CN114975588A - HEMT device with Schottky/ohmic drain structure and preparation method thereof - Google Patents

HEMT device with Schottky/ohmic drain structure and preparation method thereof Download PDF

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CN114975588A
CN114975588A CN202210153548.4A CN202210153548A CN114975588A CN 114975588 A CN114975588 A CN 114975588A CN 202210153548 A CN202210153548 A CN 202210153548A CN 114975588 A CN114975588 A CN 114975588A
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metal
layer
schottky
drain
electrode
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王洪
高升
谢子敬
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South China University of Technology SCUT
Zhongshan Institute of Modern Industrial Technology of South China University of Technology
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South China University of Technology SCUT
Zhongshan Institute of Modern Industrial Technology of South China University of Technology
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    • H01L29/41725—Source or drain electrodes for field effect devices
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    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
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    • H01L29/66462—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET] with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
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Abstract

The invention discloses an HEMT device with a Schottky/ohmic drain structure and a preparation method thereof. The HEMT device of the Schottky/ohmic drain structure comprises a silicon substrate, an AlN nucleating layer, an AlGaN buffer layer, a GaN channel layer, an AlN inserting layer and an AlGaN barrier layer from bottom to top; a gate electrode, a source electrode and a drain electrode are arranged above the AlGaN barrier layer, and the gate electrode is positioned between the source electrode and the drain electrode. The GaN-based solar cell comprises a silicon substrate, an AlN nucleating layer, an AlGaN buffer layer, a GaN channel layer, an AlN inserting layer and an AlGaN barrier layer from bottom to top; a gate electrode, a source electrode and a drain electrode are arranged above the AlGaN barrier layer, and the gate electrode is positioned between the source electrode and the drain electrode. The source-drain electrode and the cap layer prepared by the method form a double-layer contact interface, and a Schottky/ohmic drain structure is formed after annealing, so that the electric field distribution at the side of the drain electrode is optimized, and the breakdown voltage and the distribution stability thereof are improved.

Description

HEMT device with Schottky/ohmic drain structure and preparation method thereof
Technical Field
The invention relates to the field of semiconductors, in particular to a High Electron Mobility Transistor (HEMT) device with a Schottky/ohmic drain structure and a preparation method thereof.
Background
Due to the excellent material properties of gallium nitride (GaN), GaN-based High Electron Mobility Transistors (HEMTs) have been widely used in power electronics and radio frequencies. With the upgrading of the requirements of power electronic applications, it is extremely important to further improve the breakdown voltage of the device and improve the stability of the device. Wherein the source-drain contact is one of the key factors influencing the breakdown voltage and reliability of the device. Early studies showed that the profile of the ohmic metal, especially the drain metal near the gate, has a significant impact on the breakdown voltage of the Device (y.lian, et al, IEEE Electron Device Letters,33(7), 2012). After high-temperature annealing, the metal appearance becomes rough, and extra metal spikes are easily introduced, so that the leakage current of the device is increased and the device breaks down in advance.
Currently, the main methods for improving the above problems are to use low temperature annealing or other optimized ohmic electrode structures. The low-temperature annealing generally refers to the temperature of 600 ℃ or below, the low-temperature annealing can well improve the metal morphology, the research is mainly carried out on a gold-free metal system, an AlGaN barrier layer is generally required to be partially etched, the etching precision requirement of the step is very high, and the thickness of the residual barrier layer below a source electrode and a drain electrode is generally about 1 nm. In addition, the deterioration of the ohmic contact formed by low-temperature annealing under high temperature and high stress has a plurality of uncertain factors, and the long-term reliability of the ohmic contact is still to be verified. The ohmic contact process formed by high-temperature annealing is relatively more mature, and still remains the mainstream choice for electrode annealing in the industry at present. Based on this, the related art has proposed schottky drain, schottky/ohmic drain, and the like to improve this phenomenon. The schottky drain structure can produce a more uniform electric field distribution and thus the breakdown voltage of the device is higher. The schottky drain can improve the electrode topography and increase the device breakdown voltage, but its on-resistance also becomes large, so that the device loss increases (y. lian, et al, IEEE Transactions on Electron Devices,62(2), (2015)). The schottky/ohmic drain structure can have both breakdown voltage and on-resistance (w.zhang, et al, IEEE Journal of the Electron Devices Society,6(99), 2018). From the device characteristics, the schottky/ohmic drain structure is more suitable. In addition, the metal surface roughness of the gold-free metal system under high-temperature annealing is lower than that of the gold-containing metal system, and the improvement effect on the breakdown voltage of the device is also very obvious.
The conventional Schottky/ohmic drain electrode structure is realized by adopting a two-step photoetching process means, the process steps are more, and the problems of small photoetching register window and the like exist. The Schottky/ohmic drain electrode structure is realized through a single-step process, so that the process steps are simplified, the problem of secondary registration is avoided, and the process feasibility is higher.
Disclosure of Invention
Based on the above, in order to solve the problems in the prior art, the invention provides an HEMT device with a Schottky/ohmic drain structure and a preparation method thereof. Due to different electron beam evaporation angles, through one-time photoetching, the source and drain electrodes and the AlGaN barrier layer form a double-layer contact interface, and a Schottky/ohmic drain structure is formed after annealing, so that the field distribution on the drain side is optimized, and the breakdown voltage and the distribution stability thereof are improved.
The object of the invention is at least achieved by one of the prior art solutions.
An HEMT device with a Schottky/ohmic drain structure comprises a silicon substrate, an AlN nucleating layer, an AlGaN buffer layer, a GaN channel layer, an AlN inserting layer and an AlGaN barrier layer from bottom to top; a gate electrode, a source electrode and a drain electrode are arranged above the AlGaN barrier layer, and the gate electrode is positioned between the source electrode and the drain electrode.
Further, the source electrode and the drain electrode are obtained by adopting a one-step photoetching and two-step variable-angle electron beam metal evaporation mode; the source electrode and the drain electrode both comprise a first step metal and a second step metal, wherein the first step metal is obtained by oblique angle incidence evaporation, and the second step metal is obtained by vertical incidence evaporation.
Further, the first step metal is located on the inclined lower side of the second step metal, and the first step metal and the second step metal are both in contact with the AlGaN barrier layer.
Further, after the source electrode and the drain electrode are annealed, the first step metal in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer, and the second step metal forms Schottky contact with the AlGaN barrier layer.
Further, the first metal is an X/Y bilayer metal system, wherein the first metal X comprises Ta or Ti and the second metal Y comprises Al.
Further, the second-step metal is a Z/W bilayer metal system, wherein the third metal Z comprises Ni and the fourth metal W comprises Ti, TiN or TiW.
Further, the work function of the first metal X is smaller than that of the third metal Z.
A preparation method of an HEMT device with a Schottky/ohmic drain structure comprises the following steps:
s1, constructing a silicon substrate, an AlN nucleating layer, an AlGaN buffer layer, a GaN channel layer, an AlN inserting layer and an AlGaN barrier layer from bottom to top, defining a source-drain photoetching area on the AlGaN barrier layer by adopting photoresist, and depositing first-step metal by oblique-angle incidence based on electron beam evaporation equipment;
s2, after the first step of metal deposition is completed, depositing the second step of metal by adopting vertical incidence to complete the deposition of the whole source electrode and the whole drain electrode;
s3, after the source electrode and the drain electrode are stripped, annealing treatment is carried out, so that the first step metal in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer, and the second step metal forms Schottky contact with the AlGaN barrier layer;
and S4, preparing a gate electrode on the AlGaN barrier layer to obtain the HEMT device with the Schottky/ohmic drain structure.
Further, when the first step metal is deposited at oblique angle incidence, the oblique angle incidence is in the range of 5-20 °.
Furthermore, in the first step metal, the thickness of the first metal X is 5-20nm, and the thickness of the second metal Y is 60-120 nm; the thickness of the third metal Z is 10-20nm, and the thickness of the fourth metal W is 60-100 nm.
Compared with the prior art, the invention has the following beneficial effects and advantages:
1. according to the invention, different contact interfaces are obtained by using electron beam evaporation modes at different angles and adopting one-step photoetching, the Schottky/ohmic mixed contact drain electrode is formed after annealing, the process steps are simple, and the problem of extra photoetching alignment is not required to be considered.
2. The process provided by the invention has better repeatability, and the breakdown voltage of the HEMT device adopting the Schottky/ohmic drain structure is obviously improved and is more uniformly distributed.
Drawings
Fig. 1 is a schematic diagram of a schottky/ohmic drain structure of an HEMT device of a schottky/ohmic drain structure in embodiment 1 of the present invention.
Fig. 2 is a cross-sectional view of a finished HEMT device of the schottky/ohmic drain structure in embodiment 1 of the present invention.
FIG. 3 is an I-V plot of the second-step metal Ni/TiN (20/100nm) of example 1 of the present invention with an electrode spacing of 10 μm after high temperature annealing.
Fig. 4 is a graph showing transfer characteristics of HEMT devices of a schottky/ohmic drain structure according to example 1 and the control group.
FIG. 5a is the electric field profile at the drain side of the device of example 1 for a Schottky/ohmic drain structure based on the first step Ti/Al metal and the second step Ni/TiN metal; FIG. 5b is a graph showing the electric field distribution at the drain side of the control electron beam conventionally evaporated Ti/Al/Ni/Au ohmic contact device.
FIG. 6 is a graph of the breakdown voltage distribution of devices of Schottky/ohmic drain structures prepared in example 1 based on the first step Ti/Al metal and the second step Ni/TiN metal and a control group of electron beam conventional evaporation Ti/Al/Ni/Au ohmic contact devices, wherein each group of devices is tested in a number of 50.
Detailed Description
In the following description, technical solutions are set forth in conjunction with specific figures in order to provide a thorough understanding of the present invention. This application is capable of embodiments in many different forms than those described herein and it is intended that all such variations would be within the scope of the invention unless expressly stated otherwise.
The terminology used in the description is for the purpose of describing particular embodiments only and is not intended to be limiting of the description. As used in one or more embodiments of the present specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used in one or more embodiments of the present specification refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It should be understood that although the terms first, second, etc. may be used herein to describe various information in one or more embodiments of the specification, these information should not be limited by these terms, which are used only for distinguishing between similar items and not necessarily for describing a sequential or chronological order of the features described in one or more embodiments of the specification. Furthermore, the terms "having," "including," and similar referents, are intended to cover a non-exclusive scope, such that a process, method, system, article, or apparatus that comprises a list of steps or modules is not necessarily limited to the particular details set forth, but may include other inherent information not expressly listed for such steps or modules.
The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art.
Example 1:
a HEMT device of schottky/ohmic drain structure, as shown in fig. 2, includes, from bottom to top, a silicon substrate 101, an AlN nucleation layer 102, an AlGaN buffer layer 103, a GaN channel layer 104, an AlN insertion layer 105, and an AlGaN barrier layer 106; above the AlGaN barrier layer 106, a gate electrode 110, a source electrode, and a drain electrode are provided, with the gate electrode 110 being located between the source electrode and the drain electrode.
The source electrode and the drain electrode are obtained by adopting a one-step photoetching and two-step variable-angle electron beam evaporation metal mode; the source electrode and the drain electrode both comprise a first-step metal 108 and a second-step metal 109, wherein the first-step metal 108 is obtained by oblique incidence evaporation, and the second-step metal 109 is obtained by vertical incidence evaporation; the first-step metal 108 is located obliquely below the second-step metal 109, and both the first-step metal 108 and the second-step metal 109 are in contact with the AlGaN barrier layer 106.
After annealing of the source electrode and the drain electrode, the first step metal 108 in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer 106, and the second step metal 109 forms schottky contact with the AlGaN barrier layer 106.
In this embodiment, the first step metal 108 is Ti/Al; the second-step metal 109 is Ni/TiN.
A method for manufacturing an HEMT device with a schottky/ohmic drain structure, as shown in fig. 1, includes the following steps:
s1, constructing a silicon substrate 101, an AlN nucleating layer 102, an AlGaN buffer layer 103, a GaN channel layer 104, an AlN insert layer 105 and an AlGaN barrier layer 106 from bottom to top, defining a source-drain photoetching area on the AlGaN barrier layer 106 by adopting photoresist 107, and depositing first-step metal 108 by oblique-angle incidence based on electron beam evaporation equipment;
s2, after the first step of metal 108 deposition is completed, depositing the second step of metal 109 by adopting vertical incidence to complete the deposition of the whole source electrode and drain electrode;
s3, after the source electrode and the drain electrode are stripped, annealing treatment is carried out, in the embodiment, the annealing temperature is 830 ℃, the annealing time is 1min, the annealing atmosphere is nitrogen, so that the first-step metal 108 in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer 106, and the second-step metal 109 forms Schottky contact with the AlGaN barrier layer 106;
and S4, preparing a gate electrode 110 on the AlGaN barrier layer 106 to obtain the HEMT device with a Schottky/ohmic drain structure.
In this embodiment, the oblique incidence range of the deposited first step metal 108Ti/Al is 10 °.
In this example, the thickness of Ti/Al of the first step metal 108 is 10/100nm, and the thickness of Ni/TiN of the second step metal 109 is 20/100 nm.
In this example, the control group was a Ti/Al/Ni/Au10/100/20/100nm gold metal system, the annealing conditions were the same as in example 1, and the other device fabrication processes were the same as in example 1. The edge of the drain becomes abnormally rough after the high temperature anneal in the control, while the metal of example 1 is divided into two parts, one side near the gate is the second layer of metal 109Ni/TiN, which has a smoother profile after the high temperature anneal.
FIG. 3 is an I-V plot of the second step metal 109Ni/TiN20/100nm with an electrode spacing of 10 μm after high temperature annealing. It can be seen that schottky characteristics are exhibited between the second-step metal 109 and the AlGaN barrier layer even under the treatment of high-temperature annealing.
FIG. 4 is a graph showing transfer characteristics of example 1 and a control group. It can be seen that the transfer characteristics of both are substantially identical, so that example 1 is comparable to the control in terms of static characteristics.
FIG. 5a is a graph showing the drain side electric field distribution of example 1 and the control group. FIG. 5b is a graph showing the electric field distribution at the drain side of a control group of Ti/Al/Ni/Au ohmic contact devices conventionally evaporated by an electron beam. It can be seen that the schottky/ohmic drain introduces one more peak of the electric field on the drain side, which pulls down the peak of the electric field of the individual ohmic drain and redistributes the electric field.
FIG. 6 is a graph of the breakdown voltage distribution of example 1 and the control group, wherein the number of devices tested in each group is 50. The test data for both groups met the positive distribution, and the breakdown voltage for example 1 was generally higher, with an average breakdown voltage of 1150V, which was a 28.5% increase over 895V for the control group. The process provided by the invention has better repeatability, and the breakdown voltage of the HEMT device adopting the Schottky/ohmic drain structure is obviously improved and is more uniformly distributed.
Example 2:
a HEMT device of schottky/ohmic drain structure, as shown in fig. 2, includes, from bottom to top, a silicon substrate 101, an AlN nucleation layer 102, an AlGaN buffer layer 103, a GaN channel layer 104, an AlN insertion layer 105, and an AlGaN barrier layer 106; above the AlGaN barrier layer 106, a gate electrode 110, a source electrode, and a drain electrode are provided, with the gate electrode 110 being located between the source electrode and the drain electrode.
The source electrode and the drain electrode are obtained by adopting a one-step photoetching and two-step variable-angle electron beam evaporation metal mode; the source electrode and the drain electrode both comprise a first-step metal 108 and a second-step metal 109, wherein the first-step metal 108 is obtained by oblique incidence evaporation, and the second-step metal 109 is obtained by vertical incidence evaporation; the first-step metal 108 is located obliquely below the second-step metal 109, and both the first-step metal 108 and the second-step metal 109 are in contact with the AlGaN barrier layer 106.
After annealing of the source electrode and the drain electrode, the first step metal 108 in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer 106, and the second step metal 109 forms schottky contact with the AlGaN barrier layer 106.
In example 2, the thickness of the first step metal 108Ti/Al was 10/100nm, and the thickness of the second step metal 109Ni/Ti was 20/100 nm. The rest of the conditions were set to be the same as in example 1.
Example 2 provides a HEMT device of a schottky/ohmic drain structure having an I-V curve, a transfer characteristic curve, an electric field distribution, and a breakdown voltage distribution similar to those of example 1, and the specific properties can be found in fig. 3, fig. 4, fig. 5a, fig. 5b, and fig. 6 of example 1.
Example 3:
a HEMT device of schottky/ohmic drain structure, as shown in fig. 2, includes, from bottom to top, a silicon substrate 101, an AlN nucleation layer 102, an AlGaN buffer layer 103, a GaN channel layer 104, an AlN insertion layer 105, and an AlGaN barrier layer 106; above the AlGaN barrier layer 106, a gate electrode 110, a source electrode, and a drain electrode are provided, with the gate electrode 110 being located between the source electrode and the drain electrode.
The source electrode and the drain electrode are obtained by adopting a one-step photoetching and two-step variable-angle electron beam evaporation metal mode; the source electrode and the drain electrode both comprise a first-step metal 108 and a second-step metal 109, wherein the first-step metal 108 is obtained by oblique incidence evaporation, and the second-step metal 109 is obtained by vertical incidence evaporation; the first-step metal 108 is located obliquely below the second-step metal 109, and both the first-step metal 108 and the second-step metal 109 are in contact with the AlGaN barrier layer 106.
After annealing of the source electrode and the drain electrode, the first step metal 108 in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer 106, and the second step metal 109 forms schottky contact with the AlGaN barrier layer 106.
In example 3, the thickness of the first step metal 108Ti/Al was 10/100nm, and the thickness of the second step metal 109Ni/TiW was 20/100 nm. The first step metal 108Ti/Al deposition was performed at an oblique angle of incidence of 15. The rest of the conditions were set to be the same as in example 1.
Example 3 provides a HEMT device of a schottky/ohmic drain structure having an I-V curve, a transfer characteristic curve, an electric field distribution, and a breakdown voltage distribution similar to those of example 1, and specific properties can be found in fig. 3, fig. 4, fig. 5a, fig. 5b, and fig. 6 of example 1.
According to the invention, different contact interfaces are obtained by using electron beam evaporation modes at different angles and adopting one-step photoetching, the Schottky/ohmic mixed contact drain electrode is formed after annealing, the process steps are simple, and the problem of extra photoetching alignment is not required to be considered. In addition, the process provided by the invention has better repeatability, the breakdown voltage of the HEMT device adopting the Schottky/ohmic drain structure is improved by 28.5 percent compared with that of a control group Ti/Al/Ni/Au gold metal system device, and the breakdown voltage distribution is more uniformly and intensively under the condition that a test sample is 50, as shown in figure 6.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features. Accordingly, it will be appreciated by those skilled in the art that changes, substitutions, modifications and the like can be made without departing from the spirit of the invention.

Claims (10)

1. An HEMT device with a Schottky/ohmic drain structure is characterized by comprising a silicon substrate (101), an AlN nucleating layer (102), an AlGaN buffer layer (103), a GaN channel layer (104), an AlN insert layer (105) and an AlGaN barrier layer (106) from bottom to top; a gate electrode (110), a source electrode and a drain electrode are arranged above the AlGaN barrier layer (106), and the gate electrode (110) is positioned between the source electrode and the drain electrode.
2. The HEMT device of claim 1, wherein said source and drain electrodes are obtained by one-step photolithography, two-step variable angle electron beam evaporation of metal; the source electrode and the drain electrode each comprise a first step metal (108) and a second step metal (109), wherein the first step metal (108) is obtained by oblique angle incidence evaporation and the second step metal (109) is obtained by perpendicular incidence evaporation.
3. The HEMT device of claim 2, wherein said first-step metal (108) is located on the lower side of said second-step metal (109), and said first-step metal (108) and said second-step metal (109) are in contact with said AlGaN barrier layer (106).
4. The HEMT device of claim 3, wherein after annealing the source and drain electrodes, the first-step metal (108) of the source and drain electrodes forms an ohmic contact with the AlGaN barrier layer (106), and the second-step metal (109) forms a schottky contact with the AlGaN barrier layer (106).
5. The HEMT device of claim 2, wherein said first-step metal (108) is an X/Y bilayer metal system, wherein the first metal X comprises Ta or Ti and the second metal Y comprises Al.
6. The HEMT device of claim 2, wherein said second-step metal (109) is a Z/W bi-layer metal system, wherein the third metal Z comprises Ni and the fourth metal W comprises Ti, TiN or TiW.
7. The HEMT device with a Schottky/ohmic drain structure according to any one of claims 1 to 6, wherein the work function of the first metal X is smaller than that of the third metal Z.
8. The method of fabricating a HEMT device of schottky/ohmic drain structure according to claim 7, comprising the steps of:
s1, constructing a silicon substrate (101), an AlN nucleating layer (102), an AlGaN buffer layer (103), a GaN channel layer (104), an AlN inserting layer (105) and an AlGaN barrier layer (106) from bottom to top, defining a source-drain photoetching area on the AlGaN barrier layer (106) by adopting photoresist (107), and depositing first-step metal (108) by oblique-angle incidence based on electron beam evaporation equipment;
s2, after the first-step metal (108) deposition is completed, depositing a second-step metal (109) by adopting vertical incidence to complete the deposition of the whole source electrode and the drain electrode;
s3, after the source electrode and the drain electrode are stripped, annealing treatment is carried out, so that the first step metal (108) in the source electrode and the drain electrode forms ohmic contact with the AlGaN barrier layer (106), and the second step metal (109) forms Schottky contact with the AlGaN barrier layer (106);
and S4, preparing a gate electrode (110) on the AlGaN barrier layer (106) to obtain the HEMT device with the Schottky/ohmic drain structure.
9. The method of claim 8, wherein the first step metal (108) is deposited at an oblique angle of incidence in a range of 5-20 °.
10. The method for manufacturing an HEMT device of a schottky/ohmic drain structure according to claim 8, wherein in the first step metal (108), the first metal X has a thickness of 5 to 20nm, and the second metal Y has a thickness of 60 to 120 nm; the thickness of the third metal Z is 10-20nm, and the thickness of the fourth metal W is 60-100 nm.
CN202210153548.4A 2022-02-18 2022-02-18 HEMT device with Schottky/ohmic drain structure and preparation method thereof Pending CN114975588A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117133805A (en) * 2023-10-16 2023-11-28 重庆邮电大学 Mixed drain electrode enhanced GaN high electron mobility transistor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117133805A (en) * 2023-10-16 2023-11-28 重庆邮电大学 Mixed drain electrode enhanced GaN high electron mobility transistor

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