Wafer Level MEMS Device with Silicon Pillar and Smart Cap
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Solution Overview
Problem
Conventional fabrication techniques for multi-cavity multi-pressure MEMS device chips are inefficient, particularly when attempting wafer-to-wafer bonding without a gas pressure adjustment vent and sealing system, leading to complications in accurately setting cavity pressures and potential outgassing issues.
Innovation Solution
A MEMS package design that includes a capping substrate with recessed regions for different MEMS devices, a ventilation trench for independent pressure adjustment, and a conductive silicon pillar for electrical connection, allowing for hermetic sealing and precise pressure control within individual cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication techniques are used for wafer-to-wafer bonding without a gas pressure adjustment vent and sealing system, then the manufacturing process is simpler, but the cavity pressure control precision deteriorates and outgassing issues occur
Solution Approach 1:
The patent divides the bonding interface into multiple functional zones: a vent region with opening(s) that allows gas pressure adjustment independent of the bonding process, and a bonding region with bonding pads for wafer-to-wafer bonding. This segmentation enables simultaneous pressure control and bonding operations without interfering with each other, resolving the contradiction between pressure control precision and process simplicity.
Solution Approach 2:
The patent introduces a vent structure with opening(s) as an intermediary element between the bonding interface and the cavity interior. This vent structure serves as a mediator that allows gas pressure adjustment during bonding without compromising the bonding process itself, enabling precise pressure control while maintaining fabrication simplicity.
2Productivity
If multiple MEMS devices are integrated on a single substrate, then the device integration density increases and footprint is reduced, but the pressure control complexity for each device increases
Solution Approach 1:
The patent implements a universal vent structure that serves multiple functions: it provides independent pressure control for different cavities containing different MEMS devices, maintains hermetic sealing during bonding, and allows gas pressure adjustment without affecting other devices. This multi-functional design enables high device integration density while keeping pressure control manageable through a standardized approach.
Solution Approach 2:
The patent creates independently controllable cavities for different MEMS devices on the same substrate, with each cavity having its own pressure control capability through the vent structure. This segmentation allows each device to operate at its optimal pressure independently, reducing the overall system complexity compared to a unified pressure control approach.
3Reliability
If wafer-to-wafer bonding is performed without a vent structure, then the bonding process is faster, but the gas pressure adjustment capability is lost and outgassing issues arise
Solution Approach 1:
The patent incorporates the vent structure with opening(s) into the wafer design before bonding occurs. This preliminary action ensures that gas pressure adjustment capability is already in place during the bonding process, preventing outgassing issues without requiring additional time for pressure adjustment after bonding. The vent structure is pre-positioned to allow simultaneous bonding and pressure management.
Solution Approach 2:
The vent structure serves as an intermediary that mediates between the bonding process and gas pressure management. It allows the bonding process to proceed quickly while simultaneously providing a pathway for gas pressure adjustment, preventing outgassing issues without slowing down the bonding operation.
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
Enables efficient integration of multiple MEMS devices on a single substrate with independent pressure control, optimizing the performance of each device, such as accelerometers and gyroscopes, while maintaining a small footprint and reducing fabrication costs.
Implementation Method 1
a conductive silicon pillar for electrical connection
Implementation Method 2
bonding the device substrate to the capping substrate hermetically sealing a cavity at a gas pressure
Data Source
AI summary
The present disclosure relates to a micro-electro mechanical system (MEMS) package and a method of achieving differential pressure adjustment in multiple MEMS cavities at a wafer-to-wafer bonding level. In some embodiments, a ventilation trench and an isolation trench are concurrently within a capping substrate. The isolation trench isolates a silicon region and has a height substantially equal to a height of the ventilation trench. A sealing structure is formed within the ventilation trench and the isolation trench, the sealing structure filing the isolation trench and defining a vent within the ventilation trench. A device substrate is provided and bonded to the capping substrate at a first gas pressure and hermetically sealing a first cavity associated with a first MEMS device and a second cavity associated with a second MEMS device. The capping substrate is thinned to open the vent to adjust a gas pressure of the second cavity.