A method for preparing a cerium-doped hafnium oxide-based ferroelectric thin film capacitor and the capacitor
A cerium-doped hafnium oxide-based ferroelectric thin film was prepared by combining atomic layer deposition and magnetron sputtering, which solved the problem of instability of films with a thickness of less than 50 nm in the prior art and realized the preparation of high-performance ferroelectric thin films suitable for advanced microelectronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIANGTAN UNIV
- Filing Date
- 2026-04-30
- Publication Date
- 2026-07-14
Smart Images
Figure CN122395958A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of ferroelectric materials and semiconductor storage, and particularly relates to a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin film capacitor and the capacitor itself. Background Technology
[0002] With the rapid development of emerging technologies such as artificial intelligence, big data, and the Internet of Things, the requirements for read / write speed, power consumption, integration density, and reliability of non-volatile memories are constantly increasing. Ferroelectric memories, due to their nanosecond-level read / write speeds, ultra-low power consumption, and strong radiation resistance, have become an important development direction for next-generation semiconductor memories. Among numerous ferroelectric materials, hafnium oxide (HfO2)-based ferroelectric thin films have attracted widespread attention from academia and industry due to their complete compatibility with complementary metal-oxide-semiconductor (CMOS) processes, excellent miniaturization, and lead-free environmental friendliness.
[0003] Among the many factors affecting the ferroelectric properties of hafnium oxide thin films, elemental doping can effectively induce and stabilize the ferroelectric orthorhombic phase. Cerium doping, in particular, can significantly improve the polarization intensity of hafnium oxide-based ferroelectric thin films and exhibit excellent thickness scalability, maintaining stable ferroelectric properties in the range of tens of nanometers to near micrometers. However, currently, cerium-doped hafnium oxide-based ferroelectric thin films prepared by methods such as sputtering deposition, chemical solution deposition, and pulsed laser deposition typically have thicknesses of 50 nm or greater, and generally require high annealing temperatures, making it difficult to meet the thermal budget requirements for device miniaturization and downstream processes. When the thickness is reduced to below 50 nm, the ferroelectric orthorhombic phase becomes unstable, and insufficient crystallization occurs when the annealing temperature decreases, resulting in low residual polarization intensity and poor fatigue performance. Summary of the Invention
[0004] This application provides a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor, comprising: S1: Select and clean the substrate; S2: In an inert gas atmosphere, a bottom electrode layer is deposited on the upper surface of the substrate by magnetron sputtering; S3: Using tetradimethylaminohafnium as a hafnium precursor, tetramethylheptanedioate cerium as a cerium precursor, and ozone as an oxygen source, an atomic layer deposition method was used to deposit a ferroelectric layer on the bottom electrode layer at a deposition temperature of 250~300℃. The pulse cycle ratio of hafnium precursor to cerium precursor is controlled to make the cerium doping concentration in the ferroelectric layer 2~8 at%; the total number of atomic layer deposition cycles is controlled to make the thickness of the ferroelectric layer 10~25 nm. S4: In an inert gas atmosphere, a top electrode layer is deposited on the ferroelectric layer by magnetron sputtering. S5: The sample obtained in step S4 is rapidly annealed in a nitrogen atmosphere to obtain a cerium-doped hafnium oxide-based ferroelectric thin film capacitor; wherein the annealing temperature is 600~800℃ and the holding time is 30~60s.
[0005] Furthermore, the substrate material is one of silicon, germanium, silicon oxide, silicon carbide, silicon nitride, gallium nitride, gallium oxide, zinc oxide, aluminum oxide, and strontium titanate; The bottom electrode layer and the top electrode layer are made of one or more of titanium nitride, tantalum nitride, ruthenium oxide, tungsten, platinum, aluminum, and gold.
[0006] Further, the deposition of the bottom electrode layer in step S2 includes: The substrate is placed in the transfer chamber of the magnetron sputtering process, and the vacuum level is evacuated to 1×10⁻⁶. -9 ~1×10 -6 Torr; Open the baffle and send the substrate into the sputtering chamber; set the sputtering power to 80~140W and the sputtering time to 1000~1400s, introduce argon gas as the working gas, and perform magnetron sputtering deposition to obtain a bottom electrode layer with a thickness of 30~50nm.
[0007] Furthermore, in step S2, after depositing the bottom electrode layer, the following steps are also included: In the same sputtering chamber, argon plasma is excited to treat the surface of the bottom electrode layer with a power of 50~150W, a treatment time of 30~90s, and an argon flow rate of 10~15sccm.
[0008] Further, before depositing the ferroelectric layer in step S3, the following steps are included: The substrate with the bottom electrode layer deposited is placed into the transfer chamber of the atomic layer deposition system, and the vacuum is evacuated to a vacuum level of 0.5~2 hPa. The reaction chamber is preheated to 250-300°C, the hafnium precursor source bottle is preheated to 70-100°C, and the cerium precursor source bottle is preheated to 150-180°C. Atomic layer deposition formulations were set up, and pre-deposition cycles were performed in the reaction chamber to stabilize the precursor dosage; After pre-deposition, the gate valve between the transfer chamber and the reaction chamber is opened to send the substrate from the transfer chamber into the reaction chamber.
[0009] Furthermore, the atomic layer deposition method described in step S3 employs multiple supercycles, with each supercycle including multiple hafnium oxide deposition subcycles and multiple cerium oxide deposition subcycles; One hafnium oxide deposition subcycle includes, in sequence: introducing tetradimethylaminohafnium with a pulse time of 1s; purging with nitrogen for 8s; introducing ozone with a pulse time of 2s; and purging with nitrogen for 8s. A cerium oxide deposition subcycle consists of the following steps: introducing cerium tetramethylheptanedionate with a pulse duration of 2 s; purging with nitrogen gas for 4 s; introducing ozone with a pulse duration of 2 s; and purging with nitrogen gas for 4 s.
[0010] Furthermore, the rapid annealing process in step S5 also includes a heating stage before the holding stage, and a cooling stage and a natural cooling stage after the holding stage; among which, The heating rate during the heating phase is 20~50℃ / s; The cooling rate during the cooling phase is 20~40℃ / s, cooling down to 200℃; During the heat preservation stage and the cooling stage, a DC electric field is applied through the bottom electrode layer and the top electrode layer. The direction of the DC electric field is perpendicular to the ferroelectric layer film surface to stabilize the ferroelectric orthogonal phase and induce the polarization axis to be oriented perpendicular to the film surface. The electric field strength is 2~15kV / cm.
[0011] Furthermore, the temperature during the heat preservation stage is 700℃, and the electric field strength of the DC electric field is 10kV / cm.
[0012] Another aspect of this application proposes a capacitor prepared by the preparation method of cerium-doped hafnium oxide-based ferroelectric thin film capacitor in any of the above-described technical solutions.
[0013] The above-described technical solution of the present invention has at least the following beneficial technical effects: (1) The cerium-doped hafnium oxide-based ferroelectric thin film prepared by atomic layer deposition in this application is dense and uniform, with precise and controllable thickness, and is highly compatible with complementary metal oxide semiconductor (CMOS) process, which is expected to meet the development needs of advanced microelectronic devices.
[0014] (2) By combining tetradimethylaminohafnium and tetramethylheptanedioate cerium precursors, a specific deposition temperature window of 250~300℃ and a doping concentration range of 2~8at%, and combined with annealing at 600~800℃, cerium-doped hafnium oxide-based ferroelectric thin film capacitors with excellent ferroelectric properties were prepared at ultrathin thickness and low annealing temperature. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments 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.
[0016] Figure 1This is a flowchart of a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor as described in Example 1.
[0017] Figure 2 This is a comparison diagram of the hysteresis loops of the samples in Example 1 and Comparative Example 1 of this application.
[0018] Figure 3 This is a graph showing the relative permittivity of the samples in Example 1 and Comparative Example 1 of this application as a function of voltage.
[0019] Figure 4 These are comparison diagrams of hysteresis loops for samples of different thicknesses in Examples 1, 3-6 of this application.
[0020] Figure 5 This is a comparison diagram of the hysteresis loops of samples obtained at different annealing temperatures in Examples 1, 7 and 8 of this application.
[0021] Figure 6 This is a characteristic curve of the residual polarization intensity of the sample in Example 1 of this application changing with the electric field cycle.
[0022] Figure 7 This is a schematic diagram of the capacitor structure prepared in the embodiments of this application.
[0023] The attached figures are labeled as follows: 1. Substrate; 2. Bottom electrode layer; 3. Ferroelectric layer; 4. Top electrode layer. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.
[0025] Example 1 This embodiment provides a method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor, including: S1: An n-type heavily doped single-crystal silicon wafer is selected as the substrate. The substrate size is 4 inches, the thickness is 525μm, and the resistivity is <0.01Ω·cm.
[0026] Place the substrate in a PTFE cleaning frame; place the cleaning frame in the cleaning tank of an ultrasonic cleaner, add acetone solution, and immerse the substrate in the solution; set the ultrasonic power to 100W, temperature to 25℃, and cleaning time to 10 minutes. Start the ultrasonic cleaning process to remove organic contaminants from the silicon wafer surface using the cavitation effect.
[0027] After ultrasonic cleaning, the substrate inside the cleaning frame is repeatedly rinsed with deionized water. Then, the cleaning frame is placed in a cleaning tank filled with deionized water, and the ultrasonic power is set to 100W for 10 minutes to remove residual acetone solution.
[0028] Remove the cleaning frame and use high-purity nitrogen to dry the substrate.
[0029] S2: Place the cleaned substrate onto the sample holder in the magnetron sputtering transfer chamber, and evacuate to 1×10⁻⁶. -9 -1×10 -6 Torr. Open the transfer chamber baffle and feed the substrate into the stage within the sputtering chamber. Using titanium nitride (TiN) as the target, set the sputtering power to 100W, sputtering time to 1200s, and argon flow rate to 12sccm to deposit a 40nm thick TiN bottom electrode layer. After deposition, keep the stage rotating and allow it to cool naturally to obtain a 40nm thick titanium nitride bottom electrode layer.
[0030] In step S2, after depositing the bottom electrode layer, the following steps are also included: In the same sputtering chamber, argon plasma is excited to treat the surface of the bottom electrode layer. The power source for exciting the argon plasma can be a DC power source or a radio frequency power source, with a power of 100W, a treatment time of 60s, and an argon flow rate of 12sccm. Capacitively coupled plasma is generated between the target and the substrate. Under self-biasing, the argon plasma bombards the surface of the bottom electrode layer to remove native titanium oxide and adsorbed impurities, while introducing active sites to increase the surface energy of the bottom electrode.
[0031] S3: Deposition of the ferroelectric layer. Before the formal deposition of the ferroelectric layer, a pre-deposition is performed within the reaction chamber. This pre-deposition includes: The substrate with the bottom electrode layer deposited is placed into the transfer chamber of the atomic layer deposition system and evacuated to a vacuum level of 1.5 hPa. The reaction chamber was preheated to 280°C, the hafnium precursor source bottle was preheated to 75°C, and the cerium precursor source bottle was preheated to 170°C. An atomic layer deposition (ALD) formulation was developed, using tetradimethylaminohafnium as a hafnium precursor, tetramethylheptadecanoate cerium as a cerium precursor, and ozone as an oxygen source. Four supercycles of pre-deposition were performed in the reaction chamber to stabilize the precursor dosage.
[0032] After pre-deposition, the gate valve between the transfer chamber and the reaction chamber is opened to send the substrate from the transfer chamber into the reaction chamber.
[0033] After pre-deposition, formal deposition is carried out. Tetramethylaminohafnium is used as the hafnium precursor, tetramethylheptadecyl cerium is used as the cerium precursor, and ozone is used as the oxygen source. Atomic layer deposition is used to deposit a ferroelectric layer on the bottom electrode layer at a deposition temperature of 280°C. The pulse cycle ratio of hafnium precursor to cerium precursor is controlled at 10:10 to make the cerium doping concentration in the ferroelectric layer 5 at%; the total number of atomic layer deposition cycles is controlled at 12 to make the thickness of the ferroelectric layer 18 nm.
[0034] In step S3, the atomic layer deposition method employs multiple supercycles. Each supercycle includes multiple hafnium oxide deposition subcycles and multiple cerium oxide deposition subcycles. The number of supercycles is the total number of cycles mentioned above.
[0035] One hafnium oxide deposition subcycle includes, in sequence: introducing tetradimethylaminohafnium with a pulse time of 1s; purging with nitrogen for 8s; introducing ozone with a pulse time of 2s; and purging with nitrogen for 8s. A cerium oxide deposition subcycle consists of the following steps: introducing cerium tetramethylheptanedionate with a pulse duration of 2 s; purging with nitrogen gas for 4 s; introducing ozone with a pulse duration of 2 s; and purging with nitrogen gas for 4 s.
[0036] S4: In an inert gas atmosphere, a top electrode layer is deposited on the ferroelectric layer using an excited argon plasma method. Before depositing the top electrode layer, the sample with the deposited ferroelectric layer is divided into multiple segments. A circular aperture mask is attached to the surface of the ferroelectric layer of each segmented sample. The size of the segmented sample is 1.4 cm × 2.2 cm, and the radius of the circular aperture in the mask is 70–80 μm. Then, a circular top electrode is deposited on the circular aperture mask. The deposition process is as follows: the sample is placed in a transfer chamber, and a vacuum of 1 × 10⁻⁶ is applied. -6 The material is transferred to the sputtering chamber. The sputtering power is set to 100W, the argon flow rate to 12 sccm, and the sputtering time to 1200 s. A top electrode layer of titanium nitride with a thickness of 40 nm is deposited. No plasma treatment is required after deposition.
[0037] S5: The sample obtained in step S4 is sent into an annealing furnace and rapidly annealed in a nitrogen atmosphere at a temperature of 700℃, a heating rate of 20℃ / s, and a holding time of 30s to rapidly crystallize the ferroelectric layer and obtain a cerium-doped hafnium oxide-based ferroelectric thin film capacitor.
[0038] Optionally, the substrate material is one of silicon, germanium, silicon oxide, silicon carbide, silicon nitride, gallium nitride, gallium oxide, zinc oxide, aluminum oxide, and strontium titanate; The bottom electrode layer and the top electrode layer are made of one or more of titanium nitride, tantalum nitride, ruthenium oxide, tungsten, platinum, aluminum, and gold.
[0039] Example 2 In this embodiment, an electric field application device is added to the annealing furnace. The electric field application device mainly includes an upper electrode, a lower electrode, and a controller. The upper and lower electrodes are disposed within the quartz annealing chamber of the annealing furnace. The upper electrode is a flexible electrode probe used to contact the top electrode. The lower electrode is a conductive support plate disposed within the annealing furnace, used to support and contact the substrate of the capacitor sample. The upper and lower electrodes are connected to a DC power supply to form a DC electric field. The controller is used to control the DC voltage. The control process of electric field-assisted rapid annealing includes: The rapid annealing process in step S5 also includes a heating stage before the holding stage, and a cooling stage and a natural cooling stage after the holding stage; wherein, the heating stage has a heating rate of 20~50℃ / s; the cooling stage has a cooling rate of 20~40℃ / s, cooling down to 200℃.
[0040] No auxiliary electric field is applied during the heating stage. During the heat preservation and cooling stages, a DC electric field is applied through the bottom electrode layer and the top electrode layer. The direction of the DC electric field is perpendicular to the ferroelectric layer film surface to stabilize the orthogonal ferroelectric phase and induce the polarization axis to be perpendicular to the film surface. The electric field strength is 2~15 kV / cm. The positive terminal of the high-voltage power supply is connected to the upper electrode probe, and the negative terminal of the high-voltage power supply is connected to the conductive plate of the lower electrode. When the high-voltage power supply outputs a positive voltage, the upper electrode is at a high potential, the lower electrode is at a low potential, and the electric field direction is from the upper electrode to the lower electrode, that is, from the top electrode to the bottom electrode, perpendicularly passing through the ferroelectric layer.
[0041] Preferably, the temperature during the heat preservation stage is 700℃, and the electric field strength of the DC electric field is 10kV / cm.
[0042] In this embodiment, no electric field is applied during the heating phase when the capacitor is heated from room temperature to 700°C at a rate of 20°C / s. The purpose is to avoid electric field-induced pre-nucleation at low temperatures and to ensure uniform nucleation of the ferroelectric layer after reaching the target crystallization temperature. Rapid heating helps to obtain fine grain size and improve the film density.
[0043] During the heat preservation stage, the ferroelectric thin film is in the high-temperature paraelectric phase, and a large number of grains nucleate and begin to grow. The applied DC electric field induces the dipoles to initially align along the direction perpendicular to the film surface through the principle of minimizing electrostatic energy (domains tend to align along the direction of the electric field to reduce energy). At the same time, a certain amount of in-plane tensile stress has been generated during the heat preservation stage. This stress begins to suppress the formation of the non-ferroelectric monoclinic phase, providing mechanical conditions for the stability of the ferroelectric orthorhombic phase.
[0044] During the cooling phase, the temperature is reduced from 700℃ to 200℃ at a rate of 20℃ / s. The ferroelectric phase gradually forms and grows. At this stage, the electric field not only induces growth but also provides a constant orientation driving force for the forming ferroelectric grains through continuous application, guiding their polarization axes to align perpendicular to the film surface and preventing orientation relaxation of the oriented grains under thermal disturbance. Simultaneously, as the temperature decreases, the thermal mismatch between the top electrode layer and the ferroelectric layer intensifies, increasing the in-plane tensile stress. This in-plane tensile stress suppresses the formation of the non-ferroelectric monoclinic phase by clamping and stabilizes the already formed orthorhombic phase.
[0045] The natural cooling stage is from 200°C to room temperature. The ferroelectric orthorhombic phase has been fully formed and the polarization axis has been frozen. The electric field is removed, and the sample is allowed to cool naturally to room temperature.
[0046] Example 3 In this embodiment, the hafnium to cerium cycle ratio remains 10:10 (cerium doping concentration is 5 at%) during the formal deposition of the ferroelectric layer. The difference from Embodiment 1 is that in step S3, the total number of cycles during ferroelectric layer deposition is 8, and the ferroelectric layer thickness is 12 nm. Other steps and parameters are the same as in the embodiment.
[0047] Example 4 In this embodiment, the hafnium to cerium cycle ratio remains 10:10 (cerium doping concentration is 5 at%) during the formal deposition of the ferroelectric layer. The difference from Example 1 is that in step S3, the total number of cycles during ferroelectric layer deposition is 10, and the ferroelectric layer thickness is 15 nm. Other steps and parameters are the same as in Example 1.
[0048] Example 5 In this embodiment, the hafnium to cerium cycle ratio remains 10:10 (cerium doping concentration is 5 at%) during the formal deposition of the ferroelectric layer. The difference from Example 1 is that in step S3, the total number of cycles during ferroelectric layer deposition is 14, and the ferroelectric layer thickness is 21 nm. Other steps and parameters are the same as in Example 1.
[0049] Example 6 In this embodiment, the hafnium to cerium cycle ratio remains 10:10 (cerium doping concentration is 5 at%) during the formal deposition of the ferroelectric layer. The difference from Example 1 is that in step S3, the total number of cycles during ferroelectric layer deposition is 16, and the ferroelectric layer thickness is 24 nm. Other steps and parameters are the same as in Example 1.
[0050] Example 7 The difference between this embodiment and Embodiment 1 is that the temperature during the rapid annealing stage is 600°C. All other steps and parameters are the same as in Embodiment 1.
[0051] Example 8 The difference between this embodiment and Embodiment 1 is that the temperature during the rapid annealing stage is 800°C. All other steps and parameters are the same as in Embodiment 1.
[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, in the deposition of the ferroelectric layer, only tetradimethylamine hafnium was used as the hafnium precursor and ozone as the oxygen source, and an 18 nm thick ferroelectric layer (undoped with cerium) was deposited by atomic layer deposition. Other steps and parameters were the same as in Example 1.
[0053] This application compares and analyzes the performance of capacitors prepared in the above embodiments and comparative examples, and the analysis results are as follows: Figure 2 This is a comparison diagram of the hysteresis loops of the samples in Example 1 and Comparative Example 1 of this application; the measurement conditions were: after 1×10 4 Ferroelectric performance was measured after multiple electric field cycles. The horizontal axis represents voltage (V), and the vertical axis represents polarization (μC / cm). 2 .
[0054] from Figure 2 It can be seen that, compared with the undoped cerium in Comparative Example 1, the remanent polarization of the hafnium oxide-based ferroelectric thin film with a cerium doping concentration of 5 at% in Example 1 is improved, with a remanent polarization value of 19.4 μC / cm. 2 This demonstrates that cerium doping can effectively induce and stabilize the ferroelectric orthorhombic phase of hafnium oxide.
[0055] Figure 3 This is a graph showing the relative permittivity of the samples in Example 1 and Comparative Example 1 of this application as a function of voltage. The measurement conditions were: after 1 × 10⁻⁶ days... 4 Ferroelectric performance testing after multiple electric field cycles, with the horizontal axis representing the applied DC bias voltage and the vertical axis representing the relative permittivity. ε r ).from Figure 3 It can be seen that, compared with the undoped cerium in Comparative Example 1, the relative permittivity of the hafnium oxide-based ferroelectric thin film with a cerium doping concentration of 5 at% in Example 1 is significantly improved, and it shows the butterfly-shaped curve characteristic of ferroelectric materials.
[0056] Figure 4 These are comparison diagrams of hysteresis loops for samples of different thicknesses in Examples 1, 2-6 of this application. The measurement conditions were as follows: after a 1×10⁻⁶ cycle... 4Ferroelectric performance was measured after multiple electric field cycles. The horizontal axis represents voltage (V), and the vertical axis represents polarization (μC / cm). 2 .
[0057] from Figure 4 It can be seen that the ferroelectric thin films have large remanent polarization in thicknesses ranging from 12 to 24 nm, with the sample with a thickness of 12 nm exhibiting a remanent polarization value of 15.1 µC / cm. 2 .
[0058] Figure 5 This is a comparison of hysteresis loops of samples obtained at different annealing temperatures in Examples 1, 7, and 8 of this application. The measurement conditions were: after 1×10... 4 Ferroelectric performance was measured after multiple electric field cycles. The horizontal axis represents voltage (V), and the vertical axis represents polarization (μC / cm). 2 .
[0059] Annealing at 600℃ resulted in poor film crystallinity and low ferroelectric orthorhombic phase content, leading to poor ferroelectric performance. When the annealing temperature increased to 800℃, numerous defects were introduced into the film, significantly increasing leakage current density and almost completely destroying the ferroelectric properties. In contrast, annealing at 700℃ yielded the best crystallinity and optimal ferroelectric performance.
[0060] Figure 6 This is a characteristic curve of the remanent polarization intensity of the sample in Example 1 of this application as a function of electric field cycling. The horizontal axis represents the number of electric field cycles (Cycles), a logarithmic scale; the vertical axis represents the remanent polarization intensity (Remanent Polarization), in μC / cm. 2 from Figure 6 It can be seen that the hafnium oxide-based ferroelectric thin film with a cerium doping concentration of 5 at% and a thickness of 18 nm in Example 1 exhibits excellent durability, passing 1×10⁻⁶ cycles under an electric field of 4V and 100kHz. 9 The residual polarization intensity did not decrease significantly, proving that the film has excellent fatigue resistance and durability, meeting the requirements for long-term cyclic use of memory.
[0061] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this application and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this application should be included within the protection scope of this application. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor, characterized in that, include: S1: Select and clean the substrate; S2: In an inert gas atmosphere, a bottom electrode layer is deposited on the upper surface of the substrate by magnetron sputtering; S3: Using tetradimethylaminohafnium as a hafnium precursor, tetramethylheptanedioate cerium as a cerium precursor, and ozone as an oxygen source, an atomic layer deposition method was used to deposit a ferroelectric layer on the bottom electrode layer at a deposition temperature of 250~300℃. The pulse cycle ratio of hafnium precursor to cerium precursor is controlled to make the cerium doping concentration in the ferroelectric layer 2~8 at%; the total number of atomic layer deposition cycles is controlled to make the thickness of the ferroelectric layer 10~25 nm. S4: In an inert gas atmosphere, a top electrode layer is deposited on the ferroelectric layer by magnetron sputtering. S5: The sample obtained in step S4 is rapidly annealed in a nitrogen atmosphere to obtain a cerium-doped hafnium oxide-based ferroelectric thin film capacitor; wherein the annealing temperature is 600~800℃ and the holding time is 30~60s.
2. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 1, characterized in that, The substrate material is one of silicon, germanium, silicon oxide, silicon carbide, silicon nitride, gallium nitride, gallium oxide, zinc oxide, aluminum oxide, and strontium titanate; The bottom electrode layer and the top electrode layer are made of one or more of titanium nitride, tantalum nitride, ruthenium oxide, tungsten, platinum, aluminum, and gold.
3. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 2, characterized in that, Step S2 involves depositing the bottom electrode layer, including: The substrate is placed in the transfer chamber of the magnetron sputtering process, and the vacuum level is evacuated to 1×10⁻⁶. -9 ~1×10 -6 Torr; Open the baffle and send the substrate into the sputtering chamber; set the sputtering power to 80~140W and the sputtering time to 1000~1400s, introduce argon gas as the working gas, and perform magnetron sputtering deposition to obtain a bottom electrode layer with a thickness of 30~50nm.
4. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 3, characterized in that, In step S2, after depositing the bottom electrode layer, the following steps are also included: In the same sputtering chamber, argon plasma is excited to treat the surface of the bottom electrode layer with a power of 50~150W, a treatment time of 30~90s, and an argon flow rate of 10~15sccm.
5. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 1, characterized in that, Before depositing the ferroelectric layer in step S3, the following steps are included: The substrate with the bottom electrode layer deposited is placed into the transfer chamber of the atomic layer deposition system, and the vacuum is evacuated to a vacuum level of 0.5~2 hPa. The reaction chamber is preheated to 250-300°C, the hafnium precursor source bottle is preheated to 70-100°C, and the cerium precursor source bottle is preheated to 150-180°C. Atomic layer deposition formulations were set up, and pre-deposition cycles were performed in the reaction chamber to stabilize the precursor dosage; After pre-deposition, the gate valve between the transfer chamber and the reaction chamber is opened to send the substrate from the transfer chamber into the reaction chamber.
6. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 1, characterized in that, The atomic layer deposition method described in step S3 employs multiple supercycles, with each supercycle including multiple hafnium oxide deposition subcycles and multiple cerium oxide deposition subcycles. One hafnium oxide deposition subcycle includes, in sequence: introducing tetradimethylaminohafnium with a pulse time of 1s; purging with nitrogen for 8s; introducing ozone with a pulse time of 2s; and purging with nitrogen for 8s. A cerium oxide deposition subcycle consists of the following steps: introducing cerium tetramethylheptanedionate with a pulse duration of 2 s; purging with nitrogen gas for 4 s; introducing ozone with a pulse duration of 2 s; and purging with nitrogen gas for 4 s.
7. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 1, characterized in that, The rapid annealing process in step S5 also includes a heating stage before the holding stage, and a cooling stage and a natural cooling stage after the holding stage; among which, The heating rate during the heating phase is 20~50℃ / s; The cooling rate during the cooling phase is 20~40℃ / s, cooling down to 200℃; During the heat preservation stage and the cooling stage, a DC electric field is applied through the bottom electrode layer and the top electrode layer. The direction of the DC electric field is perpendicular to the ferroelectric layer film surface to stabilize the ferroelectric orthogonal phase and induce the polarization axis to be oriented perpendicular to the film surface. The electric field strength is 2~15kV / cm.
8. The method for preparing a cerium-doped hafnium oxide-based ferroelectric thin-film capacitor according to claim 7, characterized in that, The temperature during the heat preservation stage is 700℃, and the electric field strength of the DC electric field is 10kV / cm.
9. A capacitor, characterized in that, It is prepared by the method for preparing cerium-doped hafnium oxide-based ferroelectric thin film capacitors according to any one of claims 1-8.