KR20100109169A - Fabrication method of light emitting diode and the light emitting diode fabricated by the method - Google Patents

Abstract

PURPOSE: A fabrication method of a light emitting diode and the light emitting diode fabricated by the method are provided to prevent a sacrificial substrate from being bent due to the difference between coefficients of thermal expansion. CONSTITUTION: In a light emitting diode and a manufacturing thereof, a compound semiconductor layer including a first conductive compound semiconductor, an active layer, and a second conductive compound semiconductor is formed on a sacrificial substrate. A compensation layer(63) having different coefficient of thermal expansion from a support substrate is formed on the support substrate. The support substrate is bonded through a junction layer. The sacrificial substrate is separated from the compound semiconductor to expose a first conductive compound semiconductor layer.

Description

Light emitting diode manufacturing method and light emitting diode manufactured by the same {FABRICATION METHOD OF LIGHT EMITTING DIODE AND THE LIGHT EMITTING DIODE FABRICATED BY THE METHOD}

The present invention relates to a light emitting diode manufacturing method and a light emitting diode manufactured by the same, in particular to prevent wafer cracks caused by the difference in thermal expansion coefficient between the sacrificial substrate and the support substrate in the light emitting diode manufacturing method using a substrate separation process A light emitting diode manufacturing method capable of stabilizing a manufacturing process and a light emitting diode manufactured by the same.

In general, nitrides of group III elements, such as gallium nitride (GaN) and aluminum nitride (AlN), have excellent thermal stability and have a direct transition energy band structure. It is attracting much attention as a substance. In particular, blue and green light emitting devices using gallium nitride (GaN) have been used in various applications such as large-scale color flat panel display devices, traffic lights, indoor lighting, high density light sources, high resolution output systems, and optical communications.

The nitride semiconductor layer of such a group III element, in particular GaN, is difficult to fabricate a homogeneous substrate capable of growing it, and thus, it is difficult to fabricate a homogeneous substrate capable of growing it. MBE) and other processes. As a hetero substrate, a sapphire substrate having a hexagonal structure is mainly used. However, since sapphire is an electrically insulator, it restricts the light emitting diode structure and is very stable mechanically and chemically, making it difficult to process such as cutting and shaping. Accordingly, in recent years, after the nitride semiconductor layers are grown on a dissimilar substrate such as sapphire, a technique of manufacturing a light emitting diode having a vertical structure by separating the dissimilar substrate has been studied.

1 is a cross-sectional view illustrating a method of manufacturing a vertical light emitting diode according to the prior art.

Referring to FIG. 1A, gallium nitride-based compound semiconductor layers are sequentially grown on a sacrificial substrate 11 such as a sapphire substrate. The compound semiconductor layers include a first conductivity type semiconductor layer 15, an active layer 17, and a second conductivity type semiconductor layer 19. In addition, a buffer layer 13 is generally interposed between the first conductive semiconductor layer 15 and the sacrificial substrate 11.

Referring to FIG. 1B, a support substrate 21 is attached on the compound semiconductor layers. The support substrate 21 is generally attached on the compound semiconductor layers by the bonding layer 23. On the other hand, a reflective layer (not shown) may also be interposed between the support substrate 21 and the compound semiconductor layers.

Referring to FIG. 1C, the sacrificial substrate 11 is separated from the compound semiconductor layers. At this time, the buffer layer 13 is also removed, and the first conductivity type compound semiconductor layer 15 is exposed. The sacrificial substrate 11 may be separated from the compound semiconductor layers using a laser lift-off process. Thereafter, an electrode pad 17 is formed on the exposed first conductive compound semiconductor layer 15, and individual light emitting diode chips are completed by cutting the support substrate 21.

According to the prior art, by adopting a support substrate 21 having excellent heat dissipation performance and electrical conductivity, such as silicon or metal, the light emitting efficiency of the light emitting diode can be improved, and a light emitting diode having a vertical structure can be provided. However, since the support substrate 21 generally has a coefficient of thermal expansion different from that of the sacrificial substrate 11, when the support substrate 21 is bonded at a temperature of, for example, 250 ° C. to 300 ° C. using the bonding layer 23. As a result, the warpage of the wafer occurs at room temperature due to the difference in thermal expansion coefficient between the sacrificial substrate 11 and the support substrate 21. This bending phenomenon is due to the difference in thermal expansion coefficient between the sacrificial substrate 11 and the support substrate 21, because a significant stress (stress) is applied to the sacrificial substrate in the bonded state of the support substrate 21.

In this state, when performing a substrate separation process, such as a laser lift-off process, not only is it difficult to focus the laser precisely, but also the stress relaxation occurs rapidly during the process, and cracks are generated in the sacrificial substrate 11 and the compound semiconductor layers. And thus process failure.

The warpage phenomenon can be solved to some extent by adjusting the thermal expansion coefficient or the thickness of the support substrate, but it is difficult to control the thermal expansion coefficient of the support substrate, and the material of the support substrate cannot be variously selected.

SUMMARY OF THE INVENTION The present invention provides a light emitting diode manufacturing method capable of preventing occurrence of cracks in a sacrificial substrate due to a difference in thermal expansion coefficient between a support substrate and a sacrificial substrate in a light emitting diode manufacturing method using a substrate separation process. will be.

Another technical problem to be solved by the present invention is that the bending of the sacrificial substrate occurs due to the difference in the coefficient of thermal expansion of the support substrate and the sacrificial substrate in the state in which the supporting substrate and the sacrificial substrate are bonded in the LED manufacturing method using the substrate separation process. It is to provide a light emitting diode manufacturing method that can be suppressed.

Another object of the present invention is to provide a method of manufacturing a light emitting diode capable of variously selecting a support substrate.

In order to solve the above problems, an aspect of the present invention provides a light emitting diode manufacturing method. The method forms a compound semiconductor layer comprising a first conductivity type compound semiconductor layer, an active layer and a second conductivity type compound semiconductor layer on the sacrificial substrate, and has a coefficient of thermal expansion different from that of the support substrate on the support substrate. Forming a thermal expansion coefficient compensation layer. A support substrate having the thermal expansion coefficient compensation layer on the compound semiconductor layers is bonded through a bonding layer. Thereafter, the sacrificial substrate is separated from the compound semiconductor layers to expose the first conductive compound semiconductor layer. Accordingly, the thermal expansion coefficient compensation layer may alleviate warpage of the sacrificial substrate due to the difference in thermal expansion coefficient between the sacrificial substrate and the support substrate or the stress applied to the sacrificial substrate, thereby stabilizing the substrate separation process.

In addition, the sacrificial substrate may have a larger coefficient of thermal expansion than the support substrate, and the thermal expansion coefficient compensation layer may have a relatively large coefficient of thermal expansion compared to the support substrate. Furthermore, the coefficient of thermal expansion compensation layer may have a coefficient of thermal expansion that is relatively greater than or equal to that of the sacrificial substrate. Therefore, when the sacrificial substrate has a relatively large coefficient of thermal expansion compared to the supporting substrate, the thermal expansion coefficient compensation layer compensates for the difference in thermal expansion coefficient between the supporting substrate and the sacrificial substrate.

On the other hand, the sacrificial substrate may have a relatively smaller coefficient of thermal expansion than the support substrate, the thermal expansion coefficient compensation layer may have a relatively small coefficient of thermal expansion compared to the support substrate. Furthermore, the coefficient of thermal expansion compensation layer may have a coefficient of thermal expansion that is relatively smaller than or equal to that of the sacrificial substrate. Therefore, when the sacrificial substrate has a relatively small coefficient of thermal expansion compared to the supporting substrate, the thermal expansion coefficient compensation layer compensates for the difference in thermal expansion coefficient between the supporting substrate and the sacrificial substrate.

In addition, the thermal expansion coefficient compensation layer may be bonded onto the compound semiconductor layers through the bonding layer. Alternatively, the support substrate may be bonded onto the compound semiconductor layers through the bonding layer, and the thermal expansion coefficient may be The compensation layer may be located on the opposite side of the bonding surface of the support substrate.

According to another aspect of the present invention, a light emitting diode is provided. The light emitting diode includes a support substrate; A thermal expansion coefficient compensation layer disposed on the support substrate and having a thermal expansion coefficient different from that of the support substrate; Compound semiconductor layers on the thermal expansion coefficient compensation layer; And a bonding layer interposed between the compound semiconductor layers and the thermal expansion coefficient compensation layer.

According to the present invention, a thermal expansion coefficient compensation layer for compensating for a difference in thermal expansion coefficient between a supporting substrate and a sacrificial substrate is formed on a supporting substrate, whereby the sacrificial substrate is formed by rapid relaxation of stress in a light emitting diode manufacturing method using a substrate separation process. The occurrence of cracks and the like can be prevented. In addition, the bending of the sacrificial substrate can be suppressed due to the difference in thermal expansion coefficient between the support substrate and the sacrificial substrate in the bonded state of the support substrate and the sacrificial substrate. Further, by adopting the coefficient of thermal expansion compensation, it is possible to select various materials of the support substrate.

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.

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

Referring to FIG. 2, compound semiconductor layers are formed on the sacrificial substrate 51. The sacrificial substrate 51 is generally a sapphire substrate, but may be another hetero substrate. The compound semiconductor layers include a first conductive compound semiconductor layer 55, an active layer 57, and a second conductive compound semiconductor layer 59. The compound semiconductor layers are III-N-based compound semiconductor layers, and may be grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The first conductivity type and the second conductivity type represent N-type and P-type, or P-type and N-type.

Meanwhile, before forming the compound semiconductor layers, the buffer layer 53 may be formed. The buffer layer 53 is adopted to mitigate lattice mismatch between the sacrificial substrate 51 and the compound semiconductor layers, and generally may be a gallium nitride-based single or multiple material layer.

Referring to FIG. 3, apart from forming compound semiconductor layers on the sacrificial substrate 51, a thermal expansion coefficient compensation layer 63 is formed on the support substrate 61.

The support substrate 61 is a substrate such as Si, GaAs, GaP, AlGaINP, Ge, SiSe, GaN, AlInGaN or InGaN, but Al, Zn, Ag, W, Ti, Ni, Au, Mo, Pt, Pd, Cu, It may be a single metal of Cr or Fe or an alloy substrate thereof.

The coefficient of thermal expansion compensation layer 63 is formed of a material layer having a coefficient of thermal expansion different from that of the supporting substrate 61 to compensate for the coefficient of thermal expansion of the entire supporting substrate 61. For example, when the sacrificial substrate 51 has a larger coefficient of thermal expansion than the support substrate 61, the thermal expansion coefficient compensation layer 63 is formed of a material layer having a relatively large coefficient of thermal expansion compared to the support substrate 61. Can be. In addition, the coefficient of thermal expansion compensation layer 63 may be formed of a material layer having a coefficient of thermal expansion that is relatively greater than or equal to that of the sacrificial substrate 51.

In contrast, when the sacrificial substrate 51 has a coefficient of thermal expansion relatively smaller than that of the supporting substrate 61, the coefficient of thermal expansion compensation layer 63 is a material layer having a coefficient of thermal expansion relatively smaller than that of the supporting substrate 61. Can be formed. Further, the coefficient of thermal expansion compensation layer 63 may be formed of a material layer having a coefficient of thermal expansion relatively smaller than or equal to that of the sacrificial substrate 51.

The thermal expansion coefficient compensation layer 63 may be deposited on the support substrate 61 using a deposition technique such as physical vapor deposition or chemical vapor deposition, and may be formed of the same material as the sacrificial substrate 51.

Referring to FIG. 4, a support substrate 61 is bonded to the compound semiconductor layers through the bonding layer 65, and a reflective layer (not shown) is interposed between the support substrate 61 and the compound semiconductor layers. Can be. The bonding layer 65 may be formed by forming a bonding metal on both sides of the sacrificial substrate 51 and the supporting substrate 61, and then bonding them, and the bonding metal may be formed of, for example, AuSn (80 / 20wt%). Can be.

Referring to FIG. 5, the sacrificial substrate 51 is separated from the compound semiconductor layers. The sacrificial substrate 51 may be separated by laser lift off (LLO) technology or other mechanical or chemical methods. In this case, the buffer layer 53 is also removed to expose the first conductivity type compound semiconductor layer 55.

Referring to FIG. 6, an electrode pad 67 is formed on light emitting diode chip regions. Rough surfaces (not shown) may be formed on the first conductive compound semiconductor layer 55 before or after the electrode pad 67 is formed. In addition, the thermal expansion coefficient compensation layer 63 may be removed, and a part of the support substrate 61 may also be removed by a polishing technique or the like.

Thereafter, the light emitting diode is completed by cutting the supporting substrate 61 along the scribing lines and separating them into individual light emitting diode chips.

According to this embodiment, by forming the thermal expansion coefficient compensation layer 63 on the support substrate 61, it is possible to compensate for the difference in thermal expansion coefficient between the sacrificial substrate 51 and the support substrate 61. Accordingly, if necessary, the bending of the sacrificial substrate 51 generated after bonding the support substrate 61 can be prevented, or the stress applied to the sacrificial substrate 51 can be reduced.

In the present embodiment, the thermal expansion coefficient compensation layer 63 has been described as being removed, but may not be removed.

7 and 8 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 7, as described above with reference to FIGS. 2 and 3, the compound semiconductor layers are formed on the sacrificial substrate 51, and the thermal expansion coefficient compensation layer 63 is formed on the support substrate 61. Is formed. Thereafter, a thermal expansion coefficient compensation layer 63 is bonded through the bonding layer 65 on the compound semiconductor layers on the sacrificial substrate 51. That is, the support substrate 61 is bonded on the semiconductor layers such that the thermal expansion coefficient compensating layer 63 and the compound semiconductor layers face each other.

Referring to FIG. 8, electrode pads 67 are formed on light emitting diode chip regions. Rough surfaces (not shown) may be formed on the first conductive compound semiconductor layer 55 before or after the electrode pad 67 is formed. In addition, part of the support substrate 61 can also be removed by a polishing technique or the like.

According to the present embodiment, the thermal expansion coefficient compensation layer 63 remains between the compound semiconductor layers and the support substrate 61. Therefore, in order to manufacture a vertical light emitting diode, it is preferable that the thermal expansion coefficient compensation layer 63 is formed of a conductive film. However, the thermal expansion coefficient compensation layer 63 is not limited to being formed of a conductive film, but may be formed of an insulating film. In this case, a portion of the compound semiconductor layers may be removed to expose the second conductivity-type semiconductor layer 59 or the bonding layer 65, and the exposed layer may be used as a contact layer.

According to embodiments of the present invention, by adopting the coefficient of thermal expansion compensation layer 63, it is possible to compensate for the difference in coefficient of thermal expansion between the sacrificial substrate 51 and the support substrate 61, and thus light emission using a substrate separation process In the diode manufacturing method, it is possible to prevent bending of the sacrificial substrate 51 or to relieve stress applied to the sacrificial substrate, thereby stabilizing the substrate separation process. In addition, by adopting the thermal expansion coefficient compensation layer 63, the material of the support substrate can be variously selected regardless of the thermal expansion coefficient.

1 is a cross-sectional view illustrating a method of manufacturing a vertical light emitting diode according to the prior art.

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

7 and 8 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to another embodiment of the present invention.

Claims (8)

Forming compound semiconductor layers including the first conductive compound semiconductor layer, the active layer, and the second conductive compound semiconductor layer on the sacrificial substrate, Forming a thermal expansion coefficient compensation layer having a thermal expansion coefficient different from that of the supporting substrate on the supporting substrate, Bonding a support substrate having the thermal expansion coefficient compensation layer on the compound semiconductor layers through a bonding layer, And separating the sacrificial substrate from the compound semiconductor layers to expose a first conductive compound semiconductor layer. The method according to claim 1, The sacrificial substrate has a relatively large coefficient of thermal expansion compared to the support substrate, The thermal expansion coefficient compensation layer is a light emitting diode manufacturing method having a relatively large thermal expansion coefficient compared to the supporting substrate. The method according to claim 2, The thermal expansion coefficient compensation layer is a light emitting diode manufacturing method having a thermal expansion coefficient relatively greater than or equal to the sacrificial substrate. The method according to claim 1, The sacrificial substrate has a relatively small coefficient of thermal expansion compared to the support substrate, The thermal expansion coefficient compensation layer is a light emitting diode manufacturing method having a relatively small thermal expansion coefficient compared to the supporting substrate. The method according to claim 4, The thermal expansion coefficient compensation layer has a thermal expansion coefficient relatively smaller than or equal to the sacrificial substrate. The method according to claim 1, And the thermal expansion coefficient compensation layer is bonded onto the compound semiconductor layers through the bonding layer. The method according to claim 1, The support substrate is bonded onto the compound semiconductor layers through the bonding layer, the thermal expansion coefficient compensation layer is located on the opposite side of the bonding surface of the support substrate. Support substrate; A thermal expansion coefficient compensation layer disposed on the support substrate and having a thermal expansion coefficient different from that of the support substrate; Compound semiconductor layers on the thermal expansion coefficient compensation layer; And And a junction layer interposed between the compound semiconductor layers and the thermal expansion coefficient compensation layer.

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