SIMS quantification of Si1−xGex alloys using polyatomic secondary ions

The matrix effect in Si1-xGex alloys (x less than or equal to 0.5) grown by ultrahigh vacuum chemical vapour deposition was investigated with an O-2(+) primary beam in a Cameca IMS 6f instrument. The results showed that the matrix effect in Si1-xGex alloys was significant when the Ge fraction was > 0.25, and it turned out to be more pronounced at low impact energies. Nevertheless, the composition of Si1-xGex alloys could be quantified based on the linear variation of appropriate secondary ion intensity ratios against the Ge concentration. The use of polyatomic secondary ions to measure the composition of SiGe alloys is reported in this paper. By this method, both the dopant and matrix elements in a Si/Si1-xGex/Si heterojunction bipolar transistor sample have been quantified by SIMS. The germanium fractions thus determined agree well with values obtained by double-crystal x-ray diffraction. Copyright (C) 2001 John Wiley & Sons, Ltd.