HF/HNO3 Etching of the Saw Damage

Wet chemical etching of multicrystalline Si wafer in mixtures of hydrofluoric (HF) and nitric acid (HNO3) combines the removal of the saw damaged silicon lattice on top of the wafer with the creation of a certain surface morphology (texture) on the surface of the underlying bulk silicon. However, it is yet unclear how the kinetics of silicon etching, the constitution of the saw damage, and the resulting surface morphology are related to each other. As a first step to answer this question the etching of the saw damage was studied at three different levels: (i) The development of the surface morphology was studied with increasing etch depth. Regions of key morphological features were identified and parameters describing the morphological development were derived from the surface topography. (ii) The etch rate was studied as parameter that is very sensitive to changes regarding the bonding state of the etched silicon atoms. (iii) The surface chemistry of HF/HNO3 etched Si wafer was monitored by diffuse reflectance Fourier-transform infrared spectroscopy (DRIFT) in order to identify processes that are related to changes in the surface termination of silicon. By the combination of these three approaches a detailed picture from the etching of the saw damage, the development of the texture, and the interaction between structure and etch rate can be drawn.