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众所周知,在N~+衬底上生长极低杂质浓度和极厚的N~-外延层是困难的。T.Suzuki等人利用三氯氢硅氢还原法在立式射频加热反应器内生长出杂质浓度为5～8×10~(13)cm~(-3)、150μm厚的N~-/N~+外延层;并用这种材料成功地制造出cb结击穿电压高达2300V的彩色电视机行输出管。显然,在生长极低杂质浓度外延层时,控制背景杂质浓度是极其重要的。背景杂质的来源有:(1)运载或还原气体、硅源化合物、管道系统、基座和支架、反应器、最终残留在衬底表面上的杂质等(以下统称工艺非控杂质);(2)自掺杂。因此,除了环境控制和外延工艺中的清洁工作外,重要的是抑制自掺杂效应,以使背景杂质浓度降低到足够低的水平。本工作采用多晶硅自封
It is well known that it is difficult to grow extremely low impurity concentrations and very thick N ~ - epilayers on N ~ + substrates. T. Suzuki et al. Used trichlorosilane hydrogen reduction method to grow N ~ - / N (superscript -) with impurity concentration of 5-8 × 10 ~ (13) cm ~ (-3) ~ + Epitaxial layer; and using this material successfully produced cb junction breakdown voltage up to 2300V color TV line output tube. Obviously, it is extremely important to control the background impurity concentration when growing extremely low impurity concentration epitaxial layers. Background impurities are sourced from: (1) impurities that carry or reduce the gas, silicon source compounds, piping, susceptors and supports, reactors, and ultimately residues on the surface of the substrate (hereinafter referred to as process uncontrolled impurities); (2) Self-doping. Therefore, in addition to cleaning work in environmental control and epitaxy processes, it is important to suppress self-doping effects so that the background impurity concentration is reduced to a sufficiently low level. This work uses polysilicon self-styled