Evaluation of lanthanum based gate dielectrics deposited by atomic layer deposition

Abstract

Articles you may be interested inElectrical behavior of atomic layer deposited high quality SiO2 gate dielectric Atomic layer deposition grown metal-insulator-metal capacitors with RuO 2 electrodes and Al-doped rutile TiO 2 dielectric layer J. Vac. Sci. Technol. B 29, 01AC09 (2011); 10.1116/1.3534023 Lanthanum aluminate by atomic layer deposition and molecular beam epitaxyIn this article, we evaluated physical and electrical characteristics of La-based gate dielectrics ͑La 2 O 3 and LaAl x O y ͒ deposited by atomic layer deposition ͑ALD͒. The precursors used for La 2 O 3 and LaAl x O y are lanthanum tris͓bis͑trimethylsilyl͒amide͔ La͓N͑SiMe 3 ͒ 2 ͔ 3 , trimethyl aluminum ͓Al͑CH 3 ͒ 3 ͔, and water. Physical properties of these dielectric films were studied using ellipsometry, x-ray photoelectron spectroscopy ͑XPS͒, and transmission electron microscopy ͑TEM͒. To investigate electrical properties of these La-based dielectrics, metal oxide semiconductor capacitors ͑MOSCAPs͒ were fabricated using metal gates ͑Ta-Si-N, TiN and Pt͒. Linear growth rate characteristics were observed for ALD ͑La 2 O 3 and LaAl x O y films deposited at temperatures of 225 to 275°C. XPS and XTEM analysis of La-based films grown on a chemical oxide starting surface revealed a rough La-based dielectric/Si interface and chemical interaction with the Si substrate. In general, adding Al into La 2 O 3 improved electrical properties of the films. Devices with La based dielectric deposited on a ϳ10 Å Al 2 O 3 underlayer had better capacitance-voltage characteristics compared to those deposited directly on a chemical oxide surface. Adding Al to the dielectric also resulted in lower leakage current and smaller hysteresis. For devices with Ta-Si-N gates, a significant decrease in maximum capacitances was observed after forming gas annealing, probably due to interaction between the gate electrode and the dielectric. XTEM images for these devices indicated an indistinct interface between the Ta-Si-N gate and the La-based dielectrics. The XTEM images also showed microcrystals in Ta-Si-N that may be formed in Si deficient regions of the metal gate. No interaction between TiN or Pt with La gate dielectrics was observed by XTEM up to 800°C annealing temperature. After 900°C annealing, some interaction between LaAl x O y and Pt gate was observed. Our results indicated that silicon substrate interactions may limit the utilization of ALD La based dielectrics in future complementary metal-oxide semiconductor processing.

Atomic Layer Deposition and Properties of Lanthanum Oxide and Lanthanum‐Aluminum Oxide Films

“…[54] On the other hand, the leakage current densities in La x Al y O z films are lower than in pure La 2 O 3 films. [36] As expected, the Al-rich films in this study (Fig. 8) demonstrated lower leakage current densities than La-rich La x Al y O z [36] or LaAlO 3 films.…”

“…[36] As expected, the Al-rich films in this study (Fig. 8) demonstrated lower leakage current densities than La-rich La x Al y O z [36] or LaAlO 3 films. [10] However, for the LaAlO 3 films deposited by molecular beam, permittivity values as high as 25 were achieved, probably due to higher purity compared to ALD or CVD films.…”

“…The saturation of the growth rate at higher pulse-length values would be an indication of the achievement of the self-limiting growth regime. In another study, [36] case of the shorter pulses. The refractive-index value was insignificantly affected by the La[N(SiMe 3 ) 2 ] 3 pulse length.…”

“…[7,35] Below 275°C, only [1,4] and also for the ALD of La-rich La x Al y O z films. [36] The results have revealed that amorphous La 2 O 3 grows at 250°C [1] and 275°C [4] on a silicon substrate, and the stoichiometry of resulting films was that of the La 2 O 3 , although considerable contribution from silicon was observed as well. Stoichiometric LaAlO 3 has been obtained using tris(N,N′-diisopropylacetamidinato)lanthanum, La( i PrAMD) 3 , and water as La and oxygen precursors, respectively, in the growth temperature range 300-330°C.…”

“…[11,27] LaAlO 3 films can be processed by various techniques, such as molecular-beam epitaxy (MBE), [11,24,26,28] pulsed laser deposition, [27,29] magnetron sputtering, [15] or using 158 chemical methods such as alkoxide-based sol-gel chemistry, [16] thermolysis of hydrated nitrates, [18,23] gelation-precipitation techniques, [30] or metal-organic (MO) CVD. [8,[31][32][33] More recently, atomic layer deposition (ALD) has been examined as a low-temperature growth technique for synthesizing La 2 O 3 and LaAlO 3 films [1,4,7,[34][35][36] The lanthanum b-diketonate La(thd) 3 (thd = 2,2,6,6-tetramethyl-3,5 heptanedione) has been examined as a lanthanum precursor, [7,35] with ozone as an oxygen precursor, resulting in the growth of cubic La 2 O 3 at 300-350°C and higher temperatures. [7,35] Below 275°C, only [1,4] and also for the ALD of La-rich La x Al y O z films.…”