Avalanche Diode Pixel Isolation Structure for Charge Leakage Reduction
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Solution Overview
Problem
Conventional photo-detection devices face challenges in enhancing detection performance, particularly in reducing charge leakage and improving sensitivity, especially when using avalanche diodes for detecting faint light at a single photon level.
Innovation Solution
The proposed photo-detection device incorporates a semiconductor substrate with a specific configuration of semiconductor regions and electric potential supply, including a PN junction formed by a third semiconductor region of a first conductivity type and a fourth semiconductor region of a second conductivity type, with an isolation portion using a sixth semiconductor region of the second conductivity type to electrically isolate pixels and suppress charge leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating region containing insulating material is provided between pixels to reduce charge leakage, then charge leakage is reduced, but device complexity increases
Solution Approach 1:
The patent extracts the insulating material from the traditional insulating region and replaces it with a semiconductor region having a third conductivity type. This removes the need for separate insulating layers while maintaining the charge isolation function, thereby reducing device complexity while preserving reliability.
Solution Approach 2:
The patent changes the parameter of the isolation region from using insulating material with infinite resistance to using semiconductor material with controlled resistance characteristics. By adjusting the conductivity type and doping concentration of the third semiconductor region, the isolation effect is achieved through parameter optimization rather than material substitution, simplifying the device structure.
2Measurement precision
If a PN junction is formed with high impurity concentration P-type region to improve avalanche amplification, then detection sensitivity is improved, but noise due to tunneling effects increases
Solution Approach 1:
The patent segments the semiconductor structure into distinct regions with different conductivity types arranged in sequence (first conductivity type → second conductivity type → third conductivity type). This segmentation allows the avalanche multiplication to occur in the PN junction while the subsequent third conductivity type region suppresses tunneling noise, achieving both high sensitivity and low noise through spatial separation of functions.
Solution Approach 2:
The third semiconductor region acts as an intermediary between the high-impurity PN junction and the external circuit. It serves as a buffer that suppresses tunneling effects generated in the high-field region while allowing the avalanche signal to pass through, thereby mediating between the conflicting requirements of high gain and low noise.
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 detection performance by reducing noise due to tunneling effects and improving sensitivity, allowing for effective avalanche amplification and efficient charge management, thereby improving the device's ability to detect faint light at a single photon level.
Implementation Method 1
a photo-detection device capable of detecting a faint light at a single photon level by utilizing avalanche (electron avalanche) amplification
Implementation Method 2
a photo-charge caused by a single photon that enters a photoelectric conversion unit causes avalanche amplification
Implementation Method 3
a reverse bias voltage is applied to the PN junction
Data Source
AI summary
Provided is a photo-detection device including: a semiconductor substrate having a first face; a pixel unit in which a pixel having an avalanche diode is arranged in the semiconductor substrate; and a sixth semiconductor region arranged so as to surround a first semiconductor region to a fifth semiconductor region that form the avalanche diode in a planar view from a direction perpendicular to the first face, and an electric potential that is different from the electric potential supplied to the avalanche diode is supplied to the sixth semiconductor region.