Optics: measuring and testing – By alignment in lateral direction – With registration indicia
Reexamination Certificate
1993-10-21
2001-12-25
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By alignment in lateral direction
With registration indicia
C250S548000, C700S121000
Reexamination Certificate
active
06333786
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an aligning method for correctly positioning different portions of a workpiece to a desired site in sequence. More particularly, the invention is concerned with an aligning method usable in a semiconductor device manufacturing step-and-repeat type exposure apparatus, for measuring positions or positional errors related to some of the shot areas on a semiconductor wafer, then for determining from the results the disposition of all of the shot areas of the wafer and for correctly positioning these shot areas of the wafer in sequence to a site related to a reticle (photomask) on the basis of the thus determined shot disposition.
As an aligning method usable in a semiconductor device manufacturing step-and-repeat type exposure apparatus (stepper), for correctly positioning different shot areas of a wafer to a site related to a reticle (photomask), a proposal has been made in Japanese Laid-Open Patent Application, Laid-Open No. Sho 63-232321 filed in the name of the assignee of the subject application. According to this proposal, positions or positional errors related to some shot areas on a semiconductor wafer are measured and, by using the results, the disposition of all the shot areas on the wafer is determined. Then, by using the thus determined shot disposition, the wafer is moved stepwise so as to correctly position each shot area of the wafer with respect to a site related to a reticle (photomask), in a predetermined order.
SUMMARY OF THE INVENTION
More specifically, in the aligning method according to this proposal, any extraordinary value or values included in the measured position data are rejected and, from the measured positional data related to some shot areas, the disposition of all the shot areas on the wafer is determined by using a statistical method, for example. However, during this determination, all the measured positional data are processed on an assumption that they have the same reliability. Accordingly, in this aligning method, those measured positional data having high reliability and those measured data having lower reliability, have the same influence upon determination of the shot disposition (chip disposition).
Such a difference in reliability of the measured data may be disregarded from the standpoint of conventionally required alignment precision. However, in consideration of increasing resolving power of a stepper which requires corresponding enhancement of the alignment precision, such a difference in reliability of the measured data should be considered.
In this respect, it is accordingly a primary object of the present invention to provide an improved aligning method which ensures further enhancement of the alignment precision.
It is another object of the present invention to provide an aligning method usable, for example, in a semiconductor device manufacturing step-and-repeat type exposure apparatus, for measuring positions or positional errors related to some shot areas on a semiconductor wafer, then for determining from the results the disposition of all the shot areas of the wafer and for correctly positioning each shot area of the wafer to a site related to a reticle on the basis of the thus determined shot disposition, with enhanced alignment precision.
In accordance with an aspect of the present invention, to achieve at least one of these objects, the reliability of each measured positional data is determined on the basis of the state of each mark detection signal (mark signal) obtained as a result of detection of each mark provided in each shot area, or on the basis of the state of each measured positional data related to each shot area. Then, from values related to these measured positional data having been weighted in accordance with the determined reliability, the disposition (corrected position data) of all the shot areas of a wafer (workpiece) is determined. This means that those measured position data having high or higher reliability, have stronger influence upon determination of the shot disposition and, therefore, the alignment precision can be enhanced.
In accordance with an aspect of the present invention, the reliability of each measured positional data is determined on the basis of fuzzy reasoning, from the states of mark signals obtained from alignment marks of shot areas or, alternatively, from the states of measured positional data of the shot areas. The fuzzy reasoning is a best method for determination of the reliability of each measured positional data by using plural conditional propositions.
In accordance with another aspect of the present invention, the determined shot disposition may be represented by an approximation function and, on that occasion, the square or absolute value of a difference (hereinafter “remainder”) between the actual position of each shot area as represented by a corresponding measured positional data and the position of that shot area as represented by the approximation function, may be weighted in accordance with the reliability of the corresponding measured positional data, and the approximation function may be determined so that the sum of the weighted remainders is reduced to a minimum. This makes it possible to determine the approximation function so as to ensure that those measured positional data having high or higher reliability are more influential than those measured positional data having low or lower reliability.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
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Japanese patent document 59-027525, Feb. 1984, English Abstract. Only.
Japanese patent document 61-114529, Jun. 1986, English Abstract. Only.
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Imaizumi Masaaki
Kaneko Yoshio
Nakai Akiya
Takakura Noburu
Tanaka Hiroshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Turner Samuel A.
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