KR101031350B1 - Method for fabricting light emitting diode - Google Patents

Abstract

Forming semiconductor layers including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the first substrate; Forming a metal pattern on the semiconductor layers and bonding a second substrate on the metal pattern; Separating the first substrate from the semiconductor layers, and patterning the semiconductor layers to expose the metal pattern to form light emitting cells spaced apart from each other; Irradiating a laser to scribe the second substrate for each of the light emitting cells; And breaking the scribed second substrate for each light emitting cell and separating the scribed second substrate into individual devices.

Light Emitting Diode, LED, Sapphire, Parallel, AC, Light Emitting Cell

Description

METHODS FOR FABRICTING LIGHT EMITTING DIODE}

The present invention relates to a method of manufacturing a light emitting diode, and more particularly, to a method of manufacturing a light emitting diode using laser scribing.

In general, a light emitting diode (LED) is a structure that emits light by growing a GaN-based material on a substrate such as GaN, sapphire, silicon, or silicon nitride. In this structure, light emitted from the upper light emitting layer proceeds to the upper and lower portions, and is emitted to the outside of the light emitting diode through a process of reflection, scattering, and refraction. In order to increase light emission efficiency by refracting and reflecting the light emitted from the upper and lower parts of the light emitting layer, it is necessary to use a reflective substrate having a high unevenness or a high reflectivity at the bottom.

However, the upper P layer of the light emitting layer is thin so that it cannot provide unevenness or the efficiency is small even if unevenness occurs. In addition, even though a highly reflective metal material is deposited under the sapphire substrate, there is always light absorbed and extinguished by the sapphire itself. As such, the light exiting through the substrate is largely lost when passing through the substrate. To reduce these losses, growth substrates were removed and Si or metal substrates were added to avoid irregularities on the surface of the substrate and to increase irregularities or to use metals with high reflectivity.

If the growth substrate is removed and different types of substrates are used, it is necessary to have an intermediate layer in order to bond the substrates together, and heat and pressure must be applied to the upper and lower layers of each layer. When heat and pressure are applied, heterogeneous substrates have different coefficients of thermal expansion, causing deformation at room temperature. This deformation causes problems with the properties and yields that occur in subsequent processes.

In addition, there is a problem that the process of separating into individual elements when using a Si substrate or a metal substrate is not easy.

The problem to be solved by the present invention is to provide a method of manufacturing a light emitting diode using laser scribing that can solve such a conventional problem.

According to one aspect of the invention, forming a semiconductor layer including a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on a first substrate; Forming a metal pattern on the semiconductor layers and bonding a second substrate on the metal pattern; Separating the first substrate from the semiconductor layers, and patterning the semiconductor layers to expose the metal pattern to form light emitting cells spaced apart from each other; Irradiating a laser to scribe the second substrate for each of the light emitting cells; And breaking the scribed second substrate for each light emitting cell and separating the scribed second substrate into individual devices.

Preferably, the second substrate is the same type as the first substrate.

Preferably, the first substrate and the second substrate are sapphire substrate.

Preferably, the focus of the laser is formed on the exposed metal pattern.

Advantageously, bonding the second substrate comprises: forming a first metal intermediate layer on the semiconductor layers; Forming a second metal intermediate layer on a second substrate of the same type as the first substrate; And bonding the metal intermediate layers such that the first metal intermediate layer and the second metal intermediate layer face each other.

Preferably, the bonding of the second substrate may further include forming a metal reflective layer on the semiconductor layers before forming the first metal intermediate layer.

According to the present invention, in the case of manufacturing a light emitting diode by removing the growth substrate through the LLO process, the support substrate is used as the growth substrate and the substrate having the same thermal expansion coefficient. It is possible to effectively prevent deformation caused in the process of bonding of high pressure and pressure accompanying, thereby increasing the production yield of the light emitting diode and improving the light emission characteristics.

In addition, for example, a second substrate, such as a GaN-based compound semiconductor substrate or a sapphire substrate, is difficult to focus on the laser as it is transparent. Accurate adjustment can improve process accuracy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention to those skilled in the art will fully convey. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode manufactured by applying a laser scribing method according to an embodiment of the present invention.

Referring to FIG. 1, the support substrate 51 metal pattern 40 is positioned. The support substrate 51 may include a sapphire substrate, AlN, GaN. The support substrate 51 uses a substrate of the same type as the substrate for growing the semiconductor layers constituting the light emitting cell 30. In this embodiment, the support substrate 51 will be described in the case of using a sapphire substrate which is an insulating substrate.

The metal pattern 40 includes bonded metal layers, for example, a metal reflective layer 31a, a metal protective layer 32a, a first metal interlayer 33a, and a second metal interlayer 53a. The metal reflection layer 31a is formed of a metal material having a high reflectance such as silver (Ag) or aluminum (Al). The metal protective layer 32a is a diffusion barrier layer for preventing the metal elements from being diffused into the metal reflective layer 31a to maintain the reflectivity of the metal reflective layer 31a. The first metal mediation layer 33a and the second metal mediation layer 53a are for bonding the metal reflection layer 31a and the support substrate 51 to each other, and may be, for example, Au or an alloy of Au and Sn.

The light emitting cells 30 are positioned on some regions of the metal patterns. The light emitting cell 30 includes a P-type semiconductor layer 29a, an active layer 27a, and an N-type semiconductor layer 25a. The active layer 27a is interposed between the P-type semiconductor layer 29a and the N-type semiconductor layer 25a, and the P-type semiconductor layer 29a and the N-type semiconductor layer 25a may be interchanged with each other.

The N-type semiconductor layer 25a may be formed of N-type Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1), and may include an N-type cladding layer. In addition, the P-type semiconductor layer 29a may be formed of P-type Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1), and may include a P-type cladding layer. The N-type semiconductor layer 25a may be formed by doping silicon (Si), and the P-type semiconductor layer 29a may be formed by doping zinc (Zn) or magnesium (Mg).

The active layer 27a is a region where electrons and holes are recombined, and includes InGaN. The emission wavelength emitted from the light emitting cell is determined according to the type of material constituting the active layer 27a. The active layer 27a may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. The barrier layer and the well layer may be binary to quaternary compound semiconductor layers represented by general formula Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1).

On the other hand, the metal wiring 57 supplies power to the metal pattern 40, and the metal wiring 59 supplies power to the N-type semiconductor layer 25a. To this end, an electrode pad 55 may be formed on each of the N-type semiconductor layers 25a. The electrode pad 55 is in ohmic contact with the N-type semiconductor layer 25a to lower the contact resistance.

2 to 6 are cross-sectional views illustrating a method of manufacturing a light emitting diode using laser scribing according to an embodiment of the present invention.

Referring to FIG. 2, semiconductor layers including a buffer layer 23, an N-type semiconductor layer 25, an active layer 27, and a P-type semiconductor layer 29 are formed on the first substrate 21. The metal reflective layer 31 is formed on the layers.

The first substrate 21 is transparent, like a sapphire substrate, and a substrate lattice matched to the semiconductor layers is advantageous.

The buffer layer 23 and the semiconductor layers 25, 27, and 29 may be formed using metal organic chemical vapor deposition (MOCVD), molecular beam growth (MBE), or hydride vapor deposition (HVPE). In addition, the semiconductor layers 25, 27, and 29 may be continuously formed in the same process chamber.

The buffer layer 23 is not particularly limited as long as it can mitigate lattice mismatch between the first substrate 21 and the semiconductor layers 25, 27, and 29, and may be formed of, for example, undoped GaN.

The metal reflective layer 31 is formed of a metal in ohmic contact with the P-type semiconductor layer, and preferably a metal having high reflectance, for example, Ag or Al. In addition, the thermally conductive metal layer is preferably a metal having high thermal conductivity, but may be, for example, Au or a stack of Au and Sn. The metal protective layer 32 is formed on the metal reflective layer 31. The metal protective layer 32 acts as a diffusion barrier layer. The first metal intermediate layer 33 is formed on the metal protective layer 32. The first metal intermediate layer 33 is for metal bonding and is not particularly limited and may be Au or a stack of Au and Sn.

The second metal intermediate layer 53 is formed on the second substrate 51 separate from the first substrate 21. The second substrate 51 uses a substrate of the same type as the first substrate 21.

The second metal mediation layer 53 is for metal bonding with the first metal mediation layer 31 and is not particularly limited, and may be Au or a stack of Au and Sn.

Referring to FIG. 3, the first metal intermediate layer 33 and the second metal layer 53 are bonded to face each other. Such bonding can be easily performed by applying constant pressure and / or heat.

Thereafter, the laser is irradiated from the first substrate 21 side. The laser may for example be a KrF (248 nm) laser. Since the first substrate 21 is a light transmissive substrate like the sapphire substrate, the laser passes through the first substrate 21 and is absorbed by the buffer layer 23. Accordingly, the buffer layer 23 is decomposed by the absorbed radiation energy at the interface between the buffer layer 23 and the first substrate 21, so that the substrate 21 is separated from the semiconductor layers. do.

Referring to FIG. 4, after the substrate 21 is separated, the remaining buffer layer 23 is removed to expose the surface of the N-type semiconductor layer 25. The buffer layer 23 may be removed using an etching technique or a polishing technique.

Referring to FIG. 5, the semiconductor layers 25, 27, and 29 are patterned using photolithography and etching techniques to form the light emitting cells 30 spaced apart from each other by exposing the metal reflective layer 31.

The light emitting cell 30 includes a patterned P-type semiconductor layer 29a, an active layer 27a, and an N-type semiconductor layer 25a. These semiconductor layers 25a, 27a, 29a may be patterned into the same shape.

In the state where the light emitting cells 30 are separated from each other, the focus of a laser for scribing the first substrate 51 for each light emitting cell is adjusted to match the exposed surface of the metal reflective layer 31. Since the second substrate 51 such as sapphire is transparent, it is difficult to focus the laser, but since the surface of the metal reflective layer 31 is not transparent, the laser can be effectively focused.

Referring to FIG. 6, the laser is irradiated with the laser focused on the exposed metal reflective layer 31 to scribe the second substrate 51 for each light emitting cell. The wavelength of the laser that can be used for laser scribing can be, for example, wavelengths of 265 nm, 305 nm, and 365 nm. As the laser scribing is performed, the metal reflective layer 31, the metal protective layer 32, the first metal intermediate layer 33, and the second metal intermediate layer 53 shown in FIG. 5 are irradiated by a laser beam. The metal pattern 40 which consists of the metal reflection layer 31a, the metal protective layer 32a, the 1st metal intermediate layer 33a, and the 2nd metal intermediate layer 53a starting from the part which is decomposed at high temperature and irradiated with a laser. And part of the second substrate 51 is also removed.

Subsequently, the second substrate 51 is separated into individual devices by breaking the light emitting cells 30. Subsequently, when the metal wirings 57 and 59 for supplying power to the metal pattern 40 and the upper surfaces of the light emitting cells 30 are formed, the light emitting diode shown in FIG. 1 is completed. Meanwhile, before breaking the second substrate 51, the second substrate 51 may be thinned through a lapping process. The lapping process for the second substrate 51 may be performed before laser scribing or after laser scribing.

Meanwhile, before forming the metal wires, an electrode pad 55 may be formed on the N-type semiconductor layer 25a. The electrode pad 55 is in ohmic contact with the N-type semiconductor layer 25a. In this case, although the metal wire 57 is connected to the upper right side of the metal pattern 40, it may be connected to the upper left side as necessary.

According to the present embodiment, as the metal pattern 40 is formed, a process of forming a separate electrode pad on the P-type semiconductor layer 29a is omitted.

In the present exemplary embodiment, the P-type semiconductor layer 29 and the N-type semiconductor layer 25 may be formed in a reversed order. In this case, after removing the buffer layer 23, a transparent electrode may be formed on the P-type semiconductor layer 29.

The present invention is not limited to the above described embodiments, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

1 is a cross-sectional view illustrating a light emitting diode manufactured by applying a laser scribing method according to an embodiment of the present invention.

2 to 6 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Claims (6)

Forming semiconductor layers including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the first substrate; Forming a metal pattern on the semiconductor layers and bonding a second substrate on the metal pattern; Separating the first substrate from the semiconductor layers, and patterning the semiconductor layers to expose the metal pattern to form light emitting cells spaced apart from each other; Irradiating a laser to scribe the second substrate for each of the light emitting cells; And And breaking the scribed second substrate for each light emitting cell and separating the scribed second substrate into individual devices. The method according to claim 1, The second substrate is a light emitting diode manufacturing method, characterized in that the same as the first substrate. The method according to claim 2, The first substrate and the second substrate is a light emitting diode manufacturing method, characterized in that the sapphire substrate. The method according to claim 1, The focus of the laser is a light emitting diode manufacturing method, characterized in that formed on the exposed metal pattern. The method according to claim 1, Bonding the second substrate, Forming a first metal intermediate layer on the semiconductor layers; Forming a second metal intermediate layer on a second substrate of the same type as the first substrate; And Bonding the metal intermediate layers such that the first metal intermediate layer and the second metal intermediate layer face each other. The method according to claim 5, Bonding the second substrate, And forming a metal reflective layer on the semiconductor layers before forming the first metal intermediate layer.

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