JP2006234647A - Method and device for position measurement, exposure method and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of position measurement with high precision. <P>SOLUTION: During the reticle alignment, firstly positions are measured of the reticle mark and the wafer fiducial mark at a field of view standard of an alignment sensor as a preliminary measurement, and then their biases are measured. Next, driving positions of the reticle and the wafer stage so as to make each mark to be the center of field of view, the biases of reticle mark and wafer fiducial mark are measured in this condition as a full measurement. Since the marks are placed at the center of field of view of the alignment sensor to observe and since the same component of both the distortion of optical system of the alignment sensor or the fixed pattern noise and the like of the imaging device are superimposed at each time, degradation of reproducibility of measurement caused by them can be prevented to implement the stable reticle alignment. As a result, an alignment can be completed of the reticle alignment mark RM and the wafer fiducial mark. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a position measuring method and position measuring apparatus for measuring the position of a mark formed on an object such as a mask suitable for use in an exposure apparatus used in a lithography process when manufacturing an electronic device such as a semiconductor element, and The present invention relates to an exposure method and an exposure apparatus to which these are applied.

  In the manufacture of electronic devices such as semiconductor devices, liquid crystal display devices, CCD imaging devices, plasma display devices, thin film magnetic heads and the like (hereinafter collectively referred to as electronic devices), an exposure apparatus is used to manufacture photomasks and reticles (hereinafter referred to as electronic devices). The image of the fine pattern formed on the reticle is generally projected and exposed onto a substrate (hereinafter referred to as a wafer) such as a semiconductor wafer or a glass plate coated with a photosensitive agent such as a photoresist. At that time, it is necessary to align the reticle and the wafer with high accuracy and to superimpose the reticle pattern on the pattern on the wafer with high accuracy. 2. Description of the Related Art In recent years, pattern refinement and high integration in electronic devices are rapidly progressing, and there is a demand for higher-precision alignment in exposure apparatuses than ever before.

  Wafer position measurement is performed by detecting an alignment mark formed on the wafer and measuring the position. As an alignment system that measures the position of the alignment mark, the mark is irradiated with light with a wide wavelength bandwidth, the reflected light is imaged with a CCD camera, etc., and the image data of the resulting alignment mark is processed to measure the mark position An FIA (Field Image Alignment) type off-axis alignment sensor is known. According to this FIA-based alignment sensor, it is difficult to be affected by thin film interference due to the resist layer, and high-accuracy position measurement is also possible for aluminum marks, asymmetric marks and the like.

  Similarly to wafer position measurement, reticle position measurement is performed by detecting an alignment mark formed on the reticle and measuring the position. An alignment system that measures the position of the reticle alignment mark generally uses exposure light or light having the same wavelength as the exposure light as a mark detection light beam. For example, exposure light is applied to an alignment mark formed on the reticle. A VRA (Video Reticle Alignment) type sensor (hereinafter also referred to as a reticle alignment sensor) that irradiates and reflects reflected light with a CCD camera or the like, performs image processing on the obtained alignment mark image data, and measures the mark position. Is known).

In this type of reticle alignment sensor, a wafer fiducial mark (wafer reference mark) patterned on a reference plate fixed on the wafer stage and a reticle alignment mark patterned on the reticle are imaged. The image is taken in the same field of view through the optical system, and the relative positional relationship between the wafer fiducial mark and the reticle alignment mark, in other words, the shift amount is obtained based on the obtained signal, and the reticle alignment (reticle) is obtained based on this. Alignment) and baseline measurement.
At this time, since the imaging optical system usually has its own imaging characteristics such as distortion, there is a possibility that an image captured by the camera will be distorted by passing through the imaging optical system, and an error may occur in the obtained position. There is. Therefore, in order to cope with such a state and detect the position of the reticle alignment mark with high accuracy, the imaging characteristics of the imaging optical system are detected in advance and stored, and the information about the imaging characteristics is stored. An alignment system (position detection device) that corrects the position of a wafer fiducial mark or reticle alignment mark based on this has also been proposed (see, for example, Patent Document 1).

In addition, when a reticle alignment mark (sometimes simply referred to as a reticle mark) is detected by a reticle alignment sensor, immediately after the reticle is placed on the reticle stage, it is caused by a reticle drawing error, a reticle loader loading reproducibility error, etc. Thus, the alignment sensor center and the alignment mark center are greatly deviated. For this reason, when aligning the reticle, a low-magnification search sensor (search camera) that can measure a wide field of view is used to first roughly measure the position of the reticle alignment mark. The reticle stage is driven so that the alignment mark is arranged at the center of the visual field of the fine sensor (fine camera). In addition, focus measurement is performed using a high-magnification fine sensor, focusing is performed, and final alignment mark detection and position measurement are performed with the fine sensor.
At this time, a position measuring method and a position measuring apparatus that can accurately measure the mark position by irradiating the optimum alignment illumination light in the search alignment process and the fine alignment process have also been proposed (for example, Patent Document 2).
Japanese Patent Laid-Open No. 8-167571 JP 2004-111473 A

  In the above-described reticle alignment sensor, exposure light is incident on the projection optical system via the reticle during the exposure process, and a light beam for detecting the mark is received through the reticle and the projection optical system during wafer alignment. Is provided with an epi-illumination mirror for emitting illumination light from the reticle alignment sensor in the direction of the projection optical system. The epi-mirror is disposed at a predetermined retracted position during the exposure process, and is mechanically moved and disposed at a predetermined measurement position when measuring the reticle alignment mark.

Incidentally, reticle alignment may be measured in the middle of a lot in addition to the first wafer in one lot. In that case, the above-described epi-illumination mirror is inserted into the measurement position every time reticle alignment is performed.
However, the epi-illumination mirror may be mechanically driven, and some variation occurs in the insertion position. That is, there is a limit to the position throwing accuracy. Therefore, there is a problem that the mark position in the visual field of the alignment sensor may be different for each measurement depending on the insertion accuracy of the epi-mirror.

For example, even if the signal waveform obtained by reticle alignment performed at the lot head is as shown in FIG. 7A with respect to the alignment sensor field of view, the signal waveform obtained by the next reticle alignment is As shown in FIG. 7B, the waveform may be entirely deviated from the initial waveform. 7A and 7B are signal waveforms for detecting the position of the mark in the X direction obtained from the image signal of the mark imaged by the alignment sensor, and the signal appearing near the center is a wafer fidu. A line segment in the Y direction of the char mark is shown, and two signals on each side indicate a line segment in the Y direction of the reticle mark RM.
In this way, if the position of the mark in the field of view is different, the influence of the distortion of the optical system of the alignment sensor, the noise (fixed pattern noise) of the light receiving element (imaging CCD camera), etc. will be different. The measurement results differ depending on the influence, and there arises a problem that the measurement accuracy is lowered.

The present invention has been made in view of such problems, and its purpose is to suppress the influence of the distortion of the optical system of the alignment sensor, the fixed pattern noise of the image sensor, etc., and perform highly accurate position measurement. An object of the present invention is to provide a position measurement method and a position measurement apparatus that can be used.
Another object of the present invention is to provide an exposure method and an exposure apparatus capable of exposing and transferring a desired pattern with high accuracy by performing such highly accurate position measurement.

In order to solve the above problems, a position measuring method according to the present invention is obtained by irradiating a mark formed on an object with a light beam, receiving a reflected beam from the mark with an observation system, and receiving the light. A position measurement method for measuring the position of the mark based on a mark signal,
A first step of detecting the amount of deviation of the mark signal in the observation field of the observation system from a predetermined position in the observation field (step S12), based on the amount of deviation detected in the first step, A second step of correcting the position of the reflected beam from the mark so that the mark signal is observed at the predetermined position in the observation field (step S13), and the position is corrected in the second step and the position is corrected; A third step of measuring the position of the mark signal observed in the observation field of the observation system (step S14), a correction amount related to the correction in the second step, and a measurement in the third step And a fourth step (step S15) for detecting the position of the mark based on the position of the mark signal (see FIG. 5) (Claim 1).

Preferably, in the second step, the mark signal is moved within the observation field of view by moving the position of the object on which the mark is formed based on the shift amount detected in the first step. Observation is performed at a predetermined position (claim 2).
Preferably, the mark formed on the object is irradiated with the light beam via a projection optical system, and a reflected beam from the mark is received by the observation system via the projection optical system, and the light reception In the position measurement method for measuring the position of the mark based on the mark signal obtained in this way, in the second step, the optical characteristic of the projection optical system is based on the deviation amount detected in the first step. The mark signal is observed at the predetermined position in the observation field.
Preferably, the observation system includes a position adjusting optical system for moving the position of the reflected beam in a plane perpendicular to the optical axis of the reflected beam. In the second step, The mark signal is observed at the predetermined position in the observation field by the action of the position adjusting optical system.
Further preferably, in order to guide the light beam onto the mark and guide the reflected beam to the observation system, it further includes a movable optical system that can be inserted into and removed from the optical path of the light beam and the reflected beam. The position of the mark is measured by performing the first to fourth steps after the movable optical system is moved (Claim 5).

  The position measuring apparatus according to the present invention irradiates a mark formed on an object with a light beam, receives a reflected beam from the mark by an observation system, and based on the mark signal obtained by receiving the light A position measuring device for measuring a position of a mark, wherein the mark signal in the observation field of the observation system detects a deviation amount from a predetermined position in the observation field, and the detected deviation Correction means for correcting the position of the reflected beam from the mark so that the mark signal is observed at the predetermined position in the observation field based on the amount, and the position is corrected to correct the position of the observation system. Based on the position measuring means for measuring the position of the mark signal observed in the observation field, the correction amount for the correction, and the position of the detected mark signal, A position detecting means for detecting the position, the (claim 6).

  An exposure method according to the present invention is an exposure method for transferring a pattern formed on a mask onto a substrate via a projection optical system, and the substrate as the object is obtained by any one of the position measurement methods described above. Alternatively, the relative position between the first mark formed on the stage on which the substrate is placed and the second mark formed on the mask is measured, and the first mark and the second mark are measured. Based on the measurement result of the relative position of the mark, the substrate and the mask are aligned, and a pattern formed on the mask is projected and exposed at a desired position of the aligned substrate. Item 10).

  An exposure apparatus according to the present invention is an exposure apparatus that transfers a pattern formed on a mask onto a substrate via a projection optical system, the substrate serving as the object, or a stage on which the substrate is placed. Any one of the above-described position measuring devices for measuring a relative position between the first mark formed on the mask and the second mark formed on the mask; and the first mark and the second mark Positioning means for aligning the substrate and the mask based on the result of relative position measurement of the mark, and a pattern and projection formed on the mask at a desired position of the aligned substrate Exposure means for exposing (claim 11).

  In this column, the reference numerals of the corresponding components shown in the attached drawings are shown for each component, but this is only for easy understanding and does not relate to the present invention. It is not intended to indicate that the means is limited to the embodiments described below with reference to the accompanying drawings.

According to the present invention, it is possible to provide a position measurement method and a position measurement apparatus that can suppress the influence of the distortion of the optical system of the alignment sensor, the fixed pattern noise of the image sensor, and the like and perform highly accurate position measurement.
In addition, by performing such highly accurate position measurement, it is possible to provide an exposure method and an exposure apparatus capable of exposing and transferring a desired pattern with high accuracy.

An embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the present invention will be described by exemplifying a projection exposure apparatus for manufacturing an electronic device that exposes a device pattern on a reticle onto a wafer.
FIG. 1 is a diagram schematically showing the overall configuration of the projection exposure apparatus.
An exposure apparatus 100 shown in FIG. 1 has a circuit pattern formed on a reticle R while synchronously moving a reticle R as a mask and a wafer W as a substrate in a one-dimensional direction (Y direction in the example shown in FIG. 1). Is a step-and-scan type scanning exposure apparatus (scanning stepper) that transfers the image to a shot area defined on the wafer W.

First, the overall configuration of the exposure apparatus 100 will be described.
The exposure apparatus 100 includes an illumination system 110, a reticle stage unit 120, a reticle alignment system 200, a projection optical system 130, a wafer stage unit 140, a main focus system 150, a main controller 160, and a wafer alignment sensor 170.

The illumination system 110 includes, for example, a light source 111 made of an excimer laser, an illuminance uniformizing optical system 112 including a beam shaping lens and an optical integrator (fly eye lens), an illumination system aperture stop plate (revolver) 113, a revolver drive system 114, A relay optical system 116 and a bending mirror 117 are included. In addition to these components, the illumination system 110 further includes components (not shown) such as optical members such as condenser lenses and reticle blinds.
In such an illumination system 110, first, an illumination beam IL such as KrF excimer laser light or ArF excimer laser light is emitted from the light source 111, for example. The light emission of the laser pulse in the light source 111 is controlled by the main controller 160. Note that an ultra-high pressure mercury lamp may be used as the light source 111. In that case, bright lines in the ultraviolet region such as g-line and i-line are used as the illumination beam IL.

  The illumination beam IL emitted from the light source 111 is uniformed by the illuminance uniformizing optical system 112, and speckle reduction or the like is performed.

A relay optical system 116 is disposed behind the illumination system aperture stop plate 113 with a reticle blind (not shown) interposed therebetween. The installation surface of the reticle blind has a conjugate relationship with the reticle R, and an area illuminated by the illumination beam IL on the reticle R is defined by the reticle blind.
A folding mirror 117 that reflects the illumination beam IL that has passed through the relay optical system 116 toward the reticle R is disposed at the subsequent stage of the relay optical system 116, and further downstream of the folding mirror 117 (light of the reflected illumination beam IL). A condenser lens (not shown) is disposed on the rear stage of the road.
When the illumination beam IL that has passed through the illumination system aperture stop plate 113 passes through the relay optical system 116, the illumination area of the reticle R is defined by a movable reticle blind (not shown), and is reflected vertically downward by the bending mirror 117. The predetermined region of the reticle R placed on the reticle stage 121 is illuminated with uniform illuminance through the condenser lens that is not.

The reticle stage unit 120 includes a reticle stage 121, a laser interferometer 122, a moving mirror 123, and a motor 124.
The reticle stage 121 sucks and holds the mounted reticle R via a vacuum chuck, electrostatic chuck or the like (not shown). The reticle stage 121 can be finely moved in the direction of the optical axis AX of the projection optical system 130 by a motor 124 and can be moved two-dimensionally and finely rotated in a plane (horizontal plane, XY plane) perpendicular to the optical axis AX. The
On the reticle stage 121, there are provided movable mirrors (only the movable mirror 123 in the X-axis direction is shown in FIG. 1) having the X-axis direction and the Y-axis direction as reflection surface directions, respectively. With the provided laser interferometer (in FIG. 1, only the X-axis direction laser interferometer 122 is shown), the positions in the X-axis direction and the Y-axis direction are measured with a resolution of about 0.01 μm, for example.

The reticle alignment system 200 includes alignment sensors 201 and 202 disposed above the reticle R, and the reticle mark RM and wafer fiducial mark as shown in FIG. 3, for example, formed on the reticle R by these alignment sensors. WFM is detected (imaged), and the position information is output to main controller 160. In main controller 160, based on the input positional information of reticle mark RM, motor 124 is controlled to move reticle stage 121 so that reticle R is positioned. Specifically, the position of reticle stage 121 is controlled so that the center point of pattern area PA of reticle R coincides with optical axis AX of projection optical system 130.
In reticle R, reticle alignment mark RM is formed near the periphery of reticle R as shown in FIG.
The reticle R is appropriately replaced by a reticle exchange device (not shown).

  The projection optical system 130 includes a plurality of lens elements that have an optical axis AX and are arranged so as to have a telecentric optical arrangement on both sides. As the projection optical system 130, a projection magnification of 1/4 or 1/5 is used as an example. When the illumination area on the reticle R is illuminated by the illumination beam IL, the pattern formed on the pattern surface of the reticle R is reduced and projected onto the wafer W whose surface is coated with the resist R by the projection optical system 130. The reduced image of the pattern of the reticle R is transferred to one shot area on the wafer W.

  The wafer stage unit 140 places the wafer W in a desired state at a desired position so that the pattern of the reticle R is appropriately transferred to a desired area of the wafer W by exposure light irradiated through the projection optical system 130. Hold on. In the wafer stage unit 140, the wafer stage 142 is placed on a surface plate (stage surface plate) 141 disposed below the projection optical system 130. The wafer stage 142 is actually composed of an XY stage that can move two-dimensionally in a horizontal plane (XY plane), a Z stage that is mounted on the XY stage and can be moved in the optical axis direction (Z direction), and the like. However, in FIG. 1, these are simply shown as a wafer stage 142. The wafer stage 142 is driven in the XY two-dimensional direction along the upper surface of the surface plate 141 by the drive system 147, and is also driven in the optical axis AX direction within a minute range of, for example, about 100 μm. Note that the surface of the surface plate 141 is processed to be flat and is uniformly plated with a low reflectance material such as black chrome.

A wafer W is held on the wafer stage 142 by vacuum suction or electrostatic suction through a wafer holder 143.
Further, on the wafer stage 142, there are provided movable mirrors (only the movable mirror 144 in the X-axis direction is shown in FIG. 1) with the X-axis direction and the Y-axis direction as the reflecting surface directions. The position of the wafer stage 142 is measured with a resolution of about 1 nm in each of the X-axis direction and the Y-axis direction by a laser interferometer provided in the direction (only the X-axis direction laser interferometer 145 is shown in FIG. 1). The The position measurement result of the wafer stage 142 by the laser interferometer 145 is output to the main controller 160, and the main controller 160 controls the drive system 147 based on the information. By such a closed loop control system, for example, the wafer stage 142 is stepped to the exposure position of the next shot when the transfer exposure (scan exposure) of the pattern of the reticle R on one shot area on the wafer W is completed. When exposure for all shot positions is completed, the wafer W is exchanged with another wafer W by a wafer exchange device (not shown). The wafer exchange device is arranged at a position off the wafer stage 142, and is configured to deliver the wafer W via a wafer transfer system such as a wafer loader.

  As shown in FIG. 3, a reference plate 146 on which one or more wafer fiducial marks WFM (wafer reference marks) for later-described reticle alignment and baseline measurement are formed is provided on the wafer stage 142. ing. The surface position of the reference plate 146 (Z-direction position / reference mark formation surface) is set to be the same as the surface position of the wafer W. In the present embodiment, a wafer fiducial mark WFM as shown in FIG. 3 is formed on the reference plate 146.

The main focus system 150 measures the position of the surface of the wafer W in the Z direction.
The main focus system 150 includes an irradiation optical system 151 that irradiates light on the surface of the wafer W or the reference plate 146 from an oblique direction, and a light incident optical system 152 that receives reflected light of the light and detects obliquely incident light type focus. It is a system. The light receiving optical system 152 receives a reflected light beam on the surface of the wafer W or the reference plate 146 of the imaging light beam or the parallel light beam irradiated by the irradiation optical system 151, and outputs the obtained detection signal to the main controller 160. . Based on this signal, main controller 160 controls the position of wafer W in the Z direction with respect to the best image plane of projection optical system 130 via drive system 147.

  The main control device 160 controls each part of the exposure apparatus 100 so that each constituent part cooperates and the exposure apparatus 100 as a whole performs a desired exposure process. Specifically, for example, alignment (alignment) of the reticle R and the wafer W, stepping of the wafer W, control and adjustment of the exposure timing, etc. are performed. Note that the main control device 160 is constituted by, for example, a microcomputer.

  The wafer alignment sensor 170 measures the position of the wafer fiducial mark (WFM) formed on the reference plate 146 provided on the wafer stage 142 or the wafer alignment mark on the wafer W, and controls the measurement result as a main control. Output to the device 160. In this embodiment, the wafer alignment sensor 170 is provided with an index serving as a measurement reference, and the position of the mark is measured using the index as a reference. For example, the result of the image processing method disclosed in Japanese Patent Laid-Open No. 4-65603 is disclosed. An image sensor is used. However, other types such as a laser scanning sensor known in Japanese Patent Laid-Open No. 10-141915 or a laser interference sensor may be used.

  The reticle alignment system 200 performs reticle alignment (reticle alignment), for example, every time the lot head is processed or every time a predetermined number of wafers are processed in the lot in addition to the lot head. Since the configuration and function of the two alignment sensors 201 and 202 of the reticle alignment system 200 are the same, the configuration, function, and operation of the alignment sensor 201 will be described in detail below.

FIG. 2 is a diagram illustrating a configuration of the alignment sensor 201.
The alignment sensor 201 includes a base 205, an alignment light source 211, image pickup devices 226X and 226Y such as a CCD, a monitor image pickup device 222, half mirrors 215, 216 and 225, optical elements 212, 214, 218 such as a condenser lens and an objective lens. 221 and 224, a reflection mirror 223, an illumination field stop 213, a stop 217, and an internal focusing lens 219.
Further, as shown in FIG. 1, a retracted position where the exposure light incident on the projection optical system 130 cannot be shifted between the alignment sensor 201 and the reticle R, and a measurement position for measuring the alignment of the reticle R or the wafer W. The epi-illumination mirror 203 (204 for the alignment sensor 202 is also the same) that is driven between them is installed.

The alignment light source 211 is a light source that emits a detection beam for alignment. In the present embodiment, the alignment light source 211 is configured to guide and use exposure illumination light emitted from the light source 111 (see FIG. 1). That is, a part of the light beam of the illumination beam IL is branched by a mirror (not shown), guided into the alignment sensor 201 by an optical fiber, and emitted as a detection beam (illumination beam) from the end of the optical fiber as the alignment light source 211.
The detection beam emitted from the alignment light source 211 reaches the inner focusing lens 219 via the optical elements 212, 214, 218, the illumination field stop 213, the half mirrors 215, 216, and the stop 217.
The inner focus system lens 219 is a focus adjustment mechanism (AF lens) that is moved along the optical path of the detection beam by a driving unit (not shown). The position information of the internal focusing lens 219 is measured by a position measuring unit (not shown) and output to the main controller 160. Based on this information, the detection beam emitted from the alignment sensor 201 by the main controller 160 is desired. The position of the in-focus lens 219 is controlled via the drive system so that the focus state becomes.

The detection beam whose focus is adjusted by the inner focus lens 219 is emitted from the alignment sensor 201, reflected by the epi-illumination mirror 203, and at the illumination field defined by the illumination field stop 213, the reticle as shown in FIG. An alignment mark RM (one of the two reticle alignment marks RM) is illuminated, and a wafer fiddle on the reference plate 146 is also shown in FIG. 3 through the reticle R and the projection optical system 130 (see FIG. 1). The char mark WFM (one of the two wafer fiducial marks WFM) is illuminated.
Reflected beams from the reticle alignment mark RM and the wafer fiducial mark WFM are reflected by the epi-illumination mirror 203, reach the half mirror 216 via the internal focusing lens 219, the optical element 218, and the aperture 217, and are reflected by the half mirror 216. The light is branched and incident on the rough measurement system 228 and the fine observation system 229, respectively.
FIG. 3 shows two reticle alignment marks RM and wafer fiducial mark WFM, which are marks detected by two alignment sensors 201 and 202, respectively. Therefore, in one alignment sensor 201 described here, one of the reticle alignment mark RM and the wafer fiducial mark WFM is detected.

The reflected beam branched by the half mirror 216 and incident on the rough measurement system 228 enters the monitor image sensor (rough measurement camera) 222 via the optical element 221. The monitor imaging element 222 is for observing a wider measurement visual field range (in other words, at a lower magnification) than the X direction sensor 226X and the Y direction sensor 226Y of the fine observation system 229 described later. An imaging signal obtained by observing the wide visual field range 222 is output to an observation monitor (not shown) and to the main controller 160 (FIG. 1).
Main controller 160 measures the amount of misalignment between reticle alignment mark RM and wafer fiducial mark WFM in each of the X and Y directions based on the input imaging signal, and the reticle stage based on the misalignment amount. The position of 121 is controlled. That is, the position of the reticle stage 121 is controlled so that the reticle mark is arranged at the center of the visual field of the fine measurement system 229.

  The reflected beam branched by the half mirror 216 and incident on the fine observation system 229 reaches the half mirror 225 via the reflection mirror 223 and the optical element 224, and is further branched by the half mirror 225, so that the X direction sensors 226X and Y Each is incident on the direction sensor 226Y. The X direction sensor 226X measures an image in a predetermined imaging area Px extended in the X direction set within the visual field range as shown in FIG. 4A in order to measure the position of the observed mark in the X direction. The Y-direction sensor 226Y is an image pickup device that picks up an image, and in order to measure the position of the observed mark in the Y-direction, the Y-direction sensor 226Y extends in the Y-direction that is set within the visual field range as shown in FIG. This is an image sensor that measures an image in the imaging area Py. For example, a signal waveform indicating the signal intensity of the pattern signal in the X-axis direction as shown in FIG. 4B is obtained from the X-direction sensor 226X. The imaging signals obtained by these X direction sensor 226X and Y direction sensor 226Y are output to main controller 160.

The base 205 is a surface plate on which a reticle alignment system is mounted. The base 205 is composed of a member formed of a nonmagnetic material or a member whose surface is coated with a nonmagnetic material.
The above is the description of the schematic configuration of the exposure apparatus 100.

Next, a reticle alignment method according to the present invention in the exposure apparatus 100 having such a configuration, that is, a method for measuring the position of the reticle R will be described with reference to FIGS.
In the exposure apparatus 100, the reticle alignment is performed when a new reticle is loaded on the exposure apparatus 100, or immediately before the exposure process is performed on the first wafer of each lot, or a predetermined number of wafers are processed in the lot. It is performed at times.
FIG. 5 is a flowchart showing the flow of the reticle alignment process.

  When performing reticle alignment, first, the epi-illumination mirrors 203 and 204 (see FIG. 1) (refer to FIG. 1) arranged in the retracted position for the exposure process (the alignment sensor 201 relating to the epi-illumination mirror 203 will be described below) mechanically. And is inserted into the measurement position (step S11). Thereby, for example, the detection beam from the alignment light source 211 (see FIG. 2) is reflected by the incident mirror 203, and the wafer fiducial mark WFM is illuminated through the reticle mark RM and the projection optical system 130.

Next, alignment measurement is performed as preliminary measurement. That is, the shift amount of the reticle mark RM and the wafer fiducial mark WFM with respect to the field center (corresponding to a predetermined position in the observation field) within the field range of the alignment sensor 201 is detected (step S12).
In the preliminary measurement, first, search measurement using the search observation system 228 is performed. In search measurement, first, main controller 160 drives motor 124 based on design information and the like so that reticle alignment mark RM of reticle R is arranged at the center of the visual field of search observation system 228 of alignment sensor 201. The reticle stage 121 is moved. In this state, the reticle alignment mark RM is observed at a relatively low magnification with respect to the fine observation system 229 by the search observation system 228, and the image is captured by the monitor image sensor 222. The amount of deviation from the center O (the position of the reticle alignment mark RM) is measured. Then, based on the amount of deviation, main controller 160 drives motor 124 to move reticle stage 121 so that reticle alignment mark RM is at the center of the field of view, and adjusts its position.

After such search measurement is completed, next, fine measurement using the fine observation system 229 is performed. In the fine measurement, the reticle alignment mark RM is observed at a relatively high magnification with respect to the search observation system 228 by the fine observation system 229, and the waveform data is detected by the X direction sensor 226X and the Y direction sensor 226Y. Based on the waveform data, in this preliminary measurement, a deviation amount of the reticle mark RM and the wafer fiducial mark WFM with respect to the center O of the visual field range (the visual field center O) is measured.
Specifically, assuming that a signal waveform as shown in FIG. 6A is detected by the alignment measurement as a preliminary measurement, a deviation amount Δr of the reticle mark RM with respect to the visual field center O based on this, The amount of deviation Δw of the wafer fiducial mark WFM with respect to the visual field center O is measured.

  When the preliminary measurement is completed, the reticle mark RM and the wafer fiducial mark WFM are set so that the measured deviation amounts Δr and Δw become 0 (zero), that is, in the observation field of the alignment sensor 201 (fine observation system 229). The positions of the reticle R (reticle stage 121) and the wafer stage 121 are adjusted so that the observed image is arranged at the observation center O (step S13). Specifically, based on the measured deviation amounts Δr and Δw, main controller 160 drives reticle stage 121 via motor 124, and also drives wafer stage 142 via drive system 147 to provide reticle R The positions of (reticle stage 121) and wafer stage 121 are adjusted. The main controller 160 stores the adjustment amount (correction drive amount, that is, the deviation amounts Δr and Δw) at this time for use in correcting the measurement result after the main measurement.

Next, alignment measurement as main measurement, that is, detection of the deviation amount of reticle mark RM and wafer fiducial mark WFM is performed (step S14).
In this measurement, first, the reticle alignment mark RM is observed at a relatively high magnification by the fine observation system 229, the waveform data is detected by the X direction sensor 226X and the Y direction sensor 226Y, and the reticle mark RM and the wafer fiducial are detected. The position of the char mark WFM is measured.
As described above, the reticle mark RM and the wafer fiducial mark WFM are adjusted so as to be arranged at the center of the visual field of the alignment sensor 201 as shown in FIG. The amount of deviation is very close to 0 (zero). However, in the preliminary measurement, as shown in FIG. 6A, the reticle mark RM and the wafer fiducial mark WFM are observed at a position deviated from the center of the visual field in the visual field range of the alignment sensor 201 (Δr and When Δw is not 0 (zero), the adjustment includes an error caused by a difference in distortion of the alignment sensor 201 (a difference in distortion between the observation position and the visual field center at the time of preliminary measurement). In this main measurement, the amount of deviation when the reticle mark RM and the wafer fiducial mark WFM are observed at a position very close to the visual field center O of the alignment sensor 201, and therefore, such a difference in distortion. Observe any amount including errors caused by.

After the position measurement of the reticle mark RM and the wafer fiducial mark WFM is completed, next, based on the position measurement result and the correction drive amount based on the preliminary measurement result stored in the main controller 16, that is, For each of the reticle mark RM and the wafer fiducial mark WFM, the amount of deviation from the current visual field center O and the correction driving amount (deviation amount from the visual field center O at the time of preliminary measurement) are added to obtain the final deviation. The amount (true shift amount) is detected (step S15). Then, these relative positional relationships are measured, and an alignment measurement result including a baseline check (BCHK) is obtained.
Further, based on this result, the reticle R (reticle alignment mark RM) and the wafer fiducial mark WFM are aligned with high accuracy.

  When the main measurement of the reticle mark RM and the wafer fiducial mark WFM is completed, the epi-illumination mirror 203 is returned to the retracted position (step S16), and a series of reticle alignment processes are completed.

As described above, in the exposure apparatus 100 of the present embodiment, at the time of reticle alignment, first, as preliminary measurement, the positions of the reticle mark RM and the wafer fiducial mark WFM with respect to the field of view of the alignment sensor 201 are measured, Each shift amount from the center of the visual field is measured, and based on the measurement result, the positions of the reticle R and the wafer stage 142 are driven so that the reticle mark RM and the wafer fiducial mark WFM are both in the visual field center. The amount of deviation between the reticle mark RM and the wafer fiducial mark WFM is measured. Accordingly, the reticle mark RM and the wafer fiducial mark WFM are always observed at the center of the visual field of the alignment sensor 201, and the distortion of the optical system of the alignment sensor 201 or the fixed pattern noise of the image sensor (CCD camera). For (defects of specific pixels) and the like, the same component is superimposed each time. As a result, deterioration of measurement reproducibility due to such distortion and fixed pattern noise can be prevented, and stable reticle alignment can be performed.
As a result, the reticle alignment mark RM and the wafer fiducial mark can be aligned with high accuracy.

  In addition, this embodiment is described in order to make an understanding of this invention easy, and does not limit this invention at all. Each element disclosed in the present embodiment includes all design changes and equivalents belonging to the technical scope of the present invention, and various suitable modifications can be made.

  For example, in the reticle alignment measurement of the present embodiment, the amount of deviation of the reticle mark RM and the wafer fiducial mark WFM with respect to the visual field center O of the alignment sensor 201 is measured in preliminary measurement and main measurement, and these positions are also measured. Adjustments were made to match the visual field center O. However, the reference position (measurement reference and alignment reference) is not limited to the center of the visual field, and may be an arbitrary position within the measurement visual field. An object of the present invention is to make the components such as distortion superimposed in each measurement the same by specifying the reference position as a predetermined position and matching it. Therefore, as long as the same position is used as a reference in each measurement, the position is not limited to the center of the visual field, and may be an arbitrary position.

In this embodiment, the positions of the reticle R (reticle stage 121) and the wafer stage 142 are driven and adjusted based on the result of the preliminary measurement, and the reticle mark RM and the wafer fiducial mark WFM are aligned with the alignment sensor 201. Correction was made so that it was placed at the center of the field of view. However, this correction is not limited to the movement of the mark and the stage as long as these marks are observed at a predetermined position of the alignment sensor 201 (in this embodiment, the center of the visual field). You can do it.
For example, the main control device 160 adjusts the optical characteristics (imaging characteristics) of the projection optical system 130 by adjusting the position of a predetermined lens of the projection optical system 130 or by adjusting the atmospheric pressure of the projection optical system. Then, the image of the wafer fiducial mark WFM may be arranged at a predetermined position of the alignment sensor 201.

Further, an optical member for correcting the position of the reflected beam may be provided in the alignment sensor 201 so that the position of the reflected beam passing through the alignment sensor 201 is adjusted to a predetermined position. For example, the position of the incident beam may be adjusted by translating the incident beam in a direction parallel to the surface and using a herving member that emits light at the same angle as the incident angle.
Moreover, the structure which uses the adjustment means as mentioned above together may be sufficient.

FIG. 1 is a view showing the arrangement of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is a view showing the arrangement of the alignment sensor of the exposure apparatus shown in FIG. FIG. 3 is a diagram showing a reticle alignment mark and a wafer fiducial mark. FIG. 4 is a diagram showing an image observed by superimposing the reticle alignment mark and the wafer fiducial mark shown in FIG. 3 and its signal waveform. FIG. 5 is a flowchart showing the flow of reticle alignment. FIG. 6 is a diagram for explaining the reticle alignment processing shown in FIG. FIG. 7 is a diagram for explaining a conventional reticle alignment process.

Explanation of symbols

100: Exposure apparatus.
DESCRIPTION OF SYMBOLS 110 ... Illumination system 112 ... Illuminance equalization optical system 113 ... Illumination system aperture stop plate (revolver)
DESCRIPTION OF SYMBOLS 114 ... Revolver drive system 116 ... Relay optical system 117 ... Bending mirror 120 ... Reticle stage part 121 ... Reticle stage 122 ... Laser interferometer 123 ... Moving mirror 124 ... Motor 130 ... Projection optical system 140 ... Wafer stage part 141 ... Surface plate 142 ... Wafer stage 143 ... Wafer holder 144 ... Moving mirror 145 ... Laser interferometer 146 ... Reference plate 147 ... Drive system 150 ... Main focus system 151 ... Irradiation optical system 152 ... Light receiving optical system 160 ... Main controller 200 ... Reticle alignment system 201 , 202 ... Alignment sensor 203, 204 ... Epi-illumination mirror 205 ... Base 211 ... Alignment optical system 212, 213, 218, 221, 224 ... Optical element 213 ... Illumination diaphragm 214, 223 ... Reflection mirror 217 ... Diaphragm 219 ... In-focus Lens 222 ... monitor image sensor 226 ... imaging element 228 ... search observation system 229 ... Fine observation system

Claims (11)

A position measurement method in which a mark formed on an object is irradiated with a light beam, a reflected beam from the mark is received by an observation system, and the position of the mark is measured based on the mark signal obtained by the light reception. And
A first step of detecting an amount of deviation of the mark signal in the observation field of the observation system from a predetermined position in the observation field;
A second step of correcting the position of the reflected beam from the mark so that the mark signal is observed at the predetermined position in the observation field based on the shift amount detected in the first step;
A third step of measuring the position of the mark signal observed in the observation field of the observation system by correcting the position in the second step;
A fourth step of detecting the position of the mark based on the correction amount related to the correction in the second step and the position of the mark signal measured in the third step;
A position measurement method characterized by comprising:   In the second step, the mark signal is observed at the predetermined position in the observation field by moving the position of the object on which the mark is formed based on the shift amount detected in the first step. The position measurement method according to claim 1, wherein the position measurement method is performed. A mark obtained by irradiating the mark formed on the object with the light beam through a projection optical system, receiving a reflected beam from the mark with the observation system through the projection optical system, and receiving the light. A position measurement method for measuring the position of the mark based on a signal,
In the second step, the mark signal is observed at the predetermined position in the observation field by correcting the optical characteristics of the projection optical system based on the shift amount detected in the first step. The position measuring method according to claim 1, wherein: The observation system has a position adjusting optical system for moving the position of the reflected beam in a plane perpendicular to the optical axis of the reflected beam,
2. The position measuring method according to claim 1, wherein, in the second step, the mark signal is observed at the predetermined position in the observation field by the action of the position adjusting optical system. . In order to guide the light beam onto the mark and guide the reflected beam to the observation system, the optical system further includes a movable optical system that can be inserted into and removed from the optical path of the light beam and the reflected beam.
5. The position of the mark is measured by performing the first to fourth steps after the movable optical system is moved. 6. Position measurement method. A position measurement device that irradiates a mark formed on an object with a light beam, receives a reflected beam from the mark by an observation system, and measures the position of the mark based on the mark signal obtained by the light reception. And
A deviation detecting means for detecting a deviation amount of the mark signal in the observation visual field of the observation system from a predetermined position in the observation visual field;
Correction means for correcting the position of the reflected beam from the mark so that the mark signal is observed at the predetermined position in the observation field based on the detected shift amount;
Position measuring means for measuring the position of the mark signal that is corrected in the position and observed in the observation field of the observation system;
Position detection means for detecting the position of the mark based on the correction amount related to the correction and the position of the detected mark signal;
A position measuring device comprising:   The correction means moves the position of the object on which the mark is formed based on the amount of deviation detected by the deviation detection means, so that the mark signal is observed at the predetermined position in the observation field. The position measuring device according to claim 6, wherein the position measuring device is configured as described above. A mark obtained by irradiating the mark formed on the object with the light beam through a projection optical system, receiving a reflected beam from the mark with the observation system through the projection optical system, and receiving the light. A position measuring device that measures the position of the mark based on a signal,
The correction means corrects the optical characteristic of the projection optical system based on the shift amount detected in the first step so that the mark signal is observed at the predetermined position in the observation field. The position measuring device according to claim 6.   The observation system moves the position of the reflected beam in a plane perpendicular to the optical axis of the reflected beam so that the mark signal is observed at the predetermined position in the observation field. The position measuring apparatus according to claim 6, further comprising an optical system. An exposure method for transferring a pattern formed on a mask onto a substrate via a projection optical system,
The position measurement method according to any one of claims 1 to 5, wherein a first mark formed on a substrate as the object or a stage on which the substrate is placed, and a first mark formed on the mask. Measure the relative position with the 2 mark,
Based on the relative position measurement result of the first mark and the second mark, the substrate and the mask are aligned,
An exposure method comprising: projecting exposure with a pattern formed on the mask at a desired position of the aligned substrate. An exposure apparatus for transferring a pattern formed on a mask onto a substrate via a projection optical system,
10. The relative position between a first mark formed on the substrate as the object or a stage on which the substrate is placed and a second mark formed on the mask is measured. A position measuring device according to any one of
An alignment means for aligning the substrate and the mask based on a relative position measurement result of the first mark and the second mark;
An exposure unit that performs projection exposure with a pattern formed on the mask at a desired position of the aligned substrate;
An exposure apparatus comprising:

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