JPH08255926A - Semiconductor light emitting element and fabrication thereof - Google Patents

Abstract

PURPOSE: To obtain a high performance semiconductor light emitting element, and a fabrication method thereof, in which contamination due to etching of gallium nitride based semiconductor layer is prevented. CONSTITUTION: The semiconductor light emitting element comprises a semiconductor layer of gallium nitride based compound having an emission layer comprising an n-type layer 13 and a p-type layer 14 formed on a sapphire substrate 11, and electrodes connected with the n-type layer and the p-type layer 14. One electrode 15 on the p-side or n-side is connected with the surface layer of a laminated semiconductor layer and the other electrode 16 on the n-side or p-side is provided on the rear surface of the sapphire substrate 11 while being connected with the semiconductor layer through a through hole 17 made on the saphire substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and its manufacturing method. More specifically, it relates to a semiconductor light emitting device made of a gallium nitride based compound semiconductor suitable for blue light emission and a method for manufacturing the same.

Here, a gallium nitride compound semiconductor is a compound of a group III element Ga and a group V element N or
A semiconductor made of a compound in which a part of Ga of the group III element is replaced with another group III element such as Al and In and / or a part of N of the group V element is replaced with another group V element such as P and As. Say.

A semiconductor light emitting element is a light emitting diode having a pn junction or a double heterojunction (hereinafter referred to as L
A semiconductor element that emits light, such as an ED), a superluminescent diode (hereinafter, SLD), or a semiconductor laser diode (hereinafter, LD).

[0004]

2. Description of the Related Art Conventionally, blue LEDs have a lower brightness than red and green and are difficult to put into practical use. In recent years, however, gallium nitride compound semiconductors have been used, and a low resistance p-type semiconductor layer doped with Mg has been formed. By being obtained by the annealing treatment or electron beam irradiation treatment, the brightness is improved and the spotlight is exposed.

By the way, gallium nitride LEDs are
For example, the structure is as shown in FIG. In order to manufacture this LED, first, an organic metal compound is formed on a sapphire (Al ₂ O ₃ single crystal) substrate 21 at a low temperature of 400 to 700 ° C. together with a carrier gas H ₂ by a metal organic compound vapor phase growth method (hereinafter, referred to as MOCVD method). Compound gas trimethylgallium (hereinafter referred to as TMG) or triethylgallium (TEG) and ammonia (NH ₃ ) are supplied to form a low temperature buffer layer 22 made of n-type GaN, and then at a high temperature of 900 to 1200 ° C. High temperature buffer layer 23 made of n-type GaN having the same composition and supplying the same gas
To form.

Then, trimethylaluminum (hereinafter referred to as TMA) is further introduced into the above-mentioned gas to form an n-type Al _x Ga _1-x N (0 <x <1) layer to form a tabular heterojunction. An n-type clad layer 24 for forming is formed.
To form these n-type layers, S is added to each of the above component gases.
It is formed by introducing i as SiH ₄ gas.

Next, a material having a bandgap energy smaller than that of the clad layer, for example, trimethylindium (hereinafter T
MI) is introduced, and Ga _y In _1-y N (0 <y ≦
An active layer 25 consisting of 1) is formed.

[0008] Then, in the same feed gas with the formation of the n-type cladding layer 24, biscyclopentadienyl magnesium (Mg (C ₅ H for Mg or Zn in the impurity source gas as a p-type impurity in place of SiH _{4 5} ) ₂ ) (hereinafter C
p ₂ Mg) or dimethyl zinc (hereinafter DMZn)
Said) and introducing into the reaction tube, the p-type cladding layer 26 made of p-type Al _x Ga _1-x N.
To form. Thereby, the n-type cladding layer 24 and the active layer 2
5 and the p-type cladding layer 26 form a double heterojunction.

Further, in order to form the cap layer 27, Cp ₂ Mg or DMZn is supplied as an impurity source gas with the same gas as that of the buffer layer 23 described above to vapor-deposit a p-type GaN layer.

After that, a protective film such as SiO ₂ is provided on the entire surface of the growth layer of the semiconductor, and the temperature is 400 to 800 ° C. for 15 to 6
Annealing is performed for about 0 minutes to activate the p-type cladding layer 26 and the cap layer 27. Then, after removing the protective film, in order to form an n-side electrode, a resist is applied and patterned, and as shown in FIG. 5, a part of each grown semiconductor layer is subjected to reactive ion etching by chlorine-based plasma. A certain dry etching is performed to expose the buffer layer 23, which is an n-type GaN layer. Then Al, Au
An LED chip is formed by forming a metal film such as by sputtering to form the p-side and n-side electrodes 28 and 29, and dicing.

[0011]

Since the conventional semiconductor light emitting device using the gallium nitride based compound semiconductor uses the sapphire substrate as the substrate as described above, the n-side electrode can be taken from the back surface side. Therefore, a part of the stacked semiconductor layers is etched to expose the buffer layer 23, which is an n-type semiconductor layer, and the n-side electrode 29 is provided on the exposed surface. To perform this etching, the gallium nitride-based semiconductor layer must be wet-etched at a temperature of 250 ° C. or higher, which is a difficult task. Further, when the dry etching is performed, the surface of the semiconductor layer is damaged, and the resistance increases as the surface is damaged. In particular, dry etching is performed with chlorine-based plasma such as a mixed gas of Cl ₂ and BCl ₃ because of its good selection ratio with respect to SiO ₂ as a mask, but Cl ₂ has Al in the composition of the semiconductor layer. And Al and Cl combine to generate aluminum chloride, which adheres to the surface exposed by etching. If the compound of Al and Cl adheres to the side wall exposed by etching, there is a problem that the output of generated light is reduced or scattered. Further, there is a problem that the contact resistance is increased at the time of forming the electrode, or it causes leakage between the p layer and the n layer, resulting in loss of applied power.

Further, there is a problem that Cl ₂ gas is generally toxic and difficult to handle.

It is an object of the present invention to solve such a problem and provide a semiconductor light emitting device in which the other electrode is taken out from the back surface side of the sapphire substrate and the gallium nitride based semiconductor layer does not have to be etched. .

Still another object of the present invention is that even if the gallium nitride based semiconductor layer is etched, the semiconductor layer is not damaged, and contamination is not adhered to the etching surface, etc. It is an object of the present invention to provide a method for producing a semiconductor light emitting device.

[0015]

In the semiconductor light emitting device of the present invention, a gallium nitride-based compound semiconductor layer having a light emitting layer including at least an n-type layer and a p-type layer is laminated on a sapphire substrate, and the n-type layer is formed. And a p-type layer, each of which is provided with an electrode connected to the p-type layer, wherein the p-side or n-side electrode is provided so as to be connected to a surface layer of the stacked semiconductor layers. The other electrode on the n-side or the p-side is provided on the back surface of the sapphire substrate so as to be connected to the exposed semiconductor layer through the through-hole provided in.

Here, the light emitting layer is not limited to an active layer sandwiched between clad layers, and is meant to include the vicinity of a pn junction that generates light by the combination of electrons and holes in a pn junction LED or the like.

According to the method of manufacturing a semiconductor light emitting device of the present invention, a gallium nitride based compound semiconductor having at least an n-type layer and a p-type layer and having a light-emitting layer is laminated on a sapphire substrate, and the n-type layer and the p-type layer are formed. A method of manufacturing a semiconductor light-emitting device, wherein electrodes to be connected to each other are provided, wherein one of the electrodes is provided on a surface of the laminated semiconductor layers, and the other of the electrodes has a through hole provided by a focused ion beam on the sapphire substrate. It is characterized in that an electrode material is attached to the back surface of the sapphire substrate so as to come into contact with the semiconductor layer exposed through the electrode material.

[0018]

According to the semiconductor light emitting device of the present invention, one electrode is laminated by forming a through hole in the sapphire substrate from the back side of the sapphire substrate and exposing a part of the lower semiconductor layer to the back side. Surface layer of semiconductor layer (for example, p-type)
And the other electrode is provided on the back surface of the sapphire substrate to be connected to the lower layer (for example, n-type) of the semiconductor layer through the through hole. Therefore, both electrodes are provided without etching the semiconductor layer, and a semiconductor light emitting element in which the light emitting area for the same chip area is large and the chip bonding is easy can be obtained.

In order to form the through hole in the sapphire substrate, the sapphire substrate can be processed to form the through hole by using an ion beam such as a focused ion beam (hereinafter referred to as FIB) device.

According to the method for manufacturing a semiconductor light emitting device of the present invention, an ion beam such as FIB is used for etching the gallium nitride based compound semiconductor layer.
The particles irradiated onto the semiconductor layer are much smaller by the ion beam, and the energy is larger. As a result, a clean etching surface can be obtained without adhesion of contamination. Therefore, it is possible to improve the light emission characteristics of the LED or the semiconductor laser that emits light from the side surface.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor light emitting device of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view of an LED which is an embodiment of the semiconductor light emitting device of the present invention, FIG. 2 is an explanatory sectional view of a process showing the manufacturing process thereof, and FIGS. 3 to 4 are other manufacturing methods of the semiconductor light emitting device of the present invention. FIG. 6 is a process cross-sectional explanatory view of the semiconductor laser chip of the example.

In FIG. 1, a low temperature buffer layer 12 made of, for example, n-type GaN is formed on a sapphire (Al ₂ O ₃ single crystal) substrate 11 at a low temperature of 400 to 700 ° C.
It is formed to have a thickness of about 01 to 0.2 μm, and 900 to 1 on it.
N-type Ga doped with Si or the like at a high temperature of 200 ° C.
An n-type layer 13 made of N or the like is formed, and a p-type layer 14 made of p-type GaN or the like using Mg or the like as a dopant is further formed thereon to form a homo-pn junction made of a GaN layer. Al, Ti, C are formed on the p-type layer 14.
A p-side electrode 15 made of r, Ni, Au, Mg or the like is provided, and the sapphire substrate 1 is provided on the back surface of the sapphire substrate 11.
The n-side electrode 16 connected to the n-type low temperature buffer layer 12 through the through hole 17 provided in No. 1 is provided to form a pn junction LED.

The present invention is characterized in that the sapphire substrate 11 is provided with the through hole 17 and the rear surface thereof is provided with the n-side electrode 16. That is, since the conventional sapphire substrate 11 is provided, the n-side electrode is formed by etching a part of the p-type layer 14 to expose the n-type layer 13, and the n-side electrode is provided on the exposed surface of the n-type layer 13. According to the FIB of the present invention, it was found that the sapphire substrate 11 can also be processed, and the through hole 17 is formed from the back surface of the sapphire substrate 11 to electrically connect the n-type low temperature buffer layer 12 or the n-type layer 13 to each other. The n-side electrode to be connected is provided on the back surface side of the sapphire substrate 11.

According to the present invention, since the n-side electrode 16 is provided on the back surface side of the sapphire substrate 11, the p-type layer 14 is provided.
It is not necessary to etch the gallium nitride-based compound semiconductor layer made of GaN or the like. Therefore, Cl ₂ and Cl ₂
The emission efficiency is improved without the adhesion of contamination such as a compound of Al and Cl generated by dry etching of chlorine-based plasma such as a mixed gas of BCl ₃ and BCl ₃ , and the pn junction of the entire chip area can be used. , A large amount of light emission can be obtained for the same chip area. Moreover, since the electrode is exposed on the back surface, one electrode can be connected only by bonding to a lead frame or the like, and the number of wire bonding steps can be reduced.

Next, an embodiment of this LED manufacturing method is shown in FIG.
Will be described with reference to. First, as shown in FIG. 2A, a sapphire substrate 11 having a thickness of about 300 to 500 μm is placed in a reaction tube, and TMG is 50 sccm and NH ₃ is 15 sccm together with H _{2 as a} carrier gas at 400 to 700 ° C. , SiH _{4 as} dopant Si
Is introduced at 10 sccm and reacted for 5 to 10 minutes to 0.0
The low temperature buffer layer 12 having a thickness of about 1 to 0.2 μm is formed. This low-temperature buffer layer 12 has a lattice matching between the sapphire substrate 11 and the GaN single crystal layer, and grows as a polycrystal at the above-mentioned low temperature, but becomes a single crystal at a high temperature in the next growth layer of the GaN single crystal. To be done.

Next, as shown in FIG. 2 (b), the temperature inside the reaction tube is raised to a high temperature of 900 to 1200 ° C., the same gas as described above is introduced into the reaction tube, and an n-type GaN single crystal layer is formed. The mold layer 13 is laminated.

Further, as shown in FIG. 2 (c), Mg or Zn is replaced with Cp ₂ Mg or DMZn at 50 sc instead of SiH ₄ gas as a dopant at the same temperature.
cm to introduce the p-type layer 14 made of p-type GaN by 1 to 2 μm.
It grows to a thickness of about m.

After that, the reaction tube is cooled down to room temperature, and the substrate is taken out of the reaction tube and Al, Ti, Cr, Ni, and
A metal such as Au or Mg is deposited on the p-type layer 14 and patterned to form the p-side electrode 15. After that, a photoresist film 18 is formed on the back surface side of the sapphire substrate 11 by 1.5 to 2
The sapphire substrate 11 is processed by processing the sapphire substrate 11 by, for example, irradiating a focused ion beam to form an opening by patterning a place where the through hole 17 is provided and providing the through hole 1.
7 is provided (see FIG. 2D).

Then, similarly to the p-side electrode 15, Ti, Al
As shown in FIG.
, The n-side electrode 1 on the back surface of the sapphire substrate.
An LED chip provided with 6 is obtained. The n-side electrode 16 is connected by die-bonding this LED chip to a lead frame or the like, assembled by wire-bonding only the p-side electrode 15, and covered with a transparent resin to obtain an LED.

In the above example, GaN was used as the gallium nitride based compound semiconductor layer and the example was a homo pn junction. However, LEDs such as a hetero pn junction and a double hetero junction,
The same can be done for SLD and LD. In addition to GaN, gallium nitride compound semiconductors are generally Al
_p Ga _q In _lpq N (0 ≦ p <1, 0 <q ≦ 1, 0 <
A material in which p and q of p + q ≦ 1) are appropriately selected,
Furthermore, the present invention can be similarly applied to a material in which a part or all of N is replaced with As and / or P or the like. Next, a method of manufacturing a semiconductor laser, which is another embodiment of the manufacturing method of the present invention, will be described with reference to FIGS.

First, as shown in FIG. 3A, in the same manner as described in the prior art, a low temperature composed of n-type GaN is formed on the sapphire substrate 1 by the MOCVD method by introducing an organic metal gas and an impurity gas. The buffer layer 2 is 0.01 to
The high temperature buffer layer 3 made of n-type GaN at about 0.2 μm and 900 to 1200 ° C. is formed at about 2 to 4 μm and n-type Al _x G.
The lower clad layer 4 made of a _1-x N (0 <x <1) has a band gap energy smaller than that of the clad layer by about 0.1 to 0.3 μm, for example, non-doped Ga _y In _1-y N 2. The active layer 5 made of (0 <y ≦ 1) has a thickness of about 0.02 to 0.1 μm, the upper clad layer 6 made of p-type Al _x Ga _1-x N has a thickness of about 0.1 to 0.3 μm, and p-type GaN. The cap layer 7 consisting of 0.3 to 1 μm is continuously formed.

Next, as shown in FIG. 3B, a resist film 10 is applied to the surface of the laminated semiconductor layers and patterned so that the etched portions of the semiconductor layers are opened.

Next, the semiconductor layer exposed through the opening 11 is etched by, for example, FIB, and penetrates the active layer 5 to pass through the n-type high temperature buffer layer as shown in FIG. 3 (c). Etch until 3 is exposed. The manufacturing method of this embodiment is characterized in that the stack of gallium nitride based compound semiconductor layers is etched by using FIB.

Al, Ti, Cr, N are formed on the surface of the laminated semiconductor layer and the surface of the semiconductor layer exposed by etching.
A p-side electrode 8 and an n-side electrode 9 are formed on the cap layer 7 and the high temperature buffer layer 3 exposed by etching, respectively, by depositing and patterning a metal film made of i, Au, Mg or the like (FIG. 4). (See (d)).

After that, the cap layer 7 and a part of the upper cladding layer 6 are etched by dry etching using the p-side electrode 8 as a mask to form a mesa shape, and the substrate 1 is diced, whereby 4 to 10 μm of the p-side electrode 8 is formed. A semiconductor laser chip in which stripes are formed in a strip shape is obtained (see FIG. 4E). It is desirable that this mesa etching be similarly performed by dry etching using FIB. In the case of an LED, a double heterojunction LED can be obtained by dicing in the state of FIG. 4 (d) to form a chip without performing the mesa shape etching.

In the above-mentioned embodiment, the semiconductor laser is explained as an example in which the current injection region is formed into a stripe shape by mesa etching. However, for example, a current blocking layer of the opposite conductivity type having a stripe groove formed in the cladding layer is provided. Even a semiconductor laser having a structure or a planar stripe type structure can obtain a clean etching surface by the present invention,
A blue semiconductor laser using a gallium nitride based compound semiconductor layer can be obtained. The same applies not only to laser diodes but also to LEDs, and the gallium nitride-based semiconductor material is not limited to the above-mentioned composition, and is generally Al _p Ga.
_q In _1-pq N (0 ≦ p <1, 0 <q ≦ 1, 0 <p + q
It can be applied to a semiconductor light emitting device having a double heterojunction or a pn junction consisting of ≦ 1). Further, the Al _p Ga _q In
_1-pq N part or all of N is As and / or P
The present invention can be similarly applied to a material substituted with, for example.

[0037]

According to the semiconductor light emitting device of the present invention, since the light emitting region can be formed over the entire chip area, a light emitting device with high brightness can be obtained and contamination is not attached, so that the light emitting efficiency is improved. .

Further, according to the manufacturing method of the present invention, since the etching is performed by using FIB, it is possible to form the through hole in the sapphire substrate, and the back surface side of the semiconductor light emitting device formed on the insulating sapphire substrate. The electrode can be taken out from the device, which facilitates the assembly.

Further, when the gallium nitride compound semiconductor layer is etched, contamination is not adhered, a clean etched surface is obtained, and a semiconductor light emitting device having high luminous efficiency is obtained.

[Brief description of drawings]

FIG. 1 is an example of an LE of a semiconductor light emitting device of the present invention.
It is a section explanatory view of D.

2A and 2B are cross-sectional explanatory views showing the manufacturing process of FIG.

FIG. 3 is a diagram showing a manufacturing process of another embodiment of the method for manufacturing the semiconductor light emitting device of the present invention.

FIG. 4 is a diagram showing a manufacturing process of another embodiment of the method for manufacturing the semiconductor light emitting device of the present invention.

FIG. 5 is a cross-sectional explanatory view of an LED using a conventional gallium nitride based compound semiconductor.

[Explanation of symbols]

 1 substrate 4 n-type clad layer 5 active layer 6 p-type clad layer 11 sapphire substrate 13 n-type layer 14 p-type layer 15 p-side electrode 16 n-side electrode

Claims (2)

[Claims] 1. A gallium nitride based compound semiconductor layer having at least an n-type layer and a p-type layer and having a light emitting layer is laminated on a sapphire substrate, and electrodes provided respectively to the n-type layer and the p-type layer are provided. A semiconductor light-emitting device having the above structure, wherein a p-side or n-side electrode connected to a surface layer of the stacked semiconductor layers is provided, and the semiconductor is exposed through a through hole provided in the sapphire substrate. A semiconductor light emitting device, which is connected to a layer and is provided with the other electrode on the n side or the p side on the back surface of the sapphire substrate. 2. A semiconductor in which a gallium nitride based compound semiconductor having at least an n-type layer and a p-type layer and having a light emitting layer is laminated on a sapphire substrate, and electrodes provided respectively to the n-type layer and the p-type layer are provided. A method of manufacturing a light emitting device, wherein one of the electrodes is provided on a surface of the stacked semiconductor layers, and the other of the electrodes is in contact with a semiconductor layer exposed through a through hole provided by a focused ion beam on the sapphire substrate. A method for manufacturing a semiconductor light emitting device, characterized in that the electrode material is provided on the back surface of the sapphire substrate as described above.