Laser device and laser processing device

Abstract

The present invention provides a compact laser device and laser processing device that output laser light in the ultraviolet wavelength range with high power and high directivity. [Solution] The laser device comprises a photonic crystal laser element 1 and a nonlinear crystal element 2 that multiplies the frequency of the laser light oscillated by the photonic crystal laser element 1 and outputs it, and outputs laser light having a wavelength in the range of 180 nm to less than 300 nm from the nonlinear crystal element 2. The laser processing device comprises the laser device and an optical system that irradiates a target to be processed with the laser light output from the laser device.

Description

Technical Field

[0001] The present invention relates to a laser device and a laser processing device in the ultraviolet wavelength range.

Background Art

[0002] In recent years, as a semiconductor for power devices, wide bandgap semiconductors (such as gallium nitride, gallium oxide, silicon carbide, etc.) that exhibit high performance in terms of switching and breakdown voltage have attracted attention (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to manufacture a single crystal substrate of a wide bandgap semiconductor, it is necessary to crystallize an amorphous film epitaxially grown on a base such as a substrate by applying energy to the film. On the other hand, in order to crystallize such a wide bandgap semiconductor, it is necessary to apply a large amount of energy (heat) to the semiconductor.

[0005] In the field of semiconductor technology, laser light is often used as a technique to supply energy to semiconductors. By using laser light, it is possible to efficiently irradiate a semiconductor with only the wavelength of light that the semiconductor can absorb, thereby supplying it with energy. However, with conventional laser devices (gas lasers, solid-state lasers, semiconductor lasers, etc.), achieving crystallization of wide-bandgap semiconductors presented problems, such as the laser device becoming expensive and requiring a large size. Specifically, even if it is possible to irradiate a wide-bandgap semiconductor with laser light of a wavelength that the semiconductor can absorb (in this case, laser light in the ultraviolet wavelength range), achieving crystallization requires improving the power and directivity of the irradiated laser light. This necessitates a complex configuration and control of the laser device, which in turn makes the laser device expensive and large.

[0006] Therefore, the objective of the present invention is to enable the output of laser light in the ultraviolet wavelength range with high power and high directivity using a compact laser device. [Means for solving the problem]

[0007] The laser device according to the present invention comprises a photonic crystal laser element and a nonlinear crystal element that multiplies the frequency of the laser light oscillated by the photonic crystal laser element (for example, by second-order high-frequency generation (SHG) or third-order high-frequency generation (THG)) and outputs the laser light in the ultraviolet wavelength range from the nonlinear crystal element.

[0008] According to the above laser device, by multiplying the frequency of the laser light emitted from the photonic crystal laser element using a nonlinear crystal element and outputting it, even if the photonic crystal laser element can only emit long-wavelength laser light (for example, if the wavelength is halved by the nonlinear crystal element 2, laser light with a wavelength in the range of 360 nm to 800 nm; if the wavelength is reduced to 1 / 3 by the nonlinear crystal element 2 (in the case of THG), laser light with a wavelength in the range of 540 nm to 1200 nm), the laser light can be converted by the nonlinear crystal element to ultraviolet wavelength laser light (for example, a wavelength in the range of 180 nm to 400 nm; preferably, laser light with a wavelength in the range of 205 nm to 310 nm) and output. Furthermore, the photonic crystal laser element can emit laser light with higher power and higher directivity compared to conventional oscillators. Therefore, even when the conversion efficiency of a nonlinear crystal element is extremely low compared to laser light with wavelengths longer than the ultraviolet wavelength range, such as in the ultraviolet wavelength range, the converted laser light (laser light with multiplied frequency) can be output with greater power and higher directivity than before. Moreover, since the photonic crystal laser element is significantly smaller in size than conventional oscillators, the entire device can be significantly miniaturized. [Effects of the Invention]

[0009] According to the present invention, it becomes possible to output laser light in the ultraviolet wavelength range with high power and high directivity using a compact laser device. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a conceptual diagram showing a laser device according to an embodiment. [Figure 2] Figure 2 is a conceptual diagram showing a photonic crystal laser device. [Modes for carrying out the invention]

[0011] [1] Configuration of the laser device Figure 1 is a conceptual diagram showing a laser device according to an embodiment. As shown in this figure, the laser device comprises a photonic crystal laser element 1, a nonlinear crystal element 2, and a power control unit 3.

[0012] Figure 2 is a conceptual diagram showing a photonic crystal laser element 1. In the photonic crystal laser element 1, a photonic crystal layer 12 is placed near the active layer 11, and the light confined in the active layer 11 is subjected to the resonance and diffraction effects of the photonic crystal layer 12. In addition, multiple through holes 12h are formed in the photonic crystal layer 12, and these are arranged in a lattice pattern. By changing the shape of the through holes 12h themselves and the shape of the lattice, the diffraction effect on the light in the active layer 11 can be adjusted. The photonic crystal laser element 1 oscillates laser light when power is supplied from the power control unit 3.

[0013] This photonic crystal laser element 1 can generate laser light with higher power and greater directivity compared to conventional oscillators. Furthermore, because the photonic crystal laser element 1 is significantly smaller in size than conventional oscillators, the entire laser device can be significantly miniaturized.

[0014] Nonlinear crystal element 2 is an element that enables the conversion of the frequency (in other words, wavelength) of light, such as BBO (β-BaB2O4) (absorption wavelength 190 nm) and CLBO (CsLiB6O 10 It is formed from a crystal such as (absorption wavelength 180 nm). Specifically, the nonlinear crystal element 2 multiplies the frequency of the input light (for example, by second-order high-frequency generation (SHG) or third-order high-frequency generation (THG)) and outputs it. In this embodiment, the laser light emitted from the photonic crystal laser element 1 has its frequency doubled by the nonlinear crystal element 2 and is output (in other words, its wavelength is halved and output).

[0015] With such a nonlinear crystal element 2, even if the photonic crystal laser element 1 can only emit laser light in the wavelength range where the absorption rate of the wide-bandgap semiconductor (the object to be annealed for crystallization) is low, it becomes possible to convert that laser light into laser light in the wavelength range where the absorption rate of the wide-bandgap semiconductor is high and output it.

[0016] In this way, by multiplying the frequency of the laser light emitted from the photonic crystal laser element 1 using the nonlinear crystal element 2 and outputting it, even if the photonic crystal laser element 1 can only emit long-wavelength laser light (for example, if the wavelength is halved by the nonlinear crystal element 2, laser light with a wavelength in the range of 360 nm to 800 nm; if the wavelength is reduced to 1 / 3 by the nonlinear crystal element 2 (in the case of THG), laser light with a wavelength in the range of 540 nm to 1200 nm), the laser light can be converted by the nonlinear crystal element 2 into ultraviolet wavelength laser light (for example, a wavelength in the range of 180 nm to 400 nm; preferably, laser light with a wavelength in the range of 205 nm to 310 nm) and output. Furthermore, as described above, the photonic crystal laser element 1 can emit laser light with higher power and higher directivity compared to conventional oscillators. Therefore, even if the conversion efficiency of the nonlinear crystal element 2 is low, the converted laser light (laser light with multiplied frequency) can be output with greater power and higher directivity than conventional methods.

[0017] Therefore, it becomes possible to output laser light in the ultraviolet wavelength range with high power and high directivity using a compact laser device.

[0018] Here, in the above laser device, the lower limit of the wavelength of the output laser light is determined by the absorption wavelength of the nonlinear crystal element 2, in other words, the wavelength at which frequency doubling becomes impossible. Specifically, the lower limit of 180 nm is the absorption wavelength of the BBO crystal or CLBO crystal forming the nonlinear crystal element 2. On the other hand, in the above laser device, the upper limit of the wavelength of the output laser light is determined on the premise of frequency doubling in the nonlinear crystal element 2. When outputting laser light with a wavelength longer than 400 nm, frequency doubling in the nonlinear crystal element 2 is not necessarily required, and the laser light oscillated from the photonic crystal laser element 1 can be output as it is.

[0019] In addition, the laser device may be appropriately modified to further include an optical system (such as a separator) for adjusting the characteristics of the laser light oscillated from the photonic crystal laser element 1 and the characteristics of the laser light output from the nonlinear crystal element 2.

[0020] Also, the laser device may further include a scanner that linearizes and scans the laser light output in a dot shape with a cylindrical lens or a galvano scanner that scans two-dimensionally while remaining in a dot shape as an irradiation means for the laser light.

[0021] [2] Applications of the laser device As an example, the above-described laser device can be used for annealing to crystallize a wide-bandgap semiconductor. According to the nonlinear crystal element 2 included in the laser device, even when the photonic crystal laser element 1 can only oscillate laser light in a wavelength range where the absorption rate in the wide-bandgap semiconductor (the annealing target for crystallization) is low, the laser light can be converted into laser light in a wavelength range where the absorption rate in the wide-bandgap semiconductor is high and output.

[0022] For example, when the annealing target for crystallization is gallium oxide, which is a type of wide-bandgap semiconductor, the wavelength range of light that gallium oxide can absorb is generally in the range of 247 nm or more and 354 nm or less (in terms of photon energy, it is in the range of 3.5 eV or more and 5.0 eV or less). Even for such gallium oxide, it becomes possible to efficiently absorb laser light by using the above-described laser device.

[0023] Thus, according to the above-described laser device, it becomes possible to output laser light in a wavelength range where the absorption rate in a wide-bandgap semiconductor (annealing target for crystallization) is high (for example, laser light having a wavelength within the range of 180 nm or more and 400 nm or less). As a result, it becomes possible to give sufficient energy (energy sufficient to achieve crystallization) to the wide-bandgap semiconductor.

[0024] More specifically, as a laser annealing device, it is possible to configure one including the above-described laser device and an optical system that irradiates the annealing target with the laser light output from the laser device. According to this laser annealing device, laser light having a power within the range of 100 mJ / cm 2 or more and 1000 mJ / cm 2 or less can be output from the non-linear crystal element 2. Therefore, even if the annealing target for crystallization is gallium oxide, which is a type of wide-bandgap semiconductor, it becomes possible to give sufficient energy to achieve crystallization for it.

[0025] Other examples include the use of the aforementioned laser devices in the field of semiconductor manufacturing technology, such as via manufacturing equipment (TSV (Through Silicon Via) and TGV (Through Glass Via) etc.) for forming vias (used for connecting semiconductor chips) on interposers such as silicon substrates and glass substrates, laser trimming equipment, and support material removal equipment (LLO (Laser Lift Off) etc.). Furthermore, in the field of analytical technology, it can be used in Raman analyzers for analyzing the surface of samples. In addition, in the field of medical technology, it can be used in laser ablation equipment.

[0026] The above description of embodiments should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the embodiments described above. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0027] 1. Photonic crystal laser element 2. Nonlinear Crystal Elements 3 Power Control Unit 11 Active layer 12 Photonic crystal layer 12h through hole

Claims

1. Photonic crystal laser element, A nonlinear crystal element that multiplies the frequency of the laser light oscillated by the aforementioned photonic crystal laser element and outputs it, A laser device comprising a nonlinear crystal element that outputs laser light having a wavelength in the range of 180 nm to less than 300 nm.

2. The aforementioned nonlinear crystal element is a nonlinear crystal BBO(β-BaB ２ O ４ ) or CLBO (CsLiB ６ O １０ The laser apparatus according to claim 1, wherein the element multiplies the frequency of the laser light and outputs it.

3. A laser apparatus according to claim 1 or 2, An optical system that irradiates a target to be processed with laser light output from the aforementioned laser device, A laser processing device equipped with the following features.

Images