| 초록 |
Low temperature polycrystalline Si (LTPS) technology has been gaining the industrial significance due to much higher mobilities than the counterpart in amorphous Si thin films, ranging from 10 to 500cm2/Vsec. Higher mobility in charge carriers allows the incorporation of driver ICs onto glass substrates and the application to next-generation active matrix organic light-emitting diodes. The LTPS technology requires sophisticated control in Si channels, gate dielectrics, and source/drains which affect the transistor characteristics, i.e., threshold voltage, S-slope, leakage current, and on-off ratios. This work places major emphases on the ion activation of doped polycrystalline Si thin films, being tailored for source/drains or lightly-doped drains. Up to now, most of activation techniques have been performed using furnace annealing or excimer laser annealing. The thermal annealing suffers from lengthy processing time and the laser annealing faces the maintenance issues since the activation is highly sensitive to laser densities imposed on the Si thin films. Rapid thermal annealing (RTA) can be chosen as an alternative, in terms of processing time and activation efficiency. Despite the benefits of RTA, the relevant information is rarely available. In this work, the processing variables of RTA are investigated with the aim to obtaining high degree of activation efficiency in low temperature polycrystalline Si thin films. The activation result is interpreted in terms of electrical and structural issues, using Hall measurements and Raman spectroscopy. The detailed information on electrical properties includes the charge carrier concentration, charge mobility, and the conductivity. Raman spectroscopy is employed to estimate the relative proportion of amorphous, defective, and crystalline portions. The combined interpretation allows the systematic understanding on the correlation between rapid thermal annealing and ion activation. Ultimately, sophisticated control in rapid thermal annealing will be discussed in conjunction with the feasibility to large-scale mass production in low temperature polycrystalline Si technology. |
