Volume 89, Issue 5, 01 March 2001
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
89(2001); http://dx.doi.org/10.1063/1.1345519View Description Hide Description
A two-dimensional model has been used to understand the physics and process engineering issues associated with a conceptual 300 mm Cu internal-coil ionized physical vapor deposition reactor. It has been found that inductive coupling from the coil is the primary source of plasma production. Since the coil is in direct contact with the plasma, a significant fraction of the coil power is deposited in the gas capacitively as well. This results in sputtering of the Cu coil, which tends to improve Cu flux uniformity at the outer edges of the wafer. Since the Cuionization threshold is much lower than Ar, density is comparable to density even though ground stateCu density is much smaller than Ar. Significant fraction of the neutral Cu flux to the wafer is in the metastable or athermal state. The effects of several actuators, reactor dimensions, and buffer gas on important plasma and process quantities have also been investigated. Electron density in the reactor and Cuionization fraction increases with increasing total coil power because of enhanced ionization. Total coil power however does not affect the Cu density appreciably, except near the coil where enhanced coil sputtering increases the Cu density. Decrease in dc target voltage with increasing coil power decreases loss to the target and results in an increase in total Cu flux to the wafer. Electron and Cu density in the reactor increase with increasing dc target power. This is due to enhancement in target sputtering and consequent ionization of the sputteredCu. While this increases the total Cu flux to the wafer, ionization fraction is not affected much. It is demonstrated that uniformity of Cu flux to the wafer and ionization fraction can be controlled by means of the terminating capacitor at the coil. Decreasing the terminating capacitance increases the coil voltage, enhances coil sputtering and enhances Cu flux toward the outer edges of the wafer. This, however, decreases the amount of power that is transferred to the plasma inductively, reducing the ionization efficiency. Increasing the coil–wafer distance results in fewer sputteredCu atoms being ionized as the target–coil distance becomes smaller than the mean free path for thermalization of hot sputteredCu atoms. Also, one can control the ionization fraction of Cu flux to the wafer by replacing Ar by Ne or Xe, without significantly impacting the total Cu flux.
89(2001); http://dx.doi.org/10.1063/1.1345520View Description Hide Description
Ionized physical vapor deposition of Cu in a mixture of three rare gases (He–Ar–Xe) is explored in this article. Results indicate that total Cu flux to the wafer, ionization fraction of Cu at the wafer, and ratio of total effective ion flux to total Cu flux increase with increasing Xe concentration in the gas mixture. This is because of enhancement of electron density and ions having a larger sputter yield on Cu than other ions. Increase in He concentration decreases the ionization fraction due to a lower electron density. However, Cu flux to the wafer increases because He is less effective in thermalizing the hot sputtered neutrals. One major consequence of these trends is that one can independently control total Cu flux to the wafer (corresponding to deposition rate) and ionization fraction (a major factor controlling the deposition profile) over a wide range by means of the buffer gas composition.
Temporal behavior of the wall voltage in a surface-type alternating current plasma display panel cell using laser induced fluorescence spectroscopy89(2001); http://dx.doi.org/10.1063/1.1343893View Description Hide Description
Electric fields were measured using laser induced fluorescencespectroscopy and the wall voltage was estimated from the measuredelectric fields in a surface-type alternating currentplasma display panel cell with a helium discharge (100 Torr) driven by square sustaining pulses. The wall voltage showed very complicated, temporally dynamic behavior. The polarity of the wall voltage changed rapidly as soon as the plasma was ignited, and its magnitude continuously increased due to the continuous injection of charged particles onto the dielectric surface from the afterglow plasma during the rest of the pulse-on period. When there was a self-erasing discharge at the instant of the pulse turn-off, the wall voltage dropped sharply by about 110 V and decreased continuously owing to the diffusion-induced charge redistribution or leakage. The decay rate of the wall voltage during the pulse-off period was very dependent on the surface condition of the protecting layer of the dielectric.
89(2001); http://dx.doi.org/10.1063/1.1346655View Description Hide Description
We report on mass spectroscopicmeasurements of species originating from a microwave (MW) dischargeplasma under simulated diamonddeposition conditions. The plasma is produced in a 30 W MW flow tube through which flows a gas mixture of about 1% methane admixed in hydrogen. Plasma composition was investigated as a function of gas component ratio by -ion attachment mass spectrometry. C, and together with the free-radical species of and were observed on the mass spectra as -ion adducts. Atomic carbon was the most abundant species, suggesting an important role for atomic carbons in diamond film growth.