SPAD Guard Ring Layout to Prevent Edge Breakdown

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Solution Overview

Problem

Single photon avalanche diode (SPAD) photodetectors face limitations due to edge breakdown, where the electric field gradient is higher at the edges of the avalanching junction, leading to diode degradation.

Innovation Solution

Incorporating a guard ring within the doped well between the cathode and anode of the SPAD, where the semiconductor material of the guard ring has opposite doping types to the doped well, effectively counteracting the electric field strength and reducing edge breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a SPAD photodetector is operated with high electric field strength to enhance sensitivity, then radiation detection sensitivity is improved, but edge breakdown occurs causing diode degradation

Engineering Contradiction:

Improvediode reliabilityVSAvoidedge breakdown

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A guard ring structure is introduced as an intermediary element between the anode and cathode terminals. This guard ring, formed with opposite doping type to the doped well, acts as a mediator that redistributes and reduces the electric field strength at the edges of the avalanching junction, thereby preventing edge breakdown while allowing the SPAD to operate at high electric field strengths for enhanced sensitivity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The guard ring is strategically positioned at specific locations where edge breakdown is most likely to occur. By applying the opposite doping type locally at these critical edge regions, the electric field distribution is modified only where needed, reducing field strength at vulnerable edges while maintaining high field strength in the bulk region for effective photon detection

Inventive Principle:

Principle #3Local quality

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 guard ring reduces or prevents premature edge breakdown, enhancing the reliability and longevity of the SPAD by maintaining the avalanche junction functionality while reducing electric field strengths at critical edges.

Implementation Method 1

wherein a semiconductor material of the guard ring and the doped well have opposite doping types

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

an avalanche photodiode (APD)... the internal gain of the avalanche photodiode is much more sensitive to incoming radiation

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Data Source

PatentEP4513576A1Structure with guard ring between terminals of single photon avalanche diode photodetector and related method

Publication Date: 2025.02.26 GLOBALFOUNDRIES DRESDEN MODULE ONE LLC & CO KG

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AI summary

The disclosure provide a structure with a guard ring between the terminals of a single photon avalanche diode photodetector (SPAD), and related methods. A structure (100) according to the disclosure includes a SPAD with an anode (108) within a doped well (104) and a cathode (110) within the doped well. A guard ring (106) includes a semiconductor material (112) within the doped well. The semiconductor material and the doped well have opposite doping polarities.