Integrated Photodiode ESD Protection via Parallel Si-Ge Coupling

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Solution Overview

Problem

High-speed Ge photodiodes in silicon photonics communication devices are vulnerable to electrostatic discharge damage due to their low ESD threshold, leading to low assembly yield and reliability issues, as conventional ESD protection techniques are not suitable for silicon photonics devices and require separate chip formation and mounting.

Innovation Solution

An integrated photodiode circuit is formed by coupling a Si photodiode with a Ge photodiode in parallel on the same SOI substrate, leveraging the higher ESD threshold of Si photodiodes while maintaining high data rates, with the Si photodiode adding minimal capacitance to ensure enhanced ESD protection without impacting Ge photodiode performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If Ge photodiode is used for high-speed optical signal detection, then detection speed is improved, but ESD threshold deteriorates (becomes lower)

Engineering Contradiction:

Improvedetection speedVSAvoidESD threshold

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent combines a Ge photodiode and a Si photodiode into a single integrated device on an SOI substrate. The Ge photodiode provides high-speed detection capability while the Si photodiode provides high ESD threshold protection. The two photodiodes are electrically connected in parallel with their p-type regions connected together and their n-type regions connected together, allowing the device to simultaneously achieve both high detection speed and high ESD resistance.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If external Zener diode is used for ESD protection, then ESD threshold is improved, but device complexity and assembly process deteriorate

Engineering Contradiction:

ImproveESD thresholdVSAvoidassembly process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of using a separate external Zener diode chip that requires solder bump or wire bonding connections, the patent integrates the ESD protection function directly into the photodiode structure by combining Ge and Si photodiodes in parallel on the same SOI substrate. This eliminates the need for separate ESD protection components and simplifies the assembly process while maintaining high ESD threshold protection.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated photodiode structure serves multiple functions simultaneously: the Ge photodiode component provides high-speed optical signal detection while the Si photodiode component provides ESD protection. This multi-functional integration eliminates the need for separate dedicated ESD protection components and reduces overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If Si photodiode is added for ESD protection, then ESD threshold is improved, but capacitance increases

Engineering Contradiction:

ImproveESD thresholdVSAvoidcapacitance

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent optimizes the structure of the Si photodiode component to minimize its capacitance contribution. By carefully designing the Si photodiode with appropriate doping levels and geometric dimensions, the device achieves high ESD threshold protection while keeping the added capacitance to a minimum, thus not degrading the high-speed performance of the overall photodetector.

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 integrated photodiode achieves an ESD threshold of ±100V, significantly improving protection against electrostatic discharge while maintaining high-speed data communication capabilities, with the added Si photodiode's low capacitance ensuring no impact on Ge photodiode performance.

Implementation Method 1

Ge photodiode is commonly used as a photon detector for monitoring high-speed optical signal transmission

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

high-speed Ge photodiode is vulnerable to electrostatic discharge damage (ESD). Because of its low ESD threshold

Methodology Applied

Scientific EffectElectrostatic Discharge: Electrostatic Discharge

Data Source

PatentUS10262983B2Integrated photo detector, method of making the same

Publication Date: 2019.04.16 MARVELL ASIA PTE LTD

AI summary

An integrated photo detector with enhanced electrostatic discharge damage (ESD) protection. The integrated photo detector includes a first photodiode formed in the SOI substrate and associated with a first p-electrode and a first n-electrode. Additionally, the integrated photo detector includes a second photodiode formed in the SOI substrate associated with a second p-electrode and a second n-electrode forming a capacitance no larger than a few femto Faradays. Moreover, the integrated photo detector includes a first electrode and a second electrode disposed respectively on the SOI substrate. The first/second electrode is respectively connected to the first p/n-electrode via a first/second metallic layer patterned with a reduced width from the first/second electrode to the first p/n-electrode and connected to the second p/n-electrode via a first/second metallic wire to make a parallel coupling between the first photodiode and the second photodiode with an ESD threshold of about 100V.