Bond Pad Isolation Structure for Reduced Step Height and Noise
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Solution Overview
Problem
The increased thickness of the substrate in CMOS image sensors leads to higher step heights between bond pads and the substrate, causing non-uniform filling of dielectric layers, resulting in cracking and delamination, increased noise, and fabrication complexities.
Innovation Solution
A bond pad structure with reduced step height is formed by creating a passivation layer, patterning to define bond pad openings, and using first and second bond pad isolation structures to separate the bond pad from the substrate, ensuring uniform dielectric layer filling and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If substrate thickness is increased to improve sensor performance, then sensor performance is improved, but step height between bond pad and substrate increases causing non-uniform dielectric filling, cracking and delamination
Solution Approach 1:
The patent divides the bond pad structure into multiple segments: a first bond pad isolation structure at the bottom, a bond pad in the middle, and a second bond pad isolation structure at the top. This segmentation allows each component to address specific issues - the bottom isolation structure reduces step height, while the top isolation structure provides electrical isolation, collectively solving both reliability and manufacturing precision problems
Solution Approach 2:
The bond pad isolation structures act as intermediary elements between the bond pad and the substrate. These isolation structures mediate the interface by reducing step height and providing uniform dielectric filling, thereby preventing cracking and delamination while maintaining electrical isolation
2Reliability
If substrate thickness is increased, then sensor performance is improved, but cracking and delamination occur due to non-uniform dielectric layer filling
Solution Approach 1:
By segmenting the bond pad structure with isolation structures at both bottom and top, the patent creates a stepped configuration that enables uniform dielectric layer filling. This segmentation prevents the formation of voids and ensures consistent dielectric material distribution, thereby preventing cracking and delamination while maintaining sensor performance
Solution Approach 2:
The bottom bond pad isolation structure is formed preliminarily before the bond pad to reduce step height. This preliminary action creates a favorable foundation for subsequent dielectric layer deposition, ensuring uniform filling and preventing structural defects before they occur
3Ease of manufacture
If bond pad is formed without isolation structures, then fabrication is simpler, but electrical isolation between bond pad and substrate is insufficient leading to increased noise
Solution Approach 1:
The patent segments the bond pad structure by introducing isolation structures that physically separate the bond pad from the substrate. This segmentation provides electrical isolation that prevents noise while maintaining a relatively simple fabrication process through standardized isolation structure formation
Solution Approach 2:
The isolation structures are applied locally at critical interfaces where electrical isolation is needed. This local quality approach provides noise protection at specific locations without requiring complex global modifications to the fabrication process
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an integrated chip. The integrated chip includes a substrate having an upper surface vertically below a top surface. A conductive structure is in the substrate. The conductive structure includes a first segment overlying the upper surface of the substrate and one or more vertical segments under the first segment. A first isolation structure is in the substrate and on opposing sides of the conductive structure. A second isolation structure is in the substrate and around the one or vertical segments. A top surface of the first isolation structure and a top surface of the second isolation structure are vertically below the top surface of the substrate. A bottom surface of the first isolation structure and a bottom surface of the second isolation structure are vertically above a bottom surface of the substrate.