Crystallization technique of epitaxial HfO2 thin films on Si substrates and their potential for advanced high-k gate stack technology

Crystalline phase high-k films are promising gate stack structure for the advanced CMOS technology because they are thermodynamically stable and have higher dielectric constant when compared with amorphous phase high-k films. A disadvantage of crystalline high-k films, however, is the large leakage current, which is sometimes caused by grain boundaries and non-crystallized region in ultra-thin crystalline high-k films. We developed a unique crystallization technique that realizes epitaxial growth of HfO2 films on Si substrates. MOS capacitors of closely packed epitaxial HfO2 films achieved extremely small EOT with suppressed leakage current. It demonstrates that crystallization process is the key for the application of high-k crystal films.