HEMT device with Ga2O3 / Al2O3 protective layer and preparation method thereof

Abstract

The present invention discloses a HEMT device with a Ga2O3 / Al2O3 protective layer and a preparation method thereof. The device comprises an AlGaN / GaN epitaxy, and both ends of the upper surface of the AlGaN / GaN epitaxy are respectively connected to source and drain electrodes. The source and drain electrodes are formed by a method combining electron beam evaporation and magnetron sputtering. Before the source and drain electrodes are subjected to high-temperature annealing, the entire wafer is subjected to N2O plasma treatment. After the Ga2O3 / Al2O3 protective layer is formed, a high-temperature annealing process is performed, and a gate electrode is arranged on the source and drain electrodes near the source side. The Ga2O3 / Al2O3 protective layer effectively suppresses the interface state introduced to the (Al)GaN surface during the high-temperature annealing process, and the N2O plasma treatment process has no deteriorating effect on the annealing effect of the source and drain electrodes. The HEMT device with a Ga2O3 / Al2O3 protective layer has a low interface state density and excellent high-frequency and dynamic characteristics.

Description

Technical Field

[0001] The present invention relates to an AlGaN / GaN HEMT device in the semiconductor field, and in particular to a HEMT device with a Ga2O3 / Al2O3 protective layer and a preparation method thereof. Background Art

[0002] GaN materials are widely used in high-frequency power amplifiers and high-voltage power switches due to their high electron mobility, low on-resistance, excellent heat dissipation and high breakdown. At present, the formation of ohmic contacts of GaN HEMT devices still relies on high-temperature annealing (generally over 800°C). During the high-temperature annealing process, due to the purity and vacuum of N2, O2 and H2O are inevitably present in the entire cavity atmosphere, which causes oxidation reaction on the (Al)GaN surface during the high-temperature annealing process, increasing the surface state of the device and causing degradation of the dynamic performance of the device (T. Hashizume, et al, Appl.Surf. Sci., 2004, 234(1-4)).

[0003] Some scholars have proposed a method of laser annealing the source and drain electrode regions (M. Hou, et al, Electron. Lett., 2019, 55(11)). This method avoids areas other than the source and drain electrodes from participating in the annealing process and optimizes the dynamic resistance of the device. However, there are problems with self-alignment and cost, making it difficult to use in large quantities.

[0004] N2O plasma treatment is currently widely used as an oxidation method for (Al)GaN interfaces. Through this method, a thin Ga2O3 / Al2O3 oxide film is formed at the (Al)GaN interface, which can effectively protect the (Al)GaN interface, effectively suppress current collapse and reduce parasitic parameters (M. H, et al, AIP Adv., 2019, 9(04)).

[0005] In summary, N2O plasma treatment can form Ga2O3 / Al2O3 thin film, which can be used as a passivation layer for devices. The preparation temperature of thin films deposited by traditional CVD and other methods is usually below 800°C. After high-temperature annealing, the thin film is prone to cracking, which in turn causes the reliability of the device to degrade. Therefore, traditional passivation processes are carried out after the high-temperature annealing process; however, passivation before high-temperature annealing is beneficial to avoid the oxidation reaction on the (Al)GaN surface during the high-temperature annealing mentioned above, which causes the dynamic performance to degrade. Therefore, the present invention uses N2O plasma treatment to form a Ga2O3 / Al2O3 passivation layer. The thin film obtained by this method is directly formed on the surface of the (Al)GaN material, and can still maintain a good thin film interface after high-temperature annealing. On the one hand, it suppresses the interface state introduced by the high-temperature annealing process, and on the other hand, it also plays a role in interface passivation protection, which helps to improve the dynamic characteristics of the device. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a HEMT device with a Ga2O3 / Al2O3 protective layer and a preparation method thereof. The device adopts a Ga2O3 / Al2O3 protective layer structure, effectively reducing or avoiding the interface state introduced to the (Al)GaN interface during the high temperature annealing process, inhibiting current collapse, reducing leakage, and improving the dynamic performance of the device.

[0007] The Ga2O3 / Al2O3 protective layer is formed mainly by subjecting the entire wafer to N2Oplasma treatment before high-temperature annealing of the source and drain electrodes.

[0008] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0009] The present invention provides a HEMT device with a Ga2O3 / Al2O3 protective layer, the device comprises an AlGaN / GaN epitaxy, two ends of the upper surface of the AlGaN / GaN epitaxy are respectively connected to a source and a drain electrode, the source and the drain electrode adopts a method combining electron beam evaporation and magnetron sputtering, the whole wafer is subjected to N2O plasma treatment before high-temperature annealing (over 800° C.) of the source and the drain electrode, and a high-temperature annealing process is performed after forming a Ga2O3 / Al2O3 protective layer, and a gate electrode is arranged near the source side of the source and the drain electrode.

[0010] The present invention provides a HEMT device with a Ga2O3 / Al2O3 protective layer, comprising an AlGaN / GaN epitaxial, a source-drain electrode, a Ga2O3 / Al2O3 protective layer and a gate electrode; two ends of the upper surface of the AlGaN / GaN epitaxial are respectively connected to the source-drain electrode; the Ga2O3 / Al2O3 protective layer is stacked on the AlGaN / GaN epitaxial; and the gate electrode is arranged on the Ga2O3 / Al2O3 protective layer.

[0011] Furthermore, the distance between the gate electrode and the source electrode is smaller than the distance between the gate electrode and the drain electrode, that is, the gate electrode is arranged near the side source electrode of the source-drain electrode.

[0012] Furthermore, the thickness of the Ga2O3 / Al2O3 protective layer is 3-5 nm.

[0013] The present invention provides a method for preparing a HEMT device having a Ga2O3 / Al2O3 protective layer, comprising the following steps:

[0014] (1) After the AlGaN / GaN epitaxy is isolated on the mesa, the source and drain electrode regions are defined, and then the source and drain electrodes are deposited;

[0015] (2) After the source and drain electrodes are stripped, N2O plasma treatment is performed to obtain a Ga2O3 / Al2O3 protective layer, and a high-temperature annealing process is performed after the treatment; finally, a gate region is defined, and a gate electrode is deposited to obtain the HEMT device with the Ga2O3 / Al2O3 protective layer.

[0016] Furthermore, the N2O plasma treatment in step (2) is implemented in plasma enhanced chemical vapor deposition (PECVD).

[0017] Furthermore, the specific process conditions of the N2O plasma treatment in step (2) are: N2O flow rate of 50-150sccm, power of 100-300 W, chamber pressure of 600-800 mTorr, temperature of 200-300°C, and treatment time of 10-30 min.

[0018] Furthermore, the temperature of the high temperature annealing process in step (2) exceeds 800°C.

[0019] The present invention performs N2O plasma treatment on the entire wafer before high-temperature annealing of the source and drain electrodes to form a Ga2O3 / Al2O3 protective layer, and then performs a high-temperature annealing process. The source and drain electrodes are provided with a gate electrode close to the source side.

[0020] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0021] The present invention adopts a Ga2O3 / Al2O3 protective layer structure, and by protecting the (Al)GaN surface other than the source and drain electrodes, effectively reduces or avoids the interface state introduced to the (Al)GaN surface by the high-temperature annealing process, thereby improving the dynamic performance of the device. When the drain off-state stress is 600V, the increase in dynamic resistance of the device (sample A) using N2O plasma to generate the Ga2O3 / Al2O3 passivation layer before high-temperature annealing and the device (sample B) using N2O plasma to generate the Ga2O3 / Al2O3 passivation layer after high-temperature annealing is 8.6% and 49%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the device structure after ohmic contact is completed in the embodiment;

[0023] Figure 2 This is a schematic diagram of the device structure after forming a Ga2O3 / Al2O3 protective layer in the embodiment;

[0024] Figure 3 A schematic diagram of a device structure after forming a gate electrode in an embodiment;

[0025] Figure 4 A curve showing the relationship between the increase in dynamic resistance and the drain off-state stress of the device prepared in Example 2 in which the Ga2O3 / Al2O3 passivation layer is formed by N2O plasma treatment before high temperature annealing and the device in which the Ga2O3 / Al2O3 passivation layer is formed by N2O plasma treatment after high temperature annealing;

[0026] In the figure, there is AlGaN / GaN epitaxy 1, source and drain electrodes 2, Ga2O3 / Al2O3 protective layer 3, and gate electrode 4. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described below in conjunction with examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0028] Example 1

[0029] This embodiment provides a HEMT device with a Ga2O3 / Al2O3 protective layer, such as Figure 3As shown, the device includes an AlGaN / GaN epitaxy 1, and the two ends of the upper surface of the AlGaN / GaN epitaxy are respectively connected to source and drain electrodes 2. The source and drain electrodes are formed by a method combining electron beam evaporation and magnetron sputtering. Before the source and drain electrodes are subjected to high-temperature annealing (over 800°C), the entire wafer is subjected to N2O plasma treatment to form a Ga2O3 / Al2O3 protective layer 3, and then a high-temperature annealing process is performed. The source and drain electrodes are provided with a gate electrode 4 close to the source side.

[0030] The HEMT device with a Ga2O3 / Al2O3 protective layer includes an AlGaN / GaN epitaxial 1, a source-drain electrode 2, a Ga2O3 / Al2O3 protective layer 3 and a gate electrode 4; the two ends of the upper surface of the AlGaN / GaN epitaxial 1 are respectively connected to the source-drain electrode 2; the Ga2O3 / Al2O3 protective layer 3 is stacked on the AlGaN / GaN epitaxial 1; and the gate electrode 4 is arranged on the Ga2O3 / Al2O3 protective layer.

[0031] This embodiment also provides a method for preparing the HEMT device with the Ga2O3 / Al2O3 protective layer, comprising the following steps:

[0032] (1) After the mesa isolation, the source-drain electrode region is defined, and then the source-drain electrode 2 is deposited on the upper surface of the AlGaN / GaN epitaxial 1. The source-drain electrode structure used is TiAlNiTi (20 / 100 / 10 / 100 nm), where TiAl is obtained by electron beam evaporation and NiTi is obtained by magnetron sputtering. After metal stripping, the NiTi obtained by magnetron sputtering completely covers the TiAl obtained by electron beam evaporation below, as shown in FIG. Figure 1 As shown;

[0033] (2) After the source and drain electrodes are stripped, N2O plasma treatment is performed. The N2O flow rate is 87 sccm, the power is 200 W, the chamber pressure is 600 mTorr, the temperature is 250 °C, and the treatment time is 20 min. The thickness of the formed Ga2O3 / Al2O3 protective layer 3 is 3 nm. Figure 2 As shown;

[0034] (3) After N2O plasma treatment, a high-temperature annealing process is performed at a temperature of 830°C, in a N2 atmosphere, and for 1 min. Finally, the gate region is defined and a gate electrode 4NiAu (50 / 250 nm) is deposited. Figure 3 As shown, the HEMT device with the Ga2O3 / Al2O3 protective layer is obtained.

[0035] The HEMT device with Ga2O3 / Al2O3 protective layer prepared in Example 1 has low interface state density and excellent high frequency and dynamic characteristics. Figure 4 shown.

[0036] Example 2

[0037] This embodiment provides a HEMT device with a Ga2O3 / Al2O3 protective layer. Figure 3 As shown, the device includes an AlGaN / GaN epitaxy 1, and the two ends of the upper surface of the AlGaN / GaN epitaxy are respectively connected to source and drain electrodes 2. The source and drain electrodes are formed by a method combining electron beam evaporation and magnetron sputtering. Before the source and drain electrodes are subjected to high-temperature annealing (over 800°C), the entire wafer is subjected to N2O plasma treatment to form a Ga2O3 / Al2O3 protective layer 3, and then a high-temperature annealing process is performed. The source and drain electrodes are provided with a gate electrode 4 close to the source side.

[0038] The HEMT device with a Ga2O3 / Al2O3 protective layer includes an AlGaN / GaN epitaxial 1, a source-drain electrode 2, a Ga2O3 / Al2O3 protective layer 3 and a gate electrode 4; the two ends of the upper surface of the AlGaN / GaN epitaxial 1 are respectively connected to the source-drain electrode 2; the Ga2O3 / Al2O3 protective layer 3 is stacked on the AlGaN / GaN epitaxial 1; and the gate electrode 4 is arranged on the Ga2O3 / Al2O3 protective layer.

[0039] This embodiment also provides a method for preparing the HEMT device with the Ga2O3 / Al2O3 protective layer, comprising the following steps:

[0040] (1) After the mesa isolation, the source-drain electrode region is defined, and then the source-drain electrode 2 is deposited on the upper surface of the AlGaN / GaN epitaxial 1. The source-drain electrode structure used is TiAlNiAuTi (20 / 100 / 10 / 100 / 100 nm), where TiAlNiAu is obtained by electron beam evaporation and the last layer of Ti is obtained by magnetron sputtering. After metal stripping, the Ti obtained by magnetron sputtering completely covers the TiAlNiAu obtained by electron beam evaporation below, as shown in FIG. Figure 1 As shown;

[0041] (2) After the source and drain electrodes are stripped, N2O plasma treatment is performed. The N2O flow rate is 120 sccm, the power is 250 W, the chamber pressure is 800 mTorr, the temperature is 250 °C, and the treatment time is 10 min. The thickness of the formed Ga2O3 / Al2O3 protective layer 3 is 4 nm. Figure 2 As shown;

[0042] (3) After N2O plasma treatment, a high-temperature annealing process is performed at a temperature of 830°C, in a N2 atmosphere, and for 1 min. Finally, the gate region is defined and a gate electrode 4NiAu (50 / 250 nm) is deposited. Figure 3 As shown, the HEMT device with the Ga2O3 / Al2O3 protective layer is obtained.

[0043] Figure 4 The relationship curve between the increase in dynamic resistance and drain off-state stress of the device (sample A) prepared in Example 2 and the device (sample B) prepared and treated with N2O plasma to generate the Ga2O3 / Al2O3 passivation layer before high temperature annealing, and the stress application time is 10s. The only difference between the two samples is that the N2O plasma treatment process is before high temperature annealing and after high temperature annealing. It can be seen that with the increase of the drain off-state stress, the increase in dynamic resistance of both samples increases, but the increase in dynamic resistance of sample B is more prominent. When the drain off-state stress is 600V, the increase in dynamic resistance of the device of sample A is only 8.6%, while that of sample A is 49%. This shows that the use of the Ga2O3 / Al2O3 protective layer structure effectively reduces or avoids the interface state introduced by the high temperature annealing process to the (Al)GaN interface by protecting the (Al)GaN surface outside the source and drain electrodes, thereby improving the dynamic performance of the device.

[0044] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a HEMT device having a Ga2O3 / Al2O3 protective layer, characterized in that: The steps include: (1) After the AlGaN / GaN epitaxy is isolated on the mesa, the source and drain electrode regions are defined, and then the source and drain electrodes are deposited; (2) After the source and drain electrodes are stripped, N2O plasma treatment is performed to obtain a Ga2O3 / Al2O3 protective layer, and a high-temperature annealing process is performed after the treatment; finally, a gate region is defined, and a gate electrode is deposited to obtain the HEMT device with the Ga2O3 / Al2O3 protective layer.

2. The method for preparing a HEMT device with a Ga2O3 / Al2O3 protective layer according to claim 1, characterized in that: The N2O plasma treatment in step (2) is implemented in plasma enhanced chemical vapor deposition.

3. The method for preparing a HEMT device with a Ga2O3 / Al2O3 protective layer according to claim 1, characterized in that: The specific process conditions of the N2O plasma treatment in step (2) are: N2O flow rate of 50-150 sccm, power of 100-300 W, chamber pressure of 600-800 mTorr, temperature of 200-300 °C, and treatment time of 10-30 min.

4. The method for preparing a HEMT device with a Ga2O3 / Al2O3 protective layer according to claim 1, characterized in that: The temperature of the high temperature annealing process in step (2) exceeds 800°C.

5. A HEMT device having a Ga2O3 / Al2O3 protective layer prepared by the preparation method of claim 1, characterized in that: It includes AlGaN / GaN epitaxy, source-drain electrodes, Ga2O3 / Al2O3 protective layer and gate electrode; two ends of the upper surface of the AlGaN / GaN epitaxy are respectively connected to the source-drain electrodes; the Ga2O3 / Al2O3 protective layer is stacked on the AlGaN / GaN epitaxy; and the gate electrode is arranged on the Ga2O3 / Al2O3 protective layer.

6. The HEMT device with Ga2O3 / Al2O3 protective layer according to claim 5, characterized in that: The distance from the gate electrode to the source electrode is smaller than the distance from the gate electrode to the drain electrode.

7. The HEMT device with Ga2O3 / Al2O3 protective layer according to claim 5, characterized in that: The thickness of the Ga2O3 / Al2O3 protective layer is 3-5 nm.

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