A microwave-induced plasma source: Characterization and application for the fast deposition of crystalline silicon films

Abstract

A microwave-induced plasma source is developed and is applied for the fast deposition of crystalline silicon films. In this paper, the plasma source is diagnosed first. Electron density, electron temperature, and discharge gas temperature of the plasmas generated in ambient air are studied using the optical emission spectroscopy method. The electron density is estimated by analyzing the Stark broadening of the hydrogen Hβ emission profile and is found to be as high as >1015 cm−3 over wide conditions. The Boltzmann plot method is used to calculate the electron temperature, which shows a value smaller than 1 eV. Analysis of the rotational structure of OH molecular emission reveals a discharge gas temperature in a range of ∼400–800 °C. Preliminary efforts of using the plasma source for Si film fast deposition are performed at a reduced pressure by using SiCl4 as the source gas. A fast deposition rate of 150 nm/s has been achieved for Si film with a high Raman crystallinity of Ic/Ia>10 even without using substrate heating and under a low H2 dilution condition. Mechanisms for these results are discussed in detail.

High rate synthesis of crystalline silicon films from SiH4+He using high density microwave plasma

“…Diagnosis of the plasma parameters has shown that the plasma source has an electron density larger than 10 15 cm −3 at atmospheric pressure conditions. 33 On the other hand, we have verified previously that in the plasmas with He as one of the source gases, number density of the excited He atoms is quite large and most of the excited He atoms are in the metastable states He ‫ء‬ , leading to the occurrences of the Penning ionization and excitation. 34,42,43 The He ‫ء‬ atoms have energies of 19.8 or 20.1 eV that are extremely larger than the dissociation energy of SiH 4 of around 10 eV.…”

“…Plasma characterizations have demonstrated that the discharging gas in the plasma shows a high temperature of ϳ800°C ͑depends on the plasma generation conditions͒. 33 Through frequent collisions with the energized radicals in the gas phase, the film precursors gain sufficient energy that finally can promote their surface diffusions. Next, the high temperature discharge gas also heats up the growing surface and therefore the growing surface exhibits an elevated temperature.…”

“…1͑b͒ employs a hybrid-mode resonator cavity. 33,34 The cavity was designed by taking into account the resonance frequency shift caused by plasma, such that it is resonant to the microwaves in a transverse magnetic 010-like mode before the plasma ignition and in a transverse electromagnetic ͑TEM͒like mode after the plasma ignition. 35 The 2.45 GHz microwaves generated from magnetron propagate through waveguides and coaxial cable, and are coupled into the cavity through a rod antenna.…”

“…By using this system, plasmas can be produced easily both in open atmosphere environment and at reduced pressure conditions. 33 During the plasma deposition process ͓Fig. 1͑c͔͒, the reactive source gases are homogeneously supplied into plasma region and decomposed into reactive species that contribute to the film growth.…”

Antimicrobial effects of microwave‐induced plasma torch (MiniMIP) treatment on Candida albicans biofilms

“…So far, microwave‐induced plasmas (MIPs) are mainly used in spectroscopy for the analysis of gas components (Broekaert and Engel, ), surface modifications (Jia, Kuraseko et al , ) or the processing of biogas (Tippayawong, Chaiya et al , ). Not much is known about microwave plasmas which are already used in medical technology apart from SteriPlas (Adtec, Hounslow, UK).…”