Calibration studies of pattern top resist loss detection by CD-SEM for advanced lithography process

Toru Ishimoto; Miki Isawa; Maki Tanaka; Shaunee Cheng

doi:10.1117/12.880916

20 April 2011 Calibration studies of pattern top resist loss detection by CD-SEM for advanced lithography process

Toru Ishimoto, Miki Isawa, Maki Tanaka, Shaunee Cheng

Author Affiliations +

Proceedings Volume 7971, Metrology, Inspection, and Process Control for Microlithography XXV; 79712H (2011) https://doi.org/10.1117/12.880916
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

We have been developing a resist loss measurement function which is based on quantified pattern top roughness. In order to use practically the resist loss detection function, the PTR index must be calibrated to amount of resist loss. Furthermore, the evaluation of different chemical formulation and different film thicknesses of the resist is also required. In this study, we explore the calibration technique of resist loss detection. In order to convert measured PTR index into amount of resist loss, a reference measurement to pattern height is required. Techniques that can measure local pattern height are limited to off-line techniques such as AFM or cross-sectional SEM with current technology. These techniques have a very long Turnaround Time (TAT), and also highly skilled engineer is required, it cannot be used for in-line processing. Then, we examined the reasonable calibration method by short TAT. At first, the calibration wafer with changed resist film thickness is exposed using an "open frame" condition. It is measured by an optical film thickness metrology (FTM) tool and CD-SEM, a conversion factor is determined and converted PTR index of measured target patterns into resist loss amount. The validity of converted resist loss amount by this method has been proven by comparing to the resist height obtained by AFM and cross-sectional SEM images. The calibration technique using PTR index of un-patterned resist allowed us to understand the relationship between un-patterned resist thickness and resist surface roughness. We have demonstrated a simple and easy way to calibrate pattern resist loss using CD-SEM top-down images.

Citation Download Citation

Toru Ishimoto, Miki Isawa, Maki Tanaka, and Shaunee Cheng "Calibration studies of pattern top resist loss detection by CD-SEM for advanced lithography process", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79712H (20 April 2011); https://doi.org/10.1117/12.880916

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KEYWORDS

Calibration

Semiconducting wafers

Metrology

Scanning electron microscopy

Photoresist processing

Surface roughness

Atomic force microscopy

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