WO2018139867A1

WO2018139867A1 - Mask cleaning apparatus and laser annealing apparatus

Info

Publication number: WO2018139867A1
Application number: PCT/KR2018/001109
Authority: WO
Inventors: 황대순
Original assignee: (주)이오테크닉스
Priority date: 2017-01-26
Filing date: 2018-01-25
Publication date: 2018-08-02
Also published as: KR101872441B1

Abstract

A mask cleaning apparatus is disclosed. The disclosed mask cleaning apparatus comprises: a laser source for generating a laser beam; and a laser emitting unit for emitting a laser beam at an adhesive on a photomask, wherein the laser emitting unit includes: a rotational driving unit for providing a rotational driving force; and a rotating optical system disposed on a moving path of the laser beam, rotated by the rotational driving unit, and moving, by the rotation, the location of the laser beam emitted at the adhesive on the photomask so as to compensate for a spatial energy variation of the laser beam.

Description

Mask cleaning device and laser annealing device

The present invention relates to a mask cleaning apparatus and a laser annealing apparatus.

In the lithography process at the time of manufacture of circuit patterns, such as a semiconductor device and a liquid crystal display, the base for exposure, such as a photomask or a reticle, is used. However, when foreign matter adheres to the substrate for exposure, the precision of the lithography process may be reduced. In order to prevent foreign matter adhesion, a dust cover called a pellicle is mounted on the photomask or the reticle.

In manufacturing processes, such as semiconductor devices, such as LSI and ultra-LSI, and a liquid crystal display panel, patterning is performed by irradiating light to a photosensitive layer etc. through a photomask (it is also called an exposure disc and a reticle). At this time, if a foreign matter adheres to the photomask, light is absorbed or bent by the foreign matter. For this reason, there arises a problem that the pattern to be formed is deformed or the edges are jagged and the dimension, quality and appearance of the patterning are damaged. To solve this problem, a dust cover called a pellicle is mounted on the photo mask.

The pellicle includes a pellicle frame made of metal and a pellicle film disposed on one end face of the pellicle frame. In addition, a mask adhesive layer for fixing the pellicle to the photomask may be formed at another end face of the pellicle frame. The pellicle must be replaced when its life is over or broken, and the adhesive layer must be removed for this purpose.

Conventionally, the adhesive layer is removed by a wet removal method using sulfuric acid or an organic chemical, but in this case, not only the adhesive layer but also the photo mask may be damaged together, and the adhesive layer removing process may be quite difficult.

The present invention provides a mask cleaning device and a laser annealing device for removing adhesive on a mask using a laser beam.

In addition, the present invention provides a mask cleaning device and a laser annealing device that can irradiate a uniform laser beam to the object to be processed by overlapping the laser beam irradiated to the adhesive through a rotating optical system to compensate for the spatial energy variation of the laser beam. do.

Mask cleaning apparatus according to an aspect of the present invention,

A laser source for generating a laser beam,

A laser irradiation part for irradiating the laser beam to the adhesive on the photo mask,

The laser irradiation unit,

A rotation drive unit providing a rotation drive force; And

It may be disposed in the movement path of the laser beam, rotated by the rotation drive unit, to rotate the position of the laser beam irradiated to the adhesive on the photo mask by the rotation; may include a.

In one embodiment, the variation width of the laser beam irradiated to the adhesive on the photo mask by the rotation of the rotating optical system may be 10% or less of the size of the laser beam irradiated to the adhesive on the photo mask.

In one embodiment, the number of overlap of the laser beam irradiated on the same area of the adhesive on the photo mask may be determined by the frequency of the laser beam and the rotation speed of the rotating optical system.

In one embodiment, the number of overlap of the laser beam irradiated on the same area of the adhesive on the photo mask may be 2 to 100 times.

In one embodiment, the size of the rotating optical system may be 1 mm or more.

In one embodiment, the size of the laser beam irradiated to the adhesive on the photo mask may be 1 mm or more.

In one embodiment, by rotating to the rotating optical system, the irradiation position of the laser beam with respect to the adhesive can be moved in the width direction of the adhesive.

In one embodiment, the laser irradiation unit may be configured to irradiate a laser beam to the same region of the adhesive for 30 seconds or more.

In one embodiment, the cross-sectional shape of the rotating optical system may be a trapezoidal shape.

In one embodiment, the cross-sectional shape of the rotating optical system may be rectangular.

Laser annealing apparatus according to an aspect of the present invention

A laser source for generating a laser beam,

It includes a laser irradiation unit for irradiating the laser beam to the object to be processed,

The laser irradiation unit,

A rotation drive unit providing a rotation drive force; And

Is disposed in the movement path of the laser beam, is rotated by the rotation drive unit, for rotating the position of the laser beam irradiated to the object to be processed by the rotation, may include; may include.

The laser annealing apparatus, wherein the variation range of the laser beam irradiated to the processing object by the rotation of the rotating optical system is 10% or less of the size of the laser beam irradiated to the processing object.

In one embodiment, the number of overlap of the laser beam irradiated on the same region of the object to be processed may be determined by the frequency of the laser beam and the rotation speed of the rotating optical system.

In one embodiment, the number of overlap of the laser beam irradiated onto the same region of the object may be 2 to 100 times.

In one embodiment, the size of the rotating optical system may be 1 mm or more.

In an embodiment, the size of the laser beam irradiated onto the object may be 1 mm or more.

In one embodiment, by rotating to the rotating optical system, the irradiation position of the laser beam with respect to the processing object can be moved in the width direction of the processing object.

In one embodiment, the laser irradiation unit may be configured to irradiate the laser beam to the same region of the object to be processed for 30 seconds or more.

The mask cleaning apparatus and the laser annealing apparatus including the same according to the embodiment of the present invention can remove the adhesive without damaging the mask by selectively removing the adhesive on the mask using a laser.

In addition, the mask cleaning apparatus and the laser annealing apparatus including the same according to an embodiment of the present invention, by overlapping the laser beam irradiated to the adhesive through a rotating optical system to compensate for the spatial energy deviation of the laser beam, uniform to the object to be processed The laser beam can be irradiated.

1 is a perspective view showing a state where a pellicle is attached on a photo mask,

FIG. 2 is a cross-sectional view illustrating a cross section of the photomask and the pellicle shown in FIG. 1.

3 is a view showing an adhesive remains on the surface of the photo mask after removing the pellicle from the photo mask.

4 and 5 are views schematically showing the removal of the adhesive using a laser beam.

6A is a line chart showing the spatial energy intensity of a laser beam irradiated to an adhesive, according to a comparative example, and FIG. 6B is a raster showing the spatial energy intensity of a laser beam irradiated to an adhesive, according to a comparative example It is a chart.

7 is a view conceptually illustrating a mask cleaning apparatus according to an embodiment, and FIG. 8 is a perspective view illustrating an example of the laser irradiation part of FIG. 7.

9 is a view for explaining an example of a rotating optical system, Figure 10a is a view for explaining the operation of the rotating optical system of Figure 9, Figures 10b and 10c is a view that the laser beam of Figure 10a is irradiated to the adhesive It is conceptually explained.

11A and 11B are line charts and raster charts showing spatial energy intensities of a laser beam applied to an adhesive when the rotating optical system according to FIG. 10 is rotated.

12A is a diagram illustrating another embodiment of a rotating optical system, and FIG. 12B is a diagram for describing an operation of the rotating optical system of FIG. 12A.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; Like reference numerals in the drawings refer to like elements, and the size or thickness of each element may be exaggerated for clarity.

Terms including ordinal numbers such as “first” and “second” may be used to describe various components, but the components are not limited by the terms. The terms are only used to distinguish one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term “and / or” includes any combination of a plurality of related items or any one of a plurality of related items.

FIG. 1 is a perspective view illustrating a state in which a pellicle 20 is attached to a photo mask 10, and FIG. 2 is a cross-sectional view illustrating a cross section of the photo mask 10 and the pellicle 20 illustrated in FIG. 1.

1 and 2, the pellicle 20 may be attached to the photo mask 10. The mask pattern 12 may be formed on the photo mask 10. The shape of the mask pattern 12 may vary depending on a patterning shape to be formed through a lithography process in a semiconductor device such as an LSI, an ultra LSI, or a liquid crystal panel. The photo mask 10 may include various materials. In exemplary embodiments, the photo mask 10 may include quartz. In addition, the photo mask 10 may include a quartz layer and a chromium (Cr) layer provided on the quartz layer. As another example, the photomask 10 may include a quartz layer and a molybdenum silicide (MoSi) layer provided on the quartz layer. Accordingly, the photo mask 10 may include at least one of quartz, chromium, and molybdenum silicide on the surface that meets the adhesive 30. The above materials are merely exemplary and are not limited thereto.

The pellicle 20 may be attached to the photo mask 10. The pellicle 20 may include a pellicle frame 24 and a pellicle film 22 provided on the pellicle frame 24. The size and shape of the pellicle frame 24 may vary in accordance with the size and shape of the photo mask 10 used in the lithography process. In addition, the size and shape of the pellicle frame 24 may not necessarily correspond to the size and shape of the photo mask 10. The pellicle film 22 may be attached to one surface of the pellicle frame 24. The pellicle film 22 may be attached through the pellicle frame 24 and the pellicle adhesive layer 26. However, the present invention is not limited thereto, and the pellicle film 22 and the pellicle frame 24 may be integrally connected without the pellicle adhesive layer 26. The pellicle film 22 is a transparent material and may transmit light through the pellicle film 22 during the lithography process. The light transmitted through the pellicle film 22 can pattern the object to be processed via the photomask 10.

When the pellicle 20 is attached on the photo mask 10, a predetermined space may be provided between the pellicle film 22 and the photo mask 10. The predetermined space may be blocked from the outside by the pellicle film 22 and the pellicle frame 24. Therefore, foreign matters may be prevented from entering the photo mask 10.

The pellicle 20 may be attached to the photo mask 10 through the adhesive 30. The adhesive 30 is made of an adhesive material having an adhesive force, and the pellicle 20 may be fixed on the photo mask 10. In exemplary embodiments, the adhesive 30 may include a fluoropolymer-based material. Exemplary of the fluoropolymer series materials include polytetrafluoroethylene polymer, tetrafluoroethylene (TFE) / perfluoro (alkyl vinyl ether) polymer and ethylene / tetrafluoroethylene polymer, chlorotrifluoroethylene (CTFE) And the like, but are not limited thereto. In addition to the fluoropolymer series, the adhesive 30 may include other materials. For example, the adhesive 30 may include a hydrogenated substance of a block polymer having a saturated cyclic hydrocarbon structure such as styrene / isoprene / styrene-based triblock polymer, and an adhesive material containing a tackifier. It may also comprise a hot melt adhesive material containing styrene / ethylene / propylene / styrene triblock copolymers and aliphatic petroleum resins.

3 is a view showing a state in which the adhesive 30 remains on the surface of the photo mask 10 after removing the pellicle 20 from the photo mask 10.

As shown in FIG. 3, when the adhesive 30 remains on the photo mask 10, it may be difficult to replace the pellicle 20 and attach the photo mask 10 to the photo mask 10 again. Conventionally, an organic compound or a sulfuric acid compound was used to remove the adhesive on the photo mask 10. That is, the adhesive 30 may be removed through a wet cleaning process using the organic compound or the sulfuric acid compound. However, when the wet cleaning process is performed, a problem may occur in that the transmittance of the mask pattern 12 or the material of the photomask 10 of the photomask 10 is changed. In addition, the cleaning process itself is cumbersome and time consuming.

4 and 5 are views schematically showing the removal of the adhesive 30 using the laser beam (L).

4 and 5, the adhesive 30 may be removed from the photomask 10 by irradiating the laser beam L on the adhesive 30. In the method of removing the adhesive 30 shown in FIGS. 4 and 5, instead of the wet cleaning process described above, the adhesive 30 may be removed using the energy of the laser beam L. FIG. The adhesive 30 may have a predetermined width w. For example, the width w of the adhesive 30 may be at least 1 mm. The size of the laser beam L irradiated onto the adhesive 30 may be 1 mm or more.

When removing the adhesive 30 with the laser beam L, it is important to remove the adhesive 30 completely. In addition, it is important to selectively remove only the adhesive 30 without affecting the mask pattern 12, transmittance, etc. of the photomask 10. For this purpose, the parameters related to the optical characteristics of the laser beam L can be controlled appropriately.

In order to remove the adhesive 30 without leaving the photo mask 10, it is necessary to irradiate the laser beam L at a constant energy intensity for a predetermined time. The processing time of the laser beam L irradiated onto the same region of the adhesive 30 may be 30 seconds or more. The processing time of the laser beam L irradiated onto the same region of the adhesive 30 may be 10 minutes or less.

In order to irradiate the laser beam L with a constant energy intensity, a beam homogenizer for constantly adjusting the energy intensity of the laser beam L may be used. However, even if such a beam homogenizer is used, due to the optical interference phenomenon, there is a spatial energy deviation of the laser beam (L).

6A is a line chart showing the spatial energy intensity of the laser beam L irradiated to the adhesive 30, and FIG. 6B is a raster illustrating the spatial energy intensity of the laser beam L irradiated to the adhesive 30. raster) chart.

Referring to FIG. 6A, the laser beam L irradiated to the adhesive 30 through the beam homogenizer may have a predetermined deviation depending on its position in the X and Y directions. Referring to FIG. 6B, regions D1, D2, and D3 of the laser beam L irradiated onto the adhesive 30 have lower energy intensities than adjacent regions.

When such a laser beam L is irradiated to the adhesive 30 for a predetermined time, most of the adhesive 30 is removed, but a portion of the adhesive 30 irradiated with a laser beam L having a relatively low energy intensity. Is left on the photo mask 10.

The mask cleaning apparatus 1 according to the embodiment may further include a rotation optical system 210 (see FIG. 7) capable of compensating for spatial energy variation of the laser beam L. FIG.

FIG. 7 is a view conceptually illustrating a mask cleaning apparatus 1 according to an exemplary embodiment, and FIG. 8 is a perspective view illustrating an example of the laser irradiator 200 of FIG. 7.

Referring to FIG. 7, the mask cleaning apparatus 1 includes a laser source 100 and a laser irradiator 200.

The laser source 100 generates a laser beam L. The laser beam L may have a wavelength capable of removing the adhesive 30 without damaging the photo mask 10. For example, the wavelength of the laser beam L may be 193 nm to 290 nm.

The laser beam L may be a pulsed laser beam. However, the laser beam L is not limited thereto and may be a continuous wave laser beam.

The laser irradiation part 200 irradiates the laser beam L to the adhesive agent 30 on the photomask 10. The laser beam L irradiated onto the adhesive 30 by the laser irradiator 200 may have a spatial energy deviation. For example, the spatial energy variation of the laser beam L may be 3% to 10% of the maximum energy intensity.

Referring to FIG. 8, the laser irradiator 200 may include a rotating optical system 210 and a rotating driver 230 that provides a rotating driving force to the rotating optical system 210. The laser irradiator 200 may further include a belt 250 that transmits the rotation driving force of the rotation driver 230 to the rotation optical system 210. In addition, although not shown in the drawings, the laser irradiator 200 may further include an optical system used as a beam homogenizer.

The rotating optical system 210 is disposed in the movement path of the laser beam L and passes the laser beam L. FIG. The rotation optical system 210 may be rotated by the rotation driver 230.

The rotation optical system 210 may overlap the laser beam L irradiated to the adhesive 30 by rotation to compensate for the spatial energy deviation of the laser beam L irradiated to the adhesive 30.

9 is a view for explaining an example of the rotating optical system 210a, Figure 10a is a view for explaining the operation of the rotating optical system 210a of Figure 9, Figures 10b and 10c is a laser beam of Figure 10a L) is conceptually described how the irradiation on the adhesive (30).

Referring to FIG. 9, the rotation optical system 210a may be rotated about a predetermined rotation axis R. Referring to FIG. The predetermined rotation axis R may be parallel to the incident direction of the laser beam L.

The cross-sectional shape of the rotating optical system 210a may be a trapezoidal shape. The rotating optical system 210a includes a first surface 2101 perpendicular to the incident direction of the laser beam L, and a second surface 2102 forming an acute angle θ with the incident direction of the laser beam L.

The laser beam L generated by the laser source 100 is refracted in the process of being incident on the rotating optical system 210a and exiting to the second surface 2102.

Referring to FIG. 10A, as the rotating optical system 210a rotates, the emission direction of the laser beam L incident to the rotating optical system 210a is changed. The laser beam L irradiated onto the adhesive 30 moves in position. As an example, referring to FIG. 10B, the laser beam L irradiated onto the adhesive 30 is moved in the width direction (X direction) of the adhesive 30. As another example, referring to FIG. 10C, the laser beam L irradiated onto the adhesive 30 moves in the width direction (X direction) as well as in the longitudinal direction (Y direction) of the adhesive 30.

Accordingly, even if the energy intensity of the laser beam L varies with position, since the laser beam L is moved in position, the total energy of the laser beam L irradiated to the adhesive 30 for a predetermined time. The amount becomes similar throughout.

If the laser beam L is irradiated for a predetermined time without moving the position when the energy intensity of the laser beam L varies depending on the position, the total amount of energy of the laser beam L irradiated to the adhesive 30 is Appear differently locally. As a result, the total amount of energy of the laser beam L irradiated to a portion of the adhesive 30 is smaller than that of the other regions, and the adhesive 30 remains in the partial region without being removed.

However, according to the embodiment, since the irradiation position of the laser beam L is moved by the rotating optical system 210a, the total amount of energy of the laser beam L irradiated to the adhesive 30 for a predetermined time is generally the same. Therefore, it is possible to prevent or significantly reduce the phenomenon in which the adhesive 30 remains.

Referring back to FIGS. 10A and 10B, the variation width N of the laser beam L irradiated to the adhesive 30 by the rotation of the rotating optical system 210a is the laser beam L irradiated to the adhesive 30. It may be less than 10% of the size (N) of.

The variation width N of the laser beam L is related to the angle θ of the second surface 2102 with respect to the first surface 2101 of the rotating optical system 210a and the focal length f of the rotating optical system 210a. It can be determined by the following equation (1).

N = 2ftan (sin ^-1 (nsintheta) -θ) ... (1)

On the other hand, as the irradiation position of the laser beam L moves, the laser beam L overlaps and irradiates to the same area 30-1 of the adhesive agent 30. For example, as shown in FIG. 10B, the laser irradiator 200 irradiates the laser beam L slightly to the right with respect to the same region 30-1 of the adhesive 30, and then rotates the rotating optical system 210a. Thereby, the laser beam L1 can be irradiated to the left side with respect to the same area | region 30-1 of the adhesive agent 30 slightly. In this case, the number of overlaps of the laser beam L with respect to the same region 30-1 of the adhesive 30 may be two times. Referring to FIG. 10C, the number of overlaps of the laser beam L with respect to the same region 30-1 of the adhesive 30 may be four times.

The number of overlaps n of the laser beams L applied to the same region 30-1 of the adhesive 30 may be 2 to 100 times. The number of overlaps of the laser beam L may be determined by the frequency ω of the laser beam L and the rotational speed per minute of the rotating optical system 210a.

The number of overlaps of the laser beam L may be determined by the following equation (2).

n = (60ω) / rpm ... (2)

Referring again to FIG. 10B, the size (or height) of the rotating optical system 210a of the laser irradiator 200 used to irradiate the laser beam L to the adhesive 30 is the width w of the adhesive 30. Can be greater than The size of the rotating optical system 210a may be 1 mm or more. The size of the rotating optical system 210a may be 200 mm or less.

The material of the rotating optical system 210a may be freely used as long as the material is used as an optical configuration. For example, the rotation optical system 210a may include at least one of fused silica, quartz, silica, nbk7, and bk7.

11A and 11B are line charts and raster charts showing spatial energy intensities of the laser beam L applied to the adhesive 30 when the rotating optical system 210a according to FIG. 10 is rotated.

Referring to FIG. 11A, it can be seen that the energy intensity profile of the laser beam L is moved left and right as the rotating optical system 210a rotates. As a result, it can be seen that the laser beam L applied to the predetermined position for a predetermined time becomes constant.

Referring to FIG. 11B, it can be seen that the rectangular laser beam L applied to the adhesive 30 has a uniform distribution with each other in two dimensions. Accordingly, the laser beam L applied to the adhesive 30 on the photo mask 10 is constant for a predetermined time, thereby preventing or minimizing the phenomenon in which the adhesive 30 is not removed.

12A is a view showing another embodiment of the rotating optical system 210b, and FIG. 12B is a view for explaining the operation of the rotating optical system 210b of FIG. 12A.

12A and 12B, the cross-sectional shape of the rotating optical system 210b may be rectangular. The rotating optical system 210b may be disposed obliquely with respect to the incident direction. Accordingly, the position of the laser beam L applied to the adhesive 30 may be changed by the rotation of the rotating optical system 210b.

On the other hand, in the above-described embodiment, the mask cleaning apparatus 1 has been described centering on the example used to remove the adhesive 30 on the photo mask 10. However, the use of the mask cleaning apparatus 1 according to the embodiment is not limited thereto, and may be used as a laser annealing apparatus for annealing an object to be processed other than the adhesive 30 using the laser beam L.

Although embodiments of the present invention have been described above, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Claims

A laser source for generating a laser beam,

A laser irradiation part for irradiating the laser beam to the adhesive on the photo mask,

The laser irradiation unit,

A rotation drive unit providing a rotation drive force; And

Is disposed in the movement path of the laser beam, is rotated about the axis of rotation parallel to the direction of incidence of the laser beam by the rotation drive unit, for moving the position of the laser beam irradiated to the adhesive on the photo mask by the rotation And a rotating optical system.
The method of claim 1,

The fluctuation range of the laser beam irradiated to the adhesive on the photo mask by the rotation of the rotating optical system is 10% or less of the size of the laser beam irradiated to the adhesive on the photo mask.
The method of claim 1,

The number of superimposition of the said laser beam irradiated on the same area | region of the adhesive agent on the said photo mask is determined by the frequency of the said laser beam and the rotational speed of the said rotational optical system.
The method of claim 1,

And the number of overlapping of the laser beams irradiated on the same area of the adhesive on the photomask is 2 to 100 times.
The method of claim 1,

The size of the rotating optical system is 1 mm or more, the mask cleaning apparatus.
The method of claim 5,

The size of the said laser beam irradiated to the adhesive agent on the said photo mask is 1 mm or more, The mask cleaning apparatus.
The method of claim 1,

The rotation position of the said rotation optical system WHEREIN: The mask cleaning apparatus which moves the irradiation position of the said laser beam with respect to the said adhesive agent to the width direction of the said adhesive agent.
The method of claim 1,

And the laser irradiation part is configured to irradiate a laser beam to the same region of the adhesive for 30 seconds or more.
The method of claim 1,

The cross-sectional shape of the rotating optical system is a trapezoidal shape, mask cleaning apparatus.
The method of claim 1,

The cross-sectional shape of the said rotating optical system is rectangular, The mask cleaning apparatus.
A laser source for generating a laser beam,

It includes a laser irradiation unit for irradiating the laser beam to the object to be processed,

The laser irradiation unit,

A rotation drive unit providing a rotation drive force; And

Is disposed in the movement path of the laser beam, rotated about the axis of rotation parallel to the direction of incidence of the laser beam by the rotation drive unit, the rotation to move the position of the laser beam irradiated to the processing object by the rotation Optical system; comprising, laser annealing device.
The method of claim 11,

The laser annealing apparatus, wherein the variation range of the laser beam irradiated to the processing object by the rotation of the rotating optical system is 10% or less of the size of the laser beam irradiated to the processing object.
The method of claim 11,

The number of superimposition of the said laser beam irradiated on the same area | region of the said to-be-processed object is determined by the frequency of the said laser beam and the rotational speed of the said rotating optical system.
The method of claim 11,

A laser annealing apparatus, wherein the number of times of superimposition of the laser beam irradiated on the same region of the object to be processed is 2 to 100 times.
The method of claim 11,

The size of the rotating optical system is 1 mm or more, the laser annealing device.
The method of claim 15,

The laser annealing apparatus of Claim 1 whose magnitude | size of the said laser beam irradiated to the process object is 1 mm or more.
The method of claim 11,

The laser annealing apparatus, wherein the irradiation position of the laser beam with respect to the object to be processed is moved in the width direction of the object by the rotation to the rotating optical system.
The method of claim 11,

The laser annealing device is configured so that the laser beam is irradiated to the same region of the object to be processed for 30 seconds or more.
The method of claim 11,

The cross-sectional shape of the rotating optical system is a trapezoidal shape, laser annealing device.
The method of claim 11,

A laser annealing device, wherein the cross-sectional shape of the rotating optical system is rectangular.