Image Sensor Capping Structure to Block Active Layer Etchant Damage
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Solution Overview
Problem
CMOS image sensors face damage during fabrication due to etchants penetrating the active layer during the removal process, leading to void formation and decreased performance.
Innovation Solution
A capping structure is formed over the active layer, extending over its outer edges, which impedes etchants from reaching the active layer, thereby protecting it during the removal process of excess conductive material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etchants are used to remove excess conductive material during fabrication, then the removal process is effective, but the etchants penetrate the active layer causing damage and void formation
Solution Approach 1:
A capping structure is introduced as an intermediary element between the etchants and the active layer. This capping structure selectively impedes the etchants from reaching the active layer while allowing the etchants to effectively remove excess conductive material from the sensor element, thus resolving the contradiction between removal effectiveness and active layer protection
2Ease of manufacture
If the active layer is exposed during the removal process, then excess material can be removed, but the active layer suffers damage and performance decreases
Solution Approach 1:
The capping structure is formed over the active layer before the removal process begins. This preliminary action protects the active layer in advance, preventing etchant penetration and subsequent damage while still allowing the removal process to proceed effectively on the excess conductive material
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an image sensor. The image sensor includes and image sensor element disposed within a substrate. The substrate comprises a first material. The image sensor element includes an active layer comprising a second material different from the first material. A buffer layer is disposed between the active layer and the substrate. The buffer layer extends along outer sidewalls and a bottom surface of the active layer. A capping structure overlies the active layer. Outer sidewalls of the active layer are spaced laterally between outer sidewalls of the capping structure such that the capping structure continuously extends over outer edges of the active layer.