Impact of the Plasma Ambient and the Ruthenium Precursor on the Growth of Ruthenium Films by Plasma Enhanced Atomic Layer Deposition

Abstract

We compare the growth behavior of nm-thin ruthenium layers using N 2 /NH 3 -and N 2 /H 2 -based plasmas during plasma enhanced atomic layer deposition for two ruthenium precursors. For bis(ethylcyclopentadienyl)ruthenium, we have found a large incubation time on titanium nitride when using N 2 /NH 3 plasma. With N 2 /H 2 plasma the incubation was reduced and tunable with the Ru dose per pulse. In contrast to the incubation, the steady state growth does not depend significantly on the plasma ambient given that there are H 2 or NH 3 species. For (methylcyclopentadienylpyrrolyl)ruthenium, no significant incubation was observed for either plasmas, which is attributed to the presence of the pyrrolyl group.Recently, ruthenium films obtained by atomic layer deposition (ALD) have attracted a lot of interest as enabling material in future technology nodes for several applications such as dynamic random access memory (DRAM) and interconnect metallization. 1 For DRAM metal-insulator-metal capacitors (MIMCAP), Ru and/or RuO 2 are candidates to replace TiN electrodes in metal-insulator-metal capacitor structures. Ru has the advantage, when compared to other metals, that it remains conducting when oxidized and hence does not contribute to the equivalent oxide thickness (EOT) of the capacitor.Ultrathin, smooth, conformally deposited Ru films are needed for future 3D devices structures. This is a challenge given the multiple reports on nucleation issues for ALD Ru on various substrates. Thermal ALD of Ru using O 2 as a co-reactant is studied most frequently. 2,3,4 Alternatively, a plasma such as N 2 /H 2 or NH 3 is used as co-reactant. The latter is called plasma enhanced ALD (PE-ALD). In general, the use of plasma during or before Ru ALD has been shown to significantly reduce the incubation. 5,6,7 The most reported Ru precursor for PE-ALD Ru is bis(ethylcyclopentadienyl)-ruthenium or Ru(EtCp) 2 (references see Table I). However, the initial growth behavior as well as and the growth-per-cycle (GPC) values (Table I) vary strongly from report to report. This is likely due to the extreme sensitivity of the ALD Ru process to the substrate preparation and/or process conditions such as reactor temperature, reactor pressure, precursor dose and plasma conditions. The impact of the plasma, usually N 2 /H 2 or NH 3 based, on the nucleation and the growth, is not yet reported. Besides, the direct comparison of the PE-ALD Ru process for Ru(EtCp) 2 and one of the more recently reported Ru percursors like methylcyclopentadienylpyrrolylruthenium (MCPRu) 3,7 has not been described in literature.In this letter, we report on the deposition of PE-ALD Ru from Ru(EtCp) 2 and MCPRu using similar process conditions. For both precursors, we compare the impact of N 2 /NH 3 and N 2 /H 2 plasma on the nucleation and growth of PE-ALD Ru.Ru thin films were deposited by PE-ALD in a 300 mm ALD chamber with direct plasma capability. The plasma is generated between the substrate and the showerhead using a high frequency generator. The ALD chamber is attached to...

Diffusion‐Mediated Growth and Size‐Dependent Nanoparticle Reactivity during Ruthenium Atomic Layer Deposition on Dielectric Substrates

“…The surface dependence of Ru ALD has been reported for a variety of processes, yet the underlying growth mechanisms are often not well understood. Long inhibition periods are common for Ru ALD, especially in processes based on combustion reactions .…”

Reactions of Ruthenium Cyclopentadienyl Praecursor in the Metal Precursor Pulse of Ru Atomic Layer Deposition

“…46 PE-ALD can significantly reduce the incubation time. 13 The most commonly used precursor for PE-ALD of Ru is Ru(EtCp)2. The reported growth rate varies from 0.16 /cycle to 0.80 /cycle, depending on the process condition such as reactor temperature (temperature range 100 °C to 300 °C) and plasma conditions (N2/H2 plasma and NH3 plasma varies with operating temperatures and Ru metal precursors.…”

“…The reported growth rate varies from 0.16 /cycle to 0.80 /cycle, depending on the process condition such as reactor temperature (temperature range 100 °C to 300 °C) and plasma conditions (N2/H2 plasma and NH3 plasma varies with operating temperatures and Ru metal precursors. 13,26 From our previous theoretical study 37…”

“…12 In addition to thermal ALD, plasma-enhanced ALD (PE-ALD) has been used with ammonia or a mixture of N2 and H2 as the N-plasma source. [13][14][15] For the PE-ALD of Ru using RuCp2 and NH3 plasma at a temperature of 300 °C, a growth rate of 1.2 Å/cycle has been reported, while a growth rate of 1.8 Å/cycle was reported using Ru(EtCp)2 at 300 °C. 16 Organometallic compounds such as β-diketonates have also been used as Ru precursors and the deposited Ru thin films show higher impurity concentration compared to using metallocenes such as RuCp2 as the Ru precursor.…”

Direct Electrodeposition of Cu on Ru-Al2O3Layer

“…[1][2][3][4][5][6][7] It can be deposited by various methods, such as electrodeposition, physical vapor deposition, electroless deposition, chemical vapor deposition, and atomic layer deposition (ALD). [8][9][10][11][12][13][14][15][16][17][18] Ru has the advantages that the Cu could be directly electrodeposited with excellent properties and the superfilling of Cu on the Ru layer was also feasible. 2,3 However, it is not a suitable material for the diffusion barrier, 19,20 because Cu atoms diffuse along the Ru grain boundaries of the columnar structure.…”