Switching Device Thermal Stress Crack Prevention
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Solution Overview
Problem
The existing switching devices face issues with thermal stress leading to cracks in the first metal layer and increased resistance in the second region due to mismatched thermal expansion coefficients, and poor charge supply to the body region, resulting in high resistance during switching on.
Innovation Solution
The switching device incorporates a semiconductor substrate with first and second metal layers, where the first metal layer is in contact with the semiconductor substrate and the second metal layer is in contact with the first metal layer, and a wide contact hole is provided in the ineffective range to ensure efficient charge supply and reduce thermal stress by using a second conductivity type peripheral region that extends deeper than the first trenches, thereby reducing resistance and suppressing electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first metal layer is formed with recesses above contact holes to improve soldering connection, then the connection to exterior is enhanced, but thermal stress concentrates at the boundary between recessed and flat regions causing cracks in the first metal layer
Solution Approach 1:
The patent applies local quality by providing recesses only in specific regions where contact holes are located, while maintaining a flat surface in other regions. This localized structural modification allows the first metal layer to have different geometries in different areas, optimizing both soldering connection at contact hole positions and thermal stress distribution in flat regions, thereby preventing cracks while ensuring reliable external connection.
2Stability of the object's composition
If the second metal layer is made to contact the insulating protective film to prevent gaps, then gap formation is suppressed, but thermal expansion mismatch causes stress concentration and cracks
Solution Approach 1:
The patent applies local quality by making the second metal layer contact the insulating protective film only in specific regions, while leaving it non-contacting in other regions. This selective contact approach prevents gaps in critical areas while avoiding stress concentration zones, thereby maintaining both structural integrity and compositional stability without causing cracks due to thermal expansion mismatch.
3Stability of the object's composition
If contact holes are not provided in the ineffective range to maintain insulating film integrity, then film continuity is preserved, but charge supply to the body region becomes insufficient increasing resistance
Solution Approach 1:
The patent applies local quality by providing wide contact holes specifically in the ineffective range where no first trenches are present, while maintaining the insulating film structure in other regions. This localized modification enables sufficient charge supply to the body region in the ineffective range without compromising the overall insulating film integrity and continuity, thereby improving switching performance while preserving structural stability.
4Reliability
If the second conductivity type peripheral region extends deeper than first trenches to suppress electric field concentration, then breakdown voltage is maintained, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the second conductivity type peripheral region to extend deeper than the first trenches before subsequent processing steps. This preliminary structural configuration proactively suppresses electric field concentration at trench ends, ensuring sufficient breakdown voltage is achieved from the outset, while the extended region serves multiple functions simultaneously, managing manufacturing complexity through strategic advance preparation.
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 effectively suppresses cracks in the first metal layer, reduces the resistance of the second region upon switching on, and maintains low loss operation while ensuring sufficient breakdown voltage.
Implementation Method 1
A linear expansion coefficient of the second metal layer is generally smaller than a linear expansion coefficient of the first metal layer
Data Source
AI summary
A switching device includes a semiconductor substrate having a first element range including first trenches for gates, and an ineffective range not including the first trenches. In an interlayer insulating film, a contact hole is provided within the first element range, and a wide contact hole is provided within the inactive range. The first metal layer contacts the semiconductor substrate within the contact hole and the wide contact hole. The insulating protective film covers an outer peripheral side portion of a bottom surface of a second recess which is provided in a surface of the first metal layer above the wide contact hole. A side surface of an opening provided in a portion of the insulating protective film that includes the first element range is disposed in the second recess. The second metal layer contacts the first metal layer and the side surface of the opening.