JP3407536B2 - Nitride semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nitride semiconductor (In
_X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), light emitting diode (LED), laser diode (L
The present invention relates to a nitride semiconductor element used as a light emitting element such as ED), a light receiving element such as a solar cell, and an optical sensor.

[0002]

2. Description of the Related Art Generally, a light emitting chip made of a nitride semiconductor is provided with positive and negative electrodes on the same surface side. This is because nitride semiconductors are often grown on insulating substrates. Such a light emitting chip is mounted on a support such as a stem, a lead frame, a heat sink, or a submount in a face-down state or a face-up state to form a light emitting element.

The applicant of the present invention has previously filed Japanese Patent Application Laid-Open No. 7-235729.
In the publication, a laser device is shown in which a nitride semiconductor light emitting chip is mounted face down on a support. In this technique, for the purpose of improving the heat dissipation of a nitride semiconductor laser chip using an insulating substrate such as sapphire, the laser chip is face-down mounted on an insulating heat sink.

[0004]

Usually, when a semiconductor chip having two kinds of electrodes provided on the same surface side is bonded face down to a support, a heated solder material is placed at a predetermined position of the support. At the same time when a predetermined amount is discharged by a dispenser, a semiconductor chip is placed on the solder material and a means for electrically connecting the support and the semiconductor chip by cooling is performed. Solder material is silver paste, I
A low melting point metal such as n paste or Pb / Sn is often used. However, as is well known, the solder material has a drawback that it has a large fluidity in the overheated state. Therefore, in a nitride semiconductor chip in which positive and negative electrodes are provided on the same surface side, the solder material may flow out from a predetermined position to contact one electrode and cause a short circuit between the electrodes.

An element in which a semiconductor chip having electrodes provided on the same surface side is mounted facedown has to have improved reliability. In particular, in order to realize a device having a large amount of heat generation such as a laser element, when the solder material is deformed or deteriorated by heat, the reliability as an element is significantly lowered.
Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a highly reliable nitride semiconductor element free from a short circuit between electrodes.

[0006]

In a nitride semiconductor device according to the present invention, a nitride semiconductor chip having a pair of electrodes provided on the same surface side is formed at a position corresponding to the pair of electrodes of the semiconductor chip, respectively. And the first electrode (21a) and the second electrode (21b), which are electrically connected to the first electrode (21a) and the second electrode (21b), respectively. 21b) a nitride semiconductor device, which is mounted facedown on a support on which a third electrode (22a) and a fourth electrode (22b) having an area larger than that of the support is formed. Has a groove formed between a first electrode (21a) and a second electrode (21b) formed at positions corresponding to the pair of electrodes of the semiconductor chip, respectively. electrodes, one of which is work function Selection large Ni, Au, platinum group of
Nitride semiconductor positive electrode, the other has a low work function
Nitride semiconductor negative electrode selected from Ti, Al, and W
With it, the first electrode, respectively (21a), is directly connected to the second electrode (21b), a first electrode (21
a), said second electrode (21b) is connected respectively
Positive electrode, Ri same metal der negative electrode, further, the third electrode (22a), a fourth electrode (22b) comprises a first layer formed on the side in contact with the support, the first Electrode (21
a) and a second layer formed on the side in contact with the second electrode (22b) side, at least a two-layer structure.

In addition, a nitride semiconductor chip having a pair of electrodes provided on the same surface side has a first electrode (21a) and a second electrode (21a) respectively formed at positions corresponding to the pair of electrodes of the semiconductor chip. The electrode (21b) and a third electrode (22a) electrically connected to the first electrode and the second electrode, respectively, and having a larger area than the first electrode (21a) and the second electrode (21b). ), A nitride semiconductor device mounted facedown on a support having a fourth electrode (22b) formed thereon, the support having a position corresponding to the pair of electrodes of the semiconductor chip. A groove is formed between the first electrode (21a) and the second electrode (21b) respectively formed on the first electrode (21a) and the second electrode (21b), and the groove of the support is the third electrode (22a) and the fourth electrode. (22
b) is provided in the first groove between the semiconductor chip and
Has a nitride semiconductor layer provided on the sapphire substrate.
Then, the uppermost layer of the nitride semiconductor layer and a part thereof are removed.
A pair of positive and negative electrodes are provided, and the pair of electrodes are subjected to thermocompression bonding.
From the first electrode (21a) and the second electrode (2
1b), the third electrode (22a) and the fourth electrode (22b) are directly connected to the first layer formed on the side in contact with the support, and the first electrode (21a). ) And a second layer formed on the side in contact with the second electrode (22b) side, at least a two-layer structure is provided.

Further, a nitride semiconductor chip having a pair of electrodes provided on the same surface side is provided with a first electrode (21a) and a second electrode (21a) respectively formed at positions corresponding to the pair of electrodes of the semiconductor chip. The electrode (21b) and a third electrode (22a) electrically connected to the first electrode and the second electrode, respectively, and having a larger area than the first electrode (21a) and the second electrode (21b). ), A nitride semiconductor device mounted facedown on a support having a fourth electrode (22b) formed thereon, the support having a position corresponding to the pair of electrodes of the semiconductor chip. A groove is formed between the first electrode (21a) and the second electrode (21b) respectively formed on the first electrode (21a) and the second electrode (21b), and the groove of the support is the third electrode (22a) and the fourth electrode. (22
b) is provided in a first groove portion, and the first groove portion is provided in a second groove portion between the first electrode (21a) and the second electrode (21b). The pair of electrodes are directly connected to the first electrode (21a) and the second electrode (21b) by thermocompression bonding, and further, the third electrode (22a) and the fourth electrode (22b). ) Is at least 2 consisting of a first layer formed on the side in contact with the support and a second layer formed on the side in contact with the first electrode (21a) and the second electrode (21b) side. It is characterized by having a layered structure.

Further, in the element of the present invention, the third electrode (22a) formed on the support is formed up to the back surface of the support, and the fourth electrode (22b) is wire-bonded. Is preferably provided.

Furthermore, the third electrode 22a and the fourth electrode 22b are a first layer formed on the side in contact with the support and a second layer formed on the side in contact with the first electrode. When,
Further, it is preferable to have at least a three-layer structure including an intermediate layer formed between the first layer and the second layer.

The first layer is titanium (Ti), chromium (Cr), aluminum (Al), zirconium (Z).
r) comprising at least one selected from the group consisting of
The nitride semiconductor device according to claim 2 or 3, wherein the second layer contains at least gold (Au). Further, the intermediate layer includes platinum (Pt), nickel (Ni),
It is preferable to contain at least one selected from the group consisting of molybdenum (Mo) and tungsten (W).

The nitride semiconductor device of the present invention can be obtained by the following method. That is, the third electrode 22a, the fourth electrode 22b having a large area, and the third electrode 22a
The first electrode 21a and the second electrode 21b each having a smaller area than the second electrode 22a and the fourth electrode 22b are formed. The first electrode 21a and the second electrode 21b are previously formed at positions corresponding to the electrode positions of the nitride semiconductor. On the other hand, after mounting the semiconductor chip having the positive and negative electrodes on the same surface side on the support so as to correspond to the positions of the first electrode 21a and the second electrode 21b of the support, , The first electrode 21 and the semiconductor chip electrode by heating the entire
The semiconductor chip is mounted on a support by alloying a portion where a and the second electrode 21b are in contact with each other. It is not necessary to use a special method for forming the electrodes, and the electrodes can be formed by a commonly used method such as vapor deposition, sputtering, printing or plating.

[0013]

FIG. 1 is a schematic cross-sectional view showing one structure of the nitride semiconductor device of the present invention, specifically showing the structure of a laser device. In this figure, reference numeral 100 denotes a light emitting chip made of a nitride semiconductor.
Reference numeral 0 mainly includes a substrate 101 and a nitride semiconductor layer 102 that emits laser light to emit light.
A negative electrode 103 and a positive electrode 104 are provided on the same surface side of 02.

On the other hand, on the support 20 on which the light emitting chip 100 is mounted, the negative electrode 103 of the semiconductor chip 100,
A first electrode 21a and a second electrode 21b are formed at positions corresponding to the positive electrode 104 and the positive electrode 104, respectively, and are further electrically connected to the first electrode 21a and the second electrode 21b, respectively. The third electrode 22a and the fourth electrode 22b, which have a larger area than the electrodes 21a and the second electrode 21b, are formed so as to be in contact with the support. Then, the first electrode 21a and the second electrode 21b formed on the support side and the negative electrode 103 and the positive electrode 104 on the semiconductor chip side are directly connected to each other without using a conductive adhesive such as solder. Has been done.

The materials for the first electrode 21a and the second electrode 21b are not particularly limited, but it is desirable to select a material that easily alloys with the electrode of the nitride semiconductor and has a low contact resistance. For example, the material of the positive electrode of the nitride semiconductor is N
A material having a large work function such as i, Au, or a platinum group element is often selected, and a material having a small work function such as Ti, Al, or W is often selected as the material of the negative electrode. Therefore, for the first electrode 21a and the second electrode 21b, it is desirable to use the same metal as the nitride semiconductor electrode, or to select a metal or alloy having a melting point of 600 ° C. or less. A metal having a melting point of 600 ° C. or lower, specifically an alloy containing Au, for example, Au / Sn, Au / S
There are alloys such as i and Au / Ge, and it is desirable to select an alloy containing In.

As described above, in the nitride semiconductor device of the present invention, the electrode of the semiconductor chip and the electrode formed on the support are connected without the intermediary of a conductive adhesive, so that the adhesive does not flow out. As a result, the short circuit between the electrodes is eliminated, and the reliability of the device is significantly improved.

In the device of the present invention, the first electrode 21
Areas of the third electrode 22a and the fourth electrode 22b are larger than those of the second electrode 21b. That is, in the element of the present invention, the first electrode 21a and the second electrode 21b are for connecting to the electrodes of the semiconductor chip, and the third electrode 2
The second electrode 4a and the fourth electrode 22b are formed on the surface of the support 20 and act as electrodes for supplying electric power from the outside, such as external leads and a power source. Therefore, the third electrode 22
It is necessary that the a and the fourth electrode 22b have a larger area than the first electrode 21a and the second electrode 21b so that they are not easily peeled off from the support. Therefore, in a preferred embodiment of the present invention, by making the third electrode 22a and the fourth electrode 22b have a layered structure, it is possible to prevent the third electrode 22a and the fourth electrode 22b from coming off from the support.

A number of materials are used for the support 20,
For example, when the semiconductor chip is a laser chip, A
A heat sink with good thermal conductivity such as 1N, SiC, GaAs, BN, Si, C (diamond) is used.
For the D chip, an insulating green sheet such as Al2O3 or SiO2 is used. The material of the support is not particularly limited and may be either an insulating material or a conductive material. When a conductive support is used, in order to prevent a short circuit between the electrodes, an insulating film is formed on the surface of the support before forming the third electrode 22a and the fourth electrode 22b. You can also

As shown in FIG. 1, each of the third electrode 22a and the fourth electrode 22b has a first layer 221a, 221b (hereinafter the first layer is referred to as a reference numeral 2) on the side in contact with the support.
21. ) Is formed, and the second layer 222a is formed on the side in contact with the first electrode 21a and the second electrode 21b,
222b (hereinafter, the reference numeral of the second layer is referred to as 222) is formed. For the first layer 221, a metal having good adhesiveness (adhesiveness) to the support 20 is selected, and for the second layer 222, the first layer is used.
It is desirable to select a metal having good adhesiveness to the electrode 21 of FIG. Specifically, the first layer 221 is made of Ti, Cr, Al, Z.
It is desirable that the second layer 222 include at least one selected from the group consisting of r, and at least the gold (Au). In particular, the first layer 221 is formed on the support 20 with Al2O3,
Insulator such as SiO2, or SiC, AlN, GaAs
The adhesiveness is very good when using semiconductors such as. Further, when Au is used for the second layer 222, it is possible to reduce the contact resistance between the first electrode 21a and the second electrode 21b for connection, and the adhesiveness of the gold wire during wire bonding is good.

Further, in a preferred embodiment of the present invention, as shown in FIG. 1, the third electrode 22a and the fourth electrode 2 are
2b is the first layer 221 formed on the side in contact with the support.
And the second layer 22 formed on the side in contact with the first electrode side.
2 and intermediate layers 223a and 223b formed between the first layer and the second layer (hereinafter, reference numeral of the intermediate layer is 2).
23. ) And at least a three-layer structure. The intermediate layer 223 is composed of the first layer 221 and the second layer 2
It has the effect of further increasing the adhesiveness with 22. Further, it also has a function as a barrier layer for preventing the first layer 221 and the second layer 222 from being alloyed with each other at the time of heat bonding to reduce the effect of each electrode material. The specific intermediate layer preferably contains at least one selected from the group consisting of Pt, Ni, Mo, and W. These metals include, in particular, a second layer 222 containing Au, Ti, Cr, Al,
It has a function of improving the adhesiveness with the Zr first layer 221.

That is, in the device of the present invention, the first electrode 21a and the second electrode 21b formed on the support side are formed.
Is an electrode for adhesion which is alloyed with the electrodes 103 and 104 of the nitride semiconductor by heating to be integrated, and the third electrode 22a and the fourth electrode 22b are externally wire-bonded, die-bonded or the like. And functions as an electrode for connecting to a power supply means. When the third electrode 22a and the fourth electrode 22b are made of a material containing Au, for example, when the wire bonding is performed with a gold wire, the third electrode 22a and the fourth electrode 22b have good adhesiveness with the gold wire, but further have good adhesiveness with the support 20. In order to do so, the third electrode 22a and the fourth electrode 22b have a layered structure. When the third electrode 22a and the fourth electrode 22b have a layered structure, the third electrode 22a
And the fourth electrode 22b has a first layer 221 having good adhesiveness to the support 20, and a second layer 221 having good adhesiveness to the first electrode 21.
Layer 222. However, the first
If the layer 221 and the second layer 222 are alloyed, the adhesiveness with the support 20 and the adhesiveness of the gold wire may be impaired. Therefore, by further adding the intermediate layer 223,
It is possible to improve the adhesiveness of the entire first electrode 21a and the second electrode 21b to the support 20, and also the adhesiveness to the gold wire during wire bonding.

[0022]

EXAMPLES Example 1 Hereinafter, the device of the present invention will be described in detail with reference to the drawings. Figure 1
2 is a schematic cross-sectional view showing the structure of the device according to Example 1, and FIG. 2 is a plan view showing the structure of only the support as viewed from the light emitting chip side.

A nitride semiconductor 102 having at least an n-type nitride semiconductor layer, an oscillating active layer, and a p-type nitride semiconductor layer on a sapphire substrate 101.
A μm square laser chip 100 is prepared. In this laser chip, as shown in FIG. 1, a part of the uppermost nitride semiconductor layer is removed by etching and the positive electrode 10 is formed on the same surface side.
4 and the negative electrode 103. An alloy containing Ni and Au is used for the positive electrode 104, and T is used for the negative electrode 103.
An alloy containing i and Al is used.

On the other hand, a 5 mm square submount made of AlN is used as the support 20, and a protective film having an appropriate shape is formed on the surface of the submount by photolithography. Including first layer 221
a and 221b are formed by vapor deposition.

Subsequently, intermediate layers 223a and 223 containing Pt and Ni respectively are formed on the first layers 221a and 221b.
Similarly, b and b are formed by vapor deposition.

Further, second layers 222a and 222b made of Au are similarly formed by vapor deposition on the intermediate layers 223a and 223b, and then the protective film is removed. By the above operation, the third electrode 22a and the fourth electrode in which the first layer 221 containing Ti / Al, the intermediate layer 223 containing Pt / Ni, and the second layer 222 containing Au are stacked are stacked. 22b is formed.

After forming the third electrode 22a and the fourth electrode 22b, a protective film having an appropriate shape is formed on the second layer, and then a first layer made of an alloy containing Au and Sn is formed.
The electrode 21a and the second electrode 21b are similarly formed by vapor deposition. FIG. 2 is a plan view of the support 10 after the electrodes are formed, and the positions of the electrodes correspond to those in FIG.

The laser chip 100 having the electrodes formed as described above is placed on the support 20 so that the electrodes face each other, and the electrodes are thermocompression bonded at 500 ° C. By this thermocompression bonding, the electrodes 103 and 10 of the laser chip are
4 and the first electrode 21a and the second electrode 21 of the support 20.
b is alloyed and adhered, and the third electrode 22
a, the fourth electrode 22b and the first electrode 21a, the second electrode 22b and the third electrode 22a, the fourth electrode 22b and the support 20 are firmly bonded.

Next, the support 20 is set on a conductive heat sink. The third electrode 22a formed up to the back surface of the support is attached to the heat sink by bonding the heat sink with solder. Further, a gold wire is wire-bonded to the uppermost layer of the fourth electrode 22b formed on the surface of the support 20 to form a laser element.

When the laser chip was die-bonded to the support in a face-down state in the above process, the yield of the die bond itself due to electrode displacement was 95% or more. Among them, the yield due to short circuit between the electrodes of the laser chip. Was 0%. The yield due to peeling of the wire was 0%. Furthermore, this laser element is 100
When pulse oscillation was performed continuously for a time, none of the electrodes short-circuited during oscillation.

Example 2 First electrode 21a and second electrode 21 of support 100
The material of b is an alloy containing Au and Si. Further, in the third electrode 22a and the fourth electrode 22b, the same as Example 1 except that the first layer 221 is an alloy containing Cr and Zr and the intermediate layer 223 is an alloy containing Mo and W. As a result, the laser device showed substantially the same characteristics as those of Example 1 in terms of electrode characteristics, yield and the like.

Example 3 First electrode 21a and second electrode 21 of support 100
The material of b is an alloy containing Au and Ge. Further, in the third electrode 22a and the fourth electrode 22b, the same as Example 1 except that the first layer 221 is an alloy containing Al and Cr and the intermediate layer 223 is an alloy containing Ni and Mo. As a result, the laser device showed substantially the same characteristics as those of Example 1 in terms of electrode characteristics, yield and the like.

[Embodiment 4] The material of the second electrode 21b of the support 100 is an alloy containing Ni and Au, and the material of the first electrode 21a is Ti and Al.
An alloy containing and. That is, the same material as the electrode material of the laser chip is used. In the third electrode 22a and the fourth electrode 22b, the first layer 221 is made of an alloy containing Al and Cr, and the intermediate layer 223 is made of Ni.
When a laser device was prepared in the same manner as in Example 1, the characteristics of the electrode, the yield and the like were almost the same as those in Example 1.

[0034]

As described above, in the nitride semiconductor device of the present invention, the electrode of the semiconductor chip and the electrode of the support are bonded together without a conductive adhesive, so that the reliability is very high. A highly reliable semiconductor device can be realized. Further, although the laser element has been described in the embodiments of the present invention, it is needless to say that the present invention is not limited to the laser element and can be applied to any semiconductor device such as an LED element and a light receiving element using a nitride semiconductor.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a nitride semiconductor device according to an example of the present invention.

FIG. 2 is a plan view of the support body of FIG. 1 viewed from a semiconductor chip mounting side.

[Explanation of symbols]

100 ... Semiconductor chip 103 ... Negative electrode 104 ... Positive electrode 20 ... Support 21a ... First electrode 21b ... second electrode 22a ... The third electrode 22b ... the fourth electrode 221a, 221b ... the first layer 222a, 222b ... second layer 223a, 223b ... Intermediate layer

Continuation of the front page (56) Reference JP-A-56-112774 (JP, A) JP-A-52-130295 (JP, A) JP-A-7-235729 (JP, A) JP-A-6-177429 (JP , A) JP-A-6-232510 (JP, A) JP-A-63-160292 (JP, A) JP-A-60-157284 (JP, A) JP-A-6-112596 (JP, A) 2-138454 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (7)

(57) [Claims] 1. A nitride semiconductor chip having a pair of electrodes provided on the same surface side, and a first electrode (21) formed at a position corresponding to the pair of electrodes of the semiconductor chip, respectively.
a), the second electrode (21b) and its first electrode, the second
Of the first electrode (21
a) and a nitride which is mounted facedown on a support on which a third electrode (22a) and a fourth electrode (22b) each having a larger area than the second electrode (21b) are formed. In the semiconductor element, a groove portion is formed on the support body between a first electrode (21a) and a second electrode (21b) respectively formed at positions corresponding to the pair of electrodes of the semiconductor chip. One of the pair of electrodes of the semiconductor chip has a large work function.
Nitride semiconductors selected from Ni, Au and platinum group
Select the electrode, Ti, Al, or W, which has a small work function
A negative electrode of a selected nitride semiconductor, and a first electrode (21a) and a second electrode (21b) , respectively.
Directly connected to the first electrode (21a), the second electrode
(21b) are connected to the positive electrode and the negative electrode, respectively.
Ri same metal der, further said third electrode (22a), a fourth electrode (22
b) comprises at least a first layer formed on the side in contact with the support, and a second layer formed on the side in contact with the first electrode (21a) and second electrode (22b) side. A nitride semiconductor device having a two-layer structure. 2. A nitride semiconductor chip having a pair of electrodes provided on the same surface side, a first electrode (21) formed at a position corresponding to the pair of electrodes of the semiconductor chip, respectively.
a), the second electrode (21b) and its first electrode, the second
Of the first electrode (21
a) and a nitride which is mounted facedown on a support on which a third electrode (22a) and a fourth electrode (22b) each having a larger area than the second electrode (21b) are formed. In the semiconductor element, a groove portion is formed on the support body between a first electrode (21a) and a second electrode (21b) respectively formed at positions corresponding to the pair of electrodes of the semiconductor chip. The groove of the support is provided in the first groove between the third electrode (22a) and the fourth electrode (22b), and the semiconductor chip is provided on the sapphire substrate.
An uppermost layer of the nitride semiconductor layer and its uppermost layer.
The portion is removed to provide a pair of positive and negative electrodes, and the pair of electrodes are respectively subjected to thermocompression bonding to form the first electrode (21a),
The third electrode (22a) and the fourth electrode (22) are directly connected to the second electrode (21b).
b) comprises at least a first layer formed on the side in contact with the support, and a second layer formed on the side in contact with the first electrode (21a) and the second electrode (22b) side. A nitride semiconductor device having a two-layer structure. 3. A nitride semiconductor chip having a pair of electrodes provided on the same surface side, a first electrode (21) formed at a position corresponding to the pair of electrodes of the semiconductor chip, respectively.
a), the second electrode (21b) and its first electrode, the second
Of the first electrode (21
a) and a nitride which is mounted facedown on a support on which a third electrode (22a) and a fourth electrode (22b) each having a larger area than the second electrode (21b) are formed. In the semiconductor element, a groove portion is formed on the support body between a first electrode (21a) and a second electrode (21b) respectively formed at positions corresponding to the pair of electrodes of the semiconductor chip. And a groove portion of the support is provided in a first groove portion between the third electrode (22a) and the fourth electrode (22b), and the first groove portion is provided with the first electrode (21a). The pair of electrodes of the semiconductor chip provided in the second groove portion between the second electrode (21b) and the second electrode (21b) are directly bonded to the first electrode (21a) and the second electrode (21b) by thermocompression bonding. Connected to the third electrode (22a) and the fourth electrode (22a). Electrode (22
b) comprises at least a first layer formed on the side in contact with the support, and a second layer formed on the side in contact with the first electrode (21a) and the second electrode (21b) side. A nitride semiconductor device having a two-layer structure. 4. A third electrode (2) formed on the support.
2a) is formed up to the back surface of the support, and further,
It said fourth electrode (22b) is a nitride semiconductor device according to claim 1 to 3, characterized in that it is wire bonding. 5. The third electrode (22a) and the fourth electrode (22b) are formed on the first layer formed on the side contacting the support and on the side contacting the first electrode side. The second layer,
Further, the first layer and the nitride semiconductor device according to claim 1 to 4, characterized in that at least three-layer structure consisting of an intermediate layer formed between the second layer. 6. The first layer comprises titanium (Ti), chromium (Cr), aluminum (Al), zirconium (Z).
r) comprising at least one selected from the group consisting of
The nitride semiconductor device according to claim 1 to 5 wherein the second layer is characterized in that it comprises at least gold (Au). Wherein said intermediate layer is of platinum (Pt), nickel (Ni), molybdenum (Mo), in claim 5 or 6, characterized in that it comprises at least one member selected from the group consisting of tungsten (W) The nitride semiconductor device described.