Performing atomic layer etch using silane-based chemicals

Abstract

Examples disclosed relate to atomic layer etching using a silane-based volatile compound. One example proposes a method for performing atomic layer etching on a substrate. The method includes performing a plurality of atomic layer etch cycles. An atomic layer etch cycle of the plurality of atomic layer etch cycles includes exposing a substrate including a metal oxide surface to a fluorinating agent, wherein the exposure of the metal oxide surface forms a fluorinated metal oxide surface. The atomic layer etch cycle further includes exposing the fluorinated metal oxide surface of the substrate to a silane-based volatile compound, the silane-based volatile compound including at least one non-fluoride, non-chloride halide ligand, wherein the exposure of the fluorinated metal oxide surface forms a volatile product.

Description

BACKGROUND

[0001] Semiconductor device fabrication processes can involve many steps of material deposition, patterning, and removal to form integrated circuits on a substrate. Various methods can be used to selectively remove a material film from a substrate. As an example, atomic layer etching (ALE) can be used to remove substrate material layer-by-layer using etching cycles. In an atomic layer etching cycle, a modification step is used to modify material at a substrate surface. Then, a volatilization step volatilizes and removes the modified material. Using one or more atomic layer etching cycles can achieve a highly uniform etch. SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all of the problems mentioned in any part of this disclosure.

[0003] Disclosed examples involve the use of silane-based volatile compounds in atomic layer etching. One example presents a method for performing atomic layer etching, the method comprising performing a plurality of atomic layer etching cycles. An atomic layer etching cycle of the plurality of atomic layer etching cycles comprises exposing a substrate comprising a metal oxide surface to a fluorinating agent, wherein the exposing of the metal oxide surface forms a fluorinated metal oxide surface. The atomic layer etching cycle further comprises exposing the fluorinated metal oxide surface of the substrate to a silane-based volatile compound comprising at least one non-fluoride, non-chloride halide ligand, wherein the exposing of the fluorinated metal oxide surface forms a volatile product.

[0004] In some such examples, the silane-based volatile compound comprises one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibromobutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

[0005] Additionally or alternatively, in some such examples, the substrate is disposed in a process chamber, and the atomic layer etch cycle further includes purging the process chamber after exposing the substrate to the fluorination agent.

[0006] Additionally or alternatively, in some such examples, the method further includes heating the substrate to a temperature in a range from 175 °C to 650 °C while performing the plurality of atomic layer etch cycles.

[0007] Additionally or alternatively, in some such examples, the fluorination agent includes one or more of molecular fluorine, hydrogen fluoride, nitrogen trifluoride, xenon difluoride, sulfur tetrafluoride, or sulfur hexafluoride.

[0008] Additionally or alternatively, in some such examples, the method additionally or alternatively includes forming a plasma to form a reactive fluorine-containing species from the fluorination agent.

[0009] Additionally or alternatively, in some such examples, the method is additionally or alternatively performed in a cold-wall reactor.

[0010] Additionally or alternatively, in some such examples, the exposing of the fluorinated metal oxide surface to the silane-based volatile compound includes performing a ligand exchange, thereby brominating or iodinating the metal oxide surface.

[0011] Another example provides an atomic layer etch tool for performing atomic layer etching on a substrate, the atomic layer etch tool including a process chamber. The atomic layer etch tool further includes a substrate support disposed within the process chamber. The atomic layer etch tool further includes a substrate heater disposed within the process chamber. The atomic layer etch tool further includes flow control hardware configured to control gas flow from a fluorination agent source and a volatile compound source to the process chamber. The atomic layer etch tool further includes a controller operatively coupled to the flow control hardware and the substrate heater. The controller is configured to operate the substrate heater to heat the substrate. The controller is further configured to operate the flow control hardware to introduce a fluorination agent into the process chamber in a modification step. The controller is further configured to operate the flow control hardware to introduce a silane-based volatile compound into the process chamber in a volatilization step. The silane-based volatile compound includes at least one non-fluorinated, non-chlorinated halide ligand.

[0012] Additionally or alternatively, in some such examples, the atomic layer etch tool further includes an exhaust system, and wherein the controller is further configured to operate the flow control hardware and the exhaust system to purge the process chamber after the modification step.

[0013] Additionally or alternatively, in some such examples, the atomic layer etching tool further comprises the volatile compound source, wherein the volatile compound source comprises one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

[0014] Additionally or alternatively, in some such examples, the atomic layer etching tool further comprises the fluorinating agent source. The fluorinating agent source comprises one or more of molecular fluorine, hydrogen fluoride, nitrogen trifluoride, xenon difluoride, sulfur tetrafluoride, or sulfur hexafluoride.

[0015] Additionally or alternatively, in some such examples, the controller is configured to operate the substrate heater to heat to a temperature in a range of 175 °C to 650 °C during the modification step and the volatilization step.

[0016] Additionally or alternatively, in some such examples, during processing, walls of the processing chamber are at a lower temperature than the substrate heater.

[0017] Additionally or alternatively, in some such examples, the controller is configured to perform a plurality of atomic layer etching cycles. Each atomic layer etching cycle of the plurality of atomic layer etching cycles comprises the modification step and the volatilization step.

[0018] Additionally or alternatively, in some such examples, the atomic layer etching tool further comprises a remote plasma generator. The controller is configured to operate the remote plasma generator to generate reactive fluorine-containing species.

[0019] Another example presents a method of implementing atomic layer etching. The method includes heating, in a cold-wall reactor, a substrate comprising a metal oxide surface. The method also includes performing a plurality of atomic layer etching cycles while heating the substrate. An atomic layer etching cycle of the plurality of atomic layer etching cycles includes exposing the substrate to a fluorinating agent, wherein the exposing of the metal oxide surface forms a fluorinated metal oxide surface. The atomic layer etching cycle includes exposing the fluorinated metal oxide surface of the substrate to a volatile compound comprising at least one non-fluoride halide ligand, wherein the exposing of the fluorinated metal oxide surface forms a volatile product. The volatile compound is aluminum-free.

[0020] Additionally or alternatively, the non-fluoride halide ligand comprises a non-fluoride, non-chloride halide ligand.

[0021] Additionally or alternatively, in some such examples, the volatile compound comprises a silane-based volatile compound comprising one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibromobutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

[0022] Additionally or alternatively, in some such examples, heating the substrate includes heating the substrate to a temperature in a range of 175 °C to 650 °C during the modifying step and the volatilizing step. BRIEF DESCRIPTION OF DRAWINGS

[0023] FIGS. 1A-1C schematically show a substrate structure formed in an atomic layer etching (ALE) process using dimethylammonium chloride as a volatile compound.

[0024] FIGS. 2A-2C schematically show growth of aluminum fluoride deposits on a chamber wall resulting from the ALE process of FIGS. 1A-1C.

[0025] FIG. 3 shows a flowchart depicting an example method of implementing an ALE process using a silane-based volatile compound.

[0026] FIGS. 4A-4E schematically show a substrate structure formed in an exemplary ALE process utilizing a silane-based volatile compound.

[0027] FIGS. 5A-5C schematically show exemplary chemical processes occurring on a process chamber wall during the ALE process of FIGS. 4A-4E.

[0028] FIG. 6 shows a block diagram of an exemplary ALE tool.

[0029] FIG. 7 shows a block diagram of an exemplary computing system. DETAILED DESCRIPTION

[0030] The term "aspect ratio" generally refers to the ratio between a depth or height of a substrate feature and a width of the substrate feature.

[0031] The term "atomic layer etching" (ALE) generally refers to a process that removes material from a substrate layer-by-layer using an etch cycle ("ALE cycle"). An ALE cycle includes a modification step in which a layer of material on a substrate surface is exposed to a modification compound in a self-limiting reaction to form a modified layer. An ALE cycle also includes a volatilization step in which the modified layer is removed from the substrate by exposure to a volatile compound.

[0032] The term "cold-wall reactor" generally refers to a process chamber having walls that are not actively heated during substrate processing.

[0033] The term "etchable material" generally refers to a substrate surface that can be modified and volatilized in an ALE process.

[0034] The term "feature" generally refers to a topographical structure on a substrate surface.

[0035] The term "ligand" generally refers to a functional group that binds to a metal atom through a coordinate bond.

[0036] The term "ligand exchange" generally refers to a chemical reaction in which a ligand bound to a metal atom is replaced by a different ligand.

[0037] The term "modification compound" generally refers to a chemical species that is used as part of an ALE cycle to chemically alter a substrate material surface so that it volatilizes. The term "fluorinating agent" generally refers to a modification compound used to fluorinate a substrate material surface. Exemplary fluorinating agents include molecular fluorine (F2), hydrogen fluoride (HF), xenon difluoride (XeF2), nitrogen trifluoride (NF3), sulfur tetrafluoride (SF4), and sulfur hexafluoride (SF6).

[0038] The term "plasma" can generally mean a gas containing ions and free electrons. Plasma can be used to generate reactive chemical species from precursor molecules introduced into the plasma. The term "remote plasma" can generally mean a plasma located away from a substrate being processed.

[0039] The term "processing chamber" can generally mean a housing in which chemical and / or physical processing is performed on a substrate. Pressure, temperature, and gas composition within a processing chamber can be controllable to perform chemical and / or physical processing.

[0040] The term "processing tool" can generally mean a machine that includes a processing chamber and other hardware configured to implement processing to be performed on a substrate. The term "ALE tool" can generally mean a processing tool used to perform atomic layer etching.

[0041] The term "purge" and variants thereof can generally mean a process of at least partially removing unwanted species from a processing chamber.

[0042] The term "substrate" can generally mean any article from which layers of material can be etched.

[0043] The term "substrate support" can generally mean any structure used to support a substrate in a processing chamber.

[0044] The term "volatile compound" can generally mean a chemical species that can react with a modified substrate surface in an atomic layer etching process to volatilize the modified substrate surface. The term "silane-based volatile compound" means a volatile compound that includes silicon and one or more non-fluoride, non-chloride halide ligands that can be used in a ligand exchange reaction. The one or more non-fluoride, non-chloride halide ligands can include bromine for brominating a surface in a ligand exchange reaction. Additionally or alternatively, the one or more non-fluoride, non-chloride halide ligands can include iodine for iodinating a surface in a ligand exchange reaction. Examples of silane-based volatile compounds include volatile compounds having the general formula R a -Si-X 4-aalkylhalosilanes, where R represents an alkyl group (e.g., methyl, ethyl, propyl, t-butyl, pentyl, etc.) or hydrogen, X represents bromine or iodine, and a = 1 to 3. Examples include trimethylbromosilane (Me3SiBr, where Me represents a methyl group CH3) and trimethyliodosilane (Me3SiI). Examples also include tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, and tribromo(pent-2-yl)silane. In some examples, the silane-based volatile compound can have more than one silicon atom, such as 2,3-bis(bromomethylsilyl)butane (C4H8Br2Si2).

[0045] The term "3D NAND" is an acronym for three-dimensional NOT AND memory, and refers to a memory architecture based on NOT AND logic gates.

[0046] As described above, atomic layer etching (ALE) involves performing one or more ALE cycles to remove material from a substrate surface. During an ALE cycle, a modification step is performed in which a modification compound is introduced into a process chamber that includes the substrate. The modification compound reacts with the substrate surface to form a modified surface. For example, the substrate can be exposed to hydrogen fluoride (HF) or other fluorinating agent to form a fluorinated surface. Next, a volatilization step is performed in which a volatile compound is introduced into the process chamber. The volatile compound reacts with the modified surface to volatilize at least some of the modified substrate material. This removes material from the substrate surface. Repeat ALE cycles can be performed in which the modification compound coats the substrate surface, removing a selected amount of substrate material in a highly uniform manner.

[0047] ALE processing can be used to uniformly etch features in a substrate, including high aspect ratio features. One example process where uniform etching can be advantageous is the etching of oxide films within a channel hole in a 3D NAND memory fabrication process. A channel hole is a high aspect ratio recess formed through a stack of alternating material layers. An example stack of alternating material layers includes alternating silicon oxide / silicon nitride layers. In an example 3D NAND memory fabrication process, a film of oxide material is deposited on the sidewall surfaces in the channel hole. The film of oxide material is then etched to form a gate oxide structure. If the gate oxide thickness as a function of channel hole depth is not uniform, device performance can be impacted. For example, a gate oxide that is too thick can result in a high switching voltage. In addition, a gate oxide that is too thin can cause electrical shorts.

[0048] Accordingly, ALE can be used to form gate oxide structures with more uniform thickness as a function of depth. However, some ALE processes can form deposits on surfaces in the processing chamber of the processing tool. Such deposits can result in a risk of contaminating the substrate during processing. As an example of such processing, FIGS. 1A-1C depict an example ALE process using dimethylaluminum chloride (DMAC) as a volatile compound to etch a substrate. First, FIG. 1A shows an example processing chamber 100 including a wall 102. The wall 102 includes aluminum, such as anodized aluminum. A substrate 106 is disposed on a substrate support 108 within the processing chamber 100. The substrate 106 includes a metal oxide that is etched in the ALE process. Example metal oxides include hafnium oxide (Hf02, also known as hafnium dioxide), silicon-doped hafnium dioxide, hafnium silicate, hafnium zirconium oxide, tungsten oxide, aluminum oxide (AI2O3), zirconium oxide (Zr02), indium oxide, silicon dioxide, gallium oxide, zinc oxide, and indium gallium zinc oxide (InGaZnO).

[0049] FIG. IB also shows a modification step in which hydrogen fluoride (HF) 110 is introduced into the processing chamber 100 as a fluorinating agent. In other examples, different fluorinating agents can be used. Other example fluorinating agents can include molecular fluorine (F2), xenon difluoride (XeF2), nitrogen trifluoride (NF3), sulfur tetrafluoride (SF4), and sulfur hexafluoride (SF6). The metal oxide is fluorinated in a self-limiting reaction to form a fluorinated surface 112. The fluorinated surface 112 generally includes a surface region having the general composition of MFx, where M represents the metal component in the metal oxide. For example, hafnium oxide exposed to a fluorine-containing modification compound can result in HfF4. x O y 2y O 2-y .

[0050] ​Fluorination of metal oxides with hydrogen fluoride removes oxygen from the surface to produce water vapor (H2O), as shown in 114. The water vapor and excess fluorinating agent can be removed by purging the process chamber 100 after the modification step.

[0051] Figure 1C shows the introduction of DMAC 120 during the evaporation step of the ALE cycle. The DMAC reacts with the fluorinated surface 112 to form a volatile metal-containing species, thereby etching the substrate 106. The volatile metal-containing species is generally represented as MCl x F y 124. MCl x F y 124 is produced by fluorine-chlorine ligand exchange. Metal halide oxides can also be removed from the surface. For example, where the fluorinated surface includes HfF 2y O 2-y , the evaporation step can produce species including hafnium chloride (HfCl4), mixed chloride / fluoride (HfCl x F 4-x , x = 1-3), and / or hafnium chloride oxide (HfCl2O).

[0052] The volatile ligand exchange reaction can also produce a volatile aluminum-containing species, such as dimethyl aluminum fluoride 128. The volatile aluminum-containing species can cause aluminum fluoride to deposit as a solid residue on the process chamber walls. An example of such a process is shown schematically in Figures 2A-2C. As described above, during the modification step, HF 110 is introduced into the process chamber 100. Thus, the process chamber 100 walls are also exposed to the fluorinating agent. The enlarged view 200 of Figure 2A shows this process. The wall contains anodized aluminum with an aluminum oxide layer 202 at the interior surface of the process chamber. The HF 110 fluorinates the surface to form an aluminum fluoride layer 204.

[0053] Second, during the evaporation step of the ALE cycle, DMAC 120 is introduced into the process chamber. Figure 2B schematically shows an enlarged view 210 of the wall 102 after exposure to the DMAC 120. The DMAC reacts with the fluorinated surface to form adsorbed aluminum fluoride compounds 212 and produce HCl 214 as a byproduct.

[0054] Figure 2C shows an enlarged view 220 of the wall 102 after the modification step of a subsequent ALE cycle. The fluorinating agent HF 110 can react with the adsorbed aluminum fluoride compounds 212 to deposit an additional aluminum fluoride layer 222 on the aluminum fluoride layer 204. This process produces CH4 224 as a byproduct. Thus, through repeated ALE cycles, the aluminum fluoride layer 204 grows thicker.

[0055] Fluorided aluminum deposits can occur at temperatures of 175 °C or less. Such deposits can be difficult to remove from the chamber walls, resulting in machine downtime. While the fluorided aluminum deposits can be mitigated by heating the chamber walls to temperatures above 175 °C, aluminum oxide can be etched at temperatures above 175 °C. This can damage the processing chamber walls. Furthermore, heating the processing chamber walls can be expensive or infeasible for commercial scale reactors.

[0056] Accordingly, disclosed examples involve ALE processing that utilizes silane-based volatile compounds to avoid aluminum deposits on processing chamber walls. The ALE processing includes fluoridating a metal oxide surface to form a fluorided surface. The fluorided surface is then exposed to a silane-based volatile compound that includes bromine or iodine to exchange fluorine on the substrate surface for bromine or iodine. The disclosed example ALE processing avoids forming fluorided aluminum deposits on walls or other surfaces within the processing chamber.

[0057] In some examples, the silane-based volatile compounds can be used in thermal ALE processing. In thermal ALE, the substrate is heated to provide energy for the modification and volatilization reactions. In some examples, the substrate can be heated to a temperature in a range of 175 °C to 650 °C, inclusive. In other examples, temperatures outside of this range can be used. Thermal ALE can facilitate isotropically etching features, including high aspect ratio features with a depth-to-width ratio of 1 : 10 or more. The ALE processing can be performed in a cold wall reactor, where the processing chamber walls are at a lower temperature than the substrate being processed in the processing chamber.

[0058] FIG. 3 shows a flowchart of an example method 300 for performing ALE using silane-based volatile compounds. FIGS. 4A-4E schematically show example chemical processes that occur on a metal oxide surface during the method 300. The method 300 can be performed on any suitable material that can be etched in ALE processing. Examples include metal oxides such as hafnium oxide (hafnium dioxide, Hf02), silicon-doped hafnium dioxide, hafnium zirconium oxide, tungsten oxide, hafnium silicate, aluminum oxide (AI2O3), zirconium oxide (Zr02), indium oxide, silicon dioxide, gallium oxide, zinc oxide, and indium gallium zinc oxide (InGaZnO). The etchable materials can also include metalloids compounds. Example etchable metalloids include arsenides such as indium gallium arsenide (InGaAs) and indium aluminum arsenide (InAlAs). In some examples, the substrate includes features such as trenches, holes, or pillars. In some examples, the substrate can include one or more high aspect ratio features.

[0059] The method 300 includes, at 302, heating a substrate disposed in a processing chamber of a processing tool. In some examples, at 304, the method includes heating the substrate to a temperature in a range from 175 °C to 650 °C. In other examples, temperatures outside of this range can be used. In some examples, at 306, the processing chamber includes a cold-wall reactor. For example, the walls of the processing chamber can be below 175 °C during processing. In some such examples, the processing chamber walls are not heated.

[0060] Continuing, at 308, the method 300 includes performing a plurality of ALE cycles. One of the plurality of ALE cycles includes, at 310, exposing a metal oxide surface of the substrate to a fluorinating agent in a modification step to form a fluorinated metal oxide surface. Any suitable fluorinating agent can be used. In some examples, at 312, the fluorinating agent includes one or more of molecular fluorine, hydrogen fluoride, xenon difluoride, nitrogen trifluoride, sulfur tetrafluoride, or sulfur hexafluoride. Further, in some examples, at 314, the method includes forming a plasma to form reactive fluorine-containing species from the fluorinating agent. In some such examples, the fluorinating agent can be introduced into a remote plasma generator. The reactive fluorine-containing species formed in the remote plasma generator can then be introduced into the processing chamber to fluorinate the metal oxide surface. An example ALE tool including an optional remote plasma generator is described in more detail below.

[0061] The modification step at 310 is schematically shown in FIGS. 4A-4B. FIG. 4A shows a substrate 400 including a metal oxide layer 401. Examples of metal oxides include hafnium oxide, silicon-doped hafnium dioxide, hafnium zirconium oxide, tungsten oxide, hafnium silicate, aluminum oxide, zirconium oxide, indium oxide, silicon dioxide, gallium oxide, zinc oxide, and indium gallium zinc oxide. In other examples, the metal oxide layer 401 can include another material other than an oxide. Examples include a metalloid, such as indium gallium arsenide (InGaAs) and indium aluminum arsenide (InAlAs).

[0062] FIG. 4B shows the metal oxide layer 401 after a modification step 402 using HF 404 as the fluorinating agent. As a result, the metal oxide layer 401 is fluorinated to form a fluorinated surface 406 including MFyOz, where M represents the metal of the metal oxide, y is greater than zero, and z depends on the oxidation state of the metal atom. For example, where M is hafnium, the fluorinated surface can have a composition of HfFyOz. FIG. 4B also shows fluorine atoms 408 at the surface, which can be used for ligand exchange. Fluorination of the metal oxide surface produces water vapor 409 as a byproduct. 2y O z-y 2y O 2-y

[0063] ​​Returning to FIG. 3, at 316, the method 300 optionally includes purging the processing chamber. As shown in FIGS. 4B-4C, a purge step 410 can be performed to remove water vapor 409 as well as residual HF 404 from the processing chamber.

[0064] With continued reference to FIG. 3, the method 300 further includes, at 318, exposing the fluorinated metal oxide surface of the substrate to a silane-based volatile compound to perform a ligand exchange reaction. The silane-based volatile compound includes at least one non-fluoride halide ligand. In some examples, the non-fluoride halide ligand includes a non-fluoride, non-chloride halide ligand. In such examples, the non-fluoride, non-chloride halide ligand can include bromine or iodine. The ligand exchange reaction exchanges the bromine or iodine for fluorine. This brominates or iodinates the metal oxide surface to form a volatile metal product. Examples of the silane-based volatile compound include alkylhalosilanes having the general formula Ra-Si-X 4-a where R represents an alkyl group (e.g., methyl, ethyl, propyl, t-butyl, pentyl, etc.) or hydrogen, X represents bromine or iodine, and a = 1 to 3. Examples include trimethylbromosilane (Me3SiBr) and trimethyliodosilane (Me3SiI). Examples also include tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibromobutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, and tribromo(pent-2-yl)silane. Further examples of the silane-based volatile compound include 2,3-bis(bromosilyl)butane.

[0065] An example of the volatilization step is shown schematically in FIGS. 4C-4D. Here, the volatilization step 420 includes introducing a silane-based volatile compound 422. As described above, the silane-based volatile compound includes bromine or iodine, as shown by atoms 424. In the depicted example, the silane-based volatile compound includes one or more of trimethylbromosilane or trimethyliodosilane. The silane-based volatile compound 422 reacts with the fluorinated surface 406 to perform a ligand exchange of the atoms 424 with the fluorine atoms 408 to form a volatile metal-containing species 428. The volatilization causes etching of the substrate. The arrow 426 indicates that the fluorinated surface layer 406 has been removed by etching from FIG. 4C. Further, the surface of the metal oxide 401 is capped with the atoms 424. The volatile metal-containing species 428 includes a compound having the general formula MX 2y O z-yMxSyXzwhere M represents the metal of the metal oxide, each X represents iodine or bromine, y is greater than zero, and z depends on the oxidation state of the metal atom. The volatile metal-containing species can also include other metal-containing species, such as metal fluorides. Ligand exchange can also produce trimethylfluorosilane. However, unlike the use of DMAC, the use of silane-based volatile compounds 422 in the volatilization step 420 avoids the formation of volatile aluminum-containing species.

[0066] Returning to FIG. 3, the method 300 optionally includes, at 322, purging the processing chamber. As shown in FIGS. 4D-4E, a purge step 430 can be performed to remove the volatile metal-containing species 428 as well as the residual silane-based volatile compounds 422 from the processing chamber.

[0067] The method 300 also includes, at 324, determining whether to perform an additional ALE cycle. If yes, the method returns to 310 and performs a modification step, as shown at 326. Referring to FIG. 4E, the modification step 440 fluorinates the metal oxide layer 401. This can remove at least some of the atoms 424 on the surface of the metal oxide. During a subsequent ALE cycle, additional material is etched from the metal oxide layer 401.

[0068] If, at 324, it is determined that an additional ALE cycle is not to be performed, the method 300 terminates at 328. The ALE process can include any suitable number of ALE cycles 308 to remove a desired amount of etchable material from the substrate.

[0069] As described above, the use of silane-based volatile compounds can help avoid the formation of chemical deposits on the processing chamber walls. FIGS. 5A-5C schematically show an exemplary chemical interaction between a silane-based volatile compound and a processing chamber wall. More specifically, FIG. 5A shows an aluminum oxide layer 502 on a wall that includes anodized aluminum. During a modification step of an ALE cycle, a fluorinating agent (hydrogen fluoride 504) is introduced into the processing chamber. As a result, a fluorinated aluminum oxide layer 506 is formed on the aluminum oxide layer 502.

[0070] During the volatilization step, a silane-based volatile compound 510 is introduced into the processing chamber. As shown in FIG. 5B, the silane-based volatile compound 510 can react to form trimethylfluorosilane 512 and / or HX 514, where X represents bromine or iodine. Such reaction products are volatile, even in a cold wall reactor at temperatures below 175 °C. In contrast, AlF3 is non-volatile at temperatures below 175 °C. Thus, the use of silane-based volatile compounds will result in less residue on the chamber walls than in the example that uses aluminum-containing volatile compounds (e.g., DMAC).

[0071] Second, FIG. 5C shows the wall after a subsequent modification step in which HF 504 is introduced into the process chamber. The HF can react with the species adsorbed onto the process chamber wall to reform a fluorinated aluminum oxide layer 506. As a result, the trimethylfluorosilane 512 or HX 514 adsorbed to the process chamber wall is removed. Thus, the silane-based volatile compound 510 does not result in the accumulation of deposits on the process chamber wall. Accordingly, the use of a silane-based volatile compound can help avoid the accumulation of aluminum fluoride that occurs when other volatile compounds, such as DMAC, are used.

[0072] FIG. 6 shows a schematic diagram of an example ALE tool 600 for performing ALE using a silane-based volatile compound. For example, the ALE tool 600 can be used to perform the method 300. The ALE tool 600 includes a process chamber 602, and a substrate support 604 within the process chamber. The substrate support 604 is configured to support a substrate 606 disposed within the process chamber 602. The substrate support 604 can include a pedestal (e.g., an electrostatic chuck pedestal), or other suitable structure. The process chamber 602 also includes a substrate heater 608 for heating the substrate 606. The substrate heater 608 can be controlled to heat the substrate to a selected temperature for ALE processing of the substrate 606. Examples include temperatures in a range of 175 °C to 650 °C. In other examples, substrate temperatures outside of this example can be used.

[0073] The ALE tool 600 also includes a showerhead 610, a gas inlet 612A, and flow control hardware 614. In other examples, the processing tool can include a nozzle or other device for introducing gas into the process chamber 602 in place of or in addition to the showerhead. The flow control hardware 614 is connected to a fluorination agent source 616, a volatile compound source 618, and a purge gas source 620.

[0074] The fluorination agent source 616 includes any suitable chemical that can be used to fluorinate a dielectric metal oxide surface. Examples of fluorination agents include molecular fluorine (F2), hydrogen fluoride (HF), xenon difluoride (XeF2), nitrogen trifluoride (NF3), sulfur tetrafluoride (SF4), and sulfur hexafluoride (SF6).

[0075] The volatile compound source 618 includes any suitable silane-based volatile compound that includes at least one non-fluoride, non-chloride halide ligand. The halide ligand can include bromine or iodine. Examples of silane-based volatile compounds include those having the general formula Ra-Si-X 4-aalkylhalosilane, where R represents an alkyl group (e.g., methyl, ethyl, propyl, t-butyl, pentyl, etc.) or hydrogen, X represents bromine or iodine, and a = 1 to 3. Examples include trimethylbromosilane (Me3SiBr) and trimethyliodosilane (Me3SiI). Examples also include tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromo(methylisopropyl)silane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromo(methylpropyl)silane, dibromo(di-propyl)silane, dibromo(di-isopropyl)silane, dibromo(butyl)methylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, and tribromo(pent-2-yl)silane. Further examples of silane-based volatile compounds include 2,3-bis(bromosilyl)butane. As noted above, use of silane-based volatile compounds can help avoid chemical deposits on the walls 624 of the processing chamber 602, or on other surfaces within the processing chamber 602.

[0076] In some examples, the silane-based volatile compound is a liquid. In such examples, the volatile compound source 618 can include a flow-over vapor (FOV) system to deliver the silane-based volatile compound to the processing chamber 602. For example, the FOV system can include a gas inlet to flow a carrier gas into an ampoule including the silane-based volatile compound. The carrier gas assists in pushing the silane-based volatile compound vapor out of the ampoule through a gas outlet. The carrier gas can include any suitable inert gas, such as helium, neon, nitrogen, argon, and mixtures of two or more inert gases. In other examples, the volatile compound source 618 can include any suitable system for flowing a chemical vapor.

[0077] The purge gas source 620 can include any suitable inert gas that can be used to purge the processing chamber 602. Examples include helium, neon, nitrogen, argon, and mixtures of two or more inert gases.

[0078] The flow control hardware 614 is configured to control the flow of gases from one or more selected gas sources into the processing chamber 602. For example, the flow control hardware 614 can include one or more mass flow controllers and / or valves that are controllable to fluidly connect selected chemical sources with the gas inlet 612A. The flow control hardware 614 is configured to control the flow of fluorinating agent from the fluorinating agent source 616 into the processing chamber 602. The flow control hardware 614 is also configured to control the flow of silane-based volatile compound from the volatile compound source 618 into the processing chamber 602. The flow control hardware 614 is also configured to control the flow of inert gas from the purge gas source 620 into the processing chamber 602.

[0079] The ALE tool 600 optionally includes a remote plasma chamber 630 for forming a reactive fluorine-containing species. The remote plasma chamber 630 is configured to generate a remote plasma from a fluorinating agent to produce a reactive fluorine-containing species. In some examples, the remote plasma chamber 630 is configured to generate an inductively coupled plasma. In other examples, the remote plasma chamber 630 is configured to generate a capacitively coupled plasma. In further examples, a microwave plasma can be used. In such examples, the flow control hardware 614 is also configured to control the flow of the fluorinating agent from the fluorinating agent source 616 into the remote plasma chamber 630. The reactive fluorine-containing species can flow into the processing chamber 602 via the process gas inlet 612B.

[0080] The ALE tool 600 also includes an exhaust system 632. The exhaust system 632 is configured to receive gases flowing from the processing chamber 602, including volatilized substrate species. In some examples, the exhaust system 632 is configured to actively remove gases from the processing chamber 602, and / or to apply a partial vacuum. The exhaust system 632 can include any suitable hardware, including one or more low vacuum pumps and / or one or more high vacuum pumps.

[0081] The ALE tool 600 also includes a radio frequency (RF) power source 634 electrically connected to plasma generation circuitry in the remote plasma chamber 630. Examples of the plasma generation circuitry include a capacitor plate to generate a capacitively coupled plasma, or a coil to generate an inductively coupled plasma. The ALE tool 600 can also include a matching network 636 for impedance matching of the RF power source 634. The RF power source 634 is configured to provide a suitable frequency and power to form a plasma in the remote plasma chamber 630. Examples of suitable frequencies include 400 kHz, 13.56 MHz, 27 MHz, 60 MHz, and 90 MHz. Examples of suitable power include power between 50 W (watts) and 50 kW. In some examples, the RF power source 634 is configured to operate at multiple different frequencies and / or powers. In other examples, a microwave plasma can be used.

[0082] The ALE tool 600 also includes a controller 650. The controller 650 is operatively coupled to the substrate heater 608, the flow control hardware 614, the remote plasma generator 630, the exhaust system 632, and the radio frequency power source 634. The controller 650 can be further operatively coupled to any other suitable components of the ALE tool 600. The controller 650 is configured to control the functions of the ALE tool 600 to perform ALE processing on a substrate. For example, the controller 650 is configured to operate the substrate heater 608 to heat the substrate. The controller 650 is also configured to operate the flow control hardware 614 to flow a selected chemical or mixture of chemicals into the processing chamber 602 at a selected rate. The controller 650 is also configured to operate the exhaust system 632 to remove gases from the processing chamber 602. For example, the controller 650 can control the ALE tool 600 to perform a purge of the processing chamber 602. The processing chamber 602 can be purged by flowing an inert gas into the processing chamber 602 and / or removing gases from the processing chamber 602.

[0083] The controller 650 is also configured to operate the flow control hardware 614 and the exhaust system 632 to maintain a selected pressure within the processing chamber 602. In addition, the controller 650 is configured to operate the remote plasma generator 630 and / or the radio frequency power source 634 to form a remote plasma to form a reactive fluorine-containing species. The controller 650 can include any suitable computing system, examples of which are described below with reference to FIG. 7.

[0084] In certain embodiments, the methods and processes described herein can be tied to a computing system of one or more computing devices. In particular, such methods and processes can be implemented as a computer-application or service, an application-programming interface (API), a library, and / or other computer-program product.

[0085] FIG. 7 schematically shows a non-limiting embodiment of a computing system 700 that can enact one or more of the methods and processes described above. Computing system 700 is shown in simplified form. Computing system 700 can take the form of one or more personal computers, servers, workstation, computer clusters integrated with a substrate processing tool, and / or network accessible computing devices. Controller 650 is an example of computing system 700.

[0086] Computing system 700 includes a logic subsystem 702 and a storage subsystem 704. Computing system 700 can optionally include a display subsystem 706, input subsystem 708, communication subsystem 710, and / or other components not shown in FIG. 7.

[0087] The logic subsystem 702 includes one or more physical devices configured to execute instructions. For example, the logic subsystem can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[0088] The logic subsystem can include one or more processors configured to execute software instructions. Additionally or alternatively, the logic subsystem can include one or more hardware or firmware logic subsystems configured to execute hardware or firmware instructions. The processors of the logic subsystem can be single-core or multi-core, and the instructions executed thereon can be configured for sequential, parallel, and / or distributed processing. Individual components of the logic subsystem optionally can be distributed among two or more separate devices, which can be remotely located and / or configured for coordinated processing. Various aspects of the logic subsystem can be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[0089] The storage subsystem 704 includes one or more physical devices configured to hold instructions 712 executable by the logic subsystem to implement the methods and processes described herein. When such methods and processes are implemented, the state of the storage subsystem 704 can be transformed— e.g., to hold different data.

[0090] The storage subsystem 704 can include removable and / or built-in devices. The storage subsystem 704 can include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and / or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.). The storage subsystem 704 can include volatile, nonvolatile, dynamic, static, read / write, readonly, random access, sequential access, location- addressable, file- addressable, and / or content- addressable devices.

[0091] It will be appreciated that the storage subsystem 704 includes one or more physical devices. However, aspects of the instructions described herein can be propagated by a communication medium that does not have a physical storage subsystem 704. For example, aspects of the instructions described herein can be propagated by an electromagnetic signal, an optical signal, etc.

[0092] Aspects of logic subsystem 702 and storage subsystem 704 can be integrated together into one or more hardware-logic components. Such hardware-logic components can include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and application-specific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[0093] When included, display subsystem 706 can be used to present a visual representation of data held by storage subsystem 704. This visual representation can take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage subsystem, and thus the state of the storage subsystem, the state of display subsystem 706 can likewise be transformed to visually represent changes to the underlying data. Display subsystem 706 can include one or more display devices utilizing virtually any type of technology. Such display devices can be combined with logic subsystem 702 and / or storage subsystem 704 in a shared enclosure, or such display devices can be peripheral display devices.

[0094] When included, input subsystem 708 can comprise or interface with one or more user-input devices such as a keyboard, mouse, or touch screen. In some examples, the input subsystem can comprise or interface with selected natural user input (NUI) componentry. Such componentry can be integrated or peripheral, and the transduction and / or processing of input actions can be handled on-board the componentry or by a processing device off-board of the componentry. Example NUI componentry can include a microphone for speech and / or voice recognition; and an infrared, color, stereoscopic, and / or depth camera for machine vision and / or gesture recognition.

[0095] When included, communication subsystem 710 can be configured to communicatively couple computing system 700 with one or more other computing devices. Communication subsystem 710 can include wired and / or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem can be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some examples, the communication subsystem can allow computing system 700 to send and / or receive messages to and / or from other devices via a network such as the Internet.

[0096] It should be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein can represent one or more of any number of processing strategies. As such, acts shown and / or described can be performed in the sequence shown, in other sequences, concurrently, at different times, or omitted. Likewise, the order of the above-described processes can be changed.

[0097] The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

1. A method for performing atomic layer etching, the method comprising: performing a plurality of atomic layer etching cycles, an atomic layer etching cycle of the plurality of atomic layer etching cycles comprising: exposing a substrate comprising a metal oxide surface to a fluorinating agent, wherein the exposing of the metal oxide surface forms a fluorinated metal oxide surface, and exposing the fluorinated metal oxide surface of the substrate to a silane-based volatile compound comprising at least one non-fluoride, non-chloride halide ligand, wherein the exposing of the fluorinated metal oxide surface forms a volatile product.

2. The method of claim 1, wherein the silane-based volatile compound comprises one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(tert-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(tert-butyl)silane, dibromomethylpropylsilane, dibromo(dipropyl)silane, dibromodi(isopropyl)silane, dibromobutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

3. The method of claim 1, wherein the substrate is disposed in a process chamber, the atomic layer etch cycle further comprising: purging the chamber after exposing the substrate to the fluorinating agent.

4. The method of claim 1, further comprising: heating the substrate to a temperature in a range of 175 °C to 650 °C while performing the plurality of atomic layer etching cycles.

5. The method of claim 1, wherein the fluorinating agent comprises one or more of molecular fluorine, hydrogen fluoride, nitrogen trifluoride, xenon difluoride, sulfur tetrafluoride, or sulfur hexafluoride.

6. The method of claim 1, further comprising: forming a plasma to form reactive fluorine-containing species from the fluorinating agent.

7. The method of claim 1, wherein the method is performed in a cold-wall reactor.

8. The method of claim 1, wherein the exposing of the fluorinated metal oxide surface to the silane-based volatile compound comprises: performing a ligand exchange, whereby the metal oxide surface is brominated or iodinated.

9. An atomic layer etching tool for performing atomic layer etching on a substrate, the processing tool comprising: a process chamber; a substrate support disposed within the process chamber; a substrate heater disposed within the process chamber; flow control hardware configured to control gas flow from a fluorinating agent source and a volatile compound source to the process chamber; and a controller operably coupled to the flow control hardware and the substrate heater, the controller configured to: operate the substrate heater to heat the substrate, operate the flow control hardware to introduce a fluorinating agent from the fluorinating agent source into the process chamber in a modification step, and operate the flow control hardware to introduce a silane-based volatile compound from the volatile compound source into the process chamber in a volatilization step, the silane-based volatile compound comprising at least one non-fluoride, non-chloride halide ligand. ​ 10. The atomic layer etching tool of claim 9, further comprising a purge system, and wherein the controller is further configured to operate the flow control hardware and the purge system to purge the process chamber after the modification step.

11. The atomic layer etching tool of claim 9, further comprising the source of volatile compounds, wherein the silane-based volatile compound comprises one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromo(methylisopropyl)silane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromo(methylpropyl)silane, dibromo(dipropyl)silane, dibromo(diisopropyl)silane, dibromo(butyl)methylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(pentyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

12. The atomic layer etching tool of claim 9, further comprising the source of fluorinating agent, wherein the source of fluorinating agent comprises one or more of molecular fluorine, hydrogen fluoride, nitrogen trifluoride, xenon difluoride, sulfur tetrafluoride, or sulfur hexafluoride.

13. The atomic layer etching tool of claim 9, wherein the controller is configured to operate the substrate heater to heat to a temperature in a range of 175 °C to 650 °C.

14. The atomic layer etching tool of claim 13, wherein during processing, walls of the process chamber are at a temperature lower than the substrate heater.

15. The atomic layer etching tool of claim 9, wherein the controller is configured to perform a plurality of atomic layer etching cycles, each atomic layer etching cycle of the plurality of atomic layer etching cycles comprising the modification step and the volatilization step.

16. The atomic layer etching tool of claim 9, further comprising a remote plasma generator, and wherein the controller is configured to operate the remote plasma generator to generate reactive fluorine-containing species.

17. A method of performing atomic layer etching, the method comprising: heating, in a cold-wall reactor, a substrate comprising a metal oxide surface; and while heating the substrate, performing a plurality of atomic layer etching cycles, an atomic layer etching cycle of the plurality of atomic layer etching cycles comprising: exposing the substrate to a fluorinating agent, wherein the exposing of the metal oxide surface forms a fluorinated metal oxide surface, and exposing the fluorinated metal oxide surface of the substrate to a volatile compound comprising at least one non-fluoride halide ligand, wherein the exposing of the fluorinated metal oxide surface forms a volatile product, the volatile compound being aluminum-free.

18. The method of claim 17, wherein the non-fluoride halide ligand comprises a non-fluoride, non-chloride halide ligand.

19. The method of claim 17, wherein the volatile compounds include silane-based volatile compounds including one or more of trimethylbromosilane, trimethyliodosilane, tetrabromosilane, bromo(butyl)silane, bromo(t-butyl)silane, bromo(triethyl)silane, dibromo(dimethyl)silane, dibromomethylisopropylsilane, dibromo(butyl)silane, dibromo(sec-butyl)silane, dibromo(t-butyl)silane, dibromomethylpropylsilane, dibromo(di-propyl)silane, dibromodi(isopropyl)silane, dibromobutylmethylsilane, dibromo(butyl)iodosilane, tribromo(methyl)silane, tribromo(butyl)silane, tribromo(sec-butyl)silane, tribromo(amyl)silane, tribromo(pent-2-yl)silane, or 2,3-bis(bromosilyl)butane.

20. The method of claim 17, wherein heating the substrate comprises: During the modifying step and the volatilizing step, the substrate is heated to a temperature in a range of 175 °C to 650 °C.

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