Technical Briefs

Thermal Modeling of Ultraviolet Nanoimprint Lithography

[+] Author and Article Information
Ankur Jain

e-mail: jaina@uta.edu
Mechanical and Aerospace Engineering Department,
The University of Texas at Arlington,
500 W First Street, Rm 211,
Arlington, TX 76019

1Corresponding author.

Manuscript received April 26, 2013; final manuscript received September 21, 2013; published online November 5, 2013. Assoc. Editor: Yung Shin.

J. Manuf. Sci. Eng 135(6), 064501 (Nov 05, 2013) (5 pages) Paper No: MANU-13-1184; doi: 10.1115/1.4025564 History: Received April 26, 2013; Revised September 21, 2013

Nanoimprint lithography (NIL) is a promising nanomanufacturing technology that offers an alternative to traditional photolithography for manufacturing next-generation semiconductor devices. This technology involves coating an ultraviolet (UV)-curable monomer layer on the substrate and then imprinting it with a template containing topography corresponding to the desired substrate features. While the template is close to contact with the substrate, the monomer is cured by UV exposure. This results in definition of desired features on the substrate. While NIL has the potential of defining very small feature sizes, thermal management of this process is critical for ensuring accuracy. Heat generation in the monomer layer due to UV absorption needs to be managed and dissipated in order to avoid thermal expansion mismatch and consequent misalignment between the template and wafer. In addition, thermal dissipation must occur in a timeframe that does not adversely affect the required lithography throughout. This paper develops a numerical simulation model of the nanoimprinting process and utilizes the model to study the effect of various geometrical parameters on the accuracy and throughput of the process. The effect of the UV power characteristics on heat dissipation and consequently on misalignment due to thermal expansion is studied. Results indicate that the thermal expansion mismatch due to commonly used UV exposure parameters may be minimized by utilizing a lower exposure power for longer time. A transient model enables a study of the effect of die imprint sequencing on the overall temperature rise during the process. Results indicate a critical trade-off between minimizing temperature rise on one hand, and maximizing system-level throughput on the other. By identifying and quantifying this trade-off, this work contributes to development of error-free nanoimprint lithography for future technology nodes.

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Grahic Jump Location
Fig. 4

Plot of the maximum temperature for a number of power density values, for the same total energy density being transferred to the monomer

Grahic Jump Location
Fig. 3

Cross-section temperature plot of the nanoimprinting geometry indicating the temperature distribution due to the nanoimprint lithography process

Grahic Jump Location
Fig. 2

Schematic of the geometry of UV exposure and development process during nanoimprinting

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Fig. 1

Schematic of the nanoimprinting process

Grahic Jump Location
Fig. 5

Plot showing the dependence of maximum stress on power density for the same total energy density being transferred to the monomer

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Fig. 6

Transient temperature plot resulting from sequential exposure of multiple fields on a substrate

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Fig. 7

Plot of peak temperature rise and total distance traveled for seven different sequencing schemes for a seven-field exposure, indicating a fundamental trade-off between thermal design and system throughput



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