[0007] In one of the embodiments, the reflectivity of the wafer under test is calculated according to the differential operation result, which comprises: taking the second lock-in signal as a reference, performing amplitude normalization on the differential operation result to obtain a normalized result; and performing conversion on the normalized result based on a pre-set calibration coefficient to obtain the reflectivity.

[0008] In one of the embodiments, the method further comprises: extracting direct current or low frequency components from the first electrical signals and / or the second electrical signals to obtain a radiation signal representing thermal radiation in the reaction chamber; and adjusting process parameters of the reaction chamber according to the reflectivity and / or the radiation signal to control epitaxial growth of the wafer under test.

[0009] In one of the embodiments, the growth parameters of the epitaxial layer are determined according to the reflectivity and / or the radiation signal, and the process parameters of the reaction chamber are adjusted according to the growth parameters to control the epitaxial growth of the wafer under test, which comprises: for one measurement period, at each pre-set wavelength, the growth parameters are calculated according to the reflectivity and / or the radiation signal; wherein the growth parameters include at least one of the epitaxial layer thickness, the substrate temperature and the growth rate; after the screening of all pre-set wavelengths is completed, the growth parameters are aggregated and output; the growth parameters are compared with a pre-set process setting range; if the comparison result exceeds a pre-set requirement, a control instruction is generated to adjust the process parameters of the reaction chamber to control the epitaxial growth of the wafer under test; and the process parameters include at least one of the source flow, the temperature, the pressure, the component ratio, the precursor switching parameter and the doping parameter.

[0010] In a second aspect, the application provides an epitaxial growth control device, comprising: an irradiation module configured to output an ultra-continuum spectrum laser source, and irradiate a wafer surface in an epitaxial growth process to generate a measurement light signal, and irradiate a reference irradiation surface to generate a reference light signal; an optical path collection module configured to obtain a reflected light signal, wherein the reflected light signal comprises the measurement light signal and the reference light signal; a wavelength selection module configured to synchronously scan and filter the measurement light signal and the reference light signal to output first narrowband light and second narrowband light with the same center wavelength at any time; and a processing module configured to perform differential operation on the first narrowband light and the second narrowband light to suppress common-mode noise, and calculate reflectivity of the wafer based on a differential operation result; determine a growth parameter of an epitaxial layer based on the reflectivity, and adjust a process parameter of a reaction chamber based on the growth parameter to control epitaxial growth of the wafer.

[0011] In one embodiment, the irradiation module comprises: a light source generator configured to output an ultra-continuum spectrum laser source; and a light splitting unit configured to split the ultra-continuum spectrum laser source into a reference light beam and a measurement light beam according to a preset ratio.

[0012] The reference irradiation surface is configured to receive the reference light beam and generate a reference light signal based on the reference light beam.

[0013] In one embodiment, the processing module comprises: a first detector configured to convert the first narrowband light into a corresponding first electrical signal; a second detector configured to convert the second narrowband light into a corresponding second electrical signal; a lock-in amplifier configured to synchronously demodulate the first electrical signal and the second electrical signal to obtain a first lock-in signal and a second lock-in signal; an operation unit configured to perform differential operation on the second lock-in signal after leveling based on pre-calibrated channel matching parameters and the first lock-in signal to obtain a differential operation result; and a control unit configured to calculate reflectivity based on the differential operation result, and adjust a process parameter of a reaction chamber based on the reflectivity to control epitaxial growth of the wafer.

[0014] In one embodiment, the operation unit comprises: a programmable gain amplifier configured to level the second lock-in signal based on pre-calibrated channel matching parameters; and a differential amplifier configured to perform differential operation on the first lock-in signal and the leveled second lock-in signal to obtain a differential operation result.

[0015] In one embodiment, the device further comprises a spectrometer configured to monitor the first narrowband light and / or the second narrowband light to obtain optical path information, wherein the optical path information is used for judging the effectiveness of wavelength selection, and the optical path information comprises at least one of center wavelength, bandwidth, and spectral purity information.

[0016] In one embodiment, the apparatus further comprises a signal separation module configured to extract a direct current or low frequency component from the first electrical signal and / or the second electrical signal to obtain a radiation signal representing thermal radiation in the reaction chamber; and the processing module is further configured to determine a growth parameter of the epitaxial layer based on the reflectivity and / or the radiation signal, and adjust a process parameter of the reaction chamber based on the growth parameter to control the epitaxial growth of the wafer under test.

[0017] In a third aspect, the present application provides a computer device. The computer device comprises a memory and a processor, the memory stores a computer program, and the processor implements the method steps of the first aspect when executing the computer program.

[0018] In a fourth aspect, the present application provides a computer readable storage medium. The computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method steps of the first aspect.

[0019] The epitaxial growth control method, apparatus, computer device and storage medium have at least the following advantages:

[0020] The present application uses a supercontinuum laser light source to irradiate the surface of the wafer under test and the reference irradiation surface during epitaxial growth, and obtains a reflected light signal; the reflected light signal is synchronously scanned and filtered to output first narrowband light and second narrowband light with the same center wavelength at any time; the first narrowband light and the second narrowband light are converted into electrical signals and then subjected to differential operation, and the reflectivity of the wafer under test is calculated based on the differential result; the growth parameter of the epitaxial layer is determined based on the reflectivity, and the process parameter of the reaction chamber is adjusted based on the growth parameter to control the epitaxial growth of the wafer under test. The supercontinuum laser light source of the present application can scan multiple characteristic wavelengths within one process step, realize synchronous monitoring of multiple growth parameters, meet the monitoring needs of VCSEL complex epitaxial structures; further, the present application uses a double-beam differential measurement technology to eliminate common-mode noise in the measurement process in real time, greatly improves the signal-to-noise ratio, improves the measurement accuracy, and realizes precise control of epitaxial growth. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 An application environment of the epitaxial growth control apparatus in one embodiment;

[0022] Figure 2 A structural block diagram of the epitaxial growth control apparatus in one embodiment;

[0023] Figure 3 A structural block diagram of the irradiation module in one embodiment;

[0024] Figure 4 A structural block diagram of a processing module in one embodiment;

[0025] Figure 5 A structural block diagram of an epitaxial growth control device in another embodiment;

[0026] Figure 6 A structural block diagram of an epitaxial growth control device in another embodiment;

[0027] Figure 7 A schematic diagram of a working flow of an epitaxial growth control device in one embodiment;

[0028] Figure 8 A schematic diagram of a working flow of an epitaxial growth control method in one embodiment;

[0029] Figure 9 An internal structural diagram of a computer device in one embodiment. DETAILED DESCRIPTION

[0030] The present application is described and explained through specific detailed examples, and one skilled in the art can easily deduce other advantages and effects of the present application from the disclosure herein. The present application can also be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details herein based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Some exemplary embodiments of the present application are described for illustrative purposes, and it should be understood that the present application can be implemented in other ways not specifically shown in the drawings.

[0032] Optionally, in one embodiment, the present application provides an epitaxial growth control device, which can be applied in an application environment as shown in Figure 1 .

[0033] Please refer to Figure 1 , for example, a reaction chamber 1 is provided with a machine tray 11 and at least one wafer 12 to be tested, and each wafer 12 to be tested is placed on the machine tray 11. The epitaxial growth control device is arranged above the reaction chamber 1, which is used to monitor the surface of the wafer 12 to be tested in the epitaxial growth process in real time, obtain the growth parameters of the epitaxial growth, and adjust the process parameters of the reaction chamber in real time according to the growth parameters, so as to accurately control the epitaxial growth of the wafer 12 to be tested. Among them, the growth parameters include at least one of the epitaxial layer film thickness, the substrate temperature and the growth rate.

[0034] Please refer to Figure 2Optionally, the epitaxial growth control device comprises an irradiation module, an optical path collection module, a wavelength selection module, and a processing module.

[0035] The irradiation module is configured to output the supercontinuum laser light source, and irradiate the surface of the wafer under epitaxial growth to generate a measurement light signal, and irradiate the surface of the reference irradiation surface to generate a reference light signal.

[0036] Specifically, the supercontinuum laser light source in the embodiment refers to a continuous white light source with a wavelength range of 400-1600 nm.

[0037] The reference irradiation surface refers to a standard reference mirror surface made of a material with a fixed reflectivity. The standard reference mirror surface is used to provide a stable and known reflected light signal in the subsequent data detection process, so as to calibrate the errors introduced by light source fluctuation or environmental interference in the measurement process.

[0038] It should be understood that the supercontinuum laser light source irradiates the surface of the wafer under epitaxial growth refers to that the light source is perpendicular to the surface of the wafer under test.

[0039] The optical path collection module is configured to obtain the reflected light signal, wherein the reflected light signal comprises the measurement light signal and the reference light signal.

[0040] Exemplarily, the optical path collection module comprises a double optical path collection channel, each collection channel comprising a collection objective lens and a fiber probe. One collection objective lens is arranged on the surface of the wafer under test, and is configured to converge the measurement light signal reflected from the surface of the wafer under test. The receiving end of one fiber probe is arranged at the focal point of the collection objective lens, and is configured to collect the measurement light signal. Another collection objective lens is arranged on the surface of the reference irradiation surface, and is configured to converge the reference light signal reflected from the reference irradiation surface. The receiving end of another fiber probe is arranged at the focal point of the collection objective lens, and is configured to collect the reference light signal.

[0041] The wavelength selection module is configured to synchronously scan and filter the measurement light signal and the reference light signal, so as to output first narrowband light and second narrowband light with the same center wavelength at any time.

[0042] Specifically, multiple characteristic wavelength points are preset in the VCSEL process recipe, hereinafter referred to as preset wavelengths. For example, 940 nm for GaAs-based DBR monitoring, 850 nm for InGaAs quantum well monitoring, and an absorption edge wavelength for temperature calculation, etc. The wavelength selection module is used to quickly switch to any one of the above preset wavelengths, and at the same time complete the screening of the measurement light signal and the reference light signal at the preset wavelength, so that the processing module obtains the reflectivity of each preset wavelength according to the screened light signal. Exemplarily, the wavelength selection module in the embodiment of the present application adopts an acousto-optic tunable filter (AOTF). By applying a specific radio frequency signal, the acousto-optic tunable filter deflects a specific wavelength of light in the form of Bragg diffraction, separates it from the main light path, and obtains a narrowband light. The acousto-optic tunable filter is a non-mechanical moving part, and the wavelength switching speed can reach microseconds, and can be accurately controlled by electronics. It can quickly scan multiple characteristic wavelength points in one process step, realize multi-parameter synchronous monitoring, and adapt to the needs of complex VCSEL epitaxial structure. Specifically, each preset wavelength is pre-stored in the memory of the processing module in the form of a wavelength list. During measurement, the processing module generates control instructions according to the preset order, so that the acousto-optic tunable filter switches to any one of the wavelengths in the wavelength list in response to the control instructions. Further, in actual application, in the case where the switching speed requirement is relatively wide, the wavelength selection module can also use liquid crystal tunable filter (LCTF), Fabry-Perot tunable filter (FPTF) and other devices.

[0043] The processing module is configured to perform a differential operation on the first narrowband light and the second narrowband light to suppress common-mode noise, and calculate the reflectivity of the wafer under test based on the differential operation result; determine the growth parameter of the epitaxial layer based on the reflectivity, and adjust the process parameter of the reaction chamber based on the growth parameter to control the epitaxial growth of the wafer under test.

[0044] Specifically, during the epitaxial growth of the VCSEL, the reflected light signal of the wafer under test is easily disturbed by the strong high-temperature background radiation, plasma light, and air flow disturbance in the reaction chamber, resulting in low signal-to-noise ratio of the measured parameter and large data fluctuation, and the measurement accuracy and reliability decrease sharply in a complex process environment. Based on this, the present application forms a reference light signal by setting a reference irradiation surface, and performs a differential operation on the reference light signal and the measurement light signal reflected by the wafer under test, which effectively eliminates the common-mode noise generated by the light source intensity fluctuation, the detector drift, and the chamber background radiation, greatly improves the signal-to-noise ratio, and enables stable and accurate measurement data to be obtained in the high-temperature and high-pressure reaction chamber.

[0045] Further, the processing module calculates the growth parameter based on the reflectivity, adjusts the value of the process parameter according to the growth parameter, and uploads the adjusted process parameter to the MES system, so that the MES system outputs a control instruction to the target machine according to the process parameter to execute the wafer epitaxial growth process.

[0046] The epitaxial growth control device adopts an ultrashort pulse laser source to irradiate the surface of the wafer under test and the reference irradiation surface during the epitaxial growth process, and adopts an acousto-optic tunable filter to quickly switch to any one characteristic wavelength point, so that multiple characteristic wavelength points can be quickly scanned within one process step, multi-parameter synchronous monitoring is realized, and the demand of the VCSEL complex epitaxial structure is adapted; further, the application adopts a double-beam differential measurement technology of measuring light signals and reference light signals to eliminate common-mode noise in the measurement process in real time, greatly improves the signal-to-noise ratio, improves the measurement accuracy, and realizes accurate control of epitaxial growth.

[0047] Please refer to Figure 3 Optionally, the irradiation module comprises a light source generator, a light splitting unit and a reference irradiation surface.

[0048] The light source generator is configured to output an ultrashort pulse laser source.

[0049] Exemplarily, the light source generator in the embodiment of the application adopts a white light ultrashort pulse laser, which has extremely high brightness, a wide spectral range and good spatial coherence, and can generate a continuous white light source with a wavelength range of 400-1600nm, thereby providing a high signal-to-noise ratio original light signal for subsequent processes. By using the above scheme, the embodiment of the application can realize real-time monitoring of the entire VCSEL complex epitaxial structure by using one light source, thereby providing data support for accurate control of the growth process and process optimization, and significantly improving product yield and performance consistency.

[0050] The light splitting unit is configured to split the ultrashort pulse laser source into a reference light beam and a measuring light beam according to a preset ratio.

[0051] Specifically, the preset ratio is set according to the measurement accuracy requirement, and exemplarily, the preset ratio in the embodiment of the application is set to 1:9, that is, 10% of the ultrashort pulse laser source is divided into a reference light beam and irradiated to a fixed irradiation surface; 90% of the ultrashort pulse laser source is divided into a measuring light beam and vertically irradiated to the surface of the wafer under test. Exemplarily, the light splitting unit in the embodiment of the application adopts a beam splitter, and in other embodiments, a fiber beam splitter, a customized diffractive optical element (DOE), or a half-transmission half-reflection mirror can also be selected as needed.

[0052] The reference irradiation surface is configured to receive the reference light beam and generate a reference light signal according to the reference light beam.

[0053] Specifically, the reference irradiation surface is made of a material with a fixed reflectivity, constituting a standard reference mirror surface. The reference mirror surface can provide a stable and known reflected light signal in the subsequent data detection process, thereby calibrating the errors introduced by light source fluctuations or environmental interference in the measurement process.

[0054] Referring to Figure 4 Optionally, the processing module comprises: a first detector, a second detector, a lock-in amplifier, an operation unit and a control unit.

[0055] The input ends of the first detector and the second detector are connected with the wavelength selection module. The first detector is configured to convert the first narrow-band light into a corresponding first electrical signal; and the second detector is configured to convert the second narrow-band light into a corresponding second electrical signal.

[0056] The lock-in amplifier is configured to synchronously demodulate the first electrical signal and the second electrical signal to obtain a first lock-in signal and a second lock-in signal.

[0057] Specifically, the purpose of the lock-in amplifier is to selectively extract the weak signal component with the same frequency as the reference from the strong noise background under the known modulation reference, and extract the amplitude and / or phase as the output, while suppressing the direct current drift and non-same-frequency noise in the first electrical signal and the second electrical signal.

[0058] Further, the lock-in amplifier in the embodiment of the present application is a double-channel lock-in amplifier. The first electrical signal and the second electrical signal are sent into the input end of the lock-in amplifier in parallel, and the common modulation reference is connected to the reference end of the lock-in amplifier. The lock-in amplifier first locks the common modulation reference and generates the local oscillator in phase or quadrature. Under the common trigger and unified integration time, the first electrical signal and the second electrical signal are subjected to phase-sensitive multiplication with the local oscillator and low-pass integration with the same time constant and filter order, and finally the first lock-in signal and the second lock-in signal are obtained in the same integration window. The common modulation reference can be taken from the synchronous output of the amplitude jitter of the acousto-optic tunable filter, and the acousto-optic tunable filter is provided with a synchronous reference output port with the same frequency as the amplitude jitter. The integration window refers to the sampling window entered after the acousto-optic tunable filter is quickly switched to a stable state.

[0059] The operation unit is configured to perform differential operation on the first lock-in signal and the second lock-in signal after balancing based on the pre-calibrated channel matching parameters to obtain a differential operation result.

[0060] Optionally, the operation unit comprises: a programmable gain amplifier and a differential amplifier.

[0061] The programmable gain amplifier is configured to balance the second lock-in signal based on the pre-calibrated channel matching parameters.

[0062] The differential amplifier is configured to perform differential operation on the first lock-in signal and the second lock-in signal after the second lock-in signal is leveled, and obtain a differential operation result.

[0063] Specifically, the channel matching parameter refers to a plurality of parameters obtained and stored in a calibration stage to offset the inherent difference between the measurement channel and the reference channel, which are usually obtained by measuring a standard part and pre-stored in a table, and the corresponding channel matching parameter values can be obtained by looking up the table according to the current wavelength in subsequent applications. Exemplarily, the channel matching parameter includes at least one of a gain leveling parameter, a zero point, a configuration item, a temperature drift compensation item, and a time drift compensation item.

[0064] The leveling is to adjust the amplitudes of the first lock-in signal and the second lock-in signal to the same scale to maximize the common mode component in the subsequent differential operation. Since the first lock-in signal is derived from the real reflected light signal of the wafer surface to be measured, active attenuation or gain adjustment of the signal distorts the real physical signal and may directly introduce system errors. Based on this, the present application only levels the second lock-in signal representing the reference signal.

[0065] By using the above scheme, the processing module converts the two collected light signals into corresponding two electric signals at each preset wavelength, extracts useful components by synchronously demodulating the two electric signals respectively, and obtains two lock-in signals; then levels the lock-in signal representing the reference signal to adjust the amplitudes of the two lock-in signals to the same scale, and finally performs differential operation on the two adjusted signals to obtain a differential operation result.

[0066] The control unit is configured to calculate the reflectivity of the wafer to be measured according to the differential operation result, determine the growth parameter of the epitaxial layer based on the reflectivity, and adjust the process parameter of the reaction cavity according to the growth parameter to control the epitaxial growth of the wafer to be measured.

[0067] Optionally, the control unit calculates the reflectivity according to the differential operation result, including: taking the second lock-in signal as a reference, performing amplitude standardization on the differential operation result to obtain a standardization result; and converting the standardization result based on a preset calibration coefficient to obtain the reflectivity.

[0068] Specifically, the lock-in signal of the reference channel is used as a reference in the embodiment of the present application, which is normalized to a unit scale at the current wavelength point, and the differential operation result is scaled to the unit system by the same proportion to obtain a dimensionless normalized value, and the standardization result is obtained.

[0069] The calibration coefficient is used to represent the proportional relationship between the differential operation result and the reflectivity, and can be obtained by pre-measuring a standard sheet with known reflectivity. For example, at each preset wavelength, the differential operation result is obtained based on the standard sheet, and the calibration coefficient is the result of dividing the reflectivity of the standard sheet by the differential operation result. Finally, the calibration coefficients of all preset wavelengths are obtained and stored in a table. During actual operation, the reflectivity at the wavelength can be calculated by querying the corresponding calibration coefficient.

[0070] The control unit determines the growth parameters of the epitaxial layer according to the reflectivity, including: the control unit inputs the reflectivity into an optical interference model to calculate the thickness of the epitaxial layer. Further, according to the rate of change of the thickness of the epitaxial layer over time, the growth rate can also be calculated.

[0071] Referring to Figure 5 Optionally, the epitaxial growth control device further comprises a signal separation module.

[0072] The signal separation module is configured to extract a direct current or low frequency component from the first electrical signal and / or the second electrical signal to obtain a radiation signal representing thermal radiation in the reaction chamber.

[0073] Specifically, the electrical signal output by the detector is a superposition of multiple components, wherein the direct current or low frequency part in the electrical signal is mainly derived from the spontaneous thermal radiation of the wafer and the reaction chamber. By extracting this part of the signal, a radiation signal representing the thermal radiation in the reaction chamber can be obtained. Further, the signal separation module extracts the direct current or low frequency component by at least one of low-pass filtering, notch filtering of the same frequency and harmonics of the modulated reference, integral period averaging and / or gated integration.

[0074] Further, the control unit is further configured to determine the growth parameters of the epitaxial layer according to the reflectivity and / or the radiation signal, and to adjust the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer under test.

[0075] Since the radiation signal is essentially the intensity of the thermal radiation of the substrate, it has a monotonic correspondence with the temperature, so based on the radiation signal, the temperature of the substrate can also be obtained.

[0076] Further, the control unit determines the growth parameters of the epitaxial layer according to the reflectivity and / or the radiation signal, and adjusts the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer under test, including:

[0077] For a measurement period, at each preset wavelength, the control unit calculates the growth parameters according to the reflectivity and the radiation signal; wherein the growth parameters include at least one of the thickness of the epitaxial layer, the temperature of the substrate and the growth rate.

[0078] After the screening of all the preset wavelengths is completed, the output of each growth parameter is summarized; each growth parameter is compared with the preset process setting range.

[0079] If the comparison result exceeds the preset requirement, the process parameters of the reaction chamber are adjusted according to the preset rule to control the epitaxial growth of the wafer under test.

[0080] Specifically, the length of the measurement period can be set as needed, which should be greater than the time required to complete the screening of all the preset wavelengths. Further, the above-mentioned preset requirement can also be set according to the measurement accuracy requirement. For example, in the case of high accuracy requirement, it can be set that each growth parameter meets the preset process setting range to be considered as meeting the preset requirement; in the case of general accuracy requirement, it can be set that the growth parameter corresponding to the key wavelength meets the preset process setting range to be considered as meeting the preset requirement.

[0081] For one processing technology, there are at least one process recipe, each process recipe is associated with a specific process target, and contains a set of process parameters that are pre-optimized to achieve the process target, and the upper and lower limit ranges of the growth parameters allowed by the machine when executing the process according to the process parameters.

[0082] Before the process starts, the control unit uploads the generated process recipe to the manufacturing execution system (MES), and the MES system stores and schedules the recipe after receiving the process recipe, and issues the corresponding control instructions to the target machine during process execution; the target machine calls the corresponding process parameters according to the control instructions and executes the epitaxial growth process, thereby ensuring that the process flow automatically runs according to the predetermined process recipe.

[0083] When executing the process, the control unit detects the reflectivity and / or radiation signal under each preset wavelength one by one in a measurement period, and then calculates the growth parameter and compares it with the preset process setting range. If the comparison result exceeds the preset requirement, the process parameters of the reaction chamber are adjusted according to the preset rule and uploaded to the MES system, so that the MES system generates new control instructions to control the epitaxial growth of the wafer under test. The preset rule is used to represent the corresponding relationship between the growth parameter and the process parameter, which can be a functional relationship, a lookup table relationship, or an empirical rule. Illustratively, when the substrate temperature is detected to be higher than the set upper limit, the preset rule indicates to reduce the heating power or increase the cooling gas flow; when the epitaxial layer thickness is detected to be insufficient, the preset rule indicates to increase the source flow or extend the growth time; when the growth rate is detected to be low, the preset rule indicates to increase the reaction chamber pressure or increase the precursor flow.

[0084] It should be understood that the process flow includes multiple stages, and the process parameters in the process recipe are different for each stage. The process parameters adjusted in the embodiments of the present application are only for the current stage, and if the growth parameters of other stages are not detected to be abnormal, the process parameters of the stage are maintained unchanged. Further, if the comparison result is within the preset process setting range, the process parameters are also maintained unchanged.

[0085] Further, the comparison method can be a one-by-one comparison method, that is, each acquired growth parameter is compared with the corresponding set range one by one to determine whether it is within the set value interval; in addition, the comparison method can also be a dynamic trend comparison, that is, whether the change law of the growth parameter with the wavelength or time meets the requirement of the preset process setting trend is analyzed.

[0086] Specifically, in the embodiments, the process parameters include at least one of source flow, temperature, pressure, component ratio, precursor switching parameter, and doping parameter; wherein the precursor switching parameter includes at least one of pre-flow time, overlap time, underlap time, purge time length, and growth interruption time. It should be noted that the above-mentioned component ratio, precursor switching parameter, and doping parameter are associated with different material layers alternately grown, and by adjusting the above-mentioned parameters, the alternately grown layer system (DBR / MQW) can be stabilized at the target specification.

[0087] In the next measurement cycle, the control unit repeats the above steps until the entire process flow is completed.

[0088] Please refer to Figure 6 Optionally, the epitaxial growth control device further includes a spectrometer.

[0089] The spectrometer is configured to monitor the first narrowband light and / or the second narrowband light to obtain optical path information, wherein the optical path information includes at least one of center wavelength, bandwidth, and spectral purity information, and the optical path information is used for judging the selection wave effectiveness.

[0090] Specifically, in the embodiments of the present application, a high-speed spectrometer is selected, a small proportion of light is extracted at the output end of the acousto-optic tunable filter, and the extracted small amount of light is sent into the high-speed spectrometer. It should be understood that the trigger signal of the spectrometer is shared with the acousto-optic tunable filter and the lock-in amplifier, and the exposure time of the spectrometer is aligned with the sampling window of the acousto-optic tunable filter. For example, the control unit triggers the acousto-optic tunable filter to quickly switch to the target wavelength, triggers the spectrometer to expose after a preset delay, so that the spectrometer acquires the narrowband spectrum line in the sampling window, and then processes the narrowband spectrum line to obtain the optical path information. The control unit determines whether the values of the optical path information are within the preset threshold range, and if any of the values is not within the range, it is considered that the selection wave effectiveness requirement is not met, and automatic correction is performed and re-sampling is triggered.

[0091] The above scheme can ensure that the collected light signal has a correct center wavelength and acceptable passband quality, and further improves the detection accuracy.

[0092] Please refer to Figure 7 , the following will be combined Figure 7 The working process of the epitaxial growth control device of the present application is described in detail:

[0093] During the detection process, the irradiation module continuously outputs the supercontinuum spectrum laser light source, which simultaneously irradiates the surface of the wafer under test in the epitaxial growth process and the surface of the reference irradiation surface, generating measurement light signals and reference light signals.

[0094] For one measurement period:

[0095] The light path collection module synchronously collects the measurement light signals and the reference light signals.

[0096] The wavelength selection module, according to the control instructions of the processing module, synchronously scans and filters the measurement light signals and the reference light signals in a predetermined order, to obtain first narrowband light and second narrowband light with the same center wavelength at different predetermined wavelengths.

[0097] The processing module converts the first narrowband light and the second narrowband light into first electrical signals and second electrical signals respectively; synchronously demodulates the first electrical signals and the second electrical signals to obtain first lock-in signals and second lock-in signals; performs differential operation on the second lock-in signals after balancing and the first lock-in signals, to obtain a differential operation result; and calculates the reflectivity according to the differential operation result.

[0098] The signal separation module extracts direct current or low frequency components from the first electrical signals and / or the second electrical signals to obtain radiation signals.

[0099] Further, the processing module calculates growth parameters of each predetermined wavelength according to the reflectivity and / or the radiation signals; wherein the growth parameters include at least one of epitaxial layer thickness, substrate temperature and growth rate. In the case where the target wavelength in the wavelength list is completed, the processing module outputs all growth parameters of this round, and compares each growth parameter with a preset process setting range, if the comparison result exceeds the preset requirement, adjusts the process parameters of the reaction chamber according to the preset rule to control the epitaxial growth of the wafer under test; if the comparison result meets the preset requirement, the current process parameters are maintained, and the current cycle is completed.

[0100] During the above detection process, the spectrometer monitors the first narrowband light and / or the second narrowband light in real time, and if it does not meet the selected wave effectiveness requirement, it performs automatic correction and triggers re-sampling.

[0101] In the next measurement period, the above steps are repeated until the entire process flow is completed.

[0102] The epitaxial growth control device adopts an ultrabroadband laser light source to irradiate the surface of the wafer under test and the reference irradiation surface during the epitaxial growth process, and adopts an acousto-optic tunable filter to quickly switch to any one feature wavelength point, so that multiple feature wavelength points can be quickly scanned in one process step, multi-parameter synchronous monitoring is realized, and the demand of the VCSEL complex epitaxial structure is adapted. Further, the application adopts a double-beam differential measurement technology of a measurement light signal and a reference light signal to eliminate common-mode noise in the measurement process in real time, greatly improves the signal-to-noise ratio, improves the measurement accuracy, and realizes closed-loop accurate control in the epitaxial growth process.

[0103] Each module in the epitaxial growth control device can be realized by software, hardware, and a combination thereof, in whole or in part. Each module can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a memory in a computer device in software form, so as to be called and executed by a processor to perform the operations corresponding to each module.

[0104] Based on the same inventive concept, the embodiment of the application also provides an epitaxial growth control method, which is applicable to the epitaxial growth control device. The implementation scheme for solving the problem provided by the method is similar to the implementation scheme described in the device, so the specific limitations in one or more method embodiments provided below can be referred to the limitations of the device described above, which will not be repeated here.

[0105] Please refer to Figure 8 In one embodiment, the application provides an epitaxial growth control method, specifically comprising the following steps:

[0106] Step 802, obtaining a reflected light signal. The reflected light signal includes a measurement light signal and a reference light signal. The measurement light signal is generated by reflecting a preset light source on the surface of the wafer under test during the epitaxial growth process, and the reference light signal is generated by reflecting the preset light source on the reference irradiation surface. The preset light source is an ultrabroadband laser light source.

[0107] Step 804, synchronously scanning and filtering the measurement light signal and the reference light signal to output first narrowband light and second narrowband light with the same center wavelength at any time.

[0108] Step 806, converting the first narrowband light and the second narrowband light into electrical signals and then performing differential operation to suppress common-mode noise, and calculating the reflectivity of the wafer under test according to the differential operation result.

[0109] Step 808, determining the growth parameters of the epitaxial layer based on the reflectivity, and adjusting the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer under test.

[0110] Optionally, the differential operation after converting the first narrow-band light and the second narrow-band light into electrical signals comprises: converting the first narrow-band light and the second narrow-band light into corresponding first electrical signals and second electrical signals respectively; performing synchronous demodulation on the first electrical signals and the second electrical signals to obtain first lock-in signals and second lock-in signals; and performing the differential operation after leveling the first lock-in signals and the second lock-in signals based on pre-calibrated channel matching parameters to obtain a differential operation result.

[0111] Optionally, the reflectivity of the wafer under test is calculated according to the differential operation result, comprising: taking the second lock-in signal as a reference, performing amplitude normalization on the differential operation result to obtain a normalized result; and performing conversion on the normalized result based on a pre-set calibration coefficient to obtain the reflectivity.

[0112] Optionally, the epitaxial growth control method further comprises:

[0113] The direct current or low frequency component is extracted from the first electrical signal and / or the second electrical signal to obtain a radiation signal representing thermal radiation in the reaction chamber; the growth parameters of the epitaxial layer are determined according to the reflectivity and / or the radiation signal, and the process parameters of the reaction chamber are adjusted according to the growth parameters to control the epitaxial growth of the wafer under test.

[0114] Optionally, the process parameters of the reaction chamber are adjusted according to the reflectivity and / or the radiation signal to control the epitaxial growth of the wafer under test, comprising: for one measurement period, at each pre-set wavelength, the growth parameters are calculated according to the reflectivity and / or the radiation signal; wherein the growth parameters include at least one of the epitaxial layer thickness, the substrate temperature and the growth rate; after screening all pre-set wavelengths, the growth parameters are output; the growth parameters are compared with a pre-set process setting range; if the comparison result exceeds the pre-set requirement, the process parameters of the reaction chamber are adjusted according to a pre-set rule to control the epitaxial growth of the wafer under test; the process parameters include at least one of the source flow, the temperature, the pressure, the component ratio, the precursor switching parameter and the doping parameter. The epitaxial growth control method uses a super-continuum spectrum laser source to irradiate the surface of the wafer under test and the reference irradiation surface during the epitaxial growth process, and uses an acousto-optic tunable filter to quickly switch to any one characteristic wavelength point, which can quickly scan multiple characteristic wavelength points in one process step, realize multi-parameter synchronous monitoring, and adapt to the demand of VCSEL complex epitaxial structure; further, the application uses a double-beam differential measurement technology of measurement light signal and reference light signal to eliminate common-mode noise in the measurement process in real time, greatly improves the signal-to-noise ratio, improves the measurement accuracy, and realizes closed-loop precise control in the epitaxial growth process.

[0115] It should be understood that although the steps in the flowcharts involved in the embodiments described above are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, at least some of the steps in the flowcharts involved in the embodiments described above can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be alternately or alternately executed with at least part of other steps or steps or stages in other steps.

[0116] In a feasible embodiment, a computer device, which can be a terminal, has an internal structure diagram as shown in Figure 9 The computer device includes a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface, the display unit and the input device are connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium to run. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used for wired or wireless communication with external terminals, and wireless communication can be achieved through WIFI, mobile cellular network, NFC (Near Field Communication) or other technologies. The computer program is executed by the processor to implement the epitaxial growth control method described above. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball or touchpad arranged on the shell of the computer device, or an external keyboard, touchpad or mouse, etc.

[0117] Those skilled in the art can understand that Figure 9 The structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different component arrangement.

[0118] In an implementable embodiment, a computer device is provided, comprising a memory and a processor, the memory storing a computer program, and the processor implementing the method steps in the epitaxial growth control method when executing the computer program.

[0119] In an implementable embodiment, a computer readable storage medium is provided, storing a computer program, and the computer program implementing the method steps in the epitaxial growth control method when executed by a processor.

[0120] In an implementable embodiment, a computer program product is provided, comprising a computer program, and the computer program implementing the method steps in the epitaxial growth control method when executed by a processor.

[0121] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. Any reference to memory, database or other medium in the embodiments provided by the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided by the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided by the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0122] Any combination of the technical features in the above embodiments can be made. For the sake of brevity, the foregoing description has not described all possible combinations of the technical features in the above embodiments. However, as long as the combination of the technical features does not contradict, it should be considered within the scope of the present disclosure.

[0123] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An epitaxial growth control method, characterized by, The method comprises: acquiring a reflected light signal, wherein the reflected light signal comprises a measurement light signal and a reference light signal, the measurement light signal is generated by reflecting a preset light source by a wafer surface to be measured in an epitaxial growth process, and the reference light signal is generated by reflecting the preset light source by a reference irradiation surface, the preset light source is an ultrashort supercontinuum laser source; the preset light source is divided into a measurement light beam and a reference light beam according to a preset ratio, the measurement light beam is vertically irradiated to the wafer surface to be measured, and the reference light beam is irradiated to the reference irradiation surface; synchronously scanning and filtering the measurement light signal and the reference light signal to output first narrowband light and second narrowband light with the same center wavelength at any time; performing differential operation on the first narrowband light and the second narrowband light after converting the first narrowband light and the second narrowband light into electrical signals to suppress common-mode noise, and calculating the reflectivity of the wafer to be measured according to the differential operation result; wherein the step of differential operation comprises: converting the first narrowband light and the second narrowband light into corresponding first electrical signals and second electrical signals respectively; synchronously demodulating the first electrical signals and the second electrical signals to obtain first lock-in signals and second lock-in signals; performing differential operation on the second lock-in signals based on pre-calibrated channel matching parameters and the first lock-in signals to obtain a differential operation result; determining the growth parameters of the epitaxial layer based on the reflectivity, and adjusting the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer to be measured.

2. The method of claim 1, wherein, The method further comprises: extracting a direct current or low frequency component from the first electrical signal and / or the second electrical signal to obtain a radiation signal representing thermal radiation in the reaction chamber; determining the growth parameters of the epitaxial layer based on the reflectivity and / or the radiation signal, and adjusting the process parameters of the reaction chamber according to the growth parameters to control the epitaxial growth of the wafer to be measured.

3. The method of claim 1, wherein, The method further comprises: for one measurement period, at each preset wavelength, the growth parameters are calculated according to the reflectivity and / or the radiation signal; wherein the growth parameters include at least one of the epitaxial layer thickness, the substrate temperature and the growth rate; after screening all preset wavelengths, the growth parameters are outputted; 4. The method of claim 3, wherein, comparing the growth parameters with a preset process setting range; if the comparison result exceeds the preset requirement, adjusting the process parameters of the reaction chamber according to a preset rule to control the epitaxial growth of the wafer to be measured; the process parameters include at least one of the source flow, the temperature, the pressure, the component ratio, the precursor switching parameter and the doping parameter. The device comprises: ​ ​ 5. An epitaxial growth control apparatus characterized by comprising: ​ An irradiation module is configured to output a supercontinuum laser source and irradiate a wafer under test in an epitaxial growth process to generate a measurement light signal and irradiate a reference irradiation surface to generate a reference light signal; The irradiation module comprises a light splitting unit configured to split the supercontinuum laser source into a reference light beam and a measurement light beam according to a preset ratio; A light path collection module is configured to collect a reflected light signal, wherein the reflected light signal comprises the measurement light signal and the reference light signal; A wavelength selection module is configured to synchronously scan and filter the measurement light signal and the reference light signal to output first narrowband light and second narrowband light with the same center wavelength at any time; A processing module is configured to perform differential operation on the first narrowband light and the second narrowband light to suppress common-mode noise, and the processing module comprises a first detector, a second detector, a lock-in amplifier, and an operation unit; The first detector is configured to convert the first narrowband light into a corresponding first electrical signal; The second detector is configured to convert the second narrowband light into a corresponding second electrical signal; The lock-in amplifier is configured to synchronously demodulate the first electrical signal and the second electrical signal to obtain a first lock-in signal and a second lock-in signal; The operation unit is configured to perform differential operation on the second lock-in signal after leveling and the first lock-in signal based on pre-calibrated channel matching parameters to obtain a differential operation result; The processing module is further configured to calculate reflectivity of the wafer under test based on the differential operation result, determine growth parameters of an epitaxial layer based on the reflectivity, and adjust process parameters of a reaction chamber based on the growth parameters to control epitaxial growth of the wafer under test.

6. The apparatus of claim 5, wherein, The irradiation module further comprises: a light source generator configured to output a supercontinuum laser source; a reference irradiation surface configured to receive the reference light beam and generate a reference light signal based on the reference light beam.

7. The apparatus of claim 5, wherein, The processing module further comprises: a control unit configured to calculate reflectivity of the wafer under test based on the differential operation result, determine growth parameters of an epitaxial layer based on the reflectivity, and adjust process parameters of a reaction chamber based on the growth parameters to control epitaxial growth of the wafer under test.

8. The apparatus of claim 5, wherein, The operation unit comprises: a programmable gain amplifier configured to level the second lock-in signal based on pre-calibrated channel matching parameters; a differential amplifier configured to perform differential operation on the first lock-in signal and the leveled second lock-in signal to obtain a differential operation result.

9. The apparatus of claim 5, wherein, The apparatus further comprises: a spectrometer configured to monitor the first narrowband light and / or the second narrowband light to obtain light path information, wherein the light path information is used for judging wave selection effectiveness, and the light path information comprises at least one of center wavelength, bandwidth, and spectral purity information.

10. The apparatus of claim 9, wherein, The apparatus further comprises: a signal separation module configured to extract a direct current or low frequency component from the first electrical signal and / or the second electrical signal to obtain a radiation signal representing thermal radiation in a reaction chamber. The processing module is further configured to determine growth parameters of the epitaxial layer according to the reflectivity and / or the radiation signal, and adjust process parameters of a reaction cavity according to the growth parameters to control epitaxial growth of the wafer under test. 11.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-10. The computer program, when executed by the processor, implements the steps of the method of any one of claims 1-4.

12. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program, when executed by the processor, implements the steps of the method of any one of claims 1-4.

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