ICP Etching Deep Features in Silicon Dioxide
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Solution Overview
Problem
Current fabrication technologies for silicon dioxide materials like quartz and fused silica are limited to shallow etches with non-vertical sidewalls, hindering the production of deep, high-aspect ratio features essential for advanced MEMS, microelectronic, and photonic devices.
Innovation Solution
An Inductively-Coupled Plasma (ICP) etch process is employed to etch deep, high-aspect ratio features with near-vertical sidewalls into silicon dioxide materials, using a reactive-ion etcher system with controlled gas flows and RF bias to achieve precise dimensional control and high anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional wet etching or plasma etching techniques are used on silicon dioxide, then the etching process is simple and well-established, but the etch depth is limited to a few microns and aspect ratios are very limited
Solution Approach 1:
The patent applies parameter changes by modifying multiple etching process parameters simultaneously: using inductively coupled plasma with specific RF power settings (13.56 MHz frequency), controlling chamber pressure (1-100 mTorr range), optimizing gas composition (SF6, CF4, C4F8, or C3F8 at specific flow rates), and maintaining substrate temperature (20-100°C). These parameter adjustments enable deep etching (10-1000 microns) with high aspect ratios (1:1 to 10:1 or higher) while maintaining vertical sidewalls, resolving the contradiction between etch depth capability and process complexity.
2Manufacturing precision
If conventional plasma etching is used, then the process is relatively simple, but the etched features have non-vertical sidewalls and limited aspect ratios
Solution Approach 1:
The patent achieves vertical sidewalls and high aspect ratios by optimizing parameter combinations: RF bias power (50-500 Watts) for ion directionality, chamber pressure (1-100 mTorr) for mean free path control, gas flow rates (10-100 sccm for SF6/CF4/C4F8/C3F8) for etch rate and polymer formation balance, and substrate temperature (20-100°C) for reaction kinetics. These changes transform the etching process from conventional shallow, tapered profiles to deep, vertical features.
Solution Approach 2:
The patent replaces conventional capacitive coupling with inductive coupling to generate plasma. This substitution creates a more uniform plasma distribution and allows better control over ion flux and energy, enabling consistent vertical sidewalls and high aspect ratios that are difficult to achieve with traditional plasma sources.
3Length of stationary object
If deep etching is attempted with existing technologies, then feature depth increases, but sidewalls become non-vertical and process control becomes difficult
Solution Approach 1:
The patent implements feedback control through real-time monitoring and adjustment of process parameters. RF power, gas flow rates, chamber pressure, and substrate temperature are continuously controlled to maintain optimal etching conditions throughout the deep etching process. This feedback mechanism prevents sidewall deviation and maintains dimensional accuracy even at depths of 10-1000 microns with aspect ratios of 1:1 to 10:1 or higher.
Solution Approach 2:
The patent uses parameter changes to maintain etch profile control during deep etching. By adjusting RF bias power (50-500 Watts) for ion directionality, controlling chamber pressure (1-100 mTorr) for stable plasma, optimizing gas composition (SF6, CF4, C4F8, or C3F8) for appropriate etch rates and sidewall protection, and regulating substrate temperature (20-100°C) for reaction control, the process maintains vertical sidewalls and precise dimensional control throughout deep feature fabrication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the fabrication of devices with deep, high-aspect ratio features and vertical sidewalls, enhancing the capabilities for MEMS gyroscopes, resonators, and other microelectronic devices by overcoming the limitations of traditional etching techniques.
Implementation Method 1
using an Inductively-Coupled Plasma (ICP) etch process technology
Implementation Method 2
using a reactive-ion etcher system with controlled gas flows and RF bias to achieve precise dimensional control and high anisotropy
Implementation Method 3
using a reactive-ion etcher system with controlled gas flows and RF bias to achieve precise dimensional control and high anisotropy
Data Source
AI summary
A method or process is disclosed for etching deep, high-aspect ratio features into silicon dioxide material layers and substrates, including glass, fused silica, quartz, or similar materials, using a plasma etch technology. The method has application in the fabrication and manufacturing of MEMS, microelectronic, micro-mechanical, photonic and nanotechnology devices in which silicon dioxide material layers or substrates are used and must be patterned and etched. Devices that benefit from the method described in this invention include the fabrication of MEMS gyroscopes, resonators, oscillators, microbalances, accelerometers, for example. The etch method or process allows etch depths ranging from below 10 microns to over 1 millimeter and aspect ratios from less than 1 to 1 to over 10 to 1 with etched feature sidewalls having vertical or near vertical angles. Additionally, the disclosed method provides requirements of the etched substrates to reduce or eliminate undesired effects of an etch.