Growth mechanism of atomic-layer-deposited Ti Al C metal gate based on TiCl_4 and TMA precursors

TiAlC metal gate for the metal-oxide-semiconductor field-effect-transistor(MOSFET) is grown by the atomic layer deposition method using TiCl_4 and Al(CH_3)_3(TMA) as precursors. It is found that the major product of the TiCl_4 and TMA reaction is TiAlC, and the components of C and Al are found to increase with higher growth temperature. The reaction mechanism is investigated by using x-ray photoemission spectroscopy(XPS), Fourier transform infrared spectroscopy(FTIR), and scanning electron microscope(SEM). The reaction mechanism is as follows. Ti is generated through the reduction of TiCl_4 by TMA. The reductive behavior of TMA involves the formation of ethane. The Ti from the reduction of TiCl_4 by TMA reacts with ethane easily forming heterogenetic TiCH_2, TiCH=CH_2 and TiC fragments. In addition,TMA thermally decomposes, driving Al into the Ti C film and leading to TiAlC formation. With the growth temperature increasing, TMA decomposes more severely, resulting in more C and Al in the TiAlC film. Thus, the film composition can be controlled by the growth temperature to a certain extent.