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Overlay Booster
Off-line Applications

    The material on this page describes Overlay Booster features and applications in off-line mode only. Real-time features are described elsewhere. >>Real-time details...

  • Overlay Booster is a Windows-based analysis software for stepper and scanner control in production.

  • As input, Overlay Booster takes data files generated by overlay metrology tools such as IVS, Accent or KLA. It then performs model specific analysis and provides feedback parameters for steppers and scanners to achieve tightest overlay on product wafers. At the same time, it also produces raw data and residuals statistics for decision making and lot disposition in production. The maximum predicted modeled error is available for display and output as a user selectable option.

  • All the information the user needs, including vector map and lot or wafer statistics, is displayed on a single screen.

  • For off-line analysis, Overlay Booster can operate in two different modes: Standard and Advanced. In standard mode, the analysis method is always single-pass optimization. In advanced mode, user can input other transformation commands.

  • Here are some of the things you can do in off-line analysis mode:
    - Open data files directly, no format conversion is required
    - Reanalysis View all results for each lot on a single screen
    - View vector maps with hot buttons in the graphics for display of site information
    - Display vector maps for both raw data and residuals in the same graphic
    - Spot the worst offending data point for both raw data and residuals
    - Interactive data culling and filtering from menu or hot buttons in the graphics
    - Quickly scroll through and view individual wafers in a multi-wafer lot
    - Export high quality graphics for reports and publications
    - Multi-lot analysis with capability to export results to Excel for trend charts
    - Use Advanced mode to formulate other 'What if' scenarios

  • In addition to the above capabilities, features below are available and separately licensed.

  • Delta Feature: Subtraction of Two Data Files - You can subtract two data files and also one data file form a collection of data files. The measurement results of the first wafer of first lot are subtracted from any data file subsequently loaded. You can even subtract a file from itself. In this way, wafer-to-wafer variations in a multiple wafer lot can be investigated. This feature is available in multiple data file (batch) mode. Applications: indirect overlay to a third level as needed for some implant layers, photo-to-etch overlay bias, wafer-to-wafer variations within lot, lens heating, stepper matching, ...

  • Stepper Matching - You can find the best match for a specific stepper among a group of steppers. The method relies on data files from stepper calibration/monitoring wafers. The method uses the capability to subtract data files. A new feature has been added to allow saving of lens fingerprint as an overlay data file. This lens fingerprint file conversion feature is also available in multiple file (batch) mode. Correction offsets for initial exposure as well as estimates of residual error are also provided. You can find the best match based on either calibration files (whole wafer results) or lens fingerprint files (matching of intrafield residuals only).

  • Database - Overlay Booster can export the analysis results in real-time mode to a database. Database application makes it much easier to obtain trend information about overall manufacturing line performance for specific devices or layers or exposure tools. Separately, a utility is provided to leverage the existing files stored by IVS tools by analyzing them and exporting the results to that database. This leads to a substantial benefit to the customers by providing them with the ability to add the database the results for lot measurements collected in the prior months.

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