Effects of Structure and Sputtering Parameters on the Device Properties of Tin-Oxide Thin-Film Transistors

We investigated the device properties of sputter-deposited tin-oxide (SnO) thin-film transistors (TFTs) in which the SnO (x) active layers were deposited by using a SnO sputtering target. The developed SnO-TFTs had a bottom-gate staggered or coplanar structure, which used a heavilydoped Si wafer as a gate electrode and 300-nm-thick SiO2 as a gate dielectric layer. The TFTs with SnO (x) thin-films deposited using a high radio-frequency (RF) power of 100 W, a very high working pressure of 20 mTorr, and an oxygen ratio of 0% revealed n-type characteristics. The coplanar SnOxbased TFTs showed better n-type characteristics than the staggered ones, which was attributed to the good quality of the sputtered damage-free SnO (x) films. On the other hand, the staggered TFTs with SnO (x) deposited at a low RF power of 50 W, a low working pressure of 4 mTorr, and an oxygen ratio of 12% exhibited p-type characteristics, which included an onset voltage (V (on) ) of-1.5 V, a saturated hole mobility of 39 cm(2)/Vs at gate-to-source voltage (V (GS) ) = -10 V, a sub-threshold swing of 1 V/decade at V (GS) - V (on) = -0.5 V, and an on/off ratio of 1.1 x 10(2). We believe that our results can contribute to the development of p-type SnO-based TFTs with good performance.