Piezoelectric Device Package with Through-Substrate Vias for 3D Stacking
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Solution Overview
Problem
Current packaging technologies for SAW and BAW devices face challenges such as large UBM pad area requirements, limited design flexibility, hermeticity issues, dome cracking, and lack of metal shielding, which hinder the miniaturization and flexibility of three-dimensional chip arrangements, especially in wafer-level packaging.
Innovation Solution
A package design featuring a substrate with a piezoelectric layer, a mechanical support layer forming domes to enclose device structures, and contact pads on both surfaces, allowing for stacked configurations and external contact from either side, with a method involving wafer-level processing and metallization to connect pads and form cavities, enabling compact and flexible integration of devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UBM pads are used to connect device structures, then electrical connectivity is achieved, but large area consumption on the active surface occurs
Solution Approach 1:
The patent moves contact pads from the top surface to the back surface of the substrate, utilizing the third dimension (depth/thickness) to resolve the area conflict. Through-holes provide vertical electrical pathways, eliminating the need for large UBM pads on the active surface while maintaining reliable electrical connectivity.
2Adaptability or versatility
If contact pads are positioned flexibly, then design flexibility is improved, but hermeticity is compromised due to openings in SiN layer
Solution Approach 1:
The patent segments the electrical connection path into two parts: contact pads on the back surface and through-holes penetrating the substrate. This segmentation allows contact pads to be positioned flexibly on the back surface without compromising the hermeticity of the top surface SiN layer, as the electrical connection is achieved through the substrate thickness rather than through openings in the SiN layer.
3Volume of stationary object
If domes are made large to enclose device structures, then cavity volume is increased, but mechanical stability decreases leading to cracking
Solution Approach 1:
The patent resolves the mechanical stability issue by moving contact pads to the back surface and using through-holes for electrical connection. This dimensional change eliminates the need for large domes with protruding contact structures, allowing domes to be optimized for mechanical stability while maintaining adequate cavity volume for device enclosure.
4Area of stationary object
If contact pads are positioned close to device structures, then area consumption is reduced, but design flexibility is limited
Solution Approach 1:
By relocating contact pads to the back surface of the substrate, the patent decouples pad positioning from device structure positioning on the top surface. This allows independent optimization of both: device structures can be compactly arranged on the top surface while contact pads are flexibly positioned on the back surface, achieving both small area consumption and high design flexibility.
Data Source
AI summary
A package for an electric device is proposed based on a substrate (SU, SU1, SU2) that comprises at least a piezoelectric layer. Device structures are enclosed in a cavity of an integrally formed package layer structure (PK) of a thin film package applied on the first surface (SI). A first contact pad (PI) is arranged on the first surface of the substrate and electrically connected to the device structures. A second contact pad (P2) is arranged on a second surface (S2) of the substrate opposite to the first surface (SI). A via (V) is guided through the substrate and interconnects first and second contact pads electrically. Packages may be stacked on one another and connected via two pads of different kind. The first substrate (SU1) is connected via its second pad (P2) on the second surface thereof to the first pad of a second substrate (SU2) by means of connection means (CM).