23 August 2000 Small signal ac-surface photovoltage technique for noncontact monitoring of near-surface doping for IC-processing
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Small signal non-contact ac-SPV method for monitoring near surface doping (NSD) in silicon has recently been introduced in commercial diagnostic tools. This technique has the advantage of producing fast, non-destructive full wafer measurements. High chopping frequency light with a submicron penetration depth is used to generate small SPV signal and this signal is in turn monitored using a transparent pickup electrode. Under certain conditions, the magnitude of this ac-SPV signal is inversely proportional to the depletion layer capacitance. If a depletion layer barrier height is known, this allows the calculation of the concentration of ionized donors or acceptors in the depletion layer. NSD measurements by ac-SPV method were typically done for doping concentrations up to about 1016 cm-3. Only recently this range has been extended to 1018 cm-3, making it a very attractive technique for monitoring low and medium dose implants and especially for wafer scale mapping of implant uniformity and implant activation efficiency. This paper addresses three issues that are critical for extending this technique to monitoring of production wafers in IC-processing, namely: 1) a quantitative correction for oxide reflectivity, 2) the fundamental and practical problems in reduction of the SPV probing site to below 100 micrometers , and 3) sensitivity of the technique to small variations in the implantation dose.
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Dmitriy N. Marinskiy, Dmitriy N. Marinskiy, Jacek J. Lagowski, Jacek J. Lagowski, M. Wilson, M. Wilson, Lubek Jastrzebski, Lubek Jastrzebski, R. Santiesteban, R. Santiesteban, Kim Elshot, Kim Elshot, } "Small signal ac-surface photovoltage technique for noncontact monitoring of near-surface doping for IC-processing", Proc. SPIE 4182, Process Control and Diagnostics, (23 August 2000); doi: 10.1117/12.410062; https://doi.org/10.1117/12.410062


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