Study on crystallinity of tin-doped indium oxide films deposited by DC magnetron sputtering

Tin-doped indium oxide (ITO) films were deposited by dc magnetron sputtering using oxide (ITO) or alloy ITO targets. The ITO films sputter-deposited using Ar at total pressure (P-tot) lower than 1.2 Pa showed polycrystalline structure, whereas entirely amorphous films were deposited at P-tot higher than 1.4 Pa, indicating that the crystallinity of the ITO films were heavily affected by P-tot. This was quantitatively explained in terms of the kinetic energy of sputtered particles reaching to the substrate surface, which decreased due to an increase in collision frequency between the sputtered particles and sputtering gas molecules. ITO films were also deposited using Xe or He as sputtering gases, where amorphous films were deposited at P-tot higher than 0.7 Pa (Xe) and 12 Pa (He), respectively. Based on a hard sphere collision model, the energy loss rates of the sputtered particles due to collision with sputtering gas molecules were estimated to be consistent with the experimental results for the case of using He, Ar or Xe gases.