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Advanced Topographic Resistivity AnalysisOf Semi-insulating SiC Substrates
Wolfgang Jantz , Rudolf Stibal , Stefan Müller , Ruyue Yan and Jianmin Hao1a 1a 1a 2b 2b
1 Semimap Scientific Instruments GmbH, Tullastr. 67, D79108 Freiburg, Germany
2 Electronic Material Research Institute of Tianjin, 26 Yanfeng Rd., Tianjin 300220, China
a [email protected] b [email protected]
COREMA System
Basics of ntactlesssistivity pping
CORE MA
Capacitive probe
chuckchuck
waferwaferguardguard
electrodeelectrode
1 mm
measured
volumeair gap
1 mm
measured
volumeair gap
1 mm
measured
volumeair gap
Equivalent circuitEquivalent circuit
t = Rs(Cs+Ca)
Equivalent circuit
UUU
t = Rs (Cs+Ca)
Charge transient aftervoltage step application
0
¥
tt0
Q
Q
Charge transient aftervoltage step application
0
¥
tt0
Q
Q
0
¥
tt0
Q
Q¥
tt0
Q
Q
tt0
Q
Q
S.i. SiC Crystal Growth
Q0/ Q¥ = Cs / (Cs+Ca)
r = Q0 t (Q¥ ee0)-1
Evaluation of electrical material properties
Resistivity r = Q0 t (Q¥ e e0)-1
Mobility µ = 1/B [ r(B) / r(0) - 1] ½
Activation energy Ea = (kT1T2)/(T2-T1) * ln [r(T1) / r(T2)]
Rs = r d/A
Cs = e e0 A/d
RsCs= r e e0
dA
dA
Semi-insulating semiconductor
Resistivity
Activation Energy
2.0 2.2 2.4 2.6 2.8 3.0 3.210
5
106
107
108
109
1010
1011
Rho
(Ohm
*cm
)
1/Temperature (1000/K)
s.i. SiCActiv. Energy: 816 meV
225 200 175 150 125 100 75 50
Temperature (°C)
Mobility measurement
150 mm GaAs wafer
2“ SiC wafer
Temperature range
40 – 200°C
Resistivity range
3x105 – 1x1010 Ohm*cm
Not semi-insulating at
300°C
150 mm GaAs wafer
Mean: 3.96x107 Ohm*cm
Stdv: 4.3 %
Radial variation
Fourfold symmetry
Dislocation network
The growing complexity and maturity of SiC
based high frequency, high power
microelectronic devices and modules
continually tightens the demand on the
electrical quality of semi-insulating SiC
substrates.
The topographic measurement system
COREMA-WT and the temperature dependent
measurement system COREMA-VT are used to
characterize exploratory 40 mm diameter SiC
wafers. We demonstrate that the combined
analytic capabilities of these tools allow a very
detailed assessment of the resistivity
distribution across the entire wafer area. Both
macroscopic variations, resulting from the
growth process, as well as local intermixtures
of material phases with different resistivities,
resulting from incomplete compensation, are
assessed with respect to absolute resistivity
values and the respect ive volume
cont r ibut ions. We show that loca l
inhomogeneity results in a temperature
dependent activation energy.
Resistivity Measurement
Mobility Measurement
Activation EnergyPosition B, Volume = 58%
Position C, Volume = 10%
Position D, Volume = 50%
Position A, Volume = 100%
Resistivity Topogram
Volume Topogram