Selective UV-Ozone Etching of MEMS Anti-Stiction Coatings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for fabricating MEMS devices face challenges with stiction issues due to anti-stiction coatings, which reduce bond shear strength and yield, and are non-selective, affecting the adhesion and functionality of MEMS devices.
Innovation Solution
A UV-Ozone dry etching technique is used to selectively remove anti-stiction coatings from specific areas of MEMS devices, employing two wavelengths of ultraviolet light (184.9 nm and 253.7 nm) with masking or a hybrid approach combining heat and UV exposure to expose bond lines and other structures, allowing for improved adhesion and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anti-stiction coating is applied to cover the entire wafer surface, then stiction is reduced, but adhesion and bond shear strength are compromised
Solution Approach 1:
The patent applies selective removal of anti-stiction coating from bond lines while preserving it on other wafer surfaces. This creates local differentiation where bond lines have high adhesion (no coating) and other surfaces maintain stiction prevention (coating intact), resolving the contradiction between these two requirements
Solution Approach 2:
The patent extracts the anti-stiction coating material from specific areas (bond lines) where it is harmful to adhesion, while leaving it intact in areas where it provides stiction prevention. This selective extraction allows both functions to coexist in different locations
2Strength
If plasma etching is used to remove anti-stiction coating from bond lines, then adhesion is improved, but the process is non-selective and removes coating from movable MEMS structures
Solution Approach 1:
The patent uses a shadow mask to create local differentiation in the etching process, allowing selective removal of coating from bond lines while protecting movable structures. This achieves both adhesion improvement and manufacturing precision through spatially selective processing
Solution Approach 2:
The shadow mask acts as an intermediary tool that enables selective etching. It physically blocks the etching process from reaching certain areas (movable structures) while allowing it to proceed in other areas (bond lines), achieving the desired selectivity
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 enhances bond shear strength and adhesion, reducing stiction-related failures and increasing the yield of MEMS devices by selectively removing anti-stiction coatings from areas that require bonding while preserving them on movable structures.
Implementation Method 1
The UV-Ozone etching process involves exposing the wafer to a mixture of ultraviolet light and ozone, which generates highly reactive oxygen species that oxidize and remove organic coating materials from the wafer surface
Implementation Method 2
The process employs two wavelengths of ultraviolet light (184.9 nm and 253.7 nm) with masking or a hybrid approach combining heat and UV exposure to expose bond lines and other structures
Data Source
AI summary
Organic anti-stiction coatings such as, for example, hydrocarbon and fluorocarbon based self-assembled organosilanes and siloxanes applied either in solvent or via chemical vapor deposition, are selectively etched using a UV-Ozone (UVO) dry etching technique in which the portions of the organic anti-stiction coating to be etched are exposed simultaneously to multiple wavelengths of ultraviolet light that excite and dissociate organic molecules from the anti-stiction coating and generate atomic oxygen from molecular oxygen and ozone so that the organic molecules react with atomic oxygen to form volatile products that are dissipated, resulting in removal of the exposed portions of the anti-stiction coating. A hybrid etching process using heat followed by UVO exposure may be used. A shadow mask (e.g., of glass or quartz), a protective material layer, or other mechanism may be used to selective expose the portions of the anti-stiction coating to be UVO etched. Such selective UVO etching may be used, for example, to expose wafer bond lines prior to wafer-to-wafer bonding in order to increase bond shear and adhesion strength, to expose bond pads in preparation for electrical or other connections, or for general removal of anti-stiction coating materials from metal or other material surfaces. One specific embodiment uses two wavelengths of ultraviolet light, one at around 184.9 nm and the other at around 253.7 nm.