Air-Box Gate Encapsulation for High-Frequency Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-frequency active circuits, such as those operating above 50 GHz, face damage risks due to fragility and environmental exposure, and conventional dielectric encapsulation methods provide protection but increase parasitic capacitance, degrading performance by reducing gain, frequency stability, and efficiency.
Innovation Solution
A semiconductor device with transistors mounted on a substrate, where the gate terminals are encapsulated within cavities formed in multiple layers of dielectric material, reducing parasitic capacitance and maintaining performance by isolating the gate terminals from the dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric encapsulation is used to protect high-frequency circuits, then physical protection and mechanical support are improved, but parasitic capacitance increases causing performance degradation
Solution Approach 1:
The encapsulation structure is segmented into multiple dielectric layers with air gaps between them. The air gaps act as separators that reduce parasitic capacitance between the gate terminal and the dielectric material, while still providing physical protection through the layered dielectric structure.
Solution Approach 2:
Air gaps are introduced as intermediary spaces between the gate terminal and the dielectric material. These air gaps serve as mediators that reduce the parasitic capacitance coupling between conductive elements and the dielectric enclosure, while the dielectric layers continue to provide mechanical support and environmental protection.
2Object-affected harmful factors
If dielectric material is placed around transistor gates for encapsulation, then environmental protection is improved, but gain and frequency stability deteriorate
Solution Approach 1:
The continuous dielectric material is segmented into discrete layers separated by air gaps. This segmentation allows the dielectric to provide environmental protection while the air gaps prevent the formation of continuous parasitic capacitance paths that would degrade frequency stability and gain.
Solution Approach 2:
The encapsulation structure uses different materials and configurations in different locations: dielectric material is used where environmental protection is needed, while air gaps are positioned specifically around gate terminals where parasitic capacitance would most adversely affect performance. This local differentiation optimizes both protection and electrical performance.
3Strength
If multi-layer dielectric encapsulation is used, then mechanical support for interconnects is improved, but device complexity increases
Solution Approach 1:
The encapsulation is divided into multiple dielectric layers with air gaps, where each layer can independently support specific interconnect levels. This segmentation provides mechanical support for complex multi-level interconnect structures while the repetitive layered pattern actually simplifies the manufacturing process compared to monolithic encapsulation.
Solution Approach 2:
The multi-layer dielectric structure with embedded air gaps creates a nested configuration where dielectric layers and air gaps are alternately positioned. This nested structure efficiently uses vertical space to provide mechanical support for multiple interconnect levels while maintaining a compact overall device profile.
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
The solution effectively protects high-frequency circuits from environmental damage while minimizing performance degradation, maintaining significant gain and frequency stability, and supporting multi-level interconnects for scalability and flexibility.
Implementation Method 1
two or more layers of dielectric material encapsulate a front side of the one or more transistors
Implementation Method 2
the presence of dielectric material around gates of components of the circuit causes parasitic capacitance to increase
Data Source
AI summary
A semiconductor device comprises one or more transistors and two or more layers of dielectric material encapsulating a front side of said one or more transistors. The gate of each of said one or more transistors is located within a cavity, or air-box, in at least one of the dielectric layers, so that the gate terminal is physically separated from said dielectric material. Such an arrangement may reduce parasitic capacitance. In another arrangement, a semiconductor device comprises one or more gallium nitride high electron mobility transistors and one or more dielectric layers encapsulating a front side of said one or more transistors, wherein the gate terminal of each of said one or more transistors is located within a cavity in at least one of the one or more dielectric layers, separated from said dielectric material.