AlN single crystal plate

Abstract

This AlN single crystal plate comprises a first surface in the thickness direction, and a second surface facing the first surface. The AlN single crystal plate comprises a metal component-containing region whereinto a plurality of metal components have been introduced in a dispersed manner and which is present approximately in parallel to the first surface in an intermediary portion between the first surface and the second surface.

Description

[Technical field]

[0001] The technology disclosed in this specification relates to an AlN single crystal plate. [Background technology]

[0002] An AlN single crystal plate is sometimes used as a substrate for an ultraviolet light emitting device. For example, Non-Patent Document 1 discloses a method for manufacturing an ultraviolet light emitting device fabricated on an AlN single crystal plate. In Non-Patent Document 1, a functional layer of an ultraviolet light emitting device is formed on an AlN single crystal plate. After the functional layer is formed on the AlN single crystal plate, the AlN single crystal plate is thinned by mechanical polishing in order to improve the ultraviolet light transmittance. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Yoshinao Kumagai and 2 others, "HVPE homoepitaxial growth on sublimation AlN wafers and its application to deep UV LEDs", Journal of the Japanese Society for Crystal Growth, Vol. 41, No. 3, 2014, pp. 131-137 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ultraviolet light-emitting device described in Non-Patent Document 1, an AlN single crystal plate is used as a handling substrate for producing an ultraviolet light-emitting device. Therefore, after forming a functional layer on a thick AlN single crystal plate, the AlN single crystal plate is thinned to a required thickness by mechanical polishing. However, when the AlN single crystal plate is thinned by mechanical polishing, the functional layer may be affected during mechanical polishing. Therefore, in the past, when the AlN single crystal plate is thinned by mechanical polishing, it is necessary to perform the mechanical polishing carefully in order to suppress the effect on the functional layer. As a result, the time required to manufacture an ultraviolet light-emitting device increases. Therefore, there is a need for an AlN single crystal plate that can be easily thinned.

[0005] This specification discloses an AlN single crystal plate that can be easily thinned. [Means for solving the problem]

[0006] The AlN single crystal plate disclosed herein has a first surface in the thickness direction and a second surface opposite to the first surface, and a metal component-containing region is present in an intermediate portion between the first surface and the second surface, extending generally parallel to the first surface.

[0007] In the above AlN single crystal plate, a metal component-containing region in which a plurality of metal components are dispersed and introduced is present in the intermediate portion between the first surface and the second surface. Therefore, for example, by irradiating the AlN single crystal plate with a laser and sublimating (vaporizing) the metal components, fine cracks are generated in the metal component-containing region, and the AlN single crystal plate can be thinned. That is, the above AlN single crystal plate can be thinned by a method other than mechanical polishing, such as laser lift-off. Therefore, the AlN single crystal plate can be easily thinned, and the influence on the functional layer of an ultraviolet light-emitting device or the like when thinning the AlN single crystal substrate can be reduced. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram of an ultraviolet light-emitting device fabricated using an AlN single crystal plate according to the embodiment. [Diagram 2] FIG. 2 is a schematic diagram of an AlN single crystal plate according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The main features of the embodiments described below are listed below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

[0010] The AlN single crystal plate disclosed in this specification has a low Al content compared to, for example, sapphire. x Gay The nitride semiconductor such as N(0≦x≦1, 0<y≦1) has a lattice constant that is close to or the same as that of the AlN single crystal plate disclosed in this specification. Therefore, the AlN single crystal plate disclosed in this specification is useful as a growth substrate for an ultraviolet light-emitting device (UV LED) having a nitride semiconductor as a functional layer. Further, the AlN single crystal plate, for example, compared with sapphire, Al x Ga yThe nitride semiconductor such as N(0≦x≦1,0<y≦1) has a thermal expansion coefficient close to or the same as that of sapphire and has mechanical strength comparable to that of sapphire. Therefore, it is useful as a handling substrate when manufacturing an ultraviolet light-emitting device. The AlN single crystal plate disclosed in this specification has a metal component-containing region in which a metal component is dispersed and introduced in the middle portion between the first surface and the second surface in the thickness direction. The metal component-containing region is substantially parallel to the first surface (or the first surface and the second surface). Therefore, for example, after manufacturing an ultraviolet light-emitting device on the AlN single crystal plate, by irradiating the AlN single crystal plate with a laser from the opposite side of the surface on which the ultraviolet light-emitting device is manufactured, the metal component in the metal component-containing region absorbs the laser, and the back side (the side where the functional layer of the ultraviolet light-emitting device is not provided) from the metal component-containing region can be lifted off. Since the AlN single crystal plate can be thinned in a short time regardless of the thickness of the AlN single crystal plate to be lifted off (removed), the manufacturing time of the ultraviolet light-emitting device can be shortened. That is, even when an ultraviolet light-emitting device is manufactured using a thick AlN single crystal plate, it is possible to suppress an increase in the time required for manufacturing the ultraviolet light-emitting device. In addition, the thinning of the AlN single crystal plate by laser lift-off can reduce the force (vibration) applied to the functional layer of the ultraviolet light-emitting device compared with thinning by mechanical polishing, and can reduce the influence on the functional layer. The metal component-containing region and the portion other than the metal component-containing region in the AlN single crystal plate can be distinguished by observing the AlN single crystal plate using SEM or the like. The "first surface" means one of the front and back surfaces of the AlN single crystal plate, and the "second surface" means the other of the front and back surfaces of the AlN single crystal plate. For example, the "first surface" means the surface of the AlN single crystal plate, and the "second surface" means the back surface of the AlN single crystal plate. Alternatively, the "first surface" means the back surface of the AlN single crystal plate, and the "second surface" means the surface of the AlN single crystal plate. The "the metal component-containing region is substantially parallel to the first surface" means a form in which the metal component-containing region extends along the first surface at an angle of less than 5 degrees with respect to the first surface. The AlN single crystal plate disclosed in this specification is not particularly limited, but the thickness (distance between the front and back surfaces) may be 0.3 to 1.0 mm.

[0011] In the AlN single crystal plate disclosed in this specification, the metal component-containing region is locally provided between the front surface and the back surface. That is, the metal component-containing region exists in a part of the thickness direction of the AlN single crystal plate. For example, the thickness of the metal component-containing region in the AlN single crystal plate may be 0.1 μm or more and 5.0 μm or less. If the thickness of the metal component-containing region is 0.1 μm or more, when the AlN single crystal plate is irradiated with a laser, the metal component sufficiently absorbs the laser and sublimes, fine cracks are generated in the metal component-containing region, and a part (a part to be removed) of the AlN single crystal plate can be lifted off. In addition, if the thickness is 5.0 μm or less, when the AlN single crystal plate is irradiated with a laser, it is possible to suppress the cracks generated in the metal component-containing region from extending to a part other than the metal component-containing region (the cracks can be easily contained within the metal component-containing region), and the AlN single crystal plate can be suitably laser lifted off without adversely affecting the ultraviolet light emitting device. The thickness of the metal component-containing region may be 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more. The thickness of the metal component-containing region may be 4.5 μm or less, 4.0 μm or less, 3.0 μm or less, 2.0 μm or less, 1.0 μm or less, or 0.5 μm or less.

[0012] In the AlN single crystal plate disclosed in the present specification, the distance between adjacent metal components in the metal component-containing region may be 1 μm or more and 300 μm or less. In other words, the gap between the metal components may be 1 μm or more and 300 μm or less. If the distance between adjacent metal components is 1 μm or more, it is possible to suppress adverse effects on the ultraviolet light emitting device caused by cracks occurring in the metal component-containing region. Furthermore, if it is 300 μm or less, the cracks occurring in the metal component-containing region are connected, and the back side of the AlN single crystal plate can be reliably separated by laser lift-off. Note that "adjacent metal components" refers to metal components adjacent in a direction along (approximately parallel to) the first surface. The distance between adjacent metal components may be 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 25 μm or more. Furthermore, the distance between metal components in the metal component-containing region may be 275 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less.

[0013] In the AlN single crystal plate disclosed in this specification, the metal component-containing region may contain at least one metal component selected from Al, Ga, Cu, Fe, Mo, Ni, Ta, and Ti, or may contain at least one of the above metal components as a main component. Moreover, "mainly containing at least one of the metal components" means that the metal component-containing region contains 50% by weight or more of the above metal component. These elements have high performance in absorbing light in a predetermined range of wavelengths, specifically light of 245 to 1200 nm, and are easily absorbed by laser light. Therefore, with this configuration, the AlN single crystal plate can be suitably laser lifted off. The metal component in the metal component-containing region may be, for example, a simple metal, an alloy containing the above metal component, or an oxide, composite oxide, nitride, composite nitride, or composite oxynitride containing the above metal component.

[0014] In the AlN single crystal plate disclosed in this specification, the metal component-containing region may contain at least one metal component selected from Al, Ga, Cu, and Ni. The above-mentioned metal component materials are relatively easy to obtain, and are particularly good at absorbing laser light, making them suitable for laser lift-off.

[0015] In the AlN single crystal plate disclosed herein, the metal component may be in the form of particles. In this case, the metal component (particles containing the metal component) may have an aspect ratio greater than 1 and less than or equal to 10. In this case, the metal component may be present in the metal component-containing region such that its long side is along (approximately parallel to) the first surface (or the first surface and the second surface). Specifically, the metal component may be disposed such that its long side forms an angle of less than 20 degrees with respect to the first surface. If the aspect ratio of the metal component is greater than 1, the area of ​​the surface along the first surface is sufficiently large, the laser absorption efficiency is improved, and laser lift-off can be efficiently performed, and cracks occurring in the metal component-containing region tend to occur along approximately parallel to the first surface (or the first surface and the second surface), thereby suppressing adverse effects on the ultraviolet light-emitting device. In addition, if the aspect ratio is less than or equal to 10, the metal component can be easily introduced into the AlN single crystal plate. The aspect ratio may be 0.5 or more, 1.0 or more, 1.5 or more, or 2.0 or more. The aspect ratio may be 8 or less, 7 or less, 5 or less, or 3 or less. EXAMPLES

[0016] An AlN single crystal substrate 10 according to an embodiment will be described below. The AlN single crystal substrate 10 is used as a handling substrate for fabricating an ultraviolet light-emitting device 1. Therefore, before describing the AlN single crystal substrate 10 in detail, an ultraviolet light-emitting device 1 that uses the AlN single crystal substrate 10 as a handling substrate will be briefly described.

[0017] The ultraviolet light emitting device 1 is an ultraviolet light emitting diode (UV LED), and includes an AlN single crystal substrate 10a, an n-type nitride semiconductor layer 2, a p-type nitride semiconductor layer 3, and a light emitting layer 4. The n-type nitride semiconductor layer 2 is provided on the surface of the AlN single crystal substrate 10a. The light emitting layer 4 is provided on a part of the surface of the n-type nitride semiconductor layer 2 (the right side in FIG. 1). Therefore, the light emitting layer 4 is provided on a part of the surface of the n-type nitride semiconductor layer 2, and the other part is exposed. The p-type nitride semiconductor layer 3 is provided on the surface of the light emitting layer 4. That is, the light emitting layer 4 is provided between the n-type nitride semiconductor layer 2 and the p-type nitride semiconductor layer 3. Electrodes (not shown) are provided on the surface of the p-type nitride semiconductor layer 3 and on the exposed part of the surface of the n-type nitride semiconductor layer 2. Although not shown in the drawings, in practice, the n-type nitride semiconductor layer 2 may be formed of a plurality of layers, the p-type nitride semiconductor layer 3 may be formed of a plurality of layers, and the light emitting layer 4 may be formed of a plurality of layers. The materials and the number of layers of the n-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3, and the light emitting layer 4 can be appropriately selected depending on the application of the ultraviolet light emitting device 1.

[0018] When the ultraviolet light emitting device 1 is produced, first, the n-type nitride semiconductor layer 2 is formed on the surface of the AlN single crystal plate 10 of this embodiment. Next, the light emitting layer 4 is formed on the surface of the formed n-type nitride semiconductor layer 2, and the p-type nitride semiconductor layer 3 is formed on the surface of the formed light emitting layer 4. After that, the light emitting layer 4 and the p-type nitride semiconductor layer 3 are partially removed to expose a part of the surface of the n-type nitride semiconductor layer 2. The AlN single crystal plate 10 is used to form the high-quality nitride semiconductor layers 2, 3, and 4. In addition, in order to facilitate the formation and processing of the n-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3, and the light emitting layer 4, a thick AlN single crystal plate 10 is used as a handling substrate when producing the ultraviolet light emitting device 1. On the other hand, if a thick AlN single crystal plate 10 is used as it is as a substrate for the ultraviolet light emitting device 1, the thickness of the AlN single crystal plate 10 makes it difficult for emitted light (ultraviolet light) to pass through the AlN single crystal plate 10 (AlN single crystal plate 10a). For this reason, after the n-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3, and the light emitting layer 4 are formed, the AlN single crystal plate 10 is thinned to a required thickness. That is, the AlN single crystal plate 10 has the unnecessary portion 10b removed so that only the AlN single crystal substrate 10a required as a substrate remains. Hereinafter, the n-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3, and the light emitting layer 4 may be collectively referred to as the "functional layer".

[0019] 2, the AlN single crystal plate 10 is made of single crystal AlN. The AlN single crystal plate 10 can be formed by, for example, a sublimation method. The method for forming the AlN single crystal plate 10 is not particularly limited, and the AlN single crystal plate 10 can also be formed by other methods, such as a vapor phase film formation method such as a CVD method, a HVPE method, a MBE method, or a sputtering method, a liquid phase film formation method such as a hydrothermal method or a Na flux method, or room temperature bonding in which two sheets of single crystal AlN are bonded using a surface activation method.

[0020] The AlN single crystal plate 10 also has a metal component-containing region 16 provided between the front surface 12 and the back surface 14. In this embodiment, when the AlN single crystal plate 10 is used as a handling substrate to fabricate the ultraviolet light-emitting device 1, the surface of the AlN single crystal plate 10 on which a functional layer is formed is referred to as the front surface 12, and the opposite surface is referred to as the back surface 14. The metal component-containing region 16 is provided locally in the thickness direction of the AlN single crystal plate 10, and is provided approximately parallel to the intermediate portion between the front surface 12 and the back surface 14 (the intermediate portion in the thickness direction).

[0021] In the metal component-containing region 16, a plurality of metal particles are dispersed and introduced into the single crystal AlN. Specifically, the metal particles in the metal component-containing region 16 have an aspect ratio greater than 1 and adjusted to 10 or less, and are arranged so that their long sides are aligned along the front surface 12 and the back surface 14. The metal particles are also arranged at intervals such that the distance between adjacent metal components is 1 μm to 300 μm. The method of introducing the metal particles (metal components) is not particularly limited. For example, the metal component-containing region 16 can be formed by mixing a raw material containing a metal component into the raw material (solid raw material or raw material gas) that forms the AlN single crystal layer 12. Alternatively, after forming an AlN single crystal layer, a raw material containing a metal component is attached to its surface, and then an AlN single crystal layer is formed again on the surface of the AlN single crystal layer (the surface to which the raw material containing the metal component is attached), thereby introducing the metal component into the middle part of the AlN single crystal layer 12. The metal particles are single metals selected from Al, Ga, Cu, Fe, Mo, Ni, Ta, and Ti. The metal component-containing region 16 contains at least one of the above metal components as a main component. The metal particles may be alloys containing the above metal elements, oxides or composite oxides containing the above metal elements, nitrides or composite nitrides containing the above metal components, or composite oxynitrides containing the above metal components.

[0022] The introduction of metal particles into the metal component-containing region 16 prevents the laser light from passing from the front surface 12 to the back surface 14 (or from the back surface 14 to the front surface 12) of the AlN single crystal plate 10. Specifically, when the back surface 14 of the AlN single crystal plate 10 is irradiated with laser light, the metal particles in the metal component-containing region 16 absorb the laser light. As a result, the metal component sublimes (vaporizes), and the removed portion 10b (see FIG. 1) can be removed (lifted off). The metal particles introduced into the metal component-containing region 16 are selected from those that easily absorb laser light. Specifically, metal particles that easily absorb light with a wavelength of 245 nm to 1200 nm are introduced into the metal component-containing region 16.

[0023] Table 1 below shows examples of metals that easily absorb light with wavelengths of 245 nm to 1200 nm. The metals shown in Table 1 (Al, Ga, Cu, Fe, Mo, Ni, Ta, Ti) favorably absorb laser light with wavelengths of 245 nm to 1200 nm. Table 1 also shows the absorbance of the above metals for light with wavelengths of 400 nm and 800 nm. The metals shown in Table 1 (Al, Ga, Cu, Fe, Mo, Ni, Ta, Ti) absorb light with wavelengths of 245 nm to 1200 nm well. Therefore, when irradiated with laser light with a wavelength of 245 nm to 1200 nm, metal particles containing these elements absorb the laser light and vaporize. The metal component-containing regions 16 are provided on the front surface 12 and the back surface 14 of the AlN single crystal plate 10 in approximately parallel relation, and therefore the AlN single crystal plate 10 is divided by the metal component-containing regions 16. Therefore, the AlN single crystal plate 10 into which metal particles containing at least one of the above elements have been introduced can be thinned at the metal component-containing region 16 by laser lift-off.

[0024] [Table 1]

[0025] In this embodiment, for example, the thickness L1 of the AlN single crystal plate 10 is adjusted to 0.3 mm to 1.0 mm, and the thickness L2 of the metal component-containing region 16 is adjusted to 0.1 μm to 5.0 μm. The thickness L1 of the AlN single crystal plate 10 is the length between the front surface 12 and the back surface 14, and indicates the length in the direction perpendicular to the front surface 12 and the back surface 14. The thickness L2 of the metal component-containing region 16 also indicates the length in the direction perpendicular to the front surface 12 and the back surface 14. By making the thickness L2 of the metal component-containing region 16 0.1 μm or more, the metal particles (metal components) can reliably absorb the laser light, and the effect of heating the metal component-containing region 16 can be obtained. As a result, laser lift-off can be performed in the metal component-containing region 16. Furthermore, by making the thickness L2 5.0 μm or less, the generation of cracks due to the irradiation of the laser light can be contained within the metal component-containing region 16. Therefore, adverse effects on the ultraviolet light-emitting device can be suppressed.

[0026] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

Claims

1. An AlN single crystal plate having a first surface in a thickness direction and a second surface opposite to the first surface, a metal component-containing region having a plurality of metal components dispersed therein and present in an intermediate portion between the first surface and the second surface, the metal component-containing region being approximately parallel to the first surface; The metal component is an AlN single crystal plate having Ga as a main component.

2. 2. The AlN single crystal plate according to claim 1, wherein the thickness of the metal component-containing region is not less than 0.1 μm and not more than 5.0 μm.

3. 3. The AlN single crystal plate according to claim 1, wherein in said metal component-containing region, a distance between adjacent metal components is 1 μm or more and 300 μm or less.

4. The AlN single crystal plate according to any one of claims 1 to 3, wherein the metal component has an aspect ratio greater than 1 and equal to or less than 10, and the long side of the metal component is disposed along the first surface.

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