Asml Netherlands B.v.

Paul Alexander McKenzie

Robert A Bergstedt

Robert Jay Rafac

David Wayne Myers

Rong Liu

Paul William Binun

An extreme ultraviolet light system includes a target material delivery system configured to produce a target material; and a beam delivery system that is configured to receive an amplified light beam emitted from a drive laser system and to direct the amplified light beam toward a target location that receives the target material. The beam delivery system includes a final focus assembly that focuses the amplified light beam at a focal location to enable interaction between the amplified light beam and the target material to cause the target material to be converted into a plasma that emits extreme ultraviolet light. The final focus assembly includes at least one transmissive optical element having at least one curved surface through which the amplified light beam travels; and at least one reflective optical element having at least one curved surface on which the amplified light beam is reflected.

Final focus assembly for extreme ultraviolet light source

In a laser-produced plasma (LPP) extreme ultraviolet (EUV) system, laser pulses are used to produce EUV light. To determine the energy of individual laser pulses, a photoelectromagnetic (PEM) detector is calibrated to a power meter using a calibration coefficient. When measuring a unitary laser beam comprising pulses of a single wavelength, the calibration coefficient is calculated based on a burst of the pulses. A combined laser beam has main pulses of a first wavelength alternating with pre-pulses pulses of a second wavelength. To calculate the energy of the main pulses in the combined laser beam, the calibration coefficient calculated for a unitary laser beam of the main pulses is used. To calculate the energy of the pre-pulses in the combined laser beam, a new calibration coefficient is calculated. When the calculated energy values drift beyond a pre-defined threshold, the calibration coefficients are recalculated.

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Encinitas, CA, United States of America

Paul Alexander McKenzie