Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
1999-11-03
2001-10-02
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S022000
Reexamination Certificate
active
06296977
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a method for the measurement of an aberration of an optical projection system and, more particularly, to an aberration measurement method for measuring an aberration of an optical projection system of a projection exposure apparatus to be utilized in particular for the manufacture of devices such as semiconductor elements and liquid crystal display elements.
2. Description of the Related Art
As the extent of integration of circuit patterns for semiconductor elements and so on develops greater and greater, the structure of such patterns is being made finer and finer from year to year. Accordingly, an exposure apparatus of a projection type for resolving a pattern should be developed so as to catch up with developments of making the pattern finer and making the exposing wavelength from 365 nm to 248 nm. At the same time, various aberrations of an optical projection system of the exposure apparatus should be made considerably less because of such developments.
Hitherto, the measurement of an asymmetrical aberration of a projection lens, which includes a comatic aberration of a projection lens and a comatic aberration caused by eccentricity of a mechanical center of the projection lens from the light axis, has been made by locating a light shade pattern at a light transmission section on a reticle in such a state where the projection lens is disposed in the projection exposure apparatus, transcribing the light shade pattern onto a substrate coated with a photoresist and then inspecting an asymmetrical amount of the photoresist image of the pattern transcribed with an electronic microscope or other means.
In order to inspect such an asymmetrical amount of the photoresist image, however, a measuring device having a resolving power of 0.005 &mgr;m is required and only a scanning type electronic microscope (SEM) of the latest type can meet such requirements. The SEM may cause problems, however, in that the resolving power thereof may vary with alignment of the optical axis of an optical electronic system or pressure of inner gases, i.e., a degree of vacuum, or other conditions and, therefore, that the resolving power of the SEM may vary with the ability of researchers who handle it, the state of the apparatus, or the like. Further, the difference of the resolving power can exert a big influence upon an amount of an aberration to be measured.
SUMMARY OF THE INVENTION
Therefore, the present invention has an object to provide a method for the measurement of an amount of an aberration of an optical projection system at a high speed and with a high degree of precision, without using any complicated microscope.
Another object of the present invention is to provide an aberration measurement method of an optical projection system, which can be effected by an optical microscope, by determining an amount of an aberration on the basis of a difference between line widths of patterns.
A further object of the present invention is to provide the aberration measurement method which can be effected by an optical microscope by determining an amount of an aberration on the basis of a ratio of an amount of exposure in which an image of a line disappears to an amount of exposure in which an image of another line disappears.
A still further object of the present invention is to provide the aberration measurement method which allows a measurement by an optical microscope by determining an amount of an aberration by measuring a pitchwise width of a line-and-space pattern containing plural lines having different line widths.
Further, the present invention has a still further object to provide the aberration measurement method of an optical projection system, which does not require a preparation of plural pattern groups, each pattern group consisting of lines each having a line width different from each line of the other pattern group, by measuring an amount of an aberration on the basis of information in respect of a shape of an image of a wedge-shaped pattern.
A still further object of the present invention is to provide the aberration measurement method of an optical projection system, which can improve a degree of precision of measurement, by measuring an aberration while predicting an amount of exposure in which to cause the images of lines to disappear, in association with a variation in lengths of the lines.
Furthermore, the present invention has another object to provide the aberration measurement method of an optical projection system, which can be applied to an aberration measurement method for measuring an amount of an aberration at a high speed and with a high degree of precision by an observation method such as, for example, FIA, LSA, LIA or the like, when no electronic microscope is used.
Still further, the present invention has another object to provide the aberration measurement method of an optical projection system, which can measure the aberration by measuring an amount of a deviation of a position of an image of a line-and-space pattern or an isolated line pattern, each formed on a substrate.
Furthermore, the present invention has another object to provide the aberration measurement method of an optical projection system, which corrects a deviation of a position of an image to be measured for determining the aberration.
Moreover, the present invention has another object to provide the aberration measurement method of an optical projection system, which can accurately measure an enlarged deviation of the positions between the images by taking advantage of a Moire mark, without using a microscope with a complicated construction, by forming first and second groups of line-and-space pattern images as a zigzag pattern.
In addition, the present invention has another object to provide the aberration measurement method of an optical projection system, which can measure an amount of a deviation of positions between the first and second line-and-space pattern images by correcting the deviation with a Moire mark formed by third and fourth line-and-space pattern images.
The other objects and the constructions to achieve the objects according to the present invention will become apparent in the course of the description which follows.
In order to achieve the objects of the present invention, there is provided a method for the measurement of an amount of an aberration of an optical projection system, which comprises the step of locating a mask in an optical path of the optical projection system, the mask being formed with a line-and-space pattern containing lines each having an equal line width; the step of locating a substrate coated with a photoresist in a projection position of the optical projection system; the step of exposing the line-and-space pattern to the photoresist coated on the substrate at a predetermined amount of exposure by projecting with the optical projection system; the step of developing the substrate exposed; and the step of determining an amount of an aberration on the basis of a difference between line widths of the lines of the pattern on the both end sides in the pitch direction of the line-and-space pattern images, in the images of the line-and-space patters, by the photoresist coated on the substrate by the developing step.
This construction of the present invention allows a measurement of the amount of the aberration on the basis of the line widths of the patterns so that the measurement can be effected with an optical microscope.
Further, the present invention provides the aberration measurement method for measuring the amount of the aberration of the optical projection system, which comprises the step of locating a mask in an optical path of the optical projection system, the mask being formed with a line-and-space pattern containing lines, each line having an equal line width; the step of locating a substrate coated with a photoresist in a projection position of the optical projection system; the step of exposing the line-and-space pattern to the photoresist coated on the substrate by vary
Hayashi Tsunehito
Kaise Koji
Tsukakoshi Toshio
Armstrong Westerman Hattori McLeland & Naughton LLP
Nikon Corporation
Rosasco S.
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