Defect Inspection Device Using Pattern Chip for Focus Stabilization
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Solution Overview
Problem
Existing defect inspection methods in semiconductor and flat panel display manufacturing face challenges in maintaining high-resolution, stable defect detection due to variations in ambient temperature and atmospheric pressure, which affect the focus position of detection optical systems, leading to decreased sensitivity and accuracy.
Innovation Solution
A defect inspection method using a movable table with a pattern chip featuring repeating patterns, where linearly-formed illumination light is used to generate scattered light detected by multiple detection optical systems, allowing for precise alignment of image sensors and stabilization of focus positions across multiple detection systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution detection optical system is designed with greatly suppressed wavefront aberration, then defect detection sensitivity is improved, but the focus position becomes highly sensitive to ambient temperature and atmospheric pressure variations
Solution Approach 1:
The patent implements an off-axis focus detection system that continuously monitors the focus position and provides feedback signals. When temperature or pressure variations cause focus drift, the system detects this through the off-axis detection arrangement and generates correction signals to maintain optimal focus, thus resolving the contradiction between high sensitivity and environmental stability.
Solution Approach 2:
The patent replaces mechanical focus adjustment mechanisms with an optical focus detection and correction system. Instead of physically moving lenses or mirrors in response to environmental changes, the system uses optical detection of focus position and electronic signal processing to maintain focus stability, reducing mechanical sensitivity to temperature and pressure variations.
2Reliability
If temperature control design is implemented to stabilize focus position, then focus stability is improved, but the system cannot fully compensate for heat releasing from motors and electric circuits and atmospheric pressure variations
Solution Approach 1:
The patent introduces an off-axis focus detection system as an intermediary between the optical system and environmental disturbances. This detection system monitors focus position changes caused by temperature and pressure variations and generates correction signals, acting as a mediator that compensates for environmental effects without requiring complex active temperature control.
3Adaptability or versatility
If multiple detection optical systems are used to improve inspection coverage, then detection capability is improved, but aligning object points of each system becomes difficult due to independent focus position variations
Solution Approach 1:
The patent implements a universal focus detection and correction mechanism that serves all multiple detection optical systems simultaneously. The off-axis focus detection system monitors and corrects focus positions across all detection channels, ensuring that object points remain aligned despite independent variations in each system, thus enabling multi-system operation without sacrificing alignment precision.
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 approach enables stable, high-resolution defect detection by ensuring the focus of illumination light and detection optical systems coincide, thereby improving sensitivity and maintaining consistent performance over time.
Implementation Method 1
irradiating a pattern chip which is mounted on a table and in which a plurality of repeating patterns are periodically formed with linearly-formed illumination light; detecting images of scattered light incident on respective objective lenses of a plurality of detection optical systems which include the objective lenses and image sensors and are disposed at a plurality of positions above the table among the scattered light generated from the pattern chip
Data Source
AI summary
A defect inspection device inspecting a sample includes a movable table on which the sample as an inspection object and a pattern chip are mounted, an illumination light irradiation unit which irradiates a surface of the sample or a surface of the pattern chip with linearly-formed illumination light, a detection optical system section where a plurality of detection optical systems are disposed at a plurality of positions above the table and which detect images of scattered light generated from the sample, and a signal processing unit which processes detected signals to detect a defect of the sample surface, and a plurality of repeating patterns for generating the scattered light according to positions of the objective lenses of the plurality of detection optical systems of the detection optical system section when the linearly-formed illumination light is irradiated by the illumination light irradiation unit are periodically formed in the pattern chip.