Pulse energy control for excimer laser
US6005879A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 4, 1998 |
| Grant date | Dec 21, 1999 |
| Priority date | — |
| Expiry date | Mar 4, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S3/2256
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A process for controlling pulse energy and integrated energy dose in bursts of pulses produced by an excimer laser. The energy of each pulse in each burst is measured. The rate of change of pulse energy with charging voltage is determined. A pulse energy error is determined for a previous pulse of the present burst. An integrated dose error is also determined for all previous pulses in the current burst. A charging voltage for the next pulse is determined using the pulse energy error, the integrated dose error, the rate of change of energy with charging voltage and a reference voltage. In a preferred embodiment, the rate of change of energy with voltage is determined by dithering the voltage during two pulses of each burst, once lower and once higher. The reference voltage is a voltage calculated using prior energy and voltage data. In this embodiment, the method of determining the reference voltage during a first portion of the pulse is different from the method used during a latter portion of the burst. During the first set of pulses (40 in this embodiment), for each pulse, a specified voltage calculated using voltage and energy data from a corresponding pulse in a previous burst…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.