Enhanced Performance of MOCVD ZnO TFTs on Glass Substrates with Nitrogen-Rich Silicon Nitride Gate Dielectric

Abstract

Thin-film transistors ͑TFTs͒ on glass substrates were fabricated using ZnO, grown by a metallorganic chemical vapor deposition ͑MOCVD͒ technique, with N-and Si-rich silicon nitrides as gate dielectrics. This is a report on MOCVD-grown ZnO TFTs that use silicon nitride as gate dielectrics. The ZnO TFTs using N-rich silicon nitride exhibited a field-effect mobility of 6.5 cm 2 /V s, a subthreshold slope of 0.8 V/decade, an on/off current ratio of 10 8 , and a threshold voltage of 2.05 V. The performance of these TFTs is better than that of TFTs employing Si-rich silicon nitride. This enhanced device performance can be attributed to a larger average grain size of 126 nm observed in the ZnO film grown on the N-rich silicon nitride compared to an average grain size of 69 nm for the ZnO film grown on Si-rich silicon nitride.

Synthesis and characterization of sol–gel derived gallium-doped zinc oxide thin films

“…Polycrystalline ZnO-based semiconductor thin films have higher carrier mobility, greater chemical stability, and lower photosensitivity levels than conventional hydrogenated amorphous silicon (a-Si:H) thin films. Therefore, they can replace a-Si:H thin films as the active channel layers in TFTs to improve electrical performance [6][7][8][9][10]. Recently, it has also been demonstrated that they can be used in transparent memory [11,12].…”

Electrical properties of amorphous-Al2O3/single-crystal ZnO heterointerfaces

“…It has attracted considerable attentions as channel layers for metal-insulator-semiconductor field effect transistors (MISFETs). [7][8][9][10][11][12][13][14] Recently, high-quality single crystalline ZnO wafers grown by a hydrothermal method have been commercially available, 15 which enables us to fabricate ZnO-based MISFETs with excellent electrical properties.…”

High Field-Effect Mobility Bottom-Gated Metallorganic Chemical Vapor Deposition ZnO Thin-Film Transistors with SiO[sub 2]∕Si[sub 3]N[sub 4] Bilayer Gate Dielectric

“…21,22 This explanation is consistent with our previously published result that the grain size of ZnO films grown on the Si-rich Si 3 N 4 layer is smaller than that of the films grown on the N-rich Si 3 N 4 layer. 8 This is due to the fact that Si-rich Si 3 N 4 films have higher density of Si dangling bonds in comparison with N-rich Si 3 N 4 films. 19,23 Characteristics of ZnO TFTs with SiO 2 /Si 3 N 4 bilayer gate dielectric.- Figure 3a shows the output characteristics ͑drain current ͑I D ͒ versus drain-source voltage ͑V DS ͒͒ of ZnO TFTs using the SiO 2 /Si 3 N 4 bilayer gate dielectric for a gate-source voltage ͑V GS ͒ ranging from 15 to 0 V in steps of −5 V. These devices exhibit clear pinch-off and saturation behaviors.…”

“…Due to the increasing interest in the ZnO TFTs, various techniques, including molecular beam epitaxy, 1 sputtering, 2,3 pulsed laser deposition, 4 atomic layer deposition, 5 and metallorganic chemical vapor deposition [6][7][8] ͑MOCVD͒, are under investigation to realize ZnO channel layer of the TFTs. Among them, MOCVD has certain advantages, such as good reproducibility, capability of uniformly fabricating thin films of high quality, and the possibility of scaling up the process to commercial base production.…”

“…These devices employed a SiO 2 gate insulator, but this material was thermally grown and therefore not suitable for glass substrates. Very recently, we have reported MOCVD grown bottom-gated ZnO TFTs with a silicon nitride gate dielectric, 8 exhibiting a FE of 6.5 cm 2 /V s and an on/off current ratio of 10 8 . For device applications of MOCVD grown ZnO TFTs, FE is one of the parameters which required improvement and higher values of FE are highly desirable.…”