Backside Illuminated Image Sensor Bonding Pad Composite Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in semiconductor manufacturing is to create bonding pads that are both strong enough to withstand physical contact and small enough in size and thickness, particularly in applications like CMOS image sensors, where thin metal layers are prone to peeling or defects.
Innovation Solution
A method for fabricating semiconductor devices involves forming a bonding pad that partially fills an opening extending through an interconnect structure, with a shield structure over a buffer layer, using materials like aluminum, copper, or their alloys, and a passivation layer to support the bonding pad and prevent cracking or peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If thin metal layers are used in CMOS image sensors, then the device complexity and integration are improved, but the bonding pads exhibit peeling or other defects
Solution Approach 1:
The bonding pad structure uses a composite material system consisting of a first metal layer (e.g., aluminum or aluminum alloy) and a second metal layer (e.g., copper or copper alloy). This composite structure combines the advantages of different metals to achieve both electrical performance and mechanical reliability, preventing peeling defects while maintaining thin profile integration.
Solution Approach 2:
The solution transitions from a single-layer thin metal bonding pad to a multi-layer vertical structure. By stacking multiple metal layers with different materials and properties, the design achieves improved reliability through the additional dimensional complexity of layered construction, while maintaining overall thin profile for sensor integration.
2Productivity
If bonding pads are made smaller, then the functional density is improved, but the bonding pads must still withstand physical contact from probing or wire bonding
Solution Approach 1:
The multi-layer metal composite structure provides enhanced mechanical strength and ductility compared to single-layer pads of the same size. The combination of different metal materials allows the bonding pad to withstand probing and wire bonding forces while maintaining a compact footprint for high functional density.
Solution Approach 2:
The bonding pad structure employs different metal materials with specific local properties optimized for their functions. The first metal layer provides electrical connectivity, while the second metal layer enhances mechanical strength and bonding characteristics, allowing small-sized pads to withstand physical contact forces.
Data Source
AI summary
A semiconductor device including a device substrate having a front side and a back side. The semiconductor device further includes an interconnect structure disposed on the front side of the device substrate, the interconnect structure having a n-number of metal layers. The semiconductor device also includes a bonding pad disposed on the back side of the device substrate, the bonding pad extending through the interconnect structure and directly contacting the nth metal layer of the n-number of metal layers.