KR102629307B1 - Methods for fabricating nitride semiconductor device - Google Patents

Abstract

The present invention relates to a method of manufacturing a nitride semiconductor device that can easily separate a nitride-based thin film structure from a growth substrate, the method comprising: forming a nitride-based thin film structure on a growth substrate; A carrier substrate bonding step of bonding a carrier substrate on the nitride-based thin film structure; and a peeling process step of separating the growth substrate from the nitride-based thin film structure through wet etching.

Description

Methods for manufacturing nitride semiconductor device {Methods for fabricating nitride semiconductor device}

The present invention relates to a method for manufacturing a nitride semiconductor device, and more specifically, to the application of separating a nitride-based thin film structure from a growth substrate to a wafer scale and transferring it onto a heterogeneous substrate, using the existing epitaxial lift off (Epitaxial Lift). This relates to a method of manufacturing a nitride semiconductor device that overcomes the limitations of the -Off; ELO) technique and enables separation of a nitride-based thin film structure from a growth substrate in a large area and with zero defects.

Nitride semiconductor devices are widely used in blue/green/ultraviolet light emitting devices, power devices, and power ultra-high frequency devices.

The manufacturing method of such nitride semiconductor devices generally uses metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), etc. to fabricate materials such as sapphire, silicon, or silicon carbide. A nitride semiconductor device structure is formed on the substrate.

However, even after the manufacturing of the nitride semiconductor device is completed, the structure of the nitride semiconductor device is integrated with the substrate, so the thermal, optical, and electrical properties of the nitride semiconductor device are likely to deteriorate depending on the characteristics of the substrate.

Among the methods to solve this problem, the currently widely used method is the epitaxial lift-off technique, which may include laser lift-off (LLO) and chemical lift-off (CLO) techniques. there is.

The laser lift-off (LLO) method is mainly used in the manufacture of vertically structured nitride light-emitting devices, and can be applied to substrates with low heat transfer coefficients or through which lasers can penetrate, such as sapphire substrates.

However, in the laser lift-off (LLO) method, the active part of the nitride semiconductor device is thermally damaged due to the use of a laser, and cracks easily occur in the epi layer due to the difference in thermal expansion coefficient between the epi layer and the sapphire substrate. Because of this, the characteristics of the nitride semiconductor device deteriorate. As a result, the yield of the final nitride semiconductor device is not only uneven but also relatively low.

The chemical lift-off method (CLO) does not use a laser, so it has the advantage of causing no thermal damage to the active part of the nitride semiconductor device compared to the laser lift-off method.

However, the chemical lift-off (CLO) method grows an epi layer on a seed with an imperfect structure such as a sacrificial film, so there is a high possibility that many defects will occur in the crystal of the grown epi layer. As a result, the performance of the nitride semiconductor device deteriorates, making it difficult to mass-produce the nitride semiconductor device.

US 20200043790 A1 KR 10-1335937 B1 KR 10-1873255 B1

Therefore, the present invention was devised to solve the above problem, and one purpose of the present invention is to provide a method of manufacturing a nitride semiconductor device that can easily separate the nitride-based thin film structure from the growth substrate.

Other objects and advantages of the present invention will be explained below and will be learned by practice of the present invention. Additionally, the objects and advantages of the present invention can be realized by the means and combinations indicated in the claims.

In order to achieve the above object, a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention includes a thin film structure forming step of forming a nitride-based thin film structure on a growth substrate; A carrier substrate bonding step of bonding a carrier substrate on the nitride-based thin film structure; and a peeling process step of separating the growth substrate from the nitride-based thin film structure through wet etching.

The peeling process step includes forming a buffer layer between the growth substrate and the nitride-based thin film structure; etching a portion of the rear surface of the growth substrate using a deep etching process to form a plurality of trenches to expose a portion of the buffer layer; forming a protective layer for etching in the trench; and removing the growth substrate by performing wet etching with an etchant.

An area damaged by the deep etching process exists at the interface between the trench and the buffer layer.

The protective layer for etching is characterized in that it is selected from a SiO ₂ layer or a SiN _x layer.

The etching solution is characterized as being a potassium hydroxide (KOH)-based etching solution with a concentration of 30 to 50%.

The growth substrate is characterized as a silicon substrate having a [110] crystal orientation.

It further includes transferring the nitride-based thin film structure from which the growth substrate is separated in the peeling process step onto a heterogeneous substrate, wherein the heterogeneous substrate is a diamond substrate, a CMOS substrate, a sapphire substrate, a silicon carbide (SiC) substrate, and a flexible substrate. It is characterized by being one of the following.

The nitride-based thin film structure is characterized in that it includes a Group III nitride-based epitaxial layer or a Group III nitride-based semiconductor layer.

The Group 3 nitride-based epi layer includes any one of a GaN epi layer, an InGaN/GaN LED epi layer, an AlGaN/GaN HEMT epi layer, and a GaN/AlScN epi layer, and the Group 3 nitride-based semiconductor layer is an InGaN/GaN LED. It is characterized in that it includes a device or AlGaN/GaN HEMT device.

The InGaN/GaN LED device includes an n-GaN layer; GaN/InGaN MQW structure; and p-GaN layers are sequentially stacked, and the AlGaN/GaN HEMT device includes a GaN layer; an AlN intermediate layer formed on the GaN layer; An AlGaN barrier layer formed on the AlN intermediate layer; and a GaN cap layer formed on the AlGaN barrier layer.

As described above, according to the method for manufacturing a nitride semiconductor device according to an embodiment of the present invention, the nitride-based thin film structure can be easily separated from the growth substrate.

In other words, the present invention is about the application of separating a nitride-based thin film structure from a growth substrate to a wafer scale (2 to 12 inches in size) and transferring it onto a heterogeneous substrate, overcoming the limitations of the existing epitaxial lift-off (ELO) technique. This has the effect of enabling separation of the nitride-based thin film structure from the growth substrate in a large area and without defects.

1 is a flowchart for explaining a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention;
2A to 2F are cross-sectional process views showing a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention;
Figure 3 is a diagram showing the structure of a nitride semiconductor device according to an embodiment of the present invention.

Specific details of other embodiments are included in the detailed description and drawings.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. In the description below, when a part is connected to another part, this is not only the case when it is directly connected. This also includes cases where they are connected through other media in between. In addition, in the drawings, parts unrelated to the present invention are omitted to clarify the description of the present invention, and similar parts are given the same reference numerals throughout the specification.

The terminology used herein is for describing embodiments and is not intended to limit the invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used herein, “comprises” and/or “comprising” refers to the presence of one or more other components, steps, operations and/or elements. or does not rule out addition.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings that can be commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly specifically defined.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically shown for convenience and clarity of explanation. Additionally, the size and area of each component do not entirely reflect the actual size or area.

Hereinafter, the present invention will be described with reference to the attached drawings.

1 is a flowchart for explaining a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention, and FIGS. 2A to 2E are cross-sectional process diagrams showing a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention. Figure 3 is a diagram showing the structure of a nitride semiconductor device according to an embodiment of the present invention.

Referring to FIG. 1, the method of manufacturing a nitride semiconductor device according to an embodiment of the present invention may include a thin film structure forming step (S10), a carrier substrate bonding step (S20), and a peeling process step (S30). .

In the thin film structure forming step (S10), the nitride-based thin film structure 13 is formed on the growth substrate 10. At this time, a buffer layer 11 may be formed between the growth substrate 10 and the nitride-based thin film structure 13.

In the carrier substrate bonding step (S20), the carrier substrate 14 is bonded to the nitride-based thin film structure 13.

In the peeling process step (S30), the growth substrate 10 is separated from the nitride-based thin film structure 13 through wet etching.

In the peeling process step (S30), a portion of the rear surface of the growth substrate 10 is etched by a deep etching process to form a plurality of trenches 17 so that a portion of the buffer layer 11 is exposed, and an etching layer is formed within the trench 17. It may include a process of forming a protective layer 19 and removing the growth substrate 10 by performing wet etching with an etchant.

Afterwards, the separated nitride-based thin film structure 13 can be transferred onto the heterogeneous substrate 20, which is the desired target substrate.

Hereinafter, with reference to FIGS. 2A to 2F, a method of manufacturing a nitride semiconductor device according to an embodiment of the present invention will be described in detail.

First, as shown in FIG. 2A, a buffer layer 11 is formed on the growth substrate 10, and a nitride-based thin film structure 13 is sequentially formed on the buffer layer 11.

As the growth substrate 10, for example, a sapphire substrate, a silicon substrate, a silicon carbide substrate, etc. can be used.

Preferably, a silicon substrate having a [110] crystal direction can be used as the growth substrate 10, because anisotropic wet etching is possible with a high aspect ratio.

The buffer layer 11 may be made of, for example, AlN, but is not limited thereto, and may be made of at least one of GaN, InN, InGaN, AlGaN, InAlGaN, and AlInN.

The buffer layer 11 may be formed to have a thickness of about 0.1 μm to about 10 μm, but is not limited thereto.

The nitride-based thin film structure 13 may include, for example, a Group III nitride-based epitaxial layer or a Group III nitride-based semiconductor layer.

Here, the Group 3 nitride-based epi layer is, for example, any one of a GaN epi layer, an InGaN/GaN LED (light emitting diode) epi layer, an AlGaN/GaN HEMT (high electron mobility transistor) epi layer, and a GaN/AlScN epi layer. It can be included.

Additionally, the Group III nitride-based semiconductor layer may include an InGaN/GaN LED device or an AlGaN/GaN HEMT device.

The InGaN/GaN LED device includes an n-GaN layer; GaN/InGaN MQW (multi quantum well) structure; and p-GaN layers may be sequentially stacked, and the AlGaN/GaN HEMT device may include a GaN layer; an AlN intermediate layer formed on the GaN layer; An AlGaN barrier layer formed on the AlN intermediate layer; and a GaN cap layer formed on the AlGaN barrier layer.

Next, referring to FIG. 2B, the carrier substrate 14 is bonded to the nitride-based thin film structure 13 by a bonding member (not shown).

The carrier substrate 14 may include, for example, one of sapphire, silicon carbide, ZnO, silicon, and gallium arsenide.

Next, referring to FIG. 2C, a process of separating the growth substrate 10 from the nitride-based thin film structure 13 begins.

To this end, a portion of the rear surface of the growth substrate 10 is etched, thereby forming a plurality of trenches 17 in the growth substrate 10. At this time, a portion of the buffer layer 11 may be exposed on the bottom of the trenches 17.

Here, etching of the growth substrate 10 may be performed through a deep etching process. By a deep etching process, trenches 17 may be formed in the growth substrate 10 with a thickness of several hundred micrometers to a depth that reaches the buffer layer 11 . At this time, a damaged region 15 may exist at the boundary of the buffer layer 11 by the deep etching process. For example, this damaged area 15 may be formed by expanding into the inside of the buffer layer 11 and may function as an etching stopper in a subsequent etching process using the etching protection layer 19.

Next, a protective layer for etching 19 is conformally formed in the trench 17 to a thickness of several hundred nm. This protects the sides of the trench 17 in the subsequent etching process and assists the etchant to focus on etching the interface between the buffer layer 11 and the growth substrate 10.

The protective layer 19 for etching may be selected from, for example, a SiO ₂ layer or a SiN _x layer.

Next, as shown in FIG. 2D, wet etching is performed using an etching solution using the etching protective layer 19. At this time, a portion of the previously formed etching protective layer 19, particularly the etching protective layer 19 formed on the bottom of the trench 17, is etched, and the buffer layer 11 and the growth substrate ( Part of 10) is revealed. Accordingly, horizontal etching of the growth substrate 10 may occur mainly at the bottom of the trench 17 .

As the etching solution, for example, a potassium hydroxide (KOH)-based etching solution having a concentration of 30 to 50%, preferably 40%, can be used, and the temperature is above room temperature (20°C ± 5°C), preferably between room temperature and 60%. Dip into KOH solution at a temperature of ℃ and proceed with etching.

The potassium hydroxide (KOH)-based etchant has a Si etching rate that is more than 100 times faster in the horizontal direction than in the vertical direction. Accordingly, most etching at the interface between the buffer layer 11 and the growth substrate 10 etches Si, that is, occurs in the horizontal direction.

Meanwhile, the etching time may vary depending on, for example, the hole size of the trenches 17 or the substrate size.

As a result, as shown in FIG. 2E, the growth substrate 10 is completely removed, and a nitride semiconductor structure (NS) including the buffer layer 11, the nitride-based thin film structure 13, and the carrier substrate 14 is obtained. Lose.

Finally, the nitride semiconductor structure NS is bonded on an arbitrary heterogeneous substrate 20, which is the desired target substrate.

Referring to FIG. 2F, the nitride semiconductor structure NS is transferred onto an arbitrary heterogeneous substrate 20. At this time, the carrier substrate 14 is shown in a removed state.

The heterogeneous substrate 20 may include any one of a diamond substrate, a CMOS substrate, a sapphire substrate, a silicon carbide (SiC) substrate, and a flexible substrate. Here, the CMOS substrate refers to a substrate on which the CMOS process (including etching, lithography, ion implantation, annealing, etc.) has been completed based on a silicon substrate, and includes one or more semiconductor devices (e.g., transistors, resistors, diodes, etc.) may include.

Preferably, the separated nitride semiconductor structure (NS) can be transferred to a diamond substrate or flexible substrate with high thermal conductivity properties, and can have improved properties or a new form factor.

Referring to FIG. 3, the structure of a nitride semiconductor device according to an embodiment of the present invention is shown.

The nitride semiconductor device in FIG. 3 includes a buffer layer 11 and a group III nitride-based semiconductor layer 30 on a heterogeneous substrate 20.

Here, the group III nitride-based semiconductor layer 30 is an AlGaN/GaN HEMT device, and includes a GaN layer 31; an AlN intermediate layer 32 formed on the GaN layer 31; an AlGaN barrier layer 33 formed on the AlN intermediate layer 32; and a GaN cap layer 34 formed on the AlGaN barrier layer 33. For example, the GaN layer 31 has a thickness of approximately 2 μm, the AlN intermediate layer 32 has a thickness of approximately 1 nm, and the AlGaN barrier layer 33 has a thickness of approximately 25 nm, The GaN cap layer 34 may have a thickness of approximately 3 nm.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the scope of the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. must be interpreted.

10: growth substrate
11: buffer layer
13: Epi layer structure
15: Damaged area
17: Trench
19: protective layer
NS: Nitride semiconductor structure
20: heterogeneous substrate

Claims (10)

A thin film structure forming step of forming a nitride-based thin film structure on a growth substrate;
A carrier substrate bonding step of bonding a carrier substrate on the nitride-based thin film structure; and
A peeling process step of separating the growth substrate from the nitride-based thin film structure through wet etching,
The peeling process step is,
forming a buffer layer between the growth substrate and the nitride-based thin film structure;
etching a portion of the rear surface of the growth substrate using a deep etching process to form a plurality of trenches to expose a portion of the buffer layer;
forming a protective layer for etching in the trench; and
A method of manufacturing a nitride semiconductor device, comprising the step of removing the growth substrate by performing wet etching with an etchant. delete According to paragraph 1,
A method of manufacturing a nitride semiconductor device, characterized in that there is a damaged area by the deep etching process at the interface between the trench and the buffer layer. According to paragraph 1,
A method of manufacturing a nitride semiconductor device, wherein the protective layer for etching is selected from a SiO ₂ layer or a SiN _x layer. According to paragraph 1,
A method of manufacturing a nitride semiconductor device, characterized in that the etching solution is a potassium hydroxide (KOH)-based etching solution with a concentration of 30 to 50%. According to paragraph 1,
A method of manufacturing a nitride semiconductor device, wherein the growth substrate is a silicon substrate having a [110] crystal direction. According to paragraph 1,
Further comprising transferring the nitride-based thin film structure from which the growth substrate is separated in the peeling process step onto a heterogeneous substrate,
A method of manufacturing a nitride semiconductor device, wherein the heterogeneous substrate is any one of a diamond substrate, a CMOS substrate, a sapphire substrate, a silicon carbide (SiC) substrate, and a flexible substrate. According to paragraph 1,
A method of manufacturing a nitride semiconductor device, wherein the nitride-based thin film structure includes a Group III nitride-based epitaxial layer or a Group III nitride-based semiconductor layer. According to clause 8,
The group 3 nitride-based epi layer includes any one of a GaN epi layer, an InGaN/GaN LED epi layer, an AlGaN/GaN HEMT epi layer, and a GaN/AlScN epi layer,
A method of manufacturing a nitride semiconductor device, wherein the group III nitride-based semiconductor layer includes an InGaN/GaN LED device or an AlGaN/GaN HEMT device. According to clause 9,
The InGaN/GaN LED device includes an n-GaN layer; GaN/InGaN MQW structure; and p-GaN layers are sequentially stacked,
The AlGaN/GaN HEMT device includes a GaN layer; an AlN intermediate layer formed on the GaN layer; An AlGaN barrier layer formed on the AlN intermediate layer; and a GaN cap layer formed on the AlGaN barrier layer.