Selective and Isotropic Etching of Silicon-Germanium Alloys and Dielectric-Transcending Silicon by Novel Chemistry and Surface Modification

Abstract

Selective protection and etching that can be used for etching a silicon-containing layer with respect to a Ge or SiGe layer are provided. In one example, layers are stacked and an oxide is on the side surfaces of the layers. A process for providing a modified surface or a termination surface on the side surfaces of the Ge / SiGe layer is used, and after a gas treatment, a heat treatment is provided to selectively sublime a layer portion on the side surfaces of the Si-containing layer. The gas treatment and the heat treatment are preferably performed in a non-plasma environment. Thereafter, a plasma process is performed to form a protective layer on the Ge-containing layer, and the Si-containing layer can be etched with plasma.

Description

Technical Field

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 339,895, filed May 9, 2022, and U.S. Patent Application No. 17 / 964,601, filed Oct. 12, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure generally relates to semiconductor manufacturing, and in certain embodiments, to plasma etching techniques.

Background Art

[0003] The integrated circuit (IC) manufacturing industry is striving to increase device density in order to improve speed, performance, and cost. Due to continuous scaling to smaller node sizes, device architectures have evolved from two-dimensional (2D) planar structures to three-dimensional (3D) vertical structures such as nanowires or vertically oriented transistors. Inadequate control of the conductive channel by the gate potential is accelerating the demand for this change. As the gate dimensions shrink, the short-channel effect (SCE) can become very prominent, and it may increase current conduction when no voltage is applied to the gate (I off ). The change in device architecture can result in better electrostatic control of the gate, reducing SCE and power loss. The manufacture of nanowire devices can present challenges in 3D etching when a highly selective isotropic etching process is beneficial. For example, it may be necessary to etch exposed material layers relative to each other to form depressions in the film stack or other selective etching in the film stack.

Summary of the Invention

Means for Solving the Problems

[0004] Some embodiments of the present invention describe selective and isotropic etching of silicon with respect to germanium-containing materials and dielectric materials. In certain embodiments, a method for processing a semiconductor substrate is described that includes receiving a semiconductor substrate including a film stack. The film stack includes a first germanium (Ge)-containing layer and a second Ge-containing layer, and a first silicon (Si) layer disposed between the first Ge-containing layer and the second Ge-containing layer. The method further includes removing an oxide layer, such as a native oxide layer, from the film stack and processing the film stack with a processing gas including a fluorine agent and an oxygen agent, and heat treating the film stack to form a termination layer on the first germanium-containing layer and the second germanium-containing layer. The method further includes exposing the film stack to a plasma including a fluorine agent and a nitrogen agent, wherein the plasma selectively etches the first silicon layer and converts the termination layer to an etching protection layer that inhibits etching of the first germanium-containing layer and the second germanium-containing layer during exposure of the film stack to the plasma. An apparatus for providing selective removal or etching and related processes is also disclosed.

[0005] For a more complete understanding of the present disclosure and its advantages, reference is made to the following description, to be read in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0006]

Fig. 1A-1E

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Fig. 3

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Fig. 7A-7B

Embodiments for Carrying Out the Invention

[0007] There are various techniques for attempting to selectively etch one material with respect to another. In some cases, the chemical properties of the two materials are sufficiently different that a plasma that selectively etches one material can be used without concern for etching the other material. In other cases, it may be more difficult to determine the appropriate etching conditions for selective etching because the chemical properties of the materials may be similar, or the available etching process may be limited by other factors. Certain materials present a more difficult selectivity challenge when it is desirable to etch one material without substantially or at all etching another material. Conventional processes for this type of selective etching may not be able to achieve selectively etching one material over another, or may not be able to meet process requirements such as selectivity, etching profile (e.g., local uniformity and / or surface roughness).

[0008] The issue of selectivity can arise when forming nanowires or nanosheets that function as channel regions in 3D vertical structures of semiconductor devices, such as gate-all-around (GAA) devices. Forming such nanowires involves forming a film stack on a base layer, where the film stack includes an alternating arrangement of Si layers and Ge or Si-Ge (SiGe) alloy layers. Part of this process can include, for example, etching depressions in the film stack at both ends of the Si layers while minimizing the etching of the Ge-containing layers, to expose the end portions of the Ge-containing layers for later use as conductive devices. Due to various issues, including partially containing a native oxide layer (NOL) and / or other residues present on the surface of the film stack (e.g., reactive ion etching (RIE) residues), conventional etching techniques may not be sufficient.

[0009] For example, some prior arts employ a single etching step using a plasma of nitrogen trifluoride (NF 3 )(or another etchant) and oxygen (O 2 ). Fluorine radicals in this plasma etch the Si layers, and oxygen reacts with Ge in the Ge-containing layers to form a Ge oxide (e.g., GeO 2 ) protection layer on the Ge-containing layers. However, the resulting structure after etching generally exhibits an unacceptable level of surface roughness along the exposed surfaces of the Si layers and Ge-containing layers, and part of the cause is the etching of the NOL. Furthermore, the GeO 2 protection layer may help selectively etch the Si layers, but the GeO 2 layer consumes a significant portion of the Ge-containing layers.

[0010] The embodiments described below explain various methods of selective etching. For example, an embodiment can be used to selectively etch a portion of a film stack on a substrate (e.g., a film stack including an alternating arrangement of Si layers and Ge-containing layers). For example, it may be desirable to selectively etch (or optionally completely remove) a depression in the edge portion of the Si layer to form Ge-containing layer nanowires. Further, embodiments of the present invention reduce plasma damage during selective Si etching.

[0011] Figures 1A - 1E show cross-sectional views of an exemplary substrate 102 in an exemplary process 100 for processing a substrate 102 according to certain embodiments of the present disclosure. In certain embodiments, process 100 incorporates an oxygen-free plasma etching process to etch a portion of a particular layer of the film stack on substrate 102, resulting in a substrate 102 having a recessed film stack after execution of process 100. Oxygen-free does not necessarily mean that all oxygen is excluded from process 100, but rather reflects that oxygen-containing gases such as O 2 and CO 2 are not intentionally introduced as part of the plasma etching process.

[0012] As shown in Figure 1A, substrate 102 is a semiconductor substrate including a film stack 104 disposed on a base layer 106. Film stack 104 includes an alternating arrangement of Si layers 108 and Ge-containing layers 110. Film stack 104 can have any suitable shape and can include any suitable number of layers. By way of example, the vertical thicknesses of Si layer 108 and Ge-containing layer 110 can each be from about 10 nm to about 25 nm, and in a particular example can be about 10 nm or about 20 nm. Additionally, Si layers 108 can have the same thickness or different thicknesses from each other, Ge-containing layers 110 can have the same thickness or different thicknesses from each other, and Si layers 108 and Ge-containing layers 110 can have the same thickness or different thicknesses from each other. In a particular example, all of Si layers 108 and Ge-containing layers 110 have substantially the same thickness.

[0013] The material of the Si layer 108 can be, for example, pure Si or silicon nitride (SiN). In certain embodiments, all of the Si layers 108 contain the same material, although the Si layers 108 can contain different materials as needed.

[0014] The material of the Ge-containing layer 110 can be, for example, pure Ge or a SiGe alloy. As a specific example, the Ge-containing layer 110 contains a SiGe alloy (mixture) in an appropriate ratio (e.g., Si 0.7 Ge 0.3 、Si 0.75 Ge 0.25 etc.) for the desired etching characteristics of a given application or for the desired performance of a semiconductor device obtained as a result of being formed using in part the process 100. In certain embodiments, all of the Ge-containing layers 110 contain the same material, although the Ge-containing layers 110 can contain different materials as needed.

[0015] The base layer 106 can be any suitable material, and in one example, includes Ge or a SiGe alloy. In a specific example, the film stack 104 is formed by alternately growing heteroepitaxial layers of Si (e.g., Si layer 108) and Ge or SiGe (e.g., Ge-containing layer 110) on the base layer 106.

[0016] An optional hard mask 112 may be included over the film stack 104. The hard mask 112 can be, for example, one that was used to form the structure of the film stack 104 in a previous etching process. In certain embodiments, the hard mask 112 is SiN, although it can contain any suitable material.

[0017] The barrier layer 114 is formed on the film stack 104 (including the hard mask 112) and, in this example, on the base layer 106. The barrier layer 114 may result from a previous manufacturing process (e.g., RIE) applied to the substrate 102 or other processing of the substrate 102 (e.g., exposure to ambient air when moving between processing tools). As a specific example, the barrier layer 114 may include a native oxide layer (NOL), RIE residues, or both. The NOL may be, for example, a thin layer of SiO 2 and H 2 O, having a thickness of, for example, about 1 nm to about 2.0 nm, formed on the surface of the substrate 102 when the substrate 102 is exposed to ambient air containing O 2 (or other suitable material). For example, the surfaces of the base layer 106, the Si layer 108, the Ge-containing layer 110, and the hard mask 112 may interact with the ambient air, and as a result, the barrier layer 114 may be formed on those surfaces. As another example, the surfaces of the base layer 106, the Si layer 108, the Ge-containing layer 110, and the hard mask 112 may include residues obtained as a result of a previous RIE process.

[0018] The barrier layer 114 may have etching characteristics different from those of the layer below it. The barrier layer 114 is shown as covering the film stack 104 (including the hard mask 112) and the base layer 106 substantially uniformly, but it may or may not have a uniform coverage.

[0019] Each of the layers in the film stack 104 has exposed surfaces at a pair of both ends when viewed from a cross-sectional perspective as shown. That is, each of the Si layers 108 has exposed surfaces 116 (at both ends), and each of the Ge-containing layers 110 has exposed surfaces 118 (at both ends). In addition, in the state shown in FIG. 1A, since the substrate 102 includes the barrier layer 114, the exposed surfaces 116 of the Si layer 108 and the exposed surfaces 118 of the Ge-containing layer 110 include the barrier layer 114.

[0020] In FIG. 1B, to remove at least a portion of the barrier layer 114 containing NOL, the film stack 104 is, in one example, treated with a processing gas containing a fluorinating agent and an oxidizing agent, and then the film stack 104 is heat treated. Thereby, the barrier layer 114 is removed from the exposed surface 116 of the Si layer 108 (or in the region 116 of the layer 114 adjacent to the Si layer 108) and from the exposed surfaces of the base layer 106 and the hard mask 112. Further, exposure to the processing gas reacts with the barrier layer 114 to form a termination layer 117 or a modified surface on the exposed surface 118 of the Ge-containing layer 110. According to one embodiment, the treatment is performed in the absence of plasma. In one example, the treatment results in a reduction of about 60 atomic % of O in the Ge-containing layer 110 (reduction of O in the termination layer 117 compared to the layer 114), where the loss of O was accompanied by an increase in the atomic % of Ge and F. In one example, the termination layer or modified surface 117 contains H, Si, F, and Ge, and this layer reacts with plasma (described below) to form germanium nitride in the region occupied by the layer or modified surface 117. Further, as a result of the gas treatment of the barrier layer 114, the modified barrier layer has H, Si, F, and Ge in the region 118 and does not sublime during the heat treatment, but the region 116 of the barrier layer 114 (adjacent to the Si-containing layer) sublimes during the heat treatment and little or no nitridation occurs in the region adjacent to or on such side surfaces of the Si-containing layer in subsequent plasma steps. Thus, the gas treatment and heat treatment provide for the selective removal or selective sublimation of the layer portion of the region 116 (adjacent to or on the surface of the Si-containing layer).

[0021] The termination layer or modified surface 117 can have any suitable thickness, but in certain embodiments, the termination layer 117 is relatively thin, such as 2 nm or less. The termination layer can be, for example, a single layer. In certain embodiments, the termination layer 117 contains fluorine such as Ge-F. In some examples, the processing gas further includes a hydrogenating agent. In some examples, the processing gas is a fluorine-containing gas and a hydroxide-containing gas (e.g., H 2comprising O and / or OH and typically a carrier gas (e.g., Ar and / or N). In one example, the processing gas comprises hydrogen fluoride (HF) gas and water (H 2 O) gas (e.g., aerosolized water and / or water vapor). In some embodiments, exposure to the processing gas can be carried out at a substrate temperature of about 0 °C to about 35 °C. In certain embodiments, the heat treatment can be carried out at a substrate temperature of about 100 °C to 250 °C, preferably about 150 °C to about 200 °C. In one example, the heat treatment can be carried out at a pressure lower than atmospheric pressure in the presence of an inert gas (e.g., N 2 and / or Ar). Preferably, the heat treatment is carried out at a pressure of 1000 mTorr to 3000 mTorr, and a pressure in the range of 1800 mTorr to 2200 mTorr is particularly preferred.

[0022] To distinguish from the plasma phase, the term "gas phase" processing is referred to herein, but some components, such as water, can be in aerosolized form or vapor phase form. Thus, unless otherwise specified, the gas phase can include vapors or aerosolized components such as water.

[0023] In one example, the substrate shown in FIG. 1A is aerosolized H 2The barrier layer 114 is subjected to non-plasma treatment to be treated with a processing gas containing O, fluorine, and a carrier gas (e.g., N and / or Ar). The processing gas will modify layer 114 differently depending on which layer (Si-containing layer or Ge-containing layer) the barrier layer covers. In particular, in one example, in portion 118 (covering the Ge-containing layer 110), the modified layer contains H, Si, Ge, and F, while in region 116 (covering the Si-containing layer 108), the modified portion 116 of the barrier layer 114 contains H, Si, and F but does not contain Ge (or, if any Ge is present, it is present in an amount lower than that in region 118). In one example, the treatment is performed in a first chamber, and in the next step, the heat treatment (resulting in the substrate shown in FIG. 1B) is performed in a second chamber, although it is possible to perform multiple steps in the same chamber. After the treatment of the barrier layer 114 to form regions 116 and 118, in the heat treatment, residual water vapor is removed, and the remaining amount of layer portion 116 is also removed, whereby a termination layer 117 or a modified surface 117 is present on the side surface of the germanium layer 110, and this termination layer 117 or modified surface 117 preferably contains H, Si, Ge, and F. The heat treatment is performed, for example, at 100 °C to 250 °C, preferably 150 °C to 200 °C, and in an inert atmosphere (e.g., N and / or Ar) as described above. Then, the termination layer 117 or modified surface 117 is converted into a protective layer 121 using plasma as further described below.

[0024] As shown in FIG. 1C, in the plasma process 120 of process 100, the substrate 102 is exposed to plasma to process the semiconductor substrate. The plasma 122 selectively etches the silicon layer 108 and converts the termination layer 117 to form an etching protection layer 121 on the side surface 118 of the Ge-containing layer 110. For example, the volatile etching by-products of Si etching may contain a fluorosilicate material, and the etching protection layer 121 may contain Ge nitride. The plasma process 120 is performed at a substrate temperature below the sublimation temperature of the etching protection layer 121. In some embodiments, the plasma process 120 can be performed at a substrate temperature in the range of about -50°C to 25°C, preferably -40°C to about 20°C. The pressure during plasma processing can be, for example, 25 mTorr to 700 mTorr, preferably 50 mTorr to 500 mTorr, more preferably 150 mTorr to 400 mTorr. As described below, the plasma process can include two parts or two steps, which include a first plasma containing H and N but no introduced F or another halogen, and a second plasma containing each of H, N, and F (or another halogen) introduced into the plasma. The same pressure and temperature are advantageously used for each part, but different temperatures and / or pressures can be used.

[0025] The nitride (e.g., Ge nitride) etching protection layer 121 may be insoluble in water, and the etching protection layer 121 contains O 2 and H 2 and enables it to function as an O diffusion barrier, thereby improving the stability of the nanowires formed from the Ge-containing layer 110. The plasma 122 (e.g., a fluorine-containing plasma, a hydrogen-containing plasma, and a nitrogen-containing plasma) is also selective to Ge and SiGe, and in addition, since the plasma 122 does not contain oxygen which causes conventional F / O-based plasmas to etch these materials, SiO 2 , Si 3 N 4 , oxides, and low-k materials can also be selective.

[0026] In an example of the plasma treatment of FIG. 1C, there is an initial plasma treatment with a plasma that contains hydrogen and nitrogen, preferably without fluorine (or another halogen) or oxygen, after which fluorine (or another halogen) is added to the plasma. In the fluorine-free initial plasma, the plasma containing hydrogen and nitrogen reacts with the modified layer 117 to form a nitride, thereby providing a protective layer (shown at 121 in FIG. 1D). Then, when fluorine is introduced, the silicon-containing layer 108 is etched. The continuous supply of H and N in the plasma prevents or reduces the consumption of the layer 117 / 121, while the fluorine plasma etches the Si-containing layer 108. Optionally, after exposure to a fluorine-containing plasma, exposure to a fluorine-free plasma can also be repeated (e.g., for 5 to 25 seconds, preferably 8 to 20 seconds, more preferably 10 to 15 seconds), then fluorine is introduced again to ensure that the protective layer 121 is not completely etched while etching the silicon-containing layer 108. As described below, by using repeated exposure to a non-halogen plasma (containing H and N), followed by a halogen plasma, a protective layer can be obtained on the newly exposed Ge (or SiGe) surface, which is exposed during the etching of the Si-containing layer as, for example, the top and bottom surfaces of the Ge-containing layer are exposed as the Si-containing layer is recessed.

[0027] In a preferred example, for both a fluorine-free plasma (e.g., the first plasma) and a fluorine-containing plasma (the second plasma), ions are removed from the plasma before the substrate is exposed to the plasma, whereby the radicals of the plasma react with the substrate to form the protective layer 121 and etch the layer 108. For example, the plasma can be formed as a remote plasma, where the plasma is generated in a first chamber or a first chamber portion, and the plasma is supplied to a second chamber or a second chamber portion (where the substrate is disposed) while removing ions using, for example, a grid or mesh arrangement filled to remove ions. The chamber or chamber portion where the substrate is disposed is not separately excited to form a plasma therein. Instead, it receives the plasma generated in the first chamber or the first chamber portion. It is preferred to remove ions or process with only radicals, but favorable results have also been observed in the presence of ions, and thus the plasma can also be deposited in the same chamber (or chamber portion) where the substrate is disposed.

[0028] As used herein, the description that fluorine (or another halogen) is absent means that fluorine (or another halogen) has not been introduced, but depending on the purity of the material and / or as a result of gases released, for example, from other materials or layers, trace amounts may be present.

[0029] During plasma exposure containing H, F, and N respectively, preferably, the volume flow ratio of F:N is in the range of, for example, 1:5 to 1:10, preferably in the range of 1:5.5 to 1:9, preferably about 1:7. When excessive nitrogen is introduced, the formation of nitrides or the formation of a protective layer may penetrate into the region of the Si-containing layer and inhibit the etching of the Si-containing layer. In one example, the ratio of the volume flow rates of fluorine and hydrogen (F:H) may be in the range of 1:1.5 to 1:2.5, preferably about 1:2. When fluorine is not introduced, the ratio of N:H may be in the range of, for example, 4.5:1 to 3.5:1, for example 4:1. In one example, the RF power can be, for example, 200 to 500 watts, preferably 250 to 350 watts, and used for plasma formation (both plasmas or both parts of the plasma treatment).

[0030] In certain embodiments, plasma process 120 is an isotropic etching process. Plasma process 120 can be performed in the plasma chamber of a plasma tool. The plasma tool can be any suitable type of plasma tool including, for example, an inductively coupled plasma (ICP) tool, a capacitively coupled plasma (CCP) tool, a surface wave plasma (SWP) tool, etc. One exemplary plasma tool will be described later with reference to FIG. 3.

[0031] For example, substrate 102 can be exposed to plasma 122 which is an oxygen-free plasma. It should be understood that oxygen-free does not necessarily mean that all oxygen is excluded from plasma process 120, but rather reflects that an oxygen-containing gas is not intentionally introduced as part of plasma process 120. Since it may be difficult or impossible to remove all oxygen from plasma chamber 123, some oxygen may still be present in certain processes described below.

[0032] Plasma 122 may include a fluorine agent 126, a hydrogen agent 128, and a nitrogen agent 130. The fluorine agent 126 may mainly function as an etchant for forming etching by-products on the exposed surface 116 of the Si layer 108. The hydrogen agent 128 may function as a reducing agent in the presence of the fluorine agent 126. Further, if applicable, depending on the gas used to generate the plasma 122, the hydrogen agent 128 may further decompose specific compounds of fluorine and nitrogen to generate the fluorine agent 126 and the nitrogen agent 130. The nitrogen agent 130 reacts with Ge in the termination layer 117 from the exposed surface 118 (including H, Si, Ge, and F) of the Ge-containing layer 110 to form a nitride layer (e.g., Ge 3 N 4 such as a Ge nitride layer) on the exposed surface 118. For example, atomic nitrogen (N) generated in the plasma 122 may react with Ge on the exposed surface 118 of the Ge-containing layer 110 to form the etching protection layer 121.

[0033] In certain embodiments, the plasma 122 may be generated from a gas including fluorine gas, nitrogen gas, and hydrogen gas. As some examples, the fluorine-containing gas used to generate the plasma 122 for the second part of the plasma treatment may include F 2 , NF 3 , sulfur hexafluoride (SF 6 ), or carbon tetrafluoride (CF 4 ). Further, although fluorine is described, other halogens may be used to assist the etching process.

[0034] In certain embodiments, no oxygen-containing gas is intentionally introduced as part of the gas for generating the plasma 122. As a specific example, the gas used to generate the plasma 122 may include an appropriate combination of NF 3 , N 2 , and H 2 . As another specific example, the gas may include NF 3 , ammonia (NH 3 ), and N 2 . In certain embodiments, N 2can be replaced by a noble gas such as argon (Ar) or krypton (Kr), or such a noble gas can be used in combination with N 2 As a specific example, the gas / composite gas used to generate the plasma 122 is N 2 / H 2 / NF 3 、N 2 / NH 3 / NF 3 、Ar / NH 3 / NF 3 、N 2 / H 2 / Ar / NF 3 、NF 3 / NH 3 、NF 3 / H 2 、or N 2 / H 2 / NH 3 / NF 3 and may include.

[0035] In an example where the gas used to generate the plasma 122 contains NF 3 and N 2 the ratio of NF 3 to N 2 can be appropriately considered. In a particular embodiment, the plasma 122 contains more nitrogen than fluorine in order to reduce or eliminate the etching of the Ge-containing layer 110 by fluorine and to ensure that the etching protection layer 121 is formed quickly enough since fluorine is a more reactive chemical in the plasma 122. The appropriate ratio (or range of ratios) may depend on various factors including other process parameters and the Ge concentration in the Ge-containing layer 110. In a particular embodiment, the higher the percentage of Ge in the Ge-containing layer 110, the more quickly the etching protection layer 121 will be formed, which can lead to better results. H 2 can be added to help promote the reactions that occur in the plasma chamber 123. An exemplary range of the ratio of H 3 to NF 2 is, for example, NF 3 :H 2 =1:0.5 to NF3 :H 2 =1:10 can be mentioned. NF 3 of N 2 As an exemplary range of the ratio to NF 3 :N 2 =1:1 to NF 3 :N 2 =1:15 can be mentioned.

[0036] Other process parameters for generating plasma 122 include gas flow rate, pressure, plasma source power, plasma bias power, time, and temperature. The gas for forming plasma 122 can be supplied at any appropriate flow rate. In certain embodiments, the etchant source gas flow rate is NF 3 =20 to 50 sccm, H 2 =30 to 150 sccm, N 2 =50 to 500 sccm. In certain embodiments, plasma process 120 can be performed at an intermediate pressure (e.g., about 50 mTorr to about 500 mTorr, in one example about 300 mTorr to about 350 mTorr) and an intermediate source power (e.g., about 150 W to about 800 W, in one example about 200 W to about 300 W). The exposure time of plasma process 120 can be any appropriate time. In certain embodiments, the exposure time can be less than about 5 seconds, 10 seconds, 15 seconds, or 20 seconds. In certain embodiments, the exposure time is about 15 seconds. In certain embodiments, plasma process 120 is performed at a temperature of about -40°C to about 20°C, in one example at a temperature of about 0°C. Preferably, the temperature is in the range of -50°C to 25°C. It should be understood that the specific values and ranges provided herein are for illustrative purposes only.

[0037] One exemplary recipe for the oxygen-free etching process 120 is pressure 350 mTorr; source power (inductive coupled plasma) 300 W; bias power 0 W; wafer processing temperature 0°C; NF 3 、H 2 、and N 2include 30 sccm, 55 sccm, and 250 sccm, respectively, as the flow rates. Another exemplary recipe is: pressure 300 mTorr; source power (inductive coupled plasma) 300 W; bias power 0 W; wafer processing temperature 0 °C; NF 3 H 2 and N 2 may include 20 sccm, 36 sccm, and 250 sccm, respectively, as the flow rates. Another exemplary recipe is: pressure 50 mTorr; source power 150 W; wafer processing temperature -40 °C; and NF 3 H 2 and N 2 may include 30 sccm, 15 sccm, and 450 sccm, respectively, as the flow rates.

[0038] FIG. 1D further shows certain measurements of the resulting substrate 102, such as the exposed end spacing 142 and the etch width 144. Desorption of etch by-products from the Si layer 108 forms the depressions 136 and the additional surface 138 of the Ge-containing layer 110. For example, the exposed end spacing 142 indicates the remaining width of the Si layer 108 (in this cross-section) by measuring each Si layer 108 from the first exposed surface 116 on the first side of the film stack 104 to the opposite second exposed surface 116 on the second side of the film stack 104. The exposed end spacing 142 may be less than 20 nm in certain embodiments, and may be 2 nm to 20 nm in one embodiment. The exposed end spacing may also refer to the exposed end spacing before etching. The etch width 144 may measure how much of a particular Si layer 108 has been removed from a particular end of the particular Si layer 108. In other words, the etch width 144 may measure the amount of the depression 136 in the Si layer 108. In certain embodiments, the etch width 144 is from about 5 nm to about 15 nm. However, the exposed end spacing 142 and the etch width 144 may be outside of these ranges depending on the given application.

[0039] As shown in FIG. 1E, the Si layer 108 is further etched by longer exposure to the plasma 122 that increases the etch width 144. Further, atomic nitrogen (N) generated in the plasma 122 can react with Ge to form a passivation layer 124 (e.g., a nitride layer) on the additional surface 138 of the Ge-containing layer 110 and on the surface of the base layer 106.

[0040] In certain embodiments, the plasma process 120 can use plasma pulsing to increase etch selectivity and minimize plasma damage to the Ge-containing layer 110. Alternatively, different plasmas or cycles of plasma treatment can be used. For example, a first plasma exposure can include a nitrogen agent but not a fluorine agent, and a second plasma exposure can include both a fluorine agent and a nitrogen agent. The first and second plasma exposures (over the first and second periods) can be continuously repeated to further etch the Si layer 108 (over the third and fourth periods). In one example, the first plasma exposure can include N2 and H2 over 5 seconds to 30 seconds (preferably 8 to 25 seconds, more preferably 10 to 15 seconds), and the second plasma exposure can include NF3, N2, and H2 over 5 seconds to 30 seconds (preferably 8 seconds to 25 seconds). The use of a first plasma exposure that does not contain a fluorine agent (or another halogen) further helps to form a passivation layer 124 (e.g., a nitride layer) on the additional surface 138 of the Ge-containing layer 110 and on the surface of the base layer 106. Thus, the substrate (stack) can be exposed to the first plasma for a predetermined time (e.g., as controlled by a controller), and then to the second plasma. The first plasma does not need to be extinguished when transitioning to the second plasma. For example, the first plasma can be formed including nitrogen and hydrogen-containing gases and no fluorine. After a predetermined time has elapsed, the nitrogen and hydrogen-containing gases are continuously introduced, and a fluorine-containing gas is also introduced to continuously form a second plasma after the first plasma.

[0041] As shown in FIG. 1D, after Si is recessed, the upper and lower surfaces (facing the recess) of the Ge-containing layer are newly exposed, and when etching with a fluorine (or halogen)-containing gas plasma proceeds, the etching can be etched into the Ge-containing layer on the newly exposed surface. In one example, after etching with the introduced fluorine or halogen proceeds, for example, after the first first plasma over a first period, for a period of 5 seconds to 30 seconds, preferably 8 seconds to 25 seconds (for example) in a second period, while the flow of the fluorine (or halogen)-containing gas is interrupted, the supply of the hydrogen and nitrogen-containing gas continues over a third period, for example, 8 seconds to 20 seconds, preferably, for example, 10 seconds to 15 seconds, and then the introduction of the fluorine or halogen-containing gas resumes over a fourth period (for example, 5 seconds to 30 seconds, preferably 8 seconds to 25 seconds). As an alternative, after etching with fluorine or halogen, the plasma power can be interrupted for a predetermined time, or both the power and the introduction of the fluorine (or halogen)-containing gas can be interrupted for a predetermined time (in the third period, for example, 8 seconds to 20 seconds or 10 seconds to 15 seconds), while the introduction of hydrogen and nitrogen continues, and then etching with the fluorine or halogen-containing gas and plasma power application resume (in the fourth period). This cycle can be similarly repeated over a further period. The interruption of the plasma power and / or the interruption of the introduction of the halogen or fluorine can also be performed based on a predetermined etching amount (for example, after each etching of 2 nm to 5 nm) or the etching time (for example, 8 seconds to 25 seconds, for example, 8 seconds to 15 seconds). As a result, an additional protective or passivation layer can be formed on the newly exposed surface.

[0042] As described above, in some embodiments, the plasma process 120 may use a remote plasma that provides a high concentration of radicals that impinge on the substrate 102. This reduces plasma damage to the film stack 104, including maintaining the profiles of the protective layer 121 and the Ge-containing layer 110 during etching. For example, the plasma may be formed in one chamber or chamber portion, and a plasma may be formed from which ions are removed and the substrate is exposed.

[0043] According to one embodiment, the series of steps of exposing the film stack 104 to a processing gas, heat treating the film stack 104, exposing the film stack to a plasma containing nitrogen but not fluorine, and exposing the film stack to a plasma containing a fluorine agent and a nitrogen agent may be repeated at least once to further selectively etch the Si layer 108.

[0044] Subsequent processing may then be performed on the substrate 102. For example, the plasma process 120 may be integrated into a process for forming the Ge-containing layer 110 into corresponding nanowires for the channel regions of semiconductor devices such as GAA devices. In such devices, subsequent processing may include filling the recess 136 with an insulator or spacer, removing the remaining portion of the Si layer 108, providing a gate oxide around the Ge-containing layer 110, and other related steps (all of which are presented for illustrative purposes only). In such devices, the exposed end 118 of the Ge-containing layer 110 may function as a conductive contact to the channel region formed in the region of the film stack 104.

[0045] FIG. 2 shows an exemplary device 400 including a substrate having a recessed alternating film stack according to a particular embodiment of the present disclosure. At least a portion of the device 400 may be formed using any of the processes and methods described herein.

[0046] Device 400 includes a substrate 402 that includes a channel material 404 (e.g., Ge or SiGe) and a gate material 406 (e.g., SiGe or Si). The channel material 404 may correspond to the Ge-containing layer 110 of the substrate 102 at some point after process 100. Device 400 may be a GAA device as shown herein, or any other device such as a fin field-effect transistor (FinFET). Device 400 may also include isolation regions 408. In certain embodiments, the isolation region 408 is a shallow trench isolation (STI).

[0047] Device 400 can be manufactured by first forming a recessed alternating film stack 410 (which may correspond to the film stack 104 after process 100 with optional subsequent processes), and then depositing additional gate material 406 on the recessed alternating film stack 410. Specifically, device 400 can be formed by alternately heteroepitaxially growing Si layers and Ge layers or SiGe layers, and these layers are then patterned and recessed in the vertical direction so as to expose the Ge layer or SiGe layer laterally.

[0048] The application of the embodiments described herein can advantageously be a solution optimized for the 5nm node, 3nm node, or below. For example, the GAA device architecture may be suitable for scaling beyond the 7nm node. The GAA device architecture can address the short-channel effect seen in some FinFET architectures by wrapping the gate around the entire channel rather than just three sides. This can reduce or eliminate current leakage that occurs under the gate of the FinFET, thereby reducing the non-active power loss.

[0049] According to one embodiment, a method for processing a semiconductor substrate, including selective Si etching, can be performed in a vacuum processing tool including a processing tool, a plasma tool, and a heat treatment tool. The vacuum processing tool can be configured to process the substrate without exposing the substrate to air. For example, gas processing, heat treatment, and plasma treatment can be performed in different chambers of a multi-chamber system. According to one embodiment, substrate processing includes processing the substrate with a processing gas including a fluorinating agent and an oxidizing agent (e.g., H 2 O) in the processing tool, transferring the substrate to the heat treatment tool under reduced pressure, heat-treating the substrate in the heat treatment tool, transferring the substrate from the heat treatment tool to the plasma processing tool under reduced pressure, and then exposing the substrate to a plasma including a fluorinating agent and a nitrogenating agent in the plasma processing tool. In one example, the processing tool can also be used as the heat treatment tool.

[0050] According to some embodiments, a method for processing a semiconductor substrate can further include one or more post-etch treatments that can be performed after the plasma step 120 of process 100 to completely remove fluorine from the film stack 104. The first post-etch treatment can include the above heat treatment using a substrate temperature of, for example, about 150°C to about 200°C after the processing step. The first post-etch treatment is effective in removing fluorine or residues remaining on the film stack 104. The second post-etch treatment can include treatment with a processing gas containing a fluorinating agent and an oxidizing agent as described above with reference to FIG. 1B. The second post-etch treatment is effective in removing oxidized fluorine residues on the Si layer 108. Thereafter, the third post-etch treatment can include the above heat treatment using a substrate temperature of, for example, about 150°C to about 200°C. The third post-etch treatment is effective in removing fluorine or residues remaining on the film stack 104.

[0051] FIG. 3 shows a block diagram of an exemplary plasma tool 500 according to a particular embodiment of the present disclosure. Although a particular plasma tool 500 is illustrated and described, any suitable type of plasma tool can be used. Plasma tool 500 can be used to perform the plasma process 120 described with respect to FIGS. 1A-1E.

[0052] Plasma tool 500 includes a plasma chamber 123 that uses a plasma (e.g., plasma 122) to process a semiconductor substrate (e.g., substrate 102). Plasma chamber 123 includes a substrate table 502 configured to support substrate 102 during processing. In a particular embodiment, substrate 102 is placed on substrate table 502 in the state shown in FIG. 1B, e.g., after a processing step, for performing plasma process 120 using plasma 122. The material of the Si layer 108 of the film stack 104 of substrate 102 (e.g., as described above with reference to FIGS. 1A-1E) is selectively etched in plasma chamber 123 by injecting a plasma (e.g., plasma 122) through showerhead 504 of plasma tool 500. Showerhead 504 can include a single mixed reaction cavity filled with an etching gas, a mixed gas, and a carrier gas that are mixed to form plasma 122, and a series of outlet holes for supplying plasma 122 toward substrate 102. The plasma can be formed in a chamber upstream of showerhead 504, which can be considered a separate chamber or chamber portion from the chamber or chamber portion in which the substrate is disposed, or a separate chamber or chamber portion can be separated by a grid or mesh arrangement, where the plasma is generated and excited in a first chamber or chamber portion into which the process gas is supplied, and as the plasma moves to the chamber or chamber portion in which the substrate is disposed, ions are extracted, such that after the ions are removed, the substrate is processed with the plasma and the radicals of the plasma react with the substrate.

[0053] The plasma chamber 123 includes a vacuum pump 506 connected to a vacuum line 508 to purge residual precursor gas from the plasma chamber 123 and / or is otherwise connected to the vacuum pump 506, and in certain embodiments may include a pressure system for maintaining a target pressure and / or may be otherwise connected to the pressure system. The plasma chamber 123 may further include mechanical tools or components such as a heater 510 and a temperature sensor 512 used to heat the substrate 102 and control the temperature within the plasma chamber 123 and / or of the substrate 102.

[0054] The plasma tool 500 includes, for example, a precursor gas line 514, a mixed gas line 516, and a carrier gas line 518 connected to a showerhead 504. In certain embodiments, the etching gas supplied through the precursor gas line 514 can include a fluorine-based precursor such as fluorine or NF 3 and the mixed gas supplied through the mixed gas line 516 can include hydrogen, and the carrier gas supplied through the carrier gas line 518 can include an inert gas such as nitrogen or argon or krypton.

[0055] In certain embodiments, the plasma tool 500 may include a system of mass flow controllers and sensors to control the gas flow rate (e.g., mass flow rate). Accordingly, the plasma tool 500 may include a first flow controller 520, a second flow controller 522, a third flow controller 524, a vacuum pump 506, a heater 510, a temperature sensor 512, a voltage-current (V-I) sensor 526, and substrate sensors 528, 530, 532, and 534 (528 - 534). The precursor gas line 514, the mixed gas line 516, and the carrier gas line 518 are each connected to and controlled by the first flow controller 520, the second flow controller 522, and the third flow controller 524, respectively.

[0056] The plasma tool 500 may include a controller 536 that controls aspects of the plasma process 120. The controller 536 may be implemented in any suitable manner. For example, the controller 536 may be a computer or a processor. As another example, the controller 536 may include one or more programmable ICs programmed to provide the functions described herein. In a specific example, one or more processors (e.g., microprocessors, microcontrollers, central processing units, etc.), programmable logic devices (e.g., complex programmable logic devices), field programmable gate arrays, etc.), and / or other programmable ICs may be programmed with software or other programming instructions to implement the functions described herein for the controller 536. The software or other programming instructions may be stored on one or more non-transitory computer-readable media (e.g., memory storage devices, flash memory, dynamic random access memory, reprogrammable storage devices, hard drives, floppy disks, DVDs, CD-ROMs, etc.), and when executed by the programmable ICs, the software or other programming instructions cause the programmable ICs to perform the operations described herein.

[0057] Mechanical components such as the heater 510 and temperature sensor 512 of the plasma chamber 123, and the flow controllers 520, 522, 524, the vacuum pump 506, and other components external to the plasma chamber 123 are coupled to and controlled by the controller 536.

[0058] The machine sensors measure equipment parameters such as the temperature of the substrate table 502, heater current, speed and temperature of the vacuum pump, and provide signals to ensure that the equipment is operating properly. Various process sensors measure process parameters such as process temperature, process pressure, plasma density, gas flow rate, and gas composition, and provide signals to ensure that the process is operating properly. The data from the equipment and process sensors continuously provide feedback to the controller 536 through the plasma process 120. The controller 536 can adjust in real time to keep the equipment and process near the center of the specifications.

[0059] The controller 536 receives data from the sensors and controls the process parameters of the plasma chamber 123 based on the sensor data. The controller 536 can analyze the data collected by the sensors, determine the timing to modify or end one or more steps of the plasma process 120, and provide feedback for controlling the process parameters of the components of the plasma chamber 123.

[0060] The controller 536 is connected to the V-I sensor 526 and the substrate sensors 528-534, and can monitor the plasma 122 when the substrate 102 is exposed to the plasma 122, and provide the state of the plasma 122, and optionally the composition and thickness data in real time. This feedback data is used by the controller 536 to continuously or periodically adjust the plasma process 120 when the substrate 102 is selectively etched using the plasma 122, for example, to turn off the plasma process 120 when a target depression (e.g., etch width 144) is reached (or when the surface is newly exposed as a result of the depression as described above). The control can be based on, for example, the detected conditions (or the accumulation of the detected conditions), and the time-based conditions. For example, as described above, after the substrate is modified by non-plasma treatment and subjected to heat treatment in the first plasma treatment step, the substrate is exposed to a plasma containing nitrogen and hydrogen but not fluorine for a predetermined time, for example, 5 seconds to 20 seconds, preferably at least 8 seconds, preferably for a preferred time, for example, 10 seconds to 15 seconds. After the predetermined time has elapsed, then fluorine is introduced into the plasma, whereby the substrate is exposed to a plasma containing nitrogen, hydrogen and fluorine.

[0061] Measurement data from the substrate sensors 528-534 and the temperature sensor 512 can be received by the controller 536, while the controller 536 generates control signals transmitted to the first flow controller 520, the second flow controller 522, the third flow controller 524, the vacuum pump 506, and the heater 510. It should be understood that the gas flow rate and the number of flow controllers, and thus the number of sensors or other components, can vary.

[0062] The controller 536 receives measurement data or metrology data from the substrate sensors 528 - 534 acquired at multiple points across the substrate 102, and can measure in-situ and in real-time the process uniformity, as well as the thickness and composition of the passivation layer 124 (formed from the exposure of the substrate 102 to the plasma 122), the exposed end spacing 142, and / or the target depression (e.g., the etch width 144). For example, multiple sensors across the substrate in a multi-substrate plasma tool can be used to monitor and adjust the thickness and composition of the etch protection layer 121 and the passivation layer 124 (formed from the exposure of the substrate 102 to the plasma 122), the exposed end spacing 142, and / or the target depression (e.g., the etch width 144) from the top to the bottom of the substrate 102. Multiple sensors across the substrate in a single-substrate plasma tool can be used to monitor and adjust the thickness and composition of the etch protection layer 121 and the passivation layer 124, the exposed end spacing 142, and / or the target depression (e.g., the etch width 144) from the center to the edge of the substrate 102.

[0063] The substrate sensors 528-534 can be coupled to the plasma chamber 123 and / or disposed within the plasma chamber 123 to monitor various parameters of the substrate 102, the plasma tool 500, and / or the plasma process 120. The substrate sensors 528-534 can include various types of sensors including, but not limited to, optical sensors (cameras, lasers, light, reflectometers, spectrometers, ellipsometers, etc.), capacitive sensors, ultrasonic sensors, gas sensors, or other sensors that can monitor the state of the substrate 102, the plasma 122, and / or the plasma tool 500. In certain embodiments, one or more optical sensors can be used to measure the thickness and refractive index of materials in real time (in the plasma process 120) at the surface 118 of the Ge-containing layer and the surface of the base layer 106 (e.g., where the passivation layer 124 is formed), the exposed end spacing 142, and / or the etch width 144a (or other suitable measurements). As another example, a spectrometer can be used to measure the film thickness of materials in real time (in the plasma process 120) at the surface 118 of the Ge-containing layer and the surface of the base layer 106 (e.g., where the passivation layer 124 is formed), the exposed end spacing 142, and / or the etch width 144a (or other suitable measurements). In yet another embodiment, a residual gas analyzer (RGA) can be used to detect the decomposition of precursors in real time (in the plasma process 120) for real-time chemical reaction completion detection.

[0064] The controller 536 can receive user input process parameters including, for example, etch rate, conformality, profile, and deposition rate (e.g., of the passivation layer 124) based on standard plasma etching parameters such as chamber pressure, chamber temperature, RF source power, RF bias power, RF waveform (e.g., continuous wave RF, pulsed RF, square wave pulse, sawtooth wave pulse, etc.), etch time, and the composition and flow rate of various process gases and carrier gases. Advantageously, the user can adjust the plasma 122 to meet the target local critical dimension uniformity (LCDU).

[0065] Based on the data from substrate sensors 528 - 534 and the process parameters input by the user, controller 536 generates control signals for temperature sensor 512 and heater 510 to regulate the heat within plasma chamber 123. When heater 510 heats plasma chamber 123, controller 536 constantly or periodically monitors temperature sensor 512 to track the temperature of plasma chamber 123 and transmits a control signal to heater 510 to maintain the temperature of plasma chamber 123.

[0066] In one example, when controller 536 determines that the target temperature of plasma chamber 123 has been reached based on the data provided by temperature sensor 512, controller 536 generates control signals and data signals to activate first flow controller 520, second flow controller 522, and third flow controller 524, and based on the process parameters input by the user, provides the target flow rate of the precursor gas to first flow controller 520, the target flow rate of the mixed gas to second flow controller 522, and the target flow rate of the carrier gas to third flow controller 524. When controller 536 determines that the corresponding flow rates have been established, controller 536 supplies power to plasma chamber 123 to supply power to plasma 122 via the bias electrode and the source electrode. Based on the measurements from V - I sensor 526, the power supplied to the bias electrode and the source electrode can be adjusted. First flow controller 520, second flow controller 522, and third flow controller 524 may each be a closed - loop control system connected to a flow sensor and an adjustable proportional valve, whereby each flow controller can constantly or periodically monitor and internally maintain the target flow rate of each gas via the flow sensor and the adjustable proportional valve.

[0067] In certain embodiments, when the controller 536 determines that the etching process time has been met based on data input by the user, the controller 536 generates control signals to stop the first flow controller 520, the second flow controller 522, and the third flow controller 524, which may be stopped at the same time or at different times as appropriate.

[0068] The controller 536 may use or analyze substrate sensor data to determine when to end the plasma process 120. For example, the controller 536 may receive data from a residual gas analyzer to detect the endpoint of the plasma process 120. In another example, the controller 536 uses spectroscopic ellipsometry to detect the average film thickness of the passivation layer 124, the exposed end 141 of the Ge-containing layer 110, and / or the interval 142 between the exposed ends in the plasma process 120, which may indicate changes in the plasma process 120. In another example, the controller 536 uses spectroscopic ellipsometry to detect the refractive index of the material on the surface 118 of the Ge-containing layer and the surface of the base layer 106 (e.g., where the passivation layer 124 is formed) in the plasma process 120, which may indicate changes in the film composition in the plasma process 120. The controller 536 may automatically end the plasma process 120 when the target for the interval 142 between the exposed ends and / or the etching width 144a (or another suitable measurement) is achieved. In certain embodiments, the controller 536 may automatically adjust one or more parameters, such as the ratio of NF3 to H2 and / or the ratio of NF3 to N2, during the plasma process 120 to achieve the desired etching profile of the film stack 104. The data from the controller 536 and the substrate sensors 528 - 534 may also be used to achieve the throughput target of the desired semiconductor substrate. Further, the data from the controller 536 and the substrate sensors 528 - 534 may be used to achieve the desired etching profile of the film stack 104 and the composition, along with the desired semiconductor substrate throughput, or alternatively to target a combination.

[0069] As described above, the controller described herein may include, for example, a computer or a processor, and may include a memory that stores non-transitory computer-readable data and / or instructions. It should be understood that the controller may include a single or multiple distributed controllers or sub-controllers, together with, for example, a master or higher-level controller that gives instructions to sub-controllers that control individual chambers or components of a chamber.

[0070] A system 300 for heat treatment of a substrate is shown in FIG. 4. In one embodiment, the system 300 may also be used in a processing step. Alternatively, an initial non-plasma treatment of the barrier layer 114 (e.g., an oxide layer such as NO 2 etc.) can be performed in one chamber, and the heat treatment can be performed in a separate chamber. The system 300 includes, for example, a process chamber 310 for processing the workpiece 325 in a non-plasma vacuum environment, a workpiece holder 320 disposed within the process chamber 310 and configured to support the workpiece 325, a temperature control system 350 coupled to the workpiece holder 320 and configured to control the temperature of the workpiece holder 320 to a setpoint temperature, a gas distribution system 330 coupled to the process chamber 310 and arranged to supply one or more process gases into the process chamber 310, and a controller 360 operably coupled to the temperature control system 350 and configured to control the temperature of the workpiece holder 320 in the range of -40°C to 250°C. For example, the temperature control system 350 may be configured to control the temperature of the workpiece holder 320. The process chamber 310 may include a vacuum pump 340 for exhausting process gas from the process chamber 310. The process chamber 310 may further include a remote plasma generator or a remote radical generator configured to supply excited species, radical species, or metastable species, or combinations thereof, to the process chamber.

[0071] The gas distribution system 330 may include a showerhead gas injection system having a gas distribution assembly, and one or more gas distribution plates or conduits connected to the gas distribution assembly and configured to form one or more gas distribution plenums or supply lines. Although not shown, the one or more gas distribution plenums may include one or more gas distribution baffle plates. Preferably, the gas supply may also supply aerosolized H 2 O and / or water vapor for an initial non-plasma process (before heat treatment). The one or more gas distribution plates further include one or more gas distribution orifices for distributing process gas from the one or more gas distribution plenums to the process chamber 310. In addition, one or more gas supply lines may be connected to the one or more gas distribution plenums, for example, via a gas distribution assembly, to supply a process gas containing one or more gases. The process gases may be introduced together as a single flow or independently as separate flows.

[0072] The gas distribution system 330 may further include a branched gas distribution network designed to reduce or minimize the gas distribution volume. The branched network can effectively distribute the process gas across the diameter of the workpiece 325 while removing the plenum or minimizing the volume of the gas plenum and shortening the gas distribution length from the gas valve to the process chamber. By doing so, the gas can be switched more quickly, and the composition of the chemical environment can be changed more effectively.

[0073] The volume of the process chamber 310 that defines the chemical environment to which the workpiece 325 is exposed can be reduced or minimized to shorten or minimize the residence time, i.e., the time required to evacuate one chemical environment and replace and exchange it with another. The time to replace the chemical environment within the process chamber 310 can be estimated as the ratio of the process chamber volume to the pumping speed delivered to the process chamber volume by the vacuum pump 340.

[0074] The workpiece holder 320 can provide several operating functions for thermally controlling and processing the workpiece 325. The workpiece holder 320 includes one or more temperature control elements configured to adjust and / or raise the temperature of the workpiece holder 320.

[0075] As shown in FIG. 5, the workpiece holder 320 includes at least one fluid channel 322 to allow the flow of a heat transfer fluid therethrough and to be able to change the temperature of the workpiece holder 320. The workpiece holder 320 may further include at least one resistive heating element 324. The heating and cooling spatial uniformity of the workpiece 325 can be adjusted and controlled using multi-zone channels and / or heating elements. For example, the at least one resistive heating element 324 may include a central zone heating element and an edge zone heating element. Additionally, for example, the at least one fluid channel 322 may include a central zone fluid channel and an edge zone fluid channel. At temperatures exceeding 200 - 250 °C, other heating systems including infrared (IR) heating such as lamp heating can be used.

[0076] The power supply 358 is connected to the at least one resistive heating element 324 to supply current. The power supply 358 may include a direct current (DC) power supply or an alternating current (AC) power supply. Further, the at least one resistive heating element 324 can be connected in series or in parallel.

[0077] At least one resistive heating element 324 may include a resistive heating element made from, for example, carbon, tungsten, nickel-chromium alloy, aluminum-iron alloy, aluminum nitride, etc. Examples of commercially available materials for manufacturing resistive heating elements include Kanthal, Nikrothal, and Akrothal, which are registered trademarks of metal alloys produced by Kanthal Corporation (Bethel, Conn.). The Kanthal family includes ferritic alloys (FeCrAl), and the Nikrothal family includes austenitic alloys (NiCr, NiCrFe). According to one example, each of the at least one resistive heating element 324 may include a heating element commercially available from Watlow Electric Manufacturing Company (12001 Lackland Road, St. Louis, MO. 63146). Alternatively or in addition, a cooling element can be used in any of the embodiments.

[0078] The heat transfer fluid distribution manifold 352 is configured to pump and monitor the flow of heat transfer fluid through one or more fluid channels 322. The heat transfer fluid distribution manifold 352 can draw heat transfer fluid from a first heat transfer fluid supply bath 354 at a first heat transfer fluid temperature and / or from a second heat transfer fluid supply bath 356 at a second heat transfer fluid temperature. The manifold 352 can mix the heat transfer fluid from the first and second heat transfer fluid supply baths 354, 356 to achieve an intermediate temperature. Further, the heat transfer fluid distribution manifold 352 can include a pump, a valve assembly, a heater, a cooler, and a fluid temperature sensor to controllably supply, distribute, and mix the heat transfer fluid at a predetermined temperature.

[0079] In an alternative embodiment, the temperature control system 350 may include a high-temperature wall proximate to the workpiece holder 320. The workpiece holder 320 may further include a workpiece clamping system configured to clamp the workpiece to the workpiece holder and a backside gas supply system configured to supply a heat transfer gas to the backside of the workpiece.

[0080] The heat transfer fluid may include a high-temperature fluid having a boiling point exceeding 200°C. For example, the heat transfer fluid may include Fluorinert (trademark) FC40 (having a temperature range of -57 to 165°C) or Fluorinert (trademark) FC70 (having a temperature range of -25 to 215°C), which are commercially available from 3M.

[0081] The workpiece holder 320 can be monitored using a temperature sensing device such as a thermocouple (e.g., a K-type thermocouple, a Pt sensor, etc.) or an optical device. Further, the substrate holder temperature control system 350 may utilize the temperature measurement value as feedback to the workpiece holder 320 to control the temperature of the workpiece holder 320. For example, at least one of the fluid flow rate, fluid temperature, type of heat transfer fluid, heat transfer fluid pressure, clamping force, current or voltage of the resistive heating element, current or polarity of the thermoelectric device, etc. may be adjusted to affect the change in the temperature of the workpiece holder 320 and / or the temperature of the workpiece 325.

[0082] As described above, the controller 360 is operably connected to the temperature control system 350 and is configured to control the temperatures of various components in the system 300 including the workpiece holder 320, for example, at a temperature of -40°C to 250°C. The temperature control system 350 obtains temperature information from one or more temperature sensors configured to measure the temperature of the workpiece holder 320, the workpiece 325, the chamber wall temperature of the process chamber 310, or, in particular, the temperature of the gas distribution system 330, and can adjustably control these temperatures using the temperature information.

[0083] Other chamber components of the process chamber 310, including the chamber wall, the gas distribution system 330, etc., may include a heating element and / or a cooling element for controlling their temperature. For example, the chamber wall temperature of the process chamber 310 and the temperature of at least a part of the gas distribution system can be controlled within a temperature of up to 150°C, or within a range of 50°C to 150°C (preferably within a range of 70°C to 110°C).

[0084] While a particular use for forming nanowires / nanosheets for GAA devices has been described, the present disclosure may be used for any type of isotropic etching of Si that is more selective than the Ge-containing layer. Further, the etching performed is described as being primarily for forming a depression in the film stack 104 by removing portions at both ends of both the Si layers 108, but the process 100 may be used to remove substantially all portions of the Si layer 108, which may be referred to as liberating the Ge-containing layer 110 or channel liberation.

[0085] Now, referring to FIG. 6, an overview of an example of the process disclosed herein is provided. The flowchart of FIG. 6 may provide an algorithm for control by one or more controllers of, for example, the process chamber or system disclosed herein.

[0086] As shown in S10, a substrate having a Ge-containing layer, a Si-containing layer, and further layers on the side surfaces of the stack, such as an oxide layer as shown in 114 of FIG. 1A, is first provided.

[0087] As shown in S12, the processing is then performed in a non-plasma environment in the examples disclosed herein. In a preferred example, the non-plasma environment includes aerosolized water or water vapor provided in the example to provide H and O, and, for example, a hydrogen-containing gas, an oxygen-containing gas, and a fluorine-containing gas together with HF or F to provide, for example, fluorine. The initial processing in the non-plasma environment processes the layer 114 to form a modified layer, which is formed, for example, on the Ge-containing layer and has a modified portion 118 containing H, Si, Ge, and F, and is formed on the Si-containing layer and has a modified portion 116 containing, for example, H, Si, and F, but not containing Ge or, at a minimum, less Ge than the portion 118.

[0088] Next, the heat treatment is performed as shown in S14, which removes the remaining portion of the modified layer portion 116, and the heat treatment will also remove the residual water vapor along with some reduction of fluorine. As a result, after the heat treatment, the terminal layer 117 or the modified side surface 117 remains as shown in FIG. 1B, while the portion already disposed in 116 is removed.

[0089] As shown in S16, S18, then, preferably, a plasma process including a first portion S16 or a first plasma step S16, followed by a second portion S18 or a second plasma step S18 is performed on the substrate. In the first portion, a plasma containing nitrogen and hydrogen but not containing fluorine or another halogen is formed, whereby the terminal layer or the modified surface 117 is converted into a protective layer containing germanium nitride. Then, fluorine is added to the plasma for etching in S18, while nitrogen is continuously supplied to prevent consumption of the protective layer 121 and / or to form further protection on the Ge-containing layer. Preferably, hydrogen is introduced into the plasma for both portions S16, S18 of the plasma treatment. Also preferably, oxygen is not introduced in S16, S18.

[0090] The process can be repeated according to the amount of etching required, and additional modified surfaces can be provided as shown in 124, 138 described above, whereby additional exposed surfaces of the Ge-containing layer are protected when exposed, for example, upon removal of the Si-containing layer for forming a depression.

[0091] FIGS. 7A and 7B show further processing that can be performed, for example, after a depression is formed as shown in FIG. 1E described above.

[0092] The arrangement of FIGS. 7A and 7B includes, for example, a Ge-containing layer 104 together with Si-containing layers 102 between the layers 104, and the Si-containing layers are recessed as described above. Region 108 can be a mask, for example, a hard mask, and region 107 can initially include a dummy gate to be removed later and a gate metal to be deposited. After the aforementioned recess formation process, a spacer layer 110 is deposited to obtain an inner spacer layer 110. Layer 110 can be formed from a spacer material such as SiN or a low-k dielectric. Then, the inner spacer layer 110 is partially removed, whereby spacers 103 are left in the pre-formed depressions or recesses as described above. Then, layer 102 can be removed (channel release), whereby a channel 104 formed from the Ge-containing layer is left, and then the regions already occupied by the dummy gate 107 and the Si-containing layer 102 can be filled with a gate metal. Further, when removing or etching the inner spacer layer 110 to leave the spacers 103, the spacers 103 should be recessed with respect to the outer surface of the Ge-containing layer or the channel 104, so that the outer surface of the spacers 103s has an outer dimension smaller than the outer surface or the outer dimension 104s of the layer 104. The present invention has been described above with respect to the etching of the Si-containing layer (108 in FIGS. 1A - 1B, 102 in FIGS. 7A and 7B), but the present invention can also be used, for example, for channel release when removing layer 102 (in FIGS. 7A and 7B) while protecting the Ge-containing layer 104. As another alternative, the present invention can be applied to selectively etch the spacer material 103 with respect to the layer 104 (while protecting the layer 104), whereby the remaining portion of the inner spacer layer 110 is etched and the recessed outer surface 103s of the spacer is recessed with respect to the Ge outer surface 104s of the containing layer (or SiGe).

[0093] It should be understood that other application examples including the features of the examples disclosed herein may be used.

[0094] Although the present disclosure has been described as performing certain process / method steps in a particular order, the present disclosure contemplates that the process steps may be performed in any suitable order. While the present disclosure has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to this specification. Accordingly, the appended claims are intended to embrace any such modifications or embodiments.

Claims

1. 1. A method for processing a semiconductor substrate, the method comprising: receiving a semiconductor substrate including a film stack, the film stack including a first germanium-containing layer, a second germanium-containing layer, and a first silicon layer disposed between the first germanium-containing layer and the second germanium-containing layer; removing an oxide layer from the film stack and forming a termination layer on the first germanium-containing layer and the second germanium-containing layer; treating the film stack with a process gas comprising fluorine and oxygen; and heat treating the film stack and exposing the film stack to a plasma comprising fluorine and nitrogen, the plasma selectively etching the first silicon layer and converting the termination layer into an etch protection layer that inhibits etching of the first germanium-containing layer and the second germanium-containing layer during exposure of the film stack to the plasma; A method comprising:

2. The step of exposing the film stack to the plasma includes: exposing the film stack to a first plasma containing nitrogen and not containing fluorine; exposing the film stack to a second plasma comprising the fluorine and the nitrogen; 2. The method of claim 1, comprising:

3. 3. The method of claim 2, further comprising the steps of exposing the film stack to the first plasma and exposing the film stack to the second plasma at least once consecutively.

4. The steps of exposing the film stack to the first plasma and exposing the film stack to the second plasma include: forming the first plasma comprising nitrogen and hydrogen and exposing the film stack to the first plasma for a predetermined amount of time; after the predetermined amount of time, continuing to introduce the nitrogen and hydrogen and further introducing fluorine to form the second plasma; and The method of claim 2 , wherein the second plasma is continuous with the first plasma.

5. The method of claim 4 , wherein the predetermined amount of time is greater than or equal to five seconds.

6. 5. The method of claim 4, wherein the predetermined amount of time ranges from 5 seconds to 25 seconds, and wherein the fluorine-containing gas is introduced after the predetermined amount of time.

7. 10. The method of claim 1, wherein the treating step is performed in the absence of a plasma, the treatment gas comprises aerosolized water or water vapor, and the plasma further comprises hydrogen.

8. the first plasma is generated from a gas containing nitrogen and hydrogen and not containing fluorine; The method of claim 2 , wherein the second plasma is formed from a gas containing nitrogen, hydrogen, and fluorine.

9. The plasma is Nitrogen trifluoride (NF ３ ) and ammonia (NH ３ ), NF ３ , N.H. ３ , and nitrogen (N ２ ), NF ３ , N.H. ３ , and argon (Ar), NF ３ and hydrogen (H ２ ), NF ３ , H ２ , and N ２ ,or NF ３ , H ２ , N.H. ３ , and N ２ 10. The method of claim 1 resulting from a combination of gases comprising:

10. 10. The method of claim 1, wherein the etch protection layer formed on exposed surfaces of the first germanium-containing layer and the second germanium-containing layer comprises germanium nitride.

11. the first germanium-containing layer and the second germanium-containing layer are both germanium layers or silicon-germanium layers; the plasma selectively etching the first silicon layer selectively etches an edge of the first silicon layer to form a recess between the first germanium-containing layer and the second germanium-containing layer of the film stack; the first silicon layer is selectively etched to expose additional surfaces of the first germanium-containing layer and the second germanium-containing layer; The method of claim 1 , wherein the plasma forms a passivation layer on the additional surface.

12. 1. A method of processing a substrate, comprising: providing a substrate having a Ge-containing layer and a Si-containing layer, one of the Ge-containing layer or the Si-containing layer being on the other of the Ge-containing layer or the Si-containing layer, the Si-containing layer being free of Ge or containing a lower amount of Ge than the Ge-containing layer, and the Ge-containing layer and the Si-containing layer each having an oxide on a side surface; performing a non-plasma treatment to remove the oxide from a side surface of the Si-containing layer, the treatment providing a modified surface on the side surface of the Ge-containing layer; performing a plasma process to etch a side surface of the Si-containing layer, wherein the modified surface of the Ge-containing layer is converted into a protective surface comprising germanium nitride, and etching of the Ge-containing layer is inhibited; A method comprising:

13. The plasma process comprises: forming a first plasma comprising a fluorine-free nitrogen-containing gas; exposing the substrate to the first plasma for at least 5 seconds; After the step of exposing to the first plasma, introducing fluorine into the first plasma and continuing to supply the nitrogen-containing gas to form a second plasma; exposing the substrate to the second plasma; 13. The method of claim 12, comprising:

14. 13. The method of claim 12, wherein after the plasma process, the Si-containing layer is recessed relative to the Ge-containing layer, and the Si-containing layer has smaller lateral dimensions than the Ge-containing layer.

15. The non-plasma treatment may include: treating a lateral surface of the Ge-containing layer with a fluorine-containing gas and a hydrogen-containing gas to form the modified surface; increasing the temperature of the substrate and performing a heat treatment; and the modified surface comprises hydrogen, silicon, germanium, and fluorine; during a first portion of the plasma process, the modified surface reacts with nitrogen in a plasma to form the protective surface comprising germanium nitride, and during the first portion of the plasma process, the plasma is halogen-free; 13. The method of claim 12, wherein during a second portion of the plasma process, fluorine is introduced into the plasma to etch the Si-containing layer while the Ge-containing layer is protected by the protective surface.

16. the hydrogen-containing gas comprises aerosolized water or water vapor; 16. The method of claim 15, wherein the heat treatment removes residual water and removes residual oxide layer portions remaining on the side surfaces of the Si-containing layer, while not removing the modified surface of the side surfaces of the Ge-containing layer.

17. 1. A method of selective etching comprising: providing a substrate having a Ge-containing layer and a Si-containing layer, the Ge-containing layer comprising a higher percentage of Ge than the Si-containing layer, one of the Ge-containing layer or the Si-containing layer vertically above the other of the Ge-containing layer or the Si-containing layer, and a side surface layer on a side surface of both the Ge-containing layer and the Si-containing layer; treating the side surface layer in a non-plasma having a process gas comprising hydrogen, oxygen, and fluorine; after the treating step, selectively sublimating portions of the side surface layer, wherein after the selectively sublimating step, the side surface layer is removed from a side surface of the Si-containing layer and a modified side surface layer is present on a side surface of the Ge-containing layer; after the selectively sublimating step, exposing the substrate to a first plasma, the first plasma comprising hydrogen and nitrogen and not comprising a halogen or oxygen; after the step of exposing to the first plasma, exposing the substrate to a second plasma comprising hydrogen, nitrogen and a halogen; A method comprising:

18. the reforming-side surface layer contains hydrogen, silicon, germanium, and fluorine; the substrate is exposed to the first plasma for a first period of time in the range of 5 seconds to 25 seconds; the substrate is exposed to the second plasma for a second period of time in the range of 8 seconds to 25 seconds; After the second period of time, at least one of the plasma powers is turned off or the introduction of the halogen is interrupted for a third period of time, during which hydrogen and nitrogen continue to be introduced; 18. The method of claim 17, wherein after the third period of time, plasma power is turned on and the halogen is introduced for a fourth period of time ranging from 8 seconds to 25 seconds.

19. the halogen comprises fluorine, and the ratio of fluorine to nitrogen introduced during the second period ranges from 1:5 to 1:10; 19. The method of claim 18, wherein during the first and second periods, no oxygen is introduced and the temperature is maintained in the range of -50°C to 25°C.

20. 20. The method of claim 17, wherein the treating step is performed in a first process chamber, the selectively sublimating step is performed in a second process chamber, and the first and second plasma exposing steps are performed in a third process chamber.

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