Range Sensor Third Semiconductor Region Noise Reduction
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Solution Overview
Problem
In range sensors using the charge distribution method, unwanted noise components are generated due to charge being directly taken into depletion layers from semiconductor regions, which affects the accuracy of distance detection.
Innovation Solution
A range sensor design that includes a semiconductor substrate with a photogate electrode and gate electrodes, along with semiconductor regions, where a third semiconductor region with opposite conductivity is placed away from the first and second semiconductor regions on the light incident surface, preventing depletion layers from spreading and thus reducing unwanted noise by allowing charge to be captured only by the depletion layer from the photogate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bias voltage is applied to semiconductor regions for reset, then the regions are properly reset prior to distance measurement, but depletion layers spread from semiconductor regions and directly take in generated charge, creating unwanted noise components
Solution Approach 1:
The semiconductor substrate is divided into multiple regions with different conductivity types (first conductivity type and second conductivity type). The depletion layers are segmented to extend from regions of one conductivity type while being blocked by regions of opposite conductivity type, preventing direct charge intake and noise generation.
Solution Approach 2:
Different regions of the semiconductor substrate are assigned different conductivity types to create localized properties. Regions with first conductivity type allow depletion layer extension for proper reset, while regions with second conductivity type block depletion layer spread to prevent noise, achieving both reset function and noise suppression through local property differentiation.
2Reliability
If depletion layers spread from semiconductor regions, then reset function is achieved, but charge is directly taken into depletion layers without passing through photogate electrode region, reducing measurement accuracy
Solution Approach 1:
The semiconductor substrate is segmented into regions with alternating conductivity types, creating a pattern where depletion layers from first conductivity type regions are blocked by second conductivity type regions. This ensures charge must pass through the photogate electrode region, maintaining measurement precision while allowing reset function.
Solution Approach 2:
Regions with second conductivity type act as intermediary barriers that prevent direct charge intake by depletion layers from first conductivity type regions. These intermediary regions force charge to travel through the photogate electrode region, ensuring accurate distance measurement while allowing proper reset.
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 design enhances the accuracy of distance detection by suppressing unwanted noise components, improving the signal-to-noise ratio and enabling high-precision distance measurement.
Implementation Method 1
detect reflected light from the object with a photodetecting element
Implementation Method 2
depletion layers spread not only from the region immediately below the photogate electrode, but also from each of the semiconductor regions
Data Source
AI summary
A range image sensor 1 is provided with a semiconductor substrate 1A having a light incident surface 1BK and a surface 1FT opposite to the light incident surface 1BK, a photogate electrode PG, first and second gate electrodes TX1, TX2, first and second semiconductor regions FD1, FD2, and a third semiconductor region SR1. The photogate electrode PG is provided on the surface 1FT. The first and second gate electrodes TX1, TX2 are provided next to the photogate electrode PG. The first and second semiconductor regions FD1, FD2 accumulate respective charges flowing into regions immediately below the respective gate electrodes TX1, TX2. The third semiconductor region SR1 is located away from the first and second semiconductor regions FD1, FD2 and on the light incident surface 1BK side and has the conductivity type opposite to that of the first and second semiconductor regions FD1, FD2.