A Scanner is a lithography tool that exposes wafers by synchronously scanning the reticle and wafer stage in opposite directions through a narrow illumination slit — projecting only a small portion of the reticle at any instant through the highest-quality central region of the lens, then building up the complete exposure field by scanning, achieving larger exposure fields (26×33mm standard), better resolution, and higher throughput than steppers, making scanners the dominant lithography tool for all advanced semiconductor manufacturing.
What Is a Scanner?
- Definition: A step-and-scan lithography system where the reticle and wafer move synchronously (but in opposite directions due to image inversion) through a narrow illumination slit — at 4× reduction, the reticle moves 4× faster than the wafer, and the complete die image is built up by the scanning motion.
- Why Scanning?: Instead of illuminating the entire lens field at once (stepper), a scanner illuminates only a narrow slit (typically 8mm × 26mm). The lens only needs to be perfect across this slit, not the entire field — enabling higher numerical aperture and better aberration control.
- The Result: Larger exposure fields (26×33mm vs stepper's 22×22mm), better lens performance (optimized for slit only), and higher throughput (continuous scanning motion vs step-and-flash).
How a Scanner Works
| Step | Action | Detail |
|---|---|---|
| 1. Align | Wafer alignment marks measured | Sub-nanometer precision overlay to previous layers |
| 2. Position | Reticle and wafer positioned at scan start | Stages pre-accelerated to scan velocity |
| 3. Scan | Reticle and wafer move through illumination slit | Reticle at 4× wafer speed (opposite direction) |
| 4. Expose | Slit progressively exposes the full field | 26mm slit width × 33mm scan length = 26×33mm field |
| 5. Step | Wafer stage steps to next die position | Same step-and-repeat as stepper between fields |
| 6. Repeat | Scan-expose next field | Continue across all die positions |
Key Specifications (Modern DUV Immersion Scanner)
| Specification | Typical Value | Significance |
|---|---|---|
| Wavelength | 193nm (ArF immersion) | Deep ultraviolet, water immersion |
| Numerical Aperture | 1.35 (immersion) | Water (n=1.44) enables NA > 1.0 |
| Resolution | ~38nm single-patterning | With multi-patterning: sub-10nm features |
| Exposure Field | 26 × 33mm | Standard full-field exposure |
| Overlay | <1.5nm machine-to-machine | Critical for multi-layer alignment |
| Throughput | 250-300 wafers/hour (300mm) | High-volume manufacturing |
| Dose Uniformity | <0.3% across field | Consistent feature dimensions |
| Focus Control | <10nm range | Critical for thin resist processes |
Scanner Types
| Type | Wavelength | NA | Resolution | Application |
|---|---|---|---|---|
| DUV Dry (ArF) | 193nm | 0.93 | ~65nm | Older nodes (>45nm) |
| DUV Immersion (ArFi) | 193nm | 1.35 | ~38nm (single), sub-10nm (multi-patterning) | 7nm-28nm nodes |
| EUV | 13.5nm | 0.33 | ~13nm (single) | 3nm-7nm nodes |
| High-NA EUV | 13.5nm | 0.55 | ~8nm (single) | 2nm and below (2025+) |
Major Scanner Manufacturers
| Company | Market Share | Key Products |
|---|---|---|
| ASML (Netherlands) | ~80% (100% EUV) | TWINSCAN NXE (EUV), NXT (DUV immersion) |
| Nikon (Japan) | ~15% DUV | NSR-S631E (ArF immersion) |
| Canon (Japan) | ~5% DUV | FPA-6300 series (KrF, i-line) |
Scanners are the dominant lithography platform for all advanced semiconductor manufacturing — using synchronized reticle-wafer scanning through a narrow optical slit to achieve the highest resolution, largest exposure fields, and best throughput available in optical lithography, with ASML's EUV and immersion systems enabling the 3nm-7nm technology nodes that power today's most advanced processors.
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