JP4261706B2 - Exposure apparatus and device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure apparatus used for manufacturing semiconductor elements and a device manufacturing method using the same.
[0002]
[Prior art]
Conventionally, an apparatus called a stepper and an apparatus called a scanner are known as exposure apparatuses used for manufacturing semiconductor elements. The stepper moves the semiconductor wafer on the stage device stepwise under the projection lens, and reduces and projects the pattern image formed on the reticle onto the wafer with the projection lens, and sequentially exposes to multiple locations on a single wafer. It is something to do. The scanner moves the semiconductor wafer on the wafer stage and the reticle on the reticle stage relative to the projection lens, irradiates slit-shaped exposure light during the scanning movement, and projects the reticle pattern onto the wafer. . Steppers and scanners are regarded as mainstream exposure apparatuses in terms of performance in terms of resolution and overlay accuracy.
[0003]
FIG. 9 is a schematic top view of a wafer stage used in such an exposure apparatus. As shown in the figure, a wafer 102 to be exposed is mounted on a wafer stage 101 via a wafer chuck (not shown). With the exposure optical system as a reference, the position of the exposure optical axis center 103 can be considered as immovable. Therefore, the wafer stage 101 needs to move in the XY directions with respect to the exposure optical axis center 103 in order to expose the entire wafer surface. The wafer 102 needs to move in the Z direction and the tilt direction in order to adjust the imaging focus, but the description is omitted here. A high-resolution laser interferometer is used for measuring the position of the wafer stage 101 in the X and Y directions in order to achieve highly accurate positioning. In order to use the laser interferometer, it is necessary to provide the reflecting mirrors 107 and 108 for reflecting the laser beam on the wafer stage 101. However, the reflecting mirrors 107 and 108 are required to have a length longer than the moving distance of the wafer stage 101 in order to reflect the laser beam in the entire moving range of the wafer stage 101. That is, when the stage moving distance in the Y direction is Ly, the length Lx of the reflecting mirror 107 for measuring the X direction position needs to be equal to or larger than Ly.
[0004]
The movement range of the wafer stage 101 may be slightly larger than the wafer diameter if only exposure is performed. However, actually, the movement of the wafer stage 101 is not for performing only the exposure operation. In order to expose the wafer 102, it is necessary to align the imaging point with high accuracy. There are several types of alignment methods, and a method is widely used in which an alignment mark on a wafer that has been exposed and transferred in advance is irradiated with alignment light and the amount of misalignment is obtained from the reflected light. In this alignment technique, the alignment optical axis center and the exposure optical axis center may not be the same.
[0005]
FIG. 10 shows a conventional wafer stage when the alignment optical axis center 104 and the exposure optical axis center 103 do not coincide. As shown in the figure, the alignment optical axis center 104 is irradiated onto the wafer at a certain distance L2 from the exposure optical axis center 103. The wafer stage 101 must move the wafer 102 in the XY direction so as to irradiate the alignment light on the entire wafer surface in the same manner as the wafer 102 needs to move in the XY direction to expose the entire wafer surface. For this purpose, the movable range of the wafer stage 101 needs to be increased by the amount of deviation between the alignment optical axis center 104 and the exposure optical axis center 103. Therefore, it is necessary to lengthen the reflecting mirror 107 by an amount corresponding to the expansion of the moving range of the wafer stage 101. Referring to FIG. 10, the length Lx2 of the reflecting mirror 107 for measuring the X-direction position becomes longer by the deviation L2 between the alignment optical axis 104 and the exposure optical axis 103.
[0006]
[Problems to be solved by the invention]
However, in order to lengthen the reflecting mirror 107, there are the following problems. That is, (1) it is difficult to create a long reflector with a high-precision mirror surface, (2) it takes a lot of cost to create a mirror surface of a long reflector, and (3) the weight of the reflector itself is increased. The weight of the entire stage increases, (4) heat generation of the stage drive device increases due to the increase in the stage weight, and (5) the natural frequency of the mechanical system of the stage decreases to deteriorate the characteristics of the control system. .
[0007]
Therefore, the present invention relates to an exposure apparatus and a device manufacturing method using the same, even if the alignment optical axis and the exposure optical axis are separated from each other, an object necessary for position measurement such as a reflecting mirror and a linear scale mounted on the stage according to the alignment optical axis It is an object of the present invention to improve the throughput and accuracy while making it unnecessary to lengthen the time.
[0008]
In order to solve this problem, a first exposure apparatus of the present invention includes an exposure unit that exposes an original pattern at each exposure position on a sequentially positioned substrate, a stage for controlling the position of the substrate, An alignment optical system for performing alignment measurement on the substrate, a reflecting mirror fixed to the stage and extending in a predetermined direction, and measuring the position of the stage in a direction substantially perpendicular to the predetermined direction, with respect to the exposure optical axis The exposure laser interferometer for positioning the substrate and the distance from the reflecting mirror is substantially the same as the distance from the reflecting mirror to the exposure laser interferometer, and a direction substantially perpendicular to the predetermined direction of the stage An alignment laser interferometer that measures the position of the substrate and positions the substrate with respect to the alignment optical system, and position measurement for position control of the substrate. Serial and a switching means for switching between a position measurement by the exposing laser interferometer position measurement of the alignment laser interferometer, finally exposed by the exposure position of the exposure position on the substrate is the reflection The exposure order is determined so as to be farthest from the mirror, and after the last exposure position is exposed, switching by the switching means is performed at the stage position when the last exposure position is exposed. And
[0009]
The second exposure apparatus is characterized in that in the first exposure apparatus, there is laser light blocking means for independently blocking the laser beams irradiated from the laser interferometers to the reflecting mirror .
[0010]
According to a third exposure apparatus, in the second exposure apparatus, the laser beam blocking unit includes a light blocking unit and a driving device for driving the light blocking unit, and blocks the laser beam according to the position of the stage. It is characterized by changing the area .
[0011]
According to a fourth exposure apparatus, in the third exposure apparatus, the laser beam blocking means is a fixed light shielding plate .
[0012]
The device manufacturing method of the present invention includes a step of preparing any one of the first to fourth exposure apparatuses, and a step of performing exposure using the exposure apparatus.
[0018]
【Example】
FIG. 1 is a schematic top view of a wafer stage of an exposure apparatus according to an embodiment of the present invention. This exposure apparatus performs alignment measurement on a wafer 2 and a projection optical system for exposing a reticle pattern to each exposure position on the wafer 2 that is sequentially positioned, a wafer stage 1 for controlling the position of the wafer 2, and the wafer 2. In order to perform the alignment optical system to perform the position control of the wafer 2, the position corresponding to the position of the wafer stage 1 in the Y direction on the reflecting mirror 8 that is fixed to the wafer stage 1 and extends in the X and Y directions, A position measuring means for measuring the position in the X direction. The position measuring means includes an exposure X measurement interferometer 6 for positioning the wafer 2 with respect to the exposure optical axis 3, and a measurement optical axis 4 of the alignment optical system. And an alignment X measurement interferometer 7 for positioning the wafer 2 with respect to.
[0019]
A wafer 2 is mounted on the wafer stage 1 via a wafer chuck (not shown). The wafer stage 1 is supported to move freely with respect to a surface plate (not shown) in the XYZ directions and the rotation directions around these axes, and a linear motor (not shown) serves as an actuator for driving the wafer stage 1 in the movement direction. It is installed. An alignment optical system is configured next to the projection optical system. The alignment optical system uses light having a wavelength different from that of the exposure light, and the alignment optical axis center 4 does not coincide with the exposure optical axis center 3 but is located away from the Y-axis direction.
[0020]
The exposure apparatus also includes a first Y interferometer (not shown) and a first Y receiver (not shown) that measure the position of the wafer stage 1 in the Y direction, so that the Y passes through the exposure optical axis center 3 and the alignment optical axis center 4. The reflected light of the first Y interferometer measuring light 5a irradiated on the reflecting mirror 8 from the direction is measured. An exposure X interferometer 6 and an X receiver (not shown) for measuring the position of the wafer stage 1 in the X direction pass through the exposure optical axis center 3 and the exposure X measurement light 6a irradiated on the reflecting mirror 8 from the X direction. The reflected light 6b is measured. An alignment X measurement interferometer 7 and an alignment X receiver (not shown) for alignment X measurement are reflected light of the alignment X interferometer measurement light 7 a that is applied to the reflecting mirror 8 from the X direction so as to pass through the alignment optical axis center 4. 7b is measured. In addition, a second Y interferometer (not shown) that measures the rotational position θz around the Z axis in cooperation with the first Y interferometer is provided. The second Y interferometer measures the reflected light of the second Y interferometer measurement light 5b irradiated on the reflecting mirror 8 from the Y direction in parallel with the first Y interferometer measurement light 5a. There are also provided three laser interferometers (not shown) for measuring the position of the wafer stage 1 in the Z direction, the rotational direction position θx around the X axis, and the rotational direction position θy around the Y axis. Note that the measurement of the positions Z, θx, and θy of the wafer stage 1 does not have to be performed by a laser interferometer, and may be performed using an optical or magnetic linear scale.
[0021]
The wafer stage 1 is positioned with high accuracy by a wafer stage control system (not shown) based on a position measurement value of the wafer stage 1 and a position target value command to the wafer stage 1.
[0022]
The positions of the exposure X measurement interferometer 6 for measuring in the X direction and the alignment X measurement interferometer 7 for alignment X measurement, and the size of the reflecting mirror 8 provided on the wafer stage 1 are as follows. It has become a relationship. The wafer stage 1 is required to have a movement range sufficient to expose the entire surface of the wafer 2. Therefore, the reflecting mirror 8 of the wafer stage 1 has a length sufficient to measure the position of the wafer stage 1 in the X direction by the exposure X measurement interferometer 6 at an arbitrary wafer stage position during wafer exposure. Similarly, the wafer stage 1 is required to have a movement range sufficient for performing alignment measurement on the entire wafer surface during alignment measurement. Therefore, the reflecting mirror 8 of the wafer stage 1 is long enough to measure the position of the wafer stage 1 in the X direction by the alignment X measurement interferometer 7 for alignment X measurement at any wafer stage position during alignment measurement. Have
[0023]
Conventionally, measurement of the wafer stage 1 in the X direction during wafer exposure and alignment measurement has been performed with one laser interferometer that performs measurement in the X direction. However, the reflecting mirror 8 provided on the wafer stage 1 is desirably as small as possible. Therefore, in this embodiment, at least two interferometers for measuring the wafer stage 1 in the X direction are provided, and at least one of the interferometers irradiates the reflecting mirror 8 of the wafer stage 1. In this case, in the wafer stage moving area at the time of exposure (hereinafter referred to as “moving area at the time of exposure”), the alignment X measurement light 7 a may deviate from the reflecting mirror 8 in some cases. In addition, in the wafer stage movement region during alignment measurement (hereinafter, referred to as “alignment movement region”), the exposure X measurement light 6 a may deviate from the reflecting mirror 8 in some cases. Since the laser interferometer cannot measure the absolute value of the position, once the measurement optical axis of the interferometer deviates from the reflecting mirror, it is necessary to redetect the origin (zero point) using another sensor or physical contact. There is. However, in this embodiment, since the length of the reflecting mirror 8 is larger than the interval between the exposure X measuring light 6a and the alignment X measuring light 7a, one of the measuring lights is always applied to the reflecting mirror 8. Both measurements will not be disabled at the same time. Therefore, even if one of the measurement optical axes deviates from the reflecting mirror 8 and measurement becomes impossible, when the wafer stage 1 moves to a position where the measuring light is again irradiated on the reflecting mirror 8, the measurement value of the other interferometer is measured. And the interferometer measurement value can be reset from the measurement value in the θz direction.
[0024]
Further, the measurement accuracy by the laser interferometer is affected by changes in the temperature, pressure, etc. of the medium. When the medium is air at normal temperature and pressure, the measurement accuracy is about 1 ppm / ° C. However, in this embodiment, the distance between the exposure X measurement interferometer 6 and the alignment X measurement interferometer 7 and the reflecting mirror 8 is set at substantially the same distance, so that the length measurement of each interferometer affected by temperature is performed. The accuracy is the same, and the setting error due to the resetting of the interferometer measurement values is small.
[0025]
Further, if the laser beam is separated from the reflecting mirror 8, the laser beam hits the structural member of the exposure apparatus, and the laser beam is unintentionally emitted outside the exposure apparatus, or the removed laser beam is measured by other measurement. The measurement accuracy of the system may be deteriorated. Therefore, in this embodiment, a light shielding plate 9 for shielding the laser light deviated from the reflecting mirror 8 and a driving device 10 for driving the light shielding plate 9 are provided, and before the laser light is detached from the reflecting mirror 8. The laser beam can be shielded. In order to prevent reflection, the light shielding plate 9 is made of a material having a high absorptance with respect to the wavelength of the laser light, or is subjected to surface processing.
[0026]
Next, stage movement during exposure in the exposure apparatus of the present embodiment will be described with reference to FIGS. As shown in FIG. 2, in this embodiment, the stage is moved in the exposure order of exposure positions S1, S2, S3, Sx, Sy, and Sz, and then the length measurement value by the exposure X measurement interferometer 6 is used as the alignment X measurement interferometer. 7 is transferred to the length measurement value 7 and the alignment X measurement interferometer 7 is reset. According to this, since the exposure position Sz at which the distance between the exposure X measurement interferometer 6 and alignment X measurement interferometer 7 and the reflecting mirror 8 is the shortest is exposed lastly, the interferometer measurement values are reset accurately. Furthermore, since it is not necessary to move to the position where the distance between the exposure X measurement interferometer 6 and the alignment X measurement interferometer 7 and the reflecting mirror 8 becomes the shortest after the exposure, it is possible to quickly shift to alignment measurement. It becomes possible.
[0027]
Further, the length measurement value is transferred between the exposure X measurement interferometer 6 and the alignment X measurement interferometer 7 within the range where the exposure region (exposure field of the exposure optical system) is on the substrate as shown in FIG. The measurement may be performed at the exposure position Sa where the distance between the measurement interferometer 6 and the alignment X measurement interferometer 7 and the reflecting mirror is shortest, or when the exposure optical axis is outside the substrate as shown in FIG. . As a result, it is possible to more accurately transfer the measurement value between the exposure X measurement interferometer 6 and the alignment X measurement interferometer.
[0028]
By the way, as shown in FIG. 3, during exposure, the laser beam from the alignment X measurement interferometer 7 may come off the reflecting mirror 8 at a certain exposure position. In this case, in this embodiment, the laser light to the alignment X measurement interferometer 7 can be shielded by the light shielding plate 9 before the laser light is detached from the reflecting mirror 8. In the present embodiment, the light shielding plate 9 is installed on the upstream side of the alignment X measurement interferometer 7, but it may be arranged on the downstream side. In addition, it is not necessary to block the entire beam diameter of the laser beam, and at least only a portion that is off the reflecting mirror 8 may be blocked.
[0029]
As described above, the measurement in the X-axis direction has been described in the present embodiment, but the present invention is not limited to this, and the exposure optical axis and the alignment optical axis are shifted in the X-axis direction. Therefore, the present invention may be applied when an interferometer for alignment Y measurement that performs alignment measurement in the Y-axis direction is provided.
[0030]
FIG. 6 is a schematic top view of a wafer stage of an exposure apparatus according to another embodiment of the present invention. In order to shield the laser light coming off the reflecting mirror 8, a light shielding plate 11 fixed further downstream of the wafer stage downstream from the exposure X interferometer and alignment X interferometer 7 is installed. According to the present embodiment, since a driving device for driving the light shielding plate 11 is not required, the configuration is simplified.
[0031]
<Example of Device Manufacturing Method>
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 7 shows a flow 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), a device pattern is designed. In step 2 (mask production), a mask on which the designed pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. 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 for forming a semiconductor chip using the wafer produced in step 4, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, a semiconductor device is completed and shipped (step 7).
[0032]
FIG. 8 shows a detailed flow of the wafer process (step 4). 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 resist is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is arranged in a plurality of shot areas on the wafer and printed by exposure using the above-described exposure apparatus or exposure method. 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 repeatedly performing these steps, multiple circuit patterns are formed on the wafer.
[0033]
According to the device manufacturing method of the present embodiment, since it is not necessary to fix a long reflecting mirror on the wafer stage used at the time of exposure, exposure with good positioning characteristics is performed with a simple and low-cost apparatus, and efficiency is improved. Devices can be manufactured.
[0034]
【The invention's effect】
As described above, according to the present invention, as the position measuring means, an alignment laser interferometer for positioning the substrate relative to the exposing laser interferometer and the alignment optical system for positioning the substrate with respect to the exposure optical axis was placed so that at substantially the same distance from the reflecting mirror on the stage, when the switching between the exposing laser interferometer and alignment laser interferometer is performed, and finally the exposure of each exposure position on the substrate The exposure position is arranged to be farthest from the reflecting mirror . This eliminates the need for extra stage movement to reduce the error at the time of switching, thus improving the throughput of the exposure apparatus.
[0035]
Further, since the laser beam blocking means is provided , the laser beam coming off the reflecting mirror can be shielded and the laser beam can be prevented from going out of the exposure apparatus. Therefore, it is possible to prevent an unexpected accident for the worker .
[Brief description of the drawings]
FIG. 1 is a schematic top view of a wafer stage of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing movement of a wafer stage accompanying exposure in the apparatus of FIG.
FIG. 3 is a diagram showing a state of shielding a laser beam in the apparatus of FIG.
4 is a view showing another example of the movement of the wafer stage accompanying exposure in the apparatus of FIG. 1. FIG.
FIG. 5 is a view showing still another example of the movement of the wafer stage accompanying exposure in the apparatus of FIG.
FIG. 6 is a schematic top view of a wafer stage of an exposure apparatus according to another embodiment of the present invention.
FIG. 7 is a flowchart showing a device manufacturing method that can use the exposure apparatus of the present invention.
FIG. 8 is a detailed flowchart of the wafer process in FIG. 7;
FIG. 9 is a schematic top view of a conventional wafer stage.
FIG. 10 is a schematic top view of another conventional wafer stage.
[Explanation of symbols]
1: wafer stage, 2: wafer, 3: exposure optical axis center, 4: alignment optical axis center, 5a: first Y interferometer measurement light, 5b: second Y interferometer measurement light, 6: exposure X measurement interferometer, 6a : Exposure X measurement light, 6b: Exposure X reflected light, 7: Alignment X measurement interferometer, 7a: Alignment X measurement light, 7b: Alignment X reflected light, 8: Reflective mirror, 9, 11: Shading plate, 10: Drive Apparatus: 12: exposure X interferometer optical axis, 13: alignment X interferometer optical axis, 101: wafer stage, 102: wafer, 103: exposure optical axis center, 104: alignment optical axis center, 107, 108: reflecting mirror, S1, S2, S3, Sa, Sx, Sy, Sz: exposure positions.

Claims (5)

Exposure means for exposing the pattern of the original plate at each exposure position on the substrate that is sequentially positioned;
A stage for controlling the position of the substrate;
An alignment optical system for performing alignment measurement on the substrate;
A reflecting mirror fixed to the stage and extending in a predetermined direction;
An exposure laser interferometer that measures the position of the stage in a direction substantially perpendicular to the predetermined direction and positions the substrate with respect to the exposure optical axis;
The distance from the reflecting mirror is substantially the same as the distance from the reflecting mirror to the exposure laser interferometer, and the position of the stage in the direction substantially perpendicular to the predetermined direction is measured, and the substrate relative to the alignment optical system is measured. An alignment laser interferometer for positioning;
Switching means for switching position measurement for position control of the substrate between position measurement by the exposure laser interferometer and position measurement of the alignment laser interferometer,
The exposure order is determined so that the exposure position exposed last among the exposure positions on the substrate is farthest from the reflecting mirror,
An exposure apparatus characterized in that after the last exposure position is exposed, switching by the switching means is performed at the stage position when the last exposure position is exposed .  The exposure apparatus according to claim 1, further comprising a laser beam blocking unit that blocks the laser beam irradiated to the reflecting mirror from each laser interferometer.  3. The laser light blocking means includes a light blocking means and a driving device for driving the light blocking means, and changes the laser light blocking area according to the position of the stage. The exposure apparatus described in 1.  4. The exposure apparatus according to claim 3, wherein the laser beam blocking means is a fixed light blocking plate. A device manufacturing method characterized in that it comprises a step of exposing a substrate using an exposure apparatus according to any of claims 1 to 4, a step of developing the exposed said substrate.

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