Backside-Illuminated Image Sensor Pad Layout for Uniform Color Coating
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Solution Overview
Problem
The existing manufacturing process for backside illuminated image sensors often results in stripe defects during the spin coating of the color filter layer due to the presence of bonding pads, which affects the quality and performance of the image sensor.
Innovation Solution
The proposed solution involves forming a recess in the backside surface of the substrate with a second bonding pad of constant thickness and a third bonding pad that fills this recess, ensuring the bonding pads are positioned to prevent defects during the spin coating process, and using a light-blocking pattern layer and anti-reflective layer to facilitate even coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding pads are formed on the backside surface of the substrate, then electrical connection is achieved, but stripe defects occur during spin coating of the color filter layer
Solution Approach 1:
The bonding pads are extracted from the backside surface and relocated to the frontside surface of the substrate. This separation removes the interfering elements (bonding pads) from the spin coating area, allowing the color filter layer to be deposited uniformly without stripe defects while maintaining electrical connection functionality through the frontside bonding pads
Solution Approach 2:
The bonding pads are moved from the backside surface (one dimension) to the frontside surface (another dimension) of the substrate. This dimensional transition resolves the conflict between needing bonding pads for electrical connection and avoiding them during spin coating, as the color filter layer is only deposited on the backside surface
2Reliability
If bonding pads are present on the backside surface, then electrical connection is established, but the spin coating process is disrupted
Solution Approach 1:
The bonding pads are extracted from the backside surface and repositioned on the frontside surface. This extraction eliminates the interference with the spin coating process while preserving the electrical connection function through frontside bonding pads that connect to backend circuits through through-substrate vias or back-illuminated connections
3Reliability
If bonding pads are formed on the backside surface, then electrical connection is achieved, but color filter layer uniformity deteriorates
Solution Approach 1:
The bonding pads are extracted from the backside surface and relocated to the frontside surface. This removal from the spin coating area ensures that the color filter layer can be deposited with uniform thickness and composition across the entire backside surface, eliminating stripe defects caused by bonding pad interference
Solution Approach 2:
The bonding pads are transitioned from the backside surface to the frontside surface, separating their location from the color filter deposition area. This dimensional separation allows the color filter layer to achieve uniformity while bonding pads maintain their electrical connection function through alternative routing paths
Data Source
AI summary
A backside illuminated image sensor and a method of manufacturing the same are disclosed. The backside illuminated image sensor includes a substrate having a frontside surface, a backside surface and a recess formed in a backside surface portion thereof, pixel regions disposed in the substrate, an insulating layer disposed on the frontside surface of the substrate, a bonding pad disposed on a frontside surface of the insulating layer, a second bonding pad formed with a constant thickness on a bottom surface and an inner side surface of the recess to form a second recess in the recess and electrically connected with the bonding pad, and a third bonding pad formed in the second recess to fill the second recess.