JP4899266B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device. To the law In particular, a method for manufacturing a semiconductor device composed of a nitride-based compound semiconductor To the law In this method, the underlying growth layer can be separated together with the growth substrate, and the electrode can be efficiently formed from the back surface on the lower conductive layer. To the law Related.
[0002]
[Prior art]
Conventionally, a semiconductor growth layer stacked on a sapphire substrate is peeled from the sapphire substrate by etching. However, when the semiconductor growth layer is peeled off from the sapphire substrate by etching, there are problems such as slow etching rate and corrosion of the semiconductor growth layer due to etching.
[0003]
In the nitride compound semiconductor growth layer, it is difficult to peel off the sapphire substrate by performing wet etching, and it is peeled off from the sapphire substrate by performing dry etching such as reactive ion etching. However, since reactive gas etching uses a toxic gas, the semiconductor growth layer is greatly corroded by dry etching.
[0004]
Considering the problem of peeling the semiconductor growth layer from the growth substrate by performing such etching, the semiconductor growth is performed by irradiating laser light from the back side of the growth substrate to cause ablation at the interface between the semiconductor growth layer and the growth substrate. A method of peeling the layers was developed.
[0005]
In the case of a nitride-based compound semiconductor growth layer, the semiconductor growth layer formed on the sapphire substrate is irradiated with laser light from the back side of the sapphire substrate, and the laser light is absorbed and ablated in the undoped layer and buffer layer of the semiconductor growth layer. As a result, the semiconductor growth layer is separated from the sapphire substrate together with the undoped layer and the buffer layer. Thereafter, the undoped layer and the buffer layer are etched to form electrodes on the back surface of the element.
[0006]
[Problems to be solved by the invention]
However, since the undoped layer and buffer layer on the back side of the semiconductor growth layer peeled off from the sapphire substrate are polycrystalline or amorphous, they have high resistance and are not suitable for forming electrodes. In this case, the back surface is etched to remove the undoped layer and the buffer layer, which is not efficient.
[0007]
Further, when an electrode is formed on the back surface of the semiconductor element, the manufacturing process for forming the semiconductor element is increased together with the step of etching the back surface, and the production cost of the semiconductor element is increased. In addition, as the production cost of semiconductor elements rises, the production cost of image display devices mounted with semiconductor elements also rises.
[0008]
Therefore, a method for manufacturing the semiconductor device of the present invention Law is , A method for manufacturing a semiconductor device, in which the underlying growth layer can be separated from the growth substrate, and an electrode can be efficiently formed on the lower conductive layer from the back surface The law The purpose is to provide.
[0009]
[Means for Solving the Problems]
The method of manufacturing a semiconductor device according to the present invention includes a step of forming a base growth layer on a substrate, a step of forming a lower conductive layer having a band gap energy smaller than the base growth layer on the base growth layer, and a lower conductive layer. Forming a growth inhibiting film thereon, removing a part of the growth inhibiting film to form an opening, and laminating a semiconductor layer on a lower conductive layer exposed from the opening; A step of forming a protective film on the semiconductor layer, and a lower conductive layer and a semiconductor layer formed on the substrate. By etching A step of forming an element isolation groove that separates into regions for each element, a step of removing a protective film formed on the semiconductor layer, and an interface between the base growth layer and the lower conductive layer by irradiating the substrate with light Cause ablation Separating the lower conductive layer and the semiconductor layer from the substrate.
[0010]
The semiconductor layer formed on the substrate is irradiated with light from the back side of the substrate and separated from the substrate, but the lower conductive layer is formed using a semiconductor whose band gap energy is smaller than that of the underlying growth layer. When the laser beam having the energy value is irradiated from the back side of the growth substrate, ablation can be caused at the lower conductive layer side interface between the underlying growth layer and the lower conductive layer. Therefore, the base growth layer and the buffer layer can be easily separated together with the growth substrate from the semiconductor layer at the interface between the base growth layer and the lower conductive layer.
[0011]
Further, when the semiconductor layer is separated from the substrate by irradiating with laser light after forming an element isolation trench that separates into regions for each element having a depth reaching the underlying growth layer, the semiconductor layer is separated from the substrate and a plurality of A semiconductor element can be formed, and an electrode can be efficiently formed on the separated lower conductive layer from the back side.
[0012]
In addition, since the substrate can be easily separated together with the base growth layer and can be efficiently separated into a plurality of elements, the production cost of the semiconductor element can be reduced.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
[ Reference example ]
A base growth layer is formed on a growth substrate, a lower conductive layer, a first conductive layer, an active layer, and a second conductive layer are stacked to form a semiconductor growth layer, and an element isolation groove that reaches the base growth layer is a semiconductor. A planar type semiconductor light-emitting element formed after being formed in the growth layer and separated at the interface between the base growth layer and the lower conductive layer will be described.
[0019]
As shown in FIG. 1A, a base growth layer 12 is formed on a growth substrate 11. In general, the growth substrate 11 is not particularly limited as long as it can form a wurtzite type compound semiconductor layer next, and various types can be used. For example, as the growth substrate 11, gallium nitride ( A sapphire substrate having a C-plane as a main surface, which is often used for growing GaN-based compound semiconductor materials, can be used. Reference example The growth substrate 11 is made of a light-transmitting substrate such as a sapphire substrate because laser light is irradiated from the back side when the growth substrate 11 described later is separated.
[0020]
As the underlying growth layer 12 formed on the main surface of the growth substrate 11, various types can be generally used. As the underlying growth layer 12, for example, a group III compound semiconductor can be used, and a gallium nitride (GaN) compound semiconductor, an aluminum nitride (AlN) compound semiconductor, an indium nitride (InN) compound semiconductor, and indium gallium nitride. There are (InGaN) -based compound semiconductors, aluminum gallium nitride (AlGaN) -based compound semiconductors, and the like.
[0021]
As a method for growing the underlying growth layer 12, various vapor phase growth methods can be exemplified. For example, it can be grown using a vapor phase growth method such as an organometallic compound vapor phase growth method (MOVPD (MOVPE) method) or a molecular beam epitaxy method (MBE method), or a hydride vapor phase growth method (HVPE method). . In particular, when the MOVPE method is used, a crystal with good crystallinity can be obtained quickly. Although omitted in FIG. 1A, a required buffer layer may be formed on the bottom side of the underlying growth layer 12.
[0022]
As shown in FIG. 1B, an n-side contact layer 13 which is a lower conductive layer is formed on the underlying growth layer 12, and the first conductive layer 14, the active layer 15, the second conductive layer 16 and the p-side in this order. The contact layer 17 is laminated to form a semiconductor growth layer. At this time, the n-side contact layer 13 stacked on the base growth layer 12 is formed using a semiconductor having a smaller band gap energy than the base growth layer 12. The n-side contact layer 13 is a wurtzite type compound semiconductor layer, like the underlying growth layer 12. Reference example For example, AlGaN can be used for the base growth layer 12 and GaN can be used for the n-side contact layer 13 as a semiconductor having a bandgap energy smaller than that of the base growth layer 12.
[0023]
In general, the first conductive layer 14 is a wurtzite type compound semiconductor layer, similar to the underlying growth layer 12, and is formed of a material such as silicon-doped GaN, for example. The first conductive layer 14 functions as an n-type cladding layer, and the active layer 15 is a layer for generating light of the semiconductor light emitting element, and is laminated on the first conductive layer 14 and is suitable for emitting light. It has a film thickness. The p-side contact layer 17 and the second conductive layer 16 are wurtzite type compound semiconductor layers, and are formed of a material such as magnesium-doped GaN, for example. The second conductive layer 16 functions as a p-type cladding layer. The active layer 15 can also be composed of a single bulk active layer. However, the active layer 15 may have a quantum structure such as a single quantum well (SQW) structure, a double quantum well (DQW) structure, or a multiple quantum well (MQW) structure. A well structure may be formed. In the quantum well structure, a barrier layer is used in combination for separating the quantum well as necessary.
[0024]
FIG. 1C shows a process of forming the element isolation trench 18 in the semiconductor growth layer stacked on the growth substrate 11. The element isolation groove 18 is formed by performing a process such as reactive ion etching, and the semiconductor growth layer is separated into regions for each element. Since the depth of the element isolation trench 18 reaches the underlying growth layer 12, as will be described later, laser light is irradiated from the back side of the growth substrate 11 to separate the growth substrate 11 and the underlying growth layer 12 at the same time. The semiconductor growth layer can be efficiently separated into a plurality of semiconductor light emitting devices.
[0025]
FIG. 2D is a diagram showing a process of separating the growth substrate 11 by irradiating laser light from the back side on the growth substrate 11. As shown in FIG. 2D, the n-side contact layer 13 stacked on the underlying growth layer 12 as described above is formed using a semiconductor having a band gap energy smaller than that of the underlying growth layer 12, so that growth is possible. When laser light having an energy value between these band gap energies is used as laser light irradiated from the back side of the substrate 11, the laser light is not absorbed by the underlying growth layer 12 but is absorbed by the n-side contact layer 13. . Ablation occurs at the n-side contact layer 13 side interface between the base growth layer 12 and the n-side contact layer 13 that have absorbed the laser light, and the growth substrate 11 can be separated together with the base growth layer 12 at this interface. Examples of the laser light irradiated at this time include laser light such as excimer laser and harmonic YAG laser which are ultraviolet rays.
[0026]
For example, when AlGaN (Al composition is about 15%) is used for the underlying growth layer 12 and GaN is used for the n-side contact layer 13 and a third harmonic YAG laser (355 nm) is irradiated from the back side of the growth substrate, the band gap of AlGaN Since the energy is 3.8 eV, the band gap energy of GaN is 3.2 eV, and the energy of the laser light of the triple harmonic YAG laser light is 3.5 eV, the laser light is not absorbed by the underlying growth layer 12 and n It is absorbed in the side contact layer 13. GaN is decomposed into metallic Ga and nitrogen at the n-side contact layer 13 side interface between the n-side contact layer 13 and the underlying growth layer 12 that has absorbed the laser beam, and the growth substrate 11 and the underlying growth layer 12 are easily separated. be able to.
[0027]
As described above, when the band gap energy of the n-side contact layer 13 is smaller than the band gap energy of the underlying growth layer 12 and laser light having an energy value between them is irradiated, the laser light is absorbed in the underlying growth layer 12. Instead, it reaches the n-side contact layer 13 and is absorbed in the n-side contact layer 13. Laser light is absorbed by the n-side contact layer 13 and ablation occurs at the interface on the n-side contact layer 13 side, so that the growth substrate 11 can be easily separated together with the underlying growth layer 12.
[0028]
FIG. 2E is a diagram showing a process of forming the p-side electrode 19 and the n-side electrode 20 on the first conductive layer, the active layer, and the second conductive layer separated from the growth substrate 11. The p-side electrode 19 is formed on the p-side contact layer 17 by vapor deposition or the like, and has, for example, a Ti / Pt / Au electrode structure or a Ni (Pd) / Pt / Au electrode structure. The n-side electrode 20 has, for example, an AuGe / Ni / Au electrode structure, and is formed on the n-side contact layer 13 by vapor deposition or the like.
[0029]
Further, as described above, the n-side contact layer 13 stacked on the base growth layer 12 is formed using a semiconductor having a band gap energy smaller than that of the base growth layer 12, and an energy value is set between these band gap energies. When the growth substrate 11 and the underlying growth layer 12 are separated using the laser light that is included, and then cleaved and separated into a plurality of semiconductor light emitting elements, a cleavage plane that becomes the resonant end face of the semiconductor laser can be formed.
[0030]
As described above, when the band gap energy of the n-side contact layer 13 is smaller than the band gap energy of the underlying growth layer 12 and laser light having an energy value between them is irradiated, Ablation can occur at the interface on the n-side contact layer 13 side with the n-side contact layer 13, the semiconductor growth layer can be easily separated from the growth substrate 11 and the underlying growth layer 12, and is suitable for electrode formation. The n-side contact layer 13 that is the side conductive layer can be exposed.
[0031]
Further, when the semiconductor isolation layer is separated from the growth substrate 11 and the underlying growth layer 12 by laser light irradiation after the element isolation trench 18 is formed to a depth reaching the underlying growth layer 12, the growth substrate 11 is separated together with the underlying growth layer 12. At the same time, the semiconductor growth layer can be efficiently separated for each of the plurality of semiconductor light emitting elements, and the n-side electrode can be efficiently formed on the back surface of the n-side contact layer 13 separated into the plurality of semiconductor light emitting elements. it can.
[0032]
[ first Embodiment]
A base growth layer is formed on the growth substrate, a lower conductive layer is formed on the base growth layer, and a first conductive layer, an active layer, and a second conductive layer are stacked on the lower conductive layer by selective growth. A semiconductor light-emitting element formed after a hexagonal pyramid-shaped semiconductor growth layer having a substantially triangular cross section and separated at the interface between the base growth layer and the lower conductive layer will be described.
[0033]
As shown in FIG. 3A, a base growth layer 32 and a lower conductive layer 33 are sequentially stacked on a growth substrate 31. The growth substrate 31 is not particularly limited as long as it can form a wurtzite type compound semiconductor layer next, and various substrates can be used. For example, as the growth substrate 31, a sapphire substrate having a C-plane as a main surface, which is often used when a gallium nitride (GaN) -based compound semiconductor material is grown, can be used. In this case, the C plane as the main surface of the substrate includes a plane orientation inclined within a range of 5 to 6 degrees. here, first In this embodiment, the growth substrate 31 is a substrate having light transmissivity, such as a sapphire substrate, because laser light is irradiated from the back side when the growth substrate 31 described later is separated.
[0034]
As the underlying growth layer 32 and the lower conductive layer 33 formed on the main surface of the growth substrate 31, a wurtzite type compound semiconductor can be used because a hexagonal pyramid pyramid structure is formed in a later step. . For example, a group III compound semiconductor can be used, and further, a gallium nitride (GaN) compound semiconductor, an aluminum nitride (AlN) compound semiconductor, an indium nitride (InN) compound semiconductor, an indium gallium nitride (InGaN) compound A semiconductor, an aluminum gallium nitride (AlGaN) based compound semiconductor, or the like.
[0035]
As a method for growing the underlying growth layer 32 and the lower conductive layer 33, various vapor phase growth methods can be exemplified. For example, it can be grown using a vapor phase growth method such as an organic metal compound vapor phase growth method (MOCVD (MOVPE) method) or a molecular beam epitaxy method (MBE method), or a hydride vapor phase growth method (HVPE method). . In particular, when the MOVPE method is used, a crystal with good crystallinity can be obtained quickly. Although omitted in FIG. 3, a required buffer layer may be formed on the bottom side of the underlying growth layer 32.
[0036]
Since the underlying growth layer 32 generally functions as a conductive layer for forming an n-side electrode, the whole is doped with an impurity such as silicon. first In this embodiment, as described later, when the growth substrate 31 is separated by ablation by irradiating laser light from the back side of the growth substrate 31, a part of the underlying growth layer 32 is separated together with the growth substrate. Therefore, the portion of the layer separated together with the growth substrate 31 may not be doped with impurities.
[0037]
The lower conductive layer 33 stacked on the underlying growth layer 32 is doped with an impurity such as silicon to form an n-side electrode, and is formed using a semiconductor having a lower band gap energy than the underlying growth layer 32. For example, as a semiconductor having a band gap energy smaller than that of the base growth layer 32, AlGaN can be used for the base growth layer 32 and GaN can be used for the lower conductive layer 33.
[0038]
As shown in FIG. 3B, a growth inhibition film 34 made of a silicon oxide film, a silicon nitride film, or the like is formed on the entire surface of the base growth layer 32 in which the base growth layer 32 and the lower conductive layer 33 are sequentially stacked. This growth inhibition film 34 is a film used as a mask layer, and is formed on the surface of the underlying growth layer 32 by sputtering or other methods.
[0039]
As shown in FIG. 3C, after the growth inhibition film 34 is formed on the entire surface, a part of the growth inhibition film 34 functioning as a mask is removed to form an opening 34a. In general, the shape of the opening 34a for selective growth is not particularly limited as long as it can be formed into a facet structure having an inclined surface inclined with respect to the main surface of the substrate. As an example, a polygonal shape such as a stripe shape, a rectangular shape, a circular shape, an elliptical shape, a triangular shape, or a hexagonal shape is used. The surface of the lower conductive layer 33 below the growth inhibiting film 34 is exposed reflecting the shape of the opening 34a. first In the embodiment, there are a circular shape, a hexagonal shape, and the like as a shape capable of selectively growing the first conductive layer, the active layer, and the second conductive layer in a hexagonal pyramid shape having a substantially triangular cross section.
[0040]
After the opening 34a having such a predetermined shape is formed, as shown in FIG. 4D, the first conductive layer 35, the active layer 36, and the second conductive layer 37 are stacked by selective growth.
[0041]
The first conductive layer 35 is a wurtzite type compound semiconductor layer, similar to the underlying growth layer 32, and is made of a material such as silicon-doped GaN. The first conductive layer 35 functions as an n-type cladding layer. For example, when the growth substrate 31 is a sapphire substrate and the main surface is a C plane, the first conductive layer 35 can be formed in a hexagonal pyramid shape having a substantially triangular cross section by selective growth.
[0042]
The active layer 36 is a layer for generating light of the semiconductor light emitting device, and is composed of, for example, an InGaN layer or a layer having an InGaN layer sandwiched between AlGaN layers. The active layer 36 extends along the facet formed of the inclined surface of the first conductive layer 35 and has a thickness suitable for emitting light. The active layer 36 may be composed of a single bulk active layer. However, the active layer 36 may have a quantum structure such as a single quantum well (SQW) structure, a double quantum well (DQW) structure, or a multiple quantum well (MQW) structure. A well structure may be formed. In the quantum well structure, a barrier layer is used in combination for separating the quantum well as necessary.
[0043]
The second conductive layer 37 is a wurtzite type compound semiconductor layer, and is made of a material such as magnesium-doped GaN, for example. The second conductive layer 37 functions as a p-type cladding layer. The second conductive layer 37 also extends along the facet formed by the inclined surface of the first conductive layer 35. The hexagonal pyramid-shaped inclined surface formed by selective growth is a surface selected from, for example, an S surface, a {11-22} surface, and a surface substantially equivalent to each of these surfaces.
[0044]
4E and 4F show a process of forming the element isolation trench 39. FIG. As shown in FIG. 4E, in order to prevent the second conductive layer 37 formed on the outermost part from being eroded by the etching for forming the element isolation trench 39, the second conductive layer 37 and the growth inhibiting film 34 are used. The entire surface of the lower conductive layer 33 on which is formed is covered with a protective film 38. The protective film 38 is, for example, a silicon oxide film formed by a plasma CVD method or the like. After such a protective film 38 is formed, as shown in FIG. 4F, a process such as reactive ion etching is performed to form an element isolation groove 39, which is separated into regions for each element.
[0045]
The depth of the element isolation trench 39 is a depth reaching the underlying growth layer 32. As will be described later, when the growth substrate 31 is separated by irradiating laser light from the back side of the growth substrate 31, ablation occurs at the lower conductive layer 33 side interface between the base growth layer 32 and the lower conductive layer 33, The growth substrate 31 can be separated together with the underlying growth layer 32. At this time, by forming the element isolation trench 39 to a depth reaching the underlying growth layer 32, the growth substrate 31 and the underlying growth layer 32 can be separated and simultaneously separated into regions for each element, and the semiconductor light emitting element can be efficiently manufactured. Can be formed.
[0046]
After the element isolation trench 39 is formed, the protective film 38 is removed with acid or the like (FIG. 5G). As shown in FIG. 5 (h), after removing the protective film 38, the p-side is formed on the surface of the second conductive layer 37 which is the outermost part of the hexagonal pyramidal first conductive layer, the active layer, and the second conductive layer. The electrode 40 is formed. For example, the p-side electrode 40 has a Ni / Pt / Au electrode structure or a Pd / Pt / Au electrode structure, and is formed by a vapor deposition method or the like. Further, since the n-side electrode is formed on the back surface, it is not formed here.
[0047]
FIG. 5I is a diagram showing a process of separating the growth substrate 31 by irradiating laser light from the back side of the growth substrate 31. As described above, since the band gap energy of the lower conductive layer 33 is smaller than the band gap energy of the underlying growth layer 32, the energy value between these band gap energies is used as laser light irradiated from the back side of the growth substrate 11. When the laser beam having the above is used, the laser beam is not absorbed by the underlying growth layer 32 but is absorbed by the lower conductive layer 33. Therefore, ablation occurs at the lower conductive layer 33 side interface between the lower conductive layer 33 and the underlying growth layer 32 that absorbs laser light, and the growth substrate 31 can be separated together with the underlying growth layer 32. Further, the laser light irradiated to separate the growth substrate 31 includes laser light such as excimer laser and harmonic YAG laser which are ultraviolet rays.
[0048]
For example, when the underlying growth layer 32 is made of AlGaN (Al composition is about 15%) and the lower conductive layer 33 is made of GaN having a band gap energy smaller than that of AlN, a third harmonic YAG laser (355 nm) is applied to the growth substrate 31. When irradiated from the back side, GaN is decomposed into metallic Ga and nitrogen at the lower conductive layer 33 side interface between the lower conductive layer 33 and the underlying growth layer 32, and the growth substrate 31 and the underlying growth layer 32 are easily separated. can do.
[0049]
This is because the bandgap energy of AlGaN (Al composition is about 15%) as the underlying growth layer 32 is 3.8 eV, the bandgap energy of GaN as the lower conductive layer 33 is 3.2 eV, and the third harmonic YAG laser. This is because the energy of the laser beam of (355 nm) is 3.5 eV, so that the YAG laser is transmitted without being absorbed in the underlying growth layer 32 and is absorbed by reaching the lower conductive layer 33.
[0050]
As described above, when the lower conductive layer 33 is laminated using a semiconductor whose band gap energy is smaller than that of the base growth layer 32, and the laser beam having energy located between the two band gap energies is irradiated, It is not absorbed in the growth layer 32 but is absorbed up to the lower conductive layer 33. Ablation occurs at the lower conductive layer 33 side interface between the lower conductive layer 33 and the underlying growth layer 32 that has absorbed the laser beam, and the growth substrate 31 and the underlying growth layer 32 can be easily separated.
[0051]
As shown in FIG. 6 (j), when the growth substrate 31 and the underlying growth layer 32 are separated, the depth of the element isolation trench 39 is the depth reaching the underlying growth layer 32. At the same time as the substrate 31 and the underlying growth layer 32 are separated, the plurality of elements are separated.
[0052]
FIG. 6K is a diagram illustrating a process of forming the n-side electrode 41 on the back surface of the element. As an example, the n-side electrode 41 has a Ti / Al / Pt / Au electrode structure and is formed by a vapor deposition method or the like.
[0053]
As described above, the band gap energy of the lower conductive layer 33 is smaller than the band gap energy of the underlying growth layer 32, and the energy value between these band gap energies as laser light irradiated from the back side of the growth substrate 31. In the case of using a laser beam having the above, the laser beam is not absorbed by the underlying growth layer 32 but is absorbed by the lower conductive layer 33. By irradiating such a laser beam, ablation occurs at the lower conductive layer 33 side interface between the underlying growth layer 32 and the lower conductive layer 33, and the growth substrate 31 and the underlying growth layer 32 can be separated. The lower conductive layer 33 suitable for formation can be exposed.
[0054]
Further, when the semiconductor isolation layer is separated from the growth substrate 31 and the underlying growth layer 32 by laser light irradiation after the element isolation trench 39 is formed to a depth reaching the underlying growth layer 32, the growth substrate 31 is separated together with the underlying growth layer 32. At the same time, the semiconductor growth layer can be efficiently separated for each of the plurality of semiconductor light emitting elements, and the n-side electrode can be efficiently formed on the back surface of the lower conductive layer 33 separated into the plurality of semiconductor light emitting elements. it can.
[0055]
[ second Embodiment]
A base growth layer is formed on the growth substrate, a lower conductive layer is formed on the base growth layer, and a first conductive layer, an active layer, and a second conductive layer are stacked on the lower conductive layer by selective growth. A semiconductor light emitting device formed after a trapezoidal columnar semiconductor growth layer having a substantially trapezoidal cross section and separated at the interface between the base growth layer and the lower conductive layer will be described.
[0056]
As shown in FIG. first Similar to the first embodiment, the base growth layer 52 and the lower conductive layer 53 are stacked in this order on the growth substrate 51, and the growth inhibition film 54 is formed on the base growth layer 52. Since the underlying growth layer 52 is separated together with the growth substrate 51, it is not necessary to dope impurities.
[0057]
The growth substrate 51 may be a substrate capable of forming a wurtzite type compound semiconductor next to a sapphire substrate, second In this embodiment, the growth substrate 51 is a substrate having light transmissivity, such as a sapphire substrate, because laser light is irradiated from the back side when the growth substrate 51 described later is separated.
[0058]
The lower conductive layer 53 stacked on the underlying growth layer 52 is a wurtzite type compound semiconductor such as gallium nitride (GaN), and is doped with an impurity such as silicon to form an n-side electrode. The lower conductive layer 53 is formed using a semiconductor having a band gap energy smaller than that of the base growth layer 52. For example, first As in the first embodiment, AlGaN can be used for the base growth layer 52 and GaN can be used for the lower conductive layer 53 as a semiconductor having a band gap energy smaller than that of the base growth layer 52.
[0059]
The growth inhibition film 54 formed on the lower conductive layer 53 is made of a silicon oxide film or a silicon nitride film, and is formed by sputtering or the like.
[0060]
FIG. 7B shows a step of forming a stripe-shaped opening 54 a in the growth inhibition film 54. The shape of the opening 54a may be a stripe-shaped opening that can generally have a facet structure having an inclined surface with respect to the main surface of the substrate. second In the embodiment, the semiconductor light emitting device having a trapezoidal columnar shape with a substantially trapezoidal cross section has a stripe shape. For example, when the longitudinal direction of the opening 54a is the [1-100] direction or the [11-20] direction, A trapezoidal columnar first conductive layer, an active layer, and a second conductive layer having a substantially trapezoidal cross section can be formed.
[0061]
As shown in FIG. 7C, a trapezoidal columnar first conductive layer 55 having a substantially trapezoidal cross section is formed by selective growth from the stripe-shaped opening 54a. The first conductive layer 55 is made of a wurtzite type compound semiconductor, is formed of a material such as silicon-doped GaN, and functions as an n-type cladding layer.
[0062]
After the first trapezoidal columnar first conductive layer 55 having a substantially trapezoidal cross section as shown in FIG. first Similarly to the first embodiment, the active layer 56 and the second conductive layer 57 are sequentially stacked (FIG. 8D). The active layer 56 is a layer for generating light of the semiconductor light emitting device, and is composed of, for example, an InGaN layer or a layer having an InGaN layer sandwiched between AlGaN layers. In addition, the active layer 56 can be formed of a single bulk active layer. However, the active layer 56 has a quantum structure such as a single quantum well (SQW) structure, a double quantum well (DQW) structure, or a multiple quantum well (MQW) structure. A well structure may be formed. In the quantum well structure, a barrier layer is used in combination for separating the quantum well as necessary. The second conductive layer 57 is a wurtzite type compound semiconductor layer, which is formed of a material such as magnesium-doped GaN, for example, and functions as a p-type cladding layer.
[0063]
FIG. 8E and FIG. 8F show a process of forming the element isolation trench 59. As shown in FIG. first As in the first embodiment, a protective film 58 such as a silicon oxide film is formed on the entire surface of the second conductive layer 57 formed on the outermost side and the lower conductive layer 53 on which the growth inhibition film 54 is formed by plasma CVD or the like. Then, as shown in FIG. 8 (f), a process such as reactive ion etching is performed to form an element isolation groove 59, which is separated into regions for each element.
[0064]
The depth of the element isolation trench 59 is a depth reaching the underlying growth layer 52. As will be described later, when the growth substrate 51 is separated by irradiating laser light from the back side of the growth substrate 51, ablation occurs at the lower conductive layer 53 side interface between the base growth layer 52 and the lower conductive layer 53, The growth substrate 51 can be separated together with the underlying growth layer 52. At this time, the element isolation trench 59 is formed to a depth reaching the underlying growth layer 52, thereby separating the growth substrate 51 and the underlying growth layer 52 and simultaneously separating the lower conductive layer 53 and the semiconductor growth layer for each element. Thus, a semiconductor light emitting device can be formed efficiently.
[0065]
After the element isolation trench 59 is formed, the protective film 58 is removed with an acid or the like (FIG. 9G), and after removing the protective film 58 as shown in FIG. The p-side electrode 60 is formed on the surface of the second conductive layer 57 that is the outermost part of the growth layer. As an example, the p-side electrode 60 has a Ni / Pt / Au electrode structure or a Pd / Pt / Au electrode structure, and is formed by vapor deposition or the like. Further, since the n-side electrode is formed on the back surface, it is not formed here.
[0066]
FIG. 9I is a diagram showing a process of separating the growth substrate 51 by irradiating laser light from the back side of the growth substrate 51. As described above, since the band gap energy of the lower conductive layer 53 is smaller than the band gap energy of the underlying growth layer 52, the energy value between these band gap energies is used as laser light irradiated from the back side of the growth substrate 51. When the laser beam having the above is used, the laser beam is not absorbed by the underlying growth layer 52 but is absorbed by the lower conductive layer 53. Therefore, when such laser light is irradiated from the back side of the growth substrate 51, the laser light is transmitted through the base growth layer 52 and absorbed by the lower conductive layer 53, and the lower conductive layer 53 that absorbs the laser light and the base growth. Ablation occurs at the lower conductive layer 53 side interface with the layer 52, and the growth substrate 51 can be separated together with the underlying growth layer 52. In addition, laser light irradiated for separating the growth substrate 51 includes laser light such as excimer laser and harmonic YAG laser which are ultraviolet rays.
[0067]
For example, when the underlying growth layer 52 is AlGaN (Al composition is about 15%) and the lower conductive layer 53 is GaN having a band gap energy smaller than that of AlN, a third harmonic YAG laser (355 nm) is applied to the growth substrate 51. When irradiated from the back side, GaN is decomposed into metallic Ga and nitrogen at the lower conductive layer 53 side interface between the lower conductive layer 53 and the underlying growth layer 52, and the growth substrate 31 and the underlying growth layer 32 are easily separated. can do.
[0068]
This is because the bandgap energy of AlGaN (Al composition is about 15%) as the underlying growth layer 52 is 3.8 eV, the bandgap energy of GaN as the lower conductive layer 53 is 3.2 eV, and the triple harmonic YAG laser. This is because the energy of the (355 nm) laser beam is 3.5 eV, so that the YAG laser is transmitted without being absorbed by the underlying growth layer 52 and is absorbed by reaching the lower conductive layer 53.
[0069]
As described above, when the base growth layer 52 is laminated by using a semiconductor having a band gap energy larger than that of the lower conductive layer 53 and irradiated with laser light having energy located between the two band gap energies, It passes through the growth layer 52 without being absorbed, and reaches the lower conductive layer 53 to be absorbed. Ablation occurs at the lower conductive layer 53 side interface between the lower conductive layer 53 and the underlying growth layer 52 that has absorbed the laser beam, and the growth substrate 31 and the underlying growth layer 32 can be easily separated.
[0070]
As shown in FIG. 10J, when the growth substrate 31 and the underlying growth layer 32 are separated, the depth of the element isolation trench 59 is the depth reaching the underlying growth layer 52. The one conductive layer, the active layer, and the second conductive layer are separated for each element. As shown in FIG. 10K, the n-side electrode 61 is formed on the back surface of the element. As an example, the n-side electrode 61 has a Ti / Al / Pt / Au electrode structure and is formed by a vapor deposition method or the like.
[0071]
The thus separated trapezoidal columnar semiconductor light emitting device having a substantially trapezoidal cross section is separated into a plurality of devices by dicing or etching in a direction perpendicular to the ridgeline of the trapezoidal column. At this time, for example, a cleavage interface that becomes a resonance end face of the semiconductor laser can be formed by cleavage or the like.
[0072]
As described above, the band gap energy of the lower conductive layer 53 is smaller than the band gap energy of the base growth layer 52, and the energy value between these band gap energies as laser light irradiated from the back side of the growth substrate 51. In the case of using a laser beam having the above, the laser beam is not absorbed by the underlying growth layer 52 but is absorbed by the lower conductive layer 53. By irradiating such a laser beam, ablation occurs at the lower conductive layer 53 side interface between the underlying growth layer 52 and the lower conductive layer 53, and the growth substrate 31 and the underlying growth layer 32 can be separated. The lower conductive layer 53 suitable for formation can be exposed.
[0073]
Further, when the semiconductor isolation layer 59 is separated from the growth substrate 51 and the underlying growth layer 52 by laser light irradiation after forming the element isolation trench 59 to a depth reaching the underlying growth layer 52, the growth substrate 51 is separated together with the underlying growth layer 52. At the same time, the semiconductor growth layer can be efficiently separated for each of the plurality of semiconductor light emitting elements, and the n-side electrode can be efficiently formed on the back surface of the lower conductive layer 53 separated into the plurality of semiconductor light emitting elements. it can.
[0074]
【Effect of the invention】
According to the present invention, when a growth substrate is separated by irradiating a laser beam from the back side of the growth substrate to separate the growth substrate, the polycrystalline or amorphous buffer layer and the undoped layer are easily separated together with the growth substrate. be able to. Therefore, when the growth substrate is separated, the lower conductive layer such as the n-side contact layer made of a single crystal and having good crystallinity can be exposed, and the lower conductive layer suitable for electrode formation can be efficiently formed from the back surface. Side electrodes can be formed. In addition, since the electrode can be efficiently formed on the lower conductive layer, the production cost of the semiconductor element can be reduced, and the production cost of the image display device mounted with the semiconductor element can also be reduced.
[0075]
When an element isolation trench that separates into regions for each element is formed in the lower growth layer and the semiconductor layer so as to reach the underlying growth layer, laser light is irradiated from the back side of the growth substrate to separate the growth substrate. The semiconductor layer can be efficiently separated into a plurality of semiconductor elements simultaneously with the separation of the semiconductor layer from the growth substrate and the underlying growth layer.
[0076]
Unlike the conventional semiconductor element in which only the growth substrate is separated or separated from the middle part of the underlying growth layer as in the prior art, the growth substrate and the underlying growth layer are separated in the semiconductor element of the present invention. As a result, it is possible to realize a semiconductor device that is reduced in size as compared with the above. Miniaturized semiconductor elements are formed with various forms of wiring because the electrodes are formed on the back side even when the elements are mounted, for example, with a synthetic resin that hardens the periphery and can be easily handled. can do.
[Brief description of the drawings]
[Figure 1] Reference example The process of forming a base growth layer, the formation of a semiconductor growth layer, and the formation of an element isolation groove in a method for manufacturing a semiconductor element are shown, (a) is a process cross-sectional view of the base growth layer formation, (b) is a first step. It is process sectional drawing of formation of a conductive layer, an active layer, and a 2nd conductive layer, (c) is process sectional drawing of element isolation groove formation.
[Figure 2] Reference example The process of isolation | separation of a semiconductor growth layer and the formation of both electrodes in the manufacturing method of this semiconductor element is shown, (d) is sectional drawing of semiconductor growth layer isolation | separation, (e) is process sectional drawing of both electrode formation.
3A and 3B show a process for forming a base growth layer, a growth inhibition film, and an opening in a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. Is a process cross-sectional view of forming a growth inhibition film, and (c) is a process cross-sectional view of forming an opening.
FIG. 4 shows a step of forming a first conductive layer, an active layer, and a second conductive layer and a step of forming an element isolation groove in the method for manufacturing a semiconductor device of an embodiment of the present invention, (d) shows the first conductive layer, FIG. 6 is a process cross-sectional view of forming an active layer and a second conductive layer, (e) is a process cross-sectional view of forming a protective film, and (f) is a process cross-sectional view of forming an element isolation trench.
FIG. 5 shows a process of removing a protective film, forming a p-side electrode, and separating a growth substrate in a method for manufacturing a semiconductor device according to an embodiment of the present invention, and (g) is a cross-sectional view of the process of removing the protective film. (H) is a process sectional view of p-side electrode formation, and (i) is a process sectional view of growth substrate separation.
6A and 6B show a process of separating a growth substrate and forming an n-side electrode in a method for manufacturing a semiconductor device according to an embodiment of the present invention, wherein FIG. 6J is a process sectional view of the growth substrate separation, and FIG. It is process sectional drawing of side electrode formation.
7A and 7B show a step of forming a base growth layer, a growth inhibitory film, an opening, and a first conductive layer in a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 7A shows the base growth layer and the growth inhibitory film. It is process sectional drawing of formation, (b) is process sectional drawing of opening part formation, (c) is process sectional drawing of 1st conductive layer formation.
FIG. 8 shows a process of forming a first conductive layer, an active layer, and a second conductive layer, forming a protective film, and forming an element isolation groove in the method for manufacturing a semiconductor element according to the embodiment of the present invention; FIG. 4 is a process cross-sectional view of forming an active layer and a second conductive layer, FIG. 3E is a process cross-sectional view of forming a protective film, and FIG.
FIG. 9 shows a process of removing a protective film, forming a p-side electrode, and separating a growth substrate in the method of manufacturing a semiconductor device according to the embodiment of the present invention, and (g) is a process cross-sectional view of removing the protective film. (H) is a process sectional view of p-side electrode formation, and (i) is a process sectional view of growth substrate separation.
10A and 10B show a process for separating a growth substrate and forming an n-side electrode in a method for manufacturing a semiconductor device according to an embodiment of the present invention, wherein FIG. 10J is a process cross-sectional view of the growth substrate separation, and FIG. It is process sectional drawing of side electrode formation.
[Explanation of symbols]
11, 31, 51 Growth substrate
12, 32, 52 Base growth layer
13 n-side contact layer
14, 35, 55 First conductive layer
15, 36, 56 Active layer
16, 37, 57 Second conductive layer
17 p-side contact layer
18, 40, 60 p-side electrode
19, 41, 61 n-side electrode
33,53 Lower conductive layer
34,54 Growth inhibition film
34a, 54a opening
38,58 Protective film
39, 59 element isolation groove

Claims (12)

Forming a base growth layer on the substrate;
Forming a lower conductive layer having a band gap energy smaller than the base growth layer on the base growth layer;
Forming a growth inhibiting film on the lower conductive layer;
Removing part of the growth inhibiting film to form an opening;
Laminating a semiconductor layer on the lower conductive layer exposed from the opening; and
Forming a protective film on the semiconductor layer;
Forming an element isolation groove for separating the lower conductive layer and the semiconductor layer formed on the substrate into regions for each element by etching ;
Removing the protective film formed on the semiconductor layer;
Irradiating the substrate with light to cause ablation at the interface between the underlying growth layer and the lower conductive layer to separate the lower conductive layer and the semiconductor layer from the substrate. Method. The method for manufacturing a semiconductor device according to claim 1, wherein the lower conductive layer and the semiconductor layer are wurtzite type compound semiconductor layers. The method for manufacturing a semiconductor device according to claim 2, wherein the wurtzite type compound semiconductor layer is a nitride-based compound semiconductor layer. The method for manufacturing a semiconductor device according to claim 1, wherein the underlying growth layer is AlGaN, and the lower conductive layer is GaN. The semiconductor layer forms a crystal layer stacked on the main surface of the substrate on the substrate, and includes a first conductive layer, an active layer, and a second conductive layer extending in a plane parallel to the main surface. A first conductive layer formed on a crystal layer or having a tilted crystal plane inclined with respect to a main surface of the substrate on the substrate and extending in a plane parallel to the tilted crystal plane; A layer, an active layer, and a second conductive layer formed on the crystal layer;
A method for manufacturing a semiconductor device according to claim 1. The method of manufacturing a semiconductor element according to claim 1, wherein the substrate has light transmittance. The method of manufacturing a semiconductor element according to claim 1, wherein the light is irradiated from a back side of the substrate. The method of manufacturing a semiconductor device according to claim 1, wherein the light has an energy value between a band gap energy of the base growth layer and a band gap energy of the lower conductive layer. The method of manufacturing a semiconductor device according to claim 1, wherein the light is laser light. The method for manufacturing a semiconductor element according to claim 9 , wherein a wavelength of the laser light is not less than 340 nm and not more than 360 nm. The method of manufacturing a semiconductor element according to claim 1, wherein the element isolation trench has a depth reaching the base growth layer. The method for manufacturing a semiconductor element according to claim 1, wherein one electrode is formed on the separated back surface of the lower conductive layer of the element.

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