SOI Photographic Mask Stepped Openings for MEMS Alignment
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Solution Overview
Problem
The existing shadow masks used in MEMS microphone manufacturing have large top opening areas, making it difficult to form multiple openings and reducing alignment accuracy, which affects the manufacturing quality of MEMS microphone chips.
Innovation Solution
A photographic mask with a silicon-on-insulator (SOI) base featuring stepped openings is used to form membrane and back plate connecting pads, allowing for precise alignment and smaller opening areas, improving the ability to form multiple openings and enhancing manufacturing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shadow mask with large top opening area is used, then the opening can accommodate the small connecting pads, but it becomes difficult to form multiple openings and alignment accuracy decreases
Solution Approach 1:
The patent transitions from a traditional flat shadow mask to a three-dimensional photomask structure with stepped openings formed in an SOI substrate. The stepped openings create multiple levels (first opening portion and second opening portion at different depths) that enable precise alignment while accommodating small connecting pads. This dimensional change allows the mask to provide both precise alignment capability and the ability to form multiple openings simultaneously.
2Manufacturing precision
If the top opening area is reduced to improve alignment accuracy, then alignment precision improves, but it becomes harder to form the required connecting pads
Solution Approach 1:
The patent segments the opening structure into multiple portions at different levels. The stepped opening is divided into a first opening portion and a second opening portion, each serving different functions. The upper portion provides precise alignment while the lower portion ensures adequate opening area for forming connecting pads. This segmentation allows each part to optimize its function without compromising the other.
Solution Approach 2:
Different portions of the photomask opening have different properties tailored to their specific functions. The upper opening portion has a smaller area optimized for alignment precision, while the lower opening portion has a larger area optimized for material deposition and connecting pad formation. This local differentiation of properties resolves the contradiction between alignment precision and manufacturing capability.
Data Source
AI summary
A photographic mask is provided in the present disclosure. The photographic mask includes a silicon-on-insulator (SOI) base and a stepped opening formed in the SOI base. The SOI base includes a silicon substrate, a median layer and a silicon layer, the median layer is arranged between the insulator substrate and the insulator layer. The stepped opening includes a first opening portion and a second opening portion, the first opening portion penetrates through the silicon layer and has a first opening area; the second opening portion at least penetrates through the silicon substrate and is aligned with the first opening portion. The second opening portion has a second opening area greater than the first opening area of the first opening portion. The present disclosure further provides a method for making a photographic mask.