JP2012033729A - Semiconductor layer bonded substrate manufacturing method and light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device that improves light extraction efficiency.SOLUTION: A semiconductor layer bonded substrate manufacturing method comprises a preparation process of causing a growth of a first semiconductor layer 3 having a heat expansion coefficient different from that of a first substrate 2 on a top face 2A of the first substrate 2, a bonded structure formation process of removing, after bonding a second substrate 4 having a heat expansion coefficient nearer to the fist semiconductor layer 3 than the first substrate 2, the first substrate 2 to form a bonded structure 6 on a top face 3A of the first semiconductor layer 3 in which the second substrate 4 and the first semiconductor layer 3 are bonded, and a growth process of further causing a growth of a second semiconductor layer 5 of a composition system same as that of the first semiconductor layer 3 on an exposed surface 7 of the first semiconductor layer 3 on the removed side of the first substrate 2. Accordingly, cracks occurring at the first semiconductor layer 3 can be inhibited at the boundary surface of the first semiconductor layer 3 with the second substrate 4 when causing the growth of the second semiconductor layer 5 on the first semiconductor layer 3.

Description

  The present invention relates to a method for manufacturing a semiconductor layer bonded substrate and a semiconductor light emitting device.

  Currently, various methods for laminating a semiconductor layer on a substrate have been proposed. In that case, from the viewpoint of cost and availability, the semiconductor layer and the substrate to be stacked often have to be made of different materials. However, when materials having greatly different physical properties such as thermal expansion coefficient or lattice constant between the substrate and the semiconductor layer on which the crystal is grown on the substrate are used, dislocation or stress is likely to occur in the semiconductor layer. There is a problem that it is difficult to improve the crystallinity of the film.

  Therefore, as a technique for performing crystal growth of a semiconductor layer satisfactorily using a heterogeneous substrate having a material property value different from that of the semiconductor layer, for example, by providing a plurality of grooves on one main surface of the heterogeneous substrate, A technique for improving the crystallinity of a semiconductor layer to be grown is disclosed (for example, see Patent Document 1).

JP 2002-164296 A

  However, according to the semiconductor layer growth technique disclosed in Patent Document 1, the thicker the semiconductor layer grown on the heterogeneous substrate, the different the thermal expansion coefficient between the heterogeneous substrate and the semiconductor layer. There was a risk that cracks would easily occur. Therefore, the semiconductor layer growth technique disclosed in Patent Document 1 has a problem that it is difficult to thickly stack a semiconductor layer with good crystallinity on a different substrate.

  Further, in a light-emitting element in which an optical semiconductor layer is stacked on a different substrate, there are many cases where there is a large difference in thermal expansion coefficient between the different substrate and the optical semiconductor layer. Therefore, the stress corresponding to the heat generated when light is emitted from the optical semiconductor layer is greatly different between the heterogeneous substrate and the optical semiconductor layer, and the optical semiconductor layer may be peeled off from the heterogeneous substrate.

  This invention is made | formed in view of the said subject, The objective is to provide the manufacturing method of the semiconductor layer joining substrate which can suppress generation | occurrence | production of a crack, when growing a semiconductor layer. Another object of the present invention is to provide a light emitting device capable of suppressing the occurrence of peeling at the interface between the optical semiconductor layer and the substrate.

  A method for manufacturing a semiconductor layer bonded substrate according to an embodiment of the present invention includes a preparatory step of growing a first semiconductor layer having a thermal expansion coefficient different from that of the first substrate on an upper surface of the first substrate, and the first semiconductor After bonding a second substrate having a thermal expansion coefficient closer to the first semiconductor layer than the first substrate to the upper surface of the layer, the first substrate is removed and the second substrate and the first semiconductor layer are A bonded body forming step for forming a bonded bonded body; and a second semiconductor layer having the same composition system as the first semiconductor layer is further formed on the exposed surface of the first semiconductor layer on the side where the first substrate is removed. And a growth process for growth.

  A light-emitting device according to an embodiment of the present invention is a light-emitting device that includes a stacked body in which a buffer layer and an optical semiconductor layer are sequentially stacked on a substrate, and the substrate, the buffer layer, and the optical semiconductor layer include: The buffer layer is made of a material having the same composition system, and the buffer layer has a half-value width of the rocking curve on the surface side in contact with the substrate smaller than a half-value width of the rocking curve on the surface side in contact with the optical semiconductor layer. .

  According to the method for manufacturing a semiconductor layer bonded substrate according to one embodiment of the present invention, as described above, the second substrate having a thermal expansion coefficient closer to the first semiconductor layer than the first substrate is bonded to the first semiconductor layer. After the formed bonded body is formed, the second semiconductor layer is stacked on the exposed region of the first semiconductor layer from which the first substrate is removed, so that the semiconductor layer is grown on the first substrate. Since the second substrate has a thermal expansion coefficient close to that of the first semiconductor layer, cracks occurring at the interface between the first semiconductor layer and the second substrate can be suppressed.

  In addition, according to the light emitting device according to the embodiment of the present invention, as described above, the light emitting device includes a laminated body in which the buffer layer and the optical semiconductor layer are sequentially laminated on the substrate, and the half width of the rocking curve of the buffer layer is light. Since the substrate side is smaller than the semiconductor layer side, it is possible to provide a light-emitting element capable of suppressing peeling that occurs between the buffer layer and the substrate.

It is a perspective view which shows an example of embodiment of the semiconductor layer composite substrate manufactured by the manufacturing method of the semiconductor layer joining substrate concerning one Embodiment of this invention. It is sectional drawing which shows 1 process of an example of embodiment of the manufacturing method of the semiconductor layer joining substrate of this invention, and is equivalent to the cross section when cut | disconnected by the A-A 'line | wire of FIG. It is sectional drawing which shows 1 process of an example of embodiment of the manufacturing method of the semiconductor layer joining substrate concerning one Embodiment of this invention. It is sectional drawing which shows 1 process of an example of embodiment of the manufacturing method of the semiconductor layer joining substrate concerning one Embodiment of this invention. It is sectional drawing which shows 1 process of an example of embodiment of the manufacturing method of the semiconductor layer joining substrate concerning one Embodiment of this invention. It is a perspective view which shows the light emitting element concerning one Embodiment of this invention. It is sectional drawing which shows the light emitting element concerning one Embodiment of this invention, and is equivalent to the cross section when it cut | disconnects by the B-B 'line | wire of FIG.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  The present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

<Method for producing semiconductor layer bonded substrate>
FIG. 1 is a perspective view of a semiconductor layer bonding substrate 1 as an example of an embodiment of the present invention. FIGS. 2-5 is sectional drawing which shows the manufacturing process of the semiconductor layer joining substrate 1, and is each corresponded to the cross section when it cut | disconnects by the AA 'line of FIG.

  As shown in FIG. 1, the semiconductor layer bonded substrate 1 manufactured by the method for manufacturing the semiconductor layer bonded substrate 1 of the present embodiment includes a first substrate 2 that is removed during the manufacturing process, and a first semiconductor layer 3. The second substrate 4 and the second semiconductor layer 5 are mainly manufactured.

The semiconductor layer bonded substrate 1 manufactured in this way is used for electronic components such as a light emitting element, a semiconductor laser, or a transistor.

  Then, the manufacturing method of the semiconductor layer joining substrate 1 of embodiment of this invention is demonstrated.

(Preparation process)
As shown in FIG. 2, a first semiconductor layer 3 having a thermal expansion coefficient different from that of the first substrate 2 is grown on the upper surface 2 </ b> A of the first substrate 2. Each configuration will be specifically described below.

As the first substrate 2, a material capable of growing the first semiconductor layer 3 is used. The first substrate 2 is made of, for example, sapphire (thermal expansion coefficient 5.0 × 10 ⁻⁶ 1 / K or more and 6.0 × 10 ⁻⁶ 1 / K or less), aluminum nitride (thermal expansion coefficient 4.0 × 10 ⁻⁶ 1 / K or more and 5.5 × 10 ^-6 1 / K or less), gallium nitride (thermal expansion coefficient 3.0 × 10 ⁻⁶ 1 / K or more and 6.0 × 10 ⁻⁶ 1 / K or less), silicon nitride (thermal expansion coefficient 2.0 × 10 ⁻⁶ 1 / K or more and 3.5 × 10 ⁻⁶ 1 / K or less), indium nitride (thermal expansion coefficient 3.0 × 10 ⁻⁶ 1 / K to 4.5 × 10 ⁻⁶ 1 / K or less) or silicon carbide (thermal expansion coefficient 5.0 × 10 ⁻⁶ 1 / K) For example, 4.2 × 10 ⁻⁶ 1 / K or less) can be used. In addition, the thermal expansion coefficient value described in this specification illustrates the value at room temperature, and the measurement method described in JIS R1618-1994 can be used for this thermal expansion coefficient.

  In addition, the first substrate 2 can be set to have a polygonal shape such as a quadrangular shape or a circular shape in plan view. In addition, the thickness of the 1st board | substrate 2 can be set to 2 micrometers or more and 2000 micrometers or less, for example. In this example, the first substrate 2 is made of sapphire.

The first semiconductor layer 3 only needs to have a different thermal expansion coefficient from that of the first substrate 2. For example, gallium nitride, aluminum nitride, a mixed crystal of nitride of aluminum and indium (thermal expansion coefficient 1.0 × 10 ⁻⁶ 1 / K or more and 8.0 × 10 ⁻⁶ 1 / K or less) or silicon carbide can be used. In this example, the first semiconductor layer 3 is made of aluminum nitride.

  The thickness of the first semiconductor layer 3 can be set to 0.05 μm or more and 1500 μm or less, for example. As the thickness of the first semiconductor layer 3 increases, the crystallinity can be improved by reducing dislocations from the substrate. Therefore, by setting the thickness of the first semiconductor layer 3 to, for example, 1 μm or more and 1500 μm or less, the crystallinity on the upper surface 3A side of the first semiconductor layer 3 as compared with the first substrate 2 side of the first semiconductor layer 3 is set. Can be improved.

  As a method for growing the first semiconductor layer 3 on the upper surface 2A of the first substrate 2, a molecular beam epitaxial method, a metal organic epitaxial method, a hydride vapor phase growth method, a pulse laser deposition method, or the like can be used.

  When epitaxially growing aluminum nitride as the first semiconductor layer 3 on the first substrate 2, the growth conditions such as the composition ratio, growth temperature, and growth pressure of the aluminum nitride may be adjusted. The growth temperature can be set to, for example, 150 ° C. or more and 1500 ° C. or less. When a low temperature buffer layer of aluminum nitride is provided as the first semiconductor layer 3 on the first substrate 2, the growth temperature can be set to, for example, 150 ° C. or higher and 800 ° C. or lower.

  When the first semiconductor layer 3 is grown on the first substrate 2, irregularities or the like may be formed on the first substrate 2 to grow the first semiconductor layer 3 in the lateral direction. When the first semiconductor layer 3 is grown on the first substrate 2 in the lateral direction, dislocations extending in the thickness direction of the first semiconductor layer 3 can be reduced. Crystallinity can be further improved.

(Joint formation process)
Next, as shown in FIG. 3, a second substrate 4 having a thermal expansion coefficient closer to that of the first semiconductor layer 3 than that of the first substrate 2 is bonded to the upper surface 3 </ b> A of the first semiconductor layer 3. Each configuration will be specifically described below.

  As the second substrate 4, a material having a thermal expansion coefficient closer to that of the first semiconductor layer 3 than that of the first substrate 2 may be used. For example, gallium nitride, aluminum nitride, a mixed crystal of nitride of aluminum and gallium, or silicon Selected from among carbides. As the second substrate 4, a material having a composition system different from that of the first semiconductor layer 3 may be used, or a material having the same composition system as that of the first semiconductor layer 3 may be used. Since the second substrate 4 is bonded to the first semiconductor layer 3 in this manner, the second substrate 4 can be freely selected from a single crystal material, a polycrystalline material, and the like.

  When a material having the same composition as that of the first semiconductor layer 3 is used as the second substrate 4, the difference in thermal expansion coefficient between the second substrate 4 and the first semiconductor layer 3 can be further reduced. The adhesion between the second substrate 4 and the first semiconductor layer 3 can be further improved.

  Here, the “same composition system” material refers to a material composed of a composition of 50% or more of the component constituting a certain substance, which accounts for the majority. As an example of aluminum nitride, as a material having the same composition system as aluminum nitride, 50% of aluminum nitride is used among aluminum nitride added with several percent of silicon, aluminum nitride added with several percent of magnesium, or a mixed crystal of aluminum nitride containing indium. % Have more than%.

  Specifically, when sapphire is used as the first substrate 2 and aluminum nitride is used as the first semiconductor layer 3, aluminum nitride, which is a material of the same composition system as the first semiconductor layer 3, is used as the second substrate 4. A fired body or a crystal of aluminum nitride can be used. When an aluminum nitride sintered body is used, it is possible to change the polycrystalline aluminum nitride by changing the sintering aid, sintering conditions, additives, or crystal orientation used when the aluminum nitride is sintered. The thermal expansion coefficient of the aluminum nitride sintered body can be adjusted by changing the state. In addition, the thickness of the 2nd board | substrate 4 should just be the thickness which can support a 1st semiconductor layer, for example, is set to 50 micrometers or more and 1000 micrometers or less.

As a method for bonding the first semiconductor layer 3 and the second substrate 4, a surface activated bonding method, a thermocompression bonding method, a diffusion bonding method, an anodic bonding method, or the like can be used. It should be noted that when such bonding is performed, for example, in a vacuum state of 1.3 Pa to 1.3 × 10 ⁻⁵ Pa, the generation of voids between the first semiconductor layer 3 and the second substrate 4 is suppressed. be able to.

  Above all, when using the surface activated bonding method, the bonding surface is activated and bonded, for example, compared with bonding at a temperature of typically 600 ° C. or higher and 800 ° C. or lower, for example, 10 ° C. or higher and 550 ° C. or lower. Can be bonded at a relatively low temperature. Therefore, even when the difference in thermal expansion coefficient between the first semiconductor layer 3 and the second substrate 4 is large, when the first semiconductor layer 3 and the second substrate 4 are joined, Since the difference in stress applied to the first semiconductor layer 3 and the second substrate 4 at the interface with the second substrate 4 can be reduced, the bonding can be performed while maintaining the bonding strength.

  When the surface activated bonding method is used as a method for bonding the first semiconductor layer 3 and the second substrate 4, the upper surface 3A of the first semiconductor layer 3 and the main surface to which the second substrate 4 is bonded are activated. For example, a heat treatment, an activation treatment method using an atomic beam or plasma, or the like can be used.

  Thereafter, as shown in FIG. 4, the first substrate 2 is removed to form a joined body 6 in which the second substrate 4 and the first semiconductor layer 3 are joined.

The first substrate 2 is removed from the main surface side of the first substrate 2 where the first semiconductor layer 3 is not formed. As a method for removing the first substrate 2 from the first semiconductor layer 3, for example, an etching method such as wet etching or dry etching, a polishing method such as chemical mechanical polishing, a laser lift-off method using a laser, or the like can be used. When a material having an etching speed different from that of the first semiconductor layer 3 is used as the first substrate 2, the first substrate 2 can be efficiently removed when the first substrate 2 is removed by an etching method. Therefore, the productivity of the process of removing the first substrate 2 can be improved.

  Thus, by removing the first substrate 2 from the first semiconductor layer 3 and exposing the main surface opposite to the upper surface 3A of the first semiconductor layer 3, the second substrate 4 and the first semiconductor layer 3 are formed. A joined body 6 can be formed.

(Growth process)
Next, as shown in FIG. 5, a second semiconductor layer 5 having the same composition system as that of the first semiconductor layer 3 is further grown on the exposed surface 7 of the first semiconductor layer 3 on the side where the first substrate 2 has been removed. . Each configuration will be specifically described below.

  Here, the same material as that of the first semiconductor layer 3 can be used as the same composition system of the second semiconductor layer 5. The thickness of the second semiconductor layer 5 can be set to 0.5 μm or more and 1500 μm or less, for example. In this example, the second semiconductor layer 5 is made of aluminum nitride which is a material having the same composition system as the first semiconductor layer 3.

  Further, when a plurality of layers having different compositions are provided as the second semiconductor layer 5, the lowermost layer may be a material having the same composition system as that of the first semiconductor layer 3. Specifically, if an optical semiconductor layer that emits specific light is stacked on the first semiconductor layer 3, the second semiconductor layer 5 made of a material having the same composition system as the first semiconductor layer 3 includes a plurality of layers. What is necessary is just to use as the lowest layer of the optical-semiconductor layer which consists of a semiconductor layer.

  Specifically, in the case where aluminum nitride is used as the first semiconductor layer 3 as in this example, the optical semiconductor layer is a mixed crystal made of at least one nitride of boron, aluminum, gallium, or indium. Of these, the main component may be aluminum nitride. Such an optical semiconductor layer is configured such that a light emitting layer is sandwiched between a first conductive type semiconductor layer and a second conductive type semiconductor layer.

  In this example, after forming the joined body 6 in which the second substrate 4 having a thermal expansion coefficient closer to the first semiconductor layer 3 than the removed first substrate 2 is joined to the first semiconductor layer 3, the first semiconductor is formed. A second semiconductor layer 5 is grown on the exposed surface 7 of the layer 3. As described above, since the second substrate 4 and the first semiconductor layer 3 have close thermal expansion coefficients, the second substrate 4 and the first semiconductor layer are grown when the second semiconductor layer 5 is grown on the first semiconductor layer 3. 3, cracks occurring in the first semiconductor layer 3 can be suppressed. Therefore, the crystallinity of the second semiconductor layer 5 formed on the first semiconductor layer 3 can be improved.

  Further, in the bonded body formation step, the upper surface 3A of the first semiconductor layer 3 can be polished before the second substrate 4 is bonded to the upper surface 3A of the first semiconductor layer 3. After the upper surface 3A of the first semiconductor layer 3 is polished in this way, the second substrate 4 is bonded to the polished upper surface 3A of the first semiconductor layer 3, thereby allowing the first semiconductor layer 3 and the second substrate 4 to adhere to each other. Can be improved. Since the adhesion between the first semiconductor layer 3 and the second substrate 4 can be improved, the bonding strength between the first semiconductor layer 3 and the second substrate 4 can be improved, and on the first semiconductor layer 3 When the second semiconductor layer 5 is grown, cracks generated in the first semiconductor layer 3 can be further suppressed.

Thus, when polishing the upper surface 3A of the first semiconductor layer 3, the flatness of the upper surface 3A of the first semiconductor layer 3 is, for example, 4 μm or more and 15 μm or less, or the surface roughness of the upper surface 3A of the first semiconductor layer 3 is increased. For example, by setting the thickness to 0.005 μm or more and 0.050 μm or less, the bonding strength between the upper surface 3A of the first semiconductor layer 3 and the second substrate 4 can be improved. As the surface roughness of the upper surface 3A of the first semiconductor layer 3, the maximum height roughness Rz based on JIS B0601-2001 is used.

  Furthermore, when polishing the upper surface 3A of the first semiconductor layer 3, the first semiconductor layer 3 can be partially removed in the thickness direction. Since there are many dislocations extending in the thickness direction from the upper surface 2A of the first substrate 2 on the first substrate 2 side of the first semiconductor layer 3, the first semiconductor layer 3 exposed by removing the first substrate 2 is exposed. By removing a part from the main surface in the thickness direction, the surface state of the exposed surface 7 of the first semiconductor layer 3 can be improved.

  The first semiconductor layer of the second semiconductor layer 5 grown on the exposed surface 7 of the first semiconductor layer 3 by bonding the exposed surface 7 whose surface condition of the first semiconductor layer 3 is improved and the second substrate 4. The number of dislocations extending from 3 can be reduced. Therefore, for example, threading dislocations extending in the thickness direction of the second semiconductor layer 5 can be reduced. By improving the surface state of the exposed surface 7 of the first semiconductor layer 3 in this way, the crystallinity of the second semiconductor layer 5 grown on the exposed surface 7 of the first semiconductor layer 3 can be improved.

  When removing the first substrate 2 from the first semiconductor layer 3, the first substrate 2 is removed, and then the first semiconductor layer 3 is partially removed in the thickness direction, thereby suppressing an increase in the number of steps. Meanwhile, a part of the first semiconductor layer 3 can be removed.

  Further, when a polishing method is used as a method for removing the first substrate 2 and the first semiconductor layer 3, the first substrate 2 and the first semiconductor layer from the first substrate 2 to a part of the first semiconductor layer 3 are used. By removing the first substrate 2 and the first semiconductor layer 3 while polishing in the laminating direction 3, the surface state of the exposed surface 7 of the first semiconductor layer 3 can be improved. By using the polishing method as a method for removing the first substrate 2 and the first semiconductor layer 3 in this manner, productivity can be improved while suppressing an increase in the number of steps.

  In the growth process, the second semiconductor layer 5 can be grown in a state where the substrate temperature of the second substrate 4 is set to 1100 ° C. or higher. As in this example, since the second substrate 4 is made of a material having a thermal expansion coefficient close to that of the first semiconductor layer 3, even if the second semiconductor layer 5 is grown with the substrate temperature being raised, the second substrate 4 And cracks occurring in the first semiconductor layer 3 at the interface between the first semiconductor layer 3 and the first semiconductor layer 3 can be suppressed.

  In this example, when the joined body 6 of the first semiconductor layer 3 and the second substrate 4 is made of aluminum nitride, and the aluminum nitride is grown as the second semiconductor layer 5 on the first semiconductor layer 3, the substrate temperature is set to It can be set to 1100 ° C or higher and 1800 ° C or lower. By setting such a substrate temperature, the growth rate of the second semiconductor layer 5 is improved while suppressing cracks generated in the first semiconductor layer 3 at the interface between the first semiconductor layer 3 and the second substrate 4. Can be made. Therefore, the growth time of the second semiconductor layer 5 can be shortened, and the productivity of the growth process can be improved.

  On the other hand, when the first semiconductor layer is formed at 1100 ° C. or higher on the substrates having greatly different thermal expansion coefficients, cracks are likely to occur in the first semiconductor layer at the interface between the first substrate and the first semiconductor layer. The growth rate of the first semiconductor layer may be slow.

In the above-described growth step, the second semiconductor layer 5 can be grown so that the total thickness of the first semiconductor layer 3 and the second semiconductor layer 5 is 0.1 μm or more. Thus, even when the second semiconductor layer 5 is grown so that the total thickness of the first semiconductor layer 3 and the second semiconductor layer 5 is 0.1 μm or more, the thermal expansion of the second substrate 4 and the first semiconductor layer. Because the difference in coefficient is small,
The second semiconductor layer 5 can be grown while suppressing cracks generated in the first semiconductor layer 3 at the interface between the substrate 4 and the first semiconductor layer 3.

  On the other hand, if the second semiconductor layer is grown on the first substrate so that the total thickness of the first semiconductor layer and the second semiconductor layer is 0.1 μm or more, the heat of the second semiconductor layer is the first heat. Move to the semiconductor layer. As a result, since the thermal expansion coefficients of the first semiconductor layer and the first substrate are greatly different, the stress difference inherent in the first semiconductor layer and the first substrate is increased, and at the interface between the first semiconductor layer and the first substrate. Cracks are likely to occur in the first semiconductor layer. Therefore, it is difficult to stack the first semiconductor layer and the second semiconductor layer thickly on the first substrate.

  In the joined body forming step, a substrate made of a material having the same composition as that of the first semiconductor layer 3 and the second semiconductor layer 5 can be used as the second substrate 4. Thus, by using a substrate made of a material having the same composition system as the first semiconductor layer 3 and the second semiconductor layer 5 as the second substrate 4, heat generated when the second semiconductor layer 5 is grown is generated. In addition, heat can be efficiently radiated from the second substrate 4 and adhesion between the second substrate 4 and the first semiconductor layer 3 can be improved.

  Furthermore, since the difference in thermal expansion coefficient between the second substrate 4 and the first semiconductor layer 3 can be reduced by using a material having the same composition system as the first semiconductor layer 3 as the second substrate 4, In contrast to bonding at about 600 ° C., bonding can be performed at a relatively high temperature of, for example, 650 ° C. to 1500 ° C. In this way, the bonding strength can be improved by bonding the first semiconductor layer 3 and the second substrate 4 at a relatively high temperature.

<Light emitting element>
FIG. 6 is a perspective view of a light emitting element 8 which is an example of an embodiment manufactured using the method for manufacturing a semiconductor layer bonded substrate of the present invention. 7 is a cross-sectional view of the light-emitting element shown in FIG. 6, and corresponds to a cross section taken along line BB ′ of FIG.

  As shown in FIG. 6, the light-emitting element 1 includes a laminate 12 in which a buffer layer 10 and an optical semiconductor layer 11 are sequentially laminated on a substrate 9, and the substrate 9, the buffer layer 10, and the optical semiconductor layer 11 have the same composition system. Consists of materials.

  For the substrate 9, for example, a crystalline material such as gallium nitride, aluminum nitride, or zinc oxide can be used. Specifically, a single crystal such as gallium nitride or a polycrystal such as aluminum nitride can be used. When a polycrystal is used as the substrate 9, it is preferable to set so as to have a thermal expansion coefficient close to that of the buffer layer 10 formed on the substrate 9. The substrate 9 is set to have a polygonal shape or a circular shape in plan view, and a thickness of, for example, 50 μm or more and 800 μm or less. In this example, the substrate 9 is made of aluminum nitride.

  The buffer layer 10 is provided on the substrate 9 and is made of a material having the same composition as that of the substrate 9. Such a buffer layer 10 is set to 0.01 μm or more and 1 μm or less, for example. In the buffer layer 10, the half-value width of the rocking curve on the surface 10 A side in contact with the substrate 9 is smaller than the half-value width of the rocking curve on the surface 10 B side in contact with the optical semiconductor layer 11. Specifically, the half-value width of the rocking curve on the surface 10A side of the buffer layer 10 in contact with the substrate 9 only needs to be smaller than the half-value width of the rocking curve on the surface 10B side of contact with the optical semiconductor layer 11, for example, 300 seconds or more. Can be set to 2000 seconds or less. The full width at half maximum of the rocking curve on the surface 10B side of the buffer layer 10 in contact with the optical semiconductor layer 11 can be set to 500 seconds or more and 3500 seconds or less, for example.

  Such a buffer layer 10 can be formed by the method for manufacturing a semiconductor layer bonded substrate described above. Specifically, when aluminum nitride is used as the optical semiconductor layer 11, the first semiconductor layer 3 made of aluminum nitride is grown on the upper surface of the first substrate 2 made of sapphire, and the upper surface of the first semiconductor layer 3 is taken. A second substrate 4 made of aluminum nitride is bonded to the substrate. Thereafter, the buffer layer 10 made of the first semiconductor layer 3 can be formed on the substrate 9 made of the second substrate 4 by removing the first substrate 2.

  The optical semiconductor layer 11 is provided on the buffer layer 10 and has a thickness of, for example, 0.5 μm or more and 10 μm or less. In the optical semiconductor layer 11, a one-conductivity-type semiconductor layer 11a, a light-emitting layer 11b, and a reverse-conductivity-type semiconductor layer 11c are sequentially stacked.

  As the optical semiconductor layer 11, a group III-V semiconductor can be used. Examples of group III-V semiconductors include group III nitride semiconductors such as mixed crystals made of at least one nitride of boron, aluminum, gallium, or indium, gallium phosphide, gallium arsenide, and the like. In this example, the optical semiconductor layer 11 is made of aluminum nitride. Thus, when aluminum nitride is used as the optical semiconductor layer 11, the refractive index of each layer of the optical semiconductor layer 11 is set to, for example, 1.8 or more and 2.7 or less.

  The first conductivity type semiconductor layer 11a and the second conductivity type semiconductor layer 11b are respectively set to conductivity types in which either electrons or holes are majority carriers. The first conductivity type semiconductor layer 11a is set to a conductivity type opposite to that of the second conductivity type semiconductor layer 11c. As a method of making the semiconductor layer a desired conductivity type, for example, a method of mixing magnesium or silicon as an impurity is used. Can be used.

  The light emitting layer 11b is disposed so as to be sandwiched between the first conductive type semiconductor layer 11a and the second conductive type semiconductor layer 11c. The light emitting layer 11b uses a multi-quantum well structure (MQW: Multi Quantum Well) in which a quantum well structure composed of a barrier layer having a wide forbidden band and a well layer having a narrow forbidden band is regularly stacked multiple times. Can do. As the barrier layer and the well layer, a mixed crystal composed of a nitride of indium and aluminum and having a composition ratio of indium and aluminum adjusted can be used.

  In this example, the substrate 9, the buffer layer 10, and the optical semiconductor layer 11 constituting the laminate 12 are formed from aluminum nitride. As described above, since the substrate 9, the buffer layer 10 and the optical semiconductor layer 11 are made of the same composition system material, the difference in the thermal expansion coefficients of the substrate 9, the buffer layer 10 and the optical semiconductor layer 11 can be reduced. it can. Therefore, the stress generated by the heat generated in the optical semiconductor layer 11 can be relaxed at the interfaces between the substrate 9 and the buffer layer 10 and between the buffer layer 10 and the optical semiconductor layer 11, respectively. The occurrence of peeling can be suppressed at the interface.

  A pair of electrodes for applying a voltage to the optical semiconductor layer 11 is connected to the light emitting element 8 composed of such a laminate 12. The pair of electrodes includes a first electrode that is electrically connected to the first conductivity type semiconductor layer 11a and a second electrode that is electrically connected to the second conductivity type semiconductor layer 11c.

  As a material of such a pair of electrodes, for example, a metal such as aluminum, titanium, nickel, chromium, indium, tin, molybdenum, silver, gold, tantalum, or platinum can be used.

In this example, in the buffer layer 10, the half-value width of the rocking curve on the surface 10 A side in contact with the substrate 9 is smaller than the half-value width of the rocking curve on the surface 10 B side in contact with the optical semiconductor layer 11. That is, the surface 10A side of the buffer layer 10 in contact with the substrate 9 has better crystallinity than the surface 10B side of the buffer layer 10 in contact with the optical semiconductor layer 11.

  As described above, since the buffer layer 10 is in contact with the substrate 9 on a surface having good crystallinity, the buffer layer 10 and the substrate 9 can be bonded with high adhesion. Therefore, even when heat is generated when light is emitted from the optical semiconductor layer 11, the buffer layer 10 can be prevented from peeling off the substrate 9. As a result, light can be stably emitted from the optical semiconductor layer 11 for a long period of time, and the reliability of the light emitting element 8 can be improved.

  The optical semiconductor layer 11 is made of a single crystal made of aluminum nitride, and the c-axis of the optical semiconductor layer 11 can be oriented in a direction different from the stacking direction of the stacked body 12. Since the single crystal of aluminum nitride does not easily emit light in a direction parallel to the c-axis, when the optical semiconductor layer 11 is formed of a single crystal made of aluminum nitride, the c-axis of aluminum nitride is set in the stacking direction of the stacked body 12. By making the direction different from the above, it is possible to improve the light extraction efficiency in the stacking direction of the stacked body 12.

  On the other hand, when the optical semiconductor layer 11 is composed of a single crystal made of aluminum nitride and the c-axis of the optical semiconductor layer 11 is oriented in the same direction as the stacking direction of the stacked body 12, the single crystal of aluminum nitride is c-axis. Since light is hardly transmitted in a direction parallel to the direction, light emitted from the optical semiconductor layer 11 is not easily emitted from the upper surface of the optical semiconductor layer 11. As a result, there is a possibility that the light extraction efficiency of the light emitting element 8 is likely to be lowered.

  Here, a method for measuring the half width of the rocking curve of the buffer layer 10 will be described.

  As a method for measuring the rocking curve of the buffer layer 10, an X-ray rocking curve diffraction method can be used. The X-ray rocking curve diffraction method is a method in which X-rays with low wavelength dispersion and good parallelism are incident on a measurement sample and measured. The rocking curve of the measurement sample obtained in this way takes account of crystallinity, strain, film thickness, and the like. As the X-ray rocking curve diffraction method, measurement is performed using a measurement method based on JIS K0131-1996, and the method based on JIS K0131-1996 is also used when obtaining the half width of the rocking curve obtained by the measurement. . Hereinafter, an example of the X-ray rocking curve diffraction method will be specifically described.

  As a method for measuring the rocking curve, the X-ray emitted from the X-ray source is irradiated with the measurement sample by adjusting the wavelength dispersion and the light beam width by using a crystal body or a movable slit, and diffracted by the measurement sample. The intensity of the diffracted X-rays thus detected is detected by an X-ray detector such as a scintillation counter.

  Using the method of detecting the intensity of the diffracted X-ray with the X-ray detector in this way, the measurement sample is detected by detecting the intensity of the diffracted X-ray with the X-ray detector while rotating the measurement sample by ω within a minute angle range. The rocking curve of the diffracted X-rays diffracted at can be obtained.

  As the X-ray source, a metal such as aluminum, copper, or magnesium can be used as a target material. When copper is used, a characteristic X-ray CuKα ray or the like can be used. The apparent focal spot size of the X-ray source can be 1 mm in width and 0.5 mm in height.

  As the crystal, a crystal such as silicon or germanium can be used. Further, by using a crystal body having a lattice plane spacing close to that of the measurement target of the measurement sample as reflected by the crystal body, measurement can be performed with high angular resolution. In addition, such a crystal body can be arrange | positioned in the place 650 mm away from the X-ray source.

  The size of the opening of the slit may be determined in consideration of the size of the measurement sample and the sensitive area of the X-ray detector, and the width is the same as the apparent focal size width of the X-ray source, for example, 0.5 mm to 1 mm. In addition, the height can be set to 3 mm or more and 10 mm or less, for example.

  In this example, the half-value width of the rocking curve measured from the surface 9A side of the buffer layer 10 in contact with the substrate 9 is compared with the half-value width of the rocking curve measured from the surface 9B side of the buffer layer 10 in contact with the optical semiconductor layer 11. By doing so, the magnitude of the half-value width of the rocking curve may be determined. As a method of measuring rocking curves on the surface 9A side of the buffer layer 10 in contact with the substrate 9 and the surface 9B side of the buffer layer 10 in contact with the optical semiconductor layer 11, the substrate 9 and the optical semiconductor layer 11 of the laminate 12 are respectively removed. After that, in the buffer layer 10, the X-ray rocking curve diffraction method may be performed from the surface 9A side from which the substrate 9 is removed and from the surface 9B side from which the optical semiconductor layer 11 is removed.

  The surface 9A side of the buffer layer 10 in contact with the substrate 9 shown in this example is a portion that enters the buffer layer 10 side from the interface between the substrate 9 and the buffer layer 10 to about 10 percent of the thickness of the buffer layer 10, for example. Say. Further, the surface 9B side of the buffer layer 10 in contact with the optical semiconductor layer 11 is a portion that enters the buffer layer 10 side from the interface between the optical semiconductor layer 11 and the buffer layer 10 to about 10 percent of the thickness of the buffer layer 10, for example. Say.

  Here, when X-rays are irradiated to the buffer layer 10, the X-rays have a light beam width, and the X-rays are partially diffracted in the depth direction of the buffer layer 10. The rocking curve of the diffracted X-rays depends not only on the surface of the buffer layer 10 irradiated with the X-rays but also on the crystallinity of the region where the X-rays enter the buffer layer 10. The depth at which X-rays enter the buffer layer 10 is determined by the angle at which the X-rays enter the buffer layer 10, the intensity of the X-rays, the material of the buffer layer 10, etc., but is set to, for example, 0.5 μm to 10 μm can do.

DESCRIPTION OF SYMBOLS 1 Semiconductor layer joining board | substrate 2 1st board | substrate 2A Upper surface of 1st board | substrate 3 1st semiconductor layer 3A Upper surface of 1st semiconductor layer 4 2nd board | substrate 5 2nd semiconductor layer 6 Joined body 7 Exposed surface 8 Light emitting element 9 Substrate
10 Buffer layer
10A Surface in contact with substrate
10B Surface in contact with optical semiconductor layer
11 Optical semiconductor layer
11a One conductivity type semiconductor layer
11b Light emitting layer
11c Reverse conductivity type semiconductor layer
12 Laminate

Claims (8)

A preparatory step for growing a first semiconductor layer having a thermal expansion coefficient different from that of the first substrate on the upper surface of the first substrate;
After bonding a second substrate having a thermal expansion coefficient closer to the first semiconductor layer than the first substrate to the upper surface of the first semiconductor layer, the first substrate is removed, and the second substrate and the first substrate are removed. A joined body forming step of forming a joined body in which one semiconductor layer is joined;
And a growth step of further growing a second semiconductor layer having the same composition system as the first semiconductor layer on the exposed surface of the first semiconductor layer on the side where the first substrate is removed. A method for manufacturing a layer-bonded substrate.   2. The semiconductor layer bonded substrate according to claim 1, wherein, in the bonding body forming step, the upper surface of the first semiconductor layer is polished before bonding the second substrate to the upper surface of the first semiconductor layer. Manufacturing method.   3. The method for manufacturing a semiconductor layer bonded substrate according to claim 1, wherein, in the growth step, the second semiconductor layer is grown in a state where the substrate temperature of the second substrate is set to 1100 ° C. or higher.   The said 2nd semiconductor layer is grown in the said growth process so that the sum total of the thickness of the said 1st and 2nd semiconductor layer may be 0.1 micrometer or more. Manufacturing method of semiconductor layer bonded substrate.   5. The substrate according to claim 1, wherein a substrate made of a material having the same composition as that of the first and second semiconductor layers is used as the second substrate in the bonded body formation step. Manufacturing method of semiconductor layer bonded substrate.   A light emitting device comprising a laminate in which a buffer layer and an optical semiconductor layer are sequentially laminated on a substrate, wherein the substrate, the buffer layer, and the optical semiconductor layer are made of the same composition system material, and the buffer The layer has a half-value width of the rocking curve on the surface side in contact with the substrate smaller than a half-value width of the rocking curve on the surface side in contact with the optical semiconductor layer.   The light emitting device according to claim 6, wherein the substrate, the buffer layer, and the optical semiconductor layer contain aluminum nitride.   The light-emitting element according to claim 7, wherein the optical semiconductor layer is a single crystal having a c-axis, and the c-axis of the optical semiconductor layer faces a direction different from a stacking direction of the stacked body.

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