Pulsed liquid-injection MOCVD of high-K oxides for advanced semiconductor technologies

Abstract

HfO 2 and SrTiO 3 films were grown on silicon by liquid injection metal organic chemical vapour deposition. The microstructure and structure of the films were characterised by X-ray and electron diffraction, X-ray reflectometry, infrared spectroscopy, and microscopy techniques. In both cases, we emphasised the role of precursors in the resulting composition and microstructure of the films. Dense films of HfO 2 , either amorphous or crystalline depending on the deposition temperature, were synthesised using Hf(O t Bu) 2 (mmp) 2 precursor. Permittivity values of 14-19 were obtained, consistent with the monoclinic structure determined from X-ray diffraction. Optimised films exhibit breakdown field of6MVcm −1 and leakage current densities as low as 10 −8 Acm −2 at 1 V.Polycrystalline SrTiO 3 films were grown using either a mixture of precursors or a heterometallic precursor. The heterometallic precursor provides some advantages such as a lowering of the crystallisation temperature of the perovskite-type phase and a reduction of carbonate impurities at low temperatures. It also allows to keep the films composition constant over a wide temperature range (550-750 • C). The films are highly textured with [0 0 1] SrTiO 3 parallel to [0 0 1] Si . The permittivity depends strongly on the films thickness (ε r ∼ 30 for 10 nm and ε r ∼ 100 for 100 nm). An equivalent oxide thickness of 1.36 nm (for physical thickness of 15.0 nm) was obtained for optimised SrTiO 3 film, with a leakage current density of 10 −2 Acm −2 at 1 V.

Study of interfacial reactions and phase stabilization of mixed Sc, Dy, Hf high-k oxides by attenuated total reflectance infrared spectroscopy

“…Theory predicts this doublet to be situated at 780/694 cm À1 and 683/634 cm À1 [4], and it has been ascribed experimentally to peaks at 760 cm À1 [7] or 752 and 635 cm À1 [16,22,23]. Based on the presence of this vibration around 780 cm À1 in the spectra of HfO 2 films of all thicknesses studied, it can be concluded that all of these films contain monoclinic HfO 2 .…”

Growth by Liquid‐Injection MOCVD and Properties of HfO2 Films for Microelectronic Applications

“…For crystallized films, the structure is monoclinic, as shown by XRD. Since diffraction is performed on relatively thick samples (>30 nm), the structure was also confirmed by electron diffraction on thin films [15] and by infrared spectroscopy (see discussion below).…”

“…From X-ray diffraction (XRD) data, the films are amorphous at 350°C and below, and polycrystalline at temperatures higher than 360°C. However, at 350°C, nanocrystallites are observed on the TEM plane views [15] of 5 nm films. For crystallized films, the structure is monoclinic, as shown by XRD.…”

“…However, we recently showed that amorphous films prepared from Hf(O t Bu) 4 exhibited a porous microstructure (as evidenced by transmission electron microscopy (TEM)), not seen with other precursors. [15] The 4 ). [16][17][18][19][20][21][22][23] These precursors present the advantage of containing no oxygen; however, they are so sensitive to air and humidity that they are very difficult to handle.…”

“…Hf(O t Bu) 2 -(dmae) 2 (prepared by Epichem Oxides and Nitrides) has been recently tested, but is was shown that its poor volatility led to precursor accumulation in the source. [15] The ligand 1-methoxy-2-methyl-2-propanolate (written as mmp with formula OCMe 2 CH 2 OMe) has been also proposed for the synthesis of Hf(O t Bu) 2 (mmp) 2 , [24] which has been successfully used for MOCVD [15,21,[25][26] and ALD [27] of HfO 2 . Finally, Hf(mmp) 4 has also proven to be a suitable precursor for HfO 2 deposition.…”