MEMS Chip Packaging via Pre-Release Bonding
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Solution Overview
Problem
Conventional MEMS chip packaging methods, particularly those using CMOS compatible processes, face challenges with temperature sustainability and device damage due to packaging after the MEMS device is released, as materials like aluminum cannot withstand high temperatures and are prone to damage during the process.
Innovation Solution
A package method where the MEMS chip is packaged before releasing the MEMS device, involving bonding a capping wafer to a device wafer with an etch stop layer and material layer, followed by etching to form a via and release the MEMS device, allowing it to sustain high temperatures and reducing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MEMS device is packaged after it is released, then the MEMS device can be sealed in a protected space, but the MEMS device is more likely to be damaged during the package process and cannot sustain high temperature
Solution Approach 1:
The patent applies preliminary action by packaging the MEMS device before the release etching step. The capping wafer is bonded to the device wafer while the MEMS device is still in its sacrificial layer-protected state, creating a sealed structure. The release etching is then performed through openings in the capping wafer to remove the sacrificial layer and form the movable membrane. This sequence protects the aluminum-based MEMS device from high temperature damage during packaging while still achieving the sealed enclosure needed for stability.
2Ease of manufacture
If aluminum or other temperature-sensitive materials are used in the MEMS device, then the device can be manufactured by CMOS compatible process, but the device cannot sustain high temperature during packaging
Solution Approach 1:
The patent resolves this contradiction by performing the packaging operation before any high temperature processes. The capping wafer bonding is executed while the MEMS device structure is still intact with its temperature-sensitive aluminum layers. This preliminary packaging action eliminates the need to expose the aluminum-based device to high temperature during subsequent processing steps, thereby maintaining CMOS compatibility while achieving temperature sustainability.
3Reliability
If the MEMS device is packaged after release, then the sealing can be performed, but the device structure is vulnerable to damage during the packaging process
Solution Approach 1:
The patent applies preliminary action by establishing the sealed structure before the MEMS device is released. The capping wafer is bonded to the device wafer while the sacrificial layer is still present, providing structural support to the MEMS device. This preliminary sealing creates a protected environment before the release etching makes the device movable and potentially more vulnerable to damage.
Solution Approach 2:
The sacrificial layer serves as a protective cushion during the packaging process. By maintaining this layer in place before bonding the capping wafer, the patent provides structural reinforcement that protects the delicate MEMS device from mechanical damage during the packaging operation. The sacrificial layer is subsequently removed through controlled etching after the protective sealed structure is already in place.
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 enables the MEMS device to withstand higher temperatures and reduces the likelihood of damage during packaging, enhancing the yield and stability of the MEMS chip.
Implementation Method 1
bonding the capping wafer and the device wafer
Implementation Method 2
etching the etch stop layer through the via; and etching the material layer
Data Source
AI summary
The present invention proposes a MEMS chip and a package method thereof. The package method comprises: making a capping wafer by: providing a first substrate and forming an etch stop layer on the first substrate; making a device wafer by: providing a second substrate and forming a MEMS device and a material layer surrounding the MEMS device on the second substrate; bonding the capping wafer and the device wafer; after bonding, etching the first substrate to form at least one via; etching the etch stop layer through the via; etch the material layer; and forming a sealing layer on the first substrate.