Dielectric Grid for Backside Illuminated Image Sensors
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Solution Overview
Problem
As backside illuminated image sensor (BSI) devices continue to scale down, existing technologies have not been entirely satisfactory in improving quantum efficiency, necessitating advancements in the fabrication methods to enhance light detection and reduce interference.
Innovation Solution
The method involves forming a dielectric grid in the pixel region and a dielectric trench in the non-pixel region of an integrated circuit device, with metal pillars and dielectric layers, and aligning color filters and microlenses over the dielectric trenches to improve light uniformity and reduce obstruction, thereby enhancing light detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device scaling is continued to achieve higher integration density, then device integration density is improved, but quantum efficiency deteriorates due to increased interference and reduced light detection capability
Solution Approach 1:
The pixel region is divided into multiple pixel units with individual color filters and microlenses, while the non-pixel region is segmented into multiple dielectric trenches. This segmentation allows each pixel unit to independently optimize light detection while the overall structure maintains high integration density through compact arrangement of multiple units.
Solution Approach 2:
Different regions of the substrate are assigned different structures: the pixel region contains sensor elements with color filters and microlenses for light detection, while the non-pixel region contains dielectric trenches for light management. This local differentiation optimizes each region's function to simultaneously achieve high integration density and maintain quantum efficiency.
2Reliability
If color filters and microlenses are placed directly over sensor elements, then light detection is improved, but thickness variations and obstructions increase导致uniformity deterioration
Solution Approach 1:
Dielectric layers are introduced as intermediary structures between the sensor elements and the color filters/microlenses. These dielectric layers provide a uniform supporting platform that eliminates thickness variations and obstructions, allowing color filters and microlenses to be properly positioned over sensor elements without compromising manufacturing precision.
Solution Approach 2:
The problem of thickness variations in the planar direction is resolved by introducing vertical dielectric layers and trenches. This dimensional approach creates a uniform topography across the substrate surface, enabling precise placement of color filters and microlenses while maintaining thickness uniformity for manufacturing.
3Reliability
If dielectric trenches are formed in non-pixel regions, then light uniformity is improved, but device complexity increases due to additional fabrication steps
Solution Approach 1:
The formation of dielectric trenches in non-pixel regions is combined with the existing color filter and microlens fabrication processes. By integrating these structures into the same fabrication sequence, the additional steps are consolidated with existing operations, reducing overall process complexity while achieving improved light uniformity across the device.
Data Source
AI summary
A method of forming an image sensor device is disclosed. The method includes providing a substrate having sensor elements in a pixel region and having no sensor elements in a non-pixel region. The method further includes forming metal pillars over the pixel region and a metal shield layer over the non-pixel region. The metal pillars are disposed above spaces between adjacent sensor elements. The method further includes depositing a dielectric layer over the metal pillars and the metal shield layer; and etching the dielectric layer to form first and second trenches. The first trenches are formed over the pixel region and the second trenches are formed over the non-pixel region. Each of the first trenches aligns to a respective sensor element and is surrounded by the dielectric layer at its bottom and sidewall surfaces.