JP2000133859A - Laser marking method and device using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect the surface of a processed member against damages by a method, wherein a laser beam emitted from a laser light source is concentrated on a micro region located inside the processed member to make marking by modifying the micro region irradiated with a laser beam. SOLUTION: A laser beam 10 emitted from a laser source 1 is made to impinge on a beam-forming section 2, the laser beam 10 is shaped by the beam- forming section 2, and the shaped laser beam 11 is changed in the traveling direction by reflecting mirrors 3 and 4 to be caused to impinge on a light- condensing optical system 5. The condensing optical system 5 concentrates a condensed laser beam 12 on a micro region 8 inside a glass substrate 7, and the laser beam 12 is enhanced in energy density in the micro region 8, where it is concentrated to cause absorption due to optically nonlinear phenomenon. Absorption of laser energy cause optical damages to the micro region 8 inside the glass substrate 7 and to modify it, so that marking is made inside the glass substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a marking method and a marking device using a laser, and more particularly to a marking method and a marking device for marking inside a workpiece.

[0002]

2. Description of the Related Art There is known a method of marking a surface of a workpiece such as a transparent glass substrate using ablation by a laser beam. According to this method, fine cracks may occur on the surface of the workpiece, and the fragments may be mixed into the production line. Further, since deposits called "debris" are deposited near the marked position, it is necessary to perform cleaning to remove the deposits.

A method of focusing a laser beam inside a workpiece without damaging the surface of the workpiece and marking the interior of the workpiece is disclosed in Japanese Patent Laid-Open No. 3-124486.
No. 6,086,045. According to this method, since the surface of the member to be processed is not damaged, it is possible to prevent generation of minute cracks and adhesion of debris.

According to the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-124486, 0.5-0.5
Marking can be performed at a position having a depth of about 2.5 mm.

[0005]

According to an experiment conducted by the inventor of the present invention, even when a laser beam is strongly focused on the inside of a substrate, damage may occur not only on the inside but also on the surface of the substrate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a marking method and a marking apparatus capable of preventing damage to the surface of a workpiece when marking inside a workpiece.

[0007]

According to one aspect of the present invention, there is provided a step of holding a workpiece so that a region of the surface of the workpiece through which a laser beam passes does not directly touch another object. Converging the laser beam emitted from the laser light source onto a certain small area inside the workpiece to change the condensed portion of the workpiece to perform marking. .

According to another aspect of the present invention, the step of holding the workpiece so that a region of the surface of the workpiece through which the laser beam passes contacts the gas layer, and the step of emitting the laser emitted from the laser light source. Condensing the beam on a minute area inside the workpiece to change the condensed portion of the workpiece to perform marking.

According to another aspect of the present invention, a laser light source, a condensing optical system for condensing a laser beam from the laser light source on a small area inside a workpiece, and There is provided a marking device having a holding member for holding the processing member so that a region through which the laser beam passes does not directly touch another object.

Since the area of the surface of the workpiece through which the laser beam passes does not directly contact the holding member at the time of marking, it is necessary to prevent fine particles and the like adhering to the holding member from adhering to the surface of the workpiece. Can be prevented. Therefore, damage to the surface due to the interaction between the fine particles and the like and the laser beam is prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, preliminary experiments performed by the present inventors will be described. When a laser beam is focused on the inside of the substrate and an attempt is made to mark only the inside without damaging the surface, the surface may sometimes be damaged. It is considered that the surface damage is greatly affected by fine particles adsorbed or attached to the substrate surface. It is considered that the laser beam is scattered by the influence of the fine particles, and the laser energy density exceeds the marking threshold on the substrate surface. In order to avoid the influence of such fine particles, even if the substrate is washed before the marking process, the fine particles often adhere to the substrate from a holding table or the like during the marking.

FIG. 1 shows the principle of operation of a marking device according to a first embodiment of the present invention. From laser light source 1 to 1
The laser beam 10 is emitted. Laser beam 10
Enters the beam shaping unit 2. The beam shaping unit 2 is an optical device that shapes the beam shape and energy distribution of the laser beam 11 into a predetermined size and shape, or divides the beam into a plurality of beams. The direction of the laser beam 11 emitted from the beam shaping unit 2 is changed by the reflecting mirrors 3 and 4, and the laser beam 11 enters the focusing optical system 5.

A holding table 6 made of, for example, metal is arranged so as to face the condensing optical system 5. A glass substrate 7 as a member to be processed is placed on the holding table 6. Condensing optical system 5
Focuses the focused beam 12 on a minute area inside the glass substrate 7.

FIG. 2A is a sectional view of a region including the glass substrate 7 and the holding table 6. The energy density of the laser beam is increased in the micro region 8 inside the glass substrate 7 and in the vicinity thereof. When the energy density of the laser beam exceeds the threshold value, it is considered that absorption due to an optical nonlinear phenomenon occurs. Based on this absorption, optical damage (Optical Damage)
age) or an optical breakdown (Optical Breakdown) occurs, and the minute region 8 of the glass substrate 7 is deteriorated and can be visually recognized from the outside.

In such a configuration, the reflecting mirrors 3 and 4
Can be moved to move the focal point, thereby marking the inside of the glass substrate 7. Of course, it is also possible to perform marking of a desired shape by moving the holding table 6 while fixing the laser beam 12.

In the first embodiment shown in FIG. 2A, a through hole 9 is provided in the holding table 6. The laser beam transmitted through the glass substrate 7 is configured to pass through the through hole 9 of the holding table 6. Therefore, the region of the surface of the glass substrate 7 through which the laser beam passes is not in direct contact with another object, but is in contact with the air layer or the gas layer. For this reason, it is possible to prevent the fine particles adhering to the holding table 6 from re-adhering to the region of the surface of the glass substrate 7 where the laser beam is transmitted.

In the second embodiment shown in FIG. 2B, a spacer 13 is interposed between the holding table 6 and the glass substrate 7. The spacer 13 is arranged so as not to directly contact a region of the surface of the glass substrate 7 through which the laser beam passes. Therefore, it is possible to prevent fine particles from adhering from the holding table 6 or the spacer 13 to a region of the surface of the glass substrate 7 through which the laser beam passes. The material of the spacer 13 is desirably softer than the glass substrate 7, and may be, for example, a polymer film having a thickness of 0.2 mm. The use of the soft spacer 13 makes it difficult for the back side of the glass substrate 7 to be scratched.

In the third embodiment shown in FIG.
(A) is further provided with an optical trap 15 for absorbing the beam 12 under the holding table 6 so as not to return to the glass substrate 7.

For example, when a glass substrate is placed in contact with a mounting surface coated with black paint for antireflection and marking is performed, cracks occur on the surface of almost all substrates. . On the other hand, when the back surface of the glass substrate was not brought into contact with the mounting surface as in the first to third embodiments, cracks did not occur on the front surface.

Next, still another embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In these examples,
At the same time as preventing the attachment of fine particles to the surface of the workpiece such as a glass substrate as in the above-described embodiment, the energy density of the laser beam on the surface of the workpiece is reduced,
The occurrence of surface damage can be more effectively prevented.

FIG. 3A is a schematic sectional view of a marking device according to a fourth embodiment of the present invention. FIG. 3B shows the beam shape of the fourth embodiment. In the same figure, those having the same reference numbers as those in FIG. 1 or FIG. 2 indicate the same functional elements, and therefore the description thereof will be omitted. Also,
The illustration of the reflecting mirrors 3 and 4 is omitted.

In FIG. 3A, from the laser light source 1,
One laser beam 10 is emitted. Laser beam 10
Enters the beam shaping unit 2. The beam shaping unit 2 splits the laser beam 10 into two partial beams 11A and 11B. The split partial beams 11A and 11B are incident on the condensing optical system 5. Note that the partial beams 11A and 11A
It is preferable to divide the laser beam 10 so that the sum of the total energy and B becomes substantially equal to the energy of the laser beam 10 and no energy loss occurs.

The condensing optical system 5 includes partial beams 11A and 11A.
B is condensed on a minute region 8 inside a glass substrate 7 which is a member to be processed.

The light generated from the minute area 8 is detected by the light detector 2
3 observed. The observation result of the photodetector 23 is notified to the position adjusting means 24. Generally, when ablation occurs on the surface of the workpiece 7, the emission intensity increases and the emission spectrum changes as compared with the case where optical damage or optical insulation breakdown occurs inside the workpiece. When ablation occurs on the surface, an emission spectrum having a peak near a wavelength of 600 nm is obtained.

The position adjusting means 24 is based on the luminous intensity obtained from the photodetector 23 and the spectrum information, so as to prevent ablation from occurring on the surface of the workpiece 7 so as to prevent the ablation from occurring. The relative position of the laser beam with respect to the optical axis direction is adjusted. For example, by observing a change in the intensity of light near a wavelength of 600 nm, it is possible to detect that ablation has occurred on the surface. In this manner, it is possible to mark the inside of the workpiece (glass substrate) 7 without damaging the surface thereof.

Further, since the laser beam is divided into two partial beams 11A and 11B and focused on the minute area 8, the depth of the workpiece 7 is smaller than when one laser beam 10 is directly focused. The energy density distribution of the laser beam in the direction can be concentrated on a smaller area. For this reason, the length in the depth direction of the region to be altered can be shortened, and it is possible to prevent the altered region from reaching the surface of the workpiece 7.

In order to focus the laser beam on a finer area in the depth direction of the workpiece 7, it is preferable to use a lens having a large numerical aperture as the objective lens of the focusing optical system 5.

As the laser beam to be used, an appropriate one is selected according to the combination with the workpiece 7. For example, when marking is performed on quartz glass, a laser beam having a wavelength in a wavelength region transparent to quartz glass, that is, an infrared region, a visible light region, or an ultraviolet region can be used. When marking is performed on a general plate glass, a laser beam having a wavelength in a wavelength region transparent to the plate glass, that is, an infrared region or a visible light region can be used. In addition, when marking is to be performed on a silicon substrate or the like other than glass, for example, a laser beam in a wavelength region transparent to the silicon substrate may be used.

As the laser light source 1, for example, Nd: YA
It may be convenient to use a solid-state laser device such as a G laser or Nd: YLF laser. For example, when using a Nd: YAG laser device that outputs a laser beam having a wavelength in the infrared region, a laser beam having a wavelength in the visible light region can be obtained by doubling the wavelength using a wavelength converter. . If the fourth harmonic is used, a laser beam having a wavelength in the ultraviolet region can be obtained. The shorter the wavelength of the laser beam used, the higher the spatial resolution of the position to be marked.

Further, by using a pulse laser device as the laser light source 1, it is possible to suppress a temperature rise near the marking portion of the workpiece 7. For this reason,
It is possible to avoid the adverse effect of the temperature rise, and to make the positions in the depth direction to be marked uniform. Note that it is preferable to use one having a short pulse width. this is,
This is because the magnitude of the thermal effect is proportional to the square root of the pulse width. Specifically, it is preferable to use a laser light source that oscillates with a pulse width of 1 nanosecond or less.

FIG. 3B shows an example of the configuration of the beam shaping unit 2. The beam shaping section 2 has a first isosceles triangular section.
And a second prism 2B. The first and second prisms 2A and 2B have an apex angle equal to each other, for example, 120 °, their bottom surfaces are parallel to each other, and ridges corresponding to vertexes are opposed to each other in parallel. Are arranged as follows.

The laser beam 10 is vertically incident on the bottom surface of the first prism 2A. A light intensity distribution in a direction perpendicular to the optical axis of the laser beam 10 is shown by a curve 10a. The light intensity becomes maximum at the center, and gradually decreases as the distance from the center increases.

The laser beam emitted from the pair of inclined surfaces of the prism 2A is split into two partial beams 11A and 11B. The partial beams 11A and 11B are respectively incident on two slopes of the prism 2B. From the bottom surface of the prism 2B, two parallel partial beams 11A and 11B are emitted.

As described above, by using a pair of isosceles triangular prisms, one laser beam 10 can be divided into two partial beams 11A and 11B.
In the case of FIG. 3B, the center of the laser beam 10 is located outside each of the partial beams 11A and 11B, and the peripheral portion of the laser beam 10 is located at each of the partial beams 11A and 11B.
Located inside. For this reason, each partial beam 11A, 1
As shown by curves 11Aa and 11Ba, the light intensity distribution of 1B increases as the distance from the center of the two partial beams 11A and 11B increases.

Thus, the two partial beams 11A and 1A
The light intensity outside 1B is stronger than the light intensity inside.
For this reason, when the two partial beams are focused on the minute area, the area where the light intensity exceeds the threshold value can be narrowed to a smaller area.

Preferably, the angles of incidence of the partial beams 11A and 11B on the surface of the workpiece 7 are adjusted to be equal to the Brewster angle. By setting the Brewster angle, the loss due to reflection can be reduced.

Next, a fifth embodiment will be described with reference to FIG. As shown in FIG. 4A, in the fifth embodiment, the beam shaping unit 2 emits one beam, but the energy distribution of the cross section of the emitted beam has a special shape. Other configurations are the same as those in FIG.

Laser beam 1 emitted from laser light source 1
The light intensity distribution in the direction perpendicular to the optical axis of
As shown by a, it becomes strong at the center and becomes weaker away from the center.

The beam shaping unit 2 shapes the laser beam 10 and outputs a laser beam 11C having a light intensity distribution that is weak at the center and becomes stronger as the distance from the center increases. The light intensity distribution of the laser beam 11C is represented by a curve 11
Indicated by a.

When the laser beam 10 is focused as it is,
In a region relatively long in the optical axis direction, the light intensity near the optical axis exceeds the threshold. On the other hand, laser beam 1
In the case where a beam with low light intensity is condensed in the vicinity of the optical axis as in 1C, it is easy to control the threshold value to be exceeded only in a shorter region in the optical axis direction.

For this reason, it is possible to mark only a shorter area in the thickness direction of the workpiece (glass substrate) 7, and it is possible to suppress the crack from reaching the surface.

In order to focus the laser beam on a finer area in the depth direction of the workpiece 7, it is preferable to use a lens having a large numerical aperture as an objective lens of the focusing optical system 5.

FIG. 4B shows an example of the configuration of the beam shaping unit 2 used in the fifth embodiment. The beam shaping unit 2 is configured to include a first conical prism 20A and a second conical prism 20B. First and second conical prism 20
A and 20B are arranged so that their central axes are common to each other and their vertices face each other.

The laser beam 10 is perpendicularly incident on the bottom surface of the first conical prism 20A. The distance between the first conical prism 20A and the second conical prism 20B is adjusted so that the light beam at the outer peripheral portion of the laser beam 10 is incident on the vicinity of the vertex of the second conical prism 20B. The light intensity of the laser beam 11C emitted from the bottom surface of the second conical prism 20B is strong near its center and weakens as it goes away from the center.

As described above, by using a pair of prisms, a laser beam having a weak light intensity distribution near the center can be formed.

Next, a sixth embodiment will be described with reference to FIG. As shown in FIG. 5A, in the sixth embodiment, the beam shaping unit 2 generates a beam having an energy distribution characteristic different from that of the fifth embodiment in FIG.
Other configurations are the same as those in FIG.

The laser beam 10 has a substantially circular cross section 10b on a virtual plane perpendicular to the optical axis. The beam shaping unit 2 shapes the cross-sectional shape 10b of the laser beam 10, and emits a laser beam 11 having a cross-sectional shape 11D such that a light irradiation area on a virtual plane perpendicular to the optical axis becomes annular. That is, the light intensity near the center of the laser beam 11 becomes almost zero. It is preferable that the total energy of the laser beam 11 be substantially equal to the total energy of the laser beam 10 before shaping so that no energy loss occurs.

The laser beam 11 having such an annular beam cross section is focused on the minute area 8 in the workpiece 7. An increase in light intensity in the vicinity of the center axis of the laser beam 11 can be suppressed, and control can be easily performed so as to exceed the threshold value only in a shorter region in the optical axis direction.

In order to focus the laser beam on a finer area in the depth direction of the workpiece 7, it is preferable to use a lens having a large numerical aperture as an objective lens of the focusing optical system 5.

FIG. 5B shows an example of the configuration of the beam shaping unit 2 used in the sixth embodiment. The beam shaping unit 2 is configured to include a first conical prism 30A and a second conical prism 30B. First and second conical prism 30
A and 30B are arranged so that their central axes are common to each other and their vertices face each other.

In the case of FIG. 4B, the laser beam 10
The distance between the first conical prism 20A and the second conical prism 20B has been adjusted so that the light flux on the outer peripheral portion of the second conical prism 20B is incident on the vicinity of the vertex of the second conical prism 20B.
In (B), the interval between the first and second conical prisms is made longer. Therefore, the laser beam 11 emitted from the second conical prism 30B has an annular cross-sectional shape. In this manner, a laser beam having an annular cross section can be obtained from a laser beam having a circular cross section.

FIG. 5 shows a case where a laser beam having an annular cross section is obtained from a laser beam having a circular cross section. However, a laser light source which outputs a laser beam having an annular cross section from the beginning may be used.

FIG. 6A is a schematic sectional view showing an example of a laser light source for outputting a laser beam having an annular cross section. An optical resonator is constituted by the concave mirror 40 and the convex mirror 41 having a smaller diameter. When the light beam reciprocating inside the optical resonator reciprocates a certain number of times, the convex mirror 4
An unstable optical resonator that is configured to leak outside the edge of the first optical resonator.

A laser medium 42 is disposed in the optical resonator. Stimulated emission occurs in the laser medium 42, and laser oscillation occurs. The laser beam amplified by reciprocating a predetermined number of times in the optical resonator is emitted outside from the edge of the convex mirror 41. The cross section of the emitted laser beam perpendicular to its optical axis is annular.

FIG. 5 shows a case where the beam shaping unit 2 for shaping the laser beam 11 into an annular shape and the condensing optical system 5 for condensing the laser beam 11 are constituted by different optical systems. It can also be constituted by one optical system.

FIG. 6B shows an example of an optical system having both the function of the beam shaping unit 2 and the function of the condensing optical system 5. A large-diameter concave mirror 45 and a small-diameter convex mirror 46 are arranged so as to share the central axis thereof, and constitute a Schwarzschild reflection optical system. A through hole 45a is provided at the center of the concave mirror 45, and the laser beam 11 is applied to the through hole 45a.
a and enters the convex mirror 46.

Laser beam 11 incident on convex mirror 46
Is reflected by the convex mirror 46 and the concave mirror 45, and the convergent ray bundle 31
As a result, the light is condensed on the minute region 8 in the workpiece 7. The cross-sectional shape of the convergent light beam 31 in a virtual plane perpendicular to the optical axis is annular. By using a Schwarzschild reflection optical system, the cross section of the laser beam can be made annular and a convergent light beam can be formed.

Next, a modification of the fifth embodiment will be described with reference to FIG. These modifications are described in the fourth section.
Also, the present invention can be applied to the sixth embodiment.

As shown in FIG. 7A, when the workpiece 7 is plate-shaped, the laser beam 11C is focused from the front side toward the minute region 8, and the laser beam 11E is also focused from the back side. Light. For this reason, condensing optical systems 5A and 5B are arranged on the front side and the back side of the workpiece 7, respectively.

The laser beam 11 incident from the front side
It is not necessary to make the optical axis of C and the optical axis of the laser beam 11E incident from the back side common. One laser beam may be obliquely incident, or both laser beams may be obliquely incident. The number of laser beams is not limited to two, but may be three or more.

As shown in FIG. 7B, the liquid 5 is placed between the objective lens 5a of the condenser optical system 5 and the surface of the workpiece 7.
0 may be filled. As the liquid 50, a liquid that is transparent in the wavelength range of the laser beam to be used, for example, water can be used. Since the refractive index of the ordinary liquid is higher than the refractive index of the atmosphere, the difference in the refractive index on the surface of the workpiece 7 can be reduced. Therefore, the condensing angle θ in the workpiece 7 can be increased as compared with the case where the liquid 50 is not filled. By increasing the collection angle,
A region exceeding the threshold value near the minute region 8 can be more localized.

As shown in FIG. 7 (C), laser irradiation may be performed while blowing a gas such as clean air from the gas blowing means 55 onto a region of the surface of the workpiece 7 where the laser beam 11C is incident. Good. Due to the blown gas, adhesion of dust to the surface of the workpiece 7 can be suppressed.

Further, the laser irradiation may be performed while spraying a liquid such as water onto the area where the laser beam 11C is emitted and the vicinity thereof on the back surface of the workpiece 7. By spraying water, reflection of the laser beam on the back surface can be suppressed. Further, the cooling efficiency can be improved.

In the above-described embodiment, the member to be processed is a glass substrate. However, the present invention is not limited to glass, and can be applied to a case of performing a marking process on another material that transmits light emitted from a light source.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0066]

As described above, according to the present invention,
At the time of marking, the laser beam passage area on the surface of the workpiece does not directly contact the holding member. For this reason, adhesion of particles or the like to the laser beam passage area on the surface of the workpiece is suppressed, and damage to the surface is prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view of a marking device according to a first embodiment of the present invention.

FIG. 2 is a partial schematic diagram of a marking device according to first, second, and third embodiments of the present invention.

FIG. 3 is a schematic view of a marking device according to a fourth embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration example of a fifth embodiment of the present invention.

FIG. 5 is a schematic view of a marking device according to a sixth embodiment of the present invention.

FIG. 6 is a schematic diagram showing a configuration example of a seventh embodiment of the present invention.

FIG. 7 is a schematic diagram of a marking device according to a modification of the fifth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser light source 2 beam shaping unit 3, 4 reflecting mirror 5 focusing optical system 6 holding table 7 workpiece 8 small area 9 through hole 10, 11, 12 laser beam 11 A, 11 B partial beam 13 spacer 14 opening 15 optical trap 20A, 20B Conical prism 23 Photodetector 24 Phase adjusting means

Claims (7)

[Claims] 1. A step of holding a workpiece so that an area of the surface of the workpiece through which the laser beam passes does not directly contact another object; and processing the laser beam emitted from a laser light source. Focusing the light on a minute area inside the member to change the light-collecting portion of the workpiece and perform marking. 2. A step of holding the workpiece so that a region of the surface of the workpiece through which the laser beam passes is in contact with the gas layer, and applying the laser beam emitted from a laser light source to the inside of the workpiece. Condensing light on a minute area having the property to change the condensed portion of the workpiece to perform marking. 3. The marking method according to claim 1, further comprising a step of absorbing the laser beam transmitted through the workpiece. 4. A laser light source; a condensing optical system for condensing a laser beam from the laser light source on a small area inside a workpiece; and an area on the surface of the workpiece through which the laser beam passes. And a holding member for holding the processing member so that the processing member does not directly touch another object. 5. The marking device according to claim 4, wherein the holding member has a through hole in a region through which the laser beam transmitted through the workpiece passes. 6. The holding member according to claim 4, wherein the holding member includes a stage having a main surface, and a spacer disposed between the workpiece to be mounted on the main surface and the main surface. Marking device. 7. The marking device according to claim 5, further comprising an optical trap for absorbing a laser beam transmitted through the workpiece.