Carbon nanotube radio frequency field effect transistor and preparation method thereof

Abstract

The present disclosure provides a carbon nanotube radio frequency field-effect transistor and a method for preparing the same. The carbon nanotube radio frequency field-effect transistor in the disclosed embodiment includes: a substrate, an insulating dielectric layer, a carbon nanotube active layer, a source contact layer, a source conductive layer, a drain contact layer, a gate dielectric layer, a T-shaped metal gate, a backside via, and a backside metal layer. The carbon nanotube radio frequency field-effect transistor in the disclosed embodiment has low parasitic inductance, low gate resistance, and low substrate parasitic capacitance, and is suitable for radio frequency applications such as microwave and millimeter waves.

Description

Technical Field

[0001] The present disclosure belongs to the field of semiconductor technology, and in particular relates to a carbon nanotube radio frequency field effect transistor and a preparation method thereof. Background Art

[0002] Semiconducting carbon nanotubes have a series of advantages such as high carrier mobility, extremely low intrinsic capacitance, and ultra-high thermal conductivity. The excellent radio frequency properties of carbon nanotube field-effect transistors give them broad application prospects in the microwave and millimeter wave fields.

[0003] However, conventional carbon nanotube field-effect transistors (CNTs) use a self-aligned source-drain structure. Under the influence of a strong electric field applied by the gate, the drain of the transistor experiences significant reverse leakage current, resulting in a low breakdown voltage and limited RF output power. Furthermore, the conventional self-aligned structure easily introduces significant parasitic source-drain capacitance and gate resistance, severely degrading the transistor's RF bandwidth and gain. Therefore, a new CNT device structure suitable for RF applications is needed. Summary of the Invention

[0004] In order to solve at least one of the above technical problems, the present disclosure provides a carbon nanotube radio frequency field effect transistor and a preparation method thereof.

[0005] According to a first aspect of the present disclosure, a carbon nanotube radio frequency field effect transistor is provided, comprising:

[0006] substrate;

[0007] an insulating dielectric layer, disposed on the first side of the substrate;

[0008] A carbon nanotube active layer, disposed on the insulating dielectric layer and serving as a channel layer of the carbon nanotube radio frequency field effect transistor;

[0009] Source end contact layers, provided at both end regions of the carbon nanotube active layer;

[0010] A source end conductive layer is provided on the source end contact layer;

[0011] a drain contact layer, disposed in a middle region of the carbon nanotube active layer and separated from the source contact layer;

[0012] a gate dielectric layer, disposed on the carbon nanotube active layer and located in a region between the source contact layer and the drain contact layer;

[0013] A T-shaped metal gate is provided in the region between the source contact layer and the drain contact layer, and the gate foot is provided on the gate dielectric layer;

[0014] Back through holes are provided at both end regions of the carbon nanotube active layer, the inner surface of which is covered with a metal conductive layer, the top of which is connected to the source end contact layer, and the side of which extends downward to sequentially pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate;

[0015] A back metal layer is provided on a second side of the substrate and is connected to the source contact layer through the back through hole to form a ground plane of the carbon nanotube radio frequency field effect transistor. The second side is opposite to the first side.

[0016] In some possible implementations of the first aspect of the present disclosure, the drain contact layer has a field plate structure, and the field plate structure is disposed at a junction of the drain contact layer and the carbon nanotube active layer.

[0017] In some possible implementations of the first aspect of the present disclosure, the field plate structure is eaves-shaped.

[0018] In some possible implementations of the first aspect of the present disclosure, the gate dielectric layer has a drain contact hole, and the drain contact layer passes through the gate dielectric layer and is connected to the carbon nanotube active layer via the drain contact hole; the width of the side of the field plate structure exceeding the drain contact hole is a first predetermined width.

[0019] In some possible implementations of the first aspect of the present disclosure, the drain contact layer has an upper electrode and a lower electrode, the upper electrode has a first width, the lower electrode has a second width, the first width is greater than the second width and the difference between the first width and the second width is greater than a first predetermined threshold.

[0020] In some possible implementations of the first aspect of the present disclosure, the upper electrode covers the gate dielectric layer, the lower electrode contacts the carbon nanotube active layer, and a sidewall of the second electrode is adjacent to the gate dielectric layer.

[0021] In some possible implementations of the first aspect of the present disclosure, when the source contact layer and / or the drain contact layer serve as an N-type ohmic contact layer, the material is a metal or alloy having a work function less than 4.5 electron volts.

[0022] In some possible implementations of the first aspect of the present disclosure, when the source contact layer and / or the drain contact layer serve as a P-type ohmic contact layer, the material is a metal or alloy having a work function greater than 4.5 electron volts.

[0023] In some possible implementations of the first aspect of the present disclosure, the source end contact layer includes a first source end contact layer and a second source end contact layer, and the first source end contact layer and the second source end contact layer are respectively arranged at two ends of the carbon nanotube active layer.

[0024] In some possible implementations of the first aspect of the present disclosure, the source-end conductive layer includes a first source-end conductive layer and a second source-end conductive layer, the first source-end conductive layer is arranged on the first source-end contact layer, and the second source-end conductive layer is arranged on the second source-end contact layer.

[0025] In some possible implementations of the first aspect of the present disclosure, the gate dielectric layer includes a first gate dielectric layer and a second gate dielectric layer; the first gate dielectric layer is distributed at intervals along a first direction in a first region on the carbon nanotube active layer and extends to above the first source contact layer, and the first region is the region between the drain contact layer and the first source contact layer; the second gate dielectric layer is distributed at intervals along the first direction in a second region on the carbon nanotube active layer and extends to above the second source contact layer, and the second region is the region between the drain contact layer and the second source contact layer.

[0026] In some possible implementations of the first aspect of the present disclosure, the T-shaped metal gate includes a first T-shaped metal gate and a second T-shaped metal gate, wherein the first T-shaped metal gate is arranged in the first region along the first direction and the gate foot is arranged on the first gate dielectric; the second T-shaped metal gate is arranged in the second region along the first direction and the gate foot is arranged on the second gate dielectric.

[0027] In some possible implementations of the first aspect of the present disclosure, a distance between the T-shaped metal gate and the drain contact layer is greater than a distance between the T-shaped metal gate and the source contact layer.

[0028] In some possible implementations of the first aspect of the present disclosure, a distance between the source contact layer and a gate foot of the T-shaped metal gate is smaller than a first predetermined distance.

[0029] In some possible implementations of the first aspect of the present disclosure, the T-shaped metal gate has a T-shaped structure that is wider at the top and narrower at the bottom.

[0030] In some possible implementations of the first aspect of the present disclosure, the gate foot of the T-shaped metal gate has an inverted trapezoidal cross section, and an angle between the sidewall of the gate foot of the T-shaped metal gate and the first side of the carbon nanotube active layer is greater than a first predetermined angle.

[0031] In some possible implementations of the first aspect of the present disclosure, the back through hole includes a first back through hole and a second back through hole, the top of the first back through hole is connected to the first source end contact layer and the side extends downward to pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate in sequence; the top of the second back through hole is connected to the second source end contact layer and the side extends downward to pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate in sequence.

[0032] In some possible implementations of the first aspect of the present disclosure, the cross-section of the back through-hole is trapezoidal.

[0033] In some possible implementations of the first aspect of the present disclosure, the bandgap width of the carbon nanotubes used in the carbon nanotube active layer is smaller than a second predetermined threshold.

[0034] In some possible implementations of the first aspect of the present disclosure, the substrate is made of a material having low dielectric loss when operating at high frequencies.

[0035] In some possible implementations of the first aspect of the present disclosure, the material of the substrate includes one of the following or any combination thereof: silicon, quartz, glass, sapphire, aluminum oxide, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, and BCB.

[0036] According to a second aspect of the present disclosure, a method for preparing a carbon nanotube radio frequency field effect transistor is provided, comprising:

[0037] providing a substrate;

[0038] forming an insulating dielectric layer over the first side of the substrate;

[0039] forming a carbon nanotube active layer on the insulating dielectric layer, wherein the carbon nanotube active layer serves as a channel layer of the carbon nanotube radio frequency field effect transistor;

[0040] forming source end contact layers at both end regions of the carbon nanotube active layer;

[0041] forming a gate dielectric layer on the source contact layer;

[0042] A drain contact layer having a field plate structure is formed in the middle region of the carbon nanotube active layer, and a source conductive layer is formed on the source contact layer.

[0043] forming a T-shaped gate metal electrode in a region between the source contact layer and the drain contact layer, wherein a gate foot of the T-shaped gate metal electrode is disposed on the gate dielectric layer;

[0044] performing passivation of the carbon nanotube radio frequency field effect transistor;

[0045] Back-side through holes are etched at both ends of the carbon nanotube radio frequency field effect transistor, wherein the inner surface of the back side is covered with a metal conductive layer, the top of which is connected to the source end contact layer, and the side surfaces extend downward and sequentially pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate;

[0046] A back metal layer is formed on the second side of the substrate, and the back metal layer is connected to the source contact layer through the back through hole to form a ground plane of the carbon nanotube radio frequency field effect transistor.

[0047] Some possible implementations of the second aspect of the present disclosure are characterized in that, after depositing a gate dielectric layer on the source contact layer, the method further includes: etching the gate dielectric layer to form a drain contact hole so that the drain contact layer is connected to the carbon nanotube active layer through the drain contact hole; etching the gate dielectric layer to form a source contact hole so that the source contact layer is connected to the carbon nanotube active layer through the source contact hole.

[0048] The carbon nanotube radio frequency field effect transistor provided by the embodiment of the present disclosure has smaller parasitic inductance, smaller gate resistance and smaller substrate parasitic capacitance, and can be applied to radio frequency application fields such as microwave and millimeter waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings illustrate exemplary embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure. These drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification.

[0050] Figure 1 is a schematic diagram of the cross-sectional structure of a carbon nanotube radio frequency field effect transistor according to some embodiments of the present disclosure.

[0051] Figure 2 Schematic diagram of the planar structure of a carbon nanotube radio frequency field effect transistor according to some embodiments of the present disclosure.

[0052] Figure 3 It is a schematic flow chart of a method for preparing a carbon nanotube radio frequency field effect transistor according to some embodiments of the present disclosure.

[0053] Description of Reference Numerals

[0054] 100 Carbon Nanotube RF Field Effect Transistor

[0055] 101 substrate

[0056] 102 insulating dielectric layer

[0057] 103 Carbon Nanotube Active Layer

[0058] 104a first source contact layer

[0059] 104b second source contact layer

[0060] 105a first source end conductive layer

[0061] 105b second source end conductive layer

[0062] 106 drain contact layer

[0063] 1061a First field plate of the drain contact layer

[0064] 1061b Second field plate of drain contact layer

[0065] 107a first gate dielectric layer

[0066] 107b second gate dielectric layer

[0067] 108a First T-shaped metal gate

[0068] 108b Second T-shaped metal gate

[0069] 1081a The gate foot of the first T-shaped metal gate

[0070] 1081b The second T-shaped metal gate foot

[0071] 1082a Gate-source spacing of the first T-shaped metal gate

[0072] 1082b Gate-source spacing of the second T-shaped metal gate

[0073] 109a first back through hole

[0074] 109b Second back through hole

[0075] 110 back metal layer

[0076] 111 T-type metal gate lead DETAILED DESCRIPTION

[0077] The present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the relevant content and are not intended to limit the present disclosure. It should also be noted that, for ease of description, only the portions relevant to the present disclosure are shown in the accompanying drawings.

[0078] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in the present disclosure can be combined with each other. The technical solution of the present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0079] Unless otherwise stated, the exemplary embodiments / examples shown are to be understood as providing exemplary features of various details of some ways in which the technical concepts of the present disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of the various embodiments / examples may be further combined, separated, interchanged, and / or rearranged without departing from the technical concepts of the present disclosure.

[0080] The use of cross hatching and / or shading in the accompanying drawings is generally used to make the boundaries between adjacent components clear. As such, unless otherwise indicated, the presence or absence of cross hatching or shading does not convey or indicate any preference or requirement for the specific materials, material properties, dimensions, proportions, commonalities between the components shown, and / or any other characteristics, attributes, properties, etc. of the components. In addition, in the accompanying drawings, the sizes and relative sizes of the components may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments can be implemented differently, the specific process sequence can be performed in a different order than described. For example, two successively described processes can be performed substantially simultaneously or in an order opposite to the order described. In addition, the same figure numbers represent the same components.

[0081] When a component is referred to as being “on,” “over,” “connected to,” or “coupled to” another component, the component may be directly on, directly connected to, or directly coupled to the other component, or intervening components may be present. However, when a component is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another component, there are no intervening components present. For this purpose, the term “connected” may refer to a physical connection, an electrical connection, etc., with or without intervening components.

[0082] For descriptive purposes, the present disclosure may use spatially relative terms such as "below," "beneath," "under," "down," "above," "upper," "above," "higher," and "side (e.g., in a "sidewall")," to describe the relationship of one component to another (other) component as shown in the accompanying drawings. The spatially relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture in addition to the orientation depicted in the accompanying drawings. For example, if the device in the drawings is turned over, a component described as "below" or "beneath" another component or feature would then be positioned "above" the other component or feature. Thus, the exemplary term "below" can encompass both the "above" and "below" orientations. Furthermore, the device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and as such, the spatially relative descriptors used herein should be interpreted accordingly.

[0083] The terms used herein are for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, the features, integral bodies, steps, operations, parts, assemblies and / or their groups stated are explained, but the presence or addition of one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups is not excluded. It should also be noted that, as used herein, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values ​​and / or the values ​​provided that will be recognized by those of ordinary skill in the art.

[0084] The following combination Figures 1 to 3 The structure and preparation method of the carbon nanotube radio frequency field effect transistor 100 disclosed in the present invention are described in detail.

[0085] Figure 1 FIG. 1 is a schematic cross-sectional structural diagram of a carbon nanotube radio frequency field effect transistor 100 according to an embodiment of the present disclosure. Figure 2 It is a schematic diagram of the planar structure of a carbon nanotube radio frequency field effect transistor according to an embodiment of the present disclosure.

[0086] refer to Figure 1 and Figure 2 The carbon nanotube radio frequency field effect transistor 100 of the embodiment of the present disclosure may include:

[0087] substrate 101;

[0088] An insulating dielectric layer 102 is disposed on a first side of the substrate 101;

[0089] The carbon nanotube active layer 103 is disposed on the insulating dielectric layer 102 and serves as a channel layer of the carbon nanotube radio frequency field effect transistor 100;

[0090] Source end contact layers (104a, 104b), provided at both end regions of the carbon nanotube active layer 103;

[0091] A source end conductive layer (105a, 105b) is disposed on the source end contact layer;

[0092] A drain contact layer 106 is provided in a middle region of the carbon nanotube active layer 103 and is separated from the source contact layers (104a, 104b);

[0093] A gate dielectric layer (107a, 107b) is provided on the carbon nanotube active layer 103 and is located in a region between the source contact layer (104a, 104b) and the drain contact layer 106;

[0094] A T-shaped metal gate (108a, 108b) is arranged in a region between the source contact layer (104a, 104b) and the drain contact layer 106, and the gate foot is arranged on the gate dielectric layer (104a, 104b);

[0095] Back through holes (109a, 109b) are provided at both end regions of the carbon nanotube active layer 103, the inner surface of which is covered with a metal conductive layer, the top of which is connected to the source end contact layer (104a, 104b), and the side of which extends downward to sequentially pass through the carbon nanotube active layer 103, the insulating dielectric layer 102 and the substrate 101;

[0096] The back metal layer 110 is arranged on the second side of the substrate 101 and is connected to the source contact layer (104a, 104b) through the back through holes (109a, 109b) to form the ground plane of the carbon nanotube RF field effect transistor 100. The second side is opposite to the first side.

[0097] In some embodiments, the drain contact layer 106 has a field plate structure, and the field plate structure can be disposed at the junction of the drain contact layer 106 and the carbon nanotube active layer 103 .

[0098] For example, Figure 1 and Figure 2 As shown in FIG, the field plate structure is eaves-shaped, that is, the drain contact layer can have an eaves-shaped field plate structure. Figure 2 As shown, the field plate structure may include a first field plate 1061 a and a second field plate 1061 b , and the first field plate 1061 a and the second field plate 1061 b are respectively disposed on both sides of the drain contact layer 106 .

[0099] In some embodiments, the gate dielectric layer (107a, 107b) may have a drain contact hole, and the drain contact layer 106 passes through the gate dielectric layer (107a, 107b) and is connected to the carbon nanotube active layer 103 through the drain contact hole. The side of the field plate structure may extend beyond the width of the drain contact hole by a first predetermined width. For example, the first predetermined width may be 10 nanometers or other values, and can be flexibly adjusted as needed.

[0100] In some embodiments, the drain contact layer 106 includes an upper electrode and a lower electrode, the upper electrode having a first width, the lower electrode having a second width, the first width being greater than the second width, and the difference between the first width and the second width being greater than a first predetermined threshold. The upper electrode of the drain contact layer 106 refers to the electrode on the drain contact layer 106 that is farther from the carbon nanotube active layer 103, and the lower electrode of the drain contact layer 106 refers to the electrode on the drain contact layer 106 that is closer to the carbon nanotube active layer 103.

[0101] For example, the first predetermined threshold value may be 20 nanometers or a value greater than 20 nanometers. In specific applications, the value may be flexibly adjusted as needed.

[0102] For example, in the carbon nanotube RF field effect transistor 100 , the width of the upper electrode on the drain contact layer 106 away from the carbon nanotube active layer 103 is greater than the width of the lower electrode on the drain contact layer 106 close to the carbon nanotube active layer 103 by more than 20 nanometers.

[0103] In some embodiments, the upper electrode of the drain contact layer 106 covers the gate dielectric layer, the lower electrode of the drain contact layer 106 contacts the carbon nanotube active layer, and the sidewall of the second electrode is adjacent to the gate dielectric layer.

[0104] like Figure 1 and Figure 2 As shown, a first field plate 1061a is provided at the junction of the drain contact layer 106 and the first gate dielectric 107a, and a second field plate 1061b is provided at the junction of the drain contact layer 106 and the second gate dielectric 107b. The upper electrode of the drain contact layer 106 covers the first gate dielectric layer 107a and the second gate dielectric layer 107b to achieve a clamping effect on the potential of the carbon nanotube active layers 103a and 103b. The lower electrode of the drain contact layer 106 is in contact with the carbon nanotube active layers 103a and 103b. The first side wall of the drain contact layer 106 is adjacent to the first gate dielectric layer 107a, and the second side wall of the drain contact layer 106 is adjacent to the second gate dielectric layer 107b, and the first side wall is opposite to the second side wall.

[0105] In some embodiments, Figure 1 and Figure 2 As shown, the source terminal contact layer may include a first source terminal contact layer 104 a and a second source terminal contact layer 104 b , and the first source terminal contact layer 104 a and the second source terminal contact layer 104 b are respectively disposed at two ends of the carbon nanotube active layer 103 .

[0106] In some embodiments, when the source contact layer (104a, 104b) and / or the drain contact layer 106 serve as an N-type ohmic contact layer, the material may be a metal or alloy having a work function less than 4.5 electron volts. When the source contact layer (104a, 104b) and / or the drain contact layer 106 serve as a P-type ohmic contact layer, the material may be a metal or alloy having a work function greater than 4.5 electron volts.

[0107] Specifically, each of the first source contact layer 104a, the second source contact layer 104b, and the drain contact layer 106 can be made of a metal or alloy having a work function less than 4.5 electron volts as an N-type ohmic contact layer. For example, the material composition of the N-type ohmic contact layer can include, but is not limited to, scandium, yttrium, aluminum, hafnium, zirconium, or any combination thereof.

[0108] Specifically, each of the first source contact layer 104a, the second source contact layer 104b and the drain contact layer 106 can select a metal or alloy with a work function greater than 4.5 electron volts as a P-type ohmic contact layer, and the material composition of the P-type ohmic contact layer can include but is not limited to one of palladium, molybdenum, nickel, gold or any combination thereof.

[0109] The source-end conductive layer includes a first source-end conductive layer 105a and a second source-end conductive layer 105b. The first source-end conductive layer 105a is disposed on the first source-end contact layer 104a, and the second source-end conductive layer 105b is disposed on the second source-end contact layer 104b. The first source-end conductive layer 105a and the second source-end conductive layer 105b can thicken the source-end metal electrode and reduce the source-end parasitic resistance.

[0110] The gate dielectric layer may include a first gate dielectric layer 107a and a second gate dielectric layer 107b; the first gate dielectric layer 107a may be spaced apart along a first direction in a first region on the carbon nanotube active layer 103 and extend to the first source contact layer 104a, and the first region is the region between the drain contact layer 106 and the first source contact layer 104a; the second gate dielectric layer 107b may be spaced apart along the first direction in a second region on the carbon nanotube active layer 103 and extend to the second source contact layer 104b, and the second region is the region between the drain contact layer 106 and the second source contact layer 104b.

[0111] In some embodiments, the gate dielectric layer in the carbon nanotube RF field effect transistor 100, that is, each of the first gate dielectric layer 107a and the second gate dielectric layer 107b, may include but is not limited to one of hafnium oxide, aluminum oxide, yttrium oxide, scandium oxide, lanthanum oxide, zirconium oxide, silicon oxide, titanium oxide, tantalum oxide, beryllium oxide, aluminum nitride, silicon nitride, boron nitride, carbon nitride, or any combination thereof.

[0112] like Figure 2 As shown, the first direction is the longitudinal direction of the planar structure of the carbon nanotube radio frequency field effect transistor.

[0113] The T-shaped metal gate may include a first T-shaped metal gate 108a and a second T-shaped metal gate 108b, wherein the first T-shaped metal gate 108a is arranged in the first region along the first direction and the gate foot is arranged on the first gate dielectric 105a; the second T-shaped metal gate is arranged in the second region along the first direction and the gate foot is arranged on the second gate dielectric 105b.

[0114] The T-shaped metal gates (108a, 108b) may have a T-shaped structure that is wider at the top and narrower at the bottom. The gate foot cross-section of the T-shaped metal gates (108a, 108b) may have an inverted trapezoidal shape, and the angle between the sidewall of the gate foot cross-section of the T-shaped metal gates (108a, 108b) and the first side of the carbon nanotube active layer is greater than a first predetermined angle. For example, the first predetermined angle may be 90 degrees.

[0115] In some embodiments, the distance between the T-shaped metal gate (108a, 108b) and the drain contact layer 106 is greater than the distance between the T-shaped metal gate (108a, 108b) and the source contact layer (104a, 104b). The distance between the source contact layer and the gate foot of the T-shaped metal gate is less than a first predetermined distance. For example, the first predetermined distance can be 100 nanometers.

[0116] In specific applications, both the first predetermined distance and the first predetermined angle can be flexibly adjusted according to actual needs.

[0117] In some embodiments, Figure 1 and Figure 2 As shown, the first T-shaped metal gate 108a and the second T-shaped metal gate 108b each have a T-shaped structure that is wider at the top and narrower at the bottom. The gate foot 1081a of the first T-shaped metal gate 108a is disposed on the first gate dielectric layer 107a, and the gate foot 1081b of the second T-shaped metal gate 108b is disposed on the second gate dielectric layer 107b. The gate foot 1081a of the first T-shaped metal gate 108a has an inverted trapezoidal cross-section, with the sidewalls of the gate foot 1081a forming an angle greater than 90 degrees with the surface of the carbon nanotube active layer 103a. The gate foot 1081b of the second T-shaped metal gate 108b has an inverted trapezoidal cross-section, with the sidewalls of the gate foot 1081b forming an angle greater than 90 degrees with the surface of the carbon nanotube active layer 103b. This reduces the electric field strength at the edges of the gate feet (1081a, 1081b) and improves the breakdown voltage of the carbon nanotube RF field-effect transistor 100.

[0118] like Figure 2As shown, the distance from the gate foot 1081a of the first T-shaped metal gate 108a to the drain contact layer 106 is greater than the distance from the gate foot 1081a of the first T-shaped metal gate 108a to the first source contact layer 104a (i.e., the gate-source spacing 1082a), and the distance from the gate foot 1081b of the second T-shaped metal gate 108b to the drain contact layer 106 is greater than the distance from the gate foot 1081b of the second T-shaped metal gate 108b to the second source contact layer 104b (i.e., the gate-source spacing 1082b). In this way, the length of the drain drift region of the carbon nanotube RF field effect transistor 100 can be increased, and the breakdown voltage and RF output power of the carbon nanotube RF field effect transistor 100 can be improved.

[0119] In some embodiments, in the carbon nanotube radio frequency field effect transistor 100, when a thinner ohmic metal is used to form the first source terminal contact layer 104a and the second source terminal contact layer 104b, the gate-source spacing (1082a, 1082b) can be less than 100 nanometers, and the thicker first source terminal conductive layer 105a and the first source terminal conductive layer 105b are respectively far away from the corresponding T-shaped metal gate (108a, 108b). Such a source terminal structure can reduce the parasitic capacitance and resistance between the source electrode and the gate electrode.

[0120] In some embodiments, in the carbon nanotube RF field effect transistor 100, the material composition of the T-shaped metal gate, that is, each of the first T-shaped metal gate 108a and the second T-shaped metal gate 108b, may include but is not limited to one of titanium, palladium, platinum, gold, nickel, aluminum, tungsten, molybdenum, copper, titanium nitride, tantalum nitride, tungsten nitride, aluminum nitride, heavily doped polysilicon, or any combination thereof.

[0121] Inspired by the technical solution disclosed herein, those skilled in the art can flexibly select and / or adjust the material composition of the gate dielectric layer (107a, 107b) and the T-shaped metal gate (108a, 108b), and the specific implementation methods should all fall within the protection scope of the present disclosure.

[0122] In some embodiments, Figure 2 As shown, a T-shaped metal gate lead 111 may be provided on the insulating dielectric layer 102 , and the T-shaped metal gate lead 111 may be used to connect the first T-shaped metal gate 107 a and the second T-shaped metal gate 107 b .

[0123] The backside vias include a first backside via 109a and a second backside via 109b. The top of the first backside via 109a is connected to the first source terminal contact layer 104a, and the side extends downward to sequentially pass through the carbon nanotube active layer 103, the insulating dielectric layer 102, and the substrate 101. The top of the second backside via 109b is connected to the second source terminal contact layer 104b, and the side extends downward to sequentially pass through the carbon nanotube active layer 103, the insulating dielectric layer 102, and the substrate 101. By way of example, the cross-section of the backside vias may be trapezoidal.

[0124] like Figure 1 and Figure 2 As shown, the cross-section of the first back through-hole 109a is trapezoidal, the inner surface is covered with a metal conductive layer, the top of the through-hole is connected to the first source contact layer 104a, and the side of the through-hole extends downward through the carbon nanotube active layer 103, the insulating dielectric layer 102 and the substrate 101 in sequence. The back metal layer 110 can be connected to the first source contact layer 104a of the RF field effect transistor 100 through the first back through-hole 109a.

[0125] like Figure 1 and Figure 2 As shown, the cross-section of the second back through hole 109b is trapezoidal, the inner surface is covered with a metal conductive layer, the top of the through hole is connected to the second source contact layer 104b, and the side of the through hole extends downward through the carbon nanotube active layer 103, the insulating dielectric layer 102 and the substrate 101 in sequence. The back metal layer 110 can be connected to the second source contact layer 104b of the RF field effect transistor 100 through the second back through hole 109b.

[0126] In some embodiments, the bandgap of the carbon nanotubes used in the carbon nanotube active layer can be less than a second predetermined threshold. For example, the second predetermined threshold can be 1.2 electron volts. In other words, the bandgap of the carbon nanotube active layer 103 in the carbon nanotube RF field effect transistor 100 can be less than 1.2 electron volts.

[0127] In carbon nanotube RF field-effect transistor 100, the carbon nanotubes used in carbon nanotube active layer 103 can be, but are not limited to, a randomly arranged carbon nanotube network or an aligned carbon nanotube array. Informed by the technical solutions disclosed herein, those skilled in the art can flexibly select and / or adjust the arrangement of carbon nanotube active layer 103, and all such implementations are intended to fall within the scope of protection of this disclosure.

[0128] Substrate 101 can be made of a material that exhibits low dielectric loss during high-frequency operation. In some embodiments, the material of substrate 101 may include, but is not limited to, silicon, quartz, glass, sapphire, aluminum oxide, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, benzocyclobutene (BCB), or any combination thereof. Selection / adjustment of the material or composition of substrate 101 by those skilled in the art falls within the scope of protection of this disclosure.

[0129] In some embodiments, the carbon nanotube RF field effect transistor 100 of the embodiment of the present disclosure can be arranged in parallel on a low-loss substrate 101, the first source terminal contact layer 104a is connected to the back metal layer 110 through the first back through hole 109a, and the second source terminal contact layer 104b is connected to the back metal layer 110 through the second back through hole 109b to reduce parasitic inductance, the first T-shaped metal gate 108a and the second T-shaped metal gate 108b are connected in parallel to reduce the gate resistance, and the drain terminal contact layer 106 is arranged in the middle area of ​​the carbon nanotube RF field effect transistor 100 to reduce the substrate parasitic capacitance.

[0130] The carbon nanotube RF field effect transistor 100 provided in the embodiment of the present disclosure has smaller parasitic inductance, smaller gate resistance and smaller substrate parasitic capacitance, and is a new type of carbon nanotube device applicable to RF application fields such as microwave and millimeter waves.

[0131] Figure 3 FIG. 1 is a flow chart showing a method for preparing a carbon nanotube radio frequency field effect transistor 100. Figure 3 As shown, the method for preparing the carbon nanotube radio frequency field effect transistor 100 may include the following steps:

[0132] Step S301, providing a substrate, and forming an insulating dielectric layer on a first side of the substrate;

[0133] As mentioned above, the substrate is preferably made of a material with low dielectric loss when operating at high frequencies. In this step, a SiO 2 insulating dielectric layer 102 is deposited on the high-resistance silicon substrate 101 .

[0134] Step S302, forming a carbon nanotube active layer on the insulating dielectric layer, the carbon nanotube active layer serving as a channel layer of the carbon nanotube radio frequency field effect transistor;

[0135] For example, the aligned carbon nanotube active layer 103 is deposited on the SiO 2 insulating dielectric layer 102 .

[0136] Step S303, forming source end contact layers at both end regions of the carbon nanotube active layer;

[0137] For example, a first source contact layer 104a and a second source contact layer 104b can be formed on the aligned carbon nanotube active layer 103. The N-type source contact layer can be made of 40-nanometer-thick metal Sc / Al, and the P-type source contact layer can be made of 40-nanometer-thick metal Pd.

[0138] Step S304, forming a gate dielectric layer on the source contact layer (104a, 104b);

[0139] For example, a 10 nm thick hafnium oxide gate dielectric layer 107a may be deposited on the aligned carbon nanotube active layer 103 and the first source contact layer 104a, and a 10 nm thick hafnium oxide gate dielectric layer 107b may be deposited on the aligned carbon nanotube active layer 103 and the second source contact layer 104b.

[0140] In some embodiments, step S304 may further include: step S305, etching the gate dielectric layer to form a drain contact hole and a source contact hole, so that the drain contact layer is connected to the carbon nanotube active layer through the drain contact hole, and at the same time, the source contact layer is connected to the carbon nanotube active layer through the source contact hole.

[0141] For example, the hafnium oxide gate dielectric layer 107 a and the hafnium oxide gate dielectric layer 107 b may be etched separately to form a drain contact hole and a source contact hole.

[0142] Step S306 , forming a drain contact layer with a field plate structure in the middle region of the carbon nanotube active layer, and forming a source conductive layer on the source contact layer.

[0143] For example, a 300-nanometer-thick Pd / Au electrode or a Sc / Al / Au metal electrode can be deposited to form a drain contact layer 106 having an eaves-shaped field plate structure (1061a and 1061b). The field plate width extends approximately 30 nanometers on each side beyond the drain contact hole, and a first source conductive layer 105a and a second source conductive layer 105b are formed at the same time. The first source conductive layer 105a and the second source conductive layer 105b can thicken the source metal electrode and reduce the source parasitic resistance.

[0144] Step S307 , forming a T-shaped metal gate electrode in the region between the source contact layer and the drain contact layer, wherein the gate foot of the T-shaped gate metal electrode is disposed on the gate dielectric layer;

[0145] For example, a T-shaped gate pattern may be first formed by electron beam lithography, and then a Ti / Au metal layer with a thickness of 300 nanometers may be deposited to form a T-shaped metal gate electrode (108a, 108b).

[0146] Step S308, performing passivation of the carbon nanotube radio frequency field effect transistor;

[0147] For example, an atomic layer deposition method may be used to grow aluminum oxide with a thickness of 30 nanometers to form the passivation layer of the field effect transistor 100 , thereby completing the passivation of the carbon nanotube radio frequency field effect transistor.

[0148] Step S309: etching backside through holes at both ends of the carbon nanotube RF field effect transistor. The inner surface of the backside is covered with a metal conductive layer, the top is connected to the source contact layer, and the side extends downward to pass through the carbon nanotube active layer, the insulating dielectric layer, and the substrate in sequence.

[0149] For example, the high-resistance silicon substrate 101 may be thinned to 150 microns, and the substrate 101 may be etched using ICP to form a circular backside via hole with a diameter of 40 microns. The backside via hole terminates at the front source contact layer.

[0150] Step S310 , forming a back metal layer on the second side of the substrate, and connecting the back metal layer to the source contact layer through a back through hole to form a ground plane of the carbon nanotube radio frequency field effect transistor.

[0151] Specifically, a back metal starting layer may be sputtered on the second side of the substrate 101, and then electroplating may be used to thicken the back metal layer 100. For example, a 100-nanometer-thick Ti / Au starting layer may be sputtered on the back side of the high-resistance silicon substrate 101, and then electroplating gold may be used to thicken the Ti / Au starting layer to 2 microns, thereby forming the back metal layer 110 that can serve as a low-resistance RF ground plane.

[0152] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present disclosure. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples described in this specification and the features of different embodiments / methods or examples, unless they are contradictory.

[0153] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0154] Those skilled in the art will appreciate that the above embodiments are merely intended to clearly illustrate the present disclosure and are not intended to limit the scope of the present disclosure. Other changes or modifications may be made based on the above disclosure, and such changes or modifications are still within the scope of the present disclosure.

Claims

1. A carbon nanotube radio frequency field effect transistor, characterized in that: include: substrate; an insulating dielectric layer, disposed on the first side of the substrate; a carbon nanotube active layer, disposed on the insulating dielectric layer and serving as a channel layer of the carbon nanotube radio frequency field effect transistor; Source end contact layers are provided at both end regions of the carbon nanotube active layer; A source end conductive layer is provided on the source end contact layer; a drain contact layer, disposed in a middle region of the carbon nanotube active layer and separated from the source contact layer; a gate dielectric layer, disposed on the carbon nanotube active layer and located in a region between the source contact layer and the drain contact layer; A T-shaped metal gate is provided in the region between the source contact layer and the drain contact layer, and the gate foot is provided on the gate dielectric layer; Back through holes are provided at both end regions of the carbon nanotube active layer, the inner surface of which is covered with a metal conductive layer, the top of which is connected to the source end contact layer, and the side of which extends downward to sequentially pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate; A back metal layer is provided on a second side of the substrate and is connected to the source contact layer through the back through hole to form a ground plane of the carbon nanotube radio frequency field effect transistor. The second side is opposite to the first side.

2. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that: The drain contact layer has a field plate structure, and the field plate structure is arranged at the junction of the drain contact layer and the carbon nanotube active layer.

3. The carbon nanotube radio frequency field effect transistor according to claim 2, characterized in that: The field plate structure is in the shape of an eaves.

4. The carbon nanotube radio frequency field effect transistor according to claim 2, characterized in that: The gate dielectric layer has a drain contact hole, and the drain contact layer passes through the gate dielectric layer through the drain contact hole and is connected to the carbon nanotube active layer; the width of the side of the field plate structure exceeding the drain contact hole is a first predetermined width.

5. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that: The drain contact layer has an upper electrode and a lower electrode, the upper electrode has a first width, the lower electrode has a second width, the first width is greater than the second width, and a difference between the first width and the second width is greater than a first predetermined threshold.

6. The carbon nanotube radio frequency field effect transistor according to claim 5, characterized in that: The upper electrode covers the gate dielectric layer, the lower electrode contacts the carbon nanotube active layer, and a sidewall of the lower electrode is closely adjacent to the gate dielectric layer.

7. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that: When the source contact layer and / or the drain contact layer serve as an N-type ohmic contact layer, the material is a metal or alloy having a work function less than 4.5 electron volts.

8. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that: When the source contact layer and / or the drain contact layer serve as a P-type ohmic contact layer, the material is a metal or alloy having a work function greater than 4.5 electron volts.

9. The carbon nanotube radio frequency field effect transistor according to any one of claims 1 to 8, characterized in that: The source end contact layer includes a first source end contact layer and a second source end contact layer, and the first source end contact layer and the second source end contact layer are respectively arranged at two ends of the carbon nanotube active layer.

10. The carbon nanotube radio frequency field effect transistor according to claim 9, characterized in that: The source-end conductive layer includes a first source-end conductive layer and a second source-end conductive layer. The first source-end conductive layer is disposed on the first source-end contact layer, and the second source-end conductive layer is disposed on the second source-end contact layer.

11. The carbon nanotube radio frequency field effect transistor according to claim 9, characterized in that: The gate dielectric layer includes a first gate dielectric layer and a second gate dielectric layer; The first gate dielectric layer is distributed in a first region on the carbon nanotube active layer at intervals along a first direction and extends to above the first source contact layer, wherein the first region is a region between the drain contact layer and the first source contact layer; The second gate dielectric layer is distributed in a second region on the carbon nanotube active layer at intervals along a first direction and extends onto the second source contact layer. The second region is a region between the drain contact layer and the second source contact layer.

12. The carbon nanotube radio frequency field effect transistor according to claim 11, characterized in that: The T-shaped metal gate includes a first T-shaped metal gate and a second T-shaped metal gate, wherein the first T-shaped metal gate is arranged in the first region along the first direction and the gate foot is arranged on the first gate dielectric; the second T-shaped metal gate is arranged in the second region along the first direction and the gate foot is arranged on the second gate dielectric.

13. The carbon nanotube radio frequency field effect transistor according to claim 1 or 12, characterized in that: The distance between the T-shaped metal gate and the drain contact layer is greater than the distance between the T-shaped metal gate and the source contact layer.

14. The carbon nanotube radio frequency field effect transistor according to claim 1 or 12, characterized in that: The distance between the source contact layer and the gate foot of the T-shaped metal gate is smaller than a first predetermined distance.

15. The carbon nanotube radio frequency field effect transistor according to claim 1 or 12, characterized in that: The T-shaped metal grid has a T-shaped structure that is wide at the top and narrow at the bottom.

16. The carbon nanotube radio frequency field effect transistor according to claim 1 or 12, characterized in that: The gate foot of the T-shaped metal gate has an inverted trapezoidal cross section, and an angle between a sidewall of the gate foot of the T-shaped metal gate and the first side of the carbon nanotube active layer is greater than a first predetermined angle.

17. The carbon nanotube radio frequency field effect transistor according to claim 9, characterized in that The back through hole includes a first back through hole and a second back through hole, the top of the first back through hole is connected to the first source end contact layer and the side extends downward to pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate in sequence; the top of the second back through hole is connected to the second source end contact layer and the side extends downward to pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate in sequence.

18. The carbon nanotube radio frequency field effect transistor according to claim 1 or 17, characterized in that: The cross section of the back through hole is trapezoidal.

19. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that The band gap of the carbon nanotubes used in the carbon nanotube active layer is smaller than a second predetermined threshold.

20. The carbon nanotube radio frequency field effect transistor according to claim 1, characterized in that The substrate is made of a material with low dielectric loss when working at high frequencies.

21. The carbon nanotube radio frequency field effect transistor according to claim 1 or 20, characterized in that: The material of the substrate includes one of the following or any combination thereof: silicon, quartz, glass, sapphire, aluminum oxide, gallium oxide, silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, silicon nitride, indium phosphide, diamond, polyimide, and BCB.

22. A method for preparing a carbon nanotube radio frequency field effect transistor, characterized in that: include: providing a substrate; forming an insulating dielectric layer over the first side of the substrate; forming a carbon nanotube active layer on the insulating dielectric layer, wherein the carbon nanotube active layer serves as a channel layer of the carbon nanotube radio frequency field effect transistor; forming source end contact layers at both end regions of the carbon nanotube active layer; forming a gate dielectric layer on the source contact layer; forming a drain contact layer having a field plate structure in the middle region of the carbon nanotube active layer, and forming a source conductive layer on the source contact layer; forming a T-shaped gate metal electrode in a region between the source contact layer and the drain contact layer, wherein a gate foot of the T-shaped gate metal electrode is disposed on the gate dielectric layer; performing passivation of the carbon nanotube radio frequency field effect transistor; Back-side through holes are etched at both ends of the carbon nanotube radio frequency field effect transistor, wherein the inner surface of the back side is covered with a metal conductive layer, the top of which is connected to the source end contact layer, and the side surfaces extend downward and sequentially pass through the carbon nanotube active layer, the insulating dielectric layer and the substrate; A back metal layer is formed on the second side of the substrate, and the back metal layer is connected to the source contact layer through the back through hole to form a ground plane of the carbon nanotube radio frequency field effect transistor.

23. The method for preparing a carbon nanotube radio frequency field effect transistor according to claim 22, characterized in that: After forming a gate dielectric layer by deposition on the source contact layer, the method further comprises: Etching the gate dielectric layer to form a drain contact hole, so that the drain contact layer is connected to the carbon nanotube active layer through the drain contact hole; The gate dielectric layer is etched to form a source contact hole, so that the source contact layer is connected to the carbon nanotube active layer through the source contact hole.

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