| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 94 === Laser assisted direct imprinting (LADI) technology is a special kind of nanoimprint technology which applies a preloaded nano-mold and a high-energy laser pulse. The laser pulse can instantaneously melt the sample surface to make the pattern transfer from the mold to the sample. In this study, we will investigate both theoretically and experimentally the melting phenomenon of the silicon substrate subjected to the irradiation of an excimer laser pulse. By comparing the experimental and simulation data we can quantitatively determine the molten time and molten depth of silicon substrate, which play an important role in the LADI process.
Experimentally, the time-resolved reflectivity (TRR) measurements are carried out with a probe He-Ne laser of 632.8 nm in wavelength. From the TRR measurements, we discover that the reflectivity signal as a function of time can be used to re-construct the time-history of substrate melting. Therefore, we could deduce the molten time and melting depth under different laser fluence.
Furthermore, this study discovers that if we measured the back surface reflectivity by a diode laser of wavelength 1310 nm, the reflectivity signal will oscillate cyclically along with the increasing molten depth. With this cyclic signal of back surface reflectivity, the molten depth can also be estimated. Good agreements between experiments and simulation are observed.
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