Backside-illuminated Image Sensor Device Isolation Layer Crosstalk Prevention
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Solution Overview
Problem
Backside-illuminated image sensors suffer from crosstalk due to the lack of a structure to isolate electrons generated by light between pixels, leading to undesirable signal interference.
Innovation Solution
A device isolation layer is formed to pass through an epitaxial layer in the semiconductor substrate, isolating pixel regions and acting as an alignment key during grinding, thereby preventing crosstalk between adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If no isolation layer is formed in backside-illuminated image sensors, then manufacturing is simpler, but crosstalk occurs between adjacent pixels
Solution Approach 1:
The patent divides the semiconductor substrate into isolated pixel regions by forming device isolation layers between adjacent pixels. These isolation layers create physical barriers that segment the continuous substrate into discrete functional units, preventing electron crosstalk while maintaining a relatively simple manufacturing process.
Solution Approach 2:
The device isolation layer acts as an intermediary structure between adjacent pixel regions. This intermediate layer serves as both an electrical barrier to prevent crosstalk and a physical reference for alignment during the thinning process, resolving the contradiction between manufacturing simplicity and crosstalk prevention.
2Measurement precision
If the semiconductor substrate is thinned for backside illumination, then light reception efficiency is improved, but alignment accuracy deteriorates due to loss of reference structures
Solution Approach 1:
The device isolation layers are formed before the substrate thinning process. These layers serve as pre-established alignment references that guide subsequent manufacturing steps, including the thinning process itself. By preparing alignment keys in advance, the patent maintains manufacturing precision while achieving the thinning necessary for backside illumination.
Solution Approach 2:
The device isolation layer serves as an intermediary reference structure that bridges the thinning process and final device assembly. It provides visible alignment markers during thinning while ultimately becoming part of the functional device structure, solving both the alignment and isolation requirements.
3Productivity
If photo diodes are minimized in size to increase pixel density, then the number of pixels per unit area increases, but isolation between pixels becomes more difficult
Solution Approach 1:
The patent uses device isolation layers to segment the substrate into discrete pixel regions, enabling high pixel density while maintaining proper isolation. The isolation layers are strategically positioned to separate adjacent photodiodes, allowing miniaturization without sacrificing electrical isolation between pixels.
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 device isolation layer effectively minimizes crosstalk and facilitates the manufacturing of backside-illuminated image sensors by providing a clear alignment key during substrate grinding, enhancing the accuracy of light reception characteristics.
Implementation Method 1
a device isolation layer which is formed to pass through an epitaxial layer in a semiconductor substrate to isolate pixel regions
Implementation Method 2
pixels of the image sensor may sense the light generated from objects and convert the sensed light into electric signals or values
Data Source
AI summary
An image sensor may include at least one device isolation layer that passes through an epitaxial layer in a semiconductor substrate to isolate pixel regions, a light-receiving element in each pixel region, and a transistor in the active region of the semiconductor substrate partitioned by the device isolation layer.