Cross-contamination reduction by beam cleaning

Beam cleaning by Ar/sup +/, Xe/sup +/, F/sup +/ and SiF/sub 3//sup +/ implants was studied for arsenic cross-contamination reduction. After As/sup +/ implantation at 40 keV with a dose of 1/spl times/10/sup 17/ ions/cm/sup 2/, cross-contamination was measured by TXRF using Ar/sup +/ implants at 40 keV with a dose of 5/spl times/10/sup 15/ ions/cm/sup 2/, to check each cleaning procedure. The concentration of the initial As cross-contamination after As/sup +/ implantation increased to about 1/spl times/10/sup 13/ atoms/cm/sup 2/. The contamination level went down to about 1/10th when using Ar/sup +/ cleaning implants with a dose of 8/spl times/10/sup 17/ ions/cm/sup 2/. For the Xe/sup +/ 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/sup +/ cleaning implant because of less beam current. Regarding F/sup +/ and SiF/sub 3//sup +/ cleaning implants, the reduction is at a higher rate than for the Ar/sup +/ case at the same cleaning dose. However, the elapsed time of the cleaning implant was almost the same as that of the Ar/sup +/ cleaning implant, but used less beam current. Therefore, for effectiveness and ease of use, an Ar/sup +/ cleaning implant with as high current as possible is recommended for beam cleaning.