Silicon nitride etching compositions and methods

Abstract

This application relates to silicon nitride etching compositions and methods. The invention provides compositions suitable for use in the selective removal of silicon nitride material from a microelectronic device having thereon silicon nitride material, polysilicon, silicon oxide material, and / or silicide material relative to the polysilicon, the silicon oxide material, and / or the silicide material. The compositions of the invention are particularly suitable for use in etching 3D NAND structures.

Description

[0001] This application is a divisional application of the application filed on November 12, 2019, with application number 201980073936.8 and invention title "Silicon Nitride Etching Composition and Method". Technical Field

[0002] The present invention relates to a composition and method for selectively etching silicon nitride in the presence of silicon oxide, polysilicon and / or metal silicides, and more specifically, to a composition and method for effectively and efficiently etching silicon nitride layers through exposed or underlayers of silicon oxide, polysilicon and / or metal silicides at high etching rates and with high selectivity, particularly in multilayer semiconductor wafer structures. Background Technology

[0003] The ongoing need for improved microelectronic device performance and the continued emphasis on minimizing device size offer the dual benefits of significantly increased device density and improved device performance. This is because reduced device size allows charge carriers (such as electrons) to travel shorter paths, thus improving device performance.

[0004] For example, the gate electrode of a metal-oxide-semiconductor field-effect transistor (MOSFET) has a gate surface, a source region, and a drain region as its electrical contact. The distance between the source and drain regions forms the channel length of the gate electrode, and thus, by reducing the device size, the channel length is also reduced. As a result, the switching speed of the device can be increased.

[0005] It goes without saying that reducing device size increases the packaging density of devices on a microelectronic device chip. This increased packaging density leads to a sharp reduction in the length of interconnect paths between devices, which reduces the relative negative impact of these interconnect paths on the overall device performance (such as resistance voltage drop, crosstalk, or RC delay).

[0006] However, such requirements lead to increased parasitic capacitance, device contact resistance (gate, source, and drain contacts in MOSFET devices), and tight tolerances for pattern definition. For extremely small submicron, sub-half-micron, or even sub-quarter-micron modern silicon devices, conventional photolithography techniques for patterning contacts will not meet the required tolerances for critical dimensions. Methods have been explored to improve resolution and feature size involving the formation of self-aligned polysilicon (polysilicon Si) gate structures, which help address the critical dimension tolerance problem. Using this method, the contacts formed for the source and drain of the gate electrode are self-aligned with the polysilicon gate.

[0007] One problem encountered during the formation of a self-aligned gate structure is the selective removal of silicon nitride material relative to polysilicon, silicon oxide, and / or metal silicide materials. For example, during anisotropic etching of the silicon nitride layer covering the gate electrode, the underlying silicon oxide layer and silicon substrate are often also damaged, leading to reduced reliability of the semiconductor device.

[0008] Conventional wet etching techniques for selectively removing silicon nitride (Si3N4) have utilized a hot (approximately 145°C to 180°C) phosphoric acid (H3PO4) solution containing water, typically 85% phosphoric acid and 15% water (by volume). Using fresh hot phosphoric acid, the typical Si3N4:SiO2 selectivity is approximately 40:1. Advantageously, as the nitride layer is removed, hydrated silicon oxide forms, which, consistent with Le Chatelier's principle, inhibits the further removal of silicon oxide from the device surface; thus, the selectivity gradually increases with use. Disadvantages associated with using hot phosphoric acid etching include, for example, corrosion of the metal silicide material of the gate contact material, etching of the silicon oxide, and difficult process control due to the need to maintain a specific amount of water in the processing solution. Furthermore, hot phosphoric acid has become a difficult medium to adapt to single-wafer tooling, which has become increasingly popular with many manufacturers.

[0009] Another method for selectively removing silicon nitride involves using a composition containing hydrofluoric acid; however, this composition also removes silicon oxide. A Si3N4:SiO2 selectivity of approximately 10:1 can be achieved through dilution; however, the etching rate of silicon nitride is compromised or pressures above ambient levels must be used. Yet another process for removing silicon nitride involves dry etching removal using gaseous halide species; however, the Si3N4:SiO2 selectivity ratio is even worse than that obtained using the aforementioned wet etching process.

[0010] The 3D-NAND structures currently being developed by all major memory chip manufacturers require high-selectivity etching of silicon nitride (SiN) beyond the high aspect ratio "slits" defined by oxides (PETEOS). In conventional thermal phosphoric acid (TPA) processes, selectivity is controlled by pre-dissolving a certain amount of nitride. The dissolved silicon nitride is converted into a slightly soluble oxide; this conversion occurs during etching, but the oxide rapidly begins to deposit near the slit opening, eventually blocking it. See also US 2017 / 0287725, specifically... Figure 1 D, which illustrates how the deposition of colloidal silica often "pinches" gaps or trenches in microelectronic devices. Therefore, the process window for pre-etched oxide concentration is extremely narrow, difficult to control, and requires frequent changes of the etch dipping agent. Thus, it is necessary to minimize the oxide redeposition rate.

[0011] Furthermore, deep slits require a longer etching time (typically ≥1 hr). Adding a small amount of HF increases the etching rate, but also increases the polymerization of soluble silica species and thus accelerates oxide redeposition. In addition, the volatility of HF and related fluorinated species makes process control difficult.

[0012] In planar NAND technology, scaling is largely driven by photolithography. In scaling 3D NAND, extreme precision and process repeatability are required to form complex 3D structures with extremely high aspect ratios (HAR). Therefore, success with 3D NAND necessitates novel patterning solutions that minimize variability. (See Overcoming Challenges in 3D NAND Volume Manufacturing. SolidState Technology website: http: / / electroig.com / blog / 2017 / 07 / overcoming-challenges-in-3d-nand-volume-manufacturing / )

[0013] The precision of etching extreme HAR features is crucial for optimizing the vias and trenches used for memory cell access, as well as their unique stepped architecture that connects the memory cells to surrounding CMOS circuitry for reading, writing, and erasing data. If the vertical pitch of the memory stack is approximately 50 nm, then a 96-layer stack would be approximately 4.8 µm high. This corresponds to a challenging aspect ratio of approximately 100:1.

[0014] Furthermore, as the stacking height increases, achieving consistent etch and deposition profiles at the top and bottom of the memory array becomes more challenging. For example, given a ratio of approximately 100:1, the selective removal of Si3N4 within the memory stack presents a wet etching challenge. The difficulty lies in continuously removing Si3N4 at the top and bottom of the stack and on the wafer without etching any of the SiO2. Below layer 96, this task is performed using thermal phosphoric acid (approximately 160°C); however, at and above layer 96, specially formulated wet etching chemicals are required to improve process margins. Summary of the Invention

[0015] In one aspect, the present invention provides a composition suitable for etching a substrate having a surface comprising silicon nitride and silicon oxide at a selectivity relative to silicon oxide etch silicon nitride. The composition comprises phosphoric acid, at least one silane compound selected from alkylaminoalkoxysilanes and alkylaminohydroxysilanes, a solvent including water, and optionally a fluoride compound. Attached Figure Description

[0017] Figures 1 to 4 This paper presents a comparison of several examples of the invention regarding etch rate and Si loading. The etch rates of silicon nitride and silicon oxide were measured using CVD silicon nitride films and PECVD silicon oxide films. The silicon oxide film was exposed to the etch mix for 4 hours to allow for the measurement of minimal film loss. The silicon nitride film was etched for 5 minutes and 10 minutes. Film thickness was measured using a spectroeltroradiometer before and after processing, and these thicknesses were used to calculate the etch rate.

[0018] Specifically, each figure is depicted as follows:

[0019] Figure 1 A graph depicting the etching rate as a function of Si load is provided.

[0020] Figure 2 The plot shows the etching rate as a function of Si load.

[0021] Figure 3 The plot shows the etching rate of 85% phosphoric acid as a function of Si loading.

[0022] Figure 4 A graph depicting the selectivity rates of (“Example B”), (“Example A”), and 85% H3PO4.

[0023] Figure 5 The structure of the exemplary substrate, as described, is schematically shown before and after the selective etching step, as also described. Detailed Implementation

[0024] One aspect of the invention relates to a composition suitable for selectively removing silicon nitride relative to polycrystalline silicon (polycrystalline Si) and silicon oxide material deposited from a silicon oxide precursor source, and therefore suitable for wet etchants acting to at least partially remove silicon nitride material from a microelectronic device. Any metal silicide material present should not be substantially etched by the removal composition.

[0025] The present invention also provides methods, processes, and systems for removing silicon nitride from a substrate containing silicon nitride and silicon oxide using a wet etching composition. The composition can produce a favorable higher etching rate for silicon nitride, a favorable higher selectivity of silicon nitride relative to silicon oxide, or a favorable balance of these performance characteristics.

[0026] For ease of reference, "microelectronic device" refers to a semiconductor substrate that includes 3D NAND structures, flat panel displays, and microelectromechanical systems (MEMS) manufactured for use in microelectronic, integrated circuit, or computer chip applications. It should be understood that the term "microelectronic device" is not intended to be limiting in any way and includes any substrate that will ultimately become a microelectronic device or microelectronic assembly, wherein said substrate includes negative channel metal-oxide-semiconductor (nMOS) and / or positive channel metal-oxide-semiconductor (pMOS) transistors.

[0027] As used herein, “suitability” for removing silicon nitride material from a microelectronic device having silicon nitride material thereon corresponds to at least partial removal of the silicon nitride material from the microelectronic device.

[0028] As used herein, “silicon nitride” and “Si3N4” refer to pure silicon nitride (Si3N4) and impure silicon nitride containing hydrogen, carbon and / or oxygen impurities in its crystal structure.

[0029] As used in this article, "silicon oxide" refers to silicon oxide (SiO2). x (e.g., SiO2), "thermal oxides" (ThO) x Silicon oxide is a thin film made from silicon dioxide and similar materials. Silicon dioxide can be placed on a substrate by any method, such as by deposition from TEOS or another source via chemical vapor deposition or by thermal deposition. Silicon dioxide generally contains commercially available low amounts of other materials or impurities. Silicon dioxide can exist as part of a substrate for microelectronic devices, or as a feature of microelectronic devices, for example, as an insulating layer.

[0030] As used herein, “at least partially remove silicon nitride material” corresponds to removing at least a portion of the exposed silicon nitride layer. For example, partially removing silicon nitride material includes anisotropically removing the silicon nitride layer covering / protecting the gate electrode to form Si3N4 sidewalls. It is also contemplated herein that the compositions of the present invention can be used more generally to substantially remove silicon nitride material relative to polysilicon and / or silicon oxide layers. In those cases, “substantially remove” is defined in one embodiment as removing at least 90% of the silicon nitride material using the compositions of the present invention, in another embodiment at least 95%, and in yet another embodiment at least 99%.

[0031] As used in this article, “about” is intended to correspond to + / - 5% of the stated value.

[0032] As used herein, “metal silicide” refers to any silicide containing the species Ni, Pt, Co, Ta, Mo, W and Ti, including but not limited to TiSi2, NiSi, CoSi2, NiPtSi, tantalum silicide, molybdenum silicide and tungsten silicide.

[0033] "Silicic acid" is a chemical with the general formula [SiO2]. x (OH) 4-2x ] n The general name for a family of silicon compounds, hydrogen compounds, and oxygen compounds, including metasilicic acid (H₂SiO₃). n ), orthosilicic acid (H4SiO4), disilicate (H2Si2O5), and pyrosilicic acid (H6Si2O7). Silicic acid can be obtained in many ways well known to those skilled in the art, such as by hydration of: fine silica powder (preferably 1 µm in diameter or smaller), alkoxysilanes (e.g., tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetra-n-propoxysilane, tetra-n-butoxysilane), alkoxysilanes having an amino group (e.g., aminotriethoxysilane, hexaethoxydisilazane), alkoxysilanes having one or more halogen or pseudohalogen groups (e.g., triethoxychlorosilane, triethoxyfluorosilane, triethoxy(isocyano)silane, diethoxydichlorosilane), or combinations thereof. For ease of reference, "alkoxysilane" will be used hereinafter to include alkoxysilanes, alkoxysilanes having an amino group, and alkoxysilanes having one or more halogen or pseudohalogen groups.

[0034] As described herein, the silicon oxide layer may be deposited from a silicon oxide precursor source such as TEOS, or may be thermally deposited silicon oxide. Other typical low-k materials, or “low-k dielectric materials,” correspond to any material used as a dielectric material in layered microelectronic devices, wherein said material has a dielectric constant of less than about 3.5. In some embodiments, the low-κ dielectric material comprises a low-polarity material, such as a silicon-containing organic polymer, a silicon-containing mixed organic / inorganic material, an organosilicon glass (OSG), TEOS, a fluorinated silicate glass (FSG), silica, silicon oxycarbide, silicon oxynitride, silicon nitride, carbon-doped oxide (CDO), or carbon-doped glass, such as CORAL™ from Novellus Systems, Inc., BLACK DIAMOND™ from Applied Materials, Inc. (e.g., BD1, BD2, and BD3 names for PECVD), SiLK™ dielectric resin from Dow (based on a cross-linked polyphenylene polymer formed by the reaction of a polyfunctional cyclopentadienone with an acetylene-containing material; see, for example, U.S. Patent No. 5,965,679, which is incorporated herein by reference), and NANOGLASS™ (silica aerogel / dry gel, known as nanoporous silica) from Nanopore, Inc., and the like. It should be understood that low-k dielectric materials can have different densities and different porosities.

[0035] The compositions of this invention must possess good metal compatibility, such as low etch rates on interconnect metals and / or interconnect metal silicide materials. Metals of interest include, but are not limited to, copper, tungsten, cobalt, molybdenum, aluminum, tantalum, titanium, and ruthenium. Silicides of interest include any silicide comprising the species Ni, Pt, Co, Ta, Mo, W, and Ti, including, but not limited to, TiSi2, NiSi, CoSi2, NiPtSi, tantalum silicide, molybdenum silicide, and tungsten silicide.

[0036] As described more fully below, the compositions of the present invention can be implemented in a wide variety of specific formulations.

[0037] In all such compositions, where a particular component of the composition is discussed in terms of a range of weight percentages (including the lower limit of zero), it will be understood that such a component may or may not be present in various specific embodiments of the composition, and in instances where such a component is present, the component may be present at a concentration as low as 0.001 weight percentages based on the total weight of the composition employing such a component.

[0038] The composition contains an amount of aqueous phosphoric acid (e.g., concentrated phosphoric acid) in which silicon nitride is to be etched, effectively producing silicon nitride. The term "aqueous phosphoric acid" refers to a component of the composition that is mixed or combined with other components of the composition to form the composition. The term "phosphoric acid solid" refers to the aqueous phosphoric acid component or a non-aqueous component of a composition prepared from the aqueous phosphoric acid component.

[0039] The amount of solid phosphate contained in the composition can be such that, when combined with other materials in the etching composition, it will provide the desired etching performance, including the desired silicon nitride etching rate and selectivity, typically requiring a relatively high amount (concentration) of solid phosphate. For example, the etching composition may contain at least about 50% by weight of solid phosphate based on the total weight of the composition, such as at least 70% by weight, or at least about 80% or 85% by weight of solid phosphate based on the total weight of the composition.

[0040] To provide the desired amount of phosphoric acid solids, the composition may contain “concentrated” phosphoric acid as a component to be mixed or combined with other components (in some forms, one component is optionally water) to produce the composition. “Concentrated” phosphoric acid refers to an aqueous phosphoric acid component containing a higher or maximum amount of phosphoric acid solids in the presence of a low or minimal amount of water, and substantially without other components (e.g., less than 0.5% or 0.1% by weight of any non-aqueous or non-phosphoric acid solid material). Concentrated phosphoric acid can generally be considered as having at least about 80% or 85% by weight of phosphoric acid solids in about 15% or 20% by weight of water. Alternatively, the composition may be considered as containing a certain amount of concentrated phosphoric acid diluted with water, representing, for example, concentrated phosphoric acid diluted with a certain amount of water before or after combination with other components of the etching composition, or an equivalent formed in any way. As another alternative, the composition may consist of concentrated or diluted phosphoric acid, and the etching composition may contain additional amounts of water provided to the composition as a component of a different component or as a separate water component.

[0041] As an example, if concentrated phosphoric acid is used to form the composition, the amount of concentrated phosphoric acid (85% by weight in water) may be at least 60% by weight of the composition, such as at least 80% by weight, or at least 90%, 93%, 95%, or at least 98% by weight.

[0042] Compositions may include, consist of, or substantially consist of any combination of the described ingredients and optional ingredients. As a general practice, throughout this specification, a composition or component thereof described as “consisting substantially of a set of specified ingredients or materials” means a composition containing the specified ingredients or materials in no more than a low or insignificant amount of other ingredients or materials, such as no more than 5 parts by weight, 2 parts by weight, 1 part by weight, 0.5 parts by weight, 0.1 parts by weight, or 0.05 parts by weight. For example, a composition comprising substantially aqueous phosphoric acid, at least one silane compound selected from (i) alkylaminoalkoxysilanes and (ii) alkylaminohydroxysilanes, a solvent including water, and optional ingredients as described represents a composition containing these ingredients and no more than 5 parts by weight, 2 parts by weight, 1 part by weight, 0.5 parts by weight, 0.1 parts by weight, or 0.05 parts by weight of any other dissolved or undissolved material or material other than the identified material (alone or in aggregate).

[0043] As used herein, “fluoride compound” refers to a compound containing ionic fluoride ions (F… -Fluoride species are either covalently bonded or contained within the fluoride species. It should be understood that fluoride species can be incorporated as fluoride species or generated in situ. In some embodiments, the compound capable of generating fluoride ions will be derived from HF, monofluorophosphoric acid (MFPA), difluorophosphoric acid (DFPA), or hexafluorophosphoric acid. In concentrated phosphoric acid compositions, HF will be predominantly present as monofluorophosphoric acid (MFPA). In some embodiments, low-volatility MFPA or DFPA can be used directly in the composition to simplify addition and blending. In other embodiments, the fluoride compound may be selected from CsF and KF. In other embodiments, the fluoride compound may be selected from tetramethylammonium hexafluorophosphate; ammonium hexafluorophosphate; ammonium fluoride; ammonium difluoride; quaternary ammonium tetrafluoroborate and quaternary phosphorus tetrafluoroborate, having the formulas NR'4BF4 and PR'4BF4, respectively, wherein each R' may be the same or different from each other, and is selected from hydrogen, straight-chain, branched or cyclic C1-C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl) and straight-chain or branched C6-C6 alkyl groups. 10 Aryl (e.g., benzyl); tetrabutylammonium tetrafluoroborate (TBA-BF4); and combinations thereof. In some embodiments, the fluoride compound is selected from ammonium fluoride, ammonium difluoride, quaternary ammonium tetrafluoroborate (e.g., tetramethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, tetrapropylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate), quaternary phosphorus tetrafluoroborate, or combinations thereof. In some embodiments, the fluoride compound includes ammonium difluoride, ammonium fluoride, or combinations thereof.

[0044] Unless the context clearly indicates otherwise, as used in this specification and the appended claims, the singular forms “a” and “the” include their plural references. Unless expressly excluded in the claims, the terms “containing” or “comprising” are intended to be synonymous with the term “including”, indicating that at least the claimed compound, element, particle, or method step is present in the composition, article, or method, but the presence of other compounds, materials, particles, method steps, etc., that have the same function as the claimed article, is not excluded.

[0045] In one aspect, the present invention provides a composition comprising:

[0046] (a) Phosphoric acid;

[0047] (b) At least one silane selected from (i) alkylaminoalkoxysilane and (ii) alkylaminohydroxysilane, wherein the silane has at least one moiety selected from alkoxy, hydroxy and fluorine groups;

[0048] (c) Solvents, including water; and optionally

[0049] (d) Fluoride compounds, wherein the limiting condition is that the fluoride compound is not hexafluorosilicic acid.

[0050] In some embodiments, phosphoric acid will be present in the composition at about 50% to about 95% by weight. In other embodiments, phosphoric acid will be present at about 70% to about 90% by weight, and in still other embodiments at about 85% by weight.

[0051] In some embodiments of the invention, the composition may further comprise a fluoride compound. In one embodiment, the fluoride compound is selected from HF and monofluorophosphate. In other embodiments, the fluoride compound is selected from cesium fluoride and potassium fluoride. In other embodiments, the fluoride compound is selected from ammonium hexafluorophosphate; tetramethylammonium hexafluorophosphate; ammonium fluoride; ammonium difluoride; fluoroboric acid; quaternary ammonium tetrafluoroborate and quaternary phosphorus tetrafluoroborate, having the formula NR'4BF4 and the formula PR'4BF4, respectively, wherein R' may be the same or different from each other and is selected from hydrogen, straight-chain, branched or cyclic C1-C6 alkyl and straight-chain or branched C6-C6 alkyl. 10 Aryl; Tetramethylammonium tetrafluoroborate (TMA-BF4); and combinations thereof.

[0052] In some embodiments, alkylaminoalkoxysilanes and alkylaminohydroxysilane compounds are represented by the following formulas.

[0053]

[0054] Each X is independently selected from fluorine, C1-C8 alkyl, or a group having the formula -OR, wherein R is hydrogen or C1-C8 alkyl, n is an integer from 1 to 6, and each R 1 Independently selected from hydrogen, C1-C8 alkyl, or having the formula C1-C8 alkoxy (CH2). n -- group. In some embodiments, alkylaminoalkoxysilanes and alkylaminohydroxysilane compounds are selected from (3-aminopropyl)triethoxysilane (CAS No. 919-30-2); (3-aminopropyl)silanetriol (CAS No. 58160-99-9); 3-aminopropyldimethylethoxysilane (CAS No. 18306-79-1); 3-aminopropylmethyldiethoxysilane (CAS No. 3179-76-8); and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (CAS No. 3069-29-2); (N,N-dimethyl-3-aminopropyl)trimethoxysilane (CAS No. 2530-86-1); and 3-aminopropyldimethylfluorosilane (CAS No. 153487-58-2).

[0055] In some embodiments, alkylaminoalkoxysilanes and alkylaminohydroxysilane compounds are represented by the following formulas.

[0056]

[0057] Each X is independently selected from fluorine, C1-C8 alkyl or a group having the formula -OR, wherein R is hydrogen or C1-C8 alkyl, n is an integer from 1 to 6, y is an integer from 1 to 6, and z is an integer from 1 to 6.

[0058] In some embodiments, the alkylaminoalkoxysilane and alkylaminohydroxysilane compounds are selected from N-(3-trimethoxysilylpropyl)diethylenetriamine (CAS No. 35141-30-1); N-(2-aminoethyl)-3-aminopropyltriethoxysilane (CAS No. 5089-72-5); N-(2-aminoethyl)-3-aminopropylsilanetriol (CAS No. 1760-24-3); (3-trimethoxysilylpropyl)diethylenetriamine (CAS No. 35141-30-1); and N-(6-aminohexyl)aminopropyltrimethoxysilane (CAS No. 51895-58-0).

[0059] In some embodiments, two alkylamino groups are attached to a silicon atom, the silicon atom carrying two X groups (as defined above) or one X group and an alkyl group, such as 3,3'-(dimethoxysilane)bis-(1-propylamine) (CAS No. 51749-36-1):

[0060]

[0061] In some embodiments, one or more aminoalkyl branches branch off alkyl or aminoalkyl chains connected to silicon atoms, the silicon atoms carrying three X groups (as defined above) or two X groups and one alkyl group, such as 2-[(dimethoxymethylsilyl)methyl]-1,4-butanediamine (CAS No. 1019109-96-6):

[0062]

[0063] In some embodiments, two or more silicon atoms connected by oxygen bridges collectively carry at least one aminoalkyl group and at least one "X" group as described above, wherein the remaining silicon substituents are alkylamines, "X" groups, or alkyl groups; for example, 1,3-bis(3-aminopropyl)-1,1,3,3-tetraethoxydisilane (CAS No. 17907-78-7):

[0064]

[0065] and its methoxy analogue 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethoxydisiloxane (CAS No. 76712-65-7):

[0066]

[0067] The amount of alkylaminoalkoxysilane and alkylaminohydroxysilane compounds in the compositions of the present invention can be such that, when combined with other materials in the etching composition, they will provide the desired etching performance, including the desired silicon nitride etching rate and selectivity. For example, the etching composition may contain a certain amount of alkylaminoalkoxysilane and alkylaminohydroxysilane compounds, which may be a single species or a combination of two or more species, in an amount ranging from about 20 to 10,000 parts per million (i.e., 0.0020 to 1.0 wt%) based on the total weight of the composition, or from about 20 to 2,000, 4,000, or 5,000 parts per million (i.e., 0.002 to 0.2, 0.4, or 0.5 wt%) based on the total weight of the composition.

[0068] Component (c) is a solvent including water. Optionally, the solvent may further include one or more water-miscible solvents, such as pyrrolidone, glycols, amines, and glycol ethers, including but not limited to methanol, ethanol, isopropanol, butanol, and higher alcohols (such as C2-C4 glycols and C3-C4 triols), tetrahydrofurfuryl alcohol (THFA), and halogenated alcohols (such as 3-chloro-1,2-propanediol, 1-chloro-2-propanol, 2-chloro-1-propanol, 3-chloro-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-propanol, ... 3-Bromo-1-propanol, 3-iodo-1-propanol, 4-chloro-1-butanol, 2-chloroethanol), acetic acid, propionic acid, trifluoroacetic acid, N-methylpyrrolidone (NMP), cyclohexylpyrrolidone, N-octylpyrrolidone, N-phenylpyrrolidone, methyl diethanolamine, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylene sulfone (sulfolane), phenoxy-2-propanol (PPh), propiophenone, emulsion Ethyl benzoate, ethyl acetate, ethyl benzoate, acetonitrile, ethylene glycol, propylene glycol (PG), 1,3-propanediol, butyryl lactone, butylene carbonate, ethylene carbonate, propylene carbonate, dipropylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether (i.e., butyl carbitol), triethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, propylene glycol... Methyl alcohol ethers, dipropylene glycol methyl ether (DPGME), tripropylene glycol methyl ether (TPGME), dipropylene glycol dimethyl ether, dipropylene glycol ethyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether (DPGPE), tripropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether acetate, tetraethylene glycol dimethyl ether (TEGDE), diesters, glyceryl carbonate, N-formylmorpholine, triethyl phosphate, and combinations thereof. When alkoxysilane additives are used, their hydrolysis produces a small amount of alcohol, such as methanol or ethanol, which is incorporated into the formulation either as the alcohol itself or as its phosphate monoester, and mostly boils at typical process temperatures. Additionally, organic solvents may include other amphiphilic species, i.e., species containing both hydrophilic and hydrophobic portions similar to surfactants.

[0069] In some embodiments, the compositions of the present invention further comprise a low molecular weight amine and an ammonium phosphate salt. In other embodiments, the low molecular weight amine and the ammonium phosphate salt are primary, secondary, or tertiary C1-C6 alkylamines or their phosphate salts. Examples include dimethylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, and the like. It will be understood that when such amines or aqueous solutions thereof are added to a concentrated H3PO4 composition, an ammonium phosphate salt will be formed.

[0070] In one embodiment, the composition comprises: (a) phosphoric acid; (b) N-(2-aminoethyl)-3-aminopropylsilanetriol; and (c) a solvent comprising water. In another embodiment, the composition further comprises HF or monofluorophosphoric acid. In yet another embodiment, the composition further comprises triethylamine or its dihydrogen phosphate salt.

[0071] The composition may optionally include a surfactant (different from other optional or desired components described herein) to improve the properties of the composition. As used herein, the term "surfactant" refers to an organic compound that reduces the surface tension (or interfacial tension) between two liquids or between a liquid and a solid, typically containing an organic amphiphilic compound with a hydrophobic group (e.g., a hydrocarbon (e.g., an alkyl) "tail") and a hydrophilic group. Preferably, the surfactant is thermally stable and remains ionic under strongly acidic conditions (such as the etching process of the present invention). Examples include perfluoroalkyl sulfonic acids and long-chain quaternary ammonium compounds (e.g., dodecyltrimethylammonium bisulfate). Fluorinated nonionic surfactants such as Chemours' Capstone® FS-31 / FS-35 may also be used. Nonionic unfluorinated surfactants such as poly(ethylene glycol)-poly(propylene glycol) copolymers ("PEG-PPG") may also be used, and said nonionic unfluorinated surfactants are preferably suitable for compositions with lower acidity (e.g., ≤ 75% H3PO4) and operation at ≤ 130°C.

[0072] The amount of surfactant in the composition can be such that, when combined with other materials in the etching composition, it will provide the desired overall performance. For example, the composition may contain a certain amount of surfactant, said amount being in the range of about 0.001 weight percent to about 10 weight percent based on the total weight of the composition, such as about 0.01 weight percent to about 0.5 weight percent, 1 weight percent, 2 weight percent, or 7 weight percent surfactant.

[0073] Optionally, the composition may contain a certain amount of a carboxylic acid compound, representing an organic compound containing at least one carboxylic acid group. According to the invention, the presence of a carboxylic acid compound in the composition as described can improve performance by inhibiting the redeposition of silica or the formation of silica particles. In some embodiments, the carboxylic acid compound supplied for use in the composition comprises acetic acid, malonic acid, succinic acid, 2-methylsuccinic acid, glutaric acid, adipic acid, salicylic acid, 1,2,3-propanetricarboxylic acid (also known as propanetricarboxylic acid), 2-phosphorylated acetic acid, 3-phosphorylated propionic acid, and 2-phosphorylated butane-1,2,4-tricarboxylic acid (PBTCA), any of which may be used alone, in combination with each other, or in combination with different carboxylic acid compounds.

[0074] The amount of carboxylic acid compound (including its derivatives) contained in the composition may be such that, when combined with other materials in the composition, it will provide the desired etching performance without otherwise affecting the performance or chemical stability of the etching composition. For example, the amount of carboxylic acid compound contained in the composition, which may be a single species or a combination of two or more species, may be in the range of about 0.01% by weight to about 10% by weight, or about 0.1% by weight to about 5% or 8% by weight, based on the total weight of the composition.

[0075] The composition may contain water from one or more sources. For example, water will be present in the aqueous phosphoric acid component. Additionally, water may be used as a carrier for one or more other components of the etching composition, and water may be added separately as a component of itself. The amount of water should be low enough to allow the composition to exhibit desired, preferred, or advantageous etching performance characteristics, including an effective (sufficiently high) silicon nitride etching rate. An increase in the presence of water tends to increase the etching rate of silicon nitride, but may also lower the boiling point of the etching composition, which leads to a decrease in the operating temperature of the etching composition and has the opposite effect. Examples of the amount of water from all sources in the etching composition may be less than about 50 wt%, 40 wt%, or 30 wt% by weight of the total weight of the composition, for example, in the range of about 5 wt% to about 25 wt%, or in the range of about 10 wt% to 20 wt% by weight of the total weight of the composition.

[0076] Optionally, the compositions described herein and other examples may contain, consist of, or consist substantially of any one or any combination of phosphoric acid, aminohydroxysilane or aminoalkoxysilane, and any of the identified optional components. Certain embodiments of the compositions of the invention do not require and may exclude other types of components not typically included in etching compositions, such as pH adjusters (other than acids mentioned herein as potential ingredients) and solid materials, such as abrasive particles.

[0077] The following table contains illustrative compositions in weight percentages that are considered suitable for practice of the present invention:

[0078]

[0079] For the purposes of this article, please refer to the following abbreviations:

[0080] (3-Aminopropyl)triethoxysilane (CAS No. 919-30-2) "APTES";

[0081] (3-Aminopropyl)silanetriol (CAS No. 58160-99-9) "APST";

[0082] N-(2-aminoethyl)-3-aminopropylsilanetriol (CAS No. 1760-24-3) "N2APST";

[0083] N 1 -(3-trimethoxysilylpropyl)diethylenetriamine) "N3APTMS";

[0084] 3,3'-(dimethoxysilane)bis-(1-propylamine) (CAS No. 51749-36-1) "DMSBP";

[0085] 1,3-Bis(3-aminopropyl)-1,1,3,3-tetraethoxydisiloxane (CAS No. 17907-78-7) "BAPTEDS";

[0086] N-(6-aminohexyl)aminopropyltrimethoxysilane (CAS No. 51895-58-0) "AHAPTMS"; and

[0087] Diethylene glycol monobutyl ether (butyl carbitol) "BC".

[0088] In another aspect, the present invention provides a method for removing silicon nitride from a microelectronic device, the method comprising contacting the microelectronic device with the composition of the present invention for a sufficient time, provided that the silicon nitride material can be at least partially removed from the microelectronic device.

[0089] For example, silicon nitride material can be removed without substantially damaging the metal and metal silicide interconnect materials. The present invention therefore provides a method for selectively and substantially removing silicon nitride material from the surface of a microelectronic device having silicon nitride, polysilicon, and / or silicon oxide material thereon, relative to said polysilicon and / or said silicon oxide material, using the compositions described herein. The existing metal silicide material is not substantially corroded by the removal composition using the method.

[0090] In etching applications, the composition is applied to the surface of a microelectronic device having silicon nitride material thereon in any suitable manner, such as by spraying the removal composition onto the surface of the device, by immersing the device containing silicon nitride material (in a static or dynamic volume of the removal composition), by contacting the device with another material on which the removal composition is adsorbed (e.g., a pad or fiber adsorbent applicator element), by contacting the device containing silicon nitride material with a circulating removal composition, or by any other suitable means, manner, or technique of contacting the removal composition with silicon nitride material removal. Application can be performed in a batch or single wafer apparatus for dynamic or static cleaning. In one embodiment, the application of the removal composition to the surface of the microelectronic device is by controlled agitation, whereby the composition is circulated through a container holding the composition.

[0091] The compositions of the present invention achieve at least partial removal of silicon nitride material in an efficient and highly selective manner by means of the selectivity of their silicon nitride material relative to other materials (such as metallides, polysilicon, silicon oxide, etc.) that may exist on the structure of a microelectronic device and exposed to the composition.

[0092] In the use of the compositions of the present invention for removing silicon nitride material from a microelectronic device structure having silicon nitride material thereon, under sufficient conditions including, but not limited to (in one embodiment) temperatures in the range of about 120°C to about 180°C, the compositions are typically contacted with the microelectronic device structure for a sufficient time of about 1 minute to about 200 minutes. In one embodiment, for a single wafer tool contact, the contact time is about 15 minutes to about 100 minutes or about 1 minute to about 3 minutes. Such contact times and temperatures are illustrative, and any other suitable time and temperature conditions within the practice of the present invention that are effective for at least partially removing silicon nitride material from the device structure may be used.

[0093] After the desired removal action is achieved, the removal composition can be easily removed from the microelectronic device to which the removal composition has been previously applied, for example by rinsing, washing, or other removal steps as may be necessary and effective in a given end-use application of the composition of the invention. For example, the device can be rinsed and / or dried (e.g., spin-drying, N2, steam drying, etc.) by a rinsing solution containing deionized water.

[0094] The removal composition of the present invention selectively etches silicon nitride material relative to polycrystalline Si and silicon oxide from the surface of a microelectronic device without causing significant corrosion of the metal and / or metal silicide interconnect materials. For example, in the presence of the removal composition of the present invention, in one embodiment at a temperature of 40°C to 100°C, in another embodiment at a temperature of 60°C to 95°C, and in yet another embodiment at a temperature of 75°C to 90°C, the selectivity of silicon nitride to silicon oxide is in the range of about 10:1 to about 7,000:1 in one embodiment, in another embodiment in the range of about 30:1 to about 3,000:1, and in yet another embodiment in the range of about 100:1 to about 2,000:1. When the silicate source comprises an alkoxysilane such as TEOS, the selectivity of silicon nitride to silicon oxide can be adjusted to about 20:1 to infinity in one embodiment, and in another embodiment in the range of about 20:1 to about 7,000:1. In fact, for some available formulations, the selectivity is negative in form, reflecting the fact that the thickness of the oxide film increases very slightly but measurably through the precipitation of silica.

[0095] The etching steps described in this specification are applicable to etching silicon nitride material from the surface of any type of substrate. According to a particular embodiment, the substrate may include an interlaced silicon nitride thin film layer as a structural feature of a substrate comprising an interlaced thin film layer of silicon nitride and silicon oxide. The silicon oxide layer is a high aspect ratio structure containing silicon nitride layers disposed between the silicon oxide layers.

[0096] Another aspect of the present invention relates to a method of manufacturing an article comprising a microelectronic device, the method comprising contacting the microelectronic device with the composition of the present invention for a sufficient time to remove the silicon nitride material from the surface of the microelectronic device having thereon by etching, and incorporating the microelectronic device into the article.

[0097] The compositions described herein are readily formulated by individually adding the respective ingredients and mixing until homogeneous. Furthermore, the compositions can be readily formulated as single-serving formulations or multi-serving formulations mixed at the point of use, preferably multi-serving formulations. Individual portions of the multi-serving formulation can be mixed at the tool or in a reservoir upstream of the tool. The concentration of the respective ingredients can vary widely by specific multiples of the composition, i.e., more dilute or more concentrated, and it will be understood that the compositions described herein may differently and alternatively comprise, consist of, or consist primarily of any combination of ingredients consistent with the disclosure herein.

[0098] Another aspect of the invention relates to a kit comprising one or more components suitable for forming the compositions described herein, in one or more containers. In one embodiment, the kit comprises, in one or more containers, a combination of at least one of the above components (a) to (c) for use in combination with water at a facility or point of use. The containers of the kit must be suitable for storing and transporting the cleaning composition components, such as NOWPak. ® Containers (Advanced Technology Materials, Inc., Danbury, Connecticut, USA). One or more containers containing components of a first cleaning composition preferably include means for introducing the components into the one or more containers in fluid communication for mixing and dispensing. For example, referring to the NOWPak® container, gas pressure may be applied to the outside of a liner in the one or more containers to at least partially expel the contents of the liner and thus achieve fluid communication for mixing and dispensing. Alternatively, gas pressure may be applied to the top space of a conventional pressurized container or a pump may be used to achieve fluid communication. Additionally, the system preferably includes a dispensing port for dispensing the mixed cleaning composition to a processing tool.

[0099] Generally chemically inert, impurity-free, flexible, and elastic polymeric film materials such as high-density polyethylene can be used to make liners for the one or more containers. The liner material is treated without requiring co-extrusion or barrier layers and without any pigments, UV inhibitors, or treatment agents that could adversely affect the purity requirements of the components to be placed in the liner. A list of liner materials includes films comprising: virgin (additive-free) polyethylene, virgin polytetrafluoroethylene (PTFE), polypropylene, polyurethane, polyvinylidene chloride, polyvinyl chloride, polyacetal, polystyrene, polyacrylonitrile, polybutene, etc. Exemplary thicknesses of such liner materials range from about 5 mils (0.005 inches) to about 30 mils (0.030 inches), such as, for example, 20 mils (0.020 inches).

[0100] Regarding the containers for the reagent kits, the following patents and patent applications are hereby incorporated herein by reference in their entirety: U.S. Patent No. 7,188,644, entitled “Apparatus and Method for Minimizing the Generation of Parts in Ultrapure Liquids”; U.S. Patent No. 6,698,619, entitled “Returnable and Reusable Bag-in-Drum Fluid Storage and Dispensing Container System”; and U.S. Patent No. 6,698,619, filed on May 9, 2007, by John E. Q. Hughes, entitled “Systems and Methods for Material Blending and Dispensing”. U.S. Patent Application No. 60 / 916,966 entitled “Systems and methods for material blending and distributing”, filed on May 9, 2008, in the name of Advanced Technology Materials, Inc., and PCT / US08 / 63276 entitled “Systems and methods for material blending and distributing”.

[0101] Therefore, in another aspect, the present invention provides a kit comprising one or more containers having components suitable for removing silicon nitride from a microelectronic device, wherein the one or more containers of the kit contain (a) phosphoric acid; (b) at least one silane compound selected from (i) alkylaminoalkoxysilanes and (ii) alkylaminohydroxysilanes as described herein; and (c) a solvent comprising water; and optionally (d) a fluoride compound, wherein the fluoride compound is not hexafluorosilicic acid.

[0102] The invention may be further illustrated by the following examples of certain embodiments thereof, but it will be understood that, unless otherwise specifically indicated, these examples are included for illustrative purposes only and are not intended to limit the scope of the invention.

[0103] Example

[0104] The high aspect ratio structure was treated first to remove any oxide film from the exposed silicon nitride. The structure was then treated in a formulation at the desired temperature in a boiling flask with stirring. For specified silicate loading conditions, tetramethylammonium silicate (TMAS) or silica nanoparticles were added. For Examples 16 and 17, TMAS was used, with the loading provided in ppm Si. For all other examples, SiO2 nanoparticles were used, with the silicate loading provided in ppm SiO2. The structure was treated for a sufficient time to adequately remove SiN, typically between 45 minutes and 2 hours. After treatment in the formulation, the structure was rinsed with hot deionized water and dried under flowing nitrogen. The etch rates shown were similarly obtained by treating a blanket-coated film, where the thickness was measured using a spectroscopic ellipsometry.

[0105] Table 1

[0106] Example of a formulation (by weight, approximately 85% H3PO4)

[0107]

[0108] The abbreviations have the same meaning as those used for examples 1 to 11 above.

[0109] Table 2

[0110] The excessive thickness of the oxides in the structure after etching (deposit buildup) varies with the amount of SiO2 added to the formulation (at 152°C).

[0111]

[0112] “OK” indicates a change of <2 nm relative to the initial oxide thickness.

[0113] Table 3

[0114] Etching rate (ER) as SiO2 is added (at 152°C)

[0115]

[0116] It should be noted that, compared to Examples 12 to 14, 85% H3PO4 exhibits poor selectivity for oxides (approximately 40:1 at 0 ppm silica, Table 3) or leads to excessive oxide redeposition (at 100 ppm and 200 ppm silica, Table 2).

[0117] Table 4

[0118] Performance overview of formulations 16 and 17:

[0119]

[0120] During processing, the addition of dissolved silicates reduces the silicon oxide etching rate without substantially altering the nitride etching rate.

[0121] At a sufficiently high concentration of dissolved silicates, silica-rich precipitates are redeposited on the SiO2 surface within the 3D NAND structure.

[0122] In this case, the load window is limited at the low end by a selectivity > 1000 and at the high end by the start of re-deposition. Different selectivity targets will result in different widths of the load window.

Claims

1. A composition comprising: (a) Phosphoric acid; (b) At least one silane selected from (i) alkylaminoalkoxysilane and (ii) alkylaminohydroxysilane, wherein the silane has at least one moiety selected from alkoxy, hydroxy and fluorine groups; (c) Solvents, including water; (d) a fluoride compound, wherein the fluoride compound is not hexafluorosilicic acid; and (e) Alkaneamines or their phosphates, The alkylaminoalkoxysilane and alkylaminohydroxysilane mentioned above are represented by the following formula: 、 、 or 。 2. The composition according to claim 1, wherein the phosphoric acid is present in the range of 50 to 95% by weight based on the total weight of the composition.

3. The composition according to claim 1, wherein the fluoride compound is selected from HF and monofluorophosphoric acid.

4. The composition according to claim 1, wherein the fluoride compound is selected from cesium fluoride and potassium fluoride.

5. The composition according to claim 1, wherein the fluoride compound is selected from fluoroboric acid; tetramethylammonium hexafluorophosphate; ammonium fluoride; ammonium difluoride; quaternary ammonium tetrafluoroborate and quaternary phosphorus tetrafluoroborate, having the formula NR'4BF4 and the formula PR'4BF4 respectively, wherein R' may be the same or different from each other, and is selected from hydrogen, straight-chain, branched or cyclic C1-C6 alkyl and straight-chain or branched C6-C6 alkyl. 10 Aryl; Tetrabutylammonium tetrafluoroborate (TBA-BF4); and combinations thereof.

6. The composition according to claim 1, further comprising a surfactant, a carboxylic acid compound, or a dissolved silicate.

7. A composition comprising: (a) Phosphoric acid; (b) N-(2-aminoethyl)-3-aminopropylsilanetriol or (3-aminopropyl)silanetriol; (c) Solvents, including water; (d) a fluoride compound, wherein the fluoride compound is not hexafluorosilicic acid; and (e) Alkaneamines or their phosphates, The alkylamine or its phosphate is present and is selected from triethylamine or its dihydrogen phosphate.

8. The composition according to claim 7, wherein the fluoride compound is selected from HF and monofluorophosphoric acid.

9. The composition according to claim 7, further comprising a surfactant, a carboxylic acid compound, or a dissolved silicate.

Images