A New Concept for Spatially-Divided Reactive Ion Etching with ALD-Based Passivation

Abstract

Conventional Deep Reactive Ion Etching (DRIE) is a plasma etch process with alternating half-cycles of 1) Si-etching with SF6 to form gaseous SiFx etch products, and 2) passivation with C4F8 polymerizing as a protecting fluorocarbon deposit on the sidewalls and bottom of the etched features. We report on a novel alternative and disruptive technology concept of Spatially-divided Deep Reactive Ion Etching, where the process is converted from the time-divided into the spatially divided regime. The spatial division can be accomplished by ~20 to 100 μm high inert gas-bearing ‘curtains’ that confine the reactive gases to individual (often linear) injection slots constructed in a gas injector head. By horizontally moving the substrate back and forth under the head one can realize the alternate exposures to compose the overall cycle.Next improvement in the spatially-divided approach is the replacement of the CVD-based C4F8 passivation steps by ALD-based oxide (e.g. SiO2) deposition cycles. The method can have industrial potential in cost-effective creation of advanced 3D TSV interconnects and MEMS, but also in advanced patterning of, e.g., nanoscale FinFET devices with reduced line edge roughness, thus approaching Atomic Layer Etching accuracy.