Esq.; John R. Ross
Inc. Cymer
Primary examiner
Rodney Bovernick
Primary examiner
Robert E. Wise
Application number
Document number
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Process for selecting operating range for narrow band excimer laser

5887014 - 9150307 - USPTO

Application Aug 20, 1997 - Publication Mar 23, 1999

Palash P. Das


A process for selecting an operating range for a narrow band KrF or ArF excimer laser. The laser is operated at a desired pulse energy until the fluorine concentration has depleted sufficiently so that the charging voltage needed for the desired pulse energy is at or near a predetermined maximum range. The average charging voltage, the average line width, and the average energy sigma are recorded; and the fluorine concentration is estimated or determined. A quantity of fluorine, at least sufficient to cause a measurable decrease in the charging voltage needed to produce the desired pulse energy, is injected; and another set of data is recorded. Another similar quantity of fluorine is injected, and another set of data is recorded. These two steps are repeated until the voltage is at or near a predetermined minimum voltage range. The recorded data are used to select an optional operating range. The data may be plotted to make the selection easier. The selection criteria may be determined based on the needs of the laser user. Normally, the selection process will involve an intelligent compromise in which minimum values of charging voltage, fluorine concentration, line width and energy sigma are desired. For most uses, the optimal operating range will be a voltage range of 20% of the total possible voltage range and not close to either the minimum operating range or the maximum operating range.



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