Field‐Aided Thermal Chemical Vapor Deposition of Copper Using Cu(I) Organometallic Precursor

Abstract

A dc substrate bias which is not enough to make a plasma was applied during the chemical vapor deposition of copper to change the adsorption behavior of the reactant. Copper films were deposited on TiN and 5i02 from Cu(hfac)(tmvs) with and without the substrate bias. The surface morphology, the thickness, the sheet resistance, and the purity of the films were investigated. When a negative substrate bias of -30 V was applied to the substrate, the deposition rate of copper increased both on TiN and 5i02. The substrate bias did not cause the change in the chemical composition of the deposited copper film. It was calculated that Cu(hfac) has the dipole moment whose direction is from copper to hfac. The local electric fields due to surface roughness may affect the adsorption behavior of the precursor, especially the direction of the molecular dipole moment. Resulting from the overlapping population value analysis, the improvement of deposition rate under negative substrate bias was explained as due to the adsorption of the copper atom in the Cu(hfac) species directly onto the substrate by the local electric fields applied between the substrate and the gas showerhead.Infroduction Chemical vapor deposition (CVD) of copper film is being studied as an alternative fabrication technique for interconnect metallization in future generations of deep submicron ultralarge scale integrated (ULSI) circuits.'5Copper offers many intrinsic advantages over Al, including lower resistivity, better electromigration resistance, and better resistance to stress-induced void formation.6The CVD process offers conformal coverage over high aspect ratio features, unlike the physical vapor deposition (PVD) method.Copper(I) hexafluoroacetylacetonate trimethylvinylsilane,' Cu(hfac)(tmvs), is one of the most promising copper precursors, because it exists as a liquid even at room temperature and shows a high vapor pressure and relatively good thermal stability. Recently, a number of studies have been made on the growth of a pure copper film from Cu(hfac)(tmvs). 1,3-5,740 It reacts through a bimolecular disproportionation reaction to produce solid Cu and gasphase by-products' 2Cu'(hfac)(tmvs)(g) -Cu°(s) + Cu2(hfac)2(g) * Electrochemical Society Active Member. + 2tmvs(g) [11Since intermediate species of Cu'(hfac) would have a permanent electric dipole, originating from the high elec-

Modeling of the Kinetics in Copper Chemical Vapor Deposition from Cu(hfac)VTMS

“…Another possibility for the first step could be the adsorption of an intact Cu(hfac)VTMS molecule at the substrate, as proposed by many authors. 19,21,29,31 This is not possible here, as it would induce a subsequent reaction of this *Cu(hfac)VTMS with an empty surface site to create *VTMS, which has been observed at the surface in adsorption experiments. 29 The monorhoic model does not allow such a reaction.…”