Ballistic transport-reaction prediction of film conformality in tetraethoxysilane O2 plasma enhanced deposition of silicon dioxide

Abstract

Conformality of SiO2 films from tetraethoxysilanesourced remote microwave plasmaenhanced chemical vapor deposition J. Vac. Sci. Technol. A 13, 676 (1995); 10.1116/1.579806Optical characteristics of SiO2 formed by plasmaenhanced chemicalvapor deposition of tetraethoxysilane Quantitative infrared analysis of the stretching peak of SiO2 films deposited from tetraethoxysilane plasmas EVOLVE, a low pressure deposition process simulator based on a fundamental model for free molecular transport and heterogeneous surface reactions in features, is used to predict the evolution of silicon dioxide film profiles during plasma enhanced chemical vapor deposition from mixtures of tetraethoxysilane (TEOS) and oxygen. The constitutive relationships required by EVOLVE are supplied by simple models for the plasma, the plasma sheath and the surface chemistry. The intrinsic kinetic model used in the simulations involves film growth by oxidative attack on adsorbed TEOS and/or TEOS fragments by both oxygen ions and oxygen atoms. Recombination of oxygen atoms on the surface of the growing film competes with TEOS oxidation by atoms. The plasma models are used to predict the fluxes of oxygen ions and oxygen atoms to the surface. The fluxes of all neutral species from the source and from all surfaces are assumed to obey cosine distribution functions. Oxygen ions are assumed to follow an exponential distribution; the standard deviation of the distribution is adjusted to match predicted film profiles with experimentally determined profiles. This combination of an almost directional component and an almost isotropic component allows the prediction of the experimental trends in deposition rate and film conformality with operating conditions. The constitutive models are used by EVOLVE to predict film profiles as a function of temperature, within their window of validity, for deposition in ideal rectangular trenches with an aspect ratio of 2. Film conformality decreases as temperature increases, even though deposition rate actually decreases. Film con formality decreases with increasing pressure and increases with increasing power. All of these predicted trends in conformality agree with our experimental results.

Step Coverage Predictions Using Combined Reactor Scale and Feature Scale Models for Blanket Tungsten LPCVD

“…As mentioned in the Introduction, two different approaches to predicting step coverage in LPCVD have achieved reasonable success in recent years; 1) "continuum-like" diffusion-reaction models (DRM) [5][6][7][8][9], and 2) modified line-of-sight or ballistic transport-deposition models (BTRM) [10][11][12][13]. For the LPCVD system con- sidered in this work, the following assumptions of the two models are the same:…”

“…These assumptions and how they impact deposition profiles have been addressed [5][6][7][8][9][10][11][12], but assumptions 3, 5 and 6 are briefly reviewed for completeness. Assumption 3 regarding diffuse reemission is central to the derivation of Knudsen diffusivities used in the DRM, but is not critical to the BTRM.…”

“…The BTRM has been detailed [10][11][12]; however, the basis is briefly reviewed for completeness. In the BTRM, molecular transport is "ballistic" and deposition within a feature on a patterned wafer depends on the local fluxes and temperature.…”

“…defines the "differential transmission probability" [10][11][12]. The differential transmission probabilities include a symmetric visibility factor KA'A = K AA· which is 1 if the two points are in line of sight and 0 if they are not.…”

“…Several other groups have developed versions of the DRM [8,9]. More recently, Cale and coworkers [10][11][12] introduced the more fundamental "ballistic transport and reaction model" (BTRM), which forms the basis for the new generation of physically based low pressure deposition and etch simulators. A similar model has since been presented by IslamRaja et of.…”