Low-temperature plasma etching using C2H2F2

Abstract

A low-temperature etching method for forming openings by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of one or more silicon-containing films includes: placing 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 proceed between the plasma and one or more silicon-containing films, thereby selectively etching one or more silicon-containing films against the patterned mask layer to form openings.

Description

TECHNICAL FIELD

[0001] Reference to Related Application This application claims the benefit of U.S. Patent Application No. 18 / 239,037 filed on August 28, 2023, the entire content of which is incorporated herein by reference.

[0002] The present invention relates to a method for low-temperature plasma etching of a silicon-containing material using the hydrofluorocarbon etching gas C2H2F2 in semiconductor chip manufacturing such as 3D NAND flash and DRAM chip manufacturing. BACKGROUND ART

[0003] High aspect ratio plasma etching is extremely challenging. An emerging technology is the use of very low substrate temperatures, lower than -20°C which is the limit of conventional etching chambers, usually about -50°C or lower. In this case, since significantly less polymerizable gas is required, the etching rate is improved, and good profile control can be achieved because the etching by-products themselves function as sidewall protection. Therefore, there is a need for new etching agents that help solve such technical problems under such low-temperature etching conditions.

[0004] Attempts at low-temperature etching have been progressed.

[0005] US Patent Application Publication No. 2023 / 0127467 discloses HF gas for etching SiN, C x F y gas or C s H t F u low-temperature etching using gas and an oxygen-containing gas, and HF gas for etching SiO2, C v F wA process for a second plasma step using a gas and an oxygen-containing gas is disclosed. Herein, the substrate is set to 0° C. or lower, and the HF generating gas or HF species includes at least one of hydrogen fluoride gas, radicals and ions. For example, CH₂F₂ gas, C₃H₂F₄ gas, C₃H₂F₆ gas, C₃H₃F₅ gas, C₄H₂F₆ gas, C₄H₅F₅ gas, C₄H₂F₈ gas, C₅H₂F₆ gas, C₅H₂F 10 gas and C₅H₃F₇ gas, and is at least one selected from the group consisting of, and has an ability to generate HF species. It is disclosed that the temperature is lower than 0° C. and -70° C. or lower. CHF₃, C₄H₂F₆ and CH₂F₂ are C s H t F u are mentioned as examples of the gas. In addition, the addition of phosphorus-containing molecules such as PF₃, PCl₃, PF₅, PCl₅, POCl₃, PH₃, PBr₃ and PBr₅ to etching is disclosed. The phosphorus-containing gas can promote the adsorption of HF species in plasma to the substrate surface.

[0006] Kihara et al. (Beyond 10μm Depth Ultra-High speed Etch Process with 84% Lower Carbon Footprint for Memory Channel Hole of 3DNAND Flash over 400 layers, 2023 Symposium on VLSI Technology and Circuits Digest of Technical Papers) disclose an etching process using an HF generating gas. In this process, HF is generated by CF₄ / H₂ plasma, the surface reaction rate between HF and SiO₂ increases sharply at low temperatures, and a high SiO₂ etching rate is achieved. HF species show great potential for high aspect ratio etching of dielectric materials.

[0007] Dussart et al. investigated low-temperature etching of a-Si, SiO₂ and Si₃N₄ materials using CHF₃ / Ar inductively coupled plasma at temperatures ranging from -140°C to +20°C in (Dussart et al., "Cryogenic Etching of Silicon Compounds Using a CHF₃Based Plasma", J. Applied Physics 133, 113306 (2023)). Samples of three different materials were placed together on the same silicon carrier wafer. Depending on the experimental conditions, etching or deposition behavior was obtained on the samples. A process window of -120°C to -80°C was identified: under these conditions, the Si₃N₄ surface is etched, while CF on the a-Si and SiO₂ surfaces x deposition occurs, resulting in Si₃N₄ exhibiting infinite etching selectivity over other materials. At a sufficiently high self-bias (-120 V) and very low temperature (below -130°C), the etching of Si₃N₄ decreases to an extremely low value, while a-Si and SiO₂ continue to be etched, which reverses the selectivity between Si₃N₄ and the other two materials. EDX analysis of the Si₃N₄ / a-Si / SiO₂ stack after performing the same etching process at 20°C and -100°C confirmed the presence of carbon and fluorine on a-Si at low temperatures, demonstrating the effect of low temperature on the switching from etching mode to deposition mode for this material.

[0008] U.S. Patent No. 9460935 discloses a semiconductor device manufacturing method using C₂H₂F₂ for high aspect ratio etching. However, the disclosed temperature range is 25°C to about 600°C, and in some embodiments the temperature is from about 25°C to about 200°C.

[0009] CN111154490 discloses an etching method for high aspect ratio containers (HARC), wherein the etching gas includes C₂F₆, C₂HF₅, C₂H₂F₄, C₂H₃F₃, C₂H₄F₂, C₂H₅F, C₂F₄, C₂HF₃, C₂H₂F₂ and C₂H₃F. No temperature is disclosed.

[0010] International Publication No. 2018182968 discloses a method and apparatus for etching features within a substrate, in which the substrate is etched at low temperatures and using a specific type of reactant. In various embodiments, the substrate may be etched at temperatures below approximately -20°C, using a reactant mixture containing at least one reactant, which is an iodine-containing fluorocarbon, an iodine-containing fluoride, a bromine-containing fluorocarbon, a sulfur-containing reactant, or one of another selected group of reactants.

[0011] Japanese Patent Publication No. 2001-044173 describes C2H2F2 gas and other C n H n F n Etching gas (n>=2) and low C / F ratio C gas such as C2HF5 gas x H y F z A plasma etching process using gas (x<=3, x+y+z>=8) is disclosed. This allows for control of selectivity by C2H2F2 gas and C x H y F z Control of etching defects using gas is achievable. For example, by appropriately adjusting the cooling refrigerant with a temperature control device, a temperature range of -50°C to 100°C can be maintained.

[0012] U.S. Patent No. 5,814,563 discloses a dielectric etching method, which is also applicable to etching other films such as TiN, and includes an etching agent such as C2H2F2 or CF4, a nitrogen gas such as NH3, an oxidizing agent such as CO, and Ar for sputtering. The NH3 gas can generate NH3-containing species such as gases, ions, or molecules containing NH2-, NH3, or NH4+ (e.g., NH3, NH4OH, CH3NH2, C2H5NH2, C3H8NH2, and mixtures thereof). The substrate temperature is maintained within a range of approximately ±50°C.

[0013] Specification KR19980085478 discloses a method for forming contact holes in semiconductor devices, which involves using a photoresist as a mask to form contact holes and using C4F8 and C3F8 gases for highly selective etching. The specification discloses a process down to -40°C for forming contact holes by plasma etching and the use of C2H2F2 (usually deposited using a spin-on process) for etching the photoresist mask material.

[0014] U.S. Patent No. 9,514,959 discloses etching gases such as C4H2F6 used in plasma etching processes for etching high aspect ratio silicon materials at substrate temperatures ranging from -196°C to 500°C.

[0015] Shin et al. ("SiO2 Etching Characteristics of Perfluoro-2-butene(l-C4F8) and Hexafluoropropene(l-C3F6)", Environmentally Benign Etching Technology Laboratory Association of Super-advanced Electronics Technologies 3-1 Morinosato Wakamiya, Atsugi-shi, 243-0198 JAPAN) disclose a comparison of the etching properties of two isomers of C4F8, which differ in their etching rates of SiO2 and their selectivity for materials such as PR, SiN, and Si. This suggests that etching properties are related not simply to the C:F ratio but to the structure of the etching gas.

[0016] Ohiwa et al. ("SiO2 Tapered Etching Employing Magnetron Discharge of Fluorocarbon Gas", Jpn.J.Appl.Phys. Vol.31(1992) p405-410) disclose an etching process using CHF3 down to -70°C. In this process, although the deposition rate increases at low temperatures, the etching rate of SiO2 increases sharply below -20°C. They also disclose that as the temperature decreases, a large amount of volatile fluorine compounds are adsorbed onto the film, promoting polymer formation. These species evaporate as the temperature rises. [Overview of the project] [Problems that the invention aims to solve]

[0017] Conventional fluorocarbon and hydrofluorocarbon gases can have high global warming potentials (GWPs), and when exposed to high-power plasma, they can decompose, producing species with similarly high GWPs. These high-GWP species are then emitted. Table 1 shows the GWP values ​​of etching gases commonly used in the semiconductor industry, as well as other molecules that can become plasma byproducts, and other chemical substances. As is clear from the table, the GWPs of CF4 (6630) and CHF3 (12400) are extremely high. Therefore, these molecules have a negative impact on global warming. Other commonly used fluorocarbons or hydrofluorocarbons include CH2F2, CH3F, C4F8, C4F6, C2F6, and C3F8. In addition, etching byproducts may include NO2, CO, CO2, COF4, and SiF4.

[0018] [Table 1]

[0019] In some cases, these high-GWP species may pass through the cleaning apparatus, but these high-GWP species have varying efficiencies. Therefore, both low-GWP etching gases that function in the low-temperature etching process window, and gases that decompose in the plasma to produce low-GWP byproducts are required. [Means for solving the problem]

[0020] A low-temperature etching method for forming an opening by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of one or more silicon-containing films, The substrate is placed in the reaction chamber; Cool the substrate to a temperature of approximately 25°C or less; Introducing etching gas C2H2F2 into the reaction chamber; Converting etching gas into plasma; An etching reaction is carried out between the plasma and one or more silicon-containing films, and one or more silicon-containing films are selectively etched against the patterned mask layer to form openings. A method including the following is disclosed. The disclosed etching method may include one or more of the following features: · C4F6, C4F8, C4H2F6, CHF3, CH2F2, CH3F, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, C4F 10 , C5F8, C6F6, C1~C6C x F y H z Numerator (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF 5、 Further comprising adding one or more hydrofluorocarbons or fluorocarbon etching gases, selected from C3H2F4 or combinations thereof, to C2H2F2; · H2, SF6, NF3, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, IF 7、The further method involves adding an additive to C2H2F2 selected from P-containing gases, specifically B2H6, HF, PF3, PCl3, PBr3, PH3, POCl3, PF5, POF3, PH3, or P(R)3 (wherein R is a fluorinated alkyl group selected from alkyl groups or CF3); • Select from O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, COF2, C2O2F2 x O y F z (x, y, and z are integers), C is selected from alcohols, ketones, acidic molecules, and ester-type molecules selected from CF3OH, CF3OCF3, (CF3)2C=O, and CF3COOH. x O y F z H m The further comprising adding a co-reactant with the additive, selected from (x, y, z, and m are integers) or combinations thereof; · O2, CO, CO2, NO, NO2, N2O, SO2, H2S, COS, O3, C x O y F z (x, y, and z are integers), C x O y F z H m The method further comprises adding a co-reactant with the additive, selected from (x, y, z, and m are integers), ester-type molecules, or combinations thereof; · C x O y F z (x, y, and z are integers) are selected from COF2 and C2O2F2; · C x O y F z H m (x, y, z, and m are integers) are selected from alcohols, ketones, and acids; • The esterified molecule is selected from CF3OH, CF3OCF3, (CF3)2C=O, and CF3COOH; Further comprising adding an inert gas selected from Ar, Kr, Xe, Ne, N2, He, or a combination thereof to C2H2F2; • Etching gas C2H2F2 is an isomer of C2H2F2 with CAS number 75-38-7; • Etching gas C2H2F2 is an isomer of C2H2F2 with CAS number 1630-78-0; • Etching gas C2H2F2 is an isomer of C2H2F2 with CAS number 1630-77-9; • Etching gas C2H2F2 is an isomer of C2H2F2 with CAS number 1691-13-0; • The temperature must be below approximately -50°C; • The temperature must be in the range of approximately -196°C to approximately 300°C; • The temperature must be in the range of approximately -196°C to approximately 60°C; • The temperature must be in the range of approximately -196°C to approximately 25°C; • The temperature must be in the range of approximately -196°C to approximately -50°C; • One or more silicon-containing films are selected from silicon oxide, silicon nitride, crystalline Si, polysilicon, polycrystalline silicon, amorphous silicon, low k SiCOH, SiOCN, SiC, SiON, or alternating stacked silicon oxide and silicon nitride (ONON) films, or alternating stacked silicon oxide and polysilicon (OPOP) films. a O b H c C d N e The formula includes layers where a > 0 and b, c, d, and e ≥ 0; • The aspect ratio of the opening must be in the range of 1:1 to 5:1; • The aspect ratio of the opening is greater than 1:1; • The aspect ratio of the opening is greater than 5:1; • The aspect ratio of the opening is greater than 10:1; • The aspect ratio of the opening is greater than 20:1; • The aspect ratio of the opening must be in the range of approximately 5:1 to 500:1; • The aspect ratio of the high-aspect-ratio aperture is in the range of approximately 20:1 to approximately 400:1; • The aspect ratio of the high-aspect-ratio aperture is higher than 50:1; • The aperture has a diameter in the range of approximately 0.1 nm to approximately 500 nm; • The aperture has a diameter in the range of approximately 5 nm to approximately 500 nm; • The aperture has a diameter of less than 100 nm; and • After the opening is formed, the temperature of the substrate rises to a temperature higher than -50°C.

[0021] Notation and Nomenclature The following detailed description and claims utilize a number of abbreviations, symbols, and terms that are commonly known in the art, including:

[0022] As used herein, the indefinite article "a" or "an" means one or more.

[0023] As used herein, "about," "around," or "approximately" in the text or claims means ±10% of the stated value.

[0024] As used herein, “room temperature” in the text or claims means approximately 20°C to approximately 25°C.

[0025] The term "substrate" refers to a material or a group of materials on which a process is performed. A substrate may refer to a wafer having a material or a group of materials on which a process is performed. A substrate may be any suitable wafer used in the manufacture of semiconductors, solar cells, flat panels, or LCD-TFT devices. A substrate may also have one or more layers of different materials already deposited on it from a previous manufacturing step. For example, a wafer may include a silicon layer (including, but not limited to, crystalline, amorphous, porous, etc.), a silicon-containing layer (including, but not limited to, SiO2, SiN, SiON, SiCOH, etc.), a metal or metal-containing layer (including, but not limited to, copper, cobalt, ruthenium, tungsten, platinum, palladium, nickel, ruthenium, gold, etc.), or a combination thereof. Furthermore, a substrate may be planar or patterned. A substrate may be an organically patterned iodine-treated carbon layer film. The substrate may include a layer of oxide used as a dielectric in field-effect transistors (FETs) such as FinFETs, MOFSETs, GAAFETs (Gate all-around FETs), Ribbon-FETs, Nanosheets, Forksheet FETs, Complementary FETs (CFETs), MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (e.g., ZrO2-based materials, HfO2-based materials, TiO2-based materials, rare-earth oxide-based materials, ternary oxide-based materials, etc.), or a nitride-based film (e.g., TaN, TiN, NbN) used as an electrode. 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 placed on or spread across a surface, and that the surface may be grooved or linear. Throughout this specification and the claims, a wafer and any associated layers thereon are referred to as a substrate. The substrate can be any solid having functional groups on its surface that tend to react with the reactive top layer of a self-assembled monolayer (SAM), and may include, without limitation, 3D objects or powders.

[0026] 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 film stack has topographic features or patterns created in a step prior to etching, and the patterned topmost film is formed for pattern etching.

[0027] The term “processing” as used herein includes patterning, exposure, development, etching, deposition, washing, and / or removal of by-products, as required in forming the structures described.

[0028] The term "deposit" or "deposition" refers to a series of processes in which a material, at the atomic or molecular level, is deposited onto a wafer surface or substrate as a thin layer in a solid state from a gaseous (vapor) state. Chemical reactions that occur after the generation of a plasma of reactive gases or the thermal activation of reactive gases are included in this process. The plasma may be, but is not limited to, a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron cyclotron resonance (ECR) plasma, or a microwave plasma. Suitable commercially available plasma etching chambers include, but are not limited to, the Lam Rese arch Dual CCP reactive ion etcher, the trademark Flex® or Tokyo Electron Tactras® or the Dielectric etching product line sold under Episode® UL. Non-plasma irradiation steps may be performed in a different chamber from the plasma irradiation steps.

[0029] The term "aspect ratio" refers to the ratio of the height of a groove (or aperture) to the width of the groove (or the diameter of the aperture).

[0030] The term "High Aspect Ratio (HAR)" refers to aspect ratios in the range of approximately 1:1 to approximately 500:1, preferably approximately 20:1 to approximately 400:1.

[0031] The term "high aspect ratio etching" refers to the formation of a vacancy pattern in a target film using a plasma etching method when the aspect ratio of the formed vacancy structure exceeds a value of 5.

[0032] It should be noted that in this specification, the terms “film,” “layer,” and “material” may be used interchangeably. It will be understood that a film may correspond to or be related to a layer or material, and that a layer may refer to both films and materials. 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 placed on or spread across a surface, and that the surface may range in size from as large as an entire wafer to as small as a groove or line.

[0033] In this specification, the terms “aperture,” “via,” “void,” “groove,” and “structure” may be used interchangeably to refer to openings formed in semiconductor structures.

[0034] As used herein, the abbreviation "NAND" refers to a "negative AND" or "non-AND" gate; the abbreviation "2D" refers to a two-dimensional gate structure on a planar substrate; and the abbreviation "3D" refers to a three-dimensional or vertical gate structure, where the gate structures are stacked vertically.

[0035] In this specification, the terms “etching gas” and “etchant” may be used interchangeably when the etching gas is in a gaseous state at room temperature and ambient temperature. It is understood that etching gas may correspond to or be related to etchant, and that etchant may refer to etching gas.

[0036] The terms "doping" are used interchangeably to refer to the process of incorporating one or more elements into a membrane by various means, where the elements may be chemically or physically bonded, and the process involves intentionally incorporating atoms of different elements into the membrane composition. Elements can be doped interlattally or substitutionally within the membrane.

[0037] Standard abbreviations for elements from the periodic table are used herein. It should be understood that elements may be referred to by these abbreviations (for example, Si refers to silicon, N to nitrogen, O to oxygen, C to carbon, H to hydrogen, F to fluorine, etc.).

[0038] A unique CAS registry number (i.e., "CAS") assigned by the Chemical Abstract Service is provided to identify the specific molecule being disclosed.

[0039] As used herein, the term "hydrofluorocarbon" refers exclusively to saturated or unsaturated functional groups containing carbon, fluorine, and hydrogen atoms.

[0040] As used herein, the term "fluorocarbon" refers exclusively to saturated or unsaturated functional groups containing fluorine and hydrogen atoms.

[0041] As used herein, the term "GWP" refers to Global Warming Potential, which typically compares CO2 and its global warming potential on a 100-year scale.

[0042] As used herein, "CO2 emissions" or "CO2 equivalent emissions" refers to a comparison between C2H2F2 and gases such as CH2F2, which are commonly used hydrofluorocarbon etching gases, and to the types of GWPs emitted from plasma etching processes.

[0043] A range may be expressed herein as approximately from one specific value to and / or approximately from another specific value. Where such a range is expressed, it should be understood that another embodiment, together with all combinations within the range, is from one specific value to and / or from another specific value. Any and all ranges enumerated herein, whether the term “inclusively” is used or not, include their endpoints (i.e., the x range x=1 to 4 or 1 to 4 includes x=1, x=4, and any number in between).

[0044] Any reference in this specification to “one embodiment” or “a particular embodiment” means that certain features, structures, or characteristics described in relation to that embodiment may be included in at least one embodiment of the present invention. The occurrence of the phrase “in one embodiment” in various places in this specification does not necessarily refer to the same embodiment, nor does it mean that different or alternative embodiments do not necessarily exclude other embodiments from one another. The same applies to the term “implementation.”

[0045] As used in this application, the term “exemplary” is used herein to mean an example, example, or illustration. No aspect or design described herein as “exemplary” should necessarily be construed as being preferable or advantageous to any other aspect or design. Rather, the use of the term “exemplary” is intended to present a concept in a concrete way.

[0046] Furthermore, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified, "or" is clear from the context. "X uses A or B" is intended to mean either of the natural inclusive sortings. That is, if X uses A, then X uses B; or X uses both A and B, in which case "X uses A or B" is satisfied under either of the aforementioned examples. In addition, the articles "a" and "an," as used in this application and the attached claims, should generally be interpreted as meaning "one or more" unless otherwise specified or unless it is clear from the context that they are introduced into the singular form.

[0047] In the claims, “including” is an open transitional term meaning that any claim elements subsequently identified are non-exclusive items (i.e., anything else may be further included and remain within the scope of “including”). “Including” is defined herein as not necessarily encompassing the more restrictive transitional terms “essentially from” and “consisting of”; “including” can therefore be replaced by “essentially from” or “consisting of” and remain within the explicitly defined scope of “including.”

[0048] In the claims, “to provide” is defined as meaning to give, supply, make available, or prepare something. The step may be performed by any party if there is no explicit language in the claims.

[0049] For a further understanding of the nature and purpose of the present invention, the following detailed description, used in conjunction with the accompanying drawings, should be referenced, where similar elements are given the same or similar reference numerals: [Brief explanation of the drawing]

[0050] [Figure 1] Figure 1 is a graph showing the emissions of HF produced by C2H2F2 > CH2F2 > C4H2F6, based on a comparison with Example 1. [Figure 2] Figure 2 shows graphs of HF emissions generated by C2H2F2 and CH2F2 and N2, respectively, based on Example 2. [Figure 3] Figure 3 is a graph comparing etching data for C2H2F2 and CH2F2 based on Example 3. [Figure 4] Figure 4 is a graph comparing the sediment data of C2H2F2 and CH2F2 based on Example 4. [Figure 5] Figure 5 is a graph showing the amount of HF and other by-products generated by C2H2F2, CH2F2, and C4H2F6, based on Example 5. [Modes for carrying out the invention]

[0051] A method for low-temperature plasma etching of silicon-containing materials using hydrofluorocarbon etching gas C2H2F2 is disclosed for manufacturing semiconductor chips such as 3D NAND flash and DRAM chips. Other applications include plasma etching processes in logic etching such as back-end-of-line (BEOL). Such high aspect ratio structures are extremely difficult to etch using conventional fluorocarbon and hydrofluorocarbon plasma etching methods, especially when new technology nodes are being sought. The disclosed method using low-temperature substrates may offer an opportunity to improve the etching process. By limiting volatile byproducts, the etching profile can be controlled at low temperatures, and the etching profile can be controlled to achieve highly vertical shapes. For example, SiF4 becomes volatile at temperatures above -86°C, and CO2 becomes volatile at temperatures above -70°C, but other etching byproducts may not be volatile at these temperatures.

[0052] In addition, conventional fluorocarbon and hydrofluorocarbon gases have high global warming potentials (GWPs) and can decompose when exposed to high-power plasma, potentially producing compounds with similarly high GWPs. These high-GWP species are emitted. In some cases, these high-GWP species pass through scrubbing equipment, but they have varying efficiencies. C2H2F2 is particularly attractive due to its extremely low GWP of less than 1, while other conventional fluorocarbon and hydrofluorocarbon etching gases have very high GWPs; for example, as shown in Table 1, CH2F2 has a GWP of 677.

[0053] Here, C2H2F2 can be used as a gas and / or deposition gas to generate HF or F in an etching chamber containing a low-temperature substrate. HF should be generated by the recombination of H and F in the plasma, which is directly related to the atomic concentration of the gas input to the chamber. C2H2F2 can function as both an HF source and a polymer source to protect the sidewalls of the etched structure. The addition of phosphorus to the etching recipe is known to increase the etching rate as a catalytic effect. Therefore, adding a gas such as PF3 or other P-containing gas to C2H2F2 may contribute to improving the etching rate. Furthermore, different hydrofluorocarbons and fluorocarbon isomers have different species and different species concentrations (for example, U.S. Patent No. 9514959 shows that the mass spectra of two isomers of C4H2F6 are different). This makes the amount of HF generated by hydrofluorocarbon etching gases unpredictable.

[0054] C2H2F2 has four major isomers, as listed in Table 2. The preferred C2H2F2 molecule is CAS number 75-38-7.

[0055] [Table 2]

[0056] C2H2F2 is supplied to gas cylinders at various filling volumes, pressures, and specifications. Preferably, the C2H2F2 in the cylinder has a water content of less than 40 ppm, preferably less than 10 ppm. The C2H2F2 may be purified by distillation, molecular sieving adsorption, or other existing methods to remove important impurities such as other fluorocarbons, hydrofluorocarbons, chlorofluorocarbons (CFCs), air-derived impurities, such as N2, O2, CO2, water (H2O), HF, and other hydrocarbons such as CH4. Some impurities may form azeotropic mixtures, and other purification methods using chemical methods may be necessary to separate them.

[0057] The disclosed low-temperature plasma etching method includes exposing a substrate in a reaction chamber to an etching gas C2H2F2 and / or one of its isomers, preferably C2H2F2 (CAS number: 75-38-7), during the etching process and / or the chamber preparation process.

[0058] A low-temperature plasma etching method of the present disclosure for forming an opening by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of one or more silicon-containing films, The substrate is placed in the reaction chamber; Cool the substrate to a temperature below 25°C; Introducing etching gas C2H2F2 into the reaction chamber; Converting etching gas into plasma; An etching reaction is carried out between the plasma and one or more silicon-containing films, and one or more silicon-containing films are selectively etched against the patterned mask layer to form openings. Includes.

[0059] The reaction chamber may be any enclosure or chamber within the apparatus in which the etching method is performed, and may include, for example, but not limited to, reactive ion etching (RIE), CCP with a single or multi-frequency RF source, inductively coupled plasma (ICP), microwave plasma reactor, or plasma processing, i.e., other types of etching systems capable of selectively removing a portion of a dielectric film, generating active species, or depositing a film.

[0060] The reaction chamber is equipped with a parallel-plate electrode plasma generator. With the electrode gap maintained in the range of 10 to 35 mm, 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. This combination of electric fields allows for power supply to the upper electrode in the range of 0 to 2000 W and to the lower electrode in the range of 1500 to 7000 W. Plasma can be generated with RF power ranging from approximately 25 W to approximately 100 kW. Plasma can be generated remotely or inside the reaction chamber. The RF frequency of the plasma is in the range of 100 kHz to 1 GHz. The plasma can be pulsed or continuous waves. In some embodiments, the power applied to the chamber ranges from 0 to several kW for bias power and several hundred to several thousand kW for source power.

[0061] The temperature and pressure within the reaction chamber are maintained at conditions suitable for the film to be processed to react with the activated etching gas C2H2F2. For example, the pressure within the chamber is maintained at approximately 0.1 mTorr to approximately 1000 Torr, preferably approximately 1 mTorr to approximately 10 Torr, more preferably approximately 10 mTorr to approximately 1 Torr, and even more preferably approximately 10 mTorr to approximately 100 mTorr, depending on the etching parameters. The pressure within the etching chamber during the plasma etching process can be maintained at 15 to 30 mTorr by introducing a process gas mixture. Similarly, the substrate temperature within the reaction chamber may be less than 25°C, preferably less than -50°C. Alternatively, the substrate temperature within the reaction chamber may be in the range of approximately -196°C to approximately 300°C, preferably approximately -196°C to approximately 60°C, more preferably approximately -196°C to approximately 25°C, and even more preferably approximately -196°C to approximately -50°C. The substrate can be cooled by various sources, including commercially available cooling devices, or by liquid nitrogen. The reaction chamber wall temperature may be less than 25°C, preferably less than -50°C. Depending on the process requirements, the reaction chamber wall temperature may range from approximately -196°C to approximately 25°C.

[0062] The reaction chamber wall temperature may be higher than approximately 20°C, preferably below 50°C. Depending on the process requirements, the reaction chamber wall temperature may be at or above room temperature, but may be below 50°C.

[0063] One or more additional hydrofluorocarbons or fluorocarbon etching gases may be added to C2H2F2. These additional hydrofluorocarbons or fluorocarbon etching gases may include C4F6, C4F8, C4H2F6, CH2F2, CH3F, CHF3, CF4, C2F6, C3F8, SF6, NF3, C2F4, C3F6, and C4F 10 , C5F8, C6F6, C1~C6C x F y H z Numerator (x, y, and z are integers), C2H5F, C3H7F, C3H2F6, C2HF 5、 C3H2F4 or a combination thereof may be selected.

[0064] Referring to Table 1, some hydrofluorocarbons or fluorocarbons have a higher GWP compared to C2H2F2. To improve etching performance and quality, one or more hydrofluorocarbons or fluorocarbon etching gases may be added to C2H2F2 to fine-tune the etching performance. When small amounts of hydrofluorocarbons or fluorocarbons with high GWP values ​​are added, the total CO2 equivalent emissions from the reaction chamber may not have a significant impact considering the improved etching performance. For example, when one or more hydrofluorocarbons or fluorocarbon etching gases are added to C2H2F2 at a concentration of less than 10% of C2H2F2, the CO2 equivalent emissions from the reaction chamber may not change significantly compared to the significantly improved etching performance. In practice, it is necessary to balance the reduction of CO2 equivalent emissions with high etching performance.

[0065] Other gases, such as additives, may be added to C2H2F2. These additives include H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, FNO, FNO3, HBr, HCl, HI, IF5, and IF. 7、 Examples include HF, B2H6, and P-containing gases such as PF3, PCl3, PBr3, PH3, POCl3, PF5, POF3, PH3, and P(R)3 (wherein R is an alkyl or a fluorinated alkyl group such as CF3).

[0066] An inert gas may be added to C2H2F2. The inert gas can be selected from Ar, Kr, Xe, Ne, N2, He, or a combination thereof.

[0067] The disclosed low-temperature plasma etching method further comprises sequentially or simultaneously exposing a substrate to a co-reactant with or without additives before activating the plasma, wherein the co-reactant is O2, CO, CO2, NO, NO2, N2O, SO2, H2S, or COS, O3, C x O y F z(x, y, and z are integers), for example, COF2, C2O2F2, C x O y F z H m (x, y, z, and m are integers), selected from, for example, alcohols, ketones, acids, ester-type molecules, such as CF3OH, CF3OCF3, (CF3)2C=O, CF3COOH, or combinations thereof.

[0068] The substrate contains silicon-containing materials such as SiO2, SiN, or Si. One example is an alternating lamination of SiO and SiN used in 3D NAND applications. The silicon-containing film or material is Si a O b H c C d N e The formula includes a layer (wherein a>0 and b, c, d, and e≧0) and is selected from silicon oxide, silicon nitride, crystalline Si, polysilicon, polycrystalline silicon, amorphous silicon, low k SiCOH, SiOCN, SiC, SiON, or alternating layered (ONON) films of silicon oxide and silicon nitride or alternating layered (OPOP) films of silicon oxide and polysilicon.

[0069] A mask layer or mask material is present on the silicon-containing film or material. The mask material may be an amorphous carbon, doped amorphous carbon, spin-on carbon (SOC), Si, SiN, Al, AlO, Ti, TiO, or other metal and metal oxide mask, or a layer of other nitrides such as TiN, with or without dopants.

[0070] C2H2F2 is supplied to gas cylinders at various filling volumes, pressures, and specifications. Preferably, this material has a low moisture content of less than 40 ppm, preferably less than 10 ppm. C2H2F2 may be purified by distillation, adsorption using molecular sieving, or other methods commonly known in the art to remove important impurities such as chlorine species or organochlorine compounds, other fluorocarbons, hydrofluorocarbons, chlorofluorocarbons (CFCs), air-derived impurities (N2, O2, CO2), moisture (H2O), HF, and other hydrocarbons (such as CH4). Since some impurities may form azeotropic mixtures, other purification methods using chemical means may be necessary to separate them.

[0071] After etching, heating the substrate to a temperature higher than -50°C allows the reaction byproducts to evaporate and be removed into the vacuum discharged from the reaction chamber.

[0072] C2H2F2 not only has a much lower GWP than standard fluorochemical etching gases, but also results in lower CO2 equivalent emissions from the etching process. The disclosed low-temperature plasma etching method uses C2H2F2 as the etching gas to form openings such as channel holes, gate trenches, stepped contacts, capacitor holes, contact holes, contact etching, slit etching, self-aligned contacts, self-aligned vias, and supervias in a silicon-containing film. The resulting openings may have an aspect ratio in the range of about 5:1 to about 500:1, preferably about 20:1 to about 400:1. The resulting openings may have a diameter in the range of about 0.1 nm to about 500 nm, preferably about 0.1 nm to about 500 nm, more preferably less than 100 nm. The resulting openings may 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 openings may have an aspect ratio in the range of 1:1 to 5:1. For example, those skilled in the art will recognize that channel hole etching can form openings in a silicon-containing film having an aspect ratio greater than 50:1.

[0073] The disclosed low-temperature plasma etching method is not limited to any of the experimental conditions described above, and the type of plasma etching apparatus (e.g., capacitively coupled or inductively coupled plasma), process conditions (e.g., pressure, power, temperature, process time), process gas mixture, combination and ratio of gases in the process gas mixture, gas flow rate, workpiece, and plasma etching chamber itself can be changed during each process.

[0074] In summary, the disclosed low-temperature plasma etching method uses C2H2F2 to improve the control of the polymer film deposition profile and enables etching of silicon oxides and silicon nitrides, or combinations thereof, with high etching rates and selectivity due to enhanced HF generation in the plasma. Furthermore, C2H2F2 has a lower GWP compared to commonly used materials (e.g., CF4, C4F8, CH2F2), resulting in a more environmentally friendly process. [Examples]

[0075] A more detailed description of the disclosed method is provided by the following examples. However, the disclosed method is not limited to any of the presented examples, and the process conditions, process gas mixture, combination and proportion of gases in the gas mixture, workpiece, and plasma etching chamber itself can be modified.

[0076] In the following embodiments, the primary plasma etching source may be a CCP plasma, but other sources such as ICP, microwave, and ECR may also be included. The plasma may be used as a continuous source or as a pulsed plasma having a specific frequency and duty cycle. The substrate surface temperature may be cooled or raised by a cryogenic cooler or by supplying liquid nitrogen and a heating stage. Additional fluorocarbon gases may be added to fine-tune the etching performance. Additional inert gases such as hydrogen source gases such as Kr, Xe, Ne, and H2, and hydrocarbons may also be added. Mask materials may include TiN or other metal nitride materials, SiN, Si, carbon materials, etc. For comparative purposes, the etching and evacuation performance of CH2F2 and C4H2F6 disclosed in U.S. Patent Application Publication No. 2023 / 0127467 is also shown in the following embodiments.

[0077] Example 1. Comparison of HF emissions of C2H2F2, CH2F2, and C4H2F6 in an O2 plasma process. This example demonstrates the ability to generate HF species by using C2H2F2 as the etching gas. In a 300 mm CCP plasma etching chamber, HF generating gases, C4F8, and O2 were introduced together with an inert gas (e.g., argon) at the flow rates shown in Table 3 below. The flow rates of the HF generating gases C2H2F2, CH2F2, and C4H2F6 were selected to ensure equivalent molar amounts of F in the chamber. The amount of HF generated by the plasma for these gases was measured downstream using FTIR and quantified for each condition. As shown in Figure 1, under these process conditions, the amount of HF generated by these gases is C2H2F2 > CH2F2 > C4H2F6. C2H2F2 generates 16% more HF than CH2F2 and 81% more HF than C4H2F6. Therefore, compared to CH2F2 and C4H2F6, C2H2F2 generates a higher concentration of HF in the plasma, which can be advantageous for low-temperature etching applications.

[0078] [Table 3]

[0079] Example 2. Comparison of HF emissions of CH2F2 and C2H2F2 in an N2 plasma process. In a 300 mm CCP plasma etching chamber, two types of gases (CH2F2 and C2H2F2) were introduced into each chamber in different experiments, and their performance was compared. The experimental conditions are shown in Table 4 below. Each gas was introduced at a flow rate of 20 sccm, along with N2 at a flow rate of 40 sccm and argon at a flow rate of 150 sccm. Oxygen was not used in this experiment. As shown in Figure 2, under these conditions, the amount of HF generated during the etching chamber evacuation using FTIR was observed to be more than twice as high for C2H2F2 than for CH2F2, demonstrating the superiority of C2H2F2. One explanation for this result is that N2 in the plasma generates multiple different radical species, which can alter the fragmentation of the fluorocarbon gas. According to Yao et al. (Nanomaterials 2022, 12(21), 3798), nitrogen plasma contains more atoms and molecules in metastable and vibrational states with higher energy than oxygen plasma. Therefore, nitrogen plasmas offer more pathways for dissociating various species within the plasma. Despite each molecule having only two H atoms and two F atoms, C2H2F2 generates far more HF species in an N2 plasma environment, as shown in Figure 2.

[0080] [Table 4]

[0081] Example 3. Etching rates of CH2F2 and C2H2F2 C2H2F2 and CH2F2 were introduced into a 300 mm CCP plasma etching chamber along with O2 and argon. The experimental conditions described in Table 5 were used, with a source power of 950 / 200W, a bias power of 6000 / 200W, and a duty cycle of 70%. The etching rates of SiO and SiN wafers were measured and are shown in Figure 3. The etching rate of C2H2F2 for SiO and SiN was higher than that of CH2F2. This indicates that C2H2F2 improves the etching rate of SiO and SiN, even though both molecules supply the same number of fluorine atoms per molecule. A possible reason is that C2H2F2 can more efficiently supply fluorine radicals that are effective for etching.

[0082] [Table 5]

[0083] Example 4. Deposition rate of CH2F2 and C2H2F2 The deposition rates of C2H2F2 and CH2F2 were measured in a 200 mm CCP plasma etching chamber. Each hydrofluorocarbon was introduced into the chamber separately at a rate of 15 sccm with an argon flow rate of 250 sccm. The source power was 750 W, and there was 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 is 23% higher than that of CH2F2. The improved polymer formation of C2H2F2 may be beneficial for sidewall protection during low-temperature etching processes. The etching rates of SiO and SiN wafers were measured and are shown in Figure 4.

[0084] Example 5. HF emissions of CH2F2, C4H2F6, and C2H2F2 In a 300mm CCP plasma etching chamber, HF emissions were measured for three different etching gases, C2H2F2, CH2F2, and C4H2F6, using an FTIR meter installed downstream of the etching chamber. The three different etching gases were introduced into the etching chamber in three separate experiments at a flow rate of 20 sccm, source power of 950 W, and bias power of 6000 W (including plasma pulses and a 70% duty cycle). The chamber pressure was 15 mTorr. O2 was introduced at a flow rate of 40 sccm and argon at 150 sccm. The experiment duration was 180 seconds, and the wafer temperature was 60°C. As shown in Table 6, under these conditions, the amount of HF generated in the etching chamber exhaust was very similar among the three gases. However, comparing C2H2F2 and C4H2F6, C4H2F6 introduced three times the amount of F into the chamber plasma chemistry. The trend in the amount of HF generated per F atom input to the process is C2H2F2 > CH2F2 >> C4H2F6. Therefore, C2H2F2 generates more HF per F number in the plasma. Figure 5 shows a more detailed composition of the emissions from the etching process for each of the three gases. Less undecomposed molecules of C2H2F2 were observed to be emitted than those of C4H2F6, indicating that C2H2F2 is decomposed more effectively in the plasma. In addition, the amount of high GWP byproducts generated in C2H2F2 plasmas is significantly less compared to C4H2F6 and CH2F2. For example, C2H2F2 generates fewer CF4 and CH2F2 byproducts compared to CH2F2. C2H2F2 also generates fewer CHF3 byproducts compared to C4H2F6. These byproducts each have high GWP (see Table 1). Therefore, C2H2F2 is a gas with a lower GWP than CH2F2 and C4H2F6, and its plasma emission byproducts have a lower GWP compared to CH2F2 and C4H2F6.

[0085] [Table 6]

[0086] It will be understood that many additional modifications in details, materials, steps, and arrangement of parts, which have been described and illustrated herein to illustrate the nature of the present invention, can be made by those skilled in the art within the principles and scope of the present invention as set forth in the appended claims. Accordingly, the present invention is not intended to be limited to the specific embodiments in the above-described examples and / or the appended drawings.

[0087] Embodiments of the present invention have been shown and described, and modifications thereof can be made by those skilled in the art without departing from the spirit or teachings of the invention. The embodiments described herein are illustrative and not limiting. Many variations and modifications of 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 limited only by the following claims, which shall encompass all equivalents of the subject matter of the claims.

Claims

1. A low-temperature etching method for forming an opening by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of one or more silicon-containing films, The substrate is placed in the reaction chamber; The substrate is cooled to a temperature of less than approximately 25°C; Etching gas C ２ H ２ F ２ Introducing the above into the reaction chamber; Converting the etching gas into plasma; An etching reaction is carried out between the plasma and the one or more silicon-containing films, and the one or more silicon-containing films are selectively etched with respect to the patterned mask layer to form the opening. A method that includes this.

2. said etching gas C ２ H ２ F ２ , further comprising adding one or more hydrofluorocarbon or fluorocarbon etching gases to said etching gas, wherein said one or more hydrofluorocarbon or fluorocarbon etching gases are C ４ F ６ , C ４ F ８ , C ４ H ２ F ６ , CHF ３ , CH ２ F ２ , CH ３ F, CF ４ , C ２ F ６ , C ３ F ８ , SF ６ , NF ３ , C ２ F ４ , C ３ F ６ , C ４ F １０ , C ５ F ８ , C ６ F ６ , C １ to C ６ C ｘ F ｙ H ｚ molecule (wherein x, y and z are integers), C ２ H ５ F, C ３ H ７ F, C ３ H ２ F ６ , C ２ HF ５、 C ３ H ２ F ４ , or a combination thereof. The method according to claim 1.

3. The etching gas C ２ H ２ F ２ The further includes adding an additive, wherein the additive is H ２ SF ６ NF ３ NH ３ , Cl ２ , BCl ３ BF ３ , Br ２ F ２ FNO, FNO ３ , HBr, HCl, HI, IF ５ , IF ７、 HF, B ２ H ６ , or PF ３ , PCL ３ , PBr ３ PH ３ , POCl ３ , PF ５ , POF ３ PH ３ Or P(R) ３ (In the formula, R is an alkyl group or CF ３ The method according to claim 1, wherein the P-containing gas is selected from (a fluorinated alkyl group selected from)

4. The etching gas C ２ H ２ F ２ further comprises adding a co-reactant to, wherein the co-reactant is O ２ , CO, CO ２ , NO, NO ２ , N ２ O, SO ２ , H ２ S, COS, O ３ , COF ２ , C ２ O ２ F ２ C selected from ｘ O ｙ F ｚ (wherein x, y and z are integers), CF ３ OH, CF ３ OCF ３ , (CF ３ ) ２ C=O, CF ３ C selected from alcohol, ketone, acidic, and ester-type molecules selected from COOH, C ｘ O ｙ F ｚ H ｍ (wherein x, y, z and m are integers), or a combination thereof. The method according to claim 1.

5. The etching gas C ２ H ２ F ２ The method further includes adding an inert gas, wherein the inert gas is Ar, Kr, Xe, Ne, N ２ The method according to claim 1, selected from , He, or a combination thereof.

6. The etching gas C ２ H ２ F ２ However, CAS number: 75-38-7 C ２ H ２ F ２ The method according to any one of claims 1 to 5, wherein the isomer is...

7. The etching gas C ２ H ２ F ２ However, CAS number: 1630-78-0 C ２ H ２ F ２ The method according to any one of claims 1 to 5, wherein the isomer is...

8. The etching gas C ２ H ２ F ２ However, C of CAS number 1630-77-9 ２ H ２ F ２ The method according to any one of claims 1 to 5, wherein the isomer is...

9. The etching gas C ２ H ２ F ２ However, C of CAS number 1691-13-0 ２ H ２ F ２ The method according to any one of claims 1 to 5, wherein the isomer is...

10. The method according to any one of claims 1 to 5, wherein the temperature of the substrate is less than approximately -50°C.

11. The method according to any one of claims 1 to 5, wherein the temperature of the substrate is in the range of about -196°C to about 300°C.

12. The method according to any one of claims 1 to 5, wherein the temperature of the substrate is in the range of about -196°C to about 60°C.

13. The method according to any one of claims 1 to 5, wherein the temperature of the substrate is in the range of about -196°C to about -50°C.

14. The method according to any one of claims 1 to 5, wherein the aspect ratio of the opening is in the range of 1:1 to 5:

1.

15. The method according to any one of claims 1 to 5, wherein the aspect ratio of the opening is greater than 5:

1.

16. The method according to any one of claims 1 to 5, wherein the aspect ratio of the opening is higher than 20:

1.

17. The method according to any one of claims 1 to 5, wherein the aspect ratio of the opening is in the range of about 5:1 to about 500:

1.

18. The method according to any one of claims 1 to 5, wherein the aperture has a diameter in the range of about 0.1 nm to about 500 nm.

19. The method according to any one of claims 1 to 5, wherein the opening has a diameter of less than 100 nm.

20. The method according to any one of claims 1 to 5, wherein after the opening is formed, the temperature of the substrate rises to a temperature higher than -50°C.

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