JP3060931B2 - Nitride semiconductor device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a display, an optical communication, an O.D. A device and F. Light emitting devices that can be used for light emitting diodes and laser diodes that can emit red light from ultraviolet light used as light sources for equipment A, and nitride semiconductors used for light receiving devices such as photodiodes and solar cells (formula _{In x Al y Ga 1-xy} N, however
And 0 <x, 0 <y , x + y <1), and more particularly to a nitride semiconductor device having an electrode that makes good ohmic contact with a nitride semiconductor having N-type conductivity and a method of manufacturing the same.

[0002]

2. Description of the Related Art High-brightness light-emitting diodes widely used today as display elements such as full-color displays and various light sources, and short-wavelength laser diodes for improving the recording density of compact disks (CDs) and digital video disks (DVDs). Social demands are strong. Examples of semiconductor materials for light-emitting diodes (hereinafter, referred to as LEDs) capable of emitting light in the visible region from ultraviolet light and semiconductor lasers (hereinafter, referred to as LDs) that emit short-wavelength laser light include ZnSe, ZnS, and SiC. Compound semiconductor. However, the compound semiconductor has not been able to emit light with high efficiency and stability.

On the other hand, the band gap is 1.9 to 6.0e.
Because of V, LEDs and LDs using nitride semiconductors have been developed as light-emitting devices and light-receiving devices in the ultraviolet to red region. Nitride semiconductors have attracted attention as semiconductor materials capable of emitting and receiving light with high output and high efficiency. ing. Such a nitride semiconductor device is disclosed in, for example, JP-A-7-4.
No. 5867 and the like. FIG. 6 shows a specific example of a semiconductor element using a nitride semiconductor. An N-type contact layer made of N-type GaN and an N-type Al on a sapphire substrate
And _X Ga _1-X N formed by an N-type cladding layer and In _Y Ga _1-Y N consisting active layer, and a P-type cladding layer composed of P-type _{Al Z Ga 1-Z N,} P -type made of P-type GaN It has a structure in which a contact layer is laminated, a positive electrode containing Ni and Au is formed on almost the entire surface of the P-type contact layer, and Ti is firstly applied to the N-type contact layer exposed by etching.
A negative electrode is formed by forming Al on the second layer and performing an annealing process in the range of 400 ° C. to 1200 ° C. The positive electrode and the negative electrode of this semiconductor element are connected to external lead wires by wire bonding, and operate as an LED by applying power.

In order to lower the forward voltage of the nitride semiconductor device including such an LED, it is necessary to obtain a preferable ohmic contact between the semiconductor layer and each electrode. Also in the LED having the above-described structure, good ohmic contact is obtained between the P-type nitride semiconductor and the positive electrode (hereinafter, referred to as “P-type electrode”). Similarly, good ohmic contact is obtained with a negative electrode (hereinafter, referred to as “N-type electrode”) in contact with the N-type nitride semiconductor.

However, the physical properties of N-type nitride semiconductors have not been sufficiently elucidated, and it has been difficult to form a semiconductor device having excellent electrical characteristics and the like and operating under severe operating conditions with good reproducibility. In particular, a good ohmic contact with the N-type nitride semiconductor layer is obtained, and a hemispherical member (hereinafter, referred to as “ball”) or an N-type nitride formed at the time of melting a bonding wire connecting the N-type electrode and an external power supply. N with good adhesion to semiconductor
As for the type electrode, it is not yet satisfactory. Insufficient adhesion of the electrodes causes the ball and the N-type electrode, and the N-type electrode and the nitride semiconductor layer to peel off in a severe environment with a large temperature difference, such as outdoors, causing problems such as an increase in _Vf and heat generation. It does not exhibit the desired properties. In severe cases, it may not function as a semiconductor element.

[0006]

Accordingly, in view of the above problems, the present invention provides a nitride semiconductor device capable of forming a good ohmic contact as a semiconductor device and stably driving the semiconductor device even under severe conditions of use environment, and a method of manufacturing the same. Is to do.

[0007]

The present invention relates to a nitride semiconductor device having an N-type electrode provided on a nitride semiconductor having N-type conductivity, wherein the N-type electrode has W. A nitride semiconductor device is a layer and a second layer including Al provided on the first layer. Further, the nitride semiconductor device is provided with a third layer having at least one selected from W, Cr, Ni, Mo, and Ti on the second layer. Furthermore, the surface of the electrode connected to the electrical connection member is a nitride semiconductor element of one kind selected from Au and Pt. The nitride semiconductor having N-type conductivity is a nitride semiconductor element containing Si and / or Ge. A step of forming a nitride semiconductor having N-type conductivity on the base; a step of forming a first layer having W as a material forming an N-type electrode on the nitride semiconductor; Forming a second layer having Al as an electrode material constituting the N-type electrode on the first layer, and annealing the N-type nitride semiconductor on which the N-type electrode is formed at 350 ° C. or lower; A method for producing a nitride semiconductor. Furthermore, the annealing temperature is 80 ° C. or more and 280 ° C.
The following is a method for manufacturing a nitride semiconductor.

[0008]

According to the first aspect of the present invention, it is possible to obtain a nitride semiconductor device having an N-type electrode having improved adhesion while making good ohmic contact. By adopting the configuration of claim 2 of the present invention, it is possible to obtain a nitride semiconductor device having an N-type electrode having improved adhesion while making better ohmic contact. With the configuration of claim 3 of the present invention, oxidation of the N-type electrode is suppressed, and the N-electrode is further improved in the adhesion while improving the ohmic contact.
A nitride semiconductor device having a mold electrode can be obtained.
By adopting the structure of claim 4 of the present invention, a nitride semiconductor device having excellent ohmic characteristics and further improved adhesion can be obtained. According to the method of claim 5 of the present invention, it is possible to manufacture a nitride semiconductor device having an N-type electrode with improved adhesion while making good ohmic contact. According to the method of claim 6 of the present invention, it is possible to manufacture a nitride semiconductor device having an N-type electrode with improved adhesion while making better ohmic contact.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various experiments, the present inventors have found that the characteristics greatly change depending on the device characteristics of the nitride semiconductor and the electrode material for forming the electrode adhesion and the annealing conditions. Invented based on.

Although the reason for the improvement of the characteristics by the structure of the present invention is not clear, it is considered that there is a great relation to the prevention of the change in characteristics due to the oxidation of the electrode material and the alloying of the electrode material formed during the annealing step. That is, in order to make the ohmic contact between the N-type electrode and the N-type nitride semiconductor satisfactorily in the related art, the annealing treatment (400 to
1200 ° C.). However, after the completion of the annealing process at such a relatively high temperature, it is necessary to sufficiently cool the inside of the annealing chamber, and the working efficiency may be reduced. On the other hand, when exposed to outside air or the like with insufficient cooling after the annealing step, the electrodes may be oxidized to form an insulating thin film and adversely affect device characteristics. That is, such an insulating thin film does not exhibit ohmic properties particularly at a low applied voltage, and exhibits ohmic properties only after the formed insulating thin film is increased to a voltage at which dielectric breakdown occurs. Therefore, an unstable element is left in driving the semiconductor, and in a severe case, the element may be destroyed. Also,
There is also a problem that desired ohmic characteristics are not obtained due to alloying between materials constituting the N-type electrode. It is considered that the annealing process for improving the ohmic properties is reversed, and the elements and the semiconductor material constituting the N-type electrode are mutually diffused and alloyed to form an N-type electrode having a poor surface condition. An N-type electrode having a poor surface state not only deteriorates the electrical characteristics between the nitride semiconductor element and the external electrode, but also lowers the contact strength and cannot be a nitride semiconductor element having good electrical contact.

A test was conducted to examine the adhesive strength between the N-type electrode of the present invention and a ball formed on the electrode. FIG. 5 is a sectional view of an electrode showing the test method, and the test method is as follows. First, the etched Si-doped N
30 N-type electrodes for the N-type nitride semiconductor having a size of 120 μmφ are formed on the
Annealing was performed at 0 ° C. Then, at 60 ° C 80% R
A temperature / humidity cycle test was performed for 1 hour at 20 ° C. for 1 hour. A gold wire was wire-bonded on each N-type electrode to form a ball 602 having a diameter of 100 μm to electrically connect the N-type electrode and the gold wire. Then, as shown in FIG. 6, the blade 601 is scraped horizontally from the side of the ball by the blade 601 until the ball 602 is peeled off from the N-type electrode or the ball is crushed without peeling.
Was evaluated by applying a load. Table 1 shows the results. (However, the film thickness of the metal film in each N-type electrode is the same.) In Table 1, the numerical value at each load shows the number of balls that were peeled from 100 electrodes, and the ball was not peeled. Those that have been crushed are described as “crushed”. As shown in Table 1, the N-type electrode of only the Ti / Al (laminated structure) peeled off all the balls under a load of up to 30 g.
At a load of up to g, it was found that there was no peeling at all and that it had an extremely strong adhesive force.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a nitride semiconductor device of the present invention, in which a nitride semiconductor 103 having N-type conductivity is formed on a substrate 104 and a pair of N-type electrodes are formed on the nitride semiconductor 103. . Hereinafter, each component will be described.

(N-type electrode 401) An N-type electrode 401 which is an electrode for a nitride semiconductor having N-type conductivity of the present invention.
Can be formed by various methods such as a vapor deposition method and a sputtering method at a desired place, respectively, using a metal such as tungsten or aluminum or an alloy material thereof as a vapor deposition material or a sputtering material. In order to form a stacked structure as an N-type electrode, by setting the first layers 101 and 301 to W and setting the second layers 102 and 302 to Al, favorable ohmic contact with the N-type nitride semiconductor can be obtained. . W of the first layer and Al of the second layer may be formed of an alloy. As a specific alloy material, the first layer is made of A
l, using at least one material selected from Si,
As the alloy material used for the second layer, W, Cu, S
At least one material selected from i.
Further, the electrode structure can be further made a multilayer structure.
Specifically, on the second layer, a material having a higher melting point than that of the second layer is applied to the third layer 303 in order to prevent alloying between the metal material of the second layer and the layer laminated thereon. To be laminated.
Further, a metal having good electrical connection with the electrical connection member is further laminated as the fourth layer 304 on the third layer. Specific examples of the third layer 303 include W, Cr, Ni, Mo, and T.
i and their alloys. The fourth layer 304 includes Au, Pt, and alloys thereof. Note that a plurality of metal multilayer films may be formed as desired, but the surface connected to the electrical connection member is preferably a fourth layer. Still further, the N-type electrode of the present invention has
i or / and Ge is 2 × 10 ¹⁸ as an N-type dopant
Ohmic contact and adhesion with an N-type nitride semiconductor contained at a density of from 1 / cm ³ to 1 × 10 ¹⁹ / cm ³ are particularly good. Although the reason is not clear, it is considered that there is some correlation between the first layer and Si and / or Ge contained in the N-type nitride semiconductor.

Although a sufficient ohmic contact can be formed without annealing in the nitride semiconductor device of the present invention, annealing may be performed in order to obtain a more stable and high mechanical strength semiconductor device. In this case, the annealing temperature is preferably 350 ° C. or less so that an annealing effect is generated and the adhesion between the formed N-type electrode and the electrical connection member or the N-type nitride semiconductor is not adversely affected. The temperature is more preferably from 80 ° C to 280 ° C, and still more preferably from 100 ° C to 220 ° C. In addition, it is preferable to perform the annealing in an inert gas such as Ar, He, or N ₂ .

(Nitride semiconductor 103, 305) The nitride semiconductor 101 used in the present invention is formed by a liquid phase growth method, VP
E method (Vapor Phase Epitaxy), M
OVPE method (Metal Organic Vapor)
Phase Epitaxy) or MOCVD (Me
talOrganic Chemical Vapor
Deposition) or the like. Examples of the structure of the semiconductor element include various structures such as a homo structure having a MIS junction or a PN junction, a hetero structure, a double hetero structure, and a Schottky junction, as desired. The emission wavelength and the reception wavelength can be variously selected from the ultraviolet light to the red region depending on the material of the semiconductor and the degree of mixed crystal thereof. In particular, when the N-type electrode of the present invention is used, an ohmic contact can be obtained without applying an excessive voltage to the nitride semiconductor device, which is particularly effective for a semiconductor device having an extremely thin semiconductor. Specifically, it is particularly useful in a nitride semiconductor device having a structure in which one layer constituting the semiconductor active layer has a quantum effect of 100 Å or less.

The gallium nitride-based compound semiconductor can be formed as a single crystal under high temperature and high pressure, so that the base can be omitted. However, it is preferable to form the gallium nitride on the substrate from the viewpoint of mass productivity. As a substrate on which a nitride semiconductor is formed, a single crystal semiconductor substrate of Si, Ge, SiC, or the like, GaAs, InAs, InP, GaSb, AlN,
Group III-V compound semiconductor substrate such as GaN, AlN, sapphire (Al ₂ O _3), spinel (MgAl ₂ O _4), silica _{(SiO 2), Ti 2 O} , MgO, MgF 2, CaF 2,
A substrate using a material such as SrTiO ₃ , ZnO or the like can be given. The thickness of the substrate can be variously selected depending on the semiconductor device to be formed and the material of the substrate, but when light is emitted or received through the substrate, the thinner the better, the thinner the light transmittance and the ease of formation as a chip. . On the other hand, the mechanical strength of the substrate is required during the process of forming the element and during the handling. Therefore, the preferable thickness of the substrate is 0.01 to 3.0 mm. More preferably, it is 0.05 to 2.0 mm. Note that a sapphire substrate is preferably used to form a nitride semiconductor with good crystallinity. A light emitting element and a light receiving element can be formed by forming a buffer layer such as GaN or AlN on the sapphire substrate to alleviate lattice mismatch and forming a nitride semiconductor having a PN junction or the like thereon.

A nitride semiconductor shows N-type conductivity without being doped with an impurity.
It is preferable to appropriately introduce Ge, Se, Te, C, Sn and the like. Further, double doping in which an N-type dopant and a small amount of a P-type dopant are doped can also be performed. By changing the type and doping amount of these dopants, the carrier density can be controlled and the electric resistance can be reduced. In this case, the carrier density is 1710 ¹⁷ c
It is preferably at least m ^-3 , more preferably at least 10 ¹⁸ cm ^-3 . On the other hand, when a P-type nitride semiconductor is formed, Zn, Mg, Be, Ca, S
Doping with r, Ba, etc. The gallium nitride semiconductor is P
Since it is difficult to form a p-type simply by doping with a p-type dopant, the p-type may be formed by irradiating with a slow electron beam or annealing by plasma irradiation or the like after the introduction of the p-type dopant.

Next, a semiconductor wafer or the like on which a semiconductor on a substrate is formed is directly full-cut by a dicing saw in which a blade having a diamond blade is rotated, or
Alternatively, after cutting a groove having a width wider than the blade edge width (half cut), the semiconductor wafer is cracked by an external force. Alternatively, a very thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a grid pattern using a scriber in which a diamond needle at the tip reciprocates linearly. A semiconductor chip can be formed.

In order to form an electrode having a different polarity on the emission observation surface side, it is preferable that each semiconductor is etched into a desired shape. As etching, dry etching,
There is wet etching. Examples of the dry etching include reactive ion etching, ion milling, focused beam etching, and ECR etching.
For wet etching, a mixed acid of nitric acid and phosphoric acid can be used. However, it goes without saying that a mask is formed in a desired shape using a material such as silicon nitride or silicon dioxide before etching. The electrode of the present invention shows sufficient adhesion and electric characteristics even on such an etched surface.

(P-type electrode 404) The P-type electrode 404, which is a nitride semiconductor electrode having P-type conductivity, needs to be in ohmic contact with the P-type nitride semiconductor layer to be brought into contact. When light is emitted as a light-emitting element through a P-type electrode, a light-transmitting layer formed of a metal thin film or the like (here, light-transmitting means that light passes through the electrode with respect to the wavelength of light emitted from the light-emitting element). Should be used.)

As materials satisfying these conditions, for example, Au, Ni, Pt, Al, Cr, Mo, W, In, G
Metals such as a, Tl, Ag, and Rh and alloys thereof are included. In addition, ITO as a translucent electrode material,
Metal oxides such as SnO ₂ and NiO ₂ are also included. Furthermore, it is also possible to laminate the metal thin film on these. In order to make a metal or the like light-transmitting, it may be formed to be extremely thin using an evaporation method, a sputtering method, or the like. Also,
After a metal is formed by vapor deposition or sputtering, annealing is performed to diffuse the metal into the semiconductor layer having P-type conductivity and to scatter the metal to the outside to obtain a desired film thickness (the thickness of the electrode that becomes translucent). ) Can be formed. The thickness of the metal electrode that becomes translucent varies depending on the desired emission wavelength and the type of metal, but is preferably 0.001 to 0.1 μm, more preferably 0.05 to 0.2 μm. is there. Further, when the electrode is translucent, the shape of the P-type electrode can be linear or planar, depending on the purpose. A planar electrode formed over the entire semiconductor layer having P-type conductivity can spread current over the entire surface and emit light over the entire surface.

Further, when the P-type electrode is formed extremely thin, if wire bonding is performed directly on the electrode,
Since the ball tends to be hardly connected, it is preferable to form a pedestal electrode for bonding separately from the P-type electrode or to form the P-type electrode in a multilayer structure in order to improve the adhesion. Au, Pt, Al, or the like can be used as the material of the pedestal electrode. The thickness of the pedestal electrode is preferably on the order of microns. In the case where at least a part of the P-type electrode has a multilayer structure, the contact electrodes to be brought into contact with the nitride semiconductor include Cr, Mo, W, Ni, Al, In,
A metal selected from Ga, Tl, and Ag or an alloy thereof is preferably used, and a metal such as Al or Au or an alloy thereof is preferably used as a bonding electrode that comes into contact with the bonding. When the semiconductor element is energized,
Since the bonding electrode material may migrate into the P-type electrode, it is particularly preferable to use the bonding electrode Au alone or an Au alloy having a low content of Al and / Cr. In the case of a P-type nitride semiconductor, P
It is preferable to anneal at 400 ° C. or more in order to improve the ohmic characteristics by blending the mold electrode material and the semiconductor material, and to remove hydrogen contained during the formation of the nitride semiconductor. Further, it is preferable to anneal at 1100 ° C. or lower for the purpose of suppressing the decomposition of the gallium nitride semiconductor. Further, by performing the annealing in a nitrogen atmosphere, nitrogen in the gallium nitride-based compound semiconductor can be suppressed from decomposing and leaving, and the crystallinity can be maintained.
In the present invention, when the annealing temperature of the P-type electrode is high, the N-type electrode is preferably formed after the formation of the P-type electrode.

(Electrical Connection Member 410) The electrical connection member 410 is for making electrical connection between the nitride semiconductors 103 and 305 and an external power supply, and has ohmic and mechanical connections with each electrode. It is required to have good properties, electrical conductivity and thermal conductivity. In particular, when a nitride semiconductor is used as a light emitting device, the semiconductor itself generates heat, so that the semiconductor device has a thermal conductivity of 0.01 c.
al / cm.degree. C. or more, more preferably 0.5
cal / cm · ° C. or more. Specifically, a bonding wire using gold, copper, platinum, aluminum, or the like, or an alloy thereof may be used. In addition, a conductive adhesive or the like in which a filler such as silver or carbon is filled with a resin can be used, but platinum, an aluminum wire, or a gold wire is preferable in consideration of adhesion to an N-type electrode. When an electrical connection member is connected to each electrode by wire bonding or the like, the ball 403 is formed in a hemispherical shape by melting or the like. Hereinafter, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to only specific embodiments.

[Embodiment 1] H for forming a light receiving element
An NH ₃ gas and a TMG gas are used as source gases on a 2 inch φ sapphire substrate whose surface has been cleaned with Cl / HNO _3.
A GaN layer was grown to 3000 angstroms using the CVD method. Next, Si ions are implanted at 4 KeV / cm ³ using ion implantation.
Was doped to form GaN having N-type conductivity. On this gallium nitride semiconductor, W was added to the first layer by 200 Å by sputtering, and A was added to the second layer by A.
1 was set to 2000 angstroms and laminated by sputtering. Thereafter, a mask having a desired shape was formed, and a pair of electrodes was formed by dry etching as shown in FIG. After the wafer was separated into 1500 chips by a scriber, it was die-bonded on a lead frame, and the N-type electrodes on the semiconductor chip were electrically connected by gold wire by wire bonding.

The nitride semiconductor on which the N-type electrode according to the present invention is formed is arbitrarily taken out, and 10 pieces are taken out at 80 ° C.
FIG. 2 shows the average dark current-voltage characteristics obtained by annealing for 1 minute at a temperature of 300 ° C. and 300 ° C., respectively, and that obtained without annealing. In addition, 100 pieces were randomly extracted from this gallium nitride semiconductor element,
Was applied 50 times, and a continuous repetition test of 12 hours at room temperature and 12 hours at a high-temperature and high-humidity chamber at 60 ° C. and 80% RH was performed 50 times. No peeling of the N electrode ball was confirmed.

Comparative Example 1 A nitride was formed in the same manner as in Example 1 except that the first layer electrode material was Ti and the second layer electrode material was Al on the N-type gallium nitride semiconductor device. A semiconductor device was formed. FIG. 7 shows dark current-voltage characteristics obtained by annealing the semiconductor element formed on the N-type electrode at 80 ° C., 150 ° C., and 300 ° C. for 1 minute. (Note that the measurement range of the current-voltage characteristics is the same as that of the first embodiment.
It is the same as. ) Further, 100 pieces were randomly extracted from the gallium nitride semiconductor device, and a voltage of 4 V was applied thereto, for 12 hours at normal temperature, and a high-temperature and high-humidity tank 12 at 60 ° C. and 80% RH.
When a continuous repetition test with time was performed 50 times, peeling of the ball of the N electrode was confirmed in 10% of the gallium nitride semiconductor devices.

Example 2 A GaN buffer layer was grown on a sapphire substrate by MOCVD using a NH ₃ gas and a TMG gas to a thickness of 150 Å. further,
NH ₃ gas and TM on the buffer layer using MOCVD
The N-type GaN layer is formed using G gas and SiH ₄ / H ₂ gas.
000 Å. After forming a negative resist film thereon, W (13) is used as a first layer.
200 Å, Al (14) 2 in the second layer
000 angstroms, 20 W (13) in the third layer
00 Å, Au (15) 300 in the fourth layer
0 Å was laminated by sputtering with a different target. Unnecessary resist film was removed to form an N-type electrode. FIG. 3 shows an example in which an aluminum wire is electrically connected to the N-type electrode by wire bonding.
Was formed. As in Example 1, good ohmic contact with the N-type gallium nitride-based compound semiconductor can be obtained without annealing. Also,
100 pieces were randomly extracted from this gallium nitride semiconductor device, and a voltage of 4 V was applied thereto.
When a continuous repetition test was performed 50 times in a high-temperature and high-humidity tank of 0% RH for 12 hours, none of the N-electrode balls was confirmed to be peeled off.

Example 3 A nitride semiconductor device was formed in the same manner as in Example 2 except that W in the third layer was changed to Ti. As in Example 2, excellent characteristics were obtained.

[Embodiment 4] A GaN buffer layer and a GaN buffer layer were formed on a 2 inch φ sapphire substrate to form a light emitting device.
i-doped N-type GaN contact layer, Si-doped N-type Ga
AlN cladding layer, undoped InGaN active layer, M
g-doped P-type GaAlN cladding layer, Mg-doped P-type G
A wafer having a double hetero structure in which an aN contact layer was sequentially laminated was formed. The active layer has a single well structure (SQW) of 20 angstroms in order to have a quantum effect.

Next, the N-type GaN contact layer is exposed on the surface by partially etching the P-type GaN contact layer of the wafer in the depth direction so that a semiconductor device having the cross-sectional shape of FIG. 4 can be formed. After a mask having a desired shape is applied, Ni is deposited as a P-type electrode on the surface of the P-type GaN contact layer in a thickness of 1000 Å and Au is deposited in a thickness of 5000 Å. After the formation of the P-type electrode, the mask is removed, and the wafer is placed in an annealing apparatus and annealed at 600 ° C. for 5 minutes in an N ₂ gas atmosphere. After annealing, a mask having a predetermined shape is formed, and W is 200 angstroms as the first layer, 2000 angstroms of Al as the second layer, and 2000 angstroms as the third layer and the fourth layer which is the final layer. An N-type electrode is formed by depositing Pt as a layer in order to change the target to a thickness of 2000 angstroms.
After the formation of the N-type electrode, the mask is removed and the mask is removed in an Ar gas atmosphere.
Anneal at 70 ° C. for 3 minutes. Next, the wafer was separated into chips by a scriber, and 15,000 chips were obtained from a 2-inch φ wafer. As a result of measuring current-voltage characteristics, good ohmic characteristics were obtained as in Example 1. After the thus obtained light emitting chip made of a nitride semiconductor is die-bonded and mounted on a lead frame, Au wires are connected to each of the P-type and N-type electrodes with a wire bonder, and then epoxy resin is used. The whole was molded to form an LED element. This LED element had a forward voltage _{Vf of} 3.5 V at a forward current _{If of} 20 mA. Further, 100 LEDs were randomly extracted from the LED element, turned on for 12 hours at room temperature, and heated to 60 ° C. and 80% RH. When a continuous repetition test of lighting for 12 hours in a high-humidity tank was performed 50 times, none of the LEDs turned off due to peeling of the ball of the N-type electrode.

[0031]

As described above, the nitride semiconductor device according to the present invention can be manufactured with an excellent nitride semiconductor device which can simplify the manufacturing process and has good ohmic contact and mechanical strength with the N-type nitride semiconductor. can do.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a nitride semiconductor device of the present invention.

FIG. 2 is a graph showing dark current-voltage characteristics of the nitride semiconductor device of FIG.

FIG. 3 is a schematic diagram of another nitride semiconductor device of the present invention.

FIG. 4 is a schematic sectional view of another nitride semiconductor device of the present invention.

FIG. 5 is a schematic view showing a test method for examining the adhesion between an N-type nitride semiconductor, an N-type electrode, and an electrical connection member.

FIG. 6 is a schematic sectional view of a nitride semiconductor device shown for comparison with the present invention.

FIG. 7 is a diagram showing dark current-voltage characteristics of the nitride semiconductor device of Comparative Example 1.

[Explanation of symbols]

 Reference Signs List 101 first layer 102 second layer 103 N-type nitride semiconductor 104 sapphire substrate 301 first layer 302 second layer 303 third layer 304 fourth layer 305 N-type nitride semiconductor 306 sapphire substrate 401 N Type electrode 402 N-type contact layer 403 Ball 404 P-type electrode 405 P-type contact layer 406 P-type clad layer 407 Active layer 408 N-type clad layer 409 Sapphire substrate 410 Electrical connection member 501 Blade 502 Ball 503 Fourth metal layer 504 Third metal layer 505 Second metal layer 506 First metal layer 507 N-type nitride semiconductor 601 N-type electrode 602 N-type nitride semiconductor 603 Ball 604 P-type electrode 605 P-type contact layer 606 P-type cladding layer 607 Active layer 608 N-type cladding layer 609 Substrate 610 Electrical Connection member

[Table 1]

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A nitride semiconductor device in which an electrode is provided on a nitride semiconductor having N-type conductivity, wherein the electrode is formed of W
A nitride semiconductor device comprising: a first layer having Al; and a second layer having Al provided on the first layer. 2. The method according to claim 2, wherein W, Cr, Ni, Mo,
2. The nitride semiconductor device according to claim 1, further comprising a third layer having one kind of metal selected from Ti. 3. The nitride semiconductor device according to claim 1, wherein the surface of the electrode connected to the electrical connection member is one of Au and Pt. 4. The nitride semiconductor having N-type conductivity is S
2. The nitride semiconductor device according to claim 1, containing i and / or Ge. 5. A step of forming a nitride semiconductor having N-type conductivity on a substrate, a step of forming a first layer having W as a material forming an electrode on the nitride semiconductor, A second layer having Al as a material constituting an electrode on the first layer;
And a step of annealing the nitride semiconductor on which the electrode is formed at 350 ° C. or lower. 6. An annealing temperature of 80 ° C. or more and 280 ° C.
The method for manufacturing a nitride semiconductor device according to claim 5, wherein: