TWI702733B - Mounting method of light-emitting element - Google Patents

Abstract

A method for mounting light-emitting elements on a starting substrate, with the starting substrate phase lattice matching The first semiconductor layer, the active layer, the second semiconductor layer, and the buffer layer are sequentially formed by epitaxial growth; on the buffer layer, the non-lattice-matched material for the starting substrate is formed by epitaxial growth Forming the window layer and supporting substrate; removing the starting substrate; forming the first ohmic electrode on the first semiconductor layer; forming part of the exposed second semiconductor layer, buffer layer or window layer and supporting substrate to remove the part to set the step; Part forms the second ohmic electrode; separates the light-emitting element formed with the first and second ohmic electrodes to produce a light-emitting element chip, and flip-chip mounts the light-emitting element chip on the mounting substrate to form the first and second ohmic electrodes on the light-emitting element chip The side is the mounting board side.

Description

Mounting method of light-emitting element

The present invention relates to a mounting method of a light-emitting element, and particularly relates to a mounting method of a light-emitting element in which a light-emitting element chip is flip-chip mounted on a mounting substrate.

Products such as Chip On Board (COB) are excellent in the heat dissipation of LED elements, so they are an LED chip mounting method used in lighting and other applications. In the case of mounting LEDs such as COB, a flip-chip mounting system that directly bonds the chip to the board is necessary. In the case of flip-chip mounting of LED components, there are methods such as Au-Au bonding by ultrasonic waves and eutectic soldering.

In the case of fabricating flip-chip mounted chips using yellow to red LEDs, AlGaInP-based materials are used for the light-emitting layer. Since there is no crystal block in AlGaInP-based materials and the LED part is formed by epitaxial method, the starting substrate is selected as a different material from AlGaInP. The starting substrate is mostly selected as GaAs or Ge. Because these substrates have light absorption characteristics for visible light, the starting substrate will be removed when fabricating flip-chip mounted chips.

However, since the epitaxial layer forming the light-emitting layer is an extremely thin film, it cannot survive independently after removing the starting substrate. Therefore, it is necessary to replace the starting substrate with a material and structure that has a function as a window layer when the light-emitting layer is slightly transparent to the emission wavelength, and has a function as a supporting substrate for independent existence and a sufficient thickness.

As mentioned above, since there is no crystal block in AlGaInP-based materials, GaP, GaAsP, sapphire, etc. are selected as the material having the function of the aforementioned window layer and supporting substrate. regardless Which of these materials is selected is also different from AlGaInP, and mechanical properties such as thermal expansion coefficient and Young's modulus are different from AlGaInP.

With the ultrasonic Au-Au bonding, as described in a non-patent document 1, it is difficult to support the wafer without tilting, and there are problems such as the inability to efficiently propagate ultrasonic waves to the wafer, and the wafer will be damaged during ultrasonic propagation. .

In order to solve the above problems, the technique of forming AuSn eutectic bumps and performing bonding with the substrate by thermal melting (reflow temperature 211~280°C) has been disclosed. Compared with the ultrasonic method, the eutectic method is less likely to cause physical damage accompanying the ultrasonic wave. However, during the melting and solidification process of eutectic welding, the eutectic metal itself will heat shrink. As a result, stress occurs in the vicinity of the semiconductor-side interface where the eutectic metal and the LED are in contact, and this stress can cause damage to the wafer and cause problems.

Furthermore, the difference in thermal expansion coefficient caused by the difference between the material of the window layer and supporting substrate and the material of the AlGaInP light-emitting layer will also increase the problems caused by the above-mentioned thermal melting step. That is, the linear expansion coefficient of AlGaInP-based materials is 5.4E-6[/k], the linear expansion coefficient of GaP is 4.5E-6[/k], and the linear expansion coefficient of sapphire is 7.0E-6[/k]. Therefore, in the case of mounting by thermal fusion treatment, when the window layer and supporting substrate is GaP, compressive stress occurs in the AlGaInP light-emitting layer, and tensile stress occurs in the window layer and supporting substrate. When the window layer and support substrate is sapphire, tensile stress occurs in the AlGaInP light-emitting layer, and compressive stress occurs in the window layer and support substrate. This stress can also cause wafer damage.

During flip chip mounting, the surfaces formed on the first and second ohmic electrode sides of the light-emitting element chip will press the mounting substrate side. At this time, although the light-emitting element chip sinks into the mounting surface side due to the deformation of the metal portion on the mounting surface side due to the pressure of the light-emitting element chip, the deformation is not large. Therefore, the section of the first ohmic electrode and the second ohmic electrode on the light-emitting element chip disposed on the mounting surface In the case of a large difference, the amount of deformation of the metal of the first ohmic electrode connected to the mounting surface is insufficient. Although the surface of the first ohmic electrode fully contacts the mounting surface, it may happen that the surface of the second ohmic electrode does not contact the mounting surface. phenomenon. As a result, there will be a short circuit, so there will be a problem that it cannot be installed. Therefore, generally speaking, bumps are provided on the first ohmic electrode and the second ohmic electrode to increase the deformation of the electrode. However, the bump system must be thickly formed of Au (gold) using a gold plating method or the like, and the material cost becomes very expensive.

[Prior technical literature] 〔Non-patent literature〕

[Non-Patent Document 1] Nikkei Electronics, Nikkei BP, February 11, 2008

In view of the above-mentioned problems, the present invention provides a method for mounting light-emitting elements that can suppress the damage accompanying the use of ultrasonic flip-chip mounting, and can suppress the heat shrinkage caused by the flip-chip mounting using eutectic soldering Furthermore, even when the step difference between the first ohmic electrode and the second ohmic electrode is large, the light-emitting element chip can be easily mounted.

In order to achieve the above-mentioned object, the present invention provides a method for mounting a light-emitting element, which includes the following steps: on a starting substrate, growing by epitaxial growth with a material that is lattice-matched to the starting substrate, A first semiconductor layer, an active layer, a second semiconductor layer, and a buffer layer are sequentially formed; on the buffer layer, a material that is non-lattice-matched to the starting substrate is formed by epitaxy Long and forming a window layer and supporting substrate; removing the starting substrate; forming a first ohmic electrode on the first semiconductor layer; forming part of the second semiconductor layer, the buffer layer or the window layer and supporting substrate The exposed removal part is provided with a step; a second ohmic electrode is formed in the removed part; the light-emitting element formed with the first and second ohmic electrodes is separated to produce a light-emitting element chip, and the flip chip is mounted on the mounting substrate The light-emitting element wafer is formed on the side on which the first and second ohmic electrodes are formed as the mounting substrate side.

In this way, by forming the window layer and support substrate by epitaxial growth, a large number of rows are inserted into the window layer and support substrate. When ultrasonic mounting is subjected to stress that applies pressure to the chip, the window layer The supporting substrate is deformed along the differential surface, which can suppress the stress damage of the wafer. Furthermore, in flip-chip mounting using eutectic metal, the window layer and support substrate will deform along the differential surface due to the expansion due to heating and the shrinkage when returning to room temperature, which can suppress Stress failure of the wafer. Furthermore, even if the level difference between the first ohmic electrode and the second ohmic electrode is large, it is possible to prevent damage to the light-emitting element during flip-chip mounting, and to easily mount the light-emitting element chip.

At this time, the first semiconductor layer, the active layer, and the second semiconductor layer are preferably AlGaInP or AlGaAs.

In this way, as the first semiconductor layer, the active layer, and the second semiconductor layer, the materials described above can be suitably used.

In addition, at this time, the window layer and supporting substrate are preferably GaP or GaAsP.

In this way, as the window layer and supporting substrate, the same material as described above is used, which is suitable as the window layer system and can reliably suppress the stress breakage of the wafer during flip chip mounting.

Furthermore, at this time, the step difference between the first ohmic electrode and the second ohmic electrode can be 3 μm or more and 11 μm or less.

In this way, even if the step difference between the first ohmic electrode and the second ohmic electrode is large as described above, the effect can be fully exerted.

The mounting method of the light-emitting element of the present invention, by forming the window layer and support substrate by epitaxial growth and inserting a large number of rows into the window layer and support substrate, when ultrasonic mounting is subjected to stress that applies pressure to the chip Because the window layer and supporting substrate deform along the differential surface, the stress damage of the chip can be suppressed. In the flip chip mounting using eutectic metal, the expansion due to heating shrinks when returning to room temperature Among them, since the window layer and supporting substrate deform along the differential surface, stress damage of the chip can be suppressed. Furthermore, even if the level difference between the first ohmic electrode and the second ohmic electrode is large, it is possible to prevent damage to the light-emitting element during flip-chip mounting, and to easily mount the light-emitting element chip.

1: Light-emitting element chip

11: Light-emitting component chip

101: starting substrate

102: Select etching layer

102A: second choice etching layer

102B: First choice etching layer

103: The first semiconductor layer

103A: Low Al composition layer

103B: High Al composition layer

104: active layer

105: second semiconductor layer

106: buffer layer

107: Window layer and supporting substrate

108: light-emitting part

109: Epitaxy substrate

110: Light-emitting element substrate

121: first ohm electrode

122: second ohm electrode

122a: predetermined range

123: photoresist mask

140: range

141: Formation Department

142: Scribe range

150: insulating protective film

170: removal part

180: Non-removal part

201: light-emitting element chip

301: Starting substrate

302: Select etching layer

302A: second selective etching layer

302B: First choice etching layer

303: The first semiconductor layer

304: active layer

305: second semiconductor layer

306: buffer layer

307: Current Diffusion Layer

308: Light-emitting part

309: Epitaxy substrate

310: GaP single crystal substrate

311: Light-emitting element substrate

321: first ohm electrode

322: second ohm electrode

340: range

342: Scribe Range

350: insulating protective film

380: Non-removal part

Fig. 1 is a step diagram showing an example of the mounting method of the light-emitting element of the present invention.

Fig. 2 is a schematic diagram of an epitaxial substrate having a selective etching layer, a light emitting portion, and a window layer and supporting substrate grown on a starting substrate in the method for mounting a light emitting element of the present invention.

FIG. 3 is a schematic view of the light-emitting element substrate in which the starting substrate and the second selective etching layer are removed from the epitaxial substrate in the method of mounting a light-emitting element of the present invention.

Fig. 4 is a schematic view of a light-emitting element substrate on which a first ohmic electrode is formed in the method of mounting a light-emitting element of the present invention.

Fig. 5 is a schematic view of a light-emitting element substrate that has been subjected to the first surface roughening treatment in the light-emitting element mounting method of the present invention.

Fig. 6 is a schematic view of the light-emitting element substrate on which the removed portion and step formation step of the light-emitting element mounting method of the present invention have been performed.

Fig. 7 is a schematic view of a light-emitting element substrate on which a second ohmic electrode is formed and an insulating protective film is formed in the light-emitting element mounting method of the present invention.

Fig. 8 is a schematic diagram showing a light-emitting element wafer produced by separating light-emitting elements in the method of mounting a light-emitting element of the present invention.

Fig. 9 is a schematic diagram of a light-emitting element substrate subjected to the first surface roughening treatment according to the embodiment.

Fig. 10 is a schematic view showing the light-emitting element substrate on which the step of forming the removed portion and the step of the embodiment has been performed.

Fig. 11 is a schematic diagram showing a light-emitting element substrate on which a second ohmic electrode is formed and an insulating protective film is formed according to the embodiment.

Fig. 12 is a schematic diagram showing a light-emitting element wafer produced by separating the light-emitting elements of the example.

FIG. 13 is a schematic view showing an epitaxial substrate in which a selective etching layer, a light-emitting portion, and a window layer and supporting substrate are grown on the starting substrate of the comparative example.

Fig. 14 is a schematic diagram showing a substrate in which a GaP single crystal substrate is bonded to an epitaxial substrate of a comparative example.

FIG. 15 is a schematic diagram showing the bonding substrate in which the starting substrate and the second selective etching layer are removed from the epitaxial substrate of the comparative example.

Fig. 16 is a schematic view showing the bonded substrate on which the first ohmic electrode is formed in the comparative example.

Fig. 17 is a schematic diagram showing the bonded substrate on which the first surface roughening treatment has been performed in the comparative example.

Fig. 18 is a schematic view showing the bonded substrate on which the removed portion, the step forming step, and the second ohmic electrode are formed in the comparative example.

Fig. 19 is a schematic view showing a bonded substrate on which an insulating protective film is formed in a comparative example.

Fig. 20 is a schematic diagram showing a light-emitting element wafer prepared by separating the light-emitting elements of the comparative example.

Fig. 21 is a graph showing the incidence of defects when mounting using ultrasonic waves in Examples and Comparative Examples.

Fig. 22 is a graph showing the incidence of defects when mounting using a eutectic metal layer in Examples and Comparative Examples.

Fig. 23 is a graph showing the relationship between the first ohmic electrode and the second ohmic electrode in the example and the comparative example when the step difference is changed.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these.

As mentioned above, there is a problem of causing damage to the light-emitting device chip during flip-chip mounting. Herein, the inventors of the present invention have studied diligently to solve such problems. As a result, it was found that by epitaxially growing the window layer and support substrate with a non-lattice-matched material for the starting substrate, it was discovered that there are many gaps inserted in the window layer and support substrate. It was found that it is possible to suppress the destruction of the chip during ultrasonic mounting and flip-chip mounting using eutectic metal. Furthermore, even when the step difference between the first ohmic electrode and the second ohmic electrode is large, it can be While preventing the damage of the light-emitting element during flip-chip mounting, the light-emitting element chip is easily mounted.

Hereinafter, the mounting method of the light-emitting element of the present invention will be described with reference to FIGS. 1 to 8.

First, the starting substrate 101 shown in FIG. 2 (SP1 in FIG. 1) is prepared.

As the starting substrate 101, it is preferable to use the starting substrate 101 whose crystal axis is inclined from the [001] direction to the [110] direction. Furthermore, as the starting substrate 101, GaAs or Ge can be suitably used. In this way, since the material of the active layer 104 described later can be epitaxially grown in a lattice matching system, the quality of the active layer 104 can be easily improved, and the brightness and life characteristics can be improved.

Next, a selective etching layer 102 (SP2 in FIG. 1) may also be formed on the starting substrate 101. The selective etching layer 102 is on the starting substrate 101 and can be grown by, for example, MOVPE (metal organic vapor growth method), MBE (molecular epitaxy) or CBE (chemical epitaxy).

The selective etching layer 102 is composed of a layer structure of two or more layers, and preferably has at least a second selective etching layer 102A connected to the starting substrate 101 and a first selective etching layer 102B connected to the first semiconductor layer 103 described later . The second selective etching layer 102A and the first selective etching layer 102B are preferably composed of different materials or compositions.

Next, on the starting substrate 101, it is grown by epitaxial growth to sequentially form a light emitting layer composed of a first semiconductor layer 103 of a first conductivity type, an active layer 104, and a second semiconductor layer 105 of a second conductivity type. Section 108 and buffer layer 106 (SP3 in FIG. 1).

The first semiconductor layer 103, the active layer 104, and the second semiconductor layer 105 are preferably AlGaInP or AlGaAs. In this way, materials as described above can be suitably used as the first semiconductor layer, the active layer, and the second semiconductor layer.

Furthermore, it is better to form the buffer layer 106 with InGaP.

In order to improve the characteristics of the first semiconductor layer 103 or the second semiconductor layer 105, it is common to include multiple layers in each layer. Needless to say, the first semiconductor layer 103 or the second semiconductor layer 105 is not limited to a single layer.

At this time, the first semiconductor layer 103 may be composed of two or more layers. The low-Al composition layer 103A on the side to be subjected to surface roughening treatment of the first semiconductor layer 103 can be formed of a material with a lower Al composition than the high-Al composition layer 103B on the active layer side.

In this way, while maintaining the carrier limitation effect of the cladding layer, the decrease in the mechanical strength of the pad electrode due to over-etching and the chip breakage during wire bonding can be suppressed, and the roughness of the required unevenness can be manufactured. Surface of the light-emitting element.

Next, on the buffer layer 106, for the starting substrate 101, the window layer and supporting substrate 107 are formed by epitaxial growth with a non-lattice-matched material, and an epitaxial substrate 109 (in FIG. 1 SP4).

As the window layer and supporting substrate 107, GaP or GaAsP is preferred.

Next, the starting substrate 101 and the second selective etching layer 102A are removed from the epitaxial substrate 109. As shown in FIG. 3, only the first selective etching layer 102B remains on the surface of the first semiconductor layer 103 of the light-emitting element substrate 110 ( SP5 in Figure 1).

Specifically, from the epitaxial substrate 109, by using the second selective etching layer 102A and removing the starting substrate 101 by wet etching, only the first selective etching layer 102B can remain on the surface of the first semiconductor layer 103 .

Next, as shown in FIG. 4, on the surface of the first selective etching layer 102B on the first semiconductor layer 103, a first ohmic electrode 121 for supplying a potential to the light-emitting element is formed (SP6 in FIG. 1).

Next, as shown in FIG. 4, the first selective etching layer 102B in the range other than the bottom of the first ohmic electrode 121 is removed (SP7 in FIG. 1).

Specifically, using the first ohmic electrode 121 as an etching mask, the first selective etching layer 102B in a range other than the bottom of the first ohmic electrode 121 can be removed by etching.

Next, as shown in FIG. 5, a first surface roughening treatment step can be performed, and at least a part of the surface of the first semiconductor layer 103 other than the formation portion of the first ohmic electrode 121 is surface roughened ( SP8 in Figure 1).

Specifically, for example, a first surface roughening solution composed of a mixture of inorganic acid and organic acid can be used to perform the first surface roughening solution on the surface of the first semiconductor layer 103 except for the portion where the first ohmic electrode 121 is formed. Surface roughening treatment.

Next, as shown in FIG. 6, a step of forming a step (removed portion, step forming step, step 1) is performed to partially form the removed portion 170 exposing the second semiconductor layer, the buffer layer, or the window layer and supporting substrate to provide a step. SP9). As shown in FIG. 6, a step is provided between the removed portion 170 and the non-removed portion 180 other than that.

Specifically, for example, the ICP dry etching method with low material selectivity can be used to etch from the first semiconductor layer in the range 140 to a part of the window layer and supporting substrate. In this way, the portion (removed portion 170) where the window layer and supporting substrate 107 is exposed as shown in FIG. 6 can be formed. The removal part 170 inherits the surface roughness pattern formed by the first surface roughening treatment step, and has a surface roughness pattern.

Next, as shown in FIG. 7, the second ohmic electrode 122 (SP10 in FIG. 1) is formed on the surface of the window layer and supporting substrate 107 of the removed portion 170.

In this way, the first ohmic electrode 121 and the second ohmic electrode 122 are formed with a step difference. In the present invention, for example, the step difference between the first ohmic electrode 121 and the second ohmic electrode 122 can be 3 μm or more and 11 μm or less. In this way, even if the step difference between the first ohmic electrode and the second ohmic electrode is large, as will be described later, it is possible to easily mount the light-emitting element chip while preventing damage to the light-emitting element during flip-chip mounting.

Next, as shown in FIG. 7, at least a part of the surface of the first semiconductor layer 103 and the side surface of the light-emitting portion 108 can be covered by the insulating protective film 150 (SP11 in FIG. 1).

If it is a transparent and insulating material, the insulating protective film 150 can be any material. As the insulating protective film 150, it is suitable to use, for example, SiO or SiN _x system. If this is the case, the openings can be easily processed on the top of the first ohmic electrode 121 and the second ohmic electrode 122 by the photolithography method and the etching solution containing hydrofluoric acid.

Next, a step of separating the light-emitting element formed with the first and second ohmic electrodes 121 and 122 to produce a light-emitting element wafer is performed (SP12 in FIG. 1).

Specifically, the scribe line can be scribed along the scribe area 142 (refer to FIG. 7), and the light-emitting element can be separated by breaking, thereby fabricating the light-emitting element chip 1 (die).

Next, as shown in FIG. 8, the second surface roughening treatment step can be performed by the second surface roughening liquid, so that the side surface and the back surface of the window layer and supporting substrate 107 can be surface roughened.

In addition, since the light-emitting angle is expanded by the second surface roughening treatment, the treatment may not be performed if the light-emitting angle is not desired to be expanded.

Next, the step of flip-chip mounting the light-emitting element chip on the mounting substrate (SP14 in Fig. 1) is performed so that the side of the light-emitting element chip 1 on which the first and second ohmic electrodes are formed becomes the mounting substrate ( Not shown) on the side.

[First Embodiment]

In the above-mentioned flip-chip mounting step (SP14), in the first embodiment, after the mounting substrate (mounting board) is crystal-fixed, the flip-chip mounting can be performed by ultrasonic bonding. At this time, the mounting joint portion of the first ohmic electrode is provided at the edge of the wafer.

In the first embodiment, during the ultrasonic installation, because the ultrasonic propagation system propagates in the single crystal part other than the sliding surface (through the differential surface), in addition to being efficiently performed, it is also from the top When the wafer is pressed, the window layer and supporting substrate are easily deformed along the sliding surface and are not easily damaged.

[Second Embodiment]

In the above-mentioned flip chip mounting step (SP14), in the second embodiment, as a structure in which eutectic metal is further laminated on the first ohmic electrode and the second ohmic electrode, after die bonding, it can be used Flip-chip mounting is performed through heating and cooling treatments.

The first ohmic electrode and the second ohmic electrode have eutectic solder layers such as AuSn with a low melting point, and the window layer and supporting substrate have a flip-chip structure with high-density through-difference rows. In the second embodiment, during the thermal contraction of the eutectic welding, although tensile stress is applied to the window layer and support substrate, it has a sliding surface (penetrating the differential row surface), which is larger than the single crystal deformation. It is not concentrated, but can avoid chip damage.

In this way, by epitaxially growing the window layer and supporting substrate with a non-lattice-integrated material for the starting substrate, a large number of differential rows are inserted into the window layer and supporting substrate (the differential row density is 10/cm ² the above). By making the window layer and supporting substrate have high-density differential rows, during flip-chip mounting using ultrasonic waves (first embodiment), when stress is applied to the chip, the window layer and supporting substrate will follow The differential surface is deformed, and the breakage of the wafer can be suppressed. Furthermore, in the flip-chip mounting using eutectic metal (the second embodiment), due to the expansion of heating and the shrinkage when returning to room temperature, the window layer and supporting substrate will follow the differential surface Deformation can suppress chip breakage.

Furthermore, as in the present invention, the step difference is provided when the removed portion is formed. Even when the step difference between the first ohmic electrode and the second ohmic electrode is large, when the light-emitting element chip is pressed during flip-chip mounting, the light-emitting element chip will Due to the deformation, it is possible to prevent damage to the light-emitting element during flip-chip mounting. In particular, because the window layer and supporting substrate has a sliding surface, it is easy to deform when pressed against the light-emitting element chip. While the first ohmic electrode 121 is in contact with the mounting surface, the second ohmic electrode 122 is also in contact with the mounting surface. Bumps are not necessarily required in flip chip mounting. Thereby, the light-emitting element wafer can be easily mounted.

Specifically, the step difference between the first ohmic electrode and the second ohmic electrode can be 3 μm or more and 11 μm or less as described above. In this way, even if the step difference between the first ohmic electrode and the second ohmic electrode is large, the present invention can fully exert its effect.

Examples and comparative examples of the present invention are shown below to explain the present invention more specifically, but the present invention is not limited to these.

[Example]

On a starting substrate 101 composed of n-type GaAs with a thickness of 280 μm inclined at 15° from the crystal axis [001] direction to the [110] direction, the n-type GaAs buffer layer was formed by the MOVPE method (metal organic vapor phase growth method) (Not shown) After the second selective etching layer 102A composed of an n-type AlInP layer grows to 0.5 μm, and the first selective etching layer 102B composed of an n-type GaAs layer grows to 1 μm, it will be The light emitting part 108 composed of the n-type cladding layer (first semiconductor layer 103), the active layer 104, and the p-type cladding layer (second semiconductor layer 105) composed of AlGaInP is formed to 5.5 μm on top of it, The buffer layer 106 composed of p-type GaInP is formed to 0.3 μm, and the window layer composed of p-type GaInP serves as one of the supporting substrate 107 Partially grow 1.0μm. Next, it was transferred to the HVPE furnace, and the window layer and support substrate 107 made of p-type GaP was grown by 120 μm to obtain an epitaxial substrate 109 (refer to FIG. 2).

Next, from the epitaxial substrate 109, the starting substrate 101, the GaAs buffer layer, and the second selective etching layer 102A are etched and removed to produce a light-emitting element substrate 110 with only the first selective etching layer 102B remaining (refer to FIG. 3) . Specifically, from the epitaxial substrate 109, the second selective etching layer 102A is used as a selective etching layer, and the starting substrate 101 is removed by a wet etching method to become the light-emitting element substrate 110.

Next, the first ohmic electrode 121, which is an electrode for supplying electric potential to the light-emitting element, is formed. Specifically, as shown in FIG. 4, the first ohmic electrode 121 is formed on the first selective etching layer 102B of the light-emitting element substrate 110. Then, using the first ohmic electrode 121 as a mask, the first selective etching layer 102B outside the first ohmic electrode 121 is removed by etching.

Next, as shown in FIG. 9, by photolithography, a photoresist mask 123 is disposed on the second ohmic electrode formation predetermined range 122a, and the first surface roughening liquid is used to perform a first surface roughening treatment. The first surface roughening solution is made of a mixed solution of acetic acid and hydrochloric acid, and the surface is roughened by etching at room temperature for 1 minute.

Next, by photolithography, an open pattern is formed in the area 140 (refer to FIG. 9), and the step of removing the portion and step formation is performed by the ICP plasma etching method containing hydrochloric acid gas to remove the light-emitting portion 108 and The buffer layer 106 is formed to expose the removed portion 170 of the window layer and supporting substrate 107 and the non-removed portion 180 (refer to FIG. 10). At this time, although the removed portion 170 inherits the surface roughness pattern formed in the first surface roughening treatment step, the portion of the second ohmic electrode forming portion 141 is not roughened in the first surface roughening treatment step. It is not a rough surface pattern but a flat surface.

Next, the second ohmic electrode 122 is formed in the second ohmic electrode forming portion 141 in FIG. 10 (refer to FIG. 11). Next, the laminate formed by the SiO ₂ insulating protective film 150, and the cover is protected by the SiO ₂ insulating film composed of the side surface of the first semiconductor layer 103 and the surface 150 of the light emitting portion 108 to be formed.

Next, a scribe line is scribed along the scribe range 142, the crack line is extended along the scribe line, and then the elements are separated by splitting, thereby forming the light-emitting element wafer 11.

After the light-emitting element wafer 11 is formed, the light-emitting element wafer 11 is transferred to the supporting tape so that the surface provided with the first ohmic electrode 121 is on the side of the tape surface, and then the second surface roughening solution is used to implement the surface roughening window layer It also serves as a second surface roughening treatment step for the side and back surfaces of the support substrate 107 (refer to FIG. 12). As the second surface roughening solution, a mixed solution of acetic acid, hydrofluoric acid, and iodine was prepared. Then, the second surface roughening treatment was performed by etching at room temperature for 1 minute.

[Comparative example]

On a starting substrate 301 made of n-type GaAs with a thickness of 280 μm inclined 15° from the crystal axis [001] direction to the [110] direction, the n-type GaAs buffer layer (not shown) was grown to 0.5 by the MOVPE method μm, the second selective etching layer 302A formed by the n-type AlInP layer is grown to 1 μm, and the first selective etching layer 302B formed by the n-type GaAs layer is grown to 1 μm, there is a second selective etching layer 302A and On the selective etching layer 302 of the first selective etching layer 302B, an n-type cladding layer (first semiconductor layer 303) composed of AlGaInP, an active layer 304 and a p-type cladding layer (second semiconductor layer 305) will be formed The light-emitting part 308 is formed to 5.5 μm, and the buffer layer 306 made of p-type GaInP is formed to 0.3 μm on it, and the current diffusion layer 307 is epitaxially grown by 1.0 μm to produce an epitaxial substrate 309 (Refer to Figure 13).

Next, as shown in FIG. 14, a GaP single crystal substrate 310 with a thickness of 300 μm is bonded to the epitaxial substrate 309. For the joining of the epitaxial plate 309 and the GaP single crystal substrate 310, both the epitaxial substrate 309 and the GaP single crystal substrate 310 are cleaned with an alkaline solution, and are joined by a BCB adhesive.

Next, from the epitaxial substrate 309, the starting substrate 301, the GaAs buffer layer, and the second selective etching layer 302A are etched and removed to produce a light-emitting element substrate 311 with only the first selective etching layer 302B remaining (refer to FIG. 15) . Specifically, from the epitaxial substrate 309, the second selective etching layer 302A is used as a selective etching layer, and the starting substrate 301 is removed by a wet etching method to become the light emitting element substrate 311.

Next, the first ohmic electrode 321, which is an electrode for supplying electric potential to the light-emitting element, is formed. Specifically, as shown in FIG. 16, the first ohmic electrode 321 is formed on the first selective etching layer 302B of the bonding substrate 311. Then, using the first ohmic electrode 321 as a mask, the first selective etching layer 302B outside the first ohmic electrode 321 is removed by etching.

Next, as shown in FIG. 17, the first surface roughening liquid is used to perform the first surface roughening treatment. The first surface roughening solution is made of a mixed solution of acetic acid and hydrochloric acid, and the surface is roughened by etching at room temperature for 1 minute.

Next, by the photolithography method, an opened pattern is formed in the area 340 (refer to FIG. 17), and the step of removing the part and the step is performed by the ICP plasma etching method containing hydrochloric acid gas, and the area 340 is etched. A non-removed portion 380 that exposes the current diffusion layer 307 and the outside is formed (refer to FIG. 18).

Next, as shown in FIG. 18, the second ohmic electrode 322 is formed. Next, as shown in FIG. 19, the protective laminate of an insulating film 350 composed of SiO _2, to form a protective insulating film is formed of SiO ₂ covers the surface 350 and the light emitting portion 308 of the side surface of the first semiconductor layer 303.

Next, scribe the scribe line along the scribe area 342 (refer to Figure 19), extend the crack line along the scribe line, and then separate the elements by splitting, as shown in Figure 20, to form a light emitting Component wafer 201.

After the light-emitting element wafer 201 is formed, the light-emitting element wafer 201 is transferred to the supporting tape so that the surface provided with the first ohmic electrode 321 is on the side of the tape surface, and then the second surface roughening solution is used to implement the surface roughening GaP sheet. The second surface roughening treatment step of the side surface and the back surface of the crystalline substrate 310 (refer to FIG. 20). As the second surface roughening solution, a mixed solution of acetic acid, hydrofluoric acid, and iodine was prepared. Then, the second surface roughening treatment was performed by etching at room temperature for 1 minute.

100 of the light-emitting element wafers manufactured in the Examples and Comparative Examples were respectively subjected to Au-Au ultrasonic mounting, and the results of the comparison are shown in FIG. 21. In the comparative example, damage caused by the wafer pressure bonding or the vibration during ultrasonic printing, which is considered to be the cause, occurs, and the defect rate increases. On the other hand, in the examples, compared with the comparative examples, the occurrence rate of wafer breakage due to the same reason is less.

Next, 100 of the light-emitting element wafers manufactured in the Examples and Comparative Examples were each provided with an AuSn layer on the electrode and on the mounting substrate, and then thermally melted (above 220°C) to mount, and the results of comparison were shown In Figure 22. In the comparative examples and the examples, it is considered that the damage due to the thermal shrinkage of AuSn after thermal fusion occurs, but as shown in Fig. 22, the damage rate of the examples is smaller than that of the comparative example.

In the embodiment, since the window layer and supporting substrate 107 is formed by epitaxial growth, it is formed in a temperature range of about 600 to 800°C. The linear expansion coefficient of AlGaInP is larger than that of GaP. When the temperature is lowered to room temperature after growth, due to the difference in the expansion coefficient, a concave warpage of the substrate removal surface will occur. Furthermore, between AlGaInP/GaP, there is a 3.7% difference in the lattice constant. This lattice constant The number difference will also increase the warpage. On the other hand, due to the difference in the lattice constant, there are high-density differences in the window layer and supporting substrate. In this way, the window layer and supporting substrate in the embodiment has a high-density through row. Because the differential surface has the characteristics of sliding when an external force is applied to the crystal, when the stress during vibration or pressure bonding is applied to the crystal, the crystal slides along the sliding surface before the crystal is destroyed, avoiding the installation As a result of the stress, it can be expected that the chip breakage rate will decrease.

On the other hand, in the comparative example, although the warpage caused by the difference in linear expansion is the same as that of the example, the bonding temperature is 350°C, which is lower than the case of the example. In the examples, the warpage is 1/10 or less.

Next, in the examples and comparative examples, the step difference between the first ohmic electrode and the second ohmic electrode is changed to manufacture a light-emitting element chip. When the manufactured light-emitting element chip is not provided with bumps, and when flip chip mounting is performed Determination of productivity. This result is shown in Figure 23. In Fig. 23, the horizontal axis represents the step difference between the first ohmic electrode and the second ohmic electrode of the examples and comparative examples, and the vertical axis represents the productivity of the number of wafers that can be mounted during mounting.

During flip-chip mounting, the light-emitting element chip will be pressed against the mounting surface. Due to the pressure of the light-emitting element chip, the metal part on the side of the mounting surface may be deformed. Although the light-emitting element chip may sink to the side of the mounting surface, the deformation is not large. Therefore, in the comparative example, as shown in FIG. 23, if the level difference between the first ohmic electrode 321 and the second ohmic electrode 322 on the light-emitting element wafer provided on the mounting surface is 3 μm or more, the first The deformation of the metal of the ohmic electrode 321 is insufficient. Although the surface of the first ohmic electrode 321 fully contacts the mounting surface, the second ohmic electrode 322 may not contact the mounting surface. This result will cause a short circuit, making it impossible to install. Therefore, in order to increase the deformation of the electrode, generally, bumps are provided on the first ohmic electrode 321 and the second ohmic electrode 322. However, the bumps must be thickly formed with Au (gold) using a gold plating method or the like, and the material cost becomes very high.

On the other hand, in the embodiment, the window layer and supporting substrate has a sliding surface, and as a result, the shape is variable to exert another effect. Specifically, when the light-emitting element chip is pressed during flip-chip mounting, because the light-emitting element chip is deformed, bumps are not necessary in flip-chip mounting. That is, because the window layer and support substrate have a sliding surface, the light-emitting element chip is easily deformed by pressing, and when the first ohmic electrode 121 contacts the mounting surface, the second ohmic electrode 122 also contacts the mounting surface. Since both the first ohmic electrode 121 and the second ohmic electrode 122 are in contact with the mounting surface, a strong joint can be formed between the mounting surface and the electrode by ultrasonic bonding method or the like. Therefore, as shown in Figure 23, even if the step difference between the first ohmic electrode and the second ohmic electrode of the embodiment is within the range of 3 μm to 11 μm, it is possible to perform flip-chip mounting with good productivity without using expensive bumps. .

In addition, the present invention is not limited to the above-mentioned embodiment. The above-mentioned embodiments are examples. Anything that has substantially the same structure as the technical idea described in the scope of the patent application of the present invention and produces the same effect is included in the technical scope of the present invention.

Claims (5)

A method for mounting a light-emitting element includes the following steps: on a starting substrate, using a material that matches the crystal lattice of the starting substrate to grow by epitaxial growth to sequentially form a first semiconductor layer, an active layer, A second semiconductor layer and a buffer layer; on the buffer layer, a window layer and supporting substrate are formed by epitaxial growth with a material that is non-lattice-matched to the starting substrate, the window layer and supporting substrate system Insertion with a differential row; removing the starting substrate; forming a first ohmic electrode on the first semiconductor layer; partially forming a removal portion exposing the second semiconductor layer, the buffer layer, or the window layer and supporting substrate , And set the step; form a second ohmic electrode in the removed part; separate the light-emitting element formed with the first and second ohmic electrodes to produce a light-emitting element chip, and flip-chip mount the light-emitting element chip on the mounting substrate , And the side of the light-emitting element wafer on which the first and second ohmic electrodes are formed becomes the mounting substrate side, wherein the row density of the window layer and supporting substrate is 10 pieces/cm ² or more. The method for mounting a light emitting element according to claim 1, wherein the first semiconductor layer, the active layer and the second semiconductor layer are AlGaInP or AlGaAs. The method for mounting a light-emitting element according to claim 1, wherein the window layer and supporting substrate is GaP or GaAsP. The method for mounting a light-emitting element according to claim 2, wherein the window layer and supporting substrate is GaP or GaAsP. The mounting method of the light emitting element according to any one of claims 1 to 4, wherein the step difference between the first ohmic electrode and the second ohmic electrode is 3 μm or more and 11 μm or less.

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