HZO ferroelectric capacitor

Abstract

The HZO ferroelectric capacitor comprises at least two capacitor units, each capacitor unit comprises an HZO ferroelectric film and electrode layers located on the two sides of the HZO ferroelectric film, and the at least two capacitor units are connected in series. According to the invention, the overall ferroelectricity of the HZO ferroelectric capacitor is improved, the driving voltage applied to the two ends of each HZO ferroelectric film is obviously reduced, and the consumption of the single-layer HZO ferroelectric film is directly reduced, so that the limit cycle index of the device can be obviously improved, and the fatigue characteristic and the reliability are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a HZO ferroelectric capacitor. Background Art

[0002] Ferroelectric memory is based on the spontaneous polarization and non-volatile properties of ferroelectric materials. It can store data without refreshing the circuit. It is an emerging memory with high-speed reading and writing, low power consumption and high reliability, and has been widely used in various fields.

[0003] The core part of ferroelectric memory is ferroelectric capacitor, which is generally an MFM structure, that is, the upper and lower layers of metal constitute the capacitor electrodes, and the middle is a ferroelectric thin film material. Ferroelectric thin film materials have ferroelectric effect. Under the external electric field applied by the upper and lower electrodes, the iron domains of ferroelectric thin film materials show different polarization states with electric fields in different directions, and the capacitance will change with the change of polarization state, so that the amount and polarity of charge stored in the capacitor change with the change of polarization direction and size of the capacitor. At the same time, because the polarization strength of the material can still be maintained when the external electric field is removed, the capacitor has non-volatile charge storage capacity, realizing data storage.

[0004] Compared with traditional ferroelectric materials that have been commercialized (such as PZT, lead zirconate titanate piezoelectric ceramics), although HZO (zirconium-doped hafnium oxide) ferroelectric films have obvious advantages in scalability and read and write speeds, and are more in line with the development path of high-speed and miniaturization of semiconductor devices, after multiple polarization reversals, the polarization of HZO ferroelectric films decreases faster and the fatigue effect is more obvious, which seriously affects its durability and is a major challenge in its commercialization process. Summary of the invention

[0005] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. The Summary of the Invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0006] In response to the current problems, an embodiment of the present invention provides a HZO ferroelectric capacitor, which includes at least two capacitor units, each of which includes a HZO ferroelectric film and electrode layers located on both sides of the HZO ferroelectric film, and the at least two capacitor units are connected in series.

[0007] In one embodiment, the at least two capacitor units are vertically stacked.

[0008] In one embodiment, two adjacent capacitor units share the same electrode layer.

[0009] In one embodiment, the HZO ferroelectric capacitor includes a first electrode layer, a first HZO ferroelectric film, a second electrode layer, a second HZO ferroelectric film and a third electrode layer stacked in sequence, the first electrode layer, the first HZO ferroelectric film and the second electrode layer constitute a first capacitor unit, the second electrode layer, the second HZO ferroelectric film and the third electrode layer constitute a second capacitor unit, and the first electrode layer and the third electrode layer are used to obtain an external electric field.

[0010] In one embodiment, the at least two capacitor units are spaced apart from each other and are connected in series via an interconnection structure.

[0011] In one embodiment, the at least two capacitor units are arranged in parallel.

[0012] In one embodiment, the HZO ferroelectric capacitor includes a first capacitor unit and a second capacitor unit, the first capacitor unit includes a first electrode layer, a first HZO ferroelectric film and a second electrode layer, the second capacitor unit includes a third electrode layer, a second HZO ferroelectric film and a fourth electrode layer, the second electrode layer is electrically connected to the third electrode layer through an interconnection structure, and the first electrode layer and the fourth electrode layer are used to obtain an external electric field.

[0013] In one embodiment, the electrode layer is formed by atomic layer deposition to tune the growth stress of the electrode layer.

[0014] In one embodiment, the material of the electrode layer includes at least one of the following: TiN, TaN, Pt, W, Ru, RuO2, Pd, and IrO2.

[0015] In one embodiment, the thickness of the electrode layer is 10 nm to 40 nm, and the thickness of the HZO ferroelectric thin film is 8 nm to 15 nm.

[0016] The HZO ferroelectric capacitor of the embodiment of the present invention connects at least two capacitor units in series, thereby improving the overall ferroelectricity of the HZO ferroelectric capacitor. At the same time, the driving voltage applied to both ends of each HZO ferroelectric film is significantly reduced, directly reducing the consumption of the single-layer HZO ferroelectric film, thereby significantly increasing the number of limit cycles of the device and improving fatigue characteristics and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following drawings of the present invention are used to understand the present invention as part of the present invention. The embodiments of the present invention are shown in the drawings and the description thereof is used to explain the principle of the present invention.

[0018] In the attached figure:

[0019] Figure 1A schematic diagram of a HZO ferroelectric capacitor according to an embodiment of the present invention is shown;

[0020] Figure 2 A schematic diagram of a HZO ferroelectric capacitor according to another embodiment of the present invention is shown;

[0021] Figure 3 The corresponding relationship between the number of cycles and the residual polarization intensity of a single-layer HZO ferroelectric film and a series-connected multilayer HZO ferroelectric film is shown;

[0022] Figure 4 A comparison of PV curves before and after interface stress adjustment is shown;

[0023] Figure 5 The concave-convex characteristics of the polarization intensity of a single-layer HZO ferroelectric film with an applied electric field are shown;

[0024] Fig. 6A and Figure 6B Schematic diagram of the change of PV characteristics of a single-layer ferroelectric film with voltage. DETAILED DESCRIPTION

[0025] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0026] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0027] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be represented as a second element, component, region, layer or part.

[0028] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0029] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0030] Hf 1-x Zr x O2 (HZO, zirconium-doped hafnium oxide) is an extension of HfO (hafnium oxide) based ferroelectric materials and is a new type of ferroelectric material. 1-x Zr xHfO2 (hafnium dioxide) and ZrO2 (zirconium dioxide) have been used in the gate oxide of MOSFET (metal oxide semiconductor field effect transistor) and the dielectric layer of DRAM (dynamic random access memory). Therefore, HZO ferroelectric materials are well compatible with CMOS (complementary metal oxide semiconductor) processes. At the same time, they can also show strong ferroelectricity at an ultra-thin thickness of about 10nm, and have excellent scalability. In addition, based on the ultra-thin thickness, Hf 1-x Zr x O2 also shows significant advantages in ferroelectricity and erase speed.

[0031] However, after multiple polarization reversals, the polarization of HZO ferroelectric films decreases faster and the fatigue effect is more obvious, which seriously affects its durability and is a major challenge in its commercialization process. At present, the mainstream solutions to improve the fatigue properties of HZO ferroelectric films are mostly through element doping and finding the best electrode materials. The variety of doping elements and electrode materials indirectly shows that the best solution has not yet been found. Although some solutions have improved the ferroelectricity and fatigue properties of HfO-based ferroelectric films, most of these materials are not compatible with the current CMOS manufacturing process and are difficult to manufacture on a large scale in a short period of time, which greatly increases their potential manufacturing costs.

[0032] To solve the above problems, an embodiment of the present invention provides a HZO ferroelectric capacitor, comprising at least two capacitor units, each capacitor unit comprising a HZO ferroelectric film and electrode layers located on both sides of the HZO ferroelectric film, and at least two capacitor units are connected in series.

[0033] The HZO ferroelectric capacitor of the embodiment of the present invention connects at least two capacitor units in series, and utilizes the characteristic that the residual polarization intensity (2Pr) is first convex and then concave with the external electric field intensity to improve the overall ferroelectricity of the HZO ferroelectric capacitor. At the same time, according to the series voltage division principle, the driving voltage applied to both ends of each HZO ferroelectric film is significantly reduced, which will also lead to a reduction in the energy applied to a single HZO ferroelectric film by the external electric field in each cycle, directly reducing the consumption of a single-layer HZO ferroelectric film, thereby significantly increasing the number of limit cycles of the device, and improving fatigue characteristics and reliability, which will help promote the further commercialization of HZO ferroelectric capacitors based on HZO ferroelectric films.

[0034] In order to fully understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0035] The HZO ferroelectric capacitor of the embodiment of the present invention comprises at least two capacitor units, and at least two capacitor units are arranged in series. In one embodiment, at least two capacitor units of the HZO ferroelectric capacitor are arranged in a vertical stack, that is, two adjacent capacitor units are attached to each other so that adjacent capacitor units are connected in series with each other. Exemplarily, when at least two capacitor units are arranged in a vertical stack, the top electrode layer of the capacitor unit at the top and the bottom electrode layer of the capacitor unit at the bottom are respectively used as the top electrode layer and the bottom electrode layer of the HZO ferroelectric capacitor as a whole, for obtaining an external electric field, that is, connected to an external wiring.

[0036] Furthermore, when at least two capacitor units are stacked vertically, two adjacent capacitor units can share the same electrode layer, that is, the electrode layer located between two adjacent layers of HZO ferroelectric films is used as both the bottom electrode layer of the capacitor unit located above and the top electrode layer of the capacitor unit located below, thereby reducing the number of film layers.

[0037] Optionally, two adjacent capacitor units may also have independent electrode layers, and the adjacent electrode layers are attached to each other to achieve series connection.

[0038] For example, see Figure 1 , wherein the HZO ferroelectric capacitor includes a first electrode layer 101, a first HZO ferroelectric film 102, a second electrode layer 103, a second HZO ferroelectric film 104 and a third electrode layer 105 stacked in sequence, the first electrode layer 101, the first HZO ferroelectric film 102 and the second electrode layer 103 constitute a first capacitor unit, the second electrode layer 103, the second HZO ferroelectric film 104 and the third electrode layer 105 constitute a second capacitor unit, the first electrode layer and the third electrode layer are respectively the top electrode layer and the bottom electrode layer of the HZO ferroelectric capacitor, for obtaining an external electric field, the second electrode layer 103 is an intermediate electrode layer, shared by the first capacitor unit and the second capacitor unit.

[0039] based on Figure 1 The stacked series HZO ferroelectric capacitor shown in the figure can reduce the driving voltage applied to each HZO ferroelectric film to half of the original value according to the series voltage division principle. This will also lead to a reduction in the energy applied to the individual HZO ferroelectric film by the external electric field in each cycle, directly reducing the consumption of the ferroelectric polarity of the individual HZO ferroelectric film, thereby significantly increasing the limit cycle number of the HZO ferroelectric capacitor while increasing the polarization strength, thereby improving the fatigue characteristics and reliability of the HZO ferroelectric capacitor.

[0040] Figure 1 Two capacitor units are used as an example for description, but the number of capacitor units of the HZO ferroelectric capacitor is not limited to two. When the HZO ferroelectric capacitor includes more capacitor units, more HZO ferroelectric thin films and electrode layers can be alternately stacked.

[0041] In another embodiment, at least two capacitor units of the HZO ferroelectric capacitor are spaced apart from each other and connected in series via an interconnection structure, wherein different capacitor units are not in direct contact with each other and do not share a film layer. The relative spatial positions of the at least two capacitor units can be various, and in some embodiments, in order to facilitate design and manufacture, the at least two capacitor units can be arranged in parallel, that is, the electrode layers and the HZO ferroelectric film of the at least two capacitor units are respectively located on the same plane.

[0042] For example, see Figure 2 In one example, the HZO ferroelectric capacitor includes a first capacitor unit and a second capacitor unit, the first capacitor unit includes a first electrode layer 201, a first HZO ferroelectric film 202 and a second electrode layer 203, the second capacitor unit includes a third electrode layer 204, a second HZO ferroelectric film 205 and a fourth electrode layer 206, the second electrode layer 203 is electrically connected to the third electrode layer 204 via an interconnection structure 207, and the first electrode layer 201 and the fourth electrode layer 206 are used to obtain an external electric field.

[0043] exist Figure 2 In the example, the second electrode layer 203 and the third electrode layer 204 are electrically connected through the interconnection structure 207 to connect the first capacitor unit and the second capacitor unit in series. Exemplarily, the interconnection structure includes two horizontal structures parallel to the second electrode layer 203 and the third electrode layer 204, respectively, and a vertical structure connecting the two horizontal lines. The first electrode layer 201 and the fourth electrode layer 206 are the bottom electrode layer and the top electrode layer of the HZO ferroelectric capacitor as a whole, and are used to connect external lines. Figure 2 In addition to the series connection method, the first capacitor unit and the second capacitor unit may also be connected in other series connection methods, such as electrically connecting the first electrode layer 201 and the fourth electrode layer 206 through an interconnection structure.

[0044] Figure 2 Two capacitor units are used as an example for description, but the number of capacitor units of the HZO ferroelectric capacitor is not limited to two. When the HZO ferroelectric capacitor includes more capacitor units, more capacitor units can be connected in series through more interconnection structures.

[0045] The above two series structures have their own advantages respectively and can be selected according to different application scenarios. Figure 1 The stacked series structure shown requires a smaller area and has better scalability. Figure 2 The separated series structure shown is easier to achieve consistency of different capacitor units, more balanced voltage division, and does not need to consider the effect of interface stress on each layer of HZO ferroelectric film, which is simpler to implement in terms of process.

[0046] In manufacturing, for example Figure 1 In the process of vertically stacking the HZO ferroelectric capacitor in series as shown, the stress of each electrode plate can be adjusted to ensure the consistency of each layer of HZO ferroelectric film. For example, the electrode layer can be formed by atomic layer deposition (ALD) to tune the growth stress of the electrode layer. The atomic layer deposition method can deposit the material layer by layer in the form of a single atomic film, so it is easier to tune the growth stress of the electrode layer.

[0047] Specifically, taking the electrode layer based on TiN material as an example, when the TiN electrode layer is prepared by the ALD process, the growth stress of each electrode layer can be tuned by changing the flow rate, pressure, power and temperature parameters when the precursors TiCl4 and NH3 are introduced during the film deposition process, so that the average growth stress of the TiN electrode layer can be adjusted between tension and compression to ensure the consistency between each layer of HZO ferroelectric film, so that the polarization reversal position of each layer of HZO ferroelectric film is kept as the same as possible, avoiding the misalignment and rotation of the polarization current, resulting in PV anomalies and misreading and miswriting of the circuit. Exemplarily, the interface stress of each film layer in the HZO ferroelectric capacitor can be tested by testing methods such as in-situ wafer curvature and non-in-situ X-ray diffraction to ensure the consistency between each layer of HZO ferroelectric film.

[0048] See also Figure 4 , which shows the comparison of PV curves before and after interface stress adjustment. Figure 4 It can be seen that the abnormality of the PV curve can be corrected by tuning the growth stress of the electrode layer.

[0049] Exemplarily, the material of the electrode layer, in addition to TiN, includes at least one of the following: TaN, Pt, W, Ru, RuO2, Pd, IrO2, and the specific material can be selected according to actual needs.

[0050] For example, the doping elements in the HZO ferroelectric thin film may include one or more of Si, Y, Al, Gd, Sr, La and the like in addition to Zr.

[0051] For example, in a ferroelectric capacitor structure, setting the thickness of the electrode layer to 10 nm to 40 nm and setting the thickness of the HZO ferroelectric film to 8 nm to 15 nm can achieve better performance.

[0052] The above exemplary embodiment of the HZO ferroelectric capacitor of the present invention is described. The present invention utilizes the characteristic that the residual polarization intensity (2Pr) of a single-layer HZO ferroelectric film first becomes convex and then becomes concave as the external electric field intensity increases. Figure 5As shown, at 1 / 2 of the applied electric field of 2.5V, the polarization intensity only drops to about 3 / 5 of the original, indicating that the ferroelectricity of the HZO film can be enhanced by series voltage division.

[0053] By testing the PV characteristics as the driving voltage changes, it can be further demonstrated that multilayer ferroelectric films can improve the reliability of the device. Fig. 6A , Figure 6B As shown in the figure, the test shows that when the driving voltage is greater than 2V, the number of cycles of the HZO ferroelectric film decreases with the increase of voltage, approaching linearity. In this voltage range, the reliability of the HZO ferroelectric film is affected by fatigue and leakage. The higher the voltage, the faster the failure. When the voltage is below 2V, the influence of leakage disappears, and the voltage drops to a level that no longer affects the formation of leakage oxygen vacancies. At this time, the HZO ferroelectric film only has fatigue effects, and the number of cycles is no longer linearly related to the voltage. This further shows that the internal voltage division of ferroelectric capacitors through multilayer HZO ferroelectric films can greatly increase the number of cycles and its reliability.

[0054] To sum up, the HZO ferroelectric capacitor in the embodiment of the present invention connects at least two capacitor units in series, which improves the overall ferroelectricity of the HZO ferroelectric capacitor. At the same time, the driving voltage applied to both ends of each HZO ferroelectric film is significantly reduced, which directly reduces the consumption of the single-layer HZO ferroelectric film, thereby significantly improving the number of limit cycles of the device and improving fatigue characteristics and reliability.

[0055] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A HZO ferroelectric capacitor, characterized in that: The HZO ferroelectric capacitor comprises at least two capacitor units, each of which comprises a HZO ferroelectric film and electrode layers located on both sides of the HZO ferroelectric film, and the at least two capacitor units are connected in series.

2. The HZO ferroelectric capacitor according to claim 1, characterized in that: The at least two capacitor units are vertically stacked.

3. The HZO ferroelectric capacitor according to claim 2, characterized in that: Two adjacent capacitor units share the same electrode layer.

4. The HZO ferroelectric capacitor according to claim 3, characterized in that: The HZO ferroelectric capacitor includes a first electrode layer, a first HZO ferroelectric film, a second electrode layer, a second HZO ferroelectric film and a third electrode layer stacked in sequence, the first electrode layer, the first HZO ferroelectric film and the second electrode layer constitute a first capacitor unit, the second electrode layer, the second HZO ferroelectric film and the third electrode layer constitute a second capacitor unit, and the first electrode layer and the third electrode layer are used to obtain an external electric field.

5. The HZO ferroelectric capacitor according to claim 1, characterized in that: The at least two capacitor units are spaced apart from each other and are connected in series via an interconnection structure.

6. The HZO ferroelectric capacitor according to claim 5, characterized in that: The at least two capacitor units are arranged in parallel.

7. The HZO ferroelectric capacitor according to claim 5 or 6, characterized in that: The HZO ferroelectric capacitor includes a first capacitor unit and a second capacitor unit, the first capacitor unit includes a first electrode layer, a first HZO ferroelectric film and a second electrode layer, the second capacitor unit includes a third electrode layer, a second HZO ferroelectric film and a fourth electrode layer, the second electrode layer is electrically connected to the third electrode layer through an interconnection structure, and the first electrode layer and the fourth electrode layer are used to obtain an external electric field.

8. The HZO ferroelectric capacitor according to claim 1, characterized in that: The electrode layer is formed by atomic layer deposition to tune the growth stress of the electrode layer.

9. The HZO ferroelectric capacitor according to claim 1 or 8, characterized in that: The material of the electrode layer includes at least one of the following: TiN, TaN, Pt, W, Ru, RuO2, Pd, and IrO2.

10. The HZO ferroelectric capacitor according to claim 1, characterized in that: The thickness of the electrode layer is 10 nm to 40 nm, and the thickness of the HZO ferroelectric film is 8 nm to 15 nm.

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