Optical Science and Engineering ETDs

Publication Date

Fall 12-15-2016

Abstract

Metrology technologies are an essential adjunct to Integrated Circuit (I.C.) Semiconductor manufacturing. Scatterometry, an optical metrology, was chosen to measure 50 nm half pitch feature structures. A bread-board scatterometry system has been assembled to provide a non-contact, non-destructive, accurate and flexible measurement. A real-time, on-line scatterometry system has also been demonstrated and proven to provide a high throughput measurement.

Three different types of samples have been measured using the scatterometry setup. The wire-grid polarizer (WGP) sample has been made by Jet and Flash Nanoimprint Lithography with ~100 nm pitch and ~50 nm wide ~200 nm tall Al gratings on fused silica substrates. One of the resist grating samples has been made by Roll-to-Roll Nanoimprint Lithography with ~130 nm pitch and ~65 nm wide ~100 nm tall resist gratings on polycarbonate substrate. The other resist grating samples have been made by Immersion Interference Lithography with ~80 nm pitch and ~70 nm tall resist gratings on silicon substrate.

For the WGP, four wavelengths (244 nm, 405 nm, 633 nm and 982 nm) were used to study the dependence of the parametric scatterometry on a function of the wavelength to sample pitch ratio ( /p: from 2.4 to 9.8). Results show that even for a laser wavelength ten times larger than the sample pitch, scatterometry can still provide the characteristic structure information. The definition of the grating structure in the simulation has improved from a simple trapezoidal structure to a more complicated model with top rounding structure and an Al2O3 “skin”. With a better model and definition of the structure, simulation results have been closer to measurement results for all four wavelengths and the parameter sets present a very close results from scatterometry measurements. For the resist grating samples, scatterometry has less sensitivity because of lower index contrast than WGP, but a 405 nm laser source can still provide effective measurement on ~100 nm pitch resist samples. The scatterometry results are also sensitive to inhomogeneity of the resist sample and show a capability for classifying different types of macroscopic defects.

A model-based limitation study for both WGP and resist grating shows the fundamental limits of scatterometry for different materials and structures based on current noise levels. We have simulated a reducing linewidth and height of gratings with fixed pitch and the conditions with scaling the entire grating structure and have demonstrated that the potential capability of scatterometry can approach down to 10 nm feature size with a 405 nm laser.

Degree Name

Optical Science and Engineering

Level of Degree

Doctoral

Department Name

Optical Science and Engineering

First Committee Member (Chair)

Steven R. J. Brueck

Second Committee Member

Mansoor Sheik-Bahae

Third Committee Member

P. Randall Schunk

Fourth Committee Member

Francesca Cavallo

Keywords

optical metrology, scatterometry, imprint lithography, interference lithography, wire grid polarizer, RCWA

Sponsors

NSF

Document Type

Dissertation

Language

English

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