KR101259991B1 - Method for fabricating a compound semiconductor device - Google Patents

Abstract

The method for manufacturing a compound semiconductor device according to the present invention includes a first step of preparing a substrate, a second step of forming an Si intermediate layer on the substrate, and a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the Si intermediate layer. And a fourth step of forming the compound semiconductor layer, and a fourth step of separating the substrate from the compound semiconductor layer by decomposing the Si intermediate layer by irradiating a laser to the substrate.

According to the present invention, a laser having a different wavelength range is used in the manufacture of a compound semiconductor device by inserting a Si intermediate layer having a low energy band gap between the substrate and the compound semiconductor layer and decomposing the Si intermediate layer through a laser. The substrate can be easily separated from the compound semiconductor layer.

Nitride Semiconductors, Sapphire, Substrate Separation, LLO, Wavelength

Description

METHODS FOR FABRICATING A COMPOUND SEMICONDUCTOR DEVICE

1 is a process flowchart illustrating a manufacturing process of a compound semiconductor device according to an embodiment of the present invention.

2 to 4 are cross-sectional views of the manufacturing process of FIG. 1.

<Description of the symbols for the main parts of the drawings>

100 substrate 200 Si interlayer

300: nitride semiconductor layer 310: buffer layer

320: undoped GaN semiconductor layer 330: first conductive semiconductor layer

340 active layer 350 second conductive semiconductor layer

400: transparent electrode 500: reflective layer

600a, 600b: electrode pad

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a compound semiconductor device. In detail, in the fabrication of a compound semiconductor device, a silicon intermediate layer having an energy band gap smaller than that of the buffer layer is formed between the substrate and the buffer layer of the compound semiconductor layer. It is related with the method of manufacturing a compound semiconductor element separately.

Group III-V compound semiconductors provide superior performance in applications such as high speed and high temperature electronics, light emitters and photo detectors. In particular, gallium nitride (GaN) included in nitride compound semiconductors has a bandgap required for a blue laser and a light emitting diode emitting a blue wavelength spectrum. Doing. In addition, alloys of aluminum nitride (AlN), indium nitride (InN), and gallium nitride (GaN) are used in various light emitting devices by providing a spectrum over the entire visible region.

In general, a light emitting device includes a light emitting diode having a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer interposed between these semiconductor layers. Light is generated by the recombination of electrons and holes in the active layer and emitted to the outside.

Recently, vertical LEDs have been disclosed to shorten the recombination distance between electrons and holes to reduce energy loss in light emitting diodes.

Conventionally, in order to manufacture such a vertical light emitting device, a buffer layer, a first semiconductor layer, an active layer, and a second semiconductor layer are sequentially formed on a substrate, and then the buffer layer is formed by irradiating a laser to the substrate by a laser lift off (LLO) technique. The substrate is separated to separate the substrate, and electrodes are formed in the first semiconductor layer and the second semiconductor layer, respectively.

When the first semiconductor layer is AlN or AlGaN, GaN or InGaN is used as the buffer layer.

Therefore, in order to decompose a buffer layer of GaN or InGaN by irradiating a laser to the substrate, the irradiated laser must have a large energy compared to the energy band gap of the GaN or InGaN buffer layer. For example, a laser having a wavelength of 355 nm or 248 nm whose wavelength is less than 360 nm is used. As such, there is a problem in that the wavelength range of the laser that can be used is limited to 360 nm or less.

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is not only a laser having a wavelength longer than 360 nm but also a laser having a wavelength smaller than 360 nm, such as a wavelength of 355 nm or 248 nm, which is conventionally used to separate a substrate in manufacturing a compound semiconductor device. In this case, the compound semiconductor layer can be separated from the substrate.

According to an aspect of the present invention for achieving the above technical problem, a first step of preparing a substrate, a second step of forming a Si intermediate layer on the substrate, and a first conductive semiconductor layer, an active layer and a first layer on the Si intermediate layer And a fourth step of forming a compound semiconductor layer comprising two conductive semiconductor layers and a fourth step of separating the substrate from the compound semiconductor layer by decomposing the Si intermediate layer by irradiating a laser to the substrate. A semiconductor device manufacturing method is provided.

The substrate may include sapphire (Al 2 O 3), spinel (spinel), silicon carbide (SiC), zinc oxide (ZnO), gallium arsenide (GaAs), gallium phosphorus (GaP), lithium-alumina (LiAl 2 O 3), boron nitride (BN) , Aluminum nitride (AlN) or gallium nitride (GaN) substrate.

The compound semiconductor layer may be a stack of semiconductor layers selected from gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), or alloys thereof.

The third step may include forming a buffer layer on the Si intermediate layer, and forming the compound semiconductor layer on the buffer layer.

The laser is selected to have an energy less than the energy bandgap of the substrate and the buffer layer, and to have an energy greater than the energy bandgap of the Si interlayer.

The method may further include a fifth step of forming electrodes on the upper and lower surfaces of the compound semiconductor layer in which the substrate is separated by the fourth step.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, lengths, thicknesses, and the like of layers and regions may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a process flowchart illustrating a manufacturing process of a compound semiconductor device according to an embodiment of the present invention, Figures 2 to 4 is a cross-sectional view according to the manufacturing process. Here, the manufacturing process of the nitride semiconductor device among the compound semiconductor devices will be described.

1 and 2, a substrate 100 is prepared in a process chamber (not shown) for forming a nitride semiconductor layer (S1). The substrate 100 has a lattice constant similar to that of the nitride semiconductor layer to be formed thereon.

The substrate 100 may be any substrate having an energy band gap larger than the energy band gap of the Si intermediate layer 200 formed on the substrate 100.

For example, sapphire (Al 2 O 3), spinel (spinel), silicon carbide (SiC), zinc oxide (ZnO), gallium arsenide (GaAs), gallium phosphorus (GaP), lithium-alumina (LiAl 2 O 3), boron nitride (BN) It may be an aluminum nitride (AlN) or gallium nitride (GaN) substrate, and may be selected according to the material of the semiconductor layer to be formed on the substrate 21. When forming a gallium nitride based semiconductor layer, a sapphire or silicon carbide (SiC) substrate is mainly used as the substrate.

Thereafter, the Si intermediate layer 200 is formed on the substrate 100 (S2).

Chemical vapor deposition (Chemical Vapor Deposition) may be used to form the Si interlayer 200 on the substrate 100. The Si interlayer 200 heats the substrate 100 in the process chamber to a temperature of 1000 ° C. and introduces silane into the process chamber through the gas inlet member to deposit it. Accordingly, the Si intermediate layer 200 is deposited on the substrate 100 in the form of silicon single crystal and grown. The thickness of the Si intermediate layer 200 may be about 20 nm to about 50 nm.

The reason for forming the Si interlayer 200 between the substrate 100 and the buffer layer 310 is to facilitate the separation operation when the substrate 100 is separated after the multilayer nitride semiconductor layer 300 is formed on the substrate 100. It is to let.

That is, in the prior art, an AlN or GaN buffer layer for forming the multilayer nitride semiconductor layer 300 is formed in the substrate, and when the substrate is separated, a laser having a wavelength smaller than 360 nm, such as a wavelength of 355 nm or 248 nm, on the substrate. The buffer layer could be disassembled only when using.

However, in the present invention, the Si intermediate layer having an energy bandgap of 1.1 eV lower than the energy bandgap of the buffer layer 310 without decomposing the AlN or GaN buffer layer 310 for forming the multilayer nitride semiconductor layer 300. It is not necessary for the laser for separating the substrate by inserting the laser to be a laser smaller than 360 nm as in the conventional case, and it is also possible to use a laser having a wavelength longer than 360 nm, for example, 436 nm. Therefore, the wavelength selection range of the laser used for separating the substrate can be widened. The bandgap energy of the Si interlayer is 1.1 eV, allowing lasers with wavelengths up to 1128 nm.

In other words, although it is described here as decomposing the Si intermediate layer 200 using a laser having a wavelength longer than 436 nm, when using a laser smaller than 360 nm, the Si intermediate layer 200 and the buffer layer 310 are decomposed. Thus, the substrate 100 can be separated.

Thereafter, a buffer layer 310 is formed on the Si intermediate layer 200 (S3).

The buffer layer 310 is used to mitigate the lattice mismatch between the semiconductor layers to be formed thereon and the substrate 100. The buffer layer 310 may be, for example, an AlN or GaN layer and may be grown to a thickness of 20 nm to 50 nm at a low temperature, for example, at a temperature of about 400 to about 700 ° C. and a pressure of 50 Torr to 700 Torr.

Thereafter, an undoped GaN semiconductor layer 320 is formed on the buffer layer 310 (S4).

The undoped GaN semiconductor layer 320 is interposed between the buffer layer and the first conductive semiconductor layer 330 and is made of undoped GaN.

The undoped GaN semiconductor layer 320 provides a high quality GaN semiconductor layer so that the first conductive semiconductor layer 330 made of GaN-based material can be effectively formed at high quality.

The buffer layer 310 and the undoped GaN semiconductor layer 320 may include metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), or molecular beam epitaxy. , MBE) and the like.

Referring to FIGS. 1 and 3, a compound semiconductor layer including a first conductive semiconductor layer 330, an active layer 340, and a second conductive semiconductor layer 350 is sequentially formed on the undoped GaN semiconductor layer 320. (S5).

The first conductive semiconductor layer 330 may be formed of N-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include a N-type clad layer . The first conductive semiconductor layer 330 may be formed by doping silicon (Si).

The active layer 340 is a region where electrons and holes are recombined, and includes InGaN. The emission wavelength emitted from the light emitting diode is determined by the type of material constituting the active layer 340. The active layer 340 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).

A second conductive semiconductor layer 350 may be formed of P-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include a P-type clad layer . The second conductive semiconductor layer 350 may be formed by doping zinc (Zn) or magnesium (Mg).

Thereafter, the transparent electrode 400 is formed on the second conductive semiconductor layer 350 (S6).

Thereafter, the laser beam is irradiated toward the substrate 100 to separate the substrate 100 from the Si intermediate layer 200 (S7).

At this time, the laser is selected to have an energy smaller than the energy band gap of the substrate and the nitride semiconductor layer, and to have an energy larger than the energy band gap of the Si layer. In this case, the laser has energy absorbed more strongly by the Si intermediate layer 200 than the substrate 100 and the nitride semiconductor layer 300. Thus, the laser is not limited to a laser having a wavelength of 355 nm or 248 nm as in the prior art, but may be a laser having a longer wavelength such as, for example, 436 nm, and the maximum as the band gap energy of the Si interlayer is 1.1 eV. Lasers with wavelengths up to 1128 nm are possible.

When the laser is irradiated from the substrate 100, since the substrate 100 is a light transmissive substrate, the Si intermediate layer 200 is decomposed by the energy absorbed at the interface between the substrate 100 and the Si intermediate layer 200, thereby forming a nitride semiconductor layer. The substrate 100 is separated from the 300. The lower surface of the separated nitride semiconductor layer 300 may be cleaned. Accordingly, separation of the substrate 100 from the nitride semiconductor layer 300 is completed.

Referring to FIGS. 1 and 4, after the substrate 100 is separated, the buffer layer 310 and the undoped GaN semiconductor layer 320 are etched to expose one surface of the first conductive semiconductor layer 330 ( S8).

Thereafter, the reflective layer 500 is formed on one exposed surface of the first conductive semiconductor layer 330 (S9).

The reflective layer 500 may be formed of Ag and / or Al, for example, and reflects the light emitted from the active layer 340 upward to increase the luminous efficiency of the light emitting diode.

Thereafter, first and second electrode pads 600a and 600b are formed on the transparent electrode 400 and the reflective layer 500, respectively (S10). The electrode pads 600a and 600b may be formed by a lift off method.

The invention being thus described, it will be obvious that the same way may be varied in many ways. Such modifications are intended to be within the spirit and scope of the invention as defined by the appended claims.

For example, in the exemplary embodiment of the present invention, the first conductive semiconductor layer is an N-type semiconductor layer and the second conductive semiconductor layer is a P-type semiconductor layer. However, the first conductive semiconductor layer is a P-type semiconductor layer. 2 can be applied even when the conductive semiconductor layer is an N-type semiconductor.

According to the present invention, a silicon intermediate layer having a lower energy bandgap than a buffer is inserted between the substrate and the buffer layer of the compound semiconductor layer, and the silicon intermediate layer is decomposed through a laser, thereby decomposing the buffer layer to separate the substrate. Since the nitride semiconductor layer can be separated from the substrate using a wavelength longer than the wavelength used to separate the substrate by separating the buffer layer as well as the laser, the nitride semiconductor layer is separated from the substrate by using a laser having various wavelength ranges. can do.

Claims (6)

A first step of preparing a substrate, Forming a Si intermediate layer on the substrate; Forming a compound semiconductor layer including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the Si intermediate layer; Irradiating the substrate with a laser to decompose the Si intermediate layer to separate the substrate from the compound semiconductor layer, And said laser has an energy smaller than an energy band gap of said substrate and said compound semiconductor layer and having an energy greater than an energy band gap of said Si intermediate layer. The method according to claim 1, wherein the substrate, Sapphire (Al2O3), spinel, silicon carbide (SiC), zinc oxide (ZnO), gallium arsenide (GaAs), gallium phosphorus (GaP), lithium-alumina (LiAl2O3), boron nitride (BN), aluminum nitride ( AlN) or gallium nitride (GaN) substrate, characterized in that the method for producing a compound semiconductor device. The method of claim 1, wherein the compound semiconductor layer, A method for manufacturing a compound semiconductor device, characterized in that the stack of semiconductor layers selected from gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN) or alloys thereof. The method of claim 1, wherein the third step, Before forming the first conductive semiconductor layer, Forming a buffer layer on the Si intermediate layer, characterized in that it comprises a compound semiconductor device manufacturing method. The method according to claim 4, wherein the laser, And having an energy smaller than an energy band gap of the buffer layer. The method according to claim 1, After the substrate is separated, And a fifth step of forming an electrode electrically connected to the first conductive semiconductor layer and the second conductive semiconductor layer, respectively.

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