Solid-State Image Sensor Color Filter Thickness Optimization
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Solution Overview
Problem
High-definition solid-state image sensors with small pixel sizes face challenges in achieving high sensitivity and preventing color mixture due to limitations in color filter layer thickness and pigment concentration, leading to issues like residue formation and peeling off during photolithography.
Innovation Solution
A method for manufacturing solid-state image sensors where all color filters have a small thickness, with a specific configuration of thermosetting and photocurable resins, and a unique patterning process using dry etching and photolithography to ensure high sensitivity and minimize color mixture, involving a lower and upper flattening layer to optimize the distance from the microlens to the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the color filter layer thickness is increased to obtain satisfactory spectral characteristics, then the spectral characteristics are improved, but the resolution performance deteriorates due to rounded corners and the total distance from microlens to device increases
Solution Approach 1:
The patent changes the chemical composition parameters of the color filter material by incorporating both photocurable resins and thermosetting resins in specific ratios. This allows the color filter to achieve satisfactory spectral characteristics with reduced thickness, thereby improving resolution performance while maintaining spectral quality.
Solution Approach 2:
The patent uses composite materials by combining photocurable resins and thermosetting resins in the color filter layer. This composite approach enables the color filter to achieve both good spectral characteristics and adequate mechanical properties at reduced thickness, solving the contradiction between spectral performance and resolution.
2Reliability
If the pigment concentration in color filter material is increased to obtain desired spectral characteristics, then the spectral characteristics are improved, but the photocuring reaction becomes insufficient due to light not reaching the bottom of the color filter layer
Solution Approach 1:
The patent changes the chemical composition by incorporating thermosetting resins that can be cured through thermal reactions in addition to photocuring. This dual-curing mechanism ensures complete curing even when high pigment concentration blocks UV light, while maintaining high pigment concentration for good spectral characteristics.
Solution Approach 2:
The patent uses composite materials combining photocurable and thermosetting resins. The thermosetting component provides alternative curing pathways that are not dependent on light penetration, ensuring complete curing throughout the color filter layer thickness while allowing high pigment concentration for spectral quality.
3Productivity
If the pixel size is reduced to increase the number of pixels, then the number of pixels is increased, but the resolution performance of the color filter layer deteriorates due to pattern shape defects
Solution Approach 1:
The patent changes the material composition parameters to include both photocurable and thermosetting resins with specific properties that enable precise patterning. This composition allows the color filter layer to maintain sharp edges and accurate pattern shapes even at reduced pixel sizes, preventing resolution deterioration.
Solution Approach 2:
The patent applies local quality by ensuring the color filter material has appropriate local properties for precise patterning. The dual-resin system provides both the photosensitivity needed for photolithography precision and the mechanical stability needed to maintain pattern integrity at small dimensions.
4Reliability
If the opening area is increased to improve sensitivity, then the sensitivity is improved, but color mixture occurs when light leaks from one color filter enter adjacent color filters
Solution Approach 1:
The patent changes the thickness parameter of the color filter layer by using reduced thickness with optimized material composition. This allows larger opening areas for improved sensitivity while the reduced thickness and optimized materials prevent excessive light scattering that would cause color mixture between adjacent 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 approach results in a high-definition solid-state image sensor with reduced color mixture and enhanced sensitivity, where all color filters have high sensitivity and a shorter total distance from the microlens to the device, improving the manufacturing process and sensor performance.
Implementation Method 1
a first-color color filter layer 14A is formed, and then a photosensitive resin mask layer 20 is formed on the first-color color filter layer 14A
Implementation Method 2
the first-color color filter layer 14A is heat cured by heating at a high temperature
Implementation Method 3
a microlens for focusing light on the photoelectric conversion element
Implementation Method 4
photoelectric conversion elements arranged in respective pixels
Data Source
Figure 1~2
Figure 3(a)~3(g)
Figure 4(a)~4(b)
AI summary
Provided is a high-definition solid-state image sensor with good sensitivity and less color mixture. The solid-state image sensor includes: a semiconductor substrate (10) including photoelectric conversion elements (11) two-dimensionally arranged; a color filter layer (30) including color filters of colors two-dimensionally arranged corresponding to respective photoelectric conversion elements (11) in a preset regular pattern; and a lower layer flattening layer (12) arranged only between a first-color color filter (14) of a first color and the semiconductor substrate (10). The following formulas: 200 [nm] ≤ A ≤ 700 [nm]; 0 [nm] ≤ B ≤ 200 [nm]; and C ≤ A + B + 200 [nm] are satisfied, where A [nm] represents a thickness of the first-color color filter (14), B [nm] represents a thickness of the lower layer flattening layer (12), and C [nm] represents a thickness of color filters (15, 16) of colors other than the first color.