In microelectronics, continuous shrinking of devices is necessary to improve the performance, which sets challenging requirements for fabrication of integrated circuits (ICs). New manufacturing techniques are required for growing very thin blanket films and thin films covering deep trenches and other three dimensional (3D) structures with good conformality. Atomic layer deposition (ALD) has gathered interest in the microelectronic industry from the unique characteristics that the method offers: ultra-thin films can be deposited on large substrates with excellent conformality and with control of thickness and composition at the nanometer level. ALD has high potential for use in microelectronics for high-k film growth for complementary metal oxide semiconductor (CMOS) devices and dynamic random access memory (DRAM) capacitors as well as for ferroelectrics, barrier materials, and conductors such as metal gates.
High-k materials have been extensively studied due to the fact that SiO2, which is traditionally used as a gate oxide in metal-oxide semiconductor field effect transistors (MOSFETs), can no longer function as an effective gate insulator as higher capacitance density with decreased gate oxide thickness is required for near-future device generations. High-k materials usually refer to materials having a dielectric constant greater than SiO2 (k=3.9). Silicon oxynitride, SiOxNy, has been used to extend the use of silicon oxide-based gate dielectrics but a long term alternative solution is required. Many high-k materials under evaluation suffer from various problems, including film crystallization during anneals, growth of interface layers during film deposition and further processing, large densities of interface traps, reduced channel mobility, reaction with poly-silicon (poly-Si) gates, and Fermi level pinning with metal gate electrodes. Other problems encountered with many high-k materials include dielectric constants that are too low compared to desired values for advanced semiconductor devices. The dielectric constant of a film stack containing a high-k film may be further reduced by the presence of an interface layer between the high-k material and the underlying substrate. Accordingly, further developments for forming high-k materials are needed to solve these and other problems of prior art high-k materials.