JP2015010017A - Doping method using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for doping a dopant material into a substrate such as a glass, etc. by using a laser beam.SOLUTION: A substrate 2 such as a glass, etc. is prepared. A dopant material 6 desired to be doped is placed atop the surface 4 of this substrate 2. Next, a carbon dioxide gas laser is applied onto the vicinity of the border plane of the surface 4 of the substrate 2 and the dopant material 6. The carbon dioxide gas laser beam 8 is applied within a range targeted for doping at this time by scanning the carbon dioxide gas laser beam 8. The substrate 2 is melted as a result of the irradiation thereof with the carbon dioxide gas laser, and the dopant material 6 comes to be mingled therewith. After the irradiation, the substrate 2 is cooled, and doping is performed as a result of the solidification of the substrate 2 in a state where the mingled dopant material 6 remains included therein.

Description

  The present invention relates to a doping method using laser light.

  In order to change electrical characteristics of a semiconductor substrate or the like, an ion implantation method for doping impurities is used. The electrical characteristics can be adjusted depending on the amount of implanted ions.

  A thermal diffusion method is also used. A gas containing impurities is sprayed at a high temperature on the wafer surface and diffused into the wafer.

  On the other hand, a method of processing glass or the like using laser light is disclosed. For example, Patent Document 1 discloses an apparatus for forming a three-dimensional image in a glass beam by condensing and irradiating a laser beam to crack or damage glass.

JP2002-154845

  However, when the ion implantation method is used, the lattice is damaged by the ion implantation. For this reason, it is necessary to recover a damaged crystal by performing a heat treatment such as annealing, and the process becomes complicated.

  On the other hand, although the thermal diffusion method does not require a heat treatment such as annealing as a separate step, it is difficult to accurately control the range to be doped.

  In addition, in the prior art described in Patent Document 1, although a point in which a desired three-dimensional shape is engraved in glass using a laser is disclosed, processing for doping impurities or the like in glass is disclosed. Absent.

  An object of the present invention is to provide a method of doping a doping material into a substrate such as glass using a laser beam.

(1) A doping method according to the present invention includes a step of placing a dope material on a substrate, and a step of irradiating a laser on the substrate on which the dope material is placed and doping the dope material into the substrate. ing.

  Therefore, doping can be performed locally without performing heat treatment before and after processing.

(2) A method for producing a doped substrate according to the present invention includes a step of placing a doped material on the substrate, and irradiating the substrate on which the doped material is placed with a laser to dope the doped material in the substrate. And a step of performing.

  Therefore, a locally doped substrate can be obtained without performing heat treatment before and after processing.

(3) The method according to the present invention is characterized in that the dope material is any one of a fluorescent material, iron, copper, and aluminum.

(4) The method according to the present invention is characterized in that the substrate is glass.

(5) The method according to the present invention is characterized in that the laser irradiation position is moved with respect to the substrate.

(6) The method according to the present invention is characterized in that the moving speed of the laser irradiation position is changed according to the output of the laser.

It is a figure which shows the process of the doping method (manufacturing method of the doped base | substrate) by one Embodiment of this invention. It is a figure which shows the dope condition at the time of using the low melting point dope material. It is a figure which shows the dope condition at the time of using a high melting point dope material. FIG. 4 shows an optical system for carrying out the doping method. FIG. 5 is an optical microscope image of the glass surface doped with a fluorescent material. FIG. 6a is a cross section of a sample glass. FIG. 6b is a cross section showing the distribution of carbon. FIG. 6c is a cross section showing the distribution of silicon. FIG. 6d is a cross section showing the distribution of sodium. FIG. 7a is a cross section of a sample glass. FIG. 7b is a cross section showing the distribution of iron. FIG. 7c is a cross section showing the distribution of silicon. FIG. 7d is a cross section showing the distribution of sodium. FIG. 8 shows the relationship between laser output and dope spread. FIG. 9 shows the relationship between laser power and dope depth. FIG. 10a is a cross section of a sample glass. FIG. 10b is a cross section showing the copper distribution. FIG. 10c is a cross section showing the distribution of silicon. FIG. 10d is a cross section showing the distribution of sodium. FIG. 11 shows the relationship between laser output and dope spread. FIG. 12 shows the relationship between laser power and dope depth. FIG. 13 is a diagram showing the relationship between the laser operation speed, the laser output, and the success or failure of the doping.

  FIG. 1 shows a doping method according to an embodiment of the present invention. First, a substrate 2 such as glass is prepared (FIG. 1A). Subsequently, a doping material 6 to be doped is placed on the surface 4 of the substrate 2 (FIG. 1B). Next, in this state, a carbon dioxide laser is irradiated near the boundary surface between the surface 4 of the substrate 2 and the dope material 6 (FIG. 1C). At this time, the carbon dioxide laser beam 8 is scanned to irradiate the carbon dioxide laser beam 8 in a region where doping is desired. The substrate 2 is melted by the irradiation of the carbon dioxide laser, and the dope material 6 is mixed. After the irradiation, the substrate 2 is cooled, and the substrate 2 is solidified with the mixed doping material 6 included therein, and doping is performed.

  When excess dope material on the surface is removed, the state shown in FIG. 1D is obtained. That is, a doped body 2 can be obtained.

  2A, 2B, and 2C schematically show changes when a low melting point dope material 6 is placed. As shown in FIG. 2B, when the laser beam 8 is irradiated, the dope material 6 is melted and mixed with the melted substrate 2. When the irradiation of the laser beam 8 is stopped, as shown in FIG. 2C, the substrate 2 is hardened in a state where the doping material 6 is doped.

  3A, 3B, and 3C schematically show changes when the high melting point dope material 6 is placed. As shown in FIG. 3B, when the laser beam 8 is irradiated, the base 2 is melted to form a recess, and the dope material 6 falls. When the irradiation of the laser beam 8 is stopped, as shown in FIG. 3C, the base 2 is solidified with the doping material 6 being doped.

  In this embodiment, the laser beam is irradiated to the processing site and melted. Therefore, it is not necessary to perform heat treatment (annealing) before and after processing.

  The laser light source needs to be laser light that is absorbed by the substrate 2. When the substrate 2 is glass, it is preferable to use a carbon dioxide laser, YAG laser, which is an infrared laser, or an excimer laser, which is an ultraviolet laser. A gas laser, a solid laser, a liquid laser, or the like can be used as long as it can irradiate light that causes absorption in the substrate.

  As the dope material 6, metal materials such as copper powder, iron powder, and aluminum powder, fluorescent dyes, and the like can be used.

1. Experimental Procedure Here, an experiment was performed according to the following procedure.

(1) A doped region is formed by horizontally moving a glass sample placed perpendicular to the laser optical axis. The distance from the laser light source to the glass sample was 2 mm, and the horizontal movement speed was 1 mm / second.

(2) The glass sample was hardened with polyester, and then the sample surface was polished.

(3) The cross section of the sample was analyzed by energy dispersive X-ray analysis (EDX) in a scanning electron microscope to clarify the components in the glass.

2. Experimental device
2.1 Laser Driving a continuous laser requires an electrical pulse signal generated by a function generator. The voltage of the pulse signal was 2.5 V, and the repetition frequency was 5,000 KHz. The laser output was adjusted by the duty ratio.

2.2 Sample Table 2 shows the characteristics of the glass sample (S-BAL7) to be treated.

  A fluorescent material was prepared as a low melting point doping material, and iron and copper were prepared as high melting point doping materials. As the fluorescent material, the one contained in the fluorescent paint was used. The diameters of iron and copper were both less than 32 μm.

2.3 Optical system Figure 4 shows the optical system used in this study. A CO2 laser is irradiated from the upper surface of the glass sample. The single-axis stage was controlled using the control software LabVIEW (trademark) of National Instruments Japan. Thereby, the scanning speed and the scanning distance in the single axis stage can be adjusted.

3. Experimental result
3.1 Low Melting Point Doping Material FIG. 5 shows an optical microscope image of the glass surface doped with a fluorescent material. A polka dot pattern is observed in the laser irradiation region.

  FIG. 6a is a sample glass. FIG. 6b shows the carbon distribution, FIG. 6c shows the silicon distribution, and FIG. 6d shows the sodium distribution. Silicon and sodium are distributed in the region irradiated with the laser, and carbon is distributed in the peripheral and the laser irradiation region of the glass sample surface. It can be seen that the carbon in the fluorescent material has been doped into the glass.

3.2 High melting point doping material
3.2.1 Iron Doping FIGS. 7b to 7d show the distribution of iron, silicon and sodium when iron doping is performed. FIG. 7b shows the iron distribution, FIG. 7c shows the silicon distribution, and FIG. 7d shows the sodium distribution. FIG. 7a is a sample glass.

  In FIG. 7b, white spots are observed between the glass and the polyester. This spot indicates iron. Furthermore, silicon and sodium are reduced in the spots (see FIGS. 7c and 7d). Therefore, it turns out that iron is doped.

  FIG. 8 shows the relationship between laser output and dope spread. The horizontal axis is the laser output, and the vertical axis is the dope width. FIG. 9 shows the relationship between the laser output and the dope depth. The horizontal axis is the laser output, and the vertical axis is the doping depth. This is the depth from the surface of the deepest position of the doped region.

  The doped region tends to become wider as the laser power is increased. This is because the thermal diffusion length increases as the laser output increases. Similarly, as the laser output increases, the doping depth increases. When the laser output was 9 W to 10 W, the maximum dope width was about 3.0 mm and the maximum dope depth was 227 μm.

3.2.2 Copper Doping FIGS. 10b to 10d show the distribution of copper, silicon and sodium when copper is doped. 10b shows the copper distribution, FIG. 10c shows the silicon distribution, and FIG. 10d shows the sodium distribution. FIG. 10a is a sample glass.

  FIG. 11 shows the relationship between laser output and dope spread. The horizontal axis is the laser output, and the vertical axis is the dope width. FIG. 12 shows the relationship between the laser output and the dope depth. The horizontal axis is the laser output, and the vertical axis is the doping depth. This is the depth from the surface of the deepest position of the doped region.

  The doped region tends to become wider as the laser power is increased. This is because the thermal diffusion length increases as the laser output increases. Similarly, as the laser output increases, the doping depth increases. When the laser output was 8.5 W to 9 W, the maximum dope width was about 2.8 mm and the maximum dope depth was 96 μm.

3.3 Scanning speed and doping success / failure FIG. 13 shows the relationship between scanning speed and doping success / failure when copper is doped. A circle indicates successful doping, a cross indicates unsuccessful doping, and a triangle indicates successful doping with deformation.

As is apparent from this figure, it is understood that a laser output (W) exceeding about 7 times the scanning speed (mm) is required. It can also be seen that the laser output (W) must not exceed 10 times the scanning speed (mm) in order to prevent deformation.

3.4 Summary The width and depth of the doped region can be increased by increasing the laser power. This is due to the thermal diffusion effect.

  Doping is not successful if the laser power is too small. In the case of iron, dope was not successful if the laser output was 6.5 W or less. In the case of copper, dope was not successful if the laser output was 5.5 W or less.

  Regarding the success or failure of doping, it has been found that an appropriate laser output corresponding to the scanning speed is necessary.

  As described above, doping can be performed locally without performing heat treatment before and after processing.

Claims (6)

Placing a dope material on a substrate;
Irradiating a substrate on which the doping material is placed with a laser, and doping the doping material into the substrate;
A doping method comprising: Placing a dope material on a substrate;
Irradiating a substrate on which the doping material is placed with a laser, and doping the doping material into the substrate;
A method of manufacturing a doped substrate comprising:   3. The method according to claim 1, wherein the doped material is any one of a fluorescent material, iron, copper, and aluminum. In the method in any one of Claims 1-3,
The method wherein the substrate is glass. In the method in any one of Claims 1-4,
A method of moving a laser irradiation position with respect to the substrate. 6. The method of any of claims 5
A method of changing a moving speed of an irradiation position of the laser in accordance with an output of the laser.