Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2002-02-20
2004-03-09
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S055000
Reexamination Certificate
active
06704093
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a scanning exposure apparatus, scanning exposure method, and device manufacturing method.
BACKGROUND OF THE INVENTION
The influence of the positional shift between a reticle and a wafer during scanning exposure on a transfer image depends on the variation period of the relative shift amount. The average shift component between a reticle and a wafer while an exposure slit (slit-shaped exposure light) passes an arbitrary point on a wafer to be exposed is called a moving average (MA), which corresponds to the shift amount of a reticle image transfer position from a desired position. A component which vibrates while the exposure slit passes an arbitrary point on a wafer, i.e., a relatively short vibration period component is represented by the variance of the deviation or the moving standard deviation (MSD), which corresponds to the half-shade (blur) amount of a reticle pattern transfer image generated by a stage control error. Both the moving average and moving standard deviation are desirably small. It is important to provide these values as numerical evaluation measures.
Conventionally, the moving average or moving standard deviation within a shot is monitored and used as an index for analyzing a production lot error factor. More specifically, the worst value of the absolute moving average of each shot and the maximum value of the moving standard deviation of each shot are saved as logs of an exposure result. These values are compared with those of a shot determined as defective in the inspection step, and yield decrease factors can be tracked. The upper limit values of the moving average and moving standard deviation are set in advance. If the moving average and moving standard deviation exceed their upper limit values in scanning exposure, the exposure apparatus is stopped and overhauled before another defective lot is generated.
FIG. 3
is a graph showing the simulation results of the relationship between the moving standard deviation (MSD) and the CD (Critical Dimension) value during scanning exposure. The difference from the CD value at a position MSD=0 is a decrease in line width depending on MSD. For a large MSD, the half-shade amount becomes large, and the transfer line width becomes small.
Variations in the line width of a reticle pattern transfer image on a wafer serve as an important factor representing the performance of an integrated circuit. Variations in line width correspond to variations in moving standard deviation (MSD). As a prior art, MSD and MA values are sequentially calculated. However, an apparatus or method for evaluating MSD variations and utilizing the evaluation result has not been proposed yet.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide an apparatus and method for evaluating, e.g., variations in moving standard deviation and utilizing the evaluation result.
The first aspect of the present invention relates to a scanning exposure apparatus for transferring a pattern of a master onto a substrate with slit-shaped exposure light while a master stage holding the master and a substrate stage holding the substrate are moved at a predetermined speed ratio. The scanning exposure apparatus comprises a measurement unit arranged to measure a sync deviation between the master stage and the substrate stage, an arithmetic unit arranged to calculate variations in a plurality of moving standard deviations corresponding to a plurality of points on the substrate on the basis of a plurality of sync deviations measured by the measurement unit, and a control unit arranged to control an exposure job on the basis of an arithmetic result by the arithmetic unit.
According to a preferred aspect of the present invention, the control unit preferably has a determination unit arranged to determine whether the variations in the plurality of moving standard deviations calculated by the arithmetic unit satisfy a predetermined criterion, and preferably controls the exposure job on the basis of a determination result by the determination unit.
According to another preferred aspect of the present invention, the arithmetic unit preferably calculates, as the variations in the plurality of moving standard deviations, maximum and minimum values serving as predetermined confidence limit values in a &khgr;
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distribution. The control unit preferably has a determination unit arranged to determine whether the maximum and minimum values satisfy corresponding predetermined criteria, and preferably controls the exposure job on the basis of a determination result by the determination unit. Alternatively, the control unit preferably has a determination unit arranged to determine whether a difference between the maximum and minimum values satisfies a predetermined criterion, and preferably controls the exposure job on the basis of a determination result by the determination unit. The control unit preferably has a determination unit arranged to determine whether a mean value between the maximum and minimum values satisfies a predetermined criterion, and preferably controls the exposure job on the basis of a determination result by the determination unit. Alternatively, the control unit preferably has a determination unit arranged to determine whether a difference between the maximum and minimum values and a mean value between the maximum and minimum values satisfy corresponding predetermined criteria, and preferably controls the exposure job on the basis of a determination result by the determination unit.
According to still another preferred aspect of the present invention, the arithmetic unit preferably calculates, as the variations in the plurality of moving standard deviations, at least one of a contrast value and contrast variations of an image transferred onto the substrate.
According to still another preferred aspect of the present invention, the control unit preferably controls a subsequent exposure job so as to adjust the variations in the plurality of moving standard deviations calculated by the arithmetic unit to satisfy a predetermined criterion.
According to still another preferred aspect of the present invention, the control unit preferably controls a subsequent exposure job on the basis of variations in a plurality of moving standard deviations obtained in the past so as to adjust the variations in the plurality of moving standard deviations to satisfy the predetermined criterion in the subsequent exposure job. The control unit preferably has an adjustment unit arranged to adjust a settling time between start of constant-speed traveling and start of exposure after the master stage and the substrate stage are accelerated, and preferably controls a subsequent exposure job so as to adjust, by adjusting the settling time, the variations in the plurality of moving standard deviations to satisfy the predetermined criterion in the subsequent exposure job. Alternatively, the control unit preferably has an adjustment unit arranged to adjust moving speeds of the master stage and the substrate stage, and preferably controls a subsequent exposure job so as to adjust, by adjusting the moving speeds, the variations in the plurality of moving standard deviations to satisfy the predetermined criterion in the subsequent exposure job. Alternatively, the control unit preferably has an adjustment unit arranged to adjust an exposure order of a plurality of shots of the substrate, and preferably controls a subsequent exposure job so as to adjust, by adjusting the exposure order, the variations in the plurality of moving standard deviations to satisfy the predetermined criterion in the subsequent exposure job. Alternatively, the control unit preferably has an application unit arranged to apply a vibration to at least one of the master stage and the substrate stage, and an adjustment unit arranged to adjust an amplitude of the vibration, and preferably controls a subsequent exposure job so as to adjust, by adjusting the amplitude of the vibration, the va
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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