DRY ETCHING OF AL-ALLOY FILMS USING HBR MIXED GASES

Al/1%Si films were dry-etched at 20-degrees-C using an HBr/BCl3 or HBr/BCl3/Cl2 plasma. Conventional reactive ion etch equipment was used. Etch rates of the Al films and photoresist, self DC bias, and selectivities for photoresist and thermal oxide were studied as functions of RF power, gas pressure, gas flow rate ratio, and total gas flow rates. A 0.9-mu-m/min etch rate, a 6.8 photoresist selectivity, and a 18.9 thermal oxide selectivity were obtained for the former plasma. A 2.3-mu-m/min etch rate, a 7.7 photoresist selectivity, and a 45.5 thermal oxide selectivity were obtained for the latter plasma. Etched Al films showed highly anisotropic profiles with very slight etch residues for both plasma. Consequently, very high selectivities as well as high Al etch rates and anisotropy were obtained using HBr containing gases.