Annealing-free hafnium-based ferroelectric capacitor device and preparation method thereof

Abstract

The invention relates to the technical field of capacitors, in particular to an annealing-free hafnium-based ferroelectric capacitor device and a preparation method thereof, and the method comprises the following steps: S1, oxidizing a silicon wafer to form a silicon dioxide layer as a substrate; s2, depositing a bottom electrode layer on the silicon dioxide layer; s3, oxidizing the bottom electrode layer to form a bottom electrode surface oxide layer; s4, depositing an Hf < 0.5 > Zr < 0.5 > O < 2 > ferroelectric film on the oxide layer on the surface of the bottom electrode, wherein the deposition temperature is 300-320 DEG C; and S5, depositing a top electrode layer on the Hf < 0.5 > Zr < 0.5 > O < 2 > ferroelectric film. According to the method, the hafnium-based ferroelectric capacitor with good ferroelectricity can be prepared without rapid thermal annealing, and the ferroelectric capacitor has high residual polarization and high read-write durability.

Description

Technical Field

[0001] The present invention relates to the technical field of memory devices, and in particular to an annealing-free hafnium-based ferroelectric capacitor device and a preparation method thereof. Background Art

[0002] In just over a decade, HfO2-based ferroelectric memory devices have advanced from the early research stage to the stage where they can be integrated into the back-end-of-line (BEOL) process and even industrialized. As capacitors in 1T1C ferroelectric random access memory (FRAM) chips, the thermal budget of HfO2-based ferroelectric films must be compatible with the thermal budget of the back-end-of-line (BEOL) process (<400°C), especially at advanced process nodes. However, for HfO2-based thin films, the emergence of ferroelectricity requires a rapid thermal annealing (RTA) temperature of 400°C or higher. For example, patent application CN117580445A discloses the fabrication of hafnium oxide-based ferroelectric thin film capacitors using an atomic layer deposition process with an annealing temperature of 400-600°C. Therefore, in the field of HfO2-based ferroelectric materials, seeking lower thermal budgets and eliminating annealing will be future technological trends.

[0003] Recent research has shown that pulsed laser deposition (PLD) can achieve ultra-high remnant polarization (Pr) through epitaxial deposition. Although annealing is not required, this technique requires high temperatures exceeding 750°C during thin film deposition, making it incompatible with back-end processes. Currently, there are still no annealing-free HfO2-based ferroelectric devices. Theoretical and process approaches to achieving annealing-free hafnium-based ferroelectric devices remain a significant challenge.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide an annealing-free hafnium-based ferroelectric capacitor device and a preparation method thereof, wherein the method can prepare an HZO capacitor device with good ferroelectricity without the need for rapid thermal annealing, and the ferroelectric capacitor device has high remnant polarization and high read and write durability.

[0006] A first aspect of the present invention provides a method for preparing an annealing-free hafnium-based ferroelectric capacitor device, comprising the following steps:

[0007] S1, oxidizing a silicon wafer to form a silicon dioxide layer as a substrate;

[0008] S2, depositing a bottom electrode layer on the silicon dioxide layer;

[0009] S3, oxidizing the bottom electrode layer to form an oxide layer on the bottom electrode surface;

[0010] S4, deposit Hf on the oxide layer on the bottom electrode surface 0.5 Zr0.5 O2 (HZO) ferroelectric thin film, deposition temperature is 300℃-320℃;

[0011] S5, in Hf 0.5 Zr 0.5 A top electrode layer is deposited on the O2 ferroelectric thin film.

[0012] Preferably, before step S1, the silicon wafer is chemically cleaned. The cleanliness of the substrate will affect the growth quality of the bottom electrode layer, thereby affecting the overall performance of the capacitor. The cleaning of the silicon wafer should ensure a smooth bottom interface as much as possible.

[0013] Preferably, in step S1, the substrate is a SiO2 / Si substrate.

[0014] Preferably, the thickness of the silicon dioxide layer is 100-300 nm, and the thickness of the silicon dioxide layer can be reduced or increased according to actual process conditions.

[0015] Preferably, in step S2, an ion beam sputtering process is used to deposit a bottom electrode layer on the silicon dioxide layer, and the bottom electrode layer is a TiN bottom electrode layer.

[0016] Preferably, the thickness of the bottom electrode layer is 30-50 nm, more preferably 40 nm.

[0017] Preferably, in step S3, an atomic layer deposition process is used, and ozone is used as an oxygen source to oxidize the bottom electrode layer to form a bottom electrode surface oxide layer. The bottom electrode surface oxide layer is a TiN surface oxide layer, i.e., a TiO2 layer, which promotes the subsequent process of Hf 0.5 Zr 0.5 Crystallization of the ferroelectric phase during the growth of O2 ferroelectric thin films.

[0018] Preferably, in step S3, the deposition condition is 1000 ms / cycle, with a total of 30-50 cycles.

[0019] Preferably, the thickness of the TiN surface oxide layer (TiO2 layer) is 1-3 nm; more preferably 1.75-2.3 nm.

[0020] Preferably, in step S4, an atomic layer deposition process is used to deposit Hf on the oxide layer on the bottom electrode surface by alternately growing one cycle of HfO2 and one cycle of ZrO2. 0.5 Zr 0.5 O2 ferroelectric thin film.

[0021] Preferably, the thickness of HfO2 in one cycle is 0.1 nm, and the thickness of ZrO2 in one cycle is 0.1 nm.

[0022] Preferably, in step S4, Hf[N(CH3)2]4(TDMAH) is used as the hafnium source, and Zr[N(CH3)2]4(TDMAZ) is used as the zirconium source. The use of TDMAH and TDMAZ as two metal sources results in minimal carbon residue.

[0023] Preferably, ozone is used as the oxygen source, which has stronger oxidizing properties.

[0024] Preferably, the deposition temperature is 320°C. At this temperature, Hf 0.5 Zr 0.5 The tetragonal phase and ferroelectric phase in O2 ferroelectric films tend to crystallize first.

[0025] Preferably, the Hf 0.5 Zr 0.5 The thickness of the O2 ferroelectric film is 11-15 nm, more preferably 11 nm, 13 nm, or 15 nm.

[0026] Preferably, in step S5, an ion beam sputtering process is used to deposit Hf 0.5 Zr 0.5 A top electrode layer is deposited on the O2 ferroelectric thin film, and the top electrode layer is a TiN top electrode layer.

[0027] Preferably, the thickness of the top electrode layer is 30-50 nm, more preferably 40 nm.

[0028] The second aspect of the present invention provides an annealing-free hafnium-based ferroelectric capacitor device prepared by the above-mentioned preparation method, comprising a bottom electrode layer, a bottom electrode surface oxide layer, a Hf 0.5 Zr 0.5 O2 ferroelectric thin film and top electrode layer.

[0029] Preferably, the substrate is a SiO2 / Si substrate.

[0030] Preferably, the bottom electrode layer is a TiN bottom electrode layer.

[0031] Preferably, the bottom electrode surface oxide layer is a TiN surface oxide layer, that is, a TiO2 layer.

[0032] Preferably, the top electrode layer is a TiN top electrode layer.

[0033] Preferably, the thickness of the silicon dioxide layer is 100-300 nm, more preferably 300 nm. The thickness of the silicon dioxide layer can also be reduced or increased according to actual process conditions.

[0034] Preferably, the thickness of the bottom electrode layer is 30-50 nm, more preferably 40 nm.

[0035] Preferably, the thickness of the TiN surface oxide layer (TiO2 layer) is 1-3 nm; more preferably 1.75-2.3 nm.

[0036] Preferably, the Hf 0.5 Zr 0.5 The thickness of the O2 ferroelectric film is 11-15 nm, more preferably 11 nm, 13 nm, or 15 nm.

[0037] Preferably, the thickness of the top electrode layer is 30-50 nm, more preferably 40 nm.

[0038] The present invention has the following beneficial effects:

[0039] (1) The method of the present invention forms an oxide layer on the surface of the bottom electrode by performing an oxidation process on the surface of the bottom electrode layer, thereby promoting the crystallization of the ferroelectric phase during the subsequent growth of the HZO ferroelectric thin film.

[0040] (2) When depositing the HZO ferroelectric thin film, the method of the present invention uses a specific deposition temperature so that the tetragonal phase and the ferroelectric phase in the HZO thin film tend to crystallize first.

[0041] (3) The method of the present invention can realize an HZO capacitor device with good ferroelectric properties without the need for rapid thermal annealing, and the ferroelectric capacitor device has high remnant polarization and high read and write durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 A schematic flow chart of a method for preparing an annealing-free hafnium-based ferroelectric capacitor device provided by the present invention;

[0044] Figure 2 A schematic structural diagram of an annealing-free hafnium-based ferroelectric capacitor device provided by the present invention;

[0045] Figure 3 This is a transmission electron microscope image of the annealing-free hafnium-based ferroelectric capacitor device prepared in Example 1 of the present invention;

[0046] Figure 4 Polarization-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1-4 of the present invention;

[0047] Figure 5Graph showing the double remanent polarization (2Pr) results of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1-4 of the present invention;

[0048] Figure 6 Polarization-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 of the present invention in the initial state;

[0049] Figure 7 The annealing-free hafnium-based ferroelectric capacitor device prepared in Examples 1, 5, and 6 of the present invention was 6 Polarization-electric field curve when ;

[0050] Figure 8 The butterfly-shaped dielectric constant-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 of the present invention;

[0051] Figure 9 Graph showing the read and write endurance characteristics of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 of the present invention.

[0052] Explanation of reference numerals: 1, substrate; 2, bottom electrode layer; 3, bottom electrode surface oxide layer; 4, Hf 0.5 Zr 0.5 O2 ferroelectric thin film; 5. Top electrode layer. DETAILED DESCRIPTION

[0053] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] Example 1

[0057] like Figure 1As shown, this embodiment provides a method for preparing an annealing-free hafnium-based ferroelectric capacitor device, comprising the following steps:

[0058] S1. Oxidation is performed on a silicon wafer to form a silicon dioxide layer (SiO2 / Si) as a substrate. The thickness of the silicon dioxide layer is 300 nm.

[0059] Before step S1, the silicon wafer is chemically cleaned to ensure a smooth bottom interface as much as possible;

[0060] S2. At room temperature, a TiN bottom electrode layer with a thickness of 40 nm is deposited on the silicon dioxide layer using an ion beam sputtering process.

[0061] Specifically, the process parameters for ion beam sputtering TiN are:

[0062] Beam voltage: 800 V, beam current: 46 mA, argon flow rate: 8 sccm, nitrogen flow rate: 5 sccm.

[0063] S3. Place the sample in an atomic layer deposition system and use ozone (O3) as an oxygen source to oxidize the bottom electrode layer to form a TiN surface oxide layer (TiO2 layer) with a thickness of about 1.75-2.3 nm; the deposition conditions are 1000 ms / cycle, for a total of 40 cycles.

[0064] S4, using an atomic layer deposition system, using Hf[N(CH3)2]4(TDMAH) as the hafnium source, Zr[N(CH3)2]4(TDMAZ) as the zirconium source, and ozone as the oxygen source; Hf is deposited on the TiN surface oxide layer by alternately growing 1 cycle of HfO2 and 1 cycle of ZrO2. 0.5 Zr 0.5 O2 ferroelectric film, deposition temperature is 320℃, thickness is 11nm; 1 cycle HfO2 thickness is 0.1nm, 1 cycle ZrO2 thickness is 0.1nm; where 1 cycle HfO2 = 1 cycle , HZO ferroelectric films of different thicknesses were deposited by changing the number of ZrO2:HfO2 growth cycles.

[0065] S5, at room temperature, using ion beam sputtering process on Hf 0.5 Zr 0.5 A TiN top electrode layer with a thickness of 40 nm is deposited on the O2 ferroelectric film.

[0066] Specifically, the process parameters for ion beam sputtering TiN are:

[0067] Beam voltage: 800 V, beam current: 46 mA, argon flow rate: 8 sccm, nitrogen flow rate: 5 sccm.

[0068] like Figure 2 As shown, this embodiment also provides an annealing-free hafnium-based ferroelectric capacitor device, comprising a bottom electrode layer 2, a bottom electrode surface oxide layer 3, a Hf 0.5 Zr 0.5 O2 ferroelectric thin film 4 and top electrode layer 5.

[0069] The TEM image of the annealing-free hafnium-based ferroelectric capacitor device obtained by the preparation method of this embodiment is shown in FIG. Figure 3 From the figure, we can see that the TiN bottom electrode layer, TiN surface oxide layer (TiO2 layer), Hf 0.5 Zr 0.5 O2 ferroelectric thin film (HZO) and TiN top electrode layer.

[0070] Example 2

[0071] This embodiment is basically the same as embodiment 1, except that in step S4, the deposition temperature is 250°C.

[0072] Example 3

[0073] This embodiment is basically the same as embodiment 1, except that in step S4, the deposition temperature is 280°C.

[0074] Example 4

[0075] This embodiment is basically the same as embodiment 1, except that in step S4, the deposition temperature is 300°C.

[0076] Example 5

[0077] This embodiment is basically the same as embodiment 1, except that: Hf 0.5 Zr 0.5 The thickness of the O2 ferroelectric film is 13 nm.

[0078] Example 6

[0079] This embodiment is basically the same as embodiment 1, except that: Hf 0.5 Zr 0.5 The thickness of the O2 ferroelectric film is 15 nm.

[0080] Comparative Example 1

[0081] This comparative example is basically the same as Example 1, except that in step S4, the deposition temperature is greater than 320°C (330°C-400°C).

[0082] Comparative Example 2

[0083] This comparative example is basically the same as Example 1, except that step S3 is not performed, that is, the TiN surface oxide layer (TiO2 layer) is not formed.

[0084] Test Example 1

[0085] After testing, the polarization-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1-4 are shown in FIG. Figure 4 As can be seen from the figure: when the atomic layer deposition temperature is 250℃, 280℃ and 300℃, the capacitor device does not show obvious polarization-electric field hysteresis curve and residual polarization intensity (polarization intensity corresponding to the electric field intensity of 0); only when the deposition temperature reaches 320℃, the capacitor device shows a hysteresis curve and the residual polarization intensity reaches 4μC / cm 2 .

[0086] The statistical results of the double remanent polarization (2Pr) of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1-4 are shown in Figure 5 , it can be seen from the figure: after 10 4 After the electric field cycle, as the deposition temperature changes, at 320℃, an obvious residual polarization value appears, that is, ferroelectricity appears.

[0087] In addition, it was tested that in Comparative Example 1, when the deposition temperature was greater than 320°C (330°C-400°C), ferroelectricity did not appear; in Comparative Example 2, when step S3 was not performed, that is, when the TiN surface oxide layer (TiO2 layer) was not formed, ferroelectricity also did not appear.

[0088] Test Example 2

[0089] After testing, the polarization-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 in the initial state are shown in FIG. Figure 6 , it can be seen from the figure that: when Hf 0.5 Zr 0.5 When the thickness of the O2 film is 11nm, 13nm and 15nm, the capacitor devices all show ferroelectricity, and the 2Pr can reach up to 11μC / cm 2 .

[0090] The annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 were 6 The polarization-electric field curve is shown in Figure 7 , it can be seen from the figure: when the number of read and write reaches 10 6 When the polarization-electric field curve becomes a more rectangular curve, the maximum value of 2Pr increases to 17μC / cm 2 , that is, the wake-up effect of the hafnium-based ferroelectric device occurs. It is worth noting that the 2Pr of Example 6 (15nm) does not change, and the wake-up-free effect is achieved.

[0091] The butterfly-shaped dielectric constant-electric field curves of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 are shown in FIG. Figure 8 , it can be seen from the figure that: when Hf 0.5 Zr 0.5 When the thickness of the O2 film is 11nm, 13nm and 15nm, the dielectric response of the capacitor device is a typical butterfly-shaped curve of the ferroelectric film, which verifies the ferroelectricity of the annealing-free hafnium-based film from another aspect.

[0092] The read and write endurance characteristics of the annealing-free hafnium-based ferroelectric capacitor devices prepared in Examples 1, 5, and 6 are shown in FIG. Figure 9 , it can be seen from the figure: different thickness Hf 0.5 Zr 0.5 The O2 ferroelectric capacitor device shows different 2Pr changes with the increase of read and write times. Example 1 (11nm) and Example 5 (13nm) show obvious wake-up effects, while Example 6 (15nm) does not show any wake-up effect. The 2Pr curve with read and write times can verify the read and write endurance of the ferroelectric memory device. The read and write endurance of Example 1 reaches 10 10 , meeting the requirements of storage devices.

[0093] In summary, the preparation method of the present invention meets the thermal budget compatibility of hafnium-based ferroelectric memory devices in the back-end process. Through this process, hafnium-based ferroelectric memory devices that do not require rapid thermal annealing are realized. The maximum temperature of the entire process flow is as low as 320°C, which can fully meet the thermal budget temperature of less than 400°C required by existing back-end processes.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an annealing-free hafnium-based ferroelectric capacitor device, characterized in that: The following steps are involved: S1, oxidizing a silicon wafer to form a silicon dioxide layer as a substrate; S2, depositing a bottom electrode layer on the silicon dioxide layer; S3, oxidizing the bottom electrode layer to form an oxide layer on the bottom electrode surface; S4, deposit Hf on the oxide layer on the bottom electrode surface 0.5 Zr 0.5 O2 ferroelectric film, deposition temperature is 300℃-320℃; S5, in Hf 0.5 Zr 0.5 A top electrode layer is deposited on the O2 ferroelectric thin film.

2. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S2, an ion beam sputtering process is used to deposit a bottom electrode layer on the silicon dioxide layer, wherein the bottom electrode layer is a TiN bottom electrode layer.

3. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S3, an atomic layer deposition process is used, and ozone is used as an oxygen source to oxidize the bottom electrode layer to form a bottom electrode surface oxide layer, wherein the bottom electrode surface oxide layer is a TiN surface oxide layer.

4. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 3, wherein: In step S3, the deposition condition is 1000 ms / cycle, with a total of 30-50 cycles.

5. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S4, an atomic layer deposition process is used to deposit Hf on the oxide layer on the bottom electrode surface by alternately growing one cycle of HfO2 and one cycle of ZrO2. 0.5 Zr 0.5 O2 ferroelectric thin film; the thickness of HfO2 in one cycle is 0.1nm, and the thickness of ZrO2 in one cycle is 0.1nm.

6. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S4, the deposition temperature is 320°C.

7. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S4, Hf[N(CH3)2]4 is used as the hafnium source, Zr[N(CH3)2]4 is used as the zirconium source, and ozone is used as the oxygen source.

8. The method for preparing an annealing-free hafnium-based ferroelectric capacitor device according to claim 1, wherein: In step S5, an ion beam sputtering process is used to deposit Hf 0.5 Zr 0.5 A top electrode layer is deposited on the O2 ferroelectric thin film, and the top electrode layer is a TiN top electrode layer.

9. The annealing-free hafnium-based ferroelectric capacitor device prepared by the preparation method according to any one of claims 1 to 8, characterized in that: It includes a bottom electrode layer, a bottom electrode surface oxide layer, a Hf 0.5 Zr 0.5 O2 ferroelectric thin film and top electrode layer.

10. The annealing-free hafnium-based ferroelectric capacitor device according to claim 9, characterized in that: The Hf 0.5 Zr 0.5 The thickness of the O2 ferroelectric film is 11-15 nm.

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