A method for preparing HZO ferroelectric material

Abstract

The present invention discloses a preparation method of HZO ferroelectric material. A bottom electrode is grown on a substrate, and atomic layer deposition (ALD) is used to deposit on the bottom electrode. After deposition, an amorphous HZO thin film is obtained. The HZO is subjected to rapid thermal annealing to obtain a ferroelectric thin film. During the annealing process, a top electrode is not required for assistance, and robust ferroelectricity can be obtained. In addition, by annealing under oxygen, the cycling durability is increased to more than 10<supgt;10< / supgt> cycles. By optimizing the growth process, annealing process and subsequent electrode layer stacking method of HZO, the ferroelectric polarization and durability of HZO are successfully improved. This method mainly involves defect regulation and interface engineering technologies to improve the defects existing in HZO and enhance the interface quality, thereby reducing the leakage current and increasing the fatigue life. Through this method, the HZO thin film exhibits a remanent polarization intensity as high as 29 μC / cm<supgt;2< / supgt> and a cyclicity of more than 3×10<supgt;10< / supgt>, improving the ferroelectric properties of HZO and providing the possibility for its application in high-performance electronic devices.

Description

Technical Field

[0001] The invention belongs to the field of ferroelectric materials, and in particular relates to a method for preparing a HZO ferroelectric material. Background Art

[0002] As a silicon-compatible material, hafnium oxide (HfO 2 ) is considered to be a substitute for SiO 2 It is reported that HfO-based materials are key high dielectric constant materials to further reduce the size of advanced complementary metal oxide semiconductor (CMOS) devices and circuits. 2 The nanofilm has ferroelectricity even below 10nm, which has great potential in the scalability and CMOS compatibility of ferroelectric memory. 2 Nanofilms of HfO are expected to become key materials for future non-volatile memory devices and low-power / high-performance logic devices. 2 Ferroelectricity in nanofilms is believed to be a metastable orthorhombic (o) phase (Pca2 1 ) is formed. Studies have shown that during the annealing process, the mechanical stress provided by the top electrode is very important for improving the HfO 2 However, the process of growing electrodes increases the difficulty of adding HfO 2 The difficulty of integrating HfO-based ferroelectric films into advanced CMOS processes. Most importantly, the underlying physical mechanism of the top electrode effect is still unclear, which cannot guide experiments to further improve the performance of HfO 2 On the other hand, there are few studies to optimize the ferroelectric properties of HfO films without the assistance of top electrodes. 2 Ferroelectricity in the substrate film. Ferroelectric films with good ferroelectricity but without the assistance of top electrodes are not only conducive to the integration in CMOS devices, but also can be used for functional expansion. Therefore, it is necessary to develop HfO without top electrode constraints. 2 The ferroelectric films based on ferroelectric materials are studied in more detail to elucidate the physical mechanism behind their ferroelectricity and optimize their ferroelectric properties. Summary of the invention

[0003] The object of the present invention is to provide a high ferroelectricity, high durability Hf 0.5 Zr 0.5 O 2 The invention discloses a method for preparing a ferroelectric thin film of SiO. The technical problem to be solved is: the HZO provided by the invention is an excellent ferroelectric thin film, wherein the structure is SiO 2 / Si is used as the substrate, W is grown on the substrate as the bottom electrode, HZO is grown on the bottom electrode, and the W array is grown on the HZO as the electrode. After the HZO is grown, rapid thermal annealing is performed under oxygen. Since there is no top electrode during the annealing process, there is no interface layer between the HZO and the W top electrode. In addition, the use of oxygen annealing can well compensate for the oxygen vacancies of HZO, reduce defects, and improve the quality of HZO.

[0004] The method for preparing the HZO ferroelectric material provided by the present invention comprises the following steps:

[0005] The W bottom electrode was deposited by magnetron sputtering.

[0006] In the above method, the magnetron sputtering gas pressure is 4.5×10 -4 Pa, the deposition power is 30 W, the deposition time is 10 min, the W electrode thickness is 30 nm, and the HZO thickness is 10 nm.

[0007] The magnetron sputtering is performed on a substrate.

[0008] The substrate is specifically SiO 2 / Si.

[0009] HZO thin film is deposited by ALD, and HZO / W / SiO is obtained after deposition. 2 / Si structure.

[0010] In the above method, the ratio of Hf to Zr is 1:1.

[0011] In the ALD deposition step, the carrier gas is nitrogen, the flow rate of the carrier gas is 20 s.ccm, and the system pressure is 0.17 Torr.

[0012] The deposition temperature was 200°C.

[0013] The deposition time was 7 hours.

[0014] The W / SiO 2 / Si substrate is located in the center of the cavity.

[0015] The method further comprises the following step: after the ALD deposition step, naturally cooling the system to room temperature.

[0016] The HZO is rapidly thermally annealed in a rapid annealing furnace to obtain polycrystalline HZO.

[0017] The annealing temperature is 600°C.

[0018] The annealing time is 10s.

[0019] The annealing atmosphere is an oxidizing atmosphere, specifically oxygen.

[0020] The annealing pressure is normal pressure, specifically 1.01×10 5 Pa.

[0021] The W top electrode was deposited by magnetron sputtering, and a hard mask was used during the array growth process.

[0022] The sputtering pressure is 4.5×10 -4 Pa, the deposition power is 30 W, the deposition time is 19 min, the W top electrode thickness is 50 nm, and the diameter is 100 μm.

[0023] The HZO ferroelectric film has a thickness of 10 nm and a residual polarization intensity of 29 μC / cm 2 , cycle durability exceeds 3×10 10 .

[0024] The HZO ferroelectric thin film prepared according to the above method is applied to ferroelectric random access memory, ferroelectric tunnel junction, etc. related to spin electronics, and also falls within the protection scope of the present invention.

[0025] The technical effects of the present invention are:

[0026] The present invention proposes a new method for preparing HZO ferroelectric thin films, which can obtain robust ferroelectricity without the assistance of top electrodes during the annealing process. In addition, by annealing under oxygen, the cycle durability is increased to more than 10 10 Cycles. The HZO film grown by ALD on the W bottom electrode. After oxygen annealing, the oxygen vacancies in the film are well compensated, the film quality is improved, and the polarization characteristics are enhanced. In addition, since there is no top electrode during the annealing process, there is no interface reaction layer between HZO and the top electrode, which greatly improves the cycle durability of the HZO film.

[0027] The HZO ferroelectric film of the present invention is annealed after deposition and annealed under oxygen, which is recorded as PDA-O. As a control, the PDA sample annealed under nitrogen is recorded as PDA-N. After the HZO film is deposited by ALD and the top electrode is grown, it is annealed under nitrogen, that is, the top electrode is required to assist in the metallization annealing of the ferroelectric polarization phase, and the control sample is recorded as PMA. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 (a) is a schematic diagram of the capacitor structure of Example 1 of the present invention;

[0029] Figure 1 (b) is a schematic diagram of the preparation process of Example 1 of the present invention and Comparative Examples 1 and 2, from left to right, respectively, PMA, PDA-N, and PDA-O;

[0030] Figure 1(c) is the GIXRD characterization results of Example 1 of the present invention and Comparative Examples 1 and 2;

[0031] Figure 2 (a) is the ferroelectric polarization test results of Example 1 of the present invention and Comparative Examples 1 and 2;

[0032] Figure 2 (b) is the residual polarization test results of Example 1 of the present invention and Comparative Examples 1 and 2;

[0033] Figure 2 (c) is the residual polarization value of Example 1 of the present invention under different frequencies and electric fields;

[0034] Figure 2 (d) is the durability test result of comparative example 1 of the present invention;

[0035] Figure 2 (e) is the durability test result of comparative example 2 of the present invention;

[0036] Figure 2 (f) is the durability test result of Example 1 of the present invention;

[0037] Figure 3 (a) is a high-resolution transmission electron microscopy photograph of Comparative Example 1 of the present invention;

[0038] Figure 3 (b) Yes Figure 3 (a) A partial enlarged view;

[0039] Figure 3 (c) is a high-resolution transmission electron microscope photograph of Example 1 of the present invention;

[0040] Figure 3 (d) Yes Figure 3 (c) A partial enlarged view;

[0041] Figure 4 (a) is the XPS characterization result of Hf element of Example 1 of the present invention and Comparative Example 2;

[0042] Figure 4 (b) is the XPS characterization result of Zr element of Example 1 of the present invention and Comparative Example 2;

[0043] Figure 4 (c) is the XPS characterization result of the O element of Example 1 of the present invention and Comparative Example 2; DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to the following examples.

[0045] The above methods are conventional methods unless otherwise specified. The above raw materials can be obtained from public commercial channels unless otherwise specified. Figure 1 As shown;

[0046] Example 1

[0047] SiO 2 The Si substrate was placed upside down in the magnetron sputtering equipment, and the metal tungsten target was located below the substrate. -4 Pa, and the power was 30 watts for 10 minutes to obtain the metal electrode. 2 The / Si structure is placed in the center of the ALD vacuum chamber, with tetrakis(diethylamino)hafnium, tetrakis(diethylamino)zirconium and H 2 O is deposited on the substrate in an atomic layer according to a molar ratio of 1:1:2 to obtain amorphous HZO. The amorphous HZO is placed in the center of a rapid annealing furnace and annealed at 600°C for 10s in an oxygen atmosphere to obtain HZO crystal PDA-O.

[0048] Comparative Example 1

[0049] The order of first performing rapid thermal annealing on HZO and then depositing the top electrode in the embodiment is changed to first depositing the top electrode and then performing rapid thermal annealing, and the oxygen annealing is changed to nitrogen annealing to obtain the comparative example 1 sample PMA.

[0050] Comparative Example 2

[0051] The process is substantially the same as that of the embodiment, except that the oxygen annealing process is replaced by a nitrogen annealing process to obtain the comparative example 2 sample PDA-N.

[0052] Figure 1 (c) is the GIXRD result of Example 1 of the present invention and Comparative Examples 1 and 2. As can be seen from the figure, both the Example and the Comparative Example are polycrystalline and can obtain good crystal structures. This shows that the present invention can obtain a crystal structure that is basically similar to that of HZO grown with the assistance of the top electrode without the assistance of the top electrode.

[0053] Figure 2 (a) is the ferroelectric polarization test results of Example 1 of the present invention and Comparative Examples 1 and 2. Example 1 shows a high ferroelectric polarization of 29 μC / cm 2 The remanent polarization intensity is more than 3×10 10 That is, robust ferroelectricity can be obtained without the assistance of the top electrode.

[0054] Figure 2 (b) is the residual polarization test results of Example 1 of the present invention and Comparative Examples 1 and 2. Figure 2 (a) The same.

[0055] Figure 2 (c) is the residual polarization value of Example 1 of the present invention under different frequencies and electric fields, which ensures that the subsequent cycle test is effective.

[0056] Figure 2 (d) is the durability test result of comparative example 1 of the present invention. The awakening effect and fatigue effect are obvious.

[0057] Figure 2 (e) is the durability test result of comparative example 2 of the present invention. The awakening effect is obvious, and the fatigue effect is not obvious

[0058] Figure 2 (f) is the durability test result of Example 1 of the present invention. Neither the awakening effect nor the fatigue effect is obvious.

[0059] Figure 3 (a) is a high-resolution transmission electron microscopy photograph of comparative example 1 of the present invention. The W / HZO / W structure can be clearly seen.

[0060] Figure 3 (b) Yes Figure 3 (a) A local enlarged view. An interface reaction layer of about 1 nm can be clearly seen at the interface between HZO and the top electrode. This interface layer will lead to the generation and migration of oxygen vacancies during the cycle process, resulting in reduced durability.

[0061] Figure 3 (c) is a high-resolution transmission electron microscopy photograph of Example 1 of the present invention. The W / HZO / W structure can be clearly seen.

[0062] Figure 3 (d) Yes Figure 3 (c) is a partial enlarged view. There is a clear delamination between HZO and the top electrode, indicating that no obvious interface reaction occurred during the annealing process, reducing the defect content during the cycle. It proves that not using the top electrode can significantly reduce the interface reaction.

[0063] Figure 4 (a) is the XPS characterization result of Hf element in Example 1 of the present invention and Comparative Example 2. There is no obvious difference in the binding energy of Hf element in the Example and the Comparative Example.

[0064] Figure 4 (b) is the XPS characterization result of the Zr element in Example 1 of the present invention and Comparative Example 2. There is no obvious difference in the binding energy of the Zr element in the Example and the Comparative Example.

[0065] Figure 4(c) is the XPS characterization result of the O element in Example 1 of the present invention and Comparative Example 2. There is a significant difference in the oxygen vacancy content between the Example and the Comparative Example. The oxygen vacancy content in the Example is 24.11%, which is much lower than 32.11% in Comparative Example 2. It is proved that oxygen annealing can reduce the oxygen vacancy concentration in HZO.

Claims

1. A method for preparing a HZO ferroelectric material, characterized in that: A bottom electrode is grown on a substrate, wherein the bottom electrode is W, and atomic layer deposition ALD is used to deposit on the bottom electrode, using tetrakis(diethylamino)hafnium, tetrakis(diethylamino)zirconium and H2O as raw materials, and the molar ratio of tetrakis(diethylamino)hafnium, tetrakis(diethylamino)zirconium and H2O is 1:1:2, and an amorphous HZO film is obtained after deposition, wherein in the step of deposition, the carrier gas is nitrogen, the system pressure is 0.17 Torr, and the deposition temperature is 200°C. The HZO is subjected to rapid thermal annealing to obtain a polycrystalline HZO ferroelectric film, wherein the annealing atmosphere is oxygen and the annealing time is 10 seconds; and no top electrode assistance is required during the annealing process.

2. The method according to claim 1, characterized in that: The bottom electrode is formed on a substrate by magnetron sputtering, and the substrate is SiO2 / Si.

3. The method according to claim 1, characterized in that: The deposition time was 7 h; the flow rate of the carrier gas was 20 sccm.

4. The method according to claim 1 or 3, characterized in that: The method further comprises the following step: after the deposition step, naturally cooling the system to room temperature.

5. The method according to claim 1, characterized in that: The annealing pressure is normal pressure, specifically 1.01×10 5 Pa.

6. A method for preparing a metal / oxide / metal capacitor structure, characterized in that: After annealing the ferroelectric film prepared by any method of claims 1-5, a top electrode is grown to obtain a W / HZO / W / SiO2 / Si capacitor structure; during the top electrode deposition process, a mask plate is used to deposit the top electrode array, and the specific size is: a cylinder with a diameter of 100μm.

7. The method according to claim 6, characterized in that: The deposition of the bottom and top electrodes as well as the ALD deposition are all performed in a vacuum chamber.

8. The method according to claim 6, characterized in that: During the deposition of the top electrode and the bottom electrode, the target material is located below the substrate and the base is located at the center of the substrate; during the ALD deposition process, the raw material is located in the source bottle below and the base is located at the center of the vacuum chamber.

9. The method according to claim 6, characterized in that: The capacitor structure has a bottom electrode thickness of 30nm, a HZO thickness of 10nm, and a top electrode thickness of 50nm.

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