Diffraction order measurements are typically used in mastering, stamper manufacturing, and replication to determine the quality of pit / groove formation.
Variations from measurements taken at optimum production rapidly indicate when the respective process step is not running at optimum performance, thus triggering corrective action at the source.
Pythagoras measures glass masters, stampers, and discs up to a diameter of 400 mm. Measurements can be performed in transmission mode for transparent glass masters and disc substrates, and in reflective mode for metallized glass masters, stampers and metallized discs. The Pythagoras uses a 405 nm blue-violet solid state laser to measure zero, first and second order diffraction for track pitches down to 500 nm (zero and first order even down to track pitches of 250 nm).
The systems PT-250 and the option PT-PResTO make up the Pythagoras family. They provide fast feedback in mastering for optimization of the electroforming process for stampers, or for the replication quality in the molding process.
Pythagoras PT-250 scans the complete surface of the glass master, stamper or disc with an angular step width of 3 degrees and a selectable radial step width. The typical measurement time for a complete scan of a 120 mm disc is approximately 10 seconds. The PT-250 scans radial profiles on dedicated angles on the disc as chosen by the operator. Positioning of the diffraction sensors is performed manually by the operator.
Measured and evaluated results can be displayed as radial diagrams, in angular charts or in full surface distribution. All data can be saved for archiving purposes or for additional statistical analysis.
Pythagoras PT-PResTO provides the analysis of the photo resist layer thickness on glass masters. This is an essential parameter for determining the depth of the pits or grooves of the master and stamper and by this finally of the disc. The PT-PResTO is already prepared to be upgraded later on to the full performance of a PT-250 by installing the laser and the diffraction sensors.
The Pythagoras PT-250 can be equipped with the PResTO photo resist option that measures the thickness of photo resist layers of glass masters. Photo resist measurement saves money and reduces scrap by checking and qualifying the spin coating process to guarantee stable master performance.