TRIHALOSILANES

    Trihalosilanes, along with dihalosilanes and tetrahalosilanes, are some of the most used precursors for the CVD growth of various Si-containing layers, including epitaxial Si, polycrystalline Si, silicon carbide SiC etc.

Trichlorosilane SiHCl3

Fig. Vapor pressure of trichlorosilane CHCl3 between -80°C to +210°C

Trichlorosilane SiHCl3 (M= 135.45 g/mol) is colourless liquid with a sharp acidic odor (density d= 1.342 g/cm3 at 25 °C), highly corrosive in humid conditions, resistivity 600 Ω/cm, flammability range in air (% volume) 1.2-90.5

melting point −126.6 °C (146.6 K),

boiling point 31.8 °C (89.2 °F; 304.9 K) (other data - boiling point 31.9°C at 1.013 bar),  

vapor density    1 (vs air) (other data - vapor is heavier than air) ,

Density 6.016 at 1 atm (at 1.013 bar, 15 °C [kg/m³]) (or 0.366 lb/ft³] at 70 °F)

SiHCl3 Vapour Pressure

Fig. CHCl3 vapor pressure equation (for 27.3 to 305K range): (log10(P, bar) = 4.21609− (1170 / (T(K) -27))

    Vapor pressure of trichlorosilane SiHCl3 , as well as of dichlorosilane and tetrachlorosilane, was studied in the temperature range 300 K to 420 K by  Marsh et al. [[i]

[i] K. N. Marsh, T. K. Morris, G. P. Peterson, Th. J. Hughes, Q. Ran, J. C. Holste, J. Chem. Eng. Data, 2016, 61 (8), pp 2799–2804, « Vapor Pressure of Dichlorosilane, Trichlorosilane, and Tetrachlorosilane from 300 K to 420 K »,  DOI: 10.1021/acs.jced.6b00142, https://pubs.acs.org/doi/abs/10.1021/acs.jced.6b00142

    Vapor pressure (bar): 0.29 at 0 °C (4.17 psi at 32 °F); 0.66 at 20 °C (9.92 psi at 70 °F).  Vapor pressure equation: log10(P) = A − (B / (T + C)),  A= 4.21609, B = 1170, C= -27 , (temperature range 275.3 - 304.8 K ), (for P = vapor pressure (bar), T = temperature (K) ) [i]

For vapor pressure in mbar vapor pressure equation:

log10(P, mbar) =  7.2217 − (1170 / (T(K) -27))  

[i] A.C. Jenkins, G.F. Chambers, Ind. Eng. Chem., 1954, 46 (11), pp 2367–2369, « Vapor Pressures of Silicon Compounds », DOI: 10.1021/ie50539a043, pubs.acs.org/doi/abs/10.1021/ie50539a043?journalCode=iechad

SiHCl3 for polycrystalline Si layers by CVD

     The application of trichlorosilane CHCl3 as precursor for the growth of polysilicon and the required fluid dynamic conditions in the traditional Siemens reactor were described by del Coso et al. []. Analytical solutions for the deposition process provided information on maximizing amount of polysilicon obtained vs. consumed energy during the deposition process. The analysis of the the growth rate, deposition efficiency, and power-loss dependence on the surface temperature, reactor pressure, gas velocity, the mixture of gas composition was performed. It was found that at atmospheric pressure, the H2 molar fraction 0.85–0.90 at the inlet should be adjusted, the gas inlet temperature should be raised to 673-773K , and the gas velocity should reach the Reynolds number 800; what would result in the growth rate 6-6.5μm/min. If Si growth using CHCl3 is to be performed at pressures above atmospheric, the growth rates of 20μm/min at 6atm is found to be optimal. [i]

[i] G. del Coso, C. del Cañizo, A. Luque, J. Electrochem. Soc. 2008, Vol.155, Iss.6, D485-D491, Chemical Vapor Deposition Model of Polysilicon in a Trichlorosilane and Hydrogen System, http://jes.ecsdl.org/content/155/6/D485.short , doi: 10.1149/1.2902338   

SiHCl3 for SiC layer growth by CVD

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