Study On Preparation And Properties Of Indium Gallium Zinc Oxide Thin Film Transistor

With the development of the size of the display and the organic light-emitting diodes(OLEDs),the traditional crystalline silicon thin film and organic thin film transistor has already can't satisfy the demand of modern useage.As the core of thin film transistor,especially modern transparent display technology,the more mainstream amorphous indium gallium zinc oxide(a-IGZO)film as the composition of the thin film transistor channel layer draws more and more attention.Due to its superior performance: high mobility,good homogeneity,low preparation temperature and permeability,good optical,it was selected as the next generation of the mainstream of the transistor channel layer material.In order to get good performance of the thin film transistor,this thesis points the following sections discuss in a-IGZO channel layer of the preparation and properties of the thin film transistor.By using the method of magnetron sputtering at room temperature for Ultra high Vacuum(Ultra-high Vacuum),we prepared a series of IGZO thin film of different oxygen partial pressure and supttering power.Then the thin film was characterized by many equipments.XRD results show that the thin films prepared under different oxygen partial pressure at room temperature was amorphous.And the transmittance in the visible band of the films was above 80%.Moreover,the thin films prepared with pure Ar had a band gap of 3.20 eV and those with 10% oxygen content had a band gap of 3.47 eV.We also succeeded modulating the resistivity of the thin film from 10-4-106(?·cm)and the carrier concentration from 1019 down to 1011(cm-3)simply through oxygen content during sputtering.We fabricated top-contact/bottom gate thin film transistor with “FTO-HfO2-IGZO-Al” structure and then deep research was conducted to realise the relation between the TFT performance and the IGZO thin film of different oxygen content.Results manifest the TFTs with 10% oygen content IGZO have a lower off current ~10-9A,higher mobility ~10.4cm2/V·s,threshold voltage nearly 0V.We also compared the effect of different channel length/width ratio on TFT performance and then we found that adopting the method of “Shadow Mask” when sputtering channel structure can reduce the effect of electric field on the channel around the edge of the source/drain.Meanwhile,we compared the different materials of Cu/Al/ITO as the electrode of the TFTs.The results indicated that Al/ITO are the best choice to IGZO thin film transistors.At the same time,we use a double-layer IGZO structure to boost up the performance of the TFT.By depositing a thin IGZO film layer of pure Ar under the IGZO monolayer which was deposited with 10% oxygen content and we studied the effect of the new layer on the overall device.Experiments show that the semiconductor with double-layer IGZO structure has an excellent performance: on current up to 1.3mA?mobility up to 54 cm2/V·s?threshold voltage 0.4V and current on/off ratio 106.