Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1998-03-30
2001-03-13
Rosasco, S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S022000
Reexamination Certificate
active
06200708
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the art of photolithography in the manufacture of semiconductor integrated circuits, and more particularly, to a process for automatically determining alignment adjustments for stepping photolithography exposures.
BACKGROUND OF THE INVENTION
In semiconductor manufacturing, the accuracy of the stepping of a reticle mask for photolithography exposures is very important. It is crucial that during each stepping action, the stepper equipment moves the reticle a precise predetermined distance in both the x and y directions. Minor accuracy errors in the exposures may produce an unusable product, particularly as the critical dimensions of features in the integrated circuits are reduced.
Currently, stepping is manually analyzed for accuracy with the aid of a microscope. The prior art manual method is time consuming because alignment is analyzed during the execution of a test pattern. Also, inaccuracies, such as rotation, may be misanalyzed due to human error.
The present invention is an improved method for insuring stepper alignment.
SUMMARY OF THE INVENTION
In accordance with this invention, a method and system for analyzing the stepping of a reticle mask is provided. The system includes a reticle mask with a first and second corner mask for blocking exposure of a first rectangular area on the wafer surface, a third corner mask for blocking exposure of a second rectangular area on the wafer surface, wherein the first rectangular area is larger than the second rectangular area, and a fourth corner mask of the reticle mask for allowing exposure of a third rectangular area that is smaller than the second rectangular area. The system also includes a metrology machine for producing alignment adjustment values of the result of stepping the reticle mask over the wafer's surface according to reticle mask overlapped exposed corners.
In accordance with other aspects of this invention, the alignment adjustment values comprise an x and y value, and a rotation value. The alignment adjustment values are determined from the difference between the centers of the overlapping results of the third and fourth corner mask.
REFERENCES:
patent: 5733690 (1998-03-01), Jeong et al.
patent: 5868560 (1999-02-01), Tamada et al.
Blakely , Sokoloff, Taylor & Zafman LLP
Rosasco S.
Worldwide Semiconductor Manufacturing Corporation
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