JPH04129209A - Exposure apparatus - Google Patents

Abstract

PURPOSE:To enable improvement in positioning accuracy and shortening in positioning time through enhancement of rigidity of a wafer stage by executing coarse alignment in state that a wafer is received by a transfer means and by sucking it onto a wafer chuck after theta correction. CONSTITUTION:Upon transfer of a wafer 2-l to a wafer transfer pin 2-4, a controller confirms it to issue movement command to an XY stage at a prealignment position. The transfer pin 2-4 drives a Z-driving piezo in such a manner that the wafer top agrees with the focus position of an off-axis alignment scope. After focusing, a prealignment mark on the wafer 2-1 is measured, and the transfer pin 2-4 rotates in the theta direction in a state of vacuum suck of the wafer, resulting in completion of prealignment. The wafer is vacuum sucked by a wafer chuck 2-2, so that a chuck support plate 2-3 is locked at this position. When suction of the wafer and locking are confirmed, movement command is issued to the XY stage with the result that action is made likewise as by a normal exposure apparatus.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs, and in particular improves the control characteristics of a wafer stage to improve positioning accuracy and shorten positioning time. When exposing and transferring a pattern such as an electronic circuit formed on a reticle onto a square surface through optical means such as a lens, exposure is performed to align the reticle and the sea urchin with high precision. It is related to the device.

[Prior Art] Exposure apparatuses for manufacturing semiconductor devices such as ICs and LSIs are required to have two basic performances: resolution performance and overlay performance. The former is a semiconductor substrate (hereinafter referred to as a "wafer")
The ability to form fine patterns on the photoresist surface applied to the wafer surface, and the latter refers to the ability to accurately position the pattern on the photomask relative to the pattern formed on the wafer surface in the previous process. It is the ability to transfer at the same time.

Exposure apparatuses are broadly classified into, for example, contact, proxy midi, mirror 1:1 projection, stepper, X-ray aligner, etc., depending on their exposure method, and the optimum overlaying method has been devised and implemented for each of them.

Generally, for the manufacture of semiconductor devices, an exposure method with a good balance between resolution performance and overlay performance is preferred, and for this reason, reduction projection type exposure apparatuses, so-called steppers, are currently frequently used.

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

On the other hand, the overlay accuracy is generally 173~
A value of 115 is required, and achieving this accuracy is generally as difficult or more difficult than achieving resolution performance.

Alignment in an exposure apparatus refers to relative positioning of a pattern on a reticle surface and a pattern on a wafer surface, and positioning of each step arrangement during first layer exposure.

Conventionally, in this type of exposure apparatus, when transferring a wafer, a wafer transfer means (specifically, a three-point pin or center-up) built into the wafer stage receives the wafer, transfers the wafer to the wafer chuck, and vacuum-chucks the wafer to the chuck. Rough alignment (pre-alignment) was then performed.

On the other hand, in order to perform pre-alignment, it is necessary to perform pre-alignment in the vertical direction (
Regarding the Z direction) and rotation direction (θ direction), the stroke needs to be about 1.5 mm in two directions and about ±3° in the θ direction, and the resolution needs to be about 0.1 mm in the Z direction and about 25'' in the θ direction. Conventionally, during pre-alignment, only the wafer chuck was driven while the wafer was vacuum-suctioned, and the distance from the reference position was measured using a reference mirror using a laser and interferometer fixed to a fine movement stage. Therefore, a mechanism for driving the wafer chuck and a locking mechanism for maintaining the state after completion of pre-alignment are required inside the fine movement stage.
Conventionally, as shown in FIG. 4, two coarse movement stages and a θ coarse movement stage were both stacked on a θ fine movement stage and a Z fine movement stage.

[Invention tries to solve! ! However, in the above conventional example, a wafer transfer means built in the wafer stage receives the wafer, transfers the wafer to the wafer chuck, vacuum-chucks the wafer to the chuck, and then drives the wafer chuck while the wafer is sucked. Since alignment was performed, a locking mechanism was required to lock the wafer chuck in the vertical and rotational directions after the rough alignment was completed. Further, since the wafer chuck itself is locked in θ after it is moved through θ, it takes time and effort to securely lock the chuck, which increases the stage positioning time and lowers the throughput. Furthermore, the step-and-repeat process causes lock wrinkles and deteriorates alignment accuracy.

In addition, as mentioned above, in the conventional structure shown in Fig. 4, the overall height of the fine movement stage increases and the stage center of gravity moves upward, which deteriorates positioning accuracy when moving in the plane direction (X, Y direction). This increases the positioning time, lowering the throughput of the entire device and deteriorating the alignment accuracy. In addition, as the diameter of the wafer becomes larger and the printing pattern becomes finer, the diameter of the wafer chuck becomes larger and
It is necessary to improve the flatness, and the weight of the wafer chuck increases. On the other hand, the stipper drives the wafer chuck for each step in order to expose the entire wafer while performing step-and-repeat operations. Therefore, due to the increased weight of the wafer chuck due to the above reasons, the locking force of the fine movement stage and the wafer chuck must be increased. If the locking force is weak, the wafer chuck will shift during each exposure, resulting in deterioration of alignment accuracy. Furthermore, if this is to be prevented, the moving acceleration of the XY stage must be reduced, which lowers the throughput.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide an exposure apparatus that increases lock rigidity, improves positioning accuracy, and shortens positioning time.

[Means and operations for solving the problem] In order to achieve the above object, according to the present invention, rough alignment (pre-alignment) is performed while a wafer is received by a delivery means built in a wafer stage, By adsorbing the wafer to the wafer chuck after θ correction, the rigidity of the wafer stage is increased, making it possible to improve positioning accuracy and shorten positioning time.

[Embodiment] Figs. 1 and 2 show an embodiment of the present invention, in which Fig. 1 is an overall view of the apparatus, and Fig. 2 is a detailed view of the fine movement stage portion. In FIG. 1, 1-1 is a projection lens, which projects the pattern of the reticle 1-2 onto the wafer 1-4. 1-2 is an original plate (reticle) on which patterns of semiconductors, circuits, etc. are drawn.

A reticle stage 1-3 attracts the reticle 1-2 and aligns it with reference marks (not shown). The reticle stage 1-3 is supported by a lens barrel base 1-9.

1-4 is a projection lens 1-4 for projecting the pattern of the reticle 1-2.
1 is a wafer chuck that vacuum-chucks the wafer 1-4, and a fine movement stage 1-6
．． It is fixed on an XY stage consisting of an X stage 1-7, a Y stage 1-8, and a stage base 1-16. The fine movement stage 1-6 is fixed to the X stage 1-7, and has built-in means for transferring the wafer 1-4. This fine movement stage 1-6 has the function of aligning the wafer 1-4 with the focal position of the projection lens 1-1 and off-axis 1-10, and rotates and drives the projection lens 1-1 in the direction around the optical axis (θ direction). function, and around X and Y% in the XY plane perpendicular to the paper surface (
It has the function of rotating in the α and β directions). 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 base 1-
16 and is movable in the Y direction. 1-9 is
This is a lens barrel surface plate that supports the projection lens 1-1, the reticle stage 1-3, and the off-axis 1-10. The off-axis 1-10 is fixed to the lower surface of the lens barrel surface plate at a predetermined distance from the optical axis of the projection lens 1-1, and performs pre-alignment by observing alignment marks on the wafer. 1-11 is the foundation surface plate 1
-15, is an illumination system for illuminating the reticle 1-2 and exposing the wafer 1-4 through the projection lens 1-1. A CCD camera 1-10a, a CCUI-10b, and an image processor 1-10c are provided to observe alignment marks and coarse alignment marks on the wafer 1-4 using an off-axis alignment scope 1-10 and measure alignment errors. On the fine movement stage 1-6 is a Y that serves as a reference for position measurement of the XY stage.
A directional interferometer reference mirror 1-12Y is fixed. 1-
13 is a laser head for laser length measurement fixed to the basic surface plate 1-15. 1-14 is a mount for supporting the entire device and insulating it from floor vibrations, etc., 1-15 is a foundation surface plate that is the foundation of the entire device, and 1-16 is a foundation surface plate that supports the Y stage 1-8. It is a fixed stage surface plate. 1-2
0 is a fine movement stage 1-6 based on the alignment error determined by the image processor (IP) 1-100.
This is a control device that drives 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 suction and flattening the wafer 2-1, and 2-3 is a wafer chuck 2
-2, a check holding plate that can move downward during wafer transfer and move upward after prealignment is completed;
2-4 has a function of suctioning the wafer 2-1, is movable in the Z direction and the θ direction, and aligns the surface of the sea urchin with the focal position of the off-axis alignment scope 1-10 when the wafer 2-1 is vacuum suctioned. This is a wafer transfer bin. 2
-5 is a ball bush, and the wafer transfer pin 2-
4 serves as a guide when the chuck support plate 2-3 moves in the θ and two directions and when the chuck support plate 2-3 moves in the two directions. 2-6
is a piezo element for Z drive, and the wafer transfer pin 2-
The wafer 2-1 attracted to the wafer 4 is driven 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 pin in the θ direction based on the prealignment error signal measured by the IPI-10c, and 2-8 is the driving force of the coarse θ drive motor 2-7. A gear train 2-9 for transmitting the wafer to the wafer transfer pin 2-9 moves the chuck support plate 2-3 in two directions to transfer the wafer 2-1 from the wafer transfer pin 2-4 to the wafer chuck 2-2. This is a coarse 2 drive motor. 2-10 is the coarse 2 drive motor 2
-7 is a worm gear for transmitting the driving force of Z to the cam 2-11.
drive in the direction. 2-12 is supported by the second substrate and has a slight θ
In order to rotate the substrate 2-16 in the θ direction, it is a piezo element for θ driving that expands and contracts in a direction perpendicular to the plane of the paper and presses the small θ substrate 2-16 through point contact via a steel ball. 2-13 is a plate spring for driving θ, which is connected to θ board 2-16 and 2 board 2.
-17 is connected. This plate spring 2-13 has a small rigidity in the direction perpendicular to the plane of the paper and a large rigidity in the z direction, so that it functions as a guide in the θ direction when the θ is driven. 2-14 is X
This is a drive piezo element installed at three or more force points on the stage 1-7, which drives the substrate 2-17 in two directions and moves the wafer 2-1 in two directions and in the α and β directions. let

2-15 is a Z drive guide leaf spring that connects the X stage 1-7 and the Z board 2-17, and has rigidity in the direction perpendicular to the plane of the paper and less rigidity in the vertical direction (Z direction). ,2
-18 is θ when the chuck support plate 2-3 moves 2 times.
This is a rotation regulating part for regulating rotation in the direction and driving the chuck support plate 2-3 and the through-theta substrate 2-16 as one unit during through-theta driving after Z movement. The details of this rotation regulating portion 2-18 are shown in FIG. 3. Reference numeral 2-21 is a biasing spring that is attached to one end of the chuck support plate and the other end to the non-theta substrate in order to abut the full-theta substrate 2-16 and the chuck support plate 2-3 with a constant force. Reference numeral 2-19 denotes a bearing for transmitting force to the chuck support plate during rotation regulation and during θ driving. 2-20 is a reference mirror.

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

First, a reticle 1-2 is transported to a reticle stage 1-3 by a reticle transport system (not shown), and a wafer 1-4 (not shown), which has been subjected to zero-order measurable alignment, is aligned at a predetermined position by the reticle stage 1-3. Transfer pin 2-4 to the sea urchin built in the XY stage positioned at the wafer transfer position by the wafer supply hand of
handed over to. At this time, wafer chuck 1-5 (
2-2) and the chuck support plate 2-3 are located below. Wafer 1-4 (2-1) is the wafer transfer pin 2
-4, the control device 1-20 confirms this and then issues a command to move the XY stage to the pre-alignment position.

The XY stage is controlled by a laser length measuring device (not shown),
Move to pre-alignment position.

Next, the wafer transfer bin 2 is placed at the pre-alignment position.
-4 drives the 2-driving piezo in the fine movement stage 1-6 according to a command from the control device so that the upper surface of the wafer 1-4 matches the focal position of the off-axis alignment scope 1-10. The amount of drive is measured by the autofocus function of the off-axis alignment scope 1-10 and communicated to the control system. After focusing, wafer 1-4 (2-1) is detected using off-axis alignment scope 1-10.
Measure the upper pre-alignment mark and calculate the error by IPI-
10c and communicated to the control device 1-20. When the control device 1-20 issues a drive command to the coarse θ drive motor in the fine movement stage 1-6, the wafer transfer pin 2-4 rotates in the θ direction with the wafer 1-4 (2-1) vacuum-adsorbed. prealignment is completed.

Next, the control device 1-20 that received the pre-alignment completion signal controls the fine movement stage 1-6 to control the wafer 1-4 (
2-1) to the wafer chuck 2-2, and the wafer chuck 2-2 transfers the coarse Z drive motor 2-9 to the wafer chuck 2-2.
, worm gear 2-10, and cam 2-11 drive the wafer 1-4 in the Z direction from the wafer transfer pin 2-4.
Receive (2-1). The wafer is in this wafer chuck 2
-2 is vacuum-adsorbed. In this case, the stem and wafer chuck will not rotate in the θ direction due to the rotation regulating portion 2-18.
Further, by locking the chuck support plate 2-3 and the Z drive motor in the θ substrate 2-16, the chuck support plate 2-3 is locked in that position.

When the controller 1-20 confirms that the wafer 1-4 (2-1) is attracted to the wafer chuck 2-2 and the chuck support plate is locked, the controller 1-20 moves the wafer 1-4 (2-1) to the alignment position with respect to the XY stage. A movement command is issued. Thereafter, operations are performed in the same manner as those of a normal exposure apparatus. However, after the pre-alignment is completed, the exposure apparatus can operate normally by driving only the θ fine movement and Z fine movement.

[Effects of the Invention] As explained above, in the present invention, the wafer transfer means built in the stage executes pre-alignment while the wafer transfer means receives the wafer, corrects the wafer transfer means by θ, and then transfers the queue to the wafer chuck. By adsorbing,
Since the rigidity of the wafer stage is increased, the stage positioning accuracy is improved, and the positioning time is shortened, it is possible to achieve high precision and high throughput of the exposure apparatus.

[Brief explanation of the drawing]

Fig. 341 is a main configuration diagram of an exposure apparatus according to an embodiment of the present invention, Fig. 2 is a detailed view of the fine movement stage portion of the exposure apparatus shown in Fig. 's1, Fig. 3 is an enlarged view of , and Fig. 4 is an enlarged view of , be. Rotation regulating section of fine movement stage in Fig. 2 A diagram explaining the 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-
B: Y stripe, 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: Z drive piezo element.

Claims (2)

[Claims] (1) a first object on which a pattern to be transferred is formed, a second object on which the pattern is printed, a first stage that supports the first object, and a second stage on which the second object is mounted; a projection optical system provided between the first and second objects; an illumination system that exposes the second object via the first object and the projection optical system; and the second object mounted on the second stage. a transfer means for fixing the second object on the second stage; and a control device for driving and controlling the second stage to align the first and second objects with each other. The second stage is movable in the X, Y, and Z directions and rotatable around the X, Y, and Z axes, and the control device is configured to move the second stage when the transfer means receives the second object. An exposure apparatus characterized in that the exposure apparatus is configured to perform alignment and rotational positioning around the Z-axis, and then fix the second object by the suction means. (2) The second stage is composed of an X stage, a Y stage, and a fine movement stage, and the fine movement stage is equipped with drive means in the Z direction and rotational drive means around the Z axis provided at three or more locations, 2. The exposure apparatus according to claim 1, wherein the delivery means is capable of protruding onto the upper surface of the fine movement stage, and the suction means is configured to be movable in the Z direction with respect to the delivery means.