Contamination reduction system
A contamination reduction system for reducing contamination of a patterning system in a plasma environment, comprising: a support arranged to hold a patterning system in a radiation beam; a shutter configured to shield a portion of the radiation beam from the patterning system; and an electrode positioned between the shutter and the support, the electrode connected to a voltage source and configured to generate an electric field between the electrode and the patterning system held by the support.
1 . A contamination reduction system comprising:
a support arranged to hold a patterning system in a path of a radiation beam;
a movable shutter configured to shield a portion of the radiation beam from the patterning system; and
a single electrode coupled to the shutter and positioned between the shutter and the support, the electrode connected to a voltage source and configured to generate a first electric field between the electrode and the patterning system held by the support and a second electric field between the electrode and the shutter;
wherein the electrode is configured to move with the shutter such that the electrode is shielded from the radiation beam by the shutter.
2 . The contamination reduction system of claim 1 , wherein the first electric field and the second electric field are configured to steer contaminants toward the electrode and away from the patterning system and the shutter.
3 . The contamination reduction system of claim 1 , wherein the electrode is mounted separate from the support.
4 . The contamination reduction system of claim 1 , wherein:
the first electric field is greater in magnitude than a predetermined value, the predetermined value representing a third electric field corresponding to an electric field at the patterning system when no voltage is applied to the electrode, and
the first electric field and the third electric field are of opposite polarity.
5 . The contamination reduction system of claim 4 , further comprising a measuring device configured to measure the third electric field at the patterning system, and wherein the predetermined value comprises the electric field measurement.
6 . The contamination reduction system of claim 4 , further comprising a memory configured to store the predetermined value.
7 . The contamination reduction system of claim 5 , wherein:
the predetermined value comprises a function which varies with time, and
a voltage applied by the voltage supply varies with time and is selected in dependence on the predetermined value.
8 . The contamination reduction system of claim 1 , further comprising a gas outlet configured to provide a gas to a surface of the patterning system and arranged to be illuminated by the radiation beam.
9 . The contamination reduction system of claim 8 , wherein the gas outlet and electrode are unitary.
10 . The contamination reduction system of claim 1 , further comprising a cooling system configured to remove heat from the electrode.
11 . The contamination reduction system of claim 1 , wherein the electrode comprises a flat surface extending generally parallel to a plane of the patterning system and/or shutter.
12 . The contamination reduction system of claim 1 , wherein:
the electrode comprises a first portion and a second portion electrically isolated from the first portion;
the first portion is configured to generate the first electric field such that contaminants are attracted by the first portion; and
the second portion is configured to generate the second electric field such that contaminants are steered away from the second portion.
13 . A reticle stage comprising the contamination reduction system of claim 1 .
14 . A lithographic apparatus comprising the reticle stage of claim 13 .
15 . A method comprising:
moving a single electrode coupled to a shutter to a location of a patterning system, wherein the electrode is positioned between the shutter and the patterning system;
illuminating the patterning system with a radiation beam such that the shutter shields a portion of the radiation beam from the patterning system and the electrode; and
applying a voltage to the electrode such that a first electric field is generated between the electrode and the patterning system and a second electric field is generated between the electrode and the shutter.
16 . The method of claim 15 , wherein:
the voltage applied is such that the first electric field is greater in magnitude than a predetermined value, the predetermined value representing a third electric field corresponding to an electric field at the patterning system when no voltage is applied to the electrode, and
the first electric field and the third electric field are of opposite polarity.
17 . The method of claim 16 , further comprising measuring the third electric field at the patterning system when no voltage is applied to the electrode.
18 . The method of claim 15 , wherein:
applying the voltage comprises applying a first voltage during a first time interval and applying a second voltage during a second time interval, and
the first voltage and second voltage are different.
19 . A metrology system comprising:
a contamination system configured for determining contamination characteristics in a plasma environment, the contamination system comprising:
a support arranged to hold a patterning system in a path of a radiation beam;
a movable shutter configured to shield a portion of the radiation beam from the patterning system; and
a single electrode coupled to the shutter and positioned between the shutter and the support, the electrode connected to a voltage source and configured to generate a first electric field between the electrode and the patterning system held by the support and a second electric field between the electrode and the shutter;
wherein the electrode is configured to move with the shutter such that the electrode is shielded from the radiation beam by the shutter; and
a sensing apparatus, the sensing apparatus being operable to determine one or more characteristics of one or more contaminant particles on a surface of the electrode.
20 . The metrology system of claim 19 , wherein the one or more characteristics comprises a volume, density, and/or composition of the one or more contaminant particles.
21 . A lithographic apparatus comprising the contamination reduction system of claim 1 .