JP3514401B2 - Scanning exposure apparatus and method, and semiconductor device manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a semiconductor device manufacturing process, and more particularly to a projection exposure apparatus and method for projecting and transferring a photomask pattern onto a wafer, and a semiconductor device manufacturing method. The present invention relates to a scanning exposure apparatus and method for scanning a mask and a wafer in synchronization with a projection optical system (projection exposure system) when the mask pattern is projected and exposed on the wafer, and a semiconductor device manufacturing method.

[0002]

2. Description of the Related Art The recent progress in manufacturing technology of semiconductor devices is remarkable, and accompanying it, the progress of fine processing technology is remarkable. In particular, the mainstream of optical processing technology is reduction projection exposure equipment with a resolution of submicron, commonly called stepper, and it is necessary to increase the numerical aperture (NA) of the optical system and shorten the exposure wavelength to further improve the resolution. Has been.

Further, a conventional type scanning exposure apparatus using a catoptric projection optical system is improved, a refracting element is incorporated in the projection optical system, and a reflecting element and a refracting element are combined.
Alternatively, a scanning-type exposure apparatus that uses a reduction projection optical system composed of only refracting elements to synchronously scan both the mask stage and the photosensitive substrate stage (hereinafter referred to as the wafer stage) at a speed ratio according to the reduction magnification is also noted. Has been done.

An example of this scanning type exposure apparatus is shown in FIG.
As shown in the figure, the mask 1 on which the original image is drawn is supported by the mask stage 4, and the wafer 3 which is a photosensitive substrate is supported by the wafer stage 5. Mask 1 and wafer 3
Is placed at an optically conjugate position via the projection optical system 2, and slit exposure light 6 extending in the Y direction in the drawing from an illumination system (not shown) illuminates the mask 1 and the projection optical system 2 An image is formed on the wafer 3 at a size larger than the projection magnification of.
Scanning exposure is performed by scanning the mask 1 and the wafer 3 by moving both the mask stage 4 and the wafer stage 5 in the X direction with respect to the slit-shaped exposure light 6, that is, the projection optical system 2 at a speed ratio according to the optical magnification. The entire device pattern 21 on the mask 1 is transferred to the transfer area on the wafer 3.

In this scanning exposure, two wafers are actually exposed. That is, the wafer on which the mask pattern is not transferred (hereinafter referred to as the first wafer) and the wafer on which the mask pattern is formed (hereinafter referred to as the second wafer) are exposed. In particular, when another mask pattern is overlaid and exposed on a second wafer, a laser interferometer is used to detect the arrangement of patterns on the mask 1 and the wafer 3 as disclosed in Japanese Patent Application No. 7-187171. Exposure is performed after the positions are adjusted by monitoring the positions of the respective stages with 80 and 81.

[0006]

However, when the above-mentioned reduction projection optical system is used, the mask 1 which is larger than the pattern area formed on the wafer 3 by the projection magnification must be used.

Therefore, in order to support such a large mask 1, the mask stage 4 also becomes large, and the weight increases in consideration of the drive system for driving it. As a result, when the mask stage 4 is slid during the actual exposure, a posture error of the projection optical system 2 due to the movement of the center of gravity of the mask stage 4 or a serious eccentricity occurs.

Further, in order to drive such a heavy mask stage 4, vibration of the projection optical system 2 and pitching of the mask stage 4 itself occur due to reaction when the mask stage 4 is accelerated to a certain speed. This vibration also causes a change in the posture of the projection optical system 2, and due to this change in the posture, the exposure is deviated from the desired exposure area. Further, the pitch of the mask stage 4 also causes image shift on the exposure surface. When the vibrations occur in the scanning direction, the deviations cause superposition accuracy to deteriorate, and the vibrations in the direction perpendicular to the scanning direction result in a focus deviation (defocus and tilt) on the surface of the wafer 3, resulting in the first wafer. It also leads to deterioration of the exposure accuracy during the production of the second wafer.

Even if the position of the second wafer is detected in advance, the alignment accuracy is deteriorated as a result, and the yield at the time of semiconductor manufacturing is deteriorated.

Further, conventionally, in order to eliminate the influence of the vibration of the projection optical system 2 due to the driving of the mask stage 4, the mask stage 4 is driven from the start of acceleration to a position where the influence of the vibration can be ignored, and from that position. Start exposure. Therefore, a certain amount of time is required from the start of the scanning operation to the exposure, which lowers the throughput and makes the mask stage 4 as a whole larger in scale, making it difficult to save space.

Further, the scanning distance of the mask stage 4 becomes longer than the time until the speed and vibration of the mask stage 4 at the time of exposure reach a negligible amount, and in the scanning type exposure apparatus, in order to improve the throughput. For example, in the odd-numbered shots and the even-numbered shots, the mask stage 4 is exposed by reversing the scanning direction, so that the scanning distance is extended on both sides in the scanning direction, which further enlarges the entire exposure apparatus.

An object of the present invention is to eliminate the influence of the vibration due to the driving of the stage without lowering the throughput or increasing the scanning distance, in view of the problems of the prior art.

[0013]

In order to achieve the above object, according to the present invention, a first object such as a mask is placed.
The movable first stage and the second object such as a wafer.
A second movable stage that is placed and moves, and on the first object
And a projection optical system for projecting the pattern on the second object.
And driving the first and second movable stages in synchronization with each other.
While moving, the pattern on the first object is moved through the projection optical system.
In a scanning exposure apparatus that projects a turn onto the second object
Of the first and second movable stages measured in advance.
For the deviation of the projected image due to the deformation of the device generated by driving
It has a means to perform exposure using the correction value for
To collect .

Further, by using the first and the plurality of acceleration or velocity and the correction value corresponding to their direction of the second movable stage for exposure, it may be exposed while correcting the velocity.

Also, the correction value should be on the second object.
To the image shift of the projected image of the pattern on the first object
The first and second stages are based on the correction value.
The scanning speed or exposure position of the image may be corrected .

Further, the correction value should be placed on the second object.
Defocus of the projected image of the pattern on the first object
And the second object based on the correction value.
When exposing while correcting the position of the body in the focus direction
Yes .

Further, the scanning speed or exposure position is supplemented.
When correcting, control the amount of exposure light according to the scanning speed
It is good to expose while . The details will be described below.

A case where the projection optical system 2 is vibrated by driving the mask stage 4 will be described with reference to FIG. Although the projection optical system 2 vibrates as the mask stage 4 is driven, the projection optical system 2a is located at the center of vibration, that is, at an ideal position (hereinafter referred to as an ideal position) when there is no vibration.
On the other hand, 2b shown by a broken line represents a projection optical system at a position deviated by vibration or movement of the center of gravity of the mask stage 4 (hereinafter referred to as maximum amplitude position). 50a
Indicates the optical axis of the projection optical system at the ideal position, while 50b indicates the optical axis of the projection optical system at the maximum amplitude position.

Now, the light 51 passing through one point in the exposure area is
It passes through the pupil 52a of the projection optical system 2a and reaches the position of 51a. On the other hand, in the case of the projection optical system 2b at the maximum amplitude position, the light 51 reaches the position of 51b through the pupil 52b. Therefore, it can be seen that the imaging position also changes due to the position change due to the vibration of the projection optical system 2. That is, the imaging magnification of the projection optical system 2 is β, and the projection optical system 2
When the maximum amplitude amount of is a, the image forming position is displaced by βa.

FIG. 3 shows how the vibration amplitude changes with respect to the change in scanning speed. FIG. 3A shows a change in speed of the mask stage 4 with respect to time, and a solid line shows an ideal change in speed at the time of exposure in which the projection optical system 2 is not affected by vibration.
On the other hand, the alternate long and short dash line shows the change in speed when the scanning speed is doubled.

Further, FIG. 3B shows changes in the vibration amplitude of the projection optical system 2 with respect to the respective scanning speeds, which can be read as a state of image shift on the surface of the wafer 3. The solid line shows the case of the ideal exposure speed, and the one-dot chain line shows that the speed is 2
When the speed doubles, the vibration amplitude at point B also increases. Therefore, at the ideal exposure speed, the effect of vibration disappeared at point A, whereas at double speed, when exposure was started at the same position (point B), the effect of image shift was large, and the scanning distance was extended to point C. Without it, the effect of vibration cannot be eliminated. Therefore, if the speed is doubled, a distance for moving to the optimum exposure position C point is required, and as a result, the scanning distance becomes long. further,
The time until the start of exposure becomes long, and the throughput decreases as it is. Alternatively, when the moving distance of the mask stage 4 has only a stroke determined by the case of the ideal exposure speed of the solid line, if the speed is doubled and exposure is performed as it is, an image shift is included, and the exposure accuracy deteriorates.

Therefore, for example, in order to perform exposure with the scanning speed doubled, the amount of offset generated by the vibration after the point B is measured in advance, and the speed of the wafer stage 5 and the mask stage 4 at the time of exposure is measured. It is advisable to change the speed (exposure position) in consideration of the offset amount before exposure. At that time, optimum scanning exposure can be performed by changing the control of the exposure amount for the resist on the wafer 3 with respect to the speed.

In this control, not only the position in the scanning direction but also the offset amount of the focus shift (defocus, tilt) on the surface of the wafer 3 is measured in advance, and the offset amount of the wafer stage 5 is independently measured. It is recommended that the exposure be performed by reflecting it on the focus drive.

[0024]

DETAILED DESCRIPTION OF THE INVENTION

[Embodiment 1] FIG. 1 is a schematic view of a scanning exposure apparatus according to an embodiment of the present invention, and FIG. 2 is a detailed view thereof. In this apparatus, as shown in these figures, the exposure light 23 from an illumination system (not shown) is a slit-shaped exposure area extending in the direction perpendicular to the paper surface (Y direction) of the mask (reticle) supported by the mask stage 4. Illuminate. The position of the mask stage 4 in the X direction is observed by the interferometer 80. Similarly, the wafer stage 5 supporting the wafer 3 can be driven in the X and Y directions, and its position is monitored by the interferometer 81. The wafer stage 5 and the mask stage 4 are controlled with respect to their respective positions, and their positions are driven based on the information described below. Position detection system (observation microscope) 7 and 8 for mask alignment
Are used for observing the alignment marks provided on the mask 1 and the mask stage 4 and performing alignment with respect to the mask stage 4. A position detection system (off-axis observation microscope) provided above the wafer 3
Reference numeral 31 is used for observing an alignment mark formed on the wafer 3, performing alignment measurement for each chip, and performing alignment.

Wafer stage 5 and mask stage 4
Simultaneously scans the wafer stage 5 at the scan speed Vw and the mask stage 4 at the scan speed Vm = βVw based on the alignment measurement values by the position detection systems 7, 8, 31 and the imaging magnification β of the projection optical system 2. During this, exposure is performed.

Here, consider a case where the projection optical system 2 vibrates due to the acceleration motion at the start of scanning of the mask stage 4 and the exposure area fluctuates. As shown in FIGS. 3A and 3B, the projection optical system 2 vibrates under the influence of acceleration. The amplitude of this vibration depends on the acceleration A, and the fluctuation amount of the image shift is unique to each device and reproducibly generated. That is, the offset due to the image shift is the scanning position P (which can also be called the time from the start of scanning) for each device.
And acceleration A are expressed as variables, and image shift offset =
It becomes OSF (A, P). Therefore, the amount of image deviation generated in advance with respect to the acceleration A and the scanning position P is measured, and the speed at the time of scanning exposure (exposure start position)
To correct. It should be noted that the vibration of the projection optical system 2 accompanying the speed change at this time does not occur because the speed change is sufficiently small.

Furthermore, this correction value also differs depending on the scanning direction. FIG. 3C shows a state of vibration when scanning is performed from a direction opposite to that in the case of FIG. In this case, for example, the amplitude at the corresponding point of condition 3 in FIG. 3 (c) is a negative value with respect to the amplitude at the point of condition 2 in FIG. 3 (b), indicating that the vibration is inverted. . Therefore, it is necessary to hold a correction value according to the scanning direction, and reflect it according to each scanning direction at the time of exposure. In the following, the scanning exposure from condition 2 will be referred to as “left scanning exposure”, and the scanning exposure from condition 3 will be referred to as “right scanning exposure” in correspondence with the orientation of FIG.

As an example, the scanning exposure in the case where the above correction value is taken into consideration for the scanning exposure of the second wafer will be described below.

FIG. 5 shows a flowchart of the scanning exposure operation. First, step S200 and step S2
In 01, the image shift offset generated with respect to the acceleration A is measured prior to scanning exposure. The offset generated during right scanning exposure is OFS _-r (A, P), and the offset during left scanning exposure is OFS _-l (A, P). These offsets are values measured for the acceleration A and the scanning position P by actually performing scanning exposure, and various accelerations A
It is possible to deal with the case where the scanning speed is changed by measuring with respect to and storing it as a table. Also,
It is also possible to hold the offset as a function of the acceleration A, and by holding this function, the offset measurement for the arbitrary acceleration A becomes unnecessary.

Next, in step S202, the exposure sequence is started, and in step S203, the alignment marks 42a and 42 provided on the mask 1 are aligned.
b is measured by the position detection system 7, and the mask 1 and the mask stage 4 are aligned with each other. Further, the position detection system 31 provided above the wafer 3 observes an alignment mark on the wafer 3 (not shown) and performs alignment so as to perform optimal overlapping exposure. Based on this, scanning exposure described later is performed. In the scanning type exposure apparatus, in order to improve the throughput, the mask stage 4 is reciprocally driven and exposed according to the shot layout on the wafer 3 at the time of actual exposure. Therefore, in step S204, the scanning direction of the mask stage 4 is determined, and when right scanning exposure is performed, the process proceeds to step S205a, and when left scanning exposure is performed, the process proceeds to step S205b. In step S205a, scanning exposure is performed while controlling the exposure speed based on the offset OFS _-r (A, P) measured prior to the alignment measurement value. At this time, it is possible to eliminate the influence of the uneven exposure amount in the wafer 3 or the shot by performing the exposure while controlling the exposure amount so that the illuminance of the exposure region of the wafer 3 becomes constant against the fluctuation of the scanning speed. Therefore, for example, when a pulsed light source such as a KrF laser is used, it can be solved by controlling the number of exposure pulses or controlling the frequency. Similarly, in step S205b, scanning exposure is performed based on the offset OFS- ₁ (A, P). As described above, since the projection exposure is performed while controlling the offset, the time and stroke until the influence of the vibration of the projection optical system 2 can be ignored can be omitted. Therefore, the throughput can be improved and the device can be downsized.

In step S206, it is determined whether or not exposure of all shots of one wafer has been completed. If it is determined that exposure has not been completed, the process returns to step S204,
If completed, the process proceeds to step S207 to end the exposure sequence. Unless the state of the exposure apparatus (acceleration A of the mask stage 4 or the like) is changed, steps S202 to S207 are repeated to expose a plurality of wafers.

When the acceleration A of the mask stage 4 is changed, the scanning exposure is performed by controlling the scanning speed and the exposure amount with the corresponding offsets based on the above table.

[Second Embodiment] In the first embodiment, the influence of the image shift caused by the vibration of the projection optical system 2 has been described, but the focus shift and the tilt component on the wafer 3 surface due to the vibration of the projection optical system 2 are also included. Occur. These error components can be similarly corrected. That is, an offset that occurs according to the acceleration A and the scanning direction is measured in advance, and based on this, the exposure is performed while performing the correction drive of the wafer stage 5 in the focus direction of the projection optical system 2 when performing scanning exposure. As a result, it is possible to perform highly accurate scanning exposure, prevent enlargement of the apparatus, and improve throughput.

As described above , the above-mentioned embodiment
According to 1 and 2, a scanning semiconductor exposure device, a first
Since the change of the exposure condition due to the deformation of the apparatus caused by the driving of the second movable stage is measured in advance and the scanning exposure is performed while reflecting the correction value for the change of the exposure condition measured at the time of the actual exposure, the stage is driven. The effects of vibration can be eliminated without reducing throughput or increasing scan distance . Also, increase the scanning distance.
Since there is no addition, there is no need to enlarge the stage,
It is possible to avoid an increase in storage space .

[0035]

As described above, according to the present invention, the stay
The influence of vibration due to drive
It can be eliminated without increasing the distance .

[Brief description of drawings]

FIG. 1 is a schematic diagram of a scanning exposure apparatus according to a first embodiment of the present invention.

2 is a detailed view of the device of FIG.

FIG. 3 is a graph illustrating vibration of the projection optical system due to driving of the mask stage.

FIG. 4 is a diagram showing a state of image shift on a wafer due to vibration of a projection optical system.

FIG. 5 is a flowchart showing an operation.

[Explanation of symbols]

1: mask, 2, 2a, 2b: projection optical system, 3: wafer, 4: mask stage, 5: wafer stage, 6: exposure light slit, 7, 8, 31: position detection system, 10, 1
1: mask reference plate, 12: wafer reference plate,
13: projection optical system support, 21: pattern area, 22:
Transfer area, 23: exposure light, 42: mask alignment mark, 50a, 50b: optical axis, 51, 51a, 51b:
Exposure light, 52a, 52b: pupil, 80, 81: laser interferometer, 101: mark detecting means, 102: arithmetic processing circuit,
103: drive control means, 104: error correction value.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-7-302754 (JP, A) JP-A-60-140826 (JP, A) JP-A-7-307284 (JP, A) JP-A-5- 197158 (JP, A) JP 8-51063 (JP, A) JP 7-94388 (JP, A) JP 9-180989 (JP, A) JP 7-57985 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (20)

(57) [Claims] 1. A first movable stage that mounts and moves a first object, a second movable stage that mounts and moves a second object, and a pattern on the first object on the second object. And a projection optical system for projecting onto the second object, and scanning for projecting a pattern on the first object onto the second object via the projection optical system while driving the first and second movable stages in synchronization. A scanning exposure apparatus, which comprises means for performing exposure using a correction value for a deviation of a projected image caused by deformation of the apparatus, which is measured in advance by driving the first and second movable stages. . 2. A using the correction value corresponding to a plurality of acceleration or velocity and their directions of the first and second movable stage for exposure, claims, characterized in that it comprises means for exposing while correcting the speed of Item 2. The scanning exposure apparatus according to item 1. 3. The correction value is for an image shift of a projected image of a pattern on the first object on the second object, and the scanning speed of the first and second stages based on the correction value or scanning exposure apparatus according to claim 1, wherein the correcting the exposure position. 4. The correction value is for a focus shift of a projected image of a pattern on the first object on the second object, and the position of the second object is corrected in the focus direction based on the correction value. scanning exposure apparatus according to claim 1, wherein the exposure while. 5. The scanning exposure apparatus according to claim 3, wherein when correcting the scanning speed or the exposure position, the exposure is performed while controlling the light amount of the exposure light according to the scanning speed. 6. A first movable stage on which a first object is placed and moves, a second movable stage on which a second object is placed and moves, and a pattern on the first object on the second object. And a projection optical system for projecting onto the second object, and scanning for projecting a pattern on the first object onto the second object via the projection optical system while driving the first and second movable stages in synchronization. In the mold exposure apparatus, there is provided means for performing exposure by using a correction value for a change in exposure condition due to deformation of the apparatus which is generated by driving the first and second movable stages, which is measured in advance, and the first and second exposures are performed. using a correction value corresponding to the acceleration or velocity and their direction of the movable stage, the scan type exposure apparatus characterized by having means for exposure while correcting the velocity. 7. A first movable stage on which a first object is placed and moves, a second movable stage on which a second object is placed and moves, and a pattern on the first object on the second object. And a projection optical system for projecting onto the second object, and scanning for projecting a pattern on the first object onto the second object via the projection optical system while driving the first and second movable stages in synchronization. In a die exposure apparatus, based on a pre-measured correction value for an image shift of a projected image of a pattern on the first object on the second object due to deformation of the apparatus generated by driving the first and second movable stages A scanning type exposure apparatus comprising means for correcting the scanning speed of the first and second movable stages. 8. A first movable stage that mounts and moves a first object, a second movable stage that mounts and moves a second object, and a pattern on the first object on the second object. And a projection optical system for projecting onto the second object, and scanning for projecting a pattern on the first object onto the second object via the projection optical system while driving the first and second movable stages in synchronization. In a die exposure apparatus, based on a pre-measured correction value for an image shift of a projected image of a pattern on the first object on the second object due to deformation of the apparatus generated by driving the first and second movable stages A scanning type exposure apparatus comprising means for correcting the exposure positions of the first and second movable stages. 9. A first movable stage that mounts and moves a first object, a second movable stage that mounts and moves a second object, and a pattern on the first object on the second object. And a projection optical system for projecting onto the second object, and scanning for projecting a pattern on the first object onto the second object via the projection optical system while driving the first and second movable stages in synchronization. In a mold exposure apparatus, based on a correction value for a focus shift of a projected image of a pattern on the first object on the second object, which is measured in advance by deformation of the apparatus generated by driving the first and second movable stages. A scanning type exposure apparatus comprising means for correcting the position of the second object in the focus direction. 10. A pattern on the first object via the projection optical system while driving the first movable stage on which the first object is placed and the second movable stage on which the second object is placed in synchronization with each other. In the scanning exposure method of projecting onto the second object, the deviation of the projected image due to the deformation of the device caused by the driving of the first and second movable stages is measured in advance,
A scanning-type exposure method, wherein exposure is performed using a correction value for the measured deviation of the projected image. Claims 11. using the correction value corresponding to a plurality of acceleration or velocity and their directions of the first and second movable stage is exposed, and wherein the scanning exposure is performed while correcting the velocity 10. The method according to 10. 12. The correction value is an image shift of a projected image of a pattern on the first object on the second object, and the scanning speed or the exposure position of the first and second stages based on the correction value. claim, characterized in that to correct the 10
The method described. 13. The correction value is a focus shift of a projected image of a pattern on the first object on the second object, and the position of the second object is corrected in the focus direction based on the correction value. The method according to claim 10 , characterized in that 14. The method according to claim 12, wherein when the scanning speed or the exposure position is corrected, the exposure is performed while controlling the light amount of the exposure light according to the speed. 15. A pattern on the first object via the projection optical system while driving the first movable stage on which the first object is placed and the second movable stage on which the second object is placed in synchronization with each other. In the scanning exposure method of projecting onto the second object, a change in the exposure condition due to the deformation of the apparatus caused by the driving of the first and second movable stages is measured in advance, and a correction value for the measured change in the exposure condition is measured. When performing exposure by using, the scanning exposure method is characterized in that the acceleration or velocity is corrected using a correction value according to the acceleration or velocity of the first and second movable stages and their directions. 16. A first movable stage on which a first object is placed and a second movable stage on which a second object is placed are synchronized with each other to scan and drive the projection optical system through the projection optical system. A scanning type exposure method for projecting a pattern on the first object onto the second object, wherein the first object on the second object due to deformation of a device generated by driving the first and second movable stages Measure the image shift of the projected image of the pattern in advance,
Actual based on the correction value for the measured image deviation at the time of exposure, the first, scanning exposure method and correcting the scanning speed of the second stage. 17. A first movable stage on which a first object is mounted and a second movable stage on which a second object is mounted are synchronously driven to scan the projection optical system, and through the projection optical system. A scanning type exposure method for projecting a pattern on the first object onto the second object, wherein the first object on the second object due to deformation of a device generated by driving the first and second movable stages Measure the image shift of the projected image of the pattern in advance,
Actual based on the correction value for the measured image deviation at the time of exposure, the first, scanning exposure method characterized by correcting the exposure light position of the second stage. 18. A pattern on the first object via the projection optical system while driving the first movable stage on which the first object is placed and the second movable stage on which the second object is placed in synchronization with each other. A projection image of a pattern of a pattern on the first object on the second object due to deformation of an apparatus generated by driving the first and second movable stages. A scanning-type exposure method, wherein the deviation is measured in advance, and the exposure is performed while correcting the position of the second object in the focus direction based on a correction value for the measured focus deviation of the projected image. 19. A method for manufacturing a semiconductor device, which comprises exposing the second object using the scanning exposure apparatus according to claim 1. Description: 20. Preparing a wafer that is the second object,
A method of manufacturing a semiconductor device, which comprises exposing the prepared wafer by using the scanning type exposure method according to claim 10.