SOURCE AND MASK OPTIMIZATION BY CHANGING INTENSITY AND SHAPE OF THE ILLUMINATION SOURCE AND MAGNITUDE AND PHASE OF MASK DIFFRACTION ORDERS

• US 20140247975A1
• Filed: 05/19/2014
• Published: 09/04/2014
• 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
• Granted Patent: US 10,657,641 B2
• Time in Patent Office: Days
• US Class Current: 382/144
• 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 of obtaining a target source and a target mask comprising the steps of:

determining how an illumination is provided from an illumination source to a plurality of source points and a mask corresponding to a predetermined mask pattern;

selecting fragmentation points in an image plane of an image formed by the illumination provided to the predetermined mask pattern;

determining an intensity and image log slope of illumination at each fragmentation point; and

simultaneously changing the intensity and shape of the illumination source and the magnitude and phase of diffraction orders of the mask to form an image in the image plane that maximizes the minimum image log slope at the fragmentation points while forcing the intensity at the fragmentation points to be within a predetermined intensity range, thereby obtaining the target source and the target mask from the changed illumination source and mask, respectively.