Transcript p-type resistance change

Measurements of
Piezoresistive
Coefficients in Lightly
Doped (111) Silicon
Chun Hyung Cho & John Sunwoo
Electrical & Computer Engineering
Auburn University
OUTLINE

Introduction

Piezoresistive Theory

Results of Measurements

Discussion

Conclusion
INTRODUCTION

Stress due to mechanical loadings

Degradation of performance

Stress analyses of electronic packages
and their components have been
performed
INTRODUCTION(continued)


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The basic application
concepts
Semiconductor chips
are incorporated into
electronic packages
The sensors have most
often been resistors
Schematic of normal 4PB
fixture
Basic BMW2 Test Chip (200 x 200 mils)

The doped active region is
typically designed using a
serpentine pattern

Electrical isolation between
the doped surface resistor
and the bulk of the chip
(111) silicon wafer & stressinduced resistance changes
Result: p-type resistance
change
Typical vaule: B1p =507/TPa, B2p = -145/TPa
R90/R90 vs. Stress: P-type (111 Silicon)
2.0000E-03
0.0000E+00
 R/R
-2.0000E-03
0
20
40
60
-4.0000E-03
-6.0000E-03
-8.0000E-03
y = -1.249E-04x + 1.453E-04
R2 = 9.986E-01
-1.0000E-02
-1.2000E-02
Uniaxial Stress (:Mpa)
80
100
Result: n-type resistance
change
Typical vaule: B1n =-230/TPa, B2n = 207/TPa
 R90/R90 vs. Stress: n-type (111 Silicon)
1.4000E-02
1.2000E-02
y = 1.967E-04x
R2 = 9.967E-01
1.0000E-02
 R/R
8.0000E-03
6.0000E-03
4.0000E-03
2.0000E-03
0.0000E+00
-2.0000E-03
0
10
20
30
40
50
Uniaxial Stress (:Mpa)
60
70
Discussion: Typical piezo-resistive
coefficient values for BMW2
Typical Piezoresistive Coefficient Values For BMW -2
Test Chips (TPa)-1
Piezoresistiv e
p-type
n-type
Coefficient
Silicon
Silicon
B1
507
-230
B2
-145
207
[From J. C. Suhling, R. W. Johnson, and R. C. Jaeger]
DISCUSSION

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
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
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IntelliSuite software is used
Under-estimated result
Measured resistance changes was
assumed to be independent of T
Beam rotation error
Loading symmetry error
Weight and length measurement error
CONCLUSION




Measurements of piezoresistive coefficients
in lightly doped (111) silicon
Applications of piezoresistive sensors in
electronic packaging.
The sensors are not mounted on the chips.
Integral part of the structure to be analyzed
by the way of the fabrication process.
CONCLUSION (Continued)


The sensor are capable of providing
non-intrusive measurements of surface
on chip even within encapsulated
packages.
Piezoresistive stress sensors have much
higher sensitivity than metallic stress
sensors.