Deposition of zinc oxide film using high power impulse magnetron sputtering

Zinc oxide (ZnO) is a semiconductor material with a hexagonal crystal structure and a wide band gap of 3.37 eV and is expected for various applications such as channel layer in thin film transistors (TFTs), transparent conductive film, and so on. It is reported that c-axis oriented crystalline ZnO achieved high mobility. High power impulse magnetron sputtering (HiPIMS) can produce many energetic ions due to high plasma density and enhance the ion bombardment. In this study, the oxygen gas flow ratio dependence on the deposition of crystalline ZnO by HiPIMS was investigated.

A peak power density applying the Zn target was 1.0 kw/cm² with a pulse width of 9 μs and a frequency of 500 Hz. A distance between a target and a substrate was 50 mm. The oxygen gas flow ratio to argon gas was varied from 10 to 30% at a pressure of 3 Pa.

The X-ray diffraction peaks (100) at the angle of 31° and (101) at 36° were observed for all samples. The (002) peek at 34° was clearly appeared and the grain size evaluated from the (002) peak increased with decreasing the oxygen gas flow ratio. These results indicate that the c-axis oriented crystalline ZnO can be obtained at lower oxygen gas flow ratio on HiPIMS process.