Multi-Vt E-HEMT Driver Transistors for Full-Rail Pull-Up
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Solution Overview
Problem
Existing semiconductor devices with identical threshold voltages face challenges in achieving near full-rail pull-up voltage and fast slew rate due to Vt drops across multi-stage E-HEMT drivers, compromising noise immunity and static current reduction.
Innovation Solution
Fabrication of semiconductor devices with multiple transistors having different threshold voltages through varying gate materials, p-type doping materials, AlGaN layer thicknesses, and material compositions to create transistors with distinct Vt values, allowing for significant over-drive voltage and reduced static current without compromising noise immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multi-stage E-HEMT based drivers are used to minimize static current, then static current is reduced, but over-drive voltage becomes insufficient due to Vt drops across each stage
Solution Approach 1:
The patent applies local quality by creating transistors with different threshold voltages in different regions of the same wafer. Specifically, transistors in a first region have a first threshold voltage while transistors in a second region have a second threshold voltage that is lower than the first. This allows the driver circuit to use transistors with lower Vt to provide sufficient over-drive voltage while maintaining the multi-stage architecture for static current minimization.
Solution Approach 2:
The patent changes the threshold voltage parameter of transistors by varying the thickness of the AlGaN layer in different regions of the wafer. By controlling the AlGaN layer thickness, the patent achieves different threshold voltages for different transistor regions, enabling the driver to provide adequate over-drive voltage while maintaining low static current through the multi-stage configuration.
2Use of energy by moving object
If Vt of pull-up E-HEMT transistors is reduced to provide enough over-drive voltage, then over-drive voltage is sufficient, but noise immunity is compromised
Solution Approach 1:
The patent resolves this contradiction by assigning different threshold voltages to different transistor regions based on their functional requirements. Transistors in the pull-up region can have higher Vt for noise immunity, while transistors in the driver region have lower Vt for sufficient over-drive voltage. This spatial differentiation of transistor characteristics allows both requirements to be satisfied simultaneously.
3Use of energy by moving object
If Vt is reduced to provide over-drive voltage, then over-drive voltage is sufficient, but power switch HEMT cannot withstand large back-feed-through impulse voltage
Solution Approach 1:
The patent addresses this issue by implementing region-specific transistor characteristics where the power switch HEMT is positioned in a region with higher threshold voltage that can withstand back-feed-through impulse voltage, while the driver transistors in a different region have lower threshold voltage to provide sufficient over-drive voltage. This spatial separation of functional requirements resolves the contradiction.
Data Source
AI summary
A semiconductor device includes: a plurality of transistors on a substrate, each transistor of the plurality of transistors including a source region, a drain region, a gate structure, a polarization modulation portion, and a polarization layer. The polarization modulation portion of each of the plurality of transistors is on the polarization layer, the plurality of transistors includes a first transistor having a first threshold voltage that has a first fixed value, and the plurality of transistors includes a second transistor having a second threshold voltage that has a second fixed value different from the first fixed value.