| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS1-WeM |
| Session: | Plasma Based Ion Implantation and Ion-Surface Interactions |
| Presenter: | David Urrabazo, University of Texas at Dallas |
| Authors: | D. Urrabazo, University of Texas at Dallas M.J. Goeckner, University of Texas at Dallas L.J. Overzet, University of Texas at Dallas |
| Correspondent: | Click to Email |
A few recent publications point to the possibility of controlling the ion induced electron emission (IIEE) yield from semiconductor surfaces in real time through controlling the numbers of electrons in the semiconductor’s conduction band (ne,CB). Of course, ion bombardment induced electron emission also occurs in the plasma processing of semiconductors, and should cause differences between processing n- and p-type wafers if it truly depends upon ne,CB. Hagstrum’s Auger neutralization theory for semiconductors1 assumes that the IIEE yield should NOT depend upon ne,CB, and as a result most models make the assumption that the IIEE yield is independent of ne,CB (and the position of the Fermi level as well as temperature). To our knowledge, no one has investigated this assumption! Therefore, we have experimentally and theoretically investigated it by using and extending Hagstrum’s theory as well as by measuring the IIEE yield from semiconductor samples versus doping density and type. Our results for Si demonstrate good agreement with the assumption both theoretically and experimentally. The IIEE yields of p-type, intrinsic and n-type samples are essentially the same. In direct contradiction to the theory/assumption, however; the IIEE yield for p-type Ge was measured to be 2.5 times greater than that of intrinsic and n-type samples. Precisely the opposite of what one might first expect! This result indicates that there can be other significant factors controlling the IIEE yield. One likely factor is a surface electric field. (It could have been induced by Fermi level pinning in the case of our Ge measurements, and in plasmas it could be induced by the sheath.) As a result, the new principle question becomes: Can a moderate surface electric field control the IIEE yield from semiconductors? To our knowledge, there are no unambiguous measurements answering this question either . Therefore, we will introduce a device we have designed, modeled, and begun fabricating for measuring the IIEE yield while allowing independent control over the ion flux to the surface and electric field imposed on that surface.
Acknowledgement: This material is based upon work supported by the Department of Energy under Award Number DE-SC-0009308.
1H.D. Hagstrum, Phys. Rev. 122 83 (1961)