Angular ion emission characteristics of a laser triggered tin vacuum arc as light source for extreme ultraviolet lithography

作者：Verbraak Harald^*; Kuepper Felix; Jonkers Jeroen; Bergmann Klaus

来源：Journal of Applied Physics, 2010, 108(9): 093304.

DOI：10.1063/1.3499611

The angular resolved emission of tin ions from a laser triggered vacuum arc to be used as light source for extreme ultraviolet lithography is presented. Ion energies of more than 200 keV for emission angles up to 50 degrees with respect to the optical axis are observed. The angular emission characteristic is strongly anisotropic with a pronounced peak for fast ions into a cone with an opening angle of roughly 10 degrees at an angle of 35 degrees with respect to the optical axis. These ions also exhibit a distinct energy distribution function compared to the more isotropic emitted bulk of ions, which can be referred to different mechanisms of production. Looking at the discharge current parameters, the production of the directed fast ions can be connected with a peaked increase in the impedance, which gives hint to a plasma instability as origin of those ions. The emission of isotropic emitted ions is in agreement with a model of plasma expansion into vacuum. The emission characteristic is also strongly dependent on the parameter of the trigger laser. It is shown that using a double trigger laser pulse the fast ion production can be suppressed by more than one order of magnitude.

• 出版日期2010-11-1