MEMS Lead Structure to Prevent Insulation Layer Undercutting
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Solution Overview
Problem
The existing methods for forming MEMS elements on a silicon on insulator (SOI) substrate are inefficient due to long and complex processing, leading to increased costs and a decrease in the strength of the insulation layer, particularly at the lead portions which can result in structural weaknesses and electrical insulation failures.
Innovation Solution
A MEMS element design that includes protruding portions on the lead portions to enhance bonding strength, preventing undercutting during etching and maintaining electrical insulation, while simplifying the production process to improve productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slits are formed by etching to separate fixed portions, moveable portion, and outer peripheral fixed pattern, then electrical insulation between these components is achieved, but undercutting of the insulation layer occurs causing decreased bonding strength at lead portions
Solution Approach 1:
The patent applies preliminary action by forming protective films on the lateral surfaces of fixed portions before etching the slits. This protective coating prevents the etchant from undercutting the insulation layer at critical locations like lead portions, while still allowing the slit to form for electrical insulation. The protective film is applied in advance to protect vulnerable areas during the subsequent etching process.
2Strength
If protective films are formed on lateral surfaces of fixed portions before etching to prevent undercutting, then bonding strength is maintained, but the processing process becomes long and complicated reducing productivity
Solution Approach 1:
The patent applies local quality by forming protective films selectively only on the lateral surfaces of fixed portions that require protection during etching, rather than coating entire structures. This targeted approach minimizes the amount of protective material applied and reduces the complexity of the process while still preventing undercutting at critical locations. The selective application simplifies subsequent removal steps and improves overall productivity.
3Area of stationary object
If lead portions are made narrow to fit in compact spaces, then device integration is improved, but bonding strength becomes insufficient making them susceptible to breaking under impact
Solution Approach 1:
The patent applies preliminary action by forming protective films on the lateral surfaces of narrow lead portions before etching. This protective coating compensates for the reduced bonding area caused by narrow dimensions, preventing the etchant from further undermining the already limited bonding interface. The protective film effectively increases the functional bonding strength without requiring the lead portions to be wider, maintaining compact device integration.
Data Source
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Figure 3(A)~3(B)
AI summary
A MEMS element according to the present invention is provided with a base, an insulation layer fixed to one surface of the base, a first upper layer at least portions of which are fixed to the insulation layer, and a second upper layer provided surrounding the first upper layer and disposed being separated from the first upper layer by slits, wherein the first upper layer includes, at predetermined portions, protruding portions protruding toward the second upper layer, and the protruding portions are fixed to the insulation layer.