Ultra-Thick Metal Passivation Stack With Fewer Stress Interfaces
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Solution Overview
Problem
The existing passivation layers in semiconductor devices with ultra-thick metal structures are prone to cracking due to stress concentration at film interfaces, particularly where unbias films are present, leading to reduced yield and potential damage during manufacturing processes.
Innovation Solution
A modified passivation layer structure with reduced unbias films and minimized film interfaces, comprising a first passivation oxide with an unbias and bias film, and a second and third passivation oxide as single films, positioned to avoid stress concentration points, thereby reducing cracking likelihood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer with multiple unbias films is used to protect the ultra-thick metal structure, then the protection coverage is improved, but the likelihood of cracking increases due to stress concentration at film interfaces
Solution Approach 1:
The patent removes the unbias film from the second passivation oxide layer, extracting the problematic element that causes stress concentration and cracking. This leaves only the essential bias film in that layer, eliminating the interface between unbias and bias films that serves as a crack initiation point, while maintaining protection coverage through the remaining unbias film in the first passivation oxide layer.
Solution Approach 2:
The patent uses a composite passivation layer structure with three different passivation oxides (first passivation oxide with unbias and bias films, second passivation oxide with only bias film, third passivation oxide with only bias film) to achieve both protection and crack resistance. The composite structure allows different regions to serve different functions while minimizing harmful interfaces.
2Reliability
If multiple passivation oxide layers are formed to ensure adequate protection, then the protection effectiveness is improved, but the number of film interfaces increases leading to more stress concentration points
Solution Approach 1:
The patent extracts the unbias film component from the second passivation oxide layer, reducing the total number of film interfaces by one. This elimination of the unbias/bias interface in the second layer directly reduces stress concentration points while maintaining three-passivation-oxide-layer protection effectiveness through the remaining layers.
3Reliability
If unbias films are included in all passivation oxide layers to maximize protection, then the protection capability is improved, but the manufacturing yield decreases due to increased cracking
Solution Approach 1:
The patent extracts the unbias film from the second passivation oxide layer, removing the source of stress concentration that causes cracking during manufacturing. This extraction eliminates crack initiation at unbias/bias interfaces in the second layer, thereby improving manufacturing yield while maintaining adequate protection capability through the unbias film in the first layer and bias films in all layers.
Data Source
AI summary
A semiconductor device includes an ultra-thick metal (UTM) structure. The semiconductor device includes a passivation layer including a first passivation oxide. The first passivation oxide includes an unbias film and a first bias film, where the unbias film is on portions of the UTM structure and on portions of a layer on which the UTM structure is formed, and the first bias film is on the unbias film. The passivation layer includes a second passivation oxide consisting of a second bias film, the second bias film being on the first bias film. The passivation layer includes a third passivation oxide consisting of a third bias film, the third bias film being on the second bias film.