SPUTTERED INDIUM-GALLIUM-ZINC-OXIDE (IGZO) FILM FOR ELECTRONIC AND PHOTONIC DEVICES: MATERIAL ASSESSMENT, DEVICE FABRICATION AND CHARACTERIZATION

Abstract

Indium-Gallium-Zinc-Oxide (IGZO) is an excellent amorphous oxide semiconductor (AOS) candidate which is being actively explored as an alternative material for fabrication of thin film transistor (TFT) array in backplane of flat panel displays. The thesis aims to address material and device aspects of IGZO which was deposited through sputtering and subsequently cured with post deposition anneal (PDA) depending on the specific need of improvement of electrical/optical characteristics of device. The first part of the thesis deals with material aspects of sputter deposited IGZO film that impact its electrical behavior. In this regard, we assessed breakdown (BD) characteristics of sputtered and PDA IGZO films within the framework of E-field model and characterized time dependent dielectric breakdown (TDDB) of films. It was observed that, safe field for ten years projected time to fail (TTF) had been remarkably increased while as-deposited IGZO film received ozone (O3) anneal treatment, and the improvement had been explained using XPS correlation. However, PDA can also impact traps in IGZO film which degrade low field current, as indeed was the case with O3 recipe. Thus, detailing the trap states was made subsequently using random telegraph noise (RTN) measurements conducted on PDA – IGZO (Al/IGZO/Al) capacitors and space-energy distributions of process induced traps were extracted. We found that, PDA with O3 impacts shallower trap states near the conduction band (CB) edge of IGZO, whereby significant shallower trap states were found in as-deposited samples as well which eventually degrade low field current as we found from measurements conducted on IGZO capacitors. In the second part, we have designed and fabricated a Schottky diode based IGZO vertical current driver that can potentially eliminate the roadblock of large footprint mandate of conventional planar TFT drivers. The driver was found to preserve its electrical characteristics even under long hour bias-temperature stressing. From data storage point of view employing a gradient O3 anneal scheme an IGZO based eight-level multi-level/cell resistive random access memory (MLC-ReRAM) was fabricated furthermore, and resistance variability effect between the levels was examined. We found that, variable duration of O3 anneal could reduce high resistance state (HRS) leakage of memory and significantly improve its on to the off ratio as suitable for MLC-ReRAM. Finally, to assess IGZO as a material for photonic devices, we demonstrated an IGZO based solar blind deep UV (<280 nm) MSM photodetector, spectral response (SR) of which was tailored by sputter deposition of films in diluted O2 and PDA.