Intensity variation of extreme ultra-violet (EUV) radiation from high-density laser-produced xe plasmas

Summary form only given, as follows. The extreme ultra-violet (EUV) lithography is the most promising candidate for the next generation lithography technology. EUV radiation of wavelength 10 nm or photon energy 100 eV can be generated from very high-density and high temperature plasmas, which are produced by a fast pulse discharge or a focused pulse laser beam. In the present study, a laser-produced plasma EUV light source has been developed. The system includes a pulsed high power laser, pulsed gas injection target system, plasma producing vacuum chamber and focusing optics Xe gas was injected at the pressure of several tens bar through a submillimeter diameter hole into a vacuum chamber by a magnetically coupled valve. A high energy Q-switched Nd YAG laser with energy of 2 J, pulse width of 7 ns, and frequency of 10 Hz was used to generate the plasma Its second harmonic in the peen was used in order to reach a higher critical plasma density, which is expected to result in a higher absorption of laser energy into the plasma. Intensity profiles of laser produced Xe-plasma were studied and visualized by means of a laser interferometer, where a small fraction of laser light emitted was bypassed to give rise to time delay. Variations of EUV radiation intensity with respect to experimental parameters such as laser pulse energy, laser pulse delay time, laser beam size, Xe gas injection pressure, Xe gas temperature, Xe gas pulse width have also been investigated.