JP2003197966A - Gallium nitride-based compound semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gallium nitride-based compound semiconductor element that can be improved in light emitting efficiency and yield. <P>SOLUTION: In the gallium nitride-based compound semiconductor element, an Au electrode 9 is formed on the upper surface of a wafer provided with a gallium nitride-based compound semiconductor layer 4 having a p-n junction on the upper surface of a sapphire substrate 2. In addition, an Al/Si/Ni/Au electrode 10 is formed on the lower surface of the wafer so that the electrode 10 may come into contact with at least a part of the semiconductor layer 4 exposed by removing an arbitrary portion of the sapphire substrate 2 from the lower surface to the semiconductor layer 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride compound semiconductor device, and more particularly to a gallium nitride compound semiconductor device using an insulating substrate, for example, a sapphire substrate.

[0002]

2. Description of the Related Art A conventional gallium nitride-based compound semiconductor device using a sapphire substrate is shown in FIG.

This gallium nitride compound semiconductor device 10
The manufacturing procedure of No. 1 will be described. First, on the sapphire substrate 102, the n-type GaN buffer layer 103 with a predetermined film pressure,
n-type gallium nitride compound semiconductor layer 104, n-type Ga _1-y A
l _y N (0 <y <1) cladding layer 105, n-type In _z Ga _1-z N (0 <z <1) active layer 106, p-type Ga _1-x Al _x N (0 <x <0.5) Clad layer 10
7 and the p-type GaN layer contact layer 108 are sequentially stacked to produce a wafer.

Then, from the top surface of the wafer, the p-type contact layer 108, the p-type cladding layer 107, and the n-type active layer 106 are formed.
Also, a part of the n-type cladding layer 105 is etched in the bonding direction to expose the n-type gallium nitride compound semiconductor layer 104 on the upper surface side of the wafer.

After that, on the p-type contact layer 108, the p-side Au electrode 109 and the n-type gallium nitride compound semiconductor layer 1 are formed.
By providing Al electrodes 110 on the n-side as transparent electrodes on 04, gallium nitride-based compound semiconductor device 1
01 is completed. At this time, the pair of electrodes 109 and 110 are usually arranged on a diagonal line on the upper surface of the wafer as shown in FIG. 7 or at a position corresponding to the opposite surface as shown in FIG. 8 in consideration of current diffusion.

[0006]

However, the structure of such a gallium nitride-based compound semiconductor device 101 is as follows.
It causes the following problems. That is, in the light emitting element, light emission leaks to the lower surface of the wafer (hence, the lower surface of the sapphire substrate 102) side, and in the light receiving element, transmission loss to the lower surface side of the sapphire substrate 102 occurs.

Further, since both the n-side and p-side electrodes 109 and 110 are provided on the upper surface of the wafer, the effective light emitting region or light receiving region is narrowed, and there is a problem that the efficiency of each is lowered. . In addition, the electrostatic breakdown voltage on the upper surface side of the wafer becomes extremely low, and the yield is reduced in the assembly process. Further, it is necessary to connect two wires to each of the electrodes 109 and 110 in the final step of assembly, and there is a problem that there are many working steps and manufacturing is troublesome.

By the way, the gallium nitride-based compound semiconductor element 101 may be processed into a light emitting device by bonding it to a frame 111 as shown in FIG. In this case, there are two
Since it is necessary to directly bond the two electrodes 109 and 110 to the frame 111 via the gold bumps 112,
Highly accurate assembly technology is required. Along with that, the yield in the assembly is lowered, and the unit price of the product is soared.

Further, the gallium nitride-based compound semiconductor device 101 is likely to be displaced on the frame 111, which leads to deterioration in quality. Moreover, as described above, in consideration of current diffusion, the electrodes 109 and 1 on the n-side and the p-side are formed.
Since 10 is arranged on a diagonal line or close to the facing position, migration or the like is easily induced during bonding, which further causes deterioration of quality.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a gallium nitride-based compound semiconductor device which is expected to have improved luminous efficiency and increased yield.

[0011]

In order to achieve the above object, a gallium nitride compound semiconductor device of the present invention is an upper surface of a wafer provided with a gallium nitride compound semiconductor layer having a pn junction on an insulating substrate. A positive or negative electrode is formed on the insulating substrate, and any part of the lower surface of the insulating substrate is removed to a depth reaching the gallium nitride compound semiconductor layer, thereby exposing at least one part of the exposed gallium nitride compound semiconductor layer portion. The negative or positive electrode is formed on the lower surface of the wafer so that the parts contact each other.

According to this structure, since the current is injected from the direction perpendicular to the pn junction surface, the current flow becomes smooth and the luminous efficiency or the light receiving efficiency of the gallium nitride compound semiconductor device is improved. .

Further, the present invention is characterized in that the electrodes formed on the lower surface of the wafer cover 50% or more of the total area of the insulating substrate.

With this structure, the electrode on the lower surface of the wafer also functions as a reflection film or a transmission blocking film, and the light emission efficiency or the light reception efficiency on the upper surface of the wafer is further improved.

A sapphire substrate can be preferably used as the insulating substrate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing a gallium nitride-based compound semiconductor device.

A procedure for manufacturing the gallium nitride-based compound semiconductor device 1 will be described with reference to FIG. First, in the reaction tube, the sapphire substrate 2 as an insulating substrate is
After cleaning, the growth temperature is set to 510 ° C., hydrogen is used as a carrier gas, ammonia and trimethylgallium (TMG) are used as a source gas, and a GaN buffer layer 3 is grown on the sapphire substrate 2 by about 200 angstroms. After forming the GaN buffer layer 3, only TMG is stopped and the temperature is raised to 1030 ° C. At 1030 ° C., TMG and ammonia gas are used as a source gas, and silane gas is used as a dopant gas, and an n-type GaN layer 4 doped with Si is grown to 4 μm. After forming the Si-doped n-type GaN layer 4, the source gas and the dopant gas are stopped, the temperature is set to 800 ° C., TMG and TMA (trimethylaluminum) and ammonia gas are used as the source gas, and silane gas is used as the dopant gas.
Si-doped n-type Ga _0.85 Al _0.14 N layer 5 as the n-type cladding layer
Are grown to 0.15 μm.

Next, the source gas and the dopant gas are stopped,
The temperature is set to 800 ° C, the carrier gas is switched to nitrogen, and TMG and TMI (trimethylindium) are used as raw material gases.
And ammonia gas, silane gas as dopant gas, and Si-doped n-type In _0.01 Ga _0.99 N layer 6 as n-type active layer 6
Grow 100 Angstroms. In addition, raw material gas,
Stop the dopant gas, raise it to 1020 ℃ again, and use TMG, TMA and ammonia gas as the source gas and Cp ₂ Mg (dicyclopentyl magnesium) as the dopant gas.
Mg-doped p-type Ga _0.85 Al as a p-type cladding layer
_{A 0.14} N layer 7 is grown to 0.15 μm. Then, the TMA is stopped and the Mg-doped p-type GaN layer 8 is used as the p-type contact layer.
Grow 0.4 μm.

Next, the sapphire substrate 2 was taken out from the reaction tube and was annealed at 700 ° C. in a nitrogen atmosphere.
Annealed at ℃ for 20 minutes, Mg-doped p-type Ga _0.85 Al
_The resistance of the _0.14 N layer 7 and the Mg-doped p-type GaN layer 8 is reduced.

On the upper surface of the wafer thus obtained (therefore, the upper surface of the Mg-doped p-type GaN layer 8), the Au electrode 9 is formed as one (positive) electrode. After that, the lower surface of the wafer (hence, the lower surface of the sapphire substrate 2) is partially etched by laser irradiation or the like, and the Si-doped n-type GaN layer 4 is formed.
The sapphire substrate 2 and the GaN buffer layer 3 are removed to a depth reaching 1 to expose the Si-doped n-type GaN layer 4. After that, the Al / Si / Ni / Au electrode 10 is placed on the other side (negative) on the lower surface of the wafer.
Is formed as an electrode. At this time, at least exposed
The Si-doped n-type GaN layer 4 is covered.

Further, annealing is performed again at 500 ° C. to make the Al / Si / Ni / Au electrode 10 and the Si-doped n-type GaN layer 4 conform to each other. Finally, this wafer-electrode integrated product is cut into chips to complete the gallium nitride-based compound semiconductor device 1.

FIG. 2 is a bottom view of a gallium nitride-based compound semiconductor device 1 in which a part of the central portion of the sapphire substrate 2 is circularly removed to form the electrode 10. This FIG. 2 corresponds to a bottom view of the device shown in FIG.

Next, FIG. 3 shows a bottom view of the gallium nitride-based compound semiconductor device 1 of the example in which the electrode 10 is formed by removing the sapphire substrate 2 in a circular shape at several places. By doing so, since a plurality of irregularities is formed on the electrode 10, light can be reflected in a wide range. Further, a plurality of contact points between the electrode 10 and the layer 4 can be formed, so that electrical connection can be ensured.

Then, FIG. 4 shows a bottom view of the gallium nitride-based compound semiconductor device 1 of the example in which the electrode 10 is formed by removing the sapphire substrate 2 in a cross shape. With such a shape, the substrate 2 can be formed by dicing in addition to laser irradiation.
Can be removed, and a plurality of manufacturing methods can be supported.

In any case, the electrode 10 on the lower surface of the wafer
Are provided so as to cover 50% or more of the entire area of the sapphire substrate 2. Therefore, most of the light traveling toward the lower surface of the wafer is reflected by the electrode 10, and light can be efficiently emitted from the upper surface of the wafer.

FIG. 5 is a sectional view showing a light emitting device in which the gallium nitride compound semiconductor element 1 is mounted on a frame 11. As a manufacturing procedure of this device, first, the gallium nitride-based compound semiconductor element 1 is adhered onto the frame 11 with the conductive adhesive 13, and the electrode 9 on the upper surface of the wafer and the frame lead 12 are connected with the wiring 14. Finally, a light emitting device is completed by molding with a transparent resin (not shown) or the like.

Therefore, only one wiring 14 is required for assembling this light emitting device, and the number of working steps can be reduced. Also, regarding the luminous efficiency, the electrode 9 is 1 on the upper surface of the wafer.
As a result, the light emitting region is substantially expanded. Moreover, current injection occurs from the direction perpendicular to the pn junction surface, and it becomes possible to efficiently inject current into the Si-doped n-type In _0.01 Ga _0.99 N layer 6 which is the active layer, and accordingly, the electrostatic discharge. Withstand voltage is also improved. Further, the emitted light is reflected by the electrode 10 formed on the lower surface of the sapphire substrate 2, the light can be efficiently extracted to the upper surface side of the wafer, and the light emitting efficiency of the entire light emitting device is further improved.

Although sapphire is used as the substrate in the above description, the present invention is applicable to the case where a semiconductor substrate such as silicon carbide (SiC) having a relatively large resistance and exhibiting an insulating property or another insulating substrate is used. Can also be applied.

Further, although the light emitting element has been described as an example in the above description, the same effect can be obtained in the light receiving element according to the present invention. The present invention can also be applied to the case where a compound semiconductor element other than a gallium nitride-based compound semiconductor element is used as the semiconductor formed on the substrate.

[0030]

As described above, according to the gallium nitride compound semiconductor device of the present invention, the light emitting region on the upper surface of the wafer is substantially expanded, and the current injection is performed from the direction perpendicular to the pn junction surface. It can be done efficiently.

Further, since the electrode on the lower surface side of the wafer is provided so as to cover 50% or more of the total area of the sapphire substrate, most of the light traveling toward the lower surface side is reflected by the electrode, and the upper surface of the wafer is efficiently supplied. It can emit light.

In the device in which the gallium nitride-based compound semiconductor element is mounted on the frame or the like, only one wiring is required for assembling, so that the number of work steps can be reduced, the unit price of the product can be reduced, and the yield can be increased. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a gallium nitride-based compound semiconductor device according to the present invention.

FIG. 2 is a bottom view showing an example in which an electrode is formed by removing a part of a fire substrate of a gallium nitride-based compound semiconductor device in the same manner as above.

FIG. 3 is a bottom view showing an example in which electrodes are formed by circularly removing several places of the fire substrate of the gallium nitride-based compound semiconductor device.

FIG. 4 is a bottom view showing an example in which an electrode is formed by removing the sapphire substrate of the gallium nitride-based compound semiconductor device in a cross shape in the same manner.

FIG. 5 is a cross-sectional view showing a light emitting device in which a gallium nitride compound semiconductor element is mounted on a frame.

FIG. 6 is a cross-sectional view of a gallium nitride-based compound semiconductor device using a conventional general sapphire substrate.

FIG. 7 is a plan view showing an example in which a pair of electrodes are arranged on a diagonal line on the upper surface of the wafer of the same gallium nitride-based compound semiconductor device.

FIG. 8 is a plan view showing an example in which a pair of electrodes are arranged at positions corresponding to the upper surface of the wafer of the gallium nitride-based compound semiconductor device.

FIG. 9 is a cross-sectional view showing a light emitting device in which a gallium nitride compound semiconductor element is mounted on a frame.

[Explanation of symbols]

1 gallium nitride-based compound semiconductor device 2 sapphire substrate 3 GaN buffer layer 4 Si-doped n-type GaN layer (gallium nitride-based compound semiconductor layer) 5 Si-doped n-type Ga _0.85 Al _0.14 N layer 6 Si-doped n-type In _0.01 Ga _0.99 N Layer 7 Mg-doped p-type Ga _0.85 Al _0.14 N layer 8 Mg-doped p-type GaN layer 9 Au electrode 10 Al / Si / Ni / Au electrode

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Claims (3)

[Claims] 1. A positive or negative electrode is formed on the upper surface of a wafer having a gallium nitride-based compound semiconductor layer having a pn junction on the insulating substrate, and an arbitrary portion of the lower surface of the insulating substrate is formed. The negative or positive electrode is formed on the lower surface of the wafer so that the negative electrode is removed to a depth reaching the gallium nitride compound semiconductor layer, and at least a portion of the gallium nitride compound semiconductor layer exposed by the gallium nitride compound semiconductor layer is in contact therewith. Gallium nitride compound semiconductor device. 2. The gallium nitride-based compound semiconductor device according to claim 1, wherein the electrode formed on the lower surface of the wafer covers 50% or more of the total area of the insulating substrate. 3. The gallium nitride-based compound semiconductor device according to claim 1, wherein a sapphire substrate is used as the insulating substrate.