Rear Surface CAPD Sensor Inversion for Distance Measurement
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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, as well as increased noise from external light, which degrades the signal-to-noise ratio and distance measuring accuracy.
Innovation Solution
A rear surface irradiation type CAPD sensor configuration with an on-chip lens, semiconductor layer, and wiring layer, where the signal extraction units are positioned on the side opposite to the light incidence, allowing for improved charge detection and voltage application, and a reflection member overlaps with the charge detection units, enhancing the aperture ratio and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wiring and control lines are arranged on the light receiving surface side of the photodiode, then charge extraction and control functions are ensured, 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 light receiving surface is formed on the back side of the substrate, while wiring and control lines are arranged on the front surface. This inversion allows the light to enter the photodiode through the rear surface without being blocked by wiring, maximizing the photoelectric conversion region and pixel sensitivity while maintaining charge extraction functionality through the front surface wiring.
2Measurement precision
If wiring capacity is increased to ensure sufficient saturated signal quantity, then signal to noise ratio is improved, 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 simply arranged on the front surface without interfering with light reception, naturally achieving sufficient wiring capacity for saturated signal quantity while maintaining simple device structure and low complexity.
3Reliability
If signal extraction units are arranged on the light incidence surface, then charge detection is enabled, but photoelectric conversion in inactive regions increases and distance measuring accuracy degrades
Solution Approach 1:
The patent relocates the signal extraction units from the light incidence surface to the opposite surface. The light enters through the rear surface and travels through the entire substrate thickness, ensuring that photoelectric conversion occurs primarily in the active region. The signal extraction units positioned on the front surface can then detect charges without causing premature photoelectric conversion in inactive regions, thereby maintaining distance measuring accuracy.
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 improves pixel sensitivity, charge separation efficiency, and distance measuring characteristics by maximizing the quantum efficiency and aperture ratio, while minimizing noise and increasing the extraction efficiency of signal carriers.
Implementation Method 1
a sensor capable of sorting signal charges obtained by receiving active light
Implementation Method 2
a reflection member, and in which the reflection member is provided to overlap with the first charge detection unit or the second charge detection unit, in plan view
Implementation Method 3
a first voltage application unit to which a first voltage is applied, a second voltage application unit to which a second voltage is applied
Data Source
AI summary
The present technology relates to a light receiving element, an imaging element, and an imaging device. 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, a first charge detection unit, and a second charge detection 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 that overlaps 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.