Solution-Processed Rare-Earth Oxide Thin Films for Alternative Gate Dielectric Application

Abstract

Previous investigations on rare-earth oxides (REOs) reveal their high possibility as dielectric films in electronic devices, while complicated physical methods impede their developments and applications. Herein, we report a facile route to fabricate 16 REOs thin insulating films through a general solution process and their applications in low-voltage thin-film transistors as dielectrics. The formation and properties of REOs thin films are analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), spectroscopic ellipsometry, water contact angle measurement, X-ray photoemission spectroscopy (XPS), and electrical characterizations, respectively. Ultrasmooth, amorphous, and hydrophilic REO films with thickness around 10 nm have been obtained through a combined spin-coating and postannealing method. The compositional analysis results reveal the formation of RE hydrocarbonates on the surface and silicates at the interface of REOs films annealed on Si substrate. The dielectric properties of REO films are investigated by characterizing capacitors with a Si/LnO/Au (Ln = La, Gd, and Er) structure. The observed low leakage current densities and large areal capacitances indicate these REO films can be employed as alternative gate dielectrics in transistors. Thus, we have successfully fabricated a series of low-voltage organic thin-film transistors based on such sol-gel derived REO films to demonstrate their application in electronics. The optimization of REOs dielectrics in transistors through further surface modification has also been studied. The current study provides a simple solution process approach to fabricate varieties of REOs insulating films, and the results reveal their promising applications as alternative gate dielectrics in thin-film transistors.

Solution Processed Metal Oxide High‐κ Dielectrics for Emerging Transistors and Circuits

“…Large Δ G means increased system energy, which will tend to suppress moisture absorption . Although the lanthanides, apart from the radioactive Pm 2 O 3 , have been demonstrated as promising alternatives, their high moisture absorption degraded electrical properties and limited their practical applications in CMOS technologies due to formation of low permittivity hydroxide . Therefore, lanthanide oxides have been excluded as high κ candidates.…”

High-κ Lanthanum Zirconium Oxide Thin Film Dielectrics from Aqueous Solution Precursors

“…In the case of gate components, incorporation of high-κ dielectrics into devices is attractive for reducing power consumption . Zirconium oxide (ZrO 2 ) − and lanthanum oxide (La 2 O 3 ) ,− are two high-κ materials (κ = 22 and 27, respectively) that have attracted interest as gate dielectric layers in MISFETs . However, ZrO 2 crystallizes at relatively low annealing temperatures (∼500 °C), which results in undesirable grain boundary formation, and La 2 O 3 suffers from water and carbonate absorption, − both of which result in increased leakage currents and poor device properties .…”

Photoinduced Charge Transfer versus Fragmentation Pathways in Lanthanum Cyclopentadienyl Complexes

“…4,5 Other applications include protective and corrosion-resistive coatings 6,7 and phosphors. 8 Metal−organic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) techniques have been employed to grow lanthanide oxide thin films using a number of precursors including lanthanide cyclopentadienyl complexes. 9−13 The high volatility of lanthanide cyclopentadienyl complexes makes them potential candidates for fabrication of lanthanide oxide thin films by laser-assisted chemical vapor deposition (LCVD), where low film deposition temperatures are allowed.…”