Piezoelectric Microphone Deflection Control via Interlock Stopper
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Solution Overview
Problem
Conventional piezoelectric microphones face challenges with deflection mismatch between the bridge and membrane, leading to potential stiction and the need for multiple hardmasks to achieve the desired gap thickness.
Innovation Solution
A process involving the formation of an interlock/stopper structure and micro-bump structure is implemented, using sacrificial layers and hardmasks to control deflection mismatch and prevent stiction, while reducing the number of hardmasks required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piezoelectric microphone fabrication is used, then the device can be manufactured, but deflection mismatch between bridge and membrane causes stiction and requires multiple hardmasks
Solution Approach 1:
The patent introduces a preliminary support structure formed during the fabrication process that maintains the gap between the bridge and membrane throughout manufacturing. This preliminary structure prevents deflection mismatch and stiction before the device is fully assembled, eliminating the need for multiple hardmasks and complex post-fabrication adjustments.
Solution Approach 2:
The patent uses an intermediary support structure that acts as a temporary mediator between the bridge and membrane. This intermediary element maintains proper spacing during fabrication and is subsequently removed or integrated into the final device, solving the stiction problem without requiring multiple hardmask layers.
2Manufacturing precision
If multiple hardmasks are used to achieve desired gap thickness, then the gap precision is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent replaces the mechanical hardmask system with a support structure-based approach. Instead of using multiple hardmask layers to define and maintain the gap, the invention uses a mechanically robust support structure that inherently maintains the desired gap thickness throughout the fabrication process, simplifying the manufacturing steps.
Solution Approach 2:
The patent changes the approach from controlling gap thickness through multiple hardmask thickness parameters to controlling it through the geometry and mechanical properties of a support structure. This parameter change allows for better gap control with fewer fabrication steps.
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
The solution effectively controls deflection mismatch, prevents stiction, and reduces the number of hardmasks needed, enhancing the operational reliability and manufacturing efficiency of piezoelectric microphones.
Implementation Method 1
A piezoelectric microphone is a device that senses audio vibrations through contact with solid objects
Data Source
AI summary
A method of forming a piezoelectric microphone with an interlock/stopper and a micro-bump and a resulting device are provided. Embodiments include forming a membrane over a Si substrate having a first and second sacrificial layer disposed on opposite surfaces thereof, the membrane being formed on the first sacrificial layer, forming a first HM over the membrane, forming first and second vias through the first HM, forming a first pad layer in the first and second vias and over an exposed top thin film, forming a trench to the first sacrificial layer between the first and second vias and a gap between the trench and second via, patterning a second HM over the membrane, in the first and second vias, the trench and the gap, and forming a second pad layer over the second HM and in exposed areas around the first and second vias to form pad structures.