Back-Illuminated CAPD Sensor with On-Chip Lens for Distance Measurement
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Solution Overview
Problem
CAPD sensors of the front-illuminated type face challenges in achieving sufficient photoelectric conversion and signal extraction due to wiring layout restrictions, leading to degraded pixel sensitivity and noise interference from outside light, which affects the accuracy of distance measurement using the indirect ToF method.
Innovation Solution
A light reception device with an on-chip lens, wiring layer, and semiconductor layer configuration that includes first and second taps with different voltage application portions and charge detection portions, where the on-chip lens position varies across the pixel array to ensure uniform optical path length and contrast, combined with a light source that illuminates with varying brightness and a light emission controlling section to manage illumination timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wires and control lines are arranged on the light reception face side to extract charge, then charge extraction is enabled, but the photoelectric conversion region is restricted and pixel sensitivity degrades
Solution Approach 1:
The patent inverts the conventional front-illuminated structure to a back-illuminated structure, where the light reception face is positioned opposite to the wiring layer. This allows light to enter the semiconductor layer without being blocked by wires, while charge extraction is still achieved through the tap structure. The inversion resolves the contradiction by eliminating wire obstruction from the light path while maintaining charge extraction functionality.
2Quantity of substance
If additional transistors are provided to secure saturation signal amount, then signal capacity is improved, but device complexity increases
Solution Approach 1:
The tap structure in the patent serves multiple functions simultaneously: it acts as both a charge extraction point and a signal amplification element. By making the tap region functionally versatile, the patent achieves sufficient saturation signal amount without requiring additional dedicated transistors, thus improving signal capacity while avoiding increased device complexity.
3Quantity of substance
If photoelectric conversion occurs in inactive Tap region, then charge is generated, but distance measurement accuracy degrades due to noise
Solution Approach 1:
The patent implements localized control of the semiconductor layer through the tap structure, where different regions (active tap vs. inactive tap) have different electrical potentials. By applying voltage selectively to the active tap region, the patent creates a localized electric field that directs charge carriers only to the intended collection region. This local quality differentiation ensures that charge generated in inactive regions does not contaminate the active tap signal, maintaining distance measurement accuracy while still allowing broad 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
This configuration enhances pixel sensitivity and charge separation efficiency, improving the distance measurement characteristics by minimizing noise and optimizing signal extraction, thereby enhancing the overall performance of the CAPD sensor.
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
active light illuminated using an LED (Light Emitting Diode) or a laser with a certain phase
Data Source
AI summary
The present technology relates to a light reception device and a distance measurement module. The light reception device includes an on-chip lens, a wiring layer, and a semiconductor layer between the on-chip lens and the wiring layer. The semiconductor layer includes a first tap to which a first voltage is applied and a first charge detection portion, and a second tap to which a second voltage different from the first voltage is applied and a second charge detection portion. The position of the on-chip lens differs depending upon an in-plane position of a pixel array section, so that an optical path length or a DC contrast of a chief ray from an object is uniform at in-plane pixels of the pixel array section. 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.