Segmented Transistor Contact Structure to Prevent Bonding Cracks
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Solution Overview
Problem
The final metallization layer of power semiconductor devices is prone to cracking during wire bonding, which allows contaminants to enter the underlying oxide layer, leading to electrical failures due to the stress-induced movement of underlying layers and subsequent contamination.
Innovation Solution
The semiconductor device features trenches with segmented field plate and mesa contacts that reduce the movement of the insulating layer, minimizing the likelihood of cracks in the final metallization layer and preventing contaminants from entering the underlying oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the final metallization layer is used for wire bonding, then electrical connection is achieved, but cracks form in the metallization layer due to stress-induced movement of underlying layers
Solution Approach 1:
The contact structure is divided into multiple discrete contact pads arranged in a specific pattern, rather than using a continuous metallization layer. This segmentation allows the underlying insulating layer to move slightly during wire bonding without causing cracks that would compromise electrical connection reliability.
2Reliability
If adhesion promotion treatment is applied to contact pads, then mold compound adhesion is improved, but contaminants such as sodium deposit on the metallization layer and passivation layer
Solution Approach 1:
The contact pads are segmented and positioned to allow adhesion promotion treatments to be applied effectively while minimizing contaminant deposition in critical areas. The specific arrangement of segmented contacts enables selective treatment application.
3Reliability
If contaminants are present on the metallization layer, then electrical failure occurs due to contaminant entry into cracks and underlying oxide, but segmented contact structure reduces crack formation
Solution Approach 1:
The segmented contact structure eliminates continuous metallization cracks that would allow contaminant infiltration. By dividing the contact into discrete pads, the pathway for contaminants to reach the underlying oxide is blocked, preventing electrical performance degradation.
Data Source
AI summary
A transistor device includes field plate contacts that electrically connect a final metallization layer to field electrodes in underlying trenches, and mesa contacts that electrically connect the final metallization layer to semiconductor mesas confined by the trenches. Each field plate contact is divided into field plate contact segments that are separated from one another. Each mesa contact is divided into mesa contact segments that are separated from one another. In a first area adjacent to an end of the trenches, a first line that runs perpendicular to the trenches intersects a first field plate contact segment of the field plate contacts and a first mesa contact segment of the mesa contacts. In a second area spaced inward from the first area, a second line that runs perpendicular to the trenches intersects a second field plate contact segment of the field plate contacts and a second mesa contact segment of the mesa contacts.