Selective etchant compositions and methods

Abstract

The present invention relates to compositions and methods for selectively etching silicon nitride in the presence of silicon oxide, polysilicon and / or metal silicides at high etch rates and high selectivity. Additives are described that can be used at various fused silica loading windows to provide and maintain high selective etch rates and selectivity.

Description

[Technical field]

[0001] The present invention relates to compositions and methods for selectively etching silicon nitride in the presence of silicon oxide, polysilicon and / or metal silicides, and more particularly to compositions and methods for effectively and efficiently etching layers of silicon nitride with high etch rates and high selectivity to exposed or underlying layers of silicon oxide, polysilicon and / or metal silicides. [Background technology]

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

[0003] Shrinking feature and device sizes requires finding new ways to improve the steps of the multi-step process of manufacturing microelectronic devices. The step of removing silicon nitride is common in the methods of making many types of microelectronic devices. For example, a thin layer of silicon nitride (Si3N4), typically deposited by chemical vapor deposition from silane (SiH4) and ammonia (NH3), can be useful in microelectronic devices as a water and sodium barrier. Also, a patterned silicon nitride layer is used as a mask for spatially selective silicon oxide growth. In addition, methods are being explored to improve the resolution and feature size of MOSFET devices by forming self-aligned polysilicon (poly-Si) gate structures. Using this method, contact points are formed for the source and drain of the gate electrode, which is often covered with silicon nitride, self-aligned with the poly-Si gate.

[0004] However, after application, removal of all or part of the silicon nitride material may be required, which is typically accomplished by etching. Removal of silicon nitride by etching must be accomplished in a manner that does not damage or destroy other exposed or covered features of the microelectronic device. Specifically, the process for removing silicon nitride must not preferentially remove other materials that are also present on the surface of the microelectronic device substrate, such as silicon oxide.

[0005] According to various commercially available methods, silicon nitride can be removed from microelectronic device surfaces by a wet etching process that involves exposing the substrate surface to concentrated phosphoric acid (H3PO4) in a bath having an elevated temperature, for example, a temperature in the range of 150°C to 180°C. For example, a conventional wet etching technique for selectively removing silicon nitride relative to silicon oxide uses an aqueous solution of phosphoric acid (H3PO4), typically about 85% phosphoric acid and 15% water by weight. Using fresh hot phosphoric acid, a typical Si3N4:SiO2 selectivity can be about 40:1.

[0006] Advantageously, as the nitride layer is removed, hydrated silicon oxide is formed, which inhibits further removal of silicon oxide from the device surface. Thus, selectivity gradually increases with use. However, process control is often problematic due to the difficulties associated with maintaining a specific amount of water in the process solution. As a result, the amount of dissolved silica can vary during the process, which can lead to complications arising from silica precipitation. For example, 3D-NAND structures typically require highly selective etching of silicon nitride (SiN) due to the high aspect ratio "slits" defined by oxide (PETEOS). During the high temperature phosphoric acid etching process, oxide quickly begins to deposit near the opening of the slit. This colloidal silica deposition tends to "pinch off" the gaps or trenches in the microelectronic device.

[0007] As a result, there is a need to minimize the rate of oxide redeposition from phosphoric acid-based etching compositions. Thus, there remains a need for compositions and methods that have a stable target amount of dissolved silicate (sometimes referred to as the "silicon loading window") during selective removal of silicon nitride. Summary of the Invention

[0008] The present invention generally relates to an etchant composition for selectively removing silicon nitride relative to silicon oxide from the surface of a microelectronic device. The etchant composition includes phosphoric acid, water, dissolved silica, and at least one additive. In one embodiment, the additive is an alkylamine additive selected from the group consisting of diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof, or the additive is selected from the group consisting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane ... The silane additive is selected from the group consisting of silane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsesquioxane, salts thereof, or combinations thereof.In other embodiments, the etchant composition comprises 400 ppm or more of dissolved silica and the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, tripropylamine, tri-butylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; or the etchant composition comprises 400 ppm or less of dissolved silica and the additive is an alkylamine additive selected from N-trimethoxysilane. and n is an integer from 1 to 3. The silane additive is selected from the group consisting of trimethylsilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsilsesquioxane, salts thereof, or combinations thereof.

[0009] The present invention further relates to a method for selectively etching silicon nitride relative to silicon oxide from a surface of a substrate, the method comprising providing an etchant composition comprising phosphoric acid, water, dissolved silica, and at least one additive, providing a substrate having a surface comprising silicon nitride and silicon oxide, and contacting the substrate with the etchant composition under conditions to selectively remove silicon nitride relative to silicon oxide. In one embodiment, the additive of the etchant composition is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof, or the additive is selected from N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof. and n is an integer from 1 to 3. The silane additive is selected from the group consisting of diphenyl diethyl silane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsesquioxane, salts thereof, or combinations thereof.In other embodiments, the etchant composition comprises 400 ppm or more of dissolved silica and the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, tripropylamine, tri-butylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; or the etchant composition comprises 400 ppm or less of dissolved silica and the additive is an alkylamine additive selected from N-trimethoxysilane. and n is an integer from 1 to 3. The silane additive is selected from the group consisting of trimethylsilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsilsesquioxane, salts thereof, or combinations thereof.

[0010] Other embodiments, features, and advantages will become more fully apparent from the following disclosure and the appended claims. It has been found that such etchant compositions and methods can achieve high etch selectivity for removal of silicon nitride relative to silicon oxide, while also providing specifically targeted levels of dissolved silica. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention relates to compositions and methods for selectively etching silicon nitride in the presence of silicon oxide. The compositions and methods effectively and efficiently remove silicon nitride from surfaces of microelectronic devices with high etch rates and high selectivity relative to silicon oxide, polysilicon, and / or metal silicide layers.

[0012] As used herein, the term "microelectronic device" (or "microelectronic device substrate" or simply "substrate") is used consistent with the commonly understood meaning of the term in electronics, microelectronics, and semiconductor manufacturing arts to refer to any of a variety of different types, such as, for example, semiconductor substrates; integrated circuits; solid state memory devices; hard memory disks; read, write, and read / write heads and their mechanical or electronic components; flat panel displays; phase change memory devices; solar panels and other products that include one or more solar cell devices; photovoltaics; and microelectromechanical systems (MEMS) fabricated 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 in-process microelectronic device or microelectronic device substrate that contains, or is being prepared to contain, functional electronic (current carrying), functional semiconductor, and insulating structures for the final electronic device used in the microelectronic device or microelectronic assembly.

[0013] As used herein, the term "silicon nitride" is given a meaning consistent with that of the term as used in the microelectronics and semiconductor manufacturing industries. Consistent with this, silicon nitride refers to materials including thin films of amorphous silicon nitride deposited by chemical vapor deposition, e.g., from silane and ammonia, and containing commercially useful low levels of other materials or impurities. Silicon nitride may be present as a functional feature of a device, e.g., as a barrier or insulating layer, as part of a microelectronic device substrate, or may be present to function as a material that facilitates a multi-step manufacturing process for making a microelectronic device.

[0014] As used herein, the term "silicon oxide" is given a meaning consistent with that of the term used in the microelectronics and semiconductor manufacturing industries. Consistent with this, silicon oxide refers to silicon oxide (SiO x Silicon oxide refers to a thin film of silicon oxide such as SiO2, "thermal oxide" (ThOx), PETEOS, etc. The silicon oxide can be disposed on the substrate by any method, such as by deposition by chemical vapor deposition from TEOS or another source, or by thermal deposition. The silicon oxide can preferably contain commercially useful low levels of other materials or impurities. Silicon oxide may be present as part of a microelectronic device substrate as a feature of the microelectronic device, for example as an insulating layer.

[0015] Conventional wet etching techniques for selectively removing silicon nitride use hot (approximately 145-180°C) aqueous phosphoric acid (H3PO4) solutions that are typically 85% phosphoric acid and 15% water (by volume). Fresh hot phosphoric acid can result in a typical silicon nitride:SiO2 selectivity of approximately 40:1. Advantageously, as the nitride layer is removed, hydrated silicon oxide is formed, which inhibits further removal of silicon oxide from the device surface, consistent with Le Chatelier's principle. As a result, selectivity gradually increases with use.

[0016] However, process control issues can often arise due to the difficulty of maintaining a specific amount of water in the etchant solution. As a result, dissolved silicon oxide can begin to precipitate out of solution. In some applications requiring highly selective etching of silicon nitride due to high aspect ratio "slits" defined by oxides (PETEOS), such as 3D-NAND, silicon oxide deposition near the openings of the slits tends to "pinch off" gaps or trenches in the microelectronic device and eventually block them. As a result, the process window of pre-etch oxide concentration (sometimes referred to as the "silicon loading window") is very narrow and can be difficult to control, necessitating frequent replacement of etchant baths. Thus, the oxide redeposition rate must be minimized to maintain the targeted silicon loading window.

[0017] The etchant composition of the present disclosure surprisingly contains certain additives that have been found to be able to maintain the target amount of dissolved silica in the composition in a desired range. The additives are various alkylamine additives and various silane additives. The inclusion of these additives in the phosphoric acid aqueous composition can minimize the amount of dissolved silica redeposition during use while maintaining high etch selectivity.

[0018] In all such compositions where a particular component of a composition is discussed in terms of a weight percent range, it will be understood that such component may be present in a concentration as low as 0.001 weight percent, based on the total weight of the composition in which such component is used. As used herein, "about" is intended to correspond to + / - 5% of the stated value.

[0019] As used herein, the singular forms "a," "an," and "the" include their plural referents unless the context clearly dictates otherwise. The terms "containing" or "including" are intended to be synonymous with the term "comprising" and mean that at least the specified compounds, elements, particles, method steps, etc. are present in a composition or article or method, but do not exclude the presence of other compounds, materials, particles, method steps, etc., even if they have the same function as the specified ones, unless other compounds, materials, particles, method steps, etc. are expressly excluded in the claim.

[0020] The compositions comprise, consist of, or consist essentially of the components described herein. As a general convention throughout this specification, an etchant composition or component thereof that is said to "consist essentially of" a particular group of components or materials refers to a composition that contains the particular component or material, and the amount of other components or materials is small or insignificant, e.g., 5, 2, 1, 0.5, 0.1, or 0.05 parts by weight or less. For example, an etchant composition that consists essentially of phosphoric acid, water, at least one additive selected from phosphoric acid, amine additive, or silane additive, and any additional components described means a composition that includes each of these components and 5, 2, 1, 0.5, 0.1, or 0.05 weight percent or less of any other dissolved or undissolved materials other than the specified materials (individually or collectively).

[0021] The etchant composition is an aqueous phosphoric acid composition that includes phosphoric acid dissolved in water in an amount effective to produce the desired etching of silicon nitride. Phosphoric acid is typically available as a concentrate in water. Thus, the term "phosphoric acid" as used herein refers to the non-aqueous component of the aqueous phosphoric acid solution that is a component of the etchant composition, while the term "aqueous phosphoric acid" or "concentrated phosphoric acid" refers to the component that is mixed or combined with other components to form the etchant composition or to form the final composition itself. "High concentration" phosphoric acid refers to an aqueous phosphoric acid solution that has a large or large amount of phosphoric acid dissolved in a small or small amount of water and is substantially free of other components (e.g., less than 0.5 or 0.1 weight percent of any non-aqueous or non-phosphoric solid material). High concentration phosphoric acid can typically be considered to have at least about 80 or 85 weight percent phosphoric acid in about 15 or 20 weight percent water.

[0022] The amount of phosphoric acid included in the etchant composition can be any amount that, in combination with other components described herein, provides the desired etching performance, including the desired silicon nitride etching rate and selectivity. Typically, this requires a relatively large amount of phosphoric acid. For example, the etching composition can include phosphoric acid in an amount of at least about 50% by weight based on the total weight of the composition. Preferably, the amount of phosphoric acid is at least about 70 percent by weight, more preferably at least about 80 or 85 percent by weight based on the total weight of the etchant composition.

[0023] The etchant composition further comprises water, which may result from the addition of the components of the composition or may be provided as a separately added component. Preferably, the amount of water is less than 50 weight percent based on the total weight of the composition. For example, to provide the desired amount of phosphoric acid, the etchant composition may be prepared using concentrated phosphoric acid (85% by weight phosphoric acid in water), which may be further diluted with water before or after combining with the other components of the etchant composition. In one embodiment, the composition comprises concentrated phosphoric acid in an amount of at least 60, such as at least 80, or at least 90, 93, 95, or at least 98% by weight of the composition based on the total weight of the composition. In a particularly preferred embodiment, the etchant composition comprises concentrated phosphoric acid with less than 5% by weight of added water based on the total weight of the composition without added water.

[0024] The etchant composition further includes an amount of silica dissolved in phosphoric acid and water, such as by dissolving a solid silica material in phosphoric acid or by adding a soluble silicon-containing compound capable of forming dissolved silica by reaction with aqueous phosphoric acid. Such compounds include TMAS (tetramethylammonium silicate), tetraacetoxysilane, or tetraalkoxysilanes, such as tetramethoxysilane, tetraethoxysilane, etc. The dissolved silica can be effective to improve the selectivity of the etching composition to silicon nitride, and the amount can be any useful amount that does not result in pretreatment silica supersaturation at the conditions of the etching process, such as about 5 to 50,000 ppm of dissolved silica or soluble silicon-containing compound based on the total weight of the etching composition, or about 20 to about 5,000, 3,000, 1,000, 700, 500, or 200 ppm based on the total weight of the etching composition.

[0025] The etchant composition further comprises at least one additive, which can be either an alkylamine additive or a silane additive. When the additive is an alkylamine additive, suitable alkylamines include, for example, diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, tripropylamine, tri-butylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof. Preferably, the alkylamine additive is selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof.

[0026] In another embodiment, the additive is a silane additive.Suitable silanes include N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphetoethyl)triethoxysilane, aminoethylaminopropylsiloxane, salts thereof, or combinations thereof.

[0027] The selection of additives and amounts may depend at least in part on the desired level of dissolved silica to be maintained in the etchant composition. Generally, the amount of additive is 5.0 weight percent or less based on the total weight of the composition. For example, the additive may be present in the composition in an amount of about 10 ppm to about 5.0 weight percent. Preferably, the amount of additive is 50 ppm to about 1.0 weight percent, more preferably about 100 ppm to about 2000 ppm. It has been found that certain alkylamine additives can be used in these small amounts to provide relatively high levels of dissolved silica in the etchant composition. Additionally, low levels of dissolved silica can be provided and maintained with low total amounts of certain silane additives. In either case, high silicon nitride:SiO2 etch selectivity and etch rate are produced.

[0028] For example, in one embodiment, the etchant composition comprises 400 ppm or more of dissolved silica, and in this embodiment, the additive is preferably an alkylamine additive. Any of the alkylamines listed above may be used. If a higher level of dissolved silica is desired, such as 500 ppm, 700 ppm, or more, the alkylamine additive is preferably selected from tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof.

[0029] In another embodiment, the etchant composition comprises 400 ppm or less of dissolved silica, and in this embodiment, the composition comprises a silane additive. Depending on the target level of soluble silica, any of the above silane additives may be used. For example, the etchant composition may comprise 200 ppm or less of dissolved silica, and for this lower level of dissolved silica, the silane additive is selected from N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsilsesquioxane, salts thereof, or combinations thereof.

[0030] The etchant composition includes phosphoric acid, water, dissolved silica, and at least one alkylamine or silane additive, although the composition may also include various optional ingredients. For example, the etchant composition may further include at least one additional silane additive and / or at least one additional alkylamine additive or a phosphate salt thereof. These additives are different from those mentioned above as the specific alkylamine or silane additives. In particular, examples of suitable additional silane additives include alkylaminoalkoxysilanes or alkylaminohydroxylsilanes, such as (3-aminopropyl)triethoxysilane, (3-aminopropyl)silanetriol, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, 3-aminopropyldimethylfluorosilane, N-(3-trimethoxysilylpropyl)diethylenetriamine, N-(2-aminopropyl)dimethylfluorosilane ... ethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylsilanetriol, (3-trimethoxysilylpropyl)diethylenetriamine and N-(6-aminohexyl)aminopropyltrimethoxysilane, 3,3'-(dimethoxysilylene)bis-(1-propanamine), 2-[(dimethoxymethylsilyl)methyl]-1,4-butanediamine, 1,3-bis(3-aminopropyl)-1,1,3,3-tetraethoxydisiloxane, or 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethoxydisiloxane.

[0031] The further alkylamine additive or its phosphate salt may be a primary, secondary or tertiary C1-C6 alkylamine or its dihydrogen phosphate salt. For example, the further alkylamine additive may be, for example, an organic alkyl compound containing an amine substituent (e.g., a primary amine) of the formula R-NH2, where R is a linear or branched, preferably saturated, preferably unsubstituted alkyl chain containing about 2 to about 15 carbon atoms, for example, about 4 to about 12 carbon atoms. Examples of suitable further alkylamine additives include hexylamine, octylamine, 2-ethylhexylamine, dihexylamine, and decylamine. The alkylamines may be effective in providing improved etching rates or selectivity of silicon nitride, especially when used in the presence of certain alkylamine additives described above. The amount of any further alkylamine additive in the etchant composition may be about 5 to 10,000 ppm, for example about 20 to 1,000 ppm, based on the total weight of the etchant composition.

[0032] The etchant composition may optionally further comprise at least one surfactant (different from other optional or required components herein) to improve the performance of the etchant 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 an organic amphiphilic compound that contains hydrophobic and hydrophilic groups such as hydrocarbon (e.g., alkyl) "tails". Preferred surfactants are thermally stable and remain ionic under strongly acidic conditions, such as those of the etching process of the present invention. Examples include perfluoroalkylsulfonic acids and long-chain quaternary ammonium compounds (e.g., dodecyltrimethylammonium hydrogen sulfate). Fluorinated nonionic surfactants such as Chemours' Capstone® FS-31 / FS-35 can also be used. Non-ionic non-fluorinated surfactants such as poly(ethylene glycol)-poly(propylene glycol) copolymers ("PEG-PPG") can also be used and may be more suitable for low temperature applications using lower concentrations of phosphoric acid (e.g., 100-130°C and 50-75 weight percent H3PO4). The amount of surfactant in the etchant composition, if present, can be any amount that provides the desired overall performance in combination with other components. For example, the etchant composition may include an amount of surfactant ranging from about 0.001 to about 10 weight percent, e.g., from about 0.01 to about 0.5, 1, 2, 7, or 7 weight percent, based on the total weight of the etchant composition.

[0033] Additionally, the etchant composition may optionally further comprise at least one water-miscible organic solvent. Any organic (non-aqueous) solvent may include any organic compound that is liquid at the relevant operating temperature (e.g., the temperature of the etching bath) and is substantially miscible, compatible, and / or stable in the presence of phosphoric acid of the etchant composition. Examples of suitable non-aqueous solvents include organic compounds such as ethers, polyols, alcohols, sulfones, and phosphate esters. Specific examples include sulfolane, tetraethylene glycol dimethyl ether (tetraglyme), diethylene glycol ethyl ether, dipropylene glycol methyl ether, triethyl phosphate, and the like, which may be used alone or in combination with one or more other organic solvents. The amount of organic solvent, if present in the etchant composition, may be in the range of about 0.1 to about 25% by weight, e.g., about 0.5 to about 10, 15, or 20% by weight of the water-miscible organic solvent, based on the total weight of the etchant composition.

[0034] The etchant compositions described herein have been found to be useful for selectively etching silicon nitride relative to silicon oxide from the surface of a microelectronic device substrate. As such, the present disclosure further relates to methods, processes, and systems for using these etchant compositions to effectively and efficiently remove silicon nitride from the surface of a microelectronic device, advantageously with a high silicon nitride etch rate, advantageously with a high selectivity of silicon nitride relative to silicon oxide, or an advantageous balance of these performance characteristics.

[0035] The method provides an etchant composition as described herein, comprising phosphoric acid, water, dissolved silica, and at least one alkylamine additive or at least one silane additive. The additive can be any of those described in more detail above. A microelectronic device substrate having a surface comprising silicon nitride and silicon oxide is also provided. The substrate is contacted with the etchant composition under conditions sufficient to selectively remove silicon nitride relative to silicon oxide. The method can remove silicon nitride material without substantially damaging metal and metal silicide interconnect materials. Thus, the method is a method of selectively and substantially removing silicon nitride material relative to polysilicon and / or silicon oxide material from a surface of a microelectronic device using the composition as described herein. Any metal silicide material present is not substantially corroded by the etchant composition using the method.

[0036] In this method, the composition can be applied or contacted to the surface of the microelectronic device having the silicon nitride material thereon using any suitable method, including, for example, spraying the etchant composition onto the surface of the device, immersing the device in a static or dynamic volume of the etchant composition, contacting the device with another material such as a pad or fibrous sorbent applicator element having the etchant composition thereon, contacting the device including the silicon nitride material with a circulating etchant composition, or any other suitable means by which the etchant composition and the surface of the microelectronic device can be removed and contacted. Applications may be batch or single wafer machines for dynamic or static cleaning. In one embodiment, application of the etchant composition to the surface of the microelectronic device is controlled by agitation, whereby the composition is circulated through a vessel containing the composition.

[0037] The etchant composition and the microelectronic device substrate can be contacted for a time and temperature sufficient for etchant removal of silicon nitride. For example, contacting can be for a sufficient time, including from about 1 minute to about 200 minutes, in one embodiment, from about 15 minutes to about 100 minutes or from about 1 minute to about 3 minutes for a single wafer tool. Additionally, contacting under sufficient conditions can include, but is not limited to, in one embodiment, a temperature in the range of from about 120°C to about 200°C, including from about 150°C to about 200°C or from about 160°C to about 200°C. Such contact times and temperatures are exemplary, and any other suitable time and temperature conditions effective to at least partially remove silicon nitride material from the device structure can be used. Thus, the method achieves at least partial removal of silicon nitride material in a highly efficient and selective manner by using the selectivity of the etchant composition for silicon nitride material relative to other materials present on the microelectronic device structure and that may be exposed to the composition, such as metallization, polysilicon, silicon oxide, etc.

[0038] After selective etching of silicon nitride, the method may further include removing the composition from the microelectronic device to which it was previously applied, such as by rinsing, cleaning, or other removal steps, as may be desired for a given end use. For example, the treated microelectronic device may be rinsed with a rinsing solution including deionized water and / or dried by dehydration, N2, steam drying, etc.

[0039] As noted above, the etchant compositions and methods described herein selectively etch silicon nitride materials relative to poly-Si and silicon oxide from the surface of a microelectronic device without causing substantial corrosion of the metal and / or metal silicide interconnect materials. For example, the selectivity of silicon nitride relative to silicon oxide resulting from use of the etchant compositions may be within the range of about 10:1 to about 7000:1, including about 30:1 to about 3000:1 or about 100:1 to about 2000:1, particularly when etching is performed at temperatures of about 40-100°C, such as 60-95°C and 75-90°C. In fact, the selectivity may be nominally poor in some available formulations, reflecting the fact that the oxide film thickness is very slightly but measurably increased by silica precipitation. Advantageously, selectivity can be adjusted within the recited ranges by using certain additives in combination with the target dissolved silica levels.

[0040] The method may be useful for etching silicon nitride material from the surface of any type of substrate. According to certain embodiments, the substrate may include alternating thin layers of silicon nitride as structural features of the substrate, the structural features including alternating thin layers of silicon nitride and silicon oxide. The silicon oxide layers may be high aspect ratio structures including silicon nitride layers disposed between layers of silicon oxide.

[0041] The resulting selectively etched microelectronic device can be used to manufacture an article comprising the device. As such, the present disclosure further relates to a method of manufacturing an article comprising a microelectronic device, the method comprising contacting the microelectronic device with an etchant composition described herein under conditions, such as time and temperature, sufficient to selectively etch silicon nitride material from a surface of the microelectronic device relative to silicon oxide, and incorporating the etched microelectronic device into the article.

[0042] The etchant compositions described herein can be easily formulated by simply adding each component and mixing as necessary to form a homogenous state. The compositions can be easily formulated as single package formulations or multi-component formulations that are mixed at the point of use, preferably multi-component formulations. The individual components of the multi-component formulation can be mixed at the tool or in a storage tank upstream of the tool. It will be understood that the concentration of each component may vary widely, at a particular multiple of the composition, i.e., more dilute or more concentrated, and that the compositions described herein can variously and alternatively comprise, consist of, or consist essentially of any combination of components consistent with the disclosure herein.

[0043] As such, the present disclosure further relates to a kit comprising one or more components in one or more containers adapted to form the etchant compositions described herein. In one embodiment, the kit comprises in one or more containers a combination of at least one of phosphoric acid, water, dissolved silica, and at least one alkylamine additive and / or silane additive selected from the specific group above for combination at a manufacturing plant or at a point of use. The container of the kit should be suitable for storage and transportation of the composition components, e.g., NOWPak® containers (Advanced Technology Materials, Inc., Danbury, Conn., USA). The one or more containers preferably include a means for fluidly communicating the components contained therein for mixing and dispensing. For example, NOWPak® containers (Advanced Technology Materials, Inc., Danbury, Conn., USA) may be used. With reference to the 3000 Series (Agilent Technologies, Inc.) vessel, gas pressure may be applied to the outside of the liner in said vessel or vessels to expel at least a portion of the contents of the liner, thus enabling fluid communication for mixing and dispensing. Alternatively, gas pressure may be applied to the head space of a conventional pressurized vessel, and a pump may be used to enable fluid communication. Additionally, the system preferably includes a dispense port for dispensing the mixed cleaning composition to a process tool.

[0044] Substantially chemically inert, impurity-free, flexible and resilient polymeric film materials, such as high density polyethylene, can be used to manufacture liners for one or more containers. Desirable liner materials are processed without the need for coextrusion or barrier layers, and without pigments, UV inhibitors, or processing agents that may adversely affect the purity requirements of the components placed within the liner. A list of desirable liner materials includes films including virgin (unadded) polyethylene, virgin polytetrafluoroethylene (PTFE), polypropylene, polyurethane, polyvinylidene chloride, polyvinyl chloride, polyacetal, polystyrene, polyacrylonitrile, polybutylene, and the like. 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, a thickness of 20 mils (0.020 inches).

[0045] With respect to containers for kits, the disclosures of the following patents and patent applications are incorporated herein by reference in their entireties: U.S. Patent No. 7,188,644, entitled "Apparatus and Method for Minimizing Particle Generation in Supercritical Fluids," U.S. Patent Application No. 6,698,619, entitled "Returnable and Reusable Bag-in-Drum Fluid Storage and Dispensing Container System," and U.S. Patent Application No. 60 / 916,966, entitled "System and Method for Material Blending and Dispensing," filed May 9, 2007 in the name of John E.Q. Hughes, and PCT / US08 / 63276, entitled "System and Method for Material Blending and Dispensing," filed May 9, 2008 in the name of Advanced Technology Materials, Inc.

[0046] The present invention can be further illustrated by the following examples of specific embodiments thereof, however, it will be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the invention unless specifically stated. EXAMPLES

[0047] Example 1 - Alkylamine Additive Etchant compositions containing various alkylamine additives were prepared. For each composition, a base composition was prepared by containing 89% concentrated phosphoric acid and water. To this was added the particular alkylamine additive in the amount shown in Table 1 below. Trimethylammonium silicate (TMAS) was then added as a dissolved silica source at 160° C. and mixing at 240 rpm. The maximum dissolved silica amounts obtained are shown below. TIFF0007641406000001.tif109170

[0048] As the data show, certain alkylamine additives result in high levels of dissolved silica (greater than 500 ppm, preferably greater than 700 ppm) in the aqueous phosphoric acid solution. Each of these compositions is expected to result in highly selective etching of silicon nitride relative to silicon oxide.

[0049] Example 2 - Silane Additive Etchant compositions containing various silane additives were prepared. For each composition, a base composition was prepared by containing 89% concentrated phosphoric acid and water. To this was added the particular silane additive in the amount shown in Table 2 below. TMAS was then added as a dissolved silica source at 160° C. and mixing at 240 rpm. The maximum dissolved silica amounts obtained are shown below. TIFF0007641406000002.tif127170A=N-Trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (CAS number: 35141-36-7) B = 3-aminopropylmethyldiethoxysilane (CAS number: 3179-76-8) C=N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole (CAS number: 58068-97-6) D = N-(6-aminohexyl)aminomethyltriethoxysilane (CAS number: 15129-36-9) E = N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane (CAS number: 23410-40-4) F = N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (CAS number: 3069-29-2) G = (N,N-diethylaminomethyl)triethoxysilane (CAS number: 15180-47-9) H=N-methylaminopropyltrimethoxysilane (CAS number: 3069-25-8) I = 3-(trihydroxysilyl)propyl methylphosphonate, monosodium salt (CAS number: 84962-98-1) J = 3-(trihydroxysilyl)-1-propanesulfonic acid (CAS number: 70942-24-4) K = (2-diethylphosphatoethyl)triethoxysilane (CAS number: 757-44-8) L = aminoethylaminopropylsilsesquioxane

[0050] As the data shows, the particular silane additive provides dissolved silica of 400 ppm or less, preferably 200 ppm or less, in the aqueous phosphoric acid solution, and also provides highly selective etching of silicon nitride relative to silicon oxide.

[0051] Example 3 - Alkylamine Additive Etchant compositions containing various alkylamine additives were prepared. For each composition, a base composition was prepared by containing 89% concentrated phosphoric acid and water. To this was added the particular alkylamine additive in the amount shown in Table 3 below. Trimethylammonium silicate (TMAS) was then added as a source of dissolved silica with mixing at 160° C. and 240 rpm.

[0052] The etchant compositions were applied to a device surface containing a SiO2 layer having a predetermined thickness, and the resulting SiO2 thickness was measured. Based on the relative change in thickness, the maximum amount of dissolved silica for the composition that did not significantly increase the SiO2 thickness (i.e., minimal or no redeposition of dissolved silica occurred) was determined and is shown in Table 3 below. TIFF0007641406000003.tif54170

[0053] As the data shows, certain alkylamine additives provide high levels of dissolved silica (greater than 500 ppm, preferably greater than 700 ppm, as high as 800 ppm) in aqueous phosphoric acid solutions without significant redeposition of silica. Each of these compositions is expected to result in highly selective etching of silicon nitride relative to silicon oxide.

[0054] Although the present invention has been variously disclosed herein with reference to exemplary embodiments and features, it will be understood that the above-described embodiments and features are not intended to limit the present invention, and that other variations, modifications, and alternative embodiments will suggest themselves to those skilled in the art based on the disclosure herein. Accordingly, the present invention should be broadly construed as embracing all such variations, modifications, and alternative embodiments within the spirit and scope of the claims set forth below.

Claims

1. 1. An etchant composition comprising: (a) phosphoric acid; (b) water; (c) dissolved silica; (d) at least one additive, wherein the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; and (e) at least one additional alkylamine or its phosphate salt; the etchant composition comprises at least 400 ppm of dissolved silica; An etchant composition, wherein the etchant composition selectively etches silicon nitride relative to silicon oxide from a surface of a substrate.

2. 1. An etchant composition comprising: (a) phosphoric acid; (b) water; (c) dissolved silica; and (d) at least one additive; i) the etchant composition comprises 400 ppm or more of dissolved silica and the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, tripropylamine, tri-butylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; or ii) the etchant composition comprises 400 ppm or less of dissolved silica and the additive is a silane additive selected from N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, (N,N-diethylaminomethyl)triethoxysilane, N-methylaminopropyltrimethoxysilane, 3-(trihydroxysilyl)propylmethylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethylsilanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropylsilsesquioxane, salts thereof, or combinations thereof; An etchant composition, wherein the etchant composition selectively etches silicon nitride relative to silicon oxide from a surface of a substrate.

3. The etchant composition of claim 1 or claim 2, wherein the additive is present in an amount of about 10 ppm to about 5.0% based on the total weight of the composition.

4. 1. A method for selectively etching silicon nitride relative to silicon oxide from a surface of a substrate, comprising: 1) providing an etchant composition comprising: (a) phosphoric acid; (b) water; (c) dissolved silica; (d) at least one additive, wherein the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; and (e) at least one additional alkylamine or its phosphate salt; 2) providing a substrate having a surface comprising silicon nitride and silicon oxide; and 3) contacting the substrate with an etchant composition under conditions that selectively remove silicon nitride relative to silicon oxide. Including, The etchant composition comprises at least 400 ppm of dissolved silica; method.

5. 1. A method for selectively etching silicon nitride relative to silicon oxide from a surface of a substrate, comprising: 1) providing an etchant composition comprising: (a) phosphoric acid; (b) water; (c) dissolved silica; and (d) at least one additive, i) the etchant composition comprises 400 ppm or more of dissolved silica and the additive is an alkylamine additive selected from diethylethylenediamine (DEEDA), tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA), tri(aminoethyl)amine (TAEA), polyethyleneimine (PEI), ethylamine, diethylamine, tripropylamine, tri-butylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), N-ethylethylenediamine, 3-amino-5-methylpyrazole, creatinine, N,N'-dimethylpiperazine, hydroxylamine sulfate, dodecyltrimethylammonium chloride (DTAC), phosphate salts thereof, or combinations thereof; or ii) the etchant composition contains 400 ppm or less of dissolved silica and the additive is selected from the group consisting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium halide, 3-aminopropylmethyldiethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-(6-aminohexyl)aminomethyltriethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethysilane. at least one additive which is a silane additive selected from 2-(trihydroxysilyl)propyl methylphosphonate, 3-(trihydroxysilyl)-1-propanesulfonic acid, carboxyethyl silanetriol, (2-diethylphosphatoethyl)triethoxysilane, aminoethylaminopropyl silsesquioxane, salts thereof, or combinations thereof; 2) providing a substrate having a surface comprising silicon nitride and silicon oxide; and 3) contacting the substrate with an etchant composition under conditions that selectively remove silicon nitride relative to silicon oxide. A method comprising:

Images