Use of a composition and a process for selectively etching silicon

Abstract

The present invention relates to the use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy, the composition comprising: (a) 0.0005 to 3 % of a nitroaromatic compound of formula E1, E2, or E3, its tautomers or its salts, as described herein, wherein one ring carbon atom in formula E1 may be substituted by a nitrogen atom if XE1 is N; excluding 2-hydroxy-5-nitropyridine; (b) 1 to 10 % by weight of an amine of formula E2 as described herein; and (c) water.

Description

[0001] Use of a composition and a process for selectively etching silicon

[0002] The present invention relates to a composition, its use and a process for selectively etching silicon at a surface of a microelectronic device substrate, relative to etching a silicon-germanium containing material at the same surface.

[0003] Background of the Invention

[0004] Steps of preparing certain microelectronic devices, e.g., integrated circuits, may include selectively removing silicon (Si) material from a surface that contains the Si in combination with silicon-germanium (SiGe). According to certain example fabrication steps, Si may be used as a sacrificial layer in a structure that also contains SiGe. Based on such fabrication steps, advanced device structures may be prepared, such as silicon nanowires and silicon on nothing (SON) structures. Steps in these processes include epitaxial deposition of a structure of alternating layers of Si and SiGe, followed by patterning and, eventually, selective lateral etching to remove the Si layers and generate a three- dimensional silicon structure.

[0005] In certain specific methods of preparing a field effect transistors (FET) for an integrated circuit, Si and SiGe materials are deposited as layers onto a substrate, i.e. , as an "epitaxial stack" of Si and SiGe. The layers are subsequently patterned using standard techniques, such as by use of a standard lithographically generated mask. Next, a directional isotropic etch may be useful to laterally etch away the sacrificial Si material, leaving behind a SiGe nanowire or sheet structure.

[0006] By way of example, an epi-stack can be formed of alternating Si and SiGe layers, wherein the Si layers are the sacrificial layers and the SiGe layers are the channel layers. The Si layers can then be removed by selective etching, which also inadvertently recesses trenches into the bulk substrate due to the similarity of materials composing the sacrificial layers and the substrate.

[0007] To enable smaller structures within Semiconductor structures electronic industry is searching for solutions to remove selectively amorphous or crystalline silicon against SiGe layers. This is needed to realize well defined nanowire or nanosheet structures.

[0008] Another potential application of Si etching against SiGe is back-side power delivery routing (BS PDN). A backside- PDN configuration contains dense microthrough silicon vias (pTSVs) and power / ground metal stack on the backside of the die. This approach separates the PDN from a conventional signaling network of the back-end-of-the-line (BEOL) and improves power integrity and core utilization. This approach is a complete redesign of existing architectures in that both sides of the silicon have metallization layers. To achieve this, one silicon wafer is extremely thinned via CMP and chemical etching and connected to another wafer. A number of alkaline etchants have been reported for wet etching of silicon. TMAH and ammonium hydroxide are the most commonly used silicon etchants due to their known high selectivity between Si and SiC>2. However, when employed in a process to selectively etch silicon over SiGe, these etchants suffer from low horizontal etching power in releasing Si from SiGe / Si stacks. Furthermore, selectivity of these etchants for removal of Si over SiGe is usually low, i.e. <100:1.

[0009] EP 3 447 109 A1 discloses an etching composition comprising water; at least one of a quaternary ammonium hydroxide compound and an amine compound; water-miscible solvent; optionally surfactant and optionally corrosion inhibitor; and a method of using the etching composition for the selective silicon removal. US 2019 / 0085240 A1 discloses the selective removal of Si over SiGe from a microelectronic device comprising: water; at least one of a quaternary ammonium hydroxide compound and an amine compound; water-miscible solvent; optionally surfactant and optionally corrosion inhibitor; and the method of using the etching composition for the selective silicon removal.

[0010] WO 2023 / 280637 discloses the use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy, the composition comprising:

[0011] (a) 4 to 15 % by weight of an amine of formula E1

[0012] X— NH2

[0013] (b) water; wherein XE1, XE1, and XE1are independently selected from a chemical bond and Ci-Ce alkanediyl; YEis selected from N, CRE1, and P; and RE1is selected from H and Ci-Ce alkyl.

[0014] European patent application No. 23189280.3 discloses the use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy comprising 0.1 to 5 % by weight of specific pyridine compounds substituted with carboxy, hydroxy, amino, amido, or cyanide groups, and optionally an amine.

[0015] However, the state-of-the-art solutions are not able to fulfil all requirements since they still have at least one of the following deficiencies:

[0016] (a) a too low Si / SiGe selectivity, to remove the Si layer(s) without attacking the SiGe layer;

[0017] (b) a too low Si etch rate which leads to a long time to completely remove the Si layer(s);

[0018] (c) a too high SiGe etch rate which makes it difficult to remove the Si layer(s) while not compromising the SiGe layer(s); an / or

[0019] (d) a high Si etching anisotropy indicated by a drop of the etch rate over the time. It is therefore an object of the invention to increase the Si etch rates, to increase the Si etch rates while keeping constant or even improving the Si vs. SiGe selectivity and / or keeping constant or even improving the Si etching isotropy.

[0020] Summary of the Invention

[0021] It has now been found that the use of nitro (-NO2) substituted carbocyclic or heterocyclic aromatic compounds in combination with amines enable either an increase in the Si etch rates, a stabilization of the Si etch rates over a longer period of time, which partially results from an increased isotropy of the etch rates (at least for Si100 and Si110), and / or an improvement in the Si vs. SiGe selectivity.

[0022] Therefore, one embodiment of the present invention relates to the use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy, the composition comprising:

[0023] (a) 0.0005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2, or E3, its tautomers, or its salts wherein

[0024] RE1is a Ci to C4 alkyl, Cl or CN;

[0025] RE2is -OH, -COOH or CHO;

[0026] XE1. XE2are independently selected from C and N; i is the number of substituents RE2and is 1 , 2 or 3; j is the number of substituents RE1and is 0, 1 , 2, or 3; k is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 may be substituted by a nitrogen atom if XE1is N; excluding 2-hydroxy-5-nitropyridine;

[0027] (b) 1 to 10 % by weight of an amine of formula A1 wherein

[0028] XA1, XA2are independently selected from a C2-C3 alkanediyl;

[0029] YAis selected from NH2 and OH; n is 0, 1 , 2 or 3; and

[0030] (c) water.

[0031] It was particularly surprising that the etching composition according to the invention is suited to allow for a very controlled, uniform , and selective etching of silicon layers (Si), preferably of amorphous silicon (aS!) or crystalline silicon, while at the same time not or not significantly compromising silicon germanium (SiGe) layers.

[0032] Another embodiment of the present invention is a process of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer, the process comprising:

[0033] (a) providing a microelectronic device surface that includes the silicon layer and the layer comprising the silicon germanium alloy;

[0034] (b) providing an etching composition comprising a composition as defined above and described herein; and

[0035] (c) contacting the surface with the composition for a time and at a temperature effective to selectively remove the silicon layer relative to the silicon-germanium layer.

[0036] Detailed Description of the Invention

[0037] The purpose of the etching composition is the etching of silicon (Si) layers in the presence of layers comprising or consisting of a silicon-germanium alloy (SiGe).

[0038] The composition used according to the subject invention comprises, essentially consists of, or consists of

[0039] (a) 0.0005 to 3 % of a nitroaromatic compound of formula E1 , E2, or E3 or its tautomers, and if applicable its salts, as described herein, wherein one ring carbon atom in formula E1 or E2 may be substituted by a nitrogen atom if XE1is N; with the exception that if XE1in formula E1 is N and i for RE2is 1 , the -NO2 substituent must not be in 5 position;

[0040] (b) 1 to 10 % by weight of an amine of formula A1 as described herein; and

[0041] (c) water.

[0042] Definitions

[0043] As used herein, a “silicon layer” or “Si layer" is a layer that essentially consists of elemental silicon, preferably consists of elemental silicon. It particularly includes, but is not limited to, a layer consisting of amorphous, polycrystalline or (single-)crystall ine silicon; p-doped silicon; or n-doped silicon. The etching composition is particularly useful when etching silicon, in particular amorphous silicon (aS!) or crystalline silicon (cSi) in the presence of SIGe. The term “essentially consisting of silicon” means that the silicon content in the layer is more than 90% by weight, preferably more than 95% by weight, even more preferably more than 98% by weight. When undoped silicon is used, it is particularly preferred that the silicon layer does not comprise any other elements than silicon. When n- or p- doped silicon is used, it is particularly preferred that the silicon layer is free of any other elements besides the n- or p- dopants, which may be present in an amount below 10 % by weight, preferably below 2 % by weight. Preferably, the germanium content of the silicon layer is less than 5 % by weight, preferably less than 2 % by weight, more preferably less than 1 % by weight, even more preferably less than 0.1 % by weight. Most preferably the silicon layer comprises no germanium.

[0044] As used herein, a “silicon-germanium layer” or “SIGe layer” corresponds to layers comprising or preferably consisting of silicon-germanium (SIGe) alloys known in the art and represented by the formula: SixGey, wherein x is in a range from about 0.50 to 0.90, particularly 0.60 to 0.85, and y is in a range from about 0.10 to about 0.50, particularly 0.15 to 0.40, with x+y =1 .00. SIGe25 here means that y is 0.25.

[0045] As used herein, “selectively etching” (or “selective etch rate”) preferably means that upon applying a composition according to the invention to a layer comprising or consisting of a first material, in this case Si, most particularly aSi, cSi or poly-Si, in the presence of a layer comprising or consisting of a second material, in this case SIGe, the etch rate of said composition for etching the first layer is at least 150 times, preferably at least 200 times, most preferably at least 240 times the etch rate of said composition for the second layer. Depending on the substrate to be etched, other layers like SIOX, SION or SIN should also not be jeopardized.

[0046] As used herein, “layer” means a part of a substrate that was separately disposed on the surface of a substrate and has a distinguishable composition with respect to adjacent layers.

[0047] The term “Cx” means that the respective group comprises x numbers of C atoms. The term "Cxto Cyalkyl" means alkyl with a number x to y of carbon atoms and, unless explicitly specified, includes unsubstituted linear, branched and cyclic alkyl. As used herein, “alkanediyl” refers to a diradical of linear, branched or cyclic alkanes or a combination thereof.

[0048] All percent, ppm or comparable values refer to the weight with respect to the total weight of the respective composition except where otherwise indicated. The terms “wt%” and “% by weight” are used herein synonymously.

[0049] The term “about” herein includes any values close to the specified number and the specific number itself. If not specifically specified, “close to” means plus or minus 10%, preferably plus or minus 5%, more preferably plus or minus 1 % relative to the specified number. Most preferably “about” means the exact number it refers to.

[0050] All cited documents are incorporated herein by reference.

[0051] Si etch rate enhancer

[0052] The composition comprises a Si etch rate enhancer, also referred to herein as “nitroaromatic compound” or “enhancer”, to either increase the Si etch rates, to stabilize the Si etch rates over a longer period of time, which partially results from an increased isotropy of the etch rates (at least for Si 100 and Si1 10), and / or an improvement in the Si vs. SiGe selectivity.

[0053] The enhancer used in the present invention is a nitroaromatic compound of formula E1 , E2, or E3 or its tautomers or its salts Herein, RE1is a linear or branched Ci to C4 alkyl, Cl or CN. RE2may be -OH (hydroxy), -COOH (carboxy) or -CHO (aldehyde) substituent. XE1. XE2may independently be selected from C and N. i is the number of substituents RE2and is 1 , 2 or 3. j is the number of substituents RE1in formula E1 and E2, and is 0, 1 , 2, or 3, preferably 0, 1 , or 2, more preferably 0 or 1 , most preferably 0. k is the number of substituents RE1in formula E3 and is 0 or 1 , preferably 0. In formula E1 one ring carbon atom may also be substituted by a nitrogen atom if XE1is N. In this case the nitroaromatic compounds comprise two nitrogen atoms in the ring.

[0054] Depending on the pH used in the composition, the nitroaromatic compounds may be protonated or deprotonated or may even be employed in form of their salts. Counterions in its salts may be any ion that does not interfere with the etching. Without limitation, typical anionic compound salts are those with group 1 or 2 metal ions, tetraalkyl ammonium ions like tetramethylammonium or tetraethylammonium ions. Without limitation, typical cationic compound salts are those with sulfate, sulfonate, halide, particularly chloride, phosphate, and the like.

[0055] It was particularly surprising that the etching composition according to the invention is suited to allow for a very controlled, uniform, and selective etching of silicon layers (Si), preferably of amorphous silicon (aS!) or (semicrystalline silicon, while at the same time not or not significantly compromising silicon germanium (SIGe) layers.

[0056] In a first preferred embodiment of formula E1 , the enhancer is a nitroaromatic compound, i.e., XE1is N: or, if one carbon atom in the ring is substituted by a nitrogen atom

[0057] From the compounds of formula E1 a 2-hydroxy-5-nitropyridine needs to be excluded since it did not show the required performance. Preferably, in the compounds of formula E1 a the -NO2 substituent should not be in 5-position if RE2is -OH and I is 1 .

[0058] Preferred examples of nitroaromatic compounds of formula E1 are those with:

[0059] RE1is selected from methyl, ethyl and propyl, Cl or CN, preferably from methyl, ethyl, Cl or CN; RE2is -OH; i is the number of substituents RE2and is 1 or 2; and j is the number of substituents RE1and is 0, 1 , 2, or 3, preferably 0; 1 or 2, even more preferably 0 or 1 , most preferably 0;

[0060] In this embodiment, the hydroxy pyridine derivative as well as its tautomeric form may be used:

[0061] The nitroaromatic compound may also be used in form of its salts with counter-ions that do not interfere with the substrate, such as but not limited to sulfate, chloride, nitrate (anionic), or ammonium, tetraalkylammonium, alkaline or alkaline earth metal ions (cationic).

[0062] Particularly preferred examples of N-heteroaromatic compounds of formula E1 a are:

[0063] In a second preferred embodiment of formula E1 , the additive is a carbocyclic aromatic compound, i.e., in formula E1 XE1is C. Such carbocyclic aromatic compounds may be nitrophenolic compounds, i.e., RE1is -OH, or may be nitrobenzoic acid or nitro-benzenedicarboxylic acid compounds, i.e., RE1is -COOH.

[0064] Particularly preferred examples of nitrophenolic compounds are:

[0065] Particularly preferred examples of nitrobenzoic acid compounds are:

[0066] Particularly preferred examples of nitro-substituted benzenedicarboxylic acid compounds are:

[0067] In a third preferred embodiment compounds of formula E2 are used, wherein RE1is selected from methyl, ethyl and propyl, preferably from methyl and ethyl; j is the number of substituents RE1and is 0, 1 , 2, or 3, preferably 0; 1 or 2, even more preferably 0 or 1 , most preferably 0.

[0068] Particularly preferred examples of N-heterocyclic compounds of formula E2 are:

[0069] In a fourth preferred embodiment compounds of formula E3 are used, wherein

[0070] RE1is selected from methyl, ethyl and propyl, preferably from methyl and ethyl;

[0071] XE1is C or N, preferably C; k is the number of substituents RE1and is 0 or 1 , preferably 0.

[0072] Particularly preferred examples of N-heterocyclic compounds with one, two, or three nitrogen atoms of formula E3

[0073] The enhancer may be present in an amount of from about 0.0005 to about 3 % by weight. If the amount is too low, the enhancing effect is too low. A further increase of the concentration is technically possible but does not make sense for commercial reasons. Preferred concentrations are from about 0.001 to about 2 % by weight, more preferred from about 0.01 to about 1 .5 % by weight, even more preferred from about 0,02 to about 1.2 % by weight. The most preferred concentration range is of from about 0.05 to about 1 % by weight.

[0074] Amine

[0075] Depending on the respective Si etch rate enhancer used, the composition may comprise 1 to 10 % by weight of an amine of formula A1 (also referred to as “etchant”) which further supports the selective etching of silicon layers, preferably aSi, whereas the etch rate of layers comprising or consisting of SiGe, preferably of SIGe25, are still high.

[0076] In formula A1 , spacer groups XA1and XA2are independently selected from a C2-C3 alkanediyl, preferably selected from 1 ,2-ethanediyl, 1 ,2-propanediyl, and 1 -3-propanediyl.

[0077] YAmay be NH2 or OH, preferably NH2. n may be 0, 1 , 2 or 3, preferably 0, 1 or 2, most preferably 0 or 1 . In a first preferred embodiment the amine is an alkanolamine, preferably ethanolamine.

[0078] In a second preferred embodiment the amine is a diamine, triamine, or tetramine, preferably ethylenediamine or propane-1, 2-diamine or propane-1 , 3-diamine.

[0079] Particularly preferred amines are ethylenediamine, ethanolamine, propane-1 , 2-diamine, propane-1 , 3-diamine, and diethylene triamine.

[0080] The amine may be present in an amount of from about 1 to about 10 % by weight. If the amount is too low, the enhancing effect is too low. A further increase of the concentration is technically possible but does not make sense for commercial reasons. Preferred concentrations are from about 1 .5 to about 8 % by weight, more preferred from about 2 to about 7 % by weight. The optimal concentration window is of from about 3 to about 6 % by weight.

[0081] Alkanolamines are well-known for reacting with carbon dioxide even from the atmosphere resulting in the formation of carbamic acids, carbamates or ammonium (bi)carbonate adducts. A small quantity of the CO2 reaction products was found to be beneficial for Si etching. To produce the CO2 reaction products, ethanolamine or the etch bath may be exposed to air or treated with pure carbon dioxide. Alternatively, the etch bath may be prepared with addition of a carbonate or hydrogen carbonate. Without limitation, useful carbonates or hydrogen carbonates are those with ammonium, Ci to Ce tetraalkylammonium, Ci to Ce tetraalkylphosphonium, alkaline metals or earth alkaline metals. In a preferred embodiment, the carbonate or hydrogen carbonate may be added in an amount from about 0.01 to about 5 % by weight, more preferred from about 0.05 to about 2 % by weight, most preferred from about 0.1 to about 1 % by weight.

[0082] The composition according to the invention may comprise one or more of the amines described herein.

[0083] Water

[0084] The etching compositions of the present development are aqueous-based and, thus, comprise water. Water has several functions such as, for example, to dissolve one or more components of the composition, as a carrier of the components, as an aid in the removal of residue, as a viscosity modifier of the composition, and as a diluent. Preferably, the water employed in the composition is de-ionized (DI) water. The ranges of water described in the next paragraph include all of the water in the composition from any source.

[0085] For most applications, the weight percent of water in the composition will be present in a range with start and end points selected from the following group of numbers: 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 92, 94, 96, 98, 99. Examples of the ranges of water that may be used in the composition include, for examples, from about 45 to about 99 % by weight, or about 50 to about 94% by weight of water; or from about 60 to about 99 % by weight, or from about 70 to about 96 % by weight, or from about 80 to about 96 % by weight, or from about 85 to about 99 % by weight, or from about 90 to about 99% by weight. Still other preferred embodiments of the present invention may include water in an amount to achieve the desired weight percent of the other ingredients.

[0086] Organic solvents

[0087] In one embodiment the etching composition may optionally comprise one or more water-miscible organic solvents.

[0088] Examples of water-miscible organic solvents that can be employed are ethylene glycol, propylene glycol, 1 ,4- butanediol, glycerol, tripropylene glycol methyl ether, propylene glycol propyl ether, diethylene gycol n-butyl ether (BDG), dipropylene glycol methyl ether (DPM), hexyloxypropylamine, poly(oxyethylene)diamine, dimethylsulfoxide (DMSO), tetrahydrofurfuryl alcohol, glycerol, alcohols, sulfolane, sulfoxides, diethanolamine, triethanolamine or mixtures thereof. Preferred solvents are alcohols, diols, or mixtures thereof. Most preferred solvents are C2 to Ce polyols, particularly C2 to C4 polyols, including diols, such as, for example, ethylene glycol or propylene glycol, and triols, such as, for example, glycerol.

[0089] For most applications, the amount of water-miscible organic solvent in the composition may be in a range having start and end points selected from the following list of weight percents: 0.5, 1 , 5, 7, 10, 12, 15, 20, 25, 29, 30, 33, 35, 40, 44, 49.5, 50. Examples of such ranges of solvent include from about 0.5 to about 50 % by weight; or from about 1 to about 45 % by weight; or from about 1 to about 40 % by weight; or from about 0.5 % to about 30% by weight; or from about 1 to about 30 % by weight; or from about 5 to about 30 % by weight; or from about 5 to about 20 % by weight; or from about 7 to about 20 %, or from about 10 to about 30 % by weight; or from about 15 to about 25 % by weight of the composition.

[0090] In individual cases, a composition according to the invention as defined herein may further comprise as an optional additional component: One or more water-miscible organic solvents, preferably selected from the group consisting of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethanol, isopropanol, butyldiglycol, butylglycol, sulfolane (2,3,4,5-tetrahydrothiophene-1 ,1 -dioxide) and mixtures thereof; more preferably selected from the group consisting of THF, NMP, DMF, DMSO, sulfolane and mixtures thereof.

[0091] The term “water-miscible organic solvent” in the context of the present invention preferably means that an organic solvent fulfilling this requirement is miscible with water at least in a 1 : 1 (w / w) ratio at 20 °C and ambient pressure. Particularly, preferred are compositions according to the present invention which do not comprise one or more water- miscible organic solvents.

[0092] In a preferred embodiment, a composition according to the invention as defined herein is preferred wherein the total amount of the one or more water-miscible organic solvents is present in an amount of from about 0.1 to about 30 % by weight, preferably of from about 0.5 to about 25 % by weight, more preferably of from about 5 to about 20 % by weight, even more preferably of from about 1 to about 6 % by weight, based on the total weight of the composition.

[0093] In another preferred embodiment, a composition according to the invention as defined herein is preferred wherein the total amount of the one or more water-miscible organic solvents is present in an amount of from about 20 to about 55 % by weight, preferably of from about 25 to about 50 % by weight, more preferably of from about 30 to about 45 % by weight, based on the total weight of the composition.

[0094] In yet another preferred embodiment, a composition according to the invention as defined herein is an aqueous solution that is essentially free of organic solvents (besides the amine). “Essentially free” in this context means that the content of organic solvents is below 1 % by weight, preferably below 0.1 % by weight, even more preferably below 0.01 % by weight, even more preferably below 0.001 % by weight, most preferably below the detection limit. Most preferably the composition does not comprise any solvent besides water (and the amine).

[0095] Coordinating agents

[0096] The etching composition may optionally comprise one or more coordinating agents.

[0097] Preferred coordinating agents are 1 ,2-cyclohexylenedinitrilotetraacetic acid, 1 ,1 , 1,5,5, 5-hexafluoro-2,4-pentane- dione, acetylacetonate, 2,2’-azanediyldiacetic acid, ethylenediaminetetra-acetic acid, etidronic acid, methanesulfonic acid, acetyl acetone, 1 ,1 , 1 -trifluoro-2,4-pentanedione, 1,4-benzoquinone, 8-hydroxyquinoline, salicyli-dene aniline; tetrachloro-1 ,4-benzoquinone, 2-(2-hydroxyphenyl)-benzoxazol, 2-(2-hydroxyphenyl)-benzothiazole, hydroxyquinoline sulfonic acid, sulfosalicylic acid, salicylic acid, gallic acid, pyridine, 2 -ethylpyridine, 2- methoxypyridine, 3-methoxypyridine, 2-picoline, dimethylpyridine, piperidine, piperazine, ethylamine, methylamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diglycol amine, methyldiethanolamine, pyrrole, isoxazole, bipyridine, py-rimidine, pyrazine, pyridazine, quinoline, isoquinoline, indole, 1 -methylimidazole, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidinedithiocarbamate, dimethyl malonate, methyl acetoacetate, N-methyl acetoacetamide, tetramethylammonium thiobenzoate, 2,2,6,6-tetramethyl-3,5-heptanedione, tetramethylthiuram disulfide, lactic acid, ammonium lactate, formic acid, propionic acid, gamma-butyrolactone, and mixtures thereof.

[0098] The coordinating agent may be 1 ,2-cyclohexylenedinitrilotetraacetic acid (CDTA) or may comprise CDTA as well as one or more of the other coordinating agents above.

[0099] A composition according to the invention as defined herein is also preferred wherein the amount of the one or more coordinating agents present is of from about 0.01 to about 4 % by weight, preferably of from about 0.02 to about 1 % by weight, more preferably of from about 0.05 to about 0.8 % by weight, based on the total weight of the composition. In some embodiments the compositions of this invention will be free of or substantially free of any or all of the abovelisted coordinating agents.

[0100] Surfactants

[0101] The composition may also further comprise one or more surfactants.

[0102] Preferred surfactants are selected from the group consisting of

[0103] (i) anionic surfactants, preferably selected from the group consisting of ammonium lauryl sulfate, fluorosurfactants, preferably selected from the group consisting of perfluorinated alkylsulfonamide salts (preferably perfluorinated, N- substituted alkylsulfonamide ammonium salts, PNAAS), perfluorooctanesulfonate, perfluorobutanesulfonate, perfluorononanoate and perfluorooctanoate; alkyl-aryl ether phosphates and alkyl ether phosphates;

[0104] (II) zwitterionic surfactants, preferably selected from the group consisting of (3-[(3- cholamidopropyl)dimethylammonio]-1 -propanesulfonate) (“CHAPS”), cocamidopropyl hydroxysultaine (CAS RN 68139-30-0), {[3-(dodecanoylamino)propyl](dimethyl)-ammonio}acetate, phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine; and

[0105] (ill) non-ionic surfactants, preferably selected from the group consisting of glucoside alkyl ethers, glycerol alkyl ethers, cocamide ethanolamines and lauryldimethylaminoxide.

[0106] More preferred surfactants in compositions according to the invention are or comprise perfluorinated, N-substituted alkylsulfonamide ammonium salts. Preferred surfactants (E) in compositions according to the invention do not comprise metals or metal ions.

[0107] Specific surfactants for use in the compositions described herein include, but are not limited to, bis(2- ethylhexyl)phosphate, perfluoroheptanoic acid, prefluorodecanoic acid, trifluoromethanesulfonic acid, phosphonoacetic acid, dodecenylsuccinic acid, dioctadecyl hydrogen phosphate, octadecyl dihydrogen phosphate, dodecylamine, dodecenylsuccinic acid monodiethanol amide, lauric acid, palmitic acid, oleic acid, juniperic acid, 12 hydroxystearic acid and dodecyl phosphate; polyoxyethylene lauryl ether (Emalmin NL-100 (Sanyo), Brij 30, Brij 98, Brij 35), dodecenylsuccinic acid monodiethanol amide (DSDA, Sanyo), ethylenediamine tetrakis(ethoxylate-block- propoxylate) tetrol (Tetronic 90R4), polyethylene glycols (e.g., PEG 400), polypropylene glycols, polyethylene or polypropylene glycol ethers, block copolymers based on ethylene oxide and propylene oxide (Newpole PE-68 (Sanyo), Pluronic L31 , Pluronic 31 R1 , Pluronic L61 , Pluronic F-127) (Dynol 607), polyoxypropylene sucrose ether (SN008S, Sanyo), t-octylphenoxypolyethoxyethanol (Triton X100), 10-ethoxy-9,9-dimethyldecan-1 -amine (TRITON® CF-32), Polyoxyethylene (9) nonylphenylether, branched (IGEPAL CO-250), polyoxyethylene (40) nonylphenylether, branched (IGEPAL CO-890), polyoxyethylene sorbitol hexaoleate, polyoxyethylene sorbitol tetraoleate, polyethylene glycol sorbitan monooleate (Tween 80), sorbitan monooleate (Span 80), a combination of Tween 80 and Span 80, alcohol alkoxylates (e.g., Plurafac RA-20), alkyl-polyglucoside, ethyl perfluorobutyrate, 1 ,1 ,3,3,5,5-hexamethyl-1 ,5- bis[2-(5-norbornen-2-yl)ethyl]trisiloxane, monomeric octadecylsilane derivatives such as SIS6952.0 (Siliclad, Gelest), siloxane modified polysilazane such as PP1 -SG10 Siliclad Glide 10 (Gelest), silicone-polyether copolymers such as Silwet L-77 (Setre Chemical Company), Silwet ECO Spreader Momentive), and ethoxylated fluorosurfactants (ZONYL® FSO-100, ZONYL® FSN-100); cetyl trimethylammonium bromide (CTAB), heptadecanefluorooctane sulfonic acid, tetraethylammonium, stearyl trimethylammonium chloride (Econol TMS-28, Sanyo), 4-(4- diethylaminophenylazo)-1-(4-nitrobenzyl)pyridium bromide, cetylpyridinium chloride monohydrate, benzalkonium chloride, benzethonium chloride benzyldimethyldodecyl ammonium chloride, benzyldimethyl hexadecylammonium chloride, hexadecyltrimethylammonium bromide, dimethyldioctadecylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium p-toluenesulfonate, didodecyldimethylammonium bromide, dehydrogenated tallow) dimethylammonium chloride, tetraheptylammonium bromide, tetrakis(decyl)ammonium bromide, Aliquat® 336 and oxyphenonium bromide, guanidine hydrochloride (C(NH2)3CI) or triflate salts such as tetrabutylammonium trifluoromethanesulfonate, dimethyldioctadecylammonium chloride, dimethyldihexadecylammonium bromide and dehydrogenated tallow)dimethylammonium chloride (e.g., Arquad 2HT- 75, Akzo Nobel), bromide-containing surfactants, such as, 1 -hexadecyltrimethylammonium bromide.

[0108] A composition according to the invention as defined herein is also preferred wherein the amount of the one or more surfactants of the surfactant present is of from about 0.0001 to about 1 % by weight, preferably of from about 0.0005 to about 0.5 % by weight, more preferably in an amount of from about 0.001 to about 0.01 % by weight, based on the total weight of the composition.

[0109] In some embodiments the compositions of this invention will be free of or substantially free of any or all of the abovelisted surfactants.

[0110] Corrosion Inhibitors

[0111] The etching composition of the present invention may optionally include one or more corrosion inhibitors. The corrosion inhibitors, if present, may protect the silicon-germanium from etching. Examples of corrosion inhibitors include aliphatic amino carboxylic acids, for example, triethylenetetraminehexaacetic acid (TTHA), 1 ,3-diamino-2- hydroxypropane-N,N,N’,N’-tetraacetic acid (DHPTA), methyliminodiacetic acid, propylenediaminetetraacetic acid, ethylenediaminetetraacetic acid (EDTA), butylenediaminetetraacetic acid, (1,2-cyclohexylenediamine)tetraacetic acid (CyDTA), diethylenetriaminepentaacetic acid (DETPA), ethylenediaminetetrapropionic acid, (hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), and nitrotriacetic acid (NTA), aminophosphonic acids, such as, N, N,N’, N’-ethylenediaminetetra(methylenephosphonic) acid (EDTMP); carboxylic acids, such as, decanoic acid, citric acid, tartaric acid, gluconic acid, saccharic acid, glyceric acid, oxalic acid, ascorbic acid, phthalic acid, benzoic acid, mercaptobenzoic acid, maleic acid, mandelic acid, malonic acid, lactic acid and salicylic acid. Other possible corrosion inhibitors include propyl gallate, pyrogallol, quinolines, such as, 8-hydroxyquinoline, piperazines, such as, 1-(2-aminoethyl)piperazine, cysteine, and N,N,N’,N",N"-pentamethyldiethylenetriamine (Polycat 5). Another corrosion inhibitors may include hexylamine. Some preferred corrosion inhibitors may comprise sulfur-containing groups. Other preferred corrosion inhibitors may comprise aminocarboxylic acids such as EDTA, CyDTA, quinolines, such as, 8- hydroxyquinoline, decanoic acid, 11 -mercaptoundecanoic acid, piperazines, such as, 1 -(2-aminoethyl)piperazine, benzimidazoles, such as, 2-mercapto-5-methylbenzimidizole, and carboxylic acids, such as, oxalic acid, decanoic acid, and ascorbic acid. More preferred corrosion inhibitors include decanoic acid, ascorbic acid, 11 - mercaptoundecanoic acid, 1-(2-aminoethyl)piperazine, and 8-hydroxyquinoline.

[0112] For most applications, the amount of the corrosion inhibitors, such as, amino carboxylic acids, carboxylic acids, quinolines, or piperazines, etc, in the composition may be in a range having start and end points selected from the following list of weight percents: 0.01 , 0.05, 0.07, 0.1 , 0.12, 0.15, 0.17, 0.2, 0.5, 1 , 1.2, 1.5, 1.7, 2, 3, 4, 6, 8, 10, 12, 15. By way of example, the corrosion inhibitors may be present in the composition from about 0.05 wt% to about 3 wt%, or from about 0.01 to about 3 wt%, or about 0.1 wt% to about 5 wt%, or from about 0.1 wt% to about 15 wt%; or from about 0.1 wt% to about 10 wt%, or from about 0.5 wt. % to about 5 wt%, or from about 0.05 wt% to about 2 wt%, or about 0.5 wt% to about 5 wt% based on the total weight of the composition.

[0113] In some embodiments the compositions of this invention will be free of or substantially free of any or all of the abovelisted corrosion inhibitors, that is, the composition is free of any or all of the above-listed aminocarboxylic acids and / or carboxylic acids and / or quinolines and / or piperazines, etc..

[0114] Composition

[0115] Other commonly known components such as dyes, chemical modifiers, biocides, etc. can be included in the etchant composition in conventional amounts, for example, amounts up to a total of about 1 or 5 or 10 % by weight of the composition to the extent that they do not adversely affect the performance of the composition.

[0116] Alternatively, the compositions of this invention may be free or substantially free of any or all of dyes, chemical modifiers, or biocides.

[0117] The etching solution composition of the present invention is typically prepared by mixing the components together in a vessel at room temperature until all solids have dissolved in the aqueous-based medium.

[0118] Generally, the pH of the composition may be in the range of from 8 to 14. In a preferred embodiment the pH of the etching composition is from about 8.5 to about 13, more preferably from about 9 to about 12 or from about 9.5 to about 12.5, most preferably from about 9.5 to about 12. A composition according to the invention as defined herein is specifically preferred wherein the composition essentially consists of or consists of:

[0119] (a) 0.0005 to 3 %, preferably 0.001 to 2 %, more prefered 0.01 to 1 .5 %, even more preferably 0.03 to 1 .2 %, most preferably 0.05 to 1 % by weight of the nitroaromatic compound of formula E1; E2 or E3, preferably of formula E1;

[0120] (b) 1 to 10 %, preferably 1 .5 to 8 %, more preferably 2 to 7 %, most preferably 3 to 6 %, by weight of the amine of formula A1 ;

[0121] (c) 0 to 3%, preferably 0 or 0.0005 to about 0.5 % by weight of a surfactant as described above;

[0122] (d) 0 to 3%, preferably 0 or 0.01 to 4 % by weight of a coordinating agent as described above;

[0123] (e) rest water.

[0124] A composition according to the invention as defined herein is specifically preferred wherein the composition essentially consists of or consists of:

[0125] (a) 0.0005 to 3 %, preferably 0.01 to about 2 %, more preferred from about 0.02 to about 1 .5 %, even more preferred from about 0.03 to about 1.2 %, most preferred 0.05 to 1 % by weight of the nitroaromatic compound of formula E1 ; E2 or E3, preferably of formula E1 ;

[0126] (b) 1 to 10 %, preferably 1 .5 to 8 %, more preferably 2 to 7 %, most preferably 3 to 6 %, by weight of the amine of formula A1 ;

[0127] (e) rest water.

[0128] In a particularly preferred embodiment the composition essentially consists of the nitroaromatic compound, the amine and water.

[0129] “Essentially” in this context means that the content of any other compounds except the specifically mentioned ones are below 1 % by weight, preferably below 0.1 % by weight, even more preferably below 0.01 % by weight, even more preferably below 0.001 % by weight, most preferably below the detection limit.

[0130] A composition according to the invention as defined herein is specifically preferred wherein the composition consists of the nitroaromatic compound of formula E1 , E2 or E3, preferably of formula E1 , the amine of formula A1 , and water as defined herein and to be defined based on the examples.

[0131] Application

[0132] In another aspect there is provided a process of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer, the process comprising:

[0133] (a) providing a microelectronic device surface that includes the silicon layer and the layer comprising the silicon germanium alloy;

[0134] (b) providing an etching composition comprising (i) 0.005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2 or E3 or its tautomers wherein

[0135] RE1is a Ci to C4 alkyl, Cl or CN;

[0136] RE2is -OH, -COOH or -COH;

[0137] XE1. XE2are independently selected from C and N; is the number of substituents RE2and is 1 , 2 or 3; is the number of substituents RE1and is 0, 1 , 2, or 3; is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 may be substituted by a nitrogen atom if XE1is N; excluding 2-hydroxy-5-nitropyridine;

[0138] (II) 1 to 10 % by weight of an amine of formula A1 wherein are independently selected from a C2-C3 alkanediyl; is selected from NH2 and OH; is 0, 1 , 2 or 3; and

[0139] (iii) water; and

[0140] (c) contacting the surface with the composition for a time and at a temperature effective to selectively remove the silicon layer relative to the silicon-germanium layer.

[0141] In yet another aspect there is provided a method for the manufacture of a semiconductor device, comprising the step of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer.

[0142] In yet another aspect there is provided a method of for selectively enhancing the etch rate of silicon relative to silicon- germanium in a microelectronic device, e.g., a composite semiconductor device comprising silicon and silicon- germanium, by etching the microelectronic device (composite semiconductor device) by using a composition as described herein.

[0143] The composition is particularly useful for selectively etching a silicon layer (Si), in the presence of a layer comprising a silicon-germanium alloy (SiGe). Such layers may be present when preparing field effect transistors (FET) for an integrated circuit. Si and SiGe materials are deposited as layers onto a substrate, i.e., as an "epitaxial stack" of Si and SiGe. The Si layers can then be removed by selective etching, which also inadvertently recesses trenches into the bulk substrate due to the similarity of materials composing the sacrificial layers and the substrate.

[0144] Another potential application of Si etching against SiGe is back-side power delivery routing (BS PDN) as described in IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 67, 11 -17. A backside-PDN configuration contains dense microthrough silicon vias (pTSVs) and power / ground metal stack on the backside of the die. This approach separates the PDN from a conventional signaling network of the back-end-of-the-line (BEOL) and improves power integrity and core utilization. This approach is a complete redesign of existing architectures in that both sides of the silicon have metallization layers. To achieve this, one silicon wafer is extremely thinned via CMP and chemical etching and connected to another wafer. The current invention describes a method for the part of the chemical etching.

[0145] It will be appreciated that it is common practice to make concentrated forms of the compositions to be diluted prior to use. For example, the compositions may be manufactured in a more concentrated form and thereafter diluted with water, at least one oxidizing agent, or other components at the manufacturer, before use, and / or during use. Dilution ratios may be in a range from about 0.1 parts diluent to 1 parts composition concentrate to about 100 parts diluent to 1 part composition concentrate.

[0146] In the use of the compositions described herein, the composition typically is contacted with the device structure for a sufficient time of from about 1 minute to about 200 minutes, preferably about 5 minutes to about 60 minutes, at temperature in a range of from about 30 °C to about 80 °C, preferably about 40 °C to about 70 °C. Such contacting times and temperatures are illustrative, and any other suitable time and temperature conditions may be employed that are efficacious to achieve the required removal selectivity. One advantage of the composition according to the present invention is its low temperature dependence of the Si / SIGe etch ratio. It was found that the Si / SIGe etch ratio is particularly advantageous at temperatures above room temperature but should be well below the boiling point of water.

[0147] Following the achievement of the desired etching action, the composition can be readily removed from the microelectronic device to which it has previously been applied, e.g., by rinse, wash, or other removal step(s), as may be desired and efficacious in a given end use application of the compositions of the present invention. For example, the device may be rinsed with a rinse solution including deionized water, an organic solvent, and / or dried (e.g., spindry, N2, vapor-dry etc.).

[0148] It may be useful to clean the blanket wafer surfaces (removal of oxide) for about 10 s to about 120 s with an aqueous solution containing about 0.1 % to 5% by weight HF at room temperature.

[0149] Preferably the Si, etch rates of the compositions according to the invention are 300 nm / min or more, more preferably 400 nm / min or more. Preferably the SiGe, particularly SiGe25 etch rates of the compositions according to the invention are 3.5 nm / min or below, more preferably 3.0 nm / min or below. Preferably the etch rate of the silicon layer is at least 100, preferably 120, even more preferably 150, even more preferably preferably 200, most preferably more than 240 times faster than the etch rate of the layer comprising silicon-germanium (Si / SIGe selectivity).

[0150] After the contacting step is an optional rinsing step. The rinsing step may be carried out by any suitable means, for example, rinsing the substrate with de-ionized water by immersion or spray techniques. In preferred embodiments, the rinsing step may be carried out employing a mixture of de-ionized water and an organic solvent such as, for example, isopropanol.

[0151] After the contacting step and the optional rinsing step is an optional drying step that is carried out by any suitable means, for example, isopropanol (IPA) vapor drying, heat, or by centripetal force.

[0152] Embodiments

[0153] The following embodiments including their subcombinations of the present invention are particularly preferred:

[0154] 1 . The use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy, the composition comprising: (a) 0.0005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2, or E3, its tautomers or its salts wherein

[0155] RE1is a Ci to C4 alkyl, Cl or CN;

[0156] RE2is -OH, -COOH or -CHO;

[0157] XE1. XE2are independently selected from C and N;

[0158] I is the number of substituents RE2and is 1 , 2 or 3; j is the number of substituents RE1and is 0, 1 , 2, or 3; k is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 may be substituted by a nitrogen atom if XE1is N; excluding 2-hydroxy-5-nitropyridine, preferably excluding compounds in which, if XE1in formula E1 is N and I for RE2is 1 , the -NO2 substituent are in 5 position;

[0159] (b) 1 to 10 % by weight of an amine of formula A1 wherein

[0160] XA1, XA2are independently selected from a C2-C3 alkanediyl;YA is selected from NH2 and OH; n is 0, 1 , 2 or 3; and

[0161] (c) water.

[0162] 2. The use according to embodiment 1 , wherein j or k or both j and k are 0.

[0163] 3. The use according to embodiments 1 or 2, using a nitroaromatic compound of formula E1 a or E1 b, preferably

[0164] E1a

[0165] 4. The use according to anyone of the embodiments 1 to 3, wherein i is 1 .

[0166] 5 The use according to embodiment 2, wherein the nitroaromatic compound is selected from

[0167] (a) 4-Hyd roxy-3-n itropy rid ine and its tautomer 3-n itropy rid in-4-one,

[0168] (b) 3-Hydroxy-2-nitropyridine, and

[0169] (c) 2,4-Dihydroxy-3-nitropy ridine and its tautomers 2-Hydroxy -3-n itropy ridin-4-one and 4-Hydroxy-3- nitropyridin-2-one.

[0170] 6 The use according to embodiment 2, wherein the nitroaromatic compound is selected from

[0171] (a) 4-carboxy-3-nitropyridine,

[0172] (b) 3-carboxy-2-n itropy ridine, and

[0173] (c) 2,4-Dicarboxy-3-nitropyridine.

[0174] 7 The use according to embodiment 1 , using a nitroaromatic compound of formula E2. 8 The use according to embodiment 7, wherein the nitroaromatic compound is selected from 2-Nitropyridine-N- oxide, 3-Nitropyridine-N-oxide, and 4-Nitropyridine-N-oxide.

[0175] 9. The use according to embodiment 1 , using a nitroaromatic compound of formula E3.

[0176] 10. The use according to embodiment 9, wherein the nitroaromatic compound is selected from

[0177] (a) 4-Nitroimidazole, and

[0178] (b) 3-Nitro-1 H-1 ,2,4-triazol

[0179] 11 . The use according to anyone of the preceding embodiments, wherein

[0180] YAis NH2; and n is 0 or 1 .

[0181] 12. The use according to anyone of the preceding embodiments, wherein XA1is selected from ethane-1 ,2-diyl, propane-1, 3-diyl, and propane-1 , 2-diyl.

[0182] 13. The use according to anyone of the preceding embodiments, wherein the amine is selected from ethanolamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, and diethylenetriamine.

[0183] 14. The use according to anyone of the preceding embodiments, wherein the amine is present in the composition in an amount of from 2 to 8 % by weight, preferably from 3 to 6 % by weight.

[0184] 15. The use according to anyone of the preceding embodiments, wherein the nitroaromatic compound is present in the composition in an amount of from 0.001 to 0.75 % by weight, preferably from 0.01 to 0.5 % by weight.

[0185] 16. The use according to anyone of the preceding embodiments, wherein the composition essentially consists of or consists of:

[0186] (a) 0.001 to 1 % by weight of the nitroaromatic compound of formula E1 , E2 or E3;

[0187] (b) 2 to 10 % by weight of an amine of formula A1 ;

[0188] (c) 0 to 3% by weight of a surfactant;

[0189] (d) 0 to 3% by weight of a coordinating agent;

[0190] (e) rest water.

[0191] 17. The use according to anyone of the preceding embodiments, wherein the composition essentially consists of or consists of:

[0192] (a) 0.001 to 1 % by weight of the nitroaromatic compound of formula E1 , E2 or E3;

[0193] (b) 2 to 10 % by weight of an amine of formula A1 ;

[0194] (d) 0 to 3% by weight of a coordinating agent; (e) rest water.

[0195] 18. The use according to anyone of the preceding embodiments, wherein the composition essentially consists of or consists of:

[0196] (a) 0.001 to 1 % by weight of the nitroaromatic compound of formula E1 , E2 or E3, preferably E1 ;

[0197] (b) 2 to 10 % by weight of an amine of formula A1 ;

[0198] (c) 0 to 3% by weight of a surfactant;

[0199] (e) rest water.

[0200] 19. The use according to anyone of the preceding embodiments, wherein the composition has a pH of 9 to 13, particularly from 9.5 to 12.5.

[0201] 20. A process of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer, the process comprising:

[0202] (a) providing a microelectronic device surface that includes the silicon layer and the layer comprising the silicon germanium alloy;

[0203] (b) providing an etching composition comprising

[0204] (I) 0.0005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2 or E3 or its tautomers or its salt wherein RE1is a Ci to C4 alkyl, Cl or CN;

[0205] RE2is -OH, -COOH or -CHO;

[0206] XE1. XE2are independently selected from C and N; i is the number of substituents RE2and is 1 , 2 or 3; j is the number of substituents RE1and is 0, 1 , 2, or 3; k is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 or E2 may be substituted by a nitrogen atom if

[0207] XE1is N; with the exception that if XE1in formula E1 is N and I for RE2is 1 , the -NO2 substituent must not be in 5 position.

[0208] (ii) 1 to 10 % by weight of an amine of formula A1 wherein

[0209] XA1, XA2are independently selected from a C2-C3 alkanediyl;

[0210] YAis selected from NH2 and OH; n is 0, 1 , 2 or 3; and

[0211] (ill) water; and

[0212] (c) contacting the surface with the composition for a time and at a temperature effective to selectively remove the silicon layer relative to the silicon-germanium layer.

[0213] 21 . A process for the manufacture of a semiconductor device, comprising the step of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer according to embodiment 20.

[0214] The following examples shall further illustrate the present invention without restricting the scope of this invention.

[0215] Examples

[0216] General Procedures and Substrates

[0217] The following substrates were used as coupons of about 2.5 x 2.5 cm:

[0218] Blanket wafer coupons comprised of crystalline Si(100), Si(110) and Si(11 1 ).

[0219] Blanket Wafer Coupons comprised of SIGe25 (50 nm or 100 nm) on Si. Etch bath preparation:

[0220] The etchant was prepared by adding the respective enhancer and the amine in the specified amounts into DI water. The etchant was transferred into a plastic beaker equipped with a thermostat.

[0221] Pre-etching:

[0222] UPW and 1 wt% hydrogen fluoride were filled into two plastic beakers. Each coupon (SiGe25, Si(100), Si(110), Si(111)) was pre-etched in 1 wt% hydrogen fluoride for 60 s, then dipped into UPW for 2-3 s and dried with compressed air.

[0223] The etchant was set to 50 °C + / - 0.5 °C. Once the temperature was reached, the Si(100) or SiGe25 wafer coupons were submerged into the etchant. Each coupon was etched separately for 0.25 to 60 minutes, depending on substrate thickness, under stirring, subsequently rinsed with DI water and dried.

[0224] The resulting thickness was determined by spectroscopic ellipsometry. Si etch rates were determined gravimetrically employing Si(100) which was fully immersed into the etchant (surface area of 2 x 6.25 cm2; p(Si)=2.329 g / cm2). To determine etching isotropy, Si(100), Si(110) or Si( 111 ) coupons were partially submerged into the etchant. The height of the step resulting from etching was subsequently analyzed by confocal laser scanning microscopy (CLSM) and / or stylus profilometry.

[0225] Example 1

[0226] Compositions in water depicted in table 1 were prepared as described above. The etching rates were determined by ellipsometry by comparing the layer thickness before and after etching (SiGe25) or gravimetrically (SHOO) as described. The results are also depicted in table 1 .

[0227] Table 1 wt% are given with respect to the total weight of the employed whole composition.

[0228] The results depicted in Table 1 show that the combination of ethylenediamine and nitro-substituted heterocycles increases the Si etch rate in comparison with ethylenediamine up to a factor of 2. Moreover, these additives facilitate an enhanced Si / SIGe selectivity of more than 520. Pyridine derivatives bearing at least one hydroxy-group in 2- and or 4-position and a nitro-substituent in 3- or 5-position as well as nitroimidazoles and nitro-substituted pyridine-N- oxides show the best results.

[0229] The comparison of examples C1 .2 with examples 1 .3 and 1 .4 also shows that the addition of an amine is required for Si etching and observable Si / SIGe selectivity.

[0230] Example 2

[0231] Compositions in water depicted in table 2 were prepared as described above. The etching rates were determined by ellipsometry by comparing the layer thickness before and after etching (SiGe25) or gravimetrically (SHOO) as described. The results are also depicted in table 2. Table 2

[0232] Compositions in water depicted in table 3 were prepared as described above. The etching rates were determined by ellipsometry by comparing the layer thickness before and after etching (SiGe25) or gravimetrically (Si100) as described. The results are also depicted in table 3. Table 3

[0233] The examples displayed in table 3 showcase the increase of SH OO and SI110 etch rates by the presented nitrosubstituted additives in combination with an amine.

Claims

Claims1 . The use of a composition for selectively etching a silicon layer in the presence of a layer comprising a silicon germanium alloy, the composition comprising:(a) 0.0005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2, or E3, its tautomers or its saltswhereinRE1is a Ci to C4 alkyl, Cl, or CN;RE2is -OH, -COCH or -CHO;XE1. XE2are independently selected from C and N;I is the number of substituents RE2and is 1 , 2 or 3; j is the number of substituents RE1and is 0, 1 , 2, or 3; k is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 may be substituted by a nitrogen atom if XE1is N; excluding 2-hydroxy-5-nitropyridine;(b) 1 to 10 % by weight of an amine of formula A1whereinXA1, XA2are independently selected from a C2-C3 alkanediyl;YAis selected from NH2 and OH; n is 0, 1 , 2 or 3; and(c) water.

2. The use according to claim 1, wherein j or k is 0.

3. The use according to claim 1 or 2, using a nitroaromatic compound of formula E1 a or E1 b4. The use according to anyone of claims 1 to 3, wherein i is 1 or 2.5 The use according to claim 1 , using a nitroaromatic compound of formula E2.

7. The use according to claim 1 , using a nitroaromatic compound of formula E3.

8. The use according to anyone of the preceding claims, whereinYAis NH2; and n is 0 or 1 .

9. The use according to anyone of the preceding claims, wherein XA1is selected from ethane-1 ,2-diyl, propane-1 ,3-diyl, and propane-1 , 2-diyl.

10. The use according to anyone of the preceding claims, wherein the amine is selected from ethanolamine, ethylenediamine, propane-1 ,2-diamine, propane-1, 3-diamine, and diethylenetriamine.11 . The use according to anyone of the preceding claims, wherein the amine is present in the composition in an amount of from 2 to 8 % by weight, preferably from 3 to 6 % by weight.

12. The use according to anyone of the preceding claims, wherein the nitroaromatic compound is present in the composition in an amount of from 0.001 to 0.75 % by weight, preferably from 0.01 to 0.5 % by weight.

13. The use according to anyone of the preceding claims, wherein the composition has a pH of 9 to 13, particularly from 9.5 to 12.5.

14. A process of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer, the process comprising:(a) providing a microelectronic device surface that includes the silicon layer and the layer comprising the silicon germanium alloy;(b) providing an etching composition comprising(I) 0.0005 to 3 % by weight of a nitroaromatic compound of formula E1 , E2 or E3 or its tautomers or its saltswhereinRE1is a Ci to C4 alkyl, Cl, or CN;RE2is -OH, -COOH or -CHO;XE1. XE2are independently selected from C and N; i is the number of substituents RE2and is 1 , 2 or 3; j is the number of substituents RE1and is 0, 1 , 2, or 3; k is the number of substituents RE1and is 0 or 1 ; and wherein one ring carbon atom in formula E1 or E2 may be substituted by a nitrogen atom ifXE1is N; excluding 2-hydroxy-5-nitropyridine.(II) 1 to 10 % by weight of an amine of formula A1whereinXA1, XA2are independently selected from a C2-C3 alkanediyl;YAis selected from NH2 and OH; n is 0, 1 , 2 or 3; and(ill) water; and(c) contacting the surface with the composition for a time and at a temperature effective to selectively remove the silicon layer relative to the silicon-germanium layer.

15. A process for the manufacture of a semiconductor device, comprising the step of selectively removing a silicon layer from a surface of a microelectronic device relative to a silicon-germanium layer according to claim

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