Mist CVD Modulated High-κ a-Al_1-xTi_xO_y Films for p-WS_0.3Se_1.7-Channel Metal Oxide Field Effect Transistors (MOSFETs)

When and Where

Nov 28, 2023
8:00pm - 10:00pm

Hynes, Level 1, Hall A

Presenter

Abdul Kuddus

Kojun Yokoyama

Shinichiro Mouri

Keiji Ueno

Hajime Shirai

Co-Author(s)

Abdul Kuddus¹,Kojun Yokoyama²,Shinichiro Mouri¹,Keiji Ueno²,Hajime Shirai²

Ritsumeikan University¹,Saitama University²

Abstract

Abdul Kuddus¹,Kojun Yokoyama²,Shinichiro Mouri¹,Keiji Ueno²,Hajime Shirai²

Ritsumeikan University¹,Saitama University²

Introduction: High-κ amorphous (a)-AlOx, and a-TiO2 thin films from Al(acac)3 and Ti(acac)2OiPr2 precursors dissolved in alcohol solvent investigated by mist CVD method in our previous reports [1,2]. In addition, the AlOx, and TiO2 alloy of a-Al1-xTixOy (ATO) films revealed an adjustable dielectric constant of 6.23-25.12 and band gap of 4.25-6.38 eV studied. Further, an exfoliated MoSe2-channel MOSFET on Al0.74Ti0.26Oy thin film as gate insulator with Au as the source and drain electrodes showed a mobility of 85 cm2/Vs, the threshold voltage of 0.92 V, and an on/off current ratio of 108 [3]. However, a consistent fabrication of TMDCs such as MoS2, MoSe2, and WS2, WSe2, or their alloys such as WS2-xSex film and the high-κ dielectric is highly promising toward large-scale device fabrication. To date, the synthesis of high-quality defect-free large-area TMDCs films and transfer-free device fabrication are major hindrances to further advancing in TMDCs-based devices technology. In this study, we investigated a consistent fabrication technique of metal oxide and TMDCs films as high-κ dielectric and channel layers in MOSFETs toward transfer-free large-scale TMDCs device fabrications. Experiment: A 0.015 M Al(acac)3 and Ti(acac)2OiPr2 solution with CH3OH dilution was placed directly above a 3 MHz atomizer, N2 was used as a generator, and dilution gas (500 and 2400 sccm) was used to transport the mist. A cleaned Si substrate was placed 16 cm inside the tube furnace in the open air. On the other hand, ammonium tetrathiotungstate (NH4)2WS4 dissolved in N-methyl-2-pyrrolidone (NMP) solvent was used as a precursor of WS2-xSex. The WS2-xSex films were synthesized by mist CVD with Ar gas containing H2 (25%) at a Tf of 400-600 °C at atmospheric pressure. Subsequent selenization of mist CVD WSx was executed to further improve the flake's quality at Tf of 600 °C for 20 min. The p-WS2-xSex channel MOSFETs on ATO dielectric were fabricated with Pt source and drain electrodes [4]. Results and Discussion: The deposition rates were found of 11 nm/min for Al0.74Ti0.26Oy with an adjustable dielectric constant of 6.23-25.12 and band gap of 4.25-6.38 eV. While, an average flake size of over 700-800 µm on ATO substrate. the mobility over 40 cm2/Vs, the threshold voltage around 0.30 V, and an on/off current ratio in the range of 106 were obtained in p-WS0.3Se1.7-channel MOSFETs on ATO dielectric retaining reduced leakage current. Thus, a strong potential is revealed by the mist CVD to be used as a consistent manufacturing process for the fabrication of metal oxides and TMDCs films as high-κ dielectric and channel layers in MOSFETs toward transfer-free, large-scale TMDCs device technology. References [1] A. Rajib ACS Appl. Electron. Mater. 3, 2, 658-667 (2021). [2] A. Rajib et al., J. Appl. Phys. 131, 105301 (2022). [3] K Yokoyama et al., ACS Appl. Electron. Mater. 4, 5, 2516–2524 (2022). [4] A. Kuddus et al., Semicond. Sci. Technol. 37 095020 (2022).