Image Sensor Photodiode Stacking for Photosensitivity
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Solution Overview
Problem
The manufacturing process of CMOS image sensors often results in increased bad pixels and defects due to the increased distance between photodiodes and microlenses caused by multi-layers, leading to reduced photosensitivity.
Innovation Solution
A method of manufacturing an image sensor that involves forming a color filter array and microlens after the photodiode, with a reduced number of metal lines above the photodiode to minimize the distance between the photodiode and microlens, and integrating an image chip and logic chip using a single pad, which includes a driver IC and logic array for additional functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-layers including metal lines and insulating layers are formed after photodiode fabrication, then device functionality is improved, but the distance between photodiode and microlens increases, reducing photosensitivity
Solution Approach 1:
The patent transitions from a planar multi-layer structure to a three-dimensional stacked structure where the photodiode, color filter, and microlens are vertically integrated on the same substrate. This eliminates the need for separate metal line layers, thereby reducing the optical path distance while maintaining device functionality through vertical stacking of functional layers.
2Adaptability or versatility
If multi-layers are formed after photodiode fabrication, then device functionality is improved, but the number of defects and bad pixels increases
Solution Approach 1:
The color filter and microlens are formed on the same substrate as the photodiode before final assembly, rather than adding multiple metal line layers afterward. This preliminary integration approach reduces the number of subsequent processing steps, thereby minimizing the introduction of defects and bad pixels while achieving the required device functionality.
3Reliability
If the optical path distance is reduced, then photosensitivity is enhanced, but the structural complexity must be minimized
Solution Approach 1:
The patent merges the photodiode, color filter, and microlens fabrication processes into a single integrated flow on one substrate. By combining these functions into a unified structure rather than separate stacked layers with metal interconnections, the optical path is shortened and photosensitivity is enhanced while the overall structural complexity is managed through process integration.
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
This approach significantly reduces the optical path length, enhancing photosensitivity and minimizing defects, thereby improving the performance of the image sensor by reducing the number of bad pixels.
Implementation Method 1
bonding a silicon on a substrate where a first metal interconnection is formed
Implementation Method 2
performing multiple times a process for implanting impurities into the bonded silicon formed through the bonding of the silicon
Implementation Method 3
image sensors are semiconductor devices which can convert optical images into electrical signals
Data Source
AI summary
Provided are an image sensor and a method for manufacturing the same. The image sensor comprises a substrate, a bonding silicon, an interlayer dielectric, a first contact plug, a second contact plug, a second metal interconnection, and a color filter layer and a microlens. The substrate comprises a first metal interconnection. The bonding silicon is formed on the substrate, and comprises a plurality of impurity regions. The interlayer dielectric is formed on the bonding silicon. The first contact plug penetrates the bonding silicon and is electrically connected to the first metal interconnection. The second contact plug penetrates the interlayer dielectric and is connected to a surface of the bonding silicon. The second metal interconnection is formed on the interlayer dielectric, and is connected to the second contact plug. The color filter layer and a microlens are formed over the second metal interconnection.