Rear-Surface Irradiation CAPD Sensor for High Sensitivity Distance Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Front surface irradiation type CAPD sensors face limitations in photoelectric conversion region due to wiring and control lines, leading to decreased pixel sensitivity and accuracy in distance measurement due to noise interference from external light and inefficient charge separation.
Innovation Solution
A rear surface irradiation type CAPD sensor configuration with on-chip lens, wiring layer, and semiconductor layer, where signal extraction units are placed on the side opposite to the light incidence, allowing for improved light path shielding and increased aperture ratio, enhancing charge detection and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wiring and control lines are arranged on the light receiving surface side of the photodiode, then charge extraction and control functions are enabled, but the photoelectric conversion region is limited and pixel sensitivity decreases
Solution Approach 1:
The patent inverts the conventional front-surface irradiation structure to a rear-surface irradiation structure. The photodiode's light receiving surface is positioned on the back side where no wiring exists, while wiring and control lines are arranged on the front surface. This inversion eliminates wiring shadow effects on the photoelectric conversion region, maximizing pixel sensitivity while maintaining charge extraction functionality through the inverted architecture.
2Measurement precision
If wiring capacity is increased to ensure sufficient saturated signal quantity, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
By inverting the sensor structure to rear-surface irradiation, the patent eliminates the need for complex wiring layouts on the light receiving surface. The wiring can be freely arranged on the front surface without compromising photoelectric conversion efficiency, thereby achieving sufficient saturated signal quantity through simplified wiring architecture rather than increased wiring capacity.
3Ease of operation
If signal extraction units are arranged on the light incidence surface, then charge detection is enabled, but photoelectric conversion occurs in inactive regions creating noise
Solution Approach 1:
The patent positions signal extraction units (taps) on the rear surface along with the light receiving surface, while charge accumulation regions are positioned on the front surface. This spatial separation ensures that photoelectric conversion occurs only in active regions where signal extraction units are present, preventing noise generation from inactive regions and improving distance measurement accuracy.
4Measurement precision
If aperture ratio is increased to improve light reception, then pixel sensitivity improves, but wiring space is reduced
Solution Approach 1:
By inverting the structure to rear-surface irradiation, the patent allows the entire front surface to be dedicated to photoelectric conversion with no wiring present, maximizing the aperture ratio. Wiring is relocated to the rear surface where it does not interfere with light reception, thereby achieving high pixel sensitivity while maintaining adequate wiring space through the inverted architecture.
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 rear surface irradiation type configuration maximizes quantum efficiency and aperture ratio, improving pixel sensitivity and distance measurement accuracy by reducing noise and increasing light reception, thereby enhancing the overall performance of the CAPD sensor.
Implementation Method 1
a sensor capable of sorting signal charges obtained by receiving active light
Implementation Method 2
the reflection member is provided to overlap with the first charge detection unit or the second charge detection unit, in plan view
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present technology relates to a light receiving element, an imaging element, and an imaging device, in which characteristics can be improved. A light receiving element includes an on-chip lens, a wiring layer, and a semiconductor layer arranged between the on-chip lens and the wiring layer. The semiconductor layer includes a first voltage application unit to which a first voltage is applied, a second voltage application unit to which a second voltage is applied, the second voltage being different from the first voltage, a first charge detection unit arranged around the first voltage application unit, and a second charge detection unit arranged around the second voltage application unit. The wiring layer includes at least one layer including first voltage application wiring configured to supply the first voltage, second voltage application wiring configured to supply the second voltage, and a reflection member, and the reflection member is provided to overlap with the first charge detection unit or the second charge detection unit, in plan view. The present technology, for example, can be applied to a light receiving element configured to measure a distance.