TWI837151B - Remote plasma based deposition of silicon carbide films using silicon-containing and carbon-containing precursors - Google Patents

Abstract

A doped or undoped silicon carbide film can be deposited using a remote plasma chemical vapor deposition (CVD) technique. One or more silicon-containing precursors are provided to a reaction chamber. Radical species, such as hydrogen radical species, are provided in a substantially low energy state or ground state and interact with the one or more silicon-containing precursors to deposit the silicon carbide film. A carbon-containing precursor may be flowed with the one or more silicon-containing precursors, where the carbon-containing precursor has one or more carbon-to-carbon double bonds or triple bonds and each silicon-containing precursor is a silane-based precursor with at least a silicon atom having two or more hydrogen atoms bonded to the silicon atom.

Description

Remote plasma-based silicon carbide film deposition using silicon- and carbon-containing precursors

Embodiments described herein relate to remote plasma based silicon carbide film deposition using silicon-containing and carbon-containing precursors.

Silicon carbide (SiC) types in thin films have unique physical, chemical, and mechanical properties and are used in a variety of applications, especially in integrated circuit applications. Types of SiC thin films include oxygen-doped silicon carbide (also known as silicon oxycarbide), nitrogen-doped silicon carbide (also known as silicon carbonitride), and oxygen- and nitrogen-doped silicon carbide (also known as silicon oxycarbonitride), as well as undoped silicon carbide.

The prior art description provided here is for the purpose of generally introducing the background of the present invention. The achievements of the inventors named in this case within the scope described in this prior art section, as well as the embodiments of the specification that are not qualified as prior art at the time of application, are not intended or implied to be admitted as prior art against the present invention.

A method for depositing a silicon carbide film on a substrate is provided herein. The method comprises: providing a substrate in a reaction chamber; flowing a silicon-containing precursor into the reaction chamber and toward the substrate; and flowing a co-reactant into the reaction chamber together with the silicon-containing precursor. The silicon-containing precursor has at least two hydrogen atoms bonded to silicon atoms, and the co-reactant is a hydrocarbon molecule. The method further comprises: generating hydrogen radicals from a hydrogen source gas in a remote plasma source, the hydrogen radicals being generated upstream of the silicon-containing precursor and the co-reactant; and introducing the hydrogen radicals into the reaction chamber and toward the substrate, wherein the hydrogen radicals are in a ground state to react with the silicon-containing precursor and the co-reactant to form a doped or undoped silicon carbide film on the substrate.

In some embodiments, all or substantially all of the free radicals of hydrogen in the environment adjacent to the substrate are free radicals of hydrogen in the ground state. In some embodiments, the hydrocarbon molecule has one or more carbon-carbon double or triple bonds. The hydrocarbon molecule may include propylene, butene, pentene, butadiene, pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne, butyne, pentyne, or hexyne. In some embodiments, the silicon-containing precursor includes silane, disilane, trisilane, methylsilane, or dimethylsilane. In some embodiments, the doped or undoped silicon carbide film has no C-C bonding or substantially no C-C bonding. In some embodiments, the method further comprises: providing a nitriding agent together with the hydrogen source gas in the remote plasma source, wherein radicals of the nitriding agent are generated in the remote plasma source; and introducing the radicals of the nitriding agent together with the radicals of hydrogen into the reaction chamber and toward the substrate, wherein the nitriding agent and the radicals of hydrogen react with the silicon-containing precursor and the co-reactant to form a silicon carbonitride (SiCN) film. The SiCN film has no C-C bonding or substantially no C-C bonding, and has no C-N bonding or substantially no C-N bonding. In some embodiments, the method further comprises: providing an oxidant in the remote plasma source together with the hydrogen source gas, wherein free radicals of the oxidant are generated in the remote plasma source; and introducing the free radicals of the oxidant together with the free radicals of hydrogen into the reaction chamber and toward the substrate, wherein the oxidant and the free radicals of hydrogen react with the silicon-containing precursor and the co-reactant to form a silicon oxycarbide (SiCO) film. The SiCO film has no or substantially no C-C bonds and no or substantially no C-O bonds. In some embodiments, the silicon carbide film, doped or undoped, has a conformality of at least 75%. In certain embodiments, the silicon-containing precursor does not have (i) C-O bonds and (ii) C-N bonds.

These and other implementations are further described below with reference to the drawings.

In the present disclosure, the terms "semiconductor wafer", "wafer", "substrate", "wafer substrate", and "partially processed integrated circuit" are used interchangeably. Those of ordinary skill in the art will understand that the term "partially processed integrated circuit" can refer to a silicon wafer during any of many stages of integrated circuit processing. Wafers or substrates used in the semiconductor device industry typically have a diameter of 200 mm, or 300 mm, or 450 mm. The following implementation description assumes that the present disclosure is implemented on a wafer. However, the present disclosure is not so limited. The workpiece can be of various shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that can utilize the present disclosure include various objects, such as printed circuit boards. Introduction

The fabrication of semiconductor devices generally involves depositing one or more thin films on a substrate during an integrated fabrication process. In certain aspects of the fabrication process, various types of thin films, such as silicon carbide, silicon oxycarbide, silicon carbonitride, and silicon oxycarbonitride, are deposited using atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma assisted chemical vapor deposition (PECVD), or any other suitable deposition method. As used herein, the term silicon carbide includes undoped or doped silicon carbide, such as oxygen-doped silicon carbide (SiCO), nitrogen-doped silicon carbide (SiCN), and nitrogen and oxygen-doped silicon carbide (SiOCN). For many cases, the doped silicon carbide has up to about 50 atomic % of dopant atoms, whether oxygen, nitrogen, or atoms of other elements. The doping level provides the desired film properties.

Precursor molecules used to deposit silicon carbide may include silicon-containing molecules having silicon-hydrogen (Si-H) and/or silicon-silicon (Si-Si) bonds and silicon-carbon (Si-C) bonds. Precursor molecules used to deposit silicon oxycarbide may include silicon-containing molecules having silicon-hydrogen (Si-H) bonds and/or silicon-silicon (Si-Si) bonds, and silicon-oxygen (Si-O) bonds and/or silicon-carbon (Si-C) bonds. Precursor molecules for depositing silicon carbonitrides include silicon-containing molecules having silicon-hydrogen (Si-H) bonds and/or silicon-silicon (Si-Si) bonds, and silicon-nitrogen (Si-N) bonds and/or silicon-carbon (Si-C) bonds. Precursor molecules for depositing silicon carbonitride oxides include silicon-containing molecules having silicon-hydrogen (Si-H) bonds and/or silicon-silicon (Si-Si) bonds, and silicon-nitrogen (Si-N) bonds, silicon-oxygen (Si-O) bonds and/or silicon-carbon (Si-C) bonds. Current PECVD processes may use in-situ plasma processing, in which plasma is provided directly adjacent to the substrate.

We have discovered that depositing high quality silicon carbide films can present certain challenges, such as providing films with excellent step coverage, low dielectric constant, high breakdown voltage, low leakage current, high porosity, and/or covering bare metal surfaces without oxidizing the metal surfaces.

Although the present invention is not limited to any particular theory, it is generally believed that the plasma conditions in a typical PECVD process fragment the silicon-containing precursor molecules in a manner that produces undesirable effects. For example, PECVD may break Si-O and/or Si-C bonds in the precursor molecules to produce highly reactive free radicals or other fragment types with high viscosity coefficients. The resulting fragments of the doped silicon carbide film may contain silicon, carbon, and/or oxygen atoms with "dangling bonds," meaning that the silicon, carbon, and/or oxygen atoms have reactive unpaired valence electrons. The high viscosity of the precursor molecules and their fragments may deposit silicon carbide films with poor step coverage because the reactive precursor fragments may disproportionately adhere to the sidewalls and upper regions of other structures in recessed features.

Dangling bonds may generate silanol groups (Si–OH) in the deposited silicon oxycarbide or silicon oxycarbonitride films. Dangling bonds may also generate silylamine groups (Si-NH ₂ ) in the deposited silicon carbonitride films. Due to these functional groups, the films may have an undesirably high dielectric constant. Direct plasma conditions may also adversely affect film quality because they tend to extract carbon from the deposited films.

Furthermore, the dangling bonds can produce more silicon-hydrogen bonds (Si–H) in the deposited silicon carbide film. Under direct plasma deposition conditions, the broken bonds of Si–C can be replaced by Si–H. The presence of Si–H bonds in silicon carbide films may produce films with undesirable electrical properties. For example, the presence of Si–H bonds may reduce the breakdown voltage and may increase the leakage current because Si–H bonds provide leakage paths for electrons.

Additionally, dangling bonds may result in uncontrolled chemical or morphological structures in the silicon carbide film. In some cases, such structures are dense fragments with low or no porosity, resulting in films with unacceptably high dielectric constants. The lack of porosity may result from direct plasma conditions breaking Si-C and/or Si-O bonds in the cyclosiloxane, which otherwise would provide porosity in ultra-low-k dielectric materials.

Direct plasma conditions sometimes used in PECVD can result in directionality in deposition, since the energy used to break the precursor molecules can be of low frequency, producing a large number of ion bombardments at the surface. Directional deposition can also result in deposited silicon carbide films with poor step coverage. Direct plasma is a plasma (moderate concentration of electrons and positive ions) that resides near the substrate surface (sometimes separated from it by only a plasma sheath) during deposition.

Typical PECVD processes are sometimes not suitable for depositing silicon carbide films over exposed copper or other metal surfaces because such processes may oxidize the metal. PECVD processes may use oxidants such as oxygen (O ₂ ), ozone (O ₃ ), carbon dioxide (CO ₂ ), or other oxidizing species to form silicon oxycarbide films. The environment on the substrate surface during deposition

FIG. 1A shows a cross-section of an exemplary silicon carbide film deposited on a substrate. The silicon carbide film 101 may be formed under process conditions that produce a relatively mild environment adjacent to the substrate 100. The substrate 100 may be any wafer, semiconductor wafer, partially processed integrated circuit, printed circuit board, display screen, or other suitable workpiece. The process for depositing the silicon carbide film 101 may involve one or more silicon-containing precursors having one or more Si-H bonds and/or one or more Si-Si bonds. Depending on the type of doped structure to be produced, the one or more silicon-containing precursors may optionally include other bonds, such as Si-C bonds, Si-O bonds, and/or Si-N bonds.

Some applications using silicon carbide films are shown in Figures 1B-1E. In some embodiments, the silicon-containing precursor may include a silicon-oxygen-containing precursor, a silicon-nitrogen-containing precursor, and/or a silicon-carbon-containing precursor. The silicon-oxygen-containing precursor may include one or more Si-O bonds, the silicon-nitrogen-containing precursor may include one or more Si-N bonds, and the silicon-carbon-containing precursor may include one or more Si-C bonds. In some embodiments, for example, the silicon-containing precursor may include a single reactant A having Si-O and Si-C bonds, or Si-N and Si-C bonds. In some embodiments, the silicon-containing precursor may include a reactant B having a Si-O bond, or a Si-N bond, and a reactant C having a Si-C bond. It should be understood that any number of suitable reactants may be used within the scope of the present invention. The chemical structures of exemplary silicon-containing precursors are discussed in further detail below.

The silicon-containing precursor includes one or more Si-H bonds and/or one or more Si-Si bonds. However, it should be understood that the additional silicon-containing precursors may not necessarily include Si-H or Si-Si bonds. Such additional silicon-containing precursors may be provided simultaneously with the silicon-containing precursor having one or more Si-H and/or Si-Si bonds. During the deposition process, the Si-H bonds and/or Si-Si bonds are broken and used as reaction sites for forming bonds between the silicon-containing precursor or other precursors in the deposited silicon carbide film 101. The broken bonds can also be used as sites for crosslinking during the deposition period or during a subsequent heat treatment. The bonds and cross-links at the reaction sites may together form the main backbone or matrix in the resulting silicon carbide film 101.

In certain embodiments, the process conditions may preserve or substantially preserve Si-C bonds and, if present, Si-O and Si-N bonds in the deposited film layer of the silicon carbide film 101. Thus, the reaction conditions adjacent to the substrate 100 provide for selective breaking of Si-H and/or Si-Si bonds, such as extracting hydrogen from broken Si-H bonds, but the reaction conditions do not extract oxygen from Si-O bonds, nitrogen from Si-N bonds, or carbon from Si-C bonds. However, the introduction of a co-reactant (e.g., oxygen) may extract carbon from Si-C bonds. It should be understood that other reaction mechanisms may occur in the environment adjacent to the substrate surface, including kinetically less favorable reaction mechanisms, such as substitution reactions. Generally, the reaction conditions described above exist at the exposed surface of the substrate 100 (the surface where the silicon carbide film 101 is deposited). They may further exist at a certain distance above the substrate 100, for example, from about 0.5 microns to about 150 mm above the substrate 100. In fact, the activation of the precursor may occur in the vapor phase at a substantial distance above the substrate 100. Typically, the relevant reaction conditions are uniform or substantially uniform over the entire exposed surface of the substrate 100, but some applications may allow for a certain degree of variation.

In addition to the silicon-containing precursor, the environment adjacent to the workpiece (such as substrate 100) may include one or more free radical species, preferably free radical species in a substantially low energy state. An example of such species includes hydrogen radicals (i.e., atomic hydrogen radicals). In some embodiments, all, or substantially all, or a substantial portion of the atomic hydrogen radicals may be in the ground state, for example, at least about 90% or 95% of the atomic hydrogen radicals of the adjacent workpiece are in the ground state. In some embodiments, the source gas is provided in a carrier gas (e.g., helium). For example, hydrogen may be provided in a helium carrier gas at a hydrogen concentration of about 1-10%. The pressure, fraction, and other process conditions of the carrier gas (e.g., helium) are selected so that the hydrogen atoms encounter the substrate 100 in the form of free radicals in a low energy state without recombination.

As described elsewhere, hydrogen gas may be supplied to a remote plasma source to generate hydrogen atomic radicals. The remote plasma source may be positioned upstream of the substrate surface and the environment adjacent to the substrate surface. Once generated, the hydrogen atomic radicals may be in an excited energy state. For example, hydrogen in an excited energy state may have an energy of at least 10.2 eV (first excited state). The excited hydrogen atomic radicals may cause non-selective decomposition of silicon-containing precursors. For example, the hydrogen atomic radicals in an excited state may easily break Si-H, Si-Si, Si-N, Si-O, and Si-C bonds, which may change the composition, or physical or electrical properties of the silicon carbide film 101. In some embodiments, when the excited hydrogen radical loses its energy or relaxes, the excited hydrogen radical may become a substantially low-energy state hydrogen radical or a ground state hydrogen radical. The substantially low-energy state or ground state hydrogen radical may selectively break Si-H and Si-Si bonds while substantially retaining Si-O, Si-N, and Si-C bonds. In some embodiments, process conditions may be provided to cause the excited hydrogen radical to lose energy or relax to form a substantially low-energy state or ground state hydrogen radical. For example, the remote plasma source or related components may be designed so that the residence time of the hydrogen radical diffused from the remote plasma source to the substrate 100 is greater than the energy relaxation time of the excited hydrogen radical. The energy relaxation time of the excited hydrogen radical may be approximately equal to or less than approximately 1×10 ⁻³ seconds.

A substantial portion of the hydrogen atomic radicals being in the ground state can be achieved by a variety of techniques. Certain equipment, such as the equipment described below, is designed to achieve this state. Equipment characteristics and process control characteristics can be tested and tuned to produce a mild state in which a substantial portion of the hydrogen atomic radicals are in the ground state. For example, the equipment can be operated and tested for charged particles downstream of the plasma source (i.e., near the substrate 100). The process and equipment can be tuned until substantially no charged species are present near the substrate 100. In addition, the equipment and process characteristics can be tuned to a configuration that begins forming the silicon carbide film 101 from a standard silicon-containing precursor. Relatively mild conditions are selected to support the deposition of these films.

Other examples of free radical species include oxygen-containing species such as elemental oxygen radicals (atomic or diatomic), nitrogen-containing species (e.g., elemental nitrogen radicals) (atomic or diatomic), and N-H-containing radicals (e.g., amine radicals), wherein nitrogen is optionally incorporated into the film. Examples of N-H-containing radicals include, but are not limited to, radicals of methylamine, dimethylamine, and aniline. The above-mentioned free radical species can be generated from a source gas containing hydrogen, nitrogen, N-H-containing species, or a mixture thereof. In some embodiments, substantially all or a substantial portion of the atoms of the deposited film are provided by precursor molecules. In such cases, the low-energy free radicals used to drive the deposition reaction can be hydrogen or other species that do not substantially contribute to the quality of the deposited film. In some embodiments, as discussed in more detail below, free radical species may be generated by a remote plasma source. In some embodiments, some free radicals or ions in higher energy states may potentially exist near the wafer plane.

In some embodiments, process conditions use radical species in substantially low energy states sufficient to break Si-H bonds and/or Si-Si bonds while substantially preserving Si-O, Si-N, and Si-C bonds. Such process conditions may not have a significant number of ions, electrons, or radical species in high energy states (e.g., energy states above the ground state). In some embodiments, the ion concentration in the region adjacent to the film is no greater than about 10 ⁷ /cm ³ . The presence of significant numbers of ions or high energy radicals tends to break Si-O, Si-N, and Si-C bonds, which may produce a film with undesirable electrical properties (e.g., high dielectric constant and/or low breakdown voltage) and poor conformality. It is generally believed that an overly reactive environment produces reactive precursor fragments with high viscosity coefficients (representing the tendency to chemically or physically adhere to the sidewalls of the workpiece), which leads to poor conformality.

The silicon-containing precursor is typically transported to an environment adjacent to the substrate 100 using other species, particularly a carrier gas. In some embodiments, the silicon-containing precursor is present with radical species and other species, including other reactive species and/or a carrier gas. In some embodiments, the silicon-containing precursor may be introduced as a mixture. Upstream of the deposition reaction surface, the silicon-containing precursor may be mixed with an inert carrier gas. Exemplary inert carrier gases include, but are not limited to, argon (Ar) and helium (He). In addition, the silicon-containing precursor may be introduced with a mixture of major and minor species, wherein the minor species include certain elements or structural features (such as ring structures, cage structures, unsaturated bonds, etc.) that are present in relatively low concentrations in the silicon carbide film 101. However, it should be understood that the minor species may not significantly affect the composition and structural characteristics of the silicon carbide film 101. The various precursors may be present in equimolar amounts or in relatively similar proportions suitable to form the primary backbone or matrix in the resulting silicon carbide film 101. In other embodiments, the relative amounts of the different precursors deviate substantially from equimolar concentrations by volume.

In some embodiments, the one or more silicon-containing precursors provide substantially all of the mass of the silicon carbide film 101, with only a small amount of hydrogen or other elements from the remote plasma providing less than about 5 atomic % or less than about 2 atomic % of the film mass. In some embodiments, only radical species and the one or more silicon-containing precursors contribute to the composition of the deposited silicon carbide film 101. In other embodiments, the deposition reaction includes co-reactants other than the one or more silicon-containing precursors and the radical species, which may or may not contribute to the composition of the deposited silicon carbide film 101. Examples of such co-reactants include carbon dioxide (CO ₂ ), carbon monoxide (CO), water (H ₂ O), methanol (CH ₃ OH), oxygen (O ₂ ), ozone (O ₃ ), nitrogen (N ₂ ), nitrous oxide (N ₂ O), ammonia (NH ₃ ), diazene (N ₂ H ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ), acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), diborane (B ₂ H ₆ ), and combinations thereof. Such materials can be used as nitriding agents, oxidizing agents, reactants, etc. In some cases, it can be used to tune the amount of carbon in the deposited film by removing or adding a portion of the carbon provided by the silicon-containing precursor. In certain embodiments using a non-hydrogen co-reactant, the co-reactant is introduced into the reaction chamber through the same flow path as the silicon-containing precursor; for example, a path that includes a gas outlet or showerhead and is not typically directly exposed to the plasma. In certain embodiments, oxygen and/or carbon dioxide are introduced with the precursor during deposition to change the composition of the silicon carbide film 101 by removing carbon from the film or precursor. In certain embodiments using a non-hydrogen co-reactant, the co-reactant is introduced into the reaction chamber through the same flow path as hydrogen, so that at least a portion of the co-reactant is converted to free radicals and/or ions. In these embodiments, both hydrogen radicals and co-reactant radicals react with the silicon-containing precursor(s) to produce the deposited silicon carbide film 101 .

In certain embodiments where a co-reactant is used and introduced into the reaction chamber along with the species to be converted into free radicals (e.g., hydrogen), the co-reactant is provided to the reaction chamber in a relatively small amount relative to the other gases in the reaction chamber (including the source of free radicals (e.g., hydrogen) and any carrier gas(es) (e.g., helium). For example, the co-reactant may be present in the process gas in a proportion of about 0.05 mass % or less, 0.01 mass % or less, or 0.001 mass % or less. For example, the reactant mixture (which enters the plasma source) may be about 10-20 liters per minute (L/m) of He, about 200-500 standard cubic centimeters per minute (sccm) of _H2 , and about 1-10 sccm of oxygen. However, it should be understood that in certain embodiments, the co-reactant may be present in the process gas at a ratio of about 0.05 mass % or more, or 1 mass % or more, or 20 mass % or more. When the co-reactant is introduced into the reaction chamber together with the silicon-containing precursor (e.g., through a gas outlet or showerhead), it may be present at a higher concentration; for example, about 2 mass % or less, or about 0.1 mass % or less. When the co-reactant is a relatively weak reactant (e.g., a weak oxidant such as carbon dioxide), it may be present at an even higher concentration (e.g., about 10 mass % or less, or about 4 mass % or less). When the co-reactant is an additive or an additional precursor, it may be present at an even higher concentration (e.g., about 10 mass % or more, or about 20 mass % or more).

The temperature in the environment adjacent to the substrate 100 can be any suitable temperature that promotes the deposition reaction, but is sometimes limited by the application of the device containing the silicon carbide film 101. In some embodiments, the temperature in the environment adjacent to the substrate 100 during the deposition of the silicon carbide film 101 can be largely controlled by the temperature of the base on which the substrate 100 is supported. In some embodiments, the operating temperature can be between about 50°C and about 500°C. For example, in many integrated circuit applications the operating temperature can be between about 250°C and about 400°C. In some embodiments, increasing the temperature can result in increased crosslinking on the surface of the substrate.

The pressure in the environment adjacent to the substrate 100 can be any suitable pressure for generating reactive radicals in the reaction chamber. In some embodiments, the pressure can be about 35 Torr or less. For example, in embodiments using microwave generated plasma, the pressure can be between about 10 Torr and about 20 Torr. In other examples, such as in embodiments using radio frequency (RF) generated plasma, the pressure can be less than about 5 Torr or between about 0.2 Torr and about 5 Torr.

The environment adjacent to the substrate 100 facilitates deposition of a silicon carbide film 101 on the substrate 100 by remote plasma CVD. A source gas is supplied to the remote plasma source, and power is provided to the remote plasma source, which power can cause the source gas to dissociate and generate ions and radicals in an excited energy state. After excitation, the radicals in the excited energy state relax to radicals in a substantially low energy state or to radicals in a ground state, such as hydrogen radicals in a ground state. Bonds in the silicon-containing precursor can be selectively broken by hydrogen radicals in a relaxed energy state. The co-reactant or other precursor can be activated by selectively breaking bonds in the co-reactant or other precursor by hydrogen radicals in a relaxed energy state.

Silicon carbide films are often used in semiconductor devices. For example, doped or undoped silicon carbide films can be used as metal diffusion barriers, etch stop layers, hard mask layers, gate spacers for source and drain implants, capping barriers for magnetoresistive random access memory (MRAM) or resistive random access memory (RRAM), and airtight diffusion barriers in air gaps. Figures 1B–1E show cross-sections of structures that include silicon carbide films in various applications. Figure 1B shows a vertical film of silicon carbide conformally deposited on a feature of a substrate. Figure 1C shows a silicon carbide vertical structure on the sidewall of a gate electrode structure of a transistor. Figure 1D shows a silicon carbide vertical structure on the exposed sidewall of a copper wire in an air-gap metallization layer. Figure 1E shows a silicon carbide pore filler in a porous dielectric material. Each of these applications is discussed in more detail below. Chemical Structure of Precursor

As discussed, the precursors used in forming the silicon carbide film may include silicon-containing precursors, wherein at least some of the silicon-containing precursors have at least one Si—H and/or at least one Si—Si bond. In certain embodiments, the silicon-containing precursors have at most one hydrogen atom bonded to each silicon atom. Thus, for example, a precursor having one silicon atom has at most one hydrogen atom bonded to that silicon atom; a precursor having two silicon atoms has one hydrogen atom bonded to one silicon atom and optionally has another hydrogen atom bonded to a second silicon atom; a precursor having three silicon atoms has one hydrogen atom bonded to one silicon atom and optionally has one or two hydrogen atoms bonded to one or both of the remaining silicon atoms; and so on. However, in some embodiments, the silicon-containing precursor has two or more hydrogen atoms bonded to one or each silicon atom. In addition, the silicon-containing precursor may include at least one Si-O bond, at least one Si-N bond, and/or at least one Si-C bond. Although any number of suitable precursors may be used in forming a silicon carbide film, at least some of the precursors will include a silicon-containing precursor having at least one Si-H bond or Si-Si bond, and optionally at least one Si-O bond, Si-N bond, and/or Si-C bond. In various embodiments, the silicon-containing precursor(s) do not contain O—C or N—C bonds; for example, the precursor(s) do not contain alkoxy (—OR), where R is an organic group (e.g., a hydrocarbon group), or amine (—NR ₁ R ₂ ) groups, where R ₁ and R ₂ are independently hydrogen or an organic group. It is generally believed that these groups can cause the precursor or fragment in which they reside to have a high viscosity coefficient.

In some embodiments, a portion of the carbon provided in the silicon carbide film may come from one or more hydrocarbon functional moieties on the silicon-containing precursor. Such functional moieties may come from alkyl groups, alkene groups, alkynyl groups, aryl groups, etc. In some embodiments, the hydrocarbon group has a single carbon atom to minimize steric hindrance of Si-H and/or Si-Si bonds that interrupt the reaction during deposition. However, the precursor is not limited to a single carbon group; a higher number of carbon atoms, such as 2, 3, 4, 5, or 6 carbon atoms, may be used. In some embodiments, the hydrocarbon group is linear. In some embodiments, the hydrocarbon group is cyclic.

In some embodiments, a portion of the carbon provided in the silicon carbide film may come from one or more hydrocarbon molecules in the silicon-containing precursor. These hydrocarbon molecules may include carbon-carbon chains, in which a number of carbon atoms may be used, such as 2, 3, 4, 5, 6, or 7 carbon atoms. In some embodiments, the hydrocarbon molecules include one or more carbon double bonds and/or carbon triple bonds.

In certain embodiments, the silicon-containing precursor falls into a chemical class. It should be understood that other chemical classes of silicon-containing precursors may be used and the silicon-containing precursors are not limited to the chemical classes discussed below.

In some embodiments, the silicon-containing precursor may be a siloxane. In some embodiments, the siloxane may be cyclic. The cyclosiloxane may include cyclotetrasiloxanes, such as 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS), decamethylcyclotetrasiloxane (OMCTS), and heptamethylcyclotetrasiloxane (HMCTS). Other cyclosiloxanes may also include (but are not limited to) cyclotrisiloxane and cyclopentasiloxane. An embodiment using cyclosiloxane is a ring structure, which can introduce porosity into the silicon carbide film and the size of the pore corresponds to the radius of the ring. For example, the ring of cyclotetrasiloxane may have a radius of about 6.7 Å.

In certain embodiments, the siloxane may have a three-dimensional or cage-like structure. FIG. 2 shows an example of a representative cage-like siloxane precursor. A cage-like siloxane has silicon atoms bridged to each other by oxygen atoms to form a polyhedron or any 3-D structure. An example of a cage-like siloxane precursor molecule is a silsesquioxane. The cage-like siloxane structure is described in more detail in U.S. Patent No. 6,576,345, co-owned by Cleemput et al., all of which is incorporated herein by reference for all purposes. Similar to cyclosiloxanes, cage-like siloxanes can introduce porosity into silicon carbide films. In certain embodiments, the porosity is on the scale of mesopores.

In some embodiments, the siloxane may be linear. Examples of suitable linear siloxanes include, but are not limited to, disiloxanes (e.g., pentamethyldisiloxane (PMDSO) and tetramethyldisiloxane (TMDSO)), and trisiloxanes (e.g., hexamethyltrisiloxane, heptamethyltrisiloxane).

In certain embodiments, the silicon-containing precursor may be an alkylsilane or other alkyl-substituted silane. Alkylsilanes comprise a central silicon atom, and one or more alkyl groups bonded to the central silicon atom and one or more hydrogen atoms bonded to the central silicon atom. In certain embodiments, any one or more of the alkyl groups comprises 1-5 carbon atoms. The alkyl groups may be saturated or unsaturated (e.g., alkenes (such as ethylene), alkynes, and aromatic groups). Examples include, but are not limited to, trimethylsilane (3MS), triethylsilane, pentamethyldisilane ((CH ₃ ) ₂ Si—CH ₂ —Si(CH ₃ ) ₃ ), and dimethylsilane (2MS).

In some embodiments, the silicon-containing precursor may be an alkoxysilane. However, in some embodiments, it is understood that the silicon-containing precursor is not an alkoxysilane to avoid the presence of alkoxy groups. Alkoxysilanes include a central silicon atom, and one or more alkoxy groups bonded to the central silicon atom and one or more hydrogen atoms bonded to the central silicon atom. Examples include, but are not limited to, trimethoxysilane (TMOS), dimethoxysilane (DMOS), methoxysilane (MOS), methyldimethoxysilane (MDMOS), diethoxymethylsilane (DEMS), dimethylethoxysilane (DMES), and dimethylmethoxysilane (DMMOS).

Disilane, trisilane, or other higher silanes may be used in place of the monosilane. An example of such a disilane from the class of alkylsilanes is hexamethyldisilane (HMDS). Another example of such a disilane from the class of alkylsilanes may include pentamethyldisilane (PMDS). Other types of alkylsilanes may include alkylcarbosilanes, which may have a branched polymeric structure, and carbons bonded to silicon atoms and alkyl groups bonded to silicon atoms. Examples include dimethyltrimethylsilylmethane (DTMSM) and bis-dimethylsilylethane (BDMSE). In certain embodiments, one of the plurality of silicon atoms may have a carbon-containing or alkyl-containing group attached thereto, and one of the plurality of silicon atoms may have a hydrogen atom attached thereto.

In some embodiments, the silicon-containing precursor may be a nitrogen-containing compound, such as a silicon-nitrogen hydride (e.g., silazane). Generally, such compounds contain carbon, but the carbon is only bonded to silicon atoms and not to nitrogen atoms. In some embodiments, the nitrogen-containing compound does not have any carbon-nitrogen bonds. In some embodiments, the nitrogen-containing compound does not have any amine functional groups (-C- _NR1R2 ), wherein _R1 and _R2 are _the same or different groups such as hydrogen atoms and alkyl groups (e.g., alkyl groups, alkenyl groups, or alkynyl groups). Examples of suitable silicon-nitrogen precursors include various silazanes, such as cyclic or linear silazanes comprising: one or more hydrocarbon functional groups bonded to one or more silicon atoms, and one or more hydrogen atoms bonded to one or more silicon atoms. Examples of silazanes include methyl-substituted disilazanes, and trisilazanes, such as tetramethyldisilazane and hexamethyltrisilazane.

When depositing silicon carbide, a plurality of silicon-containing precursors may be present in the process gas. For example, a siloxane may be used together with an alkylsilane, or a siloxane may be used together with an alkoxysilane. The relative proportions of the individual precursors may be selected based on the chemical structure of the selected precursors and the application of the resulting silicon carbide film. For example, the molar percentage amount of siloxane may be greater than the molar percentage amount of silane to produce a porous film as discussed in more detail below.

For the deposition of oxygen-doped silicon carbide films, examples of suitable precursors may include cyclosiloxanes, such as cyclotetrasiloxanes (e.g., heptamethylcyclotetrasiloxane (HMCTS) and tetramethylcyclotetrasiloxane). Other cyclosiloxanes may also include, but are not limited to, cyclotrisiloxane and cyclopentasiloxane. For the deposition of oxygen-doped silicon carbide films, other examples of suitable precursors include linear siloxanes, such as, but are not limited to, disiloxanes, such as pentamethyldisiloxane (PMDSO), tetramethyldisiloxane (TMDSO), hexamethyltrisiloxane, and heptamethyltrisiloxane.

For the deposition of undoped silicon carbide films, examples of suitable precursors may include monosilanes substituted with one or more alkane, alkene, and/or alkynyl groups containing, for example, 1-5 carbon atoms. Examples include, but are not limited to, trimethylsilane (3MS), dimethylsilane (2MS), triethylsilane (TES), and pentamethyldisilane. In addition, disilane, trisilane, or other higher silanes may be used to replace the monosilane. Examples of disilanes include hexamethyldisilane (HMDS) and pentamethyldisilane (PMDS). Other types of alkyl silanes may include alkyl carbosilanes. Examples include dimethyltrimethylsilylmethane (DTMSM) and di-dimethylsilylethane (BDMSE).

For the deposition of nitrogen-doped silicon carbide films, examples of suitable precursors may include silazanes such as alkyldisilazanes, and possible compounds including an amine group (-NH2) and an alkyl group each bonded to one or more silicon atoms. Alkyldisilazanes include silazane and an alkyl group bonded to two silicon atoms. One example includes 1,1,3,3-tetramethyldisilazane (TMDSN).

As described, the silicon-containing precursor is selected to provide a highly conformal silicon carbide film. It is generally believed that a silicon-containing precursor having a low viscosity coefficient is capable of producing a highly conformal film. The term "viscosity coefficient" is used to describe the ratio of the number of adsorbed species (such as fragments or molecules) adsorbed/adhered to a surface to the total number of species impinging on the surface during the same period of time. The symbol Sc is sometimes used to refer to the viscosity coefficient. The value of Sc ranges between 0 (meaning no species adheres) and 1 (meaning all impinging species adhere). Various factors that affect the viscosity coefficient include the type of impinging species, the surface temperature, the surface step coverage, the structural details of the surface, and the kinetic energy of the impinging species. Some species are inherently more "sticky" than others, making them more likely to adhere to a surface each time they impact the surface. Such stickier species have a larger viscosity coefficient (when other factors are equal), and species with a larger viscosity coefficient are more likely to adhere near the entrance of a recessed feature than low-viscosity species with a lower viscosity coefficient. In some cases, the viscosity coefficient of the precursor (under relevant deposition conditions) can be about 0.05 or less, such as about 0.001 or less. Equipment

One aspect of the invention is an apparatus configured to perform the methods described herein. Suitable apparatus includes hardware for performing process operations and a system controller having instructions for controlling process operations in accordance with the invention. In some embodiments, the apparatus for performing the process operations includes a remote plasma source. A remote plasma source provides milder reaction conditions than direct plasma. Examples of suitable remote plasma apparatus are described in U.S. Patent Application No. 14/062,648, filed October 24, 2013, which is hereby incorporated by reference in its entirety for all purposes.

FIG3 is a schematic diagram of a remote plasma apparatus according to certain embodiments. The apparatus 300 includes a reaction chamber 310 having a showerhead 320. In the reaction chamber 310, a substrate 330 is seated on a platform or base 335. In certain embodiments, the base 335 may be provided with a heating/cooling element. A controller 340 may be connected to a plurality of elements of the apparatus 300 to control the operation of the apparatus 300. For example, the controller 340 may include instructions for controlling process conditions for the operation of the apparatus 300, such as temperature process conditions and/or pressure process conditions. In certain embodiments, the controller 340 may include instructions for controlling the flow rates of a precursor gas, a co-reactant gas, a source gas, and a carrier gas. The controller 340 may include instructions for varying the flow rate of the co-reactant gas over time. Additionally or alternatively, the controller 340 may include instructions for varying the flow rate of the precursor gas over time. A more detailed description of the controller 340 is provided below.

During operation, a gas or gas mixture is introduced into the reaction chamber 310 via one or more gas inlets coupled to the reaction chamber 310. In some embodiments, two or more gas inlets are coupled to the reaction chamber 310. A first gas inlet 355 can be coupled to the reaction chamber 310 and connected to a container 350, and a second gas inlet 365 can be coupled to the reaction chamber 310 and connected to the remote plasma source 360. In embodiments including a remote plasma source configuration, the delivery lines for delivering the precursor and the radical species generated in the remote plasma source are separated from each other. Therefore, the precursor and the radical species do not substantially interact with each other before reaching the substrate 330. It should be understood that in certain embodiments, the gas lines may be reversed such that the container 350 may provide the precursor gas flow via the second gas inlet 365 , while the remote plasma source 360 may provide the ions and radicals via the first gas inlet 355 .

One or more free radical species may be generated in a remote plasma source 360 and configured to enter the reaction chamber 310 through a second gas inlet 365. Any type of plasma source may be used in the remote plasma source 360 to generate the free radical species. This includes, but is not limited to, capacitively coupled plasma, inductively coupled plasma, microwave plasma, DC plasma, and radio-generated plasma. An example of a capacitively coupled plasma may be a radio frequency (RF) plasma. A high frequency plasma may be configured to operate at a frequency of 13.56 MHz or higher. An example of such a remote plasma source 360 may be GAMMA® manufactured by Colin Research and Development, Fremont, California. Another example of such a remote plasma source 360 may be the Astron® manufactured by MKS Instruments of Wilmington, Massachusetts, which may operate at 440 kHz and may be provided as a subunit latched onto a large-scale apparatus for processing one or more substrates in parallel. In some embodiments, a microwave plasma may be used as the remote plasma source 360, such as in the Astex® also manufactured by MKS Instruments. Microwave plasma may be used to operate at a frequency of 2.45 GHz. The gas provided to the remote plasma source may include hydrogen, nitrogen, oxygen, and other gases mentioned elsewhere herein. In some embodiments, hydrogen is provided in a carrier gas (e.g., helium). For example, hydrogen gas may be provided at a hydrogen concentration of about 1–10% in a helium carrier gas.

The precursor may be provided in a container 350 and may be supplied to the showerhead 320 via a first gas inlet 355. The showerhead 320 distributes the precursor into the reaction chamber 310 toward the substrate 330. The substrate 330 may be located below the showerhead 320. It should be understood that the showerhead 320 may have any suitable shape and may have any number and configuration of interfaces for distributing gas to the substrate 330. The precursor may be supplied to the showerhead 320 and ultimately to the substrate 330 at a controlled flow rate.

One or more free radical species formed in the remote plasma source 360 may be carried in the gas phase toward the substrate 330. The one or more free radical species may flow through the second gas inlet 365 and into the reaction chamber 310. It should be understood that the second gas inlet 365 need not span the surface of the substrate 330 as shown in FIG. 3. In some embodiments, the second gas inlet 365 may be located directly above the substrate 330 or at other locations. The distance between the remote plasma source 360 and the reaction chamber 310 may be configured to provide mild reaction conditions so that the ionized species generated in the remote plasma source 360 are substantially neutralized, but at least a portion of the free radical species in a substantially low energy state remain in the environment adjacent to the substrate 330. These low energy free radical species will not recombine to form stable compounds. The distance between the remote plasma source 360 and the reaction chamber 310 may be a function of the aggressiveness of the plasma (e.g., determined in part by the source RF power level), the density of the gas in the plasma (e.g., if there is a high concentration of hydrogen atoms, most of them may recombine to form H ₂ before reaching the reaction chamber 310), and other factors. In some embodiments, the distance between the remote plasma source 360 and the reaction chamber 310 may be between about 1 cm and 30 cm, such as about 5 cm or about 15 cm.

In some embodiments, a co-reactant that is not a predominantly silicon-containing precursor or a hydrogen radical is introduced during the deposition reaction. In some embodiments, the apparatus is configured to introduce the co-reactant via the second gas inlet 365, wherein the co-reactant is at least partially converted to plasma. In some embodiments, the apparatus introduces the co-reactant via the first gas inlet 355 through the showerhead 320. Examples of co-reactants include oxygen, nitrogen, ammonia, carbon dioxide, carbon monoxide, etc. The flow rate of the co-reactant can be varied over time to produce a composition gradient in the gradient film.

According to certain other embodiments, FIG. 4 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source. The plasma processing apparatus 400 includes a remote plasma source 402 separated from a reaction chamber 404. The remote plasma source 402 is fluidly coupled to the reaction chamber 404 via a multi-port gas distributor 406, which may also be referred to as a showerhead. Free radical species are generated in the remote plasma source 402 and supplied to the reaction chamber 404. One or more silicon-containing precursors are supplied to the reaction chamber 404 downstream of the remote plasma source 402 and the multi-port gas distributor 406. The one or more silicon-containing precursors react with the radical species in a chemical vapor deposition region 408 of the reaction chamber 404 to deposit a silicon carbide film on the surface of the substrate 412. The chemical vapor deposition region 408 includes an environment adjacent to the surface of the substrate 412.

The substrate 412 is supported on a substrate support or pedestal 414. The pedestal 414 can be moved within the reaction chamber 404 to position the substrate 412 within the chemical vapor deposition zone 408. In the embodiment shown in FIG. 4 , the pedestal 414 is shown as having raised the substrate 412 within the chemical vapor deposition zone 408. In some embodiments, the pedestal 414 can also adjust the temperature of the substrate 412. The pedestal 414 can provide some selective control over thermally activated surface reactions on the substrate 412.

FIG4 shows a coil 418 disposed around a remote plasma source 402, wherein the remote plasma source 402 includes an outer wall (e.g., a quartz dome). The coil 418 is electrically coupled to a plasma generator controller 422, which can be used to form and maintain a plasma in a plasma region 424 through inductively coupled plasma generation. In some embodiments, the plasma generator controller 422 can include a power supply that supplies power to the coil 418, wherein the power can be in the range of about 1 to 6 kilowatts (kW) during plasma generation. In some embodiments, electrodes or antennas used for parallel plate or capacitively coupled plasma generation can be used to generate a continuous supply of free radicals through plasma excitation rather than using inductively coupled plasma generation. Regardless of the mechanism used to ignite and maintain the plasma in plasma region 424, free radical species may be continuously generated during film deposition using plasma excitation. In certain embodiments, hydrogen radicals are generated under near steady-state conditions during steady-state film deposition, but may be transient at the beginning and end of film deposition.

When hydrogen or other source gas is supplied to the remote plasma source 402, a supply of hydrogen radicals may be continuously generated within the plasma region 424. Excited hydrogen radicals may be generated in the remote plasma source 402. The excited hydrogen radicals lose their energy or relax if not re-excited or re-energized or recombined with other radicals. Thus, the excited hydrogen radicals may relax to form hydrogen radicals in a substantially low energy state or ground state.

The hydrogen or other source gas may be diluted using one or more additional gases. The one or more additional gases may be supplied to the remote plasma source 402. In some embodiments, the hydrogen or other source gas is mixed with one or more additional gases to form a gas mixture, wherein the one or more additional gases may include a carrier gas. Non-limiting examples of additional gases may include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and nitrogen ( _N2 ). The one or more additional gases may support or stabilize a steady plasma state within the remote plasma source 402, or assist in the ignition or extinguishing process of a transient plasma. In some embodiments, diluting hydrogen or other source gases with, for example, helium can facilitate higher total pressures without causing an accompanying plasma breakdown. In other words, a dilute gas mixture of hydrogen and helium can facilitate higher total gas pressures without increasing the plasma power supplied to the remote plasma source 402. As shown in FIG. 4 , a source gas supply 426 is fluidly coupled to the remote plasma source 402 to supply hydrogen or source gas. In addition, an additional gas supply 428 is fluidly coupled to the remote plasma source 402 to supply one or more additional gases. The one or more additional gases may also include the co-reactant gas described above. 4 shows a gas mixture of a source gas and one or more additional gases being introduced through separate gas outlets, it should be understood that the gas mixture may be introduced directly into the remote plasma source 402. That is, a pre-mixed, dilute gas mixture may be supplied to the remote plasma source 402 through a single gas outlet.

Gases (e.g., excited hydrogen and helium radicals, and relaxed gases/radicals) flow from the remote plasma source 402 and flow into the reaction chamber 404 through the multi-port gas distributor 406. The gases within the multi-port gas distributor 406 and within the reaction chamber 404 are typically not subjected to continuous plasma excitation therein. In some embodiments, the multi-port gas distributor 406 includes an ion filter and/or a photon filter. Filtering the ions and/or photons can reduce substrate damage, undesired molecular re-excitation, and/or selective cleavage or decomposition of silicon-containing precursors within the reaction chamber 404. The multi-port gas distributor 406 can have a plurality of gas ports 434 to diffuse the gas flow into the reaction chamber 404. In some embodiments, the plurality of gas ports 434 may be spaced apart from one another. In some embodiments, the plurality of gas ports 434 may be arranged as an array of regularly spaced channels or through holes extending through a plate separating the remote plasma source 402 from the reaction chamber 404. The plurality of gas ports 434 may smoothly disperse and diffuse the free radicals exiting the remote plasma source 402 into the reaction chamber 404.

A typical remote plasma source is quite different from a reaction vessel. Therefore, free radical destruction and recombination (e.g., through wall collision events) may significantly reduce reactive species. In contrast, in some embodiments, the size of the plurality of gas ports 434 may be configured based on the mean free path or gas flow residence time under typical processing conditions to assist free radicals in entering the reaction chamber 404. In some embodiments, the openings of the plurality of gas ports 434 may occupy between about 5% and about 20% of the exposed surface area of the multi-port gas distributor 406. In some embodiments, the plurality of gas ports 434 may each have an axial length to diameter ratio between about 3:1 and 10:1, or between about 6:1 and 8:1. Such aspect ratios can reduce the frequency of wall collisions of radical species passing through the plurality of gas ports 434, while providing sufficient time for most excited radical species to relax to ground state radical species. In some embodiments, the dimensions of the plurality of gas ports 434 can be configured so that the residence time of the gas passing through the multi-port gas distributor 406 is greater than the typical energy relaxation time of the excited radical species. The excited radical species of the hydrogen source gas can be represented by •H ^* in FIG. 4 , and the ground state radical species of the hydrogen source gas can be represented by • H in FIG. 4 .

In certain embodiments, excited radical species exiting the plurality of gas ports 434 may flow into a relaxation region 438 contained within the interior of the reaction chamber 404. The relaxation region 438 is located upstream of the chemical vapor deposition region 408 but downstream of the multi-port gas distributor 406. Substantially all or at least 90% of the excited radical species exiting the multi-port gas distributor 406 are converted into relaxed radical species in the relaxation region 438. In other words, substantially all excited radical species (excited hydrogen radicals) that enter the relaxation region 438 become de-excited, or are converted into relaxed radical species (e.g., ground state hydrogen radicals) before exiting the relaxation region 438. In certain embodiments, the process conditions or geometry of the relaxation region 438 may be configured such that the residence time (e.g., time determined by the mean free path and the mean molecular velocity) of the radical species flowing through the relaxation region 438 causes the relaxed radical species to flow out of the relaxation region 438.

As the free radical species are delivered from the multi-port gas distributor 406 to the relaxation zone 438, one or more silicon-containing precursors and/or one or more co-reactants may be introduced into the chemical vapor deposition zone 408. The one or more silicon-containing precursors may be introduced through the gas distributor or gas outlet 442, wherein the gas outlet 442 may be fluidly coupled to the precursor supply 440. The relaxation zone 438 may be contained within a space between the multi-port gas distributor 406 and the gas outlet 442. The gas outlet 442 may include openings spaced apart from one another so that a flow of the one or more silicon-containing precursors may be introduced in a direction parallel to the gas mixture flowing out of the relaxation zone 438. The gas outlet 442 may be located downstream of the multi-port gas distributor 406 and the relaxation zone 438. The gas outlet 442 may be located upstream of the chemical vapor deposition zone 408 and the substrate 412. The chemical vapor deposition zone 408 is located within the reaction chamber 404 and between the gas outlet 442 and the substrate 412.

Substantially all of the flow of the one or more silicon-containing precursors may be prevented from mixing with the excited radical species adjacent to the multi-port gas distributor 406. The relaxed or ground state radical species mix with the one or more silicon-containing precursors in a region adjacent to the substrate 412. The chemical vapor deposition region 408 includes a region adjacent to the substrate 412 in which the relaxed or ground state radical species mix with the one or more silicon-containing precursors. During CVD formation of the silicon carbide film, the relaxed or ground state radical species mix with the one or more silicon-containing precursors in a gas phase.

In some embodiments, a co-reactant may be introduced from the gas outlet 442 and flow with one or more silicon-containing precursors. The co-reactant may include a carbon-containing precursor as described below. The co-reactant may be introduced downstream of the remote plasma source 402. The co-reactant may be supplied from the precursor supply source 440 or other source (not shown) fluidly coupled to the gas outlet 442. The co-reactant may be a carbon-containing precursor as described below. In some embodiments, the co-reactant may be introduced from the multi-port gas distributor 406 and flow with the free radical species generated in the remote plasma source 402 and flow into the reaction chamber 404. This may include free radicals and/or ions of the co-reactant gas provided in the remote plasma source 402. The co-reactants may be supplied from an additional gas supply 428.

The gas outlet 442 may be separated from the multi-port gas distributor 406 by a sufficient distance to prevent reverse diffusion or reverse flow of one or more silicon-containing precursors. In some embodiments, the gas outlet 442 may be separated from the plurality of gas ports 434 by a distance between about 0.5 inches and about 5 inches, or between about 1.5 inches and about 4.5 inches, or between about 1.5 inches and about 3 inches.

Process gases may be removed from the reaction chamber 404 via an outlet 448 configured to be fluidly coupled to a pump (not shown). Thus, excess silicon-containing precursors, co-reactants, radical species, and dilution and displacement or purge gases may be removed from the reaction chamber 404. In some embodiments, a system controller 450 is in operative communication with the plasma processing apparatus 400. In some embodiments, the system controller 450 includes a processor system 452 (e.g., a microprocessor) configured to execute instructions stored in a data system 454 (e.g., a memory). In some embodiments, the system controller 450 may communicate with the plasma generator controller 422 to control plasma parameters and/or conditions. In some embodiments, the system controller 450 can communicate with the pedestal 414 to control the pedestal height and temperature. In some embodiments, the system controller 450 can control other processing conditions, such as RF power settings, frequency settings, duty cycle, pulse time, pressure within the reaction chamber 404, pressure within the remote plasma source 402, gas flow rates from the source gas supply 426 and the additional gas supply 428, gas flow rates from the precursor supply 440 and other sources, the temperature of the pedestal 414, and the temperature of the reaction chamber 404.

The aspects of the controller 450 of FIG. 4 described below are also applicable to the controller 340 of FIG. 3 . The controller 450 may include instructions for controlling process conditions for the operation of the plasma processing apparatus 400. The controller 450 typically includes one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, a stepper motor controller board, etc. Instructions for performing appropriate control operations are executed on the processor. These instructions may be stored on a memory device associated with the controller 450 or they may be provided via a network.

In some embodiments, the controller 450 controls all or most of the activities of the plasma processing apparatus 400 described herein. For example, the controller 450 may control all or most of the activities of the plasma processing apparatus 400 associated with depositing a silicon carbide film and optionally other operations in a manufacturing process involving the silicon carbide film. The controller 450 may execute system control software including sets of instructions for controlling timing, gas composition, gas flow rates, process chamber pressure, chamber temperature, RF power levels, substrate position, and/or other parameters. Other computer programs, scripts, or routines stored on a memory device associated with the controller 450 may be used in some embodiments. In order to provide relatively mild reaction conditions in the environment adjacent to the substrate 412, parameters such as RF power level, gas flow rate to the plasma region 424, gas flow rate to the chemical vapor deposition region 408, and timing of plasma ignition may be adjusted and maintained by the controller 450. Additionally, adjusting the substrate position may further reduce the presence of high energy radical species in the environment adjacent to the substrate 412. In a multi-station reactor, the controller 450 may include different or identical instructions for different equipment sites, thereby enabling the equipment sites to operate independently or synchronously.

In some embodiments, the controller 450 may include instructions for, for example, flowing one or more silicon-containing precursors into the reaction chamber 404 through the gas outlet 442, providing a source gas to the remote plasma source 402, generating one or more radical species of the source gas in the remote plasma source 402, and introducing the one or more radical species in a substantially low energy state from the remote plasma source 402 into the reaction chamber 404 to react with the one or more silicon-containing precursors to deposit a silicon carbide film on the substrate 412. The one or more radical species in the environment of the reaction chamber 404 adjacent to the substrate 412 may be hydrogen radicals in a ground state. In some embodiments, controller 450 may include instructions to flow a co-reactant with one or more silicon-containing precursors into reaction chamber 404. The co-reactant may be a hydrocarbon molecule, and each of the one or more silicon-containing precursors may have at least two hydrogen atoms bonded to silicon atoms.

In some embodiments, the apparatus 400 may include a user interface associated with the controller 450. The user interface may include a display screen, a graphical software display of the apparatus 400 and/or process conditions, and a user input device such as a pointing device, a keyboard, a touch screen, a microphone, etc.

The computer program code for controlling the above operations may be written in any known computer readable programming language, such as assembly language, C, C++, Pascal, Fortran or other languages. The compiled object code or script may be executed by a processor to perform the tasks specified in the program.

Signals for monitoring the processing may be provided via analog and/or digital input connections of the system controller. Signals for controlling the processing are output on analog and digital output connections of the processing system.

In general, the methods described herein may be performed on a system that includes semiconductor processing equipment, such as one or more processing tools, one or more chambers, one or more workstations for processing, and/or specific processing components (wafer pedestals, gas flow systems, etc.). Such systems may be integrated with electronic devices to control their operation before, during, and after processing of semiconductor wafers or substrates. Generally, such electronic devices are referred to as controllers, which may control various components or subcomponents of one or more systems. Depending on the requirements of the process and/or the type of system, the controller can be programmed to control any of the processes disclosed herein, including the delivery of process gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operating settings, wafer transport in and out of tools and other transport tools connected to or interfaced with a particular system and/or load locks.

Broadly speaking, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and/or software that receive commands, send commands, control operations, enable clean operations, enable endpoint measurements, etc. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors or microcontrollers that execute program instructions (such as software). Program instructions may be instructions sent to the controller in the form of various individual settings (or program files) that define operating parameters for performing specific processes on or for a semiconductor wafer, or for a system. In some implementations, the operating parameters may be part of a recipe defined by a process engineer for performing one or more processing steps during the fabrication of one or more layers, materials (e.g., silicon carbide), surfaces, circuits, and/or die of a substrate.

In some embodiments, the controller may be part of or coupled to a computer that is integrated with the system, coupled to the system, connected to the system via a network, or a combination thereof. For example, the controller may be located in the "cloud" or may be all or part of a wafer fab host computer system that allows remote access to substrate processing. The computer may enable remote access to the system to monitor the current progress of manufacturing operations, view the history of past manufacturing operations, view trends or performance indicators from multiple manufacturing operations, change parameters of the current process, set processing steps to continue the current process, or start a new process. In some examples, a remote computer (such as a server) may provide process recipes to the system via a network, which may include a local area network or the Internet. The remote computer may include a user interface that enables input or programming of parameters and/or settings that are then transmitted from the remote computer to the system. In some examples, the controller receives instructions in the form of data that, during one or more operation periods, specifies parameters for each of the processing steps to be performed. It should be understood that the parameters may be specific to the type of processing to be performed, and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be decentralized, such as by including one or more separate controllers that are connected together via a network and work toward a common goal, such as the processing and control described herein. An example of a separate controller used for such purposes would be one or more integrated circuits on the chamber that communicate with one or more integrated circuits located remotely (e.g., at the platform level, or as part of a remote computer) that combine to control processing on the chamber.

In addition to silicon carbide deposition as described herein, example systems may include plasma etching chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, bevel etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the fabrication and/or production of semiconductor wafers.

As described above, depending on the (plurality) of process steps to be performed by the tool, the controller may communicate with one or more of the following in the semiconductor manufacturing plant: other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools throughout the plant, a host computer, another controller, or tools used in material transport that transport wafer containers to and from tool locations and/or loading ports.

The apparatus/processes described herein may be used together with lithographic patterning tools or processes, such as those used to manufacture semiconductor devices, displays, LEDs, photovoltaic panels, etc. Typically, although not necessarily, such tools/processes are used or performed together in a common manufacturing plant. Lithographic patterning of thin films typically includes some or all of the following operations, each of which is provided by several possible tools: (1) coating of photoresist on a workpiece (i.e., substrate) using a spin-on or spray-on tool; (2) curing of the photoresist using a hot plate or oven or a UV curing tool; (3) exposing the photoresist to visible light or UV light or x-ray light using a tool (e.g., a wafer stepper); (4) developing the photoresist so that it can be selectively removed and patterned using a tool (e.g., a wet bench); (5) transferring the photoresist pattern to an underlying film or workpiece using a dry or plasma-assisted etch tool; and (6) removing the photoresist using a tool (e.g., an RF or microwave plasma photoresist stripper). Remote plasma CVD using silicon-containing precursors and carbon-containing precursors

The deposition of silicon carbide films (including silicon carbonitride films) using ALD presents a number of challenges, including thermodynamic challenges that may make ALD of silicon carbide films difficult to achieve. In addition, the deposition rate of ALD is slower than that of typical CVD techniques, which may be undesirable in a manufacturing process. In addition, it may be difficult to incorporate carbon into a silicon-based film or a silicon nitride-based film without compromising the step coverage, film density, and/or film quality characteristics of the silicon carbide film. The present invention relates to the deposition of silicon carbide films using remote plasma CVD. In the present invention, incorporation of carbon into a silicon-based film or a silicon nitride-based film may be achieved without forming any C-C bonds and N-C bonds. The presence of C-C or N-C bonds may adversely affect the properties of silicon carbide films.

As described above, the deposition reaction of the deposited silicon carbide film may include co-reactants in addition to the silicon-containing precursor and the free radical species. The introduction of the co-reactants can be used to tune the composition of the silicon carbide film. The co-reactants can be flowed into the reaction chamber together with the silicon-containing precursor, wherein the co-reactants can flow downstream of the remote plasma source. For example, the gas outlet for introducing the silicon-containing precursor and the co-reactants can be located downstream of the remote plasma source. The remote plasma source is considered to be upstream of the substrate and the environment adjacent to the substrate. In some embodiments, the gas outlet for introducing the silicon-containing precursor and the co-reactants can be located downstream of the remote plasma source and upstream of the environment adjacent to the substrate.

In addition to the silicon-containing precursor, a co-reactant may be introduced as a second precursor. The second precursor has chemical properties for tuning the composition of the silicon carbide film. In some embodiments, the second precursor has chemical properties for improving the step coverage of the silicon carbide film. The step coverage of the deposited silicon carbide film may be measured relative to one or more features of the substrate. "Feature" as used herein may refer to a non-planar structure on a substrate, typically a surface that is modified during semiconductor device processing operations. Examples of features include trenches, through holes, pads, columns, domes, etc. Features typically have an aspect ratio (depth or height to width). In certain embodiments, the step coverage of the silicon carbide film is at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99%.

In some embodiments, the co-reactant is a hydrocarbon molecule. The co-reactant of the present invention may also be referred to as a carbon-containing precursor, which flows with the silicon-containing precursor. In some embodiments, the hydrocarbon molecule may be a short-chain hydrocarbon molecule having at least one double bond or at least one triple bond. For example, the hydrocarbon molecule comprises a carbon chain between 3 carbon atoms and 7 carbon atoms. The hydrocarbon molecule may comprise one or more unsaturated carbon bonds, such as one or more carbon-carbon double bonds or triple bonds. Thus, the hydrocarbon molecule may comprise an alkene or alkynyl group. Examples of suitable hydrocarbon molecules include propylene, ethylene, butene, pentene, butadiene, pentadiene (e.g., 1,4-pentadiene), hexadiene, heptadiene, toluene, and benzene. Other examples of suitable hydrocarbon molecules include acetylene, propyne, butyne, pentyne (eg, 1-pentyne), and hexyne (eg, 2-hexyne).

The carbon-containing precursor may flow with one or more silicon-containing precursors. In some embodiments, each of the silicon-containing precursors does not have C-O bonding and C-N bonding. Each of the silicon-containing precursors may include two or more Si-H bonding. In practice, each of the silicon-containing precursors has at least one silicon atom and two or more hydrogen atoms bonded thereto. Therefore, the at least one silicon atom does not have more than two carbon atoms, nitrogen atoms, and/or oxygen atoms bonded thereto. Examples of silicon-containing precursors include (but are not limited to) silanes and higher silanes, or alkyl silanes and higher alkyl silanes. For example, the silicon-containing precursor may be silane, disilane, trisilane, methylsilane, or dimethylsilane. Therefore, the silicon-containing precursor flowing with the carbon-containing precursor may be a silane-based precursor. The silane-based precursor has a silicon atom and four substituents bonded to the silicon atom. Among the four substituents on the silicon atom, at least two of the substituents are hydrogen.

The carbon-containing precursor and the silicon-containing precursor are introduced into the reaction chamber downstream of one or more free radical species. The free radical species may be generated in a remote plasma source upstream of a gas outlet for introducing the carbon-containing precursor and the silicon-containing precursor. The free radical species may include hydrogen radicals, wherein the hydrogen radicals are in a substantially low energy state or ground state when mixed or interacted with the carbon-containing precursor and the silicon-containing precursor.

When depositing silicon carbide films by remote plasma CVD, most, if not all, of the Si-C bonds in the silicon carbide film may typically be provided by existing Si-C bonds in the silicon-containing precursor. This may limit the ability to tune the composition of the silicon carbide film. Flowing a co-reactant with the silicon-containing precursor may add greater flexibility in tuning the composition of the silicon carbide film so that more or less carbon may be incorporated into the silicon carbide film. However, when the co-reactant is a carbon-containing precursor, the co-reactant does not contribute to the composition tuning of the silicon carbide film, or the co-reactant adds C-C bonds, C-O bonds, or C-N bonds that may adversely affect the electrical properties and/or step coverage of the silicon carbide film. In the present invention, the carbon-containing co-reactant and the silicon-containing precursor are selected so that the carbon-containing co-reactant contributes to the composition tuning of the silicon carbide film without adding C-C bonds, C-O bonds, or C-N bonds. The carbon-containing co-reactant and the silicon-containing precursor add additional process parameters for tuning the composition of the silicon carbide film, while maintaining or improving film quality, compared to silicon carbide films deposited using existing Si-C bonding in the silicon-containing precursor.

Hydrogen radicals in a substantially low energy state or ground state can interact with carbon-containing precursors and silane-based precursors. Without being bound by any theory, one of the more kinetically favorable reaction mechanisms in the deposition reaction includes hydrogen abstraction, which involves selective scission of Si-H bonds in the silane-based precursor. The hydrogen abstraction reaction results in an activated silane-based precursor. Without being bound by any theory, hydrogen radicals in a substantially low energy state or ground state can interact with alkyne or alkene groups in hydrocarbon molecules, resulting in the formation of activated alkanes (e.g., methane). In some cases, the hydrocarbon molecules are broken into short-chain hydrocarbon molecules or radicals. Activated alkanes contain carbon radicals as activation sites, and activated silane-based precursors contain silicon radicals as activation sites, and these activation sites can react together to form Si-C bonds. Figure 5 shows the chemical reaction between activated alkanes from carbon-containing precursors and activated silane-based precursors.

Rather than being a passive bystander, the carbon-containing precursor can contribute significantly to the composition of the silicon carbide film. The carbon-containing precursor, and byproducts of any reaction with hydrogen radicals in a substantially low energy state or ground state, can be incorporated into the silicon carbide film in a substantial amount. As used herein, with respect to the case where carbon from the carbon-containing precursor is incorporated into the silicon carbide film, the term "substantial amount" can refer to a change in atomic concentration of carbon equal to or greater than about 5% compared to a silicon carbide film deposited without the use of the carbon-containing precursor. The contribution of carbon from the carbon-containing precursor avoids or minimizes the addition of C-C bonds. The silicon carbide film has no C-C bonds, or substantially no C-C bonds. In certain embodiments, the percentage of C-C bonds in the silicon carbide film is equal to or less than about 2%, equal to or less than about 1%, equal to or less than about 0.5%, or even 0%.

The remote plasma CVD process of the present invention may include a remote hydrogen plasma, wherein hydrogen radicals interact with a carbon-containing precursor and a silicon-containing precursor downstream of the remote plasma source. In some embodiments, the remote hydrogen plasma may further include a remote nitrogen plasma or a remote oxygen plasma. A nitriding agent or an oxidizing agent may be added to the remote plasma source to generate nitrogen radicals or oxygen radicals, respectively. The nitriding agent may promote the formation of a silicon carbonitride (SiCN) film, while the oxidizing agent may promote the formation of a silicon oxycarbide (SiCO) film.

When forming a SiCN film, a nitriding agent and hydrogen may be provided to a remote plasma source. In some embodiments, a carrier gas (e.g., helium) is provided to the remote plasma source to mix with the nitriding agent and hydrogen. Free radicals of the nitriding agent and hydrogen may be generated in the remote plasma source. In some embodiments, the nitriding agent comprises nitrogen ( _N2 ) or ammonia ( _NH3 ). The free radicals of the nitriding agent may be introduced from the remote plasma source into the reaction chamber along a flow path of the free radicals of hydrogen. The free radicals of the nitriding agent and hydrogen react with one or more silicon-containing precursors and co-reactants to form a SiCN film. Without being bound by any theory, the amine radicals or nitrogen radicals interact with the activated silicon-containing precursor to form Si-N bonds. The SiCN film has no or substantially no CC bonds, and has no or substantially no CN bonds. In some embodiments, the percentage of CC bonds or CN bonds in the SiCN film is equal to or less than about 2%, equal to or less than about 1%, equal to or less than about 0.5%, or even 0%.

When forming a SiCO film, an oxidant and hydrogen may be provided to a remote plasma source. In certain embodiments, a carrier gas (e.g., helium) is provided to the remote plasma source to mix with the oxidant and hydrogen. Free radicals of the oxidant and hydrogen may be generated in the remote plasma source. In certain embodiments, the oxidant comprises carbon dioxide (CO ₂ ), carbon monoxide (CO), oxygen (O ₂ ), ozone (O ₃ ), or nitrous oxide (N ₂ O). Free radicals of the oxidant may be introduced from the remote plasma source into a reaction chamber along a flow path of free radicals of hydrogen. The free radicals of the oxidant and hydrogen react with one or more silicon-containing precursors and co-reactants to form a SiCO film. Without being bound by any theory, oxygen radicals interact with the activated silicon-containing precursor to form Si-O bonds. The SiCO film has no or substantially no CC bonding, and has no or substantially no CO bonding. In some embodiments, the percentage of CC bonding or CO bonding in the SiCO film is equal to or less than about 2%, equal to or less than about 1%, equal to or less than about 0.5%, or even 0%.

FIG6A shows an FTIR spectrum of remote plasma CVD of silicon carbide films using a silicon-containing precursor and varying amounts of a carbon-containing precursor. FIG6B shows an enlarged view of a portion of the FTIR spectrum in FIG6A. The carbon-containing precursor and the silicon-containing precursor are provided downstream of the remote plasma. The remote plasma contains hydrogen radicals and nitrogen radicals. In FIGS. 6A–6B , the FTIR spectrum shows several plots, the plot with the highest peak having a carbon-containing precursor with a flow rate of 0 sccm, the plot with the second highest peak having a carbon-containing precursor with a flow rate of 1 sccm, the plot with the third highest peak having a carbon-containing precursor with a flow rate of 3 sccm, the plot with the fourth highest peak having a carbon-containing precursor with a flow rate of 5 sccm, the plot with the fifth highest peak having a carbon-containing precursor with a flow rate of 10 sccm, the plot with the sixth highest peak having a carbon-containing precursor with a flow rate of 15 sccm, and the plot with the shortest peak having a carbon-containing precursor with a flow rate of 24 sccm. The presence of Si—N bonding can be observed at about 835 cm ⁻¹ , and the presence of Si—C bonding can be observed at about 790 cm ⁻¹ .

A silicon nitride film is deposited when a silicon-containing precursor reacts with a remote plasma containing nitrogen radicals in the absence of a carbon-containing precursor. Introducing a carbon-containing precursor causes a silicon carbonitride film to form. The silicon carbonitride film contains both Si-N bonds and Si-C bonds. As shown in FIGS. 6A-6B , increasing the flow rate of the carbon-containing precursor increases the amount of Si-C bonds in the silicon carbonitride film. The Si-C bonds are a result of the carbon-containing precursor. Although Si-C bonds typically exist from a single silicon-containing precursor, the present invention can introduce a silicon-containing precursor and a carbon-containing precursor to form Si-C bonds in a doped or undoped silicon carbide film.

FIG7 shows a TEM image of a silicon carbide film deposited on a substrate feature using a silicon-containing precursor and a carbon-containing precursor. The remote plasma contains hydrogen radicals and nitrogen radicals. X-ray photoelectron spectroscopy (XPS) data can identify the composition of the deposited film including the silicon carbide film in FIG7. A summary of the XPS data compiled for the silicon carbide film is shown in Table 1. The elemental composition is expressed as atomic percent concentration and shows the atomic percent ratio between carbon and silicon (C/Si), nitrogen and silicon (N/Si), and carbon and nitrogen (C/N). As shown in Table 1, the introduction of a carbon-containing precursor can produce a doped silicon carbide film with a high carbon content. Table 1

The introduction of a second precursor, particularly a carbon-containing precursor, significantly improves the step coverage of the silicon carbide film. In certain embodiments, the step coverage of the silicon carbide film is at least 75%, at least 80%, at least 85%, or at least 90%. The film quality and film density are also substantially maintained when the carbon-containing precursor is introduced. For example, the film density can be equal to or greater than about 2.0 g/cm ^3. Structure and Properties of Deposited Films

The deposited film includes silicon, carbon, and in some cases oxygen, nitrogen, and/or one or more other elements. In some embodiments, the atomic concentration of silicon is between about 15% and 45% (or about 25% to 40%), the atomic concentration of carbon is between about 10% and 50%, the atomic concentration of oxygen is between about 0% and 45%, and the atomic concentration of nitrogen is between about 0% and 45%. In one example, the atomic concentration of silicon is about 30%, the atomic concentration of oxygen is about 25%, and the atomic concentration of carbon is about 45%. In another example, the atomic concentration of silicon is about 30%, the atomic concentration of oxygen is about 45%, and the atomic concentration of carbon is about 25%. In another example, the film contains about 10-15% carbon and about 30-40% oxygen, both based on atomic concentrations. In all cases, the film contains some hydrogen. However, it should be understood that the relative atomic concentration of hydrogen is small, for example, equal to or less than about 5%. It should be understood that the relative atomic concentration may vary depending on the choice of precursor. Silicon atoms form bonds with carbon and optionally with nitrogen and/or oxygen atoms. In some embodiments, the deposited film contains more Si-C bonds than Si-N bonds. In some examples, the deposited film contains a ratio of Si-C bonds to Si-N bonds between about 0.5:1 and 3:1. In some embodiments, the film density is between about 2 and 2.7 g/ ^cm3 .

When using a carbon-containing precursor and a silicon-containing precursor having at least two hydrogen atoms bonded to silicon atoms, the relative atomic concentrations of silicon and carbon can be relatively high compared to other elements in the silicon carbide film. In certain embodiments, the relative atomic concentration of silicon can be at least 25% or at least 30%, and the relative atomic concentration of carbon can be at least 25% or at least 30% or at least 40%. In addition, for doped silicon carbide films, the relative atomic concentration of oxygen can be less than about 10%, and the relative atomic concentration of nitrogen can be less than about 10%.

In certain embodiments, the internal structure of the precursor is retained in the deposited film. This structure may retain all or most of the Si-C, and Si-O and/or Si-N bonds (if present) in the precursor, while linking or cross-linking the functional moieties of the respective precursors through bonding at Si-H and/or Si-Si bonding sites present in the precursor molecules, and/or through additional condensation reactions on the growth surface if sufficient heat is provided.

The process conditions previously described herein can provide highly conformal thin film structures. The relatively mild process conditions can minimize the extent of ion bombardment at the substrate surface so that deposition is non-directional. In addition, the relatively mild process conditions can reduce the number of free radicals with high viscosity coefficients, which tend to adhere to the side walls of previously deposited film layers or films. In certain embodiments, for aspect ratios of about 2:1 to 10:1, silicon carbide films can be deposited with a conformality of between about 25% and 100%, more typically between about 50% and 100%, and even more typically between about 80% and 100%. Conformality can be calculated by comparing the average thickness of the deposited film on the bottom, sidewalls, or top of the feature to the average thickness of the deposited film on the bottom, sidewalls, or top of the feature. For example, conformality can be calculated by dividing the average thickness of the deposited film on the sidewalls by the average thickness of the deposited film at the top of the feature and multiplying by 100 to get the percentage. For some applications, a conformality of between about 85% and 95% is sufficient. In some examples, silicon carbide is deposited on features having an aspect ratio of between about 2:1 and about 4:1, and the conformality is at least about 90%. Certain BEOL processes (back end of line processes) fall into this category. In some examples, silicon carbide is deposited on features having aspect ratios between about 4:1 and about 6:1 with a conformality of at least about 80%. Certain spacer deposition processes fall within this category. In some examples, silicon carbide is deposited on features having aspect ratios between about 7:1 and about 10:1 (and even higher) with a conformality of at least about 90%. Certain DRAM (dynamic random access memory) manufacturing processes fall within this category.

The process conditions can also provide a thin film structure with high breakdown voltage and low leakage current. By introducing a limited amount of oxygen or nitrogen into SiC-like materials, leakage paths provided by Si-H bonds and/or Si-CH ₂ -Si bonds can be blocked by oxygen or nitrogen. The conduction modes in Si-O and Si-N may be different at low electric fields. This can provide improved electrical properties while maintaining a relatively low dielectric constant. In various embodiments, the film has an effective dielectric constant of about 5 or less, or about 4.0 or less, in some cases about 3.5 or less, in some cases about 3.0 or less, and even about 2.5 or less in some embodiments. The effective dielectric constant may depend on bonding and density. In some embodiments, SiOC films are made to have a dielectric constant of 6 or more, especially when the carbon content is relatively high. If leakage current is an important consideration, then SiOC films require a dielectric constant of less than 5. The lower the dielectric constant, the poorer the sealing and barrier and thermal resistance properties. In certain embodiments where applications require low sealing and diffusion confinement, excellent etch resistance, thermal stability, etc., the silicon carbide film can be made dense and highly cross-linked. This can be accomplished, for example, by a) depositing the film at relatively high temperatures, and/or b) providing a relatively high radical:precursor ratio. In certain embodiments, the silicon carbide film can be relatively thin and still serve as an effective seal and diffusion barrier.

In certain embodiments, the deposited film may be porous. As discussed previously herein, silicon-containing precursors may include cyclic siloxanes and cage siloxanes. Such precursors, and others with significant internal open space, may introduce significant porosity into the structure of the deposited film. The porosity in the deposited film may further reduce the dielectric constant. In certain embodiments, the deposited silicon carbide film has a porosity of between about 20% and 50%. The pore size of the porous film may follow the pore size of the ring or cage precursor. In certain embodiments, the average pore size of the film is between about 5Å and 20Å, for example, about 16Å. Applications

The present invention can be further understood by referring to the applications of high-quality silicon carbide films described below, which are purely illustrative. The present invention is not limited to the scope of specific applications, which are only examples of the present invention.

In some embodiments, a silicon carbide film may be deposited over the exposed copper. In some embodiments where the silicon carbide film is deposited, the reaction conditions adjacent to the substrate may be free of oxidants (e.g., O ₂ , O ₃ , and CO ₂ (including radicals thereof)). Thus, the silicon carbide film may be deposited directly over the exposed copper without oxidizing the copper (e.g., producing copper oxide). Such a film may be used as an etch stop layer, which may also be used as a copper diffusion barrier. The presence of the silicon carbide film may provide sufficiently low dielectric constant and excellent leakage characteristics to serve as a diffusion barrier. The silicon carbide film itself can be an etch stop and/or diffusion barrier layer, or a bilayer stack (e.g., a SiCO/SiNC bilayer deposited over exposed copper). In some embodiments, the silicon carbide film can be placed between adjacent metallization layers, typically produced by a damascene process. The silicon carbide film can resist etching and can be sufficiently dense to minimize diffusion of copper ions into adjacent regions of the dielectric material. In some embodiments, nitrogen can be incorporated into the film by using nitrogen-containing precursors or plasmas to activate nitrogen-containing radicals (e.g., elemental nitrogen radicals or amine radicals).

In some embodiments as shown in FIG. 1B , silicon carbide film 111 may be conformally deposited on features 112 of substrate 110. Features 112 may be isolated or densely packed features, wherein features 112 may have a relatively small critical dimension (CD). In some embodiments, features may have a CD equal to or less than about 20 nm, equal to or less than about 10 nm, or equal to or less than about 5 nm. The aspect ratio of the height to the width of features 112 may be greater than 2:1, greater than 5:1, greater than 10:1, or greater than 20:1. The step coverage of silicon carbide film 111 deposited on features 112 is at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99%.

In some embodiments, a silicon carbide film may be deposited as a vertical structure adjacent to a metal or semiconductor structure. The deposition of silicon carbide provides excellent step coverage along the sidewalls of the metal or semiconductor structure to produce the vertical structure. In some embodiments, the vertical structure may be referred to as a spacer or pad.

FIG1C shows a cross-section of a silicon carbide liner deposited on the sidewalls of a gate electrode structure of a transistor. As shown in FIG1C , the transistor may be a CMOS transistor, wherein a silicon substrate 120 has a source 122 and a drain 123. A gate dielectric 124 may be deposited over the silicon substrate 120, and a gate electrode 125 may be deposited over the gate dielectric 124 to form the transistor. A silicon carbide spacer or liner 121 may be deposited on the sidewalls of the gate electrode 125 and the gate dielectric 124.

In another example, FIG. 1D shows a cross-section of silicon carbide deposited on the sidewalls of an exposed copper line in an air-gap metallization layer. Air gaps 130 may be introduced into an integrated circuit layer between copper lines 132, which may reduce the effective dielectric constant value of the film layer. Silicon carbide pads 131 may be deposited on the sidewalls of copper lines 132, and a non-conformal dielectric layer 133 may be deposited on the air gaps 130, pads 131, and copper lines 132. Examples of such air-gap metallization layers are described in U.S. Patent Publication No. 2004/0232552 to Fei Wang et al., which is incorporated herein by reference in its entirety for all purposes.

In some embodiments, silicon carbide films may be deposited on the sidewalls of a patterned porous dielectric material. Ultra-low-k dielectric materials may be made from porous structures. The pores in such materials may provide areas for metal to enter during the deposition of subsequent film layers, including during the deposition of diffusion barriers containing metals such as tantalum (Ta). If too much metal migrates into the dielectric material, the dielectric material may cause shorts between adjacent copper metallization lines.

FIG. 1E shows a cross-section of a silicon carbide film as a pore filler for a porous dielectric material. The porous dielectric layer 142 may have trenches or through holes cut into the porous dielectric layer 142 to form the pores 140. The silicon carbide film 141 may be deposited along the pores 140 to effectively seal the pores 140. Sealing the pores 140 with the silicon carbide film 141 may avoid damage to the porous dielectric layer 142 that may be incurred by other sealing techniques using plasma. The silicon carbide film 141 may be sufficiently dense to act as a pore filler. In certain embodiments, the etched dielectric material (e.g., porous dielectric layer 142) may first be subjected to a "k-recovery" process that exposes porous dielectric layer 142 to UV radiation and a reducing agent. This recovery process is further described in co-owned U.S. Patent Publication No. 2011/0111533 to Varadarajan et al., which is hereby incorporated by reference in its entirety for all purposes. In another "k-recovery" process, porous dielectric layer 142 may be exposed to UV radiation and a chemical silanizing agent. This recovery process is further described in co-owned U.S. Patent Publication No. 2011/0117678 to Varadarajan et al., which is hereby incorporated by reference in its entirety for all purposes. After exposing the pores 140 to a recovery treatment to render the surface more hydrophilic and provide a monolayer of material, a conformally deposited silicon carbide film 141 may be deposited to effectively seal the pores 140 of the porous dielectric layer 142.

In certain embodiments, a silicon carbide film may be deposited as an ultra-low dielectric material itself. An ultra-low dielectric material is conventionally defined as a material having a dielectric constant less than 2.5. In such configurations, the ultra-low dielectric material of silicon carbide may be a porous dielectric layer. Porosity in the dielectric layer may be introduced by using ring-shaped or cage-shaped precursor molecules, including cyclosiloxanes and silsesquioxanes. In one example, the porosity of the ultra-low dielectric layer of silicon carbide may be between about 20% and 50%. Furthermore, the ultra-low dielectric layer may have an average pore size of less than about 100 Å, such as between about 5 Å and 20 Å. For example, a cyclosiloxane ring may have a radius of about 6.7 Å. Although increasing the number and size of pores can reduce the dielectric constant, making the dielectric layer too porous may compromise the mechanical integrity of the dielectric layer. Conclusion

In the above description, numerous specific details are set forth to provide a thorough understanding of the embodiments presented. The disclosed embodiments may be practiced without some or all of these specific details. In other examples, in order not to obscure the present invention, well-known process operations are not described in detail. Although the disclosed embodiments are described in conjunction with specific embodiments, it should be understood that they are not intended to limit the disclosed embodiments.

The above embodiments have been described in detail to enable those skilled in the art to clearly understand the present invention, and it should be understood that certain changes and modifications may be made within the scope of the attached patent claims. It should be noted that there are many alternative ways to implement the processes, systems, and apparatus of the embodiments herein. Therefore, the embodiments herein should be considered to be illustrative rather than restrictive, and the embodiments are not limited to the details provided herein.

100: substrate 101: silicon carbide film 110: substrate 111: silicon carbide film 112: feature 120: silicon substrate 121: silicon carbide spacer/pad 122: source 123: drain 124: gate dielectric 125: gate electrode 130: air gap 131: pad 132: copper wire 133: non-conformal dielectric layer 140: pores 141: silicon carbide film 142: porous dielectric layer 300: device 310: reaction chamber 320: showerhead 330: substrate 335: base 340: controller 350: container 355: a gas inlet 360: remote plasma source 365: second gas inlet 400: equipment 402: remote plasma source 404: reaction chamber 406: multi-port gas distributor 408: chemical vapor deposition area 412: substrate 414: base 418: coil 422: plasma generator controller 424: plasma area 426: source gas supply 428: gas supply 434: multiple gas ports 438: relaxation area 440: precursor supply source 442: gas outlet 448: outlet 450: controller 452: processor system 454: data system

FIG. 1A shows a schematic cross-sectional view of an exemplary doped or undoped silicon carbide film deposited on a substrate.

FIG. 1B shows a schematic cross-sectional view of an exemplary doped or undoped silicon carbide film conformally deposited on a feature of a substrate.

FIG. 1C is a schematic cross-sectional view of an exemplary doped or undoped silicon carbide vertical structure on the sidewall of the gate electrode of a transistor.

FIG. 1D is a schematic cross-sectional view of an exemplary doped or undoped silicon carbide vertical structure on the exposed sidewall of a copper line in an air-gap metallization layer.

FIG. 1E is a schematic cross-sectional view of an exemplary doped or undoped silicon carbide pore filler of a porous dielectric material.

FIG2 shows the chemical structures of representative examples of cage-type siloxane promotors.

FIG. 3 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source, according to some embodiments.

According to some other embodiments, FIG. 4 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source.

FIG. 5 shows an example of the chemical reaction between activated alkanes (plurality) from carbon-containing precursors and activated silane-based precursors.

FIG. 6A shows FTIR spectra of remote plasma CVD of silicon carbide films using a silicon-containing precursor and varying amounts of carbon-containing precursors.

FIG6B shows an enlarged view of a portion of the FTIR spectrum in FIG6A.

FIG. 7 shows a TEM image of a silicon carbide film deposited on a substrate feature using a silicon-containing precursor and a carbon-containing precursor.

400: Equipment

402: Remote plasma source

404: Reaction chamber

406: Multi-port gas distributor

408: Chemical vapor deposition area

412: Substrate

414: Base

418: Coil

422: Plasma generator controller

424: Plasma area

426: Source gas supply department

428: Gas supply department

434: Multiple gas ports

438: Relaxation area

440: Source of supply of precursor materials

442: Gas outlet

448:Export

450: Controller

452: Processor system

454:Data system

Claims (17)

A method for depositing a silicon carbide film on a substrate, the method comprising: providing a substrate in a reaction chamber; flowing a silicon-containing precursor into the reaction chamber and toward the substrate, wherein the silicon-containing precursor has at least two hydrogen atoms bonded to silicon atoms; flowing a carbon-containing precursor into the reaction chamber together with the silicon-containing precursor, wherein the silicon-containing precursor and the carbon-containing precursor flow into the reaction chamber through one or more gas outlets downstream of a gas distributor for delivering free radical species, wherein the The carbon-containing precursor is a hydrocarbon molecule having one or more carbon-carbon double bonds or triple bonds; hydrogen radicals are generated from a hydrogen source gas in a remote plasma source, and the hydrogen radicals are generated upstream of the silicon-containing precursor and the carbon-containing precursor; and the hydrogen radicals are introduced into the reaction chamber and toward the substrate through the gas distributor, wherein the hydrogen radicals are in a ground state to react with the silicon-containing precursor and the carbon-containing precursor, thereby forming a doped or undoped silicon carbide film on the substrate. As in the method of depositing a silicon carbide film on a substrate as claimed in item 1 of the patent application, all or substantially all of the hydrogen radicals in the environment adjacent to the substrate are hydrogen radicals in the ground state. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the hydrocarbon molecule comprises propylene, butene, pentene, butadiene, pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne, butyne, pentyne, or hexyne. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor comprises silane, disilane, trisilane, methylsilane, or dimethylsilane. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor having at least two hydrogen atoms bonded to the silicon atom does not have more than two carbon atoms, nitrogen atoms, and/or oxygen atoms bonded to the silicon atom. A method for depositing a silicon carbide film on a substrate as in item 1 of the patent application, wherein the doped or undoped silicon carbide film has no C-C bonding or substantially no C-C bonding. A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application scope, further comprising: providing a nitriding agent together with the hydrogen source gas in the remote plasma source, wherein the free radicals of the nitriding agent are generated in the remote plasma source; and introducing the free radicals of the nitriding agent together with the free radicals of hydrogen into the reaction chamber and toward the substrate, wherein the free radicals of the nitriding agent and the hydrogen react with the silicon-containing precursor and the carbon-containing precursor to form a silicon carbonitride (SiCN) film. As in item 7 of the patent application scope, a method for depositing a silicon carbide film on a substrate, wherein the SiCN film has no C-C bonding or substantially no C-C bonding, and has no C-N bonding or substantially no C-N bonding. The method for depositing a silicon carbide film on a substrate as claimed in claim 7, wherein the nitriding agent comprises nitrogen (N ₂ ) or ammonia (NH ₃ ). A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application scope further comprises: providing an oxidant together with the hydrogen source gas in the remote plasma source, wherein the free radicals of the oxidant are generated in the remote plasma source; and introducing the free radicals of the oxidant together with the free radicals of hydrogen into the reaction chamber and toward the substrate, wherein the free radicals of the oxidant and hydrogen react with the silicon-containing precursor and the carbon-containing precursor to form a silicon oxycarbide (SiCO) film. As in item 10 of the patent application scope, a method for depositing a silicon carbide film on a substrate, wherein the SiCO film has no C-C bonding or substantially no C-C bonding, and has no C-O bonding or substantially no C-O bonding. In the method for depositing a silicon carbide film on a substrate as claimed in claim 10, the oxidant comprises carbon dioxide (CO ₂ ), carbon monoxide (CO), oxygen (O ₂ ), ozone (O ₃ ), or nitrous oxide (N ₂ O). A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application, wherein the silicon-containing precursor is a silane-based precursor. A method of depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application, wherein the doped or undoped silicon carbide film has a conformality of at least 75%. A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application, wherein the silicon carbide film is undoped silicon carbide (SiC). A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application, wherein the atomic concentration of silicon in the doped or undoped silicon carbide film is at least 25%, and wherein the atomic concentration of carbon in the doped or undoped silicon carbide film is at least 25%. A method for depositing a silicon carbide film on a substrate as claimed in any one of items 1 to 6 of the patent application, wherein the silicon-containing precursor does not have (i) C-O bonding and (ii) C-N bonding.