A carbene stabilized precursor for the spatial atomic layer deposition of copper thin films

Abstract

This is the first report on a plasma enhanced spatial atomic layer deposition (APP-ALD) process at atmospheric pressure to grow conducting metallic Cu thin films from a carbene stabilized precursor.

Role of Anionic Backbone in NHC‐Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition**

“…[51,52] The starting materials [Cu(NHC)(hmds)] and [Ag(NHC)(hmds)] which are used in all following reactions for the formation of the final complexes was synthesized and characterized using a procedure reported earlier by our group (Boysen et al). [31,32] [Cu(NHC)(acac)]: The starting material [Cu(NHC)(hmds)] (4.2 g, 10.3 mmol) is dissolved in 100 ml of hexane and acetylacetone (1.0 g, 10.3 mmol) is slowly added to the solution at RT and stirred. The resulting microcrystalline yellow precipitate is allowed to settle at the bottom of the flask after which the solvent is decanted.…”

“…At least for [Cu( tBu NHC)(acac)], a signal for the carbenic carbon atom could be located in the 13 C NMR spectrum at 203.16 ppm which is slightly shifted downfield compared to the already reported [Cu( tBu NHC)(hmds)] complex from our earlier studies (201.6 ppm) and indicates a smaller degree of π-back bonding from the metal to the carbene. [32] Nevertheless, a more detailed insight into the bonding situation for all complexes in the solid state and a validation of the results seen in NMR studies could be gained by SC-XRD measurements which are discussed in the next section.…”

“…[30] The same concept was later adopted in our recent studies for the spatial ALD of Cu and Ag metal films using [Cu( tBu NHC)(hmds)] and [Ag( tBu NHC)(hmds)] and H2 plasma at low deposition temperatures of 100 °C and 120 °C, respectively, while also comparing the similarities and differences between the nature, thermal stability and reactivity of the Cu and Ag complexes. [31,32] While Coyle et al investigated cyclic and acyclic carbenes with different substitution patterns for Cu complexes to assess their influence on volatility and thermal stability while keeping the anionic backbone as a constant in the respective complexes, [33] we envisioned to systematically vary the anionic backbone within NHC stabilized complexes of Cu and Ag. This should not only increase the understanding of the influence of the anionic backbone variation on parameters like thermal stability, volatility and reactivity but also possibly eliminate unwanted elements in the ligand sphere that are prone to incorporate into the thin films such as fluorine, phosphorous or silicon which is one of the drawbacks of the most established Cu(I) and Ag(I) precursors.…”

Role of anionic backbone in NHC-stabilized coinage metal complexes: New precursors for atomic layer deposition

“…[51] The starting materials [Cu(NHC)(hmds)] and [Ag(NHC)(hmds)] which are used in all following reactions for the formation of the final complexes was synthesized and characterized using a procedure reported earlier by our group (Boysen et al). [31,32] [Cu(NHC)(acac)]: The starting material [Cu(NHC)(hmds)] (4.2 g, 10.3 mmol) is dissolved in 100 ml of hexane and acetylacetone (1.0 g, 10.3 mmol) is slowly added to the solution at RT and stirred. The resulting microcrystalline yellow precipitate is allowed to settle at the bottom of the flask after which the solvent is decanted.…”

Investigations into the structure, reactivity, and AACVD of aluminium and gallium amidoenoate complexes

“…[12][13][14] Recently, investigations into the structural parameters of metal-containing molecular precursors have been carried out in order to probe relationships between a precursor's molecular geometry (dictated by the bonding modes of the ligands bound to the metal) and their suitability for deposition. 15 For example, recent studies have shown that molecular complexes to be employed as precursors which crystallize with a distorted geometry are able to be deposited at lower temperatures due to their inherent molecular strain, 16,17 which can be quantified using the degree of distortion denoted as a ' value'. 18,19 Methods employed by synthetic chemists to control such parameters include varying the chemical nature of the complex by choosing specific ligands to perform certain functions.…”