Abstract
Development of the “System-on-glass (SOG)” display with low temperature poly-silicon thin film transistor has rapidly advanced recently due to the advancement of low temperature poly-silicon technology. Low temperature poly-silicon thin film transistor possibly realizes more value-added display. For a system, memory devices seem to be basic and important elements. However, there are various kinds of technology for memory devices. Taking temperature and process into consideration, SONOS-type structure seems the one of the appropriate choice of them. In the process of depositing silicon nitride, we take different way to deposit it. In conventional process, Silane and NH3 are the precursors to be used to deposit it with low process chemical deposition. And we use Silane and N2 as precursors to deposit si-rich silicon nitride with plasma enhanced chemical vapor deposition at room temperature. Besides, we fix the flow rate of Silane and adjust the rate of N2 flow to change to ratio of silicon in si-rich silicon nitride to observer the influence of silicon content on memory performances. In the consideration of substrate, we employ low temperature poly silicon as the substrate rather than single crystal silicon substrate. The mobility of the LTPS is 5 cm2/V.S. Therefore, the performance of the current-voltage relation will be affected seriously and the efficiency of the device is not as good as the efficiency of single crystal silicon substrate. Fortunately, there are substantially improvements in the mobility presently to achieve batter performances. The blocking oxide and tunneling oxide which stacked above and below the silicon nitride have great influences on efficiency and reliability issues. With the restriction of process temperature, the quality of the oxide will be the key issue. Here, we use TEOS and O3 as the precursors with PECVD at 400 oC to deposit blocking and tunneling oxide. The fabrication temperature is blow 400 oC in the whole memory processes in addition to the temperature for the source and drain activation is 725 oC, 20 second. But this one is still under the tolerance of the glass.