EUV LPP source with dose control and laser stabilization using variable width laser pulses
US9832852B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 2016 |
| Grant date | Nov 28, 2017 |
| Priority date | — |
| Expiry date | Nov 4, 2036 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S2301/08
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method and apparatus for control of a dose of extreme ultraviolet (EUV) radiation generated by a laser produced plasma (LPP) EUV light source. Each laser pulse is modulated to be of a width that is determined to be 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 by modulating its magnitude or by modulating the amplification of the pulse by one or more amplifiers, but without decreasing the determined width of the laser pulse.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.