JP2006053056A - Position measuring method, position measuring instrument, aligner, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position measuring method capable of enhancing measuring precision. <P>SOLUTION: This position measuring instrument detects a mark comprising periodical patterns formed on an object via an imaging optical system, and measures positional information of the mark, based on a detection result therein. Diffraction lights of even order other than diffraction lights of zero order is removed in mark lights obtained from an irradiated area including the mark, a frequency component corresponding to the each diffraction light of odd degree included in the mark lights is extracted from an image signal of the mark lights, and the positional information of the mark is measured using the extracted frequency component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a position measuring method and a position measuring apparatus for measuring position information of a mark formed on an object, and more particularly to a technique used in an exposure apparatus used in a device manufacturing process such as a semiconductor element or a liquid crystal display element. .

  In the manufacture of semiconductor elements, liquid crystal display elements, and other devices, an image of a fine pattern formed on a mask or reticle (hereinafter collectively referred to as a mask) using an exposure apparatus is exposed to a photosensitive material such as a photoresist. Projection exposure is repeatedly performed on a substrate such as a semiconductor wafer or a glass plate to which an agent is applied. The exposure apparatus measures the positional information of the marks formed on the mask and the substrate, calculates the relative positional deviation amount between the mask and the substrate from these measurement results, and corrects the positional deviation amount to be projected. The alignment (alignment) between the pattern image to be formed and the pattern already formed on the substrate is performed accurately. In recent years, there has been an increasing demand for pattern miniaturization, and improvement in overlay accuracy has become increasingly severe. In order to improve the overlay accuracy, it is first necessary to increase the measurement accuracy of the marks formed on the mask and the substrate.

  An alignment sensor that measures position information of a mark formed on a mask generally measures position information by irradiating the mark with exposure light used when exposing a substrate. As this alignment sensor, for example, there is one using a VRA (Visual Reticle Alignment) system. In the VRA method, an optical image obtained by irradiating exposure light onto a mark formed on a mask is converted into an image signal by an imaging element such as a CCD (Charge Coupled Device) before the substrate is transported on the stage. The image signal is subjected to image processing to detect mark position information.

  In addition, the alignment sensor that measures the position information of the mark formed on the substrate changes the surface state (roughness) of the substrate to be measured in the device manufacturing process. Since it is often difficult to accurately detect information, a plurality of different types of alignment sensors are generally provided. Among these, there are LSA (Laser Step Alignment) method, FIA (Field Image Alignment) method, and LIA (Laser Interferometric Alignment) method.

  An outline of these types of alignment sensors is as follows. In other words, the LSA alignment sensor irradiates a mark formed on a substrate with laser light and measures the position information of the mark using diffracted / scattered light. Is widely used in manufacturing. The FIA alignment sensor illuminates a mark using a light source having a wide wavelength bandwidth such as a halogen lamp, converts the image of the resulting mark into an image signal by an image sensor, and then performs image processing to measure the position. It is effective for measuring asymmetric marks formed on the aluminum layer or the substrate surface. The LIA type alignment sensor irradiates a diffraction grating-shaped mark formed on the substrate surface with laser beams having slightly different wavelengths from two directions, and causes the resulting two diffracted beams to interfere with each other. Is used to detect the position information of the mark.

The above-described alignment sensors are classified into a TTL (through-the-lens) method and an off-axis method depending on whether or not the mark position information is measured via the projection optical system. For details of each type of alignment sensor described above, see, for example, Patent Document 1 and Patent Document 2 below.
Japanese Patent Laid-Open No. 10-289871 JP-A-5-217835

  Among the various alignment sensors described above, in the FIA type alignment sensor that measures the position information of the mark from the image signal of the mark, the image of the mark is easily distorted due to the asymmetry (aberration) of the optical system provided in the alignment sensor. On the other hand, in the LIA method, the phase of the diffracted light of a predetermined order can be extracted from the optical image of the mark, so that correction can be made by measuring in advance the influence of asymmetry (aberration) of the optical system. In the FIA method, since the electric field of each order is detected as the intensity, it has been difficult to extract the phase for each order. However, in the LIA method, when a mark is formed on a transparent object, scattered light (scattered light from other than the focal point) is easily detected from the lower layer structure of the mark to be measured. There is a problem that the measurement accuracy tends to decrease.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a position measurement method and a position measurement apparatus capable of improving measurement accuracy.
Another object of the present invention is to provide an exposure apparatus capable of improving the exposure accuracy.
Another object of the present invention is to provide a device manufacturing method capable of manufacturing a highly accurate device.

In order to achieve the above object, the present invention adopts the following configuration corresponding to FIGS. 1 to 11 showing the embodiment.
In the position measurement method of the present invention, a mark (AM) formed of a periodic pattern formed on an object (W) is detected via an imaging optical system (46, 45, 49), and the above-described position measurement method is used. In the position measurement method for measuring the position information of the mark, the mark light obtained from the irradiated region including the mark has the even-order diffracted light other than the 0th-order diffracted light removed, and from the image signal of the mark light, A frequency component corresponding to odd-order diffracted light included in the mark light is extracted, and position information of the mark is measured using the extracted frequency component.

  In this position measurement method, the position information of the mark is measured from the image signal of the mark. However, even-order diffracted light other than the 0th-order diffracted light included in the mark light is removed in advance, thereby corresponding to the diffracted light included in the mark light. The frequency component can be extracted.

In the position measuring method, optical characteristic information that the imaging optical system acts on the odd-order diffracted light is stored in advance, and the mark is obtained using the extracted frequency component and the optical characteristic information. It is good to measure the position information.
Thereby, the influence of asymmetry (aberration) of the imaging optical system can be removed, and the mark position information can be measured more accurately.

  The position measuring device of the present invention is a position measuring device (16) for measuring position information of a mark (AM) formed of a periodic pattern formed on an object (W), and for an irradiated region including the mark. The irradiation system (41, 42, 43, 44, 45, 46) for irradiating the detection light and the mark light obtained from the irradiated region by the irradiation of the detection light, and outputting an image signal corresponding to the mark light An imaging optical system (46, 45, 49) guided to the photoelectric conversion means (50), and an extraction unit (extracting a frequency component corresponding to odd-order diffracted light contained in the mark light from the image signal of the mark light) 83a to 83n) and a calculation unit (88) for obtaining position information of the mark using the extracted frequency component.

  In this position measuring apparatus, the position measuring method of the present invention can be implemented by the above configuration.

  In the above position measuring apparatus, for example, the mark (AM) has a 1: 1 ratio of the length of the pattern line width and the pattern interval in the periodic direction (duty ratio (Duty)), so that the mark light is converted into mark light. Even-numbered diffracted light other than the 0th-order diffracted light included can be removed.

  The irradiation system (41, 42, 43, 44, 45, 46) includes a stop for irradiating the detection light substantially perpendicularly to the irradiated region, and the imaging optical system (46, 45 and 49) can also remove even-order diffracted light other than the 0th-order diffracted light included in the mark light by including a blocking member that blocks even-order diffracted light other than the 0th-order diffracted light on the pupil plane.

  In the above position measurement apparatus, the extraction units (83a to 83n) may perform the extraction using a Fourier transform or a bandpass filter.

  The imaging optical system (46, 45, 49) further includes a storage unit (84) for storing optical characteristic information acting on the odd-order diffracted light, and the calculation unit (88) The position information of the mark may be obtained using the frequency component and the optical characteristic information. As a result, it becomes possible to eliminate the influence of asymmetry (aberration) of the imaging optical system, and the position information of the mark can be measured more accurately.

  An exposure apparatus according to the present invention is an exposure apparatus that transfers a predetermined pattern onto a substrate (W), and measures a mark (AM) formed on the substrate using the position measurement device (16). A positioning unit (9, 13) for positioning the substrate based on the measurement result, an exposure unit (PL) for transferring the predetermined pattern onto the positioned substrate, the positioning unit, and the exposure unit. And a control unit (15) for controlling.

  The device manufacturing method of the present invention includes an exposure step (S26) for transferring a device pattern onto the substrate using the exposure apparatus described above, and a development step (S27) for developing the substrate on which the device pattern is transferred. , Including.

According to the position measuring method and the position measuring apparatus of the present invention, the frequency component corresponding to the odd-order diffracted light included in the mark light is extracted, and the position information of the mark is measured using the extracted component, thereby measuring accuracy. Can be improved.
Further, according to the exposure apparatus of the present invention, since the measurement accuracy of the position information is improved, the substrate can be positioned with high accuracy and the exposure accuracy can be improved.
Further, according to the device manufacturing method of the present invention, since the exposure accuracy is improved, a highly accurate device can be manufactured.

Next, the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining a position measurement method of the present invention.
In FIG. 1, a mark formed on an object (substrate) has a diffraction grating-like periodic pattern. When the mark is irradiated with single-wavelength detection light, the mark light obtained from the irradiated region including the mark includes nth-order diffracted light (n = 0, ± 1, ± 2,...). If the phase of the diffracted light of a predetermined order can be extracted from the mark light, position information relating to the position of the mark can be obtained from the phase information. When an optical image of a mark is detected as an image signal via an image pickup device (photoelectric conversion means) such as a CCD camera, the electric field of each order is observed as an intensity, so that it is difficult to separate and extract independently.

  The position measurement method of the present invention separates and extracts frequency components corresponding to the respective orders from the image signal of the optical image of the mark by previously removing even-order diffracted light other than the 0th-order diffracted light from the mark light.

Here, when the electric field of the nth-order diffracted light is written as in the following formula (1) (the real part An and the imaginary part e− ^iφn of the complex amplitude of the light), an image of a normal bright field optical system is formed. The electric field is expressed by equation (2).

  What is observed is the intensity, and the intensity is expressed by Equation (3).

  Here, Expression (4) is derived from Expression (1).

  Since the intensity of the optical image is the square of the electric field, when the electric field is developed in the diffraction order, the image includes a combination product term selected from all terms. The (l + m) component of the intensity cannot be separated because all combinations (interference light) of the diffracted light whose sum is this value are mixed. However, when the even-order diffracted light other than the 0th-order is removed, the intensity of the interference light of the odd-order diffracted light becomes all even-order components (odd + odd = even).

Odd l-order components of the ^intensity, and _E * ^{0 E} _{* ^l,} is only _{E *} -l _{E 0,} odd -l-order components of the ^intensity, and _E * ⁰ _{E * ^-l,} only _E * l _{E 0} It is. These are represented by Formula (5)-Formula (8).

  Here, when the mark is symmetrical, the amplitudes of the odd ± l order components are almost the same, and the formula (9) is derived.

  Therefore, the sum of Expression (5) to Expression (8) is expressed by Expression (10).

Usually, φ _l + φ _−l << 1 and the wave number lk component of intensity is only this, so this frequency component is determined by the phase difference φ ₁ −φ ₋₁ . That is, the sum phase shown in Expression (10) corresponds to the phase difference of the odd ± l order light. Therefore, for example, the phase difference of the odd ± l order light can be detected by separating and extracting the odd order component from the intensity signal using Fourier transform or a plurality of band pass filters.

Here, as a method of removing even-order diffracted light other than the 0th-order light from the mark light, for example, a mark design method, specifically, the duty ratio of the mark to be measured is set to 1: 1. A method is mentioned. That is, as shown in FIG. 2, the ratio of the length of the pattern line width W _L and the pattern interval W _C about periodic direction is 1: using a mark consisting of a periodic pattern. As for the light from such a mark, the odd-order diffracted light becomes dominant, and even-order diffracted light other than the 0th-order light hardly occurs.

  In this case, the position of each component can be measured by a method such as an inverted autocorrelation method after removing other components from the image signal of the optical image by a band pass filter that transmits only a desired pitch. . The inverted autocorrelation method (folded autocorrelation method) is a method of obtaining mark position information by folding a signal obtained from a measurement system symmetrically at a predetermined point and obtaining a degree of matching between both signals. It is described in JP-A-56-2284.

  Further, even-order diffracted light other than the 0th-order light may be removed by providing a self-blocking member in the optical system. That is, as shown in FIG. 3, an irradiation system (illumination system) having a small σ including a diaphragm for irradiating detection light substantially perpendicularly to the irradiated region including the mark is used, and the imaging optical system A blocking member that blocks even-order diffracted light other than 0th-order diffracted light is provided on the pupil surface. The mark light transmitted through the blocking member is obtained by removing even-order diffracted light other than zero-order diffracted light. In FIG. 3, for simplification of explanation, the irradiation system and the imaging optical system are arranged symmetrically with respect to the mark. However, when detecting reflected light from the mark, they are arranged on the same side. .

  In this case, the phase of a desired pitch component can be measured by Fourier transforming the image signal of the optical image. The amplitude of each component may be measured, and this component may be used to determine which component is used.

  Note that the method of removing even-order diffracted light other than the 0th-order light is not limited to the above. Moreover, you may combine the method by the mark design mentioned above, and the method of providing a self-shielding member in an optical system.

  Thus, in the position measurement method of the present invention, by removing even-order diffracted light other than 0th-order diffracted light from the mark light in advance, a component (frequency component) corresponding to odd-order diffracted light included in the mark light is extracted, It is possible to measure mark position information using the extracted frequency components.

  In this method, since multi-beam interference is used, when the mark is formed on the transparent object, the scattered light from other than the focal point is blurred, so that the measurement accuracy degradation due to the scattered light is small.

  Further, in this method, the phase of the diffracted light of a predetermined order is extracted from the optical image of the mark. Therefore, by measuring the offset (positional deviation) for each order using an ideal mark, the mark light is converted into the mark light. It is possible to eliminate the influence of asymmetry of the optical system (imaging optical system) acting on the optical system. That is, the aberration of the optical system can be managed and corrected by the phase difference for each order.

FIG. 4 is a diagram illustrating an example of a position measurement method for removing the influence of asymmetry (aberration) of the optical system.
First, an optical image of an ideal reference mark is detected, and the phase difference of each component corresponding to odd-order diffracted light included in the optical image of the mark is measured. The reference mark is, for example, a point image below the optical resolution limit (when correcting aberrations in two dimensions) or a line image below the optical resolution limit (when correcting aberrations in one dimension). It can be formed by performing a process such as etching. If the optical system is perfectly symmetric, the phase of all pitch components should be aligned, so a phase shift indicates asymmetry of the optical system. As described above, the phase of the odd-order component of the image corresponds to the phase difference of each order diffracted light. Assuming that the reference mark is the target, this phase difference corresponds to an optical system asymmetry (aberration) as optical characteristic information of the optical system that acts on each diffracted light. The phase difference between these components is measured and stored in advance.

  Next, the actual measurement target mark is detected, and the mark position information is obtained from the detection result. At this time, only the odd-order component of the image is used, and the phase shift in the case of using the reference mark is subtracted from the measurement result of each order component (offset processing). Thereby, the influence of the asymmetry of the optical system can be removed from the position information obtained from the mark.

Next, an example in which the above-described position measurement method of the present invention is applied to alignment (alignment) of a substrate (wafer) in an exposure apparatus will be described.
FIG. 5 is a view showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention provided with a position measuring apparatus according to an embodiment of the present invention. In the following description, the XYZ orthogonal coordinate system shown in FIG. 5 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Z axis are parallel to the paper surface, and the Y axis is perpendicular to the paper surface. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward. In the present embodiment, a step-and-repeat reduction projection exposure apparatus will be described as an example.

In FIG. 5, reference numeral 1 denotes a condenser lens that forms part of the illumination optical system. The illumination optical system is provided with a light source (not shown) such as an ultra-high pressure mercury lamp or an excimer laser, and the exposure light EL emitted from this light source is formed on a reticle R as a mask through a condenser lens 1. The pattern area PA is irradiated with a uniform illuminance distribution. As the exposure light EL, for example, light emitted from g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm), or F ₂ excimer laser (157 nm) is used. .

  The reticle R can be finely moved by the motor 2 in the direction of the optical axis AX of the projection optical system PL, and is attracted and held on a reticle stage 3 that can be two-dimensionally moved and rotated in a plane perpendicular to the optical axis AX. Yes. The reticle R is used after being appropriately replaced by a reticle exchanger (not shown). A movable mirror 5 that reflects the laser beam from the laser interferometer 4 is fixed to the end of the reticle stage 3, and the two-dimensional position of the reticle stage 3 is determined by the laser interferometer 4 with a resolution of, for example, about 1 nm. Always detected. Reticle alignment sensors 6A and 6B are disposed above the reticle R.

  The reticle alignment sensors 6A and 6B are a reference member 10 or a wafer stage 9 formed on a wafer stage 9 to be described later via a position detection reticle mark RM formed near the outer periphery of the reticle R and the projection optical system PL. The mark formed on the wafer W placed thereon is observed at the same time, and the relative positional relationship between the reticle R and the wafer stage 9 or the X direction or Y direction between the reticle R and the wafer W (predetermined measurement direction) ) To directly measure (observe) the relative positional relationship.

  The measurement results of the reticle alignment sensors 6A and 6B are output to a main control system 15 to be described later, and subjected to processing such as image processing, arithmetic processing, filtering processing, and the like, so that the relative relationship between the reticle R and the wafer stage 9 or the wafer W is obtained. A displacement amount is obtained. Then, the main control system 15 drives the motor 2 to finely move the reticle stage 3 in accordance with the positional deviation amount, so that the center point of the pattern area PA formed on the reticle R coincides with the optical axis AX. Positioned. The reticle alignment sensors 6A and 6B are TTR (through the reticle) type alignment sensors which are a kind of TTL (through the lens) type alignment sensor. This is a VRA type alignment sensor that measures position information.

  The exposure light EL transmitted through the pattern area PA of the reticle R is incident on, for example, both side (or one side) telecentric projection optical system PL and projected onto each shot area on the wafer W as a substrate. Here, the projection optical system PL is best corrected for aberration with respect to the wavelength of the exposure light EL, and the reticle R and the wafer W are optically conjugate with each other under the wavelength. The illumination light (exposure light EL) is Keller illumination and is formed as a light source image at the center of the pupil (not shown) of the projection optical system PL. The projection optical system PL has an optical element such as a plurality of lenses, and the glass material of the optical element is selected from optical materials such as quartz and fluorite according to the wavelength of the exposure light EL, and the projection magnification is For example, it is set to 1/4 or 1/5. For this reason, when the illumination area on the reticle R is illuminated by the exposure light EL, the pattern image formed on the pattern surface of the reticle R is reduced and projected onto the wafer W by the projection optical system PL, and the photoresist is applied to the surface. A reduced image of the circuit pattern of the reticle R is transferred to one shot area on the wafer W coated with a photosensitizer such as.

  The wafer W is sucked and held on the wafer stage 9 via the wafer holder 8. On the wafer holder 8, a reference member 10 used for position measurement of the reticle R, baseline measurement, and the like is provided. Here, the base line refers to the distance between the center position of the projection image of the pattern formed in the pattern area PA of the reticle R by the projection optical system PL and the center of the measurement visual field of the wafer alignment sensor 16 described later, for example. As a reference mark, the reference member 10 has, for example, a slit pattern formed of five light-transmitting L-shaped patterns, and two reference patterns formed of light-reflective chromium (duty ratio (Duty) is 1: 1).

  One set of reference patterns includes, for example, a diffraction grating mark in which seven dot marks arranged in the Y direction are arranged in three rows in the X axis direction, and three linear patterns in the X axis direction. A diffraction grating mark and twelve bar marks extending in the Y direction are arranged in the X-axis direction. The other set of reference patterns is obtained, for example, by rotating the reference pattern of one set by 90 °.

  The wafer stage 9 is an XY stage that two-dimensionally positions the wafer W in a plane perpendicular to the optical axis AX of the projection optical system PL, and the wafer W in a direction (Z direction) parallel to the optical axis AX of the projection optical system PL. Z stage for positioning the wafer W, a stage for minutely rotating the wafer W, a stage for adjusting the inclination of the wafer W with respect to the XY plane by changing the angle with respect to the Z axis, and the like. An L-shaped movable mirror 11 is attached to one end of the upper surface of the wafer stage 9, and a laser interferometer 12 is disposed at a position facing the mirror surface of the movable mirror 11.

  Although simplified in FIG. 5, the movable mirror 11 is composed of a plane mirror having a reflecting surface perpendicular to the X axis and a plane mirror having a reflecting surface perpendicular to the Y axis. The laser interferometer 12 includes two X-axis laser interferometers that irradiate the moving mirror 11 with a laser beam along the X axis and a Y-axis that irradiates the movable mirror 11 with a laser beam along the Y axis. The X coordinate and Y coordinate of the wafer stage 9 are measured by one laser interferometer for the X axis and one laser interferometer for the Y axis. Further, the rotation angle of the wafer stage 9 in the XY plane is measured by the difference between the measurement values of the two X-axis laser interferometers.

  The two-dimensional coordinates of the wafer stage 9 are always detected by the laser interferometer 12 with a resolution of about 1 nm, for example, and the stage coordinate system (stationary coordinate system) of the wafer stage 9 is determined by the coordinates in the X-axis direction and the Y-axis direction. (X, Y) is defined. That is, the coordinate value of the wafer stage 9 measured by the laser interferometer 12 is a coordinate value on the stage coordinate system (X, Y). A position measurement signal PDS indicating the X coordinate, the Y coordinate, and the rotation angle measured by the laser interferometer 12 is output to the main control system 15.

  The main control system 15 outputs a control signal for controlling the position of the wafer stage 9 to the motor 13 while monitoring the supplied position measurement signal PDS. By such a closed loop control system, for example, the wafer stage 9 is stepped to the next shot position when the transfer exposure of the pattern of the reticle R on one shot area on the wafer W is completed. The main control system 15 controls whether or not the exposure light EL is emitted from a light source provided in an illumination optical system (not shown), the intensity of the exposure light EL when the exposure light EL is emitted, and the like. A detailed description of the configuration of the main control system 15 will be given later.

  The exposure apparatus of this embodiment includes an off-axis wafer alignment sensor 16 on the side of the projection optical system PL. The wafer alignment sensor 16 forms a part of the position measuring apparatus of the present invention, and measures the position information in the X direction and Y direction (predetermined measurement direction) of the mark formed on the wafer W. Used. By correcting the measurement result of the wafer alignment sensor 16 with the above-described baseline measurement result, the mark position information in the stage coordinate system (X, Y) can be obtained. The details of the wafer alignment sensor 16 will be described later.

  Further, an oblique incidence type multi-point main focus sensor 17 for measuring the position of the wafer W in the Z-axis direction and the amount of inclination with respect to the XY plane is installed on the side surface of the projection optical system PL. The main focus sensor 17 includes an irradiation optical system 18 that projects a slit image on a plurality of preset measurement points in an exposure region on which an image of the reticle R is projected on the wafer W, and reflected light from these slit images. And a focusing optical system 19 that re-images the slit images and generates a plurality of focus signals corresponding to the lateral shift amounts of the re-imaged slit images. It is supplied to the main control system 15. The main control system 15 moves the wafer stage 9 via the motor 13 so that the surface of the wafer W is always positioned on the best imaging plane of the projection optical system PL based on the focus signal output from the condensing optical system 19. Control. The wafer stage 9 and the motor 13 correspond to the positioning unit referred to in the present invention, the illumination optical system and the projection optical system PL correspond to the exposure unit referred to in the present invention, and the main control system 15 corresponds to the control unit referred to in the present invention. It corresponds to.

  The overall configuration of the exposure apparatus of the present invention has been outlined above. Next, details of the wafer alignment sensor 16 constituting the position measurement apparatus of the present invention will be described.

  FIG. 6 is a configuration diagram showing a configuration example of the wafer alignment sensor 16. Note that the wafer alignment sensor 16 shown in FIG. 6 is an FIA (Field Image Alignment) type alignment sensor. The wafer alignment sensor 16 includes a light source 41 that emits a light beam having a predetermined broadband wavelength as a detection beam DL. The light source 41 is commonly used for observing and focusing (focusing) the mark AM formed on the wafer W. The detection beam DL corresponds to the detection light referred to in the present invention.

  On the optical path of the light source 41, a condenser lens 42, a field stop 43, an illumination relay lens 44, and a beam splitter 45 are sequentially arranged. As shown in FIG. 6, the field stop 43 has a main opening K1 and sub-openings K2 and K3. The main opening K1 is formed in a substantially square shape and is disposed at the center of the field stop 43, and is inserted into the optical path so that the centers thereof substantially coincide with the optical axes of the condenser lens 42 and the illumination relay lens 44. .

  The sub-openings K2 and K3 are formed in the shape of an elongated rectangular slit, and the positions in the vicinity of the main opening K1 in a state where the sides in the longitudinal direction are inclined at a predetermined angle (for example, 5 °) with respect to the two opposite sides of the main opening K1 Is arranged. A direction perpendicular to the side of the main opening K1 and substantially perpendicular to the longitudinal direction of the sub-openings K2 and K3 (orthogonal when not tilted) is a focus measurement direction to be described later. In the following description, the substantially longitudinal direction of the sub-openings K2 and K3 is referred to as a non-measurement direction. The focus measurement direction can be set in various directions. In this embodiment, the focus measurement direction is set to the reference line direction (X direction or Y direction) of the pattern on the surface of the wafer W. .

  A first objective lens 46 is disposed in the direction in which the detection beam DL from the light source 41 via the illumination relay lens 44 is reflected by the beam splitter 45, that is, on the optical path that travels downward from the beam splitter 45 in FIG. A wafer stage 9 for placing the wafer W is disposed at the tip of the optical path.

  In a state where the surface of the wafer W is positioned so as to coincide with the reference plane F1, the surface of the wafer W is optically conjugate with the field stop 43. A mark AM for position detection is formed on the wafer W. When the mark AM is arranged in the measurement field of view of the wafer alignment sensor 16 as shown in FIG. 6, the mark AM is incident on the detection beam DL. Illuminated. Note that the area where the detection beam DL is incident on the wafer stage 9 corresponds to the irradiated area in the present invention.

  Here, the detection beam DL for illuminating the irradiated region on the wafer W is set to partial incoherent illumination light. For this purpose, the illumination σ of the wafer alignment sensor 16 is set to 0.1, for example. That is, as shown in FIG. 3, a small σ stop is provided on the optical path of the light source 41. This is for selectively blocking diffracted light on the crystal side.

  A second objective lens 48, a beam splitter 49, a light shielding plate 51, and a light path that passes through the reflecting surface of the beam splitter 45 along the optical axis of the first objective lens 46, that is, an upward optical path in the drawing, The first relay lens 52 and the pupil-dividing reflection prism 53 are sequentially arranged. The light shielding plate 51 is disposed on a surface F2 optically conjugate with the reference surface F1, is reflected by the surface of the wafer W, and includes the first objective lens 46, the beam splitter 45, the second objective lens 48, and the beam splitter 49. A part of the light that has passed in order is blocked. Details of the light shielding plate 51 will be described later.

  The pupil splitting reflective prism 53 is a light beam splitting member that splits a light beam incident through the first relay lens 52 into a plurality of light beams (divided into two light beams in this embodiment), and is conjugated with the light source 41. It is arrange | positioned in the near position. Here, the pupil-dividing reflection prism 53 is an optical member in which two surfaces of a prism formed in a mountain shape with an obtuse angle close to 180 degrees are finished as reflection surfaces. In the present embodiment, the intersecting line (ridge line) of the two surfaces intersects with the optical axis of the first relay lens 52, and the optical axis is inclined so as to be bent by approximately 90 degrees.

  The detection beam DL that has entered the pupil-dividing reflective prism 53 via the first relay lens 52 is split and reflected rightward in the drawing. A second relay lens 54, a cylindrical lens (cylindrical lens) 55, which is a cylindrical optical system, and an AF (autofocus) sensor 56 are sequentially arranged on the optical path to the right after the pupil splitting reflective prism 53. Is done. Here, the cylindrical optical system is a lens whose front and rear surfaces are cylindrical surfaces having generatrices parallel to each other. One of the front and rear surfaces may be a flat surface. In this case, specifically, there is a refractive power in the direction perpendicular to the generatrix of the cylindrical surface, but the refractive power in the generatrix direction is zero. In the present embodiment, the cylindrical lens 55 is arranged so that its generatrix line substantially coincides with the focus measurement direction. Moreover, in this specification, it is set as the concept including the lens from which refractive power differs in two orthogonal directions, and a toric lens.

  The AF sensor 56 is disposed on the first imaging surface V1 that is optically conjugate with or near the surface F2, and detects the positional relationship of the image formed on the first imaging surface V1 for focusing. The signal FS2 is output. Further, the reference plane F1 and the optical surface are arranged in the direction in which the light beam passing through the first objective lens 46, the beam splitter 45, and the second objective lens 48 in order is reflected by the beam splitter 49, in FIG. The light receiving surface of the image pickup device 50 such as a CCD image pickup device is disposed on the second image pickup surface V <b> 2 set to “1”. The image sensor 50 converts an image formed on the second imaging surface V2 into an image signal VS2 and outputs the image signal VS2. The focusing signal FS2 from the AF sensor 56 and the image signal VS2 from the image sensor 50 are output to the main control system 15.

  The light source 41, the condenser lens 42, the field stop 43, the illumination relay lens 44, the beam splitter 45, and the first objective lens 46 correspond to the irradiation system according to the present invention, and the first objective lens 46, the beam splitter 45, The second objective lens 48 and the beam splitter 49 correspond to the imaging optical system referred to in the present invention, and the image sensor 50 corresponds to the photoelectric conversion means referred to in the present invention.

  Further, as shown in FIG. 3, the pupil surface of the imaging optical system is provided with a blocking member that cuts (blocks) even-order diffracted light other than the 0th order. By removing even-order diffracted light other than the 0th order from the reflected light beam from the wafer W, it is possible to separate and extract frequency components corresponding to each order from the image signal of the optical image of the mark AM. It is to make it.

  Next, the operation of the wafer alignment sensor 16 having the above configuration will be briefly described. When the detection beam DL is emitted from the light source 41, it is condensed by the condenser lens 42 and uniformly illuminates the field stop 43 having the main aperture K1 and the sub apertures K2 and K3. The light beam that has passed through the main aperture K1 and the sub apertures K2 and K3 of the field stop 43 is collimated by the illumination relay lens 44 and reflected by the beam splitter 45.

  The reflected light beam is collected by the first objective lens 46 and irradiated onto the surface of the wafer W placed on the wafer stage 9 perpendicularly. When the surface of the wafer W is arranged on the reference plane F1, the surface of the wafer W and the field stop 43 are optically conjugate, so the images of the main opening K1 and the sub-openings K2 and K3 are the illumination relay lenses. An image is formed on the surface of the wafer W through the first objective lens 46 and the first objective lens 46.

  Here, the reflected light beam from the image of the main opening K1 imaged on the surface of the wafer W is L1, the light beam from the image of the sub-opening K2 is L2, and the light beam from the image of the sub-opening K3 is L3. These light beams L1 to L3 are collimated by the first objective lens 46, pass through the beam splitter 45, are condensed again by the second objective lens 48, and are transmitted and reflected by the beam splitter 49.

  Of the reflected and branched light beams, the light beam L1 is focused and an image of the mark AM is formed on the light receiving surface of the image sensor 50. The image sensor 50 photoelectrically converts the image of the mark AM formed on the light receiving surface and outputs an image signal VS2. On the other hand, the light beams L1 to L3 transmitted and branched by the beam splitter 49 are provided at the position of the surface F2 conjugate with or near the surface of the wafer W by the imaging action of the first objective lens 46 and the second objective lens 48. The images K1 to K3 are formed again on the light shielding plate 51. That is, on the light shielding plate 51, an intermediate image of the main opening K1 and the sub-openings K2 and K3 formed on the surface of the wafer W by the first objective lens 46 and the second objective lens 48 is formed.

  FIG. 6 shows a configuration example of the light shielding plate 51 viewed from the optical axis direction. The light-shielding plate 51 is provided with two slit-shaped light beam passage portions K12 and K13 at positions symmetrical to the optical axis so as to correspond to the sub-openings K2 and K3. Of the light beams L1 to L3, the light beam L1 is shielded, and only the light beams L2 and L3 can pass through K12 and K13, respectively. Further, another configuration example of the light shielding plate 51 is also shown in FIG. That is, only the range in which the light beam L1 is incident on the light shielding plate 51 (shown by hatching in the drawing) may be shielded, and the entire area K14 may be configured as the light beam passage portion.

  The light beams L2 and L3 that have passed through the light shielding plate 51 are collimated by the first relay lens 52, and then form an image of the light source 41 on the pupil-dividing reflective prism 53. Further, the light beams L2 and L3 are respectively divided into two light beams by the pupil-dividing reflection prism 53, reflected to the right in the drawing, and condensed again by the second relay lens 54. Then, the slit images of the sub-openings K2 and K3 by the light beams L2 and L3 are respectively divided into two images on the AF sensor 56 via the cylindrical lens 55.

  The image forming position of the two-divided light beam on the light receiving surface of the AF sensor 56 changes according to the position of the surface of the wafer W in the Z direction. For this reason, the distance of the imaging position of the two-divided light beam detected when the wafer W is placed on the reference plane F1 is set in the main control system 15 as a reference distance in advance, and the main control system 15 sets the reference distance. Is compared with the distance of the imaging position of the two-part luminous flux detected by the AF sensor 56, whether or not the surface of the wafer W is located at the focal position of the wafer alignment sensor 16 (in-focus). Or not).

  If not in focus, the displacement direction of the wafer W is obtained from the relationship between the reference distance and the calculated distance, and the wafer stage 9 is driven in a direction opposite to the displacement direction. Even when the wafer stage 9 is being driven in the Z direction, the above-described detection and various processes are performed by the AF sensor 56, and when the distance between the imaging positions of the two-part split beam becomes equal to the reference distance, the wafer stage 9 is stopped. The main control system 15 performs image processing, arithmetic processing, filtering processing, and the like on the image signal VS2 output from the imaging device 50 in a state where the wafer W is disposed at the focal position of the wafer alignment sensor 16. Position information of the mark AM arranged in the measurement visual field of the wafer alignment sensor 16 is measured.

  The configuration and operation of the wafer alignment sensor 16 have been described above. Next, the main control system 15 will be described in detail. FIG. 7 is a block diagram showing the internal configuration of the main control system 15. In FIG. 7, the same members as those shown in FIGS. 5 and 6 are denoted by the same reference numerals. As shown in FIG. 7, the main control system 15 includes a focus detection unit 60, an image processing unit 61, a focus detection unit 62, an FIA calculation unit 63, an alignment data storage unit 64, an EGA calculation unit 65, a storage unit 66, and a shot map. The data section 67, the system controller 68, the wafer stage controller 69, and the reticle stage controller 70 are configured.

  The image processing unit 61 performs processing such as image processing, arithmetic processing, filtering processing, and the like on the image signal VS1 output from the reticle alignment sensors 6A and 6B, and the reference mark formed on the reticle mark RM and the reference member 10 The relative position with respect to the mark is obtained, and the processing result is output to the system controller 68. Further, the FIA arithmetic unit 63 performs processing such as image processing, arithmetic processing, and filtering processing on the image signal VS2 output from the wafer alignment sensor 16, and obtains position information of the mark AM formed on the wafer W. Obtained and output to the alignment data storage unit 64. Specific examples of the image processing performed by the image processing unit 61 and the FIA arithmetic unit 63 include processing for obtaining the contour of the mark, processing for detecting the edge position of each mark element forming the mark from the obtained contour, There is a process for obtaining the mark center from the detected edge position.

  The focus detection unit 60 uses the focusing signal FS1 output from the reticle alignment sensors 6A and 6B to detect defocus of the imaging optical system provided in the reticle alignment sensors 6A and 6B. The focus detection unit 62 detects the amount of deviation of the surface of the wafer W from the focal position of the wafer alignment sensor 16 using the focusing signal FS2 output from the wafer alignment sensor 16. The calculation results of the focus detection units 60 and 62 are output to the system controller 68.

  The alignment data storage unit 64 stores the position information of the mark AM output from the FIA arithmetic unit 63. The EGA arithmetic unit 65 is measured by the wafer alignment sensor 16 on the mark AM formed in association with each of several typical (3 to 9) shot areas preset on the wafer W. EGA (enhanced global alignment) calculation is performed based on the position information and the position information on the design, and the regularity of the arrangement of all shot areas set on the wafer W is determined by a statistical method. .

  The storage unit 66 temporarily stores various conversion parameters and residual error components (for example, simple sum of squares of residuals between design values and measured values) obtained while the EGA arithmetic unit 65 performs EGA arithmetic. Remember. The shot map data unit 67 stores in advance shot map data including design position information of the plurality of shot areas set on the wafer W and position information of the marks AM provided along with the shot areas. ing.

  The system controller 68 drives the wafer stage 9 shown in FIG. 5 via the motor 13 while monitoring the measurement value of the laser interferometer 12 via the wafer stage controller 69 based on the calculation result of the EGA arithmetic unit 65. Then, positioning of each shot area on the wafer W and exposure control for each shot area are performed. Further, the system controller 68 monitors the measurement value of the laser interferometer 4 via the reticle stage controller 70 and drives the reticle stage 3 shown in FIG. 5 via the motor 2 to adjust the position of the reticle R. Do.

  Further, when a defocus of the imaging optical system included in the reticle alignment sensors 6A and 6B is detected, the system controller 68 varies the focal position of the imaging optical system according to the detection result. Furthermore, when the surface of the wafer W is not disposed at the focal position of the wafer alignment sensor 16, the wafer stage 9 shown in FIG. 5 is driven via the motor 13 in accordance with the detection result of the focus detection unit 62. Then, the wafer W is moved in the Z direction.

Next, the configuration of the FIA arithmetic unit 63 provided in the main control system 15 will be described.
FIG. 8 is a diagram showing an internal configuration of the FIA arithmetic unit 63. As shown in FIG. 8, the FIA calculation unit 63 includes an image signal amplification unit 81, an A / D conversion unit 82, filter units 83a to 83n, an image signal storage unit 84, a phase correction unit 85, a phase characteristic information storage unit 86, and A position information calculation unit 88 is included.

  The image signal amplifying unit 81 amplifies the image signal VS2 output from the wafer alignment sensor 16 with a predetermined amplification factor. The amplification factor of the image signal amplification unit 81 is appropriately determined in consideration of the overall level of the image signal VS2, the S / N ratio (signal-to-noise ratio), and the like. The amplification factor information indicating the amplification factor is the phase correction unit 85. Is output. The A / D converter 82 samples and quantizes the image signal VS2 that is an analog signal, and converts the image signal VS2 into a digital signal.

  The filter units 83a to 83n extract a predetermined frequency component from the digitized image signal. Here, each of the filter units 83a to 83n is, for example, a band filter (a band-pass filter, each extracting a frequency component corresponding to a diffracted light of a different order. As described above, the wafer alignment sensor 16 uses 0. The even-order diffracted light other than the following is removed, and the filter units 83a to 83n extract frequency components corresponding to the odd-order diffracted light, which is illustrated in FIG. However, the number of filter units can be arbitrarily set, and the image signal storage unit 84 temporarily stores image signals composed of frequency components extracted by the filter units 83a to 83n.

  The phase correction unit 85 reads out the image signal for each frequency component temporarily stored in the image signal storage unit 84, and the image for each frequency component based on the phase characteristic information stored in the phase characteristic information storage unit 86. Correct the phase shift of each signal. At this time, the phase correction unit 85 selectively reads out the phase characteristic information for each frequency component from the phase characteristic information storage unit 86 as phase characteristic information corresponding to the amplification factor information output from the image signal amplification unit 81.

  Here, when the light from the surface of the wafer W passes through the wafer alignment sensor 16, a different phase shift occurs for each frequency component corresponding to each order diffracted light. Information indicating the phase shift for each frequency component is phase characteristic information (optical characteristic information), which is stored in the phase characteristic information storage unit 86.

  The phase characteristic information includes, for example, a point image below the optical resolution limit (when correcting aberrations in two dimensions) or a line image below the optical resolution limit (when correcting aberrations in one dimension) on wafer alignment. The image signal obtained by observation with the sensor 16 is obtained by spectral analysis (Fourier transform). This measurement is performed in advance before observing the mark formed on the wafer W, and the obtained phase characteristic information is stored in the phase characteristic information storage unit 86.

  The position information calculation unit 88 performs processing such as spectrum analysis (Fourier transform) on the image signal output from the phase correction unit 85, obtains the contour of the mark, and each mark element that forms a mark from the obtained contour. The position information of the mark AM is obtained by performing processing such as processing for detecting the edge position, processing for obtaining the mark center from the detected edge position, and the like. The filter units 83a to 83n, the phase characteristic information storage unit 86, and the position information calculation unit 88 correspond to the extraction unit, the storage unit, and the calculation unit according to the present invention, respectively.

  Next, the operation when measuring the position information of the mark AM of the wafer alignment sensor 16 in the above configuration will be described. When the wafer W is loaded into the exposure apparatus and sucked and held on the wafer stage 9, the main control system 15 drives the motor 13 to move the wafer stage 9 in the XY plane, and the mark formed on the wafer W One of the AMs is placed in the measurement field of view of the wafer alignment sensor 16, and the mark AM on which the detection beam DL is placed is irradiated. The light reflected or diffracted on the surface of the wafer W by this irradiation is received by the image sensor 50 and the AF sensor 56 via the first objective lens 46 and the second objective lens 48 shown in FIG.

  The AF sensor 56 detects the distance between the imaging positions of the two-divided light beams and outputs a focusing signal FS2. This focus signal FS2 is compared with a reference distance set in advance in the focus detection unit 62 of the main control system 15. If these are different, the main control system 15 moves the wafer stage 9 in the Z direction via the motor 13. Move. After the wafer stage 9 is moved, the focus detection unit 62 again compares the focusing signal FS2 with the reference distance. If they are different, the wafer stage 9 is similarly moved. When the above operation is repeated and the focusing signal FS2 and the reference distance coincide with each other and the surface of the wafer W is placed at the focal position of the wafer alignment sensor 16, the FIA arithmetic unit 63 displays the wafer alignment sensor. The image signal VS2 output from 16 is captured.

  The image signal VS2 captured by the FIA arithmetic unit 63 is first amplified at a predetermined amplification rate in the image signal amplifier 81 shown in FIG. At this time, the amplification factor set by the image signal amplification unit 81 is output to the phase correction unit 85 as amplification factor information.

  Further, the image signals output from the A / D conversion unit 82 to the filter units 83a to 83n are extracted from the image signals including only frequency components corresponding to the odd-order diffracted lights set in the filter units 83a to 83n. It is temporarily stored in the image signal storage unit 84. Next, the phase correction unit 85 sequentially reads out the image signals extracted from the image signal storage unit 84 and sequentially reads out the optical characteristic information for each component from the phase characteristic information storage unit 86. Each time the image signal and the optical characteristic information for each component are read, the phase correction unit 85 performs an offset process on the read optical characteristic information to correct the phase shift of the read image signal.

  The corrected image signals are sequentially output to the position information calculation unit 88. The position information calculation unit 88 performs processing for obtaining the contour of the mark AM from the input image signal, processing for detecting the edge position of each mark element forming the mark from the obtained contour, and determining the mark center from the detected edge position. The position information of the mark AM is obtained by performing processing such as obtaining processing.

  The position information is calculated by, for example, averaging the calculation results for each frequency component corresponding to the order of the diffracted light. At this time, the amplitude of each component may be measured, and it may be determined which component is used based on this value.

  The position information calculated by the position information calculation unit 88 is output to the alignment data storage unit 64 shown in FIG. 7 and temporarily stored. In this manner, the position information of the mark AM is obtained from the image signal in which the phase shift generated in the imaging optical system is corrected.

Next, an operation for positioning each shot area on the wafer W and projecting and exposing an image of a pattern formed on the reticle R in each shot area will be described.
First, the arrangement of shot areas on the wafer W and the shape of marks as alignment marks will be described. FIG. 9 is a diagram for explaining the arrangement of shot areas on the wafer W and the shape of the marks. In FIG. 9, shot areas ES1, ES2,..., ESN are regularly formed on a wafer W along a coordinate system (X, Y) set on the wafer W. Each device pattern is formed by the above steps.

  Further, each shot area ESi is divided by street lines having a predetermined width in the X direction and the Y direction, and the X-axis direction as the mark AM is formed at the center of the street line extending in the X direction adjacent to each shot area ESi. A mark Mxi is formed, and a mark Myi in the Y direction is formed at the center of the street line extending in the Y direction adjacent to each shot area ESi. The marks Mxi and Myi are three linear patterns arranged at a predetermined pitch in the X direction and Y direction, respectively, and these patterns are formed as concave or convex patterns under the wafer W.

  When performing exposure on the wafer W, nine shot areas indicated by hatching, for example, are selected from the shot areas ESi. The shot areas thus selected are referred to as sample shots SA1 to SA9. Marks Mxi and Myi are formed close to each sample shot SAi. In this example, the position information on the stage coordinate system (X, Y) of each of the sample shots SA1 to SA9 is measured by measuring the positions of the marks Mxi and Myi. At the time of measuring the position information, the above-described processing is performed, and the stage coordinate system (X, X) of the sample shots SA1 to SA9 is obtained from the image signal in which the phase shift generated in the detection optical system OS and the electrical path ES is corrected. Y) is required. Thereby, the position information of the marks Mxi and Myi is measured with extremely high accuracy. The measurement result is stored in the alignment data storage unit 64 of the main control system 15 shown in FIG.

  When the position information of each sample shot SA1 to SA9 on the stage coordinate system (X, Y) is measured, the EGA arithmetic unit is used using the position information and shot map data stored in the shot map data section 67. In 65, an EGA calculation is performed, and the regularity of the arrangement of all shot areas set on the wafer W is determined. The system controller 68 uses the determined shot area arrangement so that the shot area to be exposed is arranged in the projection area of the projection optical system PL (area where the pattern formed on the reticle R is projected). The stage 9 is moved and positioned. When the positioning of the wafer W is completed, the exposure light EL is irradiated onto the reticle R, and the shot area is exposed. Thereafter, similarly, the wafer stage 9 is positioned by step movement using the determined arrangement of shot areas, and the shot areas are sequentially exposed.

  In this embodiment, since the stage coordinate system (X, Y) of each sample shot SA1 to SA9 is obtained from the image signal in which the phase shift generated in the imaging optical system is corrected, measurement is performed with high accuracy. . The above-described EGA calculation is performed using this highly accurate measurement result, and the regularity of the shot region arrangement determined is also highly accurate. As a result, each shot area of the wafer W can be accurately positioned in the projection area of the projection optical system PL at the time of exposure, and the overlay accuracy can be improved.

The position measuring apparatus and the exposure apparatus according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention.
For example, in the other embodiments described above, the image signals extracted by the filter units 83a to 83n are temporarily stored in the image signal storage unit 84, the phase correction unit 85 sequentially corrects the phase shift, and the position information is calculated. The correction position information is obtained by the unit 88. However, in order to shorten the processing time required by the FIA arithmetic unit 63, the phase correction unit 85 and the position information calculation unit 88 may be provided in parallel corresponding to each of the filter units 83a to 83n to perform parallel processing. good.

  Further, the residual aberration differs depending on whether the mark AM is arranged at the center of the measurement visual field of the wafer alignment sensor 16 or when the mark AM is arranged at the end of the measurement visual field, and the phase shift of each frequency component. May also be different. Therefore, the optical characteristic information for each image height (distance from the center of the measurement visual field of the wafer alignment sensor 16) may be stored in the phase characteristic information storage unit 86.

  In the above embodiment, the case where the position information of the mark formed on the wafer W is obtained has been described as an example. However, the present invention is not limited to this, and the mark formed on the reticle R is not limited to this. When obtaining position information, the present invention can be applied to obtaining position information of marks formed on other objects. Furthermore, each block shown in FIG. 7 and FIG. 8 may be configured by hardware by an electronic circuit or may be configured by software. When each block is configured in software, each block is realized by a CPU (Central Processing Unit) executing a program that defines the function of each block. Further, when each block shown in FIG. 7 is configured in hardware or software, all the illustrated blocks may not be configured as a single unit, or may be configured in a distributed manner. For example, the focus detection units 60 and 62 may be provided separately from the main control system 15.

  In the above-described embodiment, the reticle alignment sensors 6A and 6B are VRA type alignment sensors, and the wafer alignment sensor 16 is an FIA type alignment sensor. The sensors 6A and 6B and the wafer alignment sensor 16 may further include an LSA type and LIA type alignment sensor. The present invention can also be applied to a TTL type alignment sensor that observes the reference pattern of the reference member 10 only through the projection optical system PL, not through the reticle R.

  In addition, the exposure apparatus of the present invention is not limited to the step-and-repeat reduction projection exposure apparatus shown in FIG. 5, for example, a step-and-scan exposure apparatus, a mirror projection system, a proximity system, It can be applied to an exposure apparatus such as a contact method.

  Further, not only an exposure apparatus used for manufacturing a semiconductor element and a liquid crystal display element, but also an exposure apparatus used for manufacturing a plasma display, a thin film magnetic head, and an imaging element (CCD, etc.), a reticle, or a mask are manufactured. Therefore, the present invention can also be applied to an exposure apparatus that transfers a circuit pattern to a glass substrate or a silicon wafer. In other words, the present invention can be applied regardless of the exposure method and application of the exposure apparatus.

In addition, the exposure apparatus (FIG. 5) according to the embodiment of the present invention described above can control the position of the wafer W with high accuracy and high speed, and can perform exposure with high exposure accuracy while improving throughput. Illumination optical system, motor 2, reticle stage 3, laser interferometer 4, moving mirror 5, mask alignment system including reticle alignment sensors 6A and 6B, wafer holder 8, wafer stage 9, reference member 10, moving mirror 11, laser interference After the elements shown in FIG. 5 such as the wafer alignment system including the meter 12 and the motor 13 and the projection optical system PL are assembled by being electrically, mechanically or optically connected, the total adjustment (electrical adjustment) , Operation check, etc.).
The exposure apparatus is preferably manufactured in a clean room in which the temperature, cleanliness, etc. are controlled.

  Next, an embodiment of a micro device manufacturing method using an exposure apparatus according to an embodiment of the present invention will be briefly described. FIG. 10 is a flowchart showing a manufacturing example of a micro device (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micro machine, etc.). As shown in FIG. 10, first, in step S10 (design step), a function / performance design (for example, circuit design of a semiconductor device) of a micro device is performed, and a pattern design for realizing the function is performed. Subsequently, in step S11 (mask manufacturing step), a mask (reticle) on which the designed circuit pattern is formed is manufactured. On the other hand, in step S12 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.

  Next, in step S13 (wafer processing step), using the mask and wafer prepared in steps S10 to S12, an actual circuit or the like is formed on the wafer by lithography or the like, as will be described later. Next, in step S14 (device assembly step), device assembly is performed using the wafer processed in step S13. This step S14 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary. Finally, in step S15 (inspection step), inspections such as an operation confirmation test and a durability test of the microdevice manufactured in step S14 are performed. After these steps, the microdevice is completed and shipped.

  FIG. 11 is a diagram showing an example of a detailed flow of step S13 of FIG. 11 in the case of a semiconductor device. In FIG. 11, in step S21 (oxidation step), the surface of the wafer is oxidized. In step S22 (CVD step), an insulating film is formed on the wafer surface. In step S23 (electrode formation step), an electrode is formed on the wafer by vapor deposition. In step S24 (ion implantation step), ions are implanted into the wafer. Each of the above steps S21 to S24 constitutes a pre-processing process at each stage of the wafer processing, and is selected and executed according to a necessary process at each stage.

  At each stage of the wafer process, when the above pre-process is completed, the post-process is executed as follows. In this post-processing process, first, in step S25 (resist formation step), a photosensitive agent is applied to the wafer. Subsequently, in step S26 (exposure step), the circuit pattern of the mask is transferred to the wafer by the lithography system (exposure apparatus) and the exposure method described above. Next, in step S27 (development step), the exposed wafer is developed, and in step S28 (etching step), the exposed members other than the portion where the resist remains are removed by etching. In step S29 (resist removal step), the resist that has become unnecessary after the etching is removed. By repeatedly performing these pre-processing steps and post-processing steps, multiple circuit patterns are formed on the wafer.

  As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

It is a figure for demonstrating the position measuring method of this invention. It is a plane schematic diagram which shows the structural example of the mark of measurement object. It is a figure which shows typically the structural example of the position measuring apparatus for enforcing the position measuring method of this invention. It is a figure which shows an example of the position measurement method which removes the influence of the asymmetry (aberration) of an optical system. It is a figure which shows schematic structure of the exposure apparatus by one Embodiment of this invention provided with the position measuring device by one Embodiment of this invention. It is a block diagram which shows the structural example of a wafer alignment sensor. It is a block diagram which shows the internal structure of a main control system. It is a block diagram which shows the internal structure of a FIA arithmetic unit. It is a figure for demonstrating the arrangement | sequence of the shot area on a wafer, and the shape of a mark. It is a flowchart which shows an example of the manufacturing process of a microdevice. It is a figure which shows an example of the detailed flow of step S13 of FIG. 10 in the case of a semiconductor device.

Explanation of symbols

6A, 6B ... reticle alignment sensor, 9 ... wafer stage (positioning part), 13 ... motor (positioning part), 15 ... main control system (control part), 16 ... wafer alignment sensor (position measuring device), 41 ... Light source (irradiation system), 42 ... condenser lens (irradiation system), 43 ... field stop (irradiation system), 44 ... illumination relay lens (irradiation system), 45 ... beam splitter (irradiation system, imaging optical system), 46 ... First objective lens (irradiation system, imaging optical system), 48 ... second objective lens (imaging optical system), 49 ... beam splitter (imaging optical system), 50 ... imaging device (photoelectric conversion means), 81 ... Image signal amplifiers 83a to 83n Filter unit (extraction unit) 85 Phase correction unit (calculation unit) 86 Phase characteristic information storage unit (storage unit) 88 Position information calculation unit (calculation unit) AM ... Mark, DL Detecting beam (detection light), Mxi, MYi ... marks, PL ... projection optical system (exposure unit), R ... reticle, RM ... reticle mark, VS1, VS2 ... image signal, W ... wafer (object, substrate).

Claims (9)

A position measurement method for detecting a mark formed of a periodic pattern on an object via an imaging optical system and measuring position information of the mark based on the detection result,
The mark light obtained from the irradiated region including the mark has the even-order diffracted light other than the 0th-order diffracted light removed,
A position measurement characterized in that a frequency component corresponding to odd-order diffracted light contained in the mark light is extracted from an image signal of the mark light, and position information of the mark is measured using the extracted frequency component. Method. Optical characteristic information that the imaging optical system acts on the odd-order diffracted light is stored in advance,
The position measurement method according to claim 1, wherein the position information of the mark is measured using the extracted frequency component and the optical characteristic information. A position measuring device that measures position information of a mark formed of a periodic pattern formed on an object,
An irradiation system for irradiating the irradiated region including the mark with detection light;
An imaging optical system that guides the mark light obtained from the irradiated region by irradiation of the detection light to a photoelectric conversion unit that outputs an image signal corresponding to the mark light;
An extraction unit for extracting a frequency component corresponding to odd-order diffracted light contained in the mark light from the image signal of the mark light;
And a calculation unit that obtains the position information of the mark using the extracted frequency component.   4. The position measuring apparatus according to claim 3, wherein the mark has a ratio (duty ratio) of a length between a pattern line width and a pattern interval in the period direction of 1: 1. The irradiation system includes a diaphragm for irradiating the detection light substantially perpendicular to the irradiated region,
The position measuring apparatus according to claim 3, wherein the imaging optical system includes a blocking member that blocks even-order diffracted light other than zero-order diffracted light on the pupil plane.   The position measuring apparatus according to claim 3, wherein the extraction unit performs the extraction using a Fourier transform or a bandpass filter. The image-forming optical system further includes a storage unit that stores optical characteristic information acting on the odd-order diffracted light,
7. The position measurement apparatus according to claim 3, wherein the calculation unit obtains position information of the mark using the extracted frequency component and the optical characteristic information. An exposure apparatus for transferring a predetermined pattern onto a substrate,
A mark formed on the substrate is measured using the position measurement device according to any one of claims 3 to 7, and a positioning unit that positions the substrate based on the measurement result;
An exposure unit that transfers the predetermined pattern onto the positioned substrate;
An exposure apparatus comprising: a positioning unit and a control unit that controls the exposure unit. An exposure process for transferring a device pattern onto the substrate using the exposure apparatus according to claim 8;
And a developing step of developing the substrate on which the device pattern has been transferred.

Images