Hf02-based ferroelectric capacitors and methods of making, memory

Abstract

The present disclosure provides a HfO2-based ferroelectric capacitor applied to the field of microelectronic technology, which comprises, from top to bottom, a substrate, a lower electrode, a dielectric layer, an upper electrode and a protective layer. The device can complete wake-up only by applying a voltage excitation once, and its residual polarization strength is close to or slightly greater than the limit of the residual polarization strength of the device after wake-up under conventional pulse operation. It is equivalent to avoiding the fluctuation of the initial residual polarization strength by a one-time pretreatment before the memory is put into use, greatly improving the reliability of the device.

Description

Technical Field

[0001] This application relates to the field of microelectronics technology, and in particular to an HfO2-based ferroelectric capacitor and its preparation method, and an HfO2-based ferroelectric memory. Background Technology

[0002] With the development of information technology, people's demand for information storage is constantly increasing, placing higher and higher demands on the capacity, size, power consumption, and price of memory. As a typical representative of traditional non-volatile memory, flash memory devices are facing their development bottlenecks. On the one hand, the ever-shrinking device size is leading to increasingly higher manufacturing costs; on the other hand, a series of reliability issues brought about by size reduction make it difficult for flash memory devices to continue developing along Moore's Law. Therefore, the need to find and develop new types of non-volatile memory is urgent. Among them, HfO2-based ferroelectric memory has become one of the popular candidates for new non-volatile memory in the post-Moore's Law era due to its advantages such as high speed, low power consumption, simple structure and easy integration, and good compatibility with existing CMOS processes.

[0003] Ferroelectric memories utilize the characteristic that the polarization direction of ferroelectric domains in their dielectric layer changes with the direction of the applied electric field, and that the polarization remains even after the external electric field is removed to store information. Upward or downward polarization directions represent binary "0" and "1". Therefore, the amount of polarization that remains in the ferroelectric dielectric after the external electric field is removed, also known as "residual polarization intensity," has become one of the key indicators for evaluating memory performance. By plotting the "polarization intensity-electric field intensity" curve, also known as the "polarization hysteresis curve," the change in polarization intensity within the device with the external electric field can be accurately reflected. Initially, the device is in a partially activated state, and the polarization hysteresis curve appears "pinched," indicating a small residual polarization intensity. As pulse voltage excitation is applied to the device, within a certain number of cycles, the hysteresis curve gradually opens, the residual polarization intensity gradually increases, and eventually reaches its maximum value; this process is called "wake-up." The number of cycles required for the remanent polarization of a device to reach its maximum value varies, depending on the doping type of the HfO2-based ferroelectric dielectric, the amplitude and width of the applied pulse voltage, and the process parameters during device fabrication, and is approximately 10^3 to 10^6 cycles. Due to this characteristic, ferroelectric memories exhibit fluctuations in remanent polarization during the initial stages of use. This can potentially lead to misreading of information and also negatively impact the device's robustness and reliability. Summary of the Invention

[0004] The main objective of this application is to provide an HfO2-based ferroelectric capacitor and its preparation method, as well as an HfO2-based ferroelectric memory. By applying a DC voltage or a unipolar, wide-pulse voltage to the ferroelectric capacitor, the device can complete wake-up with only one voltage excitation, thereby avoiding fluctuations in residual polarization intensity during electrical cycling and improving the reliability of the device.

[0005] To achieve the above objectives, a first aspect of this application provides an HfO2-based ferroelectric capacitor, comprising:

[0006] From top to bottom, it includes a substrate, a lower electrode, a dielectric layer, an upper electrode, and a protective layer.

[0007] Optionally, the substrate material is SiO2 and Si;

[0008] The thickness of the SiO2 is between 100 and 500 nanometers;

[0009] The thickness of the Si is between 300 and 600 micrometers.

[0010] Optionally, the thickness of both the lower electrode and the upper electrode is between 10 and 60 nanometers.

[0011] Optionally, the thickness of the dielectric layer is between 8 and 15 nanometers.

[0012] Optionally, the material of the dielectric layer is HZO, wherein the molar ratio of Hf to Zr is 1:1.

[0013] Optionally, the thickness of the dielectric layer is 8 to 15 nanometers.

[0014] Optionally, the dielectric layer includes multiple sets of alternately grown ZrO2 layers and HfO2 layers, with the top layer being a ZrO2 layer.

[0015] The second aspect of this application provides a method for preparing an HfO2-based ferroelectric capacitor, comprising:

[0016] Provide a substrate and clean the substrate;

[0017] The lower electrode is prepared by sputtering on the cleaned substrate;

[0018] A dielectric layer is deposited on the lower electrode;

[0019] Photoresist is coated onto the dielectric layer, and then exposed and developed.

[0020] An upper electrode is fabricated on the dielectric layer after the above treatment;

[0021] A protective layer is prepared by sputtering onto the formed upper electrode;

[0022] After removing the photoresist and excess metal, an annealing process is performed.

[0023] Optionally, when depositing a dielectric layer on the lower electrode, a ZrO2 layer is first grown, followed by a HfO2 layer, and the process is repeated until the last layer is ZrO2.

[0024] The third aspect of this application provides an HfO2-based ferroelectric memory, including the HfO2-based ferroelectric capacitor described in the first aspect or the HfO2-based ferroelectric capacitor obtained by the preparation method described in the second aspect.

[0025] As can be seen from the above embodiments of this application, the HfO2-based ferroelectric capacitor and its preparation method, as well as the HfO2-based ferroelectric memory proposed in this invention, can achieve wake-up of the device with only a single voltage excitation, and its residual polarization intensity is close to or slightly greater than the limit value of the residual polarization intensity after wake-up under conventional pulse operation. This is equivalent to avoiding fluctuations in the initial residual polarization intensity through a pre-processing step before the memory is put into use, greatly improving the reliability of the device. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of an HfO2-based ferroelectric capacitor provided in an embodiment of this application;

[0028] Figure 2 This is a schematic flowchart of a method for preparing an HfO2-based ferroelectric capacitor according to an embodiment of this application;

[0029] Figure 3 The diagram shows the hysteresis curves of Embodiment 1 and Comparative Example 1 of this application. Detailed Implementation

[0030] To make the purpose, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged and may have been omitted for clarity. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary. In practice, deviations may occur due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] In the context of this disclosure, a layer / element is referred to as being on top of another layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is on top of another layer / element in one orientation, then when the orientation is reversed, that layer / element may be "below" that other layer / element.

[0033] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an HfO2-based ferroelectric capacitor provided in an embodiment of this application.

[0034] The present invention provides an HfO2-based ferroelectric capacitor, which includes, from bottom to top, a substrate 1, a lower electrode 2, a dielectric layer 3, an upper electrode 4, and a protective layer 5.

[0035] Optionally, the substrate 1 is made of SiO2 and Si; the thickness of the SiO2 is between 100 and 500 nanometers; and the thickness of the Si is between 300 and 600 micrometers.

[0036] Optionally, the thickness of both the lower electrode 2 and the upper electrode 4 is between 10 and 60 nanometers.

[0037] Optionally, the thickness of the dielectric layer 3 is between 8 and 15 nanometers.

[0038] Optionally, the dielectric layer 3 is made of HZO, wherein the molar ratio of Hf to Zr is 1:1. Alternatively, other component ratios close to 1:1 may be used to maximize the remanent polarization intensity.

[0039] Optionally, the thickness of the dielectric layer 3 is 8 to 15 nanometers.

[0040] Furthermore, the material of protective layer 5 can be an inert metal with a thickness of 10 to 30 nanometers.

[0041] Please see Figure 2 , Figure 2 This is a schematic flowchart illustrating a method for preparing an HfO2-based ferroelectric capacitor according to an embodiment of this application.

[0042] This invention provides a method for preparing the HfO2-based ferroelectric capacitor, comprising the following steps:

[0043] S201, providing a substrate and cleaning the substrate.

[0044] The substrate was soaked, cleaned, and dried in acetone and anhydrous ethanol in sequence; then it was soaked, rinsed, and dried in deionized water.

[0045] S202, the lower electrode is prepared by sputtering on the cleaned substrate.

[0046] The lower electrode is fabricated on the substrate using ion beam sputtering. Sputtering processes include, but are not limited to, ion beam sputtering, DC sputtering, and reactive sputtering.

[0047] For example, an ion beam sputtering process is used: a TiN target, a beam voltage of 700–900 V, a beam current of 40–60 mA, an accelerating voltage of 150–170 V, and an Ar / N2 mixed gas with flow rates of (7–9 sccm) / (4–6 sccm). Within this process range, good film contrast can be obtained, which is beneficial for the generation of ferroelectric properties.

[0048] S203, a dielectric layer is deposited on the lower electrode.

[0049] For example, the HZO dielectric layer is prepared using the ALD process. During deposition, a ZrO2 layer is grown first, followed by a HfO2 layer, and this process is repeated until a final ZrO2 layer is used as a capping layer. Various other options are available for the precursors and oxygen source, and the deposition temperature range is typically 280-300°C. The Zr and Hf precursors are heated to 100-140°C, deionized water is maintained at room temperature (20°C), and N2 is selected as the carrier gas at a flow rate of 40-80 sccm. For example, the Hf precursor is tetrakis(ethylmethylamido)hafnium(IV) (TEMAH), chemical formula Hf(NCH3C2H5)4; the Zr precursor is tetrakis(ethylmethylamido)zirconium(IV) (TEMAZ), chemical formula Zr(NCH3CH5)4; and deionized water is used as the oxygen source.

[0050] S204, photoresist is coated on the dielectric layer and exposed and developed.

[0051] A negative adhesive was coated on the HZO dielectric layer 4, pre-baked at 150°C for 1 min, exposed and then post-baked at 120°C for 1 min. The mixture was then immersed in the developer for 30 s for development, rinsed with deionized water and dried.

[0052] S205, an upper electrode is prepared on the dielectric layer after the above treatment.

[0053] The preparation process includes, but is not limited to, evaporation and sputtering. For example, an electron beam evaporation process is used, with a Pt source, a vacuum degree of 4×10^-7 torr, a rated voltage of 10kV, a common evaporation rate of 0.6 angstroms / second, and a chamber temperature of less than or equal to 35 degrees Celsius during coating.

[0054] S206, a protective layer is prepared by sputtering on the formed upper electrode.

[0055] For example, an ion beam sputtering process is used: W target, beam voltage 700-900V, beam current 40-60mA, accelerating voltage 150-170V, gas is Ar, flow rate 7-9sccm.

[0056] S207, after removing photoresist and excess metal, undergoes annealing.

[0057] In one specific embodiment, firstly, a SiO2 / Si substrate is provided, with the upper SiO2 layer having a thickness of 300 nm and the lower Si layer having a thickness of 500 μm. Then, the substrate is sequentially immersed and cleaned with acetone and anhydrous ethanol for 3 min, and then dried. Next, it is immersed and rinsed with deionized water for 3 min, and then dried to complete the cleaning of the substrate.

[0058] Next, on the cleaned SiO2 / Sj substrate, a TiN lower electrode was sputtered using an ion beam sputtering process. The TiN target was set with a beam voltage of 800V, a beam current of 46mA, an accelerating voltage of 160V, and an Ar / N2 mixed gas with flow rates of 8sccm / 5sccm. The thickness of the TiN lower electrode could be 40nm.

[0059] Then, on the sputtered lower electrode, an HZO dielectric layer was prepared using the ALD process, employing TEMAH and TEMAZ as Hf and Zr precursors, and deionized water as the oxygen source. The deposition temperature was 280℃, the Zr and Hf precursors were heated to 120℃, the deionized water was maintained at room temperature (20℃), and N2 was selected as the carrier gas at a flow rate of 50 sccm. During deposition, a ZrO2 layer was grown first, followed by a HfO2 layer, and this cycle was repeated until a final ZrO2 layer capped the deposition. The deposition rates were as follows: (Right now Each cycle (ZrO2), (Right now Each cycle (HfO2) ensures that the stoichiometric ratio of Hf and Zr is approximately 1:1, meaning the component ratio of Hf and Zr is 1:1. The dielectric layer is deposited to a thickness of 10 nm to complete the preparation of the dielectric layer.

[0060] Then, a Pt top electrode was prepared on the HZO dielectric layer using electron beam evaporation. The Pt source had a vacuum of 4×10^-7 torr and a rated voltage of 10kV. The commonly used evaporation rate was 0.6 Å / s. The chamber temperature during coating was less than or equal to 35 degrees Celsius. The thickness of the top electrode was 40nm.

[0061] Next, a W metal protective layer was sputtered onto the formed upper electrode using an ion beam sputtering process. The target was W, the beam voltage was 800V, the beam current was 46mA, the accelerating voltage was 160V, the gas was Ar, the flow rate was 8sccm, and the thickness of the metal protective layer was 20nm.

[0062] Subsequently, the HfO2-based ferroelectric device with a substrate layer, lower electrode, dielectric layer, upper electrode, and metal protective layer obtained through the above operations was immersed in acetone solution until the photoresist and excess metal were removed; then it was immersed in anhydrous ethanol to remove the acetone; and finally rinsed with deionized water and dried.

[0063] Finally, the rinsed and dried HfO2-based ferroelectric devices were annealed in a N2 atmosphere at 500°C for 30 seconds to obtain HfO2-based ferroelectric capacitors.

[0064] In this disclosure, a voltage excitation is applied to an HfO2-based ferroelectric capacitor to achieve a fast wake-up, including the following two methods with specific steps as follows:

[0065] Please see Figure 3 , Figure 3 Hysteresis curves for embodiments and comparative examples of this application.

[0066] exist Figure 3 In this embodiment, a DC voltage excitation is applied to the HfO2-based ferroelectric capacitor to achieve rapid wake-up. The specific steps are as follows:

[0067] A DC voltage is applied to the lower electrode in voltage scanning mode, increasing the voltage from 0V to 4.5V, with a current limit of 1μA. The upper electrode Pt is grounded.

[0068] The polarization hysteresis curve of the device was measured using PUND mode with an applied pulse amplitude of 3V and a pulse width of 100μs. (The lower electrode was voltage-applied, and the upper electrode was grounded.)

[0069] exist Figure 3 In the comparative example, applying a pulsed voltage excitation to the HfO2-based ferroelectric capacitor requires approximately 1000 cycles to achieve wake-up. The specific steps are as follows:

[0070] The polarization hysteresis curve of the device was measured using PUND mode with an applied pulse amplitude of 3V and a pulse width of 100μs. (Voltage applied to the lower electrode, grounded to the upper electrode; this is the initial state.)

[0071] A triangular wave pulse voltage with an amplitude of ±3V and a pulse width of 100μs is applied to the lower electrode TiN, while the upper electrode is grounded. This is repeated cyclically until the device completes wake-up; in this example, the cycle is repeated 1000 times.

[0072] The polarization hysteresis curve of the device was measured using PUND mode with an applied pulse amplitude of 3V and a pulse width of 100μs. (Voltage applied to the lower electrode, grounded to the upper electrode; this is the completed state.)

[0073] The difference between the above embodiments and the comparative examples is that the embodiments can complete the wake-up with only one DC voltage scan operation; while the comparative examples require multiple cycles to achieve the same wake-up effect by applying pulse voltage.

[0074] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0075] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0076] The above is a description of an HfO2-based ferroelectric capacitor and its preparation method, as well as an HfO2-based ferroelectric memory provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An HfO2-based ferroelectric capacitor, characterized in that, From top to bottom, it includes a substrate, a lower electrode, a dielectric layer, an upper electrode, and a protective layer; The method of applying a DC voltage excitation to HfO2-based ferroelectric capacitors to achieve rapid wake-up includes: Apply a DC voltage to the lower electrode in voltage scanning mode, increasing the voltage from 0V to 4.5V, with a current limit of 1μA, and ground the upper electrode; With voltage applied to the lower electrode and the upper electrode grounded, the polarization hysteresis curve of the HfO2-based ferroelectric capacitor was measured using PUND mode. The thickness of the dielectric layer is between 8 and 15 nanometers; The dielectric layer is made of HZO, wherein the molar ratio of Hf to Zr is 1:1; The dielectric layer comprises multiple sets of alternately grown ZrO2 layers and HfO2 layers, with the top layer being a ZrO2 layer.

2. The HfO2-based ferroelectric capacitor according to claim 1, characterized in that, The substrate is made of SiO2 and Si; The thickness of the SiO2 is between 100 and 500 nanometers; The thickness of the Si is between 300 and 600 micrometers.

3. The HfO2-based ferroelectric capacitor according to claim 1, characterized in that, The thickness of both the lower electrode and the upper electrode is between 10 and 60 nanometers.

4. A method for preparing the HfO2-based ferroelectric capacitor according to claim 1, characterized in that, include: Provide a substrate and clean the substrate; The lower electrode is prepared by sputtering on the cleaned substrate; A dielectric layer is deposited on the lower electrode; Photoresist is coated onto the dielectric layer, and then exposed and developed. An upper electrode is fabricated on the dielectric layer after the above treatment; A protective layer is prepared by sputtering onto the formed upper electrode; After removing the photoresist and excess metal, annealing is performed. The method of applying a DC voltage excitation to HfO2-based ferroelectric capacitors to achieve rapid wake-up includes: Apply a DC voltage to the lower electrode in voltage scanning mode, increasing the voltage from 0V to 4.5V, with a current limit of 1μA, and ground the upper electrode; With voltage applied to the lower electrode and the upper electrode grounded, the polarization hysteresis curve of the HfO2-based ferroelectric capacitor was measured using PUND mode.

5. The preparation method according to claim 4, characterized in that, When depositing a dielectric layer on the lower electrode, a ZrO2 layer is first grown, followed by a HfO2 layer, and the process is repeated until the last layer is ZrO2.

6. An HfO2-based ferroelectric memory, characterized in that, Includes the HfO2-based ferroelectric capacitor as described in any one of claims 1-3 or the HfO2-based ferroelectric capacitor prepared by the method described in any one of claims 4-5.

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