The Research And Preparation Of 4H-SiC PIN Type Solar Blind UV Detector

UV detector is a dual-use detector and has important applications in missile warming, water quality testing, severe weather forecasting and other fields.4H-Si C has the characteristics of wide bandgap, high breakdown electrical field, high thermal conductivity and high carrier saturation drift rate, etc. These make it one of the ideal materials for the preparation of UV detector. With respect to the early silicon-based UV detector, 4H-Si C UV detector has the advantages of good visible-blind, no expensive filter system, can be operated at room temperature and low dark current, etc. Researches on 4H-Si C PIN UV detector are related to reports in recent decades, UV detector of PIN structure has a low noise, high quantum efficiency and fast response speed.In this paper, based on the design of device structure and material parameters, Sentaurus device simulation software is used to simulate the electric and spectral response characteristics of 4H-Si C PIN type UV detector. It was found that :(1)The change of the pdoped layer doping concentration or thickness has little influence on the dark current. Reducing the concentration or the thickness of the p-doped layer will help improve the photocurrent and spectral response and the wavelength of the peak spectral response will be moved to the short-wave direction;(2)Within a certain range, the change of the i-layer doping concentration or thickness has little influence on the dark current and photocurrent. Reducing the concentration or increasing the thickness of the i-layer will help improve the spectral response and the wavelength of the peak spectral response will be moved to the long-wave direction. Through the simulation, we can find that the changes of the p-doped layer material parameters have more significant influences on the photocurrent and spectral response of the device with respect to the intrinsic layer.It also presents three methods to reduce the surface reflectivity and improve the external quantum efficiency. The feasibility of these three methods is verified by the simulation. These three methods are reducing the area of the positive electrode, adding an antireflection film and increasing the surface roughness of the device. The former two methods is quite easy to implement, and therefore the design of the two methods should be considered in the preparation of the device. For the third method, we usually use the patterned surface to increase the surface roughness of the device in the process. And this method requires high technology of the preparation of the device.Finally, the relevant experiments of the preparation of the device have been carried on. The main key processes include standard wafer cleaning, lithography, lift-off, ICP dry etching, thermal oxidation and ohmic contact electrode, etc. We have done a major study on the lithography, lift-off, ICP dry etching of 4H-Si C and 4H-Si C p-type ohmic contact experiments:(1)In the lithography and lift-off experiments, we use a positive photoresist to lithograph and magnetron sputtering to deposit the metal. Finally, the metal is stripped in acetone and the results of the lift-off meet the requirements of the experiment;(2)In the 4HSi C ICP etching experiment, we use a mixed gas of SF6 and O2 and the gas flow rate is respectively 50 sccm and 10 sccm. The profile after etching is relatively steep;(3)In the 4HSi C p-type ohmic contact experiment, the electrode metals are Ti/Al(30nm/120nm). After lift-off, the metals are annealed at 1000℃ in the atmosphere of N2. After measurement and calculation, the result of the specific contact resistivity is about 5.37×10-4Ω?cm2. During the experiments, the appropriate process scheme is determined by the results and the reproducibility of each process.