Self-Supported MEMS Structure via Oxide Liner
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Solution Overview
Problem
Conventional MEMS devices face challenges in scaling down support structures due to visco-elastic properties of polymer sacrificial layers, which lead to structural instability and susceptibility to chemical attacks, making it difficult to achieve robust and scalable self-supported MEMS structures.
Innovation Solution
The method involves forming a self-supported MEMS structure using an oxide liner to coat the sidewalls and bottom of trenches in a carbonaceous sacrificial material, preventing outgassing and deformation, and enhancing adhesion between the metal structures and the sacrificial material, while also providing mechanical rigidity and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large vias and trenches are used to support suspended sensor membranes, then mechanical and electrical robustness is improved, but scaling down the MEMS structures becomes difficult
Solution Approach 1:
An oxide liner is introduced as an intermediary layer between the metal fill and the polymer sacrificial material. This oxide liner prevents direct contact between the metal and polymer, eliminating the harmful outgassing interaction while maintaining structural integrity during thermal processing
Solution Approach 2:
The support structure uses a composite approach with multiple materials: oxide liner (for chemical resistance), metal fill (for mechanical strength), and polymer sacrificial material (for structural support during fabrication). This composite structure allows small dimensions while maintaining robustness
2Reliability
If metal is deposited in trenches formed in polymer sacrificial material, then electrical connectivity is achieved, but the polymer outgassing causes trench and metal filament deformation
Solution Approach 1:
The oxide liner serves as a protective intermediary barrier that prevents the polymer sacrificial material from outgassing directly onto the metal fill during thermal processing, eliminating deformation while maintaining electrical connectivity
3Reliability
If the support structure uses metal filling, then electrical conductivity is improved, but the structure becomes susceptible to chemical attacks during BEOL processes
Solution Approach 1:
The oxide liner acts as a chemical barrier intermediary that protects the metal fill from exposure to aggressive chemicals during BEOL processes, preventing corrosion while maintaining electrical conductivity through the metal pathway
4Length of moving object
If via dimensions are reduced to enable scaling, then surface area conservation is achieved, but structural instability and mechanical detachment increase
Solution Approach 1:
The via structure uses a composite design with oxide liner providing chemical stability, metal fill providing mechanical strength, and polymer providing structural support during fabrication. This composite approach enables small via dimensions while maintaining structural stability
Solution Approach 2:
The oxide liner provides a stable interface between the metal and polymer, preventing direct harmful interactions that would cause deformation and detachment in smaller structures
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 approach results in robust, scalable, and chemically resistant self-supported MEMS structures with improved mechanical and electrical integrity, enabling more aggressive BEOL processing and high-volume manufacturing of MEMS devices.
Implementation Method 1
an oxide liner to prevent outgassing and deformation
Implementation Method 2
adhesion promoting layers, followed by deposition of dielectric and metal etch stop layers
Data Source
AI summary
Self-supported MEMS structure and method for its formation are disclosed. An exemplary method includes forming a polymer layer over a MEMS plate over a substrate, forming a trench over the MEMS plate, forming an oxide liner in the trench on sidewalls of the trench, forming a metal liner over the oxide liner in the trench, and depositing a metallic filler in the trench to form a via. The method further includes removing the polymer layer such that the via and the MEMS plate form the self-supported MEMS structure, where the oxide liner provides mechanical rigidity for the metallic filler of the via. An exemplary structure formed by the disclosed method is also disclosed.