Modeling the KrF laser discharge

Abstract

In this letter we describe modeling of an E-beam-controlled discharge operated in gas mixtures containing mainly argon with approximately 10% krypton and a few tenths of a percent fluorine. The discharge physics is dominated by electron impact ionization and excitation of the rare-gas metastables. The ionization of the metastables impacts the discharge stability directly while their excitation strongly affects the efficiency of pumping KrF*. Predictions of the model are compared with experimental results.

Measurement of Cross Sections for Electron Excitation out of the Metastable Levels of Argon

“…These cross sections are of great interest both for a fundamental understanding of atomic collisions and for a wide variety of gaseous electronics applications, ranging from gas discharge lasers to flat-panel displays to plasma-aided manufacturing [1][2][3]. In ionized gas applications, the plasma frequently has metastable densities that exceed 10 25 of the ground state density in the gas.…”

“…Thus there are orders of magnitude more electrons with sufficient energy for excitation out of the metastable levels (ϳ1.5 eV for Ar) than there are with enough energy to excite atoms out of the ground state (ϳ13 eV for Ar). This combination of low excitation threshold energies and large cross sections means that metastable atoms play a major or even dominant role in many low-temperature plasma properties including optical emissions [4,5], electron temperature [1,6], and both the ionization and energy balance [1,6]. Therefore cross sections for excitation out of metastable levels are essential for a quantitative description of the dynamics of ionized gas systems.…”

Discharge physics, formation and quenching processes of XeF. Final technical report

“…So we will assume a mean rate of 2 x 10 cm /sec for reaction -32 3 (1-4) and 10 cm/sec for reaction (1)(2)(3)(4)(5). The argon metastables react with NFj to form ArF with a rate constant of 1.4 x 10" cm 3 / S ec.…”

Metal vapor excimer laser. Quarterly progress report, May 1, 1977--July 31, 1977. [CdHg vapors]

“…Because of the lack of control, i. e., rapidly varying electric field and current density, Hg will be created, leading to Hg2' which photo This discharge is also more ine ffic ient than the e-beam (3) controlled discharges. Finally, the rapidly varying impedance makes (4) electrical matching difficult and the scale size is limited by inductance.…”