KR100858322B1 - Manufacturing method of vertically structured gan led device - Google Patents

Abstract

A method for manufacturing a gallium nitride-based LED having a vertical structure is provided to enhance a yield and reliability by removing rapidly a sapphire substrate from an LED structure. A buffer layer is formed on a sapphire substrate in order to remove the sapphire substrate. A gallium nitride-based LED structure including an N type gallium nitride layer, an active layer, and a P type gallium nitride layer(135) is divided into a plurality of LED elements. The LED elements are formed on the buffer layer. A sacrificial layer(140) is formed between the LED elements. An electrode layer and a structure supporting layer are stacked on the LED elements and the sacrificial layer. The buffer layer is removed by using a chemical lift-off process so that the sapphire substrate is isolated from the LED elements.

Description

Manufacturing method of a gallium nitride based LED device having a vertical structure {Manufacturing method of vertically structured GaN LED device}

1 and 2 are cross-sectional views illustrating a method of manufacturing a conventional gallium nitride based LED device;

3 to 9 are cross-sectional views of each step for explaining a method of manufacturing a gallium nitride-based LED device having a vertical structure according to an embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

110: sapphire substrate 115: buffer layer

120: guide pattern 125: N-type gallium nitride layer

130: active layer 135: P-type gallium nitride layer

140: sacrificial layer 145: P-type electrode

150: reflective layer 155: structural support layer

165: lattice groove

The present invention relates to a method of manufacturing a gallium nitride-based LED device having a vertical structure, in particular a vertical structure to improve the yield and device characteristics by minimizing the physical stress applied to the LED device when performing the separation process of the sapphire substrate It relates to a method of manufacturing a gallium nitride-based LED device having a.

In general, a light emitting diode (LED) refers to a semiconductor device capable of realizing various colors of light by constituting a light emitting source by changing compound semiconductor materials such as GaAs, AlGaAs, GaN, InGaN, and AlGaInP. Thanks to the rapid development of semiconductor technology, LED devices have escaped from general-purpose products with low brightness, enabling the production of high-brightness and high-quality products, and the realization of high-performance blue and white diodes. The application value of LED is being expanded to display, next generation lighting source, etc. In particular, the gallium nitride (GaN) -based LED device is focused on the characteristic that the transition method is a direct transition type with a high probability of laser oscillation and the possibility of blue laser oscillation. I am getting it.

1 and 2 are cross-sectional views illustrating a method of manufacturing a conventional gallium nitride based LED device.

As shown in FIG. 1, according to the conventional method of manufacturing a gallium nitride-based LED device, an N-type gallium nitride layer 20, an active layer 30, a P-type gallium nitride layer 40, and a P-type on a sapphire substrate 10 are provided. After stacking the electrodes 50 sequentially, as shown in FIG. 2, the structure is etched in a predetermined pattern to form the N-type electrode 70 and to separate the LED elements, and then the N-type electrode 70. ) Is formed on the N-type gallium nitride layer 20, and then, after scribing or dicing, a chip breaking process is performed and separated into individual devices.

That is, the gallium nitride-based LED device completed by this manufacturing method is a horizontal structure in which the P-type electrode and the N-type electrode are disposed in the same direction of the LED device. Therefore, the area of the LED element must be relatively large in order to provide sufficient light emitting area. In addition, since the P-type electrode and the N-type electrode are located close to each other, there is a problem vulnerable to electrostatic discharge (ESD). Above all, the sapphire substrate is hard, electrically nonconductive, and has poor thermal conductivity. Accordingly, the sapphire substrate has a limitation in reducing the size of the gallium nitride-based LED device, thereby reducing manufacturing cost or improving the light output and chip characteristics. In particular, it is very important to solve the heat dissipation problem of the LED device because the application of a large current is necessary for the high output of the LED device.

Therefore, as a way to solve this problem, a method of manufacturing a gallium nitride-based LED device having a vertical structure to remove the sapphire substrate using a technique called laser lift-off (hereinafter referred to as 'LLO'). This is proposed in Korean Unexamined Patent Publication No. 2007-20840 (hereinafter referred to as 'quotation citation'). Here, the main configuration of the cited invention as described in claim 1, "(a) forming an insulating pattern defining a unit LED forming region of a predetermined size on the substrate (sapphire substrate); ( b) forming a light emitting structure having a structure in which an n-type gallium nitride-based semiconductor layer, an active layer, and a p-type gallium nitride-based semiconductor layer are sequentially stacked on a substrate except for the region where the insulating pattern is formed (c) the insulating pattern Separating the light emitting structure into unit LEDs having a predetermined size by removing the light emitting structure; and (d) forming p-type electrodes on the separated light emitting structure, respectively ; (e) forming a structural support layer on the p-type electrode; (F) the n-type gallium nitride system by removing the substrate Exposing a semiconductor layer ; And (g) forming n-type electrodes on the exposed n-type gallium nitride-based semiconductor layer, respectively. "In particular, the step (f) is as follows. This is accomplished by the LLO process.

In addition, although not mentioned in the detailed description of the invention, step (d) is generally performed by applying a photoresist on the light emitting structure separated by step (c), followed by step (c). By placing a mask patterned to cover the lattice grooves formed between the light emitting structures on the photoresist-coated light emitting structure, and then illuminating the mask pattern for a predetermined time, and then exposing the light to a portion of the mask pattern. After the photoresist on the structure is developed, a p-type electrode is formed on the developed portion, and then a photoresist that is not exposed to light is also removed through a series of mask pattern processes.

However, according to the above-mentioned cited invention, firstly, expensive laser equipment must be used to remove the sapphire substrate, and high temperature heat generated during the LLO process causes physical stress on the LED device, thereby degrading the LED device characteristics. Of course, there were problems such as poor yield and reliability.

Second, as described above, the p-type electrode is formed by a very complicated and multi-step process by a mask pattern process, and thus, there is a problem in that the overall manufacturing process is long and productivity is lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and after forming a buffer layer on a sapphire substrate, and forming an LED structure including an N-type gallium nitride layer, an active layer, and a P-type gallium nitride layer on the buffer layer, the chemical lift Vertical structure that allows the sapphire substrate to be removed from the LED structure more easily and safely without physically impacting the LED structure by removing the buffer layer using a chemical lift-off process (CLO). An object of the present invention is to provide a method for manufacturing a gallium nitride-based LED device having a.

Furthermore, by separating the LED structures into unit LED elements and forming a sacrificial layer that insulates each LED element between the grid grooves formed accordingly, it is easy to stack the electrode layer and the structure support layer on the LED structure filled with the sacrificial layer. Another method is to provide a method of manufacturing a gallium nitride-based LED device having a vertical structure that does not require a separate mask pattern process for forming the electrode layer and the structure support layer, thereby shortening the overall manufacturing time of the LED device.

In order to achieve the above object, a method of manufacturing a gallium nitride-based LED device having a vertical structure of the present invention comprises the steps of (a) forming a buffer layer for removal of the sapphire substrate on the sapphire substrate; (B) separating and forming a gallium nitride-based LED structure including a N-type gallium nitride layer, an active layer, and a P-type gallium nitride layer into a plurality of LED elements on the buffer layer formed in step (a); (C) sequentially forming an electrode layer and a structure support layer on the plurality of LED elements formed in step (b); And (d) removing the buffer layer using a chemical lift-off process to separate the sapphire substrate from the plurality of LED elements formed in step (b).

Here, the step (c) is to form a sacrificial layer between the plurality of LED elements formed in the step (b) (c1) and the plurality of LED elements formed in the step (b) and the (c1) formed It is preferable that the (c2) comprising the step of laminating the electrode layer and the structure support layer on the sacrificial layer.

In addition, in step (d), after removing the sacrificial layer formed in step (c1), the buffer layer is removed using a chemical lift-off process to separate the sapphire substrate from the plurality of LED devices formed in step (b). It is desirable to.

In addition, (b) step (b1) to form a guide pattern used to separate and grow a plurality of LED elements on the buffer layer formed in the step (a); And separating and forming a gallium nitride based LED structure including an N-type gallium nitride layer, an active layer, and a P-type gallium nitride layer on the buffer layer into a plurality of LED elements by using the guide pattern formed in step (b1) ( It is preferred to include a step b2).

In addition, in the step (c1), after the photoresist is applied between the plurality of LED elements formed in the step (b), after performing an exposure process, the photoresist on the plurality of LED elements is removed through a developing process. It is desirable to. At this time, it is preferable that a surfactant is added to the developing solution used in the said developing process.

In addition, it is preferable to adjust the viscosity of the photoresist or the speed of the development process so that there is a step between the plurality of LED elements formed in step (b) and the sacrificial layer formed in step (c1).

Hereinafter, a method of manufacturing a gallium nitride-based LED device having a vertical structure according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in detail.

3 to 9 are cross-sectional views of each step for explaining a method of manufacturing a gallium nitride-based LED device having a vertical structure according to an embodiment of the present invention.

First, as shown in FIG. 3, the buffer layer 115 is stacked on the sapphire substrate 110, and then a guide pattern 120 is formed on the buffer layer 115 to guide the growth of the LED device. In this case, the buffer layer 115 is preferably made of a metal, and the buffer layer 115 has a buffering function so that stress is not applied to the LED structure which will be described later in the process of removing the sapphire substrate 110. In addition, the guide pattern 120 forms a silicon oxide film on the buffer layer 115, evenly spreads a photoresist on the surface of the silicon oxide film, raises a mask having a predetermined lattice pattern thereon, and then emits light. After splitting, it can be formed by developing a part with or without light. Next, a gallium nitride based LED structure including the N-type gallium nitride layer 125, the active layer 130, and the P-type gallium nitride layer 135 by the guide pattern 120 is formed on the buffer layer 115. Will grow separately.

Meanwhile, as shown in FIG. 4, the process of separating the LED structures described above into unit LED elements is performed on the sapphire substrate 100, the buffer layer 115, the N-type gallium nitride layer 125, and the active layer 130. And after the P-type gallium nitride layer 135 is sequentially formed, a predetermined etching process may be performed, for example, by dry etching. However, as described in the cited invention, rather, in order to minimize the physical stress applied to the LED device by the etching process, as shown in Figure 3, it would be more desirable to separate and grow the LED device from the beginning.

Next, as shown in FIG. 5, the sacrificial layer 140 is formed in the lattice grooves 165 formed between the LED elements by using photoresist. Here, the sacrificial layer 140 is later removed before the buffer layer 115 is removed, and its main function is to facilitate formation of the electrode and structure support layer and a CLO process, which will be described later.

In addition, as shown in FIG. 6, the sacrificial layer 140 is completely filled with the photoresist 140a in the lattice groove 165 and uniformly coated on the P-type gallium nitride layer 135, and then subjected to an exposure process. In some embodiments, the photoresist on the P-type gallium nitride layer 135 may be formed by a development process. Here, FIG. 7 is a plan view illustrating the sacrificial layer 140 to be filled in the lattice groove 165 at another angle, and the cross-sectional view taken along the AA direction is FIG. 6.

At this time, it is preferable that there is a slight step between the sacrificial layer 140 and the P-type gallium nitride layer 135. In order to give the step, the thickness of the photoresist 140a applied on the P-type gallium nitride layer 135 is provided. Is important and the development speed of the photoresist must be properly controlled. In particular, the most influential factor of the thickness of the photoresist is its viscosity. As the viscosity decreases, the thickness of the photoresist becomes thinner, but the flatness of the sacrificial layer 140 after the lithography becomes uneven. On the other hand, the higher the viscosity, the better the flatness, but the thickness of the photoresist to be applied is too thick, it is difficult to remove the residual photoresist as a step and the development process. Meanwhile, the sacrificial layer 140 may be implemented with a photoresist that is a polymer-based material containing a photo active compound (PAC) having good reactivity to light or a thermal active compound (TAC) having good heat reactivity. In addition, it may be implemented as a silicon oxide film (SiO ₂ ), a silicon nitride film (SiN), or BCB (benzo cyclobutene). In addition, the addition of a surfactant to the developer used during the development process will be effective in removing residual photoresist.

Next, as shown in FIG. 8, the P-type electrode 145, the reflective layer 150, and the structure support layer 155 are sequentially stacked on the P-type gallium nitride layer 135 and the sacrificial layer 140. That is, the existing mask pattern process is not necessary. Here, the structural support layer 155 is made of a metal, and serves to maintain the shape of the device so that the device is not damaged by external shock that may occur during the manufacturing process and final packaging process of the light emitting diode device. .

Meanwhile, in FIG. 8, the structural support layer 155 is formed on the reflective layer 150 as a whole, but may be formed separately for each LED device. The method for forming a structural support layer for this purpose is to load a metal mask fabricated in a predetermined pattern on the reflective layer 150, apply a solder paste onto the metal mask thus loaded, and then remove the metal mask, and then remove the metal mask. It is to heat-treat the solder paste patterned by. That is, when the heat treatment process is completed, the solder paste melts and hardens, and is then bonded to the reflective layer 150 to complete the convex structure supporting layer. At this time, the solder paste used to form the structural support layer is Au-Sn, Sn-Sb, Sn-Ag, Sn-Cu, Bi-Sb, Sn-Cu-Sb, Sn-Bi, Sn-Ag-Cu, Sn- Ag-Cu-Bi, Sn-Ag-Cu-In, Sn-Ag-Bi, Sn-Ag-Bi-In, Sn-Zn-In, Sn-Zn-Bi, Sn-Ag-Cu-Sb, In- A solder composed of an alloy such as Ga, Sn-In-Ga, Sn-Pb, Sn-Pb-Ag, or Sn-Pb-Bi can be used.

In addition, when the thickness of the structural support layer formed using the solder paste is less than 10 μm, it is difficult to have a function of maintaining the shape of the device, and the other conductive material and the LED structure, which may be formed on the top, are shorted with each other ( can be short). On the other hand, when the thickness is 200 mu m or more, the LED element becomes too large. Therefore, the thickness of the structural support layer 155 is preferably 10 μm to 200 μm.

Finally, the process of removing the sacrificial layer 140, the guide pattern 120, the buffer layer 115 and the sapphire substrate 110, the gallium nitride having a vertical structure according to the present invention as shown in FIG. The LED system will be manufactured.

To this end, first, the sacrificial layer 140 is removed using a solution such as acetone. In this case, as well as the sacrificial layer 140, the guide pattern 120 is an insulating material rather than a semiconductor, unlike other portions, it can be easily removed using a solution such as buffered oxide etchant (BOE) that reacts with the insulating material. . That is, the sacrificial layer 140 is removed as the solution penetrates into the side of the LED structure as shown in FIG. 7.

Next, the sapphire substrate 110 is separated from the LED device by removing the buffer layer 115 using the CLO process, wherein the CLO solution used for the CLO is known as the tunneling effect, the sacrificial layer 140. ) Is removed to penetrate into the formed space, that is, the grid groove 165. Accordingly, in the buffer layer 115, a chemical reaction occurs according to CLO over the entire orientation except for the bonding surface with the sapphire substrate 110, which is faster and more stable than the conventional manufacturing method of directly forming an LED structure on the sapphire substrate 110. As a result, the sapphire substrate 110 is separated from the LED structure. Then, an N-type electrode (not shown) is formed on the N-type gallium nitride layer 125 that is exposed to the outside through the removal process of the sapphire substrate 110, that is, each LED device.

The manufacturing method of the gallium nitride-based LED device having a vertical structure of the present invention is not limited to the above-described embodiment can be carried out in various modifications within the range allowed by the technical idea of the present invention.

According to the manufacturing method of the gallium nitride-based LED device having a vertical structure of the present invention as described above, the sapphire substrate can be removed from the LED structure more quickly and safely without physically impacting the LED structure, the original LED device characteristics can be obtained, thereby improving yield and reliability.

In addition, as described above, the electrode layer and the structure support layer may be easily stacked on the LED structure without complicated and multi-step processes as in the conventional mask pattern process, thereby reducing the manufacturing time.

Claims (8)

delete (A) forming a buffer layer on the sapphire substrate to remove the sapphire substrate; (B) separating and forming a gallium nitride-based LED structure including a N-type gallium nitride layer, an active layer, and a P-type gallium nitride layer into a plurality of LED elements on the buffer layer formed in step (a); (C1) forming a sacrificial layer between the plurality of LED elements formed in step (b); (C2) stacking an electrode layer and a structure support layer on the plurality of LED elements formed in step (b) and the sacrificial layer formed in step (c1); and (D) separating the sapphire substrate from the plurality of LED elements formed in the step (b) by removing the buffer layer by using a chemical lift-off process. Way. The method of claim 2, Step (d) is: After removing the sacrificial layer formed in the step (c1) by removing the buffer layer using a chemical lift off process, the vertical structure characterized in that the sapphire substrate is separated from the plurality of LED elements formed in the step (b) Method of manufacturing a gallium nitride-based LED device having. The method of claim 3, wherein Step (b) is: (B1) forming a guide pattern used to separate and grow a plurality of LED elements on the buffer layer formed in the step (a); And By using the guide pattern formed in the step (b1), the gallium nitride-based LED structure including the N-type gallium nitride layer, the active layer and the P-type gallium nitride layer formed on the buffer layer to form a plurality of LED elements (b2 Method of manufacturing a gallium nitride-based LED device having a vertical structure characterized in that it comprises a) step. The method of claim 4, wherein Step (c1) is: After applying the photoresist between the plurality of LED elements formed in the step (b), after performing the exposure process, a vertical structure characterized in that the photoresist on the plurality of LED elements are removed through a developing process Method of manufacturing a gallium nitride-based LED device having. The method of claim 5, Method for producing a gallium nitride-based LED device having a vertical structure, characterized in that the surfactant is added to the developing solution to be used in the developing step. The method of claim 6, Method of manufacturing a gallium nitride-based LED device having a vertical structure characterized in that the viscosity of the photoresist is adjusted so that there is a step between the plurality of LED devices formed in step (b) and the sacrificial layer formed in step (c1). . The method of claim 7, wherein Method of manufacturing a gallium nitride based LED device having a vertical structure characterized in that for controlling the speed of the development process so that there is a step between the plurality of LED devices formed in step (b) and the sacrificial layer formed in step (c1). .

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