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Makyoh-topography study of the swirl defect in Si wafers
|Ferenc Riesz , Andrea E. Pap , Mária Ádám , István E. Lukács
Hungarian Academy of Sciences, Research Institute for Technical Physics and Materials Science, P.O.Box 49, Budapest H-1525, Hungary
|Swirl defects in heavily p-doped CZ Si single crystals have been known for a long time [1, 2]. Such defects are spiral features that are generated by the agglomeration of point defects while the crystals cools after pulling. Swirl defects are usually studied by microscopy after preferential etching and various X-ray methods. Swirl defects are detrimental to device quality and yield.
Makyoh topography (MT) is an optical method for the qualitative observation of the surface topography of mirror-like surfaces. The studied surface is illuminated by a collimated light beam, and an image is projected onto a distant screen, where an image is formed due to the focusing/defocusing action of the morphological features of the surface . MT has been used in semiconductor technology from the 90’s, mainly for the assessment of the polishing quality of wafers.
Although swirl defects have also been observed by MT , a systematic study is still lacking. The aim of the present paper is just to perform such a systematic investigation. We compare two series of p-type wafers of varying dopant concentration from different vendors. We show the unambiguous correlation with the high dopant concentration, and point out the differences between the wafers of the two vendors. Other detects are also observed and the possible origins are discussed.
The results are interpreted using a geometrical optical model of MT imaging of sine surfaces which predicts the observed contrast as a function of surface feature amplitude and period . The results are compared to surface stylus measurements, and the possibility and limitations of the extraction of quantitative data are discussed.
1. P. M. Petroff, A. J. R. De Kock, J. Cryst. Growth 30 (1975) 117.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium H, by István E. Lukács
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-11 15:01 Revised: 2009-06-07 00:44