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We present a systematic approach for converting a legacy wafer fab from manual wafer handling to fully automatic wafer handling. Our strategy began by quantifying the need for automation in terms of impact on die yield, identifying a seven percent die loss associated with scratches from wafer handling. We then addressed the fundamental changes in production equipment and processes as well as overall fab goals and attitudes that are required to achieve full wafer handling automation. After considering several approaches to staged fab automation, we selected an approach which eliminated all manual handling within specific fab modules, completing the automation within one group of modules before embarking on another module set. In this way, we limited both the initial scope and cost of the project while preparing to leverage its initial successes. This paper summarizes the methodology and metrics found useful for preparing the fab for change, executing the change, and successfully managing the overall project.

New measurements of the radioactive tracer diffusion coefficients of selenium-75 and lead-2l 0 in PbSe, obtained using a vapor source diffusion technique, are reported. These measurements yield significantly lower values of the diffusion coefficients for both species than those previously reported by others. For selenium-saturated PbSe, D;e = 8.13 X 10-4 exp( -1.33 eV I k T) and D;b = 9.81 X 10-4 exp( -1.67 eV I k T), while for lead-saturated PbSe, D;e = 0.553 exp ( -2.22 eV I k T) and D;b = 3.74 X 10-2 exp( -2.05 eV I k T). An analysis of these results indicates that selenium atoms diffuse by means of interstitial defects in selenium-rich material and most probably through selenium vacancies in lead-rich material, and that lead atoms diffuse through lead vacancies in selenium-rich material and most probably through lead interstitials in lead-rich material. The tracer data are used in conjunction with a theoretical model of interdiffusion to predict values of the p-n junction diffusion coefficients in PbSe which are in excellent agreement with published experimental results. A similar comparison of the tracer data with n -p junction diffusion data shows good qualitative agreement. Quantitative discrepancies are observed which are explained by the theoretical model.The point-defect mechanisms to be considered are (i) diffusion of lead through lead vacancy sites, (ii) diffusion of lead through interstitial sites, (iii) diffusion of the chalcogen through chalcogen vacancy sites, and (iv) diffusion of the chalcogen through interstitial sites. The mechanisms (ii) and (iv) include either the interstitial or the interstitialcy mechanisms as subcases with minor modifications.The concentrations of the atomic point defects (vacancies or interstitials) associated with the above mecha-

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