JP2756865B2 - Exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs, and more particularly to improving control characteristics of a wafer stage to improve positioning accuracy and shorten a position setting time. And an exposure apparatus for performing high-accuracy alignment (alignment) between a reticle and a wafer when exposing and transferring a pattern of an electronic circuit or the like formed on the reticle onto a wafer surface through optical means such as a lens. Things.

[Prior Art] An exposure apparatus for manufacturing a semiconductor element such as an IC.LSI is required to have two basic performances, that is, a resolution performance and a superposition performance. The former is the ability to form a fine pattern on the photoresist surface applied on the semiconductor substrate (hereinafter referred to as “wafer”) surface, and the latter is the ability to form the pattern formed on the wafer surface in the previous process. On the other hand, it is the ability to accurately align and transfer the pattern on the photomask.

The exposure apparatus is, for example, a contact,
Proximity, mirror 1: 1 projection, stepper, X-ray aligner, etc. are roughly classified, and among them, the most suitable superposition method has been devised and implemented.

In general, an exposure method that balances both resolution performance and overlay performance is preferable for semiconductor device manufacturing. For this reason, a reduced-projection type exposure apparatus, a so-called stepper, is frequently used at present.

The resolution required for future exposure equipment is 0.5
Exposure method that can achieve this performance is, for example, a stepper using an excimer laser as a light source, X
Proximity type aligner using line as exposure source,
There are three methods of direct EB drawing. From the viewpoint of productivity, the former two methods are preferable.

On the other hand, overlay accuracy is generally 1/3 to 1
A value of / 5 is required, and achieving this accuracy is generally as difficult or even more difficult as achieving resolution.

The alignment in the exposure apparatus refers to the relative alignment between the pattern on the reticle surface and the pattern on the wafer surface, and the alignment of each step arrangement during the first layer exposure.

Conventionally, this type of exposure apparatus uses a wafer transfer means (specifically, 3
(Point pin or center-up) receives the wafer, transfers the wafer to the wafer chuck, and performs vacuum alignment (pre-alignment) after vacuum chucking the wafer to the chuck.

On the other hand, in order to perform pre-alignment, the stroke requires about 1.5 mm in the Z direction and about ± 3 ° in the θ direction in the vertical direction (Z direction) and the rotation direction (θ direction).
The resolution must be about 0.1 mm in the Z direction and about 25 ″ in the θ direction. Conventionally, during pre-alignment, only the wafer chuck is driven while the wafer is vacuum-sucked, and reference is made using a laser and interferometer fixed to the fine movement stage Therefore, a pre-alignment is performed by measuring a distance from a reference position by a mirror for the wafer, and therefore, a mechanism for driving the wafer chuck and a lock mechanism for maintaining a state after the completion of the pre-alignment are required inside the fine movement stage. Therefore, conventionally, the Z coarse movement stage and the θ coarse movement stage are both stacked on the θ fine movement stage and the Z fine movement stage as shown in FIG.

[Problems to be Solved by the Invention] However, in the above-described conventional example, the wafer transfer means built in the wafer stage receives the wafer, transfers the wafer to the wafer chuck, vacuum-sucks the wafer to the chuck, and then holds the wafer chuck in a wafer-sucked state. , Rough alignment is performed, and after the completion of the rough alignment, a lock mechanism for locking the wafer chuck in the vertical and rotational directions is required. Further, after the wafer chuck itself is moved by θ, it is time-consuming to secure the θ lock, so that the stage positioning time increases and the throughput decreases. further,
The step-and-repeat causes a lock deviation and deteriorates the alignment accuracy.

Further, as described above, in the conventional structure shown in FIG. 4, the overall height of the fine movement stage is increased, and the position of the center of gravity of the stage is moved upward, thereby deteriorating the positioning accuracy when moving in the plane direction (X, Y directions). However, the positioning time has been increased to reduce the throughput of the entire apparatus, and the alignment accuracy has been deteriorated. In addition, as the baking pattern becomes larger and larger, the wafer chuck becomes larger and the wafer chuck becomes larger.
The flatness needs to be improved, and the weight of the wafer chuck increases. On the other hand, the stepper drives the wafer chuck for each step in order to expose the entire wafer while performing step-and-repeat. Therefore, the locking force of the fine movement stage and the wafer chuck must be increased by increasing the weight of the wafer chuck for the above-described reason. If the locking force is weak, the wafer chuck is displaced for each exposure, and the alignment accuracy is deteriorated. In order to prevent this, the moving acceleration of the XY stage must be reduced, which lowers the throughput.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described drawbacks of the related art, and has as its object to provide an exposure apparatus that increases locking rigidity, improves positioning accuracy, and shortens positioning time.

[Means and Actions for Solving the Problems] In order to achieve the above object, according to the present invention, coarse alignment (pre-alignment) is performed in a state in which a wafer is received by a transfer means built in a wafer stage,
After the θ correction, it is adsorbed on the wafer chuck,
This increases the rigidity of the wafer stage, thereby improving the positioning accuracy and shortening the positioning time.

[Embodiment] FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is an overall view of the apparatus, and FIG. 2 is a detailed view of a fine movement stage. In FIG. 1, reference numeral 1-1 denotes a projection lens which projects a pattern of a reticle 1-2 onto a wafer 1-4. 1-2
Is an original plate (reticle) on which patterns of semiconductors, circuits and the like are drawn. A reticle stage 1-3 sucks the reticle 1-2 and aligns it with a reference mark (not shown). The reticle stage 1-3 is supported by a lens barrel base 1-9. 1-4, a wafer for recording the pattern of the reticle 1-2 via the projection lens 1-1, 1-5, a wafer chuck for vacuum-sucking the wafer 1-4, and a fine movement stage 1-6, an X stage 1 -7, fixed on an XY stage composed of a Y stage 1-8 and a stage base 1-16. Fine movement stage 1-6 is fixed to X stage 1-7, and has a built-in transfer means for wafer 1-4. The fine movement stage 1-6 has a function of aligning the wafer 1-4 with the focal position of the projection lens 1-1 and the off-axis 1-10, and rotates and drives the projection lens 1-1 in a direction around the optical axis (θ direction). And a function of rotating about the X and Y axes (α and β directions) in the XY plane perpendicular to the paper surface. The X stage 1-7 is provided above the Y stage 1-8 and is movable in the X direction. Y stage 1-8 is stage table 1
-16 and is movable in the Y direction. 1-9 is
A lens barrel base that supports the projection lens 1-1, the reticle stage 1-3, and the off-axis 1-10. Off Axis 1
Numeral -10 is fixed to the lower surface of the lens barrel base at a predetermined distance from the optical axis of the projection lens 1-1 and observes alignment marks on the wafer to perform pre-alignment. Reference numeral 1-11 denotes an illumination system fixed to the base plate 1-15 for illuminating the reticle 1-2 and exposing the wafer 1-4 via the projection lens 1-1. Wafer 1 with off-axis alignment scope 1-10
CCD camera 1-10a, CCU1-10b and image processor 1 to observe alignment marks and coarse alignment marks on -4 to measure alignment errors
-10c is provided. On the fine movement stage 1-6, a reference mirror 1 for the Y-direction interferometer, which is a reference for measuring the position of the XY stage,
12Y is fixed. Reference numeral 1-13 denotes a laser head for laser measurement fixed to the base plate 1-15. 1-14 is a mount for supporting the entire apparatus and isolating it from floor vibration and the like.
Reference numeral 15 denotes a base platen serving as a base of the entire apparatus, and 1-16 denotes a stage base plate which supports the Y stage 1-8 and is fixed to the base platen. 1-20 is a fine movement stage 1 based on an alignment error obtained by an image processor (IP) 1-10c.
-6, a control device for driving the X stage 1-7 and the Y stage 1-8.

FIG. 2 is a detailed view of the fine movement stage 1-6. 2-
1 is a wafer, 2-2 is a wafer chuck for vacuum-adhering and flattening the wafer 2-1, 2-3 is supporting a wafer check 2-2, and is moved downward at the time of wafer transfer, and is moved upward after completion of pre-alignment. The movable check holding plate 2-4 has a function of sucking the wafer 2-1 and is movable in the Z direction and the θ direction so that the wafer surface is off-axis alignment scope 1-10 during vacuum suction of the wafer 2-1.
Are the wafer transfer pins to be matched with the focal position.
2-5 is a ball bush, which is a wafer transfer pin 2
-4 serves as a guide when moving in the θ and Z directions and when the chuck support plate 2-3 moves in the Z direction. 2-
Reference numeral 6 denotes a piezo element for Z drive, which is a wafer transfer pin 2
Then, the wafer 2-1 sucked at -4 is driven so as to match the focal position of the off-axis alignment scope 10.
2-7 is a coarse θ drive motor for driving the wafer transfer pins in the θ direction based on the pre-alignment error signal measured by IP1-10c, and 2-8 is a driving force of the coarse θ drive motor 2-7. Is transmitted to the wafer transfer pin, and 2-9 is a gear transfer pin for transferring the wafer.
Is a coarse Z drive motor for driving the chuck support plate 2-3 in the Z direction in order to transfer the wafer 2-1 from the wafer chuck 2-2 to the wafer chuck 2-2. Reference numeral 2-10 denotes a worm gear for transmitting the driving force of the coarse Z drive motor 2-7 to the cam 2-11. The cam 2-11 drives the wafer support plate 2-3 in the Z direction. 2-12 is supported on the fine Z substrate, and expands and contracts in the direction perpendicular to the paper to rotate the fine θ substrate 2-16 in the θ direction.
This is a fine θ driving piezo element that presses the fine θ substrate 2-16 at a point contact via a steel ball. Reference numeral 2-13 denotes a fine θ driving leaf spring which couples between the fine θ substrate 2-16 and the fine Z substrate 2-17. The leaf spring 2-13 has a small rigidity in a direction perpendicular to the plane of the paper and has a large rigidity in the Z direction. Reference numeral 2-14 denotes a piezo element for fine Z driving provided at three or more positions on the X stage 1-7, and drives the fine Z substrate 2-17 in the Z direction to move the wafer 2-1 in the Z direction and α, Move in the β direction. 2-15 is X stage 1-7
And a fine Z driving guide leaf spring for connecting the micro Z board 2-17 to the micro Z board 2-17. 2-18 is a chuck support plate 2-3
Regulates rotation in the θ direction when the Z moves, and after the Z movement,
This is a rotation restricting unit for driving the chuck support plate 2-3 and the fine θ substrate 2-16 as a unit during the fine θ drive. FIG. 3 shows details of the rotation restricting portion 2-18. Reference numeral 2-21 denotes a one-sided spring attached to the chuck support plate at one end and the other end attached to the fine .theta. Substrate in order to contact the fine .theta. Reference numeral 2-19 denotes a bearing for transmitting a force to the chuck support plate at the time of rotation regulation and at the time of fine θ drive. 2-20 is a reference mirror.

 Next, the operation of the exposure apparatus having the above configuration will be described.

First, a reticle 1-2 is moved by a reticle transport system (not shown).
Is transported to the reticle stage 1-3 and is aligned at a predetermined position by the reticle stage 1-3. Next, wafer pre-aligned wafer 1-4 is transferred to a wafer transfer position by a wafer supply hand (not shown).
Passed to. At this time, the wafer chuck 1-5
(2-2) and the chuck support plate 2-3 are located below. The wafer 1-4 (2-1) is the wafer transfer pin 2
-4, the control device 1-20 confirms this, and then issues a movement command to the XY stage to the pre-alignment position. The XY stage is controlled by a laser length measuring device (not shown) and moves to a pre-alignment position.

Next, at the pre-alignment position, the wafer transfer pin 2-4 is moved to the Z position in the fine movement stage 1-6 by a command from the control device so that the upper surface of the wafer 1-4 coincides with the focal position of the off-axis alignment scope 1-10. Drive the driving piezo. The drive amount is measured by the auto-focus function of the off-axis alignment scope 1-10 and is communicated to the control system. After focusing, the pre-alignment mark on the wafer 1-4 (2-1) is measured by the off-axis alignment scope 1-10, the error is calculated by IP1-10c, and the error is communicated to the controller 1-20. Control device 1-20
Issues a drive command to the coarse θ drive motor in the fine movement stage 1-6, the wafer transfer pins 2-4 move the wafers 1-4 (2
The pre-alignment is completed by rotating in the θ direction while -1) is vacuum-sucked.

Next, the controller 1-4 receives the pre-alignment completion signal and sends the wafer 1-4 to the fine movement stage 1-6.
A command to deliver (2-1) to the wafer chuck 2-2 is issued, and the wafer chuck 2-2 is driven by the coarse Z drive motor 2-
9, driven in the Z direction by the worm gear 2-10 and the cam 2-11, the wafer 1-4 is transferred from the wafer transfer pin 2-4 to the wafer 1-4.
(2-1) is received. The wafer is the wafer chuck 2
-2. At this time, the wafer chuck is not rotated in the θ direction by the rotation restricting portion 2-18, and the Z plate in the chuck support plate 2-3 and the fine θ substrate 2-16 is not rotated.
By locking the drive motor, the chuck support plate 2
-3 is locked in that position.

When the suction of the wafer 1-4 (2-1) to the wafer chuck 2-2 and the lock of the chuck support plate are confirmed by the controller 1-20, the controller 1-20 controls the XY stage.
A command to move to the alignment position is issued. Thereafter, the operation is performed in the same manner as the operation of a normal exposure apparatus. However, after the completion of the pre-alignment, a normal exposure apparatus can be operated by driving only the θ fine movement and the Z fine movement.

[Effects of the Invention] As described above, according to the present invention, the wafer is adsorbed to the wafer chuck after the wafer transfer means incorporated in the stage performs pre-alignment while the wafer is being received and corrects the wafer transfer means by θ. By doing so, the rigidity of the wafer stage is increased, the stage positioning accuracy is improved, and the positioning time is shortened, so that the exposure apparatus can have high accuracy and high throughput.

[Brief description of the drawings]

FIG. 1 is a main configuration diagram of an exposure apparatus according to an embodiment of the present invention, FIG. 2 is a detailed view of a fine movement stage portion of the exposure apparatus of FIG. 1, and FIG. FIG. 4 is an enlarged view of a rotation restricting portion, and FIG. 4 is an explanatory view of a configuration of a conventional fine movement stage. 1-1: Projection lens, 1-2: Reticle, 1-4: Wafer, 1-6: Fine movement stage, 1-7: X stage, 1-8: Y stage, 1-10: Off-axis alignment scope 2- 1: wafer, 2-2: wafer chuck, 2-3: chuck holding plate, 2-4: wafer transfer pin, 2-6: piezo element for Z drive.

Claims (2)

(57) [Claims] 1. A first object having a pattern to be transferred formed thereon, a second object for printing the pattern, a first stage for supporting the first object, and a second stage for mounting the second object. A projection optical system provided between the first and second objects; an illumination system for exposing the second object via the first object and the projection optical system; and a second optical system mounted on the second stage. Transfer means for two objects, suction means for fixing the second object on the second stage, and control for driving and controlling the second stage for aligning the first and second objects with each other The second stage is movable in X, Y and Z directions and is rotatable around X, Y and Z axes, and the control device is in a state where the transfer means receives the second object. Pre-alignment and around Z axis Performs rotational positioning, then the second object is characterized by being configured so as to fix by the suction means to the exposure apparatus. 2. The second stage comprises an X stage, a Y stage, and a fine movement stage, and the fine movement stage has three or more driving means in the Z direction and rotation driving means around the Z axis. 2. An exposure apparatus according to claim 1, wherein said transfer means is capable of protruding above the fine movement stage, and said suction means is configured to be movable in the Z direction with respect to said transfer means.