22 May 1995 Charge effect elimination for automatic CD inspection of 0.4-μm contact holes in resist
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Abstract
This paper deals with a technique recently developed at France Telecom/CNET for increasing the electrical conductance of novolak and polyvinylphenol based photoresist patterns and consequently for avoiding any charge effect occurring during SEM inspection. The process consists in subjecting the photoresist patterns to an argon plasma, which, under specific conditions, creates the graphitization of the surface of the photoresist, leading to a significant decrease in electrical resistivity and total suppression of the charge effect. When the size of the hole becomes sufficiently small, and despite the high resolution capability of the equipment, only the top of the hole is well defined. Due to charge effects, the image at the bottom of the hole is badly resolved and therefore the dimensions cannot be registered. However if the resist layer is previously exposed to an argon plasma, the charge effects totally disappear and the contour of the image can then be very clearly defined, by the sharp transitions of the intensity profile. The process is cost effective, principally nondestructive and has been demonstrated to be a real industrial method. When wafers are treated using the plasma process described above, an automatic, highly reliable, nondestructive inspection of a 7 X 7 matrix can be performed in less than 45 min. The results include top and bottom measurement using standard low energy SEM CD equipment.
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Philippe Romand, Jean-Pierre Panabiere, Sandrine Andre, Andre P. Weill, "Charge effect elimination for automatic CD inspection of 0.4-μm contact holes in resist", Proc. SPIE 2439, Integrated Circuit Metrology, Inspection, and Process Control IX, (22 May 1995); doi: 10.1117/12.209219; https://doi.org/10.1117/12.209219
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