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1. (WO2018085071) EUV LPP SOURCE WITH DOSE CONTROL AND LASER STABILIZATION USING VARIABLE WIDTH LASER PULSES

Pub. No.:    WO/2018/085071    International Application No.:    PCT/US2017/057895
Publication Date: Sat May 12 01:59:59 CEST 2018 International Filing Date: Tue Oct 24 01:59:59 CEST 2017
IPC: H05G 2/00
Applicants: ASML NETHERLANDS B.V.
Inventors: FOMENKOV, Igor Vladimirovich
RAFAC, Robert Jay
Title: EUV LPP SOURCE WITH DOSE CONTROL AND LASER STABILIZATION USING VARIABLE WIDTH LASER PULSES
Abstract:
A method and apparatus tor control of a dose of extreme ultraviolet (EUV) radiation generated fay a laser produced plasma (LPP) EUV Sight source. Each laser pulse is modulated to be of a width that is determined to he sufficient to allow for extraction of a suitable uniform amount of energy in the laser source gain medium; in some embodiments the suitable uniform amount of energy to be extracted may be selected to avoid self-lasing, The EUV energy created by each pulse is measured and total EUV energy created by the fired pulses determined,, and a desired energy for the next pulse is determined based upon whether the total EUV energy is greater or less than a desired average EUV energy times the number of pulses. The energy of the next pulse is modulated, either fey modulating its 'magnitude or by modulating the amplification of the pulse by one or mote amplifiers, but without decreasing the determined width of the laser pulse.