Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-11-28
2003-07-22
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C355S053000, C355S055000, C355S067000, C356S401000
Reexamination Certificate
active
06597002
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning exposure apparatus and its making method, and a device manufacturing method. More particularly, the present invention relates to a scanning exposure apparatus used to manufacture semiconductor devices and liquid crystal display devices and the like in a lithographic process and the method of making the apparatus, and a device manufacturing method using the scanning exposure apparatus to manufacture microdevices such as semiconductor devices.
2. Description of the Related Art
In recent years, in the lithographic process to manufacture devices such as semiconductors, scanning exposure apparatus based on the so-called method such as a slit-and-scan method, and a step-and-scan method have been used with these exposure apparatus, a rectangular or an arcuated illumination area on the mask or a reticle where a pattern is formed (hereinafter generally referred to as a “reticle”) is illuminated by an illumination light. The reticle and a substrate such as a wafer are synchronously moved in a one-dimensional direction, and the pattern is sequentially transferred onto the substrate.
With such an apparatus, in order to prevent the areas other than the pattern area on the reticle from being exposed during exposure, a shielding unit (also referred to as a movable reticle blind) is used (see Japanese Patent Laid-Open 04-196513 and the corresponding U.S. Pat. No. 5,473,410 for reference) to drive a movable blade restricting the illumination area on the reticle synchronously with the reticle with the conventional shielding unit, the movable blade is driven in the direction of synchronous movement by the rotational movement of a rotary motor serving as a driving source being converted into a linear motion with a feed screw or a ball screw.
In the manufacturing process of semiconductor devices, it is required to accurately overlay and transfer the pattern formed on the reticle onto the wafer.
With the conventional shielding unit, however, the rotary motor used as the driving source of the movable blade continues to rotate at a constant speed when the movable blade and the reticle are driven synchronously at a constant speed during scanning exposure. This rotation caused vibration to occur due to the rotational inertia eccentric amount, and the vibration affected other members, which in turn reduced the exposure accuracy of the scanning exposure apparatus. In addition, when the number of rotation increased, the vibration component caused by the rotation also increased. This, therefore, was a barrier to high speed of the reticle stage, in other words, a barrier to high scanning exposure performance, which led to a difficulty in improving the throughput.
To keep the vibration caused when driving the shielding unit from affecting other parts of the apparatus, a structure may be considered to physically separate the reticle blind portion including the shielding unit (movable reticle blind), the reticle stage, the wafer stage, and the main column portion (hereinafter referred to as “body” appropriately) incorporating components such as the projection optical system so that the vibration does not spread to the respective parts. The reticle blind, however, does not function as originally planned by simply decoupling the reticle blind and the main column portion.
That is, the fixed reticle blind (fixed field stop) determines the illumination area on the reticle. If, therefore, the vibration affects the fixed reticle blind independently from the body, the illumination area changes on the reticle pattern surface, and this means that the image plane illuminance loses stability during exposure. Also, for the shielding unit or the movable reticle blind to fully exercise its shielding properties, the image of the movable blade which is arranged near the surface conjugate to the reticle pattern surface has to be within the range of the shielding area of the reticle with the current scanning exposure apparatus, therefore, the vibration isolation unit (active vibration isolation unit) which isolates the main column from the vibration is required to maintain the position and posture of the main column at the initial state at all times. This is possible by controlling the vibration so that the affects of the reaction force that occurs when driving the reticle stage or wafer stage will be cancelled out almost simultaneously.
In the case, however, a damped harmonical deformation occurs to the body by the reaction force, even if the vibration isolation unit tries to control the vibration of the body to maintain the position and posture of the body at the initial state, since the body has an extremely high mass and the responsiveness of the driving portion of the vibration isolation unit (actuator) is not that high, it would be difficult to suppress the initial displacement of the body even if a counter-force was applied to cancel the vibration by monitoring the vibration, displacement, and the like.
With the scanning exposure apparatus, higher stage acceleration will be required in future, therefore, in the future scanning exposure apparatus, the tendency of creating vibration that has a vibration period faster than the response speed of the actuator is expected to increase. In such a case, as a consequence, the movable blade of the shielding unit and the reticle cannot be synchronized, therefore, the shielding properties cannot be effectively exercised.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the inconvenience of the prior art, and has as its object to provide a scanning exposure apparatus capable of reducing the influence of the vibration, caused by driving the shielding unit, on other parts of the apparatus, thereby providing a higher exposure accuracy.
According to the first aspect of the present invention, there is provided a first scanning exposure apparatus which synchronously moves a mask and a substrate to transfer a pattern on the mask onto the substrate, the exposure apparatus comprising: an illumination system which illuminates the mask with an illumination light; a driving system which drives the mask and the substrate in synchronous; a movable blade which limits an illumination area on the mask; a linear motor which drives the movable blade; and a separate portion where the linear motor is arranged, the separate portion being independent at least in respect to vibration from a main portion which exposes the substrate with an illumination light via the mask.
According to this exposure apparatus, the driving system drives the mask and substrate in synchronous in a state where the mask is illuminated by the illumination light of the illumination system. By doing so, the pattern formed on the mask is sequentially transferred onto the substrate. During this scanning exposure, in order to prevent unnecessary portions (portions on the mask other than the pattern area) from being irradiated by the illumination light, the movable blades limiting the illumination area on the mask are driven synchronously with the mask by linear motors. Therefore, problems such as vibration due to rotational inertia eccentric amount which occur when using rotary motors as in the conventional art do not occur. Also, the linear motor is arranged in a separate portion, being separate from a main portion that exposes the substrate with an illumination light via the mask and independent at least in respect to vibration. Therefore, the vibration of the linear motor is not the direct cause of vibration occurring on the main portion side. Accordingly, this removes a major factor of vibration during scanning exposure, and as a consequence, can improve the exposure precision.
With the first scanning exposure apparatus according to the present invention, the exposure apparatus can further comprise a projection optical system which is arranged in the main portion and projects the illumination light onto the substrate.
With the first scanning exposure apparatus according to the present invention, a portion
Lee John R.
Nikon Corporation
Smith II Johnnie L
LandOfFree
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