CN110648902A - Preparation method and application of lanthanum-doped hafnium oxide ferroelectric film - Google Patents
Preparation method and application of lanthanum-doped hafnium oxide ferroelectric film Download PDFInfo
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- 229910000449 hafnium oxide Inorganic materials 0.000 title claims abstract description 32
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000010408 film Substances 0.000 claims abstract description 52
- 238000000034 method Methods 0.000 claims abstract description 37
- 239000000758 substrate Substances 0.000 claims abstract description 37
- 239000002243 precursor Substances 0.000 claims abstract description 21
- 238000000137 annealing Methods 0.000 claims abstract description 16
- 239000011248 coating agent Substances 0.000 claims abstract description 15
- 238000000576 coating method Methods 0.000 claims abstract description 15
- 239000010409 thin film Substances 0.000 claims abstract description 9
- 238000001035 drying Methods 0.000 claims abstract description 8
- 150000002362 hafnium Chemical class 0.000 claims abstract description 8
- 150000002603 lanthanum Chemical class 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 31
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(iv) oxide Chemical compound O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 claims description 14
- 239000003990 capacitor Substances 0.000 claims description 11
- 239000002244 precipitate Substances 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
- 239000003929 acidic solution Substances 0.000 claims description 9
- 238000004528 spin coating Methods 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 239000012670 alkaline solution Substances 0.000 claims description 7
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 239000012153 distilled water Substances 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 5
- 239000011259 mixed solution Substances 0.000 claims description 5
- 230000001681 protective effect Effects 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 3
- 239000003292 glue Substances 0.000 claims description 2
- XEMZLVDIUVCKGL-UHFFFAOYSA-N hydrogen peroxide;sulfuric acid Chemical compound OO.OS(O)(=O)=O XEMZLVDIUVCKGL-UHFFFAOYSA-N 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 2
- 229910001868 water Inorganic materials 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 abstract description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 5
- 239000010703 silicon Substances 0.000 abstract description 5
- 239000002994 raw material Substances 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract 1
- 229910052746 lanthanum Inorganic materials 0.000 description 16
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 15
- 239000004065 semiconductor Substances 0.000 description 7
- 230000010287 polarization Effects 0.000 description 6
- 238000009210 therapy by ultrasound Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 238000000151 deposition Methods 0.000 description 3
- 238000001341 grazing-angle X-ray diffraction Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000005621 ferroelectricity Effects 0.000 description 2
- 230000015654 memory Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000231 atomic layer deposition Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- -1 finally Substances 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Abstract
The invention provides a preparation method and application of a lanthanum-doped hafnium oxide ferroelectric film. Firstly, preparing a clear and transparent lanthanum-doped hafnium oxide precursor solution by taking inorganic hafnium salt and inorganic lanthanum salt as raw materials; then coating the precursor on the treated silicon substrate according to the experimental requirements; finally drying, preheating and annealing to obtain La-HfO with different crystalline phase structures2A ferroelectric thin film. The invention can realize the accurate control of the thickness of the film, has good film forming uniformity, simple operation, flexible and controllable content of doped elements, simple equipment requirement, low cost, repeatable process and easy realization of industrial production.
Description
Technical Field
The invention relates to preparation of a ferroelectric material, in particular to a preparation method and application of a lanthanum-doped hafnium oxide ferroelectric film.
Background
The ferroelectric material not only has good ferroelectricity, but also is a piezoelectric body and a pyroelectric body, can be applied to the fields of micro-nano electronic technology, optical particle detection, circuit and optical integration, micro-mechanical electronic processing systems and the like, and is one of the leading edges and characteristic subjects of current high and new technology research. Over the past few years, HfO has been demonstrated2In non-volatile memory and energy storageHas great potential in the device. In HfO2In the thin film, the ferroelectric orthogonal phase is most often obtained by doping elements such as Si, Zr, Al, Y, La, etc. Non-centrosymmetric orthogonal HfO2Has attracted considerable attention as a possible alternative to ternary perovskite materials in ferroelectric memory devices, and, at thicknesses of greater than 10 nm, orthogonal HfO2Ferroelectricity is observed in thin films, which further indicates its suitability as a replacement for conventional perovskite materials in ferroelectric random access memories. Especially its good compatibility with CMOS processes, has received a high degree of attention from both academia and industry.
Preparation of HfO2Methods for forming thin films are many, and can be roughly classified into atomic layer deposition, physical vapor deposition, chemical vapor deposition, sol-gel, and the like. The sol-gel method belongs to one of chemical solution methods, mainly utilizes chemical reaction to generate sol, and has the advantages of cheap equipment, simple operation, energy conservation, environmental protection and the like, however, the conventional sol-gel method for preparing HfO2The film has the defects of large sol particles, low deposition speed, easy formation of holes and cracks by heating, poor process repeatability and the like, and does not meet the requirements of the ferroelectric property of the film.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method and application of a lanthanum-doped hafnium oxide ferroelectric film.
The invention firstly takes inorganic hafnium salt as raw material, generates precipitate under alkaline environment, dissolves the precipitate in acid solution, and takes inorganic lanthanum salt as additive to prepare clear and transparent precursor solution. Then coating the precursor on the cleaned substrate, drying, preheating and annealing to obtain a crystallized lanthanum-doped hafnium oxide ferroelectric film, and finally coating an electrode on the surface of the film to prepare the metal-La-HfO2Ferroelectric thin film-substrate (MIS) structure capacitors.
The invention prepares HfO from inorganic chemical solution2The ferroelectric film is doped with lanthanum, and the thickness and annealing process parameters of the film are controlled to realize the stable generation of highly symmetrical monoclinic phase, cubic phase or mixed phase thereof at room temperature, so that the film has good performanceHas ferroelectric properties that are initially intrinsic or can be induced by an external field.
The technical scheme of the invention is as follows:
a preparation method of a lanthanum-doped hafnium oxide ferroelectric film comprises the following steps:
(1) adding inorganic hafnium salt into deionized water, stirring until the inorganic hafnium salt is completely dissolved, then dropwise adding an alkaline solution into the mixture until the pH value is about 8 ~ 9, generating a white precipitate, separating and cleaning the precipitate by using a high-speed centrifuge, dropwise adding an acidic solution into the separated precipitate until the pH value is about 0.6 ~ 0.8.8, continuously stirring for 6 ~ 8 days, then adding lanthanum salt, and uniformly stirring to obtain a clear and transparent lanthanum-doped hafnium dioxide precursor solution;
(2) cleaning the substrate, namely heating the substrate for 25 ~ 30 min at 65 ~ 75 ℃ by using acetone ultrasonic waves for 4 ~ 6min, absolute ethyl alcohol ultrasonic waves for 4 ~ 6min, hydrogen peroxide-sulfuric acid mixed liquid with the volume ratio of 3: 1 at 65: 1 for 25 ~ min, distilled water ultrasonic waves for 4 ~ 6min, hydrofluoric acid ultrasonic waves for 4 ~ 6min and hydrogen peroxide ultrasonic waves for 15 ~ 25 min, washing, soaking and drying the substrate by using a large amount of distilled water, and performing surface pretreatment on the dried substrate to increase the wettability of the surface of the substrate and a precursor solution;
(3) coating and drying, namely coating the precursor solution obtained in the step (1) on the substrate cleaned in the step (2), wherein the substrate is placed on a glue baking machine at 140 ~ 160 ℃ for baking for 1 ~ 3 min for each coating, then carrying out surface pretreatment on the heated and dried substrate to increase the wettability of the film, and repeating the steps until the required film thickness is prepared;
(4) preheating the thin film: and (4) placing the film obtained in the step (3) in an annealing furnace filled with protective gas for preheating treatment, then annealing, and cooling to room temperature along with the furnace to obtain the crystalline lanthanum-doped hafnium oxide ferroelectric film.
Further, in the step (1), the inorganic hafnium salt is preferably HfOCl2•8H2O; the lanthanum salt is preferably La (NO)3)3•6H2O, La/Hf with a molar ratio of 0.031 ~ 0.098, and an alkaline solution, preferably NH3•H2O, basicThe solution is used for adjusting pH and is used as a precipitating agent; the acidic solution is preferably a nitric acid solution, which is used to adjust the pH and dissolve the precipitate.
Further, in the step (1), the acidic solution is a mixed solution of nitric acid and hydrogen peroxide, wherein the volume ratio of the nitric acid to the hydrogen peroxide is 0.25 ~ 0.30.30, and the hydrogen peroxide is used for accelerating precipitation and dissolution.
Further, in the step (1), when the alkaline or acidic solution is dripped, the alkaline or acidic solution is slowly dripped at a constant speed, and the pH value of the mixed solution is measured in real time while stirring in the dripping process.
Further, in the step (1), the concentration of the precursor solution may be adjusted by adding deionized water, so as to control the thickness of the thin film.
Further, in the step (1), the substrate is a P-type single crystal silicon substrate, and the surface pretreatment mode of the dried substrate is plasma bombardment for 8 ~ 12 min.
Further, in the step (3), the coating mode is spin coating.
Further, in the step (3), the coating and drying steps can be repeated for a plurality of times according to the film thickness requirement, and the thickness of the lanthanum-doped hafnium oxide film is controlled to be 10 ~ 20 nm.
Further, in the step (4), the annealing process parameters are that the temperature is heated to 120 ~ 380 ℃ at the heating rate of 0.03 ~ 0.13.13 ℃/s, then the temperature is heated to 550 ~ 850 ℃ at the heating rate of 5.6 ~ 15.6.6 ℃/s, the temperature is kept for 50 ~ 65 s, and then the annealing process is cooled to room temperature along with the furnace, and the protective gas in the furnace is nitrogen.
Further, in the step (4), the annealing process may adopt a method of clamping an upper electrode, and the spin-coated film is dried, then the upper electrode is deposited, and then the rapid annealing treatment is performed.
The prepared lanthanum-doped hafnium oxide ferroelectric film is integrated into a capacitor structure, and an electric property test is carried out on the film by utilizing a ferroelectric analyzer and a semiconductor measuring instrument. Wherein the capacitor structure is a metal upper electrode-La-HfO2The ferroelectric film-substrate (MIS) structure, the metal upper electrode is a platinum electrode, and the substrate is a P-type silicon substrate.
The lanthanum-doped hafnium oxide precursor solution is prepared by adopting an all-inorganic chemical solution method, and the stable existing monoclinic phase, cubic phase or mixed phase lanthanum-doped hafnium oxide ferroelectric film is obtained at room temperature by controlling the film thickness, the content of doped elements, an annealing process and other process parameters.
Compared with the prior art, the invention has the following advantages:
(1) the invention adopts a preparation method of an all-inorganic precursor solution, takes deionized water as a solvent and an inorganic salt precursor as a raw material, has no organic matter in the whole sol preparation process, and has low raw material cost.
(2) The invention does not need advanced and expensive coating equipment and harsh operation environment, can complete experimental operation at room temperature, has simple requirements on equipment and environment, and is suitable for mass production of equipment with low cost.
(3) According to the invention, the thickness of the film is controlled by regulating and controlling the amount of the solvent added into the colloid, the number of film deposition layers, spin coating process parameters and the like, and the operation is simple and controllable.
(4) The invention has the advantages of flexible and controllable content of doped elements and simple operation process.
(5) The invention can stably grow the ferroelectric orthogonal phase in the film without pre-depositing the upper electrode, simplifies the preparation process of the film and saves the preparation time of the film.
Drawings
FIG. 1 is a thermogravimetric plot of a sample of example 2 with a lanthanum doping concentration of 6 mol%.
FIG. 2 is a GIXRD pattern of a sample having a lanthanum doping concentration of 6 mol% and a film thickness of 10 nm in example 2.
FIG. 3 is a hysteresis chart of a sample having a lanthanum doping concentration of 6 mol% and a film thickness of 10 nm in example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear, the operation of the present invention will be described in further detail below.
Example 1
A preparation method of a lanthanum-doped hafnium oxide ferroelectric film comprises the following steps:
(1) weighing appropriate amount of HfOCl2·8H2Dissolving O in deionized water to prepare a solution with the concentration of 0.12 mol/L, after the solute is completely dissolved, slowly dropwise adding 1 mol/L ammonia water solution into the solution while stirring until the pH value of the solution is stabilized at about 8.5, white precipitate is generated when ammonia solution is dripped, then deionized water is used for high-speed centrifugal washing until no chloride ion exists in the supernatant, finally, mixed solution of 2 mol/L nitric acid and 10 mol/L hydrogen peroxide with the volume ratio of 0.28 is slowly added into the centrifuged precipitate while stirring, stopping dropwise adding until the pH value of the solution is stabilized to about 0.7, stirring for a week to obtain clear and transparent sol with the concentration of 0.2 mol/L, and dissolving lanthanum nitrate with a certain mass in the clear sol to prepare lanthanum-doped hafnium oxide-based sol with the doping concentration of 3 mol%;
(2) selecting a p-Si substrate as a substrate, and when cleaning the substrate, sequentially performing acetone ultrasonic treatment for 5 min, absolute ethyl alcohol ultrasonic treatment for 5 min and hydrogen peroxide: cleaning a mixed solution with a volume ratio of sulfuric acid of 3: 1 at 70 ℃ for 30 min, performing ultrasonic treatment with distilled water for 5 min, performing ultrasonic treatment with hydrofluoric acid for 5 min, performing ultrasonic treatment with hydrogen peroxide for 20 min, finally washing and soaking with a large amount of distilled water, and performing plasma treatment on the dried substrate for 10 min to increase the wettability of the surface of the substrate and the precursor solution;
(3) coating the sol on the surface of a silicon substrate by adopting a spin coating process, then placing the silicon substrate on a baking machine at 150 ℃ for heating for 1 min, then bombarding the silicon substrate by using plasma for 10 min, repeating the steps, and co-spin coating two layers to obtain a lanthanum-doped hafnium oxide film with the film thickness of 10 nm;
(4) and (2) placing the coated substrate in an annealing furnace filled with nitrogen protective gas for annealing treatment, wherein the process parameters are as follows: heating from room temperature to 120 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 60 s; heating to 240 ℃ at the heating rate of 6 ℃/min, and preserving heat for 60 s; heating to 380 ℃ at the heating rate of 4.5 ℃/min, heating to 380 ℃ at the heating rate of 7.5 ℃/min, preserving the heat for 60 s, rapidly heating to the annealing temperature of 650 ℃ for 30 s, keeping the temperature for 60 s, and cooling to room temperature along with a furnace to obtain the crystalline lanthanum-doped hafnium oxide ferroelectric film;
(5) using small ion sputtering instrument to deposit platinum as upper electrode to obtain capacitor with MIS structure, and using ferroelectric tester and semiconductor tester to test the electric performance of the capacitor to obtain the sample with monoclinic phase and residual polarization value range of-9.36 ~ 10.86.10.86μC/cm2。
Example 2
Preparing a hafnium oxide precursor solution with lanthanum doping concentration of 6 mol%, and obtaining the metal-La-HfO by the same process steps and process conditions as those in example 12The ferroelectric property of the capacitor is tested by a ferroelectric analyzer and a semiconductor tester, the sample is a mixed phase of a monoclinic phase and an orthorhombic phase, and the range of the remanent polarization value is-16.25 ~ 18.70.18.70μC/cm2. The thermogravimetric curves and GIXRD patterns and the hysteresis loops of the samples are shown in fig. 1, 2 and 3.
Example 3
Preparing a hafnium oxide precursor solution with lanthanum doping concentration of 9 mol%, and obtaining the metal-La-HfO by the same process steps and process conditions as those in example 12The ferroelectric property of the capacitor is tested by a ferroelectric analyzer and a semiconductor tester, and the sample is mainly cubic phase and has a remanent polarization value range of-8.59 ~ 8.14.14μC/cm2。
Example 4
Preparing a hafnium oxide precursor solution with lanthanum doping concentration of 3 mol%, spin-coating three layers to obtain a lanthanum-doped hafnium oxide film with a film thickness of 15 nm, wherein the rest of the process steps and process conditions are the same as those in example 1 to obtain metal-La-HfO2The ferroelectric property of the capacitor is tested by a ferroelectric analyzer and a semiconductor tester, and the range of the residual polarization value of the sample is 3.05 ~ 4.71.71μC/cm2。
Example 5
Preparing a hafnium oxide precursor solution with the lanthanum doping concentration of 6 mol%, spin-coating three layers to obtain a lanthanum-doped hafnium oxide film with the film thickness of 15 nm, wherein the rest of the process steps and process conditions are the same as those in example 1 to obtain the metal-La-HfO2The ferroelectric property of the capacitor is tested by a ferroelectric analyzer and a semiconductor tester, and the range of the residual polarization value of the sample is measured to be-5.54 ~ 6.63.6.63μC/cm2。
Example 6
Preparing a hafnium oxide precursor solution with lanthanum doping concentration of 9 mol%, spin-coating three layers to obtain a lanthanum-doped hafnium oxide film with a film thickness of 15 nm, wherein the rest of the process steps and process conditions are the same as those in example 1 to obtain metal-La-HfO2The ferroelectric property of the capacitor is tested by a ferroelectric analyzer and a semiconductor tester, and the range of the residual polarization value of the sample is measured to be-2.54 ~ 3.83.83μC/cm2。
In the above embodiment, the hafnium oxide films with different doping concentrations of lanthanum all exhibit ferroelectricity, wherein the window of hysteresis loop is the largest and the best when the doping concentration of lanthanum is 6 mol%. When the doping concentration of lanthanum is 3 mol% and 9 mol%, the measured GIXRD pattern analysis shows that the lanthanum is a monoclinic phase and a cubic phase, and when the doping concentration of lanthanum is 6 mol%, the lanthanum is a mixed phase of the monoclinic phase and an orthorhombic phase.
Claims (10)
1. A preparation method of a lanthanum-doped hafnium oxide ferroelectric film is characterized by comprising the following steps:
(1) adding inorganic hafnium salt into deionized water, stirring until the inorganic hafnium salt is completely dissolved, then dropwise adding an alkaline solution into the mixture until the pH value is 8 ~ 9, generating a white precipitate in the solution, separating and cleaning the precipitate by using a centrifugal machine, dropwise adding an acidic solution into the separated precipitate until the pH value is 0.6 ~ 0.8.8, continuously stirring for 6 ~ 8 days, adding lanthanum salt, and uniformly stirring to obtain a clear and transparent lanthanum-doped hafnium dioxide precursor solution;
(2) cleaning the substrate, namely heating the substrate for 25 ~ 30 min at 65 ~ 75 ℃ by using acetone ultrasonic waves for 4 ~ 6min, absolute ethyl alcohol ultrasonic waves for 4 ~ 6min, hydrogen peroxide-sulfuric acid mixed liquid with the volume ratio of 3: 1 at 65: 1 for 25 ~ min, distilled water ultrasonic waves for 4 ~ 6min, hydrofluoric acid ultrasonic waves for 4 ~ 6min and hydrogen peroxide ultrasonic waves for 15 ~ 25 min, washing, soaking and drying the substrate by using a large amount of distilled water, and performing surface pretreatment on the dried substrate to increase the wettability of the surface of the substrate and a precursor solution;
(3) coating and drying, namely coating the precursor solution obtained in the step (1) on the substrate cleaned in the step (2), wherein the substrate is placed on a glue baking machine at 140 ~ 160 ℃ for baking for 1 ~ 3 min for each coating, then carrying out surface pretreatment on the heated and dried substrate to increase the wettability of the film, and repeating the steps until the required film thickness is prepared;
(4) preheating the thin film: and (4) placing the film obtained in the step (3) in an annealing furnace filled with protective gas for preheating treatment, then annealing, and cooling to room temperature along with the furnace to obtain the crystalline lanthanum-doped hafnium oxide ferroelectric film.
2. The method of claim 1, wherein in step (1), the inorganic hafnium salt is HfOCl2•8H2O; the inorganic lanthanum salt is La (NO)3)3•6H2O, La/Hf molar ratio of 0.031 ~ 0.098 and alkaline solution of NH3•H2O; the acidic solution is a nitric acid solution.
3. The method for preparing a lanthanum-doped hafnium oxide ferroelectric film according to claim 1, wherein in the step (1), the acidic solution is a mixture of nitric acid and hydrogen peroxide, wherein the volume ratio of nitric acid to hydrogen peroxide is 0.25 ~ 0.30.30.
4. The method according to claim 1, wherein in the step (1), the alkaline or acidic solution is slowly added dropwise at a constant speed, and the pH value of the mixed solution is measured in real time during the dropwise addition while stirring.
5. The method of claim 1, wherein in step (1), the precursor solution is adjusted in concentration by adding deionized water to control the thickness of the film.
6. The method of claim 1, wherein in step (1), the substrate is a P-type single crystal silicon substrate, and the surface pretreatment of the dried substrate is plasma bombardment for 8 ~ 12 min.
7. The method of claim 1, wherein in step (3), the coating is performed by spin coating.
8. The method of claim 1, wherein in the step (3), the coating and drying steps are repeated according to the film thickness requirement, and the thickness of the lanthanum-doped hafnium oxide film is controlled to be 10 ~ 20 nm.
9. The method for preparing a lanthanum-doped hafnium oxide ferroelectric thin film according to claim 1, wherein in the step (4), the annealing process parameters are heating to 120 ~ 380 ℃ at a heating rate of 0.03 ~ 0.13.13 ℃/s, heating to 550 ~ 850 ℃ at a heating rate of 5.6 ~ 15.6.6 ℃/s, keeping the temperature for 50 ~ 65 s, and cooling to room temperature along with the furnace, wherein the protective gas in the furnace is nitrogen.
10. Use of the lanthanum-doped hafnium oxide ferroelectric thin film obtained by the preparation method according to any one of claims 1 to 9 in a capacitor.
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| CN112176315A (en) * | 2020-08-19 | 2021-01-05 | 有研工程技术研究院有限公司 | Rare earth doped hafnium oxide based ferroelectric film and preparation method thereof |
| CN112447508A (en) * | 2020-11-24 | 2021-03-05 | 湘潭大学 | Method for enhancing hafnium oxide (HfO) by plasma technology2) Method for determining ferroelectric properties of ferroelectric thin film |
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