Technology Development of Silicon Plasma Etching Process at Nanoscale

Project type: Ph.d. project
Project responsible: Vy Thi Hoang Nguyen
Supervisors:Henri Jansen, Flemming Jensen, Jörg Hübner
Partners involved: DTU Danchip
Project start: November 2017

Project Description

Plasma processes are important for silicon-based micro electromechanical systems (MEMS) with critical dimensions around a few microns. Although widely utilized and largely understood, silicon plasma etching fails to reproduce at the nanoscale. Transport effects ‘down the etched cavity’ limit rate and selectivity while high aspect ratios, profile and passivation control are more challenging. The so-called Bosch etch process is probably the most popular technique in MEMS production facilities today. However, the high roughness with finite sidewall scallop size and hard to remove fluorocarbon (FC) residue on the sidewalls of etched structures make the process less favorable for nanoscale engineering. In this project, the usability of SF6 and O2 plasma will be studied as a replacement for Bosch process to avoid FC residue and facilitate the nanoscale silicon etching with profile control and sufficient mask selectivity preferably at room temperature. The focus will be on the development of a fundamental understanding of the special challenges in SF6-O2 plasma etching at the nanoscale including the physics and chemistry involved. The aim is to establish a generic knowledge platform for future applications such as injection molding. For this, modern lithography tools (MLA, DUV stepper, e-beam) will be utilized to define the structure down to 10nm critical dimension on top of a silicon wafer. Subsequently, the pattern will be transferred into the silicon layer using a modern plasma tool (SPTS, DRIE-Pegasus). During the process, various etching parameters (flow, pressure, power, etc.) are varied to discover performance-affecting factors. Finally, etching results are characterized under scanning electron microscopy (Carl Zeiss AG, SEM Supra 60VP).

Publications

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