Backside-Illuminated Image Sensor Pad Layout to Prevent Striation
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Solution Overview
Problem
Conventional backside illuminated CMOS image sensors face issues with reduced light reception due to metal wirings, stripe-like patterns caused by uneven photosensitive liquid application during spin coating, and damage to the corner portion of the conductive film.
Innovation Solution
The proposed solution involves forming the upper conductive film within the separation space of the substrates, without extending onto the back surfaces, thereby reducing the overall thickness and preventing stripe-like patterns and corner damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conductive film is extended to the back surfaces of substrates within the pad region, then the electrical connection is improved, but the overall thickness of the structure on back surfaces increases causing stripe-like patterns during spin coating
Solution Approach 1:
The conductive film formation process is segmented into two distinct films: a lower conductive film that extends to the back surface for electrical connection, and an upper conductive film that is confined within the separation space and does not extend to the back surface. This segmentation allows the lower film to provide electrical connectivity while the upper film's restricted placement prevents thickness-related manufacturing defects during spin coating.
2Manufacturing precision
If the overall thickness of structure on back surfaces is reduced, then stripe-like patterns are prevented, but the electrical connection capability may be compromised
Solution Approach 1:
The conductive system is divided into lower and upper conductive films with distinct functional responsibilities. The lower conductive film maintains electrical connection by extending to the back surface, while the upper conductive film is restricted to the separation space to minimize overall thickness and prevent stripe-like patterns during spin coating.
Solution Approach 2:
Different regions of the conductive film structure are assigned different qualities and extents: the lower conductive film extends to the back surface in the pad region for electrical connection, while the upper conductive film is confined within the separation space. This local differentiation allows each region to optimize its function without compromising the other.
3Reliability
If the conductive film is formed on the back surfaces, then the electrical connectivity is enhanced, but the corner portion of the conductive film becomes damaged during formation
Solution Approach 1:
The conductive film is segmented into lower and upper portions with different spatial extents. The lower conductive film provides electrical connectivity by extending to the back surface, while the upper conductive film is confined within the separation space and does not reach the back surface, thereby avoiding the corner damage issue that occurs when conductive film is formed on the back surfaces.
Data Source
AI summary
A backside illuminated image sensor and a method of manufacturing the same include an upper conductive film formed within a separation space of substrates but not formed on back surfaces of the substrates, thereby reducing the overall thickness of a structure formed on the back surfaces of the substrates within a pad region, thereby preventing a stripe-like pattern (striation) from forming on the substrates and preventing damage to a corner portion of the upper conductive film.