Metalorganic Chemical Vapor Deposition of Copper on Ruthenium Thin Film

Abstract

Ultrathin Cu seed layer was deposited by metallorganic chemical vapor deposition ͑MOCVD͒ on Ru layer using hexafluoroacetylacetonate copper vinyltrimethylsilane ͓͑hfac͒Cu I ͑vtms͔͒. On Ru, the incubation time for Cu MOCVD was nonexistent. As compared with MOCVD Cu on TaN, the nuclei density of Cu was considerably increased on Ru and the wetting angle of Cu on Ru was small ͑22°͒. Therefore, the coalescence between Cu islands on Ru layer begins earlier by prohibiting the severe threedimensional Cu growth that is generally observed on TaN layer. As a result, 10 nm thick continuous Cu film with 1.75 nm root-mean-squared surface roughness was easily prepared on 40 nm thick Ru at 150°C.Copper ͑Cu͒ interconnection has been used extensively in fabricating metal interconnections for large scale integrated circuits because of its favorable electrical conductivity ͑1.67 ⍀ cm͒ and superior resistance to electromigration. 1 The most widely used deposition method for Cu is electrochemical plating ͑ECP͒, which is capable of refilling dual-damascene structures in a fashion of bottom-up, so-called superfilling. In this ECP of Cu, a Cu seed layer is a prerequisite for an electrode, 2 and it should be prepared as thin as possible, having a continuous and smooth film surface, to achieve the Cu superfilling without leaving any voids on dual-damascene structures. 3,4 In forming the Cu seed layer, physical vapor deposition ͑PVD͒ methods are currently in wide use. However, as the aspect ratio of dual-damascene structures increases, the Cu seed layer formed by PVD begins to show practical disadvantages on its step coverage owing to the line-of-sight approach of PVD. As an alternative to overcoming this inherent demerit of PVD, metallorganic chemical vapor deposition ͑MOCVD͒ of Cu has been studied for several years because of its conformal deposition characteristics. 5,6 However, in MOCVD of Cu, the film growth on the Cu diffusion barrier metals, such as TiN, Ta, and TaN, generally follows a three-dimensional island growth mode, 7 and has a relatively long incubation time to form a continuous Cu film. Thus, the deposited Cu film normally has a severe surface roughness. 7 In addition, the Cu film formed by MOCVD does not adhere well to the diffusion barrier metals, showing an easy peeling-off during a post process as chemical mechanical polishing. 8,9 Recently, it has been reported that a 1-2 nm thick Ru film as an interlayer between MOCVD Cu and its diffusion barrier metals improves the adhesion property. 10 Furthermore, Ru itself is regarded as a promising candidate for a Cu diffusion barrier metal, because it is a noble transition metal with high melting point ͑2310°C͒, and has lower electrical resistivity ͑7.6 ⍀ cm͒ 11 than those of Ta and TaN, and is immiscible with Cu. 12 In this work, Cu MOCVD has been preformed on a Ru layer to investigate the film growth behaviors of MOCVD Cu. On Ru thin films, no incubation time is detected and three-dimensional island growth is also suppressed during the initial stage of the Cu film growth. As a...

Direct-on-barrier copper electroplating on ruthenium from the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide

“…The deposition of barriers of a few nanometers thick and consisting of TaN, TiN, Ta or Ru is currently achieved by atomic layer deposition (ALD). Ruthenium is an interesting material for barrier in advanced interconnect schemes, because of its high melting point (2310°C), low electrical resistance (7.6 lX cm -1 ) and immiscibility with copper [1].…”

“…The deposition of copper on barrier materials such as TaN, TiN and Ta, proceeds as three-dimensional island growth as described by the Volmer-Weber model, with high induction times and the formation of rough layers [1][2][3][4]. The deposition of continuous and ultrathin films of copper on ruthenium has been executed by several thechniques: chemical vapor deposition (CVD) [2], metal-organic chemical vapor deposition (MO-CVD) [1], catalystenhanced chemical vapor deposition (CE-CVD) [5] and atomic layer deposition (ALD) [6] have been reported.…”

“…The deposition of continuous and ultrathin films of copper on ruthenium has been executed by several thechniques: chemical vapor deposition (CVD) [2], metal-organic chemical vapor deposition (MO-CVD) [1], catalystenhanced chemical vapor deposition (CE-CVD) [5] and atomic layer deposition (ALD) [6] have been reported. One of the main benefits of the CVD process is the possibility to achieve a continuous coverage inside the feature with a high aspect ratio.…”

Microstructural Evolution of Nanoindented Ag/Si Thin-Film under Different Annealing Temperatures

“…Furthermore, various physical and chemical bonding methods have been proposed for fabricating Ag/Si systems with coherent layers. [19][20][21][22] Although the nanoindentation properties of Ag/Si thin films and the characteristics of Ag/Si silicides compound have been studied, 16,23) the combined effects of nanoindentation deformation and annealing on the microstructural evolution and the formation of silicides phase of Ag/Si thin films are not yet fully understood. Accordingly, this study uses a nanoindentation technique to examine the nano-mechanical properties of asdeposited Ag/Si thin films indented to a depth of 800 nm.…”

Dependence of Microstructural Evolution of Nanoindented Cu/Si Thin Films on Annealing Temperature

“…14,15) Various physical and chemical methods have been proposed for the fabrication of Cu/Si systems with coherent layers. [16][17][18][19] It is known that the bonding strength of the Cu/Si system is enhanced via the precipitation of copper silicide particles via a solid state reaction when the interface between the thin Cu film and the Si substrate is heated to a sufficient temperature. Accordingly, this study investigates the nano-mechanical properties of as-deposited Cu/Si samples indented to a depth of 2000 nm and then anneals the indented samples at temperatures of either 160 C or 210 C, respectively.…”