JPWO2009102032A1 - GaN-based LED element and manufacturing method thereof - Google Patents

Abstract

Novel structure relating to suppression of light emission at a pn junction immediately below a bonding pad in a pn junction GaN-based LED element having a TCO film on a p-type layer and a bonding pad on a part of the TCO film To provide. an n-type GaN-based semiconductor layer, a p-type GaN-based semiconductor layer stacked on the n-type GaN-based semiconductor layer, an n-electrode connected to the n-type GaN-based semiconductor layer, and the p-type GaN-based semiconductor layer. In a region where the resistance between the TCO film formed on the surface, the conductive sputtered film partially formed on the TCO film, and the resistance between the p-type GaN-based semiconductor layer and the TCO film is partially increased A GaN-based LED element comprising: a resistance increasing region corresponding to a contact region between the TCO film and the conductive sputtered film; and a bonding pad formed on the resistance increasing region.

Description

  The present invention relates to a pn-junction type GaN-based LED element having a light-emitting element structure composed of p-type and n-type GaN-based semiconductors and a method for manufacturing the same, and in particular, has a TCO film on the surface of a p-type GaN-based semiconductor layer. The present invention also relates to a GaN-based LED element having a bonding pad on a part of the TCO film and a method for manufacturing the same.

The GaN-based semiconductor is a compound semiconductor represented by the chemical formula Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ a + b ≦ 1), a group 3 nitride semiconductor, Also called a nitride-based semiconductor. A pn-junction type GaN-based LED element, which has a light-emitting element structure composed of p-type and n-type GaN-based semiconductors, can generate green to near-ultraviolet light, and is put to practical use in applications such as traffic lights and display devices. Has been.

  FIG. 16 is a sectional view showing a structure of a typical pn junction type GaN-based LED element. The GaN-based LED element 100 is also referred to as an n-type GaN-based semiconductor layer (hereinafter also referred to as “n-type layer”) 102 and a p-type GaN-based semiconductor layer (hereinafter also referred to as “p-type layer”) on a substrate 101 made of sapphire or the like. .) 103, and an n-electrode 104 is formed on the surface of the n-type layer 102 partially exposed by etching, and a p-electrode 105 is formed on the surface of the p-type layer 103. The n-electrode 104 is an electrode that serves both as an ohmic electrode and a bonding pad, and uses a material (Ti, TiW, Al, TCO, etc.) in which the n-type layer 102 is in ohmic contact with the n-type GaN-based semiconductor. Is formed. The p-electrode 105 includes a TCO film 105a (transparent electrode) that is an ohmic electrode formed on the surface of the p-type layer 103, and a bonding pad 105b formed on a part of the TCO film.

  Here, TCO is a transparent conductive oxide, typically ITO (indium tin oxide), indium oxide, tin oxide, IZO (indium zinc oxide), AZO (aluminum). Zinc oxide), zinc oxide, FTO (fluorine-doped tin oxide) and the like are exemplified. At present, ITO is a TCO material widely used for electrodes for GaN-based LED elements.

  In a pn junction type GaN-based LED element having a transparent electrode on a p-type layer and a bonding pad on a part of the transparent electrode, such as the element shown in FIG. 16, a metal film constituting the bonding pad Conventionally, a decrease in luminous efficiency due to absorption or shielding of light generated at the pn junction has been a problem. In order to solve this problem, an insulating structure is inserted between the bonding pad and the p-type layer so that carriers are hardly injected into the p-type layer immediately below the bonding pad. A GaN-based LED element configured to suppress light emission at a pn junction immediately below has been devised (Patent Documents 1, 2, and 3).

  In Patent Document 4, a metal film is used as a transparent electrode, but the above problem can be solved by partially destroying the ohmic contact between the p-type layer and the electrode immediately below the bonding pad. The illustrated GaN-based LED element is disclosed. In particular, the method described in this document for damaging the metal / GaN interface after the formation of a transparent electrode (in this document “contact metal layer”) can cause contamination or damage to the p-type layer surface. There is an advantage that it is not necessary to perform this before forming the transparent electrode.

JP 9-129922 A International Publication No. 98/4420 Pamphlet JP 2000-164928 A International Publication No. 2006/11936 Pamphlet

In the GaN-based LED elements described in Patent Documents 1 to 3, there is a problem that the structure of the element and the manufacturing process become complicated as an insulating structure is provided under the bonding pad.
Moreover, since the LED element described in Patent Document 1 allows light emission below the contact surface between the bonding pad and the transparent electrode, the effect of improving the light emission efficiency is not sufficient. On the other hand, if the area of the contact surface is reduced in order to increase the effect of improving the luminous efficiency, there arises a problem that a stable electrical connection between the bonding pad and the transparent electrode cannot be secured. For this reason, it is difficult to reduce the area of the bonding pad in this LED element.
Further, in the LED elements described in Patent Documents 2 and 3, since a step of forming an insulating structure on the p-type layer surface is necessary before the formation of the transparent electrode, the surface of the p-type layer is required during this step. May be contaminated or damaged, and the contact resistance between the p-type layer and the transparent electrode may increase, which may increase the operating voltage of the device.
Further, if the method disclosed in Patent Document 4 for damaging the metal / GaN interface after the formation of the transparent electrode can be realized, all of the above problems are considered to be solved. However, the invention of Patent Document 4 is intended for GaN-based LED elements using metal electrodes, and the definition of high-energy plasma required to damage the metal / GaN interface is also generated. Since no method is disclosed, it is unclear whether the method described in Patent Document 4 can be applied to a GaN-based LED element in which an ohmic electrode is formed of TCO.
The present invention has been made in view of the above-described problems of the prior art. In a pn junction type GaN-based LED element having a TCO film on a p-type layer and a bonding pad on a part of the TCO film. The main object of the present invention is to provide a new configuration relating to suppression of light emission at the pn junction immediately below the bonding pad.

The following invention is disclosed.
(1) an n-type GaN-based semiconductor layer;
A p-type GaN-based semiconductor layer stacked on the n-type GaN-based semiconductor layer;
An n-electrode connected to the n-type GaN-based semiconductor layer;
A TCO film formed on the surface of the p-type GaN-based semiconductor layer;
A conductive sputtered film formed on a part of the TCO film;
A region where the resistance between the p-type GaN-based semiconductor layer and the TCO film is partially increased, the resistance increasing region corresponding to a contact region between the TCO film and the conductive sputtered film;
A bonding pad formed on the resistance increasing region;
A GaN-based LED element comprising:
(2) The GaN-based LED element according to (1), wherein the thickness of the TCO film is 0.4 μm or less.
(3) In the GaN-based LED element according to (1), the TCO film is a first TCO film that is a flat film, a current diffusion layer formed on a part of the first TCO film, A GaN-based LED element comprising:
(4) The GaN-based LED element according to (3), wherein the first TCO film has a thickness of 0.2 μm or less.
(5) The GaN-based LED element according to any one of (1) to (4), wherein the conductive sputtered film is a bonding pad or a part thereof.
(6) The GaN-based LED element according to any one of (1) to (5), wherein the conductive sputtered film is made of a TCO material.
(7) In the GaN-based LED element according to any one of (1) to (6), the resistance between the p-type GaN-based semiconductor layer and the TCO film is substantially affected on the TCO film. A GaN-based LED element having a passivation film formed by a film forming method that does not apply.
(8) The GaN-based LED element according to any one of (1) to (6), wherein the GaN-based LED element has a passivation film formed by an electron beam evaporation method on the TCO film.
(9) A wafer including an n-type GaN-based semiconductor layer, a p-type GaN-based semiconductor layer stacked on the n-type GaN-based semiconductor layer, and a TCO film formed on the surface of the p-type GaN-based semiconductor layer The process of preparing
A region in which the resistance between the p-type GaN-based semiconductor layer and the TCO film is partially increased by covering the surface of the wafer with a protective film having an opening at a bonding pad formation scheduled site on the TCO film. Forming a conductive sputtered film on the surface of the TCO film through the opening so as to correspond to the opening;
The manufacturing method of the GaN-type LED element characterized by having.
(10) In the manufacturing method according to (9), the thickness of the TCO film is 0.4 μm or less.
(11) In the manufacturing method according to (9), the TCO film includes a first TCO film that is a flat film, and a current diffusion layer formed in a part on the first TCO film. A method for producing a GaN-based LED element.
(12) In the manufacturing method described in (11), the film thickness of the first TCO film is 0.2 μm or less.
(13) The method according to any one of (9) to (12), wherein the conductive sputtered film is a bonding pad or a part thereof.
(14) The method according to any one of (9) to (13), wherein the conductive sputtered film is made of a TCO material.
(15) In the manufacturing method according to any one of (9) to (14), the resistance between the p-type GaN-based semiconductor layer and the TCO film is not substantially affected on the TCO film. A method for producing a GaN-based LED element, comprising a step of forming a passivation film by a film forming method.
(16) In the manufacturing method according to any one of (9) to (14), the method includes a step of forming a passivation film on the TCO film by an electron beam evaporation method. Method.

The GaN-based LED element according to the present invention has a resistance increasing region which is a region where the resistance between the p-type layer and the TCO film is partially increased, and a bonding pad formed on this region. Since the carrier injection from the TCO film to the p-type layer is suppressed in the resistance increasing region, light emission at the pn junction is suppressed below the region. Therefore, this LED element has a configuration in which light emission at the pn junction immediately below the bonding pad is suppressed.
This LED element can be configured such that the region where the bonding pad is formed and the resistance increasing region are almost perfectly aligned. In such a case, only light emission directly under the bonding pad is possible. Can be reliably suppressed.

  In addition, in the GaN-based LED element according to the present invention, since the electrical connection between the TCO film and the bonding pad is sufficiently ensured even in the resistance increasing region, the electrical characteristics of the element are destabilized. The area of the bonding pad can be reduced without incurring. By reducing the area of the bonding pad, the total amount of light absorbed by the bonding pad can be reduced.

  In addition, in the GaN-based LED element according to the present invention, since the resistance increasing region is formed after the formation of the TCO film, the operation caused by contamination or damage of the p-type layer surface before the formation of the TCO film. It is unlikely that the problem of voltage rise will occur.

  Moreover, according to the manufacturing method of the GaN-type LED element which concerns on this invention, the GaN-type LED element provided with the above preferable characteristics can be manufactured simply.

It is the cathodoluminescence image of the surface of the epitaxial layer contained in the GaN-type LED chip which was produced using the manufacturing method concerning one embodiment of the present invention, and was made to light continuously under accelerated degradation conditions. It is a cathode luminescence image of the surface of the epitaxial layer contained in the GaN-type LED chip as produced using the manufacturing method concerning one embodiment of the present invention. It is sectional drawing which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the GaN-type LED element which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the GaN-type LED element which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the GaN-type LED element which concerns on one Embodiment of this invention. It is a figure which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention, Fig.7 (a) is the top view which looked at the element from the electrode arrangement surface side, FIG.7 (b) is FIG.7 (a). It is sectional drawing in the position of XX. It is a figure which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention, FIG.8 (a) is the top view which looked at the element from the electrode arrangement | positioning surface side, FIG.8 (b) is FIG.8 (a). It is sectional drawing in the position of XX. It is a top view which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention. It is a top view which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention. It is a figure which illustrates a net-like pattern. It is a figure which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention, Fig.12 (a) is the top view which looked at the element from the electrode arrangement | positioning surface side, FIG.12 (b) is FIG.12 (a). It is sectional drawing in the position of XX. It is a top view which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention. It is a top view which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention. It is a figure which shows the structure of the GaN-type LED element which concerns on one Embodiment of this invention, Fig.15 (a) is the top view which looked at the LED element from the electrode arrangement | positioning surface side, FIG.15 (b) is FIG.15 (a). It is sectional drawing in the position of line XX. It is sectional drawing which shows the structure of a typical pn junction type GaN-type LED element.

Explanation of symbols

10, 20, 30, 40, 50, 60, 70, 80, 90, 100 GaN-based LED elements
11, 21, 31, 61, 91, 101 Board
12, 22, 32, 42, 52, 62, 72, 82, 92, 102 n-type GaN-based semiconductor layer
13, 23, 33, 43, 53, 63, 73, 83, 93, 103 p-type GaN-based semiconductor layer
14, 24, 34, 44, 54, 64, 74, 84, 94, 104 n-electrode
15, 25, 35, 45, 55, 65, 75, 85, 95, 105 p-electrode
15a, 25a, 35a, 45a, 55a, 65a, 75a, 85a, 95a, 105a TCO membrane
15b, 25b, 35b, 45b, 55b, 65b, 75b, 85b, 95b, 105b Bonding pads
25c, 35c, 45c, 55c, 65c, 75c, 85c, 95c Current spreading layer
16, 36, 66, 96 Resistance increase area
P Protective film

  First, the action mechanism of the present invention will be described based on the results of prototyping and evaluation of GaN-based LED elements conducted by the present inventors (experimental example).

(Experimental example)
First, by using a normal MOVPE method, a 4 μm thick undoped GaN layer, a 4 μm thick n-type GaN contact layer made of Si doped GaN, and a InGaN / GaN multiple quantum well active layer (emission wavelength: 405 nm), p-type cladding layer having a thickness of 170 nm made of Mg-doped Al _0.1 Ga _0.9 N, and thickness of 40 nm made of Mg-doped Al _0.03 Ga _0.97 N The epitaxial wafers were fabricated by sequentially laminating the p-type contact layers.

  Next, an ITO film for forming a p-side ohmic electrode was formed on the p-type contact layer of the epitaxial wafer to a thickness of about 0.2 μm by using an electron beam evaporation method. Then, the formed ITO film was subjected to a heat treatment at 500 ° C. for 20 minutes in an air atmosphere. After the heat treatment, this ITO film was formed into a predetermined shape by dissolving and removing unnecessary portions by hydrochloric acid etching. In addition, it was confirmed from cross-sectional SEM observation that the obtained ITO film | membrane has a columnar structure.

  Next, a recess was formed by RIE (reactive ion etching) at a place where the n electrode of the epitaxial layer was to be formed, and the n-type contact layer was exposed at the bottom of the recess.

  Next, the lift-off method is used to simultaneously form an n-electrode (also used as a bonding pad) on the n-type contact layer surface exposed in the above process and a p-side bonding pad on the ITO film surface. It was.

The lift-off method is a technique for forming a desired thin film on a wafer surface in a desired pattern, and is a technique well known in the art.
(i) After forming a photoresist film on the wafer surface and providing a predetermined opening pattern in the photoresist film by photolithography;
(ii) forming a target thin film on the wafer;
(iii) Thereafter, the photoresist film is removed (at this time, a portion of the target thin film formed on the photoresist film is lifted off);
Through this step, the target thin film is formed in the same pattern as the opening pattern provided in the photoresist film in (i).

In this experimental example, an n-electrode and a p-side bonding pad were formed by a lift-off method using a photoresist film formed to a thickness of 6 μm. A naphthoquinonediazide-novolak resin-based positive photoresist (manufactured by AZ Electronic Materials, product name: AZ P4620) was used as the photoresist. The photoresist applied to the wafer surface was baked at 100 ° C. for 30 minutes, and then exposed and developed. The photoresist after development was not baked. The metal film for the electrode (bonding pad) was a two-layer structure film in which an Au film having a thickness of 500 nm was laminated on a TiW film having a thickness of 100 nm. Therefore, the film thickness of the photoresist film is 10 times that of the metal film. Both the TiW film and the Au film were formed by sputtering. When forming a TiW film, a Ti—W target having a Ti content of 10 wt% is used as a target, Ar (argon) is used as a sputtering gas, RF power is 200 W, and sputtering gas pressure is 1.0 × 10 ⁻¹ Pa. Sputtering was performed. After the formation of the metal film, the metal film was formed into a predetermined electrode shape by removing the photoresist film from the wafer using a remover solution.

  Next, a protective coating (passivation film) made of silicon oxide was formed on the wafer surface excluding the surfaces of the n-electrode and the p-side bonding pad by using an electron beam evaporation method. Thereafter, the back surface of the sapphire substrate was lapped to reduce the thickness of the wafer to 80 μm, and then the wafer was divided using a scriber to obtain a 350 μm square plate-like GaN-based LED chip. The forward voltage Vf (20 mA) of this chip was 3.3V.

  The LED chip produced by the above procedure was deteriorated under accelerated deterioration conditions. Specifically, the LED chip is flip-chip mounted on the stem via the submount, and continuously for 1000 hours under the conditions of an environmental temperature of 100 ° C. and a forward current of 114 mA so that the temperature of the pn junction is 230 ° C. Lighted up. After deteriorating in this way, the LED chip is removed from the submount, the protective coating and the ITO film are removed from the surface of the epitaxial layer using acid, and then the surface of the epitaxial layer (the surface of the p-type contact layer) is removed. A cathodoluminescence (CL) image was obtained. The acquired CL image is shown in FIG.

As shown in FIG. 1, on the surface of the epitaxial layer included in the LED chip deteriorated by continuous lighting, a dark spot appearing in a portion where dislocation defects exist (because the efficiency of luminescence recombination is locally low). The density of the dark portion) was clearly different between the area immediately below the bonding pad and the surrounding area. That is, the density of dislocation defects was clearly lower in the region immediately below the p-side bonding pad than in the surrounding region.
On the other hand, FIG. 2 shows a CL image of the epitaxial layer surface obtained in the same manner and included in the as-manufactured LED chip. As apparent from FIG. 2, the distribution of the transition defects on the surface of the epitaxial layer was uniform in the undegraded state.

The present inventors measured the temperature of the pn junction when the LED chip was turned on under the above conditions by a method using a thermocouple, but a significant temperature was found between the area directly below the p-side bonding pad and the surrounding area. There was no difference. From this, the obvious difference in dislocation density between the area immediately below the bonding pad and the surrounding area seen in the epitaxial layer of the chip deteriorated by continuous lighting is not caused solely by the thermal action. The present inventors concluded. The conclusion of the present inventors is that an electrical effect is involved in the increase in defect density associated with continuous lighting, and the density of carriers injected from the ITO film into the p-type layer is low immediately below the p-side bonding pad. Therefore, an increase in defect density is suppressed. The method of forming the bonding pad is related to the decrease in the injected carrier density immediately below the bonding pad. When the metal film constituting the bonding pad is formed by sputtering, the surface of the ITO film is protected by a thick photoresist film outside the region where the bonding pad is to be formed. On the other hand, the surface of the ITO film is exposed in the region where the bonding pad is to be formed. Therefore, when the bonding pad is formed, in this region, the surface of the p-type layer that is only covered with the thin ITO film is damaged by the impact of sputtered particles or high-energy particles. As a result, the resistance between the ITO film and the p-type layer is relatively high immediately below the bonding pad, and as a result, when a forward current is supplied to the LED chip, carriers from the ITO film to the p-type layer are obtained. Implantation is unlikely to occur directly below the bonding pad.
The increase in resistance at the damaged part is explained as follows. That is, in the GaN-based semiconductor, nitrogen vacancies are formed at a high concentration in the damaged portion due to the high vapor pressure of nitrogen, which is a group V component. Since these nitrogen vacancies serve as donors, the p-type GaN-based semiconductor causes a decrease in p-type carrier concentration due to self-compensation. This increases the resistivity of the semiconductor and the contact resistance between the semiconductor and the electrode. In particular, the generation efficiency of p-type carriers is essentially low in a GaN-based semiconductor that is a wide gap semiconductor, that is, the carrier concentration of the p-type layer is basically low, so that the carrier concentration is further reduced by being damaged. The increase in contact resistance when this occurs is significant.

  The GaN-based LED element and the manufacturing method thereof disclosed by the experimental examples described above are included in the embodiment of the present invention.

Next, various embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 3 is a cross-sectional view of the GaN-based LED element 10 according to Embodiment 1 of the present invention. The GaN-based LED element 10 has a laminated body composed of an n-type GaN-based semiconductor layer 12 and a p-type GaN-based semiconductor layer 13 on a substrate 11, and the surface of the n-type layer 12 that is partially exposed by etching. The n-electrode 14 is formed on the p-type layer 13, and the p-electrode 15 is formed on the surface of the p-type layer 13. The n-electrode 14 is an electrode that serves both as an ohmic electrode and a bonding pad, and a portion in contact with the n-type layer 12 is formed using a material that is in ohmic contact with the n-type GaN-based semiconductor. The p electrode 15 includes a TCO film 15a (transparent electrode) that is an ohmic electrode formed on the surface of the p-type layer 13, and a bonding pad 15b formed on a part of the TCO film.

The GaN-based LED element 10 has a resistance increasing region 16 that is a region where the resistance between the p-type GaN-based semiconductor layer 13 and the TCO film 15a is partially increased, and the bonding pad 15b has an increased resistance. It is formed on region 16. The resistance increasing region 16 is formed when the bonding pad 15b is deposited on the surface of the TCO film 15a by a sputtering method, and corresponds to a contact region between the TCO film 15a and the bonding pad 15b.
Since the carrier injection from the TCO film 15a to the p-type layer 13 hardly occurs in the resistance increasing region 16, light emission at the pn junction is suppressed below the carrier increasing region 16. Therefore, in this LED element 10, it can be said that light emission at the pn junction immediately below the bonding pad 15b is suppressed.

  In the GaN-based LED element 10, the bonding pad and the GaN-based semiconductor are separated by a TCO film having a refractive index lower than that of the GaN-based semiconductor. This configuration is a preferable configuration in order to reduce a loss caused by the bonding pad absorbing light. This is because light propagating in the GaN-based semiconductor layer is difficult to enter the back surface of the bonding pad due to total reflection occurring at the interface between the GaN-based semiconductor and the TCO film.

Next, a manufacturing method of the GaN-based LED element 10 will be described with reference to the drawings (for the sake of convenience, only a portion corresponding to one of a large number of chips formed on the wafer is shown).
First, as shown in FIG. 4A, vapor phase epitaxial growth methods such as MOVPE method (organometallic compound vapor phase growth method), MBE method (molecular beam epitaxy method), and HVPE method (hydride vapor phase growth method) are used. Then, an n-type GaN-based semiconductor layer 12 and a p-type GaN-based semiconductor layer 13 are sequentially grown and stacked on the substrate 11.

  Next, as shown in FIG. 4B, on the p-type GaN-based semiconductor layer of the epitaxial wafer obtained in the above step, TCO is used using an appropriate method such as a vacuum deposition method, a spray method, or a sol-gel method. A film 15a is formed. Then, unnecessary portions are removed using photolithography and etching (wet or dry) techniques, thereby forming the TCO film into a predetermined shape as shown in FIG. A heat treatment may be applied to the TCO film 15a before or after molding, if necessary.

  Next, as shown in FIG. 4D, a part of the epitaxial layer is removed by RIE (reactive ion etching) to form a recess, and the n-type GaN-based semiconductor layer 12 is exposed at the bottom of the recess. Let

  Next, a protective film P that covers the entire wafer surface is formed, and an opening is formed in the protective film P as shown in FIG. Then, as shown in FIG. 5B, by depositing a metal film through the opening of the protective film P, the n electrode 14 is formed on the exposed surface of the n-type GaN-based semiconductor layer 12, and the TCO film 15a. Bonding pads 15b are respectively formed on a part of the surface of the substrate. A sputtering method is used for depositing the metal film. After the sputtering process, the protective film P is lifted off.

There are two important points in the manufacturing method of the GaN-based LED element 10 described above.
The first point is that, in the sputtering step, the p-type GaN-based semiconductor layer 13 and the region corresponding to the region where the bonding pad 15b is deposited on the surface of the TCO film 15a (the region where the protective film P has an opening) are formed. Sputtering conditions are set so that a region 16 having a partially increased resistance with the TCO film 15a is formed. This increase in resistance is considered to be caused by the impact of sputtered particles or high-energy particles as described above, and can be promoted, for example, by lowering the sputtering atmosphere. This is because, under a low-pressure atmosphere, the probability that sputtered particles or high-energy particles reach the wafer surface without losing energy due to collision with atmospheric gas molecules increases. In general, high energy particles damage the substrate and the sputtered film. Therefore, it is preferable that the high energy particles are not incident on the substrate as much as possible. In contrast, in forming the resistance increasing region, The action of high energy particles can be preferably used.
In one embodiment, a low pressure atmosphere may be used at the beginning of the sputtering process to increase the effect of high energy particles, and the pressure may be increased during the process.

  The second point is that in the region covered with the protective film P, the resistance between the p-type GaN-based semiconductor layer 13 and the TCO film 15a is not changed substantially before and after the sputtering process, depending on the sputtering conditions used. The material and film thickness of the protective film P are determined so that a sufficient protective effect is produced. Since the organic material is inferior in protective effect to the inorganic material, the film thickness should be larger when the protective film P is formed of the organic material than when the inorganic material is used. Photoresists capable of forming a thick film of 10 μm or more, mainly used for forming bumps (microelectrodes) by electroplating, are commercially available, and can be preferably used as the protective film P.

According to this manufacturing method, since it is not necessary to process the surface of the p-type layer 13 before the TCO film 15a is formed, the p-type layer 13 and the TCO film are caused by contamination or damage on the surface of the p-type layer 13. The possibility that the problem of an increase in contact resistance with 15a occurs is reduced.
Further, according to this manufacturing method, the region where the bonding pad 15b is formed and the resistance increasing region 16 are substantially perfectly aligned. That is, the resistance increasing region 16 is selectively formed at a site most highly necessary to suppress carrier injection from the TCO film 15a to the p-type layer 13. Therefore, it is possible to reliably suppress only light emission directly under the bonding pad.

As a modified embodiment, the protective film P can have a two-layer structure including an insulating transparent inorganic thin film P1 that can be used as a passivation film and a photoresist P2 laminated thereon.
In this embodiment, after completing the step of partially exposing the n-type GaN-based semiconductor layer 12, as shown in FIG. 6A, this two-layer protective film P is formed on the entire surface of the wafer. . Here, when the transparent inorganic thin film P1 is formed, the resistance between the p-type GaN-based semiconductor layer 13 and the TCO film 15a is not substantially increased. To do so, it is preferable to use an electron beam evaporation method, a laser ablation method, or a sol-gel method as a method of forming the transparent inorganic thin film P1.
Next, as shown in FIG. 6B, the photoresist P2 is patterned by a normal method to form an opening. When the transparent inorganic thin film P1 is selectively etched using the photoresist P2 as a mask, the same opening pattern is formed in the transparent inorganic thin film P1 and the photoresist P2 as shown in FIG. 6C. can do.
When a metal film is deposited by sputtering on the wafer with the protective film P thus patterned and only the photoresist P2 is lifted off, bonding pads 14 and 15b are formed on the wafer surface as shown in FIG. 6 (d). A structure is obtained in which the transparent inorganic thin film P1 covers the portion other than the portion. The transparent inorganic thin film P1 is left on the LED element surface and used as a passivation film.
Although the manufacturing efficiency is low, in the embodiment using such a two-layer protective film, formation and patterning of the transparent inorganic thin film can be completed first, and then formation and patterning of the photoresist film can be performed. . In this case, it is not always necessary to match the opening pattern formed in the transparent inorganic thin film with the opening pattern formed in the photoresist.

Next, the preferable aspect of each part which comprises the GaN-type LED element 10 is demonstrated.
Substrate 11 includes sapphire, spinel, silicon carbide, silicon, GaN-based semiconductor (GaN, AlGaN, etc.), gallium arsenide, gallium phosphide, gallium oxide, zinc oxide, LGO, NGO, LAO, zirconium boride, boride A crystal substrate (single crystal substrate, template) made of a material such as titanium can be preferably used.
Among these, conductivity can be imparted to a substrate made of silicon carbide, silicon, GaN-based semiconductor, gallium arsenide, gallium phosphide, gallium oxide, zinc oxide, zirconium boride, or titanium boride. When a conductive substrate is used, an electrode connected to the n-type GaN-based semiconductor layer 12 can be formed on the back surface of the substrate instead of being formed on the surface of the layer.
When a substrate that does not lattice match with the GaN-based semiconductor crystal is used, it is desirable to interpose a buffer layer between the substrate and the GaN-based semiconductor layer. With reference to a known technique, a buffer layer such as a low-temperature buffer layer, a high-temperature buffer layer (single crystal buffer layer), or a superlattice buffer layer made of a GaN-based semiconductor or other materials can be appropriately selected and used.

The n-type layer 12 can be formed of GaN, AlGaN, InGaN, or AlInGaN to which an n-type impurity such as Si or Ge is added. Preferably, as a contact layer for forming the n-electrode 14, a GaN layer having a thickness of 2 μm to 6 μm in which Si is added to a concentration of 1 × 10 ¹⁸ cm ⁻³ to 1 × 10 ¹⁹ cm ⁻³ is provided.
The p-type layer 13 can be formed of GaN, AlGaN, InGaN, or AlInGaN to which p-type impurities such as Mg and Zn are added. The p-type layer 13 is preferably formed using Al _a Ga _1-a N (0 ≦ a ≦ 0.2) in which Mg is added to a concentration of 2 × 10 ¹⁹ cm ⁻³ to 1 × 10 ²⁰ cm ^−3. , 0.1 μm to 2.0 μm, more preferably 0.1 μm to 0.5 μm. When adopting a double hetero structure in which an active layer is provided at the pn junction, a cladding layer having a relatively high mixed crystal ratio of AlN is provided in a portion adjacent to the active layer, while a surface on which the p electrode 15 is formed On the side, it is desirable to reduce the mixed crystal ratio of AlN.

It is desirable to provide an active layer, in particular, an active layer having a multiple quantum well structure, at the pn junction formed between the n-type layer 12 and the p-type layer 13.
In addition, stress between the substrate 11 and the n-type layer 12, inside the n-type layer 12, between the n-type layer 12 and the p-type layer 13, and inside the p-type layer 13 can be stressed by referring to a known technique. A GaN-based semiconductor layer (including a stacked body) having various purposes such as relaxation of strain, reduction of dislocation density, improvement of electrostatic withstand voltage characteristics, and improvement of light emission efficiency can be provided.

  The n-electrode 14 is formed of a material capable of forming an ohmic contact with the n-type GaN-based semiconductor at least a portion in contact with the n-type layer 12. As such a material, Ti (titanium), Al (aluminum), W (tungsten) or V (vanadium) alone or an alloy containing these as a main component, or TCO is preferably exemplified. The surface layer of the n-electrode 14 is made of Ag (silver), Au (gold), Sn (tin), In (indium), Bi (bismuth), Cu (copper) so that bonding wires, solder, bumps, etc. can be easily joined. , Zn (zinc) or the like is preferable. The n-electrode can also be composed of an ohmic electrode made of TCO and a bonding pad formed on a part thereof.

The TCO film 15a can be formed using various known TCOs such as indium oxide, zinc oxide, tin oxide, and titanium oxide. Preferred TCO materials include ITO, IZO (indium zinc oxide), AZO (aluminum zinc oxide), GZO (gallium zinc oxide), FTO (fluorine-doped tin oxide), and the like.
The film thickness of the TCO film 15a is preferably 0.01 μm to 0.4 μm. The inventors of the present invention have the following conditions: an ambient temperature of 145 ° C. and a forward current of 100 mA for a GaN-based LED chip manufactured in the same manner as in Experimental Example 1 except that the thickness of the ITO film is changed to 0.4 μm. After 320 hours of continuous lighting, the CL image of the epitaxial layer surface was observed in the same manner as in Experimental Example 1. As a result, as in Experimental Example 1, it was confirmed that the density of dislocation defects was clearly lower in the region immediately below the p-side bonding pad than in the surrounding region.
There is no limitation on the method of forming the TCO film 15a, and an appropriate method may be adopted with reference to known techniques. Use of the sputtering method is not hindered. By preventing the high energy particles from entering the surface of the p-type layer by increasing the pressure in the sputtering atmosphere, it is possible to form a TCO film having a low resistance with the p-type layer even by the sputtering method. It is.

  The material of the bonding pad 15b is not particularly limited, but in order to increase the reflectivity, the portion in contact with the TCO film 15a is made of Ag (silver), Al (aluminum), platinum group metal (Ru, Rh, Pd). , Os, Ir, Pt), nickel (Ni), or other silver-white metal, or TCO is preferably used. The surface layer portion of the bonding pad 15b is preferably formed of Ag, Au, Sn, In, Bi, Cu, Zn or the like so that bonding wires, solder, bumps, and the like can be easily bonded.

  Although not shown in FIG. 3, a protective coating (passivation film) may be provided on the surface of the LED element 10 except for the surfaces of the n-electrode 14 and the bonding pad 15b. The protective coating can be formed of a metal oxide, a metal nitride, or a metal oxynitride having good transparency at the emission wavelength of the LED element. Specific examples include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, spinel, aluminum nitride, tantalum oxide, zirconium oxide, and hafnium oxide.

(Embodiment 2)
In the GaN-based LED element 10 according to the first embodiment, the resistance between the TCO film and the p-type layer becomes more conspicuous in the resistance increasing region 16 than in other regions as the thickness of the TCO film 15a is reduced. growing. This is because, as the film thickness decreases, the action as a protective material of the TCO film (the action of protecting the p-type layer surface in the sputtering process) becomes smaller.
Further, when the thickness of the TCO film is reduced, there is an advantage that loss due to light absorption of the film can be reduced. This advantage is particularly remarkable in LED elements that generate light in the near-ultraviolet to violet wavelength range, which is a wavelength range in which the permeability of the TCO film is low.

  However, when the thickness of the TCO film is simply reduced, there arises a problem that the current diffusion function in the horizontal direction that the TCO film should bear decreases due to an increase in sheet resistance. Here, the horizontal current spreading function is a function of spreading the current supplied from the bonding pad in a direction (horizontal direction) parallel to the pn junction surface. If the current does not spread in the TCO film in the horizontal direction, even if there is a difference in resistance between the p-type layer and the TCO film between the resistance increasing region and other regions, it is injected into the p-type layer. The carrier density is not sufficiently different between regions.

Therefore, in the GaN-based LED element according to an embodiment, a current diffusion layer made of a conductive material is formed on a part of the TCO film so that the above problem does not occur even when the thickness of the TCO film is reduced. . This current spreading layer is a layer that functions to assist the horizontal current spreading function of the TCO film.
The structure of the GaN-based LED element configured as described above is shown in FIG. Fig.7 (a) is the top view which looked at the LED element from the electrode arrangement | positioning surface side, FIG.7 (b) is sectional drawing in the position of the XX line of Fig.7 (a).
A GaN-based LED element 20 shown in FIG. 7 has a laminate composed of an n-type layer 22 and a p-type layer 23 on a substrate 21, and an n-electrode is formed on the surface of the n-type layer 22 that is partially exposed by etching. 24 is formed, and a p-electrode 25 is formed on the surface of the p-type layer 23. The n-electrode 24 is an electrode that serves both as an ohmic electrode and a bonding pad, and a portion in contact with the n-type layer 22 is formed using a material that is in ohmic contact with the n-type GaN-based semiconductor. The p electrode 25 is a first TCO film 25a (transparent electrode) that is an ohmic electrode formed on the surface of the p-type layer 23, and a p-side bonding pad 25b formed on a part of the first TCO film 25a. And a current diffusion layer 25c formed on a part of the first TCO film 25a. A through hole is formed in the current diffusion layer 25c, and the first TCO film 25a and the p-side bonding pad 25b are in contact with each other through the through hole. The broken line in FIG. 7A shows the outline of the through hole formed in the current diffusion layer 25c (hidden under the p-side bonding pad 25b). In the region inside the broken line, the resistance between the p-type layer 23 and the TCO film 25a is particularly high.

The GaN-based LED element 20 can be manufactured as follows.
First, an n-type layer and a p-type layer are sequentially laminated on a substrate using a normal MOVPE method to produce an epitaxial wafer. A preferred substrate and a preferred epitaxial growth layer configuration are the same as those in the first embodiment.

  Next, a first TCO film for forming an ohmic electrode is formed on the p-type layer of the formed epitaxial wafer by using a vacuum deposition method. The film thickness of the first TCO film can be, for example, 0.01 μm to 0.2 μm, preferably 0.01 μm to 0.15 μm, more preferably 0.01 μm to 0.10 μm, and particularly preferably Is 0.01 μm to 0.05 μm. After the film formation, the first TCO film is patterned into a predetermined electrode shape by removing unnecessary portions by wet or dry etching. The wafer may be heat treated before or after patterning.

  Next, a current diffusion layer is formed in a predetermined region on the first TCO film formed on the p-type layer. The current spreading layer is formed by vacuum deposition using a TCO material. It is preferable to use a lift-off method for patterning the current spreading layer. The thickness of the current diffusion layer formed of the TCO material is preferably set so that the sum of the thickness of the first TCO film and the thickness of the current diffusion layer is 0.15 μm to 0.5 μm.

  Next, a part of the epitaxial layer is removed by RIE (reactive ion etching) to form a recess, and the n-type layer is exposed at the bottom of the recess.

Next, a p-side bonding pad is formed on the TCO film by using a lift-off method. At this time, the n electrode may be formed at the same time. The photoresist film used in the lift-off method is preferably formed to a thickness of 6 μm or more. As for the p-side bonding pad, at least a portion in contact with the TCO film is formed by a sputtering method. At that time, sputtering is performed so that a region where the resistance between the p-type layer and the first TCO film is partially increased is formed at least corresponding to the contact region between the first TCO film and the sputtered film. Set conditions.
The lowermost part of the n-electrode and the p-side bonding pad may be formed of a TCO material or a metal material, but is preferably formed of a TCO material. The surface layers of the n-electrode and the p-side bonding pad are formed using a metal material. A preferred metal material is the same as that in the first embodiment.

  Next, a transparent protective coating (passivation film) is formed on the wafer surface excluding the surfaces of the n-electrode and the p-side bonding pad by using an electron beam evaporation method. The material of the protective coating is preferably a metal oxide, metal nitride, metal oxynitride or the like. Thereafter, if necessary, the back surface of the substrate is lapped to reduce the thickness of the wafer, and then the wafer is divided using a scriber or the like to obtain a chip-like GaN-based LED element.

(Embodiment 3)
In the GaN-based LED element 20 according to the second embodiment, a part of the current diffusion layer 25c is configured to be sandwiched between the first TCO film 25a and the bonding pad 25b. Such a configuration is essential. is not. In one embodiment, the bonding pad and the current spreading layer may be separated from each other on the TCO film.
The structure of the GaN-based LED element 30 configured as described above is shown in FIG. FIG. 8A is a plan view of the element as viewed from the electrode arrangement surface side, and FIG. 8B is a cross-sectional view taken along the line XX in FIG. As shown in FIG. 8, in the GaN-based LED element 30, the bonding pad 35 b and the current diffusion layer 35 c are separated from each other on the first TCO film 35 a that is an ohmic electrode with respect to the p-type layer 33. When manufacturing the LED element 30, the bonding pad 35b may be formed before the current diffusion layer 35c or may be formed later.

(Embodiment 4)
In one embodiment, the current diffusion layer may have a portion exhibiting a strip pattern on the TCO film.
FIG. 9 is a plan view of the GaN-based LED element 40 configured as described above. A portion 45c− in which the current diffusion layer 45c is formed in a strip pattern on the first TCO film 45a which is an ohmic electrode with respect to the p-type layer 43. It has two 1's. Each of the portions 45c-1 in which the current spreading layer exhibits a belt-like pattern has a straight portion and a bent portion. In one embodiment, the belt-like pattern may be provided with a curved portion, a meandering portion, an annular portion, and the like.

Compared with the GaN-based LED element 20, since the area of the current diffusion layer 45c covering the surface of the first TCO film 45a is smaller in the GaN-based LED element 40, the current diffusion layer 45c may be formed of a metal material. . Preferable metal materials include platinum group metals, Ag, Al, Ni, and the like that exhibit a silver white color when formed into a thick film. The current diffusion layer 45c made of a metal film may be formed to a thickness that exhibits light transmission properties, or may be formed to a thickness that allows light transmission properties (light reflection properties). Metal materials have the drawback of having higher light absorption in the near-UV to visible region than TCO materials, but because of their excellent electrical conductivity, current spreading layers made of metal materials have good horizontal orientation even in small areas. The current diffusivity is provided.
On the other hand, when the current diffusion layer 45c is formed of a TCO material, the thickness thereof is such that the sum of the film thickness of the first TCO film 45a and the film thickness of the current diffusion layer 45c is 0.15 μm to 0.5 μm. It is preferable to set.

  When a sputtering method is used to form the current diffusion layer 45c, the resistance between the p-type layer 43 and the first TCO film 45a may increase immediately below the current diffusion layer 45c, but in the GaN-based LED element 40, the current diffusion layer 45c. This is acceptable because of the small area. In this case, a photoresist film used when the current diffusion layer 45c is formed by a lift-off method so that the resistance between the p-type layer 43 and the first TCO film 45a does not increase in a region where the current diffusion layer 45c is not formed. The film thickness should be sufficiently large.

(Embodiment 5)
In one embodiment, on the TCO film that is an ohmic electrode for the p-type layer, the current diffusion layer may include a portion exhibiting a pattern having a branch. The pattern having a branch includes a net pattern, a comb pattern, and a dendritic pattern.
FIG. 10 is a plan view of the GaN-based LED element 50 configured as described above. On the first TCO film 55a which is an ohmic electrode for the p-type layer 53, the current diffusion layer 55c has a square lattice pattern. A square lattice pattern is a kind of net-like pattern. In addition to the square lattice, various lattice patterns such as a triangular lattice, a hexagonal lattice, and a kagome lattice are included in the net pattern.
The net pattern is not limited to the lattice pattern described above, but penetrates the film structure to be patterned such as the pattern shown in FIG. 11A (the pattern exhibited by the hatched portion). Including a pattern in which a plurality of circular through holes (outlined portions) are formed. Further, the net pattern includes the patterns shown in FIGS. 11B to 11D related to the deformation of the pattern shown in FIG. In the pattern shown in FIG. 11B, the plurality of through holes have different sizes. In the pattern shown in FIG. 11C, the plurality of through holes have different shapes. In the pattern shown in FIG. 11D, the arrangement of the through holes is different from the pattern shown in FIG. As described above, the net pattern includes a pattern in which a plurality of through holes having various sizes and shapes are formed in various arrangements in the film structure to be patterned.

In the GaN-based LED element 50, the current diffusion layer 55c also exhibits the same square lattice pattern as the other portions even in the portion sandwiched between the first TCO film 55a and the bonding pad 55b (in FIG. 10). The broken line indicates the outline of the current diffusion layer 55c hidden under the p-side bonding pad 55b), but such a configuration is not essential.
Compared with the GaN-based LED element 20, since the area of the current diffusion layer 55c covering the surface of the first TCO film 55a is smaller in the GaN-based LED element 50, the current diffusion layer 55c may be formed of a metal material. . In that case, the current diffusion layer 55c made of a metal film may be formed to a thickness that exhibits light transmittance, or may be formed to a thickness that allows light transmission (light reflectivity).
When the current diffusion layer 55c is formed of a TCO material, the thickness thereof is set so that the sum of the thickness of the first TCO film 55a and the thickness of the current diffusion layer 55c is 0.15 μm to 0.5 μm. It is preferable.

  When a sputtering method is used to form the current diffusion layer 55c, the resistance between the p-type layer 53 and the first TCO film 55a may be increased immediately below the current diffusion layer 55c. However, in the GaN-based LED element 50, the current diffusion layer 55c. This is acceptable because of the small area. In this case, a photoresist film used when the current diffusion layer 55c is formed by the lift-off method so that the resistance between the p-type layer 53 and the first TCO film 55a does not increase in a region where the current diffusion layer 55c is not formed. The film thickness should be sufficiently large.

(Embodiment 6)
In one embodiment, a step of forming a current diffusion layer having a portion exhibiting a strip pattern or a pattern having a branch on the first TCO film, and a step of forming a p-side bonding pad on the first TCO film. May be performed simultaneously.

  A structural example of a GaN-based LED element manufactured by such a manufacturing method is shown in FIG. 12A is a plan view of the LED element as viewed from the electrode arrangement surface side, and FIG. 12B is a cross-sectional view taken along the line XX of FIG.

  A GaN-based LED element 60 shown in FIG. 12 has a laminate composed of an n-type layer 62 and a p-type layer 63 on a substrate 61, and an n-electrode is formed on the surface of the n-type layer 62 partially exposed by etching. 64 is formed, and a p-electrode 65 is formed on the surface of the p-type layer 63. The n-electrode 64 is an electrode that serves both as an ohmic electrode and a bonding pad, and a portion in contact with the n-type layer 62 is formed using a material that is in ohmic contact with the n-type GaN-based semiconductor. The p-electrode 65 is a first TCO film 65a (transparent electrode) which is an ohmic electrode formed on the surface of the p-type layer 63, and a p-side bonding pad 65b formed on a part of the first TCO film 65a. And a current diffusion layer 65c formed on a part of the first TCO film 65a as a structure integrated with the bonding pad. As shown in FIG. 12A, the two current diffusion layers 65c have a strip pattern. In the example of the GaN-based LED element 60, each of the current diffusion layers 65c has a linear portion and a bent portion, but may be formed in a strip shape having a curved portion or a meandering strip shape, Moreover, it can also form so that it may form a ring.

(Embodiment 7)
In one embodiment, the bonding pad and the current diffusion layer that are simultaneously formed on the first TCO film may be independent structures. FIG. 13 is a plan view of the GaN-based LED element 70 configured as described above. On the first TCO film 75a that is an ohmic electrode for the p-type layer 73, a current diffusion layer that forms a strip pattern with the p-side bonding pad 75b. 75c are separated from each other.

(Embodiment 8)
In one embodiment, the current diffusion layer formed simultaneously with the bonding pad on the first TCO film may include a portion formed in a pattern having a branch.
FIG. 14 is a plan view of the GaN-based LED element configured as described above. In the GaN-based LED element 80 shown in this figure, on the first TCO film 85a that is an ohmic electrode for the p-type layer 83, the current diffusion layer 85c has a square lattice pattern. In the GaN-based LED element 80, the bonding pad 85b and the current diffusion layer 85c are integrally formed, but they may be formed apart from each other.

(Embodiment 9)
In one embodiment, only a part of the bonding pad may be formed simultaneously with the current diffusion layer. For example, only the lowermost part of the bonding pad is formed simultaneously with the current diffusion layer. In this case, the current spreading layer includes a portion exhibiting a belt-like pattern or a pattern having a branch.

FIG. 15 is a view showing the structure of the GaN-based LED element 90 configured as described above. FIG. 15A is a plan view of the LED element as viewed from the electrode arrangement surface side, and FIG. It is sectional drawing in the position of XX of ().
In the GaN-based LED element 90, a p-side bonding pad 95b formed on the TCO film 95a that is an ohmic electrode for the p-type layer 93 includes a base layer portion 95b-1 in contact with the first TCO film 95a, The surface layer portion 95b-2 is formed. A base layer portion 95b-1 of the p-side bonding pad and a current diffusion layer 95c exhibiting a strip pattern are integrally formed. The base layer portion 95b-1 and the current diffusion layer 95c of the p-side bonding pad are formed of a sputtered film, and below the p-type layer 93 and the TCO film so as to correspond to the contact area between the TCO film 95a and these layers. A region 96 having a partially increased resistance with respect to 95a is formed. It is not essential that the base layer portion 95b-1 of the bonding pad and the current diffusion layer 95c are integral, and they can be separated from each other. Further, the current spreading layer 95c may be formed in a shape having a portion exhibiting a branched pattern.

  The base layer portion 95b-1 and the current diffusion layer 95c of the p-side bonding pad are preferably formed using a TCO material that is weaker in light absorption in the near ultraviolet to visible wavelength region than the metal material. However, formation using a metal material is not hindered. When the base layer portion 95b-1 and the current diffusion layer 95c of the bonding pad are formed of the TCO material, the sum of the thickness of the first TCO film 95a and the thickness of the current diffusion layer 95c is 0.15 μm to 0. It is preferable to set it to be 5 μm. Preferred metal materials when the base layer portion 95b-1 of the bonding pad and the current diffusion layer 95c are metal films, such as platinum group metals, Ag, Al, Ni, and the like that exhibit a silver white color when formed into a thick film. Can be mentioned. In this case, the metal film may be formed to have a light-transmitting thickness, or may be formed to have a light-transmitting (light reflecting) thickness. A preferable material for the surface layer portion 95-2 of the bonding pad is the same as that in the first embodiment. The surface layer portion 95-2 is not necessarily made of a sputtered film.

  In the GaN-based LED element 90, the n-electrode 94 is also composed of two parts, a contact part 94-1 and a pad part 94-2. The contact portion 94-1 is an ohmic electrode, and has a portion formed in a belt-like pattern in order to assist the horizontal current diffusing function of the n-type layer 92. The pad portion 94-2 is a bonding pad made of a metal material. The contact portion 94-1 can be formed using any material that is in ohmic contact with the n-type GaN-based semiconductor, but is preferably formed using a TCO material. In a preferred embodiment, the n-electrode contact portion 94-1 and the p-side bonding pad base layer portion 95b-1 are simultaneously formed by sputtering using a TCO material. In the preferred embodiment, the n-electrode pad portion 94-2 and the p-side bonding pad surface portion 95b-2 are simultaneously formed using a metal material.

  In any of the GaN-based LED elements according to the first to ninth embodiments, a substrate (hereinafter referred to as an “epitaxial growth substrate”) used when the n-type and p-type GaN-based semiconductor layers are formed by epitaxial growth is used in the element. However, such a configuration is not essential. Nowadays, a technique for removing an epitaxial growth layer from an epitaxial growth substrate by a technique such as laser lift-off and replacing it with a separately prepared support substrate is well known among those skilled in the art. Further, by using the technique disclosed in Japanese translations of PCT publication No. 2007-517404 (WO2005 / 062905), the epitaxial growth substrate can be removed from the element after the LED element is flip-chip mounted.

  Although various embodiments of the present invention have been described above by way of examples, the present invention is not limited to individual embodiments.

  This application includes a Japanese patent application filed on February 15, 2008 (Japanese Patent Application No. 2008-034968), a Japanese patent application filed on March 26, 2008 (Japanese Patent Application No. 2008-082070), and March 26, 2008. This is based on a Japanese patent application (Japanese Patent Application No. 2008-082071), the contents of which are incorporated herein by reference.

Claims (16)

an n-type GaN-based semiconductor layer;
A p-type GaN-based semiconductor layer stacked on the n-type GaN-based semiconductor layer;
An n-electrode connected to the n-type GaN-based semiconductor layer;
A TCO film formed on the surface of the p-type GaN-based semiconductor layer;
A conductive sputtered film formed on a part of the TCO film;
A region where the resistance between the p-type GaN-based semiconductor layer and the TCO film is partially increased, the resistance increasing region corresponding to a contact region between the TCO film and the conductive sputtered film;
A bonding pad formed on the resistance increasing region;
A GaN-based LED element comprising:   The GaN-based LED element according to claim 1, wherein the TCO film has a thickness of 0.4 μm or less.   2. The GaN-based LED element according to claim 1, wherein the TCO film includes a first TCO film that is a flat film, and a current diffusion layer formed on a part of the first TCO film. A GaN-based LED element.   4. The GaN-based LED element according to claim 3, wherein the first TCO film has a thickness of 0.2 [mu] m or less.   5. The GaN-based LED element according to claim 1, wherein the conductive sputtered film is a bonding pad or a part thereof.   The GaN-based LED element according to any one of claims 1 to 5, wherein the conductive sputtered film is made of a TCO material.   The GaN-based LED element according to claim 1, wherein the film-forming method does not substantially affect the resistance between the p-type GaN-based semiconductor layer and the TCO film on the TCO film. A GaN-based LED element comprising a passivation film formed by   The GaN-based LED element according to claim 1, further comprising a passivation film formed on the TCO film by an electron beam evaporation method. A wafer including an n-type GaN-based semiconductor layer, a p-type GaN-based semiconductor layer stacked on the n-type GaN-based semiconductor layer, and a TCO film formed on the surface of the p-type GaN-based semiconductor layer is prepared. Process,
A region in which the resistance between the p-type GaN-based semiconductor layer and the TCO film is partially increased by covering the surface of the wafer with a protective film having an opening at a bonding pad formation scheduled site on the TCO film. Forming a conductive sputtered film on the surface of the TCO film through the opening so as to correspond to the opening;
The manufacturing method of the GaN-type LED element characterized by having.   10. The method for manufacturing a GaN-based LED element according to claim 9, wherein the thickness of the TCO film is 0.4 [mu] m or less.   10. The manufacturing method according to claim 9, wherein the TCO film includes a first TCO film that is a flat film, and a current diffusion layer formed in a part on the first TCO film. A method for manufacturing a GaN-based LED element.   12. The manufacturing method according to claim 11, wherein the thickness of the first TCO film is 0.2 [mu] m or less.   The manufacturing method according to claim 9, wherein the conductive sputtered film is a bonding pad or a part thereof.   14. The manufacturing method according to claim 9, wherein the conductive sputtered film is made of a TCO material.   15. The manufacturing method according to claim 9, wherein passivation is performed on the TCO film by a film forming method that does not substantially affect a resistance between the p-type GaN-based semiconductor layer and the TCO film. A method for producing a GaN-based LED element, comprising a step of forming a film.   15. The method for manufacturing a GaN-based LED element according to claim 9, further comprising a step of forming a passivation film on the TCO film by an electron beam evaporation method.

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