Metal Shield Trenches in PMD Layer for Light Sensors
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Solution Overview
Problem
Front-side illuminated light sensors require effective optical shielding and metal substrate contacts within the premetallization dielectric layer to prevent light intrusion and ensure electrical connectivity, which existing technologies struggle to support simultaneously.
Innovation Solution
The integration of metal shield trenches and substrate contacts within the premetallization dielectric layer, where trenches are formed and filled with metal material without penetrating certain layers, providing optical shielding and electrical connectivity while avoiding interference with sensitive regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal shield trenches are formed in the PMD layer to prevent light intrusion, then optical shielding performance is improved, but the complexity of supporting both shield trenches and substrate contacts within the same layer increases
Solution Approach 1:
The patent divides the PMD layer into multiple regions with different functions: some regions contain metal shield trenches for optical shielding, while other regions contain metal substrate contacts for electrical connectivity. This segmentation allows both optical shielding and electrical connections to coexist within the same PMD layer without interference, resolving the technical contradiction by spatially separating the two functions.
2Reliability
If metal substrate contacts penetrate through the PMD layer to ensure electrical connectivity, then electrical connection reliability is improved, but the ability to provide optical shielding within the same layer is compromised
Solution Approach 1:
The patent applies local quality by giving different portions of the PMD layer different properties: regions containing metal substrate contacts maintain transparency for electrical connection, while regions containing metal shield trenches provide optical shielding. This local differentiation allows the PMD layer to simultaneously fulfill both electrical connectivity and optical shielding requirements without compromising either function.
Data Source
AI summary
A semiconductor substrate includes a photodiode region, a charge storage region electrically coupled to the photodiode region and a capacitive deep trench isolation (CDTI) structure including a conductive region positioned between the photodiode region and the charge storage region. A contact etch stop layer overlies the semiconductor substrate and a premetallization dielectric layer overlies the contact etch stop layer. A first trench, filled with a metal material, extends through the premetallization dielectric layer and bottoms out at or in the contact etch stop layer. A second trench, also filled with the metal material, extends through the premetallization dielectric layer and the contact etch stop layer and bottoms out at or in the conductive region of the CDTI structure. The metal filled first trench forms an optical shield between the photodiode region and the charge storage region. The metal filled second trench forms a contact for biasing the CDTI structure.