CN102280553A - Flip-chip Light Emitting Diode (LED) crystal grain and crystal grain array thereof - Google Patents

Abstract

The invention discloses a crystal grain of a flip-chip light-emitting diode and a crystal grain array thereof. The second type doped semiconductor layer is laid on the bottom surface of the first type doped semiconductor layer, the first electrode layer is laid on the bottom surface of the first type doped semiconductor layer and does not contact with the second type doped semiconductor layer, and the first electrode layer has an exposed area for directly coating a conductive bonding agent. The second electrode layer is laid on the bottom surface of the second type doped semiconductor layer and has an exposed area for directly coating the conductive bonding agent. The insulating layer is positioned between the first electrode layer and the second electrode layer so as to electrically isolate and support the first electrode layer and the second electrode layer.

Description

Flip Chip Light Emitting Diode Die and Die Array

technical field

The present invention relates to a light-emitting diode, and in particular to a flip-chip light-emitting diode.

Background technique

Please refer to FIG. 1 . FIG. 1 is a flowchart of steps of a known flip chip (flip chip) LED packaging process. The conventional flip-chip LED manufacturing process includes at least seven steps: First, as shown in step 101 , a plurality of die 110 on the wafer is taken out by the die expansion technology. Next, as shown in step 102, a first robotic arm 210 and its vacuum suction nozzle 211 are used to remove the die; as shown in step 103, the first robotic arm 210 turns over the die 110; as shown in step 104, the die is After the grain 110 is turned over, it is handed over to a second robot arm 220 and its vacuum suction nozzle 221 . Of course, another feasible method is to use the blue film flipping technology to realize the above process. Then, as shown in step 105 , the metal bumps 111 on the die 110 are precisely positioned on the conductive contacts 121 on a flip-chip interposer (Board) 120 . Afterwards, as shown in step 106 , the metal bump 111 is heated by means of microwaves or the like, so that the die 110 is electrically connected to the flip-chip interposer 120 . Finally, as shown in step 107, the gap between the die 110 and the flip-chip interposer 120 is encapsulated by dispensing technology, so far the packaging of a chip (chip) 130 is completed; in addition, the chip 130 usually needs to be baked again. Bake to cure the filling material when dispensing. So far, the chip 130 is a product that can be used directly; when in use, the chip 130 is electrically connected to a circuit on a circuit board by using the preset conductive structure on the flip-chip interposer 120 .

Contents of the invention

Therefore, the object of the present invention is to provide a flip-chip light-emitting diode chip and its chip array, which avoids the packaging process of the chip.

According to an object of the present invention, a flip-chip light-emitting diode grain is proposed, including a first-type doped semiconductor layer, a second-type doped semiconductor layer, a first electrode layer, a second electrode layer and an insulating layer . The second type doped semiconductor layer is laid on the bottom surface of the first type doped semiconductor layer, the first electrode layer is laid on the bottom surface of the first type doped semiconductor layer and does not contact the second type doped semiconductor layer, and has an exposed area For direct coating of a conductive adhesive. The second electrode layer is laid on the bottom surface of the second-type doped semiconductor layer, and has an exposed area for direct coating of conductive bonding agent. The insulating layer is located between the first electrode layer and the second electrode layer to electrically isolate and support the first electrode layer and the second electrode layer.

According to yet another object of the present invention, a flip-chip LED die array is provided, comprising a plurality of the aforementioned flip-chip LED dies and a metal pattern layer. The metal pattern layer is used for selectively electrically connecting the first electrode layer and the second electrode layer in each flip-chip LED grain, so as to connect the flip-chip LED grains in series and parallel.

It is worth noting that, according to other embodiments of the present invention, when silver glue is used as the conductive adhesive, the above-mentioned bare area must be at least 625 square microns for direct coating. When solder paste is used as the conductive bonding agent, the above exposed area must be at least 10,000 square microns for direct coating. In addition, on the detailed structure of the flip-chip LED grain, a metal reflective layer can also be laid between the second-type doped semiconductor layer and the second electrode layer; a Bragg reflective structure can be laid between the metal reflective layer and the second-type doped semiconductor layer. between the doped semiconductor layers; and laying a light-transmitting cover layer on the top surface of the first-type doped semiconductor layer. Based on the above, on the detailed structure of the flip-chip LED grain, a roughening structure can also be designed on the outer surface of the light-transmitting cover layer and the side surface of the first-type doped semiconductor layer. In addition, the transparent covering layer can be a patterned sapphire substrate.

Therefore, the flip-chip light-emitting diode die and its array in the above-mentioned various embodiments can realize a complete finished product that can be used directly in the wafer manufacturing process; therefore, all steps of the traditional flip-chip light-emitting diode packaging process are omitted; no matter in Great progress has been made in terms of equipment, cost and time-consuming.

Description of drawings

In order to make the above and other objects, features, advantages and embodiments of the present invention more comprehensible, the accompanying drawings are described as follows:

FIG. 1 is a flow chart of steps of a known flip-chip LED chip packaging process;

2 is a schematic structural view of a flip-chip light-emitting diode grain according to an embodiment of the present invention;

3A is a schematic structural view of a flip-chip light-emitting diode grain according to another embodiment of the present invention;

3B is a schematic structural view of a flip-chip light-emitting diode grain according to another embodiment of the present invention;

FIG. 3C is a schematic structural view of a flip-chip light-emitting diode grain according to another embodiment of the present invention;

4 is a schematic structural view of a flip-chip light-emitting diode die array according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of the detailed structure of the flip-chip light-emitting diode grain in FIG. 3A;

FIG. 6 is a schematic diagram of the detailed structure of the flip-chip LED die in FIG. 3A .

[Description of main component symbols]

101-107: Steps 110: Known Flip Chip LED Dies

111: Metal bump 121: Conductive contact

120: Flip chip adapter board 210: The first robot arm

130: Known flip-chip light-emitting diode chips 211, 221: Vacuum nozzle

220: Second robot arm

300, 310, 320, 330, 401: flip-chip light-emitting diode die

301: first type doped semiconductor layer

302: The second type doped semiconductor layer 303: The first electrode layer

304: Second electrode layer 305: Insulation layer

306: Protective layer 311: Light-transmitting covering layer

312: Metal reflective layer 313: Bragg reflective structure

314: Coarse structure 315: Pattern

400: Flip chip LED die array 420: Metal pattern layer

Detailed ways

When the flip-chip packaging technology was proposed, it was to solve the problem of over-sensitivity of traditional logic operation chips to electrical properties. For example, when the traditional logic operation chip is packaged into a chip, wire bonding is required, but the wire bonding will generate additional inductance effects; therefore, flip-chip packaging technology proposes to replace the wire bonding with a flip-chip interposer . However, this technology has become an existing stereotype, and has always been used in the placement of flip-chip light-emitting diode chips. Based on many years of practical experience and long-term observation and hard work, the inventor of the present invention has studied the above-mentioned technical stereotypes, and combined with the various characteristics of light-emitting diodes that are different from logic operation chips, finally proposed the present invention to eliminate serious illnesses.

Please refer to FIG. 2 . FIG. 2 is a schematic structural diagram of a flip-chip light-emitting diode die according to an embodiment of the present invention. In FIG. 2 , the flip-chip light-emitting diode die 300 of this embodiment includes a first-type doped semiconductor layer 301 , a second-type doped semiconductor layer 302 , a first electrode layer 303 , a second electrode layer 304 and An insulating layer 305 . The second type doped semiconductor layer 302 is laid on the bottom surface of the first type doped semiconductor layer 301, the first electrode layer 303 is laid on the bottom surface of the first type doped semiconductor layer 301 and does not contact the second type doped semiconductor layer 302, And there is an exposed area for directly coating a conductive bonding agent. The second electrode layer 304 is laid on the bottom surface of the second-type doped semiconductor layer 302 and has an exposed area for direct coating of conductive bonding agent. The insulating layer 305 is located between the first electrode layer 303 and the second electrode layer 304 to electrically isolate and support the first electrode layer 303 and the second electrode layer 304 .

Among them, in order to realize the elongated upright first electrode layer 303 on the wafer manufacturing process, so as to use its side area to increase the overall exposed area for direct coating of conductive adhesive, the insulating layer 305 is used to support the first electrode layer 303 in this embodiment. The electrode layer 303 prevents it from collapsing (Peeling) during the manufacturing process, and is more firm in the finished product, so as not to bend and contact the second electrode layer 304 due to external force to cause a short circuit. On the other hand, when both the first electrode layer 303 and the second electrode layer 304 have a relatively large volume, the two may generate an arc and short circuit; therefore, the insulating layer 305 can isolate the first electrode layer 303 and the second electrode layer 304 to prevent short circuits. In addition, although the insulating layer 305, the first electrode layer 303 and the second electrode layer 304 will inevitably produce a capacitive effect; but it does not constitute a hazard to the flip-chip LED die 300 for the purpose of emitting light; on the contrary, a large-scale The exposed area of the first electrode layer 303 and the second electrode layer 304 is good for heat dissipation, so as to fight against the problem of light attenuation which is really concerned by the LED.

It is worth noting that if silver glue is to be directly coated as a conductive bonding agent, the exposed area of the first electrode layer 303 and the second electrode layer 304 is 25 micrometers (micrometer) by more than 25 micrometers; The paste is used as a conductive bonding agent, and the exposed area of the first electrode layer 303 and the second electrode layer 304 is more than 100 microns by 100 microns. In addition, the first-type doped semiconductor layer 301 can be a p-type semiconductor layer, and the second-type doped semiconductor layer 302 can be an n-type semiconductor layer, or vice versa. The material of the semiconductor layer can be aluminum gallium arsenide, gallium arsenide phosphide, gallium phosphide, indium gallium aluminum phosphide, indium gallium aluminum phosphide, indium gallium nitride, gallium nitride, aluminum gallium phosphide, zinc selenide , silicon carbide and other materials.

Please refer to FIG. 3A , FIG. 3B and FIG. 3C , all of which are structural schematic diagrams of flip-chip light-emitting diode dies in three embodiments of the present invention. It is a large electrode structure that can be used directly on the crystal grain during the wafer manufacturing process, thereby eliminating the post-process process of packaging the traditional crystal grain into a chip. In FIG. 3A, the second electrode layer 304 can be firstly placed on the second-type doped semiconductor layer 302 in a large area; when the applicable side area of the first electrode layer 303 may still be insufficient to directly stick the conductive adhesive The insulating layer 305 may partially cover the second electrode layer 304 , and the first electrode layer 303 is laid on the insulating layer 305 toward the direction of the second electrode layer 304 . In FIG. 3B, both the first electrode layer 303 and the second electrode layer 304 can be manufactured in two stages; that is, two metal layers are respectively realized on the first type doped semiconductor layer 301 and the second type doped semiconductor layer by conventional manufacturing processes. On the layer 302, an insulating layer 305 and two large electrodes are formed on the two metal layers by adding wafer process to complete the first electrode layer 303 and the second electrode layer 304 respectively. In FIG. 3C , if there is concern that the first electrode layer 303 and the second electrode layer 304 are too close to each other, it may be easy to short circuit; the insulating layer 305 can be used to distance the first electrode layer 303 from the second electrode layer 304 .

It should be noted that, in FIG. 3B , the flip-chip LED die 300 also includes a protective layer 306 . The protection layer 306 is an insulating film formed of an insulating material, which is used to form a film protection function to increase the lifetime of the flip-chip LED die 300 . In terms of manufacturing process, the protective layer 306 can be formed on the front or side surfaces of the first-type doped semiconductor layer 301 and the second-type doped semiconductor layer 302 by using techniques such as spin coating or E-gun.

As mentioned above, the flip-chip light-emitting diode grains in FIG. 3A, FIG. 3B and FIG. 3C are formed during the wafer fabrication process, such as deposition, exposure, development, etching and other steps, which are used as positive and negative electrodes. The first electrode layer 303 and the second electrode layer 304 . Then, after dicing, it can become flip-chip LED chips that can be used independently. In other words, the equipment required for packaging processes such as expansion, flipping, transposition, microwave, dispensing, and even baking of traditional flip-chip technology can be saved. In addition, the time spent on traditional flip-chip LEDs such as chip expansion, flipping, ball planting, die-substrate bonding, glue injection, and baking can also be saved.

Please refer to FIG. 4 again. FIG. 4 is a schematic structural diagram of a flip-chip LED die array according to another embodiment of the present invention. In FIG. 4 , the chip array 400 of flip-chip light-emitting diodes in this embodiment is formed in the final stage of the aforementioned wafer processing, and then a metal pattern layer 402 spanning between the chips 401 is formed by the metal layer manufacturing process, so as to provide electrical A plurality of dies 401 are connected in series and parallel. Then, each crystal grain 401 is no longer cut and separated, but used as an array according to the number of grains defined by its metal pattern layer 402 . In this way, the electrical series-parallel structure of the plurality of flip-chip LED dies 401 has been completed at the wafer stage, so that they can be directly electrically connected to an AC or DC power supply. In contrast to traditional flip-chip light emitting diodes, the chips must first be packaged into chips with a flip-chip interposer, and then electrically connected in series and parallel on an additional circuit board.

Next, please refer to Figure 5 again. FIG. 5 is a schematic diagram of the detailed structure of the flip-chip LED die in FIG. 3A . In order to improve the luminous efficiency of the flip-chip LED die 310, on the detailed structure of the flip-chip LED die 301, a light-transmitting cover layer 311 can also be laid on the top surface of the first-type doped semiconductor layer 301, and a The metal reflective layer 312 is between the second-type doped semiconductor layer 302 and the second electrode layer. The metal reflective layer 312 is located under the PN junction that actually emits light, and can be used to reflect the light that diverges downwards back to the light-transmitting cover layer 311 , that is, the light-emitting side of the flip-chip LED die 310 . Furthermore, it is also possible to design a reflective surface on the circuit board to which the flip-chip LED die 310 is attached to reflect the light diverging downward from the PN junction.

Please refer to Figure 6 again. FIG. 6 is also a schematic diagram showing the detailed structure of the flip-chip LED die in FIG. 3A . In FIG. 6, a Bragg reflector 313 can also be laid between the metal reflective layer and the second-type doped semiconductor layer. Wherein, the Bragg reflection structure 313 is formed by two or more materials with different dielectric coefficients arranged in a staggered manner. Moreover, the thickness of each layer is designed to be a quarter of the wavelength of light to form a quarter-wave-stack multi-layered system, which is equivalent to a simple one-dimensional photonic crystal. In this way, since the electromagnetic wave whose frequency falls within the energy gap cannot penetrate, the reflectivity of the Bragg reflection structure 313 can be as high as 99%. It does not have the absorption problem of general metal mirrors, and the position of the energy gap can be adjusted by changing the refractive index or thickness of the material.

On the other hand, a roughened structure 314 can be designed on the upper surface of the light-transmitting cover layer, that is, the backside emitting side of the flip-chip LED die 310 . Similarly, the roughened structure 314 can be provided on the surrounding side surfaces of the light-transmitting covering layer and the first-type doped semiconductor layer. The design principle of coarsening structure 314 is introduced as follows:

Generally speaking, the refractive index of the LED semiconductor layer is about 2.4, and the total reflection angle for air is about 24.5 degrees. LED chips are usually cut into rectangles, about 8% of the light can be emitted outside the chip, and 92% of the light is enclosed in the chip and converted into heat. Destroying the total reflection angle can increase the LED light output rate, and the surface roughening project on the surface of the chip can increase the light output rate. It is worth noting that the surface roughness of the LED surface must be greater than 2 times the wavelength to have a significant light extraction efficiency. Non-rectangular chip shapes or small non-rectangular cuts in chips can also improve light extraction efficiency.

In addition, the material of the light-transmitting cover layer can be a light-transmitting material such as a sapphire substrate (Al2O3), gallium phosphide (GaP), silica gel, glass or Teflon. It should be noted that when the sapphire substrate is selected as the light-transmitting covering layer, a pattern 315 can be designed on the side where it borders the second-type doped semiconductor layer, thereby forming a patterned sapphire substrate. Finally, from the point of view of the process, the aforementioned metal reflective layer and the second electrode layer can be completed simultaneously in the same process.

In summary, the flip-chip light-emitting diode of this embodiment can eliminate the need for a wire bonding machine (about 120,000 US dollars) or a flip-chip ball planting machine (about 600,000 US dollars), a die-bonding machine or a surface mount machine (Surface MountingTechnology, SMT) and other equipment, as well as expenditures on consumable materials and flip-chip interposer boards. Both the manufacturing cost and the production capacity per unit time have been significantly improved.

Although the present invention has been disclosed above with various embodiments, it is not intended to limit the present invention. Any person familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, this The protection scope of the invention should be determined by the scope defined in the claims.

Claims (10)

1. A flip-chip light-emitting diode grain, characterized in that, comprising: a first type doped semiconductor layer; a second-type doped semiconductor layer laid on the bottom surface of the first-type doped semiconductor layer; A first electrode layer laid on the bottom surface of the first-type doped semiconductor layer without contacting the second-type doped semiconductor layer, and having an exposed area for direct coating of a conductive bonding agent; a second electrode layer laid on the bottom surface of the second-type doped semiconductor layer, and has an exposed area for directly coating the conductive bonding agent; and An insulating layer is located between the first electrode layer and the second electrode layer to electrically isolate and support the first electrode layer and the second electrode layer. 2 . The flip-chip light-emitting diode die according to claim 1 , wherein the exposed area is at least 625 square micrometers, and the conductive bonding agent is a silver glue. 3 . The flip-chip LED die according to claim 1 , wherein the exposed area is at least 10,000 square micrometers, and the conductive bonding agent is a solder paste. 4 . The flip-chip light-emitting diode die according to claim 1 , further comprising a metal reflective layer laid between the second-type doped semiconductor layer and the second electrode layer. 5 . The flip-chip LED die according to claim 4 , further comprising a Bragg reflection structure located between the metal reflection layer and the second-type doped semiconductor layer. 6 . The flip-chip light-emitting diode die according to claim 1 , further comprising a light-transmitting cover layer laid on the top surface of the first-type doped semiconductor layer. 7 . The flip-chip LED die according to claim 6 , further comprising a roughened structure located on the outer surface of the light-transmitting covering layer. 8 . The flip-chip light-emitting diode die according to claim 6 , further comprising a roughening structure located on a side surface of the first-type doped semiconductor layer. 9 . The flip-chip LED die according to claim 6 , wherein the light-transmitting covering layer is a patterned sapphire substrate. 10. A flip-chip light-emitting diode die array, characterized in that it comprises: A plurality of flip-chip light-emitting diode dies according to any one of claims 1-9; and A metal pattern layer is used for selectively electrically connecting each of the first electrode layers and the second electrode layers to connect the flip-chip light-emitting diode chips in series and parallel.

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