EUV LPP source with improved dose control by combining pulse modulation and pulse control mode
US9755396B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 29, 2016 |
| Grant date | Sep 5, 2017 |
| Priority date | — |
| Expiry date | Nov 29, 2036 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S3/2232
- 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 that combines pulse control mode and pulse modulation. The EUV energy created by each pulse is measured and total EUV energy created by the fired pulses determined, 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. If the desired pulse energy for the next droplet is within the range of one or more pulse modulation actuators, the pulse is modulated; otherwise, the pulse is fired to miss the droplet. This provides greater control of the accumulated dose as well as uniformity of the EUV energy over time, greater ability to compensate for pulses that generate EUV energy that is higher or lower than nominal expected values, and ability to provide an average EUV energy per pulse that is less than the nominal minimum EUV energy per pulse of the system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.