Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2000-11-17
2003-04-15
Nguyen, Hung Henry (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S075000
Reexamination Certificate
active
06549268
ABSTRACT:
CROSS-REFERENCE
This is a Continuation of Application No. PCT/JP99/03070 filed Jun. 9, 1999. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety.
BACKGROUND ON THE INVENTION
1. Field of the Invention
The present invention relates to an exposure method and an apparatus for transferring a mask pattern onto a photosensitive substrate in the lithography step for producing, for example, semiconductor devices, image pickup devices (for example, CCD), liquid crystal display devices, or thin film magnetic heads. In particular, the present invention is preferably used for a scanning type exposure apparatus based on, for example, the so-called step-and-scan system for transferring a mask pattern onto a substrate by synchronously moving a mask and the substrate with respect to a projection optical system.
2. Description of the Related Art
For example, when a semiconductor device is produced, a projection exposure apparatus is used, in which an image of a pattern on a reticle as a mask is transferred to respective shot areas on a wafer (or a glass plate or the like) as a substrate applied with a resist. Conventionally, a projection exposure apparatus (stepper) of the full field exposure type (static exposure type) has been frequently used as the projection exposure apparatus. Recently, the attention is also attracted by a scanning exposure type projection exposure apparatus (scanning type exposure apparatus) such as those based on the step-and-scan system in which a reticle and a wafer are subjected to scanning in a synchronized manner with respect to a projection optical system.
In general, in the case of the projection exposure apparatus of the full field exposure type, if the vibration, which acts to incline the optical axis of the projection optical system, is generated by the driving reaction force caused, for example, when the wafer stage is subjected to stepping movement, the relative positional relationship between the reticle and the wafer is changed by the vibration during the exposure. As a result, for example, it is feared that any overlay error occurs. For this reason, the conventional projection exposure apparatus is designed as follows as described in Japanese Patent Application Laid-Open No. 5-136023. That is, a sensor for detecting the vibration is arranged, for example, for the reticle stage and the wafer stage, and the exposure is stopped until the vibration disappears, for example, on the basis of the vibration information fed from the sensor. Alternatively, the positional discrepancy amount between the reticle and the wafer is postulated from the detected amount of vibration. The driving is controlled, for example, for the reticle stage on the basis of the result of the postulation. By doing so, it is intended that the relative positional relationship between the reticle and the wafer is not changed during the exposure.
In the case of the conventional full field exposure type projection exposure apparatus, it is enough that the movement stroke of the reticle stage is short. Therefore, a laser interferometer based on the double-pass system, which radiates the measuring laser beam from a main interferometer body to a corner cube to serve as a movement mirror in two directions perpendicular to one another, has been used to detect the position of the reticle stage. When the corner cube is used as the movement mirror, the laser beam, which comes into the corner cube, returns along an optical path which is parallel to the incoming direction. Therefore, even when the reticle stage is rotated in a minute amount, the laser beam, which is returned from the corner cube, is not greatly deviated from the laser beam which is returned from the reference mirror fixed, for example, to the projection optical system. Therefore, an advantage is obtained such that the position of the reticle stage can be detected highly accurately.
As described above, in the case of the conventional projection exposure apparatus of the full field exposure type, the exposure is stopped until the vibration disappears on the basis of the vibration information fed from the sensor provided, for example, for the stage, or the positional discrepancy amount between the reticle and the wafer is corrected by means of the postulation control depending on the detected amount of the vibration. Thus, the influence of the driving reaction force of the wafer stage or the like is reduced. However, in the case of the scanning type exposure apparatus based on the step-and-scan system or the like, the exposure is performed while moving the reticle stage and the wafer stage. Therefore, it is impossible to stop the exposure until the vibration disappears. Further, it is difficult to perform the exposure while postulating the positional discrepancy amount between the reticle and the wafer from the amount of vibration.
In the case of the scanning type exposure apparatus, the reticle stage is moved over a wide range (approximately corresponding, for example, to the width of the reticle in the scanning direction) in the scanning direction. Therefore, it is impossible to use the corner cube for the movement mirror for measuring the position of the reticle stage in the non-scanning direction perpendicular to the scanning direction. In place of the corner cube, it is necessary to use a plane mirror having a length equivalent to the movement range of the reticle stage. In this case, if the distance between the plane mirror (movement mirror) and the reference mirror is long, for example, even when the laser interferometer based on the double-pass system is used, the laser beam, which is returned from the plane mirror, is deviated relatively greatly, when the reticle stage is rotate in a minute amount. It is feared that the position of the reticle stage cannot be detected. For this reason, in the case of the conventional scanning type exposure apparatus, in order to arrange the movement mirror and the reference mirror closely to one another, the reference mirror has been arranged on a reticle support stand in the vicinity of the movement mirror. In this arrangement, the vibration of the projection optical system is not directly reflected to the measured value of the laser interferometer. Therefore, an inconvenience arises such that it is impossible to highly accurately measure the relative positional relationship of the reticle on the basis of the projection optical system if the vibration is large.
In the case of the projection exposure apparatus of the full field exposure type, it is also necessary to use the plane mirror as the movement mirror when a structure, in which the movement amount of the reticle stage is large, is used. Therefore, the same inconvenience as described above arises.
Taking the foregoing points into consideration, a first object of the present invention is to provide an exposure apparatus and an exposure method which make it possible to highly accurately detect the relative positional relationship between the reticle stage and the projection optical system so that the reticle and the wafer may be subjected to highly accurate positional alignment, even when the movement range of the reticle stage is wide. A second object of the present invention is to provide an exposure apparatus and an exposure method which make it possible to reduce the influence of the driving reaction force of the reticle stage or the wafer stage on the positioning accuracy so that the exposure may be performed highly accurately.
Still another object of the present invention is to provide a method for producing the exposure apparatus as described above, and a method for producing a device, which makes it possible to produce the highly accurate device by using the exposure apparatus as described above.
SUMMARY OF THE OF THE INVENTION
A first exposure apparatus according to the present invention is an exposure apparatus for exposing a substrate (W) with an image of a pattern on a mask (R); comprising a projection optical system (
5
) which is arranged between the mask (R) and the substrate
Nguyen Hung Henry
Nikon Corporation
LandOfFree
Exposure method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Exposure method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exposure method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3059950