An AlGaInP mini LED with periodically distributed contact point electrodes and a preparation method thereof

Abstract

The present invention relates to the field of LED technology, and in particular to an AlGaInP mini LED with a periodically distributed contact point electrode and a preparation method thereof, comprising the following specific steps: growing an epitaxial structure of an AlGaInP mini LED on a GaAs substrate; transferring the epitaxial layer to a sapphire substrate by bonding flipping; making a table and a P electrode; making a periodically arrayed GaAs ohmic contact point and an N contact point electrode; evaporating ITO on the surface and etching; making an N electrode; depositing a passivation layer and etching a contact hole; making a pad electrode; performing laser invisible cutting and splitting to complete core particle production. The present invention produces periodically arrayed GaAs ohmic contacts on the surface of the entire chip, and when the overall GaAs material area is the same as or smaller than that of a finger-type electrode, the current distribution is more uniform, thereby improving the overall luminous efficiency of the chip.

Description

Technical Field

[0001] The present invention relates to the technical field of LEDs, and in particular to an AlGaInP mini LED with periodically distributed contact point electrodes and a preparation method thereof. Background Art

[0002] AlGaInP material is the most suitable material for making red light LEDs, but since AlGaInP material itself is difficult to form ohmic contact directly with metal electrodes, a layer of GaAs material must be made on the top layer of the material to make ohmic contact on the N side. And since GaAs material itself has a high absorption of red light, the GaAs material except the contact electrode must be etched away.

[0003] The current popular technology is to make finger-shaped electrodes, which are fixed on the surface of semiconductor materials. As a result, when the LED chip is injected with current, most of the current flows directly from the bottom of the electrode, and only a small amount of current flows through the remaining large area, resulting in low luminous efficiency of the LED chip. If finger electrodes are added directly, the reserved area of ​​GaAs will increase. Although the current distribution is improved, the light absorption effect will be increased, and the overall luminous efficiency of the chip will still be low. Therefore, it is necessary to study how to improve the chip luminous efficiency while improving the current distribution. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an AlGaInP mini LED with periodically distributed contact point electrodes and a preparation method thereof. The present invention produces periodically and evenly distributed GaAs ohmic contact points on the surface of the entire chip. When the overall GaAs material area is the same as or smaller than the finger-type electrode area, the low light absorption effect is maintained, the current distribution is very even, and the overall luminous efficiency of the chip is improved.

[0005] The first object of the present invention is to provide a method for preparing an AlGaInP mini LED having periodically distributed contact point electrodes, comprising the following specific steps:

[0006] S1. Growing an epitaxial structure of an AlGaInP mini LED on a GaAs substrate, the epitaxial structure includes a GaAs buffer layer, a GaInP corrosion cutoff layer, a GaAs ohmic contact layer, an AlGaInP current spreading layer, a first AlInP confinement layer, a first AlGaInP waveguide layer, a multi-quantum well structure (MQW), a second AlGaInP waveguide layer, a second AlInP confinement layer, a transition layer, and a GaP window layer in sequence;

[0007] S2, depositing SiO2 on the surface of the epitaxial structure and the surface of the sapphire substrate respectively, and bonding the epitaxial structure to the sapphire substrate after polishing;

[0008] S3, etching and removing the GaAs substrate, GaAs buffer layer, and GaInP etching stop layer of the epitaxial structure to expose the GaAs ohmic contact layer;

[0009] S4, using photolithography mask technology to make a mesa pattern on the GaAs ohmic contact layer, ICP (inductively coupled plasma) etching the mesa, and using negative resist stripping technology to make a P electrode;

[0010] S5, using photolithography mask technology to make a periodic array of GaAs ohmic contact point patterns on the table, using photoresist as a mask, and ICP etching the GaAs ohmic contact points until the AlGaInP current expansion layer;

[0011] S6, using negative resist stripping technology to make an N contact point electrode on the surface of the GaAs ohmic contact point;

[0012] S7, first using electronic book evaporation technology to deposit an ITO (indium tin oxide) film on the surface of the device obtained in S6, then using photolithography mask technology to make an ITO mirror pattern, and finally etching the pattern with ITO;

[0013] S8, fabricating an N electrode on the ITO film using a negative photoresist stripping technique;

[0014] S9, using PECVD (plasma enhanced chemical vapor deposition) technology to deposit SiO2 on the surface of the device obtained in S8 to form a passivation layer;

[0015] S10, using photolithography mask technology to make contact hole patterns on the passivation layer, and then using ICP to etch the contact holes until the P / N electrodes, and using negative resist stripping technology and electron beam evaporation technology to make pad electrodes;

[0016] S11. Use mechanical grinding technology to thin and polish the sapphire, and finally perform laser cutting and splitting to complete the core particle production.

[0017] The AlGaInP mini LED of the present invention manufactures GaAs ohmic contact points distributed in a periodic array on the table of the GaAs ohmic contact layer and covers the N contact electrode, then deposits a layer of ITO film to connect the contact electrodes, and finally connects to the pad electrode. When in use, the current will flow through the entire chip and be distributed very evenly, thereby improving the overall luminous efficiency of the chip.

[0018] Furthermore, in the above technical solution S5, the etching shape of the GaAs ohmic contact point is pyramidal or conical, and the etching method is: using Cl2 / BCl3 / HBr as etching gas, back-cooling the etching disk with He, the He gas pressure is 5mTorr, and the flow rate is 4-5sccm.

[0019] The present invention uses He gas to cool the etching disk, so that the GaAs ohmic contact point can be designed into a pyramid or cone shape, which is beneficial to the subsequent coverage of the N contact electrode and the ITO film and improves the chip quality and stability.

[0020] Furthermore, in the above technical solution, the bottom diameter of the GaAs ohmic contact point is 1.5-3μm, the top diameter is less than 1.5μm, and the sum of the bottom areas of the GaAs ohmic contact points distributed in the periodic array is less than or equal to the bottom area of ​​the N electrode. The area of ​​each GaAs ohmic contact point in this technical solution is very small, and the total area is less than or equal to the contact area of ​​the finger electrode. While improving the current distribution, it does not increase the light absorption effect, greatly improving the overall luminous efficiency of the chip.

[0021] Furthermore, in the above technical solution S7, the thickness of the ITO film is 1-1.5 μm, and the transmittance is greater than or equal to 95% at 620 nm. The present invention controls the light absorption effect to a minimum by controlling the thickness and transmittance of the ITO film, and ensures that the current passes uniformly without affecting the luminous efficiency when in use.

[0022] Furthermore, in the above technical solution, the ITO film covers the entire table except the P electrode area.

[0023] Furthermore, in the above technical solution S1, the thickness of the AlGaInP current spreading layer is 3-3.5 μm, the thickness of the first AlGaInP waveguide layer is 95-105 nm, the thickness of the second AlGaInP waveguide layer is 85-95 nm, and the thickness of the GaP window layer is 9-10 μm.

[0024] Furthermore, in the above technical solution S4, the depth of the etched surface is 5.5-6.5 μm; the material of the P electrode includes Au, AuZn or AuBe, and the thickness is 700-1000 nm. The use of negative resist stripping technology in this technical solution can ensure uniform electrode patterns and improve product quality.

[0025] Furthermore, in the above technical solution S6, the material of the N contact point electrode includes Au / AuGeNi or AuGe, and the thickness is 50-100nm.

[0026] Furthermore, in the above technical solution, in S8, the material of the N electrode includes Cr / Ni / Au, and the thickness is 500-1000nm.

[0027] The second object of the present invention is to provide an AlGaInP mini LED having periodically distributed contact point electrodes manufactured by the above manufacturing method.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The AlGaInP mini LED of the present invention is manufactured by manufacturing periodically arrayed GaAs ohmic contact points on the table of the GaAs ohmic contact layer, covering the N contact electrode, then depositing a layer of ITO film to connect the contact electrodes, and finally connecting to the pad electrode. When in use, the current will flow through the entire chip and be very evenly distributed, thereby improving the overall luminous efficiency of the chip; by designing the GaAs ohmic contact points into a pyramid or cone shape, it is beneficial to the subsequent coverage of the N contact electrode and the ITO film, and improving the chip quality and stability; by designing the area of ​​each GaAs ohmic contact point to be very small, the total area is less than or equal to the contact area of ​​the finger electrode, while improving the current distribution, the light absorption effect will not be increased, and the overall luminous efficiency of the chip is greatly improved; the preparation method only needs to manufacture periodically distributed GaAs ohmic contact points on the basis of the existing technology, so as to improve the overall light output efficiency of the chip, and has high repeatability, which is of great significance for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of an AlGaInP mini LED with periodically distributed contact point electrodes according to the present invention;

[0031] Figure 2 This is a 3D schematic diagram of the GaAs ohmic contact of the present invention.

[0032] Description of the numbers in the schematic diagram:

[0033] 1. Sapphire substrate; 2. GaP window layer; 3. AlGaInP current spreading layer; 4. GaAs ohmic contact point; 5. N contact point electrode; 6. ITO film; 7. N electrode; 8. P electrode; 9. Passivation layer; 10. Pad electrode. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In the description of the present application, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present application.

[0036] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0037] See also Figure 1 to Figure 2 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the form, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1As shown, an embodiment of the present invention is an AlGaInP mini LED with periodically distributed contact point electrodes, including a sapphire substrate 1; a GaP window layer 2; an AlGaInP current spreading layer 3; a GaAs ohmic contact point 4; an N contact point electrode 5; an ITO film 6; an N electrode 7; a P electrode 8; a passivation layer 9; and a pad electrode 10; wherein some structures are the same as those of conventional mini LEDs and are omitted here. Specifically, on the transferred sapphire substrate 1, from bottom to top, there are GaP window layer 2, transition layer, second AlInP confinement layer, second AlGaInP waveguide layer, multi-quantum well structure, first AlGaInP waveguide layer, first AlInP confinement layer, AlGaInP current expansion layer 3; a P electrode 8 is formed at one end of the GaP window layer 2, and a periodic matrix distributed GaAs ohmic contact point 4 is formed on the surface of the AlGaInP current expansion layer 3, and an N contact point electrode 5 is covered on each GaAs ohmic contact point 4, and then a layer of ITO film 6 is deposited, the ITO film layer covers the entire table, and a P electrode area is reserved; an N electrode is formed at the end of the ITO film away from the P electrode, a passivation layer 9 is deposited on the entire table, and a pad electrode 10 is formed at a position corresponding to the P / N electrode. Among them, the 3D schematic diagram of the GaAs ohmic contact point is shown in the figure. Figure 2 shown.

[0040] The embodiment of the present invention further provides a method for preparing an AlGaInP mini LED having periodically distributed contact point electrodes, comprising the following specific steps:

[0041] S1. On a GaAs substrate, using MOCVD technology, grow the epitaxial structure of AlGaInP mini LED, and sequentially epitaxially grow GaAs buffer layer, GaInP corrosion cutoff layer, GaAs ohmic contact layer, AlGaInP current spreading layer, first AlInP confinement layer, first AlGaInP waveguide layer, multi-quantum well structure (MQW), second AlGaInP waveguide layer, second AlInP confinement layer, transition layer, GaP window layer;

[0042] Specifically, the thickness of the AlGaInP current spreading layer needs to be between 3-3.5 μm, the thickness of the first AlGaInP waveguide layer is 100 nm±5 nm, the thickness of the second AlGaInP waveguide layer is 90 nm±5 nm, and the thickness of the GaP window layer is 9-10 μm.

[0043] S2, depositing 3 μm thick SiO2 on the surface of the epitaxial structure and the surface of the sapphire substrate respectively, and after polishing the surface of the SiO2, bonding the epitaxial structure to the sapphire substrate;

[0044] Specifically, the surface of the epitaxial structure is roughened before depositing SiO2. The roughening solution is an iodic acid solution, including iodic acid, sulfuric acid, hydrofluoric acid, and water. The roughening depth is 0.3-0.5 μm.

[0045] S3, etching and removing the GaAs substrate, GaAs buffer layer, and GaInP etching stop layer of the epitaxial structure to expose the GaAs ohmic contact layer; specifically, using NH4OH:H2O2:H2O=1:5:5 (volume ratio) solution to remove the substrate, react until the GaInP etching stop layer is cut off, and the stop layer is removed by rinsing with hydrochloric acid to expose the GaAs ohmic contact layer.

[0046] S4. Use photolithography mask technology to make a mesa pattern on the GaAs ohmic contact layer, ICP (inductively coupled plasma) etches the mesa, and use negative photoresist stripping technology to make the P electrode; specifically, the etching depth of the mesa is controlled at 5.5-6.5μm, and the etching gas is Cl2 / BCl3 / HBr; when making the P electrode, first use photoresist to make the P electrode pattern, and then use electron beam evaporation technology to evaporate the metal to the wafer surface, and then remove the photoresist. The metal on the photoresist is removed along with the photoresist, leaving a specific pattern of metal as the electrode. The benefit of using negative photoresist stripping here makes the electrode pattern more uniform. The P electrode material specifically includes Au, AuZn or AuBe, with a thickness of 700-1000nm.

[0047] S5, using photolithography mask technology to make a periodic array of GaAs ohmic contact point patterns on the table, using photoresist as a mask, and ICP etching the GaAs ohmic contact points until the AlGaInP current expansion layer;

[0048] Specifically, the contact point pattern is first made using photolithography mask technology, and the photoresist is used as a mask to etch the GaAs ohmic contact point through ICP, all the way to the AlGaInP current expansion layer, wherein the etching gas is Cl2 / BCl3 / HBr. To ensure that the etched GaAs ohmic contact point is in a pyramid or conical shape, the etching disk is back-cooled with He, and the He gas pressure is set to 5mTorr, and the flow rate is controlled at 4-5sccm. The advantage of designing it in a pyramid or conical shape here is that it can improve the quality of subsequent N contact electrode coverage and ITO film coverage; the bottom diameter of the GaAs ohmic contact point is 1.5-3μm, and the top diameter is less than 1.5μm.

[0049] S6. Use negative resist stripping technology to make an N contact point electrode on the surface of the GaAs ohmic contact point; specifically, first use photolithography mask etching technology, then use negative resist stripping, combined with electron beam evaporation technology, to make the N contact point electrode, the specific process is consistent with the P electrode production process; the N contact point electrode specifically includes Au / AuGeNi or AuGe, with a thickness of 50-100nm.

[0050] S7, first using electronic book evaporation technology to deposit an ITO film on the surface of the device obtained in S6, then using photolithography mask technology to make an ITO mirror pattern, and finally etching the pattern with ITO;

[0051] Specifically, the thickness of the deposited ITO film is 1-1.5 μm, the transmittance is greater than or equal to 95% at 620 nm, and the ITO film pattern covers the entire table surface, exposing the P electrode area.

[0052] S8. Using negative photoresist stripping technology to make an N electrode on the ITO film; the specific process is consistent with the P electrode production process; the N electrode specifically includes Cr / Ni / Au, with a thickness of 500-1000nm.

[0053] S9. Use PECVD technology to deposit SiO2 on the surface of the device obtained in S8 to form a passivation layer; specifically, use PECVD technology to deposit SiO2 on the entire device surface with a thickness requirement of 2-5μm, and ensure that the refractive index is controlled between 1.45-1.46, wherein the reaction gases used in PECVD technology are SiH4 and N2O with a flow ratio of 1:4, and the carrier gas used is N2, accounting for 50% of the total gas flow, the RF power is 50-60W, and the cavity pressure is 90-110Pa.

[0054] S10. Use photolithography mask technology to make contact hole patterns on the passivation layer, then use ICP to etch contact holes until the P / N electrodes, and use negative photoresist stripping technology and electron beam evaporation technology to make pad electrodes; specifically, the ICP etching gas is SF6 / O2; the specific structure of the pad electrode is Ti / Al, with thicknesses of Ti100nm and Al500nm respectively, cycled 5 times, then Ni100nm, Au300nm, with a total thickness of 3.4μm.

[0055] S11, thinning and polishing the sapphire using mechanical grinding technology, and finally laser cutting and splitting to complete the core particle production. Specifically, the thinning thickness is 80-100 μm, and the polishing process is consistent with the SiO2 polishing process in S2.

[0056] The existing finger mini LED chip and the AlGaInP mini LED chip prepared by the present invention were placed in the LED wafer spot tester for voltage, wavelength and brightness tests, and the test results are shown in Table 1. Among them, the chip size is 106μm×106μm, the test current is 20mA, and the test equipment is an LED chip spot tester.

[0057] Table 1 Test results

[0058]

[0059] From the results in Table 1, it can be seen that the brightness of the AlGaInP mini LED chip prepared by the present invention can be increased by 12% compared with the existing finger mini LED chip. It can be seen that after being improved by the preparation method of the present invention, the brightness of the mini LED chip is significantly improved.

[0060] In summary, the present invention produces GaAs ohmic contacts distributed in a periodic array on the table surface of the entire chip, and produces them in a pyramid shape or a cone shape, while controlling the total area of ​​the GaAs ohmic contacts to be the same as or smaller than the area of ​​the finger-type electrodes in the entire GaAs material, so that the current distribution is very even while not increasing the light absorption effect, which can greatly improve the overall luminous efficiency of the chip.

[0061] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an AlGaInP mini LED having periodically distributed contact point electrodes, characterized in that: The specific steps include: S1. Growing an epitaxial structure of an AlGaInP mini LED on a GaAs substrate, the epitaxial structure includes a GaAs buffer layer, a GaInP corrosion cutoff layer, a GaAs ohmic contact layer, an AlGaInP current spreading layer, a first AlInP limiting layer, a first AlGaInP waveguide layer, a multi-quantum well structure, a second AlGaInP waveguide layer, a second AlInP limiting layer, a transition layer, and a GaP window layer in sequence; S2, depositing SiO2 on the surface of the epitaxial structure and the surface of the sapphire substrate respectively, and bonding the epitaxial structure to the sapphire substrate after polishing; S3, etching and removing the GaAs substrate, GaAs buffer layer, and GaInP etching stop layer of the epitaxial structure to expose the GaAs ohmic contact layer; S4, using photolithography mask technology to make a mesa pattern on the GaAs ohmic contact layer, ICP etching the mesa, and using negative resist stripping technology to make a P electrode; S5. Using photolithography mask technology to make a periodic array of GaAs ohmic contact point patterns on the table, using photoresist as a mask, ICP etching the GaAs ohmic contact points until the AlGaInP current expansion layer; the etching shape of the GaAs ohmic contact points is pyramidal or conical, and the etching method is: using Cl2 / BCl3 / HBr as etching gas, back-cooling the etching disk with He, the He gas pressure is 5mTorr, and the flow rate is 4-5sccm; S6, using negative resist stripping technology to make an N contact point electrode on the surface of the GaAs ohmic contact point; S7, first using electron beam evaporation technology to deposit an ITO film on the surface of the device obtained in S6, then using photolithography mask technology to make an ITO mirror pattern, and finally etching the pattern with ITO; S8. Fabricate an N electrode on the ITO film using a negative resist stripping technique; the bottom diameter of the GaAs ohmic contact point is 1.5-3 μm, the top diameter is less than 1.5 μm, and the sum of the bottom areas of the GaAs ohmic contact points distributed in a periodic array is less than or equal to the bottom area of ​​the N electrode; S9, using PECVD technology to deposit SiO2 on the surface of the device obtained in S8 to form a passivation layer; S10, using photolithography mask technology to make contact hole patterns on the passivation layer, and then using ICP to etch the contact holes until the P / N electrodes, and using negative resist stripping technology and electron beam evaporation technology to make pad electrodes; S11. Use mechanical grinding technology to thin and polish the sapphire, and finally perform laser cutting and splitting to complete the core particle production.

2. The preparation method according to claim 1, characterized in that: In S7, the thickness of the ITO film is 1-1.5 μm, and the transmittance at 620 nm is greater than or equal to 95%.

3. The preparation method according to claim 1, characterized in that: The ITO film covers the entire mesa except the P electrode area.

4. The preparation method according to claim 1, characterized in that: In S1, the thickness of the AlGaInP current spreading layer is 3-3.5 μm, the thickness of the first AlGaInP waveguide layer is 95-105 nm, the thickness of the second AlGaInP waveguide layer is 85-95 nm, and the thickness of the GaP window layer is 9-10 μm.

5. The preparation method according to claim 1, characterized in that: In S4, the depth of the etched mesa is 5.5-6.5 μm; the material of the P electrode includes Au, AuZn or AuBe, and the thickness is 700-1000 nm.

6. The preparation method according to claim 1, characterized in that: In S6, the material of the N-contact point electrode includes Au / AuGeNi or AuGe, and the thickness is 50-100 nm.

7. The preparation method according to claim 1, characterized in that: In S8, the material of the N electrode includes Cr / Ni / Au, and the thickness is 500-1000 nm.

8. An AlGaInP mini LED having periodically distributed contact point electrodes prepared by the preparation method according to any one of claims 1 to 7.

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