Plasma Etching Techniques

Abstract

In a particular embodiment, a method for processing a semiconductor substrate includes receiving a semiconductor substrate including a film stack. The film stack includes a first germanium-containing layer and a second germanium-containing layer, and a first silicon layer disposed between the first germanium-containing layer and the second germanium-containing layer. The method includes selectively etching the first silicon layer by exposing the film stack to a plasma including a fluorine agent and a nitrogen agent. The plasma etches the first silicon layer and forms a passivation layer on exposed surfaces of the first germanium-containing layer and the second germanium-containing layer to inhibit etching of the first germanium-containing layer and the second germanium-containing layer upon exposure of the film stack to the plasma.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims the benefit of U.S. patent application Ser. No. 17 / 161,199, entitled "PLASMA ETCHING TECHNIQUES," filed Jan. 28, 2021, the entire contents of which are incorporated herein by reference.

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

[0003] The integrated circuit (IC) manufacturing industry strives to increase device density to improve speed, performance, and cost. To continue 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 vertical transistors. Such a change is desirable due to the poor control of the conduction channel by the gate potential. Short channel effects (SCEs) become non-negligible as gate dimensions are scaled down, resulting in a large current conduction (I off ) can be increased. Modifications to the device architecture can allow better electrostatic control of the gate, reducing SCE and power losses. Fabrication of nanowire devices can present 3D etching challenges where highly selective isotropic etching processes are beneficial. For example, it may be necessary to etch exposed layers of material relative to each other to create recesses in the film stack. Summary of the Invention [Means for solving the problem]

[0004] In a particular embodiment, a method for processing a semiconductor substrate 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 includes selectively etching the first Si layer by exposing the film stack to a plasma including a fluorine agent and a nitrogen agent. The plasma etches the first Si layer and forms a passivation layer on exposed surfaces of the first Ge-containing layer and the second Ge-containing layer to inhibit etching of the first Ge-containing layer and the second Ge-containing layer upon exposure of the film stack to the plasma.

[0005] In a particular embodiment, a method for processing a semiconductor substrate includes placing the semiconductor substrate in a plasma chamber of a plasma tool. The semiconductor substrate includes a film stack including Si and Ge-containing layers in an alternating stacked arrangement, with at least two Si layers and at least two Ge-containing layers. The method includes generating a plasma including a fluorine agent, a nitrogen agent, and a hydrogen agent in a plasma chamber of the plasma tool. The plasma is generated without intentionally introducing an oxygen-containing gas into the plasma chamber. The method includes exposing the film stack to the plasma in the plasma chamber of the plasma tool. The plasma forms a nitride passivation layer on an exposed surface of the Ge-containing layer and selectively etches both exposed edges of the Si layer to form a recess in the Si layer relative to both exposed edges of the Ge-containing layer. The nitride passivation layer inhibits etching of the Ge-containing layer by the plasma.

[0006] A method for processing a semiconductor substrate includes placing the semiconductor substrate in a plasma chamber of a plasma tool. The semiconductor substrate includes a film stack including a first layer of a first material and a second layer of a second material in an alternating stacked arrangement. The first material is Si. The method includes generating a plasma to selectively etch the first layer of the first material. Generating the plasma includes introducing a gas including fluorine and nitrogen into the plasma chamber and maintaining a temperature of the semiconductor substrate between about -40°C and about 40°C. The method includes exposing the film stack to the plasma in the plasma chamber for a period of time. The plasma selectively etches both exposed edges of the first layer of the first material to form a recess in the first layer of the first material relative to both exposed edges of the second layer of the second material. [Brief description of the drawings]

[0007] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following description, which should be read in conjunction with the accompanying drawings.

[0008] [Figure 1A] 1A-1D illustrate cross-sectional views of an exemplary semiconductor substrate during an exemplary process for processing the semiconductor substrate in accordance with certain embodiments of the present disclosure. [Figure 1B] 1A-1D illustrate cross-sectional views of an exemplary semiconductor substrate during an exemplary process for processing the semiconductor substrate in accordance with certain embodiments of the present disclosure. [Figure 1C] 1A-1D illustrate cross-sectional views of an exemplary semiconductor substrate during an exemplary process for processing the semiconductor substrate in accordance with certain embodiments of the present disclosure. [Figure 1D] 1A-1D illustrate cross-sectional views of an exemplary semiconductor substrate during an exemplary process for processing the semiconductor substrate in accordance with certain embodiments of the present disclosure. [Diagram 2] 1 illustrates an exemplary method for processing a semiconductor substrate in accordance with certain embodiments of the present disclosure. [Diagram 3] 1 illustrates an exemplary method for processing a semiconductor substrate in accordance with certain embodiments of the present disclosure. [Figure 4]1 illustrates an exemplary device including a substrate having a recessed layer-by-layer film according to certain embodiments of the present disclosure. [Diagram 5] FIG. 1 illustrates a block diagram of an exemplary plasma tool, in accordance with certain embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] There are various techniques that attempt to selectively etch one material over another. In some cases, the chemistries of the two materials are sufficiently different that a plasma that is selective to etching one of the materials can be used without worrying about etching the other material. In other cases, the chemistries of the materials may be similar, or the available etching processes may be limited by other factors, making it more difficult to determine the appropriate etching conditions for selective etching. Certain materials present more difficult selectivity challenges when it is desirable to etch one material with little or no etching of another material. Conventional processes for this type of selective etching may not achieve selective etching of one material over another or may fail to achieve process requirements such as selectivity, etching profile (e.g., local uniformity and / or surface roughness).

[0010] Selectivity challenges can arise in 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 layers of Si and Ge or Si-Ge (SiGe) alloys in an alternating stacked arrangement. Part of this process can include etching recesses in the film stack at both ends of the Si layer while minimizing etching of the Ge-containing layer to expose end portions of the Ge-containing layer for later use as a conductive device. Conventional etching techniques may not be sufficient due to various challenges including, in part, native oxide layers (NOLs) and / or other residues (e.g., reactive ion etching (RIE) residues) present on the surface of the film stack.

[0011] For example, some conventional techniques use nitrogen trifluoride (NF 3 ) (or another etchant) and oxygen (O 2 The present invention employs a single etching step using a plasma of fluorine (fluorine) to etch the Si layer, and oxygen reacts with Ge in the Ge-containing layer to form Ge oxide (e.g., GeO 2 However, the etched structures generally exhibit unacceptable levels of surface roughness along the exposed surfaces of the Si and Ge-containing layers, due in part to the etching of the NOL. 2 The protective layer may help selectively etch the Si layer, but the GeO 2 The layer consumes a substantial portion of the Ge-containing layer.

[0012] As another example, some conventional techniques use wet or dry processes to remove NOL before performing a plasma etch to form a recess in the film stack. The film stack may be treated using dilute hydrofluoric (HF) acid or a chemical oxide removal process. However, removing NOL on the surfaces of both the Si layer and the Ge-containing layer may result in subsequent (e.g., NF 3 and O 2This can reduce the selectivity of the recess plasma etch process (which uses a SiO 2 etch process) to etch the Si layer with minimal or no etching of the Ge-containing layer.

[0013] The embodiments presented below describe various methods of selective etching. For example, the embodiments can be used to selectively etch portions of a film stack (e.g., a film stack including Si and Ge-containing layers in an alternating stacked arrangement) of a substrate. It may be desirable to selectively etch recesses (or even completely remove) at edge portions of the Si layer to form nanowires in the Ge-containing layer.

[0014] Certain embodiments use an oxygen-free plasma to form recessed regions or recesses in a film stack that includes an alternating stack arrangement of Si and Ge-containing layers. The oxygen-free plasma can form a passivation layer (e.g., a Ge nitride passivation layer) on the exposed surfaces of the Ge-containing layers. Prior to exposing the substrate to the oxygen-free plasma, a barrier layer (e.g., NOL) can be substantially removed from the exposed surfaces of the film stack using a suitable dry or wet etching process.

[0015] 1A-1D illustrate cross-sectional views of an exemplary substrate 102 during an exemplary process 100 for processing the substrate 102, in accordance with certain embodiments of the present disclosure. In certain embodiments, the process 100 incorporates an oxygen-free plasma etch process to etch portions of a particular layer of a film stack of the substrate 102, resulting in the substrate 102 having a recessed film stack after performance of the process 100. Oxygen-free does not necessarily mean that all oxygen is excluded from the process 100, but rather that oxygen is not necessarily present in the substrate 102. 2 and CO 2 It should be understood that this reflects that oxygen-containing gases such as are not intentionally introduced as part of the plasma etching process.

[0016] As shown in FIG. 1A, the substrate 102 is a semiconductor substrate including a film stack 104 disposed on a base layer 106. The film stack 104 includes a Si layer 108 and a Ge-containing layer 110 in an alternating stacked arrangement. The film stack 104 may have any suitable shape and may include any suitable number of layers. As an example, the vertical thickness of the Si layer 108 and the Ge-containing layer 110 may each be about 10 nm to about 25 nm, and as a specific example, may be about 10 nm or about 20 nm. In addition, the Si layers 108 may have the same thickness or may have different thicknesses from each other, the Ge-containing layers 110 may have the same thickness or may have different thicknesses from each other, and the Si layers 108 and the Ge-containing layers 110 may have the same thickness or may have different thicknesses from each other. In a specific example, the Si layers 108 and the Ge-containing layers 110 all have substantially the same thickness.

[0017] The material of the Si layers 108 can be, for example, pure Si or SiN. In certain embodiments, all of the Si layers 108 include the same material, although the Si layers 108 can include different materials if desired.

[0018] 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 can be selected from the appropriate ratios (e.g., SiGe, Ge, Ge) for the desired etching characteristics of a given application or the desired performance of the resulting semiconductor device formed in part using the process 100. 0.7 Ge 0.3 , Si 0.75 Ge 0.25 In certain embodiments, all of the Ge-containing layers 110 include the same material, although the Ge-containing layers 110 can include different materials if desired.

[0019] The base layer 106 can be any suitable material, and in one example includes Ge or a SiGe alloy. In a particular example, the film stack 104 is formed by growing alternating heteroepitaxial layers of Si (e.g., Si layer 108) and Ge or SiGe (e.g., Ge-containing layer 110) on the base layer 106.

[0020] An optional hardmask 112 may also be included over the film stack 104. The hardmask 112 may have been used, for example, in a previous etching process to define the structures of the film stack 104. In a particular embodiment, the hardmask 112 is SiN, but may comprise any suitable material.

[0021] A barrier layer 114 is formed over the film stack 104 (including the hard mask 112) and, in this example, the base layer 106. The barrier layer 114 may result from a previous manufacturing step (e.g., RIE) applied to the substrate 102 or from other processing of the substrate 102 (e.g., exposure to ambient air as it moves between processing tools). As a particular example, the barrier layer 114 may include NOL, RIE residue, or both. NOL may result from the substrate 102 being O 2 and H 2 When exposed to ambient air containing O, for example, a SiO 2 film having a thickness of about 1 nm to about 2.0 nm is formed on the surface of the substrate 102. 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, which may result in the formation of a barrier layer 114 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 resulting from a previous RIE step.

[0022] The barrier layer 114 may have different etching characteristics than the layers below the barrier layer 114. Although the barrier layer 114 is shown as being generally uniformly coated over the film stack 104 (including the hard mask 112) and the base layer 106, the barrier layer 114 may or may not be uniformly coated.

[0023] Each of the layers in the film stack 104 has a pair of oppositely located exposed surfaces when viewed from a cross-sectional perspective as shown. That is, each of the Si layers 108 has an exposed surface 116 (at both ends) and each of the Ge-containing layers 110 has an exposed surface 118 (at both ends). In addition, in the state shown in FIG. 1A, the substrate 102 includes a barrier layer 114, and therefore the exposed surface 116 of the Si layer 108 and the exposed surface 118 of the Ge-containing layer 110 include the barrier layer 114.

[0024] As shown in FIG. 1B, the barrier layer 114 is etched to remove some or all of the barrier layer 114 from the exposed surface 116 of the Si layer 108, from the exposed surface 118 of the Ge-containing layer 110, and from the exposed surfaces of the base layer 106 and the hard mask 112. The barrier layer 114 may be removed using any suitable process, including any suitable wet or dry etching process. In certain embodiments, the substrate 102 is treated with dilute HF acid or a chemical oxide removal process to remove some or all of the barrier layer 114. The process used to etch the barrier layer 114 may or may not remove some or all of the hard mask 112, but for purposes of this example, it is shown that the hard mask 112 is not removed or etched. However, removing the barrier layer 114 from the exposed surface 116 of the Si layer 108 and from the exposed surface 118 of the Ge-containing layer 110 may be difficult with a subsequent conventional oxygen-based recess plasma etch process (e.g., NF 3 and O 2 This may reduce the selectivity of the reaction (using

[0025] 1C, in a plasma step 120 of process 100, substrate 102 is exposed to plasma 122 to selectively etch Si layer 108. For example, substrate 102 may be exposed to plasma 122, which may be an oxygen-free plasma, to selectively etch exposed surface 116 of Si layer 108 to form a recess 136 in film stack 104 relative to adjacent Ge-containing layer 110, with both end portions of Si layer 108 in an intermediate state of removal / etching. In certain embodiments, plasma step 120 is an isotropic etching process.

[0026] The plasma process 120 may occur in a plasma chamber 123 of a plasma tool. The plasma tool may be any suitable type of plasma tool, including an inductively coupled plasma (ICP) tool, a capacitively coupled plasma (CCP) tool, a surface wave plasma (SWP) tool, etc. One exemplary plasma tool is described below with reference to FIG.

[0027] In certain embodiments, the plasma process 120 is an oxygen-free plasma etch process that etches portions of a particular layer of a film stack of the substrate 102, resulting in the substrate 102 having a recessed or concave film stack after the process 100 is performed. It should be understood that oxygen-free does not necessarily mean that all oxygen is excluded from the plasma process 120, but rather reflects that no oxygen-containing gas is intentionally introduced as part of the plasma process 120. It may be difficult or impossible to remove all oxygen from the plasma chamber 123, so some oxygen may still be present in certain processes described below.

[0028] Upon exposing the substrate 102 to the plasma 122, and to aid in the selective etching of the Si layer 108, the plasma 122 may form a passivation layer 124 on the exposed surface 118 of the Ge-containing layer 110. The plasma 122 may form the passivation layer 124 on the exposed surface 118 of the Ge-containing layer 110 by removing, replacing, or otherwise modifying portions of the Ge-containing layer 110 at the exposed surface 118 of the Ge-containing layer 110. In certain embodiments, the passivation layer 124 may also be formed on the exposed surface of the base layer 106, such as when the base layer 106 is pure Ge or includes Ge (e.g., a SiGe base layer 106).

[0029] Upon exposing the substrate 102 to the plasma 122, the passivation layer 124 on the exposed surface 118 of the Ge-containing layer 110 (and, in the illustrated example, on the exposed surface of the base layer 106) inhibits etching of the Ge-containing layer 110 (and, in the illustrated example, on the base layer 106). In other words, the plasma 122 selectively etches the Si layer 108 due at least in part to the formation and presence of the passivation layer 124 on the exposed surface 118 of the Ge-containing layer 110 (and, in the illustrated example, on the exposed surface of the base layer 106).

[0030] While the passivation layer 124 can have any suitable thickness, in certain embodiments, the passivation layer is relatively thin, such as 2 nm or less. The passivation layer 124 can be, for example, a single layer. In certain embodiments, the passivation layer 124 is a Ge nitride (e.g., Ge 3 N 4 ) and other nitrides.

[0031] As the plasma 122 etches the Si layer 108, an additional surface 138 of the Ge-containing layer 110 is exposed. That is, due to the selective etching of the Si layer 108, a recess 136 is formed in the film stack 104, exposing the additional surface 138 of the Ge-containing layer 110. The plasma 122 may proceed to form a passivation layer 124 on the additional surface 138. The passivation layer 124 formed on the additional surface 138 may also be formed of Ge nitride (e.g., Ge 3 N 4), etc. In other words, as the Si layer 108 is etched above, below, and / or between the Ge-containing layer 110, a passivation layer 124 is further formed on a newly exposed surface (e.g., additional surface 138) of the Ge-containing layer 110. The passivation layer 124 on the additional surface 138 inhibits etching of the Ge-containing layer 110 at the additional surface 138, and the passivation layer 124 at the exposed surface 118 of the Ge-containing layer 110 inhibits etching of the Ge-containing layer 110 at the exposed surface 118.

[0032] The plasma 122 may include a fluorine agent 126, a hydrogen agent 128, and a nitrogen agent 130. The fluorine agent 126 may function primarily as an etchant to etch the Si layer 108 at the exposed surface 116 of the Si layer 108. The hydrogen agent 128 may function as a reducing agent and, in the presence of the fluorine agent 126, aid in etching the Si layer 108 at the exposed surface 116 of the Si layer 108. Furthermore, if applicable, depending on the gas used to generate the plasma 122, the hydrogen agent 128 may further decompose certain compounds of fluorine and nitrogen to produce the fluorine agent 126 and the nitrogen agent 130. The nitrogen agent 130 may react with Ge at the exposed surface 118 of the Ge-containing layer 110 to form a nitride layer (e.g., Ge) at the exposed surface 118. 3 N 4 For example, atomic nitrogen (N) generated in the plasma 122 may react with Ge molecules at the exposed surface 118 of the Ge-containing layer 110 (and the exposed surface of the base layer 106) to form a passivation layer 124 (e.g., a nitride layer) on the exposed surface 118 of the Ge-containing layer 110 (and the exposed surface of the base layer 106).

[0033] In certain embodiments, the plasma 122 may be generated from gases including fluorine gas, nitrogen gas, and hydrogen gas. As some examples, the fluorine-containing gas used to generate the plasma 122 may be NF 3 , sulfur hexafluoride (SF 6 ), or carbon tetrafluoride (CF 4 Additionally, although fluorine is mentioned, other halogens may be used to aid in the etching process.

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

[0035] When the Si layer 108 and the Ge-containing layer 110 are exposed to a plasma (e.g., plasma 122) containing the fluorine agent 126 and the nitrogen agent 130 (and optionally the hydrogen agent 128), the fluorine agent 126 may react with the Si (e.g., at the exposed surface 116 of the Si layer 108) faster than the hydrogen agent 128 or the nitrogen agent 130 react with the Si, resulting in etching of the Si layer 108. Furthermore, although the fluorine agent 126 is generally considered to be more reactive than the hydrogen agent 128 or the nitrogen agent 130, when the Ge-containing layer 110 is exposed to the plasma 122 including the fluorine agent 126 and the nitrogen agent 130 (and optionally the hydrogen agent 128), the hydrogen agent 128 and / or the nitrogen agent 130 may react with Ge (e.g., at the exposed surface 118 and the additional surface 138 of the Ge-containing layer 110) faster than the fluorine agent 126 reacts with Ge to form the passivation layer 124 (e.g., Ge nitride). Furthermore, since the reaction of the hydrogen agent 128 and / or the nitrogen agent 130 with Ge is largely responsible for the formation of the passivation layer 124 on the exposed surface 118 and the additional surface 138 of the Ge-containing layer 110, a higher Ge concentration in the Ge-containing layer 110 may increase the likelihood of the passivation layer 124 forming on the exposed surface 118 and the additional surface 138 of the Ge-containing layer 110.

[0036] The gas used to generate the plasma 122 is NF 3 and N 2 In the example containing NF 3 N 2 The ratio of nitrogen to Ge may be appropriately considered. In certain embodiments, the plasma 122 contains more nitrogen than fluorine to reduce or eliminate etching of the Ge-containing layer 110 by fluorine, and to ensure that the passivation layer 124 forms quickly enough since fluorine is the 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 certain embodiments, a higher percentage of Ge in the Ge-containing layer 110 may result in the passivation layer 124 forming more quickly, leading to better results. 2NF may be added to help facilitate reactions taking place in the plasma chamber 123, including etching the Si layer 108 and forming a passivation layer 124 on the exposed surface 118 and additional surface 138 of the Ge-containing layer 110. 3 H 2 Exemplary ranges for the ratio of NF 3 :H 2 =1:1.5~NF 3 :H 2 =1:3. NF 3 N 2 Exemplary ranges for the ratio of NF 3 :N 2 =1:2.5~NF 3 :N 2 =1:10 is an example.

[0037] Other process parameters for generating the plasma 122 include gas flow rates, pressure, plasma source power, plasma bias power, time, and temperature. The gases for forming the plasma 122 may be provided at any suitable flow rates. In a particular embodiment, the etchant source gas flow rate is NF 3 =20-50sccm, H 2 =30~150sccm, N 2 =50-500 sccm. In certain embodiments, the plasma process 120 can be performed at an intermediate pressure (e.g., about 100 mTorr to about 500 mTorr, in one example, about 300 mTorr to about 350 mTorr) and an intermediate source power (e.g., about 100 W to about 400 W, in one example, about 200 W to about 300 W). The exposure time of the plasma process 120 can be any suitable time. In certain embodiments, the exposure time can be only about 5 seconds or less, 10 seconds or less, 15 seconds or less, or 20 seconds or less. In certain embodiments, the exposure time is about 15 seconds. In certain embodiments, the plasma process 120 is performed at a temperature of about -40°C to about 20°C, in one example, about 0°C. It should be understood that the specific values ​​and ranges provided herein are for illustrative purposes only.

[0038] One exemplary recipe for the oxygen-free etch process 120 is: pressure 350 mtorr, source power (inductively coupled plasma) 300 W, bias power 0 W, wafer processing temperature 0° C., NF 3 , H 2 , and N 2 Another exemplary recipe includes a pressure of 300 mtorr, a source power (inductively coupled plasma) of 300 W, a bias power of 0 W, a wafer processing temperature of 0° C., and a NF 3 , H 2 , and N 2 The flow rates may include 20 sccm, 36 sccm, and 250 sccm, respectively.

[0039] 1D shows the substrate 102 after the plasma process 120. In the state shown in FIG. 1D, the film stack 104 includes depressions 136 (two examples of which are labeled). Furthermore, due to the formation of the depressions 136, exposed edges 141 of the Ge-containing layer 110 (one example of which is labeled) may be formed.

[0040] FIG. 1D illustrates certain measurements of the resulting substrate 102, such as exposed edge spacing 142 and etch width 144. For example, exposed edge spacing 142 indicates the remaining width (in this cross section) of the Si layer 108 by measuring each Si layer 108 from a first exposed surface 116 on a first side of the film stack 104 to an opposing second exposed surface 116 on a second side of the film stack 104. Exposed edge spacing 142 may be less than 20 nm in certain embodiments, and in one embodiment, between 2 nm and 20 nm. Exposed edge spacing may also refer to the exposed edge spacing before etching. Etch width 144 may measure how much of a particular Si layer 108 has been removed from a particular edge of a particular Si layer 108. In other words, etch width 144 may measure the amount of recession 136 in the Si layer 108. In certain embodiments, etch width 144 is between about 5 nm and about 15 nm. However, the exposed end spacing 142 and etch width 144 may be outside of these ranges for a given application.

[0041] Subsequent processing may then be performed on the substrate 102. For example, the plasma step 120 may be integrated into a process for forming the Ge-containing layer 110 into corresponding nanowires for a channel region of a semiconductor device, such as a GAA device. In such a device, the subsequent processing may include filling the recess 136 with an insulator, removing remaining portions 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 a device, the exposed end 141 of the Ge-containing layer 110 may serve as a conductive contact to a channel region formed in a region of the film stack 104.

[0042] Process 100 may provide one or more technical advantages. Conventional techniques for selectively etching Si layers over Ge-containing layers use an etchant (e.g., fluorine) and oxygen (e.g., NF 3 / O 2 or CF 4 / O 2 ) (abbreviated as F / O-based plasma). Such F / O-based plasma oxidizes the surface of the Ge-containing layer, forming Ge dioxide (GeO 2 ) or Ge oxynitride (GeO x N y ) etch stop layer. This etch stop layer inhibits the ability of the etchant to etch the Ge-containing layer, but this etch stop layer is thick and may displace a significant portion of the Ge-containing layer, reducing the thickness of the Ge-containing layer by an undesirable amount. As device sizes decrease, this loss may become a large percentage of the Ge-containing layer in the channel region (and ultimately the nanowires / nanosheets). Additionally, in the time it takes for this etch stop layer to form, the etchant may attack areas where the etch stop layer has not yet formed. Additionally, the oxide etch stop layer may be water soluble.

[0043] In addition, F / O-based plasmas can be used to form silicon dioxide (SiO 2 ), silicon nitride (Si3 N 4 ), oxides, and other materials such as low-k materials, which may be undesirable. In other words, such oxygen-containing plasmas (e.g., F / O-based plasmas) may etch SiO 2 , Si 3 N 4 , oxides, and low-k materials.

[0044] According to an embodiment of the process 100, the passivation layer 124 formed on the Ge-containing layer 110 may include a thinner nitride (e.g., Ge nitride) than an etch stop layer formed by oxidizing the Ge-containing layer by conventional techniques. In a particular embodiment, selectively etching the Si layer 108 by exposing the substrate 102 (including the film stack 104) to the plasma 122 reduces the thickness of the Ge-containing layer 110 by less than about 2.0 nm. Thus, the process 100 may reduce the loss of the Ge-containing layer 110 in the selective etching of the Si layer 108 compared to using conventional techniques.

[0045] Additionally, due at least in part to the high selectivity of the plasma 122 relative to the Ge-containing layer 110 (which itself is due at least in part to the rapid formation of the passivation layer 124 on the exposed surface 118 and the additional surface 138 of the Ge-containing layer 118), the film stack 104 may have an improved etch profile. The improved etch profile may include reduced surface roughness along the surface 116 of the Si layer 108 (to the extent that the Si layer 108 is not completely removed), particularly along the exposed surface 118 and the remaining surface 138 of the Ge-containing layer after the plasma step 120. Additionally or alternatively, the improved etch profile may include sharp edges and a square shaped profile of the exposed edge 141 of the Ge-containing layer after the plasma step 120. In certain embodiments, the plasma process 120, including the use of plasma 122, provides a relatively straight Si etch front along the surface 116 of the Si layer 108 (to the extent that the Si layer 108 is not completely removed) and provides good local uniformity with respect to the amount of Si removed from each Si layer 108 of the film stack 104.

[0046] The nitride (e.g., Ge-nitride) passivation layer 124 may be insoluble in water, and the passivation layer 124 may be O 2 and H 2 The Ge-containing layer 110 can function as an O diffusion barrier, thereby improving the stability of nanowires formed from the Ge-containing layer 110. In addition to being selective to Ge and SiGe, the plasma 122 (e.g., fluorine-containing, hydrogen-containing, and nitrogen-containing plasmas) can also etch SiO because the plasma 122 does not contain oxygen, which causes conventional F / O-based plasmas to etch these materials. 2 , Si 3 N 4 , oxide, and low-k materials. Furthermore, removing the barrier layer 114 prior to the recess etch may reduce surface roughness, but in addition, the plasma 122 also improves the selectivity of etching the Si layer 108 relative to the Ge-containing layer 110 due to the increased rate at which the passivation layer 124 forms relative to the oxide etch stop layer.

[0047] 2 illustrates an exemplary method 200 for processing a substrate 102 according to certain embodiments of the present disclosure. The method 200 begins at step 202. At step 204, the substrate 102 is received. The substrate 102 has a film stack 104 including a Si layer 108 and a Ge-containing layer 110 in an alternating stacked arrangement. That is, the film stack 104 may include an alternating Si layer 108 and a Ge-containing layer 110 (e.g., as shown in FIG. 1A ). A barrier layer 114 (e.g., a NOL) may be present on a surface of the film stack 104, such as on an exposed surface 116 of the Si layer 108, on an exposed surface 118 of the Ge-containing layer 110, and on exposed surfaces of the base layer 106 and the hard mask 112.

[0048] In step 206, the barrier layer 114 on the surface of the film stack 104 is etched, e.g., to remove the barrier layer 114 from the exposed surface 116 of the Si layer 108, from the exposed surface 118 of the Ge-containing layer 110, and from the exposed surfaces of the base layer 106 and the hard mask 112. The barrier layer 114 may be removed using any suitable process, such as a wet or dry etching process.

[0049] In step 208, the Si layer 108 is selectively etched by exposing the substrate 102 (including the film stack 104) to a plasma 122. The plasma 122 may include a fluorine agent 126 and a nitrogen agent 130. In certain embodiments, the plasma 122 further includes a hydrogen agent 128. The plasma 122 etches the Si layer 108 and forms a passivation layer 124 on the exposed surface 118 of the Ge-containing layer 110 to inhibit etching of the Ge-containing layer 110 upon exposure of the semiconductor device 102 (including the film stack 104) to the plasma 122. In certain embodiments, step 208 is an isotropic etching process.

[0050] In certain embodiments, the plasma 122 is NF 3 Generated from gas containing fluorine, 126 is NF 3 In a particular embodiment, the plasma 122 comprises N 2 The plasma 122 may be generated from a gas containing nitrogen gas, and the nitrogen agent 130 may include nitrogen. 3 and N.H. 3 , N.F. 3 , N.H. 3 , and N 2 , N.F. 3 , N.H. 3 , and Ar, NF 3 and H 2 , N.F. 3 , H 2 , and N 2 , or NF 3 , H 2 , N.H. 3 , and N 2In a particular embodiment, the passivation layer 124 formed on the exposed surface 118 of the Ge-containing layer 110 is formed of Ge nitride (Ge 3 N 4 ).

[0051] Selectively etching the Si layer 108 may include selectively etching an edge portion of the Si layer 108 to form a recess 136 in the film stack 104 above, below, or between the Ge-containing layer 110. As the Si layer 108 is selectively etched, an additional surface 138 of the Ge-containing layer 110 is exposed, and the plasma 122 forms a passivation layer 124 on the additional surface 138. In certain embodiments, selectively etching the Si layer 108 includes selectively removing substantially all of the Si layer 108 such that the Ge-containing layer 110 is released. In certain embodiments, selectively etching the Si layer 108 by exposing the substrate 102 (including the film stack 104) to the plasma 122 reduces the thickness of the Ge-containing layer 110 by less than about 2.0 nm.

[0052] In step 210, additional fabrication steps are performed. The discussion of potential additional processing steps discussed above with reference to Figure ID is incorporated by reference. For example, in certain embodiments, step 208 is integrated into a process for forming Ge-containing layer 110 into corresponding nanowires for a channel region of a semiconductor device, such as a GAA device. In step 212, the method ends.

[0053] 3 illustrates an exemplary method 300 for processing a substrate 102 in accordance with certain embodiments of the present disclosure. The method 300 begins at step 302. At step 304, the substrate 102 is placed in a plasma chamber 123 of a plasma tool. The substrate 102 has a film stack 104 including a Si layer 108 and a Ge-containing layer 110 in an alternating stacked arrangement (e.g., as shown in FIG. 1A ).

[0054] In step 306, a plasma 122 is generated in a plasma chamber 123 of a plasma tool. The plasma 122 includes a fluorine agent 126, a nitrogen agent 130, and a hydrogen agent 128. The plasma 122 may be generated without intentionally introducing an oxygen-containing gas into the plasma chamber 123. The plasma 122 may include a NF 3 ,SCIENCE FICTION 6 , or CF 4 The fluorine agent 126 may be generated from a gas that includes a fluorine-containing gas, such as NH, NH. The fluorine agent 126 may include fluorine dissociated from a fluorine-containing gas. In certain embodiments, the plasma 122 is generated from a gas that includes a nitrogen-containing gas, such as NH, NH. 2 , or NH 3 and the nitrogen agent 130 comprises nitrogen dissociated from a nitrogen-containing gas.

[0055] In a particular embodiment, the plasma 122 is N 2 Gas and H 2 The plasma 122 may be generated from a gas containing nitrogen gas, nitrogen agent 130 may include nitrogen, and hydrogen agent 128 may include hydrogen. 3 and N.H. 3 , N.F. 3 , N.H. 3 , and N 2 , N.F. 3 , N.H. 3 , and Ar, NF 3 and H 2 , N.F. 3 , H 2 , and N 2 , or NF 3 , H 2 , N.H. 3 , and N 2 The gas may be generated from a composite gas including:

[0056] In step 308, the substrate 102 (including the film stack 104) is exposed to a plasma 122 in a plasma chamber 123. The plasma 122 causes a passivation layer 124, which may be a nitride layer, to form on the exposed surface 118 and the additional surface 138 of the Ge-containing layer 110. In certain embodiments, the passivation layer 124 is Ge nitride (e.g., Ge 3 N 4). The plasma 122 also selectively etches the exposed surface 116 (e.g., both exposed edges) of the Si layer 108 to form a recess 136 in the Si layer 108 relative to the exposed surface 118 (e.g., both exposed edges) of the Ge-containing layer 110. The passivation layer 124 inhibits etching of the Ge-containing layer 110 by the plasma 122. In certain embodiments, step 308 is an isotropic etching process.

[0057] Additional manufacturing steps are performed in step 310. The discussion of potential additional processing steps discussed above with reference to step 210 of Figure 2 is incorporated by reference. In step 312, the method ends.

[0058] 4 illustrates an exemplary device 400 including a substrate having a recessed layer-by-layer film according to certain embodiments of the present disclosure. At least a portion of device 400 may be formed using any of the processes and methods described herein.

[0059] The 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 the process 100. The device 400 may be a GAA device as shown herein or any other device, such as a Fin Field Effect Transistor (FinFET). The device 400 may also include an isolation region 408. In a particular embodiment, the isolation region 408 is a shallow trench isolation (STI).

[0060] Device 400 may be fabricated by first forming a recessed layer-by-layer film 410 (which may correspond to layer 104 after process 100, possibly with additional subsequent processes), and then depositing additional gate material 406 onto recessed layer-by-layer film 410. In particular, device 400 may be formed by heteroepitaxially growing alternating Si and Ge or SiGe layers, which are then vertically patterned and recessed to laterally expose the Ge or SiGe layers.

[0061] Application of the embodiments described herein may advantageously be an optimal solution for the 5 nm node, 3 nm node, or below. For example, the GAA device architecture may be suitable for scaling beyond the 7 nm node. The GAA device architecture may address short channel effects found in some FinFET architectures by wrapping the gate around the entire channel rather than just on three sides. This may reduce or eliminate current leakage that occurs under the gate of the FinFET, thereby reducing non-active power losses.

[0062] 5 illustrates a block diagram of an exemplary plasma tool 500 in accordance with certain embodiments of the present disclosure. Although a particular plasma tool 500 is shown and described, any suitable type of plasma tool may be used. The plasma tool 500 may be used to perform the plasma process 120 described with respect to FIGS. 1A-1D and 2-4.

[0063] The plasma tool 500 includes a plasma chamber 123 for processing a semiconductor substrate (e.g., substrate 102) using a plasma (e.g., plasma 122). The plasma chamber 123 includes a substrate table 502 configured to support the substrate 102 during processing. In a particular embodiment, the substrate 102 is positioned on the substrate table 502 as shown in FIG. 1B, for example after removal of the barrier layer 114, to perform the plasma process 120 using the plasma 122. A material of the Si layer 108 (e.g., as described above with reference to FIGS. 1A-1D) of the film stack 104 of the substrate 102 is selectively etched in the plasma chamber 123 by injecting a plasma (e.g., plasma 122) through a showerhead 504 of the plasma tool 500. The showerhead 504 may include a single mixing reaction cavity filled with a precursor gas, a mixed gas, and a carrier gas that are mixed to form the plasma 122, and a set of outlet holes for delivering the plasma 122 toward the substrate 102.

[0064] The plasma chamber 123 may include and / or be otherwise coupled to a vacuum pump 506 coupled to a vacuum line 508 to purge residual precursor gas from the plasma chamber 123, and in certain embodiments may include and / or be otherwise coupled to a pressure system to maintain a target pressure. The plasma chamber 123 may further include mechanical tools 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 the substrate 102.

[0065] The plasma tool 500 includes a precursor gas line 514, a mixed gas line 516, and a carrier gas line 518 coupled to a showerhead 504. In a particular embodiment, the precursor gas supplied through the precursor gas line 514 is fluorine or NF 3The gas mixture supplied through gas mixture line 516 can include hydrogen, and the carrier gas supplied through carrier gas line 518 can include nitrogen or an inert gas such as argon or krypton.

[0066] In certain embodiments, the plasma tool 500 may include a system of mass flow controllers and sensors to control gas flow rates (e.g., mass flow rates). Thus, 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 (VI) 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 coupled to and controlled by the first flow controller 520, the second flow controller 522, and the third flow controller 524, respectively.

[0067] 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. In another example, the controller 536 may include one or more programmable ICs programmed to provide the functionality described herein. In a particular example, one or more processors (e.g., microprocessors, microcontrollers, central processing units, etc.), programmable logic devices (e.g., composite 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 functionality 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.), which, when executed by the programmable ICs, cause the programmable ICs to perform the operations described herein.

[0068] The heater 510 and temperature sensor 512 of the plasma chamber 123 as well as mechanical components such as 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 .

[0069] Equipment sensors measure equipment parameters such as the temperature of the substrate table 502, heater current, vacuum pump speed and temperature, 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. Data from the equipment and process sensors provides feedback to the controller 536 continuously throughout the plasma process 120. The controller 536 can adjust the equipment and process in real time to keep them close to the center of specification.

[0070] The controller 536 receives data from the sensors and controls process parameters of the plasma chamber 123 based on the sensor data. The controller 536 can analyze the data collected by the sensors to determine when to modify or terminate one or more steps of the plasma process 120 and provide feedback to control process parameters of the components of the plasma chamber 123.

[0071] The controller 536 may be connected to the VI sensor 526 and the substrate sensors 528-534 to monitor the plasma 122 as the substrate 102 is exposed to the plasma 122 and provide real-time status, and optionally compositional and thickness data, of the plasma 122. This feedback data may be used by the controller 536 to continuously adjust the plasma process 120 as the substrate 102 is selectively etched with the plasma 122, for example, to turn off the plasma process 120 when a target recess (e.g., etch width 144) is reached.

[0072] Specifically, measurement data from the substrate sensors 528-534 and the temperature sensor 512 may be received by the controller 536, while the controller 536 generates control signals that are sent to the first flow controller 520, the second flow controller 522, the third flow controller 524, the vacuum pump 506, and the heater 510.

[0073] The controller 536 may receive measurement or metrology data from the substrate sensors 528-534 taken at multiple points across the substrate 102 to measure in situ and in real time the process uniformity, as well as the thickness and composition of the passivation layer 124 (formed from exposure of the substrate 102 to the plasma 122), the spacing of exposed edges 142, and / or the target recess (e.g., etch width 144). For example, sensors across multiple substrates in a multi-substrate plasma tool may be used to monitor and adjust the thickness and composition of the passivation layer 124 (formed from exposure of the substrate 102 to the plasma 122), the spacing of exposed edges 142, and / or the target recess (e.g., etch width 144) from the top to the bottom of the substrate 102. Sensors across multiple substrates in a single substrate plasma tool can be used to monitor and adjust the thickness and composition of the passivation layer 124 (formed from exposure of the substrate 102 to the plasma 122) from the center to the edge of the substrate 102, the spacing 142 of the exposed edges, and / or the target recess (e.g., etch width 144).

[0074] The substrate sensors 528-534 may be coupled to 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 may include various types of sensors including, but not limited to, optical sensors (camera, laser, light, reflectometer, spectrometer, ellipsometric, etc.), capacitive sensors, ultrasonic sensors, gas sensors, or other sensors that may monitor the condition of the substrate 102, the plasma 122, and / or the plasma tool 500. In certain embodiments, one or more optical sensors may be used to measure in real time (in the plasma process 120) the thickness and refractive index of materials 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 edge spacing 142, and / or the etch width 144a (or other suitable measurements). As another example, a spectrometer may be used to measure (in plasma process 120) in real time the thickness of material at the surface 118 of the Ge-containing layer and at the surface of the base layer 106 (e.g., where the passivation layer 124 is formed), the spacing 142 of the exposed edges, and / or the etch width 144a (or other suitable measurements). In yet another embodiment, a residual gas analyzer (RGA) may be used to detect (in plasma process 120) the breakdown of precursors in real time for real time chemical reaction completion detection.

[0075] The controller 536 may receive user input process parameters including, for example, etch rate, conformality, profile, and deposition rate (e.g., deposition rate of the passivation layer 124) based on standard plasma etch 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 pulse, etc.), etch time, and composition and flow rates of various process and carrier gases. Advantageously, the plasma 122 may be adjusted by a user to meet a target local critical dimension uniformity (LCDU).

[0076] Based on the data from the substrate sensors 528-534 and user-entered process parameters, the controller 536 generates control signals to the temperature sensor 512 and the heater 510 to regulate the heat in the plasma chamber 123. As the heater 510 heats the plasma chamber 123, the controller 536 constantly or periodically monitors the temperature sensor 512 to track the temperature of the plasma chamber 123 and sends control signals to the heater 510 to maintain the temperature of the plasma chamber 123.

[0077] When the controller 536 determines that the target temperature of the plasma chamber 123 has been reached based on the data provided by the temperature sensor 512, the controller 536 generates control and data signals to operate the first flow controller 520, the second flow controller 522, and the third flow controller 524 to provide a target flow rate of the precursor gas to the first flow controller 520, a target flow rate of the mixed gas to the second flow controller 522, and a target flow rate of the carrier gas to the third flow controller 524 based on the process parameters entered by the user. When the controller 536 determines that the corresponding flow rates have been established, the controller 536 provides power to the plasma chamber 123 to power the plasma 122 through the bias electrode and the source electrode. Based on measurements from the VI sensor 526, the power provided to the bias electrode and the source electrode may be adjusted. The first flow controller 520, the second flow controller 522, and the third flow controller 524 may each be a closed loop control system connected to a flow sensor and an adjustable proportional valve, such that each flow controller can constantly or periodically monitor and internally maintain a target flow rate for each gas via the flow sensor and adjustable proportional valve.

[0078] In certain embodiments, when the controller 536 determines that the etch process time has been met based on user-entered data, 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.

[0079] The controller 536 may use or analyze the substrate sensor data to determine when to terminate the plasma process 120. For example, the controller 536 may receive data from a residual gas analyzer to detect the end point of the plasma process 120. In another example, the controller 536 may use spectroscopic ellipsometry to detect the average thickness of the passivation layer 124, the exposed edge 141 of the Ge-containing layer 110, and / or the exposed edge spacing 142 during the plasma process 120 to indicate a change during the plasma process 120. In another example, the controller 536 may use spectroscopic ellipsometry to detect the refractive index of the material at the surface 118 of the Ge-containing layer and at the surface of the base layer 106 (e.g., where the passivation layer 124 is formed) during the plasma process 120 to indicate a film composition change during the plasma process 120. The controller 536 may automatically terminate the plasma process 120 when a target for the exposed edge spacing 142 and / or the etch width 144a (or another suitable measurement) is achieved. In certain embodiments, the controller 536 may adjust the NF during, for example, the plasma process 120 to achieve a desired etch profile of the film stack 104. 3 H 2 Ratio to NF 3 N 2 The controller 536 may automatically adjust one or more parameters, such as the ratio of the composition to the etching rate. Data from the controller 536 and the substrate sensors 528-534 may also be used to achieve a desired semiconductor substrate throughput target. Additionally, data from the controller 536 and the substrate sensors 528-534 may be used to achieve a desired etch profile, or alternatively target a combination, of the film stack 104 and composition along with the desired semiconductor substrate throughput.

[0080] Although described for the specific application of forming nanowires / nanosheets for GAA devices, the present disclosure may be used for any type of isotropic etch of Si that is selective to a Ge-containing layer. Additionally, although the etch performed is described as being primarily to form a recess in film stack 104 by removing portions of both ends of Si layer 108, processes 100 and 400 may be used to remove substantially all portions of Si layer 108, which may be referred to as releasing Ge-containing layer 110.

[0081] Although the present disclosure describes certain process / method steps as occurring in a particular order, the present disclosure contemplates that the process steps may occur in any suitable order. Although 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 the description. It is therefore intended that the appended claims cover 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; selectively etching the first silicon layer by exposing the film stack to a plasma including a fluorine agent and a nitrogen agent, the plasma etching the first silicon layer while forming a passivation layer on exposed surfaces of the first germanium-containing layer and the second germanium-containing layer to inhibit etching of the first germanium-containing layer and the second germanium-containing layer upon exposure of the film stack to the plasma; A method comprising:

2. The method of claim 1 , wherein the plasma further comprises a hydrogen agent.

3. The plasma is nitrogen trifluoride (NF ３ ) gas, and the fluorine agent is generated from the gas containing the NF ３ The method of claim 1 comprising dissociating fluorine from the gas.

4. The plasma is N ２ 2. The method of claim 1, wherein the nitrogen agent is generated from a gas containing gas, and the nitrogen agent is nitrogen.

5. The plasma is Nitrogen trifluoride (NF ３ ) and ammonia (NH ３ ), N.F. ３ , N.H. ３ , and nitrogen (N ２ ), N.F. ３ , N.H. ３ , and argon (Ar); N.F. ３ and hydrogen (H ２ ), N.F. ３ , H ２ , and N ２ or N.F. ３ , H ２ , N.H. ３ , and N ２ The method of claim 1 , wherein the gas is generated from a composite gas comprising:

6. The passivation layer formed on the exposed surfaces of the first and second germanium-containing layers is germanium nitride (Ge ３ N ４ 2. The method of claim 1 , comprising:

7. 2. The method of claim 1, wherein the first germanium-containing layer and the second germanium-containing layer are both germanium layers or both silicon germanium layers.

8. 2. The method of claim 1, wherein one of the first germanium-containing layer and the second germanium-containing layer is a germanium layer, and the other of the first germanium-containing layer and the second germanium-containing layer is a silicon germanium layer.

9. 2. The method of claim 1 , wherein selectively etching the first silicon layer comprises selectively etching an edge portion of the first silicon layer to form a recess in the film stack between the first germanium-containing layer and the second germanium-containing layer.

10. 2. The method of claim 1 , wherein when the first silicon layer is selectively etched, additional surfaces of the first germanium-containing layer and the second germanium-containing layer are exposed, and the plasma forms the passivation layer on the additional surfaces.

11. 2. The method of claim 1 , wherein selectively etching the first silicon layer comprises selectively removing substantially all of the first silicon layer between the first germanium-containing layer and the second germanium-containing layer.

12. prior to selectively etching the first silicon layer; a native oxide layer is present on the surface of the laminated film; The method of claim 1 , wherein the method further comprises etching the native oxide layer.

13. the stacked film further includes a second silicon layer and a third germanium-containing layer, the second silicon layer being disposed between the second germanium-containing layer and the third germanium-containing layer; 2. The method of claim 1, wherein the method comprises selectively etching the second silicon layer by exposing the film stack to the plasma, the plasma forming the passivation layer on an exposed surface of the third germanium-containing layer to inhibit etching of the third germanium-containing layer upon exposure of the film stack to the plasma.

14. 1. A method for processing a semiconductor substrate, the method comprising: placing a semiconductor substrate in a plasma chamber of a plasma tool, the semiconductor substrate including a film stack including silicon layers and germanium-containing layers in an alternating stacked arrangement, with at least two silicon layers and at least two germanium-containing layers; generating a plasma in the plasma chamber of the plasma tool, the plasma including a fluorine agent, a nitrogen agent, and a hydrogen agent, the plasma being generated without intentionally introducing an oxygen-containing gas into the plasma chamber; exposing the film stack to the plasma in the plasma chamber of the plasma tool, the plasma selectively etches the exposed edges of the silicon layer to form recesses in the silicon layer relative to the exposed edges of the germanium-containing layer while forming a nitride passivation layer on exposed surfaces of the germanium-containing layer, the nitride passivation layer inhibiting etching of the germanium-containing layer by the plasma; A method comprising:

15. The plasma is generated from a gas that includes a fluorine-containing gas, the fluorine-containing gas being nitrogen trifluoride (NF ３ ), sulfur hexafluoride (SF ６ ), or carbon tetrafluoride (CF ４ ), The method of claim 14 , wherein the fluorine agent comprises fluorine dissociated from the fluorine-containing gas.

16. The plasma is generated from a gas that includes a nitrogen-containing gas, the nitrogen-containing gas being N ２ , N.F. ３ , or NH ３ Including, The method of claim 14 , wherein the nitrogen agent comprises nitrogen dissociated from the nitrogen-containing gas.

17. The plasma is nitrogen (N ２ ) gas and hydrogen (H ２ ) gases, including the nitrogen agent comprises nitrogen; 15. The method of claim 14, wherein the hydrogen agent comprises hydrogen.

18. The plasma is Nitrogen trifluoride (NF ３ ) and ammonia (NH ３ ), N.F. ３ , N.H. ３ , and nitrogen (N ２ ), N.F. ３ , N.H. ３ , and argon (Ar); N.F. ３ and hydrogen (H ２ ), N.F. ３ , H ２ , and N ２ or N.F. ３ , H ２ , N.H. ３ , and N ２ 15. The method of claim 14, wherein the gas is generated from a composite gas comprising:

19. The nitride passivation layer formed on the exposed surface of the germanium-containing layer is germanium nitride (Ge ３ N ４ 15. The method of claim 14, comprising:

20. 1. A method for processing a semiconductor substrate, the method comprising: placing a semiconductor substrate in a plasma chamber of a plasma tool, the semiconductor substrate including a film stack including a first layer of a first material and a second layer of a second material in an alternating stacked arrangement, the first material being silicon; generating a plasma for selectively etching the first layer of the first material, the generating the plasma including introducing a gas including fluorine and nitrogen into the plasma chamber and maintaining a temperature of the semiconductor substrate between about −40° C. and about 40° C., the plasma including a greater amount of nitrogen than fluorine; exposing the film stack to the plasma in the plasma chamber for a period of time, the plasma selectively etching both exposed edges of the first layer of the first material to form a recess in the first layer of the first material relative to both exposed edges of the second layer of the second material; A method comprising:

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