CN1236496C - Logic NOT gate device made of carbon nano tube - Google Patents

Abstract

The present invention relates to a logic NOT gate device made of carbon nano tubes, which comprises a Si substrate, wherein a SiO2 insulating layer is arranged on the substrate; a single wall carbon nano tube, a grid electrode and electrodes are arranged on the Si substrate. The present invention is characterized in that the grid electrode is composed of a Al2O3 insulating layer which is formed by the surface oxidation of Al which is deposited in a groove in the SiO2 insulating layer positioned on the Si substrate; the electrodes whose number is two are parallel to the grid electrode and are arranged on both sides of the grid electrode; the electrodes are arranged under or above the single wall carbon nano tube; the single wall carbon nano tube is placed on the surface of the SiO2 insulating layer and contacts the surface of the Al2O3 insulating layer of the grid electrode and the surface of a noble metal layer of the electrode; the first electrode is connected with a constant voltage source, and the grid electrode is an input end. A logic 'NOT' function is realized by using the grid electrode to control the turn-on or the turn-off of the single wall carbon nano tube. Compared with other carbon nano tube logic devices, the present invention has the advantages of simple structure and easy fabrication and integration.

Description

The logic inverter device that utilizes carbon nano-tube to make

Technical field

The invention belongs to a kind of logical device, particularly a kind of logic inverter device based on carbon nano-tube.

Technical background

After the mankind entered " information age ", " digitlization " become people's a kind of important life style.And be that the various circuit of media are the important carriers of information with the semiconductor integrated circuit.In these circuit, Digital Logical Circuits has accounted for very big proportion.Look around of the present invention around, to electronic computer, household electrical appliance, none can not find the figure of Digital Logical Circuits from spaceship, airliner, constitutes and these logical circuits all are gates by various bases.In these gates, the logic inverter is one of base components of Digital Logical Circuits.Traditional logic semiconductor inverter is basic engineering and making with the semiconductor field.Be subjected to restrictions such as semi-conductive technology and principle, semi-conductive gate exposes a series of defectives such as size and speed gradually.These defectives are that semi-conducting material itself can't overcome, and can only replace semi-conducting material just can address these problems by new material.With carbon nano-tube and semiconductor nanowires is that the nano material of representative becomes and replaces the semi-conducting material first-selection.And based on the circuit of these nano materials also than replacing traditional semiconductor integrated circuit.The logic inverter is the main basic device of Digital Logical Circuits, so the logic inverter that designs and produces based on nano material has important meaning.

Calendar year 2001, people such as Adrian Bachtold produce the logic inverter based on carbon nano-tube.It is at room temperature worked, and good electrology characteristic is arranged.Compare with traditional semiconductor device outstanding advantages such as size is little, speed is fast are arranged.But what people's such as Adrian Bachtold carbon nano tube logic inverter used is the more special carbon nano-tube of a kind of conduction property.This carbon nano-tube is in not on-state under the not biased situation of grid; Under grid bias increased to a certain degree situation, carbon nano-tube was in the state of conducting.So just require the grid of carbon nano-tube will act on and whole carbon nano-tube, so require grid that bigger area is arranged.This has just brought difficulty for the design of circuit and making.

Summary of the invention

The objective of the invention is to have used than larger area grid, and cause the big and big defective of manufacture difficulty of logical device in order to solve in the above-mentioned existing logical device; The carbon nano-tube inverter logical device that thereby the structure that the comparatively general Single Walled Carbon Nanotube of a kind of use is provided is more simple, can reduce manufacture difficulty.

Provided by the invention utilize that carbon nano-tube makes logic inverter device, comprise a Si substrate, a SiO is arranged on this substrate ₂Insulating barrier is at SiO ₂Single Walled Carbon Nanotube, grid and electrode are set on the insulating barrier; It is characterized in that: described grid is positioned at SiO on the Si substrate ₂The Al that deposits among the groove in the insulating barrier, and the Al that forms through surface oxidation ₂O ₃Insulating barrier is formed; Described electrode comprises first electrode and second electrode, and first electrode and second electrode are parallel to grid and are arranged on the grid both sides, and under the Single Walled Carbon Nanotube or be positioned on the Single Walled Carbon Nanotube; The Al of described Single Walled Carbon Nanotube and grid ₂O ₃The layer of precious metal surface of surface of insulating layer and electrode contacts, and first electrode connects constant pressure source, and grid is an input.

It is SiO at the Si substrate that described first electrode and second electrode are arranged under the carbon nano-tube ₂The depositing noble metal layer is made among two grooves in the insulating barrier, and noble metal comprises gold and platinum.

Described carbon nano-tube is the Single Walled Carbon Nanotube of a semiconductive.

Described electrode is arranged on SiO ₂Respectively cover a layer of precious metal on insulating barrier and the carbon nano-tube two ends.

Described carbon nano-tube is placed on SiO ₂Direction on the insulating barrier is vertical placement with a grid, first electrode and second electrode, and the straight placement of carbon nano-tube.

SiO on the described Si substrate ₂The thickness of insulating barrier is between 35nm to 100 μ m; Be positioned at SiO on the substrate ₂A grid in the insulating barrier and the gash depth of two electrodes are between 10nm to 95 μ m, and wherein grid width is between 10nm to 50 μ m; First electrode and second electrode width are between 5nm to 50 μ m; The grid and first electrode and second distance between electrodes are between 5nm to 100 μ m.

The Al of described grid ₂O ₃Thickness of insulating layer is between 1 nanometer to 5 nanometer.

The insulating barrier upper surface of the upper surface of described grid and substrate maintains an equal level.

The upper surface and the SiO of described first electrode and second electrode ₂The upper surface of insulating barrier maintains an equal level.

The manufacturing process of circuit of the present invention is earlier at insulation SiO ₂Erode away the 3 road grooves that are used for plated metal on the substrate, respectively Al and the required metal (as Au) of metal electrode are deposited in the groove again, form grid and electrode.With the Al anodizing, form Al again ₂O ₃Insulating barrier.Again carbon nano-tube is placed on electrode and the grid at last, and to guarantee between carbon nano-tube and the metal electrode contact good.The purpose of Zhi Zuoing is to guarantee that carbon nano-tube is on the planar structure like this, influences device performance to avoid forming tunnel junctions because of carbon nano-tube is crooked.

The present invention compares with existing carbon nano-tube inverter, has used comparatively general Single Walled Carbon Nanotube, has reduced the manufacture difficulty of device; Structurally, the present invention has greatly reduced the area of grid, and the structure of device more is tending towards rationally, is easy to more make, and is easy to large-scale production application.And just can realize traditional complicated logic circuits identical functions by the simple device of the present invention.Because the carbon nano-tube of selecting for use has good electrical properties, so the present invention does not need large-area grid, the making that this has simplified device to a great extent diminishes device volume.And the carbon nano-tube that the present invention selects for use is comparatively general, and material is easy to realize.

Description of drawings

Fig. 1 is the carbon nano-tube inverter that people such as Adrian Bachtold makes;

Fig. 2 is the schematic diagram of carbon nano-tube inverter logical device of the present invention;

Fig. 3 is the structure chart according to the carbon nano-tube inverter logical device of the embodiment of the invention 1;

Fig. 4 is the structure chart according to the carbon nano-tube inverter logical device of the embodiment of the invention 2;

Indicate among the figure: 1, carbon nano-tube; 2, resistance; 3, first electrode 4, grid; 5, constant pressure source; 6, second electrode; 7, SiO ₂Layer; 8, Si substrate.

Embodiment

Embodiment 1:

With reference to Fig. 2 and 3, the present invention is described in further detail in conjunction with manufacture method and present embodiment:

(1) silicon of choosing (001) orientation utilizes organic vapor phase deposition method (PECVD) as substrate 8, the thick SiO of preparation 300nm on substrate 8 ₂ Layer 7;

(2) at first make grid 4: at SiO ₂Even smearing thickness is the thick electric lithography glue (PMMA) of 80nm on the insulating barrier, and the photoresist process behind the electron beam exposure is developed, photographic fixing, behind the photoresist of removal exposure, and the groove that is used to make grid of a wide 30nm of formation in photoresist layer; The SiO that uses dry etching method etching not have photoresist to cover ₂, at SiO ₂Form wide 30nm on the insulating barrier, the groove of dark 30nm utilizes the method for electron beam evaporation again, at the thick Al of surface deposition one deck 30nm, with photoresist lift off, cleaning, again through peroxidating, makes the Al surface form the thick Al of 2-3nm ₂O ₃Insulating barrier has so just prepared a grid 4;

(3) prepare electrode 3,6 then: repeat above lithography step, evenly smear the photoresist that a layer thickness is 80nm on the entire device surface, behind the resist exposure, in photoresist layer, form two in the grid both sides,, width parallel with grid apart from grid 50nm, direction be the groove of 30nm, use dry etching, do not having the SiO of photoresist ₂Etch the groove that is used to make electrode 3,6 of wide 30nm, dark 30nm on the insulating barrier; Utilizing the method for electron beam evaporation again, is the gold of 30nm at whole surface deposition one layer thickness, has prepared electrode 3,6 after then electric lithography glue being peeled off, cleaned;

(4) getting a diameter is that 1nm, length are 200nm, and carrier concentration is 9 * 10 ⁶Cm ^-1Single Walled Carbon Nanotube 1, be placed on the entire device with atomic force microscope, require carbon nano-tube to place and do not have bending, direction is basic vertical with the grid direction with electrode, and to contact with grid well with electrode, after device encapsulated, first electrode 3 connected constant pressure sources 5, finishes the preparation of entire device.

After device was finished, the outward appearance of entire device should be formed (referring to Fig. 3) by two electrodes and a grid.For fear of the crooked tunnel junctions that produces of carbon nano-tube, electrode and grid all should and SiO ₂Layer maintains an equal level, and carbon nano-tube is positioned on grid and the electrode.

The structure principle chart of the carbon nano-tube inverter that people such as Adrian Bachtold make as shown in Figure 1.From schematic diagram as can be seen, when grid 4 is input as logical zero, when promptly carbon nano-tube is in cut-off state, output 3 output logic values " 1 "; And when grid 4 was input as " 1 ", the nanotube of its control will be in conducting state, and at this moment output 3 is " 0 " just.

It is the Single Walled Carbon Nanotube of semiconductive that the present invention selects electric conductivity for use.The incompatibility of the carbon nano-tube in the carbon nano-tube inverter that people such as the Adrian Bachtold of the character of the Single Walled Carbon Nanotube of this semiconductive and above introduction make: conductivity is preferably arranged at normal temperatures, and its resistance is generally a hundreds of k Ω.Its charge carrier is the hole as can be known by experiment, so conduction type is the p type.Its electric conductivity changes with the change of grid voltage.When grid voltage increases to certain value, carbon nano-tube will be in cut-off state.

Electrical properties and schematic diagram of the present invention 2 below in conjunction with carbon nano-tube illustrate operation principle of the present invention.

Diameter is the Single Walled Carbon Nanotube of 1nm, and resistance is generally several K Ω at normal temperatures.Under the effect of forward grid bias, the concentration in charge carrier---hole will reduce.Thickness of insulating layer be 140nm, grid voltage under the situation about 6V, the hole in the carbon nano-tube will be exhausted fully, carbon nano-tube is in cut-off state.Simultaneously, the present invention as can be known: at this moment, if keep the cut-off state of carbon nano-tube, added bias voltage should be not more than 1.5V at the carbon nano-tube two ends.So the present invention is defined in the circuit of the present invention, 1.2V is logical value " 1 ", and 0V is logical value " 0 ".

In logical circuit, unified logical value is very important, all should observe this regulation in all parts of logical circuit, can guarantee that like this circuit structure is simple, efficient is higher, calculating is reliable.Will observe this regulation except the input and the output at carbon nano-tube two ends, the grid of controlling carbon nanotube also must be observed this regulation.

By above discussion the present invention as can be known: when the gate insulator layer thickness was 140nm, the voltage that exhausts of grid was 6V.The present invention determines by following calculating, during the exhausting voltage and be 1.2V of grid, and the thickness of gate insulator.

Known, there is following relationship in the voltage that blocks between carbon nano-tube and the grid:

Q＝CV _G，T (1)

V _{G, T}For blocking voltage, Q is electrically charged by charge carrier, and C is the electric capacity between carbon nano-tube and the grid.

Q and carrier concentration satisfy formula:

Q＝peL (2)

P is a carrier concentration; E is electrically charged by charge carrier, and charge carrier is the hole in p type carbon nano-tube, so e=+1.6 * 10 here ^-19Coulomb; L is the length of carbon nano-tube and grid contact portion.

Know that again the electric capacity between carbon nano-tube and the grid satisfies formula:

C≈2πεε ₀L/ln(2h/r) (3)

H is the distance between carbon nano-tube and the grid, i.e. the thickness of gate insulator; R is the carbon nano-tube diameter; ε is a dielectric constant, and the present invention here gets ε=2.5.

Formula (2), (3) are brought in the formula (1) and can be got:

peln(2h/r)＝2πεε ₀V _G，T

$h=\frac{1}{2}{\mathrm{re}}^{\left(\frac{{2\mathrm{\π\ϵ\ϵ}}_0{V}_{G,T}}{\mathrm{pe}}\right)}---\left(4\right)$

It is 9 * 10 that the present invention selects carrier concentration ⁶Cm ^-1P type carbon nano-tube carbon nano-tube diameter be

1nm, cut-ff voltage are 1.2V.Bringing formula (4) into can get: h ≈ 3nm.That is: in the present invention, work as Al ₂O ₃Thickness of insulating layer is not more than under the situation of 3nm, and carbon nano-tube is in cut-off state.

The present invention has utilized the conducting state of the grid controlling carbon nanotube of the carbon nano-tube realization output valve function opposite with input value.First electrode 3 connects constant pressure source 5, and constant source voltage is 1.2V.Grid 4 is an input.When input 4 input logic values " 1 ", promptly during voltage 1.2V, carbon nano-tube is in the state of not conducting under the effect of grid.Output 3 is output as 0V, i.e. logical value " 0 "; In like manner: when grid 4 is input as logical value " 0 ", promptly during voltage 0V, carbon nano-tube is in conducting state, and output 3 voltages are identical with constant source voltage, are 1.2V, i.e. logical value " 1 ".Like this, the present invention has just realized the upset of output and input logical value.Truth table of the present invention is as shown in table 1.

Table 1

X in(4)	Y out(3)
		1	0
0	1

Embodiment 2:

Making one with reference to Fig. 2 and Fig. 4, to have two absolute electrodes be to be positioned at Single Walled Carbon Nanotube and SiO ₂The carbon nano-tube inverter logical device of structure on the surface of insulating layer.

The silicon of selecting (001) orientation for use is as substrate 8.Utilize organic vapor phase deposition side (PECVD), form the thick SiO of 300nm ₂Layer 7 is at SiO ₂Even cladding thickness is the electric lithography glue (PMMA) of 80nm on the insulating barrier, behind the resist exposure, forms the groove of a wide 30nm in photoresist; Use dry etching, the SiO that exposes at photoresist ₂Etch wide 30nm on the insulating barrier, the groove of dark 30nm.Utilize electron beam evaporation method, at the thick Al of surface deposition one deck 30nm.After peeling off, cleaning, utilize the intrinsic oxidizing process again, make the Al surface form the thick Al of 2-3nm ₂O ₃Insulating barrier has so just prepared grid 4.Select a Single Walled Carbon Nanotube 1 that diameter 1nm, length are 400nm, utilize atomic force microscope (AFM) technology that it is positioned on two grids.Require two grids should approximately be in the centre position of carbon nano-tube, two grids contact well with carbon nano-tube, and carbon nano-tube do not have bending, and direction is vertical with two grids.After carbon nano-tube is in place,, on carbon nano-tube, prepares two width with focused ion beam (FIB) method and be 0.1 μ m, highly be the gold electrode 3,6 of 200nm in the position of the outside of two grids 50nm.Connect constant pressure source 5, finish the encapsulation of device at last.

After encapsulation finished, the monnolithic case of device should be by one and SiO ₂The grid that layer maintains an equal level and two place SiO ₂Electrode on the layer is formed (referring to Fig. 4).Carbon nano-tube is put on the grid, and two ends are fixed by two electrodes.

Claims (9)

1. a logic inverter device that utilizes carbon nano-tube to make comprises a Si substrate, and a SiO is arranged on this substrate ₂Insulating barrier is at SiO ₂Single Walled Carbon Nanotube, grid and electrode are set on the insulating barrier; It is characterized in that: described grid is the SiO on the Si substrate ₂Groove of etching on the insulating barrier, depositing Al in this groove, and to Al surface oxidation formation Al ₂O ₃Insulating barrier constitutes; Described electrode comprises first electrode and second electrode, and first electrode and second electrode are parallel to grid and are arranged on the grid both sides, and under the Single Walled Carbon Nanotube or be positioned on the Single Walled Carbon Nanotube; The Al of described Single Walled Carbon Nanotube and grid ₂O ₃The layer of precious metal surface of surface of insulating layer and electrode contacts, and first electrode connects constant pressure source, and grid is an input.

2. the logic inverter device that utilizes carbon nano-tube to make according to claim 1 is characterized in that: the SiO on the described Si substrate ₂The thickness of insulating barrier is between 35nm to 100 μ m.

3. the logic inverter device that utilizes carbon nano-tube to make according to claim 1 is characterized in that: the Al of described grid ₂O ₃Thickness of insulating layer is between 1 nanometer to 5 nanometer; The gash depth of grid is between 10nm to 95 μ m, and wherein grid width is between 10nm to 50 μ m.

4. the logic inverter device that utilizes carbon nano-tube to make according to claim 1 is characterized in that: the upper surface of described grid and the SiO of substrate ₂The insulating barrier upper surface maintains an equal level.

5. the logic inverter device that utilizes carbon nano-tube to make according to claim 1, it is characterized in that: the described grid and first electrode and second distance between electrodes are between 5nm to 100 μ m.

6. the logic inverter device that utilizes carbon nano-tube to make according to claim 1, it is characterized in that: described first electrode and second electrode are respectively to cover a layer of precious metal on the Single Walled Carbon Nanotube two ends, and described noble metal comprises gold and platinum.

7. the logic inverter device that utilizes carbon nano-tube to make according to claim 1 is characterized in that: described first electrode and second electrode SiO on the Si substrate ₂The depositing noble metal layer is made among two grooves in the insulating barrier, and described noble metal comprises gold and platinum.

8. the logic inverter device that utilizes carbon nano-tube to make according to claim 1 is characterized in that: be positioned at SiO on the substrate ₂First electrode in the insulating barrier and the gash depth of second electrode are between 10nm to 95 μ m, and first electrode and second electrode width are between 5nm to 50 μ m.

9. according to claim 1 or the 3 described logic inverter devices that utilize carbon nano-tube to make, it is characterized in that: the upper surface and the SiO of described first electrode and second electrode ₂The upper surface of insulating barrier maintains an equal level.

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