KR20160119324A

KR20160119324A - Nitride semiconductor device and method for fabricating the same

Info

Publication number: KR20160119324A
Application number: KR1020150046979A
Authority: KR
Inventors: 김성복; 배성범; 고영호
Original assignee: 한국전자통신연구원
Priority date: 2015-04-02
Filing date: 2015-04-02
Publication date: 2016-10-13

Abstract

The present invention is to provide a normally-off nitride semiconductor device. In particular, the present invention provides a nitride semiconductor device structure and a manufacturing method thereof that replace the conventional dry etching process by a selective growth method using a dielectric mask patterned on a substrate surface.
To this end, the present invention provides a method of manufacturing a semiconductor device, comprising depositing a first nitride layer on a sapphire substrate, patterning a dielectric mask on the first nitride layer, patterning a second nitride on the dielectric mask, And a method of selectively growing the nitride semiconductor device using a vapor growth method.

Description

[0001] NITRIDE SEMICONDUCTOR DEVICE AND METHOD FOR FABRICATING THE SAME [0002]

The present invention relates to compound semiconductor technology. More specifically, the present invention relates to a nitride semiconductor device and a manufacturing method thereof.

Nitride compound semiconductors including a group III element such as gallium (Ga), aluminum (Al), indium (In), and the like and nitrogen (N) As semiconductor, it is possible to control an optical element having various wavelengths from ultraviolet rays to visible rays. In addition, nitride based compound semiconductors have high thermal and chemical stability, high electron mobility and fast saturation electron velocity, and can be fabricated using conventional gallium arsenide (GaAs) and indium phosphide (InP) And has excellent physical properties. Based on these characteristics, nitride semiconductors can be used as optical devices such as light emitting diodes (LEDs) and laser diodes (LD) in the ultraviolet region and visible region, which are limitations of existing compound semiconductors, Electronic devices and power semiconductors used in next-generation wireless communication or satellite communication systems requiring high-frequency characteristics have been increasingly used.

In the case of optical devices and electronic devices based on nitride semiconductors, it is based on the production of devices through dry etching after epitaxial growth. In addition, a high-quality active layer is fabricated by lowering the threading dislocation density going to the upper part of the active layer through some selective growth, thereby manufacturing high efficiency LED and laser diode. Particularly, when a sapphire substrate is used without using a gallium nitride (GaN) substrate in the fabrication of a laser diode, the through-dislocation density is high. Therefore, the ELOG (epitaxy lateral overgrowth) The use of wing parts is well known.

On the other hand, when the gate voltage is 0 V, the normally-off electronic device in which the channel is completely depletioned and the current does not flow can be applied to portable terminals because of low power consumption. A GaN-based field-effect transistor (FET) has excellent properties in terms of physical properties compared to silicon, but it is difficult to fabricate a normally-off device at all times and thus is not adopted in portable terminals.

Generally, in order to fabricate a normally-off electronic device with a nitride semiconductor, a device having a recess structure in which an aluminum gallium nitride (AlGaN) layer under the gate is etched with a thickness of only 10 nm should be fabricated . However, in the case of nitride-based semiconductors, since the material is chemically very stable, it is difficult to use wet etching which is easily used in semiconductor processes such as Si, GaAs and InP, and dry etching of inductively coupled plasma reactive ion etching (ICP-RIE) use. The biggest disadvantage of dry etching is that it is very difficult to control the exact etching depth because there is little etching selectivity depending on the material. These disadvantages increase the possibility of process failures and thus decrease the productivity. Particularly, in the case of an electronic device having a recess structure in which the depth of the etching is very important, the conventional dry etching method has a limitation. Therefore, there is a need to develop a device fabrication method that can control the exact etch depth of various nitride devices.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a normally-off nitride semiconductor device. In particular, the present invention provides a nitride semiconductor device structure and a manufacturing method thereof that replace the conventional dry etching process by a selective growth method using a dielectric mask patterned on a substrate surface.

According to various embodiments of the present invention, it is possible to replace the conventional dry etching process by using selective growth characteristics of MOCVD in a process of manufacturing a nitride semiconductor.

Also, according to various embodiments of the present invention, the visual height can be controlled on a nanometer scale through a selective growth method.

Further, according to various embodiments of the present invention, Removal of the etching process eliminates the need for equipment and cost of the etching process.

Figure 1 shows a sapphire substrate patterned with a dielectric mask.
2 is a view showing a thickness profile of GaN to which selective growth on a sapphire substrate patterned with a dielectric mask is applied.
3 is a diagram illustrating the structure of a normally-off AlGaN-FET device through a conventional recess process.
4 is a view illustrating the structure of an AlGaN-FET fabricated using selective growth according to an embodiment of the present invention.
5 is a graph showing a growth rate of the dielectric mask pattern according to the width thereof.
6 is a graph showing an increase in growth rate with respect to a dielectric mask width.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the embodiments of the present invention, descriptions of techniques which are well known in the technical field of the present invention and are not directly related to the present invention will be omitted. This is for the sake of clarity of the present invention without omitting the unnecessary explanation.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. It is provided to fully inform the owner of the scope of the invention.

For the sake of convenience, the manufacturing process of the normally-off AlGaN-FET device is described as an example on the sapphire substrate, but the present invention is applicable to the nitride semiconductor device.

Figure 1 shows a sapphire substrate patterned with a dielectric mask.

Referring to FIG. 1, a dielectric mask 101 is patterned along the direction 1100 on a sapphire substrate 100. At this time, the dielectric mask 101 for selective growth is formed of SiNx or SiO2 with a band width of 100 mu m. The thickness of the dielectric mask is 0.1 um.

2 is a view showing a thickness profile of GaN to which selective growth on a sapphire substrate patterned with a dielectric mask is applied.

Here, the width of the dielectric mask is 100 mu m, and GaN is grown by selective growth of metal-organic chemical vapor deposition (MOCVD).

FIG. 2 shows the thickness profile of the GaN film as it is moved away from the pattern when GaN is grown on the patterned substrate.

Referring to FIG. 2, as a result of the experiment, when the GaN is grown by 1um, near the dielectric mask, the source gas flowing from the mask increases and the growth becomes thicker (2.2 .mu.m). As the distance from the mask pattern decreases, The growth of 1 um is observed in the region.

3 is a diagram illustrating the structure of a normally-off AlGaN-FET device through a conventional recess process.

In general, the biggest disadvantage of AlGaN-FETs is that it is difficult to obtain a normally-off device at all times. This is because the channel must be depleted by injecting a voltage to the gate at all times, thereby consuming power. In order to solve this problem, a normally-off device is fabricated through a recess process in which an AlGaN layer of a gate region is etched.

3, the GaN layer 301 and the AlGaN layer 302 may be grown on the sapphire substrate 300, and then the gate region 303 may be etched. After that, a source 304, a drain 305, and a gate 306 metal are deposited to fabricate an AlGaN-FET.

In order to completely cut off the current during the fabrication process, it is necessary to etch the AlGaN layer 302 under the gate with a thickness of 10 nm or less. However, it is very difficult and low-yield process to control the depth of 10 nm by the dry etching method of inductively coupled plasma reactive ion etching (ICP-RIE). Accordingly, the present invention proposes a method of manufacturing an AlGaN-FET device by replacing the step of etching the region under the gate by the ICP-RIE method with the selective growth process. A method of manufacturing a nitride semiconductor using selective growth according to the present invention will be described in detail with reference to FIG.

4 is a view illustrating the structure of an AlGaN-FET fabricated using selective growth according to an embodiment of the present invention.

4, a GaN layer 301 is grown on a sapphire substrate 300, a dielectric mask 401 having a predetermined width of SiNx or SiO2 is deposited, and then an AlGaN layer 402 ).

Since the growth mechanism of the MOCVD is grown by diffusion and surface migration of the raw material gas, growth does not occur in the dielectric mask portion, and the raw material gas moves on the surface, so that the growth occurs only in the portion where the GaN substrate is exposed do.

Therefore, as shown in the profile of FIG. 2, the portion near the dielectric mask 401 has a high growth rate, and the farther away from the mask, the lower the growth rate. That is, in the case of the AlGaN layer 402 adjacent to the dielectric mask 401, the growth rate is increased, and the height of the AlGaN layer 402 is higher than that of the gate 306. That is, the grown selectively grown AlGaN layer 402 may have a shape with a thin middle portion and a thick left and right portion. At this time, although the thickness depends on the width of the mask pattern, it is also possible to selectively grow three times or more thicker than the middle portion (see FIG. 5).

Adjusting the thickness of the middle region of the grown AlGaN layer 402 to a thickness of less than 10 nm generally results in a recessed process through dry etch for the normally-off FET fabrication can do.

After the selective growth, a normally-off AlGaN-FET device can be fabricated by depositing source 304, drain 305, and gate 306 metal.

5 is a graph showing a growth rate of the dielectric mask pattern according to the width thereof.

According to FIG. 5, as the width of the dielectric mask pattern is increased from 50 .mu.m to 300 .mu.m, the thickness difference between the periphery of the mask and the central portion gradually increases. This is because the source gas injected into the dielectric mask does not participate in the growth in the dielectric mask but moves on the surface and grows in the region where the GaN crystal plane meets. Therefore, it can be seen that the wider the mask width, the larger the amount of the raw material gas is introduced, and thus the thicker the mask.

6 is a graph showing an increase in growth rate with respect to a dielectric mask width.

According to Fig. 6, the growth rate of the dielectric mask is increased by 2.8 times when the dielectric mask is 300 mu m wide. As a result, it can be seen that the growth rate increases as the width of the dielectric mask increases.

5 and 6, it can be seen that the height of the gate side and the height of the source side and the drain side can be controlled according to the width of the dielectric mask, and a difference of up to 3 times can be shown at most .

In the case of the AlGaN-FET described in this specification, a normally-off FET can be fabricated by controlling the thickness of the AlGaN layer under the source and the drain to be 28 nm and the thickness of the AlGaN layer under the gate to be 10 nm when the dielectric mask pattern of 300 μm is used. have.

In order to solve the above-mentioned problems of dry etching, the present invention is mainly characterized in that the nitride semiconductor is grown in the MOCVD equipment and the growth condition is changed to control the shape of the selective growth, thereby replacing the etching process.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the equivalents of the appended claims, as well as the appended claims.

In the embodiments described above, all of the steps may optionally be performed or omitted. Also, the steps in each embodiment need not occur in order, but may be reversed. It should be understood, however, that the embodiments herein disclosed and illustrated herein are illustrative only and are not intended to limit the scope of the present disclosure. That is, it will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are feasible.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And is not intended to limit the scope of the invention. It is to be understood by 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.

100: sapphire substrate
101: dielectric mask

Claims

Depositing a first layer of nitride on a sapphire substrate;
Patterning a dielectric mask on the first nitride layer;
Patterning a second nitride over the dielectric mask; And
And selectively growing the second nitride by an organic metal vapor deposition method.