JP2005085851A - Method for manufacturing nitride compound semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a nitride compound semiconductor light emitting device whose electrode formation process is easy and that has high heat dissipation and high external quantum efficiency. <P>SOLUTION: An n-GaN layer 20 and a Ti film 30 are formed in order on a sapphire substrate 10, and they are heated to change the Ti film 30 into a mesh and to form cavities in the n-GaN layer 20. Then a light emitting device structure 40 made of nitride semiconductor is formed on the meshed Ti film 30, and a CuW substrate 50 is adhered to the surface of the light emitting device structure 40, and then the sapphire substrate 10 and the n-GaN layer 20 are peeled off from the light emitting device structure 40. An upper electrode 60 is provided on the peeling surface, and a bottom electrode 70 is provided on the bottom surface of the CuW substrate 50, resulting in a nitride compound semiconductor light emitting device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor light emitting device. Furthermore, in the manufacturing process of a light emitting device made of a nitride compound semiconductor, the electrode forming process is facilitated by peeling the first substrate and the first nitride compound semiconductor layer thereon from the light emitting device structure. The present invention relates to a method for manufacturing a nitride-based compound semiconductor light-emitting device having high heat dissipation and high light emission output.

The simplest method in semiconductor epitaxial growth is to perform epitaxial growth on a substrate made of the same material as the semiconductor to be grown. However, it is difficult to obtain a single crystal substrate with a nitride-based compound semiconductor, or it must be grown on a dissimilar material substrate such as sapphire or silicon carbide because it is not industrially used in terms of cost. The situation which cannot be obtained continues (patent document 1). For this reason, there has been a problem that the substrate is warped due to a difference in lattice constant and a difference in thermal expansion coefficient between the substrate and the nitride-based compound semiconductor layer.
Japanese Patent Laid-Open No. 06-291367

  As in Patent Document 1, in a light emitting device manufactured from a wafer in which a nitride compound semiconductor is epitaxially grown on a sapphire substrate, the sapphire substrate is an insulating substrate. Must be formed on the epitaxial growth surface side. Since both the electrodes are formed on the epitaxial growth surface side, many process steps are required for manufacturing the light emitting device.

  And in the manufactured light emitting element, since the electric current injected from the electrode has to flow in the lateral direction of the element, the resistance value becomes large.

  Furthermore, since the thermal conductivity of the sapphire substrate is low, the heat dissipation of the light emitting element is also low, and the fact that the light emitting element is provided with the sapphire substrate itself is a factor that decreases the light emitting characteristics and lifetime of the light emitting element. It was.

  In addition, there are more crystal defects when an AlGaN layer is epitaxially grown on a sapphire substrate than when GaN is grown on the same substrate. Therefore, in the manufacturing process of a nitride-based compound semiconductor light emitting device, a high quality GaN layer is first epitaxially grown on a sapphire substrate, and a light emitting device structure including an AlGaN layer is grown thereon. Here, when the emission wavelength of the compound semiconductor light emitting device is about 380 nm or less, there is a problem that the absorption of light in the GaN layer on the sapphire substrate increases, and the external quantum efficiency is greatly reduced.

  Therefore, the problem to be solved by the present invention is to provide a manufacturing method capable of obtaining a nitride compound semiconductor light emitting device having an easy electrode formation process, high heat dissipation, high external quantum efficiency, and high light emission output. That is.

A first means for solving the above-described problem is a method for manufacturing a nitride-based compound semiconductor light-emitting element,
(A) laminating a first nitride-based compound semiconductor layer on a first substrate;
(B) forming a metal film on the first nitride-based compound semiconductor layer;
(C) forming a void in the nitride compound semiconductor layer by heat-treating the first nitride compound semiconductor layer having the metal film formed on a surface thereof to form a network; and
(D) forming a light emitting element structure including a second nitride-based compound semiconductor layer on the network-like metal film;
(E) attaching a second substrate on the light emitting element structure;
(F) peeling off the layer made of the first substrate and the first nitride-based compound semiconductor from the light-emitting element structure;
It is a manufacturing method of the nitride type compound semiconductor light-emitting device characterized by including this.

A second means is a method for manufacturing the nitride-based compound semiconductor light-emitting element according to the first means,
A thickness of the first nitride compound semiconductor layer is set to 1000 nm or less.

A third means is a method for manufacturing the nitride-based compound semiconductor light-emitting element according to the first or second means,
A method for producing a nitride-based compound semiconductor light emitting device, wherein the second substrate has a thermal conductivity higher than that of the first substrate.

A fourth means is a method for producing a nitride-based compound semiconductor light-emitting element according to any one of the first to third means,
The method for producing a nitride-based compound semiconductor light-emitting element is characterized in that the peeling method in the step (f) is an etching method.

A fifth means is a method for producing a nitride-based compound semiconductor light-emitting element according to any one of the first to fourth means,
In the step of attaching the second substrate in the step (e), the surface of the light-emitting element structure to which the second substrate is attached is a p-type layer. Is the method.

As described above in detail, the present invention is a method for manufacturing a semiconductor light emitting device,
(A) laminating a first nitride-based compound semiconductor layer on a first substrate;
(B) forming a metal film on the first nitride-based compound semiconductor layer;
(C) forming a void in the nitride compound semiconductor layer by heat-treating the first nitride compound semiconductor layer having the metal film formed on a surface thereof to form a network; and
(D) forming a light emitting element structure including a second nitride-based compound semiconductor layer on the network-like metal film;
(E) attaching a second substrate on the light emitting element structure;
(F) peeling off the layer made of the first substrate and the first nitride-based compound semiconductor from the light-emitting element structure;
A nitride-based compound semiconductor light-emitting device comprising: a nitride-based LED that facilitates the electrode manufacturing process, has excellent heat dissipation, and has high light output. I can do it.

  Embodiments of a method for manufacturing a nitride-based compound semiconductor light-emitting element (hereinafter referred to as a nitride-based LED) according to the present invention will be described below with reference to the drawings based on examples.

  FIG. 1 is a schematic cross-sectional view of a wafer in steps (a) to (f) in the method for manufacturing a nitride LED described in the first means, and FIG. FIG. 3 is a more detailed cross-sectional view of the wafer and the nitride-based LED manufactured from the wafer in the step (e) described, and FIG. 3 is a cross-sectional view of the second embodiment of the nitride-based LED according to the present embodiment. FIG. 4 is a cross-sectional view of a nitride LED according to a comparative example.

  The manufacture of the nitride LED according to the present invention is performed as follows.

  First, as shown in FIG. 1A, a first nitride-based compound semiconductor layer (hereinafter referred to as a first nitride semiconductor layer) 20 is epitaxially grown on a first substrate 10. Here, the first substrate 10 is preferably a sapphire substrate, but is not limited thereto, and a single crystal substrate made of a nitride semiconductor, silicon carbide, silicon, an oxide material, or the like can also be used. The first nitride semiconductor layer 20 is preferably GaN, for example. A preferable film thickness will be described later.

  Next, as shown in FIG. 1B, a metal film 30 is formed on the first nitride semiconductor layer 20. Here, as the metal film 30, a Ti film can be preferably used.

  Next, as shown in FIG. 1C, the first substrate 10, the first nitride semiconductor layer 20, and the metal film 30 are heat-treated. Then, first, the metal film 30 has a mesh shape, and voids are formed in the first nitride semiconductor layer 20 starting from the mesh-shaped opening.

  In this embodiment mode, the heat treatment was performed in an atmosphere of 80% hydrogen and 20% ammonia at 1100 ° C. for 30 minutes.

  Next, as shown in FIG. 1 (d), a light emitting device structure including a second nitride-based compound semiconductor layer (hereinafter referred to as a second nitride semiconductor layer) on a network-like metal film 30. 40 is formed.

  Next, as shown in FIG. 1E, a second substrate 50 is attached on the light emitting element structure 40. Here, it is preferable to use the second substrate 50 having a higher thermal conductivity than the first substrate 10. By using a substrate having a high thermal conductivity for this portion, the heat dissipation of the nitride LED according to the present invention can be enhanced and the light emission output can be increased. The second substrate 50 is preferably CuW (copper tungsten), but is not limited thereto, and AlN (aluminum nitride), CuMo (copper molybdenum), Cu (copper), or the like can be used.

  Next, as shown in FIG. 1F, the first substrate 10 and the first nitride semiconductor layer 20 are peeled from the light emitting element structure 40 and the second substrate 50.

  In this peeling step, it was found that the influence of the void ratio, which is the ratio of the voids provided to the first nitride semiconductor layer 20 in the step (c), is large. It was found that the porosity is substantially determined by the film thickness of the first nitride semiconductor layer 20. That is, the thinner the film thickness, the higher the porosity of the first nitride semiconductor layer 20. And the yield at the time of peeling improves, so that the said porosity is high.

  Further, the peeling method includes a mechanical peeling method and a peeling method by etching, but it has been found that peeling by etching is preferable from the viewpoint of production yield in the peeling process.

  The relationship between the film thickness of the first nitride semiconductor layer 20, mechanical peeling and etching peeling, and the yield is shown as a list in FIG.

  In this embodiment mode, the etching separation is performed by etching with hydrofluoric acid for 30 minutes.

  From the result of FIG. 7, when the film thickness of the first nitride semiconductor layer 20 is 1000 nm or less, a satisfactory yield can be obtained by etching peeling, and the thinner the film thickness of the first nitride semiconductor layer 20 is. It has also been found that the yield is improved in mechanical peeling and etching peeling, and that if the film thickness of the first nitride semiconductor layer 20 is 400 nm or less, 100% yield can be obtained by any peeling method. .

(Example 1)
Here, Example 1 will be described with reference to FIGS.

  FIG. 2A is a schematic cross-sectional view of a wafer formed on a substrate, and FIG. 2B is a schematic cross-sectional view of a nitride LED manufactured from the wafer.

  2A, reference numeral 10 denotes a sapphire substrate as a first substrate, reference numeral 20 denotes an n-GaN layer as a first nitride semiconductor layer, and in FIGS. 2A and 2B, reference numeral 30 denotes a metal. Ti film as a film, reference numeral 41 is an n-A1GaN layer, reference numeral 42 is a GaN / A1GaN multiple quantum well layer, reference numeral 43 is a p-AlGaN layer, reference numeral 50 is a CuW substrate as a second substrate, FIG. Reference numeral 60 denotes an upper electrode, and reference numeral 70 denotes a bottom electrode. Note that the n-A1GaN layer 41, the GaN / A1GaN multiple quantum well layer 42, and the p-AlGaN layer 43 serve as the second nitride semiconductor layer and constitute the light emitting element structure 40.

  The production of the nitride LED according to Example 1 will be described.

  First, an n-GaN layer 20 is grown to 500 nm on the sapphire substrate 10, and then a Ti film 30 is formed to 30 nm. Then, heat treatment is performed in an atmosphere of 1100 ° C. of 80% hydrogen and 20% ammonia for 30 minutes to form a Ti film in a mesh shape A gap was generated in the n-GaN layer to form a base substrate. An n-A1GaN layer 41 (thickness 3 μm), a GaN / A1GaN multiple quantum well layer 42 (GaN thickness 2 nm, AlGaN thickness 4 nm), and p-AlGaN layer 43 (thickness 0.5 μm) are sequentially formed on the base substrate. Then, a CuW substrate 50 was stuck on the p-AlGaN layer 43.

At this time, the composition of the n-A1GaN layer _{41 n-Al X Ga 1-} X N (X = 0.2), the composition of the p-AlGaN layer _{43 p-Al X Ga 1-} X N (X = 0.2), and the pasting was performed by fusion by heat treatment at a high temperature.

  Thereafter, the base substrate was mechanically peeled off, and the upper electrode 60 was provided on the surface of the n-A1 GaN layer 41, and the bottom electrode 70 was provided on the bottom surface of the CuW substrate 50, thereby producing the nitride LED shown in FIG. . When a current of 20 mA was passed through the nitride LED, the emission wavelength was 354 nm and the emission output was 3.2 mW.

  The light emission characteristics of the manufactured nitride LED according to Example 1 are shown in FIG.

  FIG. 5 is a graph in which the horizontal axis represents the injection current value (mA) and the vertical axis represents the light emission output (mW).

(Comparative example)
Here, the comparative example which concerns on a prior art is demonstrated, referring FIG.

  FIG. 4 is a schematic cross-sectional view of a nitride-based LED according to the prior art.

  In FIG. 4, each symbol is the same as in FIGS. 2A and 2B described above, but does not have the Ti film 30, the CuW layer 50, and the bottom electrode 70, but has a counter electrode 80 instead.

  The production of a nitride LED according to the prior art will be described.

  First, the n-GaN layer 20 is grown on the sapphire substrate 10 by 500 nm, then the n-A1 GaN layer 41 (thickness 3 μm), the GaN / A1GaN multiple quantum well layer 42 (GaN thickness 2 nm, AlGaN thickness 4 nm), A p-AlGaN layer 43 (thickness 0.5 μm) was sequentially formed to produce a wafer. The compositions of the n-A1 GaN layer 41 and the p-AlGaN layer 43 were the same as those in Example 1.

  The surface of the fabricated wafer is partially removed by RIE (Reactive Ion Etching), a part of the n-GaN layer 20 is exposed, and a counter electrode 80 is provided here, and the conventional technique shown in FIG. A nitride-based LED was produced. When a current of 20 mA was passed through the nitride LED, the emission wavelength was 354 nm and the emission output was 0.05 mW.

  The light emission characteristics of the fabricated nitride LED are shown in FIG.

  FIG. 6 is a graph with the injection current value (mA) on the horizontal axis and the light emission output (mW) on the vertical axis, as in FIG.

(Evaluation 1)
Comparing Example 1 and the comparative example, when each of the nitride LEDs was energized with 20 mA, as described above, the emission output of Example 1 was 3.2 mW at the emission wavelength of 354 nm. The comparative example was 0.05 mW.

  When the emission wavelength is 380 nm or less, the light emission begins to be absorbed by the GaN layer. In the nitride LED according to Example 1, both the sapphire substrate and the GaN layer are separated from the nitride LED. It is considered that the light absorption is reduced due to this separation, the external quantum efficiency is improved, and the light emission output is increased.

  Furthermore, in the nitride-based LED according to Example 1, the insulating sapphire substrate was peeled off and the conductive CuW substrate was used, so that the surface of the nitride-based LED epitaxial wafer was formed by a method such as RIE in the electrode formation process. The man-hour for etching was saved.

  Further, as is clear from the comparison between FIG. 5 and FIG. 6, the light emission output of the nitride LED according to Example 1 increased temporarily as the injection current value increased, and a high light output was obtained. On the other hand, in the nitride-based LED according to the prior art, the light emission output tends to saturate without increasing temporarily as the injection current value increases, and the light emission output itself is also the nitride according to the present invention described above. Compared with system LED, it remained at about 1/60 or less. This is because, in the nitride LED according to the present invention, the sapphire substrate having a low thermal conductivity is peeled off, and the CuW substrate having a higher thermal conductivity than the sapphire substrate is attached, so that the heat dissipation is improved and the injection current value is increased. This is considered to be because the light emission output is less likely to be saturated even if the increase is increased.

(Example 2)
Here, Example 2 will be described with reference to FIG.

  FIG. 3 is a schematic cross-sectional view of the nitride LED according to the second embodiment.

  In FIG. 3, each symbol is the same as that in FIGS. 2A and 2B described above, but an n-A1GaN layer 41, a GaN / A1GaN multiple quantum well layer 42, and a p-AlGaN layer are sequentially formed on the CuW substrate 50. 43 is provided to form the second nitride semiconductor layer and constitute the light emitting element structure 40. An upper electrode 60 is provided on the p-AlGaN layer 43, and a bottom electrode 70 is provided on the bottom surface of the CuW substrate 50.

  The production of a nitride LED according to Example 2 will be described.

  Similarly to Example 1, after forming the n-GaN layer 20 and the Ti film 30 on the sapphire substrate 10, heat treatment was performed to form a base substrate. A p-AlGaN layer 43 (thickness 0.5 μm), a GaN / A1GaN multiple quantum well layer 42 (GaN thickness 2 nm, AlGaN thickness 4 nm), and n-A1GaN layer 41 (thickness 3 μm) are sequentially formed on the base substrate. Finally, a CuW substrate 50 was pasted thereon. The compositions of the n-A1 GaN layer 41 and the p-AlGaN layer 43 were the same as those in Example 1.

  Thereafter, the base substrate was mechanically peeled off, and the upper electrode 60 was provided on the surface of the p-A1 GaN layer 43, and the bottom electrode 70 was provided on the bottom surface of the CuW substrate 50, thereby producing the nitride LED shown in FIG.

  When a current of 20 mA was passed through the nitride LED, the emission wavelength was 354 nm and the emission output was 1.4 mW.

(Evaluation 2)
Comparing Example 1 and Example 2, when each nitride LED was energized with a current of 20 mA, as described above, the emission wavelength of 354 nm and the emission output of Example 1 was 3.2 mW. On the other hand, Example 2 was 1.4 mW.

  The cause of this difference in light emission output is considered as follows.

  That is, since it is generally difficult to reduce the resistance of the p-type layer in a nitride semiconductor, the p-type layer is less susceptible to current dispersion than the n-type layer. Here, in the nitride LED according to Example 1, since the CuW substrate 50 is attached to the p-AlGaN layer 43 side which is a p-type layer, even if current distribution of the p-type layer is difficult to occur, Current can be injected over the entire surface. As a result, the problem that current dispersion hardly occurs in the p-type layer is overcome, and the nitride LED according to Example 1 is considered to be able to obtain a high light emission output.

  On the other hand, in the nitride-based LED according to Example 2, the p-AlGaN layer 43 side which is a p-type layer is the light extraction side and the upper electrode 60 is provided, so that the upper electrode 60 is spread over the entire surface of the layer. I can't. For this reason, the injection current is diffused in the p-AlGaN layer 43. However, since the current diffusion in the p-type layer is difficult as described above, the light emitting area is reduced. It is considered that the light output remained lower than that of the LED.

It is typical sectional drawing of the wafer in the wafer manufacturing process which concerns on the Example of this invention. It is a more detailed sectional view of a wafer concerning Example 1 of the present invention, and nitride system LED produced from the wafer concerned. It is sectional drawing of nitride type LED which concerns on Example 2 of this invention. It is sectional drawing of nitride type LED which concerns on the comparative example of this invention. It is a LI characteristic figure of nitride system LED concerning Example 1 of the present invention. It is a LI characteristic figure of nitride system LED concerning a comparative example of the present invention. 6 is a table showing the relationship between the film thickness of the first nitride semiconductor layer and the presence / absence of combined use of the metal film and the yield at the time of mechanical peeling.

Explanation of symbols

10 First substrate (sapphire substrate)
20 First nitride semiconductor layer (n-GaN layer)
30 Metal film (Ti film)
40 Light emitting device structure (second nitride semiconductor layer)
41 n-AlGaN layer 42 GaN / AlGaN multiple quantum well layer 43 p-AlGaN layer 50 Second substrate (CuW substrate)
60 Upper electrode 70 Bottom electrode 80 Counter electrode

Claims (5)

A method for manufacturing a nitride-based compound semiconductor light-emitting device, comprising:
(A) laminating a first nitride-based compound semiconductor layer on a first substrate;
(B) forming a metal film on the first nitride-based compound semiconductor layer;
(C) forming a void in the nitride compound semiconductor layer by heat-treating the first nitride compound semiconductor layer having the metal film formed on a surface thereof to form a network; and
(D) forming a light emitting element structure including a second nitride-based compound semiconductor layer on the network-like metal film;
(E) attaching a second substrate on the light emitting element structure;
(F) peeling off the layer made of the first substrate and the first nitride-based compound semiconductor from the light-emitting element structure;
A method for producing a nitride-based compound semiconductor light-emitting device comprising: A method for producing a nitride-based compound semiconductor light-emitting device according to claim 1,
A method for manufacturing a nitride-based compound semiconductor light-emitting element, wherein the first nitride-based compound semiconductor layer has a thickness of 1000 nm or less. A method for producing a nitride-based compound semiconductor light-emitting device according to claim 1 or 2,
A method for producing a nitride-based compound semiconductor light-emitting element, wherein the second substrate has a thermal conductivity higher than that of the first substrate. A method for producing a nitride-based compound semiconductor light-emitting device according to claim 1,
The method for producing a nitride-based compound semiconductor light-emitting element, wherein the peeling method in the step (f) is an etching method. A method for producing a nitride-based compound semiconductor light-emitting device according to claim 1,
In the step of attaching the second substrate in the step (e), the surface of the light-emitting element structure to which the second substrate is attached is a p-type layer. Method.

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