TCAD Analog Research Based On VDMOS Structure Parameters

With the rapid development of the power electronic technology, high performance and voltage power device VDMOS become more and more important. Although we have made progress in manufacture of VDMOS power device, we have not achieved a mature stage in process. Because of the advantage in the excellent performance and self-property right, device made in foreign countries occupied a great share of the market. Therefore, the research on technological process and process control has practical significance.In this paper, a VDMOS device which has reliable performance (threshold voltage is 3.2V, breakdown voltage is 500V) is selected. The package and Aluminum layer on the surface of chip has been removed by thermal decomposition of concentrated sulfuric acid, and internal lead wire has been analyzed. Through observing and testing the chip surface by scanning electron microscope (SEM), the surface structure and vertical structure parameters has been obtained.Based on the extracted structure parameters, technological process and conditions are designed by the ATHENA module of Silvaco. Then cell structure model of VDMOS has been obtained. All the results got in process simulation has been introduced into device simulation software ATLAS. The transfer characteristic, output characteristic, breakdown voltage and switching time of the cell are simulated. The simulation results indicate the breakdown voltage is 515V, threshold voltage is 3.2V, opening time is 0.28μs, turn off time is 0.19μs.Through the process of structure dissection, process simulation and device simulation, a reverse design will be completed. The performance of devices on which oxide thickness, P-well concentration and the outer temperature influence has been analyzed. The research results indicate that transfer characteristic shifts to right gradually and threshold voltage increases with the increasing of oxide thickness and P-well concentration. When oxide thickness increases, threshold voltage improves linearly. Within the temperature range of -50~125℃, the threshold voltage decreases with the increase of temperature.