WLP BAW Resonator Oxide Adhesion Layer for Compact Via Packaging
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Solution Overview
Problem
Conventional wafer-level packaged (WLP) bulk acoustic wave (BAW) devices face challenges in reducing device size and achieving superior adhesion between the WLP enclosure and the BAW resonator, which affects the reliability and performance due to space constraints and potential chemical intrusion.
Innovation Solution
The implementation of a WLP BAW device design that includes a piezoelectric layer with a first interface opening, a bottom electrode, a bottom electrode lead, a first interface structure, a WLP enclosure with a first through-WLP via, a passivation layer, and an oxide adhesion layer, where the oxide adhesion layer provides superior adhesion between the WLP enclosure and the piezoelectric layer, reducing the need for extra space and enhancing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the opening of the piezoelectric layer is positioned far away from the WLP enclosure to accommodate the copper pillar connection, then the external electrical connection is ensured, but the device cross-sectional area increases
Solution Approach 1:
The patent transitions the electrical connection from a lateral arrangement (copper pillar extending horizontally from the piezoelectric layer) to a vertical arrangement (through-WLP via extending vertically through the WLP enclosure). This dimensional change allows the connection to be made directly beneath the piezoelectric layer opening, eliminating the need for lateral space and reducing the device footprint while maintaining electrical connectivity
2Reliability
If the WLP enclosure is adhered tightly to the piezoelectric layer to prevent chemical intrusion, then the performance stability is improved, but the adhesion reliability deteriorates due to thermal expansion mismatch
Solution Approach 1:
The patent introduces an adhesion layer as an intermediary between the WLP enclosure and the piezoelectric layer. This adhesion layer has intermediate thermal expansion properties between the WLP enclosure and the piezoelectric layer, acting as a buffer that accommodates thermal expansion mismatch while maintaining strong adhesion and preventing chemical intrusion during temperature cycling
Solution Approach 2:
The patent employs a composite structure with multiple layers having different material properties. The adhesion layer is specifically designed with thermal expansion properties that are intermediate between the WLP enclosure and the piezoelectric layer, creating a graded composite structure that manages thermal stress while maintaining structural integrity and adhesion strength
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 design reduces the device size by eliminating the need for extra space between the WLP enclosure and interconnects, while ensuring reliable adhesion and preventing chemical intrusion, thus maintaining performance stability during temperature cycling and assembly processes.
Implementation Method 1
an oxide adhesion layer, wherein the oxide adhesion layer provides superior adhesion between the WLP enclosure and the BAW resonator
Data Source
AI summary
The present disclosure relates to a wafer-level packaged (WLP) bulk acoustic wave (BAW) device, which includes a BAW resonator and a WLP enclosure. The BAW resonator includes a piezoelectric layer with an interface opening, a bottom electrode lead underneath the interface opening, an interface structure extending over the interface opening and connected with the bottom electrode lead, a passivation layer with a passivation opening over the interface structure, and an oxide adhesion layer with an adhesion opening over the passivation layer. The WLP enclosure includes an outer wall directly residing over the oxide adhesion layer, and a through-WLP via encompassed by the outer wall and vertically aligned with the adhesion opening and the passivation opening. A portion of the interface structure is exposed to the through-WLP via through the adhesion opening and the passivation opening.