JP2004087562A - Position detection method and apparatus thereof, exposure method and apparatus thereof, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection method whereby position information of a mark formed by an exposure apparatus can accurately be detected. <P>SOLUTION: The position detection method includes steps 342 to 362 of first imaging a mark region including a mark having a plurality of line patterns arranged in a prescribed direction on an object to obtain imaging signals respectively corresponding to a plurality of the line patterns, thereafter selecting at least one particular line pattern among a plurality of the line patterns and obtaining position information of the particular line pattern by using the imaging signal corresponding to the particular line pattern; and a step 364 of using the position information (measurement result) of the particular line pattern and an offset amount on the basis of the design value to calculate the position information of the mark; that is, selecting only line patterns forming the mark such as those with the same tendency of positional deviation or without deformation of the signal waveform as detection objects, obtaining the position information of the line patterns, and calculating the position of the mark on the basis of the position information and the offset amount. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position detection method and apparatus, an exposure method and apparatus, and a device manufacturing method, and more particularly, to a position detection method and a position detection apparatus for detecting position information of a mark including a plurality of line patterns, The present invention relates to an exposure method using a position detection method, an exposure apparatus including the position detection device, and a device manufacturing method using the exposure method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor element, a liquid crystal display element, or the like, a pattern formed on a mask or a reticle (hereinafter, collectively referred to as a “reticle”) is exposed to a photosensitive agent such as a resist through a projection optical system. An exposure apparatus is used that transfers an image onto a substrate such as a coated wafer or a glass plate (hereinafter, appropriately referred to as a “wafer”). As such an exposure apparatus, a stationary exposure type projection exposure apparatus such as a so-called stepper and a scanning exposure type projection exposure apparatus such as a so-called scanning stepper are mainly used. In such an exposure apparatus, it is necessary to perform high-precision alignment (alignment) between the reticle and the wafer prior to exposure. The demand for this alignment accuracy has become more severe with the miniaturization of patterns, and various devices have been devised for alignment.
[0003]
In order to perform the above alignment with high accuracy, it is necessary to perform the reticle position detection and the wafer position detection with high accuracy. For example, in order to detect the position of a reticle, it is common to use exposure light. The exposure light is applied to a reticle alignment mark formed on the reticle, and image data of the reticle alignment mark captured by a CCD camera or the like is subjected to image processing. A VRA (Visual Reticle Alignment) method of measuring the mark position by using the method is adopted. On the other hand, to detect the position of a wafer, an FIA (Field) that illuminates with light having a wide wavelength bandwidth using a halogen lamp or the like as a light source, processes image data of an alignment mark captured by a CCD camera or the like, and measures the mark position is used. An Image Alignment method is used.
[0004]
In these optical alignments, first, alignment marks on a reticle are detected and processed, and position coordinates are measured. Next, the position of the shot to be superimposed is determined by detecting and processing the alignment mark on the wafer and measuring the position coordinates. Based on these results, the wafer is moved by a wafer stage so that the reticle pattern image overlaps the shot position, and the reticle pattern image is transferred onto the wafer via the projection optical system.
[0005]
Usually, an alignment mark for performing position measurement is composed of a plurality of line patterns having the same line width in order to perform stable measurement. Then, when detecting the position of the alignment mark, the position detection device generally performs position measurement on each of the plurality of line patterns, and determines the average value as the position of the entire mark.
[0006]
[Problems to be solved by the invention]
For example, due to the influence of residual aberration of the projection optical system at the time of exposure or the influence of wafer processing after exposure, for example, the shape of a plurality of line patterns forming an alignment mark formed on a wafer may vary. As a result, the signal waveform of each line pattern detected (observed) by the position detection device also varies in shape.
[0007]
Further, if coma aberration or the like remains in the detection optical system (imaging optical system) of the position detection device, the position measurement result deviates from the true mark position. Since the tendency of this shift depends on the shape of the signal waveform obtained as a result of imaging the mark, if the shape of the waveform of each line pattern in the group of line patterns constituting the alignment mark is different, the positional shift will also be different for each line. You will have a different tendency.
[0008]
However, in a conventional position detecting device that detects a mark such as an alignment mark by an image processing method, position measurement is performed while a plurality of marks having different characteristics, in other words, having different tendencies of positional deviation are mixed. For this reason, the tendency of the positional shift changes for each mark, and as a result, there is a possibility that the final overlay accuracy may deteriorate.
[0009]
Further, it is conceivable to correct a detection error caused by the collapse of the signal waveform of the mark as described above, for example, by inputting an offset value. However, an appropriate correction amount (offset value) can be obtained by a subtle change in the state of the mark. , The effect of correction may be reduced.
[0010]
The present invention has been made under such circumstances, and a first object of the present invention is to provide a position detection method and a position detection device capable of accurately detecting position information of a mark on an object.
[0011]
A second object of the present invention is to provide an exposure method and an exposure apparatus that can accurately expose a substrate.
[0012]
A third object of the present invention is to provide a device manufacturing method capable of improving device productivity.
[0013]
[Means for Solving the Problems]
According to the first aspect of the present invention, a plurality of line patterns (L) are arranged along a predetermined direction. _m ), A position detection method for detecting position information of a mark (WM) including a mark area including the mark on an object (W), and an image signal (MWF) corresponding to each of the plurality of line patterns. _m Obtaining the position information of the specific line pattern by using at least one specific line pattern of the plurality of line patterns, and using an imaging signal corresponding to the specific line pattern; Calculating the position information of the mark using position information of the specific line pattern and an offset amount based on a design value of the specific line pattern.
[0014]
According to this, first, an image of a mark area including a mark including a plurality of line patterns arranged along a predetermined direction on an object is taken, and image signals respectively corresponding to the plurality of line patterns are obtained. Next, at least one specific line pattern of the plurality of line patterns is selected, and position information of the specific line pattern is obtained using an imaging signal corresponding to the specific line pattern. Then, the position information of the mark, that is, the position information of the reference point of the mark, is obtained using the position information (measurement result) of the specific line pattern and the offset amount (offset amount from the reference point) based on the design value of the specific line pattern. calculate.
[0015]
That is, in the position detection method of the present invention, not all of a plurality of line patterns forming a mark, but only a part of specific line patterns, for example, only a line pattern having the same tendency of positional deviation or having no signal waveform collapse are detected. As an object, position information of the specific line pattern is obtained, and a mark position is calculated based on the position information and an offset amount from a reference point based on a design value of the specific line pattern. For this reason, even if a mark having a distorted shape or a mark having a different tendency of positional shift is mixed, the positional information of the mark can be accurately obtained without being affected by the mixed shape.
[0016]
In this case, as in the position detection method according to claim 2, the specific line pattern is selected by selecting a pattern in which at least one waveform of the imaging signal and its n-th derivative signal (n is a natural number) has the same characteristic amount. Can be performed by selecting.
[0017]
The invention according to claim 3 is a position detection method for detecting position information of a mark including a plurality of line patterns arranged along a predetermined direction, wherein an image of a mark area including the mark on an object is taken, Obtaining image signals respectively corresponding to the plurality of line patterns; and a predetermined characteristic obtained from the signal waveform based on one of the signal waveforms of the image signal and its n-th derivative signal (n is a natural number). Determining a quantity for each of the plurality of line patterns; comparing the predetermined feature quantity determined for each of the line patterns among the plurality of line patterns, and determining the feature quantity in another line pattern. Extracting a specific line pattern different from the amount; excluding the extracted specific line pattern from its calculation, and removing the remaining specific line pattern obtained based on the imaging signal. A position detecting method characterized by comprising: using the position information of the in-pattern, a step of calculating the positional information of the mark.
[0018]
According to this, an image of a mark area including a mark including a plurality of line patterns arranged along a predetermined direction on the object is taken, and an image signal corresponding to each of the plurality of line patterns is obtained. Next, a predetermined feature amount obtained by using one of the signal waveforms of the imaging signal and its n-th differential signal (n is a natural number) is obtained for each of a plurality of line patterns. Next, a predetermined feature amount is compared between a plurality of line patterns, and a specific line pattern whose feature amount is different from the feature amounts of other line patterns is extracted. When calculating the position information of the mark, the extracted specific line pattern is excluded from the calculation, and the position information of the mark is obtained by using the position information of the remaining line patterns obtained based on the imaging signal. Is calculated.
[0019]
That is, according to the position detection method of the present invention, not all of the plurality of line patterns forming the mark, but the predetermined signal obtained from any one of the image signals corresponding to the plurality of line patterns and the n-th derivative signal thereof Is extracted, a line pattern having the predetermined characteristic amount different from the characteristic amount in another line pattern is extracted, and the position of the mark is calculated using the remaining line patterns excluding the extracted pattern. For this reason, even if a mark having a distorted shape or a mark having a different tendency of positional shift is mixed, the positional information of the mark can be accurately obtained without being affected by the mixed shape.
[0020]
In this case, as in the position detecting method according to claim 4, in the step of calculating the position information of the mark, the position information of the remaining line pattern and a design value of the remaining pattern are used to calculate the position information of the remaining line pattern. The position information of the mark can be calculated.
[0021]
In each of the position detection methods according to claims 2 to 4, various amounts can be considered as the feature amount. For example, as in the position detection method according to the fifth aspect, the feature amount is the number of peaks of at least one signal of an imaging signal corresponding to each of the line patterns and an n-th derivative signal (n is a natural number). It can be. Alternatively, as in the position detection method according to claim 6, the feature amount is a degree of symmetry of at least one of an imaging signal corresponding to each of the line patterns and an m-th order differential signal (m is an even number). It can be. Alternatively, as in the position detection method according to claim 7, the feature amount is a signal intensity of a first portion corresponding to a line portion of the imaging signal corresponding to the line pattern and a second portion corresponding to the other portion. The ratio can be set as follows. Alternatively, as in the position detection method according to claim 8, the characteristic amount is a ratio of a signal intensity between a first portion and a second portion corresponding to edges at both ends of a line portion of the imaging signal corresponding to the line pattern. It can also be set as.
[0022]
The invention according to claim 9 is an exposure method for exposing a substrate (W) by an energy beam (IL) to form a predetermined pattern on the substrate, wherein the predetermined direction is formed on the substrate in advance. A plurality of line patterns (L _m A step of detecting position information of a mark (WM) containing the mark using the position detection method according to any one of claims 1 to 8; and determining a position of the substrate based on the detected position information of the mark. Exposing the substrate with the energy beam while controlling the energy beam.
[0023]
According to this, the position information of the mark including a plurality of line patterns arranged in a predetermined direction formed on the substrate in advance is obtained by using the position detection method according to any one of claims 1 to 8. Detected. As a result, even if a mark having a deformed shape or a mark having a different tendency of the positional deviation of the mark is mixed, the positional information of the mark can be accurately detected without being affected by this. Then, the substrate is exposed to the energy beam while accurately controlling the position of the substrate based on the position information of the mark detected accurately. Therefore, according to the exposure method of the present invention, it is possible to form a predetermined pattern on a substrate with high accuracy by high-precision exposure.
[0024]
According to a tenth aspect of the present invention, there is provided a device manufacturing method including a lithography step, wherein the lithography step uses the exposure method according to the ninth aspect.
[0025]
According to this, in the lithography process, a predetermined pattern is formed on the substrate with high accuracy by using the exposure method according to claim 9, and as a result, the yield of devices as final products is improved, and It is possible to improve the performance.
[0026]
According to an eleventh aspect of the present invention, a plurality of line patterns (L _m ) That detects a position of a mark (WM) including an image signal (MWF) corresponding to each of the plurality of line patterns. _m ); A selection device (20) for selecting at least one specific line pattern from the plurality of line patterns; and an imaging device corresponding to the specific line pattern selected by the selection device. A processing device (20) for performing predetermined processing using a signal to obtain position information of the specific line pattern; and using the position information of the specific line pattern and an offset amount based on a design value of the specific line pattern. And a computing device (20) for calculating position information of the mark.
[0027]
According to this, the imaging device captures an image of a mark area including a mark including a plurality of line patterns arranged on the object along a predetermined direction, and obtains an imaging signal corresponding to each of the plurality of line patterns. Is done. Further, at least one specific line pattern among the plurality of line patterns is selected by the selection device. Then, a predetermined process is performed by the processing device using the imaging signal corresponding to the specific line pattern selected by the selecting device, and position information of the specific line pattern is obtained. Next, the arithmetic unit calculates the position information of the mark, that is, the position information of the reference point of the mark, using the position information of the specific line pattern and the offset amount (offset amount from the reference point) based on the design value of the specific line pattern. Is calculated. Therefore, according to the position detection device of the present invention, even if a mark having a deformed shape or a mark having a different tendency of positional shift is mixed, the position information of the mark can be accurately obtained without being affected by this. Can be.
[0028]
In this case, as in the position detection device according to claim 12, the selection device specifies the pattern in which at least one waveform of the imaging signal and its n-th derivative signal (n is a natural number) has the same characteristic amount. It can be selected as a pattern.
[0029]
The invention according to claim 13 is a position detection device that detects position information of a mark including a plurality of line patterns arranged along a predetermined direction, and images a mark area including the mark on an object, An imaging device that obtains an imaging signal corresponding to each of the plurality of line patterns; and a predetermined signal obtained from the signal waveform based on one of the signal waveforms of the imaging signal and an n-th derivative signal (n is a natural number). A feature value determining device for determining a feature value for each of the plurality of line patterns; and comparing the predetermined feature value obtained by the feature value determining device between the plurality of line patterns to determine whether the feature value is different. An extraction device for extracting a specific line pattern that is different from the feature amount of the line pattern of the above; and calculating the specific line pattern extracted by the extraction device A position detecting apparatus which comprises a; excluded, by using the position information of the remaining line pattern obtained based on the imaging signal, calculation unit and for calculating a position information of the mark.
[0030]
According to this, first, the imaging device captures an image of a mark area including a mark including a plurality of line patterns arranged along a predetermined direction on the object, and obtains imaging signals corresponding to the plurality of line patterns, respectively. You. Next, a predetermined characteristic amount obtained by using a signal waveform of any one of the imaging signal and its nth-order differential signal (n is a natural number) is obtained for each of the plurality of line patterns by the characteristic amount determination device. Then, the extraction device compares the predetermined feature value obtained by the feature value determination device between the plurality of line patterns, and extracts a specific line pattern whose feature value is different from the feature value of another line pattern. You. Then, the calculation device excludes the specific line pattern extracted by the extraction device from the calculation, and calculates the position information of the mark by using the position information of the remaining line pattern obtained based on the imaging signal.
[0031]
That is, in the position detecting device of the present invention, not all of the plurality of line patterns forming the mark, but a predetermined signal obtained from one of the image signals corresponding to the plurality of line patterns and the n-order differential signal thereof. Are extracted, a pattern in which the predetermined characteristic amount is different from the characteristic amount in another line pattern is extracted, and the position of the mark is calculated using the remaining line patterns excluding the extracted pattern. For this reason, even if a mark having a distorted shape or a mark having a different tendency of positional shift is mixed, the positional information of the mark can be accurately obtained without being affected by the mixed shape.
[0032]
In this case, as in the position detection device according to claim 14, the calculation device calculates the position information of the mark based on the position information of the remaining line pattern and the design value of the remaining pattern. It can be done.
[0033]
In each of the position detection devices according to the twelfth to fourteenth aspects, various amounts can be considered as the feature amount. However, as in the position detection device according to the fifteenth aspect, the feature amount corresponds to each of the line patterns. The number of peaks of at least one of an imaging signal and its n-th order differential signal (n is a natural number), and at least one of the m-th order differential signal (m is an even number) of the imaging signal corresponding to each line pattern. The degree of symmetry, the ratio of the signal intensity of the first part corresponding to the line part of the imaging signal corresponding to the line pattern to the second part corresponding to the other part, and the line of the imaging signal corresponding to the line pattern The signal intensity ratio between the first portion and the second portion corresponding to the edges at both ends of the portion.
[0034]
The invention according to claim 16 is an exposure apparatus for exposing a substrate with an energy beam to form a predetermined pattern on the substrate, wherein the exposure apparatus is formed on the substrate and arranged in a predetermined direction. A position detection device according to any one of claims 11 to 15, wherein position information of a mark including a plurality of line patterns is detected; and when the substrate is exposed by the energy beam, the position information is detected by the position detection device. And a controller (19, 20) for controlling the position of the substrate based on the position information of the mark.
[0035]
According to this, the position information of the mark including a plurality of line patterns arranged in a predetermined direction formed on the substrate in advance by the position detection device according to any one of claims 11 to 15 is accurate. Is detected. When exposing the substrate with the energy beam, the control device controls the position of the substrate with high accuracy based on the position information of the mark detected by the position detecting device. As a result, it becomes possible to form a predetermined pattern on the substrate with high accuracy by high-precision exposure.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0037]
FIG. 1 shows a schematic configuration of an exposure apparatus 100 according to an embodiment suitable for carrying out the position detection method and the exposure method of the present invention. The exposure apparatus 100 is a step-and-scan type projection exposure apparatus. Exposure apparatus 100 controls illumination system 10, reticle stage RST holding reticle R as a mask, projection optical system PL, wafer stage WST on which wafer W as a substrate is mounted, reticle stage RST, and wafer stage WST. A stage control system 19 and a main control system 20 for controlling the entire apparatus overall are provided.
[0038]
The illumination system 10 includes a light source, an illuminance uniforming optical system including an optical integrator (a fly-eye lens, a rod integrator, a diffractive optical element, or the like), a relay lens, as disclosed in, for example, JP-A-6-349701. , A variable ND filter, a reticle blind, a dichroic mirror and the like (all not shown). In the illumination system 10, a slit-shaped illumination area on the reticle R defined by a reticle blind (not shown) and elongated in the X-axis direction (the left-right direction in the plane of FIG. 1) is substantially irradiated with illumination light IL as an energy beam. Illuminate with uniform illuminance. Here, as the illumination light IL, far ultraviolet light such as KrF excimer laser light (wavelength 248 nm), ArF excimer laser light (wavelength 193 nm), or F ₂ Vacuum ultraviolet light such as laser light (wavelength 157 nm) is used. As the illumination light IL, an ultraviolet bright line (g-line, i-line, etc.) from an ultra-high pressure mercury lamp can be used.
[0039]
On the reticle stage RST, a reticle R having a circuit pattern PA formed on its pattern surface (the lower surface in FIG. 1) is fixed by, for example, vacuum suction. The reticle stage RST is in an XY plane perpendicular to an optical axis of the illumination system 10 (coincident with an optical axis AX of a projection optical system PL described later) by a reticle stage drive unit 12 including actuators such as a linear motor and a voice coil motor. , And can be driven at a scanning speed designated in a predetermined scanning direction (here, the Y-axis direction which is a direction orthogonal to the plane of FIG. 1).
[0040]
The position of the reticle stage RST in the stage movement plane is constantly detected by a reticle laser interferometer (hereinafter, referred to as “reticle interferometer”) 16 through a movable mirror 15 with a resolution of, for example, about 0.5 to 1 nm. . Position information of reticle stage RST from reticle interferometer 16 is supplied to stage control system 19 and main control system 20 via the same. The stage control system 19 drives and controls the reticle stage RST via the reticle stage drive unit 12 based on the position information of the reticle stage RST in response to an instruction from the main control system 20. Note that the end surface of reticle stage RST may be mirror-finished to form a reflection surface (corresponding to the reflection surface of movable mirror 15 described above).
[0041]
The projection optical system PL is disposed below the reticle stage RST in FIG. 1, and the direction of the optical axis AX is the Z-axis direction. As the projection optical system PL, for example, a refracting optical system having a predetermined reduction magnification (for example, 1/5 or 1/4) which is telecentric on both sides is used. Therefore, when the illumination area of the reticle R is illuminated by the illumination light IL from the illumination optical system, the illumination light IL that has passed through the reticle R causes the circuit of the reticle R in the illumination area to pass through the projection optical system PL. A reduced image (partially inverted image) of the pattern PA is formed on the wafer W having a surface coated with a resist (photosensitive agent).
[0042]
The wafer stage WST is arranged below the projection optical system PL in FIG. 1 and on a base (not shown), and a wafer table 25 is mounted on the wafer stage WST. A wafer W is fixed on the wafer table 25 via a wafer holder (not shown) by, for example, vacuum suction. The wafer table 25 can be tilted in an arbitrary direction with respect to a plane orthogonal to the optical axis of the projection optical system PL by a driving unit including a voice coil motor and the like, and the optical axis AX direction (Z-axis direction) of the projection optical system PL. It is also configured to be finely movable. Further, the wafer table 25 can also perform a minute rotation operation around the Z axis.
[0043]
The wafer stage WST moves not only in the scanning direction (Y-axis direction) but also in a non-intersecting manner perpendicular to the scanning direction so that a plurality of shot areas on the wafer W can be positioned in an exposure area conjugate with the illumination area. It is configured to be movable also in the scanning direction (X-axis direction). This wafer stage WST is driven in the XY two-dimensional directions by a drive system including a motor and the like. As described above, the drive unit of wafer table 25 and the drive system of wafer stage WST are separately provided, but are collectively shown as wafer drive device 24 in FIG. Therefore, the following description is based on the assumption that wafer stage WST is driven in the XY two-dimensional directions and wafer table 25 is minutely driven in the directions of four degrees of freedom of Z, θx, θy, and θz by wafer driving device 24. I do.
[0044]
The position of wafer stage WST (and wafer table 25) in the XY plane is determined by wafer laser interferometer system 18 via movable mirror 17 provided on wafer table 25 with a resolution of, for example, about 0.5 to 1 nm. Always detected. Here, actually, on the wafer table 25, a Y moving mirror having a reflecting surface orthogonal to the scanning direction (Y axis direction) and an X moving mirror having a reflecting surface orthogonal to the non-scanning direction (X axis direction) are provided. Corresponding to this, the wafer laser interferometer is also provided with a Y interferometer that irradiates the interferometer beam vertically to the Y moving mirror, and an X interferometer that irradiates the interferometer beam vertically to the X moving mirror. However, these are typically shown in FIG. 1 as a moving mirror 17 and a wafer laser interferometer system 18. Note that, for example, the end surface of the wafer table 25 may be mirror-finished to form a reflection surface (corresponding to the reflection surface of the movable mirror 17). The X interferometer and the Y interferometer are multi-axis interferometers having a plurality of length measuring axes, and in addition to the X and Y positions of the wafer table 25, rotation (yaw (rotation around the Z axis, θz rotation), pitching) (Rotation around the X axis, θx rotation) and rolling (rotation around the Y axis, θy rotation) can also be measured. Therefore, in the following description, it is assumed that the wafer laser interferometer system 18 measures the positions of the wafer table 25 in the X, Y, θz, θy, and θx directions of five degrees of freedom. In the present embodiment, a stationary coordinate system (orthogonal coordinate system) that defines the movement position of wafer stage WST is defined by the measurement axes of the Y interferometer and X interferometer of wafer laser interferometer system 18. Hereinafter, this stationary coordinate system is also referred to as a “stage coordinate system”. Further, the multi-axis interferometer irradiates a laser beam onto a reflection surface installed on a pedestal (not shown) on which the projection optical system PL is mounted via a reflection surface installed on the wafer table 25 at an angle of 45 °. Alternatively, relative position information about the optical axis direction (Z-axis direction) of the projection optical system PL may be detected.
[0045]
Position information (or speed information) of the wafer stage WST on the stage coordinate system is supplied to the stage control system 19 and the main control system 20 via the stage control system 19. The stage control system 19 controls the wafer stage WST via the wafer driving device 24 based on the position information (or speed information) of the wafer stage WST in accordance with an instruction from the main control system 20.
[0046]
A reference mark plate FM is fixed near the wafer W on the wafer table 25. The surface of the fiducial mark plate FM is set at the same height as the surface of the wafer W, and is a fiducial mark used for so-called baseline measurement of an alignment detection system described later, a fiducial mark used for reticle alignment, and other marks (FIG. No. 1 is representatively shown by reference numeral GM).
[0047]
Further, the exposure apparatus 100 includes an off-axis type alignment detection system AS as an imaging device. The alignment detection system AS irradiates illumination light having a predetermined wavelength width to a mark on the reference mark plate FM or an alignment mark (hereinafter, also appropriately referred to as a “wafer mark”) as a position detection mark on the wafer W. Then, an image of the mark and an image of the index mark on the index plate disposed in a plane conjugate with the wafer are formed on a light receiving surface of an image sensor (CCD or the like) by an objective lens or the like. The obtained imaging signal is subjected to predetermined processing to calculate position information of the detected mark with respect to the center of the index mark, and outputs the position information to the main control system 20.
[0048]
The alignment detection system AS includes, for example, a light source 103 such as a halogen lamp, a light guide 104 such as an optical fiber, an illumination aperture stop 127, a condenser lens 129, an illumination relay lens 105, a beam splitter 106, a first objective lens 107, a reflecting prism. 108, a second objective lens 111, an index plate 112, a relay lens system (113, 114), an imaging aperture stop 130, a beam splitter 115, a Y-direction CCD 116, an X-direction CCD 117, a signal processing system 118, and the like. I have.
[0049]
Explaining the operation of the alignment detection system AS, the alignment light AL from the light source 103 is guided to a predetermined position via the light guide 104. The alignment light AL emitted from the exit end of the light guide 104 is restricted by the illumination aperture stop 127 as necessary, and then enters the condenser lens 129 as an illumination light beam having an appropriate cross-sectional shape.
[0050]
The alignment light AL emitted from the condenser lens 129 is once collected, and then enters the illumination relay lens 105 via an illumination field stop (not shown). The alignment light AL converted into parallel light via the illumination relay lens 105 passes through the beam splitter 106 and then enters the first objective lens 107. The alignment light AL condensed by the first objective lens 107 is reflected vertically downward on the reflecting surface of the reflecting prism 108, and thereafter is used as a mark to be detected on the wafer stage WST, for example, a measurement mark on the reference mark plate FM. The mark GM, another reference mark, or an alignment mark on the wafer W is illuminated.
[0051]
The reflected light from the above-described detected mark (hereinafter, referred to as “mark M” for convenience) illuminated by the alignment light AL enters the beam splitter 106 via the reflecting prism 108 and the first objective lens 107. . The light vertically reflected by the beam splitter 106 forms an image of the mark M on the index plate 112 on which the index mark (not shown) is formed, via the second objective lens 111.
[0052]
The light emitted from the index plate 112 passes through the relay lens system (113, 114), is restricted by the imaging aperture stop 130 as necessary during the passage, and enters the beam splitter 115. One light (reflected light) split by the beam splitter 115 enters the Y-direction CCD 116 and the other light (transmitted light) enters the X-direction CCD 117.
[0053]
In this way, an image of the mark M is formed on the imaging surface of the CCD 116 for the Y direction and the CCD 117 for the X direction together with the image of the index mark on the index plate 112. Output signals from the Y-direction CCD 116 and the X-direction CCD 117 are supplied to a signal processing system 118, where the signal processing system 118 performs predetermined signal processing (for example, noise removal) and A / D conversion. The converted image signal, that is, image data, is supplied to the main control system 20. The main control system 20 calculates the position of the mark M with reference to the center of the index mark based on the imaging signal, and calculates the stage coordinates based on the calculation result and the measurement value of the wafer laser interferometer system 18 at that time. The position coordinates of the mark M in the system are calculated.
[0054]
The exposure apparatus 100 further supplies an irradiating optical system (not shown) that supplies an image forming light beam for forming a plurality of slit images toward the best image forming plane of the projection optical system PL from an oblique direction with respect to the optical axis AX direction. An oblique incidence type multi-point focus detection system comprising a system and a light-receiving optical system (not shown) for receiving each reflected light beam of the image-formed light beam on the surface of the wafer W through a slit is used as the projection optical system PL. It is fixed to a supporting portion (not shown). As the multipoint focus detection system, one having the same configuration as that disclosed in, for example, JP-A-6-283403 is used, and the stage control system 19 uses the wafer position information from the multipoint focus detection system. The wafer table 25 is driven in the Z-axis direction and the tilt direction based on the above.
[0055]
The main control system 20 is configured to include a microcomputer or a workstation, and controls the components of the apparatus in an integrated manner. Further, a command for the illumination aperture stop 127 and a command for the imaging aperture stop 130 are supplied to the main control system 20 via an input device 126 such as a keyboard. The main control system 20 drives the illumination aperture stop 127 via the drive system 128 or drives the imaging aperture stop 130 via the drive system 131 based on these commands.
[0056]
Next, an operation when the exposure apparatus 100 of the present embodiment configured as described above performs exposure processing of the second and subsequent layers (second layer) on the wafer W will be described.
[0057]
First, under control of the main control system 20, a reticle load and a wafer load are performed by a reticle loader and a wafer loader (not shown).
[0058]
Next, in response to an instruction from the main control system 20, the wafer drive unit 24 is controlled by the stage control system 19, and a pair of reticle alignment marks on the reticle R and a pair of reticle alignment marks on the reference mark plate FM corresponding thereto. The wafer stage WST is moved (positioned) to a position where the first reference mark can be simultaneously detected by a pair of reticle microscopes (not shown). Then, the main control system 20 detects the positional relationship between the reticle alignment mark and the corresponding first reference mark using the reticle microscope.
[0059]
Next, based on an instruction from the main control system 20, the wafer drive unit 24 is controlled by the stage control system 19, and the position at which the second reference mark for baseline measurement on the reference mark plate FM can be detected by the alignment detection system AS. Then, wafer stage WST is moved. Then, the main control system 20 uses the alignment detection system AS to position the second reference mark (in this case, the position of the second reference mark with respect to the center of the index mark of the alignment detection system AS, that is, the center of the index mark and the second reference mark). Position relationship with the mark) is detected with high accuracy. In the main control system 20, the positional relationship between the reticle alignment mark and the corresponding first fiducial mark, the positional relationship between the index center of the alignment detection system AS and the second fiducial mark, and the reticle interferometer at the time of each measurement. The base line amount (the positional relationship between the index center of the alignment detection system AS and the projection position of the reticle pattern) is calculated based on the measured values of the wafer 16 and the wafer laser interferometer system 18 and the designed baseline distance.
[0060]
After the completion of such preparation work, the EGA type wafer alignment shown in the flowchart of FIG. 2 is started. FIG. 2 corresponds to a processing algorithm relating to a series of wafer alignments by the CPU in the main control system 20. It is assumed that a counter i indicating the number of a wafer mark to be detected, which will be described later, is initialized to 1.
[0061]
As a premise, the rotation error of wafer W has been accurately corrected by pre-alignment performed prior to the above-described wafer loading, and when loaded on a wafer holder on wafer stage WST, the rotation error is negligible. Shall be smaller. Therefore, in this embodiment, so-called search alignment for rotational position alignment of the wafer W is unnecessary.
[0062]
Further, it is assumed that each shot area on the wafer W is provided with a wafer alignment mark (wafer mark) formed of a line and space pattern (L / S pattern). As shown in FIGS. 3A and 3B, the width W of the line portion is used as the wafer mark WM. _l And space width W _s A step mark (phase mark) composed of an L / S mark having a ratio (duty ratio) of 1: 1 is used. The wafer mark WM has a line portion width W _l And space width W _s Are, for example, 6 μm, the pitch p is 12 μm, and five line portions L composed of step portions having a depth h (for example, 25 μm) with respect to the space portion ₁ ~ L ₅ have.
[0063]
Here, in each shot area on the wafer W, a wafer Y mark WM having a Y-axis direction as a periodic direction (pitch direction) is actually set as a wafer mark WM. _y X mark WM with the X-axis direction as the periodic direction _x Are provided at least one each. These wafer Y marks WM _y , Wafer X mark WM _x Are arranged at the same position in each shot area in terms of design. Incidentally, actually, the wafer Y mark WM _y , Wafer X mark WM _x Are arranged on a street line between adjacent shot areas, but here, for convenience of explanation, it is assumed that they are arranged at predetermined positions in the shot area. The number of the wafer marks WM is not limited to the L / S pattern including the five line patterns, but may be another number. In the present embodiment, the line intervals are the same, but may be different.
[0064]
First, in step 302 of FIG. 2, the wafer W is moved with reference to the counter i so that the area (mark area) where the i-th wafer mark is formed falls within the imaging area of the alignment detection system AS. For this purpose, an instruction is given to the stage control system 19. In response to this instruction, the stage control system 19 moves the wafer stage WST via the wafer driving device 24 based on the position information of the wafer stage WST measured by the wafer laser interferometer system 18, and The region where the i-th (here, the first) wafer mark is formed is positioned within the imaging region of the alignment detection system AS. In this case, the first mark (for example, wafer X mark WM) of the first alignment shot area (sample shot area) on wafer W _x1 (Hereinafter referred to as “first mark area” for convenience) is positioned within the imaging area of the alignment detection system AS.
[0065]
Next, in step 304, an image of the i-th mark area (the first mark area in this case) on the wafer W is captured using the alignment detection system AS, and the imaging result is stored in a memory (RAM or the like) (not shown). I do.
[0066]
Next, in a subroutine 106, the i-th wafer mark WM (in this case, the first mark WM _x1 ) Is calculated.
[0067]
In the subroutine 106, as shown in FIG. 4, first, in step 342, the imaging data stored in the memory is read, and the signal waveform I (X) (or I (Y)) is extracted. Here, the wafer X mark WM _x The case where the signal waveform I (X) corresponding to the above is extracted will be described.
[0068]
In extracting the signal waveform I (X), first, a plurality of (for example, 50) XP axis directions near the center in the YP axis direction conjugate to the Y axis direction on the wafer W in the imaging area of the alignment detection system AS By calculating the average of the intensity distribution on the scanning line (direction conjugate to the X-axis direction on the wafer W), the white noise is canceled, and the average signal intensity distribution in the XP-axis direction, that is, the signal waveform I (X) is extracted. ing. In the present embodiment, smoothing is further performed after obtaining the average of the intensity distribution. An example of the signal waveform I (X) thus extracted is shown in FIG. In FIG. 5, the horizontal axis indicates the position on the XP axis, and the vertical axis indicates the signal intensity I.
[0069]
As shown in FIG. 5, the signal waveform I (X) has a line pattern L _m (M = 1 to 5) Five mark waveforms MWF corresponding to each _m have. Of these, the mark waveform MWF ₁ ~ MWF ₄ Is the corresponding line pattern L ₁ ~ L ₄ From the steps at both ends of each of the two peak waveforms (the signal level of the space portion, I ₁ (A waveform having a peak at a point where the difference from the peak value is equal to or more than a predetermined value) is the observed waveform. Such a waveform from which two peak waveforms can be obtained from one line is called a double mark, and the waveform is called a double mark waveform. In the double mark waveform, when the cross section of the line pattern has a step structure, and a phase difference occurs between the upper surface and the lower surface of the step, one signal (peak waveform) is observed from each step at both ends of the line. Is what is done.
[0070]
On the other hand, the mark waveform MWF ₅ Is the corresponding line pattern L ₅ Is a waveform in which only one peak waveform is observed. Such a waveform in which only one peak waveform is obtained from one line is called a single mark, and the waveform is called a single mark waveform. The single mark waveform is observed when there is a large difference in reflectance between inside and outside the line. Further, even when the cross section has a stepped structure, a single waveform may be obtained depending on the relationship between the illumination wavelength and the stepped depth and the focus state.
[0071]
Also, as can be seen from FIG. 5, the mark waveform MWF _m Is the center position X in each design ₁ ~ X ₅ Is generally left-right symmetric (reflection symmetry) on the basis of. Therefore, if attention is paid to this mirror symmetry, the mark waveform MWF _m , Ie, the line pattern L _m Can be specified to some extent accurately.
[0072]
Therefore, in the present embodiment, the mark waveform MWF is _m Specify the approximate location of. That is, in step 344, as shown in FIG. 6, five regions PFD arranged at a predetermined period (arrangement pitch PW1) along the XP axis direction ₁ , PFD ₂ , PFD ₃ , PFD ₄ , PFD ₅ And define the area PFD _m (M = 1 to 5) is set as the scanning initial position. Here, the area PFD _m Is the same width PW in the XP axis direction (PW is the mark waveform MWF _m Greater than the width of In the following, the region PFD _m The signal waveform in _m (X).
[0073]
The area PFD _m Is set at the initial scanning position, the region PFD _m The initial position and the end position of the scan are determined. Here, the area PFD _m In setting the scanning initial position, for example, the area PFD ₁ It is possible to make the position in the XP axis direction (XP position) sufficiently small, but the first mark WM _x1 Mark waveform MWF expected by design immediately before imaging ₁ Is set to a value slightly smaller than the minimum value of the range of the XP position of the first mark WM. _x1 It is desirable from the viewpoint of performing the detection of swiftly. In setting the scanning end position, for example, the area PFD ₁ May be set sufficiently large, but the first mark WM _x1 Mark waveform MWF expected by design immediately before imaging ₁ Is set to a value slightly larger than the maximum value of the XP position range of the first mark WM. _x1 It is desirable from the viewpoint of performing the detection of swiftly.
[0074]
FIG. 7 shows the region PFD _m Shows an example of a state where is set to the scanning initial position.
[0075]
In the next step 346, the area PFD _m Signal waveform I _m The reflection symmetry of (X) is calculated by a predetermined calculation, and the calculation result is stored in the memory.
[0076]
In the next step 348, the area PFD _m Is determined to be at the movement end position. In this case, the area PFD _m Is set only at the initial scanning position, the determination here is denied, and the routine proceeds to step 350, where the region PFD _m Is moved in the + XP direction by a predetermined pitch ΔXP, the process returns to step 346, and thereafter the above processing and determination are repeated in a loop of steps 346, 348 and 350.
[0077]
In the above description, for convenience of explanation, the region PFD _m Is described in the + XP direction at a pitch ΔXP interval, but actually, the region PFD _m Starts scanning from the initial position in the + XP direction while maintaining the mutual distance, and calculates the degree of reflection symmetry in step 346 at a predetermined sampling interval. That is, the pitch ΔXP is equal to the area PFD in the sampling interval. _m Is the distance traveled.
[0078]
FIG. 8 shows that the region PFD _m Center position of XPP _m Is the line pattern L _m Mark waveform MWF corresponding to _m 3 shows a state in which the position coincides with the design center position.
[0079]
And the area PFD _m When the scanning is completed and the scanning end position is reached, the determination in step 348 is affirmative, and the routine goes to step 352. When the determination in step 348 is affirmative, the area PFD is stored in the memory. _m The signal waveform I corresponding to each XP position at the ΔXP interval including the scan start position and the scan end position _m The calculation result of the mirror symmetry of (X) is stored.
[0080]
In step 352, the signal waveform I stored in the memory _m Based on the calculation result of the mirror symmetry of (X), the position where each mirror symmetry is maximum is determined by the corresponding mark waveform MWF. _m XP position of mark, that is, mark waveform MWF _m Line pattern L corresponding to _m , Respectively.
[0081]
Note that the wafer Y mark WM _y Is extracted in the same procedure as described above.
[0082]
In this manner, the approximate position in the detection direction (measurement direction) of each line pattern constituting the i-th (here, first) wafer mark WM, in this case, the first mark WM _x1 A line pattern L constituting _m After calculating the approximate X position and storing the calculation result in the memory, the process proceeds to step 354.
[0083]
In step 354, the signal waveform I (X) (or (I (Y))) in the memory and the mark waveform MWF constituting the signal waveform _m Line pattern L corresponding to _m The mark waveforms corresponding to the line patterns are classified for each set having the same first feature amount, based on the approximate X position information and the wafer mark design information. Here, for example, the number of peaks (signals) will be described as the first feature amount.
[0084]
That is, in step 354, for example, the obtained signal waveform is differentiated, and each mark waveform MWF is obtained. _m If the differential signal has only one pair of peaks, the mark waveform MWF _m Is the single mark waveform described above, and when there are two pairs of peaks, the mark waveform MWF _m Is classified as the above-described double mark waveform, and the result is stored in the memory. For example, in the case of the signal waveform I (X) in FIG. 5, the mark waveform MWF ₁ ~ MWF ₄ Is double mark waveform, mark waveform MWF ₅ Are classified as single mark waveforms.
[0085]
In the next step 356, as a result of the above classification, only mark waveforms belonging to the set having the largest number of elements are extracted. For example, in the case of the signal waveform I (X) in FIG. 5, since there are four double mark waveforms and one single mark waveform, the mark waveform MWF belonging to the set of double mark waveforms ₁ ~ MWF ₄ Only those will be extracted.
[0086]
In the next step 358, the extracted mark waveform (in the above case, the mark waveform MWF ₁ ~ MWF ₄ ) Are classified for each set having the same second feature amount. Here, the difference between the signal intensity from the inside of the line pattern and the signal intensity from the outside of the line pattern (space portion) within a predetermined range is defined as a second feature amount. For example, in the above case, as shown in FIG. 5, the signal strength from inside the line pattern to be evaluated is Iin, and the signal strength from the space between the line pattern to be evaluated and the adjacent line pattern is Iin. In the case of Iout, a value D represented by the following equation (1) can be used as an index of the difference between the two.
[0087]
D = (Iout−Iin) / Iout (1)
[0088]
D is 0 when the signal intensity is equal inside and outside the line pattern, and takes a positive value when the inside of the line pattern is dark with respect to the outside and a negative value when the inside is bright.
[0089]
Therefore, for example, when D ≦ 0 is set as the second feature amount, in the case of FIG. ₁ ~ MWF ₃ Then, D ≦ 0 is satisfied, and the mark waveform MWF ₄ Then, D> 0, and D ≦ 0 is not satisfied. As a result, the mark waveform MWF ₁ ~ MWF ₃ Set and mark waveform MWF ₄ And a set consisting only of
[0090]
In the next step 360, only the mark waveforms belonging to the set having the largest number of elements are extracted as a result of the classification in step 358. For example, in the case of FIG. 5, since there are three mark waveforms satisfying D ≦ 0 and one mark waveform not satisfying D ≦ 0, the mark waveform MWF belonging to the set satisfying D ≦ 0 is satisfied. ₁ ~ MWF ₃ Only those will be extracted.
[0091]
In the next step 362, predetermined processing is performed using the mark waveform (imaging signal) extracted in step 360, and a line pattern corresponding to the extracted mark waveform (in this case, the mark waveform MWF) ₁ ~ MWF ₃ Line pattern L corresponding to ₁ ~ L ₃ ) Is calculated. That is, a predetermined calculation process is performed on the extracted mark waveform based on each mark waveform, and the position information of each specific line pattern corresponding to the extracted mark waveform in the imaging region of the alignment detection system AS, that is, the XP position (In the case of a wafer X mark) or YP position (in the case of a wafer Y mark), and an offset with respect to a design reference point in each line pattern is obtained.
[0092]
In the next step 364, the sum of the simple average value of the XP position (or YP position) of the specific line pattern and the simple average value of the offset is obtained, and the converted value of the value is calculated based on the detection direction of the wafer mark WM. Calculate as position.
[0093]
For example, in the case of FIG. ₁ ~ MWF ₃ Based on each of them, a predetermined operation is performed to obtain a mark waveform MWF. ₁ ~ MWF ₃ XP position X of ₁ ', X ₂ ', X ₃ 'Respectively. Then, according to the following equation (2), the wafer X mark WM _x XP position X ′ is determined.
[0094]
X ′ = k ｛(X ₁ '+ X ₂ '+ X ₃ ') / 3 + (2PW1 + PW1 + 0) / 3｝ (2)
In equation (2), k is a conversion coefficient determined by the imaging magnification of the imaging optical system that forms the alignment detection system AS.
[0095]
In this case, the mark waveform MWF ₁ XP position X of ₁ And the offset (−2PW1), and the wafer X mark WM by the following equation (3). _x It is also possible to obtain the XP position X ′ of
[0096]
X ′ = k (X ₁ '+ 2PW1) ... (3)
Alternatively, mark waveform MWF ₂ XP position X of ₂ ′ And its offset (−PW1), and the wafer X mark WM by the following equation (4). _x It is also possible to obtain the XP position X ′ of
[0097]
X ′ = k (X ₂ '+ PW1) …… (4)
Alternatively, mark waveform MWF ₃ XP position X of ₃ (In this case, the offset is zero), the wafer X mark WM is calculated by the following equation (5). _x It is also possible to obtain the XP position X ′ of
[0098]
X '= kX ₃ '…… (5)
Alternatively, the wafer X mark WM is determined based on the sum of the average value of the XP position and the average value of the offset of any two mark waveforms MWF. _x It is also possible to obtain the XP position X ′ of
[0099]
However, in order to reduce the measurement error due to the averaging effect, it is desirable to use the above equation (2).
[0100]
Then, based on the position of the wafer mark WM thus determined with reference to the detection center of the alignment detection system AS of the wafer mark WM and the measurement value of the wafer laser interferometer system 18 at the time of imaging the wafer mark WM. The position coordinates of the wafer mark WM on the stage coordinate system are represented by the i-th wafer mark WM (here, the first mark WM). _x1 ) Is calculated as position information. Then, the process of the subroutine 106 is completed, and the process returns to step 310 of the main routine.
[0101]
The inventor performed an optical simulation on the calculation of the position of the wafer mark WM, and as a result, obtained a good result. Here, this optical simulation will be briefly described.
[0102]
The simulation conditions assume a halogen lamp light source as a light source, and a detection optical system (corresponding to the imaging optical system of the alignment detection system AS) having a numerical aperture of 0.3 and a coma aberration of 0.01λ in RMS value. As the wafer mark, an L / S pattern composed of a step mark having a line width of 6 μm, a line interval (arrangement period) of 12 μm, the number of line patterns of 5, and a step depth of 25 nm similar to the above-mentioned wafer mark WM was used ( FIGS. 3A and 3B. Also, three line patterns L on the left side ₁ ~ L ₃ , The reflectivity inside and outside the line is uniform, but the two lines on the right ₄ , L ₅ In this example, the internal reflectance is reduced by 0.02 and 0.15 from the left, respectively.
[0103]
As a result, a signal waveform I (X) substantially similar to FIG. 5 was obtained. In other words, the line pattern L ₄ , L ₅ In this case, the signal intensity from the inside of the line pattern decreases, and the three line patterns L on the left side ₁ ~ L ₃ It has a different shape.
[0104]
In this case, when the average value of the calculation results of the positions of all five line patterns was determined, all the line patterns L ₁ ~ L ₅ It is confirmed that the position of the wafer mark is shifted by 6.1 nm as compared with an ideal case having the same shape and the same reflectance.
[0105]
Next, as described above, the line pattern L that is a single mark ₅ And the line pattern L which is a double mark is excluded. ₁ ~ L ₄ When the sum of the average value of the position and the average value of the respective offsets was calculated, the amount of positional deviation was 3.2 nm. From this, the line pattern L ₁ ~ L ₄ It was confirmed that the position measurement accuracy was improved when using the position and the respective offsets.
[0106]
Further, a line pattern L which is a double mark ₁ ~ L ₄ The index D indicating the difference in signal strength between the inside and outside of the line pattern is a positive line pattern L. ₄ And a line pattern L having the same shape and the same reflectance ₁ ~ L ₃ When the sum of the average value of the position and the average value of the respective offsets is calculated, the detection position of the entire wafer mark is determined by all line patterns ₁ ~ L ₅ Was found to substantially match the ideal case having the same shape and the same reflectance.
[0107]
Returning to FIG. 2, in step 310, it is determined with reference to the counter i whether or not the position information of the wafer marks of all the preselected alignment shot areas has been calculated. Here, the first wafer mark WM _x1 Since the position information has only been calculated, the determination in step 310 is denied, and the process proceeds to step 312.
[0108]
In step 312, after incrementing the counter i (i ← i + 1), the process returns to step 302, and the processing and determination are repeated in the loop of steps 302 to 312.
[0109]
Then, when the position information of the wafer marks (X position information of the wafer X mark and Y position information of the wafer Y mark) of all the alignment shot areas selected in advance is calculated, the determination in step 310 is affirmed, and the process proceeds to step 314. In this step 314, using the calculated position information of the wafer mark, a statistical operation using the least square method disclosed in, for example, Japanese Patent Application Laid-Open No. 61-44429 is performed to obtain six types of error parameters, Calculate rotation θ, wafer scaling Sx, Sy, wafer orthogonality Ort, and offsets Ox, Oy.
[0110]
In the next step 316, the above-mentioned six types of error parameters and the design position information of each shot area are substituted into a predetermined model formula from which the error parameters are calculated, and all the error parameters on the wafer W After calculating the array coordinates of the shot area (that is, the overlay correction position), a series of processing of this routine ends.
[0111]
After the completion of such wafer alignment, the exposure operation of the step-and-scan method is performed as follows.
[0112]
In this exposure operation, the stage control system 19 monitors the measurement value of the wafer laser interferometer system 18 and performs the first shot of the wafer W in response to an instruction based on the wafer alignment result and the baseline measurement result from the main control system 20. Wafer stage WST is moved to a scanning start position (acceleration start position) for exposure of (first shot area). Then, the stage control system 19 starts scanning in the Y-axis direction between the reticle stage RST and the wafer stage WST via the reticle stage driving unit 12 and the wafer driving device 24, and the two stages RST and WST perform their respective target scanning speeds. Is reached, the pattern area of the reticle R starts to be illuminated by the illumination light IL, and scanning exposure is started.
[0113]
In the stage control system 19, the moving speed Vr of the reticle stage RST in the Y-axis direction and the moving speed Vw of the wafer stage WST in the Y-axis direction during the above-described scanning exposure are set to a speed ratio corresponding to the projection magnification of the projection optical system PL. Reticle stage RST and wafer stage WST are synchronously controlled so as to be maintained.
[0114]
Then, different areas of the pattern area of the reticle R are sequentially illuminated with the illumination light IL, and the illumination of the entire pattern area is completed, thereby completing the scanning exposure of the first shot on the wafer W. Thereby, the circuit pattern of the reticle R is reduced and transferred to the first shot via the projection optical system PL.
[0115]
In this manner, when the first-shot scanning exposure is completed, the wafer stage WST is step-moved in the X and Y-axis directions by the stage control system 19 in accordance with the instruction from the main control system 20, and the second shot (second shot) is performed. Is moved to a scanning start position for exposure of the shot area of FIG.
[0116]
Then, under the control of the main control system 20, the same scanning exposure as described above is performed on the second shot.
[0117]
In this manner, the scanning exposure of the shot area on the wafer W and the stepping operation for the next shot area exposure are repeatedly performed, and the circuit pattern of the reticle R is sequentially transferred to all the exposure target shot areas on the wafer W. You.
[0118]
As is apparent from the above description, in the present embodiment, the components of the position detection device except the alignment detection system AS are realized by the main control system 20, more specifically, the CPU and the software program. . That is, the selection device is realized by the processing of steps 342 to 360 performed by the CPU, the processing device is realized by the processing of step 362, and the processing device is realized by the processing of step 364.
[0119]
In the present embodiment, in the flowchart of FIG. 4 described above, instead of the steps 356 to 362 surrounded by the two-dot chain line, a step 356 ′ shown in FIG. To 362 '. Here, FIG. 9 will be simply described.
[0120]
In the above-described step 354, the mark waveforms are classified for each set having the same first feature amount. _m Are classified into the aforementioned single mark waveform and the aforementioned double mark waveform, and the results are stored in the memory. After this classification, the process moves to step 356 'in FIG.
[0121]
In this step 356 ′, as a result of the above classification, only the mark waveforms belonging to the set having the minimum number of elements are extracted. For example, in the case of the signal waveform I (X) of FIG. 5, since there are four double mark waveforms and one single mark waveform, the mark waveform MWF belonging to the set of single mark waveforms ₅ Only those will be extracted.
[0122]
In the next step 358 ', the extracted mark waveform (in the above case, the mark waveform MWF ₅ ) Except for the mark waveform (mark waveform MWF in the above case) ₁ ~ MWF ₄ ) Are classified for each set having the same second feature amount. Here, similarly to the above, the difference between the signal strength from the inside of the line pattern and the signal strength from the outside of the line pattern (space portion) is within a predetermined range is defined as the second feature amount. In this case, for example, the aforementioned D value can be used as an index of the difference between the two. For example, when D ≦ 0 is set as the second feature amount, in the case of FIG. ₁ ~ MWF ₃ Then, D ≦ 0 is satisfied, and the mark waveform MWF ₄ Then, D> 0, and D ≦ 0 is not satisfied. As a result, the mark waveform MWF ₁ ~ MWF ₃ Set and mark waveform MWF ₄ And a set consisting only of
[0123]
In the next step 360 ', only the mark waveforms belonging to the set having the minimum number of elements are extracted as a result of the classification in step 358'. For example, in the case of FIG. 5, since there are three mark waveforms satisfying D ≦ 0 and one mark waveform not satisfying D ≦ 0, the mark waveform MWF belonging to the set not satisfying D ≦ 0 is satisfied. ₄ Only those will be extracted.
[0124]
In the next step 362 ', predetermined processing is performed using the remaining mark waveforms (imaging signals) excluding the mark waveform extracted in step 360', and a specific line pattern corresponding to the remaining mark waveforms (in this case, Mark waveform MWF ₁ ~ MWF ₃ Line pattern L corresponding to ₁ ~ L ₃ ) And the offset with respect to the design reference point in each line pattern. Thereafter, the process proceeds to step 364 in FIG.
[0125]
When the processing algorithm of FIG. 9 is adopted, the processing of steps 354 and 358 ′ performed by the CPU realizes the feature amount determination device that constitutes the position detection device together with the alignment detection system AS, and the processing of steps 356 ′ and 360 ′ The extraction device is realized, and the calculation device is further realized by the processing of steps 362 'and 364.
[0126]
Needless to say, at least a part of the components realized by the above software program may be configured by hardware. In the present embodiment, when the wafer W is exposed by the illumination light IL by the main control system 20 and the stage control system 19, the position of the wafer W is determined based on the position information of the mark detected by the position detecting device. A control device for controlling is realized.
[0127]
As described above in detail, according to the position detection device and the position detection method according to the present embodiment, the lines arranged along the X-axis direction (or the Y-axis direction) on the wafer W by the alignment detection system AS. Pattern L _m An image of a mark area including a wafer mark WM including an L / S mark including an image signal (MWF) corresponding to a plurality of line patterns is taken. _m ) Is obtained. Further, the main control system 20 controls at least one specific line pattern (for example, the line pattern L ₁ ~ L ₃ ) Is selected (steps 342 to 360). Then, the main control system 20 controls the imaging signal (for example, MWF) corresponding to the selected specific line pattern. ₁ ~ MWF ₃ ) Is performed to obtain position information of a specific line pattern (step 362). Next, the main control system 20 uses the position information of the specific line pattern and the offset amount (offset amount from the reference point) based on the design value of the specific line pattern, that is, the position information of the wafer mark WM, that is, the position of the wafer mark WM. The position information of the reference point is calculated (step 364). Therefore, according to the position detecting device and the position detecting method of the present embodiment, even if a mark (line pattern) having a distorted shape or a mark (line pattern) having a different tendency of positional deviation of the mark (line pattern) is mixed. The position information of the wafer mark WM can be accurately obtained without being affected by this.
[0128]
Further, in the present embodiment, the main control system 20 uses the number of peaks obtained from the imaging signal of the line pattern or the differential signal thereof as the first feature amount, and converts the plurality of line patterns into the first feature amount. Classification is performed for each same set (step 354), and a specific line pattern among a plurality of line patterns, for example, a line pattern belonging to a set having the largest number of elements (for example, a line pattern L which is a double mark) ₁ ~ L ₃ ). Next, the main control system 20 determines the ratio of the signal intensity of the first portion corresponding to the line portion of the imaging signal corresponding to the line pattern to the second portion corresponding to the other portion (space portion) as the second feature amount. The specific line pattern selected above is classified for each set having the same second feature amount using the above-described D value which is an index of the specific line pattern, for example, a line belonging to the set having the largest number of elements. Pattern (Line pattern L with negative D value) ₁ ~ L ₃ ) Only.
[0129]
The reason for performing the two-stage classification and selection in this way is to more reliably select only line patterns having very similar shapes and the like and having the same tendency of positional deviation. Therefore, if only line patterns having somewhat similar shapes and similar displacement tendency are selected, the line patterns may be classified and selected in one stage. In this case, the number of peaks obtained from the image signal of the line pattern or its differential signal can be used as the feature amount. Note that if it is known in advance that all the line patterns are single marks (or double marks), the above-described D value or the like can be used as the feature amount. Instead of selecting a set having the maximum number of elements, a group having a feature specified in advance may be selected. For example, a double mark can always be selected regardless of the number of elements.
[0130]
Further, in the present embodiment, when the processing algorithm of FIG. 9 is employed, the main control system 20 does not perform all of the plurality of line patterns forming marks based on the imaging signal from the alignment detection system AS. A predetermined characteristic amount obtained from one of signal waveforms of an imaging signal corresponding to each of the plurality of line patterns and an n-th differential signal thereof is obtained (steps 354 and 358 ′). Then, a line pattern different from the feature value in is extracted (steps 356 ', 360'). Then, the main control system 20 calculates the position of the mark by using the remaining line pattern excluding the extracted pattern (steps 362 ', 364). For this reason, even if a mark having a distorted shape or a mark having a different tendency of positional shift is mixed, the positional information of the mark can be accurately obtained without being affected by the mixed shape.
[0131]
Further, according to the exposure apparatus 100 and the exposure method according to the present embodiment, at the time of wafer alignment, the wafer X mark (L / S whose periodic direction is the X-axis direction) attached to the alignment shot area on the wafer W A mark composed of a pattern) and a wafer Y mark (a mark composed of an L / S pattern whose periodic direction is the Y-axis direction) are detected by using the above-described position detecting device and the position detecting method. As a result, even if a wafer mark having a distorted shape or a wafer mark having a different tendency of the positional shift of the mark is mixed, the position information of the wafer mark can be accurately detected without being affected by this. Then, based on the position information of the accurately detected wafer mark, the main control system 20 determines the array coordinates of the shot area on the wafer W by a predetermined statistical operation.
[0132]
Then, the main control system 20 and the stage control system 19 determine the XY of the wafer W based on the array coordinates (and the baseline amount) of each shot area on the wafer W calculated (detected) with high accuracy as described above. The wafer W is exposed using the illumination light IL while controlling the position in the plane.
[0133]
Therefore, the position of the wafer W at the time of exposure can be controlled with high accuracy, and high-precision exposure with an extremely small pattern transfer position error can be performed. That is, the relative positional relationship between the wafer W and the reticle R at the time of scanning exposure can be maintained in a desired state, and the pattern of the reticle R can be transferred onto each shot area on the wafer W with high accuracy. it can.
[0134]
As a method of classifying the mark waveform, the following classification method can be adopted in addition to or instead of the classification method of the above embodiment.
[0135]
That is, as shown in FIG. 10A, the extracted mark waveform (the mark waveform MWF in FIG. ₁ '~ MWF ₃ ') Are classified for each set having the same third feature value.
[0136]
Here, the line portion of the mark waveform corresponding to the line pattern (the line portion L in FIG. 10B) ₁ '~ L ₃ The ratio of the signal intensities of the two portions corresponding to the edges at both ends of ()) is defined as a third feature value. Here, as shown in FIG. 10A, the signal intensity from the portion corresponding to the left edge in FIG. 10A of the line portion of the mark waveform corresponding to the line pattern to be evaluated is Ileft, and the right edge is When the signal strength from the portion corresponding to the edge of the pattern is Iright, and the signal strength from the space between the line pattern to be evaluated and the adjacent line pattern is Iout, The value Q shown in the equation (6) can be used.
[0137]
Q = (Ileft-Iright) / Iout (6)
[0138]
Q becomes 0 when the signal intensities from the portions corresponding to the respective edges of the left and right ends of the line pattern are equal (in the case of Ileft = Iright). ), The absolute value of Q increases. Therefore, by determining the allowable range of Q and using the range as a reference for classification of the mark waveform corresponding to the line pattern, a line pattern in which the shape of the line pattern is left-right asymmetric and the observed signal waveform is asymmetric is obtained. By excluding it, it is possible to improve the position measurement accuracy.
[0139]
Here, as a result of the simulation by the inventor, a signal waveform I (x) ′ substantially similar to FIG. 10A was obtained. Hereinafter, the simulation result will be briefly described.
[0140]
In this case, the line portion L ₃ The position measurement was performed using only the line pattern L, and it was confirmed that the position was shifted by 11.1 nm as compared with the ideal case. ₁ '~ L ₃ As a result of the position measurement, it was confirmed that a deviation of 3.7 nm occurred in comparison with the ideal case.
[0141]
Therefore, if it is assumed that −0.05 <Q <0.05 is the third feature amount and only a line pattern that satisfies this condition is used for position measurement, the line portion L ₁ ', L ₂ '(Mark waveform MWF ₁ ', MWF ₂ In FIG. 10A, since Ileft = Iright as shown in FIG. 10A, Q = 0, and the line portion L ₃ '(Mark waveform MWF ₃ In '), since Iout = 0.32, Ileft = 0.21, and Iright = 0.19, Q ≒ 0.06, and the line portion L ₃ 'Will be excluded.
[0142]
Thus, the line portion L which is asymmetrical ₃ 'Is excluded from the position measurement target, and the line portion L ₁ ', L ₂ It was confirmed that the position measurement result of the mark almost coincided with the ideal case by performing the position measurement using only '.
[0143]
In the above embodiment, the case where the present invention is applied to a scanning stepper has been described. However, the present invention is not limited to this, and can be applied to a stationary exposure apparatus such as a step-and-repeat type stepper. In such a case, when performing static exposure, the wafer can be accurately positioned at the exposure position (projection position of the reticle pattern), and the reticle pattern is accurately superimposed and transferred onto a desired partitioned area on the wafer. can do.
[0144]
In addition, the illumination optical system, the projection optical system, and the alignment detection system AS composed of a plurality of lenses are incorporated in the exposure apparatus main body, and optical adjustment is performed. The exposure apparatus according to the above-described embodiment can be manufactured by connecting wires and pipes to the apparatus and further performing overall adjustment (electrical adjustment, operation confirmation, and the like). It is desirable that the exposure apparatus be manufactured in a clean room in which the temperature, the degree of cleanliness, and the like are controlled.
[0145]
In addition, the present invention is not limited to an exposure apparatus for manufacturing a semiconductor, but is used for manufacturing a display including a liquid crystal display element and the like, an exposure apparatus for transferring a device pattern onto a glass plate, and a device used for manufacturing a thin film magnetic head The present invention can also be applied to an exposure apparatus that transfers a pattern onto a ceramic wafer, an imaging device (such as a CCD), an exposure apparatus used for manufacturing a micromachine, a DNA chip, and the like. In addition to micro devices such as semiconductor elements, glass substrates or silicon wafers for manufacturing reticles or masks used in light exposure equipment, EUV exposure equipment, X-ray exposure equipment, electron beam exposure equipment, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern to a substrate. Here, in an exposure apparatus using DUV (far ultraviolet) light or VUV (vacuum ultraviolet) light, a transmission type reticle is generally used, and as a reticle substrate, quartz glass, fluorine-doped quartz glass, fluorite, Magnesium fluoride, quartz, or the like is used. In a proximity type X-ray exposure apparatus, an electron beam exposure apparatus, or the like, a transmission mask (stencil mask, membrane mask) is used, and a silicon wafer or the like is used as a mask substrate.
[0146]
Further, the position detection method and position detection device according to the present invention are not limited to the exposure device, but can be applied to any device provided with an image-forming mark detection system.
[0147]
《Device manufacturing method》
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 100 and its exposure method in a lithography process will be described.
[0148]
FIG. 11 shows a flowchart of a manufacturing example of a device (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, or the like). As shown in FIG. 11, first, in step 201 (design step), a function / performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step 202 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 203 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.
[0149]
Next, in step 204 (wafer processing step), an actual circuit or the like is formed on the wafer by lithography or the like using the mask and the wafer prepared in steps 201 to 203, as described later. Next, in step 205 (device assembly step), device assembly is performed using the wafer processed in step 204. This step 205 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary.
[0150]
Finally, in step 206 (inspection step), inspections such as an operation check test and a durability test of the device created in step 205 are performed. After these steps, the device is completed and shipped.
[0151]
FIG. 12 shows a detailed flow example of step 204 in the semiconductor device. In FIG. 12, in step 211 (oxidation step), the surface of the wafer is oxidized. In step 212 (CVD step), an insulating film is formed on the wafer surface. In step 213 (electrode formation step), electrodes are formed on the wafer by vapor deposition. In step 214 (ion implantation step), ions are implanted into the wafer. Each of the above steps 211 to 214 constitutes a pre-processing step in each stage of the wafer processing, and is selected and executed according to a necessary process in each stage.
[0152]
In each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 215 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 216 (exposure step), the circuit pattern of the mask is transferred onto the wafer by the exposure apparatus and the exposure method described above. Next, in step 217 (development step), the exposed wafer is developed, and in step 218 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 219 (resist removing step), unnecessary resist after etching is removed.
[0153]
By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.
[0154]
When the device manufacturing method of the present embodiment described above is used, the exposure apparatus 100 and the exposure method of the above embodiment are used in the exposure step (step 216), so that the reticle pattern and each shot area on the wafer W are overlapped. The alignment accuracy can be improved and the reticle pattern can be accurately transferred onto the wafer. Therefore, the yield of micro devices as final products is improved, and the productivity thereof can be improved.
[0155]
【The invention's effect】
As described above, according to the position detection method and the position detection device of the present invention, there is an effect that position information of a mark on an object can be accurately detected.
[0156]
Further, according to the exposure method and the exposure apparatus according to the present invention, there is an effect that the substrate can be exposed with high accuracy.
[0157]
Further, according to the device manufacturing method of the present invention, there is an effect that the productivity of the device can be improved.
[Brief description of the drawings]
FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to one embodiment.
FIG. 2 is a flowchart illustrating an EGA type wafer alignment processing algorithm;
FIGS. 3A and 3B are diagrams schematically showing a wafer mark WM. FIG.
FIG. 4 is a flowchart showing a subroutine 106 of FIG. 2;
FIG. 5 is a diagram illustrating an example of a signal waveform I (X).
FIG. 6 is a diagram showing five regions arranged at a predetermined period along the XP axis direction.
FIG. 7: area PFD _m FIG. 5 is a diagram showing an example of a state where is set to a scanning initial position.
FIG. 8: area PFD _m Center position of XPP _m Is the mark waveform MWF _m FIG. 5 is a diagram showing a state where the position matches the designed center position.
FIGS. 9A and 9B are diagrams illustrating a method of classifying mark waveforms according to a modification.
FIG. 10 is a flowchart illustrating a modification.
FIG. 11 is a flowchart illustrating a device manufacturing method according to the present invention.
FIG. 12 is a flowchart showing a specific example of step 204 in FIG. 11;
[Explanation of symbols]
19: Stage control system (part of control device) 20: Main control system (selection device, processing device, arithmetic device, feature value determination device, extraction device, calculation device, part of position detection device, part of control device ), AS: Alignment detection system (part of imaging device, position detection device), IL: Illumination light (energy beam), L _m ... Line pattern, MWF _m .., An imaging signal, W: wafer (object, substrate), WM: wafer mark (mark).

Claims (16)

A position detection method for detecting position information of a mark including a plurality of line patterns arranged along a predetermined direction,
Imaging a mark area including the mark on the object and obtaining imaging signals respectively corresponding to the plurality of line patterns;
Selecting at least one specific line pattern from the plurality of line patterns, and obtaining position information of the specific line pattern using an imaging signal corresponding to the specific line pattern;
Calculating the position information of the mark using position information of the specific line pattern and an offset amount based on a design value of the specific line pattern. The method according to claim 1, wherein the selection of the specific line pattern is performed by selecting a pattern in which at least one waveform of the imaging signal and its n-th derivative signal (n is a natural number) has the same characteristic amount. The position detection method described. A position detection method for detecting position information of a mark including a plurality of line patterns arranged along a predetermined direction,
Imaging a mark area including the mark on the object and obtaining imaging signals respectively corresponding to the plurality of line patterns;
A step of obtaining, for each of the plurality of line patterns, a predetermined characteristic amount obtained from the signal waveform based on one of the signal waveforms of the imaging signal and its n-th derivative signal (n is a natural number);
Comparing the predetermined feature value obtained for each line pattern among the plurality of line patterns, and extracting a specific line pattern whose feature value is different from the feature value of another line pattern;
Excluding the extracted specific line pattern from the calculation, and calculating the position information of the mark by using the position information of the remaining line pattern obtained based on the imaging signal. Position detection method. The method according to claim 3, wherein in the step of calculating the position information of the mark, the position information of the mark is calculated based on the position information of the remaining line pattern and a design value of the remaining pattern. The position detection method described. 5. The image processing apparatus according to claim 2, wherein the feature quantity is a number of peaks of at least one signal of an imaging signal corresponding to each of the line patterns and an n-th order differential signal (n is a natural number). The position detection method described in the section. 5. The method according to claim 2, wherein the characteristic amount is a degree of symmetry of at least one of an imaging signal corresponding to each of the line patterns and an m-th order differential signal (m is an even number). The position detection method according to claim 1. 5. The characteristic amount is a ratio of a signal intensity of a first portion corresponding to a line portion of the imaging signal corresponding to the line pattern and a signal intensity of a second portion corresponding to another portion. The position detection method according to claim 1. 5. The apparatus according to claim 2, wherein the characteristic amount is a ratio of a signal intensity between a first portion and a second portion corresponding to edges at both ends of a line portion of the imaging signal corresponding to the line pattern. 6. The position detection method according to claim 1. An exposure method for exposing a substrate by an energy beam to form a predetermined pattern on the substrate,
A step of detecting the position information of a mark including a plurality of line patterns arranged in a predetermined direction on the substrate in advance, using the position detection method according to any one of claims 1 to 8. When;
Exposing the substrate with the energy beam while controlling the position of the substrate based on the detected position information of the mark. A device manufacturing method including a lithography step,
10. A device manufacturing method using the exposure method according to claim 9 in the lithography step. A position detection device that detects a position of a mark including a plurality of line patterns arranged along a predetermined direction,
An imaging device that images a mark area including the mark on an object and obtains imaging signals respectively corresponding to the plurality of line patterns;
A selection device for selecting at least one specific line pattern from the plurality of line patterns;
A processing device that performs predetermined processing using an imaging signal corresponding to the specific line pattern selected by the selection device and obtains position information of the specific line pattern;
A calculating device that calculates position information of the mark using position information of the specific line pattern and an offset amount based on a design value of the specific line pattern. 12. The position according to claim 11, wherein the selection device selects, as the specific pattern, a pattern in which at least one waveform of the imaging signal and its n-th derivative signal (n is a natural number) has the same characteristic amount. Detection device. A position detection device for detecting position information of a mark including a plurality of line patterns arranged along a predetermined direction,
An imaging device that images a mark area including the mark on an object and obtains imaging signals respectively corresponding to the plurality of line patterns;
A feature value determining device for obtaining a predetermined feature value obtained from the signal waveform based on one of the signal waveforms of the imaging signal and an n-th derivative signal (n is a natural number) for each of the plurality of line patterns; ;
An extraction device that compares the predetermined feature value obtained by the feature value determination device among the plurality of line patterns and extracts a specific line pattern whose feature value is different from a feature value of another line pattern; When;
A calculation device that excludes the specific line pattern extracted by the extraction device from the calculation, and calculates the position information of the mark by using the position information of the remaining line pattern obtained based on the imaging signal. Position detection device. 14. The position detecting device according to claim 13, wherein the calculating device calculates the position information of the mark based on position information of the remaining line pattern and a design value of the remaining pattern. The feature amount includes the number of peaks of at least one signal of the imaging signal corresponding to each line pattern and its n-th differential signal (n is a natural number), the imaging signal corresponding to each line pattern, and its m-th differential signal (M is an even number) the degree of symmetry of at least one signal, the ratio of the signal intensities of the first portion corresponding to the line portion of the image signal corresponding to the line pattern and the second portion corresponding to the other portion, 15. The signal intensity ratio of a first portion and a second portion corresponding to edges at both ends of a line portion of an imaging signal corresponding to the line pattern. The position detecting device according to claim 1. An exposure apparatus for exposing a substrate by an energy beam to form a predetermined pattern on the substrate,
The position detection device according to any one of claims 11 to 15, which detects position information of a mark including a plurality of line patterns arranged in a predetermined direction on the substrate in advance.
A control device that controls a position of the substrate based on position information of a mark detected by the position detection device when exposing the substrate with the energy beam.

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