WO2019241905A1

WO2019241905A1 - Heterojunction field effect transistor and preparation method therefor

Info

Publication number: WO2019241905A1
Application number: PCT/CN2018/091797
Authority: WO
Inventors: 刘新科; 王磊; 敖金平
Original assignee: 深圳大学
Priority date: 2018-06-19
Filing date: 2018-06-19
Publication date: 2019-12-26

Abstract

Provided are a heterojunction field effect transistor and a preparation method therefor. The preparation method comprises the following steps: providing a substrate (S01); preparing an AlGaN/GaN heteroepitaxial layer on the substrate (S02); preparing a source electrode and a drain electrode on the AlGaN/GaN heteroepitaxial layer (S03); and depositing a p-type oxide on the AlGaN/GaN heteroepitaxial layer by means of a magnetron sputtering method to obtain a p-type oxide grid electrode (S04). The preparation method has a simple process, so that a p-type oxide can be prevented from being polluted, a p-type oxide grid electrode with a higher concentration can also be prepared, the capability of positive regulation of a threshold voltage of a GaN-based heterojunction field effect transistor can also be ensured, and finally the device power of the heterojunction field effect transistor is remarkably improved.

Description

Heterojunction field effect transistor and preparation method thereof

The invention belongs to the field of semiconductor technology, and particularly relates to a heterojunction field effect transistor and a preparation method thereof.

Cuprous oxide (Cu ₂ O) is an excellent group I-IV semiconductor material because it has a direct band gap of 2.1eV and a very high visible light absorption coefficient. In addition, it has non-toxic, low-cost, raw materials Rich and other advantages, it is often used in the preparation of solar cells and photodetector elements. At the same time, Cu ₂ O has photocatalytic activity, which can directly use visible light to catalyze the cracking of water to generate hydrogen, which has become the material of choice for energy conservation and environmental protection in the field of hydrogen production. In addition, due to the presence of Cu vacancies in the Cu ₂ O crystal structure, Cu ₂ O is a p-type semiconductor of this certificate. Because Cu ₂ O has a high mobility, it is often used as a channel material in combination with an n-type semiconductor. For the preparation of thin film transistors (TFTs). Therefore, Cu ₂ O will be a thin film material with very important application prospects in the fields of electricity, optics and semiconductors. With its thin-film nanostructure, it is possible to manufacture smaller-sized, more energy-efficient semiconductor chips, making it widely used in the field of nanoelectronic components. In addition, Cu ₂ O has important application value in the field of gas monitoring. With the increasing development of semiconductor optoelectronics, Cu ₂ O stands out as a natural p-type conductive material.

Following the development of practical first-generation Ge, Si-based devices and second-generation SiC, InP-based devices, the research and development of third-generation wide-band-gap semiconductor materials represented by GaN-based has attracted the attention of scientists. At present, GaN-based LEDs have fully entered the industrialization stage, and GaN-based materials can form AlGaN with a high concentration of two-dimensional electron gas (2DEG) due to its large band gap E _g , high electron saturation speed, and good thermal conductivity. The / GaN heterostructure makes GaN-based power electronic devices particularly suitable for use in hostile environments such as high temperatures, high frequencies, high power, and radiation resistance.

In the field of semiconductor technology, a conventional method for preparing a p-type Cu ₂ O thin film is generally to grow p-type Cu ₂ O by thermal oxidation using metal copper. Although this technology can form p-type Cu ₂ O by adjusting the thermal oxidation temperature at a low temperature, it has a very fatal disadvantage. Later, it must be prepared for subsequent processes by photolithography. In this process, Cu ₂ O will be oxidized to Copper oxide (CuO) and its surface may also be contaminated or introduce defects, and p-type Cu ₂ O grown by the traditional thermal oxidation method often has a hole concentration below 1 × 10 ¹⁶ cm ^-3 .

Summary of the Invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, to provide a heterojunction field effect transistor and a preparation method thereof, and to solve the technical problems of poor threshold voltage regulation ability and low power of the existing GaN heterojunction field effect transistor. .

In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

One aspect of the present invention provides a method for preparing a heterojunction field effect transistor, including the following steps:

Providing a substrate;

Preparing an AlGaN / GaN heteroepitaxial layer on the substrate;

Preparing a source electrode and a drain electrode on the AlGaN / GaN heteroepitaxial layer;

A p-type oxide is deposited on the AlGaN / GaN heteroepitaxial layer by a magnetron sputtering method to prepare a p-type oxide gate.

The method for preparing a heterojunction field-effect transistor provided by the present invention uses a magnetron sputtering method to deposit a p-type oxide on an AlGaN / GaN heteroepitaxial layer to obtain a p-type oxide gate. The preparation method has a simple process. The p-type oxide can be prevented from being polluted, and a higher-concentration p-type oxide gate can be prepared, and the forward regulation ability of the threshold voltage of the GaN-based heterojunction field effect transistor can be ensured. The device power of the field effect transistor is significantly increased.

Another aspect of the present invention provides a heterojunction field effect transistor, which includes an AlGaN / GaN heteroepitaxial layer. The AlGaN / GaN heteroepitaxial layer is provided with an active electrode and a drain electrode; and the AlGaN / GaN heteroepitaxial layer. A p-type oxide gate cap layer structure composed of a p-type oxide is also disposed on the layer.

The heterojunction field effect transistor provided by the present invention is a GaN-based heterojunction field effect transistor, in which a p-type oxide gate cap structure composed of a p-type oxide is provided; compared with a traditional Schottky metal gate electrode The p-type oxide direct bandgap semiconductor material can regulate the hole concentration and forbidden band width, which can more effectively adjust the GaN-based heterojunction band structure, and then control the threshold voltage to achieve enhanced (threshold voltage greater than 0) Volt) GaN-based heterojunction field-effect transistor power device; the heterojunction field-effect transistor can reduce unnecessary power loss and the number of devices in the secondary circuit, improve integration, and achieve GaN-based heterojunction field effect The application of transistors in power electronics conversion is of great significance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a relationship between hole carrier density, resistivity, and sputtering power of a cuprous oxide thin film in a base heterojunction field effect transistor prepared in Example 1 of the present invention. Graph;

FIG. 2 is a comparison diagram of transfer characteristics between a GaN heterojunction field effect transistor having a p-type Cu ₂ O gate cap structure and a conventional GaN heterojunction field effect transistor prepared in Example 1 of the present invention.

Specific embodiment mode

In order to make the technical problems, technical solutions, and beneficial effects of the present invention clearer and clearer, the present invention is further described in detail in combination with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

In one aspect, an embodiment of the present invention provides a method for manufacturing a heterojunction field effect transistor, including the following steps:

S01: providing a substrate;

S02: preparing an AlGaN / GaN heteroepitaxial layer on the substrate;

S03: preparing a source electrode and a drain electrode on the AlGaN / GaN heteroepitaxial layer;

S04: A p-type oxide is deposited on the AlGaN / GaN heteroepitaxial layer by a magnetron sputtering method to prepare a p-type oxide gate.

A method for manufacturing a heterojunction field effect transistor provided by an embodiment of the present invention uses a magnetron sputtering method to deposit a p-type oxide on an AlGaN / GaN heteroepitaxial layer to obtain a p-type oxide gate; the preparation method has a simple process , Not only can prevent the p-type oxide from being contaminated, but also can produce a higher concentration of the p-type oxide gate, and can also ensure the positive control of the threshold voltage of the GaN-based heterojunction field effect transistor. The device power of the QJFET has been significantly improved.

Further, in the above step S01: the substrate may be sapphire (Sapphire), and the main component is alumina.

Further, in the above step S03, before preparing the source electrode and the drain electrode, an etching depth of 120 nm is formed through an inductively coupled plasma (ICP) system to ensure the disappearance of the two-dimensional electron gas channel between the devices and complete the device isolation. . The steps of preparing the source electrode and the drain electrode include: depositing Ti / Al / Ti / Au (50/200/40 / 40nm) multilayer metal by magnetron sputtering to complete the preparation of the source electrode and the drain electrode at 850 ° C. Anneal in an N ₂ environment for 3 minutes to form an ohmic contact. If the annealing temperature is lower than 850 ° C, ohmic contact cannot be formed well. Above 850 ° C will increase the series resistance and contact resistance value, affecting the device performance; if the annealing time is less than 3 minutes, the source electrode and drain electrode metal cannot It fully reacts with the AlGaN epitaxial layer, and can not form an ohmic contact well. If it is more than 3 minutes, it will increase the contact resistance value and reduce the effect on the device performance. Therefore, the optimal source and drain electrodes can be obtained by annealing at this temperature and time.

Further, in the above step S04, the p-type oxide is selected from any one of p-type copper oxide, p-type cuprous oxide, p-type nickel oxide, and p-type magnesium oxide. The embodiments of the present invention innovatively use the magnetron sputtering method to form a high-quality p-type oxide thin film as a gate electrode at a normal temperature and change the sputtering power. After one photolithography, the foregoing is deposited by the magnetron sputtering method. Any one of the p-type oxides is made into a gate, so that a GaN heterojunction field-effect transistor with a high-performance p-type oxide gate cap structure is produced. Specifically, the p-type oxide is preferably p-type cuprous oxide (Cu ₂ O). This preparation method can prevent Cu ₂ O from being contaminated with copper oxide (CuO) and Cu ₂ O.

In the manufacturing process of the embodiment of the present invention, p-type Cu ₂ O gate electrode and subsequent Ni / Au deposition can be deposited by one-time photolithography and magnetron sputtering under normal temperature conditions, which simplifies the process flow and prevents Cu ₂ O is contaminated during the preparation process and the problem of lower hole concentration when Cu ₂ O is prepared under thermal oxidation conditions is avoided.

Further, the step of depositing the p-type oxide includes performing a magnetron sputtering process using a copper target as a copper source and a mixed gas of argon and oxygen as a sputtering gas and a reaction gas. Specifically, the volume ratio of the argon to the oxygen is 15: 3-4. The reaction power of the magnetron sputtering process is 10-100W; the reaction pressure of the magnetron sputtering process is 0.2-0.3Pa. The oxide on the surface of the copper target is removed, and before the reactive sputtering, a step of deoxidizing the copper target surface with argon gas is further included. Specifically, the step of removing the oxide includes: 150-160W The sputtering power is 10-12min.

On the other hand, an embodiment of the present invention further provides a heterojunction field effect transistor, which includes an AlGaN / GaN heteroepitaxial layer, and the AlGaN / GaN heteroepitaxial layer is provided with an active electrode and a drain electrode; the AlGaN A / GaN heteroepitaxial layer is further provided with a p-type oxide gate cap structure composed of a p-type oxide.

The heterojunction field-effect transistor provided by the embodiment of the present invention is a GaN-based heterojunction field-effect transistor, in which a p-type oxide gate cap structure composed of a p-type oxide is provided; and a conventional Schottky metal gate electrode Compared with the p-type oxide direct bandgap semiconductor material, the adjustable hole concentration and forbidden band width can more effectively adjust the GaN-based heterojunction band structure, and then control the threshold voltage to achieve enhanced (threshold voltage > 0 volts) GaN-based heterojunction field-effect transistor power device; the heterojunction field-effect transistor can reduce unnecessary power loss and the number of devices in the secondary circuit, improve integration, and achieve GaN-based heterojunctions The application of field-effect transistors in power electronics conversion is of great significance.

Specifically, the p-type oxide is selected from any one of p-type copper oxide, p-type cuprous oxide, p-type nickel oxide, and p-type magnesium oxide. These p-type oxides can be used to prepare the p-type oxide gate cap structure in the device of the embodiment of the present invention. More preferred is p-type cuprous oxide.

The present invention has been tested many times in succession, and a part of the test results is used as a reference to further describe the invention in detail. The detailed description is given below in conjunction with specific examples.

Example 1

A heterojunction field effect transistor includes an AlGaN / GaN heteroepitaxial layer. An active electrode and a drain electrode are disposed on the AlGaN / GaN heteroepitaxial layer. A p is also disposed on the AlGaN / GaN heteroepitaxial layer. Cu ₂ O type composed of a p-type Cu ₂ O gate cap layer structure.

The method for preparing the heterojunction field effect transistor includes the following steps:

First, first deposit a layer of AlGaN / GaN heteroepitaxial structure material on the sapphire substrate, and clean the deposited AlGaN / GaN heteroepitaxial structure material. The specific process is as follows:

Boil with a mixture of sulfuric acid: hydrogen peroxide = 4: 1 at 100 ° C for several minutes, and then clean in a deionized water beaker with deionized water cleaning, acetone ultrasonic cleaning, and ethanol ultrasonic cleaning.

Second, the specific process of preparing the source electrode, drain electrode and gate in the device is as follows (all preparation processes are based on the AlGaN / GaN heteroepitaxial structure material on the sapphire substrate to prepare the p-type Cu ₂ O gate cap structure GaN Heterojunction Field Effect Transistor):

Firstly, an etching depth of 120 nm is formed by an inductively coupled plasma (ICP) system, and then Ti / Al / Ti / Au (50/200/40 / 40nm) multilayer metals are deposited by magnetron sputtering to complete the source and drain electrodes. After the preparation, annealed in an N ₂ environment at 850 ° C. for 3 minutes to form an ohmic contact. Then, p-type Cu ₂ O gate (100nm) was deposited by adjusting the argon to oxygen ratio and reaction power by magnetron sputtering, and finally Ni / Au (70 / 30nm) was deposited on it by magnetron sputtering. To form a gate ohmic contact.

The preparation process of the p-type Cu ₂ O grid is as follows: a high-purity copper target (99.99%, analytical purity) is used as a copper source, and a mixed gas of argon and oxygen is used as a sputtering gas and a reaction gas to prepare p-type Cu ₂ O Grid; where the deposition temperature is room temperature, the ratio of argon to oxygen = 15: 4, the reaction power is 10W, and the reaction pressure is 0.2pa. In order to remove the oxide on the surface of the copper target, before the reactive sputtering, the copper target was surface-treated with argon at a sputtering power of 150 W for 10 minutes.

The product obtained under the process conditions of this embodiment is a GaN heterojunction field effect transistor (ie, Cu ₂ O / HFET) having a p-type Cu ₂ O gate cap structure.

Before discussing device performance, the quality of p-type Cu ₂ O thin films in the device was evaluated by atomic force microscope (AFM) and Hall test (Hall). The surface roughness of p-type Cu ₂ O thin films was characterized by atomic force microscope. With the decrease of the deposition power, the surface roughness of the p-type Cu ₂ O film shows a downward trend. When the deposition power is reduced to 10W, a quasi-amorphous p-type Cu ₂ O film is formed. At the same time, according to the Hall test, as shown in Figure 1, as the deposition power decreases, the hole concentration shows an upward trend. Especially when the deposition power is reduced to 10W, a maximum hole concentration of 1 × 10 ¹⁷ cm ^-3 is obtained. . Then based on this optimized p-type Cu ₂ O film formation conditions (magnetron sputtering reaction power = 10W), a p-type Cu ₂ O gate cap structure GaN heterojunction field effect transistor was prepared to study its electrical characteristics. .

In order to compare the device performance superiority of this embodiment, a conventional GaN heterojunction field effect transistor is also prepared. The gate leakage current characteristic test results show that, as shown in Figure 2, a GaN heterojunction field effect transistor with a p-type Cu ₂ O gate cap structure is better than the gate of a conventional GaN heterojunction field effect transistor. Leakage current is nearly two orders of magnitude smaller. According to the output characteristics of the device, it was found that the output current of the GaN heterojunction field-effect transistor with a p-type Cu ₂ O gate cap structure was improved to a certain extent compared with the traditional GaN heterojunction field-effect transistor. At the same time, we also found through device transfer characteristics (logarithmic coordinates), as shown in Figure 2: GaN heterojunction field effect transistor with p-type Cu ₂ O gate cap structure (Cu ₂ O / HFET in Figure 2), Compared with the traditional GaN heterojunction field-effect transistor (HFET in Figure 2), in addition to a threshold shift of 0.55V, it has an improvement of two orders of magnitude in the ON / OFF characteristic and electron mobility. With a certain increase, the sub-threshold swing (SS) has also been greatly reduced.

The above description is only the preferred embodiments of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be included in the protection of the present invention. Within range.

Claims

A method for preparing a heterojunction field-effect transistor includes the following steps:
Providing a substrate;
Preparing an AlGaN / GaN heteroepitaxial layer on the substrate;
Preparing a source electrode and a drain electrode on the AlGaN / GaN heteroepitaxial layer;
A p-type oxide is deposited on the AlGaN / GaN heteroepitaxial layer by a magnetron sputtering method to prepare a p-type oxide gate.
The method according to claim 1, wherein the p-type oxide is selected from any one of p-type copper oxide, p-type cuprous oxide, p-type nickel oxide, and p-type magnesium oxide.
The method according to claim 1, wherein the p-type oxide is p-type cuprous oxide, and the step of depositing the p-type oxide includes: using a copper target as a copper source, and argon and oxygen The mixed gas is a sputtering gas and a reaction gas, and is subjected to a magnetron sputtering process.
The method of claim 3, wherein a volume ratio of the argon gas to the oxygen gas is 15: 3-4.
The method according to claim 3, wherein the reaction power of the magnetron sputtering process is 10-100W; and / or the reaction pressure of the magnetron sputtering process is 0.2-0.3Pa.
The method according to claim 3, wherein before the magnetron sputtering treatment, the method further comprises a step of performing an oxide removal treatment on the surface of the copper target with argon.
The method according to claim 6, wherein the step of deoxidizing treatment comprises: passing a argon gas at a sputtering power of 150-160W for 10-12 minutes.
The preparation method according to any one of claims 1 to 7, wherein the substrate is sapphire.
A heterojunction field-effect transistor includes an AlGaN / GaN heteroepitaxial layer, and an active electrode and a drain electrode are disposed on the AlGaN / GaN heteroepitaxial layer; the AlGaN / GaN heteroepitaxial layer is characterized in that A p-type oxide gate cap structure composed of a p-type oxide is also provided.
The heterojunction field effect transistor of claim 9, wherein the p-type oxide is selected from any one of p-type copper oxide, p-type cuprous oxide, p-type nickel oxide, and p-type magnesium oxide Species.