APD Sensor Chip Lens Layout for Infrared Carrier Collection
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Solution Overview
Problem
In CMOS image sensors and distance measurement sensors using the Time-of-Flight method, the configuration of on-chip lenses for avalanche photodiodes (APDs) becomes difficult to form with large curvature as pixel size increases, leading to reduced light receiving sensitivity, especially for infrared light, where the photoelectric conversion occurs away from the multiplication region, making it hard to efficiently use carriers generated through photoelectric conversion.
Innovation Solution
A sensor chip with a semiconductor substrate that includes multiple avalanche multiplication regions in each pixel region, combined with a plurality of on-chip lenses arranged to condense light onto the substrate, ensuring efficient collection and use of carriers generated through photoelectric conversion, even with a thinner substrate, thereby enhancing light receiving sensitivity and reducing timing jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixel size is increased, then manufacturing ease is improved, but light receiving sensitivity deteriorates due to inability to form on-chip lenses with large curvature
Solution Approach 1:
The pixel region is divided into multiple areas with different on-chip lenses (first, second, and third on-chip lenses) having different curvatures. This segmentation allows each lens to be optimized for specific light incident angles, resolving the contradiction by maintaining high light receiving sensitivity across various angles while accommodating larger pixel sizes.
Solution Approach 2:
Different regions of the pixel are assigned different lens curvatures tailored to local light incident angle requirements. The first on-chip lens handles oblique incident light with high curvature, while the second and third lenses handle light at different angles with appropriate curvatures, optimizing local light concentration efficiency throughout the pixel region.
2Reliability
If on-chip lens curvature is increased to concentrate light, then light receiving sensitivity is improved, but manufacturing difficulty increases for larger pixel sizes
Solution Approach 1:
The lens system is segmented into multiple on-chip lenses with different curvatures positioned at different locations. This allows the high curvature needed for light concentration to be applied only where needed (first on-chip lens), while other regions use lenses with curvatures suitable for their specific light incident angles, making the overall structure manufacturable in larger pixels.
Solution Approach 2:
The solution moves from a single lens design to a multi-lens arrangement in the planar dimension, where lenses with different curvatures are positioned at different locations within the pixel. This dimensional approach allows high curvature lenses to be used selectively without requiring the entire pixel structure to accommodate the most demanding curvature requirements.
3Adaptability or versatility
If photoelectric conversion region is positioned away from multiplication region to enable infrared detection, then infrared light detection is achieved, but carrier collection efficiency deteriorates
Solution Approach 1:
The on-chip lenses act as intermediaries that guide and concentrate infrared light from the photoelectric conversion region (located away from the multiplication region) onto the multiplication region. This intermediary optical system enables efficient carrier collection despite the spatial separation required for infrared detection in silicon substrates.
Solution Approach 2:
The on-chip lenses perform preliminary light concentration and guidance before the light reaches the multiplication region. By pre-concentrating the infrared light onto the multiplication region, the system ensures high carrier collection efficiency even though the photoelectric conversion occurs at a distance from the multiplication region.
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 allows for efficient use of carriers generated through photoelectric conversion, enhancing light receiving sensitivity and enabling accurate distance measurement by concentrating light onto the avalanche multiplication region, which can be achieved even with a thinner semiconductor substrate, thus reducing timing jitter and improving detection efficiency.
Implementation Method 1
an on-chip lens condensing light incident on the semiconductor substrate
Implementation Method 2
carriers generated through photoelectric conversion
Implementation Method 3
avalanche multiplication regions multiplying carriers generated through photoelectric conversion
Data Source
AI summary
The present disclosure relates to a sensor chip and an electronic apparatus each of which enables carriers generated through photoelectric conversion to be efficiently used. At least one or more avalanche multiplication regions multiplying carriers generated through photoelectric conversion are provided in each of a plurality of pixel regions in a semiconductor substrate, and light incident on the semiconductor substrate is condensed by an on-chip lens. Then, a plurality of on-chip lenses is arranged in one pixel region. The present technology, for example, can be applied to a back-illuminated type CMOS image sensor.