JP3624057B2 - Exposure equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure apparatus used in manufacturing a semiconductor device such as an IC or LSI, a liquid crystal device, an imaging device such as a CCD, or a device such as a magnetic head, in particular, to reduce the weight of an original stage that holds the original, The present invention relates to an exposure apparatus that improves throughput.
[0002]
[Prior art]
In a batch exposure type exposure apparatus (stepper), when the projection optical system is constituted by a lens, the imaging region has a circular shape. However, since the semiconductor integrated circuit is generally rectangular, the transfer area in the case of collective exposure is a rectangular area inscribed in the imaging area of the circle of the projection optical system. Therefore, even the largest transfer region is a square with sides 1 / √2 of the diameter of the circle. On the other hand, the transfer area is enlarged by scanning and moving the reticle and wafer in synchronism using the slit-shaped exposure area having the diameter of the circular image formation area of the projection optical system. A scanning exposure method (step-and-scan method) has been proposed. In this method, when a projection optical system having an imaging region of the same size is used, a larger transfer area is ensured compared to the step-and-repeat method in which batch exposure is performed for each transfer region using a projection lens. be able to. In other words, since there is no restriction by the optical system in the scanning direction, it is possible to ensure only the stroke of the scanning stage, and it is possible to ensure a transfer area approximately √2 times in the direction perpendicular to the scanning direction. .
[0003]
An exposure apparatus for manufacturing a semiconductor integrated circuit is desired to expand a transfer region and improve resolution in order to cope with manufacture of a highly integrated chip. The adoption of a smaller projection optical system is advantageous in terms of optical performance and cost, and the step-and-scan type exposure method is attracting attention as a mainstream of future exposure apparatuses.
[0004]
In such a step-and-scan exposure apparatus, it is necessary to align the reticle and the wafer with high accuracy. For example, the reticle placed on the reticle stage by reticle exchange or the like is placed on the reticle stage by the reticle alignment scope. The position relative to the reference mark is measured with high accuracy. The higher the accuracy of this reticle scope, the narrower the measurement range, and the measurement range of the reticle alignment scope in the exposure apparatus compatible with 256M, which the present inventors aim at, is about 2 μm square.
[0005]
In the conventional reticle hand, it is impossible to place the reticle on the reticle stage with an error of about 2 μm. Therefore, it is conceivable that an XYθ fine movement mechanism is provided on the reticle stage, and the reticle alignment scope is switched to a low magnification to drive the reticle positional deviation within 2 μm. However, if the XYθ fine movement mechanism is provided on the reticle stage, the reticle stage becomes heavy. In particular, in a scanning type exposure apparatus that scans the reticle, the moving speed of the stage is slowed down, resulting in a decrease in throughput or the stage due to the weight of the reticle stage. There arises a problem that the exposure accuracy is lowered due to bending of the surface plate.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the problems in the above-described conventional example, and an object of the present invention is to reduce the weight of an original stage and improve throughput and exposure accuracy in an exposure apparatus.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a part of a pattern of an original is projected onto a substrate via a projection optical system, and the original and the substrate are scanned together relative to the projection optical system. In an exposure apparatus that exposes a pattern of an original on the substrate, an original stage that includes a first air pad and sucks and holds the original placed on the air pad substantially horizontally, and the original of the original on the original stage Means for detecting a positional deviation with respect to the stage at a predetermined original plate alignment position, an elevating shaft that moves up and down substantially vertically at the original plate alignment position, and attached to the elevating shaft via a leaf spring to hold the original plate on the original stage by suction A possible second air pad, and an original that is sucked and held by the second air pad in the pattern drawing plane of the original and an axis perpendicular to the plane through the lifting shaft Means for finely moving the original stage, sending the original stage to the original plate alignment position, lowering the elevating shaft to adsorb the original on the original stage by the second air pad, and supplying air from the first air pad. And a control means for causing the original plate to float by a small amount, causing the detection means to detect the positional deviation, and causing the fine movement means to finely move the original plate in accordance with the positional deviation detection result. .
[0008]
In a preferred embodiment of the present invention, the master further includes a master replacement means for replacing the master on the master stage at a predetermined master replacement position outside the exposure area, and the master alignment position is different from the master replacement position. The position is set so as not to interfere with the operation of the exchange means. In this case, the original plate alignment position can be set to the exposure standby position of the first shot.
[0009]
[Action]
According to the present invention, the fine movement mechanism for aligning the original plate is not placed on the original plate stage, that is, the original plate stage is reduced in weight by being separately placed, thereby improving throughput (up scanning speed) and improving exposure accuracy. Is possible.
[0010]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view schematically showing an exposure apparatus according to an embodiment of the present invention as viewed from the side, and FIG. 2 is a perspective view showing the appearance of the exposure apparatus. As shown in these drawings, this exposure apparatus projects a part of the pattern of the original on the reticle stage 1 onto the wafer on the wafer stage 3 via the projection optical system 2, and is relative to the projection optical system 2. In addition, the reticle pattern is exposed to the wafer by synchronously scanning the reticle and the wafer in the Y direction, and step movement is performed to repeatedly perform this scanning exposure on a plurality of transfer areas (shots) on the wafer. A step-and-scan type exposure apparatus.
[0011]
Reticle stage 1 is driven in the Y direction by linear motor 4, X stage 3 a of wafer stage 3 is driven in the X direction by linear motor 5, and Y stage 3 b is driven in the Y direction by linear motor 6. . In the synchronous scanning of the reticle and the wafer, the reticle stage 1 and the Y stage 3b are driven in the Y direction at a constant speed ratio (for example, 4: -1, where “−” indicates that the direction is opposite). Do. Further, the step movement in the X direction is performed by the X stage 3a. A Z-tilt stage (not shown) is mounted on the X stage 3a, and a wafer chuck (not shown) for holding the wafer is mounted thereon.
[0012]
The wafer stage 3 is provided on a stage surface plate 7, and the stage surface plate 7 is supported on a floor or the like at three points via three dampers 8. The reticle stage 1 and the projection optical system 2 are provided on a lens barrel base plate 9, and the lens barrel base plate 9 is supported on a base frame 10 placed on a floor or the like via three dampers 11 and a column 12. Yes. The damper 8 is an active damper that actively dampens or dampens vibrations in the six-axis direction. However, a passive damper may be used, or the damper 8 may be supported without a damper.
[0013]
The exposure apparatus also includes distance measuring means 13 such as a laser interferometer and a micro encoder that measure the distance between the lens barrel surface plate 9 and the stage surface plate 7 at three points.
[0014]
The light projecting means 21 and the light receiving means 22 constitute a focus sensor for detecting whether or not the wafer on the wafer stage 3 is positioned on the focus surface of the projection optical system 2. That is, the light projecting means 21 fixed to the lens barrel base plate 9 irradiates the wafer with light from an oblique direction, and the position of the reflected light is detected by the light receiving means 22, whereby the optical axis direction of the projection optical system 2 is detected. The position of the wafer surface is detected.
[0015]
In the apparatus of FIG. 1, light emitted from a laser interferometer light source (not shown) is introduced into the Y-direction laser interferometer 24 for reticle stage. The light introduced into the Y-direction laser interferometer 24 is transmitted to the fixed mirror (not shown) in the laser interferometer 24 by the beam splitter (not shown) in the laser interferometer 24 and the Y-direction moving mirror 26. It is divided into the light to go. The light traveling toward the Y-direction moving mirror 26 enters the Y-direction moving mirror 26 fixed to the reticle stage 4 through the Y-direction measuring optical path 25. The light reflected here returns again to the beam splitter in the laser interferometer 24 through the Y-direction measuring optical path 25 and is superposed on the light reflected by the fixed mirror. The movement distance in the Y direction is measured by detecting a change in light interference at this time. The movement distance information thus measured is fed back to a scanning control device (not shown), and the positioning control of the scanning position of the reticle stage 4 is performed. Similarly, in the Y stage 3b, the scanning position is controlled based on the length measurement result by the Y direction laser interferometer 23 for wafer stage.
[0016]
In this configuration, when the wafer is loaded onto the wafer stage 3 by the transfer means (not shown) via the transfer path between the two support columns 12 at the front of the apparatus and the predetermined alignment is completed, the exposure apparatus performs scanning exposure and While repeating step movement, the reticle pattern is exposed and transferred to a plurality of exposure areas on the wafer. In scanning exposure, the reticle stage 1 and the Y stage 3b are moved in the Y direction (scanning direction) at a predetermined speed ratio, and the pattern on the reticle is scanned with slit-shaped exposure light, and the projected image is used for the wafer. , The pattern on the reticle is exposed to a predetermined exposure area on the wafer. During the scanning exposure, the height of the wafer surface is measured by the focus sensor, and the height and tilt of the wafer stage 3 are controlled in real time based on the measured values, and focus correction is performed. When the scanning exposure for one exposure region is completed, the X stage 3a is driven in the X direction to move the wafer stepwise, thereby positioning the other exposure region with respect to the scanning exposure start position and performing the scanning exposure. Note that each exposure region can be sequentially and efficiently exposed to a plurality of exposure regions on the wafer by combining the step movement in the X direction and the movement for scanning exposure in the Y direction. , The Y scanning direction to positive or negative, the exposure order to each exposure area, and the like are set.
[0017]
At the time of reticle replacement, the reticle stage 1 moves to a reticle replacement position outside the exposure area and receives a reticle from a reticle changer (not shown). The received reticle is held on the reticle stage 1 by a vacuum suction pad. Next, the reticle stage 1 is moved to the reticle alignment position, and reticle alignment is performed. At the time of reticle alignment, a reticle handler (not shown) descends onto the reticle stage 1 to grab the reticle, and drives the reticle alignment stage (not shown) to align the reticle with the reference mark on the reticle stage 1. A vacuum suction pad is attached to the lower end of the reticle handler via a leaf spring. During alignment, the reticle is held by the vacuum suction pad, and air is blown out from the vacuum suction pad of the reticle stage 1 to expose the reticle. The reticle alignment stage is driven while floating from the stage 1.
[0018]
FIG. 3 shows the configuration of the reticle alignment mechanism in the apparatus of FIG. In this apparatus, the reticle alignment mechanism is not placed on the reticle stage but is placed separately, thereby reducing the weight of the reticle stage and increasing its scanning speed to improve the throughput. In the figure, reference numeral 1 denotes a reticle stage, the solid line indicates the state at the reticle alignment position, and the two-dot chain line indicates the state at the reticle replacement position (left side in the figure) or the exposure area (right side in the figure). Show. 2 is a projection optical system (projection lens), 3 is a wafer stage, 31 is an illumination optical system, 32 is a reticle changer, 33 is a substrate position detection microscope (reticle alignment scope), 34 is a reticle, and 35 is provided on the reticle stage 1. The reference mark 36 is a reticle handler, 37 is a reticle alignment stage, 38 is a reticle alignment stage support member, 39 is a reticle stage guide, 40 is a wafer, and 41 is a wafer stage guide.
[0019]
FIG. 4 shows the operation of each part during reticle replacement and reticle alignment. That is, at the time of reticle replacement, the reticle stage 1 is positioned at the reticle replacement position (position shown in FIG. 4A). At the same time, a new reticle 34 is transported from a reticle library (not shown) by a transport means (not shown), delivered to the reticle changer 32, and placed on the reticle stage 1 that has reached the reticle replacement position by the reticle changer 32. As shown in FIG. 5, the reticle stage 1 is provided with a reticle chuck 56, and the mounted reticle 34 is vacuum-sucked by the reticle chuck 56 and held on the reticle stage 1. In FIG. 5, reference numeral 54 denotes a reticle stage top plate.
[0020]
At the time of reticle alignment, the reticle stage 1 moves to the reticle alignment position (position shown in FIG. 4B). FIG. 5 shows details of the reticle alignment operation at this reticle alignment position. When the reticle stage 1 comes to the reticle alignment position (FIG. 5A), the reticle handler 36 is lowered, and the reticle is sucked by the reticle suction pad 53 attached to the lower end of the lift shaft 51 of the reticle handler 36 via the leaf spring 52. 34 is vacuum-adsorbed (FIG. 5B). Next, the vacuum of the reticle chuck 56 on the reticle stage 1 is switched to air blowing, and the air flow causes the reticle 34 to be slightly smaller than the reticle chuck 56 (for example, if the depth of focus of the reticle alignment scope 33 is 10 μm), the reticle 34 Float (approximately 2 to several μm that does not deviate from the focal depth) (FIG. 5C)
[0021]
In this state, the reticle alignment scope 33 detects a misalignment between the reference mark 35 and an alignment mark (not shown) formed on the reticle 34, and drives the reticle alignment stage 37 so as to correct this misalignment. . Further, the air blowing of the reticle chuck 56 is turned off and the vacuum is turned on, so that the reticle 34 is vacuum-adsorbed to the reticle chuck 56. Next, the reticle 34 that has been aligned by turning off the vacuum of the reticle suction pad 53 of the reticle handler 36 is transferred to the reticle stage 1 and the reticle handler 36 is raised (FIG. 4C).
[0022]
When the reticle alignment is completed, the amount of positional deviation between the alignment mark on the reticle 34 and the reference mark 35 on the reticle stage 1 is measured by the reticle alignment scope 33, and the wafer stage is based on the measured value and the residual alignment error of the wafer. 3 XYθ of the wafer on 3 is set and scanning exposure is performed.
[0023]
Note that reticle alignment can be performed as appropriate other than during reticle replacement.
[0024]
When detecting the above-described misalignment, the surface of the reticle 34 is first observed with the reticle alignment scope 33 before the reticle handler 36 is lowered, and the alignment mark of the reticle 34 is within the measurement range of the reticle alignment scope 33. If there is, it is possible to perform the positional deviation amount measurement and the scanning exposure without performing the positioning process. In this case, if the alignment mark of the reticle 34 is not within the measurement range of the reticle alignment scope 33 but is within the field of view of the reticle alignment scope 33, the reticle 34 is switched without switching the magnification of the reticle alignment scope 33. When the alignment mark of the reticle 34 is not within the field of view of the reticle alignment scope 33, the magnification of the reticle alignment scope 33 is switched to a low magnification, and the position of the alignment mark is expanded. The position shift detection is performed. This magnification switching is performed in parallel with the lowering of the reticle handler 36. When the magnification is switched, the magnification is restored to the original in parallel with the raising of the reticle handler 36.
[0025]
[Examples of microdevice manufacturing]
FIG. 6 shows a manufacturing flow of a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).
[0026]
FIG. 7 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed on the wafer by exposure using the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
[0027]
By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device that has been difficult to manufacture at low cost.
[0028]
【The invention's effect】
As described above, according to the present invention, the original plate alignment mechanism is not placed on the original plate stage, but is placed separately. Therefore, the original stage can be reduced in weight, and the scanning speed of the original plate stage can be increased to improve the throughput. it can. Further, it is possible to reduce the deflection of the stage surface plate or the like due to the weight of the original stage, thereby improving the exposure accuracy.
[0029]
In addition, since the original plate adsorption portion of the alignment mechanism is elastically supported, it is possible to increase the allowable error of the descending amount of the original plate adsorption portion, and it is not necessary to provide a fine movement Z mechanism in the alignment mechanism, and the original plate is positioned at high speed. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an exposure apparatus according to an embodiment of the present invention as viewed from the side.
2 is a perspective view showing an appearance of the exposure apparatus of FIG. 1. FIG.
3 is an explanatory diagram of a reticle alignment mechanism in the apparatus of FIG. 1. FIG.
FIG. 4 is an explanatory diagram of reticle replacement and alignment processing in the apparatus of FIG. 1;
5 is a more detailed explanatory diagram of reticle alignment processing shown in FIG. 4. FIG.
FIG. 6 is a diagram showing a flow of manufacturing a microdevice.
7 is a diagram showing a detailed flow of the wafer process in FIG. 6. FIG.
[Explanation of symbols]
1: reticle stage, 1a: through hole, 2: projection optical system, 3: wafer stage, 3a: X stage, 3b: Y stage, 4, 5, 6: linear motor, 7: stage surface plate, 8: damper 9: lens base plate, 10: base frame, 11: damper, 12: support, 13: distance measuring means, 21: light projecting means, 22: light receiving means, 23, 24: laser interferometer, 25: laser length measurement Optical path, 26, 27: Moving mirror, 31: Illumination optical system, 32: Reticle changer, 33: Reticle alignment scope, 34: Reticle, 35: Reference mark, 36: Reticle handler, 37: Reticle alignment stage, 38: Reticle alignment Stage support member, 39: reticle stage guide, 40: wafer, 41: wafer stage guide, 51: lifting axis (Z axis), 52: plate I, 53: reticle suction pad, 54: reticle stage top plate, 56: reticle chuck.

Claims (4)

In an exposure apparatus that projects a part of an original pattern onto a substrate via a projection optical system, and exposes the original pattern on the substrate by scanning the original and the substrate relative to the projection optical system. ,
An original stage provided with a first air pad and holding the original placed on the air pad substantially horizontally;
Means for detecting a displacement of the original on the original stage relative to the original stage at a predetermined original alignment position;
A lifting shaft that moves up and down substantially vertically at the original plate alignment position;
A second air pad attached to the elevating shaft via a leaf spring and capable of sucking and holding the original on the original stage;
Means for finely moving the original held by suction by the second air pad in the pattern drawing plane of the original and the axis perpendicular to the plane via the lifting shaft;
The original stage is sent to the original alignment position, the lifting shaft is lowered, the original on the original stage is adsorbed by the second air pad, and air is blown out from the first air pad to slightly reduce the original. An exposure apparatus comprising: a control unit that floats, causes the detection unit to detect the positional deviation, and finely moves the original plate by the fine movement unit according to a detection result of the positional deviation. The apparatus further comprises an original exchanging means for exchanging the original on the original stage at a predetermined original exchanging position outside the exposure area, and the original alignment position is set to a position that does not interfere with the operation of the original exchanging means different from the original exchanging position. The exposure apparatus according to claim 1, wherein the exposure apparatus is provided. 3. The exposure apparatus according to claim 2, wherein the original plate alignment position is an exposure standby position for the first shot. A device manufacturing method using the apparatus according to claim 1.

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