具有纵向辅助耗尽衬底层的新型横向双扩散金属氧化物半导体场效应晶体管

为了优化横向双扩散金属氧化物半导体场效应晶体管(lateral double-diffused MOSFET,LDMOS)的击穿特性及器件性能,在传统LDMOS结构的基础上,提出了一种具有纵向辅助耗尽衬底层(assisted depletesubstrate layer,ADSL)的新型LDMOS.新加入的ADSL层使得漏端下方的纵向耗尽区大幅向衬底扩展,从而利用电场调制效应在ADSL层底部引入新的电场峰,使纵向电场得到优化,同时横向表面电场也因为电场调制效应而得到了优化.通过ISE仿真表明,当传统LDMOS与ADSL LDMOS的漂移区长度都是70μm时,击穿电压由462 V增大到897 V,提高了94%左右,并且优值也从0.55 MW/cm~2提升到1.24 MW/cm~2,提升了125%.因此,新结构ADSL LDMOS的器件性能较传统LDMOS有了极大的提升.进一步对ADSL层进行分区掺杂优化,在新结构的基础上,击穿电压在双分区时上升到938 V,三分区时为947 V.

Novel lateral double-diffused MOSFET with vertical assisted deplete-substrate layer

Lateral double-diffused MOSFETs (LDMOS) are widely used in high voltage integrate circuits and smart power integrate circuits because of their lateral channels and their electrodes located on the surface of the device, thereby facilitating integration with other low-voltage circuits and devices, and they have become the core technology of the second electronic revolution. In order to optimize the breakdown characteristics and the performance of the LDMOS, in this paper, a novel LDMOS is proposed with the vertical assisted deplete-substrate layer (ADSL) on the basis of traditional LDMOS structure. The new ADSL layer makes the vertical depletion region below the drain expand to substrate excessively, thus introduces a new electric field peak at the bottom of the ADSL layer by using the electric field modulation effect, so that the vertical electric field is optimized. The ISE simulation results show that when the lengths of the drift region of ADSL LDMOS and traditional LDMOS are both 70 μm, the breakdown voltage is increased from 462 V to 897 V, improved by about 94%. Also, the figure-of-merit (FOM) is upgraded from 0.55 MW/cm² to 1.24 MW/cm², increased by 125%. Therefore, the new structure ADSL LDMOS has a great improvement in device performance compared with that of the traditional LDMOS. Moreover, authors have studied the ADSL LDMOS from three parts, all of these confirm that the new structure has a great potential application in power device. Firstly, through the lateral surface electric field distributions and vertical electric filed distributions of conventional LDMOS and ADSL LDMOS, a new electric field peak at the bottom of the ADSL is introduced in the vertical direction. Secondly, the mechanism for the new structure can present a deeper understanding through the ADSL LDMOS concentration and structural parameter optimization process. The FOM is optimized when the drift region concentration and ADSL concentration are 1.8×10¹⁵ cm^-3 and 6.5×10¹⁵ cm^-3, respectively, and it can reach a best value when the ADSL length is 40 μm. Thirdly, the ADSL layer is further partitioned and optimized. On the basis of the new structure, the breakdown voltage is increased to 938 V when the new structure is based on the dual partition, and in the triple partition the breakdown voltage reaches 947 V. In this paper, through simulations, the detailed analyses of the proposed new structure of the mechanism and its performance are conducted, and the breaking of the breakdown characteristics of silicon-based devices is of special significance for developing the lateral power devices.