Selective SiGe etching using thermal F2 and additives

Abstract

Embodiments described herein relate to methods, apparatus, and systems for selectively etching a substrate. The substrate typically includes one or more layers of silicon and one or more layers of silicon germanium. The method may include housing the substrate in a process chamber, exposing the substrate to F2, and exposing the substrate to an additive. Exposing the substrate to F2 and the additive selectively etches the silicon germanium relative to silicon. The substrate is not exposed to a plasma during exposure to F2. The use of the additive results in a more uniform etch rate for the etched material than would be possible without the additive.

Description

[Technical Field]

[0001] (Incorporated by reference) A PCT application form is being filed concurrently herewith as part of this application. Each application to which this application claims benefit or priority, identified in the concurrently filed PCT application form, is hereby incorporated by reference in its entirety for all purposes. (Background technology) As the semiconductor device industry advances, feature sizes are becoming smaller and smaller. This scaling allows for an increased density of functional features on a semiconductor substrate. One recent advancement is the development of the gate-all-around field-effect transistor (GAA FET). In a GAA FET, the conductive channel is completely enveloped by the gate, making it easier to control the current flowing through the channel. The channel may be implemented in various forms, for example, as a nanowire or nanosheet. The channel is covered by a gate oxide, which is in turn covered by the gate. Source and drain regions are located at either end of the channel.

[0002] The background art provided herein is intended to provide a general background to the present disclosure. The inventors' work within the scope of this background art, and aspects of the description that may not otherwise be admitted as prior art at the time of filing, are not admitted, explicitly or implicitly, as prior art to the present disclosure. Summary of the Invention

[0003] Various embodiments described herein relate to methods, apparatus, and systems for processing a substrate. The substrate typically includes one or more layers of silicon and one or more layers of silicon germanium. Processing the substrate includes selectively etching the silicon germanium relative to silicon.

[0004] In one aspect of an embodiment of the present disclosure, a method for processing a substrate is provided. The method includes placing a substrate including one or more layers of silicon and one or more layers of silicon germanium in a process chamber, exposing the substrate to F2, and exposing the substrate to an additive. Exposing the substrate to F2 and the additive selectively etches the silicon germanium relative to silicon. The substrate is not exposed to a plasma during the exposure to F2.

[0005] In various embodiments, the additive may comprise a reducing reactant selected from the group consisting of hydrogen (H), hydrogen fluoride (HF), carbon monoxide (CO), sulfur dioxide (SO), and methane (CH). In these or other embodiments, the additive may comprise an oxidizing reactant selected from the group consisting of an oxygen-containing reactant and an elemental halogen other than F. In these or other embodiments, the additive may comprise one or more materials selected from the group consisting of heterocyclic aromatic compounds, heterocyclic aliphatic compounds, alcohols, amines, amino acids, organophosphorus compounds, difluoride sources, aldehydes, carbenes, organic acids, and combinations thereof. In these or other embodiments, the additive may be adsorbed onto the substrate. In these or other embodiments, the additive may comprise an organic molecule.

[0006] In various implementations, silicon germanium may be etched at a more uniform rate than if the substrate were not exposed to the additive.

[0007] Various timing schemes may be used to provide F2 and the additive. For example, in some embodiments, the substrate may be exposed to both F2 and the additive simultaneously and / or for overlapping periods of time. In some embodiments, the substrate may be exposed to F2 at a first timing and then exposed to the additive at a second timing that is later than the first timing. In some such embodiments, exposing the substrate to F2 at a first timing may etch a first portion of the silicon germanium, and exposing the substrate to the additive at a second timing may etch a second portion of the silicon germanium. Here, the silicon germanium is etched more uniformly after etching the second portion than after etching the first portion. In some cases, the first and second portions of the silicon germanium may have different compositions. In these or other embodiments, the first and second portions of the silicon germanium may have different material properties. In some embodiments, the substrate may be exposed to an additive at a first timing to modify the silicon germanium, thereby forming modified silicon germanium, and then the substrate may be exposed to F2 at a second timing that is later than the first timing. In various embodiments, F2 and the additive may be supplied to the process chamber in alternating pulses.

[0008] In another aspect of an embodiment of the present disclosure, an apparatus for etching a substrate is provided. The apparatus includes one or more process chambers, each including a substrate support pedestal; one or more gas inlets to the process chambers and associated flow control hardware; and a controller having at least one processor and memory. The at least one processor and the memory are communicatively connected to each other. The at least one processor is at least operatively connected to the flow control hardware. The memory stores computer-executable instructions for controlling the at least one processor to place a substrate including one or more silicon layers and one or more silicon germanium layers in one of the one or more process chambers, expose the substrate to F2, and expose the substrate to an additive. Exposing the substrate to F2 and the additive selectively etches the silicon germanium relative to silicon. The substrate is not exposed to plasma during the exposure to F2.

[0009] In various embodiments, the apparatus may include two or more process chambers and a load lock for transferring substrates between the two or more process chambers without exposing them to the atmosphere.

[0010] Various additives can be used. For example, in some embodiments, the additive may include a reducing reactant selected from the group consisting of hydrogen (H), hydrogen fluoride (HF), carbon monoxide (CO), sulfur dioxide (SO), and methane (CH). In some embodiments, the additive may include an oxidizing reactant selected from the group consisting of an oxygen-containing reactant and an elemental halogen other than F. In these or other embodiments, the additive may include one or more materials selected from the group consisting of heterocyclic aromatic compounds, heterocyclic aliphatic compounds, alcohols, amines, amino acids, organophosphorus compounds, difluoride sources, aldehydes, carbenes, organic acids, and combinations thereof. In these or other embodiments, the additive may be adsorbed onto the substrate. In these or other embodiments, the additive may include an organic molecule.

[0011] In various implementations, silicon germanium may be etched at a more uniform rate than if the substrate were not exposed to the additive.

[0012] Various timing schemes may be used to provide F2 and the additive. For example, in some embodiments, the substrate may be exposed to both F2 and the additive simultaneously and / or for overlapping periods of time. In some embodiments, the substrate may be exposed to F2 at a first timing and then exposed to the additive at a second timing that is later than the first timing. In some such embodiments, exposing the substrate to F2 at a first timing may etch a first portion of the silicon germanium, and exposing the substrate to the additive at a second timing may etch a second portion of the silicon germanium. Here, the silicon germanium may be more uniformly etched after etching the second portion than after etching the first portion. In some cases, the first and second portions of the silicon germanium may have different compositions. In these or other embodiments, the first and second portions of the silicon germanium may have different material properties. In some embodiments, the substrate may be exposed to an additive at a first timing to modify the silicon germanium, thereby forming modified silicon germanium, and then the substrate may be exposed to F2 at a second timing that is later than the first timing. In various embodiments, F2 and the additive may be supplied to the process chamber in alternating pulses.

[0013] These and other aspects are described in further detail below with reference to the drawings. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a flowchart of a method for selectively etching a substrate, according to various embodiments.

[0015] [Figure 2A]FIG. 2A is a diagram showing the process of etching a substrate according to the method of FIG. [Figure 2B] FIG. 2B is a diagram illustrating the process of etching a substrate according to the method of FIG.

[0016] [Figure 3] FIG. 3 is a flowchart of a method for selectively etching a substrate, according to various embodiments.

[0017] [Figure 4A] FIG. 4A is a diagram showing the process of etching a substrate according to the method of FIG. [Figure 4B] FIG. 4B illustrates the process of etching a substrate according to the method of FIG. [Figure 4C] FIG. 4C illustrates the process of etching a substrate according to the method of FIG.

[0018] [Figure 5] FIG. 5 is a flowchart of a method for selectively etching a substrate, according to various embodiments.

[0019] [Figure 6A] FIG. 6A is a diagram showing the process of etching a substrate according to the method of FIG. [Figure 6B] FIG. 6B is a diagram showing the process of etching a substrate according to the method of FIG. [Figure 6C] FIG. 6C illustrates the process of etching a substrate according to the method of FIG.

[0020] [Figure 7A] FIG. 7A illustrates a process chamber according to various embodiments described herein.

[0021] [Figure 7B] FIG. 7B illustrates a vapor delivery system that can be used in the process chamber of FIG. 7A, according to various embodiments.

[0022] [Figure 8] FIG. 8 illustrates a multi-station apparatus for performing various process steps, according to certain embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0023] In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments presented; however, embodiments of the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process steps are not described in detail to avoid unnecessarily obscuring the embodiments of the present disclosure. While the embodiments of the present disclosure will be described in conjunction with these specific embodiments, it should be understood that they are not intended to limit the embodiments of the present disclosure.

[0024] Gate-all-around (GAA) technology is rapidly evolving. One commonly used material in the fabrication of GAA devices is silicon germanium (SiGe). For example, SiGe may be used as a sacrificial material to form the channel of a GAA device. In various embodiments, silicon and silicon germanium are deposited in alternating layers on a substrate. Recessed features are etched into these alternating layers. The SiGe is then selectively removed while substantially preserving the Si to form the Si channel. The SiGe removal may be performed in stages, with additional steps (e.g., deposition of spacers or other structures) occurring between these stages. Various embodiments described herein relate to selective removal of SiGe (relative to Si) with respect to the formation of GAA devices. However, the embodiments are not limited thereto. The invention described herein is applicable to other contexts, such as any embodiment in which SiGe is selectively etched relative to another material (e.g., but not limited to, Si). Such embodiments may be provided in the context of logic or memory applications, for example. The SiGe may be only partially removed or may be nearly completely removed.

[0025] As used herein, "etching selectivity" refers to the ratio of etching rates between materials. For example, an etching process that is selective for a first material relative to a second material has a higher etching rate for the first material and a lower etching rate for the second material. Such an etching process is understood to preferentially etch the first material relative to the second material.

[0026] Numerous techniques have been developed to selectively remove SiGe. Broadly speaking, these techniques can be classified as either plasma-driven or thermal-driven processes. Existing plasma-driven SiGe removal processes rely on F radicals generated from fluorine-containing sources such as NF3, CF4, SF6, SiF4, or F2, or the recombination products of these radicals (primarily F2). Unfortunately, these plasma-based processes have low selectivity. These plasma-based processes typically remove more Si than necessary, potentially resulting in thinner Si channels and significant limitations on device geometries. To compensate for the low selectivity, plasma-based processes typically operate at relatively high pressures and low temperatures, resulting in reduced throughput.

[0027] On the other hand, existing thermally driven SiGe removal processes that rely on F2 chemistry are significantly more selective than plasma-driven processes, removing significant amounts of SiGe while removing little or no Si. However, such thermally driven processes have other drawbacks, including being highly sensitive to variations in the SiGe material being etched. This sensitivity results in non-uniform etch rates between SiGe materials with different compositions and other properties. In some cases, the non-uniform etch rates can result in the formation of non-ideal etched surfaces within the SiGe material.

[0028] SiGe materials used in semiconductor manufacturing can vary widely in their composition and properties. The compositions can vary with respect to the concentrations of Si and Ge, as well as the concentrations of other elements that may be present in the material. Such elements may be present intentionally (e.g., as dopants) or unintentionally (e.g., through contamination, diffusion, or impurities). Examples of other elements that may be present in SiGe include, but are not limited to, oxygen, carbon, nitrogen, boron, gallium, and chlorine. In some embodiments, the SiGe material being removed may have a certain level of compositional heterogeneity. For example, the SiGe may have a first portion having a first composition and a second portion having a second composition. The first and second portions of the SiGe may be present in different layers of the SiGe or may be present within the same layer. The first and second compositions may differ by a certain amount. For example, the first and second compositions may differ by at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, or at least about 20% with respect to one or more elements in the composition (e.g., Si, Ge, C, O, N, etc.). Note that these percentages are atomic percentages. For example, within a SiGe layer, if a first portion contains 50% Si and 50% Ge and a second portion contains 60% Si and 40% Ge, the Si composition and Ge composition may each be said to vary by 10% (e.g., |50%-40%|=10% and |50%-60%|=10%). Similarly, if a first portion contains 1% oxygen and a second portion contains 3% oxygen within the SiGe layer, the oxygen concentration may be said to vary by 2% (e.g., |1%-3%|=2%).

[0029] In these or other embodiments, the removed SiGe material may have a certain level of heterogeneity with respect to one or more material properties other than (or in addition to) composition. For example, the SiGe may be heterogeneous with respect to material properties such as electrical conductivity or density. For example, the SiGe may have a first portion having a first material property and a second portion having a second material property. As noted above, the first and second portions of the SiGe may be in different layers of the SiGe or may be in the same layer. The first and second material properties may differ by a certain amount. For example, the first material property may be at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 40%, at least about 60%, at least about 100%, or at least about 200% greater than the second material property. For example, within a layer of SiGe, the density of the first portion may be about 4.5 g / cm. 3 and the density of the second portion is about 3.8 g / cm 3 , the density of the first portion is said to be about 18% higher than the density of the second portion (e.g., 4.5 g / cm 3 -3.8g / cm 3 ) / (3.8g / cm 3 )×100=18%).

[0030] To address these non-uniformity concerns, various embodiments described herein utilize a thermally driven etching process that uses an additive in combination with F2 to selectively remove SiGe relative to a second material (e.g., Si). Traditionally, such additives have not been used in combination with F2 to selectively thermally etch SiGe. Various types of additives can be used. Additives include, but are not limited to, oxidizing reactants and reducing reactants, as described in more detail below.

[0031] While this specification focuses on embodiments in which SiGe is selectively removed relative to Si (or vice versa), it should be understood that other materials may be used in place of Si, and thus any discussion herein of silicon is also applicable to other materials present on the substrate and exposed to etching conditions, such as, but not limited to, SiN or SiO.

[0032] FIG. 1 is a flowchart of a method for etching SiGe selectively relative to Si, according to various embodiments described herein. The method of FIG. 1 is described in conjunction with FIGS. 2A and 2B, which illustrate how a substrate is etched. The method of FIG. 1 begins in step 101 by providing a substrate having a stack of alternating layers of Si 202 and SiGe 204 in a process chamber. The SiGe may have non-uniformities with respect to composition and / or one or more other material properties described herein. Recessed features are present on both sides of the stack, penetrating each of the Si 202 and SiGe 204 layers, as shown in FIG. 2A.

[0033] In step 103, the substrate is exposed to a chemistry containing F2 and one or more additives to laterally etch the SiGe selectively relative to Si. Exposing the substrate to a mixed flow of F2 and additives results in a much more uniform etch rate for the SiGe material than without the additive. Figure 2B shows the substrate after step 103. As a result of the selective etching, the SiGe is laterally recessed relative to the Si.

[0034] 1, F2 and the additive are supplied simultaneously to the process chamber. In a related embodiment, F2 and the additive may be alternately pulsed into the process chamber. Indeed, any of the embodiments and / or processes described herein in which F2 and the additive are supplied together may be modified to alternately pulse F2 and the additive into the process chamber.

[0035] FIG. 3 is a flowchart illustrating a method for etching SiGe selectively relative to Si, according to various embodiments described herein. The method of FIG. 3 differs from the method of FIG. 1 in that it uses a multi-step approach, which may improve etch rates and therefore throughput compared to the single-step approach shown in FIG. 1. The method of FIG. 3 is described with reference to FIGS. 4A-4C, which illustrate how a substrate is etched. The method of FIG. 3 begins in step 301 by providing a substrate having a stack of alternating layers of Si 402 and SiGe 404 in a process chamber. The SiGe may have non-uniformities with respect to composition and / or one or more other material properties described herein. Recessed features are present on both sides of the stack, penetrating each of the Si 402 and SiGe 404 layers, as shown in FIG. 4A.

[0036] In step 303, the substrate is 24B, the first portion of SiGe 404 is selectively etched relative to Si 402. The first portion of SiGe 404 is also selectively etched relative to the second portion of SiGe 404. In the embodiment shown in FIGS. 4A-4C, the first portion of SiGe 404 corresponds to a central portion of SiGe 404, centered about the midpoint between the layers of Si 402. This portion is effectively etched by F (without additive) due to the relatively high concentration of Ge near the middle of the layers of SiGe 404. The second portion of SiGe 404 is located at both ends (e.g., top and bottom) of SiGe 404. At these ends, SiGe 404 contacts Si 402. Compared to the first portion of SiGe 404, the second portion of SiGe 404 has a higher concentration of Si and a lower concentration of Ge. This difference in Si and Ge concentrations (and other material property differences described herein) can result from a variety of factors. These factors include, but are not limited to, upstream deposition techniques and conditions used to deposit Si 402 and / or SiGe 404, upstream techniques and conditions used to etch or treat these layers (which may result in, for example, ion damage or differential passivation), diffusion between Si 402 and SiGe 404, diffusion between (i) Si 402 and / or SiGe 404 and (ii) other materials on the substrate, and / or waiting time. As shown in Figure 4B, the etch in step 303 etches more extensively near the center of SiGe 404 while etching less near the top and bottom edges of SiGe 404, forming a depression in SiGe 404. This less etched portion of SiGe 404 is sometimes referred to as the "foot."

[0037] Typically, the foot forms in an F2 thermal etching process (without additives) because this process has a high selectivity for removing SiGe and Ge relative to Si. As a result of this high selectivity, the relatively Si-rich SiGe is not sufficiently removed (e.g., because it is too similar in composition to the Si that is not targeted for removal in this step). The relatively Si-rich SiGe that is not sufficiently removed in step 303 forms the foot shown in FIG. 4B.

[0038] Next, in step 305, the substrate is exposed to a combination of F and an additive to etch the second portion of SiGe 404 selectively relative to Si 402. Step 305 also etches the second portion of SiGe 404 selectively relative to the first portion of SiGe 404. This prevents over-etching of the first portion of SiGe 404 laterally, resulting in a uniform / nearly vertical etched surface, as shown in FIG.

[0039] In effect, the additive can be used to tailor the selectivity of the etch process to target the remaining SiGe material after step 303 for removal. In general, the inclusion of an additive reduces the selectivity for removing SiGe (and Ge) relative to Si. In other words, the additive can be used to reduce the selectivity, thereby tailoring the etch process in step 305 to target or enable removal of a particular remaining SiGe composition (which may have a higher Si content than the SiGe removed in step 303 using F2 alone). The reduced selectivity achieved by the additive allows for the effective removal of the remaining SiGe material with a higher Si content, which is a significant improvement over using F2 alone.

[0040] As described above, the method of FIG. 3 can achieve high-quality etching results with high throughput. The multi-step approach can improve throughput compared to the single-step approach shown in FIG. 1 because the use of various additives described herein can reduce the etch rate compared to when no additives are used. In other words, the use of additives can slow the etching process. Therefore, it is beneficial to quickly etch a first portion of the SiGe using F2 alone, and then more slowly etch a second portion of the remaining SiGe using a combination of F2 and additives. The advantage of this is that the bulk of the SiGe can be removed quickly, while the remaining SiGe can be removed more slowly and more targetedly, if desired. This results in high-quality etching with high throughput.

[0041] FIG. 5 is a flow chart illustrating a method for selectively etching SiGe relative to Si, according to various embodiments described herein. The method of FIG. 5 is similar to the method of FIG. 3, except that the substrate is exposed to an additive prior to exposure to F2. The method of FIG. 5 will be described in conjunction with FIGS. 6A-6C, which illustrate how a substrate having Si 602 and SiGe 604 is etched. The method of FIG. 5 begins with step 501, which is similar to steps 101 and 301 and will not be described again for brevity.

[0042] The method then proceeds to step 503, where the substrate is exposed to an additive as described herein. The additive modifies at least the exposed surface of the SiGe 604 to form modified SiGe 606, as shown in FIG. 6B. The additive may also modify the Si 602 (such modification is not shown). As one example, the modified SiGe 606 may be oxidized SiGe. As another example, the modified SiGe 606 may be reduced SiGe. Various examples are possible. Modifying the surface of the SiGe 604 to form the modified SiGe 606 may offset and / or eliminate non-uniformities in the SiGe 604, potentially providing a more uniform SiGe material for subsequent etching.

[0043] Next, in step 505, the substrate is exposed to F to etch the modified SiGe 606 (and possibly some of the unmodified SiGe 604). The substrate may optionally be exposed to one or more additives during step 505. In various other cases, no additives are provided during step 505, and F (or F with an inert gas) is the only gas provided to the process chamber during that step. It may be desirable to omit the additive during step 505 to maximize the etch rate.

[0044] The methods described in connection with Figures 3 and 5 all use a multi-step approach, with each step providing a different set of reactants. Note that while Figures 3 and 5 show each step performed only once, these steps may be repeated periodically. For example, with respect to the method of Figure 3, steps 303 and 305 may be repeated any number of times. Similarly, with respect to the method of Figure 5, steps 503 and 505 may be repeated any number of times.

[0045] While in Figures 2A, 4A, and 6A the substrate starts with a Si / SiGe stack with vertical sidewalls (e.g., neither the Si nor the SiGe are laterally recessed), and in Figures 2B, 4C, and 6C ends with a laterally recessed SiGe, this is not always the case. Any of the methods described herein can also be performed on different structures, such as structures where the SiGe has already been partially laterally etched. In such cases, the SiGe material may be partially removed (as shown in Figures 2B, 4C, and 6C), or may be completely or nearly completely removed. In some cases, one or more of the methods described herein may be performed in a first timing sequence to remove a portion of the SiGe material from the substrate, as shown in Figures 2A, 2B, 4A-4C, and 6A-6C, and then one or more of the methods described herein may be performed in a second timing sequence to remove all remaining SiGe material. Other processing steps may occur between the first and second timing sequences. Such processing steps include, but are not limited to, deposition of spacer materials, thinning of silicon wires, and any other steps associated with the formation of gate-all-around devices and other semiconductor devices utilizing both Si and SiGe.

[0046] (additives) In embodiments described herein, a substrate is etched using a combination of F2 and an additive. As used herein, an additive is a material (excluding F2 or an inert gas) supplied to a process chamber to etch a material on the substrate. In some embodiments, the additive may undergo a chemical reaction with one or more materials on the substrate and / or one or more other reactants supplied to the process chamber. In some embodiments, the additive (or a material at least partially derived from the additive) may act as a catalyst. In some embodiments, the additive (or a material at least partially derived from the additive) may adsorb to the substrate (e.g., by non-reactive chemisorption and / or physisorption). This may have the effect of blocking access to such sites by other reactants, such as F2. These mechanisms may also be used in combination. The additive may be supplied simultaneously with F2, as described in the method of FIG. 1, or separately from F2 (e.g., before and / or after exposing the substrate to F2), as described in the methods of FIGS. 3 and 5.

[0047] The additive may be selected from many types of additives. For example, in some cases, the additive may be a heterocyclic compound, a heteroaromatic compound, a halogen-substituted heteroaromatic compound, a heteroaliphatic compound, an alcohol, an amine, a fluoroamine, an amino acid, an organophosphorus compound, an oxidizing reactant, a reducing reactant, a difluoride source, ammonia, an aldehyde, a carbene, or an organic acid. In some cases, multiple additives may be used. In some embodiments, the additive may be a boron-containing Lewis acid or Lewis adduct. Boron trifluoride (BF3) can be used to form the acid-base adduct BF4 - In some cases, an additive may fall into more than one of the above categories.

[0048] Heteroaromatic compounds: In certain embodiments, the additive is a heteroaromatic compound. The term "aromatic" is defined above. A heteroaromatic compound is an aromatic compound containing a 5-, 6-, or 7-membered ring containing one to four non-carbon heteroatoms (e.g., independently selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, and halo), unless otherwise specified. Examples of usable heteroaromatic compounds include, but are not limited to, picoline, pyridine, pyrrole, imidazole, thiophene, N-methylimidazole, N-methylpyrrolidone, benzimidazole, 2,2-bipyridine, dipicolinic acid, 2,6-lutidine, 4-N,N-dimethylaminopyridine, and azulene. In some cases, the heteroaromatic compound may be methylated. In some cases, the heteroaromatic compound may conform to Hückel's 4n+2 rule. In some cases, the additive is a halogen-substituted aromatic compound. A halogen-substituted aromatic compound is an aromatic compound containing at least one halogen bonded to an aromatic ring. As used herein, "halogen" or "halo" refers to F, Cl, Br, or I. Examples of halogen-substituted aromatic compounds include, but are not limited to, 4-bromopyridine, chlorobenzene, 4-chlorotoluene, fluorobenzene, and the like.

[0049] Heterocyclic Aliphatic Compounds: In some embodiments, the additive is a heterocyclic aliphatic compound. As used herein, "aliphatic" refers to a compound having at least 1 carbon atom and up to 50 carbon atoms (C 1-50 ), e.g., 1 to 25 carbon atoms (C 1-25 ), or 1 to 10 carbon atoms (C 1-10Heterocyclic aliphatic compounds refer to hydrocarbon groups having a cyclic structure, such as alkane (or alkyl), alkene (or alkenyl), alkyne (or alkynyl), and cyclic structures thereof, as well as linear and branched chain arrangements, and all stereoisomers and positional isomers. Heterocyclic aliphatic compounds, unless otherwise specified, are aliphatic compounds containing a 5-, 6-, or 7-membered ring containing one to four non-carbon heteroatoms (e.g., independently selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, and halo). Examples of heterocyclic aliphatic compounds include pyrrolidine, piperidine, and the like.

[0050] alcohol: In some embodiments, the additive is C n H (2n+1) It is an alcohol having a formula of OH (n is the number of carbon atoms in the molecule). Examples of alcohols include, but are not limited to, methanol, ethanol, propanol, butanol, pentanol, etc. In a particular example, the additive is isopropyl alcohol.

[0051] Amine: In some embodiments, the additive is NR 1 R 2 R 3 is an amine having the formula: where R 1 , R 2 , and R 3 is independently selected from hydrogen, hydroxyl, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. R 1 and R 2 can optionally form a cycloheteroaliphatic group together with the atom to which each is attached. R 1 , R 2 , and R 3 can optionally form a cycloheteroaliphatic group together with the atom to which each is attached.

[0052] In some embodiments, R1 , R 2 , and R 3 is independently selected from alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, haloalkyl, haloalkenyl, haloalkynyl, haloheteroalkyl, haloheteroalkenyl, haloheteroalkynyl, aryl, heterocyclyl, heteroaryl, alkyl-aryl, alkenyl-aryl, alkynyl-aryl, alkyl-heterocyclyl, alkenyl-heterocyclyl, alkynyl-heterocyclyl, alkyl-heteroaryl, alkenyl-heteroaryl, alkynyl-heteroaryl, heteroalkyl-aryl, heteroalkenyl-aryl, heteroalkynyl-aryl, heteroalkyl-heterocyclyl, heteroalkenyl-heterocyclyl, heteroalkynyl-heterocyclyl, heteroalkyl-heteroaryl, heteroalkenyl-heteroaryl, heteroalkynyl-heteroaryl, or any combination thereof. In certain embodiments of the present disclosure, the amine may be further substituted with one or more substituents. These substituents include alkoxy, amide, amine, hydroxyl, thioether, thiol, acyloxy, silyl, cycloaliphatic, aryl, aldehyde, ketone, ester, carboxylic acid, acyl, acyl halide, cyano, halogen, sulfonate, nitro, nitroso, quaternary amine, pyridinyl (or pyridinyl functionalized on the nitrogen atom with an aliphatic or aryl group), alkyl halide, or any combination thereof.

[0053] In some embodiments, R 1 , R 2 , and R 3 When at least one of is aliphatic, haloaliphatic, haloheteroaliphatic, or heteroaliphatic, the additive is an alkylamine. The alkylamine can include dialkylamine, trialkylamine, and derivatives thereof. Examples of alkylamines include dimethylisopropylamine, N-ethyldiisopropylamine, trimethylamine, dimethylamine, methylamine, triethylamine, t-butylamine, etc.

[0054] In other embodiments, R 1 , R 2 , and R 3 If at least one of R contains a hydroxyl group, the additive is an alcoholamine. 1 , R 2 , and R 3 at least one of which is an aliphatic group substituted with one or more hydroxyl groups. Examples of alcoholamines include 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 2-(dipropylamino)ethanol, 2-(dibutylamino)ethanol, N-ethyldiethanolamine, and N-tert-butyldiethanolamine.

[0055] In some embodiments, R 1 and R 2 When each of these groups, together with the atom to which it is attached, forms a cycloheteroaliphatic group, the additive can be a cyclic amine. Examples of cyclic amines include piperidine, N-alkylpiperidines (e.g., N-methylpiperidine, N-propylpiperidine, etc.), pyrrolidine, N-alkylpyrrolidines (e.g., N-methylpyrrolidine, N-propylpyrrolidine, etc.), morpholine, N-alkylmorpholine (e.g., N-methylmorpholine, N-propylmorpholine, etc.), piperazine, N-alkylpiperazines, N,N-dialkylpiperazines (e.g., 1,4-dimethylpiperazine), etc.

[0056] In other embodiments, R 1 , R 2 , and R 3 When at least one of R comprises an aromatic group, the additive is an aromatic amine. 1 , R 2 , and R 3 At least one of R is aromatic, aliphatic-aromatic, or heteroaliphatic-aromatic. 1 and R 2 In yet another embodiment, both R 1 , R 2, and optionally R 3 taken together with the atom to which each is attached form a cycloheteroaliphatic, aromatic group. Examples of aromatic amines include aniline, histamine, pyrrole, pyridine, imidazole, pyrimidine, and derivatives thereof.

[0057] In some embodiments, the additive may comprise an amine selected from the group consisting of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, isopropylamine, 1,2-ethylenediamine, aniline (and aniline derivatives such as N,N-dimethylaniline), N-ethyldiisopropylamine, tert-butylamine, and combinations thereof.

[0058] In some embodiments, the additive may include a fluoroamine. A fluoroamine is an amine having one or more fluorinated substituents. Examples of usable fluoroamines include, but are not limited to, 4-trifluoromethylaniline.

[0059] In some embodiments, the additive is R 1 NC(NR 2 )-NR 3 The additive may be a nitrogen analog of carbonic acid, having the formula: Example additives include, but are not limited to, guanidine or its derivatives.

[0060] In some embodiments, the additive may be a relatively low molecular weight amine (e.g., a molecular weight less than 200 g / mol, or in certain embodiments, less than 100 g / mol). In some embodiments, higher molecular weight amines (including those with long chains and / or heterocyclic compounds with aromatic rings) may be used.

[0061] amino acid: In some embodiments, the additive may include an amino acid, which may have the formula R-CH(NR')-COOH. wherein each R and R' is independently a hydroxyl group, an aliphatic group, a haloaliphatic group, a haloheteroaliphatic group, a heteroaliphatic group, an aromatic group, an aliphatic-aromatic group, a heteroaliphatic-aromatic group, or any combination thereof.

[0062] Examples of amino acids that can be used include, but are not limited to, histidine, alanine, and derivatives thereof.

[0063] Organophosphorus compounds: In some embodiments, the additive may include an organophosphorus compound. The organophosphorus compound may be a phosphate ester, a phosphoric acid amide, a phosphonic acid, a phosphinic acid, a phosphonate, a phosphinate, a phosphine oxide, a phosphine imide, or a phosphonium salt. Examples of organophosphorus compounds include phosphoric acid and trialkylphosphates. In some embodiments, the organophosphorus compound is a phosphazene. A phosphazene is an organophosphorus compound containing phosphorus(V) with a double bond between P and N. The phosphazene may have the formula RN=P(NR2)3, where each of R and R2 is independently selected from hydroxyl, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. In some embodiments, the phosphazene may be a [X2PN] n (X is a halide, alkoxide, or amide). Other types of phosphazenes may be used if desired.

[0064] Oxidizing Reactants In some embodiments, the additive comprises an oxidizing reactant.

[0065] An oxidizing reactant (also called an oxidizing agent) is a substance that tends to be reduced and accept electrons, thereby causing oxidation. Examples of oxidizing reactants include, but are not limited to, oxygen-containing reactants (e.g., oxygen (O2), nitric oxide (NO), nitrous oxide (N2O), ozone (O3), water (H2O), hydrogen peroxide (H2O2), sodium hypochlorite (NaOCl), tetramethylammonium hydroxide (N(CH3)4), + OH - ), elemental halogens other than F (e.g., chlorine (Cl)), and other oxidizing reactants known to those skilled in the art. The oxidizing reactant acts to oxidize or passivate exposed surfaces on the substrate, such as exposed portions of SiGe. Without being bound by theory or mechanism of action, it is believed that such passivation results in a more uniform modified SiGe material suitable for etching, which in turn allows the F chemistry to etch the modified SiGe at a more uniform rate than would be possible without the use of the oxidizing reactant. As discussed above, because the F chemistry and associated etch rates are sensitive to variations in the SiGe material, providing a more uniform SiGe material suitable for etching results in a more uniform etch rate between different portions of the SiGe.

[0066] Reducing reactant: In some embodiments, the additive includes a reducing reactant. A reducing reactant (also called a reducing agent) is a substance that tends to be oxidized to release electrons, thereby causing reduction. Examples of reducing reactants include, but are not limited to, hydrogen (H), hydrogen fluoride (HF), carbon monoxide (CO), sulfur dioxide (SO), methane (CH), and other reducing reactants known to those skilled in the art. Reducing reactants may be particularly useful when the SiGe contains suboxide impurities. The use of reducing reactants can modify the SiGe material by removing oxygen impurities, thereby forming a more uniform modified SiGe material that is suitable for etching. Because the modified SiGe is more uniform, the etch rate between different portions of the modified SiGe is also more uniform.

[0067] Difluoride source: In some embodiments, the additive comprises a difluoride source. The difluoride source is difluoride (HF - ) into the reaction chamber. Examples of difluorides that can be used include, but are not limited to, ammonium fluoride, aqueous HF, gaseous HF, buffered oxide etch mixtures (e.g., mixtures of HF and a buffer such as ammonium fluoride), and hydrogen fluoride pyridine. In some embodiments, the difluoride source (and / or one or more of the other additives described herein) is added to the reaction chamber before or after delivery to the reaction chamber. - may be subjected to a reaction to form

[0068] aldehyde: In some embodiments, the additive comprises an aldehyde having the formula X—[C(O)]—H. where X is hydrogen, -R 1 , -C(R 2 )3, or -[C(R 3 )2] m -C(O)H, where each R 1 , R 2 , and R 3 are each independently selected from hydrogen, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. m is an integer from 0 to 10.

[0069] In some embodiments, R 1 , R 2 , and R 3is independently alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, haloalkyl, haloalkenyl, haloalkynyl, haloheteroalkyl, haloheteroalkenyl, haloheteroalkynyl, aryl, heterocyclyl, heteroaryl, alkyl-aryl, alkenyl-aryl, alkynyl-aryl, alkyl-heterocyclyl, alkenyl-heterocyclyl, alkynyl-heterocyclyl, alkyl-heteroaryl, alkenyl-heteroaryl, alkynyl-heteroaryl, heteroalkyl-aryl, heteroalkenyl-aryl, heteroalkynyl-aryl, heteroalkyl-heterocyclyl, heteroalkenyl-heterocyclyl, heteroalkynyl-heterocyclyl, heteroalkyl-heteroaryl, heteroalkenyl-heteroaryl, heteroalkynyl-heteroaryl, or any combination thereof. In certain embodiments of the present disclosure, the aldehyde or ketone may be further substituted with one or more substituents. Substituent groups include aldehyde (-C(O)H), oxo (=O), alkoxy, amide, amine, hydroxyl, thioether, thiol, acyloxy, silyl, cycloaliphatic, aryl, aldehyde, ketone, ester, carboxylic acid, acyl, acyl halide, cyano, halogen, sulfonate, nitro, nitroso, quaternary amine, pyridinyl (or pyridinyl functionalized on the nitrogen atom with an aliphatic or aryl group), alkyl halide, or any combination thereof.

[0070] In some embodiments, when X=aromatic, the additive can be an aromatic aldehyde. Examples of aromatic aldehydes include benzaldehyde, 1-naphthaldehyde, phthalaldehyde, and the like.

[0071] In other embodiments, when X=aliphatic, the additive can be an aliphatic aldehyde. Examples of aliphatic aldehydes include acetaldehyde, propionaldehyde, butyraldehyde, isovaleryl aldehyde, and the like.

[0072] In yet another embodiment, X=-[C(R 3 )2] m When X is —C(O)H and m is 0-10, or when X=aliphatic or heteroaliphatic substituted with —C(O)H, the additive can be a dialdehyde. Examples of dialdehydes include glyoxal, phthalaldehyde, glutaraldehyde, malondialdehyde, succinaldehyde, and the like.

[0073] In some cases, the aldehyde used as the additive may be selected from the group consisting of acrolein, acetaldehyde, formaldehyde, benzaldehyde, propionaldehyde, butyraldehyde, cinnamaldehyde, vanillin, and tolualdehyde. In these or other cases, the aldehyde used as the additive may be selected from the aldehydes described in the Aldehydes and Organic Solvents section described in this section.

[0074] Carbenes: In some embodiments, the additive comprises a carbene. The carbene may have the formula X-(C:)-Y. wherein each of X and Y is independently H, halo, -[C(R 1 )2] m -C(R 2 )3, -C(O)-R 1 , or -C(=NR 1 )-R 2 , -NR 1 R 2 , -OR 2 , -SR 2 , or -C(R 2 )3 can be selected. 1 and R 2 is independently selected from hydrogen, hydroxyl, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. m is an integer from 0 to 10. R 1 and R 2may optionally form a cycloheteroaliphatic group together with the atom to which each is attached. X and Y, together with the atoms to which they are each attached, can optionally form a cycloaliphatic or cycloheteroaliphatic group.

[0075] Furthermore, the additive is R 1 -C + (R)-R 2 where R, R 1 , and R 2 are each independently selected from hydrogen, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof.

[0076] In some embodiments, each R, R 1 , and R 2are each independently selected from alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, haloalkyl, haloalkenyl, haloalkynyl, haloheteroalkyl, haloheteroalkenyl, haloheteroalkynyl, aryl, heterocyclyl, heteroaryl, alkyl-aryl, alkenyl-aryl, alkynyl-aryl, alkyl-heterocyclyl, alkenyl-heterocyclyl, alkynyl-heterocyclyl, alkyl-heteroaryl, alkenyl-heteroaryl, alkynyl-heteroaryl, heteroalkyl-aryl, heteroalkenyl-aryl, heteroalkynyl-aryl, heteroalkyl-heterocyclyl, heteroalkenyl-heterocyclyl, heteroalkynyl-heterocyclyl, heteroalkyl-heteroaryl, heteroalkenyl-heteroaryl, heteroalkynyl-heteroaryl, or any combination thereof. In certain embodiments of the present disclosure, the carbene may be further substituted with one or more substituents. These substituents include alkoxy, amide, amine, hydroxyl, thioether, thiol, acyloxy, silyl, cycloaliphatic, aryl, aldehyde, ketone, ester, carboxylic acid, acyl, acyl halide, cyano, halogen, sulfonate, nitro, nitroso, quaternary amine, pyridinyl (or pyridinyl functionalized on the nitrogen atom with an aliphatic or aryl group), alkyl halide, or any combination thereof. In any embodiment using a carbene, R 1 and R 2 Each of these can be selected independently.

[0077] In some embodiments, when at least one of X or Y is halo, the additive can be a halocarbene. Examples of halocarbenes include, but are not limited to, dihalocarbenes, such as dichlorocarbene and difluorocarbene.

[0078] In some embodiments, both X and Y are —NR 1 R 2In one example, the additive may be a diaminocarbene. 1 and R 2 are each independently aliphatic. An example of a diaminocarbene is bis(diisopropylamino)carbene.

[0079] In other embodiments, at least one of X or Y is —NR 1 R 2 and R in X or Y 1 and R 2 When both of these, taken together with the nitrogen atom to which they are attached, form a cycloheteroaliphatic group, the additive can be a cyclic diaminocarbene. Examples of cyclic diaminocarbenes include bis(N-piperidyl)carbene, bis(N-pyrrolidinyl)carbene, and the like.

[0080] As an example, both X and Y are -NR 1 R 2 and X's R 1 R of the group and Y 2 When the groups, together with the nitrogen atom to which they are attached, form a cycloheteroaliphatic group, the additive is an N-heterocyclic carbene. Examples of N-heterocyclic carbenes include imidazol-2-ylidene (e.g., 1,3-dimesityl imidazol-2-ylidene, 1,3-dimesityl-4,5-dichloroimidazol-2-ylidene, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, 1,3-di-tert-butylimidazol-2-ylidene, etc.), imidazolidin-2-ylidene (e.g., 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), triazol-5-ylidene (e.g., 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene), etc.

[0081] In some embodiments, X=—NR 1 R 2 , Y=-SR 2 and X's R 1 R of the group and Y 2When the groups, taken together with the nitrogen atom to which they are attached, form a cycloheteroaliphatic group, the additive is a cyclic thioalkylaminocarbene. Examples of cyclic thioalkylaminocarbenes include thiazol-2-ylidenes, such as 3-(2,6-diisopropylphenyl)thiazol-2-ylidene.

[0082] In some embodiments, X=—NR 1 R 2 , Y=-C(R 2 )3 and X's R 1 R of the group and Y 2 When the groups, taken together with the atoms to which they are attached, form a cycloheteroaliphatic group, the additive is a cyclic alkylaminocarbene. Examples of cyclic alkylaminocarbenes include pyrrolidin-2-ylidene (e.g., 1,3,3,5,5-pentamethyl-pyrrolidin-2-ylidene) and piperidin-2-ylidene (e.g., 1,3,3,6,6-pentamethyl-piperidin-2-ylidene).

[0083] Further examples of carbenes and their derivatives include compounds having a thiazol-2-ylidene moiety, a dihydroimidazol-2-ylidene moiety, an imidazol-2-ylidene moiety, a triazol-5-ylidene moiety, or a cyclopropenylidene moiety. Other carbenes and carbene analogs further include aminothiocarbene compounds, aminooxycarbene compounds, diaminocarbene compounds, heteroaminocarbene compounds, 1,3-dithiolium carbene compounds, mesoionic carbene compounds (e.g., imidazoline-4-ylidene compounds, 1,2,3-triazolylidene compounds, pyrazolinylidene compounds, tetrazol-5-ylidene compounds, isoxazol-4-ylidene compounds, thiazol-5-ylidene compounds, etc.), cyclic alkylaminocarbene compounds, boranylidene compounds, silylene compounds, stannylene compounds, nitrene compounds, phosphinidene compounds, foilcarbene compounds, and the like. Further examples of carbenes include dimethylimidazol-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene, (phosphanyl)(trifluoromethyl)carbene, bis(diisopropylamino)carbene, bis(diisopropylamino)cyclopropenylidene, 1,3-dimesityl-4,5-dichloroimidazol-2-ylidene, 1,3-diadamantylimidazol- 2-ylidene, 1,3,4,5-tetramethylimidazol-2-ylidene, 1,3-dimesitylimidazol-2-ylidene, 1,3-dimesitylimidazol-2-ylidene, 1,3,5-triphenyltriazol-5-ylidene, bis(diisopropylamino)cyclopropenylidene, bis(9-anthryl)carbene, norbornene-7-ylidene, dihydroimidazol-2-ylidene, methylidenecarbene, and the like.

[0084] Organic acids: In some embodiments, the additive comprises an organic acid. The organic acid may have the formula R-COH, where R is selected from hydrogen, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. In certain embodiments, R is alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, haloalkyl, haloalkenyl, haloalkynyl, haloheteroalkyl, haloheteroalkenyl, haloheteroalkynyl, aryl, heteroaryl, alkyl-aryl, alkenyl-aryl, alkynyl-aryl, alkyl-heteroaryl, alkenyl-heteroaryl, alkynyl-heteroaryl, heteroalkyl-aryl, heteroalkenyl-aryl, heteroalkynyl-aryl, heteroalkyl-heteroaryl, heteroalkenyl-heteroaryl, heteroalkynyl-heteroaryl, or any combination thereof. In certain embodiments of the present disclosure, R may be further substituted with one or more substituents. These substituents may be alkoxy, amide, amine, thioether, hydroxyl, thiol, acyloxy, silyl, cycloaliphatic, aryl, aldehyde, ketone, ester, carboxylic acid, acyl, acyl halide, cyano, halogen, sulfonate, nitro, nitroso, quaternary amine, pyridinyl (or pyridinyl where the nitrogen atom is functionalized with an aliphatic or aryl group), alkyl halide, or any combination thereof. In certain implementations, the organic acid may be selected from formic acid and acetic acid.

[0085] Substituents: All examples of materials described herein include unsubstituted and / or substituted forms of the compounds. Examples of substituents include, but are not limited to, one, two, three, or four or more substituents independently selected from the group consisting of: (1) C 1-6 Alkoxy (e.g., -OR (R is C 1-6 alkyl), (2) C 1-6 Alkyl sulfinyl (e.g., -S(O)-R (where R is C 1-6alkyl), (3)C 1-6 Alkylsulfonyl (e.g., -SO2-R (R is C 1-6 alkyl), (4) amines (e.g., —C(O)NR 1 R 2 or -NHCOR 1 (R 1 and R 2 are each independently selected from hydrogen, aliphatic, heteroaliphatic, haloaliphatic, haloheteroaliphatic, aromatic, or any combination thereof, as defined herein, or R 1 and R 2 each taken together with the nitrogen atom to which it is attached forms a heterocyclyl group as defined herein), (5) aryl, (6) arylalkoxy (e.g., -OLR (L is alkyl and R is aryl)), (7) aryloyl (e.g., -C(O)-R (R is aryl)), (8) azido (e.g., -N), (9) cyano (e.g., -CN), (10) aldehyde (e.g., -C(O)H), (11) C 3-8 Cycloalkyl, (12) halo, (13) heterocyclyl (e.g., a 5-, 6-, or 7-membered ring containing 1 to 4 non-carbon heteroatoms, as defined herein), (14) heterocyclyloxy (e.g., —OR (wherein R is heterocyclyl as defined herein)), (15) heterocyclyloyl (e.g., —C(O)—R (wherein R is heterocyclyl as defined herein), (16) hydroxyl (e.g., —OH), (17) N-protected amino, (18) nitro (e.g., —NO), (19) oxo (e.g., ═O), (20) C 1-6 Thioalkoxy (e.g., -SR (R is C 1-6 alkyl), (21) thiol (e.g., -SH), (22) -COR 1 (R 1 is (a) hydrogen, (b) C 1-6 Alkyl, (c) C 4-18 aryl, and (d) C 1-6 Alkyl-C 4-18 Aryl (e.g., -LR (where L is C 1-6 Alkyl, R is C 4-18(23) —C(O)NR 1 R 2 (R 1 and R 2 each independently represents (a) hydrogen, (b) C 1-6 Alkyl, (c) C 4-18 aryl, and (d) C 1-6 Alkyl-C 4-18 Aryl (e.g., -LR (where L is C 1-6 Alkyl, R is C 4-18 (24) -SO2R 1 (R 1 is (a)C 1-6 Alkyl, (b) C 4-18 aryl, and (c) C 1-6 Alkyl-C 4-18 Aryl (e.g., -LR (where L is C 1-6 Alkyl, R is C 4-18 (25)-SONR 1 R 2 (R 1 and R 2 each independently represents (a) hydrogen, (b) C 1-6 Alkyl, (c) C 4-18 aryl, and (d) C 1-6 Alkyl-C 4-18 Aryl (e.g., -LR (where L is C 1-6 Alkyl, R is C 4-18 (26)-NR 1 R 2 (R 1 and R 2 each independently represents (a) hydrogen, (b) an N-protecting group, or (c) C 1-6 Alkyl, (d) C 2-6 Alkenyl, (e) C 2-6 Alkynyl, (f) C 4-18 Aryl, (g) C 1-6 Alkyl-C 4-18 Aryl (e.g., -LR (where L is C 1-6 Alkyl, R is C 4-18 aryl), (h)C 3-8cycloalkyl, and (i) C 1-6 Alkyl-C 3-8 Cycloalkyl (e.g., -LR (where L is C 1-6 Alkyl, R is C 3-8 In one embodiment, there are no two groups attached to the nitrogen atom via a carbonyl or sulfonyl group.

[0086] In certain embodiments, the additive acts as a proton acceptor and - In some such cases, the formation of HF2 - may actively etch one or more materials on the substrate, such as an oxide material or another material.

[0087] As discussed above, in some embodiments, the additive adsorbs to the substrate via chemisorption and / or physisorption. Such adsorption may affect the way F2 and / or other chemicals interact with the substrate, thereby allowing for precise tuning of etch selectivity. For example, the additive may adsorb to Si and / or Ge. This may, at least to some extent, prevent F2 and other chemicals from adsorbing to or reacting with SiGe.

[0088] In various embodiments described herein, additives are used to reduce the selectivity of F2-based thermal etching processes. While high etch selectivity is generally desirable, in some cases it may be too high. This is particularly true when a layer to be selectively etched (e.g., SiGe) has a portion that is relatively rich in an element (e.g., Si) that is selectively retained in another layer. In such cases, high selectivity would result in this relatively rich portion being under-etched. By including the additives described herein, the selectivity can be controlled to reduce the selectivity, allowing the etching process to be tailored to target and remove the desired material. This is a significant improvement.

[0089] While the description herein generally focuses on the use of "one additive," it should be understood that in some embodiments, different additives may be used in combination. For example, multiple etching additives may be used (e.g., in some cases, two or more oxidizing reactants, two or more reducing reactants, or a combination of an oxidizing reactant and a reducing reactant may be used). Similarly, combinations of additives may be selected to achieve a particular combination of effects. As an example, an additive that reacts directly with the substrate and / or another reactant may be combined with an additive that acts as a catalyst and / or an additive that simply adsorbs to the substrate. Similarly, an additive that acts as a catalyst may be combined with an additive that simply adsorbs to the substrate. Depending on the particular embodiment, multiple additives may be combined.

[0090] Process Conditions In various embodiments, one or more process conditions may be controlled during etching. Such process conditions may include the temperature of the substrate support pedestal and / or other substrate temperature controls, pressure, reactant flow rates, timing, etc. Examples of process conditions are provided but are not intended to limit the disclosure unless otherwise stated.

[0091] In various embodiments, the temperature of the substrate is controlled during etching. This is done, for example, by controlling one or more heaters and / or coolers configured to heat and / or cool the substrate. Exemplary mechanisms for controlling the substrate temperature are described in more detail below. In some cases, the temperature of the substrate support pedestal may be controlled. The temperature of the substrate and / or substrate support pedestal may be controlled within a minimum and maximum temperature range. The minimum temperature may be about −60° C., about −40° C., about −20° C., or about 0° C. In these or other embodiments, the maximum temperature may be about 20° C., about 40° C., about 60° C., about 100° C., or about 130° C.

[0092] The pressure within the process chamber may be controlled. For example, the pressure may be controlled within a range of a minimum pressure and a maximum pressure. The minimum pressure may be about 100 mTorr, about 250 mTorr, or about 1 Torr. In these or other embodiments, the maximum pressure may be about 1 Torr, about 3 Torr, or about 10 Torr.

[0093] The flow rates of various reactants may be controlled. For example, the flow rates of the reactants may be controlled within a range between a minimum flow rate and a maximum flow rate. In various embodiments, the minimum flow rate of F2 may be about 5 sccm, about 10 sccm, about 50 sccm, or about 100 sccm. In these or other embodiments, the maximum flow rate of F2 may be about 50 sccm, about 100 sccm, or about 300 sccm. In these or other embodiments, the minimum flow rate of the additive may be about 5 sccm, about 10 sccm, about 50 sccm, about 100 sccm, or about 200 sccm. In these or other embodiments, the maximum flow rate of the additive may be about 25 sccm, about 100 sccm, about 200 sccm, about 250 sccm, or about 300 sccm. In some cases, an inert gas may be supplied in addition to F2 and the additive. The minimum flow rate of the inert gas may be about 10 sccm, about 40 sccm, about 100 sccm, or about 1000 sccm. In these or other embodiments, the maximum flow rate of the inert gas may be about 100 sccm, about 500 sccm, about 1000 sccm, about 1500 sccm, or about 2000 sccm.

[0094] Another type of process condition that can be controlled is the ratio between different species in the process gas. For example, the flow rate ratio of F2 to the additive delivered to the process chamber may be controlled within a minimum and maximum range. The minimum flow rate ratio of F2 to the additive delivered to the process chamber may be about 0.5:1, about 1:1, or about 5:1. The maximum flow rate ratio of F2 to the additive delivered to the process chamber may be about 5:1, about 10:1, about 15:1, about 20:1, or more.

[0095] The timing of exposure to the reactants can be controlled. As described above, the additives can be supplied simultaneously with F2 or at different times. The exposure time to each reactant can be controlled within a minimum and maximum time range. In various embodiments, the minimum time for exposing the substrate to F2 can be about 500 milliseconds, about 1 second, about 5 seconds, or about 60 seconds. In these or other embodiments, the maximum time for exposing the substrate to F2 can be about 10 seconds, about 60 seconds, about 500 seconds, or more. In these or other embodiments, the minimum time for exposing the substrate to the additive can be about 1 second, about 5 seconds, or about 60 seconds. In these or other embodiments, the maximum time for exposing the substrate to the additive can be about 10 seconds, about 60 seconds, about 500 seconds, or more.

[0096] Another controllable factor is exposure of the substrate to the atmosphere. Specifically, such exposure may be prevented so as not to damage or otherwise affect the material on the substrate surface. In particular, it may be beneficial to avoid exposure to the atmosphere from (1) when the SiGe / Si stack is cut to form the recessed features (which often precedes the methods described in FIGS. 1, 3, and 5) until (2) when the method of FIG. 1, 3, or 5 is completed (at which point the SiGe may have been partially or completely removed from the substrate). Depending on the particular application, load locks and / or other suitable substrate transfer mechanisms may be used to transfer substrates between different process chambers without exposure to the atmosphere.

[0097] Device The methods described herein can be performed by any suitable apparatus or combination of apparatuses. Suitable apparatus includes hardware for performing process steps and a system controller having instructions for controlling the process steps in accordance with the present invention. For example, in some embodiments, the hardware may include one or more process stations included in a process tool. At least one process station is an etching station.

[0098] FIG. 7A illustrates an example of a substrate processing chamber 700 for etching or cleaning under vacuum. While a particular substrate processing chamber is illustrated and described, the present invention may be practiced using other types of substrate processing systems. For example, a substrate processing system operating at atmospheric pressure may be used. In some cases, one or more features described in connection with the substrate processing chamber may be omitted. Such features include, but are not limited to, hardware for generating plasma. While some implementations may use plasma, in some cases the present invention may be practiced without the use of plasma. In some cases, plasma may be used for different processing steps, such as pre- and / or post-etch substrate processing or substrate or processing chamber cleaning.

[0099] 7A, the substrate processing chamber 700 includes a lower chamber region 702 and an upper chamber region 704. The lower chamber region 702 is defined by a chamber sidewall surface 708, a chamber bottom surface 710, and a lower surface of a gas distribution apparatus 714.

[0100] The upper chamber region 704 is defined by the top surface of the gas distributor 714 and the inner surface of the dome 718. In some examples, the dome 718 rests on a first annular support 721. In some examples, the first annular support 721 has one or more spaced apart holes 723 for supplying process gas to the upper chamber region 704. In some examples, the process gas is supplied upward by the one or more spaced apart holes 723 at an acute angle relative to a plane containing the gas distributor 714; however, other angles / directions may be used. In some examples, a gas passage 734 in the first annular support 721 supplies gas to the one or more spaced apart holes 723.

[0101] The first annular support 721 may rest on a second annular support 725. The second annular support 725 defines one or more spaced apart holes 727 for supplying process gas from gas passages 729 to the lower chamber region 702. In some examples, holes 731 in the gas distributor 714 are aligned with the spaced apart holes 727. In other examples, the gas distributor 714 has a smaller diameter and does not require holes 731. In some examples, the process gas is supplied by the one or more spaced apart holes 727 downward toward the substrate at an acute angle relative to a plane containing the gas distributor 714; however, other angles / orientations may be used.

[0102] In other examples, the upper chamber region 704 may be cylindrical with a flat top and may use one or more planar induction coils. Still other examples may use a single chamber with a spacer disposed between the showerhead and the substrate support pedestal.

[0103] A substrate support pedestal 722 is disposed in the lower chamber region 702. In some examples, the substrate support pedestal 722 includes an electrostatic chuck (ESC), although other types of substrate support pedestals can be used. A substrate 726 is disposed on top of the substrate support pedestal 722 during etching. In some examples, the temperature of the substrate 726 may be controlled by a heater plate 717, an optional channeled cooling plate, and one or more sensors (not shown). However, other suitable substrate support temperature control systems may also be used.

[0104] In some examples, the gas distribution apparatus 714 includes a showerhead (e.g., a plate 733 having a plurality of spaced apart holes 735). The plurality of spaced apart holes 735 penetrates the plate 733 from its top surface to its bottom surface. In some examples, the diameter of the spaced apart holes 735 is between 0.1 inches and 0.75 inches (2.54 mm and 19.5 mm). In some examples, the showerhead is formed of a conductive material such as aluminum, or a non-conductive material such as ceramic with embedded electrodes formed from a conductive material.

[0105] One or more induction coils 740 are positioned around the periphery of the dome 718. When energized, the one or more induction coils 740 generate an electromagnetic field inside the dome 718. In some examples, an upper coil and a lower coil are used. A gas injector 742 injects one or more gas mixtures from a gas supply system 750-1.

[0106] In some examples, gas delivery system 750-1 includes one or more gas sources 752, one or more valves 754, one or more mass flow controllers (MFCs) 756, and a mixing manifold 758. However, other types of gas delivery systems may be used. In some cases, mixing manifold 758 may be omitted, and gases may be supplied individually to gas injectors 742. An optional vapor delivery system 759 supplies a vapor containing a carrier gas and another gas to the process chamber.

[0107] A gas splitter (not shown) may be used to vary the flow rate of the gas mixture. A separate gas supply system 750-2 may be used to supply an etching gas or etching gas mixture to the gas passages 729 and / or 734 (in addition to or instead of the etching gas from the gas injector 742). As used herein, a process gas includes at least F2 and an additive. Any combination of the gas supply system 750-1, the gas supply system 750-2, and / or the vapor supply system 759 may be used to supply the F2 and additive to the process chamber 700. In various embodiments, the F2 may be supplied separately from the additive. For example, F2 may be supplied to the lower chamber region 702 via the holes 731 and the spaced holes 727, and the additive may be supplied to the upper chamber region 704 via the gas injector 742 (or vice versa). The F2 and / or additive may be supplied with a carrier gas, such as N2 or a noble gas. In some embodiments, gas delivery system 750-1, gas delivery system 750-2, and / or vapor delivery system 759 may be configured to deliver two or more reactants in a pulsed mode. As one example, F and an additive (either or both may be delivered with an inert gas) may be alternately pulsed into substrate processing chamber 700.

[0108] A suitable gas delivery system is shown and described in commonly assigned U.S. patent application Ser. No. 14 / 945,780, entitled "Gas Delivery System," filed Nov. 19, 2015, which is incorporated herein by reference in its entirety. Suitable single or dual gas injectors and other gas injection locations are shown and described in commonly assigned U.S. Patent No. 10,825,659, entitled "Substrate Processing Chamber Including Multiple Gas Injection Points and Dual Injectors," filed Jan. 5, 2017, which is incorporated herein by reference in its entirety.

[0109] In some examples, the gas injector 742 includes a central injection position that directs gas downward and one or more side injection positions that inject gas at an angle relative to the downward direction. In some examples, the gas delivery system 750-1 delivers a first portion of a gas mixture at a first flow rate to the central injection position of the gas injector 742 and a second portion of the gas mixture at a second flow rate to the side injection positions of the gas injector 742. In other examples, multiple different gas mixtures are delivered by the gas injector 742. In some examples, the gas delivery system 750-1 delivers one or more process gases to the gas flow paths 729, 734 and / or other positions within the process chamber.

[0110] An optional plasma generator 770 may be used to generate RF power that is output to the one or more inductive coils 740. A plasma 790 is generated in the upper chamber region 704. In some examples, the plasma generator 770 includes an RF source 772 and a matching network 774. The matching network 774 matches the impedance of the RF source 772 to the impedance of the one or more inductive coils 740. In some examples, the gas distributor 714 is connected to a reference potential, such as ground. Valves 778 and pumps 780 may be used to control the pressure in the lower and upper chamber regions 702, 704 and to evacuate reactants.

[0111] A controller 776 communicates with gas supply systems 750-1, 750-2, valves 778, pumps 780, and / or plasma generator 770 to control the flow rates of process gases, purge gases, RF plasma, and chamber pressure. In some examples, the plasma is maintained within the dome 718 by one or more inductive coils 740. One or more gas mixtures are introduced from the top of the chamber by gas injectors 742 (and / or spaced holes 723), and the plasma is confined within the dome 718 by a gas distributor 714.

[0112] In some examples, an RF bias 784 is provided. The RF bias 784 includes an RF source 786 and an optional matching network 788. The RF bias power can be used to generate a plasma between the gas distributor 714 and the substrate support pedestal or to create a self-bias on the substrate 726 to attract ions. A controller 776 can be used to control the RF bias power.

[0113] Referring now to FIG. 7B, optional vapor supply system 759 can include a bubbler or ampoule. Vapor supply system 759 includes a carrier gas source 792 connected to a mass flow controller 794 by valve V1. Vapor supply system 759 further includes valves V2, V3, V4, V5, and V6 configured to block or control the flow of carrier gas or a carrier gas and solvent mixture. Temperature sensor 797 and heater 798 are used to control the temperature of the solvent in ampoule 796. Carrier gas can be supplied by opening valves P1, V2, V4, V5, and V6. Carrier gas and solvent can be supplied by opening valves V1, V2, V3, V5, and V6 and closing valve V4.

[0114] 8, a substrate processing tool 810 according to the present disclosure is shown. The substrate processing tool 810 includes a robot 812 located in a central position. The robot 812 can operate at vacuum or atmospheric pressure. The substrate processing tool 810 includes multiple stations 816-1, 816-2, ..., 816-S (collectively referred to as stations 816), where S is an integer greater than 1, located around the robot 812. The stations 816 may be arranged with uniform or irregular angular offsets around the center of the substrate processing tool 810. Examples of stations 816 include deposition, etch, pre-clean, post-clean, spin-clean, etc. Substrates may be initially placed in a cassette 834. A robot and load lock, generally designated 838, may be used to move substrates from the cassette 834 to the substrate processing tool 810. Once processing is complete, the robot and load lock 838 may return the substrates to the cassette 834 and / or another cassette 839.

[0115] In some examples, one of the stations 816 performs deposition or etching. Another of the stations 816 performs the cleaning or etching described above. Another of the stations (such as a spin clean chamber) performs the quick wet cleaning step described above. In some examples, the substrate is moved by a robot 812 from the deposition or etching station to the cleaning or etching station and then to the quick wet cleaning station.

[0116] In some cases, two or more etching stations may be provided. One etching station may be configured to etch recessed features into the Si / SiGe stack to form structures such as those shown in Figures 2A, 4A, and 6A, and another etching station may be configured to selectively etch SiGe relative to Si, as described throughout this specification. In some cases, one of these stations (or another station) may be configured to perform depositions, such as deposition of spacer materials or other structures associated with forming the GAA device.

[0117] Summary Although the above-described embodiments have been described in some detail for clarity of understanding, it will be apparent that certain changes and modifications may be made within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Accordingly, the present embodiments should be considered as illustrative only and not limiting of the disclosure, and the embodiments are not limited to the details set forth herein.

Claims

1. 1. A method for processing a substrate, comprising: placing a substrate including one or more layers of silicon and one or more layers of silicon germanium in a process chamber; The substrate is F 2 and exposing the exposing the substrate to an additive; Including, The substrate is F 2 and the silicon germanium is selectively etched relative to the silicon by exposure to the additive, and the substrate is 2 not be exposed to plasma while being exposed to method.

2. 10. The method of claim 1, The additive is hydrogen (H 2 ), hydrogen fluoride (HF), carbon monoxide (CO), sulfur dioxide (SO 2 ), and methane (CH 4 ) a reducing reactant selected from the group consisting of:

3. 10. The method of claim 1, The additive comprises an oxygen-containing reactant and F 2 and an elemental halogen other than

4. 10. The method of claim 1, The method, wherein the additive comprises one or more materials selected from the group consisting of heterocyclic aromatic compounds, heterocyclic aliphatic compounds, alcohols, amines, amino acids, organophosphorus compounds, difluoride sources, aldehydes, carbenes, organic acids, and combinations thereof.

5. 10. The method of claim 1, The method wherein the additive is adsorbed onto the substrate.

6. 10. The method of claim 1, The method, wherein the additive comprises an organic molecule.

7. 10. The method of claim 1, The method wherein the silicon germanium is etched at a more uniform rate than if the substrate were not exposed to the additive.

8. 10. The method of claim 1, The substrate is F 2 and said additive simultaneously and / or for periods that overlap with each other.

9. 10. The method of claim 1, The substrate is F 2 and the substrate is exposed to the additive at a second time later than the first time.

10. 10. The method of claim 9, The substrate is subjected to F 2 a first portion of the silicon germanium is etched by exposing the substrate to the additive at the second time, and a second portion of the silicon germanium is etched by exposing the substrate to the additive at the second time, wherein the silicon germanium is etched more uniformly after etching the second portion than after etching the first portion.

11. 11. The method of claim 10, The method, wherein the first portion of the silicon germanium and the second portion of the silicon germanium differ in composition.

12. 11. The method of claim 10, The method, wherein the first portion of the silicon germanium and the second portion of the silicon germanium have different material properties.

13. 10. The method of claim 1, The substrate is exposed to the additive at a first time to modify the silicon germanium, thereby forming modified silicon germanium, and the substrate is exposed to F at a second time later than the first time. ２ A method of exposure to

14. 10. The method of claim 1, Said F 2 and the additive is supplied to the process chamber in alternating pulses.

15. 1. An apparatus for etching a substrate, comprising: one or more process chambers each including a substrate support pedestal; one or more gas inlets and associated flow control hardware to the process chamber; a controller having at least one processor and a memory; Equipped with the at least one processor and the memory are communicatively coupled to each other; the at least one processor is at least operatively connected to the flow control hardware; The memory controls the at least one processor to: placing a substrate including one or more layers of silicon and one or more layers of silicon germanium in one of the one or more process chambers; The substrate is F 2 and exposing the exposing the substrate to an additive; storing computer-executable instructions for performing the The substrate is F 2 and the silicon germanium is selectively etched relative to the silicon by exposure to the additive, and the substrate is 2 not be exposed to plasma while being exposed to Device.

16. 16. The apparatus of claim 15, The apparatus comprises two or more process chambers and a load lock for transferring the substrate between the two or more process chambers without exposing the substrate to the atmosphere.

17. 16. The apparatus of claim 15, The additive is hydrogen (H 2 ), hydrogen fluoride (HF), carbon monoxide (CO), sulfur dioxide (SO 2 ), and methane (CH 4 ).

18. 16. The apparatus of claim 15, The additive comprises an oxygen-containing reactant and F 2 and an elemental halogen other than .

19. 16. The apparatus of claim 15, the additive comprises one or more materials selected from the group consisting of heterocyclic aromatic compounds, heterocyclic aliphatic compounds, alcohols, amines, amino acids, organophosphorus compounds, difluoride sources, aldehydes, carbenes, organic acids, and combinations thereof.

20. 16. The apparatus of claim 15, The additive is adsorbed onto the substrate.

21. 16. The apparatus of claim 15, The device, wherein the additive comprises an organic molecule.

22. 16. The apparatus of claim 15, The apparatus wherein the silicon germanium is etched at a more uniform rate than if the substrate were not exposed to the additive.

23. 16. The apparatus of claim 15, The substrate is F 2 and said additive simultaneously and / or for periods of time that overlap with each other.

24. 16. The apparatus of claim 15, The substrate is F 2 and the substrate is exposed to the additive at a second time later than the first time.

25. 25. The apparatus of claim 24, The substrate is subjected to F 2 a first portion of the silicon germanium is etched by exposing the substrate to the additive at the second time, and a second portion of the silicon germanium is etched by exposing the substrate to the additive at the second time, and the silicon germanium is etched more uniformly after etching the second portion than after etching the first portion.

26. 26. The apparatus of claim 25, The device, wherein the first portion of the silicon germanium and the second portion of the silicon germanium differ in composition.

27. 26. The apparatus of claim 25, The device, wherein the first portion of the silicon germanium and the second portion of the silicon germanium have different material properties.

28. 16. The apparatus of claim 15, The substrate is exposed to the additive at a first time to modify the silicon germanium, thereby forming modified silicon germanium, and the substrate is exposed to F at a second time later than the first time. ２ The device is exposed to

29. 16. The apparatus of claim 15, Said F 2 and wherein the additive is supplied to the process chamber in alternating pulses.

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