GaN-on-Silicon Interconnect Layout With Low-k Capacitance Isolation
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Solution Overview
Problem
Gallium nitride-on-silicon semiconductor devices face performance limitations due to parasitic capacitance between interconnects and the ground plane, which degrades their performance at high frequencies.
Innovation Solution
Replacing a portion of the substrate between interconnects and the ground with a material having a lower dielectric constant, such as silicon dioxide, formed using a LOCOS process, to reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silicon substrate is used for GaN devices, then mechanical strength and thermal conductivity are improved, but parasitic capacitance between interconnects and ground increases due to the high dielectric constant of silicon
Solution Approach 1:
The patent applies local quality by replacing the silicon substrate material specifically in the interconnect regions with a low-k dielectric material, while maintaining silicon substrate in other areas. This creates spatially varying material properties where the interconnect regions have low parasitic capacitance (low-k material) and other regions maintain the mechanical and thermal benefits of silicon substrate.
Solution Approach 2:
The patent uses composite materials by combining silicon substrate with low-k dielectric materials in a multi-layer structure. The silicon substrate provides mechanical support and thermal management, while the low-k dielectric layers (such as silicon dioxide or organic dielectrics) are inserted between interconnects and ground to reduce parasitic capacitance. This composite approach allows simultaneous optimization of mechanical strength and electrical performance.
2Reliability
If the dielectric constant between interconnects and ground is reduced, then parasitic capacitance is reduced improving RF performance, but the complexity of the fabrication process increases
Solution Approach 1:
The patent applies preliminary action by forming the low-k dielectric material layers during the early stages of fabrication, before metal interconnect layers are deposited. The low-k dielectric layers are formed as part of the substrate preparation process, and subsequent interconnect layers are built upon this pre-prepared structure. This sequencing simplifies the overall process by avoiding later modifications.
Solution Approach 2:
The patent changes material parameters by selecting low-k dielectric materials with specific dielectric constants (k < 3.9) to replace or supplement the silicon substrate in interconnect regions. This parameter change directly reduces parasitic capacitance (C = kε₀A/d) while the fabrication process uses standard semiconductor processing techniques to minimize complexity increases.
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 effectively reduces parasitic capacitance, enhancing the RF performance of GaN-on-silicon structures by lowering the dielectric constant between interconnects and the ground, thereby improving device performance at high frequencies.
Implementation Method 1
Replacing a portion of the substrate between interconnects and the ground with a material having a lower dielectric constant, such as silicon dioxide
Implementation Method 2
oxidizing the silicon substrate in the trenches to form silicon dioxide regions
Data Source
AI summary
Semiconductor structures with reduced parasitic capacitance between interconnects and ground, for example, are described. In one case, a semiconductor structure includes a substrate and a low dielectric constant material region in the substrate. The low dielectric constant material region is positioned between a first device area in the semiconductor structure and a second device area in the semiconductor structure. The semiconductor structure also includes a III-nitride material layer over the substrate. The III-nitride material layer extends over the substrate in the first device area, over the low dielectric constant material region, and over the substrate in the second device area. The semiconductor structure can also include a first device formed in the III-nitride material layer in the first device area, a second device in the III-nitride material layer in the second device area, and an interconnect formed over the low dielectric constant material region. The interconnect can provide a continuous conductive path of metal from the first device area, over the low dielectric constant material region, and to the second device area.