X-Ray Lithography Mask Metrology: Use of Transmitted Electrons in an SEM for Linewidth Measurement

Area of Science:

• Semiconductor metrology
• Electron beam lithography
• Materials science

Background:

• X-ray masks, crucial for semiconductor fabrication, possess unique x-ray transparent membranes.
• Traditional metrology often relies on secondary electron signals, which may not be optimal for these structures.

Purpose of the Study:

• To investigate the efficacy of transmitted electron signals for X-ray mask metrology.
• To develop a more precise edge location algorithm for linewidth measurements.
• To establish a foundation for an SEM-based linewidth measurement standard.

Main Methods:

• Utilizing transmitted electron signals instead of secondary electron signals for metrology.
• Employing Monte Carlo modeling to optimize detector parameters and analyze electron beam interaction.
• Comparing experimental data with theoretical models to validate findings.

Main Results:

• Achieved excellent contrast and signal-to-noise ratios using transmitted electrons.
• Demonstrated strong agreement between Monte Carlo simulations and experimental data, especially for wall slope characteristics.
• Validated the use of transmitted electron signals for accurate edge determination.

Conclusions:

• Transmitted electron signal provides a viable and accurate method for X-ray mask linewidth metrology.
• The developed theoretical model aids in precise edge location for feature size measurement.
• This work contributes to establishing SEM-based measurement standards and improving lithography instrumentation.