Silicon-Rich Oxide Adhesion Layer for MEMS Sacrificial Release
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Solution Overview
Problem
In MEMS device fabrication, the poor adhesion between sacrificial and dielectric materials leads to delamination issues during the removal of sacrificial material, affecting the reliability and quality of the device.
Innovation Solution
A method involving the deposition of a silicon-rich silicon oxide layer over the sacrificial material before applying a dielectric layer to enhance adhesion, using a higher silicon-to-oxygen gas ratio during the silicon-rich layer deposition, and subsequent removal of the sacrificial material to free the switching element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric layer is deposited directly over sacrificial material, then the fabrication process is simple, but the adhesion between dielectric and sacrificial material is poor leading to delamination
Solution Approach 1:
A silicon-rich silicon oxide layer is deposited as an intermediate layer between the sacrificial material and the dielectric layer. This intermediate layer acts as a mediator that improves adhesion between the two materials, preventing delamination during sacrificial material removal while maintaining process feasibility.
Solution Approach 2:
The deposition process is segmented into two distinct steps: first depositing a silicon-rich silicon oxide layer with a higher silicon-to-oxygen gas ratio, then depositing the dielectric layer with a lower ratio. This segmentation allows optimization of each layer's properties for its specific function, with the silicon-rich layer providing adhesion and the dielectric layer providing electrical isolation.
2Ease of operation
If sacrificial material is removed to free the switching element, then the device structure is completed, but delamination occurs due to poor adhesion
Solution Approach 1:
The silicon-rich silicon oxide layer is deposited in advance before the dielectric layer, creating a strong adhesion interface beforehand. This preliminary action ensures that when the sacrificial material is later removed and structural stresses occur, the dielectric layer remains firmly attached and does not delaminate.
3Reliability
If a stoichiometric silicon oxide layer is used, then the dielectric properties are optimal, but adhesion to sacrificial material is insufficient
Solution Approach 1:
Different silicon-to-oxygen ratios are used at different locations in the deposition process. The silicon-rich silicon oxide layer uses a higher silicon-to-oxygen gas ratio to maximize adhesion to the sacrificial material, while the subsequent dielectric layer uses a lower ratio to achieve optimal dielectric properties. This local quality variation resolves the contradiction between adhesion and dielectric performance.
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
Ensures good adhesion between sacrificial and dielectric materials, preventing delamination and improving the fabrication conditions of MEMS devices by maintaining structural integrity and device performance.
Implementation Method 1
depositing a silicon rich layer comprising silicon oxide over the organic based sacrificial layer with a silicon containing gas and an oxygen containing gas
Implementation Method 2
depositing a dielectric layer comprising silicon oxide over the silicon rich layer
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
The present invention generally relates to a method for forming a MEMS device and a MEMS device formed by the method. When forming the MEMS device, sacrificial material is deposited around the switching element within the cavity body. The sacrificial material is eventually removed to free the switching element in the cavity. The switching element has a thin dielectric layer thereover to prevent etchant interaction with the conductive material of the switching element. During fabrication, the dielectric layer is deposited over the sacrificial material. To ensure good adhesion between the dielectric layer and the sacrificial material, a silicon rich silicon oxide layer is deposited onto the sacrificial material before depositing the dielectric layer thereon.