Enclosed RF Cavity Packaging for Low-Loss Semiconductor Signals
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Solution Overview
Problem
Semiconductor device packaging faces challenges in accommodating sophisticated features and applications while maintaining reliability, performance, and minimizing costs, leading to potential lower reliability and higher costs.
Innovation Solution
A semiconductor device with an enclosed resonant RF cavity is formed by using a semiconductor die and a pre-formed RF sub-assembly partially encapsulated with an encapsulant on a carrier substrate, where a sacrificial blank with a conductive radiant element and shield is exposed after encapsulation, and a conductive lid is attached to enclose the cavity, creating a low loss RF signal propagation environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional semiconductor device packaging is used to accommodate sophisticated features, then device functionality is improved, but reliability decreases and costs increase
Solution Approach 1:
The device is divided into distinct functional regions: an RF cavity region for radio frequency operations and a non-RF region for other functions. This segmentation allows each region to be optimized independently, enabling sophisticated features while maintaining overall reliability through isolated design control.
Solution Approach 2:
Different structural configurations are applied to different regions of the device. The RF cavity region employs a enclosed structure with specific electromagnetic properties, while other regions use conventional packaging. This local differentiation enables sophisticated RF functionality without compromising the reliability of the entire device.
2Adaptability or versatility
If conventional semiconductor device packaging is used to accommodate sophisticated features, then device functionality is improved, but manufacturing costs increase
Solution Approach 1:
The RF cavity structure is pre-formed as an integrated part of the substrate before final device assembly. The cavity walls and shielding structures are created during substrate fabrication rather than as separate components, reducing assembly complexity and manufacturing costs while enabling sophisticated RF functionality.
Solution Approach 2:
Multiple functions are combined into a single integrated structure. The substrate simultaneously serves as the device base, the RF cavity wall, and the shielding structure. This merging eliminates the need for separate RF cavity components and their associated assembly processes, reducing manufacturing costs while maintaining advanced functionality.
3Loss of energy
If an enclosed RF cavity is formed by removing a sacrificial blank, then RF signal propagation loss is reduced, but device complexity increases
Solution Approach 1:
A sacrificial blank is introduced as a temporary intermediary structure during fabrication. This blank defines the RF cavity space and is removed after encapsulation to create the enclosed cavity. The intermediary approach enables the formation of complex enclosed structures through a relatively simple subtractive process, reducing RF signal loss without proportionally increasing device complexity.
Solution Approach 2:
The physical state of the sacrificial blank material is changed to enable its removal after serving its structural purpose. The blank is made of a material that can be selectively removed through etching or dissolution, allowing the transition from a solid structural element to a void cavity while maintaining the integrity of the encapsulated device.
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 approach enables low loss RF signal propagation and increased gain for frequencies like 5G and radar signals by forming a continuous conductive resonant cavity with a signal reflector, enhancing the semiconductor device's performance and reliability while controlling costs.
Implementation Method 1
forming a resonant RF cavity
Implementation Method 2
the package lid configured to serve as a signal reflector for propagation of an RF signal
Data Source
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AI summary
A method of forming a semiconductor device is provided. The method includes placing a semiconductor die and an RF sub-assembly on a carrier substrate. The RF sub-assembly includes a sacrificial blank, a conductive radiant element, and a conductive shield. At least a portion of the semiconductor die and the RF sub-assembly is encapsulated with an encapsulant. The carrier substrate is separated from the encapsulated semiconductor die and RF sub-assembly to expose a side of the sacrificial blank. The sacrificial blank is removed to form a cavity in the RF sub-assembly such that the conductive radiant element and the conductive shield are exposed through the cavity. A package lid is affixed on the encapsulated semiconductor die and RF sub-assembly and configured to serve as a signal reflector for propagation of an RF signal.