Surface modification to achieve selective isotropic etching

Abstract

The surface of a substrate is modified, the substrate comprising at least two distinct layers or films of different materials, and the modified layer is then selectively converted into a protective layer on one layer while the other layer is etched.

Description

[Technical Field]

[0001] Cross-references to related patents and applications This application claims priority to and the benefit of the filing date of U.S. Non-Provisional Patent Application No. 17 / 945,897, filed September 15, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to the processing of substrates and related equipment, particularly where plasma or gas phase etching is used for part of the process. [Background technology]

[0003] Etching semiconductor materials often requires selectively etching one material with respect to (or relative to) another material while both are disposed in the same environment, such as a plasma or gas-phase chemical etching environment. Selective etching can be particularly challenging in that in certain parts of the manufacturing flow, a first material may need to be selectively etched relative to a second material, while different parts of the process may require different etch selectivities, including selective etching of the second material relative to the first material or selective etching of another material relative to the first and / or second material. Additionally, selective etching can be problematic in that it complicates the overall process due to the challenges of ever-smaller device and layer sizes, the need for precision in etching, and the need to avoid damage. Summary of the Invention

[0004] The present invention provides an advantageous method and associated apparatus for selective etching, in which an initial treatment process is provided, after which the treatment facilitates various selectivities for different materials and different combinations of materials. In one example, first and second films or layers are provided on a substrate, with the first and second films each formed of different materials, including silicon. Both films are subjected to a treatment to provide modified surfaces on both films. In one example, the treatment is performed in a non-plasma environment, followed by a thermal treatment. After the thermal treatment, a subsequent etching treatment selectively converts the modified surface to a protective layer or etch stop layer on one surface of the materials, while the other material is etched (in a plasma etching chemistry or a gas-phase etching chemistry), thereby providing selective etching. The initial treatment and / or the etching treatment can be varied to provide various selectivity combinations. [Brief explanation of the drawings]

[0005] [Figure 1A] Treatment or surface modification and etching methods are shown. [Figure 1B] Treatment or surface modification and etching methods are shown. [Figure 1C] Treatment or surface modification and etching methods are shown. [Figure 2] 1 is an example of an apparatus that can be used with the present invention. [Figure 3] 1 is a flowchart or algorithm illustrating an example of a process. [Figure 4A] Additional processing is shown. [Figure 4B] Additional processing is shown. DETAILED DESCRIPTION OF THE INVENTION

[0006] Aspects and advantages of the present invention will become apparent from the description herein. It will be understood that, in practicing the invention, certain aspects or advantages can be utilized without the use of other aspects or advantages. Thus, the present invention can be practiced using variations and / or a subset of the example features or advantages described herein.

[0007] While an example is described with respect to a recess process, it should be understood that the present invention can also be utilized when selective etching of two different materials is desired for other applications. For example, aspects of the present method can be used in SiGe and Si nanosheet fabrication, channel release or channel trim, breakthrough process steps, or oxide layer removal for various n-type and p-type field effect transistor (nFET and pFET) operations. The methods described herein can improve surface functionality for subsequent processing, e.g., improving or imparting selectivity and avoiding or reducing damage. Additionally, the methods described herein can render the surface hydrophobic, so that subsequent processing, e.g., etching silicon oxide, can be more effective, e.g., using hydrogen, oxygen, and fluorine-containing gases, e.g., aerosolized HO and fluorine-containing gases. Additionally, while example materials are described herein, it should be understood that alternative materials can also be utilized. Furthermore, some examples are described as not presenting an element or material. This should be understood to mean that such elements or materials are not intentionally introduced, although trace amounts may be present depending on the purity of the materials utilized and / or as a result of outgassing or release of elements from other materials during processing.

[0008] The disclosed examples can provide selective isotropic etching of different materials and different combinations of materials relative to each other.

[0009] In one example, an initial surface treatment is provided to each of at least two layers or two films (first and second films). Preferably, the treatment is a non-plasma gas-phase treatment. As used herein, gas-phase is used to mean a non-plasma treatment unless otherwise specified, although the gas-phase may include an aerosolized component, such as aerosolized water, and / or may also use a gas-phase component. After the initial treatment, a modified surface is obtained and provided on the surface of the film, for example, on both sides of the film. The modified surface is then selectively converted to a protective surface or layer on one film while the other film is etched, thereby providing selective etching of the unprotected film relative to the protected film. Varying which materials are selectively converted or remain unprotected can provide different etch selectivities for different materials. Additionally, in certain examples, different etch selectivities for different materials can be provided while utilizing the same or substantially the same pretreatment or surface modification step. Modifications to the pretreatment and / or subsequent etching treatment can provide numerous additional combinations of selectivity.

[0010] The films may be formed from different materials, although in one example, each of the films is a silicon-containing film, and at least two films of different materials are provided. For example, the first film may comprise epitaxial silicon, polysilicon, silicon oxide (of various qualities or types), or silicon germanium (SiGe). The second film may be selected from the same group, but will be different from the first film. The two different films may also include two different silicon oxide films. One of the films may also be a silicon nitride film.

[0011] An example embodiment is described with reference to FIGS. 1A-1C. In the initial structure of FIG. 1A, the substrate includes a semiconductor base 100, which may include, for example, a wafer or substrate base and additional layers on the substrate base underlying the material being processed as described herein. In this example, the material being processed includes at least a first film 104 and a second film 102 arranged in alternating layers. Additionally, a mask 108 may be present, formed from, for example, SiN, an inorganic material, or a low-k material. While two films are shown at 102 and 104, it should be understood that other films may be present. In the example, at least one of the films 102 and 104 is vertically above the other film, and multiple films may be arranged in an alternating configuration. Additionally, the films are formed from different materials, and each of the films or layers 102 and 104 is a silicon-containing film. For example, the first film 104 can be formed from epitaxial silicon, polysilicon, silicon oxide, or silicon germanium (SiGe). The second film 102 can also be formed from, for example, epitaxial silicon, polysilicon, silicon oxide, or SiGe, with the second film being formed from a different material than the first film. In another example, one of the films can be a silicon nitride film.

[0012] In an initial processing step, modified surfaces 116 are formed on the sides of the first and second films, as shown in FIG. 1B. In a preferred example, the modified surfaces are formed in a gas-phase, non-plasma environment where a gas containing hydrogen, fluorine, and oxygen is introduced. For example, the processing gas may include HF, aerosolized HO, and a carrier gas such as argon and / or nitrogen. In one example, as a result of processing, the modified surfaces include hydrogen, silicon, and fluorine. Additionally, if one of the films includes Ge (e.g., SiGe), the modified surfaces typically also include Ge in that layer or region of the film, resulting in the modified surfaces including hydrogen, silicon, fluorine, and germanium.

[0013] According to one example, the first film may include epitaxial silicon and the second film may include silicon germanium (SiGe), with the process resulting in modified surfaces 116 on the sides of both layers, with the modified surfaces including H, Si, F, and Ge on the sides of the SiGe layer, while the modified surfaces on the sides of the epitaxial silicon layer include H, Si, and F. As previously mentioned, the process environment includes introduced gases, which may include hydrogen, fluorine, and oxygen, as well as carrier gases such as nitrogen and / or argon. The duration of the vapor-phase process may vary but is preferably at least 10 seconds. The vapor-phase process is performed at a temperature ranging from -20°C to 200°C and a pressure ranging from 10 mTorr to 4 Torr. For example, if one of the films is epitaxial silicon and the other is SiGe, the temperature may preferably range from 0°C to 35°C, and the pressure may range from 1 Torr to 4 Torr. Example gas flow rates can be 200 sccm to 1000 sccm of aerosolized HO, 300 sccm to 1000 sccm of HF, and 100 sccm to 450 sccm of N. Other fluorine- or halogen-containing gases can also or alternatively be used, and alternative carrier gases such as argon can also be used. Furthermore, while aerosolized HO is provided in preferred examples, water can be provided in a different form, e.g., vapor form. Alternative gases can also be utilized to provide gases containing hydrogen and oxygen. Aerosolized HO is currently preferred. In some examples herein, the gases present during processing include at least hydrogen, oxygen, and fluorine, and typically also include a carrier gas such as argon and / or nitrogen.

[0014] Then, after the treatment to form the modified surface, an optional but preferred heat treatment is also carried out, mainly to remove residual water or water vapor. The heat treatment is preferably carried out in an inert atmosphere (e.g., containing nitrogen and / or argon, but without reactive gases, e.g., without halogen gases). For example, the heat treatment can be carried out at a pressure in the range of 1 Torr to 3 Torr and at a temperature in the range of 100°C to 350°C, e.g., 100°C to 300°C, preferably 100°C to 250°C. Preferably, the flow of gases containing hydrogen, fluorine (or another halogen), and oxygen is stopped during the heat treatment.

[0015] After forming and heat-treating the modified surface 116, the modified surface is selectively converted into a protective surface, as indicated at 116a. In the illustrated example, the modified surface 116 is converted into a protective surface or layer 116a adjacent to the first film 104, and the second film 102 is selectively etched relative to the first film to recess the second film 102, resulting in the second film having smaller outer dimensions than the outer dimensions of the first film. However, the selective conversion of the modified film into a protective film and the selective etching can be reversed, e.g., the modified surface converts into a protective surface or layer on the sides of the second film 102, and the selective etching of the first film 104 recesses the first film relative to the second film.

[0016] For modified surfaces 116 on films or layers that are subsequently etched, the modified surface 116 may be removed or partially removed during the thermal treatment step (before the plasma or vapor etching) so that the only portions of the film 116 that remain during the plasma or vapor etching process are those portions of the layer 116 (or modified surface 116) that then become the protective surface or layer 116a. Alternatively, if portions of the modified surface 116 adjacent to the film or layer to be etched are present after the thermal treatment, they are then removed in the plasma or vapor etching process, which then etches the recessed film or layer. Due to the nature of the surface modification, in areas of the layer to be etched, the areas may sublimate (or partially sublimate) during the thermal treatment or be removed during the etching.

[0017] For example, if the recessed (etched) film includes SiGe and the film being protected includes epitaxial silicon, the etching gas chemistry may include fluorine (F) and a carrier gas such as argon in a gas-phase etch. In one example, the gas chemistry is nitrogen-free, and more preferably both nitrogen and hydrogen-free, because such gases may form nitrides on the surface of the SiGe layer or film that may interfere with etching. Conversely, if the SiGe layer is to be protected and the epitaxial silicon layer is to be etched, the plasma etching gas chemistry may include F, N, and H to convert the modified surface into a germanium nitride surface that can protect the SiGe layer or film, and the epitaxial silicon can be selectively etched relative to the SiGe film.

[0018] In an example where the SiGe layer is protected by a surface 116a or protective layer 116a and Si is to be etched, an initial portion of the plasma process (e.g., 5-25 seconds, preferably 8-20 seconds, more preferably 10-15 seconds) can be performed in which N and H are introduced but fluorine (or another halogen) is not, thereby converting the modified surface 116a into a protective surface or protective layer 116a. Then, in a second portion of the plasma process, fluorine (or another halogen) can be introduced while continuing to introduce nitrogen and hydrogen, and the silicon-containing layer (epitaxial silicon in this example) is etched. The first portion of the process (or first plasma) can be sequential with the second portion (or second plasma), with the difference being that a halogen (e.g., fluorine) is introduced in the second portion. The protective surface or protective layer 116a includes germanium nitride, which protects the SiGe layer during the etching of the epitaxial silicon layer. The flow of hydrogen or halogen-containing gas can be periodically interrupted for a period as etching progresses, while the flow of other gases (such as nitrogen and hydrogen) continues, thereby providing additional protection or passivation of newly exposed surfaces (as recesses form) (thereby exposing protected surfaces on the top and bottom of the film facing the recesses, as shown in FIG. 1C). For example, after a first treatment with a halogen-free plasma followed by a halogen-containing plasma (the second portion being, e.g., 5-30 seconds, preferably 8-25 seconds), the flow of halogen and / or plasma-generating power can be interrupted for a period (e.g., 8-20 seconds, preferably 10-15 seconds) while the hydrogen and nitrogen flows continue, after which the treatment is resumed with the halogen (fluorine) introduced and the plasma-generating power applied.

[0019] A single-step etch (without periodically stopping the fluorine or halogen-containing gas) can also be used. Additionally, if a two-step etch is used, the first and second steps can be alternated a predetermined number of times or multiple times based on one or more sensed parameters (e.g., amount of etching measured or detected, total etching time). Furthermore, the initial modification can be repeated periodically in either a one-step etch or a two-step etch.

[0020] In the above example, the same pretreatment (gas phase) can be advantageously used for both the selective etching of epitaxial silicon relative to SiGe (e.g., using H, F, and N plasma etch chemistries) and conversely, the selective etching of SiGe relative to epitaxial silicon (e.g., using, for example, F and Ar etch chemistries in a non-plasma gas phase etch), with improved etch selectivity for both as a result of the pretreatment.

[0021] This can be advantageous when a substrate may have different features or devices in different regions of the substrate. For example, a substrate may include a first region containing a first device or a first set of devices, where an epitaxial silicon or other silicon layer forms a channel, then a recess is formed in a germanium or SiGe layer, and then released (removed), and a second region containing a second device or a second set of devices, where a germanium or SiGe layer forms a channel, then a recess is formed in a silicon layer, such as epitaxial silicon, and then released. In an example of the present invention, the same surface modification can be used for both devices and regions of the substrate. Different etching steps can then be used for the different devices or regions, while the unetched devices are covered with an organic material, such as OPL. Advantageously, the etching pretreatment improves the selectivity of both etches.

[0022] Although the presently disclosed methods may be applicable when one or two layers contain a metal, according to some examples, one or both of the films or layers 102, 104 are metal-free, and preferably the processing gases and / or etching process gases are metal-free.

[0023] In another example, the first and second films can be different silicon oxides; for example, the first film can be thermal oxide or TEOS, and the second layer can be an ALD oxide (atomic layer deposited silicon oxide). They can be etched relative to each other using the same etch pretreatment described herein. During etching (after pre-etch modification as discussed previously herein), a fluorine-containing gas is introduced in the range of 500 sccm to 1500 sccm, and the etching gas also includes aerosolized HO in the range of 100 sccm to 1000 sccm, preferably in the range of 200 sccm to 1000 sccm, and a carrier gas (e.g., nitrogen and / or argon in the range of 50 to 500 sccm, preferably in the range of 100 sccm to 450 sccm). This results in a selective etch of the ALD oxide selective to the thermal oxide in the gas-phase etch.

[0024] According to another example, the second layer or film can include silicon oxide, and the first film can include silicon nitride or a low-k dielectric. For example, the low-k dielectric (before treatment) can include one or more of silicon, oxygen, carbon, and hydrogen (e.g., SiCOH). The pretreatment can be as described above with respect to temperature and pressure. In one example, a fluorine-containing gas can be introduced in the range of 500 sccm to 1500 sccm, aerosolized HO can be introduced in the range of 100 sccm to 500 sccm, and a carrier gas can be introduced in the range of 800 sccm to 2000 sccm. A thermal treatment can then be performed as described above. The etching process may involve a fluorine-containing gas (e.g., 10 sccm to 300 sccm), a catalyst-containing gas such as NH3 (e.g., 20 sccm to 300 sccm), and a carrier gas such as argon (50 sccm to 500 sccm) in a vapor phase etch at a pressure preferably in the range of 20 mTorr to 800 mTorr and a temperature preferably in the range of 20°C to 140°C.

[0025] In another example, the first film can be thermal oxide or TEOS, and the second film can be SiN. In this example, SiN can be etched relative to thermal oxide using a pretreatment preferably containing 300 sccm to 800 sccm of a fluorine-containing gas, 100 sccm to 500 sccm of aerosolized HO, and 20 sccm to 500 sccm of a carrier gas (e.g., nitrogen and / or argon), using the same temperature and pressure as the previous example. The thermal treatment can be as described above. The main etch can be, for example, a plasma etch using RF power of 400 Watts to 800 Watts, preferably using remote plasma, with a process gas including hydrogen (10 sccm to 100 sccm), oxygen (100 sccm to 600 sccm), and a fluorine-containing gas (10 sccm to 75 sccm), a pressure of 50 mTorr to 500 mTorr, and a temperature in the range of 10°C to 90°C, which provides a highly selective etch of SiN over thermal oxide, with the improved selectivity provided by the etch pretreatment.

[0026] Table 1 further summarizes Examples 1-11 in which the present method is used. In Table 1, Film 2 is the layer or film that is selectively etched. In other words, Film 2 is etched preferentially (i.e., at a greater etch rate) relative to Film 1. For example, Film 2 corresponds to layer 102 in the example of FIGS. 1A-1C, and Film 1 corresponds to layer 104. Table 1 specifies the process conditions for the modification and further etching. As shown, according to the example, the modification is gas phase (as shown in parentheses), while the etching can be gas phase or plasma etching (also shown in parentheses). Gas flow rates for the gases used in one example are shown in Table 1, and examples of other (alternative or additional) gases are also listed.

[0027] [Table 1]

[0028] [Table 2]

[0029] [Table 3]

[0030] [Table 4]

[0031] FIG. 2 illustrates an example of a process chamber in which one or more of the processing operations disclosed herein can be utilized. A gas supply 204 is provided for plasma or gas-phase processing, and the gas supply may include one or more supply lines and a reservoir or source for containing and providing a supply of process gas. To form the plasma, at least one power source 202 is preferably provided. The power source may be, for example, a radio frequency (RF) power source for supplying power to an electrode 218, which can form the plasma using process gas introduced from a gas supply or gas source GS 204. For example, the process gas may be introduced through the electrode 218 in a showerhead configuration, although alternatively or in addition, the process gas may be introduced elsewhere. It should be understood that the number of electrodes may vary, and alternative plasma generating sources, such as those using an inductive or microwave power source to generate the plasma, may also be utilized. Additionally, for gas-phase etching, electrodes and plasma generating power are not required.

[0032] In the illustrated example, the plasma is formed as a remote plasma, e.g., a first plasma is generated as represented by P1. When the plasma generated in the first chamber or chamber portion 210 moves to the second chamber or chamber portion 212, ions are removed by a mesh or grid structure 230, which removes ions so that radicals in the plasma P2 are primarily used for plasma processing of the substrate 222 residing on the substrate support 220. However, it should be understood that the plasma can also be generated in the same chamber or chamber portion in which the substrate resides. Thus, while in some examples it may be preferable to use a remote plasma so that the processing of the substrate is radical-based, this is optional, and the element (e.g., the grid or mesh structure) 230 can be eliminated if necessary. Additionally, in the case of gas-phase etching, the structure 230 is not required. The substrate 222 is mounted on a substrate support 220 that can electrostatically attract the substrate 222. When a remote plasma is used or gas-phase etching is performed, it is not necessary to supply plasma-generating power to the support 220 (and region 220). However, bias power and / or plasma generating power may also be applied to the substrate holder 220 or to an electrode of the substrate holder 220, in which case the plasma is generated in the region where the substrate is located.

[0033] A controller 200 is provided to control the various operations and processes as described herein. The controller 200 may include, for example, a processor or computer and memory, which may include non-transitory computer-readable memory. It should be understood that the controller may include a centralized controller as well as multiple controllers or sub-controllers that may control different chambers or chamber components. Additionally, the controller may store recipe data and data related to substrates or wafers to control substrate transfer operations and / or update or modify processes based on feedback or measurement data of previously processed substrates (or data specific to the particular substrate being or to be processed).

[0034] A vacuum pump VP 224 is provided for evacuating process gases and may also vary the pressure within one or more chambers in conjunction with the flow of input gases. A temperature control TC is represented at 206 and may include various temperature, heating, or cooling means for heating and / or cooling the process chamber and / or the substrate support 220. For example, electrical heating may be provided within the substrate support 220, and / or fluid heating or cooling (or heat exchange) may be provided within the substrate support 220. Similarly, heating and / or cooling means including electrical and / or fluid cooling or heat exchange elements may be provided in the chamber walls or chamber wall portions 214, 216.

[0035] Referring to Figure 3, an overview of the process disclosed herein is provided, which may be provided, for example, as an algorithm for processing controlled by the processing device controller 200. While Figure 3 shows an overview of the process, further details of the process under the control of the controller may be provided as disclosed herein.

[0036] As shown in S10, a substrate having first and second layers is first provided, e.g., in an alternating stacked configuration. The layers are formed of different materials, preferably silicon-containing materials. For example, as described above, one layer may include a material selected from the group consisting of epitaxial silicon, polysilicon, SiGe, or silicon oxide, while the other layer may be formed of a different material selected from the group consisting of epitaxial silicon, polysilicon, SiGe, or silicon oxide. One of the layers may also include silicon oxide, while the other may include a different silicon oxide. According to one example, one of the layers or films may include a silicon nitride layer or film. According to another example, the substrate may also include different devices (e.g., different stacked material configurations) in different regions, e.g., one or more first devices each having first and second layers (or films) in a first region and one or more second devices provided in a second region having third and fourth layers or films. The devices may have different layers requiring different selectivities, e.g., a first device may have a first layer selectively etched relative to a second layer, while a second device may have a third layer selectively etched relative to a fourth layer, and the required selectivity may be different for the different devices. For example, one of the devices may require selective etching of SiGe relative to Si, while the other device requires selective etching of Si relative to SiGe. Using the methods herein, the first and second devices can be subjected to the same initial treatment, with the first, second, third, and fourth layers exposed to the treatment. Subsequently, to achieve the desired etch selectivity, a different etching process can be used for the first device compared to the second device, e.g., a plasma etch for the first device and a gas-phase non-plasma etch for the second device. Benefits of the method include improving the selectivity of both etches by the etch pretreatment described herein. During etching of one device (or devices), the other device can be covered with a carbon-containing layer, such as an OPL.

[0037] A gas-phase process is first performed, as shown in S12, to provide modified surfaces on the respective surfaces of the first and second layers, e.g., on the sides of the first and second layers, as shown at 116 in FIGS. 1A-1C. A thermal process is then performed, as shown in S14, to remove residue or residual water vapor. In some instances, the thermal process may remove portions of the modified surface 116, while other portions of the modified surface 116 are not removed by sublimation and subsequently become a protective surface or layer (116a). Where the thermal process does not remove portions of the modified surface 116 adjacent to the layer to be etched, these portions are removed in a plasma or gas-phase etching process S16. In the plasma process, portions of the layer that are not to be etched (or are protected) are converted to the protective layer 116a, while the layer to be etched (102) is etched, for example, using a fluorine- or halogen-containing gas in the etching process.

[0038] After etching, particularly for vapor phase etching, heat treatment is preferably carried out at a temperature higher than the temperature during etching, for example, in the range of 100°C to 250°C.

[0039] 4A and 4B illustrate additional processing that may be performed after the depressions have been formed, for example as shown in FIGS. 1A-1C above.

[0040] The configuration of FIGS. 4A and 4B may include, for example, Ge (or SiGe)-containing layers 104 with Si-containing layers 102 between the layers 104, the Si-containing layers being recessed as described above. Region 108 may be a mask, e.g., a hard mask, and region 107 may initially include a dummy gate, which is later removed and gate metal is deposited. After the recess-forming process described above, spacer layer 110 is deposited to obtain inner spacer layer 110. Layer 110 may be formed from a spacer material, such as SiN or a low-k dielectric. Inner spacer layer 110 is then partially removed, thereby leaving spacer 103 in what was previously formed as the recess or depression described above. Layer 102 may then be removed (channel release), thereby leaving channel 104 formed from the Ge- or SiGe-containing layer, and the area previously occupied by dummy gate 107 and Si-containing layer 102 may then be filled with gate metal. Additionally, upon removal or etching of the inner spacer layer 110 to leave the spacers 103, the spacers 103 should be recessed relative to the outer surface of the Ge or SiGe-containing layer or channel 104, such that the outer surface of the spacers 103s has outer dimensions that are smaller than the outer surface or outer dimensions 104s of the layer 104.

[0041] While the invention has been described above with respect to etching to form recesses, the invention may also be utilized for channel release, for example, when removing layer 102 (FIGS. 4A and 4B) while protecting layer 104 (e.g., a SiGe layer). As another alternative, the invention may be applied to etch spacer material 103 selectively to or relative to layer 104 (while protecting layer 104), whereby the remaining portion of inner spacer layer 110 is etched and the recessed outer surface 103s of the spacer is recessed relative to the outer surface 104s of the Ge-containing layer (or SiGe).

[0042] It should be understood that other applications incorporating the example features disclosed herein may be utilized, for example, the method may be applied to liner removal, mask removal or mask trim, channel trim, or other processing operations where selective etching is desired.

[0043] Although the present disclosure describes certain process / method steps as occurring in a particular order, the present disclosure contemplates that the process steps may be performed in any suitable order. While the present disclosure has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. 1. A method of selective etching comprising: providing a substrate having a film stack thereon including first and second films, one of the first film or the second film being vertically above the other of the first film or the second film, the first film being formed of a different material than the second film, and each of the first and second films comprising one of epitaxial silicon, polysilicon, silicon oxide, silicon germanium, or silicon nitride, and each of the first and second films comprising a side surface; treating the sides of the first and second films to form a first modified surface on the first film and a second modified surface on the second film, the treatment being a gas phase non-plasma treatment using a gas including hydrogen, fluorine, and oxygen; and after said treating, performing an etching process to convert the first modified surface into a protective surface and to etch the second film selectively relative to the first film to remove a portion of the second film.

2. 2. The method of claim 1, wherein the etching process is a plasma process that etches the second film to form a recess in the second film such that the outer dimensions of the second film are smaller than the outer dimensions of the first film.

3. The gases in the process are HF, aerosolized H ２ 10. The method of claim 1 comprising O and a carrier gas.

4. 4. The method of claim 3, wherein the treatment is carried out at a temperature ranging from -20°C to 200°C and a pressure ranging from 10 mTorr to 4 Torr.

5. 5. The method of claim 4, wherein the treatment is carried out at a temperature ranging from 0°C to 35°C.

6. 6. The method of claim 5, further comprising performing a heat treatment at a temperature in the range of 100° C. to 350° C. after said treatment and before said etching.

7. The method of claim 1 , wherein the etching process is a non-plasma gas phase etch.

8. the film stack including the first and second films forms one of a first plurality of devices in a first region of the substrate, the substrate further including a second plurality of devices in a second region of the substrate, and both the first plurality of devices and the second plurality of devices are exposed to the process; the etching process is a plasma etch performed on the first plurality of devices but not on the second plurality of devices; The method of claim 1 , wherein the second plurality of devices is exposed to a gas-phase non-plasma etch after the processing.

9. 1. A method of selective etching comprising: providing a substrate having first and second films thereon, one of the first and second films being vertically above the other of the first and second films, the first film being formed of a different material than the second film, and each of the first and second films comprising silicon, and each of the first and second films having sides; processing the substrate to form a first modified surface on a side of the first film and a second modified surface on a side of the second film; and performing an etching process to convert the first modified surface into a protective layer, remove the second modified surface, and etch the second film such that the second film is recessed relative to the first film.

10. the first film is formed from a first material selected from the group consisting of epitaxial silicon, polysilicon, silicon germanium, silicon nitride, and silicon oxide; 10. The method of claim 9, wherein the second film is formed from a second material different from the first material and selected from the group consisting of epitaxial silicon, polysilicon, silicon germanium, silicon nitride, and silicon oxide.

11. 10. The method of claim 9, wherein the treatment is in a non-plasma environment at a temperature ranging from -20°C to 200°C and a pressure ranging from 10 mTorr to 4 Torr.

12. 10. The method of claim 9, wherein the treatment is performed in a non-plasma environment using a treatment gas comprising a halogen, oxygen, and hydrogen.

13. The treatment involves aerosolized H ２ 10. The method of claim 9, carried out in a non-plasma environment using a process gas comprising O, HF, and a carrier gas.

14. 10. The method of claim 9, further comprising: after the treatment and before the etching process, increasing the temperature of the substrate to perform a heat treatment, the heat treatment being performed at a temperature in the range of 100°C to 300°C and in a halogen-free environment.

15. 15. The method of claim 14, wherein a halogen and a carrier gas are introduced during the etching process, and no nitrogen is introduced.

16. 15. The method of claim 14, wherein a halogen, nitrogen, and hydrogen are introduced during the etching process.

17. The treatment is carried out with HF in the range of 300 sccm to 1000 sccm and aerosolized H in the range of 200 sccm to 1000 sccm. ２ 10. The method of claim 9, carried out using a gas flow rate of O and also introducing a carrier gas comprising argon and / or nitrogen.

18. 10. The method of claim 9, wherein the substrate includes a first plurality of devices and a second plurality of devices, and wherein each of the first plurality of devices and the second plurality of devices is exposed to the process, and after the process, the first plurality of devices is exposed to a gas-phase non-plasma etch and the second plurality of devices is exposed to a plasma etch.

19. 1. A method of selective etching comprising: providing a substrate including a first plurality of devices in a first region and a second plurality of devices in a second region, the first plurality of devices including a first layer and a second layer, the first layer being formed of a different material than the second layer, and the second plurality of devices including a third layer and a fourth layer, the third layer being formed of a different material than the fourth layer; treating the first and second plurality of devices with a non-plasma gas phase chemistry comprising hydrogen, a halogen, and oxygen; after said processing, exposing said first plurality of devices to a plasma etching process to selectively etch said first layer relative to said second layer; after said processing, exposing said second plurality of devices to a gas-phase non-plasma etch to selectively etch said third layer relative to said fourth layer.

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