Lithography scanner

Abstract

The present disclosure relates to a lithography scanner including: a light source configured to emit extreme ultra-violet (EUV) light; a pellicle including an EUV transmissive membrane that is configured to scatter the EUV light into an elliptical scattering pattern having a first major axis; a reticle configured to reflect the scattered EUV light through the pellicle; and an imaging system configured to project a portion of the reflected light that enters an acceptance cone of the imaging system onto a target wafer, wherein a cross section of the acceptance cone has a second major axis, and wherein the pellicle is arranged such that the first major axis is oriented at an angle relative to the second major axis.

Claims

1. A lithography scanner comprising: a light source configured to emit extreme ultra-violet (EUV) light; a pellicle comprising an EUV transmissive membrane that is configured to scatter the EUV light into an elliptical scattering pattern having a first major axis; a reticle configured to reflect the scattered EUV light through the pellicle; and an imaging system configured to project a portion of the reflected light that enters an acceptance cone of the imaging system onto a target wafer, wherein a cross section of the acceptance cone has a second major axis, and wherein the pellicle is arranged such that the first major axis is oriented at an angle relative to the second major axis.

2. The lithography scanner of claim 1, wherein a first numerical aperture corresponding to a minor axis of the acceptance cone is less than a second numerical aperture corresponding to the second major axis.

3. The lithography scanner according to claim 1, wherein the EUV transmissive membrane comprises at least one sheet of carbon nanotube bundles.

4. The lithography scanner according to claim 3, wherein the at least one sheet of carbon nanotube bundles comprises a plurality of substantially parallel carbon nanotube bundles.

5. The lithography scanner according to claim 3, wherein the at least one sheet of carbon nanotube bundles comprises single-walled carbon nanotubes.

6. The lithography scanner according to claim 3, wherein the at least one sheet of carbon nanotube bundles comprises multi-walled carbon nanotubes.

7. The lithography scanner according to claim 3, wherein the at least one sheet of carbon nanotube bundles are substantially parallel to a surface of the at least one sheet of carbon nanotube bundles.

8. The lithography scanner according to claim 1, wherein the first major axis is oriented transverse to the second major axis.

9. The lithography scanner of claim 1, wherein the light source is configured to emit light having a wavelength between 5 nm and 40 nm.

10. The lithography scanner of claim 1, wherein the light source is a plasma light source.

11. The lithography scanner of claim 1, wherein the light source comprises collimating optical components.

12. The lithography scanner of claim 1, wherein the light source comprises a pupil mirror.

13. The lithography scanner of claim 1, wherein the light source is configured for off-axis illumination of the reticle.

14. The lithography scanner of claim 1, wherein the light source is configured for dipole illumination.

15. The lithography scanner of claim 1, wherein the light source is configured for quadrupole illumination.

16. The lithography scanner of claim 1, wherein the light source is configured for free-form illumination.

17. The lithography scanner of claim 1, wherein the reticle comprises a line pattern.

18. The lithography scanner of claim 1, wherein the reticle comprises a rectangular pattern.

19. A method of operating a lithography scanner, the method comprising: emitting extreme ultra-violet (EUV) light via a light source; scattering, via a transmissive membrane of a pellicle, the EUV light into an elliptical scattering pattern having a first major axis; reflecting, via a reticle, the scattered EUV light through the pellicle; and projecting, via an imaging system, a portion of the reflected light that enters an acceptance cone of the imaging system onto a target wafer, wherein a cross section of the acceptance cone has a second major axis, and wherein the pellicle is arranged such that the first major axis is oriented at an angle relative to the second major axis.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The above, as well as additional, features will be better understood through the following illustrative and non-limiting detailed description of example embodiments, with reference to the appended drawings.

(2) FIG. 1A is a schematic representation of an EUVL scanner comprising a light source, a reticle, a pellicle, and an anamorphic high-NA imaging system, according to an example embodiment.

(3) FIG. 1B schematically illustrates, in a pupil plane of the scanner, a cross section of an acceptance cone of the anamorphic high-NA imaging system and scattering patterns of light scattered by the pellicle with the EUV light source arranged for conventional illumination, according to an example embodiment.

DETAILED DESCRIPTION

(4) Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings. That which is encompassed by the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example. Furthermore, like numbers refer to the same or similar elements or components throughout.

(5) FIG. 1A is a schematic representation of an EUVL scanner 10. The EUVL scanner 10 comprises an EUV light source 110, a reticle 120, a pellicle 130, and an anamorphic high-NA imaging system 140. The EUVL scanner 10 may have an optical axis 100 as exemplified in FIG. 1A.

(6) The EUV light source 110 may emit light having a wavelength between 5 nm and 40 nm. The EUV light source 110 may comprise a plasma. The EUV light source 110 may comprise optics. The optics may be reflective optics. The optics may comprise collimating optics and/or optics arranged for illuminating the reticle 120. The optics may comprise a pupil mirror. The pupil mirror may define a pupil plane of the scanner. The EUV light source 110 may be arranged for off-axis illumination of the reticle 120. The EUV light source 110 may be arranged for dipole illumination of the reticle 120. The EUV light source 110 may be arranged for quadrupole illumination of the reticle 120. The EUV light source 110 may be arranged for free-form illumination. The arrangement of the EUV light source 110 may be based on the pattern on the reticle 120. For instance, the EUV light source 110 may be arranged for dipole illumination for projecting a line pattern of the reticle 120 on a target wafer 150.

(7) The reticle 120 may comprise a line pattern. The line pattern may have a main direction. The main direction of the line pattern may be a longitudinal direction of the line pattern. The reticle 120 may comprise a rectangular pattern. The reticle 120 may comprise a plurality of rectangular patterns. The reticle 120 may comprise rectangular patterns that define Via or Block layers (e.g. for interconnect layer patterning in the back-end-of-line). In a further example, the reticle 120 may comprise layers of dense rectangles for use in standard cell, logic and memory applications, such as dynamic random-access memory (DRAM).

(8) The pellicle 130 is mounted in front of the reticle 120. The pellicle 130 comprises an EUV transmissive membrane 132. The transmissive membrane 132 may comprise at least one sheet or film of carbon nanotube bundles. The at least one sheet of carbon nanotube bundles may comprise a plurality of substantially parallel carbon nanotube bundles, comprising single-walled and/or multi-walled carbon nanotubes. The plurality of substantially parallel carbon nanotube bundles may be substantially parallel to a surface of the at least one sheet of carbon nanotube bundles. Examples of processes for synthesis of carbon nanotubes include techniques based on arc-discharge methods, laser ablation, and chemical vapor deposition (CVD) methods including floating catalyst (aerosol) CVD synthesis.

(9) The EUV transmissive membrane 132, in use, scatters transmitted light into an elliptical scattering pattern 112 having a major axis 114. The elliptical scattering pattern 112 will be described with reference to FIG. 1B.

(10) The anamorphic high-NA imaging system 140 is configured to project light reflected by the reticle 120 through the pellicle 130 onto the target wafer 150. The anamorphic high-NA imaging system 140 may comprise optics. The optics may be reflective optics.

(11) A cross section 162 of an acceptance cone 160 of the imaging system 140 has a major axis 164. The cross section 162 of the acceptance cone 160 of the imaging system 140 may have a minor axis. The cross section 162 of the acceptance cone 160 may be a transverse cross section of the acceptance cone 160. The major axis 164 of the cross section 162 of the acceptance cone 160 of the imaging system 140 may correspond to a (reticle side) numerical aperture greater than 0.1. A minor axis of the cross section 162 of the acceptance cone 160 of the imaging system 140 may correspond to a (reticle side) numerical aperture less than than 0.1. The numerical aperture corresponding to the major axis 164 of the cross section 162 of the acceptance cone 160 may be larger than the numerical aperture corresponding to the minor axis of the cross section 162 of the acceptance cone 160.

(12) FIG. 1B illustrates, in the pupil plane, a cross section 162 of the acceptance cone 160 of the anamorphic high-NA imaging system 140 and an elliptical scattering pattern 112 of light scattered in the pellicle 130. The cross section 162 of the acceptance cone 160 has a major axis 164.

(13) The elliptical scattering pattern 112 may be an intensity distribution of the light in a plane transverse to the optical axis 100. The elliptical scattering pattern 112 has a major axis 114. The major axis 114 may be a largest full width at half maximum of the intensity distribution of light in the plane transverse to the optical axis 100.

(14) As exemplified in FIG. 1B, the EUV light source 110 may be arranged for conventional illumination of the reticle 120. The EUV light source 110 may be arranged for annular illumination of the reticle 120, dipole illumination of the reticle 120, or quadrupole illumination of the reticle 120, or freeform illumination of the reticle 120. It is to be understood that different patterns on the reticle 120 may have different illumination arrangements of the EUV light source 110.

(15) The pellicle 130 is arranged relative to the imaging system 140 such that the major axis 114 of the scattering pattern 112 is oriented at an angle relative to the major axis 164 of the cross section 162 of the acceptance cone 160 of the imaging system 140. The pellicle 130 may be arranged relative to the imaging system 140 such that the major axis 114 of the scattering pattern 112 is oriented transverse to the major axis 164 of the cross section 162 of the acceptance cone 160 of the imaging system 140, as shown in FIG. 1B.

(16) When the major axis 114 of the scattering pattern 112 of light scattered by the pellicle 130 is oriented at an angle relative to the major axis 164 of the cross section 162 of the acceptance cone 160 of the imaging system 140, an amount 116, 118 of light scattered outside the acceptance cone 160 of the imaging system 140 may be controlled by controlling the angle between the major axes 114, 164. The amount 116, 118 of light scattered outside the acceptance cone 160 of the imaging system 140 may be maximized or increased when the major axis 114 of the scattering pattern 112 of light scattered by the pellicle 130 is oriented transverse to the major axis 164 of the cross section 162 of the acceptance cone 160 of the imaging system 140, as shown in FIG. 1B.

(17) While some embodiments have been illustrated and described in detail in the appended drawings and the foregoing description, such illustration and description are to be considered illustrative and not restrictive. Other variations to the disclosed embodiments can be understood and effected in practicing the claims, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures or features are recited in mutually different dependent claims does not indicate that a combination of these measures or features cannot be used. Any reference signs in the claims should not be construed as limiting the scope.