Abstract

In this paper, a new methodology is presented to derive the aberration state of a lithographic projection system from wafer metrology data. For this purpose, new types of phase-shift gratings (PSGs) are introduced, with special features that give rise to a simple linear relation between the PSG image displacement and the phase aberration function of the imaging system. By using the PSGs as the top grating in a diffraction-based overlay stack, their displacement can be measured as an overlay error using a standard wafer metrology tool. In this way, the overlay error can be used as a measurand based on which the phase aberration function in the exit pupil of the lithographic system can be reconstructed. In practice, the overlay error is measured for a set of different PSG targets, after which this information serves as input to a least-squares optimization problem that, upon solving, provides estimates for the Zernike coefficients describing the aberration state of the lithographic system. In addition to a detailed method description, this paper also deals with the additional complications that arise when the method is implemented experimentally and this leads to a number of model refinements and a required calibration step. Finally, the overall performance of the method is assessed through a number of experiments in which the aberration state of the lithographic system is intentionally detuned and subsequently estimated by the new method. These experiments show a remarkably good agreement, with an error smaller than $5\mathrm{m}\lambda$, among the requested aberrations, the aberrations measured by the on-tool aberration sensor, and the results of the new wafer-based method.

© 2014 Optical Society of America

Aberration measurement of projection optics in lithographic tools based on two-beam interference theory

Mingying Ma, Xiangzhao Wang, and Fan Wang
Appl. Opt. 45(32) 8200-8208 (2006)

Measurement technique for in situ characterizing aberrations of projection optics in lithographic tools

Fan Wang, Xiangzhao Wang, and Mingying Ma
Appl. Opt. 45(24) 6086-6093 (2006)

Optimized wavelength selection for diffraction-based overlay measurement by minimum asymmetry factor variation with finite-difference time-domain simulation

Hung-Chih Hsieh, Jui-Ming Cheng, and Yun-Chi Yeh
Appl. Opt. 61(6) 1389-1397 (2022)

Translational-symmetry alternating phase shifting mask grating mark used in a linear measurement model of lithographic projection lens aberrations

Zicheng Qiu, Xiangzhao Wang, Qunyu Bi, Qiongyan Yuan, Bo Peng, and Lifeng Duan
Appl. Opt. 48(19) 3654-3663 (2009)

Calibration method of overlay measurement error caused by asymmetric mark

Juyou Du, Fengzhao Dai, Yang Bu, and Xiangzhao Wang
Appl. Opt. 57(33) 9814-9821 (2018)