Method and apparatus for detecting aberrations in an optical system

• US 6,788,400 B2
• Filed: 12/04/2001
• Issued: 09/07/2004
• Est. Priority Date: 12/06/2000
• Status: Expired due to Term

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Masktools B.V. (ASML Holding NV)
• Inventors: Chen, J. Fung
• Primary Examiner(s): Nguyen, Tu T.
• Application Number:
  US10/001,196
• Publication Number:
  US 20020088951A1
• Time in Patent Office: 1,008 Days
• Field of Search: 356/124-127, 356/239--23, 356/342, 356/399, 356/400-401, 250/492.22, 250/398, 430/5, 430/22, 430/30, 359/566
• US Class Current: 356/124
• CPC Class Codes: G03F 7/706 Aberration measurement

Abstract

A method of detecting aberrations associated with a projection lens utilized in an optical lithography system. The method includes the steps of forming a mask for transferring a lithographic pattern onto a substrate, forming a plurality of non-resolvable features disposed on the mask, where the plurality of non-resolvable features are arranged so as to form a predetermined pattern on the substrate, exposing the mask using an optical exposure tool so as to print the mask on the substrate, and analyzing the position of the predetermined pattern formed on the substrate and the position of the plurality of non-resolvable features disposed on the mask so as to determine if there is an aberration. If the position of the predetermined pattern formed on the substrate differs from an expected position, which is determined from the position of the plurality of non-resolvable features, this shift from the expected position indicates the presence of an aberration.

Claims

1. A method of detecting aberrations associated with an optical system utilized in a lithographic projection apparatus comprising:

a radiation system for supplying a projection beam of radiation;

a support structure for supporting patterning means, the patterning means 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,

said optical system comprising at least one of the radiation system and projection system,

said method comprising the steps of;

providing said desired pattern to comprise a monitor having a plurality of sub resolution features, where the plurality of sub-resolution features are arranged so as to form a predetermined test pattern when projected on the substrate;

projecting the monitor onto the substrate using the projection system, and;

analyzing the position of said predetermined test pattern and the position of the plurality of sub-resolution features in the monitor so as to determine if there is an aberration,

wherein none of said plurality of sub-resolution features are individually imaged on said substrate.

2. The method of claim 1, wherein each of said plurality of sub-resolution features is provided with a square-shaped cross-sectional configuration, said plurality of sub-resolution features being positioned with respect to one another so as to form a substantially circular shape.

3. The method of claim 2, wherein each of said plurality of sub-resolution features is provided with a side length of at most 0.30 (λ

/NA), λ

being the wavelength of the radiation in the projection beam and NA being the Numerical Aperture of the projection system.

4. The method of claim 3, wherein the spacing between adjacent edges of adjacent sub-resolution features is at most 0.15 (λ

/NA).

5. The method of claim 1, wherein said predetermined test pattern is a substantially ring-shaped pattern.

6. The method of claim 1, wherein, in addition to said monitor, said desired pattern is further provided to comprise a device pattern, corresponding to an integrated device layer to be formed on said substrate.

7. The method of claim 1, wherein a first set of said plurality of sub-resolution features which are adjacent one another overlap in an X-direction, and a second set of said plurality of sub-resolution features overlap in a Y-direction, substantially orthogonal to said X-direction, said overlap in said X-direction being substantially equal to said overlap in said Y-direction.

8. The method of claim 1, wherein the patterning means is provided as mask.

9. The method of claim 8, wherein each of said plurality of sub-resolution features is a π

-phase shifting element.

10. The method of claim 8, wherein said mask is one of a 6% attenuated phase-shift mask and a binary chrome mask.

11. A construction for detecting aberrations in an optical system utilized in a lithographic projection apparatus comprising:

a radiation system for supplying a projection beam of radiation;

a mask table for holding a mask;

a substrate table for holding a substrate; and

a projection system for projecting a pattern in the mask onto a target portion of the substrate,

said optical system comprising at least one of the radiation system and projection system,

said construction comprising a mask plate carrying a monitor pattern, said monitor pattern comprising a plurality of sub-resolution features disposed on said mask plate, said plurality of sub-resolution features arranged so as to form a predetermined test pattern on said substrate, said predetermined pattern being utilized to detect said aberrations,

wherein none of said plurality of sub-resolution features are individually imaged on said substrate.

12. A construction according to claim 11, further comprising a device pattern disposed on said mask plate and corresponding to an integrated device layer to be formed on said substrate.

13. A device manufacturing method comprising the steps of:

(a) providing a substrate that is at least partially covered by a layer of radiation-sensitive material;

(b) providing a projection beam of radiation using a radiation system;

(c) using patterning means to endow the projection beam with a pattern in its cross-section;

(d) using a projection system to project the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material,

wherein, prior to the use of an integrated device pattern in step (d), an aberration monitoring step is performed comprising the steps of;

providing the pattern of step (C) to comprise a monitor having a plurality of sub-resolution features, where the plurality of sub-resolution features is arranged so as to form a predetermined test pattern when projected on the substrate;

projecting the monitor onto the substrate using the projection system, and;

analyzing the position of said predetermined test pattern and the position of the plurality of sub-resolution features in the monitor so as to determine if there is an aberration in at least one of the radiation system and projection system,

wherein none of said plurality of sub-resolution features are individually imaged on said substrate.

14. A lens aberration monitor for detecting lens aberrations, said monitor comprising:

a plurality of sub-resolution features disposed on a mask, said plurality of sub-resolution features arranged so as to form a predetermined pattern on a substrate,

wherein said predetermined pattern is utilized in the detection of said lens aberrations, and

wherein none of said plurality of sub-resolution features are individually imaged on said substrate.

15. A computer program product for controlling a computer comprising a recording medium readable by the computer, means recorded on the recording medium for directing the computer to generate at least one file corresponding to a mask for use in a lithographic imaging process, said generation of the file comprising the steps of:

generating data representing a mask pattern for transferring a lithographic pattern onto a substrate, and

generating data representing a plurality of sub-resolution features, said plurality of sub-resolution features arranged so as to form a predetermined pattern on said substrate, said predetermined pattern being utilized to detect lens aberrations,

wherein none of said plurality of sub-resolution features are individually imaged on said substrate.

16. The computer program product according to claim 15, wherein each of said plurality of sub-resolution features has a square-shaped cross-sectional configuration, said plurality of sub-resolution features being positioned with respect to one another so as to form a circular-shape.

17. The computer program product according to claim 16, wherein each of said plurality of sub-resolution features having said square-shaped cross-sectional configuration, exhibits a length of about 0.30 (λ

/NA) or less per side, where λ

equals the wavelength of a light source utilized to image said mask and NA equals the numerical aperture of an objective lens used to image the mask onto the substrate.

18. The computer program product according to claim 16, wherein the spacing between adjacent edges of adjacent sub-resolution features is about 0.15 (λ

/NA) or less per side, where λ

equals the wavelength of a light source utilized to image said mask and NA equals the numerical aperture of an objective lens used to image the mask onto the substrate.

19. The computer program product according to claim 16, wherein a first set of said plurality of sub-resolution features which are adjacent one another overlap in an X-direction, and a second set of said plurality of sub-resolution features overlap in a Y-direction, substantially orthogonal to said X-direction, said overlap in said X-direction being equal to said overlap in said Y-direction.

20. The computer program product according to claim 15, wherein each of said plurality of sub-resolution features is a π

-phase shifting element.

21. The computer program product according to claim 15, wherein said predetermined pattern formed on said substrate is a ring-shaped pattern.