Source and mask optimization by changing intensity and shape of the illumination source and magnitude and phase of mask diffraction orders

• US 10,657,641 B2
• Filed: 05/19/2014
• Issued: 05/19/2020
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Socha, Robert
• Primary Examiner(s): Kim, Peter B
• Application Number:
  US14/281,539
• Publication Number:
  US 20140247975A1
• Time in Patent Office: 2,192 Days
• 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 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 7/70433 Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

An illumination source is optimized by changing the intensity and shape of the illumination source to form an image in the image plane that maximizes the minimum ILS at user selected fragmentation points while forcing the intensity at the fragmentation points to be within a small intensity range. An optimum mask may be determined by changing the magnitude and phase of the diffraction orders to form an image in the image plane that maximizes the minimum ILS at user selected fragmentation points while forcing the intensity at the fragmentation points to be within a small intensity range. Primitive rectangles having a size set to a minimum feature size of a mask maker are assigned to the located minimum and maximum transmission areas ad centered at a desired location. The edges of the primitive rectangle are varied to match optimal diffraction orders O(m,n). The optimal CPL mask O_CPL(x,y) is then formed.

Claims

1. A method for obtaining a lithographic process for creating an image of a pattern at an image plane using a patterning device, the method comprising:

by a hardware computer system,

based on intensities determined for the subset of diffraction orders, selecting one or more illumination points in an illumination system and determining a transmission mask for the pattern, for which minimum image log slope is maximized in the image at each of a plurality of points, wherein determining the transmission mask comprises determining mask diffraction orders, and determining mask diffraction orders comprises performing a non-linear optimization to find optimal diffraction orders, and

performing a linear optimization by selecting quantized mask transmission to match the optimal diffraction orders,

where the (a) illumination points, (b) the transmission mask, and/or (c) information derived from (a) and/or (b), is configured to design, control and/or modify the physical lithographic process involving the pattern and/or design, control and/or modify a physical object or apparatus to be used in the physical lithographic process.

2. The method of claim 1, wherein determining the transmission mask comprises determining mask diffraction orders in a spatial frequency domain.

3. The method of claim 1, wherein determining the mask diffraction orders is performed in one or both of horizontal and vertical directions of the pattern.

4. The method of claim 1, wherein determining the mask diffraction orders includes determining magnitudes and phases of the mask diffraction orders.

5. The method of claim 1, further comprising determining one or both of a minimum pupil fill and minimum ring width using specifications of an actual illumination system of the lithographic process.

6. The method of claim 1, comprising selecting one or more illumination points in the illumination system and determining a transmission mask for the pattern, for which an intensity is a specified value or within a specified range.

7. The method of claim 1, further comprising selecting, based on a calculation involving a value of a wavelength of radiation and a value representing an extent of distribution of a beam of the radiation from a radiation source for illuminating the pattern, a subset of diffraction orders.

8. A non-transitory computer-readable storage medium having stored instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

based on intensities determined for the subset of diffraction orders, select one or more illumination points in an illumination system and determine a transmission mask for a pattern to be imaged to an image plane in a lithographic process using a patterning device, for which minimum image log slope is maximized in the image at each of a plurality of points, wherein determination of the transmission mask comprises determination of mask diffraction orders, and determination of mask diffraction orders comprises performance of a non-linear optimization to find optimal diffraction orders, and

perform a linear optimization by selecting quantized mask transmission to match the optimal diffraction orders,

where the (a) illumination points, (b) the transmission mask, and/or (c) information derived from (a) and/or (b), is configured to design, control and/or modify the physical lithographic process involving the pattern and/or design, control and/or modify a physical object or apparatus to be used in the physical lithographic process.

9. The non-transitory computer-readable storage medium of claim 8, wherein the instructions configured to determine the transmission mask are further configured to determine mask diffraction orders in a spatial frequency domain.

10. The non-transitory computer-readable storage medium of claim 8, wherein the determination of the mask diffraction orders is performed in one or both of horizontal and vertical directions of the pattern.

11. The non-transitory computer-readable storage medium of claim 8, wherein the determination of the mask diffraction orders includes determination of magnitudes and phases of the mask diffraction orders.

12. The non-transitory computer-readable storage medium of claim 8, wherein the instructions are further configured to determine one or both of a minimum pupil fill and minimum ring width using the specifications.

13. The non-transitory computer-readable storage medium of claim 8, wherein instructions are further configured to perform the selection of the one or more illumination points in the illumination system and determination of the transmission mask for the pattern, for which an intensity is a specified value or within a specified range.

14. The non-transitory computer-readable storage medium of claim 8, wherein the instructions are further configured to cause the computer system to select, based on a calculation involving a value of a wavelength of radiation and a value representing an extent of distribution of a beam of the radiation from a radiation source for illuminating the pattern, a subset of diffraction orders.

15. A method for obtaining a lithographic process for creating an image of a pattern at an image plane using a patterning device, the method comprising:

identifying fragmentation points; and

by a hardware computer system, selecting one or more illumination points in an illumination system and determining a mask configuration for the pattern, by using a non-linear optimization in a spatial frequency domain, by using kernels derived from diagonalization of transmission cross coefficients of the lithographic process and for which minimum image log slope is maximized in the image at each of the fragmentation points,

where the (a) illumination points, (b) the mask configuration, and/or (c) information derived from (a) and/or (b), is configured to design, control and/or modify the physical lithographic process involving the pattern and/or design, control and/or modify a physical object or apparatus to be used in the physical lithographic process.

16. The method of claim 15, wherein determining the mask configuration comprises determining mask diffraction orders in the spatial frequency domain.

17. The method of claim 16, wherein determining the mask diffraction orders is performed in one or both of horizontal and vertical directions of the pattern.

18. The method of claim 16, wherein determining the mask diffraction orders includes determining magnitudes and phases of the mask diffraction orders.

19. The method of claim 15, comprising:

performing the non-linear optimization to find optimal diffraction orders; and

performing a linear optimization by selecting quantized mask transmission to match the optimal diffraction orders.

20. The method of claim 15, further comprising determining one or both of a minimum pupil fill and minimum ring width using specifications of the illumination system.

21. The method of claim 15, wherein determining the mask configuration comprises:

locating areas of maximum transmission and minimum transmission,

assigning a primitive area as an area centered on an area of maximum transmission or minimum transmission, and

varying edges of the primitive area to match optimum diffraction orders,

wherein the primitive area has a minimum size which is substantially equal to a minimum feature size of a patterning device to implement the pattern.

22. The method of claim 15, comprising selecting the one or more illumination points in the illumination system and determining the mask configuration for the pattern, for which an intensity is a specified value or within a specified range.

23. A non-transitory computer-readable storage medium having stored instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

identifying fragmentation points; and

select one or more illumination points in an illumination system and determine a mask configuration for a pattern to be imaged using a lithographic process for creating an image of the pattern using a patterning device, by using a non-linear optimization in a spatial frequency domain, by using kernels derived from diagonalization of transmission cross coefficients of the lithographic process and for which minimum image log slope is maximized in the image at each of the fragmentation points,

where the (a) illumination points, (b) the mask configuration, and/or (c) information derived from (a) and/or (b), is configured to design, control and/or modify the physical lithographic process involving the pattern and/or design, control and/or modify a physical object or apparatus to be used in the physical lithographic process.