KR101303592B1 - Method for manufacturing nitride semiconductor device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride based semiconductor device having an improved ohmic bonding characteristic capable of simultaneously satisfying on-resistance and leakage current characteristics by improving ohmic bonding characteristics, and a method of manufacturing the same. Forming an n-type nitride layer including an n-type dopant on the epitaxial layer, forming a source electrode and a drain electrode at regular intervals above the n-type nitride layer, and n-type nitride layer on the epitaxial layer After the selective removal of the, by forming an ohmic junction on the source electrode and the drain electrode through the heat treatment, it is possible to improve the contact resistance of the ohmic junction, it is possible to form the ohmic junction through a relatively low temperature heat treatment process.

Description

A method for manufacturing a nitride semiconductor device

The present invention relates to a nitride-based semiconductor device and a method of manufacturing the same, and more particularly to a nitride-based semiconductor device having an epi structure capable of satisfying the ohmic characteristics and leakage current characteristics and a selective etching method for the implementation thereof It is about a method.

Semiconductor devices made of III-nitride materials (hereinafter referred to as " nitride based semiconductor devices ") are known to have very large dielectric breakdown fields of 2.2 MV / cm or more. In addition, since III-nitride heterojunction structures can carry very large currents, nitride-based semiconductor devices are excellent in power applications. In general, nitride-based semiconductor devices based on III-nitride materials have been developed for high power-high frequency applications such as emitters used in base stations of cellular phones. Nitride-based semiconductor devices fabricated for these types of applications are based on common device structures capable of obtaining high electron mobility, which structures include heterojunction field effect transistors (HFETs), High Electron Mobility Transistors (HEMTs) or Doped Modulated Field Effect Transistors (Modulation doped FETs (MODFETs), and the like. Nitride-based semiconductor devices of this type are generally capable of withstanding high voltages of about 100V while operating in a high frequency region of 2 to 100 kHz.

These types of nitride-based semiconductor devices may be modified for many applications, but produce a 2-Dimensional Electron gas (2DEG) that has very low resistive losses and enables very high current density transport. It is common to operate using piezoelectric polarization fields. In these conventional nitride-based semiconductor devices, 2DEG is formed at the interface of AlGaN / GaN.

In the case of a nitride semiconductor device, a source electrode, a drain electrode, and a gate electrode are formed on an epitaxial layer such as AlGaN / GaN. The source electrode and the drain electrode may be formed by an ohmic junction. At this time, the ohmic resistance of the source-drain electrode is important. If the ohmic resistance is high, the on-resistance of the device is reduced.

The ohmic junction may be formed by depositing a plurality of ohmic metals including Ti and Al through a heat treatment process.

However, according to the conventional method, a high temperature heat treatment process is required for ohmic formation, and thermal stress is added to the nitride semiconductor device through these high temperature heat treatment processes to increase the trap site of the device, which results in leakage current of the device. Cause to increase.

On the other hand, when the high concentration of nitride layer is laminated on the surface, the ohmic resistance and heat treatment temperature between the metal and the semiconductor can be lowered, but the high concentration nitride layer formed on the surface of the device causes leakage current and the high concentration nitride layer on the surface portion. The non-uniformity of etching that occurs when etching is a cause of deterioration of the overall device characteristics.

Accordingly, the present invention has been proposed to solve the conventional problems, and more particularly, a nitride-based semiconductor device having improved ohmic junction characteristics and its on-resistance characteristics and leakage current characteristics which can be simultaneously satisfied by improving ohmic junction characteristics and its It is intended to provide a manufacturing method.

The present invention is a means for solving the above problems, a substrate; A nitride epitaxial layer formed on the substrate; An n-type nitride layer including an n-type dopant formed in a predetermined source and drain electrode region on the nitride-based epi layer; A source electrode and a drain electrode formed on the n-type nitride layer; And a gate electrode formed on the epitaxial layer.

In the nitride semiconductor device according to the present invention, the epi layer comprises: a transition layer formed on the substrate; A GaN layer formed on the transition layer; And an AlGaN layer formed on the GaN layer to form a two-dimensional electron cloud (2DEG) layer on an interface portion of the GaN layer.

In the nitride semiconductor device according to the present invention, the n-type nitride layer is a GaN layer doped with n-type.

In the nitride semiconductor device according to the present invention, the n-type nitride layer is selectively etched by a dry etching method including an F-containing gas.

In addition, the present invention as another means for solving the above problems, forming a nitride-based epi layer on the substrate; Forming an n-type nitride layer including an n-type dopant on the epi layer; Forming a source electrode and a drain electrode at predetermined intervals on the n-type nitride layer; Etching the remaining n-type nitride layer except the lower portion of the source electrode and the drain electrode; Forming an ohmic junction on the source electrode and the drain electrode through a heat treatment; And it provides a method for manufacturing a nitride-based semiconductor device comprising the step of forming a gate electrode on the epi layer.

In the method of manufacturing a nitride-based semiconductor device according to the invention, the step of forming the nitride-based epi layer, forming a transition layer on a substrate; Forming a GaN layer on the transition layer; And forming an AlGaN layer on the GaN layer to form a two-dimensional electron cloud (2DEG) layer at an interface portion of the GaN layer.

In the method for manufacturing a nitride-based semiconductor device according to the present invention, the n-type nitride layer is characterized in that the GaN layer doped with n-type.

In the method of manufacturing a nitride-based semiconductor device according to the present invention, the etching of the n-type nitride layer, it is made by dry etching using an F-containing gas containing at least one of SF6, CF4, CHF ₃ , C2F8. It features.

According to the present invention, by forming a high concentration of n-type GaN layer under the source and drain electrodes, and then forming an ohmic bond, contact resistance in the ohmic junction can be improved, and an ohmic junction is formed through a relatively low temperature heat treatment process. Make it possible.

In addition, the present invention can reduce unnecessary thermal stress through the lowering of the heat treatment temperature, as a result can suppress the trap site increase through the movement of defects, and has the effect of reducing the leakage current.

In addition, in the present invention, in performing an etching process for forming a high concentration of n-type GaN layer under the source and drain electrodes, by performing a recess etching using a high selectivity of GaN and AlGaN, the etching rate is uniform. By improving the properties, more precise etching control can be performed.

In addition, in the present invention, since the ohmic layer is separated into the doped GaN layer, the non-uniformity of the on resistance due to the non-uniform end shape of the ohmic layer may be removed after the heat treatment.

1 is a flowchart illustrating a method of manufacturing a nitride semiconductor device according to the present invention.
2 is a view for explaining a process of forming a nitride epitaxial layer in the method for manufacturing a nitride semiconductor device according to the present invention.
3 is a view for explaining a process of removing an n-type nitride layer in the method for manufacturing a nitride semiconductor device according to the present invention.
It is a figure explaining the formation process of a source electrode / drain electrode in the manufacturing method of the nitride semiconductor element by this invention.
5 is a view for explaining the overall structure of a nitride semiconductor device manufactured according to the method for producing a nitride semiconductor device according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

Also, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should use the concept of terms to explain their own invention in the best way. Based on the principle that it can be properly defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention, various modifications that can be substituted for them at the time of the present application It should be understood that there may be equivalents and variations.

1 is a flowchart illustrating a method of manufacturing a nitride semiconductor device according to the present invention. 2 to 5 are diagrams for explaining each process in the method of manufacturing a nitride semiconductor device according to the present invention. Hereinafter, a method of manufacturing a nitride semiconductor device according to the present invention will be described with reference to FIGS. 1 to 5.

First, referring to FIGS. 1 and 2, in the method of manufacturing the nitride semiconductor device according to the present invention, the substrate 10 is first prepared in step S110.

Here, the substrate 10 may be formed of a material suitable for growing a nitride semiconductor single crystal. The substrate 10 includes sapphire (Al ₂ O ₃ ), silicon (Si), zinc oxide (ZnO), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), aluminum nitride (AlN), magnesium oxide It may be made of an element or a compound such as (MgO). In the case of the sapphire, a sapphire substrate having a c plane ({0001} plane), an R plane ({1-102}), an M plane ({1-100}), and an A plane ({11-20}) may be used. have. In addition, in the case of a silicon substrate, a silicon substrate having a {111} plane or the like may be used.

Subsequently, as illustrated in FIG. 2, a nitride epitaxial layer 100 is formed on the substrate 10 (S120). The nitride epitaxial layer 100 may be formed by growing a nitride material in multiple layers. In more detail, in order to enable growth of a nitride-based material on the substrate 10, a transition layer 20 is formed, and a GaN layer 30 is formed on the transition layer 20. Afterwards, an AlGaN layer 50 is formed on the GaN layer 30 to form a two-dimensional electron cloud (2DEG) layer 40 at the interface portion with the GaN layer 30.

The transition layer 20 is a layer for growing a nitride layer on the substrate 10, and may be formed of different materials and structures according to the material of the substrate 10.

The GaN layer 30 may be formed to a thickness of 1 to 3 μm, the 2DEG layer 40 may be formed to a thickness of several nm, and the AlGaN layer 50 may be formed of Al _X Ga _1-X N. It can be formed to a thickness of several tens nm with a composition of (0.1 <x <0.6).

Subsequently, according to the method of manufacturing a nitride-based semiconductor device according to the present invention, an n-type nitride layer 60 including an n-type dopant is further formed on the epitaxial layer 100 (S130). The n-type nitride layer 60 may be formed of, for example, a GaN layer having a concentration of 3 × 10 ¹⁸ / cm 3.

In addition, as shown in FIG. 3, the source electrode and the drain electrode 70 are formed at a predetermined distance from each other on the n-type nitride layer 60 (S140). The source electrode and the drain electrode 70 may be formed by, for example, stacking an ohmic metal in the order of Ti / Al / M / Au, and then removing metal other than the electrode region through a lift-off process. It can form by. Where M may be one of Ni, Ti, Pt, Mo, Ta.

In this embodiment, the source electrode and the drain electrode 70 are formed by stacking Ti / Al / Ni / Au in a thickness of 30/100/30/100 nm, respectively.

Subsequently, before forming the ohmic junction through heat treatment, the remaining regions of the n-type nitride layer 60 except for the region covered by the source electrode and the drain electrode 70 are removed (S150). In this case, a dry etching method is used to remove the n-type nitride layer 60, and a gas containing F may be used as the gas for etching. For example, the gas containing F, there may be mentioned a SF6, CF4, CHF _3, C2F8. Dry etching using the F-containing gas serves to slow the etching of the AlGaN layer 50 located below the n-type nitride layer 60 through the generation of Al-F reactants. As a result, selective etching between the n-type nitride layer 60 and the AlGaN layer 50 is possible.

More specifically, in the present embodiment, dry etching was performed through ICP etching equipment (Inductively Coupled Plasma), in particular, ICP power 200W, RF power 30W, BCI3 20 sccm, SF6 5 sccm, Only n-type nitride layer 60 (n-type GaN layer) was selectively etched using a chamber pressure of 37.5 mTorr at a selectivity of 25: 1.

3 is a view illustrating a process of etching an n-type GaN layer in the method of manufacturing a nitride semiconductor device according to the present invention, and FIG. 4 is a view showing a state after etching. As shown, the exposed n-type nitride layer 60, which is not protected by the source electrode and drain electrode 70, is selectively etched by the F-containing plasma, and only below the source electrode and drain electrode 70 The n-type nitride layer 60 remains.

As such, after the n-type nitride layer 60 other than the lower portion of the source electrode and the drain electrode 70 is removed, the ohmic junction is bonded to the source electrode and the drain electrode 70 through heat treatment in a nitrogen atmosphere at 800 ° C. for 30 seconds. To form (S160).

At this time, since there is a high concentration of n-type GaN layer by the n-type nitride layer 60 in the ohmic junction portion, it is possible to improve the contact resistance and to reduce the heat treatment temperature for forming the ohmic junction.

That is, in the method of manufacturing the nitride semiconductor device according to the present invention, heat treatment for forming an ohmic junction between the source electrode and the drain electrode 70 is possible at a lower temperature than without the n-type nitride layer 60. The ohmic resistance decreases with the heat treatment temperature, and after the optimum heat treatment temperature, it becomes constant or begins to increase. The optimum heat treatment temperature is influenced by the required ohmic resistance, the degree of doping of the semiconductor of the junction, the thickness of the metal for the electrode, the type of the metal for the electrode, and the like.

In the present embodiment, ohmic is formed through rapid heat treatment in an atmosphere of 30 ° C. and 800 sec.

Thus, by forming the ohmic junction through the low temperature heat treatment temperature, it is possible to suppress the occurrence of defects due to the high temperature heat treatment of 900 ° C or more, and also to reduce the leakage current.

Next, as shown in FIG. 5, after ohmic formation, a gate electrode 80 is formed on the nitride epitaxial layer 100, particularly, the AlGaN layer 50 (S170). The gate electrode 80 is positioned between the source electrode and the drain electrode 70.

In this case, the gate electrode 80 may be formed of Ti, Pt, Cr, Pt / Au, Ni / Au, Ti / W, or platinum silicide, and may be formed of another metal material. For example, the gate electrode 80 may be formed by stacking metals of 40 nm Ni and 200 nm Au in order.

5 is a view showing the overall structure of the nitride semiconductor device according to the present invention, with reference to this, will be described the structure of the nitride semiconductor device manufactured by the manufacturing method according to the present invention.

In the nitride semiconductor device according to the present invention, a source is set at regular intervals between the substrate 10, the nitride epitaxial layer 100 formed on the substrate 10, and the nitride epitaxial layer 100. And an n-type nitride layer 60 formed in the drain region, a source electrode and a drain electrode 70 formed on the n-type GaN layer 60, and a gate electrode formed on the nitride epitaxial layer 100. And 80.

The substrate 10 may be made of a material suitable for growing a nitride semiconductor single crystal. The substrate 10 includes sapphire (Al ₂ O ₃ ), silicon (Si), zinc oxide (ZnO), gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), aluminum nitride (AlN), magnesium oxide It may be made of an element or a compound such as (MgO).

The nitride epitaxial layer 100 is formed on the transition layer 20 formed on the substrate 10, the GaN layer 30 formed on the transition layer 20, and on the GaN layer 30. The GaN layer 30 may include an AlGaN layer 50 forming an electron cloud layer (2DEG) 40 at an interface with the GaN layer 30.

The transition layer 20 is a layer for allowing the growth of the nitride layer on the substrate 10, and may be made of different materials and structures according to the material of the substrate 10. Here, the GaN layer 30 may be formed to a thickness of 1 to 3㎛, the 2DEG layer 40 may be formed to a thickness of several nm, AlGaN layer 50 is Al _X Ga _1-X N It can be formed to a thickness of several tens nm with a composition of (0.1 <x <0.6).

 The n-type nitride layer 60 is a high concentration GaN layer including an n-type dopant, and is formed in the source and drain regions set at regular intervals on the epi layer 100.

The source and drain electrodes 70 may be formed on the n-type nitride layer 60 through ohmic bonding. In this case, the source and drain electrodes 70 may be formed by stacking two or more ohmic metals and then performing a heat treatment process. At this time, the ohmic metal may be formed by laminating in order of Ti / Al / M / Au. Where M may be one of Ni, Ti, Pt, Mo, Ta.

In this embodiment, Ti / Al / Ni / Au were laminated in order of thickness of 30/100/30/100 nm, respectively, and then ohmic was formed through rapid heat treatment at 850 ° C. and 30 sec nitrogen atmosphere.

The gate electrode 80 is formed between the source and drain electrodes 70. It may be formed of Ti, Pt, Cr, Pt / Au, Ni / Au, Ti / W, or Platinum Silicide, and may be formed of other metal materials. In the present embodiment, the gate electrode 80 is formed by stacking Ni / Au in a thickness of 40/200 nm in order.

As described above, the present invention has been described, but the embodiments of the present invention disclosed in the specification and drawings are only presented as specific examples for clarity and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: substrate
20: transition layer
30: GaN layer
40: 2DEG layer
50: AlGaN layer
60: n type nitride layer
70: source electrode and drain electrode
80: gate electrode
100: nitride epi layer

Claims (8)

Forming a nitride-based epi layer on the substrate;
Forming an n-type nitride layer including an n-type dopant on the nitride-based epi layer;
Forming a source electrode and a drain electrode at predetermined intervals on the n-type nitride layer;
Selectively removing the n-type nitride layer on the nitride-based epilayer except for the region covered by the source and drain electrodes of the n-type nitride layer;
Forming an ohmic junction on the source electrode and the drain electrode through a heat treatment; And
A method of manufacturing a nitride-based semiconductor device comprising the step of forming a gate electrode on the epi layer. The method of claim 1, further comprising: forming an epi layer;
Forming a transition layer on the substrate;
Forming a GaN layer on the transition layer; And
Forming an AlGaN layer on the GaN layer in which a two-dimensional electron cloud (2DEG) layer is formed at an interface portion of the GaN layer;
Wherein the nitride-based semiconductor layer is formed on the surface of the nitride-based semiconductor layer. The method of claim 2, wherein the n-type nitride layer
A method of manufacturing a nitride-based semiconductor device, characterized in that the GaN layer doped with n-type. The method of claim 2, wherein the step of selectively removing the n-type nitride layer
A method of manufacturing a nitride-based semiconductor device, characterized by dry etching using an F-containing gas. 5. The method of claim 4,
The F-containing gas manufacturing method of the nitride-based semiconductor device comprising at least one of SF6, CF4, CHF ₃ , C2F8. The method of claim 1, wherein the forming of the source electrode and the drain electrode is performed.
And stacking the ohmic metal and removing the metal other than the electrode region through a lift-off process to form the source electrode and the drain electrode. The method according to claim 6,
The ohmic metal has a structure measured in the order of Ti / Al / M / Au, wherein M is one of Ni, Ti, Pt, Mo and Ta. The method of claim 1,
The gate electrode may be formed of Ti, Pt, Cr, Pt / Au, Ni / Au, Ti / W, or platinum silicide.

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