Importance of Si surface flatness to realize high-performance Si devices utilizing ultrathin films with new material system

Abstract

The importance of Si surface flatness on metal-oxide-semiconductor field-effect transistor (MOSFET) characteristics with ultrathin hafnium oxynitride (HfON) high-k gate insulator formed by electron cyclotron resonance (ECR) plasma sputtering was described. The surface roughness of Si substrate was reduced by Ar/4.9%H₂ annealing utilizing conventional rapid thermal annealing (RTA) system. Si surface root-mean-square (RMS) roughness was well controlled by changing the annealing temperature from 700 to 1000°C. Si surface RMS roughness after 1000°C/1 hr annealing was 0.078 nm for Si(100) and 0.082 nm for Si(110), respectively. Clear dependence of electrical characteristics of MOS diodes such as equivalent oxide thickness (EOT) and leakage current on the surface RMS roughness of Si(100) and Si(110) was observed, and the electrical characteristics were remarkably improved by decreasing of surface RMS roughness. The MOSFET characteristics with HfON gate insulator fabricated on Si(100) substrates after flattening process were also improved.