Thermal atomic layer deposition of rhenium nitride and rhenium metal thin films using methyltrioxorhenium.

The growth of rhenium nitride and rhenium metal thin films is presented using atomic layer deposition (ALD) with the precursors methyltrioxorhenium and 1,1-dimethylhydrazine. Saturative, self-limiting growth was determined at 340 °C for pulse times of ≥4.0 s for methyltrioxorhenium and ≥0.1 s for 1,1-dimethylhydrazine. An ALD window was observed from 340 to 350 °C with a growth rate of about 0.60 Å per cycle. Films grown at 340 °C revealed a root mean square surface roughness of 2.7 nm for a 70 nm thick film and possessed a composition of ReN0.14 with low O and C content of 1.6 and 2.6 at%, respectively. Enhanced nucleation on in situ grown TiN, relative to thermal SiO2, enabled a conformality of 98% on high aspect ratio trenched structures. Subjecting the ReN0.14 thin films to thermal or chemical and thermal treatments reduced the nitrogen content to ≤1.6 at%, yielding a film purity of about 96 at% rhenium and resistivities as low as 51 µΩ cm. The Re metal film thicknesses on the trenched structures remained intact during the post-deposition annealing treatments and the films did not delaminate from the substrate surfaces.

Volatility and high thermal stability in mid-to-late first-row transition-metal complexes containing 1,2,5-triazapentadienyl ligands.

Treatment of first-row transition-metal MCl(2) (M = Ni, Co, Fe, Mn, Cr) with 2 equiv of the potassium 1,2,5-triazapentadienyl salts K(tBuNNCHCHNR) (R = tBu, NMe(2)) afforded M(tBuNNCHCHNR)(2) in 18-73% isolated yields after sublimation. The X-ray crystal structures of these compounds show monomeric, tetrahedral molecular geometries, and magnetic moment measurements are consistent with high-spin electronic configurations. Complexes with R = tBu sublime between 155 and 175 °C at 0.05 Torr and have decomposition temperatures that range from 280 to 310 °C, whereas complexes with R = NMe(2) sublime at 105 °C at 0.05 Torr but decompose between 181 and 225 °C. This work offers new nitrogen-rich ligands that are related to widely used ß-diketiminate and 1,3,5-triazapentadienyl ligands and demonstrates new complexes with properties suitable for use in atomic-layer deposition.

Efficient hydride and pyrazolyl redistribution upon thermolysis of a calcium complex containing dihydrobis(pyrazolyl)borate ligands.

Thermolysis of CaBp(2)(THF)(2) (THF = tetrahydrofuran) at 190-200 °C and 0.05 Torr leads to a redistribution reaction to afford CaTp(2) (90%) and CaTp(BH(4)) (84%). Treatment of CaTp(BH(4)) with THF affords CaTp(BH(4))(THF)(2) and [CaTp(BH(4))(THF)](4), both of which were structurally characterized. Methanolysis or ethanolysis/hydrolysis of the BH(4)(-)-containing complexes affords [TpCa(HOMe)(2)(µ(4)-B(OMe)(4))Ca(HOMe)(2)Tp][B(OMe)(4)] and [{TpCa}(3){µ(6)-B(OB(OEt)(3))(3)]·EtOH.

Volatility, high thermal stability, and low melting points in heavier alkaline earth metal complexes containing tris(pyrazolyl)borate ligands.

Treatment of MI(2) (M = Ca, Sr) or BaI(2)(THF)(3) with 2 equiv of potassium tris(3,5-diethylpyrazolyl)borate (KTp(Et2)) or potassium tris(3,5-di-n-propylpyrazolyl)borate (KTp(nPr2)) in hexane at ambient temperature afforded CaTp(Et2)(2) (64%), SrTp(Et2)(2) (64%), BaTp(Et2)(2) (67%), CaTp(nPr2)(2) (51%), SrTp(nPr2)(2) (75%), and BaTp(nPr2)(2) (39%). Crystal structure determinations of CaTp(Et2)(2), SrTp(Et2)(2), and BaTp(Et2)(2) revealed monomeric structures. X-ray structural determinations for strontium tris(pyrazolyl)borate (SrTp(2)) and barium tris(pyrazolyl)borate ([BaTp(2)](2)) show that SrTp(2) exists as a monomer and [BaTp(2)](2) exists as a dimer containing two bridging Tp ligands. The thermogravimetric analysis traces, preparative sublimations, and melting point/decomposition determinations demonstrate generally very high thermal stabilities and reasonable volatilities. SrTp(2) has the highest volatility with a sublimation temperature of 200 degrees C/0.05 Torr. [BaTp(2)](2) is the least thermally stable with a decomposition temperature of 330 degrees C and a percent residue of 46.5% at 450 degrees C in the thermogravimetric analysis trace. SrTp(Et2)(2), BaTp(Et2)(2), CaTp(nPr2)(2), SrTp(nPr2)(2), and BaTp(nPr2)(2) vaporize as liquids between 210 and 240 degrees C at 0.05 Torr. BaTp(Et2)(2) and BaTp(nPr2)(2) decompose at about 375 degrees C, whereas MTp(Et2)(2) and MTp(nPr2)(2) (M = Ca, Sr) are stable to >400 degrees C. Several of these new complexes represent promising precursors for chemical vapor deposition and atomic layer deposition film growth techniques.