LINE NARROWING MODULE, GAS LASER DEVICE, AND ELECTRONIC DEVICE MANUFACTURING METHOD

A line narrowing module includes: a prism; a mirror including a reflective surface, first and second adjacent surfaces, and an opposing surface; a grating wavelength-dispersing light reflected by the reflective surface; a holding part holding the mirror; a first adhesive provided between the holding part and the first adjacent surface or between the holding part and the opposing surface and bonding the mirror to the holding part; a second adhesive provided between the holding part and the second adjacent surface and bonding the mirror to the holding part; and a driving unit rotating the holding part to rotate the mirror about an axis perpendicular to a plane where the light is wavelength-dispersed. The second adhesive is located on an opposite side of the first adhesive with respect to a center line of the mirror in parallel to the axis.

BACKGROUND

1. Technical Field

The present disclosure relates to a line narrowing module, a gas laser device, and an electronic device manufacturing method.

2. Related Art

Recently, in a semiconductor exposure device, improvement in resolution has been desired for miniaturization and high integration of semiconductor integrated circuits. For this purpose, an exposure light source that outputs light having a shorter wavelength has been developed. For example, as the gas laser device for exposure, a KrF excimer laser device that outputs a laser beam having a wavelength of about 248.0 nm and an ArF excimer laser device that outputs a laser beam having a wavelength of about 193.4 nm are used.

Spectral linewidths of natural oscillation beams of the KrF excimer laser device and the ArF excimer laser device are as wide as from 350 pm to 400 pm. Therefore, when a projection lens is composed of a material that transmits ultraviolet light such as KrF laser beam and ArF laser beam, chromatic aberration may occur. As a result, the resolution may decrease. Given this, a spectral line width of laser beam output from the gas laser device needs to be narrowed to the extent that the chromatic aberration is ignorable. Therefore, in the laser resonator of the gas laser device, a line narrowing module (Line Narrow Module: LNM) including a line narrowing element (etalon or grating, etc.) may be provided in order to narrow the spectral linewidth. Hereinafter, a gas laser device with a narrowed spectral line width is referred to as a line narrowing gas laser device.

LIST OF DOCUMENTS

Patent Documents

SUMMARY

A line narrowing module according to an aspect of the present disclosure may include a prism; a mirror including a reflective surface, a first adjacent surface and a second adjacent surface adjacent to the reflective surface, and an opposing surface opposed to the reflective surface, the reflective surface reflecting light transmitted through the prism; a grating that wavelength-disperses the light reflected by the reflective surface; a holding part that holds the mirror; a first adhesive provided between the holding part and the first adjacent surface or between the holding part and the opposing surface and bonding the mirror to the holding part; a second adhesive provided between the holding part and the second adjacent surface and bonding the mirror to the holding part; and a driving unit configured to rotate the holding part so that the mirror rotates about an axis perpendicular to a plane in which the light is wavelength-dispersed. The second adhesive may be located on an opposite side of the first adhesive with respect to a center line which passes through a center of the mirror in parallel to the axis when the reflective surface is viewed from the front.

A gas laser device according to an aspect of the present disclosure may be provided with a line narrowing module, the line narrowing module including a prism; a mirror including a reflective surface, a first adjacent surface and a second adjacent surface adjacent to the reflective surface, and an opposing surface opposed to the reflective surface, the reflective surface reflecting light transmitted through the prism; a grating that wavelength-disperses the light reflected by the reflective surface; a holding part that holds the mirror; a first adhesive provided between the holding part and the first adjacent surface or between the holding part and the opposing surface and bonding the mirror to the holding part; a second adhesive provided between the holding part and the second adjacent surface and bonding the mirror to the holding part; and a driving unit configured to rotate the holding part so that the mirror rotates about an axis perpendicular to a plane in which the light is wavelength-dispersed. The second adhesive may be located on an opposite side of the first adhesive with respect to a center line which passes through a center of the mirror in parallel to the axis when the reflective surface is viewed from the front.

A method of manufacturing an electronic device according to an aspect of the present disclosure may include: generating a laser beam by a gas laser device provided with a line narrowing module, the line narrowing module including a prism, a mirror including a reflective surface, a first adjacent surface and a second adjacent surface adjacent to the reflective surface, and an opposing surface opposed to the reflective surface, the reflective surface reflecting light transmitted through the prism, a grating that wavelength-disperses the light reflected by the reflective surface, a holding part that holds the mirror, a first adhesive provided between the holding part and the first adjacent surface or between the holding part and the opposing surface and bonding the mirror to the holding part, a second adhesive provided between the holding part and the second adjacent surface and bonding the mirror to the holding part, and a driving unit configured to rotate the holding part so that the mirror rotates about an axis perpendicular to a plane in which the light is wavelength-dispersed, the second adhesive being located on an opposite side of the first adhesive with respect to a center line which passes through a center of the mirror in parallel to the axis when the reflective surface is viewed from front; outputting the laser beam to an exposure device; and exposing a photosensitive substrate to the laser beam in the exposure device to produce the electronic device.

DESCRIPTION OF EMBODIMENTS

1. Description of Electronic Device Manufacturing Apparatus Used in Exposure Process of Electronic Device

2. Description of Gas Laser Device of Comparative Example

3. Description of Line Narrowing Module of First Embodiment

3.2 Function and Effect

4. Description of Line Narrowing Module of Second Embodiment

4.2 Function and Effect

5. Description of Line Narrowing Module of Third Embodiment

5.2 Function and Effect

6. Description of Line Narrowing Module of Fourth Embodiment

6.2 Function and Effect

7. Description of Line Narrowing Module of Fifth Embodiment

7.2 Function and Effect

8. Description of Line Narrowing Module of Sixth Embodiment

8.2 Function and Effect

The embodiments described below show some examples of the present disclosure and do not limit the contents of the present disclosure. In addition, all configurations and operation described in the embodiments are not necessarily essential as configurations and operation of the present disclosure. Here, the same components are denoted by the same reference numerals, and redundant description thereof is omitted.

1. Description of Electronic Device Manufacturing Apparatus Used in Exposure Process of Electronic Device

FIG.1is a schematic diagram illustrating an overall configuration example of an electronic device manufacturing apparatus used in an exposure process of an electronic device. As shown inFIG.1, the manufacturing apparatus used in the exposure process includes a gas laser device100and an exposure device200. The exposure device200includes an illumination optical system210including a plurality of mirrors211,212, and213and a projection optical system220. The illumination optical system210illuminates a reticle pattern of a reticle stage RT by the laser beam entering from the gas laser device100. The projection optical system220performs reduction projection of the laser beam transmitted through the reticle and forms an image on a workpiece (not illustrated) disposed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer on which photoresist is applied. The exposure device200synchronously translates the reticle stage RT and the workpiece table WT to expose the workpiece to a laser beam reflecting the reticle pattern. Through the exposure process as described above, a device pattern is transferred onto the semiconductor wafer, whereby a semiconductor device, which is an electronic device, can be manufactured.

2. Description of Gas Laser Device of Comparative Example

The gas laser device100of the comparative example will be described. The comparative example of the present disclosure is an example recognized by the applicant as known only by the applicant, and is not a publicly known example admitted by the applicant.

FIG.2is a schematic diagram illustrating an overall configuration example of the gas laser device100of the present example. The gas laser device100is, for example, an ArF excimer laser device using a mixed gas including argon (Ar), fluorine (F2), and neon (Ne). In this case, the gas laser device100outputs a pulsed laser beam having a center wavelength of about 193.4 nm. The gas laser device100may be a gas laser device other than the ArF excimer laser device, and may be, for example, a KrF excimer laser device using a mixed gas including krypton (Kr), F2, and Ne. The gas laser device100outputs a pulsed laser beam having a center wavelength of about 248.0 nm. A mixed gas containing Ar, F2and Ne which are laser media, or a mixed gas containing Kr, F2, and Ne, which are laser media, may be referred to as a laser gas. In the mixed gas used in each of the ArF excimer laser device and the KrF excimer laser device, high-purity nitrogen (N2) or helium (He) may be used instead of Ne.

The gas laser device100of the present example mainly includes a housing110, a laser oscillator130disposed in an internal space of the housing110, a detection unit151, and a processor190.

The laser oscillator130mainly includes a chamber device CH, a charger (not illustrated), a pulse power module (not illustrated), a line narrowing module60, and an output coupling mirror70.

InFIG.2, the interior configuration of the chamber device CH is illustrated as viewed from a direction substantially perpendicular to the traveling direction of the laser beam. The chamber device CH mainly includes a housing30, a pair of windows31aand31b, and a pair of electrodes32aand32b. Hereinafter, a direction parallel to the optical axis direction of the pulsed laser beam output from the chamber device CH will be described as a Z direction, a direction orthogonal to the Z direction will be described as an H direction, and a direction orthogonal to the Z direction and the H direction will be described as a V direction.

The housing30is supplied with the laser gas from a laser gas supply device (not illustrated) to an internal space of the housing30via a pipe (not illustrated), and encloses the laser gas in the internal space. The light generated by the excitation of the laser gas travels in the windows31aand31b.

The window31aand the window31bare provided at positions facing each other in the housing30. The window31ais located on a front side in the traveling direction of the laser beam from the gas laser device100to the exposure device200, and the window31bis located on a rear side in the traveling direction. The windows31aand31bare inclined so as to form a Brewster's angle with respect to the traveling direction of the laser beam so that reflection of P-polarized light of the laser beam is suppressed. The window31ais disposed in a hole on a front-side wall surface of the housing30, and the window31bis disposed in a hole on a rear-side wall surface of the housing30.

The longitudinal direction of the electrodes32aand32bis along the traveling direction of the laser beam, and the electrodes32aand32bare disposed to face each other in the inner space of the housing30. The electrode32bis located below the electrode32ain the V direction and is shown larger than the electrode32afor ease of viewing, but the electrode32bis substantially the same in size as the electrode32a. The space between the electrode32aand the electrode32bis sandwiched between the window31aand the window31b. The electrodes32aand32bare discharge electrodes for exciting the laser medium by glow discharge. In the present example, the electrode32ais the cathode and the electrode32bis the anode.

The electrode32ais supported by an insulating portion (not illustrated). The insulating portion closes an opening (not illustrated) that is continuous with the housing30. The insulating portion includes an insulator. Examples of the insulator include alumina ceramics having poor reactivity with F2gases. In addition, a feedthrough (not illustrated) made of a conductive member is disposed in the insulating portion. The feedthrough applies a voltage supplied from the pulse power module to the electrode32a. The electrode32bis supported by an electrode holder (not illustrated) and is electrically connected to the electrode holder.

The charger (not illustrated) is a DC power supply device that charges a capacitor (not illustrated) provided in the pulse power module with a predetermined voltage. The charger is disposed outside the housing30and is connected to the pulse power module. The pulse power module includes a switch (not illustrated) controlled by the processor190. When the switch is switched from OFF to ON under the control of the processor190, the pulse power module boosts the voltage applied from the charger to generate a pulsed high voltage and applies this high voltage to the electrodes32aand32b. When a high voltage is applied, breakdown occurs between the electrode32aand the electrode32band discharge occurs. The laser gas in the housing30is excited by the energy of the discharge and shifts to a high energy level. When the excited laser gas then transitions to a low energy level, it outputs light corresponding to the energy level difference. The outgoing light passes through the windows31aand31band is output to the outside of the housing30.

The line narrowing module60mainly includes a housing68, prisms61,62,63, and64disposed in an internal space of the housing68, a mirror unit300, and a grating66. The housing68is connected to the rear side of the housing30via the optical path pipe68a. Specifically, one end of the optical path pipe68ais connected to the rear side of the housing30so as to surround the window31b. Further, the other end of the optical path pipe68ais connected to the housing68so as to surround the opening which is continuous with the housing68.

The prisms61,62,63, and64expand the beam-width of the light output from the window31band cause the light to enter the grating66. Further, the prisms61,62,63, and64reduce the beam width of the light reflected from the grating66and return the light to the inner space of the housing30through the window31b.

Each of the prisms61,62,63, and64is constituted by, for example, calcium fluoride, quartz, or a combination of calcium fluoride and quartz. Each of the prisms61,62,63, and64has a right-angled triangular prism shape having a right-angled triangular bottom surface. A film is formed on a side surface of the three side surfaces of the prism61including the oblique side of the bottom surface so as to suppress the reflection of the P-polarized light of the laser beam traveling to the side surface. The remaining two of the three side surfaces are perpendicular to each other. Films are formed on the two side surfaces so that reflection of the laser beam traveling on the two side surfaces is suppressed. The films may be films including at least one of SiO2, MgF2, LaF3, and GdF3. In particular, a fluoride-based material resistant to ultraviolet light may be used as the material of the film. It is preferred that a material of the same type as that of the prism61is used as the material of the film. Although the bottom surface and the side surface of the prism61have been described above, the same applies to the other prisms62,63, and64.

The prisms61,62,63, and64are respectively fixed to mounting portions61D,62D,63D, and64D which are stages. The mounting portions61D,62D, and64D are fixed to the bottom surface of the housing68in the inner space of the housing68. Thus, the prisms61,62, and64do not move relative to the housing68and the grating66. On the other hand, the mounting portion63D is fixed to a rotating stage63a, and the rotating stage63ais fixed to the bottom surface of the housing68in the inner space of the housing68. The rotating stage63arotates the mounting portion63D and the prism63around the V-axis perpendicular to an HZ plane in which the light output from the prism63is wavelength-dispersed. The rotating stage63ais connected to a prism driving unit (not illustrated) disposed outside the housing68. The prism driving unit is a motor, and the rotating stage63ais rotated under the control of the prism driving unit. The prism driving unit is electrically connected to the processor190. The processor190is electrically connected to the exposure device200and the detection unit151. To the processor190, a signal relating to the wavelength of light to be output by the gas laser device100is input from the exposure device200. Further, a signal indicating the pulse energy of the pulsed laser beam measured by the detection unit151is input to the processor190from the detection unit151. The processor190controls the prism driving unit on the basis of these signals. Therefore, the processor190can adjust the rotation angle of the rotating stage63aby controlling the prism driving unit. The mounting portion63D may be integrated with the rotating stage63a.

The mirror unit300mainly includes a mirror310, a holding part320, a rotating stage330, a shaft340, and driving units351aand351b.

The mirror310is disposed between the prism63and the prism64on the optical path of the light in the line narrowing module60. The mirror310reflects the light from the prism63toward the prism64and reflects the light from the prism64toward the prism63. That is, the mirror310folds back the light traveling in the internal space of the housing68, so that the optical path of the light is adjusted so as to fit a limited space in the internal space of the housing68. The mirror310may be disposed between other prisms or may be disposed between the prism64and the grating66so long as the optical path of the light can be adjusted.

The mirror310is held by the holding part320via an adhesive, and the holding part320is fixed to the rotating stage330. The shaft340is disposed on the rotating stage330along the V direction. The rotating stage330is connected to the driving units351aand351b, and rotates the holding part320and the mirror310about the shaft340by rotating the shaft340about the axis under the control of the driving units351aand351b. The driving units351aand351bare electrically connected to the processor190. The processor190controls the driving units351aand351bon the basis of the signal from the exposure device200and the signal from the detection unit151, similarly to the rotating stage63a. Therefore, the processor190can adjust the rotation angle of the rotating stage330by controlling the driving units351aand351b. Details of the configuration of the mirror unit300will be described later with reference toFIGS.5and6.

When the prism63and the mirror310are slightly rotated and the orientation is changed, the direction of the light output from the prism63and the mirror310is changed, whereby the incident angle of the light incident on the grating66is adjusted. By adjusting the incident angle of the light to the grating66, the wavelength of the light reflected by the grating66and incident on the chamber device CH is adjusted. Accordingly, the light output from the window31bof the housing30is reflected by the grating66through the prisms61,62,63, and64and the mirror310, and thus the wavelength of the light incident on the housing30is adjusted to a desired wavelength. Although the number of prisms is four in the present example, if at least one prism rotating like the prism63is included, it may be three or less, or may be five or more.

The grating66is a dispersive optical element. The surface of the grating66is made of a highly reflective material, and a large number of grooves are provided on the surface at predetermined intervals. The cross-sectional shape of each groove is, for example, a right-angled triangle. Light entering the grating66from the prism64is reflected by these grooves in a wavelength dispersive manner in the HZ plane, and is diffracted in a direction corresponding to the wavelength of the light. The grating66is disposed so that the incident angle of the light incident on the grating66from the prism64coincides with the diffraction angle of the diffracted light having a desired wavelength. As a result, light having a desired wavelength is returned to the housing30via the prisms61,62,63, and64and the mirror310. In the present example, the grating66may be an echelle grating blazed to a wavelength of about 193.4 nm. The grating66is fixed to the mounting portion66D which is a stage, and the mounting portion66D is fixed to the housing68in the inner space of the housing68. Thus, the grating66does not move relative to the housing68.

The output coupling mirror70faces the window31a. The output coupling mirror70is coated with a partially reflective film. The output coupling mirror70transmits a part of the laser beam from the window31a, reflects another part of the laser beam, and returns the laser beam to the inner space of the housing30through the window31a. The output coupling mirror70includes, for example, an element in which a dielectric multilayer film is formed on a substrate of calcium fluoride. The output coupling mirror70is connected to the front-side of the housing30and is fixed to the inner space of the optical path pipe70asurrounding the window31avia a damper (not illustrated).

The grating66and the output coupling mirror70provided across the housing30constitute a resonator that resonates light output from the laser gas. The housing30is disposed on the optical path of the resonator, and the light output from the housing30reciprocates between the grating66and the output coupling mirror70. The reciprocating light is amplified each time it passes through the laser gain space between the electrode32aand the electrode32b. A part of the amplified light passes through the output coupling mirror70as a pulsed laser beam and travels to the detection unit151.

The detection unit151mainly includes a housing151a, a beam splitter151b, and an optical sensor151c. An opening is continuously formed in the housing151a, and an optical path pipe70ais connected to surround the opening. Therefore, the housing151acommunicates with the optical path pipe70athrough the opening.

The beam splitter151bis disposed on the optical path of the pulsed laser beam in the inner space of the housing151a. The beam splitter151btransmits a part of the pulsed laser beam traveling from the output coupling mirror70to the exit window161with a higher transmittance. The beam splitter151breflects another part of the pulsed laser beam toward the light receiving surface of the optical sensor151c.

The optical sensor151cis disposed in an inner space of the housing151a. The optical sensor151cmeasures the pulse energy of the pulsed laser beam entering the light receiving surface of the optical sensor151c. The optical sensor151cis electrically connected to the processor190and outputs a signal indicating pulse energy to be measured to the processor190. The processor190controls a voltage applied to the electrodes32aand32bon the basis of the signal.

An opening is connected to a side of the housing151aopposite to a side to which the optical path pipe is connected, and the optical path pipe161ais connected so as to surround the opening. Therefore, the internal space of the housing151aand the internal space of the optical path pipe161aare in communication with each other. Further, the optical path pipe161ais connected to the housing110. An exit window161is provided at a position surrounded by the optical path pipe161ain the housing110. The light transmitted through the beam splitter151bof the detection unit151is output from the exit window161to the exposure device200outside the housing110.

The optical path pipes68a,70a, and161aand the inner space of the housings68and151aare filled with a purge gas via a pipe (not illustrated). The purge gas includes an inert gas such as high-purity nitrogen having less impurities such as oxygen. The purge gas is supplied from a purge gas supply source (not illustrated) disposed outside the housing110to the optical path pipes68a,70a, and161aor the inner space of the housings68and151athrough a pipe (not illustrated).

The processor190of the present disclosure is a processing device including a storage device in which a control program is stored and a CPU which executes the control program. The processor190is specifically configured or programmed to perform various processes included in the present disclosure. The processor190controls the entire gas laser device100. The processor190is electrically connected to a processor (not illustrated) of the exposure device200, and transmits and receives various signals to and from the processor.

Next, a first overall configuration example of the mirror unit300of the comparative example will be described.FIG.3is a schematic diagram showing a first overall configuration example of the mirror unit300of the comparative example, andFIG.4is a front view of the mirror unit300shown inFIG.3. In the mirror unit300shown inFIGS.3and4, a part of the configuration is different from that of the mirror unit300shown inFIG.2, in that the rotating stage330and the driving units351aand351bare not provided, a pair of leaf springs360aand360bare provided, and a driving unit371is provided. InFIG.4, the part covered by the leaf springs360aand360bof the mirror310and the holding part320is indicated by a broken line, and the shaft340and the driving unit371arranged below the holding part320in the H direction are indicated by a broken line different from the broken line.

The mirror310has a quadrangular prism shape. The mirror310includes a reflective surface310athat reflects light passing through the prism and a surface other than the reflective surface310a. The reflective surface310ais the surface of the mirror310that is along a VZ plane, and has a rectangular shape elongated in the Z direction in the VZ plane. The surface other than the reflective surface310aincludes a side surface and a rear surface of the mirror310facing the reflective surface310a. The side surface is an adjacent surface adjoining the reflective surface310a, and the rear surface is an opposing surface facing the reflective surface310a.

The holding part320is a frame-shaped member having a bottom portion, and an opening is provided inside a peripheral wall that is a frame of the holding part320, and the peripheral wall and the opening have a rectangular shape that is elongated in the Z direction in the VZ plane. In the holding part320, the mirror310is placed on the surface of the bottom portion via the rear surface of the mirror310. The peripheral wall of the holding part320surrounds the side surface of the mirror310so that a gap is provided between the side surface of the mirror310and the inner peripheral surface of the peripheral wall of the holding part320. In the H direction, the upper surface of the peripheral wall is located at a position lower than the reflective surface310a. A V-groove is provided on a rear surface of a bottom portion opposite to the front surface on which the mirror310is placed. A shaft340is disposed in the V-groove, and the V-groove and the shaft340are along the V direction perpendicular to the HZ plane in which the light is wavelength-dispersed. The V-groove and the shaft340are provided on the end side of the holding part320in the Z direction. The shaft340shown inFIGS.3and4is a rod-shaped member.

Main surfaces of the leaf springs360aand360beach have a rectangular shape that is elongated in the V direction in the VZ plane. Each of the leaf springs360aand360bis disposed at both ends of the reflective surface310ain the Z direction, and presses the mirror310against the bottom wall, which is the bottom wall of the holding part320, to fix the mirror310to the holding part320.

The driving unit371is disposed on the rear surface of the bottom portion of the holding part320, and the driving shaft of the driving unit371is fixed to the rear surface of the bottom portion of the holding part320along the H direction. The driving unit371is disposed on the end side of the holding part320on the opposite side of the shaft340in the Z direction. In addition, the driving unit371is disposed substantially in the center of the holding part320in the V direction. The driving unit371is, for example, a stepping motor. When a driving shaft pushes and pulls the holding part320in the H direction by the driving of the driving unit371, the holding part320rotates about the shaft340. As a result, the mirror310rotates about the shaft340, whereby the rotation angle of the mirror310is adjusted.

Next, a second overall configuration example of the mirror unit300of the comparative example will be described.FIG.5is a schematic diagram illustrating a second overall configuration example of the mirror unit300of the comparative example.FIG.6is a front view of the mirror unit300shown inFIG.5. InFIG.5andFIG.6, configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified. InFIG.6, adhesives380a,380b, and380cdisposed below the mirror310in the H direction are indicated by broken lines. The mirror unit300illustrated inFIGS.5and6is the mirror unit300illustrated inFIG.2, and is different from the mirror unit300illustrated inFIG.3. InFIG.2, the adhesives380a,380b, and380care omitted for ease of viewing.

Each of the adhesives380a,380b, and380cis provided between the surface of the mirror310other than the reflective surface310aand the holding part320, adheres to the surface and the holding part320, and bonds the mirror310to the holding part320. In the comparative example, each of the adhesives380a,380b, and380cis provided in the VZ plane between the rear surface of the mirror310and the surface of the bottom portion of the holding part320, and bonds the mirror310to the holding part320. The adhesives380a,380b, and380cmay include, for example, an epoxy resin, and the adhesives380a,380b, and380ccure and shrink upon bonding. The heights of the adhesives380a,380b, and380care substantially the same in the H direction. The adhesive380ais provided on the opposite side to the adhesives380band380cwith respect to the shaft340, in particular with respect to a center line341parallel to the shaft340and passing through the center of the mirror310. Although two adhesives may be used, three or more adhesives define and fix a surface, so that the orientation of the mirror310is stabilized. Further, when four or more adhesives are provided on the VZ plane, the reflective surface310amay be distorted due to the difference in height of the respective adhesives. Therefore, the number of adhesives is preferably three.

As described above, the holding part320holds the mirror310via the adhesives380a,380b, and380c. The holding part320is mounted on the surface of the rotating stage330and fixed to the rotating stage330by a fastening member (not illustrated). The mirror310is replaceable together with the holding part320with respect to the rotating stage330. The rotating stage330may be integrated with the holding part320.

The V-groove is provided on the rear surface of the rotating stage330, and the shaft340is disposed in the V-groove. The V-groove and the shaft340are along the V direction. The shaft340shown inFIGS.5and6is a rod-shaped member, but may be a virtual shaft without a substance. In addition, the V-groove and the shaft340are provided substantially in the center of the mirror310and the rotating stage330in the Z direction, and pass through the center of the mirror310when the reflective surface310ais viewed from the front.

Further, the driving units351aand351bare disposed on the rear surface of the rotating stage330. The driving units351aand351bare piezoelectric devices. The driving units351aand351bare arranged symmetrically with respect to the center line341. The driving units351aand351bare arranged generally in the center of the rotating stage330in the V direction.

Next, the operation of the gas laser device100of the comparative example will be described. Hereinafter, the mirror unit300illustrated inFIGS.5and6will be used for explanation.

Before the gas laser device100outputs the pulsed laser beam, the internal spaces of the optical path pipes68a,70a, and161aand the internal spaces of the housings68and151aare filled with the purge gas from a purge gas supply source (not illustrated). A laser gas is supplied to the internal space of the housing30from a laser gas supply device (not illustrated).

When the gas laser device100outputs the pulsed laser beam, the processor190sets a predetermined charging voltage to the charger and turns ON the switch. As a result, the pulse power module generates a pulsed high voltage from the electric energy held in the charger, and a high voltage is applied between the electrode32aand the electrode32b. When a high voltage is applied, breakdown occurs between the electrode32aand the electrode32band discharge occurs. When the discharge occurs, the laser medium contained in the laser gas between the electrode32aand the electrode32bis brought into an excited state and outputs spontaneous emission light when returning to the ground state. A part of this radiation is ultraviolet light and is transmitted through the window31b. When the transmitted light passes through the prisms61,62,63, and64, the width of the transmitted light is enlarged in the traveling direction of the light and is wavelength-dispersed. The light from the prism63is reflected by the mirror310toward the prism64, and is guided to the grating66through the prism64. The light is incident on and diffracted by the grating66at a predetermined angle, and light of a desired wavelength is reflected by the grating66at the same reflection angle as the incident angle. The light reflected by the grating66propagates again from the window31bto the inner space of the housing30through the prisms61,62,63, and64and the mirror310. The light propagating to the internal space of the housing30is narrowed. With this narrowed light, the laser medium in the excited state undergoes stimulated emission, and the light is amplified. The light passes through the window31aand travels to the output coupling mirror70. A part of the light is transmitted through the output coupling mirror70, and a remaining part of the light is reflected by the output coupling mirror70, passes through the window31a, and propagates to the inner space of the housing30. The light propagated to the inner space of the housing30travels to the grating66through the window31b, the prisms61,62,63, and64, and the mirror310as described above. Thus, light of a predetermined wavelength reciprocates between the grating66and the output coupling mirror70. The light is amplified every time the light passes through the discharge space in the internal space of the housing30, and laser oscillation occurs. Then, a part of the laser beam passes through the output coupling mirror70as a pulsed laser beam and travels to the beam splitter151b. Incidentally, as described above, the windows31aand31bare inclined so as to form a Brewster's angle with respect to the traveling direction of the laser beam so as to suppress the reflection of the P-polarized light of the laser beam. In addition, as described above, films are formed on the respective side surfaces of the prisms61,62,63, and64so as to suppress the reflection of the P-polarized light of the laser beam traveling from the outside of the respective prisms61,62,63, and64to these side surfaces. Therefore, the pulsed laser beam traveling to the beam splitter151bis narrowed, and the polarization component in the H direction is increased.

A part of the pulsed laser beam traveling to the beam splitter151bis reflected by the beam splitter151b. The reflected pulsed laser beam is received by the optical sensor151c, and the optical sensor151cmeasures the pulse energy of the received pulsed laser beam. The optical sensor151coutputs a signal indicating the pulse energy to be measured to the processor190. Further, a signal indicating the wavelength of light to be output from the gas laser device100is input to the processor190from the exposure device200. The processor190controls the prism driving unit and the driving units351aand351bon the basis of the signal from the optical sensor151cand the exposure device200, and rotates the rotating stages63aand330. During the rotation of the rotating stage330, the driving units351aand351brotate the holding part320via the rotating stage330so that the mirror310rotates about the shaft340. Specifically, when the driving units351aand351bare driven in opposite directions to each other, the rotating stage330is pushed and pulled by the driving units351aand351band rotates about the shaft340together with the holding part320. The rotation angle of the rotating stages63aand330is, for example, in an approximate range of ±2.5 degrees. The rotation of the rotating stages63aand330changes the orientations of the prism63and the mirror310. Even when the shaft340is a virtual axis without a substance, the driving units351aand351bare driven in opposite directions, so that the rotating stage330is pushed and pulled by the driving units351aand351band rotate about the shaft together with the holding part320.

By changing the orientations of the prism63and the mirror310, the wavelength of the light reflected by the grating66and returned into the housing30of the chamber device CH is adjusted. That is, the processor190adjusts the rotational angle of the prism63and the mirror310on the basis of the signal from the optical sensor151cand the exposure device200, and feedback-controls the charging voltage of the charger so that the difference between the pulse energy and the target pulse energy is within an allowable range. When the difference is within the allowable range, the light passes through the beam splitter151band the exit window161and enters the exposure device200. The pulsed laser beam is an ArF laser beam which is ultraviolet light having a center wavelength of 193.4 nm.

The gas laser device100of the present embodiment performs two-wavelength oscillation in which the oscillation wavelength of the pulsed laser beam output from the gas laser device100toward the exposure device200is repeatedly switched between two wavelengths every one to several pulses. In the two-wavelength oscillation, the two wavelengths are switched by changing the angle of incidence on the grating66by adjusting the rotation angle of the mirror310. By this two-wavelength oscillation, the workpiece is irradiated with two pulsed laser beams having different focal depths. The focal depths of the two pulsed laser beams are shifted between a shallow portion and a deep portion with respect to the workpiece as compared with the case of one-wavelength oscillation in which the focal depth is not changed. By irradiating the two pulsed laser beams to the same portion of the workpiece, for example, a thin and deep uniform hole is formed in the workpiece as compared with the case of the one-wavelength oscillation.

When the gas laser device100performs two-wavelength oscillation, the mirror310needs to rotate at a high speed in order to repeatedly switch the oscillation wavelength between two wavelengths. Incidentally, in the first overall configuration example of the mirror unit300shown inFIGS.3and4, when a stepping motor is used as the driving unit371, the rotation speed of the mirror310rotated by the stepping motor may be slower than the speed obtained by the two-wavelength oscillation. If the rotation speed is slow, the gas laser device100may not be able to perform the two-wavelength oscillation. Therefore, in the driving unit371, a piezo element is used instead of the stepping motor, and the piezo element provides the rotation speed of the mirror310required for the two-wavelength oscillation.

Incidentally, when the rotational velocity of the mirror310increases, the load applied to the leaf springs360aand360bby the rotation of the mirror310increases, and the positional deviation occurs in the leaf springs360aand360bdue to the load, and the fixing force of the leaf springs360aand360bmay decrease. If the fixing force decreases, the rigidity of the entire mirror unit300may decrease. When the rigidity decreases, the responsiveness of the rotation of the mirror310, that is, the controllability of the rotation of the mirror310decreases. Therefore, the mirror unit300shown inFIGS.5and6in which the adhesives380a,380b, and380care provided instead of the leaf springs360aand360bis used.

During bonding, the adhesives380a,380b, and380cpull the mirror310toward the rotating stage330in the H direction perpendicular to the reflective surface310aby the respective curing shrinkage. As a result, the tensile force of the adhesives380a,380b, and380cmay be applied to the mirror310and propagated to the reflective surface310avia the mirror310. When the tensile force propagates to the reflective surface310a, the reflective surface310amay be distorted. In particular, when the adhesives380a,380b, and380cadhere to the rear surface of the mirror310and the surface of the bottom portion of the holding part320, the mirror310is more stable, but the distortion is increased. In order to suppress the distortion, it may be contemplated to reduce the quantity of the adhesives380a,380b, and380c. However, when the quantity of the adhesives380a,380b, and380cis reduced, the respective adhesive forces are reduced. When the adhesive force decreases, the mirror310may be detached from the adhesives380a,380b, and380cdue to loads applied to the adhesives380a,380b, and380cwhen the mirror310rotates. In addition, when a fastening member is used to fix the holding part320and the rotating stage330, the holding part320may be deformed by the fastening force of the fastening member. With the deformation, the holding part320may warp around the fastening member. When the holding part320is deformed as described above, the stress generated by the deformation may propagate to the adhesives380a,380b, and380c. Further, the stress may propagate from the adhesives380a,380b, and380cto the reflective surface310avia the mirror310, and the reflective surface310amay be distorted. As described above, the distortion of the reflective surface310aand the detachment of the mirror310may cause the gas laser device100not to output a pulsed laser beam satisfying the performance required from the exposure device200, and thus the reliability of the gas laser device100may deteriorate.

Therefore, in the following embodiments, the line narrowing module60is exemplified in which a decrease in reliability of the gas laser device100can be suppressed.

3. Description of Line Narrowing Module of First Embodiment

Next, the line narrowing module60according to the first embodiment will be described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

FIG.7is a schematic diagram illustrating an overall configuration example of the mirror unit300of the present embodiment.FIG.8is a front view of the mirror unit300shown inFIG.7.FIG.9is a side view of the mirror unit300viewed from a plate member325side.

The mirror unit300of the present embodiment is different from the mirror unit300shown inFIGS.5and6in that the holding part320includes a member that can be detachably attached to the holding part320. Hereinafter, the plate member325is used as an example of the member, but a wall member or the like may also be used. Further, the mirror unit300is different from the mirror unit300shown inFIGS.5and6in that the adhesive380aadheres to the side surface of the mirror310and the plate member325included in the peripheral wall of the holding part320, and that the adhesives380band380cadhere to the side surface of the mirror310and the inner peripheral surface of the peripheral wall of the holding part320.

The plate member325is disposed in the cutout portion327aprovided in the peripheral wall of the holding part320. The cutout portion327ais provided in one of the wall portions along the HV plane of the peripheral wall, penetrates the peripheral wall in the Z direction, and is longer than the mirror310in the V direction. The plate member325is shorter than the cutout portion327aand the mirror310in the V direction. The plate member325has a quadrangular prism shape and is made of the same material as the holding part320. A side surface of the plate member325along the HV plane faces one side surface along the HV plane of the mirror310. The plate member325is disposed in the holding part320in a state in which the adhesive380aadheres to a base329a(described later) of the plate member325, after the mirror310passes through the cutout portion327aand is disposed inside the peripheral wall. Incidentally, the plate member325is a wall to which the adhesive380aadheres, and the plate member325is provided with a pair of through-holes325a. The through-hole325ais longer in the Z direction than in the V direction and penetrates the plate member325in the H direction. The plate member325is fixed to the holding part320with an adjustment of the position of the adhesive380ain the thickness direction by fastening the fastening member325b, which is a screw, passing through the through-hole325aand fastening it to the holding part320. The thickness direction is the Z direction connecting the mirror310, the adhesive380a, and the plate member325of the holding part320, and is a direction perpendicular to the shaft340when the reflective surface310ais viewed from the front. The thickness direction is a direction perpendicular to the axis perpendicular to the reflective surface310aand the center line341, and is a direction connecting the adhesive surface between the plate member325and the adhesive380aand the adhesive surface between the mirror310and the adhesive380a. The method of fixing the plate member325is not limited to the foregoing, and the plate member325may be fixed to the holding part320by adhesion.

The plate member325is provided with the base329a. Bases329band329care also provided on the inner peripheral surface of the peripheral wall of the holding part320. The bases329band329care provided on the other side of the base329awith respect to the center line341.

The holding part320includes holding surfaces320a,320b, and320cto which adhesives380a,380b, and380cadhere to hold the mirror310. The holding surfaces320a,320b, and320cdiffer from each other. The holding surface320ais a surface of the base329ato which the adhesive380awhich is the first adhesive adheres. The holding surface320bis a surface of the base329bto which the adhesive380bwhich is the second adhesive adheres. The holding surface320cis a surface of the base329cto which the adhesive380cwhich is the third adhesive adheres. The holding surfaces320a,320b, and320cof the present embodiment intersect the VZ plane along the in-plane direction of the reflective surface310aand extend along the HV plane. The holding surface320ais provided on a side opposed to the holding surfaces320band320cwith respect to the center line341. The holding surfaces320a,320b, and320ceach have a circular shape, but the shape is not particularly limited. The shaft340is a rod-shaped member, but may be a virtual axis without a substance. The shaft340includes a line perpendicular to the HZ plane in which the light output from the prism63is wavelength-dispersed.

The adhesive380aadheres to the holding surface320aand the side surface of the mirror310facing the holding surface320ain the base329ato bond the mirror310to the plate member325. The adhesive380badheres to the holding surface320band the side surface of the mirror310facing the holding surface320bin the base329bto bond the mirror310to the holding part320. Meanwhile, the adhesive380cadheres to the holding surface320cof the base329cand the side surface of the mirror310facing the holding surface320cto bond the mirror310to the holding part320. Accordingly, the adhesives380band380care positioned on an opposite side of the adhesive380awith respect to the shaft340, specifically with respect to the center line341, when the reflective surface310ais viewed from the front. The front view indicates that the reflective surface310ais viewed along the H direction perpendicular to the reflective surface310a. The center of the mirror310of the present embodiment is an intersection of diagonal lines of the reflective surface310awhen the reflective surface310ais viewed from the front. The side surface of the mirror310to which the adhesive380aadheres is a side surface that is different from the side surface of the mirror310to which the adhesives380band380cadhere, and faces the side surface. In the mirror unit300of the present embodiment, the side surface of the mirror310to which the adhesive380aadheres is the first adjacent surface310cadjacent to the reflective surface310a, and the side surface of the mirror310to which the adhesives380band380cadhere is the second adjacent surface310dadjacent to the reflective surface310a. The first adjacent surface310cof the present embodiment faces the second adjacent surface310d. The adhesive380band the base329bare located in the same HV plane as the adhesive380cand the base329c, but misaligned in the V direction. Therefore, the adhesive380bis provided at a position that is different from the adhesive380con the second adjacent surface310d. Thus, the mirror310is held at one location by an adhesive380aon the left side of the shaft340and at two locations by the adhesives380band380con the right side of the shaft340.

The adhesives380a,380b, and380cand the bases329a,329b, and329care positioned closer to the reflective surface310athan the surface of the bottom portion of the holding part320in the H direction perpendicular to the reflective surface310a. Thus, the mirror310is held by the holding part320by the adhesives380a,380b, and380cwhile the rear surface310f, which is the opposing surface facing the reflective surface310a, is spaced apart from the surface of the bottom portion of the holding part320. The center of each of the adhesives380a,380b, and380cand the bases329a,329b, and329cis located at approximately the same height in the H direction perpendicular to the reflective surface310a. In the Z direction, the adhesives380a,380b, and380cand the bases329a,329b, and329care generally the same length. The base329ais provided such that the adhesive380aadheres generally centrally to the mirror310in the V direction. The bases329band329care provided so that the adhesives380band380cadhere to both ends of the mirror310in the V direction.

When viewed along the V direction, the adhesive380aand the base329aare located above the driving unit351a, while the adhesives380band380cand the bases329band329care located above the driving unit351b. The upper side is the reflective surface310aside. Further, when viewed along the H direction, the adhesive380aand the base329aare disposed above the driving unit351a, and the driving unit351bis disposed between: the adhesive380band the base329b; and the adhesive380cand the base329c. The adhesive380band the base329bare provided on an opposite side of the adhesive380cand the base329cwith respect to the driving unit351b. In addition, the adhesive380band the base329b, as well as the adhesive380cand the base329care symmetrically provided with respect to the driving unit351b.

The area of the holding surface320ain the base329ais substantially the same as the sum of the area of the holding surface320bin the base329band the area of the holding surface320cin the base329c. The area of the holding surface320ais approximately twice the area of the holding surface320band the area of the holding surface320c, respectively. Each of the adhesives380a,380b, and380cadheres to the entirety of each of the holding surfaces320a,320b, and320c. Therefore, the area of the adhesive surface between the holding surface320aand the adhesive380ais substantially the same as the sum of the area of the adhesive surface between the holding surface320aand the adhesive380b, and the area of the adhesive surface between the holding surface320aand the adhesive380c. Further, the area of the adhesive surface between the holding surface320aand the adhesive380ais approximately twice the area of the adhesive surface between the holding surface320aand the adhesive380b, and the area of the adhesive surface between the holding surface320aand the adhesive380c, respectively. The relationship between the areas of the adhesive surfaces of the holding surfaces320a,320b, and320cand the adhesives380a,380b, and380chas been described above, but the same applies to the relationship between the areas of the adhesive surfaces of the mirror310and the adhesives380a,380b, and380c.

The mirror unit300further includes fastening members401a,401b,401c, and401dthat fix the rotating stage330to the holding part320. The fastening members401a,401b,401c, and401dare disposed below the mirror310in the bottom portion of the holding part320, and are therefore indicated by broken lines inFIG.8. The longitudinal direction of the fastening members401a,401b,401c, and401dextends in the H direction. The fastening members401a,401b,401c, and401dare arranged such that they are each located at the apex of the rectangle. The fastening member401ais disposed on the opposite side of the fastening member401bwith respect to the center line341, and the fastening member401cis disposed on the opposite side of the fastening member401dwith respect to the center line341. Further, the fastening member401ais disposed on the opposite side of the fastening member401cwith respect to the HZ plane, and the fastening member401bis disposed on the opposite side of the fastening member401dwith respect to the HZ plane. The number and positions of the fastening members are not limited to the foregoing.

3.2 Function and Effect

In the line narrowing module60of the present embodiment, the adhesive380a, which is the first adhesive, is provided between the first adjacent surface310c, which is the side surface of the mirror310, and the holding part320. The adhesive380b, which is the second adhesive, is provided between the second adjacent surface310d, which is the side surface of the mirror310, and the holding part320. The adhesive380aand the adhesive380bbond the mirror310to the holding part320.

Since the adhesive380bpulls the mirror310toward the holding part320in the in-plane direction of the mirror310during bonding, the tensile force of the adhesive380bis applied to the mirror310in the in-plane direction. In this case, the adhesive380badheres to the rear surface310fand the surface of the bottom portion of the holding part320, and the tensile force propagating to the reflective surface310amay be reduced as compared with the case where the tensile force is applied to the mirror310in the H direction perpendicular to the reflective surface310a. When the tensile force is reduced, distortion of the reflective surface310acan be suppressed. In addition, since the distortion of the reflective surface310ais suppressed, it is not necessary to reduce the amount of the adhesives380aand380bin order to suppress the distortion of the reflective surface310a, and it is possible to suppress the decrease in the respective adhesive forces caused by reducing the amount of the adhesives380aand380b. When the decrease in the adhesive force is suppressed, the durability against the loads applied to the adhesives380aand380bwhen the mirror310is rotated can be increased, and the detachment of the mirror310can be suppressed, compared with the case where the decrease in the adhesive force is suppressed. As described above, when the distortion of the reflective surface310aand the detachment of the mirror310are suppressed, the gas laser device100can output a pulsed laser beam satisfying the performance required from the exposure device200. Therefore, a decrease in the reliability of the gas laser device100can be suppressed.

In addition, the adhesive380bis located parallel to the shaft340and on the opposite side to the adhesive380awith respect to the center line341passing through the center of the mirror310when the reflective surface310ais viewed from the front. In this case, even if a load is applied to the adhesives380aand380bby the rotation of the mirror310, detachment of the mirror310from the adhesives380aand380bcan be suppressed as compared with a case where the adhesives380aand380bare provided on the same side with respect to the center line341.

Incidentally, when the fastening members401a,401b,401c, and401dare used to fix the holding part320and the rotating stage330, the holding part320may be deformed by the fastening force of the fastening members401a,401b,401c, and401d. In this deformation, the holding part320may warp around the fastening members401a,401b,401c, and401d. When the adhesives380a,380b, and380cadhere to the rear surface310fand the holding part320as in the comparative example, a stress caused by the deformation may propagate to the adhesives380a,380b, and380cwhen the holding part320is deformed as described above. Further, the stress may propagate from the adhesives380a,380b, and380cto the reflective surface310avia the mirror310, and the reflective surface310amay be distorted. Incidentally, the adhesive380bof the present embodiment adheres to the holding surface320band the side surface of the mirror310. In this case, even if the holding part320is deformed by the fastening force, the stress caused by the deformation may be less likely to propagate through the adhesive380band the mirror310to the reflective surface310athan in the case where the adhesive380badheres to the rear surface310fand the holding part320. When the stress is less likely to propagate, the distortion of the reflective surface310acan be suppressed. Further, in order to suppress the distortion of the reflective surface310adue to the fastening force, reduction of fastening members401a,401b,401c, and401dmay be contemplated. However, as described above, since the distortion of the reflective surface310adue to the fastening force is suppressed by the adhesive380b, it is not necessary to reduce the fastening members401a,401b,401c, and401d. In addition, a displacement of the holding part320with respect to the rotating stage330due to reduction in the fastening members401a,401b,401c, and401dcan be suppressed.

In the line narrowing module60of the present embodiment, the first adjacent surface310cfaces the second adjacent surface310d. Therefore, the adhesives380aand380bare provided on both sides of the mirror310in the Z direction, and the mirror310is held by the holding part320from both sides. In this case, as compared with a case where the adhesives380aand380bare not provided on both sides of the mirror310, detachment of the mirror310can be suppressed.

Further, the line narrowing module60of the present embodiment further includes the adhesive380cwhich is the third adhesive that is provided between the second adjacent surface310d, which is the side surface of the mirror310to which the adhesive380badheres, and the holding part320, and bonds the mirror310to the holding part320. In this case, detachment of the mirror310can be suppressed as compared with a case where the adhesive380cis not provided. The adhesive380cis not necessarily required. If no adhesive380cis provided, the adhesive380ais preferably provided symmetrically to the adhesive380bwith respect to the center line341.

Further, in the line narrowing module60of the present embodiment, the adhesives380a,380b, and380care located at the same height position in the H direction perpendicular to the reflective surface310a. In this case, detachment of the mirror310can be suppressed as compared with a case where the adhesives380a,380b, and380care not positioned at the same height position in the H direction. Each of the adhesives380a,380b, and380cmay not be positioned at the same height position in the H direction.

Further, in the line narrowing module60of the present embodiment, when the mirror310and the holding part320rotate about the shaft340, loads are applied to the adhesives380a,380b, and380cin the Z direction. The mirror310is held at one position by the adhesive380aon the left side of the shaft340inFIG.8, and at two positions by the adhesives380band380con the right side of the shaft340. Incidentally, the area of the adhesive surface between the base329aand the adhesive380ais substantially the same as the sum of the area of the adhesive surface between the base329band the adhesive380band the area of the adhesive surface between the base329cand the adhesive380c. In this case, the variation in the loads applied to the adhesive380aand the adhesives380band380ccan be suppressed as compared with a case where the area of the adhesive380ais not substantially the same as the sum of the areas of the adhesives380band380c. When the variation is suppressed, the variation in the deterioration of the adhesives380a,380b, and380ccan be suppressed. Further, the area of the adhesive surface between the base329aand the adhesive380ais approximately twice the area of the adhesive surface between the base329band the adhesive380band the area of the adhesive surface between the base329cand the adhesive380crespectively. In this case, as compared with a case where the area of the adhesive380ais not twice the respective areas on the adhesives380band380c, the variation in the loads applied to the adhesives380a,380b, and380cand the variation in the deterioration of the adhesives380a,380b, and380ccan be further suppressed. In the adhesion to the holding part320, the area on the adhesive380aside may not be substantially the same as the sum of the areas on the adhesive380bside and the adhesive380cside. In addition, the area on the adhesive380aside may not be approximately twice the area on the adhesive380bside and the area on the adhesive380cside.

In the line narrowing module60of the present embodiment, the adhesives380a,380b, and380cadhere to the holding surfaces320a,320b, and320cof the bases329a,329b, and329c. The spreading of the adhesive380afrom the holding surface320acan be suppressed by the edge of the holding surface320aand the surface tension of the adhesive380a. Therefore, the area of the adhesive surface between the holding surface320aand the adhesive380amay be substantially the same as the area of the holding surface320a. In addition, by suppressing the above-described spreading, the spreading of the adhesive380aon the first adjacent surface310ccan be suppressed. Due to the suppression, the area of the adhesive surface between the mirror310and the adhesive380amay be substantially the same as the area of the adhesive surface between the holding surface320aand the adhesive380a. Therefore, the area of the adhesive surface of the adhesive380abetween the base329aside and the mirror310side can be adjusted by the holding surface320a. Although the adhesive380ahas been described above, the same applies to the adhesives380band380c. Thus, the area of the adhesive surface between the mirror310and the adhesive380ais substantially the same as the sum of the area of the adhesive surface between the mirror310and the adhesive380band the area of the adhesive surface between the mirror310and the adhesive380c. In this case, the variation in the loads applied to the adhesive380aand the adhesives380band380ccan be suppressed as compared with a case where the area on the adhesive380aside is not substantially the same as the sum of the areas on the adhesive380bside and the adhesive380cside. When the variation is suppressed, the variation in the deterioration of the adhesives380a,380b, and380ccan be suppressed. The area of the adhesive surface between the mirror310and the adhesive380ais approximately twice the area of the adhesive surface between the mirror310and the adhesive380band the area of the adhesive surface between the mirror310and the adhesive380c. In this case, variations in the loads applied to the adhesive380aand the adhesives380band380ccan be further suppressed, and variations in the deterioration of the adhesives380a,380b, and380ccan be further suppressed. In the bonding between the mirror310and the adhesives380a,380b, and380c, the area of the adhesive surface on the adhesive380aside may not be substantially the same as the sum of the areas of the adhesive surfaces on the adhesive380bside and the adhesive380cside. In addition, the area of the adhesive surface on the adhesive380aside may not be approximately twice the area of the adhesive surface on the adhesive380bside and the area of the adhesive surface on the adhesive380cside.

Further, in the line narrowing module60of the present embodiment, the plate member325is fixed to the holding part320by adjusting the position in the Z direction, which is the thickness direction of the adhesive380a. Accordingly, the plate member325can absorb the dimensional tolerance of the mirror310and the processing tolerance of the holding part320in the Z direction. When the plate member325absorbs the dimensional tolerance and the processing tolerance, deformation of the adhesives380a,380b, and380cdue to the dimensional tolerance and the processing tolerance can be suppressed. Thus, the misalignment of the mirror310can be suppressed. Further, when the plate member325absorbs the dimensional tolerance and the processing tolerance, the change in the length of the adhesives380a,380b, and380cin the Z direction due to the dimensional tolerance and the processing tolerance is suppressed, and the change in the adhesive force due to the change in the length can be suppressed.

The plate member325of the present embodiment is provided on the adhesive380aside, but may also be provided on the adhesive380bside and the adhesive380cside. Here, one plate member325may be provided for the adhesives380band380c, or may be provided for each of the adhesives380band380c. Accordingly, the plate member325may be fixed to the holding part320by adjusting the position of one of the adhesives380a,380b, and380cin the thickness direction. Further, the spreading of the adhesive380ato adhere to the plate member325and the mirror310may also be adjusted by, for example, a frame member (not illustrated) other than the base329a. Here, the adhesive380ais provided inside the frame member and hardened, so that the area of the adhesive surface between the holding part320and the adhesive380ais adjusted. If a frame member is used, the base329amay be omitted. As described above, the method of adjusting the area of the adhesive surface is not particularly limited. Adjusting the area of the adhesive surface has been described with reference to the adhesive380a, but the same applies to the adhesives380band380c. The base329ais integral with the plate member325, but may be separate. The bases329band329care integral with the peripheral wall, but may be separate. The bases329a,329b, and329cmay be provided on the mirror310. As long as the adhesive surfaces of the adhesives380a,380b, and380cwith respect to the mirror310, the holding part320, and the plate member325are along the HV plane, the positions of the adhesives380a,380b, and380cand the base329a,329b, and329care not particularly limited. The mirror310is only required to have a columnar shape.

In the arrangement positions of the adhesives380a,380b, and380cof the present embodiment, the adhesives380a,380b, and380care provided on the HV plane, but the present invention is not limited thereto. Other examples of the arrangement positions of the adhesives380a,380b, and380cwill be described with reference to first and second modifications below.

FIG.10is a front view of a mirror unit300in the first modification of the first embodiment. The mirror unit300of the present modification is different from the mirror unit300of the first embodiment in that the plate member325and the cutout portion327aare provided on one of the wall portions along the HZ plane of the peripheral wall of the holding part320. The mirror unit300of the present modification is different from the mirror unit300of the first embodiment in that a third adjacent surface310e, which is a side surface to which the adhesive380cof the mirror310adheres, is opposed to a second adjacent surface310d, which is a side surface to which the adhesive380badheres. The third adjacent surface310eis a surface adjacent to the reflective surface310a. The mirror unit300of the present modification is different from the mirror unit300of the first embodiment in that the adhesive380badheres to the plate member325and the mirror310.

The plate member325and the cutout portion327aare provided on the end side of the mirror310on the side opposite to the adhesive380ain the Z direction. The cutout portion327apenetrates the circumferential wall in the V direction. In addition, the cutout portion327ais made shorter than the mirror310in the Z direction together with the plate member325. The plate member325is provided with a base329b, and the holding surface320bof the base329bis along the HZ plane. Further, the base329cis provided on the other side of the base329bwith respect to the mirror310, and the holding surface320cof the base329cis along the HZ plane. Thus, the adhesive380bis provided on the opposite side of the adhesive380cwith respect to the mirror310. In addition, the adhesives380band380care symmetrically provided with respect to the mirror310. The plate member325and the cutout portion327amay be positioned on the opposite side to the base329c, and the adhesive380cmay adhere to the base329bof the plate member325.

The holding part320further includes a cutout portion327bthrough which the mirror310passes so that the mirror310is disposed inside the peripheral wall. The cutout portion327bis provided in a wall portion of the peripheral wall of the holding part320along the HV plane, on a wall portion opposite to the wall portion to which the adhesive380aadheres with respect to the center line341. The cutout portion327bpenetrates the circumferential wall in the Z direction and is longer than the mirror310in the V direction.

Since the plate member325and the cutout portion327aare not provided at the positions described in the first embodiment, the peripheral wall of the holding part320is provided at the positions instead of the plate member325and the cutout portion327a. The peripheral wall is provided with the base329a, and the base329ais provided with the holding surface320a. The adhesive380aadheres to the holding surface320aand is positioned on the opposite side to the adhesives380band380cwith respect to the center line341. The adhesive surface between the mirror310and the adhesive380ais along the HV plane, and the respective adhesive surfaces between the mirror310and the adhesives380band380care along the HZ plane. In addition, a first normal line391aon the adhesive surface between the mirror310and the adhesive380aintersects a second normal line391bon the adhesive surface between the mirror310and the adhesive380binside the mirror310. Further, the first normal line391afurther intersects a third normal line391con the adhesive surface between the mirror310and the adhesive380cinside the mirror310. In addition, the first normal line391aintersects the third normal line391cat an intersection391ebetween the first normal line391aand the second normal line391b. The intersection391eis located on the opposite side to the adhesive380awith respect to the center line341.

In the mirror unit300of the present modification, the adhesive380apulls the mirror310in the Z direction as in the first embodiment. Further, a side surface of the mirror310to which the adhesive380cadheres is opposed to a side surface to which the adhesive380badheres, and the adhesives380band380care provided so as to sandwich the mirror310, and pulls the mirror310in the V direction and shears it in the Z direction. Therefore, the thickness direction of the adhesives380band380cis the V direction, the shearing direction of the adhesives380band380cis the Z direction, and the force combined in the oblique direction between the V direction and the Z direction is applied to the mirror310. In this case, the rigidity of the entire mirror unit300may be increased as compared with a case where the combined force is not applied to the mirror310.

In the mirror unit300of the present modification, the first normal line391aintersects the second normal line391binside the mirror310. In this case, the rigidity of the entire mirror unit300may be increased and the responsiveness of the rotation of the mirror310may be improved as compared with a case where the normal lines391a,391bdo not intersect. Further, in the mirror unit300of the present modification, the first normal line391aintersects the third normal line391cat the intersection391eof the first normal line391aand the second normal line391b. In this case, the rigidity of the entire mirror unit300may be increased and the responsiveness of the rotation of the mirror310may be improved as compared with a case where the first normal line391adoes not intersect the third normal line391cat the intersection391e.

Next, the second modification of the first embodiment will be described.FIG.11is a schematic diagram illustrating an overall configuration example of the mirror unit300according to the second modification of the first embodiment.FIG.12is a front view of the mirror unit300shown inFIG.11. The mirror unit300of the present modification is different from the mirror unit300of the first embodiment in that the adhesive380ais provided between the rear surface310fand the surface of the bottom portion of the holding part320facing the rear surface310fin the same manner as in the comparative example, and the mirror310adheres to the holding part320. The mirror unit300of the present modification is different from the mirror unit300of the first embodiment in that the plate member325and the cutout portion327aare not provided. InFIG.12, the adhesive380aarranged below the mirror310is shown by a broken line. The adhesives380band380care provided in the same manner as in the first embodiment. Therefore, the mirror310is held in the rear surface310fand the second adjacent surface310dwhich is the side surface.

In the mirror unit300of the present modification, the base329ais provided on the surface of the bottom portion of the holding part320. The holding surface320aof the base329ais along the VZ plane. Therefore, the adhesive surface of the adhesive380awith respect to the mirror310and the holding surface320ais along the VZ plane. The base329aand the adhesive380aare provided substantially in the center of the mirror310in the V direction.

Further, in the mirror unit300of the present modification, the adhesive380aadheres to the rear surface310fand to the holding surface320aof the base329aat the bottom portion of the holding part320facing the rear surface310f. In addition, the adhesives380band380care provided in the same manner as in the first embodiment, and adhere to the second adjacent surface310dwhich is a side surface of the mirror310and to the holding surfaces320band320cof the holding part320which face the side surface. Thus, the adhesive surface of the adhesive380awith respect to the mirror310and the holding surface320ais along the VZ plane, and the adhesive surfaces of the adhesives380band380cwith respect to the mirror310and the holding surface320aare along the HV plane. Therefore, since the shear direction of the adhesive380ais perpendicular to the shear direction of the adhesives380band380c, the rigidity of the entire mirror unit300may be increased as compared with the cases where the respective shear directions are not perpendicular. Further, by the adhesives380band380c, distortion of the reflective surface310acan be suppressed as compared with the case where all the adhesives380a,380b, and380cadhere to the rear surface310fand to the surface of the bottom portion of the holding part320as in the comparative example. Further, since it is no longer necessary to absorb the dimensional tolerance of the mirror310and the processing tolerance of the holding part320by the plate member325due to the adhesive380a, the plate member325may be omitted, and processing of the cutout portion327ain the holding part320may be omitted. Even if the mirror310is tilted due to the curing shrinkage of the adhesive380a, the inclination is allowed by the rotation control of the rotating stage330by the driving units351aand351b.

In the mirror unit300of the present modification, as shown inFIG.11, when viewed from the V direction, the first normal line391aof the adhesive380athree-dimensionally intersects the second normal line391bof the adhesive380bin the mirror310. Although not illustrated, the first normal line391aalso intersects the third normal line391cof the adhesive380cthree-dimensionally in the mirror310. In such a case, the rigidity of the entire mirror unit300may be increased as compared with the case where the respective normal lines of the adhesives380a,380b, and380cdo not intersect three-dimensionally. Further, since vibration of the mirror310is suppressed in the H direction by the adhesive380a, the rigidity of the entire mirror unit300can be increased as compared with the case where the mirror310is fixed only on the HV plane. Therefore, the natural frequency of the mirror310may be improved.

4. Description of Line Narrowing Module of Second Embodiment

Next, the line narrowing module60of the second embodiment is described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

FIG.13is a front view of the mirror unit300according to the present embodiment. In the mirror unit300of the present embodiment, the shape of the mirror310is different from the shape of the mirror310of the first embodiment.

In the mirror310of the present embodiment, the adjacent surfaces310d,310e, which are side surfaces to which the adhesives380band380cadhere, are chamfered. The chamfering is, for example, C-chamfering. In this case, the normal lines391b,391care inclined toward the shaft340side by the chamfering as compared with the case with no chamfering, the intersection391eis located between the shaft340and the line391fconnecting the adhesives380band380cin the VZ plane along the in-plane direction of the reflective surface310a. In addition, the intersection391eis closer to the shaft340as compared with the case with no chamfering.

4.2 Function and Effect

In the mirror unit300of the present embodiment, the intersection391eis located between the shaft340and the line391fon the VZ plane. In this case, the rigidity of the entire mirror unit300may be increased as compared with a case where the intersection391eis located on the line391f, and the responsiveness of the rotation of the mirror310may be improved.

In the line narrowing module60of the present embodiment, the intersection391eis located between the shaft340and the line391f, but the present invention is not limited thereto.FIG.14is a front view of the mirror unit300in the first modification of the second embodiment. As shown inFIG.14, the intersection391emay overlap the shaft340when the reflective surface310ais viewed from the front. In this case, the rigidity of the entire mirror unit300may be increased and the responsiveness of the rotation of the mirror310may be improved as compared with the case where the intersection391eis located between the shaft340and the line391f.FIG.15is a front view of a mirror unit300in the second modification of the second embodiment. The mirror310is cylindrical in shape, and the adhesives380a,380b, and380cadhere to the same side surface of mirror310at different positions. If the mirror310is cylindrical, the intersection391ecan easily overlap the shaft340when the reflective surface310ais viewed from the front, as compared to the case where the mirror310is not cylindrical. The intersection391emay be located between the shaft340and the adhesive380awhen the reflective surface310ais viewed from the front.

Description of Line Narrowing Module of Third Embodiment

Next, the line narrowing module60of the third embodiment is described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

Configuration

FIG.16is a front view of the mirror unit300according to the present embodiment. InFIG.16, the mirror310is indicated by a dotted line, the fastening members401a,401b,401c, and401dare indicated by solid lines, and the illustration of the driving units351aand351bis omitted for ease of viewing. In the mirror unit300of the present embodiment, the holding part320is different from the holding part320of the first embodiment in further including slits403a,403b,403c,403d,403e.

Each of the slits403a,403b,403c,403dhas the same size and is L-shaped, and the slit403ehas a rectangular shape elongated in the Z direction. Each of the slits403a,403b,403c,403dsurrounds a part of the fastening members401a,401b,401c, and401dthat fasten the holding part320to the rotating stage330. When the reflective surface310ais viewed from the front, the slit403ais provided between the fastening member401aand the adhesive380a, and the slit403bis provided between the fastening member401band the adhesive380c. Further, the slit403cis provided between the fastening member401cand the adhesive380a, and the slit403dis provided between the fastening member401dand the adhesive380b. The slit403ais located on the opposite side of the slit403bwith respect to the center line341, and the slit403cis located on the opposite side of the slit403dwith respect to the center line341. Further, the slit403ais located on the opposite side of the slit403cwith respect to the HZ plane, and the slit403bis located on the opposite side of the slit403dwith respect to the HZ plane. In addition, the slit403eis located between the slits403a,403band the slits403c,403d.

5.2 Function and Effect

In the mirror unit300of the present embodiment, stress generated in the holding part320in the H direction due to the fastening force of the fastening members401a,401b,401c, and401dcan be reduced by the slits403a,403b,403c,403d,403e. When the stress is reduced, deformation of the holding part320due to the stress can be suppressed. Further, due to the slits403a,403b,403c,403d,403e, the propagation of the stress to the adhesives380a,380b, and380ccan be suppressed, and the deformation of the adhesives380a,380b, and380ccan be suppressed. Therefore, distortion of the reflective surface310acan be suppressed. At least one of the slits403a,403b,403c,403dmay be provided.

The shapes of the slits403a,403b,403c,403d,403eare not limited to the foregoing.FIG.17is a front view of the mirror unit300according to a modification of the present embodiment. As shown inFIG.17, each of the slits403a,403b,403c,403dhas the same size and has a rectangular shape elongated in the V direction, and the slit403ehas a triangular shape. An apex among the three apexes of the slit403eis provided toward the adhesive380aside, and the remaining two apexes are provided toward the adhesive380bside and the adhesive380cside. Further, the holding part320is further provided with a rectangular slit403felongated in the V direction. The slit403fis longer than the slit403aand is provided on the opposite side of the slit403ewith respect to the center line341. One end of the slit403fis located between the slit403aand the slit403b, and the other end of the slit403fis located between the slit403cand the slit403d. The slit403fmay be connected to the slit403e.

6. Description of Line Narrowing Module of Fourth Embodiment

Next, the line narrowing module60of the fourth embodiment is described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

FIG.18is an enlarged view of a periphery of the adhesive380aof the fourth embodiment. The mirror310mainly includes a substrate311, a reflective film313that reflects a part of the light transmitted through the prism63toward the grating66, and a light shielding film315that shields the light transmitted through the reflective film313and traveling to the adhesive380a. The reflective film313includes a reflective surface310a. Although the adhesives380band380care not illustrated inFIG.18, the light shielding film315also shields light passing through the reflective film313and traveling to the adhesives380band380c.

The substrate311may be made of, for example, glass, and the adhesives380a,380b, and380cadhere to a side surface of the substrate311. The light shielding film315is made of, for example, aluminum, and the light shielding film315is formed on the surface of the substrate311by vapor deposition. Since the reflective film313is overlaid on the light shielding film315, the light shielding film315is provided between the substrate311and the reflective film313. The reflective film313is provided on an opposite side of the substrate311with respect to the light shielding film315. The reflective film313is a laminated film in which silicon layers and molybdenum layers are alternately laminated. The outermost layer of the reflective film313is a silicon layer. A film other than the silicon layer and the molybdenum layer may be used for the reflective film313, and a single-layer film of, for example, ruthenium may be provided.

6.2 Function and Effect

In the mirror unit300of the present embodiment, since the light shielding film315shields the light transmitted through the reflective film313, the progress of the light toward the adhesives380a,380b, and380ccan be suppressed. When the progress of the light is suppressed, deterioration of the adhesives380a,380b, and380cdue to the radiation with the light can be suppressed. Further, for example, it may no longer be necessary to widen the area of the adhesive surface between the mirror310and each of the adhesives380a,380b, and380con the assumption of deterioration of the adhesives380a,380b, and380c, and waste of the adhesives380a,380b, and380cdue to the widening may be suppressed. The light shielding film315is provided between the substrate311and the reflective film313. In this case, the attachment of the light shielding film315can be facilitated as compared with the case where the light shielding film315surrounds each of the adhesives380a,380b, and380c.

When the light shielding film315absorbs light, the light shielding film315serves as a heat source, and the adhesives380a,380b, and380cand the reflective film313may be deteriorated by the heat, and the reflective film313may be distorted by the heat. Therefore, it is preferable that the light shielding film315reflects light. The light shielding film315may be overlaid on at least a part of the surface of the substrate311. The light shielding film315may shield light traveling to at least one of the adhesives380a,380b, and380c.

The position of the light shielding film315is not limited to the foregoing.FIG.19is an enlarged view of a periphery of an adhesive380aaccording to a modification of the present embodiment. As illustrated inFIG.19, the light shielding film315may be provided between the substrate311and the adhesive380a. For example, the light shielding film315is provided on the entire side surface of the substrate311facing the adhesive380a. The light shielding film315may be provided on at least a part of a surface facing the adhesive380a. AlthoughFIG.19has been described with reference to the adhesive380a, the same applies to the adhesive380bside and the adhesive380cside. Further, the light shielding film315may be disposed between the substrate311and at least one of the adhesive380a, the adhesive380b, and the adhesive380c.

7. Description of Line Narrowing Module of Fifth Embodiment

Next, the line narrowing module60of the fifth embodiment is described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

FIG.20is a front view of the mirror unit300according to the fifth embodiment. In the mirror unit300of the present embodiment, the holding part320includes slits417a,417b, and417cadjacent to the adhesives380a,380b, and380c, respectively. The slit417ais provided in the plate member325, and the slit417band417care provided in the peripheral wall of the holding part320. The longitudinal direction of the slits417a,417b, and417cextends along the shaft340, i.e., along the V direction. In the V direction, the slit417ahas a length greater than or equal to that of the adhesive380a. Further, when viewed from the Z direction perpendicular to the longitudinal direction and the H-axis perpendicular to the reflective surface310a, the slit417aoverlaps at least a part of the adhesive380a. Although the relationship between the slit417aand the adhesive380ahas been described above, the same applies to the relationship between the slit417band the adhesive380band the relationship between the slit417cand the adhesive380c. The slits417a,417b, and417care located at the same height position as the adhesives380a,380b, and380cin the H direction perpendicular to the reflective surface310a.

7.2 Function and Effect

In the mirror unit300of the present embodiment, when the adhesives380a,380b, and380charden and shrink, the plate member325and the holding part320are pulled toward the mirror310by the tensile force of the adhesives380a,380b, and380c. When the plate member325and the holding part320are pulled toward the mirror310, the slits417a,417b, and417care deformed in the Z direction. Due to the deformation, the deformation of the plate member325and the holding part320due to the tensile force can be suppressed. In addition, when the mirror310is irradiated with the light, the holding part320and the mirror310may be deformed by the heat of the light. When the holding part320and the mirror310are to be deformed, the slits417a,417b, and417care deformed in the Z direction, and the deformation of the plate member325and the holding part320can be suppressed due to the deformation of the slits417a,417b, and417c. Therefore, the slits417a,417b, and417cabsorb the stress in the Z direction caused by the tensile force and the heat, and suppresses deformation of the plate member325and the holding part320. When the deformation of the plate member325and the holding part320is suppressed as described above, the distortion of the reflective surface310acan be suppressed.

In the mirror unit300of the present embodiment, the slits417band417cmay be omitted, or the slit417amay be omitted. Therefore, the holding part320is only required to include a slit that overlaps at least a part of the adhesive among the adhesives380a,380b, and380cthat adheres to the side surface of the mirror310in the thickness direction and is provided on the wall of the holding part320to which the adhesive adheres. The slits417a,417b, and417cmay be grooves or through holes.

8. Description of Line Narrowing Module of Sixth Embodiment

Next, the line narrowing module60of the sixth embodiment is described. Configurations similar to those described above are denoted by identical reference signs, and duplicate description thereof is omitted unless otherwise specified.

FIG.21is a diagram for describing the arrangement of the driving unit in the sixth embodiment. In the mirror unit300of the present embodiment, four driving units, specifically a pair of driving units351aand a pair of driving units351bare respectively arranged. The pair of driving units351ais disposed on the opposite side of the pair of driving units351bwith respect to the center line341. The pair of driving units351aand the pair of driving units351bare arranged so as to be located at the apexes of the rectangle. The pair of driving units351aand the pair of driving units351bare arranged in parallel at intervals in the V direction which is the axial direction. One of the driving units351ais disposed on the opposite side of the other of the driving units351awith respect to the adhesive380aand the base329a. One of the driving units351bis disposed below the adhesive380band the base329b, and the other of the driving units351bis disposed below the adhesive380cand the base329c. Driving of the pair of driving units351aand driving of the pair of driving units351bare opposite to each other in the H direction, whereby the pair of driving units351aand the pair of driving units351brotate the mirror310about the shaft340.

8.2 Function and Effect

In the mirror unit300of the present embodiment, the pair of driving units351aand the pair of driving units351bare respectively arranged. As a result, as compared with the case where only either one of the pair of driving units351aand the pair of driving unit351bis disposed, the pitching occurring in the V direction can be reduced, and the rotational property of the mirror310can be stabilized. Further, by individually controlling each of the pair of driving units351aand the pair of driving unit351b, the pitching can be further reduced. When the pair of driving units351aor351bis arranged, the mirror310may rotate about the Z axis. However, if two pairs of driving units351aand351bare provided, the rotational speed may be suppressed, and stability of the mirror310can be improved. The pair of driving units351aneed not be arranged in parallel at an interval in the V direction, which is the axial direction, but may be arranged to be misaligned in the Z direction. Although the pair of driving unit351ahas been described, the same applies to the pair of driving unit351b. It is preferable that the number of the driving units351aand351bis the same, but it may be different.

Arrangement of the driving units is not limited to the foregoing.FIG.22is a schematic diagram illustrating an overall configuration example of the mirror unit300in the modification of the present embodiment.FIG.23is a diagram for explaining the arrangement of the driving units in the present modification. In the mirror unit300of the present modification, the shaft340is provided on the end side of the holding part320in the V direction, and is provided below the plate member325. Further, in the mirror unit300of the present modification, the pair of driving units351ais not provided, and only the pair of driving units351bis provided. The pair of driving units351bis arranged at a position misaligned from the center line341in the Z direction perpendicular to the shaft340, and is arranged in parallel at an interval in the V direction which is the axial direction. In the mirror unit300of the present modification, the number of components can be reduced and a finer amplitude-width can be realized as compared with the case where the pair of driving units351aand the pair of driving units351bare provided. In the present modification, the arrangement positions of the shaft340and the pair of driving units351bmay be reversed.

The description above is intended to be illustrative and the present disclosure is not limited thereto. Thus, it would be obvious to those skilled in the art that changes may be made to the embodiments of the present disclosure without departing from the scope of the claims set out below. Further, it would be also obvious to those skilled in the art that embodiments of the present disclosure would be appropriately combined.

Terms used throughout the specification and the claims should be interpreted as “non-limiting” terms unless expressly stated otherwise. For example, terms such as “comprise”, “include”, and “contain” should not be interpreted to be exclusive of other structural elements. For example, terms such as “have”, and “having” should not be interpreted to be exclusive of other structural elements. Further, indefinite articles “a/an” should be interpreted to mean “at least one” or “one or more.” Further, “at least one of A, B, and C” should be interpreted to mean any of A, B, C, A+B, A+C, B+C, and A+B+C. In addition, combinations thereof with other matters than A, B, and C should also be construed as being encompassed.