Electrical and Optical Detection and Heating of the High Pressure MetallicPhase of Silicon In-situ During Scratching with Diamond and its effect on thematerial’s hardness

Scratching experiments were carried out on silicon wafers (100) with diamond styli of nominal 2, 5, and 10 μm radius. Relevant parameters varied and investigated were: load (10 to 100 mN) and depth of penetration, material hardness, electrical current effects and measured resistance, and speed effects. Direct electrical heating of the metallic high pressure phase of silicon during scratching experiments with currents ranging from 1 mA to 1 A (for resistance heating the material) resulted in substantial thermal softening of the metallized silicon. In addition to the in-situ measurements, post process analysis included AFM and SEM imaging and analysis. For currents above 100 mA (and loads of 50 mN and higher), substantial electrical resistance heating took place resulting in estimated temperatures of 600°C and a corresponding dramatic drop in hardness to about one-half (6 GPa) the nominal ambient conditions value. Direct heating and subsequent softening of the high pressure metallic phase of silicon is proposed as a possible manufacturing augmentation mechanism to reduce tool wear and increase productivity for silicon processing. Further testing with infrared-optical heating will be discussed and reviewed.