JP2008124375A - Method of manufacturing light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light-emitting device with which the light-emitting device can be manufactured without reflectance reduction through a simple method without alloying metals on joint faces. <P>SOLUTION: A selective working layer 2 and a light-emitting device layer 8 are sequentially formed on a seed substrate 1. Then, a first metal layer 9 that becomes a reflection layer, is formed over all or in a part of the light-emitting device layer, and a second metal layer 10 having etching resistant characteristics is formed at least on a side surface of the first metal layer 9. Furthermore, the second metal layer 10 is bonded on a support substrate 11 and the seed substrate is removed from the selective working layer. In the present invention, the first metal layer is covered with the second metal layer with high corrosion resistance, alloying is obviated and high reflectance can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, in a light-emitting element, many structures have been proposed in which light directed toward a substrate is reflected by being attached to a material substrate having a mirror effect or a substrate having good thermal conductivity for high luminance and high efficiency.

  In this method, first, a light emitting device portion grown on a seed substrate is attached to another substrate on which a material having a high reflectance with respect to the light emission wavelength band of the device is formed. Thereafter, the seed substrate which is a light-emitting absorption layer is selectively removed by etching, and light is extracted from the removed surface. In this method, since the chemical solution for etching away the seed substrate is often a reactive chemical solution having strong erodibility, it is necessary to use a material having high corrosion resistance for the metal on the bonding surface.

Therefore, as described in Patent Document 1, there is a method using Ag as a main component and an alloy with another metal in order to maintain high reflectivity and provide corrosion resistance to the etching solution. .
JP 2005-197296 A

  In the method of Patent Document 1, when Ag having high reflectivity with respect to the green to red wavelength band of GaAs and InP is alloyed with other dissimilar metals, the reflectivity decreases in proportion to the composition of the contained components. To do.

  In addition, in order to form an alloy having both reflectivity and corrosion resistance, it is necessary to control the composition within a certain range, and it is necessary to create a sputter target controlled by stoichiometry. This leads to a complicated manufacturing process.

  An object of the present invention is to provide a method for manufacturing a light-emitting device capable of manufacturing a light-emitting device that does not cause a decrease in reflectance by a simple method without alloying the metal on the bonding surface.

  In the present invention, a separation layer and a light emitting device layer are sequentially formed on a first substrate, and then a first metal layer that becomes a reflective layer is formed on the entire surface or part of the light emitting device layer. Next, a second metal layer having etching resistance characteristics is formed on at least the side surface of the first metal layer. Further, after the second metal layer is bonded to the second substrate, the first substrate is removed from the separation layer. In the present invention, since the first metal layer is covered with the second metal layer having high corrosion resistance, alloying is unnecessary and high reflectance can be obtained.

  According to the present invention, since it is not necessary to alloy the bonding surface, a high reflectance can be obtained and the manufacturing process can be simplified. Moreover, it can bond favorably with respect to a support substrate.

  Next, a method for manufacturing a light emitting device according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 7 are conceptual diagrams for explaining a manufacturing process of an embodiment of a light emitting device according to the present invention.

  FIG. 1 shows a state in which a light emitting device layer 8 is stacked on a seed substrate 1. First, a selective processing layer (separation layer) 2, a first contact layer 3 doped with a first conductivity type impurity at a high concentration, and a first conductivity type carrier are diffused on the seed substrate 1. 1 current diffusion layer 4 and light emitting layer 5 are laminated in this order.

  The light emitting layer 5 is made of n homojunction type, quantum well type, or double hetero type. A second current diffusion layer 6 for diffusing carriers of the second conductivity type and a second contact layer 7 doped with a high concentration of impurities of the second conductivity type are stacked in this order on the light emitting layer 5. . FIG. 1 is a schematic cross-sectional view during the manufacture of a light-emitting device.

  Here, a stack of the first contact layer 3, the first current diffusion layer 4, the light emitting layer 5, the second current diffusion layer 6, and the second contact layer 7 is referred to as a light emitting device layer 8. The first and second contact layers 3 and 7 are preferably formed in order to improve electrical continuity with the upper and lower wirings and the substrate.

  Next, as shown in FIG. 2, the first metal layer 9 having a high reflectance in the emission wavelength band of a light emitting device such as Ag or Al is formed on a part (or all) of the second contact layer 7. As a film forming method, a method having excellent flatness is preferable in consideration of bonding to a support substrate described later. For example, a vapor deposition method, a sputtering method, etc. are mentioned.

  As the patterning method, unnecessary portions may be selectively removed with a lithography pattern after film formation on the entire surface, or selective film formation of a region using a metal mask may be used.

  Subsequently, as shown in FIG. 3, a second metal layer 10 having excellent corrosion resistance such as Au and Pt is formed over the entire surface so as to cover the first metal layer 9. That is, the second metal layer 10 is formed so as to cover not only the surface of the first metal layer 9 but also the side surfaces. This film forming method is also preferably formed by vapor deposition, sputtering, or the like for the same reason as the first metal layer 9.

  Next, as shown in FIG. 4, a device substrate in which the selective processing layer 2, the light emitting device layer 8, the first and second metal layers 9, 10 are formed on the seed substrate 1 is separated from the metal layer side to another support substrate. 11 to produce a composite member. When the support substrate 11 is a Si substrate, it is easy to obtain a bond with high adhesion particularly when the second metal layer 10 is Au. In order to increase the bonding force, the application of pressure and temperature is commonly used.

  Further, since Au-Au bonding is less likely to cause surface oxidation and change of state, generally direct bonding is easy and high strength can be obtained. It is also a useful technique to form metal for use.

  FIG. 5 shows a step of removing the seed substrate 1 from the composite member by immersing the composite member produced by the above process in the first chemical solution 12 having a high etching rate in the selective processing layer 2. In general, these chemical solutions are acid-based chemical solutions having strong reactivity. However, by coating the side portion exposed to the chemical solution with the second metal layer 10 (Au, Pt, etc.) having strong corrosion resistance, The first metal layer 9 (Ag, Al, etc.) that is easily eroded can be protected.

  FIG. 6 shows another process for removing the seed substrate 1. That is, the step of removing the seed substrate 1 from the composite member by immersing the composite member manufactured by the above process in the second chemical solution 13 having a high etching rate in the seed substrate 1 is shown.

  Similar to the removing step shown in FIG. 5, the first metal layer 9 (Ag, Al, etc.) can be protected by coating with the second metal layer 10 (Au, Pt, etc.) having strong corrosion resistance. If a material having a significantly lower rate than the second chemical solution 13 is used for the selective processing layer 2, the margin of the seed substrate removal process can be expanded.

  FIG. 7 is a sectional view showing a light emitting device according to the present invention. As shown in FIG. 7, the light emitting device layer 8 is transferred onto the support substrate 11 by the above process, and the seed substrate 1 and the selective processing layer 2 are removed. A second conductivity type current injection electrode 14 is formed on the exposed first contact layer 3. Electrons and holes injected by energization between the electrode 14 and the support substrate 11 recombine and emit light in the light emitting layer 5.

  Here, of the light emitted from the light emitting layer 5 as shown in FIG. 7, the light 15 traveling to the support substrate 11 side is reflected by the first metal layer 9 and contributes to the improvement of the extraction efficiency. Alloying for improving the corrosion resistance of one metal layer 9 is unnecessary. Therefore, the man-hour for preparing the alloy target can be reduced and the luminous efficiency can be improved.

  Here, the seed substrate 1, the selective processing layer 2, and the light emitting layer 5 are made of a material selected from any group of GaAs, AlGaAs, InGaAs, InGaAsP, InP, and InGaP, for example.

  Next, a preferred embodiment of the present invention will be described by way of example.

(First embodiment)
A manufacturing method of the first embodiment of the light emitting device according to the present invention will be described with reference to FIGS. As shown in FIG. 1, for example, the structure of each layer in the case of a double hetero LED element is as follows. The following layer numbers correspond to the layer numbers in FIGS. For example, 1 is a seed substrate and 2 is a selective processing layer. First, as shown in FIG. 1 and the following table, each layer is laminated on the seed substrate 1.
Layer Material (Composition) Film thickness (nm) Dopant Dope level Polar Film type 1 GaAs-C 1e18 P Substrate 2 AlAs 50 C 1e18 P Separation layer 3 GaAs 100 C 1e20 P Contact layer 4 AlxGaAs 20 C 1e18 P Current diffusion layer
x (0.05⇒0.40)
5 Al0.40GaAs 400 C 1e18 P cladding layer 5 Al0.13GaAs 300 Zn 2e17 P light emitting layer 5 Al0.23GaAs 600 Si 3e18 N cladding layer 6 AlxGaAs 20 Si 3e18 N current diffusion layer
x (0.23⇒0.05)
7 GaAs 50 Si 4e18 N Contact Layer Next, after the device layer is formed, the wafer edge is shielded with a metal mask, and Ag 50 nm (first metal layer) is formed by sputtering (FIG. 2).

  Next, the metal mask is removed, and Au is sputtered to a thickness of 100 nm (second metal layer) over the entire surface (FIG. 3).

  The device substrate is bonded to the Au sputtering surface side on a Si substrate (support substrate 11) that has been cleaned and subjected to natural oxide film removal, and is crimped under conditions of 0.05 MPa, 200 ° C., and 10 minutes to form a composite member. (FIG. 4).

  Next, the composite member is immersed in a chemical solution of 1: 10 = HF: H20 (FIG. 5). Since the etching rate of the selective processing layer (AlAs) 2 is faster than other constituent materials, the seed substrate 1 (GaAs) is removed by continuing the immersion.

  Subsequently, as shown in FIG. 7, the second conductivity type current injection electrode 14 is formed on the exposed first contact layer 3 of the light emitting device layer 8 transferred onto the Si substrate (support substrate 11) manufactured by the above process. Form. As described above, electrons and holes injected by energization between the support substrate 11 and the electrode 14 recombine and emit light in the light emitting layer 5.

  Here, out of the light emitted from the light emitting layer 5, the light 15 traveling toward the support substrate 1 is reflected by the first metal layer 9 and emitted from the surface, so that the extraction efficiency is improved.

(Second embodiment)
Next, a second embodiment of the present invention will be described. The device layer configuration such as the selective processing layer, the configuration of the metal layer, and the formation of the composite member are the same as those in the first embodiment.

  In Example 2, it is immersed in NH4OH / H2O2 / H2O2 = 1: 1: 10 mixed solution chemical | medical solution (FIG. 6). Since this chemical solution has a very high selection ratio with respect to GaAs / AlAs, the seed substrate 1 is dissolved in the chemical solution from the back surface and can be removed up to the AlAs by continuing the immersion. As described above, a material (slow material) having a significantly lower rate than the second chemical liquid 13 is used as the selective processing layer 2. By doing so, the selective processing layer 2 becomes a selective stopper layer when the seed substrate 1 is etched.

  At this time, the light emitting device layer 8 is also etched from the side surface, but the dimension in the side surface direction is sufficiently large with respect to the substrate thickness, and the overlap amount of the first metal layer 9 and the second metal layer 10 is sufficiently large. Design large. By doing so, the influence of etching from the side surface does not affect the subsequent process and device structure.

  Further, since the selective processing layer 2 (AlAs) used as the selective stopper layer is unnecessary for the device, it is removed by HF immersion after the removal of the seed substrate (GaAs) 11. The subsequent light-emitting device manufacturing procedure is the same as in Example 1. In the second embodiment, it is possible to improve the extraction efficiency as in the first embodiment.

It is a figure which shows typically the cross section of the light emitting element in which the light emitting element structure was formed through the separated layer on the seed substrate. It is a figure which shows typically the cross section of the light emitting element in which the 1st metal layer was partially formed on the device layer of a seed substrate. It is a figure which shows typically the cross section of the light emitting element in which the 2nd metal layer was formed into the whole surface so that the 1st metal layer partially formed on the seed substrate might be covered. It is a figure which shows typically the composite member cross section which bonded the seed substrate to the support substrate with the electrode surface facing down. It is a figure which shows typically the structure cross section at the time of removing a board | substrate by immersing the composite member after bonding in a chemical | medical solution and etching a separated layer. It is a figure which shows typically the structure cross section at the time of removing a board | substrate by immersing the composite member after bonding in a chemical | medical solution and etching a seed board | substrate. It is a figure which shows typically the light emitting device cross section which formed the metal electrode in the exposed surface of the light emitting device layer after board | substrate removal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Seed substrate 2 Selective processing layer 3 1st conductivity type contact layer 4 1st conductivity type current spreading layer 5 Light emitting layer 6 2nd conductivity type current spreading layer 7 2nd conductivity type contact layer 8 Light emitting device layer 9 2nd conductivity type 1st 1 metal layer 10 2nd conductivity type 2nd metal layer 11 support substrate 12 1st chemical | medical solution 13 2nd chemical | medical solution 14 2nd conductivity type metal electrode 15 light

Claims (8)

Forming a separation layer on the first substrate;
Forming a light emitting device layer on the separation layer;
Forming a first metal layer to be a reflective layer on the entire surface or part of the light emitting device layer;
Forming a second metal layer having etching resistance on at least a side surface of the first metal layer;
Bonding the second metal layer to a second substrate;
Removing the first substrate from the separation layer;
Forming an electrode on the light emitting device layer on the second substrate;
A method for manufacturing a light-emitting device comprising: In the step of removing the first substrate, the first substrate is removed from the separation layer by etching the separation layer using a chemical having a high etching rate with respect to the separation layer. The manufacturing method of the light-emitting device of Claim 1. In the step of removing the first substrate, the first substrate is etched by using a chemical solution having a high selection ratio with respect to the first substrate and using the separation layer as a stopper layer. The method for manufacturing a light-emitting device according to claim 1, wherein the substrate is removed from the separation layer. 4. The method of manufacturing a light emitting device according to claim 1, wherein the second metal layer is formed on the entire surface including a side surface of the first metal layer. 5. The first substrate, the separation layer, and the light emitting device layer are made of a material selected from any one of GaAs, AlGaAs, InGaAs, InGaAsP, InP, and InGaP groups. 5. A method for producing a light emitting device according to any one of 4 above. The method of manufacturing a light emitting device according to claim 1, wherein the first metal layer is made of Ag or Al. The method for manufacturing a light-emitting device according to claim 1, wherein the second metal layer is Au or Pt. The method for manufacturing a light emitting device according to claim 1, wherein the second substrate is a Si substrate.

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