Film deposition utilizing reactant in secondary purge gas flow

Abstract

Examples are disclosed that provide a reactant, such as an etching or passivation agent, in a secondary purge gas flow. One example provides a processing tool. The processing tool comprises a processing chamber, a showerhead, a secondary purge gas outlet configured to flow a secondary purge gas into the processing chamber around an outside edge of the showerhead, and flow control hardware configured to connect one or more processing gas sources with the showerhead and the secondary purge gas outlet. The processing tool further comprises a controller configured to control the flow control hardware to introduce a flow of a film precursor and a first reactant into the processing chamber through the showerhead during a deposition process, and to introduce a flow of a secondary purge gas comprising at least a second reactant into the processing chamber through the secondary purge gas outlet during the deposition process.

Description

FILM DEPOSITION UTILIZING REACTANT IN SECONDARY PURGEGAS FLOWBACKGROUND

[0001] Electronic device fabrication processes can involve many steps of material deposition, patterning, and removal to form integrated circuits on substrates. Various methods can be used to deposit films of materials onto a substrate. As one example, chemical vapor deposition (CVD) can be used to deposit a film by exposing a substrate to a flow of gas phase precursors. The gas phase precursors undergo chemical reactions to form a film on the substrate. Plasma-enhanced CVD (PECVD) utilizes a plasma to provide energy for the chemical conversion of the precursors to the film. CVD processes can be used to deposit a wide variety of films, including carbon films.SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] One example provides a processing tool. The processing tool comprises a processing chamber, a showerhead, a secondary purge gas outlet configured to flow a secondary purge gas into the processing chamber around an outside edge of the showerhead, and flow control hardware configured to connect one or more processing gas sources with the showerhead and the secondary purge gas outlet. The processing tool further comprises a controller configured to control the flow control hardware to introduce a flow of a film precursor and a first reactant into the processing chamber through the showerhead during a deposition process, and to introduce a flow of a secondary purge gas comprising at least a second reactant into the processing chamber through the secondary purge gas outlet during the deposition process.

[0004] In some such examples, the first reactant and the second reactant are a same reactant.

[0005] In some such examples, the first reactant is different from the second reactant.

[0006] Alternatively or additionally, in some such examples, the processing tool further comprises a carbon-containing precursor source.

[0007] Alternatively or additionally, in some such examples, the controller is configured to control the flow control hardware to include the carbon-containing precursor in the secondary purge gas.

[0008] Alternatively or additionally, in some such examples, the processing tool further comprises a silicon-containing precursor source.

[0009] Alternatively or additionally, in some such examples, the processing tool further comprises a reactant source, wherein the reactant comprises one or more of hydrogen (H2), carbon dioxide (CO2), ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb, wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O) oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

[0010] Another example provides a method of depositing a film. The method comprises introducing a flow of a film precursor and a first reactant into a processing chamber through a showerhead during a deposition process, and introducing a flow of a secondary purge gas comprising at least a second reactant into the processing chamber through the secondary purge gas outlet during the deposition process.

[0011] In some such examples, the second reactant comprises one or more of an etching agent, a passivation agent, an inhibitor, or an oxidant.

[0012] Alternatively or additionally, in some such examples, the first reactant and the second reactant are a same reactant.

[0013] Alternatively or additionally, in some such examples, the film precursor is a carbon-containing precursor.

[0014] Alternatively or additionally, in some such examples, the secondary purge gas further comprises the carbon-containing precursor.

[0015] Alternatively or additionally, in some such examples, the reactant comprises one or more of hydrogen (H2) or carbon dioxide (CO2), ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb,wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O) oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

[0016] Alternatively or additionally, in some such examples, the secondary purge gas further comprises a silicon-containing precursor.

[0017] Alternatively or additionally, in some such examples, the method further comprises tuning one or more of a concentration of the second reactant added to the secondary purge gas or a flow rate of the second reactant added to the secondary purge gas to achieve a selected film thickness uniformity.

[0018] Another example provides a method of depositing a film, the method comprising introducing a flow of a film precursor and a first reactant into a processing chamber through a showerhead during a deposition process, and introducing a flow of a secondary purge gas comprising at least the film precursor into the processing chamber through a secondary purge gas outlet during the deposition process.

[0019] In some such examples, the film precursor comprises a carbon- containing precursor.

[0020] In some such examples, the film precursor comprises a silicon- containing precursor.

[0021] Alternatively or additionally, in some such examples, the first reactant comprises one or more of hydrogen (H2), carbon dioxide (CO2) ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb, wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

[0022] Alternatively or additionally, in some such examples, the method further comprises tuning one or more of a concentration of film precursor added to the secondary purge gas or a flow rate of film precursor added to the secondary purge gas to achieve a selected film thickness uniformity.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1 A-1D schematically show examples of structures that are formed in a three-dimensional (3D) memory fabrication process.

[0024] FIG. 2 schematically shows a film deposition process in which a reactant is included in a secondary purge gas.

[0025] FIG. 3 shows a plot of a radial film thickness profile for an example carbon film deposited without a reactant gas in the secondary purge gas, and a plot of a radial film thickness profile for an example carbon film deposited with carbon dioxide (CO2) in the secondary purge gas.

[0026] FIG. 4 shows a plot of a radial film thickness profile for an example carbon film deposited without a reactant gas in the secondary purge gas, and a plot of a radial film thickness profile for an example carbon film deposited with hydrogen (H2) in the secondary purge gas.

[0027] FIGS. 5 A and 5B show a schematic depiction of a modification of a processing gas delivery system of a processing tool to connect a reactant gas to a secondary purge outlet for a processing chamber.

[0028] FIG. 6 shows a schematic depiction of an example processing tool.

[0029] FIG. 7 shows a block diagram of an example computing device.DETAILED DESCRIPTION

[0030] The term “carbon-containing precursor” generally represents any material that can be introduced into a processing chamber in a gas phase to form a carbon-containing film on a substrate. Examples of carbon-containing precursors include alkanes having a general formula CnH2n+2 where n is an integer in a range of 1 to 10 (such as, methane, ethane, etc.), alkenes having a general formula CnEEn where n = 2 to 10 (such as, ethylene, propylene, etc.), and alkynes having a general formula CnH2n-2 where n = 2 to 10 (such as, acetylene, propyne, etc.), that are gas-phase under processing conditions. Other examples of carbon-containing film precursors comprise cyclic hydrocarbons (including aromatics), and alkyl amines and other nitrogencontaining compounds, that are gas-phase under processing conditions.

[0031] The term “chemical vapor deposition” (CVD) generally represents a process in which a solid phase film is formed on a substrate by directing a flow of one or more precursor gases over the substrate surface under processing conditions configured to cause the chemical conversion of the precursor gases to the solid phase film. The term “plasma-enhanced chemical-vapor deposition” (PECVD) generally represents a CVD process in which a plasma is used to facilitate the chemical conversion of one or more precursor gases to a solid phase film on a substrate. The terms “growth”, “deposition”, and variants thereof, also can be used to refer to film formation.

[0032] The term "etching agent" generally represents any material used in a PECVD processing gas mixture to remove materials from a substrate. Example etching agents include hydrogen (H2), halogen-containing gases, and oxygen-containing gases. Example halogen-containing etching agents include chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), halogen acids (hydrofluoric acid (HF), hydrochloric acid (HC1), hydrobromic acid (HBr), hydroiodic acid (HI)), nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), halocarbon gases having a general formula CaXb (where X comprises one or more of fluorine, chlorine, bromine, or iodine and where a = 1-10), and halohydrocarbon gases having a general formula CaHbXc (where X comprises one or more of fluorine, chlorine, bromine, or iodine and where a = 1-10). Example oxygen-containing etching agents include carbon monoxide (CO), carbon dioxide (CO2), carbon oxysulfide (COS), sulfur dioxide (SO2), and molecular oxygen (O2).

[0033] The term “flow control hardware” generally represents components configured to place one or more chemical sources in fluid connection with a processing chamber. Flow control hardware can comprise one or more mass flow controllers, valves, and various conduits, for example. Example chemical sources include film precursor sources, purge gas sources, and reactant gas sources.

[0034] The term "passivating agent" generally represents a material in a PECVD processing gas mixture that can physisorb or chemisorb to a substrate surface to reduce a rate of PECVD film formation on the substrate surface. Example passivating agents that can provide hydrogen ions and / or hydrogen radicals include hydrogencontaining molecules. Example hydrogen-containing molecules that can be used as passivating agents include molecular hydrogen (H2) and ammonia (NH3).

[0035] The term “plasma” generally represents an ionized gas comprising gasphase cations and free electrons.

[0036] The term “processing chamber” generally represents an enclosure in which chemical and / or physical processes are performed on substrates. The pressure, temperature, gas flow rate, and atmospheric composition within a processing chamber can be controllable to perform chemical and / or physical processes.

[0037] The term “reactant” generally represents a chemical that can participate in chemical vapor deposition processes together with a film precursor. A reactant can be any substance that undergoes a chemical reaction during a deposition process.Examples of reactants include etching agents, passivation agents, inhibitors, oxidants, and film precursors.

[0038] The term “secondary purge gas flow” generally represents a flow of gas formed around an outside edge of a showerhead to help isolate the processing environment to the region between the showerhead and the substrate holder from the processing environment outside of this region.

[0039] The term “secondary purge gas outlet” generally represents a gas outlet configured to form secondary purge gas flow around an outside edge of the showerhead.

[0040] The term “showerhead” generally represents a processing chemical outlet comprising a plurality of holes distributed across an area.

[0041] The term “silicon-containing precursor” generally represents any material that can be introduced into a processing chamber in a gas phase to form a silicon-containing film on a substrate. Example silicon-containing films include silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, and silicon oxycarbonitride. Example silicon-containing film precursors for forming silicon-containing films using PECVD can comprise materials having the general structure:where Ri, R2 and R3 can be the same or different substituents. In various examples, Ri, R2, and R3 can include silanes, siloxy groups, amines, halides, hydrogen, or organic groups such as alkylamines, alkoxy, alkyl, alkenyl, alkynyl, and cyclic groups (such as aromatic groups).

[0042] In some examples, the silicon-containing precursor is an alkoxysilane. Alkoxysilanes that can be used include those having a composition of Hx-Si-(OR)y, where x = 1-3, x+y = 4 and each R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, or substituted or unsubstituted aromatic group; and Hx(RO)y,-Si-Si-(OR)yHx, where each R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, or substituted or unsubstituted aromatic group. Example alkoxysilanes include tetramethoxysilane (TMOS), diethoxymethylsilane (DEMS),diethoxysilane (DES), dimethoxymethylsilane, dimethoxysilane (DMOS), methyldiethoxysilane (MDES), methyl-dimethoxysilane (MDMS), t-butoxydisilane, triethoxysilane (TES), and trimethoxysilane (TMS or TriMOS).

[0043] In some examples, the silicon-containing precursor is a siloxane. Siloxanes include materials having Si-O-Si linkages. Example siloxanes include octamethylcyclotetrasiloxane (OMCTS), octamethoxydodecasiloxane (OMODDS), and tetramethylcyclotetrasiloxane (TMCTS).

[0044] In some examples, the silicon-containing precursor is an aminosilane. Aminosilanes include materials having the general formula Hx-Si-(NR)y, where x = 1- 3, x+y = 4, and R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aromatic group, or hydride group. Example aminosilanes include bisdiethylaminosilane, diisopropylaminosilane, bis(t-butylamino) silane (BTBAS), di-sec-butylaminosilane, and tris(dimethylamino)silane (3DMAS).

[0045] In some examples, the silicon-containing precursor can be a halosilane. In some examples, a halosilane can comprise at least one hydrogen atom. Such a silane can have a chemical formula of SiXaHy where y = 1-3, a+y = 4. Examples of halosilanes can include dichlorosilane (EESiCh), hexachlorodi silane (Si2Cle), and diiodosilane (H2SH2).

[0046] More specific examples of silicon-containing precursors include polysilanes (SinH211+2, where n >1, such as silane, disilane, trisilane, and tetrasilane), trisilylamine, tetraethyl orthosilicate (TEOS), methylsilane, trimethylsilane (3MS), ethylsilane, butasilanes, pentasilanes, octasilanes, heptasilane, hexasilane, cyclobutasilane, cycloheptasilane, cyclohexasilane, cyclooctasilane, cyclopentasilane, l,4-dioxa-2,3,5,6-tetrasilacyclohexane, triethoxysiloxane (TRIES), and tetraoxymethylcyclotetrasiloxane (TOMCTS).

[0047] An example precursor for providing nitrogen for formation of a silicon nitride film is nitrogen (N2). An example precursor for providing nitrogen and oxygen for formation of a silicon oxynitride film is N2O.

[0048] In some examples, an oxidant is used to react with a silicon-containing film precursor. Examples include molecular oxygen (O2), water (H2O), hydrogen peroxide (H2O2), ozone (O3), carbon dioxide (CO2), and nitrogen oxides such as nitrous oxide (N2O).

[0049] The term “substrate” generally represents any object on which a film can be deposited.

[0050] The term “3D NAND” is an abbreviation of three-dimensional NOT AND, and generally represents memory architecture based upon NOT AND logic gates.

[0051] The term “3D NOR” is an abbreviation of three-dimensional NOT OR, and generally represents memory architecture based upon NOT OR logic gates.

[0052] The term “3D DRAM” is an abbreviation of three-dimensional dynamic random access memory.

[0053] As described above, the fabrication of electronic devices involves many steps of material deposition, patterning, and removal to form integrated circuits and / or memory structures on substrates. For example, some three-dimensional (3D) integrated circuits, such as 3D NAND (Not AND) memory devices, are fabricated using stacked pairs of materials, with the "active" device layer being one of the pairs and the other being a dielectric for electrical isolation. By stacking these pairs of layers, manufacturers are able to create more active layers. A stack of such alternating layers can be referred to as a mold stack. As a more specific example, alternating silicon oxide and silicon nitride layers can be deposited to form an ONON (oxide-nitride-oxide- nitride) mold stack in a 3D NAND fabrication process. As another example, a mold stack can comprise alternating silicon layers and polysilicon layers (OPOP), where the term polysilicon generally represents polycrystalline silicon. Other examples of 3D integrated circuits include 3D DRAM and 3D NOR memory devices.

[0054] Patterning and device integration in a 3D integrated circuit fabrication process often involves etching holes through a mold stack. However, etching of deep, high aspect ratio features, such as channel holes in a 3D NAND mold stack, can be challenging. Thus, the etching of a deep, high aspect ratio feature can be performed in more than one discrete etching process. In the example of a 3D NAND mold stack, a first set of alternating layers (a first “deck” of the mold stack) can be deposited, and then a first hole can be etched through the first deck. Next, the first hole in the first deck can be plugged with a material having sufficiently high selectivity to the etching process to form an etch stop layer. Carbon is one example of an etch stop layer. Then, a second set of alternating layers (a second deck) can be deposited, and a second hole can be etched through the second deck in alignment with the first hole. The carbon plug then can be removed, joining the first hole and the second hole.

[0055] Plasma enhanced chemical vapor deposition (PECVD) can be used to form a carbon etch stop layer. In such a process, PECVD is used deposit carbon in the hole and on surrounding regions of the substrate. Planarization (e.g. chemical mechanical planarization (CMP)) then is performed to remove the carbon from the surrounding regions of the substrate.

[0056] FIGS. 1 A-1D illustrate structures that can be formed during an example 3D NAND fabrication process. First, FIG. 1A shows a structure 100 that represents a first mold stack 102 with a hole 104 etched therethrough to an underlying layer 103. Field regions 105 of the first mold stack 102 are adjacent to the hole 104. Next, FIG. IB shows structure 106 that represents the first mold stack 102 after deposition of an amorphous carbon film, but prior to planarization. In structure 106, the carbon film has formed a carbon plug 108 within the hole 102 as an etch stop layer. Further, the carbon film also includes a carbon overburden 110 formed over the field regions 105.

[0057] Next, in FIG. 1C, structure 112 shows the carbon plug 108 after the carbon overburden 110 has been removed by planarization. Planarization can be performed, for example, by chemical mechanical planarization (CMP). Continuing to FIG. ID, structure 114 shows a second mold stack 116, and a hole 118 etched through the second mold stack 116. The etching process to form the hole 118 through the second mold stack 116 substantially slows upon reaching the carbon plug 108, thereby protecting the surfaces within the hole 102 of the first mold stack 102 from the etching process that forms the hole 118 in the second mold stack. Then, the carbon plug 108 can be removed (e.g. by oxidation to volatile carbon oxides), thereby connecting holes 118 and 104.

[0058] In some PECVD systems, processing chemicals are introduced into a reduced-pressure processing chamber through a showerhead. The term “showerhead” generally represents a processing chemical outlet with a plurality of outlet holes spatially distributed over an area. The outlet holes face a substrate on which a film is being deposited. The substrate is positioned on a substrate holder, and can be heated. The substrate holder and the showerhead can form a pair of electrodes. Radiofrequency energy can be applied to one of the substrate holder or the showerhead, while the other can be at ground potential or other suitable potential. The radiofrequency energy creates a capacitively coupled plasma between the showerhead and the substrate holder. The plasma can create reactive species from precursor molecules introduced through the showerhead. The reactive species then can adsorb to the surface of the substrate andreact to form a desired film on the substrate. In other examples, an inductively coupled plasma or microwave plasma can be generated.

[0059] In some PECVD systems, a secondary flow of gas is formed around the outside edge of the showerhead. This flow of gas can be referred to as a secondary purge gas flow. Typically, a gas that is inert to a process being performed is used as a secondary purge gas. For example, helium, argon, and / or nitrogen, including mixtures thereof, can be used as a secondary purge gas. The secondary purge gas flow helps to isolate the processing environment to the region between the showerhead and the substrate holder from the processing environment outside of this region.

[0060] One challenge that can be encountered in depositing a film using PECVD is non-uniformity in film thickness. Film thickness variations outside of a specified tolerance for a process can potentially cause issues in downstream processing. For example, as described above, a hardmask plug can be formed by a deposition process followed by a planarization process. As amorphous carbon is an electrical conductor, carbon remaining behind after planarization can cause electrical shorts between mold stacks. Thus, it is important to remove the carbon overburden 110 before depositing a second mold stack on the first mold stack. However, if the nonuniformity of the carbon film is outside of a specified maximum, removal of the carbon overburden 110 by planarization can pose issues. For example, performing CMP for sufficiently long to remove carbon from thicker overburden regions can result in removing too much material (e.g. removal of a portion of a carbon plug from within a hole and / or removing a portion of a mold stack layer), thereby causing damage to the structure. This can impact the performance of the resulting integrated circuit.

[0061] Carbon PECVD can be performed by introducing a carbon-containing precursor and another reactant, such as carbon dioxide (CO2) and / or hydrogen gas (H2), through the showerhead. The carbon dioxide or hydrogen can act as a passivating or etching agent, providing for more controlled deposition. Example carbon-containing precursors can include alkanes having a general formula CnH2n+2 where n = 1 to 10 (such as methane, ethane, etc.), alkenes having a general formula CiJLn where n = 2 to 10 (such as ethylene, propylene, etc.), alkynes having a general formula CnH2n-2 where n = 2 to 10 (such as acetylene, propyne, etc.), cyclic hydrocarbons (including aromatics), and alkyl amines and other nitrogen-containing compounds, that are gasphase under processing conditions. Other example reactants include ammonia (NH3), and halocarbons (CaXb, wherein X is a halogen).

[0062] PECVD also can be used to deposit films of other materials, such as silicon-containing films. Examples include silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, and silicon carbonitride films. Silicon- containing films can be deposited, for example, to form a mold stack, or as part of a gapfill process. Silicon oxide PECVD can be performed by introducing a silicon- containing precursor, and a second reactant, such as nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), hydrogen peroxide (H2O2), or carbon dioxide (CO2). In PECVD of silicon nitride films, ammonia can be used as a second reactant. Examples of silicon-containing precursors include silane (SiEU), halosilanes (e.g., chlorosilane), aminosilanes, and alkoxysilanes such as tetraethyl orthosilicate (TEOS). In further examples, PECVD can be used to deposit a metal oxide film, such as aluminum oxide, molybdenum oxide, tungsten oxide, or hafnium oxide.

[0063] When depositing carbon films using PECVD, thicker carbon regions can form closer to an edge of a substate relative to regions closer to a center of the substrate. Such thicker regions can result in film thickness nonuniformities outside of a specification. This can arise from the etching or passivation agent (e.g. CO2 or H2) having higher concentrations at a central region of the substrate than at an edge region of the substrate. More generally, when depositing films using PECVD, nonuniformities in film thickness can form closer to an edge of a substrate relative to regions closer to a center of the substrate.

[0064] Accordingly, the disclosed examples provide a reactant, such as an etching or passivation agent, in a secondary purge gas flow. FIG. 2 schematically depicts such an example. In FIG. 2, a substrate 202 is positioned on a substrate holder 204 beneath a showerhead 206. A plasma 208 is formed between the substrate holder 204 and the showerhead 206. The substrate holder 204 can include a heater to heat the substrate 200. The depicted components are located inside of a processing chamber, which is not shown in FIG. 2.

[0065] A mixture of reactants, here shown as a carbon-containing precursor and hydrogen gas and / or carbon dioxide, is introduced through the showerhead 206. The plasma 208 forms reactive species from the reactants. The reactive species react to form an amorphous carbon film on the substrate 202. The hydrogen or carbon dioxide reacts with the growing film to etch and / or passivate the carbon film surface by forming hydrocarbons and / or carbon oxides. This helps to control the deposition rate and profile.

[0066] However, as mentioned above, the concentrations of reactive hydrogen and / or reactive carbon oxide / oxygen species formed in the plasma can be lower in an edge region of the substrate than in a center region of the substrate. This can result in the carbon film being thicker at the edge region than at the center region. Thus, as shown in FIG. 2, a reactant (here hydrogen and / or carbon dioxide) can be introduced into a secondary purge gas flow around the showerhead. This can increase a concentration of hydrogen and / or carbon dioxide at the edge region of the substrate. The hydrogen and / or carbon dioxide from the secondary purge gas then can be converted into reactive species by the plasma 208. This increases a concentration of such reactive species compared to examples in which inert gas is used alone is used as a secondary purge gas. This, in turn, can help reduce nonuniformities in film thickness compared to examples in which inert gas is used alone as a secondary purge gas. In some examples, a same reactant or reactants are provided through the showerhead and through the secondary purge gas outlet. In other examples, one or more different reactants can be provided through the showerhead and through the secondary purge gas outlet.

[0067] Deposition can be performed using any suitable processing conditions. Examples of suitable processing conditions include substrate heater temperatures of 350 °C to 1000 °C and pressures of 50 mTorr to 40 Torr. When depositing films using PECVD, a radiofrequency (RF) plasma can be formed using single frequency RF power, or multifrequency RF power. Examples of single frequency RF power include frequencies of 13.56 MHz to 40 MHz and powers of 50 W to 5000 W. Multifrequency RF power comprises two or more RF power components at a corresponding two or more different frequencies. Multifrequency RF power comprises at least a first, lower- frequency RF power component and a second, higher-frequency RF power component. The lower-frequency RF power component comprises a frequency within a range of 400 kHz to 3 MHz, and a power of 0 to 1000 W. The higher-frequency RF power component comprises a frequency within a range of 3 MHz to 300 MHz, and a power of 50 W to 5000 W. Unless otherwise stated, values for RF power refers to power per station. RF power for a multi-station processing chamber can be scaled accordingly.

[0068] Additionally, a secondary purge gas can include any suitable mixture of gases. For example, when CO2 is included in the secondary purge gas, the gas flow can include 0% to 55% CO2 by mole fraction in some examples. As another example, when H2 is included in the secondary purge gas, the gas flow can include 0% to 55% H2 by mole fraction. In other examples, mole fractions outside these ranges can be used.

[0069] FIG. 3 shows a plot of a radial film thickness profile for a carbon film deposited without a reactant gas in the secondary purge gas (lower dashed line in the plot), and a plot of a radial film thickness profile for a carbon film deposited with CO2 in the secondary purge gas (upper solid line in the plot). The secondary purge gas included approximately 60% nitrogen and 40% argon for the deposition that omitted the CO2 (dashed line). The secondary purge gas flow included approximately 40% nitrogen, 9% argon, and 51% CO2 for the deposition in which CO2 was included (solid line). Percentages indicate a mole fraction of a gas. Further, dynamic temperature control (DTC) was used to dynamically adjust power to an outer radius of the substrate to help reduce a film nonuniformity as a function of radial location for the film deposited without CO2 in the secondary purge gas. The radial position of zero on the x- axis corresponds to a center of the substrate. The dots at each radial position correspond to measurements made at different angular locations for each radial distance. The lines through the dots correspond to an average thickness at each radial distance (i.e. an average of all of the data from different angular locations at a selected radial distance). As can be seen, the deposition that utilized the CO2 in the secondary purge gas produced a carbon film with a more uniform thickness compared to the deposition that omitted the CO2 in the secondary purge gas.

[0070] FIG. 4 shows a plot of a radial film thickness profile for a carbon film deposited without a reactant gas in the secondary purge gas (dashed line), and a plot of a radial film thickness profile for a carbon film deposited with H2 in the secondary purge gas (solid line). The secondary purge gas again included nitrogen and argon for the deposition that omitted the H2. For the deposition that included H2, the secondary purge gas included nitrogen / argon / Fb, with a mole fraction of H2 of approximately 10%. Further, a temperature differential was used to reduce the radial thickness increase closer to the edge for the film deposited without H2 in the secondary purge gas. The radial position of zero on the x-axis corresponds to a center of the substrate. The dots at each radial position correspond to measurements made at different angular locations for each radial distance. The lines through the dots correspond to an average thickness at each radial distance (i.e. an average of all of the data from different angular locations at a selected radial distance). As can be seen, the deposition that utilized the H2 in the secondary purge gas produced a carbon film with a more uniform thickness compared to the deposition that omitted the H2 in the secondary purge gas.

[0071] FIGS. 5 A and 5B show a schematic depiction of a modification of a processing gas delivery system of a processing tool to connect a reactant gas to a secondary purge outlet for a processing chamber. The processing gas delivery system comprises a first manifold 502, a second manifold 504, a third manifold 506, and a fourth manifold 508. In FIG. 5A, first manifold 502, second manifold 504, and fourth manifold 508 each provide a respective flow of gas to the showerhead of the processing tool. Additionally, third manifold 506 provides a flow of an inert purge gas to the secondary purge gas outlet. To modify the processing gas delivery system of FIG. 5 A to deliver a reactant (e.g. an etching and / or passivation agent) to the secondary purge gas outlet, a manifold that provides a flow of the reactant (fourth manifold 508 in this example) is also connected to the secondary purge gas outlet. Various hardware items, such as conduits, valves, T-connectors, joints, etc. can be provided as a conversion kit to modify a deposition tool to provide reactant gas to a secondary purge gas outlet.

[0072] A concentration and / or flow rate of reactant added to a secondary purge gas can be adjusted to provide a range of tuneability for achieving a desired film thickness uniformity. This may provide a larger window of tuneability than dynamic temperature control, which allows radial variations of substrate temperature to be achieved. The addition of a reactant to a secondary purge gas further provides an additional control besides dynamic temperature control, such that the two together can be controlled in some examples to achieve or surpass a desired nonuniformity specification for a film. Also, the addition of a reactant to a secondary purge can help to avoid potential damage to a substrate holder that can arise due to temperature differentials as a function of radial location on the substrate holder. Further, while the examples described above disclose the addition of a reactant in the form of an etching agent or passivating agent to the secondary purge gas, in other examples, a film precursor can be added to the secondary purge gas flow. For example, in a carbon deposition process in which a central region of a carbon film on a substrate tends to grow thicker than an edge region of the carbon film, a carbon-containing precursor can be included in a secondary purge gas flow to increase a deposition rate of carbon in the edge region. In some such examples, the secondary purge gas flow can comprise a carbon-containing precursor and a second reactant. Additionally, while the disclosed examples are in the context of depositing carbon films, in other examples, similar strategies of including one or more reactants in a secondary purge gas flow can be usedto address nonuniformities in other chemical vapor deposition processes, such as for the PECVD deposition of silicon-containing films and metal oxide films.

[0073] FIG. 6 schematically shows a schematic depiction of a processing tool 600 configured for performing plasma-enhanced chemical vapor deposition (PECVD). Processing tool 600 comprises a processing chamber 602 and a substrate holder 604 within the processing chamber. The substrate holder 604 is configured to support a substrate 606 disposed within processing chamber 602. The substrate holder 604 comprises a substrate heater 608. In other examples, a heater can be omitted, or can be located elsewhere within processing chamber 602. The processing tool 600 further comprises a showerhead 610 for introducing processing chemicals into the processing chamber. In some examples, the processing tool 600 comprises a heater configured to heat showerhead 610.

[0074] The processing tool 600 further comprises a secondary purge gas outlet 611, as described above. Secondary purge gas outlet 611 is configured to form secondary purge gas flow around the outside edge of showerhead 610. The secondary purge gas outlet 611 can be configured to provide a flow of a secondary purge gas including one or more inert gases and one or more reactants. Example reactants include one or more passivation agents and / or one or more etching agents. The use of such a reactant (or reactants) in a flow of a secondary purge gas in a carbon film deposition process can help to provide for more uniform film growth than the use of a secondary purge gas without such a reactant (or reactants). Further, in some examples, a carbon- containing precursor can be provided in a secondary purge gas flow, alternatively or additionally to a passivation agent and / or etching agent.

[0075] The processing tool 600 further comprises flow control hardware 612. The flow control hardware 612 connects processing chemical source(s) to the processing chamber. In the depicted example, the flow control hardware 612 connects a carbon-containing precursor source 616, one or more reactant source(s) 618, and an inert gas source 622 to the processing chamber. The flow control hardware 612 can include any suitable components. Examples include mass flow controllers, valves, and conduits. For example, the flow control hardware 612 can comprise one or more valves controllable to place a selected gas source or selected gas sources in fluid connection with showerhead 610. The flow control hardware 612 also can comprise one or more mass flow controllers or other controllers for controlling a mass flow rate of gas.

[0076] The carbon-containing precursor source 616 comprises any suitable precursor compound(s) for forming a carbon film. Examples of carbon-containing precursors include alkanes having a general formula CnH2n+2 where n is an integer in a range of 1 to 10 (such as, methane, ethane, etc.), alkenes having a general formula CnEEn where n = 2 to 10 (such as, ethylene, propylene, etc.), and alkynes having a general formula CnH2n-2 where n = 2 to 10 (such as, acetylene, propyne, etc.), that are gas-phase under processing conditions. Other examples of carbon-containing film precursors comprise cyclic hydrocarbons including aromatics, nitrogen-containing compounds including alkyl amines, and oxygen-containing compounds including alcohols, ketones, esters, aldehydes, and ethers that are gas-phase under processing conditions, alkanes, alkenes, alkynes, cyclic hydrocarbons, aromatics, alcohols, aldehydes, esters, ethers, ketones, aldehydes, alkyl halides, alkyl amines, and alkyl diamines.

[0077] In other examples, a silicon-containing precursor source can be used instead of carbon-containing precursor source 616. Examples of silicon-containing precursors for forming silicon-containing films include silane (SiEU), halosilanes, and tetraethyl orthosilicate (TEOS). Further examples of silicon-containing precursors include alkoxysilanes, siloxanes, aminosilanes, and polysilanes. Specific examples of silicon-containing precursors are listed above.

[0078] The one or more reactant source(s) 618 comprises any suitable reactant or reactants. Examples include passivation agents and etching agents. A passivating agent adsorbs to a surface of a substrate, thereby reducing a film growth rate. An etching agent reacts with a previously deposited film to remove film material. Some processing chemicals can act both as a passivating agent and an etching agent. For example, exposure of a film material to a reactant that is capable of forming a volatile product with the film material can cause the reactant to adsorb to the film, but not react to completion, under some deposition conditions (e.g. shorter exposure, lower concentration) thereby passivating the film surface. The same material, under different conditions (e.g. higher exposure, higher concentration) can react with the film material to form a volatile product, thereby etching the film. Example reactants that can act as passivating agents and etching agents and that can be added to a secondary purge gas flow to help achieve a desired degree of film thickness uniformity can include hydrogen (H2), carbon dioxide (CO2), and ammonia (NH3). Example halogen-containing etching agents include chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), halogen acids (hydrofluoric acid (HF), hydrochloric acid (HC1), hydrobromic acid (HBr), hydroiodicacid (HI)), nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), halocarbons (CaXb, wherein X is a halogen and a = 1-10), and halohydrocarbons (CaHbXc, wherein X is a halogen and a = 1-10). Example oxygen-containing etching agents include carbon monoxide (CO), carbon dioxide (CO2), carbon oxysulfide (COS), sulfur dioxide (SO2), and molecular oxygen (O2). In further examples, where a silicon- containing precursor is used to deposit a silicon-containing film, a second reactant can comprise an oxidant. Examples of oxidants include nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), hydrogen peroxide (H2O2), and carbon dioxide (CO2).

[0079] The inert gas source 622 comprises any suitable inert gas. Examples include argon, helium, neon, krypton, xenon, nitrogen, or a combination thereof.

[0080] The processing tool 600 further comprises an exhaust system 632. The exhaust system 632 is configured to exhaust gases from the processing chamber 602. The exhaust system 632 can comprise any suitable hardware, including one or more low vacuum pumps, one or more high vacuum pumps, and one or more valves for controlling an exhaust flow. Together, flow control hardware 612 and exhaust system 632 can be operated to achieve a selected pressure in processing chamber 602 during substrate processing. Example pressures include pressures of 50 mTorr to 40 Torr. Further, exhaust system 632 can be operated to purge processing chamber 602.

[0081] The processing tool 600 further comprises an RF power source 634 configured to form a RF plasma in processing chamber 602 using a gas mixture. The RF power source 634 can supply RF power to the showerhead electrode or substrate holder electrode in various examples. As shown in FIG. 6, the RF power is provided to substrate holder 604, and showerhead 610 is configured as a grounded opposing electrode. As mentioned above, use of a powered substrate holder helps attract ions towards the substrate to increase etching rates and avoid top-heavy growth. In other examples, the RF power source 634 can supply RF power to showerhead 610, and substrate holder 604 can be grounded. In the depicted example, a capacitively coupled plasma can be formed in processing chamber 602 between showerhead 610 and substrate holder 604. In other examples, an inductively coupled plasma can be used.

[0082] The processing tool 600 further includes a matching network 636 for impedance matching of the RF power source 634. The radiofrequency power source 634 is configured to provide RF power comprising a lower-frequency (LF) RF power 634A and a higher-frequency (HF) RF power 634B. Example frequencies for the lower- frequency RF power include frequencies of 40 kHz to 3 MHz. Examples of lower-frequency RF power include powers of 0 to 1000 W. Example frequencies for the higher-frequency RF power include frequencies of 3 MHz to 300 MHz. Examples of higher-frequency RF power include powers of 50 to 5000 W.

[0083] The processing tool 600 further comprises a controller 650 configured to control operation of the processing tool. The controller 650 is operatively coupled to the substrate heater 608, the flow control hardware 612, the exhaust system 632, and the RF power source 634. The controller 650 is configured to control various functions of processing tool 600 to perform PECVD.

[0084] Controller 650 can comprise any suitable computing system. FIG. 7 schematically shows a non-limiting example of a computing system 700 that can enact one or more of the methods and processes described above. Computing system 700 is shown in simplified form. Computing system 700 can take the form of one or more personal computers, workstations, computers integrated with substrate processing tools, and / or network accessible server computers.

[0085] Computing system 700 includes a logic subsystem 702 and a storage subsystem 704. Computing system 700 can optionally include a display subsystem 706, input subsystem 708, communication subsystem 710, and / or other components not shown in FIG. 7. Controller 650 is an example of computing system 700.

[0086] Logic subsystem 702 includes one or more physical devices configured to execute instructions. For example, the logic machine can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[0087] The logic machine can include one or more processors configured to execute software instructions. Additionally or alternatively, the logic machine can include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of the logic machine can be single-core or multi-core, and the instructions executed thereon can be configured for sequential, parallel, and / or distributed processing. Individual components of the logic machine optionally can be distributed among two or more separate devices, which can be remotely located and / or configured for coordinated processing. Aspects of the logicmachine can be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[0088] Storage subsystem 704 includes one or more physical devices configured to hold instructions 712 executable by the logic machine to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage subsystem 704 can be transformed — e.g., to hold different data.

[0089] Storage subsystem 704 can include removable and / or built-in devices. Storage subsystem 704 can include optical memory (e.g., CD, DVD, HD-DVD, Blu- Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and / or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), among others. Storage subsystem 704 can include volatile, nonvolatile, dynamic, static, read / write, read-only, random-access, sequential-access, location-addressable, file- addressable, and / or content-addressable devices.

[0090] It will be appreciated that storage subsystem 704 includes one or more physical devices. However, aspects of the instructions described herein alternatively can be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration.

[0091] Aspects of logic subsystem 702 and storage subsystem 704 can be integrated together into one or more hardware-logic components. Such hardware-logic components can include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and applicationspecific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[0092] When included, display subsystem 706 can be used to present a visual representation of data held by storage subsystem 704. This visual representation can take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem 706 can likewise be transformed to visually represent changes in the underlying data. Display subsystem 706 can include one or more display devices utilizing virtually any type of technology. Such display devices can be combined with logic subsystem 702 and / or storage subsystem 704 in a shared enclosure, or such display devices can be peripheral display devices.

[0093] When included, input subsystem 708 can comprise or interface with one or more user-input devices such as a keyboard, mouse, or touch screen. In some examples, the input subsystem can comprise or interface with selected natural user input (NUI) componentry. Such componentry can be integrated or peripheral, and the transduction and / or processing of input actions can be handled on- or off-board. Example NUI componentry can include a microphone for speech and / or voice recognition, and an infrared, color, stereoscopic, and / or depth camera for machine vision and / or gesture recognition.

[0094] When included, communication subsystem 710 can be configured to communicatively couple computing system 700 with one or more other computing devices. Communication subsystem 710 can include wired and / or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem can be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some examples, the communication subsystem can allow computing system 700 to send and / or receive messages to and / or from other devices via a network such as the Internet.

[0095] It will be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific examples or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein can represent one or more of any number of processing strategies. As such, various acts illustrated and / or described can be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes can be changed.

[0096] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

CLAIMS:

1. A processing tool, comprising: a processing chamber; a showerhead; a secondary purge gas outlet configured to flow a secondary purge gas around an outside edge of the showerhead; flow control hardware configured to connect one or more processing gas sources with the showerhead and the secondary purge gas outlet; and a controller configured to control the flow control hardware to introduce a flow of a film precursor and a first reactant into the processing chamber through the showerhead during a deposition process, and to introduce a flow of a secondary purge gas comprising at least a second reactant into the processing chamber through the secondary purge gas outlet during the deposition process.

2. The processing tool of claim 1 , wherein the first reactant and the second reactant are a same reactant.

3. The processing tool of claim 1, wherein the first reactant is different from the second reactant.

4. The processing tool of claim 1, further comprising a carbon-containing precursor source.

5. The processing tool of claim 4, wherein the controller is configured to control the flow control hardware to include the carbon-containing precursor in the secondary purge gas.

6. The processing tool of claim 1, further comprising a silicon-containing precursor source.

7. The processing tool of claim 1, further comprising a reactant source, wherein the reactant comprises one or more of hydrogen (H2), carbon dioxide (CO2), ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb,wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

8. A method of depositing a film, the method comprising: introducing a flow of a film precursor and a first reactant into a processing chamber through a showerhead during a deposition process; and introducing a flow of a secondary purge gas comprising at least a second reactant into the processing chamber through a secondary purge gas outlet during the deposition process.

9. The method of claim 8, wherein the second reactant comprises one or more of an etching agent, a passivation agent, an inhibitor, or an oxidant.

10. The method of claim 8, wherein the first reactant and the second reactant are a same reactant.

11. The method of claim 8, wherein the film precursor is a carbon-containing precursor.

12. The method of claim 11, wherein the secondary purge gas further comprises the carbon-containing precursor.

13. The method of claim 8, wherein the reactant comprises one or more of hydrogen (H2), carbon dioxide (CO2) ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb, wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

14. The method of claim 8, wherein the film precursor comprises a silicon- containing precursor.

15. The method of claim 8, further comprising tuning one or more of a concentration of the second reactant added to the secondary purge gas or a flow rate ofthe second reactant added to the secondary purge gas to achieve a selected film thickness uniformity.

16. A method of depositing a film, the method comprising: introducing a flow of a film precursor and a first reactant into a processing chamber through a showerhead during a deposition process; and introducing a flow of a secondary purge gas comprising at least the film precursor into the processing chamber through a secondary purge gas outlet during the deposition process.

17. The method of claim 16, wherein the film precursor comprises a carbon- containing precursor.

18. The method of claim 16, wherein the film precursor comprises a silicon- containing precursor.

19. The method of claim 16, wherein the first reactant comprises one or more of hydrogen (H2), carbon dioxide (CO2) ammonia (NH3), chlorine (Ch), fluorine (F2), bromine (Bn), iodine (I2), a halogen acid, nitrogen trifluoride (NF3), boron trifluoride (BF3), sulfur hexafluoride (SFe), a halocarbon (CaXb, wherein X is a halogen), a halohydrocarbon (CaHbXc, wherein X is a halogen), nitrous oxide (N2O), oxygen (O2), ozone (O3), water (H2O), or hydrogen peroxide (H2O2).

20. The method of claim 16, further comprising tuning one or more of a concentration of film precursor added to the secondary purge gas or a flow rate of film precursor added to the secondary purge gas to achieve a selected film thickness uniformity.

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