ELECTRON-CYCLOTRON RESONANCE ETCHING OF ALUMINUM-ALLOYS WITH BCL3-CL2-N2

Etching of submicron aluminum features is required in the manufacture of advanced integrated circuits. In this study the etching of aluminum-1% silicon-0.5% copper alloys with BCl3-Cl2-N2 chemistry has been characterized using a remote electron cyclotron resonance (ECR) plasma source. Mirror magnetic fields were used to modify the extracted plasma. The dependence of etch rate, uniformity, and selectivity has been measured as a function of gas flow rates, pressure, distance from the plasma source to the wafer, microwave power, and radio-frequency (rf) power applied to the wafer holder. Pressures in the range of 0.75 to 6.4 mTorr, microwave powers in the range of 600 to 1200 W, and rf powers in the range of 125 to 375 W were used. Optimal processes demonstrate etch rates above 1.0-mu/min, uniformities less than +/-4%, and selectivity to photoresist of 2.0 to 3.8. Etched feature profiles are vertical for submicron lines and spaces.