Backside Illumination Image Sensor Light Blocking Structure
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Solution Overview
Problem
Backside illumination image sensors face challenges with light reflection from peripheral regions, leading to image failures due to diffused reflections, which affect the sensitivity and noise levels of the images captured.
Innovation Solution
A method of manufacturing image sensors that involves forming a light blocking structure using a metal layer and an anti-reflective layer in the peripheral region to block incident light and reduce reflections, while also creating a pad structure with via contacts and pad patterns in the I/O region to minimize the incidence of reflected light onto the active pixel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a backside illumination image sensor is used to improve light receiving efficiency and optical sensitivity, then more light can hit each pixel from the backside, but light reflection from peripheral regions causes diffused reflections that affect image quality
Solution Approach 1:
The patent applies anti-reflective layers and light blocking structures to convert the harmful light reflection from peripheral regions into beneficial light absorption or controlled reflection. The anti-reflective layer reduces unwanted reflections by creating optical interference, while the light blocking structure directs stray light away from the active pixel region, effectively converting the harmful diffused reflection into a controlled optical path that improves image quality
Solution Approach 2:
The patent introduces intermediary structures between the peripheral region and the active pixel region, specifically the light blocking structure and anti-reflective layer. These intermediary elements act as mediators that intercept and control the light path, preventing direct reflection from reaching the pixel region while maintaining the backside illumination architecture's light receiving efficiency
2Ease of manufacture
If the peripheral region is left open to allow manufacturing simplicity, then the manufacturing process is easier, but reflected light from the peripheral region enters the active pixel region causing image failures
Solution Approach 1:
The patent applies preliminary action by forming the anti-reflective layer and light blocking structure during the manufacturing process before the sensor is completed. These structures are integrated into the fabrication sequence, with the light blocking structure being formed between the formation of the semiconductor layer and the final packaging, ensuring that the optical control features are built in advance to prevent reflection issues in the final product
3Device complexity
If no light blocking structure is formed in the peripheral region, then the manufacturing process is simpler, but diffused reflections from the peripheral region reduce sensitivity and increase noise in captured images
Solution Approach 1:
The patent applies local quality by implementing the light blocking structure and anti-reflective layer specifically in the peripheral region, while leaving the active pixel region untouched. This localized approach addresses the reflection problem only where it occurs (in the peripheral region) without adding unnecessary complexity to the entire device structure, maintaining manufacturing precision in the critical pixel areas while controlling reflections locally
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 solution effectively reduces diffused reflections and minimizes image failures by blocking incident light in the peripheral region, enhancing the sensitivity and low-light performance of the image sensor.
Implementation Method 1
a light blocking structure including the first metal layer and the anti-reflective layer in the peripheral region
Implementation Method 2
The semiconductor layer and a first insulating interlayer of the plurality of insulating interlayers on the I/O region may be partially etched to form a via hole therethrough
Data Source
AI summary
In a method of manufacturing an image sensor, photodiodes may be formed on a semiconductor layer in an active pixel region and a peripheral region. A structure including insulating interlayers and wiring structures may be formed on a first surface of the semiconductor layer in the active pixel region, the peripheral region and an input/output (I/O) region. The semiconductor layer and a first insulating interlayer of the insulating interlayers on the I/O region may be partially etched to form a via hole exposing a first wiring structure of the wiring structures. A first metal layer and a second metal layer may be formed on a second surface of the semiconductor layer and the via hole. The second metal layer may be patterned to form a second pad pattern on the semiconductor layer in the I/O region. An anti-reflective layer may be formed on the first metal layer and the second pad pattern. The anti-reflective layer and the first metal layer may be patterned to form a light blocking structure including the first metal layer and the anti-reflective layer in the peripheral region, and a pad structure including a via contact, a first pad pattern, the second pad pattern and an anti-reflective pattern in the I/O region. An image failure due to the reflected light may be minimized.