Transient Temperature Measurements of Resist Heating using Nano Thermocouples

Chu, D., Wong, W.K., Goodson, K.E., and Pease, R.F.W., 2003, "Transient Temperature Measurements of Resist Heating using Nano Thermocouples," Journal of Vacuum Science and Technology B, Vol. 21, pp. 2985-2989.

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Resist heating is one of the major factors that causes feature size variation and pattern displacement in photomask fabrication.Anumber of models have been published to predict the rise in temperature during resist heating, but no transient temperature experimental results are available to verify those models. We have fabricated thin film gold/nickel thermocouples with junction areas as small as 100 nm2 on silicon and 500 nm2 on quartz. Microsecond scale transient resist heating measurements were obtained using these thermocouples. Irradiation by a 15 keV, 150 nA electron beam of 1.7 mm radius for 100 ms yielded temperature rises at the resist bottom surface of approximately 62 K on quartz substrates and of 18 K on silicon substrates. Simulation results using a multilayer Green’s function model are in reasonable agreement with these experimental data for smaller temperature rises but tend to overestimate by about 10% for larger rises in temperature. In our experiments, a 100 ms exposure is equivalent to a dose of 150 mC/cm2. Under the same electron beam conditions electron dosages of 5 and 15 mC/cm2 result in temperature rises of 25 and 40 K, respectively, on quartz substrates.

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