Fluorescence radiation filter

• US 20010050762A1
• Filed: 12/01/2000
• Published: 12/13/2001
• Est. Priority Date: 12/01/1999
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Van der Veen, Paul, Mulkens, Johannes C.
• Granted Patent: US 6,473,163 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70216 Mask projection systems

Abstract

The filter comprises alternating layers of relatively high and relatively low refractive index media. The layers are formed as a coating on an optical component in the projection lens system of a lithographic projection apparatus. The filter transmits radiation at a wavelength of 157 nm for exposing an image of a mask pattern on a resist-coated substrate whilst attenuating radiation resulting from fluorescence in optical components of the lithographic projection apparatus, caused by the imaging radiation, and which if not attenuated would reduce the contrast of the image exposed in the resist.

Claims

1. A lithographic projection apparatus for imaging of a mask pattern in a mask onto a substrate provided with a radiation sensitive layer, the apparatus comprising:

a radiation system for supplying a projection beam of electromagnetic radiation with a wavelength less than 160 nm;

a first object table for holding a mask;

a second object table for holding a substrate;

a projection system for imaging irradiated portions of the mask onto target portions of the substrate;

characterised by further comprising;

a filter, located in the projection beam path, for attenuating fluorescence radiation with a wavelength longer than that of the projection beam.

2. An apparatus according to

claim 1

, wherein the filter comprises a plurality of layers, each layer having a refractive index, wherein the refractive index alternates between a relatively high value and a relatively low value, or vice versa, between successive layers.

3. An apparatus according to

claim 1

or

2

, wherein the filter comprises at least one pair of layers, the or each pair comprising a layer of relatively low refractive index material and a layer of relatively high refractive index material.

4. An apparatus according to

claim 2

or

3

, wherein the layer or layers of relatively high refractive index are made of one or more materials selected from the group consisting of:

Al₂O₃, LaF₃, NdF₃, GdF₃, DyF₃, LnF₃, ThF₄ and CeF₃.

5. A apparatus according to

claim 2

,

3

or 4, wherein the layer or layers of relatively low refractive index are made of one or more materials selected from the group consisting of:

SiO₂, MgF₂, AlF₃, NaF, Na₃AlF₆, Na₅Al₃F₁₄.

6. An apparatus according to any one of

claims 2

to

5

, wherein the filter is a cut-off filter comprising 6-10 layers.

7. An apparatus according to any one of

claims 2

to

5

, wherein the filter is a band-pass filter comprising 30-50 layers.

8. An apparatus according to any one of the preceding claims, wherein the filter is adapted to transmit radiation with a wavelength in the range 155-159 nm and/or 124-128 nm.

9. An apparatus according to any one of the preceding claims, wherein the filter is adapted to attenuate visible light.

10. An apparatus according to any one of the preceding claims, wherein said filter comprises a coating on an optical component present in the projection system or radiation system.

11. An apparatus according to any one of the preceding claims, wherein said filter is located between said first and second object tables.

12. An apparatus according to any one of the preceding claims, wherein said projection beam comprises radiation with a wavelength in the range 155-159 nm or 124-128 nm.

13. An apparatus according to any one of the preceding claims, wherein said filter comprises a plurality of sub-filters in series arrangement, each such sub-filter serving to attenuate a given portion of a wavelength spectrum of the said fluorescence radiation.

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

a radiation system for supplying a projection beam of electromagnetic radiation with a wavelength less than 160 nm;

a first object table for holding a mask;

a second object table for holding a substrate; and

a projection system for imaging irradiated portions of the mask onto target portions of the substrate;

the method comprising the steps of;

providing a mask bearing a pattern to said first object table;

providing a substrate provided with a radiation-sensitive layer to said second object table;

irradiating portions of the mask and imaging said irradiated portions of the mask onto said target portions of said substrate;

characterised the step of;

employing a filter, located in the projection beam path, to attenuate fluorescence radiation with a wavelength longer than that of the projection beam.

15. A device manufactured according to the method of

claim 14

.