Description:
We studied nitrogen (N) incorporation effects on the electrical characteristics of silicon dioxide (SiO2) fabricated by plasma-enhanced atomic layer deposition (PEALD). To determine whether N could be incorporated into the SiO2, the oxygen (O2) or nitrous oxide (N2O) plasma were used during the SiO2 deposition. In addition, the N2O plasma power was controlled to 100, 150, and 200 W. All the SiO2 films fabricated using the N2O plasma reactant show reduced soft breakdown phenomena. Furthermore, compared to the O2 plasma reactant, the hard breakdown is improved by 27.5% as N2O plasma power increases up to 150 W, whereas it is degraded at a N2O plasma power of 200 W. These results are found to describe the relationship between the N content and film properties. The N content in the SiO2 films fabricated using increasing N2O plasma power of 100, 150, and 200 W gradually increased as 0.2, 0.4, and 0.5%, respectively. However, the N2O plasma power of 200 W results in increased O deficient Si bonding. To investigate the effects of continuous plasma exposure at the bottom layer during the SiO2 deposition, we fabricated indium-zinc oxide (IZO) top-gate bottom-contact (TGBC) thin film transistors (TFTs) using the SiO2 as a gate insulator (G.I). The plasma conditions for G.I deposition are as follows: i) O2 plasma with 100 W power (device A), ii) N2O plasma with 100 W power (device B), iii) N2O plasma with 150 W power (device C), and iv) N2O plasma with 200 W power (device D). The device A shows loose switching characteristics, whereas the positive threshold voltage (VTH) shifts and decreases the field effect mobility (µFE) from the device B to D. The device C shows the optimal positive/negative bias temperature stress (P/NBTS) results, with VTH variations of 0.0 and -0.3 V, respectively