# Homework Help: Graphs analysis Microelectronics

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1. Nov 15, 2015

### gl0ck

1. The problem statement, all variables and given/known data
Hello,
I have to estimate the junction depth and layer thickness from the graph I am given.
I know that when Phosphorus and boron are crossing, at this point is the Junction depth. What about the oxide layer grown, how would you estimate its thickness?

For the second graph how we can decide which element has been used to dope the initial wafer?

Thanks

2. Nov 15, 2015

### phyzguy

In both cases, do you understand what causes the step discontinuity on the left hand side of the graphs?

3. Nov 15, 2015

### gl0ck

No actually, I would guess Abrupt pn junction or what happens when a N-type semiconductor is in contact with a P-type semiconductor?

4. Nov 15, 2015

### gl0ck

What I got found is for the first plot shows, phosphorus concentration, and the donor boron concentration as a function of depth in an N-type wafer, subject to a p-type diffusion, and for the second one, the net dopant concentration |Na - Nd| as a function of depth for the n-type wafer that has been subjected to a p-type diffusion.
If that is correct as stated in the given, that phosphorus implant is made into a boron-doped wafer.
Would this mean that the initial wafer for the second plot is either boron or gallium? I tend to think is boron, as I can see it more often than the gallium. Am I correct?

What I can also add to the previous reply to the phyzguy's question is that when the both dopants cross to the left is Na>Nd (effectively p-type material) and to the right is Nd > Na (effectively n-type material)

5. Nov 16, 2015

### phyzguy

No. The step discontinuity at the dotted line on the left side of the plots is the Si/SiO2 interface. The region to the left of the dotted line is SiO2, and the region to the right is the Si. Notice in the first graph how the Boron is preferentially included in the SiO2, and the Phosphorous is preferentially excluded.

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