Kinetic model for the chemical vapor deposition of tungsten in the silane reduction process

Abstract

Silane reduced chemical vapor deposition tungsten as a nucleating step in blanket W

(Invited) Ultra-Conformal CVD at Low Temperatures: The Role of Site Blocking and the Use of Growth Inhibitors

“…( 7) has been shown to reproduce the experimental behavior of various experimental systems, including Si growth from SiH 4 or from SiH 4 /H 2 , and W growth from WF 6 + H 2 . (11,(33)(34)(35) Note that the saturation of the growth rate with pressure that is experimentally observed and described by Eq. ( 7) is an intrinsic feature of the surface kinetics and is not controlled by the mass transport inside the reactor.…”

“…( 12) However, Hsieh pointed out that a power law does not hold when the growth rate is measured across a sufficiently wide pressure range: the dependence is nearly linear at low pressure and tends to a saturation at high pressure. (11) It is the near-saturation regime that affords the most conformal films and is the primary focus of the kinetic model used in this work. Our work on low temperature HfB 2 growth from the precursor Hf(BH 4 ) 4 , which has a remarkably high vapor pressure of 15 Torr at room temperature, shows that low temperature CVD can afford ultra-conformal films and even fill high AR features (Fig.…”

“…(29,36) This can be derived by assuming that the rate limiting steps of the growth process are the reversible adsorption/desorption of the precursor molecule to an intermediate state P (ads) and its subsequent irreversible reaction to form film M and byproducts B. (11) Neglecting the possible role of B leads to: GR = γ k r k ads p k r + k des + k ads p [12] where k r and k des are the reaction and desorption rate coefficients and γ is a conversion factor from monolayers/sec to nm/sec. The growth rate can also be expressed as the product of the reaction rate coefficient and the fractional coverage of the surface by adsorbed precursor, GR(T, p) = γk r (T)θ( p,T), where θ(T, p) = k ads p k des + k r + k ads p [13] Comparing Eqs.…”

“…One important consequence is that, in order to predict the conditions that will lead to conformal films, one must understand the dependence of β on the precursor pressure and substrate temperature, β = β( p,T) . (11,12) However, a more direct approach is to model the conformality as a function of the (p,T) dependence of the film growth rate (GR). In this work, we identify the allowed space of (p,T) values where conformal coverage will occur for a given precursor and aspect ratio feature to be coated.…”