Optical Microscope Defect Review for Semiconductor Wafer Inspection
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Solution Overview
Problem
Conventional methods for detecting defects on semiconductor wafers using optical inspection apparatuses result in high error components, leading to reduced throughput and increased time in analyzing defects with scanning electron microscopes due to the need to reposition the defect within the microscope's small visual field, especially when defects are not initially within the field of view.
Innovation Solution
An apparatus and method that utilize an optical microscope to re-detect defects with high sensitivity, correct position information, and position the defect within the scanning electron microscope's visual field using an optical height detection system and focus adjustment, ensuring the defect is securely within the SEM's field for detailed review.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an external optical inspection apparatus uses a large spot laser to scan the substrate for high inspection throughput, then inspection throughput is improved, but the position information of the defect includes a large error component
Solution Approach 1:
An optical microscope is introduced as an intermediary device between the external optical inspection apparatus and the scanning electron microscope. The optical microscope uses a small spot size to precisely locate defects and provides accurate position information to the SEM, thereby resolving the position accuracy issue while maintaining the high throughput capability of the external inspection apparatus
Solution Approach 2:
The patent replaces the mechanical scanning method with a large spot laser with an optical microscopy method using a small spot. The optical microscope provides precise defect location information that is then used to guide the SEM to the exact defect position, substituting the imprecise mechanical scanning approach with a more accurate optical detection approach
2Reliability
If the visual field of the scanning electron microscope is changed to search for the defect, then the defect can be located within the visual field, but the throughput of the scanning electron microscope is reduced and the analysis time is increased
Solution Approach 1:
The optical microscope performs preliminary defect location before the SEM analysis. By pre-locating the defect with the optical microscope and providing accurate position information to the SEM, the system eliminates the need for the SEM to perform time-consuming visual field changes and searching, thereby maintaining high SEM throughput while ensuring reliable defect location
3Reliability
If the numerical aperture of the objective lens in the optical microscope is increased to detect foreign material with high sensitivity, then detection sensitivity is improved, but the focal depth of the optical microscope is reduced
Solution Approach 1:
The patent implements dynamic focus adjustment in the optical microscope to compensate for the reduced focal depth caused by using a high numerical aperture objective lens. The focus position is automatically adjusted based on the detected defect position, allowing the system to maintain both high detection sensitivity and adequate focal depth by adapting the focus dynamically rather than relying on a fixed focal plane
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 significantly increases the throughput of defect inspection by accurately positioning defects within the SEM's field, reducing the time required for detailed analysis and enhancing sensitivity in defect detection.
Implementation Method 1
an optical height detection system which optically detects a vertical position of an upper surface of the sample
Implementation Method 2
an illumination optical system which illuminates the existing defect on the sample with light; an image detection optical system which converges and detects reflected light or scattered light generated from the existing defect
Implementation Method 3
an image detection optical system which converges and detects reflected light or scattered light generated from the existing defect
Implementation Method 4
a focus adjusting means which adjusts a focus position of the optical microscope based on the vertical position of the upper surface of the sample
Data Source
AI summary
The present invention provides an apparatus and a method for reviewing a defect with high throughput by detecting the defect to be reviewed with high sensitivity, comprising: an optical microscope; a correction means; and a scanning electron microscope which reviews the existing defect on the sample; wherein the optical microscope has: an optical height detection system which optically detects a vertical position of an upper surface of the sample placed on the stage; an illumination optical system which illuminates the defect with light; an image detection optical system which converges and detects reflected light or scattered light generated from the defect illuminated by the illumination optical system to obtain an image signal; and a focus adjusting means which adjusts a focus position of the optical microscope based on the vertical position of the upper surface of the sample, which is detected by the optical height detection system.