JP2021166308A - Manufacturing method for nitride semiconductor light-emitting element - Google Patents

Abstract

To provide a manufacturing method for a nitride semiconductor light-emitting element, by which the warpage of a substrate can be suppressed without complicating a manufacturing process.SOLUTION: A manufacturing method for a nitride semiconductor light-emitting element includes the step of forming a wafer by stacking the following layers in this order on a substrate layer with a thickness of 400 μm or more: an n-type clad layer formed of n-type AlGaN, an active layer including a well layer and a barrier layer formed of AlGaN, an electron block layer, a p-type clad layer and a p-type contact layer formed of p-type AlGaN. The wafer has a diameter of 10 mm order. In the step of forming the wafer, the semiconductor layer is formed with a thickness of less than 8 μm on the substrate layer. In the formed wafer, the warpage of the substrate layer is less than or equal to 180 μm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing a nitride semiconductor light emitting device.

In recent years, nitride semiconductor light emitting devices such as light emitting diodes and laser diodes that output blue light have been put into practical use, and development of nitride semiconductor light emitting devices with improved light emitting output is underway (see Patent Document 1). ..

Patent Document 1 describes a method for manufacturing an ultraviolet light emitting element, which divides a wafer in which a nitride semiconductor layer is laminated on the first surface of a sapphire wafer into individual ultraviolet light emitting elements, and is a method for manufacturing the nitride semiconductor layer side of the wafer. After the first step of forming a split groove that reaches halfway in the thickness direction of the sapphire wafer, and after the first step, the wafer is polished from the second surface side of the sapphire wafer so as to reduce the thickness of the wafer. A method for manufacturing an ultraviolet light emitting device is described, which comprises a second step of performing the process and a third step of dividing the wafer along the split groove after the second step.

JP-A-2015-29039

However, according to the method described in Patent Document 1, the manufacturing process may be complicated by providing the first step of forming the split groove on the substrate.

Therefore, an object of the present invention is to provide a method for manufacturing a nitride semiconductor light emitting device capable of suppressing warpage of a substrate without complicating the manufacturing process.

The present invention aims to solve the above problems by providing an n-type clad layer formed of n-type AlGaN, a barrier layer formed of AlGaN, and a well layer on a substrate layer having a thickness of 400 μm or more. A step of laminating an active layer including an electron block layer, a p-type clad layer formed of p-type AlGaN, and a p-type contact layer in this order to form a wafer is provided, and the wafer has a diameter on the order of 10 mm. In the step of forming the wafer, a semiconductor layer is formed on the substrate layer so as to have a thickness of less than 8 μm, and the formed wafer has an amount of warpage of the substrate layer of 180 μm or less. Provided is a method for manufacturing a nitride semiconductor light emitting device that satisfies the above conditions.

According to the present invention, it is possible to provide a method for manufacturing a nitride semiconductor light emitting device capable of suppressing warpage of a substrate without complicating the manufacturing process.

It is sectional drawing which shows typically an example of the structure of the nitride semiconductor light emitting device which concerns on 1st Embodiment of this invention. It is a graph which shows an example of the measurement result which investigated the relationship between the thickness of a sapphire substrate and the amount of warpage. It is sectional drawing which shows typically an example of the structure of the nitride semiconductor light emitting device which concerns on 2nd Embodiment of this invention.

Embodiments of the present invention will be described with reference to the drawings. It should be noted that the embodiments described below are shown as suitable specific examples for carrying out the present invention, and there are some parts that specifically exemplify various technically preferable technical matters. , The technical scope of the present invention is not limited to this specific aspect. Further, the dimensional ratio of each component in each drawing does not necessarily match the dimensional ratio of the actual nitride semiconductor light emitting device.

Further, in the following description, regardless of whether the nitride semiconductor light emitting device is a face-up type or a flip-chip type, the “top” uniformly refers to the p-side electrode 92 (see FIG. 1) side. The “bottom” uniformly refers to the substrate layer 10 (see FIG. 1) side. Unless otherwise specified, "above" or "below" means the relative positional relationship between one object and another object, and the one object refers to the third object. Not only is the one object placed above or below the other object without being sandwiched between them, but the one object is placed above or below the other object with the third object in between. It shall also include the state of being.

[First Embodiment]
(Construction of nitride semiconductor light emitting device)
FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a nitride semiconductor light emitting device according to the first embodiment of the present invention. The nitride semiconductor light emitting device 1 (hereinafter, also simply referred to as “light emitting device 1”) includes, for example, a laser diode and a light emitting diode (LED). In the present embodiment, as the light emitting element 1, a light emitting diode (LED) that emits ultraviolet light having a center wavelength of 250 nm to 360 nm (preferably 295 nm to 360 nm) will be described as an example.

As shown in FIG. 1, the light emitting element 1 includes a substrate layer 10, a semiconductor layer 100, an n-side electrode 90, and a p-side electrode 92. The semiconductor layer 100 includes an n-type clad layer 30, an active layer 50 including a barrier layer 51 and a well layer 52, an electron block layer 60, a p-type clad layer 70, and a p-type contact layer 80 in this order. It is configured by stacking. Hereinafter, each component will be described.

[Substrate layer 10]
(1) Structure of Substrate Layer 10 The substrate layer 10 is composed of, for example, _{a sapphire substrate 11 formed of sapphire (Al 2} O ₃ ) and a buffer layer 12 formed on the sapphire substrate 11. There is. The substrate layer 10 may be an AlN single crystal substrate formed of aluminum nitride (AlN). In this case, the buffer layer 12 does not necessarily have to be included.

(2) Sapphire substrate 11
The sapphire substrate 11 has a phenomenon in which points on the surface are displaced in a direction orthogonal to the reference plane corresponding to the (0001) plane, that is, “warp” occurs. FIG. 2 is a graph showing an example of measurement results for investigating the relationship between the thickness of the sapphire substrate 11 and the amount of warpage of the sapphire substrate 11. The data shown in FIG. 2 is the relationship between the thickness of the sapphire substrate 11 and the amount of warpage of the sapphire substrate 11 when the thickness of the semiconductor layer 100 described later is about 4 μm. Here, the amount of warpage (μm) was determined as the amount in which the central portion of the surface of the sapphire substrate 11 was displaced with respect to the above-mentioned reference plane in the direction orthogonal to the reference plane. Further, the inventors prepared two sapphire substrates 11 as samples and measured the thickness and the amount of warpage, respectively.

As shown in FIG. 2, as the thickness of the sapphire substrate 11 is increased, the amount of warpage becomes smaller. For example, the amount of warpage is inversely proportional to the thickness of the sapphire substrate 11 to the power of 1.5 to 1.6. In order to process the sapphire substrate 11 into chips, it is preferable to keep the amount of warpage below a certain level. For example, the sapphire substrate 11 has a thickness in the range of 400 μm or more and 1000 μm or less. The amount of warpage of the sapphire substrate is preferably suppressed to 180 μm or less, and in this case, the thickness of the sapphire substrate 11 needs to be 400 μm or more.

(2) Buffer layer 12
The buffer layer 12 is formed of AlN. In other words, the surface of the substrate layer 10 on the semiconductor layer 100 side, more specifically, the surface on the n-type clad layer 30 side (hereinafter, also referred to as “outermost surface”) is formed of AlN. The roughness of the outermost surface of the buffer layer 12 is larger than 2 Å, preferably 10 Å or more and 50 Å or less. Further, the buffer layer 12 has a thickness of 1.0 μm to 4.5 μm. The buffer layer 12 may have a single layer or a multi-layer structure.

[Semiconductor layer 100]
As the semiconductor constituting the semiconductor layer 100, for example, _{a binary or ternary group III nitride semiconductor represented by Al x} Ga _1-x N (0 ≦ x ≦ 1) can be used. Further, a part of nitrogen (N) may be replaced with phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) or the like.

The semiconductor layer 100 includes an n-type clad layer 30, an active layer 50 including a barrier layer 51 and a well layer 52, an electron block layer 60, a p-type clad layer 70, and a p-type contact layer 80 in this order. It is configured to include. The semiconductor layer 100 has a thickness of less than 8 μm. Preferably, the semiconductor layer 100 has a thickness of 2 μm or more and 6 μm or less.

(1) n-type clad layer 30
The n-type clad layer 30 is formed on the substrate layer 10. The n-type clad layer 30 is a layer formed of n-type AlGaN (hereinafter, also simply referred to as “n-type AlGaN” or “n-AlGaN”), and for example, silicon (Si) is doped as an n-type impurity. This is the AlGaN layer. As the n-type impurity, germanium (Ge), selenium (Se), tellurium (Te), carbon (C) and the like may be used.

The Al composition ratio (also referred to as “AlN mole fraction”) forming the n-type clad layer 30 is 20% or more, preferably 25% or more and 55% or less. The n-type clad layer 30 has a thickness of about 1 μm to 4 μm, and has a thickness of, for example, about 3 μm. The n-type clad layer 30 may be a single layer or a multilayer structure.

(2) Active layer 50
The active layer 50 is formed on the n-type clad layer 30. The active layer 50 includes one barrier layer 51 located on the n-type clad layer 30 side and one well layer located on the electron block layer 60 side (that is, the opposite side of the n-type clad layer 30 in the thickness direction), which will be described later. It is configured to include a single quantum well structure 50A composed of 52. Further, the active layer 50 is configured to have a band gap of 3.4 eV or more in order to output ultraviolet light having a wavelength of 360 nm or less. The barrier layer 51 has a thickness in the range of, for example, 5 nm to 50 nm. Further, the well layer 52 has a thickness in the range of 1 nm to 5 nm, for example.

Both the barrier layer 51 and the well layer 52 are formed of AlGaN. Specifically, the barrier layer 51 is _{configured to include Al r} Ga _1-r N, and the well layer 52 is configured to include Al _s Ga _1-s N (0 ≦ r ≦ 1, 0 ≦). s ≦ 1, r> s). That is, the Al composition ratio of AlGaN forming the barrier layer 51 is larger than the Al composition ratio of AlGaN forming the well layer 52. The arrangement of one barrier layer 51 and one well layer 52 in the quantum well structure 50A is not limited to the above-mentioned one, and the arrangement order may be the reverse of the above-mentioned order.

(3) Electronic block layer 60
The electron block layer 60 is formed on the active layer 50. The electron block layer 60 is a layer formed of p-type AlGaN (hereinafter, also simply referred to as “p-type AlGaN” or “p-AlGaN”). The electron block layer 60 has a thickness of about 1 nm to 30 nm. The electron block layer 60 may include a layer formed of AlN. Further, the electron block layer 60 is not necessarily limited to the p-type semiconductor layer, and may be an undoped semiconductor layer.

(4) p-type clad layer 70
The p-type clad layer 70 is formed on the electron block layer 60. The p-type clad layer 70 is a layer formed of p-type AlGaN, and is, for example, an AlGaN clad layer doped with magnesium (Mg) as a p-type impurity. As the p-type impurity, zinc (Zn), beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba) and the like may be used. The p-type clad layer 70 has a thickness of about 10 nm to 1000 nm, and has a thickness of, for example, about 50 nm to 800 nm.

(5) p-type contact layer 80
The p-type contact layer 80 is formed on the p-type clad layer 70. The p-type contact layer 80 is, for example, a p-type GaN layer doped with impurities such as Mg at a high concentration.

〔electrode〕
(1) n-side electrode 90
The n-side electrode 90 is formed on a part of the n-type clad layer 30. The n-side electrode 90 is formed of, for example, a multilayer film in which titanium (Ti) / aluminum (Al) / Ti / gold (Au) are sequentially laminated on the n-type clad layer 30.

(2) p-side electrode 92
The p-side electrode 92 is formed on the p-type contact layer 80. The p-side electrode 92 is formed of, for example, a nickel (Ni) / gold (Au) multilayer film that is sequentially laminated on the p-type contact layer 80.

[Other configurations]
An undoped u-AlGaN layer may be further provided on the buffer layer 12. Further, in addition to the AlN substrate, an aluminum gallium nitride (AlGaN) substrate may be used for the substrate layer 10.

(Manufacturing method of light emitting element 1)
Next, a method of manufacturing the light emitting element 1 will be described. First, the buffer layer 12 is grown at a high temperature on the sapphire substrate 11 to produce a substrate layer 10 having an AlN outermost surface. Next, the n-type clad layer 30, the active layer 50, the electron block layer 60, and the p-type clad layer 70 are laminated on the substrate layer 10 to have a disk-like shape having a predetermined diameter (for example, 50 mm). A nitride semiconductor laminate (also referred to as a "wafer" or "wafer") is formed.

These n-type clad layer 30, active layer 50, electron block layer 60, and p-type clad layer 70 are formed by a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy method (Molecular Beam Epitaxy). It can be formed by using a well-known epitaxial growth method such as MBE) and Halide Vapor Phase Epitaxy (NVPE).

Next, a mask is formed on the p-type clad layer 70, and the exposed regions of the active layer 50, the electron block layer 60, and the p-type clad layer 70 where the mask is not formed are removed. The active layer 50, the electron block layer 60, and the p-type clad layer 70 can be removed by, for example, plasma etching.

The n-side electrode 90 is formed on the exposed surface 30a (see FIG. 1) of the n-type clad layer 30, and the p-side electrode 92 is formed on the p-type contact layer 80 from which the mask has been removed. The n-side electrode 90 and the p-side electrode 92 can be formed by a well-known method such as an electron beam deposition method or a sputtering method. By cutting the wafer into predetermined dimensions, the light emitting element 1 shown in FIG. 1 is formed.

[Second Embodiment]
FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the light emitting element 1 according to the second embodiment of the present invention. The first embodiment is characterized in that the light emitting element 1 according to the second embodiment has a multiple quantum well layer instead of the single quantum well structure 50A of the light emitting element 1 according to the first embodiment. It is different from the light emitting element 1 of. Hereinafter, the points different from those of the first embodiment will be mainly described.

As shown in FIG. 3, the n-type clad layer 30 side of the multiple quantum well layer composed of _{Al r} Ga _1-r N instead of the single quantum well structure 50A according to the first embodiment. Three-layer well layers 54a, 54b, 54c (0 ≦ r ≦ 1, 0 ≦ s) including three barrier layers 52a, 52b, 52c including the barrier layer 52a and Al _s Ga _{1-s N.} It may include a multiple quantum well layer in which ≦ 1, r> s) are alternately laminated.

The number of barrier layers 52a, 52b, 52c and well layers 54a, 54b, 54c is not limited to three, and may be two or four or more. The Al composition ratio of AlGaN forming the barrier layers 52a, 52b, 52c and the well layers 54a, 54b, 54c may be appropriately adjusted.

(Actions and effects of embodiments)
As described above, in the light emitting device 1 according to the first embodiment and the second embodiment of the present invention, the thickness of the semiconductor layer 100 from the n-type clad layer 30 to the p-type contact layer 80 is less than a certain value. In the configuration (for example, less than 8 μm), the amount of warpage of the sapphire substrate 11 is suppressed to a certain level or less (for example, 150 μm or less) by setting the thickness of the sapphire substrate 11 to a certain level or more (for example, 450 μm or more). Can be done. Thereby, for example, the amount of warpage of the sapphire substrate 11 can be suppressed to a certain level or less without obtaining the step of forming the split groove described in Patent Document 1 described above. That is, the amount of warpage of the sapphire substrate 11 can be suppressed to a certain level or less without complicating the manufacturing process. By doing so, the productivity of the light emitting element 1 can be improved without complicating the process of processing the wafer into chips.

The above-mentioned effect is that the n-type clad layer 30 formed of AlGaN having a relatively small Al composition ratio (Al composition ratio is 0.25 or more and 0.55 or less. The center wavelength of the light emitting element 1 is changed from 295 nm to 360 nm. It is particularly effective for a light emitting element 1) that emits a corresponding amount of ultraviolet light.

(Summary of Embodiment)
Next, the technical idea grasped from the above-described embodiment will be described with reference to the reference numerals and the like in the embodiment. However, the respective reference numerals and the like in the following description are not limited to the members and the like in which the components in the claims are specifically shown in the embodiment.

[1] An n-type clad layer (30) formed of n-type AlGaN, a barrier layer (51) and a well layer (52) formed of AlGaN on a substrate layer (1) having a thickness of 400 μm or more. The active layer (50) containing the above, the electron block layer (60), and the p-type clad layer (70) and the p-type contact layer (80) formed of p-type AlGaN are laminated in this order to form a wafer. The wafer has a diameter on the order of 10 mm, and in the step of forming the wafer, a semiconductor layer (100) is formed on the substrate layer (1) so that the thickness is less than 8 μm. A method for manufacturing a nitride semiconductor light emitting device (1), wherein the formed wafer satisfies the amount of warpage of the substrate layer (1) of 180 μm or less.
[2] The method for manufacturing a nitride semiconductor light emitting device according to claim 1, wherein the wafer has a diameter of 2 inches.
[3] The method for manufacturing a nitride semiconductor light emitting device (1) according to claim 1 or 2, wherein the formed wafer further satisfies the amount of warpage of the substrate layer (1) to 150 μm or less.
[4] The method for manufacturing a nitride semiconductor light emitting device (1) according to any one of claims 1 to 3, wherein the thickness of the substrate layer (1) is 450 μm or more.
[5] Further comprising a step of forming the buffer layer (12) constituting the substrate layer (1), the buffer layer (12) is placed on the n-type clad layer (30) side of the substrate layer (1). The surface of the n-type clad layer (30) is formed of AlN while being positioned, and in the step of forming the buffer layer (12), the n-type clad layer (12) in the buffer layer (12) is formed. 30) The nitride semiconductor light emitting device (1) according to any one of claims 1 to 4, wherein the buffer layer (12) is formed so that the surface roughness of the surface on the side is 10 Å or more and 50 Å or less. Manufacturing method.
[6] Any of claims 1 to 5, wherein in the step of forming the wafer, the semiconductor layer (100) is formed on the substrate layer (1) so that the thickness is 2 μm or more and 6 μm or less. The method for manufacturing a nitride semiconductor light emitting device (1) according to item 1.
[7] In the step of forming the wafer, the n-type AlGaN is formed so that the Al composition ratio is 25% or more and 55% or less, and the nitride semiconductor light emitting device (1) manufactured has a center wavelength. The method for manufacturing a nitride semiconductor light emitting device (1) according to any one of claims 1 to 6, which emits ultraviolet light having a wavelength of 295 nm or more and 365 nm or less.

1 ... Nitride semiconductor light emitting element (light emitting element)
10 ... Substrate layer 11 ... Sapphire substrate 12 ... Buffer layer 100 ... Semiconductor layer 30 ... n-type clad layer 30a ... Exposed surface 50 ... Active layer 50A ... Quantum well structure 51, 52a, 52b, 52c ... Barrier layers 52, 54a, 54b , 54c ... well layer 60 ... electron block layer 70 ... p-type clad layer 80 ... p-type contact layer 90 ... n-side electrode 92 ... p-side electrode

Claims (7)

An n-type clad layer formed of n-type AlGaN, an active layer including a barrier layer and a well layer formed of AlGaN, an electron block layer, and a p-type AlGaN on a substrate layer having a thickness of 400 μm or more. A step of laminating the p-type clad layer and the p-type contact layer to be formed in this order to form a wafer is provided.
The wafer has a diameter on the order of 10 mm and has a diameter on the order of 10 mm.
In the step of forming the wafer, a semiconductor layer is formed on the substrate layer so as to have a thickness of less than 8 μm.
The formed wafer satisfies the amount of warpage of the substrate layer of 180 μm or less.
A method for manufacturing a nitride semiconductor light emitting device. The wafer has a diameter of 2 inches.
The method for manufacturing a nitride semiconductor light emitting device according to claim 1. The formed wafer further satisfies the amount of warpage of the substrate layer of 150 μm or less.
The method for manufacturing a nitride semiconductor light emitting device according to claim 1 or 2. The thickness of the substrate layer is 450 μm or more.
The method for manufacturing a nitride semiconductor light emitting device according to any one of claims 1 to 3. A step of forming a buffer layer constituting the substrate layer is further provided.
The buffer layer is located on the n-type clad layer side of the substrate layer, and the surface of the n-type clad layer side is formed of AlN.
In the step of forming the buffer layer, the buffer layer is formed so that the surface roughness of the surface of the buffer layer on the n-type clad layer side is 10 Å or more and 50 Å or less.
The method for manufacturing a nitride semiconductor light emitting device according to any one of claims 1 to 4. In the step of forming the wafer, the semiconductor layer is formed on the substrate layer so that the thickness is 2 μm or more and 6 μm or less.
The method for manufacturing a nitride semiconductor light emitting device according to any one of claims 1 to 5. In the step of forming the wafer, the n-type AlGaN is formed so that the Al composition ratio is 25% or more and 55% or less.
The produced nitride semiconductor light emitting device emits ultraviolet light having a center wavelength of 295 nm or more and 365 nm or less.
The method for manufacturing a nitride semiconductor light emitting device according to any one of claims 1 to 6.

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