Background technique
It is the advanced subject in high voltage and insulation technology field that nanoscale vacuum, which electrically punctures with insulation characterisitic research,.Closely
Nian Lai, along with the further development of micro-nano technology technology, micro/nano-scale electric component and electronic device are continuously emerged and in army
Thing and civil field are widely used.However, this kind of micro-nano devices (such as NEMS, Field Emission Display FED) is past
Toward the working environment for needing to face high field strength, insulating reliability problem is received more and more attention.For example, being in space
Spacecraft in radiation environment needs to operate in charged particle, neutral particle, micrometeor, sky with various energy and ingredient
Between fragment, various wave bands the exceedingly odious space environment such as electromagnetic radiation, spacecraft irradiated by high energy particle, and inside will be filled
The electronics and proton of full certain energy can generate the aggregation of charged particle on surface due to the result of random thermal motion of particle.If electric
When potential difference reaches sufficiently large, electric discharge phenomena will occur for equipment surface.Electric discharge phenomena will lead to physical damage, including microelectronics
Device, Sensitive Apparatus etc., and then interfere the normal work of spacecraft.Astronics Corp's space science application experiment room
The discovery in 298 spacecraft on-orbit fault reason statistics such as Fennell charges caused spacecraft on-orbit fault more than total
The 50% of failure becomes the main problem of space environment research.Therefore, with the characteristic size of electric component and electronic device from
Micron is reduced to nanometer even molecular atoms scale, the operational reliability in complex electromagnetic environment and receives more and more
Pay attention to and concern, electrical breakdown and insulation characterisitic especially in vacuum environment have been increasingly becoming domestic and international related fields
Research hotspot.
In traditional high voltage and insulation technology field, the experiment of the electrology characteristics such as dielectric discharge rule and breakdown mechanism
Research is typically based on the electrode system and mechanical displacement mechanism of macro-scale, the adjusting of electrode gap and electrode surface situation
Control is also easier to realize.However, due to the difference of research object physical size, the experiment of nanoscale vacuum breakdown characteristic
The experimental study of traditional discharge breakdown is mainly reflected in there are sizable difference under research and macro-scale:
(1) reduction of electrode gap size causes to further increase for what electrode surface situation and processing technology required.
By the electrode surface of polishing treatment, roughness is generally up to several microns, this is for micron and its scale above gap
Measurement can rationally be ignored, however can but significantly affect the accuracy of nano-scale gap measurement.On the other hand, to ensure
Receive the smoothness of scale vacuum gap lower electrode surface, the diameter of inevitable requirement electrode also in micro-nano-scale, this adds increased
The difficulty of electrode system processing.
(2) the real-time observation and adjusting of nano-scale gap.It, can be by optical microphotograph for micron and its scale above
Mirror and mechanical displacement platform realize observation in real time and accurate adjustment;And for nanoscale, optical microscopy is had been unable to meet point
Resolution requirement, can only carry out under an electron microscope.
(3) measurement of breakdown process electrical signal parameter.During dc breakdown, the magnitude of prebreakdown current is generally in skin
Peace and Naan are horizontal, and the magnitude of breakdown current is generally more than milliampere level, and therefore, it is necessary to establish weak current and arteries and veins respectively
Current measurement circuit is rushed, realizes the precise measurement of electric signal parameter.
Summary of the invention
It is an object of the invention to the electrology characteristics and breakdown Mechanism Study for nanoscale vacuum gap, provide one kind
Nano vacuum gap breakdown characteristic experimental apparatus and method based on FIB-SEM double-beam system, it is above-mentioned in macro-scale to overcome
Technological deficiency present in vacuum breakdown research, the present invention can be realized the add in-place including micro/nano-scale metal electrode system
Work, the control of nanoscale vacuum gap, the feed-in of high-voltage signal, the measurement of electricity parameter and the original position point of electrode pattern
Analysis receives scale vacuum breakdown rule for further investigation and insulation characterisitic provides strong technical support.
In order to achieve the above objectives, the present invention adopts the following technical scheme:
Receive what scale vacuum gap punctured based on focused ion beam (FIB)-scanning electron microscope (SEM) double-beam system
Electrology characteristic test device, including FIB-SEM double-beam system, FIB-SEM double-beam system is by focused ion beam (FIB) and scanning electricity
Sub- microscope (SEM) composition, FIB-SEM double-beam system, which is tested, places micro/nano-scale electrode system, micro/nano-scale electrode in cavity
System includes the five axis sample stages and nano-manipulation instrument testing electrode and being attached thereto, and micro/nano-scale electrode system passes through current limliting
Resistance and voltage and current test circuit connection, and voltage and current test circuit includes high-voltage electricity potential source and weak current measuring unit,
Pulses of current sensor passes through test loop and connect with oscillograph, and oscillograph and voltage and current test circuit are connected with computer
Carry out the record of test data.
Further, FIB-SEM double-beam system is the Helios Nanolab 600i model of FEI Co., scanning electron
Microscopical minimum space resolution ratio is 0.9nm;The minimum space resolution ratio of its focused ion beam is 2nm.
Further, nano-manipulation instrument is the MM3A-EM model of Kleindiek Nanotechnik company, displacement essence
Degree is 5nm, and maximum withstanding voltage is 100V.The insulation adapter unit and test electrode phase that nano-manipulation instrument passes through polytetrafluoroethylene (PTFE)
Even, guarantee electrode and manipulate the electric insulation of instrument, maximum withstanding voltage can be promoted to ± 1000V.
Further, voltage and current test circuit is made of Keithley 6517B electrometer.
Further, voltage and current test circuit high-voltage electricity potential source direct voltage output range be -1000V~+
1000V, the current measuring range of weak current measuring unit are 1pA-20mA.
Further, pulses of current sensor is 6585 type Rogowski coil of Pearson composition, with oscillograph
The waveform measurement of breakdown current is realized in cooperation.
Further, the maximum frequency response of pulses of current sensor is 200MHz, and current measurement susceptibility is 0.5V/A
(50 ohm of characteristic impedance)
Further, test electrode is metal tungsten electrode, and the smallest needle point radius of curvature is 15nm, total length 5mm.
Based on FIB-SEM double-beam system receive scale vacuum gap breakdown electrology characteristic test method, using above-mentioned
Electrology characteristic test device, comprising the following steps:
Step 1: the opposite position of nano-manipulation instrument and five axis sample stages is adjusted under the home position observation of scanning electron microscope
It sets, adjusts the gap between two test electrodes;
Step 2: circuit is tested by voltage and current and is boosted step by step to test electrode according to the speed of 1V/s, simultaneously
Using voltage and current test circuit measuring and the electric current in circuit is recorded, obtains its current-voltage change curve;
Step 3: continuing to boost step by step until vacuum gap punctures, and test electrode both end voltage is rapid at this time
It reduces, loop current rises rapidly, and the electric current at breakdown moment is measured and recorded using pulses of current sensor, and record and survey at this time
That tries electrode both ends applies the breakdown voltage that voltage is the vacuum gap;
Step 4: step 1 is repeated to step 3, continues the length for adjusting two test electrode gaps, then measurement obtains
Current-voltage change curve and breakdown current and breakdown voltage under the conditions of different vacuum gaps.
Compared with prior art, the invention has the following beneficial technical effects:
The present invention can be realized first receive scale electrode gaps it is real-time observation and adjusting: by nano-manipulation instrument and five axis
Sample stage is connected with test electrode, by adjusting nano-manipulation instrument and five axis samples under the home position observation of scanning electron microscope
The relative position of sample platform, may be implemented the control of accurate reliable test electrode spacing, error range in 3.0nm or so,
The secondary present invention can be realized receive scale discharge breakdown during electricity parameter measuring technology: the device, which can be obtained accurately, receives scale
Electric current and voltage when the prebreakdown and breakdown of vacuum gap, and in the breakdown process of vacuum gap, since discharge time is general
In nanosecond order, so that discharge process is difficult to be observed, which can measure the voltage and current waveform of breakdown instantaneous process,
Finally present invention firstly provides based on super-resolution micro-imaging technique, piezoelectric nano shift technique, weak current measurement etc.
The scale vacuum gap of receiving of technology punctures experimental system in situ.The shape for the vacuum gap that the present invention can be realized from 20nm to 1 μm
At and corresponding high voltage test and weak current measurement function, for further investigation receive scale vacuum breakdown rule and insulation it is special
Property strong technical support is provided.
The method of the present invention uses above-mentioned apparatus, is based on super-resolution micro-imaging technique, the displacement of multi-degree-of-freedom nanometer scale
Technology and micro/nano-scale electrode fabrication realize and receive the electrology characteristic research of scale vacuum gap, receive scale for research
The intrinsic rule of the electric discharge of vacuum gap and physical mechanism have important Technical Reference.
Specific embodiment
Present invention is further described in detail below:
Nano vacuum gap breakdown characteristic experimental apparatus based on FIB-SEM double-beam system, including FIB-SEM double-beam system
Micro/nano-scale electrode system 4, the nanometer of micro/nano-scale electrode system 4 are provided in the experiment cavity of 1, FIB-SEM double-beam system 1
Manipulation instrument 7 and five axis sample stages 6 are connected separately with a test electrode 5, and two test electrodes 5 pass through 8 He of current-limiting resistance respectively
Pulses of current sensor 12 is connect with voltage and current test circuit 9, and pulses of current sensor 12 passes through voltage and current and tests circuit 9
And connect with oscillograph 13, oscillograph 13 and voltage and current test circuit 9 be connected with computer 14 progress test data record.
FIB-SEM double-beam system 1 is the Helios Nanolab 600i model of FEI Co., scanning electron microscope 3
Minimum space resolution ratio be 0.9nm;The minimum space resolution ratio of its focused ion beam 2 is 2nm;Micro/nano-scale electrode system 4
Including nano-manipulation instrument 7, five axis sample stages 6 and test electrode 5, while selecting polytetrafluoroethylene (PTFE) (PTFE) as nano-manipulation instrument
Insulation adapter unit 15 between 7 and test electrode 5, improves the high pressure circuit portion of nano-manipulation instrument 7, passes through increase
External high-tension line replaces original circuit, guarantees the electric insulation of test electrode 5 and nano-manipulation instrument 7, can bear highest
For the voltage of ± 1kV, nano-manipulation instrument 7 is the MM3A-EM model of Kleindiek Nanotechnik company, displacement accuracy
For 5nm, voltage and current test circuit 9 is made of Keithley 6517B electrometer, the voltage output model of high-voltage electricity potential source 10
It encloses for -1000V~+1000V, the current measuring range of weak current measuring unit 11 is 1pA-20mA, pulse current sensing
Device 12 is Pearson6585 type Rogowski coil composition, and the waveform measurement for realizing breakdown current is cooperated with oscillograph 13,
The maximum frequency response of pulses of current sensor 12 is 200MHz, and current measurement susceptibility is (50 Europe of characteristic impedance 0.5V/A
Nurse), test electrode 5 be metal tungsten electrode, respectively by mechanical lapping, twin-jet electropolishing polishing, FIB ion milling and etc. realization
Nanoscale tests the preparation of electrode, the obtained minimum 15nm of eletrode tip radius of curvature;Utilize electrochemical corrosion and joule
Hot melt can prepare the clean surface that radius is 3 μm~20 μm, the hemisphere electrode structure of regular shape.
It is specifically used the following steps are included:
(1) by mechanical lapping, twin-jet electropolishing polishing, FIB ion milling and etc. complete nanoscale tungsten needle electrode
Preparation;
(2) preparation of micro-meter scale ball electrode is completed by electrochemical corrosion and joule hot melt;
(3) by adjusting the opposite of nano-manipulation instrument 7 and five axis sample stages 6 under the home position observation of scanning electron microscope
Position is realized and receives the real-time regulation and control of scale gap;
(4) it is carried out step by step by 10 pairs of the high-voltage electricity potential source test electrodes 5 of Keithley 6517B according to the speed of 1V/s
Boosting, while using the electric current in the measurement of the weak current measuring unit 11 of Keithley 6517B and record circuit, obtain it
Current-voltage change curve (I-V curve);
(5) continue to boost step by step until vacuum gap punctures, electrode both end voltage reduces rapidly at this time, circuit
Electric current rises rapidly, and the electric current at breakdown moment is measured and recorded using pulses of current sensor 12, and record electrode both ends at this time
Apply voltage be the vacuum gap breakdown voltage;
(6) step (3) are repeated, continues the length for adjusting vacuum gap, measurement obtains the I-V under the conditions of different vacuum gaps
The physical parameters such as change curve, breakdown voltage and breakdown voltage.
The processing technology of preparing of present invention realization micro/nano-scale electrode system: the preparation of nanoscale electrode is realized, is obtained
The tungsten needle electrode of the minimum 15nm of eletrode tip radius of curvature arrived.And mature technology of preparing is formed, radius can be prepared
For the hemisphere electrode structure of 3 μm~20 μm of clean surfaces, regular shape, and avoid well oxygen molecule, hydrone, with
And the pollutant effects such as granulometric impurity, meet the needs of receiving scale gap electrology characteristic.
The present invention realize receive scale electrode gaps it is real-time observation and adjust: by Kleindiek-MM3A nano-manipulation instrument
And the sample stage in double-beam system is connected with micro/nano-scale electrode, by adjusting nanometer behaviour under the home position observation of scanning electron microscope
The control of accurate reliable electrode spacing may be implemented in the relative position of vertical instrument and sample stage, and error range is on the left side 3.0nm
It is right.
The present invention, which realizes, receives the measuring technology of electricity parameter during scale discharge breakdown: the device, which can be obtained accurately, receives ruler
Electric current and voltage when spending the prebreakdown and breakdown of vacuum gap, and in the breakdown process of vacuum gap, due to discharge time one
As in nanosecond order so that discharge process is difficult to be observed, which can measure the voltage and current wave of breakdown instantaneous process
Shape.
Present invention firstly provides surveyed based on super-resolution micro-imaging technique, piezoelectric nano shift technique, weak current
The scale vacuum gap of receiving of the technologies such as amount punctures experimental system in situ.The system can be realized the original position of micro/nano-scale metal electrode
The function of processing, the formation of the vacuum gap from 20nm to 1 μm and corresponding high voltage test and weak current measurement.
Operating process of the invention is described in detail with reference to the accompanying drawing:
It is special that scale vacuum gap electricity is received based on focused ion beam (FIB)-scanning electron microscope (SEM) double-beam system
System safety testing device, as shown in Figure 1, including FIB-SEM double-beam system 1, FIB-SEM double-beam system 1 is by focused ion beam 2 (FIB)
It is formed with scanning electron microscope 3 (SEM), is tested in FIB-SEM double-beam system 1 and place micro/nano-scale electrode system 4 in cavity,
Micro/nano-scale electrode system 4 includes the five axis sample stages 6 and nano-manipulation instrument 7 testing electrode 5 and being attached thereto, in scanning electricity
The regulation and control for the vacuum gap that achievable minimum clearance distance is 20nm under the real-time observation of sub- microscope 3, nano-manipulation
Instrument 7 is connected by the insulation adapter unit 15 of polytetrafluoroethylene (PTFE) with test electrode 5, is guaranteed electrode and is manipulated the electric insulation of instrument,
Maximum withstanding voltage can be promoted to ± 1000V, as shown in Figure 2.Micro/nano-scale electrode system 4 passes through current-limiting resistance 8 and voltage
Current testing circuit 9 connects, and it includes high-voltage electricity potential source 10 and weak current measuring unit 11, high pressure that voltage and current, which tests circuit 9,
The voltage output range of voltage source 10 is -1000V~+1000V, and the current measuring range of weak current measuring unit 11 is 1pA
~20mA, pulses of current sensor 12 pass through test loop and connect the waveform measurement for realizing breakdown current with oscillograph 13, show
Wave device 13 and voltage and current test circuit 9 are connected with computer 14 carries out the record of test data.
Nano vacuum gap breakdown characteristic experimental apparatus based on FIB-SEM double-beam system, specifically includes the following steps:
(1) tungsten is chosen as electrode material, passes through mechanical lapping, twin-jet electropolishing polishing, FIB ion milling etc. respectively
Step completes the preparation of nanoscale tungsten needle electrode, the obtained minimum 15nm of eletrode tip radius of curvature.It is specific former
Position processing method is as follows:
1) mechanical lapping: by abrasive paper for metallograph grinding by length be 4mm, diameter be 0.5mm tungsten wire be machined to a thickness of
100 μm of thin slices below;
2) twin-jet electropolishing: preparing corresponding electrolytic solution (NaOH solution that concentration is 2mol/L), double by magnetic drive
Boost electrolysis thinner carries out electrolysis to the tip portion of thin tungiten plate and is thinned, and is formed with a thickness of 10 μm of samples below (in such as Fig. 3
(a) shown in);
3) FIB roughing: the good tungsten thin slice of twin-jet electropolishing is fixed on FIB sample stage, uses larger ion beam first
It flows (21nA) and processes generation width less than 5 μm on its top, the rectangular segment (in Fig. 3 shown in (b)) that length is about 10 μm, then
Gradually flowing away cutting formation width with 6.5nA, 2.8nA or smaller ion beam is in 5 μm of rectangular segments such as Fig. 3 below
(c) shown in;
4) FIB retrofit: continuation gradually reduces ion beam line, and (wherein cut mode uses CIRCLE mode, line
Can be required according to tip dimensions and process time selects) needle point for forming needle point radius of curvature 15nm or so is cut, in Fig. 3
(d) shown in.
(2) micro-meter scale ball electrode is prepared by electrochemical corrosion and joule hot melt, and preparation process is divided into two ranks
Section.
1) first stage by electrochemical etching method by the tungsten needle that diameter is 0.5mm be thinned to diameter be 50nm~
The pyramidal structure of 200nm, in Fig. 4 shown in (a);Although tungsten tip is provided with nanoscale curvature after electrochemical corrosion
Radius, but pass through further elemental composition and analyze, find the surface of tungsten tip there are considerable impurity, surface there is also
Etch pit not of uniform size is unable to satisfy the demand of fine nano gap realized and controlled, it is therefore desirable to further add
Work and processing.
2) second stage uses joule hot melt.It is above-mentioned 1) obtained in apply in tungsten needle certain DC voltage (3V~
10V), under the action of nano-manipulation instrument that two tungsten needles are slowly close, when its gap is reduced to a certain value (generally in sub-nanometer
Rank) when two electrodes between puncture, the short circuit current in circuit gap location generate amount of heat, so as to cause tungsten needle tip
It is partially melting to form molten state.Under the driving of liquid metal surface energy, the tungsten after fusing is to reach surface minimum energy
State and final cooled and solidified is hemisphere, and then obtain the ball electrode that radius of curvature is 3 μm~20 μm, (b) institute in Fig. 4
Show.
(3) tungsten electrode that above-mentioned (1) and (2) are prepared is separately mounted to nano-manipulation instrument 7 and five axis sample stages 6,
Under the real-time observation of scanning electron microscope 3, the X, Y, Z, θ, Tilt of nano-manipulation instrument 7 and five axis sample stages 6 are adjusted separately
Direction, two test electrodes 5 are mutually slowly close.When the distance of two electrodes reaches 1 μm, increase the amplification factor of SEM, reduces
The displacement step-length of nano-manipulation instrument 7 realizes that minimum range is the control of the vacuum gap of 20nm by the displacement of nano-manipulation instrument 7
System.
(4) it when vacuum gap distance reaches requirement, is programmed by LabVIEW and realizes Keithley6517B high tension voltage
The boosting step by step of the 1V/s in source 10, while the real-time measurement that its weak current measuring unit 11 completes loop current is controlled, measurement
Frequency is 1 time/s, and draws I-V change curve automatically.It boosts step by step since 0V, until vacuum gap punctures, this
When breakdown voltage can be read by I-V curve, breakdown current can by pulses of current sensor 12 measure obtain.Meanwhile
The electrode surface shape characteristic of breakdown front and back is characterized also by scanning electron microscope 3.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, it is not used to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.