Relative Critical Dimension Measurement via Reference Image Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional charged-particle beam instruments face challenges in accurately measuring relative critical dimensions during electron beam inspection of substrates, particularly in detecting abnormalities and aligning reference and target images effectively.
Innovation Solution
A method and apparatus that involve obtaining a reference image, defining a region of interest, aligning the target and reference images, and measuring relative critical dimensions by scanning perpendicular to the critical dimension, with optional filtering of point RCDs to compute averages, using a charged-particle beam apparatus with a source, scanning system, and detection system for generating and processing image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electron beam inspection is used to measure critical dimensions, then the inspection can be performed on substrate surfaces, but the measurement precision of relative critical dimensions is insufficient
Solution Approach 1:
The patent applies preliminary action by obtaining a reference image before the target image and performing alignment operations in advance. The reference image is captured first, then the target image is acquired and aligned to the reference image before RCD measurement. This preliminary alignment and reference establishment enables more precise relative critical dimension measurements by providing a stable baseline for comparison, directly addressing the measurement precision limitation of conventional inspection methods.
2Measurement precision
If image alignment is performed between target and reference images, then measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent uses copying by creating a reference image that serves as a template or copy of the expected substrate pattern. This reference image is then used to align and compare against the actual target image. The copying approach simplifies the alignment process by providing a known reference pattern, reducing the complexity of the image processing system while improving measurement precision through systematic comparison.
Solution Approach 2:
The reference image acts as an intermediary between the target image and the measurement process. By introducing this intermediate reference layer, the system can perform alignment and RCD measurements more accurately without requiring direct complex processing of the target image alone. The intermediary reference image mediates the comparison process, simplifying the overall system architecture while enhancing measurement capabilities.
3Measurement precision
If scanning is performed perpendicular to the critical dimension, then measurement precision of RCD improves, but the inspection time increases
Solution Approach 1:
The patent applies segmentation by dividing the inspection process into distinct phases: reference image acquisition, target image acquisition, alignment processing, and RCD measurement. By segmenting the process and performing alignment once on the reference image, the system avoids repeated time-consuming operations for each measurement point. The scanning perpendicular to the critical dimension is performed efficiently within this segmented framework, improving RCD measurement precision without proportionally increasing total inspection time.
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 precise measurement of relative critical dimensions within a region of interest, enhancing defect inspection and classification capabilities by improving image alignment and data processing, thereby improving hotspot defect detection and control.
Implementation Method 1
a source for generating an incident electron beam
Implementation Method 2
results in the emission of secondary electrons from the substrate surface
Implementation Method 3
a scanning system for controllably deflecting the incident electron beam to scan the incident electron beam over a surface
Implementation Method 4
a detection system for detecting the secondary electrons so as to generate an image data
Data Source
AI summary
One embodiment relates to a method of measuring a relative critical dimension (RCD) during electron beam inspection of a target substrate. A reference image is obtained. A region of interest is defined in the reference image. A target image is obtained using an electron beam imaging apparatus. The target and reference images are aligned, and the region of interest is located in the target image. Measurement is then made of the RCD within the region of interest in the target image. Another embodiment relates to a method of measuring a RCD which involves scanning along a scan length that is perpendicular to the RCD. Point RCDs along the scan length are measured. A filter is applied to the point RCDs, and an average of the point RCDs is computed. Other embodiments, aspects and features are also disclosed.