Substrate processing using selective etching

Abstract

The etching is performed selectively, and the selectivity is altered using a nitrogen radical treatment or pre-treatment before etching. The etching is performed by gas phase chemical etching. The selective use and non-use of treatments can also provide different selectivities for different processes or different areas of the substrate (or different devices or different locations).

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. Patent Application Publication No. 17 / 885,228, filed August 10, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to the processing of substrates, such as semiconductor substrates, and in particular to the selective etching of layers or materials. [Background technology]

[0003] In various types of semiconductor architectures, Si x Ge y In order to achieve this, selective etching of Si and Ge relative to each other is required. Current methods can be unsatisfactory in that the selectivity is unsatisfactory or the steps to achieve selectivity can cause damage or unacceptable permanent changes to one or more of the layers or materials. In addition, some processes performed on a substrate require selective etching of one material (first material) relative to another (e.g., Si xy Ge y or etching Ge relative to Si), while in other parts of the substrate or processing, selective etching of another material relative to the first material (e.g., Si relative to Ge) may be required. x Ge y In some cases, it may be difficult to achieve the desired selectivity, in that selective etching of silicon (or silicon) may be required. Summary of the Invention [Means for solving the problem]

[0004] The present invention provides for pre-etch material treatment or pre-treatment, which allows for selective etching of one material relative to another, for example, selective etching of SiGe relative to Ge or Si, or vice versa, depending on whether pre-treatment is used.

[0005] In a preferred example, part of the process is performed using a plasma to treat one or more layers of a substrate and then provide selective etching, preferably after ions are removed from the plasma, the plasma is used to treat the layers.

[0006] In one example, the treatment is performed using a nitrogen-containing plasma, where the nitrogen ions of the plasma are removed, thereby performing the treatment using a plasma of nitrogen radicals. Etching is then performed with a selectivity determined based on whether the material has been treated. In addition, treated surfaces (such as nitride surfaces) may be removed during the etching and optional heat treatment. Although optional, it is currently preferred to perform an additional heat treatment step after the etching.

[0007] The present invention may be applied to a variety of processes, including, but not limited to, recess machining processes, channel release processes, or channel trimming processes.

[0008] Also disclosed is an apparatus configured to perform the selective etching disclosed herein.

[0009] The present invention will be better appreciated and understood by reference to the detailed description herein taken in conjunction with the drawings. [Brief explanation of the drawings]

[0010] [Figures 1A-1C] An example of selective etching is shown below. [Figure 2] 1 illustrates an example of an apparatus for processing or modifying a substrate. [Figure 3]An example of selective etching is shown below. [Figure 4] 1 is a flow chart of an example of selective etching. [Figure 5] 1 is a flow chart of an example of selective etching. [Figures 6A-6C] An example of a channel release etch is shown. [Figure 7A-7C] An example of channel trimming etching is shown. [Figure 8] 1 is a graph showing the change in selectivity with or without treatment or pretreatment. [Figure 9] 1 is a graph showing the reversibility of treatment and nitrogen effects. [Figures 10A-10B] 1 illustrates an example of selective processing of different portions or regions of a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be further understood through the description of exemplary embodiments and advantages herein. It should be understood that it is not necessary to utilize all of the aspects of a particular example to practice the present invention, and thus some of the features of a particular example may be utilized without utilizing other aspects. Similarly, advantages that may be achieved by the present invention are described herein, but certain aspects or advantages may be utilized without others, or other advantages may be achieved, in practicing the present invention.

[0012] In one example, treatment or pre-treatment (pre-etching) is performed using a nitrogen plasma from which nitrogen ions are removed, thereby performing treatment using nitrogen radicals from the plasma. In a currently preferred, but non-limiting example, the nitrogen plasma can be formed in a separate chamber or separate chamber portion and then supplied to another chamber or chamber portion into which a substrate is placed, while nitrogen ions are removed from the plasma. The chamber or chamber portion into which the substrate is placed does not require additional excitation of the plasma or additional bias power, but may provide substrate holder power or bias to hold the substrate or attract it to the substrate holder (e.g., electrostatically using an electrostatic chuck). Additionally, heating can be provided within the plasma-forming chamber or chamber portion, and optionally heating of the substrate and / or the chamber portion into which the substrate is placed can also be provided.

[0013] In the example shown in FIG. 1A , the device includes a base 100, which may include the base of a semiconductor wafer and additional layers below the layer being processed as discussed herein. Alternating layers are stacked on the base 100, with the stacked layers including at least two distinct layers having different material compositions. For example, in the illustrated configuration, multiple layers 102 are provided that include silicon material Si, and the silicon-containing material of the layers 102 may also include germanium Ge or other materials. Additionally, alternating with the layers 102 are layers 104 that include germanium. The germanium in the layers 104 has a higher germanium content than the germanium present in the layers 102, and the layers 104 may be pure Ge or may have a higher alloying amount of Ge. The layers 102 may have a lower percentage content or a lower alloying amount of germanium compared to the layers 104, or alternatively, there may be no germanium present in the layers 102. In this example, two alternating layers 102, 104 are provided, but it should be understood that the stack of alternating layers may have three or more layers.

[0014] In this example, layer 104 is subjected to a treatment or pretreatment whereby a nitrided or nitrided surface is formed on the sides of germanium, i.e., Ge, layer 104, while nitride is either not formed or is formed to a lesser extent (or to a lesser extent) on layer 102. The treatment with nitrogen radicals is selective to the material containing more Ge, thereby resulting in subsequent selective etching of other layers (e.g., layers with less Ge or no Ge) relative to the layer containing more Ge. As used herein, providing a treatment of one layer or material selective to other layers or materials means that the treated layer has more nitrogen or nitride, which includes at least one of a higher concentration of nitrogen on the surface of the treated or protected material or a thicker nitride layer or nitride surface, compared to other layers or materials (which either do not form nitride or have a thinner nitride layer or lower nitrogen concentration on the surface).

[0015] In the illustrated example, element 106 may be a dummy gate formed, for example, of amorphous silicon (a-Si), element 108 may be a gate spacer, and element 110 may be a mask, such as a hard mask. The gate spacer may be formed of SiN or a low-k dielectric. Mask 110 may be formed, for example, of SiO2 or SiN and may be formed of a different material than gate spacer 108.

[0016] After the treatment process, an etching step is performed to form one or more recesses in each of layers 102, in this example, the recesses preferably being formed on at least two sides of layer 102. In the illustrated example, four sides are recessed, so that layer 102 is recessed or recessed relative to layer 104. However, Ge layer 104 is not etched (or is substantially not etched) because it is protected by the nitride formed on its surface, i.e., in this example, its sides, thereby allowing the etching process to etch Si-containing layer 102 (which either does not contain germanium or contains less germanium than layer 104). The etching process is described in more detail herein. In a currently preferred example, the etching is by gas-phase chemistry without plasma, in other words, no plasma is formed for the subsequent etching.

[0017] Preferably, the nitrogen treatment of the Ge layer 104 saturates the layer with more Ge. The process conditions during treatment are such that there is no (or substantially no) treatment or reaction of silicon with nitrogen. For example, the energy of this process is not high enough to form SiN from pure silicon. The nitrogen treatment with nitrogen radicals is highly selective for pure or highly alloyed SiGe over SiGe with lower or no Ge alloying amounts. For SiGe with an alloying amount of Ge of 30% or less, there is little or no bonding or nitriding of nitrogen to the SiGe material, and any nitriding can be easily removed during subsequent etching or post-etch heat treatment. Therefore, for low-Ge alloy materials, a Ge content of less than 30% may be preferred. For gas-phase etching (discussed below), the presence of some Ge may be preferred because it etches faster, so it may be desirable to have, for example, at least 5% Ge. However, if the pure Ge or highly alloyed Ge layer is protected by a nitrogen radical treatment, ultra-low Ge alloy or Ge-free Si material can be used, since although this material etches slower, it can be etched without damaging the pure Ge or highly alloyed Ge layer due to the protection provided by nitridation.

[0018] 1C, a spacer material 112 is deposited over the device to form an inner spacer layer, whereby the spacer material fills the recesses formed between layers 104 by the etched portions of layer 102. Spacer material 112 may be formed of, for example, a low-k dielectric and is formed of a material different from the materials of gate spacers 108 and mask 110.

[0019] Referring to FIG. 2 , an example of an apparatus that may be utilized for processing or pre-processing using nitrogen plasma is shown. The apparatus is controlled by a controller 200, which controls the apparatus to perform the processes disclosed herein, including controlling power from a power supply 202, supplying gas from a gas supply GS 204, and controlling temperature via a temperature control system TC 206, which may include one or more heaters. Heaters may be provided in a first chamber (or chamber portion) 210 and, optionally, in a second chamber (or chamber portion) 212 in which a substrate is processed. Heaters may include heaters associated with one or more of the chamber walls 214, 216 and / or electrodes 218 associated with the chamber or chamber portion 210, and / or heating may also be provided for a substrate holder or substrate support 220 on which a substrate 222 is placed during processing. The substrate support 220 or other components may also have components for cooling, as needed, for example, using liquid or gas cooling or a heat exchanger. The plasma process gases are exhausted using a vacuum pump VP shown at 224. A combination of gas flow into the system and exhaust of gases by the vacuum pump can also be used to control the pressure within the apparatus.

[0020] The controller 200 may include, for example, one or more processors or computers, and may also include memory for storing, for example, process commands, recipes, recipe data, substrate data, or other control data. Control information may also be provided to the controller 200 from devices or memories separate from the controller 200. The control and recipe data is preferably stored on a non-transitory computer-readable medium. While one controller is identified at 200, it should also be understood that one or more sub-controllers or separate controllers may also be provided, operating independently or under command from the controller 200 to control various power, gas supply, and temperature control equipment and functions for carrying out the processes described herein.

[0021] The gas supply 204 includes a source of nitrogen gas and typically at least one other carrier gas, such as Ar. The additional gas, Ar, provides plasma stability and allows for variable nitrogen concentrations. Preferably, the chamber or chamber portion 210, 212 does not contain an etchant. For example, they do not contain fluorine or other halogen-containing gases during nitrogen processing. Additionally, in preferred examples, oxygen is also absent. As used herein, reference to an unused or absent gas or element means that the gas or element is not intentionally added, but trace amounts of the material may be present depending on the purity of the material used.

[0022] Although electrodes are shown schematically at 218, other types of plasma generation may be utilized, such as one or more electrode arrangements with one or more radio frequency or inductive elements on or outside the chamber to provide inductive power, or microwave components to generate the plasma with, for example, microwave energy. In one example, power in the range of 300-900 watts is provided to generate the plasma. Gases from gas source 204 may be supplied through electrode 218 (e.g., in a showerhead arrangement) and / or other gas inlets, and the gases may be mixed upstream of the chamber or within chamber 210.

[0023] Thus, a first plasma, generally designated P1, is formed in chamber or chamber portion 210. Additionally, in the illustrated example, a separator, such as a mesh or grid, provides filter or separator 230, which, when powered, filters or removes ions (prevents ions from passing therethrough). Thus, plasma passing from chamber 210 to chamber (or chamber portion) 212 passes through separator or filter 230, but nitrogen ions do not. Consequently, a second plasma, generally designated P2, is ion-free (or at least contains fewer ions than plasma P1). In a preferred embodiment, plasma P2 does not contain nitrogen ions, but does contain nitrogen radicals, which react to form a nitrogen-treated surface or nitride layer on the Ge layer of the substrate. The configuration of FIG. 2 may be considered as including separate chambers or as one chamber including separate chamber portions. Additionally, plasma P1 and plasma P2 are represented schematically because they differ from each other in that the second plasma is free of ions. However, rather than being illustrated as separate and distinct plasmas P1 and P2, the first and second plasmas P1 and P2 may be represented as extending continuously from the first chamber portion to the second chamber portion, but the second plasma to which the substrate is exposed in the second chamber portion is a different plasma, i.e., the second plasma, in that ions have been removed.

[0024] The pressure is controlled within a range of 10 mTorr to 1000 mTorr. The temperature is below 300°C during nitrogen radical treatment and preferably below 150°C for nitrogen radical plasma treatment. The temperature is preferably in the range of 0°C to 100°C, more preferably in the range of 15°C to 90°C or 15°C to 85°C, and even more preferably in the range of 20°C to 85°C. At higher temperatures and higher pressures within the specified ranges, the reaction will occur more rapidly. However, lower temperatures and pressures within the specified ranges allow for better control but take longer. Generally, higher pressures shorten the time to reach saturation of the treated layer. Higher temperatures shorten the time and increase the saturation level or amount of nitridation. Higher temperatures allow for a thicker nitride layer or nitrided surface to be formed. Excessive thickness can make it difficult to remove the nitride (e.g., during subsequent etching and heat treatment) if it is desired to remove it after surface modification and etching. Therefore, temperatures in the range of 15°C to 90°C or 15°C to 85°C may be preferred.

[0025] The nitrogen radical treatment process can be adjusted to vary the thickness of the nitride layer formed or the amount of nitridation. The primary control is based on temperature (higher temperatures result in a thicker nitride layer on the surface of the Ge layer 104), but the process can also be modified by the pressure and nitrogen gas concentration used to form the plasma. As previously mentioned, the Ge-containing layer is preferably saturated and has its maximum thickness at a given temperature upon completion of the nitrogen treatment. However, it may be possible to have a nitride surface that is not completely saturated or does not have the maximum possible surface thickness or nitrogen content. The temperature of the substrate on the substrate holder 220 is preferably maintained at the same temperature or at least within the same temperature range (e.g., 15°C to 85°C) as the chamber in which the plasma P1 is formed, i.e., the first chamber or chamber portion 210.

[0026] During the subsequent etching process, a portion of the nitride layer may be removed, but preferably enough of the nitride layer is maintained so that the layer 104 with the highest Ge content is not exposed during the subsequent etching (in other words, at least a portion of the nitride layer is maintained on the layer 104 to prevent etching of the layer 104 during the etching).

[0027] Additionally, as mentioned above, because the plasma P2 used in the process contains radicals and unexcited species (no ions or a low amount of ions), there is no (or substantially no) nitridation of silicon, and the nitridation of layers with a low amount of Ge (compared to layer 104) is substantially less than that of layer 104. The nitridation of low Ge alloy content SiGe is loose, i.e., not well bonded (e.g., at Ge content below 30%). Therefore, after the nitrogen treatment, the low-alloy SiGe material is etched better (selectively) than pure Ge or SiGe with a higher Ge alloy content. In the case of lower Ge alloy content (e.g., below 30%), any nitrogen formed or bonded can be easily removed by a subsequent gas-phase etch. In the case of high Ge alloy or pure Ge, the Ge layer is strongly protected by the nitrogen radical treatment. Therefore, low-alloy SiGe can be etched selectively relative to high Ge alloy SiGe or Ge. Because the nitrogen treatment has substantially no effect on the Si material and the subsequent gas phase chemical etch does not strongly etch silicon-containing materials that are Ge-free or very Ge-poor, SiGe can also be selectively etched relative to Si material. Therefore, the present process can be particularly advantageous for SiGe etching of Ge or SiGe relative to high Ge alloys, and for SiGe etching selective to Si.

[0028] After the nitrogen radical treatment, an etching process is performed using the plasma from which the nitrogen ions have been removed. While the etching can occur in the same chamber as the nitrogen radical treatment, in a presently preferred example, the etching occurs in a separate chamber 301, as shown in FIG. 3 . Chamber 301 is controlled by controller 300, which may include one or more processors or computers configured to control the operations and processes occurring in chamber 301. As noted with respect to controller 200, controller 300 may store instructions or process commands or may receive instructions or data from a separate memory or controller. Also as previously noted, controller 300 may be a single controller or may include distributed controllers or sub-controllers for controlling the various components and operations discussed herein.

[0029] Gas source GS2, shown at 304, controllably supplies process gases from one or more sources at designated concentrations, and the temperature may be controlled by various temperature control means, represented by TC2 306, which may include temperature control means for substrate holder 320 and / or chamber walls and / or radiation or other forms of temperature control means. A substrate 322 is placed on substrate holder 320 and may be held by electrostatic attraction, for example, by an electrostatic chuck. A vacuum pump VP2 at 324 is provided for evacuating the gases. In a presently preferred example, the gases from gas supply 304 are not excited into a plasma, but rather are provided in the vapor phase, whereby etching is performed by vapor-phase chemistry.

[0030] Gas phase chemistries include an etchant such as 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 may also be present, but the gases are not excited and therefore do not essentially react with the substrate layer under the etching process conditions.

[0031] If a more aggressive fluorine gas-phase chemistry is desired, gases other than HF, i.e., F2, ClF3, and / or XeF2, are preferred. As described below, a thermal treatment is preferably performed after the gas-phase etch. The thermal treatment can be performed in the same chamber 301 as the gas-phase etch chemistry, but preferably a separate chamber is provided that is more suitable for higher temperature control, e.g., temperatures between 100°C and 500°C. Preferably, after etching, the temperature is increased, e.g., to 100°C to 300°C, more preferably to 150°C to 250°C. The duration or elapsed time of the thermal treatment can vary depending on the temperature and the amount of residue or other material that may need to be removed. For example, the thermal treatment can be performed for at least 30 seconds, e.g., up to 10 minutes. By way of example, the thermal treatment can be performed for at least 1 minute or at least 2 minutes. Preferably, no fluorine-containing or other halogen-containing gases are introduced into the chamber containing the substrate during the thermal treatment. For example, the gas in the chamber during the thermal treatment can include an inert gas, including N or Ar.

[0032] Referring to Figure 4, an overview of example process steps is shown. Steps refer to steps and operations described herein, which may be provided as an algorithm under the control of one or more controllers.

[0033] As shown in S10, a plasma (P1) is formed from a nitrogen-containing gas, which may contain one or more other gases, such as Ar, for plasma stability and / or nitrogen concentration control. In S12, ions are removed from the plasma, leaving the remaining plasma (or second plasma P2) containing nitrogen radicals but no nitrogen ions, or at least a reduced amount of nitrogen ions compared to the first plasma. After removing the nitrogen ions, one or more Ge-containing layers are then treated with the plasma (P2). As previously mentioned, the Ge-containing layer may contain Si or other materials, but the amount of Ge (in layer 104) is greater than the amount of Ge in the Si-containing layer or layers (102) being etched. Layer 104 may be Si-free, and layer 102 may be Ge-free. The layer with a lower Ge content preferably contains less than 50% Ge, more preferably less than 30% Ge. With a Ge content less than 30%, the nitrogen bonds are loose or slight, and all of the nitrogen or nitride may be removed during the gas-phase etch, thereby etching the layer 102 with a lower (or no) Ge content relative to the layer 104 with a higher or pure Ge content. Thus, in step S16, the silicon-containing layer is etched relative to the Ge-containing layer.

[0034] In S18, a thermal treatment is performed. The thermal treatment is optional, but is currently preferred to achieve better results. The thermal treatment is preferably performed at a temperature higher than the temperature at which the Ge-containing layer is treated with nitrogen radicals and higher than the temperature of the gas-phase etching. For example, the temperature of the thermal treatment is preferably higher than 100° C.

[0035] The thermal treatment can remove residues such as fluorine- or halogen-containing residues, and can also remove nitrogen-containing residues. A more aggressive etchant gas (during gas-phase etching) can be beneficial in removing nitrides during etching or forming by-products / residues that are a combination of the etching gas, nitrogen / nitride, and etchant. The by-products or residues can also include material from the Si layer being etched. These by-products or residues can then be removed during the thermal treatment. When a more aggressive treatment (and at least partial removal of nitrides) is desired during gas-phase etching, the aforementioned etchant gases (e.g., F2, ClF3, XeF2) other than HF are preferred.

[0036] It should also be understood that steps can be repeated depending on 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, S18, these steps can be repeated. Additionally, if nitrogen protection is no longer present, step S14 can be performed again before repeating S16, S18.

[0037] 5, according to one advantageous embodiment that can be utilized in this example, nitrogen treatment can be utilized on some Ge-containing layers of a substrate but not others, for example, when, in a process or portion of a process flow (or a portion or first region of a substrate), it is desirable to selectively etch a Ge-containing layer (high Ge alloy layer or pure Ge) relative to a Si-containing layer (low Ge alloy layer or Ge-free layer), and thus nitrogen radical treatment is not utilized. However, in another portion of the process or a different portion of the substrate (e.g., a different second region) or another process step, it is desirable to etch the Si-containing layer selectively to or relative to the Ge-containing layer, and thus nitrogen radical treatment is utilized on the Ge-containing layer (pure Ge layer or layer with a higher proportion of Ge compared to the Si layer), and the Ge layer is not etched during the selective etching of the Si layer.

[0038] Thus, as shown in S20, a substrate can be provided having a first layer containing a first plurality of Ge atoms, and a second layer containing a second plurality of Si atoms can be provided. As previously described, the Ge-containing layer can contain Si atoms, and the Si-containing layer can contain Ge atoms, but the amount of Ge in the Si-containing layer is less than that in the Ge-containing layer. Of course, the Si-containing layer can also contain no Ge atoms, and the Ge-containing layer can be Si-free. In a preferred example, when the Si-containing layer is selectively etched relative to the Ge-containing layer and both layers contain Ge, the Si-containing layer preferably contains less than 30% Ge, preferably 5% to 30% Ge. However, in certain devices, it may be desirable to have no Ge atoms in the device, for example, to provide a pure Si channel. The Ge-containing layer can contain a higher amount of Ge, preferably greater than 30%, more preferably greater than 50%, and can even be pure Ge. Other variations are possible in which the Ge content of the Ge-containing layer is higher than that of the Si-containing layer.

[0039] 5, a first subset of first layers containing Ge are selectively etched relative to a first subset of second layers containing Si, and thus the first subset of Ge-containing layers are not provided with a treatment or pretreatment with nitrogen radicals. Thus, the first subset of Ge-containing layers can be selectively etched relative to the first subset of second layers with, 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 advantage, the same or substantially the same gas-phase etching process can be used to etch Ge-containing layers selectively relative to Si-containing layers and also to etch Si-containing layers selectively relative to Ge-containing layers, the difference being whether a pretreatment with nitrogen radicals is used.

[0040] Thereafter, as shown in S24, a second subset of the first layers (Ge layers) are treated with nitrogen radicals by the process described above to provide a nitride layer to protect the second subset of Ge-containing layers. Thus, as shown in S26, a second subset of the second layers (Si-containing layers with less Ge) are etched relative to the second subset of the first layers. Pure Si (or Si with very little or no Ge) etches slowly, but can nevertheless be etched selectively relative to or to the Ge layers if the Ge layers have been protected by treatment with nitrogen radicals as described above.

[0041] 5 is provided as an example, and alternatively, a first subset of first layers (Ge-containing layers) can be treated with nitrogen radicals to provide etching of a first subset of second layers (Si-containing layers) relative to the first subset of first layers by gas-phase etching, after which the second subset of first layers is not treated with nitrogen radicals, whereby the second subset of first layers comprising Ge is therefore etched relative to the second subset of second layers comprising Si.

[0042] Similarly, while the nitrogen radical treatment described with reference to FIGS. 1A-C was described in connection with processing Ge and subsequently etching a Si-containing layer to create recesses, it can also be used to reverse materials or provide additional material or process steps. For example, in the configuration of FIGS. 1A-C, the Ge-containing layer can be etched to form recesses relative to the Si-containing layer without treating or pretreating the Ge-containing layer, followed (or preceded) by a process in which the Si-containing layer is etched relative to the Ge-containing layer. In this case, the Ge-containing layer is treated with nitrogen radicals before etching the Si-containing layer relative to or selective to the Ge-containing layer. When the Ge-containing and Si-containing layers are exposed simultaneously, particularly if the Si-containing layer contains very little or no Ge, little or no etching of the Si-containing layer occurs during etching of the Ge-containing layer because the Ge-containing layer is rapidly etched. Thus, if it is desired to etch Ge selectively relative to Si and also Si selectively relative to Ge, the Ge-containing layer can be etched first to provide the desired amount of etching, and the Ge layer is etched quickly, resulting in little or no etching of the Si layer. The Ge layer can then be protected, and the Si layer can be etched. Although the Si layer progresses more slowly (compared to unprotected Ge), because the process is occurring on the Ge layer, the etching can proceed to the desired amount without affecting the previously etched Ge layer.

[0043] As already indicated with respect to Figure 4, the process shown in Figure 5 may also be provided as an algorithm executed by an apparatus under the control of one or more controllers. The process of Figure 5 preferably also includes a thermal treatment after the gas phase chemical etching.

[0044] 6A-6C provide another example where this processing can be utilized.

[0045] FIG. 6A shows a configuration in which a spacer 600 is provided within a previously formed recess, and a source 650 and a drain 652 are provided on each side of the stack assembly. A channel 654 extends from the source 650 to the drain 652, and the channels are separated by a layer 656. As shown in FIG. 6B, the channel 654 is then released by removing the layer 654. In this operation, if the layer 654 is a Ge-containing layer (pure Ge or a layer with more Ge than the layer 656), it can be treated with nitrogen radicals as previously described herein, thereby protecting the Ge layer 654 when removing the layer 656. Alternatively, if the layer 656 has a higher germanium content, this process can be performed without utilizing a nitrogen radical treatment of the layer 654, and the layer 656 is etched without pre-treatment of the layer 654. This latter example can be used in processes where other upstream or downstream processes selectively use protection of the Ge layer with a nitrogen radical treatment.

[0046] After the channel is released, as shown in FIG. 6C , gate metal 670 is deposited in the regions between the gate spacers 608 and between the channels 654. Preferably, a barrier layer is deposited before depositing the gate metal 670. Note that one of the layers 654 or 656 may have previously been treated with a nitride treatment, but the nitride treatment has already been subsequently removed during another process operation, e.g., an earlier etch. Therefore, the nitride treatment or pretreatment process can be utilized in certain process operations but cannot be selectively utilized in other process operations. As a result, selective etching of both Ge relative to low Ge alloy (or no Ge) can be achieved, and selective etching of low Ge alloy (or no Ge) relative to high Ge alloy layers can also be achieved, depending on whether or not a pretreatment process is used.

[0047] According to the methods herein, different selectivities can be used for different features or devices in different regions of a substrate. Selective etching of a Ge-containing layer relative to a Si-containing layer (containing less Ge or no Ge) in one portion of a substrate or a first region of the substrate, while providing the reverse selective etching in another portion of a substrate or a second region of the substrate, i.e., selective etching of a Si layer (containing no Ge or a small amount of Ge) relative to a Ge-containing layer, can be provided in two ways. For example, with brief reference to FIGS. 10A and 10B, different devices or device features can be provided in different regions of a substrate, e.g., device 700 is provided in a first region of the substrate, and device 500 is provided in a second region of the substrate. Device 500 in the second region of the substrate can be coated with layer 600, such as an organic layer or OPL. Devices 700 and 500 typically also include liners, e.g., 702 and 502, to avoid damage during deposition of film 600. The liner or layer 702 can be removed to expose the device 700, as shown in FIG. 10B, while the device 500 in the second region of the substrate remains covered. Thus, the device or device feature in the first region 700 can be treated, for example, using a nitrogen radical treatment to etch the Si-containing layer. For example, if the device or feature in the first region 700 includes a Ge channel, the Ge channel can be protected and the layer between the channels can be etched and removed to provide channel release, but the Ge channel in the first region is not etched due to its protection from the nitrogen radical treatment. In the same substrate, other devices may include channels formed of Si material that contains no or a reduced amount of Ge compared to the material of the layer or layers between the channels. Thus, the device or feature 700 can be covered with a film, e.g., a carbon-containing film such as OPL, and the device or feature 500 is exposed upon removal of the layer or film 600 in the second region.The Ge layer between the channels (the channels are formed of Si with no Ge or a lower alloy amount of Ge compared to the Ge layer) can then be etched to provide channel release without pre-processing of the second region features or device 500.

[0048] In the example shown in Figures 10A and 10B, the recess machining process has already been performed and spacers have been formed. However, the same approach can be used for recess machining processes of different materials in different regions of the substrate. The Si layer can be recessed at features or devices in a first region, while the Ge layer in the first region is protected using a nitrogen radical treatment, and the devices or features in a second region are covered. With the devices or features in the first region covered and the second region uncovered, the Ge layer in the second region can be etched (e.g., to recess the Ge layer) without the nitrogen radical treatment.

[0049] Another example is given below in which two different devices or features can be exposed simultaneously in different regions of a substrate, and the selective use (or non-use) of nitrogen treatment and timing of the nitrogen treatment can be used to provide different selective etching of different materials in different regions.

[0050] 7A-7C show another example in which the present nitrogen radical processing may be utilized in conjunction with multiple processing operations in which nitride processing is provided in this operation or in other operations. In the arrangement of Figures 7A-C, a channel trimming and cladding operation is performed. The reference numerals used in Figures 6A-C are the same as in Figures 7A-C unless otherwise stated, and therefore their descriptions will not be repeated.

[0051] Figure 7A shows the channels 654 after layer 656 has been removed and released. The channels each include a first end 654a and a second end 654b, with spacers 600 disposed adjacent (above and below) each of the first and second ends 654a, 654b. As shown in Figure 7B, a channel trimming or channel thinning operation is performed, thereby trimming or thinning a portion 654c between the first end 654a and the second end 654b.

[0052] 6C, a channel cladding operation can then be performed in which cladding material is deposited or wrapped around the entire surface of the exposed channel 654, including the previously trimmed portion at 654c, to provide cladding 656. For example, the cladding can be formed by growing a Si, Ge, or SiGe layer 656 on the trimmed channel 654.

[0053] For example, in an earlier etch (such as channel release), the channel 654 can be protected and the Si material between the channels etched. The nitride is removed and the channel can be etched with a fluorine vapor phase etch, but without a nitrogen radical treatment before channel trimming.

[0054] According to another example, a given substrate may include devices in a first region having a channel (first channel) formed in a Ge-containing layer (pure Ge or highly alloyed SiGe), and devices in a second region may have another channel (second channel) that is a Si layer (e.g., having a lower Ge alloy content compared to the Ge layer or no Ge). Etching or trimming of the Si layer may be performed in one region while protecting the Ge layer (using a nitrogen radical treatment), and etching (e.g., trimming) of the Ge layer may be performed in another region without protection (without using a nitrogen radical treatment) in a separate etching process.

[0055] As discussed above with respect to Figures 10A and 10B, if different devices or features are provided for which different selectivities are desired, one region of the substrate can be coated while other regions are treated using a treatment with nitrogen radicals, and then the originally coated region can be exposed while other regions are coated, thereby taking advantage of the reverse selectivity by not using the treatment with nitrogen radicals.

[0056] A channel trimming operation is an example of a process in which two different types of devices can be simultaneously exposed (e.g., without the need for selective organic layer coverage and exposure) and the selective use (or timing) of nitrogen radical treatment can be utilized to provide selective trimming of the different types of channel materials. For example, a first region of a substrate may contain a first device or feature whose first channel is formed of a Ge material (pure Ge or a channel of a device or feature in a second region of the substrate), and the second region of the substrate may contain a second device whose second channel is formed of a different channel material than the first channel in the first region (e.g., a Si material that is Ge-free or a Si material that contains a lower amount of Ge than the channel of the device in the first region). With this configuration, etching can be performed without first treating with nitrogen radicals, with both the first device in the first region and the second device in the second region exposed. In this case, the Ge channel in the first region (the first channel) is rapidly etched to achieve the desired amount of etching or trimming because Ge is rapidly etched in gas-phase chemical etching. The nitrogen radical treatment is then performed so that the Ge channel of the first device in the first region is protected. Therefore, the second channel in the second region can be etched or trimmed to the desired trimming amount, while the first channel is protected by the nitrogen radical treatment. While the Ge channel (first channel) in the first region is being etched, the second channel in the second region may also be etched, but because the etching of the second channel in the second region of the substrate is slow, any etching is minimal and not etched to the desired trimming amount. Therefore, the first channel is treated, and thus, after the nitrogen radical treatment of the Ge channel (first channel), it is protected and the desired trimming amount previously obtained is maintained. Then, etching of the Si layer or Si channel (second channel) in the second region can proceed in a second etching operation.Although this etching is relatively slow, the previously etched Ge layer or channel in the first region is maintained without further etching by using the nitrogen radical treatment, and etching of the second channel in the second region is allowed to proceed until the desired amount of etching or trimming is achieved. Thus, by selectively using or not using the nitrogen radical treatment, different devices or features formed of different materials in different regions of the substrate can be etched with different selectivities. The use or not of the nitrogen radical treatment can be advantageously applied to nFET and pFET applications.

[0057] FIG. 8 illustrates the advantageous selectivity and selectivity change that can be achieved using the nitrogen radical treatment disclosed herein. Specifically, each of the four materials was subjected to the same gas-phase etching process (non-plasma etching using a fluorine-containing gas), with the left portion of the graph showing the etch rate without pretreatment using nitrogen radicals, and the right portion of the graph showing the etch rate with the same gas-phase etching process but with pre-etching using nitrogen radicals as disclosed herein. In the illustrated example, the nitrogen radical treatment was performed at 85°C. As can be seen, without pretreatment, the Ge layer etches more rapidly than a layer containing both Si and Ge (e.g., the SiGe25 layer shown, with 25% Ge). Ge also etches more rapidly relative to polysilicon and SiN.

[0058] In contrast, when pretreatment is used (right portion of the graph), Ge is not etched or is only minimally etched, demonstrating the effectiveness of the treatment. Furthermore, when selective etching of a material containing SiGe (such as a 25% alloy) is desired, highly selective etching can be provided for etching SiGe selectively to or relative to Ge. Using process gases in a gas-phase chemical etch, poly-Si or SiN (deposited by low-pressure CVD in this example) had very low etch rates both without and with pretreatment. Therefore, using the same etch chemistry during gas-phase etching without nitrogen radical treatment can provide highly selective etching of Ge layers relative to layers with lower Ge content, which is highly selective to other silicon-containing materials, such as poly-Si or SiN, as shown by the left portion of Figure 8. Furthermore, by utilizing pretreatment, SiGe can be etched relative to Ge (or other Si-containing layers with less or no Ge, e.g., poly-Si or SiN), since substantially no etching was observed in the Ge layer. Thus, using substantially the same gas-phase etch, depending on whether or not nitrogen radical treatment is used, Ge (higher Ge content) containing layers can be selectively etched relative to SiGe layers with lower Ge content, or alternatively, SiGe layers can be selectively etched relative to Ge layers with gas-phase etch chemistries (e.g., fluorine or halogen gases such as F2, ClF3, HF and / or XeF2).

[0059] Thus, for example, if a substrate includes different devices or features in first and second regions of the substrate, etching of the Ge-containing layer can be performed for a first device in the first region by not using a nitrogen radical treatment, after which a nitrogen radical treatment can be used to etch the Si layer having less or no Ge while protecting the Ge layer (e.g., the first channel).

[0060] Figure 9 shows that the use of nitrogen radical treatment is substantially reversible or does not damage the material being processed. In other words, after the nitrogen radical treatment, selective vapor-phase etching, and thermal treatment, the material (SiGe25 in the example of Figure 9) substantially returns to its original state. Therefore, the properties or composition of the material are not damaged or substantially changed by the use of nitrogen radical treatment. In the two graphs in Figure 9, the atomic percentages of the different materials are shown before processing (before undergoing nitrogen radical treatment) on the left and also after processing, i.e., after radical nitrogen treatment, vapor-phase etching, and thermal treatment. Tests were performed using SiGe25 formed as a film on a substrate to determine the composition of the film before and after processing. The film is nominally silicon and 25% germanium, although other materials are present. Pretreatment was performed using nitrogen radicals (as shown in Figure 2, using a remote plasma to remove ions) at 85°C, a pressure of 850 mTorr, a source power of 850 Watts, and a volumetric gas flow rate of 75% nitrogen and 25% argon into the remote plasma chamber. Gas-phase chemical etching was performed at 60°C, 250 mTorr, and a volumetric flow rate of 50% fluorine etchant (F2 and ClF3) and 50% carrier gas (N2 and Ar). The post-etch thermal treatment was at 2 Torr and 150°C in a nitrogen and argon environment. As can be seen, only a slight decrease in carbon content (material 900) is observed. Additionally, a slight increase in the amount of fluorine (represented by the lower material 910) is also observed, but only to a small extent. However, the amounts of Ge (region 902), Si (region 904), nitrogen (region 906), and oxygen (region 908) remain essentially the same. Thus, nitrogen radical treatment or pretreatment can be used to effectively provide selective etching or to change the degree of selectivity of one material over another, but the treatment does not substantially change the composition of or damage the material being processed. In this method, for materials that are selectively etched and materials that are protected by nitrogen radical treatment, the atomic percentage of each of oxygen, germanium, and silicon will change by no more than 5% when the composition after processing is compared to the composition before processing.Additionally, surface damage can also be avoided or minimized by removing ions before treating the material so that the pre-treatment modification is with nitrogen radicals and not with excited species, and by performing the etch using gas phase etch chemistry.

[0061] The disclosed methods and apparatus can be utilized in a variety of applications, including but not limited to, nFETs, pFETs, nanosheets, GAAs, FinFETs, CFETs, and other devices or device features.

[0062] It is to be understood that modifications and variations not inconsistent with the teachings herein may be incorporated. It is therefore to be understood that within the scope of the claims, the invention may be practiced otherwise or with variations on the examples disclosed herein.

Claims

1. An etching method, A step of providing a substrate having a base, a first layer on the base, and a second layer on the base, wherein the first layer contains Ge, the second layer contains Si, the second layer does not contain Ge, or contains less Ge than the first layer, and the first and second layers are stacked vertically such that one of the first and second layers is perpendicular to the other of the first and second layers. The steps include treating the side surface of the first layer with nitrogen radicals to form a nitrided surface on the side surface of the first layer, The steps include etching the side surface of the second layer while the side surface of the first layer is protected by the nitrided surface, thereby causing the side surface of the second layer to be recessed relative to the side surface of the first layer, thereby providing a recess in the second layer, A method having

2. The method according to claim 1, further comprising the step of filling the recessed area of ​​the second layer with a spacer material.

3. The step of processing the side surface of the first layer is: The steps include forming a first plasma with a gas containing nitrogen in a first chamber or a first chamber section, The steps include: supplying the plasma to the second chamber or second chamber section in which the substrate is placed, removing nitrogen ions from the first plasma, and providing a second plasma in the second chamber or second chamber section; The steps include: treating the sides of the first layer with nitrogen radicals in the second plasma, after the step of removing nitrogen ions, The method according to claim 1, comprising:

4. The step of processing the side surface of the first layer is selective with respect to the second layer, After the processing step and before the etching step, as a result of the processing step, the second layer is not nitrided, or is nitrided less than the first layer, and is not nitrided less than the first layer. (a) The second layer has a nitrided surface that is thinner than the nitrided surface of the first layer, or (b) The second layer has a nitrided surface that has a lower nitrogen concentration compared to the nitrided surface of the first layer. The method according to claim 3, meaning at least one of the above.

5. The first layer has a Ge content of more than 30%, and the second layer has a Ge content in the range of 5% to 30%. The processing step is carried out at a temperature in the range of 15°C to 90°C, and the processing step is carried out without introducing a halogen-containing gas into the first chamber or the first chamber portion. The etching step includes a non-plasma gas-phase chemical etching, and the gas-phase chemical etching includes a fluorine-containing gas. The method further includes, after the etching step, a step of increasing the temperature of the substrate and performing heat treatment at a temperature in the range of 100°C to 300°C. The method according to claim 4, wherein the heat treatment is carried out without introducing a fluorine-containing gas.

6. The method according to claim 5, further comprising the steps of etching and heat treatment in separate chambers.

7. The method according to claim 1, further comprising the step of removing the nitrided surface from the first layer.

8. The etching step is F ２ , CLF ３ HF or XeF ２ This includes vapor-phase non-plasma etching using a gas containing at least one of the following: The method further includes a step of performing heat treatment at a temperature in the range of 100°C to 300°C after the etching step. The method according to claim 1, wherein no fluorine-containing gas is introduced during the heat treatment.

9. Furthermore, the method includes a step of selectively etching a third layer onto a fourth layer on the substrate. The third layer has a higher Ge content than the fourth layer, and the step of etching the third layer is F ２ , CLF ３ HF or XeF ２ The process includes performing vapor-phase non-plasma etching using a fluorine-containing gas containing at least one of the following, to selectively etch the third layer with respect to the fourth layer, The method according to claim 8, wherein, before commencing the step of etching the third layer, the third layer and the fourth layer are exposed and no nitrogen radical treatment is performed on the third layer or the fourth layer.

10. The method according to claim 8, wherein the change in the composition of the material of the first layer and the material of the second layer after the heat treatment compared to before the treatment using nitrogen radicals is 5% or less with respect to silicon, germanium, and oxygen, respectively.

11. The substrate comprises a first plurality of first layers and a second plurality of second layers. A portion of the first plurality of first layers is processed in the side surface processing step, a portion of the second plurality of second layers is selectively etched with respect to the portion of the first plurality of first layers, and the other layers of the first plurality of first layers are not processed. The method further comprises the step of selectively etching the other layers of the first plurality of first layers with respect to the other layers of the second plurality of second layers, The method according to claim 1, wherein the other layer among the first plurality of first layers or the other layer among the second plurality of second layers is not treated with nitrogen radicals.

12. The step of processing the side surface of the first layer comprises the step of processing two side surfaces of the first layer, The step of etching the side surface of the second layer comprises etching two side surfaces of the second layer to form two recesses on opposite sides of the second layer that are recessed relative to the first layer, This method further, The steps include filling the two recesses with spacers to provide spacers to the two recesses, A step of removing the second layer, leaving a channel formed from the first layer, wherein the channel includes first and second ends, one of the two spacers adjacent to the first end, and the other of the two spacers adjacent to the second end, The steps include trimming a portion of the channel to form a thinned channel portion between the first end and the second end, The steps include forming a cladding around the thinned channel portion, The method according to claim 1, comprising:

13. The substrate has a first region and a second region, the first layer and the second layer are part of a first device arranged in the first region, and the channel of the first device is a first channel. The substrate further has a second device in the second region, the second device having a third layer and a fourth layer, the fourth layer containing Si and not containing Ge or containing less Ge than the first layer. The method further includes the step of removing the third layer so that the fourth layer forms a second channel, During the step of trimming the portion of the first channel, the second channel is exposed, and the first channel is selectively etched relative to the second channel. This method further, A step of trimming the portion of the first channel, followed by a step of treating the first channel with nitrogen radicals of a channel-treating plasma, wherein nitrogen ions are removed to form the channel-treating plasma, and a treated and trimmed first channel is provided. The steps include: after processing the first channel, selectively etching the second channel with respect to the processed and trimmed first channel to provide a trimmed second channel; The method according to claim 12, having the following characteristics.

14. An etching method, A step of providing a substrate having a first plurality of first layers and a second plurality of second layers, wherein each of the first plurality of first layers contains Ge, each of the second plurality of second layers contains Si, and each of the second plurality of second layers does not contain Ge or contains less Ge than each of the first plurality of first layers. The steps include: processing a first subset of the first plurality of first layers with a plasma containing nitrogen radicals to provide a nitride layer on each side surface of the first subset of the first plurality of first layers; The steps include selectively etching a first subset of a second plurality of second layers with respect to a first subset of a first plurality of first layers, A method having

15. Furthermore, the process includes a step in which the second subset of the first layers is not treated with nitrogen radicals. The aforementioned second plurality of second layers includes a second subset of the aforementioned second plurality of second layers, This method further, The method according to claim 14, comprising the step of selectively etching the second subset of the first plurality of first layers with respect to the second subset of the second plurality of second layers, wherein the second subset of the first plurality of first layers is not processed.

16. The first subset of the first plurality of first layers and the first subset of the second plurality of second layers are provided within the first device in the first region of the substrate. The second subset of the first plurality of first layers and the second subset of the second plurality of second layers are provided within a second device in a second region of the substrate, which is different from the first region. The step of processing a layer containing more Ge in the first region to form a nitride is provided, which selectively etches a layer containing less Ge with respect to the layer containing more Ge in the first region. The method according to claim 15, wherein the second region is not treated to form a nitride, thereby providing a step of selectively etching a layer containing more Ge to a layer containing less Ge.

17. The step of processing the first subset of the first plurality of first layers is: A step of forming a first plasma with a gas containing nitrogen, A step of removing nitrogen ions from the first plasma to form a second plasma, wherein the second plasma contains nitrogen radicals but does not contain nitrogen ions or contains a reduced amount of nitrogen ions compared to the first plasma. The steps of processing a first subset of the first plurality of first layers with the second plasma, The method according to claim 16, comprising:

18. A method for processing a substrate, A step of providing a substrate having a first feature and a second feature, The first feature comprises a first layer and a second layer, the first layer containing more than 30% Ge, and the second layer containing more than 5% but less than 30% Ge. The second feature comprises a third layer and a fourth layer, the third layer comprising Ge, and the fourth layer comprising Si, the fourth layer comprising no Ge or comprising less Ge than the third layer. Steps and (a) A step of selectively etching the second layer of the first feature with respect to the first layer by a first process, wherein at the start of the first process, the surface portions of both the first layer and the second layer are exposed. The first process described above is (i) A step of forming a first plasma with a gas containing nitrogen, wherein the first plasma is formed without containing a halogen-containing gas, (ii) The step of removing ions from the first plasma and providing a second plasma having nitrogen radicals, (iii) A step of exposing the first feature to the second plasma, wherein the first layer is selectively treated with respect to the second layer by nitrogen radicals of the second plasma, and the exposure step and the selective treatment step are carried out at a temperature in the range of 15°C to 100°C. (iv) After the exposure step, a step of performing vapor-phase chemical etching in a non-plasma environment containing at least one halogen gas to selectively etch the second layer relative to the first layer, Steps having, (b) A step of selectively etching the third layer of the second feature with respect to the fourth layer of the second feature using a second etching process, wherein at the start of the second etching process, a portion of both the third layer and the fourth layer is exposed. The second etching process described above is: (i) vapor-phase chemical etching in a non-plasma environment containing at least one halogen gas to selectively etch the third layer with respect to the fourth layer, (ii) Before performing the gas-phase chemical etching, the second feature is not exposed to treatment with nitrogen radicals, Steps having, A method having

19. The third layer contains more than 30% Ge, and the fourth layer contains less than 30% Ge. The gas-phase chemical etching of the above (a)(iv) is F ２ , ClF ３ , HF or XeF ２ and contains at least one gas selected therefrom. The gas-phase chemical etching described above (b)(i) is F ２ , CLF ３ HF or XeF ２ It includes at least one gas selected from, This method further, The step of performing the gas-phase chemical etching described in (a)(iv) above, followed by the step of performing heat treatment of the first feature at a temperature in the range of 100°C to 250°C, wherein the heat treatment of the first feature is performed in an environment in which no fluorine-containing gas is introduced during the heat treatment, The step of performing the vapor-phase chemical etching described in (b)(i) above, followed by the step of performing heat treatment of the second feature at a temperature in the range of 100°C to 250°C, wherein the first region includes a first device containing the first feature, and the second region includes a second device containing the second feature, The method according to claim 18, wherein the method is characterized by having the following:

20. The substrate has a first region and a second region separated from the first region. The method according to claim 18, wherein the first feature is part of a first device in the first region, and the second feature is part of a second device in the second region.

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