Pump Produces 128-nm Excimer Emission

Rare-gas excimer lasers based on Ar₂ offer powerful extreme-ultraviolet sources for 128-nm lithography tools, but the electron-beam pumping scheme for these instruments is costly and impractical. An alternative pumping method developed by a group of researchers based at Kyushu University in Fukuoka, Japan, demonstrated a more effective approach.

The pump scheme focuses a 15-J beam from a CO₂ laser through preionized high-pressure Ar gas. The laser field heats the electrons to form a stable plasma. From this plasma, the group identified vacuum-ultraviolet signals at a gas pressure of 1.6 MPa. The signals, centered on 128 nm with a spectral width of 10 nm, strongly suggest that the plasma produced Ar₂ excimers. The researchers' next step is to confirm that these results represent stimulated emission.