CN108588677A - A kind of nano-stack dielectric film of high-k and preparation method thereof - Google Patents

A kind of nano-stack dielectric film of high-k and preparation method thereof Download PDF

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CN108588677A
CN108588677A CN201810348501.7A CN201810348501A CN108588677A CN 108588677 A CN108588677 A CN 108588677A CN 201810348501 A CN201810348501 A CN 201810348501A CN 108588677 A CN108588677 A CN 108588677A
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毕晓昉
李进
徐策
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Beihang University
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Abstract

The invention discloses nano-stack dielectric films of a kind of high-k and preparation method thereof, belong to dielectric film material technical field.The present invention controls the technological parameter of growth by the method for ALD deposition, and all very low material of two kinds of dielectric constants itself is combined in the form of nano-stack, using the charge polarization effect of interface, can obtain the promotion of tens times of dielectric constant;Nano-stack dielectric film material provided by the invention includes buffer layer, (a ZnO/b Al2O3)nThe electric charge barrier layer of nano-stack and top electrode has the advantages that size is small, dielectric constant is high, working frequency is high.

Description

A kind of nano-stack dielectric film of high-k and preparation method thereof
Technical field
The present invention relates to dielectric film material technical field more particularly to a kind of high-k, high working frequency, low damages Ultrathin nanometer laminated dielectric film of consumption and preparation method thereof.
Background technology
Material with high-k suffers from extensively in capacitor, memory and logical device, energy storage etc. Application.As the material of insulated gate electrode in the transistor for constituting electronics industry basis, they usually decide entire electronics device The part even performance of system.Along with being increasingly miniaturized for process, semi-conductor industry is for super with high-k Thin dielectric film material has very strong demand.The hot spot that high dielectric thin film material is current research is prepared, is helped In the grid for going to solve to occur in transistor miniaturization process by material to effective control area reduction of conducting channel and crystalline substance The problem of switching characteristic of body pipe declines.But due to being limited by material, structure and preparation process etc., single material Material is difficult with requirements such as high-k, small size, high working frequencies.Common high dielectric ceramic material is difficult to be made full Foot is using the ultrathin film needed, and the dielectric constant of high molecular material is too low, also cannot be satisfied and uses needs.
Nano-stack dielectric material is a kind of laminated film being made of semiconductor and insulator, is based on Maxwell- Wagner effects (i.e. Maxwell Wagner effect), the removable charge in semiconductor move to it under the action of an external electric field Interface is polarized, and electric dipole moment is generated.More laminated construction can provide a large amount of interfaces for charge polarization, greatly promote Jie of material Electric constant.But still having problems with influences it as high-performance dielectric material application.First, it has reported in lamination system Polarization charge is mostly ion, and migration pattern is greatly influenced by temperature based on hot activation, it is difficult in extraneous variation of ambient temperature In the case of steady operation;Secondly, well below the speed of electron transfer, interface has the ionic charge mobility of hot activation form Effect polarization charge number can drastically decline as frequency increases, and limit its response speed under external electric field, therefore such folded Layer structure can not maintain high dielectric constant stable to high frequency.
Invention content
The present invention is big in order to solve existing dielectric material size, dielectric constant and the low problem of working frequency, it is proposed that one High-k nano-stack dielectric film and preparation method thereof of the kind based on interface electronic polarization mechanism, the present invention is two kinds The all very low material (dielectric constant of dielectric constant itself:Al2O3=9;ZnO=8.66 it) is combined in the form of nano-stack, Using the electron charge polarity effect of interface, the promotion of tens times of dielectric constant can be obtained;And then a kind of ruler can be obtained Very little high-performance nano laminated dielectric thin-film material small, dielectric constant is high, working frequency is high.The present invention passes through ALD (Atomic Layer Deposition) deposition method, control the technological parameter of growth, prepare a series of difference Al2O3/ ZnO sublayers are thick Degree and proportional amount of nano-stack, specific preparation method include the following steps:
Step 1:Surface preparation is carried out to substrate.
The surface preparation refers to:20min is ultrasonically treated in acetone first, then in deionized water at ultrasound 20min is managed, then is ultrasonically treated 20min in ethanol, nitrogen gun drying.
The substrate is the Si substrates that single side is coated with that thickness is 150nm Pt metal layers.
Step 2:Substrate after surface preparation is put into ALD growth chambers, by deionized water, diethyl zinc (DEZn) With the source bottle of trimethyl aluminium (TMA) growth chamber is accessed by three access gas circuits.Using N2Carrier gas, and carrier gas flux is adjusted to 20Sccm, cleans the access gas circuit of the diethyl zinc (DEZn) and trimethyl aluminium (TMA), and growth chamber vacuumizes.
Step 3:150 DEG C are heated to growth chamber;Wait for that temperature is stablized, growth chamber air pressure is down to 5 × 10-1Torr with Under, it is ready for depositing.
Step 4:Using trimethyl aluminium as source, deionized water is oxidant, and the Al of 5nm thickness is deposited on the Pt layers of substrate2O3 Electric charge barrier layer as buffer layer and hearth electrode.
Step 5:Using diethyl zinc as source, then deionized water is waited for as oxidant, the ZnO sublayers of deposition thickness a 200-300s。
Step 6:Using trimethyl aluminium as source, deionized water is oxidant, the Al of deposition thickness b in ZnO sublayers2O3Son Layer waits for 200-300s.
Step 7:Step 5 is repeated to step 6, repeatedly after lamination n times, obtaining group becomes (a-ZnO/b-Al2O3)nNanometer Lamination.
Step 8:The Al of 5nm thickness is deposited on nano-stack prepared by step 72O3Electric charge barrier layer as top electrode; Obtain the nano-stack dielectric film of the high-k of the present invention.
The nano-stack dielectric film that above-mentioned preparation method is prepared includes the buffer layer being sequentially prepared in substrate, (a- ZnO/b-Al2O3)nThe electric charge barrier layer of nano-stack and top electrode, n are the positive integer more than or equal to 1.Wherein Al2O3For amorphous State, ZnO sublayers are the hexagonal wurtzite structure for keeping (002) to be orientated, (a-ZnO/b-Al2O3)nZnO sublayers are thick in nano-stack Spend a, Al2O3Molecular layers thick b, the periodicity n of nano-stack and mutual ratio a/b are adjustable.Key is to need to prepare with good The laminated construction at interface.Its relative dielectric constant is in 120-700, and cutoff frequency is 102To more than 106Hz。
In preferred nano-stack, ZnO molecular layers thicks a is in 0.8~4nm, Al2O3Molecular layers thick b is at 0.4~2nm, interface Stand-by period 300s.Relative dielectric constant is 250~700, and cutoff frequency is 103To more than 106Hz.The periodicity n can root It is chosen according to required dielectric thickness.
The advantage of the invention is that:
1. nano-stack dielectric film prepared by the present invention has high dielectric constant and working frequency.
2. the size of the overall dimensions very little of nano-stack, entire nano-stack dielectric film can be as small as nanoscale.
3. passing through modulation process parameter, it may be convenient to be accepted or rejected, be obtained between relative dielectric constant and working frequency Obtain the nano-stack dielectric film of a kind of high-k with extensive use.
Description of the drawings
Fig. 1 is the nano-stack dielectric film structural schematic diagram of high-k prepared by the present invention;
Fig. 2 is the images of transmissive electron microscope in nano-stack dielectric film section prepared by the present invention;
Fig. 3 is the dielectric constant and fissipation factor frequency spectrum of embodiment 1 and comparative example 1;
Fig. 4 is the dielectric constant and fissipation factor frequency spectrum of embodiment 2-6.
Fig. 5 is the dielectric constant and fissipation factor frequency spectrum of embodiment 7-12.
Specific implementation mode
The present invention is described in detail with reference to the accompanying drawings and examples.
The present invention provides a kind of preparation method of the nano-stack dielectric film of high-k, is as follows:
Step 1:Surface preparation is carried out to substrate:It is ultrasonically treated 20min in acetone first, then in deionized water It is ultrasonically treated 20min, then is ultrasonically treated 20min in ethanol, nitrogen gun drying.
The substrate is to be coated with the Si substrates of 150nm Pt metals.
Step 2:9100 atomic layer deposition systems of nanosecond science and technology LabNano are made using English, substrate is put into ALD growth chambers The source bottle of deionized water, diethyl zinc (DEZn) and trimethyl aluminium (TMA) is respectively connected to 1,2, No. 3 access gas circuit, access by room Gas circuit is connected to growth chamber by vent line.Open the N of ALD system2Carrier gas gas circuit, and carrier gas flux is adjusted to 20Sccm; It opens ALD system and cleans No. 2 and No. 3 access gas circuits, vacuumize.
Step 3:150 DEG C are heated to growth chamber;Wait for that temperature is stablized, growth chamber air pressure is down to 5 × 10-1Torr with Under, it is ready for depositing.
Step 4:Using trimethyl aluminium as source, deionized water is oxidant, the deposition 5nm thickness in the Pt layers side of substrate Al2O3Electric charge barrier layer as buffer layer and hearth electrode.Al2O3Growth is formulated:0.5 second-the waiting 40 of pulse trimethyl aluminium 0.5 second-waiting of second-pulse deionized water 40 seconds.It repeats the above process 50 times, each pulsed deposition thickness is about 0.1nm.This hair Bright middle depositing Al2O3Shi Jun takes above-mentioned formula.
Step 5:Using diethyl zinc as source, for deionized water as oxidant, deposition thickness is the ZnO sublayers of a.ZnO is grown Formula is:Pulse diethyl zinc 0.05 second-waiting for 20 seconds-pulse deionized water 0.05 second-waiting 20 seconds.Each deposition thickness is about For 0.2nm.Above-mentioned formula is taken when depositing ZnO in the present invention.Then 200-300s is waited for.
Step 6:It is formulated using described in step 4, deposition thickness is the Al of b2O 3Sublayer waits for 200-300s.
Step 7:It repeats step 5 and obtains (a-ZnO/b-Al repeatedly after the n period of lamination to step 62O3)nNanometer is folded Layer.
Step 8:In (the a-ZnO/b-Al2O3)nThe Al of 5nm thickness is deposited on nano-stack2O3Electricity as top electrode Lotus barrier layer.The same step 4 of deposition process.
The typical structure of the nano-stack dielectric film that above-mentioned preparation method is prepared as shown in Figure 1, on the base layer according to Secondary preparation has buffer layer (and electric charge barrier layer), (a-ZnO/b-Al2O3)nNano-stack, electric charge barrier layer, the buffer layer For alumina layer, thickness 5nm;The electric charge barrier layer is alumina layer, thickness 5nm.(the a-ZnO/b- Al2O3)nIn nano-stack, the value range of a is 0.4-4nm, and the value range of b is 0.4-3nm.The nano-stack dielectric The relative dielectric constant of film is in 120-700, and cutoff frequency is 102To more than 106Hz。
From Figure 2 it can be seen that Al2O3For amorphous state, ZnO sublayers are the hexagonal wurtzite structure for keeping (002) to be orientated.Wherein, ZnO sublayers and Al2O3Molecular layers thick a and b and its mutual ratio a/b are adjustable, and the lamination period, n was according to required dielectric thickness It chooses.Key is to need to prepare the laminated construction with good interface.
Embodiment 1
1nm-ZnO/1nm-Al is prepared using method provided by the invention2O3Nano-stack film, specific process step is such as Under:
Step 1:Substrate is surface-treated:It is ultrasonically treated 20min in acetone first, then surpasses in deionized water Sonication 20min, then it is ultrasonically treated 20min in ethanol, nitrogen gun drying.
The substrate is to be coated with the Si substrates of 150nm Pt metal layers.
Step 2:Substrate is put into ALD growth chambers, by deionized water, diethyl zinc (DEZn) and trimethyl aluminium (TMA) Source bottle connect vent lines by three access gas circuits respectively after access the growth chamber.Open the N of ALD system2It carries Gas gas circuit, and carrier gas flux is adjusted to 20Sccm;It opens ALD system and cleans the diethyl zinc (DEZn) and trimethyl aluminium (TMA) access gas circuit, vacuumizes.
Step 3:150 DEG C are heated to growth chamber and vent line;Waiting for that temperature is stablized, growth chamber air pressure is down to 5 × 10-1Torr is hereinafter, be ready for depositing.
Step 4:Using trimethyl aluminium as source, deionized water is oxidant, in the Al of deposition on substrate 5nm thickness2O3As slow Layer is rushed, the buffer layer is also the electric charge barrier layer of hearth electrode.
Step 5:Using diethyl zinc as source, deionized water deposits the ZnO sublayers of 1nm thickness, then waits for as oxidant 300s。
Step 6:Deposit the Al of 1nm thickness2O3Sublayer waits for 300s.
Step 7:Step 5 is repeated to step 6,80 times repeatedly, obtains a-ZnO/b-Al2O3Nano-stack, wherein a are 1nm, b 1nm, periodicity n are 80.
Step 8:In aZnO/bAl2O3Continue the Al of deposition 5nm thickness on nano-stack2O3Charge barrier as top electrode Layer, obtains the nano-stack dielectric film of 170nm thickness.The composition of the nano-stack dielectric film is expressed as (5nm- Al2O3)-(1nm-ZnO/1nm-Al2O3)80-(5nm-Al2O3)。
Prepared (1nm-ZnO/1nm-Al2O3)80The dielectric properties of nano-stack as shown in figure 3, as seen from the figure, Relative dielectric constant is 350, and cutoff frequency is 104-105Between Hz.Loss value is less than 0.1 under low frequency, and peak loss is less than 0.4. The relative dielectric constant of nano-stack dielectric film is far longer than its single component A l2O3(9) and ZnO (8.66) respective dielectric Constant, amplification reach 40 times.Being obviously improved for this dielectric constant is the Maxwell-Wagner effects brought due to interfacial polarization Caused by answering.As a comparison, it is prepared for the single phase solid solution 0.2nm-ZnO/0.2nm- that there is identical component ratio with embodiment 1 Al2O3
Comparative example 1
0.2nm-ZnO/0.2nm-Al is prepared using method provided by the invention2O3Nano-stack, specific process step is such as Under:
Step 1:Substrate is surface-treated, is ultrasonically treated 20min in acetone first, then surpass in deionized water Sonication 20min, then it is ultrasonically treated 20min in ethanol, nitrogen gun drying.
The substrate is the Si substrates for being coated with 150nm Pt metals.
Step 2:Substrate is put into ALD growth chambers, by deionized water, diethyl zinc (DEZn) and trimethyl aluminium (TMA) Source bottle be respectively charged into 1,2, No. 3 gas circuit.Open the N of ALD system2Carrier gas gas circuit, and carrier gas flux is adjusted to 20Sccm;It opens ALD system cleans gas circuit, vacuumizes.
Step 3:Closed in 2, No. 3 gas circuit hand-operated valves, use respectively 2, No. 3 gas circuits of 0.3s burst lengths pair into Row degasification operates, and is repeated 10 times.150 DEG C are heated to chamber and vent line.Wait for that temperature is stablized, chamber pressure is down to 5 × 10- 1Torr is hereinafter, be ready for depositing.
Step 4:Using trimethyl aluminium as source, deionized water is oxidant, in the Al of deposition on substrate 5nm thickness2O3Layer conduct The electric charge barrier layer of buffer layer and hearth electrode.
Step 5:Using diethyl zinc as source, deionized water deposits the ZnO sublayers of 0.2nm thickness as oxidant, then etc. Wait for 300s.
Step 6:Deposit the Al of 0.2nm thickness2O3Sublayer waits for 300s.
Step 7:Step 5 is repeated to step 6, repeatedly after 400 times, obtains the nano-stack film of 160nm thickness, group As 0.2nm-ZnO/0.2nm-Al2O3
Step 8:The Al of deposition 5nm thickness is put on film2O3Layer is used as top electrode and electric charge barrier layer.
Prepared (0.2nm-ZnO/0.2nm-Al2O3)400The dielectric properties of nano-stack are as shown in Figure 3.It can see Go out, compared with embodiment 1, the nano-stack preparation process in this example, component ratio, overall thickness is completely the same.The difference is that Element thickness is kept to original 20%, can not form two-phase laminated construction, but exists in the form of single phase solid solution, without interface Presence.It can be seen that dielectric constant is down to the 20% of embodiment 1, illustrate the high-k of nano-stack mainly by boundary Caused by charge polarization at face.
To probe into ZnO and Al2O3Thickness changes the affecting laws of dielectric properties using 1 identical preparation process of embodiment Become technological parameter, carries out ZnO/Al2O3The preparation of nano-stack dielectric film, probes into Al respectively2O3Sublayer and ZnO sublayers are to receiving The influence of rice laminated dielectric thin-film dielectric performance, specific process parameter are as follows:
The different embodiments of table 1 prepare technological parameter (the zinc oxide film thickness 1nm, change Al of nano-stack2O3Layer thickness)
The different embodiments of table 2 prepare the technological parameter (changing ZnO layer thickness) of nano-stack
Pass through the ZnO/Al to the above-mentioned different technical parameters being prepared2O3Nano-stack dielectric film is tested, and is obtained It is as shown in Figure 4 and Figure 5 to dielectric properties test result.In embodiment 2 to embodiment 6, fixed ZnO molecular layers thicks a=1nm is not Become, changes Al2O30.4~3.0nm of layer thickness, it can be seen that with Al2O3Layer thickness increases, and cutoff frequency takes the lead in subtracting after increasing It is small, in Al2O3Thickness reaches maximum value when being 1.4nm.This is because nano-stack dielectric film is to be based on Maxwell-Wagner Effect, carrier moving to its interface, which generates, under the action of an external electric field polarizes.Work as Al2O3When sublayer is too thin, adjacent ZnO layer it Between carrier tunnelling probability increase, Al2O3Layer can not effective trapped carrier, and make its interface polarize;Work as Al2O3Son It is again too strong to the quantum confinement of carrier in ZnO layer when layer is too thick, carrier effective mass can be caused to increase, reduce it Rate transition also results in cutoff frequency decline.The dielectric constant of nano-stack is then with Al2O3Molecular layers thick reduces and increases Add.This is because working as Al2O3When sublayer is thicker, under conditions of overall thickness is constant, carrier population in lamination and for The interface of charge polarization can all be reduced, and dielectric constant is caused to decline.But it should be noted that and maintain in nano-stack structure Al2O3Sublayer has to be larger than a minimum thickness (0.4nm).Work as Al2O3When molecular layers thick is less than this minimum value, entirely Nano-stack structure is unable to maintain that, Maxwell-Wagner effects is caused to disappear, and relative dielectric constant can decline suddenly.Meanwhile Al2O3When sublayer is too thin, loss can also dramatically increase.Consider dielectric constant, the influence of cutoff frequency and fissipation factor, choosing Take Al2O3Molecular layers thick is 0.8nm.
In embodiment 7 to 11, fixed Al2O3Layer thickness is 0.8nm, changes ZnO layer thickness.It can from test result It arrives, with the increase of ZnO molecular layers thicks, cutoff frequency occurs first increasing the changing rule reduced afterwards, and is obtained most at 3nm Big value.When ZnO sublayers are too small, quantum confinement will increase the effective mass of carrier, and rate transition is caused to decline, cutoff frequency It reduces;And when ZnO molecular layers thicks are excessive, carrier needs the distance migrated elongated in relaxation.This also leads to its work frequency Rate declines rapidly.Meanwhile as ZnO molecular layers thicks increase, relative dielectric constant also occurs first increasing the variation rule reduced afterwards Rule obtains maximum value at 3nm.When ZnO molecular layers thicks be less than 0.8nm when, proportion is too small, cause carrier population compared with It is low, affect polarization effect and dielectric constant.Meanwhile when ZnO thickness is too small, nano-stack result is unable to maintain that, it is entire thin Film transition is the Al that single-phase Zn is adulterated2O3Film loses the addition effect that laminated film is brought in dielectric properties.And work as When ZnO molecular layers thicks are more than 3nm, the ZnO orientations of growth, which are gradually orientated from (002) to hybrid orientation, to be developed, and interface roughness increases, Layer-by-layer growth quality declines, and causes dielectric constant to increase with ZnO molecular layers thicks and slowly declines.Meanwhile ZnO sublayers are blocked up can also lead It sends a telegraph loss caused by leading to rise, influences the synthesis performance of film.
Consider the dielectric constant of film, loss and working frequency, works as Al2O3It is respectively 0.8 He with ZnO molecular layers thicks When 3.0nm, film has optimal dielectric properties.Low frequency relative dielectric constant is 450,105Hz or less losses are less than 0.1, work Working frequency is more than 106Hz.Meanwhile working as Al2O3Layer is between 0.4-2nm, when ZnO layer thickness is between 0.8-4nm, Maxwell- Wagner effects are notable, and dielectric constant increases significantly compared to the constituent element of nano-stack.Technique ginseng is adjusted within the scope of this Number, can be adjusted according to the needs the dielectric constant and working frequency of film.In general, the more high then working frequency of dielectric constant more It is low, it can be accepted or rejected as needed.

Claims (9)

1. a kind of preparation method of the nano-stack dielectric film of high-k, it is characterised in that:The preparation method includes Following steps:
Step 1:Surface preparation is carried out to substrate;
Step 2:Substrate after surface preparation is put into ALD growth chambers, by deionized water, diethyl zinc and trimethyl aluminium Source bottle pass through three access gas circuits access growth chambers;Using N2Carrier gas, and carrier gas flux is adjusted to 20Sccm, described in cleaning The access gas circuit of diethyl zinc and trimethyl aluminium, growth chamber vacuumize;
Step 3:150 DEG C are heated to growth chamber;Wait for that temperature is stablized, growth chamber air pressure is down to 5 × 10-1Torr is hereinafter, standard It is standby to be deposited;
Step 4:Using trimethyl aluminium as source, deionized water is oxidant, and the Al of 5nm thickness is deposited in substrate2O3As buffer layer;
Step 5:Using diethyl zinc as source, then deionized water waits for 200- as oxidant, the ZnO sublayers of deposition thickness a 300s;
Step 6:Using trimethyl aluminium as source, deionized water is oxidant, the Al of deposition thickness b in ZnO sublayers2O3Sublayer, etc. Wait for 200-300s;
Step 7:Step 5 is repeated to step 6, repeatedly after lamination n times, obtaining group becomes (a-ZnO/b-Al2O3)nNanometer is folded Layer;N is positive integer;
Step 8:The Al of 5nm thickness is deposited on nano-stack prepared by step 72O3Electric charge barrier layer as top electrode;It obtains Nano-stack dielectric film.
2. a kind of preparation method of the nano-stack dielectric film of high-k according to claim 1, feature exist In:Surface preparation described in step 1 refers to:It is ultrasonically treated 20min in acetone first, it is then ultrasonic in deionized water 20min is handled, then is ultrasonically treated 20min in ethanol, nitrogen gun drying.
3. a kind of preparation method of the nano-stack dielectric film of high-k according to claim 1, feature exist In:Substrate described in step 1 is the Si substrates that single side is coated with that thickness is 150nm Pt metal layers.
4. a kind of preparation method of the nano-stack dielectric film of high-k according to claim 1, feature exist In:Al described in step 4 and step 62O3Growth formula be:Pulse trimethyl aluminium 0.5 second-waiting, 40 seconds-pulse deionization 0.5 second-waiting of water 40 seconds;It repeats the above process until required thickness, each pulsed deposition thickness is 0.1nm.
5. a kind of preparation method of the nano-stack dielectric film of high-k according to claim 1, feature exist In:In step 5 in the preparation process of ZnO sublayers, ZnO growth formulas are:0.05 second-waiting, the 20 seconds-pulse of pulse diethyl zinc 0.05 second-waiting of deionized water 20 seconds;It repeats the above process until required thickness;Each deposition thickness is 0.2nm.
6. a kind of nano-stack dielectric film of high-k, it is characterised in that:The nano-stack dielectric film includes The buffer layer, (a-ZnO/b-Al being sequentially prepared in substrate2O3)nThe electric charge barrier layer of nano-stack and top electrode, n be more than Positive integer equal to 1;Wherein Al2O3For amorphous state, ZnO sublayers are the hexagonal wurtzite structure for keeping (002) to be orientated.
7. a kind of nano-stack dielectric film of high-k according to claim 6, it is characterised in that:Described receives The relative dielectric constant of rice laminated dielectric film is in 120-700, and cutoff frequency is 102Hz to 106Hz。
8. a kind of nano-stack dielectric film of high-k according to claim 6, it is characterised in that:Described ZnO molecular layers thicks a is in 0.8~4nm, Al2O3Molecular layers thick b is in 0.4~2nm.
9. a kind of nano-stack dielectric film of high-k described according to claim 6 or 7, it is characterised in that:It is described Nano-stack dielectric film relative dielectric constant 250~700, cutoff frequency is 103To 106Hz。
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