JP2003131392A - Marking method and apparatus by laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a marking method and apparatus which permit marking of identification cords homogeneous in density and shape when the identification cords are marked by laser beams while an exposure unit and a stage are relatively moved. SOLUTION: The method and apparatus for marking an article 50 to be marked with the identification cords C by the laser beams outputted from the exposure unit 1 by relatively moving the stage 2 placed on with the article 50 to be marked and the exposure unit 1 arranged above this stage 2, in which the laser beams outputted from the exposure unit 1 are made to scan the object so as to be successively and time serially deflected in a direction orthogonal with the relative moving direction and are shifted in their irradiation directions so as to synchronizing with the relative moving direction, by which the irradiation points on the article 50 to be marked are aligned to an orthogonal coordinate form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a marking method and apparatus for marking an identification code with a laser beam on an article to be marked, and more specifically, history control and quality control on a photoresist-coated substrate in a liquid crystal panel manufacturing process or the like. The present invention relates to a marking method and apparatus for exposing an identification code for a laser beam with a laser beam.

[0002]

2. Description of the Related Art Generally, in a liquid crystal panel manufacturing process, in addition to exposing a circuit pattern on a glass substrate coated with photoresist (that is, photosensitive resin) by a pattern exposure device, a substrate identification code or a panel by an identification exposure device. After exposing the identification code or the like or exposing the unnecessary resist portion in the peripheral portion of the substrate by the peripheral exposure device, development processing is performed by the developing device. A liquid crystal panel divided into a plurality of pieces is manufactured from the glass substrate thus developed.

FIG. 17 exemplifies a glass substrate which has been subjected to the exposure processing and the development processing as described above.

A large number of liquid crystal panels 5 are mounted on the glass substrate 50.
1 are exposed so as to be arranged in multiple rows, and a board identification code 50a is marked around the board for history management, quality control, and the like. Further, the glass substrate 50 is marked with a panel identification code 51a in which an array number or the like is added to each liquid crystal panel 51 so that the particular liquid crystal panel 51 can be identified even after being divided into a plurality of liquid crystal panels 51.
Further, a division board identification code 50b to which division position information or the like is added is marked for each column so that each liquid crystal panel 51 can be managed in units of columns.

When a plurality of small liquid crystal panels 51 are separately manufactured from the large glass substrate 50 as described above,
The divided board identification code 50b and the panel identification code 51a are required. However, the names and division numbers of the board identification code 50a, the divided board identification code 50b, the panel identification code 51a, etc., are merely examples, and it goes without saying that they may vary depending on the type of the liquid crystal panel.

Conventionally, the board identification code 50 as described above is used.
a, divided board identification code 50b, panel identification code 51
As a method of marking an identification code such as a, a laser beam is divided into a plurality of beams while moving a stage on which a glass substrate is placed at a constant speed under NC control with respect to an exposure unit fixed at a fixed position. A method has been adopted in which an identification code is marked by selectively irradiating a predetermined position on a glass substrate with a plurality of laser beams.

However, according to the conventional method described above, when one laser beam is split into a plurality of beams and the plurality of beams are selectively irradiated to predetermined positions on the glass substrate, the stage on which the glass substrate is placed is moved relative to each other. To do it while
There is a problem in that it is not possible to mark a uniform density or shape identification code because the irradiation points between the beams are displaced and the displacement causes variations in the beam shape and energy.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a marking method capable of marking an identification code having a uniform density and shape when marking the identification code with a laser beam while relatively moving the exposure unit and the stage. And to provide a device.

[0009]

A marking method using a laser beam of the present invention that achieves the above object is achieved by relatively moving a stage on which an article to be marked is placed and an exposure unit arranged above the stage, In a method of marking an identification code on the article to be marked by a laser beam output from an exposure unit, scanning is performed so that the laser beam output from the exposure unit is sequentially and sequentially deflected in a direction orthogonal to the relative movement direction. In addition, the irradiation direction is shifted to the relative movement direction, and the irradiation point on the article to be marked is aligned with the orthogonal coordinates.

According to another marking method of the present invention, the stage on which the article to be marked is placed and an exposure unit arranged above the stage are relatively moved, and the article to be marked is produced by a laser beam output from the exposure unit. In the method of marking an identification code on the above, the orthogonal coordinates of the surface of the stage or the article to be marked on the stage are inclined with respect to the relative movement direction, and the laser beam output from the exposure unit is set to the relative movement direction. It is characterized in that the irradiation points on the article to be marked are aligned in orthogonal coordinates by scanning so as to sequentially deflect in a time series in the orthogonal direction.

The laser beam marking apparatus of the present invention allows the stage on which the article to be marked is placed and the exposure unit arranged above the stage to be relatively movable, and outputs the exposure unit from the exposure unit. Beam deflecting means for scanning the laser beam so as to sequentially deflect the laser beam in a direction orthogonal to the relative movement direction, and direction correction for shifting the irradiation direction of the laser beam deflected by the beam deflection means to the relative movement direction. It is characterized in that it is configured by means.

In another marking apparatus of the present invention, a stage on which an article to be marked is placed and an exposure unit arranged above the stage are relatively movable, and the stage or the article to be marked on the stage is movable. The Cartesian coordinates of the surface of the are inclined relative to the relative movement direction, and the exposure unit is scanned so as to sequentially deflect the laser beam output from the exposure unit in a direction orthogonal to the relative movement direction in time series. A beam deflecting means, a projection optical means for expanding the laser beam deflected by the beam deflecting means, and a direction correcting means for changing the irradiation direction of the laser beam emitted from the projection optical means. is there.

According to the present invention, the laser beam output from the exposure unit as described above is sequentially deflected and branched in time series in the direction orthogonal to the relative movement direction of the exposure unit and the stage, and the relative movement direction is scanned. Since the irradiation direction is corrected so as to eliminate the deviation of the irradiation time difference between the beams that are adjacent to each other in the direction orthogonal to, the identification code with a uniform shape and concentration is marked without the energy distribution or shape of each beam changing significantly. be able to.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention shown in the drawings will be specifically described below.

FIG. 1 illustrates a laser beam marking device according to the present invention.

Reference numeral 1 is an exposure unit, and 2 is a stage for holding the substrate 50 on the upper surface. The substrate 50 is placed on the stage 2 as an article to be marked, and the surface thereof is coated with a photoresist (that is, a photosensitive resin). Although only two sets of the exposure units 1 arranged in parallel are shown in the drawing, a plurality of columns may be arranged over the entire width direction of the substrate 50.

A substrate 5 having a photoresist coated on its surface
0 is transported and mounted on the stage 2 by a transport robot (not shown) or a transport mechanism such as a conveyor. The stage 2 has a drive mechanism and a surface for independently moving in the X-axis direction and the Y-axis direction, respectively, when the long-side direction and the short-side direction of the rectangle in plan view are the X-axis direction and the Y-axis direction of the orthogonal coordinates. A rotation mechanism (not shown) for rotating about a vertical axis is provided, and a large number of suction holes and a plurality of substrate support pins (not shown) are provided on the surface so as to project and retract. ing.

The substrate 50 transferred by the transfer mechanism is
When it is placed on the substrate support pin projected on the surface of the stage 2, the substrate support pin descends and is lowered onto the stage 2, and then negative pressure acts on the suction hole to suck and hold it.

Since the position of the substrate 50 placed on the stage 2 is not always constant, it is measured how much it is from the reference position registered in advance, and the reference position is set based on the measured value. The method for measuring the position is not particularly limited, but it can be measured by a displacement sensor or a CCD camera and a displacement measuring method by image processing. Alternatively, the substrate 5
Before holding 0 on the stage 2, a method of laterally pressing down on a reference position and performing alignment may be used.

The stage 2 holding the substrate 50 is moved to the exposure start position of the identification code based on the data registered in advance by NC control. The exposure start position is registered by an advance operation, and the shift amount is corrected and calculated.

The exposure unit 1 outputs a pulse of one laser beam 10 from a laser light source (not shown), and a beam splitter 21 splits the laser beam 10 into a straight laser beam 11 and a laser beam 12 which changes its direction. Pulse output of the laser beam 10, for example, the pulse repeats the extinction B luminescent A and time t _b of time as shown in FIG. 2 t _a alternately at a high speed.

The above-mentioned straight-ahead laser beam 11 is redirected by the prism 22 to become a laser beam 13 parallel to the other laser beam 12. The two parallel laser beams 12 and 13 pass through the beam deflection mechanism 23, respectively, so that the laser beams 12 and 13 are sequentially stepwise in a direction orthogonal to the relative movement direction of the stage 2 with respect to the exposure unit 1 (direction of arrow F). Multiple laser beams 1 deflected to
4, 14a to 14f (see FIGS. 3A to 3D). Although the number of branches is seven in the figure, the number of stages is not particularly limited.

The beam deflection mechanism 23 is not particularly limited, but an acousto-optical element is used, for example, and the emission direction of one laser beam can be deflected in a plurality of steps as described above.

As shown in FIGS. 3A to 3D, among the laser beams passing through the beam deflecting mechanism 23, the laser beam 14 which has not been deflected and has proceeded straight is a condensing lens 24.
After passing through, the light is blocked by the transmission filter 25. The laser beams 14a to 14f, which are sequentially deflected at different angles in time series by the beam deflecting mechanism 23, pass through the condensing lens 24 so that the parallel laser beams 15a to 14f.
It becomes 15f.

The laser beams 16a to 16f that have passed through the transmission filter 25 are then reflected by the angle-variable mirror 31 to change the irradiation direction, and the laser beams 17a to 17f.
f (see FIG. 5). Redirected laser beam 17
a to 17f become the laser beams 18a to 18f condensed by the condenser lens 26 as shown in FIG.
The photoresist on the surface is exposed by irradiating the laser beam on the surface 0, and the identification code C (51a) consisting of characters and / or a two-dimensional figure is marked by the accumulation of the exposure points of these laser beams 18a to 18f.

As shown in FIG. 1, the identification code C (51a) is obtained by moving the stage 2 in the direction of arrow F at a constant velocity v, and by arranging a plurality of laser beams 18a to 18f in the direction orthogonal to the moving direction. Are sequentially scanned in time series and exposed to be marked.

In the marking of this identification code, when the mirror 31 is fixed at a constant angle, the arrow F
When the laser beams 18a to 18f are sequentially scanned with respect to the substrate 50 moving in the direction so as to be orthogonal to the moving direction,
The exposure points a, b, c, d, e, and f are sequentially shifted obliquely with respect to the moving direction F due to a deviation (difference) in irradiation timing between the laser beams (see FIG. 8). Subsequently, the exposure point g, h, i, j, k, l when the laser beams 18a to 18f are scanned, and the next exposure point m, n, o,
Since p, q, and r are also inclined like the above, the identification code C
Has a distorted shape.

The exposure points a, b, c ...
In q and r, the point surrounded by the solid line is the beam deflection mechanism 23.
Is turned on, the laser beam is irradiated, and the point where the laser beam is actually exposed is indicated.
F means that the laser beam was not irradiated and was not exposed. Although the point of this broken line is a non-exposure point to be exact, it is referred to as an exposure point for convenience by displaying it with a broken line.

In the exposure unit of the present invention, as shown in FIG. 5, the mirror 31 is rotated in the direction of the arrow by the mirror rotation mechanism 32 about the rotation axis 31a parallel to the longitudinal direction, so that reflection occurs. Laser beams 17a-17
The irradiation direction of f sequentially shifts in the moving direction F of the stage 2 (substrate 50) in time series. Therefore, as shown in FIG. 9, the scanning direction of the laser beams 18a to 18f is the stage 2
In synchronism with the movement of
As a result, the exposure points a of the laser beams 18a to 18f,
b, c, d, e, f, next exposure point g, h, i, j, k,
l, and the next exposure points m, n, o, p, q, and r are aligned in a rectangular coordinate state. Therefore, the identification codes C uniformly arranged in a grid are marked.

In the illustrated embodiment, the laser beam 18a
As a method of making the scanning direction of ~ 18f oblique with respect to the moving direction F of the stage 2 (substrate 50), the reflection mirror 31
5 was rotated as shown in FIG. 5, but as shown in FIG. 6, a rotary shaft 32a was attached to the middle of the reflecting mirror 31 in the longitudinal direction so that the rotary shaft 32a was orthogonal to the rotary shaft 32a.
It may be rotated in the direction of the arrow by 2. In addition, as shown in FIG. 7, the reflection mirror is a polygonal mirror 33.
The mirror rotating mechanism 32 may rotate the polygonal mirror 33 as the axis of rotation.

Further, instead of the above mirror, a prism,
Dove prisms and other shapes and means can be used.

In any of the above methods, the reflecting surface of the mirror is made variable. However, the mounting angle of the exposure unit 1 or the reflecting mirror 31 is changed beforehand, and the beam scanning direction is changed as shown in FIG. Even when the beam exposure direction is set to be orthogonal to the substrate moving direction F instead of being orthogonal to the substrate moving direction, it is possible to obtain the same effect as the above. Alternatively, as shown in FIG. 10, the moving direction F (relative moving direction) of the stage 2 (substrate 50) may be slanted with respect to the beam scanning direction in plan view.

The laser beam used in the present invention may be a laser beam that outputs pulses, or a laser beam that outputs continuously as long as the deflection angle can be changed at high speed. In the case of a laser beam that is continuously output, as shown in FIG. 11, if the time when the beam deflection angle θ is switched is t ₁ and the time when the beam deflection angle θ is not changed is t ₂ , the beam is irradiated in both times. I will let you. However, if the time t ₁ is sufficiently shorter than the time t ₂ and the resist sensitivity is not affected, it is possible to perform exposure at a predetermined position.

In many cases, the energy distribution in the laser beam is actually not uniform, but even in that case, if the energy given to the photoresist is sufficient, it is exposed. Also,
The exposure point may not be exactly a perfect square due to actual exposure energy, photoresist sensitivity, optical system assembly accuracy, surface reflection, etc., but in most cases there is no problem with the visibility of the identification code. . The beam shape can be freely changed to a circular shape, a polygonal shape, or the like by changing the shape, spacing, or combination of filters and lenses.

In the embodiment shown in FIG. 1, the case where one laser beam is branched into two by the beam splitter 21 and used is explained, but the number of branches may be three or more, or it may not be branched. You may use it as it is. The beam splitter is not particularly limited as long as it can split the beam, and other means such as a half mirror may be used.

In the embodiment shown in FIG. 1, the beam deflection mechanism 23 is used.
The laser beams 14a to 14f deflected by (4) are collimated by the condenser lens 24. But,
In the present invention, it is not always necessary to make the deflected laser beam parallel light, and as illustrated in FIG.
The laser beam expanded by the beam deflection mechanism 23 may be directly reflected by the mirror 31 without being converted into parallel light, condensed by the optical means 26 such as a projection lens, and irradiated and exposed on the substrate 50. Further, when the deflected laser beam is focused again, the projection optical system used may be a finite system or an infinite system, and the number of mirrors used does not matter.

When the orientation of the identification code changes, marking can be performed by changing the direction of the stage and scanning. After the exposure of the identification code, the stage is moved to the substrate unloading position, the suction of the substrate is released, the substrate support pins are raised, and the substrate is placed on the substrate unloading mechanism and unloaded. After that, the unexposed substrate is again carried in to perform the exposure operation, and when the exposure is completed, the substrate is discharged, and a series of operations is repeated.

Further, in the embodiment shown in FIG. 1, the beam deflecting mechanism 23 performs deflection irradiation of a plurality of stages as means for deflecting and branching the laser beam. As in the embodiment shown in FIG. 13, the beam deflection mechanism 23 performs only selective irradiation of light emission and extinction, and the deflection operation of the laser beam uses the polygon mirror 28 rotated by the mirror rotation mechanism 30. It may be one. Further, as the polygon mirror 28 at this time, as in the example shown in FIG.
The flat mirror 29 may be rotated left and right.

In the embodiment shown in FIG. 1, the exposure unit 1 is fixed and the substrate holding stage 2 can be moved independently in the X-axis direction and the Y-axis direction of the orthogonal coordinates. However, this relationship may be reversed so that the exposure unit 1 can be moved independently in the X-axis direction and the Y-axis direction of the orthogonal coordinates.

When the exposure units are provided in parallel in a plurality of rows, the distance between the exposure units is made variable by a moving mechanism so that the exposure position of the identification code can be arbitrarily changed. It is desirable that

The present invention is applicable to a substrate coated with a metal film, a glass substrate and a silicon wafer substrate by changing the kind of the laser beam in addition to the case where the photoresist coated substrate is exposed and marked by a laser beam. It can also be applied to marking for direct engraving (direct marking).

[0042]

EXAMPLE When an identification code is marked on a photoresist-coated substrate with the identification code marking device shown in FIG. 1, a laser beam having a wavelength of the third harmonic of the YAG laser, λ = 355 nm, is used as a laser beam to coat the substrate. A resin that is sensitive to this wavelength was selected as the photoresist to be used.

The pulse frequency f of the laser beam is f = 60
The width W of the laser beam on the work surface when focused on the substrate at W = 0.050 mm, the interval p between adjacent beams p = 0.050 mm, the speed v at which the stage is moved in the beam thickness direction = 500 mm / sec.

Further, the laser beam is moved by a beam deflection mechanism.
The beams were deflected in stages, and the beams in 6 directions were irradiated onto the substrate through the transmission filter 25, and the beams in 6 directions were selectively irradiated at 10 kHz.

With the above setting, the distance D that the stage moves during one pulse of the laser beam is represented by D = v / f, and the deviation between adjacent beams is 0.0083.
(Mm), and the distance between the beams in the next row was D = 6 × 500/60000 = 0.05 (mm).

The ON time within one pulse is t _a , OF
F time t _b, the duty ratio r is defined as _{r = t a / (t a} + t b), by setting the r = 10%, 1 laser irradiation time t _a per pulse t _a = r / It became f.

Let the length d of the laser beam on the work surface be d =
If it is 0.045 mm, the actual irradiation length L is L = d + v · t _a L = d + v · r / f, and L = 0.050 mm. Therefore, each laser beam should be exposed in a grid pattern at intervals of 50 μm. I was able to.

By repeating this, it was possible to form an identification code of a dot-shaped drawing pattern consisting of characters and figures as shown in FIG.

Not limited to FIG. 15, the dot pattern can be variously changed by changing the scanning speed v of the substrate and the size of the identification code. For example, in FIG.
It is also possible to change to a shape with rounded corners, a shape with a circle as shown in 6, or other geometrical figures, and it is possible to recognize as an identification code.

[0050]

As described above, according to the present invention, the laser beam output from the exposure unit is sequentially deflected and branched in time series in the direction orthogonal to the relative movement direction of the exposure unit and the stage, and scanned. Since the irradiation direction is corrected so as to eliminate the difference in irradiation time difference between adjacent beams in the direction orthogonal to the relative movement direction, the energy distribution and shape of each beam do not change significantly, and uniform identification of shape and concentration Codes can be marked.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a laser beam marking device according to the present invention.

FIG. 2 is an output graph showing an example of a laser beam used in the present invention.

3A to 3D are explanatory views showing a state in which a laser beam is deflected by a beam deflection mechanism in the apparatus of the present invention.

FIG. 4 is an explanatory view showing a state in which a substrate is exposed to a laser beam in the apparatus of the present invention.

FIG. 5 is an explanatory diagram showing a mirror reflection mechanism that changes the irradiation direction of a laser beam in the device of the present invention.

FIG. 6 is an explanatory view showing another mirror reflection mechanism for changing the irradiation direction of the laser beam in the device of the present invention.

FIG. 7 is an explanatory view showing still another mirror reflection mechanism for changing the irradiation direction of the laser beam in the device of the present invention.

FIG. 8 is an explanatory diagram showing an exposure method for a substrate that is not based on the method of the present invention.

FIG. 9 is an explanatory diagram showing an exposure method for a substrate according to the method of the present invention.

FIG. 10 is an explanatory diagram showing another example of an exposure method for a substrate according to the method of the present invention.

FIG. 11 is a diagram showing how the deflection angle of a continuously output laser beam used in the present invention changes with time.

FIG. 12 is an explanatory view showing a case where a deflected beam is condensed into only a projection lens without being made into parallel light in the present invention.

FIG. 13 is a schematic view illustrating another example of a laser beam marking device according to the present invention.

14 is a schematic view showing another example of the beam deflecting mechanism used in the apparatus of FIG.

FIG. 15 is an explanatory diagram of an identification code marked according to the present invention.

FIG. 16 is an explanatory diagram showing another example of the identification code marked according to the present invention.

FIG. 17 is a plan view illustrating a substrate that has been subjected to exposure processing and then development processing.

[Explanation of symbols]

1 Exposure unit 2 (for holding substrates) stage 10, 11, 12, 13, 14, 15 Laser beam Deflection laser beams 14a to 14f 15a to 15f Laser beam made into parallel light 16a to 16f Laser beams selectively irradiated Laser beams reflected by the mirrors 17a to 17f Laser beam focused by 18a-18f lens 21 Beam splitter 22 Prism 23 Beam deflection mechanism 24 Condensing lens 25 transmission filter 26 Condensing lens 27 Transmission filter 28 polygon mirror 29 mirror 30 Mirror rotation mechanism 31 reflective mirror 32 Mirror rotation mechanism 33 polygon mirror 50 substrates 50a board identification code 50b cut board identification code 51 LCD panel 51a Panel identification code C identification code

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 501230199             Applied Photonics Incorporated             Itted             Applied Photonics, I             nc             Sue, Florida 32826, United States             To 300 Orlando, Research Park             Way 12565             12565 Research Parkwa             y, Suite 300 Orlando,             FL 32826, USA (72) Inventor Kodai Uehara             Toray, 1-41 Oe, Otsu City, Shiga Prefecture             Engineering Co., Ltd. (72) Inventor Seiki Mori             Toray, 1-41 Oe, Otsu City, Shiga Prefecture             Engineering Co., Ltd. (72) Inventor Kenji Sato             Toray, 1-41 Oe, Otsu City, Shiga Prefecture             Engineering Co., Ltd. F-term (reference) 2H097 AA03 CA17 GB04 LA12

Claims (8)

[Claims] 1. A stage on which an article to be marked is placed and an exposure unit arranged above the stage are relatively moved, and an identification code is marked on the article to be marked by a laser beam output from the exposure unit. In the method, the laser beam output from the exposure unit is scanned so as to be sequentially deflected in a time-series direction in a direction orthogonal to the relative movement direction, and the irradiation direction is shifted to the relative movement direction, on the article to be marked. Marking method using a laser beam that aligns the irradiation points on the rectangular coordinates. 2. An identification code is marked on the article to be marked by a laser beam output from the exposure unit by relatively moving a stage on which the article to be marked is placed and an exposure unit arranged above the stage. In the method, the orthogonal coordinates of the surface of the stage or the article to be marked on the stage are inclined with respect to the relative movement direction, and the laser beam output from the exposure unit is time-sequential in a direction orthogonal to the relative movement direction. A marking method using a laser beam in which irradiation points on the article to be marked are aligned in orthogonal coordinates by scanning so as to be sequentially deflected to. 3. The marking method with a laser beam according to claim 1, wherein the identification code is composed of characters and / or a two-dimensional figure. 4. A stage on which an article to be marked is placed and an exposure unit arranged above the stage are made relatively movable, and the exposure unit outputs a laser beam from the exposure unit in the relative movement direction. A laser beam composed of beam deflecting means for scanning so as to sequentially deflect in a direction orthogonal to each other and direction correcting means for shifting the irradiation direction of the laser beam deflected by the beam deflecting means to the relative movement direction. Marking device. 5. The laser beam marking apparatus according to claim 4, wherein the direction correcting means is a mirror that makes a reflecting surface variable. 6. A stage on which an article to be marked is placed and an exposure unit arranged above the stage are made movable relative to each other, and the orthogonal coordinates of the surface of the stage or the article to be marked on the stage are defined as the orthogonal coordinates. Beam deflecting means for inclining with respect to the relative movement direction and scanning the exposure unit so as to sequentially deflect the laser beam output from the exposure unit in a direction orthogonal to the relative movement direction in time series, and the beam deflection means. A laser beam marking device comprising a projection optical means for expanding a laser beam deflected by a deflecting means, and a direction correcting means for changing an irradiation direction of the laser beam emitted from the projection optical means. 7. A marking device using a laser beam according to claim 4, wherein a condensing unit is provided on the downstream side of the direction correcting unit. 8. The laser beam marking apparatus according to claim 4, wherein the exposure units are arranged in a plurality of rows.