GaN HEMT Threshold Voltage Tuning for Monolithic IC Integration
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Solution Overview
Problem
Existing semiconductor devices in integrated circuits lack the ability to effectively integrate semiconductor devices with different threshold voltages, limiting their performance and efficiency in high-frequency applications.
Innovation Solution
The integration of semiconductor devices with varying threshold voltages is achieved by employing techniques such as varying gate layer thickness, barrier layer thickness, channel layer thickness, gate length, gate contact offset length, dopant concentration, and metal-barrier work function, enabling monolithic integration of HEMTs and diodes with different threshold voltages on a gallium nitride platform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor devices with different threshold voltages are integrated on the same substrate, then circuit performance and efficiency are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by creating different threshold voltages in different regions of the HEMT structure. Specifically, it uses varying gate layer thicknesses, barrier layer compositions, and dopant concentrations in different areas of the same device to achieve multiple threshold voltages, allowing diverse circuit functions on a single substrate without increasing overall device complexity
Solution Approach 2:
The patent implements parameter changes by systematically varying critical structural parameters including gate layer thickness, barrier layer aluminum composition, channel layer thickness, and dopant concentrations. These parameter modifications enable the creation of HEMTs with different threshold voltages (both positive and negative) while maintaining compatibility with standard GaN fabrication processes
2Loss of energy
If multiple HEMTs with different threshold voltages are integrated, then power conversion efficiency is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the barrier layer into multiple distinct layers with different aluminum compositions (e.g., first barrier layer with 30% Al, second barrier layer with 40% Al). This segmentation allows independent control of threshold voltages for different HEMTs while using standard epitaxial growth techniques, balancing manufacturing precision requirements with performance optimization
Solution Approach 2:
The patent implements preliminary action by pre-configuring the barrier layer structure with specific aluminum compositions and thicknesses during the epitaxial growth process. This preliminary structuring enables subsequent fabrication steps to proceed with standard processes while already having the threshold voltage characteristics built into the device architecture
3Area of stationary object
If HEMTs with different threshold voltages are integrated on a single substrate, then device size is reduced, but integration difficulty increases
Solution Approach 1:
The patent applies universality by designing a single HEMT structure that can provide multiple threshold voltage characteristics through configurable parameters. The same basic GaN HEMT architecture can be tuned to provide negative threshold voltage, positive threshold voltage, or enhanced mode operation by adjusting gate thickness, barrier composition, and dopant levels, eliminating the need for entirely different device structures
Solution Approach 2:
The patent implements composite materials by using multi-layer barrier structures with different aluminum gallium nitride compositions. The combination of barrier layers with varying aluminum percentages (e.g., Al0.3Ga0.7N and Al0.4Ga0.6N) creates a composite structure that enables different threshold voltages while maintaining lattice matching and reducing dislocation densities in the GaN channel
Data Source
AI summary
The present disclosure generally relates to semiconductor devices in an integrated circuit (IC) that have different threshold voltages. In an example, a channel layer is formed on a semiconductor substrate. The channel layer includes a gallium nitride (GaN) material. A barrier layer is formed on the channel layer. A first semiconductor device is formed on the semiconductor substrate. The first semiconductor device includes a first terminal over the barrier layer, and the first semiconductor device has a first threshold voltage. A second semiconductor device is formed on the semiconductor substrate. The second semiconductor device includes a second terminal over the barrier layer, and the second semiconductor device has a second threshold voltage different from the first threshold voltage. The first and second threshold voltages are both positive or negative voltages.