Lithographic projection apparatus, device manufacturing method and device manufactured thereby

• US 20020051124A1
• Filed: 09/04/2001
• Published: 05/02/2002
• Est. Priority Date: 09/04/2000
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Jonkers, Jeroen, Banine, Vadim Y.
• Granted Patent: US 7,671,965 B2
• Time in Patent Office: Days
• US Class Current: 355/53
• CPC Class Codes: G03F 7/70883 of optical system
• CPC Class Codes: G03F 7/70916 Pollution mitigation, i.e. mitigating effect of contamination or debris, e.g. foil traps
• CPC Class Codes: G03F 7/70933 Purge, e.g. exchanging fluid or gas to remove pollutants
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
• CPC Class Codes: G03F 7/70983 Optical system protection, e.g. pellicles or removable covers for protection of mask

Abstract

A lithographic projection apparatus comprising a radiation system for supplying a projection beam of electromagnetic radiation in the extreme ultraviolet (EUV) range, a support structure for supporting patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern, a substrate table for holding a substrate and a projection system for projecting the patterned beam onto a target portion of the substrate. A space within the apparatus, which space contains a mirror, is supplied with a hydrocarbon gas which forms a protective cap layer on the mirror surface. The partial pressure of the hydrocarbon gas in the space is controlled in response to variations in the background pressure in the space and/or in the reflectivity of the mirror, such that the thickness of the cap layer on the mirror remains within an acceptable range. The partial pressure of hydrocarbon may be increased in order to sputter away the cap layer and/or, if extra multilayers are provided on the mirror, the top layer(s) of the mirror, thus providing a clean mirror surface. The hydrocarbon used may be an alcohol, in which case the cap layer formed is self-terminating.

Claims

1. A lithographic projection apparatus comprising:

a radiation system to supply a projection beam of radiation;

a support structure adapted to support patterning structure which can be used to pattern the projection beam according to a desired pattern;

a substrate table to hold a substrate;

a projection system to project the patterned beam onto a target portion of the substrate;

a gas supply, configured and arranged to supply a gaseous hydrocarbon to a space containing a mirror;

a least one sensor selected from the group comprising a reflectivity sensor to monitor a reflectivity of said mirror and a pressure sensor to monitor a background pressure in said space; and

a gas supply control, responsive to a signal from said at least one sensor to control said gas supply.

2. An apparatus according to claim 1, wherein the radiation system contains said space containing the mirror.

3. An apparatus according to claim 1, wherein the radiation system comprises one of a laser-produced plasma source and a discharge source adapted to supply a beam of extreme ultraviolet (EUV) radiation as said projection beam.

4. An apparatus according to claim 3, wherein said beam of extreme ultraviolet radiation has a wavelength of less than about 50 nm.

5. An apparatus according to claim 4, wherein said beam of extreme ultraviolet radiation has a wavelength in the range of from 8 to 20 nm

6. An apparatus according to claim 5 wherein said range is from 9 to 16 nm.

7. An apparatus according to claim 1, wherein the hydrocarbon is an alcohol.

8. An apparatus according to claim 7, wherein the alcohol is ethanol.

9. An apparatus according to claim 1 wherein the mirror is a collector mirror.

13. A method according to claim 9, wherein said mirror comprises at least 40 multilayers and wherein the method further comprises adapting the amount of gaseous hydrocarbon supplied to the space such that at least part of at least a top layer of said mirror undergoes sputtering.

10. A method of manufacturing a device using a lithographic projection apparatus comprising:

projecting a patterned beam of radiation onto a target portion of a layer of radiation-sensitive material on a substrate;

supplying a gaseous hydrocarbon to a space within the lithographic projection apparatus containing a mirror;

monitoring at least one of a reflectivity of said mirror and a background pressure in said space; and

controlling an amount of gaseous hydrocarbon supplied to said space in response to the monitoring.

11. A method according to claim 10, wherein the hydrocarbon is an alcohol.

12. A method according to claim 11, wherein the alcohol is ethanol.

15. A method according to claim 14, wherein the alcohol forms a cap layer on said mirror and wherein the gaseous alcohol is supplied to said space at a pressure sufficient to achieve a thickness of said cap layer which does not increase substantially over time.

16. A method according to claim 13, wherein the alcohol is ethanol.

17. A device manufactured in accordance with the method of claim 10.

14. A method of manufacturing a device using a lithographic projection apparatus comprising:

projecting a patterned beam of radiation onto a target portion of a layer of radiation-sensitive material on a substrate; and

supplying a gaseous alcohol to a space in a radiation system of the lithographic projection apparatus, which space contains a mirror.