Planarisation of Patterned Aluminium/Diamond Surfaces for SAWdevices

Abstract

AbstractA novel method for forming interdigitated electrodes for GHz Surface acoustic wave (SAW) devices on diamond using a damascene-like polishing technique is described. Low aspect ratio Al electrodes are recessed into the diamond substrates to create a near planar surface. This allows the deposition of higher quality oriented ZnO. CVD diamond samples were ion-beam etched with groove widths in the range 1-5μm to a depth of 80-120nm. Al (120nm thick) was sputter deposited on to the etched diamond and was polished using either (i) a solution of 0.05μm silica on a neoprene polishing cloth or (ii) using a ∼0.12mm thick PVDF (polyvinylidene difluoride) filter pad with colloidal solutions of silica. Using AFM scans and optical microscopy it was observed that the combination of method (i) with the small sample size resulted in significant hollowing-out of the Al electrodes and complete removal of Al from over 90% of the pad-interconnect area. The alternative technique in (ii) demonstrated far less Al removal and better uniformity in the electrode patterns.