CN106856220A

CN106856220A - The flip LED device and its cutting unit and preparation method of wafer level encapsulation

Info

Publication number: CN106856220A
Application number: CN201510900839.5A
Authority: CN
Inventors: 郝茂盛; 张楠; 袁根如
Original assignee: Shanghai Xinyuanji Semiconductor Technology Co Ltd
Current assignee: Shanghai Xinyuanji Semiconductor Technology Co Ltd
Priority date: 2015-12-08
Filing date: 2015-12-08
Publication date: 2017-06-16
Anticipated expiration: 2035-12-08
Also published as: CN106856220B

Abstract

The present invention relates to the flip LED device and its cutting unit and preparation method of wafer level encapsulation.The flip LED device of wafer level encapsulation, including：LED chip comprising more than one LED chip wafer/array of upside-down mounting, electrically-conductive backing plate and fluorescent material transparency carrier, the one side of wherein described electrically-conductive backing plate is provided with metal level a and is bonded with the electrode metal of LED chip, and another side is provided with the electrode that metal level b forms the LED component；The electrically-conductive backing plate is provided with groove and opens the electrode isolation of LED component；The exiting surface that the fluorescent material transparency carrier peels off growth substrates with the LED chip is combined.LED component of the invention, has peeled off growth substrates, improves light extraction efficiency of the light in chip, and the launching efficiency of fluorescent material reduces the blue light side leakage produced after encapsulation, so as to improve the overall performance of device；Also, electrode is isolated by groove, it is to avoid cumbersome wiring and insulation set, while realizing efficient film upside-down mounting, reduce packaging cost.

Description

Flip LED device packaged in wafer level, and segmentation unit and manufacturing method thereof

Technical Field

The invention relates to the field of semiconductor illumination, in particular to a wafer level packaged flip LED device, a segmentation unit and a manufacturing method thereof.

Background

In recent years, LED (light emitting diode) products have been rapidly developed for illumination. Compared with the traditional light source, the LED has the advantages of long service life, small volume, energy conservation, high efficiency, high response speed, shock resistance, no pollution and the like, and is considered as a green illumination light source which can enter the field of common illumination.

As the LED product packaging which is started and stopped in the LED industry chain, the LED packaging plays a key role in the whole industry chain. For packaging, the key technology is based on how to extract light emitted by the chip as much as possible within a limited cost range, and meanwhile, the packaging thermal resistance is reduced, and the reliability is improved. During the encapsulation process, the encapsulation material and the encapsulation mode are the main factors. With the continuous development of high luminous efficiency, power, high reliability and low cost of the LED product, the requirement on packaging is higher and higher, and on one hand, the LED product packaging must meet the requirements of having high enough light extraction efficiency and luminous flux when considering the aspects of light emitting angle, light color uniformity and the like; on the other hand, the package must meet the heat dissipation requirements of the chip. Therefore, the development and innovation of the packaging materials such as the chip, the phosphor, the substrate, the thermal interface material and the like and the corresponding packaging mode are urgently needed to improve the heat dissipation capability and the light extraction efficiency of the LED product.

Under the rapid development of the chip technology of the LED product, the packaging form of the LED product is also developed from a single chip packaging manner to a multi-chip packaging manner. Its package structure also goes from Lamp package to SMD package to CoB package and RP package technologies.

The pin type package (Lamp) adopts a lead frame as a pin of various package shapes, is an LED product package structure which is firstly researched and developed successfully to be put on the market, and has various varieties and high technical maturity. Surface mount packaging (SMD) is an advanced process because it reduces the space area occupied by the product, reduces weight, allows large allowable working current, and is particularly suitable for automated mounting production, and it is in line with the trend of the whole electronic industry to convert from Lamp packaging to SMD packaging. However, in the application, there are problems such as heat dissipation, light emission uniformity, and reduction in light emission efficiency.

The CoB (chip board) packaging structure is developed on the basis of the multi-chip packaging technology, and the CoB packaging structure is to directly mount a bare chip on a circuit board, bond the bare chip with the circuit board through a bonding wire, and then perform passivation and protection on the chip. The CoB has the advantages that: the light is soft, the circuit design is simple, the cost is high, the system space is saved, and the like, but the technical problems of integrating the brightness, the color temperature and the system are existed.

The remote fluorescent packaging technology (RP) is an LED product light source form which is characterized in that a plurality of blue light LED products and fluorescent powder are separately placed, and the blue light emitted by the LED products is uniformly incident on the fluorescent powder layer after being mixed by a reflector, a diffuser and the like, and finally uniform white light is emitted. Compared with other packaging structures, the RP packaging technology has more outstanding performance: firstly, the fluorescent powder is far away from the LED product chip, the fluorescent powder is not easily influenced by the heat generated by the PN junction, especially some silicate fluorescent powder is easily influenced by high temperature and high humidity, the thermal quenching probability of the fluorescent powder can be reduced after the fluorescent powder is far away from a heat source, and the service life of a light source is prolonged. Secondly, the structure that the fluorescent powder is far away from the chip design is beneficial to taking out light, and the light emitting efficiency of the light source is improved. Moreover, the structure can emit light with uniform spatial distribution and high color consistency. In recent years, ultraviolet-excited remote packaging technology attracts people's high attention, and compared with the traditional ultraviolet light source, the ultraviolet-excited remote packaging technology has unique advantages including low power consumption, fast light-emitting response, high reliability, high radiation efficiency, long service life, no environmental pollution, compact structure and the like, and becomes one of new research hotspots of various companies and research institutions in the world.

The flip chip technology is a relatively new technical concept in the field of LEDs, but has been widely applied and matured in the conventional IC industry, such as various Ball Grid Array (BGA), Chip Scale Package (CSP), Wafer Level Chip Scale Package (WLCSP), etc., all of which adopt the flip chip technology, and has the advantages of high production efficiency, low device cost and high reliability. The flip chip technology is applied to LED devices, and is mainly different from IC in that, in the LED chip manufacturing and packaging process, besides the stable and reliable electrical connection needs to be processed, the problem of light needs to be processed, including how to let more light come out, so as to improve the light extraction efficiency, and the distribution of light space.

Aiming at the problems of poor heat dissipation, uneven current distribution of a transparent electrode, light blocking of a surface electrode pad and a lead wire and reliability caused by a gold wire of the traditional normally-installed LED, in 1998, J.J.Wierer et al prepare a high-power AlGaInN-LED blue light chip with a 1W flip-chip welding structure, and flip-chip-weld an AIGalnN chip with metalized bumps on a silicon carrier with an anti-static protection diode (ESD). Their test results show that flip-chip LED chips (FCLEDs) have larger light emitting areas and very good electrical characteristics than the forward-chip chips under the same chip area, and the forward Voltage (VF) is relatively low in the current range of 200-.

In 2006, o.b. shchekin et al reported a new thin film flip-chip bonded multi-quantum well structured LED (TFFC-LED). The so-called thin film flip-chip LED combines the concepts of thin film LED and flip-chip LED. After the LED is flipped on the substrate, the sapphire substrate is stripped off by using a Laser lift-off (Laser lift-off) technique, and then a surface roughening is performed on the exposed N-type GaN layer by using a photoetching technique. The LED with the thin film structure can effectively increase the light extraction efficiency. However, the structure is relatively complex and expensive.

In addition, since LED was originally developed and all package supports and forms were designed based on the LED chip in its normal or vertical configuration, the flip LED chip had to be flip-mounted on a silicon substrate, then the chip was mounted on a conventional support, and then electrodes on the silicon substrate were connected to electrodes on the support with gold wires. The existence of gold wires in the packaged device is ensured, and the advantage of flip-chip gold-wire-free packaging is not utilized; but also increases the cost of the substrate, so that the price is higher, and the advantages of the flip LED chip are not exerted at all.

As silicon-based flip chips are marketed, it has been increasingly discovered that these flip LED chips are still at a disadvantage in terms of their performance and/or cost when they compete with the front-mounted chips.

Disclosure of Invention

The invention provides a wafer level packaged flip LED device, a segmentation unit and a manufacturing method thereof.

First, the present invention provides a flip-chip LED device of wafer level package, comprising: a flip-chip LED chip die/array comprising more than one LED chip, a conductive substrate and a phosphor transparent substrate,

the LED chip comprises a P-type metal bonding pad, an N-type metal bonding pad and an electrode isolation walkway for isolating the P-type metal bonding pad from the N-type metal bonding pad;

one surface of the conductive substrate is provided with a metal layer a, and the metal layer a is in metal bonding with a P-type metal bonding pad and an N-type metal bonding pad of the LED chip; the other surface of the conductive substrate is provided with a metal layer b, and the metal layer b forms a P-type metal bonding pad and an N-type metal bonding pad of the LED device; a through groove corresponding to the electrode isolation walkway is arranged on the conductive substrate and isolates a P-type metal pad and an N-type metal pad of the LED device;

the fluorescent powder transparent substrate comprises a transparent substrate and fluorescent powder colloid in the transparent substrate and/or on at least one surface of the transparent substrate, and the fluorescent powder transparent substrate is combined with the light-emitting surface of the LED chip with the growth substrate peeled off.

The invention also provides a flip LED device segmentation unit formed by segmenting the flip LED device packaged in the wafer level.

The invention also provides a manufacturing method of the flip LED device packaged in the wafer level, which comprises the following steps:

(a) providing an LED chip die/array comprising more than one LED chip with a growth substrate, the LED chip comprising a P-type metal pad, an N-type metal pad and an electrode isolation walkway separating the P-type metal pad and the N-type metal pad;

(b) providing a conductive substrate, wherein one surface of the conductive substrate is provided with a metal layer a, and the metal layer a is in metal bonding with a P-type metal bonding pad and an N-type metal bonding pad of the LED chip; the other surface of the conductive substrate is provided with a metal layer b, and the metal layer b forms a P-type metal bonding pad and an N-type metal bonding pad of the LED device; a through groove corresponding to the electrode isolation walkway is arranged on the conductive substrate and isolates a P-type metal pad and an N-type metal pad of the LED device;

(c) stripping the growth substrate of the LED chip to expose the light-emitting surface of the LED chip;

(d) providing a fluorescent powder transparent substrate, wherein the fluorescent powder transparent substrate comprises a transparent substrate and a fluorescent powder colloid in the transparent substrate and/or on at least one surface of the transparent substrate;

(e) the fluorescent powder transparent substrate is combined with the light-emitting surface of the LED chip with the growth substrate stripped off, so that a wafer level packaged flip LED device with a fluorescent powder transparent substrate structure is formed;

wherein the preparation of the LED chip wafer/array comprising more than one LED chip, the conductive substrate and the fluorescent powder transparent substrate is not in sequence.

The flip LED device of wafer level packaging of the invention strips the growth substrate, realizes the bonding and isolation of electrodes of flip and reduction, reduces the absorption of the growth substrate to light, reduces the blue light side leakage of the packaged LED, greatly improves the excitation efficiency of fluorescent powder, improves the light emitting efficiency, uniformity and reliability of light on a chip, and improves the heat dissipation and mechanical strength of the device, thereby improving the overall performance of the device.

According to the manufacturing method of the flip LED device of the wafer level packaging, wafer level packaging and flip are realized, and meanwhile, complicated insulation and wiring operations are omitted through bonding of the conductive substrate and the LED chip electrode and isolation of the through groove from the electrode, so that the process is greatly simplified, and the production cost is reduced. Furthermore, the operation of stripping the growth substrate by a chemical method can be easily realized by the matching arrangement of the deep etching walkways between the through grooves and the LED chips.

Drawings

FIG. 1 is a schematic structural diagram of a strip-shaped composite pattern substrate according to the present invention;

FIG. 2 is a schematic cross-sectional view of FIG. 1;

FIG. 3 is a schematic structural view of a bar-shaped composite pattern substrate according to a second structure of the present invention;

FIG. 4 is a schematic structural view of a striped composite pattern substrate according to a third structure of the present invention;

FIG. 5 is a schematic view of an epitaxial structure grown on a composite patterned substrate material in accordance with the present invention;

FIG. 6 is a schematic structural diagram of an LED chip die with a flip-chip structure according to the present invention;

FIG. 7 is an enlarged schematic view of a cross section of one of the LED chip units of FIG. 6;

FIG. 8 is a schematic structural diagram of a conductive substrate and an LED chip die bonded according to the present invention;

FIG. 9 is an enlarged schematic view of the cross-section of FIG. 8;

FIG. 10 is a schematic structural view of the lift-off growth substrate of FIG. 9;

FIG. 11 is a chip die with a conductive substrate with a finished device electrode according to the present invention;

FIG. 12 is a schematic view of a transparent substrate according to the present invention;

FIG. 13 is a schematic view of another transparent substrate according to the present invention;

FIG. 14 is a schematic structural view of the phosphor transparent substrate filled with the phosphor colloid of FIG. 13;

fig. 15 is a schematic structural view of the phosphor transparent substrate after the microstructure is arranged on the light-emitting surface of fig. 14;

fig. 16 is a schematic structural diagram of fig. 11 after combination with a phosphor transparent substrate (i.e., a flip-chip LED device with a die-level package having a phosphor transparent substrate structure);

fig. 17 is a schematic structural diagram of a divided unit of the flip-chip LED device of fig. 16.

Description of the element reference numerals

1 composite pattern substrate

101 growth substrate

102 AlN layer

103 silicon dioxide layer

2 LED chip unit

201N type semiconductor growth layer

202 quantum well

203P type semiconductor growth layer

204 chip N-type metal pad

205 chip P-type metal pad

206 electrode isolation walkway

207 sidewall insulating layer

208 side wall mirror layer

209P type ohmic contact layer and reflector layer

210 electrode insulating layer

3 deep etching walkway

4 conductive substrate

401 metal layer a

402 metal layer b

403 through groove

404P-type metal pad and N-type metal pad of LED device

5 fluorescent powder transparent substrate

501 transparent substrate

502 groove

503 fluorescent powder colloid

504 pyramid structure

6 fluorescent powder unit

Detailed Description

The following description of the embodiments of the present invention is provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure of the present specification. The present invention may be variously modified or changed without departing from the spirit of the present invention defined by the claims.

The term "die-level package" refers to an overall package that is implemented directly on an undivided LED chip die or LED chip array.

The term "LED chip die/array comprising more than one LED chip" refers to a combination of LED chips comprising an array arrangement of more than one LED chip (preferably more than two LED chips) obtained according to conventional methods and the methods specifically enumerated below.

The term "metal bonding" refers to the bonding of two wafers face to face by the action of a metal bond, diffusion between the metal and the wafer surface, melting of the metal, etc., through a pure metal or alloy. For further theory and examples see "metal bonding techniques and their use in optoelectronic devices" by Shexingsheng et al ("advances in laser and optoelectronics", Vol. 44, volume 1, month 1 2007, pages 31-37).

The term "coupled" is intended to describe a connection between elements, which is considered to fall within the scope of "coupled" as long as the objects of the invention are achieved; in other words, such a connection falls within the scope of "bonding" as long as it can achieve the function and effect that the connection is intended to achieve, and for this reason, further subdivision is not made, for example, whether the connection is physically or chemically bonded is not examined. For example, the adhesive bonding method is adopted, such as a thermosetting adhesive or a light curing adhesive, specifically, an adhesive composed of a binder of polyolefin, polyvinyl acetate and a vinyl acetate copolymer, polyacrylate, or a thermoplastic resin such as polyvinyl chloride and perchloroethylene. Alternatively, the adhesive may also be present as a colloidal substance (i.e., a substance having adhesive properties) in the phosphor colloid, i.e., the phosphor colloid and the light-emitting surface are cured to achieve bonding.

In the present invention, the flip-chip LED device of wafer level package includes: a flip-chip LED chip die/array comprising more than one LED chip, a conductive substrate and a phosphor transparent substrate,

wherein,

The flip LED device packaged at the wafer level is the flip LED device with the growth substrate stripped, and the light outlet surface of the flip LED device is a fluorescent powder transparent substrate surface. The device structure can reduce the packaging cost, improve the luminous efficiency of the packaged device, the uniformity and the reliability of light emission, and reduce the blue light side leakage of the packaged light-emitting diode. In addition, the combination of the fluorescent powder transparent substrate and the light-emitting surface of the LED chip with the growth substrate peeled off is adopted, so that the mechanical strength of the light-emitting surface of the final LED device is enhanced, and the light efficiency is further improved by roughening the surface of the fluorescent powder transparent substrate. In addition, through the arrangement of the conductive substrate and the through groove on the conductive substrate, on one hand, the conductive substrate can be used as a transfer substrate to fix the LED chip when the growth substrate is stripped, and on the other hand, the conductive substrate directly forms an electrode pad of the LED device.

Generally, in the prior art, a through-silicon via technology and an electroplating technology are required to be adopted to wire electrodes of a silicon-based semiconductor chip, and the side walls of the through-silicon via and the electrode regions are insulated regionally, so as to avoid short circuit of devices. According to the invention, through the arrangement of the through grooves, the through grooves directly isolate the electrode pads on the conductive substrate, so that complicated insulation and wiring operations in the traditional process are omitted.

In a specific embodiment, the electrode of the LED chip die is an electrode with a same side structure, and the LED chip die includes: the chip comprises a chip N-type metal pad, a chip P-type metal pad, an electrode isolation walkway, a chip side wall insulating layer, a chip side wall reflector layer, a chip P-type ohmic contact layer, a reflector layer, a P-type ohmic contact layer and an electrode insulating layer on the reflector layer.

In a specific embodiment, the materials of the P-type ohmic contact layer and the mirror layer may be any materials that can ensure that the metal and the P-type semiconductor form ohmic contact and ensure that all emergent light from the front surface of the chip is reflected to the direction of the substrate layer of the composite pattern, for example, one or a combination of several of ITO, ZnO, Ni, Ag, Au, Cr, Al, and the like. Preferably ITO, Ni, Ag or Ag material. In a specific embodiment, the P-type ohmic contact layer and the mirror layer are layers formed using three materials of ITO, Ni and Ag, respectively, and their thicknesses are, for example: ITO: 200A-1200A, Ni: 3A-20A, Ag: 1000-.

In particular embodiments, any epitaxy that may be used in LEDs to fabricate LED chip dies may be used, such as GaN, InP, GaAs, Ge, BN epitaxy, and the like, which are commercially available or may be self-prepared.

The conductive substrate is a substrate which is conductive, highly conductive and easy to process to form a through groove by mechanical or chemical corrosion, such as a silicon substrate, a copper substrate and the like, and preferably a silicon substrate. For the metal layer a on one surface of the conductive substrate for performing metal bonding with the P, N metal pad of the LED chip, all metals that can be bonded with the metal pad can be used as the metal layer a on the conductive substrate, specifically, Ti, Cr, Al, Au, In, Sn, or Au Sn alloy, etc. And the metal layer b on the other side of the conductive substrate can be made of the same or different material as the metal layer a, forms an ohmic contact layer with the conductive substrate, and finally forms an electrode pad of the LED device.

In an embodiment of the invention, the flip-chip LED device packaged at wafer level is provided, wherein the P-type metal pads and the N-type metal pads of the adjacent LED chips are asymmetrically arranged, so that the electrode isolation walkways of the adjacent electrodes are staggered. The electrode isolation walkways are arranged in a staggered mode, and the through grooves corresponding to the electrode isolation walkways are also arranged in a staggered mode, so that the conductive substrate is a whole piece no matter the through grooves are formed before or after the conductive substrate is in metal bonding with the LED chip, and the whole moving and processing in the processing process are facilitated. When the LED device with the structure is further divided, a single LED chip unit with the P-type metal bonding pad and the N-type metal bonding pad separated by the through groove is obtained.

Of course, it is also within the scope of the present invention for the connected through-slots to be formed on the conductive substrate by the electrode isolation walkways that are regularly arranged with the P-type metal pads and the N-type metal pads of the adjacent LED chips. The LED device with the structure has a plurality of continuous electrode bonding pads of the same type, so that a plurality of LED chips can be divided into units, and the high-voltage LED chips are formed. With this structure, it is preferable to perform the arrangement of the through-groove after the metal layer a of the conductive substrate is metal-bonded to the electrode pad of the LED chip, so that the entire operation of the conductive substrate is still achieved.

In one embodiment of the invention, in the flip-chip LED device with wafer level packaging, deep etching walkways are arranged between the LED chips, and the etching depth is up to the growth substrate layer when the growth substrate is not stripped from the LED chips; the length of the through groove is larger than that of the electrode isolation walkway, and at least one end of the through groove is communicated with the deep etching walkway. The arrangement of the deep etching walkway and the through groove can lead the through groove and the deep etching walkway to form a chemical stripping channel for the liquid medicine to enter the growth substrate, thereby being convenient for realizing the stripping of the growth substrate by adopting a chemical stripping technology.

In a specific embodiment, the deep etching path has a depth of more than 6 microns to a depth of a bottommost portion of the growth substrate layer.

In a particular embodiment, the width of the electrode isolation walkway/through groove may not exceed 30 microns, preferably not 20 microns. Preferably, the width of the through groove is smaller than the width of the electrode isolation walkway.

In a further embodiment of the present invention, the growth substrate is a growth substrate composed of a multilayer material, comprising: (A) selectingA growth substrate formed from one of a silicon wafer, a glass wafer, sapphire, a copper substrate, etc., and optionally (B) Al₂O₃、SiO₂A layer of one or more materials selected from SiN, AlN, etc., preferably Al, on the growth substrate₂O₃、SiO₂And AlN. When a chemical stripping technique is adopted to strip the growth substrate, the (B) is a necessary option.

In a further embodiment of the invention, the surface of the growth substrate, which is connected with the LED chip, is uneven, and a gap is formed between the growth substrate and the LED chip. The gap is beneficial to enabling liquid medicine to enter the growth substrate layer when the growth substrate is stripped by adopting a chemical stripping technology, so that the stripping of the growth substrate is realized more quickly. For example, the gap is a stripe-shaped gap formed by a cross section of a triangle, a trapezoid, a rectangle, etc. protruding from the growth substrate. As shown in fig. 1-4, which are schematic structural views of several different structural growth substrates of the present invention. Further, the gap is preferably larger than 1 to 10 micrometers. In a specific embodiment, the long axis of the through slots may be arranged perpendicular to the strip-shaped gaps.

In an embodiment of the invention, one surface of the transparent substrate of the flip-chip LED device with wafer level packaging has a flat surface and/or periodic grooves, the phosphor colloid is disposed on the flat surface of the transparent substrate and/or in the periodic grooves, and the surface of the phosphor colloid is combined with the light-emitting surface of the LED chip with the growth substrate peeled off. A transparent substrate having periodic grooves is preferred. Several different phosphor transparent substrate configurations are specifically shown in fig. 12-15.

In a further embodiment of the present invention, the width and length of the groove of the transparent substrate are respectively matched with the width and length of the phosphor colloid in the groove, and the width and length of the phosphor colloid in the groove are respectively greater than the width and length of the LED chip bonded to the phosphor colloid; preferably, the width and length of the phosphor gel in the groove are 1-10 micrometers greater than the width and length, respectively, of the LED chip bonded to the phosphor gel.

In a further embodiment of the present invention, the depth of the groove of the transparent substrate is matched with the thickness of the phosphor colloid, which is matched with the final color coordinate of the LED device, i.e., the amount of phosphor required by the LED chip; the groove depth of the transparent substrate is preferably 10 to 100 μm.

In a further embodiment of the present invention, the phosphor colloid is a transparent solid converted from a mixture of a phosphor and an organic solvent; the organic solvent is preferably a silica gel material. The phosphor and organic solvent are used and proportioned according to conventional techniques in the art, such as in a 1:1 or 1:2 weight ratio. More details are found in fluorescent powder and colloid recorded in a large-power LED fluorescent powder and colloid packaging process research of Wu-Yi Pink Master paper, and related preparation methods disclosed in http:// d.wanfandangdata.com.cn/Thesis/D369178. Or the related products purchased from Shenzhen jinbaisheng, Shenzhen jinsheng yuyuyuyu photoelectricity, Dalianlu ming and the like. Examples of such organic solvents are: epoxy resin, fluorine rubber, silicone rubber, etc., preferably a silicone rubber material. Wherein the conversion of the mixture of phosphor and organic solvent into a transparent solid is performed according to processes known in the art. The fluorescent powder colloid is arranged on the surface of the transparent substrate or in the groove in the modes of filling, coating and the like, and the surface of the fluorescent powder colloid is smooth and is convenient to combine with the LED chip.

In a further embodiment of the present invention, the transparent substrate is a transparent material suitable for processing the surface thereof by a mechanical or chemical etching method; preferably inorganic SiO₂Base glass and organic transparent materials. In more specific embodiments, the SiO₂The thickness of the base glass is greater than 70 microns. The light-emitting surface of the LED device is the light-emitting surface of the transparent substrate, and the light-emitting surface of the transparent substrate can be processed in a mechanical or chemical corrosion mode and the like to form a microstructure pattern (such as a tooth-shaped and/or pyramid-shaped structure) capable of improving the light-emitting effect.

In an embodiment of the invention, in the flip-chip LED device with wafer level package, the light emitting surface of the LED chip, from which the growth substrate is peeled off, is roughened (for example, after roughening, a microcavity structure is formed in the N-type semiconductor growth layer). And/or, in one embodiment of the invention, the side wall of the LED chip is provided with a side wall reflector, and the P-type ohmic contact layer of the LED chip has the function of a reflector (is the P-type ohmic contact layer and the reflector layer). And/or, in an embodiment of the present invention, the surface of the transparent substrate not provided with the phosphor colloid, that is, the light emitting surface of the LED device is roughened. This all further improves the light efficiency of the LED chip.

The roughening treatment can be processed in a mechanical or chemical corrosion mode and the like to form a microstructure pattern for improving the light emitting effect. For example, the following methods can be used: chemical roughening, photochemical roughening, and laser roughening. By chemical roughening, e.g. using KOH or H₃PO₄Coarsening the light emitting surface, wherein the temperature is more than 50 ℃ and the time is more than 5 seconds.

The invention also provides a flip LED device segmentation unit formed by segmenting the flip LED device packaged at the wafer level. In a specific embodiment, the divided flip-chip LED device division unit may be an LED division unit including one or two, three, four, five, or the like LED chips.

In the embodiments of the present invention, the growth substrate is peeled off by a laser peeling method, a grinding and polishing method, a wet etching method/a chemical etching method, and in the present invention, the wet etching method/the chemical etching method is preferably used. In a specific embodiment, the chemical etching process can be performed by referring to the method in patent application "a method for removing a growth substrate by chemical etching", which has application number of 201510290140.1 and application date of 2015, 5-29.

In one embodiment of the invention, the growth substrate is stripped using a chemical stripping technique comprising the steps of:

in the step (a), deep etching walkways are arranged among the LED chips, and the etching depth is up to the growth substrate layer of the LED chips;

in the step (b), the length of the through groove is larger than that of the electrode isolation walkway, and at least one end of the through groove is communicated with the deep etching walkway;

in the step (c), introducing a liquid medicine into a chemical stripping passage formed by the through groove and the deep etching walkway, and stripping the growth substrate.

The method makes full use of the through groove structure in the device, the through groove not only plays a role in isolating the electrode structurally, but also serves as a channel for introducing liquid medicine by a chemical stripping method in the preparation of the device, and the stripping of the growth substrate is realized efficiently.

In one embodiment of the invention, the surface of the growth substrate, which is connected with the LED chip, is uneven, and a gap is formed between the growth substrate and the LED chip.

In one embodiment of the present invention, the growth substrate is a growth substrate composed of a multilayer material, including: (A) a growth substrate formed of one selected from a silicon wafer, a glass wafer, sapphire, a copper substrate and the like, and (B) Al₂O₃、SiO₂A layer of one or more materials selected from SiN, AlN, etc., preferably Al, on the growth substrate₂O₃、SiO₂And AlN.

On the basis of the LED device prepared by the method, the cutting is carried out according to the deep etching walkway, and a divided inverted LED device dividing unit can be obtained.

The broad and preferred features of the products and methods described above can be combined with each other.

As described above, the flip LED device of wafer level package and the manufacturing method thereof according to the present invention are mainly characterized in that the device structure mainly includes a conductive substrate having a through-groove structure, a Light Emitting Diode (LED) chip having a thin film flip structure bonded to the upper surface of the substrate, and a phosphor transparent substrate bonded to the LED chip. According to the invention, the chip wafer and the conductive substrate are integrally bonded through the asymmetrical design of the chip on the wafer; meanwhile, through the design of the through groove of the conductive substrate, the insulation process and the electroplating process of silicon or other conductive substrates are reduced, and the cost is reduced; and a chemical stripping channel is formed by the through groove, the electrode isolation walkway and the deep etching walkway, so that the chemical stripping of the growth substrate is easily realized. This device structure can increase the light-emitting area of chip through reducing the pavement isolation distance between the conventional flip chip electrode, realizes wafer level encapsulation, can reduce the encapsulation cost, improves the luminous efficacy of encapsulation device, the homogeneity and the reliability of light-emitting, reduces encapsulation back emitting diode's blue light edge leakage.

Examples

The invention is illustrated below with reference to fig. 1-17. It should be noted that the drawings provided in this embodiment are only schematic illustrations of components relevant to the present invention, and do not limit the number, shape, size, manufacturing method and process window of the components in actual implementation, the type, number and ratio of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated. The process conditions involved in the examples can be varied reasonably within the effective window and achieve the effects disclosed by the present invention.

The wafer level packaged flip chip LED device is prepared according to the method, and comprises the following steps:

step 1: a composite pattern substrate 1 is provided. Several different structures of growth substrates are shown in fig. 1 to 1-4, and the present embodiment employs the structure shown in fig. 1.

The composite pattern substrate 1 includes: a growth substrate 101 (which is a sapphire substrate and has a thickness of preferably 380-450 microns, in this embodiment 410 microns), an AlN layer 102 (having a thickness of preferably 1-3 microns, in this embodiment 2 microns) on the growth substrate 101, and a strip-shaped silicon dioxide layer 103 (having a thickness of preferably 2000A-2 microns, in this embodiment 1 micron) on the AlN layer 102.

The stripe-shaped silicon dioxide 103 has a stripe-shaped interval of 2 microns and is arranged periodically.

Step 2: an epitaxial structure is grown on the composite pattern substrate 1. As shown in fig. 5.

The epitaxial structure includes: an N-type semiconductor growth layer 201 (thickness is preferably 1-7 microns, in this embodiment 6 microns), a quantum well 202 (thickness is preferably 1000A-5000A, in this embodiment 4000A) on the N-type semiconductor growth layer 201, and a P-type semiconductor growth layer 203 (thickness is preferably 500A-3000A, in this embodiment 1500A) on the quantum well 202.

And step 3: and manufacturing the LED chip wafer with the inverted structure on the epitaxial structure. As shown in fig. 6-7.

The electrode of LED chip wafer is homonymy structure electrode, the LED chip wafer comprises a plurality of LED chip units 2. The LED chip wafer comprises: the chip comprises an N-type metal pad 204 of the chip, a P-type metal pad 205 of the chip, an electrode isolation walkway 206, a deep etching walkway 3 (including a transverse and a vertical), a chip side wall insulating layer 207, a chip side wall reflector layer 208, a P-type ohmic contact layer and reflector layer 209 of the chip, and an electrode insulating layer 210 above the P-type ohmic contact layer and reflector layer 209.

The LED chip units 2 are asymmetrically arranged on the LED chip die, as shown in fig. 3, the N-type metal pads 204 and the P-type metal pads 205 on the adjacent LED chip units 2 are asymmetrically arranged, and of course, the pads may be asymmetrically arranged in a left-right or other manner. The main purpose of the design is to facilitate that after the subsequent conductive substrate 4 and the electrode pad are bonded, the corresponding through grooves 403 on the conductive substrate 4 are also arranged in a staggered manner, so as to form a structure that the conductive substrate 4 and the LED chip wafer are bonded in a whole piece.

The width of the chip electrode isolation walkway 206 is 7 microns, which is much smaller than the electrode isolation walkway 206 of the traditional flip chip. When the chip is bonded to the conductive substrate 4 subsequently, the chip electrode isolation via 206 is aligned with the through groove 403 on the conductive substrate 4 and then bonded (or after bonding, the through groove 403 may be opened in the alignment electrode isolation via 206).

The depth of the deep etching walkway 3 is 8 microns, the deep etching is carried out until reaching the substrate layer of the composite graph, namely, the etching of an epitaxial growth layer (epitaxial structure) in the walkway is ensured to penetrate, and the walkway is also used as a liquid medicine channel of a subsequent chemical stripping substrate.

The side walls of the chip have a side wall insulating layer 207 to prevent the P-N junction of the chip from shorting.

The sidewalls of the chip have a sidewall mirror layer 208 that prevents light from the chip from exiting the sidewalls of the chip.

The chip is provided with a P-type ohmic contact layer and a reflector layer, so that when ohmic contact between metal and a P-type semiconductor is formed, the emergent light on the front side of the chip is completely reflected to the composite graph substrate layer. In this embodiment, the P-type ohmic contact layer and the mirror layer are layers formed using three materials of ITO, Ni, and Ag, respectively, and their thicknesses are, in order: ITO: 200A-1200A, Ni: 3A-20A, Ag: 1000-.

The P-type ohmic contact layer and the mirror layer are provided with electrode insulation layers 210 for isolating the N-type metal pad 204 from the P-type ohmic contact layer and the mirror layer 209 and preventing short circuit of electrodes between chips.

The light-emitting surface of the LED chip unit 2 is a growth substrate 101 on the composite pattern substrate 1, namely a sapphire substrate (AL)₂O₃) And (5) kneading.

And 4, step 4: a conductive substrate 4 is provided. As shown in fig. 8-9.

The conductive substrate 4 may be a conductive substrate such as silicon, copper, etc., and in this embodiment, silicon is used as the conductive substrate 4.

The size of the conductive substrate 4 is not smaller than the chip die, and the size of the conductive substrate 4 is equal to the size of the chip die in this embodiment.

The metal layer a 401 on the conductive substrate 4 can be Ti, Cr, Al, Au, In, Sn, or Au Sn alloy, etc., and is not limited to the mentioned technology, and the metal layer a 401 is mainly used for metal bonding with the N-type metal pad 204 and the P-type metal pad 205 on the LED chip die. Any metal that can be bonded to the metal pad can be used as the metal layer a on the conductive substrate 4. The embodiment adopts the metal layer a 401 formed by Au to perform metal bonding with a plurality of metal pads.

And 5: and carrying out integral metal bonding on the LED chip wafer and the metal layer a 401 on the conductive substrate 4. As shown in fig. 8-9.

The bonding is performed by bonding a metal pad on the LED chip die to the metal layer a 401 on the one surface of the conductive substrate 4.

Step 6: through-grooves 403 are formed in the conductive substrate 4. As shown in fig. 8-9.

The through-slots 403 on the conductive substrate 4 completely correspond to the electrode isolation walkways 206 of the chip.

The width of the through groove 403 is 6 micrometers (smaller than the width of the electrode isolation walkway 206), and the length of the through groove 403 is longer than the electrode isolation walkway 206 of the chip, and reaches the edge of the side wall of the adjacent chip, namely, is communicated with the deep etching walkway 3 between the LED chips.

The through groove 403, the electrode isolation walkway 206 and the deep etching walkway 3 together form a chemical stripping passage.

And 7: and chemically stripping the composite pattern substrate 1 and transferring the chip to the conductive base plate 4. As shown in fig. 10.

The chip wafer bonded and provided with the through groove 403 is put into chemical liquid medicine (all liquid medicine capable of corroding silicon dioxide or liquid medicine capable of roughening the smooth surface is suitable for the invention, KOH solution is specifically used at the temperature of 50-80 ℃ for 10 minutes), the liquid medicine corrodes the AlN layer 102 and the silicon dioxide layer 103 on the growth substrate 101 along a channel formed by the through groove 403, the electrode isolation walkway 206, the deep etching walkway 3 and the strip-shaped gap of the composite pattern substrate 1, finally the composite pattern substrate 1 is stripped off, and the chip is completely transferred onto the conductive substrate 4, so that the chip wafer with the conductive substrate 4 is formed. The chip wafer with the conductive substrate 4 sequentially comprises the conductive substrate, the metal bonding layer and the LED chip from bottom to top.

And 8: the conductive substrate 4 is thinned (the whole LED device can be made thinner and lighter), and a metal layer b 402 (the material of the metal layer b 402 can be Ti, Ni, Al, etc., where Al is used) is evaporated on the other side of the conductive substrate 4 to form a P-type metal pad and an N-type metal pad 404 (i.e., an electrode of the LED device or a metal pad of the device) of the LED device, as shown in fig. 11. Meanwhile, the light-emitting surface of the N-type semiconductor layer of the LED chip can be roughened, and the light-emitting surface of the chip is increased.

And step 9: a phosphor transparent substrate 5 is provided.

Several configurations of the phosphor transparent substrate of the present invention are shown in fig. 12-15. The transparent substrate 501 of fig. 12 has a flat surface; the surface of the transparent substrate 501 of fig. 13 has grooves 502 arranged periodically; fig. 14 is the phosphor transparent substrate 5 after the transparent substrate 501 with the groove 502 of fig. 13 is filled with the phosphor colloid 503, wherein the single groove 502 and the phosphor colloid 503 therein form a phosphor unit 6; fig. 15 is a phosphor transparent substrate 5, on the basis of fig. 14, in which the light-emitting surface of the transparent substrate 501 (i.e., the surface of the transparent substrate 501 not provided with the phosphor colloid 503) is processed into a microstructure (pyramid structure 504). In this embodiment, the phosphor transparent substrate shown in fig. 14 is selected for the encapsulation of the LED device.

The transparent substrate 501 has high light transmittance and is easily formed by mechanical or chemical etching, and in this embodiment, SiO with a thickness of 80 μm is used₂A base glass. The transparent substrate 501 includes periodic grooves 502 (groove length 14mil, groove width 28mil), phosphor gel 503 (phosphor gel thickness 30 μm) is disposed in the grooves 502, wherein each individual groove 502 and phosphor gel 503 constitute a phosphor unit 6. The phosphor colloid 503 is a mixed colloid of phosphor and silica gel in a weight ratio of 1: 2.

The width and length of the groove 502 on the transparent substrate 501 are slightly larger than the width and length of the LED chip to be bonded to the phosphor colloid 503 (about 4 μm) respectively; the depth of the groove 502 is determined according to the final color coordinates of the LED device, i.e. how much phosphor the LED chip needs to match, where the groove 502 is about 40 microns deep.

The periodic arrangement, the interval and the like of the fluorescent powder units 6 are the same as the periodic arrangement and the interval of the LED chip units 2 on the LED chip wafer. The size of the phosphor unit 6 is slightly larger than that of the LED chip, so as to ensure that the light emitting surface of the LED chip can be completely bonded on the phosphor unit 6.

Step 10: the chip die with the conductive substrate 4 is bonded to the phosphor transparent substrate 5 in a full-sheet manner. As shown in fig. 16.

The light-emitting surface of the LED chip die (i.e. the surface close to the N-type semiconductor growth layer 201) from which the growth substrate is peeled off is permanently bonded to the phosphor colloid 503 on the phosphor transparent substrate 5. The LED chip units 2 and the fluorescent powder units 6 are in one-to-one correspondence to each other and are bonded by adhesives or cured.

The surface of the fluorescent powder transparent substrate 5, which is not provided with the fluorescent powder unit 6, is a final light-emitting surface of the LED device, and can be processed into various microstructures, such as a saw-toothed structure, which are favorable for light emission of the chip.

Step 11: the flip-chip LED device with the die-level package having the structure of the phosphor transparent substrate 5 obtained above is divided to form a desired flip-chip LED device division unit, as shown in fig. 17.

The segmentation is performed along the deep etching walkway 3 of the chip.

The light emitting surface of the LED device is a transparent substrate surface.

Evaluation of effects

1) Light transmittance

The light-emitting surface of the LED device is a transparent substrate surface, the growth substrate is peeled off, so that the light absorption of the growth substrate on the light-emitting surface of the traditional LED device is avoided, and the light transmittance of the LED device can be greatly improved by combining the selection of the transparent substrate with high light transmittance. Taking glass as the transparent substrate for example, it replaces the sapphire (Al) where the original light-emitting surface is located₂O₃) The light transmittance (300nm-700nm) of the conventional sapphire growth substrate is less than about 80%, and the glassThe light transmittance (300nm-700nm) of the substrate is more than 90%, so that the light extraction efficiency is increased.

2) Blue light side leakage

The side light of the conventional chip also comprises the side light part of the sapphire substrate because the side wall of the chip has no mirror and thus light is necessarily leaked from the side wall of the chip, and the growth substrate is not stripped. The side wall of the chip is provided with the reflector, and the sapphire substrate is stripped off, so that the blue light side leakage of the packaged light-emitting diode can be obviously reduced.

3) Excitation efficiency, light extraction uniformity and reliability

Synthesize above 1), 2) analysis, owing to adopt the higher transparent substrate of luminousness as going out the plain noodles, and adopt the flip-chip structure to avoid sheltering from of electrode, reduced the sidelight of chip simultaneously, and the chip all has the speculum structure except that the light-emitting surface, consequently, light is more concentrated, and the phosphor powder of unit area receives the excitation of more light, and the wholeness such as homogeneity and the reliability of device light-emitting efficiency, light-emitting obtains improving.

4) Heat generation condition

According to the invention, the growth substrate with poor thermal conductivity is stripped, and the heat conduction medium material is reduced, so that the heat dissipation effect of the LED device is better.

5) Mechanical strength

Compared with the LED device which directly uses fluorescent powder colloid to package the LED chip, the LED device adopting the transparent substrate structure greatly enhances the mechanical strength because the defects that the supporting substrate and the chip of the LED device are fragile and the like are overcome.

6) Brightness test

The above packaged device was fabricated using a chip die having a chip size of 12mil by 26mil, according to the above-described method of the embodiment. By adopting a Labsphere 50cm integrating sphere system, the luminous efficiency of the device reaches more than 180lm/W under 60 mA; meanwhile, the traditional 12mil by 26mil flip chip is subjected to packaging test, and the luminous efficiency of the device is 150 lm/W. Therefore, compared with the traditional chip, the LED device has the advantage that the light efficiency is improved by more than 20%.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A die-level packaged flip-chip LED device, comprising: a flip-chip LED chip die/array comprising more than one LED chip, a conductive substrate (4) and a phosphor transparent substrate (5),

wherein,

the LED chip comprises a P-type metal pad (205), an N-type metal pad (204) and an electrode isolation walkway (206) for separating the P-type metal pad (205) and the N-type metal pad (204);

one surface of the conductive substrate (4) is provided with a metal layer a (401), and the metal layer a (401) is in metal bonding with a P-type metal pad (205) and an N-type metal pad (204) of the LED chip; a metal layer b (402) is arranged on the other surface of the conductive substrate (4), and the metal layer b (402) forms a P-type metal bonding pad and an N-type metal bonding pad (404) of the LED device; a through groove (403) corresponding to the electrode isolation walkway is formed in the conductive substrate (4), and the P-type metal pad and the N-type metal pad (404) of the LED device are isolated by the through groove (403);

the fluorescent powder transparent substrate (5) comprises a transparent substrate (501) and a fluorescent powder colloid (503) in the transparent substrate (501) and/or on at least one surface of the transparent substrate, and the fluorescent powder transparent substrate (5) is combined with the light-emitting surface of the LED chip with the growth substrate stripped off.

2. The die-level packaged flip-chip LED device of claim 1, wherein the P-type metal pads (205) and the N-type metal pads (204) of adjacent LED chips are asymmetrically arranged, such that the electrode isolation runners (206) of adjacent electrodes are staggered.

3. The wafer level packaged flip-chip LED device according to claim 1 or 2, wherein deep etching walkways (3) are provided between the LED chips to the growth substrate layer when the growth substrate is not peeled off from the LED chips; the length of the through groove (403) is larger than that of the electrode isolation walkway (206), and at least one end of the through groove is communicated with the deep etching walkway.

4. The die-level packaged flip-chip LED device according to any one of claims 1 to 3, wherein one surface of the transparent substrate (501) has a flat surface and/or periodic grooves (502), the phosphor colloid (503) is disposed on the flat surface of the transparent substrate (501) and/or in the periodic grooves (502), and the surface of the phosphor colloid (503) is combined with the light-emitting surface of the LED chip peeling growth substrate.

5. The wafer-level packaged flip-chip LED device according to any one of claims 1 to 4, wherein the light emitting surface of the LED chip stripped from the growth substrate is roughened; and/or the side wall of the LED chip is provided with a side wall reflector, and the P-type ohmic contact layer of the LED chip has the function of the reflector; and/or the surface of the transparent substrate without the fluorescent powder colloid is roughened, namely the light-emitting surface of the LED device.

6. The die-level packaged flip-chip LED device of any one of claims 1 to 5 divided into flip-chip LED device divided units.

7. A method of fabricating a die-level packaged flip-chip LED device according to any one of claims 1 to 5, comprising:

(a) providing an LED chip die/array comprising more than one LED chip with a growth substrate, the LED chip comprising a P-type metal pad (205), an N-type metal pad (204), and an electrode isolation walkway (206) separating the P-type metal pad (205) and the N-type metal pad (204);

(b) providing a conductive substrate (4), wherein one surface of the conductive substrate (4) is provided with a metal layer a (401), and the metal layer a (401) is in metal bonding with a P-type metal pad (205) and an N-type metal pad (204) of the LED chip; a metal layer b (402) is arranged on the other surface of the conductive substrate (4), and the metal layer b (402) forms a P-type metal bonding pad and an N-type metal bonding pad (404) of the LED device; a through groove (403) corresponding to the electrode isolation walkway (206) is arranged on the conductive substrate, and the P-type metal pad and the N-type metal pad (404) of the LED device are isolated by the through groove (403);

(d) providing a fluorescent powder transparent substrate (5), wherein the fluorescent powder transparent substrate (5) comprises a transparent substrate (501) and a fluorescent powder colloid (503) in the transparent substrate (501) and/or on at least one surface of the transparent substrate;

(e) the fluorescent powder transparent substrate (5) is combined with the light-emitting surface of the LED chip with the growth substrate stripped off, so that a wafer level packaged flip LED device with a fluorescent powder transparent substrate structure is formed;

wherein the preparation of the LED chip wafer/array comprising more than one LED chip, the conductive substrate (4) and the fluorescent powder transparent substrate (5) is not divided into sequence.

8. The method of claim 7, wherein: stripping the growth substrate by using a chemical stripping technique, which comprises the following steps:

in the step (a), deep etching walkways (3) are arranged among the LED chips, and the etching depth is up to the growth substrate layer of the LED chips;

in the step (b), the length of the through groove (403) is larger than that of the electrode isolation walkway (206), and at least one end of the through groove is communicated with the deep etching walkway;

in the step (c), a chemical liquid is introduced into a chemical stripping passage formed by the through groove (403) and the deep etching walkway (3), and the growth substrate is stripped.

9. The method of claim 8, wherein: one surface of the growth substrate, which is connected with the LED chip, is uneven, and a gap is formed between the growth substrate and the LED chip.

10. The method according to claim 8 or 9, characterized in that: the growth substrate is a growth substrate made of multilayer materials and comprises: (A) a growth substrate formed of one selected from a silicon wafer, a glass wafer, sapphire, a copper substrate and the like, and (B) Al₂O₃、SiO₂A layer of one or more materials selected from SiN, AlN, etc., preferably Al, on the growth substrate₂O₃、SiO₂And AlN.