Image Sensor Dummy Pattern Blocks Crosstalk
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Solution Overview
Problem
Image sensors face deterioration in operating characteristics due to light entering the charge storage region from adjacent image cells, leading to issues with dynamic range, crosstalk, and parasitic light sensitivity.
Innovation Solution
Incorporating a dummy pattern and light shield layers on the substrate to inhibit light from entering the charge storage region, with the dummy pattern made of the same material as the transfer gate electrode and positioned between the charge storage region and adjacent photodiodes, and additional light shield patterns extending from the light shield layer to further block light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a charge storage region is formed in the substrate to store electrons between the charge accumulation region and floating diffusion region, then the image sensor can implement global shutter method, but light from adjacent image cells enters the charge storage region causing deterioration of operating characteristics
Solution Approach 1:
A dummy pattern is introduced as an intermediary structure between adjacent image cells. This dummy pattern absorbs or blocks light from adjacent cells before it can reach the charge storage region, thereby eliminating the harmful light interference while preserving the global shutter functionality enabled by the charge storage region.
Solution Approach 2:
The harmful light interference is extracted and isolated from the charge storage region by positioning the dummy pattern in the light path from adjacent cells. The dummy pattern acts as a separate light-blocking element that removes the harmful light component without affecting the intended light collection by the photodiode.
2Ease of operation
If transfer gate electrodes are formed on surface portions of the substrate among charge accumulation region, charge storage region and floating diffusion region, then charge can be transferred between regions, but the structure becomes more complex
Solution Approach 1:
The dummy pattern serves multiple functions: it acts as a light-blocking structure to prevent light interference, and simultaneously functions as a structural element in the device architecture. By combining light shielding with the existing gate electrode structure, the patent reduces overall device complexity while maintaining charge transfer capability.
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
Significantly reduces light entering the charge storage region, thereby enhancing the dynamic range and reducing crosstalk and parasitic light sensitivity of the image sensor.
Implementation Method 1
a dummy pattern disposed on the substrate and configured to inhibit light from being introduced into the charge storage region from an adjacent image cell
Implementation Method 2
an image sensor is a semiconductor device that converts an optical image into electrical signals
Data Source
AI summary
An image sensor includes at least one image cell having a photodiode disposed in a substrate, a charge storage region disposed in the substrate to be spaced apart from the photodiode, a transfer gate electrode disposed on a channel region between the photodiode and the charge storage region to transfer a charge from the photodiode to the charge storage region, and a dummy pattern disposed on the substrate and configured to inhibit light from being introduced into the charge storage region from an adjacent image cell.