(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

You use the solid diffusion source wafers PH-950 from St. Gobain (see data sheet on TSquare, Diffusion Chapter) to form phosphorous-doped resistors in a p-type wafer with a background doping concentration of 1015 cm-3. According to the data sheet, a 60-min predeposition at 925°C should yield a sheet resistance of 10 Ω/sq. and a junction depth of approx. xj = 1.3 μm.

(a) Verify these numbers by calculating (and plotting) the doping profile ND(x), the junction

depth xj, and the sheet resistance. Assume that the surface concentration reaches the solid

solubility at the pre-deposition temperature.

(b) What thickness must a masking oxide have to locally prevent P-diffusion?

2. Relevant equations

[tex]C(x,t)=C_serf\left\frac{x}{2\sqrt{Dt}}\right[/tex]

[tex]D=D_0^{-E_a/kT}+D_0_-^{-E_a_-/kT}+D_0_--^{-E_a_--/kT}[/tex]

3. The attempt at a solution

See attached

Briefly, I'm trying to plot concentration as a function of x, so I solved for D and plugged everything into the equation for C(x,t), with t=3600s. However, that returns an answer that the concentration > 0 only when the depth is < 0.19um. As the manufactuer claims a junction depth of 1.3um, I assume I did something very, very wrong.

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# Homework Help: Semiconductor: Solid-source Diffusion

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