Sintered Silver Paste Contacts for MEMS Actuator Reliability
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Solution Overview
Problem
Existing MEMS devices face challenges in forming reliable electrical contacts due to adverse effects from high-temperature and etch processes, which can be costly and labor-intensive, especially when using shadow masking operations.
Innovation Solution
The formation of sintered metalized electrical contacts, such as silver-paste-metalized contacts, on MEMS devices after etching processes are completed, using materials like silver paste, powder, or preforms, which are deposited and then sintered on the wafer before singulation into individual devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical contacts are formed using metal sputtering and patterning processes during wafer fabrication, then electrical contacts can be created on MEMS devices, but the contacts are adversely affected by subsequent high-temperature and etch processes
Solution Approach 1:
The patent applies preliminary action by forming the electrical contacts AFTER the wafer fabrication and etch processes are completed, rather than before. Specifically, contacts are formed on released wafers or dies using shadow masking and evaporation, ensuring the contacts are not exposed to the damaging high-temperature and etch processes that occur during wafer fabrication. This reverse sequencing of operations protects the electrical contacts from harmful processing.
2Reliability
If shadow masking operations are used to form metal contacts after release, then electrical contacts can be formed without damage from processing, but the operations become prohibitively expensive and labor intensive
Solution Approach 1:
The patent applies segmentation by dividing the manufacturing process into distinct stages: wafer-level fabrication, release, contact formation on released wafers, and final singulation. This allows electrical contacts to be formed on multiple devices simultaneously at the wafer level rather than individually, significantly reducing labor intensity and cost while maintaining reliability through the protective sequencing of operations.
3Productivity
If electrical contacts are formed during wafer fabrication, then contacts can be created early in the process, but subsequent etch processes can negatively affect the metal contacts
Solution Approach 1:
The patent applies inversion by reversing the conventional sequence of operations. Instead of forming electrical contacts early during wafer fabrication and then protecting them through subsequent processes, the patent forms contacts after the damaging etch processes are complete. This inverted sequencing eliminates the need for protective measures while maintaining process efficiency through wafer-level parallel processing.
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 method allows for the creation of robust electrical contacts that are less susceptible to semiconductor processing damages, reducing costs and complexity while ensuring reliable connections to external circuitry.
Implementation Method 1
depositing sintering material on the released MEMS wafer, and sintering the sintering material by heating the wafer
Data Source
AI summary
A microelectromechanical systems (MEMS) device may be provided with one or more sintered electrical contacts. The MEMS device may be a MEMS actuator or a MEMS sensor. The sintered electrical contacts may be silver-paste metalized electrical contacts. The sintered electrical contacts may be formed by depositing a sintering material such as a metal paste, a metal preform, a metal ink, or a metal powder on a wafer of released MEMS devices and heating the wafer so that the deposited sintering material diffuses into a substrate of the device, thereby making electrical contact with the device. The deposited sintering material may break through an insulating layer on the substrate during the sintering process. The MEMS device may be a multiple degree of freedom actuator having first and second MEMS actuators that facilitate autofocus, zoom, and optical image stabilization for a camera.