Dry etching with self-cleaning of etching by-products

Abstract

The method includes providing a base structure in an etching chamber, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer; and dry etching the target layer using thionyl chloride in the etching chamber to obtain a processed base structure and form a plurality of features. The processed base structure includes the plurality of features and the plurality of openings formed by the etching mask. The method further includes removing the processed base structure from the etching chamber. In some embodiments, the target layer includes carbon. In some embodiments, the dry etching is performed at a temperature of 0° C. or less.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the disclosure relate generally to the fabrication of electronic devices. In particular, embodiments of the disclosure relate to dry etching with self-cleaning of etch by-products.

[0002] An electronic device manufacturing apparatus may include multiple chambers, such as processing chambers and load lock chambers. In such an electronic device manufacturing apparatus, a transfer chamber may employ a robotic device configured to transfer substrates between the multiple chambers. In some cases, multiple substrates are transferred together. In an electronic device manufacturing apparatus, a processing chamber may be used to perform one or more processes on a substrate, such as a deposition process or an etching process. In many processes, gases are flowed into the processing chamber. Electronic devices, such as semiconductor devices, are manufactured by performing a series of operations, such as deposition, oxidation, photolithography, ion implantation, and etching, to form multiple patterned layers. Overview

[0003] According to an embodiment, a method is provided. The method includes providing a base structure in an etching chamber, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer; and dry etching the target layer using thionyl chloride in the etching chamber to obtain a processed base structure. The target layer includes carbon. The processed base structure includes a plurality of features and a plurality of openings defined by the etching mask. The method further includes removing the processed base structure from the etching chamber.

[0004] According to an embodiment, a method is provided. The method includes providing a base structure in an etching chamber, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer; and dry etching the target layer in the etching chamber using thionyl chloride at a temperature of 0° C. or less to obtain a processed base structure. The processed base structure includes a plurality of features and a plurality of openings defined by the etching mask. The method further includes removing the processed base structure from the etching chamber.

[0005] According to an embodiment, an etching chamber is provided. The etching chamber includes: a gas panel for supplying thionyl chloride; a substrate support assembly for holding a base structure, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer; and a showerhead with a plurality of gas supply holes for dry etching the target layer using thionyl chloride to obtain a processed base structure. The target layer includes carbon. The processed base structure includes a plurality of features and a plurality of openings formed by the etching mask. [Brief explanation of the drawings]

[0006] The present disclosure is illustrated by way of example, and not limitation, in the figures of the accompanying drawings, in which like reference numerals indicate like elements. It should be noted that different references to "an" or "one" embodiment in the present disclosure do not necessarily refer to the same embodiment, but that such references mean at least one. [Figure 1] 1 is a cross-sectional view of an etching chamber according to some embodiments. [Figure 2A] FIG. 1 illustrates an exemplary method of performing dry etching using a flash process to remove etch by-products, according to some embodiments. [Figure 2B] FIG. 1 illustrates an exemplary method for performing dry etching with self-cleaning of etch by-products, according to some embodiments. [Figure 3] FIG. 1 illustrates an exemplary method for performing dry etching with self-cleaning of etch by-products, according to some embodiments. [Figure 4A] ~ [Figure 4B] 1A-1C are diagrams of examples of low profiles resulting from performing dry etching, according to some embodiments. [Figure 5] 1 is a flowchart of an exemplary method for performing a dry etch with self-cleaning of etch by-products, according to some embodiments. Detailed Description

[0007] Embodiments described herein relate to dry etching with self-cleaning of etching by-products. Electronic devices can include multiple different types of layers. For example, electronic devices can include a dielectric layer formed from a dielectric material, a conductive layer formed from a conductive material, and a semiconductor layer formed from a semiconductor material. Processing techniques for electronic devices include performing patterning (e.g., photolithography) to create device structures. For example, patterning can include multiple iterative processes of deposition and etching.

[0008] Generally, etching refers to a process for removing material from a base structure, including a target layer, formed on a substrate. For example, etching can be performed by forming a photoresist (e.g., a "soft" etching mask) on the target layer, aligning a photomask including at least one mask layer over the photoresist, exposing the base structure to ultraviolet (UV) light while each mask layer blocks a respective region of the photoresist from exposure to the UV light, removing at least one region of the photoresist by applying a solvent (i.e., a developer) that develops the photoresist to expose at least one region of the target layer, and etching at least one exposed region of the target layer using an etching process. After etching at least one exposed region of the target layer, the remaining photoresist can be removed from the target layer using an appropriate stripping chemical.

[0009] Photoresist includes a light-sensitive material (e.g., a photosensitive organic material). In some embodiments, the photoresist is a positive photoresist. Positive photoresist materials degrade when exposed to ultraviolet light, such that areas of the photoresist exposed to ultraviolet light can be removed after applying a solvent. In some embodiments, the photoresist is a negative photoresist. In contrast to positive photoresist, negative photoresist materials strengthen when exposed to ultraviolet light, such that areas of the photoresist not exposed to ultraviolet light can be removed after applying a solvent.

[0010] In some embodiments, an anti-reflective coating (ARC) layer can be formed on the target layer before forming the photoresist. That is, the ARC layer can be referred to as a bottom ARC layer (BARC). The ARC layer can prevent UV light from reflecting below the photoresist. Therefore, the ARC layer can improve the performance of the photoresist, especially as feature sizes decrease (i.e., at smaller technology nodes).

[0011] Alternatively, a hard mask can be used instead of photoresist. For example, if the underlying material to be etched is an organic material (e.g., an organic polymer), a hard mask can be used because the etchant used to etch the underlying material will also etch the photoresist. Additionally or alternatively, a hard mask can be used if the target layer below the hard mask is formed from a material that may be damaged by the chemicals used to strip the photoresist (e.g., a low-k dielectric material). The hard mask can be formed from any suitable inorganic or organic material. The hard mask can be formed from a suitable conductive material (e.g., a metal), a dielectric material, etc. Examples of hard mask materials include silicon-based materials (e.g., silicon dioxide (SiO2), silicon carbide (SiC), silicon oxynitride (SiON)), metal nitride-based materials, metal oxide-based materials, carbon-based materials, organosiloxane-based materials, etc.

[0012] One example of etching is wet etching (i.e., liquid-phase etching). Wet etching uses wet etching chemistry to remove material from a target layer. Another example of etching is dry etching. Examples of dry etching include gas-phase etching and plasma-phase etching. Gas-phase etching uses a gas mixture at a sufficiently high temperature to remove material from a target layer. Plasma-phase etching ("plasma") uses a plasma generated from a gas mixture at a lower temperature to remove material. Examples of plasma etching include isotropic plasma etching, ion beam milling or sputter etching, reactive ion etching (RIE), etc.

[0013] A plasma can be generated from a process gas. The plasma can include reactive species, such as charged particles (e.g., ions) and / or neutral particles (e.g., atoms and radicals). The surface of at least one exposed area of ​​the target layer reacts with the plasma, etching the exposed portion of the target layer. The type of process gas in the gas mixture depends on the material of the target layer. The reaction of the target layer with the reactive species produces volatile etching by-products (e.g., small molecules), which can be removed by a vacuum system.

[0014] In some embodiments, the process gas is delivered in a gas mixture that further includes a carrier gas. More specifically, the carrier gas may be an inert gas. For example, the carrier gas may be a noble gas, such as helium (He), argon (Ar), neon (Ne), xenon (Xe), krypton (Kr), or radon (Rn). In some embodiments, the gas mixture may include a mixture of carrier gases (i.e., a carrier gas mixture). The carrier gas (or carrier gas mixture) may be used to dilute the gas mixture to control the etch rate or improve the etch performance.

[0015] In some embodiments, the process gas is supplied without a carrier gas, for example, the process gas can be supplied via a heated gas line.

[0016] As described above, an etch mask can be disposed on the target layer, and the etch mask defines features formed from the target layer. After the dry etch pulse, etch by-products or residues may form on the sidewalls of the etch mask and / or the sidewalls of the features in the target layer. More specifically, the etch products may form in openings formed between the features. The openings may form on at least the top surface of the target layer and / or the bottom surface of the target layer. In some embodiments, the openings are via holes. The etch by-products may be formed at least in part by sputtering of the mask material (e.g., silicon (Si)). For example, the etch by-products may include silicon oxide material (e.g., SiO). More specifically, during bias power-off times during the dry etch, sputtered material may recombine on the surfaces of the etch mask and / or the sidewalls of the target layer.

[0017] If the width of the opening and / or feature is sufficiently narrow (e.g., critical dimension), etching by-products may clog the opening after an etching cycle. This clogging prevents the execution of additional dry etching processes (e.g., pulses / cycles). Typically, etching by-products can be removed by performing a cleaning process (also called a "flash" process) after each etching pulse. The etching pulse and flash process can form an etching cycle that is repeated until sufficient material is removed from the target layer (e.g., until the feature reaches the target height). However, the need to perform a flash process after each etching pulse can increase processing time and reduce throughput. Furthermore, the flash process not only removes etching by-products but may also remove portions of the etching mask formed on the target layer. Therefore, the number of times that the flash process can be performed is limited and may be limited by the thickness of the etching mask. Furthermore, performing dry etching at subzero temperatures (below approximately 0°C) can result in excessive passivation, which can adversely affect the etching profile of features formed from the target layer during dry etching.

[0018] To address these and other drawbacks, embodiments described herein can enable plasma etching with self-cleaning of etch by-products. For example, the gas mixture used during plasma etching can include a process gas including thionyl chloride (SOCl2). In some embodiments, the target layer includes a polymer. In some embodiments, the target layer is a hard mask. In some embodiments, the target layer is a photoresist. For example, the target layer can be disposed on a dielectric layer (e.g., an oxide). In some embodiments, the target layer includes carbon (C). For example, the target layer can include amorphously deposited carbon, spin-on carbon, CVD-deposited carbon, etc.

[0019] An etch mask can be formed on the target layer. The etch mask can include a material that allows features to be formed from the target layer using dry etching with thionyl chloride. In some embodiments, the etch mask is a silicon-containing etch mask. For example, the etch mask can include silicon oxynitride (SiON). In some embodiments, the etch mask is a boron-containing etch mask. For example, the etch mask can include boron nitride (BN).

[0020] In some embodiments, the target layer can have dimensions (e.g., thickness and width) that enable the formation of high aspect ratio features. Aspect ratio refers to the ratio of the feature height to the feature width (e.g., critical dimension). Features can have any suitable aspect ratio according to embodiments described herein. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 30:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 40:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 50:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 60:1 or greater. For example, the feature length can be about 1000 nanometers (nm) and the feature width can be about 16 nm (aspect ratio of about 62.5:1).

[0021] Features formed from the target layer can have any suitable width according to the embodiments described herein. In some embodiments, the feature width may be about 50 nm or less. In some embodiments, the feature width may be about 40 nm or less. In some embodiments, the feature width may be about 30 nm or less. In some embodiments, the feature width may be about 20 nm or less.

[0022] Thionyl chloride can enable self-cleaning of etch byproducts formed on the sidewalls of an etch mask and / or the sidewalls of features formed from a target layer. For example, if the target layer contains H (e.g., a C- and H-containing material), thionyl chloride can scavenge H from the target layer to form HCl. The HCl can clean the etch byproducts and smooth the exposed surface. Thus, embodiments described herein can reduce the number of flush processes that need to be performed to remove etch byproducts from the sidewalls of an etch mask and / or the target layer (e.g., eliminate flush processes).

[0023] Furthermore, thionyl chloride can induce chemisorption (i.e., chemical absorption) on the surface of the sidewall of a feature formed from the target layer, improving surface quality (e.g., removing surface roughness) and passivating the surface of the feature sidewall. For example, if the target layer contains carbon, the sulfur (S) in thionyl chloride can react with the C in the target layer to form a passivation layer containing carbon disulfide (CS2) on the surface of the feature sidewall. The presence of the passivation layer can reduce etching of the passivated surface and reduce the roughness of the passivated surface. Improved smoothness can lead to improved surface roundness resulting from dry etching, such as dry etching performed at temperatures below 0°C. Therefore, the embodiments described herein can achieve sidewall passivation during dry etching with a thionyl chloride gas mixture without the use of additional passivation gases such as carbonyl sulfide (COS) or sulfur dioxide (SO2). Therefore, performing dry etching using the thionyl chloride gas mixture described herein can improve the etch profile.

[0024] The dry etching can be performed at any suitable temperature. In some embodiments, the dry etching is performed at a sub-zero temperature. A thionyl chloride gas mixture as an etchant can counteract excessive passivation that can occur with dry etching at sub-zero temperatures. For example, the dry etching can be performed at a temperature below about 0° C. As another example, the dry etching can be performed at a temperature of about −10° C. or less. As another example, the dry etching can be performed at a temperature of about −20° C. or less. As another example, the dry etching can be performed at a temperature of about −30° C. or less. As yet another example, the dry etching can be performed at a temperature of about −40° C. or less. As yet another example, the dry etching can be performed at a temperature of about −50° C. or less. As yet another example, the dry etching can be performed at a temperature of about −60° C. or less. As yet another example, the dry etching can be performed at a temperature of about −70° C. or less. As yet another example, the dry etching can be performed at a temperature of about −80° C. or less. As yet another example, the dry etching can be performed at a temperature of about −90° C. or less. When the gas mixture with the process gas includes a carrier gas, the carrier gas can drive the process gas flow into the etching chamber at a normal rate and prevent condensation of the thionyl gas at temperatures below 0°C. In some embodiments, the dry etch is performed at temperatures above 0°C. More specifically, the dry etch can be performed at temperatures above about 0°C. Further details regarding performing dry etching with self-cleaning of etch byproducts are described below with reference to Figures 1-3.

[0025] 1 is a cross-sectional view of an etch chamber 100 in accordance with some embodiments. The etch chamber 100 can be used for etch processes in which a corrosive plasma environment and / or corrosive chemicals are provided. For example, the etch chamber 100 can be a chamber for a plasma etch reactor (also called a plasma etcher). Examples of chamber components that may be exposed to plasma in the etch chamber 100 include a substrate support assembly 148, an electrostatic chuck (ESC), a ring (e.g., a process kit ring or a single ring), chamber walls, a base, a showerhead 130, a gas distribution plate, a liner, a liner kit, a shield, a plasma screen, a flow equalizer, a cooling base, a chamber viewport, a chamber lid, a nozzle, a process kit ring, etc.

[0026] In one embodiment, the etch chamber 100 includes a chamber body 102 and a showerhead 130 that enclose an interior volume 106. The showerhead 130 may or may not include a gas distribution plate. For example, the showerhead may be a multi-piece showerhead including a showerhead base and a showerhead gas distribution plate bonded to the showerhead base. Alternatively, the showerhead 130 may be replaced by a lid and a nozzle in some embodiments, or by multiple pie-shaped showerhead compartments and plasma generation units in other embodiments. The etch chamber body 102 may be fabricated from aluminum, stainless steel, or other suitable materials. The etch chamber body 102 generally includes a sidewall 108 and a bottom 110. Any of the showerhead 130 (or lid and / or nozzle), sidewall 108, and / or bottom 110 may include a multi-layer plasma-resistant coating.

[0027] An outer liner 116 may be disposed adjacent the sidewall 108 to protect the etch chamber body 102. The outer liner 116 may be a halogen-containing gas resistant material such as Al2O3 or YO3. In some embodiments, the outer liner 116 may be coated with a multi-layer plasma-resistant ceramic coating.

[0028] An exhaust port 126 may be formed in the etching chamber body 102 to couple the interior volume 106 to a pumping system 128. The pumping system 128 may include one or more pumps and a throttle valve used to evacuate and regulate the pressure in the interior volume 106 of the etching chamber 100.

[0029] The showerhead 130 can be supported on the sidewall 108 of the etch chamber body 102 and / or on the top of the etch chamber body. The showerhead 130 (or lid) can be opened to provide access to the interior volume 106 of the etch chamber 100 and can be closed to provide a seal for the etch chamber 100. A gas panel 158 can be coupled to the etch chamber 100 and supply a gas mixture including at least one process gas and / or at least one carrier gas to the interior volume 106 via the showerhead 130 or the lid and nozzles. An example of a process gas supplied by the gas panel 158 and used to process substrates / samples in the etch chamber 100 includes thionyl chloride. An example of a carrier gas (e.g., a diluent) includes an inert gas (e.g., a noble gas). The showerhead 130 includes a plurality of gas supply holes 132 throughout the showerhead 130. The showerhead 130 can be made of or include aluminum, anodized aluminum, an aluminum alloy (e.g., Al6061), or an anodized aluminum alloy. In some embodiments, the showerhead includes a gas distribution plate bonded to the showerhead. The gas distribution plate can be, for example, Si or SiC. Additionally, the gas distribution plate can include a plurality of holes that align with the holes in the showerhead.

[0030] A substrate support assembly 148 is disposed within the interior volume 106 of the etch chamber 100 below the showerhead 130. The substrate support assembly 148 holds a base structure 144 containing a substrate during processing. The substrate support assembly 148 may include an electrostatic chuck that secures the base structure 144 during processing, a metal cooling plate bonded to the electrostatic chuck, and / or one or more additional components. An inner liner may cover the periphery of the substrate support assembly 148. The inner liner may be a halogen-containing gas-resistant material such as Al2O3 or YO3. In some embodiments, the substrate support assembly 148, portions of the substrate support assembly 148, and / or the inner liner may be coated with a metal layer and a barrier layer.

[0031] The etch chamber 100 can be configured to perform dry etching with self-cleaning of etch byproducts, as described in more detail below with reference to FIGS. 2A-5. More specifically, the dry etching can be performed to etch a target layer of the base structure 144. In some embodiments, the target layer comprises a polymer. In some embodiments, the target layer is a hard mask. In some embodiments, the target layer is a photoresist. For example, the target layer can be disposed on a dielectric layer (e.g., an oxide). In some embodiments, the target layer comprises carbon. For example, the target layer can include amorphously deposited carbon, spin-on carbon, CVD-deposited carbon, etc.

[0032] In some embodiments, the target layer is disposed on a dielectric layer. For example, the target layer can be disposed on a dielectric layer including an oxide material. In some embodiments, the dry etching is performed at a temperature of 0° C. or less. For example, the dry etching can be performed at a temperature less than about 0° C. As another example, the dry etching can be performed at a temperature of about −10° C. or less. As another example, the dry etching can be performed at a temperature of about −20° C. or less. As another example, the dry etching can be performed at a temperature of about −30° C. or less. As yet another example, the dry etching can be performed at a temperature of about −40° C. or less.

[0033] For example, the base structure 144 can include an etch mask stack disposed on a target layer, which can be disposed on at least one layer of a substrate. In some embodiments, the etch mask stack includes a photoresist, a BARC layer, and an etch mask. In some embodiments, the at least one layer of the substrate includes a dielectric layer (e.g., an oxide). The etch mask can include a material that enables formation of features from the target layer during dry etching using thionyl chloride. In some embodiments, the etch mask is a silicon-containing etch mask. For example, the etch mask can include SiON. In some embodiments, the etch mask is a boron-containing etch mask. For example, the etch mask can include BN.

[0034] In some embodiments, the substrate includes a substrate layer (e.g., a dielectric layer disposed between the target layer and the substrate layer). For example, the substrate layer may be a silicon (Si) substrate layer, a glass substrate layer, a silicon germanium (SiGe) substrate layer (e.g., an alternating stack of Si and Ge sublayers), etc. Further details regarding performing dry etching with self-cleaning of etch by-products are described below with reference to FIGS. 2A-5.

[0035] 2A illustrates an example method 200A for performing dry etching and removing etch by-products using a flash process. First, a base structure is provided that includes a target layer 210A and etching mask layers 220A-1 and 220A-2 disposed on the target layer 210A.

[0036] In step 215, a portion of the material of the target layer 210A is removed using a dry etching process (e.g., dry etching pulses / cycles). For example, the dry etching process may include at least one of plasma etching, ion beam milling, RIE, etc. More specifically, the portion of material removed from the target layer 210A is in an area not protected by the etching mask layers 220A-1 and 220A-2. As a result of the dry etching process, etching byproducts 230-1 are formed on at least the sidewalls of the etching mask layers 220A-1 and 220A-2. Although not shown, the etching byproducts 230-1 may also be formed on the sidewalls of the target layer 210A. Depending on the geometry of the feature and opening (e.g., high aspect ratio and / or width), the etching byproducts may clog the opening, preventing further dry etching. In step 225, a flash process is performed to remove the etching byproducts 230-1. As further shown, the flash process also removes portions of the etching mask layers 220A-1 and 220A-2.

[0037] In step 235, another dry etching process (similar to step 215) is used to remove other portions of target layer 210A. As a result of the dry etching process, etch byproducts 230-2 are formed on at least the sidewalls of etch mask layers 220A-1 and 220A-2. Although not shown, etch byproducts 230-2 may also form on the sidewalls of target layer 210A. In step 245, another flash process is performed to remove etch byproducts 230-1. As further shown, the flash process also removes other portions of etch mask layers 220A-1 and 220A-2.

[0038] The process of using dry etching to remove portions of the target layer 210A and then removing the resulting etch by-products can continue until the feature is complete. However, the process of removing the etch by-products can be time consuming and reduce throughput. Furthermore, the flash process removes portions of the etch mask, limiting the number of dry etch pulses / cycles that can be performed. Therefore, as described below with reference to FIG. 2B , embodiments described herein enable dry etching to be performed with self-cleaning of etch by-products.

[0039] 2B illustrates an example method 200B for performing dry etching with self-cleaning of etch by-products, according to some embodiments. First, a base structure is provided that includes a target layer 210B and etch mask layers 220B-1 and 220B-2 disposed on the target layer 210B.

[0040] Target layer 210B can include any suitable material. In some embodiments, target layer 210B includes a polymer. In some embodiments, target layer 210B is a hard mask. In some embodiments, target layer 210B is a photoresist. For example, target layer 210B is a hard mask disposed on a dielectric layer (e.g., oxide). In some embodiments, target layer 210B includes carbon. For example, target layer 210B includes amorphously deposited carbon, spin-on carbon, CVD deposited carbon, etc.

[0041] Etch mask layers 220B-1 and 220B-2 may comprise any suitable material that enables formation of features from the target layer during dry etching using thionyl chloride. In some embodiments, etch mask layers 220B-1 and 220B-2 are silicon-containing etch mask layers. For example, etch mask layers 220B-1 and 220B-2 may comprise SiON. In some embodiments, etch mask layers 220B-1 and 220B-2 are boron-containing etch mask layers. For example, etch mask layers 220B-1 and 220B-2 may comprise BN.

[0042] In some embodiments, the target layer 210B can have a thickness that enables the formation of high aspect ratio features. In some embodiments, the thickness of the target layer 210B ranges from about 2 micrometers (μm) to about 20 μm. In some embodiments, the thickness of the target layer 210B ranges from about 3 μm to about 10 μm. In some embodiments, the thickness of the target layer 210B ranges from about 4 μm to about 6 μm.

[0043] In some embodiments, a high aspect ratio feature may have a height-to-width ratio of about 40:1 or greater. In some embodiments, a high aspect ratio feature may have a height-to-width ratio of about 50:1 or greater. In some embodiments, a high aspect ratio feature may have a height-to-width ratio of about 60:1 or greater. For example, the length of the feature may be about 1000 nm and the width of the feature may be about 16 nm (e.g., an aspect ratio of about 62.5:1).

[0044] Features formed from a target layer according to embodiments described herein can include any suitable width (e.g., critical dimension). In some embodiments, the width of the features can be about 50 nanometers (nm) or less. In some embodiments, the width of the features can be about 40 nm or less. In some embodiments, the width of the features can be about 30 nm or less. In some embodiments, the width of the features can be about 20 nm or less.

[0045] In step 255, portions of target layer 210B are removed using dry etching to form features. Examples of dry etching include plasma etching, ion beam milling, RIE, etc. For example, the dry etching may include a suitable number of dry etching processes (e.g., dry etching pulses / cycles). More specifically, the portions of target layer 210B are in areas not protected by etch mask layers 220B-1 and 220B-2.

[0046] The dry etch may utilize at least one process gas capable of removing etch byproducts. More specifically, the at least one process gas may include thionyl chloride. In some embodiments, the process gas is provided in a gas mixture further including at least one carrier gas. More specifically, the at least one carrier gas may include at least one inert gas. For example, the at least one carrier gas may include a noble gas (e.g., He, Ar, Ne, Xe, Kr, Rn). In some embodiments, the process gas is provided without a carrier gas. For example, the process gas may be provided via a heated gas line.

[0047] Thionyl chloride can enable self-cleaning of etch by-products that form on the sidewalls of the etch mask and / or target layer. For example, if the target layer contains H (e.g., a material containing C and H), thionyl chloride can capture H from the target layer and form HCl. The HCl can clean the etch by-products and smooth the etch front. Thus, embodiments described herein can reduce (e.g., eliminate) the number of flush processes that need to be performed to remove etch by-products from the sidewalls of the etch mask and / or target layer.

[0048] Furthermore, thionyl chloride can induce chemisorption (i.e., chemical absorption) on the surface of the sidewalls of features formed from the target layer, improving surface roughness and passivating the surface of the sidewalls of the features. For example, if the target layer contains carbon, S from thionyl chloride can react with C from the target layer to form a passivation layer containing Cs2 on the surface of the sidewalls of the features. Improved smoothness can improve the roundness of the surface resulting from dry etching, such as dry etching performed at temperatures below 0°C. Therefore, sidewall passivation can be achieved during dry etching with a thionyl chloride gas mixture without the use of additional passivation gases such as COS or SO2. Therefore, improved etch profiles can be achieved by performing dry etching using the thionyl chloride gas mixtures described herein.

[0049] Dry etching can be performed at any suitable temperature. In some embodiments, dry etching is performed at a temperature of 0° C. or less. For example, dry etching can be performed at a temperature below about 0° C. As another example, dry etching can be performed at a temperature of about −10° C. or less. As another example, dry etching can be performed at a temperature of about −20° C. or less. As another example, dry etching can be performed at a temperature of about −30° C. or less. As yet another example, dry etching can be performed at a temperature of about −40° C. or less. As yet another example, dry etching can be performed at a temperature of about −50° C. or less. As yet another example, dry etching can be performed at a temperature of about −60° C. or less. As yet another example, dry etching can be performed at a temperature of about −70° C. or less. As yet another example, dry etching can be performed at a temperature of about −80° C. or less. As yet another example, dry etching can be performed at a temperature of about −90° C. or less. When a carrier gas is included in the gas mixture with the process gas, the carrier gas can drive the process gas flow into the etching chamber at a normal rate and prevent condensation of the thionyl gas at temperatures below 0° C. In some embodiments, dry etching is performed at a temperature of 0° C. or more. For example, dry etching can be performed at a temperature above about 0° C.

[0050] In contrast to method 200A of FIG. 2A, the number of flush processes is reduced to remove etch by-products from the sidewalls of target layer 210B and / or the sidewalls of etch mask layers 220B-1 and 220B-2. In some embodiments, no flush process needs to be performed to remove etch by-products. More details regarding performing dry etching with self-cleaning of etch by-products are described below with reference to FIG. 3.

[0051] 3 is a diagram 300 of an example method for performing a dry etch with self-cleaning of etch by-products, according to some embodiments. As shown, a base structure 305 is provided. The base structure 350 includes a layer 310, a target layer 320 disposed on the layer 310, an etch mask 330, a BARC layer 340 disposed on the etch mask 330, and a photoresist 350 disposed on the BARC layer 340.

[0052] Layer 310 can include any suitable material. In some embodiments, layer 310 includes a dielectric material. For example, layer 310 can include an oxide (e.g., a metal oxide).

[0053] Target layer 320 can include any suitable material. In some embodiments, target layer 320 includes a polymer. In some embodiments, target layer 320 is a hard mask. In some embodiments, target layer 320 is a photoresist. For example, target layer 320 can be disposed on a dielectric layer (e.g., an oxide). In some embodiments, target layer 320 includes carbon. For example, target layer 320 can include amorphously deposited carbon, spin-on carbon, CVD deposited carbon, etc.

[0054] In some embodiments, the target layer 320 can have a thickness that enables the formation of high aspect ratio features and / or features with sufficiently narrow widths. In some embodiments, the thickness of the target layer 320 ranges from about 2 micrometers (μm) to about 20 μm. In some embodiments, the thickness of the target layer 320 ranges from about 3 μm to about 10 μm. In some embodiments, the thickness of the target layer 320 ranges from about 4 μm to about 6 μm.

[0055] In some embodiments, high aspect ratio features may have a height-to-width ratio of about 30:1 or greater. In some embodiments, high aspect ratio features may have a height-to-width ratio of about 40:1 or greater. In some embodiments, high aspect ratio features may have a height-to-width ratio of about 50:1 or greater. In some embodiments, high aspect ratio features may have a height-to-width ratio of about 60:1 or greater. For example, the length of the feature may be about 1000 nm and the width of the feature may be about 16 nm (e.g., an aspect ratio of about 62.5:1).

[0056] Etch mask 330 may comprise any suitable material capable of forming features from the target layer during dry etching using thionyl chloride. In some embodiments, etch mask 330 is a silicon-containing etch mask. For example, etch mask 330 may comprise SiON. In some embodiments, etch mask 330 is a boron-containing etch mask. For example, etch mask 330 may comprise BN. BARC layer 340 may comprise any suitable ARC material. In some embodiments, photoresist 350 is a positive photoresist. In some embodiments, photoresist 350 is a negative photoresist.

[0057] Dry etching can be performed in step 360. For example, dry etching can include plasma etching, ion beam milling, RIE, etc. At least one process gas can be used to perform the dry etching. More specifically, the at least one process gas can include thionyl chloride. In some embodiments, the process gas is delivered in a gas mixture further including at least one carrier gas. More specifically, the at least one carrier gas can include at least one inert gas. For example, the at least one carrier gas can include a noble gas (e.g., He, Ar, Ne, Xe, Kr, Rn). In some embodiments, the process gas is delivered without a carrier gas. For example, the process gas is delivered via a heated gas line.

[0058] The dry etch performed in step 360 forms multiple features 370 having sidewalls 375 and multiple openings 380, each separating a pair of features 370. As further shown, portions of layer 310 are removed during the dry etch to form surface 385. More specifically, features 370 are high aspect ratio features and / or have sufficiently small widths. For example, each of features 370 may have a height-to-width ratio of about 100:1 or greater.

[0059] The dry etch can be performed at any suitable temperature. In some embodiments, the dry etch is performed at a temperature of 0° C. or less. For example, the dry etch can be performed at a temperature below about 0° C. As another example, the dry etch can be performed at a temperature of about −10° C. or less. As another example, the dry etch can be performed at a temperature of about −20° C. or less. As another example, the dry etch can be performed at a temperature of about −30° C. or less. As yet another example, the dry etch can be performed at a temperature of about −40° C. or less. As yet another example, the dry etch can be performed at a temperature of about −50° C. or less. As yet another example, the dry etch can be performed at a temperature of about −60° C. or less. As yet another example, the dry etch can be performed at a temperature of about −70° C. or less. As yet another example, the dry etch can be performed at a temperature of about −80° C. or less. As yet another example, the dry etch can be performed at a temperature of about −90° C. or less. When a carrier gas is included in the gas mixture with the process gas, the carrier gas can drive the process gas flow into the etch chamber at a normal rate and prevent condensation of the thionyl gas at temperatures below 0° C. In some embodiments, the dry etch is performed at a temperature of 0° C. or greater. For example, the dry etch can be performed at a temperature above about 0°C.

[0060] The use of thionyl chloride during dry etching allows for self-cleaning of etch by-products that form on the sidewall 375. For example, if the target layer 320 contains hydrogen (e.g., a material containing carbon and hydrogen), hydrogen is removed from the target layer 320, forming HCl. HCl can clean the etch by-products and smooth the etch front. Furthermore, thionyl chloride can induce chemisorption (i.e., chemical absorption) on the surface of the sidewall 375, thereby improving surface roughness and passivating the surface of the sidewall 375. For example, if the target layer 320 contains carbon, sulfur from the thionyl chloride can react with carbon from the target layer 320 to form a passivation layer containing CS2 on the surface of the sidewall 375. The improved smoothness can improve the roundness of the surface 385 produced by dry etching, such as dry etching performed at temperatures below 0°C. Therefore, sidewall passivation can be achieved during dry etching with a thionyl chloride gas mixture without the use of additional passivation gases such as COS or SO2. Therefore, performing a dry etch using the thionyl chloride gas mixture described herein can improve the etch profile. Further details regarding improving the circularity of surface 385 are described below with reference to Figures 4A-4B.

[0061] FIG. 4A is a diagram 400A of an example bottom critical dimension profile resulting from plasma etching without the use of thionyl chloride. FIG. 4B is a diagram 400B of an example method of performing dry etching with self-cleaning etch byproducts using thionyl chloride, according to some embodiments. More specifically, FIG. 400A shows the underside profile of multiple openings (e.g., vias) including opening 410A, and FIG. 400B shows the underside profile of multiple openings including opening 410B. For example, opening 410B may be similar to opening 380 of lower profile 390-2 described above with reference to FIG. 3. Opening 410B formed according to the method described above with reference to FIGS. 2-3 exhibits improved circularity and an improved etch profile compared to opening 410A.

[0062] 5 is a flowchart of an exemplary method 500 for performing a dry etch with self-cleaning of etch by-products, according to some embodiments. For example, method 500 can be performed using an etch chamber such as etch chamber 100 described above with reference to FIG.

[0063] In block 510, a base structure including a target layer is provided. For example, the base structure is received by a substrate support assembly of an etch chamber to hold the base structure. The target layer can have a thickness that enables the formation of high aspect ratio features and / or features with sufficiently narrow widths. In some embodiments, the high aspect ratio features may have a height-to-width ratio of about 30:1 or greater. In some embodiments, the high aspect ratio features may have a height-to-width ratio of about 40:1 or greater. In some embodiments, the high aspect ratio features may have a height-to-width ratio of about 50:1 or greater. In some embodiments, the high aspect ratio features may have a height-to-width ratio of about 60:1 or greater. For example, the feature length may be about 1000 nm and the feature width may be about 16 nm (e.g., an aspect ratio of about 62.5:1).

[0064] More specifically, the base structure can include an etch mask disposed on a target layer. In some embodiments, the target layer includes a polymer. In some embodiments, the target layer includes a polymer. In some embodiments, the target layer is a hard mask. In some embodiments, the target layer is a photoresist. For example, the target layer can be disposed on a dielectric layer (e.g., an oxide). In some embodiments, the target layer includes carbon. For example, the target layer can include amorphously deposited carbon, spin-on carbon, CVD deposited carbon, etc.

[0065] The etch mask may comprise any suitable material capable of forming features from the target layer during dry etching using thionyl chloride. In some embodiments, the etch mask is a silicon-containing etch mask. For example, the etch mask may comprise SiON. In some embodiments, the etch mask is a boron-containing etch mask. For example, the etch mask may comprise BN. In some embodiments, the etch mask is included in an etch mask stack that includes an etch mask disposed on the BARC layer. In some embodiments, providing the base structure includes forming an etch mask stack on the target layer. The BARC layer may comprise any suitable ARC material. In some embodiments, the photoresist is a positive photoresist. In some embodiments, the photoresist 350 is a negative photoresist.

[0066] At block 520, the target layer is dry etched using at least one process gas comprising thionyl chloride to obtain a processed base structure. In some embodiments, the at least one process gas is supplied in a gas mixture further comprising at least one carrier gas. In some embodiments, the at least one process gas is supplied without a carrier gas. For example, the at least one process gas may be supplied via a heated gas line. Dry etching the target layer may include bringing an etch chamber to a target temperature and pressure. More specifically, one or more heating elements and pumps may be used to bring the etch chamber to the target temperature and pressure. In some embodiments, the pressure of the etch chamber may be between about 0.1 mTorr and about 500 mTorr, between about 1 mTorr and about 400 mTorr, between about 5 mTorr and about 300 mTorr, between about 10 mTorr and about 200 mTorr, between about 25 mTorr and about 100 mTorr, or between about 1 mTorr and about 100 mTorr, or any subrange or value described herein. In some embodiments, the temperature of the etch chamber may be at or below 0°C. For example, dry etching can be performed at a temperature below about 0°C. As another example, dry etching can be performed at a temperature of about -10°C or less. As another example, dry etching can be performed at a temperature of about -20°C or less. As another example, dry etching can be performed at a temperature of about -30°C or less. As yet another example, dry etching can be performed at a temperature of about -40°C or less. As yet another example, dry etching can be performed at a temperature of about -50°C or less. As yet another example, dry etching can be performed at a temperature of about -60°C or less. As yet another example, dry etching can be performed at a temperature of about -70°C or less. As yet another example, dry etching can be performed at a temperature of about -80°C or less. As yet another example, dry etching can be performed at a temperature of about -90°C or less.When a carrier gas is included in the gas mixture with the process gas, the carrier gas can drive the process gas flow into the etching chamber at a normal rate and prevent condensation of the thionyl gas at temperatures below 0° C. In some embodiments, the temperature of the etching chamber can be at a temperature above 0° C. (e.g., a temperature greater than about 0° C.).

[0067] Furthermore, dry etching the target layer can include performing a dry etching process on the base structure. Examples of dry etching processes include plasma etching, ion beam milling, RIE, etc. For example, the dry etching process can include multiple dry etching pulses or cycles. Performing the dry etching process can include forming a plasma from a gas mixture including thionyl chloride. In some embodiments, the gas mixture includes at least one additional process gas. In some embodiments, the gas mixture includes at least one carrier gas. More specifically, the at least one carrier gas can include at least one inert gas (e.g., at least one noble gas). In some embodiments, the at least one carrier gas includes Ar.

[0068] The total gas supply flow rate of the gas mixture can be any suitable total gas supply flow rate according to embodiments described herein, hi some embodiments, the total gas supply flow rate of the gas mixture is between about 50 standard cubic centimeters per minute (sccm) and about 2000 sccm, between about 100 sccm and about 1500 sccm, between about 150 sccm and about 1250 sccm, between about 200 sccm and about 1000 sccm, between about 250 sccm and about 750 sccm, or any subrange or value described herein. In some embodiments, the amount of thionyl chloride in the total gas feed stream is about 5 mol% to about 80 mol%, about 5 mol% to about 70 mol%, about 5 mol% to about 60 mol%, about 5 mol% to about 50 mol%, about 5 mol% to about 40 mol%, about 10 mol% to about 80 mol%, about 10 mol% to about 70 mol%, about 20 mol% to about 70 mol%, about 20 mol% to about 60 mol%, about 30 mol% to about 50 mol%, or any subrange or value described herein. In some embodiments, the amount of carrier gas in the total gas feed stream can be about 5 mol% to about 15 mol%, about 7.5 mol% to about 12.5 mol%, or about 9 mol% to about 11 mol%, or any subrange or value described herein.

[0069] Performing the dry etching process includes applying a bias power to the base structure to achieve a bias condition. Any suitable bias power can be applied according to embodiments described herein. In some embodiments, the bias power is about 10 watts (W) to about 5,000 W, about 200 W to about 2,000 W, about 300 W to about 3,000 W, about 400 W to about 2,500 W, about 500 W to about 2,000 W, about 600 W to about 1,500 W, or about 750 W to about 1,250 W, or any subrange or value described herein. A higher bias power can produce a straighter profile (e.g., a more vertical trench sidewall profile), reduce profile curvature, and lower selectivity to the patterned mask. The bias power can be a time-averaged power.

[0070] The bias frequency can be any suitable frequency according to embodiments described herein, hi some embodiments, the bias frequency is about 400 kilohertz (kHz) to about 60 megahertz (MHz), about 400 kHz to about 40 MHz, about 400 kHz to about 35 MHz, about 400 kHz to about 27 MHz, about 400 kHz to about 20 MHz, or about 800 kHz to about 10 MHz, or any subrange or value described herein.

[0071] The bias power can be applied for any suitable time period according to the embodiments described herein, hi some embodiments, the bias power is applied for about 10 μs to about 1 ms, about 30 μs to about 1 ms, about 50 μs to about 1 ms, about 70 μs to about 1 ms, or about 85 μs to about 1 ms, or any subrange or value described herein.

[0072] After terminating the bias power, performing the dry etching process can further include applying source power to achieve a source state. Any suitable source power can be applied according to embodiments described herein. In some embodiments, the source power is between about 10 W and about 5,000 W, between about 200 W and about 2,000 W, between about 300 W and about 3,000 W, between about 400 W and about 2,500 W, between about 500 W and about 2,000 W, between about 600 W and about 1,500 W, or between about 750 W and about 1,250 W, or any subrange or value described herein. The source power can be the time-averaged source power (e.g., source power x duty cycle).

[0073] The source frequency can be any suitable frequency according to embodiments described herein, hi some embodiments, the source frequency is between about 10 MHz and about 15 MHz, or about 13 MHz, or any subrange or value described herein.

[0074] The source power can be applied for any suitable time period according to embodiments described herein, hi some embodiments, the source power can be applied for about 10 μs to about 1 ms, about 30 μs to about 1 ms, about 50 μs to about 1 ms, about 70 μs to about 1 ms, or about 85 μs to about 1 ms, or any subrange or value described herein.

[0075] In some embodiments, the ratio of the first time interval to the second time interval is about 1:10 to about 10:1, about 1:9 to about 9:1, about 1:8 to about 8:1, about 1:7 to about 7:1, about 1:6 to about 6:1, about 1:5 to about 5:1, about 1:4 to about 4:1, about 1:3 to about 3:1, about 1:2 to about 2:1, or about 1:1, or any subrange or value described herein.

[0076] Dry etching of the target layer includes determining whether a target amount of material has been removed from the target layer. If the target amount of material has not been removed from the target layer, another dry etching cycle or pulse can be performed. If the target amount of material has been removed from the target layer, the dry etching is complete.

[0077] For example, determining whether a target amount of material has been removed from the target layer may include checking whether the target amount of material has been removed from the target layer after each dry etching cycle or pulse. Additionally or alternatively, determining whether the target amount of material has been removed from the target layer may include determining whether the time the dry etching was performed satisfies a threshold condition according to the etching recipe (e.g., is equal to or greater than a target time defined by the etching recipe). If the amount of time does not satisfy the threshold condition (e.g., the dry etching has not been performed for the target time), it is possible that the target amount of material has not yet been removed from the target layer. If the amount of time satisfies the threshold condition (e.g., the dry etching has been performed for the target time), it is likely that the target amount of material has been removed from the target layer.

[0078] In some embodiments, the target layer can have dimensions (e.g., thickness and width) that enable the formation of high aspect ratio features. Aspect ratio refers to the ratio of the feature height to the feature width (e.g., critical dimension). Features can have any suitable aspect ratio according to embodiments described herein. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 30:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 40:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 50:1 or greater. In some embodiments, high aspect ratio features can have a height-to-width ratio of about 60:1 or greater. For example, the feature length can be about 1000 nanometers (nm) and the feature width can be about 16 nm (aspect ratio of about 62.5:1).

[0079] Features formed from the target layer can have any suitable width according to the embodiments described herein. In some embodiments, the feature width may be about 50 nm or less. In some embodiments, the feature width may be about 40 nm or less. In some embodiments, the feature width may be about 30 nm or less. In some embodiments, the feature width may be about 20 nm or less.

[0080] Thionyl chloride can enable self-cleaning of etch byproducts formed on the sidewalls of an etch mask and / or the sidewalls of features formed from the target layer. For example, if the target layer contains H (e.g., a material containing C and H), it can scavenge H from the target layer to form HCl. HCl can clean the etch byproducts and smooth the exposed surface. Furthermore, thionyl chloride can induce chemisorption (i.e., chemical absorption) on the surface of the sidewalls of features formed from the target layer, thereby improving surface quality (e.g., removing surface roughness) and passivating the surface of the sidewalls of the feature. For example, if the target layer is a carbon layer, S from thionyl chloride can react with C from the target layer to form a passivation layer containing CS2 on the surface of the sidewalls of the feature. The presence of the passivation layer reduces etching of the passivated surface and reduces the roughness of the passivated surface. Improved smoothness can improve the roundness of surfaces produced by dry etches, such as dry etches performed at temperatures below 0°C. Therefore, the dry etch performed in block 520 using the thionyl chloride gas mixture can achieve sidewall passivation without the use of additional passivation gases such as COS or SO. Therefore, performing the dry etch in block 520 using the thionyl chloride gas mixture can improve the etch profile.

[0081] After the dry etching is completed (e.g., after it is determined that a desired amount of material has been removed from the target layer), the processed base structure can be removed at block 530. For example, the processed base structure can be provided to another processing chamber or an etching chamber for further device processing.

[0082] The foregoing description provides numerous specific details, such as examples of particular systems, components, methods, etc., to provide a thorough understanding of some embodiments of the present disclosure. However, it will be apparent to those skilled in the art that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods have not been described in detail or have been shown in simple block diagram form in order to avoid unnecessarily obscuring the present disclosure. Thus, the specific details described are merely examples. Particular embodiments may vary from these example details and still be considered within the scope of the present disclosure.

[0083] References throughout this specification to "one embodiment" or "embodiments" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the use of the phrase "embodiment" or "some embodiments" in various places throughout this specification do not necessarily all refer to the same embodiments. Furthermore, the term "or" means an inclusive "or" rather than an exclusive "or." When the term "about" or "approximately" is used herein, this means that the stated nominal value is accurate to within ±10%.

[0084] Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be changed so that certain operations are performed in reverse order, or so that certain operations are performed at least in part concurrently with other operations. In other embodiments, instructions or sub-operations of separate operations may be performed intermittently and / or interleaved.

[0085] It should be understood that the above description is intended to be illustrative, and not limiting. Many other embodiments will become apparent to those skilled in the art upon reading and understanding the above description. Accordingly, the scope of the disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. providing a base structure in an etching chamber, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer, the target layer comprising carbon; dry etching the target layer in an etching chamber using thionyl chloride to obtain a processed base structure including a plurality of features and a plurality of openings defined by the etching mask; The method includes removing the processed base structure from the etching chamber.

2. The method of claim 1 , wherein the substrate includes a dielectric layer and the target layer is disposed directly on the dielectric layer.

3. 10. The method of claim 1, wherein the step of providing a base structure comprises forming an etch mask stack on the target layer, the etch mask stack comprising an etch mask disposed on a bottom antireflective coating (BARC) layer.

4. The method of claim 1 , wherein each feature of the plurality of features is a high aspect ratio feature.

5. The method of claim 4 , wherein each feature of the plurality of features has an aspect ratio of 60:1 or greater.

6. The method of claim 1 , wherein the etch mask comprises at least one of silicon oxynitride or boron nitride.

7. The method of claim 1 , wherein the target layer is a hard mask.

8. providing a base structure in an etching chamber, the base structure including a target layer disposed on a substrate and an etching mask disposed on the target layer; dry etching the target layer in an etching chamber using thionyl chloride at a temperature below 0°C to obtain a processed base structure, the processed base structure including a plurality of features and a plurality of openings defined by the etching mask; The method includes removing the processed base structure from the etching chamber.

9. The method of claim 8 , wherein the substrate includes a dielectric layer and the target layer is disposed directly on the dielectric layer.

10. 10. The method of claim 8, wherein providing the base structure comprises forming an etch mask stack on the target layer including an etch mask, the etch mask stack including an etch mask disposed on a bottom antireflective coating (BARC) layer.

11. The method of claim 8 , wherein each feature of the plurality of features is a high aspect ratio feature.

12. The method of claim 11 , wherein each feature of the plurality of features has an aspect ratio of 60:1 or greater.

13. 9. The method of claim 8, wherein the temperature of 0°C or less is about -10°C or less.

14. The method of claim 8 , wherein the etch mask comprises at least one of silicon oxynitride or boron nitride.

15. 1. An etching chamber comprising: a gas panel for supplying thionyl chloride; a substrate support assembly for holding a base structure, the base structure comprising a target layer disposed on a substrate and an etching mask disposed on the target layer, the target layer comprising carbon; An etching chamber comprising a showerhead with a plurality of gas supply holes for dry etching a target layer using thionyl chloride to obtain a processed base structure, the processed base structure including a plurality of features and a plurality of openings formed by an etching mask.

16. 16. The etch chamber of claim 15, wherein the substrate includes a dielectric layer and the target layer is disposed directly on the dielectric layer.

17. 16. The etching chamber of claim 15, wherein obtaining the base structure comprises receiving the base structure from a transfer robot, the base structure comprising an etch mask stack comprising an etch mask disposed on a bottom antireflective coating (BARC) layer.

18. 16. The etch chamber of claim 15, wherein each feature of the plurality of features has an aspect ratio of 60:1 or greater.

19. 16. The etch chamber of claim 15, wherein dry etching the target layer comprises performing the dry etch at a temperature of 0° C. or less.

20. 16. The etch chamber of claim 15, wherein the etch mask comprises at least one of silicon oxynitride or boron nitride.

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