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

• Published in: Materials science in semiconductor processing 2000-06, Vol.3 (3), p.221-225
• Main Authors: Ohno, Naotsugu, Hara, Tohru, Matsunaga, Yasuhiko, Current, Michael I, Inoue, Morio
• Format: Article
• Language: English
• Subjects: Crystalline; Ion implantation; Pre-amorphization
• ISSN: 1369-8001; 1873-4081
• DOI: 10.1016/S1369-8001(00)00036-6

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 3×10 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 1×10 18 atoms/cm 3 decreases from 0.19 to 0.1 μm for implantation into a pre-amorphized layer compared to B implantation into crystalline silicon. After annealing at 950°C, B atoms diffuse much more rapidly in the pre-amorphized layers than in the crystalline silicon case. Nevertheless, shallower junctions are obtained with the use of pre-amorphization. For dual F + and B + implantation at F + doses above 1×10 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.