ECE 305 Homework #10
Due Friday, April 30
Problem 1:
Consider a MOS capacitor, in which the semiconductor is grounded and a bias is
applied to the gate.
We measure the CV relationship shown below.
a)
is the semiconductor ntype or ptype?
b)
is the MOS structure “ideal”? (i.e. is the sample flatband at zero bias?)
c)
find the oxide thickness, assuming that the capacitor has an area of 0.01 cm
2
.
It may be
helpful to remember that Si has a relative dielectric constant of 12.1 and that SiO
2
has a
relative dielectric constant of 3.9.
d)
the curve shown is for a “high frequency” measurement.
Briefly explain how the curve would
change is we made a lowfrequency measurement.
Problem 2:
Suppose that we have a metal/oxide/(psilicon) structure in which the
semiconductor is doped at N
A
= 1x10
17
cm
3
, the oxide thickness is 10 nm and T=300K. The
structure is ideal, which implies that flatband conditions would occur at zerobias.
We start the
analysis with a bias applied to the device which brings us to the onset of inversion.
Note that the
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 Spring '08
 MELLOCH
 Gate, 0.5 microns, 10 nm, bias point, 5 microns

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