Anomalous Boron Profiles Produced by BF2 Implantation Into Silicon

• Published in: Journal of the Electrochemical Society Vol. 127; no. 4; pp. 981 - 982
• Main Authors: Sigman, T W, Deline, V R, Evans, C A, Katz, W M
• Format: Journal Article
• Language: English
• Published: 01.01.1980
• ISSN: 0013-4651
• DOI: 10.1149/1.2129801

The problem of BF2 implants exhibiting anomalous 11B profiles when BF2 is used as the implant species in the production of low sheet resistance such as is used for high frequency Si bipolar transistors is explored. Secondary ion mass spectrometry (SIMS) in-depth profiles for samples of BF2 showed a pronounced shoulder on the deep side of the 11B profile. It was hypothesized that the shoulder resulted from dissociation of BF2 molecules which had undergone mass analysis but had not obtained the full terminal acceleration of the ion implanter. This was tested by implanting monoatomic B ions at various energies. The test showed that the majority of dissociation occurred prior to the exit slits of the magnetic deflection mass analyzer and not during the final acceleration. This dissociation can be reduced by better operating vacuum in the critical region of the implanter and by using a second stage mass analysis prior to the final acceleration stage of the implanter.--L.M.W.