JP3362650B2 - Method for manufacturing nitride semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor device having an n-type gallium nitride based semiconductor layer and a p-type gallium nitride based semiconductor layer.

[0002]

2. Description of the Related Art In recent years, gallium nitride-based semiconductors have been used.
A light emitting element capable of emitting blue light has been developed and used for various purposes. FIG. 8A is a sectional view schematically showing an example of a conventional nitride semiconductor device structure.
(B) is a plan view showing the electrode structure. The conventional nitride semiconductor device shown in FIG. 8 is provided with an n-type gallium nitride based semiconductor layer 12, an active layer 10a and a p-type gallium nitride based semiconductor layer 13a on a sapphire substrate 11, and includes a p-type gallium nitride based semiconductor layer. The negative electrode 14 is formed on the upper surface of the n-type gallium nitride based semiconductor layer 12 exposed by removing a part thereof, and p is formed on almost the entire upper surface of the p-type gallium nitride based semiconductor layer.
The positive electrode 15a on the side is formed. In the conventional nitride semiconductor device shown in FIG. 8, the extraction electrode 16 is formed at a predetermined position on the positive electrode 15a, and the opening on the negative electrode 14 and the opening on the extraction electrode 16 are removed. As a result, the insulating film 17 is formed.

Here, in the conventional nitride semiconductor device, after removing a part of the p-type gallium nitride based semiconductor layer in the region where the negative electrode 14 is to be formed, a positive electrode is formed and a photo is formed on the positive electrode. A positive electrode 15a was formed on the upper surface of the p-type gallium nitride based semiconductor layer 13a by forming a mask having a predetermined shape using a resist and removing the excess positive electrode by etching.

[0004]

However, in the conventional nitride semiconductor device, the positive electrode 15a has p-type gallium nitride at the end thereof in consideration of the formation accuracy of the photoresist mask used as an etching mask. It was formed so as to be located 10 to 20 μm inside from the end of the system semiconductor layer 13a (shown as 15 μm in FIG. 8). Therefore, there is a problem that the peripheral portion of the p-type gallium nitride based semiconductor layer 13a cannot be effectively used and the forward voltage cannot be sufficiently reduced. Further, in order to improve the accuracy of forming the photoresist mask and operate it sufficiently effectively in the peripheral portion of the active layer 10a, it is necessary to use an expensive device such as a stepper exposure device in forming the photoresist mask. Yes,
There was a new problem that it could not be manufactured at low cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and provide a nitride semiconductor device which can be manufactured at low cost and can reduce the forward voltage, and a manufacturing method thereof.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional example, and in the method of manufacturing a nitride semiconductor device, the above-mentioned p-type gallium nitride system is used without using an expensive exposure apparatus. This has been completed by finding a method for reducing the distance between the outer circumference of the semiconductor layer and the outer circumference of the positive electrode.

That is, in the method for manufacturing a nitride semiconductor device according to the present invention, p is formed on a substrate through at least one semiconductor layer including at least an n-type gallium nitride based semiconductor layer.
Forming a p-type gallium nitride-based semiconductor layer, forming an electrode layer on the surface of the p-type gallium nitride-based semiconductor layer, forming a mask on the electrode layer, and except immediately below the mask. An etching step of forming a positive electrode having a predetermined shape by removing the electrode layer and the p-type gallium nitride based semiconductor layer by etching, and exposing a part of the upper surface of the n-type gallium nitride based semiconductor layer; And a step of forming a negative electrode on a part of an upper surface of the exposed n-type gallium nitride based semiconductor layer, wherein the etching step is wet etching of the electrode layer. And dry etching the p-type gallium nitride based semiconductor layer. Here, in the present specification, gallium nitride based semiconductor refers to GaN and a semiconductor in which a part of gallium in GaN is replaced with one or more other elements.

In the method for manufacturing a nitride semiconductor device according to the present invention, in the etching step, the surface of the n-type gallium nitride semiconductor layer is dry-etched from the electrode layer to the p-type gallium nitride semiconductor layer. The step of exposing the electrode layer may further include wet etching the electrode layer.

In the method for manufacturing a nitride semiconductor device according to the present invention, the etching step includes wet etching the electrode layer and then dry etching the p-type gallium nitride based semiconductor layer to obtain the n-type nitride. A step of exposing the surface of the gallium-based semiconductor layer may be included.

Further, in the method for manufacturing a nitride semiconductor device according to the present invention, it is preferable that the positive electrode is formed to a thickness of 1.5 μm or less in order to accurately form the positive electrode.

Furthermore, in the method for manufacturing a nitride semiconductor device according to the present invention, the positive electrode is made of Ni, Au, P.
It is preferably formed by including at least one element selected from the group consisting of t, Co, Pd and Zn. As a result, good ohmic contact can be formed between the positive electrode and the p-type gallium nitride based semiconductor layer.

In the method for manufacturing a nitride semiconductor device according to the present invention, it is more preferable that the electrode layer is formed to contain Ni or Au.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The nitride semiconductor device of the embodiment according to the present invention is a light emitting device, and as shown in FIG. 1, for example, on a substrate 11 made of sapphire,
An n-type gallium nitride based semiconductor layer 12 made of AlInGaN doped with Si, a light emitting layer 10 made of InGaN, and AlInGa doped with Mg, for example.
It has a semiconductor layer structure in which p-type gallium nitride based semiconductor layers 13 made of N are sequentially stacked, and positive and negative electrodes are formed as follows. That is, the n-side negative electrode 14 is formed on the upper surface of the n-type gallium nitride based semiconductor layer 12 exposed by removing the p-type gallium nitride based semiconductor layer from one side surface (first side surface) to a predetermined width, A p-side positive electrode 15 is formed on almost the entire upper surface of the p-type gallium nitride based semiconductor layer 13. In addition, in the nitride semiconductor device of the embodiment, the extraction electrode 16 is formed on the positive electrode 15 at a position apart from the negative electrode 14, and except for the openings on the negative electrode 14 and the extraction electrode 16, An insulating film 17 is formed so as to cover each semiconductor layer.

Here, the nitride semiconductor device of the present embodiment is manufactured according to a manufacturing method described later, so that the distance between the outer circumference of the p-type gallium nitride based semiconductor layer and the outer circumference of the positive electrode is increased. x (shown in FIGS. 1 and 2) is manufactured to be 0.2 μm or more and less than 10 μm. As a result, the area of the positive electrode 15 can be increased as compared with the conventional example, and the forward voltage can be reduced. For example, if the chip size is 350 μm × 4
00 μm, the size of the p-type gallium nitride based semiconductor layer 13 is approximately 270 μm × 210 μm, and x = 1 μm.
When m, the area of the positive electrode 15 can be 1.29 times larger than that of the conventional example. Incidentally, x in the conventional example
Was 15 μm.

Next, the manufacturing method of this embodiment will be described with reference to FIG. In FIG. 3, the active layer 10
Is omitted. In this manufacturing method, first, as shown in FIG.
As shown in (a), an n-type gallium nitride based semiconductor layer, an active layer and a p-type gallium nitride based semiconductor layer are formed on the substrate 11, and the side surfaces of the stacked semiconductor layers are slightly inside the side surface of the substrate 11. The outer peripheral portion of the semiconductor layer so that it is located at
After etching with, the electrode layer 31 made of a metal capable of ohmic contact with the p-type gallium nitride based semiconductor layer 13 is formed so as to cover the upper surface of the semiconductor layer (upper surface of the p-type gallium nitride based semiconductor layer 13) and the side surface of the semiconductor layer. Form. next,
As shown in FIG. 3B, a mask 32 for removing the electrode layer 31, the p-type gallium nitride based semiconductor layer and the active layer is formed in the region where the positive electrode 15 is to be formed. Here, the mask 32 is made of photoresist, SiO ₂ , Si ₃ N _4, etc.
Various materials can be used.

After forming the mask 32, as shown in FIG. 3C, the electrode layer 31 except under the mask 32 is removed to form the positive electrode 15 having a predetermined shape, and the mask 32 is further formed.
Is used as it is, the p-type gallium nitride based semiconductor layer and the active layer 10 are etched by using RIE, and the p-type gallium nitride based semiconductor layer 13 and the active layer 10 having substantially the same planar shape as the positive electrode 15 are formed. (Not shown). In this etching step, when the electrode layer 31 is removed by a dry etching method such as RIE, the distance x between the side surface of the positive electrode 15 and the side surface of the p-type gallium nitride based semiconductor layer 13 becomes
It can be set to a predetermined value between 0.2 μm and several μm depending on the etching conditions. Further, after dry etching by RIE, additional etching is performed by a wet etching method using an etching solution so that the electrode layer 31 wraps around the mask, so that the distance x between the side surface of the positive electrode 15 and the side surface of the p-type gallium nitride based semiconductor layer 13 is reduced. It can be set to a predetermined value between several μm and 10 μm according to the etching conditions. For the etching of the electrode layer 31, it is preferable that the creeping distance between the positive electrode and GaN is several μm, and dry etching and wet etching are used together to reduce the leak current.

For example, Ni (100 Å) and Au (200
Å) is laminated to form the electrode layer 31, and the electrode layer 31, p
FIG. 4 shows a micrograph of the case where the type gallium nitride based semiconductor layer 13a and the active layer are removed by dry etching, and then wet etching is additionally performed on the electrode layer 31. As shown in the micrograph in the figure, the distance x between the side surface of the positive electrode 15 and the side surface of the p-type gallium nitride based semiconductor layer 13 was 3.8 μm. In this case, the distance x can be controlled to about 10 μm by changing the processing time of the above wet etching. In this method, the p-type gallium nitride based semiconductor layer and the active layer may be dry-etched after the electrode layer 31 is wet-etched.

FIG. 5 is an SEM of an example different from that of FIG.
It is a photograph showing the surface of the n-type gallium nitride based semiconductor layer 12, the p-type gallium nitride based semiconductor layer 13 and the positive electrode 15 obliquely. In this example, the distance x is formed to be extremely smaller than that in FIG. That is, Ni (100 Å) and Au (200 Å) are laminated to form the electrode layer 31, the electrode layer 31 is dry-etched, and then the p-type gallium nitride based semiconductor layer 13a and the active layer are dry-etched. It is the SEM photograph after removing by doing and further heat-treating. In the example shown in FIG. 5, the distance x between the side surface of the positive electrode 15 and the side surface of the p-type gallium nitride based semiconductor layer 13 is adjusted to an extremely small value of 0.3 μm. In the method using only dry etching as described above, the distance x between the side surface of the positive electrode 15 and the side surface of the p-type gallium nitride based semiconductor layer 13 is changed from 0.2 μm to several by changing the dry etching condition. μ
It can be set to an extremely small value in the range of m.

Then, as shown in FIG. 3D, the mask 32 is removed by using, for example, plasma ashing, and then, as shown in FIG. 3E, the negative electrode 14, the extraction electrode 16 and the insulating film 17 are removed. To form. As described above,
The nitride semiconductor device of the embodiment is manufactured.

In the manufacturing method of the above embodiment, the p-type gallium nitride based semiconductor layer 13a is partially removed to expose a part of the upper surface of the n-type gallium nitride based semiconductor layer.
After forming the electrode layer 13a on the surface of the type gallium nitride based semiconductor layer, the mask 32 is formed at a predetermined position on the electrode layer 31.
Then, using the mask 32, the electrode layer 31 and the p-type gallium nitride based semiconductor layer 13a except under the mask 32 are removed by etching. As a result, the distance x between the outer periphery of the p-type gallium nitride based semiconductor layer 13 and the outer periphery of the positive electrode 15 (shown in FIGS. 1 and 2) is
It is manufactured to have a value of 0.2 μm or more and less than 10 μm.

The results of comparing the characteristics of the nitride semiconductor device according to the present invention and the conventional nitride semiconductor device by trial manufacture will be described below. In the nitride semiconductor device according to the present invention, the distance x between the side surface of the positive electrode 15 and the side surface end of the p-type gallium nitride based semiconductor layer 13 is determined by using the above method.
A prototype (hereinafter, simply referred to as the device of the present application) was made to have a thickness of 0.3 μm, and a conventional nitride semiconductor device was prototyped (hereinafter simply referred to as the conventional device) using a conventional method for comparison. The distance x in the conventional nitride semiconductor device was measured to be about 15 μm, and no difference in appearance was observed except that the distance x was different. Regarding the electrostatic withstand voltage and the leakage current, no significant difference was found between the device of the present application and the conventional device, but regarding the forward voltage, as shown in FIG. Was recognized. That is, it was confirmed that the nitride semiconductor device according to the present invention can reduce the forward voltage as compared with the conventional example. In the nitride semiconductor device of the present embodiment, when the p-type gallium nitride layer has the same size, the positive electrode 15 is extended to the very vicinity of the side end of the p-type gallium nitride-based semiconductor layer 13 according to the present invention. It is considered that the effective region of the active layer can be expanded because it can be formed.

Further, it is considered that when the distance x between the side surface of the positive electrode 15 and the side surface end of the p-type gallium nitride based semiconductor layer 13 becomes smaller than a certain value, the electrostatic withstand voltage deteriorates and the leakage current increases. According to the present invention, it has been confirmed that the electrostatic breakdown voltage and the leakage current are the same. In the present invention, if the distance x between the side surface of the positive electrode 15 and the side surface end of the p-type gallium nitride based semiconductor layer 13 is 0.2 μm or more, electrostatic resistance and leakage current equivalent to those of the conventional example are secured. It is confirmed that you can do it.

That is, the effects of this embodiment are summarized as follows. (1) The forward voltage can be reduced without deteriorating the electrostatic breakdown voltage characteristic and the leakage current characteristic. (2) When the electrostatic breakdown voltage characteristic, the leakage current characteristic, and the forward voltage are made equal to those of the conventional example, the chip size of the nitride semiconductor element can be reduced and the number of wafers taken per wafer can be increased. This can reduce the unit price per element (chip).

In addition to the above-mentioned effect, the so-called semiconductor-side light emitting device, in which the positive electrode 15 has a light-transmitting property and outputs the light emitted through the positive electrode 15, is further added. It has the following effects. That is,
In order to improve the light emission output of the semiconductor-side light emitting element, the positive electrode 15 may be thinned to increase the light transmittance. At that time, the limit of thinning is the resistance of the positive electrode due to the thinning. It depends on how much the forward voltage can be increased. Therefore, in the present invention, as described above, the forward voltage can be reduced, and accordingly, the thickness of the light-transmissive positive electrode can be reduced, and as a result, the light output can be improved. be able to. The semiconductor-side light emitting element has an electrode structure in which a negative electrode 140 and a take-out electrode 160 are arranged on a diagonal line, for example, as shown in FIG. 7, in order to effectively output the light emission efficiency and the emitted light. And That is, the negative electrode 140 is formed on the surface of the n-type gallium nitride based semiconductor layer 12 that is exposed by removing the p-type gallium nitride based semiconductor layer at one corner.
50 is formed on substantially the entire surface of the p-type gallium nitride based semiconductor layer 130, and the extraction electrode 160 is formed at a position diagonal to the negative electrode 140. Here, the p-type gallium nitride based semiconductor layer and the positive electrode are etched by using a common mask to set the value of x within a predetermined range, as in the above embodiment.

In the above embodiments, the nitride semiconductor element which is a light emitting element has been described. However, the present invention is not limited to this, and it is also possible to use a gallium nitride based semiconductor such as a nitride semiconductor element which is a light receiving element. It can also be applied to the element of. That is, since the p-type gallium nitride based semiconductor has a higher resistance value than other materials, even if it is p-type, generally, the contact area between the p-type gallium nitride based semiconductor layer and the positive electrode is large. Therefore, the present invention can be applied to any nitride semiconductor device using a p-type gallium nitride based semiconductor, and has the same effects as the present embodiment.

In the above embodiments, the nitride semiconductor layer device including the n-type gallium nitride based semiconductor layer 12, the active layer 10 and the p-type gallium nitride based semiconductor layer 13 has been described, but the present invention is not limited to this. Needless to say, other semiconductor layers such as a buffer layer may be provided. The present invention can be applied even if other semiconductor layers are provided,
It has the same effect as the embodiment.

[0027]

As described in detail above, in the nitride semiconductor device of the present invention, the distance between the outer periphery of the p-type gallium nitride based semiconductor layer and the outer periphery of the positive electrode is 0.2 μm or more. Since the positive electrode is formed so as to be less than 10 μm, the contact area between the p-type gallium nitride based semiconductor layer and the positive electrode can be increased. As a result, the nitride semiconductor device of the present invention can reduce the current density and the forward voltage.

In the method for manufacturing a nitride semiconductor device according to the present invention, after forming an electrode layer on the surface of the p-type gallium nitride based semiconductor layer, a mask is formed on the electrode layer and the mask is used. The positive electrode is formed by removing the electrode layer and the p-type gallium nitride based semiconductor layer by etching. As a result, in the manufacturing method of the present invention, the p
Since the positive electrode can be formed such that the distance between the outer circumference of the type gallium nitride based semiconductor layer and the outer circumference of the positive electrode is 0.2 μm or more and less than 10 μm, the nitriding with low forward voltage is performed. The semiconductor device can be manufactured at low cost.

[Brief description of drawings]

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

2 is an insulating film 17 in the nitride semiconductor device of FIG.
To remove the p-type gallium nitride based semiconductor layer and the positive electrode 15
FIG. 3 is a plan view schematically showing the arrangement of the negative electrode 14 and the negative electrode.

FIG. 3 is a cross-sectional view of main steps in the method for manufacturing the nitride semiconductor device of FIG.

FIG. 4 is a micrograph showing the positional relationship between the positive electrode 15 and the p-type gallium nitride based semiconductor layer formed according to the present invention.

FIG. 5 is an SEM photograph showing the positional relationship between the positive electrode 15 and the p-type gallium nitride based semiconductor layer formed according to the present invention.

FIG. 6 is a graph showing forward voltage characteristics of a nitride semiconductor device according to the present invention.

FIG. 7 is a plan view showing an electrode structure of a nitride semiconductor device of a modified example according to the present invention.

8A is a schematic cross-sectional view of a conventional nitride semiconductor device, and FIG. 8B is a plan view showing electrodes of a conventional nitride semiconductor device.

[Explanation of symbols]

10 ... Active layer, 11 ... substrate, 12 ... n-type gallium nitride based semiconductor layer, 13 ... p-type gallium nitride based semiconductor layer, 14 ... Negative electrode, 15 ... Positive electrode, 16 ... take-out electrode, 17 ... Insulating film.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (6)

(57) [Claims] 1. A substrate having at least one semiconductor layer including at least an n-type gallium nitride-based semiconductor layer, and at least two p-type semiconductor layers.
Forming a p-type gallium nitride-based semiconductor layer, forming an electrode layer on the surface of the p-type gallium nitride-based semiconductor layer, forming a mask on the electrode layer, and except immediately below the mask. An etching step of forming a positive electrode having a predetermined shape by removing the electrode layer and the p-type gallium nitride based semiconductor layer by etching, and exposing a part of the upper surface of the n-type gallium nitride based semiconductor layer; And a step of forming a negative electrode on a part of the upper surface of the exposed n-type gallium nitride based semiconductor layer, wherein the etching step is wet etching of the electrode layer. And dry-etching the p-type gallium nitride based semiconductor layer. 2. In the etching step, the surface of the n-type gallium nitride based semiconductor layer is exposed by dry etching from the electrode layer to the p-type gallium nitride based semiconductor layer, and then the electrode layer is further formed. The method for manufacturing a nitride semiconductor device according to claim 1, comprising performing wet etching. 3. The etching step includes the step of exposing the surface of the n-type gallium nitride based semiconductor layer by dry etching the p-type gallium nitride based semiconductor layer after wet etching the electrode layer. Item 2. A method for manufacturing a nitride semiconductor device according to item 1. 4. The step of forming the electrode layer, wherein the electrode layer is formed to a thickness of 1.5 μm or less.
4. The method for manufacturing a nitride semiconductor device according to any one of 3. 5. The electrode layer is formed of Ni, Au, Pt, C.
at least 1 selected from the group consisting of o, Pd and Zn
The method for manufacturing a nitride semiconductor device according to claim 1, wherein the nitride semiconductor device is formed by including one element. 6. The method for manufacturing a nitride semiconductor device according to claim 5, wherein the electrode layer is formed to contain Ni or Au.