PiN Diode Surface Charge Suppression via Gate Electrode
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Solution Overview
Problem
The noise performance of silicon PiN diode photodetectors is limited by surface leakage current, which is exacerbated by environmental factors like ionizing radiation and humidity, and current passivation methods are not completely effective in suppressing dark current due to material defects at the silicon-SiO2 interface.
Innovation Solution
A semiconductor structure with laterally spaced PiN diodes and a gate electrode structure on the surface, where the gate is biased to pin the surface and suppress reverse bias leakage current, using a buried channel implant and channel stops to control surface potential and confine charge away from the surface, thereby reducing surface-generated dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the surface is biased in depletion to maximize surface generated dark current, then the device can detect photons, but the surface dark current limits the ultimate performance and increases noise
Solution Approach 1:
A gate electrode structure is introduced as an intermediary element between the silicon bulk and the environment. This gate structure, when biased appropriately, creates an electric field that repels minority carriers from the surface region, thereby reducing surface-generated dark current without affecting the bulk detection mechanism
Solution Approach 2:
The surface potential is dynamically controlled by applying different bias voltages to the gate electrode. By changing the gate bias parameter, the surface can be transitioned between accumulation and depletion states, allowing optimization of the trade-off between surface dark current suppression and bulk carrier collection efficiency
2Object-generated harmful factors
If channel stops are used to remove potential minima away from the surface, then surface leakage is reduced, but the device complexity increases
Solution Approach 1:
The gate electrode structure serves multiple functions simultaneously: it acts as a channel stop to remove potential minima, provides a means to dynamically control surface potential, and can be used to optimize the trade-off between surface dark current and bulk carrier collection. This multi-functionality reduces the need for separate dedicated structures
3Object-generated harmful factors
If hydrogen annealing is used to passivate interface states, then some leakage current is reduced, but the passivation is never completely effective and some defect sites remain electrically active
Solution Approach 1:
Instead of relying solely on post-manufacturing annealing processes that cannot completely passivate all interface states, the invention implements a preliminary structural design with the gate electrode that proactively prevents minority carrier accumulation at the surface. This structural approach complements the chemical passivation by creating an electric field barrier before carriers can reach problematic interface states
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 fully suppresses surface-generated dark current, allowing the PiN diodes to be limited by bulk leakage current, improving stability and enabling high Quantum Efficiency across the visible spectrum by integrating a surface-pinned, fully-depleted PiN diode array with CMOS readout.
Implementation Method 1
the structure suppresses surface generated dark current. More particularly, the structure fully suppresses reverse bias leakage current through the PiN diodes by Fermi band pinning the surface
Implementation Method 2
A photon entering the intrinsic region frees a carrier. The reverse bias field sweeps the carrier out of the region and creates a corresponding output current
Implementation Method 3
The surface of the crystal is oxidized to produce a SiO2 passivation layer
Implementation Method 4
A normal Silicon process attempts to passivate these dangling orbitals by annealing in Hydrogen, which bonds to the defect site and reduces its electrical activity
Data Source
AI summary
A semiconductor structure having: a silicon structure; and a plurality of laterally spaced PiN diodes formed in the silicon structure; and a surface of the silicon structure configured to reduce reverse bias leakage current through the PiN diodes. In one embodiment, a gate electrode structures is disposed on a surface of the silicon structure, the gate electrode structure having portions disposed between adjacent pairs of the diodes, the gate structure being biased to prevent leakage current through the diodes.