Date of Award
Doctor of Philosophy (PhD)
High aspect ratio lithography utilizes high intensity exposure sources, such as synchrotron storage rings, to deposit sufficient dose in the resist to produce a successful pattern transfer. Such highly powerful sources are known to cause undesirable thermal effects in the mask-resist-substrate system. Hence, the measurement of temperature of a mask-resist-substrate system during irradiation is an important exposure diagnostic feature. Deposition of a reasonably accurate dose in the resist is controlled by knowledge of the exposure source intensity. Periodic monitoring of the synchrotron radiation beam power and its spatial distribution at the exposure plane is necessary. In this research, diagnostic techniques based on thin gold film thermal sensors are developed to measure mask-resist-substrate temperature during exposure, and to measure the magnitude and spatial distribution of exposure radiation power. The suitability of thin gold film thermal sensors for exposure diagnostics are demonstrated. Fabrication, calibration and performance characteristics of these sensors are presented. Results of the temperature rise on the top surface of PMMA and at the interface of the Si-PMMA resist-substrate system in vacuum and at different pressures of helium are presented. Relaxation time parameter under different exposure ambiance is determined. The thermal sensor measurement is compared with that of conventional J-type miniature thermocouples, and temperature measurements are compared with results of a numerical simulation performed using the finite difference heat transfer code, HEATING. A calorimeter, based on the interlaced thermal sensors, has been developed to perform synchrotron radiation beam power measurements. The concept of internal calibration, that combines calibration and measurement into a single operation, is explained. The advantage of this technique in terms of the ambiance independent, calibration-free performance and fast response time is demonstrated in comparison with conventional calorimeters. A procedure, based on an integral type measurement to obtain the spatial power distribution in the beam is explained. The results of beam power measurement and beam profile measurement at the XRLC1 and the XRLM3 beamlines are presented. An empirical relationship between the synchrotron electron beam current and the synchrotron radiation power is developed to serve as a quick reference during exposures.
Manohara, Harish M., "Development of Thin Gold Film Thermal Sensors for Synchrotron X-Ray Exposure Diagnostics." (1997). LSU Historical Dissertations and Theses. 6394.