A small light-emitting diode structure and its manufacturing method

Abstract

The present invention relates to a small light-emitting diode structure and a manufacturing method thereof. The present invention includes a substrate, on the front surface of which an epitaxial structure is provided, on the front surface of the epitaxial structure a transparent conductive layer is provided, a step is formed on the side surface of the epitaxial structure, an insulating layer covers the step and the front surface of the transparent conductive layer, a contact area is provided on the insulating layer, a contact electrode contacts the transparent conductive layer and the epitaxial structure through the contact area, a gap area is formed between the insulating layer and the contact electrode, a dense insulating layer covers the gap area, an insulating reflective layer covers the dense insulating layer, and a via area for contacting a pad electrode is formed between the dense insulating layer and the insulating reflective layer above the contact electrode. The present invention can avoid introducing metal particles during the metal manufacturing process and reduce the risk of leakage or micro-leakage caused by metal adsorption on the epitaxial step.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a small light-emitting diode structure and a manufacturing method thereof. Background Art

[0002] In the conventional process of small light-emitting diodes (Mini LED), the contact electrodes are first made, then an insulating layer is covered above the contact electrodes, through holes are formed, and then connected to the pads. By this method, when making the contact electrodes, the steps formed by u-GaN, n-GaN, etc. on the side of the LED structure are not effectively protected, and there is a risk of metal adsorption causing leakage or micro-leakage during metal degluing. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the problem that in the prior art, when making contact electrodes for small light-emitting diodes, the steps formed by u-GaN, n-GaN, etc. on the side of the LED structure are not effectively protected, and there is a risk of metal adsorption causing leakage or micro-leakage during metal degluing. The present invention provides a small light-emitting diode structure and a manufacturing method thereof, which can avoid introducing metal particles during the metal process and reduce the risk of leakage or micro-leakage caused by metal adsorption on the epitaxial steps.

[0004] To solve the above technical problem, the present invention provides a small light-emitting diode structure, including a substrate. An epitaxial structure is provided on the front surface of the substrate. A transparent conductive layer is provided on the front surface of the epitaxial structure. Steps are formed on the side surface of the epitaxial structure. An insulating layer covers the steps and the front surface of the transparent conductive layer. A contact area is provided on the insulating layer. The contact electrode contacts the transparent conductive layer and the epitaxial structure through the contact area. A gap area is formed between the insulating layer and the contact electrode. A dense insulating layer covers the gap area. An insulating reflective layer covers the dense insulating layer. A through-hole area for contacting the pad electrode is formed between the dense insulating layer and the insulating reflective layer above the contact electrode.

[0005] In an embodiment of the present invention, the epitaxial structure includes a buffer layer, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer sequentially provided on the front surface of the substrate.

[0006] In an embodiment of the present invention, the angle formed by the side slope of the dense insulating layer and the normal line of the front surface of the substrate is smaller than the angle formed by the side slope of the insulating reflective layer and the normal line of the front surface of the substrate.

[0007] In an embodiment of the present invention, the contact area includes the bottom surface of the transparent conductive layer and the step surface of the insulating layer. The bottom end of the contact electrode contacts the bottom surface of the transparent conductive layer, and the side end of the contact electrode does not contact the step surface of the insulating layer.

[0008] In an embodiment of the present invention, the contact area includes the bottom surface of the transparent conductive layer and the step surface of the insulating layer. The bottom end of the contact electrode contacts the bottom surface of the transparent conductive layer, and the side end of the contact electrode contacts the step surface of the insulating layer.

[0009] In an embodiment of the present invention, the contact area includes a plurality of holes formed in the insulating layer. The contact electrode contacts the transparent conductive layer and the epitaxial structure through the plurality of holes.

[0010] In an embodiment of the present invention, a back-plated insulating layer is provided on the reverse side of the substrate.

[0011] In an embodiment of the present invention, the width of the small light-emitting diode structure is between 20 and 500 µm, and the length is between 20 and 1000 µm.

[0012] In an embodiment of the present invention, the back-plated insulating layer is formed by stacking low-refractive-index SiO2 and high-refractive-index TiO2.

[0013] The present invention also provides a manufacturing method based on the small light-emitting diode structure, including the following steps:

[0014] Provide a substrate, prepare an epitaxial structure on the front surface of the substrate, and etch a step on the epitaxial structure;

[0015] Prepare a layer of transparent conductive layer on the front surface of the epitaxial structure, and prepare an insulating layer on the transparent conductive layer and the step surface;

[0016] Prepare a contact area at the insulating layer. The contact electrode contacts the transparent conductive layer and the epitaxial structure through the contact area, and a gap area is formed between the insulating layer and the contact electrode. A dense insulating layer is covered in the gap area;

[0017] Cover a layer of insulating reflective layer outside the dense insulating layer, and form a via area between the dense insulating layer and the insulating reflective layer above the contact electrode to fabricate a pad electrode.

[0018] In an embodiment of the present invention, the dense insulating layer is SiO2, SiN deposited by sputtering or atomic layer deposition x , Al2O3, AlN or a stack structure layer composed of 2 to 10 layers of the above materials.

[0019] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0020] A small light-emitting diode structure and a manufacturing method thereof according to the present invention form a gap between an insulating layer and a contact electrode, and are connected to the gap through a dense insulating layer, so that the dense insulating layer is directly connected to the bottom of the contact electrode, which can effectively block the migration and penetration of water vapor in the air and active metals such as Ag and Sn in the solder balls, and improve the ability to resist metal migration; and a through-hole area is formed in the dense insulating layer and the insulating reflective layer above the contact electrode as a pad electrode contact area. The dense insulating layer and the insulating reflective layer form slopes with two angles, and the insulating reflective layer improves the overall light extraction efficiency; the epitaxial structure is provided with steps for protection, with low leakage risk and simple manufacturing, reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in conjunction with the drawings, wherein

[0022] Figure 1 is a schematic diagram of the small light-emitting diode structure in Embodiment 1.

[0023] Figure 2 is Figure 1 a partial enlarged schematic diagram of

[0024] Figure 3 is a schematic diagram of the small light-emitting diode structure with a back-plated insulating layer in Embodiment 1.

[0025] Figure 4 is a schematic diagram of the small light-emitting diode structure in Embodiment 2.

[0026] Figure 5 is Figure 4 a partial enlarged schematic diagram of

[0027] Figure 6 is a schematic diagram of the small light-emitting diode structure in Embodiment 2.

[0028] Description of the reference numerals in the drawings: 1, substrate; 2, epitaxial structure; 20, step; 21, buffer layer; 22, first semiconductor layer; 23, light-emitting layer; 24, second semiconductor layer; 3, transparent conductive layer; 4, insulating layer; 41, contact area; 411, bottom surface of the transparent conductive layer; 412, stepped surface of the insulating layer; 42, hole; 5, contact electrode; 6, dense insulating layer; 7, insulating reflective layer; 8, pad electrode; 9, back-plated insulating layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following further describes the present invention in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0030] Embodiment 1

[0031] Referring to Figure 1 、 Figure 2 As shown, a small light-emitting diode structure, the width of the small light-emitting diode structure is between 20 and 500 µm, and the length is between 20 and 1000 µm, including a substrate 1, an epitaxial structure 2 is provided on the front surface of the substrate 1, a transparent conductive layer 3 is provided on the front surface of the epitaxial structure 2, a step 20 is formed on the side surface of the epitaxial structure 2, an insulating layer 4 covers the step 20 and the front surface of the transparent conductive layer 3, the insulating layer 4 is provided with a contact area 41, a contact electrode 5 contacts the transparent conductive layer 3 and the epitaxial structure 2 through the contact area 41, a gap area is formed between the insulating layer 4 and the contact electrode 5, a dense insulating layer 6 covers the gap area, an insulating reflective layer 7 covers the dense insulating layer 6, and a through-hole area for contacting a pad electrode 8 is formed between the dense insulating layer 6 and the insulating reflective layer 7 above the contact electrode 5.

[0032] Specifically, the angle formed by the side slope of the dense insulating layer 6 and the normal of the front surface of the substrate 1 is less than the angle formed by the side slope of the insulating reflection and the normal of the front surface of the substrate 1.

[0033] Specifically, the contact area 41 includes a bottom surface 411 of the transparent conductive layer and a step surface 412 of the insulating layer. The bottom end of the contact electrode 5 contacts the bottom surface 411 of the transparent conductive layer, and the side end of the contact electrode 5 does not contact the step surface 412 of the insulating layer.

[0034] Furthermore, as Figure 3 shown, a back-plated insulating layer 9 is provided on the back surface of the substrate 1, and the back-plated insulating layer 9 is formed by stacking low-refractive-index SiO2 and high-refractive-index TiO2.

[0035] Embodiment 2

[0036] Referring to Figure 4 、 Figure 5 As shown, a small light-emitting diode structure, the width of the small light-emitting diode structure is between 20 and 500 µm, and the length is between 20 and 1000 µm, including a substrate 1, an epitaxial structure 2 is provided on the front surface of the substrate 1, a transparent conductive layer 3 is provided on the front surface of the epitaxial structure 2, a step 20 is formed on the side surface of the epitaxial structure 2, an insulating layer 4 covers the step 20 and the front surface of the transparent conductive layer 3, the insulating layer 4 is provided with a contact area 41, a contact electrode 5 contacts the transparent conductive layer 3 and the epitaxial structure 2 through the contact area 41, a gap area is formed between the insulating layer 4 and the contact electrode 5, a dense insulating layer 6 covers the gap area, an insulating reflective layer 7 covers the dense insulating layer 6, and a through-hole area for contacting a pad electrode 8 is formed between the dense insulating layer 6 and the insulating reflective layer 7 above the contact electrode 5.

[0037] Among them, the epitaxial structure 2 includes a buffer layer 21 (such as a u-GaN layer), a first semiconductor layer 22 (such as an n-GaN layer), a light-emitting layer 23 (such as a quantum well layer), and a second semiconductor layer 24 (such as a p-GaN layer) that are sequentially disposed on the front surface of the substrate 1.

[0038] Among them, the angle formed by the side slope surface of the dense insulating layer 6 and the normal line of the front surface of the substrate 1 is smaller than the angle formed by the side slope surface of the insulating reflective layer 7 and the normal line of the front surface of the substrate 1.

[0039] Specifically, the contact area 41 includes the bottom surface 411 of the transparent conductive layer and the stepped surface 412 of the insulating layer. The bottom end of the contact electrode 5 is in contact with the bottom surface 411 of the transparent conductive layer, and the side end of the contact electrode 5 is in contact with the stepped surface 412 of the insulating layer.

[0040] Embodiment Three

[0041] Referring to Figure 6 As shown, a small light-emitting diode structure includes a substrate 1. An epitaxial structure 2 is provided on the front surface of the substrate 1. A transparent conductive layer 3 is provided on the front surface of the epitaxial structure 2. A step 20 is formed on the side surface of the epitaxial structure 2. The step 20 and the front surface of the transparent conductive layer 3 are covered with an insulating layer 4. The insulating layer 4 is provided with a contact area 41. A contact electrode 5 is in contact with the transparent conductive layer 3 and the epitaxial structure 2 through the contact area 41. A gap area is formed between the insulating layer 4 and the contact electrode 5. The gap area is covered with a dense insulating layer 6. The dense insulating layer 6 is covered with an insulating reflective layer 7. A through-hole area for contacting a pad electrode 8 is formed between the dense insulating layer 6 and the insulating reflective layer 7 above the contact electrode 5.

[0042] Among them, the epitaxial structure 2 includes a buffer layer 21 (such as a u-GaN layer), a first semiconductor layer 22 (such as an n-GaN layer), a light-emitting layer 23 (such as a quantum well layer), and a second semiconductor layer 24 (such as a p-GaN layer) that are sequentially disposed on the front surface of the substrate 1.

[0043] Among them, the angle formed by the side slope surface of the dense insulating layer 6 and the normal line of the front surface of the substrate 1 is smaller than the angle formed by the side slope surface of the insulating reflective layer 7 and the normal line of the front surface of the substrate 1.

[0044] Specifically, the contact area 41 includes a plurality of holes 42 formed in the insulating layer 4. The contact electrode 5 is in contact with the transparent conductive layer 3 and the epitaxial structure 2 through the plurality of holes 42.

[0045] Embodiment Four

[0046] A method for manufacturing the small light-emitting diode structure described in Embodiments One to Three, characterized by including the following steps:

[0047] Provide a substrate 1, prepare an epitaxial structure 2 on the front surface of the substrate 1, and etch a step 20 on the epitaxial structure 2;

[0048] Prepare a layer of transparent conductive layer 3 on the front surface of the epitaxial structure 2, and prepare an insulating layer 4 on the surfaces of the transparent conductive layer 3 and the step 20;

[0049] Prepare a contact area 41 at the insulating layer 4. The contact electrode 5 contacts the transparent conductive layer 3 and the epitaxial structure 2 through the contact area 41, and a gap area is formed between the insulating layer 4 and the contact electrode 5. A dense insulating layer 6 is covered in the gap area;

[0050] Cover an insulating reflective layer 7 outside the dense insulating layer 6, and form a via hole area between the dense insulating layer 6 and the insulating reflective layer 7 above the contact electrode 5 to fabricate a pad electrode 8.

[0051] Wherein, the dense insulating layer 6 is SiO2, SiN deposited by sputtering or atomic layer deposition x , Al2O3, AlN or a stacked structure layer of 2 to 10 layers composed of the above materials, such as a multi-layer structure composed of Al2O3 / SiO2 / Al2O3 / SiO2.

[0052] Wherein, the substrate 1 includes but is not limited to sapphire, silicon wafer, silicon carbide wafer or metal.

[0053] In this embodiment, when using an MOCVD device to grow an epitaxial structure on a substrate, the epitaxial structure is a multi-layer structure, which is determined according to actual needs. For example, it can be a buffer layer, a U-GaN layer, an N-GaN layer, a multi-quantum well layer and a P-GaN layer grown in sequence, or an N-GaN layer, a multi-quantum well layer and a P-GaN layer grown in sequence. The LED chip epitaxial structure covers the entire surface of the substrate 1. MOCVD is a new type of gas-phase epitaxial growth technology developed on the basis of vapor-phase epitaxial growth (VPE).

[0054] The transparent conductive layer 3 is an ITO film. The ITO film is deposited on the P-GaN layer, and a good ohmic contact is formed between the ITO film and the P-GaN layer. Specifically, the ITO film 2 (ITO, Indium Tin Oxide) is deposited on the chip structure by using magnetron sputtering or electron beam evaporation technology, and high-temperature rapid annealing (RTA, Rapid Thermal Annealing) of an annealing furnace is used to make a good ohmic contact between the ITO film and the P-GaN layer.

[0055] Etch out the N-GaN layer in the exposed area through ICP etching technology (ICP, Inductively Coupled Plasma etching) to form an N-GaN step.

[0056] Deposit a SiO2 insulating layer on the surface of the chip structure using PECVD technology, fabricate the pad electrode pattern using negative photolithography masking technology, and fabricate N and P pad electrodes through electron beam evaporation technology.

[0057] By forming a gap between the insulating layer 4 and the contact electrode 5, and connecting the dense insulating layer 6 to the gap, so that the dense insulating layer 6 is directly connected to the bottom of the contact electrode 5, it can effectively block the migration and penetration of water vapor in the air and active metals such as Ag and Sn in the solder balls, and improve the ability to resist metal migration; and form a via area in the dense insulating layer 6 and the insulating reflective layer 7 above the contact electrode 5 as the contact area 41 of the pad electrode 8. The dense insulating layer 6 and the insulating reflective layer 7 form slopes with two angles, and the insulating reflective layer 7 improves the overall light extraction efficiency; the epitaxial structure 2 is provided with a step 20 for protection, with low leakage risk and simple fabrication, reducing the cost.

[0058] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A small light-emitting diode structure, characterized in that, It includes a substrate (1), on the front surface of the substrate (1) there is an epitaxial structure (2), on the front surface of the epitaxial structure (2) there is a transparent conductive layer (3), on the side surface of the epitaxial structure (2) there is a step (20), the step (20) and the front surface of the transparent conductive layer (3) are covered with an insulating layer (4), the insulating layer (4) is provided with a contact area (41), a contact electrode (5) contacts the transparent conductive layer (3) and the epitaxial structure (2) through the contact area (41), a gap area is formed between the insulating layer (4) and the contact electrode (5), a dense insulating layer (6) is covered above the gap area, an insulating reflective layer (7) is covered on the dense insulating layer (6), a via area for contacting a pad electrode (8) is formed between the dense insulating layer (6) and the insulating reflective layer (7) above the contact electrode (5); The angle formed by the side slope of the dense insulating layer (6) and the front normal of the substrate (1) is less than the angle formed by the side slope of the insulating reflective layer (7) and the front normal of the substrate (1); The dense insulating layer (6) is SiO2, SiN deposited by sputtering or atomic layer deposition x , Al2O3, AlN or a stack structure layer of 2 to 10 layers composed of the above materials.

2. The small light-emitting diode structure according to claim 1, characterized in that The epitaxial structure (2) includes a buffer layer (21), a first semiconductor layer (22), a light-emitting layer (23) and a second semiconductor layer (24) sequentially arranged on the front surface of the substrate (1).

3. A small light-emitting diode structure according to claim 1, characterized in that, The contact area (41) includes the bottom surface of the transparent conductive layer (411) and the stepped surface of the insulating layer (412), the bottom end of the contact electrode (5) contacts the bottom surface of the transparent conductive layer (411), and the side end of the contact electrode (5) does not contact the stepped surface of the insulating layer (412).

4. A small light-emitting diode structure according to claim 1, characterized in that The contact area (41) includes the bottom surface of the transparent conductive layer (411) and the stepped surface of the insulating layer (412), the bottom end of the contact electrode (5) contacts the bottom surface of the transparent conductive layer (411), and the side end of the contact electrode (5) contacts the stepped surface of the insulating layer (412).

5. A small light emitting diode structure according to claim 1, characterized in that, The contact area (41) includes a plurality of holes (42) formed in the insulating layer (4), and the contact electrode (5) contacts the transparent conductive layer (3) and the epitaxial structure (2) through the plurality of holes (42).

6. The small light-emitting diode structure according to claim 1, characterized in that, On the back surface of the substrate (1) there is a back plating insulating layer (9).

7. A small light emitting diode structure according to claim 1, characterized in that, The width of the small light-emitting diode structure is between 20 and 500 µm, and the length is between 20 and 1000 µm.

8. The manufacturing method of the small light-emitting diode structure according to any one of claims 1-7, characterized in that, It includes the following steps: Provide a substrate (1), prepare an epitaxial structure (2) on the front surface of the substrate (1), and etch a step (20) on the epitaxial structure (2); Prepare a layer of transparent conductive layer (3) on the front surface of the epitaxial structure (2), and prepare a layer of insulating layer (4) on the surfaces of the transparent conductive layer (3) and the step (20); Prepare a contact area (41) at the insulating layer (4), the contact electrode (5) contacts the transparent conductive layer (3) and the epitaxial structure (2) through the contact area (41), and make a gap area be formed between the insulating layer (4) and the contact electrode (5), and cover a dense insulating layer (6) in the gap area; Cover an insulating reflective layer (7) outside the dense insulating layer (6), and form a via area between the dense insulating layer (6) and the insulating reflective layer (7) above the contact electrode (5) to fabricate a pad electrode (8).

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