Method for vapor phase selective etching of silicon germanium layers

Abstract

Methods for selectively etching SiGe relative to Si are provided. Some of the methods include forming a passivation layer on the surface of a Si layer to enhance SiGe etchant selectivity, and using a halogen intercompound gas that preferentially etches SiGe over Si in the presence of the passivation layer. The methods can be performed in a cyclical manner until a desired thickness of the SiGe layer is obtained.

Description

Technical Field

[0001] This invention relates to the selective etching of silicon-germanium layers on wafers in relation to semiconductor manufacturing. More specifically, this invention relates to a method for improving the selectivity ratio of the silicon-germanium layer to silicon during semiconductor manufacturing, which is not possible with conventional etchant techniques. Background Technology

[0002] Amorphous silicon (a-Si), polycrystalline silicon (poly-Si), and single-crystal Si, combined with silicon germanium (“SiGe”), are widely used in the semiconductor industry for various applications. For technology nodes below 20nm, the integration of SiGe as source-drain materials has shown potential to improve the electrical performance of transistors. Various transistors can be formed on the substrate.

[0003] At technology nodes above 5nm, the semiconductor device industry is moving from FinFET transistor structures to so-called Gate All-Around (GAA) device architectures. A fundamental requirement for GAA implementation is the formation of SiGe and Si nanowires (NW) and Si nanosheets (NS). Specifically, horizontally stacked silicon nanowires (HNW) and horizontally stacked nanosheets (HNS) are being investigated. HNS has been identified as the next-generation device structure at the 3nm node and below.

[0004] However, to successfully fabricate HNS structures, advanced methods are needed to address the challenges and meet the demand for aggressive patterning that continues to reduce the size of critical feature structures. The ability to successfully combine patterning schemes with highly selective etching processes is crucial for reliable pattern transfer. Pattern transfer can be performed as follows: After forming the circuit pattern, a protective layer (e.g., a photosensitive material patterned using photolithography, a mechanically imprinted patterned layer, or a direct self-assembled layer) is used to mask certain areas of the semiconductor substrate, while other areas remain exposed. The remaining exposed areas allow the circuit pattern to be transferred to the underlying layer of the substrate using a dry etching process. The ability to fabricate HNS feature structures requires high etch selectivity between SiGe and Si, which is currently unavailable. Etching selectivity is defined as the ratio of the etching rates of two different surfaces when exposed to an etchant process. For example, a 100:1 etch selectivity between SiGe and Si under a given etchant process means that the etching rate of the SiGe surface is 100 times higher than that of the Si surface when using that etchant process.

[0005] Conventional etchant techniques such as direct plasma etching, plasma atomic layer etching (ALE), or ion milling cannot achieve the high SiGe to Si etch selectivity ratio required to produce the characteristic structures of HNS. For example, for a triple-stacked silicon NS, there are four SiGe sacrificial layers. Removing the SiGe sacrificial layers without damaging the Si NS is necessary and represents a critical process step in GAA HNS devices. Undercut or cavity SiGe etching requires highly precise and selective isotropic chemical etching, which is not possible with conventional etching techniques.

[0006] Other conventional etchant methods include oxidative wet etching, commonly used in the microelectromechanical systems (MEMS) industry and early GAA HNS research for selectively etching SiGe onto Si. However, in general, the semiconductor industry prefers to avoid wet-based etchant methods. Instead, the industry seeks selective dry chemical etching to achieve better Si HNS release quality and simpler high-volume manufacturing processes.

[0007] Dry thermal etching processes have been developed for the selective etching of SiGe on Si, SiO3, SiC, and Si3N4. However, these dry thermal etchant processes still have drawbacks. Specifically, current methods, such as remote CF4 / O2-based plasma, can only produce an etching selectivity of 50:1. In other words, when using a CF4 / O2 remote plasma process, the etching rate of the SiGe surface is 50 times higher than that of the Si surface.

[0008] Currently, as alternatives, thermal dry etching processes using interhalogen compound materials such as ClF3 or different mixtures of F2 and inert gases from early MEMS research activities have been investigated (US Patent Publication No. 2020027741; Loubet et al., A Dry Selective Etching of SiGe for Realizing High-Performance Logic Stacked All-Around Gate Nanosheet Devices, International Electron Devices Conference, pp. 1-4, 2019). When using ClF3 as an interhalogen compound etchant, etching selectivity of up to 150:1 for superlattice SiGe:Si layers has been reported.

[0009] Despite ongoing research and development activities, there remains a persistent need for higher etch selectivity to improve the performance of GAA nanostructures and increase manufacturing productivity. The current requirement for etch selectivity greater than 150:1 between SiGe and Si, SiO2, Si3N4, and SiC has not yet been met. Summary of the Invention

[0010] In one aspect, a method for selectively dry etching a substrate is disclosed, the method comprising the steps of: providing a substrate comprising a silicon-germanium alloy layer and a silicon layer in an etching chamber; introducing a fluorinated interhalogen compound gas into the etching chamber; selectively etching a first portion of the silicon-germanium alloy layer, the first portion subsequently being removed from the etching chamber as a first portion of volatile silicon and germanium fluorides; converting the silicon layer into a non-volatile fluorinated silicon layer; recovering any residual amount of the fluorinated interhalogen compound gas from the etching chamber; introducing a passivation gas into the etching chamber to selectively convert the non-volatile fluorinated silicon layer into a passivated silicon layer, wherein the passivation gas substantially does not react with the silicon-germanium alloy layer; recovering any residual amount of the passivation gas from the etching chamber; reintroducing the fluorinated interhalogen compound gas into the etching chamber; and selectively etching a second portion of the silicon-germanium alloy layer, the second portion subsequently being removed from the etching chamber as a second portion of volatile silicon and germanium fluorides, while substantially not etching the passivated silicon layer.

[0011] In a second aspect, a method for selectively dry etching a substrate is disclosed, the method comprising the steps of: providing a substrate comprising a silicon-germanium alloy layer and a silicon layer in an etching chamber; introducing a first etchant gas into the etching chamber, wherein the first etchant gas comprises a fluorinated interhalogen compound gas; selectively etching a first portion of the silicon-germanium alloy layer, the first portion subsequently being removed from the etching chamber as a first portion of volatile silicon and germanium fluorides; converting the silicon layer into a non-volatile fluorinated silicon layer; recovering any residual amount of the fluorinated interhalogen compound gas from the etching chamber; introducing a passivation gas into the etching chamber to selectively convert the non-volatile fluorinated silicon layer into a passivated silicon layer, wherein the passivation gas substantially does not react with the silicon-germanium alloy layer; recovering any residual amount of the passivation gas from the etching chamber; introducing a second etchant gas into the etching chamber; and selectively etching a second portion of the silicon-germanium alloy layer, the second portion subsequently being removed from the etching chamber as a second portion of volatile silicon and germanium fluorides, while substantially not etching the passivated silicon layer.

[0012] In a third aspect, a method for selectively dry etching a substrate is disclosed, the method comprising the steps of: providing a substrate in an etching chamber, the substrate comprising a silicon-germanium alloy layer and a silicon layer, wherein the silicon-germanium alloy layer is in situ doped with an n-type or p-type dopant; exposing the substrate to an etchant gas; and selectively removing a portion of the silicon-germanium alloy layer of silicon and germanium, while substantially not removing the passivated silicon layer.

[0013] In a fourth aspect, a method for selectively dry etching a substrate is disclosed, the method comprising the steps of: providing a substrate in an etching chamber, the substrate comprising a silicon-germanium alloy layer and a silicon layer; and selectively etching the silicon-germanium alloy layer using an interhalogen compound fluorine-containing gas, while forming and maintaining a passivation layer on the Si layer. Attached Figure Description

[0014] Figure 1 A flowchart of the etchant process according to a first embodiment of the present invention is shown;

[0015] Figure 2 It shows that according to Figure 1 and Figure 4 One of the steps in the etchant process is the representative surface obtained after etching a first portion of the SiGe alloy layer with a fluorinated halide gas and exposing the fluorinated halide gas to the Si surface to form a fluorine-terminated layer on the Si surface.

[0016] Figure 3 It shows that according to Figure 1 and Figure 4 One step in the etchant process is the selective formation of a representative passivated Si layer on the Si surface, rather than on the SiGe surface; and

[0017] Figure 4 A flowchart of an etchant process according to a second embodiment of the present invention is shown. Detailed Implementation

[0018] As will be described, the present invention provides a method for performing selective dry etching of a substrate. By using the method of the present invention, SiGe can be etched preferentially relative to Si. The high SiGe to Si selectivity ratio of the present invention allows for the fabrication of GAA device architectures.

[0019] As used herein and throughout, the terms “etch selectivity” or “selectivity” or “selectivity ratio” are used interchangeably to refer to the ratio of the etch rates of two different surfaces when exposed to an etchant process, where the etch rate is typically measured in nanometers per minute.

[0020] As used herein and throughout, the term “layer” is intended to refer to a continuous, semi-continuous, or discontinuous deposition of a material along a substrate, which may consist of a single layer or one or more layers.

[0021] As used in this article and throughout the text, the term "interhalogen compound" refers to a compound consisting of two or more different halogen atoms.

[0022] Unless otherwise stated, all passivating compounds and etchants described herein and throughout are intended to be in the gas phase.

[0023] As used herein and throughout the text, "SiGe" or "SiGe alloy" or "silicon-germanium alloy" may be used interchangeably to denote an alloy of silicon and germanium having different Si to Ge composition ratios.

[0024] As used herein and throughout the text, "Si" or "silicon" may be used interchangeably.

[0025] As used herein and throughout the text, "substrate" is intended to denote any part of a semiconductor or other electronic device such as a semiconductor wafer, or one or more layers located on or covering a substrate structure.

[0026] Where a range of values describes a parameter, all sub-ranges, point values, and endpoints within that range or defining a range are explicitly disclosed herein. All physical property, dimension, and ratio ranges, as well as sub-ranges (including endpoints) between the endpoints of those property, dimension, and ratio ranges, are considered to be explicitly disclosed herein.

[0027] The embodiments described herein are intended to relate to epitaxially grown SiGe and Si structures. However, the present invention can be applied to other growth modes.

[0028] Selective etching of SiGe with respect to Si will be described below, where the SiGe can preferably have a composition of Si with the balance being Ge between 40 atomic percent and 99 atomic percent; or a SiGe composition of Ge with the balance being Si between 1 atomic percent and 60 atomic percent; or a SiGe composition of Ge with a minimum Ge content of 15 atomic percent and the balance being Si.

[0029] The embodiments described below are for illustrative purposes only, and the present invention is not limited to the embodiments shown in the figures. It should be understood that the figures are not drawn to scale and that in some cases details unnecessary for understanding the embodiments, such as details of conventional manufacturing and assembly, are omitted. It should also be understood that the exact GAA device architecture, configurations of NW, NS, HNW, and HNS are not drawn to scale and that certain features are intentionally omitted in each figure to better illustrate various aspects of the etchant process in accordance with the principles of the present invention.

[0030] The embodiments are described with reference to the accompanying drawings, in which similar reference numerals denote similar elements. The relationships and functions of the various elements of the embodiments will be better understood through the following detailed description. This detailed description contemplates features, aspects, and embodiments in various arrangements and combinations as within the scope of this disclosure. This disclosure can therefore be specified to include any such combination and arrangement of these specific features, aspects, and embodiments, or one or more of them selected, consisting of or substantially consisting of any such combination and arrangement of these specific features, aspects, and embodiments, or one or more of them selected.

[0031] In a first embodiment of the invention, an improved dry etching process is provided for selectively etching SiGe relative to Si on a substrate. The etching process is performed by sequentially exposing the Si and SiGe surfaces with different gas compositions. This process achieves an etching selectivity greater than 150:1. Figure 1 The process scheme is described. As will now be explained, the etching process is performed using the following steps. A substrate is provided and loaded into the etching chamber. The substrate comprises one or more layers of SiGe and Si. The substrate is maintained at a temperature ranging from -60°C to +150°C. The etching process is preferably performed at a chamber pressure ranging from about 1 mTorr to about 10 Torr.

[0032] Next, a fluorinated halide compound gas is introduced into the etching chamber. Figure 1 (Step 1). By way of example and not intended to be limiting, the fluorinated interhalogen gas may include ClF3, ClF5, BrF3, BrF5, IF5, and IF7 or any combination thereof. Other gases may be introduced together with the fluorinated interhalogen gas. The flow rates of the fluorinated interhalogen gas and any other gases introduced therewith may each be in the range of 10 sccm to 2000 sccm.

[0033] The substrate is exposed to a fluorinated interhalogen compound gas. Specifically, the fluorinated interhalogen compound reacts with the silicon and silicon-germanium alloy layer to form a fluoride-terminated layer. The pressure in the chamber is then reduced. Figure 1 Step 2) enables the desorption of the Si and Ge fluoride layers. The exposed portions of Si and SiGe are in the form of volatile Si and Ge fluorides. An inert gas is introduced into the etching chamber to remove the desorbed Si and Ge fluorides from the etching chamber.

[0034] In addition to selectively etching the first portion of SiGe, the fluorinated interhalogen gas also transforms the silicon layer into a non-volatile fluorinated silicon layer. Specifically, as... Figure 2 As shown, a fluorine-terminated layer is formed on the surface of the Si layer. Any remaining residual fluorinated halide gas in the etching chamber can be recovered. The surface obtained after exposing the substrate to the fluorinated halide gas is shown. Figure 2middle.

[0035] Next, you can execute Figure 1 Step 3, thus... Figure 2 The resulting fluorinated Si surface is exposed to a passivation gas in contact with the non-volatile Si fluorinated layer. The passivation gas reacts with the non-volatile Si fluorinated layer to convert it into a passivated silicon layer. The passivated Si layer is formed only on the Si layer, not on the SiGe layer. The passivation layer obtained on Si is as follows... Figure 3 As shown.

[0036] Different passivation gases include, but are not limited to, NH3, H2O, O2, compounds with alcohol functional groups, H2S, H2Se, or any combination thereof. The passivation layer can be a layer of silicon oxide, silicon sulfide, silicon nitride, or silicon selenide, or any mixture thereof. The passivation layer may also contain additional carbon or hydrogen on its surface as self-assembling monomers or alkyl chains. The passivation layer may also include fluorosilicates, such as (NH4)2SiF6.

[0037] After the passivation layer is formed, it can be executed. Figure 1 Step 4, wherein the pressure in the etching chamber is reduced to below the pressure in step 3, and the chamber is purged or evacuated to remove any residual passivation compound from the etchant chamber.

[0038] After forming the Si passivation layer, and after removing the first portion of SiGe, it is possible to Figure 1 The fluorinated interhalogen gas used in step 1 is reintroduced into the etching chamber. This fluorinated gas selectively etches a second portion of the silicon-germanium alloy layer, which is then removed from the etching chamber, while the passivated silicon layer is essentially left unetched. Etching the second portion releases volatile silicon and germanium fluorides from the SiGe layer.

[0039] Execute sequentially and in a loop Figure 1 Steps 1, 2, 3, and 4 are performed until the SiGe layer has been etched to a predetermined amount (e.g., a desired distance or desired thickness). Alternatively, the entire SiGe layer can be completely removed.

[0040] When in Figure 1 Once it is confirmed in step 5 that the predetermined amount of SiGe has been etched, the final step 6 is performed to remove the passivation layer from the Si surface. The resulting product is horizontally stacked Si nanosheets (HNS).

[0041] During the etching process described above, the passivation gas is reintroduced in step 3 during the cyclic operation of steps 1 to 4. This may be necessary to rebuild the passivated silicon layer before selectively etching SiGe with a fluorinated interhalogen compound gas. However, it should be understood that the invention can be implemented by eliminating the reintroduction of the passivation gas. Methods for eliminating the reintroduction of the passivation gas may include, for example, determining that a substantial portion of the initially formed passivation layer has remained intact on the surface of the silicon layer; or determining that a sufficient amount of passivation layer remains after performing multiple selective etchings of SiGe, such that the SiGe to Si selectivity ratio remains sufficiently high to perform one or more additional SiGe etchings.

[0042] In a second embodiment of the invention, an improved dry etching process is provided for selectively etching SiGe and Si on a substrate. The etching process is performed by sequentially exposing the Si and SiGe surfaces with different gas compositions. This process achieves an etching selectivity greater than 150:1. Figure 4 The process plan is explained. Figure 4 Steps 1, 2, 3, and 4 Figure 1 The steps are the same. Therefore, refer to the first implementation scheme and Figure 2 and Figure 3 The discussion of steps 1, 2, 3 and 4 is hereby incorporated by reference.

[0043] However, with Figure 1 The flowcharts shown are different. Figure 4 The flowchart includes a distinct step 5, which involves subjecting the SiGe and passivated Si layers to a second etchant gas having different chemical properties than the fluorinated interhalogen compound gas introduced in step 1. The second etchant gas is introduced into an etching chamber to react with the silicon-germanium alloy layer. This second etchant gas etches a second portion of the silicon-germanium alloy layer, which is subsequently removed from the etching chamber as a second portion of volatile silicon and germanium fluorides, without substantially etching the passivated silicon layer. Examples of alternative etching chemicals that can be used in step 5 include fluorocarbons and hydrofluorocarbons, such as CF4, C4F8, C4F6, CH3F, or fluorinated compounds such as F2, XeF2, NF3, or any mixture of the foregoing. The second etchant gas is chosen to ensure preferential etching of SiGe on the passivated Si layer, thereby achieving an etching selectivity greater than 150:1. The purpose of choosing the second etchant gas is to achieve a higher etching selectivity compared to that provided by the etching chemicals used in step 1. Step 5 is performed cyclically until the SiGe layer has been etched to a predetermined amount (e.g., a desired distance or desired thickness). Alternatively, the entire SiGe layer can be removed completely.

[0044] When in Figure 1 Once step 5 determines that the predetermined amount of SiGe has been etched or the entire SiGe layer has been removed, the final step 6 is performed to remove the passivation layer from the Si surface. The resulting product is horizontally stacked Si nanosheets (HNS).

[0045] Figure 4 The process also considers reintroducing the passivation gas once or multiple times as needed to re-establish the passivation layer on the surface of the Si layer, thereby improving the etch selectivity of SiGe to Si to greater than 150:1. Alternatively, or in addition, if necessary, before achieving the predetermined amount of etching of SiGe, Figure 4 The process also considers repeating any or all of steps 1 through 4.

[0046] Other aspects of the invention, independent of the formation of the passivation layer, are contemplated. For example, during the formation of a SiGe layer on a substrate, the SiGe layer can be in-situ doped with an n-type or p-type dopant. Then, both surfaces of SiGe and Si are etched with a fluoride compound or an interhalogen compound. The dopant previously implanted in SiGe can improve the etch selectivity of SiGe to Si to greater than 150:1. The gaseous material used to generate the n-type or p-type dopant can be any compound containing atoms from Group 13 or 15 of the periodic table, and can include, but is not limited to, BF3, NF3, NH3, PH3, AsH3, PF3, PF5, AsF3, AsF5, B2H6, SbF5, dimethylaluminum chloride, trimethylgallium, trimethylaluminum, AlCl3, AlI3, GaCl3, GaI3, SbF3, Sb2O3, and trimethylantimony. The ranges of temperature, pressure, and flow rate are those disclosed above with respect to other embodiments.

[0047] In another example, the selective etchant process involves introducing an interhalogen compound gas and one or more additional gaseous substances into an etchant chamber to contact the SiGe and Si surfaces, and to increase the selective etching of SiGe compared to Si to a ratio greater than 150:1. The temperature, pressure, and flow rate ranges are those disclosed above with respect to other embodiments. The one or more additional gaseous substances can be rate inhibitors or rate enhancers, or a combination of either. Rate inhibitors reduce the etching rate on both the SiGe and Si surfaces, but the rate reduction on the Si surface is greater than the rate reduction on the SiGe surface, thus having the overall effect of increasing the selective etching of SiGe compared to Si. Conversely, rate enhancers increase the etching rate on both surfaces, but the rate increase on the SiGe surface is greater than the rate increase on the Si surface, thus having the overall effect of increasing the selective etching of SiGe compared to Si.

[0048] Different interhalogenated compound gases include, but are not limited to, ClF3, ClF5, BrF3, BrF5, IF5, and IF7, or any mixture thereof. Different rate-depressing gases include, but are not limited to, Cl2, Br2, I2, BCl3, HCl, HBr, HI, NCl3, and SF6, or any mixture thereof. Different rate-enhancing gases include, but are not limited to, F2, HF, XeF2, OF2, COF2, CF4, and NF3, or any mixture thereof.

[0049] Rate inhibitors reduce the etching rate on a Si surface to a greater extent than that on a SiGe surface, given a specific temperature and pressure. Achieving this greater reduction in Si etching rate compared to SiGe can be accomplished by introducing substances containing halogens such as Cl, Br, or I, which are less reactive to Si etching than fluorine. Unbound by any theoretical constraints, halogen-containing substances remain adsorbed on the Si surface and block sites for F atom adsorption. This effect can be more pronounced on Si surfaces compared to SiGe because fewer empty Si sites are available for adsorption due to the higher desorption rate of GeFx.

[0050] The role of rate-enhancing agents is to increase the etching rate of SiGe by a greater margin than that of Si at a given temperature and pressure. Without any theoretical constraints, the lattice spacing of Si-Ge compared to Si-Si allows for a similar increase to that of SiF. x Compared to desorption, GeF x It is easier for F atoms to desorb from the SiGe surface, thus providing more vacant sites for F atoms to adsorb onto the surface and combine with the surface Si-F material to form SiF. x The SiF x Then it can be desorbed from the surface. The rate-limiting step in the etching process of Si by interhalogen compounds can be SiF... x Desorption of the product.

[0051] For all disclosed embodiments, certain etching gases and accompanying co-current gases may be stored in and transported from a premixed storage container. Similarly, certain etching gas mixtures may be stored in and transported from a premixed storage container. Alternatively, each etchant gas may be stored in a separate storage container and then flowed into the etching chamber at a desired ratio via a separate flow manifold to generate the resulting mixture upstream of or inside the etchant chamber. Furthermore, external heat may be applied to one or more storage containers to generate sufficient driving force for transporting the etching gases from the one or more storage containers to the etching chamber. Additionally, a carrier gas may be bubbled through the storage container to carry the etchant gases, thereby enabling delivery to the etching chamber.

[0052] While all embodiments disclose methods for selectively etching SiGe and Si, the principles of the present invention can also be applied to selectively etching SiGe onto various other semiconductor compounds, including but not limited to Si, SiO2, SiC, Si3N4, or Si alloyed with elements other than Ge.

[0053] While certain embodiments believed to be part of the invention have been shown and described, it should be understood that modifications and changes to its form or details can be readily made without departing from the spirit and scope of the invention. Therefore, the invention is not limited to the exact forms and details shown and described herein, nor to anything within the entirety of the invention disclosed herein and claimed hereinafter.

Claims

1. A method for selectively dry etching a substrate, the method comprising the following sequential steps: A substrate is provided in an etching chamber, the substrate comprising a silicon-germanium alloy layer and a silicon layer; A fluorinated halide gas is introduced into the etching chamber; A first portion of the silicon-germanium alloy layer is selectively etched, and the first portion is subsequently removed from the etching chamber as a first portion of the volatilized silicon and germanium fluoride; The silicon layer is converted into a non-volatile fluorinated silicon layer; Recover any residual amount of the fluorinated interhalogen compound gas from the etching chamber; A passivation gas is introduced into the etching chamber to selectively convert the non-volatile fluorinated silicon layer into a passivated silicon layer, wherein the passivation gas does not react substantially with the silicon-germanium alloy layer. Recover any residual amount of the passivation gas from the etching chamber; The fluorinated interhalogen compound gas is reintroduced into the etching chamber; as well as A second portion of the silicon-germanium alloy layer is selectively etched, and the second portion is subsequently removed from the etching chamber as a second portion of volatile silicon and germanium fluorides, while the passivated silicon layer is substantially not etched.

2. The method of claim 1, further comprising repeating the step of reintroducing the fluorinated interhalogen compound gas into the etching chamber once or more to further react with the silicon-germanium alloy layer until a predetermined amount of the silicon-germanium alloy layer is selectively etched and subsequently removed from the etching chamber, without substantially etching the passivated silicon layer.

3. The method according to claim 2, further comprising the following step: When the predetermined amount of the silicon-germanium alloy layer has been selectively etched and subsequently removed from the processing chamber, the passivated silicon layer is removed to expose the silicon layer.

4. The method according to claim 1, wherein the passivating gas is selected from NH3, H2O, O2, compounds having alcohol functional groups, H2S, H2Se, and any combination thereof.

5. The method according to claim 1, wherein the passivated silicon layer is selected from silicon oxide, silicon sulfide, silicon nitride, silicon selenide, and fluorosilicate.

6. The method of claim 1, wherein the passivated silicon layer comprises introducing carbon or hydrogen as a self-assembling monomer or alkyl chain.

7. The method of claim 2, further comprising, prior to repeating the step of reintroducing the fluorinated interhalogen compound gas into the etching chamber once or more, reintroducing the passivation gas into the etching chamber to rebuild the passivated silicon layer.

8. The method of claim 1, further comprising, after converting the silicon layer into the non-volatile fluorinated silicon layer, and before introducing the passivation gas into the etching chamber, recovering the residual amount of the fluorinated interhalogen compound gas.

9. The method of claim 1, wherein the step of recovering the residual amount of the passivation gas is performed after the non-volatile fluorinated silicon layer is converted into the passivated silicon layer and before the fluorinated interhalogen compound gas is reintroduced into the etching chamber.

10. A method for selectively dry etching a substrate, the method comprising the following sequential steps: A substrate is provided in an etching chamber, the substrate comprising a silicon-germanium alloy layer and a silicon layer; A first etchant gas is introduced into the etching chamber, wherein the first etchant gas includes a fluorinated halide compound gas; A first portion of the silicon-germanium alloy layer is selectively etched, and the first portion is subsequently removed from the etching chamber as a first portion of the volatilized silicon and germanium fluoride; The silicon layer is converted into a non-volatile fluorinated silicon layer; Recover any residual amount of the fluorinated interhalogen compound gas from the etching chamber; A passivation gas is introduced into the etching chamber to selectively convert the non-volatile fluorinated silicon layer into a passivated silicon layer, wherein the passivation gas does not react substantially with the silicon-germanium alloy layer. Recover any residual amount of the passivation gas from the etching chamber; A second etchant gas is introduced into the etching chamber; as well as A second portion of the silicon-germanium alloy layer is selectively etched, and the second portion is subsequently removed from the etching chamber as a second portion of volatile silicon and germanium fluorides, while the passivated silicon layer is substantially not etched.

11. The method of claim 10, wherein the second etchant gas is selected from CF4, C4F8, C4F6, CH3F, F2, XeF2, NF3, and any combination thereof.

12. The method of claim 10, further comprising the step of: An additional amount of the second etchant gas is reintroduced into the etching chamber to further react with the silicon-germanium alloy layer until a predetermined amount of the silicon-germanium alloy layer is selectively etched without substantially etching the passivated silicon layer.

13. The method of claim 12, further comprising the step of: The passivated silicon layer is removed when the predetermined amount of the silicon-germanium alloy layer is selectively etched and subsequently removed from the etching chamber.

14. The method of claim 12, further comprising, prior to the step of reintroducing the additional amount of the second etchant gas into the etching chamber to rebuild the passivated silicon layer.

15. The method of claim 10, further comprising, after converting the silicon layer into the non-volatile fluorinated silicon layer, and before introducing the passivation gas into the etching chamber, recovering the residual amount of the fluorinated interhalogen compound gas.

16. The method of claim 10, further comprising recovering the residual amount of the passivation gas after converting the non-volatile fluorinated silicon layer into the passivated silicon layer and before introducing the second etchant gas into the etching chamber.

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