Carburization of Tungsten Filaments in a Hot-Wire Chemical Vapor Deposition Process using 1,1,3,3-Tetramethyl-1,3-disilacyclobutane

Abstract

The alloying of tungsten filament when using 1,1,3,3-tetramethyl-1,3-disilacyclobutane (TMDSCB) in a hot-wire chemical vapor deposition reactor was systematically studied by scanning electron microscopy, Auger electron spectroscopy, analysis of the power consumed by the filament, and in situ mass spectrometric measurements of the gas-phase species produced in the process. Only carburization of the W filament was observed. The carburization is mainly caused by the interaction of methyl radicals with the filament. Graphite as well as both WC and W2C alloys can form on the filament surface, depending on the filament temperatures and source gas pressures. Both WC and graphite are converted to W2C with the diffusion of C into the filament. It is shown that filament carburization affects the consumption rate of the source gas and the intensities of gas-phase reaction products. Gas-phase reactions dominate at T < or = 1400 degrees C. The carburization rate increases with increasing filament temperatures and dominates at T > or = 1800 degrees C.

Structural Changes in Tungsten and Tantalum Wires in Catalytic Chemical Vapor Deposition Using 1,3-Disilacyclobutane

“…Although the formation of cubic 3C-SiC was not observed in our previous studies using SCB 8 Further LeBail refinement supported this observation and determined the cell parameters as a = 4.785(6) Å, b = 6.074(7) Å, c = 5.245(7) Å, and V = 152.4(6) Å 3 . The observation of crystalline W 2 C is similar to our recent study using TMDSCB 12,20 and other studies. [10][11][12]19 For the W filaments exposed to DSCB for longer time of 3 hr and beyond, weak XRD peaks due to W 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 the parabolic law where the thickness is linearly proportional to the square root of time.…”

“…It is known that the formation of WC/W 2 C is due to decomposition of the gaseous precursors on the heated filament surface, followed by diffusion of carbon into the bulk tungsten. 12,20,27 The silene and silylene species (I -V) are very reactive and rich in both carbon and silicon. Therefore, they are good precursors to form SiC as well as W 2 C. The transformation from W 2 C to SiC observed at 1200 ºC in our experiments is due to the fact that W 2 C is unstable below 1250 °C.…”

“…The catalytic dissociation reactions are key to the success of the actual deposition since they initiate the gas-phase reaction chemistry and thin film growth. However, the heterogeneous reactions between the gaseous reactive species and the heated metal wire itself also result in the formation of metal alloys, such as metal silicides − and metal carbides, − on the wire surface. Several studies showed that the filament alloying affects the catalytic ability of the metal wire , as well as the quality of the deposited thin films. , A more detrimental effect from the filament alloying is the shortening of its lifetime.…”

Catalytic decomposition of phosphorus compounds to produce phosphorus atoms

“…13) They explained these results by boron accommodation into the wire, based on secondary ion mass spectroscopic analysis. Similar processes of silicidation [14][15][16][17][18][19][20][21] and carburization [21][22][23][24] of W wires have been observed, although silicidation is less remarkable at high wire temperatures. In the present phosphorus systems, however, phosphorization does not occur at any temperature.…”

High Densification of Tungsten via Hot Pressing at 1300 °C in Carbon Presence

“…The W2C phase has lower Gibbs energy than C in W solid solution, which leads to the following hemicarbide forming reaction: 2W + C → W 2 C in the case when an appropriate C concentration is present in the green body. The diffusivity of carbon in W2C was shown to be an order of magnitude less than that of carbon in pure tungsten [ 27 , 28 ]. Therefore, as soon as the hemicarbide is formed, further carbon accumulation in hemicarbide slows down, and this prevents WC nucleation.…”