JP2002367878A - Alignment correcting method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alignment correcting method and an aligner wherein errors in shot components can be corrected with accuracy. SOLUTION: A reticle 2 and the reference plate 13 of a wafer stage 5 are respectively provided with first and second slit marks 11A, 11B, 12A, and 12B comprising straight patterns orthogonal to each other. Exposure light L is transmitted through the first slit marks 11A and 11B on the reticle 2 side and the wafer stage 5 side and the second slit marks 12A and 12B on the reticle 2 side and the wafer stage 5 side, and the transmitted light is detected by a photodetector 14. Based on the level of the received light, the relative position between the reticle 2 and the wafer stage 5 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment correction method and an exposure apparatus suitable for use in a photolithography process in the manufacture of a semiconductor device, for example, for aligning a reticle and a wafer stage.

[0002]

2. Description of the Related Art Conventionally, in a photolithography process in the manufacture of a semiconductor device, a liquid crystal display device, or the like, a circuit pattern formed on a reticle or a mask (hereinafter, simply referred to as a reticle) is exposed to a semiconductor wafer through a projection optical system. A projection exposure apparatus that performs projection exposure on a glass substrate (hereinafter, simply referred to as a wafer) is used.

An exposure apparatus of this type generally includes a light source for irradiating exposure light, a reticle stage for supporting a reticle,
It is composed of a wafer stage on which a wafer is placed, and a projection lens arranged between these two stages. In such an exposure apparatus, since a plurality of layers of patterns are formed on a wafer in an overlapping manner, a pattern already formed on the wafer and a pattern to be transferred next can be accurately aligned (aligned). Required.
For this reason, when forming a circuit pattern on a wafer, highly accurate alignment work between the reticle stage and the wafer stage is performed for each layer.

FIG. 9 shows a flow example of a conventional alignment operation. First, reticle alignment is performed (step S1). A reference mark for alignment is provided on the reticle, and alignment with the reference mark on the exposure apparatus side is performed using the reference mark. Subsequently, the measurement of the baseline amount is performed (step S2). In the measurement of the baseline amount, the movement amount (displacement amount) of the wafer stage from the alignment position determined based on the alignment reference mark to the actual exposure position is measured. The amount of movement of the wafer stage is detected, for example, by a length measurement value of a laser interferometer, and based on the detected value, the coordinate position (X, Y) from the origin position of the wafer stage.
Is measured.

In general, the alignment position can fluctuate due to various causes such as a mechanical error of the exposure apparatus itself and a reticle manufacturing error. At this time, as shown in FIG. 10A, when the actual position (solid line, the same applies hereinafter) is offset in the X and Y directions with respect to the designed position (the dashed line, the same applies hereinafter), Correction, that is, correction of the coordinate position of the alignment mark is performed. If there are errors due to wafer scaling (FIG. 10B), errors due to wafer rotation (FIG. 10C), errors due to wafer orthogonality (FIG. 10D), etc., alignment correction of wafer components is performed to cancel these errors (FIG. 10B). Step S3). After relative positioning between the reticle and wafer stage has been performed as described above,
Production of a product wafer (exposure operation) is started (step S4).

However, the shot component errors shown in FIGS. 11A and 11B cannot be corrected by the above-described wafer alignment. Therefore, conventionally, a method has been used in which a reference wafer is prepared and periodically burned to correct the fluctuation amount. For example, when there are four exposure apparatuses A to D,
The wafer exposed by the A-unit is etched by using the A-unit as a reference unit to prepare a reference wafer. Then, using this reference wafer, baking at each unit periodically,
As shown in FIGS. 11A and 11B, shot scaling (FIG. 11A) and shot rotation (FIG. 11B)
Is corrected when it does not overlap with the shot of the reference wafer.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 2000-81712, there is also an example in which a so-called trend method is adopted in which the value is fed back to the next lot for each lot processing with respect to minute fluctuations every day. is there. For example, as shown in FIG. 12, when working on the next lot (No. 16), the offset amount is determined in consideration of the results of the previous time (No. 15). In this scheme,
This is performed for each of the six types of components shown in FIGS.

[0008]

However, in the current exposure apparatus in which the line width is reduced to 0.18 .mu.m or less, even if slight pressure fluctuations occur in the exposure apparatus, the constituent lens groups of the projection optical system are not affected. The shot component fluctuates by about 0.015 to 0.020 μm due to a change in the geometrical arrangement, the refractive index of the air layer formed between the lenses, and the like. Then, it is difficult to cope with further miniaturization of the exposure pattern.

In other words, as the process becomes more complicated and finer, the reticle alignment standard with respect to the wafer becomes stricter, and the reproduction rate deteriorates due to shot component errors.

An object of the present invention is to provide an alignment method and an exposure apparatus which can perform shot component error correction with high accuracy.

[0011]

In order to solve the above-mentioned problems, an alignment correction method according to the present invention provides a reticle and a wafer stage with first and second slit marks each having a linear pattern orthogonal to each other. The first slit mark on the reticle side and the wafer stage side, and the second slit mark on the reticle side and the wafer stage side, respectively, the received light intensity of the transmitted light when the exposure light is transmitted. Based on this, the relative position between the reticle and the wafer stage is corrected.

In the present invention, when correcting the relative position between the reticle and the wafer stage, the two slit marks are provided on both the reticle side and the wafer stage side, and one slit mark on the reticle side is Exposure light is transmitted to the corresponding one of the slit marks on the wafer stage side, and the alignment position is corrected based on the received light intensity of the transmitted light. In other words, if the image of the exposure light transmitted through the slit mark on the reticle side completely overlaps with the slit mark on the wafer stage side, the light reception level of the exposure light transmitted from the slit mark on the wafer stage side becomes the maximum, If the overlap is slightly deviated, the light receiving level of the exposure light decreases. Then, by performing the alignment between the reticle and the wafer stage so that the light receiving level of the exposure light becomes the maximum, it is possible to realize the highly accurate alignment between the reticle and the wafer stage.

Particularly, since the slit marks provided on both the reticle side and the wafer stage side have patterns orthogonal to each other, a highly accurate positioning action in the X and Y2 directions is ensured by these two slit marks. be able to. Thereby, highly accurate alignment correction of the shot component can be performed. At this time, if any one of the slit marks provided on the reticle side is provided in parallel and separated from each other, alignment between the reticle and the wafer stage is performed by performing alignment using the pair of slit marks. Can be corrected in the rotation direction.

On the other hand, the exposure apparatus of the present invention is provided on both the reticle and the wafer stage, and includes first and second slit marks formed of linear patterns orthogonal to each other, and first and second slit marks on the reticle side and the wafer stage side. A slit detector, and a photodetector that receives exposure light transmitted through the second slit mark on the reticle side and the second slit mark on the wafer stage side in a superimposed state, and a scanning unit that swings the wafer stage. It is characterized by having.

Exposure light transmitted through the first and second slit marks on the reticle side and the wafer stage side is detected by the photodetector. At this time, by detecting the exposure light while swinging the wafer stage by the scanning means, and detecting the stage position when the light receiving level is the maximum, it is possible to know the positional deviation amount between the reticle and the wafer stage. it can.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an outline of an exposure apparatus according to an embodiment of the present invention. Exposure apparatus 1 of the present embodiment includes a reticle stage 3 that supports reticle 2 on which a predetermined reticle pattern is formed, a wafer stage 5 on which wafer 4 is mounted, and a reticle stage 3 and a wafer stage 5. A projection lens 6 as a projection optical system and a light source 15 for irradiating exposure light L.
In FIG. 1, the Z axis is taken parallel to the optical axis LX of the projection lens 1, and the X axis and the Y axis are taken in two directions orthogonal to each other in a plane perpendicular to the Z axis.

The reticle stage 3 is provided on the object plane side (+ Z direction side) of the projection lens 6, supports the periphery of the reticle 2 on which a predetermined circuit pattern is formed, and has a center on the optical axis LX of the projection lens 6. And a fine movement in the X and Y directions within a plane perpendicular to the optical axis LX. The other wafer stage 5 is provided on the image plane side (−Z direction side) of the projection lens 6, supports the wafer 4 on which the reticle pattern is to be transferred, and drives the X direction and Y direction drive motors 7 (only the X direction in the figure). ), It is possible to move in the X and Y directions. The drive motor 7 is constituted by a stepping motor or the like capable of controlling the feed amount with high accuracy. Further, the projection lens 6 in the present embodiment is configured as a reduction projection lens that forms a reticle pattern image formed on the reticle 2 on the wafer 4 at a reduction rate of 1/5.

Both the reticle stage 3 and the wafer stage 5 are configured so that the amounts of movement in the X and Y directions are detected by the laser interferometers 8 and 9. The outputs (measured values) of the laser interferometers 8 and 9 are output from the alignment controller
0 is supplied. The alignment control unit 10 is configured to adjust the amount of movement of the reticle stage 3 and the wafer stage 5 based on these outputs.

FIG. 2 shows the configuration of the reticle 2 supported by the reticle stage 3 (the circuit pattern and the reticle alignment reference marks are not shown). The reticle 2 has a square shape, a first slit mark 11A is provided on one side 2a, and second slit marks 12A, 12A are provided on two side parts 2b, 2b orthogonal to the one side 2a. Are provided in parallel and separated from each other.

As shown in FIGS. 4A and 4B, the first slit mark 11A is composed of a plurality of linear patterns parallel to the X direction, and the second slit marks 12A, 12A
It is composed of a plurality of linear patterns parallel to the Y direction. Therefore, the linear patterns of the first and second slit marks 11A and 12A have a relationship orthogonal to each other. The pattern interval (slit width) of each of the first and second slit marks 11A and 12A is set to five times the wavelength of the exposure light. In this embodiment, for example, a KrF excimer laser having a wavelength of 248 nm is used as the exposure light L.

Referring to FIG. 1, at the edge of wafer stage 5, first and second slit marks 11B and 11B corresponding to the first and second slit marks on reticle 2 side, respectively.
A reference plate 13 on which 12B is formed is arranged. In the present embodiment, as shown in FIG.
The slit marks 11B and 12B are composed of a plurality of linear patterns provided on the upper surface of the reference plate 13. The slit width of the slit marks 11B and 12B provided on the reference plate 13 side is made equal to the wavelength of the exposure light L.

Below the reference plate 13 having the above structure,
A photodetector 14 for receiving exposure light L passing through the first and second slit marks 11B and 12B is movably disposed (FIG. 1). The photodetector 14 includes a light-receiving sensor having a known configuration capable of detecting a light-receiving level of the exposure light L passing through the first and second slit marks 11B and 12B.
The output is supplied to the alignment control unit 10.

When the transmitted light is detected by the photodetector 14, the wafer stage 5 is configured to swing by a predetermined amount (X or Y direction) by a drive motor 7 or the like. The drive control of the drive motor 7 and the like at this time is performed by the alignment control unit 10, and the alignment control unit 10 constitutes a scanning unit according to the present invention.

Next, through the operation of the present embodiment, the alignment method and the exposure apparatus 1 according to the embodiment of the present invention will be described.
Will be described.

FIG. 6 is a flowchart for explaining the operation of the embodiment of the present invention. First, reticle alignment is performed (step S11). The reticle 2 is provided with a reference mark (not shown) for alignment, and the alignment with the reference mark on the exposure apparatus 1 side is performed using the reference mark. The reticle alignment is performed by slightly moving the reticle stage 3 in the X and Y directions by the alignment control unit 10, and the amount of the movement is detected by the laser interferometer 8.

Subsequently, the measurement of the baseline amount is performed (step S12). In the measurement of the baseline amount, the movement amount (displacement amount) of the wafer stage 5 from the alignment position determined based on the alignment reference mark to the actual exposure apparatus is measured. The wafer stage 5 is moved by the drive of the drive motor 7, and the movement amount is detected by the laser interferometer 9, and the coordinate position (X, Y) from the origin position of the wafer stage 5 is measured based on the detected value. Is done. Here, if there is a deviation in the baseline amount, the baseline amount is corrected.

Next, shot component correction is performed (step S13). In this step, the reticle 2 is irradiated with the exposure light L from the light source 15 via the reflection mirror 16, and the first and second slit marks 11A, 11A,
The projection images of 12A, 12A are formed on the wafer stage 5 side. First, the wafer stage 5 is moved to a position where the projected image of the first slit mark 11A on the reticle side overlaps the first slit mark 11B on the reference plate 13, and the photodetector is located immediately below the slit mark 11B. Fourteen light receiving surfaces are positioned (FIG. 5).

At this time, as shown in FIG.
If the received light intensity of the first slit mark 11A does not reach the peak value, the projected image of the first slit mark 11A on the reticle 2 side completely overlaps the first slit mark 11B on the wafer stage 5 (reference plate 13) side. Will not be. Therefore, the wafer stage 5 is swung in the Y direction by a predetermined amount by driving the drive motor, and a position where the received light intensity reaches a peak value is detected as shown in FIG. 7B.

Similarly, this time, the projected images of the second slit marks 12A, 12A on the reticle 2 side are superimposed on the second slit marks 12B on the wafer stage 5 side, and the light receiving surface of the photodetector 5 is moved to the slit. It is positioned immediately below the mark 12B, and the position at which the received light intensity reaches a peak is detected while swinging the wafer stage 5 in the X direction by a predetermined amount. In the present embodiment, the above-described operation is performed on each of the projected images of the second slit marks 12A provided on the reticle 2 side.

The alignment control unit 10 includes a light detector 14
, The scaling amount and the rotation amount of the shot component are measured, and the alignment position is corrected at the same time. For example, when a scaling error as shown in FIG. 11A occurs, the magnification of the projection lens 6 is adjusted to match the design value. In addition, when a rotation error as shown in FIG. 11B occurs, the reticle 2 is rotated around the optical axis LX to match the designed value.

After the shot component is corrected as described above, the wafer component is corrected (step S14). In this wafer component correction step, scaling and rotation error components caused by errors in the rotation direction of the wafer 4 are corrected. After the above processing,
Production of a product wafer (exposure operation) is started (step S15).

As described above, according to the present embodiment, the first and second two slit marks 11A, 11B, 12A, 12B formed of linear patterns orthogonal to each other.
Is used to correct the shot component, so that the alignment accuracy in the X and Y directions can be improved. Further, since the pair of second slit marks 12A, 12A is provided on the reticle 2 side, the amount of rotation (rotation amount) of the shot component in the rotation direction can be detected with high accuracy.

Moreover, in the present embodiment, the alignment is corrected based on the intensity of the transmitted light of each slit mark, so that a high alignment accuracy can be ensured and even a slight shot component error can be detected. Thus, an appropriate alignment operation can be performed. Further, the detection of the position where the received light intensity reaches the peak can be easily detected during the swing operation of the wafer stage 5.
In particular, the swinging of the wafer stage 5 can use an existing alignment means such as the drive motor 7, and can suppress the complexity of the apparatus configuration and increase in cost.

The above-described alignment correction operation may be performed for each exposure operation on the wafer.
Sufficient effects can be obtained simply by performing it at the beginning of the first lot at the time of reticle exchange, and in this case, there is no effect on throughput.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the first and second slit marks 11B, 12B on the wafer stage 5 side are used.
B is provided on the reference plate 13 in a manner as shown in FIG. 4A, but is not limited to this, and each mark 11B,
The arrangement position of 12B can be set arbitrarily.
Further, as schematically shown in FIG. 4B, the slit marks 11B ′, 12B ′, and 12B correspond to the reduced projection images of all the slit marks 11A, 12A, and 12A on the reticle 2 side.
B ′ may be arranged. In this case, it is not necessary to align the wafer stage 5 for each mark.

Similarly, the slit mark 1 on the reticle 2 side
The arrangement position of 1A, 12A, 12A is not limited to the embodiment shown in FIG. 2; for example, as shown in FIG. 8, all slit marks 11A ', 12A', 1 are provided on one side 2a of reticle 2.
2A 'may be arranged. Further, instead of the second slit marks 12A, 12A ', a pair of first slit marks 11A, 11A' may be provided. Further, each slit mark is composed of a plurality of linear patterns, but it is also possible to configure this with only a single linear pattern.

Further, the method of reticle alignment and baseline measurement is not limited to the above embodiment. For example, as a configuration of an alignment sensor for detecting an alignment mark (reference mark), a laser beam is irradiated on an alignment mark formed in a dot row on a scribe line on a wafer, and the mark is formed by using the diffracted light or the scattered light. Various alignment methods are adopted, such as a method of detecting the position or a method of measuring the mark position by processing the image data of the alignment mark captured by illuminating with a wide wavelength band light using a halogen lamp or the like as a light source. It is possible, and the present invention can be effectively applied to these alignment corrections.

[0040]

As described above, according to the alignment correction method of the present invention, highly accurate positioning of the reticle with respect to the wafer stage can be performed. For example, shot components can be accurately corrected. Becomes

According to the second aspect of the invention, it is possible to easily detect the position of the wafer stage at which the detected light receiving level of the exposure light reaches a peak.

According to the third aspect of the invention, for example, a rotation error of a shot component can be detected with high accuracy.

Further, according to the exposure apparatus of the present invention, highly accurate alignment between the reticle and the wafer can be performed, and variations in alignment caused by slight pressure fluctuations in the exposure apparatus can be reduced. It is possible to reduce the pattern shift defect rate.

According to the invention of claim 5, for example, a rotation error of a shot component can be detected with high accuracy.

According to the sixth aspect of the present invention, it is possible to suppress the complexity of the device configuration and increase the cost.

According to the present invention, the signal waveform of the light transmitted through each slit mark can be monitored with high accuracy.

According to the eighth aspect of the present invention, the present invention can be effectively applied to an exposure apparatus using a reduction projection optical system.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a reticle used in the exposure apparatus shown in FIG.

FIG. 3 is an enlarged view of a main part in FIG. 2, in which A indicates a first slit mark and B indicates a second slit mark.

4 is a plan view of a reference plate attached to a wafer stage of the exposure apparatus shown in FIG. 1, wherein A shows an embodiment of the present invention, and B shows a modified example thereof.

FIG. 5 is an explanatory diagram of the operation of the present embodiment.

FIG. 6 is a flowchart illustrating the operation of the present embodiment.

7 shows a waveform of transmitted light received by a photodetector provided in the exposure apparatus shown in FIG. 1, wherein A shows a state where the light receiving level has not reached a peak, and B shows a state where the light receiving level has reached a peak Is shown.

FIG. 8 is a plan view showing a modification of the configuration of the reticle shown in FIG.

FIG. 9 is a flowchart illustrating a conventional alignment process.

FIG. 10 is a schematic diagram for explaining an aspect of a positional shift in an alignment step, wherein A is an error due to offset, B is an error due to wafer scaling, C is an error due to wafer rotation, and D is an error due to wafer orthogonality. I have.

FIG. 11 is a schematic diagram for explaining a mode of a positional shift of a shot component, wherein A indicates a scaling error, and B indicates a rotation error.

FIG. 12 is a diagram illustrating alignment data management by a conventional trend method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 2 ... Reticle, 3 ... Reticle stage,
4 wafer, 5 wafer stage, 6 projection lens (projection optical system), 7 drive motor, 10 alignment control unit (alignment means), 11A first slit mark (on reticle side), 11B ... ( On the reticle side)
2nd slit mark, 12A ... 1st slit mark (on the wafer stage side), 12B ... 2nd slit mark (on the wafer stage side), 13 ... reference plate,
14 photodetector, 15 light source, L exposure light, LX optical axis.

Continuation of the front page F term (reference) 2F065 AA03 AA07 AA20 AA39 BB01 CC20 FF01 FF67 GG05 GG22 HH06 JJ15 LL10 LL28 MM24 PP03 PP12 QQ29 TT02 UU08 5F046 EA07 EB02 EB03 ED03 FA09 FA16 FA19 FA19

Claims (8)

[Claims] 1. An alignment correction method for performing relative alignment between a wafer on a wafer stage and a reticle supported on a reticle stage, wherein both the reticle and the wafer stage are orthogonal to each other. First and second slit marks each having a linear pattern are provided. Each of the first slit marks on the reticle side and the wafer stage side, and each of the second slits on the reticle side and the wafer stage side. An alignment correction method, comprising: correcting a relative position between the reticle and the wafer stage based on the received light intensity of the transmitted light when the exposure light is transmitted through each mark. 2. The alignment correction method according to claim 1, wherein the detection of the exposure light is performed while swinging the wafer stage. 3. The apparatus according to claim 1, wherein one of said slit marks provided on said reticle is provided in parallel and spaced apart from each other, and the position correction in the rotation direction is performed by said pair of slit marks. Alignment correction method. 4. A light source for irradiating exposure light, a reticle stage for supporting a reticle, a wafer stage on which a wafer is mounted, and an alignment for performing relative positioning between the reticle stage and the wafer stage. Means, provided on both the reticle and the wafer stage, and first and second slit marks each formed of a linear pattern orthogonal to each other, and each of the first and second slit marks on the reticle side and the wafer stage side. 1 slit mark, and each of the second slit marks on the reticle side and the wafer stage side,
An exposure apparatus comprising: a photodetector that receives measurement light transmitted therethrough in a superposed state; and a scanning unit that swings the wafer stage. 5. The exposure apparatus according to claim 4, wherein a pair of the first or second slit marks on the reticle side are provided in parallel. 6. An exposure apparatus according to claim 4, wherein said alignment means includes said scanning means. 7. The method according to claim 1, wherein the first and second slit marks are:
The exposure apparatus according to claim 4, wherein each of the exposure apparatuses comprises a plurality of linear patterns. 8. A projection optical system for reducing and projecting the pattern of the reticle onto the wafer is provided between the reticle stage and the wafer stage, and the first and second slits on the wafer stage side are provided. The slit width of each mark is formed at a reduction ratio substantially equal to the reduction projection ratio of the projection optical system with respect to the slit width of the first and second slit marks on the reticle side. The exposure apparatus according to claim 4, wherein