Compositions and methods for selective etching of silicon nitride films

Abstract

The present invention provides a wet etching composition and method for etching the surface of a microelectronic device, the surface comprising silicon nitride (SiN), silicon oxide and polycrystalline silicon, the polycrystalline silicon in one embodiment being in contact with a surface comprising a compound that is electrochemically more inert than silicon, and optional other materials, which may include conductive, semiconductive or insulating materials suitable for microelectronic devices, or processing materials suitable for fabricating microelectronic devices.

Description

Technical Field

[0001] The present invention generally relates to compositions and methods for selectively etching silicon nitride films in the presence of silicon dioxide and polycrystalline silicon. Background Technology

[0002] In the microelectronics industry, there is a continuous demand for improved device performance, as well as reduced device size and feature size. Reducing feature size offers the dual benefits of increased device feature density and increased device speed.

[0003] Reducing feature size and device dimensions requires finding new ways to improve the steps of multi-step methods for fabricating microelectronic devices. Among the methods used to fabricate many types of microelectronic devices, the removal of silicon nitride is a common step. Thin layers of silicon nitride (Si3N4), typically deposited from silane (SiH4) and ammonia (NH3) via chemical vapor deposition, can be used as barriers against water and sodium in microelectronic devices. Similarly, patterned silicon nitride layers are used as masks for spatially selective silicon oxide growth. After application, it may be necessary to remove all or part of this silicon nitride material, which is typically done by etching.

[0004] Removing silicon nitride from a substrate by etching is advantageously performed without damaging or destroying other exposed or covered features of the microelectronic device. Typically, silicon nitride removal methods prioritize removing it relative to other materials (such as silicon oxide) still present on the surface of the microelectronic device substrate. According to various commercial methods, silicon nitride is removed from the surface of a microelectronic device by wet etching, which involves exposing the substrate surface to concentrated phosphoric acid (H3PO4) at high temperatures, such as in a bath between 150°C and 180°C. Conventional wet etching techniques for selectively removing silicon nitride relative to silicon oxide use an aqueous solution of phosphoric acid (H3PO4), typically about 85 wt% phosphoric acid and 15 wt% water. Using fresh, hot phosphoric acid, a typical Si3N4:SiO2 selectivity can be about 40:1.

[0005] In other device structures, in addition to silicon oxide, there may be exposed polycrystalline silicon surfaces, which further complicates the required selective silicon nitride etching methods. Therefore, there is a need for compositions and methods suitable for preferentially etching silicon nitride in the presence of both silicon oxide and polycrystalline silicon surfaces. Summary of the Invention

[0006] In general, the present invention relates to wet etching compositions for etching surfaces of microelectronic devices containing silicon nitride (SiN), silicon oxide, and polycrystalline silicon; in some embodiments, the polycrystalline silicon is in contact with a surface comprising a compound that is electrochemically more inert than silicon. Optionally, other materials are present, such as conductive, semiconductive, or insulating materials suitable for microelectronic devices, or processing materials suitable for fabricating microelectronic devices. The etching compositions described herein comprise phosphoric acid, aminoalkylsilanols, certain polycrystalline silicon etching inhibitors, optional fluorine compounds, and a certain amount of water added in connection with or separately from the composition of the etching composition. Attached Figure Description

[0007] Figure 1 The illustration shows a front and back view of the etching step in practice with the method of the present invention, with reference to an illustrative substrate.

[0008] Figure 2 As described in Table 1, the provided instances are supported. Detailed Implementation

[0009] In a first aspect, the present invention provides a method for etching silicon nitride on a microelectronic device substrate, said substrate comprising a surface comprising silicon nitride, a surface comprising silicon oxide, and a surface comprising polysilicon, said method comprising:

[0010] An etching composition is provided, the composition comprising:

[0011] a. Concentrated phosphoric acid, in an amount of at least 60% by weight based on the total weight of the composition;

[0012] b. Polysilicon corrosion inhibitor compounds;

[0013] c. aminoalkylsilanols; and

[0014] d. Optional fluorine compounds;

[0015] A substrate is provided having a surface comprising silicon nitride and a surface comprising polycrystalline silicon.

[0016] The substrate is brought into contact with the composition under conditions of effective etching of silicon nitride.

[0017] In one embodiment, the surface comprising polycrystalline silicon is in contact with a surface comprising a composition that is electrochemically more inert than silicon. In one embodiment, the composition is free of fluorine compounds.

[0018] The compositions of the present invention are suitable as etching compositions for etching or removing silicon nitride films on certain microelectronic devices. These compositions have unexpectedly shown excellent selectivity in etching silicon nitride in the presence of other materials commonly found in certain microelectronic devices.

[0019] As used herein, the term “microelectronic device” (or “microelectronic device substrate” or simply “substrate”) is used in a manner consistent with its common understanding in the fields of electronic devices, microelectronics, and semiconductor manufacturing, for example, to refer to any of a variety of different types of: semiconductor substrates; integrated circuits; solid-state memory devices; hard disk storage; read heads, write heads, read / write heads, and their mechanical or electronic components; flat panel displays; phase-change memory devices; solar panels and other products including one or more solar cell devices; photovoltaic devices; and microelectromechanical systems (MEMS) for use in microelectronic, integrated circuit, energy harvesting, or computer chip applications. It should be understood that the term “microelectronic device” can refer to any process-defined microelectronic device or microelectronic device substrate containing or prepared to contain functional electronic (current-carrying) structures, functional semiconductor structures, and insulating structures for final electronic use in a microelectronic device or microelectronic assembly.

[0020] As used herein, the term "silicon nitride" is given a meaning consistent with that used in the microelectronics and semiconductor manufacturing industries. Consistent with this, silicon nitride refers to a material comprising a thin film of amorphous silicon nitride, wherein the silicon oxide has commercially available low levels of other materials or impurities, and some variations may exist around the nominal stoichiometry of Si3N4. Silicon nitride may be present as part of a substrate for a microelectronic device, as a functional feature of the device, such as as a barrier or insulating layer, or may be present to act as a material facilitating multi-step fabrication methods for preparing microelectronic devices.

[0021] As used herein, the term "silicon oxide" is given a meaning consistent with that used in the microelectronics and semiconductor manufacturing industries. Consistent with this, silicon oxide refers to silicon oxide (SiO₂). x (e.g., SiO2), "thermal oxides" (ThO) x Thin films made of silicon oxide and similar materials. Silicon oxide can be placed on a substrate by any method, such as by chemical vapor deposition from TEOS or another source, or by thermal deposition. Silicon oxide may advantageously contain commercially available low amounts of other materials or impurities. Silicon oxide can be present as part of a substrate for a microelectronic device, or as a feature of a microelectronic device, for example, as an insulating layer.

[0022] As used herein, the term "polycrystalline silicon" has the common understanding as used in the microelectronics and semiconductor manufacturing industries as a polycrystalline form of silicon. In other words, polycrystalline silicon, or "poly-Si," is a high-purity polycrystalline form of silicon that can be doped to modify its electrical properties.

[0023] The reference in this document to polycrystalline silicon surfaces in contact with compositions that are electrochemically more inert than silicon is intended to describe surfaces that can influence the current corrosion of polycrystalline silicon when in contact with it. As used herein, the term "inert" is intended to refer to the qualities of various inert elements, reflecting their properties as elements resistant to oxidation and corrosion in aqueous environments. Thus, a surface and a composition containing such a surface are sufficiently "inert" than silicon when they readily generate electrochemical flux and therefore undergo corrosive degradation over time when in close contact with polycrystalline silicon in an aqueous environment. As described herein, the methods and compositions of the present invention are particularly suitable for selectively etching silicon nitride on substrates of microelectronic devices that also have such polycrystalline silicon structures or surfaces in contact with such "more inert surfaces." Examples of such surfaces include tungsten silicide, nickel silicide, platinum silicide, and titanium silicide.

[0024] Examples of certain etching compositions include compositions in aqueous solution form comprising, substantially comprising, or consisting of: an aqueous solution of phosphoric acid (e.g., concentrated phosphoric acid and optionally an amount of added water) of a fluorinated compound in an amount effective to produce the desired etching (including applicable or advantageous etching rates) of silicon nitride; an amount of aminoalkylsilanol in an amount effective to improve the selectivity of silicon nitride relative to silicon oxide; an effective amount of one or more specific current inhibitors; and optionally dissolved silica. These and other example compositions may comprise, consist of, or consist substantially of: the listed components and optional components. As a general convention, throughout this specification, a composition of a substance such as an etching composition or its components or components as described herein, which is claimed to "consist substantially of a specified set of components or materials," means a composition containing the specified components or materials, having no more than a low or insignificant amount of other components or materials, such as no more than 5, 2, 1, 0.5, 0.1, or 0.05 parts by weight of other components or materials. For example, an etching composition containing a material substantially consisting of an aqueous solution of phosphoric acid, an aminoalkylsilane, a polysilicon corrosion inhibitor, and optional ingredients as described means an etching composition containing these ingredients and any one or more other dissolved or undissolved materials (alone or in total) in no more than 5, 2, 1, 0.5, 0.1, or 0.05 parts by weight, other than the identified material.

[0025] The etching composition includes an aqueous solution of phosphoric acid (e.g., concentrated phosphoric acid) in an amount sufficient to effectively produce the desired silicon nitride etching. The term "aqueous phosphoric acid solution" refers to a component of the etching composition that is mixed or combined with other components of the etching composition to form the etching composition. The term "solid phosphoric acid" refers to an aqueous phosphoric acid component or a non-aqueous component of the etching composition prepared from an aqueous phosphoric acid component.

[0026] The amount of solid phosphate contained in the etching composition can be such that, in combination with other materials in the etching composition, it will provide the desired etching performance (including the desired silicon nitride etching rate and selectivity), which typically requires a relatively high amount (concentration) of solid phosphate. For example, the etching composition may contain a certain amount of solid phosphate at least about 50% by weight of the total weight of the etching composition, such as at least 70, or at least about 80 or 85% by weight of the total weight of the etching composition.

[0027] To provide the required 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 an etching 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 no 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 about 15 or 20% by weight of water containing at least about 80 or 85% by weight of phosphoric acid solids. Alternatively, an etching composition may be considered as comprising a certain amount of concentrated phosphoric acid diluted with water, meaning, 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 component of the etching composition may be concentrated or dilute phosphoric acid, and the etching composition may contain additional amounts of water provided to the etching composition as a separate component or as a separate water component.

[0028] As an example, if concentrated phosphoric acid is used to form an etching composition, the amount of concentrated phosphoric acid (85% by weight in water) may be at least 60, for example at least 80, or at least 90, 93, 95, or at least 98% by weight of the etching composition.

[0029] As used herein, the term "fluorine compound" refers to certain etchants optionally added to increase the etching rate of titanium nitride. Such compounds include, but are not limited to: HF, ammonium fluoride, tetrafluoroboric acid, hexafluorosilicic acid, other compounds containing BF or Si-F bonds, tetrabutylammonium tetrafluoroborate (TBA-BF4), tetraalkylammonium fluoride (NR1R2R3R4F), and combinations thereof. In one embodiment, the fluoride compound is selected from HF, ammonium fluoride, tetrafluoroboric acid, hexafluorosilicic acid, tetrabutylammonium tetrafluoroborate, tetra(C1-C6 alkyl)ammonium fluoride, and combinations thereof. In another embodiment, the fluorine compound may include any fluorine compound covalently bonded to carbon, which may be any CF2 or CF3 group or any fluorinated surfactant group.

[0030] The amount of optional fluorine compound contained in the compositions of the present invention can be such that, in combination with other materials of the etching composition, it will provide the desired etching performance, including the desired silicon nitride etching rate and selectivity. For example, the etching composition may contain a fluorine source compound in an amount ranging from about 5 to 10,000 or even up to 50,000 parts per million (i.e., 0.0005 to 1 or even 5% by weight) based on the total weight of the etching composition, such as about 20 to 2,000 parts per million (i.e., 0.002 to 0.2% by weight) based on the total weight of the etching composition.

[0031] The composition comprises an aminoalkylsilanol, which, as used herein, refers to a silane (--SiO-) based compound or molecule containing at least one silicon atom and at least one amino group located on an alkyl substituent (i.e., an aminoalkyl substituent attached to a silicon atom) of the compound. The silanol functional group may be present in the formulated mixture as manufactured or may be formed by hydrolysis upon addition to the formulated mixture or under process conditions. For example, silanolates are known to hydrolyze rapidly under strongly acidic conditions, and siloxanes will hydrolyze under process conditions.

[0032] In some embodiments, the aminoalkylsilane alcohol compound has the following formula:

[0033] (HO)3Si-(C1-C 12 alkyl)-NH2, and

[0034] (HO)3Si-(C1-C6 alkyl)-NH-(C1-C6 alkyl)-NH2.

[0035] According to the present invention, the applicant has discovered that aminoalkylsilanol compounds present as a portion of an etching composition containing a combination of phosphoric acid and fluorine compounds and a polysilicon corrosion inhibitor can exhibit the improved properties described herein.

[0036] Examples of aminoalkylsilane alcohols include 3-aminopropylsilanetriol, N-(6-aminohexyl)aminopropylsilane alcohol, N-(2,aminoethyl)-(2,aminoethyl)-3-aminopropylsilanetriol and (3-trimethoxysilylpropyl)diethylenetriamine.

[0037] In the compositions of the present invention, the amount of aminoalkylsilanol contained in such compositions may be such that, in combination with other materials in the etching composition, it will provide the desired selective etching performance, including the desired silicon nitride etching rate and selectivity relative to silicon dioxide and polysilicon. For example, the etching composition may contain an amount of aminoalkylsilanol compound, which may be a single species or a combination of two or more species, in the range of 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 in the range of 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.

[0038] The compositions of the present invention utilize at least one compound that acts as a polysilicon inhibitor during selective etching of silicon nitride in the presence of polysilicon. In this regard, not wishing to be bound by theory, the applicant believes that when such a polysilicon surface comes into contact with a surface comprising a material more inert than silicon, this component in the composition serves to inhibit the etching of the polysilicon surface by suppressing the electron flow and / or transport of etching products. In this regard, various compounds have been discovered that can achieve this polysilicon etching inhibition target, some of which can be classified as surfactants. Examples include:

[0039] Decyltrimethylammonium chloride

[0040] Dodecyltrimethylammonium chloride

[0041] Hexadecyltrimethylammonium chloride

[0042] 4-Phenyridine N-oxide

[0043] CAPS (3-(cyclohexylamino)-1-propanesulfonic acid)

[0044] Trimethylamine N-oxide

[0045] 4-Aminobenzenesulfonic acid

[0046] Dodecylamine

[0047] Isonicotinic acid N-oxide

[0048] Trimethylphenylammonium chloride

[0049] 4-(cyclohexylamino)-1-butyric acid (CABS)

[0050] Lauryl dimethylamine oxide

[0051] 1-Decyl-3-methylimidazolium chloride

[0052] [2-(dicyclohexylphosphino)ethyl]trimethylammonium chloride

[0053] Tomamine AO-405

[0054] Nicotinic acid N-oxide

[0055] Poly(4-vinylpyridine)

[0056] 4-(Benzyloxy)pyridine N-oxide

[0057] 1-Octy-2-pyrrolidone

[0058] 1-Dodecyl-2-pyrrolidone

[0059] Dinonylsulfosuccinate ammonium

[0060] Poly(4-styrenesulfonic acid)

[0061] Tolyltriazole

[0062] Tetradecyldimethylamine N-oxide (N-oxide, tetradecyldimethylamine)

[0063] 1-Octanonic acid

[0064] benzyltrimethylammonium chloride

[0065] p-Aminobenzenesulfonamide

[0066] Pyridine N-oxide

[0067] Polyethylene imine

[0068] Polyacrylic acid

[0069] Polyvinylpyrrolidone

[0070] Thetawet FS-8150

[0071] 2,5-Dimethylphenylacetic acid

[0072] 2-Hydroxypyridine N-oxide

[0073] 4-(cyclohexylamino)-1-butyric acid (CABS)

[0074] Tetradecyl dimethylamine oxide)

[0075] benzalkonium chloride

[0076] Hexyl diphenyl oxide disulfonic acid (5-hexyl-2-(4-hexyl-2-sulfophenoxy)benzenesulfonic acid)

[0077] Dodecyl diphenyl oxide disulfonic acid (5-dodecyl-2-(4-dodecyl-2-sulfophenoxy)benzenesulfonic acid)

[0078] Capstone FS-35 (Fluorosurfactant)

[0079] Dodecylbenzenesulfonic acid (DDBSA)

[0080] NF (low-foaming, anionic fluorinated surfactant)

[0081] NI-M (Fluorinated Nonionic Surfactant)

[0082] heptane-4-sulfonic acid

[0083] p-Tolylacetic acid

[0084] sulfosuccinic acid

[0085] Thetawet FS-8050 (Nonionic Ethoxylated Fluorosurfactant)

[0086] Tomamine AO-14-2 (50% active bis-(2-hydroxyethyl)isodecoxypropylamine oxide)

[0087] In one embodiment, the polysilicon corrosion inhibitor is selected from straight-chain and branched-chain C8-C4. 16 Alkylbenzene sulfonic acids. Examples include octylbenzene sulfonic acid, nonylalkylbenzene sulfonic acid, decylbenzene sulfonic acid, undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid, tridecylbenzene sulfonic acid, tetradecylbenzene sulfonic acid, tetradecylbenzene sulfonic acid, pentadecylbenzene sulfonic acid, hexadecylbenzene sulfonic acid, heptadecanylbenzene sulfonic acid, octadecylbenzene sulfonic acid, and C6-C... 16 Alkyl diphenyl sulfide disulfonic acid and C6-C 16 Alkyl diphenylamine disulfonic acid. In one embodiment, the polysilicon corrosion inhibitor is dodecylbenzenesulfonic acid.

[0088] In one embodiment, the polysilicon corrosion inhibitor is selected from chalcogenides or C6-C. 16 Alkyl diphenyl oxide disulfonic acid. In one embodiment, the polysilicon corrosion inhibitor is selected from alkyl diphenyl oxide disulfonic acid and dodecyl diphenyl oxide disulfonic acid.

[0089] Optionally, the compositions of the present invention may also contain a certain amount of silica dissolved in phosphoric acid, for example by dissolving solid silica material in phosphoric acid or by adding a soluble silicon-containing compound that can react with aqueous phosphoric acid to form dissolved silica. Examples of such compounds include TMAS (tetramethylammonium silicate), tetraacetoxysilane, or tetraalkoxysilane, such as tetramethoxysilane, tetraethoxysilane, or the like. Dissolved silica can effectively improve the selectivity of the etching composition toward silicon nitride. The amount can be any suitable amount that does not cause the pretreated silica to become supersaturated under etching process conditions, such as about 5 to 10,000 parts per million of dissolved silica or soluble silicon-containing compound by weight of the total etching composition, or about 20 to 5,000, 3,000, 1,000, or 500 parts per million by weight of the total etching composition.

[0090] The etching composition may contain water from one or more sources. For example, water may be present in the aqueous phosphoric acid component. Additionally, water may serve as a carrier for one or more of the other components of the 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 performance characteristics, including suitable (sufficiently high) silicon nitride etching rates. The presence of water tends to increase the silicon nitride etching rate but may also lower the boiling point of the composition, leading to a reduction in the operating temperature of the etching composition and the opposite effect. Examples of the amount of water from all sources in the etching composition may be less than about 50, 40, or 30% by weight of the total weight of the etching composition, for example, in the range of about 5% to about 25% by weight, or in the range of about 10 to 20% by weight of water of the total weight of the etching composition.

[0091] Optionally, the etching compositions described in these and other examples may contain, consist of, or consist essentially of: phosphoric acid, aminoalkylsilane, at least one polysilicon etching inhibitor, and any or any combination of the identified optional components. In some embodiments, the compositions of the present 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 abrasives.

[0092] The compositions of the present invention can be prepared by any method suitable for producing the etched compositions as described. In one method, aqueous or solid components can be combined, optionally accompanied by heating, and any mixture can be stirred until homogeneous.

[0093] The compositions described herein are applicable to methods for removing silicon nitride from the surface of a microelectronic device substrate. The substrate may contain other materials suitable for microelectronic devices, such as one or more of the following: insulators, barrier layers, conductive materials, semiconductive materials, or materials suitable for processing microelectronic devices (e.g., photoresists, masks, and others). Example substrates have surfaces comprising silicon nitride, thermal oxide (ThOx), and PETEOS (using plasma-enhanced tetraethyl orthosilicate), as well as polycrystalline silicon.

[0094] When used, the compositions of the present invention can provide etch performance based on commercial performance requirements and desired applicability, and can provide improved etch rate and selectivity relative to silicon nitride compared to comparative etch compositions.

[0095] Methods for etching substrates of microelectronic devices are known in semiconductor manufacturing technology and can be performed on known and commercially available equipment. Generally, to etch a substrate to selectively remove material at the substrate surface, an etching composition can be applied to the surface and brought into contact with the surface structure to selectively remove certain structures chemically.

[0096] The silicon nitride film may have a thin oxide surface that can suppress the etching process because the composition is designed to etch the oxide very slowly. In such cases, a very brief treatment with dilute HF can be an advantageous first step.

[0097] In the etching step, the etching composition can be applied to the surface in any suitable manner, such as by spraying the etching composition onto the surface; by immersing the substrate (in a static or dynamic volume of the composition) into the etching composition; by contacting the surface with another material (e.g., a pad or fiber absorbent feeder element) on which the etching composition has been absorbed; by contacting the substrate with a quantity of the etching composition in a circulating pool; or by any other suitable means, method, or technique to remove contact between the etching composition and the surface of a microelectronic substrate containing silicon-germanium and silicon. Applications can be made in batch or single wafer equipment for dynamic or static cleaning.

[0098] The conditions (e.g., time and temperature) suitable for the etching method can be any conditions found to be effective or advantageous. Generally, the etching composition contacts the surface, such as by immersion in a bath of the etching composition for a period sufficient to selectively remove silicon nitride. The exposure time to the etching composition and the temperature of the etching composition are effective for the desired amount of silicon nitride removed from the substrate surface. The etching step time should not be too short, as this would mean that the silicon nitride etching rate may be too high, which can make process control difficult and degrade the quality of the microelectronic device at the end of the etching step. Of course, the required etching step time is preferably not too long to ensure good efficiency and throughput of the etching process and semiconductor manufacturing line. Examples of suitable etching step times are in the range of about 5 minutes to about 200 minutes, or about 10 minutes to about 60 minutes, at temperatures in the range of about 100°C to about 180°C. Such contact times and temperatures are illustrative, and any other suitable time and temperature conditions effective for obtaining the desired removal selectivity can be used.

[0099] 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 alternating thin film layers of silicon nitride as a structural feature of the substrate, said substrate comprising alternating thin film layers of silicon nitride and silicon oxide, as well as polysilicon, conductive metal silicides, and dielectrics (such as zirconium oxide or aluminum oxide). The silicon oxide layer is a high aspect ratio structure containing silicon nitride layers disposed between the silicon oxide layers. See also Figure 1 This illustrates a substrate before and after a selective etching step, as described herein, which selectively and efficiently removes silicon nitride from the substrate in a manner that can be selectively adopted (e.g., preferentially over silicon oxide). The substrate prior to the etching step comprises alternating layers of silicon nitride disposed in openings between high aspect ratio silicon oxide structures. The etching step removes the silicon nitride to leave a silicon oxide layer, as... Figure 1 As shown on the right-hand substrate, an opening or "slit" separates the silicon oxide layer. According to this specification, a method such as... Figure 1 The etching method described uses etching Figure 1 The substrate shown. Compared with existing technologies and similar etching compositions and methods, the example etching method exhibits a significantly increased SiN etching rate, good selectivity relative to silicon oxide (>50, preferably close to or greater than 100), and avoidance of large silicon dioxide redeposition (as demonstrated by the closure or near closure of the slit opening).

[0100] After the desired amount of selective silicon nitride etching is completed, the etched composition remaining on the etched microelectronic device surface can be removed from the surface by any desired and applicable method, such as by rinsing, washing, or other removal steps, using water (or optionally phosphoric acid, followed by water). For example, after etching, the microelectronic device substrate can be rinsed with deionized water (e.g., at a temperature between about 20 and about 90°C), followed by drying, such as spin drying, N2 drying, vapor drying, etc. After rinsing, the substrate surface can be measured for the presence and amount of particles at the surface.

[0101] As noted above, due to the presence of the polysilicon etching inhibitor component, the compositions of the present invention unexpectedly exhibit excellent selectivity in wet etching environments on microelectronic device substrates having polysilicon coated areas. Therefore, in another aspect, the present invention provides a composition comprising:

[0102] a. Concentrated phosphoric acid, in an amount of at least 60% by weight based on the total weight of the composition;

[0103] b. Selected from straight chains and branched chains C8-C 16 Alkylbenzenesulfonic acid and C6-C 12 Alkyl diphenyl oxide disulfonic acid polycrystalline silicon corrosion inhibitor compounds; and

[0104] c. Aminoalkylsilanols.

[0105] In some embodiments, the aminoalkylsilanol is selected from 3-aminopropylsilanetriol, N-(6-aminohexyl)aminopropylsilanol, 3-aminopropyltriethanol, 3-aminopropyltriethanol, and (3-trimethoxysilylpropyl)diethylenetriamine. In some embodiments, the polysilicon corrosion inhibitor is selected from acetyl diphenyl oxide disulfonic acid, dodecyl diphenyl oxide disulfonic acid, and dodecylbenzenesulfonic acid. In some embodiments, the composition further comprises a fluorine compound, such as HF.

[0106] In one embodiment, the composition comprises:

[0107] a. Concentrated phosphoric acid, in an amount of at least 60% by weight based on the total weight of the composition;

[0108] b. Dodecylbenzenesulfonic acid; and

[0109] c. 3-Aminopropylsilanetriol. In one embodiment, the composition further comprises HF.

[0110] In one embodiment, the composition comprises:

[0111] a. Concentrated phosphoric acid, in an amount of at least 60% by weight based on the total weight of the composition;

[0112] b. Selected from straight chains and branched chains C6-C 16 Alkylbenzenesulfonic acid and C6-C 16 Alkyl diphenyl oxide disulfonic acid polycrystalline silicon corrosion inhibitor compound

[0113] c. aminoalkylsilanols; and optional

[0114] d. Fluorine compounds.

[0115] In one embodiment, the polysilicon corrosion inhibitor compound is selected from dodecylbenzenesulfonic acid, dodecyl diphenyl oxide disulfonic acid, and hexyl diphenyl oxide disulfonic acid.

[0116] In one embodiment, the aminoalkylsilane alcohol compound has the following formula:

[0117] (HO)3Si-(C1-C 12 alkyl)-NH2, and

[0118] (HO)3Si-(C1-C6 alkyl)-NH-(C1-C6 alkyl)-NH2.

[0119] In one embodiment, the alkylaminosilanol is selected from 3-aminopropylsilanetriol and N-(6-aminohexyl)aminopropylsilanol. In another embodiment, the fluorine compound is HF, the polysilicon corrosion inhibitor compound is dodecylbenzenesulfonic acid, and the aminoalkylsilane is 3-aminopropylsilanetriol.

[0120] It should be understood that the conventional practice is to prepare a concentrated form of a semi-aqueous composition for dilution before use. For example, the composition may be manufactured in a more concentrated form and subsequently diluted at the manufacturer, before use, and / or during use at the factory with at least one solvent. Dilution ratios can range from about 0.1 parts diluent: 1 part composition concentrate to about 100 parts diluent: 1 part composition concentrate. The compositions described herein can be readily formulated by simply adding the corresponding ingredients and mixing to a homogeneous state. Furthermore, the compositions can be readily formulated as single-package formulations or multi-component formulations, preferably multi-component formulations, mixed at or before use. The individual components of a multi-component formulation can be mixed at the tool or in a mixing zone / area, such as an inline mixer or in a reservoir upstream of the tool. It is considered that the various components of a multi-component formulation may contain any combination of ingredients / components that, when mixed together, form the desired composition. The concentration of the corresponding components can vary widely in a specific multiple of the aqueous composition, i.e., more dilute or more concentrated, and it should be understood that the aqueous composition may contain, consist of or consist substantially of any combination of components consistent with the disclosure herein.

[0121] Therefore, in a third aspect, the present invention provides a kit comprising one or more components adapted to form the compositions described herein, in one or more containers. The containers of the kit must be suitable for storing and transporting the semi-aqueous composition components, for example... Container (Advanced Technology Materials, Inc., Danbury, Connecticut, USA). One or more containers containing components of a composition preferably include components for providing fluid communication between the components in the one or more containers for blending and dispensing. For example, see reference... The container allows for the application of gas pressure to the exterior of a liner within one or more containers, causing at least a portion of the contents of the liner to be released and thus enabling fluid communication for blending and dispensing. Alternatively, gas pressure can be applied to the top space of a conventional pressurized container or pump capable of enabling fluid communication. Additionally, the system preferably includes a dispensing port for dispensing the blended composition to a processing tool.

[0122] Essentially chemically inert, impurity-free, flexible, and elastic polymeric film materials such as high-density polyethylene can be used to manufacture the liners of the one or more containers. Typically, processing suitable liner materials does not require co-extrusion or a barrier layer, and no pigments, UV inhibitors, or treatment agents are needed, which could adversely affect the purity requirements for the components to be placed in the liner. A list of suitable liner materials includes films comprising virgin (additive-free) polyethylene, virgin polytetrafluoroethylene (PTFE), polypropylene, polyurethane, polyvinylidene chloride, polyvinyl chloride, polyacetal, polystyrene, polyacrylonitrile, polybutene, etc. The preferred thickness of the liner material is in the range of about 5 mils (0.005 inches) to about 30 mils (0.030 inches), for example, a thickness of 20 mils (0.020 inches).

[0123] Regarding containers used in reagent kits, the disclosures of 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 Particulates in Ultrapure Liquids”; U.S. Patent No. 6,698,619, entitled “Returnable and Reusable Bag-in-Drum Fluid Storage and Dispensing Container System”; and PCT / US08 / 63276, filed May 9, 2008, entitled “Systems and Methods for Material Blending and Dispensing”.

[0124] The invention can 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.

[0125] Example

[0126] Selective silicon nitride etching of polysilicon can be improved by adding small amounts of various polysilicon etching inhibitors. Without these inhibitors, the polysilicon surface exhibits a high overall etch rate and non-uniform etch, resulting in a rough film. An example of a selective silicon nitride etching formulation is shown in Example A. This consists of concentrated phosphoric acid with a small amount of 3-aminopropylsilanetriol added to reduce redeposition of dissolved silicon. A small amount of HF is also included to increase the silicon nitride removal rate.

[0127] Several compounds have been found to alter the etching behavior of polysilicon in selective nitride etching (i.e., act as inhibitors). Figure 2 (See Table 1). The performance of some of these polysilicon etching inhibitors is shown in Table 3. Before exposure to the selective silicon nitride etch formulation, native oxides were removed for 60 seconds at ambient temperature using water containing 0.5 wt% HF, followed by rinsing with flowing deionized water for 2 minutes. The etching rate was measured using the polysilicon loss during 1 hour of exposure at 150°C. The current-induced polysilicon etching rate was measured using a structure with a polysilicon film in contact with a more inert metal and two films in contact with the etching solution.

[0128] legend:

[0129] APST: 3-Aminopropylsilanetriol

[0130] DIW: Deionized Water

[0131] Aromox 14D-W970: Tetradecyl dimethylamine oxide

[0132] PSSA: Poly(4-styrenesulfonic acid)

[0133] CAPS: 3-(cyclohexylamino)-1-propanesulfonic acid

[0134] PAA: Poly(acrylic acid)

[0135] NF: Low-foaming fluorosurfactant

[0136] NI-M: Water-soluble nonionic fluorinated surfactant

[0137] Thetawet TM FS-8050: 50% active water-soluble nonionic surfactant

[0138] Q22: Cationic fluorinated surfactants

[0139] DDBSA: Dodecylbenzenesulfonic acid

[0140] Thetawet TM FS-8150: Nonionic fluorinated surfactant

[0141] 6LA-70: 72% active C-6 linear diphenyl oxide disulfonic acid

[0142] DBA-70: 71% active C-12 branched diphenyl oxide disulfonic acid

[0143] Performance data:

[0144]

[0145]

[0146] Example A demonstrates the polysilicon etching rate of the base formulation. This exhibits the highest polysilicon etching rate and a current etching rate approximately 50% higher. In Examples B through N, 45 ppm of dissolved silicon was added to the solution using tetramethylammonium silicate to simulate the typical solution concentration that would exist after partial etching of silicon nitride during a typical silicon nitride removal process. Example B consists of a base formulation with added dissolved silicon. Both general etching and current etching are slightly reduced. In Examples C through N, current inhibitors and 45 ppm of dissolved silicon were added to the base formulation. In Examples C, D, E, and F, the etching rate was not reduced by the additives, but removal was more uniform, resulting in a smoother surface. In Examples G through N, the etching rate was suppressed.

[0147] The present invention has been described in detail with particular reference to certain embodiments thereof, but it should be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims

1. A method for etching silicon nitride on a substrate of a microelectronic device, said substrate comprising a surface comprising silicon nitride, a surface comprising silicon oxide, and a surface comprising polysilicon, said method comprising: providing an etching composition comprising: a. concentrated phosphoric acid, in an amount of at least 60% by weight of the total weight of said composition; b. a polysilicon etching inhibitor selected from linear and branched C8-C. 16 Alkylbenzenesulfonic acid, C6-C 16 Alkyl diphenyl oxide disulfonic acid, C6-C 16 Alkyl diphenyl sulfide disulfonic acid or C6-C 16 Alkyl diphenylamine disulfonic acid; c. aminoalkylsilanol; and d. optional fluorine compound; providing a substrate having a surface comprising silicon nitride and a surface comprising polycrystalline silicon, and contacting the substrate with the composition under conditions that effectively etch silicon nitride.

2. The method of claim 1, wherein the surface of the polycrystalline silicon is in contact with a surface comprising a composition that is electrochemically more inert than silicon, said surface being selected from tungsten silicide, nickel silicide, platinum silicide, and titanium silicide.

3. The method according to claim 1, wherein the fluorine compound is present and selected from HF, ammonium fluoride, tetrafluoroboric acid, hexafluorosilicic acid, tetrabutylammonium tetrafluoroborate, tetra(C1-C6 alkyl)ammonium fluoride, and combinations thereof.

4. The method according to claim 1, wherein the aminoalkylsilanol is a reaction product of 3-aminopropylsilanetriol, N-(6-aminohexyl)aminopropylsilanol, 3-aminopropyltriethanol, 3-aminopropyltriethanol, or (3-trimethoxysilylpropyl)diethylenetriamine.

5. The method according to claim 4, wherein the aminoalkylsilanol is formed in situ from an aminoalkoxysilane.

6. The method according to claim 1, wherein the polysilicon corrosion inhibitor is selected from alkyl diphenyl oxide disulfonic acid, dodecyl diphenyl oxide disulfonic acid, and dodecylbenzenesulfonic acid.

7. The method of claim 1, wherein the composition comprises a. concentrated phosphoric acid, in an amount of at least 60% by weight of the total weight of the composition; b. C6-C 16 Alkyl diphenyl oxide disulfonic acid, C6-C 16 Alkyl diphenyl sulfide disulfonic acid or C6-C 16 Alkyl diphenylamine disulfonic acid; and c. 3-aminopropylsilanetriol.

8. A composition comprising: a. concentrated phosphoric acid, in an amount of at least 60% by weight of the total weight of the composition; b. a polysilicon etching inhibitor selected from linear and branched C8-C... 16 Alkylbenzenesulfonic acid and C6-C 16 Alkyl diphenyl oxide disulfonic acid, C6-C 16 Alkyl diphenyl sulfide disulfonic acid or C6-C 16 Alkyl diphenylamine disulfonic acid; and c. aminoalkylsilanol.

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