JP2016184718A - Manufacturing method for light emission element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of the electrical characteristics of a light emitting element by reducing damage of a semiconductor layer due to irradiation of a laser beam when a substrate is divided by irradiation of a laser beam.SOLUTION: A wafer including a substrate 11 and a semiconductor laminate body 12 is prepared. The semiconductor laminate body 12 includes a first p-type semiconductor layer 122 made of nitride semiconductor, an n-type semiconductor layer 123 which is formed of nitride semiconductor and has an n-side electrode 13 formed thereon, an active layer 124 formed of nitride semiconductor, and a second p-type semiconductor layer 125 formed of nitride semiconductor and having a p-side electrode 14 formed thereon, which are laminated successively on the substrate 11 from the substrate 11 side. A laser beam is applied to the substrate 11 from the lower surface side of the substrate 11 to form a modified region 11a on the substrate 11, and the wafer is individualized into individual light emission elements 1 with the modified region 11a as a starting point, thereby manufacturing a light emission element 1.SELECTED DRAWING: Figure 3H

Description

  The present disclosure relates to a method for manufacturing a light emitting element using a nitride semiconductor.

  A light emitting device such as an LED (light emitting diode) using a nitride semiconductor is manufactured by forming a plurality of devices on a substrate such as sapphire by a wafer process and then dividing (dividing) each device into individual pieces. Is done. As a method of dividing into pieces, a method has been proposed in which a processing mark is formed by irradiating a laser beam with a converging point inside the substrate, and a wafer is divided along the processing mark (for example, a patent). Reference 1 and Patent Reference 2).

JP 2013-42119 A JP 2011-181909 A

  However, in the methods described in Patent Document 1 and Patent Document 2, laser light is irradiated not only on the substrate on which the focusing points are aligned but also on the semiconductor layer. For this reason, the portion of the semiconductor layer irradiated with the laser light may be damaged, and the electrical characteristics of the light emitting element may be deteriorated.

  Embodiments according to the present disclosure provide a method for manufacturing a light-emitting element including a singulation process of cutting a substrate by laser light irradiation, reducing damage to a semiconductor layer due to laser light irradiation, and electrical characteristics of the light-emitting element. It is an object to suppress deterioration of the material.

  A method for manufacturing a light emitting device according to an embodiment of the present disclosure includes a substrate, a first p-type semiconductor layer made of a nitride semiconductor, an n-type semiconductor layer made of a nitride semiconductor and having an n-side electrode formed thereon, and a nitride semiconductor. A step of preparing a wafer having a semiconductor stacked body in which a second p-type semiconductor layer made of an active layer and a nitride semiconductor and having a p-side electrode formed thereon is stacked on the substrate in order from the substrate side; The substrate is configured to include a step of forming a modified region on the substrate by irradiating the substrate with laser light, and a step of separating the wafer into individual light emitting elements starting from the modified region.

  According to the method for manufacturing a light emitting element according to the embodiment of the present disclosure, the presence of the first p-type semiconductor layer absorbs laser light, and thus the light emission manufactured by reducing damage to the semiconductor layer due to laser light irradiation. Deterioration of the electrical characteristics of the element can be suppressed.

It is a typical top view showing the structure of the light emitting element manufactured by the manufacturing method of the light emitting element concerning an embodiment. It is typical sectional drawing which shows the structure of the light emitting element manufactured by the manufacturing method of the light emitting element which concerns on embodiment, and shows the cross section in the IB-IB line | wire of FIG. 1A. It is a flowchart which shows the procedure of the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the board | substrate preparation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the base layer formation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the light absorption layer formation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the n-type semiconductor layer formation process, active layer formation process, and p-type semiconductor layer formation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the n-type semiconductor layer exposure process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the electrode formation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the protective film formation process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the laser beam irradiation process which is a sub process of the individualization process in the manufacturing method of the light emitting element which concerns on embodiment. It is a schematic plan view which shows the wafer before the individualization process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the isolation | separation process which is a sub process of the individualization process in the manufacturing method of the light emitting element which concerns on embodiment. It is typical sectional drawing which shows the other example of the isolation | separation process which is a sub process of the individualization process in the manufacturing method of the light emitting element which concerns on embodiment.

  Hereinafter, a method for manufacturing a light emitting device according to an embodiment will be described with reference to the drawings. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference sign indicate the same or the same member in principle, and the detailed description is omitted as appropriate.

<Embodiment>
[Configuration of Light Emitting Element]
The structure of the light emitting element manufactured by the method for manufacturing a light emitting element according to the embodiment will be described with reference to FIGS. 1A and 1B.

A light emitting device 1 manufactured by the method for manufacturing a light emitting device according to this embodiment includes a substrate 11, a semiconductor stacked body 12 stacked on the substrate 11, and a pair of electrodes electrically connected to the semiconductor stacked body 12. N-side electrode 13 and p-side electrode 14, and a protective film 15.
The semiconductor stacked body 12 is a stacked body of a plurality of semiconductor layers made of a nitride semiconductor, and in order from the substrate 11 side, an underlayer 121, a first p-type semiconductor layer 122, an n-type semiconductor layer 123, and an active layer. The layer 124 and the second p-type semiconductor layer 125 are stacked. In the present embodiment, the first p-type semiconductor layer 122 is a light absorption layer, and the second p-type semiconductor layer 125 is a p-type semiconductor layer.

  In the method for manufacturing a light emitting element according to the present embodiment, a plurality of light emitting elements 1 are formed on one substrate 11 by a wafer process. After that, the substrate 11 is cut by a laser dicing method in which laser light is irradiated from the lower surface side of the substrate 11 so that the light emitting elements 1 are separated.

In the present embodiment, the semiconductor stacked body 12 has an LED structure, and the active layer 124 is formed by connecting the n-side electrode 13 and the p-side electrode 14 to an external power source and supplying power to the semiconductor stacked body 12. It is configured to emit light. In addition, the semiconductor laminated body 12 is not limited to what has a LED structure, For example, you may have a LD (laser diode) structure. In addition, the outer shape of the light emitting element 1, the shape of the electrode, the arrangement region, and the like are merely examples, and can be appropriately formed.
Hereinafter, the configuration of each unit will be sequentially described in detail.

The substrate 11 is a substrate for supporting the semiconductor stacked body 12 and epitaxially growing (crystal growth) the semiconductor. As a substrate 11 suitable for a nitride semiconductor used for the semiconductor laminate 12, for example, an insulating property such as sapphire or spinel (MgAl ₂ O ₄ ) whose main surface is any one of the C-plane, R-plane, and A-plane. Examples of the substrate include silicon carbide (SiC), ZnS, ZnO, Si, GaAs, diamond, and oxide substrates such as lithium niobate and neodymium gallate that are lattice-bonded to a nitride semiconductor.
Moreover, you may make it form a some convex part in the main surface of the board | substrate 11 with which the semiconductor laminated body 12 is crystal-grown. Thereby, when the semiconductor stacked body 12 is crystal-grown, crystal defects such as dislocation penetrating to the upper surface of the semiconductor stacked body 12 can be reduced.

  The semiconductor laminate 12 is formed by laminating a base layer 121, a light absorption layer 122, an n-type semiconductor layer 123, and a p-type semiconductor layer 125 on one main surface that is the upper surface of the substrate 11. Light is emitted by passing a current between the p-side electrodes 14. As shown in FIG. 1B, an active layer 124 is preferably provided between the n-type semiconductor layer 123 and the p-type semiconductor layer 125.

The semiconductor stacked body 12 can use a nitride semiconductor suitable for a semiconductor light emitting element. In addition, when a part of light emitted from the light emitting element 1 is converted into light having a different wavelength by providing a phosphor layer, the semiconductor stacked body 12 that emits blue or violet light having a short emission wavelength is preferable. Therefore, each semiconductor layer of the semiconductor stacked body 12 is preferably a nitride-based compound semiconductor represented by In _X Al _Y Ga _1- XYN (0 ≦ X, 0 ≦ Y, X + Y ≦ 1). Can be used.
Each semiconductor layer of the semiconductor stacked body 12 is formed by a known technique such as MOCVD (metal organic vapor phase epitaxy), HVPE (hydride vapor phase epitaxy), MBE (molecular beam epitaxy), or sputtering. Can be formed. The thickness of each semiconductor layer is not particularly limited, and various thicknesses can be applied.

The semiconductor stacked body 12 is provided with a stepped portion 12a in which the entire p-type semiconductor layer 125 and the active layer 124 and a part of the n-type semiconductor layer 123 are removed in a thickness direction in a partial region of the upper surface. It has been. The bottom surface of the stepped portion 12a is composed of an n-type semiconductor layer 123, and the n-side electrode 13 is provided on the bottom surface. In addition, a full-surface electrode 141 that is a lower layer portion of the p-side electrode 14 is provided in substantially the entire region of the upper surface of the p-type semiconductor layer 125. In addition to the region where the n-side electrode 13 is provided, a step portion 12 a is also provided in a region along the outer periphery of the semiconductor stacked body 12. The step portion 12a in the outer peripheral region is provided in a region (dicing street) along a boundary line (scheduled cutting line) that is a virtual line that individually partitions the light emitting elements 1 in the wafer state.
The other surface of the semiconductor stacked body 12 is covered with a protective film 15 together with the n-side electrode 13 and the p-side electrode 14.

The base layer 121 is a semiconductor layer for improving the crystallinity of a semiconductor layer that functions as a light emitting element including the n-type semiconductor layer 123, the active layer 124, and the p-type semiconductor layer 125. In the base layer 121, a buffer layer 121a and a first semiconductor layer 121b are stacked in this order from the substrate 11 side.
Note that the stacked structure of the base layer 121 is not limited to a two-layer structure, and may be one layer or three or more layers.

The buffer layer 121a is a layer for relaxing the difference between the lattice constant of the substrate 11 and the lattice constant of the semiconductor stacked above the buffer layer 121a. The buffer layer 121a is preferably made of an undoped nitride semiconductor represented by Al _X Ga _1-X N (0 <X ≦ 1), and more preferably undoped AlGaN. The buffer layer 121a can be preferably formed by MOCVD.

  The film thickness of the buffer layer 121a should be in the range of about 5 nm or more that allows the buffer layer 121a to sufficiently cover the entire top surface of the substrate 11 and about 300 nm or less where the crystallinity of the light absorption layer 122 stacked on the top surface is improved. It is more preferable that the thickness be in the range of about 10 nm to 200 nm.

The first semiconductor layer 121b is stacked in direct contact with the upper surface of the buffer layer 121a. The first semiconductor layer 121b can be preferably grown by MOCVD. The first semiconductor layer 121b is formed in a film thickness in which a minute recess formed in the process of crystal growth is embedded and the upper surface is a flat surface.
The first semiconductor layer _121b, it is preferable to use the _{In X Al Y Ga 1-X} -Y N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) compound semiconductors undoped nitride represented by the undoped It is more preferable to use GaN. In the present embodiment, the undoped nitride-based compound semiconductor is a semiconductor layer having an impurity concentration of 1 × 10 ¹⁶ cm ⁻³ or less.
Further, the thickness of the first semiconductor layer 121b may be about 500 nm or more and 6000 nm or less, for example, as long as the upper surface is a flat surface.

  Note that the first semiconductor layer 121b may have a single-layer structure in which crystals are grown under the same conditions, but may have a multilayer structure of two or more layers by changing the crystal growth conditions in the middle.

The light absorption layer (first p-type semiconductor layer) 122 absorbs laser light irradiated from the lower surface side of the substrate 11 when the substrate 11 is cut by a laser dicing method, and is a semiconductor on the upper layer side than the light absorption layer 122. This is a layer for reducing the intensity of the laser light irradiated to the layer, particularly the p-type semiconductor layer 125.
The light absorption layer 122 uses a semiconductor material that absorbs laser light used in laser dicing and can favorably grow the crystal of the n-type semiconductor layer 123 stacked above the light absorption layer 122. Can be formed. As such a semiconductor material, similarly to the p-type semiconductor layer 125, a nitride-based semiconductor doped with Mg as a p-type impurity can be preferably used. As the composition of the semiconductor, GaN is preferably used so that good crystallinity can be continuously obtained on the upper surface of the base layer 121. The concentration of Mg as a p-type impurity is preferably about 1 × 10 ¹⁷ cm ^{−3 to} 1 × 10 ²¹ cm ⁻³ so that good light absorption and crystallinity can be obtained. More preferably, it is about ¹⁸ cm ⁻³ or more and about 1 × 10 ²¹ cm ⁻³ or less, and further preferably about 1 × 10 ¹⁹ cm ⁻³ or more and about 5 × 10 ²⁰ cm ⁻³ or less.
Here, the light absorption layer 122 is a nitride semiconductor layer containing a p-type impurity, and normally activates the p-type impurity by desorbing hydrogen in the nitride semiconductor layer containing the p-type impurity by annealing. Make it. The inventors of the present application have found that when laser dicing is performed on a nitride semiconductor layer containing a p-type impurity before annealing, the nitride semiconductor layer is less damaged, and when laser dicing is performed after annealing, nitriding is performed. Since the active semiconductor layer is easily damaged, the activated p-type impurity easily absorbs laser light, and if the energy density exceeds a certain energy density, the weak portion of the crystal of the p-type nitride semiconductor layer may be damaged. Thought.

  The film thickness of the light absorption layer 122 is preferably 10 nm or more so that the laser light used in laser dicing can be absorbed to the extent that the p-type semiconductor layer 125 is not damaged. In addition, in order to allow the n-type semiconductor layer 123 stacked on the upper layer to be crystal-grown satisfactorily, the thickness of the light absorption layer 122 is preferably set to 1000 nm or less.

Note that the light absorption layer 122 may be provided on the upper layer side of the substrate 11 and on the lower layer side of the n-type semiconductor layer 123 than the n-type semiconductor layer 123. When the n-type semiconductor layer 123 has a multilayer structure in which an n-type contact layer, an n-side cladding layer, and the like are stacked, the light absorption layer 122 is on the upper layer side of the substrate 11, and the n-type contact It can be provided on the lower layer side than the layer. The light absorption layer 122 is preferably provided on the upper layer side of the buffer layer 121a so that the semiconductor stacked body 12 is formed with good crystallinity, and the first semiconductor layer 121b whose upper surface is a mirror-like flat surface. Is also preferably provided on the upper layer side.
Further, any layer of the base layer 121 may be doped with Mg so as to also serve as the light absorption layer 122.

Further, the second semiconductor is in direct contact with the upper surface of the light absorption layer 122, in other words, between the light absorption layer 122 and the n type semiconductor layer 123 so that the n type semiconductor layer 123 is formed with good crystallinity. A layer may be provided. The second semiconductor _{layer, In X Al Y Ga 1-} X-Y N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) layer formed of a compound semiconductor of the nitride-based undoped represented by is preferable, undoped It is more preferable to use a layer made of GaN.

A stacked body including the n-type semiconductor layer 123, the active layer 124, and the p-type semiconductor layer 125 is a light emitting element structure stacked on the upper surface of the light absorption layer 122, and has an LED structure in this embodiment. These semiconductor layers are preferably formed continuously by the MOCVD method after the light absorption layer 122 is formed. These semiconductor _{layers, In X Al Y Ga 1-} X-Y N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) can be suitably used a nitride semiconductor represented by.

The n-type semiconductor layer 123 is composed of a semiconductor crystal in which an n-type impurity such as Si, Ge, or Sn is doped into the nitride semiconductor having the above composition, and it is particularly preferable to dope Si.
The n-type semiconductor layer 123 is formed by laminating an n-type contact layer that is a layer for providing the n-side electrode 13, an n-side cladding layer that is a layer for injecting and confining carriers into the active layer 124, and the like. A multilayer structure may be adopted.

The n-type impurity concentration of the n-type semiconductor layer 123 is preferably about 1 × 10 ¹⁷ cm ^{−3 to} 1 × 10 ²⁰ cm ⁻³ and is preferably 1 × 10 ¹⁸ cm ^{−3 to} 1 × 10 ¹⁹ cm ^−3. More preferably, it is about the following. The thickness of the n-type semiconductor layer 123 is not particularly limited, but is preferably about 0.5 μm to 10 μm, and preferably about 1 μm to 8 μm so that the semiconductor crystallinity is maintained well. It is more preferable.

The active layer 124 is a layer that is provided between the n-type semiconductor layer 123 and the p-type semiconductor layer 125 and emits light by combining carriers supplied from these semiconductor layers.
The active layer 124 preferably has a single quantum well or multiple quantum well structure in which thin films that generate quantum effects are stacked.
In the case of a multiple quantum structure, for example, In _X Ga _1-X N (0 <X <0.4) is used as a well layer, and Al _X Ga _1-X N (0 ≦ _X ) having a band gap energy larger than that of the well layer. X <0.3) can be a barrier layer. The thickness of the well layer can be set to such a thickness that a quantum effect can be obtained, for example, about 1 nm to 10 nm, preferably about 2 nm to 6 nm. Further, the thickness of the barrier layer is appropriately determined according to the thickness of the well layer.

The p-type semiconductor layer (second p-type semiconductor layer) 125 is composed of a semiconductor crystal in which a nitride semiconductor having the above composition is doped with a p-type impurity such as Mg.
The p-type semiconductor layer 125 includes a p-type contact layer that is a layer for providing the p-side electrode 14 and a p-side cladding layer that is a layer for injecting and confining carriers into the active layer 124. A multilayer structure may be adopted.

The p-type impurity concentration of the p-type semiconductor layer 125 is about 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less in order to obtain good ohmic contact with the entire surface electrode 141 and good crystallinity. it is preferable that a, more preferably on the order 5 × ¹⁰ 19 ^{cm -3} or more 5 × ¹⁰ 20 ^{cm -3} or less. The thickness of the p-type semiconductor layer 125 is not particularly limited, but is preferably about 10 nm to 500 nm, and more preferably about 50 nm to 200 nm so that high light emission output can be obtained.

The n-side electrode 13 is electrically connected to the n-type semiconductor layer 123 at the bottom surface of the stepped portion 12 a of the semiconductor stacked body 12, and is a pad electrode for supplying current from the outside to the light emitting element 1.
The n-side electrode 13 is made of, for example, a single metal such as Ag, Al, Ni, Rh, Au, Cu, Ti, Pt, Pd, Mo, Cr, or W so as to be suitable for connection to the outside by wire bonding or the like. An alloy mainly composed of these metals can be used, and further, a single layer or a laminate of these metal materials can be used. In the case where an alloy is used for the n-side electrode 13, for example, a non-metallic element such as Si may be contained as a composition element, such as an Al—Si—Cu alloy.
The n-side electrode 13 is covered with a protective film 15 except for a predetermined region on the upper surface for connection to the outside.

The p-side electrode 14 includes a full-surface electrode 141 and a pad electrode 142, and is electrically connected to the p-type semiconductor layer 125 of the p-type semiconductor layer 125, so as to supply an external current to the light emitting element 1. Electrode.
The p-side electrode 14 is covered with a protective film 15 except for a predetermined region on the upper surface of the pad electrode 142 for connection to the outside.

The entire surface electrode 141 is provided so as to cover substantially the entire region of the upper surface of the p-type semiconductor layer 125, and a current for diffusing a current supplied from the outside through the pad electrode 142 to the entire surface of the p-type semiconductor layer 125. It has a function as a diffusion layer.
When the light emitting element 1 is a face-up mounting type, the light emitted from the semiconductor stacked body 12 is extracted to the outside through the entire surface electrode 141. Therefore, the entire surface electrode 141 preferably has a good light-transmissive to the wavelength of light that the semiconductor laminate 12 is emitted, for _{example, ZnO, In 2 O 3,} ITO (Sn -doped _In 2 _{O 3)} etc. The conductive metal oxide can be used. Among these, ITO can be preferably used because it is a material having high translucency in the visible light region and high conductivity.
On the other hand, when the light emitting element 1 is a face-down mounting type (flip chip mounting type), the light emitted from the semiconductor laminate 12 is extracted to the outside through the substrate 11. For this reason, the entire surface electrode 141 preferably has good light reflectivity with respect to the wavelength of light emitted from the semiconductor laminate 12, and for example, as a metal material having good light reflectivity particularly in the visible light region, Ag, Al, or an alloy mainly containing any one of these metals can be preferably used.

  The pad electrode 142 is a pad electrode for supplying a current from the outside to the light emitting element 1, and is provided on a part of the upper surface of the entire surface electrode 141. The pad electrode 142 is electrically connected to the p-type semiconductor layer 125 via the entire surface electrode 141. The pad electrode 142 is formed in a substantially circular shape in plan view and is a region for connecting to the outside. The external connection part 142a and the extending part 142b disposed so as to extend from the external connection part 142a along the outer edge of the p-type semiconductor layer 125 to the n-side electrode 13 side.

The extending portion 142b is provided for evenly diffusing the current through the entire surface electrode 141 when the light emitting element 1 is a face-up type and the entire surface electrode 141 has translucency, so that the electrical resistance is relatively high. is there. When the light-emitting element 1 is a face-down mounting type and the entire surface electrode 141 is formed of a metal material having good conductivity and light reflectivity, the extending portion 142b is not necessarily provided.
For the pad electrode 142, the same material as that of the n-side electrode 13 can be used.

The protective film 15 has a light transmitting property and an insulating property, and is a film that covers the semiconductor stacked body 12, the n-side electrode 13, and the p-side electrode 14. Further, the protective film 15 has an opening 15 n on the upper surface of the n-side electrode 13, and an opening 15 p on the upper surface of the external connection portion 142 a of the pad electrode 142 of the p-side electrode 14.
As the protective film 15, for example, oxides such as SiO ₂ , TiO ₂ , and Al ₂ O ₃ , nitrides such as SiN, and fluorides such as MgF ₂ can be suitably used.

[Operation of light emitting element]
Next, the operation of the light emitting element 1 will be described with reference to FIGS. 1A and 1B.
In the light emitting element 1, when an external power source is connected between the n-side electrode 13 and the p-side electrode 14, current is supplied between the n-type semiconductor layer 123 and the p-type semiconductor layer 125, and the active layer 124 emits light.
When the light-emitting element 1 is a face-up mounting type, light emitted from the active layer 124 by the light-emitting element 1 propagates through the semiconductor stacked body 12 and is extracted mainly from the upper surface of the light-emitting element 1 to the outside.
When the light emitting element 1 is a face-down mounting type, the light emitted from the active layer 124 by the light emitting element 1 propagates through the semiconductor stacked body 12 and is mainly extracted from the lower surface of the light emitting element 1 to the outside.

[Method for Manufacturing Light-Emitting Element]
Next, a method for manufacturing a light emitting device according to the embodiment will be described with reference to FIGS.

  The light emitting device manufacturing method according to the present embodiment includes a substrate preparation step S101, an underlayer formation step S102, a light absorption layer formation step S103, an n-type semiconductor layer formation step S104, an active layer formation step S105, a p A type semiconductor layer formation S106, an n-type semiconductor layer exposure step S107, an electrode formation step S108, a protective film formation step S109, and an individualization step S110 are included.

  First, in the substrate preparation step S101, a substrate 11 for supporting the semiconductor stacked body 12 and for crystal growth is prepared. As the substrate 11, a sapphire substrate whose main surface for crystal growth of the semiconductor stacked body 12 is preferably a C plane can be used. In addition, a plurality of convex portions may be formed on the main surface of the substrate 11 by an etching method or the like so that crystal defects such as dislocations during crystal growth of the semiconductor stacked body 12 can be reduced.

  Next, in the base layer forming step S102, the base layer 121 is formed so that good crystallinity is obtained above the n-type semiconductor layer 123 which is the light emitting element structure. The underlayer forming step S102 includes a buffer layer forming step S102a and a first semiconductor layer forming step S102b as substeps.

  In the buffer layer forming step S102a, the buffer layer 121a is formed on the substrate 11 using the above-described material. The buffer layer 121a is formed directly on the substrate 11 by, for example, MOCVD or sputtering, more preferably by MOCVD.

Specifically, in the case of the MOCVD method, in order to form the buffer layer 121a, TMA (trimethylaluminum) is used as a raw material for group III element Al, TMG (trimethylgallium) is used as a raw material for Ga, and an In raw material is used. TMI (trimethylindium) can be used respectively. Further, NH ₃ (ammonia) gas can be used as a raw material for N which is a group V element. A semiconductor layer having an arbitrary composition can be formed by adjusting the ratio of the supply amounts of these source gases. In addition, for example, H ₂ , N _2, or a mixed gas thereof can be used as a carrier gas when supplying these raw materials.

In addition to the formation of the buffer layer 121a, the MOCVD method is a method for forming the other layers of the base layer 121, the light absorption layer 122, the n-type semiconductor layer 123, the active layer 124, and the p-type semiconductor layer 125. Also preferably used. In the MOCVD method, for example, SiH ₄ (silane) can be used as a raw material for Si that is an n-type impurity, and for example, Cp ₂ Mg (biscyclopenta) is used as a raw material for Mg that is a p-type impurity. Dienylmagnesium) can be used.

In the first semiconductor layer forming step S102b, the first semiconductor layer 121b is formed on the buffer layer 121a.
Note that the upper surface of the first semiconductor layer 121b, which is the uppermost surface of the base layer 121, is preferably formed to be a mirror-like flat surface.

  Next, in the light absorption layer forming step S103, the light absorption layer 122 is formed on the first semiconductor layer 121b. The light absorption layer 122 is formed using a semiconductor having the above composition doped with a p-type impurity, preferably Mg. The light absorption layer 122 has such a film thickness that the laser light irradiated from the lower surface side of the substrate 11 can be absorbed to such an extent that the laser light does not damage the p-type semiconductor layer 125 in the individualization step S110 described later. And p-type impurity concentration.

Next, in the n-type semiconductor layer forming step S104, the n-type semiconductor layer 123 is formed on the light absorption layer 122. In the active layer forming step S105, the active layer 124 is formed on the n-type semiconductor layer 123. In p-type semiconductor layer formation S <b> 106, the p-type semiconductor layer 125 is formed on the active layer 124. When these semiconductor layers have a multilayer structure such as an n-type contact layer and an n-side cladding layer, or a p-side cladding layer and a p-type contact layer, the composition and impurity doping concentration suitable for each layer are set. By forming differently, a stacked body having a light-emitting element structure can be formed.
In addition, it is preferable that the p-type semiconductor layer 125 and the light absorption layer 122 be made p-type by annealing after the semiconductor layers are stacked.

Next, in the n-type semiconductor layer exposing step S107, a region where the n-side electrode 13 is provided and a region serving as a dicing street, that is, a region having a predetermined width along the boundary line BD which is a virtual line indicating the outer edge of the light emitting element 1 Then, the step portion 12a is formed by etching from the upper surface of the semiconductor stacked body 12. The step portion 12a is formed to a depth at which the n-type semiconductor layer 123 is exposed on the bottom surface. When the n-type semiconductor layer 123 has a multilayer structure including an n-type contact layer, the stepped portion 12a is formed to a depth at which the n-type contact layer is exposed. Further, a part of the p-type semiconductor layer 125, the active layer 124, and the n-type semiconductor layer 123 is exposed on the side surface of the stepped portion 12a.
For etching the semiconductor stacked body 12, a dry etching method such as RIE (reactive ion etching) can be suitably used, but a wet etching method can also be used.

Next, in the electrode forming step S108, the n-side electrode 13 and the p-side electrode 14 are formed on the n-type semiconductor layer 123 exposed on the bottom surface of the stepped portion 12a and the p-type semiconductor layer 125, respectively.
In this step, the entire surface electrode 141 is formed so as to cover substantially the entire region of the upper surface of the p-type semiconductor layer 125 by sputtering or vapor deposition. Thereafter, the pad electrode 142 is formed on a part of the upper surface of the full-surface electrode 141 by sputtering or vapor deposition. Further, the n-side electrode 13 is formed on the bottom surface of the stepped portion 12a by sputtering or vapor deposition.
When the pad electrode 142 and the n-side electrode 13 are formed using the same material, the pad electrode 142 and the n-side electrode 13 may be formed in the same process.

The n-side electrode 13, the entire surface electrode 141, and the pad electrode 142 are each formed on the entire surface of the wafer using a material for forming these electrodes, and then a mask that covers the arrangement region of these electrodes is formed by photolithography. It can be patterned by forming and etching.
Alternatively, after forming a mask having an opening in the arrangement region of these electrodes, a film can be formed on the entire surface of the wafer using a material for forming these electrodes, and then patterned by a lift-off method in which the mask is removed. .
The protective film 15 to be described later can also be patterned using the same method.

  Next, in the protective film forming step S109, the protective film 15 is formed so as to cover substantially the entire surface of the wafer by sputtering or vapor deposition. The protective film 15 is patterned to have openings 15n and 15p in regions for external connection of the n-side electrode 13 and the pad electrode 142.

In the electrode forming step S108, after forming the entire surface electrode 141, the protective film 15 is formed so as to have an opening in a part of the upper surface of the entire surface electrode 141 and a part of the bottom surface of the stepped portion 12a, and then the pad The electrode 142 and the n-side electrode 13 may be formed. At that time, the pad electrode 142 and the n-side electrode 13 may be formed so as to extend to the upper surface of the protective film 15.
As described above, the wafer is prepared by performing each of the substrate preparation step S101 to the protective film formation step S109.

Next, in the individualization step (individualization step) S110, the light emitting element 1 is separated into individual pieces by cutting the wafer along a boundary line BD that is a cutting scheduled line by a laser dicing method.
The singulation process S110 includes a laser light irradiation process S110a and a separation process S110b as sub-processes.

First, in the laser beam irradiation step (step of forming a modified region) S110a, the laser beam irradiation apparatus 201 is used to collect light from the lower surface side of the substrate 11 to the inside of the substrate 11 along the boundary line BD. Is irradiated with a laser beam L2. As a result, the modified region 11 a is formed on the substrate 11 in the region near the condensing point F. The substrate 11 can be easily separated starting from the modified region 11a.
The modified region 11a may be formed in a part of the substrate 11 in the thickness direction. However, by changing the condensing point F in multiple steps in the thickness direction and irradiating the laser beam multiple times, A wide modified region 11a may be formed. As a result, the wafer can be more easily separated.

  The laser beam L2 irradiated from the lower surface side of the substrate 11 is used to modify the substrate 11 at and near the condensing point F set inside the substrate 11, but a part of the laser beam L2 is used. Transmits through the substrate 11, enters the inside of the semiconductor stacked body 12 from the lower surface, and further propagates upward. The laser light L2 incident from the lower surface of the semiconductor stacked body 12 is absorbed by the light absorption layer 122 because the light absorption layer 122 made of a p-type semiconductor is formed. For this reason, the intensity | strength of the laser beam L3 which permeate | transmits the light absorption layer 122 and propagates further upwards is reduced.

The p-type semiconductor layer 125 absorbs the laser light L3 and is more easily damaged than the other semiconductor layers of the semiconductor stacked body 12. In particular, when the p-type semiconductor layer 125 in the vicinity of the region etched to form the stepped portion 12a is damaged by etching, it is more easily damaged by absorbing the laser light L3. . Further, the p-type semiconductor layer 125 is damaged, so that the electrical characteristics of the light emitting element 1 are deteriorated.
In the present embodiment, by providing the light absorption layer 122 between the substrate 11 and the n-type semiconductor layer 123, the intensity of the laser light L3 irradiated to the p-type semiconductor layer 125 can be reduced. For this reason, damage to the p-type semiconductor layer 125 due to the laser light L3 can be reduced. As a result, deterioration of the electrical characteristics of the light emitting element 1 can be suppressed.

  Further, by using a semiconductor layer having the same or similar composition as that of the p-type semiconductor layer 125 constituting the semiconductor stacked body 12 as the light absorption layer 122, the light absorption layer 122 is stacked above the light absorption layer 122 and has a light emitting element structure. The body can be formed with good crystallinity.

The laser beam irradiation apparatus 201 includes a light source unit 201a and a condensing unit 201b such as a condensing lens. The laser beam irradiation device 201 emits the laser beam L2 so that the laser beam L1 emitted from the light source unit 201a is condensed by the condensing unit 201b so as to be condensed at the condensing point F.
Further, the laser beam irradiation apparatus 201 is configured to move the condensing point F of the laser beam L2 in an arbitrary direction within the plane of the wafer by moving the position relative to the wafer.

As the laser light used for laser dicing, it is preferable to use a pulse laser such as a femtosecond laser, a picosecond laser, or a nanosecond laser having a center wavelength in the range of 500 nm to 1100 nm, preferably in the range of 700 nm to 1000 nm. In particular, a femtosecond laser is more preferable.
Examples of the light source unit 201a that emits such laser light include an Nd: YAG (yttrium, aluminum, garnet) laser, an NdYVO ₄ laser, an Nd: YLF (yttrium, lithium, fluoride) laser, and a titanium sapphire laser. Can do.

  Next, in the separation step (separation step) S110b, the light emitting element 1 is separated by separating (cutting) the wafer along the boundary line BD starting from the modified region 11a formed in the laser light irradiation step S110a. Tidy up. The separation step S110b can be performed by a method using the expanded sheet 301 or a method using the blade 302.

  In the method using the expanded sheet 301 (see FIG. 3J), the expanded sheet 301 is attached to the lower surface side of the substrate 11 after performing the laser light irradiation step, and the expanded sheet 301 is extended. As a result, starting from the modified region 11 a formed along the boundary line BD, the semiconductor stacked body 12 and the protective film 15 stacked on the substrate 11 can be separated for each light emitting element 1 together with the substrate 11. .

  In the method using the blade 302 (see FIG. 3K), the knife edge of the blade 302 is pressed from the lower surface side of the substrate 11 along the boundary line BD. Thus, the semiconductor stacked body 12 and the protective film 15 stacked on the substrate 11 together with the substrate 11 can be separated for each light emitting element 1 from the modified region 11a. Note that a protective sheet may be attached to the upper surface side of the wafer before the blade 302 is pressed from the lower surface side of the substrate 11.

  Further, since it becomes easy to promote cleaving when the output of the laser beam is increased, it is possible to singulate without performing the breaking process. However, if the output of the laser beam is increased too much, the semiconductor laminate 12 is easily damaged. The electrical characteristics may be deteriorated. According to this embodiment, the laser beam directed toward the semiconductor stacked body 12 can be suitably absorbed by the light absorption layer 122, and damage to the semiconductor stacked body 12 can be suppressed. Therefore, it is possible to separate the wafers by omitting the breaking process.

  The light emitting element 1 can be manufactured by performing the above process.

[Confirmation test for suppressing deterioration of electrical characteristics]
In order to confirm the effect of the manufacturing method of the light emitting device according to the present embodiment, a light emitting device of an experimental example provided with a light absorbing layer and a light emitting device of a comparative example having no light absorbing layer were manufactured, and laser light was produced. As the deterioration of the electrical characteristics due to laser light irradiation in the irradiation process, the difference in the rate of occurrence of leakage was investigated.
For each wafer, for each light-emitting element formed on the wafer, a probe is brought into contact with the electrode to inspect for leakage before and after laser light irradiation, and without leaking before laser light irradiation, The ratio of light emitting elements that leaked after laser light irradiation was calculated.

  In addition, as a sample of the light emitting element of the experimental example provided with the light absorption layer, it was manufactured by changing the stacking position of the light absorption layer, the film thickness, and the flow rate of Mg as the p-type impurity as described later. Unless otherwise specified, other manufacturing conditions of the light-emitting element are the same in each experimental example and comparative example.

  The stacked structure of the semiconductor stacked body is substantially the same as the stacked structure shown in FIG. 1B, but an undoped second semiconductor layer is formed between the light absorption layer and the n-type semiconductor layer. The composition and film thickness of the semiconductor of each layer are as follows.

(Configuration of substrate and semiconductor laminate)
Substrate: Sapphire (main surface is C-plane), 150μm
Buffer layer: AlGaN, 18 nm
First semiconductor layer: GaN, 3000 nm
Light absorption layer: GaN (Mg doped), 200 nm
Second semiconductor layer: GaN, 4800 nm
n-type semiconductor layer: GaN (Si-doped), 5000 nm
Active layer: InGaN / GaN with a total film thickness of 60 nm
p-type semiconductor layer: AlGaN (Mg doped), 150 nm
(Conditions for forming the light absorption layer)
Light absorption layer thickness: 0 nm (comparative example), 200 nm (experimental examples 1 and 2)
Mg flow rate: 10 cm ³ / min (Experiment 1), 100 cm ³ / min (Experiment 2)

The rate of leakage due to laser light irradiation of a light emitting element manufactured under each condition is shown below.
In addition, the light emitting element of a comparative example and experiment examples 1 and 2 produced the semiconductor laminated body with a different manufacturing apparatus, respectively.

(Leakage rate)
Comparative example (without light absorbing layer): 4.5%
Experimental Example 1 (film thickness: 200 nm, Mg flow rate: 10 cm ³ / min, Mg concentration: 1.02 × 10 ¹⁹ cm ⁻³ ): 3.5%
Experimental Example 2 (film thickness: 200 nm, Mg flow rate: 100 cm ³ / min, Mg concentration: 3.37 × 10 ¹⁹ cm ⁻³ ): 1.0%

  According to the test results of each sample shown in this experiment, when the thickness of the light absorption layer is the same, increasing the Mg flow rate when forming the light absorption layer to increase the impurity concentration in the light absorption layer causes leakage. It was confirmed that the incidence could be reduced.

  As described above, it was confirmed that by providing the light absorption layer, it is possible to reduce the rate of leakage due to laser light irradiation, that is, to suppress the deterioration of the electrical characteristics of the light emitting element.

  As mentioned above, although the manufacturing method of the light emitting element which concerns on embodiment of this invention was concretely demonstrated by the form for inventing, the meaning of this invention is not limited to these description, Claim It should be interpreted broadly based on the scope description. Needless to say, various changes and modifications based on these descriptions are also included in the spirit of the present invention.

  A light emitting device manufactured by a method of manufacturing a light emitting device according to an embodiment of the present disclosure includes a backlight source of a liquid crystal display, various lighting fixtures, a large display, various display devices such as an advertisement and a destination guide, and a digital video camera It can be used for various light sources such as an image reading device in a facsimile, a copier, a scanner, a projector device, and the like.

DESCRIPTION OF SYMBOLS 1 Light emitting element 11 Substrate 11a Modified area | region 12 Semiconductor laminated body 12a Step part 121 Base layer 121a Buffer layer 121b 1st semiconductor layer 122 Light absorption layer (1st p-type semiconductor layer)
123 n-type semiconductor layer 124 active layer 125 p-type semiconductor layer (second p-type semiconductor layer)
13 n side electrode 14 p side electrode 141 full surface electrode 142 pad electrode 142a external connection part 142b extension part 15 protective film 15n, 15p opening part 201 laser light irradiation apparatus 201a light source part 201b light collecting part 301 expanding sheet 302 blade BD boundary line ( Scheduled cutting line)
F Condensing point L1, L2, L3 Laser light

Claims (10)

A substrate, a first p-type semiconductor layer made of nitride semiconductor, an n-type semiconductor layer made of nitride semiconductor and formed with an n-side electrode, an active layer made of nitride semiconductor, and a p-side electrode made of nitride semiconductor are formed Preparing a wafer having a semiconductor stacked body in which the second p-type semiconductor layer is stacked on the substrate in order from the substrate side;
Irradiating the substrate with laser light from the lower surface side of the substrate to form a modified region on the substrate;
And a step of separating the wafer into individual light emitting elements starting from the modified region.   The light emitting device manufacturing method according to claim 1, wherein the first p-type semiconductor layer is doped with Mg as an impurity.   The method for manufacturing a light emitting element according to claim 1, wherein the first p-type semiconductor layer has a thickness of 10 nm or more. 4. The method for manufacturing a light-emitting element according to claim 1, wherein the first p-type semiconductor layer has an impurity concentration of 10 ¹⁷ cm ⁻³ or more and 10 ²¹ cm ⁻³ or less.   5. The method for manufacturing a light-emitting element according to claim 1, wherein a part of the second p-type semiconductor layer is removed from the semiconductor stacked body by etching.   The light emitting device according to any one of claims 1 to 5, wherein the semiconductor stacked body includes an undoped nitride semiconductor layer between the first p-type semiconductor layer and the n-type semiconductor layer. Method.   The method for manufacturing a light-emitting element according to claim 1, wherein the semiconductor stacked body includes a buffer layer formed in contact with an upper surface of the substrate. In the step of forming the modified region,
By irradiating the laser beam along the planned cutting line for dividing the laser light into a plurality of the light emitting elements in a plan view with the converging point aligned inside the substrate, the wafer is formed on the planned cutting line. The method for manufacturing a light emitting element according to claim 1, wherein the modified region for cutting along the substrate is formed inside the substrate.   The light emitting element manufacturing method according to any one of claims 1 to 8, wherein in the step of forming the modified region, a femtosecond laser having a center wavelength in a range of 500 nm to 1100 nm is used as the laser light. Method. A substrate, a first p-type semiconductor layer made of nitride semiconductor, an n-type semiconductor layer made of nitride semiconductor and formed with an n-side electrode, an active layer made of nitride semiconductor, and a p-side electrode made of nitride semiconductor are formed Preparing a wafer having a semiconductor stacked body in which the second p-type semiconductor layer is stacked on the substrate in order from the substrate side;
Irradiating the substrate with laser light from the lower surface side of the substrate to divide the wafer into individual light emitting elements.

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