Via Electrode Definition in MEMS Transducers
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Solution Overview
Problem
The precision of via electrode location and surface area is difficult to define in MEMS devices due to variations in DRIE etching, affecting the accurate actuation and sensing of movable elements like micro-mirrors and accelerometers.
Innovation Solution
A semiconductor device with a shielded electrode structure where a conductive layer and insulating material mask are used to precisely define and align the active electrode area on the via surface, utilizing lithographic methods for high accuracy alignment and etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If DRIE etching is used to create deep via trenches, then via connections can be formed through the substrate, but the location and surface area of the via electrode become difficult to define precisely
Solution Approach 1:
A mask layer is deposited and patterned over the via surface before the via is formed, defining the electrode area in advance. This preliminary masking action ensures that when the via is etched through deep trenches using DRIE, the exposed electrode surface area is precisely controlled by the pre-applied mask pattern, resolving the contradiction between deep via formation capability and electrode definition precision.
Solution Approach 2:
The mask layer acts as an intermediary element between the DRIE etching process and the final electrode surface. It mediates the interaction by protecting specific areas during etching and defining the exact boundaries of the electrode, allowing deep trenches to be formed while maintaining precise electrode geometry through the intermediary masking function.
2Force
If the electrode surface area is enlarged to improve actuation strength, then stronger electric field interaction is achieved, but alignment precision with movable elements deteriorates
Solution Approach 1:
The mask layer enables local quality control by allowing different regions of the via surface to have different functions. The mask pattern can be designed to expose only the specific local area that requires high precision alignment with the movable element, while other areas remain masked. This local differentiation resolves the contradiction by concentrating the active electrode area precisely where alignment is critical, maintaining both actuation strength and alignment precision.
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 allows for precise actuation and sensing by ensuring the electrode area and position are accurately defined, reducing misalignment tolerance to less than 5 µm and achieving precise alignment between the electrode and movable elements.
Implementation Method 1
utilizing lithographic methods for high accuracy alignment and etching
Implementation Method 2
The vias are in this process formed by DRIE (Deep Reactive Ion Etch) etching of trenches defining the vias
Data Source
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AI summary
The present invention relates to a semiconductor device, comprising a semiconductor substrate (10) having a first (12a) and a second (12b) side. There is provided at least one via (15) extending through said substrate (10) having first (16a) and second (16b) end surfaces, said first end surface (16a) constituting an transducer electrode for interacting with a movable element (14) arranged at the first side (12a) of the substrate (10). A shield (17) is provided on and covers at least part of the first side (12a) of the substrate (10), the shield/mask (17) comprising a conductive layer (19a) and an insulating material layer (19b) provided between the substrate (10) and the conductive layer (19a). The mask has an opening (18) exposing only a part of the first surface (16a) of the via. Preferably the opening (18) in the mask is precisely aligned with the movable element, and the area of the opening is accurately defined.