CN112768583A

CN112768583A - Flip LED chip and preparation method thereof

Info

Publication number: CN112768583A
Application number: CN202110371016.3A
Authority: CN
Inventors: 梁福盛; 肖祖峰; 黄嘉明; 张超宇; 丁亮
Original assignee: Zhongshan Dehua Chip Technology Co ltd
Current assignee: Zhongshan Dehua Chip Technology Co ltd
Priority date: 2021-04-07
Filing date: 2021-04-07
Publication date: 2021-05-07
Anticipated expiration: 2041-04-07
Also published as: CN112768583B

Abstract

The invention discloses a flip LED chip and a preparation method thereof, and belongs to the technical field of chips. The flip LED chip comprises an ITO layer, wherein one side of the ITO layer is provided with a rough surface; the composite reflection layer comprises a silver mirror layer, a silicon dioxide layer and a DBR layer which are sequentially stacked along the rough surface. In the invention, because the rough surface of the ITO layer increases the bonding strength between the ITO layer and the silver mirror layer, a metal bonding layer between the ITO layer and the silver mirror layer in the traditional flip LED chip can be omitted, the cost is saved, and the brightness is improved; the silicon dioxide layer has the effect of the protective layer of insulating layer and silver mirror layer concurrently, consequently can leave out traditional flip-chip LED chip, and the cost has been practiced thrift in the setting of metal protection layer, has increased the yield.

Description

Flip LED chip and preparation method thereof

Technical Field

The invention belongs to the technical field of chips, and particularly relates to a flip LED chip and a preparation method thereof.

Background

The problem that the light-emitting area is occupied by the electrodes in a squeezed mode to influence the light-emitting efficiency can occur in the normally-installed LED chip, so that a chip research and development worker designs an inverted structure, namely, the normally-installed chip is inverted, and light excited by a light-emitting layer is directly emitted from the other surface of the electrodes (a substrate is finally stripped, and the chip material is transparent), and the structure is used in a large number of high-power chips.

The flip LED chip has the following remarkable advantages that firstly, the flip LED chip can be used by passing large current; secondly, the size can be smaller, and the optics are easier to match; thirdly, the heat dissipation function is improved, so that the service life of the chip is prolonged; fourthly, the antistatic ability is improved; fifthly, a foundation is laid for the development of a subsequent packaging process.

The current flip LED chip mainly comprises two process directions, one is to use DBR as a reflecting layer, and the other is to use a silver mirror as a reflecting layer. However, both of these reflective layer flip-chip LED chips have their own disadvantages: the DBR reflecting layer is brittle in film quality, cracks are easy to occur during cutting and cracking, reliability is further influenced, and meanwhile, the brightness of the DBR reflecting layer is lower than that of a silver mirror reflecting layer; the silver mirror reflecting layer is easy to oxidize, so a metal protective layer is required to be added to prevent the oxidation of the silver mirror reflecting layer; in addition, the silver mirror layer has poor adhesion to the ITO layer, so a Ni metal layer is required to be added between the silver mirror layer and the ITO layer as a transition layer, and Ni itself has a light absorption effect, which reduces the reflectance of the silver mirror, thereby causing a decrease in brightness.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the flip LED chip provided by the invention has the advantages that through adjusting the chip structure and the preparation process, on the basis of simultaneously arranging the DBR reflecting layer and the silver mirror layer, the metal protective layer of the silver mirror layer and the metal bonding layer between the silver mirror layer and the ITO layer are omitted, so that the brightness of the flip LED chip is improved, the process is simplified, and the cost is saved.

The invention also provides a preparation method of the flip LED chip.

According to one aspect of the present invention, there is provided a flip LED chip including,

an ITO layer, one side of which has a rough surface;

the composite reflection layer is arranged on the rough surface and comprises a silver mirror layer, a silicon dioxide layer and a DBR layer, wherein the silver mirror layer, the silicon dioxide layer and the DBR layer are sequentially overlapped on the rough surface.

According to a preferred embodiment of the present invention, at least the following advantages are provided:

(1) in the invention, because the rough surface of the ITO layer increases the bonding strength between the ITO layer and the silver mirror layer, the metal bonding layer between the ITO layer and the silver mirror layer in the traditional flip LED chip can be omitted, and the cost is saved.

(2) Because the metal bonding layer has certain light absorption in the traditional flip LED chip, the metal bonding layer is omitted, and the brightness of the flip LED chip is further improved.

(3) In the invention, the silicon dioxide layer has the functions of the metal protective layer of the insulating layer and the silver mirror layer, so that the metal protective layer in the traditional flip LED chip can be omitted, and the cost is saved.

(4) In the invention, the silicon dioxide layer also has an insulating effect, so that the electric leakage phenomenon caused by the cracking of the DBR layer in the cutting process of the flip LED chip is avoided, and the yield of products is increased.

(5) The protective layer on traditional silver mirror layer is the TiW layer, and the crackle appears because of the stress is uneven easily after this material carries out the superalloy reaction, and this application has saved the metal protection layer, has consequently promoted the yield.

(6) According to the composite reflecting layer provided by the invention, the silver mirror layer and the DBR layer are used in a composite mode, and the silver mirror layer and the DBR layer generate a synergistic effect, so that the brightness of the flip LED chip is improved.

In some embodiments of the present invention, the thickness of the ITO layer is 30nm to 45 nm.

In some embodiments of the invention, the silver mirror layer has a thickness of 150nm to 200 nm.

In some embodiments of the invention, the thickness of the silicon dioxide layer is 250nm to 400 nm.

In some embodiments of the invention, the DBR layer has a thickness of 2500nm to 3000 nm.

According to another aspect of the present invention, a method for manufacturing the flip LED chip is provided, which includes the following steps:

s1, sequentially arranging an N-type GaN layer, a light-emitting quantum well, a P-type GaN layer and the ITO layer on a substrate;

s2, starting from the ITO layer, etching a local area of the part obtained in the step S1 until the N-type GaN layer is exposed to form an N-GaN table top;

s3, corroding the ITO layer to form the rough surface;

s4, etching the edge position of the part obtained in the step S3 until reaching the substrate to form an engraved groove;

s5, arranging a metal binding layer on the surface of the N-GaN table top;

s6, arranging the silver mirror layer on the rough surface of the component obtained in the step S5;

s7, arranging the silicon dioxide layer and the DBR layer which are fully covered on one side, away from the substrate, of the part obtained in the step S6 in sequence;

s8, etching the part obtained in the step S7 from the DBR layer to the metal binding layer to form an N conductive hole and forming a P conductive hole from the silver mirror layer in a manner of being vertical to the DBR layer;

and S9, arranging a negative electrode from the N conductive hole, and arranging a positive electrode from the P conductive hole to obtain the flip LED chip.

In some embodiments of the invention, in step S1, the substrate is sapphire.

In some embodiments of the present invention, in step S1, the method for disposing the N-type GaN layer, the light emitting quantum well, and the P-type GaN layer is MOCVD.

In some embodiments of the invention, in step S1, the ITO layer is disposed by magnetron sputtering.

In some embodiments of the invention, in step S2, the etching is performed by first fully over-etching the ITO layer in the corresponding region, and then dry-etching the light-emitting quantum well and the P-type GaN layer to the N-type GaN layer.

In some embodiments of the invention, the sufficient over-etching is to etch off 2-3 μm of the ITO protected by the photoresist by using an etching solution.

In some embodiments of the present invention, in step S3, the rough surface is provided by etching with an aqueous acid solution.

In some embodiments of the invention, the aqueous acid solution is at least one of aqueous nitric acid and aqueous sulfuric acid.

In some embodiments of the invention, the rough surface is formed by etching concentrated sulfuric acid (mass percent is more than or equal to 90%) at 50-70 ℃ for 6-10 min.

In some preferred embodiments of the present invention, the rough surface is formed by etching with concentrated sulfuric acid (98% by mass) at 60 ℃ for 8 min.

In some embodiments of the present invention, in step S3, the rough surface has rough protrusions with a height of 3nm to 5 nm.

In some embodiments of the present invention, in step S4, the etching groove is set by protecting a region outside the etching groove by photolithography, and then etching to the substrate by plasma etching.

In some embodiments of the present invention, in step S5, the metal binding layer is a metal composite layer, and the metal composite layer includes a Cr layer disposed on a surface of the N-GaN layer, and at least one of an Al layer, a Ti layer, a Pt layer, and an Au layer disposed along the Cr layer.

In some embodiments of the present invention, in step S5, the metal binding layer is disposed by combining a photolithography protection with a metal evaporation.

In some embodiments of the present invention, in step S6, the silver mirror layer is disposed by combining photolithography protection with magnetron sputtering.

In some embodiments of the present invention, the wait time between steps S6 and S7 is ≦ 3 h.

The purpose of limiting the waiting time is to minimize the contact of the silver mirror layer with oxygen in the air and to prevent oxidation of the silver mirror layer.

In some embodiments of the present invention, in step S7, the silicon dioxide layer is deposited by a plasma enhanced chemical vapor deposition method.

In some embodiments of the invention, in step S7, the DBR layer is provided by vacuum evaporation.

In some embodiments of the present invention, in step S8, the N conductive via and the P conductive via are disposed by combining a photolithography protection with a dry etching.

In some embodiments of the invention, in step S9, the material of the positive electrode and the negative electrode is AuSn alloy.

In some embodiments of the present invention, in the preparation method, after all the lithography protection steps, acetone is used to dissolve the photoresist used in the lithography protection.

Since the reagent for cleaning the photoresist is acetone after the step S6, the oxidation of the silver mirror layer is not caused; since the waiting time between the step S6 and the step S7 is less than or equal to 3h, the operation in the step S7 needs to be carried out in vacuum, which further avoids the contact between the silver mirror layer and oxygen in the air; because the fully-covered silicon dioxide layer is arranged, the silver mirror layer is isolated from being in contact with air. In conclusion, the flip LED chip provided by the invention does not need to be provided with a metal protection layer due to the special structure arrangement and the unique preparation method.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is a schematic structural view of a part obtained in step S1 of example 1 of the present invention;

FIG. 2 is a schematic structural view of a part obtained in step S2 according to example 1 of the present invention;

FIG. 3 is a schematic structural view of a part obtained in step S4 according to example 1 of the present invention;

FIG. 4 is a schematic structural view of a part obtained in step S5 in example 1 of the present invention;

FIG. 5 is a schematic structural view of a part obtained in step S6 in example 1 of the present invention;

FIG. 6 is a schematic structural view of a part obtained in step S8 in example 1 of the present invention;

fig. 7 is a schematic structural diagram of a flip LED chip obtained in embodiment 1 of the present invention.

Reference numerals:

100: a substrate;

200: an epitaxial layer; 201: an N-type GaN layer; 202: a light emitting quantum well; 203: a P-type GaN layer;

300: an ITO layer;

400: an N-GaN mesa;

500: grooving;

600: a metal binding layer;

700: a silver mirror layer;

800: a silicon dioxide layer;

900: a DBR layer;

1000: a P conductive via;

1100: an N conductive via;

1200: a positive electrode;

1300: and a negative electrode.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present numbers, and the above, below, within, etc. are understood as including the present numbers. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

The embodiment prepares a flip LED chip, and the specific process is as follows:

s1, sequentially arranging an N-type GaN layer 201, a light-emitting quantum well 202 and a P-type GaN layer 203 on a sapphire substrate 100 by an MOCVD method, and arranging an ITO layer 300 with the thickness of 30nm on the surface of the P-type GaN layer by a magnetron sputtering method;

s2, etching part of the part obtained in the step S1 from the ITO layer 300 until the N-type GaN layer 201 to form an N-GaN table 400;

s3, treating the ITO layer 300 by using concentrated sulfuric acid with the mass fraction of 98% for 8min to form a rough surface;

s4, etching the edge position of the part obtained in the step S3 to the substrate by a method of combining photoetching protection and plasma etching to form an engraved groove 500;

s5, arranging a metal binding layer 600 on the surface of the N-GaN table top 400 by adopting a method of combining photoetching protection and metal evaporation;

s6, adopting a method of combining photoetching protection with metal evaporation, and arranging a silver mirror layer 700 on the rough surface of the component obtained in the step S5, wherein the thickness of the silver mirror layer is 150 nm;

s7, within 3h after the step S6 is completed, arranging a full-coverage silicon dioxide layer 800 (with the thickness of 270 nm) and a full-coverage DBR layer 900 (with the thickness of 2800 nm) in sequence on the side, away from the substrate, of the part obtained in the step S6 by a plasma enhanced chemical vapor deposition method;

s8, a vertical DBR layer 900 is used for etching the part obtained in the step S7 from the DBR layer 900 to the metal binding layer 600 in a dry mode to form an N conductive hole 1100, and a silver mirror layer to form a P conductive hole 1000;

and S9, arranging a negative electrode 1300 made of AuSn alloy from the N conductive hole 1100, and arranging a positive electrode 1200 made of AuSn alloy from the P conductive hole 1000 to obtain the flip LED chip.

The structural schematic diagram of the component obtained in step S1 of this embodiment is shown in fig. 1; the structural schematic diagram of the part obtained in step S2 is shown in fig. 2; the structural schematic diagram of the part obtained in step S4 is shown in fig. 3; the structural schematic diagram of the part obtained in step S5 is shown in fig. 4; the structural schematic diagram of the part obtained in step S6 is shown in fig. 5; the structural schematic diagram of the part obtained in step S8 is shown in fig. 6; the schematic structure of the flip LED chip obtained in this embodiment is shown in fig. 7.

Comparative example 1

This comparative example prepared a flip-chip LED chip, which was different from example 1 in that the specific process was:

(1) in step S7, the DBR layer 900 is not provided;

(2) in step S8, etching is started perpendicular to the silicon dioxide layer.

Comparative example 2

The present embodiment prepares a flip LED chip, and the difference from embodiment 1 is that the specific process is as follows:

(1) without performing step S6, a fully-covered silicon dioxide layer and a fully-covered DBR layer were sequentially formed by a plasma-enhanced chemical vapor deposition method and a vacuum evaporation method on the side of the part obtained in step S5 away from the substrate.

Test examples

This experimental example tested the performance of the flip LED chips prepared in the examples and comparative examples. Wherein:

the brightness test method comprises the following steps: and 3 pieces of each implementation case are taken, the chip finished products obtained in each embodiment are tested by a point testing machine, and the range value of the test result is taken. The test results are shown in table 1.

Table 1 brightness results for flip LED chips obtained in the specific embodiment.

The specific cost accounting is as follows:

relative to an LED chip with a TiW metal protective layer: the price of the TiW target material is about 1000 yuan/piece; the invention omits a TiW protective layer, and can save the cost of 0.4 yuan/chip.

Relative to an LED chip with a TiW metal protective layer: the price of the TiW target material is about 1000 yuan/piece; one target can work 180RUN, 16 pieces of target work in each RUN, the invention omits a TiW protective layer, can save the cost of 0.35 yuan per piece, has the TiW thickness of 200nm, and adopts a sputtering film plating machine to carry out film plating.

Relative to an LED chip with an AgTiW/Pt/TiW/Pt/TiW/Pt metal protective layer: by referring to the common thickness of each layer in commerce, 60 pieces of film are coated by an electron beam metal evaporator, the thickness of TiW is 200nm, the thickness of Pt is 100nm, the cost of Pt is 240 yuan/g, the weight of Pt is 12g, the recovery rate of Pt is about 80%, TiW2.5 yuan/g, and about 10g is required. Therefore, the average calculation shows that the cost of the single chip is saved by about 10 yuan.

In summary, the flip-chip LED chip provided by the present invention has higher brightness than the chip with a single silver mirror layer as the reflective layer and a single DBR reflective layer, although only 2 mW to 3 mW of data is increased, those skilled in the art know that it is very difficult to increase 1 mW of data when the brightness is greater than 95 mW. In addition, the invention omits the structures of a metal protective layer and a metal bonding layer by controlling the preparation method of the flip LED chip, thereby saving the cost.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims

1. A flip-chip LED chip, comprising,

an ITO layer, one side of which has a rough surface;

2. The flip LED chip of claim 1, wherein the ITO layer is 30nm to 45nm thick.

3. The flip LED chip of claim 1, wherein the silver mirror layer is 150nm to 200nm thick.

4. The flip LED chip of claim 1, wherein the silicon dioxide layer is 250nm to 400nm thick.

5. The flip LED chip of claim 1, wherein said DBR layer thickness is 2500nm to 3000 nm.

6. A method for preparing the flip LED chip as claimed in any one of claims 1 to 5, comprising the following steps:

s3, corroding the ITO layer to form the rough surface;

s5, arranging a metal binding layer on the surface of the N-GaN table top;

7. The method according to claim 6, wherein in step S3, the rough surface is formed by etching with an aqueous acid solution.

8. The method of claim 6, wherein the waiting time between steps S6 and S7 is less than or equal to 3 h.

9. The method according to claim 6, wherein in step S7, the silicon dioxide layer is deposited by plasma enhanced chemical vapor deposition.

10. The method according to claim 6, wherein in step S9, the positive electrode and the negative electrode are made of AuSn alloy.