Laser device and laser annealing device

Abstract

This laser device includes: a photonic crystal laser element; and a nonlinear crystal element that multiplies a frequency of a laser beam oscillated by the photonic crystal laser element and outputs the multiplied frequency. A laser beam in the ultraviolet wavelength region is output from the nonlinear crystal element. This laser annealing device is provided with: the laser device; and an optical system that projects a laser beam output from the laser device onto an annealing target.

Description

Laser device and laser annealing device

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

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

[0003] Japanese Patent Application Laid-Open No. 2021-158391

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

[0005] In the field of semiconductor technology, laser light is often used to provide energy to semiconductors. Laser light allows for efficient energy transfer by irradiating semiconductors with only light of a wavelength that can be absorbed by the semiconductor. However, conventional laser devices (such as gas lasers, solid-state lasers, and semiconductor lasers) have problems with the cost and size of laser devices required to achieve crystallization of wide-bandgap semiconductors. Specifically, even if wide-bandgap semiconductors can be irradiated with laser light of a wavelength that can be absorbed by the semiconductor (here, laser light in the ultraviolet wavelength range), achieving crystallization requires increasing the power and directionality of the irradiated laser light, which in turn complicates the configuration and control of the laser device, resulting in increased cost and size of the laser device.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to make it possible to output laser light in the ultraviolet wavelength range with high power and high directivity using a small laser device.

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

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

[0009] According to the present invention, it is possible to realize a small-sized laser device that outputs laser light in the ultraviolet wavelength range with high power and high directivity.

[0010] Fig. 1 is a conceptual diagram showing a laser device according to an embodiment, and Fig. 2 is a conceptual diagram showing a photonic crystal laser element.

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

[0012] 2 is a conceptual diagram showing the photonic crystal laser element 1. The photonic crystal laser element 1 is configured such that a photonic crystal layer 12 is disposed near an active layer 11, and light confined in the active layer 11 is subjected to the resonance and diffraction effects of the photonic crystal layer 12. A plurality of through-holes 12h are formed in the photonic crystal layer 12, and these are arranged in a lattice pattern. The diffraction effect on the light in the active layer 11 can be adjusted by changing the shape of the through-holes 12h themselves or the shape of the lattice. The photonic crystal laser element 1 emits laser light when power is supplied from a power control unit 3.

[0013] Such a photonic crystal laser element 1 can emit laser light with higher power and higher directionality than conventional oscillators. Furthermore, since the photonic crystal laser element 1 is significantly smaller in size than conventional oscillators, the entire laser device can be significantly miniaturized.

[0014] The nonlinear crystal element 2 is an element that enables conversion of the frequency (in other words, wavelength) of light, and is made of BBO (β-BaB ２ O ４ ) (absorption wavelength 190 nm) and CLBO (CsLiB ６ O １０ ) (absorption wavelength 180 nm). Specifically, the nonlinear crystal element 2 doubles the frequency of the input light (for example, by second harmonic generation (SHG) or third harmonic generation (THG)). In this embodiment, the laser light oscillated from the photonic crystal laser element 1 is output after its frequency is doubled by the nonlinear crystal element 2 (in other words, the wavelength is halved).

[0015] With such a nonlinear crystal element 2, even if the photonic crystal laser element 1 can only emit laser light in a wavelength range with low absorption in the wide band gap semiconductor (the target of annealing for crystallization), it is possible to convert that laser light into laser light in a wavelength range with high absorption in the wide band gap semiconductor and output it.

[0016] In this way, by multiplying the frequency of the laser light oscillated from the photonic crystal laser element 1 by the nonlinear crystal element 2 and outputting it, even if the photonic crystal laser element 1 can only oscillate long-wavelength laser light (for example, laser light having a wavelength in the range of 360 nm to 800 nm when the wavelength is halved by the nonlinear crystal element 2, or laser light having a wavelength in the range of 540 nm to 1200 nm when the wavelength is halved by the nonlinear crystal element 2 (in the case of THG)), it is possible to convert the laser light into laser light in the ultraviolet wavelength range (for example, laser light having a wavelength in the range of 180 nm to 400 nm, preferably laser light having a wavelength in the range of 205 nm to 310 nm) and output it by the nonlinear crystal element 2. Furthermore, as described above, the photonic crystal laser element 1 can oscillate laser light that has higher power and higher directionality than conventional oscillators. Therefore, even if the conversion efficiency of the nonlinear crystal element 2 is low, the converted laser light (laser light whose frequency has been multiplied) can be output with greater power and higher directivity than before.

[0017] Therefore, it becomes possible to realize a small laser device that outputs laser light in the ultraviolet wavelength range with high power and high directivity.

[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 doubling is not possible. Specifically, the lower limit of 180 nm is the absorption wavelength of the BBO crystal or CLBO crystal that forms 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 that the frequency will be multiplied by the nonlinear crystal element 2. When outputting laser light with a wavelength longer than 400 nm, frequency doubling by 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 is.

[0019] Furthermore, 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 emitted from the photonic crystal laser element 1 and the characteristics of the laser light output from the nonlinear crystal element 2.

[0020] The laser device may further include, as a laser light irradiation means, a scanner that converts laser light output in a dot shape into a line shape using a cylindrical lens for scanning, or a galvano scanner that scans the dot shape in two dimensions.

[0021] [2] Uses of the Laser Device As an example, the laser device described above can be used for annealing to crystallize a wide bandgap semiconductor. Even if the photonic crystal laser element 1 can only oscillate laser light in a wavelength range that is poorly absorbed by the wide bandgap semiconductor (the target of annealing for crystallization), the nonlinear crystal element 2 included in the laser device can convert the laser light into laser light in a wavelength range that is highly absorbed by the wide bandgap semiconductor and output the converted laser light.

[0022] For example, when the target of annealing for crystallization is gallium oxide, which is a type of wide band gap semiconductor, the wavelength range of light that can be absorbed by gallium oxide is generally in the range of 247 nm to 354 nm (equivalent to a range of 3.5 eV to 5.0 eV in photon energy), but even for such gallium oxide, it is possible to efficiently absorb laser light by using the above-mentioned laser device.

[0023] In this way, the above-described laser device can output laser light in a wavelength range (e.g., laser light having a wavelength in the range of 180 nm or more and 400 nm or less) that has a high absorption rate in the wide band gap semiconductor (the target of annealing for crystallization), and as a result, it becomes possible to provide sufficient energy (enough energy to achieve crystallization) to the wide band gap semiconductor.

[0024] More specifically, the laser annealing apparatus can be configured to include the above-described laser apparatus and an optical system that irradiates the laser light output from the laser apparatus onto the object to be annealed. According to the laser annealing apparatus, it is possible to obtain a laser beam having a power of 100 mJ / cm. ２ More than 1000mJ / cm ２ It becomes possible to output laser light having a power within the following range from the nonlinear crystal element 2. Therefore, even if the object to be annealed for crystallization is gallium oxide, which is a type of wide band gap semiconductor, it becomes possible to provide it with sufficient energy to achieve crystallization.

[0025] As another example, in the field of semiconductor manufacturing technology, the above-mentioned laser device can be used in via manufacturing devices (such as TSV (Through Silicon Via) and TGV (Through Glass Via)) that form vias (vias used for connecting semiconductor chips, etc.) in interposers such as silicon substrates and glass substrates, laser trimming devices, and peeling devices (such as LLO (Laser Lift Off)) that peel off support materials. Furthermore, in the field of analytical technology, the laser device can be used in Raman analysis devices that analyze the surface of samples. Furthermore, in the field of medical technology, the laser device can be used in laser ablation devices, etc.

[0026] The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications that are equivalent to the scope of the claims and fall within the scope thereof.

[0027] REFERENCE SIGNS LIST 1 Photonic crystal laser element 2 Nonlinear crystal element 3 Power control unit 11 Active layer 12 Photonic crystal layer 12h Through hole

Claims

1. A laser device comprising: a photonic crystal laser element; and a nonlinear crystal element that multiplies the frequency of laser light oscillated by the photonic crystal laser element and outputs the laser light, wherein laser light in the ultraviolet wavelength range is output from the nonlinear crystal element.

2. A laser device according to claim 1, wherein said nonlinear crystal element outputs laser light having a wavelength within the range of 180 nm to 400 nm.

3. The nonlinear crystal element is a nonlinear crystal, BBO (β-BaB ２ O ４ 3. The laser device according to claim 1, wherein the laser device is an element that multiplies the frequency of the laser light by a frequency converter.

4. The nonlinear crystal element is a nonlinear crystal, CLBO (CsLiB ６ O １０ 3. The laser device according to claim 1, wherein the laser device is an element that multiplies the frequency of the laser light by a frequency converter.

5. A laser annealing device comprising: a laser device according to any one of claims 1 to 4; and an optical system that irradiates an object to be annealed with laser light output from said laser device.

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