Volatile Guanidinato-based Metalorganic Precursors for Ald Process

Film properties of TaN-based metal (TaCN and TaSiN) have been precisely controlled for plasma enhanced ALD (PEALD) and thermal ALD with additives of N2 or NH3. Film resistivity (ρ) strongly depended on the nitrogen concentration of TaN-based metal. These films showed conformal step-coverage for high-aspect (>6) 50nm-wide trenches. Consequently, ALD TaN-based metal is promising for microelectronic applications such as resistor of RF devices, electrode of high-k MIM capacitors, and Cu barrier metal. Experiment: TaN-based films were deposited on thermally oxidized Si wafer with Eagle12 reactor. The precursor for PEALD TaCN was metal organic precursor, Taimata (Ta(N-t-C5H11)[N(CH3)3]3 ) and RF plasma was generated between shower head and substrate stage using H2 gas. RF power was fixed at 300W or 400W. The precursors for thermal ALD TaSiN were TaF5 and TSA (Trisilylamine). The substrate temperature was fixed at 300C. Nitrogen was added during PEALD process and NH3 gas cycle in thermal ALD process. Result and Discussion: The film properties without using additive gases were shown in Table 1. For PEALD TaCN films, ρ became lower with the higher RF power and the longer RF time. The ρ value saturated as low as 200 μΩcm with RF 400W for 2sec. The N concentration in film was relatively low so that ρ was almost same as that of beta-phase Ta. Thermal ALD TaSiN process showed self-limiting growth and ρ saturated at around 500μΩcm. For PEALD TaCN film, ρ increased with N2 flow rate (Fig. 1). The resistivity increased with higher RF power and longer RF time. The film step-coverage factor became relatively the smaller as ρ became the higher. In the case of thermal ALD TaSiN, dielectric-like Ta2N3 film was formed when only TaF5 and NH3 precursors were used. We added NH3 once every several TaF5/TSA cycles. The ρ value increased with increasing additive NH3 cycle time (Fig.2), while the film step-coverage factor was still high (Fig.3). Conclusion: TaN-based film resistivity could be precisely controlled from 200 to 15000μΩcm by ALD with nitrogen or NH3 additives. 1)D.Jeong, S.Ozawa, H.Inoue, A.Tashiro A.Shimizu, and H.Shinriki, proceedings of Advanced Metallization 2007. 2)W.Li, E.Tois, R.Matero, R.Huggare, S.Haukka and M.Tuominen, 16 Europian Conference on Chemical Vapor Deposition— Book of Extended Abstract, 2007. Table 1. Film property Ta Precursor Precursor Composition Low Resistivity Density Depo Rate PEALD Taimata H2 plasma TaCN=56:25:4 200 μΩcm 13 g/cm 0.5 Å/cycle ALD TaF5 TSA TaSiN=50:18:30 2) 500μΩcm 10 g/cm 2.8 Å/cycle Fig.3 Cross section of AR 6 Trench TaN deposited thetmal ALD with NH3 cycle. Fig.2 NH3 cycle ratio dependence of resistivity of thermal ALD film. Fig.1 N2 flow rarte dependence of resistivity of PEALD film. Organic-inorganic hybrid thin films containing unsaturated carboxylic acids by ALD K. B. Klepper, O. Nilsen, and H. Fjellvåg University of Oslo, Department of Chemistry, Centre for Materials Science and Nanotechnology, P.O. Box 1033 Blindern, N-0315 Oslo, Norway [email protected] Ongoing research on unsaturated carboxylic acids combined with both TMA (TMA = trimethylaluminium) and TiCl4 (titaniumtetrachloride) shows promising results. The systems investigated so far show ALD-type growth. The maleic acid (HOOCCH=CHCOOH) – TMA-system is such an example. Growth rate as function of deposition temperature of the system, and an atomic force microscopy (AFM) image of the surface deposited at 186 °C is shown in Fig. 1. A surface roughness (RMS) of 0.23 nm is measured for a film with a thickness of 81.4 nm when deposited at 186 °C using 150 cycles. The low surface roughness corresponds well with the results obtained by X-ray diffraction, which reveales that the as-deposited films are x-ray amorphous. In-situ analysis by quarts crystal microbalance have been used to establish growth parameters for the systems. Growth rates as function of deposition temperature are established using X-ray reflectometry. As-deposited films have been investigated by infrared spectroscopy, atomic force microscopy, and Xray diffraction. Fig.1: Growth rates as function of deposition temperature of the maleic acid – TMA-system, and an AFM image of the surface of a 81.4 nm thick film deposited at 186 °C. Improvement of Vth and Device Performance of HfSiON/Metal Gate-First n-MOSFETs by using an ALD-La2O3 Capping Layer Satoshi Kamiyama, Dai Ishikawa, Etsuo Kurosawa, Hiroyuki Nakata, Masashi Kitajima, Minoru Ootuka, Takayuki Aoyama, and Yasuo Nara Research Dept.1, Semiconductor Leading Edge Technologies (Selete), Inc. 16-1, Onogawa, Tsukuba, Ibaraki 305-8569, Japan (e-mail : [email protected]) HfSiON films are the most promising of the high-k gate dielectrics for scaled devices. Recently, HfSiON/metal gate with La2O3 capping layers have been reported to improve Vth control [1-3]. However these are still challenging technologies to apply to real devices due to the increased EOT and degraded carrier mobility. In this study, we have investigated the effect of the La2O3 capping layers on Vth-control and device performance of HfSiON/metal gate-first stacks with TaSiN gate electrode materials. Furthermore, Vth can be effectively controlled by post-deposition-annealing (PDA) temperature with excellent uniformity over 300 mm wafers. The EOT ranges are applicable to hp 32 nm metal gated bulk devices and these devices are demonstrated to exhibit high performance and reliability. A La(i-PrCp)3 precursor was used for ALD-La2O3 film formation because the melting point (~38 C) is the lowest of the typical La precursors [3]. La2O3 films were deposited for Vth-control capping layers on HfSiON based films with La(i-PrCp)3 and O3 at 250 C. Following La2O3 capping layer deposition, these samples were annealed in N2 as PDA. TaSiN(30 nm)/ W(50 nm) gate electrodes were deposited by PVD. After SiN hard mask formation, metal gate stacks were formed using dry etching. Dopants were activated using spike-RTA at 950 C . Fig. 1 shows the dependence of Vth on the number of ALD-La2O3 cycles for HfSiON/TaSiN gate stacks. Thickness of HfSiON based films were formed from 1.4 nm to 2.5 nm. The value of Vth clearly becomes more negative with the increasing number of ALD cycles and Vths are dependent on the HfSiON thickness. PDA at 1050C caused La diffusion into the HfSiON/SiON gate stack by SIMS analyses, forming La-O bonds at the Hf(La)SiON/Si(La)ON interface and increasing the dielectric constant. It is thought that the number of La-O bonds is greater than the number of Hf-O bonds for thick capping layers, so that the shift in VFB is changed by La2O3 and HfSiON film thickness. As shown in Fig. 2, the Id-Vg curves clearly shift to more negative values as the number of ALD cycles increases, Vth can be effectively controlled by the number of cycles. The sub-threshold swing, S, for all samples is good, being less than 75 mV /decade. The drain current (Id) at Vg= +1.1 V improve dramatically with the increasing number of ALD cycles that of capped gate stacks being more than 1.5 times that of uncapped gate stacks. In Fig. 3, Vth can be effectively controlled by PDA temperature and the Vth distributions of HfSiON/TaSiN gate stacks are seen to be very tight over 300 mm wafers, both with and w/o ALD-La2O3 cap layers. The leakage current densities are reduced further with the increasing number of ALD cycles. EOTs and gate leakage current densities clearly meet the criteria for hp 32 nm metal gate bulk devices in ITRS 2006 [4]. Furthermore, the positive-bias -temperatureinstability (PBTI) over a 10-year lifetime can be held to an acceptably low level at Vg= +1.0 V. 1) H. N. Alshareef, et. al, Symp. VLSI Tech., p. 10, 2006 2) P. Sivasubramani. et. al., Symp. VLSI Tech., p. 68, 2007 3) S. Kamiyama, et. al., Tech. Dig, IEDM, p.539, 2007 4) International Technology Roadmap for Semiconductors, 2006 Fig.1 Dependence of Vth on the number of ALD-La2O3 cycles for HfSiON/TaSiN gate stacks. Fig.2 Sub-threshold characteristics of HfSiON/TaSiN gate stacks with ALD-La2O3 capping layers. Fig.3 Dependence of Vth distribution on PDA temperature for HfSiON(1.4 nm)/TaSiN gate stacks with La2O3 capping layers. .01 .1 1 5 20 50 80 95 99 99.9 99.99 -0.2 0.0 0.2 0.4 0.6 Vth (V) D is tr ib ut io n (% ) 0 cycle 105