Atomic Layer Deposition of Hafnium Based Gate Dielectric Layers for CMOS Applications

Abstract

To increase CMOS device performance, new materials are introduced in the gate stack (high-k dielectrics, metal gates) and the transistor channel (Ge, III-V). In this work, we study the Atomic Layer Deposition (ALD) of hafnium based gate dielectric oxides. Depositing by means of surface controlled reactions implies that the chemical sites at the surface can determine the growth behavior. First, the starting surface effect is analyzed for HfO2 ALD on Ge and GaAs substrates. Either substrate inhibition or enhancement occurs, both associated with an initial regime of island growth. The presence of oxygen enhances the GPC in the first reaction cycle. Second, the steady ALD of ternary oxides (hafnium silicate, aluminate, zirconate) is discussed. HfCl4 (and ZrCl4) chemisorption are much less affected by the composition of ternary oxides than by the starting surface. On the other hand, the SiCl4 chemisorption rate is significantly affected by the Hf-content of hafnium silicates.