Reference Substrate With Nanoscale Features For Inspection Calibration
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Solution Overview
Problem
Modern particle/defect inspection systems face challenges in calibrating for sizes below 18 nm due to damage from high energy laser light and degradation of silica/PSL particles, making accurate detection and measurement difficult or impossible.
Innovation Solution
A reference substrate with environmentally inert surface features of controlled size dimensions below 18 nm is created, using materials and techniques that withstand high laser energy and provide contrast for accurate detection, such as etched void regions filled with different materials or particle-emulating structures formed using e-beam lithography or focused ion beam processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silica or polystyrene latex particles are used for calibration, then calibration is possible with conventional methods, but the particles are damaged by high energy laser light and degrade over time
Solution Approach 1:
The patent creates artificial surface features that copy the optical scattering characteristics of particles but are physically integrated into the substrate. These features replicate the light scattering behavior needed for calibration while avoiding the material degradation issues of conventional particles
Solution Approach 2:
The patent changes the material parameter from conventional particles (silica/PSL) to substrate-integrated artificial features with controlled optical properties. This parameter change enables the features to withstand high laser energy while maintaining calibration functionality
2Measurement precision
If conventional particle deposition methods are used, then calibration can be performed, but accurate detection of sizes below 18 nm is not achieved
Solution Approach 1:
The patent replaces mechanical particle deposition methods with lithographic patterning processes. This substitution enables precise control of feature sizes below 18 nm through lithographic resolution rather than particle synthesis and deposition limitations
Solution Approach 2:
The patent performs preliminary lithographic patterning to create the artificial surface features with precisely controlled dimensions before the calibration process. This preliminary action establishes the known reference sizes that enable accurate measurement of smaller particles
3Difficulty of detecting and measuring
If high energy laser light is used for inspection, then detection capability for small particles is improved, but the calibration particles are damaged or destroyed
Solution Approach 1:
The patent introduces artificial surface features as an intermediary calibration reference that can withstand the high energy laser light. These features serve as a mediator between the inspection system and the calibration process, enabling calibration without the harmful effects of laser damage to conventional particles
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 reliable calibration of inspection systems to detect particle/defect sizes below 18 nm without damage, providing a standardized method for identifying the size of detected particles/defects through recorded waveform data.
Implementation Method 1
the wafer is scanned during calibration of a particle/defect inspection system, where light scattered from particles 52 differs from light scattered by surface 51
Implementation Method 2
such modern inspection systems utilize high energy laser light that can damage or destroy the silica/PSL particles disposed on a reference wafer
Implementation Method 3
Pin-hole defects can be created by subjecting a substrate to a process involving deposition of reactive particles and/or focused ion beam processing
Data Source
AI summary
A reference substrate for calibrating high-energy inspection systems includes permanently affixed particle-emulating and/or integral void-type environmentally inert surface features that emulate particles/defects having sizes below about 18 nm. Particle-emulating surface features are fabricated directly onto the substrate's surface (or an intervening barrier film layer) using e-beam lithography or over-etch processing. Void-type defect features having sizes below 18 nm are etched into the substrate's surface using, for example, focused ion beam, reactive particle or pin-hole etching processes. Once formed, the actual size of each surface feature is measured (e.g., using SEM) and then recorded. During a subsequent inspection tool calibration session, the reference substrate is scanned and waveform data corresponding to light reflected/scattered from each surface feature is correlated with the scanned feature's actual size data. During subsequent inspection procedures, the sizes of detected particles/defects are determined by matching detected particle/defect waveform data with corresponding surface feature waveform data.