Hafnium-based ferroelectric memory based on oxide electrode and preparation method thereof

Abstract

The invention discloses a hafnium-based ferroelectric memory based on an oxide electrode and a preparation method of the hafnium-based ferroelectric memory. The preparation method comprises the following steps: growing a metal bottom electrode on a substrate; growing a hafnium-based ferroelectric material layer; growing a TiN layer as a covering layer, carrying out annealing, and then removing the TiN covering layer; forming an oxide top electrode; wherein the interface characteristics of the electrode and the ferroelectric functional layer are optimized by regulating and controlling the oxygen vacancy content and thickness in the oxide electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of ferroelectric memory manufacturing process, and in particular to a hafnium-based ferroelectric memory based on oxide electrodes and a preparation method thereof. Background Art

[0002] Hafnium-based ferroelectric memory has broad application prospects in the field of non-volatile storage due to its non-volatility, high-speed read / write characteristics and low energy consumption. This type of memory usually relies on the polarization properties of ferroelectric materials to store information, among which hafnium-based materials have been widely studied due to their excellent ferroelectric and piezoelectric properties.

[0003] At present, the preparation of hafnium-based ferroelectric memory mainly relies on traditional metal electrodes, such as platinum and gold. However, the insufficient stability of these metal electrodes under high temperature and high electric field limits the performance and reliability of the memory. In addition, the high cost of these materials also significantly increases the production cost. The existing preparation methods face several major problems: 1) Poor stability of electrode materials: Traditional metal electrodes are prone to degradation after long-term operation, affecting the reliability of the memory; 2) Cost issues: The high cost of metal materials increases the overall manufacturing cost. 3) Interface compatibility: The poor interface compatibility between metal electrodes and hafnium-based ferroelectric materials may lead to charge traps and accelerated degradation. In view of the above problems, we proposed a new preparation method, that is, using oxide (indium tin oxide) as electrodes to improve the reliability of the device. Oxide electrodes can provide better chemical and physical stability, reduce interface defects, improve the performance of memory and reduce manufacturing costs, which is an urgent need in the industry. Summary of the invention

[0004] The invention discloses a method for preparing a hafnium-based ferroelectric memory based on an oxide electrode, comprising the following steps: growing a metal bottom electrode on a substrate; growing a hafnium-based ferroelectric material layer; growing a TiN layer as a covering layer, annealing it, and then removing the TiN covering layer; forming an oxide top electrode; wherein the interface characteristics between the electrode and the ferroelectric functional layer are optimized by regulating the oxygen vacancy content and thickness in the oxide electrode.

[0005] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the bottom electrode is W, TiN, TaN or Ru.

[0006] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the top electrode is indium tin oxide or lanthanum strontium manganese oxide.

[0007] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the oxide top electrode is formed by magnetron sputtering.

[0008] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the oxygen flux during the growth of the oxide top electrode is 0% to 20%.

[0009] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the thickness of the oxide top electrode is 50 nm to 150 nm.

[0010] In the method for preparing the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, it is preferred that the hafnium-based ferroelectric material layer is formed by an atomic layer deposition method.

[0011] The present invention also discloses a hafnium-based ferroelectric memory based on oxide electrodes, which is formed by the above-mentioned method for preparing the hafnium-based ferroelectric memory based on oxide electrodes, and includes: a substrate; a metal bottom electrode formed on the substrate; a hafnium-based ferroelectric material layer formed on the metal bottom electrode; and an oxide top electrode formed on the hafnium-based ferroelectric material layer.

[0012] In the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the bottom electrode layer is W, TiN, TaN or Ru.

[0013] In the hafnium-based ferroelectric memory based on oxide electrodes of the present invention, preferably, the top electrode is indium tin oxide or lanthanum strontium manganese oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of a method for preparing a hafnium-based ferroelectric memory based on oxide electrodes.

[0015] Figure 2 to Figure 5 It is a structural schematic diagram of each stage of the preparation method of hafnium-based ferroelectric memory based on oxide electrodes.

[0016] Fig. 6A This is a test chart of the durability (reliability) of traditional W / HZO / TiN ferroelectric memory.

[0017] Figure 6B This is a durability (reliability) test diagram of the W / HZO / ITO ferroelectric memory of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be noted that the terms "upper", "lower", "vertical", "horizontal", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0020] In addition, many specific details of the present invention are described below, such as the structure, materials, dimensions, processing technology and techniques of the device, so that the present invention can be more clearly understood. However, as can be understood by those skilled in the art, the present invention can be implemented without following these specific details. Unless otherwise specified below, the various parts of the device can be made of materials known to those skilled in the art, or can be made of materials with similar functions developed in the future.

[0021] Figure 1 The following is a flow chart of the preparation method of hafnium-based ferroelectric memory based on oxide electrode. 0.5 Zr 0.5 The preparation of a high-reliability ferroelectric memory using an O2 / ITO device and 5% O2-doped ITO as the top electrode is described as an example.

[0022] like Figure 1 As shown, the method for preparing a hafnium-based ferroelectric memory based on an oxide electrode comprises the following steps:

[0023] Step S1, provide a Si / SiO2101 substrate, clean it by standard RCA process, and then use magnetron sputtering (PVD) to grow a 80nm thick W film as the bottom electrode 102. The obtained structure is as follows: Figure 2 The bottom electrode metal layer may also be TiN, TaN, Ru, etc., which can be annealed with Hf-based ferroelectric materials to obtain ferroelectric properties.

[0024] Step S2, using atomic layer deposition (ALD) to grow 10nm thick Hf 0.5Zr 0.5 O2 is used as the ferroelectric functional layer 103, and the resulting structure is as follows Figure 3 As shown. The doping elements of the Hf-based ferroelectric material layer include but are not limited to Zr, Al, La, Y, Si, etc. Using the ALD method to deposit the Hf-based ferroelectric material can achieve high step coverage and improve device performance and reliability.

[0025] Step S3, using magnetron sputtering to grow 50nm thick TiN as the cover layer 104, the resulting structure is as follows Figure 4 Then, rapid thermal annealing (RTP) was performed at 500°C for 60 seconds.

[0026] Step S4, prepare a solution of hydrogen peroxide (H2O2), ammonia (NH3·H2O) and deionized water (DIW) in a ratio of 1:1:5 for wet etching of the TiN cover layer. Soak the device in the etching solution for 10 minutes to remove the TiN cover layer 104, take it out, rinse it with deionized water, and blow it dry for later use.

[0027] Step S5: In order to pattern the ITO top electrode, the device needs to be photolithographically processed. First, the adhesive (LOR3A) and the photoresist (S1813) are sequentially spin-coated on the annealed Hf 0.5 Zr 0.5 O2 ferroelectric functional layer 103; then, exposure is performed; then, it is immersed in a developer (NMD-W), taken out, rinsed with ionized water and blown dry with a nitrogen gun.

[0028] Afterwards, the indium tin oxide (ITO) layer 105 grown by magnetron sputtering is used as the top electrode. The thickness of the ITO electrode is 100nm, and the oxygen permeability is 0%-20%. The electrode is lifted off using a degumming solution (NMP), and the device is completed. The resulting structure is as follows: Figure 5 As shown. The top electrode can also be a lanthanum strontium manganese oxide (LSMO) electrode. By adjusting the thickness of the oxide electrode and the process conditions of the amount of oxygen filled during the electrode growth process, the oxygen vacancy content in the oxide electrode can be controlled, the interface characteristics of the electrode and the ferroelectric functional layer can be optimized, and the preparation of a high fatigue performance ferroelectric memory can be achieved, which provides a direction for improving the reliability and stability of ferroelectric memory.

[0029] The present invention optimizes the oxygen flow rate during the electrode growth process, including five gradients of 0%, 5%, 10%, 15% and 20%. Introducing oxygen during the electrode growth process can affect the oxidation state of the electrode material and the formation of oxygen vacancies. A higher oxygen partial pressure usually increases the oxygen content in the oxide film, thereby reducing the number of oxygen vacancies. This can improve the interface quality, reduce the leakage current and interface trap states of the ferroelectric layer, but may also reduce the conductivity of the electrode. By performing PV / IV / endurance / retension tests on the device, it was found that during the ITO growth process, the device prepared by introducing 5% oxygen had the best Pr and durability, indicating that the conductivity and interface quality of the oxide electrode prepared at 5% oxygen content reached the best balance.

[0030] In addition, under the condition of ensuring 5% oxygen permeability, the thickness of the ITO electrode is changed, including five gradients of 50nm, 80nm, 100nm, 120nm, and 150nm. The thickness of the ITO top electrode will affect the conductivity and interface quality of the HZO-based ferroelectric memory, and thus affect the switching speed, leakage current and ferroelectric performance of the memory. Moderate thickness can optimize these properties, but too thick or too thin will lead to performance degradation. Through PV / IV / endurance / retension testing of the device, it was found that the ITO top electrode has the best ferroelectricity and durability when the thickness is 100nm, indicating that the conductivity and interface quality of the 100nm thick oxide electrode have reached the best balance.

[0031] Fig. 6A This is a test chart of the durability (reliability) of traditional W / HZO / TiN ferroelectric memory. Figure 6B This is a durability (reliability) test diagram of the W / HZO / ITO ferroelectric memory of the present invention. From the test results, it can be seen that the introduction of O2 during the ITO electrode deposition process can greatly improve the reliability of the device. Specifically, Fig. 6A The number of cycles before and after wake-up of the conventional W / HZO / TiN device is shown in 10 7 -10 8 There is even a slight decrease. Figure 6B The battery life of the W / HZO / ITO device of the present invention before and after being awakened at a voltage of 4V is shown in FIG. 1 . It can be seen that the Pr of the device is very small before being awakened, 10 8 -10 9 After 10 cycles, it will be broken down, and the number of cycles after wake-up can exceed 10 12The results show that after applying a large voltage to wake up, the reliability of the device of the W / HZO / ITO structure of the present invention is significantly improved. The reason for the enhanced reliability of the device after awakening is that when a high voltage is applied to wake up the oxidized ITO electrode, part of the oxygen ions in the ITO are injected into the HZO ferroelectric functional layer, thereby reducing the oxygen vacancies in the HZO, suppressing the breakdown effect, and ultimately improving the reliability of the device to a great extent.

[0032] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a hafnium-based ferroelectric memory based on an oxide electrode, characterized in that: The following steps are involved: growing a metal bottom electrode on the substrate; growing a hafnium-based ferroelectric material layer; growing a TiN layer as a capping layer, performing annealing, and then removing the TiN capping layer; forming an oxide top electrode; Among them, the oxygen vacancy content and thickness in the oxide electrode are regulated to optimize the interface properties of the electrode and the ferroelectric functional layer.

2. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The bottom electrode is W, TiN, TaN or Ru.

3. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The top electrode is indium tin oxide, lanthanum strontium manganese oxide.

4. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The hafnium-based ferroelectric material layer is formed by an atomic layer deposition method.

5. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The oxide top electrode is formed by magnetron sputtering.

6. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The oxygen flow rate during the growth of the oxide top electrode is 0% to 20%.

7. The method for preparing a hafnium-based ferroelectric memory based on an oxide electrode according to claim 1, characterized in that: The thickness of the oxide top electrode is 50nm-150nm.

8. A hafnium-based ferroelectric memory based on an oxide electrode, formed by the preparation method of a hafnium-based ferroelectric memory based on an oxide electrode according to any one of claims 1 to 7, characterized in that: include: substrate; a metal bottom electrode formed on the substrate; A hafnium-based ferroelectric material layer formed on the metal bottom electrode; An oxide top electrode is formed on the hafnium-based ferroelectric material layer.

9. The hafnium-based ferroelectric memory based on oxide electrodes according to claim 8, characterized in that: The bottom electrode is W, TiN, TaN or Ru.

10. The hafnium-based ferroelectric memory based on oxide electrodes according to claim 8, characterized in that: The top electrode is indium tin oxide, lanthanum strontium manganese oxide.

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