CN1831184A - Displacement ferroelectric super-lattice thin film material having stress-limiting layer and preparation method thereof - Google Patents
Displacement ferroelectric super-lattice thin film material having stress-limiting layer and preparation method thereof Download PDFInfo
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- CN1831184A CN1831184A CN 200510020476 CN200510020476A CN1831184A CN 1831184 A CN1831184 A CN 1831184A CN 200510020476 CN200510020476 CN 200510020476 CN 200510020476 A CN200510020476 A CN 200510020476A CN 1831184 A CN1831184 A CN 1831184A
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Abstract
The invention supplies displacement ferroelectric super lattice film material that has stress constraint layer and a manufacture method. The material structure includes basal piece, buffer layer, displacement ferroelectric super lattice film, and metal electrode. The film decreases dielectric loss by adding stress constraint layer, and the remnant polarization would be sharply increased. The invention adopts laser beam extending growth technology to grow buffer layer, displacement ferroelectric super lattice film, and stress constraint layer, using vacuum vaporizing technology coating metal electrode. The material of stress constraint layer is LaA103.
Description
Technical field
The invention belongs to the material technology field, particularly the low-dimensional electronic information material technical field of displacement ferroelectric superlattice film.
Background technology
The prerequisite that a kind of material has a ferroelectric properties is that its structure must be non-centrosymmetrical, promptly has a unique spontaneous polarization axle.As BaTiO
3In temperature is more than 120 ℃ the time, belongs to symmetric cube of phase, and this moment, it did not have ferroelectricity, but when temperature drops to below 120 ℃, BaTiO
3Belong to non-centrosymmetrical tetragonal phase structure, be typical ferroelectric material.
Ferroelectric material can be divided into the ferroelectric material of displacement type transformation and ferroelectric material two classes that orderly one unordered type changes by the micromechanism that changes mutually.The phase-change mechanism of displacement ferroelectric material is that same class ionic sublattice is with respect to the whole displacement of another kind of ionic sublattice in the material, and its representative materials is BaTiO
3, LiNbO
3And PbTiO
3Deng the double oxide that contains the oxygen octahedra structure.The displacement ferroelectric material is to use maximum class ferroelectric materials at present.Technical scheme of the present invention is mainly formulated at the displacement ferroelectric material.
Present blocky ferroelectric crystal study comparative maturity, and be widely used in fields such as transmitter, surface acoustic wave device, ferroelectric memory, second harmonic generator.But development along with microelectronics, requirement to device is more and more littler, storage density is more and more higher, so closely during the last ten years, ferroelectric membranc is developed rapidly, so that can combine, it is used widely in fields such as microwave monolithic integrated circuit, optical waveguides, microelectromechanical systemss with the integrated semiconductor technology.
Many materials are after size or film thickness reduce, its degradation or disappearance.Such as, generally speaking, when the thickness of ferroelectric membranc was reduced to a certain degree, its specific inductivity or remnant polarization reduced rapidly, and this has just greatly limited their application.Adapt to the requirement of microelectronics development for the device that ferroelectric thin-flim materials is made, the thickness that promptly requires ferroelectric thin-flim materials guarantees that again material has enough ferroelectric propertiess simultaneously in being reduced to certain degree (being generally the scope of ten nanometer scale), this is one of unsolved technical problem still in the prior art.
Because the existence at no symmetrical center is to guarantee on the structure that material has ferroelectric prerequisite, so one of method that improves its ferroelectric properties is the asymmetry that increases structure, the method for taking usually is to increase material strain to increase the asymmetric of material structure.The ferroelectric superlattice of low dimensional structures is exactly the lattice mismatch that utilizes two kinds of materials that constitute superlattice, produce strain, make film under ultrafine condition, still present that common bulk just has and electric property that general ferroelectric membranc does not possess, as very high specific inductivity or higher remnant polarization etc.Therefore, the research of ferroelectric superlattice has begun to be subjected to increasing concern, has become one of focus of present material technology area research.
But, adopt the ferroelectric superlattice technology can only improve the ferroelectric properties of ferroelectric membranc to a certain extent, can not guarantee that still it can use in industrial production; Moreover, because various ferroelectric materials under the same conditions, the performance difference that is presented is very big, as specific inductivity, remnant polarization and stored charge density etc., so the ferroelectric superlattice of different components material also exists very big difference on performance.At present, the more ferroelectric material of research has BaTiO
3, SrTiO
3, Pb is ferroelectric material and the stratiform ferroelectric material that contains Bi, the research of corresponding ferroelectric superlattice also mainly concentrates on the film that is made of these materials.But because the Pb element is volatile, poisonous, make that Pb is that ferroelectric superlattice is restricted on the one hand on using, seem very difficult when growing superlattice on the other hand, and BaTiO
3/ SrTiO
3The loss of superlattice is bigger always.Therefore how to reduce the wastage, improve polarizability, the ferroelectric superlattice practicability of low-dimensional is had great importance.
Summary of the invention
As previously mentioned, technical problem to be solved by this invention is exactly will solve after the thickness of displacement ferroelectric superlattice film is reduced to a certain degree (ten nanometer scale), how to guarantee that the displacement ferroelectric superlattice film still has the ferroelectric properties equal with bulk material, just to solve after the thickness of displacement ferroelectric superlattice film is reduced to a certain degree (ten nanometer scale), how improve the problem of self specific inductivity or remnant polarization.
The bright detailed technology scheme of we is: the displacement ferroelectric superlattice film material with stress limitation preparative layer, comprise substrate, buffer layer, displacement ferroelectric superlattice film and metal electrode on the structure, it is characterized in that between displacement ferroelectric superlattice film and metal electrode, also having one deck stress limitation preparative layer.
Because the effect of stress limitation preparative layer is that the strain that will produce in the ferroelectric superlattice is limited in the film, so require the crystalline network of the used material of stress limitation preparative layer should be similar with the crystalline network of displacement ferroelectric superlattice film layer material, and the lattice parameter of the material that the stress limitation preparative layer is used should be less than the lattice parameter of displacement ferroelectric superlattice film layer material, and the dielectric loss of material is low.The present invention selects LaAlO for use
3As the material of stress limitation preparative layer, because LaAlO
3Crystalline network and displacement ferroelectric superlattice film layer material (BaTiO
3, SrTiO
3Deng) crystalline network similar, and, LaAlO
3Be the dielectric material of a kind of low-k, low-dielectric loss, also have its dielectric properties less with temperature and frequency change.
In addition, the invention provides a kind of ferroelectric superlattice preparation methods with stress limitation preparative layer, concrete steps are as follows:
1, substrate surface planeness and surface clearness are handled;
2, adopt laser beam epitaxial growth technology, at first the buffer layer behind the about 5nm of substrate surface deposition one deck;
3, adopt laser beam epitaxial growth technology on buffer layer, to prepare the displacement ferroelectric superlattice film, specifically be to adopt intermittent type growth technology alternating growth, promptly grow behind the thin film, stop laser, give the surface certain thermal diffusion time, and then another layer film of growing, the intermittent time is determined according to material surface primitive unit cell thermal diffusion time.
4, behind the growth ferroelectric superlattice, under identical technology, growth one layer thickness is the stress limitation preparative layer of 5～6nm on the displacement ferroelectric superlattice film;
5, adopt vacuum evaporation technique evaporation metal electrode on the stress limitation preparative layer.
Unlike the prior art be that the present invention increases one deck stress limitation preparative layer between displacement ferroelectric superlattice film and metal electrode.Like this, this stress limitation preparative layer can make superlattice film strain at the interface more remain in the superlattice film effectively on the one hand, reduce its burst size, bigger strain increases the spontaneous polarization strength of superlattice film, thereby has strengthened the ferroelectric properties of superlattice film; The stress limitation preparative layer has also suppressed the diffusion of the atoms metal in the metal electrode in superlattice film on the other hand, has reduced the dielectric loss of superlattice film.Thereby obtained the ferroelectric superlattice material that remnant polarization is big, loss is little.
The present invention increases the stress limitation preparative layer between displacement ferroelectric superlattice and top electrode, and adopt dielectric loss little, with temperature and the little LaAlO of frequency change
3As this layer material, adopt RADIANT Precision LC 2000 ferroelectric test macros and TH2816 molded breadth LCR digital electric bridge frequently, dielectric and ferroelectric properties to ferroelectric superlattice are tested, found that to add the dielectric loss that has reduced film after the stress limitation preparative layer greatly its loss ratio same thickness, with the BaTiO of sampling technology growth
3/ SrTiO
3Superlattice and individual layer ferroelectric membranc BaTiO
3An all little order of magnitude, and the remnant polarization of ferroelectric superlattice increases nearly 40 times, and its ferroelectric hysteresis loop is seen accompanying drawing 2.
Description of drawings
Fig. 1 is the structural representation with ferroelectric superlattice material of stress limitation preparative layer, wherein: 1-substrate, 2-buffer layer, 3-ferroelectric superlattice, 4-stress limitation preparative layer, 5-metal electrode.
Fig. 2 is the influence of stress limitation preparative layer to the superlattice film ferroelectric properties, and wherein curve a is the ferroelectric hysteresis loop that the ferroelectric superlattice of stress limitation preparative layer is arranged, and curve b is the ferroelectric hysteresis loop that does not have the ferroelectric superlattice of stress limitation preparative layer.
Embodiment
Ferroelectric superlattice material with stress limitation preparative layer, substrate are to mix (100) SrTiO Nb, conduction
3Cushioning layer material is LaAlO
3, thickness is about 5nm; Ferroelectric superlattice adopts BaTiO
3Make; The stress limitation preparative layer adopts LaAlO
3Material is made, and thickness is about 5nm; The metal electrode diameter is 0.3mm.
Concrete preparation process is:
1, substrate venusian surface planeness is handled, the substrate surface r.m.s. roughness after handling well is preferably less than 5nm;
2, substrate is cleaned according to common cleaning;
3, adopt the laser beam growth technology, LaAlO successively grows on substrate
3Buffer layer, BaTiO
3Ferroelectric superlattice and LaAlO
3The stress limitation preparative layer;
Need to prove, intermittent type growth technology alternating growth is adopted in the preparation of ferroelectric superlattice, behind the thin film of promptly growing, stop laser, give a surperficial thermal diffusion time, and then another layer film of growing, the intermittent time is determined according to material surface primitive unit cell thermal diffusion time;
Used processing condition can be: adopt ArF excimer laser (248nm) as light source, laser power density is 1J/cm2, and frequency is 2Hz, and used target is LaAlO
3Monocrystalline and BaTiO
3Polycrystalline target, target-substrate distance are 55mm, and the background vacuum is higher than 10
-5Pa, in the thin film growth process, substrate temperature remains on 650 ℃;
In whole growth for Thin Film process, carry out original position with refletcion high-energy electron diffraction (RHEED) and monitor in real time;
4, adopt vacuum evaporation technique evaporation metal electrode on the stress limitation preparative layer;
Claims (6)
1, the displacement ferroelectric superlattice film material that has the stress limitation preparative layer, comprise substrate, buffer layer, displacement ferroelectric superlattice film and metal electrode on the structure, it is characterized in that between displacement ferroelectric superlattice film and metal electrode, also having one deck stress limitation preparative layer.
2, the displacement ferroelectric superlattice film material with stress limitation preparative layer according to claim 1, it is characterized in that stress limitation preparative layer material therefor is similar with the crystalline network of displacement ferroelectric superlattice film on crystalline network, its lattice parameter is less than the lattice parameter of displacement ferroelectric superlattice film.
3, the displacement ferroelectric superlattice film material with stress limitation preparative layer according to claim 2 is characterized in that stress limitation preparative layer material therefor is LaAlO
3
4, according to claim 1,2 or 3 described displacement ferroelectric superlattice film materials, it is characterized in that stress limitation preparative layer thickness is 5-6nm with stress limitation preparative layer.
5, have the displacement ferroelectric superlattice film preparation methods of stress limitation preparative layer, it is characterized in that adopting following steps:
1), substrate surface planeness and surface clearness are handled;
2), adopt laser beam epitaxial growth technology, at the thick buffer layer of the substrate surface deposition about 5nm of one deck;
3), adopt laser beam epitaxial growth technology on buffer layer, to prepare the displacement ferroelectric superlattice film, specifically be to adopt intermittent type growth technology alternating growth, promptly grow behind the thin film, stop laser, give the surface certain thermal diffusion time, and then another layer film of growing, the intermittent time is determined according to material surface primitive unit cell thermal diffusion time;
4), the growth ferroelectric superlattice after, under identical technology, on the displacement ferroelectric superlattice film growth one layer thickness be the stress limitation preparative layer of 5～6nm;
5), adopt vacuum evaporation technique evaporation metal electrode on the stress limitation preparative layer.
6, the displacement ferroelectric superlattice film preparation methods with stress limitation preparative layer according to claim 5 is characterized in that the substrate surface r.m.s. roughness after handling well is preferably less than 5nm; The used processing condition of laser beam growth technology can be: adopt ArF excimer laser (248nm) as light source, laser power density is 1J/cm2, and frequency is 2Hz, and used target is LaAlO
3Monocrystalline and BaTiO
3Polycrystalline target, target-substrate distance are 55mm, and the background vacuum is higher than 10
-5Pa, in the thin film growth process, substrate temperature remains on 650 ℃; In whole growth for Thin Film process, carry out original position with refletcion high-energy electron diffraction (RHEED) and monitor in real time.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111403417A (en) * | 2020-03-25 | 2020-07-10 | 无锡拍字节科技有限公司 | Structure of memory device and manufacturing method thereof |
| CN114023876A (en) * | 2021-10-29 | 2022-02-08 | 华中科技大学 | Based on HfO2/ZrO2Or HfO2/Al2O3Superlattice ferroelectric memristor and preparation thereof |
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|---|---|---|---|---|
| JP2651784B2 (en) * | 1993-06-22 | 1997-09-10 | 川崎重工業株式会社 | Ferroelectric thin film having superlattice structure and infrared sensor / pressure sensor provided with the thin film |
| CN1123655C (en) * | 1999-03-10 | 2003-10-08 | 中国科学院物理研究所 | New structure multi-performance BaTiO3Superlattice materials |
| JP2002324895A (en) * | 2001-04-26 | 2002-11-08 | Sony Corp | Ferroelectric memory element and its manufacturing method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111403417A (en) * | 2020-03-25 | 2020-07-10 | 无锡拍字节科技有限公司 | Structure of memory device and manufacturing method thereof |
| CN111403417B (en) * | 2020-03-25 | 2023-06-16 | 无锡舜铭存储科技有限公司 | Structure of memory device and manufacturing method thereof |
| CN114023876A (en) * | 2021-10-29 | 2022-02-08 | 华中科技大学 | Based on HfO2/ZrO2Or HfO2/Al2O3Superlattice ferroelectric memristor and preparation thereof |
| CN114023876B (en) * | 2021-10-29 | 2023-08-25 | 华中科技大学 | HfO-based method 2 /ZrO 2 Or HfO 2 /Al 2 O 3 Superlattice ferroelectric memristor and preparation thereof |
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