Enabling Quantitative Optical Imaging for In-die-capable Critical Dimension Targets.

Area of Science:

• Semiconductor metrology
• Optical physics
• Nanotechnology

Background:

• Semiconductor critical dimensions (CDs) are approaching atomic scales, necessitating advanced measurement techniques.
• Existing in-die metrology targets face limitations in precision and size for future semiconductor nodes.

Purpose of the Study:

• To adapt and optimize finite sets of features for in-die metrology targets.
• To enable accurate measurement of sub-10 nm critical dimensions using optical techniques.
• To minimize parametric uncertainty in critical dimension measurements.

Main Methods:

• Utilized simulation studies and experiments at 193 nm wavelength.
• Employed a finite element based solver for time-harmonic Maxwell's equations.
• Optimized target design by varying line lengths, number of lines, focal positions, and illumination wavelength.

Main Results:

• Developed metrology targets as short as 3 micrometers with as few as eight lines for 193 nm light.
• Demonstrated extensibility to sub-10 nm critical dimensions.
• Achieved target areas up to fifteen times smaller than current state-of-the-art scatterometry targets.

Conclusions:

• The new methodology offers a promising alternative for optical model-based in-die critical dimension metrology.
• Optimized targets provide a pathway for accurate measurement of future semiconductor CDs.
• Reduced target size and complexity enhance efficiency in semiconductor manufacturing.