FBAR Packaging Structure Using Elastic Bonding and Grooved Cover
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Solution Overview
Problem
The existing packaging process for film bulk acoustic resonators (FBARs) is complex, costly, and introduces gold-related pollution, with insufficient mechanical strength due to the Au—Au bonding process and passivation layer gaps, leading to reliability risks.
Innovation Solution
A packaging method using an elastic bonding material layer to bond a resonant cavity main structure with a second substrate having a groove, forming through holes and a conductive interconnection layer, and patterning a passivation layer to create a stable and reliable FBAR structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Au—Au bonding process is used to bond the carrier wafer with the resonant cavity main structure, then bonding strength is improved, but manufacturing complexity and cost increase, and gold-related pollution is introduced
Solution Approach 1:
The patent extracts and removes the carrier wafer after bonding, replacing the complex Au—Au bonding process with a simpler bonding method using a release layer. The release layer allows the resonant cavity main structure to be separated from the carrier wafer without requiring expensive gold bonding, thereby reducing manufacturing complexity and cost while maintaining bonding strength.
Solution Approach 2:
The patent introduces a release layer as an intermediary between the carrier wafer and the resonant cavity main structure. This release layer facilitates bonding during manufacturing and then enables easy separation, serving as a mediator that replaces the need for complex Au—Au bonding and subsequent carrier wafer removal, thus reducing manufacturing complexity and eliminating gold-related pollution.
2Reliability
If passivation layer is deposited to protect the structure, then protection is improved, but gaps in holes remain causing insufficient mechanical strength
Solution Approach 1:
The patent performs preliminary action by filling the holes with conductive material before depositing the passivation layer. This ensures that the passivation layer is deposited over a continuous, gap-free surface, eliminating the gaps that would otherwise compromise mechanical strength. The preliminary filling action prevents the formation of weak points in the final structure.
Solution Approach 2:
The patent uses composite materials by combining the conductive filling material with the passivation layer to create a structurally sound composite structure. The conductive material fills and strengthens the hole regions, while the passivation layer provides protective coverage, together forming a composite structure with both electrical conductivity and enhanced mechanical strength.
3Manufacturing precision
If multiple process steps including carrier wafer removal are used, then packaging precision is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent extracts and removes the carrier wafer through a simplified process using a release layer, eliminating the need for complex carrier wafer removal steps. The release layer enables clean separation without damaging the resonant cavity main structure, maintaining packaging precision while significantly reducing manufacturing time and the number of process steps.
Solution Approach 2:
The release layer provides self-service functionality by automatically enabling separation of the resonant cavity main structure from the carrier wafer through its designed release mechanism. This eliminates the need for additional complex removal processes, allowing the structure to be separated cleanly and efficiently, thereby reducing manufacturing time while maintaining precision.
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 simplifies the process, reduces costs, eliminates gold-related pollution, and enhances mechanical strength and reliability by using an elastic bonding material that adapts to step height differences, improving the stability and resonance performance of the FBAR.
Implementation Method 1
bonding the resonant cavity main structure and the resonator cover together through the elastic bonding material layer, and removing elasticity of the elastic bonding material layer
Data Source
AI summary
The present disclosure provides a packaging method and packaging structure of an FBAR. A second cavity in a resonator cover provided includes a groove in a second substrate and a space surrounded by an elastic bonding material layer. The elastic bonding material layer bonds the resonator cover to a resonant cavity main structure, and elasticity of the elastic bonding material layer is removed after the bonding. Through holes and a conductive interconnection layer on inner surfaces of the through holes are formed on the resonator cover. Since the second cavity includes the groove in the second substrate and the space surrounded by the elastic bonding material layer, which can avoid problems that performance of the elastic bonding material layer is unstable with temperature and humidity changes when the second cavity is entirely surrounded by the elastic bonding material layer, that is, the stability of the resonator is improved.