Deposition of Dielectric Ta2O5 and Nb2O5 Films with Noble N-alkoxy-b- ketoiminate Complexes

초록

Several Ta(N-alkoxy-b-ketoiminate)(OEt)3 and Nb(N-alkoxy-b-ketoiminate)(OEt)3 complexes have been synthesized and tested as MOCVD precursors for the deposition of Ta2O5 and Nb2O5 thin films. They are relatively inert in moisture, highly volatile and thermally stable during the bubbling procedure. We have found that Ta[2-N-(2-hydroxy-2-methylethylimino)-4-pentanone](OEt)3 and Nb[2-N-(2-hydroxy-2-methylethylimino)-4-pentanone](OEt)3, which have methyl group in the N-hydoxyethyl backbone, show the highest deposition rate for Ta2O5 and Ta2O5 layer. Deposition rates of these precursors are 5~7 times of conventional Ta or Nb precursors, such as Ta(OC2H5)5 or Nb(OC2H5)5. The deposition rates begin to be saturated at about 500oC, which suggests that N-alkoxy-b-ketoiminate ligand is easily released from the central Ta or Nb metals. We studied the thermal dissociation behavior by measuring the carbon or nitrogen residues in the films, prepared at several deposition conditions. The film deposited at 550oC and subsequently post-annealed at 700oC shows a high dielectric constant and low leakage current. The films also demonstrated very good step coverage.