DRY ETCHING OF SINGLE-CRYSTAL SILICON TRENCH IN HYDROGEN IODIDE CONTAINING PLASMAS .1. PURE HI

Hydrogen iodide (HI) has been introduced for plasma etching of single-crystal silicon trench. For part I of this work, pure HI chemistry has been investigated. HI forms an intensive, easily ignitable, and sustainable plasma, characterized by a very low self-bias voltage, typically less than - 80 V. The etching of silicon is only successful in the pressure range below 12 Pa. A suitable RF power range is from 150 to 300 W with an HI flow from 10 to 70 sccm. In these parameter ranges etch rates up to 400 rim/min can be obtained. The selectivity to the mask SiO2 varies in the range from 30 to more than 150:1. The etch profile is tapered with a slope of 60 to 89-degrees. In practical use we did not encounter any problems with the handling of HI or with contamination of the chamber and the pumps.