JP2003338448A - Method and apparatus for measuring position, method and apparatus for exposure, and mark measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-precision focus measurement without depending on the surface condition of an object. <P>SOLUTION: A measurement beam is projected to the surface of an object. A measurement result of the measurement beam reflected on the surface and a prescribed relational expression are used to measure the object position information in a normal direction on the surface. Based on the condition of a measured region on the surface of the object to which the measurement beam is projected, the prescribed relational expression is calibrated, as calibration processes S4-S7. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring method and a position measuring apparatus, an exposure method, an exposing apparatus and a mark measuring method, and a position suitable for use in measuring position information of a substrate or the like in a normal direction. The present invention relates to a measuring method and a position measuring device, an exposure method, an exposing device, and a mark measuring method.

[0002]

2. Description of the Related Art In a process of manufacturing a device such as a semiconductor device or a liquid crystal display device, an image of a pattern formed on a photomask (or reticle) is formed on a substrate (wafer, glass plate, etc.) coated with a photosensitive material. An exposure device that transfers to a predetermined shot area is used. As this type of exposure apparatus, for example, the substrate is placed on a stage that is two-dimensionally movable, and the substrate is stepped by this stage to sequentially expose the pattern image of the reticle to each shot area on the substrate. There is known an exposure apparatus of a so-called step-and-repeat method in which the above operation is repeated. Further, after the processing by this exposure apparatus, a circuit pattern is formed by performing a predetermined post-processing on the substrate,
A wiring circuit of the device is formed by stacking a large number of layers of the circuit pattern. In the exposure apparatus, for example, when transferring a pattern image of the second and subsequent layers onto a substrate, a two-dimensional direction for accurately superimposing a shot area on the substrate on which a circuit pattern has already been formed and a pattern of a reticle to be exposed from now on. The substrate is positioned (alignment).

Alignment is usually performed on the basis of positional information regarding the positions of marks formed on the substrate.
For example, EGA (enhanced global alignment) disclosed in JP-A-61-44429.
In the global alignment represented by the method, the marks in several shot areas in one photosensitive substrate are photoelectrically detected through a predetermined optical system, and the two-dimensional direction of each mark is detected based on the detection result. Measure each position. Then, based on the measurement result, by using a statistical method, the array coordinates of all shot areas in one substrate on a predetermined two-dimensional coordinate axis are calculated, and the substrate positioning is performed based on the calculated array coordinates. I do. Global alignment is an alignment method that utilizes the fact that the positioning accuracy in the two-dimensional direction of the stage and the linearity of the shot area array coordinates are sufficiently ensured, and high throughput is achieved because the number of measurement points is small. There is an advantage that it is easy to plan.

At the time of alignment, usually, in order to accurately measure the position of the mark in the two-dimensional direction,
Focusing (alignment AF) is performed to align the mark to be detected with the focus of the optical system in the alignment position measuring device. Conventionally, this alignment AF
The above-mentioned focusing is performed by arranging a mark to be detected in the visual field of the alignment optical system and then actually photoelectrically detecting the position where the mark is formed.

Conventionally, in this type of focusing device, as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-223517,
Projecting a slit image on the surface of the wafer, dividing the slit image reflected from the slit image into two on the pupil plane, and measuring the distance between the slit images on the image plane with a focus sensor to obtain information on the in-focus position. ing. Specifically, assuming that the distance between slit images (hereinafter, simply referred to as slit interval) is X and the focus (difference with respect to the in-focus position) is Z, the slit interval is converted into focus by the following relational expression. Z = a × (X−X ₀ ) ... (1) In formula (1), X ₀ is the slit spacing at the focus position, and a is a constant for focus conversion.

If the above a and X ₀ are obtained as coefficients in advance, the above focusing can be easily performed by using the measured slit spacing and the equation (1).

[0007]

However, the above-mentioned conventional techniques have the following problems.
The signal from the focus sensor that detects the slit image is affected by the underlying state of the wafer onto which the slit image is projected. For example, as shown in FIG. 13A when the pattern or the like does not exist on the base of the wafer, the signal of each slit image is the target, but when the pattern exists in a part of the slit, FIG. ), The signal of each slit image becomes asymmetric depending on the position.

Conventionally, as shown in FIG. 13A, the coefficients a and X ₀ of the equation (1) are obtained in the state where no pattern exists in the background, but a signal as shown in FIG. 13B is obtained. When used, the coefficients a and X ₀ may fluctuate (to a ′ and X ′ ₀ ). That is, conventionally, as shown in FIG. 14, a single coefficient a, X ₀ is set in advance, and the focus Z can be obtained with high accuracy by measuring the slit interval X. _The optimum value of ₀ varies depending on the underlying condition of the wafer, for example, constants a ′ and X ′ _0. Therefore, even if the focus Z ′ obtained using the constants a and X ₀ is used, the state of the measured region on the wafer is Depending on the situation, it may not be possible to perform focusing accurately.

Therefore, when the same relational expression is used for wafers having different patterns, or when the measurement is carried out at a plurality of positions where the patterns entering the slits are changed even within the same wafer, the focus state varies for each alignment mark. Will be done. In general, the position measurement result at the time of aligning the substrate varies depending on the focus, and thus the variation of the focus causes the accuracy of the entire alignment to deteriorate.

The present invention has been made in consideration of the above points, and a position measuring method and a position measuring device capable of performing highly accurate focus measurement without depending on the surface state of an object, and An object of the present invention is to provide an exposure method, an exposure apparatus, and a mark measuring method.

[0011]

In order to achieve the above object, the present invention employs the following configurations associated with FIGS. 1 to 11 showing an embodiment. The position measuring method of the present invention irradiates the surface of an object (W) with a measurement beam, and uses the measurement result of the measurement beam reflected by the surface and a predetermined relational expression to determine the object (W) in the normal direction of the surface. Is a position measuring method for measuring the position information of the object (W), and a calibration step (S4 to S7) for calibrating a predetermined relational expression based on the state of the measurement area irradiated with the measurement beam on the surface of the object (W). ) Is included.

Further, the position measuring device of the present invention irradiates the surface of the object (W) with the measurement beam, and uses the measurement result of the measurement beam reflected by the surface and a predetermined relational expression to determine the normal direction of the surface. A position measuring device (10) for measuring the position information of the object (W) in, the predetermined relational expression based on the state of the measured region on the surface of the object (W) irradiated with the measurement beam. It is characterized by having a calibration device for calibrating.

Therefore, according to the position measuring method and the position measuring apparatus of the present invention, even when the predetermined relational expression is set depending on the presence or absence of the pattern and the state of the measured region on the object (W) is changed, It is possible to obtain a relational expression according to the state of the measured region when obtaining the position information in the normal direction. Therefore, the position information of the object (W) in the normal direction can be measured with high accuracy by using the measurement result of the measurement beam reflected on the surface of the measurement region and the calibrated relational expression.

The mark measuring method of the present invention is a mark measuring method for picking up an image of a mark (AM) formed on an object (W) through an imaging optical system (10). Using the position information in the normal direction of the object measured by the position measuring method according to any one of 1 to 16, the mark (AM) is matched with the best image forming plane of the image forming optical system (10), Mark existing on best image plane (AM)
Is imaged through the imaging optical system (10), and the mark (A
It is characterized by measuring the position information in the two-dimensional plane of M).

Therefore, according to the mark measuring method of the present invention, even if the state of the measured region changes from when the predetermined relational expression is set, the mark (AM) on the object (W) is best detected by the imaging optical system. It becomes possible to pick up the image of the mark (AM) in a stable state by aligning it with the image forming plane.
The position information in the two-dimensional plane of M) can be measured with high accuracy.

On the other hand, in the exposure method of the present invention, the mask (R) is used.
An exposure method for transferring a pattern formed on a substrate (W) onto a substrate (W), the position information of a mark (AM) on the substrate (W) measured using the mark measuring method according to claim 17. Based on this, the substrate (W) is positioned at a predetermined transfer position in the two-dimensional plane, and the pattern is transferred onto the substrate (W) positioned at the transfer position.

Further, the exposure apparatus of the present invention has a mask (R).
An exposure device (1) for transferring the pattern formed on a substrate (W) positioned at a predetermined transfer position in a two-dimensional plane, wherein the exposure device (1) is any one of claims 19 to 27. Position measuring device (10), an imaging device (20) for imaging the mark (AM) formed on the substrate (W) via an imaging optical system, and the substrate (W) measured by position measurement. Using the position information in the normal direction of, the moving device (4) for moving the substrate (W) in the normal direction so that the mark (AM) coincides with the best imaging plane of the imaging optical system, and the best imaging The mark (AM) present on the surface is captured by the image pickup device (2
0), the position information of the mark (AM) in the two-dimensional plane is measured based on the result of imaging, and the mark (A
A positioning device (30) for positioning the substrate (W) at a predetermined transfer position based on the position information of M).

Therefore, according to the exposure method and the exposure apparatus of the present invention, the mark (AM) obtained with the mark aligned with the best image forming plane of the image forming optical system (10) is highly accurate in the two-dimensional plane. Since the substrate (W) can be positioned at a predetermined transfer position based on the position information of the mask (R)
It becomes possible to accurately transfer the pattern No. 1 to a predetermined position on the substrate (W).

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a position measuring method, a position measuring apparatus, an exposure method, an exposure apparatus and a mark measuring method according to the present invention will be described below with reference to FIGS. Here, as an exposure apparatus, for example, a scanning exposure that transfers the circuit pattern of the semiconductor device formed on the reticle onto the wafer while synchronously moving the reticle and the wafer in different directions (reverse directions) in the scan direction. An example of using an apparatus (scanning stepper) will be described. Moreover, in this exposure apparatus,
An example of applying the position measuring device of the present invention to a wafer alignment system for measuring an alignment mark on a wafer will be described.

FIG. 1 schematically shows the structure of a reduction projection type exposure apparatus 1 for manufacturing a semiconductor device, which is preferably used in this embodiment. First, the overall configuration of the exposure apparatus 1 will be described below.

The exposure apparatus 1 includes an illumination system 2 for illuminating a reticle R as a mask with an energy beam (exposure illumination light) from an exposure light source (not shown), and exposure light emitted from the reticle R as an object. A projection optical system PL that projects onto a wafer (substrate) W, a reticle stage RS that holds a reticle R, a wafer stage (stage) WS that holds a wafer W, and a main control unit 30 that totally controls the entire apparatus. It is configured to include.

The illumination system 2 includes various lens systems such as a relay lens (not shown), a fly-eye lens (or a lot integrator), a condenser lens, and a blind arranged at a position conjugate with the aperture stop and the pattern surface of the reticle R. The illumination light from the exposure light source is applied to a predetermined illumination area on the reticle R with a uniform illuminance distribution.

The projection optical system PL includes a plurality of lenses (not shown), and illuminates the illumination light transmitted through the reticle R at a predetermined reduction ratio 1 / β (β is, for example, 1/4, 1 /
5), and projection exposure is performed on the wafer W coated with a photosensitive material (photoresist or the like). Here, the direction parallel to the optical axis AX of the projection optical system PL (the normal direction of the surface of the wafer W) is the Z direction, and the direction of relative scanning between the reticle R and the illumination area in a plane perpendicular to the optical axis AX. (Direction parallel to the page)
Is the X direction, the direction orthogonal thereto is the Y direction, and the projection optical system P
A rotation direction around an axis parallel to the optical axis AX of L is defined as a θ direction.

The reticle stage RS is configured to be one-dimensionally scanned and moved in the Y direction (scan (scanning) direction at the time of scan (scanning) exposure) by a driving device (not shown) and to be finely driven in the X and θ directions. Has been done. In addition, the X and Y directions of the reticle stage RS,
The positions in the and θ directions are constantly monitored by a measuring device (not shown) such as a laser interferometer, and the position information obtained by this is supplied to the main control unit 30.

The wafer stage WS is an XY stage 3 which can be driven in a two-dimensional plane (an XY plane in FIG. 1), and a Z which can hold the wafer W by suction and can be finely driven in the Z direction on the XY stage 3. The leveling stage (moving device) 4 is included, and it is arranged on a base (not shown). The XY stage 3 has a drive device 28 including, for example, a magnetic levitation type two-dimensional linear actuator and the like, and under the command of the main control unit 30, positions and moves the wafer W to a predetermined position. Note that during scan exposure, the XY stage 3 performs scan movement in the scan direction (Y direction) in synchronization with the reticle stage RS.

Further, the Z leveling stage 4 has a drive mechanism (not shown), and under the command of the main control unit 30, minutely moves the wafer W in the Z direction. In addition,
The X-direction, Y-direction, and θ-direction positions of the Z-leveling stage 4 are constantly monitored by a measuring device 33 such as a laser interferometer, and the position information obtained thereby is supplied to the main control unit 30.

Above the wafer stage WS, the wafer W
Focus position detection system (second measuring device, hereinafter, for measuring the position of the surface (exposure surface) in the Z direction (normal direction)
A main AF sensor 5) is provided. The main AF sensor 5 emits a slit light obliquely to the surface of the wafer W through a plurality of slits, and a reflected light (reflected slit light) reflected on the surface of the wafer W. And a light receiving system 7 for receiving light,
The height position (focus amount) of the surface of the wafer W in the Z direction with respect to the image plane of the projection optical system PL is calculated based on the detection signal obtained from the reflected light from the surface of the wafer W.

In this exposure apparatus 1, when the circuit pattern of the reticle R is transferred onto the wafer W, the main AF sensor 5
Focusing (main AF) operation of driving the Z leveling stage 4 to move the wafer W in the Z direction on the basis of the focus amount calculated in step (a) to bring the surface of the wafer W into the focal depth of the projection optical system PL. I do. Further, in parallel with this, the XY stage 3 is driven to step the wafer W by a predetermined amount in the X direction and the Y direction in the XY plane perpendicular to the optical axis AX of the projection optical system PL, so that the wafer W is moved. The image of the circuit pattern of the reticle R is sequentially transferred to each of the shot areas set to.

At this time, the exposure apparatus 1 performs an alignment operation for aligning the center of each shot area of the wafer W with the optical axis AX (exposure position) of the projection optical system PL. This alignment operation is performed based on the position information of the alignment marks formed on the reticle R and the wafer W. The reticle R mark is the reticle alignment system 8
The mark of the wafer W is detected by the wafer alignment system (position measuring device, first measuring device) 10 as an imaging optical system. In this embodiment, the position measuring method according to the present invention is applied to one of the alignment operations.

Although not shown in FIG. 1, in the present embodiment, as shown in FIG.
As S, a wafer (substrate) W as an object
A so-called double stage system is adopted which is composed of wafer stages WS1 and WS2 which hold 1 and W2 and move independently in a two-dimensional plane. The wafer alignment system 10 is also arranged symmetrically with the projection optical system PL interposed therebetween. Each wafer alignment system 10 includes a wafer stage W while one of the wafer stages WS1 and WS2 is performing an exposure process at a position directly below the projection optical system PL.
The other of S1 and WS2 is arranged above a position retracted from a position directly below the projection optical system PL, and an alignment operation is possible while retracting at the retracted position.

On the reticle stage RS, a movable mirror 41 is provided at the end on the + X side and extends in the Y-axis direction.
Two movable mirrors 42 and 43 are arranged at the end on the Y side. Measuring axis BI6X toward the reflecting surface of the movable mirror 41
The position of the reticle stage RS in the X direction is measured by irradiating the interferometer beam indicated by and measuring the relative displacement with respect to the reference surface by receiving the reflected light. Here, the interferometer having this length measurement axis BI6X actually has two interferometer optical axes that can be independently measured, and measures the position of the reticle stage RS in the X axis direction and the yaw amount. It is possible to measure. In addition, the movable mirrors 42 and 43
Is irradiated with an interferometer beam indicated by measuring axes BI7Y and BI8Y, receives the respective reflected lights reflected there, and based on the average value of the measured values, reticle stage R
The position of S in the Y-axis direction is measured.

On the wafer stage WS1, -X
The movable mirror 44 is provided at the end portion on the side and extends in the Y-axis direction.
The movable mirror 45 is arranged at the end on the + Y side.
Then, the interferometer beam indicated by the length-measuring axis BI1X is radiated toward the reflecting surface of the movable mirror 44, and the reflected light is received to measure the relative displacement with respect to the reference surface. The position is being measured. Further, this interferometer beam has three optical axes, and tilt measurement and θ measurement are possible in addition to measurement in the X-axis direction of wafer stage WS1.

The movable mirror 45 is irradiated with an interferometer beam indicated by the length measuring axis BI4Y, and the reflected light thereof is received to measure the relative displacement with respect to the reference plane, whereby the position of the wafer stage WS1 in the Y direction is determined. I am measuring. On the wafer stage WS2, similarly to the stage WS1, a movable mirror 46 irradiated with an interferometer beam indicated by a length measuring axis BI2X and a movable mirror irradiated by an interferometer beam indicated by a length measuring axis BI3Y. 47 is installed, and the relative displacement with respect to the reference surface is measured by receiving the reflected light of the interferometer beam, thereby performing the measurement of the wafer stage WS2 in the X-axis direction and the Y-axis direction, and the tilt measurement and the θ measurement. It is possible.

In the following description, the wafers W1 and W2 are
Are collectively referred to as the wafer W, and the wafer stage WS1,
WS2 is generically referred to as wafer stage WS. Further, in the reticle stage RS, two reticles R1,
R2 is installed in series in the scanning direction (Y-axis direction).
Then, the reticles R1 and R2 on the reticle stage RS
For example, it is selectively used in double exposure, and any reticle can be scanned synchronously with the wafer side. The reticle stage RS of this embodiment is a double reticle holder type that holds a plurality of (two) reticles, but the configuration of this reticle stage side is the same as that of the wafer stage side. A type having two independently movable reticle stages) may be used.

Next, a configuration example of the reticle alignment system 8 and the wafer alignment system 10 will be described.
In this embodiment, the reticle alignment system 8 is a so-called TTR method (through method) that simultaneously detects the reticle mark RM formed on the reticle R and the reference mark FM provided on the Z leveling stage 4 by an imaging method. -The reticle type image detection optical system is used.
In the reticle R, the center of the reticle R is the optical axis AX of the projection optical system PL based on the position information (X coordinate, Y coordinate) of the reticle mark RM measured by the reticle alignment system 8.
Is aligned to match. It should be noted that the distance between the reticle mark RM and the center of the reticle R is a predetermined value in design, and this value is calculated based on the reduction ratio of the projection optical system PL to obtain the image plane side of the projection optical system PL. The distance between the projection point of the reticle mark RM on the (wafer side) and the center of the projection optical system PL is calculated. This distance is used as a correction value when arranging each shot area on the wafer W within the visual field of the projection optical system PL. Also,
The reference mark FM is formed, for example, in the same shape as an alignment mark (wafer mark) formed on the wafer W, and has the same height as the surface of the wafer W.
It is formed on a reference mark plate provided on the Z leveling stage 4.

FIG. 3 shows a structural example of the wafer alignment system 10. In the wafer alignment system 10, the light source 1
Reference numeral 1 denotes a light source that emits a light beam having a predetermined broadband wavelength as a measurement beam, and is used as a single light source for observation and focusing (focusing) operations. A condenser lens 12 on the optical path of the light source 11 and a main aperture K as shown in FIG.
1 and field stop 13 having sub-apertures (slits) K2, K3, illumination relay lens 14, and beam splitter 1
5 are arranged in this order, and in the direction in which the measurement beam from the light source 11 via the illumination relay lens 14 is reflected by the beam splitter 15, that is, on the optical path traveling downward from the beam splitter 15 in FIG. , And a wafer stage WS on which the wafer W is placed.

The surface of the wafer W is placed so as to coincide with the first surface F1 as a reference surface, and at this time, the surface of the wafer W (reference surface F1) is at a position conjugate with the field stop 13.
On the wafer W, a position detection alignment mark AM as an observation mark (not shown) is formed. In the following description, it is assumed that the reference plane (planned focal plane) F1 and the surface of the wafer W match.

The main aperture K1 of the field stop 13 is formed in a substantially square shape and is arranged at the center of the field stop 13, and the center thereof is the condenser lens 12 to the illumination relay lens 14.
It is inserted in the optical path so that it almost coincides with the optical axis of.
The sub-openings K2 and K3 are formed in long and narrow rectangular slits, and are provided 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. It is arranged. Then, a direction orthogonal to the side of the main opening K1 and substantially orthogonal to the longitudinal direction of the sub-openings K2 and K3 (direction orthogonal to each other in a non-tilted state) is a focus measurement direction described later. In the following description, the substantially longitudinal direction of the sub-openings K2 and K3 is called the non-measurement direction. Further, the focus measurement direction can be set in various directions, but in the present embodiment, it is adjusted to the direction (x direction or y direction) of the reference line of the pattern on the wafer surface to be inspected.

Next, along the optical axis of the first objective lens 16, a second objective lens 18 is arranged on the optical path in the direction of passing through the reflecting surface of the beam splitter 15, that is, in the upward direction in the figure. The light shielding plate 21 is arranged at a position F2 conjugate with the surface F1 of the wafer W on the first surface (reference surface F1),
Following the first relay lens 22, a pupil division reflective prism 23 (in the present embodiment, divided into two luminous fluxes) which is a luminous flux splitting member for splitting the incident luminous flux into a plurality of luminous fluxes.
It is placed at or near the position conjugate with.

Here, the pupil division reflective prism 23 has two
This is an optical member in which two surfaces of a prism formed into a mountain shape with an obtuse angle close to 180 degrees are finished as reflecting surfaces. In the present embodiment, the line of intersection (ridgeline of the mountain) of the two surfaces intersects with the optical axis of the first relay lens 22, and the optical axis is tilted so as to swing approximately 90 degrees.

The measurement beam incident on the pupil-division reflective prism 23 via the second objective lens 22 is split and reflected rightward in the drawing, and the pupil-division reflection is reflected on the optical path to the right. The second relay lens 24 following the mold prism 23,
Cylindrical lens, which is a cylindrical optical system
25 and the AF sensor 26 are sequentially arranged.

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 25 is arranged so that the generatrix thereof substantially coincides with the measurement direction of the main focusing optical system. And here, the cylindrical optical system is
The concept includes a lens and a toric lens that have different refractive powers (degrees) in two orthogonal directions.

The AF sensor 26 is arranged at the position of the first image pickup surface V1 which is conjugate with or near the second surface F2 and detects the positional relationship of the image formed on the image pickup surface. And sends a focus (auto focus (AF)) signal. In addition, the beam splitter 19 is disposed between the first surface F1 and the second surface F2, more specifically, between the second objective lens 18 and the light shielding plate 21, and the first surface F1 and the second surface F2.
The beam splitter 19 splits the optical path connecting the two with the reflection direction, that is, in the left direction in the figure, and on the optical path in that direction, a position conjugate with the first surface F1 and the second imaging surface V2 for image detection and reading. An image pickup device 20, for example, a CCD image pickup device, is arranged as the image pickup device. The above optical element 12
To 16, 18 to 19, and 21 to 25 form an image forming optical system according to the present invention.

The above-mentioned stage driving device 28 is connected to the wafer stage WS, and the AF sensor 26 and the image pickup element 2 are connected.
A signal processing device 29 is connected to 0, and the main control unit 30 described above is connected to the stage driving device 28 and the signal processing device 29. The main control unit 30 functions as a storage device and stores the relational expression (1) between the slit spacing and the focus. The Z leveling stage 4, the main AF sensor 5, the wafer alignment system 10 including the image sensor 20, the signal processing device 29, and the main control unit 30 constitute a calibration device according to the present invention.

The operation of the wafer alignment system 10 having the above configuration will be described below with reference to FIG. First, the measurement beam (illumination light beam) emitted from the light source 11 is condensed by the condenser lens 12 and uniformly illuminates the field stop 13 having the main aperture K1 and the sub apertures K2 and K3. The main aperture K1 and the sub-aperture (slit) K2 of the field stop 13,
The light flux passing through K3 is collimated by the illumination relay lens 14 and is branched by the beam splitter 15 in the reflection direction thereof, that is, in the downward direction in the drawing. The branched light flux is
The light is condensed by the first objective lens 16 and is vertically irradiated onto the surface of the wafer W placed on the wafer stage WS.

Since the surface of the wafer W is at a position conjugate with the field stop 13, the images of the main aperture K1 and the sub-apertures K2 and K3 are the illumination relay lens 14 and the first aperture of the illumination optical system.
An image is formed on the surface of the wafer 17 on the first surface (reference surface) F1 via the objective lens 16. Wafer stage WS
A stage drive device 28 is connected to the wafer stage WS, and the wafer stage WS moves and adjusts the position of the wafer W by the stage drive device 28.

Here, the reflected light flux from the image of the main aperture K1 formed on the surface of the wafer W is L1, the light flux from the image of the sub aperture K2 is L2, and the light flux from the image of the sub aperture K3 is L3. . These light fluxes L1, L2, and L3 are collimated by the first objective lens 16, and the beam splitter 15
Through the second objective lens 18 and is condensed again,
It is transmitted and reflected by the beam splitter 19.

The light beam L1 of the reflected and branched light beam forms an image of the wafer mark on the surface of the image pickup device 20. The output signal from the image pickup device 20 is processed by the signal processing device 29, and based on this, the position detection of the wafer mark and the observation by the television monitor are performed.

On the other hand, the light beams L1, L2, and L3 that are transmitted and branched by the beam splitter 19 are conjugate with the surface of the wafer W or the position of the second surface F2 near the surface of the wafer W by the image forming action of the two objective lenses 16 and 18. The images of K1, K2, and K3 are re-imaged on the light shielding plate 21 provided in the. That is,
An intermediate image (space image) of the images of the main aperture K1 and the sub apertures (K2, K3) formed on the surface of the wafer 17 by the two objective lenses (16, 18) is formed on the light shielding plate 21. .

FIG. 3B shows the form of the light shielding plate 21 as seen from the optical axis direction. The light shielding plate 21 is provided with two slit-shaped light beam passing portions K12 and K13 at positions symmetrical with respect to the optical axis so as to correspond to the sub-openings K2 and K3, and as shown in FIG. Of the light fluxes L1, L2, and L3 that are image-reflected in
Only 2, L3 are configured to pass through K12 and K13, respectively. Incidentally, the light shielding plate 21 may be in the form shown in (c) of FIG. That is, only the range in which the light flux L1 enters the light shielding plate 21 (shown by the diagonal lines in the drawing) is shielded, and the entire region K14 around the area may be configured as a light flux passing portion.

The light beams L2 and L3 that have passed through the light shielding plate 21 are collimated by the first relay lens 22 and then form an image of the light source 11 on the pupil division reflective prism 23. Further, the light beams L2 and L3 are reflected by the pupil division reflective prism 2.
Each of the light beams is split into two light beams by 3 and is reflected to the right in the drawing, and is condensed again by the second relay lens 24. Then, through the cylindrical lens 25, the sub-openings K2 and K formed by the light fluxes L2 and L3 on the AF sensor 26.
Each of the three slit images is divided into two images.

Next, the focusing mechanism of the wafer alignment system 10 will be described with reference to FIG. 4A, 4B, and 4C show the image formation on the AF sensor 26 of the light fluxes L2 and L3 that are split into two light fluxes on the pupil division reflective prism 23, respectively. The in-focus state and the out-of-focus state are shown by taking the light flux L2 as an example.

In FIG. 4B, the surface of the wafer W is the image pickup device 2
0 is in focus (that is, the objective optical system (1
6 and 18) shows the image formation state of the light beam L2 in the case where the surface of the AF sensor 26 at a position conjugate with the reference plane F1 as the planned focal plane is also in focus). Let P1 and P2 be the centers of the image forming positions of the two divided light beams (two divided light beams), and d be the distance between P1 and P2. In this case P1 and P2
Correspond to the center of the position of the image formed by the two-divided light flux of the light flux L2 in FIG. For convenience of explanation, the direction from the optical axis to the L2 side is R and the direction to the L3 side is L in the measurement direction.

On the other hand, when the surface of the wafer W is in the in-focus state, it is lower than the reference position F1 (in-focus position) in FIG. 3, that is, in the far direction from the first objective lens 16. As shown in FIG. 4A, the focus points of the two split light fluxes are located to the left of the image plane of the AF sensor 26 in the figure, that is, to the relay lens 24.
Positions P1a and P2a of the image forming position center or the light amount center on the image forming surface of 6 are shifted to directions closer to each other than P1 and P2 described above (distance da between P1a and P2a da <
d).

On the contrary, the surface of the wafer W is focused on the focus position F1.
3 in the upper direction, that is, in the direction closer to the first objective lens 16, as shown in FIG. 4C, the center of the image forming position or the light amount center of the two-divided light flux is more than P1 and P2. The positions P1c and P2c are displaced from each other (distance dc> d between P1c and P2c).

That is, by adjusting the position of the wafer stage WS in the vertical direction in FIG. 3 and moving the surface of the wafer W on the wafer stage WS up and down in the normal direction, the slit images of the two-divided light fluxes are separated from each other in the measurement direction. Approach and leave. Then, the AF sensor 26 detects information about the image forming positions of the two-divided light flux, and a signal including this information is sent from the AF sensor 26 to the signal processing device 29 for processing, and the distance between the image forming positions is calculated. It Then, the relational expression (1) between the slit interval and the focus, which is stored in advance,
Is calculated as focal point position information and output to the main control unit 30. In the main control unit 30, when the wafer stage WS is moved up and down via the stage driving device 28 based on the input information and adjustment is performed so that the state of FIG. 4B is obtained, the images of K2 and K3 are detected by the FA sensor. 26
At the same time, the wafer mark image on the wafer W is focused on the image pickup element 20.

In FIG. 1, the optical axis AX on the projection image plane side (wafer side) of the wafer alignment system 10 is used.
a is arranged parallel to the optical axis AX of the projection optical system PL. Therefore, the reference mark FM on the wafer stage WS is arranged in the visual field region (illumination region) of the wafer alignment system 10 to measure its position information (X coordinate, Y coordinate), and the reference mark FM is set to the reticle alignment system. 8
Of the wafer alignment system 10 and the projection optical system PL
It is possible to calculate the distance between the optical axis AX and the so-called baseline amount. This baseline amount is the wafer W
It serves as a reference amount when the above shot areas are arranged within the visual field of the projection optical system PL. That is, the wafer alignment system 10 measures the X coordinate and the Y coordinate of the wafer mark for alignment, and based on the value obtained by adding the baseline amount to the measurement result, the wafer stage WS is driven and the wafer W is moved. By performing stepping movements in the X and Y directions, the center of each shot area of the wafer W can be aligned with the optical axis AX of the projection optical system PL.

Next, an example of the alignment operation in this embodiment will be described. As shown in FIG. 5, the wafer W
A plurality of partitioned shot areas, that is, partitioned areas D, D, ... To which the image of the circuit pattern formed on the reticle R is transferred, are formed on each shot area.
The wafer alignment marks (marks) AM, AM, ... Observed when measuring the position in a two-dimensional plane on the wafer corresponding to D, ... Are formed in a predetermined layer (for example, the first layer). . The alignment mark AM extends at a distance in the X direction, and the alignment mark AM extends at a distance in the Y direction from a wafer mark (first mark) AM _X observed when measuring the position of the wafer W in the X direction. it is a mark consisting of AM _Y line and space that is observed when measuring the position in the Y direction. These alignment marks AM are
It is formed on the street line ST on the wafer W. The form of the alignment mark AM is not limited to this, and a two-dimensional mark having line-and-space marks arranged in a two-dimensional direction in one mark (for example, filed by the applicant) Japanese Patent Application 8
-311410) or a two-dimensional line mark arranged in a box shape. Although a search mark for search alignment is also formed on the wafer W corresponding to each shot area, it is omitted here.

Further, each wafer alignment mark AM
Are arranged in the scribe line (street line) so that they have the same positional relationship with the center of a predetermined shot area. In the present embodiment, for example, Japanese Patent Laid-Open No.
The shot areas D on the wafer W are aligned by the EGA (enhanced global alignment) method disclosed in JP-A-1-44429.

In the EGA method, the main control unit 30
Shows the wafer marks AM in at least three shot areas selected as alignment shot areas among all the shot areas D.
And the coordinate position of each alignment shot area is obtained based on the detection result. Then, the wafer W
For the model function that represents the array of shot areas above,
The obtained coordinate position and a known coordinate position (design value, etc.) are substituted for each alignment shot area, and the parameters of the model function are determined by statistical calculation such as the least square method. Then, the main control unit 30 substitutes the known coordinate position for each shot area D on the wafer W into the model function, so that the coordinate position (X
(Coordinate, Y coordinate) is calculated. Based on the movement amount determined by the calculated coordinate position and the baseline amount of the wafer alignment system 10 described above, the wafer stage W
By driving S in the X and Y directions, the wafer W
The center of each shot area D is the optical axis AX of the projection optical system PL.
Be aligned with.

When the position of the wafer mark AM is detected by the wafer alignment system 10, the wafer mark A is detected.
Prior to the detection of M, alignment AF is performed to bring the wafer surface into focus with the wafer alignment system 10. Hereinafter, this alignment AF will be described in detail with reference to the flowchart shown in FIG. Incidentally, the main control unit 30, the relational expression between the slit spacing and the focus (1), the wafer mark AM _X, for each of the AM _Y, assumed to be stored is determined using the previously marked.

First, in step S1, the wafer W is moved in the XY plane via the wafer stage WS so that, for example, the wafer mark AM _X is positioned at the center of the visual field formed by the main opening K1. At this time, as shown in FIG. 5B, the wafer mark AM _X is located in the measured region on the wafer W by the main opening K1 of the wafer alignment system 10. On the other hand, the slit images of the sub-apertures K2 and K3 are measured areas on the wafer (street line ST
It will be located in (above). At this time, as shown in FIG. 5B, a part of the slit light of the sub-opening K2 and the sub-opening K
It is assumed that a part of the slit light of No. 3 is on the shot area D (on the pattern).

Next, in step S2, the sub-aperture K2 is formed using the wafer alignment system 10 on the wafer W at a predetermined focus position (for example, the exposure focus position set by using the main AF sensor 5). The slit spacing of the slit light image by K3 is measured. After measuring the slit interval, it is judged whether the wafer W is at the top of the lot and is the shot area to be measured first (step S3), and the wafer W at the top of the lot is the shot area to be measured first. In step S4 (first step), a predetermined focus position (for example, an exposure focus position; when using this, the wafer W transferred to the wafer stage WS is projected by the main AF sensor 5 in the projection optical direction). The wafer W is moved in the Z direction with the focus on the system PL as the third step), and the slit spacing is measured at this position in step S5 (second step). Then, by repeating this procedure, a plurality of Zs centered on a predetermined focus position are obtained.
The slit spacing is measured at each position (step S
6). In the case of the alignment AF, since the linear approximation of the equation (1) holds in a wide focus range, it is sufficient that the Z positions for measuring the slit interval are about three places. for that reason,
For example, considering the flatness of the wafer W, the exposure focus position and three-point measurement of ± 5 μm centering on this focus position may be performed.

Then, in step S7 (fourth step), the signal processing device 29 serves as an arithmetic device based on the amount of movement of the wafer stage WS in the Z direction and the slit spacing measured at each Z position by the least square method or the like. Coefficient a of equation (1),
X ₀ is newly obtained, and the equation (1) is calibrated and reset by the obtained coefficients a and X ₀ . Note that these steps S4 to S7
A calibration process is constituted by After that, the focus adjustment amount in the Z direction is calculated again from the calibrated formula (1) and the measured slit spacing, and the wafer stage WS is driven in the Z direction, so that the surface of the wafer W is focused on the wafer alignment system 10. Focus adjustment is performed by adjusting to the position (the best image plane) (step S8). Further, the EGA measurement described above is performed (step S9), the coordinate position (X coordinate, Y coordinate) of all shot areas D is calculated, and the wafer stage WS is driven to align the wafer W.

On the other hand, in the above step S3, in the case of the wafer W that is not the lot head, or in the case of the shot area to be measured after the second, the state of the measured area is different from that when the equation (1) is set. Therefore, in step S8, the focus adjustment amount in the Z direction is calculated from the measured slit spacing and the equation (1) that has already been set, and the wafer stage WS is driven in the Z direction.
The surface of the wafer W can be aligned with the focus position of the wafer alignment system 10.

That is, since a plurality of wafers have undergone the same process and it is assumed that the wafers have substantially the same surface condition such as the presence or absence of patterns (marks), the equation (1) is calibrated at the beginning of the lot. Then, for wafers in the same lot, even if focus adjustment is performed using this calibrated formula (1), no problem will occur. In addition, since the relative positional relationship between the shot area and the wafer mark AM is almost the same in the wafer, it is 2
In the shot area to be measured after the second, the state of the wafer surface (underlying pattern or mark, etc.) that enters (is illuminated) the slit light on the wafer (presence or absence of pattern or mark,
The areas occupied by patterns and marks are almost the same. Therefore, if the formula (1) is calibrated in the shot area where the measurement is performed first, there is no problem even if the focus adjustment is performed using the calibrated formula (1) in the other shot areas.

When the wafer marks AM _X and AM _Y are separately provided for each shot area as in this embodiment, the equation (1) is set for each mark and the above-mentioned flowchart is used. The steps (S1) to (S7) in (1) are executed to calibrate the equation (1). Further, in the case of performing so-called multi-point EGA measurement within a shot in which a plurality of marks for performing measurement in the X direction and the Y direction are provided in each shot area, the above relational expression is calibrated for each measurement point, and Focus adjustment may be performed using a relational expression corresponding to the position.

As the focus origin of the relational expression calibrated and reset, the exposure focus position set using the main AF sensor 5 may be used, but the wafer mark AM is used.
_X, each AM _Y, and in order to prevent the focus variation occurs between each measurement point during the shot Uchida point measurement, to determine the origin by using the mark measurement information when calibrating the relationship It is also possible.

Specifically, first, the above steps S4 to S
When the Z position of the wafer W is changed at 6 to measure the slit spacing, the mark image (FI
The A signal) is also imaged and captured in the fifth step.
Next, the signal strength at each focus position is calculated from the captured signal waveform, and the focus position where the signal strength is maximized is obtained. Then, when obtaining the coefficient of the relational expression (1) from the slit spacing measured at each Z position, the origin is calculated so that the focus position has the maximum signal intensity. When the FIA signal intensity is also measured, it is desirable to select an appropriate Z position interval and the number of measurement points, for example, 11 points of ± 10 μm are measured at intervals of 2 μm. Further, in this step, the relational expression (1) is calibrated by taking the signal strength of the image pickup signal into consideration, but in addition to this, the sharpness of the image pickup signal is taken into consideration, or both the signal strength and the sharpness are taken into consideration. It may be calibrated in consideration.

After that, in the exposure apparatus 1, after the wafer alignment, the imaging characteristics such as the projection magnification of the projection optical system PL are adjusted based on the calculated EGA parameter (scaling parameter). Further, the main control unit 30 as the positioning device drives the drive device in accordance with the position information (coordinate value) of each shot on the wafer W calculated based on the EGA parameter and the design coordinate value of each shot area. Sequential exposure position (transfer position) of the wafer via 28
Then, the pattern formed on the reticle R is sequentially transferred (exposed) onto each of the positioned shot areas.

Subsequently, the two wafer stages WS1 and W
The parallel processing by S2 will be described. In the present embodiment, while the wafer W2 on the wafer stage WS2 is being exposed through the projection optical system PL, the wafer is exchanged on the wafer stage WS1, and the alignment operation and the autofocus are performed following the wafer exchange. / Auto leveling is performed. The position control of the wafer stage WS2 during the exposure operation is performed based on the measurement values of the length measurement axes BI2X and BI3Y of the interferometer system, and the wafer stage WS in which the wafer exchange and the alignment operation are performed.
The position control of No. 1 is the measuring axes BI1X, B of the interferometer system.
It is performed based on the measured value of I4Y.

While the above wafer exchange and alignment operations are being performed on the wafer stage WS1 side, exposure is performed by the step-and-scan method on the wafer stage WS2 side. In this embodiment, it is assumed that two reticles R1 and R2 are used for this exposure operation, and double exposure is continuously performed by a step-and-scan method while changing the exposure conditions. Regarding the exposure sequence and the wafer exchange / alignment sequence which are performed in parallel on the two wafer stages WS1 and WS2, the wafer stage which has completed first is in a standby state, and when both operations are completed, the wafer stage WS1 and The movement of WS2 is controlled. Then, the wafer W2 on the wafer stage WS2 after the exposure sequence is exchanged at the loading position, and the wafer W1 on the wafer stage WS1 after the alignment sequence is subjected to the exposure sequence under the projection optical system PL. .

As described above, while the wafer exchange and the alignment operation are performed on one wafer stage, the exposure operation is performed on the other wafer stage, and when the both operations are completed, the operations are switched to each other. By doing so, the throughput can be significantly improved.

As described above, in the present embodiment, the wafer W irradiated with the measurement beam of the wafer alignment system 10
Based on the state of the measurement area above (marked or not),
Since the relational expression (1) between the slit spacing and the focus adjustment amount is calibrated, the focus adjustment can be performed accurately and stably without depending on the surface state. Therefore, the wafer W can be aligned with high accuracy, and the pattern transfer accuracy can be improved.
In addition, in the present embodiment, when the possibility that the surface condition of the wafer W is changed is not the case where the alignment AF is performed, specifically, the slit position and the mark AM are used.
When there is a high possibility that the relative positional relationship of the number fluctuates, the relational expression (1) is calibrated when performing the alignment AF on the shot area to be measured at the beginning of the lot, so that the throughput is lowered and the productivity is deteriorated. Can be prevented.

Next, a second embodiment of the present invention will be described. If the pattern (base) to be illuminated by the slit light during the alignment AF is known in advance, it is possible to estimate and correct the change in the relational expression in advance.
In other words, the pattern that enters the slit is obvious from the design information (pattern design, mark arrangement, etc.) related to the exposure process, so the state of the measured region can be estimated based on this design information without measuring the slit interval. , The relation (1) can be calibrated.

The details will be described below with reference to the flowchart shown in FIG. In this figure, the same components as those of the first embodiment shown in FIG. 6 are designated by the same reference numerals to simplify the description.

First, since the pattern or mark that enters the slit when performing the alignment AF is obvious,
Before measuring the position of the mark AM, the state of the measured region in which the slit is located is typically estimated and classified. Next, the relational expression (1) between the slit spacing and the focus adjustment amount is calibrated and set for each state and stored in the main control unit 30 (step S11).

When actually performing the position measurement, first, the wafer W is XY through the wafer stage WS so that the wafer mark AM _X is positioned at the center of the visual field formed by the main opening K1. It is moved in the plane (step S1). Regarding the position of the wafer stage WS in the Z direction, the wafer stage WS may be positioned at a predetermined predetermined height position, or the main AF sensor 5 may be set before the focus detection by the wafer alignment system 10. When the focus detection is performed by using the focus detection, it may be positioned at the exposure focus position obtained by the focus detection. Then, the wafer alignment system 10 is used to measure the slit spacing of the image by the slit light of the sub-openings K2 and K3 (step S2).

Subsequently, the signal processing device 2 as the selection device
9 is the wafer mark AM _X based on the above design information.
A relational expression corresponding to the state of the measured region when measuring is selected from the main control unit 30 (step S12), and the focus adjustment amount is calculated from the selected relational expression and the measured slit spacing. The main control unit 30 drives the Z leveling stage 4 based on the calculated focus adjustment amount to match the wafer mark AM _X with the best image plane of the wafer alignment system 10 (step S).
8). After that, EGA measurement is performed (step S9),
The wafer W is aligned and positioned at the transfer position.

As described above, in the present embodiment, the first
In addition to the effects and advantages similar to those of the embodiment described above, in addition to the movement of the Z leveling stage 4 for calibration of the relational expression,
Since the slit interval is not measured, the time required for calibration can be shortened and the throughput can be improved.

In the above embodiment, the surface (underlying) state in the measured region is calibrated according to the presence / absence of a pattern, for example.
In addition to this, for example, the relational expression may be calibrated according to the unevenness state of the wafer surface, the reflectance state of the wafer surface, and further these plural conditions.

In the above embodiment, the field stop 13 has the sub-apertures K2 and K3 arranged on both sides of the main aperture K1, but the present invention is not limited to this.
As shown in, the sub-openings K2 and K3 may be arranged in directions orthogonal to each other with the main opening K1 as the center. In this case, the relational expression between the relative positional relation of the images formed by the sub-openings K2 and K3 and the focus adjustment amount is obtained as the slit spacing, and this relational expression may be calibrated by the various methods described above. Further, in this case, as shown in FIG. 9, the slit light is projected on the pattern or the street line, but even in such a case as described in the above embodiment. It is possible to obtain the same effect as the above.

In the above embodiment, the alignment AF system including the imaging optical system and the AF sensor 26 for performing the alignment AF and the wafer alignment system 10 for measuring the position of the mark on the XY plane are provided. Although the configuration is such that the alignment AF system is incorporated coaxially, the alignment AF system may be separately provided along with the wafer alignment system as the image pickup apparatus. In this case, the field aperture in the alignment AF system does not need the main aperture, and only the sub aperture needs to be formed. For example, when the sub-apertures are formed in directions orthogonal to each other as shown in FIG. 8, the field stop 13 has a shape as shown in FIG. 10, and the slit image formed by the field stop 13 is as shown in FIG. On the wafer mark A
It will be projected only around M.

AF for performing alignment AF
Similarly to the alignment light for performing wafer alignment, the light may be irradiated onto the mark AM. Even when the alignment mark AM is included in the alignment AF light (slit light), the same effect as above can be obtained by calibrating the relational expression in the same manner as above. Then, in the case of irradiating both the detection lights on the mark, when both detection lights are simultaneously irradiated on the mark, A
It is desirable to have different optical characteristics (wavelength, polarization state, etc.) between the F light and the alignment light. For example, the AF light is infrared light to near-infrared light from the LED or laser diode, and the alignment light is the wavelength 27 from the halogen lamp.
Broadband light of 0 nm or more, AF light and alignment light have the same wavelength range, and AF light has S polarization and alignment light has P polarization, or AF light and alignment light have the same wavelength range. Moreover, it is preferable that the intensity modulation is performed at frequencies different from each other, and it is possible to prevent the measurement accuracy from being deteriorated due to the influence of the other measurement beam during measurement of one.

On the contrary, in the case of irradiating both detection lights on the mark, the AF light and the alignment light are used for the mark AM.
When not irradiating simultaneously on top, that is, when AF alignment and wafer alignment are switched in time series for measurement, light in the non-measurement state is shielded by a photoelectric or mechanical shutter and is not irradiated on the wafer W. Alternatively, the optical path of the measurement beam may be made common, and the optical path in the middle may be switched by the switching mirror. In this case, since light (light source) having the same optical characteristics can be used, it is possible to reduce the size and cost of the device.

In the first embodiment, the lot head is also the wafer, and the relational expression is calibrated with respect to the measured region to be measured first in the wafer. Can be changed as appropriate. Instead of the first shot measured in the wafer, any one shot may be performed. Further, it may be performed for each mark, each wafer, or every predetermined number of wafers. Further, for the wafer at the beginning of the lot, the relational expression is calibrated for all marks, and the relational expression is calibrated and re-calibrated by the average. You may set it.
Further, for example, it is also possible to calibrate the relational expression in a plurality of shot areas on the wafer at the beginning of the lot and obtain the focus adjustment amount from the relational expression obtained by averaging the plurality of calibration results and the slit spacing. is there. In this case, the plurality of shot areas may be the first several locations in the measurement order, or the shot areas to be the target of EGA measurement may be selected.

Further, in the above-mentioned embodiment, the position measuring device of the present invention is used for wafer alignment in the exposure apparatus. However, the present invention is not limited to this. As long as the focus adjustment amount is measured using the light reception result and a predetermined relational expression, the reticle alignment sensor for measuring the position information of the alignment mark formed on the reticle R, various inspection devices, and manufacturing devices can be used. Applicable. Further, the alignment measurement device is not limited to the alignment sensor, and for example, an overlay measurement device that measures overlay errors of measured portions of a plurality of layers with a plurality of patterns or marks formed for each layer on the wafer W as measurement targets. It is also applicable to. In this case, the effect that the overlay error can be measured with high accuracy is obtained. Further, in the above embodiment, the example of the double stage type in which two wafer stages are provided is used.
However, the present invention is not limited to this, and one wafer stage or three or more wafer stages may be provided.

In the above embodiment, the alignment sensor is illuminated with light having a wide wavelength band using a halogen lamp or the like as a light source, and image data of the alignment mark taken by a CCD camera or the like is subjected to image processing to determine the mark position. FIA (Field Image Alignment) to measure
ent) method, the LSA (Laser Step Alignment) that irradiates a laser beam on a dot-row-shaped alignment mark on the wafer and detects the mark position using light diffracted or scattered by the mark.
nt) method or irradiating the diffraction grating-shaped alignment mark on the wafer with two coherent beams that are symmetrically inclined in the pitch direction to cause the two diffracted lights generated to interfere with each other.
LI that measures the position of the alignment mark from the phase
A (Laser Interferometric A
The light source) method may be used.

As the substrate of this embodiment, not only the 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, a mask used in an exposure apparatus, or Original reticle (synthetic quartz, silicon wafer)
Etc. apply.

As the exposure apparatus 1, other than the step-and-scan type scanning exposure apparatus (scanning stepper; USP 5,473,410) for synchronously moving the reticle R and the wafer W to scan and expose the pattern of the reticle R. To
The present invention can also be applied to a step-and-repeat type projection exposure apparatus (stepper) that exposes the pattern of the reticle R while the reticle R and the wafer W are stationary and sequentially moves the wafer W. The present invention can also be applied to a step-and-stitch type exposure apparatus that transfers at least two patterns on the wafer W by partially overlapping them.

The type of the exposure apparatus 1 is not limited to the exposure apparatus for manufacturing a semiconductor element that exposes a semiconductor element pattern on the wafer W, and an exposure apparatus for manufacturing a liquid crystal display element or a display, a thin film magnetic head, an imaging device. Element (CC
D) or an exposure apparatus for manufacturing a reticle, a mask, or the like, can be widely applied.

Further, as the light source of the illumination system 2, bright lines (g line (436 nm), h line (404.nm), i line (365 nm)), KrF excimer laser (248 nm), ArF generated from an ultra-high pressure mercury lamp. Excimer laser (1
(93 nm), F ₂ laser (157 nm), Ar ₂ laser (126 nm) as well as charged particle beams such as electron beams and ion beams can be used. For example, when an electron beam is used, thermionic emission type lanthanum hexaboride (LaB ₆ ) or tantalum (Ta) can be used as the 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 region or the visible region emitted from a DFB semiconductor laser or a fiber laser is amplified by a fiber amplifier doped with, for example, erbium (or both erbium and ytterbium), and nonlinear optical A harmonic wave whose wavelength is converted into ultraviolet light using a crystal may be used as the exposure light. If the oscillation wavelength of the single-wavelength laser is within the range of 1.544 to 1.553 μm, the 8th harmonic within the range of 193 to 194 nm,
That is, ultraviolet light having substantially the same wavelength as the ArF excimer laser can be obtained, and assuming that the oscillation wavelength is within the range of 1.57 to 1.58 μm, the 10th harmonic within the range of 157 to 158 nm, that is, almost the same as the F2 laser. Ultraviolet light having a wavelength is obtained.

Further, 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, an EUV (Extreme) having a wavelength of 13.4 nm or 11.5 nm.
Ultra Violet) light may be used as exposure light, and EUV
The exposure apparatus uses a reflective reticle, and the projection optical system is a reduction system including only a plurality of (for example, about 3 to 6) reflective optical elements (mirrors).

The projection optical system PL may be not only a reduction system but also a unity magnification system and an enlargement system. In addition, the projection optical system P
L may be a refraction system, a reflection system, or a catadioptric system. When the wavelength of the exposure light is about 200 nm or less, it is desirable to purge the optical path through which the exposure light passes with a gas (inert gas such as nitrogen or helium) that absorbs the exposure light little. When an electron beam is used, an electron optical system including an electron lens and a deflector may be used as the optical system. Needless to say, the optical path through which the electron beam passes is in a vacuum state.

Wafer stage WS and reticle stage R
When a linear motor (see USP 5,623,853 or USP 5,528,118) is used for S, either an air levitation type using an air bearing or a magnetic levitation type using Lorentz force or reactance force may be used. Also, each stage W
S and RS may be types that move along a guide,
A guideless type without a guide may be used.

As a driving mechanism of each stage WS, RS, a magnet unit having a two-dimensionally arranged magnet and an armature unit having a two-dimensionally arranged coil are opposed to each other, and each stage WS, RS is driven by an electromagnetic force. A planar motor may be used. In this case, one of the magnet unit and the armature unit is connected to the stages WS and RS, and the other of the magnet unit and the armature unit is connected to the stages WS and RS.
It may be provided on the moving surface side of.

The reaction force generated by the movement of the wafer stage RS is prevented from being transmitted to the projection optical system PL.
As described in US Pat. No. 6,166,475 (USP 5,528,118), a frame member may be used to mechanically escape to the floor (ground). The reaction force generated by the movement of the reticle stage RS is not transmitted to the projection optical system PL, and a frame member is used as described in JP-A-8-330224 (US S / N 08 / 416,558). It may be mechanically released to the floor (ground).

As described above, the exposure apparatus 1 according to the embodiment of the present application
The various subsystems including the respective constituent elements recited in the claims of the present application, predetermined mechanical accuracy, electrical accuracy,
It is manufactured by assembling so as to maintain optical accuracy. Before and after this assembly, adjustments to achieve optical precision for various optical systems, adjustments to achieve mechanical precision for various mechanical systems, and various electrical systems to ensure these various types of precision are made. Are adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus from the various subsystems includes mechanical connection, electrical circuit wiring connection, air pressure circuit pipe connection, and the like between the various subsystems. It goes without saying that there is an individual 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 adjustment is performed to ensure various accuracies of the exposure apparatus as a whole. It is desirable that the exposure apparatus be manufactured in a clean room where the temperature and cleanliness are controlled.

Microdevices such as semiconductor devices are
As shown in FIG. 12, step 201 of designing the function / performance of the microdevice, step 202 of manufacturing a mask (reticle) based on this design step, step 203 of manufacturing a wafer from a silicon material, and the step of the above-described embodiment. An exposure processing step 204 for exposing the reticle pattern onto the wafer by the projection exposure apparatus 1, a device assembly step (dicing step, bonding step,
It is manufactured through 205 including a packaging process) and an inspection step 206.

[0101]

As described above, according to the present invention, the focus adjustment can be performed with high accuracy and stability without depending on the state of the measured region of the object, and the alignment error of the object caused by the focus fluctuation can be eliminated. The effect that it can be suppressed is obtained. Further, according to the present invention, it is possible to prevent a decrease in throughput and a deterioration in productivity.

[Brief description of drawings]

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

FIG. 2 is an external perspective view showing the positional relationship between two wafer stages, a reticle stage, a projection optical system, and an alignment system.

FIG. 3 is a schematic configuration diagram of a wafer alignment system according to the present invention.

FIG. 4A to FIG. 4C are explanatory diagrams showing the image formation state of the divided measurement beam on the AF sensor.

5A is a plan view of a wafer used in the embodiment of the present invention, and FIG. 5B is a detailed view of a shot area.

FIG. 6 is a diagram showing the first embodiment of the present invention and is a flowchart diagram showing a procedure of alignment AF.

FIG. 7 is a diagram showing the first embodiment of the present invention and is a flow chart diagram showing a procedure of alignment AF.

FIG. 8 is a plan view showing another embodiment of the field stop.

9 is a partial enlarged view of a slit image formed by the field stop shown in FIG. 8 projected on a wafer.

FIG. 10 is a plan view showing another embodiment of the field stop.

11 is a partial enlarged view of a slit image formed by the field stop shown in FIG. 10 projected on a wafer.

FIG. 12 is a flowchart showing an example of a manufacturing process of a semiconductor device.

13A is a signal waveform diagram when a pattern or the like does not exist on the base of the wafer, and FIG. 13B is a signal waveform diagram when a pattern partially exists on the base.

FIG. 14 is a relationship diagram showing a relationship between a slit interval and a focus adjustment amount.

[Explanation of symbols]

AM wafer alignment marks (marks) AM _X wafer mark (first mark) AM _Y wafer mark (second mark) D divided area (shot area) R reticle (mask) W, W1, W2 wafer (object, substrate) WS, WS1, WS2 Wafer stage (stage) S4 First step S5 Second step S7 Fourth step 1 Exposure device 4 Z leveling stage (moving device) 5 Main AF sensor (focus position detection system, second measuring device) 10 Wafer alignment system (Position measuring device, first measuring device, imaging optical system) 20 Imaging element (imaging device) 29 Signal processing device (arithmetic device, selection device) 30 Main control unit (storage device, positioning device)

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F065 AA03 AA06 AA07 BB02 BB27                       CC19 FF01 FF04 GG03 HH05                       JJ03 JJ26 LL00 PP12                 5F046 BA04 DA14 DB05 EB07 EC03                       ED02 FA03 FA10 FA17 FB08                       FB12 FC04

Claims (29)

[Claims] 1. The position information of the object in the normal direction of the surface is measured by irradiating the surface of the object with a measurement beam and using a measurement result of the measurement beam reflected by the surface and a predetermined relational expression. A position measuring method including: a position measuring method for calibrating the predetermined relational expression based on a state of a measured region on the surface of the object irradiated with the measuring beam. Method. 2. The position measurement according to claim 1, wherein the predetermined relational expression is calibrated at least every time the relative positional relationship between the pattern formed on the object and the measured region is different. Method. 3. A plurality of measured regions are provided on the object, and the plurality of measured regions having the same relative positional relationship among the plurality of measured regions are the predetermined regions. 3. The same relational expression is used as the relational expression of.
Position measurement method described in. 4. A plurality of partitioned areas are formed on the object, and the measured area is provided for each of the plurality of partitioned areas, and the calibration of the predetermined relational expression is performed by the plurality of partitioned areas. The position measuring method according to claim 1, wherein the position measuring method is performed on at least one of the divided areas to be measured. 5. The plurality of divided areas each include the plurality of measured areas, and a predetermined relational expression is calibrated for each of the plurality of measured areas provided in association with each of the divided areas. The position measuring method according to claim 4. 6. The position is calculated by using a relational expression obtained by calibrating the predetermined relational expression for each of a plurality of arbitrary partitioned areas formed on the object and averaging the plurality of calibration results. 6. Requesting information, claim 4 or 5
Position measurement method described in. 7. The object includes a plurality of substrates that have undergone the same process, and the calibration of the predetermined relational expression is performed on at least the first substrate to be measured of the plurality of substrates. The position measuring method according to any one of claims 1 to 6. 8. The mark to be observed when measuring position information of the object in a two-dimensional plane is formed in the measured region on the object. 7. The position measuring method according to claim 7. 9. The mark includes a first mark and a second mark extending in different directions in the two-dimensional plane.
The position measuring method according to claim 8, further comprising a mark, wherein the predetermined relational expression is calibrated for each of the first and second marks. 10. The state of the measured region includes at least one of a presence / absence state of a pattern in the measured region, a concavo-convex state of the surface, and a reflectance state of the surface. The position measuring method according to any one of claims 1 to 9. 11. The calibration step comprises a first step of moving the object in the normal direction, and a step of moving the measurement beam at a position where the position of the object in the normal direction is different from each other when the object is moved. A second step of measuring the measured region by using the third step, a third step of measuring the position of the object in the normal direction at the time of imaging using the measurement beam without using the measurement beam, The fourth step of calibrating the predetermined relational expression by a calculation using the measurement result of the two steps and the measurement result of the third step.
11. The position measuring method according to any one of 1 to 10. 12. In the third step, a displacement of a stage on which the object is mounted in the normal direction is measured, or a surface of the object is irradiated with a measurement beam different from the measurement beam. The position measuring method according to claim 11, wherein the position is measured by measuring a displacement of the object in a normal direction. 13. The method further comprises a fifth step of imaging the mark formed on the object, wherein the fourth step performs the calibration in consideration of the imaging result obtained in the fifth step. The position measuring method according to claim 11 or 12, which is characterized. 14. The calibration according to claim 4, wherein in the fourth step, at least one of the signal intensity and the sharpness of the image pickup signal obtained in the fifth step is taken into consideration.
The position measuring method described in 3. 15. The calibration step estimates the state of the measured region on the object based on design information of a pattern formed on the object, and performs the calibration based on the estimation. The position measuring method according to any one of claims 1 to 10. 16. The relationship in which different states of the measured region are estimated based on the design information before the position measurement on the object in the normal direction is performed, and the relations are respectively calibrated based on the estimation. A plurality of equations are stored, and in the calibration step, a relational expression corresponding to a desired measured region is selected from the plurality of stored relational expressions based on the design information. Item 15
Position measurement method described in. 17. A mark measuring method for picking up an image of a mark formed on an object via an image forming optical system, the mark measuring method measuring the position by the position measuring method according to claim 1. Using the position information of the object in the normal direction, the mark is matched with the best imaging plane of the imaging optical system, and the mark existing on the best imaging surface is passed through the imaging optical system. And measuring the position information of the mark in the two-dimensional plane. 18. An exposure method for transferring a pattern formed on a mask onto a substrate, which is based on position information of a mark on the substrate measured using the mark measuring method according to claim 17. An exposure method, wherein the substrate is positioned at a predetermined transfer position in the two-dimensional plane, and the pattern is transferred onto the substrate positioned at the transfer position. 19. Irradiating a measurement beam onto the surface of an object,
Using a measurement result of the measurement beam reflected on the surface and a predetermined relational expression, a position measuring device for measuring position information of the object in the normal direction of the surface, on the surface of the object, A position measuring device comprising a calibration device that calibrates the predetermined relational expression based on a state of a measurement region irradiated with the measurement beam. 20. The calibration device calibrates the predetermined relational expression at least every time the relative positional relationship between the pattern formed on the object and the measured region is different. The position measuring device described in. 21. A plurality of measurement regions are provided on the object, and the plurality of measurement regions having the same relative positional relationship among the plurality of measurement regions are the predetermined regions. 21. The position measuring device according to claim 20, wherein the position measurement is performed using the same relational expression as the relational expression. 22. A plurality of partitioned areas are formed on the object, and the measured area is provided for each of the plurality of partitioned areas, and the calibration device is at least one of the plurality of partitioned areas. The position measuring device according to any one of claims 19 to 21, characterized in that the calibration of the predetermined relational expression is automatically performed for one divided area. 23. The object includes a plurality of substrates that have been subjected to the same process, and the calibration device has a predetermined relational expression with respect to at least a first substrate to be measured of the plurality of substrates. The position measuring device according to any one of claims 19 to 22, wherein calibration is performed automatically. 24. The state of the measured region includes at least one of a pattern presence / absence state in the measured region, an uneven state of the surface, and a reflectance state of the surface. The position measuring device according to any one of claims 19 to 23. 25. The calibration device uses the measurement beam at a position for moving the object in the normal direction and at a position where the position of the object in the normal direction is different from each other when the object moves. And a second measuring device that measures the position of the object in the normal direction at the time of imaging using the measurement beam without using the measurement beam. 25. The position according to any one of claims 19 to 24, further comprising: an arithmetic device that performs an arithmetic operation for calibrating the predetermined relational expression using the measurement results of the first and second measuring devices. Measuring device. 26. An image pickup device for picking up an image of a mark formed on the object is further provided, and the arithmetic device performs the arithmetic operation in consideration of an image pickup result obtained by the image pickup device. The position measuring device according to claim 25. 27. The calibration device estimates a state of the measured region on the object based on design information of a pattern formed on the object, and calculates the relational expression calibrated based on the estimation. A plurality of storage devices, and a selection device that selects a relational expression corresponding to a desired measured region from the plurality of relational expressions stored in the storage device based on the design information. The position measuring device according to any one of claims 19 to 24, wherein: 28. A pattern formed on a mask,
An exposure apparatus for transferring onto a substrate positioned at a predetermined transfer position within a two-dimensional plane, the position measuring apparatus according to any one of claims 19 to 27, and a mark formed on the substrate. An image pickup device for picking up an image through an imaging optical system, and using the position information in the normal direction of the substrate measured by the position measurement, the mark is formed on the best imaging surface of the imaging optical system. A moving device that moves the substrate in the normal direction so as to match, and a position of the mark in the two-dimensional plane based on a result of imaging the mark existing on the best imaging plane by the imaging device. An aligner that measures information and positions the substrate at the predetermined transfer position based on the position information of the mark. 29. The exposure apparatus according to claim 28, wherein a plurality of the image pickup devices are provided, and the position measurement device is provided for each of the plurality of image pickup devices.