Preparation method of micro digital display light emitting diode

Abstract

The present application provides a preparation method of micro digital display light emitting diode. The method comprises the following steps: etching the exposed ohmic contact layer in the area outside the display pattern to form a light emitting pattern on the surface of the LED epitaxial wafer; etching the exposed ohmic contact layer in the area outside the display pattern to the substrate; preparing a first insulating layer on the upper surface of the obtained device; preparing a first electrode on the first insulating layer, the first electrode being in contact with the light emitting pattern; evaporating a second insulating layer on the upper surface of the obtained device; preparing a second electrode N electrode on the second insulating layer; the second electrode N electrode being connected with the first electrode through a wire; then preparing a second electrode P electrode, which is in contact with the ohmic contact layer on the substrate; finally, thinning through the substrate and cutting to obtain the product. The method can integrate the required pattern into the millimeter or even micrometer light emitting diode, and does not need to perform die bonding and wire bonding operation for each section, so the cost is low and the yield is high.

Description

Technical Field

[0001] This invention relates to a method for fabricating a miniature digital display light-emitting diode, belonging to the field of optoelectronic technology. Background Technology

[0002] LED digital tubes are semiconductor light-emitting devices. Their basic unit is a light-emitting diode (LED). Different currents are input to different pins to make the LEDs light up and display numbers. They are widely used in home appliances such as air conditioners, water heaters, and refrigerators, as well as in other sophisticated micro-control systems. Traditional digital tubes are actually composed of seven LED segments arranged in an "8" shape, plus a decimal point, making eight segments. These segments are represented by a, b, c, d, e, f, g, and dp. Because each segment of a traditional digital tube consists of one or more LEDs, each LED must undergo die bonding and wire bonding on a PCB, inevitably leading to high costs and low yields; it also limits the product size for use in micro-control systems. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for fabricating miniature digital display light-emitting diodes (LEDs). This method can integrate the desired pattern onto LEDs at the millimeter or even micrometer scale, and eliminates the need for die bonding and wire bonding operations on each segment, thus resulting in low cost and high yield.

[0004] The technical solution of the present invention is as follows:

[0005] A method for fabricating a miniature digital display light-emitting diode includes the following steps:

[0006] (1) Etch the area outside and inside the display pattern on the ohmic contact layer on the surface of the LED epitaxial wafer to form a light-emitting pattern; when the LED epitaxial wafer is an AlGaInP red or yellow light epitaxial wafer, the area outside and inside the display pattern is first etched to the N-AlInP confinement layer, and then the part outside the display pattern is etched to the ohmic contact layer on the substrate; when the LED epitaxial wafer is a GaN blue or green light epitaxial wafer, the ohmic contact layer needs to be deposited on the surface of the LED epitaxial layer first, and then the area outside and inside the display pattern is directly etched to the ohmic contact layer on the substrate.

[0007] (2) In areas outside the display pattern, a portion of the exposed ohmic contact layer is etched to the substrate;

[0008] (3) Prepare a first insulating layer on the upper surface of the device obtained in step (2);

[0009] (4) A first electrode is fabricated on the first insulating layer, and the first electrode is in contact with the light-emitting pattern;

[0010] (5) A second insulating layer is deposited on the upper surface of the device obtained in step (4);

[0011] (6) Fabricate a second electrode N on the second insulating layer; the second electrode N is connected to the first electrode through a wire; then fabricate a second electrode P so that it contacts the ohmic contact layer on the substrate;

[0012] (7) Thin the substrate;

[0013] (8) Cut to obtain miniature digital display light-emitting diodes.

[0014] According to the present invention, in step (1), displaying the interior of the graphic refers to the internal area formed by the graphic, while the area outside the graphic is the external area of ​​the graphic and is not the internal area.

[0015] According to a preferred embodiment of the present invention, in step (1), the displayed graphic is one or more graphics, and each graphic may be composed of one or more segments.

[0016] According to a preferred embodiment of the present invention, in step (1), when the LED epitaxial wafer is an AlGaInP red or yellow light epitaxial wafer, a substrate replacement step is further included before etching; the substrate required for substrate replacement is an insulating substrate, preferably aluminum nitride or sapphire. The complete replacement method can be implemented according to existing technology.

[0017] According to a preferred embodiment of the present invention, in step (1), when the LED epitaxial wafer is a GaN blue light or GaN green light epitaxial wafer, the ohmic contact layer deposited on the surface of the epitaxial layer of the LED epitaxial wafer is ITO, ZnO or GZO.

[0018] According to the present invention, in step (1), the etching method is an existing method.

[0019] According to a preferred embodiment of the present invention, in step (1), when the LED epitaxial wafer is an AlGaInP red or yellow epitaxial wafer, the etching depth to the N-AlInP confinement layer is 2.5-3 μm, and the etching depth to the ohmic contact layer on the substrate is 1.8-2.2 μm; when the LED epitaxial wafer is a GaN blue or GaN green epitaxial wafer, the etching depth to the ohmic contact layer on the substrate is 1.1-1.4 μm.

[0020] According to a preferred embodiment of the present invention, in step (2), the etching depth is 0.8-1.2 μm. The etching method is an existing method.

[0021] According to a preferred embodiment of the present invention, in steps (3) and (5), the first insulating layer or the second insulating layer is SiO2 or SiN, and the thickness of the first insulating layer or the second insulating layer is 1000-5000 angstroms. The method for preparing the insulating layer can be any existing technology.

[0022] According to a preferred embodiment of the present invention, in steps (4) and (6), the first electrode or the second electrode is CrPtAu, CrAu, PtAu, PdAu or CrPdAu.

[0023] According to a preferred embodiment of the present invention, in step (8), a micro digital display light-emitting diode is obtained by laser scribing or diamond cutting.

[0024] According to the present invention, when the light-emitting pattern is a plurality of patterns, each pattern is isolated from the exposed substrate obtained by etching; when the light-emitting pattern is n patterns, n second electrodes P electrodes are provided, and each pattern corresponds to one second electrode P electrode; when a pattern is composed of multiple segments, each segment is in contact with a first electrode; one or more first electrodes are connected to one or more second electrodes N electrodes through wires.

[0025] Unless otherwise specified or limited in the above technical solutions, reference is made to existing technologies for manufacturing light-emitting diodes.

[0026] Beneficial effects:

[0027] This invention integrates the desired pattern onto a light-emitting diode at the millimeter or even micrometer scale, eliminating the need for die bonding and wire bonding operations on each segment. Only wire bonding operations are required on the second electrode, resulting in low cost and high yield. The more complex the micro-display pattern, the more significant the beneficial effects of this invention. Attached Figure Description

[0028] Figure 1 This is a light-emitting pattern of a miniature digital display light-emitting diode in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of the area outside the graphic in Example 1.

[0030] Figure 3 This is a schematic diagram of the structure of the area outside the graphic in Example 2.

[0031] In the figure, a, b, c, d, e, f, and g represent each segment of the light-emitting pattern; A, B, C, D, E, F, and G represent cathode (anode) pads; and H, I, and J represent anode (cathode) pads. 1. Substrate; 2. P-type ohmic contact layer; 3. P-GaP ohmic contact layer; 4. P-AlGaInP current spreading layer; 5. P-AlInP confinement layer; 6. MQW multiple quantum well layer; 7. N-AlInP confinement layer; 8. N-AlGaInP current spreading layer; 9. N-GaAs ohmic contact layer; 10. First insulating layer; 11. First electrode; 12. Second insulating layer; 13-1 and 13-2 are the second electrodes; 2a. N-GaN ohmic contact layer; 3a. N-type confinement layer; 4a. MQW multiple quantum well layer; 5a. P-type confinement layer; 6a. P-GaN ohmic contact layer; 7a. Ohmic contact layer. A, B, C, D, E, F, G correspond to 13-1, and H, I, J correspond to 13-2. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments and the accompanying drawings, but it is not limited thereto; any luminescent pattern can be achieved by this scheme.

[0033] Example 1

[0034] A method for fabricating a miniature digital display light-emitting diode, wherein the light-emitting pattern is as follows: Figure 1 As shown, the micro digital display light-emitting diode includes, from bottom to top, a substrate 1, a P-type ohmic contact layer 2, a P-GaP ohmic contact layer 3, a P-AlGaInP current spreading layer 4, a P-AlInP confinement layer 5, an MQW multiple quantum well layer 6, an N-AlInP confinement layer 7, an N-AlGaInP current spreading layer 8, and an N-GaAs ohmic contact layer 9; it also includes a first insulating layer 10, a first electrode 11, a second insulating layer 12, and second electrodes 13-1 and 13-2.

[0035] The preparation includes the following steps:

[0036] (1) Using the MOCVD method, according to the existing method, N-GaAs buffer layer, N-GaInP barrier layer, N-GaAs ohmic contact layer 9, N-AlGaInP current spreading layer 8, N-AlInP confinement layer 7, MQW multiple quantum well layer 6, P-AlInP confinement layer 5, P-AlGaInP current spreading layer 4, P-GaP ohmic contact layer 3, and P-type ohmic contact layer 2 are grown sequentially from bottom to top on the n-GaAs temporary substrate to obtain AlGaInP red or yellow epitaxial wafers;

[0037] (2) The wafer (i.e. the upper surface of the P-type ohmic contact layer 2) from step (1) is bonded to the AlN substrate using the existing Au-Au bonding process at a temperature of 320°C, a time of 40 minutes, and a pressure of 500 kg.

[0038] (3) Remove the n-GaAs temporary substrate, N-GaAs buffer layer and N-GaInP barrier layer of the bonded wafer: Immerse the above device in a mixed solution of ammonia water with a mass concentration of 22-25%, hydrogen peroxide with a mass concentration of 30% and water to remove the n-GaAs temporary substrate of the bonded wafer. The volume ratio of ammonia water, hydrogen peroxide and water is 2:5:6. Then immerse the device in a mixed solution of hydrochloric acid with a mass concentration of 36%-38% and phosphoric acid with a mass concentration of 85% to remove the N-GaAs buffer layer and N-GaInP barrier layer. The volume ratio of hydrochloric acid and phosphoric acid is 3:2, exposing the N-GaAs ohmic contact layer 9.

[0039] against Figure 1 The luminescent pattern (i.e., three figure-eight shapes, each composed of seven segments) is etched. A structural diagram of the area outside the figure-eight shapes (referring to the internal area not composed of figure-eight shapes) is shown below. Figure 2 As shown, the specific etching steps for each figure-eight shape are as follows:

[0040] (4) By photolithography and etching, the N-GaAs ohmic contact layer 9 outside the light-emitting pattern (i.e., the area outside the "8" shape) and inside the light-emitting pattern (i.e., the internal area composed of the "8" shape) on the surface of the device obtained in step (3) is etched away with a mixture of phosphoric acid with a mass concentration of 85% and hydrogen peroxide with a mass concentration of 30% (volume ratio 1:1:5) for 20 seconds; then ICP etching is used to etch the above area to the N-AlInP confinement layer 7, so that the N-AlInP confinement layer 7 outside the light-emitting pattern (i.e., the area outside the "8" shape) and inside the light-emitting pattern (i.e., the internal area composed of the "8" shape) is exposed, and then the resist is removed; the etching depth is 2.7um (i.e., the total thickness of the N-GaAs ohmic contact layer 9 and the N-AlGaInP current spreading layer 8).

[0041] (5) By photolithography and ICP etching, the N-AlInP confinement layer 7 outside the light-emitting pattern (i.e., the area outside the "8" shape) is partially etched to the P-type ohmic contact layer 2, so that the upper surface area of ​​the P-type ohmic contact layer 2 is exposed, and then the resist is removed; the etching depth is 2.0um.

[0042] (6) The exposed area of ​​the P-type ohmic contact layer 2 is etched to the substrate 1 again by photolithography and ICP etching process, so that the upper surface area of ​​the substrate 1 is exposed, and then the resist is removed; the etching depth is 1.0um.

[0043] Etch three figure-eight shapes using the methods described in steps (4)-(6) above, such as Figure 1 As shown, after etching, there is an exposed substrate layer separating the three figure-eight shapes.

[0044] (7) A first insulating layer 10 of SiO2 with a thickness of 3000 angstroms is deposited on the entire surface of the device obtained in step (6); the first insulating layer 10 of SiO2 on the surface of the pattern is etched away by photolithography and etching processes.

[0045] (8) A first electrode 11 is deposited on the first insulating layer 10 on the N-AlInP confinement layer 7 outside the “8” shape, and an ohmic contact is formed by an alloying process (alloying temperature is 380°C). The first electrode 11 wraps around the edge of the light-emitting pattern and is in contact with the light-emitting pattern (i.e., the edge of each segment of the “8” shape is wrapped with the first electrode 11). The electrode is Au / AuGeNi / Pt / Au.

[0046] (9) A second insulating layer 12 of SiO2 with a thickness of 3000 angstroms is vapor-deposited on the entire surface of the device obtained in step (8);

[0047] (10) Seven second electrodes 13-1 (corresponding to AG in 1) are deposited on the second insulating layer 12. Each second electrode 13-1 is connected to the first electrode wrapped by the same segment of three figure-eight shapes. Second electrodes 13-2 are fabricated on the second insulating layer 12 on the P-type ohmic contact layer 2 using photolithography and lift-off processes. The second electrodes 13-2 penetrate the second insulating layer 12, the first insulating layer 10, and contact the P-type ohmic contact layer 2. Both the second electrodes 13-1 and 13-2 are CrPtAu. Each figure-eight shape shares one second electrode 13-2.

[0048] like Figure 1 As shown, H, I, and J are all second electrodes 13-2, and AG is the second electrode 13-1.

[0049] (11) Thin the substrate 1 to 180 μm;

[0050] (12) Micro digital display light-emitting diodes are obtained by means of laser scribing, diamond knife cutting and other methods.

[0051] The digital display device obtained in this example is only 2mm thick, requiring only one die bonding operation and 10 wire bonding operations; while using the traditional method, 21 LED chips are needed, the digital display device is at least 2cm thick, and 21 die bonding operations and 21 wire bonding operations are required.

[0052] Example 2

[0053] A method for fabricating a miniature digital display light-emitting diode, wherein the light-emitting pattern is as follows: Figure 1 As shown, the micro digital display light-emitting diode includes, from bottom to top, a substrate 1, an N-GaN ohmic contact layer 2a, an N-type confinement layer 3a, an MQW multiple quantum well layer 4a, a P-type confinement layer 5a, a P-GaN ohmic contact layer 6a, and an ohmic contact layer 7a; it also includes a first insulating layer 10, a first electrode 11, a second insulating layer 12, and second electrodes 13-1 and 13-2.

[0054] The preparation includes the following steps:

[0055] (1) Using the MOCVD method, an N-GaN ohmic contact layer 2a, an N-type confinement layer 3a, an MQW multiple quantum well layer 4a, a P-type confinement layer 5a, and a P-GaN ohmic contact layer 6a are sequentially grown on a sapphire substrate according to the existing method to obtain a GaN blue or green epitaxial wafer.

[0056] (2) An ohmic contact layer 7a is fabricated on the P-GaN ohmic contact layer 6a using existing processes, wherein the ohmic contact layer 7a is ITO.

[0057] against Figure 1 The luminescent pattern (i.e., three figure-eight shapes, each composed of seven segments) is etched. A structural diagram of the area outside the figure-eight shapes (referring to the internal area not composed of figure-eight shapes) is shown below. Figure 3 As shown, the specific etching steps for each figure-eight shape are as follows:

[0058] (3) The area outside the light-emitting pattern (i.e., the area outside the "8" shape) and the area inside the light-emitting pattern (i.e., the area inside the "8" shape) are etched to the N-GaN ohmic contact layer 2a through photolithography and ICP etching processes, so that the upper surface area of ​​the N-GaN ohmic contact layer 2a is exposed, and then the resist removal operation is performed; the etching depth is 1.2um.

[0059] (4) The exposed area of ​​the N-GaN ohmic contact layer 2a is etched to the substrate 1 again by photolithography and ICP etching process, so that the upper surface area of ​​the substrate 1 is exposed, and then the resist is removed; the etching depth is 1.0um.

[0060] Etch three figure-eight shapes using the methods described in steps (3)-(4) above, such as Figure 1 As shown, after etching, there is an exposed substrate layer separating the three figure-eight shapes.

[0061] (5) A first insulating layer 10 of SiO2 with a thickness of 2000 angstroms is deposited on the entire surface of the device obtained in step (4); the first insulating layer 10 of SiO2 on the surface of the pattern is etched away by photolithography and etching processes.

[0062] (6) A first electrode 11 is deposited on the first insulating layer 10 on the N-GaN ohmic contact layer 2a outside the “8” shape. The first electrode 11 wraps around the edge of the light-emitting pattern and is in contact with the light-emitting pattern (i.e., the edge of each segment of the “8” shape is wrapped with the first electrode 11). The electrode is Cr / Pt / Au.

[0063] (7) A second insulating layer 12 of SiO2 with a thickness of 2000 angstroms is vapor-deposited on the entire surface of the device obtained in step (6);

[0064] (8) Seven second electrodes 13-1 (corresponding to AG in 1) are deposited on the second insulating layer 12. Each second electrode 13-1 is connected to the first electrode wrapped by the same segment of three figure-eight shapes. Second electrodes 13-2 are fabricated on the second insulating layer 12 on the N-GaN ohmic contact layer 2a using photolithography and lift-off processes. The second electrodes 13-2 penetrate the second insulating layer 12, the first insulating layer 10, and contact the N-GaN ohmic contact layer 2a. Both the second electrodes 13-1 and 13-2 are CrPtAu. Each figure-eight shape shares one second electrode 13-2.

[0065] like Figure 1 As shown, H, I, and J are all second electrodes 13-2, and AG is the second electrode 13-1.

[0066] (9) Thin substrate 1 to 180 μm;

[0067] (10) A miniature digital display light-emitting diode is obtained by laser scribing and invisible cutting.

[0068] The digital display device obtained in this example is only 2mm thick, requiring only one die bonding operation and 10 wire bonding operations; while using the traditional method, 21 LED chips are needed, the digital display device is at least 2cm thick, and 21 die bonding operations and 42 wire bonding operations are required.

Claims

1. A method for preparing a micro digital display light emitting diode, comprising the steps of: (1) etching a display pattern and an internal area on an ohmic contact layer on a surface of an LED epitaxial wafer to form a light emitting pattern; when the LED epitaxial wafer is an AlGaInP red or yellow epitaxial wafer, the display pattern and the internal area are etched to a N-AlInP confinement layer first, and then a part of the display pattern is etched to the ohmic contact layer on the substrate; when the LED epitaxial wafer is a GaN blue or green epitaxial wafer, an ohmic contact layer is first evaporated on the surface of the epitaxial layer of the LED epitaxial wafer, and then the display pattern and the internal area are etched to the ohmic contact layer on the substrate; (2) etching a part of the exposed ohmic contact layer to the substrate in the display pattern area; (3) preparing a first insulating layer on the surface of the device obtained in step (2); (4) preparing a first electrode on the first insulating layer, the first electrode being in contact with the light emitting pattern; (5) evaporating a second insulating layer on the surface of the device obtained in step (4); (6) preparing a second electrode N electrode on the second insulating layer, the second electrode N electrode being connected to the first electrode through a wire, and then preparing a second electrode P electrode, which is in contact with the ohmic contact layer on the substrate; (7) thinning the substrate; (8) cutting to obtain a micro digital display light emitting diode.

2. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In step (1), the display pattern is one or more than two patterns, and each pattern can be composed of one or more segments.

3. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In step (1), when the LED epitaxial wafer is an AlGaInP red or yellow epitaxial wafer, a substrate replacement step is further included before etching; the substrate required for substrate replacement is an insulating substrate, which is aluminum nitride or sapphire.

4. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In step (1), when the LED epitaxial wafer is a GaN blue or GaN green epitaxial wafer, the ohmic contact layer evaporated on the surface of the epitaxial layer of the LED epitaxial wafer is ITO, ZnO or GZO.

5. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In step (1), when the LED epitaxial wafer is an AlGaInP red or yellow epitaxial wafer, the etching depth to the N-AlInP confinement layer is 2.5-3 um, and the etching depth to the ohmic contact layer on the substrate is 1.8-2.2 um; when the LED epitaxial wafer is a GaN blue or GaN green epitaxial wafer, the etching depth to the ohmic contact layer on the substrate is 1.1-1.4 um.

6. The method for fabricating a micro digital display light-emitting diode according to claim 1, characterized in that, In step (2), the etching depth is 0.8-1.2 um.

7. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In steps (3) and (5), the first insulating layer or the second insulating layer is SiO2 or SiN, and the thickness of the first insulating layer or the second insulating layer is 1000-5000 angstroms.

8. The method for fabricating a micro digital display light-emitting diode according to claim 1, characterized in that, In steps (4) and (6), the first electrode or the second electrode is CrPtAu, CrAu, PtAu, PdAu or CrPdAu.

9. The method for fabricating a miniature digital display light-emitting diode according to claim 1, characterized in that, In step (8), the micro digital display light emitting diode is obtained by laser scribing or diamond knife cutting.

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