Performance optimization method and application of hafnium oxide / zirconium oxide ferroelectric film
By applying electric field activation to HZO ferroelectric thin films, their crystal phase purity and defect distribution are optimized, solving the problem of unstable device performance and realizing ferroelectric memory devices with high remanent polarization and low operating voltage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-17
AI Technical Summary
Existing HZO ferroelectric memory devices exhibit wake-up and imprinting effects, low initial residual polarization, insufficient performance stability, and fluctuations in device performance during electrical erase/write cycles.
After depositing hafnium oxide/zirconia ferroelectric thin films on a substrate and performing high-temperature annealing and crystallization, functional regions are defined using photolithography and etching techniques, and electric field activation is employed, including pulsed AC signal activation, to optimize the crystal phase purity, defect distribution, and domain orientation of the ferroelectric thin films.
The residual polarization intensity of the ferroelectric memory cell was increased, the wake-up effect and imprinting effect were reduced, the reliability and uniformity of the device were improved, and the operating voltage was reduced.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, and more specifically relates to the field of ferroelectric thin film technology materials, particularly to a method and application for performance optimization of hafnium oxide / zirconia ferroelectric thin films. Background Technology
[0002] In recent years, ferroelectric memory technology based on hafnium oxide / zirconia (HZO) has developed rapidly and has become an important development direction for next-generation non-volatile memory technology. Benefiting from its excellent compatibility with standard CMOS processes, HZO ferroelectric memory can be directly manufactured on existing logic chip production lines without expensive process modifications, significantly reducing the industrialization threshold and manufacturing costs. Simultaneously, this technology possesses excellent 3D integration capabilities, breaking through the physical limitations of traditional planar miniaturization and achieving high-density memory arrays through vertical stacking, thereby meeting the urgent storage needs of future big data and artificial intelligence applications. Due to these advantages, HZO ferroelectric memory is not only expected to gradually replace traditional eFlash in the embedded storage field, but also shows broad application prospects in cutting-edge applications such as in-memory computing, low-power IoT chips, and neuromorphic computing.
[0003] Currently, the wake-up effect and imprinting effect remain key reliability challenges hindering the commercialization of HZO ferroelectric devices. Newly fabricated devices typically exhibit significant wake-up characteristics: their initial remanent polarization is low, and they require high operating voltages to be driven. During subsequent electrical erase / write cycles, key parameters such as polarization and coercive field fluctuate significantly, resulting in insufficient performance stability, which directly impedes their large-scale commercialization.
[0004] The aforementioned performance challenges stem from the multifaceted complexity of the HZO thin film's microstructure. First, the actual prepared films are often multiphase coexisting systems, frequently containing antiferroelectric and paraelectric phases in addition to the target ferroelectric orthorhombic phase. This intrinsic phase composition instability is the root cause of performance degradation. Second, the high concentration of point defects (such as oxygen vacancies) and their uneven distribution at interfaces pin domain walls and induce localized built-in electric fields, directly leading to wake-up and imprinting effects. Furthermore, the random orientation of grains results in inconsistent ferroelectric domain orientations, leading to poor synergy in the switching characteristics of different grains. The combined effect of these factors ultimately manifests as drastic fluctuations in device performance and a decline in reliability on a macroscopic scale. Therefore, developing a preparation method that can simultaneously optimize phase purity, defect distribution, and domain orientation has become a critical scientific problem that urgently needs to be addressed. Summary of the Invention
[0005] The technical problem this invention aims to solve is to purify the crystal phase of the hafnium oxide / zirconia ferroelectric thin film in each memory cell to a stable ferroelectric phase, ensuring uniform distribution of defects such as oxygen vacancies and relatively consistent ferroelectric domain orientation, thereby guaranteeing a large remanent polarization intensity and significantly reducing the wake-up and imprinting effects. Therefore, this invention proposes a method for optimizing the performance of hafnium oxide / zirconia ferroelectric thin films.
[0006] The technical solution of the present invention is as follows: a bottom electrode, a hafnium oxide / zirconia ferroelectric thin film, and a top electrode are deposited sequentially on a substrate layer, followed by high-temperature annealing and crystallization treatment. Then, a series of functional regions to be activated are defined using photolithography and etching techniques. The ferroelectric thin film of the functional regions is activated by an electric field to optimize the performance of the ferroelectric thin film of the functional regions. Finally, a ferroelectric memory cell is fabricated on the functional regions with optimized performance.
[0007] Furthermore, each individual functional area to be activated can be etched through the ferroelectric thin film, leaving the bottom electrode intact so that it forms an independent circuit with the top electrode for applying voltage.
[0008] Furthermore, two electrical probes are used to connect the top electrode and the surrounding bottom electrode of each individual functional area to be activated in sequence, and the ferroelectric thin film is activated by electric field through the circuit formed by the two probes. Alternatively, multiple pairs of electrical probes can be used to connect the top electrode and the surrounding bottom electrode of each individual functional area to be activated, and several ferroelectric thin films can be simultaneously activated by electric field through the independent circuits formed by each pair of probes.
[0009] Furthermore, an electric field activation process is performed using a pulsed AC signal. By controlling the pulse period, voltage amplitude, and number of pulse trains of the pulsed AC signal, the performance of the ferroelectric thin film is optimized to the specified conditions. The pulse period and voltage amplitude of the pulsed AC signal need to satisfy the requirement that the ferroelectric thin film can complete polarization reversal.
[0010] Furthermore, the waveform of the pulsed AC signal can be a square wave or a triangular wave, supporting unipolar or bipolar modes; the pulse period is 40μs-1ms, the voltage amplitude is 1V-5V, and the number of pulse trains is 10. 3 -10 7 .
[0011] Furthermore, while performing electric field activation treatment on the ferroelectric thin film in the functional area, the polarization characteristic curve of the ferroelectric thin film is calculated by acquiring current signals. When the polarization window and / or coercive electric field strength reach the preset target, the output of AC signal pulse train can be actively stopped, saving electric field activation treatment time and preventing over-activation treatment, thus ensuring the uniformity of ferroelectric performance in each independent region.
[0012] Furthermore, the bottom electrode and top electrode include, but are not limited to, TiN, W, Ni, or combinations thereof; for conductive substrates, the bottom electrode may be omitted.
[0013] Furthermore, the hafnium oxide / zirconia ferroelectric thin film is prepared by atomic layer deposition process, the deposition temperature of the film is between 200-300℃, the deposition thickness of the film is usually between 3-15nm, and other elements can be appropriately doped, including La, Gd, Al, Si, Y, Sr and Si.
[0014] Furthermore, the high-temperature annealing crystallization treatment is carried out at a temperature between 300-800℃, a heating rate of 20-100℃ / s, an annealing time of 10s-200s, and a cooling rate of 20-80℃ / s.
[0015] The present invention also provides an application of the hafnium oxide / zirconia ferroelectric thin film prepared according to the above method in a memory.
[0016] The beneficial effects of this invention are as follows: 1. This invention provides a method for optimizing the performance of hafnium oxide / zirconia ferroelectric thin films, which can improve the residual polarization intensity of ferroelectric units while reducing the wake-up effect and imprinting effect of the device.
[0017] 2. The ferroelectric thin film prepared by this invention has a lower operating voltage, which can improve the reliability and uniformity of the device.
[0018] 3. The method of the present invention can also be used to prepare HZO antiferroelectric thin film devices. Attached Figure Description
[0019] Figure 1 This is a flowchart illustrating the steps of the performance optimization method for hafnium oxide / zirconia ferroelectric thin films in this invention. Figure 2 This is a comparison of the polarization intensity of a 10 nm thick HZO ferroelectric thin film prepared using the present invention and a 10 nm thick HZO ferroelectric thin film prepared using conventional methods. Figure 3 This is a comparison chart showing the durability of a 10 nm thick HZO ferroelectric thin film prepared using the present invention and a 10 nm thick HZO ferroelectric thin film prepared using conventional methods. Figure 4 This is a comparison of the polarization intensity of a 6 nm thick HZO ferroelectric thin film prepared using the present invention and a 10 nm thick HZO ferroelectric thin film prepared using conventional methods. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the operation process of this invention will be further described in detail below with reference to the accompanying drawings and specific examples. It should be noted that the specific examples described herein are only for explaining this invention, and the illustrations are illustrative in nature and are not intended to limit the scope of this invention.
[0021] This invention provides a method for optimizing the performance of hafnium oxide / zirconia ferroelectric thin films. The specific steps of this method are as follows: depositing a bottom electrode, a hafnium oxide / zirconia ferroelectric thin film, and a top electrode sequentially on a substrate layer, followed by high-temperature annealing and crystallization treatment, then using photolithography and etching techniques to define a series of functional regions to be activated, performing electric field activation treatment on the ferroelectric thin film of the functional regions to optimize the performance of the ferroelectric thin film of the functional regions, and then fabricating ferroelectric memory cells on the functional regions with optimized performance.
[0022] Furthermore, each individual functional area to be activated can be etched through the ferroelectric thin film, leaving the bottom electrode intact so that it forms an independent circuit with the top electrode for applying voltage.
[0023] Furthermore, two electrical probes are used to connect the top electrode and the surrounding bottom electrode of each individual functional area to be activated in sequence, and the ferroelectric thin film is activated by electric field through the circuit formed by the two probes. Alternatively, multiple pairs of electrical probes can be used to connect the top electrode and the surrounding bottom electrode of each individual functional area to be activated, and several ferroelectric thin films can be simultaneously activated by electric field through the independent circuits formed by each pair of probes.
[0024] Furthermore, an electric field activation process is performed using a pulsed AC signal. By controlling the pulse period, voltage amplitude, and number of pulse trains of the pulsed AC signal, the performance of the ferroelectric thin film is optimized to the specified conditions. The pulse period and voltage amplitude of the pulsed AC signal need to satisfy the requirement that the ferroelectric thin film can complete polarization reversal.
[0025] Furthermore, the waveform of the pulsed AC signal can be a square wave or a triangular wave, supporting unipolar or bipolar modes; the pulse period is 40μs-1ms, the voltage amplitude is 1V-5V, and the number of pulse trains is 10. 3 -10 7 .
[0026] Furthermore, while performing electric field activation treatment on the ferroelectric thin film in the functional area, the polarization characteristic curve of the ferroelectric thin film is calculated by acquiring current signals. When the polarization window and / or coercive electric field strength reach the preset target, the output of AC signal pulse train can be actively stopped, saving electric field activation treatment time and preventing over-activation treatment, thus ensuring the uniformity of ferroelectric performance in each independent region.
[0027] Furthermore, the bottom electrode and top electrode include, but are not limited to, TiN, W, Ni, or combinations thereof; for conductive substrates, the bottom electrode may be omitted.
[0028] Furthermore, the hafnium oxide / zirconia ferroelectric thin film is prepared by atomic layer deposition process, the deposition temperature of the film is between 200-300℃, the deposition thickness of the film is usually between 3-15nm, and other elements can be appropriately doped, including La, Gd, Al, Si, Y, Sr and Si.
[0029] Furthermore, the high-temperature annealing crystallization treatment is carried out at a temperature between 300-800℃, a heating rate of 20-100℃ / s, an annealing time of 10s-200s, and a cooling rate of 20-80℃ / s.
[0030] This invention optimizes the ferroelectric properties of hafnium oxide / zirconia ferroelectric thin films by subjecting them to electric field activation treatment in functional regions with relatively large areas. As a result, the ferroelectric memory cells prepared in this invention have higher residual polarization intensity, lower operating voltage, and significantly improved wake-up and imprinting effects.
[0031] Implementation Case 1 A method for performance optimization of hafnium oxide / zirconia ferroelectric thin films includes the following steps: (1) Cleaning of Si substrate: Select p + Si <100> The substrate is cut into 2cm×2cm square wafers and impurities on the surface of the Si wafer are removed using the RCA standard cleaning method. (2) Deposition of TiN bottom electrode: TiCl4 and NH3 were used as reactants, and atomic layer deposition technology was used to deposit TiN with a thickness of about 10 nm at a cavity temperature of 400℃; (3) Preparation of ferroelectric thin film: The sample was placed in the growth chamber of the atomic layer deposition system, the substrate was heated to 280°C, and TEMAH and TEMAZr were used as precursor sources of hafnium and zirconium, respectively, and plasma oxygen was used as oxygen source to prepare HZO ferroelectric thin film with an effective molar ratio of Hf to Zr of 1:1 and a thickness of 10 nm. (4) Deposition of TiN / W top electrode: TiCl4 and NH3 were used as reactants. Atomic layer deposition technology was used to deposit a TiN layer with a thickness of about 10 nm at a cavity temperature of 400 °C. Then, a W layer with a thickness of about 50 nm was deposited on the TiN using physical sputtering. (5) Annealing treatment: The RTP annealing technology was used to perform rapid annealing treatment at 500°C for 60 seconds on the samples after all films were deposited.
[0032] (6) Definition and etching of functional areas: Using photolithography and etching processes, a series of areas with a diameter of 0.25 mm are defined on the entire thin film. 2 Each functional area should have its own independent functional area, and the top electrode should be retained around the perimeter of each independent functional area.
[0033] (7) Electric field activation treatment of functional areas: For each independent functional area, a pulsed square wave with a voltage amplitude of 3.5V and a period of 40μs is applied to the thin film through a circuit formed by the top electrode and the surrounding bottom electrode. The number of square wave trains is 10. 6 indivual.
[0034] (8) Fabrication of ferroelectric memory cells: The most basic ferroelectric memory cells are etched on each functional area after electric field activation treatment.
[0035] Implementation Case 2 A method for performance optimization of hafnium oxide / zirconia ferroelectric thin films includes the following steps: (1) Cleaning of Si substrate: Select p + Si <100> The substrate is cut into 2cm×2cm square wafers and impurities on the surface of the Si wafer are removed using the RCA standard cleaning method. (2) Deposition of TiN bottom electrode: TiCl4 and NH3 were used as reactants, and atomic layer deposition technology was used to deposit TiN with a thickness of about 10 nm at a cavity temperature of 400℃; (3) Preparation of ferroelectric thin film: The sample was placed in the growth chamber of the atomic layer deposition system, the substrate was heated to 280°C, and TEMAH and TEMAZr were used as precursor sources of hafnium and zirconium, respectively, and plasma oxygen was used as oxygen source to prepare HZO ferroelectric thin film with an effective molar ratio of Hf to Zr of 1:1 and a thickness of 6 nm. (4) Deposition of TiN / W top electrode: TiCl4 and NH3 were used as reactants. Atomic layer deposition technology was used to deposit a TiN layer with a thickness of about 10 nm at a cavity temperature of 400 °C. Then, a W layer with a thickness of about 50 nm was deposited on the TiN using physical sputtering. (5) Annealing treatment: The RTP annealing technology was used to perform rapid annealing treatment at 500°C for 60 seconds on the samples after all films were deposited.
[0036] (6) Definition and etching of functional areas: Using photolithography and etching processes, a series of areas with a diameter of 0.25 mm are defined on the entire thin film. 2 Each functional area should have its own independent functional area, and the top electrode should be retained around the perimeter of each independent functional area.
[0037] (7) Electric field activation treatment of functional areas: For each independent functional area, a pulsed square wave with a voltage amplitude of 3V and a period of 40μs is applied to the thin film through a circuit formed by the top electrode and the surrounding bottom electrode. The number of square wave trains is 10. 6 indivual.
[0038] (8) Fabrication of ferroelectric memory cells: The most basic ferroelectric memory cells are etched on each functional area after electric field activation treatment.
[0039] Figure 1 A flowchart illustrating the steps of the method for optimizing the performance of hafnium oxide / zirconia ferroelectric thin films in this invention is shown.
[0040] A comparison of the polarization properties of the 10nm HZO ferroelectric thin film prepared in Case 1 and the 10nm HZO ferroelectric thin film prepared using a conventional method (without electric field activation treatment) is shown in the figure. Figure 2 It can be observed that the device prepared by the method of this invention has a larger polarization intensity and a reduced coercive electric field, compared to... Figure 3 The durability characteristics show that the devices prepared using this method do not exhibit a significant wake-up process during long-term erasing and writing.
[0041] A performance comparison of the 6nm HZO ferroelectric thin film prepared in Case 2 with that prepared using a conventional method (without electric field activation treatment) is shown below. Figure 4 It can be observed that for thinner HZO ferroelectric devices, the present invention can still enhance the polarization intensity.
[0042] Each individual functional area to be activated is relatively large, typically greater than or equal to 0.25 mm². 2 Current hafnium oxide / zirconia ferroelectric thin films, especially when the film thickness is reduced, suffer from problems such as low initial residual strength, severe wake-up effect, insufficient durability, and poor uniformity between different regions. Each memory cell often requires multiple read / write operations to achieve consistent performance. This method, however, by reasonably defining the area size of independent functional regions, allows each functional region to contain a sufficient number of memory cells (depending on the process linewidth, each independent functional region can contain 10...). 2 -10 8 (The number of memory cells may vary). By incorporating the electric field activation process into the ferroelectric thin film production process, each ferroelectric memory cell in the final fabricated memory chip exhibits higher remanent polarization intensity, lower coercive field voltage, improved durability, and eliminates the wake-up effect. Furthermore, the uniformity of devices in different regions is ensured.
[0043] The above description is merely a preferred embodiment of the present invention. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.
Claims
1. A method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films, characterized in that, The method comprises the following steps: Depositing a bottom electrode, a hafnium oxide / zirconium oxide ferroelectric film and a top electrode on a substrate layer in sequence, then performing high-temperature annealing crystallization treatment, and then defining a series of required functional areas to be activated by using photolithography and etching technology, and then performing electric field activation treatment on the ferroelectric film of the functional areas, so that the performance of the ferroelectric film of the functional areas is optimized, and then preparing a ferroelectric memory cell on the functional areas with optimized performance.
2. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, characterized in that, Each individual functional area to be activated is etched through the ferroelectric film, and the bottom electrode is reserved to form an independent loop with the top electrode to apply voltage.
3. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, characterized in that, Two electrical probes are used to connect the top electrode and the peripheral bottom electrode of each individual functional area to be activated in sequence, and the ferroelectric film is activated by electric field through the loop formed by the two probes. Alternatively, a plurality of pairs of electrical probes are used to connect the top electrode and the peripheral bottom electrode of each individual functional area to be activated in pairs, and a plurality of ferroelectric films are activated by electric field through the independent loops formed by each pair of probes.
4. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, characterized in that, The electric field activation treatment is performed by using a pulse alternating current signal, and the performance of the ferroelectric film is optimized to a specified condition by controlling the pulse period, voltage amplitude and pulse string number of the pulse alternating current signal; the pulse period and voltage amplitude of the pulse alternating current signal need to meet the condition that the ferroelectric film can complete polarization reversal.
5. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 4, characterized in that, The waveform of the pulse alternating current signal is square wave or triangle wave, supporting unipolar or bipolar mode; the pulse period is 40us-1ms, the voltage amplitude is 1V-5V, and the number of pulse strings is 10 3 -10 7 .
6. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 4, characterized in that, While the ferroelectric film of the functional area is activated by electric field, the polarization characteristic curve of the ferroelectric film is calculated by collecting current signals, and when the polarization window and / or the coercive field strength reach the preset target, the output of the alternating current signal pulse string can be actively stopped to save the electric field activation treatment time, and to prevent over-activation treatment and ensure the uniformity of the ferroelectric performance of each independent area.
7. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, wherein The bottom electrode and the top electrode are TiN, W, Ni or a combination thereof.
8. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, wherein, The hafnium oxide / zirconium oxide ferroelectric film is prepared by using an atomic layer deposition process, the deposition temperature of the film is between 200-300℃, and the deposition thickness of the film is between 3-15nm.
9. The method for optimizing the properties of hafnium oxide / zirconium oxide ferroelectric thin films according to claim 1, wherein, The high-temperature annealing crystallization treatment temperature is between 300-800℃, the heating rate is between 20-100℃ / s, the annealing time is 10s-200s, and the cooling rate is between 20-80℃ / s.
10. Application of the hafnium oxide / zirconium oxide ferroelectric film optimized by the method of any one of claims 1-9 in a memory.