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本文使用计算机模拟技术,研究了SOI结构中各部分的电势分布和载流子分布.模拟结果表明:对于有均匀掺杂的P型再结晶硅膜的SOI结构,当硅膜厚度小平相应的最大耗尽层厚度时,会出现“薄体效应”.它表现为:在内层氧化层厚度一定时,再结晶膜愈厚,阈电压愈高;在再结晶膜厚度一定时,内层氧化层愈厚,阈电压愈低,最后达到一个定值,与内层氧化层的厚度无关.正界面电荷进一步降低了由P型再结晶膜构成的SOI结构的阈电压.模拟计算表明,为使SOI结构不出现薄体效应,设计原则就是使适当掺杂的再结晶膜厚度大于最大耗尽层厚度.在硅膜厚度小于最大耗尽层厚度时,为使薄体效应的影响减小,应该采用比较低的硅膜掺杂浓度,比较厚的内层氧化硅层.模拟计算表明,利用薄体效应,可以形成以单晶硅为衬底的,阈电压较低的新型薄膜MOS晶体管.模拟计算还表明,对于薄硅膜的SOI结构,用耗尽层近似推出的阈电压公式是一个简单和比较准确的公式.
In this paper, the potential distribution and carrier distribution of each part of SOI structure are studied by using computer simulation.The simulation results show that for the SOI structure with uniformly doped P-type recrystallization silicon film, when the thickness of silicon film is correspondingly the largest Depletion layer thickness, there will be a “thin body effect.” It showed: the thickness of the inner oxide layer, the recrystallization film thicker, the higher the threshold voltage; recrystallization film thickness, the inner oxide layer The thicker the threshold voltage is, the lower the threshold voltage reaches a certain value, which is irrelevant to the thickness of the inner oxide layer.The positive interface charge further reduces the threshold voltage of the SOI structure formed by the P-type recrystallization film.The simulation shows that for the SOI The structure does not appear thin body effect, the design principle is to properly doped recrystallization film thickness greater than the maximum depletion layer thickness in the silicon film thickness is less than the maximum depletion layer thickness, in order to reduce the effect of thin body should be used A relatively low doping concentration of the silicon film, and a relatively thick inner silicon oxide layer. The simulation results show that the thin film transistor can form a new type of thin film MOS transistor with a lower threshold voltage using a thin film effect. It is also shown that for thin silicon films S OI structure, using depletion layer approximation of the threshold voltage formula is a simple and more accurate formula.