Ni-P, Ni-B and SiO₂ as Materials for Hard Mask in Deep Silicon Etching for MEMS Fabrication using ICP reactor

Abstract

Ni-P, Ni-B and SiO2 films were used as hard mask materials in Si etching using a high-density inductively coupled plasma (ICP) reactor for MEMS fabrication. The Ni-P and Ni-B films were deposited using an electroless method, and the SiO2 film was thermally grown in a conventional furnace. Two etching processes were used to characterize the masks. The first uses SF6/Ar gas mixture varying bias power and process time, and the second is a Bosch like process, using C4F8 as a passivation gas. The Ni-P mask showed the highest resistance to etching, being applicable in Si deep etching (>100m); while the SiO2 mask was found to be less resistive, especially under strong ion bombardment (high bias power). The Ni-B mask was found to be highly porous, resulting in formation of micropillars during ecthing, which may be interesting for some apllications such as sensors.

Electroless Metallization of the Elements: Survey and Progress

“…Nunes et al 310 have examined EL NiP as an etchmask directly on Si ⟨100⟩ substrates. These workers employed fluoride-based etchants to chemically remove SiO 2 , followed by catalysis of the exposed Si surface with PdCl 2 solution.…”

“…Nickel can be deposited via conventional EL ( vide infra ) and galvanic ,,,− methods, though in the latter case Ni more often functions as a sacrificial substrate for replacement by other metals than the deposited metal. ,,,,− Conventional EL Ni depositions utilize baths containing H 2 PO 2 – , − amine boranes, ,− BH 4 – , − or to a lesser extent, N 2 H 4 , − as reducing agents. Baths containing H 2 PO 2 – deposit the metal as NiP alloys, whereas those containing amine boranes or BH 4 – yield NiB alloys and those containing N 2 H 4 deposit Ni metal.…”