Overetched Mo with H2SO4 : HNO3 : H2O, 5:3:2 Ratio

Overetched Mo with H2SO4 : HNO3 : H2O, 5:3:2 Ratio

Material Name: Mo
Record No.: 150
Primary Chemical Element in Material: Mo
Sample Type: Thin film
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: Because there was no pre-made solution for molybdenum wet etching, several recipes had to be tested. The first recipe involved a combination of H2SO4, HNO3, and water. The problem with this solution was that the etching was too fast and too strong (at a ratio of 5:3:2, respectively), and the first couple attempts showed that the solution actually penetrated through the photoresist layer. Even when the concentration of H2SO4 and HNO3 were diluted by adding more water, the etching was still too fast for the purposes of this experiment.
After multipletries,a reasonable etch ratio was found: 30 mL H3PO4, 18 mL HNO3, 10 mL CH3COOH, 65 mL H2O. The etch rate for this solution was approximately ~40 Å/s.
Reference: Jim Tai, Sputtering, Electrical Conductivity and Wet Etching of Molybdenum Films, 2007, https://w3.pppl.gov/ppst/docs/tai.pdf.

Figure 1: Overetched Mo with H2SO4 : HNO3 : H2O, 5:3:2 ratio.