Metal-Halide Coating for UV-Protected MEMS Devices
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Solution Overview
Problem
Micro electro-mechanical systems (MEMS) devices, such as digital micro-mirror devices, face surface degradation and reduced reliability due to photochemical activation when exposed to UV illumination, caused by reactive gas constituents in the package headspace that generate damaging volatile compounds.
Innovation Solution
Coating the exposed surfaces of MEMS devices and optical windows with metal-halides to prevent photochemical activation, thereby protecting them from UV-induced damage and extending their reliability and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lubricants and passivants are included in the package headspace to prevent sticking of moving parts, then smooth operation of the device is ensured, but photochemical activation by UV flux generates reactive radicals that damage device surfaces and optical windows
Solution Approach 1:
A metal-halide coating layer is introduced as an intermediary between the UV flux and the device surfaces (Si, SiO2, SiB2O7). This coating absorbs the UV energy and prevents photochemical activation of the headspace gases, thereby blocking the formation of reactive radicals that would otherwise attack the device surfaces. The coating acts as a protective mediator that allows lubricants to remain in the headspace without causing damage.
2Reliability
If metal-halide coating is applied to protect surfaces from photochemical damage, then reliability and lifetime are extended, but device complexity and manufacturing process are increased
Solution Approach 1:
The metal-halide coating creates an inert protective environment on the device surfaces and optical windows. This coating layer is chemically inert to the UV flux and prevents photochemical reactions between the headspace gases and the underlying surfaces. By creating this protective inert barrier, the system achieves enhanced reliability without requiring fundamental changes to the device architecture.
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
The metal-halide coatings effectively prevent the formation of harmful volatile compounds like SiF4, SiCl4, and BCl3, maintaining the integrity of MEMS device surfaces and optical windows even under UV exposure, as shown by reduced concentrations of damaging elements and absence of nodule-like features.
Implementation Method 1
photochemical activation between the optical UV flux and package gas constituents
Implementation Method 2
coat the exposed surfaces of the MEMS device and window surface with various metal-halides to eliminate this photochemical activation
Data Source
AI summary
A process for protecting a MEMS device used in a UV illuminated application from damage due to a photochemical activation between the UV flux and package gas constituents, formed from the out-gassing of various lubricants and passivants put in the device package to prevent sticking of the MEMS device's moving parts. This process coats the exposed surfaces of the MEMS device and package's optical window surfaces with a metal-halide film to eliminate this photochemical activation and therefore significantly extend the reliability and lifetime of the MEMS device.