JP2000228347A - Aligning method and projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency in aligning. SOLUTION: A positioning method includes first processes (ST1 and 2) that measure a feature part such as the orientation flat and notch of a wafer and obtain a first amount of deviation (angle of rotation), that is equal to the amount of deviation for a specific first reference, a second process (ST3) that adjusts the position of the wafer, based on the first amount of deviation so that the position of the wafer can be adjusted to the first reference, third processes (ST4 and 5) that measure an alignment mark being transferred onto the wafer for forming by previous exposure processing, and obtain a second amount of deviation (the angle of rotation), and fourth processes (ST6 and 7) that change the first reference based on the second amount of deviation, when it is decided that the second amount of deviation is not within a specific tolerance. After this, the first processes are executed by reference after change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for positioning a substrate such as a semiconductor wafer or a glass plate, a semiconductor integrated circuit, a liquid crystal display device, an image pickup device, a thin film magnetic head,
The present invention relates to an exposure apparatus used when manufacturing other micro devices and the like using lithography technology.

[0002]

2. Description of the Related Art Projection exposure apparatuses such as steppers are used for manufacturing semiconductor devices and liquid crystal display devices. In a projection exposure apparatus, a pattern formed on a reticle or a photomask (hereinafter, referred to as a reticle) is formed on a predetermined surface of a photosensitive substrate (hereinafter, referred to as a wafer) such as a wafer or a glass plate coated with a photosensitive agent such as a resist. In order to transfer to a region with high accuracy, it is necessary to align the reticle and the wafer with high accuracy (alignment).

[0003] Therefore, this type of projection exposure apparatus incorporates a fine alignment optical system that photoelectrically detects an alignment mark formed on a wafer and aligns the reticle with the wafer. As a method of the fine alignment, an LSA (Laser Step Alignment) that irradiates a laser beam onto an alignment mark in a dot row on a wafer and detects a mark position using light diffracted or scattered by the mark is used.
FIA (Field Image) which performs image processing and measures image data of an alignment mark captured by illuminating with a wide wavelength band light using a halogen lamp or the like as a light source.
e Alignment) method, or by irradiating a laser beam with a slightly changed frequency to a diffraction grating alignment mark on a wafer from two directions, causing the two generated diffraction lights to interfere, and measuring the position of the alignment mark from its phase LIA (Laser Interferometry)
(Risk Alignment) system. In the alignment method, a TTL (Through the Lens) for measuring a position of a wafer via a projection optical system is used.
Method, a projection optical system, and a TTR (Through T) for measuring a positional relationship between a reticle and a wafer via a reticle.
(He Leticle) method and an off-axis method that directly measures the position of a wafer without using a projection optical system.

According to the fine alignment optical system, by detecting the positions of at least two points of the wafer placed on the wafer stage, the positions in the translation direction and the rotation direction can be detected with extremely high accuracy. However, since this fine alignment optical system has a narrow projection range of the spot light for irradiating the alignment mark, when there is no alignment mark near the projection light axis of the spot light, the wafer is largely moved to search a wide area. And it takes much time to search for the alignment mark.

In order to shorten the search time, the alignment mark of the wafer must be within the field of view of the fine alignment optical system when the wafer is placed on the wafer stage. Therefore, a pre-alignment device including a rotary table is provided in a wafer transfer path, the pre-alignment device controls a position of a wafer including a rotation direction with respect to the wafer transfer device, and a pre-alignment mechanism including pins on a wafer stage. And prealignment is performed by bringing the wafer into contact with the pins when the wafer is placed on the wafer stage.

For example, a conventional pre-alignment mechanism for a wafer provided with a linear notch, that is, an orientation flat (hereinafter, abbreviated as an orientation flat) in a part of the outer periphery, will be described. Three fixed pins and one moving pin are provided. The moving pin is movable in a one-dimensional direction.

The wafer having the orientation flat is positioned such that its orientation flat portion is located near the two fixed pins and the circumferential portion is located near the remaining one fixed pin, and the wafer stage is moved by the wafer transfer mechanism. Placed on the wafer holder. Subsequently, by pressing the wafer against the three fixing pins from an oblique direction by the moving pins, the wafer is uniquely positioned on the wafer stage and pre-aligned. After pre-alignment, the wafer is vacuum-adsorbed and fixed to the wafer holder.

For example, a conventional pre-alignment mechanism for a notch wafer provided with a V-shaped notch or notch in a part of the outer periphery will be described. On a wafer stage, two fixed pins are provided in a predetermined positional relationship. One moving pin is provided which is movable in a one-dimensional direction substantially orthogonal to a line connecting these fixing pins.

The notch wafer is placed on the wafer stage by the wafer transfer mechanism such that the notch portion is located near the moving pin, and the circumferential portion opposite to the notch portion is located near the two fixed pins. Placed on Subsequently, the moving pin is engaged with the notch portion of the wafer and pressed against the other two fixing pins, whereby the wafer is uniquely positioned on the wafer stage and pre-aligned. After pre-alignment, the wafer is vacuum-adsorbed and fixed to the wafer holder.

However, when the wafer is placed on the wafer holder of the wafer stage and the outer peripheral portion is brought into mechanical contact with the fixed pins and the moving pins provided on the stage as described above, the pre-alignment is performed. And the pins are in mechanical contact with each other, a part of the resist applied on the wafer is peeled off and scattered as fine particles. The scattered fine particles adhere to a wafer surface or a reticle, hindering pattern formation on the wafer, and causing a reduction in device manufacturing yield.

Therefore, in order to prevent fine particles from scattering from the wafer by the pre-alignment operation, it is desirable to perform the pre-alignment without contact.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 9-252043, a wafer is supported by a rotatable center-up or the like that moves up and down on a wafer holder, and the conventional contact pins (fixing pins and fixing pins) of the wafer are supported. Moving pin)
A non-contact type in which a portion corresponding to a portion to be contacted is imaged by an imaging device, and the center-up is rotated to match a predetermined reference based on the image, and then placed on the wafer holder. Has been developed. According to such a pre-alignment mechanism,
In addition to being able to prevent the scattering of fine particles from the wafer, the projection exposure system equipped with this mechanism is compatible with the conventional pre-alignment mechanism using contact pins, and is compatible with the projection exposure system equipped with the conventional mechanism. There is an advantage that it can be used.

[0013]

However, the pre-alignment of the wafer is performed by using the non-contact type pre-alignment mechanism as described above, the outer shape of the wafer is measured, and the posture of the wafer is determined by a predetermined reference. Even when the alignment mark is matched, the alignment mark transferred and formed on the wafer in the previous exposure processing for the fine alignment is largely displaced (rotated) in relation to the external characteristics (orifla or notch) of the wafer. In such a case, there has been a problem that the fine alignment performed later cannot be performed efficiently, or the fine alignment cannot be performed at all, resulting in an error.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is intended to provide fine alignment even when a mark formed on a wafer is displaced due to the external characteristics of the wafer. And to improve the productivity of microdevices and the like.

[0015]

Means for Solving the Problems In the following description, in order to facilitate understanding, each constituent element of the present invention will be described with reference numerals shown in the drawings of the embodiments. The constituent elements of the invention are not limited by these reference numerals.

The positioning method according to the present invention is a positioning method for positioning a substrate (6) having an outer characteristic portion (FP), wherein the characteristic portion of the substrate is measured and a deviation from a predetermined first reference is measured. A step (ST1, ST2) of obtaining a first shift amount, which is an amount, a step (ST3) of adjusting the position of the substrate based on the first shift amount, and measuring a mark formed on the substrate by a predetermined amount. Step of finding a second shift amount that is a shift amount with respect to the second reference (ST4, ST5)
And a step (ST6, ST7) of changing the first reference when it is determined that the second shift amount is not within a predetermined allowable value.

Further, according to the exposure apparatus of the present invention, an external characteristic portion (FP) held on a substrate stage (30) is provided.
An exposure apparatus for exposing a photosensitive substrate (6) having a mask via a mask (1), the substrate being placed on the substrate stage after the photosensitive substrate is adjusted in position at a predetermined transfer point above the substrate stage Position adjustment device (38)
And a first measuring device (50, 51, 52) for measuring the characteristic portion of the photosensitive substrate located at the transfer point
A first shift amount detecting device (15, ST2) for obtaining a first shift amount that is a shift amount with respect to a predetermined first reference based on a measurement result of the first measuring device; and the first shift amount detecting device (15, ST2) held on the substrate stage. A second measuring device (4) for measuring a mark formed on the photosensitive substrate, and a second shift amount detection for obtaining a second shift amount that is a shift amount with respect to a predetermined second reference based on the measurement result of the second measuring device. An apparatus (15, ST5) and a control device (15, ST6, ST7) for changing the first reference based on the second amount of deviation when it is determined that the second amount of deviation is not within a predetermined allowable value. And characterized in that:

When an exposure process is performed, a plurality of substrates are often sequentially processed, and the relationship between the external characteristic features of the substrates and the marks formed on the substrates is the same between successive substrates. Often have a tendency. Accordingly, as in the positioning method of the present invention, when the mark formed on the substrate is measured and the amount of deviation from the predetermined second reference is not within a predetermined allowable value, the first reference as the pre-alignment reference is set. By making a change (for example, correcting so as to cancel the deviation), the substrate to be processed next is brought into a state where the mark of the substrate is substantially aligned with the second reference by the pre-alignment.

Further, if the pre-alignment is performed again on the substrate being processed (the substrate after the second shift amount is obtained), the mark of the substrate is substantially aligned with the second reference. can do.

As a result, in the subsequent processing such as fine alignment, the mark exists near the projection optical axis of the spot light irradiated for detecting the mark, and the substrate is largely moved to search a wide area. This eliminates the necessity of performing, so that the time can be shortened, the occurrence of errors due to the inability to execute fine alignment is reduced, and the processing efficiency can be greatly improved.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an example of a projection exposure apparatus according to the present invention. Under illumination light IL from an illumination system IA including a light source such as a mercury lamp or an excimer laser, a fly-eye lens, and a condenser lens,
The pattern on the reticle 1 is reduced to, for example, 1/4 or 1/5 through the projection optical system 3, and is projected and exposed on each shot area of the wafer 6 coated with the photoresist. In FIG. 1, Z is parallel to the optical axis AX of the projection optical system 3.
1 in a plane perpendicular to the Z axis and parallel to the plane of FIG.
The axis is taken as the Y axis perpendicular to the plane of FIG.

The reticle 1 is held on a reticle stage 32 mounted on a reticle base 31. The reticle stage 32 is configured to be able to translate in the XY plane and rotate in the θ direction (rotation direction) by a reticle drive system (not shown). Reticle stage 3
A movable mirror 33 is installed at the upper end of both X and Y directions, and a reticle stage 32 is provided by the movable mirror 33 and a laser interferometer 34 fixed on the reticle base 31.
Of the reticle stage 32 are also detected at the same time with a predetermined resolution.

The measurement value of the laser interferometer 34 is sent to the stage control system 16, and the stage control system 16 controls the reticle drive system on the reticle gantry 31 based on the information.
Further, information on the measurement values of the laser interferometer 34 is supplied from the stage control system 16 to the central control system 18, and the central control system 18 controls the stage control system 16 based on the information.

On the other hand, the wafer 6 is held by vacuum suction on a wafer holder 30 fixed to a sample table 29 on the X stage 11. The sample stage 29 is a Z-tilt drive unit (in this example, three actuators displaced in the Z-direction, respectively) for correcting the position and tilt (tilt) of the wafer 6 in the optical axis AX direction (Z-direction) of the projection optical system 3. ), And the Z tilt drive unit 10 is fixed on the X stage 11.

The X stage 11 is mounted on a Y stage 12, and the Y stage 12 is mounted on a wafer base 14, and can be moved in the X and Y directions via a wafer stage drive system (not shown). It has become.
That is, in this embodiment, a rotary table for rotating the sample table 29 about the Z axis is omitted. This is because the speed of movement of the wafer 6 is increased, the accuracy is improved, and the like by simplifying the configuration of the entire wafer stage, reducing the weight, and the like.

An L-shaped movable mirror 1 is provided at the upper end of the sample table 29.
The coordinate 3 and the rotation angle of the sample table 29 in the X and Y directions are detected by the movable mirror 13 and the laser interferometer 17 disposed opposite to the movable mirror 13.

The measured value of the laser interferometer 17 is sent to the stage control system 16, and the stage control system 16 controls the wafer stage drive system based on the information. Further, information on the measurement values of the laser interferometer 17 is supplied from the stage control system 16 to the central control system 18, and the central control system 18 controls the stage control system 16 based on the information. A wafer transfer device 39 (see FIG. 2) for transferring the wafer 6 is disposed near the wafer stage, and a transfer mechanism to the wafer is provided in the wafer stage as described later.

This projection exposure apparatus is provided with, for example, an alignment sensor (microscope) 4 of the TTL system and alignment sensors 5a and 5b of the off-axis system for aligning the reticle 1 with the wafer 6. At the time of alignment, these alignment sensors 4, 5
a) or 5b, the position of an alignment mark formed on the wafer 6 or the position of a predetermined pattern is detected. And the pattern on the reticle are accurately aligned.

These alignment sensors 4, 5a, 5
The detection signal from b is processed by the alignment control system 15, and the alignment control system 15 is controlled by the central control system 18. A reference mark member 43 having a surface at the same height as the surface of the wafer 6 is fixed on the sample table 29, and a mark (fiducial mark) serving as a reference for alignment is formed on the surface of the reference mark member 43. Have been.

As described above, the stage control system 16 and the alignment control system 15 are controlled by the central control system 18, and the central control system 18 controls the entire projection exposure apparatus, and performs the exposure operation in a certain sequence. Is performed.

Near the end of the projection optical system 3 on the wafer side,
Three off-axis two-dimensional image processing apparatuses (imaging apparatuses) 50, 51, and 52 are arranged. These image processing apparatuses 50, 51, and 52 capture images of the edge portion of the outer peripheral portion of the wafer when the wafer is transferred to a loading position (transfer position) above the wafer holder 30 as described later. It is. The imaging signals from the image processing devices 50, 51, 52 are supplied to the alignment control system 15. The alignment control system 15 calculates a lateral shift error and a rotation error of the wafer at the transfer position from the supplied imaging signal.

Next, the wafer transfer system and the wafer transfer mechanism on the wafer stage will be described with reference to FIG. The wafer stage is a general term for the wafer holder 30, the sample stage 29, the Z tilt drive unit 10, the X stage 11, the Y stage 12, and the wafer base 14.

FIG. 2A is a plan view of the configuration around the wafer transfer system and the wafer stage, and FIG. 2B is a side view thereof. In FIGS. 2A and 2B, a wafer transfer device 39 for transferring a wafer is disposed above the wafer stage in the −X direction. The wafer transfer device 39 includes wafer arms 21 and 2 arranged in series in the X direction.
2. a slider 23 for sliding the wafer arms 21 and 22 to a predetermined position;
An arm drive system (not shown) for driving the motors 1 and 22 is provided.

The slider 23 is installed independently of the exposure apparatus main body, so that vibrations when the slider 23 is driven are not transmitted to the exposure apparatus main body. Each of the two wafer arms 21 and 22 has a U-shaped flat plate portion, and a wafer is placed on the upper surface thereof. These two wafer arms 21 and 22 can unload (unload) the exposed wafer and simultaneously load (load) the next wafer.

That is, the wafer arms 21 and 22 move to the loading position where the wafer is transferred to the wafer stage system along the slider 23 based on a command from the loader controller 24, and the wafer 6a exposed by the wafer arm 22 is Out. Thereafter, the wafer 6 to be exposed next by the wafer arm 21 is moved onto the wafer stage and placed on the center-up 38. FIG.
(B) shows a state where the exposed wafer 6 a is placed on the wafer arm 22 on the slider 23 and the wafer 6 is transferred from the wafer arm 21 to the tip of the center-up 38.

The center-up 38 is a columnar or cylindrical member that is supported by a telescopic mechanism 35 provided on the X stage 11 and that fits loosely into a through hole formed in the center of the sample table 29 and the wafer holder 30. In addition, the transfer of the wafer is performed by moving the expansion mechanism 35 in the vertical direction (Z direction) to move the wafer up and down. A suction hole or a suction groove for vacuum suction is provided at a tip of the center-up 38, and the tip of the suction arm or the wafer arm 21 or 22 at the time of wafer transfer.
When the wafer is placed on the wafer holder 30, it moves to a position lower than the surface of the wafer holder 30. Further, by suctioning the tip of the center-up 38 in a vacuum, the wafer does not shift when the center-up 38 is moved up and down.

The telescopic mechanism 35 is rotatably supported on the XY plane about its central axis 35z.
The rotary drive system 36 provided on the first drive unit 36 is engaged with a drive shaft 37 that rotates, and can be rotated to a desired angle by a command from the central control system 18 that controls the rotary drive system 36. The rotation system including the rotation control system 36, the drive shaft 37, and the expansion mechanism 35 has a sufficient angle setting resolution, and can rotate the wafer 6 with an accuracy of, for example, 20 μrad.

With reference to FIG. 3, a description will be given of the attitude control of the wafer in the wafer transfer system. FIG. 3A shows a turntable 60 provided in the wafer transfer system. FIG.
The wafer arm 21 shown in FIG.
The upper wafer 6 is transferred to the center-up 38 of the wafer stage. In the vicinity of the turntable 60, a light projecting unit 61a for irradiating the outer periphery of the wafer 6 with a slit-shaped light beam 63
And an eccentricity sensor 61 including a light receiving portion 61b for receiving the light beam passing through the outer peripheral portion of the wafer 6 and performing photoelectric conversion, and a detection signal S1 from the light receiving portion 61b is transmitted to the central control system 1
8. When the turntable 60 rotates while holding the wafer 6 by suction, the width of the wafer 6 passing through the eccentricity sensor 61 changes due to the eccentricity of the wafer 6 and the presence of the notch (orientation flat or notch), and the light receiving portion 61b
The light quantity of the light beam 63 received by the light source changes.

FIG. 3B shows a detection signal S1 output from the light receiving section 61b. The detection signal S1 has a sinusoidal waveform with respect to the rotation angle φ of the turntable 60, and changes to a high level at a portion 62 corresponding to the notch. In the central control system 18, the detection signal S1 and the turntable 6
From the rotation angle φ of ₀ , the rotation angle φ ₀ when the notch is located at the center of the eccentricity sensor 61 and the amount of eccentricity of the wafer 6 are determined, and the notch is rotated so as to be in a predetermined direction and turned. The table 60 is stopped. The central control system 18
Based on the information on the amount of eccentricity, the position of the wafer sample table 29 when the wafer 6 is received at the loading position is adjusted.

Next, the image processing apparatus 50 will be described with reference to FIG. In FIG. 4, illumination light in a wavelength band having a low photosensitivity to the photoresist applied to the wafer 6 is focused on one end of a light guide 57 from a light source 58 such as a lamp or a light emitting diode. Then, the illumination light emitted from the other end of the light guide 57 passes through the collimator lens 56, the half prism 54, and the objective lens 53 to the outer peripheral edge of the wafer 6 at the loading position on the tip of the center-up 38. Irradiated. The reflected light from the edge enters an imaging device 59 such as a two-dimensional CCD through an objective lens 53, a half prism 54, and an imaging lens 55, and the image of the edge of the wafer 6 is formed on the imaging surface of the imaging device 59. Is formed.

Although only the image processing device 50 has been described here, the other image processing devices 51 and 52 have the same configuration. The imaging signals from the imaging devices 50, 51, and 52 are supplied to the alignment control system 15. The alignment control system 15 determines the edge position of the detection target of the wafer 6 from the imaging signals, performs predetermined arithmetic processing, and performs pre-processing. The rotation angle and translation amount of the wafer required for alignment are calculated.

FIG. 5 is a diagram showing another example of the configuration of the image processing apparatus. In FIG. 5, illumination light of a wavelength band having low photosensitivity to the photoresist, emitted from a light source such as a lamp or a light emitting diode (not shown), is focused on one end of the light guide 72. The illumination light emitted from the other end of the light guide 72 is bent by the deflection mirror 73 and
It is emitted through the opening 75 on the upper surface of FIG. Sample table 29
The wafer holder 30a disposed on the upper side a is provided with a notch 74 for passing illumination light passing through the opening 75 thereof.

The outer peripheral edge of the wafer 6 at the loading position on the end of the center-up 38 is irradiated with illumination light having passed through the opening 75 and the notch 74. Then, the illumination light that has passed near the edge portion is
Through the objective lens 53a and the imaging lens 55a, a two-dimensional C
An image of the edge portion is formed on the imaging surface of the imaging element 59 made of a CD or the like. Instead of guiding the illumination light from the light source to the opening 75 of the sample table 29a by the light guide 72, the sample table 2
A light source such as a light emitting diode may be directly arranged at the position of the opening 75 of 9a.

Next, a series of processes including pre-alignment, search alignment, and fine alignment for a wafer having external features such as an orientation flat or a notch will be described with reference to the flowchart shown in FIG.

(1) Prealignment processing (ST1 to ST1)
3) The pre-alignment processing in the present embodiment refers to a reference stored in a predetermined storage area (pre-alignment reference storage area) of a storage device as data of a control program of the central processing system 18 or the alignment control system 15. The deviation amount (rotation deviation amount) of the wafer 6 with respect to (the first reference in this case) is obtained by measuring several locations near the peripheral edge portion of the wafer 6 including the external characteristic parts (orifla, notch, etc.). This is a process for matching the attitude of the wafer 6 with the reference.

That is, the wafer 6 to be processed is transported by the wafer arm 21 and transferred to the center-up 38 set at a predetermined wafer transfer position, where the wafer 6 is suction-held. Next, the imaging device 50, 51, 52 captures an image of the peripheral portion including the characteristic portion of the wafer 6 and the vicinity thereof (ST1), and stores the reference in the rotation direction stored in the pre-alignment reference storage area of the wafer 6 (ST1). In this case, the amount of rotation deviation (first deviation amount) with respect to the first reference is obtained (ST2). It should be noted that the translation deviation amount with respect to the reference in the translation direction (the X direction and the Y direction) can be obtained, but in this embodiment, only the rotation deviation amount is used. Next, Center Up 3
The wafer 6 is driven to rotate based on the rotational deviation amount, and the wafer 6 is rotated so that the rotational deviation amount disappears (ST3).

The first criterion is a criterion determined in advance in relation to external features such as orientation flats and notches.
The rotation angle of the wafer is, for example, a direction parallel to the X direction or the Y direction.

As a result, the pre-alignment is completed, the center-up 38 is lowered, and the suction of the wafer 6 is released, so that the wafer 6 is transferred onto the wafer holder 30. Vacuum adsorbed.

(2) Search Alignment Processing The search alignment processing in this embodiment is as follows.
The deviation amount in the rotation direction and translation direction of the wafer 6 with respect to the reference (second reference) stored in a predetermined storage area (reference alignment storage area for search alignment) of the storage device of the central processing system 18 or the alignment control system 15 is calculated. This deviation amount (in this embodiment, only the deviation amount in the rotational direction) is determined by measuring a search alignment mark formed on the wafer 6, and a predetermined allowable value (in the rotational direction). This is a process in which a predetermined process is selectively performed based on the result of comparison with an allowable angle, which is stored and held in advance as data of a control program.

That is, the wafer 6 held by suction on the wafer holder 30 using the LSA method or the FIA method using an off-axis type alignment sensor 5a, 5b or a search alignment sensor (not shown) or the like. Then, the search alignment mark formed in the step is measured (ST4).

Next, the amount of deviation of the wafer 6 with respect to the second reference (the amount of translational deviation X, Y and the rotational deviation angle θ) is determined (ST5). Note that the search alignment mark has a shift amount (rotation shift angle) of the wafer 6 with respect to a predetermined second reference.
And a mark transferred and formed at the time of the previous exposure processing so that a shift amount (translation shift amount) in the X and Y directions can be detected.

Next, it is determined whether or not the rotational deviation amount (second deviation amount) of the obtained deviation amounts is within the range of the predetermined allowable value (ST6), and is within the predetermined allowable value. If it is determined, the process proceeds to the next fine alignment process.

If it is determined that the deviation amount is not within the predetermined allowable value, the reference stored in the pre-alignment reference storage area of the storage device is used as the second deviation amount (rotational deviation amount). Is corrected (changed) so as to cancel the deviation, and this reference (the third reference) is overwritten and stored in the pre-alignment reference storage area (ST7). In this case, the first reference is saved in another area of the storage device in advance.

Thereafter, returning to ST1, the pre-alignment is performed again. That is, the suction holding of the wafer 6 by the wafer holder 30 is released, the center up 38 is raised, and the wafer 6
And is positioned at the wafer transfer position. Next, the peripheral portion of the wafer 6 and its vicinity are imaged by the imaging devices 50, 51, and 52 (ST1).
The rotation deviation amount (first deviation amount) of the wafer 6 with respect to a predetermined reference (in this case, the third reference) is detected in relation to the external characteristic portions (orifla, notch, etc.) (ST2).
Next, the center-up 38 is rotationally driven based on the shift amount, and the wafer 6 is rotated so as to eliminate the shift (ST3).

Next, search alignment processing is performed again (ST4 to ST6). However, in this case, since the pre-alignment process is performed based on the third criterion obtained by correcting the first criterion with the second shift amount, in this search alignment, the translation direction (X direction and Y direction) is used. Direction), the rotational displacement should be almost eliminated,
The deviation amount (second deviation amount) falls within the allowable value, and the next fine alignment is performed. The displacement of the wafer 6 in the translation direction is adjusted by finely moving the XY stages 11 and 12. In ST6, the second
If the deviation amount is not within the predetermined allowable value, it is not possible to proceed to the next fine alignment processing, so that error processing is conventionally performed.

(3) Fine Alignment Processing The EGA (Enhanced Global Alignment) method is used for this fine alignment. In the search alignment process, if the deviation amount of the wafer 6 is within a predetermined allowable value, the alignment sensor 4
Alternatively, a fine alignment sensor (not shown)
EGA using LSA, FIA, LIA, etc.
Measurement is performed (ST8).

That is, a plurality of sample shots in the wafer 6 are selected in advance, and the positions of EGA alignment marks (transferred and formed in the previous exposure process) attached to the sample shots are sequentially measured. Next, based on the measurement result and the design value of the shot array, a statistical operation is performed by a so-called least square method or the like to obtain all shot array data on the wafer. Precisely align relative positions.

(4) Next, while sequentially positioning each shot area on the wafer at the exposure position based on the coordinate position of each shot area obtained by the above-described EGA method or the like and a pre-measured baseline amount, projection is performed. Exposure processing for transferring the pattern image of the reticle 1 onto the wafer 6 via the optical system 3 is performed. In this case, the translation of the wafer 6 in the translation direction is adjusted by finely moving the XY stages 11, 12 or the reticle stage 32, and the adjustment of the rotation of the wear 6 in the rotation direction is performed by slightly rotating the reticle stage 32. Done.

When the exposure processing for all the shot areas on the wafer 6 is completed, the suction holding of the wafer 6 by the wafer holder 30 is released, the center up 38 is raised, and the wafer is moved to the wafer transfer position. The unprocessed wafer 6 to be processed next is placed on the center-up 38 by the wafer arm 21 while the processed wafer 6 is carried out by the wafer arm 22 (ST1).
0), returning to ST1, and thereafter repeating the same processing.

As described above, when the positional relationship between the external characteristic features of the wafer 6 and the alignment marks formed on the wafer 6 is displaced, it is not possible to shift to the fine alignment processing conventionally. However, according to the present embodiment, in this case, the reference used for the pre-alignment processing is corrected by the second shift amount, and the pre-alignment processing is performed again based on the correction. Since the processing is performed, it is possible to shift to the next fine alignment processing without causing an error.

In the exposure process, a plurality of wafers are usually
Since lots are often implemented in lot units,
In many cases, the relationship between the external characteristic portion of the wafer 6 and the search alignment mark formed on the wafer 6 has the same tendency in the same lot. Therefore, in the present embodiment, the determination of ST6 in the search alignment for the second and subsequent wafers should be determined to be within the allowable value as long as the tendency is followed. Although it is necessary to perform the alignment twice, this does not occur for the second and subsequent sheets, and the processing can be performed with high efficiency.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore,
Each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, the change (correction) of the predetermined reference in the pre-alignment of the above-described embodiment is performed only in the rotation direction, but it goes without saying that the same can be performed in the translation direction.

Further, the present invention can be applied to any type of exposure apparatus. In a state where the reticle and the wafer are stationary, the entire surface of the reticle pattern is irradiated with illumination light for exposure, and the reticle pattern is A step-up-repeat type reduction projection exposure apparatus (stepper) for batch exposure of one partitioned area (shot area) on a wafer to be transferred, synchronously moving a reticle and a wafer,
A step-and-scan reduction projection in which a shot area on a wafer is sequentially exposed by scanning and illuminating with a slit light of a rectangular shape or the like, and the wafer is sequentially moved to repeatedly scan and expose another shot area. The present invention can also be applied to a mold scanning exposure apparatus (scanning stepper).

[0065] As the exposure illumination light, emission lines (e.g., g-line, i-line), KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), _{F 2} laser (wavelength 157 nm), Ar
Either _two lasers (having a wavelength of 126 nm) or harmonics such as a YAG laser may be used. In addition, a single-wavelength laser in the infrared or visible region oscillated from a DFB semiconductor laser or a fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and ytterbium) as exposure illumination light. Alternatively, a harmonic converted to ultraviolet light using a nonlinear optical crystal may be used.

Further, for example, EUV (Extreme) having an oscillation spectrum at 5 to 15 nm (soft X-ray region)
Ultra Violet) light as exposure illumination light,
The illumination area on the reflection mask is defined in the shape of a circular arc slit, and a reduction projection optical system including only a plurality of reflection optical elements (mirrors) is provided. The present invention can also be applied to an EUV exposure apparatus or the like that transfers a pattern of a reflection mask onto a wafer by synchronously moving the wafer and the wafer.

In addition, a semiconductor device, a liquid crystal display,
Not only a projection exposure apparatus used for manufacturing a thin film magnetic head and an imaging device (CCD, etc.) but also a projection exposure apparatus for transferring a circuit pattern onto a glass substrate or a silicon wafer for manufacturing a reticle or a mask. The present invention can also be applied.

[0068]

According to the present invention, even when the mark formed on the wafer is shifted due to the external characteristics of the wafer, fine alignment can be performed without causing an error. There is an effect that it becomes. In particular, in the case where the displacement has the same tendency among a plurality of substrates to be continuously processed, the second and subsequent substrates can be processed at high speed and with high efficiency.

[Brief description of the drawings]

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

2A and 2B are explanatory views of a wafer transfer system and a wafer transfer mechanism on a wafer stage according to an embodiment of the present invention, wherein FIG. 2A is a plan view of a configuration around the wafer transfer system and the wafer stage, and FIG. It is the side view.

FIGS. 3A and 3B are explanatory diagrams illustrating attitude control of a wafer in a wafer transfer system according to an embodiment of the present invention, wherein FIG. 3A is a schematic diagram of a turntable, and FIG.

FIG. 4 is a diagram illustrating an example of an image processing apparatus according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of another example of the image processing device according to the embodiment of the present invention;

FIG. 6 is a flowchart showing a main part of a process according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reticle 3 ... Projection optical system 6 ... Wafer 10 ... Z tilt drive unit 11 ... X stage 12 ... Y stage 14 ... Wafer base 15 ... Alignment control system 16 ... Stage control system 18 ... Central control system 21, 22 ... Wafer arm 23 ... Slider 29 ... Sample table 30 ... Wafer holder 35 ... Expansion mechanism 36 ... Rotation control system 37 ... Drive shaft 38 ... Center up 39 ... Wafer transfer device 50,51,52 ... Image processing device (imaging device) FP ...

Claims (6)

[Claims] 1. A positioning method for positioning a substrate having an outer characteristic portion, comprising: measuring a characteristic portion of the substrate to obtain a first deviation amount that is a deviation amount from a predetermined first reference. Adjusting the position of the substrate based on the first shift amount; measuring a mark formed on the substrate to determine a second shift amount that is a shift amount with respect to a predetermined second reference; Changing the first reference when it is determined that the two shift amounts are not within a predetermined allowable value. 2. The positioning method according to claim 1, wherein the shift amount is a shift amount of the substrate in a rotation direction. 3. An exposure apparatus for exposing a photosensitive substrate having an outer characteristic portion held on a substrate stage through a mask, wherein the position of the photosensitive substrate is adjusted at a predetermined transfer point above the substrate stage. A substrate position adjustment device to be placed on the substrate stage after the first measurement, a first measurement device for measuring the characteristic portion of the photosensitive substrate positioned at the transfer point, and a predetermined measurement device based on the measurement result of the first measurement device. A first shift amount detecting device for calculating a first shift amount that is a shift amount with respect to a first reference; a second measuring device for measuring a mark formed on the photosensitive substrate held on the substrate stage; A second shift amount detecting device for obtaining a second shift amount that is a shift amount with respect to a predetermined second reference based on the measurement result of the second measuring device; and determining that the second shift amount is not within a predetermined allowable value. A control device for changing the first reference on the basis of the second shift amount. 4. The exposure apparatus according to claim 3, wherein the photosensitive substrate is a wafer, and the characteristic portion is an orientation flat or a notch. 5. The exposure apparatus according to claim 4, wherein the first measurement device is an imaging device that captures an image of an outer peripheral portion of the photosensitive substrate. 6. The exposure apparatus according to claim 3, wherein the shift amount is a shift amount in a rotation direction of the substrate.