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Focus Control

Focus may be the most difficult variable to measure. It cannot be directly measured but must be calibrated using special patterns and methods. Validation of metrology is therefore always a consideration and a major element in the analysis.

Focus variables range from the optimum focus-offset to be placed into a tool to a model of defocus errors that impart information on lens aberrations, reticle-scanning, reticle platen tilt, wafer tilt, scan-slit travel, reticle bowing, film uniformity and substrate bowing.

TEA system products derive optimum and modeled focus from many different commercial sources. Uniquely, they also apply models that go beyond the initial conversion to focus to control and characterize the whole electro-mechanical-optical interactions of the tool and process.

If you are working with sub-90 nanometer node processes the number of Reticles employing Enhancements has grown considerable in your process. No amount of simulation can anticipate the level of perturbations introduced by reticle manufacturing or local exposure variations. Also no simulation can estimate the full impact on Depth-of-Focus introduced by RET construct design convolved with lens and process perturbations.

Now Weir PW can use wafer-measurements of feature profiles to estimate reticle feature sizes to sub-nanometer accuracy. This capability not only confirms full-field reticle design and manufacture accuracy but also the level of aberrations introduced by each exposure tool in your facility. Along with this full-field contour plots of Optimum Focus, Depth-of-Focus and a Reticle Signature that can be saved in the Weir Reticle Library for improved process and bake setup. Wier PW can optimize and measure the influence of ARC on Best Focus and its variation with dose.

Select a product solution according to your needs below or directly click on a product name on the lower-right for more information.

 

Systematic Contributions to Component Focus Error

Top-Left: Wafer model reveals defocus contribution of photoresist deposition.

Bottom-Left: Lens-slit focus profile scanned from bottom-to-top of exposure. Aberrations such as shown can be from the lens or from reticle heating.

Top-Right: Reticle scan path errors measured as defocus from field.

Bottom-Right: Scanner Lens-slit profile derived from field in lower left.

DoF Uniformity before and after lens cleaning
Depth-of-Focus uniformity variance with scan-direction

 

By Solution

Products

  • Critical Feature Analysis

  • Focus Control

    • Weir PW
    • Derive focus from feature focus-matrices and line-end-shortening.
    • Calculate "Best Focus" across field (IFD) and Focal-plane uniformity from any Critical Feature metrology set, Line-End-Shortening
    • Directly read in all ASML data formats including ASML FOCAL* data.
    • Raw focus and modeled analysis of field, slit and scan.
    • Weir PSFM
      • Raw focus Works interactively with Weir PW
      • Works with Focus Matrices and whole-wafer, full-field exposures.
      • Calibrate any proprietary reticle structre including CANON Z-spin, Benchmark PSFM, Toshiba PGM, ASML FOCAL and other phase and end-of-line shortening structures.
      • Calibrate Benchmark Technologyís Phase Shift Focus Monitor (PSFM) and Phase Grating( PGM) Reticles.
      • Apply reticle calibrations to whole-wafer focus uniformity analyses.
      • Calculate both wafer and field tilt, bow, pentode etc.
      • Evaluate effects of film, trench-etch, wafer and and scanner stage using raw or modeled tools.
      • Measure wafer edge-bead and edge-die influence on scanner focus and auto-leveling.
      • Measure wafer flatness.
      • Analyze ASML FOCAL* focus data.
    • Weir DM & Weir DMA (Automation)
      • This Daily Monitor (DM) program automates the analysis of raw, modeled and calibrated data.
      • Replicate Weir PW and PSFM analyses with two mouse-clicks on any data set
      • Automated, interactive trend charts.
      • User custom-setup of analysis sequence, current and trended selected statistics.
      • Incorporate any of the above applications into a custom Weir Macro.
      • Call Weir DMA from factory control software or any APC or other software for automated  process control.
      • Output data to Internet sites in HTML format or to other programs in ASCII or Weir Spreadsheet formats.
  • Overlay & Registration Control

  • Post Exposure Bake

  • Reticle Analysis

  • Tool Characterization

  • Metrology

  • Process Setup & Control

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Weir PW
Process window, metrology and spatial feature modeling.

 

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Weir PSFM
Focus analysis from commercial patterns and programs.

 

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Weir DMA
Trend charts and automated analyses of raw or modeled data.

 

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Vector Raptor
Overlay and Registration for Double Patterning

 

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LithoWorks PEB
Thermal wafer analysis PLUS correlation to feature profile.

  
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