CN103022276B - A kind of preparation method of AC LED chip - Google Patents

Abstract

The invention provides a kind of preparation method of AC LED chip, by elder generation's deposition of microcrystalline line between the negative pole and positive pole of adjacent crystallite, on chip positive and negative electrode, realize pre-deposition, the material that namely also deposition is identical with crystallite line in advance on chip positive and negative electrode simultaneously; Then in the method deposited gold that the chip positive and negative electrode place of pre-deposition utilizes electronation gold-plated, only can deposit on the surface of gold because electronation is gold-plated, the positive and negative electrode thickness required for routing can be realized thus, namely the crystallite line thickness of pre-deposition is increased to the thickness 1.5-2 micron required for routing.Therefore, while the chip positive and negative electrode effectively forming the thick crystallite electrode of tens nanometer and 1.5-2 micron thickness, both whole the conductivity issues do not electroplated, there is no again the waste problem that electron beam evaporation is gold-plated, the waste of Au can well be avoided, significantly reduce the production cost of AC LED chip.

Description

A kind of preparation method of AC LED chip

technical field

The invention belongs to the field of semiconductors, in particular to a method for preparing an AC LED chip.

Background technique

Traditional LEDs are driven by direct current DC, and in the conversion process of AC-DC and DC-DC, the power loss reaches 20%-30%, making the circuit efficiency difficult to exceed 80%. However, the AC LED using wafer-level series technology only needs to be connected in series with a current-limiting resistor to be directly driven by the AC mains, without AC-DC conversion, and does not require a DC-DC step-down constant current source drive circuit. It completely subverts the application of traditional LEDs, and truly achieves energy saving and high efficiency.

In the AC LED chip, the microcrystals are connected by gold (Au) wires, which mainly act as a current conduction bridge, so that the current flows smoothly from the negative electrode of one microcrystal to the positive electrode of the adjacent microcrystal. Au wires of tens of nanometers are deposited. As the positive and negative electrodes of the entire AC LED chip, due to the need for wire bonding in the packaging process, the positive and negative electrodes of the chip are required to reach a certain thickness, generally between 1.5-2 microns. Therefore, when preparing AC LED chips, if the existing electron beam evaporation method is used to simultaneously vaporize the positive and negative electrodes of the chip and the microcrystalline wiring, it will lead to an extreme waste of Au wires that serve as the microcrystalline wiring; When the positive and negative electrodes of the chip are prepared by electron beam evaporation, the effective utilization rate of Au is only about 20%, which also causes a great waste of Au and increases the production cost.

Contents of the invention

The purpose of the present invention is to provide a method for preparing an AC LED chip, which can well avoid the waste of Au while effectively forming microcrystalline electrodes and positive and negative electrodes of the chip, and effectively reduce the production cost of the AC LED chip.

The purpose of the present invention is achieved through the following technical solutions:

A preparation method for an AC LED chip, comprising the following steps:

S11, growing an epitaxial wafer having a buffer layer, an n-type nitride layer, a light emitting layer and a p-type nitride layer on the substrate;

S12. Etching a plurality of steps arranged at intervals on the epitaxial wafer, the etching depth of each step reaches the n-type nitride layer;

S13, etching a groove on each step, the etching depth of the groove reaches the substrate and the etching width is smaller than the etching width of the step, thereby forming a plurality of microcrystals arranged at intervals on the epitaxial wafer;

S14, forming a passivation layer between the negative electrode and the positive electrode of adjacent crystallites;

S15, forming a current diffusion layer on the positive electrode of the chip and the microcrystal;

S16, depositing a microcrystal line between the negative electrode and the positive electrode of adjacent microcrystals, and realizing pre-deposition on the positive and negative electrodes of the chip at the same time;

S17, forming a first protection layer on the chip except for the positive and negative electrodes;

S18. Deposit gold on the pre-deposited positive and negative electrodes of the chip by chemical reduction gold plating.

In the preparation method of the AC LED chip provided by the present invention, the microcrystal wiring is first deposited between the negative and positive electrodes of adjacent microcrystals, and at the same time pre-deposition is realized on the positive and negative electrodes of the chip, that is, the positive and negative electrodes of the chip are also pre-deposited. Deposit the same material as the microcrystalline wiring; then deposit gold on the positive and negative electrodes of the pre-deposited chip by chemical reduction gold plating, because chemical reduction gold plating can only be deposited on the surface of gold, so that the required wiring can be achieved The thickness of the positive and negative electrodes, that is, increasing the thickness of the pre-deposited microcrystalline wiring to the thickness required for wiring is 1.5-2 microns. Therefore, while effectively forming the microcrystalline electrode and the positive and negative electrodes of the chip, the waste of Au can be well avoided, and the production cost of the AC LED chip can be effectively reduced.

Description of drawings

Fig. 1 is a schematic flow chart of the method for preparing an AC LED chip provided by the present invention.

Fig. 2 is a schematic structural view of an epitaxial wafer in the method for preparing an AC LED chip provided by the present invention.

Fig. 3 is a structural schematic diagram after steps are formed in the method for preparing an AC LED chip provided by the present invention.

Fig. 4 is a structural schematic diagram after grooves are formed in the method for preparing an AC LED chip provided by the present invention.

Fig. 5 is a structural schematic diagram after forming a passivation layer in the method for preparing an AC LED chip provided by the present invention.

Fig. 6 is a structural schematic diagram after forming a current diffusion layer in the method for preparing an AC LED chip provided by the present invention.

Fig. 7 is a schematic diagram of the structure of the AC LED chip preparation method provided by the present invention after forming the microcrystalline wiring and pre-depositing the positive and negative electrodes of the chip.

Fig. 8 is a schematic structural view of the AC LED chip preparation method provided by the present invention after the first protective layer is formed.

Fig. 9 is a schematic structural view of the AC LED chip preparation method provided by the present invention after the positive and negative electrodes of the chip are formed.

Fig. 10 is a schematic structural view after forming a phosphor coating in the method for preparing an AC LED chip provided by the present invention.

Fig. 11 is a schematic structural view after forming a second protective layer in the method for preparing an AC LED chip provided by the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Please refer to Figure 1, a method for preparing an AC LED chip, the method includes the following steps:

S11, growing an epitaxial wafer having a buffer layer, an n-type nitride layer, a light emitting layer and a p-type nitride layer on the substrate;

S12. Etching a plurality of steps arranged at intervals on the epitaxial wafer, the etching depth of each step reaches the n-type nitride layer;

S13, etching a groove on each step, the etching depth of the groove reaches the substrate and the etching width is smaller than the etching width of the step, thereby forming a plurality of microcrystals arranged at intervals on the epitaxial wafer;

S14, forming a passivation layer between the negative electrode and the positive electrode of adjacent crystallites;

S15, forming a current diffusion layer on the positive electrode of the chip and the microcrystal;

S16, depositing a microcrystal line between the negative electrode and the positive electrode of adjacent microcrystals, and realizing pre-deposition on the positive and negative electrodes of the chip at the same time;

S17, forming a first protection layer on the chip except for the positive and negative electrodes;

S18. Deposit gold on the pre-deposited positive and negative electrodes of the chip by chemical reduction gold plating.

In the preparation method of the AC LED chip provided by the present invention, the microcrystal wiring is first deposited between the negative and positive electrodes of adjacent microcrystals, and at the same time pre-deposition is realized on the positive and negative electrodes of the chip, that is, the positive and negative electrodes of the chip are also pre-deposited. Deposit the same material as the microcrystalline wiring; then deposit gold on the positive and negative electrodes of the pre-deposited chip by chemical reduction gold plating, because chemical reduction gold plating can only be deposited on the surface of gold, so that the required wiring can be achieved The thickness of the positive and negative electrodes, that is, increasing the thickness of the pre-deposited microcrystalline wiring to the thickness required for wiring is 1.5-2 microns. Therefore, while effectively forming tens of nanometer-thick microcrystalline electrodes and 1.5-2 micron-thick chip positive and negative electrodes, there is neither the conductive problem of the entire surface of electroplating nor the waste problem of electron beam evaporation gold plating, which can be very good. Avoiding the waste of Au effectively reduces the production cost of AC LED chips.

The following will introduce the preparation method of the AC LED chip provided by the present invention through specific embodiments.

Please refer to FIG. 2, in the step S11, an epitaxial wafer having a buffer layer 102, an n-type nitride layer 103, a light-emitting layer 104, and a p-type nitride layer 105 is grown on the substrate 101; wherein, the The material of the substrate 101 can be selected from Al ₂ O ₃ , and the specific growth method of the epitaxial wafer can be MOCVD well known to those skilled in the art, so details are not repeated here.

Please refer to FIG. 3 , in the step S12, a plurality of steps arranged at intervals are etched on the epitaxial wafer, and the etching depth of each step reaches an n-type nitride layer; wherein, the etching of the steps can be performed using Photolithography and inductively coupled plasma (ICP) technology are completed. Specifically, photolithography technology can be used to form a photoresist protective layer with the required pattern, and then ICP technology can be used to perform step (Mesa) etching on the part not protected by photoresist. Make sure to etch to the n-type nitride layer such as the GaN region, and then remove the photoresist with a glue remover, so that dozens to hundreds of steps can be etched on each chip, and each step is arranged at intervals in the epitaxial on chip. As a specific embodiment, the etching depth of the step is 1.2-1.4 microns, and the width is 40-45 microns; wherein, the width of the step is related to the design of the mask plate in photolithography, and is generally slightly larger than the chip The size of the negative electrode.

Please refer to FIG. 4, in the step S13, a groove is etched on each step, the etching depth of the groove reaches the substrate and the etching width is smaller than the etching width of the step, thereby forming a groove on the epitaxial wafer. A plurality of microcrystals arranged at intervals; wherein, the etching of the groove is similar to the etching of the steps, and can also be completed by photolithography and inductively coupled plasma (ICP) technology. Specifically, photolithography technology can be used to form the required The patterned photoresist protective layer, and then use ICP technology to perform groove etching on the part not protected by the photoresist to ensure that the etching reaches the substrate layer such as the Al ₂ O ₃ area, and then remove the photoresist with the glue remover, In this way, grooves can be etched on each step, and the etching width is smaller than the etching width of the steps; so far, the spacing arrangement of microcrystals on the epitaxial chip is completed, and the grooves can achieve the function of isolating adjacent microcrystals. As a specific embodiment, the etching depth of the trench is 6-7 microns, and the width is 20-25 microns.

Please refer to FIG. 5, in the step S14, a passivation layer 106 is formed between the negative electrode and the positive electrode of adjacent microcrystals, that is, a passivation layer is formed on the groove and the side surface of the microcrystal adjacent to the groove; wherein, the formation The method of passivation layer can be deposited on the surface of the chip by using PECVD technology, and then use BOE (Buffered Oxide Etch, referred to as oxide buffer etchant) etching solution to p-type nitride layer, steps and the p-type of each microcrystal itself. The passivation layer between the nitride layer and the step is etched to expose the positive and negative electrodes and the light-emitting area of each microcrystal, so that the microcrystal electrode can be deposited on the p-type nitride layer, thus completing the phase A structure in which a passivation layer is formed between the negative electrode and the positive electrode adjacent to the crystallite. Further, a passivation layer is formed between the negative electrode and the positive electrode of the adjacent microcrystals, which can isolate the conduction of the metal connection between the subsequent microcrystals and the light-emitting layer and the n-type nitride layer, so as to ensure that the current between the microcrystals can It flows from the negative pole of one microcrystal to the positive pole of an adjacent microcrystal to achieve the purpose of turning on the entire microcrystal chip. As a specific embodiment, the material of the passivation layer is silicon dioxide (SiO ₂ ) or silicon nitride.

Please refer to FIG. 6, in the step S15, a current diffusion layer 107 is formed on the positive electrode of the chip and the microcrystal; wherein, the formation of the current diffusion layer can be completed by photolithography technology, specifically deposited on the surface of the chip first A layer of current diffusion layer, and then use photolithography to form a photoresist protective layer with the desired pattern, and then use electrode etching solution to etch the current diffusion layer part of the steps and grooves until the n-type nitride is exposed layer and a passivation layer of SiO ₂ or silicon nitride between the negative and positive electrodes of the adjacent crystallites. As a specific embodiment, the material of the current diffusion layer is indium tin oxide (ITO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide (AZO) or indium oxide Zinc mixture (In ₂ O ₃ -ZnO).

Please refer to FIG. 7, in the step S16, a microcrystal connection line 108 is deposited between the negative and positive electrodes of adjacent microcrystals, and pre-deposition is realized on the positive and negative electrodes of the chip at the same time; wherein, the microcrystal connection line The deposition of can be accomplished by photolithography and electron beam evaporation techniques. As a specific example, the material of the microcrystalline wiring includes sequentially deposited chromium (Cr), platinum (Pt) and gold (Au), specifically deposited At this time, a Cr layer, a Pt layer, and an Au layer can be sequentially deposited on the surface of the chip, that is, deposited by electron beam evaporation three times. Etching of the Cr layer, Pt layer and Au layer in order to form a microcrystal connection between the negative and positive electrodes of adjacent microcrystals; at the same time, the Cr layer, Pt layer and Au layer on the surface of the positive and negative electrodes of the chip also need to be preserved , to realize pre-deposition on the positive and negative electrodes of the chip at the same time, the purpose of which is to effectively thicken the positive and negative electrodes of the chip on the surface of gold when the chemical reduction gold plating method is used subsequently. In fact, the microcrystalline wires are Au wires, and the deposition of Cr and Pt is only to enhance the adhesion of Au. When the microcrystalline wires are annealed, they will be in a crystalline state. At the same time, Au is selected because of its excellent electrical conductivity; of course, in the field According to the above-mentioned introduction, the skilled person can also choose other materials to replace the Au wire as the microcrystalline connection, such as silver (Ag) or copper (Cu).

Please refer to FIG. 8, in the step S17, the first protective layer 109 is formed on the chip except for the positive and negative electrodes; wherein, the method for forming the first protective layer can be carried out on the surface of the chip by using PECVD technology. Deposition, and then use photolithography technology and BOE etching solution to etch the positive electrode (p electrode) and negative electrode (n electrode) of the chip, so that the positive and negative electrodes of the chip are exposed, while other areas are protected by the first Layer protection, as a specific implementation manner, the material of the first protection layer is silicon dioxide (SiO ₂ ) or silicon nitride. The first protective layer is provided on the surface of the chip except for the positive and negative electrodes. It has two main functions. One is to effectively protect the microcrystalline connection and avoid Au being deposited on the microcrystalline connection during the subsequent chemical reduction gold plating. Continued deposition will result in waste of cost; the second is to protect the exposed light-emitting layer during the step etching to reduce the risk of leakage current.

Please refer to FIG. 9, in the step S18, gold is deposited on the positive and negative electrodes of the pre-deposited chip by chemical reduction gold plating, that is, the positive electrode 110 and the negative electrode 111 are formed respectively; as a specific implementation mode, in 1.5-2 micron thick gold is deposited at the positions of the positive and negative electrodes of the pre-deposited chip to meet the requirements of subsequent packaging and wiring. Wherein, the method of chemical reduction gold plating deposition in this step is specifically: the sample to be plated-cleaning before plating-pre-soaking, wetting the pre-deposited chip electrode surface-electroless gold plating, continuing to grow the Au layer on the pre-deposited chip electrode surface-hot water washing , Clean the potion composition on the surface of the electrode - cleaning after plating.

Further, in the method for preparing an AC LED chip provided by the present invention, after step S18, step S19 is further included: coating a phosphor coating on the microcrystalline surface between the positive and negative electrodes of the chip. Please refer to FIG. 10 for details. In the step S19, a phosphor coating 112 is coated on the microcrystalline surface between the positive and negative electrodes of the chip; wherein, the phosphor coating includes phosphor and silica gel or epoxy A mixture of resin glue, using flat coating technology or dispensing technology to form a phosphor coating on the microcrystalline surface between the positive and negative electrodes of the chip. At present, the mainstream white LED lamps on the market are all made of blue LED chips and yellow phosphor powder. Because an AC LED chip is relatively large in size, it has dozens to hundreds of crystallites, which requires both epitaxial wafers. The blue light emitted is uniform, and the yellow light emitted by the phosphor powder on each microcrystal is also required to be uniform, so as to ensure that the white light emitted by the entire AC LED is uniform. However, when using manual or automatic dispensing tools to coat the silica gel or epoxy resin mixed with phosphor powder on the surface of the chip, there are obvious deficiencies: on the one hand, the thickness of the phosphor powder coating is uneven, showing that the middle is thick, For the spherical crown with thin edges, the yellow light converted by the fluorescent powder in the middle is obviously more than the edge part, which makes the white light emitted by the LED lamp uneven in color, and locally appears yellowish or bluish uneven spots; on the other hand, whether it is manual or Automatic dispensing is dispensing one by one chip by chip, it is difficult to accurately control the dispensing amount of each chip, which will lead to different color temperatures of the same batch of dispensing chips, making the consistency of LED lights not good , limiting the popularization and application of AC LEDs.

The planar coating technology has a decisive advantage, that is, the chip is almost a pure surface emitter. When used as a white light source, this means that wavelength conversion can be performed on the chip surface to produce white light. For this purpose, the conversion material can be applied directly to the chip surface, so-called chip coating technology, instead of being incorporated into the potting compound (volume conversion), as is the case with other white light-emitting diodes. The advantage of the chip coating is that the conversion agent can be coated on the chip surface with a uniform layer thickness. Since the concentration of the phosphor powder is uniform, the light part converted by each point on the entire chip surface is almost the same. Therefore, when coating the phosphor coating on the microcrystalline surface between the positive and negative electrodes of the chip in this step, it is preferably a flat coating technology, which can ensure the uniformity of AC LED light emission to the greatest extent; further, the phosphor coating The plane coating method can be spin coating, screen printing or spray coating.

Preferably, before the step S19, it also includes: coating a layer of adhesion promoter on the microcrystalline surface between the positive and negative electrodes of the chip, which can improve the adhesion between the phosphor coating and the chip surface; specifically, the The material of the above-mentioned tackifier can be selected from hexamethyldisilazane (HMDS) or silane coupling agent: γ-(2,3-epoxypropoxy)aminopropyltriethoxysilane (KH-550) or γ-Propyltrimethoxysilane (KH-560) or γ-Methacryloxypropyltrimethoxysilane (KH-570).

Further, step S20 is also included after step S19: forming a second protective layer on the surface of the chip except the positive and negative electrodes of the chip. Please refer to FIG. 11 for details. In the step S20, a second protective layer 113 is formed on the surface of the chip except for the positive and negative electrodes of the chip; wherein, the setting of the second protective layer 113 can effectively protect the phosphor and avoid The phosphor powder is directly exposed to the air, and it can also increase the light transmission effect of the AC LED chip. As a specific implementation, the second protective layer 113 is formed by spin coating, dipping, or spraying on the surface of the chip except for the positive and negative electrodes of the chip. The material is silica gel or epoxy resin, etc.; preferably, the material of the second protective layer is silica gel, and the thickness of the coating is 1-3 microns.

So far, the preparation method of the AC LED chip provided by the present invention has completed the fabrication of the front-end of the chip, and those skilled in the art can carry out the back-end process of the chip on the basis of the aforementioned front-end fabrication, so as to complete the fabrication of the entire AC LED chip.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (12)

1. a preparation method for AC LED chip, is characterized in that, the method comprises the following steps:

S11, go out to have the epitaxial wafer of resilient coating, N-shaped nitride layer, luminescent layer and p-type nitride layer at Grown;

S12, on epitaxial wafer, etch multiple spaced step, the etching depth of each step is to N-shaped nitride layer;

S13, on each step, etch groove, the etching depth of groove is to substrate and etching width is less than the etching width of step, forms multiple spaced crystallite thus on epitaxial wafer;

S14, between the negative pole and positive pole of adjacent crystallite, form passivation layer;

S15, on the positive pole of chip and crystallite, form current-diffusion layer;

S16, between the negative pole and positive pole of adjacent crystallite deposition of microcrystalline line, simultaneously on chip positive and negative electrode, realize pre-deposition;

S17, region on chip except positive and negative electrode form the first protective layer;

S18, utilize the gold-plated method deposited gold of electronation at the chip positive and negative electrode place of pre-deposition.

2. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S12, the etching depth of step is 1.2-1.4 micron, and width is 40-45 micron.

3. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S13, the etching depth of groove is 6-7 micron, and width is 20-25 micron.

4. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S14, the material of passivation layer is silicon dioxide or silicon nitride.

5. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S15, the material of current-diffusion layer is tin indium oxide, mixes indium zinc oxide, gallium-doped zinc oxide, Al-Doped ZnO or indium oxide zinc oxide mix.

6. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S16, the deposit thickness of crystallite line is 50-100 nanometer, and its material comprises the chromium of sequential aggradation, platinum and gold.

7. the preparation method of AC LED chip according to claim 1, is characterized in that, in described step S17, the material of the first protective layer is silicon dioxide or silicon nitride.

8. the preparation method of AC LED chip according to claim 1, is characterized in that, after step S18, also comprise step S19: the microporous surface between chip positive and negative electrode applies fluorescent coating.

9. the preparation method of AC LED chip according to claim 8, is characterized in that, in described step S19, the painting method of fluorescent coating is spin coating in flat coating, silk screen printing or spraying.

10. the preparation method of AC LED chip according to claim 8, is characterized in that, also comprises before described step S19: the microporous surface between chip positive and negative electrode applies one deck tackifier.

The preparation method of 11. AC LED chips according to claim 8, is characterized in that, also comprising step S20 after step S19: form the second protective layer on the surface of chip surface except chip positive and negative electrode.

The preparation method of 12. AC LED chips according to claim 11, is characterized in that, in described step S20, the material of the second protective layer is silica gel or epoxy resin.