A method for regulating a hafnium-based thin film crystal structure

Abstract

The application provides a hafnium-based thin film crystal structure regulation method, which comprises the following steps: providing a substrate; preparing a hafnium-based thin film on the substrate; changing the strain of the hafnium-based thin film by controlling the preparation parameters of the hafnium-based thin film; and performing thermal annealing on the thin film structure, and regulating the crystal structure of the hafnium-based thin film by controlling the annealing temperature based on the temperature-strain phase diagram of the hafnium-based thin film. The application introduces different sizes of strain into the thin film by regulating the parameters in the preparation process of the hafnium-based thin film, and then cooperatively controls the temperature and the strain of the hafnium-based thin film in the annealing process, so as to effectively and finely adjust the crystal structure of the hafnium-based thin film, and optimize the material performance. The regulation method of the application is more accurate and effective than the traditional single temperature or thin film parameter control.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit device technology, and more specifically, to a method for controlling hafnium-based thin-film crystal structures. Background Technology

[0002] The semiconductor technology industry has been advancing in recent decades in line with Moore's Law. The continuous reduction in feature size has led to hafnium oxide (HfO2) replacing silicon dioxide as a new type of gate insulator material, representing a high-k dielectric. Furthermore, research has shown that the k-value can be controlled by adjusting the crystal structure of HfO2. At room temperature and pressure, HfO2 exists primarily in the thermodynamically stable monoclinic phase (M phase), with a k-value of 20. The highly symmetric tetragonal (T phase) and cubic (C phase) phases have even higher k-values, but they only exhibit thermodynamic stability under high temperature and pressure.

[0003] With continuous exploration of its dielectric properties, ferroelectricity of Si-doped HfO2 thin films was first discovered in 2011. Traditional ferroelectric materials suffer from incompatibility with CMOS, poor miniaturization performance, and environmental pollution; the emergence of ferroelectric HfO2 almost perfectly solves all the key obstacles of these traditional materials. The discovery of ferroelectric hafnium-based thin films has attracted great attention, and they hold significant research potential in energy storage and harvesting, low-energy neural computing, logic, and storage. Crystal structure probing revealed that the ferroelectricity of hafnium-based thin films originates from a non-centrosymmetric orthorhombic phase (O phase), the antiferroelectricity from the T phase, and the dielectric properties from the M phase. A transition from the T phase to the M phase occurs during thermal annealing, forming a metastable ferroelectric O phase. Therefore, by controlling the crystal structure of hafnium-based thin films, it is possible to achieve a dominant crystal structure, thereby obtaining hafnium-based thin films with different properties. Hafnium-based thin films with different crystal structures can be applied in various fields, such as novel gate materials based on dielectric properties; storage and computing based on ferroelectric properties, including ferroelectric memories, ferroelectric transistors, and negative capacitance transistors; and energy storage, thermoelectric energy harvesting, cooling, and infrared sensing thermal imaging based on antiferroelectric properties.

[0004] Controlling the crystal structure of hafnium-based thin films has been a key focus of research over the past decade. A search revealed a Chinese invention patent with publication number CN114959640A, which discloses a method and application for controlling the properties of hafnium oxide / zirconia ferroelectric thin films. This method utilizes atomic layer deposition (ALD) to prepare alternating hafnium oxide and zirconia thin films. By inserting a crystallization-guiding layer containing oxides with desired doping elements into specific atomic layer regions, the method precisely controls the formation of a specified crystal structure during annealing. This patent achieves control over the initial crystallization by manipulating the seed crystal; however, the precision of this control needs further improvement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for controlling the crystal structure of hafnium-based thin films. This method comprehensively utilizes two major factors: temperature and strain. By adjusting the preparation parameters of the hafnium-based thin film, the strain of the film is changed, and the annealing temperature is controlled in a coordinated manner, thereby causing a change in the crystal structure of the hafnium-based thin film.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a method for controlling the crystal structure of hafnium-based thin films, comprising:

[0008] Provide a substrate;

[0009] A hafnium-based thin film is prepared on the substrate, and the strain of the hafnium-based thin film is changed by controlling the preparation parameters of the hafnium-based thin film.

[0010] The crystal structure of the hafnium-based thin film was controlled by thermal annealing based on the temperature-strain phase diagram of the hafnium-based thin film and by controlling the annealing temperature.

[0011] Optionally, a substrate is provided, wherein the substrate is made of any one of Si, Ge, TiN, TaN, W, TiO2, Pt, Al2O3, and ZrO2.

[0012] Optionally, a hafnium-based thin film is prepared on the substrate, wherein the method for preparing the hafnium-based thin film includes any one of atomic layer deposition, magnetron sputtering, and laser pulse deposition.

[0013] Optionally, the strain of the hafnium-based thin film is changed by controlling the preparation parameters of the hafnium-based thin film, wherein the preparation parameters include at least one of doping parameters, oxygen vacancy concentration parameters, thin film thickness parameters, thin film planar size parameters, and top capping layer parameters.

[0014] Optionally, controlling the doping parameters includes doping the hafnium-based thin film with any one of Zr, Si, Ge, Al, Y, La and N, with the doping atom concentration ranging from 0 to 100%.

[0015] Optionally, controlling the oxygen vacancy concentration parameter includes: selecting any type of oxygen source and changing the oxygen source supply time and oxygen source flow rate.

[0016] Optionally, controlling the film thickness parameter includes: the film thickness is 1nm-100nm.

[0017] Optionally, controlling the thin film planar size parameters includes: the thin film planar size is 5nm*5nm-10cm*10cm.

[0018] Optionally, controlling the parameters of the top capping layer includes selecting any one of TiN, W, Pt, TaN, Al2O3, and ZrO2 as the top capping layer, wherein the thickness of the top capping layer is 1nm-100nm.

[0019] Optionally, the temperature-strain phase diagram based on the hafnium-based thin film is used to control the crystal structure of the hafnium-based thin film by controlling the annealing temperature, wherein the annealing temperature is 350℃-1000℃.

[0020] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0021] This invention introduces different strains into the hafnium-based thin film by adjusting the parameters during the preparation process. By synergistically controlling the temperature and strain of the hafnium-based thin film during the annealing process, the crystal structure of the hafnium-based thin film can be effectively and precisely adjusted, thereby optimizing the material properties. This invention provides a more precise and effective method for crystal structure control than traditional methods that rely solely on temperature or thin film parameter control. Attached Figure Description

[0022] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the structure of a hafnium-based thin-film device in one embodiment of the present invention;

[0024] In the figure: 1 is the substrate, 2 is the hafnium-based thin film, and 3 is the top capping layer;

[0025] Figure 2 This is a schematic diagram illustrating the principle of controlling the strain of a hafnium-based thin film by controlling different parameters in one embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram illustrating the effect of controlling the crystal structure of hafnium-based thin films by synergistically controlling temperature and thin film strain in one embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram illustrating the effect of controlling the thin film strain to regulate the crystal structure of a hafnium-based thin film in one embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram illustrating the effect of controlling the crystal structure of hafnium-based thin films by synergistically controlling temperature and thin film strain in one embodiment of the present invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0030] In experiments controlling the crystal structure of hafnium-based thin films, many factors have been shown to affect the stability of different crystalline phases. However, these factors ultimately influence the strain of the film, meaning strain is the intrinsic parameter behind these factors. Meanwhile, temperature is another important parameter affecting the crystal structure of hafnium-based thin films. Therefore, this invention modulates the crystal structure of hafnium-based thin films by synergistically controlling temperature and film strain. This crystal structure control method has significant research implications for the future industrial application of hafnium-based thin films.

[0031] Figure 1 A schematic diagram of a hafnium-based thin-film device is shown, which includes, from bottom to top, a substrate 1, a hafnium-based thin film 2, and a top capping layer 3. An embodiment of the present invention provides a method for controlling the crystal structure of a hafnium-based thin film, including:

[0032] S1. Provide a substrate;

[0033] S2. Prepare a hafnium-based thin film on a substrate and change the strain of the hafnium-based thin film by controlling the preparation parameters of the hafnium-based thin film;

[0034] S3. The thin film structure is crystallized by thermal annealing. Based on the temperature-strain phase diagram of the hafnium-based thin film, the crystal structure of the hafnium-based thin film is controlled by adjusting the annealing temperature.

[0035] On the one hand, the embodiments of the present invention regulate the crystal structure of hafnium-based thin films by adjusting the thin film strain. There are many methods for adjusting the strain, thereby expanding the selectivity of the regulation method. On the other hand, in addition to regulating the preparation parameters of the thin film, the influence of the annealing temperature is also considered. Through the coordinated control of temperature and strain, the method has richer adjustability and more precise regulation guidance.

[0036] In some embodiments, in step S1, the substrate material is any one of Si, Ge, TiN, TaN, W, TiO2, Pt, Al2O3, and ZrO2. Substrate materials with a larger coefficient of thermal expansion than hafnium-based thin films can introduce larger strain into the thin film, while substrate materials with a smaller coefficient of thermal expansion than hafnium-based thin films can introduce smaller strain into the thin film.

[0037] In some embodiments, in step S2, the method for preparing the hafnium-based thin film includes any one of atomic layer deposition, magnetron sputtering, and laser pulse deposition.

[0038] Preferably, the preparation parameters include at least one of the following: doping parameters, oxygen vacancy concentration parameters, film thickness parameters, film planar size parameters, and top capping layer parameters.

[0039] A schematic diagram illustrating the principle of controlling the strain of hafnium-based thin films by adjusting different parameters is shown below. Figure 2 As shown, different strains can be introduced into the hafnium-based thin film by adjusting factors such as substrate type, dopant type, dopant concentration, oxygen vacancy concentration, film thickness, film planar size, and top capping layer conditions.

[0040] Specifically, smaller strain can be introduced into the film by using a lower doping concentration, a lower oxygen vacancy concentration, a higher hafnium-based film thickness, a larger film planar size, a substrate / top capping layer with a higher coefficient of thermal expansion, and a thinner capping layer; while larger strain can be introduced into the film by using a higher doping concentration, a higher oxygen vacancy concentration, a lower hafnium-based film thickness, a smaller film planar size, a substrate / top capping layer with a lower coefficient of thermal expansion, and a thicker capping layer.

[0041] In some embodiments, controlling the doping parameters includes doping the hafnium-based thin film with any one of Zr, Si, Ge, Al, Y, La, and N, with the doping atom concentration ranging from 0 to 100%. For the doping concentration of these elements, a higher concentration can introduce a larger strain into the thin film, while a lower concentration can introduce a smaller strain into the thin film.

[0042] In some implementations, controlling the oxygen vacancy concentration parameter includes selecting any type of oxygen source and varying the oxygen supply time and flow rate as needed. Higher oxygen vacancy concentrations can introduce larger strain into the film, while lower oxygen vacancy concentrations can introduce smaller strain.

[0043] In some embodiments, controlling the film thickness parameters includes: film thickness ranging from 1 nm to 100 nm, and adjusting the crystal structure of the hafnium-based film, one aspect of which is to obtain a film with a ferroelectric O phase. Different fabrication processes can induce ferroelectricity in hafnium-based films within different thickness ranges. For the most widely used ALD process, a film thickness of 6 nm to 30 nm is preferred; exceeding this range makes it difficult to obtain ferroelectricity. For films deposited by methods such as laser pulse deposition, ferroelectricity can also be obtained at around 80 nm. Therefore, the film thickness needs to be determined comprehensively based on specific process methods, etc. Smaller film thicknesses can introduce larger strain into the film, while larger film thicknesses can introduce smaller strain.

[0044] In some embodiments, the control of thin film planar dimensions includes: thin film planar dimensions of 5nm*5nm-10cm*10cm, with the dimensions determined based on process feasibility. The minimum size for electron beam lithography is 5nm*5nm, and for substrates that do not require cutting, the size is 10cm*10cm. Smaller thin film planar dimensions can introduce larger strain into the thin film, while larger thin film planar dimensions can introduce smaller strain.

[0045] After depositing a hafnium-based thin film (with varying parameters), a top capping layer can be deposited. The materials for the top capping layer fall into two categories: metal electrode materials, which are generally used as the top electrode and typically have a thickness between 10 nm and 100 nm; and metal oxide thin films, which primarily introduce strain. If the metal oxide film is too thick, it is detrimental to subsequent electrical testing; its thickness is generally between 1 nm and 10 nm. In some embodiments, the control of the top capping layer parameters includes selecting any one of TiN, W, Pt, TaN, Al2O3, and ZrO2 as the top capping layer, with a thickness between 1 nm and 100 nm. Because the coefficient of thermal expansion of the top capping film is smaller than that of the hafnium-based film, capping materials with a larger difference in thermal expansion coefficient can introduce larger strain into the film, while capping materials with a smaller difference in thermal expansion coefficient can introduce smaller strain. In other words, for the same thickness, the smaller the coefficient of thermal expansion of the top capping layer, the greater the strain introduced. For example, a hafnium-based film with a thermal expansion coefficient of 10 will introduce greater strain with a capping layer of 2 than with a coefficient of 8. Similarly, for the same material, a thicker top capping layer will introduce greater strain; a thicker capping layer can introduce larger strain into the film, while a thinner capping layer can introduce smaller strain. By selecting top capping layers of different thicknesses and materials, different strains can be introduced into the film.

[0046] The temperature-strain phase diagram mentioned above was obtained by testing the two-dimensional XRD patterns of hafnium-based thin films with different parameters during the annealing process. The two-dimensional XRD patterns can provide information on strain and crystal structure, which can be plotted together with the corresponding temperatures to obtain the temperature-strain phase diagram.

[0047] In some embodiments, the annealing temperature in step S3 is 350°C-1000°C. The minimum crystallization temperature of hafnium-based thin films is generally 350°C, and the specific temperature is determined according to the target crystal structure. For crystal structures with more O phases, according to the temperature-strain phase diagram, thin films with smaller strain require annealing at higher temperatures, while thin films with larger strain require annealing at relatively lower temperatures.

[0048] like Figure 3As shown, the above embodiments of the present invention further regulate the crystal structure of hafnium-based thin films by synergistically controlling temperature and thin film strain. Larger strain and higher temperature result in a greater proportion of the T phase in the thin film, while smaller strain and lower temperature result in a greater proportion of the M phase in the thin film. The O phase is generated in the region between the M phase and the T phase.

[0049] Figure 4 Images (a) through (c) illustrate how the crystal structure of a hafnium-based thin film can be controlled by adjusting the strain within the film through variations in doping concentration, oxygen vacancies, and planar size parameters. Figure 4 When the doping concentration is increased, the oxygen vacancies are reduced, and the planar size is decreased, the crystal structure transforms from the M phase to the O phase and then to the T phase.

[0050] Figure 5 Figures (a) and (b) illustrate the effect of synergistic control of annealing temperature and thin film strain (with / without top capping layer W) on crystal structure regulation. In the case of low-temperature annealing and no capping layer, the M phase is more abundant; in the case of high-temperature annealing and no capping layer, the M phase decreases and the O phase increases; in the case of low-temperature annealing and with capping layer, the O phase is more abundant; and in the case of high-temperature annealing and with capping layer, the T phase is more abundant.

[0051] The above embodiments of the present invention introduce different strains into the hafnium-based thin film by adjusting the parameters in the preparation process of the hafnium-based thin film, and then achieve the purpose of effectively and precisely adjusting the crystal structure of the hafnium-based thin film by synergistically controlling the temperature and strain of the hafnium-based thin film during the annealing process. This enables the optimization of material properties. The above embodiments of the present invention provide a more precise and effective crystal structure control method than the traditional single temperature or thin film parameter control.

[0052] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A method for controlling the crystal structure of a hafnium-based thin film, characterized in that, include: Provide a substrate; A hafnium-based thin film is prepared on the substrate, and the strain of the hafnium-based thin film is changed by controlling the preparation parameters of the hafnium-based thin film, wherein: the preparation parameters include at least one of doping parameters, oxygen vacancy concentration parameters, thin film thickness parameters, thin film planar size parameters, and top capping layer parameters; The crystal structure of the hafnium-based thin film was controlled by thermal annealing based on the temperature-strain phase diagram of the hafnium-based thin film and the annealing temperature was controlled. The process of obtaining the temperature-strain phase diagram of the hafnium-based thin film includes: testing the two-dimensional XRD patterns of hafnium-based thin films with different parameters during the annealing process, obtaining information on strain and crystal structure through the two-dimensional XRD patterns, and plotting them together with the corresponding temperatures to obtain the temperature-strain phase diagram.

2. The method for controlling the crystal structure of hafnium-based thin films according to claim 1, characterized in that, The provision provides a substrate, wherein the substrate material is any one of Si, Ge, TiN, TaN, W, TiO2, Pt, Al2O3, and ZrO2.

3. The method for controlling the crystal structure of hafnium-based thin films according to claim 1, characterized in that, A hafnium-based thin film is prepared on the substrate, wherein the method for preparing the hafnium-based thin film includes any one of atomic layer deposition, magnetron sputtering, and laser pulse deposition.

4. The method for controlling the structure of hafnium-based thin film crystals according to claim 1, characterized in that, Controlling the doping parameters includes doping the hafnium-based thin film with any one of Zr, Si, Ge, Al, Y, La and N, with the doping atom concentration ranging from 0 to 100%.

5. The method for controlling the structure of hafnium-based thin film crystals according to claim 1, characterized in that, Controlling the oxygen vacancy concentration parameter includes: selecting any type of oxygen source and changing the oxygen source supply time and oxygen source flow rate.

6. The method for controlling the crystal structure of hafnium-based thin films according to claim 1, characterized in that, Controlling the film thickness parameter includes: the film thickness is 1nm-100nm.

7. The method for controlling the structure of hafnium-based thin film crystals according to claim 1, characterized in that, The control of the thin film planar size parameters includes: the thin film planar size is 5nm*5nm-10cm*10cm.

8. The method for controlling the structure of hafnium-based thin film crystals according to claim 1, characterized in that, The control of the parameters of the top capping layer includes: selecting any one of TiN, W, Pt, TaN, Al2O3 and ZrO2 as the top capping layer, and the thickness of the top capping layer is 1nm-100nm.

9. The method for controlling the structure of hafnium-based thin film crystals according to claim 1, characterized in that, The temperature-strain phase diagram based on hafnium-based thin films is used to control the crystal structure of hafnium-based thin films by controlling the annealing temperature, wherein the annealing temperature is 350℃-1000℃.

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