Silicon On-Chip Lens Structure for Infrared Imaging Sensitivity
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in achieving high sensitivity to infrared light due to the inefficiency of light confinement and high light loss in pinhole structures, leading to reduced sensitivity and flare issues.
Innovation Solution
A solid-state imaging device is designed with a substrate having a light shielding unit and a silicon on-chip lens that condenses incident light onto a pinhole, utilizing a higher refractive index silicon material to narrow the beam waist and reduce pinhole diameter, thereby enhancing light confinement and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pinhole structure is used to confine reflected light in the Si layer, then sensitivity to infrared light is improved, but light loss in the pinhole structure portion increases
Solution Approach 1:
The patent changes the material parameter of the on-chip lens from conventional materials to silicon, which has a higher refractive index. This parameter change enables more effective light confinement and reduces light loss in the pinhole structure while maintaining high sensitivity to infrared light.
Solution Approach 2:
The patent applies a specific material (silicon) with particular optical properties (higher refractive index) to the on-chip lens region, creating local quality enhancement that improves light confinement efficiency and reduces light loss in the pinhole structure.
2Power
If a reflection structure is provided on the opposite side of the light receiving surface to increase optical path length, then photoelectric conversion efficiency is improved, but light is not sufficiently narrowed in the on-chip lens
Solution Approach 1:
The patent changes the refractive index parameter of the on-chip lens material to that of silicon, which has a higher refractive index than conventional materials. This enables the lens to more effectively narrow the light beam while maintaining the increased optical path length provided by the reflection structure, thereby improving photoelectric conversion efficiency.
Solution Approach 2:
The on-chip lens utilizes a curved surface structure to focus and narrow the light beam. The combination of this curved geometry with silicon's higher refractive index enhances the light-narrowing effect, ensuring that reflected light is properly confined while maintaining efficient photoelectric conversion.
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 solution effectively increases the utilization efficiency of incident light, achieving higher sensitivity and reducing flare caused by reflected light, while maintaining optical path length and photoelectric conversion efficiency.
Implementation Method 1
a first lens made of silicon, the first lens being provided on the light shielding unit and condensing incident light toward the hole portion
Implementation Method 2
light is not sufficiently narrowed in an on-chip lens with respect to light emitted to a light receiving element
Data Source
AI summary
A solid-state imaging device according to an embodiment includes: a plurality of pixels, each of the plurality of pixels including a substrate having a first surface serving as a light incident surface, a photoelectric conversion unit located inside the substrate, a light shielding unit provided on a first surface side, the light shielding unit having a hole portion configured to allow light to be incident on the photoelectric conversion unit, and a first lens made of silicon, the first lens being provided on the light shielding unit and condensing incident light toward the hole portion.