SIMS ANALYSIS OF EPITAXIAL LAYERS FOR POWER-ELECTRONICS AND MICROELECTRONICS

This paper gives an overview of recent secondary ion mass spectrometry (SIMS) studies of impurities and dopants in epitaxial layers of silic on and 6H silicon carbide (SiC). Detection limits in the 10(12) cm(-3) range are demonstrated for transition metal impurities like Ti in SiC . Hydrogen is found to be mobile in SiC at temperatures in excess of 6 00 degrees C despite strong trapping by defects and dopant atoms, and the effective diffusion coefficient exhibits an activation energy of s imilar to 3.5 eV. In epitaxially grown Si layers, containing Ge delta distributions, profile broadening and shift during sputtering by Ar+ i ons are accurately described by recoil mixing. For O-2(divided by) ion s oxide formation and surface swelling must also be considered. Furthe r, at elevated sample temperature Ge is found to segregate out of the SiO2 surface layer formed during oxygen bombardment, consistent with a larger heat of oxide formation for Ge than Si and a high enough mobil ity in SiO2. (C) 1998 Elsevier Science B.V.