ABSTRACT We have recently developed a radical measurement method using infrared diode laser absorption spectroscopy (IRLAS) and succeeded in measuring the SiH3 radical density in DC pulsed and RF silane plasmas, and the diffusion coefficient and reaction rate constant of the SiH3 radical for the first time. The correlation of the SiH3 radical density and a-Si : H deposition rate in DC pulsed SiH4/H2 plasma was also measured. Although this SiH3 radical has been assumed to be the most important precursor of a-Si:H thin film formation, it has never been measured. This IRLAS can be applied also to SiH and SiH2 radicals in silane plasma, the CF radical in CF4/H2 plasma, the CH3 radical in methane plasma, etc. It has been demonstrated by studies mentioned above that IRLAS is a very widely-used spectroscopic method which is applicable to the measurement of various radicals in many processing plasmas. In this review, IRLAS and typical radical measurements by it are described.
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