JP2715182B2 - Exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing semiconductor devices and the like, and more particularly, to an exposure apparatus having an actuator for damping vibration of an apparatus main body.

[Prior Art] The miniaturization and high integration of semiconductor devices are continually progressing without knowing that they will remain. As an exposure apparatus used for manufacturing a semiconductor element, an apparatus called a stepper, which is a sequential movement type projection exposure apparatus, is a main model, and it is predicted that it will not give up in the future in the production of ultra-fine devices. Therefore, improving the resolving power of the stepper for miniaturization of the element will be an even stronger demand in the future.

The resolving power is expressed by Re = k · λ / NA according to Rayleigh's equation. Therefore, conventionally, the exposure wavelength was changed to g-line (wavelength 43
The resolution has been improved by increasing the numerical aperture (NA) of the projection lens while keeping it fixed at 6 nm. But NA
As the depth of focus has decreased along with the increase in the number of lenses, and the design and manufacturing of the projection lens have reached the limits, the wavelength of the exposure light has to be shortened in order to support the future submicron generation. At present, the i-line (wavelength 365 nm) stepper is in the stage of practical use, and the next generation is expected to be an excimer stepper using a KrF excimer laser (wavelength 248 nm) as a light source.

However, in putting the excimer system to practical use here, there are also problems that are not present in conventional steppers. An excimer laser light source is a light source unit that is considerably larger than a high-pressure mercury lamp light source that emits g-line or i-line. Therefore, when an excimer laser light source is mounted on the exposure apparatus main body as in the related art, the size and weight of the exposure apparatus are increased, which is not preferable in practical use. Therefore, arranging the light source separately from the stepper body is an effective measure. However, by separating the stepper main body and the light source in this way, the relative positional relationship between the two greatly affects the basic performance of the exposure apparatus. For example, an optical axis deviation or an incident angle deviation of the laser light occurs due to a change in the relative positional relationship due to a change in the posture of the stepper. The occurrence of illuminance non-uniformity caused by this causes problems such as a decrease in exposure accuracy and a decrease in throughput due to a decrease in illuminance. There are also countermeasures such as increasing the diameter of the laser beam, but this has the disadvantage of lowering the throughput.

On the other hand, as one of means for improving the resolving power, the throughput, and the alignment accuracy, there is an improvement in a vibration control technology of a stepper. Vibrations that pose a problem in a stepper include transmitted vibrations from the surrounding environment (floor or the like) and vibrations generated from movable parts in the apparatus. Conventionally, as a technique for suppressing such vibration, a vibration damping table having a spring portion and a damping force in a mount portion supporting a device main body has been used. That is, the vibration from the floor lowers the resonance frequency of the device by lowering the spring constant of the mount, widens the vibration isolation region, and keeps the transmission rate low. Further, with respect to the vibration generated inside the device, the vibration energy is dissipated by increasing the damping rate of the mount portion, and the convergence and stability are achieved in a short time.

In recent years, instead of the above-mentioned simple mount having a fixed spring constant and damping rate, a mount having a feedback control system and generating a variable restoring force (hereinafter referred to as a servo mount) has been marketed. This servo mount uses a measured value of the acceleration of the device body supported by the mount to generate a phase-corrected force by an actuator by electromagnetic force or liquid pressure so as to enhance the damping of vibration, and to make the device non-resonant. It is designed to have a damping effect and is currently used as a damping support device for precision equipment.

These simple mounts and servo mounts have been effective for damping the device, but when the target is a stepper, the following problems occur. In the stepper, the center of gravity of the apparatus main body changes sequentially because the XY stage on the apparatus performs step movement. For this reason, when the above-mentioned conventionally used mount is used as a vibration suppression support device, it is difficult to suppress vibration generated in a different state for each step operation in a short time, and the stepper is always kept in a predetermined posture. It becomes difficult to maintain. Therefore, when the above-mentioned separately-installed light source is used, a change in the relative position between the light source device and the stepper remains due to the change in the posture of the stepper, which may cause an optical axis deviation in the laser light incident portion. Become.

[Problem to be Solved by the Present Invention] In a conventional example, there is a vibration control mount having an auto-leveling mechanism in order to maintain a horizontal level of the apparatus main body. For example, in the case of a mount using an air spring,
The plurality of mounting legs independently open and close the valve by a mechanical mechanism in proportion to the amount of deviation from the set value of the vertical position, thereby keeping the apparatus main body horizontal.

However, in this conventional example, it is difficult to achieve a posture holding accuracy of several hundred μm required by an excimer stepper due to hysteresis of a mechanical mechanism. Further, the above-mentioned vibration damping mount cannot deal with positioning not only in the vertical direction but also in the horizontal direction.

In view of the above-described problems in the conventional type, the present invention attenuates the vibration of the apparatus main body in a short time, thereby deteriorating the exposure accuracy due to a change in the relative positional relationship between the separate light source and the exposure apparatus main body. It is an object of the present invention to provide a high-precision, high-throughput exposure apparatus that suppresses deterioration of illuminance of exposure light.

[Means and Actions for Solving the Problems] To achieve the above object, the present invention provides a projection optical system (projection lens 5) in which a pattern on an original plate (reticle 3) is projected onto a plurality of regions on a substrate (wafer 7). An exposure apparatus for step-moving the substrate in order to sequentially perform projection exposure via a lens barrel base (barrel base 6) supporting the projection optical system
A plurality of mounts (mounts 12) that support the mounts using air springs (air springs 18), a fixed frame (mount frame 20) that fixes each of the mounts, and a vibration control unit that controls vibration of the lens barrel base. An actuator (X-direction actuator 13 or Y-direction actuator 14) for applying a force to the lens barrel base from the fixed frame side is provided. More preferably, a partial acceleration pickup sensor (acceleration pickup sensor 16) that vibrates integrally with the lens barrel base is provided.

The present invention relates to, for example, an apparatus main body of an exposure apparatus (a lens barrel base).
Is supported by a plurality of mounts using an air spring, and an actuator having a positioning function in addition to a vibration damping function for the apparatus main body is used to enable the absolute positioning of the apparatus main body with six degrees of freedom. Also, according to the present invention,
It is also possible to maintain the relative positional relationship between the device main body and various functional units supported separately. The various functional units include, for example, a transport system for transferring a substrate (wafer) to and from an XY stage, an illumination system for illuminating a reticle, a reticle changer, a reticle dust inspection device, and the like.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an apparatus front view showing a basic configuration of an exposure apparatus according to one embodiment of the present invention. FIG. 2 is a detailed view of a mount section of the exposure apparatus, and FIG. 3 is a plan view of the mount section showing an arrangement of a mount actuator.

In FIG. 1, reference numeral 1 denotes an illumination system for guiding a laser beam incident from a light incident part (laser light introducing part) to an upper portion of a reticle, and reference numeral 2 denotes detection of a reticle position with respect to a reticle reference mark and detection of a wafer position with respect to the reticle. 3 is a reticle having a pattern to be transferred; 4 is an outer periphery supporting the reticle 3 and the alignment scope 2; 5 is a projection lens for reducing and projecting a pattern formed on the reticle 3 onto a wafer; Is a lens barrel base supporting the projection lens 5, the illumination system 1 and the outer cylinder 4, 7 is a wafer, 8 is an X stage which supports the wafer 7 and is movable in the X direction, and 9 is an X stage which supports the X stage 8 and Y
Y stage movable in the direction, 10 is a stage base supporting the Y stage 9, 11 is a lens barrel base 6 and a stage base.
It is a basic surface plate that supports 10.

In the description of the present invention, the attitude and absolute position of the apparatus main body are defined as values of 6 degrees of freedom (X, Y, Z directions and X, Y, The positions expressed in the directions of rotation in the Z directions are connected. Reference numeral 12 denotes a mount for supporting the base platen 11, and four units fixed to the four corners of the base platen 11, each connected by a frame, are features of the present embodiment.

31 is a control device for controlling the operation of the entire exposure apparatus, 32
Denotes a mount control device for mainly controlling the operation of the four mounts 12, and 33 denotes a drive device for driving the respective actuators of the four mounts 12.

Next, the operation of the exposure apparatus in the configuration of FIG. 1 will be described.

The wafer 7 is moved to the XY stage 8,
When the wafer is transported to 9, the control device 31 outputs a drive signal for performing a step operation to a position on the wafer to be exposed (exposure start position). X or Y stage 8, accordingly
9 steps. At the end of the step, the final position measurement is performed by the alignment scope 2, and the positioning of the stages 8, 9 is completed by the feedback of the signal.

On the other hand, the posture change due to vibration from the floor, vibration accompanying the stage movement, or stage eccentric load is measured by the mount 12 and fed back to the mount controller 32 as an acceleration signal and a displacement signal, as described later. As a result, quick vibration damping (damping) and positioning of the apparatus main body are performed. When vibration suppression and positioning are performed, the mount controller 32 sends a completion signal to the controller 31.

The control device 31 which has received the completion signal from the alignment scope 2 and the mount control device 32 issues a light emission command signal of the light source device which is a laser light source. The laser light emitted from the light source is applied to the illumination system 1, reticle 3,
The wafer 7 is irradiated through the projection lens 5, and the wafer 7 is exposed.

Further, the mount 12 of the exposure apparatus shown in FIG. 1 will be described in detail with reference to FIG. 2 and FIG. In these drawings, the same reference numerals as those in FIG. 1 indicate the same members.

The exposure apparatus of this embodiment has four mounts 12. Each mount 12 is fixed by a mount frame 20. Each mount 12 has a three-way actuator. An air spring actuator or the like can be used as the actuator 18 in the Z direction (vertical direction and a direction perpendicular to the plane of FIG. 3). As the X-direction actuator 13 and the Y-direction actuator 14, a voice coil type actuator, an air cylinder type actuator, an air spring actuator, or the like can be used.

In mounting these actuators 13, 14, and 18 in the X, Y, and Z directions, a structure for releasing a force having five degrees of freedom is required. In this embodiment, the following is performed. First,
In the Z direction, similarly to the conventional servo mount, the air spring 18 is elastically supported on the mount frame 20 with the laminated rubber 15 interposed therebetween. Thereby, the thrust force in the X, Y directions and the rotational force around the X, Y, Z directions are released. In the X and Y directions, four mounts 12 are provided.
Are fixedly supported by the mount frame 20, so that the actuators 13, 14 are connected via the rod 21 to the force application point of the basic standard 11. Thereby, the thrust force and the rotational force are absorbed by the deformation of the rod 21 and are released. The above-mentioned mechanism is practically sufficient because the change in the attitude of the exposure apparatus main body can be made up to about several millimeters at present by the displacement amount of the mount section.

Next, an acceleration pickup sensor 16 and a displacement sensor 17 are used as sensors for vibration and position control. The acceleration pickup sensor 16 is attached to a movable part (a part integral with the base platen) in the mount 12. The displacement sensor 17 is attached to a mount frame 20 (fixed portion), and measures a displacement amount of a movable portion of the mount 12 therefrom.

There are several variations in the number of these sensors 16, 17 depending on the form of the control system. For example, when the four mounts 12 are configured by independent control systems, each mount 12 requires an acceleration pickup 16 having three degrees of freedom and a displacement sensor 17 having three degrees of freedom. If the number of sensors is to be further reduced, the acceleration pickup 16 only needs to have 3 degrees of freedom × 2 and the displacement sensor 17 needs to have 3 degrees of freedom × 2 by comprehensive control of the four mounts 12. . However, if the number of sensors is not reduced, the calculation of the control system is faster and the response is better.

As shown in FIG. 3 of the present embodiment, the four mounts 12 are divided into a first mount 12-1, a second mount 12-2, and a third mount 12.
12-3 and the fourth mount 12-4. Z
Directional accelerometer 17 has all four mounts
I attached it to 12. The X-direction acceleration pickup 17 was mounted on a first mount 12-1 and a third mount 12-3.
The Y-direction acceleration pickup 17 is mounted on the second mount 12-2.
And the fourth mount 12-4. The signals from these acceleration pickups 17 are fed back to the mount controller 32.

Further, the displacement sensor 17 in the Z direction is connected to the first mount 12-.
1, the second mount 12-2 and the third mount 12-3. The displacement sensor 17 in the X direction is connected to the first mount 12.
-1 and the third mount 12-3. The Y-direction displacement sensor 17 was mounted on the fourth mount 12-4. The signals output from the respective displacement sensors 17 are fed back to the mount controller 32.

Next, the operation of the actuators of the four mounts 12 will be described. With respect to the movement in two directions and the movements about the X axis and the Y axis, vibration suppression and positioning were performed by four mount Z direction actuators. For movement in the XY plane, opposing actuators in the same direction (for example,
A pair of the X-direction actuator 13 of the first mount 12-1 and the X-direction actuator 13) of the second mount 12-2 is controlled by forces generated from four pairs of XY. X
For the movement in the direction, two pairs of X-direction actuators 13
The vibration is suppressed and the positioning is performed. Similarly, in the Y direction, vibration damping and positioning are performed by two pairs of Y direction actuators 14.
With respect to the movement around the Z axis, vibration suppression and positioning are performed by couples that can be generated from the two pairs of X-direction and two pairs of Y-direction actuators 13 and 14, respectively.

[Effects of the Invention] As described above, according to the present invention, each mount is fixed with the force of an actuator for damping the vibration of the lens barrel base supported by a plurality of mounts using air springs. Since the lens barrel base is acted on from the fixed frame side, the vibration of the lens barrel base can be attenuated in a short time at all times, and the posture can always be maintained at a predetermined level. Therefore, according to the present invention, an exposure apparatus with high accuracy and high throughput can be realized.

[Brief description of the drawings]

1 is an overall view of an exposure apparatus according to an embodiment of the present invention, FIG. 2 is a detailed view of a servo mount of the exposure apparatus of FIG. 1, and FIG. 3 is a servo mount of the exposure apparatus of FIG. FIG. 5 is a plan view of a mount unit showing an actuator arrangement in FIG. 1: Illumination system, 2: Alignment scope, 3: Reticle, 5: Projection lens, 7: Wafer, 8: X stage, 9: Y stage, 10: Stage surface plate, 12: Mount, 13: X direction actuator, 14 : Y-direction actuator, 15: laminated rubber, 16: acceleration pickup, 17: displacement sensor, 18: Z-direction actuator.

Claims (2)

(57) [Claims] An exposure apparatus for stepwise moving a substrate for projecting and exposing a pattern on an original plate to a plurality of regions on a substrate via a projection optical system in order, wherein a barrel base supporting the projection optical system is provided. A plurality of mounts supported using air springs, a fixed frame for fixing each of the mounts, and a force for damping the vibration of the lens barrel base acts on the lens barrel base from the fixed frame side. An exposure apparatus comprising an actuator for causing the exposure. 2. An exposure apparatus according to claim 1, further comprising an acceleration pickup sensor provided at a portion which vibrates integrally with said lens barrel base.