Sacrificial layers for widely tunable capacitors
Micromachined two-gap widely tunable capacitors have been fabricated with a tuning ratio of 7.3:1. The design presented requires sub-micron air gaps to enable low voltage operation and to reduce electrode curvature during operation. Photoresist and titanium have been evaluated for use as sacrificial layers in these devices. Organic deposits remaining after the sacrificial etching of photoresist make it inappropriate for use as a primary sacrificial layer. Titanium, however, etches cleanly and introduces additional surface topology into the capacitive electrodes which is beneficial for stiction avoidance. Stiction-free released device yields up to 90% have been observed.
