Graphene and carbon nanotube spiral core-shell vertical interconnection structure and preparation method thereof

Abstract

The invention discloses a graphene and carbon nanotube spiral core-shell vertical interconnection structure which comprises a substrate, a Fe nanoparticle layer is arranged on the substrate, a carbon nanotube is grown on the Fe nanoparticle layer in a vertical array mode, 2-5 graphene layers are spirally grown on the surface of the carbon nanotube, the graphene layers spirally grow in the axial direction of the carbon nanotube, and the graphene layers are arranged on the surface of the substrate. And the spiral growth angle is 10-20 degrees. The carrier mobility is improved to 1.5 * 10 < 5 > cm < 2 > / (V.s) through the spiral structure, the contact resistance reaches 8.3 * 10 <-9 > omega.cm < 2 >, and the contact resistance is 6.5 * 10 <-8 > omega.cm < 2 > of the traditional non-spiral structure. The THz time-domain spectrum shows that the dielectric loss of the spiral structure is reduced to 0.0008 at the frequency band of 10-20 GHz, and the dielectric loss of the traditional disordered structure is 0.005; extreme condition stability: the resistance change rate is less than 0.9% after aging at 300 DEG C for 1000 hours; and the current density tolerance reaches 1.2 * 10 < 9 > A / cm < 2 >.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to a graphene and carbon nanotube spiral core-shell vertical interconnected structure and a preparation method thereof. Background Art

[0002] In traditional disordered graphene coating, the graphene layer coats the CNT in a disordered manner, and the lattice matching is insufficient (<80%), resulting in significant carrier interface scattering and contact resistance still higher than 10 -8 Ω·cm 2 .

[0003] Inter-tube gap problem: There are microscopic gaps between the tubes of traditional CNT arrays (spacing > 5nm), which cause localized electromagnetic field concentration and limit the current density carrying capacity (<5×10 8 A / cm 2 ).

[0004] High-temperature metal diffusion: When a metal-CNT composite structure (such as Au / CNT) operates above 200°C, metal atoms diffuse along the CNT surface, causing resistivity degradation (increase ≥ 20% after aging for 500 hours).

[0005] Based on the above technical problems, how to achieve sub-10 -8 Ω·cm 2 The high-level contact resistance, lattice-matched carrier efficient transport path and metal-diffusion-free interconnect structure that is resistant to high-temperature aging.

[0006] To this end, a graphene and carbon nanotube helical core-shell vertical interconnected structure and a preparation method thereof are proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a graphene and carbon nanotube spiral core-shell vertical interconnection structure and a preparation method thereof, which is suitable for ultra-low loss interconnection of high-frequency, high-power gallium nitride (GaN) devices to solve the problems raised in the above background technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a graphene and carbon nanotube spiral core-shell vertically interconnected structure, comprising a substrate, an Fe nanoparticle layer provided on the substrate, carbon nanotubes grown in a vertical array on the Fe nanoparticle layer, 2 to 5 layers of graphene layers spirally grown on the surface of the carbon nanotubes, and a metal stack sputtered on the surface of the graphene layer.

[0009] Preferably, the graphene layer grows in a spiral shape along the axis of the carbon nanotube, and the spiral growth angle is 10-20°.

[0010] Preferably, the carbon nanotubes have a diameter of 30 nm and a height of 30 μm.

[0011] The method for preparing the graphene and carbon nanotube helical core-shell vertical interconnected structure according to any one of the above items comprises the following steps:

[0012] S1. Forming an Fe nanoparticle layer: First, Fe catalyst and Al catalyst are sputtered on the surface of the substrate, and annealed in hydrogen at 400-450° C. for 30-60 min to form an Fe nanoparticle layer;

[0013] S2. Growth of carbon nanotubes: reaction gas C2H2 / H2 / Ar flow ratio 200 / 400 / 1000 sccm, temperature 750-800°C, pressure 8-12 kPa, growth time 15-30 min;

[0014] S3, spiral growth of graphene layer: CH4 / H2 mixed gas is introduced into the surface of carbon nanotubes at a temperature of 850±5℃ and a pressure of 5kPa, and the axial gas flow velocity gradient is controlled to induce the spiral growth of graphene;

[0015] S4. Interface engineering: Use Ar / H2 plasma with a power of 80-120W for 20-40s to activate the surface and sputter Ti / Ni / Au metal stacks with thicknesses of 10 / 50 / 100nm, respectively, where the Ti layer forms a Ti-C bond with graphene.

[0016] Preferably, in step S1, the thickness of the Fe catalyst is 5-8 nm, the thickness of the Al catalyst is 10-15 nm, and the diameter of the Fe nanoparticles in the Fe nanoparticle layer is 10-20 nm.

[0017] Preferably, in step S3, the flow ratio of the CH4 / H2 mixed gas is 1:2 to 1:4.

[0018] Preferably, in step S3, the inlet flow rate of the axial airflow velocity gradient control is greater than 5 m / s, and the outlet flow rate is less than 2 m / s.

[0019] Preferably, in step S4, the ratio of Ar / H2 plasma is 4:1.

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

[0021] Ultra-low contact resistance: The spiral structure increases the carrier mobility to 1.5×10 5 cm 2 / (V·s), contact resistance reaches 8.3×10 -9 Ω·cm 2 , the traditional non-helical structure is 6.5×10 -8 Ω·cm 2 .

[0022] Optimization of high-frequency characteristics: THz time-domain spectroscopy shows that the dielectric loss of the spiral structure is reduced to 0.0008 in the 10-20 GHz frequency band, while that of the traditional disordered structure is 0.005.

[0023] Stability under extreme conditions: resistance change rate after aging at 300℃ for 1000h is less than 0.9%; current density tolerance reaches 1.2×10 9 A / cm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention;

[0025] Figure 2 Schematic diagram of the structure of the Fe / AI double-layer catalyst of the present invention.

[0026] In the figure: 1. Substrate; 2. Fe nanoparticle layer; 3. Carbon nanotubes; 4. Graphene layer; 5. Fe catalyst; 6. Al catalyst; 7. Metal stack. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0028] See also Figure 1-2 The present invention provides a technical solution: a graphene and carbon nanotube spiral core-shell vertical interconnected structure, comprising a substrate 1, a Fe nanoparticle layer 2 provided on the substrate 1, and carbon nanotubes 3 (CNTs) grown in a vertical array on the Fe nanoparticle layer 2, wherein the carbon nanotubes 3 have a diameter of 30 nm, a height of 30 μm, and an array density of 1×10 11 ~5×10 11 / cm 2 , filling factor > 98%, gap between tubes < 0.5nm.

[0029] Two to five layers of graphene 4 are spirally grown on the surface of the carbon nanotube 3. The graphene layer 4 grows helically along the axis of the carbon nanotube 3, with a helical growth angle of 10 to 20 degrees, preferably 15 ± 2 degrees. Selected area electron diffraction (SAED) analysis reveals a crystal plane angle deviation of less than 2%. Interfacial transmission electron microscopy (TEM) combined with Fourier filter analysis confirms a lattice match of greater than 95% between the graphene layer 4 and the carbon nanotube 3. A Ti / Ni / Au metal stack 7 is sputtered onto the surface of the graphene layer 4.

[0030] The method for preparing the graphene and carbon nanotube spiral core-shell vertical interconnected structure is characterized by comprising the following steps:

[0031] S1, sputtering Fe and Al double-layer catalyst (such as Figure 2 As shown), the thickness of the Fe catalyst 5 is 5 to 8 nm, and the thickness of the Al catalyst 6 is 10 to 15 nm;

[0032] Annealing is performed in hydrogen at 400-450° C. for 30-60 minutes to form a Fe nanoparticle layer 2 . The diameter of the Fe nanoparticles in the Fe nanoparticle layer 2 is 10-20 nm.

[0033] S2. CNT array growth: reaction gas C2H2 / H2 / Ar flow ratio 200 / 400 / 1000 sccm, temperature 750-800°C, pressure 8-12 kPa, growth time 15-30 min.

[0034] S3. Spiral graphene growth: A CH4 / H2 mixed gas (flow ratio of 1:2 to 1:4) was introduced into the surface of the carbon nanotube 3 at a temperature of 850±5°C and a pressure of 5 kPa. The spiral growth of graphene was induced by controlling the axial air flow velocity gradient (inlet flow velocity > 5 m / s, outlet flow velocity < 2 m / s).

[0035] S4. Interface engineering: Ar / H2 (4:1) plasma was used with a power of 80-120 W for 20-40 s to activate the surface and sputter Ti / Ni / Au metal stacks 7 with thicknesses of 10 / 50 / 100 nm, respectively, where the Ti layer formed a Ti-C bond with the graphene.

[0036] Example 1:

[0037] An Fe / Al catalyst was deposited and annealed on a GaN / SiC substrate. A vertical CNT array with a diameter of 30 nm and a height of 30 μm was grown. The CH₄ / H₂ flow ratio was controlled to 1:3, resulting in the growth of three-layer helical graphene. The SAED measurement showed a helical angle of 15.2°. Performance data are shown in Table 1.

[0038]

[0039] Table 1

[0040] The high-temperature reliability comparison was performed using an aging test in a 300°C nitrogen environment. The results are shown in Table 2.

[0041] Structure Type 500h resistance change rate 1000h resistance change rate Helical structure +0.45％ +0.87％ Disordered graphene coating +12.6％ +25.3％

[0042] Table 2

[0043] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A graphene and carbon nanotube helical core-shell vertical interconnected structure, comprising a substrate (1), characterized in that: An Fe nanoparticle layer (2) is provided on the substrate (1), carbon nanotubes (3) are grown in a vertical array on the Fe nanoparticle layer (2), 2 to 5 layers of graphene layers (4) are spirally grown on the surface of the carbon nanotubes (3), and a metal stack (7) is sputtered on the surface of the graphene layer (4).

2. The graphene and carbon nanotube helical core-shell vertical interconnected structure according to claim 1, characterized in that: The graphene layer (4) grows in a spiral shape along the axial direction of the carbon nanotube (3), and the spiral growth angle is 10 to 20 degrees.

3. The graphene and carbon nanotube helical core-shell vertical interconnected structure according to claim 1, characterized in that: The carbon nanotube (3) has a diameter of 30 nm and a height of 30 μm.

4. The method for preparing a graphene and carbon nanotube helical core-shell vertically interconnected structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, forming an Fe nanoparticle layer (2): first, sputtering an Fe catalyst (5) and an Al catalyst (6) on the surface of a substrate (1), and annealing in hydrogen at 400-450° C. for 30-60 minutes to form an Fe nanoparticle layer (2); S2. Growth of carbon nanotubes (3): reaction gas C2H2 / H2 / Ar flow ratio 200 / 400 / 1000 sccm, temperature 750-800°C, pressure 8-12 kPa, growth time 15-30 min; S3, spiral growth of graphene layer (4): introducing CH4 / H2 mixed gas at a temperature of 850±5°C and a pressure of 5kPa onto the surface of the carbon nanotube (3), and inducing the spiral growth of graphene by controlling the axial gas flow velocity gradient; S4. Interface engineering: Using Ar / H2 plasma with a power of 80-120W for 20-40s, the surface is activated and a Ti / Ni / Au metal stack (7) is sputtered with thicknesses of 10 / 50 / 100nm, respectively, wherein the Ti layer forms a Ti-C bond with the graphene.

5. The method for preparing a graphene and carbon nanotube helical core-shell vertically interconnected structure according to claim 4, characterized in that: In the step S1, the thickness of the Fe catalyst (5) is 5 to 8 nm, the thickness of the Al catalyst (6) is 10 to 15 nm, and the diameter of the Fe nanoparticles in the Fe nanoparticle layer (2) is 10 to 20 nm.

6. The method for preparing a graphene and carbon nanotube helical core-shell vertically interconnected structure according to claim 4, characterized in that: In step S3, the flow ratio of the CH4 / H2 mixed gas is 1:2 to 1:

4.

7. The graphene and carbon nanotube helical core-shell vertical interconnected structure and preparation method thereof according to claim 4, characterized in that: In step S3, the axial air flow velocity gradient is controlled to have an inlet flow velocity greater than 5 m / s and an outlet flow velocity less than 2 m / s.

8. The graphene and carbon nanotube helical core-shell vertical interconnected structure and preparation method thereof according to claim 4, characterized in that: In the step S4, the ratio of the Ar / H2 plasma is 4:1.

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