Raman microspectroscopy study of processing-induced phase transformations and residual stress in silicon

Raman spectroscopy was used for analysis of phase transformations and residual stress in machined silicon. Wear debris from dicing of silicon was scanned with a Raman spectrometer. Recorded spectra manifest the presence of amorphous Si, hexagonal phase (Si-IV), bc8 phase (Si-III) and pristine Si-I under residual stress. On surfaces of diced wafers as well as lapped silicon wafers, the r8 phase (Si-XII) was detected in addition to the above phases. The composition of phases in diced cross sections of silicon wafers differs dramatically between high and low speed cuts. The quantification of these phases was attempted by curve fitting each spectrum with corresponding peaks of each phase. Subsequently, relative intensity maps of specific phases were generated. Thus, Raman spectroscopy studies of machined surfaces demonstrated metallization of Si under a variety of machining conditions including lapping, grinding, scratching, dicing and slicing. All metastable phases of silicon disappear after etching and polishing of respective wafers. No evidence of phase transformations was found on a quartz-damaged silicon wafer surface. Residual stress having a characteristic distribution was observed in this case.