JP2011127981A - Displacement measuring apparatus, stage apparatus, exposure apparatus, scale manufacturing method, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement measuring apparatus capable of highly accurately measuring the amount of the displacement of an object. <P>SOLUTION: The displacement measuring apparatus as one aspect includes a scale 7 in which a grating pattern 6 is formed, a light source for irradiating the scale 7 with light, and a light-receiving element for receiving light diffracted by the grating pattern 6 of the scale 7. The shape of the grating pattern 6 is changed in the grating direction Y of the grating pattern 6 at a prescribed frequency. The light-receiving element receives light diffracted in the grating direction Y by a region 100 on the grating pattern 6 having a length of a natural number multiple of the frequency. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a displacement measuring apparatus, a stage apparatus, an exposure apparatus, a scale manufacturing method, and a device manufacturing method.

  Conventionally, displacement measuring devices such as a rotary encoder and a linear encoder have been used for the purpose of measuring displacement information such as positional information, displacement, and rotation of an object (displaced object). Among them, a grating interference type encoder that applies a diffraction interference phenomenon of light is known as a method for measuring a displacement amount with high accuracy. The grating interference type encoder makes the coherent light incident on the scale on which the diffraction grating is formed, causes the diffracted lights of different orders to interfere, and obtains the displacement amount of the scale based on the phase change of the obtained interference light Device.

  FIG. 8 is a schematic view of the lattice interference type displacement measuring apparatus described in Patent Document 1, and shows a case where the displacement measuring apparatus is applied to an exposure apparatus 300 that performs exposure, inspection, and measurement. The exposure apparatus 300 guides the radiation beam 26 emitted from the exposure unit 27 to the substrate 36 on the substrate table 11 through the gap 25, and performs exposure, inspection, and measurement of the substrate 36. The displacement measuring device has an encoder body (head) and a scale, and measures the displacement of the substrate table 11 that supports the substrate 36 with respect to the reference frame 13. Four scales 31, 32, 33, 34 are attached to the reference frame 13, and the reference of the substrate table 11 is provided by encoder bodies 21, 22, 23, 24 attached to corresponding portions 11 a to 11 d on the substrate table 11. The displacement with respect to the frame 13 is measured. In this case, for example, after the radiation beam is divided into + 1st order diffracted light and −1st order diffracted light using a reference diffraction grating, ± 1st order diffracted light is made incident on the scale, and the diffracted light is superimposed and interfered. From the change in the phase difference between the + 1st order diffracted light and the −1st order diffracted light, the displacement of the scale relative to the reference diffraction grating can be measured. In addition, since the displacements in two different directions can be measured by the encoders 21 to 24 by arranging the orientations of the lattice patterns formed on the four scales 31 to 34 so as to be at least two different directions, the substrate table 11 It is possible to measure the displacement on the XY plane.

Here, when the displacement amount of the scale is ΔX and the lattice pitch of the scale is P, the phase change amount Δφ in the single reflection of the m-th order diffracted light before and after the movement is
Δφ = 2πmΔX / P (Formula 1)
It is represented by Therefore, in the case of the first-order diffracted light (m = 1), the phase changes by 2π when the scale is moved by one pitch. For this reason, when the + 1st order diffracted light and the −1st order diffracted light are superposed, a phase shift of 4π occurs relative to the movement of the grating 1 pitch. As a result, a phase change of two periods occurs with respect to the scale movement of one pitch of the grating.

  In a grating interference encoder, how finely the phase change can be measured is important for performing highly accurate measurement. As described above, since the phase change amount Δφ is expressed as (Equation 1), the phase change amount Δφ accompanying the movement of the scale of the grating 1 pitch is increased by reducing the grating pitch. As a result, it is possible to measure the phase change finely, so that highly accurate displacement measurement can be realized. Therefore, in order to perform measurement with high accuracy, how to use a fine scale with a fine lattice pitch is an important point.

  As a method for manufacturing a fine scale, a laser drawing method for drawing a lattice pattern on a scale using a laser beam is generally known (Patent Document 2). In the laser drawing apparatus described in Patent Document 2, a laser beam is focused on a processing surface via a galvano scanner and an fθ lens, and the galvano scanner is operated according to the scale size, thereby scanning the laser beam to obtain a pattern. Draw. In principle, the beam diameter on the processing surface condensed by the fθ lens corresponds to the minimum pattern width, that is, the resolution of the pattern to be processed, so that high processing accuracy can be realized.

JP2007-318119A Special registration 04355601

  However, in the manufacture of a scale by the laser drawing method, a pattern shift caused by the optical system (mainly fθ lens characteristics) of the drawing apparatus occurs, and the scale lattice lines are bent. That is, the laser beam has a non-linear component with respect to the scanning direction. In the manufacture of a large scale, since drawing is performed while repeating the following operation by stepping by the scanning length, a lattice pattern having a periodic manufacturing error in the lattice direction is formed.

  Here, consider a case where displacement measurement is performed using a large scale in which a pattern having a periodic curve in the lattice direction is formed. As described above, in the displacement measurement, the displacement is measured by moving the scale in the periodic direction of the lattice pattern. However, due to the influence of the characteristics of the drive stage or mounting errors, there may be a deviation between the scale periodic direction and the drive stage moving direction. At this time, the area received by the light-receiving element also changes in the grating direction as the scale moves, so the phase of the interference signal changes due to periodic manufacturing errors in the grating direction of the grating pattern, and measurement is performed. An error occurs. Further, when measuring the displacement of the substrate table on the XY plane, as in the encoder described in Patent Document 1, the displacement of the substrate table in one direction is measured and the displacement measurement in the other direction is performed at the same time. Control the direction of table movement. At this time, if a measurement error occurs due to a periodic manufacturing error of the lattice pattern, incorrect information regarding the moving direction of the substrate table is acquired, and the drive stage operates based on the acquired information. It becomes difficult to make measurements.

  An object of this invention is to provide the displacement measuring apparatus which can measure the displacement amount of an object with high precision.

  In order to achieve the object, a displacement measuring apparatus according to one aspect of the present invention includes a scale on which a grating pattern is formed, a light source that irradiates light on the scale, and light diffracted by the grating pattern on the scale. And the shape of the lattice pattern changes at a constant period in the lattice direction of the lattice pattern, and the light receiving element is on the lattice pattern in the lattice direction. It receives light diffracted in a region having a length that is a natural number multiple of.

  According to the displacement measuring apparatus as one aspect of the present invention, it is possible to provide a displacement measuring apparatus that can measure with high accuracy. Other objects and aspects of the present invention will be clarified in the embodiments described below.

It is a figure which shows the structure of the displacement measuring apparatus as Embodiment 1 of this invention. It is a figure which shows the relationship between the scale in Embodiment 1 of this invention, and the light-receiving area | region on a scale. It is a figure which shows the relationship between the lattice pattern on the scale in 1st Embodiment of this invention, and a light reception area | region. It is a figure which shows the structure of the displacement measuring apparatus as Embodiment 2 of this invention. It is a figure which shows the sequence of the scale manufacturing method as Embodiment 3 of this invention. It is a figure which shows the structure of the exposure apparatus as Embodiment 4 of this invention. It is a figure which shows the measurement and exposure sequence of the exposure apparatus as Embodiment 4 of this invention. It is a figure which shows the structure of the conventional displacement measuring apparatus.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted. In the following embodiments, only the case where the orders of the two diffracted lights are ± 1st will be described. However, the order of the diffracted lights is not necessarily limited to ± 1st, and diffracted lights of different orders are used. In this case, the present invention can be applied.

[Embodiment 1]
FIG. 1 is a schematic diagram showing a configuration of a displacement measuring apparatus 200 as one aspect of the present invention. The displacement measuring device 200 is a device that measures the amount of displacement in the X direction of the scale 7 on which the lattice pattern is formed, and is configured as follows. That is, a laser light source 1, a collimator lens 2, a reference diffraction grating 3, a λ / 4 plate 4, a mirror 5, a scale 7 on which a grating pattern 6 is formed, a beam splitter (BS) 8, and a polarizing plate 9 and the light receiving element 10. In addition, the mirror 5 means 5a, 5b, 5c shown in FIG. The λ / 4 plate 4, the polarizing plate 9, and the light receiving element 10 also mean 4a and 4b, 9a and 9b, and 10a and 10b, respectively.

Hereinafter, functions of each component and preferred embodiments will be described. The laser light source 1 irradiates the scale 7 with light. Specifically, the coherent light emitted from the laser light source 1 is converted into a parallel light beam via the collimator lens 2 and then incident perpendicularly on the reference diffraction grating 3 to obtain the + 1st order diffracted light R + and the −1st order diffracted light R. Branch to-. Zero-order diffracted light and other orders of diffracted light are unnecessary light and may be blocked. Further, as the laser light source 1 of the displacement measuring apparatus 200, it is desirable to use a He—Ne laser, a solid-state laser, or a semiconductor laser that emits coherent light. Furthermore, it can also be set as the structure which guides the light from a light source using an optical fiber. Here, the diffraction angle θ1 of the + 1st order diffracted light R + and the −1st order diffracted light R− is expressed by the following equation, where m is the diffraction order, λ is the wavelength of the laser light source 1, and d is the grating pitch of the reference diffraction grating 3. Is done.
d · sin θ1 = mλ (Formula 2)
Next, after passing through the λ / 4 plates 4a and 4b, the + 1st order diffracted light R + and the −1st order diffracted light R− are reflected by the mirrors 5a and 5b, respectively, and incident on the scale on which the grating pattern is formed at an incident angle θ2. Let A one-dimensional grating pattern 6 is formed on the scale 7 along the Y direction, and the + 1st order diffracted light R + and the −1st order diffracted light R− are diffracted in the X direction. In the scale 7, the lattice direction corresponds to the Y direction, and the periodic direction corresponds to the X direction. For this reason, in the displacement measuring apparatus 200 of FIG. 1, the X direction is the measurement direction and the Y direction is the non-measurement direction.

Here, the optical axes of the λ / 4 plates 4a and 4b are arranged so as to have angles of +45 degrees and −45 degrees with respect to the polarization directions of the + 1st order diffracted light R + and the −1st order diffracted light R−, respectively. That is, after passing through the λ / 4 plates 4a and 4b, the λ / 4 plates 4a and 4b are arranged so that the + 1st order diffracted light R + and the −1st order diffracted light R− become clockwise circularly polarized light and counterclockwise circularly polarized light, respectively. Is done. In addition, in order to diffract the + 1st order diffracted light R + and the −1st order diffracted light R− in the direction perpendicular to the scale surface, the incident angle θ2 to the scale is expressed by the following equation, where P is the grating pitch of the scale.
P · sin θ2 = mλ (Formula 3)
That is, by allowing ± 1st order diffracted light to enter the scale at an incident angle θ2 satisfying (Equation 3), + 1st order diffracted light R + and −1st order diffracted light R− are diffracted in a direction perpendicular to the scale surface and superimposed. Make it interfere. Thereafter, the interference light beam reflected by the mirror 5c is split into two light beams by the beam splitter 8 and received by the light receiving elements 10a and 10b via the polarizing plates 9a and 9b, respectively. For the light receiving elements 10a and 10b, for example, a photoelectric conversion element such as a photodiode or a CCD is used, and photoelectric conversion is performed to obtain signal intensity information.

Here, the polarizing plates 9a and 9b are arranged so as to extract polarized components that are shifted from each other by 45 degrees. Thereby, the light receiving elements 10a and 10b detect two-phase sine wave signals having a phase difference of 90 degrees from each other, and the displacement amount of the scale including the direction can be identified based on the two-phase signal intensity. it can. The two-phase sine wave signal is expressed by the following equations, where the initial phase is φ0 and the relative displacement between the scale and the sensor head is ΔX.
I1 = A · cos (4π · ΔX / P + φ0) (Formula 4-1)
I2 = A · cos (4π · ΔX / P + φ0 + π / 2)
= −A · sin (4π · ΔX / P + φ0) (Formula 4-2)
Here, from I1 / I2,
I1 / I2 = −tan (4π · ΔX / P + φ0) (Formula 4-3)
Because
ΔX = {arctan (−I1 / I2) −φ0} · P / 4π (formula 4-4)
It can be expressed. In (Equation 4-1) and (Equation 4-2), the amplitude of the two-phase signal is assumed to be equal to A. However, when the strengths are different, it is necessary to multiply the amplitude in advance so that the amplitudes are aligned. There is. Further, as another configuration of the beam splitter and the polarizing plate, a configuration using a polarization beam splitter (PBS) may be used.

  In the displacement measuring apparatus of FIG. 1, when ± first-order diffracted light is used, the light / dark cycle of interference on the light receiving element 10a or 10b is the displacement of one pitch of the grating pattern formed on the scale is two cycles of the sine wave signal. It corresponds to. Accordingly, the amount of displacement of the scale can be obtained based on the number of bright and dark interference light received by the light receiving element 10a or 10b.

  In this embodiment, when the grating pattern on the scale has a periodic manufacturing error in the grating direction, the light diffracted in a region having a length that is a natural number times the period of the manufacturing error in the grating direction on the grating pattern. Is received by the light receiving element. Hereinafter, the relationship between the manufacturing error of the lattice pattern on the scale and the light receiving area will be described.

FIG. 2 is a diagram showing the relationship between the scale 7 on which the grating pattern 6 manufactured by the laser drawing method is formed and the light receiving region 100 received by the light receiving element 10. On the scale 7, a pattern having a periodic manufacturing error with a length of one cycle L 1 in the lattice direction due to the optical system of the drawing apparatus is formed at a lattice interval P. Further, the light receiving element 10 receives the light diffracted on the scale 7 in the region having the length L2 in the lattice direction. In the present embodiment, the displacement measuring apparatus 200 is configured so that the length L2 of the light receiving region 100 in the lattice direction and the period L1 of the manufacturing error of the lattice pattern 6 satisfy the following relationship.
L2 = L1 × N (N: natural number) (Expression 5)
Next, the influence of periodic manufacturing errors in the lattice direction of the lattice pattern on the measurement result will be described. FIG. 3 is a diagram in which the relationship between the grating pattern 6 having a periodic curve in the grating direction in FIG. 2 and the light receiving region 100 is simplified. FIGS. 3A to 3C show the positions of the light receiving region 100 in the grating direction. This represents a shift to. Here, consider a case where the length L2 of the light receiving region 100 in the lattice direction and the period L1 of the manufacturing error of the lattice pattern 6 satisfy the relationship shown in (Equation 5). At this time, even if the position of the light receiving region 100 changes in the lattice direction, the lattice pattern 6 having a length that is a natural number times the manufacturing error exists in the light receiving region 100 in the lattice direction. That is, in the light receiving region 100, the average value of pattern changes in the periodic direction of the lattice pattern 6 is constant. Therefore, since the phase of the interference signal received by the light receiving element 10 does not change depending on the position of the light receiving region 100, it is not affected by a periodic manufacturing error in the lattice direction of the lattice pattern 6. On the other hand, when the length L2 of the light receiving region 100 in the lattice direction and the period L1 of the manufacturing error of the lattice pattern 6 do not satisfy the relationship shown in (Equation 5), the average value of the pattern change in the light receiving region 100 is It changes according to the position of the light receiving region 100 in the lattice direction. For this reason, the phase of the interference signal received by the light receiving element 10 changes and a measurement error occurs.

  As described above, the displacement measuring device 200 is configured so that the length L2 of the light receiving region 100 in the lattice direction and the period L1 of the manufacturing error of the lattice pattern 6 satisfy the relationship shown in (Equation 5), thereby Measurement errors due to periodic manufacturing errors in the direction can be reduced.

  Next, a specific method for configuring the displacement measuring apparatus 200 so that the length L2 of the light receiving region 100 in the grating direction and the period L1 of the manufacturing error of the grating pattern 6 satisfy the relationship shown in (Expression 5) will be described. . In the present embodiment, it is necessary to obtain in advance the period L1 of the manufacturing error of the lattice pattern 6. The following three methods can be cited as methods for obtaining the period of manufacturing error. As a first method, a method of measuring a lattice pattern formed on a scale with a scanning electron microscope (SEM) is conceivable. By measuring the surface shape of the scale, the period L1 of the manufacturing error of the lattice pattern can be obtained. As a second method, there is a method of measuring a period of a manufacturing error of a lattice pattern on a scale using a test encoder head having a narrow light receiving area. Furthermore, as a third method, a method in which the scanning length of the laser beam of the drawing apparatus, which is a cause of periodic manufacturing errors, is set to L1 can be considered.

  Subsequently, the size of the light receiving region is set so that the length L2 of the light receiving region 100 in the lattice direction is a natural number times the period L1 of the manufacturing error of the lattice pattern 6 obtained in advance. In setting the size of the light receiving region, it is desirable to use a light receiving element in which the size of the light receiving surface satisfies the relationship shown in (Equation 5). Moreover, it is good also as a structure which covers the unnecessary part of a light-receiving surface with a light shielding film. Further, a light receiving element (for example, a plurality of line sensors or area sensors) that can detect light received in a selected region on the light receiving surface may be arranged to set the size of the light receiving region.

  According to this embodiment, when the scale has a periodic manufacturing error in the grating direction, the light receiving element receives light diffracted in a region having a length that is a natural number multiple of the manufacturing error period in the grating direction of the scale. . Thereby, the measurement error due to the change in the phase of the interference signal due to the periodic manufacturing error in the grating direction of the grating pattern can be reduced. As a result, the relative displacement of the scale can be measured with high accuracy. For this reason, a present Example can provide the displacement measuring apparatus which can measure the relative displacement amount of a scale with high precision.

  As a method for reducing the measurement error due to the change in the phase of the interference signal due to the periodic manufacturing error, a method using an averaging effect by enlarging the light receiving region in the detector is also conceivable. By increasing the light receiving area in the detector and increasing the number of data points, the measurement error can be reduced by averaging. However, in order to expand the light receiving area, it is necessary to use a light receiving element having a large size, which causes a problem that the apparatus becomes large or expensive. In general, the larger the size of the light receiving element, the slower the response speed, and there is a problem that it is difficult to increase the throughput. However, if the displacement measuring apparatus of this embodiment is used, those problems can also be solved.

  In this embodiment, the periodic manufacturing error in the non-measurement direction has been described. However, when there is a periodic measurement error in the measurement direction, the error number is a natural number times the error period in the measurement direction. By receiving the light diffracted in the length region, measurement errors can be reduced.

[Embodiment 2]
Next, as a second embodiment of the present invention, an embodiment applied to a displacement measuring device which is another configuration example will be described. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 4 is a schematic diagram showing the configuration of the displacement measuring apparatus 200 of the present embodiment. The displacement measuring device 200 is a device that measures the amount of displacement in the X direction of the scale 7 on which the lattice pattern is formed, and is configured as follows. That is, the laser light source 1, the collimator lens 2, the reference diffraction grating 3, the λ / 4 plate 4, the mirror 5, the scale 7 on which the grating pattern 6 is formed, the lens 12, and the light beam size adjusting means 50. , BS8, polarizing plates 9a and 9b, and light receiving elements 10a and 10b. The mirror 5 means 5a, 5b and 5c, and the lens 12 means lenses 12a, 12b and 12c. The λ / 4 plate 4, the polarizing plate 9, and the light receiving element 10 also mean 4a and 4b, 9a and 9b, and 10a and 10b, respectively. In the following embodiment, for example, a case where a field stop is used as the light beam size adjusting means 50 will be described.

  Hereinafter, functions of each component and preferred embodiments will be described. In FIG. 4, the coherent light emitted from the laser light source 1 is converted into a parallel light beam via the collimator lens 2 and then incident perpendicularly on the reference diffraction grating 3 to obtain the + 1st order diffracted light R + and −1 with a diffraction angle θ1. The light is branched to the next diffracted light R−. Then, after passing through the λ / 4 plates 4a and 4b, the + 1st order diffracted light R + and the −1st order diffracted light R− are reflected by the mirrors 5a and 5b, respectively, and incident on the scale 7 on which the grating pattern is formed at an incident angle θ2. Let A one-dimensional grating pattern 6 is formed on the scale 7 along the Y direction, and the + 1st order diffracted light R + and the −1st order diffracted light R− are diffracted in the X direction. In the scale 7, the lattice direction corresponds to the Y direction and the periodic direction (pitch direction) corresponds to the X direction, and a pattern having a periodic bend of length L1 in the lattice direction due to the optical system of the drawing apparatus has a lattice interval. P is formed (FIG. 2). Here, as for the laser light source 1, the diffraction angle θ1, the arrangement of the λ / 4 plate 5 and the incident angle θ2 of the displacement measuring apparatus 200, the contents described in the first embodiment can be applied as they are, and thus the description thereof is omitted here.

  The interference light beam reflected by the mirror 5c is collected by the lens 12a, passed through the imaging optical system 13 composed of the transmission slit plate 50 and the lenses 12b and 12c, and then split into two light beams by the beam splitter 8. The light receiving elements 10a and 10b receive the light through the polarizing plates 9a and 9b.

  In the present embodiment, a field stop 50 is disposed at a position optically conjugate with the lattice pattern surface of the scale 7 in the optical path between the scale 7 and the light receiving element 10, and the light receiving elements 10 a and 10 b. Specifies the measurement range of the received interference light. At this time, the lattice pattern 6 on the scale 7 forms an image on the field stop 50. That is, the size of the area where the field stop 50 receives light by the light receiving element 10 can be defined. Below, the field stop 50 which prescribes | regulates a light reception area | region is demonstrated. Here, it is assumed that the light receiving elements 10a and 10b have an area capable of receiving all the light through the field stop 50.

In the present embodiment, first, a manufacturing error period L1 in the lattice direction of the lattice pattern 6 on the scale 7 is obtained using, for example, a scanning electron microscope. Thereafter, the size of the field stop 50 is set so that the length L2 of the light receiving region in the lattice direction is a natural number times the period L1 of the manufacturing error obtained in advance. Here, a case where the illumination area on the scale 7 is received with a half size on the light receiving surface of the light receiving element 10, that is, a reduction optical system in which the imaging magnification by the lens 12 is 1/2 is considered. . In the field stop 50, when the length in the Y direction corresponding to the lattice direction of the scale 7 is L3, L3 is set to satisfy the following (Equation 6).
L3 = L1 / 2 × N (N: natural number) (Expression 6)
When the relationship of (Expression 6) holds, the light diffracted in a region having a length that is a natural number multiple of the period of the manufacturing error in the lattice direction on the scale 7 is received by the light receiving element 10. For this reason, the measurement error due to the phase change of the interference signal due to the periodic manufacturing error in the grating direction of the grating pattern can be reduced. The relationship between the length L3 in the Y direction in the field stop 50 and the period L1 of the manufacturing error varies depending on the optical magnification. For this reason, the length L3 of the field stop 50 in the Y direction is set so as to satisfy the following expression, where n is the optical magnification of the displacement measuring device 200.
L3 = L1 × n × N (N: natural number) (Expression 7)
In the present embodiment, the field stop 50 is arranged so that the length L2 of the light receiving region in the grating direction is a natural number times the period L1 of the manufacturing error of the grating pattern 6. Thereby, the measurement error by the phase change of the interference signal resulting from the periodic manufacture error to the grating | lattice direction of a grating pattern can be reduced. As a result, the relative displacement of the scale can be measured with high accuracy. For this reason, a present Example can provide the displacement measuring apparatus which can measure the relative displacement amount of a scale with high precision.

  The case where the field stop is used as the light beam size adjusting unit 50 has been described so far, but the form of the light beam size adjusting unit 50 is not limited to this, and for example, a transmission slit plate or a variable stop is used. Also good. FIG. 4 shows the case where the light beam size adjusting means 50 is arranged on the light receiving side, but the position of the light beam size adjusting means 50 is not limited to this. For example, the collimator lens 2 and the reference diffraction grating 3 You may arrange | position between.

[Embodiment 3]
Subsequently, a scale manufacturing method will be described as a third embodiment of the present invention. In the first and second embodiments, the displacement measuring apparatus has been described so far. In the present embodiment, a method for producing a lattice pattern on a scale substrate will be described. In the present embodiment, the scale substrate means a scale before drawing a lattice pattern using a drawing apparatus.

  As described above, when manufacturing a fine scale, a laser beam is focused on a processing surface via a galvano scanner and an fθ lens, and a pattern is drawn by scanning the laser beam with a galvano scanner according to the scale size. . In the case of a large scale, since the drawing position on the scale substrate is moved stepwise in the lattice direction, the lattice pattern shift due to the optical system (mainly the fθ lens characteristic) of the drawing device is periodic in the lattice direction. As a manufacturing error. Here, if the stepwise moving distance of the drawing apparatus in the lattice direction is L0 (not shown), L0 is equal to the length L1 of one cycle of the manufacturing error in the lattice direction. Since the movement distance L0 of the drawing apparatus in the lattice direction is variable depending on the setting conditions of the drawing apparatus, the cycle L1 of the manufacturing error in the lattice direction of the lattice pattern also changes according to the setting conditions of the drawing apparatus.

FIG. 2 shows a relationship between the scale 7 on which the lattice pattern 6 manufactured by the laser drawing method is formed and the light receiving region 100 received by the light receiving element 10 of the displacement measuring apparatus 200. On the scale 7, a pattern having a periodic manufacturing error with a length of one cycle L 1 in the lattice direction due to the optical system of the drawing apparatus is formed at a lattice interval P. Further, the light receiving element 10 receives the light diffracted by the light receiving region 100 having a length L2 in the lattice direction on the scale 7. In the present embodiment, the length L2 of the light receiving region 100 in the lattice direction and the period L1 of the manufacturing error of the lattice pattern 6 satisfy the relationship of (Equation 5).
L2 = L1 × N (N: natural number) (Expression 5)
Here, the influence of the periodic manufacturing error in the lattice direction of the lattice pattern on the measurement result is as described in the first embodiment. Therefore, by receiving the light diffracted by the light receiving element in a region having a length that is a natural number multiple of the cycle of the manufacturing error in the lattice direction of the scale 7, the measurement error due to the periodic manufacturing error can be reduced. it can.

  Below, the manufacturing method of the scale in this embodiment is demonstrated. FIG. 5 is a flowchart showing a sequence in the scale manufacturing method of the present embodiment.

  First, in step S01, the size of the region where the light diffracted on the scale 7 is received by the light receiving element is obtained. There are two methods for obtaining the size of the light receiving area: a method based on a design value and a method based on an actual measurement value. First, a first method for obtaining a light receiving area based on a design value will be described. Here, in the case of the displacement measuring apparatus 200 described in the first embodiment, the size of the region received by the light receiving element 10 can be calculated from the size of the light receiving surface of the light receiving element 10 and the optical magnification of the lens 12. it can. In the case of the displacement measuring apparatus 200 described in the second embodiment, the size of the region received by the light receiving element 10 is calculated from the size of the transmission region of the light beam size adjusting unit 50 and the optical magnification of the lens 12. Can do.

  Subsequently, as a second method for obtaining the light receiving area based on the actually measured value, there is a method in which a variable aperture is disposed in the vicinity of the surface on the scale 7 and the light beam size of the light diffracted on the scale 7 is adjusted. . Here, when the transmission area of the variable stop is smaller than the area received by the light receiving element 10, the light intensity of the interference light received by the light receiving element increases as the transmission area of the variable stop increases. When the transmission area of the variable stop is larger than the area received by the light receiving element 10, the area received by the light receiving element 10 does not change, and thus the light intensity of the interference light is constant. Therefore, the size of the area where the light diffracted on the scale 7 is received by the light receiving element 10 can be obtained from the change in the intensity of the interference light received when the transmission area of the variable aperture is enlarged.

  Next, in step S02, from the obtained length L2 of the light receiving region 100 in the lattice direction, a cycle L1 of the manufacturing error of the lattice pattern 6 that satisfies the relationship of (Equation 5) is calculated. In step S03, the conditions of the drawing apparatus are determined so that the scanning direction of the laser beam of the drawing apparatus is the lattice direction and the scanning distance is L1. By setting the drawing apparatus so as to satisfy the conditions, the drawing apparatus scans the laser beam with respect to the scale substrate by the scanning distance L1, and draws a lattice pattern on the scale substrate. Further, the drawing apparatus moves the drawing start position on the scale substrate in the scanning direction by the scanning distance L1, scans the laser beam again with respect to the scale substrate by the scanning distance L1, and the length of the grating pattern in the grating direction. Repeat the process of extending. Here, since the scanning distance of the laser beam in the grating direction is equal to the period of the manufacturing error in the grating direction of the scale 7, the grating pattern 6 having the period of the manufacturing error L1 is formed on the scale 7.

  In the present embodiment, the length L2 of the light receiving region 100 in the lattice direction on the scale 7 is obtained in advance after obtaining the size of the region in which the light diffracted on the scale 7 of the displacement measuring device 200 is received by the light receiving element. Based on the above, the lattice pattern 6 is formed on the scale 7 by the drawing apparatus. Thereby, the measurement error by the phase change of the interference signal resulting from the periodic manufacture error to the grating | lattice direction of a grating pattern can be reduced. As a result, the relative displacement of the scale can be measured with high accuracy. For this reason, a present Example can provide the displacement measuring apparatus which can measure the relative displacement amount of a scale with high precision.

[Embodiment 4]
6A and 6B are block diagrams of a semiconductor exposure apparatus provided with the displacement measuring apparatus 200 of the present embodiment. As shown in FIG. 6A, the illumination device 800, the reticle stage RS on which the reticle 14 is placed, the imaging optical system 15, the wafer stage WS on which the wafer 3 is placed, and the wafer stage WS are mounted. The displacement measuring device 200 is arranged. The displacement measuring apparatus 200 can apply the first, second, and third embodiments. Wafer stage WS includes a fine movement stage and a coarse movement stage, and displacement measuring apparatus 200 is mounted on the fine movement stage.

  The stage control unit 1000 is electrically connected to the wafer stage WS as the substrate stage, the arithmetic processing unit 81, and the displacement measuring device 200, and controls the position of the wafer stage WS based on the measurement result of the displacement measuring device 200. The central control unit 1100 is electrically connected to the stage control unit 1000, the illumination device 800, and the reticle stage RS, and controls the operation of the exposure apparatus. Note that both the stage control unit 1000 and the central control unit 1100 have a CPU and a memory, and can perform correction calculations on the obtained measurement results.

  The illumination device 800 illuminates the reticle 14 on which a circuit pattern is formed, and includes a light source unit 800 and an illumination optical system 801. A reticle 14 as an original plate is formed with a circuit pattern, and is supported and driven by a reticle stage RS. Reticle stage RS holds reticle 14 via a reticle chuck (not shown) and is connected to a moving mechanism (not shown). The moving mechanism is configured by a linear motor or the like, and can move the reticle 14 by driving the reticle stage RS in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction of each axis. A photoresist is applied on the wafer 3 as a substrate.

  Subsequently, position measurement of the wafer stage WS that holds the wafer 3 will be described. Similar to reticle stage RS, wafer stage WS moves wafer 3 in the X-axis direction, Y-axis direction, Z-axis direction, and the rotation direction of each axis using a linear motor. In the present embodiment, the displacement measuring apparatus 200 is mounted on the wafer stage WS. The displacement measuring apparatus 200 measures the position of the wafer stage WS by measuring the relative positional relationship of the wafer stage WS with respect to the scale 7 serving as a measurement reference.

  FIG. 6B shows the positional relationship between the scale 7 as a measurement reference and the wafer stage WS. A one-dimensional lattice pattern is formed on the scale 7, and four scales are arranged so as to surround the projection optical system 15. As shown in FIG. 6B, the four scales are arranged so that the lattice directions are inclined by 45 degrees with respect to the X-axis or Y-axis, and each direction is measured by the four displacement measuring devices 200 mounted on the WS. Measure the displacement at. For example, by measuring the scale 7a using the displacement measuring device 200a, it is possible to measure the displacement in the direction inclined +45 degrees with respect to the X axis. Further, by measuring the scale 7b using the displacement measuring device 200b, it is possible to measure the displacement in the direction inclined +45 degrees with respect to the Y axis. Similarly, by using the displacement measuring device 200c with respect to the scale 7c and the displacement measuring device 200d with respect to the scale 7d, the device is inclined +45 degrees with respect to the Y axis and +45 degrees with respect to the X axis. Each directional displacement can be measured. Therefore, by measuring the displacement on three appropriate scales, the displacement of the rotation Rz axis around the X axis, the Y axis, and the Z axis can be obtained. The wafer stage WS includes at least one reference mark 60 and aligns the wafer 3 and the reticle 14. At the time of alignment, the position of the reference mark 60 is detected by an alignment scope (not shown), and the wafer stage WS is driven while controlling the wafer stage WS based on the measurement value of the displacement measuring device 200 based on the detection result. Move to desired position.

  Next, an exposure method using the exposure apparatus of this embodiment will be described in detail. FIG. 7 is a flowchart showing the entire sequence of the exposure method when the exposure apparatus of this embodiment is used. First, in step S1, the wafer 3 is loaded into the apparatus, and in step S101, wafer alignment is performed on the wafer. In wafer alignment, an alignment scope (not shown) detects the position of a mark on the wafer and aligns the XY plane of the wafer with the exposure apparatus. At the time of alignment, the wafer stage WS is driven while being controlled based on the measurement result of the displacement measuring apparatus 200, and the wafer 3 is moved to a desired position.

After that, in step S102, the surface position of a predetermined location on the wafer 3 is measured by a surface position measuring device (not shown), and the surface of the wafer surface is approximately measured in units of exposure slits by driving the stage in the Z direction and tilt direction. Performs an operation to adjust to the position in the height direction. In step S103, exposure and scanning of the wafer stage WS in the Y direction are performed.
Thus, when the exposure of the first exposure shot is completed, the presence / absence of an unexposed shot is determined in step S105. If there is an unexposed shot, the process returns to step S102. Similarly to the case of the first exposure shot, based on the surface position measurement result of the next exposure shot, the shape in the height direction of the surface of the wafer 3 in units of exposure slits by driving the stage in the Z direction and the tilt direction. The exposure is performed while performing the operation for adjusting to the above. In step S104, it is determined whether or not there is a shot to be exposed (that is, an unexposed shot), and the above operation is repeated until there is no unexposed shot. When exposure of all exposure shots is completed, the wafer 3 is recovered in step S105, and the process ends.

  The wafer stage WS is not limited to a single stage, and may have a so-called twin stage configuration having two exposure stations used for exposure and a measurement station for wafer alignment and surface position measurement. In the twin stage, the two stages alternate between the exposure station and the measurement station. In this case, the displacement measuring device 200 is disposed on each of the two wafer stages WS. Further, the scale 7 serving as the measurement reference is disposed at both the exposure station and the measurement station, and the position of the wafer stage WS is controlled by the displacement measuring apparatus 200. Although the case where the displacement measuring apparatus 200 is mounted on the wafer stage has been described so far, the application of the displacement measuring apparatus 200 is not limited to the wafer stage, and may be mounted on the reticle stage. Even when mounted on a reticle stage, the displacement of the stage can be measured with high accuracy, and the reticle stage can be accurately moved to a desired position.

  With the miniaturization of semiconductor devices, accuracy in the order of nanometers is required for alignment of reticles and wafers in semiconductor exposure apparatuses. For this reason, it can be said that displacement measurement using a grating interference encoder that can accurately measure the displacement of the stage is an important technique. Among them, in order to realize a highly accurate lattice interference type encoder using a fine scale, it can be said that the effect of this embodiment for reducing the influence of the manufacturing error of the scale is great. If the displacement of the stage can be measured with high accuracy, the alignment accuracy between the wafer and the reticle will be improved, and there will be an effect of improving the performance of the semiconductor device and improving the manufacturing yield.

  In this embodiment, the case where the displacement measuring apparatus is applied as a stage position measuring apparatus of a semiconductor exposure apparatus has been described. However, the application range of the displacement measuring apparatus of the present invention is an exposure apparatus (liquid crystal exposure apparatus, EUV exposure apparatus, It is not limited to an EB exposure apparatus or the like. For example, the present invention can be widely applied to a stage apparatus in a precision machine such as a nanoimprint apparatus or a microscope.

[Embodiment 5]
Next, a method for manufacturing a device (semiconductor device, liquid crystal display device, etc.) according to an embodiment of the present invention will be described. Here, a method for manufacturing a semiconductor device will be described as an example.

  A semiconductor device is manufactured through a pre-process for producing an integrated circuit on a wafer and a post-process for completing an integrated circuit chip on the wafer produced in the pre-process as a product. The pre-process includes a step of exposing a wafer coated with a photosensitive agent using the above-described exposure apparatus, and a step of developing the wafer. The post-process includes an assembly process (dicing and bonding) and a packaging process (encapsulation). In addition, a liquid crystal display device is manufactured by passing through the process of forming a transparent electrode. The step of forming the transparent electrode includes a step of applying a photosensitive agent to a glass substrate on which a transparent conductive film is deposited, a step of exposing the glass substrate on which the photosensitive agent is applied using the above-described exposure apparatus, and a glass substrate. The process of developing is included. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

6 Lattice pattern 7 (7a-7d) Scale 1 Light source 10 (10a, 10b) Light receiving element 200 (200a-200d), 300 Displacement measuring device

Claims (10)

A scale on which a lattice pattern is formed;
A light source for irradiating the scale with light;
A light receiving element that receives light diffracted by the lattice pattern of the scale, and
The shape of the lattice pattern changes at a constant period in the lattice direction of the lattice pattern,
The said light receiving element receives the light diffracted by the area | region which has a length of the natural number multiple of the said period in the said grating | lattice direction on the said grating pattern. The displacement measuring apparatus characterized by the above-mentioned. An optical system that guides light from the light source to the scale and guides light diffracted by the grating pattern of the scale to the light receiving element;
The optical system includes a light beam size adjusting unit that adjusts a size of a light beam received by the light receiving element so that the light receiving element receives light diffracted by the region on the grating pattern. The displacement measuring apparatus according to claim 1. The light beam size adjusting means is disposed in an optical path between the scale and the light receiving element,
The displacement measuring apparatus according to claim 2, wherein light diffracted in the region on the lattice pattern out of light from the scale is transmitted. The light beam size adjusting means is disposed in an optical path between the light source and the scale, and transmits only light that irradiates the region on the lattice pattern out of light from the light source. The displacement measuring device according to claim 2. The displacement measuring apparatus according to claim 3, wherein the light beam size adjusting unit includes a stop disposed at a position conjugate with a light receiving surface of the light receiving element. The displacement measuring apparatus according to claim 4, wherein the light beam size adjusting unit includes a stop disposed at a position conjugate with a lattice pattern surface of the scale. A method for manufacturing the scale of a displacement measuring device comprising a scale, a light source that irradiates light to the scale, and a light receiving element that receives light from the scale,
Scanning a laser beam from a laser light source for a scanning distance with respect to the scale substrate, and drawing a lattice pattern on the scale substrate;
Moving the drawing position on the scale substrate in the scanning direction, and scanning the laser beam again with respect to the scale substrate by the scanning distance to extend the length of the lattice pattern in the lattice direction. And
The scanning distance is a length of a light receiving region of the light receiving element so that the light receiving element receives light diffracted in a region having a natural number times the scanning distance in the lattice direction on the lattice pattern. The scale manufacturing method is characterized in that it is determined based on the length. A stage for holding and moving the substrate;
A displacement measuring device according to any one of claims 1 to 6, which measures the displacement of the stage. A projection optical system that projects an image of an original pattern onto a substrate;
An exposure apparatus comprising: the stage apparatus according to claim 8. Exposing the substrate with the exposure apparatus according to claim 9;
A device manufacturing method comprising developing the exposed substrate.

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