Cryogenic etching using carbon OXY halides

Abstract

A cryogenic etching method for forming an aperture comprises mounting the substrate in a reaction chamber, cooling the substrate to a temperature below 25°C, introducing an etching gas having general formulae Y3-CO-X, Y-(C=O)-X, R1-CO-X, R'-CO-R", R'-(C=O)-O-(C=O)-R", and COF-CxFyHz-COF wherein X and Y each is a halogen selected from F, Cl, Br, I; R1 is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; R' and R" each is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, into the reaction chamber; and x, y and z are integers, into the reaction chamber, converting the etching gas to a plasma, and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture.

Description

CRYOGENIC ETCHING USING CARBON OXY HALIDES Cross Reference to Related Applications

[0001] The present application claims the benefit of U.S. Application No. 63 / 701,271 filed September 30, 2024 and U.S. Application No. 63 / 655,888 filed June 04, 2024, being incorporated herein by reference in their entireties for all purposes. Technical Field

[0002] The present invention relates to a method of cryogenic plasma etching silicon- containing materials using an etching gas of carbon oxy halides, to manufacture semiconductor chips, such as 3D NAND flash and DRAM chip manufacturing. Background

[0003] Carbon oxy halides have been used as etching gases, for example, difluoromalonoyl fluoride (C3O2F4, CAS # 5930-67-6) ando trifluoroacetyl fluoride (C2F4O, CAS No.: 354-34-7) are known etchants in plasma and thermal etch as shown in the prior art below. In addition, the carbon oxy halides are known as their reactivity with water at room temperature.

[0004] WO2023157441 and WO2023157442 disclose an etching method in which an etching compound may have fluorine and oxygen atoms in the molecule but do not have hydrogen atoms in the molecule including carbonyl fluoride (COF2), oxygen difluoride (OF2), and trifluoromethylhypofluoride (CF3OF). But none of the Examples uses the etching compound having fluorine and oxygen atoms.

[0005] US20220115240 discloses a dry etching method in which a dry etching agent comprises CF3I, a fluorine-containing linear nitrile compound of 2 or 3 carbon atoms and an additive gas including CF3OF.

[0006] US20050014383 discloses a mixture for etching a dielectric material in a layered substrate comprises a fluorocarbon and a fluorine-containing oxidizer that is a hypofluorite having the formula CxHyFz(OF)nOmwherein x is a number ranging from 0 to 8, y is a number ranging from 0 to 17, z is a number ranging from 0 to 17, n is 1 or 2, and m is 0, 1, or 2.

[0007] WO2012114611 discloses a cleaning gas that is a mixed gas comprising a compound expressed by CFxOy(where x is 2 or 4, and y = an integer from 1 to 3 when x = 2 or y = an integer from 1 to 4 when x = 4), and N2. The cleaning gas achieves a lowerglobal warming coefficient and a faster etching speed compared with conventional cleaning gas using NF3.

[0008] JP2000265275 A2 discloses using CF3COF activated with a plasma to cleaned unneeded deposits on a device for producing a thin film. The process temperature is at room temperature or higher. The temperature inside the reactor during cleaning is not particularly limited because the method can obtain a sufficiently high rate even at room temperature, but if the temperature is too high, device materials such as metal and resin are damaged. It is preferable to control the temperature of the metal part to 700°C or less and the temperature of the resin material to 100°C or less.” No addition of an etchant such as HF is disclosed.

[0009] US 6242359 B1 discloses plasma cleaning and etching methods using non- global-warming plasma etching and cleaning chamber using perfluoropropane dial (CFOCF2CFO) (which is C3O2F4), pentafluoropropionyl fluoride (CF3CF2CFO), trifluoroacetyl fluoride (CF3CFO), acetyl fluoride (CH3CFO), oxalyl fluoride ((COF)2), 1,1,1- trifluoroacetone (CF3COCH3)CF3COF among other gases. Substrate temperature was not specified. The etching method is for the etching of silicon containing dielectrics and metal layers from chamber walls or from silicon wafer substrates. Additionally oxygen containing gas can be added to improve the etching selectivity and enhance the formation of active species. Suitable oxygen-containing gases include, for example, oxygen, ozone, nitrous oxide and nitric oxide. No addition of an etchant such as HF is disclosed.

[0010] US6821454B2 discloses a method for removing water from surfaces in which a fluorinated non-ionic additive component A) of formula: T-ORf(CFY)-L a (per)fluoropolyether component B), wherein the ratio by weight (K) between the (per)fluorinated part and the hydrogenated L part of the additive is in the range 1.50-4.00 and the ratio KIbetween the number average molecular weight of the fluoropolyether part T-ORf- of the additive and the number average molecular weight of the component B) is higher than 1.60., but no temperature is disclosed and CF3COF is not specifically disclosed.

[0011] US20230197465A1 discloses oxygen and iodine-containing hydrofluorocarbon compound for etching semiconductor structures at a low temperature process (ranging from approximately −196°C. to approximately 500°C) that has the formula CnHxFyIzOe, wherein 0 ≤ n ≤ 10, 0 ≤ x ≤ 21, 0 ≤ y ≤ 21, 1 ≤ z ≤ 4 and 1 ≤ e ≤ 2; oxygen-fluorine molecules such as CF3COF are not disclosed and the molecule must have iodine.

[0012] Yoji Saito et al. (J. Vac. Sci. Technol. A 19, 38 - 40 (2001)) discloses remote- plasma-enhanced reaction between a silicon surface and trifluoro-acetyl-fluoride gas inwhich the etching reaction between silicon and the trifluoro-acetyl-fluoride gas is demonstrated using a remote plasma at room temperature. The CF3COF is appropriately reactive against water and will be decomposed to trifluoroacetic acid and hydrogen fluoride. The substrate temperature was room temperature during the etching experiments. O2is added to enhance the etching reaction. The etch rates of silicon dioxide films show a similar etch rate tendency as Si with O2content, but its value is about one tenth of that for etching silicon. Thus, their results show that CF3COF is not a good plasma etchant for etching SiO2selective to a material like Si, which can be a mask material.

[0013] US11183393B2 discloses atomic layer etching using acid halide etching a silicon oxide film or a silicon nitride film. Atomic layer etching (ALE) is performed by repeating three steps of (i) hydrogenation step of hydrogenating a surface by irradiating a silicon oxide film or a silicon nitride film with a plasma containing H, (ii) acid halide adsorption step of causing chemisorption of an acid halide represented by a formula of Rf-COX (Rf is H, F, a substituent consisting of C and F or consisting of C, H, and F, or -COX; each X is independently any halogen atom of F, Cl, Br and I) on the surface by reacting the acid halide with the hydrogenated surface through exposure to the acid halide, and (iii) etching step of etching a single atomic layer by inducing chemical reactions on the surface of the acid halide-adsorbed silicon oxide film or silicon nitride film through irradiation with a plasmacontaining a noble gas (at least any one of He, Ar, Ne, Kr, and Xe). CF3COF is disclosedas an etchant. Rf-COX used in the step (ii) is any of COF2, COFH, COFCl, COFBr, COFI, CF3COF, CHF2COF, CF3COCl, CHF2COCl, (COF)2, and (COF)COCl. The only statement about temperature is the reactions between the surface of a hydrogen-terminated etching target and an acid halide progress at normal temperature. Note that the use of plasma is restricted to Steps 1 and 3, a plasma is not used during the acid halide adsorption step. No addition of an etchant such as HF is disclosed.

[0014] US9623590B2 discloses fine concavo-convex structure product, heat-reactive resist material for dry etching, mold manufacturing method and mold. Examples of the sidewall protection gas are fluorine-containing gases such as CHF3, CH2F2, C2F6, C3F8, C4F6, C4F8, C4F10, C5F10, CCl2F2, CF3I, CFBr, CHF2COF, and CF3COF. These fluorine- containing gases may be used alone as the side wall protection gas, or mixed gases obtained by mixing these gases may be used as the sidewall protection gas. For example, the fluorine-containing gases (sidewall protection gases) are capable of being used in dry etching using RIE (Reactive Ion Etching), ECR (Electron Cyclotron Resonance) plasma etching, and microwave etching. Furthermore, it is possible to also use, as the side wall protection gas, mixed gases obtained by mixing the fluorine-containing gases as describedabove with gases such as O2, H2, Ar, N2, CO, HBr, NF3, HCl, HI, BBr3, BCl3, Cl2and SiCl4, as long as the gases are capable of attaining the side wall protection effect in dry etching. Note that they do not disclose to mix with HF.

[0015] US6787053B2 discloses cleaning gases and etching gases in which the first chamber cleaning gas and the first silicon-containing film-etching gas of the present invention comprise at least one compound selected from the group consisting of FCOF, CF3OCOF and CF3OCF2OCOF, and O2in the specific amount, and optionally other gases. The second chamber cleaning gas and the second silicon-containing film-etching gas comprise CF3COF, C3F7COF or CF2(COF)2(i.e., C3O2F4) and O2in specific amounts, and optionally may comprise other gases. The chamber cleaning gases and silicon-containing film etching gases of the present invention have a low global warming potential and hardly generate substances in the exhaust gases such as CF4, etc., which are harmful to the environment and have been perceived as contributing to global warming. Therefore, the gases are friendly to the global environment, and have easy handling and excellent exhaust gas treating properties. Further, the chamber cleaning gases of the invention have excellent cleaning rate. The above other gases may include gases other than the above inert gases within the limit of not missing the object of the invention. Examples of the gases other than the inert gases may include O3, H2, F2, ClF3or BrF3. The only temperature of the plasma process disclosed was in the example and was 300°C. They note that the CF3COF, C3F7COF and CF2(COF)2used in the present invention easily react with moisture to decompose into HF and CF3COOH. On this account, even if CF3COF, C3F7COF and CF2(COF)2are discharged as un-decomposed exhaust gas after chamber cleaning, they can be easily decomposed into HF and CF3COOH by a water scrubber of a conventional exhaust gas treatment system. However, this is describing a reaction with water post process and not as part of the etching process itself.

[0016] WO2023243569A1 discloses etching method, method for producing semiconductor device, etching apparatus and etching gas, in which the process temperature is preferably 20°C or more and 200°C or less, more preferably 30°C or more and 150°C or less, and 40°C or more, or 130°C or lower. The etching method for etching a film in a substrate that contains at least Si and O and a film that contains at least Si and N by bringing (i) an HF gas and (ii) at least one compound that is selected from the group consisting of a sulfonyl compound, a carbonyl compound, a sulfonyl isocyanate compound and an isocyanate compound into contact with the substrate. The carbonyl compound is represented by the formula: R2-C(=O)-R3wherein R2and R3each independently represent a straight or branched alkyl group having 1 to 6 carbon atoms, in which some or all of the hydrogen atoms may be substituted with fluorine atoms, hydrogen atom, halogen atom, or isocyanate group. Specifically the carbonyl compound represented by the above general formula is hexafluoroacetone (CF3C(=O)CF3), trifluoroacetaldehyde (CF3C(=O)H), or fluorocarbonyl isocyanate. (FC(=O)N=C=O). The etching method of described preferably etches the film containing Si and N without involving a plasma state.

[0017] US5626775A discloses plasma etch with trifluoroacetic acid and derivatives for etching of SiO2and SiN and other materials under plasma conditions to clean and remove SiO2and SiN from the walls and other surfaces within the reaction chamber such as a PECVD reactor. The process temperature is specified to be 25 to 500°C. Addition of other gases such as oxygen and inert gases are disclosed. No addition of an etchant such as HF is disclosed.

[0018] WO2019002058 discloses etching method and plasma etching material trifluoroacetic anhydride in plasma etching. C4F6O3is used to etch at -20°C to 200°C. The addition of other fluorocarbons are described including CF4, CF3I, C2F3I, C3F5I, C3F7I, C2F6, C3F6, C3F8, C4F8, C4F6, C5F8, C6F6, CH3F, CHF3, CH2F2, C2HF5, C3HF5, C3H2F4, C3H2F6, C4HF7, and C4H2F6. The addition of other oxidizing gas are described including O2, O3, CO, CO2, NO, N2O, NOF, SO2, and COS. No addition of an etchant such as HF is disclosed.

[0019] US20030216041 discloses in-situ thermal chamber cleaning. Chemistries include one or more etch gases selected from the group consisting of NF3, CF4, C2F6, C3F8, F2, ClF3, (CF3CO)2O, C4F8O, C4F8, anhydrous HF, CHF3, and mixtures thereof. Preferably, the first cleaning process is conducted at a temperature ranging from about 500 to 800°C, and at a pressure ranging from about 100 to 700 Torr. The second cleaning process is preferably conducted at a temperature ranging from about 500 to 800°C, and at a pressure ranging from about 5 to 100 Torr. The disclosed method does not include the use of a plasma.

[0020] Pruette et al. (Pruette, et al., “evaluation of trifluoroacetic anhydride as an alternative plasma enhanced chemical vapor deposition chamber clean chemistry”, J. Vac. Sci. Technol. A 16, 1577-1581 (1998)) disclose chamber cleaning times and emissions from the use of one such species, trifluoroacetic anhydride (TFAA).

[0021] Karecki et al. (“Plasma Etching of Silicon Dioxide and Silicon Nitride with Non- Perfluorocompound Chemistries: Trifluoroacetic Anhydride and Iodofluorocarbons”, MRS Online Proceedings Library 447, 67-74 (1996)) disclose etching of SiO2and SiN usingtrifluoroacetic anhydride (TFAA) via magnetically enhanced reactive ion etch tool. No reaction temperature is mentioned.

[0022] Karecki (Development of novel alternative chemistry processes for dielectric etch applications Author(s) Karecki, Simon Martin (2000)) discloses the evaluation of fluorinated compounds belonging to three principal families of modified fluorocarbon molecules: hydrofluorocarbons (HFCs), iodofluorocarbons (IFCs), and unsaturated fluorocarbons (UFCs). In addition, other chemistries, namely trifluoroacetic anhydride (TFAA), oxalyl fluoride, and octafluorotetrahydrofuran, are also disclosed.

[0023] US20240112922A1 discloses an etching method including (a) preparing a substrate, the substrate comprising a silicon-containing film and a mask, the silicon- containing film including a recess, the mask being provided on the silicon-containing film and including an opening that exposes the recess; (b) forming a carbon-containing film on a side wall of the silicon-containing film, the side wall defining the recess; and (c) by using a plasma generated from a processing gas, forming a protective film containing tungsten on the carbon-containing film and etching the silicon-containing film in the recess, the processing gas including a fluorine-containing gas and a tungsten-containing gas. The temperature is as low as -80°C. The silicon containing film is etched in the step (c). The fluorine-containing gas contained in the step (c) may be, for example, a hydrogen fluoride gas (HF gas) and / or a hydrofluorocarbon gas. The tungsten-containing gas included in the step (c) may be, for example, a gas containing tungsten and halogen such as WF6. The step (c) may further include a phosphorus-containing gas such as PF3. The step (c) may further include a carbon-containing gas. The carbon-containing gas may be, for example, either or both of a fluorocarbon gas and a hydrofluorocarbon gas. The carbon containing gas may include C4F8O (pentafluoroethyl trifluorovinyl ether) gas, a CF3COF gas (1,2,2,2- tetrafluoroethan-1-one), a CHF2COF (difluoroacetic acid fluoride) gas, and a COF2(carbonyl fluoride) gas along with a long list of gases including CF4, C4F6, C4F8, and C5F8and hydrofluorocarbon gases to include CHF3, CH2F2, and CH3F among others. No data or explanation is given on the inclusion of CF3COF, CHF2COF, and COF2.

[0024] US20240153744A1 discloses an etching method to form a recess by etching a target film where the source and bias power are cycled where in the first cycle the film is etched and in the second cycle the second process gas is adsorbed on the etching target film, in which only one of source or bias is applied. The substrate may include a silicon nitride film, and the second processing gas may include an acid component. The second processing gas may include an acid component, and in the second cycle, after the second processing gas is adsorbed onto the etching target film, a third processing gas containinga base component may be supplied into the chamber. In this case, the acid component is adsorbed onto the etching target film, and thereafter, the acid component and the base component react with each other to form a salt. The acid component may include at least one selected from the group consisting of formic acid, acetic acid, HCl, HBr, HI, trichloroacetic acid, and citric acid. In the etching method, the first processing gas may include a phosphorus-containing gas and a fluorine-containing gas. The first processing gas may include an HF gas or HF generating gas such as a hydrofluorocarbon gas. The phosphorus containing gas may be PF3. The first processing gas may include a carbon- containing gas. The carbon containing gas may be at least one or both of a fluorocarbon gas or a hydrofluorocarbon gas that may include a C4F8O (pentafluoroethyl trifluorovinyl ether) gas, a CF3COF (1,2,2,2-tetrafluoroethane-1-one) gas, a CHF2COF (difluoroacetic acid fluoride) gas, and a COF2(fluorinated carbonyl) gas. The first processing gas may also include a metal containing gas such as tungsten containing gas like WF6, an oxygen containing gas, a halogen containing gas and a noble gas such as Ar. The temperature of the substrate is not disclosed.

[0025] Thus, there is a need to explore new etchant chemistry for low temperature etching or cryogenic etching in semiconductor industry to both enhance etching rates and help dehydrate the surface of excess H2O generated during etching processes. Summary

[0025] Disclosed is a cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising the steps of: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below 25°C; introducing an etching gas having general formulae Y3-CO-X, Y-(C=O)-X, R1-CO-X, R2-CO-R3, R2-(C=O)-O-(C=O)-R3, and COF-CxFyHz-COF wherein X and Y each is a halogen selected from F, Cl, Br, I; R1is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; R2and R3each is a fluorocarbon, hydrofluorocarbon,bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, into the reaction chamber; and x, y and z are integers; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture. The disclosed etch method may include one or more of the following features: ● further comprising adding one or more hydrofluorocarbon or fluorocarbon etching gases to the etching gas, wherein the one or more hydrofluorocarbon or fluorocarbon etching gases are selected from C4F6, C4F8, C4H2F6, CHF3, CH2F2, CH3F, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F10, C5F8, C6F6, C1-C6CxFyHzmolecule (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF5,C3H2F4, or combination thereof; ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7,HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3, P(R)3wherein R is an alkyl or fluorinated alkyl group, SOF2, SOCl2, SOClF SO2F2, SO2FCl, SO2Cl2, or CF4SO2; ● the co-reactant being a Sulfur-containing gas; ● the Sulfur-containing gas having the general formula, SOmXnand R-SOmXn, wherein m and n are integers, X is a halogen and R is a fluorocarbon, hydrofluorocarbon, or hydrocarbon, into the reaction chamber; ● the Sulfur-containing gas being SOF2, SOCl2, SOClF, SO2F2, SO2FCl, SO2Cl2, and CF4SO2; ● the co-reactant being a P-containing gas; ● the P-containing gas being PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3and P(R)3wherein R is an alkyl or fluorinated alkyl group; ● P(R)3being P(CF3); ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, CxOyFz(x, y and z are integers), CxOyFzHm(x, y, z and m are integers) selected from alcohol, ketone, acidic, ester type molecules; ● further comprising adding a co-reactant O2to the etching gas; ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is an inert gas to the etching gas selected from Ar, Kr, Xe, Ne, N2, He or combinationthereof; ● the etching gas being carbon oxy halides; ● the carbon oxy halides having lower GWP compared to commonly used ones (e.g., CF4, C4F8, CH2F2); ● the etching gas being acyl halides; ● the carbon oxy halides being Y3-CO-X, or Y-(C=O)-X, wherein X and Y each is a halogen selected from F, Cl, Br, I; ● the etching gas being CF3OF; ● the etching gas being COF2; ● the carbon oxy halides being a primary family of an acyl halide, R1-CO-X, wherein X is a halide such as F, Cl, Br, I, and R1is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; ● the etching gas being C3O2F4; ● the etching gas being CF3COF; ● the etching gas being C2O2F2; ● the etching gas being C3O2F4and its isomers; ● the etching gas being CF3COF and its isomers; ● the etching gas being COF2and its isomers; ● the etching gas being C2O2F2and its isomers; ● the carbon oxy halides being a primary family of an acyl halide, R2-CO-R3, wherein R2and R3is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon; ● the carbon oxy halides being CF3-CO-CF3; ● the carbon oxy halides being CH3-CO-CH3; ● the carbon oxy halides being a primary family of an acyl halide, R2-(C=O)-O-(C=O)- R3, wherein R2and R3is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon; ● the carbon oxy halides being CF3-CO-CF3; ● the carbon oxy halides being CH3-CO-CH3; ● the carbon oxy halides being a primary family of an acyl halide, COF-CxFyHz-COF, wherein x, y and z are integers; ● the carbon oxy halides being (COF)-CF2-(COF); ● the carbon oxy halides being C3O2F4(CAS No.: 5930-67-6), CF3OF (CAS No.: 373- 91-1), CF3COF (CAS No.: 354-34-7), C3F6O (CAS No.: 422-61-7), C2F3OI (CASNo.: 354-36-9), C2F3OCl (CAS No.: 354-32-5), C2O2F2(CAS No.: 359-40-0), C4F6O3(TFAA) (CAS No.: 407-25-0), C4H3F3O (CAS No.: 162880-35-5), C3H3F3O (CAS No.: 2255428-10-3), C2HF3O (CAS No.: 2925-22-6), C2HF3O (CAS No.: 75-90-1), C3HF5O (CAS No.: 663-74-1), C3HF5O (CAS No.: 6065-84-5), C3HF5O (CAS No.: 85592-82-1), C2HClF2O (CAS No.: 381-72-6), C2HF3O (CAS No.: 814-77-7), C2HClFIO (CAS No.: 955374-72-8), C4HF5O3(CAS No.: 406727-03-5), C4H2F4O3(CAS No.: 401-67-2), C4H2F4O3(CAS No.: 406727-04-6), C4H4F2O3(CAS No.: 407- 33-0), C4H3F3O3(CAS No.: 1784758-59-3), C4H4F2O3(CAS No.: 406727-05-7), C4H3F3O3(CAS No.: 96-63-9), C2HClF2O (CAS No.: 811-96-1), C2HBrF2O (CAS No.: 353-79-7), C2HF2IO (CAS No.: 1334483-62-3), or C3F6O (CAS No.: 684-16-2); ● the temperature of the substrate being below approximately 0°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 300°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 60°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 0°C; ● an aspect ratio of the aperture ranging from 1:1 to 5:1; ● an aspect ratio of the aperture being above 5:1; ● an aspect ratio of the aperture being above 20:1; ● an aspect ratio of the aperture ranging from approximately 5:1 to approximately 500:1; ● an aperture has a diameter ranging from approximately 0.1 nm to approximately 500 nm; ● the aperture having a diameter less than 100 nm; ● after the aperture is formed, the temperature of the substrate is increased to greater than 0°C; ● the carbon oxy halide etching gases having a low moisture content of < 40 ppm; and

[0026] the carbon oxy halide etching gases having a low moisture content of < 10 ppm.

[0027] Disclosed is a cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below approximately 25°C;introducing an etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2into the reaction chamber; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture. The disclosed etch method may include one or more of the following features: ● further comprising adding one or more hydrofluorocarbon or fluorocarbon etching gases to the etching gas, wherein the one or more hydrofluorocarbon or fluorocarbon etching gases are selected from C4F6, C4F8, C4H2F6, CHF3, CH2F2, CH3F, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F10, C5F8, C6F6, C1-C6CxFyHzmolecule (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF5,C3H2F4, or combination thereof; ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7,HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3, P(R)3wherein R is an alkyl or fluorinated alkyl group, SOF2, SOCl2, SOClF SO2F2, SO2FCl, SO2Cl2, or CF4SO2; ● the co-reactant being a Sulfur-containing gas; ● the Sulfur-containing gas having the general formula, SOmXnand R-SOmXn, wherein m and n are integers, X is a halogen and R is a fluorocarbon, hydrofluorocarbon, or hydrocarbon, into the reaction chamber; ● the Sulfur-containing gas being SOF2, SOCl2, SOClF, SO2F2, SO2FCl, SO2Cl2, and CF4SO2; ● the co-reactant being a P-containing gas; ● the P-containing gas being PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3and P(R)3wherein R is an alkyl or fluorinated alkyl group; ● P(R)3being P(CF3); ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, CxOyFz(x, y and z are integers), CxOyFzHm(x, y, z and m are integers) selected from alcohol, ketone, acidic, ester type molecules; ● further comprising adding a co-reactant O2to the etching gas; ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is an inert gas to the etching gas selected from Ar, Kr, Xe, Ne, N2, He or combinationthereof; ● the temperature of the substrate being below approximately 0°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 300°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 60°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 0°C; ● an aspect ratio of the aperture ranging from 1:1 to 5:1; ● an aspect ratio of the aperture being above 5:1; ● an aspect ratio of the aperture being above 20:1; ● an aspect ratio of the aperture ranging from approximately 5:1 to approximately 500:1; ● an aperture has a diameter ranging from approximately 0.1 nm to approximately 500 nm; ● the aperture having a diameter less than 100 nm; ● after the aperture is formed, the temperature of the substrate is increased to greater than 0°C; ●the etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2having a low moisturecontent of < 40 ppm; and ● the etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2having a low moisture content of < 10 ppm.

[0028] Disclosed is a cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below approximately 25°C; introducing an etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2into the reaction chamber; adding a co-reactant O2into the reaction chamber converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture. The disclosed etch method may include one or more of the following features:● further comprising adding one or more hydrofluorocarbon or fluorocarbon etching gases to the etching gas, wherein the one or more hydrofluorocarbon or fluorocarbon etching gases are selected from C4F6, C4F8, C4H2F6, CHF3, CH2F2, CH3F, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F10, C5F8, C6F6, C1-C6CxFyHzmolecule (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF5,C3H2F4, or combination thereof; ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7,HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3, P(R)3wherein R is an alkyl or fluorinated alkyl group, SOF2, SOCl2, SOClF SO2F2, SO2FCl, SO2Cl2, or CF4SO2; ● the co-reactant being a Sulfur-containing gas; ● the Sulfur-containing gas having the general formula, SOmXnand R-SOmXn, wherein m and n are integers, X is a halogen and R is a fluorocarbon, hydrofluorocarbon, or hydrocarbon, into the reaction chamber; ● the Sulfur-containing gas being SOF2, SOCl2, SOClF, SO2F2, SO2FCl, SO2Cl2, and CF4SO2; ● the co-reactant being a P-containing gas; ● the P-containing gas being PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3and P(R)3wherein R is an alkyl or fluorinated alkyl group; ● P(R)3being P(CF3); ● further comprising adding a co-reactant to the etching gas, wherein the co-reactant is an inert gas to the etching gas selected from Ar, Kr, Xe, Ne, N2, He or combination thereof; ● the temperature of the substrate being below approximately 0°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 300°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 60°C; ● the temperature of the substrate ranging from approximately - 196°C to approximately 0°C; ● an aspect ratio of the aperture ranging from 1:1 to 5:1; ● an aspect ratio of the aperture being above 5:1; ● an aspect ratio of the aperture being above 20:1; ● an aspect ratio of the aperture ranging from approximately 5:1 to approximately500:1; ● an aperture has a diameter ranging from approximately 0.1 nm to approximately 500 nm; ● the aperture having a diameter less than 100 nm; ● after the aperture is formed, the temperature of the substrate is increased to greater than 0°C; ● the etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2having a low moisture content of < 40 ppm; and ● the etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2having a low moisture content of < 10 ppm. Notation and Nomenclature

[0029] The following detailed description and claims utilize a number of abbreviations, symbols, and terms, which are generally well known in the art, and include:

[0030] As used herein, the indefinite article “a” or “an” means one or more.

[0031] As used herein, “about” or “around” or “approximately” in the text or in a claim means ±10% of the value stated.

[0032] As used herein, “room temperature” in the text or in a claim means from approximately 20°C to approximately 25°C.

[0033] The term “substrate” refers to a material or materials on which a process is conducted. The substrate may refer to a wafer having a material or materials on which a process is conducted. The substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. The substrate may also have one or more layers of differing materials already deposited upon it from previous manufacturing steps. For example, the wafers may include silicon layers (including, but not limited to, crystalline, amorphous, porous, etc.), silicon containing layers ( including, but not limited to, SiO2, SiN, SiON, SiCOH, etc.), metal or metal containing layers (including, but not limited to, copper, cobalt, ruthenium, tungsten, platinum, palladium, nickel, ruthenium, gold, etc.) or combinations thereof. Furthermore, the substrate may be planar or patterned. The substrate may be an organic patterned Iodinated carbon layer film. The substrate may include layers of oxides that are used as dielectric materials in field effect transistor (FET) such as FinFET, MOFSET, GAAFET(Gate all-around FET), Ribbon-FET, Nanosheet, Forksheet FET, Complementary FET (CFET), MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO2based materials, HfO2based materials, TiO2based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes. The substrate may include layers of alternating oxides (e.g., SiO) and nitrides (e.g., SiN). One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates. The substrate may be any solid that has functional groups on its surface that are prone to react with the reactive head of a self-assembled monolayer (SAM), and may include without limitation 3D objects or powders.

[0034] The term “wafer” or “patterned wafer” refers to a wafer that has a stack of films on a substrate, at least the top-most film the stack of the films has topographic features or patterns that have been created in steps prior to etch and the patterned top-most film on is formed for pattern etch.

[0035] The term “processing” as used herein includes patterning, exposure, development, etching, deposition, cleaning, and / or removal of by-products, as required in forming a described structure.

[0036] The term of “etch” or “etching” refers to a series of processes wherein materials are removed from a wafer surface or other surfaces inside a process chamber. Chemical reactions are involved in the processes, which occur after creation of a plasma of the reacting gases or activation of the reacting gases by heat. Physical processes are involved in the processes when in the plasma there is a bias that accelerates ions to bombard the surface and physically sputters away the substrate material. The plasma may be capacitively coupled plasma (CCP), Inductively coupled plasma (ICP), electron cyclotron resonance (ECR) plasma, or a microwave plasma, but is not limited to. Suitable commercially available plasma etching chambers include but are not limited to the Lam Research Dual CCP reactive ion etcher Dielectric etch product family sold under the trademark Flex™ or the Tokyo Electron Tactras™ or EpisodeTMUL. The non-plasma exposure step may be performed in a different chamber than the plasma exposure step.

[0037] The term “aspect ratio” refers to a ratio of the height of a trench (or aperture) to the width of the trench (or the diameter of the aperture).

[0038] The term “high aspect ratio (HAR)” refers to an aspect ratio ranging from approximately 1:1 to approximately 500:1, preferably from approximately 20:1 to approximately 400:1.

[0039] The term “high aspect ratio etching” refers to the formation of a hole pattern in a target film by plasma etching method when aspect ratio of formed hole structures is exceeding value of 5.

[0040] Note that herein, the terms “film”, “layer” and “material” may be used interchangeably. It is understood that a film may correspond to, or related to a layer or a material, and that the layer may refer to the film and the material. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” or “material” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.

[0041] Note that herein, the terms “aperture”, “via”, “hole”, “trench”, “feature” and “structure” may be used interchangeably to refer to an opening formed in a semiconductor structure.

[0042] As used herein, the abbreviation "NAND" refers to a "Negative AND" or "Not AND" gate; the abbreviation "2D" refers to 2 dimensional gate structures on a planar substrate; the abbreviation "3D" refers to 3 dimensional or vertical gate structures, wherein the gate structures are stacked in the vertical direction.

[0043] As used herein, the term “etching gas” or “etchant” refers to one or more gaseous material(s) that are performing etching. The source of the material(s) in a container that provides the vapors to do the etching may contain a gas, liquid or solid state of the material(s) and / or combinations thereof. The etching gas and / or etchant may be one gaseous material or chemical. The etching gas and / or etchant may be a mixture of more than one gaseous materials or chemicals.

[0044] Note that herein, the term “QMS” refers to quadrupole mass spectrometry or quadrupole mass spectrometer.

[0045] Note that herein, the terms “etch gas”, “etching gas” and “etchant” may be used interchangeably when the etch gas is in a gaseous state at room temperature and ambient pressure. It is understood that an etch gas may correspond to, or be related to an etchant or an etching gas, and that the etchant may refer to the etch gas and the etching gas.

[0046] The terms “dope” or “doping” is used interchangeably to the process of incorporation of one or more elements into a film through various methods where that element may be chemically bond or physically bond, and the process of intentionally incorporating atoms of different elements into the film composition. The element(s) may be doped interstitial or substitutional within the film.

[0047] The terms “cryogenic etch”, “cryo-etch”, “cryogenic etching”, “cryo-etching”, “low temperature etch”, “low temperature etching”, are used interchangeably to etching processes disclosed herein in which a substrate is cooled to below room temperature.

[0048] The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by theseabbreviation (e.g., Si refers to silicon, N refers to nitrogen, O refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).

[0049] The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to identify the specific molecules disclosed.

[0050] As used herein, the term “hydrofluorocarbon” refers to a saturated or unsaturated function group containing exclusively carbon, fluoride and hydrogen atoms.

[0051] As used herein, the term “fluorocarbon” refers to a saturated or unsaturated function group containing exclusively fluoride and hydrogen atoms.

[0052] As used herein, the term “hydrocarbon” refers to a saturated or unsaturated function group containing exclusively hydrogen and carbon atoms.

[0053] As used herein, the term “GWP” refers to Global Warming Potentials, typically on a 100 year timescale and comparing the global warming potential to CO2.

[0054] As used herein, the term “GWP100” is the GWP over 100 years.

[0055] As used herein, the term “CO2eq” or “CO2e” is CO2equivalent emission, i.e., the amount of greenhouse gas emissions comparable to CO2by using the mass of the species being emitted and multiplying by the GWP of the species. This allows the equivalent comparison of the emissions of a process between two different etching gases utilizing the GWP of each molecule.

[0056] As used herein, “CO2emission (CO2e)” or “CO2equivalent emission (CO2eq)” are used interchangeably to refer to the relative global warming impactful emissions.

[0057] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1, x=4, and x=any number in between), irrespective of whether the term “inclusively” is used.

[0058] Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”

[0059] As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over otheraspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0060] Additionally, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

[0061] "Comprising" in a claim is an open transitional term that means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” is defined herein as necessarily encompassing the more limited transitional terms "consisting essentially of" and “consisting of”; “comprising” may therefore be replaced by "consisting essentially of" or “consisting of” and remain within the expressly defined scope of “comprising”.

[0062] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actors in the absence of express language in the claim to the contrary. Brief Description of the Drawings

[0063] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein: FIG.1 is a column graph of a comparison of etching rates of common materials SiO2, SiN, p-Si and a-C mask, respectively used in semiconductor processing with CF4as an etchant; FIG.2 is a column graph of a comparison of etching rates of common materials SiO2, SiN, p-Si and a-C mask, respectively used in semiconductor processing with C3O2F4as an etchant; FIG.3 is a column graph of a comparison of etching rates of common materials SiO2, SiN, p-Si and a-C mask, respectively used in semiconductor processing with COF2as an etchant; FIG.4 is a column graph of a comparison of etching rates of common materials SiO2, SiN, p-Si and a-C mask, respectively used in semiconductor processing with C2O2F2as anetchant; FIG.5 is a column graph of a comparison of selectivities of SiO2to a-C mask with etching gases, COF2, C2O2F2and C3O2F4, respectively; and FIG.6 is a column graph of a comparison of SiO2etch rates with etching gases, COF2, C2O2F2and C3O2F4, respectively. Description of Preferred Embodiments

[0064] Disclosed are methods of cryogenic etching silicon-containing materials in high aspect ratio (HAR) structures for manufacturing a semiconductor device using carbon oxy halides. The disclosed carbon oxy halides may be acyl halides. We believe that the disclosed carbon halides may both enhance dehydration of water in etched channel holes or features and provide a source of carbon to enhance the selectivity of etching dielectric materials, e.g., SiO, or combination of SiO and SiN, to a mask material, such as a carbon or carbon doped material.

[0065] Current generation of cryogenic etch chemistry is PF3and HF for high aspect ratio (HAR) applications, such as for HAR patternings of dielectrics such as SiO2or SiO2 / SiN alternating films like 3DNAND. Due to reactions with SiO and SiN in a substrate or device to be etched under low process temperature < 0°C, etching gases may provide a large unprecedented amount of water in features or holes etched in the substrate during etching process forming a water layer in the etched features or holes. This water layer acts as a barrier to prevent the etching process from happening (i.e., lowering etching rate or etch stop). The primary objective for cryogenic etching at such a small feature or hole in HAR etching processes is to remove water from the substrate or to reduce the thickness of this water layer. The use of PF3in the cryogenic etch process is said to react with H2O to form H3PO4. However, this reaction is known to be slow compared to the reactivity of the other phosphorus halides with water, referring to DeFrank, et al., “Phosphofluoridates: Biological Activity and Biodegradation”, Organofluorines, (2002); and “The Handbook of Environmental Chemistry”, vol. 3N, page 303, Springer, Berlin, Heidelberg. https: / / doi.org / 10.1007 / 10721878_10.

[0066] The disclosed herein is to use the disclosed carbon oxy halides or acyl halides to replace PF3or add the disclosed carbon oxy halides to PF3and HF acid gas in cryogenic etch applications, which is advantageous for cryogenic etching processes. In addition to PF3and HF, a fluorocarbon or hydrofluorocarbon gas may be added to provide a carbon source to enhance the selectivity to a mask, commonly a carbon material. Although the concept of HF + -(C=O)- family has been disclosed (WO2023243569) for thermal etch attemperatures > 20°C, it is not the same chemical family as disclosed here. In addition, due to very fast reactions between the carbon oxy halides or acyl halides and dielectric materials such as SiO2, a very fast etching rate may be obtained, leading to a high wafer throughput at the cryogenic etching.

[0067] Here are the benefits of an addition of the disclosed carbon oxy halides in etching chemistry during a cryogenic process, especially a cryogenic plasma HAR etching process. The disclosed carbon oxy halides are expected to be a low GWP low-carbon etching gases. In addition, giving the oxygen in the etching gases, it may not provide a polymer to clog features to be etched in a substrate during plasma etching processes but likely add some carbon to the plasma etching process thereby helping the selectivity to a mask. In other words, water may be removed from etched features and HX (X is a halogen) may be generated by adding the disclosed carbon oxy halides. This generation of additional HX may be beneficial to boost etching rates during HAR etching. In addition, looking at the boiling point of each species generated with the disclosed carbon oxy halides in the reaction that examples follow, one may see that the boiling point decreases compared to water, thereby, it is expected that byproducts of the HAR etching to be more easily removed from the etched features or holes due to increased volatility.

[0068] In some embodiments, the disclosed carbon oxy halides may be CF3OF, C3O2F4or CF3COF used as an addition to etching chemistry in a cryogenic plasma HAR etching process. For example, CF3COF, trifluoroacetyl fluoride, CAS No.: 354-34-7, is an etchant for use in a cryogenic etching process of silicon containing substrates to manufacture a semiconductor device. CF3COF is expected to be a low GWP low-carbon precursor. In addition, giving the oxygen in the precursor, it may not provide a polymer to clog etched features in a substrate during plasma processes but likely add some carbon to the process thereby helping the selectivity to a mask. CF3COF is known for its reaction with water i.e., CF3COF + H2O → CF3COOH + HF. In other words, water may be removed from the etched features and HF may be generated by adding CF3COF. This generation of additional HF may beneficial to boost etching rates during HAR etching. In addition, if looking at the boiling points of each species in the reaction, one may see that the boiling point decreases compared to water thereby it is expected that the byproducts to be more easily removed from the etched features or holes due to increased volatility. Here is the reaction with the boiling points. CF3COF (-59°C) + H2O (100°C) → CF3COOH (73°C) + HF (20°C)

[0069] Due to high surface tension of water (72 dyn / cm at 20°C), water will remain as a thick passivation layer in the feature. CF3COOH has a much lower surface tension (13dyn / cm at 20°C). Therefore, CF3COF layer may be much thinner as compared to water in the feature due to this combination of reactivity with water and its byproduct has lower surface tension and boiling points. Consequently, the addition of HF generation, removal of water and thinner passivation may lead to high etching rate of SiN / SiO2in HAR during cryogenic etch.

[0070] The disclosed carbon oxy halides may be a primary family of an acyl halide, for example, Y3-CO-X and Y-(C=O)-X wherein X and Y each is a halide such as F, Cl, Br, I; R1-CO-X wherein X is a halide such as F, Cl, Br, I, and R1is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; R2-CO-R3wherein R2and R3is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, such as CF3-CO-CF3, CH3-CO-CH3; R2-(C=O)-O-(C=O)-R3wherein R2and R3is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, such as CF3-CO-CF3, CH3-CO-CH3; and COF-CxFyHz-COF wherein x, y and z are integers, such as (COF)-CF2-(COF).

[0071] Note that the families of the acyl halides stated above, R1-CO-X, R2-CO-R3, R2- (C=O)-O-(C=O)-R3, and COF-CxFyHz-COF, may accomplish the tasks similar to C3O2F4Examples that follow. Specifically by tuning the amount of carbon in molecules, it is believed that the molecules in the families of the acyl halide stated above may both enhance dehydration of water in etched holes or features and provide some carbons to etching process to enhance the selectivity to a mask material, typically carbon or doped carbon such as boron-doped carbon.

[0072] Basic reactions of R1-CO-X proposed dehydration of water from etched features / holes herein are as follows: R1-CO-X + H2O → R1-COOH + HX HX + SiO2→ SiX + H2O

[0073] For example, below are the reactions with specific molecules in the families of the acyl halide, the boiling points of each species are listed in parenthesis.CF3COCl (- 27°C) + H2O (100°C) → CF3COOH (73°C) + HCl (- 85°C) HCl (- 85°C) + SiO2(solid) → SiCl4(58°C) + H2O (100°C) CF3COF (- 59°C) + H2O (100°C) → CF3COOH (73°C) + HF (20°C) HF (20°C) + SiO2(solid) → SiF4(- 90°C) + H2O (100°C)

[0074] If using a chloride version versus the fluoride version of CF3COX while the chloride is much more reactive to water, the reaction of HCl with SiO2is much slower and the formation of higher boiling point byproduct SiCl4is not ideal. However, it will still dehydrate the H2O forming more volatile byproduct CF3COOH and HCl.

[0075] In the case of C4F6O3(CAS No.: 407-25-0, 2,2,2-Trifluoroacetic anhydride, TFAA, ), the reaction is very fast. It has been known hydrolysis of acetic anhydride is a fast and very exothermic reaction that has been used widely, such as in nonlinear dynamics, multiplicity of steady states, etc. C4F6O3(40°C) + H2O (100°C) = CF3COOH (73°C) + HF (20°C) HF (20°C) + SiO2(solid) → SiF4(- 90°C) + H2O (100°C)

[0076] Table 1 lists exemplary molecules included in the above disclosed acyl halide families. Table 1

[0077] The disclosed cryogenic plasma etching method comprises exposing a substrate to an etching gas from the families of the acyl halide stated above, R1-CO-X, R2-CO-R3, R2-(C=O)-O-(C=O)-R3, and COF-CxFyHz-COF, in a reaction chamber during an etching process and / or during a chamber conditioning process.

[0078] The disclosed cryogenic plasma etch method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films comprises: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below 25°C; introducing an etching gas having general formulae Y3-CO-X, Y-(C=O)-X,R1-CO-X, R2-CO-R3, R2-(C=O)-O-(C=O)-R3, and COF-CxFyHz-COF wherein X and Y each is a halogen selected from F, Cl, Br, I; R1is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; R2and R3each is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, into the reaction chamber; and x, y and z are integers; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture.

[0079] Exemplary disclosed etching gases include CF3OF, C3O2F4, CF3COF, COF2or C2O2F2. Preferably, the disclosed carbon oxy halide etching gas may be C3O2F4, CF3COF, COF2or C2O2F2and their isomers.

[0080] The reaction chamber may be any enclosure or chamber within a device in which etching methods take place, such as, without limitation, a reactive ion etching (RIE), a CCP with single or multiple frequency RF sources, an inductively coupled plasma (ICP), a microwave plasma reactors, or other types of etching systems capable of plasma processing, that is, selectively removing a portion of a dielectric film or generating active species or depositing films.

[0081] The reaction chamber is equipped with parallel plate electrodes plasma generators where a high frequency electromagnetic field of 60 MHz is applied to the upper electrode and a 2 MHz one is applied to the lower electrode, when the gap between the electrodes is kept in a range between 10 and 35 mm. Combination of these electric fields allows applying power to the upper electrode within a range of 0-2000 W and to the lower electrode within the range of 1500-7000 W. The plasma may be generated with a RF power ranging from about 25W to about 100 kW. The plasma may be generated remotely or within the reaction chamber itself. RF frequency of the plasma may range from 100 KHz to 1GHz. The plasma may be pulsed or continuous wave. In some embodiments, the power applied to the chamber may range from 0 to several kW of bias power and hundreds to several thousand kW of source power. Both the gas flows and the plasma may be pulsed and cycled in a variety of different processing steps.

[0082] Temperature and pressure within the reaction chamber are held at conditions suitable for the processing films to react with the activated etching gas (e.g., acyl halidestated above). For instance, the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 10 Torr, more preferably between approximately 1 mTorr and approximately 1 Torr, even more preferably between approximately 1 mTorr and approximately 30 mTorr, as required by etching parameters. Pressure in the etching chamber during the plasma-etching process may be maintained between 1 and 30 mTorr with introduced the process gas mixture. Likewise, the temperature of a substrate in the reaction chamber may be < 25°C, preferably < -50°C. Alternatively, the substrate temperature in the reaction chamber may range from approximately -196°C to approximately 300°C; preferably from approximately -196°C to approximately 60°C; more preferably from approximately -196°C to approximately 25°C; even more from approximately -196°C to approximately -50°C; even more from approximately -196°C to approximately 0°C. The substrate temperature in the reaction chamber may be below approximately 0°C. The substrates may be cooled by a variety of sources including commercially available chillers or other methods such as liquid N2

[0083] Reaction chamber wall temperature may be around ^ 20°C, preferably < 150°C. The reaction chamber wall temperature may be around room temperature or larger but less than 60°C depending on process requirements.

[0084] The disclosed cryogenic plasma etching method further comprises, prior to activating a plasma, sequentially or simultaneously exposing the substrate to a co-reactant. That is, a co-reactant is added to the etching gas stated above.

[0085] The co-reactant may be selected from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, or COS, O3, CxOyFz(x, y and z are integers) such as COF2, C2O2F2, CxOyFzHm(x, y, z and m are integers) such as alcohol, ketone, acidic, ester type molecules such as CF3OH, CF3OCF3, (CF3)2C=O, CF3COOH, or combinations thereof. The co-reactant may be O2.

[0086] The co-reactant may be additional one or more hydrofluorocarbon or fluorocarbon etching gases added to the etching gas stated above. The additional one or more hydrofluorocarbon or fluorocarbon etching gases may be selected from C4F6, C4F8, C4H2F6, CH2F2, CH3F, CHF3, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F10, C5F8, C6F6, C1- C6CxFyHzmolecule (x, y and z are integers), C2H5F, C3H7F, C3H2F6, C2HF5,C3H2F4or combination thereof.

[0087] The co-reactant may be other gases added to the etching gas stated above. For example, additives include H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7,HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3and P(R)3wherein R is an alkyl or fluorinated alkylgroup such as CF3, or the like, may be added to the etching gas stated above.

[0088] The co-reactant may be other sulfur containing gases added to the etching gas stated above having the general formula SOmXn; and R-SOmXn, wherein m and n are integers, X is a halogen and R is a fluorocarbon, hydrofluorocarbon, or hydrocarbon, into the reaction chamber. Exemplary examples of the other sulfur containing gases may include SOF2, SOCl2, SOClF, SO2F2, SO2FCl, SO2Cl2, and CF4SO2.

[0089] The co-reactant may be an inert gas may also be added to the etching gas stated above. The inert gas is selected from Ar, Kr, Xe, Ne, N2, He or combination thereof.

[0090] The substrate contains silicon-containing materials, such as SiO2, SiN, or Si. One example is alternating layers of SiO and SiN as used in 3D NAND applications. The silicon-containing film or material comprises a layer of SiaObHcCdNe, wherein a > 0, b, c, d and e ≥ 0, selected from silicon oxide, silicon nitride, crystalline Si, poly-silicon, polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, or a stack of alternating silicon oxide and silicon nitride (ONON) films or alternating silicon oxide and poly-silicon (OPOP) films.

[0091] On top of the silicon-containing films or materials is a mask layer or mask material. The mask material may be a layer of amorphous carbon, doped amorphous carbon, spin on carbon (SOC), Si, SiN, Al, AlO, Ti, TiO or other metal and metal oxide masks, or other nitrides such as TiN, with or without dopants.

[0092] The disclosed carbon oxy halide etching gases (i.e., the family of an acyl halide stated above) is supplied in a gas cylinder at a variety of fill quantities, pressure and specifications. Preferably the material has a low moisture content of < 40 ppm, preferably <10 ppm. The disclosed carbon oxy halide etching gases may be purified to remove critical impurities such as chlorine-species or organochlorides, other fluorocarbons, hydrofluorocarbons, chlorofluorocarbons (CFC’s), impurities from the air (N2, O2, CO2), moisture (H2O), HF other hydrocarbons (CH4, etc.),using distillation, adsorption using molecular sieves, or other commonly known methods in the art. Some impurities may form azeotropes thus other purification methods may need to be employed using chemical means to separate them.

[0093] After etching, the substrate may be warmed up to a temperature greater than the temperature of the etching process, for example > 0°C such that byproducts of the reaction are evaporated away into a vacuum exiting the reaction chamber.

[0094] Not only does the disclosed carbon oxy halide etching gases have a much lowerGWP than standard fluorochemical etching gases, but it also produces lower CO2equivalent emissions from the etching process. The disclosed cryogenic plasma etch method uses the disclosed carbon oxy halides as etching gas to produce apertures or features, such as channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, contact etch, slit etch, self-aligned contact, self-aligned vias, super vias, etc., in silicon-containing films. The resulting apertures may have an aspect ratio ranging from approximately 5:1 to approximately 500:1, preferably from approximately 20:1 to approximately 400:1. The resulting apertures may have a diameter ranging from approximately 0.1 nm to approximately 500 nm; preferably, ranging from approximately 0.1 nm to approximately 500 nm; more preferably being less than 100 nm. The resulting apertures may have an aspect ratio above 1:1, preferably above 5:1, more preferably above 10:1, even more preferably above 20:1. The resulting apertures may have an aspect ratio ranging from 1:1 to 5:1. For example, one of ordinary skill in the art will recognize that a channel hole etch produces apertures in the silicon-containing films having an aspect ratio greater than 50:1.

[0095] The disclosed cryogenic plasma etching method is not limited to the above stated experimental conditions in any way, types of plasma etching tool (e.g., capacity coupled or inductively coupled plasma), process conditions (e.g., pressure, power, temperature, duration of process), process gas mixture, combination and proportion of gases in the process gas mixture, gas flow, workpiece and plasma etching chamber itself may be altered for each process and during the process.

[0096] In summary, the disclosed cryogenic plasma etching methods provide using the carbon oxy halide etching gases (i.e., the family of an acyl halide stated above) to enhance dehydration of the water in the etched holes or features and provide some carbons to the etch process to enhance the selectivity to the mask material, typically carbon or doped carbon such as boron doped carbon. Additionally, the disclosed carbon oxy halides have lower GWP compared to commonly used ones (e.g., CF4, C4F8, CH2F2), enabling more eco- friendly processes. Examples

[0097] A more detailed description of the disclosed methods through examples is provided as follows. However, the disclosed methods is not limited to presented examples in any way and process conditions, process gas mixture, combination and proportion of gases in the gas mixture, workpiece and plasma etching chamber itself may be altered.

[0098] In the following Examples, the primary plasma etching source may be a CCPplasma but may also include other sources such as ICP, microwave, ECR, etc. The plasma may be used in a continuous source or as a pulsed plasma of a certain frequency and duty cycle. The temperature of substrate surface may be cooled down or elevated by a cryogenic chiller, or by liquid N2supply and heating stage. Additional fluorocarbon gases may be added to slightly tune the etching performance. Additional inert gases may be added such as Kr, Xe, Ne, Ne as well as hydrogen source gases such as H2, and hydrocarbons. The mask material may include TiN or other metal nitride materials, SiN, Si, carbon materials, or the like. Example

[0099] Process conditions for measuring etch rates described below in Table 2 in which four common materials including SiO2, SiN, poly silicon (p-Si), and boron doped amorphous carbon (a-C(B)) used in semiconductor processing were placed on a Si carrier wafer and processed in a 200mm CCP plasma etch chamber. The etching gas flow rate in Table 2 represents CF4and C3O2F4gas, respectively. The boron composition in the amorphous carbon film was 35%. The etching data for CF4is shown in FIG.1 and the etching data for C3O2F4is shown in FIG.2. Table 2

[0100] As shown in FIG.1, CF4has a low carbon that may be used for cryogenic etchsince it may not clog the feature. The addition of O2is not advised since O2heavily deteriorates the thickness of mask during etch.

[0101] At O2= 0 sccm and 5 sccm, the etching rate of SiO2and SiN using C3O2F4are always higher than that of CF4, as shown in FIG.2. The preservation of carbon masks is comparable between two processes. Hence, the selectivity to mask is more favorable to C3O2F4chemistry than CF4.

[0102] If O2flowrate is slightly increased to 5 sccm, the etching rate of SiO2and SiN via C3O2F4are still higher than CF4. At the same time, CF4may not preserve the mask with 5 sccm O2. This result suggests that C3O2F4provides a wider O2process window, which is beneficial for process control. Example 2. COF2(carbonyl fluoride, CAS No.:vs C2O2F2(CAS No.: 359-40-0, )

[0103] Etching rates of COF2(FIG.3) and C2O2F2(FIG.4) were measured as a function of O2flow rate using the same process conditions as described in Example 1 and Table 2. As can be seen from FIG.4 and FIG.2 at 0 sccm O2flow rate C2O2F2and C3O2F4have very low etching rate of boron doped a-C, a common mask material, and lower than COF2, shown in FIG.3. The data at 0sccm O2flow rate is important, as it is preferential to add no O2in the process to maximize the selectivity to the mask. Example 3. SiO2etching rate and selectivity of SiO2vs boron doped a-C mask

[0104] The selectivity of SiO2vs boron doped a-C mask using etching gases CF4SO2, COF2, C2O2F2and C3O2F4, is compared in FIG.5. FIG.6 is a column graph of a comparison of SiO2etch rates with etching gases, CF4SO2, COF2, C2O2F2and C3O2F4, respectively.

[0105] Despite having similar COF structure, COF2does not provide similar selectivity of SiO2to a-C compared to its counterpart C2O2F2and C3O2F4. Therefore, we believe it is not obvious that just because a molecule has a COF, i.e., -(C=O)-F structure may not mean it may behave the same way in a plasma etching process. In a cryogenic etch process the fluorocarbon molecule acts to enhance the selectivity of the dielectric etch to the mask. Herein, the disclosed molecules that may both enhance the selectivity to the mask and act as a dehydration agent to remove water from the channel hole. As can be seen from FIG. 5, the selectivity of etching SiO2vs carbon mask is C3O2F4> C2O2F2> COF2~ CF4SO2. Therefore, surprisingly we expect that a molecule like C2O2F2,CF3COF and C3O2F4mayprovide both an enhancement to the etching selectivity of SiO2vs the mask material while also providing dehydration of the water as compared to COF2even though each molecule has the same -(C=O)-F functional group.

[0106] The selectivity of SiO2to a-C of C2O2F2and C3O2F4increases significantly as compared to that of COF2and CF4SO2, as shown in FIG.5 and FIG.6. This data suggests that fluorine species in C2O2F2and C3O2F4are much more abundant than COF2. This may favor the etching of oxide at lower temperature. Example 4. Etching rates of blanket films of CF4and CF3COF with plasma source power of 1125 W

[0107] The SiO2, a-C, SiN and p-Si etching rates of blanket films of CF4and CF3COF were compared. In a CCP plasma etch tool the source plasma power was 1125 W, bias power 2250 W, pressure was 22 mTorr, flow rate of argon 70sccm and wafer temperature was 20°C. The results for etching with CF4and CF3COF are shown in Table 3 below. The etch rates are in nm / min. Table 3

[0108] As can be seen from the results the etching rates of SiO2at 40 sccm etch gas and 10 sccm O2shows CF3COF > CF4by ~20% increase with similar etching rates to mask materials a-C and p-Si. This performance is very important and may benefit for high aspect ratio etching. In addition, it is seen that CF3COF offers increased SiN etching rate at 0 sccm O2process condition. This may be a benefit for 3DNAND etching. Example 5. Etching rates of blanket films of CF4and CF3COF with plasma source power of 500 W without O2

[0109] The same process conditions as Example 4 were repeated except with a source power of 500W with the flow rate of the etch gas of 50 sccm and no O2wasadded. The results for etching with CF4and CF3COF are shown in Table 4. The etching rates are in nm / min. Table 4

[0110] As can be seen from the results and similar to Example 4, CF3COF offers a boost to the etching rate of SiN compared to CF4at 500 W source power of 34% at similar SiO2etching rate. This mayn be a benefit for 3DNAND high aspect ratio etching. In addition, for CF3COF it is seen that from Example 4 and Example 5 the increase in source power results in an increase of SiO2and SiN etching rates more than the increase for a-C and p-Si. As well the increase in the source power increased the etching rate of SiO2and SiN for both CF4and CF3COF while the increase in a-C mask was less thereby giving a selectivity benefit for CF3COF. The increase in etching rates of SiO2and SiN under certain process conditions along with the dehydration effect of CF3COF may be a benefit for cryogenic etching applications even though both molecules have the same numbers of F atoms. Overall CF3COF offers unexpected process benefits as compared to CF4. Example 6. QMS of CF3COF and CF4

[0111] The QMS of CF3COF and CF4was measured at an electron volt of 26 eV. The percentage for each species (m / z) is shown in Table 5 for each molecule. Table 5

[0112] As can be seen CF3COF and CF4makes very different breakdown of different species in the QMS indicating they will make different species in the plasma etch process and have different etching properties. The CF3COF had a CF3 / Ar peak ratio was 0.15 and CF4was 0.04. Therefore, surprisingly CF3COF makes ~3.5x more CF3species than CF4. CF3is a very important etching species. Example 7. GWP emissions of CF3COF and CF4.

[0113] The CO2eq relative GWP emissions of a plasma etching process were measured for CF3COF and CF4. In a CCP plasma etch tool the source plasma power was 1125 W, bias power 2250 W, pressure was 22 mtorr, flow rate of argon 70 sccm and wafer temperature was 20°C. The flow rate of the etching gas was 50 sccm and the flow rate of Argon was 70 sccm. The emissions were measured using FTIR post etch tool vacuum pump and pre-abatement. The relative normalized CO2eq for CF3COF was 65% less than CF4indicating CF3COF produces significantly less CO2eq emissions and is a much more environmentally etching gas. Surprisingly CF3COF makes 86% less CF4in the emissions stream as compared to CF4even though the QMS of CF3COF shows much higher CF3species. Therefore CF3COF is more abatement friendly due to the poor abatement destruction efficiency of CF4in most abatement systems (plasma or thermal burners).

[0114] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and / or the attached drawings.

[0115] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.

Claims

What is claimed is:

1. A cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below 25°C; introducing an etching gas having general formulae Y3-CO-X, Y-(C=O)-X, R1-CO-X, R2-CO-R3, R2-(C=O)-O-(C=O)-R3, and COF-CxFyHz-COF wherein X and Y each is a halogen selected from F, Cl, Br, I; R1is a fluorocarbon, hydrofluorocarbon, or hydrocarbon; R2and R3each is a fluorocarbon, hydrofluorocarbon, bromocarbon, hydrobromocarbon, chlorocarbon, hydrochlorocarbonor hydrocarbon, iodocarbon, hydroiodocarbon, into the reaction chamber; and x, y and z are integers; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture.

2. The method of claim 1, further comprising adding one or more hydrofluorocarbon or fluorocarbon etching gases to the etching gas, wherein the one or more hydrofluorocarbon or fluorocarbon etching gases are selected from C4F6, C4F8, C4H2F6, CHF3, CH2F2, CH3F, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F10, C5F8, C6F6, C1-C6CxFyHzmolecule (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF5,C3H2F4, or combination thereof.

3. The method of claim 1, further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7,HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, POCl3, POCl5, PF5, PCl5, POF3, POCl3, POF3, PH3, P(R)3wherein R is an alkyl or fluorinated alkyl group, SOF2, SOCl2, SOClF SO2F2, SO2FCl, SO2Cl2, or CF4SO2.

4. The method of claim 1, further comprising adding a co-reactant to the etching gas, wherein the co-reactant is selected from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, CxOyFz(x, y and z are integers), CxOyFzHm(x, y, z and m are integers) selected from alcohol, ketone, acidic, ester type molecules.

5. The method of claim 1, further comprising adding a co-reactant O2to the etching gas.

6. The method of claim 1, further comprising adding a co-reactant to the etching gas, wherein the co-reactant is an inert gas to the etching gas selected from Ar, Kr, Xe, Ne, N2, He or combination thereof.

7. The method of claim 1, wherein the etching gas is CF3OF.

8. The method of claim 1, wherein the etching gas is C3O2F4.

9. The method of claim 1, wherein the etching gas is CF3COF.

10. The method of claim 1, wherein the etching gas is COF2.

11. The method of claim 1, wherein the etching gas is C2O2F2.

12. The method of claim 1, wherein the temperature of the substrate is below approximately 0°C.

13. The method of claim 1, wherein the temperature of the substrate ranges from approximately - 196°C to approximately 300°C.

14. The method of claim 1, wherein the temperature of the substrate ranges from approximately - 196°C to approximately 60°C.

15. The method of claim 1, wherein the temperature of the substrate ranges from approximately - 196°C to approximately 0°C.

16. The method of claim 1, wherein an aspect ratio of the aperture ranges from 1:1 to5:

1.

17. The method of claim 1, wherein an aspect ratio of the aperture is above 5:

1.

18. The method of claim 1, wherein an aspect ratio of the aperture is above 20:

1.

19. The method of claim 1, wherein an aspect ratio of the aperture ranges from approximately 5:1 to approximately 500:

1.

20. The method of claim 1, wherein an aperture has a diameter ranging from approximately 0.1 nm to approximately 500 nm.

21. The method of claim 1, wherein the aperture has a diameter less than 100 nm.

22. The method of claim 1, wherein after the aperture is formed, the temperature of the substrate is increased to greater than 0°C.

23. A cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below approximately 25°C; introducing an etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2into the reaction chamber; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture.

24. A cryogenic etching method for forming an aperture by selectively etching one or more silicon-containing films from a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a reaction chamber; cooling the substrate to a temperature below approximately 25°C;introducing an etching gas CF3OF, CF3COF, C3O2F4, C2O2F2, or COF2into the reaction chamber; adding a co-reactant O2into the reaction chamber converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the aperture.

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