Extracting Dimensional Parameters of Gratings Produced with Self-Aligned Multiple Patterning Using GISAXS

TL;DR

This paper demonstrates that GISAXS can effectively measure and analyze the line shape and pitchwalk of sub-50 nm gratings, showing promise for semiconductor metrology with room for faster simulations.

Contribution

The study extends GISAXS application to smaller pitch gratings and evaluates its performance with advanced data reconstruction techniques.

Findings

GISAXS results agree with previous SAXS measurements

Line height and width deviations are within nanometer range

Pitchwalk uncertainties are between 0.5 nm and 2 nm

Abstract

Background: To ensure consistent and high-quality semiconductor production at future logic nodes, additional metrology tools are needed. For this purpose, grazing-incidence small-angle X-ray scattering (GISAXS) is being considered because measurements are fast with a proven capability to reconstruct average grating line profiles with high accuracy. Aim: GISAXS measurements of grating line shapes should be extended to samples with pitches smaller than 50 nm and their defects. The method's performance should be evaluated. Approach: A series of gratings with 32 nm pitch and deliberately introduced pitchwalk is measured using GISAXS. The grating line profiles with associated uncertainties are reconstructed using a Maxwell solver and Markov-Chain Monte Carlo (MCMC) sampling combined with a simulation library approach. Results: The line shape and the pitchwalk are generally in agreement with previously published transmission small-angle X-ray scattering (SAXS) results; however the line height and line width show deviations of (1.0 +/- 0.2) nm and (2.0 +/- 0.7) nm, respectively. The complex data evaluation leads to relatively high pitchwalk uncertainties between 0.5 nm and 2 nm. Conclusions: GISAXS shows great potential as a metrology tool for small-pitch line gratings with complex line profiles. Faster simulation methods would enable more accurate results.