19 July 1989 Techniques For High Speed SEM Wafer Inspection For Production Applications
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Two techniques suited for high speed SEM wafer inspection are presented. The dependancies of beam focus variations on Linewidth Measurements (LWM) precision are reviewed. It is reasoned that high LWM precisions and high-speed operator-independent wafer inspection are mutually exclusive requirements. A more aggressive inference is made : existing SEMs may not satisfy the inspection and LWM production environment requirements of lines 0.5 micron or less. Revolutionary, new inspection techniques are needed in the SEM to make them as easy to use as today's light optics instrumentation. One such technique is presented, which is a laser-based Automatic Working Distance Control (AWDC) system. AWDC eliminates the need to re-focus the electron beam during wafer inspection. It also creates optimum scenarios for precise LWM and inspection in future sub-half micron production lines of 200 mm wafers. The second technique is an in-vacuum wafer transfer and staging mechanism. The mechanism is suited for very high speed SEM inspection, and integrates the technique described before. The design was implemented with judicious consideration of the sub-micron production requirements: high reliability, low contamination, high speed inspection, and low cost. The novel components of the design are described. Emphasis is made on a minimum volume and surface area vacuum lock, with no internal moving parts. Three commercially available vacuum pumps are evaluated. The outgassing load of 200 mm wafers with recently coated photoresist is quantified. Computer simulations show that high throughputs are feasible using standard vacuum engineering techniques. Throughput figures are given for "single-wafer" and "wafer-queueing" modes of operation. Operational speeds comparable to light optics tools are achievable.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Guillermo L. Toro-Lira, Guillermo L. Toro-Lira, } "Techniques For High Speed SEM Wafer Inspection For Production Applications", Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953075; https://doi.org/10.1117/12.953075

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