INFLUENCE OF CARBON-MONOXIDE GAS ON SILICON DIOXIDE DRY-ETCHING

For narrow gap reactive ion etching (RIE) of SiO2 using CF4, CHF3 and Ar chemistry at a pressure range of 30 to 70 Pa, we found that a highe r selectivity of Si can be obtained by adding CO gas to the plasma, Ou r optical plasma emission spectrum data showed that not only C atoms b ut also C+ ions were produced by this addition of CO gas. By controlli ng the gas now rate of CF4, the selectivity of Si can be controlled, b ecause the CF4 gas flow rate controls the CFn polymer deposition. Howe ver; we believe that, for mass production, it is better to eliminate C Fn polymer deposition completely to gain higher selectivity of Si, whi ch we achieved by increasing the carburization ratio (SiC/Si or SiC/Si N) by adding CO gas. This improves the selectivity of Si or SiN, and a higher selectivity of photo resist can be obtained.