Semiconductor Module Stress Application for Low-Temperature Resistance
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Solution Overview
Problem
The negative temperature characteristic of semiconductor switching elements leads to increased ON resistance and turn-off surge voltage, resulting in higher costs and larger sizes for semiconductor modules, as existing solutions require complex temperature monitoring and additional components to manage these issues.
Innovation Solution
Incorporating stress application portions with a higher linear expansion coefficient and thickness than the semiconductor switching element, which generate compressive or tensile stress through thermal expansion or shrinkage, thereby reducing the threshold voltage and suppressing increases in ON resistance and turn-off surge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the current-conduction area of the semiconductor switching element is increased to suppress ON resistance, then the ON resistance decreases, but the area and size of the semiconductor module increases
Solution Approach 1:
The invention changes the physical parameter of the semiconductor substrate by applying stress (through the stress application portion with different thermal expansion coefficient) to modify the threshold voltage and electrical characteristics, allowing suppression of ON resistance without increasing the current-conduction area
Solution Approach 2:
The stress application portion utilizes thermal expansion differential with the semiconductor substrate to generate stress during temperature changes, thereby dynamically adjusting the electrical characteristics of the switching element to maintain low ON resistance across temperature ranges
2Object-affected harmful factors
If the rated voltage of the semiconductor switching element is increased to suppress turn-off surge voltage, then the turn-off surge voltage is suppressed, but the thickness of the withstand voltage retaining layer must be increased which increases ON resistance and requires larger area
Solution Approach 1:
The invention changes the threshold voltage parameter through stress application, which indirectly controls the turn-off surge voltage by maintaining better control over the switching characteristics without requiring increased rated voltage or thicker insulation layers
Solution Approach 2:
The invention replaces the conventional approach of using electrical parameters (rated voltage) to control surge voltage with a mechanical stress application method that directly modifies the semiconductor material properties to achieve surge voltage suppression
3Object-affected harmful factors
If temperature monitoring and resistor switching in the gate drive circuit is implemented to suppress turn-off surge voltage, then the turn-off surge voltage is suppressed, but the number of components and device complexity increases
Solution Approach 1:
The stress application portion automatically adjusts the electrical characteristics of the semiconductor switching element in response to temperature changes through thermal expansion, eliminating the need for external temperature monitoring and active control components
Solution Approach 2:
The stress application portion acts as an intermediary element that mediates between temperature changes and the electrical characteristics of the switching element, providing passive compensation without requiring additional control circuitry
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 allows for a smaller, more cost-effective semiconductor module by moderating the temperature characteristic of the threshold voltage, reducing the area and rated voltage of the semiconductor switching element, and simplifying the manufacturing process.
Implementation Method 1
the stress application portion having a linear expansion coefficient larger than a linear expansion coefficient of a main material of the semiconductor switching element... the stress application portion generates compressive stress or tensile stress in the semiconductor switching element through thermal shrinkage or thermal expansion of the stress application portion due to change in temperature
Data Source
AI summary
Provided is a small-sized inexpensive semiconductor module in which increase of ON resistance and increase of turn-off surge voltage at low temperature are suppressed. The semiconductor module includes: a semiconductor switching element; and a stress application portion provided on one or each of a first surface and a second surface on an opposite side to the first surface of the semiconductor switching element, having a linear expansion coefficient larger than that of a main material of the semiconductor switching element, and having a larger thickness than the semiconductor switching element. The stress application portion generates compressive or tensile stress in the semiconductor switching element through thermal shrinkage or expansion of the stress application portion due to change in temperature. A threshold voltage at which the semiconductor switching element is turned on, decreases in association with increase of a magnitude of the compressive or tensile stress in the semiconductor switching element.