Simultaneous Micro- and Nanoscale Silicon Fabrication by Metal-Assisted Chemical Etch

Abstract

Simultaneous micro and nanoscale etching of silicon on a wafer-scale is nowadays performed using plasma etching techniques. These plasma techniques, however, suffer from low throughput due to Aspect-Ratio Dependent Etch (ARDE) rate, etch lag from changes in feature size, loading effects from increased etch area, and undesirable surface characteristics such as sidewall taper and scalloping, which are particularly problematic at the nanoscale and can affect the etch uniformity. Additionally, the hardware required for plasma etching can be very expensive. A potential alternative, which addresses the above issues with plasma etching is Metal Assisted Chemical Etch (MacEtch). To date, however, an integrated micro and nanoscale MacEtch process, which has uniform and clean (i.e. without nanowire-like defects in microscale areas) etch front has not been presented in the literature. In this work, we present for the first time a feasible process flow for simultaneous micro and nanoscale silicon etching without nanowire-like defects, which we call Integrated Micro- and Nanoscale MacEtch (IMN-MacEtch). Successful etching of silicon features ranging from 100 nm to 100 µm was achieved with etch rates of about 1.8 µm/min in a single step to achieve features with an Aspect Ratio (AR) ~18:1. We thus conclude that the process represents a feasible alternative to current dry etch methods for patterning feature sizes spanning three orders of magnitude.