Defect Inspection Device Correcting Inter-Beam Phase Differences
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Solution Overview
Problem
Existing defect inspection devices using differential interference contrast (DIC) face challenges in accurately detecting defects due to inter-beam phase differences caused by factors unrelated to defects, such as specimen inclination, optical system aberrations, and irregular light source power variations, which affect the detection of low aspect ratio defects.
Innovation Solution
A defect inspection device that includes a light source, polarized light separation elements, and a processing processor to correct measured signals using information around the measurement point, reducing the influence of inter-beam phase differences and enhancing the detection of low aspect ratio defects by integrating DIC inspection with scattered light inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If DIC inspection is used to detect low aspect ratio defects, then detection capability for low stage defects is improved, but measurement accuracy deteriorates due to inter-beam phase differences caused by specimen inclination, optical system aberrations, and light source power variations
Solution Approach 1:
The patent performs preliminary measurement of the inter-beam phase difference at each measurement point before conducting the actual defect inspection. This preliminary phase difference information is stored and subsequently used to correct the measurement results, thereby eliminating the adverse effects of specimen inclination, optical aberrations, and light source variations on measurement accuracy
Solution Approach 2:
The patent implements a feedback mechanism where the measured inter-beam phase difference at each point is used to correct subsequent measurements at that same point. The correction process continuously refines the measurement accuracy by compensating for phase differences caused by various external factors, enabling accurate detection of low aspect ratio defects
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 device effectively reduces the impact of unwanted inter-beam phase differences, enabling accurate detection of low aspect ratio defects and improving the overall accuracy and efficiency of defect inspection on semiconductor wafers.
Implementation Method 1
the beams are separated into two orthogonal polarized light components (for example, a P-polarized light component and an S-polarized light component) by a birefringent element
Implementation Method 2
interference measurement such as differential interference contrast (DIC) inspection using a principle of a differential interference microscope
Data Source
AI summary
Provided is a technique capable of reducing an influence of an inter-beam phase difference unrelated to a defect and accurately detecting even a defect having a low aspect ratio by a defect inspection device using differential interference contrast. To achieve the above purpose, provided is the defect inspection device using differential interference contrast that inspects a specimen using light. The defect inspection device includes: a light source configured to emit a light beam; a polarized light separation element configured to split the light beam into a first beam and a second beam which are polarized and orthogonal to each other; a sensor configured to detect a signal from the first beam and the second beam reflected from the specimen; and a processing processor configured to process the signal detected by the sensor. The processing processor uses a signal string obtained based on information around a measured point to be measured on the specimen to correct a measured signal at the measured point.