P electrode structure of GaN laser, preparation method of P electrode structure and GaN laser

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a P electrode structure of a GaN laser, a preparation method of the P electrode structure and the GaN laser, the P electrode structure comprises a substrate and a dielectric layer arranged on the substrate, the dielectric layer is provided with a P electrode, the P electrode comprises a first electrode with a Ni layer as a bottom layer and a second electrode with a Ti layer as a bottom layer, and the first electrode and the second electrode are arranged on the substrate. The second electrode surrounds the first electrode and is connected with the first electrode. The first electrode takes the Ni layer with stable chemical property as the bottom layer, the long-term electrochemical stability and aging resistance of the electrode are effectively improved by using the excellent oxidation resistance of the Ni layer, the second electrode takes the Ti layer with strong adhesive force to the dielectric layer as the bottom layer, and the shear strength of the electrode is remarkably improved by using firm chemical bonding between the Ti layer and the dielectric layer. The second electrode is arranged around the first electrode and is electrically connected with the first electrode to form a whole to serve as the P electrode, so that the Ni layer and the Ti layer act together, and the shearing strength and the long-term anti-aging capability of the chip are remarkably improved at the same time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a P-electrode structure for a GaN laser, its fabrication method, and the GaN laser itself. Background Technology

[0002] In the wafer fabrication process of GaN lasers, electron beam evaporation deposition equipment is typically used to deposit a multilayer metal film with Ni as the bottom layer on the P-side of the device as the P-electrode. However, the P-electrode prepared by this method exhibits poor performance in shear force tests after packaging due to the poor behavior of Ni metal on dielectric films such as ITO / SiO2. The measured shear force is only 50-200g, far below the acceptable standard of 400g. Summary of the Invention

[0003] The purpose of this invention is to provide a P-electrode structure for a GaN laser, a method for its fabrication, and a GaN laser, which can at least solve some of the defects in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is a P-electrode structure for a GaN laser, comprising a substrate and a dielectric layer disposed on the substrate, wherein a P-electrode is disposed on the dielectric layer, the P-electrode comprising a first electrode with a Ni layer as the bottom layer and a second electrode with a Ti layer as the bottom layer, the second electrode being disposed around the first electrode and connected to the first electrode.

[0005] As one embodiment, the first electrode is a Ni / Pd / Au electrode, comprising a Ni layer, a Pd layer and a first Au layer sequentially stacked on the dielectric layer.

[0006] As one embodiment, the second electrode is a Ti / Pt / Au electrode, comprising a Ti layer, a Pt layer, and a second Au layer sequentially stacked on the dielectric layer.

[0007] As one embodiment, the inner edge of the second electrode is disposed on the first electrode.

[0008] As one embodiment, the dielectric layer includes a contact layer and an insulating layer, the insulating layer is disposed around the contact layer, the first electrode is disposed on the contact layer, and the second electrode is disposed on the insulating layer.

[0009] As one embodiment, the contact layer is an ITO layer and the insulating layer is a SiO2 layer.

[0010] As one embodiment, the inner edge of the insulating layer is disposed on the contact layer.

[0011] The present invention also provides a GaN laser, comprising the P-electrode structure of the GaN laser described in any of the preceding claims.

[0012] The present invention also provides a method for fabricating a P-electrode structure of a GaN laser according to any one of the above claims, comprising the following steps:

[0013] S1. Prepare a dielectric layer on the substrate;

[0014] S2. A first electrode is fabricated on a dielectric layer, and then a second electrode is fabricated around the first electrode.

[0015] As one implementation method, in step S1, the dielectric layer includes a contact layer and an insulating layer disposed around the contact layer; in step S2, the first electrode is fabricated on the contact layer and the second electrode is fabricated on the insulating layer.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) In this invention, the first electrode uses a chemically stable Ni layer as the bottom layer. By utilizing its excellent antioxidant properties, the long-term electrochemical stability and anti-aging ability of the electrode are effectively improved. The second electrode uses a Ti layer with strong adhesion to the dielectric layer as the bottom layer. By utilizing its strong chemical bond with the dielectric layer, the shear strength of the electrode is significantly improved. By setting the second electrode around the first electrode and electrically connecting it to the first electrode to form a whole as the P electrode, the Ni layer and the Ti layer work together, thereby significantly improving the shear strength and long-term anti-aging ability of the chip at the same time.

[0018] (2) The present invention uses two-step vapor deposition to prepare the first electrode and the second electrode respectively, and the whole is used as the P electrode. The preparation method is simple and easy to implement and mass-produce. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic diagram illustrating the spin-coating and patterning of a first photoresist layer provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the vapor-deposited first composite metal layer provided in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of fabricating a first electrode on the surface of a dielectric layer according to an embodiment of the present invention;

[0023] Figure 4 A schematic diagram illustrating the spin-coating and patterning of a second photoresist layer provided in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the vapor-deposited second composite metal layer provided in an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the P-electrode structure of a GaN laser provided in an embodiment of the present invention;

[0026] In the figure: 1. Substrate; 2. Contact layer; 3. Insulating layer; 4. First photoresist layer; 5. First composite metal layer; 6. First electrode; 7. Second photoresist layer; 8. Second composite metal layer; 9. Second electrode. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0030] As shown in Figure 6, this embodiment provides a P-electrode structure for a GaN laser, including a substrate 1 and a dielectric layer disposed on the substrate 1. A P-electrode is disposed on the dielectric layer, comprising a first electrode 6 with a Ni layer as the bottom layer and a second electrode 9 with a Ti layer as the bottom layer. The second electrode 9 is disposed around and connected to the first electrode 6. In this embodiment, the first electrode 6 uses a chemically stable Ni layer as the bottom layer, utilizing its excellent antioxidant properties to effectively improve the long-term electrochemical stability and anti-aging ability of the electrode. The second electrode 9 uses a Ti layer with strong adhesion to the dielectric layer as the bottom layer, utilizing its strong chemical bond with the dielectric layer to significantly improve the shear strength of the electrode. By distributing the second electrode 9 around the first electrode 6 and electrically connecting it to the first electrode 6 to form a whole as the P-electrode, the Ni layer and the Ti layer work together, and the chip shear force can reach 700g-900g. The voltage remains stable after 200 hours of aging testing, thereby significantly improving the chip's shear strength and long-term anti-aging ability.

[0031] In this embodiment, the second electrode 9 can be a ring structure and is arranged to surround the first electrode 6; there can also be multiple second electrodes 9, which are arranged at intervals along the circumference of the first electrode 6.

[0032] Furthermore, the first electrode 6 includes a Ni layer, a first barrier layer, and a first solder layer sequentially stacked on the dielectric layer. Preferably, the first electrode 6 is a Ni / Pd / Au electrode, including a Ni layer, a Pd layer, and a first Au layer sequentially stacked on the dielectric layer. The Ni layer forms an ohmic contact with the semiconductor material on the substrate 1 through an opening in the dielectric layer; the first Au layer, as the first solder layer, provides good conductivity and solderability; the Pd layer, as the first barrier layer, prevents Au atoms from diffusing from the top layer to the bottom interface.

[0033] Furthermore, the second electrode 9 includes a Ti layer, a second barrier layer, and a second solder layer sequentially stacked on the dielectric layer. Preferably, the second electrode 9 is a Ti / Pt / Au electrode, including a Ti layer, a Pt layer, and a second Au layer sequentially stacked on the dielectric layer. The Ti layer forms an ohmic contact with the semiconductor material on the substrate 1 through an opening in the dielectric layer; the second Au layer, as the second solder layer, provides good conductivity and solderability; the Pt layer, as the second barrier layer, prevents Au atoms from diffusing to the bottom interface, and the Pt atoms in the Pt layer form a strong intermetallic compound with the Ti atoms in the Ti layer, improving the adhesion between the Ti and Pt layers, thereby further enhancing the shear strength of the P electrode.

[0034] In some embodiments, the inner edge of the second electrode 9 is disposed on the first electrode 6. For example... Figure 6As shown, by covering the edge of the first electrode 6 with the inner edge of the second electrode 9 close to the first electrode 6, the top edge and side surface of the first electrode 6 are connected to the second electrode 9, thereby ensuring a reliable connection between the second electrode 9 and the first electrode 6 and improving the overall integrity and shear force of the entire P electrode.

[0035] In some embodiments, the dielectric layer includes a contact layer 2 and an insulating layer 3, the insulating layer 3 surrounding the contact layer 2, the first electrode 6 being disposed on the contact layer 2, and the second electrode 9 being disposed on the insulating layer 3. The first electrode 6 is connected to the substrate 1 through the contact layer 2, and the second electrode 9 is not in contact with the substrate 1 through the insulating layer 3. In this embodiment, the substrate 1 is a GaN substrate.

[0036] Preferably, the contact layer 2 is an ITO layer, and the insulating layer 3 is a SiO2 layer. The Ti layer of the second electrode 9 is disposed on the SiO2 layer. The Ti atoms of the Ti layer can react with the O atoms of the SiO2 layer to form strong Ti-O bonds, which improves the adhesion between the second electrode 9 and the insulating layer 3, thereby enhancing the shear strength of the entire P electrode.

[0037] Preferably, the inner edge of the insulating layer 3 is disposed on the contact layer 2. For example... Figure 6 As shown, by covering the contact layer 2 with the insulating layer 3 near the inner edge of the contact layer 2, it is ensured that the second electrode 9 does not contact the substrate 1.

[0038] In some embodiments, the substrate 1 has a ridge structure, the contact layer 2 is disposed on the ridge structure, and the bottom surface of the insulating layer 3 extends from the top surface of the contact layer 2, through the side surface of the contact layer 2, to the substrate 1 surrounding the ridge structure in a direction from the inside to the outside. Figure 6 As shown, the contact layer 2 is disposed on the ridge structure, the first electrode 6 is disposed on the contact layer 2, and the bottom surface of the insulating layer 3 extends from the top surface of the contact layer 2, through the side surface of the contact layer 2, to the substrate 1 around the ridge structure. The top surface of the insulating layer 3 is a smooth curved surface, providing a flatter deposition surface for the second electrode 9. The bottom surface of the second electrode 9 extends from the top surface of the first electrode 6, through the side surface of the first electrode 6, to the top surface of the insulating layer 3.

[0039] This embodiment also provides a GaN laser, including the P-electrode structure of the GaN laser described in any of the above embodiments.

[0040] This embodiment also provides a method for fabricating the P-electrode structure of the GaN laser described in any of the above claims, comprising the following steps:

[0041] S1. Prepare a dielectric layer on substrate 1;

[0042] S2. A first electrode 6 is fabricated on a dielectric layer, and then a second electrode 9 is fabricated around the first electrode 6.

[0043] Further, the method for fabricating the first electrode 6 on the dielectric layer is as follows: a first photoresist layer 4 is spin-coated and patterned on the surface of the dielectric layer, then a first composite metal layer 5 with a Ni layer as the bottom layer is deposited by vapor deposition, and then the first photoresist layer 4 and the first composite metal layer 5 thereon are removed to obtain the first electrode 6. Specifically, the first photoresist layer 4 is spin-coated on the surface of the dielectric layer. The first photoresist layer 4 is a negative photoresist. After exposure and development, a patterned first photoresist layer 4 is formed on the surface of the dielectric layer, exposing the dielectric layer in the area where the first electrode 6 is to be fabricated; vapor deposition involves placing the substrate 1 in an electron beam evaporation device and depositing the first composite metal layer 5 with a Ni layer as the bottom layer on the surface of the dielectric layer with the patterned first photoresist layer 4. Then, the substrate 1 after vapor deposition is placed in a stripping solution to dissolve the undeveloped first photoresist layer 4, thereby removing the first photoresist layer 4 and the first composite metal layer 5 thereon to form the desired first electrode 6.

[0044] Furthermore, the method for fabricating the second electrode 9 around the first electrode 6 is as follows: a second photoresist layer 7 is spin-coated and patterned on the dielectric layer surface of the already fabricated first electrode 6, followed by the vapor deposition of a second composite metal layer 8 with a Ti layer as the bottom layer, and then the second photoresist layer 7 and the second composite metal layer 8 thereon are removed to obtain the second electrode 9. Specifically, a second photoresist layer 7 is spin-coated on the dielectric layer surface of the already fabricated first electrode 6. The second photoresist layer 7 uses a negative photoresist. After exposure and development, a patterned second photoresist layer 7 is formed on the surface of the first electrode 6, exposing the dielectric layer in the area where the second electrode 9 is to be fabricated. The vapor deposition involves placing the substrate 1 in an electron beam evaporation apparatus and vapor-depositing a second composite metal layer 8 with a Ti layer as the bottom layer on the dielectric layer surface with the patterned second photoresist layer 7. Afterward, the vapor-deposited substrate 1 is placed in a stripping solution to dissolve the undeveloped second photoresist layer 7, thereby removing the second photoresist layer 7 and the second composite metal layer 8 thereon to form the desired second electrode 9.

[0045] In some embodiments, in step S1, the dielectric layer includes a contact layer and an insulating layer disposed around the contact layer; in step S2, the first electrode is fabricated on the contact layer and the second electrode is fabricated on the insulating layer.

[0046] Furthermore, in step S1, a dielectric layer is prepared on substrate 1, including the following steps:

[0047] S11. Deposit a contact film on substrate 1, and then rapidly anneal to form an ohmic contact;

[0048] S12. Photoresist is coated and patterned on the structure obtained in step S11 to form a PR mask. Then, ICP etching is used to etch the contact film and substrate 1 to form a ridge. After that, the PR mask is removed to complete the fabrication of the ridge structure and contact layer.

[0049] S13. An insulating film is deposited on the entire surface of the structure obtained in step S12. Then, photolithography and wet etching are performed to remove the resist and remove the insulating film outside the design area of ​​the first electrode 6 to obtain the insulating layer 3.

[0050] The method of the present invention will be described in detail below through a specific embodiment.

[0051] A method for fabricating a P-electrode structure for a GaN laser includes the following steps:

[0052] 1) Deposit an ITO film on the top surface of substrate 1, and then rapidly anneal it to form an ohmic contact;

[0053] 2) Coat the structure obtained in step 1) with photoresist and pattern it to form a PR mask. Then, use ICP to etch the ITO film and substrate 1 to form a ridge. After that, remove the PR mask to complete the fabrication of the ridge structure and contact layer 2.

[0054] 3) The entire surface of the structure obtained in step 2) is coated with SiO2 film, and then photolithography, wet etching, resist removal, and removal of SiO2 film outside the design area of ​​the first electrode 6 are performed to obtain insulating layer 3;

[0055] 4) A negative photoresist is spin-coated onto the surface of the structure obtained in step 3). After exposure and development, a patterned first photoresist layer 4 is formed, such as... Figure 1 As shown, the first photoresist layer 4 has an opening in the design area of ​​the first electrode 6;

[0056] 5) Place the structure obtained in step 4) in an electron beam evaporation apparatus, and sequentially deposit a Ni layer, a Pd layer, and a first Au layer. A first composite metal layer 5 is formed on the surface of the first photoresist layer 4 and the contact layer 2, as shown below. Figure 2 As shown;

[0057] 6) Place the structure obtained in step 5) in a stripping solution to dissolve the undeveloped first photoresist layer 4, remove the first photoresist layer 4 and the first composite metal layer 5 thereon, and form the desired first electrode 6, as shown below. Figure 3 As shown;

[0058] 7) A negative photoresist is spin-coated onto the surface of the structure obtained in step 6). After exposure and development, a patterned second photoresist layer 7 is formed, such as... Figure 4 As shown, the second photoresist layer 7 has an opening in the design area of ​​the second electrode 9;

[0059] 8) Place the structure obtained in step 7) in an electron beam evaporation apparatus, and sequentially deposit a Ti layer, a Pt layer, and a second Au layer. A second composite metal layer 8 is formed on the surface of the second photoresist layer 7 and the insulating layer 3, as shown below. Figure 5 As shown;

[0060] 9) Place the structure obtained in step 8) in a stripping solution to dissolve the undeveloped second photoresist layer 7, remove the second photoresist layer 7 and the second composite metal layer 8 thereon, and form the desired second electrode 9, as shown. Figure 6 As shown.

[0061] After packaging, shear force and aging tests were performed on the chip using the above-mentioned P-electrode structure. The results showed that compared with the chip using a single Ti / Pt / Au electrode, the chip voltage increased by 0.2-0.7V after 200H aging. The chip using the P-electrode structure of this embodiment can withstand a shear force of up to 900g, and the voltage remains stable after 200H aging. It can be seen that using the P-electrode of the present invention not only improves the shear strength of the chip, but also maintains the stability of the voltage after 200H aging.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A p-electrode structure for a GaN laser, comprising a substrate and a dielectric layer disposed on the substrate, characterized in that: A P electrode is disposed on the dielectric layer. The P electrode includes a first electrode with a Ni layer as the bottom layer and a second electrode with a Ti layer as the bottom layer. The second electrode is disposed around the first electrode and connected to the first electrode.

2. The P-electrode structure of the GaN laser as described in claim 1, characterized in that: The first electrode is a Ni / Pd / Au electrode, comprising a Ni layer, a Pd layer and a first Au layer sequentially stacked on the dielectric layer.

3. The P-electrode structure of the GaN laser as described in claim 1, characterized in that: The second electrode is a Ti / Pt / Au electrode, comprising a Ti layer, a Pt layer, and a second Au layer sequentially stacked on the dielectric layer.

4. The P-electrode structure of the GaN laser as described in claim 1, characterized in that: The inner edge of the second electrode is disposed on the first electrode.

5. The P-electrode structure of the GaN laser as described in claim 1, characterized in that: The dielectric layer includes a contact layer and an insulating layer, the insulating layer being disposed around the contact layer, the first electrode being disposed on the contact layer, and the second electrode being disposed on the insulating layer.

6. The P-electrode structure of the GaN laser as described in claim 5, characterized in that: The contact layer is an ITO layer, and the insulating layer is a SiO2 layer.

7. The P-electrode structure of the GaN laser as described in claim 5, characterized in that: The inner edge of the insulating layer is disposed on the contact layer.

8. A GaN laser, characterized in that: The P-electrode structure of the GaN laser as described in any one of claims 1-7.

9. A method for fabricating a P-electrode structure for a GaN laser according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Prepare a dielectric layer on the substrate; S2. A first electrode is fabricated on a dielectric layer, and then a second electrode is fabricated around the first electrode.

10. The preparation method according to claim 9, characterized in that, In step S1, the dielectric layer includes a contact layer and an insulating layer surrounding the contact layer; in step S2, the first electrode is fabricated on the contact layer and the second electrode is fabricated on the insulating layer.

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