Defect Inspection Device Synchronizing Laser Pulses
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Solution Overview
Problem
Existing defect inspection devices face challenges in accurately detecting microscopic defects due to high dark noise from sensor devices and pulsed oscillation of laser light sources, which complicates the detection process.
Innovation Solution
A defect inspection device is designed with an irradiation system that provides pulsed laser operation, a detection system to capture scattering light, and a processing portion that generates a delay signal to synchronize sampling with the laser beam, reducing the impact of dark noise and pulsed oscillation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulsed laser beam is used to detect defects, then the detection capability for microscopic defects is improved, but dark noise from the sensor device and pulsed oscillation components interfere with the detected signal
Solution Approach 1:
The patent applies periodic action by using a pulsed laser beam that operates at a specific frequency to irradiate the sample surface. The detection system is synchronized to this periodic pulse operation, allowing the scattered light signal to be distinguished from dark noise through timing-based discrimination. The signal processing unit correlates the detected signals with the known laser pulse timing, effectively filtering out random dark noise while preserving the periodic scattered light signal from defects.
Solution Approach 2:
The patent implements feedback by using the detected scattered light signal to adjust and optimize the detection parameters. The signal processing unit analyzes the detected signals and uses this information to refine the timing and threshold settings for defect detection. This feedback mechanism allows the system to adapt to varying conditions and maintain high detection accuracy while minimizing the impact of dark noise and pulsed oscillation interference.
2Power
If the laser light source operates in pulsed mode, then energy consumption is reduced and peak power is increased, but pulse components are superimposed on the detected signal
Solution Approach 1:
The patent utilizes periodic action by synchronizing the detection system with the pulsed laser operation. The detection and signal processing are timed to coincide with the laser pulse intervals, allowing the system to capture scattered light signals during the pulse periods while ignoring the intervals between pulses. This timing synchronization enables the system to maintain high peak power for effective defect detection while preventing pulse component interference in the final detected signal.
Solution Approach 2:
The patent introduces an intermediary element in the form of a signal processing unit that acts as a mediator between the pulsed laser source and the detection system. This unit processes the raw detected signals by filtering out pulse component artifacts and extracting only the relevant scattered light information. The intermediary processing step preserves the benefits of pulsed operation while eliminating the harmful effects of pulse component superposition.
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 configuration enables accurate detection of microscopic defects by minimizing the influence of dark noise and pulsed operation, enhancing the overall detection accuracy.
Implementation Method 1
a method of detecting defects having dimensions of tens of nm to several μm or more is available, for example. The method consists of irradiating a wafer surface with a focused laser beam and gathering and detecting light scattering from defects.
Implementation Method 2
detection means for detecting scattering light generated at the surface of a sample by the irradiation provided by the irradiation means
Data Source
AI summary
When the intensity of scattering light from a defect on a sample becomes very low according to the diameter of the defect, the dark noise from a sensor device itself accounts which a large proportion of the detected signal outputted from the sensor and thus it is difficult to detect minute defects. Furthermore, since a laser light source is pulsed into oscillation, pulse components from the laser light source are superimposed on the detected signal outputted from the sensor, and therefore it is difficult to detect defects with high accuracy. The present invention is a defect inspection device having irradiation means which producing pulsed operation and irradiating a surface of a sample with a laser beam, detection means which detecting scattering light generated at the surface of the sample in response to the irradiation provided by the irradiation means, and a processing portion which generating a delay signal based on the laser beam emitted by the irradiation means and processing the scattering light detected by the detection means using the delay signal.