TY - JOUR
T1 - Defocus Effect Correction for Back Focal Plane Ellipsometry for Antivibration Measurement of Thin Films
AU - Wang, Jian
AU - Yang, Jun
AU - Peng, Lihua
AU - Tang, Dawei
AU - Gao, Feng
AU - Chen, Rong
AU - Zhou, Liping
N1 - Funding Information:
This research was supported by the National Natural Science Foundation of China (No. 52075206, 51835005) and the Key R&D Program of Hubei Province (2021BAA056).
Publisher Copyright:
© 2023 by the authors.
PY - 2023/2/1
Y1 - 2023/2/1
N2 - Back focal plane (BFP) ellipsometry, which acquires the ellipsometric parameters of reflected light at different incident and azimuthal angles through a high-NA objective lens, has recently shown great potential in industrial film measurement. In on-line metrology cases for film manufacturing, the film vibration, which is caused by equipment vibrations or environmental disturbances, results in defocus blur and distortion of the received BFP images. Thus, subsequently extracted ellipsometric spectra and film parameters significantly deviate from the ground truth values. This paper proposes a cost-effective method for correcting vibration-induced BFP ellipsometric spectral errors. The method relies on an initial incident angle calibration of BFP radii at different defocus positions. Then, corresponding ellipsometric spectral errors are corrected by inserting a calibrated Jones compensation matrix into a system model. During measurement, the defocus position of the vibrational film is first determined. Then, BFP ellipsometric spectral errors, including incident angle mapping distortion and ellipsometric parameter variations, are corrected for a bias-free film analysis using the previous calibration results. Experimental results showed that this method significantly improved measurement accuracy without vibrational defocus compensation, from over 30 nm down to less than 1 nm.
AB - Back focal plane (BFP) ellipsometry, which acquires the ellipsometric parameters of reflected light at different incident and azimuthal angles through a high-NA objective lens, has recently shown great potential in industrial film measurement. In on-line metrology cases for film manufacturing, the film vibration, which is caused by equipment vibrations or environmental disturbances, results in defocus blur and distortion of the received BFP images. Thus, subsequently extracted ellipsometric spectra and film parameters significantly deviate from the ground truth values. This paper proposes a cost-effective method for correcting vibration-induced BFP ellipsometric spectral errors. The method relies on an initial incident angle calibration of BFP radii at different defocus positions. Then, corresponding ellipsometric spectral errors are corrected by inserting a calibrated Jones compensation matrix into a system model. During measurement, the defocus position of the vibrational film is first determined. Then, BFP ellipsometric spectral errors, including incident angle mapping distortion and ellipsometric parameter variations, are corrected for a bias-free film analysis using the previous calibration results. Experimental results showed that this method significantly improved measurement accuracy without vibrational defocus compensation, from over 30 nm down to less than 1 nm.
KW - Microellipsometry
KW - Back focal plane
KW - Antivibration measurement
KW - Thin film
KW - microellipsometry
KW - back focal plane
KW - thin film
KW - antivibration measurement
UR - http://www.scopus.com/inward/record.url?scp=85147962739&partnerID=8YFLogxK
U2 - 10.3390/app13031738
DO - 10.3390/app13031738
M3 - Article
VL - 13
JO - Applied Sciences (Switzerland)
JF - Applied Sciences (Switzerland)
SN - 2076-3417
IS - 3
M1 - 1738
ER -