JP2006179803A - Aligning method and apparatus, aligner, and method of manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligning method and an aligning apparatus for precisely controlling the alignment between a reticle stage and a wafer stage, and to provide an aligner and a method of manufacturing a device. <P>SOLUTION: The aligning method comprises a step for detecting the actual positions of a first stage 25 for placing a reticle, and a second stage 45 for placing a wafer as output signals; a step for creating a correction table for correcting output signals at each position of the first stage 25 and the second stage 45; a step for comparing the actual position with a target position; a step for correcting one portion of the output signal and/or one portion of coordinates by utilizing the correction table, based on the comparison information of the comparison step; and a step for determining the position relationship between the first stage 25 or the reticle, and the second stage 45, based on the output signal corrected in the correction step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to an exposure apparatus, and more particularly to an exposure apparatus used when manufacturing various devices such as a single crystal substrate for a semiconductor wafer, a glass substrate for a liquid crystal display (LCD), a CCD, and a magnetic head. The present invention relates to alignment between a reticle (reticle stage) and a workpiece (wafer stage). The present invention is particularly suitable for an exposure apparatus that uses extreme ultraviolet (EUV) light as an exposure light source.

  When manufacturing fine semiconductor elements such as semiconductor memories and logic circuits using photolithography (baking) technology, a circuit pattern drawn on a reticle (or mask) is projected onto a wafer or the like by a projection optical system. A reduction projection exposure apparatus for transferring the image has been used conventionally.

  The minimum dimension (resolution) that can be transferred by the reduction projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength, the better the resolution. For this reason, with the recent demand for miniaturization of semiconductor elements, the exposure light has been shortened, and an ultra-high pressure mercury lamp (i-line (wavelength: about 365 nm)), KrF excimer laser (wavelength: about 248 nm), ArF excimer. The wavelength of ultraviolet light used with lasers (wavelength about 193 nm) has become shorter.

  However, semiconductor elements are rapidly miniaturized, and there is a limit in lithography using ultraviolet light. Therefore, in order to efficiently transfer a very fine circuit pattern of 0.1 μm or less, a reduction projection exposure apparatus using extreme ultraviolet (EUV) light having a wavelength shorter than that of ultraviolet light and having a wavelength of about 10 nm to 15 nm ( Hereinafter, it is referred to as “EUV exposure apparatus”).

  On the other hand, in the projection exposure apparatus, as the resolution is improved, higher accuracy is also required for alignment for aligning the relative positions of the reticle and the wafer. In particular, since an EUV exposure apparatus has a very fine circuit pattern to be transferred, for example, it is necessary to strictly align an alignment mark on a reticle and an alignment mark on a wafer.

  There is an alignment method (also called “die-by-die alignment”) in which alignment between the alignment mark on the reticle and the alignment mark on the wafer is performed every time on every shot on the wafer. Excellent global alignment. In the global alignment, the position of the alignment mark on the wafer is detected only with a plurality of shots in the wafer, and thereafter, positioning is performed with stage feed accuracy. At that time, it is necessary to accurately know the positional relationship between the reticle stage and the wafer stage.

  10 and 11 are diagrams for explaining alignment between the reticle stage 1100 and the wafer stage 1300 in the exposure apparatus using ultraviolet light or EUV light. A reference pattern 1120 is set on a reticle 1110 supported by the reticle stage 1100, and the reference light from the reference pattern 1120 is detected by a detector 1400 installed on the wafer stage 1300 via the projection optical system 1200. As shown in FIG. 11, the detector 1400 has a configuration in which a slit 1420 is formed on a slit support substrate 1410. The light passing through the opening 1430 is photoelectrically converted by a photodiode 1440 and detected as an electrical signal. To do. Under such a configuration, while the wafer stage 1300 is relatively moved, the signal of the photodiode 1440 as shown in FIGS. 13 and 15 is detected, and the wafer in which the detection signal becomes maximum (that is, the light amount is maximum). The position of the stage 1300 is set as a reference position for the reticle stage 1100 and the wafer stage 1300 with respect to the direction perpendicular to the optical axis. Here, FIGS. 13 and 15 are diagrams illustrating an example of a detection signal of the photodiode 1440. FIG. 13 and 15, the horizontal axis employs the in-plane position of the slit 1420, and the vertical axis employs the light intensity, and FIG. 13 illustrates a positional relationship in which most of the reference light passes through the opening 1430. FIG. 15 shows a positional relationship where most of the reference light is blocked by the slit 1420. In FIGS. 13 and 15, the hatched portion is the light after passing through the slit, and the output of the photodiode 1440 is proportional to the area of the shaded portion. When the reticle stage 1100 and the wafer stage 1300 are at the reference position, the light intensity distribution near the focal position has a large contrast as shown in FIG. On the other hand, the light intensity distribution at a position deviated from the focal position in the optical axis direction has a small contrast as shown in FIG. In the case of a distribution with a large contrast, as shown in FIG. 13, the signal intensity of the photodiode 1440 is large because the amount of light (light quantity) passing through the opening 1430 of the slit 1420 is large, but the distribution with a small contrast is present. In this case, as shown in FIG. 17, the signal intensity of the photodiode 1440 becomes small because the amount of light passing through the opening 1430 of the slit 1420 is small. Therefore, while the wafer stage 1300 is relatively moved in the optical axis direction, the signal of the photodiode 1440 is detected, and the position of the wafer stage 1300 where the detection signal becomes maximum (that is, the contrast is maximum) is determined as the reticle stage in the optical axis direction. A focal position between 1100 and the wafer stage 1300 is set.

Note that, when aligning the reticle stage and the wafer stage, a method has been proposed in which the speed and position in the scanning direction of the stage are corrected based on values read using a light wave interferometer (for example, Patent Document 1). reference.).
JP 2001-44098 A

  However, in Patent Document 1, in order to obtain the average of the stage speed in the scanning direction when performing position detection, the coordinates at each measurement point are equally spaced, but the actual speed and average speed at each measurement point are The difference in signal output accompanying the difference is mixed as noise.

  Actually, the stage vibrates also in a direction perpendicular to the scanning direction, and the signal intensity changes with the vibration. Conventionally, since signal output is calculated based on position information in only one axial direction with respect to the scanning direction, changes in signal intensity due to fluctuations from the target position in the direction perpendicular to the scanning direction are processed as noise, resulting in a reference The position detection accuracy was degraded. For example, FIG. 14 shows changes in signal intensity when stage scanning is performed in the + Z direction with the optical axis direction as the Z direction. If the signal intensity becomes maximum when the position in the direction X perpendicular to the scanning direction is at the reference position X = 0, as shown in FIG. 14, X = ± 1, ± 2,... As the amount of deviation from the reference position X = 0 increases, the signal intensity decreases. Assuming that the stage is controlled with the reference position X = 0 as a target, the stage is actually scanned in the + Z direction while changing in the + and − directions with X = 0 as the center. Accordingly, when scanning is performed in the + Z direction at the reference position X = 0, as shown in FIG. 18, a waveform having a difference from the ideal profile at the reference position X = 0 is obtained, and the difference becomes noise and deteriorates the detection accuracy. Let

  In general, the position detection of a stage by a light wave interferometer can be measured with high frequency and high accuracy, but the stage controlled based on such position detection is slow in response, and the position control of the stage is compared with the position detection accuracy. bad. In other words, the stage position deviates from the target position (reference position), but how much it deviates can be measured with high accuracy.

  Therefore, the present invention provides a positioning method capable of measuring the positional relationship (reference position and focal position) between the reticle stage and the wafer stage with high accuracy and controlling the alignment between the reticle stage and the wafer stage with high accuracy. And an apparatus, an exposure apparatus, and a device manufacturing method.

  In order to achieve the above object, an alignment method according to one aspect of the present invention is an alignment method between a first stage on which a reticle is placed or the reticle and a second stage on which a wafer is placed. A step of detecting actual positions of the first stage and the second stage as output signals, and a correction table for correcting the output signals at the positions of the first stage and the second stage. And a step of comparing the actual position and the target position, and using a correction table to convert a part of the output signal and / or a part of the coordinates based on the comparison information of the comparison step. Correcting the positional relationship between the first stage or the reticle and the second stage based on the correcting step and the output signal corrected in the correcting step; Characterized by a step of constant.

  An alignment method according to another aspect of the present invention is an alignment method between a first stage on which a reticle is placed or the reticle and a second stage on which a wafer is placed, wherein the first stage And a step of obtaining a function of an output signal for all positions to which the second stage moves, a step of detecting actual positions of the first stage and the second stage as output signals, and a step of detecting Among the detected output signals, a part of the output signal or a part of the coordinates at a position shifted from the target position is corrected using the function, and the output signal corrected in the correction step And determining a positional relationship between the first stage or the reticle and the second stage.

  An alignment method as still another aspect of the present invention is an alignment method between a first stage on which a reticle is mounted or the reticle and a second stage on which a wafer is mounted. Detecting the actual position of the stage and the second stage as an output signal, and using the coordinates of at least two axes including the output signal and the scanning direction of the first stage and the second stage, Obtaining a mapping from the coordinates to the output signal for each detection step; and determining a positional relationship between the first stage or the reticle and the second stage using the mapping. It is characterized by that.

  An alignment method as still another aspect of the present invention is an alignment method between a first stage on which a reticle is mounted or the reticle and a second stage on which a wafer is mounted. A step of detecting an actual position of the stage and the second stage as an output signal, and a position of the output signal detected in the detection step from a target position of the first stage and the second stage The positional relationship between the first stage or the reticle and the second stage is selected using only the output signal selected in the selection step, and the step of selecting an output signal whose deviation is within an allowable range. And determining.

  An alignment apparatus according to still another aspect of the present invention is an alignment apparatus used for alignment of a reticle stage and a wafer stage of an exposure apparatus, and has a mode for performing the above-described alignment method. .

  An exposure apparatus according to another aspect of the present invention projects an illumination optical system that illuminates a reticle placed on a first stage, and a pattern of the reticle onto an object to be treated placed on a second stage. An exposure apparatus including the above-described alignment apparatus.

  According to still another aspect of the present invention, there is provided a device manufacturing method comprising: exposing a target object using the above-described exposure apparatus; and developing the exposed target object.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, an alignment method capable of measuring the positional relationship (reference position and focal position) between the reticle stage and the wafer stage with high accuracy and controlling the alignment between the reticle stage and the wafer stage with high accuracy. And an apparatus, an exposure apparatus, and a device manufacturing method can be provided.

  Hereinafter, an exposure apparatus according to an aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted. Here, FIG. 1 is a schematic sectional view showing the structure of the exposure apparatus 1 of the present invention.

  The exposure apparatus 1 of the present invention is formed on the reticle 20 by using, for example, a step-and-scan method or a step-and-repeat method using EUV light (for example, a wavelength of 13.4 nm) as illumination light for exposure. This is a projection exposure apparatus that exposes a circuit pattern to the object to be processed 40. Such an exposure apparatus is suitable for a lithography process of submicron or quarter micron or less, and in the present embodiment, a step-and-scan type exposure apparatus (also referred to as “scanner”) will be described below as an example. Here, the “step and scan method” means that the wafer is continuously scanned (scanned) with respect to the reticle to expose the reticle pattern onto the wafer, and the wafer is stepped after completion of one shot of exposure. The exposure method moves to the next exposure area. The “step-and-repeat method” is an exposure method in which the wafer is stepped and moved to the exposure area of the next shot for every batch exposure of the wafer.

  Referring to FIG. 1, an exposure apparatus 1 includes an illumination apparatus 10, a reticle stage 25 on which a reticle 20 is placed, a projection optical system 30, a wafer stage 45 on which an object to be processed 40 is placed, and an alignment apparatus. 100.

  Further, as shown in FIG. 1, EUV light has a low transmittance to the atmosphere and generates contamination due to a reaction with a residual gas (polymer organic gas or the like) component, so at least in the optical path through which the EUV light passes. (That is, the entire optical system) is in a vacuum atmosphere VC.

  The illuminating device 10 is an illuminating device that illuminates the reticle 20 with arc-shaped EUV light (for example, a wavelength of 13.4 nm) with respect to the arc-shaped field of the projection optical system 30, and includes an EUV light source 12, an illumination optical system 14, Have

  As the EUV light source 12, for example, a laser plasma light source is used. In this method, a target material in a vacuum vessel is irradiated with high-intensity pulsed laser light to generate high-temperature plasma, and EUV light having a wavelength of about 13 nm, for example, emitted from the plasma is used. As the target material, a metal film, a gas jet, a droplet, or the like is used. In order to increase the average intensity of the emitted EUV light, the repetition frequency of the pulse laser should be high, and it is usually operated at a repetition frequency of several kHz.

  The illumination optical system 14 includes a condensing mirror 14a and an optical integrator 14b. The condensing mirror 14a collects EUV light emitted from the EUV light source 12 almost isotropically. The optical integrator 14b has a role of uniformly illuminating the reticle 20 with a predetermined numerical aperture. In addition, the illumination optical system 14 is provided with an aperture 14 c for limiting the illumination area of the reticle 20 to an arc shape at a position conjugate with the reticle 20.

  The reticle 20 is a reflective reticle, on which a circuit pattern (or image) to be transferred is formed, and is supported and driven by a reticle stage 25. The diffracted light emitted from the reticle 20 is reflected by the projection optical system 30 and projected onto the object to be processed 40. The reticle 20 and the workpiece 40 are arranged in an optically conjugate relationship. Since the exposure apparatus 1 is a scanner, the pattern of the reticle 20 is reduced and projected onto the object to be processed 40 by scanning the reticle 20 and the object to be processed 40.

  The reticle stage 25 supports the reticle 20 via a reticle chuck 25a and is connected to a moving mechanism (not shown). The reticle stage 25 can employ any structure known in the art. A moving mechanism (not shown) is constituted by a linear motor or the like, and can move the reticle 20 by driving the reticle stage 25 at least in the X direction. The exposure apparatus 1 scans the reticle 20 and the workpiece 40 in a synchronized state. Here, X is the scanning direction in the surface of the reticle 20 or the object to be processed 40, Y is the direction perpendicular to the scanning direction, and Z is the direction perpendicular to the surface of the reticle 20 or the object to be processed 40.

  The projection optical system 30 uses a plurality of reflecting mirrors (that is, multilayer mirrors) 30a to reduce and project the pattern on the reticle 20 surface onto the object to be processed 40 that is an image surface. The number of reflection mirrors 30a is about 4 to 6. In order to realize a wide exposure area with a small number of reflecting mirrors, the reticle 20 and the object to be processed 40 are simultaneously scanned using only a thin arc-shaped area (ring field) separated from the optical axis by a certain distance. Transfer large area. The numerical aperture (NA) of the projection optical system 30 is about 0.2 to 0.3.

  The object to be processed 40 is a wafer in the present embodiment, but widely includes liquid crystal substrates and other objects to be processed. A photoresist is applied to the object to be processed 40.

  The wafer stage 45 supports the workpiece 40 by a wafer chuck 45a. The wafer stage 45 moves the workpiece 40 in the XYZ directions using, for example, a linear motor. The reticle 20 and the workpiece 40 are scanned synchronously. The actual positions of the reticle stage 25 and the wafer stage 45 are monitored by, for example, a laser interferometer, and both are driven at a constant speed ratio.

  The alignment apparatus 100 has a function of aligning the reticle stage 25 and the wafer stage 45 (that is, measuring the positional relationship (reference position and focal position) between the reticle stage 25 and the wafer stage 45). The alignment apparatus 100 has the same basic configuration as that of the prior art, and includes a reference pattern 110 provided on the reticle 20, a slit 120 provided on the wafer stage 45, a photodiode 130, and a control unit 140. Have The alignment apparatus 100 detects the reference light from the reference pattern 110 with the photodiode 130 via the projection optical system 30. The control unit 140 controls each unit of the alignment apparatus 100.

  Here, an alignment method (measurement method) 200 of the alignment apparatus 100 controlled by the control unit 140 will be described. FIG. 2 is a flowchart for explaining an alignment method 200 according to one aspect of the present invention. In the present embodiment, the focus of the reticle stage 25 and the wafer stage 45 when the wafer stage 45 is scanned in the + Z direction, where the optical axis direction is the + Z direction and the direction perpendicular to the longitudinal direction of the optical axis and the slit 120 is the X direction. The position detection will be described.

  Referring to FIG. 2, first, in order to perform preliminary measurement, the reticle stage 25 and the reticle stage 45 are moved, and the slit 120 is moved to the preliminary measurement start position (step S202).

  Next, by scanning the reticle stage 25 and the wafer stage 45 relative to each other, the reference pattern 110 and the slit 120 are scanned in all coordinates, and the signal intensity of the photodiode 130 is measured (step S204).

  Then, the correction amount at each coordinate is obtained from the correspondence between the signal intensity of the photodiode 130 and the coordinate, and a correction table is created (step S206). Such a correction table is recorded in a memory (not shown) of the control unit 140, for example. The coordinates corresponding to the actual positions of the reticle stage 25 and the wafer stage 45 are obtained by using numerical values output by a laser interferometer (not shown) provided for the reticle stage 25 and the wafer stage 45, for example.

  Steps S202 to S206 are preliminary measurements, and by performing the preliminary measurement once with respect to the number of times of measurement in steps S208 to S212, which will be described later, it is possible to suppress the influence of changes in the imaging characteristics of the optical system over time. it can. In this embodiment, the case where preliminary measurement is not performed is described as an example. However, when preliminary measurement is performed, steps S202 to S206 which are preliminary measurement steps are omitted. Measurement may be performed from step S208 to step S212, which will be described later.

  When the creation of the correction table is completed, the reticle stage 25 and the wafer stage 45 are moved, the reference pattern 110 and the slit 120 are moved to the target measurement start position, and the reticle stage 25 and the wafer stage 45 are relatively moved in the Z-axis direction. Then, the signal intensity of the photodiode 130 is measured (step S208). Then, the signal intensity measured in step S208 is corrected based on the correction table created in step S206 (step S210). Next, the positions of the reticle stage 25 and the wafer stage 45 at which the corrected signal intensity is maximized are calculated and set as the focal positions of the reticle stage 25 and the wafer stage 45 (step S212).

  Here, the correction table will be specifically described. As shown in FIG. 14, when the position of X deviates from the target position, the signal intensity when the wafer stage 45 is scanned in the Z direction decreases. At this time, even if the position of X is deviated by a certain distance, the signal intensity difference from the target position varies depending on the position in the Z direction. Therefore, as shown in FIG. 3, a correction curve for the amount of deviation in the X direction can be created at each position in the Z direction. The correction curve at each position in the Z direction is tabulated, and the signal intensity of the photodiode 130 is corrected based on the X coordinate information obtained when the wafer stage 45 is scanned in the Z direction. If the sampling points in the Z direction are M points and the sampling points in the X direction are N points, the correction table can be represented by, for example, a two-dimensional array of M × N matrices. Here, FIG. 3 is a diagram illustrating an example of a correction curve for creating a correction table.

  In this embodiment, since the signal intensity shift when the X coordinate when scanned in the Z direction is shifted from the coordinate of the target position is corrected, the change in the signal intensity due to the fluctuation in the X direction is reduced. Can do. Thereby, the error in the case of performing fitting as a function with respect to only one axis in the Z-axis direction can be reduced.

  In the present embodiment, the measurement value at the point where the X coordinate is shifted from the target position is corrected by the value obtained from the correction table. However, the longitudinal direction of the slit 120 is Y, A correction table for all the coordinates of XYZ may be created by adding parameters of the Y coordinate, and correction may be performed based on the correction table. In this case, a three-dimensional correction table is created.

  Another alignment method 300 of the alignment apparatus 100 controlled by the control unit 140 will be described. FIG. 4 is a flowchart for explaining an alignment method 300 according to one aspect of the present invention. Also in the present embodiment, like the alignment method 200, the reticle stage when the wafer stage 45 is scanned in the + Z direction, where the optical axis direction is the + Z direction and the direction perpendicular to the longitudinal direction of the optical axis and the slit 120 is the X direction. The detection of the focal position of 25 and the wafer stage 45 will be described.

  Referring to FIG. 4, first, in order to perform preliminary measurement, the reticle stage 25 and the reticle stage 45 are moved, and the slit 120 is moved to the preliminary measurement start position (step S302).

  Next, by scanning the reticle stage 25 and the wafer stage 45 relative to each other, the reference pattern 110 and the slit 120 are scanned in all coordinates, and the signal intensity of the photodiode 130 is measured (step S304).

  Then, a function of a correction value for the XZ coordinates is calculated from the signal intensity and the coordinates obtained by scanning the reference pattern 110 and the slit 120 in all coordinates (step S306). Coefficients and constants of the correction value function for the XY coordinates are recorded in a memory (not shown) of the control unit 140, for example.

  When the calculation of the function of the correction value with respect to the XZ coordinate is completed, the reticle stage 25 and the wafer stage 45 are moved, the reference pattern 110 and the slit 120 are moved to the target measurement start position, and the reticle stage 25 and the wafer stage 45 are moved along the Z axis. While relatively moving in the direction, the signal intensity of the photodiode 130 is measured (step S308). Then, of the signal intensities measured in step S308, the signal intensities of coordinates that deviate by a set value or more with respect to the target coordinates are corrected based on the function of the correction value for the XZ coordinates obtained in step S306 (step S306). S310). Next, the positions of the reticle stage 25 and the wafer stage 45 at which the corrected signal intensity is maximized are calculated and set as the focal positions of the reticle stage 25 and the wafer stage 45 (step S312).

  Steps S302 to S306 are preliminary measurements. By performing the preliminary measurement once with respect to the number of times of measurement in steps S308 to S312, it is possible to suppress the influence due to the temporal change in the imaging characteristics of the optical system. In this embodiment, the case where preliminary measurement is not performed is described as an example. However, when preliminary measurement is performed, steps S302 to S306 which are preliminary measurement steps are omitted. Measurement may be performed from step S308 to step S312 described later.

  In the present embodiment, since the information on the correspondence relationship between the coordinates and the correction value is compressed as a function, the capacity of the control unit 140 in the memory can be reduced. Moreover, since the correction value in the coordinate which is not measured at the time of preliminary measurement can be generated from the obtained function, the number of measurement points at the time of preliminary measurement can be reduced.

  In the present embodiment, the measurement value at the point where the X coordinate is shifted from the target position is corrected by the value obtained from the function of the correction value. However, the longitudinal direction of the slit 120 is Y, Furthermore, a function of correction values for all the coordinates of XYZ may be created by adding parameters of the Y coordinate, and correction may be performed based on such a function.

  Further, another alignment method 400 of the alignment apparatus 100 controlled by the control unit 140 will be described. FIG. 5 is a flowchart for explaining an alignment method 400 according to one aspect of the present invention. Also in the present embodiment, like the alignment method 200, the reticle stage when the wafer stage 45 is scanned in the + Z direction, where the optical axis direction is the + Z direction and the direction perpendicular to the longitudinal direction of the optical axis and the slit 120 is the X direction. The detection of the focal position of 25 and the wafer stage 45 will be described.

  Referring to FIG. 5, first, reticle stage 25 and wafer stage 45 are moved, reference pattern 110 and slit 120 are moved to the target measurement start position, and reticle stage 25 and wafer stage 45 are relatively moved in the Z-axis direction. Then, the signal intensity of the photodiode 130 is measured (step S402).

  Next, the signal intensity obtained in step S402 is fitted with a function for the XY coordinates (step S404). This fitting will be specifically described. For example, assuming that the signal intensity is expressed by a quadratic expression regarding X and Z, the signal intensity Vs can be expressed by the following expression 1.

At this time, a set of (X ² , Z ² , XZ, X, Z, 1) is created from each (X, Z) obtained in the measurement. Here, assuming that the number of measurement points is N, N sets can be created. An N-dimensional vector in which signal strength Vs is vertically arranged is V, an N × 6 matrix in which (X ² , Z ² , XZ, X, Z, 1) are vertically arranged is A and an unknown coefficient ( A U that minimizes AU-V is calculated by using a 6-dimensional vector in which a, b, h, c, d, and e) are vertically arranged as U.

  Next, based on the parameters obtained by the fitting, the positions of the reticle stage 25 and the wafer stage 45 with the maximum signal intensity are calculated and set as the focal positions of the reticle stage 25 and the wafer stage 45 (step S406).

  FIG. 6 shows a schematic diagram when fitting is performed on the XY coordinates during scanning in the Z direction. In FIG. 6, the signal intensity with respect to the XY coordinates is adopted on the vertical axis. An arrow A indicates the scanning direction, and the target coordinate in the X direction is zero. α represents a drive curve during scanning when the wafer stage 45 performs an ideal operation. However, the drive curve obtained along with actual scanning in the Z direction does not coincide with the drive curve α, and varies in the X direction and the Z direction with respect to the drive curve α. This is because the position of the wafer stage 45 varies from the target position in the X direction perpendicular to the scanning direction, and the speed of the wafer stage 45 in the scanning direction varies. Variations due to these factors are distributed on the curved surface β according to the position and output characteristics of the alignment apparatus 100. The curved surface β can be obtained by fitting the measured points as described above. That is, the focal positions of the reticle stage 25 and the wafer stage 45 can be calculated from the maximum value of the curved surface β.

  In this embodiment, the position fluctuation in the direction perpendicular to the scanning direction is also used for fitting, so that the detection accuracy of the focal position can be improved. Further, unlike the alignment methods 200 and 300, since the same correction table or correction value function is not referred to for a relatively long time, it is difficult to cause an error due to temporal change in the imaging characteristics of the optical system. There are features. Further, according to the present embodiment, since preliminary measurement is not necessary, the number of times the photodiode 130 is used can be reduced, and the lifetime of the photodiode 130 can be extended.

  In the present embodiment, an example in which fitting is performed using XY coordinates has been described. However, the longitudinal direction of the slit 120 is set to Y, and information on the Y coordinates is further added to fit the signal intensity as a function with respect to the XYZ coordinates. May be performed.

  Further, another alignment method 500 of the alignment apparatus 100 controlled by the control unit 140 will be described. FIG. 7 is a flowchart for explaining an alignment method 500 according to one aspect of the present invention. Also in the present embodiment, like the alignment method 200, the reticle stage when the wafer stage 45 is scanned in the + Z direction, where the optical axis direction is the + Z direction and the direction perpendicular to the longitudinal direction of the optical axis and the slit 120 is the X direction. The detection of the focal position of 25 and the wafer stage 45 will be described.

  Referring to FIG. 7, first, reticle stage 25 and wafer stage 45 are moved, reference pattern 110 and slit 120 are moved to the target measurement start position, and reticle stage 25 and wafer stage 45 are moved relative to each other in the Z-axis direction. Then, the signal intensity of the photodiode 130 is measured (step S502).

  Next, among the signal intensities measured in step S502, the signal intensities of XY coordinates that do not fall within the set allowable range of the coordinate deviation from the target position of each stage are selected (deleted) (step S504). Then, fitting is performed on the signal intensity remaining in step S504 using a function for the Z coordinate (step S506). Such fitting is performed using, for example, the least square method. Then, the positions of the reticle stage 25 and the wafer stage 45 with the maximum signal intensity are calculated from the parameters obtained by the fitting, and set as the focal positions of the reticle stage 25 and the wafer stage 45 (step S508).

  In this embodiment, by removing signal intensity that does not fall within the set allowable range of coordinate deviation from the target position of the stage, change in signal intensity due to variation from the target position of the stage is within the set value. It is possible to improve the detection accuracy.

  As described above, according to the alignment apparatus 100 and the alignment methods 200 to 500, the positional information on the reticle stage 25 and the wafer stage 45 can be measured with high accuracy, and the positions of the reticle stage 25 and the wafer stage 45 can be measured. The alignment can be controlled with high accuracy. In this embodiment, the scanning direction is the + Z direction, but scanning may be performed in the -Z direction. The scanning direction may be parallel to the X axis or the Y axis. Furthermore, you may scan in the direction parallel to each axis | shaft in the coordinate system which coordinate-transformed these coordinates into another orthogonal coordinate.

  In the above description of the embodiment, the actual position has been described as being monitored by a laser interferometer. However, the actual position can also be monitored by other means such as a magnetic encoder or an optical encoder (for example, Japanese Patent Laid-Open No. 2000-1999). -187338). In essence, this is actually possible by using a high-precision monitoring means compared with the accuracy of the stage.

  In the exposure, the EUV light emitted from the illumination device 10 illuminates the reticle 20, and forms a pattern on the surface of the reticle 20 on the surface of the object to be processed 40. In the present embodiment, the image surface is an arc-shaped (ring-shaped) image surface, and the entire surface of the reticle 20 is exposed by scanning the reticle 20 and the workpiece 40 at a speed ratio of the reduction ratio. In the exposure, the exposure apparatus 1 can perform alignment between the reticle 20 and the object to be processed 40 by the alignment apparatus 100, and prevents transfer misalignment and the like. Higher quality devices (semiconductor elements, LCD elements, imaging elements (CCD, etc.), thin film magnetic heads, etc.) can be provided.

  Next, an embodiment of a device manufacturing method using the exposure apparatus 1 will be described with reference to FIGS. FIG. 8 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), a device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer created in step 4. The assembly process (dicing, bonding), packaging process (chip encapsulation), and the like are performed. Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 9 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the mask onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to this device manufacturing method, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using the exposure apparatus 1 and the resulting device also constitute one aspect of the present invention.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. It is a flowchart for demonstrating the alignment method as 1 side surface of this invention. It is a figure which shows an example of the correction curve for creating a correction table. It is a flowchart for demonstrating the alignment method as 1 side surface of this invention. It is a flowchart for demonstrating the alignment method as 1 side surface of this invention. It is a figure which shows an example of the curved surface fitting of the signal strength in XZ plane. It is a flowchart for demonstrating the alignment method as 1 side surface of this invention. It is a flowchart for demonstrating manufacture of devices (semiconductor chips, such as IC and LSI, LCD, CCD, etc.). 9 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 8. It is a figure for demonstrating position alignment with the reticle stage and wafer stage in the exposure apparatus which uses ultraviolet light or ultraviolet light. It is a schematic plan view which shows an example of the slit support substrate shown in FIG. It is a figure which shows an example of the detection signal of the photodiode shown in FIG. It is a figure which shows an example of the detection signal of the photodiode shown in FIG. It is a figure which shows the change of the signal strength at the time of scanning a stage. It is a figure which shows an example of the detection signal of the photodiode shown in FIG. It is a figure which shows an example of the detection signal of the photodiode shown in FIG. It is a figure which shows an example of the detection signal of the photodiode shown in FIG. It is a figure which shows an example of the detection signal different from the ideal profile of the reference position X = 0.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 Illumination apparatus 12 EUV light source 14 Illumination optical system 20 Reticle 25 Reticle stage 30 Projection optical system 40 To-be-processed object 45 Wafer stage 100 Positioning apparatus 110 Reference mark 120 Slit 130 Photodiode 140 Control part

Claims (11)

A method of aligning a first stage on which a reticle is placed or the reticle and a second stage on which a wafer is placed,
Detecting actual positions of the first stage and the second stage as output signals;
Creating a correction table for correcting an output signal at each position of the first stage and the second stage;
Comparing the actual position with a target position;
Correcting a part of the output signal and / or a part of coordinates based on the comparison information of the comparison step using the correction table;
And a step of determining a positional relationship between the first stage or the reticle and the second stage based on the output signal corrected in the correcting step.   The method further includes the step of detecting in advance the actual positions of the first stage and the second stage as output signals in the entire region including all the positions where the first stage and the second stage move. The alignment method according to claim 1. A first stage for placing a reticle or a method for aligning the reticle with a second stage for placing a wafer,
Obtaining a function of the output signal for all positions to which the first stage and the second stage move;
Detecting actual positions of the first stage and the second stage as output signals;
Of the output signals detected in the detection step, correcting a part of the output signal or a part of coordinates at a position shifted from a target position using the function;
And a step of determining a positional relationship between the first stage or the reticle and the second stage based on the output signal corrected in the correcting step. A first stage for placing a reticle or a method for aligning the reticle with a second stage for placing a wafer,
Detecting actual positions of the first stage and the second stage as output signals;
Using the output signal and the coordinates of at least two axes including the scanning direction of the first stage and the second stage to obtain a mapping from the coordinates to the output signal for each detection step;
And a step of determining a positional relationship between the first stage or the reticle and the second stage using the mapping. A method of aligning a first stage on which a reticle is placed or the reticle and a second stage on which a wafer is placed,
Detecting actual positions of the first stage and the second stage as output signals;
A step of selecting an output signal in which a positional deviation from a target position of the first stage and the second stage is within an allowable range among the output signals detected in the detection step;
And determining a positional relationship between the first stage or the reticle and the second stage using only the output signal selected in the selection step.   6. The actual positions of the first stage and the second stage are positions of the first stage and the second stage monitored by a monitoring unit. The alignment method as described in any one of them.   The actual positions of the first stage and the second stage are positions of the first stage and the second stage measured by an interferometer or an encoder, respectively. The alignment method according to any one of 5. An alignment apparatus used for aligning a reticle stage and a wafer stage of an exposure apparatus,
An alignment apparatus comprising a mode for performing the alignment method according to claim 1. An exposure apparatus comprising: an illumination optical system that illuminates a reticle placed on a first stage; and a projection optical system that projects a pattern of the reticle onto an object to be processed placed on a second stage,
An exposure apparatus comprising the alignment apparatus according to claim 8.   The exposure apparatus according to claim 9, wherein EUV light is used as exposure light. Exposing the object to be processed using the exposure apparatus according to claim 9 or 10;
And developing the exposed object to be processed.