Using an interferometer as a high speed variable attenuator

• US 7,898,646 B2
• Filed: 10/03/2007
• Issued: 03/01/2011
• Est. Priority Date: 10/17/2006
• Status: Active Grant

• Current Assignee: ASML Holding NV, ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Holding NV, ASML Netherlands BV (ASML Holding NV)
• Inventors: Noordman, Oscar Franciscus Jozephus, Kreuzer, Justin L., Perez Calero, Daniel, Van Den Dool, Teunis Cornelis, Vink, Henri Johannes Petrus
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): WILLIAMS, DON J
• Application Number:
  US11/866,820
• Publication Number:
  US 20080106717A1
• Time in Patent Office: 1,245 Days
• Field of Search: 250/205, 2502011-2014, 2502018-2019, 250/204, 250/559.49, 359/291, 359/308, 359/247, 359/497, 359/499, 327/308, 327/520, 355 66- 68
• US Class Current: 355/48
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G03F 7/70041 by pulsed sources, e.g. multiplexing, pulse duration, interval control or intensity control
• CPC Class Codes: G03F 7/70558 Dose control, i.e. achievement of a desired dose

Abstract

A system and method provides high speed variable attenuators. The attenuators can be used within a lithographic apparatus to control intensity of radiation in one or more correction pulses used to correct a dose of the radiation following an initial pulse of radiation.

Claims

1. A radiation dose controller, comprising:

a detector configured to determine an energy within pulses of radiation received by the radiation dose controller;

a variable attenuator configured to attenuate an intensity of at least one pulse of radiation, wherein the variable attenuator comprises one of;

(a) first and second semi-transparent reflectors;

(b) a radiation beam splitter, a radiation beam combiner, and a radiation beam path length controller;

or

(c) first and second phase gratings; and

a controller configured to determine, from the energy in a first pulse determined by the detector, a required energy in a second pulse to provide a required total radiation dose and to provide a control signal to the variable attenuator in order to set a level of transmission of the variable attenuator such that it attenuates the second pulse to the required level.

2. A radiation dose controller, comprising:

a detector configured to measure an energy of radiation within a pulse of radiation received by the radiation dose controller;

a variable attenuator configured to attenuate the energy of radiation within at least one pulse of radiation, wherein the variable attenuator comprises one of;

(a) first and second semi-transparent reflectors;

(b) a radiation beam splitter, a radiation beam combiner, and a radiation beam path length controller;

or

(c) first and second phase gratings;

an optical delay configured to provide a time delay before a pulse of radiation is input to the variable attenuator; and

a triggering unit configured to send a control signal to the variable attenuator in response to the energy of the radiation within a pulse of radiation measured by the detector, such that the variable attenuator is set to attenuate the energy in the pulse of radiation to a desired radiation dose when the pulse of radiation is input to the variable attenuator.

3. A radiation dose controller, comprising:

a detector configured to measure an intensity of radiation within a pulse of radiation received by the radiation dose controller;

a variable attenuator configured to attenuate an energy of radiation within at least one pulse of radiation, wherein the variable attenuator comprises one of;

(a) first and second semi-transparent reflectors;

(b) a radiation beam splitter, a radiation beam combiner, and a radiation beam path length controller;

or

(c) first and second phase gratings;

an optical delay configured to provide a time delay before a pulse of radiation is input to the variable attenuator; and

a triggering unit configured to send a control signal to the variable attenuator in response to the intensity of a pulse of radiation measured by the detector, such that the variable attenuator switches from a state of maximum transmissivity to a state of minimum transmissivity at a time required to trim the energy of the pulse of radiation to a desired radiation dose.