Patent ID: 12261053

DETAILED DESCRIPTION

The invention will be further appreciated according to the description of exemplary embodiments and advantages herein. It is to be understood that not every aspect of a particular example need be utilized to practice the invention, and therefore, a subset of features of particular examples could be utilized without utilizing other aspects. Similarly, advantages that can be achieved with the invention are also described herein, however, in practicing the invention, certain aspects or advantages may be utilized without others, or alternate advantages can be achieved.

In an example, the treatment or pre-treatment (before etching) is performed with a nitrogen plasma in which nitrogen ions have been removed, so that the treatment is performed with nitrogen radicals of the plasma. Although not limiting, in a presently preferred example, the plasma of nitrogen can be formed in a remote chamber or remote chamber portion, and then fed to another chamber or chamber portion in which the substrate is positioned, while removing nitrogen ions from the plasma. The chamber or chamber portion in which the substrate is positioned does not require additional excitation of the plasma or additional bias power, although power or biasing of the substrate holder can be provided for holding the substrate or attracting the substrate to the substrate holder (e.g., electrostatically with an electrostatic chuck). In addition, heating in the plasma formation chamber or chamber portion can be provided, and heating could also optionally be provided of the substrate and/or the portion of the chamber in which the substrate is positioned.

In the illustrated example ofFIG.1A, a device includes a base100, which can include the base of a semiconductor wafer as well as additional layers, below the layers being processed as discussed herein. Above the base100, layers are stacked in an alternating fashion, with the stacked layers including at least two different layers having different material compositions. For example, in the illustrated arrangement, a plurality of layers102are provided which contain a silicon material Si, the silicon-containing material of layer102can also include germanium Ge or other materials. In addition, alternating with the layers102, are layers104which include germanium. The germanium in layer104is of a higher content than the germanium present in layer102, and layer104can also be pure Ge or have a higher alloy amount of Ge. Layer102can have germanium in a lower percentage content or lower alloying amount compared to layer104, or alternately, layer102can have no germanium present. Although two alternating layers102,104are provided in this example, it is to be understood that the stack of alternating layers could have three or more different layers.

In this example, the layer104is provided with a treatment or pre-treatment so that a nitrided or nitrogen treated surface is formed on the side surfaces of the germanium or Ge layer104, but the nitrides are either not formed or are formed in a lower amount (or lesser extent) upon the layers102. The treatment with nitrogen radicals is selective to materials with higher amounts of Ge, so that later, selective etching of other layers (e.g., layers with lower amounts of Ge or no Ge) is performed with respect to the layers containing higher amounts of Ge. As used herein, providing a treatment of one layer or material which is selective to another layer or material means that the treated layer will have a higher amount of nitrogen or nitrides including at least one of a higher concentration of nitrogen on the surface of the material treated or protected, or a thickness of the nitrided layer or nitrided surface is larger compared to the other layer or material (for which nitrides are either not formed, or a nitrided layer has a smaller thickness or there is a lower nitrogen concentration on the surface).

In the illustrated example, element106can be, for example, a dummy gate formed of amorphous silicon (a-Si), elements108are gate spacers, and element110can be a mask, such as a hard mask. The gate spacers can be formed of SiN or a low-k dielectric. The mask110can be formed, for example, of SiO2 or SiN, and is formed of a material different from gate spacers108.

After the treatment process, an etching step is performed to provide one or more indentations in each of the layers102in this example, with the indentations preferably formed on at least two sides of the layers102. Indentations are provided on four sides in the example illustrated, so that the layers102are recessed or indented with respect to layers104. However, the Ge layers104are not etched (or are not substantially etched), because they are protected by the nitride formed on the surface, i.e., the side surfaces in this example, so that the Si containing layers102(which contain either no germanium or germanium in a lower amount than layer104) are etched by the etching process. The etching process is described in further detail herein. In a presently preferred example, the etching is by a gas phase chemistry without a plasma, or in other words, a plasma is not formed for the subsequent etching.

Preferably, the nitrogen treatment of the Ge layer104saturates the higher Ge containing layer. The process conditions during the treatment are such that there is no (or insubstantial) treatment or reaction of the silicon with nitrogen. For example, the process is not sufficiently energetic to form SiN from pure silicon. The nitrogen treatment with nitrogen radicals will have a high selectivity for pure Ge, or for higher alloy SiGe relative to SiGe having a lower alloy amount of Ge or having no Ge. For SiGe having an alloy amount of 30% or less Ge, there is little or no bonding or nitriding of the nitrogen to the SiGe material, and any nitriding can be readily removed during the subsequent etch or post-etch heat treatment. Accordingly, for the lower Ge alloy material, it can be preferable to have a Ge content of less than 30%. The presence of some Ge can be preferable for the gas phase etch (described later), because it will etch more rapidly, and therefore, it can be desirable to have, for example, at least 5% Ge. However, where the pure or higher alloy Ge layer is protected with the nitrogen radical treatment, a very low Ge alloy or Si material that does not include Ge can be used because, although this material will etch more slowly, it can be etched without damaging the pure Ge or higher alloy Ge layer due to the protection provided by the nitriding.

Thereafter, as shown inFIG.1C, a spacer material112is deposited over the device to form an inner spacer layer so that the spacer material fills the indentations formed by the etched portions of layer102and between the layers104. The spacer material112can be formed, for example, of a low-k dielectric, and is formed of a material different from the material of the gate spacers108and mask110.

Referring toFIG.2, an example of an apparatus which can be utilized to perform the treatment or pre-treatment using the nitrogen plasma is illustrated. The apparatus is controlled by a controller200which controls the apparatus to perform the processes disclosed herein, including control of the power from a power source202, the supply of gases from a gas supply source GS204, and the control of temperature by a temperature control system TC206which can include one or more heaters. The heaters can be provided in the first chamber (or chamber portion)210, and optionally could also be provided in the second chamber (or chamber portion)212in which the substrate is treated. The heaters can include heaters associated with one or more of the chamber walls214,216, and/or with an electrode218associated with the chamber or chamber portion210, and/or heating can also be provided in connection with the substrate holder or substrate support220, on which the substrate222being processed is positioned. The substrate support220or other components could also have the components for cooling if desired, e.g., with liquid or gas cooling or heat exchange devices. Plasma process gases are evacuated with a vacuum pump VP indicated at224. The combination of the gas flow into the system and the evacuation of gases by the vacuum pump can also be used to control the pressure within the apparatus.

The controller200can include, for example, one or more processors or computers, and can also include a memory to store e.g., process commands, recipes, recipe data, substrate data or other control data. The control information can also be supplied to the controller200from another device or a memory separate from the controller200. The control and recipe data are preferably stored in a non-transitory computer readable medium. It is also to be understood that, while one controller is identified at200, one or more sub-controllers or separate controllers can also be provided which operate independently or under commands from the controller200to control the various power, gas supply and temperature control equipment and functions to perform processes as described herein.

The gas supply204includes a source of nitrogen gas and typically at least one other carrier gas, such as Ar. The additional gas Ar allows for plasma stability and also for varying the concentration of the nitrogen. Preferably, the chambers or chamber portions210,212do not contain an etchant. For example, they do not contain fluorine or another halogen containing gas, during the nitrogen treatment. In addition, in a preferred example, oxygen is also not present. As used herein, reference to a gas or element not being used or not being present means the gas or element is not intentionally added, although trace amounts of materials might be present depending upon the purity of materials used.

Although an electrode is illustrated schematically at218, other types of plasma generation could be utilized, for example, one or multiple electrode arrangements with one or plural radio frequencies, or with an inductive element at a top or outside of the chamber to provide an inductive power or, for example, microwave components to generate plasma with microwave energy. In an example, power is provided in a range of 300-900 watts to generate the plasma. The gas from the gas source204could be supplied through the electrode218(e.g., in a showerhead arrangement), and/or through other gas inlets, and the gases can be mixed upstream from the chamber or inside of the chamber210.

A first plasma schematically represented at P1 is thus formed in the chamber or chamber portion210. In addition, in the illustrated example, a separator such as a mesh or grid provides a filter or separator230which is powered to filter or remove ions (preventing ions from passing therethrough) so that plasma passing from the chamber210to the chamber (or chamber portion)212passes without ions of the nitrogen passing through the separator or filter230. As a result, a second plasma schematically represented at P2 will have no ions (or at least fewer ions compared to the plasma P1). In a preferred form, the plasma P2 will have no nitrogen ions, but will include nitrogen radicals which will react to form a nitrogen treated surface or a nitride layer on the Ge layer of the substrate. The arrangement ofFIG.2can be considered as including separate chambers, or as one chamber including separate chamber portions. In addition, it is to be understood that the plasmas P1 and P2 are represented schematically, because they differ from each other in that the second plasma has had the ions removed. However, rather than appearing as separate distinct plasmas P1 and P2, the first and second plasmas P1 and P2 can appear as continuous extending from the first chamber portion to the second chamber portion, however, the second plasma in the second chamber portion to which the substrate is subjected will be a different plasma or second plasma in that the ions have been removed.

The pressure will be controlled within a range of 10 mTorr-1000 mTorr. The temperature is below 300° C. during the nitrogen radical treatment, and preferably below 150° C. for the nitrogen radical plasma treatment. The temperature is preferably in a range of 0° C. to 100° C., more preferably in a range of 15° C. to 90° C. or 15° C. to 85° C., and even more preferably 20° C. to 85° C. In higher temperatures within the ranges identified, and higher pressures, the reaction will occur more rapidly. However, lower temperatures and pressures within the ranges identified can provide better control, but take a longer amount of time. In general, a higher pressure will decrease the amount of time for saturation to be reached for the layer being treated. Higher temperatures will decrease the amount of time and will also increase saturation levels or the amount of nitriding. Higher temperature can result in a larger thickness of the nitride layer or nitrided surfaces that is formed. If an excessive thickness is formed, it can be difficult to remove the nitriding (for example, in the subsequent etch and heat treatment) where it is desired to eliminate the nitriding after the surface modification and etch have been performed. Therefore, temperatures in the range of 15° C. to 90° C. or 15° C. to 85° C. can be preferred.

The treatment process with nitrogen radicals can be tuned to vary the thickness of the nitride layer formed or the amount of nitriding. The primary control will be based on temperature (with a higher temperature providing a larger nitride thickness on the surface of the Ge layer104), however pressure and nitrogen gas concentration in forming the plasma can also vary the process. As noted earlier, preferably the Ge containing layer is saturated and has a maximum thickness for a given temperature upon completion of the nitrogen treatment. However, it would also be possible to have a nitride surface which is not fully saturated or does not have a maximum possible thickness or nitrogen content of the surface. The temperature of the substrate on the substrate holder220is preferably maintained at the same temperature as the chamber in which the plasma P1 is formed, i.e., the first chamber or chamber portion210, or at least in the same temperature ranges identified earlier (e.g., 15° C. to 85° C.).

During the subsequent etch process, some of the nitride layer could be removed, however, preferably the nitride layer is sufficiently maintained so that the layer104having the highest Ge content is not exposed during the subsequent etching (in other words, at least part of the nitride layer on layer104is maintained during etching to prevent etching of the layer104).

In addition, as noted earlier, the plasma P2 used in the treatment is with radicals and with non-excited species (no ions or a reduced amount of ions) so that there is no (or substantially no) nitriding of silicon, and any nitriding of layers with lower amounts of Ge (compared to layer104) is substantially lower than layer104. Nitriding of low Ge alloy amounts of SiGe will be loose or will not bond well (e.g., at Ge amounts of 30% or less), and thus, after the nitrogen treatment, lower alloy SiGe materials will etch well (selectively) compared to pure Ge or SiGe having higher Ge alloy amounts. For lower Ge alloy amounts (e.g., 30% or lower), any nitrogen formed or bonded can be readily removed by the subsequent gas phase etch. For higher Ge alloys or pure Ge, the Ge layer is strongly protected by the nitrogen radical treatment. Therefore, the low alloy SiGe can be etched selective to a higher Ge alloy SiGe or Ge. SiGe can also be etched selective to Si materials, because the nitrogen treatment will not substantially affect the Si material, and the subsequent gas phase chemistry etching will not strongly etch the silicon containing materials having no Ge or very low Ge. Thus, the present processes can be particularly advantageous for SiGe etching with respect to Ge or higher Ge alloys of SiGe, as well as in etching SiGe selective to Si.

After treatment with nitrogen radicals, with a plasma which had nitrogen ions removed, an etching process is performed. Although it would be possible to perform the etching in the same chamber in which the treatment with nitrogen radicals is performed, in a presently preferred example, the etching is performed in a separate chamber301illustrated inFIG.3. The chamber301is controlled by a controller300, which can include one or more processors or computers configured to control the operation and processes performed in the chamber301. As noted with respect to controller200, the controller300can store instructions or process commands, or can receive instructions or data from a separate memory or controller. As also discussed earlier, controller300can be a single controller or can include distributed controllers or sub-controllers to control the various components and operations discussed herein.

A gas supply GS2 shown at304controllably supplies process gases from one or more gas sources in instructed concentrations, and the temperature can be controlled by various temperature control expedients as represented at TC2306, which can include temperature control of the substrate holder320and/or of the chamber walls and/or radiant or other forms of temperature control. The substrate322is positioned on the substrate holder320and can be held, for example, by electrostatic attraction with an electrostatic chuck. A vacuum pump VP2 at324is provided to exhaust gases. In a presently preferred example, gases from the gas supply304are not excited into a plasma, but rather are provided in a gaseous phase so that the etching is performed by a gas phase chemistry.

The gas phase chemistry will include an etchant such as a fluorine or another halogen, preferably fluorine. Non-limiting examples of preferred etchant gases include F2, ClF3, HF and/or XeF2. Nitrogen and/or Argon gases can also be present but will essentially not react with the substrate layers in the etch process conditions because the gases are not excited.

If a more aggressive fluorine gas phase chemistry is desired, the gases other than HF are preferred, i.e., F2, ClF3and/or XeF2. As discussed later, after the gas phase etch, preferably a heat treatment is performed. Although the heat treatment can be performed in the same chamber301as the gas phase etch chemistry, preferably, a separate chamber is provided which is better for higher temperature control, for example, temperatures from 100° C. to 500° C. Preferably, the temperature is raised after the etching to, for example, 100° C. to 300° C. and more preferably from 150° C. to 250° C. The duration or elapsed time for the heat treatment can vary depending upon the temperature and the amount of residues or other materials which might need to be removed. For example, the heat treatment can be performed for at least 30 seconds and up to, for example, ten minutes. As an example, the heat treatment can be performed for at least one minute or at least two minutes. For the duration of the heat treatment, preferably a fluorine containing gas or other halogen containing gases not introduced into the chamber in which the substrate is positioned. For example, the gases in the chamber during the heat treatment can include inert gases, including N or Ar.

Referring toFIG.4, an overview of an example of process steps is provided. The steps refer to the steps and operations discussed herein, and which can be provided as an algorithm under the control of one or more controllers.

As indicated at S10, a plasma (P1) is formed with a nitrogen containing gas, and the gas can include one or more other gases, such as Ar, for plasma stability and/or to control the concentration of nitrogen. In S12, ions are removed from the plasma so that the remaining plasma (or second plasma P2) includes nitrogen radicals, but does not include nitrogen ions, or at a minimum has a reduced amount of nitrogen ions compared to the first plasma. One or more Ge containing layers are then treated with the plasma (P2) after the removal of the nitrogen ions. As discussed earlier, the Ge containing layers can include Si or other materials, however, the amount of Ge (in layer104) is greater than the amount of Ge of the layer or layers (102) that contain Si that will be etched. The layer104can include no Si, and the layer102can include no Ge. The layer containing the lower Ge content preferably has less than 50% Ge, and more preferably less than 30% Ge. At Ge contents of below 30%, the nitrogen bonding is loose or minimal and any nitrogen or nitriding can be removed during the gas phase etching, so that the layer102containing lower (or no) Ge content is etched with respect to the layer104having higher Ge content or which is pure Ge. In step S16, the silicon containing layer is then etched relative to the Ge containing layer.

In S18, a heat treatment is performed. Although the heat treatment is optional, it is presently preferred to achieve improved results. The heat treatment is preferably at a temperature higher than the temperature at which the Ge containing layers are treated with nitrogen radicals and higher than the temperature of the gas phase etch. For example, preferably the temperature for the heat treatment is greater than 100° C.

The heat treatment can remove residues, such as fluorine or halogen containing residues, and can also remove nitrogen containing residues. More aggressive etchant gases (during the gas phase etch) can be beneficial in removing the nitrides during etching or in forming byproducts/residues which are a combination of the etching gases and the nitrogen/nitrides and the etchant(s). The byproducts or residues can also include materials of the Si layer being etched. These byproducts or residues can then be removed during the heat treatment. If more aggressive treatment (and removal of at least some of the nitrides) is desired during the gas phase etch, the etchant gases previously mentioned other than HF are preferred (e.g., F2, ClF3, XeF2).

It is also to be understood that steps can be repeated depending upon the amount of etching performed in a given step or sequence of steps. For example, if additional etching is required after one sequence of S16, S18these steps can be repeated. In addition, if the nitrogen protection has been depleted, step S14can be performed again prior to the repetition of S16, S18.

As indicated inFIG.5, in accordance with one of the advantageous aspects in which present examples can be utilized, the treatment with nitrogen can be utilized for some Ge containing layers of a substrate, but not others, for example, where it is desirable to selectively etch Ge containing layers (higher Ge alloy layers or pure Ge) relative to Si containing layers (lower Ge alloy layers or layers which do not include Ge) in one part of a process or process flow (or in one portion or a first region of a substrate) and thus, the treatment with nitrogen radicals is not utilized. However, in other portions of a process or different portions of the substrate (e.g., a different second region) or other process steps, it is desirable to etch the Si containing layers selective to or relative to the Ge containing layers, and therefore the treatment with the nitrogen radicals is utilized for the Ge containing layers (layers of all Ge or having a higher percentage of Ge compared to the Si layers) so that the Ge layers are not etched during selective etching of the Si layers.

Accordingly, as indicated at S20, a substrate can be provided having a first plurality of first layers which include Ge, and a second plurality of second layers can be provided which contain Si. As discussed earlier, Ge containing layers can include Si, and the Si containing layers can include Ge, however, the Si containing layers have an amount of Ge which is lower than that of the Ge containing layers. Of course, the Si containing layers might also include no Ge, and the Ge containing layers could include no Si. In preferred examples, where a Si containing layer is etched selective to a Ge containing layer, and both layers include Ge, the Si containing layer will preferably have less than 30% Ge, preferably 5% to 30% Ge. However, for certain devices, it might be desired to have no Ge in the device, for example to provide a pure Si channel. The Ge containing layer will have a larger amount of Ge, preferably greater than 30%, more preferably greater than 50% Ge, and can be pure Ge. Other variations are possible where the Ge containing layers have a higher Ge content than the Si containing layers.

In the example ofFIG.5, a first subset of first layers containing Ge is selectively etched relative to a first subset of the second layers containing Si, and therefore, the Ge containing layers of the first subset are not provided with the treatment or pre-treatment with nitrogen radicals. The Ge containing layers of the first subset can thus be etched selective to or relative to the first subset of the second layers by, for example, a fluorine containing gas such as a gas phase etch including at least one of F2, ClF3, HF and/or XeF2. Thus, according to one of the advantages, the same or substantially the same gas phase etch process can be used to etch a Ge containing layer relative to or selective to an Si containing layer, and also for etching an Si containing layer relative to or selective to a Ge containing layer, with the difference being whether the pre-treatment with nitrogen radicals is used.

A second subset of the first layers (the Ge layers) is then treated with nitrogen radicals as indicated at S24, with the processing as discussed earlier so that a nitride layer is provided to protect the Ge containing layers of the second subset. A second subset of the second layers (Si containing layers with lower Ge) is then etched relative to the second subset of the first layers as indicated at S26. Although pure Si (or Si containing very low or no Ge) will etch slowly, it can nevertheless be etched relative to or selective to a Ge layer where the Ge layer is protected with the treatment with nitrogen radicals as discussed earlier.

The order of the processing inFIG.5is provided as an example, and as an alternative, a first subset of the first layers (Ge containing layer) can be treated with the nitrogen radicals to provide etching of the first subset of second layers (Si containing layers) relative to the first subset of the first layers with the gas phase etching. Thereafter, a second subset of the first layers is not treated with the nitrogen radicals so that the second subset of the first layers containing Ge are then etched relative to the second subset of the second layers containing Si.

Similarly, although the treatment with nitrogen radicals discussed in connection withFIGS.1A-Cwas discussed in relation to treating the Ge and then indenting by etching the Si containing layers, the materials could be reversed or provided in connection with additional materials or process steps. For example, in the arrangement ofFIGS.1A-C, the Ge containing layer could be etched to form indentations relative to the Si containing layers without treating or pre-treating the Ge containing layers, and thereafter (or prior thereto), a process can be performed in which the Si containing layers are etched relative to the Ge containing layers. In this case, the Ge containing layers are provided with the treatment with nitrogen radicals prior to performing the etch of the Si containing layers relative to or selective to the Ge containing layers. If a Ge containing layer and a Si containing layer are exposed at the same time, little or no etching of the Si containing layer will occur during etching of the Ge containing layer, particularly where the Si containing layer contains very low amounts of Ge or no Ge, as the Ge containing layer will etch rapidly. Thus, where it is desired to selectively etch Ge with respect to Si, and also selectively etch Si relative to Ge, the Ge containing layer can first be etched to provide a desired etch amount, and because the Ge layer etches rapidly, there will be little or no etching of the Si layer. Thereafter, the Ge layer can be protected, and the Si layer can be etched. Although the progress of the Si layer will be slower (compared to unprotected Ge), the etching can progress to the desired amount without affecting the previously etched Ge layer because the treatment has been performed on the Ge layer.

As indicated earlier, in connection withFIG.4, the process as illustrated inFIG.5can also be provided as an algorithm which an apparatus will perform under the control of one or more controllers. TheFIG.5process will preferably also include a heat treatment after the gas chemistry etch.

FIGS.6A-6Cprovide another example in which the present processing can be utilized.

FIG.6Aillustrates an arrangement in which spacers600have been provided in indentations previously formed, and in addition, a source650and a drain652have been provided on each side of the stack assembly. A channel654extends from the source650to the drain652, with the channels separated by layers656. As illustrated inFIG.6B, the channels654are then released by removal of the layers656. In this operation, where the layers654are Ge containing layers (pure Ge or Ge in an amount higher than layers656), they can be treated with the nitrogen radicals as discussed earlier herein, so that upon removal of the layers656, the Ge layers654are protected. Alternately, where the layers656have the higher germanium content, this process can be performed without utilizing the nitrogen radical treatment of the layers654, and the layers656are etched without pre-treatment of layers654. This later example could be utilized in a process in which other upstream or downstream processes selectively use protection of Ge layers with the nitrogen radical treatment.

After the channel release, as shown inFIG.6C, a gate metal670is deposited between the gate spacers608and in the regions between the channels654. Preferably, a barrier layer is deposited prior to deposition of the gate metal670. Here, one of the layers (or sets of layers)654or656could have been previously treated with the nitride treatment, but the nitride treatment was then removed in another process operation, e.g., in an earlier etch. Thus, the processing with the nitride treatment or pre-treatment can be utilized with certain process operations, but not utilized in other process operations selectively. As a result, selective etching of both Ge with respect to a lower Ge alloy (or containing no Ge) can be performed, and also, selective etching of a lower Ge alloy (or containing no Ge) can also be performed relative to a higher Ge alloy layer, depending upon use and non-use of the pre-treatment.

According to methods herein, different selectivities can be used in different features or devices in different regions of a substrate. The selective etching of Ge containing layers relative to an Si containing layers (containing a lower amount of Ge or no Ge) in one portion of a substrate or a first region of a substrate, while providing the reverse selective etching in another portion or second region of a substrate, i.e., selective etching of Si layers (containing no Ge or containing lower amounts of Ge) with respect to a Ge containing layer, can be provided, for example, in two ways. For example, briefly referring toFIGS.10A and10B, different devices or device features can be provided in different regions of a substrate, for example, with devices700provided in a first region of a substrate and devices500provided in a second region of a substrate. Devices500in the second region of the substrate can be covered, for example, with a layer600, such as an organic layer or an OPL, for example. The devices700and500will typically also include a liner, for example as illustrated at702,502, to avoid damage during depositing of the film600. The liner or layer702can be removed so that the devices700are exposed as illustrated inFIG.10B, while the devices500in the second region of the substrate remain covered. The devices or device features in the first region700can thus be processed, e.g., using the treatment with the nitrogen radicals so that Si containing layers can be etched. For example, where devices or features in the first region700include Ge channels, the Ge channels can be protected and the layers between the channels can be etched and removed to provide a channel release, while the Ge channels in the first region are not etched due to the protection with the nitrogen radical treatment. In the same substrate, other devices can include channels formed of an Si material containing no Ge or a lower amount of Ge compared to materials of the layer or layers between the channels. Thus, the devices or features700can be covered with a film, for example, a carbon containing film such an OPL, and the devices or features500are exposed upon removal of the layer or film600in the second region. The Ge layers between the channels (with the channels formed of Si containing no Ge or lower alloy amounts of Ge compared to the Ge layers) can then be etched to provide a channel release without the pre-treatment for the features or devices500in the second region.

In the example shown inFIGS.10Aand B, the indent process has already been performed and spacers formed. However, the same approach can also be used with an indent process where different materials are indented in different regions of the substrate. Si layers can be indented in features or devices of a first region while Ge layers in the first region are protected using a nitrogen radical treatment, and devices or features in the second region are covered. With devices or features in the first region covered and the second region uncovered, Ge layers of the second region can be etched (e.g., to indent the Ge layers) without performing the nitrogen radical treatment.

A further example is provided below in which two different devices or features can be exposed at the same time in different regions of the substrate, and the selective use (or non-use) of the nitrogen treatment and the timing of the nitrogen treatment can be utilized to provide different selective etching of different materials in the different regions.

FIGS.7A-7Cillustrate another example in which the present processing with nitrogen radicals can be utilized, in this operation, or in the context of plural process operations in which the nitride treatment is provided in other operations. In the arrangement ofFIGS.7A-C, a channel trim and cladding operation is performed. Reference numbers used inFIGS.6A-Care the same asFIGS.7A-C, unless otherwise noted, and thus their description is not repeated.

FIG.7Aillustrates channels654after they have been released with layers656removed. The channels each include a first end654aand a second end654b, where spacers600are provided adjacent (above and below) each of the first and second ends654a,654b. As shown inFIG.7B, a channel trimming or channel thinning operation is performed so that portions654cbetween the first and the second ends654a,654bare trimmed or thinned.

Next, as shown inFIG.7C, a channel cladding operation can be performed in which a cladding material is deposited or wrapped around all of the surfaces of the channel654that are exposed, including the portions which have been previously trimmed at654c, to provide a cladding657. For example, the cladding can be formed by growing an Si, Ge or SiGe layer657on the trimmed channel654.

By way of example, in an earlier etch (such as a channel release), the channels654can be protected, and the Si material between the channels etch. The nitriding is removed, and the channels can be etched with a fluorine gas phase etch but without performing the nitrogen radical treatment before performing the channel trim.

According to another example, a given substrate can include devices in a first region with channels (first channels) which are formed of a Ge containing layer (all Ge or a higher alloy SiGe), and devices in a second region can have other channels (second channels) which are Si layers (e.g., having a lower Ge alloy amount compared to the Ge layers or not including Ge). The etching or trimming of the Si layers can be performed while protecting the Ge layers (using the nitrogen radical treatment) in one region, and the etching (e.g., trimming) of the Ge layers can be performed in a separate etch process without protection (without using the nitrogen radical treatment) in another region.

As discussed earlier in connection withFIGS.10A and10B, where different devices or features are provided in which different selectively is desired, one region of the substrate can be covered while another region is processed using the treatment with nitrogen radicals, and then the other region can be covered while uncovering the region initially covered, and the reverse selectivity can be utilized by not using the treatment with nitrogen radicals.

The channel trim operation is an example of processing in which two different types of devices can be exposed at the same time (without requiring selective covering and uncovering, e.g., with an organic layer), and the selective use (or timing of use) of the treatment with nitrogen radicals can be utilized to provide selective trimming of different types of channel materials. For example, in a first region of the substrate, first devices or features are provided in which first channels are formed of a Ge material (pure Ge or Ge in an amount higher than channels of the devices or features of the second region of the substrate), and the second region of the substrate has second devices having second channels formed of different channel materials than the first channels in the first region (such as Si material that does not include Ge, or a Si material that includes Ge in an amount lower than the channels of devices of the first region). With such an arrangement, with first devices of the first region and the second devices of the second region both exposed, etching can be first performed without the treatment with nitrogen radicals. In this case, the Ge channels (first channels) of the first region will etch rapidly to obtain the desired etch or trim amount, because the Ge etches rapidly in the gas phase chemistry etch. Thereafter, the treatment with nitrogen radicals is performed so that the Ge channels of the first devices of the first region are protected. The second channels of the second region can then be etched or trimmed to the desired trim amount while the first channels are protected by the nitrogen radical treatment. Although during the etching of the Ge channels (first channels) of the first region, etching of the second channels of the second region may have also occurred, any etching would be minimal and they have not been etched to the desired trim amount, due to the slowness of the etching of the second channels in the second region of the substrate. The first channels are then treated so that, after the treatment with nitrogen radicals of the Ge channels (first channels), they are protected to maintain the previously obtained desired trim amount. The etching of the Si layers or Si channels (second channels) in the second region can then proceed in a second etching operation. Although this etch will be relatively slow, the Ge layers or channels of the first region that were previously etched are maintained without further etching due to the use of the treatment with nitrogen radicals, and the etching of the second channels of the second region can proceed until the desired etch or trim amount is obtained. Thus, by the selective use and non-use of the nitrogen radical treatment, different devices or features formed of different materials in different regions of a substrate can be etched with different selectivities. The use and non-use of the treatment with nitrogen radicals can be advantageously applied to nfet and pfet applications.

FIG.8illustrates an advantageous selectivity, and selectivity modification, that can be achieved with the nitrogen radical treatment disclosed herein. Specifically, each of four materials were subjected to the same gas phase etching process (non-plasma etch with a fluorine containing gas), where the left portion of the graph identifies etch rates without pre-treatment with nitrogen radicals, and the etch rates at the right portion of the graph illustrates etch rates with the same gas phase etch process but with the etch pre-treatment with nitrogen radicals as disclosed herein. For the example shown, the nitrogen radical treatment was performed at 85° C. As can be seen, where the pre-treatment was not performed, the Ge layer etches rapidly relative to a layer which contains both Si and Ge (for example, the SiGe25 layer indicated, which is 25% Ge). The Ge also etches rapidly relative to polysilicon and SiN.

By contrast, where the pre-treatment is utilized (the right portion of the graph), the Ge is not etched or minimally etched, demonstrating the effectiveness of the treatment. Further, where selective etching of a material containing SiGe (such as a 25% alloy) is desired, etching can be provided which is highly selective to etch SiGe selective to or relative to Ge. Using the process gases in a gas chemistry etch, the poly-Si or SiN (deposited by low pressure CVD in the example) had very low etch rates without the pre-treatment, and also with the pre-treatment. Thus, using the same etch chemistry during a gas phase etch, and not using the nitrogen radical treatment, a highly selective etch of Ge layer relative to a layer having a lower Ge content can be provided, with the etch also highly selective relative to other silicon containing materials, such as poly-Si or SiN, as indicated by the left portion ofFIG.8. Further, by utilizing the pre-treatment, the Ge layer exhibited substantially no etching, so that SiGe can be etched relative to Ge (or other Si containing layers which have a lower or no amount of Ge, e.g., poly-Si or SiN). Accordingly, using essentially the same gas phase etch, a Ge (higher Ge amount) containing layer can be etched selectively relative to a SiGe layer having a lower Ge amount, or alternatively, a SiGe layer can be selectively etched relative to a Ge layer with a gas phase etch chemistry (e.g., with a fluorine or halogen gas such as a F2, ClF3, HF and/or XeF2), depending upon whether the nitrogen radical treatment is used or not used.

Thus, for example, where a substrate includes different devices or different features respectively in first and second regions of the substrate, etching of Ge containing layers can be performed for first devices in the first region by not utilizing the treatment with nitrogen radicals. Thereafter, treatment with nitrogen radicals can be utilized and etching of Si layers having lower amounts of Ge or no Ge can be performed while the Ge layers or (e.g., first channels) are protected.

FIG.9illustrates that the use of the nitrogen radical treatment is substantially reversible or will not damage the material subjected to processing. In other words, after the nitrogen radical treatment, selective gas phase etch, and heat treatment, the material (SiGe25 in the example ofFIG.9) substantially returns to its original state. Thus, the nitrogen radical treatment can be used without damaging or substantially changing the properties or composition of the material. In the two graphs ofFIG.9, the atomic percentages of different materials are indicated before processing (before being subjected to the nitrogen radical treatment) in the left, and also after processing, i.e., after radical nitrogen treatment, gas phase etching and heat treatment. The test was performed with the SiGe25 formed as a film on top of a substrate, and the composition of the film determined before and after processing. Although the film is nominally silicon and 25% germanium, other materials are present. The pre-treatment was performed with nitrogen radicals (with a remote plasma and ions removed as illustrated inFIG.2), at 85° C., a pressure of 850 mTorr, source power of 850 watts, and a volumetric gas flow rate of 75% nitrogen and 25% argon to the remote plasma chamber. The gas phase chemistry etch was performed at 60° C., 250 mTorr, a volumetric flow rate of fluorine etchants of 50% (F2and ClF3) and 50% carrier gases (N and Ar). The post etch heat treatment was at 2 Torr and 150° C. in a nitrogen and argon environment. As can be seen, only a slight reduction in the carbon content (the material900) is observed. In addition, a slight increase in the amount of flourine (indicated by the lower material910) is also observed but is small. However, the amounts of Ge (region902), Si (region904), nitrogen (region906), and oxygen (region908) are essentially the same. Thus, the treatment or pre-treatment with nitrogen radicals can be utilized to effectively provide a selective etch or to vary the amount of selectivity of one material relative to another, but the treatment does not substantially change the composition of the material treated or damage the material. With the present methods, changes in the atomic percentages of each of oxygen, germanium and silicon will be 5% or less comparing the composition after processing with the composition prior to processing with respect to the material being selectively etched and with respect to the material protected with nitrogen radical treatment. In addition, surface damage can also be avoided or minimized, due to the removal of ions prior to treating the material so that the pre-treatment modification is with nitrogen radicals and without excited species, and also by performing the etch with the gas phase etch chemistry.

The disclosed method and apparatus can be utilized in various applications, including but not limited to nfet, pfet, nanosheet, GAA, finfet, CFET, and other devices or device features.

It is to be understood that modifications and variations can be incorporated consistent with the teachings herein. It is therefore to be understood that within the scope of the present claims, the invention can be practiced otherwise or with variations with respect to the examples disclosed herein.