Wavelength control system for pulse-by-pulse wavelength target tracking in DUV light source
AssigneeCymer, Inc.
InventorsRahul Ahlawat, Thomas P. Duffey
Life of this patent
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Abstract
Wafer positioning errors in stepper-scanners contribute to imaging defects. Changing the wavelength of the light source's generated light can compensate for wafer positional errors in the Z-direction. The wafer's real-time z-position is determined and a change in wavelength target to offset this error is communicated to the light source. The light source uses this change in wavelength target in a feed-forward operation and, in an embodiment, in combination with existing feedback operations, on a pulse-by-pulse basis for subsequent pulses in a current burst of pulses in addition to receiving the newly-specified laser wavelength target for a subsequent burst of laser pulses.
Claims23
A method of laser wavelength control comprising:
- (a) receiving, in a laser system controller, a newly-specified laser wavelength target;
- (b) generating, by the laser system, a burst of laser pulses at the newly-specified laser wavelength target;
- (c) receiving, in the laser system controller, a change in wavelength target based on a measured wafer positional error;
- (d) adjusting a prism position in the laser system based on the received change in wavelength target;
- (e) generating, by the laser system, a next laser pulse of the burst of laser pulses using the adjusted prism position;
- and,
- (f) repeating steps (c)-(e) as additional changes in wavelength target are received by the laser system.
A laser system for pulse-by-pulse laser wavelength control comprising:
- a laser source;
- a line narrowing module including a prism;
- a piezoelectric transducer and drive electronics;
- and,
- a controller configured to:
- (a) receive a newly-specified laser wavelength target;
- (b) direct the laser source to begin generating a burst of laser pulses at the newly-specified laser wavelength target;
- (c) receive a change in wavelength target based on a measured wafer positional error;
- (d) adjust, based on the received change in wavelength target, a prism position in the line narrowing module using the piezoelectric transducer and drive electronics;
- (e) direct the laser source to generate a next laser pulse of the burst of laser pulses passing through the adjusted prism position;
- and,
- (f) repeat steps (c)-(e) as additional changes in wavelength target are received.
In a photolithography system, a method of performing photolithography on a wafer using laser light generated using a laser system, comprising:
- receiving a laser wavelength target;
- generating a first plurality of laser pulses in a burst of laser pulses at the laser wavelength target;
- measuring a wafer positional error;
- obtaining a change in wavelength target based on the measured wafer positional error;
- adjusting a position of a prism in the laser system based on the obtained change in wavelength target;
- and
- generating a second plurality of laser pulses of the burst of laser pulses using the adjusted prism position, wherein the step of adjusting the prism position in response to the received change in wavelength target occurs at a greater frequency than the step of receiving the laser wavelength target.
A laser system for pulse-by-pulse laser wavelength control comprising:
- a laser source for producing a laser beam;
- a line narrowing module including at least one prism in an optical path of the laser beam ;
- a sensor for measuring a wafer positional error;
- a piezoelectric transducer mechanically coupled to the prism arranged to receive the laser beam;
- drive electronics electrically connected to the piezoelectric transducer;
- and,
- a controller electrically coupled to the laser source and the sensor and configured to:
- receive a newly-specified laser wavelength target;
- direct the laser source to begin generating a first plurality of pulses of a burst of laser pulses at the newly-specified laser wavelength target;
- receive a change in wavelength target based on the measured wafer positional error;
- adjust, based on the received change in wavelength target, a prism position in the line narrowing module using the drive electronics;
- direct the laser source to generate a next plurality of pulses of the laser pulse of the burst of laser pulses passing through the adjusted prism position;
- receive a second newly-specified wavelength target;
- direct the laser source to begin generating a first plurality of pulses of a burst of laser pulses at the second newly-specified laser wavelength target;
- receive a second change in wavelength target based on the measured wafer positional error;
- and
- adjust, based on the received second change in wavelength target, a prism position in the line narrowing module using the drive electronics;
- direct the laser source to generate a new plurality of pulses passing through the adjusted prism position.
Dependencies are inferred from the claim text.