Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2000-06-05
2003-07-29
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S055000, C355S077000
Reexamination Certificate
active
06600550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a device (such as a semiconductor elemental device, photo-imaging elemental device, flat panel display device such as a LCD (liquid crystal display) element device, a PDP (plasma display panel) element device, EL (electroluminescent) display element device, FED (field emission display) element device, Electric Paper display element device etc., thin film magnetic head elemental device, and so forth) that uses a projection exposure apparatus at the time of photo-transferring a mask pattern onto a substrate within the process of lithography for manufacturing the device, wherein the projection optical system for projecting the image of the pattern of the first object onto the second object and the projection optical system thereof are provided.
2. Description of the Related Art
When manufacturing a semiconductor elemental device or so forth, a projection exposure apparatus in a scanning exposure format is used like that of a batch exposure format or the step-and-scan method where a stepper is used to transfer an image of a reticle pattern through a projection optical system as a mask onto a wafer (or glass plate or so forth) that has a photo resist applied thereon. Further, in accordance with the advancement of the refining of patterns such as that of a semiconductor integrated circuit, the demand for increased performance in the projection optical system used in these projection exposure apparatuses is growing, especially in regards to the improvement of the resolving power of a projection optical system. In order to improve this resolving power, the shortening of the exposure wavelength or the increasing of the numerical aperture (N.A.) can be conceived.
With the projection exposure apparatus described above, the i line (365 nm) from the g line (436 nm) of the mercury vapor lamp is used as the exposure light with recent trends moving towards a shorter wavelength. For this reason, a projection optical system that can be used in conjunction with a short wavelength exposure light is being developed.
Furthermore, in conjunction with the improvement of the resolving power, the demand for minimized image warping in projection optical systems is ever increasing. In addition to that caused by distortion, which originates in the projection optical system, there is image warping that is caused by the bend of the wafer that is printed by the image side of the projection optical system as well as that caused by the bend of the reticle drawn by the circuit pattern on the object side of the projection optical system.
In recent years, the refinement of the transferred pattern is increasingly advanced, and the demand for minimized image warping is ever increasing. Therefore, in order to reduce the effect on the image warping due to the bend of the wafer, a so-called image-side telecentric optical system has been conventionally used that places the image side exit pupil position of the projection optical system farther away.
Meanwhile, in regard to the reduction of the image warping due to the bend of the reticle, a so-called object-side telecentric optical system can be conceived that places the entrance pupil position of the projection optical system farther away from the object plane, and there are proposals for moving the entrance pupil position of the projection optical system comparatively farther away in this manner.
In order to improve the resolving power, the problem lies in the reduction of the transmission factor of the glass material constitutes the projection optical system when using an exposure light with a short wavelength, and in the limited availability of glass material that can be used to secure a high transmission factor. Furthermore, the reduction of the transmission factor is not due exclusively to the loss of the amount of light. Rather, because a portion of the lost light is absorbed into the glass material and through its conversion to heat energy, the refractive index of the glass material of the lens changes or the shape of the lens surface changes, thereby resulting in a reduction of the performance of image formation and especially causing fluctuation in the aberration in the exposure. Moreover, the aberration fluctuation in the exposure is also a reverse phenomenon since it disappears when the heat energy in the lens composition disappears after completing exposure, or in other words, when the heated lens cools.
SUMMARY OF THE INVENTION
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
The present invention takes into account the exemplary problems described above in providing a compact yet high performance projection optical system that is extremely favorable in correcting distortion, various aberrations, and maintaining a sufficiently large numerical aperture as well as a broad exposure area while minimizing the reduction in image formation performance due to the absorption by the glass material used, and it is telecentric relative to both sides.
To solve the exemplary problems described above, the present invention provides, in a projection optical system for projecting the pattern of a first object onto a second object, in order from the first object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power and which provides at least two negative lenses.
The first lens group, while maintaining telecentricity, mainly contributes to the correction of the distortion. The second lens group and the fourth lens group contribute mainly to the correction of the Petzval sum and achieve desired flattening of the image plane. Further, the third lens group, in conjunction with the first lens group, generates positive distortion thereby performing the function of correcting the negative distortion generated by the second, fourth and fifth lens groups. In addition, the third lens group and the second lens group, when viewed from the second object, are composed of a telephoto system having a positive and negative refractive power arrangement, and on account of this, have a function that prevents the elongation of the entire projection optical system. The fifth lens group, in order to sufficiently respond to the high numerical aperture at the second object side, suppresses the generation of distortion by maintaining a state of extreme avoidance of especially spherical aberration and thereby performs the role of image formation by leading the luminous flux to the second object.
Further, it is favorable when the present invention satisfies the following conditional expressions (1), (2), (3), and (4). The fifth lens group includes a first lens, two lens surfaces of the first lens satisfy the following condition (1):
&phgr;1/&phgr;exp≦3.5, (1)
the first lens made of a first material having a refractive index that satisfies the following condition (2):
n
1≦1.57, (2)
where &phgr;exp is a diameter of an exposure area on the second object; &phgr;1 is a diameter of a clear aperture of the two lens surfaces of the first lens; and n1 is a refractive index of the first lens. Further, the radius of the clear aperture indicates the distance from the optical axis to the point where reach the reverse traced marginal ray of the beam has the maximum numerical aperture, from the peripheral point of the maximum exposure area where practically corrected aberrations (clear aperture diameter of a lens surface indicates a diameter of a circle including an area of section of a whole beam which pass through the len
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Nguyen Henry Hung
Nikon Corporation
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