[8a-PB4-1~20] 8.3 Plasma deposition of thin film and surface treatment

[8a-PB4-19] Deposition of Ga doped ZnO films using narrow-gap RF magnetron sputtering

〇Yoshinobu Matsuda¹, Kohei Sakamoto¹, Naoki Matsuo¹, Tomohiro Furusato¹, Takahiko Yamashita¹ (1.Nagasaki Univ.)

Keywords:Galium doped zinc oxide, magnetron, sputtering

In sputtering deposition of a ZnO based material, the carrier density and the mobility decrease on the substrate facing the target eroded region. In this study, short gap sputtering deposition with a Ga-doped ZnO (GZO) target with an extremely short distance between the target and the substrate was carried out. As a result, as the gap length decreased, the film resistivity greatly decreased and the uniformity of the spatial distribution has been greatly improved. When the gap length was 20 mm, a GZO film having a film thickness of 100 nm and a resistivity of about 2 × 10 ^{-4} Ωcm was obtained. A 3- inch diameter ZnO target containing 2 wt% Ga_2O_3 was used. RF magnetron sputtering was carried out with RF power of 200 W, gas flow rate of 20 sccm, operating Ar pressure of 1 Pa, with changing target-substrate distance to 55, 40, 30, 20 mm. A glass substrate with a length of 50 mm and a width of 10 mm was placed radially from just under the center of the magnetron on the substrate holder facing the target and radial spatial distribution of film thickness and film quality was investigated at intervals of 10 mm radially from the center. Film thickness and resistivity were measured using a stylus profilometer and a four-point probe resistance meter. In addition, carrier density and mobility were investigated with Hall effect measurement system and crystallinity was investigated using XRD. The shorter the distance between the target and the substrate, the thicker the film thickness at the central part, but the film thickness at the peripheral part decreased due to the influence of the ground shield plate of the magnetron cathode. As a result, the nonuniformity of the film thickness distribution increased. On the other hand, as the distance between the target and the substrate decreased, the resistivity decreased drastically (about 3 digits at the center and about 1 digit at the periphery).