Cryogenic plasma etching using c2h2f2

Abstract

A low-temperature etching method for selectively etching one or more silicon-containing films to form a hole by using a patterned masking layer deposited on top of one or more silicon-containing films in a substrate, the method comprising: mounting the substrate in a reaction chamber, cooling the substrate to a temperature below 25°C, introducing an etching gas C2H2F2 into the reaction chamber, converting the etching gas into a plasma; and allowing an etching reaction to occur between the plasma and the one or more silicon-containing films, such that the one or more silicon-containing films are selectively etched relative to the patterned masking layer to form the hole.

Description

Technical Field

[0001] This invention relates to a method for manufacturing semiconductor wafers (such as 3D NAND flash memory and DRAM wafers) by using hydrofluorocarbon etching gas C2H2F2 to perform low-temperature plasma etching on silicon-containing materials. Prior Technology

[0002] High aspect ratio plasma etching is extremely challenging. An emerging technique utilizes very low substrate temperatures, typically around -50°C or lower, below the traditional etching chamber limitations of -20°C. In this case, significantly less polymerization gas is required, thus accelerating etching and allowing for good profile control, as the etching byproducts themselves act as sidewall protectors. Therefore, novel etchants are needed to help address these technical challenges under such low-temperature etching conditions.

[0003] Low-temperature etching has been attempted.

[0004] US 2023 / 0127467 discloses a method for low-temperature etching, which uses HF gas, CxFy gas, or CsHtFu gas, and an oxygen-containing gas to etch SiN, and a second plasma step using HF gas, CvFw gas, and an oxygen-containing gas to etch SiO2. The substrate is set to 0°C or lower, wherein the HF generating gas or HF substance includes at least one of hydrogen fluoride gas, free radicals, and ions. For example, at least one gas selected from the group consisting of CH2F2 gas, C3H2F4 gas, C3H2F6 gas, C3H3F5 gas, C4H2F6 gas, C4H5F5 gas, C4H5F5 gas, C4H2F8 gas, C5H2F6 gas, C5H2F10 gas, and C5H3F7 gas, which is capable of generating HF substances. Temperatures were revealed to be below 0°C, and as low as -70°C or lower. CHF3, C4H2F6, and CH2F2 were listed as CsHtFu gases. Furthermore, the addition of phosphorus-containing molecules such as PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, and PBr5 to the etching process was disclosed. Phosphorus-containing gases can promote the adsorption of HF substances from the plasma onto the substrate surface.

[0005] Kihara et al. (Beyond 10 μm Depth Ultra-High speed Etch Process with 84% Lower Carbon Footprint for Memory Channel Hole of 3D NAND Flash over 400 layers, 2023 Symposium on VLSI Technology and Circuits Digest of Technical Papers) disclosed an etching process utilizing HF gas generated from CF4 / H2 plasma, where the surface reaction rate between HF and SiO2 rapidly increases at low temperatures, resulting in a high SiO2 etching rate. HF materials exhibit great potential for high aspect ratio etching of dielectric materials.

[0006] Dussart et al. (Dussart et al., "Cryogenic Etching of Silicon Compounds Using a CHF 3Based Plasma", J. Applied Physics 133, 113306 (2023)) investigated the cryogenic etching of a-Si, SiO 2, and Si 3N 4 materials using a CHF 3 / Ar inductively coupled plasma in a temperature range of -140°C to +20°C. Samples of the three different materials were placed together on the same silicon carrier wafer. Depending on the experimental conditions, etched or deposited states were obtained on the samples. A processing window between -120°C and -80°C was found where the Si 3N 4 surface was etched, while CF x deposition was obtained on the a-Si and SiO 2 surfaces, resulting in infinite etch selectivity for Si 3N 4 for the other materials. At sufficiently high self-bias voltages (-120 V) and very low temperatures (< -130°C), Si3N4 etching decreases to very low values, while a-Si and SiO2 are still being etched, which causes a reversal of selectivity between Si3N4 and the other two materials. EDX analysis of the Si3N4 / a-Si / SiO2 stack after the same etching process at 20°C and -100°C confirmed the presence of carbon and fluorine on a-Si at low temperatures, showing the effect of low temperature on the switching of this material from etched to deposited states.

[0007] US 9460935 discloses a method for manufacturing a semiconductor device, in which C₂H₂F₂ is used for high aspect ratio etching. However, the disclosed temperature range is from 25°C to about 600°C, and in some embodiments, the temperature is from about 25°C to about 200°C.

[0008] CN 111154490 discloses a method for etching a high aspect ratio container (HARC), and the etching gases include C₂F₆, C₂HF₅, C₂H₂F₄, C₂H₃F₃, C₂H₄F₂, C₂H₅F, C₂F₄, C₂HF₃, C₂H₂F₂, and C₂H₃F. The temperature is not disclosed.

[0009] WO 2018182968 discloses methods and apparatus for etching features in a substrate, wherein the substrate can be etched using low temperatures and specific types of reactants. In various examples, a mixture of reactants can be used to etch the substrate at a temperature of about -20°C or lower, the mixture of reactants comprising at least one of the following: an iodine-containing fluorocarbon, an iodine-containing fluoride, a bromine-containing fluorocarbon, a sulfur-containing reactant, or another selected group of reactants.

[0010] JP 2001044173 discloses a plasma etching method using CnHnFn (where n >= 2) such as C2H2F2 gas and CxHyFz gas with a low C / F ratio (x <= 3, x + y + z >= 8) such as C2HF5 gas as etching gases. This allows for selective control using the C2H2F2 gas, while controlling for under-etching using the CxHyFz gas. The temperature is maintained, for example, within a range of -50°C to 100°C by appropriately adjusting the cooling refrigerant using a temperature controller.

[0011] US 5814563 discloses a method for etching dielectrics, but can also be used to etch other films such as TiN, wherein C₂H₂F₂, an etchant such as CF₄, a nitrogen gas such as NH₃, an oxidant such as CO, and Ar for sputtering are included. The NH₃ gas can generate substances containing NH₃, such as gases containing NH₂⁻, NH₃, or NH₄⁺ ions or molecules, including, for example, NH₃, NH₄OH, CH₃NH₂, C₂H₅NH₂, C₃H₈NH₂, and mixtures thereof. The substrate temperature is maintained within approximately ±50°C.

[0012] KR 19980085478 discloses a method for forming contact holes in semiconductor devices, wherein a photoresist is used as a mask to form contact holes, and C4F8 and C3F8 gases are used for highly selective etching. A method down to -40°C and the use of C2H2F2 to etch the photoresist mask material (typically using a spin-coating process) are disclosed to form contact holes by plasma etching.

[0013] US 9514959 discloses etching gases, such as C4H2F6, used in plasma etching processes for etching high aspect ratio silicon materials with substrate temperatures ranging from -196°C to 500°C.

[0014] Shin et al. (“SiO 2 Etching Characteristics of Perfluoro-2-butene (lC 4F 8) and Hexafluoropropene (lC 3F 6)”, Environmentally Benign Etching Technology Laboratory Association of Super-advanced Electronics Technologies, Morinosato Wakamiya 3-1, Atsugi, Japan, 243-0198) revealed a comparison of the etching characteristics of two isomers of C 4F 8, in which the etching rate of SiO 2 and the selectivity relative to materials such as PR, SiN, and Si differed. This indicates that the etching characteristics are related to the structure of the etching gas, and not just the C:F ratio.

[0015] Ohiwa et al. (“SiO₂ Tapered Etching Employing Magnetron Discharge of Fluorocarbon Gas”, Jpn. J. Appl. Phys., Vol. 31 (1992), pp. 405-410) disclosed an etching process using CHF₃ at temperatures as low as -70°C, in which the SiO₂ etching rate increased sharply at temperatures below -20°C, although a higher deposition rate was observed at lower temperatures. They also revealed that as the temperature decreased, a large amount of volatile fluorinated hydrocarbons adsorbed onto the film, thereby enhancing polymer formation. These substances evaporated as the temperature increased.

[0016] Conventional fluorocarbons and hydrofluorocarbons may have high global warming potential (GWP), and when exposed to high-power plasma, they will decompose and potentially form substances with high GWP. These high-GWP substances are then emitted. [surface] [1] This table includes the GWP values ​​of etching gases commonly used in the semiconductor industry, as well as other molecules that may be plasma byproducts and other chemicals. As can be seen from the table, CF4 (6630) and CHF3 (12400) have extremely high GWPs. Therefore, these molecules are harmful to global warming. Other commonly used fluorocarbons or hydrofluorocarbons may include CH2F2, CH3F, C4F8, C4F6, C2F6, C3F8, etc. In addition, byproducts from etching may include NO2, CO, CO2, COF4, SiF4, etc. [[] [surface] [1] gas GWP 100 CHF 3 12400 C 2F 6 11100 C 4F 8 9540 CF 4 6630 CH 2F 2 677 NO 2 265 C 4H 2F 6 4 CO 2.1 CO2 1 COF 2 < 1 CF 3I < 1 C 4F 6 < 1 C 2H 2F 2 < 1

[0017] In some cases, such high-GWP materials can pass through the scrubbing apparatus, but these high-GWP materials have varying efficiencies. Therefore, both low-GWP etching gases that operate within the low-temperature etching processing window and gases that decompose in the plasma and generate low-GWP byproducts are required. Summary of the Invention

[0018] A low-temperature etching method is disclosed for selectively etching one or more silicon-containing films to form holes by using a patterned mask layer deposited on top of one or more silicon-containing films in a substrate, the method comprising: The substrate is mounted in the reaction chamber; Cool the substrate to a temperature below approximately 25°C; The etching gas C₂H₂F₂ is introduced into the reaction chamber; The etching gas is converted into plasma; and An etching reaction is permitted between the plasma and the one or more silicon-containing films, such that the one or more silicon-containing films are selectively etched relative to the patterned mask layer to form the aperture. The disclosed etching method may include one or more of the following features: • Further includes adding one or more hydrofluorocarbon or fluorocarbon etching gases selected from the following: C₂H₂F₂, C₄F₆, C₄F₈, C₄H₂F₆, CHF₃, CH₂F₂, CH₃F, CF₄, C₂F₆, C₃F₈, SF₆, NF₃, C₂F₄, C₃F₆, C₄F₁₀, C₅F₈, C₆F₆, C₆F₆, C₁-C₆C₆C₆xF₂yH₂z molecules (x, y, and z are integers), C₂H₅F, C₃H₇F, C₃H₂F₆, C₂HF₅, C₃H₂F₄, or combinations thereof; • Further includes adding an additive to C₂H₂F₂, wherein the additive is selected from H₂, SF₆, NF₃, NH₃, Cl₂, BCl₃, BF₃, Br₂, F₂, FNO, FNO₃, HBr, HCl, HI, IF₅, IF₇, B₂H₆, HF, and a P-containing gas selected from PF₃, PCl₃, PBr₃, PH₃, POCl₃, PF₅, POF₃, PH₃, or P(R)₃ (where R is an alkyl group or a fluorinated alkyl group selected from CF₃); • Further includes adding a co-reactant having the additive, wherein the co-reactant is selected from O 2, CO, CO 2, NO, NO 2, N 2O, SO 2, H 2S, COS, O 3, C xO yF z (x, y, and z are integers) selected from COF 2, C 2O ​​2F 2, C xO yF zH m (x, y, z, and m are integers) selected from alcohols, ketones, acids, ester molecules selected from CF 3OH, CF 3OCF 3, (CF 3) 2C=O, CF 3COOH, or combinations thereof; • Further includes adding a co-reactant having the additive, wherein the co-reactant is selected from O 2, CO, CO 2, NO, NO 2, N 2O, SO 2, H 2S, COS, O 3, C xO yF z (x, y, and z are integers), C xO yF zH m (x, y, z, and m are integers), ester molecules, or combinations thereof; • CxOyFz (x, y, and z are integers) are selected from COF2 and C2O2F2; • C xO yF zH m (x, y, z, and m are integers) are selected from alcohols, ketones, and acids; • Ester molecules are selected from CF3OH, CF3OCF3, (CF3)2C=O, and CF3COOH; • Further includes adding an inert gas to C₂H₂F₂, wherein the inert gas is selected from Ar, Kr, Xe, Ne, N₂, He, or combinations thereof; • An isomer of the etching gas C₂H₂F₂ series C₂H₂F₂, with CAS number: 75-38-7; • An isomer of the etching gas C₂H₂F₂ series C₂H₂F₂, with CAS number: 1630-78-0; • An isomer of the etching gas C₂H₂F₂ series, with CAS number: 1630-77-9; • An isomer of the etching gas C₂H₂F₂ series C₂H₂F₂, with CAS number: 1691-13-0; This temperature is below approximately -50°C; • The temperature range is approximately -196°C to approximately 300°C; • The temperature range is from approximately -196°C to approximately 60°C; • The temperature range is from approximately -196°C to approximately 25°C; • The temperature range is from approximately -196°C to approximately -50°C; • The one or more silicon-containing films comprise Si aO bH cC dN e layers, wherein a > 0, b, c, d, and e ≥ 0, and are selected from silicon oxide, silicon nitride, crystalline Si, polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, or alternating layers of silicon oxide and silicon nitride (ONON) films or alternating layers of silicon oxide and polycrystalline silicon (OPOP) films; The aspect ratio of this hole ranges from 1:1 to 5:1; • The aspect ratio of this hole is greater than 1:1; • The aspect ratio of this hole is higher than 5:1; • The aspect ratio of this hole is greater than 10:1; • The aspect ratio of this hole is greater than 20:1; The aspect ratio of this hole ranges from approximately 5:1 to approximately 500:1; • The aspect ratio of this high aspect ratio hole ranges from approximately 20:1 to approximately 400:1; • The aspect ratio of this high aspect ratio hole is greater than 50:1; The aperture has a diameter ranging from approximately 0.1 nm to approximately 500 nm. The aperture has a diameter ranging from approximately 5 nm to approximately 500 nm. • The pore has a diameter of less than 100 nm; and • After the hole is formed, the temperature of the substrate is raised to greater than -50°C. [] [Symbols and Nomenclature]

[0019] The following detailed description and scope of the patent application utilize many abbreviations, symbols, and terms commonly known in the art, and include:

[0020] As used in this article, the indefinite article "a / an" means one or more.

[0021] As used herein, “about” or “around / approximately” in the text or the claims means ±10% of the stated value.

[0022] As used herein, "room temperature" in the text or the scope of the patent application means approximately 20°C to approximately 25°C.

[0023] The term "substrate" refers to one or more materials on which a process is performed. A substrate can refer to a wafer having one or more materials on which a process is performed. A substrate can be any suitable wafer used in the manufacture of semiconductor, photovoltaic, flat panel, or LCD-TFT devices. A substrate can also have one or more different material layers deposited thereon from previous manufacturing steps. For example, a wafer can 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, a substrate can be planar or patterned. A substrate can be an organically patterned carbon iodide film. The substrate may include oxide layers of dielectric materials (e.g., ZrO₂-based materials, HfO₂-based materials, TiO₂-based materials, rare earth oxide-based materials, ternary oxide-based materials, etc.) used as electrodes in field-effect transistors (FETs) such as FinFET, MOFSET, GAAFET (Gate All-Around FET), strip FET, nanosheet, fork FET, complementary FET (CFET), MEMS, 3D NAND, MIM, DRAM, or FeRam device applications, or nitride-based films (e.g., TaN, TiN, NbN). The substrate may include alternating layers of oxides (e.g., SiO) and nitrides (e.g., SiN). Those skilled in the art will recognize that the terms "film" or "layer" as used herein refer to a material of a certain thickness laid or spread on a surface, and that surface may be trenches or lines. Throughout this specification and the claims, the wafer and any associated layers thereon are referred to as the substrate. The substrate can be any solid having functional groups on its surface that tend to react with reactive heads that assemble self-assembled monolayers (SAMs), and can include, but is not limited to, 3D objects or powders.

[0024] The term "wafer" or "patterned wafer" refers to a wafer having a stack of films on a substrate, wherein at least the topmost film of the stack of films has morphological features or patterns that have been generated in a step prior to etching, and a patterned topmost film is formed for patterned etching.

[0025] As used herein, the term "processing" includes patterning, exposure, development, etching, deposition, cleaning, and / or removal of byproducts, as required when forming the described structure.

[0026] The term "deposit" or "deposition" refers to a series of processes in which material at the atomic or molecular level is deposited as a thin layer from a gaseous (vapor) state onto a wafer surface or substrate, transitioning from a gaseous to a solid state. Chemical reactions are involved in the process, either after the generation of reactive gases by plasma or after the reactive gases are initiated by heating. Plasma can be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron cyclotron resonance (ECR) plasma, or microwave plasma, but is not limited to these. Suitable commercially available plasma etching chambers include, but are not limited to, the Lam Research Dual CCP reactive ion etching product family sold under the trademarks Flex™ or Tokyo Electron Tactras™ or Episode TMUL. Non-plasma exposure steps can be performed in a different chamber than plasma exposure steps. []

[0027] The term "aspect ratio" refers to the ratio of the height of a groove (or hole) to the width of the groove (or the diameter of the hole).

[0028] The term "high aspect ratio (HAR)" refers to an aspect ratio ranging from about 1:1 to about 500:1, preferably from about 20:1 to about 400:1.

[0029] The term "high aspect ratio etching" refers to the formation of a hole pattern in a target film by means of plasma etching, where the aspect ratio of the hole structure formed exceeds 5.

[0030] It should be noted that the terms "film," "layer," and "material" are used interchangeably herein. It should be understood that a film can correspond to or be associated with a layer or material, and a layer can refer to both a film and a material. Furthermore, those skilled in the art will recognize that, as used herein, the terms "film," "layer," or "material" refer to a material of a certain thickness laid or spread on a surface, and that surface can range from as large as an entire wafer to as small as a trench or line.

[0031] It should be noted that in this document, the terms “aperture,” “via,” “hole,” “trench,” and “structure” are used interchangeably to refer to openings formed in a semiconductor structure.

[0032] As used herein, the abbreviation "NAND" refers to a "Negative AND or Not AND" gate; the abbreviation "2D" refers to a 2D gate structure on a planar substrate; and the abbreviation "3D" refers to a 3D or vertical gate structure, wherein the gate structures are stacked in the vertical direction.

[0033] It should be noted that in this document, the terms "etching gas" and "etching agent" are used interchangeably when the etching gas is in a gaseous state at room temperature and ambient pressure. It should be understood that etching gas may correspond to or be associated with an etching agent, and the etching agent may refer to the etching gas.

[0034] The terms "dope" or "doping" are used interchangeably in processes that incorporate one or more elements into a film by means of various methods that can chemically or physically bond them together, as well as in processes that intentionally incorporate atoms of different elements into a film composition. One or more elements can be interstitially or alternatively doped within the film.

[0035] This article uses the standard abbreviations of the elements in the periodic table. It should be understood that elements may be referred to by these abbreviations (e.g., Si refers to silicon, N to nitrogen, O to oxygen, C to carbon, H to hydrogen, F to fluorine, etc.).

[0036] A unique CAS registry number (i.e., "CAS") assigned by the Chemical Abstracts Service is provided to identify the specific molecule disclosed.

[0037] As used herein, the term "hydrofluorocarbon" refers to a saturated or unsaturated functional group containing only carbon, fluorine, and hydrogen atoms.

[0038] As used herein, the term "fluorocarbon" refers to a saturated or unsaturated functional group containing only fluorine and hydrogen atoms.

[0039] As used in this article, the term "GWP" refers to global warming potential, typically measured on a 100-year timescale and compared to CO2.

[0040] As used herein, “CO 2 emissions” or “CO 2 equivalent emissions” refers to a comparison between the GWP of C 2H 2F 2 and gases such as CH 2F 2 (a commonly used hydrofluorocarbon etching gas) and emissions from plasma etching processes.

[0041] In this document, a range may be expressed as from about one specific value and / or to about another specific value. When such a range is expressed, it should be understood that another implementation is from that one specific value and / or to that other specific value, together with all combinations within said range. Any and all ranges listed herein include their endpoints (i.e., x = 1 to 4, or x in the range from 1 to 4, including x = 1, x = 4, and x = any number in between), regardless of whether the term "inclusive" is used.

[0042] In this document, references to "one embodiment" or "implementation" mean that a particular feature, structure, or characteristic described with respect to that embodiment may be included in at least one embodiment of the invention. The phrase "in one embodiment" appearing in different places in the specification does not necessarily refer to the same embodiment in all instances, and individual or alternative embodiments are not necessarily mutually exclusive with other embodiments. The same applies to the term "implementation."

[0043] As used herein, the term "exemplary" is used to mean serving as an instance, example, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as superior to or advantageous to other aspects or designs. Rather, the use of the term "exemplary" is intended to present the concept in a concrete manner.

[0044] Furthermore, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise stated or clearly indicated from the context, "X adopts A or B" is intended to mean any natural inclusive arrangement. That is, if X adopts A; X adopts B; or X adopts both A and B, then "X adopts A or B" is satisfied in any of the foregoing cases. Additionally, the article "a / an" as used in this application and the appended claims should generally be interpreted as meaning "one or more," unless otherwise stated or clearly indicated from the context to the singular form.

[0045] The term "include" in the request is an open transitional term, meaning that the subsequently determined elements of the request are a non-exclusive list (i.e., anything else may be additionally included and remain within the scope of "include"). "Include" is defined herein as necessary to encompass the more restrictive transitional terms "substantially consists of" and "consisting of"; therefore, "include" can be replaced by "substantially consists of" or "consisting of" and remain within the clearly defined scope of "include".

[0046] In the scope of the patent application, "providing" is defined as supplying, supplying, making available, or preparing something. The steps can, conversely, be performed by any actor in the absence of explicit language in the claim. Simple Explanation of the Diagram

[0047] To further understand the nature and purpose of this invention, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which similar elements are given the same or similar reference numerals, and wherein: [[] [picture] [1] is a graph comparing the emissions of HF produced by C₂H₂F₂ > CH₂F₂ > C₄H₂F₆, based on Example 1; [[] [picture] [2] is a graph showing the emissions of HF from C2H2F2 and CH2F2 respectively under N2 conditions, based on Example 2; [[] [picture] [3] is a comparison chart of etching data of C2H2F2 and CH2F2 based on Example 3; [[] [picture] [4] is a comparison graph based on the deposition data of C2H2F2 and CH2F2 in Example 4; and [[] [picture] [5] is a graph based on Example 5 showing the emissions of HF and other byproducts generated from C2H2F2, CH2F2 and C4H2F6. Implementation

[0048] A method for low-temperature plasma etching of silicon-containing materials using the hydrofluorocarbon (HFC) etching gas C₂H₂F₂ to fabricate semiconductor wafers (such as 3D NAND flash memory and DRAM wafers) is disclosed. Other applications may include plasma etching processes in logic etching, such as back-to-end (BEOL) processes. Etching such high aspect ratio structures using conventional fluorocarbon and HFC plasma etching methods is very challenging, especially when exploring new technology nodes. The disclosed method using a low-temperature substrate offers opportunities to improve the etching process. The etching profile can be controlled to a highly vertical feature by limiting volatile byproducts, thereby controlling the etching profile at lower temperatures. For example, SiF₄ is volatile above -86°C; CO₂ is volatile above -70°C; and other etching byproducts may not be volatile at these temperatures.

[0049] Furthermore, conventional fluorocarbons and hydrofluorocarbons may have high global warming potential (GWP), and when exposed to high-power plasma, they decompose and may form substances with high GWP as well. These high-GWP substances are emitted. In some cases, these high-GWP substances can pass through scrubbing devices, but they have varying efficiencies. C₂H₂F₂ is particularly attractive due to its very low GWP (< 1), while other conventional fluorocarbon and hydrofluorocarbon etching gases have very high GWPs, such as CH₂F₂, which has a GWP of 677. [surface] As shown in [1].

[0050] Here, C₂H₂F₂ can be used as an HF or F generating gas and / or deposition gas in an etching chamber containing a low-temperature substrate. HF should be formed by the recombination of H and F in a plasma, which should be directly related to the atomic concentration of the input gas entering the chamber. C₂H₂F₂ can act as both an HF source and a polymer source to protect the sidewalls of the etched structure. It is known that adding phosphorus to the etching formulation may increase the etching rate due to a catalytic effect. Therefore, adding gases such as PF₃ or other P-containing gases to C₂H₂F₂ can be used to increase the etching rate. Furthermore, different hydrofluorocarbon and fluorocarbon isomers have different amounts and concentrations (see, for example, US 9514959 showing different mass spectra of two isomers of C₄H₂F₆), making the amount of HF generated by the hydrofluorocarbon etching gas unpredictable.

[0051] C₂H₂F₂ has the following properties: [surface] [2] lists the four main isomers. Here, the preferred C2H2F2 molecular system has the CAS number 75-38-7. [[] [surface] [2] name Mode structure CAS number boiling point 1,1-Difluoroethylene C 2H 2F 2 75-38-7 -83°C (E)-1,2-Difluoroethylene C 2H 2F 2 1630-78-0 -86°C (Z)-1,2-Difluoroethylene C 2H 2F 2 1630-77-9 -36°C 1,2-Difluoroethylene C 2H 2F 2 1691-13-0 -28°C

[0052] C₂H₂F₂ is supplied in cylinders with various fill volumes, pressures, and specifications. Preferably, the C₂H₂F₂ in the cylinder has a low moisture content of < 40 ppm, more preferably < 10 ppm. C₂H₂F₂ can be purified by distillation, adsorption by molecular sieves, or other existing methods to remove critical impurities such as other fluorocarbons, hydrofluorocarbons, chlorofluorocarbons (CFCs), impurities from the air such as N₂, O₂, CO₂, moisture (H₂O), HF, and other hydrocarbons such as CH₄. Some impurities can form azeotropes; therefore, additional purification methods using chemical methods may be necessary to separate them.

[0053] The disclosed low-temperature plasma etching method involves exposing the substrate in a reaction chamber to one of the etching gases C₂H₂F₂ and / or its isomers, preferably C₂H₂F₂ (CAS No.: 75-38-7), during the etching process and / or during the chamber conditioning process.

[0054] The disclosed low-temperature plasma etching method for selectively etching one or more silicon-containing films to form holes by using a patterned mask layer deposited on top of one or more silicon-containing films in a substrate includes: The substrate is mounted in the reaction chamber; Cool the substrate to a temperature below 25°C; The etching gas C₂H₂F₂ is introduced into the reaction chamber; The etching gas is converted into plasma; and An etching reaction is allowed between the plasma and the one or more silicon-containing films, such that the one or more silicon-containing films are selectively etched relative to the patterned mask layer to form the hole.

[0055] The reaction chamber can be any accessory or chamber within the apparatus in which the etching method is performed, such as, but not limited to, reactive ion etching (RIE), CCP with a single or multiple frequency RF sources, inductively coupled plasma (ICP), microwave plasma reactors, or other types of etching systems capable of performing plasma processing (i.e., selectively removing a portion of the dielectric film or generating active material or depositing a film).

[0056] The reaction chamber is equipped with a parallel-plate electrode plasma generator, in which a 60 MHz high-frequency electromagnetic field is applied to the upper electrode and a 2 MHz electromagnetic field is applied to the lower electrode, with the gap between the electrodes maintained between 10 and 35 mm. This combination of electric fields allows power in the range of 0-2000 W to be applied to the upper electrode and power in the range of 1500-7000 W to be applied to the lower electrode. The plasma can be generated with RF power ranging from about 25 W to about 100 kW. The plasma can be generated remotely or within the reaction chamber itself. The RF frequency of the plasma can range from 100 kHz to 1 GHz. The plasma can be pulsed or continuous wave. In some embodiments, the power applied to the chamber can range from 0 to a few kW of bias power and hundreds to thousands of kW of source power.

[0057] The temperature and pressure within the reaction chamber are maintained under conditions suitable for the reaction of the process film with the activated etching gas C₂H₂F₂. For example, depending on the required etching parameters, the pressure in the chamber can be maintained between approximately 0.1 mTorr and approximately 1000 MTorr, preferably between approximately 1 mTorr and approximately 10 MTorr, more preferably between approximately 10 mTorr and approximately 1 MTorr, and even more preferably between approximately 10 mTorr and approximately 100 mTorr. When a process gas mixture is introduced, the pressure in the etching chamber can be maintained between 15 and 30 mTorr during the plasma etching process. Similarly, the substrate temperature in the reaction chamber can be < 25°C, preferably < -50°C. Alternatively, the substrate temperature in the reaction chamber can range from approximately -196°C to approximately 300°C; more preferably, from approximately -196°C to approximately 60°C; even more preferably, from approximately -196°C to approximately 25°C; and still more preferably, from approximately -196°C to approximately -50°C. The substrate can be cooled by various sources, including commercially available coolers or other methods such as liquid N₂. The reaction chamber wall temperature can be < 25°C, preferably < -50°C. Depending on process requirements, the reaction chamber wall temperature can range from approximately -196°C to approximately 25°C.

[0058] The reaction chamber wall temperature can be approximately >20°C, preferably <50°C. Depending on process requirements, the reaction chamber wall temperature can be approximately room temperature or higher but less than 50°C.

[0059] One or more additional hydrofluorocarbon or fluorocarbon etching gases may be added to C₂H₂F₂. These additional 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-C₆C₆C₆xF₂yH₂z molecules (x, y, and z are integers), C₂H₅F, C₃H₇F, C₃H₂F₆, C₂HF₅, C₃H₂F₄, or combinations thereof.

[0060] refer to [surface] [1] Some hydrofluorocarbons or fluorocarbons have high GWPs compared to C₂H₂F₂. To improve etching performance and etching quality, one or more hydrofluorocarbon or fluorocarbon etching gases can be added to C₂H₂F₂ to slightly adjust the etching performance. When a small amount of hydrofluorocarbon or fluorocarbon with a high GWP value is added, the total CO₂ equivalent emissions from the reaction chamber may not have a significant impact on the improved etching performance. For example, if one or more hydrofluorocarbon or fluorocarbon etching gases are added to C₂H₂F₂ at less than 10% relative to C₂H₂F₂, the CO₂ equivalent emissions from the reaction chamber may not change significantly compared to the significantly improved etching performance. In practice, it may be necessary to balance reducing CO₂ equivalent emissions with high etching performance.

[0061] Other gases (such as additives) can be added to C₂H₂F₂. 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, PH₃, POCl₃, PF₅, POF₃, PH₃, and P(R)₃ (where R is an alkyl group or a fluorinated alkyl group such as CF₃).

[0062] Inert gases can also be added to C₂H₂F₂. The inert gases are selected from Ar, Kr, Xe, Ne, N₂, He, or combinations thereof.

[0063] The disclosed low-temperature plasma etching method further includes, prior to activating the plasma, sequentially or simultaneously exposing the substrate to a co-reactant with or without additives, wherein the co-reactant is selected from O 2, CO, CO 2, NO, NO 2, N 2O, SO 2, H 2S, or COS, O 3, C xO yF z (x, y, and z are integers) such as COF 2, C 2O ​​2F 2, C xO yF zH m (x, y, z, and m are integers) such as alcohols, ketones, acids, ester molecules such as CF 3OH, CF 3OCF 3, (CF 3) 2C=O, CF 3COOH, or combinations thereof.

[0064] The substrate contains silicon-containing materials, such as SiO₂, SiN, or Si. An example is alternating layers of SiO and SiN used in 3D NAND applications. Silicon-containing films or materials include Si aO bH cC dN e layers, where a > 0, b, c, d, and e ≥ 0, selected from silicon oxide, silicon nitride, crystalline Si, polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, or stacks of alternating silicon oxide and silicon nitride (ONON) films or alternating silicon oxide and polycrystalline silicon (OPOP) films.

[0065] A mask layer or mask material is attached on top of a silicon-containing film or material. The mask material can be amorphous carbon, doped amorphous carbon, spin-coated carbon (SOC), Si, SiN, Al, AlO, Ti, TiO or other metal and metal oxide masks, or other nitride layers (such as TiN) with or without dopants.

[0066] C₂H₂F₂ is supplied in cylinders in various fill volumes, pressures, and specifications. Preferably, the material has a low moisture content of < 40 ppm, more preferably < 10 ppm. C₂H₂F₂ can be purified by distillation, adsorption using molecular sieves, or other common and known methods in the art to remove key impurities such as chlorinated substances or organochlorides, other fluorocarbons, hydrofluorocarbons, chlorofluorocarbons (CFCs), impurities from the air (N₂, O₂, CO₂), moisture (H₂O), HF, and other hydrocarbons (CH₄, etc.). Some impurities can form azeotropes; therefore, additional purification methods using chemical means may be required to separate them.

[0067] After etching, the substrate can be heated to > -50°C, causing the reaction byproducts to evaporate and leave the reaction chamber into a vacuum.

[0068] C₂H₂F₂ not only has a much lower gas filtration velocity (GWP) than standard fluorinated compound etching gases, but also produces lower CO₂ equivalent emissions from the etching process. The disclosed cryogenic plasma etching method using C₂H₂F₂ as the etching gas generates pores in silicon-containing films, such as channel holes, gate trenches, stepped contacts, capacitor holes, contact holes, contact etching, slot etching, self-aligned contacts, self-aligned vias, and supervias. The resulting pores can have an aspect ratio ranging from about 5:1 to about 500:1, preferably from about 20:1 to about 400:1. The resulting pores can have a diameter ranging from about 0.1 nm to about 500 nm; preferably, from about 0.1 nm to about 500 nm; more preferably, less than 100 nm. The resulting vias can have an aspect ratio greater than 1:1, preferably greater than 5:1, more preferably greater than 10:1, and even more preferably greater than 20:1. The resulting vias can have an aspect ratio ranging from 1:1 to 5:1. For example, those skilled in the art will recognize that channel hole etching in a silicon-containing film produces vias with an aspect ratio greater than 50:1.

[0069] The disclosed low-temperature plasma etching method is not limited in any way to the above experimental conditions. The type of plasma etching tool (e.g., capacitively coupled or inductively coupled plasma), process conditions (e.g., pressure, power, temperature, process duration), process gas mixture, combination and proportion of gases in the process gas mixture, gas flow rate, workpiece, and plasma etching chamber itself can be varied for each process and during the process.

[0070] In summary, the disclosed low-temperature plasma etching method provides improved control over the deposition profile of polymer films using C₂H₂F₂ and enables high etching rates and selectivity for etching silicon oxide and silicon nitride, or combinations thereof, due to the increased generation of HF in the plasma. Furthermore, C₂H₂F₂ exhibits a lower GWP compared to commonly used materials (e.g., CF₄, C₄F₈, CH₂F₂), making more environmentally friendly processes possible. [] [Example] []

[0071] A more detailed description of the disclosed method is provided below with reference to examples. However, the disclosed method is not limited in any way to the examples presented, and the process conditions, process gas mixtures, the combination and proportion of gases in the gas mixtures, the workpiece, and the plasma etching chamber itself can be varied.

[0072] In the following examples, the primary plasma etching source can be CCP plasma, but other sources such as ICP, microwave, ECR, etc., may also be included. The plasma can be used as a continuous source or as a pulsed plasma with a specific frequency and duty cycle. The temperature of the substrate surface can be cooled or raised by a cryogenic cooler, or by a liquid N₂ supply and heating phase. Additional fluorocarbon gases can be added to slightly adjust the etching performance. Additional inert gases such as Kr, Xe, Ne, and hydrogen source gases such as H₂, as well as hydrocarbons, can be added. Mask materials can include TiN or other metal nitride materials, SiN, Si, carbon materials, etc. For comparative purposes, the etching and emission performance of CH₂F₂ and C₄H₂F₆ disclosed in US 2023 / 0127467 is also presented in the following examples. [Example] [1]. Comparison of HF emissions from C₂H₂F₂, CH₂F₂, and C₄H₂F₆ during O₂ plasma processes.

[0073] This paper presents the ability to generate HF material using C₂H₂F₂ as the etching gas. In a 300 mm CCP plasma etching chamber, HF generating gas, C₄F₈ and O₂, and an inert gas (e.g., argon) are used. [surface] The flow rates described in [3] were used to generate HF gases C₂H₂F₂, CH₂F₂, and C₄H₂F₆ at rates where F with similar molar amounts entered the chamber. The amount of HF generated by the plasma from these gases was measured downstream using FTIR, and each condition was quantified. (See also...) [picture] As can be seen from [1], under these process conditions, the amount of HF generated by these gases is C₂H₂F₂ > CH₂F₂ > C₄H₂F₆. C₂H₂F₂ produces 16% more HF than CH₂F₂ and 81% more than C₄H₂F₆. Therefore, compared with CH₂F₂ and C₄H₂F₆, C₂H₂F₂ produces a higher concentration of HF in the plasma, which may be advantageous for low-temperature etching applications. [[] [surface] [3] Etching C 4F 8 / CH 2F 2 C 4F 8 / C 4H 2F 6 C 4F 8 / C 2H 2F 2 RF source [W] 950 / 200 950 / 200 950 / 200 RF bias [W] 6000 / 200 6000 / 200 6000 / 200 DC [%] 70 70 70 Frequency [Hz] 500 500 500 Time [s] 120 120 120 Pressure [millitor] 15 15 15 Wafer T [°C] 20 20 20 Gas flow rate [sccm] C 4F 8 4 4 4 CH 2F 2 50 0 0 C 4H 2F 6 0 16.5 0 C 2H 2F 2 0 0 50 O 2 twenty one 20 32 Ar 150 150 150 [Example] [2]. Comparison of HF emissions from CH₂F₂ and C₂H₂F₂ in N₂ plasma processes

[0074] In a 300 mm CCP plasma etching chamber 2, different gases (CH₂F₂ and C₂H₂F₂) were introduced into the etching chamber in different experiments to compare their performance. The experimental conditions are as follows: [surface] As shown in [4]. Each gas flowed at a rate of 20 sccm, with N2 flowing at 40 sccm and argon at 150 sccm. No oxygen was used in this experiment. [picture] Under the conditions shown in [2], FTIR analysis revealed that the HF produced by C₂H₂F₂ in the exhaust gas of the etching chamber was more than twice that of CH₂F₂, demonstrating the benefit of C₂H₂F₂. One explanation for this result is that N₂ in the plasma can generate a variety of different radical substances that alter the splitting of fluorocarbon gases. According to Yao et al. (Nanomaterials 2022, 12(21), 3798), nitrogen plasma has more metastable and vibrational atoms and molecules with higher energies than oxygen plasma. Therefore, there are more pathways for the dissociation of various substances in nitrogen plasma. Even though each molecule has only two H and two F, C₂H₂F₂ produces significantly more HF substances in the N₂ plasma environment, such as [picture] As shown in [2]. [[] [surface] [4] Etching CH₂F₂ / N₂ C 2H 2F 2 / N 2 RF source [W] 950 / 200 950 / 200 RF bias [W] 6000 / 200 6000 / 200 DC % 70 70 Frequency [Hz] 500 500 Time [s] 180 180 Pressure [millitor] 15 15 Wafer T [°C] 20 20 Gas flow rate [sccm] CH 2F 2 20 0 C 2H 2F 2 0 20 N 2 40 40 O 2 0 0 Ar 150 150 [Example] [3]. Etching rates of CH₂F₂ and C₂H₂F₂ []

[0075] C₂H₂F₂ and CH₂F₂, along with O₂ and argon, flowed into a 300 mm CCP plasma etching chamber. The source power was 950 / 200 W, the bias power was 6000 / 200 W, and the duty cycle was 70%. The experimental conditions were as follows: [surface] As described in [5]. The etching rates of SiO and SiN wafers were measured and... [picture] As shown in [3], C₂H₂F₂ exhibits a higher etching rate for SiO and SiN than CH₂F₂. This demonstrates that C₂H₂F₂ provides an enhanced etching rate for SiO and SiN, even though both molecules provide the same number of F atoms per molecule. A possible reason is that C₂H₂F₂ can more effectively provide fluorine radicals for etching. [[] [surface] [5] Etching CH 2F 2 / O 2 C 2H 2F 2 / O 2 RF source [W] 950 / 200 950 / 200 RF bias [W] 6000 / 200 6000 / 200 DC % 70 70 Frequency [Hz] 500 500 Time [s] 180 180 Pressure [millitor] 15 15 Wafer T [°C] 60 60 Gas flow rate [sccm] CH 2F 2 20 0 C 2H 2F 2 0 20 N 2 0 0 O 2 40 40 Ar 150 150 [Example] [4]. Deposition rates of CH₂F₂ and C₂H₂F₂ []

[0076] The deposition rates of C₂H₂F₂ and CH₂F₂ were measured in a 200 mm CCP plasma etching chamber. Each hydrofluorocarbon compound was introduced into the chamber at a rate of 15 sccm, with an argon flow rate of 250 sccm. The source power was 750 W with no bias power. The chamber pressure was 30 mTorr. The deposition rate of CH₂F₂ was 65 nm / min, and the deposition rate of C₂H₂F₂ was 80 nm / min, which was 23% higher than that of CH₂F₂. The increased polymer formation of C₂H₂F₂ may be beneficial for sidewall protection during the cryogenic etching process. The etching rates of SiO and SiN wafers were measured and... [picture] As shown in [4]. [Example] [5]. HF emissions from CH₂F₂, C₄H₂F₆ and C₂H₂F₂ []

[0077] In a 300 mm CCP plasma etching chamber, the HF emissions of three different etching gases—C₂H₂F₂, CH₂F₂, and C₄H₂F₆—presented in this paper were measured downstream of the etching chamber using FTIR. In three separate experiments, the three different etching gases flowed into the etching chamber at a flow rate of 20 sccm, a source power of 950 W, and a bias power of 6000 W, including plasma pulses and a 70% duty cycle. The chamber pressure was 15 mTorr. O₂ flowed at 40 sccm and argon at 150 sccm. The time was 180 s and the wafer temperature was 60°C. [surface] As shown in [6], under these conditions, the amounts of HF generated by these three gases in the exhaust gas of the etching chamber are very similar. However, when comparing C₂H₂F₂ with C₄H₂F₆, C₄H₂F₆ has three times the amount of F input into the chamber plasma chemicals. The trend of HF generation input into the process / F atom system C₂H₂F₂ > CH₂F₂ >> C₄H₂F₆. Therefore, C₂H₂F₂ generates more HF per unit amount of F in the plasma. [picture] [5] A more detailed composition of emissions from the etching process from each of these three gases is shown. The emission of undecomposed molecules of C₂H₂F₂ was observed to be less than that of C₄H₂F₆, indicating that C₂H₂F₂ decomposes more efficiently in the plasma. Furthermore, the C₂H₂F₂ plasma produces significantly fewer high-GWP byproducts compared to C₄H₂F₆ and CH₂F₂. For example, C₂H₂F₂ produces fewer CF₄ and CH₂F₂ byproducts compared to CH₂F₂. C₂H₂F₂ also produces fewer CHF₃ byproducts compared to C₄H₂F₆. Each of these byproducts is high-GWP (see reference). [surface] [1] Therefore, the C2H2F2 system has a lower gas gluten potential (GWP) than CH2F2 and C4H2F6, and its plasma emission byproducts have a lower GWP compared to CH2F2 and C4H2F6. [[] [surface] [6] Process Gases Amount of HF produced (grams) The amount of HF generated / F input CH 2F 2 0.089 0.045 C 4H 2F 6 0.092 0.015 C 2H 2F 2 0.092 0.046

[0078] It should be understood that those skilled in the art can make many additional changes to the details, materials, steps, and arrangements of parts that have been described and elucidated to explain the nature of the invention as set forth in the appended claims. Therefore, the invention is not intended to be limited to the specific embodiments given above and / or in the accompanying drawings.

[0079] Although embodiments of the invention have been shown and described, those skilled in the art can modify them without departing from the spirit or teachings of the invention. The embodiments described herein are exemplary and not restrictive. Many variations and modifications of the components and methods are possible and are within the scope of the invention. Therefore, the scope of protection is not limited to the embodiments described herein, but is defined only by the following claims, which should include all equivalents of the subject matter of the claims.

[0080] none

[0081] none

Claims

1. A low-temperature etching method for selectively etching one or more silicon-containing films to form holes by using a patterned mask layer deposited on top of one or more silicon-containing films in a substrate, the method comprising: The substrate is installed in the reaction chamber; Cool the substrate to a temperature below approximately 25°C; The etching gas C2H2F2 is introduced into the reaction chamber; the etching gas is converted into plasma; and an etching reaction is allowed between the plasma and the one or more silicon-containing films, such that the one or more silicon-containing films are selectively etched relative to the patterned masking layer to form the hole.

2. The method as described in claim 1, further comprising adding an additive to the etching gas C2H2F2, wherein the additive is selected from H2, SF6, NF3, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF7, HF, B2H6, or a P-containing gas selected from PF3, PCl3, PBr3, PH3, POCl3, PF5, POF3, PH3, or P(R)3, wherein R is an alkyl group or a fluorinated alkyl group selected from CF3.

3. The method as described in claim 1, further comprising adding a co-reactant to the etching gas C2H2F2, wherein the co-reactant is selected from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, CxOyFz (x, y, and z are integers) selected from COF2 and C2O2F2, CxOyFzHm (x, y, z, and m are integers) selected from alcohols, ketones, and acids, ester molecules selected from CF3OH, CF3OCF3, (CF3)2C=O, and CF3COOH, or combinations thereof.

4. The method as described in claim 1, further comprising adding an inert gas to the etching gas C2H2F2, wherein the inert gas is selected from Ar, Kr, Xe, Ne, N2, He or a combination thereof.

5. The method as described in any one of claims 1 to 4, wherein, The etching gas C2H2F2 is an isomer of C2H2F2 and has CAS number: 75-38-7.

6. The method as described in any one of claims 1 to 4, wherein, The etching gas C2H2F2 is an isomer of C2H2F2 and has CAS number: 1630-78-0.

7. The method as described in any one of claims 1 to 4, wherein, The etching gas C2H2F2 is an isomer of C2H2F2 and has CAS number: 1630-77-9.

8. The method as described in any one of claims 1 to 4, wherein, The etching gas C2H2F2 is an isomer of C2H2F2 and has CAS number: 1691-13-0.

9. The method as described in any one of claims 1 to 4, wherein, The temperature of the substrate is below approximately -50°C.

10. The method as described in any one of claims 1 to 4, wherein, The temperature range of the substrate is approximately -196°C to approximately 25°C.

11. The method as described in any one of claims 1 to 4, wherein, The temperature range of the substrate is approximately -196°C to approximately -50°C.

12. The method as described in any one of claims 1 to 4, wherein, The aspect ratio of the hole ranges from 1:1 to 5:

1.

13. The method as described in any one of claims 1 to 4, wherein, The aspect ratio of the hole is higher than 5:

1.

14. The method as described in any one of claims 1 to 4, wherein, The aspect ratio of the hole is greater than 20:

1.

15. The method as described in any one of claims 1 to 4, wherein, The aspect ratio of the hole ranges from approximately 5:1 to approximately 500:

1.

16. The method as described in any one of claims 1 to 4, wherein, The pore has a diameter ranging from approximately 0.1 nm to approximately 500 nm.

17. The method as described in any one of claims 1 to 4, wherein, The pore has a diameter of less than 100 nm.

18. The method as described in any one of claims 1 to 4, wherein, After the hole is formed, the temperature of the substrate is raised to greater than -50°C.

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