Subsurface Damage Caused by Coarse Grinding

Subsurface Damage Caused by Coarse Grinding

Material Name: Silicon
Record No.: 105
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: Grinding
Etchant Name: None
Etching Method: Grinding
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: Coarse grind and fine grind surfaces which are etched for about 60 seconds in 20 wt- % and 60 °C KOH are shown in Figs 1a and 1b. On the etched surface, it can see cracks caused by coarse grinding which are enlarged in KOH etching. KOH etchant penetrates into the cracks and etches the surrounding silicon much faster because in the crack there are many other crystal planes to attach which etch much faster than the (100) surface plane. This phenomenon can be seen when the fine grind removal is too shallow and the subsurface damage caused by coarse grind is not removed totally in the fine grind process step.
Reference: Petteri Kilpinen, KOH anisotropic silicon etching for MEMS accelerometer fabrication, PhD Thesis, Aalto University, 2014, pp. 48-49.

Figure 1: Fine-grind silicon surface, preferential etched with KOH (20 wt-% and 60 °C) for 60 s, which still has subsurface damage caused by coarse grinding.