Xenon and Tin Pinch Discharge Sources

• Published in: EUV Sources for Lithography p. 1
• Main Author: Bakshi Vivek
• Format: Book Chapter
• Language: English
• Published: SPIE 2006; SPIE Press
• Subjects: Micro; Microfabrication & Photolithography; Nanofabrication & Manufacturing; Nanotechnology; Optics & Photonics
• ISBN: 0819458457; 9780819458452
• DOI: 10.1117/3.613774.ch16

This chapter discusses the results of investigations of DPP sources for EUVL based on the pinch effect in Xe and Sn vapor. In the SRC RF TRINITI (formerly a branch of the Kurchatov Institute of Atomic Energy) in the Moscow region of Russia, these investigations have been carried out since 1999. Up to that time the institute had already had experience in the development of high-power single-pulse radiation sources based on the pinch effect and capable of producing EUV power of ≈5 × 10 W, and also in the study of pulse power systems used for high-repetition-rate (≈6 kHz) excimer lasers. The part of this work devoted to the creation of EUV sources was supported by XTREME technologies GmbH. The analysis of the discharge configurations that permit the plasma to be heated up to the temperatures (about 30 eV) required to emit EUV radiation around 13.5 nm has resulted in our choice of such known discharge configurations as the classical Z pinch and the dynamic (or spouting) pinch. These configurations permitted removing a high-temperature plasma area from the electrode and dielectric surfaces and thereby reducing plasma-surface interactions. However, in such configurations a small size (∼1 mm) of plasma pinch radiating in the EUV range is needed. Started from large-size plasma pinches of 20-mm length and 1-mm diameter, we then matched the pinch size and the emission angle to the requirements of a high-volume manufacturing (HVM) lithography tool. In this chapter the characteristics of DPP sources with different electrode configurations using Xe or Sn are described. The concepts of the rotating multidis-charge unit (RMDU) source using Xe or Sn and the rotating-disk electrode (RDE) source using Sn, which allow significant reduction of the heat load on electrodes, are discussed. The pinch effect arises from compression of a previously created plasma by the magnetic field of its own current. The phenomenon of plasma compression was first described in 1934 by W. H. Bennett. The mechanism and characteristic features of a pinch effect can be usefully considered using the examples of the classical Z pinch (Fig. 16.1) and the spouting pinch (Fig. 16.2). In the classical Z pinch the current flows along the Z axis of a cylindrical plasma volume. The lines of force of the magnetic field created by the current look like concentric circles arranged on planes perpendicular to the Z axis. The resulting electrodynamic force acting on a unit gas volume with a current density is equal to · , where is the light velocity. is directed inward along the radius to the cylinder axis and causes compression of the current channel. The magnetic compression of the plasma is counteracted by the gas-kinetic pressure of the plasma. At equilibrium the moving boundary of the pinch is a surface of equal pressure. From this condition the so-called follows: ∕8π = 2 , where is the plasma temperature and is the gas concentration. However such a mechanism of pseudo-steady compression contradicts the experimental data, and the model offered by Leontovich and Osovets is more correct.