Improvement in the mechanical performance of Czochralski silicon under indentation by germanium doping

The mechanical properties of germanium-doped Czochralski (GCz) silicon have been investigated using instrumented nanoindentation combined with an ultrasonic pulse-echo overlap technique. The GCz silicon samples showed higher Young’s modulus and hardness than germanium-free Czochralski silicon samples in nanoindentation tests. We believe this was caused by the enhanced phase transition from the Si-I phase to the stiffer Si-II phase in GCz silicon under contact load during indentation. This scenario was further confirmed by micro-Raman spectroscopy measurements.

Research highlights
► We report for the first time an improvement of mechanical properties of silicon by germanium doping under nanoindentation.
► Combined with ultrasonic pulse-echo overlap and micro-Raman spectroscopy techniques, we observed an enhancement of metallic phase transition during indentation in germanium doped silicon and it was suggested to be the mechanism of improved mechanical properties in germanium doped silicon.
► The present work gains an insight into mechanical properties of silicon at micro- and nanometer scales. Also it may provide a new approach to improving the mechanical performance of silicon wafers under contact loading and would be very beneficial for the semiconductor industry.