The New Media Field Enhancement Of Soi High Voltage Device

SOI HVIC(Silicon On Insulator High Voltage Integrated Circuit) is the mainstream and trend of the Power Integrated Circuit (PIC) due to the improved isolation, reduced leakage current, high speed performance, low power dissipation, and perfect irradiation hardness. SOI lateral high voltage devices are the key devices in SOI HVIC. Its low vertical breakdown voltage and self-heat limit the application in high voltage and power integrated circuit. In this thesis, addressed the breakdown voltage and self-heat problems of SOI, under the guidance of ENDIF (Enhanced Dielectric layer Field), using MEDICI simulation and optimization of the three new structures of SOI high voltage devices. The breakdown mechanism and thermal mechanism have been discussed.1.PTSOI(oxide trenches on partial SOI)device. The structure is characterized by oxide trenches on the top and bottom interface of the buried oxide layer on partial SOI. Inversion charges located in the trenches enhance the electric field of the buried layer in the high-voltage blocking state. The dependences of breakdown voltage and thermal mechanism on the structure parameters are investigated by MEDICI. At breakdown mechanism: RESURF,breakdown voltage,doping of the drift,length of the Si window,the length /width/ height of trenches have been discussed. The results showed that: when Ld=90μm,Nd=1×1015cm-3,NS=2×1014cm-3,LS=45μm,Lw=40μm,tS=10μm,tI=2μm,H=1μm,D=2.5μm,W=2.5μm,PTSOI device has the highest breakdown voltage 933V. The buried-layer electric field 300V/μm is 3 times larger than conventional SOI which buried-layer electric field is 80V/μm. At thermal mechanism: Studied a silicon window makes the heat spread into the substrate, it alleviates the self-heating effect. The highest lattice temperature of PTSOI is lower 10K than conventional SOI. Introduced the processing of PTSOI . A series of new processes were discussed to solve the PTSOI materials problem, and the processing is simulated by TSUPREM4.2.LkPSOI (low k partial SOI) device. Based on PSOI structure, low-k (permittivity) dielectric layer has been leaded into buried layer. Enhancing the electric field of the buried layer, it makes the breakdown voltage rising. The dependences of breakdown voltage on the structure parameters are investigated by MEDICI. Such as doping of the drift,length of the Si window,permittivity of the low k material,thickness of the buried layer. The results show that: when tI=1μm,Ts=2μm,Ld=30μm,Lw=25μm,Nd=4.5×1014cm-3,NS=2×1014cm-3,the breakdown voltage is 375V. Compared with the conventional SOI improve by 134%. Becaues of the resolving of self-heating by silicon window, when k is 2, the highest lattice temperature of LkPSOI lower 135K than low-k SOI .3.VkSOI device. This structure with the low k dielectric buried layer under the drain, and with the Si3N4 buried layer under the source. The Si3N4 buried layer alleviates the self-heating effect. Its not only keeps the advantages of SOI such as: no parasitic capacitance and high speed, but also makes the breakdown mechanism and thermal mechanism better. Doping of the drift,length of the Si window,permittivity of the low k material,thickness of the buried layer have been simulated by MEDICI. The result show that: when the buried layer thickness is 1μm,k=2,length of the window is 20μm,BVmax=258V, Tmax=321K. Compared with the conventional SOI improve by 61.3%, the highest lattice temperature lower 10K than it.Overall, based on ENDIF, the breakdown mechanism and thermal mechanism of those three structures have been improved. So those structures are mostly fit for High Voltage Power Integrated Circuit.