Optimization Method for the Synergistic Control of DRIE Process Parameters on Sidewall Steepness and Aspect Ratio

TL;DR

This paper presents a method to optimize Deep Reactive Ion Etching parameters to improve precision in silicon micromachining.

Contribution

A novel optimization method for DRIE process parameters to enhance sidewall steepness and aspect ratio control is introduced.

Findings

Dynamic adjustment of bottom RF power significantly affects sidewall angle precision.

Combining incremental bottom RF power adjustment overcomes depth limitations but causes aperture dimension variation.

Optimizing the passivation-to-etch time ratio effectively controls etch morphology characteristics.

Abstract

Deep Reactive Ion Etching (DRIE), as a key process in silicon micromachining, remains constrained in high-precision applications by sidewall angle deviation and aspect ratio limitations. This study systematically investigates the mapping relationship between process parameters and etching morphology, focusing on the following aspects: the influence mechanism of C4F8 passivation time and bottom RF power on sidewall perpendicularity; and the effect patterns of etch cycle count, single-step time, and bottom RF power on aspect ratio and top–bottom line width (CD) difference. The findings reveal that dynamic adjustment of bottom RF power significantly influences sidewall angle: incremental adjustment tends to cause sharp angles (decreased angular precision), while decremental adjustment tends to form obtuse angles. Simply increasing the cycle count leads to a bottleneck in etch depth growth. Combining incremental bottom RF power adjustment can overcome depth limitations but induces axial variation in aperture dimensions. Optimizing the passivation-to-etch time ratio effectively controls etch morphology characteristics. This study achieved an etch depth of 112.2 μm for a 5 μm wide trench with an overall aperture size difference of 0.279 μm, providing a theoretical basis and practical guidance for parameter optimization in DRIE processes for high-precision silicon structure fabrication.

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