Optical Dividing Element for Semiconductor Defect Inspection
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Solution Overview
Problem
Conventional defect inspection apparatuses face challenges in achieving high detection sensitivity and speed due to signal intensity loss, false detection caused by noise, and decreased detection accuracy as defects move away from the light spot center, leading to inefficient semiconductor wafer and mask blank inspection.
Innovation Solution
An inspection apparatus utilizing a light source, lens, optical dividing element, and photodetectors to generate and analyze multiple light beams, determining real defects by synchronizing signals from multiple photodetectors and adjusting pulse widths, and scanning overlapping light spots to enhance detection precision and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If half of the detection light is blocked in the conventional defect inspection apparatus, then the detection sensitivity against real defect can be improved by lowering the slice level, but the false detection rate increases due to noise susceptibility
Solution Approach 1:
The patent divides the detection light into multiple beams (first light beam and second light beam) that scan different regions of the sample. By segmenting the light path and using multiple photodetectors to receive different light beams, the system can compare signals from multiple scanning paths to distinguish real defects from noise, thereby reducing false detection while maintaining detection sensitivity.
2Reliability
If the light spot scans the region where it overlaps with the adjacent scan line light spot, then false detection is eliminated through comparison, but inspection speed decreases
Solution Approach 1:
The patent performs preliminary scanning with the first light beam to identify defect candidates, then uses the second light beam to verify these candidates. By preparing and comparing data from multiple light beams in advance, the system can quickly confirm or eliminate false defects without requiring slow sequential re-scanning, thus maintaining inspection speed while eliminating false detections.
3Illumination intensity
If the beam profile shows normal distribution with peak at center, then the light spot provides maximum intensity at center, but detection sensitivity degrades for defects away from center
Solution Approach 1:
The patent introduces a second scanning dimension by using multiple light beams that scan different regions. Instead of relying solely on the intensity distribution of a single centered light spot, the system scans multiple overlapping regions and compares signals, enabling detection of off-center defects through their appearance in multiple scan patterns, thus compensating for the normal distribution intensity limitation.
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
The solution enables high-sensitivity, high-speed defect detection with reduced signal loss and improved accuracy, effectively distinguishing real defects from noise-induced false detections and accurately identifying defect types.
Implementation Method 1
a lens focusing the light beam emitted from the light source to form a light spot on a sample surface
Implementation Method 2
an optical dividing element dividing the light beam reflected from the sample surface or transmitted through the sample into a plurality of different light beams
Implementation Method 3
a first photodetector receiving a first light beam divided by the optical dividing element to output a first output signal based on a beam amount of the received beam
Data Source
AI summary
A defect inspection apparatus according to an aspect of the present invention includes a laser source generating light beam, an objective lens focusing the light beam emitted from the laser source to form a light spot on a surface of a sample W, a prism dividing the light beam reflected from the sample into two light beams, two light receiving elements receiving the light beams divided by the prism to output output signals based on the beam amount of the received beams, and a real defect determination part determining a candidate detect as a real defect when output signals from the two light receiving elements are detected substantially at the same time.