Backside-Illuminated Image Sensor Structure for Pixel Cross-Talk
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Solution Overview
Problem
Conventional CMOS image sensors suffer from insufficient light sensitivity in the near infrared range due to metal wiring obstructing incident light, leading to reduced performance in applications like iris scanners and Time-Of-Flight sensors.
Innovation Solution
A backside illuminated CMOS image sensor with a light scattering portion in the substrate that converges incident light to a photoelectric conversion structure, featuring a center section and side sections of varying depths to prevent cross-talk between adjacent pixels and enhance light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a backside illuminated CMOS image sensor is used to increase light sensitivity in the near infrared range, then the structure allows light to reach the photoelectric conversion structure without obstruction from metal wiring, but cross-talk between adjacent pixels occurs due to light scattering
Solution Approach 1:
The substrate is divided into multiple unit pixels with clear boundaries. Element isolation films are introduced at the boundaries between unit pixels to segment the light paths, preventing cross-talk while maintaining the backside illuminated structure's light sensitivity advantages.
Solution Approach 2:
Different regions of the substrate are given different properties: the center section of each unit pixel has a first depth optimized for light sensitivity, while the boundary regions have element isolation films to prevent cross-talk. This local differentiation resolves the contradiction between light sensitivity and cross-talk prevention.
2Object-generated harmful factors
If element isolation films are extended to fully overlap vertical boundaries between unit pixels to prevent cross-talk, then cross-talk is effectively prevented, but the overall size of the image sensor increases
Solution Approach 1:
The element isolation films are designed to partially overlap the vertical boundaries between unit pixels rather than fully extending beyond them. This partial action is sufficient to prevent cross-talk while avoiding the excessive area increase that would result from full extension, thus resolving the size contradiction.
3Ease of manufacture
If the light scattering portion has uniform depth across the entire unit pixel to simplify manufacturing, then manufacturing is easier, but cross-talk between adjacent pixels cannot be effectively prevented
Solution Approach 1:
The light scattering portion is segmented into a center section with a first depth and boundary regions with element isolation films. This segmentation allows the center to be manufactured simply while the boundaries provide cross-talk prevention, resolving the contradiction between manufacturing ease and cross-talk prevention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The light scattering structure effectively prevents cross-talk and increases light sensitivity, simplifies manufacturing, and maintains a compact size while optimizing light paths in different color channels.
Implementation Method 1
a light scattering portion in a substrate configured to converge a path of incident light (e.g., on or in the image sensor) to a photoelectric conversion structure
Implementation Method 2
configured to converge a path of incident light to a photoelectric conversion structure, thereby preventing cross-talk between adjacent pixels
Implementation Method 3
converge a path of incident light to a photoelectric conversion structure
Data Source
AI summary
Disclosed are a backside illuminated image sensor and a method of manufacturing the same. More particularly, a backside illuminated image sensor and a method of manufacturing the backside illuminated image sensor include a light scattering portion in a substrate configured to converge a path of incident light to a photoelectric conversion structure, thereby preventing cross-talk between adjacent pixels and increasing light sensitivity.