JPH1097982A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight of an original plate stage and to improve throughput and exposure precision by employing a configuration where a fine moving mechanism for alignment of original plate/position is not placed on the original plate stage. SOLUTION: Relating to the device, a reticule alignment mechanism is not placed on a reticule stage 1 but set separately, so that the weight of reticule stage 1 is reduced, to speed up scanning and to improve throughput. When the reticule stage 1 comes to a reticule alignment position at reticule alignment, a reticule handler 36 falls and a reticule 34 is vacuum-sucked with a reticule sucking pad 53 attached to a lower end of rising/falling axis 51 of the reticule handler 36 through a leaf spring 52. Then, the vacuum of a reticule chuck 56 on the reticule stage 1 is converted into air blow, and the reticule 34 is made to soar by a small amount from the reticule chuck 56 by an air flow. Under this condition, displacement is detected.

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 for manufacturing semiconductor devices such as ICs and LSIs, liquid crystal devices, imaging devices such as CCDs, and devices such as magnetic heads. The present invention relates to an exposure apparatus that reduces the weight of a stage and thereby improves throughput.

[0002]

2. Description of the Related Art In a batch exposure type exposure apparatus (stepper), when a projection optical system is constituted by a lens,
The imaging region has a circular shape. However, since the semiconductor integrated circuit generally has a rectangular shape, the transfer area in the case of batch exposure is a rectangular area inscribed in a circular imaging area of the projection optical system. Therefore, even the largest transfer area is a square of 1 / √2 of the diameter of the circle. On the contrary,
A scanning exposure method in which a transfer area is enlarged by moving a reticle and a wafer synchronously using a slit-shaped exposure area having a diameter substantially equal to the diameter of a circular imaging area of the projection optical system ( Step-and-scan method) has been proposed. In this method, when a projection optical system having an imaging area of the same size is used, a larger transfer area is secured as compared with the step-and-repeat method in which collective exposure is performed for each transfer area using a projection lens. be able to. That is, since there is no restriction by the optical system in the scanning direction, it is possible to secure only the stroke of the scanning stage, and it is possible to secure approximately √2 times the transfer area in the direction perpendicular to the scanning direction. .

An exposure apparatus for manufacturing a semiconductor integrated circuit is required to have an enlarged transfer area and an improved resolution in order to cope with the manufacture of a chip having a high degree of integration. The fact that a smaller projection optical system can be employed is advantageous from the viewpoint of optical performance and cost, and the exposure method of the step-and-scan method is attracting attention as a mainstream of future exposure apparatuses.

In such a step-and-scan type exposure apparatus, it is necessary to align a reticle and a wafer with high accuracy. For example, a reticle placed on a reticle stage by reticle exchange or the like is controlled by a reticle alignment scope. The position of the reticle stage with respect to the reference mark is measured with high accuracy. In this reticle scope, the higher the accuracy, the narrower the measurement range,
The measurement range of the reticle alignment scope in the 256M-compatible exposure apparatus aimed at by the present inventors is 2 μm
It is about the corner.

In a conventional reticle hand, a reticle is
It is firstly impossible to mount on a reticle stage with an error of about μm. Therefore, XYθ is placed on the reticle stage.
It is conceivable to provide a fine movement mechanism and switch the reticle alignment scope to a low magnification to drive the reticle displacement to within 2 μm. However, when the XYθ fine movement mechanism is provided on the reticle stage, the reticle stage becomes heavy, and in particular, in a scanning type exposure apparatus that scans the reticle, the moving speed of the stage becomes slow and the throughput decreases. Problems such as a decrease in exposure accuracy due to bending of the surface plate occur.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to reduce the weight of an original stage in an exposure apparatus and improve throughput and exposure accuracy. And

[0007]

In order to achieve the above object, according to the present invention, a part of an original pattern is projected onto a substrate via a projection optical system, and the original is relatively moved with respect to the projection optical system. An exposure apparatus for exposing the pattern of the original onto the substrate by scanning the substrate together with the original, and an original stage having a first air pad and holding the original placed on the air pad by suction substantially horizontally, A means for detecting a positional shift of the original on the original stage with respect to the original stage at a predetermined original alignment position, an elevating shaft vertically moving up and down at the original alignment position, and being attached to the elevating shaft via a leaf spring. A second air pad capable of adsorbing and holding the original on the original stage, and a pattern of the original adsorbed and held by the second air pad via the elevating shaft. Means for finely moving within the image plane and around an axis perpendicular to the plane, and feeding the original stage to the original alignment position, lowering the elevating shaft, and adsorbing the original on the original stage by the second air pad. Then, air is blown out from the first air pad to float the original slightly, and the detecting means detects the positional deviation, and the fine moving means is finely moved by the fine moving means according to a result of the positional deviation detection. Means.

[0008] In a preferred embodiment of the present invention,
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, wherein the original alignment position is set at a position different from the original exchanging position so as not to interfere with the operation of the original exchanging means. It is characterized by having been done. In this case, the original plate alignment position can be set to the exposure standby position of the first shot.

[0009]

According to the present invention, the fine movement mechanism for aligning the original is not mounted on the original stage, that is, the original stage is reduced in weight, so that the throughput (scan speed) and the exposure accuracy are improved. Can be achieved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a state of an exposure apparatus according to an embodiment of the present invention as viewed from the side, and FIG. 2 is a perspective view showing an appearance of the exposure apparatus. As shown in these drawings, this exposure apparatus uses a projection optical system 2 to project a part of an original pattern on a reticle stage 1 through a wafer stage 3.
The reticle and the wafer are synchronously scanned in the Y direction relative to the projection optical system 2 to expose the reticle pattern to the wafer, and this scanning exposure is performed on a plurality of transfer areas on the wafer. (Shot) is a step-and-scan type exposure apparatus which performs step movement for repeated execution.

The reticle stage 1 is driven by a linear motor 4 in the Y direction,
a is driven in the X direction by the linear motor 5, and the Y stage 3 b is driven in the Y direction by the linear motor 6. The synchronous scanning of the reticle and the wafer is performed by driving the reticle stage 1 and the Y stage 3b at a constant speed ratio in the Y direction (for example, 4: -1, where "-" indicates that the directions are opposite). Do. 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 a wafer is mounted thereon.

The wafer stage 3 is provided on a stage base 7, and the stage base 7 is connected via three dampers 8.
It is supported on a floor at a point. The reticle stage 1 and the projection optical system 2 are provided on a barrel base 9, and the barrel base 9 is supported on a base frame 10 mounted on a floor or the like via three dampers 11 and columns 12. I have. The damper 8 is an active damper for actively damping or removing vibrations in six axial directions. However, a passive damper may be used, or the damper 8 may be supported without a damper.

The exposure apparatus further includes a distance measuring means 13 such as a laser interferometer or a micro encoder for measuring the distance between the lens barrel base 9 and the stage base 7 at three points.

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 located on the focus surface of the projection optical system 2. That is, the wafer is irradiated with light from an oblique direction by the light projecting means 21 fixed to the lens barrel base 9, and the position of the reflected light is detected by the light receiving means 22, whereby the direction of the optical axis of the projection optical system 2 is adjusted. Of the wafer surface is detected.

In the apparatus shown in FIG. 1, light emitted from a laser interferometer light source (not shown) is introduced into a reticle stage Y-direction laser interferometer 24. The light introduced into the Y-direction laser interferometer 24 is transmitted to the laser interferometer 24 by a beam splitter (not shown) in the laser interferometer 24.
The light is divided into light directed toward a fixed mirror (not shown) and light directed toward the Y-direction movable mirror 26. The light traveling to the Y-direction moving mirror 26 passes through the Y-direction length measuring optical path 25 and enters the Y-direction moving mirror 26 fixed to the reticle stage 4. The light reflected here returns to the beam splitter in the laser interferometer 24 through the Y-direction length measuring optical path 25 again, and is superimposed 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 measured in this way is fed back to a scanning controller (not shown), and positioning control of the scanning position of the reticle stage 4 is performed. Similarly, the Y stage 3b controls the scanning position based on the length measurement result by the wafer stage Y direction laser interferometer 23.

In this configuration, when the wafer is loaded onto the wafer stage 3 via the transport path between the two columns 12 at the front of the apparatus by the transport means (not shown) and the predetermined alignment is completed, the exposure apparatus While repeating the scanning exposure and the step movement, the reticle pattern is exposed and transferred to a plurality of exposure regions on the wafer. At the time of scanning exposure, the reticle stage 1 and the Y stage 3b are moved at a predetermined speed ratio in the Y direction (scanning direction) to scan a pattern on the reticle with slit-like exposure light, and to project a wafer with the projected image. To expose a pattern on the reticle 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 start position of the scanning exposure and performing the scanning exposure. The combination of the step movement in the X direction and the movement for scanning exposure in the Y direction allows each of the exposure areas to be sequentially and efficiently exposed to a plurality of exposure areas on the wafer. , The scanning direction of either positive or negative Y, the order of exposure to each exposure area, and the like are set.

At the time of reticle exchange, the reticle stage 1 moves to a reticle exchange 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 the vacuum suction pad. Next, reticle stage 1 moves 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 grasp the reticle, and drives a reticle alignment stage (not shown) to align the reticle with a 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. When positioning, the reticle is held by the vacuum suction pad, and air is blown out of the vacuum suction pad of the reticle stage 1 to hold the reticle. The reticle alignment stage is driven while floating from the stage 1.

FIG. 3 shows the configuration of the reticle alignment mechanism in the apparatus shown in FIG. In this apparatus, the reticle alignment mechanism is not mounted on the reticle stage, but is separately provided, thereby reducing the weight of the reticle stage, increasing the scanning speed, and improving the throughput. In the figure, reference numeral 1 denotes a reticle stage, a solid line indicates a state at a reticle alignment position, and a two-dot chain line indicates a state at a reticle exchange position (left side in the figure) or an exposure area (right side in the figure). Show. 2
Is a projection optical system (projection lens), 3 is a wafer stage, 3
1 is an illumination optical system, 32 is a reticle changer, 33 is a substrate position detection microscope (reticle alignment scope),
34 is a reticle, 35 is a reference mark provided on the reticle stage 1, 36 is a reticle handler, 37 is a reticle alignment stage support, 38 is a reticle alignment stage support member, 39 is a reticle stage guide, 40 is a wafer, and 41 is a wafer stage It is a guide.

FIG. 4 shows the operation of each unit during reticle exchange and reticle alignment. That is, when the reticle is replaced, the reticle stage 1 is in the reticle replacement position (FIG. 4).
(A position shown in (a)). At the same time, a new reticle 34 is transported from a reticle library or the like (not shown) by a transport unit (not shown), and the reticle changer 32
The reticle changer 32 places the reticle on the reticle stage 1 at the reticle exchange position.
The reticle stage 1 is provided with a reticle chuck 56, as shown in FIG.
4 is sucked in vacuum by a reticle chuck 56 and held on the reticle stage 1. In FIG. 5, reference numeral 54 denotes a reticle stage top plate.

At the time of reticle alignment, reticle stage 1 moves to a reticle alignment position (a 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 descends and the reticle is attracted by the reticle suction pad 53 attached to the lower end of the lifting 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 reticle 34 is slightly smaller than the reticle chuck 56 by the air flow (for example, if the focal depth of the reticle alignment scope 33 is 10 μm, the reticle 34 2 to several μ that does not deviate from the depth of focus
m) (FIG. 5 (c)).

In this state, the reticle alignment scope 33 detects a position shift between the reference mark 35 and an alignment mark (not shown) formed on the reticle 34, and corrects the position shift so as to correct the position shift. Drive. Further, the air blowing of the reticle chuck 56 is turned off and the vacuum is turned on, and the reticle 34 is vacuum-sucked to the reticle chuck 56.
Next, the reticle suction pad 5 of the reticle handler 36
The reticle 34 aligned with the vacuum of 3 is turned off and transferred to the reticle stage 1, and the reticle handler 36 is raised (FIG. 4C).

When the reticle alignment is completed, the alignment marks on the reticle 34 and the reference marks 3 on the reticle stage 1 are
5 is measured, and XYθ of the wafer on the wafer stage 3 is set based on the measured value and the remaining alignment error of the wafer, and scanning exposure is performed.

Note that the reticle alignment can be appropriately performed other than when the reticle is replaced.

In detecting the above-mentioned positional deviation, before lowering the reticle handler 36, first, the reticle 3
4 is observed with a reticle alignment scope 33, and if the alignment mark of the reticle 34 is within the measurement range of the reticle alignment scope 33, the above-described position shift amount measurement and scanning exposure are performed without performing the above-described positioning processing. You can also do it. In this case, when 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 not changed without changing the magnification of the reticle alignment scope 33. Is detected, and if 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 alignment mark is Is detected. This magnification switching is performed in parallel with the lowering of the reticle handler 36. When the magnification is changed, the magnification is returned to the original state in parallel with the rise of the reticle handler 36.

FIG. 6 shows a flow chart of manufacturing 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), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. On the other hand, in step 3 (wafer manufacturing), 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 called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). 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, a semiconductor device is completed and shipped (step 7).

FIG. 7 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. 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.

By using the manufacturing method of this embodiment, a highly integrated semiconductor device, which was conventionally difficult to manufacture, can be manufactured at low cost.

[0028]

As described above, according to the present invention, the original plate alignment mechanism is not mounted on the original plate stage, but is separately provided. Therefore, the original plate stage is reduced in weight, the scanning speed of the original plate stage is increased, and the throughput is improved. Can be improved. In addition, the deflection of the stage base and the like due to the weight of the original stage can be reduced, and the exposure accuracy can be improved.

Further, since the original adsorbing portion of the alignment mechanism is elastically supported, it is possible to increase the allowable error of the amount of descent of the original adsorbing portion.
There is no need to provide a mechanism, and the original can be positioned at high speed.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a state of an exposure apparatus according to one embodiment of the present invention when viewed from a side.

FIG. 2 is a perspective view showing an appearance of the exposure apparatus of FIG.

FIG. 3 is an explanatory diagram of a reticle alignment mechanism in the apparatus of FIG.

FIG. 4 is an explanatory diagram of a reticle exchange and alignment process in the apparatus of FIG. 1;

FIG. 5 is a more detailed explanatory diagram of a reticle alignment process shown in FIG. 4;

FIG. 6 is a diagram showing a flow of manufacturing a micro device.

FIG. 7 is a diagram showing a detailed flow of a wafer process in FIG. 6;

[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 base, 8: damper, 9: lens barrel base, 10: base frame, 11: damper, 12: support, 13: distance measuring means,
21: light emitting means, 22: light receiving means, 23, 24: laser interferometer, 25: laser measuring optical path, 26, 27: moving mirror,
31: illumination optical system, 32: reticle changer, 33:
Reticle alignment scope, 34: reticle, 3
5: fiducial 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: elevating axis (Z axis), 52: leaf spring, 53: reticle suction pad, 54: reticle stage top plate, 56: reticle chuck.

Claims (4)

[Claims] 1. A pattern of an original is projected onto a substrate by projecting a part of the pattern of the original onto a substrate via a projection optical system and scanning the original and the substrate together with respect to the projection optical system. An exposure apparatus for exposing, comprising: a first air pad, a master stage for holding a master placed on the air pad in a substantially horizontal suction state, and determining a positional shift of the master on the master stage with respect to the master stage. Means for detecting at the original plate alignment position, an elevating shaft which rises and falls substantially vertically at the original plate alignment position, and a second air which is attached to the elevating shaft via a leaf spring and which can hold the original plate on the original plate stage by suction. A pad and a hand for finely moving the original sucked and held by the second air pad in the pattern drawing plane of the original and around an axis perpendicular to the plane via the elevating shaft. Sending the original stage to the original alignment position, lowering the elevating shaft, adsorbing the original on the original stage with the second air pad, and blowing air from the first air pad to remove the original. Float a small amount,
An exposure apparatus, comprising: a control means for causing the detecting means to detect the position shift, and finely moving the original by the fine moving means in accordance with the result of the position shift detection. 2. An original exchanging means for exchanging an original on the original stage at a predetermined original exchanging position outside an exposure area, wherein the operation of the original exchanging means in which the original alignment position is different from the original exchanging position. 2. The exposure apparatus according to claim 1, wherein the exposure apparatus is set at a position where no interference occurs. 3. The exposure apparatus according to claim 2, wherein the original plate alignment position is a first shot exposure standby position. 4. A device manufacturing method using the apparatus according to claim 1.