Curved Anode Structure to Prevent Passivation Cracking in SiC Devices
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Solution Overview
Problem
Silicon carbide power elements face failure due to cracking of passivation layers under high temperature and humidity conditions, leading to moisture ingress and reliability issues, especially in coastal environments with stringent reliability requirements.
Innovation Solution
A semiconductor structure with a curved connection surface between the side wall and top wall of the anode layer, optimized lithography and etching conditions to reduce stress concentration at corners, and a passivation layer that covers the field oxide layer and anode layer to enhance moisture resistance and minimize cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional planar anode layer structure is used, then the manufacturing process is simple, but the passivation layer cracks easily under thermal stress leading to element failure
Solution Approach 1:
The anode layer structure transitions from a planar geometry to a curved geometry with rounded corners and edges. The connection surface between the top wall and side wall is specifically designed to be curved rather than sharp, which reduces stress concentration points and prevents passivation layer cracking under thermal stress cycles.
2Reliability
If the passivation layer is made thinner to reduce stress, then the element size is reduced, but the moisture protection capability is compromised
Solution Approach 1:
The curved connection surface design distributes thermal stress evenly across the passivation layer, allowing the use of thinner passivation layers without compromising their protective function. The rounded geometry eliminates sharp corners that would concentrate stress and cause cracking, thereby maintaining moisture protection with reduced material thickness.
3Reliability
If lithography and etching conditions are optimized to create curved surfaces, then the stress concentration is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes lithography and etching process parameters to achieve the desired curved surface geometry. By adjusting process conditions such as etching time, temperature, and chemical composition, the curved connection surfaces are formed with sufficient precision to reduce stress concentration without requiring excessively tight manufacturing tolerances.
Data Source
AI summary
A semiconductor structure includes a substrate, a semiconductor epitaxial layer, an active region and a terminal region, a field oxide layer, an anode layer, and a passivation layer. The anode layer is configured to extend from the active region to be arranged on a portion of the field oxide layer. The side wall and the top wall of the anode layer are connected to each other through a curved connection surface. By setting the upper corner of the side wall of the anode layer to be curved, the transition between the side wall and the top wall of the anode layer is smooth, preventing a sharp change in the inclination angle and preventing the stress concentration of the passivation layer at the corner of the side wall.