Micro-Raman spectral analysis of the subsurface damage layer in machined silicon wafers

In the present work we studied the depth of damage layer in machined silicon wafers that was incorporated with chemical etching using micro-Raman spectroscopy. Subsurface damage causes changes in the shape and intensity for the shoulder (450-570 cm^-1) of the most intense band (519 cm^-1) and the second band (300 cm^-1) regions of the Raman spectrum. Etching reduces the thickness of the damage layer and, hence, the intensities at the shoulder and the second band. The intensities at the shoulder and the second band become stable when the damage layer is completely etched out. The shoulder consists of two Gaussian profiles: the major and the minor. The band for the major profile is independent of etching depth, but the band for the minor profile shifts toward the longer wave numbers with increasing etching period until the damage layer is completely etched out. The depth of the damage layer is determined by the profiles of the shoulder and the second band and confirmed by the band shift of the minor profile. Transmission electron microscopy (TEM) further verified the results with respect to the depth of the damage layer. TEM observation showed that dislocations and stacking faults are responsible for the subsurface damage.