Semiconductor Transistors on Separate Metal Substrates
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Solution Overview
Problem
The challenge is to create a semiconductor device that can operate as a normally-off transistor for power circuits handling high voltages while minimizing the thermal influence from a power-consuming normally-on nitride semiconductor transistor, which affects the characteristics and reliability of the circuit.
Innovation Solution
The solution involves a semiconductor device configuration with a normally-off silicon transistor and a normally-on nitride transistor, where the transistors are physically separated on different metal substrates with low thermal conductivity, and the normally-on transistor's heat is suppressed from affecting the normally-off transistor, with additional features like a zener diode or schottky-barrier diode for overvoltage protection and current collapse prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a normally-on nitride semiconductor transistor and a normally-off silicon transistor are connected in cascode on the same substrate, then a normally-off operation can be realized for power circuits, but the heat generated by the normally-on transistor affects the operation of other elements and causes characteristics variation
Solution Approach 1:
The patent divides the semiconductor device into separate substrates: a first substrate containing the normally-on nitride semiconductor transistor and a second substrate containing the normally-off silicon transistor. This physical segmentation isolates the heat-generating normally-on transistor from other circuit elements, preventing thermal interference while maintaining the cascode connection benefits for normally-off operation.
Solution Approach 2:
The patent introduces a heat dissipation structure as an intermediary between the normally-on nitride semiconductor transistor and the normally-off silicon transistor. This intermediary component actively manages thermal energy, conducting heat away from the normally-on transistor to prevent it from affecting the characteristics and operation of the normally-off transistor and other circuit elements.
2Reliability
If a normally-on nitride semiconductor transistor is used in a cascode configuration, then overvoltage protection can be achieved, but current collapse may occur due to thermal effects
Solution Approach 1:
By separating the normally-on nitride semiconductor transistor from the normally-off silicon transistor onto different substrates, the patent prevents thermal effects from causing current collapse in the normally-off transistor while preserving the overvoltage protection function of the cascode configuration.
Solution Approach 2:
The heat dissipation structure acts as an intermediary that thermally isolates the normally-on transistor from the normally-off transistor, preventing thermal-induced current collapse while allowing the normally-on transistor to continue providing overvoltage protection through its cascode connection.
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 configuration reduces characteristics variation and enhances reliability by isolating thermal influences and providing effective overvoltage protection, ensuring stable operation and extended lifespan of the semiconductor device.
Implementation Method 1
a gate voltage limiting element which is connected between a gate of the normally-off transistor and a source of the normally-off transistor
Implementation Method 2
a schottky-barrier diode which is connected in parallel with a source-drain of the normally-off transistor
Implementation Method 3
the heat generated by the normally-on transistor which consumes a large amount of power affects the operation of other elements
Data Source
AI summary
A semiconductor device according to one embodiment is provided with a first metal substrate, a second metal substrate separated from the first metal substrate, a normally-off transistor of a silicon semiconductor provided on the first metal substrate, and a normally-on transistor of a nitride semiconductor provided on the second metal substrate.