Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-10-01
2004-01-06
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S052000
Reexamination Certificate
active
06674509
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exposure apparatus and a method for exposing a pattern formed on a master such as a reticle onto a substrate such as a wafer in a photolithography process for manufacturing a semiconductor element, a liquid crystal display element, or the like, and, more particularly, to a scanning exposure method and an apparatus for a step-and-scan scheme in which the master and substrate are synchronously scanned while part of a pattern on the master is projected onto the wafer, so that the pattern of the master is sequentially transferred to the shot regions on the substrate.
BACKGROUND OF THE INVENTION
In a conventional photolithography process for manufacturing, e.g., a semiconductor element, liquid crystal display element, image sensing element (e.g., a CCD), or thin-film magnetic head, a cell projection exposure apparatus such as a stepper has been used in which a pattern formed on a master such as a reticle is exposed onto a substrate such as a wafer coated with a photosensitive material.
In recent years, semiconductor device chips have tended to increase in size, and a pattern having a larger area on a reticle must be exposed onto a wafer. A projection exposure apparatus of a step-and-scan scheme is frequently used because it can expose an area larger than the irradiation field (pattern exposure region in a stationary state) of a projection optical system by synchronously scanning the reticle and wafer.
A cell projection exposure apparatus repeats an operation of stepping the shot region of an exposure object to the irradiation field, an operation of aligning the shot region and reticle, and an exposure operation for the shot region.
In a scanning projection (step-and-scan scheme) exposure apparatus, however, a wafer stage is stepped to the scanning start position of the next shot region. The wafer stage and a reticle stage are scanned from the scanning start position to accelerate them so that they reach predetermined scan speeds at the exposure start position. The relative positions of the reticle stage and wafer stage are set with high alignment accuracy. Exposure light irradiation is started to perform scanning exposure by driving the reticle stage and wafer stage at the predetermined scan speed.
Upon completing scanning exposure of one shot, a stepping operation to the next shot in the non-scan direction is started, and at the same time the wafer stage is scanned in the scan direction by a necessary distance in order to set the wafer stage before the start of scanning exposure. The wafer stage is then decelerated. Upon completing scanning in the scan direction, the scan direction is reversed, and then scanning exposure of the next shot is started. The series of operations described above are repeated. The setting distance necessary before the start of scanning exposure is obtained by the product of the scan speed and the time (setting time) required until the vibration generate upon accelerating the wafer stage falls within the allowable range in which the vibration does not interfere with exposure.
At present, the setting time is the sum of a margin and a value obtained by measuring a synchronization error from the end of acceleration and measuring a time until this error falls within the allowable range.
In the conventional scanning projection exposure apparatus, the synchronization setting time of the reticle stage and wafer stage at the time of scanning exposure is determined on the basis of the sum of the margin and the setting time measured beforehand, i.e., on the basis of the worst setting time value. In actual exposure, however, a time within which the synchronization accuracy falls within the allowable range may be shorter than the conventionally used setting time due to factors such as an exposure speed, acceleration, hardware factors, and slight differences in thrust of a linear motor coil serving as a driving source of the wafer stage due to driving coordinate values of the wafer stage. Even in this case, since the setting distance is determined on the basis of the worst setting time value at present, the scan distance is wasted, and an increase in throughput cannot be achieved.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to shorten the total time required for maintaining synchronization accuracy and improve the throughput by variably setting a setting distance serving as a distance for moving a wafer stage at a uniform velocity in order to guarantee that synchronization error between a master stage and the substrate stage falls within an allowable range.
According the present invention, the foregoing object is attained by providing a scanning exposure apparatus for transferring a pattern of a master onto each shot region while synchronously scanning the master and a substrate on which a plurality of shot regions are arrayed, the apparatus comprising: a master stage for moving the master; a substrate stage for moving the substrate; and a controller for controlling movement of the substrate stage over a plurality of shot regions so as to assure a setting distance serving as a distance for scanning and moving the substrate stage at a uniform velocity in order to guarantee that a synchronization error between the master stage and the substrate stage falls within an allowable range after the substrate stage is accelerated up to a scan speed for scanning exposure, wherein the controller controls the movement of the substrate stage such that a setting distance for a first shot region to be scanned and exposed upon a change in row to which a shot region of an exposure object belongs is set to be longer than a setting distance for other shot regions.
In a preferred embodiment, the controller controls the continuous movement of the substrate stage in accordance with a common setting distance for shot regions other than the first shot region to be scanned and exposed among a plurality of shot regions belonging to one row.
In a preferred embodiment, the controller controls the continuous movement of the substrate stage in accordance with a setting distance determined for each row to which a plurality of shot regions belong.
In a preferred embodiment, the setting distance is determined on the basis of a setting time until a synchronization error between the master stage and the substrate stage falls within an allowable range after the substrate stage is accelerated up to a scan speed for scanning exposure.
According to another aspect of the present invention, the foregoing object is attained by providing a scanning exposure apparatus for transferring a pattern of a master onto each shot region while synchronously scanning the master and a substrate on which a plurality of shot regions are arrayed, the apparatus comprising: a master stage for moving the master; a substrate stage for moving the substrate; and a controller for controlling movement of the substrate stage for a plurality of shot regions so as to assure a setting distance serving as a distance for scanning and moving the substrate stage at a uniform velocity in order to guarantee that a synchronization error between the master stage and the substrate stage falls within an allowable range after the substrate stage is accelerated up to a scan speed for scanning exposure, wherein the controller controls movement of the substrate stage in accordance with a setting distance determined for each row to which a plurality of shot regions belongs.
In a preferred embodiment, the setting distance is determined on the basis of a setting time until a synchronization error between the master stage and the substrate stage falls within an allowable range after the substrate stage is accelerated up to a scan speed for scanning exposure.
According to another aspect of the present invention, the foregoing object is attained by providing a scanning exposure method of transferring a pattern of a master onto each shot region while synchronously scanning the master and a substrate on which a plurality o
Adams Russell
Canon Kabushiki Kaisha
Esplin D. Ben
Fitzpatrick ,Cella, Harper & Scinto
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