Strongly asymmetric doping profiles at mask edges in high energy ion implantation


Wijburg, Rutger C. and Hemink, Gertjan J. and Middelhoek, Jan (1990) Strongly asymmetric doping profiles at mask edges in high energy ion implantation. IEEE Transactions on Electron Devices, 37 (1). pp. 79-87. ISSN 0018-9383

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Abstract:The application of high-energy ion implantation is restricted by an asymmetric doping profile at the mask edges. As a result, buried interconnect cannot easily be formed. Moreover, the holding voltage and threshold voltage of CMOS-processes with retrograde wells may be strongly affected by this asymmetry. It arises from the 7° wafer tilt, which is frequently used to avoid channeling, even in the case of nearly perpendicular (82-85°) mask edges. On the mask side, which is incoming to the ion beam, a trunk to the surface has experimentally been observed. According to two-dimensional Gaussian and advanced Monte Carlo simulations, the doping concentration in this trunk is about 20% of the maximum concentration in the case of a 85° mask angle. The simulations predict the experimental results fairly well. The asymmetry effect of high energy ion implantations can also be visualized in photoresist by means of a damaged region
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Copyright:©1990 IEEE
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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