Diffusion of ion-implanted boron impurities into pre-amorphized silicon

✍ Scribed by Naotsugu Ohno; Tohru Hara; Yasuhiko Matsunaga; Michael I Current; Morio Inoue

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 246 KB
• Volume: 3
• Category: Article
• ISSN: 1369-8001
• DOI: 10.1016/s1369-8001(00)00036-6

✦ Synopsis

Boron ion implantation into pre-amorphized silicon is studied. Pre-amorphization is performed either by F + or Si + implantation prior to B + implantation at 10 keV with 3 Â 10 15 ions/cm 2 . Broadening of the boron profile can be suppressed markedly in the pre-amorphized layers. For instance, the as-implanted depth at a B concentration of 1 Â 10 18 atoms/cm 3 decreases from 0.19 to 0.1 mm for implantation into a pre-amorphized layer compared to B implantation into crystalline silicon. After annealing at 9508C, B atoms diffuse much more rapidly in the preamorphized layers than in the crystalline silicon case. Nevertheless, shallower junctions are obtained with the use of preamorphization. For dual F + and B + implantation at F + doses above 1 Â 10 15 F + /cm 2 , fluorine is found to segregate to the peak of the boron profile during annealing. Fluorine is also trapped at the peak of the as-implanted fluorine profile peak and near the amorphous-crystalline interface. The effects of fluorine dose and anneal temperature on the F precipitation are described and compared to results for BF + 2 implants.