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.