Deep reactive ion etching of silicon using an aluminum etching mask

A method for fast and efficient deep etching of bulk silicon, using parallel capacitively coupled plasma is presented. The effects of the masking materials and RIE conditions are discussed. Based on the experimental results, a 1000 /spl Aring/ thick Al film sufficiently protects the unexposed substrate while allowing the etching of a 350 /spl mu/m deep hole with an area of 3/spl times/3mm/sup 2/ when etching with SF/sub 6//CHF/sub 3//O/sub 2/ plasma. A 2000 /spl mu/m long and 100 /spl mu/m wide (with layers of Al/SiO/sub 2//Si and thickness of 0.1/spl mu/m/2.2/spl mu/m/40/spl mu/m respectively) cantilever has been achieved. A silicon etch rate up to 2.5 to 2.8/spl mu/m/min has been obtained and an anisotropy of A = 0.5 (A=I-V/H, where V=horizontal undercut, H=etch depth) has been obtained. The technique was developed mainly for bulk micromachining of silicon or composite silicon cantilever structures.