DRY-ETCHING OF SI FIELD EMITTERS AND HIGH-ASPECT-RATIO RESONATORS USING AN INDUCTIVELY-COUPLED PLASMA SOURCE

An inductively coupled plasma (ICP) source has been used to generate a Cl-2 plasma for the etching of Si field emitters and resonators. An o ptimized etch condition was used to etch Si field emission devices wit h controllable sidewall angles as well as good uniformity for large ar rays of emitters. A mask erosion technique was used to control the Si emitter profile. The sidewall angle of Si emitters increased from 55 d egrees to 75 degrees as plasma pressure was increased from 0.1 to 5.0 mTorr. Sharp tips with good uniformity and a high packing density of 6 .25 x 10(6) tips/cm(2) were fabricated using 200 W ICP source power, 1 00 W stage power at 1 mTorr with 20 seem of Cl-2 flowing and an ICP so urce to sample distance of 8 cm. Released Si mechanical resonators wer e also fabricated with a vertical etch profile and smooth surfaces. An optimized etch condition of 250 W ICP source power and 70 W stage pow er at 5 mTorr with 20 seem of Cl-2 flow and an ICP source to sample di stance of 6 cm provided an etch rate of 219 nm/min and a selectivity t o a Ni-Ti mask of 26. Due to the high selectivity and etch rate, reson ators and cantilevered beams as thick as 40 mu m were fabricated givin g improved device performance compared to thinner devices. Submicromet er Si resonators were also fabricated that were 3.1 mu m thick with 1. 7 mu m wide comb drive fingers and 0.2 mu m gaps between them. (C) 199 8 American Vacuum Society.