Lithographic apparatus, and device manufacturing method

1. A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate, the apparatus comprising:

a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission; and

a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface,

wherein at least one of the radiation dose detectors is arranged separately from a surface of an optical component of the lithographic apparatus.

2. The apparatus according to claim 1 , wherein the optical component of the apparatus is located between the first and second radiation dose detectors.

3. The apparatus according to claim 1 , further comprising a data processor configured to compare measurement results of the meter to detect a change in radiation received by the radiation dose detectors.

4. A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate, the apparatus comprising:

a radiation dose detector substantially insensitive to a contaminant that is likely to contaminate the detector during operation of the apparatus, the detector comprising a secondary electron emission surface configured to receive a radiation flux, and which may also receive the contaminant, and to emit secondary electrons due to the receipt of the radiation flux, the surface substantially made of the contaminant or a material with a secondary electron emission similar to that of the contaminant; and

a meter, connected to the surface, to detect a current or voltage resulting from the secondary electron emission.

5. The apparatus according to claim 4 , wherein the surface is a surface of an optical component.

6. The apparatus according to claim 4 , wherein the contaminant is carbon, tin, tin oxide, zinc, zinc oxide, manganese, manganese oxide, tungsten, tungsten oxide, or any combination thereof.

7. A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate, the apparatus comprising:

a radiation dose detector sensitive to a contaminant that is likely to contaminate the detector during operation of the apparatus, the detector comprising a secondary electron emission surface configured to receive a radiation flux, and which can also receive the contaminant, and to emit secondary electrons due to the receipt of the radiation flux, the detector positioned to receive a contaminant emanating from the substrate during operation; and

a meter, connected to the detector surface, to detect a current or voltage resulting from the secondary electron emission,

wherein the detector is arranged separately from a surface of an optical component of the lithographic apparatus.

8. The apparatus according to claim 7 , further comprising:

a projection system configured to project the patterned beam of radiation onto the substrate; and

a gas shower configured to provide a gas curtain between the substrate and the projection system,

wherein the detector is located between the substrate and projection system, in the gas curtain, between the gas curtain and the substrate, or between the gas curtain and the projection system.

9. The apparatus according to claim 7 , further comprising a cleaning system configured to remove contamination from the detector surface.

10. A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate, the apparatus comprising:

an etch detector comprising a detector body having a secondary electron emission surface, the surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, wherein the composition of the detector body varies in a direction perpendicular from the surface;

a meter, connected to the detector body, to detect a current or voltage resulting from the secondary electron emission; and

a data processor configured to detect etching of the detector from a measurement by the meter.

11. The apparatus according to claim 10 , wherein the detector body comprises different layers consisting of different materials, at least one (compositionally) graded layer having a gradually changing composition, different graded layers, at least one layer having a thickness of about 1 nm or less, or any combination thereof.

12. A lithographic method performed in a lithographic apparatus, the method comprising:

projecting a patterned beam of radiation onto a target portion of a substrate; and

detecting a radiation dose utilizing a radiation dose detector substantially insensitive to a contaminant that is likely to contaminate the detector during operation of the apparatus, the detector comprising a secondary electron emission surface substantially made of the contaminant or a material with a secondary electron emission similar to that of the contaminant, wherein radiation received by the surface results in emission of secondary electrons from the surface and a current or voltage resulting from the secondary electron emission is detected, the current or voltage being independent of the presence of the contaminant on the surface.