Defect Inspection Device Using Linear Illumination and Signal Accumulation
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Solution Overview
Problem
Current defect inspection methods for semiconductor substrates struggle to detect infinitesimal defects of 20 nm or less due to feeble scattered light signals being lost in noise, and increasing illumination power can damage the sample or reduce inspection speed.
Innovation Solution
A defect inspection method involving linear illumination and detection of reflected and scattered light using a two-dimensional array sensor to diffuse and image light perpendicular to the illumination direction, allowing for precise defect detection without sample damage and high-speed inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If illumination power is increased to enhance detection sensitivity for infinitesimal defects, then detection sensitivity is improved, but the sample temperature rises causing thermal damage
Solution Approach 1:
The illumination is divided into multiple pulses instead of continuous illumination, allowing the sample to cool down between pulses and preventing thermal damage while maintaining detection sensitivity through accumulated signal from multiple measurements
Solution Approach 2:
Periodic pulsed illumination is used instead of continuous illumination, with duty cycle control to limit average power and prevent overheating while maintaining peak power for sensitive detection
2Measurement precision
If scanning rate is reduced to enhance detection sensitivity, then detection sensitivity is improved, but inspection speed decreases
Solution Approach 1:
Multiple pulses are accumulated at each measurement position without moving the sample, maintaining continuous inspection progress while enhancing signal through temporal integration of multiple pulses
Solution Approach 2:
Multiple illumination pulses are prepared and accumulated in advance at each position before making a detection decision, ensuring high sensitivity without requiring slow scanning
3Productivity
If conventional detection methods are used for infinitesimal defects, then inspection speed is maintained, but detection sensitivity is insufficient due to feeble scattered light signals being lost in noise
Solution Approach 1:
Multiple scattered light signals from successive pulses are accumulated and combined at each measurement position, enhancing the signal-to-noise ratio while maintaining high inspection speed through parallel processing
Solution Approach 2:
A signal accumulation and processing system acts as an intermediary between the feeble scattered light signals and the detection threshold, amplifying weak signals through multiple pulse integration before final defect determination
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 the detection of infinitesimal defects with precise measurement of dimensions and stable results, reducing thermal damage to the sample while maintaining high inspection speed and sensitivity.
Implementation Method 1
detection sensitivity is enhanced by illuminating the same defect plural times in one inspection by an illumination optical system that linearly illuminates and a detection optical system that divides and detects an illuminated region on a line sensor and adding their scattered light
Implementation Method 2
detecting light which is reflected and scattered from the linear region on the sample
Data Source
AI summary
To detect an infinitesimal defect, highly precisely measure the dimensions of the detect, a detect inspection device is configured to comprise: a irradiation unit which irradiate light in a linear region on a surface of a sample; a detection unit which detect light from the linear region; and a signal processing unit which processes a signal obtained by detecting light and detecting a defect. The detection unit includes: an optical assembly which diffuses the light from the sample in one direction and forms an image in a direction orthogonal to the one direction; and a detection assembly having an array sensor in which detection pixels are positioned two-dimensionally, which detects the light diffused in the one direction and imaged in the direction orthogonal to the one direction, adds output signals of each of the detection pixels aligned in the direction in which the light is diffused, and outputs same.