Ultrathin continuous metal film and preparation method and application thereof

Abstract

The invention relates to an ultrathin continuous metal film and a preparation method and application thereof, and the preparation method comprises the following steps: (1) in an atomic layer deposition system, carrying out first deposition on a substrate by using a metal organic matter precursor to obtain a pretreated substrate; wherein the surface of the pretreated substrate is provided with a monomolecular layer; (2) depositing a metal film on one side, far away from the substrate, of the monomolecular layer in the pretreated substrate by adopting physical vapor deposition to obtain the ultrathin continuous metal film; and the thickness of the ultrathin continuous metal film is less than or equal to 10nm. According to the method, the monomolecular layer is formed on the substrate, then the metal film is deposited on the monomolecular layer through physical vapor deposition, the monomolecular layer can enhance interaction between the substrate and the metal film, migration and agglomeration of metal atoms on the surface of the substrate in the deposition process of the metal film are further restrained, and therefore the metal film is formed. Therefore, the threshold value of the continuous thickness of the metal film is remarkably reduced, and the ultrathin continuous metal film with the thickness smaller than or equal to 10 nm is obtained

Description

Technical Field

[0001] This invention relates to the field of ultrathin metal materials technology, and in particular to an ultrathin continuous metal film, its preparation method, and its application. Background Technology

[0002] As device dimensions continue to shrink and integration levels increase, specific requirements are placed on the morphology and quality of ultrathin continuous metal films, such as conductivity, light transmittance, flexibility, and stability. In particular, minimizing film thickness while maintaining continuity is crucial; that is, reducing the critical thickness for film continuity is necessary. This ensures that the ultrathin continuous metal film not only possesses good conductivity but also superior light transmittance, making it suitable as a conductive and transparent film for solar cells, flat panel displays, structural color filters, flexible wearable electronics, smart windows, and more.

[0003] Generally, the growth pattern of thin films—island-like, layered, or a combination of islands and layers—is closely related to the surface energies of the substrate and the film material, and the strength of their interaction. When the interaction between the film material and the substrate is strong and the surface energy is low, the particles constituting the film material tend to be small, leading to layered growth and a relatively small critical thickness for forming a continuous film. Typically, for physical vapor deposition, the critical thickness for forming a continuous metal film, i.e., the thickness threshold, is related to the metal particle size by h. t ≈k×d(h t Here, h represents the thickness threshold for a continuous metal film, k is a coefficient between 1 and 3, and d is the average particle size. For gold, the thickness threshold h is [value missing] when forming a continuous film using conventional processes. t Typically 10nm <h t <30nm (substrate-dependent).

[0004] Generally, it is difficult to fabricate smooth, continuous metal films with a thickness of sub-10 nm on non-metallic substrates using conventional processes. The resulting films often exhibit high electrical resistance, inconsistent optical properties, and instability. Therefore, developing a method for fabricating smooth, high-quality sub-10 nm ultrathin continuous metal films is both challenging and urgent.

[0005] As mentioned earlier, the key to obtaining high-quality sub-10nm ultrathin continuous metal films with smooth and flat surfaces lies in ensuring a layered growth pattern. Currently, the main methods for preparing sub-10nm ultrathin continuous metal films include seed layer introduction, co-doping, and substrate surface modification. During processing, a metal adhesion layer, such as titanium, chromium, copper, germanium, or nickel, is typically introduced onto the substrate. Introducing this adhesion layer enhances both the interaction with the substrate and the interaction with the film material, thus changing the film material's growth pattern to layered growth. However, the introduction of a metal adhesion layer with a certain thickness (typically 1-3nm) often significantly alters the properties and performance of the system composed of the substrate and film material. For example, the additional interface increases interface light or electron scattering and optical losses, which are detrimental to device performance. This effect is particularly pronounced for ultrathin films. In recent years, methods have emerged that allow the preparation of ultrathin metal films without the introduction of an adhesion layer, using a "top-down" approach. Examples include the preparation of ultrathin silver films using ion beam thinning technology or ultrathin single-crystal gold films using wet etching.

[0006] CN114855122A discloses a method for preparing an ultrathin metal film, comprising the following steps: S1: providing a target metal and a substrate, and depositing a buffer layer with wettability to the target metal on the surface of the substrate, wherein the target metal is a metal grown in a three-dimensional island pattern; S2: obtaining a thickness threshold at which the target metal just forms a complete and continuous thin film on the substrate, and depositing a target metal film with a thickness greater than or equal to the thickness threshold on the surface of the substrate using a thin film deposition method; S3: under high vacuum, using an ion beam oblique angle etching method to etch the surface of the target metal film with an inert gas ion beam at a certain angle, causing the metal atoms on the surface of the target metal film to escape, and thinning in the reverse direction until the thickness is less than the thickness threshold, thereby completing the preparation of the ultrathin metal film. The target metal is gold, silver, copper, aluminum, or their respective alloys; the substrate is made of silicon, silicon oxide, quartz, glass, polyethylene terephthalate, polyethylene naphthalate, or polyimide; the buffer layer is made of titanium dioxide, zinc oxide, or zinc sulfide. The thickness of its metal film is less than or equal to 15 nm.

[0007] It is obvious that these methods not only cause significant damage to the thin film itself, but can also adversely affect the substrate material, thereby negatively impacting the device structure and performance. Therefore, these methods are difficult to implement on a large scale and across a wide range of applications.

[0008] Therefore, to minimize the impact of introduced materials on the properties / performance of the film system, two aspects need to be considered: first, the material replacing the metal adhesion layer should have minimal impact on optical performance; second, the adhesion layer or modified layer material should have adjustable thickness, especially the ability to achieve monolayer growth, i.e., minimal impact on electrical performance. Thus, it is evident that exploring alternative pathways to introduce reasonable monolayer adhesion modification layers and developing mild and universal methods for fabricating high-quality ultrathin continuous metal films is an inevitable requirement for current and future generations of forward-looking innovative structures and devices, and is therefore extremely urgent. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides an ultrathin continuous metal film, its preparation method, and its applications. The invention first forms a monolayer on a substrate, and then deposits a metal film on the monolayer using physical vapor deposition. The monolayer enhances the interaction between the substrate and the metal film, thereby inhibiting the migration and aggregation of metal atoms on the substrate surface during the metal film deposition process. This significantly reduces the threshold of the continuous thickness of the metal film, resulting in an ultrathin continuous metal film with a thickness ≤10 nm. The ultrathin continuous metal film prepared by this invention features high flatness, good continuity, high adhesion, low resistivity, and high transmittance. It has significant application value and prospects in metal interconnects, transistor electrodes, transparent electrodes in flexible wearable devices, biosensing, enhanced spectroscopy, and photothermal therapy.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing an ultrathin continuous metal film, the method comprising the following steps:

[0012] (1) In an atomic layer deposition system, a metal-organic precursor is used to perform a first deposition on a substrate to obtain a pretreated substrate; wherein the surface of the pretreated substrate has a monolayer.

[0013] (2) A metal film is deposited in the pretreated substrate on the side away from the substrate by physical vapor deposition to obtain the ultrathin continuous metal film;

[0014] The materials of the organometallic precursor and the metal film are different.

[0015] The thickness of the ultrathin continuous metal film is ≤10nm, for example, it can be 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] This invention first uses a metal-organic compound as a precursor to form a monolayer on a substrate surface through a self-limiting reaction. Then, a metal film is deposited on the monolayer by physical vapor deposition. The metal atoms in the monolayer and the metal atoms introduced by physical vapor deposition have strong interactions. The metal atoms in the monolayer can provide dense nucleation centers for the subsequently deposited metal atoms. This not only inhibits the migration and aggregation of deposited metal atoms on the substrate surface, but also significantly enhances the interaction between the substrate and the metal film. As a result, the metal film growth mode changes from island growth to layer growth, significantly reducing the "threshold thickness" for achieving continuous film and obtaining an ultrathin continuous metal film with a thickness ≤10nm.

[0017] It should be noted that the material of the metal-organic precursor in this invention is different from the material of the metal film. Compared with using the same material as the metal film to pretreat the substrate to obtain an ultrathin continuous metal film, the processing of this invention is more difficult. This is because, compared with homogeneous materials, heterogeneous materials have the influence of surface energy and interface energy, which affect the nucleation in the initial stage of film growth and thus affect the film quality.

[0018] Meanwhile, the thickness of the ultrathin continuous metal film in this invention refers to the thickness of the metal film deposited on a monolayer.

[0019] As a preferred embodiment of the present invention, the first deposition includes:

[0020] S1.1. Heat the metal-organic precursor to the target temperature to obtain the heated metal-organic precursor;

[0021] S1.2. The substrate is treated in situ using oxygen plasma to obtain a hydroxylated substrate;

[0022] S1.3 Deposit the heated organometallic precursor on the hydroxylated substrate to obtain the pretreated substrate;

[0023] There is no specific order between S1.1 and S1.2.

[0024] It should be noted that this invention only requires depositing a heated organometallic precursor on a hydroxylated substrate to form an organic monolayer on the substrate surface, which serves as a nucleation site for the subsequent metal film. This ensures that the metal film tends to grow in a layered manner in the early stages, which is beneficial for the formation of ultrathin continuous metal films. If an oxidation treatment is performed after depositing the heated organometallic precursor, an oxide dielectric film will be formed, resulting in an island-like growth mode in the early stages of metal film growth, which is not conducive to the formation of ultrathin continuous metal films.

[0025] As a preferred technical solution of the present invention, the target heating temperature is 25~90℃, for example, it can be 25℃, 35℃, 45℃, 55℃, 65℃, 85℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] It should be noted that the organometallic precursor in this invention is volatile at 25~90°C.

[0027] Preferably, the pipeline for transporting the heated metal-organic precursor is heated to 80~125°C, for example, 80°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or 125°C, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0028] Preferably, the vacuum degree of the in-situ treatment is ≤3Pa, for example, it can be 1Pa, 1.5Pa, 2Pa, 2.5Pa or 3Pa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0029] Preferably, the power of the in-situ processing is 50~200W, for example, it can be 50W, 80W, 120W, 150W or 200W, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the temperature of the in-situ treatment is 25~100℃, for example, it can be 25℃, 40℃, 60℃, 80℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the oxygen flow rate of the in-situ treatment is 50~200 sccm, for example, it can be 50 sccm, 80 sccm, 100 sccm, 150 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the in-situ treatment time is 0.5 to 10 minutes, for example, it can be 0.5 minutes, 1 minute, 2 minutes, 5 minutes or 10 minutes, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] As a preferred technical solution of the present invention, the deposition in S1.3 includes: placing the hydroxylated substrate in the deposition chamber of the atomic layer deposition system, introducing the heated metal-organic precursor into the deposition chamber of the atomic layer deposition system through a carrier gas, causing the heated metal-organic precursor to undergo chemical adsorption on the surface of the hydroxylated substrate, and purging the deposition chamber with the carrier gas.

[0034] Preferably, the temperature for chemical adsorption is 25~100℃, for example, it can be 25℃, 40℃, 60℃, 80℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the pressure of the chemical adsorption is 15~30 Pa, for example, it can be 15 Pa, 18 Pa, 20 Pa, 25 Pa or 30 Pa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, the chemisorption time is 60~300ms, for example, it can be 60ms, 100ms, 150ms, 200ms, 250ms or 300ms, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] This invention limits the chemisorption time to 60~300ms to form a uniform, dense, stable and ordered monolayer on the substrate surface, so that an ultrathin continuous metal film with a thickness of ≤10nm can be finally prepared. If the chemisorption time is less than 60ms, the nucleation sites will be uneven and not dense. If the chemisorption time is greater than 300ms, the source material will be wasted and the by-products will be not completely removed, which will cover some nucleation sites and affect the subsequent metal film deposition.

[0038] Preferably, the carrier gas purging time is 20~60s, for example, it can be 20s, 30s, 40s, 50s or 60s, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the flow rate of the carrier gas is 100~400 sccm, for example, it can be 100 sccm, 200 sccm, 300 sccm or 400 sccm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the carrier gas includes nitrogen and / or an inert gas, with nitrogen being the most preferred.

[0041] Preferably, the inert gas includes any one or a combination of at least two of helium, neon, or argon, wherein typical but non-limiting combinations include: a combination of helium and neon, a combination of helium and argon, a combination of neon and argon, and a combination of helium, neon, and argon.

[0042] As a preferred technical solution of the present invention, the physical vapor deposition includes evaporation and / or magnetron sputtering.

[0043] Preferably, the evaporation method includes any one or a combination of at least two of electron beam evaporation, thermal evaporation, or pulsed laser evaporation, wherein typical but non-limiting combinations include: a combination of electron beam evaporation and thermal evaporation, a combination of electron beam evaporation and pulsed laser evaporation, a combination of pulsed laser evaporation and thermal evaporation, and a combination of electron beam evaporation, thermal evaporation, and pulsed laser evaporation.

[0044] Preferably, the deposition rate of the physical vapor deposition is 0.5~15 Å / s, for example, it can be 0.5 Å / s, 1 Å / s, 3 Å / s, 5 Å / s, 10 Å / s or 15 Å / s, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] Preferably, the vacuum degree of the physical vapor deposition is ≤1×10⁻⁶. -6 torr, for example, could be 0.2 × 10 -6 torr, 0.4×10 -6 torr, 0.6×10 -6 torr, 0.8×10 -6 torr or 1×10 -6 torr, but not limited to the listed values, applies to other unlisted values ​​within the above range as well.

[0046] Preferably, the thickness of the metal film during the physical vapor deposition process is ≤10nm, for example, it can be 6nm, 7nm, 8nm, 9nm or 10nm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] As a preferred embodiment of the present invention, the substrate material includes a rigid substrate and / or a flexible substrate.

[0048] Preferably, the hard substrate comprises any one or a combination of at least two of glass, silicon wafer, silicon oxide, sapphire, diamond, or group III-V semiconductors, wherein typical but non-limiting combinations include: a combination of glass and silicon wafer, a combination of silicon wafer and silicon oxide, a combination of sapphire and diamond, and a combination of silicon oxide, diamond, and group III-V semiconductors.

[0049] Preferably, the flexible substrate comprises any one or a combination of at least two of polyimide (PI), polydimethylsiloxane (PDMS), or polyethylene terephthalate (PET), wherein typical but non-limiting combinations include: a combination of polyimide and polyethylene terephthalate, a combination of polyimide and polydimethylsiloxane, a combination of polyethylene terephthalate and polydimethylsiloxane, and a combination of polyimide, polyethylene terephthalate, and polydimethylsiloxane.

[0050] As a preferred embodiment of the present invention, the organometallic precursor comprises any one or a combination of at least two of tetra(dimethylamino)hafnium, trimethylaluminum, tetra(dimethylamino)tin, tetra(dimethylamino)titanium, tetraisopropoxidetitanium, tri(dimethylacetylacetone)gold, or tri(diethylamino)niobium. Typical but non-limiting combinations include: a combination of tetra(dimethylamino)hafnium and trimethylaluminum, a combination of tetra(dimethylamino)tin and tetra(dimethylamino)titanium, a combination of tetraisopropoxidetitanium and tri(dimethylacetylacetone)gold, a combination of tetra(dimethylamino)hafnium and tri(diethylamino)niobium, a combination of trimethylaluminum, tetra(dimethylamino)tin and tetra(dimethylamino)titanium, and a combination of tetraisopropoxidetitanium, tri(dimethylacetylacetone)gold, and tri(diethylamino)niobium.

[0051] It should be noted that monolayer materials should have as little impact as possible on the properties or performance of the membrane system. Therefore, three aspects need to be considered: first, monolayer materials should have little impact on optical performance; second, monolayer materials should have adjustable thickness, especially the ability to achieve monolayer growth, i.e., have as little impact as possible on electrical performance; and third, monolayer materials should have good stability in different environments.

[0052] Preferably, the material of the metal film includes any one or a combination of at least two of gold, platinum, palladium, silver or copper, wherein typical but non-limiting combinations include: a combination of gold and platinum, a combination of gold and palladium, a combination of silver and copper, and a combination of gold, platinum and copper.

[0053] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0054] (1) In an atomic layer deposition system, the metal-organic precursor is heated to 25~90℃ to obtain the heated metal-organic precursor;

[0055] (2) The substrate is treated in situ with oxygen plasma at 25~100℃ for 0.5~10 min to obtain a hydroxylated substrate; wherein the oxygen flow rate is 50~200 sccm;

[0056] (3) The hydroxylated substrate is placed in the deposition chamber of the atomic layer deposition system, and the heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system through a carrier gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with a carrier gas to obtain a pretreated substrate; wherein the surface of the pretreated substrate has a monolayer.

[0057] (4) A metal film with a thickness of ≤10 nm is obtained by physical vapor deposition on the side of the pretreated substrate away from the substrate.

[0058] The materials of the organometallic precursor and the metal film are different.

[0059] There is no specific order between steps (1) and (2).

[0060] Secondly, the present invention provides an ultrathin continuous metal film, which is prepared by the preparation method described in the first aspect. The thickness of the ultrathin continuous metal film is ≤10nm, for example, it can be 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, and the surface roughness is 0.3~1.1nm, for example, it can be 0.3nm, 0.4nm, 0.6nm, 0.7nm, 0.9nm or 1.1nm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0061] The ultrathin continuous metal film prepared by this invention has the characteristics of high flatness, good continuity, high adhesion, low resistivity and high light transmittance, and has great application value and prospects.

[0062] Thirdly, the present invention provides an application of the ultrathin continuous metal film according to the second aspect, wherein the ultrathin continuous metal film is used in metal interconnects, transistor electrodes, transparent electrodes in flexible wearable devices, biosensing, enhanced spectroscopy or photothermal therapy.

[0063] The ultrathin continuous metal film prepared by this invention has the characteristics of high flatness, good continuity, high adhesion, low resistivity and high light transmittance. It has great application value and prospects in metal interconnects, transistor electrodes, transparent electrodes in flexible wearable devices, biosensing, enhanced spectroscopy or photothermal therapy.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] This invention first uses a metal-organic compound as a precursor to form a monolayer on a substrate surface through a self-limiting reaction. Then, a metal film is deposited on the monolayer using physical vapor deposition. The strong interaction between the metal atoms in the monolayer and the metal atoms introduced by physical vapor deposition inhibits the migration and aggregation of deposited metal atoms on the substrate surface and enhances the interaction between the substrate and the metal film. This transforms the metal film growth mode from island-like growth to layer-like growth, significantly reducing the "threshold thickness" for achieving continuous film thickness. This results in an ultrathin continuous metal film with a thickness ≤10 nm, exhibiting high adhesion, high transmittance, and a controllable resistivity of 2.6 × 10⁻⁶. -7 The surface roughness can be controlled to be below 1.1 nm and below Ω·m. Attached Figure Description

[0066] Figure 1 This is a flowchart illustrating the preparation process of the ultrathin continuous metal film provided in Embodiment 1 of the present invention.

[0067] Figure 2 This is a schematic diagram of the preparation of the ultrathin continuous metal film provided in Embodiment 1 of the present invention.

[0068] Figure 3 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 1 of the present invention.

[0069] Figure 4 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 2 of the present invention.

[0070] Figure 5 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 3 of the present invention.

[0071] Figure 6 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 4 of the present invention.

[0072] Figure 7 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 5 of the present invention.

[0073] Figure 8 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 6 of the present invention.

[0074] Figure 9 This is a surface morphology diagram of the ultrathin continuous metal film provided in Embodiment 7 of the present invention.

[0075] Figure 10 This is a surface morphology diagram of the ultrathin continuous metal film provided in Comparative Example 1 of the present invention.

[0076] Figure 11 This is a surface morphology diagram of the ultrathin continuous metal film provided in Comparative Example 2 of the present invention.

[0077] Figure 12 This is a surface morphology diagram of the ultrathin continuous metal film provided in Comparative Example 3 of the present invention.

[0078] Figure 13 This is a surface morphology diagram of the ultrathin continuous metal film provided in Comparative Example 4 of the present invention.

[0079] Figure 14 This is a surface morphology diagram of the ultrathin continuous metal film provided in Comparative Example 5 of the present invention. Detailed Implementation

[0080] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0081] The present invention uses the following instruments to prepare ultrathin continuous metal films: Sentech's SI ALD plasma-enhanced thin film deposition system, Cello's high-vacuum evaporation coating system (O-50B), and Nippon Vacuum Corporation's magnetron sputtering coating system (Acs-4000). However, it is not limited to the listed equipment. Any related equipment that can achieve the technical effect of the present invention is applicable to the present invention.

[0082] Performance characterization was performed using a UV-Vis-NIR spectrophotometer (Lambda-950), a spectroscopic ellipsometry (SE-850), a thermal field emission scanning electron microscope (NOVA NanoSEM430), and a multimode scanning probe microscope (Bruker-M8). The invention will be further described below with reference to the embodiments.

[0083] Example 1

[0084] This embodiment provides a method for preparing an ultrathin continuous metal film, see [link to documentation]. Figure 1 The preparation method includes the following steps:

[0085] (1) In the atomic layer deposition system, tetra(dimethylamino)hafnium is heated to 80°C to obtain a heated organometallic precursor, and the pipeline for transporting the heated organometallic precursor is heated to 125°C;

[0086] (2) The vacuum level in the deposition chamber of the atomic layer deposition system is reduced to 1 Pa. The silicon wafer is transferred into the deposition chamber and the silicon wafer is treated in situ using remote oxygen plasma to obtain a hydroxylated substrate. The in situ treatment temperature is 25℃, the power is 150W, the oxygen flow rate is 200sccm, and the treatment time is 1min.

[0087] (3) The heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system through nitrogen gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with nitrogen gas to obtain a pretreated substrate; wherein, the surface of the pretreated substrate has a monolayer; the temperature of chemical adsorption is 25°C, the pressure is 20Pa, and the time is 200ms; the flow rate of nitrogen gas is 100sccm, and the nitrogen purging time is 20s;

[0088] (4) Place the pretreated substrate in an electron beam evaporation system and evacuate it to 1×10⁻⁶. -6 The deposition rate and thickness of the thin film were monitored in real time using a quartz crystal oscillator. A gold film with a thickness of 10 nm was deposited on the side of the pretreated substrate away from the substrate using electron beam deposition at a deposition rate of 9 Å / s.

[0089] There is no specific order between steps (1) and (2).

[0090] A schematic diagram of the fabrication of the ultrathin continuous metal film is shown below. Figure 2 As shown, the surface morphology of the ultrathin continuous metal film is as follows. Figure 3 As shown, from Figure 3 It can be seen that the ultrathin continuous metal film is uniform and dense.

[0091] Example 2

[0092] This embodiment provides a method for preparing an ultrathin continuous metal film, the method comprising the following steps:

[0093] (1) In the atomic layer deposition system, trimethylaluminum is heated to 25°C to obtain a heated organometallic precursor, and the pipeline for transporting the heated organometallic precursor is heated to 100°C.

[0094] (2) The vacuum degree in the deposition chamber of the atomic layer deposition system is evacuated to 3 Pa, silicon oxide is transferred into the deposition chamber, and the silicon oxide is treated in situ using remote oxygen plasma to obtain a hydroxylated substrate. The in situ treatment temperature is 50℃, the power is 200W, the oxygen flow rate is 50sccm, and the treatment time is 10min.

[0095] (3) The heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system through helium gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with helium gas to obtain a pretreated substrate; wherein, the surface of the pretreated substrate has a monolayer; the temperature of chemical adsorption is 50°C, the pressure is 16Pa, and the time is 120ms; the flow rate of helium gas is 150sccm, and the purging time of helium gas is 30s;

[0096] (4) Place the pretreated substrate in a magnetron sputtering system and evacuate to 0.5 × 10⁻⁶. -6 The deposition rate and thickness of the thin film were monitored in real time using a quartz crystal oscillator. A 6 nm thick platinum thin film was deposited on the side of the pretreated substrate away from the substrate by magnetron sputtering at a deposition rate of 3 Å / s.

[0097] There is no specific order between steps (1) and (2).

[0098] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 4 As shown, from Figure 4 It can be seen that the platinum thin film has fewer channels and the film tends to be continuous.

[0099] Example 3

[0100] This embodiment provides a method for preparing an ultrathin continuous metal film, the method comprising the following steps:

[0101] (1) In the atomic layer deposition system, tetra(dimethylamino)tin is heated to 50°C to obtain a heated organometallic precursor, and the pipeline for transporting the heated organometallic precursor is heated to 115°C.

[0102] (2) The vacuum degree in the deposition chamber of the atomic layer deposition system is evacuated to 2 Pa, and a 200 μm thick polyimide substrate (Fossmann Beijing Technology Co., Ltd.) is transferred into the deposition chamber. The polyimide is treated in situ using remote oxygen plasma to obtain a hydroxylated substrate. The in situ treatment temperature is 100 °C, the power is 50 W, the oxygen flow rate is 100 sccm, and the treatment time is 5 min.

[0103] (3) The heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system through nitrogen gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with neon gas to obtain a pretreated substrate; wherein, the surface of the pretreated substrate has a monolayer; the temperature of chemical adsorption is 100℃, the pressure is 30Pa, and the time is 60ms; the flow rate of nitrogen gas is 200sccm, and the nitrogen purging time is 60s;

[0104] (4) Place the pretreated substrate in a magnetron sputtering system and evacuate to 0.2 × 10⁻⁶. -6 The silver film with a thickness of 9 nm was obtained by magnetron sputtering at a deposition rate of 3 Å / s on the side away from the substrate after pretreatment for 30 s.

[0105] There is no specific order between steps (1) and (2).

[0106] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 5 As shown, from Figure 5 It can be seen that the silver film has few channels and the film tends to be continuous.

[0107] Example 4

[0108] This embodiment provides a method for preparing an ultrathin continuous metal film, the method comprising the following steps:

[0109] (1) In the atomic layer deposition system, tetraisopropoxide titanium is heated to 70°C to obtain heated organometallic precursor, and the pipeline for transporting heated organometallic precursor is heated to 100°C.

[0110] (2) The vacuum degree in the deposition chamber of the atomic layer deposition system is evacuated to 3 Pa, and polydimethylsiloxane (Shengli (Nanjing) Chemical Technology Co., Ltd.) is transferred into the deposition chamber. The polydimethylsiloxane is treated in situ using remote oxygen plasma to obtain a hydroxylated substrate. The in situ treatment temperature is 75℃, the power is 100W, the oxygen flow rate is 150sccm, and the treatment time is 4min.

[0111] (3) The heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system by argon gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with argon gas to obtain a pretreated substrate; wherein the surface of the pretreated substrate has a monolayer; the temperature of chemical adsorption is 75℃, the pressure is 15Pa, and the time is 300ms; the flow rate of nitrogen gas is 400sccm, and the nitrogen purging time is 20s;

[0112] (4) Place the pretreated substrate in an electron beam evaporation system and evacuate it to 1×10⁻⁶. -6 The deposition rate and thickness of the thin film were monitored in real time using a quartz crystal oscillator. A copper thin film with a thickness of 5 nm was deposited on the side of the pretreated substrate away from the substrate using electron beam deposition at a deposition rate of 0.5 Å / s.

[0113] There is no specific order between steps (1) and (2).

[0114] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 6 As shown, from Figure 6 It can be seen that the copper thin film has few channels, uniform and dense particles, and the film tends to be continuous.

[0115] Example 5

[0116] This embodiment provides a method for preparing an ultrathin continuous metal film. The only difference from Embodiment 1 is that the substrate material is changed from silicon wafer to glass, and the deposition rate of the gold film is adjusted to 1.5 Å / s. All other aspects are the same as in Embodiment 1.

[0117] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 7 As shown, from Figure 7 It can be seen that the gold thin film has fewer channels and the film tends to be continuous.

[0118] Example 6

[0119] This embodiment provides a method for preparing an ultrathin continuous metal film. The only difference from Example 1 is that the chemical adsorption time in step (3) is adjusted from 200ms to 40ms. All other steps are the same as in Example 1.

[0120] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 8 As shown, from Figure 8 It can be seen that, with Figure 3 In contrast, gold films exhibit numerous channels due to their short adsorption time and insufficient self-limiting reaction, resulting in less dense nucleation sites.

[0121] Example 7

[0122] This embodiment provides a method for preparing an ultrathin continuous metal film. The only difference from Example 1 is that the chemical adsorption time in step (3) is adjusted from 200ms to 400ms. All other steps are the same as in Example 1.

[0123] The surface morphology of the ultrathin continuous metal film prepared in this embodiment is as follows: Figure 9 As shown, from Figure 9 It can be seen that, with Figure 3 In contrast, gold films exhibit a small number of channels. This is due to the long adsorption time and insufficient removal of self-limiting reverse byproducts, which leads to partial masking of nucleation sites.

[0124] Comparative Example 1

[0125] This comparative example provides a method for preparing an ultrathin continuous metal film. The only difference between this method and Example 1 is that the preparation method does not include steps (1), (2), and (3), i.e., directly depositing a gold film on a silicon wafer. All other aspects are the same as in Example 1.

[0126] The surface morphology of the ultrathin continuous metal film prepared in this comparative example is as follows: Figure 10 As shown, from Figure 10 It can be seen that the film has a large number of channels and poor continuity.

[0127] Comparative Example 2

[0128] This comparative example provides a method for preparing an ultrathin continuous metal film. The only difference between this method and Example 2 is that the preparation method does not include steps (1), (2), and (3), i.e., directly depositing a platinum film on silicon oxide. All other aspects are the same as in Example 2.

[0129] The surface morphology of the ultrathin continuous metal film prepared in this comparative example is as follows: Figure 11 As shown, from Figure 11 It can be seen that the thin film has many channels and poor continuity.

[0130] Comparative Example 3

[0131] This comparative example provides a method for preparing an ultrathin continuous metal film. The only difference between this method and Example 3 is that the preparation method does not include steps (1), (2), and (3), i.e., directly depositing a silver film on polyimide. All other aspects are the same as in Example 3.

[0132] The surface morphology of the ultrathin continuous metal film prepared in this comparative example is as follows: Figure 12 As shown, from Figure 12 It can be seen that the film has a large number of channels and poor continuity.

[0133] Comparative Example 4

[0134] This comparative example provides a method for preparing an ultrathin continuous metal film. The only difference between this method and Example 4 is that the preparation method does not include steps (1), (2), and (3), i.e., copper film is deposited directly on polydimethylsiloxane. All other aspects are the same as in Example 4.

[0135] The surface morphology of the ultrathin continuous metal film prepared in this comparative example is as follows: Figure 13 As shown, from Figure 13 It can be seen that the film has a large number of channels and poor continuity.

[0136] Comparative Example 5

[0137] This comparative example provides a method for preparing an ultrathin continuous metal film. The only difference between this method and Example 5 is that the preparation method does not include steps (1), (2), and (3), i.e., chromium film and gold film are deposited sequentially on the silicon wafer at a deposition rate of 1.5 Å / s, and the thickness of the chromium film is 1 nm and the thickness of the gold film is 10 nm. All other aspects are the same as in Example 5.

[0138] The surface morphology of the ultrathin continuous metal film prepared in this comparative example is as follows: Figure 14 As shown, from Figure 14 It can be seen that the film particles are large and uneven, and the roughness is significantly increased.

[0139] The thickness of the ultrathin continuous metal films prepared in Examples 1-7 and Comparative Examples 1-5 was analyzed and fitted using a spectroscopic ellipsometry. The transmittance and thickness of the prepared ultrathin continuous metal films were detected using a UV-Vis-NIR spectrophotometer (Lambda-950) and a spectroscopic ellipsometry (SE-850). The surface roughness and resistivity of the ultrathin continuous metal films were detected using a multi-mode scanning probe microscope (Bruker-M8) and a semiconductor tester (B-1500), respectively. The ultrathin continuous metal films were ultrasonically cleaned with acetone, isopropanol and water in sequence at 50W to observe whether the metal film detached from the substrate. The test results are shown in Table 1.

[0140] Table 1

[0141]

[0142] Note: The transmittance data for some examples and comparative examples in the table were not detected because their substrate materials are opaque, so transmittance could not be detected.

[0143] The test results show that:

[0144] (1) As can be seen from Examples 1 to 5, the present invention first uses a metal-organic compound as a precursor to form a monolayer on the substrate surface through a self-limiting reaction, and then uses physical vapor deposition to deposit a metal film on the monolayer, thereby changing the metal film growth mode from island growth to layer growth, significantly reducing the "threshold thickness" for achieving continuous film, and obtaining an ultrathin continuous metal film with a thickness ≤10nm. Moreover, the prepared ultrathin continuous metal film has high adhesion, high transmittance, and resistivity that can be controlled at 2.6×10 -7 The surface roughness can be controlled to be below 1.1 nm and below Ω·m.

[0145] (2) As can be seen from Examples 1 and 6-7, the chemical adsorption time in Example 1 is 200ms, which yields a uniform and dense ultrathin continuous gold film with a thickness of 9.28nm; while the chemical adsorption time in Example 6 is 40ms, which yields a gold film with a thickness of 10.25nm and a large number of channels in the gold film; and the chemical adsorption time in Example 7 is 400ms, which yields a gold film with a thickness of 9.98nm and a small number of channels on the surface of the gold film. It can be seen that the present invention limits the chemical adsorption time to form a uniform, dense, stable and ordered monolayer on the substrate surface, so that an ultrathin continuous metal film with a thickness of ≤10nm can be finally prepared.

[0146] (3) As can be seen from Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, Example 5 and Comparative Example 5, the present invention first uses a metal-organic material as a precursor to form a monolayer on the substrate surface through a self-limiting reaction, and then uses physical vapor deposition to deposit a metal film on the monolayer. This can transform the metal film growth mode from island growth to layer growth, significantly reduce the "threshold thickness" for achieving continuous film, and make the metal film roughness smaller and more continuous, and the resistivity significantly reduced.

[0147] In summary, this invention first uses a metal-organic compound as a precursor to form a monolayer on the substrate surface through a self-limiting reaction. Then, a metal film is deposited on the monolayer using physical vapor deposition. The strong interaction between the metal atoms in the monolayer and the metal atoms introduced by physical vapor deposition inhibits the migration and aggregation of the deposited metal atoms on the substrate surface and enhances the interaction between the substrate and the metal film. This causes the metal film growth mode to change from island-like growth to layer-like growth, significantly reducing the "threshold thickness" for achieving continuous film thickness and obtaining an ultrathin continuous metal film with a thickness ≤10nm.

[0148] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an ultrathin continuous metal film, characterized in that, The preparation method includes the following steps: (1) In an atomic layer deposition system, a metal-organic precursor is used to perform a first deposition on a substrate to obtain a pretreated substrate; wherein the surface of the pretreated substrate has a monolayer. (2) A metal film is deposited in the pretreated substrate on the side away from the substrate by physical vapor deposition to obtain the ultrathin continuous metal film; The materials of the organometallic precursor and the metal film are different. The thickness of the ultrathin continuous metal film is ≤10nm.

2. The preparation method according to claim 1, characterized in that, The first deposition includes: S1.

1. Heat the metal-organic precursor to the target temperature to obtain the heated metal-organic precursor; S1.

2. The substrate is treated in situ using oxygen plasma to obtain a hydroxylated substrate; S1.3 Deposit the heated organometallic precursor on the hydroxylated substrate to obtain the pretreated substrate; There is no specific order between S1.1 and S1.

2.

3. The preparation method according to claim 2, characterized in that, The target temperature for heating is 25~90℃; Preferably, the vacuum degree of the in-situ treatment is ≤3 Pa; Preferably, the power of the in-situ processing is 50~200W; Preferably, the temperature of the in-situ treatment is 25~100℃; Preferably, the oxygen flow rate of the in-situ treatment is 50~200 sccm; Preferably, the in-situ treatment time is 0.5 to 10 minutes.

4. The preparation method according to claim 2 or 3, characterized in that, The deposition in S1.3 includes: placing the hydroxylated substrate in the deposition chamber of the atomic layer deposition system, introducing the heated metal-organic precursor into the deposition chamber of the atomic layer deposition system through a carrier gas, causing the heated metal-organic precursor to undergo chemical adsorption on the surface of the hydroxylated substrate, and purging the deposition chamber with the carrier gas. Preferably, the temperature for the chemical adsorption is 25~100℃; Preferably, the pressure of the chemisorption is 15~30 Pa; Preferably, the chemisorption time is 60~300ms; Preferably, the carrier gas purging time is 20~60s; Preferably, the flow rate of the carrier gas is 100~400 sccm; Preferably, the carrier gas includes nitrogen and / or an inert gas, with nitrogen being the most preferred.

5. The preparation method according to any one of claims 1-4, characterized in that, The physical vapor deposition includes evaporation and / or magnetron sputtering; Preferably, the deposition rate of the physical vapor deposition is 0.5~15 Å / s; Preferably, the vacuum degree of the physical vapor deposition is ≤1×10⁻⁶. -6 torr; Preferably, the thickness of the metal film during the physical vapor deposition process is ≤10nm.

6. The preparation method according to any one of claims 1-5, characterized in that, The substrate material includes rigid substrates and / or flexible substrates; Preferably, the hard substrate comprises any one or a combination of at least two of glass, silicon wafer, silicon oxide, sapphire, diamond, or group III-V semiconductors; Preferably, the flexible substrate comprises any one or a combination of at least two of polyimide, polydimethylsiloxane, or polyethylene terephthalate.

7. The preparation method according to any one of claims 1-6, characterized in that, The organometallic precursor includes any one or a combination of at least two of tetra(dimethylamino)hafnium, trimethylaluminum, tetra(dimethylamino)tin, tetra(dimethylamino)titanium, tetraisopropoxidetitanium, tri(dimethylacetylacetone)gold, or tri(diethylamino)niobium; Preferably, the material of the metal film includes any one or a combination of at least two of gold, platinum, palladium, silver or copper.

8. The preparation method according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) In an atomic layer deposition system, the metal-organic precursor is heated to 25~90℃ to obtain the heated metal-organic precursor; (2) The substrate is treated in situ with oxygen plasma at 25~100℃ for 0.5~10 min to obtain a hydroxylated substrate; wherein the oxygen flow rate is 50~200 sccm; (3) The hydroxylated substrate is placed in the deposition chamber of the atomic layer deposition system, and the heated metal-organic precursor is introduced into the deposition chamber of the atomic layer deposition system through a carrier gas, so that the heated metal-organic precursor undergoes chemical adsorption on the surface of the hydroxylated substrate, and the deposition chamber is purged with a carrier gas to obtain a pretreated substrate; wherein the surface of the pretreated substrate has a monolayer. (4) A metal film with a thickness of ≤10 nm is obtained by physical vapor deposition on the side of the pretreated substrate away from the substrate. The materials of the organometallic precursor and the metal film are different. There is no specific order between steps (1) and (2).

9. An ultrathin continuous metal film, characterized in that, The ultrathin continuous metal film is prepared by the preparation method according to any one of claims 1-8, wherein the thickness of the ultrathin continuous metal film is ≤10nm and the surface roughness is 0.3~1.1nm.

10. An application of the ultrathin continuous metal film according to claim 9, characterized in that, The ultrathin continuous metal film is used in metal interconnects, transistor electrodes, transparent electrodes in flexible wearable devices, biosensing, enhanced spectroscopy, or photothermal therapy.

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