Photocopying – Projection printing and copying cameras – Focus or magnification control
Reexamination Certificate
1999-10-04
2001-07-03
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Focus or magnification control
C355S053000, C355S067000
Reexamination Certificate
active
06256086
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to a projection exposure apparatus and a device manufacturing method using the same. More particularly, the invention is suitable usable in a step-and-repeat type or step-and scan type stepper which is a microdevice manufacturing apparatus, for satisfactorily correcting a projection magnification error in projecting an electronic circuit pattern of a reticle onto a wafer surface or various aberrations such distortion, spherical aberration, coma or astigmatism, for example, to thereby produce a high precision projection pattern and accomplish production of a high integration device.
In printing apparatuses (aligners) for the manufacture of semiconductor devices such as IC or LSI, a very high assembling precision and a very high optical performance are required.
As regards the optical performance, a matching precision in the registration of a reticle having an electronic circuit pattern with a wafer is particularly important. The size of a pattern used in a reticle is becoming smaller and smaller, and thus the required matching precision becomes higher and higher. As the factors which are most influential to the matching precision, there are a projection magnification error and a distortion error of a projection optical system.
The projection magnification error is a deviation of the projection magnification (lateral magnification) of a projection optical system from a reference value. The distortion error is a deviation of distortion aberration (distortion) of a projection optical system from a reference value. Both of the projection magnification error and the distortion error appear as a difference between a grid point of a projected pattern and a reference grid point desired.
If a projection optical system has a projection magnification error, there appears an error such as shown in
FIG. 5
wherein, while the shape of an idealistic grid is unchanged and kept analogous, the size thereof is changed.
If a projection optical system has a symmetric distortion aberration, there appears an error such as shown in
FIGS. 6 and 7
wherein the idealistic grid is deformed into a spindle-like shape or a cask-like shape. If this aberration changes to produce a distortion error, the state of deformation also changes.
Generally, the projection magnification error and the distortion error of a projection optical system are corrected by the adjustment of the projection optical system in its manufacturing process or the adjustment of the projection optical system during the setting operation of an exposure apparatus wherein the projection optical system is incorporated. However, they may be changed after the setting, due to the surrounding environment thereof, particularly, the pressure or temperature. Also, a projection optical system absorbs exposure energies during exposure of a wafer and, due to an increase of the temperature of the system, optical parameters such as a refractive index or a shape, for example, may change. This may cause a projection magnification error and a distortion error, and the magnitude of such error may change thereby.
Correction of a projection magnification error and a distortion error in a stepper has been proposed in some documents such as follows.
Japanese Laid-Open Patent Application, Laid-Open No. 81019/1990 shows a projection exposure apparatus wherein the spacing between a reticle (object plane) and a projection optical system as well as the spacing between lenses of the projection optical system are changed to thereby correct a projection magnification error and a distortion error.
Japanese Laid-Open Patent Application, Laid-Open No. 214334/1985 shows an exposure apparatus wherein, based on a remaining chromatic aberration of magnification in a projection optical system, the wavelength of exposure light is changed to adjust a projection magnification.
Japanese Laid-Open Patent Application, Laid-Open No. 30411/1992 shows an exposure apparatus wherein at least one lens group of a projection optical system is moved in an optical axis direction and, also, the wavelength of exposure light is changed, by which a projection magnification error and a symmetrical distortion error are corrected.
Japanese Laid-Open Patent Application, Laid-Open No. 255748/1996 shows an exposure apparatus wherein two or more particular groups of optical elements in a projection optical system are moved in an optical axis direction, by which a projection magnification error and a distortion error are corrected.
U.S. Pat. No. 5,117,255 shows an exposure apparatus wherein a recticle or at least one lens of a projection optical system is moved three-dimensionally, by which a distortion aberration is corrected.
As the projection magnification error or the distortion aberration is corrected, aberrations of a projection optical system are changed thereby. Among these aberrations being changed, the one which has a smallest tolerance and may cause a problem is a coma aberration. If a coma aberration larger than a tolerance is left in the projection optical system, there may occur a phenomenon of a lateral shift of a circuit pattern being projected. Additionally, it may cause “frequency dependency of distortion” in which the quantity of lateral shift depends on the pattern size or the pattern direction. Since it is a lateral shift amount, it directly influences the final registration (total overlay) of plural mask patterns. Thus, it must be controlled precisely.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a projection exposure apparatus and/or a device manufacturing method using the same, by which a high optical performance can be accomplished.
In accordance with an aspect of the present invention, there is provided a projection exposure apparatus having a function for adjusting a projection magnification, a symmetric distortion aberration and another optical characteristic of a projection optical system, said apparatus comprising: first changing means for changing a first optical parameter of said projection optical system; second changing means for changing a second optical parameter of said projection optical system; and third changing means for changing a third optical parameter of said projection optical system; wherein a change in the projection magnification, a change in the symmetric distortion aberration and a change in the optical characteristic, all to be produced when the first optical parameter is changed, are &Dgr;&bgr;
1
, &Dgr;SD
1
and &Dgr;A
1
, respectively; wherein a change in the projection magnification, a change in the symmetric distortion aberration and a change in the optical characteristic, all to be produced when the second optical parameter is changed, are &Dgr;&bgr;
2
, &Dgr;SD
2
and &Dgr;A
2
, respectively; wherein a change in the projection magnification, a change in the symmetric distortion aberration and a change in the optical characteristic, all to be produced when the third optical parameter is changed, are &Dgr;&bgr;
3
, &Dgr;SD
3
and &Dgr;A
3
, respectively; wherein angles each defined by two of three vectors (&Dgr;&bgr;
1
, &Dgr;SD
1
, &Dgr;A
1
), (&Dgr;&bgr;
2
, &Dgr;SD
2
, &Dgr;A
2
) and (&Dgr;&bgr;
3
, &Dgr;SD
3
, &Dgr;A
3
) are not less than 30 deg. and not greater than 150 deg.; and wherein the quantities of all the aforementioned changes correspond to those values each being provided by standardising an amount of actual change with respect to a an amount of largest change to be produced due to corresponding one of said first to third changing means.
In one preferred form of the present invention, the first changing means may change a position of a first optical element, such as a lens, of said projection optical system in a direction of an optical axis, the second changing means may change a position of a second optical element, such as a lens, of said projection optical system in a direction of an optical axis, and the third changing means may change a wavelength of exposure light, such as excimer laser light, to be incident on said projection optical
Adams Russell
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Hung Henry
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