| EPSRC Reference: |
GR/J40287/01 |
| Title: |
THE ACTION OF FLUORINE IN POLYSILICON EMITTER BIPOLAR TRANSISTORS |
| Principal Investigator: |
Ashburn, Professor P |
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| Department: |
Electronics and Computer Science |
| Organisation: |
University of Southampton |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
01 March 1994 |
Ends: |
29 February 1996 |
Value (£): |
104,824
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Summary on Grant Application Form |
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This EPSRC project is a two year collaboration between the Department of Electronics and Computer Science, Southampton University (Dr. P. Ashburn) and the Department of Materials, Oxford University (Dr. G. R. Booker). The project aims to investigate the effects of fluorine in polysilicon emitter bipolar transistors using device and materials studies. Further aims are to optimise the beneficial effects of the fluorine and to develop an explanation for the action of the fluorine at the polysilicon/silicon interface. Progress:In the first year of the research, a good correlation has been established between the electrical properties of the polysilicon and the structure of the polysilicon and of the polysilicon/silicon interface. Electrical measurements on npn polysilicon emitters have shown that the benefits of fluorine can be obtained in npn transistors as well as pnp [1]. These include improved current gain [2], improved base current ideality [3], and reduced emitter resistance [2]. TEM studies have shown [4] that the fluorine has a strong effect on the interfacial oxide layer at the polysilicon/silicon interface. Its presence leads to the break-up of the interfacial oxide, and to the epitaxial regrowth of the polysilicon. It is so effective in this role that epitaxial regrowth of the polysilicon has been achieved at a temperature as low as 850 C [5]. This is the lowest temperature ever reported for the epitaxial regrowth of a polysilicon emitter. A good understanding of the mechanisms occurring during the regrowth is being achieved [4]. The work will continue during 1995 with optimisation of the processing and the fabrication of devices to demonstrate the passivation effects of the fluorine in npn transistors. [1] N. E. Moiseiwitsch, P. Ashburn; IEEE Trans Electron Devices, The benefits of fluorine in pnp polysilicon emitter bipolar transistors ; ED-41, p1249 (1994).[2] N. E. Moiseiwitsch, P. Ashburn; Interfacial oxide break-up in npn polysilicon emitter bipolar transistors by fluorine implantation ; Proc. 24th European Solid State Device Research Conference, p55 (1994).[3] N. E. Moiseiwitsch, P. Ashburn; Improved base current ideality in polysilicon emitter bipolar transistors by fluorine implantation ; IEE Colloquium on Advanced MOS and bipolar devices, February 1995.[4] C. D. Marsh, N. E. Moiseiwitsch, G. R. Booker, P. Ashburn; Epitaxial regrowth of As doped polycrystalline silicon at 850C induced by fluorine implantation and a pre-anneal ; Proc. 9th Microscopy of Semiconducting Materials Conference, Oxford, 1994, in press.[5] N. E. Moiseiwitsch, C. Marsh, P. Ashburn, G. R. Booker; Epitaxial regrowth of n+ polycrystalline silicon at 850 C induced by fluorine implantation ; accepted for publication in App. Phys. Lett.
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Key Findings |
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.soton.ac.uk |