Semiconductor Bonding Pad and Shield Structure with Differential Thickness
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Solution Overview
Problem
Conventional semiconductor devices face challenges in manufacturing bonding pads and metal shields with different thicknesses and materials, leading to defects such as peeling and optical cross-talk, which affect the performance and reliability of ICs, particularly in CMOS image sensors.
Innovation Solution
The method involves forming a semiconductor device with a metal shield and bonding pad of separate thicknesses and materials, using two distinct processes to create these features, allowing for a thicker bonding pad to prevent peeling and a thinner metal shield to reduce stripe defects, thereby enhancing the structural integrity and optical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thin metal layers are used for bonding pads and shields, then the device size is reduced, but peeling defects occur in the bonding pads
Solution Approach 1:
The patent divides the metal layer into two separate structures with different thicknesses: a first metal shield layer and a second bonding pad layer. This segmentation allows each structure to have optimized thickness independently, preventing peeling in bonding pads while maintaining compact device size.
Solution Approach 2:
The patent applies different thicknesses to different metal structures based on their specific functional requirements. The bonding pad layer is made thicker to prevent peeling, while the shield layer maintains its thinner profile for size reduction, achieving local optimization of each component's properties.
2Reliability
If thick metal layers are used for bonding pads, then peeling is prevented, but the device size increases
Solution Approach 1:
The patent segments the metal structures into separate layers, allowing the bonding pad to be thick for reliability while the shield remains thin for compact size. This resolves the contradiction by preventing the entire device from increasing in size.
Solution Approach 2:
The invention applies the principle of local quality by making only the bonding pad layer thick where needed for mechanical strength, while keeping the shield layer thin in areas where size reduction is critical, thus achieving localized optimization without overall size increase.
3Ease of manufacture
If the same thickness is used for both shield and bonding pad, then manufacturing is simplified, but optical cross-talk cannot be effectively prevented
Solution Approach 1:
The patent segments the metal structures into separate processable layers, allowing the shield and bonding pad to be formed in distinct manufacturing steps. This enables independent optimization of each layer's thickness for cross-talk prevention while maintaining reasonable manufacturing complexity.
Solution Approach 2:
The invention changes the thickness parameter differently for the shield layer versus the bonding pad layer. The shield layer is kept thin to reduce optical cross-talk, while the bonding pad layer is made thick for mechanical strength, resolving the contradiction through differential parameter optimization.
4Reliability
If separate processes are used to form shield and bonding pad with different thicknesses, then peeling is prevented, but manufacturing complexity increases
Solution Approach 1:
The patent segments the formation process into separate steps for the shield layer and bonding pad layer. This allows different thicknesses to be achieved through targeted deposition or etching processes, preventing peeling while managing manufacturing complexity through systematic process division.
Data Source
AI summary
A method of fabricating a semiconductor device includes providing a device substrate having a front side and a back side corresponding to a front side and a back side of the semiconductor device, forming, on the front side of the device substrate, a metal feature, forming, on the back side of the device substrate, an insulating layer, forming, on the back side of the semiconductor device, a trench exposing the metal feature, forming a bonding pad in the trench in electrical communication with the metal feature, and forming, on the insulating layer, a metal shield, in which the metal shield and the bonding pad have different thicknesses relative to each other.