JP2000343253A - LASER BEAM MARKING METHOD TO Si WAFER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely mark while controlling a dot diameter and a marking depth to an arbitrary value. SOLUTION: Based on the characteristic table prepared beforehand, marking is performed while adjusting a laser beam oscillator, laser beam attenuator, laser beam expander, etc. A shot number of a laser beam in the laser beam oscillator is adjusted with referring the characteristic table showing the relation between a marking depth and a shot number (step 2-2), the laser power in the laser beam attenuator is adjusted with referring the characteristic table showing the relation between a dot diameter and power (step 2-4), a magnification in the laser beam expander is adjusted with referring the characteristic table showing the relation among a dot diameter, a marking depth and a beam diameter (step 2-5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laser marking a Si wafer, and more particularly to a method for laser marking with high precision while controlling the dot diameter and the marking depth to arbitrary values.

[0002]

2. Description of the Related Art In a conventional laser marking method, the magnification of an expander is fixed to 2 or 3 times, the laser power value is set to a maximum value, the laser oscillation frequency is fixed to 1 KHz or 3 KHz, and Only the number of laser shots was changed.

Further, as an example of conventional laser marking, there is a laser marker described in Japanese Patent Application Laid-Open No. 61-193890. This apparatus performs marking using a variable attenuator that selectively changes the transmittance of a laser beam and a variable magnification beam expander that selectively changes the diameter of the laser beam. In this apparatus, the use of a variable attenuator and an expander is described, but the adjustment method is hardly described.

[0004]

However, in the above-mentioned prior art, when the total energy applied to the marking portion is large, the dot diameter is too large or the marking depth is too large. Conversely, when the total energy applied to the marking portion is small, the dot diameter is too small or the marking depth is too shallow. Also, if the number of shots is increased to increase the total energy to be given while the pulse energy per shot remains small, Si does not melt and evaporate sufficiently at the marking part, so It cannot be scattered as dust outside the hole, and attaches as burrs around the dot hole or inside the dot.

Therefore, there is a problem that the dot diameter is determined by the marking depth and cannot be arbitrarily changed.

Another problem is that there are many burrs attached around the holes of the marked dots or inside the dots.

[0007] Therefore, an object of the present invention is to provide a method of laser marking with high accuracy while controlling the dot diameter and the marking depth to arbitrary values in order to solve the above-mentioned problems.

[0008]

To achieve the above object, a laser marking method according to the present invention comprises a laser oscillator for oscillating a laser beam, a laser attenuator for adjusting the laser power of the laser beam, and a laser attenuator. In a laser marking method for marking a Si wafer using a beam expander that changes a beam diameter, a laser oscillator, a laser attenuator, and a beam expander are adjusted based on a marking characteristic table created in advance. It is characterized in that the marking is performed with high accuracy while controlling the values of the target dot diameter and the marking depth.

Preferably, the marking characteristic table includes a table showing a relationship between laser power and dot diameter.

[0010] Further, the marking characteristic table preferably includes a table showing a relationship between the number of shots of the laser beam and the marking depth.

Further, it is preferable that the marking characteristic table includes a table showing a relationship between the dot diameter and the marking depth and the magnification of the beam expander.

Preferably, the marking characteristic table includes a table showing a relationship between the dot diameter and the marking depth and the laser oscillation frequency.

Further, the laser marking method of the present invention comprises:
Adjusting the number of shots of the laser in the laser oscillator with reference to a characteristic table indicating the relationship between the marking depth and the number of shots, and indicating the oscillation frequency of the laser oscillator, the relationship between the dot diameter and the marking depth and the oscillation frequency. Adjusting with reference to a characteristic table, adjusting the laser power in the laser attenuator with reference to a characteristic table indicating the relationship between the dot diameter and the laser power,
The magnification in the beam expander, the step of adjusting with reference to a characteristic table showing the relationship between the dot diameter and the marking depth and the beam diameter, and a step of performing marking by scanning laser light with a mirror, I do.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a laser marker used in an embodiment of the laser marking method of the present invention. The method for laser marking a Si wafer according to the present invention performs marking on the Si wafer 7 using an optical component for adjusting the laser power and an optical component for changing the beam diameter. At this time, in order to perform marking with very little burrs around the dot holes and very little burrs adhering to the inside of the dots, the dot diameter and the marking depth can be set as desired based on the marking characteristics table confirmed in advance. Can be performed with high accuracy while controlling to the value of. In the present embodiment, a laser attenuator 2 is used as an optical component for adjusting laser power, and an expander 3 whose magnification can be changed is used as an optical component for changing a beam diameter. In FIG. 1, the laser power of a laser beam 8 emitted from a laser oscillator 1 is set to an arbitrary power value by a laser attenuator 2. Subsequently, the beam diameter of the laser beam 8 is set to an arbitrary value by the beam expander 3. Then, the galvanometer mirror 4,
5 while scanning the laser beam 8 in the form of a letter,
The laser beam 8 is focused on the surface of the Si wafer 7 by the θ lens 6 to perform marking. At this time, the combination of the laser power value set by the laser attenuator 2, the beam diameter set by the beam expander 3, the number of laser shots for one dot, and the oscillation frequency
It is determined based on a marking characteristic table that has been confirmed in advance. This makes it possible to set optimal marking conditions for the target dot diameter and marking depth for the Si wafer 7. Thereby, burrs attached to the periphery of the hole of the dot and burrs attached to the inside of the dot are extremely small, and marking with high processing accuracy can be performed.

[0016]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

First, the configuration of the embodiment of the present invention will be described with reference to FIG. Laser light 8 emitted from a Q-switched pulse YAG fundamental wave laser oscillator 1 (laser power maximum 1.5 W ＠ 1 KHz, beam diameter about φ1.5 m)
The laser power of m) is attenuated to an arbitrary power value by the polarization type laser attenuator 2 and set. continue,
The beam diameter of the laser beam 8 is set to an arbitrary value by the beam expander 3 whose magnification can be changed from 2 to 8 times. Then, the f / θ lens 6 (f = 250 mm, condensed beam diameter of about φ55 μm) while scanning the laser beam 8 by moving the scanner mirrors 4 and 5 of the two-axis galvanometer X and Y axes.
Focuses the laser beam 8 on the surface of the Si wafer 7,
Marking is performed by using an arbitrary number of shots and an oscillation frequency for one dot.

Next, the operation of the embodiment of the present invention will be described in detail.

FIG. 2 is a flowchart showing an embodiment of the method for laser marking a Si wafer according to the present invention. In this method, setting is performed with reference to a marking characteristic table. The marking characteristic table includes a characteristic table indicating a relationship between a marking depth and the number of shots, a characteristic table indicating a relationship between a dot diameter and a marking depth and an oscillation frequency, a characteristic table indicating a relationship between a dot diameter and a laser power, and a dot diameter. There is a characteristic table showing the relationship between the marking depth and the magnification. First, the target dot diameter and marking depth are determined (step 2-1), and the number of shots of the laser oscillator 1 is determined with reference to the marking depth-shot number characteristic table (step 2-2). Next, the oscillation frequency of the laser oscillator 1 is set with reference to the dot diameter and marking depth-oscillation frequency characteristic table (step 2-3). Next, the laser power value of the laser attenuator 2 is set with reference to the dot diameter-laser power characteristic table (step 2-
4). Next, the magnification of the expander is set with reference to the dot diameter and marking depth-magnification characteristic table (step 2-5). After setting each device in this way,
Marking is performed on the Si wafer 7 (Step 2-
6).

In the above-mentioned method, in order to confirm the characteristics depending on the configuration of the marking device, the above-mentioned characteristic table, for example, the value of the magnification and the laser power of the expander, the number of laser shots for one dot, and the laser The relationship between the dot diameter and the marking depth, etc., based on the oscillation frequency is determined in advance.

Next, FIGS. 3 to 6 are graphs showing the above-mentioned marking characteristic tables. 3 shows a characteristic table of dot diameter-shot number, FIG. 4 shows a characteristic table of marking depth-laser power, and FIG. 5 shows a characteristic table of dot diameter and marking depth-laser oscillation frequency. FIG. 6
Shows a characteristic table of dot diameter and marking depth-expander magnification. From the characteristic tables of FIGS. 3 to 6, the magnification of the expander and the value of the laser power for obtaining the target dot diameter and the marking depth, the number of laser shots for one dot, and the oscillation frequency are determined, and the marking is performed. Do.

For example, consider the case where marking is performed with a dot diameter of about φ80 μm and a marking depth of about 65 μm. First, referring to FIG. 4, a laser power value is set to 0.8 W from a target dot diameter of about φ80 μm. Next, referring to FIG. 3, from a target marking depth of about 65 μm,
The number of laser shots is set to 20 shots. next,
Referring to FIG. 6, the magnification of the expander is set to 6 times from the target dot diameter of about φ80 μm. Referring to FIG. 5, the oscillation frequency of the laser is set to 3.5 KHz from the target dot diameter of about φ80 μm. Target marking can be performed under these conditions. The setting order may be set from any device.

Next, a method of adjusting the apparatus when the marking method of the present invention is actually performed will be described.

FIG. 7 is a schematic diagram showing an adjustment method when the magnification of the expander is set. Around the beam expander 3 having a magnification of 2 times, beam expanders 9, 10, 11, and 12 having different magnifications of 3, 4, 5, and 6 times are arranged on the circumference. In this manner, referring to the dot diameter and marking depth-expander magnification characteristic table described above, a beam expander is selected according to a target dot diameter and marking depth, and marking is performed under optimum conditions. It can be carried out.

FIG. 8 is a schematic diagram showing an adjustment method when setting the laser output value of the laser oscillator. Instead of the polarization type laser attenuator 2, the laser output value of the laser oscillator 1 is controlled by the laser controller 13, and by referring to the above-mentioned dot diameter-laser power characteristic table, an optimum power value is obtained for the target dot. Marking.

As described above, in the laser marking method, generally, the main factors that determine the dot diameter are:
This is the spot diameter on the laser wafer or the pulse energy per shot. The spot diameter is determined by the magnification of the expander, the focal length of the f · θ laser, and the laser wavelength. The pulse energy per shot is
It is determined by the laser power and the oscillation frequency. The main factor that determines the marking depth is the amount of energy given to the marking portion, which depends on the laser power, the oscillation frequency, and the number of shots. At this time, in the laser marking method for Si wafers of the present invention, the processing conditions (expander, laser power, number of shots, oscillation frequency) at the time of performing marking depend on the total dot size and marking depth for obtaining the target dot diameter and marking depth. The amount of energy can be accurately selected.

[0027]

As described above, according to the present invention, it is possible to accurately select the total amount of energy for obtaining the dot diameter and the marking depth which are the target in the processing conditions for performing the marking.

Therefore, according to the present invention, there is an effect that the dot diameter and the marking depth can be easily controlled.

Further, there is an effect that it is possible to perform marking with very little burrs around the holes of the dots and burrs adhering inside the dots.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an apparatus used in an embodiment of the present invention.

FIG. 2 is a flowchart showing an embodiment of the present invention.

FIG. 3 is a graph showing an example of a characteristic table (marking depth−number of shots) in an example of the present invention.

FIG. 4 is a graph showing an example of a characteristic table (dot diameter-laser power) in an example of the present invention.

FIG. 5 is a graph showing an example of a characteristic table (dot diameter and marking depth-frequency) in an example of the present invention.

FIG. 6 is a graph showing an example of a characteristic table (dot diameter and marking depth-expander magnification) in the example of the present invention.

FIG. 7 is a schematic diagram showing a method of adjusting an apparatus (beam expander) used in an embodiment of the present invention.

FIG. 8 is a schematic view showing a method (laser oscillator) of adjusting an apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser oscillator 2 laser attenuator 3, 9, 10, 11, 12 beam expander 4 X-axis scanner mirror 5 Y-axis scanner mirror 6 f · θ lens 7 Si wafer 8 laser beam 13 laser controller

Claims (6)

[Claims] 1. A laser oscillator for oscillating a laser beam, a laser attenuator for adjusting a laser power of the laser beam, and a beam expander for changing a beam diameter of the laser beam, are marked on a Si wafer. In the laser marking method, the laser oscillator, the laser attenuator, and the beam expander are adjusted based on a marking characteristic table created in advance to control target dot diameters and marking depth values. A laser marking method characterized by performing accurate marking. 2. The laser marking method according to claim 1, wherein the marking characteristic table includes a table indicating a relationship between the laser power and the dot diameter. 3. The laser marking method according to claim 1, wherein the marking characteristic table includes a table indicating a relationship between the number of shots of the laser beam and the marking depth. 4. The marking characteristic table includes a table showing a relationship between the dot diameter and the marking depth and a magnification of a beam expander.
4. The laser marking method according to any one of 3. 5. The marking characteristic table includes a table showing a relationship between the dot diameter, the marking depth, and the oscillation frequency of the laser.
The laser marking method according to any one of the above. 6. A step of adjusting the number of laser shots in the laser oscillator with reference to a characteristic table showing a relationship between the marking depth and the number of shots; and adjusting the oscillation frequency of the laser oscillator to the dot diameter, the marking depth, and the oscillation frequency. Adjusting the laser power in the laser attenuator with reference to the characteristic table indicating the relationship between the dot diameter and the laser power; and adjusting the magnification in the beam expander. A laser marking method, comprising: adjusting with reference to a characteristic table indicating a relationship between a dot diameter and a marking depth and a beam diameter; and performing marking by scanning laser light with a mirror.