Overview

DMAP is a specially designed reticle set utilizing resist-based metrology and advanced software to measure:

1. Static lens distortion
2. Dynamic lens distortion
3. Scan synchronization error between reticle and wafer stages

Static lens distortion can be measured for both steppers and scanners. Dynamic lens distortion and scan synchronization errors between reticle and wafer stages can be measured for scanners only.

• Measures transverse lens distortion divorced from stage effects
• Applies to steppers or scanners operating in static mode
• Calculates distortion (DX & DY) for large structure
• Computes tilt Zernike coefficients (a2 & a3) and updates ISI aberration data
• As result, can get self-referenced distortion to within a translation, rotation, and overall scale factor
• Result is an absolute measurement of the higher order static lens distortion
• 1.0 – 1.5nm RMS repeatability

• Measures transverse lens distortion divorced from stage and scan synchronization effects
• Calculates distortion (DX& DY) for large structure
• Corrects for coma effects and appends (a2 & a3) to aberration data
• As result, can get self-referenced distortion to within a translation, rotation and x-scale factor
• ~0.4nm RMS repeatability

• Scan synchronization analyzes single field, full wafer and average field
• Measures transverse scan synchronization error (DX, DY, and DQ)

Features

Absolute technique: ‘Ruler to itself’ technique provides absolute, not relative measurements. Overlay tool forms basis for absolute measurement

Standard technique couples stage/scan and lens problem together: Standard stage metered measurement technique has error set by wafer stage accuracy and repeatability

Distortion Mapper (DMAP)® divorced from stage/scan performance: Errors in DMAP are completely independent of stage accuracy and repeatability, thus fewer measurements, less machine time, more accurate than standard techniques

Cross platform & cross vendor technique: Distortion Mapper (DMAP)® can be shared between multiple lithography tools of different models and wavelengths within the FAB and scanner dynamics measurable on a scan by scan basis

Accuracy: Repeatability < 1.0nm

Benefits

• Monitor lens bulk distortion
• Use in product simulation
• Health check for rapid lens distortion
• Monitor system distortion degradation
• Enables near perfect AB matching of stage scanning
• Improve overlay matching
  • Print smaller features (shrinking process) from reduced overlay matching
  • Machine adjustments for reduced tolerance:
    • - Minimize scan synchronization error by entering corrections
    • - Correcting scan-to-scan (up and down) variation
    • - Find scan abnormalities
  • Increase layer routing in machine set: reduced overlay matching allows other scanners to process the critical layers and higher confidence in routing
  • Reduce overlay rework rate
  • Yield improvement (non-detectable lithography yield): reduction in overlay matching can significantly reduce non-detectable lithography issues