JP2014029276A - Encoder device, optical device and exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a light amount loss of reference light upon measurement of a relative movement amount using a diffraction grating.SOLUTION: An encoder 10 comprises: a diffraction grating 12 that is provided in a first member 6 and has an X direction as a periodical direction; a laser light source 16 that emits measurement light MX and reference light RX; a polarization beam splitting (PBS) member 24X that is provided in a second member 7, enters the measurement light MX almost vertically to the diffraction grating 12 and emits the reference light RX in a direction different from the measurement light MX; and a reference member 32X that is provided in the second member 7, deflects the reference light RX via reflection surfaces 32Xa and 32Xb by the almost same angles as mutually different two diffraction angles in the diffraction grating 12 and reflects the deflected reference light RX to the PBS member 24X as reference light RX1 and RX2.

Description

  The present invention relates to an encoder apparatus for measuring a relative movement amount between relatively moving members, an optical apparatus and an exposure apparatus including the encoder apparatus, and a device manufacturing method using the exposure apparatus.

  In an exposure apparatus such as a so-called stepper or scanning stepper used in a photolithography process for producing an electronic device (microdevice) such as a semiconductor element, the position measurement of a stage that moves a substrate to be exposed has conventionally been a laser. It was done by an interferometer. However, in the laser interferometer, since the optical path of the measurement beam is long and changes, short-term fluctuations in measured values due to temperature fluctuations in the atmosphere on the optical path are becoming difficult to ignore.

  Therefore, for example, from a detection signal obtained by irradiating the diffraction grating fixed to the stage with measurement light made of laser light and photoelectrically converting interference light between the diffracted light generated from the diffraction grating and other diffracted light or reference light A so-called encoder device (interference encoder) that measures the relative movement amount of a member (such as a stage) provided with the diffraction grating is also being used (see, for example, Patent Document 1). This encoder device is excellent in short-term stability of measurement values as compared with a laser interferometer, and has a resolution close to that of a laser interferometer.

International Publication No. 2008/029757 Pamphlet

  In a conventional encoder device, for example, when laser light having a relatively short coherent length is used, it is preferable to reduce a difference in optical path length between diffracted light and reference light. However, in order to shorten the optical path length difference between the diffracted light and the reference light, for example, the optical system for the diffracted light and the optical system for the reference light are made almost symmetrical, and the reference light is also changed to the reference diffraction grating, for example. If it is made incident, there is a problem that the light amount loss of the reference light becomes large.

  In view of such a problem, an aspect of the present invention aims to suppress a light amount loss of reference light when measuring a relative movement amount using a diffraction grating.

  According to the first aspect of the present invention, there is provided an encoder apparatus for measuring a relative movement amount between a first member and a second member supported so as to be relatively movable in at least a first direction with respect to the first member. The The encoder device includes a reflective diffraction grating having a grating pattern having a periodic direction at least in the first direction, a light source unit that emits measurement light and reference light, and a second member. A first optical member that causes the measurement light to enter the grating pattern surface of the diffraction grating substantially perpendicularly and emits the reference light in a direction different from the measurement light, and the second member. It has at least one reflecting surface that reflects the reference light incident from the first optical member or a light beam branched from the reference light, and the reference light is approximately the same angle as two different diffraction angles in the diffraction grating. A first reference member that is deflected and reflected toward the first optical member as first and second reference light, and a first reference member that is provided on the second member and that is reflected from the diffraction grating by the measurement light. The first and second diffracted light beams of different orders generated with respect to the direction are incident through the first optical member, and the first and second diffracted light beams and the first diffracted light incident through the first optical member are incident on the first optical member. First and second reflection units that generate first and second interference lights with the first and second reference lights, first and second photoelectric detectors that respectively detect the first and second interference lights, and A measurement unit that obtains a relative movement amount between the first member and the second member using detection signals of the first and second photoelectric detectors.

Moreover, according to the 2nd aspect, an optical apparatus provided with the encoder apparatus of a 1st aspect and the optical system for objects is provided.
According to the third aspect, there is provided an exposure apparatus that exposes a pattern onto an object to be exposed, the stage supporting the frame and the object to be exposed and movable relative to the frame in at least the first direction. And an encoder apparatus according to a first aspect for measuring a relative movement amount of the frame and the stage in the first direction at least.

  Moreover, according to the 4th aspect, the device manufacturing method which exposes an object using the exposure apparatus of a 3rd aspect in the lithography process including the lithography process is provided.

  According to the aspect of the present invention, the reference light is deflected by approximately the same angle as two different diffraction angles in the diffraction grating and reflected toward the first optical member as first and second reference light. The reference member has at least one reflecting surface. Therefore, it is possible to suppress the light amount loss of the reference light.

It is a top view which shows the encoder which concerns on 1st Embodiment. (A) is a perspective view which shows the interferometer part and diffraction grating of the X-axis in FIG. 1, (B) is a top view which shows the irradiation position of the measurement light and diffraction light in FIG. 2 (A). (A) is a perspective view which shows the interferometer part and reference member of the X-axis in FIG. 1, (B) is a top view which shows the reference member in FIG. 3 (A). It is a figure which shows the change of the optical path of diffracted light when the relative height of a grating | lattice pattern surface changes in the interferometer part of the X-axis of FIG. 2 (A). FIG. 8A is a perspective view showing an X-axis interferometer section according to a first modification. (A) is a perspective view which shows the interferometer part of the X-axis which concerns on a 2nd modification, (B) is a top view which shows the reference member in FIG. 6 (A). (A) is a perspective view which shows the interferometer part of the X-axis which concerns on a 3rd modification, (B) is a top view which shows the reference member in FIG. 7 (A). It is a figure which shows schematic structure of the exposure apparatus which concerns on 2nd Embodiment. FIG. 9 is a plan view showing an example of the arrangement of diffraction gratings and a plurality of detection heads provided on the wafer stage of FIG. 8. It is a block diagram which shows the control system of the exposure apparatus of FIG. It is a flowchart which shows an example of the manufacturing method of an electronic device.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing an encoder 10 according to the present embodiment. In FIG. 1, as an example, the second member 7 is arranged so as to be relatively movable in three dimensions with respect to the first member 6, and the X axis is parallel to two directions of the second member 7 that are relatively movable relative to each other. The Z axis is taken along the relative movement direction perpendicular to the plane (XY plane) defined by the X axis and the Y axis. In addition, angles around axes parallel to the X axis, Y axis, and Z axis are also referred to as angles in the θx, θy, and θz directions, respectively.

  In FIG. 1, an encoder 10 includes a flat plate-like two-dimensional diffraction grating 12 fixed to the upper surface of a first member 6 and substantially parallel to the XY plane, a detection head 14 fixed to the second member 7, and a detection. Laser light source 16 and optical fiber 17 for supplying measurement laser light to head 14, optical fibers 39XA, 39XB, 39YA, 39YB, 39C for transmitting a plurality of interference lights generated by detection head 14, and optical fiber 39XA Photosensors 40XA, 40XB, 40YA, 40YB, 40C, such as photodiodes, which receive a plurality of interference lights supplied through -39C and output detection signals, and process these detection signals to process the first member 6 A measurement calculation unit 42 for obtaining a three-dimensional relative movement amount of the second member 7 in the X direction, the Y direction, and the Z direction. The detection head 14 irradiates the diffraction grating 12 with measurement light, and generates an X-axis interferometer unit 15X that generates a plurality of interference lights between the plurality of diffraction lights generated in the X direction from the diffraction grating 12 and the corresponding reference light. The Y-axis interferometer unit 15Y for irradiating the diffraction grating 12 with measurement light and generating a plurality of interference lights between the plurality of diffraction lights generated in the Y direction from the diffraction grating 12 and the corresponding reference light, and other optical elements And a member.

  On the grating pattern surface 12b substantially parallel to the XY plane of the diffraction grating 12, a two-dimensional grating pattern 12a having a predetermined period (pitch) p in the X and Y directions and having a phase type and a reflection type is formed. Yes. The period p of the lattice pattern 12a is, for example, about 100 nm to 4 μm (for example, about 1 μm). Note that the periods of the lattice pattern 12a in the X direction and the Y direction may be different from each other. The grating pattern 12a can be manufactured, for example, as a hologram (for example, a photosensitive resin baked with interference fringes) or by mechanically forming a groove or the like on a glass plate or the like and depositing a reflective film. Furthermore, the lattice pattern surface 12b may be covered with a protective flat glass.

  The laser light source 16 is made of, for example, a He—Ne laser, a semiconductor laser, or the like. Emits frequency heterodyne light. These laser beams are coherent with each other (when the polarization directions are parallel), and their average wavelength is λ. The laser light source 16 supplies a signal of a reference frequency (reference signal) obtained by photoelectric conversion of interference light of two light beams branched from the laser light to the measurement calculation unit 42. A homodyne interference method can also be used.

  The optical fiber 17 is, for example, a double-core polarization plane maintaining optical fiber that transmits the laser beams ML and RL emitted from the laser light source 16 while maintaining the polarization direction. In the present embodiment, when emitted from the optical fiber 17, the first laser light ML is linearly polarized light polarized in the X direction parallel to the XY plane, and the second laser light RL is linearly polarized in the Z direction. Polarized light. The other optical fibers 39XA to 39YB and 39C are single-core types, but may be any polarization-maintaining type or normal type. Moreover, you may provide a condensing lens in the entrance of optical fiber 39XA-39YB, 39C. Note that the intermediate portions of the optical fibers 17, 39XA to 39YB, etc. are omitted in FIG. Further, instead of the optical fiber 17, a beam transmission optical system in which a plurality of mirrors are combined may be used. Without using the optical fibers 39XA to 39YB and 39C, the interference light is directly detected by the photoelectric sensors 40XA to 40YB, Light may be received at 40C. In this embodiment, since the optical path length difference between the measurement light and the reference light is short (details will be described later), the coherence distance between the laser beams ML and RL emitted from the optical fiber 17 may be relatively short.

  The detection head 14 includes a connecting portion 18 including a lens (not shown) that converts the laser beams ML and RL emitted from the optical fiber 17 into parallel light beams, and a pair of laser beams ML and RL emitted from the connecting portion 18. A beam splitter 20A having a transmittance that is slightly larger than the reflectance for splitting the laser beam into the Y-axis measurement beam MY and the reference beam RY, and the pair of laser beams as the X-axis measurement beam MX and the reference beam. A beam splitter 20B having a high transmittance and a low reflectance that is split into RX and laser beams ML3 and RL3 for generating a reference signal, and the X-axis measurement light MX and the reference light RX are directed substantially in the −Y direction to the X-axis. Two mirrors 22A and 22B that are incident on the interferometer unit 15X. The measurement beams MX and MY and the laser beam ML3 are laser beams branched from the laser beam ML, and the reference beams RX and RY and the laser beam RL3 are laser beams branched from the laser beam RL. Each of the laser beams ML and RL has a circular cross section with a diameter of about 0.5 to several mm, for example. The cross section may be oval or rectangular. The Y-axis measurement light MY and the reference light RY enter the Y-axis interferometer unit 15Y substantially in the −X direction, and the laser beams ML3 and RL3 whose polarization directions are orthogonal to each other pass through the polarizing plate 41C. Is incident on the optical fiber 39C as interference light. The interference light transmitted through the optical fiber 39C is received by the photoelectric sensor 40C. When the laser beams ML and RL intersect at a predetermined angle, an optical for correcting the relative angles of the laser beams ML3 and RL3 between the beam splitter 20B and the polarizing plate 41C so as to be parallel to each other. A system may be provided.

In the present embodiment, the X-axis measurement light MX and the reference light RX incident on the interferometer unit 15X are heterodyne beams linearly polarized in the X direction and the Z direction, respectively, and the Y-axis measurement light incident on the interferometer unit 15Y. MY and reference light RY are heterodyne beams linearly polarized in the Y direction and the Z direction, respectively.
Further, the X-axis interferometer unit 15X has a polarization beam splitter surface (hereinafter referred to as a PBS surface) A11 on which the measurement light MX and the reference light RX reflected by the mirror 22B substantially in the −Y direction are incident (FIG. 2A). A polarizing beam splitter member (hereinafter referred to as a PBS member) 24X, a pair of roof prisms 26XA and 26XB fixed symmetrically in the X direction on the side surface in the + Y direction of the PBS member 24X, and roof prisms 26XA and 26XB A pair of large right-angle prism type reflecting members 28XA and 28XB having a reflecting surface fixed in the -Y direction and facing the ± X direction, and the roof prisms 26XA and 26XB A pair of small right-angle prism type fixed on the side surface in the + Z direction of the reflecting members 28XA and 28XB with the reflecting surface fixed in the + Y direction and the ± X direction. Reflective members 30XA and 30XB. Furthermore, the interferometer unit 15X includes a reference member 32X disposed so as to face the PBS member 24X.

  The first reflecting portion 25XA is constituted by the roof prism 26XA and the reflecting members 28XA and 30XA on the + X direction side, and the second reflecting portion 25XB is constituted by the roof prism 26XB and the reflecting members 28XB and 30XB on the -X direction side. . The second member 7 has an opening (not shown) through which the measurement light MX and the diffracted light emitted from the diffraction grating 12 pass. The PBS member 24X is fixed to the second member 7 so as to cover the opening. ing. The reference member 32X is fixed to the PBS member 24X (and thus the second member 7) via a connecting member (not shown).

  FIG. 2A shows the PBS member 24X and the reflecting portions 25XA and 25XB of the interferometer portion 15X in FIG. In FIG. 2A, the reference member 32X is indicated by a two-dot chain line in order to avoid complication of the drawing. In FIG. 2 (A), the PBS member 24X has a square cross section surrounded by two sides parallel to the Y axis and two sides parallel to the Z axis, and has a rectangular column shape elongated in the X direction. A PBS surface A11 is formed obliquely (inclined at an angle of 45 ° around the X axis with respect to the XY surface). The roof prism 26XA of the reflecting portion 25XA is symmetrical and orthogonal to the bottom surface fixed in close contact with the bottom surface of the PBS member 24X and the ridge line A16 that is parallel to the XY plane and inclined at a predetermined angle with respect to the Y axis. It has a pair of formed reflection surfaces A13 and A14 and an emission surface A15 that is parallel to the YZ surface and is in close contact with the reflection members 28XA and 30XB. The other roof prism 26XB has a symmetrical shape with the roof prism 26XA, and the roof prism 26XB also has two reflecting surfaces A23 and A24 that are orthogonal to each other.

  The measurement light MX reflected by the mirror 22B in FIG. 1 is incident on the PBS surface A11 of the PBS member 24X in FIG. 2A in the −Y direction as S-polarized light and the reference light RX as P-polarized light. The light passes through the PBS surface A11 and is ejected toward the reference member 32X in the -Y direction. On the other hand, the S-polarized measurement light MX is reflected by the PBS surface A11 and is incident perpendicularly (parallel to the Z axis) to the grating pattern surface 12b (grating pattern 12a) of the diffraction grating 12X. The term “perpendicularly incident” means that the measurement light MX is parallel to the Z-axis in order to reduce the influence of zero-order light (regular reflection light) in addition to the case where the measurement light MX is made to enter the grating pattern surface 12b exactly perpendicularly. This includes a case where the light is incident on the grating pattern surface 12b with an inclination of, for example, about 0.5 to 1.5 ° in the X direction (θy direction) and / or the Y direction (θx direction) with respect to a simple axis. In this embodiment, when including the case where the measurement light or the reference light is incident on the surface inclined at a certain angle as described above, the measurement light or the reference light is incident on the surface substantially perpendicularly. .

  In the present embodiment, ± 1st order diffracted beams DX1 and DX2 are generated symmetrically in the X direction by the measuring beam MX incident on the grating pattern surface 12b of the diffraction grating 12 substantially vertically, and the generated diffracted beams DX1 and DX2 are PBS members. The light is reflected by the PBS surface A11 of 24X and enters the roof prisms 26XA and 26XB. At this time, ± first-order diffracted light is also generated symmetrically in the Y direction, but the diffracted light in the Y direction is not used in the X-axis interferometer unit 15X. The + 1st order diffracted light DX1 is sequentially reflected by the reflecting surfaces A13 and A14 of the roof prism 26XA, shifted in the −Z direction, and incident on the reflecting member 28XA in the −X direction parallel to the X axis. The diffracted light DX1 reflected by the reflecting member 28XA is reflected by the PBS surface A11 of the PBS member 24X and enters the grating pattern surface 12b of the diffraction grating 12 substantially perpendicularly. Similarly, the −1st order diffracted light DX2 is shifted in the −Z direction via the PBS surface A11 and the reflective surfaces A23 and A24 of the roof prism 26XB, and is directed to the reflective member 28XB in the + X direction parallel to the X axis. The diffracted light DX2 that is incident and reflected by the reflecting member 28XB is reflected by the PBS surface A11 and enters the grating pattern 12a of the diffraction grating 12 substantially perpendicularly.

  As shown in FIG. 2B, the positions where the diffracted lights DX1 and DX2 are incident on the position where the measurement light MX is incident on the grating pattern 12a are shifted by the interval a1 in the −Y direction and ± X directions. Symmetrically shifted by an interval a2. The interval a1 is approximately ½ of the width of the PBS member 24X in the Y direction, and the interval a2 is approximately ¼ of the length of the PBS member 24X in the X direction. By making the measurement light MX and the diffracted lights DX1 and DX2 enter the diffraction grating 12 with such an arrangement, the configuration of the interferometer unit 15X can be reduced in size. However, the intervals a1 and a2 are arbitrary. The incident positions of the measurement light MX and the diffracted lights DX1 and DX2 are arbitrary, and the incident positions of the diffracted lights DX1 and DX2 may be arranged so as to sandwich the incident position of the measurement light MX in the Y direction, for example. .

  The diffracted lights DX1 and DX2 reflected by the reflecting members 28XA and 28XB and reflected by the PBS surface A11 generate + 1st order diffracted light EX1 and −1st order diffracted light EX2 (rediffracted light) symmetrically in the X direction from the diffraction grating 12. The generated diffracted light EX1 is reflected in the order of the PBS surface A11 and the reflecting surfaces A14 and A13 of the roof prism 26XA, shifted in the + Z direction, and incident on the reflecting member 30XA in the -X direction parallel to the X axis. To do. Then, the S-polarized diffracted light EX1 reflected in the + Y direction by the reflecting member 30XA enters the optical fiber 39XA via the polarizing plate 41XA.

The diffracted light EX2 is reflected in the order of the PBS surface A11 and the reflecting surfaces A24 and A23 of the roof prism 26XB, shifted in the + X direction, and incident on the reflecting member 30XB in the + X direction parallel to the X axis. . The S-polarized diffracted light EX2 reflected in the + Y direction by the reflecting member 30XB enters the optical fiber 39XB through the polarizing plate 41XB. In FIG. 2A, the measurement light MX is perpendicular to the grating pattern 12a of the diffraction grating 12. , The diffraction angle φx (see FIG. 4) of the + 1st order diffracted light DX1 in the X direction by the measurement light MX is obtained using the period p of the grating pattern 12a and the wavelength λ of the measurement light MX. Satisfies the following relationship: At this time, the diffraction angle of the −1st order diffracted light DX2 is −φx.

p · sin (φx) = λ (1)
As an example, if the period p is 1000 nm (1 μm) and the wavelength λ of the measurement light MX is 633 nm, the diffraction angle φx is approximately 39 °.
3A shows the PBS member 24X and the reference member 32X of the interferometer unit 15X in FIG. 1, and FIG. 3B shows the reference member 32X in FIG. 3A. In FIG. 3A, the reference member 32X is a flat surface substantially parallel to the XZ plane on which the one-dimensional grating pattern 32Xg having the same period p (see FIG. 3B) as the period of the diffraction grating 12 is formed in the X direction. And a pair of planar reflecting surfaces 32Xa and 32Xb provided in the −Z direction with respect to the lattice pattern 32Xg. The one-dimensional grating pattern 32Xg can be manufactured in the same manner as the grating pattern 12a of the diffraction grating 12. Since the grating pattern 32Xg is one-dimensional, the ± first-order diffraction efficiency is almost twice that of the diffraction grating 12.

  As shown in FIG. 3B, the reflecting surfaces 32Xa and 32Xb are inclined with respect to the XZ plane clockwise and counterclockwise at an angle φx / 2 around an axis parallel to the Z axis. The angle φx is the same as the diffraction angle (formula (1)) of the first-order diffracted light from the diffraction grating 12. The reflecting surfaces 32Xa and 32Xb are formed by, for example, forming a highly reflective metal film on a glass plane, and have a considerably large reflectance with respect to the reference light RX. The grating pattern 32Xg and the reflecting surfaces 32Xa and 32Xb are opposed to the PBS member 24X, and the distance between the grating pattern 32Xg and the PBS surface A11 of the PBS member 24X is the same as the grating pattern 12a of the diffraction grating 12 in FIG. It is substantially the same as the distance from the surface A11 (differs by the amount of relative movement between the first member 6 and the second member 7 in the Z direction).

  The reference light RX reflected by the mirror 22B of FIG. 1 is incident on the PBS surface A11 of the PBS member 24X of FIG. 3A in the approximately −Y direction as P-polarized light, and the reference light RX is transmitted through the PBS surface A11. Incidently perpendicularly to the lattice pattern 32Xg of the reference member 32X. ± first-order diffracted light RX1 and RX2 are generated symmetrically in the X direction by the reference light RX incident on the grating pattern 32Xg. Since the period p of the grating pattern 32Xg is the same as that of the grating pattern 12a, the diffraction angle φx of the ± first-order diffracted lights RX1 and RX2 (hereinafter referred to as first and second reference lights RX1 and RX2) is as shown in FIG. ) Is the same as the diffraction angle of the diffracted light DX1, DX2 (see FIG. 3B).

  The generated reference beams RX1 and RX2 (substantially P-polarized light) pass through the PBS surface A11 of the PBS member 24X and enter the roof prisms 26XA and 26XB (reflecting portions 25XA and 25XB). The optical paths of the reference beams RX1 and RX2 in the reflectors 25XA and 25XB are the same as the optical paths of the diffracted beams DX1 and DX2 of the measurement beam MX in FIG. The reference beams RX1 and RX2 are reflected by the pair of reflecting surfaces of the roof prisms 26XA and 26XB and the reflecting members 28XA and 28XB, respectively, and then pass through the PBS surface A11 of the PBS member 24X to be substantially parallel to the Y axis. The light enters the 32X reflecting surfaces 32Xa and 32Xb. The positions where the reference beams RX1 and RX2 are incident on the reference member 32X are shifted in the −Z direction and the ± X direction with respect to the position where the reference beam RX is incident. The distance between the incident positions of the reference beams RX1 and RX2 with respect to the reference member 32X and the PBS surface A11 is substantially the same as the distance between the incident positions of the diffracted beams DX1 and DX2 with respect to the grating pattern 12a in FIG. The first member 6 and the second member 7 are different by the amount of relative movement in the Z direction).

  In the present embodiment, the reflecting surfaces 32Xa and 32Xb of the reference member 32X are inclined at an angle ± φx / 2 with respect to the XZ plane. For this reason, the reference beams RX1 and RX2 incident on the reflecting surfaces 32Xa and 32Xb are reflected by the reflecting surfaces 32Xa and 32Xb so as to be inclined by the angles φx and −φx, respectively, in the X direction. The angle φx is the same as the diffraction angle of the first-order diffracted light in the grating pattern 32Xg (grating pattern 12a). Accordingly, the reflected reference beams RX1 and RX2 (substantially P-polarized light) are incident on the PBS surface A11 of the PBS member 24X symmetrically in the same direction as diffracted by the grating pattern 32Xg, and are transmitted through the PBS surface A11 and roofed. The light enters the prisms 26XA and 26XB (reflecting portions 25XA and 25XB).

  The optical paths in the reflecting portions 25XA and 25XB of the reference beams RX1 and RX2 reflected by the reflecting surfaces 32Xa and 32Xb are the same as the optical paths of the diffracted beams EX1 and EX2 of the measurement beam MX in FIG. Then, the reference light RX1 is reflected by the pair of reflecting surfaces of the roof prism 26XA and the reflecting member 30XA, and then is coaxially combined with the diffracted light EX1 and becomes interference light via the polarizing plate 41XA in FIG. This interference light is received by the photoelectric sensor 40XA through the optical fiber 39XA. Similarly, the reference light RX2 is reflected by the pair of reflecting surfaces of the roof prism 26XB and the reflecting member 30XB, and then is coaxially combined with the diffracted light EX2 to become interference light via the polarizing plate 41XB in FIG. . This interference light is received by the photoelectric sensor 40XB through the optical fiber 39XB.

  In this case, the optical path length until the measurement light MX incident on the PBS surface A11 enters the polarizing plates 41XA and 41XB as diffracted light EX1 and EX2, and the reference light RX incident on the PBS surface A11 is polarized as the reference light RX1 and RX2. Since the optical path lengths until they enter the plates 41XA and 41XB are substantially equal, the optical path length difference between the diffracted lights EX1 and EX2 and the reference lights RX1 and RX2 is considerably small, and interference light with a high S / N ratio can be obtained. In the present embodiment, the relative movement amount in the Z direction between the first member 6 and the second member 7 is set to a range that is smaller than the coherence distance between the measurement light MX and the reference light RX. Further, the light amounts of the diffracted beams EX1 and EX2 are reduced by two diffractions by the diffraction grating 12, whereas the reference beams RX1 and RX2 are diffracted only once by the reference member 32X. , RX2 is significantly reduced in light quantity. In addition, when the laser beams ML and RL emitted from the connecting portion 18 in FIG. 1 are inclined at a predetermined angle, the reflecting surface of the reference member 32X in FIG. The inclination angles of 32Xa and 32Xb may be shifted from φx / 2.

Further, the Y-axis interferometer unit 15Y in FIG. 1 includes a PBS member 24Y having a configuration in which the PBS member 24X, the reflection units 25XA and 25XB, and the reference member 32X of the X-axis interferometer unit 15X are integrally rotated by 90 °. The reflectors 25YA and 25YB and the reference member 32Y are provided. The PBS member 24Y is fixed to the second member 7 so as to cover an opening (not shown).
The measurement light MY and the reference light RY branched by the beam splitter 20A enter the PBS member 24Y of the interferometer unit 15Y, and the P-polarized reference light RY passes through the PBS surface of the PBS member 24Y and exits in the −X direction. Then, the light enters the lattice pattern of the reference member 32Y. Then, the S-polarized measurement light MY is reflected by the PBS surface of the PBS member 24Y and enters the grating pattern 12a of the diffraction grating 12 substantially perpendicularly, and the ± first-order diffracted lights generated symmetrically in the Y direction from the grating pattern 12a are Reflected by the PBS surfaces of the reflecting portions 25YA and 25YB and the PBS member 24Y, the light enters the grating pattern 12a of the diffraction grating 12 substantially perpendicularly. Then, the + 1st order diffracted light EY1 and the −1st order diffracted light EY2 in the Y direction by the pair of diffracted lights are generated from the diffraction grating 12, and the diffracted lights EY1 and EXY2 pass through the PBS surface of the PBS member 24Y and the reflecting portions 25YA and 25YB. Through the + X direction.

  Further, the reference light RY transmitted through the PBS member 24Y generates first and second reference lights RY1 and RY2 made of ± first-order diffracted light in the Y direction from the lattice pattern of the reference member 32Y. The reference beams RY1 and RY2 are transmitted through the PBS surface of the PBS member 24Y and reflected by the reflecting portions 25YA and 25YB. The reflected reference lights RY1 and RY2 are transmitted through the PBS surface of the PBS member 24Y and are incident on a pair of inclined reflecting surfaces of the reference member 32Y. The reference beams RY1 and RY2 reflected by the pair of reflecting surfaces are transmitted through the PBS surface of the PBS member 24Y and emitted in the + X direction through the reflecting portions 25YA and 25YB. One reference light RY1 is synthesized coaxially with the diffracted light EY1, passes through the polarizing plate 41YA and becomes interference light, and this interference light is received by the photoelectric sensor 40YB via the optical fiber 39YA. The other reference light RY2 is synthesized coaxially with the diffracted light EY2, passes through the polarizing plate 41YB and becomes interference light, and this interference light is received by the photoelectric sensor 40YB via the optical fiber 39YA.

  Also in the Y-axis interferometer unit 15Y, the optical path length difference between the diffracted beams EY1 and EY2 and the reference beams RY1 and RY2 is considerably small, and interference light with a high SN ratio can be obtained. Further, the amount of light of the diffracted beams EY1 and EY2 is reduced by two diffractions by the diffraction grating 12, whereas the reference beams RY1 and RY2 are diffracted only once by the reference member 32Y. , RY2 is significantly reduced in light quantity.

  In FIG. 1, the measurement calculation unit 42 includes a first calculation unit 42X, a second calculation unit 42Y, and a third calculation unit 42T. The X-axis photoelectric sensor 40XA supplies an interference light detection signal (photoelectric conversion signal) composed of the diffracted light EX1 and the reference light RX1 to the first calculation unit 42X, and the X-axis photoelectric sensor 40XB receives the diffracted light EX2. And the detection signal of the interference light which consists of reference light RX2 is supplied to the 1st calculating part 42X. The Y-axis photoelectric sensor 40YA supplies the interference light detection signal composed of the diffracted light EY1 and the reference light RY1 to the second calculation unit 42Y, and the Y-axis photoelectric sensor 40YB receives the diffracted light EY2 and the reference light RY2. The interference light detection signal is supplied to the second calculation unit 42Y. The first calculation unit 42X and the second calculation unit 42Y include a reference frequency signal (reference signal) from the laser light source 16 and a reference frequency signal (reference) of the reference interference light detected by the photoelectric sensor 40C. Signal) is also provided.

  Here, the X, Y, and Z direction relative movement amounts (relative displacements) between the first member 6 and the second member 7 are X, Y, Z, and the first calculation unit 42X and the second calculation unit 42Y. Assume that the obtained relative movement amounts in the Z direction are ZX and ZY, respectively. At this time, as an example, the first calculation unit 42X uses the detection coefficient and the reference signal (or reference signal) of the photoelectric sensor 40XA and the first relative movement amount in the X direction and the Z direction using the known coefficients a and b. (A · X + b · ZX) is obtained, and the second relative movement amount (−a · X + b · ZX) in the X direction and the Z direction is obtained from the detection signal and the reference signal (or reference signal) of the photoelectric sensor 40XB. A relative movement amount (X) in the X direction and a relative movement amount (ZX) in the Z direction are obtained from the first and second relative movement amounts, and the obtained results are supplied to the third calculation unit 42T. The second calculation unit 42Y obtains the first relative movement amount (a · Y + b · ZY) in the Y direction and the Z direction from the detection signal and the reference signal (or reference signal) of the photoelectric sensor 40YA, and detects the photoelectric sensor 40YB. The second relative movement amount (−a · Y + b · ZY) in the Y direction and the Z direction is obtained from the signal and the reference signal (or reference signal), and the relative movement in the Y direction is obtained from the first and second relative movement amounts. The amount (Y) and the relative movement amount (ZY) in the Z direction are obtained, and the obtained result is supplied to the third calculation unit 42T.

  The third calculation unit 42T calculates a value obtained by correcting the relative movement amounts (X) and (Y) supplied from the calculation units 42X and 42Y with a predetermined offset in the X direction of the first member 6 and the second member 7, Y Output as the amount of relative movement in the direction. In addition, as an example, the third calculation unit 42T calculates an average value (= (ZX + ZY) / 2) of the relative movement amounts (ZX) and (ZY) in the Z direction supplied from the calculation units 42X and 42Y with a predetermined offset. The corrected value is output as the relative movement amount in the Z direction between the first member 6 and the second member 7. The detection resolution of the relative movement amount in the X direction, the Y direction, and the Z direction is, for example, about 0.5 to 0.1 nm. In the encoder 10, since the optical paths of the measurement light MX, MY, etc. are short, short-term fluctuations in the measurement value due to the temperature fluctuation of the gas on the optical path can be reduced. Furthermore, since the interference light of the reference lights RX1 to RY2 corresponding to the + 1st order diffracted beams EX1 and EY1 and the −1st order diffracted beams EX2 and EY2 for the second time is finally detected, the detection resolution of the relative movement amount (detection accuracy) ) Can be improved to 1/2 (miniaturized). In addition, by using ± first-order diffracted light, measurement errors due to the relative rotation angles of the first member 6 and the second member 7 in the θz direction can be reduced.

Next, the optical path of the diffracted light of the measurement light of the detection head 14 of this embodiment will be described in detail.
FIG. 4 shows the main part of the X-axis interferometer unit 15X and the diffraction grating 12. In FIG. 4, the + 1st order diffracted light DX1 generated from the diffraction grating 12 by the measurement light MX becomes parallel to the measurement light MX (here, parallel to the Z axis) by the PBS surface A11 and the reflection portion 25XA of the PBS member 24X. And is incident again on the diffraction grating 12.

  At this time, it is assumed that the relative position in the Z direction of the grating pattern 12a of the diffraction grating 12 with respect to the interferometer unit 15X has changed by δZ to the position B11. At this time, the + 1st-order diffracted light DX1 by the measurement light MX is incident on the reflection part 25XA via the PBS surface A11 with the optical path shifted parallel to the position B12. However, in the reflection part 25XA, the optical path of the emitted light with respect to the incident light Shifts symmetrically about the center. For this reason, the diffracted light DX1 reflected by the reflecting portion 25XA and the PBS surface A11 has a diffraction grating 12 at a position that intersects the optical path of the + 1st order diffracted light EX1 when the relative position in the Z direction of the grating pattern surface 12b does not change. Is incident on. Therefore, even if the grating pattern surface 12b is changed to the position B11, the relative position in the Z direction of the grating pattern surface 12b of the optical path B13 of the + 1st order diffracted light EX1 generated from the diffraction grating 12 by the diffracted light DX1 is not changed. It is the same as the optical path of time. For this reason, when the interference light is generated by coaxially combining the diffracted light EX1 and the reference light RX1 on the PBS surface A2 (see FIG. 1), there is no relative lateral shift amount between the diffracted light EX1 and the reference light RX1. The ratio of the AC signal (beat signal or signal component) in the detection signal obtained when photoelectrically converting the interference light does not decrease.

  This also applies to the X-order −1st-order diffracted light DX2 and the Y-axis ± 1st-order diffracted lights DY1 and DY2, and even if the relative position in the Z direction of the grating pattern surface 12b changes, the photoelectric sensors 40XA to 40XA to The ratio of the beat signal in the 40YB detection signal does not decrease. Therefore, the relative movement amount between the first member 6 and the second member 7 can be measured with high accuracy at a high S / N ratio using these detection signals.

The effects and the like of this embodiment are as follows.
The encoder 10 of the present embodiment is a three-axis encoder device that measures the relative movement amount of a second member 7 that can be three-dimensionally moved relative to the first member 6 in the X, Y, and Z directions. . The encoder 10 is provided on the first member 6 and has a reflection type diffraction grating 12 having a grating pattern 12a whose periodic directions are the X direction and the Y direction, and a laser light source 16 that emits the measurement light MX and the reference light RX. A PBS member 24X (first optical) that is provided on the second member 7 and makes the measurement light MX enter the grating pattern surface 12b of the diffraction grating 12 substantially perpendicularly and emits the reference light RX in a direction different from the measurement light MX. Member) and reflection surfaces 32Xa and 32Xb that are provided on the second member 7 and reflect the reference lights RX1 and RX2 (light beams branched from the reference light RX) incident from the PBS member 24X, and the reference light RX is a diffraction grating. Reference member 32X (first reference member) which is deflected by substantially the same angle as the diffraction angle of the ± first-order diffracted light at 12 and is reflected toward the PBS member 24X as reference light RX1, RX2. It has a. Furthermore, the encoder 10 is provided on the second member 7 and ± 1st-order diffracted lights EX1 and EX2 generated in the X direction by two diffractions at the diffraction grating 12 by the measurement light MX are passed through the PBS member 24X. Reflecting portions 25XA and 25XB that generate first and second interference lights of the diffracted lights EX1 and EX2 and the reference lights RX1 and RX2 that are incident through the PBS member 24X and the first and second interferences thereof. Photoelectric sensors 40XA and 40XB that detect light, and a measurement calculation unit 42 (measurement) that obtains relative movement amounts of the first member 6 and the second member 7 in the X direction and the Z direction using detection signals of the photoelectric sensors 40XA and 40XB. Part).

  According to the present embodiment, the diffracted beams EX1 and EX2 and the reference beams RX1 and RX2 have a substantially common optical path in the PBS member 24X and the reflecting portions 25XA and 25XB, and the reference member 32X diffracts the reference beams RX1 and RX2. It is returned to the PBS member 24X at substantially the same angle as the ± 1st-order diffracted light at the grating 12. Accordingly, since the optical path length difference between the diffracted beams EX1 and EX2 and the reference beams RX1 and RX2 can be shortened, interference light with a high S / N ratio can be obtained and high measurement accuracy can be obtained, and the incident measurement beam MX and the reference beam RX can be obtained. A laser beam having a short coherent distance can be used. Furthermore, since the reference member 32X includes the reflecting surfaces 32Xa and 32Xb that reflect the reference beams RX1 and RX2 at substantially the same angle as the ± first-order diffracted beams from the diffraction grating 12, it is possible to suppress the light amount loss of the reference beam RX.

Further, if the relative positions of the first member 6 and the second member 7 in the X direction and the Y direction are fixed, the Z of the first member 6 and the second member 7 is detected from the detection signal of the photoelectric sensor 40XA. The relative movement amount in the direction can be measured.
Further, the laser light source 16 also generates the measurement light MY and the reference light RY, and the encoder 10 causes the measurement light MY to enter the grating pattern surface 12b of the diffraction grating 12 substantially perpendicularly, and the reference light RY becomes the measurement light MY. The PBS member 24Y that emits in different directions and the second member 7 are provided to reflect the reference light RY incident from the PBS member 24Y as the reference light RY1 and RY2 toward the PBS member 24Y through the grating pattern and the reflecting surface. And a reference member 32Y. Further, the encoder 10 is provided on the second member 7, and ± 1st-order diffracted lights EY1, EY2 generated in the Y direction by two diffractions at the diffraction grating 12 by the measurement light MY are passed through the PBS member 24Y. Reflecting portions 25YA and 25YB that generate the third and fourth interference lights of the incident diffracted light and the reference lights RY1 and RY2 that enter through the PBS member 24Y, and the third and fourth interference lights. Photoelectric sensors 40YA and 40YB for detecting And the measurement calculating part 42 calculates | requires the relative movement amount of the X direction of the 1st member 6 and the 2nd member 7, the Y direction, and the Z direction using the detection signal of photoelectric sensor 40XA, 40XB, 40YA, 40YB. Yes.

Accordingly, since the optical path length difference between the diffracted beams EY1 and EY2 and the reference beams RY1 and RY2 can be shortened, interference light with a high S / N ratio can be obtained and high measurement accuracy can be obtained. Furthermore, since the reference member 32Y has a reflecting surface that reflects the reference beams RY1 and RY2 at substantially the same angle as the ± first-order diffracted beams from the diffraction grating 12, it is possible to suppress the light amount loss of the reference beam RY.
In the above embodiment, the following modifications are possible.

  In the above-described embodiment, the two-dimensional diffraction grating 12 is used. However, a one-dimensional diffraction grating having periodicity only in the X direction may be used instead of the diffraction grating 12. In this case, the Y-axis interferometer unit 15Y and the photoelectric sensors 40YA and 40YB are omitted from the detection head 14, and the X of the first member 6 and the second member 7 is detected using the detection signals of the photoelectric sensors 40XA and 40XB. The relative movement amount in the direction and the Z direction can be measured.

  In the above embodiment, the measurement lights MX and MY are light beams having the same first polarization direction, and the reference lights RX and RY are light beams having the same second polarization direction, but the measurement light MX and the reference light. RY may be a light beam having the same first polarization direction, and measurement light MY and reference light RX may be a light beam having the second polarization direction having the same polarization direction. In this case, the light quantity ratio between the measurement light MX and the reference light RY is set so that the measurement light MX becomes large, and the light quantity ratio between the measurement light MY and the reference light RX is set so that the measurement light MY becomes large. In the final stage of interference light, the light quantity ratio between the measurement light MX (diffracted light) and the reference light RX (the light quantity ratio between the measurement light MY (diffracted light) and the reference light RY) is set to approximately 1: 1. Also good. As a result, the amount of diffracted light generated from the diffraction grating 12 can be increased, and the SN ratio of interference light can be further improved.

  In the above-described embodiment, the interference light between the diffracted beams EX1 and EX2 and the reference beams RX1 and RX2 generated by the diffraction grating 12 by the diffraction twice is detected in the X-axis interferometer unit 15X. You may detect the interference light of the diffracted light DX1, DX2 and the reference light RX1, RX2 which generate | occur | produced by 1 time of diffraction with the grating | lattice 12. FIG. However, in this case, as the reference member 32X, an optical member having a beam splitter surface and a reflection surface, which branches the incident reference light RX into the reference light RX1, RX2 and reflects it at the same angle as the diffracted light DX1, DX2. Is used. The same applies to the Y-axis interferometer unit 15Y.

  In the above embodiment, as shown in FIG. 2A, the diffracted lights DX1, DX2 and EX1, EX2 generated from the diffraction grating 12 are accurately S-polarized with respect to the PBS surface A11 of the PBS member 24X. There is a risk of light loss. Accordingly, wave plates 35XA, 35XC, and 35XB that can adjust the rotation angle of, for example, a half-wave plate for adjusting the polarization direction in the optical paths of the diffracted beams DX1, DX2 and EX1, EX2 generated from the diffraction grating 12, respectively. 35XD may be installed. In this case, by adjusting the rotation angle of the wave plates 35XA to 35XD so that the reflectance of the diffracted light DX1 to EX2 on the PBS surface A11 is maximized, for example, the light loss of the diffracted lights DX1 to EX2 can be minimized.

  Similarly, as shown in FIG. 3B, the reference lights RX1 and RX2 made of diffracted light or reflected light generated from the reference member 32X are accurately P-polarized with respect to the PBS surface A11 of the PBS member 24X. Therefore, there is a risk of light loss. Therefore, the rotation angle formed by, for example, a half-wave plate for adjusting the polarization direction is respectively provided in the optical paths of the diffracted light (reference light RX1, RX2) and the reflected light (reference light RX1, RX2) generated from the reference member 32X. Adjustable wave plates 35RA, 35RC, 35RB, and 35RD may be installed. In this case, by adjusting the rotation angle of the wave plates 35RA to 35RD so that, for example, the transmittance of the diffracted light or reflected light through the PBS surface A11 is maximized, the light loss of the diffracted light and reflected light can be minimized.

It should be noted that there is an effect that it is possible to reduce the light amount loss by providing at least one wave plate 35XA to 35XD and one wave plate 35RA to 35RD.
In the above embodiment, the measurement light MX is S-polarized light and the reference light RX is P-polarized light with respect to the PBS surface A11 of the PBS member 24X. However, the measurement light MX is P-polarized light and reference light with respect to the PBS surface A11. RX may be S-polarized light. In this case, the measurement light MX is transmitted through the PBS surface A11, and the reference light RX is reflected by the PBS surface A11.

In the above embodiment, the reflecting portions 25XA and 25XB have the roof prisms 26XA and 26XB, but a roof mirror having a pair of orthogonal reflecting surfaces may be used instead of the roof prisms 26XA and 26XB. Similarly, a plane mirror may be used as the reflecting members 28XA and 30XA. Thereby, the interferometer part 15X may be reduced in weight.
Next, as shown by the interferometer unit 15XA of the first modified example of FIG. 5, as a reference member, a first reference member 32XA having a grating pattern 32Xg with a period p and a reflecting surface 32Xc parallel to the XZ plane, and a reflecting surface A pair of wedge prisms 33XA and 33XB disposed between 32Xc and the PBS member 24X may be used. 5, parts corresponding to those in FIG. 3A are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 5, the reference light RX transmitted through the PBS surface A11 of the PBS member 24X is incident substantially perpendicularly to the grating pattern 32Xg of the first reference member 32XA, and is composed of ± first-order diffracted light in the X direction from the grating pattern 32Xg. RX1 and RX2 are generated. The reference beams RX1 and RX2 are reflected through the PBS member 24X and the reflecting portions 25XA and 25XB, then pass through the PBS surface A11, and the optical path of the diffraction angle φx is halved by the wedge-shaped prisms 33XA and 33XB in the ± X direction. And is incident on the reflecting surface 32Xc of the first reference member 32XA. Then, the reference lights RX1 and RX2 reflected by the reflecting surface 32Xc enter the PBS member 24X along the same optical path as in the case of FIG. Other configurations and effects are the same as those in the above embodiment. Accordingly, the interferometer unit 15XA can also suppress the light amount loss of the reference beams RX1 and RX2.

  Next, as shown by an interferometer portion 15XB of the second modification of FIG. 6A, as a reference member, a grating pattern 32Xg having a period p, a pair of concave refracting surfaces 33XBa, 33XBc, and A reference member 32XB having a pair of reflecting surfaces 33XBb and 33XBd on the bottom surface side of the refracting surfaces 33XBa and 33XBc may be used. 6A, parts corresponding to those in FIG. 3A are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 6A, the reference light RX transmitted through the PBS surface A11 of the PBS member 24X is incident substantially perpendicularly to the grating pattern 32Xg of the reference member 32XB, and is composed of ± first-order diffracted light in the X direction from the grating pattern 32Xg. Lights RX1 and RX2 are generated. The reference beams RX1 and RX2 are reflected through the PBS member 24X and the reflecting portions 25XA and 25XB, and then pass through the PBS surface A11 and enter the refractive surfaces 33XBa and 33XBc of the reference member 32XB.

  As shown in FIG. 6B, the reference beams RX1 and RX2 that are refracted by being incident on the refracting surfaces 33XBa and 33XBc are reflected by the reflecting surfaces 33XBb and 33XBd on the bottom surface along the optical paths B9A and B9B. The light is again refracted by the refracting surfaces 33XBa and 33XBc. Then, the reference beams RX1 and RX2 refracted and emitted by the refracting surfaces 33XBa and 33XBc are incident on the PBS member 24X along the same optical path as in FIG. Therefore, the refractive index of the reference member 32XB, the positions and angles of the refracting surfaces 33XBa, 33XBc, and the positions and angles of the reflecting surfaces 33XBb, 33XBd The direction is set so as to correspond to the positions and directions of the ± first-order diffracted beams EX1 and EX2 generated from the diffraction grating 12 of FIG. Other configurations and effects are the same as those in the above embodiment. Accordingly, the interferometer unit 15XB can also suppress the light amount loss of the reference beams RX1 and RX2.

  Next, as shown in the interferometer section 15XC of the third modification of FIG. 7A, as a reference member, a reflective surface 32XCa inclined at an angle φx / 2, and 1 of the same inclination angle as that in FIG. A first reference member 32XC having a pair of reflection surfaces 32Xa and 32Xb and a second reference member 34X having a half mirror surface and a plurality of reflection surfaces may be used. In FIG. 7A, parts corresponding to those in FIG. 3A are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 7A, the reference light RX transmitted through the PBS surface A11 of the PBS member 24X is incident on the second reference member 34X.

  In FIG. 7B, the incident reference light RX includes the first reference light RX1 directed substantially in the −Y direction on the half mirror surface 34Xa of the second reference member 34X, and the second reference light RX2 reflected at an angle −φx. And divided. 7B is a surface having the same height as the grating pattern 32Xg in FIG. 3B, and the angle φx is a diffraction angle in the diffraction grating 12 on which the measurement light MX is incident. is there. The first reference light RX1 transmitted through the half mirror surface 34Xa is reflected by the reflecting surface 32XCa of the first reference member 32XC in a direction crossing the incident reference light RX at an angle φx, and enters the PBS member 24X. . The second reference light RX2 reflected by the half mirror surface 34Xa of the second reference member 34X is reflected by the reflecting surfaces 34Xb and 34Xc parallel to the half mirror surface 34Xa, and then reflected by the reference light RX2 reflected by the reflecting surface 34Xc. The light passes through the vertical exit surface 34Xd and enters the PBS member 24X at an angle −φx with respect to the incident reference light RX.

  The reference lights RX1 and RX2 are reflected through the PBS member 24X and the reflecting portions 25XA and 25XB, and then pass through the PBS surface A11 and enter the reflecting surfaces 32Xa and 32Xb of the first reference member 32XC. The reference lights RX1 and RX2 reflected by the reflecting surfaces 32Xa and 32Xb are incident on the PBS member 24X along the same optical path as in FIG. Other configurations and effects are the same as those in the above embodiment. In addition, the shape of the second reference member 34X (the optical path length of the reference light RX2 therein) is set to be the same as the optical path length of the reference light RX1. Therefore, also in the interferometer unit 15XC, the difference in optical path length between the diffracted beams EX1 and EX2 and the reference beams RX1 and RX2 can be shortened, and the SN ratio of the interference beam can be increased. Further, in the interferometer unit 15XC, the reference beams RX1 and RX2 are not diffracted by the grating pattern, and are returned to the PBS member 24X only through the reflection surface, so that the light amount loss of the reference beams RX1 and RX2 is reduced. Can be the smallest.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. FIG. 8 shows a schematic configuration of an exposure apparatus EX including the encoder apparatus according to this embodiment. The exposure apparatus EX is a scanning exposure type projection exposure apparatus composed of a scanning stepper. The exposure apparatus EX includes a projection optical system PL (projection unit PU). Hereinafter, the Z-axis is parallel to the optical axis AX of the projection optical system PL, and a plane orthogonal to the Z-axis (a plane substantially parallel to the horizontal plane). In the following description, the Y axis is taken in the direction in which the reticle R and the wafer W are relatively scanned, and the X axis is taken in the direction perpendicular to the Z axis and the Y axis.

  The exposure apparatus EX includes an illumination system 110 disclosed in, for example, US Patent Application Publication No. 2003/0025890, and illumination light (exposure light) IL (for example, an ArF excimer laser having a wavelength of 193 nm) from the illumination system 110 A reticle stage RST that holds a reticle R (mask) illuminated by light, a harmonic of a solid-state laser (such as a semiconductor laser). Further, the exposure apparatus EX includes a projection unit PU including a projection optical system PL that projects the illumination light IL emitted from the reticle R onto the wafer W (substrate), a stage apparatus 195 including a wafer stage WST that holds the wafer W, and A control system or the like (see FIG. 10) is provided.

  The reticle R is held on the upper surface of the reticle stage RST by vacuum suction or the like, and a circuit pattern or the like is formed on the pattern surface (lower surface) of the reticle R. The reticle stage RST can be driven minutely in the XY plane by the reticle stage drive system 111 of FIG. 9 including a linear motor, for example, and can be driven at a scanning speed specified in the scanning direction (Y direction).

  Position information in the moving plane of the reticle stage RST (including the position in the X direction, the Y direction, and the rotation angle in the θz direction) is transferred to the moving mirror 115 (or mirror-finished) by the reticle interferometer 116 including a laser interferometer. For example, it is always detected with a resolution of about 0.5 to 0.1 nm via the stage end face. The measurement value of reticle interferometer 116 is sent to main controller 120 formed of a computer shown in FIG. Main controller 120 controls reticle stage drive system 111 based on the measurement value, thereby controlling the position and speed of reticle stage RST.

  In FIG. 8, the projection unit PU disposed below the reticle stage RST includes a lens barrel 140 and a projection optical system PL having a plurality of optical elements held in a predetermined positional relationship within the lens barrel 140. The projection optical system PL is, for example, telecentric on both sides and has a predetermined projection magnification β (for example, a reduction magnification of 1/4 times, 1/5 times, etc.). When the illumination area IAR of the reticle R is illuminated by the illumination light IL from the illumination system 110, an image of the circuit pattern of the reticle R in the illumination area IAR via the projection optical system PL by the illumination light IL that has passed through the reticle R. Are formed in an exposure area IA (an area conjugate to the illumination area IAR) of one shot area of the wafer (semiconductor wafer) W.

  In addition, since the exposure apparatus EX performs exposure using the liquid immersion method, the lower end of the lens barrel 140 that holds the tip lens 191 that is an optical element on the most image plane side (wafer W side) constituting the projection optical system PL is used. A nozzle unit 132 constituting a part of the local liquid immersion device 108 is provided so as to surround the periphery of the part. The nozzle unit 132 is connected to a liquid supply device 186 and a liquid recovery device 189 (see FIG. 10) via a supply tube 131A and a recovery tube 131B for supplying an exposure liquid Lq (for example, pure water). . If the immersion type exposure apparatus is not used, the local immersion apparatus 108 may not be provided.

  Wafer stage WST is supported in a non-contact manner on upper surface 112a parallel to the XY plane of base board 112 via a plurality of, for example, vacuum preload type static air bearings (air pads) (not shown). Wafer stage WST can be driven in the X and Y directions by a stage drive system 124 (see FIG. 10) including, for example, a planar motor or two sets of orthogonal linear motors. The exposure apparatus EX includes an aerial image measurement system (not shown) that aligns the reticle R, an alignment system AL (see FIG. 10) that aligns the wafer W, an irradiation system 90a, and a light receiving system 90b. An oblique incidence type multi-point autofocus sensor 90 (see FIG. 10) for measuring the Z position of the location, and an encoder device 8B for measuring position information of the wafer stage WST are provided.

  Wafer stage WST is provided in stage main body 191, stage main body 191 driven in X and Y directions, wafer table WTB mounted on stage main body 191, and wafer table WTB (wafer for stage main body 191). And a Z / leveling mechanism that relatively finely drives the position of W) in the Z direction and the tilt angle in the θx direction and the θy direction. A wafer holder (not shown) that holds the wafer W on a suction surface substantially parallel to the XY plane by vacuum suction or the like is provided at the upper center of the wafer table WTB.

In addition, the upper surface of wafer table WTB has a surface (or a protective member) that has been subjected to a liquid repellency treatment with respect to liquid Lq and is substantially flush with the surface of the wafer placed on the wafer holder. A flat plate member 128 having a high flatness is provided in which a circular opening is formed in the center of the rectangular shape and a circular opening that is slightly larger than the wafer holder (wafer mounting region).
In the configuration of the so-called immersion type exposure apparatus provided with the above-mentioned local immersion apparatus 108, the plate body 128 is further shown in the plan view of the wafer table WTB (wafer stage WST) in FIG. In addition, a plate portion (liquid repellent plate) 128a surrounding the circular opening and having a liquid repellent treatment on a surface having a rectangular outer shape (outline), and a peripheral portion 128e surrounding the plate portion 128a. A pair of two-dimensional diffraction gratings 12A and 12B elongated in the X direction so as to sandwich the plate portion 128a in the Y direction is disposed on the upper surface of the peripheral portion 128e, and elongated in the Y direction so as to sandwich the plate portion 128a in the X direction. A pair of two-dimensional diffraction gratings 12C and 12D are arranged. The diffraction gratings 12 </ b> A to 12 </ b> D are reflection type diffraction gratings in which a two-dimensional grating pattern having a periodic direction in the X direction and the Y direction is formed as in the diffraction grating 12 of FIG. 1.

  In FIG. 8, a flat measurement frame 150 substantially parallel to the XY plane is supported on a frame (not shown) that supports the projection unit PU via a connecting member (not shown). A plurality of detection heads 14 having the same configuration as the triaxial detection head 14 in FIG. 1 are fixed to the bottom surface of the measurement frame 150 so as to sandwich the projection optical system PL in the X direction, and the projection optical system PL is sandwiched in the Y direction. As described above, a plurality of detection heads 14 having the same configuration as the detection head 14 of FIG. 1 are fixed (see FIG. 9). Further, one or a plurality of laser light sources (not shown) similar to the laser light source 16 of FIG. 1 for supplying laser light (measurement light and reference light) to the plurality of detection heads 14 are also provided.

  In FIG. 9, during the period in which the wafer W is exposed with the illumination light from the projection optical system PL, any two of the plurality of detection heads 14 in one row A1 in the Y direction always face the diffraction gratings 12A and 12B. Any two of the plurality of detection heads 14 in one row A2 in the X direction are configured to face the diffraction gratings 12C and 12D. Each of the detection heads 14 in the row A1 irradiates the diffraction grating 12A or 12B with measurement light, and the corresponding measurement calculation unit 42 (corresponding to a detection signal of interference light between the diffraction light generated from the diffraction gratings 12A and 12B and the reference light (See FIG. 10). In these measurement calculation units 42, as in the measurement calculation unit 42 in FIG. 1, the relative positions (relative movement amounts) of the wafer stage WST and the measurement frame 150 in the X direction, the Y direction, and the Z direction are set to 0.5 to, for example. Each measurement value is obtained with a resolution of 0.1 nm and supplied to the switching unit 80A. In the measurement value switching unit 80A, information on the relative position supplied from the measurement calculation unit 42 corresponding to the detection head 14 facing the diffraction gratings 12A and 12B is supplied to the main controller 120.

  Each detection head 14 corresponding to one row A2 irradiates the diffraction grating 12C or 12D with measurement light, and performs a measurement calculation corresponding to a detection signal of interference light between the diffraction light generated from the diffraction gratings 12C and 12D and the reference light. It supplies to the part 42 (refer FIG. 10). In these measurement calculation units 42, as in the measurement calculation unit 42 in FIG. 1, the relative positions (relative movement amounts) of the wafer stage WST and the measurement frame 150 in the X direction, the Y direction, and the Z direction are set to 0.5 to, for example. Obtained with a resolution of 0.1 nm and supplied to the measured value switching unit 80B. In the measurement value switching unit 80B, information on the relative position supplied from the measurement calculation unit 42 corresponding to the detection head 14 facing the diffraction gratings 12C and 12D is supplied to the main controller 120.

  A plurality of detection heads 14 in one row A1, a laser light source (not shown), a measurement calculation unit 42, and diffraction gratings 12A and 12B constitute a three-axis encoder 10A. The plurality of detection heads 14 in one row A2 and the laser light source (Not shown), the measurement calculation unit 42, and the diffraction gratings 12C and 12D constitute a three-axis encoder 10B. The encoder device 8B is composed of the three-axis encoders 10A and 10B and the measurement value switching units 80A and 80B. Based on the information on the relative position supplied from encoder device 8B, main controller 120 determines the position of wafer stage WST relative to measurement frame 150 (projection optical system PL) in the X, Y, and Z directions, and in the θz direction. Information such as the rotation angle is obtained, and wafer stage WST is driven via stage drive system 124 based on this information.

  Then, at the time of exposure by the exposure apparatus EX, alignment of the reticle R and the wafer W is first performed. Thereafter, irradiation of the reticle R with the illumination light IL is started, and an image of a part of the pattern of the reticle R is projected onto one shot area on the surface of the wafer W via the projection optical system PL, while the reticle stage RST. The pattern image of the reticle R is transferred to the shot area by a scanning exposure operation that moves the wafer stage WST in synchronization with the Y direction using the projection magnification β of the projection optical system PL as a speed ratio (synchronous scanning). Thereafter, by repeating the step movement of the wafer W in the X and Y directions via the wafer stage WST and the scanning exposure operation described above, the entire wafer W is immersed by the immersion method and the step-and-scan method. The pattern image of the reticle R is transferred to the shot area.

  At this time, in the detection head 14 of the encoder device 8B, since the optical path lengths of the measurement light and the diffracted light are shorter than those of the laser interferometer, the influence of the air fluctuation on the measurement value using the detection head 14 is very small. Accordingly, the encoder device 8B of the present embodiment has much better measurement stability (short-term stability) in a short period of time when the air fluctuates than the laser interferometer. Can be transferred to W with high accuracy. Furthermore, since the detection head 14 can always detect a signal including the upper portion of the relative movement amount with a high SN ratio even if the Z positions of the diffraction gratings 12A to 12D change, the wafer stage WST can always be driven with high accuracy.

In the present embodiment, the detection head 14 is arranged on the measurement frame 150 side, and the diffraction gratings 12A to 12D are arranged on the wafer stage WST side. As another configuration, the diffraction gratings 12A to 12D may be arranged on the measurement frame 150 side, and the detection head 14 may be arranged on the wafer stage WST side.
Further, when an electronic device (or a micro device) such as a semiconductor device is manufactured using the exposure apparatus EX or the exposure method of the above embodiment, the electronic device has a function / performance design of the electronic device as shown in FIG. Step 221 for performing a step, Step 222 for fabricating a reticle (mask) based on this design step, Step 223 for fabricating a substrate (wafer) as a base material of the device and applying a resist, and the exposure apparatus ( Substrate processing step 224 including a step of exposing a reticle pattern to a substrate (photosensitive substrate) by an exposure method), a step of developing the exposed substrate, a heating (curing) and etching step of the developed substrate, and a device assembly step (dicing) (Including processing processes such as processes, bonding processes, and packaging processes) 22 And an inspection step 226, and the like.

  In other words, this device manufacturing method includes a lithography process in which an image of a reticle pattern is transferred to a substrate (wafer) using the exposure apparatus EX (exposure method) of the above embodiment, and the pattern is developed. And a step (such as etching in step 224) of processing the substrate on which the image is transferred on the basis of the image of the pattern. At this time, according to the above-described embodiment, the position of wafer stage WST of the exposure apparatus can be controlled with high accuracy, so that an electronic device can be manufactured with high accuracy.

The present invention can be applied to a step-and-repeat type projection exposure apparatus (stepper or the like) in addition to the above-described scanning exposure type projection exposure apparatus (scanner). Furthermore, the present invention can be similarly applied to a dry exposure type exposure apparatus other than an immersion type exposure apparatus.
In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure apparatus when manufacturing a mask (photomask, reticle, etc.) on which a mask pattern of various devices is formed using a photolithography process.

In addition, the encoder 10 of the above-described embodiment moves an optical system for an object to be inspected or processed (such as an optical system for condensing laser light) such as an inspection apparatus or a measurement apparatus other than the exposure apparatus, and the object. In an optical device provided with a moving device (such as a stage), the present invention can be applied to measure the relative movement amount of the moving device (object) with respect to the optical system, for example.
In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

  EX ... exposure apparatus, R ... reticle, W ... wafer, MX, MY ... measurement light, RX, RY ... reference light, DX1, EX1 ... + 1st order diffracted light, DX2, EX2 ...- 1st order diffracted light, RX1, RX2 ... reference light , 6 ... 1st member, 7 ... 2nd member, 10 ... Encoder, 12 ... Two-dimensional diffraction grating, 14 ... Detection head, 15X, 15Y ... Interferometer section, 16 ... Laser light source, 24X, 24Y ... PBS (polarization) Beam splitter) member, 25XA, 25XB, 25YA, 25YB ... reflecting part, 32X, 32Y ... reference member, 40XA, 40XB, 40YA, 40YB ... photoelectric sensor, 42 ... measurement calculation part

Claims (14)

An encoder device for measuring a relative movement amount between a first member and a second member supported so as to be relatively movable in at least a first direction with respect to the first member,
A reflective diffraction grating provided on the first member and having a grating pattern having at least the first direction as a periodic direction;
A light source unit for emitting measurement light and reference light;
A first optical member that is provided on the second member, causes the measurement light to enter the grating pattern surface of the diffraction grating substantially perpendicularly, and emits the reference light in a direction different from the measurement light;
The second member has at least one reflecting surface that reflects the reference light incident from the first optical member or a light beam branched from the reference light, and the reference light is different from each other in the diffraction grating. A first reference member deflected by approximately the same angle as two diffraction angles and reflected toward the first optical member as first and second reference beams;
The first and second diffracted lights of different orders, which are provided on the second member and are generated from the diffraction grating with respect to the first direction by the measurement light, enter through the first optical member, and First and second reflecting portions that generate first and second interference lights of the first and second diffracted lights and the first and second reference lights incident via the first optical member;
First and second photoelectric detectors for detecting the first and second interference lights, respectively;
A measurement unit for obtaining a relative movement amount between the first member and the second member using detection signals of the first and second photoelectric detectors;
An encoder device comprising:   The first reflection unit causes the first and second diffracted light generated from the diffraction grating to enter the diffraction grating via the first optical member, and causes the first and second reference lights to enter the first optical element. Diffracted light that is incident on the first reference member through a member and is generated from the diffraction grating with respect to the first direction by the first and second diffracted light, and the first and second diffracted light returned from the first reference member. The encoder apparatus according to claim 1, wherein interference light with two reference lights is generated. The first reference member includes a reference grating pattern having a period in a direction corresponding to the first direction that is the same as a period in the first direction of the grating pattern of the diffraction grating, and a reference reflector having at least one reflecting surface. Have
Two diffracted lights of different orders generated from the reference grating pattern in a direction corresponding to the first direction by the reference light incident from the first optical member become the first and second reference lights,
The first and second reference lights that are incident on the reference reflector through the first optical member and the first and second reflectors, and that are incident on the reference reflector. The encoder device according to claim 2, wherein light is returned to the first optical member.   The reference reflection unit includes first and second reflection surfaces that reflect the first and second reference lights to the first optical member in parallel with the two diffracted lights from the reference grating pattern. The encoder device according to claim 3. The reference reflecting portion has one reflecting surface,
The first reference member includes first and second deflecting units that change incident angles of the first and second reference lights that are incident on the reflecting surface of the reference reflecting unit from the first optical member. The encoder device according to claim 3.   The first reference member reflects the reference light incident from the first optical member and the first and second reference light incident from the first optical member to the first optical member side, respectively. The encoder apparatus according to claim 2, further comprising: 2 and a third reflecting surface, and at least one branch surface that branches a part of the reference light. The first reflecting portion includes a first light flux reflecting member having two orthogonal reflecting surfaces that reflect the first diffracted light,
The encoder device according to claim 1, wherein the second reflecting unit includes a second light flux reflecting member having two orthogonal reflecting surfaces that reflect the second diffracted light. . The light source unit emits the measurement light and the reference light as light having different polarization states,
The encoder device according to claim 1, wherein the first optical member includes a polarization beam splitter surface that separates the measurement light and the reference light.   It comprises at least one wave plate for adjusting a polarization direction of at least one light beam of the first and second diffracted lights and the first and second reference lights incident on the first optical member. The encoder device according to claim 8. The diffraction grating is a two-dimensional reflection type diffraction grating whose periodic direction is the first direction and a second direction orthogonal to the first direction;
A second optical member that is provided on the second member, causes the measurement light to enter the grating pattern surface of the diffraction grating substantially perpendicularly, and emits the reference light in a direction different from the measurement light;
The third member is provided on the second member, has at least one reflecting surface, and deflects the reference light incident from the second optical member by approximately the same angle as two different diffraction angles in the diffraction grating. A second reference member that reflects toward the second optical member as four reference light;
Third and fourth diffracted lights of different orders, which are provided on the second member and are generated from the diffraction grating in the second direction by the measurement light, enter through the second optical member, and 3rd and 4th refracting parts which generate the 3rd and 4th interference light of the 3rd and 4th diffracted light, and the 3rd and 4th reference lights which enter via the 2nd optical member,
A third and a fourth photoelectric detector for detecting the third and fourth interference light, respectively,
The measurement unit obtains a relative movement amount between the first member and the second member using detection signals of the first, second, third, and fourth photoelectric detectors. The encoder apparatus as described in any one of 1-9.   The measurement unit obtains a relative movement amount between the first member and the second member in the first direction, the second direction, and a third direction perpendicular to a grating pattern surface of the diffraction grating. The encoder device according to claim 10. The encoder device according to any one of claims 1 to 11,
And an optical system for an object. An exposure apparatus that exposes a pattern onto an object to be exposed,
Frame,
A stage that supports the object to be exposed and is relatively movable in at least a first direction with respect to the frame;
An exposure apparatus comprising: the encoder device according to any one of claims 1 to 11 for measuring at least a relative movement amount of the stage in the first direction. A device manufacturing method including a lithography process,
14. A device manufacturing method, comprising: exposing an object using the exposure apparatus according to claim 13 in the lithography process.

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