A method for preparing an alternately grown ferroelectric thin film

Abstract

The present invention provides a method for preparing an alternately grown ferroelectric thin film, belonging to the technical field of ferroelectric thin films. The preparation method of the present invention includes: weighing a preset proportion of an organic hafnium salt and an organic metal salt of a multi-doped element and placing them in a container, and then successively adding a monobasic acid and an organic solvent; heating and stirring until clear and then continuously stirring to room temperature to obtain a variety of precursor solutions with different solution concentrations, different doped elements, different doping amounts, etc.; dripping two or more precursor solutions onto a platinum substrate in an alternating manner for spin coating treatment; performing an annealing operation to obtain an alternately grown multi-element doped Hf 0.5 Zr 0.5 O2 (HZO) ferroelectric thin film. By using the chemical solution deposition method, an alternately grown multi-element doped HZO ferroelectric thin film can be prepared without using large-scale equipment, and the preparation process is simple, the equipment cost is low, and it is easy to scale up production.

Description

Technical Field

[0001] The present invention relates to the technical field of ferroelectric thin films, and in particular to a method for preparing an alternately grown ferroelectric thin film. Background Art

[0002] With the development of intelligent manufacturing, our lives are changing. Applications such as image recognition, speech recognition, man-machine battles, intelligent robots, deep learning, and autonomous driving are emerging in an endless stream. As the core force of these technologies, data is also in an explosive growth stage. According to statistics, in 2018, the total flash memory capacity produced globally was 0.25 ZettaBytes. According to IDC predictions, the global data will reach a total of 175 ZettaBytes in 2025. With such an astonishing and huge amount of data, semiconductor memories will have a huge market. Ferroelectric memories combine some characteristics of random access memories and read-only memories. Because of their many advantages such as non-volatility, low working power consumption, ultra-high radiation resistance, high storage density, high-speed writing, and long-term data retention, they have become strong competitors for the next-generation memories.

[0003] However, traditional ferroelectric thin films have problems such as insufficient retention performance, imprinting effect, and lattice mismatch when integrated with silicon-based materials. These problems seriously hinder the performance improvement of ferroelectric memories and are not conducive to the high-density integration and large-scale industrialization of ferroelectric memories. In contrast, ferroelectric thin films of HfO2 and its doped series have advantages such as good compatibility with advanced CMOS semiconductor processes and ferroelectricity even at extremely thin thicknesses, and have become a very promising ferroelectric thin film material for realizing high-density integration and low-power storage technologies. Among them, Zr and Hf have almost the same atomic radius, and also have similar physical and chemical properties and lattice constants. These factors enable ZrO2 and HfO2 to achieve infinite mutual solubility. Researchers have found that when Zr is doped into HfO2, a Zr atom to Hf atom ratio of 1:1 (Hf 0.5 Zr 0.5 O2) thin film can obtain the maximum Pr value. However, existing technologies all grow ferroelectric thin films layer by layer with a single precursor solution, resulting in a certain amount of non-ferroelectric phase (monoclinic phase) still remaining in the thin film, and its ferroelectricity and durability are both poor.

[0004] Existing processes for preparing HfO2-based ferroelectric thin films. These process methods include atomic layer deposition (ALD), pulsed laser deposition (PLD), sputtering, chemical solution deposition (CSD), and metalorganic chemical vapor deposition (MOCVD), etc. Among them, chemical solution deposition (CSD) has the advantages of not requiring large-scale equipment and a high-vacuum environment, having relatively low requirements for experimental hardware conditions and costs, and being easy to perform element doping, and is applied to the preparation of HfO2-based ferroelectric thin films. Summary of the Invention

[0005] The object of the present invention is to provide a method for optimizing the interface structure of a thin film by alternately growing a ferroelectric thin film, promoting the transformation from the monoclinic phase to the orthorhombic phase, and improving the ferroelectricity and durability of the HfO2-based thin film.

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an alternately grown ferroelectric thin film, comprising the following steps:

[0008] 1) Coating the precursor solution A onto a platinum substrate and then performing annealing treatment to obtain an annealed A thin film sample;

[0009] 2) Coating the precursor solution B onto the annealed A thin film sample, and performing annealing treatment to obtain an annealed AB thin film sample;

[0010] The precursor solution A and the precursor solution B independently comprise an organic hafnium salt, an organometallic salt of a multi-doped element, a monobasic acid, and an organic solvent;

[0011] The organometallic salts of the multi-doped elements in the precursor solution A and the precursor solution B are different;

[0012] 3) Using steps 1) and 2) as a unit, repeating n - 1 times to obtain a sample containing (AB) n thin film, and performing annealing treatment on the sample containing (AB) n thin film to obtain an alternately grown ferroelectric thin film;

[0013] Wherein n ≥ 2.

[0014] Further, the organic hafnium salt comprises one or more of hafnium acetylacetonate, Hf(acac)4, Hf(O-i-C3H7)4, and Hf(O n Bu)4;

[0015] The mass ratio of the organic hafnium salt to the organometallic salt of the multi-doped element is 0.1 - 0.3:0.1 - 0.2.

[0016] Further, the doped element comprises Zr, and the doped element further comprises one of Ba, Al, Gd, La, Sr, Y, Ce, and Ca.

[0017] Further, the organometallic salt of the multi-doped element comprises zirconium acetylacetonate, and the organometallic salt of the multi-doped element further comprises one of barium acetylacetonate, aluminum acetylacetonate, gadolinium acetylacetonate, strontium acetylacetonate, cerium acetylacetonate, calcium acetylacetonate, lanthanum acetylacetonate, and yttrium acetylacetonate;

[0018] The zirconium acetylacetonate accounts for 97-98% of the total mass of the organometallic salts of multiple doped elements.

[0019] Further, the monobasic acid is HNO3 and / or CH3COOH;

[0020] The organic solvent is one or more of HO(CH2)2OCH3, CH2(CH3CO)2, CH3C6H5, and CH3CH2OH;

[0021] The mass-volume ratio of the organohafnium salt, monobasic acid, and organic solvent is 0.1-0.3 g: 2.0-4.0 mL: 1.0-3.0 mL.

[0022] Further, the molar concentration of metal atoms in the precursor solution A and the precursor solution B is independently 0.1-0.2 mol / L.

[0023] Further, in step 1), the coating is spin coating, and the steps of spin coating are as follows:

[0024] Take the precursor solution A and spin coat it onto a platinum substrate with a rotation speed of 300-500 r / min for 10-20 s, and then adjust the rotation speed to 2000-3000 r / min and continue to spin coat for 25-35 s to obtain a sample containing the A film;

[0025] The temperature of the annealing treatment is 180-350 °C, and the time of the annealing treatment is 6-8 min.

[0026] Further, in step 2), the steps of spin coating are as follows:

[0027] Take the precursor solution B and spin coat it onto the annealed A film sample with a rotation speed of 300-500 r / min for 10-20 s, and then adjust the rotation speed to 2000-3000 r / min and continue to spin coat for 25-35 s to obtain a sample containing the AB film;

[0028] The temperature of the annealing treatment is 180-350 °C, and the time of the annealing treatment is 6-8 min.

[0029] Further, in step 3), the steps of the annealing treatment are as follows:

[0030] Anneal the sample containing the (AB) n film once at the first preset temperature and the first preset time, and perform a second annealing at the second preset temperature and the second preset time;

[0031] The first preset temperature is lower than the second preset temperature.

[0032] Further, the first preset temperature is 300 to 400 °C, and the first preset time is 250 to 300 s;

[0033] The second preset temperature is 400 to 800 °C, and the second preset time is 250 to 300 s.

[0034] Advantages of the present invention:

[0035] The present invention uses the method of chemical solution deposition, and uses organometallic salts as a source of various metal ions to prepare an alternately grown HZO-based ferroelectric thin film, which does not require large equipment and a high-vacuum environment, and has relatively low requirements for experimental hardware conditions and costs; it is easy to perform element doping, which can not only accurately control the stoichiometric ratio, but also realize the preparation of large-area thin films.

[0036] In the preparation method of the present invention, the chemical components are easy to control, the error rate in the preparation process is low, and no waste of resources will be caused. Description of the drawings

[0037] Figure 1 is a schematic flow chart of a method for preparing an alternately grown doped HZO ferroelectric thin film provided by the present invention;

[0038] Figure 2 is a cross-sectional SEM image of a hafnium oxide ferroelectric thin film obtained in Example 1;

[0039] Figure 3 is a GIXRD diagram of an HZO ferroelectric thin film with a molar doping ratio of Hf:Zr = 1:1, a La:HZO ferroelectric thin film with a molar doping ratio of La:(Hf+Zr) = 1.5%, a Y:HZO ferroelectric thin film with a molar doping ratio of Y:(Hf+Zr) = 1.5%, and the ferroelectric thin film obtained in Example 1;

[0040] Figure 4 is a schematic diagram of a hysteresis loop of an HZO ferroelectric thin film with a molar doping ratio of Hf:Zr = 1:1, a La:HZO ferroelectric thin film with a molar doping ratio of La:(Hf+Zr) = 1.5%, a Y:HZO ferroelectric thin film with a molar doping ratio of Y:(Hf+Zr) = 1.5%, and the ferroelectric thin film obtained in Example 1;

[0041] Figure 5 is a schematic diagram of a hysteresis loop of the ferroelectric thin film obtained in Example 2;

[0042] Figure 6 is a schematic diagram of a hysteresis loop of the ferroelectric thin film obtained in Example 3. Detailed implementation manners

[0043] The present invention provides a method for preparing an alternately grown ferroelectric thin film, including the following steps:

[0044] 1) The precursor solution A is coated on a platinum substrate and then annealed to obtain an annealed A thin film sample;

[0045] 2) The precursor solution B is coated on the annealed A thin film sample, and after annealing, an annealed AB thin film sample is obtained;

[0046] The precursor solution A and the precursor solution B independently contain an organic hafnium salt, an organometallic salt of a multi-doped element, a monobasic acid, and an organic solvent;

[0047] The organometallic salts of the multi-doped elements in the precursor solution A and the precursor solution B are different;

[0048] 3) Taking steps 1) and 2) as a unit, repeating n - 1 times to obtain a sample containing an (AB) n thin film, and annealing the sample containing the (AB) n thin film to obtain an alternately grown ferroelectric thin film;

[0049] Wherein n ≥ 2.

[0050] In the present invention, the organic hafnium salt includes one or more of hafnium acetylacetonate, Hf(acac)4, Hf(O-i-C3H7)4, and Hf(O n Bu)4, and preferably hafnium acetylacetonate.

[0051] In the present invention, the Hf(O n Bu)4 is C 16 H 36 HfO4.

[0052] In the present invention, the mass ratio of the organic hafnium salt to the organometallic salt of the multi-doped element is 0.1 - 0.3:0.1 - 0.2, preferably 0.12 - 0.15:0.11 - 0.18, and more preferably 0.1416:0.1233.

[0053] In the present invention, the doped element includes Zr, and the doped element further includes one of Ba, Al, Gd, La, Sr, Y, Ce, and Ca, and preferably further includes one of Sr, Y, Ce, and Ca.

[0054] In the present invention, the organometallic salt of the multi-doped element includes zirconium acetylacetonate, and the organometallic salt of the multi-doped element further includes one of barium acetylacetonate, aluminum acetylacetonate, gadolinium acetylacetonate, strontium acetylacetonate, cerium acetylacetonate, calcium acetylacetonate, lanthanum acetylacetonate, and yttrium acetylacetonate, and preferably further includes one of cerium acetylacetonate, yttrium acetylacetonate, barium acetylacetonate, and calcium acetylacetonate.

[0055] In the present invention, the zirconium acetylacetonate accounts for 97-98% of the total mass of the organometallic salts of the multi-doped elements, preferably 97.6%.

[0056] In the present invention, the monobasic acid is HNO3 and / or CH3COOH, preferably CH3COOH.

[0057] In the present invention, the organic solvent is one or more of HO(CH2)2OCH3, CH2(CH3CO)2, CH3C6H5 and CH3CH2OH, preferably HO(CH2)2OCH3.

[0058] In the present invention, the mass-volume ratio of the organohafnium salt, monobasic acid and organic solvent is 0.1-0.3 g: 2.0-4.0 mL: 1.0-3.0 mL, preferably 0.12-0.15 g: 3.0 mL: 2.0 mL.

[0059] In the present invention, the molar concentration of metal atoms in the precursor solution A and the precursor solution B is independently 0.1-0.2 mol / L, preferably 0.15 mol / L.

[0060] In the present invention, during the preparation of the precursor solution A and the precursor solution B, it is independently necessary to heat and stir in a water bath at 50-60 °C for 30-40 min until the solution is clear, preferably heat and stir in a water bath at 55 °C for 35 min until the solution is clear.

[0061] In the present invention, in step 1), the coating is spin coating, and the steps of spin coating are as follows:

[0062] Take the precursor solution A and spin coat it onto a platinum substrate at a rotational speed of 300-500 r / min for 10-20 s, then adjust the rotational speed to 2000-3000 r / min and continue to spin coat for 25-35 s to obtain a sample containing a film of A; preferably, take the precursor solution A and spin coat it onto a platinum substrate at a rotational speed of 400 r / min for 15 s, then adjust the rotational speed to 2500 r / min and continue to spin coat for 30 s to obtain a sample containing a film of A.

[0063] In the present invention, in step 1), the temperature of the annealing treatment is 180-350 °C, and the time of the annealing treatment is 6-8 min; preferably, the temperature of the annealing treatment is 200-300 °C, and the time of the annealing treatment is 6-7 min; more preferably, the temperature of the annealing treatment is 250 °C, and the time of the annealing treatment is 7 min.

[0064] In the present invention, in step 1), the annealing treatment is preferably carried out in an aerobic environment.

[0065] In the present invention, in step 2), the steps of spin coating are as follows:

[0066] Spin coat the precursor solution B onto the annealed A thin film sample at a rotation speed of 300 - 500 r / min for 10 - 20 s, and then adjust the rotation speed to 2000 - 3000 r / min and continue to spin coat for 25 - 35 s to obtain a sample containing the AB thin film; preferably, spin coat the precursor solution B onto the platinum substrate at a rotation speed of 400 r / min for 15 s, and then adjust the rotation speed to 2500 r / min and continue to spin coat for 30 s to obtain a sample containing the AB thin film.

[0067] In the present invention, in step 2), the temperature of the annealing treatment is 180 - 350 °C, and the time of the annealing treatment is 6 - 8 min; preferably, the temperature of the annealing treatment is 200 - 300 °C, and the time of the annealing treatment is 6 - 7 min; more preferably, the temperature of the annealing treatment is 250 °C, and the time of the annealing treatment is 7 min.

[0068] In the present invention, in step 2), the annealing treatment is preferably carried out in an oxygen-containing environment.

[0069] In the present invention, in step 3), the steps of the annealing treatment are preferably:

[0070] Anneal the sample containing the (AB) n thin film once at the first preset temperature and the first preset time, and anneal it twice at the second preset temperature and the second preset time.

[0071] In the present invention, the first preset temperature is preferably lower than the second preset temperature.

[0072] In the present invention, the first preset temperature is 300 - 400 °C, and the first preset time is 250 - 300 s; preferably, the first preset temperature is 320 - 380 °C, and the first preset time is 280 - 290 s; more preferably, the first preset temperature is 350 °C, and the first preset time is 285 s.

[0073] In the present invention, the second preset temperature is 400 - 800 °C, and the second preset time is 250 - 300 s; preferably, the second preset temperature is 500 - 700 °C, and the second preset time is 280 - 290 s; more preferably, the second preset temperature is 600 °C, and the second preset time is 285 s.

[0074] In the present invention, in the sample containing the (AB) n thin film, n ≥ 2, preferably 2.

[0075] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0076] Example 1

[0077] Step S1: Beaker A: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate and 0.0032 g of hydrated lanthanum acetylacetonate using an analytical balance and place them in the beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence; Beaker B: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate and 0.0029 g of hydrated yttrium acetylacetonate using an analytical balance and place them in the beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence.

[0078] Step S2: Seal the two beakers and place them in a thermostatic magnetic stirring water bath for stirring. The stirring temperatures are set at 55 °C respectively. After stirring for 35 minutes until the solution becomes clear, take out the two beakers and place them on an ordinary magnetic stirring device for stirring for more than 2 hours, and let it stand until room temperature to obtain precursor solution A (lanthanum acetylacetonate) and precursor solution B (yttrium acetylacetonate).

[0079] Step S3: Use a dropper with a specification of 1 ml to take the precursor solution A obtained in Step S2 and drop it on a platinum substrate with a size of 8 mm * 8 mm until the platinum substrate is completely covered.

[0080] Step S4: Place the platinum substrate in a spin coater with a rotation speed of 400 r / min and spin coat for 15 seconds, then adjust the rotation speed to 2500 r / min and continue to spin coat for 30 seconds to obtain a thin film sample containing A.

[0081] Step S5: Put the thin film sample containing A obtained in Step S4 into a rapid annealing furnace and pyrolyze it in an oxygen environment at a temperature of 250 °C for 7 min, and then cool it to 60 °C.

[0082] Step S6: Use a dropper with a specification of 1 ml to take the precursor solution B obtained in Step S2 and drop it on the annealed A thin film sample obtained in Step S5 until the surface is completely covered.

[0083] Step S7: Place the annealed A thin film sample in a spin coater with a rotation speed of 400 r / min and spin coat for 15 seconds, then adjust the rotation speed to 2500 r / min and continue to spin coat for 30 seconds to obtain a thin film sample containing AB with A and B growing alternately once.

[0084] Step S8: Put the thin film sample containing AB obtained in Step S7 into a rapid annealing furnace and pyrolyze it in an oxygen environment at a temperature of 350 °C for 7 min, and then cool it to 60 °C.

[0085] Step S9: Repeat Steps S3 to S8 in sequence on the annealed thin film sample containing AB obtained in Step S8 to obtain a thin film sample containing (AB)2 with A and B growing alternately 2 times.

[0086] Step S10: Put the thin film sample containing (AB)₂ obtained in Step S9 into a rapid annealing furnace and anneal it once for 300 seconds in an oxygen environment at a temperature of 380 °C.

[0087] Step S11: Put the thin film sample obtained in Step S10 into a rapid annealing furnace, anneal it for 300 seconds in an oxygen environment at a temperature of 500 °C, and then cool it in the furnace to obtain a hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Y:HZO)₂ and a molar doping ratio of La:(Hf+Zr) = 1.5% and Y:(Hf+Zr) = 1.5%.

[0088] Use a scanning electron microscope to test the longitudinal structure of the hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Y:HZO)₂ obtained in Step S11.

[0089] Deposit a platinum electrode on the hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Y:HZO)₂ obtained in Step S11 using a small ion sputtering instrument to obtain a structure of Pt / (La:HZO / Y:HZO)₂ / Pt / Ti / SiO₂ / Si, and measure its polarization-electric field hysteresis loop (P-E) using a ferroelectric analyzer.

[0090] Specifically, the polarization-electric field hysteresis loop is the change trajectory of the polarization intensity P of the ferroelectric thin film with the applied voltage V, and can intuitively reflect the magnitudes of values such as the maximum polarization intensity, the remanent polarization intensity, and the coercive electric field.

[0091] Figure 2 It is a cross-sectional SEM image of the hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Y:HZO)₂ and a molar doping ratio of La:(Hf+Zr) = 1.5% and Y:(Hf+Zr) = 1.5%. The cross-sectional SEM image shows the hierarchical structure of the sample and the approximate thickness of each layer, where the ferroelectric layer is about 68 nm.

[0092] Figure 3GIXRD patterns of HZO ferroelectric thin films with a molar doping ratio of Hf:Zr = 1:1, GIXRD patterns of La:HZO ferroelectric thin films with a molar doping ratio of La:(Hf + Zr) = 1.5%, GIXRD patterns of Y:HZO ferroelectric thin films with a molar doping ratio of Y:(Hf + Zr) = 1.5%, and GIXRD patterns of ferroelectric thin films with a molar doping ratio of La:(Hf + Zr) = 1.5% and Y:(Hf + Zr) = 1.5% and an alternating pattern of (La:HZO / Y:HZO)2. By comparing the diffraction peaks, the phase composition of the thin films was characterized. It can be seen that compared with other thin films, the monoclinic phase diffraction peak of the (La:HZO / Y:HZO)2 ferroelectric thin film is weak at 31.3°, and there is a stronger diffraction peak at 30.5°. This indicates that the content of the ferroelectric phase in the phase of the thin film is higher than that of HZO ferroelectric thin films, Y:HZO ferroelectric thin films, and La:HZO ferroelectric thin films, and the ferroelectric performance is better.

[0093] Figure 4 Hysteresis loops (arrow marked) of HZO ferroelectric thin films with a molar doping ratio of Hf:Zr = 1:1, hysteresis loops of La:HZO ferroelectric thin films with a molar doping ratio of La:(Hf + Zr) = 1.5%, hysteresis loops of Y:HZO ferroelectric thin films with a molar doping ratio of Y:(Hf + Zr) = 1.5%, and a schematic diagram of the hysteresis loop of ferroelectric thin films with a molar doping ratio of La:(Hf + Zr) = 1.5% and Y:(Hf + Zr) = 1.5% and an alternating pattern of (La:HZO / Y:HZO)2, where the abscissa represents the applied electric field E and the ordinate represents the remanent polarization value corresponding to the applied electric field. It can be seen that after doping trace elements on the basis of HZO thin films, the polarization values of the thin films generally increase, and the ferroelectric performance of the alternately grown (La:HZO / Y:HZO)2 ferroelectric thin films is better than that of La:HZO ferroelectric thin films and Y:HZO ferroelectric thin films at the same thickness, and the polarization value is improved compared with both Y:HZO ferroelectric thin films and La:HZO ferroelectric thin films.

[0094] Example 2

[0095] Step S1: Beaker A: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate, and 0.0032 g of lanthanum acetylacetonate hydrate using an analytical balance and place them in a beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence; Beaker B: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate, and 0.0029 g of strontium acetylacetonate hydrate using an analytical balance and place them in a beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence.

[0096] Steps S2 to S9 are the same as in Example 1;

[0097] Step S10: Place the thin film sample containing (AB)2 obtained in step S9 into a rapid annealing furnace and anneal it once for 290 seconds in an oxygen environment at a temperature of 350 °C.

[0098] Step S11: Place the thin film sample obtained in step S10 into a rapid annealing furnace, anneal it for 250 seconds in an oxygen environment at a temperature of 600 °C, and then cool it in the furnace to obtain a hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Sr:HZO)2 and a molar doping ratio of La:(Hf+Zr) = 1.5% and Sr:(Hf+Zr) = 1.5%.

[0099] Deposit a platinum electrode on the hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Sr:HZO)2 obtained in step S11 using a small ion sputtering instrument to obtain a structure of Pt / (La:HZO / Sr:HZO)2 / Pt / Ti / SiO2 / Si, and measure its polarization-electric field hysteresis loop (P-E) using a ferroelectric analyzer.

[0100] Figure 5 It is a schematic diagram of the polarization-electric field hysteresis loop of a hafnium oxide ferroelectric thin film with an alternating pattern of (La:HZO / Sr:HZO)2 and a molar doping ratio of La:(Hf+Zr) = 1.5% and Sr:(Hf+Zr) = 1.5%. It can be seen that the polarization value of this thin film is 5.93 μC / cm 2 , and its coercive electric field is 0.89 MV / cm.

[0101] Example 3

[0102] Step S1: Beaker A: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate, and 0.0032 g of strontium acetylacetonate hydrate using an analytical balance and place them in a beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence; Beaker B: Weigh 0.1416 g of hafnium acetylacetonate, 0.1201 g of zirconium acetylacetonate, and 0.0029 g of yttrium acetylacetonate hydrate using an analytical balance and place them in a beaker. Then, add 3 ml of acetic acid and 2 ml of acetylacetone in sequence.

[0103] The remaining steps are the same as in Example 2 to prepare a hafnium oxide ferroelectric thin film with an alternating pattern of (Sr:HZO / Y:HZO)2 and a molar doping ratio of Sr:(Hf+Zr) = 1.5% and Y:(Hf+Zr) = 1.5%. Coat the obtained thin film with a top electrode to form a structure of Pt / (Sr:HZO / Y:HZO)2 / Pt / Ti / SiO2 / Si, and characterize the ferroelectric properties of the thin film using a ferroelectric analyzer.

[0104] Figure 6Schematic diagram of the polarization hysteresis loop of a hafnium oxide ferroelectric thin film with an alternating pattern of Sr:(Hf+Zr)=1.5% and Y:(Hf+Zr)=1.5% and an alternating pattern of (Sr:HZO / Y:HZO)2. It can be seen that the polarization value of this thin film is 10.55 μC / cm 2 , and its coercive electric field is 0.96 MV / cm.

[0105] As can be seen from the above embodiments, the present invention provides a method for preparing an alternately grown doped Hf 0.5 Zr 0.5 O2 ferroelectric thin film, comprising: weighing organic hafnium salts and organic metal salts of multiple doping elements in a preset ratio and placing them in a container, and then sequentially adding a monobasic acid and an organic solvent; heating and stirring until clear and then continuously stirring to room temperature to obtain a variety of precursor solutions with different solution concentrations, different doping elements, different doping amounts, etc.; dropping two or more precursor solutions onto a platinum substrate in an alternating manner for spin coating treatment; performing an annealing operation to obtain an alternately grown HZO ferroelectric thin film. By using the chemical solution deposition method, an HZO ferroelectric thin film grown in an alternating manner can be prepared without using large-scale equipment, and the preparation process is simple, the equipment cost is low, and it is easy to scale up production.

[0106] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an alternately grown ferroelectric thin film, characterized in that, It includes the following steps: 1) Coating the precursor solution A onto a platinum substrate and then performing annealing treatment to obtain an annealed A thin film sample; 2) Coating the precursor solution B onto the annealed A thin film sample, and performing annealing treatment to obtain an annealed AB thin film sample; The precursor solution A and the precursor solution B independently contain an organic hafnium salt, an organometallic salt of multiple doped elements, a monobasic acid, and an organic solvent; The organometallic salts of multiple doped elements in the precursor solution A and the precursor solution B are different; 3) Taking the steps 1) and 2) as a unit, repeat (n - 1) times to obtain a sample containing (AB) n thin film, and annealing the sample containing (AB) n thin film to obtain the ferroelectric thin film with alternating growth. The n≥2; The doped elements include Zr, and the doped elements also include one of Ba, Al, Gd, La, Sr, Y, Ce, and Ca; The organometallic salt of multiple doped elements includes zirconium acetylacetonate, and the organometallic salt of multiple doped elements also includes one of barium acetylacetonate, aluminum acetylacetonate, gadolinium acetylacetonate, strontium acetylacetonate, cerium acetylacetonate, calcium acetylacetonate, lanthanum acetylacetonate, and yttrium acetylacetonate; The zirconium acetylacetonate accounts for 97-98% of the total mass of the organometallic salt of multiple doped elements.

2. The method for preparing a ferroelectric thin film according to claim 1, wherein The hafnium organic salt includes one or more of hafnium acetylacetonate, Hf(acac)4, Hf(O-i-C3H7)4, and Hf(O n Bu)4; The mass ratio of the organic hafnium salt to the organometallic salt of multiple doped elements is 0.1-0.3:0.1-0.

2.

3. The method for preparing a ferroelectric thin film according to claim 2, wherein The monobasic acid is HNO3 and / or CH3COOH; The organic solvent is one or more of HO(CH2)2OCH3, CH2(CH3CO)2, CH3C6H5, and CH3CH2OH; The mass-volume ratio of the organic hafnium salt, the monobasic acid, and the organic solvent is 0.1-0.3 g:2.0-4.0 mL:1.0-3.0 mL.

4. The method for preparing a ferroelectric thin film according to claim 3, wherein The molar concentration of metal atoms in the precursor solution A and the precursor solution B is independently 0.1-0.2 mol / L.

5. The method for preparing a ferroelectric thin film according to claim 3 or 4, characterized in that, In step 1), the coating is spin coating, and the steps of spin coating are: Taking the precursor solution A and spin coating it onto a platinum substrate with a rotation speed of 300-500 r / min for 10-20 s, and then adjusting the rotation speed to 2000-3000 r / min and continuing to spin coat for 25-35 s to obtain a sample containing an A thin film; The temperature of the annealing treatment is 180-350 °C, and the time of the annealing treatment is 6-8 min.

6. The method for preparing a ferroelectric thin film according to claim 5, wherein In step 2), the coating is spin coating, and the steps of spin coating are: Taking the precursor solution B and spin coating it onto the annealed A thin film sample with a rotation speed of 300-500 r / min for 10-20 s, and then adjusting the rotation speed to 2000-3000 r / min and continuing to spin coat for 25-35 s to obtain a sample containing an AB thin film; The temperature of the annealing treatment is 180-350 °C, and the time of the annealing treatment is 6-8 min.

7. The method for preparing a ferroelectric thin film according to claim 6, wherein In step 3), the steps of the annealing treatment are: A sample containing (AB) n is annealed once at a first preset temperature and for a first preset time, and then annealed a second time at a second preset temperature and for a second preset time; The first preset temperature is lower than the second preset temperature.

8. The method for preparing a ferroelectric thin film according to claim 7, wherein The first preset temperature is 300-400 °C, and the first preset time is 250-300 s; The second preset temperature is 400-800 °C, and the second preset time is 250-300 s.

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