Atomic Layer Deposition of Ru Thin Films Using a Ru(0) Metallorganic Precursor and O₂

Abstract

Ruthenium (Ru) thin films were grown on thermally-grown SiO2 substrate using atomic layer deposition (ALD) by a sequential supply of a zero-valent metallorganic precursor, (ethylbenzyl) (1-ethyl-1,4-cyclohexadienyl)Ru(0) (EBECHRu, C16H22Ru), and molecular oxygen (O2) between 140 and 350°C while the typical temperature was 225°C. A self-limiting film growth was confirmed at the deposition temperature of 225°C and the growth rate was ∼0.042 nm/cycle on the SiO2 substrate with a negligible number of incubation cycles (approximately 3 cycles). Plan-view transmission electron microscopy analysis showed that nucleation was started after only 3 ALD cycles and the maximum nuclei density of 1.67 × 1012/cm2 was obtained after 7 ALD cycles. A continuous Ru film with a thickness of ∼2.3 nm was formed after 60 ALD cycles. The film resistivity was decreased with increasing deposition temperature, which was closely related to its crystallinity and microstructure, and the minimum resistivity of ∼14 μΩ-cm was obtained at the deposition temperature of 350°C. The step coverage of the film deposited between 225 and 270°C was approximately 100% over the contact holes (bottom diameter: 0.065 μm) with a high aspect ratio (32:1). Finally, the ALD-Ru film was successfully evaluated in terms of its performance as a seed layer for Cu electroplating and as a bottom electrode for a metal-insulator-metal capacitor using an ALD-TiO2 single layer or an ALD HfO2/La2O3/HfO2 multilayer as a dielectric.

Highly-conformal p-type copper(I) oxide (Cu2O) thin films by atomic layer deposition using a fluorine-free amino-alkoxide precursor

“…Such an availability of the ALD deposition within the temperature window can hold another merit in terms of conformality. Indeed, it was reported that a conformality of ALD films deposited at temperatures above an ALD temperature window was degraded due to thermally decomposed components of a process [28,29]. In fact, considering potential applications of the ALD-Cu 2 O films such as a nanowire photodiode composed of p-type and n-type semiconductors [30] and gas sensing [37], preparation of the ALD-Cu 2 O films into very small-sized high AR features with an remarkable conformality is essential.…”

TaCx Thin Films Prepared by Atomic Layer Deposition as Diffusion Barriers for Cu Metallization

“…In addition, this temperature was above the ALD temperature window. The conformality of the ALD films deposited at temperatures higher than the ALD temperature window degraded due to the CVD component of the process . Therefore, an attempt was made to reduce the resistivity by modifying the conditions for the reactant pulse at a deposition temperature of 300°C, which is in the ALD temperature window.…”

Atomic Layer Deposition (ALD) of Metal Gates for CMOS

“…Ru and RuO x : the ALD of Ru was widely studied [63][64][65][66]. Because of its high work function (~4.7 eV) and conductive oxides, it is expected to be suitable to applications as p-type metal gate electrodes for SrTiO x MIM capacitor for DRAM [67][68][69] and seed layer of Cu plating for back end of line process of CMOS [70][71][72]. A nice summary on the precursors available for the ALD of Ru and the deposition reactions can be found in the reference [72].…”

“…Because of its high work function (~4.7 eV) and conductive oxides, it is expected to be suitable to applications as p-type metal gate electrodes for SrTiO x MIM capacitor for DRAM [67][68][69] and seed layer of Cu plating for back end of line process of CMOS [70][71][72]. A nice summary on the precursors available for the ALD of Ru and the deposition reactions can be found in the reference [72]. The precursors used for Ru are mainly cyclopentadienyl compounds such as RuCp 2 (Cp = cyclopentadienyl) and Ru(EtCp) 2 (Et = ethyl), and β-diketonate compounds like Ru(od) 2 (od = 2,4-octanedionato) and Ru(thd) 3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) [67,68].…”

“…Although so much effort has been made, the quality of the ALD Ru layer does not seem qualified for work function metal application. Up to now, no matter which precursor used, the ALD of the Ru all have remarkable incubation cycles, inducing surface roughness [72]. They are probably matured for the application of the MIM capacitors and interconnections, but not for the work function layer of the metal gate.…”