REACTIVE ION ETCHING OF THIN GOLD-FILMS

Reactive ion etching of thin gold films using chlorine (Cl-2), carbon tetrafluoride (CF4), carbon tetrachloride (CCl4), and a mixture of these gases was investigated. Etch rates were studied by changing the etching gas composition, pressure, and power in a parallel-plate reactive ion etcher. Reactive ion etching of gold using Cl-2 or CCl4 yields a low etch rate and a carbon residue formation on etched surfaces. The introduction of CF4 to the Cl-2 did not improve the etch rate. However, the addition of CF4 to CCl4 was found to etch the carbon residue and significantly enhance the etch rate of gold. The etch rate of gold varies from 30 Angstrom/min using a chlorine plasma to 990 Angstrom/min using a mixture of CF4 and CCl4. For a mixture of CF4 and CCl4, the etch rate of gold was found to be twice the etch rate of positive photoresist, suggesting that positive photoresist is a practical mask for most applications involving the reactive ion etching of thin gold films.