Example of an Unsuccessful Cr Lift Off

Example of an Unsuccessful Cr Lift Off

Material Name: Silicon
Record No.: 56
Primary Chemical Element in Material: Wafer
Sample Type: Layer
Uses: Etching
Etchant Name: None
Etching Method: Dry etching
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: There were also unsatisfactory results when using the Cr lift-off process instead of the Cr wet etch. This was because of a thin metal film on top of the photoresist, which came into contact with the metal layer during deposition. This caused a ripping effect during lift-off, as shown in Fig. 9 and explained schematically in Fig. 10. This effect resulted in a rough edge on the metal hard mask in Fig. 9 (the holes shown in this figure were from an early mask design with 0.5-mm-diameter holes). These rough edges created undesirable distortions in the hole profiles.
Reference: Ankita Verma, Joshah Jennings, Ryan D. Johnson, Marc H. Weber, and Kelvin G. Lynn, Fabrication of 3D charged particle trap using through-silicon vias etched by deep reactive ion etching, J. Vac. Sci. Technol. B 31, 032001 (2013); doi: 10.1116/1.4799662.

Figure 9: Example of an unsuccessful Cr lift off.