Volume 87, Issue 10, 15 May 2000
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
87(2000); http://dx.doi.org/10.1063/1.372966View Description Hide Description
Full scale reactor model based on fluid equations is widely used to analyze high density plasma reactors. It is well known that the submillimeter scale sheath in front of a biased electrode supporting the wafer is difficult to resolve in numerical simulations, and the common practice is to use results for electric field from some form of analytical sheathmodel as boundary conditions for full scale reactor simulation. There are several sheathmodels in the literature ranging from Child’s law to a recent unified sheathmodel [P. A. Miller and M. E. Riley, J. Appl. Phys. 82, 3689 (1997)]. In the present work, the cold ion fluid equations in the radio frequency sheath are solved numerically to show that the spatiotemporal variation of ion flux inside the sheath, commonly ignored in analytical models, is important in determining the electric field and ion energy at the electrode. Consequently, a semianalytical model that includes the spatiotemporal variation of ion flux is developed for use as boundary condition in reactor simulations. This semianalytical model is shown to yield results for sheath properties in close agreement with numerical solutions.
87(2000); http://dx.doi.org/10.1063/1.372967View Description Hide Description
The precursor species of fluorocarbon film growth at the reactor wall irradiated by an electron cyclotron resonance plasma have been studied by using a quadrupolemass spectrometer. The amount of polymeric neutral species and absolute densities of radicals in the vicinity of the wall were measured by electron attachment and threshold ionizationmass spectrometry, respectively. The trends in the film growth rate as a function of gas residence time, diluted hydrogen concentration, and microwave power were well accounted for by the competition between the incorporation of radicals and positive ions and the removal by F and H atoms. The fluxes of radicals and positive ions incident upon the wall were shown to be comparable with the net condensed carbon flux derived from the growth rate. In contrast, the trends in the amount of polymeric neutrals were not well correlated to the growth rate.
87(2000); http://dx.doi.org/10.1063/1.372968View Description Hide Description
The operation of a metal–vapor buffer-gas hollow cathode discharge is re-examined using modeling techniques that have been developed for electronegative plasma discharges. It is shown that a previously developed global model can be extended to give spatially resolved densities as well as more accurate values for the plasma parameters. A numerical calculation for a neon–copper (Ne–Cu) discharge is used to illustrate the results of the modeling technique. The density profiles of the neutral and ion components, and their variation with the buffer gas pressure, are similar to those found by numerical solution of the complete equations.
87(2000); http://dx.doi.org/10.1063/1.372969View Description Hide Description
Ionized metal physical vapor deposition (IMPVD) is a process in which sputtered metal atoms from a magnetron target are ionized by a secondary plasma, accelerated into the substrate, and deposited with moderately anisotropic fluxes. The momentum and energy transfer from the sputtered metal atoms and ion-produced reflected neutrals to the background gas, sputter heating, produces rarefaction which influences the operating characteristics of the discharge. To address these processes, a model was developed to simulate the sputtering of metal atoms and their transport in IMPVD reactors. The model accounts for the ion-energy-dependent yield and kinetic energy of the sputtered and reflected atoms, and for sputter heating. The model was validated by comparing its results to experimentally measured metal atom densities and the ionization fraction of the deposition flux. Sputter heating as a function of auxiliary ionization and magnetron power in an inductively coupled plasma IMPVD reactor for Al deposition was then investigated. Sputter heating produces rarefaction of the buffer gas which results in a redistribution of Al species in the reactor compared to the absence of sputter heating. Consequently, the ionization fraction of the depositing metal flux decreases, while the magnitude of the flux increases. The minimum Ar density due to sputter heating is regulated by heat transfer to the target. The electron density increases significantly with the addition of a small amount of metal atoms to the plasma.