Trap Density Measurement in 2D Semiconductors via Photoluminescence

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Solution Overview

Problem

There is currently no practical non-invasive technique to measure the trap density in 2D semiconductor materials, which is crucial for in-line measurements in semiconductor production processes.

Innovation Solution

A method using photoluminescence (PL) measurements at different carrier concentrations to determine the trap density in 2D semiconductor materials, specifically by fitting the ratio of indirect to direct PL intensity to a theoretical model that accounts for carrier concentration and trap density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional support substrates such as SiO2 are used, then device processing can be performed, but scattering increases and material performance deteriorates

Engineering Contradiction:

Improvedevice performanceVSAvoidscattering

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an atomically flat 2D dielectric layer as an intermediary between the 2D semiconductor material and the traditional SiO2 substrate. This intermediary layer acts as a buffer that prevents direct interaction between the semiconductor and the scattering-prone SiO2 surface, thereby reducing scattering while still allowing device processing to proceed on conventional substrates

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If device processing is performed to measure carrier mobility, then performance metrics can be obtained, but non-idealities are introduced that are difficult to deconvolute

Engineering Contradiction:

Improveperformance measurementVSAvoidprocessing-induced non-idealities

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent performs trap density measurements using photoluminescence techniques before device processing is carried out. This preliminary measurement captures the intrinsic material quality without the confounding effects of processing-induced defects, allowing separate characterization of material quality versus device performance

Inventive Principle:

Principle #10Preliminary action

3Loss of information

If photoluminescence-based techniques are used to study interface properties, then insights on thickness, doping, and strain can be obtained, but trap density measurement capability is lacking

Engineering Contradiction:

Improveinterface property informationVSAvoidtrap density measurement

Core Design Contradiction:

Loss of informationVSMeasurement precision

Solution Approach 1:

The patent utilizes changes in photoluminescence intensity as a function of excitation power to extract trap density information. By monitoring how PL intensity scales with excitation power and identifying deviations from linear behavior, the method transforms standard PL measurements into a quantitative trap density probe

Inventive Principle:

Principle #35Parameter changes

4Productivity

If no non-invasive measurement technique is available, then in-line measurements in production cannot be performed, but process control is limited

Engineering Contradiction:

Improvein-line measurement capabilityVSAvoidprocess control

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The patent replaces invasive electrical measurement techniques with non-invasive optical (photoluminescence) measurement methods. This substitution allows measurements to be performed without physical contact or device fabrication, enabling integration into production lines for real-time quality monitoring and process control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables non-invasive, in-line measurements of trap density in semiconductor production, avoiding material defects and improving process control by providing accurate and efficient characterization of 2D semiconductor materials.

Implementation Method 1

The layer is illuminated by a light beam configured to generate a plurality of excitons. Photons emitted from the spot are detected by a detector configured to obtain the photoluminescence spectrum

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentEP3913356B1A method for measuring the trap density in a 2-dimensional semiconductor material

Publication Date: 2025.01.22 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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AI summary

According to the method of the invention, a spot on a layer (3) of a 2D semiconductor material deposited on a support substrate (2;20,21) is irradiated so as to generate excitons, so that photons are emitted from the layer. The photoluminescence spectrum is recorded and this is repeated for different values of the charge carrier concentration in the layer. The modulation of the charge carrier concentration may be realized by modulating the output power of the light source (1) used to irradiate the sample, preferably a laser. The relation is thereby recorded between the ratio of the photoluminescence intensity of a first peak in the spectrum related to radiative recombination from indirect bandgaps to the intensity of a second peak in the spectrum related to radiative recombination from direct bandgaps, and the carrier concentration. This recorded relation is fitted to a theoretical model of the ratio that takes into account multiple recombination mechanisms, radiative and non-radiative. From this fitting process, the trap density within the bandgap is derived. The invention is equally related to an apparatus configured to perform the method of the invention.