Synthesis And Application Of Novel Cu(â… ) Complexes As Precursors For Chemical Vapor Deposition Of Copper Thin Films

Copper thin film manufacture is very important in the microelectronics and semiconductor industry owing to the high electrical conductivity of copper,second only to silver.Copper film Chemical Vapor Deposition(CVD) is an attractive technique to be researched beccause it provides several advantages such as the ability to achieve good step coverage,selective deposition and control of film density and thickness,etc.over other physical method.Cu(â… ) organometallic compounds are often used as CVD precurcors,which need lower deposition temprature than Cu(â…¡) compounds,but they are usually air and moisture sensitive,low thermal stability.In this work,we have synthesized a series of phosphite Cu(â… ) complexes, (etac)Cu(â… )(P(O-nBt)₃)₂,(etac)Cu(â… )(P(OCH(CH₃)₂)₃)₂,(mtac)Cu(â… )(P(O-nBt)₃)₂, (mtac)Cu(â… )(P(OCH(CH₃)₂)₃)₂,(btac)Cu(â… )(P(O-nBt)₃)₂ and(btac)Cu(â… )(P(OCH(CH₃)₂)₃)₂, where mtac = methyl acetyl acetate,etac = ethyl acetyl acetate and btac = tert-butyl acetyl acetate.The thermal stability of the six precursors was tested using TG and DSC.It shows that the precursors coordinated with tributyl-phosphite are more stable than those with triisopropyl-phosphite.The Electron-Spin Resonance (ESR) spectra show that the complexes are stable in the air.They could be exposed to air for weeks and only few Cu^â…¡ ions are detected.As we know,tetrahydrofuran(THF) absorbs moisture and oxygen very fast when exposed to air.We must get rid of the THF completely before filtration in the preparation process.CVD experiments were carried out under argon using these precursor in a home-made CVD system on the Si(111) substrate.The precursors were evaporated at 180℃-200℃and the films were deposited onto the Si(111) substrates under 0.1 torr -1.0 torr using argon as a carrier gas.No reductive agent such as H₂ was used.The copper films were obtained on the heated substrates at a deposition temperature of 320℃.Then the films were annealed at 320℃for 10 minutes.The growth mode of the copper film fron the precursors coordinated with tributyl-phosphite prones to Volmer-Weber(island).The growth mode of the copper film fron the precursors coordinated with triisopropyl-phosphite prones to Stranski-Krastanov(layer-by-layer plus island).The copper films were analyzed by X-ray diffraction(XRD) and x-ray photoelectron spectro- scopy(XPS).They are found to be highly pure and crystalline.AFM images of copper films formed using the two types of precursors are obtained that the morphology of the copper grains is similar.Shape of the grains is similar not only on the film but also on different films.It indicates that the growth of the grains is not random.On the copper films from the precursors with P(OCH(CH₃)₂)₃ ligand,pyramid-shaped copper grains can be obtained;The results indicates that the controllability of copper films can be improve basing on this copper film preparation methods.