Structural and interfacial studies of atomic layer deposited high-k materials on silicon

Ultra-thin, high dielectric constant (high-kappa) films that can maintain discrete interfaces and amorphous structure during high temperature fabrication processes are critical to future miniaturization of micro-electronic devices. In particular, there is considerable need to identify replacement dielectric films for the gate oxide insulator in Complementary Metal Oxide Semiconductor (CMOS) transistors.; In order to maintain thickness control at the needed dimensions of nanometers within the gate oxide and to provide sufficient conformal coverage down the deep trenches of dynamic random access memories devices, atomic layer deposition (ALD) has been identified as the preferred technique. In addition to sub monolayer thickness control and uniform, conformal deposition, ALD has the advantage of excellent control of composition and film structure of more complex films such as ternary or higher metal oxides.; There are a number of high-kappa materials that would seem suitable for these applications, but the attempt to implement most of these materials into the manufacturing process has unraveled numerous problems. In past years, HfO2 has attracted much promise in these applications. But further research has shown limited interfacial stability with silicon and material crystallization significantly below the high temperatures needed for fabrication of CMOS devices. Al2O3 has been used as an alternate high dielectric constant material in capacitive memory applications and has shown to be thermally stable. However, for CMOS application, Al2O 3 has only a modest increase in kappa value and, hence, it remains at most only a short-term replacement for SiO2.; As a result of these considerations, composite films of hafnium and aluminum oxide may be a more optimal film possessing thermal stability and interfacial properties closer to those of Al2O3, while maintaining a higher kappa value closer to that of HfO2. In gate dielectric applications, the optimization of the film composition is a key issue. It is critical to identify the lowest amount of Al needed in the HfAlOx film to obtain the highest kappa while still maintaining sufficient thermal stability. Similarly, HfSiOx films of optimum composition are also studied for morphological stability. In addition to Al2O 3, SiN and SiON have been investigated as barrier layers to control interfacial reactions between HfO2 and Si.