Application Research On Characteristic Measurement Of Semiconductor Materials By Optical Cavity Ring-down Method

The rapid development of microelectronics and optoelectronics technology has put forward higher requirements for the integration of semiconductor devices and the performance of optoelectronic devices.The performance of the device is closely related to the doping and transport properties of the semiconductor material,and the analysis of the properties of the semiconductor material needs to be obtained by precise detection of the relevant parameters.Although the commonly used contact measurement method has high accuracy,it has certain damage to the device.The traditional optical method is easily affected by the fluctuation and noise of the detection light source and has low detection sensitivity and accuracy,which are difficult to meet the needs of accurate detection of the characteristic parameters of semiconductor materials.The cavity ring-down method has extremely high sensitivity to the measurement of the absorption loss of the medium in the cavity.Combined with the absorption characteristics of semiconductor materials,it is expected to be applied to the measurement of semiconductor materials characteristic parameters,which has important guiding significance for broadening the detection methods of semiconductor materials and improving the detection accuracy.This paper focuses on the application of the cavity ring-down method in the measurement of semiconductor material properties,and the main research contents are as follows:Firstly,based on the beam transmission characteristic matrix,the theoretical model of the optical resonator of the cavity and the test cavity is established;the calculation formula of the doping concentration and resistivity of the semiconductor material is deduced;and the model of sample misalignment error in symmetric confocal cavity and general stable cavity is established.The cavity signal characteristics,including cavity transmittance,cavity transmission signal,cavity ring-down signal and cavity ring-down time constant,are analyzed by simulation before and after sample addition.The influence of cavity structure parameters and sample characteristic parameters on the signal characteristics in the cavity is analyzed.Finally,the beam offset caused by sample misalignment in the two resonators is studied respectively.Secondly,a measurement scheme based on the cavity ring-down method for the measurement of the material properties of traditional semiconductor silicon wafers is studied.The key parameters of the measurement system are calculated according to the stable conditions of the resonator and the simulation results,and the structural parameters of the resonator and the basic characteristic parameters of the sample are determined.According to the performance requirements of the system and the device selected,the cavity ring-down measurement system is built,and the cavity ring-down signal is obtained.Then,the cavity ring-down signal is processed by statistical analysis method,which improves the efficiency and precision of data processing.The cavity ring-down time constants of the empty cavity and the test cavity under different cavity lengths are fitted,and the empty cavity loss and cavity mirror reflectivity values are obtained.The measured value of the cavity mirror reflectivity is basically consistent with the factory value,which confirms the reliability of the measurement system.Furthermore,the doping concentration and resistivity of samples with different thicknesses under different cavity lengths are calculated,and the error are analyzed.Finally,the transport characteristics of semiconductor materials are studied exploratively.Based on the theory of generation and recombination of carriers and carrier transport equation,the analytical expressions of the excess carrier concentration are derived in one-dimensional and three-dimensional cases respectively,and the functional relationship between carrier transport parameters and cavity ring-down signal is obtained.The effects of parameters such as carrier transport parameters and excitation light wavelength on the cavity ring-down signal are analyzed by simulation,which confirms theoretically the application potential of technique in the study of the transport properties of semiconductor materials.