Marcello Riva

Superior etch performance of Ar/N 2 /F 2 for PECVD chamber clean

F<inf>2</inf> gas mixtures offer ideal properties to be employed as chamber cleaning gas: low dissociation energy and high reactivity, which leads to superior efficiency and ease of abatement. In this work, a new F<inf>2</inf> gas mixture was used with a combination ratio of 10% Ar, 20% F<inf>2</inf> and 70% N<inf>2</inf> in order to obtain a maximum of 20% fluorine in inert gases. This novel Ar/N<inf>2</inf>/F<inf>2</inf> gas mixture has been evaluated as a candidate to replace conventional cleaning gases, like NF<inf>3</inf>, C<inf>2</inf>F<inf>6</inf> and CF<inf>4</inf> in an industrial AMAT P5000 CVD chamber tool. Standard equipment has been used, showing complete compatibility with the new gas. The tested Ar/N<inf>2</inf>/F<inf>2</inf> mixture shows improvements in both parameters, cleaning at a faster rate (up to more 27%), even requiring a lower amount of gas (minus 96% versus NF<inf>3</inf>). The higher etching rate and the lower gas consumption assure a sensible CoO (Cost of Ownership) advantage to any potential user. The superior etch rate performance of the Ar/N<inf>2</inf>/F<inf>2</inf> gas mixture was combined with excellent etch non uniformities values, of °3% (1sigma) on SiO<inf>2</inf> and of °8% (1sigma) on Si<inf>3</inf>N<inf>4</inf>, respectively. Also amorphous Silicon (a-Si) was etched completely and uniformly. The particle performance data showing in average just 14 particle adders (0.25µm), indicating that no significant particle contamination was induced by the process and Ar/N<inf>2</inf>/F<inf>2</inf> can be used as a highly clean and efficient etching gas as well as an ideal drop-in replacement for the conventional cleaning gases.