Design of a 200-MHz RFQ for 3-MeV He⁺⁺ beam irradiation

Abstract

To produce more efficient power semiconductors by reducing the switch loss, we studied heliumion implantation instead of gold diffusion and electron irradiation. The 3-MeV energy and 0.1-mA current for about a 10 × 10¹⁴ ions/cm² dose is required for silicon wafers of ten inches in diameter. A radio-frequency quadrupole (RFQ) can be a good accelerator to meet the above requirements. We designed a four-vane type 200-MHz RFQ for this purpose. A 25-keV/u He⁺⁺ beam with a 10-mA peak current was extracted from an ion source and was matched to the RFQ by using electrostatic lenses. The RFQ is designed to accelerate He⁺⁺ ions (A/q = 2) up to 750 keV/u. A 200-kW tetrode RF amplifier drives the RFQ with a duty factor of 1%. After the RFQ, a beam wobbling system and a beam transport system are required to irradiate the beam onto large silicon wafers. This work summarizes the detailed design of the irradiation system.