• H. Ryuto, G.H. Takaoka, M. Takeuchi
  Kyoto University, Photonics and Electronics Science and Engineering Center, Kyoto

A liquid cluster ion beam irradiation system has been developed for surface processing and modification of solid materials used in the semiconductor industry. The liquid clusters are produced by the adiabatic expansion method. The vapor pressure of the source materials such as water or ethanol is increased by heating, and ejected to a vacuum chamber through a supersonic nozzle. The ionized clusters by the electron impact ionization are accelerated to typically 3-9 kV after the elimination of monomers by the retarding voltage method, and irradiated on the solid surfaces. The sputtering yield of silicon by the ethanol cluster ion beam irradiation was more than 100 times larger than that by an argon monomer ion beam. On the other hand, the radiation damage and surface roughness caused by the ethanol cluster ion beam irradiation decreased when the mean cluster size was increased by increasing the retarding voltage. Irradiation effects of liquid cluster ion beams on polymers are also discussed.

• M. Takeuchi, H. Ryuto, G.H. Takaoka
  Kyoto University, Photonics and Electronics Science and Engineering Center, Kyoto

In order to establish a shallow implantation of polyatomic carbons, a polyatomic ion source for organic liquids with a high-vapor pressure was developed. Vapor of n-octane was ionized by an electron bombardment, and the ion current of 230 μA was obtained at an extraction voltage of 2 kV. The mass spectra indicated that C₃H₇ ion was the highest in the ion concentration and some fragmentations of octane molecule took place, which might be caused by the electron bombardment. Depth profile of carbon into single crystalline silicon irradiated with C₃H₇ or C₆H₁₃ at different acceleration voltage was analyzed by X-ray photoelectron spectroscopy. As a result, the implanted depth increased with increase of the acceleration voltage. In addition, the C₆H₁₃ was implanted deeper than the C₃H₇ at the same incident energy per atom even though shallow implantation due to binary collision effect had been expected. The depth profile are also discussed in comparison with computer simulation results.