Photocopying – Projection printing and copying cameras – Focus or magnification control
Reexamination Certificate
2000-12-29
2004-06-15
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Focus or magnification control
C355S053000
Reexamination Certificate
active
06750950
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a scanning exposure method, a scanning exposure apparatus and making method thereof, and a device and a device manufacturing method. More particularly, the present invention relates to a scanning exposure method to be employed in a lithographic process for manufacturing a semiconductor device, a liquid crystal display device and so forth; a scanning exposure apparatus on which the scanning exposure method is applied and a making method thereof; as well as a device which is manufactured by using the scanning exposure apparatus and a manufacturing method thereof.
BACKGROUND ART
Conventionally, in a lithographic process for manufacturing a semiconductor device, liquid crystal display device and so forth, an exposure apparatus has been used. In such an exposure apparatus, patterns formed on a mask or reticle (to be genetically referred to as a “reticle” hereinafter) are transferred through a projection optical system onto a substrate such as a wafer or glass plate (to be referred to as a “substrate or wafer” herein after, as needed) coated with a resist or the like. In general, a projection optical system with a large numerical aperture (to be referred to as “N.A.”, hereinafter) and a shallow focal depth is used in the projection exposure apparatus. The mechanism to bring the substrate surface to a proximate level of an imaging plane in the projection optical system is necessary for the projection exposure apparatus for transferring fine circuit patterns onto a substrate with high resolution. Therefore, the exposure apparatus has a focusing system for brining the substrate surface to the range of the focal depth of the projection optical system. The system is composed of the focus/leveling detecting mechanism and the adjusting mechanism, and the system is referred to as the “Z-leveling stage” herein after. The focus/leveling detecting mechanism detects the position and tilt of the substrate surface in optical axis direction of the projection optical system (that is, Z-direction), and the adjusting mechanism adjusts the position and the posture of the substrate surface by using the detected position and the tilt of the surface in Z-direction.
On the contrary, semiconductor chip devices recently tend to be large-sized, and there is needs to transfer larger patterns onto the substrate by the projection exposure. For satisfying such needs, so-called step and scan type scanning exposure apparatus is practically used. In the apparatus, a reticle and the substrate are synchronously scanned against the projection optical system, shot areas are exposed over the effective illumination area of the projection optical system. In the scanning type exposure apparatus, in order to expose a shot area on the substrate surface, the shot area, i.e. substrate, and the reticle must be moved synchronously with the fixed velocity commensurate to the predetermined exposure dose amount, while the substrate and the reticle are positioning. Therefore, the following procedures are included: the stage on which the substrate is loaded (XY stage) is allowed to run when the shot area is far from exposure area on the substrate surface, on which exposure light is illuminated when the light is passed through the projection optical system; the stage loading the substrate and the stage loading the reticle are synchronized; and then, the exposure is begun at the time that the shot area on the substrate is reached the exposure area.
As a part of the procedure, the positional information in Z-direction and the tilt information in the synchronized moving direction and the unsynchronized moving direction (i.e., perpendicular to the synchronized direction) are detected for the substrate surface area in the exposure area. By using this detection result, the focusing operation is performed for the substrate surface area in the exposure area. In the focusing operation, the focusing operation for focusing in the optical axis direction of the projection optical system (Z-direction) and the leveling operation for focusing in tilt direction around X-axis and Y-axis are simultaneously performed. Thereby, the difference between the expose plane on the substrate and the image plane of the projection optical system becomes minimal. When the synchronous moving direction is Y-direction, the tilt for the synchronous moving direction is represented as the rotational amount around X-axis, and that in the asynchronous moving direction is represented as the rotational amount around Y-axis.
In the step and scan type scanning exposure apparatus, since the substrate to be exposed is moved during the exposure, the control is repeated successively so that the image plane of the projection optical system closes to the exposure plane on the surface of the photosensitive substrate. Accordingly, in the typical structure of the Z-leveling stage in which the driving mechanism is arranged periphery of the substrate, most of the driving load in the leveling stage is caused by the leveling operation.
In such scanning exposure apparatuses, the slit shape of the exposure area on which the exposure light passed through the projection optical system is generally In the shape of the exposure area, the length in the synchronous moving direction (for example, Y-direction) is shorter than that in the asynchronous moving direction (for example, X-direction). Based on the shape of the exposure area, focus detection points are arranged inside of the exposure area (and outside of it, if necessary). At that time, the length that is used as the base line for calculating the tilt components in the synchronous moving direction is shorter than that in asynchronous direction. Therefore, the leveling action for the asynchronous direction greatly contributes to the driving load on the Z-leveling stage.
That is, in the step and scan type scanning apparatus, most of the driving practicability of the Z-leveling stage is spent to the leveling action in the scanning direction.
Integrated circuit patterns formed on the substrate often have different number of starts, and it causes the increase of driving load for the Z-leveling stage in the leveling action for the synchronous moving direction. In the substrate having such different number of stairs, the stair pattern formed by the different number of stairs sometimes has the periodical repeating components. Furthermore, the distribution state of the period varies depending on, for example, the application or characteristics of the integrated circuit pattern. When the ratio of the short periodical components is high, the driving load for the leveling action in the synchronous moving direction. Therefore, the driving practicability of Z-leveling stage should be high must, and it causes the structure of Z-leveling stage to be complicate and large scaled.
When the performance of z-leveling stage does not fulfill the required performance for following-up the leveling in the synchronous direction, the adjustment of the leveling is insufficient. Furthermore, when 100% of the performance of Z-leveling stage is applied for following-up the leveling caused by the difference number of the stairs in the synchronous moving direction, it is impossible to correct the figure of the substrate except the difference (for example, warpage or swell in the raw substrate). Thereby nonlinear area is generated which causes to loose control, and the transfer of the pattern can be affected by more serious effect such as awful deterioration for imaging and so forth.
The present invention has been made in consideration of the above-mentioned situation. The first object of the present is to provide the exposure method for transferring a pattern without extreme deterioration of the imaging performance.
The second object of the present invention is to provide the exposure apparatus for transferring a pattern without extreme deterioration of the imaging performance.
The third object of the present invention is to provide the device on which fine patterns are precisely formed.
DISCLOSURE OF INVENTION
As mentioned a
Nguyen Henry Hung
Nikon Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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