Abstract

The films of GdScO 3 were prepared by liquid injection metal-organic chemical vapor deposition, MOCVD at 600 • C on (100) Si substrate. The as-deposited films were amorphous with a smooth surface and sharp GdScO 3 /Si interface. X-ray diffraction showed that the amorphous phase is well preserved upon rapid thermal annealing up to 1000 • C . It is shown, that exact stoichiometry of GdScO 3 is not necessary to achieve dielectric constant above 20. K e y w o r d s: CMOS technology, gate dielectric, high-κ , X-ray diffraction, X-ray reflectivity INTROUCTION GdScO 3 thin films attracted recently attention as promising candidate for next generation of high-κ dielectrics in CMOS technology. Hf-based dielectrics, that are currently implemented in a production, suffer either from low recrystallization temperature (∼ 500 • C for pure HfO 2 ) or from lowering of dielectric constant when introducing Si to enhance amorphous phase stability (κ ∼ 14 ÷ 16 for HfSiO , depending on Si content). It is desirable that gate dielectric retains its amorphous structure during transistor processing and remains stable upon source/drain activation step and/or postmetallization annealing in reduction atmosphere. The GdScO 3 films were prepared by pulsed laser deposition, PLD [1], electron beam evaporation [2], atomic layer deposition, ALD • C annealing [1, 2]. However, before introducing the GdScO 3 thin films into CMOS technology, their properties should be thoroughly analysed and advantages over HfO 2 based dielectrics clearly identified. In our contribution we present properties of GdScO 3 films prepared by liquid injection metal organic chemical vapor deposition. We describe dielectric properties and stability of the amorphous phase against recrystallization. Finally, appropriatness of GdScO 3 films as a next candidate for alternative gate dielectric is discussed. EXPERIMENTAL METHODS The GdScO 3 films were deposited at 600 • C in a low-pressure hot-wall quartz reactor. The solution of Gd(thd) 3 and Sc(thd) 3 precursors dissolved in toluene in a concentration of 0.02 M was introduced using computer controlled microvalve into the evaporation part heated at 250 • C. Opening time of the micro valve was 3 ms, resulting in the droplet mass of 5.7 mg. The reaction atmosphere was composed of O 2 (170 sccm flow) and Ar (21 sccm flow) with a total pressure of 200 Pa. Injection frequency was 0.33 Hz. Employing these parameters the film growth rate was adjusted to 0.8 nm/min. Si (100) oriented wafer slices were used as substrates. The substrates were cleaned in acetone, isopropyl alcohol and dipped in buffered HF before the deposition. Composition of the films was varied by changing ratio of Gd(thd) 3 /Sc(thd) 3 in a solution and verified by Rutherford backscattering. Backscattering spectrometry measurements were performed using 4 He + ions with energy E = 1.22 MeV. Phase composition of the films was determined by grazing incidence X-ray diffraction using incidence angle of 1 deg. Surface and GdScO 3 /Si interface quality was probed by X-ray reflectivity. The X-ray reflectivity was used to extract the thickness of the film. Both measurements were performed on Bruker AXS-D8 DISCOVER diffractometer using Cu Kα radiation. The films thicknesses determined by X-ray reflectivity were in good agreement with those obtained by Rutherford backscattering. Dielectric constant of the GdScO 3 films was determined from capacitance-voltage measurements performed at the frequency of 1 MHz. For the capacitancevoltage measurement Ru films were deposited as gate electrodes by liquid injection MOCVD at 300 • C . The