Stacked AW Filter Package Layout for Cavity-Safe 3D Integration
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Solution Overview
Problem
Conventional methods for 3D IC stacking are not applicable to acoustic wave (AW) filter devices due to the need for protective cavities around AW filter circuits, which interferes with vertical stacking.
Innovation Solution
The development of multi-level stacked AW filter packages that include structures to support stacked AW filters, featuring a first substrate with an AW filter circuit, a frame, and a second substrate that encloses an air cavity, allowing for vertical stacking without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional 3D IC stacking methods are used, then vertical stacking of ICs is achieved with reduced area, but AW filter devices cannot be stacked because protective cavities interfere with vertical stacking
Solution Approach 1:
The patent transitions from horizontal side-by-side placement to vertical stacking by introducing a cap substrate that encloses the AW filter circuit in a cavity structure. This dimensional change allows multiple AW filter devices to be stacked vertically without the cavities interfering with each other, as each device's cavity is enclosed within its own cap substrate.
Solution Approach 2:
The cap substrate encloses the AW filter circuit within a cavity, creating a nested structure where the filter circuit is contained within the cap substrate's protective cavity. This nesting allows the cavity to be self-contained and not interfere with external stacking operations, enabling vertical integration of multiple such nested structures.
2Reliability
If protective cavities are provided around AW filter circuits, then wave propagation is protected from physical contact, but vertical stacking is interfered with
Solution Approach 1:
The patent merges the protective cavity function with the stacking structure by making the cap substrate itself form the cavity enclosure. The cap substrate serves dual purposes: protecting the AW filter circuit through cavity enclosure and enabling vertical stacking through its structural design. This consolidation eliminates the need for separate protective structures that would interfere with stacking.
3Adaptability or versatility
If more AW filter circuits are added to increase functional capabilities, then device functionality is improved, but device size increases
Solution Approach 1:
The patent utilizes the vertical dimension for stacking multiple AW filter circuits instead of expanding horizontally. By stacking devices vertically within a compact footprint, the package area is reduced while maintaining or increasing the number of functional filter circuits, thereby improving functionality without proportionally increasing device size.
Solution Approach 2:
The cap substrate acts as a thin enclosing structure that provides protective cavities for the AW filter circuits while occupying minimal vertical space. This thin-film approach allows multiple such structures to be stacked closely together, increasing circuit density without significant increase in overall device volume.
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 solution enables the creation of compact AW filter packages with increased circuit density, allowing more functional capabilities in mobile wireless devices without increasing device size.
Implementation Method 1
An AW filter circuit converts an electrical input signal into acoustic waves in a piezoelectric material
Implementation Method 2
The RF signal is converted into acoustic waves that propagate through the surface of the piezoelectric material from the first IDT to the second IDT
Data Source
AI summary
A multi-level stacked AW filter package including a first acoustic wave (AW) filter stacked on a second AW filter employs semiconductor fabrication methods and structures, including a metallization layer comprising interconnects to couple a contact surface to the second AW filter. Each AW filter includes an AW filter circuit on a semiconductor substrate. A second substrate disposed on a frame on the substrate protects the AW filter circuit. In a multi-level AW filter package, the second substrate of the first AW filter comprises a glass substrate with a similar expansion rate as the semiconductor substrate. The interconnects coupling the second AW filter to the contact surface are disposed on insulators on the side wall surfaces of the semiconductor substrates of the first AW filter for isolation. In a stacked AW filter package comprising a single AW filter, the interconnects couple the contact surface to the AW filter.