Influence of surface-activated reaction kinetics on low-pressure chemical vapor deposition conformality over micro features

Abstract

The coupled effect of molecular scattering and surface-activated reactions on low-pressure chemical vapor deposition (LPCVD) film conformality is investigated. Using a single-precursor two-step surface-activated deposition as an example, film conformality can be found to depend on two first-principle dimensionless parameters-Sc, the intrinsic sticking coefficient, and Sa, the surface saturation factor. An analytical integral material balance formulation, developed for the feature-scale molecular transport, is solved numerically in a wide range ofSc and Sa. The results show that film conformality generally improves with decreasing Sc and increasing Sa. With Sc fixed in most LPCVD processes (due to the nature of the precursor species), the ability to control Sa in the process becomes the key to conformal deposition. The intrinsic surface-activated deposition rate expression shows no apparent reaction order. Therefore, previously reported Monte Carlo schemes and integral-differential models employing a single sticking parameter or a fixed reaction order to characterize LPCVD step coverage behavior are applicable only in limited cases. The two-parameter model has been found useful in understanding the H 2 -reduced tungsten CVD process, for which the first-principle parameters can be determined from kinetic data reported in the literature. 78

Conformity of Silica-like Thin Films Deposited by Atmospheric Pressure Townsend Discharge and Transport Mechanisms

“…This process can induce a local averaging of the solid angles, improving the conformity. Nevertheless, several studies [31]- [35] previously demonstrated that the influence of the surface diffusion on the conformity is very low in most cases.…”

Robust, stable, and accurate boundary movement for physical etching and deposition simulation

“…We will let , , and (molecule/ m s) denote the adsorption, desorption, and surface reaction rate constant, respectively. Similar to [21], let the adsorption probability of the precursor be (unitless) on available sites (zero on occupied sites), the surface coverage of available sites be (unitless), the surface coverage of occupied sites be (unitless), and (molecule/ m s) be the precursor impingement flux. Then the adsorption rate (molecule/ m s) will be equal to the depletion rate of in dynamic balance.…”

“…where (unitless) accounts for all first-order geometrical effects. The limiting cases of (adsorptionlimited) for a first-order reaction and (surfacereaction-limited) for a zero-order reaction is well illustrated in [21]. Moreover, if ( m) is defined as a phenomenological length to express the thickness of a region above the surface profile, and if the reaction site density is assumed to be constant within this region, the deposition rate modulation factor can be expressed as…”

“…S in (8) can be extracted from the experimental deposition rate on planar surfaces [35], as shown in Fig. 8(a), if in (7) or the rate constants can be derived from other measurement/equipmentmodeling or first-principle calculations [21]. can be extracted from the experimental curves of the step angles (more error) or the corner thickness vs. the O /O ratio [33], as shown in Fig.…”

Sealing of micromachined cavities using chemical vapor deposition methods: characterization and optimization

“…On the other hand, existing computer models cannot accurately predict deposition profile and sealing conditions of surface microcavities. Although computational models and tools have been developed and proven successful for predicting step coverage on relatively simple geometries (e.g., isolation trenches or vias in integrated circuit processes) [19]- [21], complex three-dimensional structures encountered in MEMS pose new challenges. The simulation program, SPEEDIE, has not been able to successfully predict the deposition thickness required for sealing.…”