Research And Design Of High Precision Temperature Measurement System For Epitaxy Process

It has bright prospects in applications of optoelectronics,high frequency microwave devices and power electronic devices.Metal Organic Chemical Vapor Deposition(MOCVD)method is the latest generation of compound semiconductor device manufacturing technology.MOCVD equipment has been widely used in industry because of its excellent quality and mass production capacity of its epitaxial semiconductor devices.As the NIR wavelength can be permeable through silicon epitaxial materials,the MOCVD epitaxial materials can only be used to measure the Pocket temperature at the bottom of the epitaxial film when the silicon epitaxial materials are grown by the epitaxial materials.However,the epitaxial growth of quantum wells is very sensitive to temperature.Therefore,how to precisely measure the surface temperature of epitaxial wafers is of great significance.Thisresearch activity iscomprehensive andmeticulously discusses thespecific method for realizingthe surface temperaturecontrol of silicon epitaxy andthe desian of relatedmeasuring equipment.The specific research processsteps are as follows:(1)After comparing varioustemperature measurementmethods,considering thespecial properties of thematerial,it was finally decidedto obtain the surfacetemperature value bymeasuring the thermalradiation in the near-ultravioletband.This method of weaksignal measurement and themethod of removingbackground noise are studiedaccording to thecharacteristics of signal andnoise.(2)Based on the specialstructure of the MOCVDdevice,a matching on-linetemperature control systemwas developed.The systemsspecial mechanicalconstruction and advancedvertical incidence probe opticsmake it extremely small.At the same time,the design of the large field of view for anti vibration and optical path probes makes the reflection signal intensity change less than 2% within the range of 1 tilt angle of the probe.(3)In the circuit,the amplification of the photomultiplier tube and the constant power control of the LED light source are realized in the circuit.According to the software system,the power switching of the signal magnification of the photomultiplier signal and the LED light source under the condition of the temperature corresponding to the current temperature is designed to make the reflected light signal of the LED light source are in equal order of magnitude with the current heat radiation signal intensity and have a strong output signal.(4)Test the designed temperature control system by means of experiments and field tests.According to the experimental results,the system can measure the temperature in the range of 750 to 1 200 ?,and the measurement results have a repeatability are not more than 10 ?.The accuracy of the system is slightly different for different temperature ranges.As a whole,in the measurement range of the system,the higher the temperature,the higher the accuracy of the measurement result.When the temperature exceeds 1 000 ? the error will be within 0.2.When the measured temperature is lower than 870 ?,the error will be within 3 ?.The temperature control system accurately measures the epitaxial surface temperature and is validated by the PrismoD-Blue 485 MOCVD device.