Backside Illuminated Image Sensor Recess Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Backside illuminated image sensors face issues with sensitivity and crosstalk due to the distance between pixel regions and the micro lens array, caused by the protective layer, which also leads to stripe defects during the manufacturing process.
Innovation Solution
A backside illuminated image sensor design with a recess in the substrate, featuring a metal oxide layer, silicon insulating layers, and strategically formed bonding pads, which reduces the need for a protective layer, allowing for closer proximity of the micro lens array to the pixel regions and preventing stripe defects during the photoresist coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed on the backside surface to protect the substrate and electrically isolate it from bonding pads, then the substrate is protected and electrical isolation is achieved, but the distance between pixel regions and micro lens array increases, deteriorating sensitivity and crosstalk
Solution Approach 1:
The patent removes the protective layer from the backside surface of the substrate, extracting the harmful element that caused the technical contradiction. The substrate is protected through alternative means (bonding pads design and manufacturing process control) while maintaining close proximity between pixel regions and micro lens array for improved sensitivity and reduced crosstalk
Solution Approach 2:
Instead of forming a protective layer on the backside surface to achieve electrical isolation, the patent inverts the approach by using the bonding pads themselves and the manufacturing process to achieve isolation without adding a protective layer, thereby maintaining the required proximity for optimal optical performance
2Ease of operation
If openings are formed through the anti-reflective layer and substrate to expose bonding pads, then bonding pads are accessible for wiring, but stripe defects occur during color photoresist coating and bonding pads may be partially removed during etching
Solution Approach 1:
The patent performs preliminary actions by carefully controlling the formation of openings and the subsequent color photoresist coating process. The openings are formed with precise dimensions and the color photoresist is coated with controlled thickness to prevent stripe defects before they occur, and etching parameters are optimized in advance to prevent bonding pad removal
Solution Approach 2:
The patent changes critical parameters including opening dimensions, color photoresist coating thickness, and etching conditions to optimize the process. By adjusting these parameters, the patent achieves bonding pad accessibility while preventing stripe defects and bonding pad damage during manufacturing
Data Source
AI summary
A 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, an anti-reflective layer disposed on the backside surface of the substrate, and a second bonding pad disposed in the recess and electrically connected with the bonding pad. The anti-reflective layer includes a metal oxide layer disposed on the backside surface of the substrate, a first silicon insulating layer disposed on the metal oxide layer, and a second silicon insulating layer disposed on the first silicon insulating layer. The second silicon insulating layer includes a first portion disposed on an inner side surface of the recess and a second portion disposed on a bottom surface of the recess.