Enhancing the image contrast of a high resolution exposure tool

• US 20080117399A1
• Filed: 11/22/2006
• Published: 05/22/2008
• Est. Priority Date: 11/22/2006
• Status: Active Grant

• Current Assignee: ASML Holding NV
• Original Assignee: ASML Holding NV
• Inventors: Sewell, Harry
• Granted Patent: US 8,054,449 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G03F 7/70091 Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like

Abstract

A system and method are utilized to equalize intensity or energy in various diffraction orders of a patterned beam. The patterned beam is formed using a diffractive patterning device. An attenuator is placed at a pupil of a projection system to attenuate respective diffraction orders of the patterned beam. The projection device is also used to project the patterned beam onto a target portion of a substrate, after the respective attenuations.

Claims

1. A method, comprising:

(a) illuminating a binary patterning device using at least an off axis portion of a beam of radiation;

(b) attenuating a zero diffraction order portion of the patterned beam at an annular peripheral edge of a pupil of a projection system, whereby intensity of the zero and higher diffraction order portions of the patterned beam are substantially equalized through the attenuating; and

(c) projecting the respective attenuated zero and higher diffraction order portions of the patterned beam onto a target portion of a substrate using the projection system.

2. The method of claim 1, wherein step (b) comprises using an attenuating ring or annular-shaped filter to perform the attenuating without a phase shift.

3. The method of claim 1, wherein step (b) further comprises forming an attenuating ring or an annular-shaped filter on an optical element positioned in the pupil of the projection system.

4. The method of claim 3, wherein step (b) further comprises using a lens as the optical element.

5. The method of claim 3, wherein step (b) further comprises arranging the attenuating annular-shaped filter to have attenuation bands each having different attenuation amounts, such that, depending on a desired attenuation amount of the zero order portion, an illumination system that produces the non-annular illumination, directs the zero order portion to impinge on a corresponding one of the attenuation bands.

6. The method of claim 3, wherein step (b) further comprises using a quartz material for the optical element.

7. The method of claim 1, further comprising forming an attenuating ring or an annular-shaped filter on an object, the object being arranged to move into and out of the pupil of the projection system.

8. The method of claim 1, wherein:

step (b) comprises using an attenuating ring or an annular-shaped filter to perform the attenuating and to produce a phase change in the patterned beam; and

before step (c) the method further comprises compensating for the phase change produced in step (b).

9. The method of claim 1, wherein the non-annular illumination mode of the beam of radiation is dipole, quadrapole, hexapole, or octopole.

10. A lithography system, comprising:

an illumination system configured to produce a beam of radiation having a non-annular illumination mode;

a binary patterning device configured to pattern the beam; and

a projection system configured to project the patterned beam onto a target portion of a substrate, the projection system including a ring-shaped attenuator positioned at an edge of a pupil of the projection system to attenuate a zero diffraction order portion of the patterned beam, whereby the attenuator is configured such that intensity of the zero and higher diffraction order portions of the patterned beam are substantially equalized.

11. The lithography system of claim 10, wherein the attenuator is formed on an optical element of the projection system.

12. The lithography system of claim 10, wherein the attenuator is configured to be moved into and out of the pupil of the projection system.

13. The lithography system of claim 10, wherein the attenuator is configured to have attenuation bands each having different attenuation amounts, such that, depending on a desired attenuation amount of the zero diffraction order portion of the patterned beam, the illumination system directs the zero diffraction order portion of the patterned beam to impinge on a corresponding one of the attenuation bands.

14. The lithography system of claim 10, wherein the illumination system is configured to produce the non-annular illumination mode of the beam of radiation as dipole, quadrapole, hexapole, or octopole illumination.

15. The lithography system of claim 10, further comprising:

a detector configured to detect energy of each of the diffraction order portions of the patterned beam; and

a controller configured to generate a control signal based on the detected energies,

wherein the attenuator is a variable attenuator that is configured to vary at respective areas corresponding to the control signal.

16. The lithography system of claim 10, wherein:

the attenuator is configured to produce a phase change in the patterned beam as the patterned beam passes therethrough; and

the projection system further comprises a phase change compensating system that compensates for the phase change in the patterned beam produced by the attenuator.

17. A lithography system, comprising:

an illumination system configured to produce a beam of radiation having a non-annular illumination mode;

a phase shift patterning device configured to pattern the beam; and

a projection system configured to project the patterned beam onto a target portion of a substrate, the projection system including a ring-shaped attenuator positioned at an edge of a pupil of the projection system to attenuate a first diffraction order portion of the patterned beam, whereby the attenuator is configured such that intensity of the first and higher diffraction order portions of the patterned beam are substantially equalized to a zero diffraction order portion of the patterned beam.

18. The lithography system of claim 17, wherein the attenuator comprises:

a first attenuating ring configured to attenuate the zero diffraction order portion of the patterned beam; and

a second attenuating ring configured to attenuate the first diffraction order portion of the patterned beam.

19. The lithography system of claim 17, wherein the phase shift patterning device is an attenuating phase shift patterning device.

20. The lithography system of claim 17, further comprising:

a detector configured to detect energy of each of the diffraction order portions of the patterned beam; and

a controller configured to generate a control signal based on the detected energies,

wherein the attenuator is a variable attenuator that is configured to vary at respective areas corresponding to the control signal.

21. The lithography system of claim 17, wherein:

the attenuator is configured to produce a phase change in the patterned beam as the patterned beam passes therethrough; and

the projection system further comprises a phase change compensating system that compensates for the phase change in the patterned beam produced by the attenuator.