Wafer Eutectic Bonding with Stop Structures for Stress Decoupling
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Solution Overview
Problem
Conventional MEMS sensor packaging techniques face challenges in mechanically decoupling the pressure-sensitive membrane from the rest of the sensor due to mechanical stress from external influences, requiring thin wafers that are difficult to process and necessitating carrier wafers for stress decoupling.
Innovation Solution
A method for producing a wafer connection using eutectic bonding between two wafers, where one wafer has a receiving structure filled with a first material and the other wafer has a die structure with a second material, both heated to the eutectic temperature to form a reliable mechanical and electrical connection, with stop structures ensuring a defined distance and volume for stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thin wafer is used for stress decoupling, then the pressure sensor membrane can be mechanically decoupled from the rest of the sensor, but the wafer becomes difficult to process and requires mounting on a carrier wafer
Solution Approach 1:
The patent changes the physical state parameter of the bonding material from solid to liquid (melting) to achieve eutectic bonding, enabling reliable connection without requiring thin wafer processing or carrier wafer mounting
Solution Approach 2:
The patent utilizes phase transition of the bonding material (melting and solidification) during the eutectic bonding process to create a reliable mechanical and electrical connection between wafers, eliminating the need for stress decoupling through thinning
2Reliability
If conventional eutectic bonding is used for electrical connection, then reliable electrical connection is achieved, but material loss occurs and process tolerances are not adequately accommodated
Solution Approach 1:
The patent applies preliminary action by pre-filling the receiving structure with bonding material and providing stop structures before the bonding process, which prevents material loss and accommodates process tolerances during eutectic bonding
Solution Approach 2:
The patent provides beforehand cushioning by creating a receiving structure with stop structures that define a specific volume for the bonding material, preventing material loss and accommodating variations in the bonding process
3Reliability
If heating to eutectic temperature is applied, then reliable mechanical and electrical connection is achieved, but energy consumption increases
Solution Approach 1:
The patent utilizes phase transition (melting) of the bonding material at eutectic temperature to achieve reliable wafer connection. The controlled melting and subsequent solidification creates strong mechanical and electrical bonds
Solution Approach 2:
The patent employs composite material strategy by using a eutectic alloy system (e.g., Al-Si) that melts at a lower temperature than individual components, reducing energy consumption while maintaining bonding reliability
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 enables a reliable mechanical and electrical connection between wafers, reducing material loss and accommodating process tolerances, while providing a stable and energy-efficient bonding process.
Implementation Method 1
heating at least the first and second material at least to the eutectic temperature of the eutectic alloy
Data Source
AI summary
A method for producing a wafer connection between a first and a second wafer. The method includes providing a first and second material for forming a eutectic alloy, providing a first wafer having a receiving structure for a die structure, filling the receiving structure with the first material, providing a second wafer having a die structure, the second material being situated on the die structure, providing a stop structure on the first and/or second wafer, so that when the two wafers are joined, a defined stop is provided, heating the first and second material at least to the eutectic temperature of the eutectic alloy, joining the first and second wafer so that the die structure is at least partly introduced into the receiving structure, the stop structure, the receiving structure, the die structure.