JP2006303542A - Semiconductor element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor element having a stable ohmic electrode, which is hard to be peeled off and can be formed on a nitride semiconductor by a simple process. <P>SOLUTION: On a sapphire substrate 1, an undoped GaN buffer layer 2, n-type GaN layer 3, and p-type GaN layer 4 are formed in order, part of the region from the p-type GaN layer 4 to n-type GaN layer 3 is removed, and the n-type GaN layer 3 is exposed. On the p-type GaN layer 4 and exposed upper surface of the n-type GaN layer 3, a Ti layer 5 and a Pt layer 6 are formed in oreder. Thereby, without performing alloying by heat treatment, a p-type electrode 7 coming into ohmic contact with the p-type GaN layer 4 and n electrode 8 coming into ohmic contact with the n-type GaN layer 3 are formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a III-V group nitride semiconductor such as BN (boron nitride), GaN (gallium nitride), AlN (aluminum nitride) or InN (indium nitride), TlN (thallium nitride), or a mixed crystal thereof (hereinafter referred to as “a nitride semiconductor”) And a manufacturing method thereof.

  In recent years, GaN-based semiconductor light-emitting elements have been put into practical use as semiconductor light-emitting elements such as light-emitting diodes and semiconductor laser elements that emit blue or violet light. A transistor using a GaN-based semiconductor has also been proposed. In such a GaN-based semiconductor element, an electrode in ohmic contact with the GaN-based semiconductor is required.

  6 and 7 are schematic process cross-sectional views showing an example of a conventional method for manufacturing a GaN-based light emitting diode.

  First, as shown in FIG. 6A, a GaN buffer layer 22, an n-type GaN layer 23, and a p-type GaN layer 24 are formed in this order on a sapphire substrate 21. Thereafter, a partial region from the p-type GaN layer 24 to the n-type GaN layer 23 is etched by RIE (reactive ion etching) or the like to expose the n-type GaN layer 23.

  Next, as shown in FIG. 6B, a photoresist pattern 31 is formed on the p-type GaN layer 24 and the exposed upper surface of the n-type GaN layer 23. The photoresist pattern 31 has an opening 32 on the p-type GaN layer 24. In this state, a Pt film 25a having a thickness of 2000 mm is formed on the p-type GaN layer 24 and the photoresist pattern 31 in the opening 32 by electron beam evaporation.

  Next, as shown in FIG. 6C, the Pt film 25a on the photoresist pattern 31 is removed together with the photoresist pattern 31 by a lift-off method.

  Next, as shown in FIG. 7 (d), a photoresist pattern 33 is formed on the p-type GaN layer 24, the p-electrode 25, and the exposed upper surface of the n-type GaN layer 23. The photoresist pattern 33 has an opening 34 on the exposed upper surface of the n-type GaN layer 23. In this state, a Ti film 26a having a thickness of 200 mm and an Al film 27a having a thickness of 5000 mm are sequentially formed on the upper surface of the n-type GaN layer 23 and the photoresist pattern 33 in the opening 34 by an electron beam evaporation method.

Further, as shown in FIG. 7E, the Ti film 26a and the Al film 27a on the photoresist pattern 33 are removed together with the photoresist pattern 33 by a lift-off method. Thereafter, heat treatment is performed at a temperature of 600 ° C. for 5 minutes in an N ₂ gas atmosphere.

  As described above, the p-side and n-side ohmic electrodes are formed.

  The p-electrode 25 made of a Pt film in the conventional GaN-based light-emitting diode described above has a weak adhesive force, so that peeling is likely to occur in a later process such as wire bonding, and when a measuring needle is brought into contact with an ohmic characteristic inspection or the like The peeling occurs relatively easily.

  On the other hand, in order to obtain ohmic contact, alloying by heat treatment is required. Moreover, it is necessary to form the p electrode 25 and the n electrode 30 by separate processes. Therefore, the process of forming the p electrode 25 and the n electrode 30 becomes complicated and takes time.

  An ohmic electrode having a laminated structure of a Ti film and an Au film has also been proposed. This ohmic electrode can be formed without alloying by heat treatment. However, this ohmic electrode tends to have a high resistance during the heat treatment of other layers.

  An object of the present invention is to provide a semiconductor device including a stable ohmic electrode that is unlikely to be peeled off and can be formed on a nitride semiconductor by a simple process.

  Another object of the present invention is to provide a method for manufacturing a semiconductor element, which can form a stable ohmic electrode on a nitride-based semiconductor with a simple process, which does not easily cause peeling.

  A semiconductor device according to a first invention includes a p-type nitride semiconductor and an ohmic electrode formed on the p-type nitride semiconductor, and the ohmic electrode is in close contact with the p-type nitride semiconductor. A first metal film made of titanium and having a thickness of 3 mm or more and 150 mm or less and a second metal film made of platinum or palladium formed in close contact with the first metal film.

  In the ohmic electrode of the semiconductor element according to the present invention, the first metal film made of titanium has a function of cleaning the surface of the p-type nitride semiconductor, and the second metal film made of platinum or palladium and the p-type Facilitates ohmic contact with nitride-based semiconductors. Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first metal film made of titanium has a strong adhesion to the p-type nitride semiconductor, the adhesion of the ohmic electrode to the p-type nitride semiconductor is improved. Therefore, the ohmic electrode is hardly peeled off.

  In particular, the thickness of the first metal film is preferably 3 mm to 130 mm, more preferably 3 mm to 100 mm, further preferably 3 mm to 50 mm, and more preferably 3 mm to 10 mm. Most preferred. Thereby, sufficient ohmic characteristics can be obtained while preventing the ohmic electrode from peeling off.

  The semiconductor element may further include a third metal film made of gold and formed in close contact with the second metal film. This facilitates wire bonding. In this case, since the ohmic electrode composed of the first metal film and the second metal film can be formed without performing alloying by heat treatment, the first metal film, the second metal film, and the third metal are formed. The film can be formed in the same process.

  The p-type nitride-based semiconductor may include at least one of boron, gallium, aluminum, indium, and thallium.

  A semiconductor element according to a second invention includes an n-type nitride semiconductor and an ohmic electrode formed on the n-type nitride semiconductor, and the ohmic electrode is in close contact with the n-type nitride semiconductor. A first metal film made of titanium and having a thickness of 3 mm to 100 mm, and a second metal film made of platinum or palladium formed in close contact with the first metal film.

In the ohmic electrode of the semiconductor element according to the present invention, the first metal film made of titanium has a function of cleaning the surface of the n-type nitride semiconductor, and the second metal film made of platinum or palladium and the n-type Facilitates ohmic contact with nitride-based semiconductors.
Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first metal film made of titanium has a strong adhesion to the n-type nitride semiconductor, the adhesion of the ohmic electrode to the n-type nitride semiconductor is improved. Therefore, the ohmic electrode is hardly peeled off.

  In particular, the thickness of the first metal film is preferably 3 mm to 50 mm, more preferably 3 mm to 30 mm, and still more preferably 3 mm to 10 mm. Thereby, sufficient ohmic characteristics can be obtained while preventing the ohmic electrode from peeling off.

  The semiconductor element may further include a third metal film made of gold and formed in close contact with the second metal film. This facilitates wire bonding. In this case, since the ohmic electrode composed of the first metal film and the second metal film can be formed without performing alloying by heat treatment, the first metal film, the second metal film, and the third metal are formed. The film can be formed in the same process.

  The n-type nitride-based semiconductor may include at least one of boron, gallium, aluminum, indium, and thallium.

  A semiconductor element according to a third invention is formed on a p-type nitride semiconductor, an n-type nitride semiconductor provided in contact with the p-type nitride semiconductor, and the p-type nitride semiconductor. A first ohmic electrode and a second ohmic electrode formed on the n-type nitride semiconductor, wherein the first ohmic electrode is formed in close contact with the p-type nitride semiconductor and is made of titanium. A first metal film having a thickness of 3 mm to 100 mm and a second metal film formed in close contact with the first metal film and made of platinum or palladium, and the second ohmic electrode includes n A third metal film made of titanium and having a thickness of 3 mm or more and 100 mm or less, and a fourth metal film made of platinum or palladium formed in close contact with the third metal film. The metal film is included.

  In the first ohmic electrode and the second ohmic electrode of the semiconductor element according to the present invention, the first and third metal films made of titanium are respectively formed on the surfaces of the p-type nitride semiconductor and the n-type nitride semiconductor. An ohmic contact between the second metal film made of platinum or palladium and the p-type nitride semiconductor having a cleaning function, and an ohmic contact between the fourth metal film made of platinum or palladium and the n-type nitride semiconductor To make it easier. Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first and third metal films made of titanium have strong adhesion to the p-type nitride semiconductor and the n-type nitride semiconductor, respectively, the p-type nitride semiconductor and the n-type nitride are used. The adhesion of the first ohmic electrode and the second ohmic electrode to the system semiconductor is improved. Therefore, the first and second ohmic electrodes are unlikely to peel off.

  Furthermore, since the first ohmic electrode and the second ohmic electrode have the same structure and are made of the same material, the first and second ohmic electrodes can be simultaneously formed in the same process. Therefore, the number of manufacturing steps is reduced, and the manufacturing time can be shortened.

  As a result, stable and highly reliable ohmic electrodes can be easily formed on the p-type nitride semiconductor and the n-type nitride semiconductor, respectively.

  The thickness of the first and third metal films is preferably 3 mm or more and 30 mm or less, and more preferably 3 mm or more and 10 mm or less. Thereby, sufficient ohmic characteristics can be obtained while preventing the first and second ohmic electrodes from peeling off.

  The semiconductor element is formed in close contact with the second metal film, and is formed of a fifth metal film made of gold, and a sixth metal film made of gold in close contact with the fourth metal film. May be further provided. This facilitates wire bonding. In this case, the first ohmic electrode composed of the first metal film and the second metal film and the second ohmic electrode composed of the third metal film and the fourth metal film are formed without alloying by heat treatment. Therefore, the first metal film, the second metal film, the fifth metal film, the third metal film, the fourth metal film, and the sixth metal film can be formed in the same process. .

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: forming a p-type nitride semiconductor; a first metal film made of titanium and having a thickness of 3 mm to 150 mm on the p-type nitride semiconductor; And a second metal film made of platinum or palladium in close contact with each other in this order to form an ohmic electrode without heat treatment.

  In the method of manufacturing a semiconductor device according to the present invention, the first metal film made of titanium has a function of cleaning the surface of the p-type nitride semiconductor, and the second metal film made of platinum or palladium and the p-type Facilitates ohmic contact with nitride-based semiconductors. Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first metal film made of titanium has a strong adhesion to the p-type nitride semiconductor, the adhesion of the ohmic electrode to the p-type nitride semiconductor is improved. Therefore, the ohmic electrode is hardly peeled off.

  In particular, the thickness of the first metal film is preferably 3 mm to 130 mm, more preferably 3 mm to 100 mm, further preferably 3 mm to 50 mm, and more preferably 3 mm to 10 mm. Most preferred. Thereby, sufficient ohmic characteristics can be obtained while preventing the ohmic electrode from peeling off.

  According to a fifth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: forming an n-type nitride semiconductor; and a first metal film made of titanium and having a thickness of 3 mm to 100 mm on the n-type nitride semiconductor. And a second metal film made of platinum or palladium in close contact with each other in this order to form an ohmic electrode without heat treatment.

  In the method of manufacturing a semiconductor device according to the present invention, the first metal film made of titanium has a function of cleaning the surface of the n-type nitride semiconductor, and the second metal film made of platinum or palladium and the n-type Facilitates ohmic contact with nitride-based semiconductors. Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first metal film made of titanium has a strong adhesion to the n-type nitride semiconductor, the adhesion of the ohmic electrode to the n-type nitride semiconductor is improved. Therefore, the ohmic electrode is hardly peeled off.

  In particular, the thickness of the first metal film is preferably 3 mm to 50 mm, more preferably 3 mm to 30 mm, and still more preferably 3 mm to 10 mm. Thereby, sufficient ohmic characteristics can be obtained while preventing the ohmic electrode from peeling off.

  According to a sixth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: forming a p-type nitride semiconductor and an n-type nitride semiconductor that are in contact with each other; By forming a first metal film of 100 mm or less and a second metal film made of platinum or palladium in close contact with each other in this order, a first ohmic electrode is formed without performing heat treatment, and n-type nitriding is performed. By forming a third metal film made of titanium and having a thickness of 3 mm to 100 mm and a fourth metal film made of platinum or palladium in this order in close contact with each other on a physical semiconductor, heat treatment is not performed. Forming a second ohmic electrode.

  In the method of manufacturing a semiconductor device according to the present invention, the first and third metal films made of titanium have a function of cleaning the surfaces of the p-type nitride semiconductor and the n-type nitride semiconductor, respectively, It facilitates ohmic contact between the second metal film made of palladium and the p-type nitride semiconductor and ohmic contact between the fourth metal film made of platinum or palladium and the n-type nitride semiconductor. Therefore, the ohmic electrode can be formed by a simple process without alloying by heat treatment.

  Further, since the first and third metal films made of titanium have strong adhesion to the p-type nitride semiconductor and the n-type nitride semiconductor, respectively, the p-type nitride semiconductor and the n-type nitride are used. The adhesion of the first ohmic electrode and the second ohmic electrode to the system semiconductor is improved. Therefore, the first and second ohmic electrodes are unlikely to peel off.

  Furthermore, since the first ohmic electrode and the second ohmic electrode have the same structure and are made of the same material, the first and second ohmic electrodes can be simultaneously formed in the same process. Therefore, the number of manufacturing steps is reduced, and the manufacturing time can be shortened.

  As a result, stable and highly reliable ohmic electrodes can be easily formed on the p-type nitride semiconductor and the n-type nitride semiconductor, respectively.

  The thickness of the first and third metal films is preferably 3 mm or more and 30 mm or less, and more preferably 3 mm or more and 10 mm or less. Thereby, sufficient ohmic characteristics can be obtained while preventing the first and second ohmic electrodes from peeling off.

  In the manufacturing method, a fifth metal film made of gold is formed in close contact with the second metal film, and a sixth metal film made of gold is formed in close contact with the fourth metal film. May be further provided. This facilitates wire bonding. In this case, the first ohmic electrode composed of the first metal film and the second metal film and the second ohmic electrode composed of the third metal film and the fourth metal film are formed without alloying by heat treatment. Therefore, the first metal film, the second metal film, the fifth metal film, the third metal film, the fourth metal film, and the sixth metal film can be formed in the same process. .

  FIG. 1 is a schematic cross-sectional view of a GaN-based light emitting diode according to an embodiment of the present invention.

In FIG. 1, an undoped GaN buffer layer 2 having a thickness of 0.2 μm, an n-type GaN layer 3 having a thickness of 3 μm, and a p-type GaN layer 4 having a thickness of 0.5 μm are sequentially formed on a sapphire substrate 1. . The n-type GaN layer 3 has a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ , and the p-type GaN layer 4 has a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ .

  A partial region from the p-type GaN layer 4 to the n-type GaN layer 3 is removed by etching, and the n-type GaN layer 3 is exposed. A p-electrode 7 composed of a Ti (titanium) film 5 and a Pt (platinum) film 6 is formed on the p-type GaN layer 4. The p electrode 7 is in ohmic contact with the p-type GaN layer 4. Further, an n electrode 8 made of a Ti film 5 and a Pt film 6 is formed on the exposed upper surface of the n-type GaN layer 3. The n electrode 8 is in ohmic contact with the n-type GaN layer 3.

  In this embodiment, the thickness of the Ti film 5 of the p electrode 7 and the n electrode 8 is 10 mm. The thickness of the Pt film 6 of the p-electrode 7 and the n-electrode 8 is preferably 500 mm or more, and is 4000 mm in this embodiment.

  FIG. 2 is a schematic process cross-sectional view illustrating a method of manufacturing the GaN-based light emitting diode of FIG.

  First, as shown in FIG. 2A, an undoped GaN buffer layer 2, an n-type GaN layer 3, and a p-type GaN layer 4 are formed on a sapphire substrate 1 by MOCVD (metal organic chemical vapor deposition) or the like. Form in order. Then, a partial region from the p-type GaN layer 4 to the n-type GaN layer 3 is removed by the RIE method or the like to expose the n-type GaN layer 3. Further, a photoresist made of, for example, PMMA (polymethyl methacrylate) is formed on the exposed upper surfaces of the p-type GaN layer 4 and the n-type GaN layer 3, and a photoresist pattern 11 is formed by patterning using a photolithography technique. The photoresist pattern 11 has openings 12 and 13 on the p-type GaN layer 4 and the exposed upper surface of the n-type GaN 3.

  Next, as shown in FIG. 2B, a film is formed on the p-type GaN layer 4 in the opening 12 of the photoresist pattern 11, on the n-type GaN layer 3 in the opening 13 and on the photoresist pattern 11. A Ti film 5 having a thickness of 10 mm and a Pt film 6 having a thickness of 4000 mm are sequentially formed by an electron beam evaporation method.

  Further, as shown in FIG. 2C, the Ti film 5 and the Pt film 6 on the photoresist pattern 11 are removed together with the photoresist pattern 11 by a lift-off method by cleaning using an organic solvent such as acetone. As a result, a p-electrode 7 composed of a Ti film 5 and a Pt film 6 in ohmic contact with the p-type GaN layer 4 without being alloyed by heat treatment is formed, and the Ti film 5 and Pt in ohmic contact with the n-type GaN layer 3 are formed. An n-electrode 8 made of the film 6 is formed at the same time.

  The Ti film 5 of the p-electrode 7 and the n-electrode 8 in the light emitting diode of this embodiment adsorbs, for example, oxygen components on the surface of the GaN-based semiconductor, and facilitates ohmic contact between the Pt film 6 and the GaN-based semiconductor. Therefore, the p-electrode 7 and the n-electrode 8 that are ohmic electrodes can be formed by a simple process without alloying by heat treatment.

  Further, since the Ti film 5 has a strong adhesion to the GaN-based semiconductor, the adhesion of the p-electrode 7 and the n-electrode 8 to the GaN-based semiconductor is improved. Therefore, the p-electrode 7 and the n-electrode 8 are hardly peeled off.

  Furthermore, since the p electrode 7 and the n electrode 8 have the same structure and are made of the same material, the p electrode 7 and the n electrode 8 can be formed simultaneously in the same process. Therefore, the number of manufacturing steps is reduced, and the manufacturing time can be shortened.

  As a result, it is possible to easily form the stable and reliable p-electrode 7 and n-electrode 8 in ohmic contact with the GaN-based semiconductor.

  A Pd (palladium) film may be used instead of the Pt film 6 of the p electrode 7 and the n electrode 8.

  Also in this case, ohmic contact between the Pd film and the GaN-based semiconductor is facilitated by the action of the Ti film 5. Therefore, the p-electrode 7 and the n-electrode 8 that are ohmic electrodes can be formed by a simple process without alloying by heat treatment.

  Further, the adhesion of the p electrode 7 and the n electrode 8 to the GaN-based semiconductor is improved by the action of the Ti film 5. Therefore, the p-electrode 7 and the n-electrode 8 are hardly peeled off.

  Further, since the p electrode 7 and the n electrode 8 have the same structure and are made of the same material, the p electrode 7 and the n electrode 8 can be simultaneously formed in the same process. Therefore, the number of manufacturing steps is reduced, and the manufacturing time can be shortened.

  As a result, it is possible to easily form the stable and reliable p-electrode 7 and n-electrode 8 in ohmic contact with the GaN-based semiconductor without performing heat treatment.

Further, a Ni (nickel) film may be used instead of the Pt film 6 of the p-electrode 7.
Also in this case, the action of the Ti film 5 facilitates ohmic contact between the Ni film and the p-type GaN-based semiconductor. Therefore, the p-electrode 7 that is an ohmic electrode is formed by a simple process without alloying by heat treatment.

  Further, the adhesion of the p-electrode 7 to the p-type GaN-based semiconductor is improved by the action of the Ti film 5. Therefore, peeling of the p electrode 7 does not occur.

  FIG. 3 is a schematic cross-sectional view of an ohmic electrode in which pad electrodes are stacked. As shown in FIG. 3, by forming the pad electrode 9 made of an Au film on the ohmic electrode made of the Ti film 5 and the Pt film 6, wire bonding can be easily performed.

  In this case, since the ohmic electrode composed of the Ti film 5 and the Pt film 6 is formed without alloying by heat treatment, the Ti film 5, the Pt film 6 and the pad electrode 9 are continuously formed in the same process. Can do. Accordingly, by forming an ohmic electrode having a Ti / Pt / Au structure on the GaN-based semiconductor layer, a pad electrode for wire bonding can be formed simultaneously.

  In contrast, when a pad electrode is formed on a conventional ohmic electrode made of a Ti film and an Al film, a laminated structure of a Ti film, a Pt film, and an Au film is formed on the ohmic electrode as the pad electrode. Thus, since Ti and Au are likely to react, it is necessary to insert a Pt film between the Ti film and the Au film. In this case, when forming an ohmic electrode composed of a Ti film and an Al film, alloying by heat treatment is necessary. Therefore, a step of forming an ohmic electrode composed of a laminated structure of Ti / Al, and Ti / Pt / Au It is necessary to separately perform the step of forming a pad electrode having a laminated structure.

  Here, the current-voltage characteristics of the p-electrode 7 and the n-electrode 8 in the above example were measured by changing the thickness of the Ti film 5.

  FIG. 4 is a diagram showing the measurement result of the current-voltage characteristics of the p-electrode 7. In this measurement, a pair of p-electrodes 7 was formed on the p-type GaN layer, and a voltage applied between the pair of p-electrodes 7 and a current flowing between the pair of p-electrodes 7 were measured.

First, the carrier concentration of the p-type GaN layer was 5 × 10 ¹⁷ cm ^−3, and the thickness of the Ti film 5 of the p-electrode 7 was ³ mm, 5 mm, 100 mm, 130 mm, and 150 mm. The film thickness of the Pt film 6 was 4000 mm. Next, the carrier concentration of the p-type GaN layer was set to 9 × 10 ¹⁷ cm ^−3, and the thickness of the Ti film 5 of the p-electrode 7 was set to 100 mm.

As shown in FIG. 4, when the carrier concentration of the p-type GaN layer is 5 × 10 ¹⁷ cm ⁻³ , complete ohmic characteristics can be obtained when the thickness of the Ti film 5 is ³ mm, 5 mm, and 100 mm. When the film thickness of the Ti film 5 is 130 mm, almost ohmic characteristics are obtained. When the thickness of the Ti film 5 reaches 150 mm, a rectification characteristic appears somewhat.

Even when the carrier concentration of the p-type GaN layer is 9 × 10 ¹⁷ cm ⁻³ , complete ohmic characteristics are obtained when the thickness of the Ti film 5 is 100 mm.

  Therefore, the thickness of the Ti film 5 of the p-electrode 7 is preferably 130 mm or less, and more preferably 100 mm or less. When the n electrode 8 is formed simultaneously, the thickness of the Ti film 5 is preferably 100 mm or less, more preferably 50 mm or less, further preferably 30 mm or less, and 10 mm or less. Most preferred. From the viewpoint of adhesion strength to the p-type GaN layer, the thickness of the Ti film 5 is preferably 3 mm or more, and more preferably 5 mm or more.

  Further, when the p electrode 7 formed on the p-type GaN layer was subjected to a scratch test using a measuring needle for inspecting ohmic characteristics, the thickness of the Ti film 5 was 3 mm, 5 mm, 100 mm, 130 mm, and In all cases of 150 mm, the p-electrode 7 was not peeled off. On the other hand, in the case of only the Pt film 6, peeling occurred.

  FIG. 5 is a diagram showing the measurement results of the voltage-current characteristics of the n-electrode 8. In this measurement, a pair of n electrodes 8 was formed on the n-type GaN layer, and a voltage applied between the pair of n electrodes 8 and a current flowing between the pair of n electrodes 8 were measured.

The carrier concentration of the n-type GaN layer was 9 × 10 ¹⁷ cm ^−3, and the thickness of the Ti film 5 of the n-type electrode 8 was ³ mm, 5 mm, 10 mm, 30 mm, and 100 mm.

  As shown in FIG. 5, complete ohmic characteristics are obtained when the thickness of the Ti film 5 is 3, 5, and 10 mm, and almost ohmic characteristics are obtained when the thickness of the Ti film 5 is 30 mm. When the thickness of the Ti film 5 is 100 mm, a rectification characteristic appears somewhat. It can be seen that when the thickness of the Ti film 5 is 0, that is, only the Pt film 6 is used, ohmic characteristics cannot be obtained and the resistance is high.

  Therefore, the thickness of the Ti film 5 of the n-electrode 8 is preferably about 50 mm or less, more preferably 30 mm or less, and further preferably 10 mm or less. Further, from the viewpoint of adhesion strength to the n-type GaN layer, the thickness of the Ti film 5 is preferably 3 mm or more, and more preferably 5 mm or more.

  Further, when a scratch test was performed on the n-electrode 8 formed on the n-type GaN layer using the measuring needle, the thickness of the Ti film 5 was 3 mm, 5 mm, 10 mm, 30 mm, and 100 mm. While peeling of the n electrode 8 did not occur, peeling of the n electrode 8 occurred when only the Pt film 6 was used.

  When a current-voltage characteristic measurement and a scratch test similar to those described above were performed using a Pd film instead of the Pt film 6 of the p electrode 7 and the n electrode 8, the same result as described above was obtained.

  The p-electrode 7 and the n-electrode 8 in the above embodiment can be used as ohmic electrodes for not only GaN but also other GaN-based semiconductors such as AlGaN, InGaN, InAlGaN, BGaN, BAlGaN, and BInGaN.

  In the above embodiments, the case where the present invention is applied to a light emitting diode has been described. However, the present invention can also be applied to other semiconductor light emitting elements such as a semiconductor laser element. The present invention can also be applied to other semiconductor elements such as field effect transistors and bipolar transistors formed of GaN-based semiconductors.

FIG. 1 is a schematic cross-sectional view of a GaN-based light emitting diode according to an embodiment of the present invention. FIG. 2 is a schematic process cross-sectional view showing a method for manufacturing the GaN-based light emitting diode of FIG. 1. It is a typical sectional view of an ohmic electrode by which a pad electrode was laminated. It is a figure which shows the measurement result of the electric current-voltage characteristic of a p electrode. It is a figure which shows the measurement result of the electric current-voltage characteristic of n electrode. It is typical process sectional drawing which shows the manufacturing method of the conventional GaN-type light emitting diode. It is typical process sectional drawing which shows the manufacturing method of the conventional GaN-type light emitting diode.

Explanation of symbols

1 sapphire substrate 2 GaN buffer layer 3 n-type GaN layer 4 p-type GaN layer 5 Ti film 6 Pt film 7 p electrode 8 n electrode 9 pad electrode

Claims (7)

an n-type nitride-based semiconductor;
an ohmic electrode formed on an n-type nitride semiconductor,
The ohmic electrode is
A first metal film formed in close contact with the n-type nitride-based semiconductor and made of titanium and having a thickness of 3 mm to 100 mm;
A semiconductor element comprising: a second metal film formed in close contact with the first metal film and made of platinum or palladium. a p-type nitride-based semiconductor;
An n-type nitride-based semiconductor provided in contact with the p-type nitride-based semiconductor;
A first ohmic electrode formed on the p-type nitride semiconductor;
A second ohmic electrode formed on the n-type nitride semiconductor,
The first ohmic electrode is:
A first metal film formed in close contact with the p-type nitride-based semiconductor and made of titanium and having a thickness of 3 mm to 100 mm;
A second metal film made of platinum or palladium formed in close contact with the first metal film,
The second ohmic electrode is
A third metal film formed in close contact with the n-type nitride-based semiconductor and made of titanium and having a thickness of 3 mm to 100 mm;
A semiconductor element comprising: a fourth metal film formed in close contact with the third metal film and made of platinum or palladium. The semiconductor element according to claim 2, wherein the p-type nitride-based semiconductor includes at least one of boron, gallium, aluminum, indium, and thallium. The semiconductor element according to claim 1, wherein the n-type nitride-based semiconductor includes at least one of boron, gallium, aluminum, indium, and thallium. The semiconductor element according to claim 1, further comprising a third metal film made of gold and formed in close contact with the second metal film. forming an n-type nitride-based semiconductor;
On the n-type nitride semiconductor, a first metal film made of titanium and having a thickness of 3 mm to 100 mm and a second metal film made of platinum or palladium are formed in close contact with each other in this order, thereby performing heat treatment. And a step of forming an ohmic electrode without applying the method. Forming a p-type nitride semiconductor and an n-type nitride semiconductor in contact with each other;
On the p-type nitride-based semiconductor, a first metal film made of titanium and having a thickness of 3 mm to 100 mm and a second metal film made of platinum or palladium are formed in close contact with each other in this order, thereby performing heat treatment. A first ohmic electrode is formed on the n-type nitride semiconductor, a third metal film made of titanium and having a thickness of 3 mm to 100 mm, and a fourth metal made of platinum or palladium. Forming a second ohmic electrode without performing heat treatment by forming the films in close contact with each other in this order.

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