Cross-contamination reduction by beam cleaning

Beam cleaning by Ar⁺, Xe⁺, F⁺ and SiF₃⁺ implants was studied for arsenic cross-contamination reduction. After As⁺ implantation at 40 keV with a dose of 1×10¹⁷ ions/cm², cross-contamination was measured by TXRF using Ar⁺ implants at 40 keV with a dose of 5×10¹⁵ ions/cm², to check each cleaning procedure. The concentration of the initial As cross-contamination after As⁺ implantation increased to about 1×10¹³ atoms/cm². The contamination level went down to about 1/10th when using Ar⁺ cleaning implants with a dose of 8×10¹⁷ ions/cm². For the Xe ⁺ cleaning implant, a stronger sputtering effect had been expected for its larger mass, but the contamination reduction was a little less than that of the Ar⁺ cleaning implant because of less beam current. Regarding F⁺ and SiF₃⁺ cleaning implants, the reduction is at a higher rate than for the Ar⁺ case at the same cleaning dose. However, the elapsed time of the cleaning implant was almost the same as that of the Ar⁺ cleaning implant, but used less beam current. Therefore, for effectiveness and ease of use, an Ar⁺ cleaning implant with as high current as possible is recommended for beam cleaning