TW201528541A - A method for producing light-emitting diode - Google Patents

Abstract

This invention is a kind of production method of the light emitting diode, including the following steps. We pick up a substrate and grow a non-GaN doping epitaxial layer on it. And then, we etch the non-GaN doping epitaxial layer by an etching method to form a porous structural layer. On the layer, a GaN epitaxial layer, a metal layer, and a silicon substrate will be formed. We will use mechanical method to lift off the aforementioned structure from the substrate and plate it on an electrode layer. The micrometer-scaled column structure of the porous structural layer can achieve one-off and prompt lift-off effect without applying laser lift-off and long wet-etching lift-off to it.

Description

Method for manufacturing light emitting diode

The invention relates to a method for manufacturing a light-emitting diode, and more particularly to a method for manufacturing a peeling substrate by mechanical means.

In the manufacturing process of light-emitting diodes in the semiconductor industry today, gallium nitride (GaN) materials are extremely important materials for manufacturing short-wavelength light-emitting diode elements. The gallium nitride material is currently mainly grown on a sapphire substrate, but the conductivity and thermal conductivity of the sapphire substrate are not good. To solve this problem, the method of fabricating the vertical light-emitting diode structure by replacing the substrate is to manufacture the light-emitting diode. New solution for the body.

In the industry, laser stripping technology is currently used for substrate replacement. This technique uses a pseudo-molecular laser to chemically react a gallium nitride film with a sapphire substrate to achieve the effect of separating the substrate. However, the laser stripping device is expensive and the cost is too high. Moreover, high-temperature environments are prone to damage the epitaxial layer, and there are various disadvantages such as the inability to peel off in a large area. Therefore, many scholars are working on a new process that can replace laser stripping. At present, the proposed new solution is mainly chemical wet etching stripping. The technique of chemical wet etching stripping is to add a sacrificial layer to the sapphire. Between the stone substrate and the gallium nitride film, after the structure of the gallium nitride light-emitting diode is completed, the sacrificial layer is chemically etched, thereby separating the gallium nitride film and the sapphire substrate. Although the chemical wet etching stripping technology has the advantages of low cost and mass production, this technology still needs to complete the etching of the old substrate after the bonding of the new substrate, and the processing time is long, and the etching solution is mostly strong acid. Strong alkali solution, the process is easy to cause destruction of the epitaxial layer.

In summary, the development of a novel technique for fabricating a release substrate in a light-emitting diode must be a priority.

The invention is a method for forming a light-emitting diode, which utilizes a micron or nano-pillar structure of a porous structural layer and cooperates with a wet etching process and a wafer bonding technique to complete the substrate stripping purpose to make a vertical Light-emitting diode. The micron or nano-pillar structure of the present invention, in combination with mechanical exfoliation, achieves a one-time and fast peeling effect without the need for additional laser lift-off or time-consuming and destructive wet etch stripping.

The technical feature of the present invention resides in the peeling of the old substrate in the gallium nitride light emitting diode structure. Among several conventional technologies: laser stripping technology process equipment is quite expensive and the maintenance cost of the machine is quite high, and it cannot be mass-produced on a large-sized wafer. In addition, the laser generates high heat on the gallium nitride film. The epitaxial layer causes damage and affects the properties of the component. On the chemical wet stripping technology, although the above-mentioned problems of high cost and mass production cannot be improved, a sacrificial layer is added to the sapphire substrate and the gallium nitride thin Between the films, the subsequent epitaxial quality is affected, so that the luminous efficiency is lowered, and the chemical solution of strong acid and alkali is used for etching. If the etching time is too long, the epitaxial layer or the metal layer may be damaged. Therefore, the applicant is committed to research and development of a novel stripping technology, which mainly uses a porous gallium nitride structure layer produced by wet etching technology, and a gallium nitride epitaxial layer is grown on the structure layer, and then the wafer is processed. Bonding, separating the gallium nitride film and the sapphire substrate by thermal stress and forward pressure generated during wafer bonding. This technology is a one-step process, simple in process and low in cost, and can simultaneously complete wafer bonding of new substrates. Stripping from the old substrate and rapid mass production on large-size wafers is no problem, because the sacrificial layer is not inserted, so that the gallium nitride epitaxial layer is not damaged.

The invention provides a method for manufacturing a light-emitting diode, comprising the steps of: selecting a first substrate, growing a first epitaxial layer on the first substrate; and etching, but not limited to the process of the method Forming a porous structural layer on the crystal layer, wherein the pores of the porous structural layer may be regularly or irregularly arranged, and the depth of the hole may be deep to the interface between the first substrate and the porous structural layer; Depositing a second epitaxial layer on the porous structural layer, and depositing a metal layer on the second epitaxial layer, the metal layer being a single metal layer or comprising an ohmic contact layer, a diffusion barrier layer, a composite layer of a reflective layer and a bonding layer. Forming a second substrate on the metal layer by wafer bonding; and simultaneously bonding the second epitaxial layer, the metal layer and the second substrate from the first substrate by mechanical peeling in the wafer bonding process Stripping; and performing the subsequent grain processing on the second epitaxial layer, the metal layer, and the second substrate to obtain a light emitting diode.

Preferably, the first substrate is a sapphire substrate.

Preferably, the first epitaxial layer is an undoped gallium nitride epitaxial layer.

Preferably, the porous structural layer is a porous gallium nitride structural layer.

Preferably, the porous structural layer method is a chemical wet etching method in which etching is performed in a molten state of potassium hydroxide.

Preferably, the second epitaxial layer is a gallium nitride epitaxial layer.

Preferably, the gallium nitride epitaxial layer comprises a first cladding layer, an active light emitting layer and a second cladding layer in this order from bottom to top.

Preferably, the second substrate is a metal substrate having high conductivity and high heat dissipation or a germanium substrate.

Preferably, the light emitting diode system is a vertical light emitting diode.

The present invention further provides a light-emitting diode which is a vertical light-emitting diode produced by the above-described manufacturing method.

According to the manufacturing method of the light-emitting diode of the present invention, the following advantages and effects can be achieved:

1. The light-emitting diode of the present invention does not require an expensive laser stripping device or additionally inserts a sacrificial layer, and has a simple manufacturing process, low cost, and is suitable for large-area peeling.

2. The manufacturing method of the present invention does not require wet etching during substrate transfer, and does not cause damage to the epitaxial layer, thereby destroying luminous efficiency.

3. The porous structure produced by the manufacturing method of the present invention The layers can be easily mechanically separated from the substrate and wafer bonding and stripping of the old substrate can be performed simultaneously.

1‧‧‧Sapphire substrate

2‧‧‧Undoped gallium nitride epitaxial layer

21‧‧‧Porous GaN structural layer

3‧‧‧First coating

4‧‧‧Active luminescent layer

5‧‧‧Second coating

6‧‧‧metal layer

7‧‧‧矽 substrate

8‧‧‧electrode layer

1 is an undoped gallium nitride epitaxial layer 2 grown on a sapphire substrate 1; and FIG. 2 is an etching of the undoped gallium nitride epitaxial layer 2 to form a porous gallium nitride structural layer 21 FIG. 3 is a view showing a gallium nitride epitaxial layer formed on the porous gallium nitride structural layer 21, wherein the gallium nitride epitaxial layer comprises a first cladding layer 3 and an active light emission from bottom to top. a layer 4 and a second cladding layer 5; FIG. 4 is a deposition of a metal layer 6 on the gallium nitride epitaxial layer; and FIG. 5 is a wafer bonding method to form a second layer on the metal layer 6. After the substrate 7, the gallium nitride epitaxial layer, the metal layer 6 and the second substrate 7 are simultaneously peeled off from the sapphire substrate 1 by mechanical peeling; FIG. 6 is the gallium nitride epitaxial layer, The metal layer 6 and the germanium substrate 7 are plated with an electrode layer 8 to perform a crystal grain process of the light emitting diode.

The present invention will be described in more detail with reference to the following examples and drawings to illustrate a method of producing a light-emitting diode of the present invention.

The technical contents of the present invention are described in detail below. See as in the first As shown in FIG. 1, a sapphire substrate 1 is taken, and an undoped gallium nitride epitaxial layer 2 is grown on the sapphire substrate 1 by an organometallic vapor deposition method.

Next, referring to the preparation method of FIG. 2, the undoped gallium nitride epitaxial layer 2 is subjected to a porous gallium nitride structural layer 21 by chemical wet etching, and the present invention is a potassium hydroxide in a molten state. Etching is performed, and the size of the etched porous structure is further controlled. During the etching process, the undoped gallium nitride epitaxial layer 2 is etched with a plurality of etched holes at the beginning of the etching, and then lengthened. During the etching time, the etching solution continues to be etched along the holes. When etching to the interface between the undoped gallium nitride epitaxial layer 2 and the sapphire substrate 1, the etching direction of the etching solution is turned into a horizontal etching. After a certain period of time, the etching liquid starts to be etched from the bottom to the top, thereby producing the sapphire substrate 1 having the porous gallium nitride structural layer 21 thereon, and then further re-crystallizing.

Referring to FIG. 3, the porous gallium nitride structural layer 21 is sequentially grown into a gallium nitride epitaxial layer by an organometallic chemical vapor deposition method, wherein the gallium nitride epitaxial layer is formed by The upper layer comprises a first cladding layer 3, an active luminescent layer 4 and a second cladding layer 5. Referring to FIG. 4, a composite metal layer 6 is coated on the second cladding layer 5 by electron gun evaporation. After the above steps are completed, the second substrate can be bonded by wafer bonding and the mechanical peeling can be achieved. Referring to FIG. 5, a second substrate 7 is formed on the metal layer 6. In the above, the mechanical peeling method can effectively utilize the forward pressure applied during bonding, and the thermal stress generated between the second substrate 7 and the sapphire substrate 1 during the temperature rise and fall, combining two The stress can break the porous gallium nitride structural layer 21, so that the gallium nitride epitaxial layer, the metal layer 6 and the second substrate 7 are detached from the sapphire substrate 1 to achieve the purpose of substrate transfer.

Please refer to FIG. 6 , after the substrate is transferred, the residual undoped gallium nitride epitaxial layer 2 is removed by dry etching, and then the semiconductor process technology is applied to perform the subsequent grain process. The vertical light emitting diode of the present invention.

According to the manufacturing method of the light-emitting diode of the present invention, the vertical light-emitting diode manufactured by the invention does not require an expensive laser stripping apparatus and can be applied to a large-area peeling, and does not have a chemical wet etching peeling. The etching time of the technology is too long to cause the destruction of the epitaxial layer. Furthermore, the porous gallium nitride structural layer produced by the method for producing a light-emitting diode of the present invention may be in the order of micrometers or nanometers, and the shape after etching may be columnar or other regular or irregular. The shape of the body, the porous structural system of the present invention conforms to the subsequent mechanical peeling and the requirements for subsequent re-elevation growth.

1‧‧‧Sapphire substrate

2‧‧‧Undoped gallium nitride epitaxial layer

Claims (10)

A method for manufacturing a light-emitting diode, comprising the steps of: selecting a first substrate, growing a first epitaxial layer on the first substrate; forming the epitaxial layer by etching, but not limited to the process of the method a porous structural layer, wherein the porous structural layer may be arranged in a regular or irregular manner, and the depth of the hole may be, but not limited to, a depth to the interface between the first substrate and the porous structural layer; a second epitaxial layer is grown on the structural layer, and a metal layer is deposited on the second epitaxial layer. The metal layer can be a multifunctional single layer metal or include an ohmic contact layer, a diffusion barrier layer, and a reflection layer. a composite metal layer of the layer and the bonding layer, and then forming a second substrate on the metal layer; the first substrate, the first epitaxial layer, the second epitaxial layer and the metal layer and the second layer are bonded by wafer bonding Bonding the substrates together, and simultaneously peeling off the second epitaxial layer, the metal layer, and the second substrate from the first substrate by mechanical peeling; finally, the second epitaxial layer, the metal layer, and the second Substrate through semiconductor process technology Subsequent die process, to obtain a vertical light emitting diode. The manufacturing method of claim 1, wherein the first substrate is a sapphire substrate or the remaining substrate for growing a gallium nitride material. The manufacturing method of claim 1 or 2, wherein the first epitaxial layer is an undoped gallium nitride epitaxial layer. The manufacturing method of claim 3, wherein the porous structural layer is a porous gallium nitride structural layer. The manufacturing method of claim 4, wherein the etching method is, but not limited to, chemical wet etching, and etching is performed in a molten state of potassium hydroxide. The manufacturing method of claim 5, wherein the second epitaxial layer is a gallium nitride epitaxial layer. The manufacturing method of claim 6, wherein the gallium nitride epitaxial layer comprises a first cladding layer, an active light emitting layer and a second cladding layer in this order from bottom to top. The manufacturing method of claim 6, wherein the second substrate is a substrate having high conductivity and high heat dissipation. The manufacturing method of claim 7, wherein the light emitting diode system is a vertical light emitting diode. A light-emitting diode, which is conventionally used by those skilled in the art, but is not limited to the vertical light-emitting diode produced by the manufacturing method of any one of claims 1 to 9.