VUV Metrology Calibration Pad with Multi-Site Contamination Switching
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Solution Overview
Problem
Optical metrology tools in the VUV range face challenges due to contamination of optical surfaces, leading to inaccurate measurements, especially with ultra-thin films, and require frequent calibration, which is user-dependent and not automated.
Innovation Solution
A calibration pad with multiple sites is used, where sites are evaluated and switched based on contamination criteria, such as reflectance data and exposure, to maintain accurate calibration without user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single calibration site is used, then the calibration process is simple, but the measurement accuracy deteriorates due to contamination accumulation
Solution Approach 1:
The calibration pad is divided into multiple discrete calibration sites (e.g., 6 sites arranged in a grid), allowing the system to segment the calibration function across multiple locations. This enables rotation among sites to prevent contamination accumulation at any single site while maintaining overall calibration accuracy.
Solution Approach 2:
The calibration system dynamically rotates among multiple calibration sites based on contamination levels. The system monitors reflectance data and exposure history to determine when to switch sites, making the calibration process adaptive and responsive to contamination conditions rather than static.
2Measurement precision
If calibration is performed frequently, then the measurement accuracy is maintained, but the productivity decreases due to user intervention requirements
Solution Approach 1:
The calibration system performs self-diagnosis and self-correction by automatically monitoring reflectance data and exposure history to determine when calibration site rotation is needed. This eliminates the need for continuous user intervention to check and perform calibration, allowing the system to maintain accuracy autonomously.
Solution Approach 2:
The system continuously monitors reflectance data and exposure history as feedback signals to determine calibration status. Based on this feedback, the system automatically decides when to rotate calibration sites, ensuring accurate calibration without requiring frequent manual intervention or slowing down production.
3Measurement precision
If multiple calibration sites are used, then the calibration accuracy is maintained, but the device complexity increases
Solution Approach 1:
Multiple calibration sites are merged into a single integrated calibration pad structure, allowing all sites to be accessed through one unified interface. This combining approach maintains the benefits of multiple sites for accuracy while avoiding the complexity of managing separate calibration devices or samples.
4Reliability
If calibration sites are monitored manually, then the contamination detection is thorough, but the time consumption increases
Solution Approach 1:
Manual monitoring of calibration sites is replaced by an automated optical measurement system that continuously collects reflectance data. This substitution of mechanical/manual inspection with automated optical detection maintains thorough contamination monitoring while dramatically reducing the time required for calibration site evaluation.
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 method ensures continuous accurate calibration of optical metrology tools by automatically switching to clean sites, reducing errors and the need for frequent user intervention, thus enhancing the reliability and efficiency of VUV metrology in semiconductor manufacturing.
Implementation Method 1
Optical reflectometry techniques have long been employed in process control applications in the semiconductor manufacturing industry
Implementation Method 2
VUV and DUV radiation from the optical metrology tool itself may cause the formation of a contaminant film by reacting with accumulated airborne or out-gassed contaminants via a photo-deposition process
Data Source
AI summary
A calibration pad having multiple calibration sites is provided. A particular calibration site may be utilized until that particular site has been determined to have become unacceptable for further use, for example from contamination, in which case the calibration processes may then move to use a different calibration site(s) on the calibration pad(s). A variety of techniques may be utilized to provide the determination that a site is no longer acceptable for use. Movement may thus occur over time from site to site for use in a calibration process. A variety of criteria may be established to determine when to move to another site. Though the designation of a site as “bad” may be based upon measured reflectance data, other criteria may also be used. For example, the number of times a site has been exposed to light may be the criteria for designating a site as bad. Alternatively the cumulative exposure of a site may be the criteria. Further, the plurality of calibration sites that are provided on the single calibration pad may be pre-evaluated so as to initially screen out unacceptable calibration sites prior to use. The techniques provided may be utilized in calibration processes which utilize a single calibration sample or processes which require a plurality of calibration samples.