Color Filter Hard Mask Patterning for Image Sensors
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Solution Overview
Problem
Scaling down pixel size in image sensors poses challenges for color filter design due to specific processing features, where introducing new materials can compromise light transmission, process controllability, yield, and optical performance.
Innovation Solution
The use of hard mask layers, specifically oxide layers or other materials with good light transmission properties, to pattern color filters, allowing existing mature materials to be applied to smaller pixels while maintaining optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is scaled down to improve resolution, then measurement precision is improved, but manufacturing precision deteriorates due to processing challenges
Solution Approach 1:
A hard mask layer is introduced as an intermediary between the color filter material and the patterning process. This hard mask layer enables precise patterning of sub-100nm features while protecting the underlying color filter material during etching, thus resolving the contradiction between achieving high patterning resolution and maintaining manufacturing precision
Solution Approach 2:
The color filter structure is segmented into distinct functional layers: the color filter material layer and the hard mask layer. This segmentation allows each layer to be optimized independently - the color filter material for optical properties and the hard mask for patterning precision, thereby resolving the manufacturing precision challenge at scaled dimensions
2Manufacturing precision
If new materials are introduced to improve color filter scaling, then manufacturing precision is improved, but light transmission deteriorates
Solution Approach 1:
The hard mask layer serves as a temporary intermediary during fabrication that is removed after patterning. This allows existing mature color filter materials with excellent light transmission properties to be used, while achieving high precision patterning through the hard mask, thus avoiding the need to introduce new materials that might compromise optical performance
Solution Approach 2:
The invention changes the physical state and properties of the mask material by using oxide layers that can be deposited as thin films with controlled thickness and composition. This allows the mask to provide sufficient etching protection while being removable without damaging the underlying color filter material, maintaining both manufacturing precision and light transmission
3Area of stationary object
If pixel size is scaled down, then area of moving object is reduced, but productivity deteriorates due to process complexity
Solution Approach 1:
The hard mask layer is deposited and patterned before the color filter material is finalized, allowing precise definition of pixel boundaries and color filter regions in advance. This preliminary patterning action simplifies subsequent processing steps and reduces defects, thereby maintaining productivity despite pixel size scaling
Solution Approach 2:
The hard mask layer performs multiple functions: it defines pixel boundaries, protects underlying structures during etching, and enables precise color filter patterning. This multi-functionality reduces the need for additional specialized process steps, maintaining manufacturing efficiency while achieving high precision at scaled dimensions
Data Source
AI summary
Embodiments of an apparatus including a color filter arrangement formed on a substrate having a pixel array formed therein. The color filter arrangement includes a clear filter having a first clear hard mask layer and a second clear hard mask layer formed thereon, a first color filter having the first clear hard mask layer and the second hard mask layer formed thereon, a second color filter having the first clear hard mask layer formed thereon, and a third color filter having no clear hard mask layer formed thereon. Other embodiments are disclosed and claimed.