CN-122016672-A - Asynchronous reference differential reflection spectrum system and method for MOCVD rotary sample stage

CN122016672ACN 122016672 ACN122016672 ACN 122016672ACN-122016672-A

Abstract

The invention relates to an asynchronous reference differential reflection spectrum system and method for a MOCVD rotating sample stage, wherein the system comprises a light source module, a reference light path module, a reflection light path module and a signal processing module, wherein the light source module is used for generating a wide spectrum light beam, the light source module comprises a halogen tungsten lamp, an LED and an optical fiber beam combiner, the two light sources are coupled through the optical fiber beam combiner to form a wide-band light source, the light source intensity of 400 nm to 800 nm wave bands is ensured to be proper, the incident light path module is used for collimating the light beam to the surface of a sample in a MOCVD cavity, the reference light path module is used for carrying out intensity calibration on the light beam emitted by the light source, the reflection light path module is used for converging the reflection light of a measuring light path and the reflection light of the reference light path and transmitting the light to a spectrum detection component, and the signal processing module is used for carrying out light intensity threshold judgment, spectrum average calculation and differential reflection spectrum calculation.

Inventors

SHEN WANFU
FAN GUOSHUAI
HUANG JINGTAO

Assignees

天津大学

Dates

Publication Date: 20260512
Application Date: 20260318

Claims (8)

1. An asynchronous reference differential reflectance spectrum system for a MOCVD-oriented rotating sample stage, comprising: the light source module is used for generating a wide spectrum light beam and comprises a halogen tungsten lamp, an LED and an optical fiber beam combiner, and the two paths of light sources are coupled through the optical fiber beam combiner to form a wide-band light source, so that the light source intensity of 400 nm to 800 nm bands is proper; the incident light path module is used for collimating the light beams to the surface of the sample in the MOCVD cavity; The reference light path module is used for carrying out intensity calibration on the light beam emitted by the light source; The reflection light path module is used for converging the reflected light of the measurement light path and the reflected light of the reference light path and transmitting the converged reflected light to the spectrum detection component; and the signal processing module is used for judging the light intensity threshold value, calculating the spectrum average value and calculating the differential reflection spectrum.
2. The MOCVD-oriented rotating sample stage asynchronous reference differential reflection spectrum system according to claim 1, wherein the incident light path module comprises a collimator, a plano-convex lens, a diaphragm and a beam splitter, the collimator is used for converting a divergent light beam emitted from the optical fiber into an approximately collimated light beam, the plano-convex lens is used for improving the beam collimation, the diaphragm is used for adjusting the beam size, the beam splitter is used for reflecting the incident light beam to a reference light path, transmitting the incident light beam to the surface of a sample in the MOCVD cavity to form a measuring light path, and reflecting and transmitting the light beams reflected by the sample and the reference sample in the cavity into the reflecting light path module respectively.
3. The MOCVD-oriented rotating sample stage asynchronous reference differential reflectance spectrum system of claim 1 wherein the reference light path module comprises an optical shutter and a reference sample, the optical shutter is configured to control opening and closing of the reference light path, to measure dark noise of the system when the optical shutter is closed, to measure reference light intensity signal when the optical shutter is open, and the reference sample is identical to the sample blank substrate for reflecting the reference light intensity into the reflected light path module.
4. The MOCVD-oriented rotating sample stage asynchronous reference differential reflectance spectroscopy system of claim 1 wherein the reflected light path module comprises a short focal length plano-convex lens for converging the reflected light beam, a multimode fiber held by a fiber holder, and a spectrometer, the multimode fiber held by the fiber holder collecting the converged light beam and entering the spectrometer.
5. An asynchronous reference differential reflectance spectrum measurement method for a MOCVD-oriented rotary sample stage, implemented on the basis of the system according to any of claims 1-4, characterized by comprising the steps of: S1, starting a light source module, closing a light shutter, enabling a light beam to be incident to the surface of a planetary disc but not irradiate a sample to be detected, and collecting dark noise of a system; s2, adjusting an incident light path to maximize the received reflected light intensity; s3, opening the optical shutter, placing the reference sample in the reference light path module and adjusting the reference sample so as to maximize the received reflected light intensity; S4, determining the number of sample pieces, a light intensity threshold value, the number of required points in the sample piece to be tested and the number of required points outside the piece according to the rotating speed of the planetary disc; s5, measuring, namely calculating real-time reflectivity by utilizing a signal processing module to calculate spectrum data of a sample to be measured in the rotating planetary disc, namely distinguishing reference light and a measuring light signal through a light intensity threshold value, and calculating a differential reflection spectrum based on the initial reflectivity.
6. The method for asynchronous reference differential reflectance spectroscopy measurement for a MOCVD-oriented rotating sample stage according to claim 5, wherein the resolving of the signal processing module in step S5 comprises: based on the intensity of light at a particular wavelength, distinguishing the light intensity of a reference light path through a light intensity threshold measuring the light intensity of the light path superposition reference light path; After calculating the average value of the spectrum intensities of the reference light path and the measuring light path, determining the reflectivity of the sample to be measured at the corresponding moment when the sample to be measured rotates once by utilizing the ratio of the reference light path and the measuring light path; Because the sample table is in a rotating state, the spectrum average values of the reference light path and the measurement light path respectively correspond to different moments in each circle, thereby forming an asynchronous reference mode; The reflectivity at the current moment and the reflectivity at the initial moment are subjected to difference value operation and normalization to obtain a differential reflection spectrum value of the corresponding moment of each circle, wherein the specific formula is as follows: Wherein, the For a particular wavelength of light to be used, In order to rotate the corresponding moment of each turn, In order to rotate the introduced time shift, For the actual light intensity superimposed by the reference light path and the measuring light path at the current moment, For the actual reference light path intensity corresponding to the current moment, For the original light intensity of the superposition of the reference light path and the measuring light path at the current moment, For the original reference light path light intensity corresponding to the current moment, To calculate the reflectivity at each current time, the system dark noise measured when the optical shutter is closed is calculated: Wherein, the For the reflectivity at the current moment, carrying out difference value operation and normalization on the reflectivity and the reflectivity at the initial moment to obtain a differential reflection spectrum signal at the corresponding moment of each circle: Wherein, the For the differential reflection spectrum at the current instant, Is the reflectivity at the initial moment.
7. The method for measuring asynchronous reference differential reflectance spectrum of a MOCVD rotary sample stage according to claim 6, characterized in that the specific wavelength is 600nm.
8. The method for measuring the asynchronous reference differential reflectance spectrum of the MOCVD rotary sample stage according to claim 5, wherein the method for measuring the asynchronous reference differential reflectance spectrum of the MOCVD rotary sample stage comprises the step of rotating a planetary disc at a rotating speed The calculation formula of (2) is as follows: Wherein, the And (3) with And respectively measuring the time when the edge of the same sample to be measured is measured in the nth turn and the n-1 th turn, namely measuring the time when the single-wavelength light intensity signal corresponding to the same sample to be measured reaches a preset light intensity threshold value.

Description

Asynchronous reference differential reflection spectrum system and method for MOCVD rotary sample stage Technical Field The invention belongs to the technical field of optical measurement, relates to an optical in-situ measurement technology with high efficiency, high precision and high stability for film thickness, optical constants and film growth key parameters of two-dimensional materials, semiconductor nano films and typical semiconductors, and particularly relates to an asynchronous reference differential reflection spectrum system and an asynchronous reference differential reflection spectrum method for an MOCVD rotating sample stage. Background Metal organic chemical vapor deposition is an important epitaxial growth method, and is widely used for preparing semiconductor film materials, particularly in the preparation of compound semiconductors, two-dimensional materials and novel photoelectric devices. The MOCVD film growth process is highly dependent on accurate control of technological parameters such as temperature, gas flow, reaction pressure and the like, and small changes of film thickness, refractive index and coverage rate can obviously influence the performance of the device. Therefore, a rapid, nondestructive and non-contact in-situ monitoring system is developed in the growth process, so that the abnormal problem in the growth process can be captured in real time, the growth rate and thickness change of the epitaxial wafer can be accurately monitored, further, a quantitative regulation and control basis is provided for the epitaxial growth process, and finally, the preparation of a film material with higher quality is served. In situ monitoring in MOCVD systems is mainly based on optical methods suitable for medium pressure conditions and various gas environments. At present, the thickness in-situ monitoring technology of MOCVD grown films mainly adopts a reflection method based on interference effect, and the thickness of the films is calculated by monitoring the change of single-wavelength laser or wide-spectrum reflectivity. However, this approach is susceptible to long term drift of the light source, environmental disturbances, and noise disturbances. Under the condition of a fast rotating MOCVD sample stage, the problems are more remarkable, and the high-precision and high-stability real-time monitoring of the atomic-level ultrathin film is difficult to realize. In summary, the existing optical reflection spectrum system cannot realize low-cost long-time high-stability high-precision in-situ measurement of growing an ultrathin film in a rotary sample stage of MOCVD, so that the spectrum reflection method cannot meet the high-accuracy measurement requirement of film growth. Disclosure of Invention In order to solve the problems, the invention provides an asynchronous reference differential reflection spectrum system and an asynchronous reference differential reflection spectrum method for an MOCVD rotating sample stage, which are used for reducing signal high-frequency fluctuation by adopting a high-stability wide-spectrum light source, and simultaneously introducing an asynchronous reference light path, so that the influence of long-term drift of the light source on a measurement result is effectively inhibited, and the high-stability and high-sensitivity measurement requirements of MOCVD film growth can be met. The technical proposal is as follows: an asynchronous reference differential reflectance spectrum system for a MOCVD-oriented rotating sample stage, comprising: the light source module is used for generating a wide spectrum light beam and comprises a halogen tungsten lamp, an LED and an optical fiber beam combiner, and the two paths of light sources are coupled through the optical fiber beam combiner to form a wide-band light source, so that the light source intensity of 400 nm to 800 nm bands is proper; the incident light path module is used for collimating the light beams to the surface of the sample in the MOCVD cavity; The reference light path module is used for carrying out intensity calibration on the light beam emitted by the light source; The reflection light path module is used for converging the reflected light of the measurement light path and the reflected light of the reference light path and transmitting the converged reflected light to the spectrum detection component; and the signal processing module is used for judging the light intensity threshold value, calculating the spectrum average value and calculating the differential reflection spectrum. The incident light path module comprises a collimator, a plano-convex lens, a diaphragm and a beam splitter, wherein the collimator is used for converting divergent light beams emitted by an optical fiber into approximately collimated light beams, the plano-convex lens is used for improving the beam collimation, the diaphragm is used for adjusting the beam size, the beam splitter is used for reflecting the incident l