Chemical vapor deposition of ruthenium and ruthenium oxide thin films for advanced complementary metal-oxide semiconductor gate electrode applications

Abstract

A low-temperature (320–480 °C) metal-organic chemical vapor deposition (MOCVD) process was developed for the growth of ruthenium and ruthenium oxide thin films. The process used bis(ethylcyclopentadienyl)ruthenium [Ru(C5H4C2H5)2] and oxygen as, respectively, the ruthenium and oxygen sources. Systematic investigations of film formation mechanisms and associated rate limiting factors that control the nucleation and growth of the Ru and RuO2 phases led to the demonstration that the MOCVD process can be smoothly and reversibly modified to form either Ru or RuO2 through simple and straightforward modifications to the processing conditions–primarily oxygen flow and substrate temperature. In particular, films grown at low oxygen flows (50 sccm) exhibited a metallic Ru phase at processing temperatures below 480 °C. In contrast, films grown at high oxygen flow (300 sccm) were metallic Ru below 400 °C. Above 400 °C, a phase transition was observed from Ru to RuOx (0 < x < 2.0) to RuO2 as the processing temperature was gradually increased to 480 °C.

Ruthenium Films Deposited by Liquid‐Delivery MOCVD Using Bis(ethylcyclopentadienyl)ruthenium with Toluene as the Solvent

“…The deposition of ruthenium thin films on SiO 2 /Si substrates was controlled by surface reaction kinetics as the rate-limiting step (with an activation energy of 1.4 eV) below 400°C, and by the mass-transport process above 400°C. In spite of the fact that the precursor flow rate in our investigation was several orders of magnitude lower than that reported by Papadatos et al, [16] and by Matsui et al, [17] our growth rate values are comparable with reported ones. This fact confirms the advantages of using the precursor solvent.…”

“…Above 400°C, the growth was constant at approximately 5.6 nm min -1 , which indicates a mass-transfer-limited regime, where the impingement rate of reactant species on the substrate surface is the rate-controlling step. Papadatos et al [16] and Matsui et al [17] reported comparable growth-rate values by using Ru(EtCp) 2 as a precursor, but in their investigations precur- ). Nabatame et al [15] observed the same effect by using tetrahydrofuran as precursor solvent.…”

“…Moreover, use of a precursor solvent can improve such thin-film-growth parameters as growth rate and step coverage. [15] There are some studies [15][16][17][18] in which Ru and RuO 2 thin films were deposited using Ru(EtCp) 2 , but deposition conditions and thin-film characteristics were different and analysis was not completed. We have tried in our investigation to complete and generalize information about MOCVD using Ru(EtCp) 2 as a liquid precursor, and tried to solve problems such as source decomposition and instability of the supply by dissolving the precursor material in toluene.…”

Effect oxygen exposure on the quality of atomic layer deposition of ruthenium from bis(cyclopentadienyl)ruthenium and oxygen

“…Additionally, Ru is a promising material for a gate metal in advanced complementary metal-oxide-semiconductor devices [4] and copper seed layer for direct electroplating of Cu metallization [5][6][7]. Especially, its conducting oxide phase, RuO 2 , is also a promising capacitor electrode material [8]. For all these applications, atomic layer deposition (ALD) is the most suitable thin film deposition technique due to its good conformality, uniformity, and low impurity contents.…”

“…During the whole process, the formation of RuO 2 was proposed to be hindered through the complete consumption of the subsurface oxygen. However, more recent report has shown that Ru and RuO 2 was controllably formed by changing the growth conditions, for example, O 2 / (Ar + O 2 ) ratios, for Ru ALD using Ru(EtCp) 2 as a Ru precursor [8]. Meanwhile, Kim et al reported that RuO 2 was not formed by ALD using (dimethylpentadienylethylcyclopentadienyl)Ru under similar growth conditions [13].…”