Method for electronically enhanced chemical vapor deposition of films

Abstract

A method for depositing a film includes electron enhanced chemical vapor deposition with at least one hydride precursor, at least one reactive background gas, and electrons to deposit a film on a substrate having a positive substrate voltage. In an embodiment, the method is a method for depositing a silicon film including electron enhanced chemical vapor deposition with at least one Si precursor, at least one reactive background gas, and electrons to deposit a silicon film on a substrate having a positive substrate voltage. In this embodiment, the at least one Si precursor may include Si2H6, and the at least one reactive background gas may include H2.

Description

[0001] This application is based on and claims priority to U.S. Provisional Application No. 63 / 674,633, filed July 23, 2024, with the United States Patent and Trademark Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Embodiments of this disclosure relate to a process for electron-enhanced chemical vapor deposition (EE-CVD). Background Technology

[0003] In the semiconductor industry, two common methods for film growth are atomic layer deposition (ALD) based on thermal processes and plasma-based chemical vapor deposition (CVD). While thermal processes offer some capabilities for conformal film growth, their drawback is the need for elevated deposition temperatures, making them unsuitable for applications with stringent thermal constraints. In contrast, plasma-assisted processes can deposit high-quality films at lower substrate temperatures compared to thermally driven processes; however, they come with several disadvantages associated with plasma-assisted processes, such as substrate damage, equipment complexity, contamination, and selectivity.

[0004] In the ever-evolving field of semiconductor manufacturing, the development of precise and efficient deposition methods is crucial for improving electronic devices. Among the most prominent innovative technologies are electron-enhanced deposition processes (such as electron-enhanced atomic layer deposition (EE-ALD) and electron-enhanced chemical vapor deposition (EE-CVD)). These processes offer fine control over film growth at low temperatures, and the films deposited using these processes are of high quality and free of impurities. However, these processes require increased deposition rates.

[0005] In view of the above, there is a need in the art for an improved method for membrane growth.

[0006] The information disclosed in this background section was already known to the inventors before the implementation of the disclosure of this application, or it is technical information acquired in the process of implementing this disclosure. Therefore, it may contain information that does not form prior art known to the public. Summary of the Invention

[0007] The purpose of this disclosure is to provide an improved method for membrane growth.

[0008] To achieve the above and other objectives, this disclosure employs EE-CVD (Electron Enhanced Chemical Vapor Deposition), which involves the use of electrons to enable the deposition of films on any substrate. An example is EE-CVD of Si. This process allows for the deposition of pure Si: (i) at lower temperatures (below the thermal decomposition temperature of silanes), making the process compatible with back-end processes (BEOL); (ii) without the need for direct plasma; and (iii) without the need for corrosive gases (F, Cl).

[0009] Innovations include: (especially tunable) electrons are novel reactants that activate gaseous matter near the surface, enabling reactions that would otherwise not occur at high temperatures or in plasma. For example, providing an electron-mediated process that allows the adsorption of Si2H6 via excited electron desorption (ESD) of surface hydrogen.

[0010] Applications can include logic 3D SFETs, 3D DRAM, NAND, and embedded memory.

[0011] EE-CVD uses electrons to enable the deposition of films on a substrate. The process involves using a hydride precursor (such as silane (Si2H6)) and an optional reactive background gas (such as hydrogen (H2)) to deposit films on the substrate.

[0012] The process disclosed herein may include: (1) substrate preparation; (2) introduction of precursor gas; (3) introduction of reactive background gas (which is optional in this disclosure); (4) application of electron energy and positive substrate voltage; and (5) film deposition.

[0013] Therefore, this disclosure provides many embodiments, including the following embodiments.

[0014] A first embodiment of this disclosure includes a method for electron-enhanced chemical vapor deposition of a membrane, comprising: cleaning and drying a substrate; introducing at least one hydride precursor gas into a reaction chamber containing the substrate; applying electrons to the reaction chamber to dissociate the precursor gas and generate a reactive substance; and depositing a membrane on the substrate by reacting the reactive substance with the substrate, wherein the substrate has a positive substrate voltage.

[0015] The second embodiment of this disclosure includes the method of the first embodiment, and further includes: introducing at least one reactive background gas into a reaction chamber containing a substrate.

[0016] The third embodiment of this disclosure includes the method of the first embodiment, wherein the method is a method for depositing a silicon film, comprising: performing electron-enhanced chemical vapor deposition with at least one Si precursor, at least one reactive background gas and electrons to deposit a silicon film on a substrate having a positive substrate voltage.

[0017] The fourth embodiment of this disclosure includes the method of the third embodiment, wherein the at least one Si precursor includes Si2H6.

[0018] The fifth embodiment of this disclosure includes the method of the third embodiment, wherein the at least one reactive background gas includes H2.

[0019] The sixth embodiment of this disclosure includes the method of the third embodiment, wherein the at least one Si precursor comprises Si2H6, and the at least one reactive background gas comprises H2.

[0020] The seventh embodiment of this disclosure includes the method of the first embodiment, wherein the method is a method for depositing a germanium film, comprising: performing electron-enhanced chemical vapor deposition with at least one Ge precursor, at least one reactive background gas and electrons to deposit a germanium film on a substrate having a positive substrate voltage.

[0021] The eighth embodiment of this disclosure includes the method of the seventh embodiment, wherein the at least one Ge precursor includes GeH4.

[0022] The ninth embodiment of this disclosure includes the method of the seventh embodiment, wherein the at least one Ge precursor includes Ge2H6.

[0023] The tenth embodiment of this disclosure includes the method of the seventh embodiment, wherein the at least one reactive background gas includes H2.

[0024] The eleventh embodiment of this disclosure includes the method of the seventh embodiment, wherein the at least one Ge precursor comprises GeH4, and the at least one reactive background gas comprises H2.

[0025] The twelfth embodiment of this disclosure includes the method of the seventh embodiment, wherein the at least one Ge precursor comprises Ge2H6, and the at least one reactive background gas comprises H2.

[0026] The thirteenth embodiment of this disclosure includes the method of the first embodiment, wherein the method is a method for depositing a compound semiconductor film, comprising: performing electron-enhanced chemical vapor deposition with at least two hydride precursors, at least one reactive background gas and electrons to deposit a compound semiconductor film on a substrate having a positive substrate voltage.

[0027] The fourteenth embodiment of this disclosure includes the method of the thirteenth embodiment, wherein the compound semiconductor film is a silicon-germanium film.

[0028] The fifteenth embodiment of this disclosure includes the method of the second embodiment, wherein the method is performed at room temperature.

[0029] The sixteenth embodiment of this disclosure includes the method of the third embodiment, wherein the method is performed at room temperature.

[0030] The seventeenth embodiment of this disclosure includes the method of the second embodiment, wherein the positive substrate voltage reaches 100V.

[0031] The eighteenth embodiment of this disclosure includes the method of the third embodiment, wherein the positive base voltage reaches 100V.

[0032] The nineteenth embodiment of this disclosure includes the method of the first embodiment, wherein the method is a method for depositing a silicon-containing film.

[0033] The twentieth embodiment of this disclosure includes the method of the nineteenth embodiment, wherein the silicon-containing film includes SiO2, SiN, SiC, or combinations thereof. Attached Figure Description

[0034] Exemplary embodiments of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings.

[0035] Figure 1 This is a flowchart illustrating method steps of an exemplary embodiment of the present disclosure.

[0036] Figure 2 A diagram illustrating an embodiment of the currently disclosed electron-enhanced chemical vapor deposition method is shown.

[0037] Figure 3 This is a schematic diagram of a V-shaped reactor with a hollow cathode plasma electron source above the sample at the center of the V-shape. A spectroscopic ellipsometer is connected to both ends of the V-shape, and the pumping port is connected to a mechanical pump or a turbomolecular pump via a four-way cross.

[0038] Figure 4 This is a diagram illustrating the operation of the hollow cathode in an embodiment of this disclosure.

[0039] Figure 5 The diagram illustrates the increased collimation coil current, a parameter that can affect the electronic enhancement process.

[0040] Figure 6 This is a schematic diagram illustrating a hollow cathode that generates primary electrons in an embodiment of this disclosure.

[0041] Figure 7 Various approaches for electron enhancement processes are illustrated in embodiments of this disclosure.

[0042] Figure 8 This is a schematic diagram depicting the silicon (Si) EE-CVD process disclosed herein.

[0043] Figure 9The SiEE-CVD growth on SOI (Si on Insulator) is shown with and without a positive sample bias voltage.

[0044] Figure 10A and Figure 10B Schematic diagrams are shown illustrating experimental setups used in Si EE-CVD with and without sample bias voltages, respectively.

[0045] Figure 11A and Figure 11B The in-situ elliptic polarization method thickness and XRR of the Si EE-CVD film are shown respectively.

[0046] Figure 12A and Figure 12B A comprehensive analysis of an approximately 100 nm Si EE-CVD film was described using X-ray photoelectron spectroscopy (XPS) for chemical composition and elastic recoil detection analysis (ERDA) for quantitative determination of the presence of hydrogen (H) within the film.

[0047] Figure 13 This is a diagram showing the change of Si EE-CVD thickness over time on Si(100) substrate, thermal SiO2 substrate, and Si3N4 substrate.

[0048] Figure 14 The effect of Si2H6 dosage time on film growth was depicted, and the relationship between thickness and time was shown.

[0049] Figure 15 The results of Si EE-CVD performed under various bias grid voltages are shown.

[0050] Figure 16 Experiments were conducted in the presence and absence of H2RBG.

[0051] Figure 17 The Si EE-CVD growth is shown in the presence and absence of Si2H6.

[0052] Figures 18A to 18D The surface profile determination and analysis following Si EE-CVD film deposition are shown.

[0053] Figure 19 This demonstrates the linear growth of Si EE-CVD films in the presence of only Si2H6 and electrons without any nucleation delay.

[0054] Figure 20 An exemplary embodiment of the present disclosure of Si EE-CVD with increased collimation coil current is shown.

[0055] Figure 21 An exemplary embodiment of the present disclosure of Si EE-CVD with increased bias grid voltage is shown.

[0056] Figure 22 A graph showing the relationship between film thickness and Si EE-CVD cycle number for an exemplary embodiment of the present disclosure is provided.

[0057] Figure 23 XPS Deep Profile is shown for an exemplary embodiment of this disclosure.

[0058] Figures 24A to 24C Surface roughness is shown in various embodiments including exemplary embodiments of the present disclosure.

[0059] Figure 25 XRD 2, which illustrates an exemplary embodiment of this disclosure. scanning.

[0060] Figure 26 The exemplary embodiments of the present disclosure demonstrate a significant enhancement of Si EE-CVD with increasing sampling voltage.

[0061] Figure 27 The exemplary embodiments of this disclosure are shown with and without D2 in Si EE-CVD.

[0062] Figures 28A to 28C The use of a stainless steel mesh mask during Si EE-CVD and the surface profile determination obtained after Si EE-CVD are illustrated in exemplary embodiments of the present disclosure. Detailed Implementation

[0063] The embodiments of this disclosure described herein are exemplary embodiments, and therefore, this disclosure is not limited thereto and may be implemented in various other forms. Each of the embodiments provided in the following description is not excluded from being associated with one or more features of another embodiment also provided herein or not provided herein but consistent with this disclosure. For example, even if a matter described in a particular exemplary embodiment is not described in other exemplary embodiments, it may be understood to be related to or combined with different exemplary embodiments unless otherwise mentioned in its description. Furthermore, it should be understood that all descriptions of the principles, aspects, examples, and embodiments of this disclosure are intended to cover their structural and functional equivalents. Moreover, these equivalents should be understood to include not only currently known equivalents but also equivalents to be developed in the future.

[0064] Throughout this disclosure, values ​​expressed in range format should be interpreted flexibly to include not only the numerical values ​​explicitly listed as the limits of the range, but also all individual numerical values ​​or subranges covered within that range (as if each numerical value and subrange were explicitly listed). For example, the range “about 0.1% to about 5%” or “about 0.1% to 5%” should be interpreted to include not only about 0.1% to about 5%, but also individual values ​​(e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. Unless otherwise indicated, the expression “about X to Y” has the same meaning as “about X to about Y”. Similarly, unless otherwise indicated, the expression “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z”.

[0065] In this disclosure, unless the context clearly specifies otherwise, the terms “a,” “an,” or “the (described)” are used to include one or more. Unless otherwise indicated, the term “or” is used to mean a non-exclusive “or.” The expressions “at least one of A and B” or “at least one of A or B” have the same meaning as “A, B, or A and B.” Furthermore, it will be understood that the wording or terms used herein (unless otherwise defined) are for descriptive purposes only and not for limiting purposes. Any use of section headings is intended to aid in reading the document and should not be construed as limiting; information relating to a section heading may appear within or outside that particular section.

[0066] In the methods described herein, actions can be performed in any order except where the timing or sequence of operations is explicitly stated. Furthermore, unless the specific actions are explicitly stated to be performed individually, the specified actions can be performed simultaneously. For example, the claimed action of doing X and the claimed action of doing Y can be performed simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0067] As used herein, unless otherwise defined, all technical and scientific terms generally have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In general, the nomenclature and laboratory procedures used herein are those well-known and commonly used in the art.

[0068] As used herein, the term “about” may allow for a degree of variability in the value or range, for example, within 10%, 5%, or 1% of the stated value or range limits, and includes the exact stated value or range.

[0069] As used herein, the term "CVD" refers to chemical vapor deposition as a film deposition method. In some embodiments, the processes of this disclosure can be used to produce thin films, wherein the term "thin" refers to a thickness range of about 0.1 nm to about 300 nm. The processes of this disclosure can also produce films having thicknesses greater than 300 nm, even on the order of micrometers or millimeters.

[0070] Electrons can provide non-thermal means, including at low temperatures, to enhance film growth. In particular, electrons can enhance chemical vapor deposition (CVD) and promote CVD at low temperatures. Various factors influence electron-enhanced processes, such as bias grid voltage, stage bias, the effect of H2 pressure, and how electrons interact with certain materials.

[0071] When an incident electron beam containing primary electrons interacts with the sample surface, secondary electrons are emitted. This phenomenon is called secondary electron emission (SEE). The number of secondary electrons emitted by each primary electron is called the secondary electron yield (SEY), and the ratio of the number of secondary electrons to the number of primary electrons is called the secondary electron emission coefficient.

[0072] In this disclosure, Si₂H₆ and H₂ are primarily used, but other materials may also be used as discussed further below. Electron-simulated desorption (ESD) of hydrogen reaches its maximum at electron energies of 100 eV to 150 eV. This is perfectly consistent with the dissociation cross section of Si₂H₆, which dissociates at energies of 20 eV to 100 eV, while the peak of the H₂ dissociation cross section is at 16 eV to 25 eV. Most of the backscattered secondary electrons from Si are generated by incident electrons at energies of 100 eV to 600 eV. These electron energies overlap with the peak of the H₂ dissociation cross section at approximately 16 eV to 25 eV.

[0073] Another factor that significantly contributes to electron-enhanced processes is the dissociative electron attachment (DEA) of the precursor or reactive background gas. DEA is a well-studied phenomenon in low-temperature H2 plasma research. Incident electrons are captured by neutral molecules in a resonant state, and this capture sufficiently increases the electron residence time to allow for the dissociation of relatively slow-moving atomic nuclei. This process can be schematically described as a two-step process: Where v and J represent the vibrational quantum number and rotational quantum number of the target hydrogen molecule, respectively.

[0074] This disclosure explores the conversion potential of EE-CVD, employing, for example, Si₂H₆ as a silicon precursor and hydrogen (H₂) as a reactive background gas (RBG). This disclosure addresses the complex interactions between electrons and surface chemistry. By revealing the mechanism by which electrons promote silane adsorption via electron-stimulated desorption (ESD) of surface hydrogen, this disclosure provides a novel approach for achieving highly selective silicon deposition.

[0075] Therefore, implementation of this disclosure, for example Figure 1 The flowchart is shown in the figure (which includes the optional introduction of reactive background gases):

[0076] (1) Substrate preparation (step S10): The substrate is typically a silicon wafer, which is cleaned and dried to ensure a smooth surface for deposition. However, the deposition in this disclosure is not limited to pure silicon substrates. Instead, EE-CVD technology is applicable to many substrates, including Si, dielectrics, metals, etc. One of the advantages of EE-CVD is the ability to grow films on substrates on which films cannot be grown by conventional techniques.

[0077] (2) Introduction of precursor gas (step S20): The precursor gas used in EE-CVD is usually silane (Si2H6), which is a hydride compound containing silicon and hydrogen. However, the precursor gas is not limited to silane and can be another silane (such as propane), or the precursor gas can be a different compound (such as germanium compounds, such as Ge2H6).

[0078] (3) Introduction of reactive background gas (optional) (step S30): The reactive background gas used in EE-CVD is usually hydrogen (H2), which helps to enhance the dissociation of the precursor gas and generate reactive substances. However, the reactive background gas is not limited to hydrogen and can be different reactive background gases (such as doped reactive background gases).

[0079] (4) Application of electron energy and positive substrate voltage (step S40): Electron energy is applied to the reaction chamber using a hollow cathode source, electron gun, or other device, which helps to enhance the dissociation of the precursor gas and generate reactive substances away from the electron source. A positive voltage is applied to the substrate to enhance deposition by attracting negative ions to the substrate.

[0080] (5) Deposition of film (step S50): The reactive substance reacts with the substrate to deposit a film, which may be made of various materials such as silicon, silicon dioxide or other compounds such as compound semiconductors.

[0081] One aspect of this disclosure is the elimination of nucleation delays during silicon deposition on, for example, various substrates. The inherent tunability of the electronic parameters emerges as a powerful advantage, providing precise control over the deposition rate.

[0082] This disclosure not only relates to the capabilities of EE-CVD but also highlights its potential for yield improvements, such as high-quality, impurity-free silicon films. The versatility of EE-CVD in customizing deposition parameters makes it a powerful technology with wide applications in semiconductor device fabrication and materials engineering. As the complex landscape of advanced electronic materials evolves, EE-CVD is at the forefront, poised to make significant contributions to advancements in microelectronics and nanotechnology.

[0083] Therefore, this disclosure relates to an electron-enhanced process for electron-enhanced chemical vapor deposition (EE-CVD). In EE-CVD, electrons are used along with, for example, Si₂H₆ (silyl ether) as a Si precursor and H₂ (hydrogen) as a reactive background gas (RBG). Si₂H₆ can be pulsed while H₂RBG and electrons remain continuously present in the chamber. The primary electron beam induces stimulated desorption of surface hydrogen and promotes Si₂H₆ adsorption. Due to the primary electron beam energy of approximately 100 eV, secondary electrons are emitted from the surface. These secondary electrons have much lower energies, with peak energies of approximately 2 eV to 4 eV in their distribution. These secondary electrons can dissociatively adsorb onto H₂ and Si₂H₆, undergoing dissociative electron adsorption. This process is initiated by H₂. - Generate H - +H or from Si2H6 - SiH3 is generated - +SiH3. By applying a positive voltage to the sample stage, negative ions (H+) - or SiH3 - The negative ions are attracted to the sample stage. These negative ions significantly enhance EE-CVD.

[0084] One aspect of this disclosure is the ability to deposit Si EE-CVD films at room temperature (e.g., from about 15°C to about 28°C, or more specifically, from 15°C to 28°C). Furthermore, Si EE-CVD occurs without any nucleation delay. The mechanism of Si EE-CVD is also an aspect of this disclosure. Si EE-CVD is strongly enhanced by a positive substrate voltage. For example, the positive stage voltage range can be less than or equal to 100V (e.g., from 10V to 90V). The following mechanisms can explain the result: (1) Primary electrons can generate secondary electrons from the substrate at about 100 eV. (2) Lower-energy secondary electrons can be adsorbed onto the reactive background gases H2 and / or Si2H6 in the reactor. (3) Electron adsorption then dissociates the reactive background gases through dissociative electron adsorption ionization. (4) Negative ions are adsorbed onto the sample by the positive stage voltage. (5) The incoming flow of negative ions causes an increase in the deposition rate.

[0085] The advantage of this disclosure is that Si EE-CVD occurs at room temperature. This low temperature reduces the thermal budget of the semiconductor process. Si EE-CVD also proceeds without dependence on the substrate's nucleation delay. Sequential analysis of the Si EE-CVD films reveals ultra-high quality, pure amorphous Si films with a certain hydrogen content.

[0086] Therefore, Si EE-CVD can deposit silicon at room temperature. This low-temperature growth offers many advantages compared to other methods used in semiconductor processes. Low-temperature silicon deposition can be used during device processing.

[0087] This disclosure presents an innovative method for electron-enhanced chemical vapor deposition (EE-CVD) using, for example, silane (Si₂H₆) as a silicon precursor and H₂ as a reactive background gas (RBG). The innovation lies in the electron-mediated process that promotes the adsorption of Si₂H₆ via electron-stimulated desorption (ESD) of surface hydrogen. The EE-CVD process has been systematically studied on various substrates, demonstrating a significant absence of nucleation delay during silicon deposition. A key feature of this method is the ease of tuning electronic parameters, enabling precise control of the deposition rate. The deposited films exhibit high quality and are free of impurities, highlighting the potential of this technology for fabricating advanced semiconductor devices. The versatility of the electron-enhanced method offers a promising avenue for tailoring material properties in a controlled manner, opening new possibilities for applications in microelectronics and nanotechnology.

[0088] The Si hydride precursor in this disclosure may be a silane (such as the aforementioned ethsilane, silane, propane or dichlorosilane).

[0089] Furthermore, this disclosure extends to the deposition of Ge using, for example, GeH4 or Ge2H6. Another Ge hydride precursor can be GeH2Cl2. Similarly, the EE-CVD process can be used for the deposition of any element having a hydride precursor. The deposition of compound semiconductors can utilize two hydride precursors corresponding to the two elements in the compound semiconductor.

[0090] In general, hydride precursors that can be used in the processes of this disclosure include group IV hydrides, group III and V hydrides, and group II and VI hydrides. Examples of hydride precursors for single semiconductors are Si and Ge. Examples of hydride precursors for compound semiconductors include group III and V hydrides (such as Ga and As (forming GaAs compound semiconductors), In and P (forming InP compound semiconductors), and Ga and N (forming GaN compound semiconductors)), group II and VI hydrides (such as Zn and S (forming ZnS compound semiconductors) and Zn and Se (forming ZnSe compound semiconductors)), and group IV and VI hydrides (such as Si and C (forming SiC compound semiconductors) and Si and Ge (forming SiGe compound semiconductors)).

[0091] The reactive background gas is optional and can be H2. The reactive background gas can be a doped reactive background gas (such as a reactive background gas doped with boron).

[0092] The film produced by the process disclosed herein can be a silicon film, a germanium film, a silicon-germanium film, or a semiconductor film of another element or compound.

[0093] Therefore, as indicated above, EE-CVD uses electrons to enable film deposition on a substrate. The process involves using a hydride precursor (such as silane (Si₂H₆)) and optionally a reactive background gas (such as hydrogen (H₂)) to deposit the film on the substrate. Direct plasma is not used (i.e., the precursor is not introduced into the region where the (distant) plasma resides). A distant plasma is used to generate electrons (e.g., in a hollow cathode source). The electrons are at very low energies (approximately 100 eV) and are used to dissociate precursor molecules and generate reactive material that can react with the substrate to form a film. Electrons with too low or too high energies will not induce deposition. Deposition conditions are very mild (approximately room temperature), requiring no heating, direct plasma, or other activation methods. The film is smooth, and there is no substrate damage.

[0094] Figure 2The diagram illustrates an embodiment of a currently disclosed electron-enhanced chemical vapor deposition process. The deposition reaction is activated by an electron flow that reacts with molecules at low temperatures, without the use of direct plasma. No halogens are required. The process is BEOL-compatible and has been demonstrated at 25°C. This process can provide an alternative to epitaxy. Furthermore, this process does not require a specific substrate. Moreover, there is no nucleation delay in this process, and growth occurs immediately on all substrates. This contrasts with prior art, in which (1) the deposition reaction is activated by direct plasma (radicals, ions) or high temperatures (>500°C); (2) halogens may be required; (3) the process is incompatible with BEOL; (4) epitaxy is slow and expensive; (5) a specific substrate (e.g., Si) is required; and (6) nucleation delay may occur on some substrates.

[0095] As discussed further below, the deposition of amorphous Si films has been demonstrated at low temperatures. The deposition is anisotropic by using a (large-aperture) shadow mask. Example

[0096] Further details and embodiments of this disclosure will now be explained by the following examples of electron-enhanced chemical vapor deposition, which are not intended to limit this disclosure in any way.

[0097] A. Reaction Chamber and Sample Preparation

[0098] All experiments were conducted in a specialized V-shaped reactor, characterized by an in-situ (M-2000®) spectroscopic ellipsometer (JAWoollam Co., Inc.) with an incident angle of 70 degrees. This in-situ ellipsometer was used to monitor the growth of Si EE-CVD films. A schematic diagram of the V-shaped reactor is provided in [the diagram is missing from the original text]. Figure 3 The reactor includes an iSE source 31, a steering coil 32, a bias grid 33, a hollow cathode 34, a collimation coil 35, an iSE detector 36, a reaction chamber 37, and a floating sample stage 38. Details of the operation of the M2000® ellipsometer used in the electron-enhanced thin film process can be found in Collings, MA; Junige, M.; Cavanagh, AS; Wang, V.; Kummel, AC; George, SM, Electron-Enhanced Atomic Layer Deposition of Ru Thin Films Using Ru(DMBD)(CO)3 and Effect of Forming Gas Anneal. J. Vac. Sci. Technol. A 2023, 41 (6), 062408.

[0099] The overall assembly of the reactor is a hollow cathode plasma electron source (HC-PES) designed to deliver an electron beam to the surface. The HC-PES includes molybdenum (Mo) orifices with a diameter of approximately 2 mm, serving as exit points for the electrons. Additionally, a bias grid is included to apply a positive voltage to the hollow cathode wall.

[0100] This setup enables electrons to be emitted from the HC-PES, then accelerated and directed to the sample surface via a series of electron optics devices, including steering and collimating coils. Figure 4 A diagram of hollow cathode operation is shown, which includes a MOSFET 41, a hollow cathode 42, a hole 43, a bias grid 44, a chamber ground 45, an electron beam 46, a collimation coil 47, a steering coil 48, a collimation coil 49, an acceleration power supply 50, a plasma power supply 51, a dielectric 52, and a secondary anode 53. Figure 5 The diagram illustrates the increased collimation coil current, a parameter that can affect the electron enhancement process. Other parameters that can affect the electron enhancement process include the steering coil current, bias grid voltage and electron energy, Si2H6 pressure, H2 reaction background gas pressure, and secondary electron yield. Figure 6 This is a schematic diagram illustrating a hollow cathode that generates primary electrons in an embodiment of the present disclosure, wherein the diagram includes a hollow cathode 61, a bias grid 62, a Mo hole 63, an electron optics device 64, and a substrate 65. Figure 7 Various approaches for electron enhancement processes are illustrated in embodiments of this disclosure, wherein the diagram includes a bias grid 71, a Si layer 72, and a SiO2 layer 73. Figure 7 In this process, the bias voltage limits the energy of electrons from HC-PES; the sample bias voltage adds additional electron energy and collects secondary electrons emitted due to the incident electrons; H2 and electrons are always present, and Si2H6 is pulsed into the reactor; electrons cause H2 and Si2H6 to dissociate, and stimulated desorption (ESD) of H from the surface occurs; moreover, secondary electrons can adsorb onto H2 and react according to H2 + e-. - H+H - The sample bias voltage will cause H2 to dissociate. -The electrons are attracted to the surface used for the reaction. Comprehensive details on reactor design and operation can be found in Gertsch, JC; Sobell, ZC; Cavanagh, AS; Simka, H.; George, SM Electron-Enhanced SiO2 Atomic Layer Deposition at 35°C Using Disilane and Ozone or Water as Reactants. J. Vac. Sci. Technol. A2023, 41 (4), 042404 and Collings et al., as described above. Electrons are generated using argon (Ar) plasma derived from Airgas with 99.999% purity within the HC-PES. The Ar flow rate through the hollow cathode cavity is controlled at 3 sccm by a mass flow controller (MFC) (e.g., MKS, 14 sccm range). The energy of the electrons emitted from the HC plasma is modulated using a bias grid maintained at a voltage of -50V.

[0101] The incident electron current on the substrate and sample holder is approximately 200 mA. To perform accurate current measurements, taking into account both secondary electrons and negative ions (as a result of DEA), a positive sample bias voltage of +90 V is applied to the stage. The sample current is measured using the probes of a multimeter (Keithley, DMM7510 7.5 Digit Multimeter) fixed to the sample stage.

[0102] Si EE-CVD experiments were performed on Si(100) (SOI) substrate. The SOI substrate had a device thickness of 700 Å and a box layer thickness of 20,000 Å. Thermal SiO2 with an oxide thickness of approximately 5,000 Å was also used as the insulating substrate. Experiments were also conducted on a stoichiometric SiN surface with a thickness of 1,000 Å and an intrinsic oxide layer of approximately 13 Å. The Si EE-CVD process consisted of Si2H6 pulses every 0.5 s with a 10 s purge time in between, while H2 and electrons remained continuously in the chamber. All experiments were performed at room temperature.

[0103] B. Precursors and reactants

[0104] During the Si EE-CVD experiments, electrons were continuously supplied, and the reactor had a constant flow rate of 3 sccm of hydrogen (H2, 99.999%, Airgas) controlled by an MFC (MKS, 50 sccm range). The pressure in the chamber with only H2 flow was <3 mTorr. Silane (Si2H6, 99.998%, Voltaix) at room temperature was used as the Si precursor. Si2H6 was pulsed into the chamber. The chamber pressure increased to 20 mTorr during the Si2H6 pulse. Prior to the experiment, all substrates were pre-cleaned by rinsing with acetone, isopropanol (IPA), and water in the same order, and all substrates were dried with N2.

[0105] C. Analysis

[0106] Various analytical tools were used to characterize the films. The composition of the Si EE-CVD films was measured using in-situ X-ray photoelectron spectroscopy (XPS, PHI5600) depth profiling. Elastic recoil detection analysis (ERDA) was also performed to detect the amount of hydrogen present in the films. Roughness and film density of the Si EE-CVD films were measured using X-ray reflectance (GIXRD, Bede D1 X-ray diffractometer, Bruker) and atomic force microscopy (AFM, NX10, ParkSystems). Laser microscopy was used as an optical surface profilometer to observe the surface morphology and step height of patterns made using stainless steel mesh.

[0107] D. Results and Discussion

[0108] Figure 8 A schematic diagram depicting a silicon (Si) EE-CVD process is shown. In this process, electrons and H2 are continuously present in the chamber, while Si2H6 is introduced at regular intervals of 0.5 seconds. Si EE-CVD procedures are performed across various substrates. Based on Figure 8 The diagram illustrates Si EE-CVD. Two settings exist for Si EE-CVD: with and without a positive sample bias voltage on the sample stage.

[0109] Figure 9The results show Si EE-CVD growth on SOI (Si on Insulator) with and without a positive sample bias voltage. The growth rate of Si EE-CVD without a sample bias voltage is negligible, with the measured sample current hovering at approximately 10 mA. However, once a +90 V sample bias voltage is applied, the growth rate experiences a significant spike to approximately 20 Å / min. Furthermore, Si EE-CVD growth exhibits a highly linear trend under the influence of the sample bias voltage. These results highlight the crucial role of secondary electrons in surface reaction kinetics, particularly their involvement in processes such as DEA (decoupling of reactive background gas) molecules (RBG) and Si₂H₆Si precursor molecules.

[0110] According to existing literature, the DEA of Si₂H₆ produces two different sets of anion fragments. One set includes SiH₃ - Ions, SiH2 - Ions, SiH - Ions and Si - Ions, while another group includes Si2H5 - Ions, Si2H4 - Ions, Si2H3 - Ions, Si2H2 - Ions, Si2H - Ions and Si2 - The dissociative electron adsorption of ions, H2, and Si2H6 is shown in the following equation (Equation 1): (Monosilanes and disilanes) These chemical reactions highlight the complex processes that occur at the surface interface during Si EE-CVD, further emphasizing the indispensable role of secondary electrons in mediating these reactions and influencing growth kinetics.

[0111] Figure 10A and Figure 10B Schematic diagrams illustrating experimental setups utilized in Si EE-CVD with and without sample bias voltages are presented respectively. Through experimental studies, the crucial role of secondary electrons and the DEA (deposition-exchange effect) of H2 and Si2H6 molecules is elucidated. Therefore, the capture of all secondary electrons, as well as negative ions (H... - and SiH4 - Ions are necessary for accurate measurement of sample current.

[0112] exist Figure 10AIn this setup, secondary electrons are not considered. In this case, no sample bias voltage is applied to the sample surface. The primary electron beam is directed to the sample, causing the emission of secondary electrons from the substrate. However, since there is no positive sample bias voltage on the sample surface, no secondary electrons are collected or pulled back to the surface. These emitted secondary electrons diffuse toward the ground through the chamber walls at energy levels typically in the range of 3 electron volts (eV) to 4 electron volts (eV). Notably, the measured sample current is recorded at approximately 10 mA in the absence of a positive sample bias voltage.

[0113] On the contrary, Figure 10B In this study, upon applying a positive sample bias voltage of +90V, the sample current surged to over 200mA. This significant increase in current can be attributed to the positive sample bias voltage promoting the attraction of secondary electrons back to the surface. Furthermore, some secondary electrons bind with the reactive background gas (RBG) and Si2H6 molecules, inducing a DEA reaction as shown in Equation 1. Therefore, this process brings secondary electrons and negative ions back to the surface. These entities actively participate in surface reaction kinetics, thereby influencing the overall deposition mechanism.

[0114] The difference between this disclosure and other processes is that, for example, a positive sample bias voltage attracts secondary electrons back to the surface and causes more reactions, resulting in faster deposition.

[0115] The SiEE-CVD films deposited with positive bias voltage were characterized and compared using various techniques, including in-situ ellipsometer and X-ray reflectance (XRR). The comparisons focused on film thickness, density, and roughness. Quantitative results are summarized in Table 1 below: Table 1

[0116] Figure 11A and 11B The in-situ elliptic polarization thickness and XRR of the Si EE-CVD film are shown respectively.

[0117] Figure 11A The variation of Si EE-CVD film thickness with the number of cycles was depicted. A significant increase in thickness was observed, with Si EE-CVD film thicknesses measured at 13 nm, 25 nm, and 50 nm for 50, 100, and 200 Si EE-CVD cycles, respectively. The film grew continuously without any nucleation delay, and the growth was linear.

[0118] Figure 11BThe figures show the X-ray reflectance curves for bare Si and Si EE-CVD films with thicknesses of 13 nm, 25 nm, and 50 nm. The results indicate that the amplitude of the oscillations increases with thickness due to the increased roughness resulting from thicker film growth. As summarized in Table 1, the roughness of the Si EE-CVD film increases according to the square root of the film thickness. With increasing film roughness, reflected X-rays decrease more rapidly, leading to a faster decay rate of X-ray reflectance for films with greater roughness.

[0119] Each as Figure 12A and Figure 12B The study of Si EE-CVD films, as described in the paper, is further extended by using a comprehensive analysis of approximately 100 nm Si EE-CVD films through X-ray photoelectron spectroscopy (XPS) for chemical composition and elastic recoil detection analysis (ERDA) for quantitative detection of the presence of hydrogen (H) within the film.

[0120] exist Figure 12A In the study, XPS depth profiling revealed the significant presence of Si 2p at 100 atomic percent (100 at.%), while O 1s remained negligible at 0 at.%, and the C 1s peak also remained at 0 at.%. However, after a sputtering time of 4000 s, the O 1s peak saturated at 60 atomic percent and the Si 2p peak saturated at 40 atomic percent, indicating the presence of an underlying thermal oxide layer.

[0121] Figure 12B The presence of an H 1s peak from ERDA provides insight into the hydrogen concentration in the membrane. A significant H 1s peak was observed in the Si EE-CVD membrane, contrasting with the absence of such a peak in the reference sample. The hydrogen concentration was calculated as 9 at.%, representing 9 × 10⁻⁶ H₂ molecules per unit volume. 7 H / cm 3 These results indicate that the Si EE-CVD membrane has a small but measurable H concentration in the membrane.

[0122] The process was further investigated by growing Si EE-CVD films on various substrates. Figure 13 The graph shows the Si EE-CVD thickness over time on Si(100) substrates, thermal SiO2 substrates, and Si3N4 substrates. Notably, Si EE-CVD film deposition occurs rapidly on all substrates without any discernible nucleation delay. This highlights that EE-CVD-grown Si films can be grown on any substrate, regardless of whether the substrate is insulating, conductive, or otherwise. Electron-simulated growth does not exhibit any preferential growth dependence relative to the substrate. This makes the electron-enhanced process far more promising than existing processes.

[0123] The relationship between thickness and time is shown. Figure 14 As shown, the effect of Si₂H₆ dose time on film growth was further investigated in detail. Si EE-CVD experiments were conducted with dose times of 0.5 s and 1 s. Notably, the results revealed a linear growth trend for both dose times, indicating a consistent and controlled deposition process. Furthermore, the growth rate showed a significant increase with increasing dose time. Specifically, for a Si₂H₆ dose time of 0.5 s, the growth rate was measured to be approximately 20 Å / min. Conversely, when the dose time was extended to 1 s, the growth rate increased to approximately 32 Å / min.

[0124] This observed increase in growth rate with prolonged dose-time underscores the direct correlation between precursor dose duration and film growth kinetics. These findings elucidate the crucial role of Si₂H₆ dose-time in modulating Si EE-CVD film deposition rates. The linear growth behavior across different dose times indicates the robustness and reproducibility of the deposition process. Furthermore, the ability to control the growth rate by adjusting dose-time provides valuable insights for optimizing Si EE-CVD parameters to tailor film properties for specific applications.

[0125] Further research into the Si EE-CVD process involves exploring additional parameters to fine-tune the deposition process. Figure 15 Results of Si EE-CVD at various bias gate voltages are shown. The bias gate voltage was systematically increased from 50 V to 75 V, and then to 100 V. Notably, the growth rate showed a corresponding increase with increasing bias gate voltage, from approximately 20 Å / min to 56 Å / min, and finally reaching 90 Å / min. The growth rate remained linear at all three bias gate voltages, indicating a consistent and controlled deposition process across the explored voltage range. This linear growth behavior underscores the robustness and reliability of the Si EE-CVD process under varying bias gate voltages. These findings contribute valuable insights into optimizing Si EE-CVD processes by manipulating bias gate voltage, thereby expanding the toolkit for tailoring Si film properties to meet specific technical requirements.

[0126] like Figure 16As shown, further exploration of Si EE-CVD was conducted through experiments performed in the presence and absence of H2RBG. Interestingly, Si EE-CVD film formation occurred even in the absence of H2RBG, with only the Si2H6 precursor gas present. This growth exhibited a linear trend, with a measured growth rate of approximately 12.17 Å / min. Conversely, in the presence of H2RBG, the growth rate experienced a significant increase while maintaining a linear deposition pattern. The growth rate in the presence of H2RBG was approximately 20 Å / min.

[0127] These findings demonstrate that Si EE-CVD film deposition can be efficiently performed using only Si₂H₆ precursor gas, indicating the ability of Si₂H₆ precursor gas as a viable source for Si film growth in the absence of H₂RBG. Furthermore, the presence of H₂RBG further enhances the growth rate, highlighting its role in enhancing the deposition process. Notably, deposition remains linear in both scenarios, indicating a controlled and uniform (or consistent) growth mechanism. This comparative analysis underscores the versatility of Si EE-CVD and emphasizes its potential for tailoring growth conditions to achieve desired film properties. The observed growth behavior reveals the interaction between the precursor gas and the reactive background gas, providing insights for optimizing Si EE-CVD processes for a variety of applications.

[0128] Further research on Si EE-CVD films was conducted by comparing the growth processes with and without Si2H6. In the absence of Si2H6, experiments were performed using only H2 as the RBG and electrons present in the chamber to understand the spontaneous etching phenomenon that occurs in the presence of H2 and electrons. Figure 17 The Si EE-CVD growth is shown in the presence and absence of Si2H6. H2 is used as RBG in both cases, while electrons are continuously present in the chamber.

[0129] In the presence of Si₂H₆, the film grows linearly at a growth rate of approximately 20 Å / min, consistent with previous results. When Si₂H₆ is turned off, the film begins to etch slowly in the presence of H₂RBG and electrons. This is a very interesting observation, as H₂ appears to etch at a rate of approximately 1.5 Å / min at room temperature in the presence of electrons.

[0130] We also attempted to observe isotropic deposition of Si EE-CVD films. To do this, a 3 mm thick stainless steel mesh with circular holes of approximately 600 nm was used. After 200 cycles of the Si EE-CVD process, circular plateau-like patterns were observed. Figures 18A to 18DThe surface profile measurement analysis is shown after Si EE-CVD film deposition. Figure 18A An image showing the surface morphology of the formed pattern is displayed. It can be seen that the diameter of the truncated pattern is measured to be 590 μm, which is very consistent with the size of the opening in the bare stainless steel mesh. Figure 18B A 3D image showing a plateau-shaped pattern appears very uniform. (Example) Figure 18C As shown, the step height of the mesa pattern is measured by selecting two points (one on the substrate surface and the other on the mesa pattern), illustrating Si EE-CVD film deposition. The purpose of this is to measure the step height, or thickness. Figure 18D As can be seen, the thickness of the platform-shaped pattern reaches approximately 480 nm.

[0131] The Si EE-CVD process was further investigated by using D2 instead of H2 as RBG. Given the similar chemical properties of D2 and H2, the aim was to determine whether D2 could be used to achieve Si EE-CVD films with higher purity and lower hydrogen content. Figure 19 As shown, the Si EE-CVD film grows linearly without any nucleation delay in the presence of only Si2H6 and electrons. However, when D2 is introduced into the chamber, D2 inhibits the process, causing the film to stop growing. Periodically turning D2 on and off shows that the film resumes growth in the absence of D2 and remains saturated when D2 is present.

[0132] This behavior is attributed to the difference in DEA cross-section between H2 and D2. For H2, the peak cross-section energy is approximately 3.4 eV, while for D2, it is approximately 14 eV. This significant difference in peak cross-section energy means that D2 does not effectively participate in the Si EE-CVD process.

[0133] Figure 20 An exemplary embodiment of the present disclosure of Si EE-CVD with increased collimation coil current is shown.

[0134] Figure 21 An exemplary embodiment of the present disclosure of Si EE-CVD with increased bias grid voltage is shown.

[0135] Figure 22 A graph showing the film thickness relative to the number of Si EE-CVD cycles of exemplary embodiments of the present disclosure is shown, and the advantages of Si EE-CVD films are illustrated, including high-quality films deposited at room temperature, the ability to deposit on different substrates without nucleation delay, and growth controllability through tuning of different electronic parameters.

[0136] Figure 23 XPS Deep Profile is shown for an exemplary embodiment of this disclosure.

[0137] Figures 24A to 24C Surface roughness is shown in various embodiments including exemplary embodiments of the present disclosure.

[0138] Figure 25 XRD 2, which illustrates an exemplary embodiment of this disclosure. The scan showed that the Si EE-CVD film (10 nm) grown at room temperature was amorphous.

[0139] Figure 26 The exemplary embodiments of the present disclosure demonstrate a significant enhancement of Si EE-CVD with respect to sample bias voltage.

[0140] Figure 27 This illustrates Si EE-CVD with and without D2, representing exemplary embodiments of the present disclosure. From Figure 27 As can be seen, EE-CVD is highly controllable. EE-CVD can be turned on / off by controlling the electron flow and also by changing the reactive background gas (e.g., D2 versus H2), showing that electrons are the enablers and react with gas molecules.

[0141] Figures 28A to 28C The use of a stainless steel mesh mask during Si EE-CVD and the surface profile determination obtained after Si EE-CVD are illustrated in exemplary embodiments of this disclosure. Anisotropic deposition is shown on a pattern of approximately 600 μm without any optimization.

[0142] E. Conclusion

[0143] Si₂H₆, H₂RBG, and electron-deposited Si EE-CVD films were used. Electrons play a role in the growth of the Si EE-CVD film. Electrons promote the adsorption of Si₂H₆ due to the excited desorption of surface hydrogen. Simultaneously, electrons also contribute to the dissociation of Si₂H₆ and H₂ molecules. Furthermore, secondary electrons are emitted due to the primary electron beam. Because these secondary electrons adsorb onto Si₂H₆ and H₂ molecules through a phenomenon known as dissociative electron adsorption, they play a role in the Si EE-CVD process. This further contributes to the Si EE-CVD growth.

[0144] In this disclosure, Si EECVD films are grown using EECVD, and the effects of secondary electrons, DEA, sample bias voltage, bias grid voltage, H2 flow, and many other factors influencing Si EECVD growth are investigated in detail. Si EECVD films are grown on various substrates without any nucleation delay. A positive sample bias voltage on the stage facilitates secondary electron collection and results in a significantly higher growth rate. The Si EECVD-grown films are characterized using various techniques, yielding high-quality, pure Si films with very low H2 content.

[0145] The foregoing is a description of exemplary embodiments and should not be construed as limiting this disclosure. Although some exemplary embodiments have been described, those skilled in the art will readily understand that many modifications can be made to the above embodiments without substantially departing from this disclosure.

Claims

1. A method for electron-enhanced chemical vapor deposition of films, comprising: Clean and dry the substrate; At least one hydride precursor gas is introduced into a reaction chamber containing a substrate; Electrons are applied to the reaction chamber to dissociate the at least one hydride precursor gas and generate a reactive substance; as well as A film is deposited on a substrate by reacting a reactive substance with the substrate, wherein the substrate has a positive substrate voltage.

2. The method according to claim 1, further comprising: At least one reactive background gas is introduced into the reaction chamber containing the substrate.

3. The method according to claim 1, wherein, The method is a method for depositing silicon films, comprising: Electron-enhanced chemical vapor deposition is performed using at least one Si precursor, at least one reactive background gas, and electrons to deposit a silicon film on a substrate with a positive substrate voltage.

4. The method according to claim 3, wherein, The at least one Si precursor includes Si2H6.

5. The method according to claim 3, wherein, The at least one reactive background gas includes H2.

6. The method according to claim 3, wherein, The at least one Si precursor includes Si2H6 and the at least one reactive background gas includes H2.

7. The method according to claim 1, wherein, The method is a method for depositing germanium films, comprising: Electron-enhanced chemical vapor deposition is performed using at least one Ge precursor, at least one reactive background gas, and electrons to deposit a germanium film on a substrate with a positive substrate voltage.

8. The method according to claim 7, wherein, The at least one Ge precursor includes GeH4.

9. The method according to claim 7, wherein, The at least one Ge precursor includes Ge2H6.

10. The method according to claim 7, wherein, The at least one reactive background gas includes H2.

11. The method according to claim 7, wherein, The at least one Ge precursor includes GeH4 and the at least one reactive background gas includes H2.

12. The method according to claim 7, wherein, The at least one Ge precursor includes Ge2H6 and the at least one reactive background gas includes H2.

13. The method according to claim 1, wherein, The method is a method for depositing compound semiconductor films, comprising: Electron-enhanced chemical vapor deposition is performed using at least two hydride precursors, at least one reactive background gas, and electrons to deposit compound semiconductor films on a substrate with a positive substrate voltage.

14. The method according to claim 13, wherein, The compound semiconductor film is a silicon-germanium film.

15. The method according to claim 2, wherein, The method is performed at room temperature.

16. The method according to claim 3, wherein, The method is performed at room temperature.

17. The method according to claim 2, wherein, The positive base voltage is less than or equal to 100V.

18. The method according to claim 3, wherein, The positive base voltage is less than or equal to 100V.

19. The method according to claim 1, wherein, The method described is for depositing silicon-containing films.

20. The method according to claim 19, wherein, Silicon-containing films include SiO2, SiN, SiC, or combinations thereof.

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