GROWTH OF Ge-DOPED Sb2Te3 THIN FILMS BY METAL-ORGANIC CHEMICAL VAPOR DEPOSITION

ABSTRACT

Thin films based on Ge–Sb–Te are the most popular material for non-volatile phase change memory, because this material is more stable in the over-write than other chalcogenide alloy. We fabricated the Ge-doped Sb₂Te₃ rhombohedral thin films by metal-organic chemical vapor deposition (MOCVD) with bubbler type systems for the nonvolatile PCRAM applications and also expected the effects of ratio of respective precusors pressure. In spite of the different Ge bubbler temperature, all thin films have same crystallinity of Sb₂Te₃ phase, which has c-axis orientation perpendicular to the substrates. Even though ratio of relative Ge vapor pressure (%) increases up to 63%, amount of Ge in the films is only about 0.4%. We concluded that reaction between Sb and Te are dominant than other reaction such as Ge–Te or Ge–Sb in current conditions. Also, to improve the reaction of Ge elements in the chamber, controlling amount of Ge precursors may be needed delicately. These results suggest that Ge–Sb–Te thin films can be deposited by metal organic CVD for phase change memory applications.