Light emitting diode and method for preparing the same

Abstract

The present invention provides a light-emitting diode, comprising: a light-emitting structure, a transparent conductive layer, a first insulating layer, and a first electrode layer; the first electrode layer is formed on the first insulating layer and in the first opening, and is electrically connected to the first semiconductor layer via the first opening, the first electrode layer comprises a first metal reflection layer and a stress adjustment layer, the first metal reflection layer is in contact with the first semiconductor layer in the first opening, and the first metal reflection layer is located between the first semiconductor layer and the stress adjustment layer; wherein the first metal reflection layer and the stress adjustment layer contain the same metal element, and the content of the same metal element in the first metal reflection layer is greater than that in the stress adjustment layer.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, in particular to a light emitting diode and a preparation method thereof. Background Art

[0002] A light emitting diode (LED) is a semiconductor device that uses the energy released when carriers recombine to generate light. In particular, flip-chip LED chips have the advantages of no bonding, high light efficiency, and good heat dissipation, and are increasingly used.

[0003] At present, some flip-chip LED chips are mainly used in automotive, backlight and high-power lighting fields. Due to the large driving current, high heat dissipation requirements, and low chip internal resistance requirements, most of these LED chips use metal reflective layers (such as silver and aluminum) as the main reflector material to achieve better reflection of the LED chip output light. However, the metal reflective layer of this type of chip is not covered on the entire surface of the LED chip. The chip surface in contact with the N-ohm contact electrode is not covered by the metal reflective layer. Therefore, the reflectivity of the N-ohm contact electrode material will also affect the brightness of the LED chip. In addition, the reliability of the ohmic contact electrode is also a key research object. Summary of the invention

[0004] In one aspect, the present invention provides a light emitting diode, comprising:

[0005] A light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence;

[0006] A transparent conductive layer formed on the light emitting structure;

[0007] A first insulating layer, covering the light emitting structure, comprising a first opening to expose a portion of the first semiconductor layer;

[0008] a first electrode layer, formed on the first insulating layer and in the first opening, and electrically connected to the first semiconductor layer via the first opening, the first electrode layer comprising a first metal reflective layer and a stress adjustment layer, the first metal reflective layer and the first semiconductor layer are in contact in the first opening, and the first metal reflective layer is located between the first semiconductor layer and the stress adjustment layer;

[0009] a first pad electrode electrically contacting the first semiconductor layer, wherein a first electrode layer formed on the first insulating layer is electrically contacting the first pad electrode;

[0010] a second pad electrode electrically contacting the second semiconductor layer;

[0011] Wherein, the first metal reflective layer and the stress adjustment layer contain the same metal element, and the content of the same metal element in the first metal reflective layer is greater than that in the stress adjustment layer.

[0012] In another aspect, the present invention provides a light emitting diode, comprising:

[0013] A light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence;

[0014] A transparent conductive layer formed on the light emitting structure;

[0015] A first insulating layer, covering the light emitting structure, comprising a first opening to expose a portion of the first semiconductor layer;

[0016] a first electrode layer, formed on the first insulating layer and in the first opening, and electrically connected to the first semiconductor layer via the first opening, the first electrode layer comprising a first metal reflective layer, the first metal reflective layer comprising a metal having a reflectivity greater than 70%;

[0017] a first pad electrode electrically contacting the first semiconductor layer, wherein a first electrode layer formed on the first insulating layer is electrically contacting the first pad electrode;

[0018] a second pad electrode electrically contacting the second semiconductor layer;

[0019] The metal bonding layer is at least disposed between a portion of the first semiconductor layer exposed in the first opening and a portion of the first metal reflective layer formed in the opening, and includes at least one metal selected from chromium, titanium or nickel.

[0020] In another aspect, the present invention provides a light emitting diode, comprising:

[0021] A light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence;

[0022] A transparent conductive layer formed on the light emitting structure;

[0023] A first insulating layer, covering the light emitting structure, comprising a first opening to expose a portion of the first semiconductor layer;

[0024] a first electrode layer, formed on the first insulating layer and electrically connected to the first semiconductor layer via the first opening, the first electrode layer comprising a first metal reflective layer, an etching stopper layer and an adhesion layer, the first metal reflective layer is in contact with the first semiconductor layer in the first opening, and the etching stopper layer is located between the first metal reflective layer and the adhesion layer;

[0025] a second insulating layer, covering the first electrode layer and comprising a second opening to expose a portion of the first electrode layer, the adhesion layer being in contact with the second insulating layer;

[0026] a first pad electrode electrically contacting the first semiconductor layer, wherein a first electrode layer formed on the first insulating layer is electrically contacting the first pad electrode;

[0027] a second pad electrode electrically contacting the second semiconductor layer;

[0028] The adhesion layer in the first electrode layer has a through hole at least partially overlapping with the second opening.

[0029] As described above, the present invention provides a light emitting diode and a method for manufacturing the same, which have at least the following beneficial technical effects:

[0030] (1) The present invention utilizes a first metal reflective layer with high reflectivity to directly contact the first semiconductor layer, thereby achieving a good ohmic contact effect while increasing the reflectivity of the first electrode layer, thereby increasing the reflection efficiency of the incident light, and thus improving the brightness of the light-emitting diode;

[0031] (2) The first electrode layer of the present invention comprises a first metal reflective layer with high reflectivity and a stress adjustment layer disposed on the first metal reflective layer, wherein the first metal reflective layer and the stress adjustment layer contain a same metal element, and the content of the same metal element in the first metal reflective layer is greater than that in the stress adjustment layer; so that the first electrode layer has high reflectivity, good ohmic contact effect, high reliability, low stress, good electrical and thermal conductivity, low cost, etc.;

[0032] (3) The present invention provides a metal bonding layer as thin as possible between the first semiconductor layer and the first metal reflective layer, so that the first electrode layer can achieve good adhesion with the first semiconductor layer while minimizing the influence of the metal bonding layer on the reflectivity of the first electrode layer, thereby increasing the reflection efficiency of the incident light and improving the brightness of the light-emitting diode;

[0033] (4) The first electrode layer of the present invention includes a first metal reflective layer, an etching stop layer and an adhesion layer, so that the first electrode layer is not affected by other processes in the subsequent manufacturing process of the light-emitting diode, thereby ensuring the stability and reflectivity of the first electrode layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Features will become apparent to those skilled in the art by describing in detail exemplary embodiments with reference to the accompanying drawings, in which:

[0035] Figure 1 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention;

[0036] Figure 2a for Figure 1 A magnified view of A1, the first electrode layer in the light-emitting diode;

[0037] Figure 2b for Figure 1 A1 enlarged view of another embodiment of the first electrode layer in the light emitting diode;

[0038] Figure 2c for Figure 1 A1 enlarged view of another embodiment of the first electrode layer in the light emitting diode;

[0039] Figures 3 to 10 FIG. 4 is a schematic diagram of a method for preparing a light emitting diode according to an embodiment of the present invention.

[0040] Reference numerals:

[0041] 110 substrate; 120 light emitting structure; 121 first semiconductor layer; 122 active layer; 123 second semiconductor layer; 1211 local defect area; 130 transparent conductive layer; 140 second metal reflective layer; 151 first electrode layer; 152 second electrode layer; 151a first metal reflective layer; 151b diffusion prevention layer; 151c stress adjustment layer; 151d etching stop layer; 151e adhesion layer; 151f metal bonding layer; 1511 through hole; 161 first insulating layer; 162 second insulating layer; 171 first pad electrode; 172 second pad electrode; OP1 first opening; OP2 second opening; OP3 third opening; OP4 fourth opening. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0043] Figure 1 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention.

[0044] refer to Figure 1 The light emitting diode according to the embodiment of the present invention includes: a substrate 110, a light emitting structure 120, a transparent conductive layer 130, a first insulating layer 161, a first electrode layer 151, a second insulating layer 162, a first pad electrode 171 and a second pad electrode 172.

[0045] The substrate 110 can be formed using a carrier wafer suitable for the growth of semiconductor materials. In addition, the substrate 110 can be formed of a material having excellent thermal conductivity or can be a conductive substrate or an insulating substrate. In addition, the substrate 110 can be formed of a light-transmitting material and can have a mechanical strength that does not cause the entire light-emitting structure 120 to bend and enables it to be effectively divided into separate chips through scribing and breaking processes. For example, the substrate 110 can use a sapphire (Al2O3) substrate, a silicon carbide (SiC) substrate, a silicon (Si) substrate, a zinc oxide (ZnO) substrate, a gallium nitride (GaN) substrate, a gallium arsenide (GaAs) substrate, or a gallium phosphide (GaP) substrate, etc., and in particular, a sapphire (Al2O3) substrate is preferably used. In this embodiment, the substrate 110 is a sapphire having a series of protrusions on the surface, including, for example, protrusions without a fixed slope made by dry etching, or protrusions with a certain slope made by wet etching.

[0046] The light emitting structure 120 includes a first semiconductor layer 121, a second semiconductor layer 123 and an active layer 122, which are sequentially stacked on the substrate 110. The first semiconductor layer 121 and the second semiconductor layer 123 may have different conductivity types. If the first semiconductor layer 121 is an n-type semiconductor, the second semiconductor layer 123 is a p-type semiconductor or vice versa. The active layer 122 is between the first semiconductor layer 121 and the second semiconductor layer 123.

[0047] The first semiconductor layer 121, the active layer 122, and the second semiconductor layer 123 may be formed of a compound semiconductor of the III-group gallium nitride series, for example, GaN, AlN, InGaN, AlGaN, InAlGaN, and at least one of these groups. The first semiconductor layer 121 is a layer that provides electrons and can be formed by injecting n-type dopants (for example, Si, Ge, Se, Te, C, etc.). The second semiconductor layer 123 is a layer that provides holes and can be formed by injecting p-type dopants (for example, Mg, Zn, Be, Ca, Sr, Ba, etc.).

[0048] The active layer 122 is a layer in which the electrons provided by the first semiconductor layer 121 and the holes provided by the second semiconductor layer 123 are combined again to output light of a predetermined wavelength, and can be formed by a semiconductor thin film having a single-layer or multi-layer quantum well structure with alternately stacked potential well layers and barrier layers. The active layer 122 will select different material compositions or proportions according to the different wavelengths of the output light. For example, the emission wavelength of the light-emitting diode of the embodiment of the present invention is between 420nm and 580nm. The active layer 122 can be formed into a pair structure having a well layer and a barrier layer using a III-V compound semiconductor material (for example, at least one of InGaN / GaN, InGaN / InGaN, GaN / AlGaN, InAlGaN / GaN, GaAs (InGaAs) / AlGaAs or GaP (InGaP) / AlGaP), but the present disclosure is not limited thereto. The well layer can be formed of a material having a smaller band gap than the band gap of the barrier layer.

[0049] The local defect area 1211 is located on part of the second semiconductor layer 123 and extends downward to the first semiconductor layer 121 to form a mesa structure, and the mesa structure exposes the side wall of the epitaxial structure. Specifically, the mesa structure exposes the mesa of the first semiconductor layer 121 and the side walls of the first semiconductor layer 121, the active layer 122 and the second semiconductor layer 123. It should be noted that the number of the local defect area 1211 is at least one, and it can also be increased according to the structure and area size of the LED chip.

[0050] The transparent conductive layer 130 is formed on the light emitting structure 120 and contacts the second semiconductor layer 123. The transparent conductive layer 130 can enhance the diffusion of current and form an ohmic contact with the second semiconductor layer 123. The material of the transparent conductive layer 130 can be ITO, InO, SnO, CTO, ATO, ZnO, GaP or a combination thereof. The transparent conductive layer 130 can be formed by evaporation or sputtering. The thickness of the transparent conductive layer 130 is selected from the range of 5nm to 100nm in this embodiment. In addition, it is preferably selected from the range of 10nm to 50nm.

[0051] The light emitting diode may further include a second metal reflective layer 140 disposed on the transparent conductive layer 130. Further, a metal protective layer may be coated on the second metal reflective layer 140. As an example, the second metal reflective layer 140 may be deposited on the transparent conductive layer 130 by a deposition process such as a PVD process or a magnetron sputtering process. For example, when a highly reflective metal such as Al or Ag is used as a mirror, the metal protective layer may be TiW, Ni, Cr, Pt, Ti, etc. In one embodiment, the second metal reflective layer 140 may not be provided.

[0052] The first insulating layer 161 covers the light emitting structure 120, and the first insulating layer 161 wraps the sidewalls of the second metal reflective layer 140, the sidewalls of the transparent conductive layer 130, and covers the sidewalls of the adjacent light emitting structure 120. Further, a first opening OP1 is formed in the first insulating layer 161, and the first opening OP1 can penetrate the first insulating layer 161 to expose the local defect area 1211, exposing the surface of the first semiconductor layer 121. The first insulating layer 161 can be made of silicon oxide, silicon nitride or aluminum oxide. In some embodiments, the first insulating layer 161 may have a structure in which a first sub-insulating layer and a second sub-insulating layer are alternately and repeatedly stacked. Here, the refractive index of the first sub-insulating layer and the second sub-insulating layer may be lower than the refractive index of the second semiconductor layer 123, and may be different from each other. For example, the first sub-insulating layer may be formed of a silicon oxide (SiO2) layer, and the second sub-insulating layer may be formed of a titanium oxide (TiO2) layer or a niobium oxide (Nb2O5) layer. Therefore, the first insulating layer may have an omnidirectional reflection (ODR) structure or a distributed Bragg reflection (DBR) structure.

[0053] The first electrode layer 151 is formed on the first insulating layer 161 and in the first opening OP1, and is electrically connected to the first semiconductor layer 121 through the first opening OP1. The first electrode layer 151 may include a plurality of layers. The first electrode layer 151 includes a first metal reflective layer 151a in contact with the first semiconductor layer 121, a diffusion prevention layer 151b formed on the first metal reflective layer 151a, a stress adjustment layer 151c formed on the diffusion prevention layer 151b, an etching stopper layer 151d formed on the stress adjustment layer 151c, and an adhesion layer 151e formed on the etching stopper layer 151d.

[0054] Figure 2a is based on Figure 1 An enlarged schematic diagram of the first electrode layer "A1" of the light-emitting diode.

[0055] Reference Figure 2a A first metal reflective layer 151 a , a diffusion prevention layer 151 b , a stress adjustment layer 151 c , an etching stopper layer 151 d , and an adhesion layer 151 e are sequentially stacked on the first semiconductor layer 121 .

[0056] Preferably, the first metal reflective layer 151a may include a material in contact with the first semiconductor layer 121. In conventional processes, metal chromium (Cr) is usually used as the material in contact with the first semiconductor layer 121, but the reflectivity of the metal material in contact with the first semiconductor layer 121 will also affect the brightness of the light-emitting diode. However, the reflectivity of metal chromium (Cr) is not very high, so the chromium layer is removed, and the metal with high reflectivity is directly in contact with the first semiconductor layer 121, thereby increasing the reflectivity of the first electrode layer 151, thereby increasing the reflection efficiency of the incident light, and thereby improving the brightness of the light-emitting diode. For example, the first metal reflective layer 151a can be formed of a metal with a reflectivity greater than 70%, such as aluminum (Al), silver (Ag) or rhodium (Rh).

[0057] In addition, the thickness of the first metal reflective layer 151a can be in the range of 100nm to 500nm. For example, when the thickness of the first metal reflective layer 151a is less than 100nm, the reflection effect is not good. If the thickness of the first metal reflective layer 151a is greater than 500nm, the poor coverage of the first metal reflective layer 151a by the diffusion prevention layer 151b in the subsequent process causes the first metal reflective layer 151a to migrate and diffuse, reducing the reflectivity. In one embodiment, the first metal reflective layer 151a is preferably metal Al, and the thickness is between 120nm-350nm, so that the reflectivity of the first electrode layer 151 reaches more than 85% and an excellent ohmic contact effect is achieved.

[0058] As an alternative embodiment, refer to Figure 2b A thin metal bonding layer 151f is formed between the first semiconductor 121 and the first metal reflective layer 151a. It is mentioned in the foregoing that the reflectivity of the metal material in the first electrode layer 151 and the first semiconductor layer 151 will affect the brightness of the light-emitting diode. Therefore, a thin metal bonding layer 151f can be provided between the first semiconductor 121 and the first metal reflective layer 151a, and the thickness of the metal bonding layer 151f can be reduced as much as possible, so that the first electrode layer 151 can achieve good adhesion with the first semiconductor layer 121, while reducing the influence of the metal bonding layer 151f on the reflectivity of the first electrode layer 151 as much as possible. The metal bonding layer 151f includes metals such as chromium (Cr), nickel (Ni) or titanium (Ti). The metal bonding layer 151f has a thickness of 0.5nm to 10nm. In a preferred embodiment, the thickness of the metal bonding layer 151f is preferably between 1nm and 3nm.

[0059] The diffusion prevention layer 151b may be arranged on the first metal reflective layer 151a to prevent the migration and diffusion of the metal elements of the first metal reflective layer 151a. The diffusion prevention layer 151b may be formed of a single layer or multiple layers of at least one material selected from titanium (Ti), titanium tungsten alloy (TiW), nickel (Ni), platinum (Pt), chromium (Cr), zinc (Zn), palladium (Pb), rhodium (Rh), iridium (Ir), ruthenium (Ru), tungsten (W) or copper (Cu). The thickness of the diffusion prevention layer 151b is 50-500nm. If the thickness of the diffusion prevention layer is less than 50nm, the diffusion prevention layer 172 is insufficient to prevent migration; if the thickness is greater than 500nm, the electrical performance of the diffusion prevention layer 172 will deteriorate due to the increase in specific resistance. Therefore, the diffusion prevention layer 172 is preferably formed to have a thickness of 50-300nm. In one embodiment, the diffusion prevention layer 151 b is preferably titanium (Ti), so as to maintain stable ohmic characteristics and reflective characteristics by preventing the migration and diffusion of the material (eg, Al) in the first metal reflective layer 151 a.

[0060] The stress adjustment layer 151c can be arranged on the anti-diffusion layer 151b. Since the first electrode layer 151 needs to have a certain thickness, a metal stack of a certain thickness needs to be stacked in the structure. At this time, it is necessary to consider the stress problem between the metal stacks to ensure the overall quality of the first electrode layer 151 and improve the reliability of the first electrode layer 151; therefore, it is necessary to arrange a layer of stress adjustment layer 151c on the anti-diffusion layer 151b. The stress adjustment layer 151c can be mainly formed of at least one metal or metal alloy of aluminum (Al), nickel (Ni), chromium (Cr), gold (Au), copper (Cu) or platinum (Pt). In addition, the thickness of the stress adjustment layer 151c is 100-500nm. In one embodiment, the stress adjustment layer 151c is preferably formed of an alloy material containing Al, for example, it can be a Cu-Al alloy. The Cu-Al alloy has the characteristics of good thermal stability, low stress, excellent electrical and thermal conductivity, and low cost, and can enable the first electrode layer 151 to have the advantages of excellent ohmic contact effect and high reflective characteristics while taking into account the reliability of the first electrode layer 151.

[0061] In addition, the diffusion prevention layer 151b and the stress adjustment layer 151c may be alternately stacked multiple times. Figure 2c As shown, the diffusion prevention layer 151 b and the stress adjustment layer 151 c may be alternately stacked twice.

[0062] In one embodiment, the first metal reflective layer 151a and the stress adjustment layer 151c contain the same metal element, and the content of the same metal element in the first metal reflective layer 151a is greater than that in the stress adjustment layer 151c. The first electrode layer 151 thus obtained has high reflectivity and good ohmic contact effect, while taking into account the advantages of the first electrode layer 151, such as reliability, low stress, good electrical and thermal conductivity, and low cost. Among them, the reflectivity of the same metal element is greater than 70%. For example, the first metal reflective layer 151a is Al metal, the stress adjustment layer 151c is Al alloy, and the Al content of the first metal reflective layer 151a is greater than the Al content of the stress adjustment layer.

[0063] The etching stopper layer 151d may be arranged on the stress adjustment layer 151c. The etching stopper layer 153 serves as a metal layer that is easily corroded in the first electrode layer 151 during the etching process for forming the third opening OP3 in the subsequent second insulating layer 162, and in particular, prevents damage to easily corroded metals in the stress adjustment layer 151c and the first metal reflective layer 151a, such as Al. The etching stopper layer 151d is preferably formed of a single layer or multiple layers of at least one material selected from chromium (Cr), platinum (Pt), nickel (Ni), tungsten (W), titanium tungsten alloy (TiW), gold (Au) or titanium (Ti). The etching stopper layer has a thickness of 5nm to 2000nm. In one embodiment, the etching stopper layer 151c is preferably formed of chromium (Cr) and platinum (Pt) by a wet etching process. Among them, the thickness of Cr is preferably 10-100nm, and the thickness of Pt is preferably 5-300nm. In another embodiment, a dry etching process is used, and the etching stop layer 151c is preferably composed of Au / Ti / Pt.

[0064] The adhesion layer 151e is formed on the etching stop layer 151d. Since the adhesion between the etching stop layer 151d and the second insulating layer 162 in the subsequent process is poor, a thin adhesion layer 151e must be added here to increase the adhesion between the etching stop layer 151d and the second insulating layer 162. Therefore, the adhesion layer 151e is in contact with the second insulating layer 162. The adhesion layer 151e has better adhesion with silicon dioxide or aluminum oxide, which is beneficial to improving the protection performance of the second insulating layer 162, maintaining the bonding force with the second insulating layer 162, and improving reliability. The adhesion layer 151e is composed of titanium (Ti), chromium (Cr), etc. In one embodiment, the adhesion layer is preferably Ti, and the thickness is preferably 2-20nm. Refer to Fig.10 Since the etching solution or etching gas will corrode the adhesion layer 151e in the subsequent etching process of forming the third opening OP3 in the second insulating layer 162, the adhesion layer 151e has a through hole 1511 at least overlapping with the third opening OP3.

[0065] In addition, refer again Figure 1The first insulating layer also has a second opening OP2 to expose a portion of the surface of the second metal reflective layer 140 .

[0066] The light emitting diode further includes a second electrode layer 152 formed in the second opening OP2, and the second electrode layer 152 contacts the second metal layer 140. In one embodiment, the light emitting diode is not provided with the second metal layer 140, and the second electrode layer 152 is provided on the transparent conductive layer 130, and the second electrode layer 152 contacts the transparent conductive layer 130.

[0067] In one embodiment, the second electrode layer 152 and the first electrode layer 151 include the same metal material and / or have the same metal stack.

[0068] The light emitting diode may further include a second insulating layer 162 formed on the first electrode layer 151. The second insulating layer 162 covers the first electrode layer 151, and the material of the second insulating layer 162 may be the same as or different from that of the first insulating layer 161. The second insulating layer 162 has a third opening OP3 and a fourth opening OP4, wherein the third opening OP3 exposes a portion of the surface of the first electrode layer 151, and the fourth opening OP4 penetrates the second insulating layer 162 to expose a portion of the surface of the second electrode layer 152. The size of the fourth opening OP4 of the second insulating layer may be the same as or different from that of the second opening OP2 of the first insulating layer.

[0069] The light emitting diode structure described herein is applicable to a front chip, a flip chip, a vertical chip, etc. The light emitting device 1 of the embodiment of the present invention takes a flip chip as an example, wherein the first pad electrode 171 and the second pad electrode 172 may be arranged on one side of the light emitting structure 120. Herein, the one side may be a side opposite to the main light emitting surface of the light emitting structure 120.

[0070] The first pad electrode 171 may be electrically connected to the first semiconductor layer 121 of the light emitting structure 120 , and the second pad electrode 172 may be electrically connected to the second semiconductor layer 123 .

[0071] The first pad electrode 171 contacts the first electrode layer 151 through the third opening OP3. Specifically, the first pad electrode 171 contacts the etching stopper layer 151d through the third opening OP3 and the through hole 1511. The second pad electrode 172 contacts the second electrode layer 152 through the fourth opening OP4, and the second electrode layer 152 is located between the second semiconductor layer 123 and the second pad electrode 172. The first pad electrode 171 may be electrically connected to the first semiconductor layer 121 of the light emitting structure 120, and the second pad electrode 172 may be electrically connected to the second semiconductor layer 123.

[0072] In one embodiment, the etching process for forming the fourth opening in the second insulating layer 162 may encounter the same problem as the formation of the third opening OP3 described above. The adhesion layer in the second electrode layer 152 may also be corroded by the etching solution or etching gas, and the adhesion layer in the second electrode layer 152 may have a through hole that at least overlaps with the fourth opening OP4.

[0073] Next, refer to Figures 3 to 10 A process of manufacturing the light emitting diode according to this embodiment will be described.

[0074] Reference Figure 3 , a light emitting structure 120 may be formed on a substrate 110. The light emitting structure 120 may include a first semiconductor layer 121, an active layer 122, and a second semiconductor layer 123 sequentially stacked on the substrate 110. The first semiconductor layer 121, the active layer 122, and the second semiconductor layer 123 may include the above-mentioned layers formed on the substrate 110 using a process such as metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), etc.

[0075] The substrate 110 can be formed using a carrier wafer suitable for the growth of semiconductor materials. In addition, the substrate 110 can be formed of a material having excellent thermal conductivity or can be a conductive substrate or an insulating substrate. In addition, the substrate 110 can be formed of a light-transmitting material and can have a mechanical strength that does not cause the entire light-emitting structure 120 to bend and enables it to be effectively divided into separate chips through scribing and breaking processes. For example, the substrate 110 can use a sapphire (Al2O3) substrate, a silicon carbide (SiC) substrate, a silicon (Si) substrate, a zinc oxide (ZnO) substrate, a gallium nitride (GaN) substrate, a gallium arsenide (GaAs) substrate, or a gallium phosphide (GaP) substrate, etc., and in particular, a sapphire (Al2O3) substrate is preferably used. In this embodiment, the substrate 110 is a sapphire having a series of protrusions on the surface, including, for example, protrusions without a fixed slope made by dry etching, or protrusions with a certain slope made by wet etching.

[0076] The light emitting structure 120 includes a first semiconductor layer 121, a second semiconductor layer 123 and an active layer 122, which are sequentially stacked on the substrate 110. The first semiconductor layer 121 and the second semiconductor layer 123 may have different conductivity types. If the first semiconductor layer 121 is an n-type semiconductor, the second semiconductor layer 123 is a p-type semiconductor or vice versa. The active layer 122 is between the first semiconductor layer 121 and the second semiconductor layer 123.

[0077] The first semiconductor layer 121, the active layer 122, and the second semiconductor layer 123 may be formed of a compound semiconductor of the III-group gallium nitride series, for example, GaN, AlN, InGaN, AlGaN, InAlGaN, and at least one of these groups. The first semiconductor layer 121 is a layer that provides electrons and can be formed by injecting n-type dopants (for example, Si, Ge, Se, Te, C, etc.). The second semiconductor layer 123 is a layer that provides holes and can be formed by injecting p-type dopants (for example, Mg, Zn, Be, Ca, Sr, Ba, etc.).

[0078] The active layer 122 is a layer in which the electrons provided by the first semiconductor layer 121 and the holes provided by the second semiconductor layer 123 are combined again to output light of a predetermined wavelength, and can be formed by a semiconductor thin film having a single-layer or multi-layer quantum well structure with alternately stacked potential well layers and barrier layers. The active layer 122 will select different material compositions or proportions according to the different wavelengths of the output light. For example, the emission wavelength of the light-emitting diode of the embodiment of the present invention is between 420nm and 580nm. The active layer 122 can be formed into a pair structure having a well layer and a barrier layer using a III-V compound semiconductor material (for example, at least one of InGaN / GaN, InGaN / InGaN, GaN / AlGaN, InAlGaN / GaN, GaAs (InGaAs) / AlGaAs or GaP (InGaP) / AlGaP), but the present disclosure is not limited thereto. The well layer can be formed of a material having a smaller band gap than the band gap of the barrier layer.

[0079] Reference Figure 4 , a part of the light emitting structure 120 may be etched to expose a part of the first semiconductor layer 121 to form a local defect area 1211, wherein the local defect area 1211 exposes the side wall of the light emitting structure 120, specifically, the local defect area 1211 exposes the first semiconductor layer 121 table and the side walls of the first semiconductor layer 121, the active layer 122 and the second semiconductor layer 123. For example, an ICP etching or RIE etching process may be used to etch the local defect area 1211 in the light emitting structure 120, so that the local defect area 1211 exposes the side walls of the first semiconductor layer 121, the active layer 122 and the second semiconductor layer 123, and the first semiconductor layer 121 table is used for subsequent electrical connection of the first pad electrode 171. The number of local defect areas 1211 is at least one, and may also be increased according to the structure, purpose, area size, etc. of the LED chip.

[0080] Reference Figure 5, a transparent conductive layer 130 may be formed on a portion of the surface of the light emitting structure 120. The transparent conductive layer 130 may enhance the diffusion of current. For example, the transparent conductive layer 130 may be formed by evaporation or sputtering, and form an ohmic contact with the second semiconductor layer 123 in the light emitting structure 120. The material of the transparent conductive layer 130 may be ITO, InO, SnO, CTO, ATO, ZnO, GaP or a combination thereof. The thickness of the transparent conductive layer 130, in this embodiment, is selected from the range of 5nm to 100nm. In addition, it is preferably selected from the range of 10nm to 50nm.

[0081] Reference Figure 6 , a second metal reflective layer 140 may be formed on the surface of the transparent conductive layer 130. Further, a metal protective layer may be coated on the second metal reflective layer 140. As an example, the second metal reflective layer 140 may be deposited on the transparent conductive layer 130 by a deposition process such as a PVD process or a magnetron sputtering process. For example, when a highly reflective metal such as Al or Ag is used as a mirror, the metal protective layer may be TiW, Ni, Cr, Pt, Ti, etc. In one embodiment, the second metal reflective layer 140 may not be provided.

[0082] Reference Figure 7 , a first insulating layer 161 may be formed on the light emitting structure 120 having the second metal reflective layer 140. The first insulating layer 161 wraps the sidewalls of the second metal reflective layer 140, the sidewalls of the transparent conductive layer 130, and covers the sidewalls of the adjacent light emitting structure 120. Further, it also includes etching a portion of the first insulating layer 161 by yellow light and etching process to form a series of first openings OP1 and second openings OP2. The first opening OP1 may penetrate the first insulating layer 161 to expose the local defect area 1211 and expose the surface of the first semiconductor layer 121. The number of the first openings OP1 and the local defect area 1211 is consistent. The second opening OP2 penetrates the first insulating layer 161 to expose a portion of the surface of the second metal layer 140. As an example, the first insulating layer 161 may be formed by a chemical vapor deposition process, and the first insulating layer 161 may be a single layer formed of a silicon dioxide (SiO2) layer. In some embodiments, the first insulating layer 161 may have a structure in which a first sub-insulating layer and a second sub-insulating layer are alternately and repeatedly stacked. Here, the refractive indexes of the first sub-insulating layer and the second sub-insulating layer may be lower than the refractive index of the second semiconductor layer 123, and may be different from each other. For example, the first sub-insulating layer may be formed of a silicon oxide (SiO2) layer, and the second sub-insulating layer may be formed of a titanium oxide (TiO2) layer or a niobium oxide (Nb2O5) layer. Therefore, the first insulating layer 161 may have an omnidirectional reflection (ODR) structure or a distributed Bragg reflection (DBR) structure.

[0083] Reference Figure 8 and Figure 2a, a first electrode layer 151 may be formed in the first insulating layer 161 and the first opening OP1, and the first electrode layer 151 may electrically contact the first semiconductor layer 121 through the first opening OP1. The first electrode layer 151 may include a plurality of layers. For example, the first electrode layer 151 includes: a first metal reflective layer 151a in contact with the first semiconductor layer 121, a diffusion prevention layer 151b formed on the first metal reflective layer 151a, a stress adjustment layer 151c formed on the diffusion prevention layer 151b, an etching stopper layer 151d formed on the stress adjustment layer 151c, and an adhesion layer 151e formed on the etching stopper layer 151d.

[0084] The first metal reflective layer 151a is preferably composed of a material that is in good electrical contact with the first semiconductor layer 121, and has a high reflectivity that can improve the reflectivity of the first electrode layer 151. In conventional processes, metal chromium (Cr) is usually used as a material in contact with the first semiconductor layer 121, but the reflectivity of the metal material in contact with the first semiconductor layer 121 will also affect the brightness of the light-emitting diode. However, the reflectivity of metal chromium (Cr) is not very high, so the chromium layer is eliminated, and a metal with high reflectivity is contacted with the first semiconductor layer 121 to increase the reflectivity of the first electrode layer 151, thereby increasing the reflection efficiency of the incident light, and thereby improving the brightness of the light-emitting diode. For example, the first metal reflective layer 151a can be formed of a metal with a reflectivity greater than 70%, such as aluminum (Al), silver (Ag) or rhodium (Rh). The thickness of the first metal reflective layer 151a can be, for example, in the range of 100nm to 500nm. For example, when the thickness of the first metal reflective layer 151a is less than 100nm, the reflection effect is poor. If the thickness of the first metal reflective layer 151a is greater than 500nm, the poor coverage of the first metal reflective layer 151a by the diffusion prevention layer 151b in the subsequent process causes the first metal reflective layer 151a to migrate and diffuse, thereby reducing the reflectivity. In one embodiment, the first metal reflective layer 151a is preferably Al metal, with a thickness between 120nm and 350nm, so that the reflectivity of the first electrode layer 151 can reach more than 85% and have an excellent ohmic contact effect.

[0085] It should be noted that if the first metal reflective layer 151a is directly deposited or evaporated on the first semiconductor layer 121, it will not form a good ohmic contact with the first semiconductor layer 121. Therefore, in order to improve the ohmic contact quality of the first electrode layer 151, the surface of the first semiconductor layer 121 should be treated under high vacuum conditions by plasma including oxygen (O2), nitrogen (N2), argon (Ar) or hydrogen (H2), and the oxide film on the surface of the first semiconductor layer 121 is treated by plasma physical bombardment, which effectively reduces the potential barrier on the surface. After the treatment is completed, the first metal reflective layer 151a and subsequent metal layers can be deposited or evaporated. In addition, the first metal reflective layer 151a is a metal and cannot be an alloy, because even after the surface of the first semiconductor layer is treated with plasma of oxygen (O2), nitrogen (N2), argon (Ar) or hydrogen (H2), the alloy material cannot form a good ohmic contact with the first semiconductor layer 121.

[0086] The diffusion prevention layer 151b may be arranged on the first metal reflective layer 151a to prevent the migration and diffusion of the metal elements of the first metal reflective layer 151a. The diffusion prevention layer 151b may be formed of a single layer or multiple layers of at least one material selected from titanium (Ti), titanium tungsten alloy (TiW), nickel (Ni), platinum (Pt), chromium (Cr), zinc (Zn), palladium (Pb), rhodium (Rh), iridium (Ir), ruthenium (Ru), tungsten (W) or copper (Cu). The thickness of the diffusion prevention layer 151b is 50-300nm. If the thickness of the diffusion prevention layer is less than 50nm, the diffusion prevention layer 172 is insufficient to prevent migration; if the thickness is greater than 300nm, the electrical performance of the diffusion prevention layer 172 will deteriorate due to the increase in specific resistance. Therefore, the diffusion prevention layer 172 is preferably formed to a thickness of 50-300nm. In one embodiment, the diffusion prevention layer 151 b is preferably titanium (Ti), so as to maintain stable ohmic characteristics and reflective characteristics by preventing the migration and diffusion of the material (eg, Al) in the first metal reflective layer 151 a.

[0087] The stress adjustment layer 151c can be arranged on the diffusion prevention layer 151b, and the diffusion prevention layer 151b is located between the first metal reflective layer 151a and the stress adjustment layer 151c. Since the first electrode layer 151 needs a certain thickness, a metal stack of a certain thickness needs to be stacked in the structure. At this time, it is necessary to consider the stress problem between the metal stacks to ensure the overall quality of the first electrode layer 151 and improve the reliability of the first electrode layer 151; therefore, it is necessary to arrange a layer of stress adjustment layer 151c on the diffusion prevention layer 151b. The stress adjustment layer 151c can be mainly formed of at least one metal or metal alloy of aluminum (Al), nickel (Ni), chromium (Cr), gold (Au), copper (Cu) or platinum (Pt). In addition, the thickness of the stress adjustment layer 151c is 100-500nm. In one embodiment, the stress adjustment layer 151c is preferably formed of an alloy material containing Al, for example, it can be a Cu-Al alloy. The Cu-Al alloy has the characteristics of good thermal stability, low stress, excellent electrical and thermal conductivity, and low cost, and can enable the first electrode layer 151 to have the advantages of excellent ohmic contact effect and high reflective characteristics while taking into account the reliability of the first electrode layer 151.

[0088] In addition, the diffusion prevention layer 151b and the stress adjustment layer 151c may be alternately stacked multiple times. Figure 2b As shown, the diffusion prevention layer 151 b and the stress adjustment layer 151 c may be alternately stacked twice.

[0089] In one embodiment, the first metal reflective layer 151a and the stress adjustment layer 151c contain the same metal element, and the content of the same metal element in the first metal reflective layer 151a is greater than that in the stress adjustment layer 151c. The first electrode layer 151 thus obtained has high reflectivity and good ohmic contact effect, while taking into account the advantages of the first electrode layer 151, such as reliability, low stress, good electrical and thermal conductivity, and low cost. Among them, the reflectivity of the same metal element is greater than 70%. For example, the first metal reflective layer 151a is Al metal, the stress adjustment layer 151c is Al alloy, and the Al content of the first metal reflective layer 151a is greater than the Al content of the stress adjustment layer.

[0090] The etching stopper layer 151d may be disposed on the stress adjustment layer 151c. The etching stopper layer 153 serves as a layer that protects the metal layers in the first electrode layer 151 from being easily corroded in the etching process for forming the third opening OP3 in the subsequent second insulating layer 162, and in particular, prevents damage to the easily corroded metal in the stress adjustment layer 151c and the first metal reflective layer 151a, such as Al. The etching stopper layer 151d is preferably formed of a single layer or multiple layers of at least one material selected from chromium (Cr), platinum (Pt), nickel (Ni), tungsten (W), titanium tungsten alloy (TiW), gold (Au) or titanium (Ti). The etching stopper layer has a thickness of 5nm to 2000nm.

[0091] The adhesion layer 151e is formed on the etching stop layer 151d. Since the adhesion between the etching stop layer 151d and the second insulating layer 162 in the subsequent process is poor, a thin adhesion layer 151e must be added here to increase the adhesion between the etching stop layer 151d and the second insulating layer 162. Therefore, the adhesion layer 151e is in contact with the second insulating layer 162. The adhesion layer 151e has better adhesion with silicon dioxide or aluminum oxide, which is beneficial to improving the protection performance of the second insulating layer 162, can maintain the bonding force with the second insulating layer 162, and improve reliability. The adhesion layer 151e is composed of titanium (Ti), chromium (Cr), etc. In one embodiment, the adhesion layer 151e is preferably Ti, and the thickness is preferably 2-20nm.

[0092] Refer to this Figure 8 The second electrode layer 152 may be formed in the second opening OP2 of the first insulating layer 161, and the second electrode layer 152 contacts the second metal layer 140. In one embodiment, the light emitting diode is not provided with the second metal layer 140 on the transparent conductive layer 130, and the second electrode layer 152 contacts the transparent conductive layer 130.

[0093] In one embodiment, the second electrode layer 152 and the first electrode layer 151 include the same metal material and / or have the same metal stack.

[0094] Reference Fig. 9 , a second insulating layer 162 may be formed on the first electrode layer 151, and a third opening OP3 and a fourth opening OP4 may be reserved, wherein the third opening OP3 exposes a portion of the surface of the first electrode layer 151, and the fourth opening OP4 exposes a portion of the surface of the second electrode layer 152. The second insulating layer 162 covers the sidewalls of the first electrode layer 151 and the second electrode layer 152. The third opening OP3 and the fourth opening OP4 are formed in the second insulating layer 162, and the third opening OP3 and the fourth opening OP4 expose a portion of the first electrode layer 151 and the second electrode layer 152 through an etching process. Referring to Fig.10Since the etching liquid or etching gas corrodes the adhesion layer 151e in the etching process of forming the third opening OP3 and the fourth opening OP4 in the second insulating layer 162, the adhesion layer 151e has a through hole 1511 at least overlapping the third opening OP3 and the fourth opening OP4.

[0095] In one embodiment, the third opening OP3 and the fourth opening OP4 are made by a wet etching process. As the etching solution for the second insulating layer 162, HF, BOE, NHO3, HCl, etc. can be used alone or in combination with appropriate concentrations. Therefore, in order to prevent damage to the Al metal in the stress adjustment layer 151c and the first metal reflective layer 151a, the etching stopper layer 151d is formed of chromium (Cr) and platinum (Pt). Among them, the thickness of Cr is preferably 10-100nm, and the thickness of Pt is preferably 5-300nm. Therefore, the etching stopper layer 151d can effectively prevent the etching solution from damaging the Al in the stress adjustment layer 153 and the first metal reflective layer 153. As an example, the first electrode layer 151 is composed of Al (first metal reflective layer 151a) / Ti (anti-diffusion layer 151b) / Al (stress adjustment layer 151c) / Ti (anti-diffusion layer 151) / Al (stress adjustment layer 152) / Cr / Pt (etching stop layer 151d) / Ti (adhesion layer 151e) stacked in sequence. The first electrode layer 151 obtained in this way can be unaffected by other processes in the subsequent manufacturing process of the light-emitting diode, ensuring the stability and reflectivity of the first electrode layer 151.

[0096] In another embodiment, the third opening OP3 and the fourth opening OP4 are formed by a dry etching process. In this case, since a halogen gas including a F group (e.g., CF4, C2F6, C3F8, SF6, etc.) can be used as an etching gas in the dry etching process. Since the etching gas is extremely active to the Al element, the etching stop layer 151d is preferably composed of a material having an excellent etching selectivity ratio in such a dry etching process. For example, a noble metal material such as Au or Pt can be used. In one embodiment, the etching stop layer 151d can be composed of Au / Ti / Pt. As an example, the first electrode layer 151 is composed of Al (first metal reflective layer 151a) / Ti (anti-diffusion layer 151b) / Pt (stress adjustment layer 151c) / Ti (anti-diffusion layer 151b) / Pt (stress adjustment layer 151c) / Ti (anti-diffusion layer 151) / Pt (stress adjustment layer 151c) / Au / Ti / Pt / (etching stop layer 151d) / Ti (adhesion layer 55) stacked in sequence. The first electrode layer 151 obtained in this way can be unaffected by other processes in the subsequent manufacturing process of the light-emitting diode, ensuring the stability and reflectivity of the first electrode layer 151.

[0097] Refer again Figure 1, a first pad electrode 171 and a second pad electrode 172 are formed on the second insulating layer 162, wherein the first pad electrode 171 contacts the first electrode layer 151 through the third opening OP3 and the through hole 1511, specifically, the first pad electrode 171 contacts the etching stopper layer 151d through the third opening OP3 and the through hole 1511. The second pad electrode 172 contacts the second electrode layer 152 through the fourth opening OP4, and the second electrode layer 152 is located between the second semiconductor layer 123 and the second pad electrode 172. The first pad electrode 171 may be electrically connected to the first semiconductor layer 121 of the light emitting structure 120, and the second pad electrode 172 may be electrically connected to the second semiconductor layer 123.

[0098] As described above, the present invention provides a light emitting diode and a method for manufacturing the same, which have at least the following beneficial technical effects:

[0099] (1) The present invention utilizes a first metal reflective layer with high reflectivity to directly contact the first semiconductor layer, thereby achieving a good ohmic contact effect while increasing the reflectivity of the first electrode layer, thereby increasing the reflection efficiency of the incident light, and thus improving the brightness of the light-emitting diode;

[0100] (2) The first electrode layer of the present invention comprises a first metal reflective layer with high reflectivity and a stress adjustment layer disposed on the first metal reflective layer, wherein the first metal reflective layer and the stress adjustment layer contain a same metal element, and the content of the same metal element in the first metal reflective layer is greater than that in the stress adjustment layer; so that the first electrode layer has high reflectivity, good ohmic contact effect, high reliability, low stress, good electrical and thermal conductivity, low cost, etc.;

[0101] (3) The present invention provides a metal bonding layer as thin as possible between the first semiconductor layer and the first metal reflective layer, so that the first electrode layer can achieve good adhesion with the first semiconductor layer while minimizing the influence of the metal bonding layer on the reflectivity of the first electrode layer, thereby increasing the reflection efficiency of the incident light and improving the brightness of the light-emitting diode;

[0102] (4) The first electrode layer of the present invention includes a first metal reflective layer, an etching stop layer and an adhesion layer, so that the first electrode layer is not affected by other processes in the subsequent manufacturing process of the light-emitting diode, thereby ensuring the stability and reflectivity of the first electrode layer.

Claims

1. A light emitting diode, comprising: The light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; a first insulating layer covering the light emitting structure and comprising a first opening to expose a portion of the first semiconductor layer; a first electrode layer formed on the first insulating layer and in the first opening, and electrically connected to the first semiconductor layer via the first opening, the first electrode layer including a first metal reflective layer and a stress adjustment layer, the first metal reflective layer contacting the first semiconductor layer in the first opening, and the first metal reflective layer being located between the first semiconductor layer and the stress adjustment layer; The first metal reflective layer and the stress adjustment layer contain the same metal element, and the content of the same metal element in the first metal reflective layer is greater than that in the stress adjustment layer.

2. The light emitting diode according to claim 1, characterized in that The first electrode layer further includes a metal bonding layer, and the metal bonding layer contacts the first semiconductor layer in the first opening.

3. The light emitting diode according to claim 1, characterized in that The first metal reflective layer includes aluminum, and the stress adjustment layer includes aluminum alloy.

4. A light emitting diode comprising: The light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; a first insulating layer covering the light emitting structure and comprising a first opening to expose a portion of the first semiconductor layer; a first electrode layer formed on the first insulating layer and in the first opening, and electrically connected to the first semiconductor layer via the first opening, the first electrode layer including a first metal reflective layer and a stress adjustment layer, the first metal reflective layer contacting the first semiconductor layer in the first opening, and the first metal reflective layer being located between the first semiconductor layer and the stress adjustment layer; a second metal reflective layer, formed on the light emitting structure and electrically connected to the second semiconductor layer; The first metal reflective layer and the stress adjustment layer contain the same metal element, and the second metal reflective layer and the first metal reflective layer contain different metals.

5. The light emitting diode according to claim 4, characterized in that The second metal reflective layer contains silver, and the first metal reflective layer contains aluminum.

6. The light emitting diode according to claim 4, characterized in that The device further includes a second electrode layer, which is formed on the second metal reflective layer and electrically connected to the second semiconductor layer.

7. A light emitting diode comprising: The light emitting structure comprises a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence; a first insulating layer covering the light emitting structure and comprising a first opening to expose a portion of the first semiconductor layer; A first electrode layer is formed on the first insulating layer and in the first opening, and is electrically connected to the first semiconductor layer via the first opening. The first electrode layer includes a first metal reflective layer and a stress adjustment layer located above the first metal reflective layer. The first metal reflective layer and the stress adjustment layer include aluminum elements, and the aluminum element is in direct contact with the first semiconductor layer.

8. The light emitting diode according to claim 7, characterized in that The thickness of the first metal reflective layer is 100 nm to 500 nm.

9. The light emitting diode according to claim 7, characterized in that It also includes a second metal reflective layer, a metal protective layer, and a second electrode layer; the second metal reflective layer is formed on the light-emitting structure and is electrically connected to the second semiconductor layer; the metal protective layer is formed on the second metal reflective layer; the first insulating layer also includes a second opening; the second electrode layer is formed on the light-emitting structure and is in contact with the metal protective layer through the second opening, the second electrode layer includes a first metal reflective layer, and the first metal reflective layer is in contact with the metal protective layer.

10. The light emitting diode according to any one of claims 1 to 9, characterized in that: It also includes a first pad electrode and a second pad electrode, which are formed on the light emitting structure, the first pad electrode is electrically connected to the first semiconductor layer, and the second pad electrode is electrically connected to the second semiconductor layer.

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