Impact of wide dynamic range plasma sources for advanced plasma processing

• Published in: Surface & coatings technology 2003-06, Vol.169, p.14-19
• Main Author: Engemann, J.
• Format: Article
• Language: English
• Subjects: Microwave; PACVD; Pulsed; Radio frequency (RE)
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(03)00046-X

One of the major driving forces for the development of plasma reactors for treatment of large planar structures results doubtlessly from microelectronics. In its ever increasing demand for reduced cost coupled with higher performance and reliability larger wafer processing capabilities are required. As a technological consequence for plasma-based processes scaleable high density plasma sources have been developed over the years and successfully introduced into semiconductor processing. Meanwhile there is a whole range of plasma sources available including advanced capacitively/inductively coupled r.f.-sources, helicons and a variety of microwave plasma sources. As an example the so-called SLot ANtenna 2.45 GHz microwave plasma source SLAN with active plasma diameters of up to 67 cm will be presented. The smallest of these sources with a plasma diameter of 4 cm (μSLAN) allows the formation of a free standing plasma beam with extraordinary properties. Using argon as a feed gas electron temperatures of well below 1 eV with plasma densities in the range of 10 13/cm 3 have been observed more than 30 cm downstream the source outlet. For a more controlled plasma-chemical selectivity combined with a certain degree of original monomer retention pulsed power source operation has proven to be very effective. Therefore, advanced plasma processing relies to a large extent on such a time-modulated, i.e. pulsed power source operation. Two plasma source schemes developed at the Microstructure Research Center–fmt are targeting towards these applications. One is the well-known 2.45 GHz SLAN microwave coupling scheme and the other one uses the 13.56 MHz r.f.-hollow cathode effect (hollow cathode discharge (HCD)). In combination with an innovative gas distribution system based on fractal geometries the latter employs a multitude of individual plasmajets arranged in a linear or hexagonal matrix. Thus, the sources can be easily scaled up. Currently, the largest planar HCD-version has an active area of 450×150 mm 2. Examples for functionalised thin film deposition based on the HCD-scheme with emphasis on biomedical applications are presented.