High-brightness reverse-polarity AlGaInP light-emitting diode and preparation method thereof

Abstract

The application relates to a preparation method of a high-brightness reverse-polarity AlGaInP light-emitting diode. A nano mask is evaporated on a wafer surface, a photoetching cutting path pattern is cut, then ICP etching is used to form a cutting path and roughen a light-emitting area, and finally the nano mask is removed. The process of forming the cutting path by ICP etching simultaneously completes the roughening of the light-emitting area, only one etching is needed to complete two processes, the photoetching process for roughening mask manufacturing is not needed, the preparation process is simplified, the process flow is greatly reduced, compared with the production cycle of the existing preparation method, the production cycle of the application is reduced by 10-12%, the production efficiency is greatly improved, and the production cost is reduced due to the fact that multiple photoetching and etching are not needed.

Description

Technical Field

[0001] This invention relates to a method for fabricating a high-brightness reverse polarity AlGaInP light-emitting diode, belonging to the field of optoelectronic technology. Background Technology

[0002] As one of the most valued light source technologies, LEDs are characterized by their small size, low current and low voltage operation for energy saving, robust structure, strong impact and vibration resistance, and ultra-long lifespan. Quaternary AlGaInP, a semiconductor material with a direct wide bandgap, has been widely used in the fabrication of various optoelectronic devices. Because AlGaInP emits light across the red to yellow-green wavelengths of the visible spectrum, visible light emitting diodes (LEDs) made from it have attracted considerable attention. LEDs, especially AlGaInP (quaternary) red high-brightness LEDs, are widely used in outdoor displays, surveillance lighting, automotive lighting, and many other applications.

[0003] Currently, for quaternary AlGaInP reverse polarity light-emitting diodes, AlGaInP is generally roughened to improve its brightness. To further improve the brightness, GaP in the etched channels also needs to be roughened. To achieve the above roughening effect, a mask needs to be fabricated by photolithography after ICP etching of the etched channels, and wet roughening of AlGaInP and GaP is performed separately. The process is complex and involves side etching, which affects performance, cost and efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for fabricating a high-brightness, reverse-polarity AlGaInP light-emitting diode. This method involves depositing a nanomask using PECVD or an evaporation stage, simultaneously roughening both AlGaInP and GaP during the ICP etching process. This method eliminates the need for photolithography to create a roughening mask and can simultaneously complete the etching and roughening processes, significantly reducing the number of steps, improving production efficiency, and lowering costs.

[0005] The technical solution of the present invention is as follows:

[0006] A high-brightness reverse-polarity AlGaInP light-emitting diode and its fabrication method are disclosed. The high-brightness reverse-polarity AlGaInP light-emitting diode comprises, from bottom to top, a permanent substrate ohmic contact electrode, a permanent substrate, a mirror, a dielectric film, a P-type ohmic contact layer, a P-GaP ohmic contact layer, a P-AlGaInP current spreading layer, a P-AlInP confinement layer, an MQW (Multiple Quantum Well) layer, an N-AlGaInP confinement layer, an N-AlGaInP current spreading layer, an N-AlGaInP roughening layer, an N-GaAs ohmic contact layer, and an N-face electrode. The method includes the following steps:

[0007] (1) Using the MOCVD method, N-GaAs buffer layer, N-GaInP barrier layer, N-GaAs ohmic contact layer, N-AlGaInP roughening layer, N-AlGaInP current spreading layer, N-AlInP confinement layer, MQW multiple quantum well layer, P-AlInP confinement layer, P-AlGaInP current spreading layer and P-GaP ohmic contact layer are sequentially grown on an n-GaAs temporary substrate.

[0008] (2) A dielectric layer is deposited on the epitaxial wafer in step (1), and then a P-type ohmic contact layer is formed after photolithography, evaporation, etching and stripping.

[0009] (3) A reflective mirror is deposited on the surface of the wafer obtained in step (2);

[0010] (4) Bond the wafer obtained in step (3) to the permanent substrate;

[0011] (5) Remove the n-GaAs temporary substrate and N-GaInP barrier layer from the bonded wafer;

[0012] (6) Erosion away the N-GaAs ohmic contact layer outside the electrode area;

[0013] (7) An N-surface electrode is deposited on the N-GaAs ohmic contact layer retained in step (6), and an ohmic contact is formed by an alloying process;

[0014] (8) A nanomask is deposited on the wafer surface obtained in step (7), a dicing pattern is etched, and then ICP etching is used to form the dicing and roughen the light-emitting area. The nanomask is then removed.

[0015] (9) Thin the permanent substrate, then deposit ohmic contact metal and alloy it to form a permanent substrate ohmic contact electrode;

[0016] (10) Light-emitting diodes are obtained by laser scribing or diamond cutting.

[0017] According to a preferred embodiment of the present invention, in step (3), the reflector is a gold mirror or a silver mirror.

[0018] According to a preferred embodiment of the present invention, in step (4), the bonding method is Au-Au bonding or Au-In bonding, the bonding temperature is 200-350℃, the pressure is 200-500kg, and the time is 30-50min.

[0019] According to a preferred embodiment of the present invention, in step (5), a mixed solution of ammonia, hydrogen peroxide and water is used to remove the n-GaAs temporary substrate of the bonded wafer; the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:4:5.

[0020] According to a preferred embodiment of the present invention, in step (5), a mixed solution of hydrochloric acid and water is used to remove the N-GaInP barrier layer; in the mixed solution, the volume ratio of hydrochloric acid to water is 3:2.

[0021] According to a preferred embodiment of the present invention, in step (8), the nanomask is SiO2 or ITO, and its thickness is 20 angstroms to 100 angstroms.

[0022] According to a preferred embodiment of the present invention, the specific method for forming the dicing path and roughening the light-emitting area in step (8) is as follows: Adjust the ICP etching parameters to RF power 350–450 W, ICP power 650–750 W, pressure 5.5–6.5 mT, temperature 18–22 °C, chlorine gas 55–65 sccm, boron trichloride 18–22 sccm, adjust the photoresist thickness to 2.6–3.2 μm, etch for 6–9 min, and continue etching for 2–5 min after the photoresist is completely etched away to complete the roughening of the light-emitting area. There is a very thin and relatively rough mask on the wafer surface. Before the epitaxial layer is etched, the mask is etched first. Since the mask etching rate is relatively low, the rough mask morphology is transferred to the wafer surface during etching, achieving a roughening effect.

[0023] According to a preferred embodiment of the present invention, in step (8), removing the nanomask specifically involves: after etching is completed, etching the nanomask or roughening the light-emitting area with hydrochloric acid and then continuing etching for 1 to 3 minutes.

[0024] For any technical solutions not described in detail or limited above, reference shall be made to existing technologies for manufacturing light-emitting diodes.

[0025] Beneficial effects:

[0026] This invention utilizes ICP etching to simultaneously roughen the light-emitting region during the formation of the dicing channel. In contrast, existing processes roughen the light-emitting region by fabricating a roughening mask and performing wet etching before electrode deposition. This invention only requires one etching operation to complete both processes simultaneously, eliminating the need for photolithography to fabricate the roughening mask. This simplifies the fabrication process and significantly reduces the number of steps. Compared to existing fabrication methods, the production cycle of this invention is reduced by 10-12%, greatly improving production efficiency. Furthermore, since multiple photolithography and etching processes are not required, production costs are reduced. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the high-brightness reverse polarity AlGaInP light-emitting diode of the present invention.

[0028] Figure 2 This is a SEM image of the nano-ITO mask prepared according to the present invention.

[0029] In the figure, 1 is the permanent substrate ohmic contact electrode, 2 is the permanent substrate, 3 is the mirror, 4 is the dielectric film, 5 is the P-type ohmic contact layer, 6 is the P-GaP ohmic contact layer, 7 is the P-AlGaInP current spreading layer, 8 is the P-AlInP confinement layer, 9 is the MQW (Multiple Quantum Well) layer, 10 is the N-AlInP confinement layer, 11 is the N-AlGaInP current spreading layer, 12 is the N-AlGaInP roughening layer, 13 is the N-GaAs ohmic contact layer, and 14 is the N-face electrode. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0031] Example 1

[0032] A method for fabricating a high-brightness reverse-polarity AlGaInP light-emitting diode, such as... Figure 1 As shown, the high-brightness reverse polarity AlGaInP light-emitting diode, from bottom to top, includes a permanent substrate ohmic contact electrode 1, a permanent substrate 2, a reflector 3, a dielectric film 4, a P-type ohmic contact layer 5, a P-GaP ohmic contact layer 6, a P-AlGaInP current spreading layer 7, a P-AlInP confinement layer 8, an MQW multiple quantum well layer 9, an N-AlInP confinement layer 10, an N-AlGaInP current spreading layer 11, an N-AlGaInP roughening layer 12, an N-GaAs ohmic contact layer 13, and an N-surface electrode 14, and includes the following steps:

[0033] (1) Using the MOCVD method, N-GaAs buffer layer, N-GaInP barrier layer, N-GaAs ohmic contact layer 13, N-AlGaInP roughening layer 12, N-AlGaInP current spreading layer 11, N-AlInP confinement layer 10, MQW multiple quantum well layer 9, P-AlInP confinement layer 8, P-AlGaInP current spreading layer 7 and P-GaP ohmic contact layer 6 are sequentially grown on an n-GaAs temporary substrate.

[0034] (2) A SiO2 dielectric film is deposited on the P-GaP ohmic contact layer 6, and then the ohmic contact layer 5 is formed by photolithography etching and evaporation and peeling.

[0035] (3) Deposit gold reflector 3 onto the surface of the wafer obtained in step (2);

[0036] (4) The wafer obtained in step (3) is bonded to a permanent silicon substrate with Au-Au bonded at a bonding temperature of 300°C, a bonding time of 45 minutes, and a bonding pressure of 400 kg.

[0037] (5) The temporary n-GaAs substrate of the debonded wafer is removed by a mixed solution of ammonia, hydrogen peroxide and water, wherein the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:4:5; the N-GaInP barrier layer is removed by a mixed solution of hydrochloric acid and water, wherein the volume ratio of hydrochloric acid and water in the mixed solution is 3:2, exposing the N-GaAs ohmic contact layer 13.

[0038] (6) Eroding away the N-GaAs ohmic contact layer 13 outside the electrode area;

[0039] (7) Deposit AuGeNiPtAu electrode 14 on the N-GaAs ohmic contact layer 13 retained in step (6), and alloy at 380°C for 10 min to form an ohmic contact;

[0040] (8) An ITO nanomask with a thickness of 50 angstroms was deposited using an electron beam evaporation device. Figure 2 Then, a dicing pattern is formed using photolithography. The ITO within the dicing pattern is etched away. The ICP etching parameters are adjusted to RF power 400W, ICP power 700W, pressure 6mT, temperature 20℃, chlorine gas 60sccm, and boron trichloride 20sccm. The dicing pattern is then formed using ICP etching. The photoresist thickness is adjusted to 2.8μm, and etching is performed for 9 minutes. After the photoresist is completely etched away, etching continues for 2 minutes to roughen the light-emitting area. After etching, the ITO nanomask is etched away using hydrochloric acid.

[0041] (9) The permanent substrate 2 is thinned to 160 μm, and the ohmic contact metal TiAu is deposited by vapor deposition and alloyed at 200℃ for 10 min to form the permanent substrate ohmic contact electrode 1.

[0042] (10) Light-emitting diodes are obtained by laser scribing or diamond cutting.

[0043] Example 2

[0044] A method for fabricating a high-brightness reverse polarity AlGaInP light-emitting diode, the specific steps are the same as in Example 1, except that in step (8), an ITO nanomask with a thickness of 100 angstroms is deposited by electron beam evaporation equipment, and then a dicing pattern is formed by photolithography. The ITO in the dicing pattern is etched away, and then the dicing is formed by ICP etching. The ICP etching parameters are adjusted to RF power 450W, ICP power 750W, pressure 6.5mT, temperature 22℃, chlorine gas 65sccm, boron trichloride 22sccm, and the photoresist thickness is adjusted to 3.0μm. The etching is carried out for 7.5min. After the photoresist is completely etched away, the etching continues for 2min to complete the roughening of the light-emitting area. After the etching is completed, the ITO nanomask is etched away by hydrochloric acid.

[0045] Example 3

[0046] A method for fabricating a high-brightness reverse polarity AlGaInP light-emitting diode, the specific steps are the same as in Example 1, except that in step (8), an ITO nanomask with a thickness of 20 Å is deposited by electron beam evaporation equipment, and then a dicing pattern is formed by photolithography. The ITO in the dicing pattern is etched away, and then the dicing is formed by ICP etching. The ICP etching parameters are adjusted to RF power 350W, ICP power 650W, pressure 5.5mT, temperature 18℃, chlorine gas 55sccm, boron trichloride 18sccm, and the photoresist thickness is adjusted to 2.6μm. The etching is carried out for 8.5min. After the photoresist is completely etched away, the etching continues for 2.5min to complete the roughening of the light-emitting area. The etching continues for another 1.5min to completely remove the ITO nanomask, further simplifying the process.

[0047] Comparative Example 1

[0048] A method for fabricating a high-brightness reverse-polarity AlGaInP light-emitting diode, the specific steps are the same as in Example 1, except that...

[0049] In step (8), a dicing pattern is formed using photolithography. The ICP etching parameters are adjusted to RF power 400W, ICP power 700W, pressure 6mT, temperature 20℃, chlorine gas 60sccm, and boron trichloride 20sccm. Then, the dicing pattern is formed using ICP etching. After step (8) and before step (9), an additional step is added: a roughened mask pattern is created using photolithography, and then roughened using a wet process. After roughening, the resist is removed.

[0050] Compared to the production cycle of Comparative Example 1, Example 1 of the present invention reduces one photolithography process, achieving roughening of AlGaInP, and shortens the production cycle by 10%. Example 2 shortens the production cycle by 10%, and Example 3 shortens the production cycle by 12%.

Claims

1. A method for fabricating a high-brightness reverse-polarity AlGaInP light-emitting diode, characterized in that, The high-brightness reverse polarity AlGaInP light-emitting diode comprises, from bottom to top, a permanent substrate ohmic contact electrode, a permanent substrate, a reflector, a dielectric film, a P-type ohmic contact layer, a P-GaP ohmic contact layer, a P-AlGaInP current spreading layer, a P-AlInP confinement layer, an MQW multiple quantum well layer, an N-AlGaInP confinement layer, an N-AlGaInP current spreading layer, an N-AlGaInP roughening layer, an N-GaAs ohmic contact layer, and an N-face electrode, and includes the following steps: (1) Using the MOCVD method, N-GaAs buffer layer, N-GaInP barrier layer, N-GaAs ohmic contact layer, N-AlGaInP roughening layer, N-AlGaInP current spreading layer, N-AlInP confinement layer, MQW multiple quantum well layer, P-AlInP confinement layer, P-AlGaInP current spreading layer and P-GaP ohmic contact layer are sequentially grown on n-GaAs temporary substrate; (2) A dielectric layer is deposited on the epitaxial wafer in step (1), and then a P-type ohmic contact layer is formed after photolithography, evaporation, etching and stripping. (3) A reflective mirror is deposited on the surface of the wafer obtained in step (2); (4) Bond the wafer obtained in step (3) to the permanent substrate; (5) Remove the n-GaAs temporary substrate and N-GaInP barrier layer from the bonded wafer; (6) Erosion away the N-GaAs ohmic contact layer outside the electrode area; (7) An N-face electrode is deposited on the N-GaAs ohmic contact layer retained in step (6), and an ohmic contact is formed by an alloying process; (8) A nanomask is deposited on the wafer surface obtained in step (7), a dicing pattern is etched, and then ICP etching is used to form the dicing and roughen the light-emitting area. The nanomask is then removed. The specific method for forming the dicing path and roughening the light-emitting area is as follows: Adjust the ICP etching parameters to RF power 350~450W, ICP power 650~750W, pressure 5.5~6.5mT, temperature 18~22℃, chlorine gas 55~65sccm, boron trichloride 18~22sccm, adjust the photoresist thickness to 2.6~3.2μm, etch for 6~9min, and continue etching for 2~5min after the photoresist is completely etched away to complete the roughening of the light-emitting area; The removal of the nanomask specifically involves: after etching, etching away the nanomask or roughening the light-emitting area with hydrochloric acid, and then continuing etching for 1~3min. (9) Thin the permanent substrate, then deposit ohmic contact metal and alloy it to form a permanent substrate ohmic contact electrode; (10) Light-emitting diodes are obtained by laser scribing or diamond cutting.

2. The preparation method according to claim 1, characterized in that, In step (3), the reflector is a gold mirror or a silver mirror.

3. The preparation method according to claim 1, characterized in that, In step (4), the bonding is Au-Au bonding or Au-In bonding, the bonding temperature is 200~350℃, the pressure is 200~500kg, and the time is 30~50min.

4. The preparation method according to claim 1, characterized in that, In step (5), a mixed solution of ammonia, hydrogen peroxide and water is used to remove the n-GaAs temporary substrate of the bonded wafer; the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:4:

5.

5. The preparation method according to claim 1, characterized in that, In step (5), a mixed solution of hydrochloric acid and water is used to remove the N-GaInP barrier layer; in the mixed solution, the volume ratio of hydrochloric acid to water is 3:

2.

6. The preparation method according to claim 1, characterized in that, In step (8), the nanomask is SiO2 or ITO, and its thickness is 20 angstroms to 100 angstroms.

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