A hafnium oxide-based ferroelectric thin film capacitor and a method of manufacturing the same

Abstract

The application discloses a hafnium oxide-based ferroelectric thin film capacitor and a preparation method thereof, which comprises, from bottom to top, a substrate layer, a first electrode layer, a hafnium oxide ferroelectric layer, an electrode sacrifice layer and a second electrode layer, wherein the first electrode layer and the second electrode layer are made of the same electrode; secondly, the top interface / bottom interface oxygen atom ratio of the ferroelectric layer is 0.9-1.1; the electrode sacrifice layer is a multi-component compound formed by completely oxidizing a material with stronger oxidizability than the first and second electrode layers in an annealing process, and the thickness is 1-3 nm; the design of the electrode sacrifice layer improves the concentration and distribution uniformity of oxygen vacancies in the hafnium oxide ferroelectric layer, thereby effectively improving the ferroelectricity, durability and reduced wake-up effect of the hafnium oxide-based ferroelectric thin film.

Description

Technical Field

[0001] This invention relates to the field of ferroelectric materials technology, and in particular to a hafnium oxide-based ferroelectric thin-film capacitor and its preparation method. Background Technology

[0002] Ferroelectric memories (FeRAMs) are a novel type of memory that uses ferroelectric thin films as the storage medium. Due to their advantages such as non-volatility, low power consumption, high storage density, and high write speed, they have become a strong candidate material for next-generation memories. Since the first commercialization using PZT ferroelectric thin films in the 1990s, FeRAMs have been widely used in various fields such as smart cards, smart meters, and medical devices. With the surge in applications in the Internet of Things (IoT), artificial intelligence, and wearable technologies, the demand for lower operating voltages and higher density FeRAMs is increasing. However, the limited CMOS process compatibility and thickness scalability of PZT thin films pose significant challenges to the development of ultra-low voltage, high-density FeRAMs. Hafnium oxide-based ferroelectric thin films effectively overcome the size effect caused by the reduction in PZT film thickness and possess CMOS process compatibility, enabling a renewed and extensive study of high-density FeRAMs.

[0003] One of the key challenges of high-density FeRAM is reducing the operating voltage of ferroelectric capacitors while maintaining high polarization and reliability. Reducing the thickness of the ferroelectric film can effectively lower the operating voltage while achieving higher storage density. However, with the reduction of the thickness of HfO2-based ferroelectric films, problems such as low residual polarization, significant wake-up effect, and poor durability exist at low operating voltages. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a hafnium oxide-based ferroelectric thin-film capacitor and its preparation method, achieving high residual polarization and high reliability under low operating voltage, meeting the requirements of advanced technology nodes.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a hafnium oxide-based ferroelectric thin-film capacitor, comprising: a substrate layer, a first electrode layer, a hafnium oxide ferroelectric layer, an electrode sacrificial layer, and a second electrode layer, arranged sequentially from bottom to top, wherein the first electrode layer and the second electrode layer are the same electrode; furthermore, the electrode sacrificial layer is a multi-component compound formed by the complete oxidation of a material with stronger oxidizing power than the first and second electrode layers during annealing, and the oxygen atom ratio at the top interface to the bottom interface of the ferroelectric layer is between 0.9 and 1.1.

[0007] Preferably, the substrate layer comprises one or more of silicon, germanium, gallium arsenide, gallium nitride, gallium oxide, zinc oxide, silicon carbide, silicon oxide, aluminum oxide, silicon nitride, and strontium titanate.

[0008] Preferably, the thickness of the hafnium oxide ferroelectric layer is 5–20 nm.

[0009] Preferably, the material of the hafnium oxide ferroelectric layer comprises hafnium oxide or doped hafnium oxide, wherein the doped hafnium oxide is doped with one or more of zirconium, aluminum, silicon, cerium, gallium, lanthanum and yttrium.

[0010] Preferably, the first electrode and the third electrode are W electrodes with a thickness of 20-80 nm.

[0011] Preferably, the material required for the electrode sacrificial layer is a TiN electrode with a thickness of 1–3 nm.

[0012] Preferably, the materials required for the first electrode layer, the electrode sacrificial layer and the second electrode layer are any one of titanium nitride, tantalum nitride, hafnium nitride, tungsten, titanium and molybdenum.

[0013] Secondly, embodiments of the present invention also provide a method for preparing a hafnium oxide-based ferroelectric thin-film capacitor, the method comprising:

[0014] Step 1: The substrate is selected as n-type heavily doped silicon. The silicon substrate is ultrasonically cleaned for 5 minutes in sequence with acetone solution, alcohol solution and ultrapure water to remove surface organic contaminants and impurities, and then dried with nitrogen gas.

[0015] Step 2: Place the substrate layer into the magnetron sputtering chamber, close the chamber, and evacuate to a vacuum level of 1×10⁻⁶. -7 ~1×10 -9 Between Torr; set the magnetron sputtering deposition power to 80-140W, use argon as the inert gas, and grow the W bottom electrode to obtain the first electrode layer; after completion, fill the chamber to atmospheric pressure, open the chamber, and take out the first one;

[0016] Step 3: Place the first sample into the atomic layer deposition (ALD) chamber, evacuate to a vacuum level between 0.05 and 0.6 Torr, set the ALD tray temperature to 200–300°C, the chamber temperature to 100–180°C, the precursor source bottle temperature to 100–120°C, and the temperatures of all valves and pipes to 100–150°C, and wait for all temperature parameters to reach their preset values; set the ALD formulation and grow the ferroelectric layer; after completion, purge to atmospheric pressure, open the chamber, and remove the second sample;

[0017] Step 4: Place the second sample into the magnetron sputtering chamber, evacuate to a vacuum level between 1×10⁻⁷ and 1×10⁻⁹ Torr, and then deposit a TiN electrode to obtain the material required for the electrode sacrificial layer; after completion, place it back into the chamber and then deposit a W top electrode to obtain the second electrode layer, the first electrode layer and the second electrode layer; after completion, purge to atmospheric pressure, open the chamber, and take out the third sample;

[0018] Step 5: Place the third sample into a rapid annealing furnace for rapid thermal annealing; wherein the annealing temperature is 450-550℃, preferably 500℃; the annealing time is 30-60s, preferably 30s; the vacuum degree is between 0.01-0.2hPa, so that the film crystallizes rapidly to obtain a hafnium oxide-based ferroelectric thin film capacitor.

[0019] This invention provides a hafnium oxide-based ferroelectric thin-film capacitor and its fabrication method, comprising, from bottom to top: a substrate layer, a first electrode layer, a hafnium oxide ferroelectric layer, an electrode sacrificial layer, and a second electrode layer. The electrode sacrificial layer is a multi-component compound formed by the complete oxidation of a TiN electrode (with stronger oxidizing power than the first and second electrode layers) during annealing, and has a thickness of 1–3 nm. The design of the electrode sacrificial layer improves the concentration and uniformity of oxygen vacancies in the hafnium oxide ferroelectric layer, thereby effectively improving the ferroelectricity, durability, and reducing the wake-up effect of the hafnium oxide-based ferroelectric thin film. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a hafnium oxide-based ferroelectric thin film capacitor structure provided in an embodiment of the present invention;

[0021] Figure 2 For conventional hafnium oxide-based ferroelectric thin films in the prior art, W / HZO / W 底 Schematic diagram of capacitor structure;

[0022] Figure 3 This is a schematic diagram of the hysteresis loop of this embodiment and a conventional hafnium oxide-based ferroelectric thin film capacitor structure;

[0023] Figure 4 This is a schematic diagram of GIXRD characterization of a conventional capacitor structure provided in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the EDS element line scan results for a conventional capacitor structure provided in an embodiment of the present invention;

[0025] Figure 6 For conventional hafnium oxide-based ferroelectric thin films in the prior art, W / HZO / W 底 Schematic diagram of the hysteresis loop of the capacitor structure before and after wake-up;

[0026] Figure 7 This is a schematic diagram of the hysteresis loop of a hafnium oxide-based ferroelectric thin film capacitor structure before and after wake-up, according to an embodiment of the present invention.

[0027] Figure 8 This is a comparison chart of the durability performance of an embodiment of the present invention and a conventional capacitor structure;

[0028] Figure 9 The FORC test results of the first-order rotation curve of a conventional capacitor structure are provided in an embodiment of the present invention.

[0029] The structure consists of: 1. Substrate layer; 2. First electrode layer; 3. Hafnium oxide ferroelectric layer; 4. Electrode sacrificial layer; and 5. Second electrode layer. Detailed Implementation

[0030] To better illustrate this embodiment, some components in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that those skilled in the art will find that some well-known structures and their descriptions may be omitted in the drawings. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The technical solution of this invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] See Figure 1This invention provides a hafnium oxide-based ferroelectric thin-film capacitor, characterized in that it comprises, from bottom to top, a substrate layer, a first electrode layer, a hafnium oxide ferroelectric layer, an electrode sacrificial layer, and a second electrode layer, wherein the first electrode layer and the second electrode layer use the same electrodes; the electrode sacrificial layer is a multi-component compound formed by the complete oxidation of a material with stronger oxidizing power than the first and second electrode layers during annealing, and the oxygen atom ratio at the top / bottom interface of the ferroelectric layer is 0.9-1.1.

[0034] In one embodiment, the substrate layer includes one or more of silicon, germanium, gallium arsenide, gallium nitride, gallium oxide, zinc oxide, silicon carbide, silicon oxide, aluminum oxide, silicon nitride, and strontium titanate.

[0035] In one embodiment, the thickness of the hafnium oxide ferroelectric layer is 5–20 nm.

[0036] In one embodiment, the material of the hafnium oxide ferroelectric layer comprises hafnium oxide or doped hafnium oxide, wherein the doped hafnium oxide is doped with one or more of zirconium, aluminum, silicon, cerium, gallium, lanthanum and yttrium.

[0037] In one embodiment, the first electrode and the third electrode are W electrodes with a thickness of 20-80 nm.

[0038] In one embodiment, the electrode sacrificial layer is made of TiN electrode material with a thickness of 1–3 nm.

[0039] In one embodiment, the materials required for the first electrode layer, the electrode sacrificial layer, and the second electrode layer are any one of titanium nitride, tantalum nitride, hafnium nitride, tungsten, titanium, and molybdenum.

[0040] This invention also provides a method for preparing a hafnium oxide-based ferroelectric thin-film capacitor, the method comprising:

[0041] Step 1: The substrate is selected as n-type heavily doped silicon. The silicon substrate is ultrasonically cleaned for 5 minutes in sequence with acetone solution, alcohol solution and ultrapure water to remove surface organic contaminants and impurities, and then dried with nitrogen gas.

[0042] Step 2: Place the substrate layer into the magnetron sputtering chamber, close the chamber, and evacuate to a vacuum level between 1×10⁻⁷ and 1×10⁻⁹ Torr; set the magnetron sputtering deposition power to 80–140 W, use argon as the inert gas, and deposit the W substrate electrode to obtain the first electrode layer; after completion, purge to atmospheric pressure, open the chamber, and remove the first electrode layer.

[0043] Step 3: Place the first sample into the atomic layer deposition (ALD) chamber, evacuate to a vacuum level between 0.05 and 0.6 Torr, set the ALD tray temperature to 200–300°C, the chamber temperature to 100–180°C, the precursor source bottle temperature to 100–120°C, and the temperatures of all valves and pipes to 100–150°C, and wait for all temperature parameters to reach their preset values; set the ALD formulation and grow the ferroelectric layer; after completion, purge to atmospheric pressure, open the chamber, and remove the second sample;

[0044] Step 4: Place the second sample into the magnetron sputtering chamber, evacuate to a vacuum level between 1×10⁻⁷ and 1×10⁻⁹ Torr, and then deposit a TiN electrode to obtain the material required for the electrode sacrificial layer; after completion, place it back into the chamber and then deposit a W top electrode to obtain the second electrode layer. The first and second electrode layers use the same electrodes; after completion, purge to atmospheric pressure, open the chamber, and remove the third sample.

[0045] Step 5: Place the third sample into a rapid annealing furnace for rapid thermal annealing; wherein the annealing temperature is 450-550℃, wherein the TiN thickness is 1-2nm and the temperature is 450℃, and the TiN thickness is 3nm and the temperature is 500℃; the annealing time is 30-60s, preferably 30s; the vacuum degree is between 0.01-0.2hPa, so that the film crystallizes rapidly to obtain a hafnium oxide-based ferroelectric thin film capacitor, wherein the oxygen atom ratio of the top interface to the bottom interface of the ferroelectric layer is 0.9-1.1.

[0046] based on Figure 2 The W / HZO / W bottom capacitor structure shown is... Figure 1 The capacitor structure involves inserting an ultrathin TiN electrode between the tungsten (W) top electrode layer and the ferroelectric layer, which is the hafnium oxide-based ferroelectric thin film capacitor structure provided in this embodiment of the invention, defined as W / TiN / HZO / W. 底 The structure shows that the concentration and uniformity of oxygen vacancies in the hafnium oxide ferroelectric layer are improved, thereby effectively improving the ferroelectricity, durability, and reducing the wake-up effect of hafnium oxide-based ferroelectric thin films.

[0047] Here, further, see Figure 3 The hysteresis loops are of two different structures, W / TiN / HZO / W 底 The residual polarization of the capacitor structure is greater than W / HZO / W 底 The capacitor structure further demonstrates that the addition of an ultrathin TiN electrode can improve its ferroelectricity.

[0048] Figure 4 The GIXRD characterization results for the two capacitor structures show that the W / TiN / HZO / W provided in this embodiment of the invention... 底The peak value corresponding to the ferroelectricity of the capacitor structure is higher than that of W / HZO / W. 底 The capacitor structure further confirmed that adding an ultrathin TiN electrode can improve its ferroelectricity.

[0049] Figure 5 The EDS elemental line scan results for the two capacitor structures show that a higher relative O atom fraction indicates a lower oxygen vacancy content, compared to W / HZO / W. 底 The capacitor structure provided in this embodiment of the invention is W / TiN / HZO / W 底 The relative oxygen atom fraction in the capacitor structure is significantly smaller and more uniform along the ferroelectric layer. This indicates that adding an ultrathin TiN electrode increases the oxygen vacancy content and promotes a more uniform distribution of oxygen vacancies in the ferroelectric layer, thereby improving its ferroelectricity. Figure 5 The EDS line scan results show that, in the capacitor structure without ultrathin TiN, the oxygen atom ratio at the top / bottom interface of the ferroelectric layer is in the range of 1.3-1.4, indicating that the oxygen vacancy concentration at the top interface is much lower than that at the bottom interface. With the addition of the ultrathin TiN electrode layer, the oxygen atom ratio at the top / bottom interface of the ferroelectric layer is in the range of 0.9-1.1, indicating that the oxygen vacancy concentration at the top interface is close to that at the bottom interface. This increases the oxygen vacancy content in the ferroelectric layer and promotes the uniformity of oxygen vacancy distribution, thereby improving ferroelectricity, wake-up effect, and durability.

[0050] See also Figure 6 and Figure 7 For the two capacitor structures, the hysteresis loops before and after wake-up are given by the formula "(2P r,唤醒后 -2P r,唤醒前 ) / 2P r,唤醒前 The calculated values ​​reflect the arousal effect. The W / TiN / HZO / W provided in this embodiment of the invention... 底 The capacitance value is 0.431, W / HZO / W. 底 The capacitance value was 1.178; a smaller value indicates a weaker wake-up effect. The results show that the addition of an ultrathin TiN electrode can reduce the wake-up effect.

[0051] Figure 8 This is a comparison chart of the durability performance of two capacitor structures. The chart shows that the W / TiN / HZO / W capacitor provided in this embodiment of the invention... 底 The durability of the capacitor structure is significantly better than that of W / HZO / W. 底 Capacitor structure, and W / TiN / HZO / W 底 The capacitor structure can reach 10 10 The high durability under electrical cycling indicates that the addition of ultrathin TiN electrodes can significantly improve durability.

[0052] Figure 9The figure shows the first-order gyration curves (FORC) test results for two capacitor structures. It can be seen from the figure that the W / TiN / HZO / W capacitor provided in this embodiment of the invention... 底 The built-in field Ec of the capacitor structure is significantly smaller than that of W / HZO / W. 底 The capacitor structure indicates that the improved durability is due to the W / TiN / HZO / W 底 The more uniform distribution of oxygen vacancies in the capacitor structure results in a smaller built-in electric field, further improving durability.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A hafnium oxide-based ferroelectric thin-film capacitor, characterized in that, include: The following layers are arranged sequentially from bottom to top: a substrate layer, a first electrode layer, a hafnium oxide ferroelectric layer, an electrode sacrificial layer, and a second electrode layer. The first electrode layer and the second electrode layer use the same electrodes. The electrode sacrificial layer is a multi-component compound formed by the complete oxidation of a material with stronger oxidizing properties than the first and second electrode layers during the annealing process. The oxygen atom ratio at the top / bottom interface of the hafnium oxide ferroelectric layer is between 0.9 and 1.

1.

2. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The substrate layer includes one or more of silicon, germanium, gallium arsenide, gallium nitride, gallium oxide, zinc oxide, silicon carbide, silicon oxide, aluminum oxide, silicon nitride, and strontium titanate.

3. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The thickness of the hafnium oxide ferroelectric layer is 5-20 nm, and the material of the hafnium oxide ferroelectric layer includes hafnium oxide or doped hafnium oxide. The doped hafnium oxide is doped with one or more of zirconium, aluminum, silicon, cerium, gallium, lanthanum and yttrium.

4. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The materials required to form the first electrode layer, the electrode sacrificial layer and the second electrode layer are any one of titanium nitride, tantalum nitride, hafnium nitride, tungsten, titanium and molybdenum.

5. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The combination of the first electrode layer, the second electrode layer, and the electrode sacrificial layer includes: tungsten / titanium nitride, titanium nitride / titanium, hafnium nitride / molybdenum, tungsten / molybdenum, tantalum nitride / molybdenum, and titanium nitride / molybdenum.

6. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The thickness of the first electrode layer and the second electrode layer is 20-80 nm; the material thickness required for the electrode sacrificial layer is 1-3 nm.

7. The hafnium oxide-based ferroelectric thin-film capacitor as described in claim 1, characterized in that, The first electrode and the third electrode are W electrodes, and the material required to form the electrode sacrificial layer is a TiN electrode.

8. A method for preparing a hafnium oxide-based ferroelectric thin-film capacitor, characterized in that, The method includes: Step 1: The substrate is selected as n-type heavily doped silicon. The silicon substrate is ultrasonically cleaned for 5 minutes in sequence with acetone solution, alcohol solution and ultrapure water to remove surface organic contaminants and impurities, and then dried with nitrogen gas. Step 2: Place the substrate layer into the magnetron sputtering chamber, close the chamber, and evacuate to a vacuum level of 1×10⁻⁶. -7 ~1×10 -9 Between Torr; set the magnetron sputtering deposition power to 80-140W, use argon as the inert gas, and grow the W bottom electrode to obtain the first electrode layer; after completion, fill the chamber to atmospheric pressure, open the chamber, and take out the first one; Step 3: Place the first sample into the atomic layer deposition (ALD) chamber, evacuate to a vacuum level between 0.05 and 0.6 Torr, set the ALD tray temperature to 200–300°C, the chamber temperature to 100–180°C, the precursor source bottle temperature to 100–120°C, and the temperatures of all valves and pipes to 100–150°C, and wait for all temperature parameters to reach their preset values; set the ALD formulation and grow the ferroelectric layer; after completion, purge to atmospheric pressure, open the chamber, and remove the second sample; Step 4: Place the second sample into the magnetron sputtering chamber and evacuate to a vacuum level of 1×10⁻⁶. -7 ~1×10 - 9 Between Torr, TiN electrode deposition is performed to obtain the material required for the electrode sacrificial layer; after completion, it is placed in the chamber and the W top electrode is deposited to obtain the second electrode layer; after completion, it is filled with gas to atmospheric pressure, the chamber is opened, and the third sample is taken out; Step 5: Place the third sample in a rapid annealing furnace for rapid thermal annealing, where TiN is completely oxidized to form an electrode sacrificial layer. The annealing temperature is 450–550°C; when the TiN thickness is 1–2 nm, the preferred temperature is 450°C; when the TiN thickness is 3 nm, the preferred temperature is 500°C; the annealing time is 30–60 s, preferably 30 s; the vacuum degree is between 0.01 and 0.2 hPa, allowing the film to crystallize rapidly to obtain a hafnium oxide-based ferroelectric thin film capacitor, wherein the oxygen atom ratio at the top / bottom interface of the ferroelectric layer is 0.9–1.1.

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