WO2004047156A1 - Position measurement method, position measurement device, exposure method, and exposure device - Google Patents

Abstract

Highly-accurate focus adjustment is performed by eliminating adverse affect attributed to reflectivity distribution. Detection light is applied to a measurement position on a substrate and reflected light reflected from the measurement position is received, thereby measuring position information in the normal direction of the substrate surface. The position measurement method includes a step for measuring an error component of the position information caused by reflectivity distribution of the detection light at the measurement position on the substrate and a step for correcting the position information in the normal direction according to the error component measured.

Description

 Description Position measurement method, position measurement device, exposure method, and exposure device

 INDUSTRIAL APPLICABILITY The present invention is used in a position measuring method and a position measuring device for measuring position information in a normal direction of a substrate surface by irradiating a substrate with detection light, and in a manufacturing process of a device such as a semiconductor element or a liquid crystal display element. An exposure method and an exposure apparatus.

 This application is based on Japanese Patent Application No. 2002-33036778, the contents of which are incorporated herein. Background art

 Various devices such as semiconductor elements, liquid crystal display elements, and thin-film magnetic heads have been formed by applying planar technology, and photolithographic technology is indispensable for planar technology. When manufacturing these devices using photolithography technology, a mask or reticle pattern image is exposed via a projection optical system onto a photosensitive substrate such as a wafer or a glass substrate coated with a photosensitive material such as a photoresist. Light emitting exposure devices are used.

 In general, an exposure apparatus uses a projection optical system having a large numerical aperture (N.A.A.) and a small depth of focus in order to obtain a resolution required for forming a fine pattern. Therefore, in order to transfer a fine circuit pattern with high resolution, the surface of the photosensitive substrate must be accurately and reliably aligned with the image plane (within the depth of focus (DOF)) of the projection optical system. . Therefore, the exposure apparatus includes a focus detection system that detects the position and inclination of the surface of the photosensitive substrate in the optical axis direction of the projection optical system (the direction normal to the substrate surface), and a focus detection system based on the detected height and inclination. A focusing mechanism including an adjustment mechanism for adjusting the posture of the photosensitive substrate including the position of the photosensitive substrate surface is provided.

In this type of exposure apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. H10-270703 and the corresponding U.S. Pat. No. 6,455,214, it is not perpendicular to the wafer. Slit-like detection light for focus detection is applied to the wafer from an oblique direction with an arbitrary angle. A so-called oblique reflection type focus detection system (position measurement device), which makes incident light and guides reflected light from the wafer surface to a detector serving as a light receiving unit, is often used. In this focus detection system, the detection light is irradiated on the wafer through the light transmission slit, that is, a slit image is formed on the wafer surface, and the slit image is reflected on the wafer surface and the light receiving aperture (slit) is formed. However, when the position of the wafer surface is displaced in the normal direction, the detection light (the re-formed slit image) on the light receiving slit is aligned with the optical axis direction of the focus detection system. It will be shifted laterally in the orthogonal direction. Therefore, the position of the projection optical system in the optical axis direction of the wafer surface, that is, the position in the focus direction, is measured by detecting the shift amount, that is, the change in the position of the center of gravity of the light amount of the slit image (detection light). ing.

 By the way, in recent years, with further miniaturization of semiconductor devices, the numerical aperture of the projection optical system has been increased, and the depth of focus has been increasingly reduced. Therefore, the entire surface of the exposure area where the reticle pattern image is projected within the projection field of view of the projection optical system (that is, the exposure light irradiation area), so that the wafer surface falls within the depth of focus of the projection optical system. Various efforts have been made to improve the level of public transport. For example, by performing a wafer flattening process called CMP (Chemi cal mechanical polishing), it is possible to improve the flatness of the wafer surface during resist coating. is there. However, despite the fact that there is no change in the surface shape due to the improvement in flatness, an error (hereinafter referred to as a focus error) may be included in the focus detection value due to various factors.

One cause of the focus error is thin-film multiple interference. This thin film multiple interference is caused by the light reflected on the resist surface and the base, due to the resist film thickness, the structure of the base that is the device part, and the optical constants (refractive index and extinction coefficient) between the resist and the base. And the reflected light interferes. Semiconductor devices, S i and the metal wiring portion, are formed from S 1 0 ₂ Ya i N such as an interlayer insulating film, S i O 2, S i N have substantially same optical constants and the resist, Since it becomes a dielectric at the wavelength of the detection light for focus detection (for example, illumination light generated from a halogen lamp), multiple interference is likely to occur. In particular, if there is a highly reflective portion (for example, metal wiring, etc.) on the base, the ratio of the reflected light intensity on the base to the reflected light intensity on the wafer, That is, the ratio of the reflected light intensity on the base to the reflected light intensity on the resist surface is relatively increased. Therefore, the position of the center of gravity of the light amount on the light receiving slit of the detection light reflected by the wafer is shifted laterally from the position of the center of gravity of the light amount when almost all of the light is reflected from the resist surface. turn into. Another cause of the focus error is an adjustment error of the focus detection system. If the focus detection system is adjusted out of the ideal state, the light receiving slit position will deviate from the focal position. For this reason, a slit image is a set of point images, but the point image that should become a point image at the light receiving slit position has a spread, and if the light beam forming the point image has an intensity distribution due to the incident angle to the point image, the slit image Also have an intensity distribution in the lateral displacement direction, which results in an error in the focus detection value. Furthermore, as for the detection light of the focus detection system to be incident on the wafer surface, a light beam forming a point image is incident at a different incident angle according to the numerical aperture of the light transmitting lens, and as a result, the reflected light intensity is also higher. It has an intensity distribution due to the law of reflection and refraction, or the multiple interference of thin films described above. Therefore, a focus error that does not occur when a point image is formed occurs due to the angular distribution of the reflected light intensity in the entire slit light.

 Therefore, conventionally, the detection light of the focus detection system is made incident at a large incident angle of 80 ° or more to increase the reflectivity on the resist surface or to use a light source with a wavelength bandwidth, such as a fluorescent lamp). The focus error due to thin-film multiple interference is minimized by increasing the intensity distribution of wavelengths at which errors due to interference do not occur. Regarding the adjustment error, the optical system was strictly adjusted so that the focus error was smaller than the depth of focus of the projection optical system. Regarding the difference in the incident angle, the focus optical system has a small numerical aperture of the incident light beam (for example, one hundredth level) so that the incident angle of the light beam forming the image is hardly changed, and the reflectivity is reduced. The difference was not made.

 However, in addition to the above-mentioned factors that cause the focus error, there are the following problems.

On the wafer surface, the reflectance is partially different in the projection area of the slit image by the focus detection system (that is, the irradiation area of the detection light), especially in the focus measurement direction (when the wafer is displaced in the focus direction) in that area. Slip on the wafer surface If there is a reflectance distribution in the direction of movement of the image, the reflected slit image also has an intensity distribution in the detection direction of the lateral displacement at the light receiving slit position. In this case, as shown in Fig. 15, the center of gravity of the slit image moves from the center according to the image intensity distribution, so that the surface position of the wafer in the focus direction is independent of the actual shape of the wafer surface. It is measured as if it were displaced, which hinders accurate focusing adjustment. In addition, even if the error that occurs is not so large, and as a result the wafer surface is within the depth of focus, unnecessary tilt correction is required at the time of focus adjustment. In the case of the exposure apparatus of the (type), there is also a problem that synchronization accuracy is deteriorated.

 In addition, with the progress of miniaturization of semiconductor devices, changes in the materials that make up the devices and the decrease in the film thickness of the resist have led to the projection area of the slit image on the wafer (detection light irradiation Within the region, the reflectivity distribution is easily generated, that is, the state of the thin film multiple interference greatly differs. Disclosure of the invention

 The present invention has been made in consideration of the above points, and has a position measuring method and a position measuring method capable of performing a highly accurate focus detection by eliminating an adverse effect due to a distribution of a wafer surface state such as a reflectance distribution. It is an object to provide a measuring device, an exposure method, and an exposure device.

 In order to achieve the above object, the present invention employs the following configuration corresponding to FIGS. 1 to 13 showing the embodiment.

 The position measurement method of the present invention is a position measurement method that irradiates detection light to a measurement location on a substrate, receives reflected light reflected at the measurement location, and measures positional information of the substrate surface in a normal direction. A step of measuring an error component of the position information generated by the reflectance distribution of the detection light at the measurement point on the substrate; and a step of correcting the position information in the normal direction based on the measured error component. It is characterized by the following.

Further, the position measuring device of the present invention is a position measuring device that irradiates detection light to a measurement location on a substrate, receives reflected light reflected at the measurement location, and measures positional information of the substrate surface in a normal direction. Caused by the reflectance distribution of the detection light at the measurement point on the substrate It has a storage device for storing an error component of the position information, and a correction device for correcting the position information in the normal direction based on the stored error component. Therefore, in the position measuring method and position measuring apparatus of the present invention, since the error component of the position information generated by the reflectance distribution of the detection light at the measurement location on the substrate is known in advance, the position of the substrate surface measured using the detection light is known. The error component can be eliminated from the position information in the normal direction, and the substrate can be positioned at a predetermined position without being affected by the reflectance distribution. Note that the error component can be obtained by a method of calculating based on the intensity of the detection signal obtained when the detection light is received, or by actually measuring the surface shape of the board (for example, using a separate measurement device) and measuring the error. Method based on the result of comparing the measured surface shape with the design surface shape (for example, the difference between the two surface shapes), and when the substrate surface is flattened by CMP or the like, the measured position of the substrate surface A method of directly setting information as an error component can be employed.

 An exposure method according to the present invention is an exposure method for exposing a mask pattern onto a substrate with exposure light, wherein the position information is measured by the position measurement method described above, and the surface position of the substrate is determined based on the measurement result. Is adjusted ^ ".

 Further, an exposure apparatus of the present invention is an exposure apparatus for exposing a pattern of a mask on a substrate with exposure light, wherein the position measurement apparatus (21) is used as an apparatus for measuring surface position information of the substrate. It is a feature.

 Therefore, with the exposure method and exposure apparatus of the present invention, surface position information of the substrate can be measured with high accuracy without adversely affecting the reflectance distribution of the substrate surface with respect to the detection light. Accurate positioning in the axial direction becomes possible. Therefore, for example, even when a projection optical system with a shallow depth of focus is used, the substrate surface can be adjusted within the depth of focus, and the necessary contrast (resolution) can be easily obtained. Also, even if the resulting focus error is such that the substrate surface falls within the depth of focus, the scan type (synchronous scan type) exposure apparatus does not perform unnecessary tilt correction, so synchronization accuracy is reduced. Exposure can be performed without deteriorating.

Further, the exposure apparatus of the present invention is an exposure apparatus that projects a mask pattern onto a plurality of divided areas on a substrate by synchronously moving the mask and the substrate. A surface position detector that detects the surface position of the substrate during synchronous movement by irradiating detection light onto the substrate and detecting the reflected light, and distribution information of the surface state within the partitioned area on the substrate, the synchronous movement direction And a control device for setting the surface position of the substrate based on the detection result of the surface position detection device and the distribution information stored in the storage device.

 Therefore, in the exposure apparatus of the present invention, no matter which synchronous movement direction is selected for the partitioned area on the substrate, the surface position of the substrate is corrected based on the distribution information of the surface state in the partitioned area according to the synchronous movement direction. It can be set in the state where it was done. Therefore, the surface position of the substrate can be accurately positioned in the optical axis direction of the exposure light (the imaging plane of the projection optical system) without being adversely affected by the surface condition on the substrate or the synchronous movement direction. Therefore, for example, even when a projection optical system with a shallow depth of focus is used, the substrate surface can be adjusted within the depth of focus, and even when so-called scanning exposure is performed, unnecessary tilting of the wafer surface is performed. Since no correction is performed, exposure can be performed without deteriorating synchronization accuracy, and the required contrast (resolution) can be easily obtained. BRIEF DESCRIPTION OF THE FIGURES

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

 FIG. 2 is a perspective view schematically showing a wafer stage constituting the exposure apparatus.

 FIG. 3 is a diagram showing a configuration of an oblique incidence type multipoint focus position detection system.

 FIG. 4A is a diagram of a focus measurement point and an exposure region projected on a transfer surface of a wafer, and FIG. 4B is a diagram showing a relationship between a shot region and an illumination region.

 FIGS. 5A and 5B are diagrams each showing a positional relationship between a device pattern and a focus measurement point.

 FIG. 6 is a diagram showing a control system of the wafer stage.

 FIG. 7A is a diagram showing a positional relationship between a focus measurement point and an area having different reflectance, and FIGS. 7B and 7C are diagrams showing received light intensities.

 FIGS. 8A and 8B are diagrams showing the relationship between the position and the light intensity when the measurement intervals are different.

FIG. 9 is a flowchart for focus error measurement. FIG. 10 is a diagram schematically showing a path and a measurement position where focus measurement is performed. FIG. 11A is a diagram showing a sensor position during scanning, and FIG. 11B is a diagram showing a sensing value at that time.

 FIG. 12 is a flowchart showing another form of focus correction method.

 FIG. 13 is a flowchart showing another form of focus correction method.

 FIG. 14 is a flowchart of manufacturing a device using the exposure apparatus according to the embodiment of the present invention.

 Fig. 15 is a diagram for explaining the relationship between the reflectance distribution and the focus error. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of a position measuring method, a position measuring device, an exposure method, and an exposure device according to the present invention will be described with reference to FIGS. 1 to 14.

 FIG. 1 is a view showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention. In the following description, the XYZ rectangular coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to the {Ζ.} Rectangular coordinate system. In the X-axis orthogonal coordinate system shown in FIG. 1, a reticle R as a mask having a predetermined pattern area formed thereon and a wafer W as a substrate having a photoresist coated on its upper surface are moved during scanning exposure. The direction (synchronous movement direction) is set to the Υ axis direction, the direction perpendicular to the Υ axis in the plane of reticle R is set to the X axis direction, and the normal direction of reticle R (wafer surface) is set to the Ζ axis direction. In the Ζ Υ Ζ rectangular coordinate system in Fig. 1, the Χ Υ plane is actually set as a plane parallel to the horizontal plane, and the Ζ axis is set vertically upward.

In the following, an area where the exposure light EL is irradiated on the reticle R by an illumination optical system (not shown) is referred to as an “illumination area”, and the projection optical system PL is conjugated to the illumination area via the projection optical system PL. The area on the wafer W where the exposure light EL is irradiated is referred to as an “exposure area”. The exposure apparatus (FIG. 1) of the present embodiment is a scanning exposure apparatus that transfers the pattern of the reticle R to a plurality of shot areas (partition areas) on the wafer W in a step-and-scan manner. The above-mentioned illumination area is a rectangular area extending on the reticle R in the X-axis direction with the optical axis of the illumination optical system (coincident with the optical axis AX of the projection optical system PL) as a center. In FIG. 1, the illumination optical system not shown includes a shaping optical system that makes the illumination condition of the reticle R variable, an optical integrator, and a blind (variable field stop) that defines an illumination area on the reticle R. Exposure light EL generated from a light source (not shown) (such as an excimer laser) is applied to the above-mentioned illumination area with almost uniform illuminance. The projection optical system PL generates an image of a part of the pattern of the reticle R arranged on the first surface (object surface) in the illumination area in the exposure area on the second surface (imaging plane). The image is transferred onto the wafer W whose surface is substantially aligned with the second surface. In the scanning exposure in which the pattern of the reticle R is transferred to each shot area on the wafer W, the relative movement of the reticle R with respect to the illumination area and the relative movement of the wafer W with respect to the exposure area are performed in synchronization. Is irradiated with the exposure light EL, and each shot area is irradiated with the exposure light EL via the projection optical system PL. At this time, the reticle R is scanned at a constant speed V in the positive or negative direction of the Y-axis with respect to the illumination area, while the wafer W is simultaneously fixed in the negative or positive direction of the Y-axis. Scanning is performed at the speed V / 3 (1 / β is the reduction magnification of the projection optical system PL).

 The reticle R is held on the reticle minute drive stage 1 by a vacuum chuck or the like. The reticle minute drive stage 1 can be finely moved in the X-axis direction, the Y-axis direction, and the rotation direction (0 direction) in a plane perpendicular to the optical axis AX (XY plane) of the projection optical system PL. Performs reticle R position control with high accuracy. The reticle minute drive stage 1 is mounted on a reticle Y drive stage 2 that can be driven in the Y-axis direction, and the reticle Y drive stage 2 is mounted on a reticle support 3. A movable mirror 4 is disposed on the reticle micro-drive stage 1 and an interferometer 5 disposed on the reticle support 3 constantly moves the reticle micro-drive stage 1 in the X, Y, and S directions. Is monitored. The positional information S 1 obtained by the interferometer 5 is supplied to the main control system 20.

On the other hand, the wafer W is mounted on the wafer stage. FIG. 2 is a perspective view showing a schematic configuration of the wafer stage. The wafer W is held on a Z-tilt stage 7 via a wafer holder 6 that performs vacuum suction, and each of the Z-tilt stage 7 is moved three Z-axis directions (for example, a voice coil module). , EI core, etc.) mounted on an XY stage 9 via 8a to 8c. in this case, By making the driving amounts of the three actuators 8a to 8c the same, the Z tilt ス テ ー ジ stage 7 can be moved in the Z-axis direction, and the driving amounts of the three actuators 8a to 8c can be reduced. By independently setting the tilt, the tilt angle of the stage 7 around the X axis and the tilt angle of the stage 7 around the Y axis can be controlled. The Z tilt チ ル stage 7 is configured to be able to rotate around the Z axis within a predetermined range by using an actuary (not shown) different from the three actuaries 8a to 8c. . The XY stage 9 is configured to move the Z-tilt stage 7 at a constant speed in the Y-axis direction and to move in steps in the X-axis and Y-axis directions by, for example, a linear motor. The wafer stage is constituted by the wafer holder 6, the Z-tilt stage 7, the functions 8 a to 8 c, and the XY stage 9.

 A movable mirror 10 is fixed on the Z tilt ス テ ー ジ stage 7, and the position of the Z tilt 0 stage 7 in the X axis direction, the Y axis direction, and the モ ニ タ ー direction is monitored by the interferometer 11 disposed outside, The position information obtained by the interferometer 1 is also supplied to the main control system 20. Here, as shown in FIG. 2, in order to measure the position information of the Z tilt ス テ ー ジ stage 7 in the X axis direction and the Y axis direction, the moving mirror 10 X and the moving mirror 1 are placed on the Z tilt ス テ ー ジ stage 7. 0Y is arranged, and an interferometer 1IX and an interferometer 11Y are arranged at positions facing these movable mirrors 10X and 10Y, respectively. Instead of fixing the movable mirror 10 to the Z-tilt stage 7, a reflecting surface obtained by mirror-finishing a wafer stage, for example, an “end surface (side surface) of the Z-tilt stage 7” may be used. The interferometer 11 may be capable of measuring not only the amount of rotation about the Z axis, but also the amounts of rotation about the X axis and the Y axis.

The main control system 20 controls the positioning operation of the Z tilt stage 7 and the XY stage 9 via the wafer driving device 12 and the like, and controls the operation of the entire apparatus. Also, the correspondence between the wafer coordinate system defined by the coordinates measured by the interferometer 11 on the wafer W side and the reticle coordinate system defined by the coordinates measured by the interferometer 5 on the reticle R side is described. For this purpose, a reference mark plate 13 is fixed on the Z tilt stage 7 and near the wafer W. Various reference marks are formed on the reference mark plate 13. The exposure apparatus of the present embodiment is provided above the reticle R, and includes reticle alignment systems 14 and 15 for simultaneously detecting the reference mark on the reference mark plate 13 and the mark on the reticle R. . The reticle alignment systems 14 and 15 of the present embodiment are image processing systems that use the exposure light EL as the alignment light to detect the images of the two marks with an imaging probe, and that the reticle alignment from the reticle R Deflection mirrors 16 and 17 for guiding the detection light to each are movably arranged. When the exposure sequence is started, these deflection mirrors 16 and 17 are moved out of the optical path of the exposure light EL by mirror driving devices 18 and 19, respectively, under a command from the main control system 20. Will be evacuated. Also, on the side of the projection optical system PL, the position information of the wafer W in the Z-axis direction (optical axis direction, normal direction) and the inclination angle of the wafer W with respect to the XY plane (the imaging plane of the projection optical system PL) An oblique incidence type multi-point focus detection system 21 is provided as a position measurement device (surface position detection device) for measuring the surface position of the wafer W.

 Next, an oblique incidence type multi-point focus position detection system 21 for measuring the inclination angle of the wafer W will be described. FIG. 3 is a diagram showing a configuration of the oblique incidence type multipoint focus position detection system 21. As shown in FIG. In FIG. 3, some of the members shown in FIG. 1 are omitted to simplify the illustration. The oblique incidence multi-point focus position detection system 21 shown in FIG. 3 includes illumination light having a wavelength different from that of the exposure light EL and not exposing the photoresist on the wafer W from an illumination light source (not shown). It is guided through the optical fiber bundle 25. The illumination light emitted from the optical fiber bundle 25 illuminates a pattern forming plate 27 on which a plurality of slit-shaped opening patterns are formed via a condenser lens 26.

The illumination light transmitted through the pattern forming plate 27 is projected onto the transfer surface (photoresist surface) of the wafer W through the lens 28, the mirror 29, and the irradiation objective lens 30, and the wafer W is transferred. An image (slit image) of the aperture pattern on the pattern forming plate 27 is projected and formed on the surface obliquely to the optical axis AX of the projection optical system PL. FIG. 4 is a diagram showing a state in which the aperture pattern formed on the pattern forming plate 27 is imaged on the transfer surface of the wafer W disposed below the projection optical system PL. In FIG. 4A, a rectangular area denoted by reference numeral EF indicates the above-described exposure area. The image of the pattern of the reticle R is irradiated into the exposure area EF. The pattern forming plate 27 is used to set the arrangement (number and positions) of the focus measurement points on the wafer W and the shape and size of the detection light irradiation area at the focus measurement points. is there. In this embodiment, seven focus measurement points are provided at predetermined intervals along the Y direction as the scanning direction (synchronous movement direction) and the X direction as the non-scanning direction (step movement direction) (49 in total). Set, as shown in Fig. 4A, the aperture pattern image (slit image) at 49 focus measurement points AF1;! ~ AF17, AF21 ~ AF27, '..., AF71 ~ AF77 (hereinafter referred to simply as AF) as appropriate, so that the open pattern is formed corresponding to the arrangement of the focus measurement points (Fig. 4A). Have been. Further, in the present embodiment, the longitudinal direction of the aperture pattern image (slit image) AF projected on the focus measurement point is oblique to the X-axis and the Y-axis on the transfer surface of the wafer W in FIG. Is set to 45 degrees). In the following, the aperture pattern image (slit image) AF may also be referred to as a focus measurement point. .

 Here, the setting of the slit image AF projected on the focus measurement point will be briefly described.

 As shown in FIG. 5, device patterns DP formed in a part of each shot area on the wafer W are usually arranged along the Y direction and the X direction. Therefore, when the slit image AF is arranged along the Y direction (or X direction), the slit image AF may partially overlap the device pattern DP formed on the base as shown in FIG. 5A. In this case, the presence of the device pattern DP causes a large difference in the reflectance of the detection light in the width direction (X direction) in the slit image AF over the entire length. Therefore, as shown in Fig. 5B, by inclining the slit image AF so that it is not parallel to the X or Y direction, the difference in reflectivity occurs only around the boundary of the device pattern DP. The resulting adverse effects can be minimized.

Returning to FIG. 3, the illumination light (reflected light) reflected by the wafer W passes through the converging objective lens 31, the rotating diaphragm 32, and the imaging lens 33, and is re-transmitted to the light receiving surface of the light receiver 34. The image of the pattern on the pattern forming plate 27 is re-imaged on the light receiving surface of the projected light receiver 34. Openings are arranged on the light receiving surface of the light receiver 34 in a shape similar to the pattern forming plate 27. A light shielding plate (not shown) is provided. Here, since the main control system 20 vibrates the rotational direction diaphragm 32 via the vibrating device 36, the position of the image projected on the light receiver 34 is determined by the opening formed in the light shielding plate. It vibrates in a direction inclined by 45 degrees with respect to the longitudinal direction, that is, in the X direction in FIG. This vibration direction coincides with the focus measurement direction (X direction) in which the slit image AF moves on the wafer W when the wafer W is displaced in the Z axis direction (the optical axis direction of the projection optical system PL). Detection signals from many light receiving elements of the light receiver 34 are supplied to the signal processing device 35. The signal processing device 35 synchronously detects each of the supplied detection signals with the drive signal of the vibrating device 36, and performs 49 focuses corresponding to the focus positions of the focus measurement points AF 11 to AF 77, respectively. Get the signal.

 Here, as shown in FIG. 4A, the focus measurement points AF31 to AF37 and AF51 to 57 are arranged at the periphery of the exposure area EF, and the measurement points AF41 to AF47 are exposed. The measurement points AF11 to AF17, AF21 to AF27 and measurement points AF61 to AF67, AF71 to AF77 are located inside the area EF, and the exposure area EF It is located outside. When the wafer W is scanned in the positive direction of the Y-axis, the shape of the area to be exposed using the measurement results at the measurement points AF61 to AF67, AF71 to AF77 This is for pre-measurement (pre-reading) of (position information in the Z-axis direction). Similarly, when the wafer W is scanned in the negative direction of the Y axis, the measurement results at the measurement points AF11 to AF17 and AF21 to AF27 are used to determine the area to be exposed next. This is for measuring the shape in advance. Then, exposure is performed using measurement results at measurement points AF11 to AF17 and AF21 to AF27 or measurement results at measurement points AF61 to AF67 and AF71 to AF77. The Jeha-W attitude control is performed on the part.

The signal processing device 35 performs various arithmetic processing such as least square approximation on the 49 focus signals (detection signals) to obtain the inclination angle of the transfer surface of the wafer W in the exposure area EF and the transfer thereof. The focus position of the surface is determined and output to the main control system 20. Next, the control system of the wafer stage shown in FIGS. 1 and 2 will be described in more detail. FIG. 6 is a diagram showing a control system of the wafer stage, and the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals. In FIG. 6, Z tilt Θ —Di7 is supported via three actuaries 8a-8c located at the bottom. The actuators 8a to 8c are adjusted by the drive units 41a to 41c to adjust the amount of expansion and contraction of the actuators 8a to 8c, respectively. The focus position, the scan direction tilt angle, and the non-scan direction tilt angle of the transfer surface of the wafer W mounted on the wafer holder 6 (not shown) provided above are set to desired values. Can be. In the vicinity of each of the actuaries 8a to 8c, a height sensor that can measure the displacement in the focus direction of each actuator at a resolution of, for example, about 0.001 ^ m, is used. c are attached, and the measurement results of the height sensors 38a to 38c are output to the main control system 20. The driving units 41a to 41c are provided in the wafer driving device 12 shown in FIG.

 The main control system 20 of the present embodiment scans the reticle R and the wafer W synchronously when transferring the image of the pattern formed on the reticle R to the transfer surface of the wafer W via the projection optical system PL. Therefore, various calculations are performed according to the shape of the transfer surface and the focus position obtained by the multipoint focus position detection system 21, and the attitude and the position in the Z direction of the wafer W are controlled based on the results. That is, in order to control the attitude and position of the wafer W, the main control system 20 includes a tilt angle of the transfer surface of the wafer W output from the signal processing device 35, a focus position of the transfer surface, and a height sensor 3 8 a to 3 c Output from the actuator 8 a to 8 c by controlling the driving of the drive units 41 a to 41 c according to the displacement of the 8 a to 8 c, etc. The focus position and attitude of the wafer W are controlled via c. The main control system 20 is provided with a storage device 40 for storing various calculation results and the like.

Subsequently, prior to transferring the image of the pattern formed on the reticle R to the transfer surface on the wafer W, the multipoint focus position detection system 21 is used while moving the wafer W in the XY plane in advance. A procedure for adjusting the focus of the transfer surface of the wafer W will be described. Here, when performing focus adjustment, the position in the Z direction of the transfer surface is measured at each of a plurality of focus measurement points by the multi-point focus position detection system 21. In some cases, a focus error due to the reflectance distribution on the transfer surface is included as an error component. As shown in Fig. 7A, when the focus measurement point AF on the wafer W straddles the high-reflectance part HR and the low-reflectance part LR, the positions P1 and P4 on both ends of the slit are highly reflective. As shown in Fig. ΊB, the reflected light intensity distribution in the focus measurement direction in this part is in the focus measurement direction at position P2 in the low reflectance part LR. It becomes larger than the reflected light intensity distribution. In addition, the reflected light intensity distribution in the focus measurement direction at the position P3 straddling both reflectance portions in the focus measurement direction is an intensity distribution according to the reflectance. The light receiver 34 of the focus position detection system 21 detects the average reflected light intensity in the slit at the focus measurement point. Therefore, as shown in FIG. The reflected light intensity distribution in 4 (actually in the entire direction orthogonal to the force measurement direction) is combined (added), and the center of gravity position is shifted. The focus detection method of the focus position detection system 21 measures, for example, a detection signal (voltage value V) at the maximum amplitude position of the slit image oscillating with respect to the opening on the light receiver 34. These positions are two places when the slit image is located at both ends of the opening. Then, the difference between the two measured detection signals (voltage value V) is used as a focus signal. In this case, if there is an intensity distribution in the reflected light of the slit image, an error occurs in the voltage value at each maximum amplitude position, and an accurate focus signal cannot be obtained.

 Further, when the focus detection method of the focus position detection system 21 uses, for example, the position of the center of gravity in the slit image as a focus signal, that is, in the case of the detection method using a line CCD, the displacement of the position of the center of gravity is directly considered as a focus error. It has become.

 Therefore, in order to perform focus adjustment with high accuracy, this focus error is measured in advance before exposure. In the present embodiment, the focus error is measured based on the intensity of the detection signal obtained when the reflected light of the detection light applied to the focus measurement point is received. Hereinafter, a procedure for measuring a focus error caused by a reflectance distribution at each focus measurement point will be described first. .

As described above, the detection signal at one force measurement point detected by the focus position detection system 21 is the average reflected light intensity at the focus measurement point, and is the intensity of the reflected light in the focus measurement direction in the slit. It does not show a reflectance distribution. Also, The reflectance distribution can be obtained by measuring the slit image AF projection area at the focus measurement point several times using the detection light of a slit (extremely fine slit) having an infinitesimal width. It is difficult to equip such detection light. Thus, in the present embodiment, as shown in FIG. 8A, a focus measurement point AF to be measured and a predetermined interval on both sides of the focus measurement direction (the X direction in the present embodiment) with this measurement point AF interposed therebetween. The intensity of the reflected light is measured at the measurement points AFL and AFR at the positions indicated by the arrows. Here, FIG. 8A shows a state in which a slit image is projected on each of the three focus measurement points to measure the intensity of the reflected light. However, it is not always necessary to project three slit images. By projecting a slit image only at the focus measurement points and moving the wafer W in the X direction, the reflected light intensity is measured at three locations on the wafer W corresponding to the three focus measurement points in Fig. 8A. You may make it. It should be noted that the number of measurement locations on the wafer at which reflected light intensity should be detected using at least one slit image AF is not limited to three, but may be two or four or more. From these three measurement results, the reflectance distribution r (x) is obtained by arithmetic processing such as the least square method.

 Here, it is assumed that the reflectance distribution expressed by the first order in the focus measurement direction exists on the surface of the wafer W as in the following equation (1).

 r (x) = a x + b… (1)

 The 'reflected light intensity I (X)' of a slit image having a width Δ in the focus measurement direction at a certain measurement position x is calculated as follows.

= A _Q A

 = A 'r (x)

A. ; Incident light intensity As is clear from equation (2), the reflected light intensity I (X) is the reflectance distribution! "(x), and there is no problem even if the reflectance distribution detected using the detection light having a finite width is used as the reflectance distribution detected using the detection light having an infinitesimal width.

 Next, let us consider a case where a reflectivity distribution expressed by quadratic in the focus measurement direction exists on the surface of the wafer W as in the equation (3).

r (X) = ax ² + bx + c… (3)

 The reflected light intensity I (X) in this case is calculated as follows.

= 4 2 base ⁵ ^

No

 Here, even if there is a variation due to the structure of the underlying layer, the rate of change of the second-order component is smaller than the constant reflectance component c, considering that the reflectance on the resist surface (wafer surface) is large. In this case, the reflected light intensity I (X) is calculated as follows.

,

No

≡ 4. Δ '(ax ² + bx + c)

= A-r (x) (4) As is clear from Eq. (4), the reflected light intensity I (X) of the second-order reflectance distribution is proportional to the reflectance distribution r (X). Therefore, there is no problem even if the reflectance distribution detected using the detection light having a finite width is used as the reflectance distribution detected using the detection light having an infinitesimal width. This is the same for the reflectivity distribution expressed by the third or higher order, and as a result, the intensity distribution of the detection signal (light intensity) of the focus position detection system 21 is calculated as follows. (C) It can be used for calculating the position of the center of gravity as a reflectance distribution on W. When a vibrating plate (vibrator) is used as in the focus position detecting system 21, the frequency component twice the vibration frequency of the vibrator becomes the focus detection signal. It can be obtained by detecting the amplitude.

 When the reflectance distribution r (x) is obtained by the above method, the center of gravity c (X) of the reflected light from the focus measurement point AF can be calculated by the following equation (5) for calculating the center of gravity.

After calculating the center of gravity C (x), the focus error e (X) can be obtained by the following equation (6) at the angle of incidence Θ on the wafer surface based on the focus detection principle. ·

 e (x) = (c (x) X t an / 2… (6)

 Then, the main control system 20 stores the calculated focus error e (X) in the storage device 40 in association with the coordinates of the force measurement point (the measurement position of the reflected light intensity on the wafer W). Let it.

 Next, a procedure for adjusting the focus of the transfer surface of the wafer W using the above-described position measurement method will be described with reference to a flowchart shown in FIG.

Note that focus error measurement is basically performed at all focus measurement points. However, in the present embodiment, measurement points at which focus measurement is actually performed during scanning exposure by synchronous movement, in other words, irradiation of the wafer W Of the plurality of detection lights to be used, the detection light used for focus measurement during actual exposure is used. Specifically, the focus measurement points AF11 to AF17, AF21 to AF27,... ゝ Among the multiple detection lights irradiated to AF71 to AF77, for convenience, as shown in FIG. In addition, the focus measurement points AF 57 and AF 5 that are arranged on the shot area (block area) SA and around the exposure area EF 4, the description will be made assuming that the detection light emitted to AF 51, AF 31, AF 34, AF 37 (hereinafter, referred to as S1 to S6) is used.

 In addition, as the timing of performing the focus error measurement, the head of the lot processing, the interval between the mouth processing, and the like can be selected. In the case of performing at the beginning of the lot, for example, focus error after EGA processing (Enhansed Global Arrangement; see Japanese Patent Application Laid-Open No. 61-44249 and corresponding US Pat. No. 4,780,617) Measurement is performed, and the calculated focus error is used as a correction amount (offset value) for the image plane of the projection optical system PL. If the focus error measurement is to be performed between lot processes, take out the wafer to be measured (for example, a wafer in the next exposure processing lot) and set it in the exposure apparatus. After performing wafer alignment (EGA), focus error measurement is performed and the result is stored. Then, when the lot is subjected to exposure processing, the stored information is read out and reflected in the wafer posture adjustment including the focus position. Here, it is assumed that focus error measurement is performed after EGA processing.

 As shown in FIG. 9, when the EGA processing is completed for the wafer at the beginning of the lot in step ST0, it is first determined whether or not focus error measurement is to be performed (step ST1). Move to 0 exposure processing. Usually, a plurality of shot areas S A on which the pattern of the reticle R is exposed are sectioned on the wafer W in a grid pattern. Therefore, when executing focus error measurement, a shot area to be measured is selected (step ST2).

 Normally, since the structure in each shot area on the wafer W is the same and the process program is also the same, a focus error generated in one shot area also occurs in another shot area. Therefore, if a shot area where the entire area can be measured is selected and measured, the measured focus error can be applied to other shot areas. However, in order to further improve the measurement accuracy, the reflectance distribution may be measured for a plurality of shot areas.

Next, in step ST3 ', as described above, the reflectance distribution is measured as the distribution information of the surface state of the wafer W using the detection signal of the focus position detection system 21. Here, in the present embodiment, as described above, among the plurality of focus measurement points shown in FIG. 4A, the detection light irradiated to focus measurement points S1 to S6 shown in FIG. 4B is used. Then, the reflectance distribution is measured for the path where the focus measurement is performed during the synchronous movement between the reticle R and the wafer W. More specifically, in the present exposure apparatus, the size and position of the shot area SA to be exposed on the wafer W in a short time after the shot map mapping, and the focus measurement point (the exposure area EF The measurement position on the wafer W is also known from the focus measurement signal sampling interval and the synchronous movement speed (scan speed). FIG. 10 schematically shows a path K in which focus measurement is performed at the time of scanning exposure and measurement positions P11 to P14. As described above, the measurement of the reflectance distribution is performed not only on the path K on which the focus measurement is performed, but also on the position P 1 on the wafer W where the focus measurement is performed; The interval between the positions P 11 and P 14 in FIG. 10 is set to be equal to or less than the width of the shot area on the wafer in the scanning direction (Y direction).

 Although the positions of the focus measurement points S1 to S6 are precisely adjusted, there is a possibility that a minute adjustment error may be included. Of the focus measurement paths (dotted lines with arrows) shown in Fig. 4B, for example, the path shown at the left end can measure the reflectance distribution at only one of the focus measurement points S3 and S4. Although it is possible, if there is an error in the set position of this measurement point, there is a possibility that accurate measurement of the reflectance distribution cannot be performed at the position where the focus measurement is performed. Therefore, in the present embodiment, the reflectance distribution is measured at all the focus measurement points S1 to S6, and the reflectance distribution corresponding to the coordinate position of the wafer W is stored for each measurement point (step ST4). ).

'Subsequently, in step ST5, it is determined whether or not the measurement of the set number of times of averaging has been performed, and the above steps ST3 and ST4 are repeated until the measurement of the predetermined number of times is completed. In the reflectivity distribution measurement, variations due to measurement reproducibility occur, so in order to reduce the variance due to the averaging effect, correction is performed by performing multiple reflectivity distribution measurements on one shot area SA Accuracy can be improved. Next, in step ST6, it is determined whether or not all the measurements for the selected shot area have been completed, and the above steps ST3 to ST5 are repeated until the measurement is completed. Then, when all the reflectance distribution measurements for the wafer W are completed, the reflectance distribution is then calculated using the stored reflectance distributions and the above equations (5) and (6), so that each focus measurement point is calculated. A focus error is calculated corresponding to the coordinate position of the wafer (shot area) (step ST7). Based on the calculated focus error, a map is created in which the offset data at the time of scanning exposure corresponds to the coordinate position of the focus measurement point and stored (step ST8), and an image plane correction value at the time of exposure is created. (Step ST), and store it in the storage device 40. When the series of focus error measurement is completed, the flow shifts to exposure processing (step ST10).

 In this exposure processing, under the control of the main control system 20, the reticle R and the wafer W are synchronously moved to transfer the image of the pattern formed on the reticle R to the transfer surface of the wafer W. The position and the Z position of the wafer W are controlled according to the shape of the transfer surface of the wafer W calculated above while measuring the focus position of the transfer surface at the focus measurement point using the position detection system 21. I do.

 Here, during the synchronous movement, for example, when the measurement result of the focus measurement point S 3 (see FIG. 4B) is input, the main control system 20 determines the focus error stored in the storage device 40 Select the focus error (map of) measured at the focus measurement point S3, and correct the measurement result using the selected focus error. That is, the main control system 20 corrects the measurement value input during the synchronous movement using the focus error at the force measurement point at which the measurement value was obtained. As a result, it is possible to eliminate an adjustment error when setting a focus measurement point from the measurement result.

That is, the main control system 20 serves as a correction device, and corrects the measurement results of the multipoint focus position detection system 21 by the focus error (offset data) stored in the storage device 40, and performs the corrected measurement. By performing the above calculation process using the values, ゥ: I calculates the inclination angle and the focus position of the surface. For example, as shown in Fig. 11 (a), when a wafer having an originally uniform surface position is scanned by the focus measurement point S3, a low reflection area LR is formed between the position SP1 and the position SP2. If there is, the measurement result (sensing value) at the focus measurement point S3 includes a focus error as shown in FIG. 11B. Therefore, the focus error stored in advance By correcting the measurement result using the difference, it is possible to obtain surface position information according to the actual surface position (surface state) as shown by the two-dot chain line in the figure.

 Then, the main control system 20 adjusts the surface position of the wafer W via the Z tilt ス テ ー ジ stage 7 by individually driving the actuators 8 a to 8 c based on the obtained results. Can be. At this time, the main control system 20 uses the focus error corresponding to the measurement point with respect to the measurement result of the multipoint focus position detection system 21. At this time, the position on the wafer where the focus position was actually measured at the focus measurement point (actual measurement position) and the position on the wafer corresponding to the stored focus error (error measurement position) are equal to one another. If the actual measurement position and the error measurement position do not match, the focus error at the position closest to the actual measurement position is used. By interpolating using the focus error at two points near the measurement position, the force error at the actual measurement position is calculated, and correction is performed based on the obtained focus error. A detailed calculation method of the tilt angle and the focus position of the wafer surface is described in, for example, Japanese Patent Application Laid-Open No. 2002-27098, Japanese Patent Application Laid-Open No. Since it is disclosed in Japanese Patent No. 6808510, it is omitted here.

 When the scanning exposure of one shot area SA is completed, the wafer W is moved stepwise to start the scanning exposure of the next shot area. Hereinafter, the scanning exposure and the step movement are repeatedly executed, and when the pattern of the reticle R is transferred to all the shot areas on the wafer W, the exposure processing of the wafer W is completed.

As described above, in the present embodiment, the emissivity distributions respectively measured at different positions on the wafer W (shot area) in the scanning direction (Y direction) corresponding to the focus measurement points used in the scanning exposure in advance. Since the focus error is calculated from the data, the error component due to the reflectance distribution can be eliminated and corrected when the focus position is measured for the wafer W, and the surface position of the wafer W can be easily projected. It can be positioned on the image plane of the system PL. Therefore, in the present embodiment, even when a projection optical system having a shallow depth of focus is used, high-resolution exposure processing can be realized by accurate focusing adjustment. In particular, in the present embodiment, since the focus error is measured based on the intensity of the detection signal at the time of receiving the detection light in the focus measurement, it is not necessary to separately install a reflectance distribution measuring device, and the device is compact. It can contribute to cost reduction and cost reduction. Further, in the present embodiment, the focus error is measured in advance for the path for performing the focus measurement during the synchronous movement of the reticle R and the wafer W (at the time of actual exposure), so that the focus error measurement is required. The time can be shortened, and it can contribute to the improvement of production efficiency. Further, in the present embodiment, the focus error is measured for each of the plurality of focus measurement points, and a map is created and stored for each measurement point. (Detection light used when performing focus measurement) By performing correction based on the results obtained, it is possible to eliminate the adverse effects of adjustment errors when setting the position of the focus measurement point, and to achieve more accurate focus adjustment Can be implemented.

 In the above embodiment, as shown in FIG. 8A, when measuring the reflectance distribution r (x), the focus measurement point AF and the measurement points at positions spaced from the measurement point AF are measured. AFL and AFR are used to measure the intensity of the reflected light. However, as shown in Fig. 8B, in addition to the focus measurement point AF, the detection light overlaps with each other (a pitch smaller than the slit width in the focus measurement direction). ) It may be configured to measure the intensity of reflected light at a plurality of points. At this time, for example, by moving the wafer W in the focus measurement direction with respect to the focus measurement point AF, the intensity of the reflected light is measured at a plurality of points including the measurement point AF in FIG. 8B. In this case, a more microscopic reflectance distribution can be obtained.For example, if a component in which the reflected light intensity distribution changes quadratically by the least squares approximation method or the like can be calculated, the reflectance distribution r ( X) can be used as the second order to calculate the light intensity centroid.

When measuring the reflected light intensity distribution at a plurality of points where the detection light overlaps each other, since the measurement interval is small, the center of gravity can be calculated using the following equation (7) without performing integration processing as in equation (5). May be implemented. ∑η · ^χ ι

 c x) = ~~ …… (7)

 ∑

 i: reflected light intensity at the reflected light intensity measurement point x i

 Further, in the above embodiment, the synchronous movement direction is not particularly mentioned. However, in actuality, there are two types of timing: a timing at which a coordinate position is obtained by an interferometer or the like; and a timing at which the attitude and the Z position of the wafer W are controlled. Gaps may occur. In such a case, the measurement result of the reflectance distribution may be different depending on the synchronous movement direction. Therefore, when measuring the reflectance distribution and the focus error, the reflectance distribution and the focus error corresponding to the coordinate position for each synchronous movement direction are the same as when a map is created for each focus measurement point. It is preferable that a map corresponding to the synchronous movement direction be called up when the focus is adjusted, and that the focus measurement value is corrected using the offset value included in the map. In this embodiment, the reflectance distribution ′ is measured at a plurality of positions (four in this example) that are discretely set on a path K parallel to the scanning direction (Y direction) in the shot area. However, the number of measurement positions of the reflectance distribution on the path K may be arbitrary.For example, by moving the wafer in the scanning direction at a pitch substantially equal to the width of the above-described slit image AF in the scanning direction, The reflectivity distribution may be measured over almost the entire shot area in the scanning direction.

 Subsequently, another embodiment of the present invention will be described.

 In the above embodiment, the reflectivity distribution of the wafer surface is calculated and measured by receiving the reflected light of the detection light relating to the focus measurement, but the surface shape of the wafer W is measured in advance, and the result is measured. It can also be used to obtain a focus error distribution caused by the reflectance distribution. In the following measurement method, it is preferable to perform averaging by multiple measurements within a single shot region, a plurality of shot regions, and for each synchronous movement direction in order to improve measurement accuracy.

For example, as shown in FIG. 12, the surface shape of the wafer W is measured using the focus position detection system 21 described above (step ST 11), and the measured surface shape and the focus position of the capacitance sensor and the like are measured. Surface measured in advance using a measuring instrument different from detection system 21 It is also possible to set the offset value as a focus error based on the reflectance distribution using the difference from the shape (step ST 12). In this case, if the focus measurement result is corrected using the set offset value (step ST13), an error component due to the reflectance distribution can be eliminated as in the above embodiment.

 Also, in recent device manufacturing processes, planarization is often performed by the above-mentioned CMP. For wafers whose surface shape can be regarded as flat by this processing, as shown in Fig. 13 After performing the flattening process (step ST 21), when the focus measurement is performed using the focus position detection system 21 (step ST 22), the measured values (position information, surface position information) Can be set as the focus error (step ST23). In this case, since the flatness of the wafer is not actually measured, if the wafer is not flat, an error is included in the focus error distribution. However, since the flatness of the wafer at the time of measurement can be generally grasped by the flatness of the wafer holder and the grade of the wafer itself, etc., a threshold value corresponding to the flatness is set, and the focus measurement result changes by more than the threshold value. If is included, correction may be performed assuming that a focus error due to the reflectance distribution exists. For example, the flatness of the wafer may be measured in advance, and the focus error distribution previously calculated may be corrected using the measured flatness. When focus measurement is performed using the focus position detection system 21, if the shot area to be measured is inclined with respect to a predetermined reference plane (for example, the imaging plane of the projection optical system PL), The calculated focus error distribution includes an error caused by the tendency. Therefore, for example, it is preferable to set the shot area substantially parallel to the reference plane before the focus measurement, or to subtract an error caused by the inclination from the focus error distribution.

Also, regarding the attitude control of the wafer, the allowable value of the tilt can be set in consideration of the depth of focus of the projection optical system PL. Therefore, this allowable value is set as a threshold, and when the inclination of the wafer W at the time of focus adjustment is calculated from the measurement result of the focus position detection system 21, if the threshold is exceeded, the focus position is detected. Assuming that the measurement result of the system 21 includes an error component due to the reflectance distribution, a procedure for performing the correction may be adopted. Note that, in the above-mentioned Japanese Patent Application Laid-Open No. 2002-270704, the step information in the shot area SA is measured in advance, and the focus adjustment (exposure) during the exposure process is performed according to the state. Operation) A technique for selecting a mode from a plurality of modes is disclosed.

 Also in the present embodiment, the above technique is applied, and the step state is also measured when measuring the reflectivity distribution in the shot area (when measuring the reflectivity map). A leveling correction map may be created. This focus / leveling correction map can be stored in the storage device 40 in the same manner as the above-described map based on the focus error generated by the reflectance distribution (hereinafter, the reflectance map). Good. It is preferable that the reflectance map and the focus / leveling correction map are created and stored for each synchronous movement direction (scan direction; + Y direction and -Y direction) when exposing the shot area. Since the focus / leveling correction map contains a focus error caused by the reflectance distribution, the value of the reflectance map is subtracted from the value of the focus / leveling correction map at each focus measurement point to obtain the true value. The focus and repelling correction map can be obtained. At the time of exposure, focus leveling correction is performed based on the true value map.

 In addition, the shot area existing in the wafer W is a normal shot area, an edge shot partially overlapping the peripheral edge of the wafer, a TEG shot as a dummy shot for various measurements, and the like, and focus errors and steps due to reflectance distribution. There are multiple types of shot areas with different. Therefore, in a wafer in which a plurality of types of shot regions exist, it is preferable to create and store a reflectance map and a focus / leveling correction map for each type.

 From the above, the respective numbers of the reflectance map and the focus / leveling correction map that can be stored in the exposure apparatus correspond to the process program, for example, eight types of shot areas, and this corresponds to the synchronous movement direction ( (Scanning direction), there are two types of each, so the total is eight pairs (16). This number can be further increased according to the type of the shot area.

In addition, when performing exposure processing on a small shot area, correction is performed according to each of the reflectance map and the focus and repelling correction map. The control modes of the focusing operation according to the leveling correction map include, for example, a first mode in which the height position of the wafer holder 6 is controlled so that an intermediate portion of the step coincides with the focal plane, and a predetermined tolerance. It is conceivable that a second mode in which a stepped portion exceeding the value is not driven by using the focus position detection system 21 is performed. It is preferable that the operator can switch and set these modes as appropriate. In the above-described embodiment, the focus position detection system 21 is described as a configuration using a vibrator. However, the present invention is not limited to this. For example, an image processing method using a CCD, a method using a polarization modulation element, or the like. Alternatively, the focus position (and the reflectance distribution) may be measured by another detection principle.

 In each of the above embodiments, the wafer W is moved during the focus adjustment so that the wafer surface substantially matches the image forming plane of the projection optical system PL in the above-described exposure area EF. Alternatively, or in combination therewith, the imaging plane of the projection optical system PL may be moved by, for example, driving at least one optical element of the projection optical system PL.

 Further, in each of the above embodiments, the above-described focus error is obtained by using the multipoint focus position detection system 21 arranged at the exposure position where the pattern of the reticle R is transferred via the projection optical system PL. However, for example, the wafer stage has two independently movable wafer stages, and a wafer stage is arranged at each of an exposure position and a measurement position (alignment position) at which a mark is detected by a wafer alignment system. The present invention may be applied to an exposure apparatus capable of performing the operation and the measurement operation substantially in parallel, and the above-described focus error may be obtained using a detection system arranged at the measurement position. Here, as the detection system arranged at the measurement position, for example, one having the same configuration as that of the above-described multipoint focus position detection system 21 can be used.

In this twin wafer stage type exposure apparatus, the aforementioned reflectance distribution and focus position were measured at the measurement position using the detection system, and the measurement was performed based on the focus error obtained from the reflectance distribution. The focus position is corrected, and in the exposure processing of the wafer transferred from the measurement position to the exposure position, the focus adjustment is performed using the corrected focus position. At this time, the above-mentioned multi-point focus position detection system 21 need not be provided at the exposure position. Even if the Z-tilt stage 7 is driven using an interferometer that measures the distance in the Z-axis direction between the PL (or a gantry holding it) and the wafer stage (for example, Z-tilt stage 7) Good. Alternatively, only the reflectance distribution may be measured at the measurement position, and the focus position measured at the exposure position may be corrected using a focus error obtained from the reflectance distribution to execute the exposure processing. Furthermore, on the wafer that has been subjected to the flattening process as described above, the focus position is measured at the measurement position using the detection system, and the measurement result is directly used as a “focus error” and transferred from the measurement position to the exposure position. In the wafer exposure process performed, focus adjustment is performed using the focus error. In the twin wafer stage type exposure apparatus, the reflectance distribution or the focus position can be measured in parallel with the exposure operation. Therefore, the measurement can be performed multiple times without lowering the throughput of the exposure apparatus. That is, the accuracy of focus adjustment can be improved.

 The twin wafer stage type exposure apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. H10-214 783 and corresponding US Pat. No. 6,341,073 or International Publication WO98 Z 40791 and the corresponding U.S. Patent Nos. 6,262,796, etc., to the extent permitted by the national laws of the designated or designated elected States in this International Application. The disclosure of that US patent is incorporated herein by reference. In the above embodiment, the reflectivity distribution of the wafer is measured using the multipoint focus position detection system 21. However, a sensor (detection system) different from the multipoint focus position detection system or an exposure apparatus is used. The reflectivity distribution may be measured using another measuring device or the like, and the focus error may be calculated based on the measured reflectivity distribution.

 The substrate of the present embodiment includes not only a semiconductor wafer W for manufacturing a semiconductor device, but also a glass substrate for a display device, a ceramic wafer for a thin-film magnetic head, or an original mask or reticle used in an exposure apparatus. (Synthetic quartz, silicon wafer) etc. are applied.

US Patent No. 5,473,410 US Patent No. 5,473,410 Scanning exposure apparatus using a step-and-scan method (scanning stepper) that synchronously moves reticle R and wafer W to scan and expose reticle R pattern. In addition, the reticle R and the wafer W It can also be applied to a projection exposure apparatus (stepper) of the 'and' repeat type, in which the pattern of the reticle R is exposed while the wafer is in the upright position, and the wafer W is sequentially moved in steps. The present invention is also applicable to a step-and-stitch type exposure apparatus that transfers at least two patterns on a wafer W while partially overlapping each other. Furthermore, the present invention discloses a mirror projection aligner, for example, disclosed in International Publication WO 99/49504, which is filled with a liquid (eg, pure water) between a projection optical system PL and a wafer. It can be applied to an immersion type exposure apparatus and the like.

 The type of exposure apparatus is not limited to an exposure apparatus for manufacturing a semiconductor element for exposing a semiconductor element pattern onto a wafer W, but may be an exposure apparatus for manufacturing a liquid crystal display element or a display, a thin film magnetic head, an imaging element ( The present invention can be widely applied to an exposure apparatus for manufacturing a reticle, a mask, or the like.

As the light source of the exposure light, emission lines (g-line (436 nm), h-line (404.nm), i-line (365 nm)) and KrF excimer laser (248 nm ), A r F excimer laser (1 93 nm), F ₂ laser (1 57 eta m), eight 1 _"2, single-THE (1 26 nm) not only, X-rays, or electron beam or ion beam over厶etc. For example, when using an electron beam, a thermionic emission type lanthanum hexaporite (L a B ₆ ) or tantalum (T a) can be used as an electron gun. Further, a harmonic such as a YAG laser or a semiconductor laser may be used.

For example, a single-wavelength laser in the infrared or visible range emitted from a DFB semiconductor laser or fiber laser is amplified by a fiber-amplifier doped with, for example, erbium (or both erbium and yttrium), and a nonlinear optical crystal is used. A harmonic converted to ultraviolet light by using the above method may be used as exposure light. Assuming that the oscillation wavelength of a single-wavelength laser is in the range of 1.544 to 1.553 xm, the 8th harmonic in the range of 93 to 194 nm, that is, an ArF excimer laser substantially the same wavelength and name Ru ultraviolet light is obtained, when the oscillation wavelength 1. 57 to 1. within the range of 58 xm, 1 5 7~ 10 harmonic in the range of 1 58 nm, i.e. F ₂ laser and Ultraviolet light having almost the same wavelength can be obtained. In addition, a soft X-ray region having a wavelength of about 5 to 50 nm generated from a laser plasma light source or SOR, for example, EUV (Extreme Ultra Violet) having a wavelength of 13.4 nm or 11.5 nm Light may be used as exposure light. EUV exposure apparatuses use a reflective reticle, and the projection optical system is a reduction system composed of only a plurality of (for example, about 3 to 6) reflective optical elements (mirrors). It has become.

 The projection optical system PL may be not only a reduction system but also an equal magnification system or an enlargement system. Further, the projection optical system PL may be any one of a refraction system, a reflection system, and a catadioptric system. When the wavelength of the exposure light is about 200 nm or less, the light path through which the exposure light passes may be purged with a gas that absorbs the exposure light little (an inert gas such as nitrogen or helium). desirable. When an electron beam is used, an electron optical system including an electron lens and a deflector may be used as the optical system. It goes without saying that the optical path through which the electron beam passes is in a vacuum state.

 When a linear motor (see USP5, 623, 853 or USP5, 528, 118) is used for the wafer stage and reticle stage, either an air levitation type using an air bearing or a magnetic levitation type using Lorentz force or reactance force is used. May be used. In addition, each stage may be of a type that moves along a guide or a guideless type that has no guide.

 As a driving mechanism of each stage, a planar unit that drives each stage by electromagnetic force with a magnet unit having a two-dimensionally arranged magnet and an armature unit having a two-dimensionally arranged coil may be used. . In this case, one of the magnet unit and the armature unit may be connected to the stage, and the other of the magnet unit and the armature unit may be provided on the moving surface side of the stage.

 The reaction force generated by the movement of the wafer stage is not transmitted to the projection optical system PL as described in Japanese Patent Application Laid-Open No. 8-166645 (US Pat. No. 5,528,118). It may be mechanically released to the floor (ground) using a room member.

The reaction force generated by the movement of the reticle stage 2 is not transmitted to the projection optical system PL as described in JP-A-8-330224 (US Pat. No. 5,874,820). It may be mechanically released to the floor (ground) using a frame member. As described above, the exposure apparatus according to the embodiment of the present invention performs various subsystems including each component listed in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. It is manufactured by assembling. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electrical The system will be adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus from the various subsystems includes mechanical connections, wiring connections of electric circuits, and piping connections of pneumatic circuits among the various subsystems. It goes without saying that there is an assembly process for each subsystem before the assembly process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, comprehensive adjustments are made to ensure various precisions of the entire exposure apparatus. It is desirable to manufacture the exposure equipment in a clean room where the temperature and cleanliness are controlled.

 As shown in Fig. 14, microdevices such as semiconductor devices have a step 201 for designing the function and performance of the microdevice, a step 202 for fabricating a mask (reticle) based on this design step, Step 2 of manufacturing a wafer from a silicon material Step 2 of exposing a reticle pattern to the reticle pattern by the exposure apparatus of the above-described embodiment 4 Step 4 of device assembling step (Dicing step, bonding step, package step It is manufactured through 205, inspection step 206, etc. Industrial applicability

 As described above, in the present invention, when measuring the position information of the substrate, it is possible to eliminate and correct the error component caused by the reflectance distribution, and to easily determine the surface position of the substrate by the projection optical system. Positioning on the image plane becomes possible. Therefore, according to the present invention, even when a projection optical system having a shallow depth of focus is used, high-resolution exposure processing can be realized by accurate focusing adjustment.

Claims

 The scope of the claims

1-A position measurement method for irradiating a measurement point on a substrate with detection light, receiving reflected light reflected at the measurement point, and measuring position information in a normal direction of the substrate surface, Measuring an error component of the position information caused by a reflectance distribution of the detection light at the measurement location on the substrate;

 Correcting the position information in the normal direction based on the measured error component.

2. In the position measuring method according to claim 1,

 A position measurement method, further comprising: calculating the error component based on an intensity of a detection signal obtained when the detection light is received.

3. In the position measuring method according to claim 2,

 A position measurement method for calculating the error component based on an intensity distribution of the detection signal at a plurality of points on the substrate surface along a measurement direction of the detection light.

4. The position measuring method according to claim 3, wherein the detection lights overlap with each other at the plurality of points.

5. The position measuring method according to claim 1,

 Measuring the surface shape of the substrate,

 Obtaining the error component based on a result of comparing the measured surface shape with a designed surface shape.

6. The position measuring method according to claim 1, wherein a step of flattening a surface of the substrate,

Measuring the position information of the substrate surface using the detection light, Setting the measured position information as the error component.

7. The position measuring method according to claim 6,

 Calculating a posture of the substrate based on the measured position information; and correcting the posture based on a result of comparing the calculated posture with a predetermined threshold value. .

8. The position measuring method according to any one of claims 1 to 7,

 A position measurement method that irradiates a plurality of the detection lights to a plurality of measurement locations on the substrate, and measures the error component at each of the plurality of measurement locations.

9. In an exposure method of exposing a pattern of a mask to a substrate by exposure light,

 An exposure method that measures the position information by the position measurement method according to any one of claims 1 to 8, and adjusts a surface position of the substrate based on the measurement result.

10. The exposure method according to claim 9,

 Storing the error component before the exposure,

 An exposure method comprising: exposing the substrate while synchronously moving the mask and the substrate; and driving the substrate based on the position information detected during the synchronous movement and the stored error component. .

11. The exposure method according to claim 10,

 An exposure method for setting the measurement position of the error component based on a detection position on the substrate at which the position information is detected during the synchronous movement. .

1 2. The exposure method according to claim 11,

An exposure method for measuring the error component using detection light for measuring the position information during the synchronous movement among a plurality of detection lights for measuring the position information.

13. The exposure method according to any one of claims 10 to 12, wherein the error component is stored for each of the plurality of synchronous movement directions.

14. A position measuring device for irradiating a measuring point on a substrate with detection light, receiving reflected light reflected at the measuring point, and measuring position information in a normal direction of the substrate surface, A storage device for storing an error component of the position information generated by the reflectance distribution of the detection light at the measurement location on the substrate;

 A correction device for correcting the position information in the normal direction based on the stored error component.

15. An exposure apparatus for exposing a pattern of a mask onto a substrate with exposure light, wherein the apparatus for measuring surface position information of the substrate uses the position measurement apparatus according to claim 14.

16. The exposure apparatus according to claim 15, wherein

 An exposure apparatus comprising: a control device that drives the substrate based on the corrected position information and that synchronously moves the mask and the substrate to expose the pattern on the substrate.

17. An exposure apparatus that projects a pattern of the mask onto a plurality of partitioned areas on the substrate by synchronously moving the mask and the substrate.

 A surface position detection device that irradiates the substrate with detection light and detects the reflected light to detect the surface position of the substrate during the synchronous movement;

 A storage device for storing distribution information of the surface state in the partitioned area on the substrate according to the synchronous movement direction;

An exposure apparatus comprising: a control device that sets a surface position of the substrate based on a detection result of the surface position detection device and distribution information stored in the storage device.

18. The exposure apparatus according to claim 17,

 The exposure apparatus, wherein the surface state in the partitioned area is any one of a reflectance of the detection light in the partitioned area and a step existing in the partitioned area.

19. The exposure apparatus according to claim 17 or 18, wherein

 The exposure apparatus, wherein the storage device stores the distribution information of the surface state in each of a plurality of types of partitioned areas existing in a plurality of substrates having the same process program.

20. An exposure method for transferring a mask pattern onto a substrate via a projection optical system by synchronously moving the mask and the substrate,

 A step for measuring an error component generated due to the reflectance distribution of the substrate when measuring the position information in the normal direction of the substrate by receiving the reflected light of the detection light irradiated on the substrate. When,

 Adjusting the positional relationship between the image plane of the projection optical system and the substrate using the measured error component during the synchronous movement.

2 1. An exposure apparatus that moves a mask and a substrate synchronously and transfers a pattern of the mask onto the substrate via a projection optical system.

 A position detection system that receives reflected light of the detection light applied to the substrate and measures position information in the normal direction of the substrate,

 An adjustment device that adjusts a positional relationship between an image plane of the projection optical system and the substrate by using an error component caused by a reflectance distribution of the substrate when the position information is measured by the position detection system. Exposure equipment provided.