Atomic Layer Deposition of HfO[sub 2], TiO[sub 2], and Hf[sub x]Ti[sub 1−x]O[sub 2] Using Metal (Diethylamino) Precursors and H[sub 2]O

Abstract

Tetrakis ͑diethylamino͒ hafnium ͑TDEAH͒, tetrakis ͑diethylamino͒ titanium ͑TDEAT͒, and H 2 O were used for the atomic layer deposition ͑ALD͒ of HfO 2 , TiO 2 , and Hf x Ti 1−x O 2 films on silicon substrates. The ALD temperature windows were found to be 175-250°C for HfO 2 ͑0.12 nm/cycle͒ and 150-250°C for TiO 2 ͑ ϳ0.06 nm/cycle͒. The 175-250°C overlap region is ideal for the ALD of the Hf x Ti 1−x O 2 films. Different compositions of Hf x Ti 1−x O 2 were obtained by varying the ͓TDEAH/H 2 O͔/͓TDEAT/H 2 O͔ cycle ratios, and excellent tunability of film composition was found using X-ray photoelectron spectroscopy ͑XPS͒. The Hf x Ti 1−x O 2 deposition rate was found to be the superposition of the two individual growth rates. Both as-deposited and postdeposition annealed films were studied with XPS, phase shift interferometry, and grazing incidence X-ray diffraction. As-deposited HfO 2 and TiO 2 films were found to be amorphous, and they began to crystallize after annealing at 600°C in the monoclinic phase ͑HfO 2 ͒ and in weak anatase phase ͑TiO 2 ͒. The Hf x Ti 1−x O 2 films remained amorphous after annealing up to about 1000°C in N 2 for 5 min.Structural and interfacial studies of ultrathin, high dielectric constant ͑͒ films during high temperature fabrication processes are critical to the continuous scaling of microelectronic devices. In particular, these materials are of great importance for the gate insulator of metal oxide semiconductor field effect transistors and the capacitor dielectric of dynamic random access memories. 1,2 So far, many candidate materials such as have been studied for the replacement of SiO 2 . 3 From all these materials, HfO 2 and TiO 2 seem to be promising candidates due to their favorable properties. HfO 2 is known to have relatively good thermal stability and compatibility with the Si substrate, and it has a dielectric constant of 15-30 with a large bandgap ͑5.7 eV͒. 4-6 TiO 2 is even more favorable in terms of its dielectric constant which is 80 or higher; 7 however, it has a rather small bandgap ͑3.1 eV͒, 8 which could result in more leakage current than that of HfO 2 . The reported crystallization temperature of each of these two materials has been reported to be as low as ϳ550°C. 9,10The earliest atomic layer deposition ͑ALD͒ of HfO 2 from tetrakis ͑diethylamino͒ hafnium ͑TDEAH͒ and H 2 O was published by Deshpande et al. with a growth rate of ϳ0.13 nm/cycle at 300°C. 11 Titanium tetrachloride ͑TiCl 4 ͒ and titanium isopropoxide ͑TTIP͒ have typically been used as metal precursors in the ALD of TiO 2 films, with water being the oxidant. 12-16 Growth rates of 0.03 nm/cycle or lower in these systems were reported. Our earlier ALD studies with other homoleptic metal precursors having the diethylamino ligand, such as TDEAH and tris ͑diethylamino͒ aluminum, have resulted in broad ALD temperature windows and rather high growth rates. 9,11,17,18 Such results have prompted interest in examining the suitability of tetrakis ͑diethylamino͒ titanium ͑TDEAT͒ as a precursor for the ALD of TiO 2 ...

Atomic Layer Deposition and Characterization of Amorphous ErxTi1-xOyDielectric Ultra-Thin Films

“…The growth rate of Er 2 O 3 is found to be at least two times higher than that in earlier ALD studies using Er(thd) 3 and Er( t Bu 2 amd) 3 with O 3 as oxidant. 17,18 On the other hand, the growth rate of TiO 2 is slightly lower than that obtained in our earlier study using the same precursor and moisture as oxidant in a different ALD system, 6 but higher than that reported with other titanium precursors such as titanium isopropoxide (TTIP) and TiCl 4 , using water or even oxygen plasma as oxidant. 19,20 Such findings suggest relatively high reactivity of TDEAT with oxidants (i.e., H 2 O or O 3 ) on silicon in our ALD reactors.…”

“…2). 6,21 For MOS and memory applications, impurities (e.g., C or Cl) in gate dielectric films are undesirable; they can be incorporated during deposition and often cause degradation of electrical performance, especially because of increased electronic trap centers and defects. 22 Also, it was reported that carbon contamination could notably increase crystallization temperature of oxide films.…”

“…2,5 An attractive approach to suppress crystallization of TiO 2 is doping it with other high-κ metal oxides, such as Al 2 O 3 , HfO 2 , ZrO 2 , Ta 2 O 5 and Ln 2 O 3 , forming thermally stable amorphous high-κ ternary oxides. 2,[5][6][7][8][9] For instance, a recent study of Al-doped TiO 2 dielectric showed that the incorporation of Al could mostly result in amorphous ternary oxide throughout necessary annealing processes, thereby reducing the leakage current density of anatase TiO 2 (10 1 A/cm 2 at 0.16 MV/cm) on a TaN electrode. 2 However, it was reported that optimized AlTiO x dielectrics were found to be incompatible with Si electrodes and yielded a leakage current density of 10 −4 A/cm 2 at 0.16 MV/cm.…”

Microstructure, optical properties, and optical resonators of Hf_1-xTi_xO_2 amorphous thin films

“…Considering the index of TiO 2 is 2.4, this material may be a good candidate to fill the index gap from 1.89 to 2.4 range of silicon photonics. Several previous studies investigated the optical properties of this material for narrow concentration ranges [23,24]. A further study on the full range index tunability, optical transparency and device integration is of interest for integrated photonic applications.…”

Fabrication of Drug Eluting Ti Implants for Dental/Orthopedic Applications

“…TiO 2 can be achieved [193,[292][293][294]. Compared to ALD, CVD is a one-step mechanism and using TDEAT precursor and NH 3 as catalyst and co-reactant results in growth rate of up to 10 nm/min of TiO 2 [295].…”