WO2014012322A1

WO2014012322A1 - Flip-chip bonding nitride light-emitting diode and light-transmission substrate thereof, and manufacturing method of same

Info

Publication number: WO2014012322A1
Application number: PCT/CN2012/086086
Authority: WO
Inventors: 廖丰标; 顾玲
Original assignee: 江苏扬景光电有限公司
Priority date: 2012-07-16
Filing date: 2012-12-06
Publication date: 2014-01-23
Also published as: CN102769083A

Abstract

A substrate (16) of a flip-chip bonding nitride light-emitting diode (LED). At least one of upper and lower surfaces of the substrate (16) is a rough surface. The rough surface may be manufactured by one of five methods. Also provided is an LED component chip (10) having the substrate (16) with the rough surface. The light output and luminous efficiency of the flip-chip bonding nitride LED are improved, the whole temperature of the LED is reduced, and the reliability of a product is improved.

Description

Flip-chip nitride light-emitting diode and light-transmitting substrate thereof and manufacturing method thereof

The present invention relates to a flip chip nitride light emitting diode and a light transmissive substrate therefor, and a method of fabricating the same, which is directed to forming a rough surface on at least one surface of the light transmissive substrate.

Background technique

In a flip-chip mounting configuration, the light-emitting diodes having the light-transmissive substrate and the front-side electrodes are bonded face down to the solder bumps of the mounting stage, even if the epitaxial layer is closest to the mounting stage and the light-transmitting substrate is remote from the mounting stage. The flip-chip configuration has several advantages, including improved heat dissipation and reduced shadowing loss due to the front side active layer (i.e., the light-emitting layer) being the most transparent substrate.

In a flip-chip mounting configuration, light is extracted from the substrate side. For a light-emitting diode grown in an epitaxial manner, since the substrate is mainly selected to provide a good excellent substrate for epitaxy, the choice of substrate material can be quite limited. Thus, substrate standards include a narrow range of lattice constants, a substantially atomic leveling surface for epitaxial nucleation, thermal stability at epitaxial growth temperatures, and chemical compatibility with epitaxial processes, and the like.

When the growth substrate is a suitable optically transparent substrate, such as a Group III nitride light-emitting diode that can grow on a transparent sapphire growth substrate, between the substrate and the air due to a sudden discontinuity in the refractive index A reflection optical loss occurs at the interface and at the interface of the substrate and the semiconductor layer. In the refractive index, the refractive index of the semiconductor layer is n = 2.4, the refractive index of sapphire is n = 1.7, and the refractive index of air is n = 1. In the case of a transparent substrate such as a sapphire substrate used in a Group III nitride epitaxy, the optical loss attributable to the substrate is due to reflection loss rather than absorption loss. Conventional flip-chip LEDs have a planar light-emitting surface on the upper side of the substrate and a lower surface adjacent to the semiconductor layer. Thus, when the light is emitted, part of the light is emitted outside the device, and most of the light is totally reflected. , resulting in poor light output. This is because the grown substrate material is a highly refractive material with respect to the outside air, and therefore, when the angle at which the light is emitted is greater than a critical angle, total reflection occurs. Similarly, light that is emitted from the luminescent layer toward the sapphire substrate also undergoes total reflection. The totally reflected light generates thermal energy inside the LED, which causes the overall temperature of the LED to rise, which is not conducive to the reliability requirements of the product.

Summary of the invention

OBJECTS OF THE INVENTION: In view of the problems and deficiencies of the prior art described above, an object of the present invention is to provide a flip-chip nitride light-emitting diode, a light-transmitting substrate thereof, and a manufacturing method thereof, which increase the amount of light emitted from a flip-chip nitride light-emitting diode and emit light. Efficiency, reducing the overall temperature of the LED and improving product reliability.

Technical Solution: In order to achieve the above object, the first technical solution adopted by the present invention is a light-transmissive substrate of a flip-chip nitride light-emitting diode, and at least an upper surface and a lower surface of the light-transmitting substrate A surface is a rough surface.

In order to further improve the light output and luminous efficiency of the light emitting diode, the overall temperature of the light emitting diode is lowered. The book surface and the reliability of the product are improved, and the upper surface and the lower surface of the light-transmitting substrate are both rough surfaces.

The light transmissive substrate can be a sapphire substrate.

The second technical solution adopted by the present invention is a method for manufacturing a light-transmissive substrate of a flip-chip nitride light-emitting diode, and a lithography and dry etching step is used to generate a regular pattern surface, including the following steps: (1) lithography : coating a photosensitive material on one surface of the light-transmitting substrate; placing a reticle above the surface, the reticle is provided with the same pattern as the pattern; Exposure: selecting parallel light through the reticle to select the photosensitive material Exposure, the pattern of the reticle is completely transferred to the surface of the light-transmitting substrate; developing, so that the photosensitive material obtains the same or complementary pattern as the reticle pattern; (2) dry etching: performing the photographic material Dry etching causes the light transmissive substrate to produce a regular pattern surface.

A third technical solution adopted by the present invention is a method for manufacturing a light-transmissive substrate of a flip-chip nitride light-emitting diode, which uses a lithography and a wet etching step to produce a patterned regular surface, comprising the following steps: (1) lithography: Coating a photosensitive material on one surface of the light-transmitting substrate; placing a reticle above the surface, the reticle is provided with the same pattern as the pattern; Exposure: making parallel light pass through the reticle to selectively select the photosensitive material Exposure, the pattern of the reticle is completely transferred to the surface of the light-transmitting substrate; development, so that the photosensitive material obtains the same or complementary pattern as the reticle pattern; (2) Wet etching: 200 ° C to 350 ° C The light-transmitting substrate is etched by a mixed solution of phosphoric acid and sulfuric acid such that the light-transmitting substrate produces a pattern-like surface. With this technical solution, each time the surface of the light-transmitting substrate can be roughened, if double-sided roughening is required, it can be repeated once, and the fifth and sixth technical solutions are similar.

A fourth technical solution adopted by the present invention is a method for manufacturing a light-transmissive substrate of a flip-chip nitride light-emitting diode, and a wet etching step is used to generate two irregular patterns on the surface, including the following steps: forming a light-transmitting through the crystal growth step a substrate, the upper surface and the lower surface of the light-transmitting substrate are each formed with at least one defect; etching the light-transmitting substrate with a mixed solution of phosphoric acid and sulfuric acid at 200 ° C to 350 ° C, so that the light-transmitting substrate is simultaneously Produces two irregularly patterned surfaces. With this technical solution, the roughening of the upper and lower surfaces of the light-transmitting substrate can be completed in one time.

The fifth technical solution adopted by the present invention is a method for manufacturing a light-transmissive substrate of a flip-chip nitride light-emitting diode, and a pattern-finished surface is produced by laser-scanning a surface of the light-transmitting substrate to form a scribe line.

The sixth technical solution adopted by the present invention is a method for manufacturing a light-transmitting substrate of a flip-chip nitride light-emitting diode. First, a laser beam is divided into a plurality of laser beams having uniform or uneven intensity, and the multi-beam intensity is uniform or A non-uniform laser is projected onto one surface of the light-transmitting substrate to form a score line, which correspondingly produces a regular or irregular pattern. Specifically, a laser beam first passes through a first lens for uniformly expanding a laser beam; and a second lens is used to convert a laser beam into a plurality of parallel beams; a third lens having a uniform or uneven fine structure, the multi-beam parallel light is folded The book is projected onto a surface of the light-transmissive substrate to form a score line, which correspondingly produces a regular or irregular surface.

A seventh technical solution adopted by the present invention is a flip-chip nitride light emitting diode comprising the light-transmitting substrate as described above, the upper surface of the light-transmitting substrate is deposited with a semiconductor layer stack, and the semiconductor layer stack is provided There is a p-type electrode and an n-type electrode, and the p-type electrode and the n-type electrode are respectively soldered on the first pad and the second pad of the mounting stage through a plurality of solder bumps.

Advantageous Effects: The invention increases the light output and luminous efficiency of the flip-chip nitride light-emitting diode, reduces the overall temperature of the light-emitting diode, and improves the reliability of the product. In particular, the use of a double-sided roughened substrate can further increase the light output and luminous efficiency of the flip-chip nitride light-emitting diode, reduce the overall temperature of the light-emitting diode, and improve the reliability of the product. Among them, the roughening of one surface of the sapphire substrate of the flip-chip LED can increase the light output by 10% to 30%, and the double-sided roughening can increase the light output by 15% to 80%. DRAWINGS

1 is a schematic structural view of a flip-chip nitride light emitting diode;

Figure 2 is a schematic view showing the structure of a device for pulse laser projection.

detailed description

The invention will be further clarified with reference to the accompanying drawings and specific embodiments, which are intended to illustrate the invention and not to limit the scope of the invention. Modifications of equivalent forms are intended to fall within the scope defined by the appended claims.

In accordance with an embodiment, a method for fabricating a flip-chip LED device is provided. A plurality of epitaxial layers are deposited on the growth substrate to produce epitaxial wafers. A plurality of light emitting diodes are fabricated on the epitaxial wafer. The epitaxial wafer is cut to produce a device chip. Flip the assembly chip to the mounting table. Flip-chip bonding includes securing a component chip on a mounting table by bonding at least one electrode of the component chip to at least one pad of the mounting table. After the epitaxial wafer is cut to produce a device chip or after a flip-chip bonding process, a light-emitting surface of the grown substrate (the same meaning of the light-transmitting substrate and the grown substrate in the present invention) of the component chip is generated. Rough structure.

Referring to Figure 1, there is shown an exemplary flip-chip bonded LED module chip 10 mounted on a mounting table 12 by flip chip bonding. The exemplary light emitting diode assembly chip 10 includes a semiconductor device layer stack deposited epitaxially on a growth substrate 16. The semiconductor device layer stack defines an LED assembly, such as a diode that emits ultraviolet or blue light from Group I I nitride.

In Figure 1, semiconductor layer stack 14 has two exemplary layers corresponding to a simple p/n diode; however, those skilled in the art will appreciate that more complex semiconductor layer stacks can be used. For example, in a vertical cavity surface-emitting laser diode, the layer stack can include a plurality of layers defining a Bragg reflector, a cladding layer, and a complex multi-quantum well active region. For orientation with a P-type layer on the n-type layer (p-on-n In the case of a diode of a group III nitride emitting ultraviolet or blue light, the semiconductor layer stack usually includes an aluminum nitride or other material extension buffer (not shown), an n-type gallium nitride substrate layer 14, An active region of indium gallium nitride (i.e., light emitting layer) 15. A p-type gallium nitride layer 17 and optionally a contact layer (not shown) formed on the P-type gallium nitride layer. Other semiconductor epitaxial layer stacks suitable for particular optical applications can be readily constructed by those skilled in the art.

The growth substrate 16 is made of a crystalline material that is suitable for the growth of a selected semiconductor layer stack, and is referred to herein as a transparent sapphire.

The epitaxial deposition of the semiconductor layer stack on the selected grown substrate 16 is preferably deposited by organometallic chemical gas (M0VCD; also known in the art as organometallic gas epitaxy (0MVPE) and similar terms), Molecular beam epitaxy (MBE), liquid epitaxy (LPE) or other suitable extensional growth techniques are used. As with the growth substrate 16, the epitaxial growth technique is selected based on the type of semiconductor epitaxial layer stack to be grown.

In this embodiment, a large-area substrate wafer having a semiconductor epitaxial layer stack deposited thereon is referred to as an epitaxial wafer. The epitaxial wafer is processed using a suitable fabrication process to define at least one LED assembly on the wafer, including processes such as wafer cleaning processes, lithography processes, etching processes, dielectric deposition processes, metallization processes The sub-process of its analogues. In a typical method, the fabrication process includes initial wafer cleaning, lithography and etching of the device mesas, and lithography of the n-type and p-type electrodes.

With continued reference to Figure 1, the LED assembly chip 10 is a lateral current geometry device and includes a P-type electrode 20 disposed on the surface of the assembly and an n-type electrode 22 disposed in a field region outside the mesa of the device. In this embodiment, the p-type electrode 20 and the n-type 22 are both front side electrodes. Typically, the electrodes 20, 22 are made of gold or have a gold coating to facilitate electrical contact with low electrical resistance.

The mounting table 12 includes a first pad 26 configured to be coupled to the p-type electrode 20 and a second pad 28 disposed to be coupled to the n-type electrode 22. At least one solder bump 30 is disposed on the pads 26, 28, respectively. The flip-chip LED module chip 10 is flip-chip bonded to the mounting pads 12, 28, and more specifically, the LED module chip 10 is bonded to the solder bumps 30. The flip chip bonding can be achieved by soldering, in which case the solder bumps 30 are solder bumps. Alternatively, the flip-chip bonding can be achieved by thermosonic bonding, in which case the bumps are preferably gold-coated copper bumps bonded to the electrodes by a combination of heating and implanting ultrasonic energy. 20, 22. Other joining methods can also be used.

After the flip-chip bonding process, the following five methods can be used to form a rough structure on the light-emitting surface of the grown substrate: (1) lithography and dry etching steps; (2) lithography and wet etching steps; (3) wet etching (4) Pulsed laser scanning roughening; and (5) Pulsed laser projection coarsening. The following are introduced separately:

(1) lithography and dry etching steps: first coating a photosensitive material (photoresist) on the surface of the sapphire substrate, The specification also places a reticle on top of the sapphire substrate, the reticle is provided with a pattern and a number of patterns relative to the embossed pattern, and then an exposure step is performed to selectively illuminate the photographic material through the reticle through the reticle. Then, the pattern on the mask is completely transferred to the sapphire substrate. When exposed, the development is used to obtain the same or complementary pattern of the photoresist pattern, and dry etching is performed (Dry Etching). Also known as Plasma Etching, which uses gas as the main etching medium, such as C12/BC13, and drives the reaction by plasma energy to pattern the sapphire substrate to form a regularly arranged concave and convex pattern. The height difference of the concave-convex pattern is within 20 μm. This way you can create a regular pattern.

(2) lithography and wet etching steps: The lithography process is the same as before, but when the photoresist has the same or complementary pattern as the reticle pattern, a high temperature phosphoric acid and sulfuric acid mixed solution (phosphoric acid) of 200 ° C to 350 ° C can be used. The weight percentage is 5% to 95%. The sapphire substrate is etched to form a regularly arranged concave-convex pattern having a height difference of 20 μm. This way you can create a regular pattern.

(3) Wet etching: At least one defect on the surface of the sapphire substrate is used without lithography, because the stress at each defect is high, and the chemical solution acts to form a relatively uniform pattern at each defect. A roughened surface is formed. Therefore, the sapphire substrate is immersed in a solution, for example, a mixed solution of phosphoric acid and sulfuric acid at a temperature of 200 ° C to 350 ° C (5% to 95% by weight of phosphoric acid), and can be regularly arranged on the front and back sides of the sapphire substrate. Concave pattern. The position and the number of defects of the etched sapphire substrate can be controlled by controlling the crystal growth parameters, such as the melting point temperature, the crystal pulling speed, the crucible rotation speed or the center rotation speed of the crystal rod, thereby controlling the position and the number of each grain boundary. The defects to be formed are formed on the sapphire substrate. This method does not produce a regular pattern.

(4) Pulsed laser scanning roughening: Pulsed laser has been widely used in the division of nitride light-emitting diode chips, and solid-state lasers are generally available. For example, Q-switched Nd:YV04 laser or Nd:YAG laser, which contains a harmonic frequency generator, such as LBO (lithium triborate), which causes nonlinear crystals of 1064 nm produced by a solid-state laser doped with germanium. One of the second, third, fourth and fifth harmonic frequencies provides an output of the laser. In a special system, a third harmonic frequency of approximately 355 nanometers is provided. The pulse wave has an energy density between about 10 and 100 joules per square centimeter, a pulse duration between about 10 and 30 nanoseconds, and a spot size between about 5 and 25 microns. The repetition rate of the pulse wave is greater than 5 kHz, preferably in the range of about 10 kHz and 50 kHz or higher. The sapphire substrate moves at a rate of motion, causing the pulse waves to overlap in an amount of 50 to 99 percent. By controlling the pulse rate, the rate of motion of the sapphire substrate, and the energy density, the depth of the scribe line can be precisely controlled. Generally, the depth of the scribing cut is in the range of about 35 microns to 60 microns. When the surface of the sapphire substrate is roughened, the height difference between the concave and convex patterns is within 20 μm. The beam diameter of the laser is generally smaller than the area of the sapphire substrate after flip-chip bonding, so the area of the substrate needs to be scanned. During the scanning process, it is necessary to control the magnitude of the laser driving current and the relative position of the laser and the substrate to produce a desired roughened structure. For example, when the substrate is scanned at a constant speed, the magnitude of the laser driving current is changed. The output power of the laser also changes the depth of the sapphire substrate surface; or when the laser is operated at the same driving current, if the scanning rate is increased, the scoring depth is reduced, if the scanning rate is reduced, the scoring depth is reduced. increase. This method does not require a lithography process and can produce a regular pattern.

(5) Pulsed laser projection roughening sapphire substrate: As shown in Fig. 2, using the above laser device 36, the combination of the ultraviolet lens and the laser beam completely covers the inverted sapphire substrate, and the energy of the beam The distribution is uniform or uneven to produce the desired roughened structure. The combination of UV lenses is shown in Figure 2: First, the first UV lens 38 uniformly expands the laser beam, and a second UV lens 40 is provided at the laser beam slightly larger than the area of the sapphire substrate. The second UV lens will The beam of the laser light is converted into parallel light, and the third ultraviolet lens 42 is distributed with a fine prism structure. The fine prism structure may be composed of a fine or irregularly arranged fine structure that is convex or concave. When the parallel laser beam passes through the third ultraviolet lens, the lasers in each small area are respectively refracted, so when the laser beam is projected on the sapphire substrate, uniform (corresponding to regular fine structure) or uneven (corresponding to irregularities) is formed. The intensity distribution of the fine structure) further forms a roughened structure on the surface of the sapphire substrate. Compared with pulsed laser scanning roughening, the method has the advantages that the laser does not need to be scanned (ie, the sapphire substrate does not need to be moved), and the cost is reduced; the roughening of one surface of the sapphire substrate can be completed with only one projection, which is improved. effectiveness.

Claims

claims

1. A light-transmitting substrate for flip-chip welding nitride light-emitting diodes, at least one of the upper surface and the lower surface of the light-transmitting substrate has a rough surface.

2. The light-transmitting substrate for flip-chip welding nitride light-emitting diodes according to claim 1, characterized in that: the upper surface and the lower surface of the light-transmitting substrate are rough surfaces.

3. The light-transmitting substrate for flip-chip welding nitride light-emitting diodes according to claim 1, characterized in that: the light-transmitting substrate is a sapphire substrate.

4. A method of manufacturing a light-transmitting substrate for a flip-chip soldered nitride light-emitting diode as claimed in claim 1 or 2 or 3, using photolithography and dry etching steps to produce a regularly patterned surface, including the following steps:

(1) Lithography: Coating a surface of a light-transmitting substrate with a photosensitive material; placing a photomask on top of the surface with the same pattern as the pattern; Exposure: passing parallel light through the photomask Selectively expose the photosensitive material so that the pattern of the photomask is completely transferred to the surface of the light-transmitting substrate; develop so that the photosensitive material obtains a pattern that is the same as or complementary to the photomask pattern; (2) Dry etching: The photosensitive material is dry etched so that the light-transmissive substrate produces a surface with regular patterns.

5. A method of manufacturing a light-transmitting substrate for a flip-chip soldered nitride light-emitting diode as claimed in claim 1 or 2 or 3, using photolithography and wet etching steps to produce a regularly patterned surface, including the following steps:

(1) Lithography: Coating a surface of a light-transmitting substrate with a photosensitive material; placing a photomask on top of the surface with the same pattern as the pattern; Exposure: passing parallel light through the photomask Selectively expose the photosensitive material so that the pattern of the photomask is completely transferred to the surface of the light-transmitting substrate; develop so that the photosensitive material obtains the same or complementary pattern as the photomask pattern; (2) Wet etching: use 200 The light-transmitting substrate is etched with a mixed solution of phosphoric acid and sulfuric acid at a temperature ranging from 350° C. to 350° C., so that the light-transmitting substrate produces a regularly patterned surface.

6. A method of manufacturing a light-transmitting substrate for a flip-chip soldered nitride light-emitting diode as claimed in claim 2 or 3, using a wet etching step to produce two irregularly patterned surfaces, including the following steps: formed through a crystal growth step A light-transmitting substrate, with at least one defect formed on both the upper surface and the lower surface of the light-transmitting substrate; etching the light-transmitting substrate with a mixed solution of phosphoric acid and sulfuric acid at 200°C to 350°C, so that the light-transmitting substrate Two irregularly patterned surfaces are produced simultaneously.

7. A method of manufacturing a light-transmitting substrate for a flip-chip soldered nitride light-emitting diode as claimed in claim 1, 2 or 3, using a laser to scan a surface of the light-transmitting substrate to form a scribe line to generate a pattern rule s surface.

8. A method for manufacturing a light-transmitting substrate for a flip-chip welding nitride light-emitting diode as claimed in claim 1, 2 or 3, first dividing a laser beam into multiple laser beams with uniform or uneven intensity, and then dividing the multiple laser beams into A laser beam with uniform or uneven intensity is projected onto a surface of a light-transmitting substrate to form scribed lines, correspondingly producing a surface with a regular or irregular pattern.

9. Manufacturing the flip-chip soldering nitride luminescence device according to claim 8 as claimed in claim 1 or 2 or 3. The method of claiming a light-transmitting substrate for a diode, characterized in that: a laser beam first passes through a first lens, which is used to uniformly expand the laser beam; and then passes through a second lens, which is used to expand the laser beam. Converted into multiple beams of parallel light; finally passing through the third lens with several uniform or uneven fine structures distributed on the surface, the multiple beams of parallel light are refracted and projected onto a surface of the light-transmitting substrate to form a scoring line, correspondingly generating a Surfaces with regular or irregular patterns.

10. A flip-chip soldering nitride light-emitting diode, comprising the light-transmitting substrate as claimed in claim 1, 2, or 3, with a semiconductor layer stack deposited on the upper surface of the light-transmitting substrate, and the semiconductor layer stack is provided with The p-type electrode and the n-type electrode are respectively welded to the first welding pad and the second welding pad of the mounting platform through a plurality of welding bumps.