MEMS Chemical Stop Structures to Prevent Adhesion Layer Etching
Solution Overview
Problem
MEMS structures face issues with adhesion layers being inadvertently etched by chemicals, leading to peeling and structural integrity problems, particularly in high-aspect-ratio pillars.
Innovation Solution
Incorporation of chemical stop structures, including a protective material and a base plate layer, to separate and protect adhesion layers from etching chemicals, using a combination of etching and deposition processes to form annular vias and recesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching processes are used to transfer patterns to layers below photoresist, then manufacturing precision is improved, but adhesion layers are inadvertently etched leading to peeling and structural integrity problems
Solution Approach 1:
A chemical stop layer is introduced as an intermediary between the adhesion layer and the dielectric layer. This stop layer has selective etch resistance, allowing etching chemicals to remove the dielectric layer while being blocked by the stop layer from attacking the adhesion layer underneath, thus protecting the adhesion layer from inadvertent etching
Solution Approach 2:
The protective structure is segmented into multiple functional layers: the adhesion layer for bonding, the chemical stop layer for etching protection, and the dielectric layer for electrical isolation. This segmentation allows each layer to perform its specific function without interfering with others, particularly protecting the adhesion layer during etching processes
2Adaptability or versatility
If high-aspect-ratio pillars are fabricated, then device functionality is improved, but adhesion layers become more susceptible to etching attack and peeling
Solution Approach 1:
The chemical stop layer serves as a protective intermediary that extends down to protect adhesion layers in high-aspect-ratio structures. The stop layer's selective etch resistance creates a protective barrier that prevents etching chemicals from reaching and attacking the adhesion layers, even in difficult-to-reduce geometric configurations
Solution Approach 2:
The chemical stop layer is deposited beforehand to provide preemptive protection to the adhesion layer. This protective layer is in place before etching processes begin, cushioning the adhesion layer against potential etching attack during subsequent manufacturing steps
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 chemical stop structures effectively prevent adhesion layer attack, enhancing the structural robustness and integrity of MEMS devices by reducing peeling, thus improving their performance and reliability.
Implementation Method 1
chemical stop structures, including a protective material and a base plate layer, to separate and protect adhesion layers from etching chemicals
Data Source
AI summary
In a micro-electromechanical system (MEMS) structure, at least one chemical stop structure is formed to reduce inadvertent etching of adhesion layers. A first adhesion layer and a second adhesion layer are separated by a primary dielectric layer. The primary dielectric layer includes a recess that forms a stair. The second adhesion layer includes an annular opening, and a protective material covers the sides of the second adhesion layer in the annular opening. A base plate layer covers the second adhesion layer and fills the recess and the annular opening. An annular via passes through the base plate layer and the protective material down to the primary dielectric layer. The protective material and the base plate layer each act as chemical stop structures that separate the first adhesion layer from the second adhesion layer.