Thick benzocyclobutene etching using high density SF6/O2 plasmas

Abstract

Etching of thick nonphotosensitive benzocyclobutene (BCB) was investigated using a high density SF6/O2 plasma with an inductively coupled plasma (ICP) etcher. The effects of SF6 concentration on etching characteristics, including etching rate, anisotropy, and residue, are fully discussed in this article. Moreover, experiments were designed and carried out to study the causes of BCB etching residue. A grasslike etching residue was observed for low SF6 concentration at the bottom of BCB patterns with a SiO2/SixN layer and the BCB patterns cured on a N2-purged hotplate, while residue-free etching is obtained for the BCB patterns cured in a N2-purged vacuum chamber. A high SF6 concentration and exclusion of O2 during hard curing are important to prevent the grasslike etching residue. A highly anisotropic and residue-free etching of thick (∼13 μm) BCB is achieved for BCB cured in a N2-purged vacuum chamber at 250 °C for 1 h and with a pure SF6 plasma under etching conditions of 700 W ICP power, 100 W reactive ...