Kinetic and Mechanistic Studies of the Chemical Vapor Deposition of Tungsten Nitride from Bis(Tertbutylimido)Bis(Tertbutylamido)Tungsten

Abstract

The chemical vapor deposition (CVD) of tungsten nitride from a single source reagent, bis(tertbutylimido)bis(tertbutylamido)tungsten ((t-BuN)2W(NHBu-t)2), is examined with particular focus placed on the mechanisms and energetics involved in the activation and thermal decomposition of this CVD precursor. The main reactions that take place are (1) activated adsorption of the precursor, (2) hydrogen addition/exchange, leading to the evolution of tert-butylamine, (3) ligand activation via both γ-hydride activation and β-methyl elimination processes, and (4) ligand decomposition via C−N bond rupture. The activation energies for each of these processes were examined and found to be ∼30 kcal/mol for the process(es) leading to the evolution of tert-butylamine and ∼40 kcal/mol for the various reactions which lead to the fragmentation of the precursor ligands (pathways which appear to involve both C−H and C−C bond activation as well as the rupture of the ligand C−N bonds). The growth surface of the deposited film contained extensive quantities of carbon in addition to tungsten and nitrogen. The data also suggest that the growth in UHV does not yield a stable bulk nitride phase. Rather, it was found that the nitrogen appears to be present at levels consistent with the formation of a solid solution and that annealing to 700 K results in the loss of the nitrogen from the bulk film (as N2).

Chemical vapor deposition of tantalum carbide and carbonitride thin films from Me3CETa(CH2CMe3)3 (E = CH, N)Electronic supplementary information (ESI) available: AFM and SEM images of TaC and TaCN films deposited on Si(100) at 773, 823 and 923 K. See http://www.rsc.org/suppdata/jm/b2/b208129f/

“…Previous studies have shown that the tert-butyl groups of the tert-butylimido ligand liberated isobutylene through a c-hydrogen elimination process. [16][17][18] We speculate that the source of the carbide atoms is more likely to be from the neopentyl ligands, [4][5][6][7][8][9][10][11][12] generated via the pathways shown in Scheme 1 discussed above.…”

“…Deposition of nitride thin films has been reported employing metal complexes with organo-amido and organo-imido ligands as the precursors. [13][14][15][16][17][18][19] These include the deposition of nitrides of Ti from Ti(NEt 2 ) 4 , [13][14][15] of Ta from t BuNLTa(NEt 2 ) 3 , 16 and of W from ( t BuNL) 2 W(NH t Bu) 2 . 17,18 In addition to the activation and elimination pathways of the hydrocarbon fragments of the complexes, the role of the multiply bonded carbene, carbyne and imido ligands are frequently discussed.…”

“…[13][14][15][16][17][18][19] These include the deposition of nitrides of Ti from Ti(NEt 2 ) 4 , [13][14][15] of Ta from t BuNLTa(NEt 2 ) 3 , 16 and of W from ( t BuNL) 2 W(NH t Bu) 2 . 17,18 In addition to the activation and elimination pathways of the hydrocarbon fragments of the complexes, the role of the multiply bonded carbene, carbyne and imido ligands are frequently discussed. Apparently, the multiply bonded ligands may assist the preservation of 'MLC' and 'MLN' fragments in the films to form carbides and nitrides.…”

Low Temperature Deposition of WNxCyDiffusion Barriers Using WN(NEt2)3as a Single-Source Precursor

“…• C) [15][16][17][18][19][20][21][22] that can compromise contact level structures 2,23 and neighboring dielectrics. 24 In addition, the development of ultra-low temperature CVD WN x C y has potential application to flexible and organic devices.…”

Deposition of WNxCy from the Tungsten Piperidylhydrazido Complex Cl4(CH3CN)W(N-pip) as a Single-source Precursor

“…Typically, refractory metal nitride diffusion barriers show decreasing N levels with increasing deposition temperature due to N 2 desorption. [29][30][31][32] Films deposited at 300 C show greater than 20 atom % O, but decreased significantly to 14 atom % at 450 C. As the deposition temperature increased from 450 to 700 C, the O level decreased gradually to 5 atom %. A decrease in the O levels at higher deposition temperature is consistent with the increase in grain size because oxygen is introduced into the film by post-growth diffusion.…”