Shallow Etch Pits

Shallow Etch Pits

Material Name: Silicon
Record No.: 107
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: The same kind of shallow etch pits, shown in Fig 1, are formed on the etched surface when it is exposed to oxygen plasma before etching. The main difference between shallow etch pits caused by FexOy particles and those caused by oxygen plasma is that the latter pits are always like twins. This kind of etching result indicates that the oxygen plasma induced stacking faults to the crystal structure. Stacking faults are a type of crystal defect having a twin structure like the shallow etch pit in Fig 1.
Reference: Petteri Kilpinen, KOH anisotropic silicon etching for MEMS accelerometer fabrication, PhD Thesis, Aalto University, 2014, p. 110.

Figure 1: Microscope picture of anisotropic KOH wet etched single crystalline silicon wafer surface with wide twin etch pit induced by oxygen plasma.