DUV Microscopy for Nanostructure Imaging

Summary

The project aims to develop the metrology for accurate, reliable characterization of nanostructures using the deep ultraviolet (DUV) reflective imaging microscopy with sophisticated illuminations for efficient manufacturing of the next generation computing devices. The research scope covers the quantitative parametric measurements based on modelling and the Fourier Ptychographic phase imaging for 3-D nanoscale reconstruction with sub-nanometer sensitivity and uncertainty. These measurements are developed through manipulating the illumination scheme with angle-resolving, frequency domain expansion, phase modulation, polarization variation and developing the computational phase retrieval algorithm with high reliability.

Description

Schematic diagram of DUV microscopy with angle-resolved illumination controlled at conjugate back focal plane.

The optical measurement techniques using the deep ultraviolet microscopy with sophisticated illuminations are developed to achieve accurate characterization of nanoscale features with high dimensional sensitivity and low uncertainties for the advancement of the semiconductor manufacturing process. The illumination beam is manipulated at the conjugate back focal plane to form selective intensity distributions at the image and/or Fourier planes, which correspond to the spatial and frequency domain, respectively. Through the illumination engineering, the parameters of the nanoscale features such as linewidth, pitch, height, and defects in array are characterized by two methodologies.

Sensitivity coefficient map for optimizing the illumination partial coherence to increase dimensional sensitivity.

Model-based scattered image analysis: the illumination is controlled by placing various apertures or phase plates and scanning an aperture at the conjugate of the back focal plane of the objective, so that the scattered light at the nanostructure sample can be traceable to obtain the accurate sample parameters and the optimized sensitivity.

Computational nanoscale phase imaging: DUV reflective Fourier Ptychographic microscopy with aperture-scanning illumination is developed to enable 3-dimensional reconstruction of nanoscale features by computationally extracting the amplitude and phase information with spatial frequency ranges expanded beyond the resolution limit.

Major Accomplishments

2019

• Developed the partial coherence optimization method in scatterfield imaging microscopy for quantitative dimensional metrology, achieving 0.2 nm measurement sensitivity.
• Demonstrated nanoscale Fourier Ptychography imaging using the 193 nm microscope with angle-resolved illumination through measuring high-resolution phase images for 200 nm multilines.