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

Area of Science:

• Materials Science
• Electrical Engineering
• Physics

Background:

• Deep Reactive Ion Etching (DRIE) is crucial for silicon micromachining.
• High-precision applications face challenges with sidewall angle deviation and aspect ratio limits.

Purpose of the Study:

• To investigate the relationship between DRIE process parameters and etching morphology.
• To optimize parameters for improved sidewall perpendicularity, aspect ratio, and CD uniformity.

Main Methods:

• Systematic investigation of C4F8 passivation time, bottom RF power, etch cycle count, and single-step time.
• Analysis of their effects on sidewall angle, aspect ratio, and top-bottom CD difference.

Main Results:

• Dynamic bottom RF power adjustment significantly impacts sidewall angle; incremental adjustments decrease precision, while decremental adjustments form obtuse angles.
• Increased cycle count alone limits etch depth; combining with incremental RF power overcomes this but affects aperture dimensions.
• Optimized passivation-to-etch time ratio controls etch morphology, achieving 112.2 μm etch depth with 0.279 μm aperture size difference for a 5 μm trench.

Conclusions:

• Parameter optimization, particularly dynamic bottom RF power adjustment and passivation-to-etch time ratio, is vital for high-precision DRIE.
• Provides a theoretical basis and practical guidance for fabricating high-precision silicon structures using DRIE.