Tungsten nitrido complexes as precursors for low temperature chemical vapor deposition of WN(x)C(y) films as diffusion barriers for Cu metallization.

Tungsten nitrido complexes of the form WN(NR2)3 [R = combinations of Me, Et, (i)Pr, (n)Pr] have been synthesized as precursors for the chemical vapor deposition of WN(x)C(y), a material of interest for diffusion barriers in Cu-metallized integrated circuits. These precursors bear a fully nitrogen coordinated ligand environment and a nitrido moiety (W≡N) designed to minimize the temperature required for film deposition. Mass spectrometry and solid state thermolysis of the precursors generated common fragments by loss of free dialkylamines from monomeric and dimeric tungsten species. DFT calculations on WN(NMe2)3 indicated the lowest gas phase energy pathway for loss of HNMe2 to be ß-H transfer following formation of a nitrido bridged dimer. Amorphous films of WN(x)C(y) were grown from WN(NMe2)3 as a single source precursor at temperatures ranging from 125 to 650 °C using aerosol-assisted chemical vapor deposition (AACVD) with pyridine as the solvent. Films with stoichiometry approaching W2NC were grown between 150 and 450 °C, and films grown at 150 °C were highly smooth, with a RMS roughness of 0.5 nm. In diffusion barrier tests, 30 nm of film withstood Cu penetration when annealed at 500 °C for 30 min.

Volatile organic compound detection using nanostructured copolymers.

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.