Inspection Apparatus Calibration Using Diffraction Grating
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Solution Overview
Problem
Existing inspection apparatus calibration methods using polystyrene latex standard particles face challenges such as ambiguity, instability, and size dispersion, leading to inaccurate calibration due to micronization, environmental factors, and changes over time.
Innovation Solution
The calibration of the inspection apparatus is improved by using a diffraction grating with a predetermined height and interval, which is irradiated with illumination light, and the scattered light is detected to determine defects or foreign substances, allowing for accurate calibration regardless of the use environment or time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polystyrene latex standard particles are used for calibration, then the inspection apparatus can be calibrated, but the calibration accuracy deteriorates due to size dispersion, environmental changes, and time-dependent instability
Solution Approach 1:
The patent replaces the physical standard particle (polystyrene latex) with an optical copy or simulation - the diffraction grating pattern. Instead of using actual particles that suffer from size dispersion and instability, the invention creates a standardized diffraction pattern that replicates the scattering characteristics of target particles without the physical deficiencies. This optical copying approach eliminates the reliability issues while maintaining calibration functionality.
Solution Approach 2:
The invention changes the calibration parameter from physical particle dimensions (which vary and degrade) to optical diffraction characteristics (which are stable and controllable). By using a diffraction grating with precisely controlled pitch and geometry, the calibration shifts from depending on fragile physical dimensions to depending on stable optical parameters that can be maintained over time and across environmental conditions.
2Measurement precision
If the standard particle size is reduced to detect micronized defects, then the detection capability improves, but the manufacturing difficulty and calibration accuracy worsen
Solution Approach 1:
Instead of manufacturing increasingly difficult ultra-fine standard particles to match micronized defect sizes, the invention creates an optical copy - a diffraction grating pattern - that simulates the scattering behavior of these tiny particles. This approach maintains the ability to calibrate for micron-scale defects while avoiding the manufacturing challenges of creating and maintaining physical standard particles at those scales.
Solution Approach 2:
The patent replaces the mechanical approach of using physical standard particles with precisely controlled dimensions with an optical approach using diffraction gratings. This substitution eliminates the need for mechanical manufacturing of ultra-fine particles, replacing it with optical field interactions that are governed by wave physics rather than mechanical fabrication constraints.
3Adaptability or versatility
If multiple standard particles are used for calibration, then the coverage of defect sizes improves, but the dispersion among particle sizes increases calibration uncertainty
Solution Approach 1:
The diffraction grating serves multiple calibration functions simultaneously - it can calibrate for various particle sizes and types through a single standardized component. By adjusting the illumination conditions and detection angles, the same grating structure provides calibration data across a range of defect sizes, eliminating the need for multiple different standard particles while maintaining precision.
Solution Approach 2:
Instead of changing the physical particle parameters (size, material) to cover different defect types, the invention changes the optical parameters (illumination wavelength, incident angle, detection angle) of the diffraction grating system. This allows a single grating structure to provide calibration information for multiple defect sizes by varying the optical conditions rather than the physical standard itself.
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 method enables precise calibration of the inspection apparatus, enhancing its accuracy and stability by using diffraction gratings to standardize the calibration process, overcoming the limitations of traditional methods.
Implementation Method 1
a diffraction grating having a predetermined height and interval, in which light is applied to the diffraction grating of the reference substrate supported by the support stand with light from the illumination optical section so as to be scattered by the diffraction grating
Data Source
AI summary
An inspection apparatus which can be accurately calibrated regardless of a use environment or an amount of use time is implemented. A reference substrate 100 provided with a diffraction grating 107 is mounted on a transport system 110, an illumination region 106 is formed on the diffraction grating 107 by light 105 from an illumination optical system 104, reflected light is collected by a detection optical system 108, and an output value from a sensor 111 is measured. It is determined whether or not a difference between a simulation value preserved in a processing section 112 and the output value from the sensor 111 is within a predetermined allowable range, and the optical system is adjusted so that the difference enters the allowable range. Since standard data for performing calibration on the inspection apparatus is obtained by using the diffraction grating, it is possible to implement the inspection apparatus which can be accurately calibrated regardless of a use environment or an amount of use time.