Backside Illuminated Image Sensor Anti-Reflective Layer Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing process for backside illuminated image sensors results in increased distance between pixel regions and the micro lens array due to the protective layer, leading to deteriorated sensitivity and crosstalk.
Innovation Solution
The proposed solution involves forming a backside illuminated image sensor with a substrate having a first opening to expose the insulating layer, an anti-reflective layer with spacers on the inner surfaces of openings, and a light-blocking pattern, which reduces the need for an additional protective layer, thereby minimizing the distance between pixel regions and the micro lens array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed on the inner surfaces of openings and the anti-reflective layer or planarization layer, then the inner surfaces are protected and electrical isolation is achieved, but the distance between pixel regions and the micro lens array is increased, deteriorating sensitivity and crosstalk
Solution Approach 1:
The anti-reflective layer is merged with the protective function by extending it onto the inner side surface of the opening through substrate removal. This combines the optical function (anti-reflection) with the protective and electrical isolation functions, eliminating the need for a separate protective layer that would increase the distance and deteriorate sensitivity.
Solution Approach 2:
The anti-reflective layer is extended from the backside surface onto the inner side surface of the opening, adding a dimensional aspect to the layer. This allows the same material layer to serve multiple functions: optical anti-reflection on the backside and protective/electrical isolation on the inner surface, thereby reducing the overall distance without compromising reliability.
2Ease of manufacture
If the anti-reflective layer is formed only on the backside surface, then the manufacturing process is simple, but the inner surfaces of openings lack protection and electrical isolation
Solution Approach 1:
The substrate is removed in advance to expose the inner side surface of the opening before forming the anti-reflective layer. This preliminary action allows the anti-reflective layer to be deposited directly onto the inner surface, providing protection and electrical isolation without requiring additional separate protective layers, thus maintaining manufacturing simplicity while improving reliability.
3Length of moving object
If the distance between pixel regions and micro lens array is reduced, then sensitivity and crosstalk are improved, but protective coverage and electrical isolation are compromised
Solution Approach 1:
The anti-reflective layer is designed to perform multiple functions simultaneously: optical anti-reflection on the backside surface, protective coverage on the inner side surface of the opening, and electrical isolation between the substrate and bonding pads. This multi-functionality allows the distance to be reduced while maintaining all necessary protective and isolating functions.
Data Source
AI summary
A backside illuminated image sensor includes pixel regions disposed in a substrate, an insulating layer disposed on a frontside surface of the substrate, a bonding pad disposed on a frontside surface of the insulating layer, and an anti-reflective layer disposed on a backside surface of the substrate. The substrate has a first opening for partially exposing a backside surface of the insulating layer, and the insulating layer has a third opening for partially exposing a backside surface of the bonding pad. The anti-reflective layer comprises a first portion disposed on an inner side surface of the first opening and a second portion disposed on a portion of the backside surface of the insulating layer exposed by the first opening and having a second opening connecting the first opening with the third opening, and a first spacer is disposed on inner side surfaces of the second opening and the third opening.