Modeling thermal reflow of resist contact hole arrays

Jae-Won Lee; Zhaohua Feng; Roxann L. Engelstad; Edward G. Lovell

doi:10.1117/12.517886

17 December 2003 Modeling thermal reflow of resist contact hole arrays

Jae-Won Lee, Zhaohua Feng, Roxann L. Engelstad, Edward G. Lovell

Proceedings Volume 5256, 23rd Annual BACUS Symposium on Photomask Technology; (2003) https://doi.org/10.1117/12.517886
Event: Photomask Technology, 2003, Monterey, California, United States

Abstract

Accurate contact-hole imaging depends on the relative size of the contact hole to be patterned and the resolution of the stepper. The hardbake process includes desirable thermal reflow of the resist contact-hole arrays; this effect is driven by the temperature dependence of the polymer-based resist that is densified on the silicon substrate. Thermal reflow is completely independent of current and near-term lithographic printing tools. Resist reflow is a thermomechanical phenomenon dominated by the polymer after development, during which thermal reactions of the polymer produce permanent mechanical deformations of the contact holes. Resist behavior can effectively be classified into solid and viscous, below and above the characteristic glass transition temperature, respectively. The basic states are characterized by changes in the stress states and the phases depending on the thermal behavior of the resist material. The thermal transitions of the resist in the process are strongly influenced by the temperature-dependent mechanical properties, i.e., the modulus, the yield stress, and the coefficient of thermal expansion. Other influences include the surface tension and the bake cycle parameters. This analysis assumes conventionally generated contact holes in the resist, followed by thermal cycling until the thermal reflow produces reduced size contact holes of the desired dimensions. Finite element models were utilized to identify the principal physical parameters influencing resist thermal reflow.

Citation Download Citation

Jae-Won Lee, Zhaohua Feng, Roxann L. Engelstad, and Edward G. Lovell "Modeling thermal reflow of resist contact hole arrays", Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003); https://doi.org/10.1117/12.517886

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