Outline Advanced Topographic Resistivity Analysis Of Semi-insulating SiC Substrates Wolfgang Jantz , Rudolf Stibal , Stefan Müller , Ruyue Yan and Jianmin Hao 1a 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 ntactless sistivity pping CO RE MA Capacitive probe chuck chuck wafer wafer guard guard electrode electrode 1 mm measured volume air gap 1 mm measured volume air gap 1 mm measured volume air gap Equivalent circuit Equivalent circuit t =R s (C s +C a ) Equivalent circuit U U U t =R s (C s +C a ) Charge transient after voltage step application 0 ¥ t t 0 Q Q Charge transient after voltage step application 0 ¥ t t 0 Q Q 0 ¥ t t 0 Q Q ¥ t t 0 Q Q t t 0 Q Q S.i. SiC Crystal Growth Q 0 / Q ¥ = Cs / (Cs+Ca) r = Q 0 t (Q ¥ ee 0 ) -1 Evaluation of electrical material properties Resistivity r = Q 0 t (Q ¥ ee 0 ) -1 Mobility μ = 1/B [ r(B) / r(0) - 1] ½ Activation energy E a = (kT 1 T 2 )/(T 2 -T 1 ) * ln [r(T 1 ) / r(T 2 )] R s = r d/A C s = ee 0 A/d R s C s = ree 0 d A d A Semi-insulating semiconductor Resistivity Activation Energy 2.0 2.2 2.4 2.6 2.8 3.0 3.2 10 5 10 6 10 7 10 8 10 9 10 10 10 11 Rho (Ohm*cm) 1/Temperature (1000/K) s.i. SiC Activ. 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 3x10 5 – 1x10 10 Ohm*cm Not semi-insulating at 300 ° C 150 mm GaAs wafer Mean: 3.96x10 7 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 respective volume contributions. We show that local inhomogeneity results in a temperature dependent activation energy. Resistivity Measurement Mobility Measurement Activation Energy Position B, Volume = 58% Position C, Volume = 10% Position D, Volume = 50% Position A, Volume = 100% Resistivity Topogram Volume Topogram