LED chip electrode and manufacturing method thereof, and LED chip

Abstract

The application provides an LED chip electrode manufacturing method, which comprises the following steps: providing a semi-finished LED chip to be manufactured with an electrode; manufacturing the electrode on the semi-finished chip; loading a preset load for a preset time on the electrode to form an indentation on the electrode; repeatedly loading the preset load for the preset time on different positions of the electrode to form interval indentations on the electrode and the electrode gold finger; and finally obtaining a periodic indentation structure on the electrode. The application solves the problem that the Al layer in the chip electrode in the prior art is prone to electromigration, thereby reducing the reliability of the chip.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an LED chip electrode, its fabrication method, and an LED chip. Background Technology

[0002] Traditionally, aluminum has been widely used as a metallic interconnect. Aluminum interconnects are low-cost, technologically mature, have good adhesion, and are easy to etch, making them a good metallic conductor material. However, during use, it was found that aluminum is significantly affected by electromigration and temperature fields. This is because aluminum is a very reactive metal, easily undergoing electromigration under the influence of electric current, leading to the eventual failure of the aluminum wire. From a microscopic perspective, electromigration is like the diffusion of atoms in a crystal, producing a kind of mass migration. Accumulated migration can create voids and even short circuits.

[0003] Although pure aluminum is rarely used as an electrode material nowadays, in order to reduce light absorption by the electrodes in LED chips, an Al layer is often plated in the electrodes as a reflective layer. However, while aluminum-containing reflective electrodes improve chip brightness, the electromigration of Al generated by the Al layer also reduces the reliability of the chip. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide an LED chip electrode and its manufacturing method, as well as an LED chip, in order to solve the problem that the Al layer in the chip electrode in the prior art is prone to electromigration, which leads to a decrease in chip reliability.

[0005] The embodiments of the present invention are implemented as follows: On one hand, the present invention proposes a method for fabricating LED chip electrodes, the method comprising: Provide a semi-finished LED chip with electrodes to be fabricated; Electrodes are fabricated on the semi-finished chip; A preset load for a preset time is applied to the electrode to form an indentation on the electrode; A preset load for a preset time is repeatedly applied to different positions of the electrode to form intermittent indentations on the electrode, ultimately resulting in a periodic indentation structure on the electrode.

[0006] Furthermore, in the above-mentioned LED chip electrode fabrication method, the step of applying a preset load for a preset time to the electrode to form an indentation on the electrode includes: The indenter of the nanoindenter is pressed onto the electrode with the preset load, and the load is unloaded after a preset time to form an indentation on the electrode.

[0007] Furthermore, in the above-mentioned LED chip electrode fabrication method, the indentation depth is 250nm~500nm.

[0008] Furthermore, in the above-mentioned LED chip electrode fabrication method, the indentation spacing is 1µm to 3µm.

[0009] Furthermore, in the above-mentioned LED chip electrode manufacturing method, the pressure head of the pressure needle is in the shape of a triangular pyramid, a square pyramid, or a round head.

[0010] Furthermore, in the above-mentioned method for fabricating LED chip electrodes, the step of preparing electrodes on the semi-finished chip includes: The electrode is obtained by sequentially depositing metal layers of chromium, aluminum, titanium, nickel, platinum and copper on the semi-finished chip, wherein the electrode includes a pad portion and a finger portion connected to the pad portion.

[0011] Furthermore, in the above-mentioned LED chip electrode fabrication method, the step of preparing the semi-finished LED chip includes: Provide a substrate; An epitaxial layer is grown on the substrate; The epitaxial layer is etched to expose the n-type GaN layer of the epitaxial layer. Then, a current blocking layer is deposited on at least a portion of the surface of the epitaxial layer, and a transparent conductive film is evaporated on the current blocking layer to obtain the semi-finished chip.

[0012] Furthermore, in the above-mentioned LED chip electrode fabrication method, after preparing the indentation structure on the electrode, the method further includes: A passivation layer is deposited on the electrode. The passivation layer is a silicon oxide layer and the thickness of the passivation layer is 50 nm to 100 nm.

[0013] In another aspect, the present invention provides an LED chip electrode, which is prepared by the above-described LED chip electrode manufacturing method.

[0014] On the other hand, the present invention provides a chip including the above-described LED chip electrodes.

[0015] This invention applies a preset load for a preset time to the electrodes of a chip to form indentations on the electrodes and electrode gold fingers; the preset load for a preset time is repeatedly applied to different positions on the electrodes to form intermittent indentations on the electrodes. The resulting periodic indentation structure on the electrodes can effectively slow down the electromigration of metal electrodes along the current direction, especially slow down the electromigration of Al, thus solving the problem of reduced chip reliability caused by the easy electromigration of Al layer in chip electrodes in the prior art. Attached Figure Description

[0016] Figure 1 This is a flowchart of an LED chip electrode fabrication method according to an embodiment of the present invention; Figure 2 This is a partial structural diagram of an LED chip according to an embodiment of the present invention.

[0017] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0019] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] In the prior art, in order to reduce light absorption by the electrodes in LED chips, an Al layer is often plated in the electrodes as a reflective layer. However, although the aluminum-containing reflective electrode improves the brightness of the chip, the electromigration of Al generated by the Al layer also reduces the reliability of the chip.

[0022] This invention proposes an LED chip electrode and its fabrication method, as well as an LED and a chip. The main improvement is achieved by modifying the electrode to slow down the electromigration of Al, thereby enhancing the reliability of the chip.

[0023] Please see Figure 1 The figure shows a method for manufacturing LED chip electrodes according to an embodiment of the present invention, the method including steps S10 to S12.

[0024] Step S10: Provide a semi-finished LED chip with electrodes to be fabricated.

[0025] Specifically, as one embodiment of the semi-finished LED chip for which electrodes are to be fabricated in this invention, the method for preparing the semi-finished chip can be as follows: A substrate is provided, wherein the substrate may be selected from one of the following: sapphire substrate, SiO2 sapphire composite substrate, silicon substrate, silicon carbide substrate, gallium nitride substrate, and zinc oxide substrate; In this embodiment, a sapphire substrate is selected. Sapphire is currently the most commonly used GaN-based LED substrate material. Most GaN-based LEDs on the market use sapphire as the substrate material. The biggest advantages of sapphire substrates are mature technology, good stability and low production cost. An epitaxial layer is grown on the substrate. Metal chemical vapor deposition (MOCVD) can be used to grow the epitaxial layer. The epitaxial layer can have an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer. Specifically, high-purity hydrogen is used as the carrier gas, high-purity ammonia as the nitrogen source, trimethylgallium and triethylgallium as gallium sources, trimethylindium as the indium source, silane as the N-type dopant, trimethylaluminum as the aluminum source, and magnesium thiocene as the P-type dopant. The N-type semiconductor layer is an N-type GaN layer, the P-type semiconductor layer is a P-type GaN layer, and the light-emitting layer is a multi-quantum-well active layer. The thickness of the P-type GaN layer is 1 μm-3 μm, and the Si doping concentration is 5 × 10⁻⁶. 18 ~1×10 19 cm -3 The thickness of the p-type GaN layer is 200nm-300nm, and the Mg doping concentration is 5×10⁻⁶. 17 ~1×10 20 cm -3 The molar proportion of In in the multi-quantum-well active layer is 10%-35%. The epitaxial layer is etched to expose the N-type GaN layer. After exposing the N-type GaN layer, a current blocking layer is deposited on at least a portion of the surface of the epitaxial layer, and a transparent conductive film is evaporated on the current blocking layer to obtain the semi-finished LED chip. Specifically, the N-type GaN layer morphology is exposed using ICP etching technology; then, a 300 nm thick SiO2 current blocking layer is deposited on the surface using PECVD; subsequently, an ITO transparent conductive film is evaporated using electron beam evaporation technology to ensure uniform current diffusion. Step S11: Prepare electrodes on the semi-finished chip.

[0026] Specifically, chromium, aluminum, titanium, nickel, platinum, and copper metal layers are sequentially deposited on the semi-finished chip to obtain the electrodes of the LED chip. The electrodes include a pad portion and a finger portion connected to the pad portion. Specifically, the semi-finished chip wafer is placed on the wafer tray of an electron beam evaporation machine, with the evaporation source emitter located below the wafer tray, and then chromium, aluminum, titanium, nickel, platinum, and copper metal layers are sequentially deposited to obtain the electrodes of the LED chip.

[0027] Step S12: Apply a preset load for a preset time to the electrode to form an indentation on the electrode.

[0028] Specifically, the indenter of the nanoindenter is pressed on the finger part connecting the chip electrode and the pad with a certain load external force for a certain period of time, and then unloaded to obtain an indentation of the corresponding structure on the electrode. The indentation depth is 250nm~500nm, the indentation spacing is 1um~3um, and the indenter head is triangular pyramidal, square pyramidal, or round-headed.

[0029] Step S13: Repeatedly apply a preset load for a preset time at different positions of the electrode to form intermittent indentations on the electrode, and finally obtain a periodic indentation structure on the electrode.

[0030] The process involves repeated loading and unloading, resulting in interspersed indentations that create a periodic indentation structure. This indentation structure effectively slows down the electromigration of metal electrodes along the current direction, particularly the electromigration of Al.

[0031] In addition, the present invention also proposes an LED chip electrode, which is fabricated by the LED chip electrode fabrication method described in the above embodiments.

[0032] In addition, the present invention also proposes an LED chip, which includes the aforementioned LED chip electrodes. Specifically, as shown... Figure 2 As shown, the LED chip includes an epitaxial layer and a current blocking layer 30, a passivation layer 40, and a current spreading layer 50 deposited on the epitaxial layer. An electrode 20 is formed by vapor deposition above the current blocking layer 30. An indentation 10 is provided on the electrode. The indentations 10 are arranged at intervals along the electrode 20 to form a periodic indentation structure.

[0033] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0034] Example 1 A semi-finished LED chip with electrodes to be fabricated is provided. Electrodes are fabricated on the semi-finished chip. A nanoindenter is used to repeatedly apply a preset load for a preset time at different positions on the electrodes to form indentations arranged at intervals on the electrodes, and finally a periodic indentation structure is obtained on the electrodes.

[0035] The pressure head of the pressure needle is triangular pyramidal, with an indentation depth of 250nm and an indentation spacing of 1µm.

[0036] Example 2 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The indentation interval is 2µm.

[0037] Example 3 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The indentation interval is 3µm.

[0038] Example 4 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The indentation depth is 300 nm and the indentation spacing is 2 μm.

[0039] Example 5 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The indentation depth is 500 nm and the indentation spacing is 2 μm.

[0040] Example 6 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The pressure head of the pressure needle is square-pyramidal, and the indentation interval is 2µm.

[0041] Example 7 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: The pressure head of the pressure needle is round, and the indentation interval is 2µm.

[0042] Compare with Example 1 The purpose of this embodiment is also to provide a method for fabricating LED chip electrodes, which differs from the method for fabricating LED chip electrodes proposed in Embodiment 1 in that: No indentation structure was made.

[0043] In addition, accelerated degradation tests were performed on Examples 1-7 and Control Example 1 respectively. The test current was 400mA (the conventional test current is 120mA), and the leakage failure time was recorded. The results are shown in Table 1. It is evident that the failure time of the LED was significantly improved after the indentation structure was fabricated. Therefore, the indentation structure can effectively slow down the electromigration of the metal electrode along the current direction, especially the electromigration of Al.

[0044] Furthermore, in conjunction with Examples 1-3 and Examples 2-5, it can be clearly seen that the indentation depth and the arrangement and spacing of the indentations both affect the rate of electrode migration. Among them, within a reasonable range, the larger the indentation spacing, the longer the failure time, and the better the effect of slowing down Al electromigration. From Examples 2, 6, and 7, it can be clearly seen that the indenter morphology affects the rate of electrode migration, and the square pyramid shape has a better effect of slowing down Al electromigration.

[0045] In summary, the chip fabrication method proposed in the above embodiments of the present invention forms indentations on the electrodes by applying a preset load for a preset time to the electrodes; and by repeatedly applying the preset load for a preset time at different positions on the electrodes to form intermittent indentations on the electrodes, ultimately obtaining a periodic indentation structure on the electrodes. This effectively slows down the electromigration of metal electrodes along the current direction, especially slows down the electromigration of Al, and solves the problem that the Al layer in the chip electrodes in the prior art is prone to electromigration, which leads to a decrease in chip reliability.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating LED chip electrodes, characterized in that, The method includes: Provide a semi-finished LED chip with electrodes to be fabricated; Electrodes are fabricated on the semi-finished LED chip; A preset load for a preset time is applied to the electrode to form an indentation on the electrode; A preset load for a preset time is repeatedly applied to different positions of the electrode to form intervald indentations on the electrode, ultimately resulting in a periodic indentation structure on the electrode. In this process, the pressure needle of the nanoindenter is pressed onto the electrode with the preset load, and the load is unloaded after a preset time to form an indentation on the electrode. The indentation depth is 250nm~500nm, and the pressure head of the pressure needle is triangular pyramidal, square pyramidal, or round-headed.

2. The method for fabricating LED chip electrodes according to claim 1, characterized in that, The indentation spacing is 1µm to 3µm.

3. The method for fabricating LED chip electrodes according to claim 1, characterized in that, The step of preparing electrodes on the semi-finished LED chip includes: The electrode is obtained by sequentially depositing metal layers of chromium, aluminum, titanium, nickel, platinum and copper on the semi-finished LED chip, wherein the electrode includes a pad portion and a finger portion connected to the pad portion.

4. The method for fabricating LED chip electrodes according to claim 1, characterized in that, The preparation steps of the semi-finished LED chip include: Provide a substrate; An epitaxial layer is grown on the substrate; The epitaxial layer is etched to expose the N-type GaN layer of the epitaxial layer. Then, a current blocking layer is deposited on at least a portion of the surface of the epitaxial layer, and a transparent conductive film is evaporated on the current blocking layer to obtain the semi-finished LED chip.

5. The method for fabricating LED chip electrodes according to claim 1, characterized in that, After fabricating the indentation structure on the electrode, the process further includes: A passivation layer is deposited on the electrode. The passivation layer is a silicon oxide layer and the thickness of the passivation layer is 50 nm to 100 nm.

6. An LED chip electrode, characterized in that, It is prepared using the LED chip electrode fabrication method described in any one of claims 1 to 5.

7. An LED chip, characterized in that, Includes the LED chip electrode as described in claim 6.

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