Deep Guard Ring and Noise Blocking Area for Image Sensor Crosstalk
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Solution Overview
Problem
Image sensors face challenges in reducing substrate noise and crosstalk, particularly in high-pixel sensors, where high-speed framing can lead to dark random noise and horizontal line noise, and existing deep N-well implementations are difficult to apply to pixel arrays and struggle with P-substrate ground connections.
Innovation Solution
A backside illumination image sensor with a deep photodiode guard ring formed to contact a substrate or ion implantation layer, creating a draining channel for thermoelectrons and incorporating a noise blocking area in the deep guard ring to isolate blocks and prevent substrate crosstalk noise, using deep N-type ion implantation and epitaxial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If deep N-well is used to reduce substrate noise, then substrate noise reduction is improved, but it is difficult to apply to pixel arrays and cannot overcome crosstalk through P-substrate
Solution Approach 1:
The substrate is divided into multiple isolated P-type well regions arranged in a grid pattern throughout the pixel array. Each P-type well acts as an independent noise isolation compartment, segmenting the substrate into electrically isolated zones that prevent noise propagation while maintaining pixel array functionality.
Solution Approach 2:
The noise isolation structure transitions from a single deep N-well dimension to a two-dimensional grid of P-type wells distributed across the substrate. This dimensional expansion allows noise isolation to be applied throughout the entire pixel array area rather than at isolated points, overcoming the limitation of deep N-well applicability.
2Speed
If high-speed framing is used in high-pixel sensors, then imaging speed is improved, but dark random noise and horizontal line noise increase
Solution Approach 1:
P-type wells are introduced as intermediary structures between adjacent pixels and circuit blocks. These intermediary regions act as electrical buffers that intercept and dissipate noise signals before they can propagate to sensitive photodetector elements, thereby suppressing dark random noise generated during high-speed framing operations.
3Reliability
If P-substrate is used to provide ground connections, then electrical connectivity is improved, but crosstalk occurs between blocks
Solution Approach 1:
The continuous P-substrate ground connection is segmented into discrete, isolated P-type well regions. Each well is electrically isolated from its neighbors by reverse-biased PN junctions, creating compartmentalized ground zones that maintain local electrical connectivity while preventing noise crosstalk between adjacent blocks through the substrate.
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
Effectively eliminates electrical crosstalk and substrate noise, allowing for improved picture quality and reduced dark current, enabling the manufacture of high-definition, highly-integrated image sensors with increased cell density on semiconductor substrates.
Implementation Method 1
a deep guard ring formed to contact a substrate or an ion implantation layer in a cell structure so as to form a draining channel for thermoelectrons generated at the substrate or the ion implantation layer
Implementation Method 2
a structure functioning as a thin P-substrate is formed by PIN ion-implantation on the backside
Implementation Method 3
a DNW process can be eliminated by forming a deep P/N guard ring using high-energy ion implantation
Data Source
AI summary
An image sensor including a deep guard ring and a noise blocking area and a method of manufacturing the same. The image sensor includes the deep guard ring and a deep P well surrounding the noise blocking area, thereby preventing crosstalk between adjacent pixels. In addition, an ion implantation layer is divided by the noise blocking area, so that substrate crosstalk is effectively eliminated.