Process materials (gases and chemicals)
In oxide etching, why are carbon-rich fluorocarbon gases such as C4F8 used?
- ATo make the etch rate zero
- BBecause they readily form polymer (passivation film), making it easier to achieve high selectivity to the underlayer and mask
- CTo eliminate the need for plasma
Show answer and explanation
Answer: B. Because they readily form polymer (passivation film), making it easier to achieve high selectivity to the underlayer and mask
Carbon-rich fluorocarbon gases readily form polymers of carbon and fluorine in the plasma. On oxide, oxygen in the film removes the polymer so etching proceeds, but on silicon and nitride the polymer accumulates and suppresses etching, giving high selectivity.