A doping modification method of hafnium oxide-based dielectric thin film

Abstract

This invention discloses a doping modification method for hafnium oxide-based dielectric thin films, comprising: doping modification of the Zr-layer in a hafnium-based stacked system; on the one hand, utilizing the confined oxygen vacancy migration and charge balance effect in the stacked system to suppress leakage current; on the other hand, reducing the transition barrier between the polarized O phase and the non-polarized T phase by doping, thereby obtaining a 3D integrated hafnium-based stacked system. The film thickness is 4–10 nm, and the thicknesses of the HfO2 layer and the ZrO2 layer are both 0.5–2 nm. The doping site is the Zr-layer of the stacked system, and the doping element is selected from Al, Ga, In, Sc, Y, La, Mg, Ca, and Sr. The hafnium-based stacked system obtained by the doping modification method of this invention can achieve higher k and lower leakage current, and is easier to achieve MPB, thereby improving the dielectric properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of dielectric material modification technology, specifically relating to a doping modification method for hafnium oxide-based dielectric thin films. Background Technology

[0002] As device dimensions continue to shrink, the transition to three-dimensional (3D) dynamic random-access memory (DRAM) is becoming increasingly critical. One crucial technological driver is the use of dielectric materials with high dielectric constants (k) and low leakage currents. Currently, the HfO2 system is widely used in industry due to its compatibility with CMOS processes and the mature atomic layer deposition (ALD) technology. Nevertheless, a high dielectric constant is still required to store sufficient charge for further 3D integration.

[0003] In recent years, quasi-isomorphic phase boundary (MPB) behavior has attracted widespread attention due to its high dielectric constant. In hafnium-based systems, MPB is attributed to the interconversion between a polar orthorhombic phase (o phase) and a nonpolar tetragonal phase (t phase), and a low transition barrier between the o and t phases is a prerequisite for realizing MPB. Existing research has shown that doping in the HfO2 system is an effective method for realizing MPB; by adjusting the Hf / Zr ratio, doping can be achieved in HfO2. x Zr 1-x In O2 thin films, the k-value can be increased to ~50. Recently, researchers proposed increasing the k-value to ~50 using Hf. 0.5 Zr 0.5 Further doping of O2(HZO) with Al (~68) and La (~58) can yield a higher dielectric constant. However, this results in a higher leakage current (1E-5A / cm) at the operating voltage. 2 This limits its further development. To date, achieving higher k values ​​and lower leakage currents in hafnium-based systems remains a key challenge.

[0004] Previous studies have found that in HfO2-ZrO2 stacked systems, the vertical migration of oxygen vacancies is restricted due to the large diffusion barrier of oxygen vacancies in the Hf layer, thereby reducing leakage current and improving device durability. Therefore, achieving higher k-values ​​and lower leakage currents through doping modification methods in stacked systems has become a pressing issue in current technology. Summary of the Invention

[0005] The purpose of this invention is to provide a doping modification method for hafnium oxide-based dielectric thin films. By doping the Zr-layer in a hafnium-based stacked system, leakage current is suppressed by utilizing the restricted oxygen vacancy migration and charge balance effect in the stacked system. On the other hand, the transition barrier between the polarized 0 phase and the non-polarized 0 phase is reduced by doping, thereby achieving the higher k and lower leakage current performance requirements of the hafnium-based stacked system in 3D integration.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a doping modification method for hafnium oxide-based dielectric thin films, comprising: doping modification of Zr-layer in a hafnium-based stacked system, on the one hand utilizing the restricted oxygen vacancy migration and charge balance effect in the stacked system to suppress leakage current, and on the other hand reducing the transition barrier between the polarized o phase and the non-polarized t phase by doping, thereby realizing a hafnium-based stacked system under 3D integration.

[0008] Preferably, the hafnium oxide-based dielectric thin film is a hafnium-based multilayer system, comprising a film thickness of 4–10 nm.

[0009] Preferably, the thickness of both the HfO2 layer and the ZrO2 layer is 0.5–2 nm.

[0010] Preferably, the doping position of the doping element is in the Zr-layer of the stacked system.

[0011] Preferably, the doping element is selected from one or more of Al, Ga, In, Sc, Y, La, Mg, Ca, and Sr.

[0012] Preferably, the doping concentration of the doping element is 2%-8%.

[0013] Preferably, the doping element is selected from one or more of Al, Y, La, and Sr.

[0014] More preferably, the doping element is Y.

[0015] Compared with the prior art, the hafnium-based multilayer system provided by the present invention achieves higher k and lower leakage current through doping, and has the following beneficial effects:

[0016] 1) Doping the Zr-layer in a hafnium-based multilayer system can help maintain a larger band gap in the Hf-layer system and suppress leakage current.

[0017] 2) In hafnium-based multilayer systems doped with trivalent or divalent valence, oxygen vacancies are easily induced, resulting in a charge-balanced configuration. At the same time, the phase transition barrier between the o-phase and t-phase becomes lower, making it easier to achieve MPB and thus improve the dielectric properties of the material.

[0018] 3) Under the charge balance effect, oxygen vacancy defect states tend to merge with the bottom of the conduction band, passivating the original oxygen vacancy defect states and reducing leakage current.

[0019] 4) The charge balance doping method of this invention, through theoretical calculations and actual material screening, selects Al, Ga, In, Sc, Y, La, Mg, Ca, and Sr. The above materials have been theoretically verified to achieve the beneficial effects mentioned in 1) to 3). When Al, Y, La, and Sr are selected as the metal dopant, the effects on increasing the k-value and reducing leakage current are more pronounced. Considering the combined influence of the charge balance effect of the above doping elements on the phase transition barrier and band structure, its E... o-t (The potential barrier from phase 0 to phase t) and E t-o The potential barrier (from the t phase to the o phase) is very small, which facilitates the formation of more MPB regions, increases the k value of the doped system, and exhibits better dielectric properties. At the same time, the doping-induced oxygen vacancy defect states can be passivated under charge equilibrium to achieve a large band gap, thereby suppressing leakage current. Attached Figure Description

[0020] Figure 1 The diagram shows the HfO2-ZrO2 superlattice structure in the embodiment; 1 is the ZrO2 layer; 2 is the HfO2 layer; the left side structure is the o phase; the right side structure is the t phase; the thickness of the stack is 1.0 nm.

[0021] Figure 2 This is a schematic diagram comparing the transition barriers of the polarized o phase and the non-polarized t phase in the charge balance doped systems of Examples 1 to 6; 3 is the barrier for the o phase to transform into the t phase, and 4 is the barrier for the t phase to transform into the o phase; the light gray dashed line is the barrier for the o phase to transform into the t phase in the undoped system, and the dark gray dashed line is the barrier for the t phase to transform into the o phase in the undoped system.

[0022] Figure 3 The diagram shows the band gap width under the charge balance effect in Examples 1 to 6; 5 represents the o phase and 6 represents the t phase; the light gray dashed line represents the o phase band gap of the undoped system and the dark gray dashed line represents the t phase band gap of the undoped system. Detailed Implementation

[0023] To more fully understand and demonstrate the technical solutions, objectives, and advantages of the present invention, the technical effects produced by the present invention will be further described in detail and completely below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be noted that other embodiments obtained by those skilled in the art without departing from the concept of the present invention are all within the protection scope of the present invention.

[0024] The following examples use first-principles calculations based on density functional theory and employ the PWmat software package, but are not limited to it. Other packages include VASP, CASTEP, Gaussian, and Wien2k. PWmat is a GPU-accelerated first-principles calculation package that provides most elements in the periodic table and is highly practical.

[0025] Example 1

[0026] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doping metal is Al. The specific method is as follows:

[0027] The formation energy of oxygen vacancies in HfO2-ZrO2 was calculated. When the concentration of Al to oxygen vacancies was 2:1, the formation energy was negative, indicating that this configuration was more likely to form, reflecting a charge balance effect. Al was implanted into the HfO2-ZrO2 film via doping using atomic layer deposition (ALD). The effects of Al on the phase transition barrier and band structure in HfO2-ZrO2 were predicted. The results showed that the interphase transition barriers of both phases 0 and 1 (ot) were reduced, and the barrier for the 0 phase to 1 (t) phase transition was greater than that for the 1 (t) phase to 0 (o) phase transition. Furthermore, compared to the intrinsic system, the band gap width decreased slightly, but no deep-level defects appeared. In this embodiment, using Al as the dopant metal in HfO2-ZrO2 reduced the ot phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivated the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that Al doping can significantly promote MPB formation and reduce leakage current.

[0028] Example 2

[0029] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doping metal is Ga. The specific implementation method is as follows:

[0030] The formation energy of oxygen vacancies in Ga in HfO2-ZrO2 was calculated. When the concentration of Ga to oxygen vacancies was 2:1, the formation energy was negative, indicating that this configuration was more likely to form, reflecting a charge balance effect. Ga was implanted into the HfO2-ZrO2 film through doping using atomic layer deposition (ALD). The effects of Ga on the phase transition barrier and band structure in HfO2-ZrO2 were predicted. The results showed that the interphase transition barriers of ot phase and t phase were reduced, and the barrier for ot phase to t phase was greater than that for t phase to ot phase. In addition, the band gap width was slightly reduced compared to the intrinsic system, but no deep-level defects appeared. In this embodiment, using Ga as the dopant metal in HfO2-ZrO2 can reduce the ot phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivates the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that Ga doping can significantly promote MPB formation and reduce leakage current.

[0031] Example 3

[0032] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doping metal is In. The specific implementation method is as follows:

[0033] The formation energy of oxygen vacancies in HfO2-ZrO2 was calculated. When the concentration of In to oxygen vacancies was 2:1, the formation energy was negative, indicating that this configuration was more likely to form, reflecting a charge balance effect. In was implanted into the HfO2-ZrO2 film via doping using atomic layer deposition (ALD). The effects of In on the phase transition barrier and band structure in HfO2-ZrO2 were predicted. The results showed that the interphase transition barriers of both ot and t phases were reduced, and the barrier for the ot phase to t phase transition was greater than that for the t phase to ot phase transition. Furthermore, compared to the intrinsic system, the band gap width decreased slightly, but no deep-level defects appeared. In this embodiment, using In as the dopant metal in HfO2-ZrO2 reduced the ot phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivated the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that In doping can significantly promote MPB formation and reduce leakage current.

[0034] Example 4

[0035] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doping metal is Sc. The specific implementation method is as follows:

[0036] The formation energy of oxygen vacancies in HfO2-ZrO2 was calculated. When the concentration of Sc to oxygen vacancies was 2:1, the formation energy was negative, indicating that this configuration was more likely to form, demonstrating a charge balance effect. Sc was implanted into the HfO2-ZrO2 film through doping using atomic layer deposition (ALD). The results showed that the phase transition barriers of ot phase and t phase were reduced, and the barrier for ot phase to t phase was greater than that for t phase to ot phase. In addition, the band gap width decreased slightly compared to the intrinsic system, but no deep-level defects appeared. In this embodiment, using Sc as the dopant metal in HfO2-ZrO2 can reduce the ot phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivates the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that Sc doping can significantly promote MPB formation and reduce leakage current.

[0037] Example 5

[0038] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doped metal is Y. The specific implementation method is as follows:

[0039] The formation energy of oxygen vacancies in HfO2-ZrO2 was calculated. When the concentrations of Y and oxygen vacancies were 2:1, the formation energy was negative, indicating that this configuration was more likely to form, demonstrating a charge balance effect. Y was implanted into the HfO2-ZrO2 film via doping using atomic layer deposition (ALD). The results showed that the interphase transition barriers (OT) were significantly reduced, and the barriers were similar for both. Furthermore, the band gap was slightly reduced compared to the intrinsic system, but no deep-level defects were observed. In this embodiment, using Y as the dopant metal in HfO2-ZrO2 reduced the OT phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivated the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that Y doping can significantly promote MPB formation and reduce leakage current.

[0040] Example 6

[0041] In this embodiment, the superlattice ferroelectric thin film is HfO2-ZrO2, and the doped metal is La. The specific implementation method is as follows:

[0042] The formation energy of oxygen vacancies in HfO2-ZrO2 was calculated. When the concentration of La to oxygen vacancies was 2:1, the formation energy was negative, indicating that this configuration was more likely to form, demonstrating a charge balance effect. La was implanted into the HfO2-ZrO2 film via doping using atomic layer deposition (ALD). The results showed that the phase transition barriers of both the o and t phases decreased, and the barrier for the o-phase to t-phase transition was greater than that for the t-phase to o-phase transition. Furthermore, compared to the intrinsic system, the band gap width decreased slightly, but no deep-level defects appeared. In this embodiment, using La as the dopant metal in HfO2-ZrO2 reduced the o-phase transition barrier, thereby promoting the formation of more MPB regions. Secondly, the charge balance effect passivated the defect states caused by oxygen vacancies, achieving a larger band gap and reducing leakage current, confirming that La doping can significantly promote MPB formation and reduce leakage current.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for doping modification of hafnium oxide-based dielectric thin films, characterized in that, include: By doping and modifying the Zr-layer in the hafnium-based stacked system, leakage current can be suppressed by utilizing the restricted oxygen vacancy migration and charge balance effect in the stacked system. On the other hand, the transition barrier between the polarized 0 phase and the non-polarized t phase can be reduced by doping, resulting in a hafnium-based stacked system with higher dielectric constant in 3D integration. The hafnium oxide-based dielectric thin film is a hafnium-based multilayer system with a film thickness of 4~10 nm, wherein the thickness of the HfO2 layer and the ZrO2 layer are both 0.5~2 nm. The doping element is selected from one or more of Al, Y, La, and Sr; The doping position of the doping element is in the Zr-layer of the stacked system; The doping concentration of the dopant element is 2%-8%.

2. The doping modification method for hafnium oxide-based dielectric thin films according to claim 1, characterized in that, The doping element is Y.

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