Inertial Sensor Packaging With Copper Pre-Bonding And Batch Annealing
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Solution Overview
Problem
Conventional inertial sensor packaging methods face challenges with no electrical connection between bonding surfaces and low production efficiency, particularly in fusion bonding, which involves high temperature and potential metal overflow.
Innovation Solution
A packaging method involving pre-bonding with silicon oxide dielectric parts and copper metal parts, followed by low-temperature batch annealing, ensures electrical connection and improves production efficiency by reducing temperature impact and minimizing metal overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fusion bonding method is used to bond silicon dioxide and silicon, then high quality bonding is achieved, but no electrical connection is formed between bonding surfaces requiring additional metal through holes
Solution Approach 1:
The patent combines the bonding function and electrical connection function into a single copper metal part structure. The copper part serves dual purposes: providing mechanical bonding between wafer and cover, and providing electrical conduction pathways, eliminating the need for separate metal through holes and reducing process complexity.
Solution Approach 2:
The copper metal part is designed to perform multiple functions simultaneously: structural support, sealing, and electrical conduction. This multi-functional design replaces the traditional separate components (bonding layer + through-hole electrodes), simplifying the overall device structure and manufacturing process.
2Length of moving object
If metal eutectic bonding is used to reduce bonding width, then miniaturization is achieved, but production efficiency becomes low due to single wafer processing
Solution Approach 1:
The patent segments the bonding process into two distinct stages: pre-bonding at room temperature for alignment and initial bonding, followed by annealing for permanent bonding. This segmentation allows multiple wafers to be processed simultaneously in the annealing stage, dramatically improving production efficiency while maintaining the narrow bonding width achieved through copper's low melting point.
Solution Approach 2:
The pre-bonding step is performed at room temperature before the final annealing process. This preliminary action allows for precise alignment and initial bonding of multiple wafers, ensuring proper positioning before the permanent bonding occurs during annealing, thereby enabling efficient batch processing.
3Strength
If high temperature melt bonding is used for metal bonding, then strong bonding is achieved, but metal overflow occurs and device reliability is compromised
Solution Approach 1:
The patent changes the bonding parameters by using copper's low melting point property and implementing a two-stage process with controlled temperature progression. The annealing temperature is carefully controlled to be above copper's melting point for brief periods, enabling strong bonding through diffusion while minimizing the risk of metal overflow compared to traditional high-temperature melt bonding.
Solution Approach 2:
The pre-bonding step creates an initial stable bond that prevents metal overflow during the subsequent annealing process. This preliminary bonding acts as a cushion or constraint that holds the metal in place, allowing the annealing to proceed without the metal flowing uncontrollably, thereby maintaining device reliability.
4Reliability
If conventional bonding methods are used, then sealing is achieved, but additional process steps are required for electrical conduction
Solution Approach 1:
The patent merges the sealing function and electrical conduction function into the same copper metal part structure. The copper provides both the hermetic seal for the MEMS device and the electrical pathways, eliminating the need for additional process steps to create separate conduction paths and thereby improving production efficiency.
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 method achieves stable bonding with electrical connection, enhances sealing, and increases production efficiency while maintaining high reliability and fault tolerance.
Implementation Method 1
the first dielectric part and the second dielectric part are pre-bonded through a dangling bond to obtain a pre-bonded wafer
Implementation Method 2
perform batch-annealing treatment on the plurality of pre-bonded wafers to achieve permanent bonding between the first dielectric part and the second dielectric part, as well as between the first metal part and the second metal part
Implementation Method 3
annealing treatment can be carried out at low temperature, so that the first metal part and the second metal part can be bonded by diffusion
Implementation Method 4
S1: Breaking the Si—O bond of at least one of the first dielectric part and the second dielectric part
Data Source
AI summary
Disclosed an inertial sensor packaging method and an inertial sensor, the inertial sensor packaging method comprises: steps: breaking the Si—O bond of at least one of the first dielectric part in the first bonding surface in the MEMS wafer and the second dielectric part in the second bonding surface in the cover wafer; aligning the first bonding surface with the second bonding surface and attaching thereof together, so that the first dielectric part and the second dielectric part are pre-bonded through a dangling bond to obtain a pre-bonded wafer; performing heat treatment on the pre-bonded wafer to achieve permanent bonding between the first dielectric part and the second dielectric part, as well as between the first metal part and the second metal part.