JP3839580B2 - Manufacturing method of semiconductor substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor substrate composed of a GaN-based compound semiconductor To the law Related.
[0002]
[Prior art]
Conventionally, blue LEDs have lower brightness than red and green LEDs and have had difficulties in practical use. However, in recent years, GaN-based compound semiconductor layers made of InAlGaN-based compound semiconductors are used, and Mg is doped as a dopant. By obtaining a resistive p-type semiconductor layer, a high-intensity blue LED has been put into practical use, and further, a laser diode that has not been put into practical use but continuously oscillates at room temperature has been developed.
[0003]
FIG. 8 is a cross-sectional view of a light-emitting diode (LED) using a GaN-based compound semiconductor disclosed in the document “Japanese Journal of Applied Physics vol. 34 (1995) p.L1332-L1335”.
[0004]
The LED in FIG. 8 is sapphire (Al ₂ O _Three A low-temperature buffer layer 102 made of n-type GaN, an n-type GaN layer 103, and a non-doped In _y Ga _(1-y) Active layer 104 made of N (0 <y <1) or the like, and p-type Al _x Ga _(1-x) A barrier layer 105 made of N (0 <x <1) or the like and a cap layer 106 made of p-type GaN or the like are sequentially stacked by a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method).
[0005]
An n-side electrode 108 is formed on the n-type GaN layer 103 exposed by removing a part of the laminated semiconductor layer by etching, and a p-side electrode 107 is formed on the cap layer 106. Thus, an LED is formed.
[0006]
FIG. 9 is a perspective view of an edge-emitting laser diode (LD) as shown in the document “Japanese Journal of Applied Physics vol.35 (1996) p.L74-L76”.
[0007]
The LD of FIG. 9 is similar to the LED of FIG. ₂ O _Three A low-temperature buffer layer 121 made of n-type GaN or the like, a high-temperature buffer layer 120 made of n-type GaN, and an n-type In _y Ga _(1-y) N layer 119 and n-type Al _x Ga _(1-x) N (0 <x <1) layer 118, n-type GaN layer 117, active layer 116 made of non-doped InGaN MQW, etc., p-type Al _z Ga _(1-z) N (0 <z <1) layer 115, p-type GaN layer 114, and p-type Al _u Ga _(1-u) An N (0 <u <1) layer 113 and a cap layer 112 made of a p-type GaN layer or the like are sequentially stacked by the MOCVD method.
[0008]
Then, the laminated semiconductor layer is dry-etched into a ridge shape to form an optical waveguide and a resonator end face 124, and an n-side electrode 123 is formed on the high-temperature buffer layer 120 exposed by the etching. The p-side electrode 111 is formed on the cap layer 112, thereby forming the LD.
[0009]
In addition, conventionally, in order to improve the crystallinity of a GaN-based compound semiconductor, a method of forming a thick GaN single crystal layer without cracks by selective growth and lateral growth has been proposed (reference `` Jpn. J. Appl. Phys. "Vol.36 (1997) pp.L899-L902).
[0010]
FIG. 10 is a diagram showing a mask pattern for selective growth, and FIGS. 11A to 11E are diagrams for explaining a method for producing the mask pattern of FIG. FIGS. 11A to 11E are cross-sectional views taken along the line AA ′ of FIG.
[0011]
Referring to FIG. 11, first, a GaN thin film 152 is laminated as a nucleation layer on the sapphire substrate 151 in the step of FIG. 11A, and then 7 μm is formed on the nucleation layer 152 in the step of FIG. SiO with 1 to 4 μm wide stripe pattern at pitch ₂ A selective growth mask 153 is formed. This stripe pattern is formed along the <11-20> direction of the GaN thin film 152 (see FIG. 10). Thereafter, in the steps of FIGS. 11C, 11D, and 11E, crystal growth of the GaN film 154 without cracks is performed by selective growth and lateral growth. In this case, GaN is first selectively grown on the surface of the nucleation layer 152 where the stripe pattern is exposed, and then the {1-101} plane appears and grows laterally on the mask 153 (FIG. 11 (c)). . As the growth proceeds, adjacent striped GaN crystals 154 merge together (FIG. 11 (d)), and the grooves 156 are gradually filled, and finally a GaN single crystal layer 155 having a flat (0001) plane as an upper surface is formed. It is formed on the entire surface of the wafer (FIG. 11E). By this method, a GaN thick film without cracks can be grown on the entire wafer surface. When an LED having InGaN MQW as an active layer is fabricated thereon, the crystal defect density of the laminated structure of the LED is 10 ⁷ cm ^-2 The light output has been tripled (see “Record of the 16th Electronic Materials Symposium, Minoo, July 9-11, 1997 p.291-292).
[0012]
FIG. 12 is a perspective view of a semiconductor laser disclosed in Japanese Patent Laid-Open No. 8-316571. The semiconductor laser of FIG. ₂ O _Four A laminated structure 61 is crystal-grown on the substrate 60, and a p-side electrode 62 and an n-side electrode 63 are formed on the laminated structure 61 to form a light emitting element (laser).
[0013]
Here, the light emitting surface side of this light emitting element is MgAl ₂ O _Four The cleaved surface 602 of the substrate 60 and the cleaved surface 601 of the laminated structure 61 are formed. ₂ O _Four It is formed by cleaving the substrate 60 obliquely. That is, MgAl ₂ O _Four By using the substrate 60, the end face of the optical resonator can be formed by oblique cleavage.
[0014]
[Problems to be solved by the invention]
In this way, the technology of the low-temperature buffer layer and the technology for producing a GaN thick film by selective growth enable crystal growth of a high-quality GaN-based compound semiconductor on a heterogeneous substrate such as sapphire, thereby realizing a high-intensity LED. Also, room temperature continuous oscillation of the LD was realized.
[0015]
However, since a conventional light emitting device using a GaN-based compound semiconductor grows on different substrates having different crystal structures, the cleavage planes of the substrate and the GaN-based compound semiconductor do not necessarily coincide with each other. For this reason, it is difficult to form the end face of the laser resonator by a cleavage method like a conventional AlGaAs laser or the like.
[0016]
For example, since sapphire has a poor cleavage property, the end face of the LD resonator has been manufactured by a method such as dry etching. Therefore, the manufacturing process is complicated because it requires steps such as formation of a mask for dry etching, dry etching, and mask removal. Furthermore, since the dry etching technology for GaN-based compound semiconductors has not yet been established, the formed resonator mirror has vertical streaks and is formed into a tapered shape, such as smoothness, Parallelism and perpendicularity are still not enough. For this reason, an increase in threshold current value has occurred, and it has been difficult to obtain device characteristics that can withstand practical use.
[0017]
Further, MgAl disclosed in JP-A-8-316571 ₂ O _Four In the substrate, it is possible to form the end face of the LD resonator by cleavage, but due to the difference in the crystal structure of the substrate and the GaN-based compound semiconductor, the cleavage surface of the substrate and the GaN-based compound semiconductor does not match, resulting in oblique cleavage There was a problem in reproducibility.
[0018]
In addition, since the conventional GaN-based compound semiconductor light-emitting element is crystal-grown on an insulating substrate, it cannot take an electrode from the back surface of the substrate. For this reason, the electrodes are formed on the element surface, and cannot be mounted by die bonding by forming electrodes on the back surface of the substrate like conventional AlGaAs lasers, and the chip area is increased by the space of the electrodes. The problem that remained.
[0019]
The present invention solves various problems of the above-described conventional GaN-based compound semiconductor light-emitting elements, and is a semiconductor composed of a high-quality GaN-based compound semiconductor that is free from cracks and has reduced crystal defects and distortions. Board manufacturing method The law It is intended to provide.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a nucleation layer for selective growth is laminated on a single crystal substrate surface, and a selective growth mask is laminated on the nucleation layer, A GaN compound semiconductor layer is selectively grown through the mask pattern of the selective growth mask. On this occasion The nucleation layer for selective growth is composed of an AlN layer, and the GaN-based compound semiconductor layer is separated by selectively removing the AlN layer by etching. Semiconductor substrate It is characterized by that.
[0021]
According to a second aspect of the present invention, a selective growth mask is stacked on the surface of a single crystal substrate or a crystal layer that is a nucleation layer for selective growth stacked on the surface of a single crystal substrate. A GaN compound semiconductor layer is selectively grown through the mask pattern of the growth mask. On this occasion The GaN-based compound semiconductor layer that is selectively grown has a structure in which at least one region having a higher crystal defect density than other regions in the GaN-based compound semiconductor layer exists, and this region having a higher crystal defect density is selectively removed by etching. By separating the GaN compound semiconductor layer Semiconductor substrate It is characterized by that.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of a semiconductor substrate according to the present invention, and FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 3A to 3E are diagrams showing an example of a manufacturing process of the semiconductor substrate of FIGS.
[0025]
The semiconductor substrate of the first embodiment (semiconductor substrate of FIGS. 1 and 2) has nuclei for selective growth on the surface of the single crystal substrate 21 as shown in FIGS. A generation layer 22 is stacked, a selective growth mask 23 is stacked on the nucleation layer 22, and a GaN-based compound semiconductor layer 24 is selectively grown through the mask pattern of the selective growth mask 23. The nucleation layer 22 for growth is composed of an AlN layer, and the AlN layer is selectively removed by etching, whereby the GaN-based compound semiconductor layer 24 is separated and manufactured.
[0026]
The greatest feature of this semiconductor substrate manufacturing method is that AlN is used as the material of the nucleation layer 22. Since AlN has the same crystal structure as that of the GaN-based compound semiconductor and has a lattice constant almost similar, the crystallinity of the selectively grown GaN-based compound semiconductor is higher than that when grown on a different substrate. Furthermore, the AlN layer has a high etching rate with an alkaline solution and a high selectivity with respect to the GaN-based compound semiconductor. Therefore, the GaN-based compound semiconductor layer 24 can be easily separated with an alkaline solution. Therefore, it is possible to manufacture a high-quality GaN-based compound semiconductor substrate 24 that does not cause mechanical damage as compared with a method of scraping off the substrate crystal by a method such as polishing. In addition, by using a substrate material insoluble in an alkaline solution (for example, a substrate material such as sapphire) as the substrate 21, there is an advantage that the substrate 21 can be reused.
[0027]
As the GaN-based compound semiconductor 24, for example, the general formula is In _x Al _y Ga _(1-xy) A group III nitride represented by N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1) is used.
[0028]
Next, a manufacturing process example of the semiconductor substrate of FIGS. 1 and 2 will be described in more detail with reference to FIGS. In this manufacturing process example, an AlN layer 22 as a nucleation layer for selective growth is laminated on a (0001) surface of a φ2 inch sapphire substrate 21 at a temperature of 700 ° C. to a thickness of 0.1 μm, for example, by MOCVD. (FIG. 3 (a)). Next, a selective growth mask 23 is deposited on the AlN layer 12, and then the selective growth mask 23 is patterned to expose the surface of the AlN layer 22 in the patterning pattern portion (FIG. 3B). . In this example of the manufacturing process, the material for the selective growth mask 23 is SiO. ₂ As a selective growth mask pattern, a stripe pattern having a pitch of 7 μm and a width of 3 μm was patterned by photolithography along the <11-20> direction of the GaN-based compound semiconductor layer 24 to be selectively grown.
[0029]
Next, the n-GaN single crystal layer 24 is selectively grown from the surface of the AlN layer 22 exposed in the stripe pattern portion. That is, an n-GaN single crystal 24 is grown from the surface of the AlN layer 22 exposed in the stripe pattern portion, and the GaN-based compound semiconductor 24 is formed on the selective growth mask 23 so as to embed the selective growth mask 23. Growth is performed in the lateral direction (also in the surface direction of the selective growth mask 23), and as a result, the selective growth mask 23 is embedded, and a GaN single crystal layer 24 as shown in FIG. 3C is formed. The
[0030]
The crystal growth of the n-GaN single crystal layer 24 is performed by HVPE, and SiCl _Four As an n-type doping gas, n-type GaN crystal was grown to a thickness of 200 μm as the n-GaN single crystal layer 24 (FIG. 3C).
[0031]
In this way, after the GaN single crystal layer 24 is formed, the GaN single crystal layer 24 is separated from the sapphire substrate 21. That is, in this manufacturing process example, first, SiO aqueous solution is used with SiO aqueous solution. ₂ The mask 23 is removed by etching to form a void 25 so that the AlN etching solution can easily penetrate (FIG. 3D). Thereafter, the AlN layer 22 can be etched with a 80 ° C. aqueous KOH solution to separate the GaN single crystal layer 24 from the sapphire substrate 21 (FIG. 3E). Thus, specifically, for example, an n-GaN single crystal 24 having a diameter of 2 inches and a thickness of 200 μm is obtained.
[0032]
As described above, in the first embodiment shown in FIGS. 1 to 3, the nucleation layer 22 for selective growth is laminated on the surface of the single crystal substrate 21, and the nucleation layer 22 for selective growth is formed on the nucleation layer 22. A mask 23 is stacked, and a GaN-based compound semiconductor layer 24 is selectively grown through the mask pattern of the selective growth mask. At this time, the nucleation layer 22 for selective growth is composed of an AlN layer, and the AlN layer is formed. The GaN-based compound semiconductor layer 24 is separated and formed by selective etching, and AlN has the same crystal structure as that of the GaN-based compound semiconductor and has a lattice constant almost similar. The crystallinity of the selectively grown GaN-based compound semiconductor 24 is higher than that obtained when the GaN-based compound semiconductor is grown on a different substrate. Therefore, the crystallinity of the GaN-based compound semiconductor substrate 24 manufactured separately from the substrate becomes high quality.
[0033]
Furthermore, the AlN layer 22 has a high etching rate with an alkaline solution and a high selectivity with a GaN-based compound semiconductor. Therefore, the GaN-based compound semiconductor layer 24 can be easily separated with an alkaline solution. Therefore, it is possible to produce a high-quality GaN-based compound semiconductor substrate that does not cause mechanical damage as compared with a method in which the substrate crystal is scraped off by a method such as polishing. In addition, by using a substrate material insoluble in an alkaline solution (for example, a substrate material such as sapphire) as the substrate 21, there is an advantage that the substrate 21 can be reused. Therefore, the GaN-based compound semiconductor substrate 24 manufactured in this way is inexpensive.
[0034]
Furthermore, even when a thick GaN compound semiconductor is grown on the GaN compound semiconductor single crystal substrate 24, a crack that is generated due to thermal strain due to a difference in thermal expansion coefficient does not occur, and a substrate capable of high quality crystal growth is obtained. Furthermore, the substrate can be cleaved.
[0035]
FIG. 4 is a perspective view showing a second embodiment of the semiconductor substrate according to the present invention, and FIG. 5 is a cross-sectional view taken along the line AA ′ of FIG. FIGS. 6A to 6F are diagrams showing examples of manufacturing steps of the semiconductor substrate of FIGS. As shown in FIGS. 6A to 6F, the semiconductor substrate of the second embodiment (semiconductor substrate of FIGS. 4 and 5) has a selective growth mask 42 on the surface of the single crystal substrate 41. The GaN-based compound semiconductor layer is selectively grown through the mask pattern of the selective growth mask 42. At this time, the GaN-based compound semiconductor layer to be selectively grown has a crystal defect higher than other regions in the GaN-based compound semiconductor layer. A structure having at least one high-density region exists, and the region having a high crystal defect density is selectively removed by etching, whereby the GaN-based compound semiconductor layer is separated and manufactured.
[0036]
The greatest feature of this semiconductor substrate manufacturing method is that the GaN-based compound semiconductor layer that is selectively grown has a structure in which at least one region having a crystal defect density higher than other regions in the GaN-based compound semiconductor layer exists. It is. In the example of FIGS. 6A to 6F, the other region in the GaN-based compound semiconductor layer is indicated by reference numeral 45, and the region having a high crystal defect density is indicated by reference numeral 44.
[0037]
The etching rate by the alkaline solution is greatly affected by the crystallinity of the GaN-based compound semiconductor layer. That is, the etching rate of the region 44 with a high crystal defect density is high, and the region 45 with a low crystal defect density and good crystallinity has a low etching rate and is hardly etched. Therefore, the portion 45 of the GaN-based compound semiconductor layer having good crystallinity can be easily separated by selectively etching away the region 44 having a high crystal defect density. Therefore, a high-quality GaN-based compound semiconductor substrate free from mechanical damage is produced as compared with a method of scraping off the substrate crystal by a method such as polishing. Further, by using a substrate material insoluble in an alkaline solution (for example, a substrate material such as sapphire) as the substrate 41, the substrate 41 can be reused.
[0038]
As the GaN compound semiconductors 44 and 45, for example, the general formula is In. _x Al _y Ga _(1-xy) A group III nitride represented by N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1) is used.
[0039]
Next, an example of a manufacturing process of the semiconductor substrate of FIGS. 4 and 5 will be described in more detail with reference to FIGS. In this manufacturing process example, a selective growth mask 42 is deposited on the (0001) plane of a φ2 inch sapphire substrate 41, and then the selective growth mask 42 is patterned. The surface of is exposed (FIG. 6A). In this manufacturing process example, the material of the selective growth mask 42 is SiO. ₂ As a selective growth mask pattern, a stripe pattern having a pitch of 7 μm and a width of 3 μm was patterned along the <11-20> direction of the sapphire substrate 41 by photolithography.
[0040]
Next, a GaN layer 43 was selectively grown on the surface of the sapphire substrate 41 exposed in the stripe pattern portion by a MOCVD method at a temperature of 500 ° C. to a thickness of 0.05 μm. That is, the GaN layer 43 was grown in the stripe pattern (FIG. 6B).
[0041]
Further, GaN 44 having a high crystal defect density at 900 ° C. was selectively grown by MOCVD until the {1-101} plane appeared (FIG. 6C).
[0042]
Then, SiClCl is used by HVPE method. _Four Was used as an n-type doping gas to grow a crystal of n-GaN 45 having a low crystal defect density to a film thickness of 200 μm (FIG. 6D).
[0043]
In this way, after the GaN layers 44 and 45 are formed, the GaN single crystal layer 45 is separated from the sapphire substrate 41. That is, in this manufacturing process example, first, SiO aqueous solution is used with SiO aqueous solution. ₂ The mask 42 is removed by etching to form a void 46 so that the GaN etchant can easily penetrate (FIG. 6E). Thereafter, the GaN single crystal layer 45 can be separated from the sapphire substrate 41 by etching the high crystal defect density region, that is, the GaN 44 with an aqueous KOH solution (FIG. 6 (f)).
[0044]
As described above, in the second embodiment shown in FIGS. 4 to 6, when forming the GaN layers 44 and 45, the defect density can be controlled only by changing the growth conditions. In addition, contamination of the reaction tube can be prevented. That is, the produced GaN-based compound semiconductor substrate can be produced without reducing its purity. In addition, the GaN-based compound semiconductor layer 45 with good crystallinity can be easily separated by selectively removing the region 44 with a high crystal defect density. Therefore, it is possible to produce a high-quality GaN-based compound semiconductor substrate that does not cause mechanical damage as compared with a method in which the substrate crystal is scraped off by a method such as polishing. Moreover, there is an advantage that the substrate 41 can be reused by using a substrate material insoluble in an alkaline solution (for example, a substrate material such as sapphire) as the substrate 41. Therefore, the GaN-based compound semiconductor substrate 45 manufactured in this way is inexpensive.
[0045]
Furthermore, even when a thick GaN-based compound semiconductor is grown on the GaN-based compound semiconductor single crystal substrate 45, a crack that is generated due to thermal strain due to a difference in thermal expansion coefficient does not occur, and the substrate can be grown with good quality. Furthermore, the substrate can be cleaved.
[0046]
6A to 6F, the selective growth mask 42 is directly deposited on the single crystal substrate 41, and then the selective growth mask 42 is patterned. The GaN layer 43 is grown on the surface of the sapphire substrate 41 exposed at the stripe pattern portion, and the nucleation layer (eg, AlN) for selective growth is grown on the single crystal substrate 41. Layer), a selective growth mask 42 is deposited on the nucleation layer, and then the selective growth mask 42 is patterned, and the surface of the nucleation layer is exposed at a portion of the patterning pattern to form a stripe pattern. It is also possible to grow the GaN layer 43 on the surface of the nucleation layer exposed in this part.
[0047]
In each of the above-described examples (examples of FIGS. 1 to 3 and examples of FIGS. 4 to 6), impurities of a predetermined conductivity type (n-type or p-type impurities) are added to the GaN-based compound semiconductor crystals 24 and 45. Doping is also possible, and by doping the GaN-based compound semiconductor crystals 24 and 45 with impurities of a predetermined conductivity type, the conductivity type, that is, the electrical characteristics can be controlled, and GaN having desired electrical characteristics It can be set as a system compound semiconductor crystal.
[0048]
That is, since the GaN-based compound semiconductor is a semiconductor, it is possible to control the electrical characteristics such as its conductivity type and electrical resistance by doping control of impurities, and the GaN-based compound semiconductor crystals 24 and 45 have a predetermined conductivity. A substrate having desired electrical characteristics can be formed by doping a type impurity.
[0049]
In each of the above-described examples (examples of FIGS. 1 to 3 and examples of FIGS. 4 to 6), the GaN-based compound semiconductor crystals 24 and 45 are stacked on the entire surface of the substrate during the manufacturing process. GaN compound semiconductor crystals 24 and 45 may be stacked.
[0050]
FIG. 7 is a perspective view showing a configuration example of a semiconductor light emitting device according to the present invention. 7 includes, for example, a GaN-based compound semiconductor multilayer structure including at least one pn junction formed on the semiconductor substrate 24 of FIGS. 1 and 2 or the semiconductor substrate 45 of FIGS. The light emitting device is made of
[0051]
More specifically, the semiconductor light emitting device includes an n-GaN layer 52, an n-AlGaN cladding layer 53, an AlGaN / InGaN quantum well structure active layer 54, and a p-AlGaN cladding on an n-GaN single crystal substrate 24 or 45. The layer 55 and the p-GaN cap layer 56 are sequentially stacked. On the p-GaN cap layer 56 having this stacked structure, SiO 2 is stacked. ₂ An insulating layer 57 is formed, and the insulating layer 57 has a structure in which a stripe-shaped hole having a width of 5 μm reaching the surface of the p-GaN cap layer 56 is formed.
[0052]
In the semiconductor light emitting device of FIG. 7, a p-side ohmic electrode 58 is deposited on the insulating layer 57, and the p-side ohmic electrode 58 is in contact with the exposed p-GaN cap layer 56, so that the ohmic electrode is used. Forming. An n-side ohmic electrode 59 is formed on the back surface of the n-GaN single crystal substrate 24 or 45.
[0053]
Further, the light emitting end faces 500 and 501 of this semiconductor light emitting element are formed perpendicular to the substrate 24 or 45 by cleavage, and the light emitting end faces 500 and 501 are formed in parallel to each other.
[0054]
In the semiconductor light emitting device of FIG. 7, the n-GaN layer 52, the n-AlGaN cladding layer 53, the AlGaN / InGaN quantum well structure active layer 54, the p-AlGaN cladding layer 55, and the p-GaN cap layer 56 are formed by MOCVD. Crystal growth is possible.
[0055]
The p-side ohmic electrode 58 can be formed by vacuum-depositing Au / Ni and heat treatment. The n-side ohmic electrode 59 can be formed by vacuum deposition of Al / Ti and heat treatment.
[0056]
In the semiconductor light emitting device having such a configuration, current is applied to electrodes corresponding to the p-type and n-type layers of the light-emitting device, and current is injected into the pn junction, whereby carriers are recombined. It emits light.
[0057]
That is, in this semiconductor light emitting device, when a current is applied to the p-side ohmic electrode 58 and the n-side ohmic electrode 59, a current is injected into the AlGaN / InGaN MQW active layer 54, and light is emitted by recombination of carriers in the active layer 54. Reflection amplification is repeated by the resonator formed by the light emitting end surfaces 500 and 501, and the laser light is output to the outside as the laser beams 5000 and 5001.
[0058]
Note that the GaN-based compound semiconductor multilayer structure that constitutes the light emitting element has at least one pn junction, and a current is injected into the pn junction and light is emitted by recombination of carriers. A homojunction, a single heterojunction, a double heterojunction, a quantum well structure, a multiple quantum well structure, or any other structure may be used.
[0059]
In this semiconductor light-emitting device, the main surface of the substrate comprising a GaN-based compound semiconductor laminated structure formed on the GaN-based compound semiconductor substrate of FIGS. 1 and 2 or the GaN-based compound semiconductor substrate of FIGS. Is a light emitting element having a cleavage plane perpendicular to the light emitting end face, and since the light emitting element part is formed on the same type of substrate having better crystal quality than the conventional, the crystallinity of the laminated structure constituting the light emitting element is Defects due to lattice mismatch between the substrate material and the GaN-based compound semiconductor multilayer structure, defects such as thermal distortion and cracks due to differences in thermal expansion coefficient, that is, defects that adversely affect the light emission characteristics and lifetime, are reduced in quality, Therefore, a light-emitting element with favorable light emission characteristics and a long lifetime can be provided.
[0060]
In addition, since the light exit surface is perpendicular to the main surface of the substrate and is a cleaved surface that is smooth in the atomic order, there is no unevenness like the light exit end surface formed by conventional dry etching, so the scattering loss at the light exit end surface No light emission characteristics are obtained. In the case of a laser element, the light emitting surfaces are parallel to each other and are smooth resonant mirror end faces. Therefore, compared with a laser element having a light emitting end face formed by conventional dry etching as a resonator mirror end face. It is possible to produce a laser device having a good performance with a low threshold current density and a high external differential efficiency.
[0061]
Furthermore, since a GaN-based compound semiconductor single crystal substrate is used as the substrate, it is possible to make the substrate n-type or p-type conductive. In this case, an electrode can be formed on the back surface of the substrate. In addition to mounting by conventional die bonding, the chip area can be reduced by the amount of electrode space.
[0062]
【The invention's effect】
As described above, according to the first aspect of the invention, the nucleation layer for selective growth is laminated on the surface of the single crystal substrate, and the selective growth mask is laminated on the nucleation layer. In the semiconductor substrate formed by selectively growing a GaN-based compound semiconductor layer through the mask pattern of the selective growth mask, a nucleation layer for selective growth is composed of an AlN layer, and this AlN layer is selectively etched. The semiconductor substrate is manufactured by separating the GaN-based compound semiconductor layer by removing the AlN, and since the crystal structure is the same as that of the GaN-based compound semiconductor and the lattice constant is almost similar, AlN is selectively grown. The crystallinity of the GaN-based compound semiconductor is higher than that when the GaN-based compound semiconductor is grown on a different substrate. Therefore, the crystallinity of the GaN-based compound semiconductor substrate manufactured separately from the substrate can be made high quality.
[0063]
Furthermore, since the AlN layer has a high etching rate with an alkaline solution and a large selection ratio with the GaN-based compound semiconductor, the GaN-based compound semiconductor layer can be easily separated with an alkaline solution. Compared with the method of scraping off the substrate crystal, it is possible to produce a high-quality GaN-based compound semiconductor substrate that does not cause mechanical damage.
[0064]
Furthermore, even if a thick GaN-based compound semiconductor is grown on this GaN-based compound semiconductor single crystal substrate, cracks caused by thermal strain due to the difference in thermal expansion coefficient do not occur, and the substrate can be grown with good quality crystal. Furthermore, the substrate can be cleaved.
[0065]
According to the invention of claim 2, the selective growth mask is laminated on the surface of the single crystal substrate or on the crystal layer that is a nucleation layer of selective growth laminated on the surface of the single crystal substrate, In a semiconductor substrate formed by selectively growing a GaN-based compound semiconductor layer through the mask pattern of the selective growth mask, the GaN-based compound semiconductor layer to be selectively grown has a crystal defect density higher than other regions in the GaN-based compound semiconductor layer. The structure is such that there is at least one high region, and the region having a high crystal defect density is selectively removed by etching to separate the GaN-based compound semiconductor layer to produce a semiconductor substrate. Since the defect density can be controlled only by changing the growth conditions, it is possible to prevent contamination of the reaction tube without the need to grow different materials. That is, the produced GaN-based compound semiconductor substrate can be produced without reducing its purity. In addition, by selectively etching away a region having a high crystal defect density, a GaN-based compound semiconductor layer with good crystallinity can be easily separated. Therefore, a method of scraping a substrate crystal by a method such as polishing. Compared to the above, it is possible to manufacture a high-quality GaN-based compound semiconductor substrate that does not cause mechanical damage.
[0066]
Furthermore, even if a thick GaN-based compound semiconductor is grown on this GaN-based compound semiconductor single crystal substrate, cracks caused by thermal strain due to the difference in thermal expansion coefficient do not occur, and the substrate can be grown with good quality crystal. Furthermore, the substrate can be cleaved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of a semiconductor substrate according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.
FIG. 3 is a diagram showing an example of a manufacturing process of the substrate of FIGS. 1 and 2;
FIG. 4 is a plan view showing a second embodiment of a semiconductor substrate according to the present invention.
5 is a cross-sectional view taken along line AA ′ of FIG.
6 is a diagram showing an example of a manufacturing process of the substrate of FIGS. 4 and 5. FIG.
FIG. 7 is a perspective view showing a configuration example of a semiconductor light emitting element according to the present invention.
FIG. 8 is a cross-sectional view of a conventional LED using a GaN-based compound semiconductor.
FIG. 9 is a perspective view of a conventional edge-emitting laser diode.
FIG. 10 is a diagram showing a mask pattern for selective growth.
11 is a diagram for explaining a method for producing the mask pattern of FIG. 10;
FIG. 12 is a perspective view of a conventional semiconductor laser.
[Explanation of symbols]
21, 41 Single crystal substrate (sapphire substrate)
22 Nucleation layer
23, 42 Mask for selective growth
24 GaN compound semiconductor layer (GaN single crystal layer)
44 GaN with high crystal defect density
45 GaN with low crystal defect density
52 n-GaN layer
53 n-AlGaN cladding layer
54 AlGaN / InGaN quantum well structure active layer
55 p-AlGaN cladding layer
56 p-GaN cap layer
58 p-side ohmic electrode
59 n-side ohmic electrode

Claims (2)

  A nucleation layer for selective growth is laminated on the surface of the single crystal substrate, a selective growth mask is laminated on the nucleation layer, and a GaN-based compound semiconductor layer is formed through the mask pattern of the selective growth mask. At this time, a nucleation layer for selective growth is composed of an AlN layer, and this AlN layer is selectively etched away to separate the GaN-based compound semiconductor layer and separate it from the semiconductor substrate. A method for manufacturing a semiconductor substrate, comprising:   A selective growth mask is stacked on the surface of the single crystal substrate or a crystal layer that is a nucleation layer for selective growth stacked on the surface of the single crystal substrate, and through the mask pattern of the selective growth mask, GaN-based The compound semiconductor layer is formed by selective growth. At this time, the GaN-based compound semiconductor layer to be selectively grown has a structure in which at least one region having a crystal defect density higher than other regions in the GaN-based compound semiconductor layer exists. A method of manufacturing a semiconductor substrate, wherein the GaN-based compound semiconductor layer is separated into a semiconductor substrate by selectively etching away a region having a high crystal defect density.

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