Extreme UV Sources Fill the Gap

Recent advances in nonaccelerator techniques have ushered in commercially available sources of extreme UV radiation.

Below is an excerpt. Read the full article on Photonics.com: Extreme UV Sources Fill the Gap 

An electrode-less, discharge-based approach for EUV generation, commercialized by Energetiq Technology Inc. of Woburn, Mass., completely avoids the problem of electrode loss. The company’s Z-Pinch EUV source (Figures 3 and 4) runs on pure xenon gas and comprises two copper plates with four circular through-holes. Discharge results inductively, forming three plasma loops that snake around the holes in the copper plates. The high current discharge is fed from a capacitor bank with appropriate control electronics. This current flows through magnetic coupling cores located above and below the two copper plates, which then inductively induce a current in the xenon gas, ultimately forming a plasma. Current in the plasma loops generates a strong magnetic field of its own, which pinches the plasma and confines it in such a way that it is kept away from any solid surfaces.

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The highly concentrated plasma in the center bore is the location where EUV radiation is generated. The radiation can be coupled to a highly evacuated external beam line — no radiation collection mirror is needed. Although there are no electrodes to get eroded over time, sputtering of copper in the central bore can rapidly corrode its inner wall surface. This problem is greatly mitigated by the use of a silicon carbide liner that protects the bore surface. Silicon carbide also gets sputtered by bombardment from energetic ions in the xenon plasma, but at rates that are much lower than that of copper. The bore liner is thus the only consumable part that needs replacement, typically after one billion shots.