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Browse Prior Art Database

Structures for Test of Asymmetry in Optical Imaging Systems

IP.com Disclosure Number: IPCOM000102016D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Starikov, A: AUTHOR

Abstract

Disclosed is a method for design of structures for testing asymmetry in optical imaging systems, such as in optical lithography, alignment, and measurement of overlay and size. One particular embodiment is given and others are outlined.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 58% of the total text.

Structures for Test of Asymmetry in Optical Imaging Systems

       Disclosed is a method for design of structures for
testing asymmetry in optical imaging systems, such as in optical
lithography, alignment, and measurement of overlay and size. One
particular embodiment is given and others are outlined.

      For the optical imaging system, such as those above, with
demanding requirements to residual aberrations and alignment of both
the imaging lens and the condenser, it is necessary to be able to
test, in situ, the consequences of the system deviation from
symmetrical.  It is further important to distinguish the effects of
the lens from those of a condenser.

      It is proposed to test the system using comparisons of images
of conventional lines with those of a subresolution line decorated on
one or both sides with still smaller subresolution lines.  An
illustration is given in the drawing for the case of an optical
lithography tool and the test structure being chrome on glass.  In
the imaging system of the drawing:

                            (Image Omitted)

   NA = 0.35;    436 NM; s = 0.52 COMA:  0.2g   at O@ and H =
1. Also,
         = X1 + X4        X2 + X3
     O/L  ___________  - __________
               2             2
For the chosen solubility threshold:    O/L Z .3 mm.

      It is clear that following the print in photoresist, the center
of the line decor...