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1
N.CHEUNG
EE143, Fall 2010
Homework Assignment #5 (Due Oct 8, Fri 9am)
Note: Different textbooks use either C(x) or N(x) to represent the concentration,
and Q or
to represent
the dopant dose.
Reading Assignment
1)
Jaeger
, Chapter 4 on diffusion [ Van der pauw’s Method (section 4.7.4) for sheet resistance and junction
profile measurement (section 4.8) are optional. ]
2)
Reprint in Bpsace
: Selected sections of Chapter 9 of Wolf and Tauber.
Qualitative
understanding only:
Section 9.2 Defects and Dopant Diffusion
Section 9.7 Anomalous Diffusion Effects
3)
Handout
: Notes on Doping Diffusion [ 2D Diffusion math and high concentration diffusion math for
refernce only]
Problem
1 Simple predep calculation (how to use the erfc function)
A boron predeposition step is performed into an ntype Si substrate with a background concentration
C
B
of
1
10
16
/cm
3
. The predeposition thermal cycle is 975
o
C for 15 minutes.
Given: Boron solid solubility at 975
o
C = 3.5
10
20
/cm
3
Boron diffusion constant at 975
o
C = 1.5
10
14
cm
2
/sec
(a) Calculate the junction depth x
j
.
(b) Calculate the incorporated
boron dose Q.
Problem 2
Predep followed by Drivein
A pn junction is to be formed 1
m from the surface in ntype Si substrate, which has a doping concentration
of 10
17
phosphorus atoms per cm
3
.
The junction is formed by a twostep diffusion of boron:
The predep is solidsolubility limited at 1000ｰC and the drivein is at 1100ｰC.
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This note was uploaded on 03/03/2012 for the course EECS 142 taught by Professor Ee142 during the Spring '04 term at University of California, Berkeley.
 Spring '04
 ee142

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