JP2002340804A - Observation method and observation device of mark - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for observing a mark formed by a method capable of suppressing generation of a crack reaching the surface. SOLUTION: A transparent member having the mark by the crack formed inside is irradiated with illumination light. Scattered light from the mark is observed on the position where light transmitting the transparent member in illumination light does not enter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for observing a mark, and more particularly to a method and an apparatus for observing a mark due to a crack formed inside a transparent member.

[0002]

2. Description of the Related Art There is known a method of marking a surface of a member to be processed 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. In addition, since deposits called "debris" are deposited near the marked position, it is necessary to perform cleaning to remove the deposits.

Japanese Patent Laid-Open Publication No. 3-124486 discloses a method in which laser light is condensed inside a workpiece without damaging the surface of the workpiece and marking is performed inside the workpiece. 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.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open Publication No. Hei 3-12
According to the method disclosed in Japanese Patent No. 4486, marking can be performed at a position at a depth of about 0.5 to 2.5 mm from the surface of the workpiece. When this method is used to mark a thin plate-shaped workpiece having a thickness of 1 mm or less, for example, cracks generated inside may reach the surface. The crack reaching the surface causes the generation of fine particles.

An object of the present invention is to provide a method and an observation apparatus for observing marks formed by a method capable of suppressing generation of cracks reaching the surface.

[0006]

According to one aspect of the present invention, a step of irradiating a transparent member having a mark formed by a crack formed therein with an illuminating light; Observing the scattered light from the mark at a position where the light to be incident is not provided.

According to another aspect of the present invention, there is provided an illuminating means for illuminating the illumination light into the transparent member, and a illuminating means for preventing the illuminating light from the illuminating means from being incident on the transparent member. And a light receiving means arranged at a position where a part of the scattered light of the light is incident.

Since the illumination light does not enter the light receiving means, S /
The mark can be observed with a good N ratio.

[0009]

FIG. 1A shows the principle of operation of a marking device for forming a mark to be observed by a method according to an embodiment of the present invention.

[0010] From the laser light source 1, one laser beam 1
1 is emitted. The laser beam 11 is applied to the beam splitting means 2
Incident on. The beam splitting means 2 splits the laser beam 11 into two partial beams 12A and 12B. The split partial beams 12A and 12B are incident on the focusing optical system 3. It is preferable that the division is performed so that the sum of the total energy of the partial beams 12A and 12B becomes substantially equal to the energy of the laser beam 11 and no energy loss occurs.

The holding table 4 is opposed to the condensing optical system 3.
Is arranged. The workpiece 10 is placed on the holding table 4. The condensing optical system 3 includes the partial beams 12A and 12B
Are condensed on the minute region 13 inside the workpiece 10. The density of the laser light is increased in the minute region 13 and its vicinity. When the density of the laser light is higher than a certain threshold value, it is considered that absorption due to an optical nonlinear phenomenon occurs. Based on this absorption, optical damage (Optical D
Amage) or optical breakdown (Optical Breakdown) occurs, and the minute region 13 of the workpiece 10 is altered and becomes visible from the outside. In this way, the inside of the workpiece 10 can be marked.

Light generated from the minute area 13 is observed by the photodetector 5. The observation result of the light detector 5 is notified to the position adjusting means 6. Generally, when ablation occurs on the surface of the workpiece 10, the luminous intensity increases as compared with the case where optical damage or optical insulation breakdown occurs inside the workpiece. The position adjusting means 6 controls the light of the laser beam between the condensing optical system 3 and the holder 4 based on the emission intensity information obtained from the photodetector 5 so that ablation does not occur on the surface of the workpiece 10. Adjust the relative position in the axial direction. In this way, it is possible to mark the inside of the workpiece 10 without damaging the surface thereof.

Further, by moving the beam splitting means 2 and the focusing optical system 3 in a plane parallel to the surface of the workpiece 10, marking can be performed at a desired position in the plane. Further, since the laser beam is divided into two partial beams 12A and 12B and focused on the minute region 13, one laser beam 1
Compared to the case where the laser beam 1 is condensed as it is, the density of the laser beam in the depth direction of the workpiece 10 can be concentrated on a finer area. For this reason, the length in the depth direction of the region to be transformed can be shortened, and it is possible to prevent the transformed region from reaching the surface of the workpiece 10.

In order to focus the laser beam on a finer area in the depth direction of the workpiece 10, it is preferable to use a lens having a large numerical aperture as an objective lens of the focusing optical system 3.

As the laser beam to be used, an appropriate one is selected according to the combination with the workpiece 10.
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. In addition, 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 it is desired to mark a silicon substrate or the like other than glass, for example, laser light in a wavelength region transparent to the silicon substrate may be used.

As the laser light source 1, it will be convenient to use a solid-state laser device such as a YAG laser or a YLF laser. For example, when a YAG laser device that outputs laser light having a wavelength in the infrared region is used, a laser beam having a wavelength in the visible light region can be obtained by doubling the wavelength using a wavelength converter. Further, 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.

Furthermore, 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 10. For this reason, it is possible to avoid an adverse effect due to a rise in temperature 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 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. 1B shows an example of the configuration of the beam splitting means 2. The beam splitting means 2 is configured to include a first prism 2A and a second prism 2B whose cross sections are isosceles triangles. 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.

A laser beam 11 is vertically incident on the bottom surface of the first prism 2A. The light intensity distribution in the direction perpendicular to the optical axis of the laser beam 11 is shown by a curve 11a. 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 12A and 12B. The partial beams 12A and 12B are respectively incident on two slopes of the prism 2B. From the bottom surface of the prism 2B, two parallel partial beams 12A and 12B are emitted.

As described above, by using a pair of isosceles triangular prisms, one laser beam 11 can be divided into two partial beams 12A and 12B.
In the case of FIG. 1B, the central portion of the laser beam 11 is located outside each of the partial beams 12A and 12B, and the peripheral portion of the laser beam 11 is located at each of the partial beams 12A and 12B.
Located inside. For this reason, each partial beam 12A, 1
As shown by the curves 12Aa and 12Ba, the light intensity distribution of 2B increases as the distance from the center of the two partial beams 12A and 12B increases.

Thus, the two partial beams 12A and 1
The light intensity outside 2B 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 angle of incidence of each partial beam 31 on the surface of the workpiece 10 is adjusted to be equal to the Brewster angle. By setting the Brewster angle, the loss due to reflection can be reduced.

Next, another marking device will be described with reference to FIG. In the marking device shown in FIG. 2A, a beam shaping unit 20 is used instead of the beam splitting unit 2 in FIG. Other configurations are the same as those in the case of FIG.

Laser beam 1 emitted from laser light source 1
The light intensity distribution in the direction perpendicular to the optical axis 1 is represented by curve 11
As shown by a, it becomes strong at the center and becomes weaker away from the center.

The beam shaping means 20 includes a laser beam 11
And a laser beam 21 having a light intensity distribution that is weak at the center and becomes stronger as the distance from the center increases.
Is output. The light intensity distribution of the laser beam 21 is represented by a curve 21
Indicated by a.

When the laser beam 11 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 2
In the case where a beam with low light intensity is condensed in the vicinity of the optical axis as in 1, it is easy to perform control so that the threshold value is exceeded only in a shorter region in the optical axis direction.

For this reason, it is possible to mark only a shorter region in the thickness direction of the workpiece 10,
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 10, it is preferable to use a lens having a numerical aperture as large as possible as the objective lens of the focusing optical system 3.

FIG. 2B shows an example of the configuration of the beam shaping means 20 used in the marking device shown in FIG. 2A. The beam shaping means 20 includes a first conical prism 20A.
And the second conical prism 20B. The first and second conical prisms 20A and 20B are arranged so that their central axes are common to each other and vertices are opposed to each other.

The laser beam 11 is vertically 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 on the outer peripheral portion of the laser beam 11 is incident on the vicinity of the vertex of the second conical prism 20B. The light intensity of the laser beam 21 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, another marking device will be described with reference to FIG. In the marking device shown in FIG.
Instead of the beam shaping means 20 of (A), a beam shaping means 30 having different characteristics is used. Other configurations are the same as those in the case of FIG.

The laser beam 11 has a cross-sectional shape 11b that is substantially circular on an imaginary plane perpendicular to the optical axis. The beam shaping unit 30 shapes the cross-sectional shape 11b of the laser beam 11, and emits a laser beam 31 having a cross-sectional shape 31b such that a light irradiation area on a virtual plane perpendicular to the optical axis becomes annular. That is, the laser beam 3
The light intensity near the center of 1 becomes almost zero. It should be noted that the total energy of the laser beam 31 is the laser beam 1 before shaping.
It is preferable that the total energy is approximately equal to 1 so that no energy loss occurs.

The laser beam 31 having such an annular beam cross-sectional shape is focused on a minute area in the workpiece 10. An increase in light intensity in the vicinity of the central axis of the laser beam 31 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 10, it is preferable to use a lens having a large numerical aperture as an objective lens of the focusing optical system 3.

FIG. 3B shows an example of the configuration of the beam shaping means 30 used in the marking device shown in FIG. The beam shaping means 30 includes a first conical prism 30A and a second conical prism 30A.
And the conical prism 30B. The first and second conical prisms 30A and 30B have a common central axis and are arranged so that the vertices face each other.

In the case of FIG. 2B, the laser beam 11
The distance between the first conical prism 20A and the second conical prism 20B has been adjusted so that the light beam on the outer peripheral portion of the second prism 20B enters 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 31 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. 3 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. 4A 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. 3 shows a case where the beam shaping means 30 for shaping the laser beam 31 into an annular shape and the condensing optical system 3 for condensing the laser beam 31 are constituted by different optical systems. It can also be constituted by one optical system.

FIG. 4B shows an example of an optical system having both the function of the beam shaping means 30 and the function of the condenser optical system 3. A large-diameter concave mirror 45 and a small-diameter convex mirror 46 are arranged so as to share their central axes, 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 transmitted through the through hole 4a.
The light enters the convex mirror 46 through 5a.

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 focused on the minute area 13 in the workpiece 10. 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 marking device shown in FIG. 2 will be described with reference to FIG. Note that these modifications can also be applied to the marking device shown in FIGS.

As shown in FIG. 5A, the workpiece 10
Has a plate shape, the laser beam 21A is converged from the front side toward the minute region 13, and the laser beam 21B is also condensed from the back side. Therefore, the workpiece 1
The focusing optical systems 3A and 3B are arranged on the front side and the back side, respectively, of the “0”.

The laser beam 21 incident from the front side
It is not necessary to make the optical axis of A and the optical axis of the laser beam 21B 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, and three or more laser beams may be focused on the minute region 13.

As shown in FIG. 5B, the liquid 50 may be filled between the objective lens 3a of the condenser optical system 3 and the surface of the workpiece 10. As the liquid 50, a liquid that is transparent in the wavelength range of the laser beam used, for example, water can be used. Since the refractive index of a normal liquid is higher than the refractive index of the atmosphere, the difference in the refractive index on the surface of the workpiece 10 can be reduced. Therefore, compared with the case where the liquid 50 is not filled, the converging angle θ in the workpiece 10 is
Can be increased. By increasing the converging angle, the region exceeding the threshold value in the vicinity of the minute region 13 can be more localized.

As shown in FIG. 5C, the workpiece 10
The laser irradiation may be performed while blowing a gas such as clean air from the gas blowing means 55 on the area of the surface where the laser beam 21 is incident. Due to the blown gas, adhesion of dust to the surface of the workpiece 10 can be suppressed.

Further, the laser irradiation may be performed while spraying a liquid such as water on the area of the back surface of the workpiece 10 where the laser beam 21 is emitted and the vicinity thereof. By spraying water, reflection of the laser beam on the back surface can be suppressed. Further, the cooling efficiency can be improved.

Next, a method of observing a mark according to an embodiment of the present invention will be described with reference to FIG. FIG.
It is the schematic for demonstrating the method of observing the king part. A mark 31 formed by a crack is formed inside the glass substrate 30. Illumination means 32 such as a xenon lamp irradiates the inside of the glass substrate 30 with illumination light from the end face. The illumination light that has entered the glass substrate 30 is scattered by the mark 31. The scattered light is received by a light receiving means 33 such as a CCD camera arranged on one surface side of the glass substrate 30, and the mark 31 is observed.

On the other surface side of the glass substrate 30, a low reflection plate 34 is disposed so as to cover the field of view of the light receiving means 33. The low reflection plate 34 is formed of, for example, a black plate member.

In the configuration shown in FIG. 6, since the illumination light is made to enter the inside of the glass substrate 30 from the end face, the light transmitted through the glass substrate 30 out of the illumination light
Does not enter. That is, almost only scattered light is received by the light receiving means 3.
3 is incident. On the other hand, when illumination light is emitted from the back side of the glass substrate 30, the light transmitted through the glass substrate 30 enters the light receiving unit 33. For this reason, the S / N ratio decreases.

When the mark formed by the laser irradiation was observed in detail, it was found that a planar crack including the optical axis of the irradiated laser light was formed. For this reason, it was difficult to observe the mark 31 by irradiating illumination light from the back surface of the glass substrate 30. With the configuration as shown in FIG. 6, the mark 31 can be observed with a good S / N ratio.

The background of the mark 31 has a low reflection plate 3
4, the background is darkened, and the S / N ratio can be further improved. Note that the low reflection plate 34 may be formed of a black body.

In FIG. 6, the illumination light is applied to the glass substrate 30.
The case where the light is incident from the end face of the glass substrate 3 has been described.
The illumination light may be irradiated from a direction such that the illumination light transmitted through 0 does not enter the light receiving unit 33. The lighting means 32
By using a pulsed lighting tube synchronized with the CCD camera, the S / N ratio could be further improved.

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.

[0056]

As described above, according to the present invention, a mark locally marked inside a workpiece can be easily visually recognized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a marking device for forming a mark observed by a method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of another marking device for forming a mark observed by a method according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of still another marking device for forming marks observed by a method according to an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a configuration example of the marking device illustrated in FIG. 3;

FIG. 5 is a schematic view of a modification of the marking device shown in FIG. 2;

FIG. 6 is a schematic diagram for explaining a method of observing a mark in a glass substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Beam splitting means 3 Condensing optical system 4 Holder 5 Photodetector 6 Phase adjusting means 10 Workpiece 11 Laser beam 12A, 12B Partial beam 13 Micro area 20 Beam shaping means 20A, 20B Conical prism 30 Glass substrate 31 mark 32 lighting means 33 light receiving means 34 low reflection plate

Claims (2)

[Claims] A step of irradiating a transparent member having a mark formed by cracks formed therein with illumination light; and a step of irradiating the mark with the mark at a position where, of the illumination light, light transmitted through the transparent member is not incident. Observing scattered light. 2. An illuminating means for illuminating light into a transparent member, and a part of scattered light from a crack formed in the transparent member at a position where the illuminating light of the illuminating means is not incident. And a light receiving means disposed at a position where the light is incident.