Capacitive MEMS Device With Bonded Silicon Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microelectromechanical systems (MEMS) face challenges in achieving linear response and efficient use of surface area for capacitive detection due to inaccuracies in wafer-level alignment and dimension control, particularly in comb structures, leading to suboptimal overlap and motion detection.
Innovation Solution
A MEMS structure is developed with a mechanical layer comprising a first and second silicon layer directly bonded at their interface, where the static and movable electrodes are patterned to form a capacitor with an accurately dimensioned gap, enabling precise overlap detection and linear signal response over a broader range of motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer-level alignment is used for comb structure fabrication, then manufacturing efficiency is improved, but alignment accuracy and gap dimension control deteriorate
Solution Approach 1:
The device is divided into two separately processed wafers (first wafer with movable comb, second wafer with stationary comb) that are bonded together. This segmentation allows each wafer to be processed independently with high precision, and the final alignment is achieved through the bonding interface rather than wafer-level alignment, thereby resolving the contradiction between manufacturing efficiency and alignment accuracy.
2Measurement precision
If comb fingers are arranged to move parallel between static comb fingers, then linear response is improved, but surface area utilization deteriorates due to required clearance
Solution Approach 1:
The invention transitions from in-plane motion (parallel movement between comb fingers) to out-of-plane motion (movement across the bonding interface gap). This dimensional change allows the comb fingers to move perpendicular to the bonding interface, eliminating the need for lateral clearance and maximizing surface area utilization while maintaining linear response through capacitive detection.
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 accurate detection of comb finger overlap and larger rotor motion with improved linearity and sensitivity, overcoming the limitations of conventional MEMS designs by ensuring precise gap dimensioning and efficient use of surface area.
Implementation Method 1
a first silicon layer and a second silicon layer, with portion of the first silicon layer and the second silicon layer directly bonded to each other
Implementation Method 2
the movable electrode and the static electrode form a capacitor having capacitance that varies based on an overlap between the movable electrode and the static electrode
Data Source
AI summary
A MEMS structure is provided that includes a mechanical layer that extends parallel to a reference device plane. The mechanical layer is patterned to include a static electrode and a movable electrode configured to move in relation to the static electrode parallel to the reference device plane. The static electrode and the movable electrode are connected to form a capacitor having capacitance that varies according to an overlap of the static electrode and the movable electrode. The mechanical layer includes a first silicon layer and a second silicon layer. Parts of the first silicon layer and the second silicon layer are directly bonded to each other. The movable electrode is in the first silicon layer and the static electrode is in the second silicon layer. The movable electrode is separated from the static electrode by a first gap in the interface between the first and second silicon layers.