200-mm-diameter neutral beam source based on inductively coupled plasma etcher and silicon etching

The authors developed a neutral beam source consisting of a 200-mm-diameter inductively coupled plasma etcher and a graphite neutralization aperture plate based on the design of a neutral beam source that Samukawa et al. [Jpn. J. Appl. Phys., Part 2 40, L779 (2001)] developed. They measured flux and energy of neutral particles, ions, and photons using a silicon wafer with a thermocouple and a Faraday cup and calculated the neutralization efficiency. An Ar neutral beam flux of more than 1 mA/cm2 in equivalent current density and a neutralization efficiency of more than 99% were obtained. The spatial uniformity of the neutral beam flux was within ±6% within a 100 mm diameter. Silicon etching using a F2-based neutral beam was done at an etch rate of about 47 nm/min, while Cl2-based neutral beam realized completely no undercut. The uniformity of etch rate was less than ±5% within the area. The etch rate increased by applying bias power to the neutralization aperture plate, which shows that accelerated neutral beam was successfully obtained. These results indicate that the neutral beam source is scalable, making it possible to obtain a large-diameter and uniform neutral beam, which is inevitable for application to mass production.