JP2005101305A - Inorganic nitride component and marking method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a marking method for putting a high-visibility mark on an inorganic nitride component such as a gallium nitride substrate etc. <P>SOLUTION: The marking method for the inorganic nitride component comprises a step of disposing a region having relatively higher reflectance and a region having relatively lower reflectance on the surface of the component consisting of a compound of a first element other than nitrogen and nitrogen, by forming a region having a relatively higher ratio of the number of nitrogen atoms to the number of the atoms of the first element, and a region having a relatively lower ratio on above-mentioned surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inorganic nitride member marking method and an inorganic nitride member, and more particularly to an inorganic nitride member marking method for producing a mark on the surface of the member and an inorganic nitride member having a mark formed on the surface.

  Conventionally, marking is performed on various substrates such as a silicon substrate in order to manage a production process and improve productivity. In particular, from the viewpoint of performing single wafer management, it is desired to perform simple marking on all substrates.

There is a marking method in which a symbol or the like is written on a substrate by cutting the substrate surface to form a plurality of hole-like dots or grooves. In order to form dots and grooves on the substrate surface, a method of mechanically shaving the substrate surface with a drill or the like has been used in the past. In recent years, as a method for forming finer holes and grooves, a method of irradiating a laser beam such as a CO ₂ laser or a harmonic YAG laser is used instead of a mechanical method.

  Since the marking method as described above is a method of cutting a substrate, shavings or the like generated during processing contaminates a line in a subsequent process. In addition, since this is a method of scratching the substrate, the mechanical strength of the substrate after processing decreases. For example, cracks tend to occur starting from the marking groove.

  As described below, Patent Document 1 discloses a marking method in which holes and grooves are not formed in a silicon substrate. The surface of the silicon substrate is irradiated with a laser to melt the silicon. When the melted region solidifies, it becomes minute protrusions on the substrate surface. Such a protrusion can be used instead of a hole or a groove to make a mark.

  By the way, a gallium nitride substrate is a substrate that has recently been put on the market and has attracted attention. Since it is a new substrate, a general marking method for a gallium nitride substrate has not yet been established.

Patent Document 2 proposes a marking method in which a gallium nitride substrate is irradiated with a CO ₂ laser (wavelength 10.6 μm) to form a plurality of dots having a depth of about several μm on the substrate surface. The CO ₂ laser is irradiated with a peak intensity of 170 W and a pulse width of 100 μs.

  Patent Document 2 proposes a marking method in which a gallium nitride substrate is irradiated with the third harmonic (wavelength 355 nm) of a YAG laser to form dots at a depth of 70 μm inside the substrate.

Japanese Patent Laid-Open No. 10-4040 JP 2003-209032 A

Consider marking on a gallium nitride substrate. Among the methods disclosed in Patent Document 2, in the method using a CO ₂ laser, a hole is formed on the substrate surface. As described above, the marking method for forming a recess such as a hole on the substrate surface has a problem that chips generated during processing contaminate a subsequent process, a problem that the mechanical strength of the substrate is reduced by the formation of the recess, etc. Is accompanied. Further, when the gallium nitride substrate is irradiated with a CO ₂ laser, there is a concern that cracks due to thermal stress occur in the substrate. A mark formed by this method is recognized by a step existing on the substrate surface, and thus cannot be said to have excellent visibility.

  Among the methods disclosed in Patent Document 2, in the method using a YAG laser, a mark is formed inside the substrate. Since the gallium nitride substrate is translucent with brownish brown, the visibility of the mark formed inside the substrate cannot be said to be excellent.

  Even in the marking on the gallium nitride substrate, a method in which a recess is not formed on the substrate surface is desirable. In addition, it is desirable that a mark with excellent visibility can be formed.

  In the marking method disclosed in Patent Document 1, no recess is formed on the surface of the substrate. However, this is an effective marking method for the silicon substrate, and projections cannot be formed on the surface of the gallium nitride substrate by the same method.

  An object of the present invention is to provide a novel marking method for an inorganic nitride member such as a gallium nitride substrate.

  Another object of the present invention is to provide a marking method capable of producing a highly visible mark on an inorganic nitride member such as a gallium nitride substrate.

  Another object of the present invention is to provide a marking method capable of producing a mark while suppressing damage to the inorganic nitride member such as a gallium nitride substrate.

  Another object of the present invention is to provide an inorganic nitride member such as a gallium nitride substrate on which a highly visible mark is formed on the surface.

  According to one aspect of the present invention, the ratio of the number of nitrogen atoms to the number of atoms of the first element on the surface of the member made of an inorganic compound of the first element other than nitrogen and nitrogen is relatively By forming the high region and the low region, there is provided a marking method for an inorganic nitride member including a step of disposing a relatively high region and a low region on the surface of the member.

  According to another aspect of the present invention, (a) a step of emitting a laser beam from a laser light source, and (b) an inorganic compound of nitrogen with a first element other than nitrogen and the laser beam emitted from the laser light source. And irradiating a first region defined on the surface of the member comprising: releasing nitrogen atoms out of the member; and the ratio of the number of nitrogen atoms to the number of atoms of the first element in the first region A method of marking an inorganic nitride member including a step of making the ratio smaller than the ratio of the number of nitrogen atoms to the number of atoms of the first element in a region where the laser beam on the surface of the member is not irradiated.

  According to another aspect of the present invention, a mark is formed by adjoining at least two sections having a nitrogen atom density different from each other, which are members made of an inorganic compound of a first element other than nitrogen and nitrogen. An inorganic nitride member is provided.

  By forming a region having a high reflectance in the shape of, for example, a letter on the surface of the inorganic nitride member, a mark with excellent visibility can be produced. For a plurality of inorganic nitride members formed with such marks, it is easy to distinguish one member from another member.

  When the inorganic nitride member is irradiated with a laser to release nitrogen, a deep recess can be prevented from being formed in the member. The member can be marked while preventing the mechanical strength of the member from being impaired.

  First, a novel concept for marking on a gallium nitride substrate discovered by the present inventors will be described.

  The gallium nitride substrate is translucent with a brownish brown color. Gallium nitride contained in the gallium nitride substrate is a metal element, so that nitrogen is preferentially released to the outside of the substrate surface, making it a gallium rich region (compared to the ratio of the number of nitrogen atoms to the number of gallium atoms in the original substrate). If a region where the ratio of the number of nitrogen atoms to the number of gallium atoms is small) is formed, the region has a higher reflectance than the original substrate surface. By making the gallium-rich region into a desired shape, a highly visible mark can be produced on the substrate surface.

  The present inventors examined using a laser to produce such a mark. By irradiating a gallium nitride substrate with a laser beam, the gallium-rich region could be formed by heating the substrate surface to thermally decompose gallium nitride and releasing nitrogen preferentially as a gas to the outside of the substrate.

  When a pulse laser beam is used, the pulse width and peak intensity suitable for processing can be determined by the following consideration.

When the gallium nitride substrate was irradiated with a CO ₂ laser pulse, many cracks (cracks) were generated in the substrate. This is presumed to be caused by the long pulse width of the CO ₂ laser, on the order of microseconds, as will be described below.

In order to process an object to be processed with a laser, it is necessary to perform laser irradiation with a peak intensity equal to or higher than a certain threshold. For example, when considering a pulse laser with a peak intensity near the threshold, the pulse energy increases as the pulse width increases. Since the CO ₂ laser has a long pulse width on the order of microseconds, it is considered that the pulse energy tends to be excessive even if the intensity of the pulse is appropriate.

The energy of light applied to the substrate is converted into heat and diffused in the substrate. A temperature gradient is generated in the substrate from the beam irradiation region to the non-irradiation region, and thermal stress is generated. When a gallium nitride substrate was irradiated with a CO ₂ laser, excessive energy was irradiated to the substrate, so that high thermal stress was generated in the vicinity of the beam irradiation region, and cracks were considered to have occurred. When producing such a mark, it is desirable to prevent the occurrence of such cracks.

  By the way, it is known that gallium nitride laminated on sapphire can be irradiated with a pulse having a pulse width on the order of femtoseconds to cut the gallium nitride. The fact that the gallium nitride is cut indicates that the gallium nitride substrate is scraped (or a hole is dug in the gallium nitride substrate) with such a short pulse width pulse. That is, it is shown that gallium and nitrogen constituting the gallium nitride substrate are almost equally removed from the substrate by such pulse irradiation. This is presumed to be due to the fact that the peak intensity of such short pulses is generally relatively high.

  In order to produce such a mark, it is desired to thermally decompose gallium nitride on the surface of the substrate and release nitrogen preferentially outside the substrate. Therefore, it is not preferable that gallium and nitrogen are almost equally removed from the substrate (a hole is dug in the gallium nitride substrate). Consider a pulse having such a short pulse width and a peak intensity that does not cause cutting of gallium nitride as described above. Such a pulse would have too little pulse energy and would not fully decompose gallium nitride.

  The above considerations are summarized. In order to produce the mark as described above, the pulse width needs to be shortened to such an extent that no heat storage is generated to induce cracks. On the other hand, it is not preferable to be too short. The pulse width may be between microseconds and femtoseconds. The peak intensity may be set to such a magnitude that no hole is formed in the gallium nitride substrate.

  Furthermore, the conditions of the wavelength to be irradiated are considered as follows. The emission wavelength of gallium nitride is 400 nm, and even when light of this wavelength is irradiated, the absorption to the substrate is small. Since light absorption of gallium nitride exists in a wavelength region shorter than this wavelength, it is preferable to use a wavelength of 400 nm or less for processing.

  Based on such considerations, the present inventors conducted a laser irradiation experiment on a gallium nitride substrate in order to obtain more detailed knowledge for producing the mark as described above. In this experiment, the gallium nitride substrate was irradiated with the fifth harmonic (wavelength 209 nm), fourth harmonic (wavelength 262 nm), third harmonic (wavelength 349 nm), and second harmonic (wavelength 523 nm) of the YLF laser. went. The relationship between the pulse energy density (and irradiation intensity) on the substrate surface and the quality of processing when one shot of each wavelength pulse was irradiated was examined. The cross section of the laser beam was shaped into a circle with a pinhole, and the pinhole was imaged on the substrate surface. The diameter of the beam cross section on the substrate surface was 70 to 80 μm.

When the fifth harmonic (wavelength 209 nm) was irradiated under the condition that the pulse energy density on the substrate surface was 1.1 J / cm ² , the substrate surface was dug and a recess was formed. A region having a high reflectance was not clearly formed. It is considered that no preferential release of nitrogen occurred, and both gallium and nitrogen were removed from the substrate. This is presumed to be due to the large absorption of gallium nitride for this wavelength.

  Next, with reference to FIGS. 1-4, the result of irradiating the fourth to second harmonics will be described. Each of FIGS. 1 to 4 shows a state in which a gallium nitride substrate irradiated with a laser is observed with a reflection optical microscope.

In FIG. 1, the result at the time of irradiating the 4th harmonic (wavelength 262nm) is shown. FIG. 1A shows the case where irradiation is performed under the condition that the pulse energy density on the substrate surface is 0.24 J / cm ² . On the surface of the substrate 10, a beam irradiation trace 11 a that appears bright (white in the drawing) by a reflective optical microscope is formed.

  The fact that the beam irradiation trace 11a looks bright is considered to indicate that the release of nitrogen occurred in the region irradiated with the laser beam and that a gallium rich region was formed. The gallium-rich region has a high reflectivity, so it looks bright with a reflective optical microscope.

FIG. 1B shows a case where irradiation is performed with a pulse energy density of 11.7 J / cm ² on the substrate surface. Similar to FIG. 1A, a beam irradiation trace 11 b that appears bright is formed on the surface of the substrate 10.

  The beam irradiation traces 11a and 11b shown in FIGS. 1A and 1B also have a circular shape corresponding to the beam spot (pinhole imaged on the substrate surface). A region with high reflectivity is formed according to the shape of the beam spot.

2 and 3 show the results when the third harmonic (wavelength 349 nm) is irradiated. FIGS. 2A and 2B show the cases where irradiation is performed under conditions where the pulse energy density on the substrate surface is 2.0 J / cm ² and 11.7 J / cm ² , respectively. Similar to FIG. 1, beam irradiation traces 12 a and 12 b that appear bright are formed on the surface of the substrate 10. The beam irradiation traces 12a and 12b have a circular shape corresponding to the beam spot. A region with high reflectivity is formed according to the shape of the beam spot.

3A and 3B show the cases where irradiation is performed under conditions where the pulse energy density on the substrate surface is 0.25 J / cm ² and 0.56 J / cm ² , respectively. 3A and 3B, the beam irradiation traces 13a and 13b formed on the surface of the substrate 10 do not have a circular shape corresponding to the beam spot.

  The beam irradiation traces 13a and 13b have an outer shape that generally reflects the circular shape of the beam spot, but a plurality of regions with high reflectivity (regions that appear white in the figure) are distributed discretely. This is presumed to be due to the fact that nitrogen was released only at the high light intensity portion of the beam cross section because the energy density of the irradiated pulse was low.

FIG. 4 shows the results when the second harmonic (wavelength: 523 nm) is irradiated under the condition that the pulse energy density on the substrate surface is 3.4 J / cm ² . The beam irradiation trace 14 on the surface of the substrate 10 is formed on only a part of the beam irradiation region, and the outer periphery thereof has irregular irregularities. For this wavelength longer than 400 nm, the absorption of gallium nitride is small, and it is assumed that thermal decomposition of gallium nitride did not occur much. The scale of FIG. 4 is different from that of FIGS. 1 to 3, and the beam irradiation trace 14 is enlarged as compared with the beam irradiation trace 11 a and the like shown in FIGS.

Above, of the beam irradiation track formed in the experiment described with reference to FIGS. 1 to 4, which is formed by the fourth harmonic is irradiated with each 0.24J / cm ² and 11.7J / cm ² a beam irradiation track 11a and 11b, a third harmonic, respectively 2.0 J / cm ² and 11.7J / cm irradiated beam formed by irradiation with ² traces 12a and 12b, the contrast to the original substrate surface Since it is high and has excellent visibility, it is suitable for use as a mark. In addition, these beam irradiation traces are also well controlled in shape.

On the other hand, the third harmonic respectively 0.25 J / cm ² and 0.56J / cm ² irradiation by a beam irradiation track 13a and 13b formed by the beam irradiation track 11a, 11b, as compared to 12a and 12b, The uniformity is low and the contrast to the original substrate surface is low. Further, the beam irradiation trace 14 formed by irradiating the second harmonic at 3.4 J / cm ² does not have good visibility because the region with high reflectivity is narrow.

From the above experiments, it is considered that the fourth harmonic (wavelength 262 nm) can be satisfactorily processed if irradiated with a pulse energy density of about 0.2 J / cm ² or more. The upper limit of the pulse energy density that can be satisfactorily processed is considered to be about 12 J / cm ² or more. If the pulse energy density is too high, cracks are generated on the substrate surface, or a hole is formed without generating a region having a high reflectance. For this reason, it is necessary to suppress the pulse energy density to such an extent that cracks are not generated or holes are not formed.

If the third harmonic (wavelength 349 nm) is irradiated at a pulse energy density of about 1 J / cm ² or more, it is considered that satisfactory processing can be performed. The upper limit of the pulse energy density that can be satisfactorily processed is considered to be about 12 J / cm ² or more. If the pulse energy density is too high, cracks are generated on the substrate surface, or a hole is formed without generating a region having a high reflectance. For this reason, it is necessary to suppress the pulse energy density to such an extent that cracks are not generated or holes are not formed.

  In addition, when the 3rd harmonic is used, the lower limit of the pulse energy density which can perform favorable process is high compared with the case where the 4th harmonic is used. This is presumably because the light absorption coefficient of gallium nitride for the third harmonic is smaller than the light absorption coefficient of gallium nitride for the fourth harmonic.

  The beam irradiation trace formed in the experiment described above (the region where the reflectivity is high) exists on the same plane as the region that was not irradiated with the laser on the substrate surface, as observed by a reflection optical microscope. It was. Therefore, it can be said that when a laser is irradiated under the experimental conditions described with reference to FIGS. In addition, since it is considered that nitrogen was released from the substrate by the beam irradiation, there is no possibility that the beam irradiation trace is a concave portion having an extremely small depth.

Based on the considerations and experiments described above, the present inventors have obtained the following conclusions regarding laser irradiation conditions suitable for marking. The pulse width is preferably 1 ns to 100 ns, and the peak intensity at the work surface is preferably 1 × 10 ⁶ W to 1 × 10 ⁸ W. The wavelength is preferably 245 nm to 390 nm.

  Here, the lower limit 245 nm of the wavelength is a value existing between the fifth harmonic (wavelength 209 nm) and the fourth harmonic (wavelength 262 nm) of the YLF laser. The upper limit of wavelength 390 nm is a value existing between the third harmonic (wavelength 349 nm) and 400 nm which is the emission wavelength of gallium nitride.

  Next, an example of a laser processing apparatus for marking a gallium nitride substrate will be described with reference to FIG.

The laser light source 1 emits a pulse laser beam. As the laser light source 1, for example, an Nd: YLF laser, an Nd: YAG laser, an Nd: YVO ₄ laser, or the like including a third harmonic generation unit or a fourth harmonic generation unit can be used. The pulse width is 20 ns, for example.

  The laser beam emitted from the laser light source 1 enters a mask 2 having a circular or rectangular through hole, for example, and the cross section is shaped. The laser beam emitted from the mask 2 is reflected by the folding mirror 3, converged by the lens 4, and irradiated on the surface of the substrate 5. The substrate 5 is a gallium nitride substrate. A mark is produced by irradiating the substrate 5 with a laser beam. The marking method will be described later with reference to FIG.

  The optical path length from the mask 2 to the lens 4 and the optical path length from the lens 4 to the surface of the substrate 5 are adjusted so that the through hole of the mask 2 forms an image on the surface of the substrate 5 at an appropriate reduction magnification. (Mask imaging method). The reduction magnification is, for example, about ten times. When the shape of the through hole of the mask 2 is a circle having a diameter of 1 mm, the shape of the image of the through hole on the surface of the substrate 5 is, for example, a circle having a diameter of 70 μm.

  By the mask imaging method, a laser beam is irradiated onto a region on the substrate surface having a shape similar to the through hole of the mask 2. Nitrogen emission occurs in the beam irradiation region, and the reflectance increases. By using the mask imaging method, a region having a high reflectance having a shape similar to the through hole of the mask 2 can be formed on the substrate surface.

  Incidentally, the light intensity in the cross section of the laser beam emitted from the laser light source 1 is usually not uniform, and has a distribution such as high at the center of the beam and low at the periphery. If the light intensity is non-uniform, there may be regions in the beam spot on the substrate surface where the light intensity exceeds and does not exceed the nitrogen release reaction threshold. Therefore, there may be a problem that a region having a high reflectance is not uniformly formed in the beam spot.

  With the mask 2, only the region where the light intensity in the beam cross section is substantially uniform (for example, the central region of the Gaussian beam whose light intensity distribution in the beam cross section is Gaussian distribution) can be selected and irradiated onto the substrate 5. Thereby, a region having a high reflectance can be formed uniformly in the beam spot.

  The substrate 5 is held on the XY stage 6. The XY stage 6 can move the incident position of the laser beam on the substrate 5 by moving the substrate 5 in a plane parallel to the surface of the substrate 5. The control device 7 controls the XY stage 6 so that the substrate 5 is positioned at a desired position at a desired timing.

  It should be noted that good marking can be performed to some extent without imaging the through hole of the mask 2 on the substrate surface. In this case, the shape of the beam spot on the substrate surface does not accurately reflect the shape of the through hole. However, the mask 2 can select and irradiate the substrate 5 only with a region where the light intensity of the beam cross section is substantially uniform.

  Further, even if the mask 2 is omitted from the laser processing apparatus of FIG. However, in this case, the shape of the beam spot can be changed only to the shape corresponding to the cross section of the laser beam emitted from the laser light source 1. Since it is impossible to select and irradiate a region where the light intensity of the beam cross section is substantially uniform, it is not possible to reduce the non-uniformity of the light intensity in the beam spot on the substrate. However, even if the light intensity distribution in the beam cross section is not uniform, if the laser output is increased, the threshold value for the nitrogen release reaction can be exceeded even in a region where the light intensity in the beam cross section is relatively weak.

  FIG. 5B is a schematic view showing another example of a laser processing apparatus for marking a gallium nitride substrate. Hereinafter, differences from the laser processing apparatus in FIG. 5A will be described.

  The laser beam emitted from the laser light source 1 and passed through the mask 2 is incident on the galvano scanner 8 and is swung in a two-dimensional direction. The laser beam emitted from the galvano scanner 8 is converged by the fθ lens 4 a and irradiated onto the surface of the substrate 5 held on the XY stage 6.

  When the galvano scanner 8 changes the traveling direction of the laser beam, the incident position of the laser beam on the substrate 5 can be moved. The control device 7a controls the galvano scanner 8 so as to oscillate the laser beam in a desired traveling direction at a desired timing. The control device 7a also controls the XY stage 6 so that the substrate 5 is positioned at a desired position at a desired timing. The incident position of the laser beam on the substrate 5 may be moved while simultaneously operating the galvano scanner 8 and the XY stage 6.

  Next, a marking method according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a plan view of the substrate 5 held on the XY stage 6 shown in FIG.

  A mark 20 composed of a plurality of dots 20a, 20b, 20c and the like is formed on the surface of the substrate 5. Each dot is a highly reflective area. The mark 20 represents a character “12A” composed of two Arabic numerals and one English character.

  The mark 20 is produced by the method described below. First, the substrate 5 is aligned by moving the XY stage so that the position of the dot 20a is irradiated with the laser beam. When the substrate 5 is aligned, one shot of pulse laser beam is irradiated.

  In the beam irradiation region, a thermal decomposition reaction of gallium nitride is induced, and nitrogen is released out of the substrate. In this way, a dot 20a, which is a gallium-rich and highly reflective area, is formed at the beam irradiation position.

  Next, the substrate 5 is aligned by moving the XY stage so that the position of the dot 20b is irradiated with the laser beam. When the substrate 5 is aligned, one shot of pulse laser beam is irradiated. In the same manner as the dot 20a, the dot 20b, which is an area having a high reflectance, is formed.

  Subsequently, the substrate 5 is aligned by moving the XY stage so that the position of the dot 20c is irradiated with the laser beam. When the substrate 5 is aligned, one shot of pulse laser beam is irradiated. In the same manner as the dot 20a, a dot 20c that is an area having a high reflectance is formed. Thereafter, the marks 20 are formed by forming the other dots in the same procedure.

  By using the marking method described above, by increasing the reflectance of a desired region on the surface of the gallium nitride substrate, compared to a mark formed by digging a hole or groove in the substrate surface or a mark formed inside the substrate, A mark having excellent visibility can be manufactured.

  Since holes and grooves are not formed in the substrate, the mechanical strength of the substrate is not impaired unlike a marking method in which holes or grooves are formed in the substrate. In addition, the occurrence of cracks can be suppressed by performing laser irradiation with an appropriate pulse width and the like. Thus, since the damage of the substrate can be suppressed, the processing yield can be improved. Since no holes or grooves are formed in the substrate, it is possible to prevent the substrate from being contaminated by scattered objects.

  Since the reflectance of the substrate surface can be increased by irradiation with one shot of the pulse laser beam, the processing speed can be increased and the productivity can be increased.

  The mark 20 is composed of areas with high reflectivity (dots 20a to 20c, etc.). The area outside the mark 20 on the substrate surface has a low reflectivity. As described above, since the areas having different reflectances are adjacent to each other on the substrate surface, the mark 20 can be recognized as a mark. By forming a highly visible mark on the substrate, it becomes easy to distinguish one substrate from another. Note that the two areas of the substrate surface having different reflectances correspond to the ratio of the number of nitrogen atoms to the number of gallium atoms (or the density of nitrogen atoms) differing from each other in the two areas. To do.

  The number, size, and arrangement shape of dots constituting the mark can be appropriately selected according to the mark to be produced. You may comprise a mark with one dot.

  The dots are not limited to a circle. Any shape such as a rectangle may be used. The shape of the dot can be changed, for example, by changing the shape of the through hole of the mask. The region where the reflectance is increased is not limited to a dot-like dot, but may be an arbitrary shape such as a linear shape or a planar shape. For example, by forming a plurality of dots so that adjacent dots are in contact with each other (or partially overlap) along a desired linear region, a linear region with high reflectivity can be formed. .

  A pattern may be formed such that one or a plurality of discrete areas with low reflectivity (not irradiated with laser) are present inside an area with high reflectivity (irradiated with laser). For example, it is possible to form a mark composed of areas having low reflectivity by arranging a plurality of areas having low reflectivity in a letter shape.

  Consider a case where a gallium rich region is formed on the front surface of the substrate. In the above description, it has been described that the mark is manufactured by utilizing the high reflectance of the gallium-rich region with respect to the light incident from the front side of the substrate. On the other hand, the gallium-rich region has a lower transmittance than the original substrate with respect to light incident from the back surface of the substrate. Therefore, the mark produced by the method described above will function as a mark even when viewed with transmitted light incident from the back surface of the substrate.

  As described above, the marking on the gallium nitride substrate has been described. However, the reaction of releasing nitrogen from the substrate surface is also used for substrates of other inorganic nitrides such as aluminum nitride (particularly metal nitrides composed of metal elements and nitrogen). The markings made will be effective. That is, on the surface of the inorganic nitride substrate made of an inorganic compound of an element other than nitrogen and nitrogen, a region where the ratio of the number of nitrogen atoms to the number of atoms of the elements other than nitrogen is relatively high and low is formed. Thus, by forming a region having a relatively high reflectance and a region having a relatively low reflectance, a mark having excellent visibility can be produced.

  The target on which the mark is formed is not limited to the substrate, and may be various members made of inorganic nitride.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is a microscope picture which shows the result of having irradiated the 4th harmonic of YLF laser by pulse energy density 0.24J / cm < ² >. A fourth harmonic of a YLF laser is a photomicrograph showing the result of irradiation with pulse energy density 11.7J / cm ^2. It is a microscope picture which shows the result of having irradiated the 3rd harmonic of YLF laser by pulse energy density 2.0J / cm < ² >. The third harmonic of a YLF laser is a photomicrograph showing the result of irradiation with pulse energy density 11.7J / cm ^2. It is a microscope picture which shows the result of having irradiated the 3rd harmonic of YLF laser by pulse energy density 0.25J / cm < ² >. The third harmonic of a YLF laser is a photomicrograph showing the result of irradiation with pulse energy density 0.56J / cm ^2. The second harmonic of a YLF laser is a photomicrograph showing the result of irradiation with pulse energy density 3.4 J / cm ^2. It is the schematic which shows an example of the laser processing apparatus used for the marking method. It is the schematic which shows the other example of the laser processing apparatus used for the marking method. It is an example of the mark produced with the marking method by the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Mask 3 Folding mirror 4 Lens 5 Board | substrate 6 XY stage 7, 7a Control apparatus 8 Galvano scanner 4a f (theta) lens 10 Board | substrate 11a, 11b, 12a, 12b, 13a, 13b, 14 Beam irradiation trace 20a, 20b, 20c dot 20 mark

Claims (10)

A region where the ratio of the number of nitrogen atoms to the number of atoms of the first element is relatively high and low is formed on the surface of the member made of an inorganic compound of the first element other than nitrogen and nitrogen. Thereby, the marking method of the inorganic nitride member including the process of arrange | positioning the area | region with a relatively high reflectance and a low area | region on the surface of this member. (A) emitting a laser beam from a laser light source;
(B) A laser beam emitted from the laser light source is irradiated to a first region defined on a surface of a member made of an inorganic compound of a first element other than nitrogen and nitrogen, and nitrogen atoms are emitted from the member. The ratio of the number of nitrogen atoms to the number of atoms of the first element in the first region is calculated as the number of atoms of the first element in the region not irradiated with the laser beam on the surface of the member. And a method of marking an inorganic nitride member including a step of making the ratio smaller than the ratio of the number of nitrogen atoms to the number of atoms. The marking method for an inorganic nitride member according to claim 2, wherein the laser light source emits a pulse laser beam having a pulse width of 1 ns to 100 ns. 4. The marking of an inorganic nitride member according to claim 2, wherein the laser light source emits a pulse laser beam, and a peak intensity of the pulse laser beam on the surface of the member is 1 × 10 ⁶ W to 1 × 10 ⁸ W. 5. Method. The laser light source emits a pulsed laser beam;
The marking method of the inorganic nitride member according to any one of claims 2 to 4, wherein, in the step (b), only one pulse of a pulsed laser beam is applied to the first region of the surface of the member. Furthermore, after the step (b),
The position where the laser beam is incident on the member is moved, the surface of the member is irradiated with the laser beam emitted from the laser light source, and nitrogen atoms are emitted to the outside of the member. The ratio of the number of nitrogen atoms to the number of atoms of the first element in is smaller than the ratio of the number of nitrogen atoms to the number of atoms of the first element in the region not irradiated with the laser beam on the surface of the member. The marking method of the inorganic nitride member in any one of Claims 2-5 including the process of performing a process in multiple times. The marking method for an inorganic nitride member according to any one of claims 2 to 6, wherein the first element is gallium or aluminum. A member made of an inorganic compound of a first element other than nitrogen and nitrogen, wherein the mark is formed by adjoining at least two areas having different nitrogen atom densities. The inorganic nitride member according to claim 8, wherein nitrogen atom densities are different from each other and areas adjacent to each other are formed on the same plane. The inorganic nitride member according to claim 8 or 9, wherein the first element is gallium or aluminum.

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