AVS 51st International Symposium
    Manufacturing Science and Technology Tuesday Sessions
       Session MS-TuP

Paper MS-TuP11
Silicon Isotope Enrichment by IRMPD of Si@sub 2@F@sub 6@: Development of Continuous Silicon Isotope Enrichment Technique for Large-Scale Production

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: K. Katsumata, Japan Atomic Energy Research Institute
Authors: K. Katsumata, Japan Atomic Energy Research Institute
H. Ohba, Japan Atomic Energy Research Institute
H. Akagi, Japan Atomic Energy Research Institute
A. Yokoyama, Japan Atomic Energy Research Institute
S. Arai, Hill Research Corporation, Japan
Correspondent: Click to Email
Since it had been reported that an isotopically pure @super 28@Si single crystal has high thermal conductivity, it has been growing interests in its use to the high thermal conductive semiconductor substrate. For the expansion of the market of the enriched silicon, it may be necessary to develop a large-scale silicon isotope enrichment method. We have demonstrated a highly efficient silicon isotope enrichment utilizing infrared multiphoton dissociation (IRMPD) of Si@sub 2@F@sub 6@ irradiated with two-color CO@sub 2@ laser@footnote 1@. The scheme consists of two successive steps: At first, the Si@sub 2@F@sub 6@ molecules containing @super 29@Si and @super 30@Si are excited selectively by the irradiation at nearly resonant wavelength with weak pulsed laser beam. Then, the excited molecules are dissociated by the irradiation at non-resonant wavelength with relatively high intense pulsed laser beam. In this report, we developed continuous silicon isotope enrichment technique for the large-scale production, based on this method. An apparatus for continuous isotope enrichment consists of two TEA-CO@sub 2@ lasers, a reaction cell with a gas flow system, and instruments for the monitoring of the abundance of Si in Si@sub 2@F@sub 6@ and the production rate. Si@sub 2@F@sub 6@ gas and buffer Ar gas flowed through a reaction cell with controlling pressure and flow rate. Then isotopically selective IRMPD of Si@sub 2@F@sub 6@ molecules containing @super 29@Si and @super 30@Si were done in the reaction cell by the simultaneous irradiation with two laser pulses at different wavelengths. All of the reaction products were corrected in a trap at 77 K. After the conditions for continuous isotope enrichment had been optimized, @super 28@Si enriched up to 99 % was produced at a rate of 0.7 g/h with the yield of 63 %. @FootnoteText@ @footnote 1@A. Yokoyama, et al., US patent 2003-0034243 A1 (2002).