Soonam Park

Dual Discharge Modes Operation of an Argon Plasma Generated by Commercial Electronic Ballast for Remote Plasma Removal Process

An argon plasma generated between the cone-shaped electrode powered by commercial electronic ballast and grounded plane electrode has been investigated. Since the electronic ballast has positive and negative cycle in a period, two different discharge modes of remote plasma-the normal glow discharge mode and the hollow cathode discharge mode-have been observed. It is noted that the hollow cathode discharge mode has wider operation window in gas pressure than the glow discharge one. The glow discharge started to be extinguished at pressure higher than 4.1 torr and turned to the hollow cathode discharge mode in the holes on ground plate, while the hollow cathode discharge mode kept growing until 10 torr. These results show that the stable operation window of the system could be defined by the glow discharge mode rather than the hollow cathode discharge mode and could be improved by optimizing the applied voltage waveform and electrode configuration.

Microwave plasma generation by the fast rotation and slow pulsation of resonant fields in a cylindrical cavity

A digitally controlled solid-state microwave generator allowing variable frequency operation and precise phase control is adopted for plasma generation. In this study, a resonant cylindrical cavity is used as a microwave applicator in place of conventional waveguides. In order to improve the plasma uniformity, the TE111 mode is agitated by injecting microwaves into the cavity from two spatially orthogonal directions, with a temporal phase difference . Theoretical analyses and finite-difference time-domain simulations derive the following effects of the phase control. In the case of = ±π/2, fast rotation of the cavity field takes place with a rotational frequency of ω/2π (= 2.4–2.5 GHz), where ω denotes the microwave angular frequency. On the other hand, when is linearly modulated in time with a low frequency of Ω/2π (= 0.1–1000 Hz), slow pulsation takes place, in which the cavity field alternately excites a circular rotation and a standing oscillation at the modulation frequency. These effects are experimentally confirmed in microwave discharges in argon at 0.1–20 Torr with total injection powers from 50 to 800 W. Two-dimensional images of the optical emission from the generated plasma show that both the fast rotation and slow pulsation improve azimuthal plasma uniformity.

Optimization of hollow cathode discharge electrode for damage free remote plasma removal process for semiconductor manufacturing

Cone-shaped hollow cathode electrode configuration for a damage free remote plasma removal process has been optimized for given pressures based on Paschen characteristic curves, voltage–current characteristics and time-resolved discharge observations as well as oxide film removal performances. Remote plasmas have been generated in two types of cone-shaped electrodes with mixtures of He, NF3, and NH3 for pressure range of 1–30 Torr. Paschen characteristic curves and voltage–current (V–I) characteristics define an operating pressure for low breakdown voltage and the hollow cathode effect to minimize the particles. Sinusoidal voltage waveform and asymmetry electrode configuration alternate the glow discharge and hollow cathode discharge modes in a cycle. The current and infrared emission intensity from the glow discharge increases together for both cone-shaped electrodes with increasing pressure, whereas the hollow cathode discharge plasma emits strong infrared only when pD condition is satisfied. For the wide cone electrode configuration, high voltage operation at higher pressure results in particle contamination on the processed wafer by high energy ion bombardment. Operating at optimum pressure for a given electrode configuration shows faster oxide etch rate with better uniformity over a whole 300 mm wafer.

Dual plasma modes operation of hollow cathode electrode system for remote plasma removals for semiconductor manufacturing

Summary form only given. A remote plasma source for selective removal process in semiconductor device fabrication has been investigated. Plasma has been generated between the cone-shaped electrode powered by commercial electronic ballast and the grounded plane electrode with noble gases of argon, helium or a mixture gas of He+NF3+NH3 for the pressure range from 1 Torr to 30 Torr. Sinusoidal voltage waveform and asymmetry electrode configuration alternate the glow discharge and the hollow cathode discharge modes in a cycle - two different discharge modes in a cycle. It is noted that the operating pressure windows of the hollow cathode discharge mode was wider than the glow discharge mode. The glow discharge started to extinguish at relatively higher pressure while the hollow cathode discharge mode kept growing. These results show that the stable operation window of the system could be limited by the glow discharge mode rather than the hollow cathode discharge mode and could be improved by optimizing the applied voltage waveform and electrode configuration.