Dysprosium scandate thin films as an alternate amorphous gate oxide prepared by metal-organic chemical vapor deposition

Abstract

Dysprosium scandate ͑DyScO 3 ͒ thin films were deposited on Si substrates using metal-organic chemical vapor deposition. Individual source precursors of Dy and Sc were used and deposition temperatures ranged from 480 to 700°C. Films were amorphous with low root mean square roughness ͑ഛ2 Å͒ and were stable up to 1050°C annealing. Electrical characterization yielded C-V curves with negligible hysteresis ͑Ͻ10 mV͒, high dielectric constant ͑ϳ22͒, and low leakage currents. The electrical properties of the DyScO 3 / SiO x / Si stacks were stable up to 800°C for films on native oxide; however, this limit increased to 900°C for films on special chemically grown oxide, suggesting further improvement with proper diffusion barrier. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2402121͔ Dielectric materials with sufficiently high dielectric constant ͑high k͒ are needed as early as 2007 ͑Ref. 1͒ to replace SiO 2 / SiON in the future complementary metal oxide semiconductor ͑CMOS͒ technology with a subnanometer equivalent oxide thickness. Structural invariance of the thin gate oxide layer within CMOS process thermal budget is preserved with SiO 2 ͑ = 3.9͒ and now with SiON ͑ = 7.0͒. If one considers this as a major criteria the presently favored group IVB oxides, HfO 2 and ZrO 2 , have to be alloyed with high concentrations of Si or Al in order to stabilize the amorphous structure; however, this alloying reduces the dielectric constant ͑k͒ to the values of r ϳ 10-12 ͑Ref. 2͒ for the silicates of Hf and Zr. Hence, this silicate with medium k may facilitate a smooth transition from conventional gate dielectrics to high-k dielectrics ͑k Ͼ 20͒. In order to reach this target another class of dielectrics with even higher dielectric constants and lower leakage currents is needed. Rare-earth based multicomponent oxides in the amorphous state are being considered as the next generation dielectrics after the silicates. 3 Reported work on these types of materials mainly concentrated on the pulsed laser deposition/ molecular-beam or electron beam deposition and these reports suggest a very high potential for these materials in the semiconductor industry. [4][5][6][7] An approach by atomic layer deposition of YScO 3 and metal-organic chemical vapor deposition ͑MOCVD͒ of DyScO 3 films were reported recently. 8,9 Our present effort was to realize films of the rareearth scandate, DyScO 3 , using advanced precursors in an industry friendly high throughput MOCVD process.In this work, DyScO 3 film depositions were carried out in a liquid injection MOCVD reactor ͑Aixtron 2600G3 which can handle five 6 in. wafers simultaneously equipped with a liquid delivery Trijet vaporizer͒. 10 Dy͑EDMDD͒ 3 and Sc͑EDMDD͒ 3 precursors ͑EDMDD = 6-ethyl-2,2-dimethyl-3,5-decane dionato͒ were supplied by Asahi Denka, Japan, and were dissolved in octane with 0.05M concentration. This precursor solution was injected by a TRIJET system with a flow rate in the micro-liter regime. Film depositions were carried out in the temperature range of 480-700°C and the reac...

Scandium oxide deposited by high-pressure sputtering for memory devices: Physical and interfacial properties

“…Recently, scandium oxide thin films and ternary based compounds such as GdScO 3 , 1,2 DyScO 3 , 3,4 and LaScO 3 ͑Ref. 5͒ have attracted increasing interest in the microelectronic field in two main areas: flash memories and complementary metal-oxide-semiconductor ͑CMOS͒ circuits.…”

Growth and Characterization of Ti‐Ta‐O Thin Films on Si Substrates by Liquid Injection MOCVD for High‐k Applications from Modified Titanium and Tantalum Precursors

“…This interlayer growth was present even when we used the SiO 2 -etched wafers, so for the dielectric constant (e r ) calculation, we have used a SiO 2 thickness of 2 nm. [2,8,52] The dielectric constants extracted from the accumulation were around 39 and 38 for TiO 2 and Ti-Ta-O deposits, respectively, and hence were very similar. This is not unusual as both TiO 2 (anatase) and Ta 2 O 5 linear dielectric thin films have a dielectric constant around 40.…”

“…[2,8,[24][25][26][27][28][29] A wide variety of precursor compounds have been investigated for the production of TiO 2 and Ta 2 O 5 films by CVD processes, from metal chlorides to alkoxides, nitrates, and amides, such as Ti(O i Pr) 4 , Ti(NO 3 ) 4 , Ti(NMe 2 ) 4 , and Ti(NEt 2 ) 4 . [30,31] [27] In this context, the stabilization of amide-based complexes of Ti, Zr, Hf, Nb, and Ta by means of malonate ligands is a viable means to reduce the high reactivity of parent amide compounds, resulting in improved chemical and thermal stability and thereby disclosing attractive perspectives for CVD-and ALDrelated applications.…”

“…In recent years, the search for high-k dielectric materials to replace SiO 2 in complementary metal-oxide-semiconductor (CMOS) devices and dynamic random access memory (DRAM) applications has been extended from monometallic oxides (e.g., ZrO 2 , HfO 2 , Al 2 O 3 , Ta 2 O 5 [1][2][3][4] ), to combinations of metal silicates, HfSiO x , [5] aluminates, HfAlO x , [6] mixed metal oxides, HfTiO x , [7] and rare-earth scandates, DyScO 3 [8] films. As a matter of fact, interesting perspectives are offered by the possibility of engineering the final permittivity of high-k material by the development of suitable composites.…”

Crystallization resistance of barium titanate zirconate ultrathin films from aqueous CSD: a study of cause and effect

“…Furthermore, in the literature an increase of the crystallization temperature is observed of Hf based dielectrics 26 , when silicates are deposited, or of rare earth oxides and scandates [27][28][29] , when silicates are formed through interfacial reaction. For SrTiO 3 films a Ti rich interfacial layer, consisting of TiSiO x and TiSi 2 has been reported 30 .…”