Rear-incident Range Image Sensor Aperture Ratio
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Solution Overview
Problem
Conventional surface incident type range image sensors suffer from high carrier generation density near the semiconductor substrate, leading to noise in output signals and a small aperture ratio, making accurate time of flight detection challenging.
Innovation Solution
A range image sensor with semiconductor regions arranged on the surface side of a semiconductor substrate, where first and second semiconductor regions form p-n junctions, and specific reverse bias voltages are applied to expand depleted layers, ensuring carriers are captured and noise is suppressed, thereby increasing the aperture ratio for accurate time of flight detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If semiconductor regions are arranged on the surface side of the semiconductor substrate in a surface incident type configuration, then the structure is simpler and easier to manufacture, but carrier generation density near the substrate increases causing noise and reducing aperture ratio
Solution Approach 1:
The patent inverts the conventional surface incident type configuration by making light incident from the rear surface of the semiconductor substrate. This inversion allows the semiconductor regions to be arranged on the surface side while light enters from the opposite side, thereby preventing direct carrier generation near the substrate and eliminating the noise problem while maintaining the structural simplicity of having regions on the surface.
Solution Approach 2:
The patent changes the dimension of light incidence from surface-level (parallel to substrate) to rear-surface incidence (perpendicular to substrate). By changing the direction and entry point of light into a different spatial dimension, the patent avoids the problem of high carrier generation density near the substrate while maintaining the benefits of surface-mounted semiconductor regions.
2Reliability
If depleted layers are expanded to capture carriers, then carrier capture efficiency improves, but noise from adjacent semiconductor regions increases
Solution Approach 1:
By inverting the light incidence direction to rear-surface type, the patent reverses the carrier generation location from near the substrate to deeper in the substrate. This allows depleted layers to be expanded for efficient carrier capture without the harmful side effect of noise from adjacent semiconductor regions, as carriers are generated away from the substrate surface where adjacent regions are located.
Solution Approach 2:
The patent uses the semiconductor substrate itself as an intermediary medium. By having light incident from the rear surface, the substrate acts as a mediator that allows light to reach semiconductor regions without directly generating carriers near the substrate surface, thereby separating the carrier generation zone from the region where noise would be generated by adjacent semiconductor regions.
3Ease of manufacture
If semiconductor regions are arranged on the surface side, then the aperture ratio is reduced due to the presence of depleted layers, but this arrangement is easier to implement
Solution Approach 1:
The patent inverts the light incidence configuration to rear-surface type, which allows the aperture ratio to be increased. By having light enter from the rear surface, the light path does not pass through the semiconductor regions and their associated depleted layers on the surface side, thereby increasing the effective aperture area while maintaining the ease of implementing surface-mounted regions.
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 enables accurate detection of time of flight from light irradiation to reflected light reception by reducing noise and enhancing the aperture ratio, allowing for precise range information acquisition.
Implementation Method 1
a range image sensor which images an image including range information to a target is known. In this range image sensor, a method for acquiring range information by detecting a time of flight (TOF) since light is irradiated onto a target until reflected light is received
Implementation Method 2
by applying different reverse bias voltages respectively between the first and second semiconductor regions adjacent to each other and the semiconductor substrate, the sizes of the depleted layers expanding from the p-n junctions of the first and second semiconductor regions are controlled
Implementation Method 3
the carrier generation density according to incidence of reflected light becomes higher toward the surface of the semiconductor substrate
Data Source
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AI summary
In a range image sensor 8, when a first reverse bias voltage applied between a semiconductor substrate 11 and first semiconductor regions 13 is an H bias, first depleted layers A1 and A1 expanding from the p-n junctions of the first semiconductor regions 13 adjacent to each other expand and link to each other so as to cover a second depleted layer B 1 expanding from the p-n junction of a second semiconductor region 14. Accordingly, carriers C generated near the rear surface 11 a of the semiconductor substrate 11 are reliably captured by the first depleted layers A1. Further, when a second reverse bias voltage applied between the semiconductor substrate 11 and the second semiconductor regions 14 is an H bias, the second depleted layers adjacent to each other expand and link to each other so as to cover the first depleted layer. Accordingly, carriers generated near the rear surface of the semiconductor substrate are reliably captured by the second depleted layers.