最近上到diffusion.. 这个章节不是很了解 老师出了一个题目不知道该怎麽解 请各位大大 赐教 You are diffusing phosphorus,P(an n-type dopan) into undoped silicon wafer in a 1100 degree C furnace using a continuous supply of phosphine gas PH3 that establishes a surface P concentration of 5.00*10^18 atoms*cm^-3 1)is this a case of steady-state or non-steady state diffusion? why? 2)after the wafer has been in the furnace for 80mins, phosphorus has had a chance to diffuse into the wafer. qualitatively plot the concentration of phosphorus as a function of depth from the surface. what is the name of the mathematical function that has the same shape as this concentration profile? 3)at same time as in the graph you drew for part2( after 80mins), there will be a point withn the wafer where the P concentration is exactly 0.60 of surface P concentration. Calculate this depth, in nm. The pre-exponential coefficient Dο, for diffusion of P in Si is 10.5cm^2S^-1 and the activation energy of this diffusion is 3.69eV (per atom) 希望各位大大能帮忙小弟 解这一题.... --

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