Plasma etching of aluminum

Experimental plasma etching apparatus and methods utilizing BCl3etch gas have been developed for the accurate patterning of thin Al and Al-Si alloy metallization as used in integrated circuit fabrication. A two micron linewidth capability has been achieved for the patterning of 0.5 micron thick metallization on three inch diameter wafers with positive and negative photoresist etch masks as thin as 2500Å. Etchrates of 500 to 1000 Å/min. are typical, and there is negligible etching of both the photoresist and the underlying SiO2layers. The process is CMOS compatibles, yielding threshold voltage shift and temperature-bias stability specifications of less than ±0.050 volts that are comparable to those for wet chemically etched devices.