Multi-Layer Dielectric Grid Isolation for Image Sensor Crosstalk
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Solution Overview
Problem
Image sensors face challenges with crosstalk between pixels, leading to increased noise and reduced isolation performance due to inadequate separation of light-sensitive elements.
Innovation Solution
The implementation of a multi-layer dielectric isolation structure comprising a reflective layer and two dielectric layers with different dielectric constants, forming a grid isolation structure that provides enhanced height and improved isolation performance by reducing crosstalk between pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple isolation structure is used, then device complexity is reduced, but isolation performance deteriorates due to insufficient crosstalk reduction
Solution Approach 1:
The isolation structure is divided into multiple dielectric layers (first dielectric layer, second dielectric layer, third dielectric layer) with different dielectric constants, where each layer contributes to crosstalk reduction at different depths. This segmentation allows the structure to achieve superior isolation performance compared to a single-layer structure, directly resolving the contradiction between isolation performance and structural simplicity.
Solution Approach 2:
Different dielectric materials are selectively placed at different depths within the isolation structure. The first dielectric layer (with lower dielectric constant) is positioned closer to the pixel region where crosstalk originates, while the second dielectric layer (with higher dielectric constant) is positioned deeper. This local quality differentiation optimizes the isolation effect at each depth, achieving high isolation performance without uniformly increasing complexity throughout the entire structure.
2Productivity
If pixel density is increased, then productivity is improved, but crosstalk increases leading to degraded isolation performance
Solution Approach 1:
The isolation structure extends vertically into the third dimension with multiple stacked dielectric layers at different depths. This vertical dimensionality allows the structure to effectively isolate closely spaced pixels in the horizontal plane by providing isolation barriers at multiple vertical levels, thereby enabling high pixel density while maintaining isolation performance.
Solution Approach 2:
The isolation structure employs composite dielectric materials with different dielectric constants arranged in specific layers. This composite approach creates a gradient isolation effect that effectively suppresses crosstalk between adjacent pixels, allowing higher pixel density to be achieved without degrading isolation performance.
Data Source
AI summary
A method includes depositing a first reflective layer over a substrate. A first dielectric layer is deposited over the first reflective layer. A second dielectric layer is deposited over the first dielectric layer. The second dielectric layer, the first dielectric layer, and the first reflective layer are etched to form a grid isolation structure that defines a recess. The recess is filled with a color filter.