Light Receiving Device Groove Structure for ToF Sensor Sensitivity
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Solution Overview
Problem
Distance measuring sensors using the indirect time of flight (ToF) scheme face limitations in sensitivity improvement.
Innovation Solution
A light receiving device with a pixel array unit where pixels have both a first and second tap for charge photoelectric conversion, with a groove portion on the substrate to enhance light reception, allowing for improved voltage application and charge detection, thereby increasing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a back-illumination structure is adopted to improve light receiving characteristics, then light receiving sensitivity is improved, but further sensitivity improvement is still limited
Solution Approach 1:
The invention introduces a groove structure that extends in the depth dimension of the substrate, creating a three-dimensional light reception path. This groove allows light to reach the photoelectric conversion unit through both the surface path and the groove path, effectively adding a spatial dimension to light reception and overcoming the two-dimensional limitation of conventional back-illumination structures.
Solution Approach 2:
The photoelectric conversion unit is divided into multiple independent photoelectric conversion elements arranged in a matrix. Each element can independently convert light to electrical signals, and the groove structure segments the light path into multiple routes (surface path and groove path), allowing independent optimization of each path's light reception characteristics.
2Measurement precision
If the groove portion is made deeper to improve light reception, then sensitivity increases, but manufacturing complexity and cost increase
Solution Approach 1:
The invention optimizes the groove depth parameter within a specific range (0.5μm to 5μm) to achieve the best balance between light reception efficiency and manufacturing ease. By setting the groove depth to extend to or slightly beyond the photoelectric conversion unit without excessive depth, the structure achieves effective light trapping while remaining compatible with standard semiconductor manufacturing processes.
3Measurement precision
If the groove portion overlaps with voltage application units in plan view, then charge detection sensitivity is improved, but device layout complexity increases
Solution Approach 1:
The invention merges the groove structure with the existing voltage application unit layout, allowing the groove to overlap with the voltage application units in plan view. This integration enables the groove to serve dual purposes: enhancing light reception and improving charge detection sensitivity through the voltage application regions, without requiring separate structures for each function.
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 enhances the sensitivity of distance measuring sensors, enabling more accurate and efficient distance calculations by improving charge detection and light reception capabilities.
Implementation Method 1
pixels each having a first tap detecting charge photoelectrically converted by a photoelectric conversion unit and a second tap detecting charge photoelectrically converted by the photoelectric conversion unit
Data Source
AI summary
The present technology relates to a light receiving device and a distance measuring module capable of improving sensitivity. A light receiving device includes a pixel array unit in which pixels each having a first tap detecting charge photoelectrically converted by a photoelectric conversion unit and a second tap detecting charge photoelectrically converted by the photoelectric conversion unit are two-dimensionally arranged in a matrix. The first tap and the second tap each have a voltage application unit that applies a voltage, the pixel array unit has a groove portion formed by digging from a light incident surface side of a substrate to a predetermined depth, and the groove portion is arranged so as to overlap at least a part of the voltage application unit in plan view. The present technology can be applied to a distance measuring sensor or the like of the indirect ToF scheme, for example.