Image Sensor Grid Layers With Air Isolation for Pixel Crosstalk
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Solution Overview
Problem
Image sensing devices face challenges in preventing optical crosstalk between color filters and maximizing the light guarding effect of incident light, which affects the quality of electrical signals generated.
Innovation Solution
The implementation of a grid structure with an inner and outer grid layer, where an air layer is formed between the inner and outer grid layers at the side and top surfaces, effectively isolating adjacent photoelectric conversion elements and preventing crosstalk by using a sacrificial film removal process and capping film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a grid structure is implemented to prevent optical crosstalk between color filters, then optical isolation between adjacent pixels is improved, but device complexity increases due to multiple grid layers and fabrication steps
Solution Approach 1:
The grid structure is divided into multiple independent layers (first grid layer, second grid layer, third grid layer) with different orientations. Each layer segments the optical path independently, and together they provide comprehensive crosstalk prevention without requiring a single complex structure
Solution Approach 2:
The patent introduces vertical stacking of grid layers at different orientations (first orientation, second orientation, third orientation). This multi-dimensional approach to light blocking provides superior isolation compared to single-layer planar grids, as light must pass through multiple oriented barriers
2Illumination intensity
If a grid structure with multiple layers is formed to maximize light guarding effect, then light guarding performance is improved, but manufacturing precision requirements increase due to alignment of multiple grid layers
Solution Approach 1:
Each grid layer is formed with preliminary patterning steps that establish precise geometric definitions before subsequent layers are added. The first grid layer is completely formed and stabilized before the second layer is introduced, ensuring that alignment references are already in place
Solution Approach 2:
Different grid layers are oriented in different directions (first orientation, second orientation, third orientation) to address specific crosstalk pathways locally. Each layer's orientation is optimized for its specific function in blocking light from particular adjacent pixels
3Object-affected harmful factors
If sacrificial film removal process is used to form air gaps for optical isolation, then optical isolation between color filters is improved, but manufacturing process complexity increases
Solution Approach 1:
A sacrificial film is introduced as a temporary intermediary material during fabrication. This film is deposited between grid layers, then selectively removed to create air gaps for optical isolation. The sacrificial film mediates the creation of the air gap structure without requiring direct complex processing
Solution Approach 2:
The sacrificial film is deliberately deposited and then completely removed to create the desired air gap structure. This temporary material is discarded after serving its purpose of defining the air gap space, simplifying the overall process compared to attempting to create air gaps through direct patterning
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 solution enhances the optical isolation between adjacent color filters, maximizing the light guarding effect and preventing crosstalk, thereby improving the quality of electrical signals generated by the image sensing device.
Implementation Method 1
an array of photoelectric conversion elements supported by the substrate, each photoelectric conversion element structured to convert light into an electrical signal
Implementation Method 2
an air layer formed between the inner grid layer and the outer grid layer at a side surface and a top surface of the inner grid to facilitate separating adjacent photoelectric conversion elements
Data Source
AI summary
An image sensing device and a method for forming the same are disclosed. The image sensing device includes a substrate including photoelectric conversion elements, and a grid structure disposed over the substrate. The grid structure includes an inner grid layer, and an outer grid layer formed outside the inner grid layer to provide air layer formed at a side surface and a top surface of the inner grid layer.