Flip-chip light-emitting diodes and light-emitting devices

Abstract

This application discloses a flip-chip light-emitting diode (LED) and a light-emitting device. The LED includes a semiconductor stack layer comprising, from bottom to top, a first semiconductor layer, an active layer, and a second semiconductor layer; a transparent conductive layer formed on the second semiconductor layer of the semiconductor stack layer; an insulating layer covering the semiconductor stack layer and the transparent conductive layer, the insulating layer having a first via located on the transparent conductive layer; and a first pad electrode formed on the insulating layer and filling the first via to achieve connection with the transparent conductive layer. The first via has the following shape: an arc-shaped first end, an arc-shaped second end, and a middle portion connecting the first and second ends, with the width of the first via gradually increasing from the first end to the second end. This design of the first via effectively prevents voltage rise in the flip-chip LED without affecting its anti-static performance and brightness.

Description

Technical Field

[0001] This application relates to the field of semiconductor-related technologies, and in particular to a flip-chip light-emitting diode and a light-emitting device. Background Technology

[0002] Flip-chip LEDs are widely used in various fields, such as lighting and backlighting, due to their high luminous efficiency, energy saving, environmental friendliness, and long lifespan. Among them, the biggest advantage of small-size flip-chip LED backlighting technology compared with other display technologies currently popular in the industry is that it does not present any scientific challenges in terms of materials, making it the easiest and fastest to mass-produce and bring to market.

[0003] Figure 1 This is a schematic diagram of an existing flip-chip LED. In the manufacturing process of an existing flip-chip LED, a relatively thick metal layer is formed on the semiconductor stack 20 as a contact electrode 30. The contact electrode 30 does not completely cover the semiconductor stack 20 and forms a stepped structure on the semiconductor stack 20. Subsequently, when forming the insulating layer 40, due to the thickness of the stepped structure, the insulating layer 40 has a corner above the stepped structure, making the surface of the insulating layer 40 uneven. When forming the pad electrode 50 on the insulating layer 40, the surface of the pad electrode 50 will also be uneven, resulting in poor coverage of the pad electrode 50 and a risk of breakage. Due to the poor coverage of the pad electrode 50, poor die bonding may occur during the subsequent die bonding process, or there may be a risk of breakage of the pad electrode 50, affecting the reliability of the flip-chip LED.

[0004] The traditional method to solve the above problem is to remove the contact electrode 30. However, after removing the contact electrode 30, how to prevent the voltage of the flip-chip LED from rising without affecting its anti-static performance and brightness is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a flip-chip light-emitting diode that improves the voltage rise phenomenon that easily occurs in flip-chip light-emitting diodes by changing the shape of the through hole.

[0006] Another objective is to provide a light-emitting device that employs the aforementioned flip-chip light-emitting diode.

[0007] In a first aspect, this application provides a flip-chip light-emitting diode, comprising:

[0008] The semiconductor stack layer, from bottom to top, includes a first semiconductor layer, a second semiconductor layer, and an active layer located between the two;

[0009] A transparent conductive layer is formed on the second semiconductor layer of the semiconductor stack;

[0010] An insulating layer covers the semiconductor stacked layer and the transparent conductive layer, the insulating layer having a first through-hole located on the transparent conductive layer;

[0011] The first pad electrode is formed on the insulating layer and fills the first via to achieve connection with the transparent conductive layer;

[0012] The feature is that, when viewed from directly above the flip-chip light-emitting diode, the first through-hole of the insulating layer has the following shape: a first end with an arc shape and a second end with an arc shape, and an intermediate portion connecting the first end and the second end; the width of the first through-hole gradually increases from the first end to the second end.

[0013] Secondly, this application provides a light-emitting device, which includes a substrate and a plurality of flip-chip light-emitting diodes as described in the above embodiments, fixed on the substrate.

[0014] Compared with the prior art, this application has at least the following beneficial effects: the shape design of the first through hole can effectively prevent the voltage rise of the flip-chip LED, without affecting the anti-static performance and brightness of the flip-chip LED. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of an existing flip-chip light-emitting diode;

[0017] Figure 2 This is a schematic diagram of a planar structure of a flip-chip light-emitting diode according to an embodiment of this application;

[0018] Figure 3 for Figure 2 A schematic diagram of the enlarged horizontal projection of the first through hole 601;

[0019] Figure 4 According to Figure 2 A cross-sectional view of the structure along line A-A' shown in the schematic diagram.

[0020] Figure 5 This is a schematic diagram of a planar structure of a flip-chip light-emitting diode according to another embodiment of this application;

[0021] Figure 6 This is a schematic diagram of a planar structure of a flip-chip light-emitting diode according to another embodiment of this application.

[0022] Illustration:

[0023] 10 Substrate; 20 Semiconductor stacked layer; 21 N-type semiconductor layer; 22 Active layer; 23 P-type semiconductor layer; 24 Mesa; 30 Contact electrode; 31 First contact electrode; 32 Second contact electrode; 40 Insulating layer; 50 Pad electrode; 51 First pad electrode; 52 Second pad electrode; 60 Transparent conductive layer;

[0024] 100 Substrate; 200 Semiconductor stacked layer; 201 First semiconductor layer; 202 Active layer; 203 Second semiconductor layer; 204 Mesa; 300 First current blocking layer; 310 Second current blocking layer; 400 Transparent conductive layer; 401 First groove; 501 Second groove; 600 Insulating layer; 601 First via; 602 Second via; 700 First pad electrode; 710 Second pad electrode. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or operated through other different specific embodiments, and various details in this application can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0026] In the description of this application, it should be noted that the terms "upper" and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application 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, and therefore should not be construed as a limitation on this application. In addition, the terms "first" and "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] "Viewed from directly above the flip-chip LED" refers to the view of the chip from directly above the LED when the product is conventionally positioned during use, that is, when the pad electrodes are directly above the substrate and when the substrate is below the pad electrodes. "Horizontal projected area" refers to the area obtained by projecting a structural layer directly above the LED onto the lower surface of the substrate when the product is conventionally positioned during use, that is, the area obtained by projecting a structural layer directly above the LED onto the lower surface of the substrate when the pad electrodes are directly above the substrate and when the substrate is below the pad electrodes.

[0028] According to one aspect of this application, a flip-chip light-emitting diode (LED) is provided, specifically a small-sized flip-chip LED, such as a mini-type or micro-type flip-chip LED. The size of the mini-type flip-chip LED can be as small as 90,000 μm. 2 Within this range, its length and width are 100μm to 300μm, and its height is 40μm to 100μm. The size of micro flip-chip LEDs is smaller than that of mini flip-chip LEDs, with a length and width of 1~100μm.

[0029] As an example, such as Figures 2-4 As shown, the horizontal projection shape of the flip-chip light-emitting diode is rectangular, with a long side and a short side shorter than the long side. The long side has a length L1 and the short side has a width L2.

[0030] The flip-chip light-emitting diode includes a semiconductor stack 200, which includes a first semiconductor layer 201, an active layer 202 and a second semiconductor layer 203 from bottom to top, and the semiconductor stack 200 has a mesa 204 that exposes the first semiconductor layer 201.

[0031] Preferably, the light emitted by the semiconductor stack 200 is blue or green light, and the material of the semiconductor stack is an aluminum indium gallium nitride-based semiconductor material. Specifically, the first semiconductor layer 201 is an N-type semiconductor layer, the active layer 202 is a multilayer quantum well layer, and the second semiconductor layer 203 is a P-type semiconductor layer.

[0032] When the semiconductor stack material is an aluminum indium gallium nitride-based semiconductor material, the current spreading capability of the second semiconductor layer 203 is lower than that of the first semiconductor layer 201. Therefore, a transparent conductive layer 400 is placed on the second semiconductor layer 203. The transparent conductive layer 400 almost completely covers the second semiconductor layer 203 and is electrically connected to the second semiconductor layer 203 to enhance the lateral current spreading.

[0033] An insulating layer 600 covers the semiconductor stacked layer 200 and the transparent conductive layer 400. The insulating layer 600 is provided with a first through hole 601, and the horizontal projection of the first through hole 601 falls into the horizontal projection of the transparent conductive layer 400.

[0034] The flip-chip light-emitting diode also includes a second pad electrode 710 located on the insulating layer 600. The second pad electrode 710 fills the second through hole 602 of the insulating layer 600 and contacts the first semiconductor layer 201 to achieve electrical connection.

[0035] The first pad electrode 700 is located on the insulating layer 600 and is filled with the first through hole 601 to contact the transparent conductive layer 400 to achieve connection.

[0036] Viewed from directly above the flip-chip LED, the first through-hole 601 of the insulating layer 600 has the following shape: a first end a1 with an arc shape and a second end a2 with an arc shape, and an intermediate segment a3 connecting the first end a1 and the second end. The width W3 of the intermediate segment a3, measured from the first end a1 to the second end a2, gradually increases.

[0037] The first end a1 has a relatively small and fixed radius of curvature W1, preferably, the value of W1 is at least 4 micrometers and at most 20 micrometers.

[0038] The second end a2 has a relatively large and fixed radius of curvature W2, which is greater than W1.

[0039] The first through-hole 601 is designed to be located below the first pad electrode 700, and its area, length, and width dimensions cannot exceed the area, length, and width dimensions of the pad. Preferably, the first pad electrode 700 is rectangular, and the radius of curvature W2 of the second end a2 of the first through-hole 601 is less than 1 / 2 of the length of the shorter side of the first pad electrode 700.

[0040] The middle segment a3 connects the first end a1 and the second end a2. Therefore, the width W3 of the middle segment a3 is not a fixed value. The value of W3 gradually increases from the first end a1 to the connection point of the second end a2, where it is equal to twice W2 and then gradually increases to twice W1.

[0041] It should be noted that W3 is the width of the middle segment a3, measured perpendicularly to a hypothetical centerline that runs through the first end a1, the second end a2, and the middle segment a3. The horizontal projection of the first through-hole 601 of the insulating layer 600 can be a graphic shape symmetrical about this hypothetical centerline.

[0042] The aforementioned shape design of the first via 601 effectively improves the current injection method of the first pad electrode 700, facilitating current propagation towards the second via 602 rather than concentrating below the first pad electrode 700. This improves current injection and distribution, thereby mitigating the voltage rise problem commonly encountered in flip-chip LEDs. The arc-shaped ends of the first via 601 minimize sharp corners or points, reducing the tip effect caused by current accumulation at sharp points, enhancing anti-static performance, and thus lowering the risk of electrode failure.

[0043] Preferably, the horizontal projected area of ​​the first through-hole 601 of the insulating layer 600 occupies 10-70% of the horizontal projected area of ​​the first pad electrode 700. The first through-hole 601 has a relatively large projected area, which facilitates the injection of current from the first pad electrode 700 into the transparent conductive layer 400 over a larger area, thereby facilitating the lateral expansion of the current. Preferably, the horizontal projected area of ​​the first through-hole 601 of the insulating layer 600 occupies 30-60%, 10-30%, or 60-70% of the horizontal projected area of ​​the first pad electrode 700.

[0044] Since the current spreading performance of the first semiconductor layer 201 is better than that of the second semiconductor layer 203, the horizontal projection width of the second via 602 can be smaller. For example, the horizontal projection width of the second via 602 is between 4 and 20 micrometers, and the shape of the horizontal projection of the second via 602 is preferably circular.

[0045] Preferably, the second through-hole 602 of the insulating layer 600 is located at a corner of the upper surface of the first semiconductor layer 201.

[0046] To further improve current distribution, thereby benefiting light distribution and brightness, the voltage is reduced. For example... Figure 2 As shown, the distance between the center of the second through hole 602 of the insulating layer 600 and the first end a1 of the first through hole 601 is greater than the distance between the center of the second through hole 602 of the insulating layer 600 and the second end a2 of the first through hole 601. Specifically, the first end a1 has a top point e1, the second end a2 has a top point e2, the distance between the top point e1 and the second through hole 602 (based on the center position of the second through hole 602) is D1, and the distance between the top point e1 of the first end a1 and the second through hole 602 is greater than the distance D2 between the top point e2 of the second end a2 and the second through hole 602.

[0047] By designing the distance D1 between the top e1 of the relatively narrow first end a1 and the center of the second through hole 602 to be greater than the distance D2 between the top e2 of the relatively wide second end a2 and the center of the second through hole 602, a larger proportion of the current can be injected closer to the position of the second through hole 602, thereby achieving uniformity of current distribution and uniformity of brightness.

[0048] As an example, such as Figure 2 As shown, the line connecting the first end a1 with a top point e1 and the second end a2 with a top point e2 is perpendicular to the long side L1 of the light-emitting diode.

[0049] Preferably, the transparent conductive layer 400 is made of one or two of indium tin oxide, indium oxide, tin oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, and gallium phosphide, and the thickness of the transparent conductive layer 400 is preferably 10 to 300 nm.

[0050] In this embodiment, there is no metal layer between the transparent conductive layer 400 and the insulating layer 600 covering the transparent conductive layer 400. That is, the first pad electrode 700 directly contacts the transparent conductive layer 400 through the first through hole 601.

[0051] In one implementation, see Figure 4 The transparent conductive layer 400 also includes a first groove 401, which extends from the upper surface of the transparent conductive layer 400 to the interior of the transparent conductive layer 400, and the depth of the first groove 401 is 1% to 30% of the thickness of the transparent conductive layer 400, for example, 1% to 10%.

[0052] The first groove 401 is located below the first through hole 601, and the projection of the first groove 401 in the projection direction perpendicular to the platform 210 falls into the projection of the first through hole 601. That is to say, the width of the first groove 401 is less than or equal to the width of the first through hole 601.

[0053] The angle between the wall of the first through hole 601 and the upper surface of the transparent conductive layer 400 is 15° to 60°. The first through hole 601 has a minimum width at its interface with the transparent conductive layer 400, that is, the width of the first through hole 601 near the transparent conductive layer 400 is the minimum width of the first through hole 601. The width of the first groove 401 is less than or equal to the minimum width of the first through hole 601.

[0054] Preferably, the top opening width of the first groove 401 is equal to the bottom opening width of the first through hole 601. The top opening width of the first groove 401 is greater than the bottom opening width of the first groove 401. The depth of the first groove 401 is greater than or equal to 1 nm and less than or equal to 90 nm, for example, between 1 and 10 nm.

[0055] Preferably, the first pad electrode 700 extends from the upper surface of the insulating layer 600 into the first groove 401, and the bottom and wall surfaces of the first groove 401 are rough surfaces to enhance the bonding ability between the first pad electrode 700 and the transparent conductive layer 400.

[0056] The insulating layer 600 includes, but is not limited to, a distributed Bragg reflector. The insulating layer 600 is made of at least two of different materials selected from SiO2, TiO2, ZnO2, ZrO2, Cu2O3, and Al2O3. Specifically, the insulating layer 600 includes a distributed Bragg reflector fabricated using techniques such as electron beam evaporation or ion beam sputtering, where two materials are alternately stacked in multiple layers. Alternatively, the insulating layer 600 may be a single-layer structure, including but not limited to an aluminum oxide layer, a titanium oxide layer, a silicon oxide layer, or a silicon nitride layer. The thickness of the insulating layer 600 is between 1 and 6 micrometers.

[0057] The materials of the first pad electrode 700 and the second pad electrode 710 can be materials such as aluminum, chromium, nickel, titanium, platinum, tin, gold, or alloys composed of at least two of these materials. The material of the transparent conductive layer 400 includes one or two of indium tin oxide, indium oxide, tin oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, and gallium phosphide, and the thickness of the transparent conductive layer 400 is preferably 30~300 nm.

[0058] In one implementation, see Figure 4 It also includes a second groove 501, which extends from the upper surface of the first semiconductor layer 201 to the interior of the first semiconductor layer 201, and the depth of the second groove 501 is 1% to 30% of the thickness of the first semiconductor layer 201.

[0059] The second groove 501 is located below the second through hole 602, and the projection of the second groove 501 in the projection direction perpendicular to the platform 210 falls into the projection of the second through hole 602. That is to say, the width of the second groove 501 is less than or equal to the width of the second through hole 602.

[0060] The angle between the wall of the second through hole 602 and the upper surface of the transparent conductive layer 400 is 15° to 60°. The second through hole 602 has a minimum width at its interface with the transparent conductive layer 400, that is, the width of the second through hole 602 near the transparent conductive layer 400 is the minimum width of the second through hole 602. The width of the second groove 501 is less than or equal to the minimum width of the second through hole 602.

[0061] Preferably, the top opening width of the second groove 501 is greater than the bottom opening width of the second groove 501.

[0062] Preferably, the depth of the second groove 501 is greater than or equal to 1 nm and less than or equal to 90 nm. The bottom opening width of the second groove 501 is 4~12 μm.

[0063] Preferably, the second pad electrode 710 extends from the upper surface of the insulating layer 600 into the second groove 501, and the wall surface of the second groove 501 is rough to enhance the bonding ability between the second pad electrode 710 and the transparent conductive layer 400.

[0064] In one implementation, such as Figure 5 As shown, viewed from directly above the flip-chip LED, the distance between the first end a1 and the second through hole 602 is greater than the distance between the second end a2 and the second through hole 602. Specifically, the first end a1 has a tip e1, and the second end a2 has a tip e2. The distance between the tip e1 of the first end a1 and the center position of the second through hole 602 is W1. The distance between the tip e1 of the second end a1 and the center position of the second through hole 602 is greater than the distance W2 between the tip e2 of the second end a2 and the second through hole 602.

[0065] By designing the first through hole 601 of the insulating layer 600 to have a relatively narrow first end a1 and a greater distance between it and the second through hole 602 than the relatively wide second end a2 and a greater distance between it and the second through hole 602, a larger proportion of the current can be injected closer to the position of the second through hole 602, thereby achieving uniformity of current distribution and uniformity of brightness.

[0066] like Figure 5 As shown, the line connecting the first end a1 with top point e1 and the second end a2 with top point e2 is not perpendicular to the long side of the light-emitting diode.

[0067] In another implementation, such as Figure 6 As shown, viewed from directly above the flip-chip LED, the second via of the insulating layer is located at a corner of the upper surface of the first semiconductor layer. The distance between the first end a1 and the second via 602 is greater than the distance between the second end a2 and the second via 602. Specifically, the first end a1 has a tip e1, and the second end a2 has a tip e2. The distance between the tip e1 of the first end a1 and the second via 602 (based on the center position of the second via 602) is W1. The distance between the tip e1 of the first end a1 and the second via 602 is greater than the distance W2 between the tip e2 of the second end a2 and the second via 602.

[0068] By designing the relatively narrow distance between the first end a1 and the second through hole 602 to be greater than the relatively wide distance between the second end a2 and the second through hole 602, a larger proportion of the current can be injected closer to the position of the second through hole 602, thereby achieving uniformity of current distribution and uniformity of brightness.

[0069] like Figure 6 As shown, the line connecting the first end a1 with a top point e1 and the second end a2 with a top point e2 is parallel to the long side of the light-emitting diode.

[0070] In one implementation, see Figures 2-4 The flip-chip light-emitting diode also includes a substrate 100, which is one of a sapphire flat substrate, a sapphire patterned substrate, a silicon carbide substrate, a gallium nitride substrate, a gallium arsenide substrate, or a silicon substrate. In this embodiment, the substrate 100 is selected as a sapphire patterned substrate, and the semiconductor stack layer 200 is formed on the upper surface of the sapphire patterned substrate.

[0071] According to one aspect of this application, a light-emitting device is provided, which can be a backlight display device, such as a television, mobile phone, panel, or RGB display screen. Whether it is a backlight display device or an RGB display screen, the light-emitting device includes a substrate and a plurality of flip-chip light-emitting diodes (LEDs) as described in the above embodiments, fixed on the substrate. The flip-chip LEDs are integrated and mounted on an application substrate or packaging substrate in quantities of hundreds, thousands, or tens of thousands to form the light-emitting source portion of the backlight display or RGB display.

[0072] As can be seen from the above technical solutions, this application forms a transparent conductive layer on the semiconductor stacked layer. The first pad electrode contacts the transparent conductive layer, which avoids the insulating layer covering the transparent conductive layer from having corners, thereby reducing the risk of breakage of the first pad electrode and giving the first pad electrode good coverage. The design of the first via in the insulating layer having a relatively narrow first end with a greater distance to the second via than a relatively wide second end with the second via allows a larger proportion of current to be injected closer to the second via, thereby achieving uniform current distribution and brightness, preventing current accumulation at the ends, and improving anti-static capability.

[0073] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A flip-chip light-emitting diode, comprising: The semiconductor stack layer, from bottom to top, includes a first semiconductor layer, a second semiconductor layer, and an active layer located between the two; A transparent conductive layer is formed on the second semiconductor layer of the semiconductor stack; An insulating layer covers the semiconductor stacked layer and the transparent conductive layer, the insulating layer having a first through-hole located on the transparent conductive layer; The first pad electrode is formed on the insulating layer and filled into the first through-hole to achieve connection with the transparent conductive layer; A second pad electrode is formed on the insulating layer, the insulating layer having a second via, and the second pad electrode is connected to the first semiconductor layer through the second via. The feature is that: when viewed from directly above the flip-chip light-emitting diode, the first through-hole of the insulating layer has the following shape: having an arc-shaped first end and an arc-shaped second end, and an intermediate portion connecting the first end and the second end; the width of the first through-hole gradually increases from the first end to the second end. Viewed from directly above the flip-chip LED, the second through-hole is circular, and the distance between the center of the second through-hole in the insulating layer and the first end of the first through-hole is greater than the distance between the center of the second through-hole in the insulating layer and the second end of the first through-hole.

2. The flip-chip light-emitting diode according to claim 1, characterized in that: The first and second ends of the arc have fixed radii of curvature, and the radius of curvature of the arc shape at the first end is smaller than that at the second end.

3. The flip-chip light-emitting diode according to claim 1, characterized in that: Viewed from directly above the flip-chip LED, the semiconductor stack is rectangular, with a long side and a short side that is shorter than the long side.

4. The flip-chip light-emitting diode according to claim 1, characterized in that: The first pad electrode contacts the transparent conductive layer within the first through-hole.

5. The flip-chip light-emitting diode according to claim 1, characterized in that: The horizontal projected area of ​​the first through hole in the insulating layer occupies 10-70% of the horizontal projected area of ​​the first pad electrode.

6. The flip-chip light-emitting diode according to claim 1, characterized in that, The transparent conductive layer further includes a first groove extending downward from the upper surface of the transparent conductive layer into its interior, the depth of the first groove being 1% to 30% of the thickness of the transparent conductive layer.

7. The flip-chip light-emitting diode according to claim 6, characterized in that, The first groove is located below the first through hole, and the width of the first groove is less than or equal to the width of the first through hole.

8. The flip-chip light-emitting diode according to claim 6, characterized in that, The width of the top opening of the first groove is greater than the width of the bottom opening of the first groove.

9. The flip-chip light-emitting diode according to claim 1, characterized in that, The angle between the wall of the first through hole and the upper surface of the transparent conductive layer is 15°~60°.

10. The flip-chip light-emitting diode according to claim 1, characterized in that, The second via of the insulating layer is located at a corner of the upper surface of the first semiconductor layer.

11. A light-emitting device, characterized in that, It includes a substrate and a plurality of flip-chip light-emitting diodes as described in any one of claims 1 to 10, which are fixed on the substrate.

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