Back-Illuminated CAPD Sensor Layout for Accurate ToF Ranging
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Solution Overview
Problem
CAPD sensors of the front-illuminated type face challenges in securing a sufficient photoelectric conversion region due to wiring and control line arrangements, leading to degraded pixel sensitivity and potential noise interference in distance measurement systems.
Innovation Solution
The design of a CAPD sensor as a back-illuminated type, where the wiring layer is positioned on the opposite side of the light incident face, allowing for a larger photoelectric conversion region and improved signal extraction efficiency, with periodic or mirror arrangements of voltage supply lines to enhance charge separation and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wiring and control lines are arranged on the light reception face side of a front-illuminated CAPD sensor, then charge extraction and control functions are achieved, but the photoelectric conversion region is reduced and pixel sensitivity degrades
Solution Approach 1:
The patent inverts the conventional front-illuminated structure to a back-illuminated structure. The light reception face is positioned on the opposite side from where light enters, allowing wiring layers to be located on the front surface while the active photoelectric conversion region remains on the back surface, thus eliminating wiring obstruction of the photoelectric conversion region
Solution Approach 2:
The patent separates the wiring layer and photoelectric conversion region into different spatial dimensions by using a back-illuminated structure. The wiring layers are positioned on the front surface (first surface) while the photoelectric conversion region is positioned on the back surface (second surface), allowing both functions to coexist without spatial conflict
2Measurement precision
If wiring layers are positioned on the light incident face in front-illuminated sensors, then electrical connections are established, but noise interference occurs and measurement accuracy decreases
Solution Approach 1:
The patent inverts the conventional structure so that light enters through the back surface rather than the front surface. This positions the photoelectric conversion region away from the wiring layers on the front surface, reducing electromagnetic interference and noise from wiring on the light reception face, thereby improving distance measurement accuracy
3Device complexity
If the photoelectric conversion region is reduced due to wiring arrangements, then device integration is achieved, but quantum efficiency decreases
Solution Approach 1:
The patent uses back-illumination to reverse the conventional structure, allowing the photoelectric conversion region to occupy the entire back surface area without being reduced by front-surface wiring. This maximizes the active area for light reception and photoelectric conversion, thereby improving quantum efficiency while maintaining device integration
Solution Approach 2:
The patent segments the sensor into distinct functional layers: the front surface contains wiring and control structures, while the back surface contains the photoelectric conversion region. This segmentation allows each layer to optimize its function without compromising the other, maintaining high quantum efficiency while achieving device integration
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
This configuration improves pixel sensitivity and distance measurement accuracy by maximizing quantum efficiency and aperture ratio, reducing noise, and enabling high-speed signal carrier extraction.
Implementation Method 1
a sensor capable of distributing signal charge obtained by receiving light after active light illuminated using an LED (Light Emitting Diode) or a laser with a certain phase is reflected from an object
Implementation Method 2
a technology is proposed which can modulate a wide-range region in a substrate of a sensor at a high speed by applying a voltage directly to the substrate to generate current in the substrate
Data Source
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AI summary
The present technology relates to a light reception device and a distance measurement module whose characteristic can be improved. The light reception device 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 tap having a first voltage application portion and a first charge detection portion arranged around the first voltage application portion, and a second tap having a second voltage application portion and a second charge detection portion arranged around the second voltage application portion. Furthermore, the light reception device is configured such that a phase difference is detected using signals detected by the first tap and the second tap. The present technology can be applied, for example, to a light reception device that generates distance information, for example, by a ToF method, and so forth.