Dr. Schenk GmbH

Photomask Inspection

Particle Detection Leads to Higher Yields

Dr. Schenk Pollux

Particle contamination can disrupt and delay the photolithography process, resulting in yield and productivity losses. In order to avoid this, masks need to be routinely re-qualified.

The solution is Pollux - the automated Particle Detection System by Dr. Schenk. Pollux enables fabs to perform a complete inspection on each reticle prior to its use. This approach provides a more cost-effective and more reliable solution than the method of visual inspection.

Applications

Pollux has been designed for integration into:

  • Reticle Stockers
  • Wafer Steppers
  • Cleaning Stations
  • Automatic Handling Systems
  • Stand-alone unit with manual loading

Benefits

  • Cost-Effectiveness
  • Easy Operation
  • High Speed
  • Low Maintenance

Pollux Offers

  • High Return on Investment
  • Low Capital Investment
  • Low Cost of Ownership Pollux

Leads to

  • Process Optimization
  • Yield Enhancement
  • Cost Reduction

Specification

Pollux inspects the surface of the glass side and the pellicle surface of the chrome side for imperfections down to 5/10 µm equivalent sphere diameter (ESD). Pollux detects particulate contamination and defects such as glass scratches and holes in the pellicle.

Each fab can individually determine the threshold according to the minimum size of particles that are of interest. Pollux offers highly reliable contamination control for the lithography process, independent of an operator performing a visual inspection.

Pollux automatically determines the frame height and the inspection area. No manual adjustment or parameter setting is needed to adapt the system for the reticle to be inspected.

The average cycle time takes between 45 to 70 seconds!

Optical Setup

Pollux uses a far dark-field laser inspection principle. Highly sensitive CCD line scan cameras collect the scattered light from any imperfection. The size of detected particles is determined according to the number and intensity of bright pixels.

Presentation of Results

Pollux offers a user-friendly graphical user interface (GUI) according to SEMI standards. Pollux reports the number of detected particles on the surfaces of both sides of the reticle. Contamination data, such as the number of detected particles, ESD size and xy-coordinates, will be displayed in a defect map, defect table and defect size histogram, providing a quick overview.

Options

  • Nesting Sensor - to check whether the reticle is properly nested
  • Reticle Present Sensor - verifies if a reticle is placed on the stage
  • Bright-Field Detection - to inspect holes in the pellicle

Conclusion

Pollux is a unique tool, offering objective evaluation data for the pass/fail decision of lithographic photomasks. Its low cost-of-ownership, small footprint and high speed make it an ideal solution for 100% inspection of all photomasks in a wafer fab, thus enabling process optimization and yield enhancement wherever photomasks are processed.


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