CN101232045A - Field effect transistor multilayer field plate device and manufacturing method thereof - Google Patents

Abstract

The invention relates to the technical field of microwave power devices in semiconductor materials, and discloses a method for manufacturing an aluminum gallium nitride/gallium nitride high electron mobility field effect transistor (AlGaN/GaN HEMT) multilayer field plate device. The method is based on conventional In the manufacturing process of AlGaN/GaN HEMT devices, after the gate metal contact is formed, the gate connection field plate is firstly fabricated, and then the source connection field plate is fabricated to form an AlGaN/GaN HEMT multilayer field plate device. The invention also discloses an AlGaN/GaN HEMT multilayer field plate device. The invention greatly improves the breakdown characteristic of the AlGaN/GaN HEMT device, and effectively suppresses the current collapse phenomenon of the AlGaN/GaN HEMT device.

Description

Field effect transistor multilayer field plate device and manufacturing method thereof

technical field

The invention relates to the technical field of microwave power devices in semiconductor materials, in particular to an aluminum gallium nitride/gallium nitride high electron mobility field effect transistor (AlGaN/GaN HEMT) multilayer field plate device and a manufacturing method thereof.

Background technique

Gallium nitride (GaN), as the third-generation wide-bandgap semiconductor material, has a large bandgap (3.4eV), a high breakdown voltage (3.3MV/cm), and a high two-dimensional electron gas concentration (greater than 10 ¹³ cm ² ), high saturation electron velocity (2.8×10 ⁷ cm/s) and other characteristics have attracted extensive attention in the world.

At present, the high frequency, high voltage, high temperature and high power characteristics of AlGaN/GaN HEMT devices make them have great prospects in microwave power devices.

For conventional AlGaN/GaN HEMT devices, the usual process steps are shown in Figure 1. Figure 1 is a flow chart of the current method for manufacturing conventional AlGaN/GaN HEMT devices. The method specifically includes the following steps:

Step 101: optical lithography, forming an alignment mark, and evaporating the mark metal;

Step 102: Optically lithography the source and drain pattern, and evaporate the source and drain metal;

Step 103: annealing, so that the source and drain metals form a good ohmic contact with the substrate material;

Step 104: active area isolation;

Step 105: making grid lines by optical lithography;

Step 106: evaporating grid metal;

Step 107: metal wiring;

Step 108: Make the air bridge;

Step 109: Test analysis.

However, there are still many problems in AlGaN/GaN HEMT power devices that have not been resolved. The two key problems are the current collapse effect and excessive gate reverse leakage. The study found that both phenomena are directly related to the surface states of AlGaN.

In order to reduce the surface trap effect and achieve the effect of suppressing current collapse, silicon nitride (SiN) is used as a dielectric film to passivate the device. The adoption of the passivation process effectively suppresses the current collapse effect and increases the microwave power output capability of the device. However, the breakdown voltage of the device is also reduced at the same time.

How to compromise the relationship between current collapse and breakdown voltage is an important issue to make AlGaN/GaN devices applied in the field of high frequency, high voltage and high power. For this reason, the process of connecting the gate to the field plate is introduced. The introduction of the gate connection field plate plays a role in modulating the surface state trap between the gate and the drain to suppress the current collapse; at the same time, the introduction of the field plate redistributes the electric field between the gate and the drain.

Before the field plate is made, the maximum point of the electric field intensity between the gate and the drain is located at the edge of the gate metal, and the field plate between the gate and the drain makes the area of the maximum electric field intensity expand to the drain end, the peak value is reduced, and the breakdown voltage of the device is greatly improved.

However, the addition of the gate connection field plate increases the capacitance between the gate and the drain, and also increases the length of the depletion region, resulting in a decrease in gain. To solve this problem, the concept of source-connected field plates is proposed. In this structure, the capacitance between the field plate and the channel is the drain-source capacitance, which can be absorbed by the output matching network, and the Miller feedback capacitance brought by the field plate structure of the gate field plate does not exist. Therefore, the output power and gain of the device are effectively improved at the same time.

Contents of the invention

(1) Technical problems to be solved

In view of this, an object of the present invention is to provide an AlGaN/GaN HEMT multilayer field plate device to improve the breakdown characteristics of the AlGaN/GaN HEMT device and suppress the current collapse phenomenon of the AlGaN/GaN HEMTs device.

Another object of the present invention is to provide a method for fabricating an AlGaN/GaN HEMT multilayer field plate device, so as to improve the breakdown characteristics of the AlGaN/GaN HEMTs device and suppress the current collapse phenomenon of the AlGaN/GaN HEMTs device.

(2) Technical solution

In order to achieve the above-mentioned purpose, the present invention provides a kind of AlGaN/GaN HEMT multilayer field plate device, and this device comprises gate, is positioned at the source electrode and the drain of gate both sides; Wherein,

The gate, source and drain are located on the AlGaN epitaxial layer on the top layer of the substrate material, and ohmic contacts are formed between the source and the AlGaN epitaxial layer and the drain and the AlGaN epitaxial layer by annealing the alloy;

Deposit a silicon nitride (SiN) dielectric film on the surface of the device where the gate, source and drain are formed, and evaporate the pattern of the gate connection field plate on the dielectric film; then deposit the SiN dielectric again on the surface of the device that has been formed film, on which the evaporation source is connected to the pattern of the field plate on the dielectric film.

The substrate material includes a three-layer structure of sapphire substrate, gallium nitride GaN and AlGaN epitaxial layer from bottom to top; among them, the sapphire substrate is used as the substrate material for growing GaN epitaxial layer; AlGaN/GaN epitaxial layer structure , A heterojunction is formed between the AlGaN epitaxial layer and the GaN epitaxial layer to generate a high concentration of two-dimensional electron gas, providing a large current density and power output capability.

In order to achieve the above-mentioned another object, the present invention provides a method for manufacturing AlGaN/GaN HEMT multilayer field plate devices. The method is based on the conventional AlGaN/GaN HEMT device manufacturing process. After the gate metal contact is formed, the gate connection is first made. Field plate, and then make source connection field plate to form AlGaN/GaN HEMT multilayer field plate device.

The method specifically includes:

A. Perform optical lithography on the substrate material to form an alignment mark and evaporate the mark metal;

B. After evaporating the marking metal, optically lithography the source and drain pattern on the AlGaN epitaxial layer, and evaporate the source and drain metal, and then high temperature rapid thermal annealing to form an ohmic contact between the source and drain metal and the substrate material to form the source and drain;

C. Perform ion implantation to isolate the active area;

D. Make gate lines by optical lithography at the position between the source and drain on the substrate material, evaporate the gate metal, and form the gate;

E. Deposit a SiN dielectric film on the surface of the substrate material with source, drain and gate;

F. Optical lithography grid field plate pattern, evaporated metal;

G, secondary deposition of SiN dielectric film;

H. Optical lithography source field plate pattern, evaporated metal;

I. Optical lithography metal wiring pattern, evaporated metal.

The substrate materials are AlGaN, GaN and sapphire in order from top to bottom.

The substrate material further includes a layer of AlN between AlGaN and GaN.

The evaporated source-drain metal in step B is Ti/Al/Ti/Au, and the high-temperature rapid thermal annealing condition is: annealing in a nitrogen atmosphere at 750° C. to 800° C. for 30 seconds.

The ions implanted during the ion implantation described in step C are high-energy He ⁺ ions;

The evaporated gate metal in step D is Ni/Au, the evaporated metal in step F is Ni/Au, the evaporated metal in step H is Ni/Au, and the evaporated metal in step I is Ti /Au.

The deposition in step E adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is ;

。The deposition in step G adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is

.

The method further includes: J, making an air bridge and testing and analyzing.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

1. The AlGaN/GaN HEMT multilayer field plate device and its manufacturing method provided by the present invention are based on the conventional AlGaN/GaN HEMT device manufacturing process. After the gate metal contact is formed, the gate connection field plate is firstly fabricated, and then fabricated The source is connected to the field plate to form an AlGaN/GaN HEMT multilayer field plate device, so the breakdown characteristics of the AlGaN/GaN HEMT device are greatly improved, and the current collapse of the AlGaN/GaN HEMT device is effectively suppressed.

2. Using the AlGaN/GaN HEMT multilayer field plate device manufactured by the present invention, it can be seen from the breakdown voltage test that the breakdown voltage of this structure is much higher than that of the structure that only uses the gate-connected field plate or the source-connected field plate structure This is because the use of two-layer field plates makes the electric field between the gate and the drain change from two peaks of one field plate to an E-shaped structure with three peaks, and the peaks become smaller, that is, the maximum electric field value becomes smaller. Small, so the breakdown voltage is improved.

3. The AlGaN/GaN HEMT multilayer field plate device manufactured by the present invention basically completely eliminates the current collapse phenomenon in terms of power output. Moreover, unlike the conventional structure, the power of the conventional structure HEMT device reaches saturation at a drain voltage of more than 20 volts. Even if the drain voltage can be added, the output power basically does not increase. , in the case of high voltage, when the drain voltage is greater than 40 volts, the output power still increases with the increase of the drain voltage, which proves that the HEMT structure of this structure has fully utilized the potential of the AlGaN/GaN material system in terms of power output.

Description of drawings

Fig. 1 is the flow chart of the current method for making conventional AlGaN/GaN HEMT devices;

Fig. 2 is the structural representation of the AlGaN/GaN HEMT multilayer field plate device provided by the present invention;

Fig. 3 is the flow chart of the method for making AlGaN/GaN HEMT multilayer field plate device provided by the present invention;

Fig. 4 is the process flow chart of making AlGaN/GaN HEMT multilayer field plate device provided by the present invention;

Fig. 5 is a schematic diagram of the breakdown characteristics of the AlGaN/GaN HEMT multilayer field plate device provided by the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

As shown in FIG. 2, FIG. 2 is a schematic structural diagram of an AlGaN/GaN HEMT multilayer field plate device provided by the present invention. The AlGaN/GaN HEMT multilayer field plate device includes:

gate, source and drain on either side of the gate; where,

The gate, source and drain are located on the top aluminum gallium nitride (AlGaN) epitaxial layer of the substrate material, and an ohmic contact is formed between the source and the AlGaN epitaxial layer and the drain and the AlGaN epitaxial layer through an annealing alloy;

Deposit a SiN dielectric film on the surface of the device where the gate, source and drain are formed, and evaporate the pattern of the gate connection field plate on the dielectric film; then deposit the SiN dielectric film again on the surface of the device that has been formed. The graph of the evaporation source connected to the field plate on the dielectric film.

The substrate material includes a three-layer structure of sapphire substrate, gallium nitride (GaN) and AlGaN epitaxial layer from bottom to top; among them, the sapphire substrate is used as the substrate material for growing GaN epitaxial layer; AlGaN/GaN epitaxial layer Layer structure, AlGaN epitaxial layer and GaN epitaxial layer form a heterojunction to generate a high concentration of two-dimensional electron gas, providing large current density and power output capability.

Based on the AlGaN/GaN HEMT multilayer field plate device shown in FIG. 2, FIG. 3 shows a flowchart of a method for manufacturing an AlGaN/GaN HEMT multilayer field plate device provided by the present invention. This method is based on the conventional GaN HEMT device manufacturing process. After the gate metal contact is formed, the gate connection field plate is first fabricated, and then the source connection field plate is fabricated to form an AlGaN/GaN HEMT multilayer field plate structure. The method specifically includes the following steps:

Step 301: performing optical lithography on the substrate material to form an alignment mark, and evaporating the mark metal;

In this step, the substrate material is AlGaN, GaN and sapphire in sequence from top to bottom, or a layer of AlN may be further included between AlGaN and GaN.

Step 302: After evaporating the marking metal, optically lithographic source-drain pattern on the AlGaN epitaxial layer, and evaporate the source-drain metal (Ti/Al/Ti/Au), and then high-temperature rapid thermal annealing, the source-drain metal and the substrate Ohmic contacts are formed between the materials to form source and drain electrodes;

In this step, the high-temperature rapid thermal annealing condition is: annealing in a nitrogen atmosphere at 750° C. to 800° C. for 30 seconds; the process flow chart corresponding to this step is shown in FIG. 4( a ).

Step 303: performing ion implantation to isolate the active region;

In this step, high-energy He ⁺ ions are used to perform ion implantation on the isolation region, and the process flow chart corresponding to this step is shown in Figure 4(b).

Step 304: Make gate lines by optical lithography at the position between the source and the drain on the substrate material, and evaporate the gate metal Ni/Au to form a gate; the process flow chart corresponding to this step is shown in Figure 4(c) Show.

Step 305: depositing a SiN dielectric film on the surface of the substrate material on which the source, drain and gate are formed;

In this step, the deposition adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is ; The process flow diagram corresponding to this step is shown in Figure 4 (d).

Step 306: optically lithographically patterning the grid field plate, and evaporating metal Ni/Au;

Step 307: secondly depositing a SiN dielectric film;

；与本步骤对应的工艺流程图如图4(f)所示。In this step, the deposition adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is

; The process flow diagram corresponding to this step is shown in Figure 4 (f).

Step 308: Optically lithography source field plate patterns, and evaporate metal Ni/Au; the process flow chart corresponding to this step is shown in FIG. 4(g).

Step 309: Optically lithographic metal wiring patterns, and evaporate metal Ti/Au.

Step 310: Make the air bridge;

Step 311: Test analysis. In this step, a schematic diagram of the breakdown characteristics of the AlGaN/GaN HEMT multilayer field plate device provided by the present invention is shown in FIG. 5 .

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. An aluminum gallium nitride/gallium nitride high electron mobility field effect transistor multilayer field plate device, characterized in that the device comprises a gate, a source and a drain positioned on both sides of the gate; wherein, The gate, source and drain are located on the AlGaN epitaxial layer on the top layer of the substrate material, and the ohmic contact is formed between the source and the AlGaN epitaxial layer and the drain and the AlGaN epitaxial layer through an annealing alloy; Deposit a silicon nitride SiN dielectric film on the surface of the device where the gate, source and drain are formed, and evaporate the pattern of the gate connection field plate on the dielectric film; then deposit the SiN dielectric film again on the surface of the device that has been formed, The evaporation source is connected to the pattern of the field plate on the dielectric film. 2. The AlGaN/GaN high electron mobility field-effect transistor multilayer field plate device according to claim 1, wherein the substrate material comprises sapphire substrate, GaN GaN and AlGaN epitaxial layer three-layer structure; Among them, the sapphire substrate is used as the substrate material for growing the GaN epitaxial layer; the AlGaN/GaN epitaxial layer structure forms a heterojunction between the AlGaN epitaxial layer and the GaN epitaxial layer to generate a high concentration of two-dimensional electron gas, providing a large current density and power output capability. 3. A method for making an AlGaN/GaN HEMT multilayer field plate device, characterized in that the method is based on a conventional AlGaN/GaN HEMT device manufacturing process, and after forming the gate metal contact, first make the gate connection field plate, and then make The source is connected to the field plate to form an AlGaN/GaN HEMT multilayer field plate device. 4. the method for making AlGaN/GaN HEMT multilayer field plate device according to claim 3, is characterized in that, this method specifically comprises: A. Perform optical lithography on the substrate material to form an alignment mark and evaporate the mark metal; B. After evaporating the marking metal, photolithographically source and drain patterns on the AlGaN epitaxial layer, and evaporate the source and drain metal, and then high-temperature rapid thermal annealing to form an ohmic contact between the source and drain metal and the substrate material, forming the source and Drain; C. Perform ion implantation to isolate the active area; D. Make gate lines by optical lithography at the position between the source and drain on the substrate material, evaporate the gate metal, and form the gate; E. Deposit a SiN dielectric film on the surface of the substrate material with source, drain and gate; F. Optical lithography grid field plate pattern, evaporated metal; G, secondary deposition of SiN dielectric film; H. Optical lithography source field plate pattern, evaporated metal; I. Optical lithography metal wiring pattern, evaporated metal. 5. The method for making an AlGaN/GaN HEMT multilayer field plate device according to claim 4, wherein the substrate material is AlGaN, GaN and sapphire sequentially from top to bottom. 6. The method for making an AlGaN/GaN HEMT multilayer field plate device according to claim 5, wherein the substrate material further comprises a layer of AlN between AlGaN and GaN. 7. The method for making an AlGaN/GaN HEMT multilayer field plate device according to claim 4, wherein the evaporated source-drain metal in step B is Ti/Al/Ti/Au, and the high-temperature rapid heating The annealing condition is: annealing in a nitrogen atmosphere at 750° C. to 800° C. for 30 seconds. 8. the method for making AlGaN/GaN HEMT multilayer field plate device according to claim 4, is characterized in that, The ions implanted during the ion implantation described in step C are high-energy He ⁺ ions; The evaporated gate metal in step D is Ni/Au, the evaporated metal in step F is Ni/Au, the evaporated metal in step H is Ni/Au, and the evaporated metal in step I is Ti /Au. 9. the method for making AlGaN/GaN HEMT multilayer field plate device according to claim 4, is characterized in that, The deposition in step E adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is

The deposition in step G adopts the PECVD method, the type of the deposited dielectric film is Si ₃ N ₄ , and the thickness of the deposited dielectric film is

10. The method for making an AlGaN/GaN HEMT multilayer field plate device according to claim 4, characterized in that the method further comprises: J. Make air bridge and test analysis.

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