Systems and methods for selectively etching films

Abstract

A method for pre-cleaning a substrate includes supporting a substrate having silicon oxide on its surface within a reaction chamber of a semiconductor processing system, and allowing a halogen-containing reactant and a hydrogen-containing reactant to flow into the reaction chamber. A first pre-cleaning material is formed on the surface of the substrate from a first portion of the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide. Additional halogen-containing reactant is allowed to flow into the reaction chamber, but additional hydrogen-containing reactant is not allowed to flow into the reaction chamber, and a second pre-cleaning material is formed on the surface of the substrate from a second portion of the additional halogen-containing reactant and the silicon oxide. Methods for forming structures on a substrate and semiconductor processing systems are also described.

Description

Technical Field

[0001] This disclosure generally relates to pre-cleaned substrates. More specifically, this disclosure relates to pre-cleaned substrates and the formation of structures on pre-cleaned substrates, such as during semiconductor device manufacturing. Prior Technology

[0002] Material layers are commonly deposited onto substrates during the fabrication of semiconductor devices, such as integrated circuits and power electronic components. For example, amorphous, polycrystalline, or monocrystalline material layers can be deposited onto semiconductor substrates, such as silicon wafers. These material layers are generally deposited using physical techniques (such as sputtering) or chemical techniques (such as chemical vapor deposition or atomic layer deposition). Monocrystalline material layers are typically deposited using epitaxial growth techniques.

[0003] During the formation of material layers, intermediary materials formed on the substrate surface can interfere with the deposition of the material layer onto the substrate. For example, native oxides present on the substrate surface can cause defects to develop within the material layer during deposition onto the substrate. Intermediary materials can form on the substrate surface due to exposure to oxygen during substrate handling, as can occur during substrate transfer between various manufacturing systems. Intermediary materials can also form on the substrate surface upon exposure to residual oxidants, which may be present in some manufacturing systems. Such intermediary materials may need to be removed before the desired material layer is deposited onto the substrate surface.

[0004] Such methods and systems are generally considered suitable for their intended purpose. However, there remains a need in the art for improved pre-cleaning methods, methods for forming structures on substrates, and semiconductor processing systems. This disclosure provides a solution to this need. Summary of the Invention

[0005] A method for pre-cleaning a substrate is provided. The method includes supporting a substrate in a reaction chamber of a semiconductor processing system, the substrate having silicon oxide on its surface. A halogen-containing reactant and a hydrogen-containing reactant are flowed into the reaction chamber. A first pre-cleaning material is formed on the surface of the substrate from the halogen-containing reactant, the hydrogen-containing reactant, and a first portion of the silicon oxide. Additional halogen-containing reactant is flowed into the reaction chamber without additional hydrogen-containing reactant flowing into the reaction chamber, and a second pre-cleaning material is formed on the surface of the substrate from the additional halogen-containing reactant and a second portion of the silicon oxide.

[0006] In some instances, the method may include epitaxially depositing a silicon-containing material layer onto a pre-cleaned surface of the substrate.

[0007] In some instances, flowing the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber may include flowing anhydrous hydrogen fluoride (HF) together with at least one of ammonia (NH3), hydrazine (N2H4), methanol (CH3OH), isopropanol (C3H8O), or acetic acid (C2H4O2) into the reaction chamber.

[0008] In some instances, allowing the additional halogen-containing reactant to flow into the reaction chamber may include allowing anhydrous hydrogen fluoride (HF) to flow into the reaction chamber without allowing the additional hydrogen-containing reactant to flow into the reaction chamber.

[0009] In some instances, the formation of the first pre-cleaning material may include ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O) formed from the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate.

[0010] In some instances, the formation of the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide may include the formation of silicon fluoride (SiF4) and water (H2O) from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate.

[0011] In some instances, the method may include, after the formation of the second pre-cleaning material from the additional halogenated reactant and the silicon oxide on the surface of the substrate, sublimating the first pre-cleaning material from the surface of the substrate.

[0012] In some instances, the substrate may be a patterned substrate having two or more recesses or grooves having a high aspect ratio.

[0013] In some instances, forming the second pre-cleaning material may include using water (H2O) formed during the formation of the first pre-cleaning material to initiate the formation of the second pre-cleaning material.

[0014] In some instances, the method may include flowing an inert gas into the reaction chamber before the additional halogenated reactant flows into the reaction chamber, and after the formation of the first pre-cleaning material from the halogenated reactant and the hydrogen-containing reactant.

[0015] In some instances, the method may include scavenging residual halogen-containing reactants from the reaction chamber before allowing the additional halogen-containing reactant to flow into the reaction chamber.

[0016] In some instances, the method may include scavenging residual hydrogen-containing reactants from the reaction chamber before allowing the additional halogen-containing reactant to flow into the reaction chamber.

[0017] In some instances, forming the first pre-cleaning material may include etching the silicon oxide to a first depth; forming the second pre-cleaning material may include etching the silicon oxide to a second depth; and the ratio of the second depth to the first depth may be between about 2:1 and about 50:1, or between about 3:1 and about 30:1, or between about 5:1 and about 20:1.

[0018] In some instances, the method may include terminating the formation of the first pre-cleaning material by rinsing the reaction chamber before allowing the additional halogenated reactant to flow into the reaction chamber.

[0019] The provided method is a method for forming a structure. The method includes pre-cleaning a substrate using a pre-cleaning method as described above. The substrate is a patterned substrate having two or more recesses or trenches having a high aspect ratio. Following the formation of a second pre-cleaning material from an additional halogen-containing reactant and silicon oxide on the surface of the substrate, a first pre-cleaning material is sublimated from the surface of the substrate. Following the sublimation of the first pre-cleaning material from the surface of the substrate, a silicon-containing material layer is epitaxially deposited onto the surface of the substrate.

[0020] In some instances, flowing the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber may include flowing anhydrous hydrogen fluoride (HF) and ammonia (NH3) into the reaction chamber. Flowing the additional halogen-containing reactant into the reaction chamber may include flowing anhydrous hydrogen fluoride (HF) into the reaction chamber without flowing the additional hydrogen-containing reactant into the reaction chamber.

[0021] In some instances, forming the first pre-cleaning material may include forming ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O) from the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate. Forming the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide may include forming silicon fluoride (SiF4) and water (H2O) from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate.

[0022] A semiconductor processing system is provided. The semiconductor processing system includes a gas system configured to flow a halogen-containing reactant and a hydrogen-containing reactant into a reaction chamber; a reaction chamber connected to the gas system and configured to support a substrate having silicon oxide on its surface; and a controller. The controller is operatively associated with the gas system and the reaction chamber. The controller further responds to instructions recorded on a non-transitory machine-readable medium to support the substrate in the reaction chamber, the substrate having silicon oxide on its surface; flow the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber; and form a first pre-cleaning material from a first portion of the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate. The instruction further causes the controller to allow additional halogenated reactants to flow into the reaction chamber without additional hydrogen-containing reactants; and to form a second pre-cleaning material on the surface of the substrate from the additional halogenated reactants and a second portion of the silicon oxide.

[0023] In some instances, the instructions may further cause the controller to allow anhydrous hydrogen fluoride (HF) and ammonia (NH3) to flow into the reaction chamber to form the first pre-cleaning material, and to allow additional anhydrous hydrogen fluoride (HF) to flow into the reaction chamber without allowing additional ammonia to flow into the reaction chamber.

[0024] In some instances, the instructions may further cause the controller to form ammonium hexafluorosilate ((NH4)2SiF6) as the first pre-cleaning material from the halogen-containing reactant, the hydrogen-containing reactant, and the silica on the surface of the substrate, together with water (H2O); terminate the formation of ammonium hexafluorosilate ((NH4)2SiF6) by rinsing the reaction chamber before allowing additional anhydrous hydrogen fluoride (HF) to flow into the reaction chamber; form silicon fluoride (SiF4) as the second pre-cleaning material from the additional halogen-containing reactant and the silica on the surface of the substrate, together with water (H2O); and subsequently, after the formation of silicon fluoride (SiF4) on the surface of the substrate using the additional anhydrous hydrogen fluoride (HF) and silica, sublimate ammonium hexafluorosilate ((NH4)2SiF6) from the surface of the substrate.

[0025] This invention provides a simplified overview of a series of concepts. These concepts are further described in detail in the following exemplary embodiments disclosed herein. This invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Simple Explanation of the Diagram

[0026] The following description will use drawings, which are intended to illustrate rather than limit the invention, to describe these and other features, features, and advantages of the invention disclosed herein.

[0027] Figure 1 is a schematic view of a semiconductor processing system according to the present disclosure, showing a reaction chamber operatively associated with a controller, and the reaction chamber being configured to pre-clean a substrate supported within the reaction chamber; Figures 2 to 4 are block diagrams of a method for pre-cleaning a substrate according to the present disclosure, showing the operation of the method according to illustrative and non-limiting examples; Figures 5A to 5D are cross-sectional side views of a substrate having silicon oxide on its surface, showing, in sequence, the silicon oxide being removed from the surface of the substrate according to illustrative and non-limiting examples of the method; Figure 6 is a block diagram of a method for forming a structure on a substrate according to the present disclosure, showing the operation of the method according to illustrative and non-limiting examples of the method; and Figures 7A to 7E are cross-sectional side views of a patterned substrate having silicon oxide on its surface, showing, in sequence, the silicon oxide being removed from the substrate and a silicon-containing material layer being formed on the substrate.

[0028] It should be understood that the elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the relative size of some elements in the drawings may be exaggerated relative to other elements to help improve the understanding of the illustrated embodiments of this disclosure. Implementation

[0029] The similar structural features or forms disclosed herein are now identified by reference to the accompanying drawings, with similar element symbols. For purposes of explanation and illustration, and not limitation, partial views of examples of semiconductor processing systems according to this disclosure are shown in FIG1 and are generally designated by reference character 100. As will be described, FIG2 through 7E provide other examples of semiconductor processing systems, methods for pre-cleaning substrates, and methods for forming structures on pre-cleaned substrates according to this disclosure or its forms. The systems and methods disclosed herein can be used to remove silicon oxide from the surface of a patterned substrate during semiconductor device manufacturing, such as during the manufacturing of integrated circuit semiconductor devices on patterned substrates having high aspect ratio trenches, although this disclosure is not limited to any particular type of patterned substrate or the manufacturing of semiconductor devices in general.

[0030] Referring to FIG1, a semiconductor processing system 100 is shown. The semiconductor processing system 100 includes a reaction chamber 102, a transfer tube 104, and a remote plasma unit 106. The semiconductor processing system 100 also includes a halogen-containing reactant source 108, a hydrogen-containing reactant source 110, and a carrier / purging gas source 112. The semiconductor processing system 100 further includes a controller 114. While FIG1 shows and describes a specific type of semiconductor processing system, namely a plasma-enhanced chemical vapor deposition (CVD) system, it will be understood and appreciated that other types of CVD systems, such as atmospheric CVD systems and atomic layer deposition (ALD) systems, may also benefit from this disclosure.

[0031] The reaction chamber 102 includes a base 116, a spray head 118, and a reaction chamber gas inlet 120. The base 116 is disposed within the interior 122 of the reaction chamber 102 and configured to support a substrate 10, such as a silicon wafer formed from a semiconductor material. The spray head 118 is disposed within the interior 122 of the reaction chamber 102, between the reaction chamber gas inlet 120 and the base 116, and configured to distribute gas received at the reaction chamber gas inlet 120 to the surface 12 of the substrate 10. The reaction chamber gas inlet 120 couples the interior 122 of the reaction chamber 102 to a transfer tube 104.

[0032] The transfer tube 104 includes a reaction chamber end 124, a remote plasma unit end 126, and a transfer tube gas inlet 128. The reaction chamber end 124 of the transfer tube 104 is connected to the reaction chamber 102 and is in fluid communication with the reaction chamber gas inlet 120. The transfer tube gas inlet 128 is disposed between the reaction chamber end 124 and the remote plasma unit end 126 of the transfer tube 104 and is connected to at least one of a halogen-containing reactant source 108, a hydrogen-containing reactant source 110, and a carrier / purging gas source 112. The remote plasma unit end 126 of the transfer tube 104 is connected to a remote plasma unit 106 and fluidly couples the remote plasma unit 106 to the reaction chamber 102.

[0033] The distal plasma unit 106 includes an inlet 130 and an outlet 132. The outlet 132 of the distal plasma unit 106 is connected to the distal plasma unit end 126 of the transfer tube 104. The inlet 130 of the distal plasma unit 106 is connected to at least one of a halogen-containing reactant source 108, a hydrogen-containing reactant source 110, and / or a carrier / purging gas source 112. It is envisioned that the distal plasma unit 106 is configured to activate the fluid received at the inlet 130, and the activated fluid is provided to the reaction chamber 102 through the outlet 132 and via the transfer tube 104.

[0034] A halogen-containing reactant source 108 is connected to reaction chamber 102 (e.g., via inlet 130 of remote plasma unit 106 and / or transfer tube gas inlet 128) and contains halogen-containing reactant 14. A hydrogen-containing reactant source 110 is also connected to reaction chamber 102 (e.g., also via inlet 130 of remote plasma unit 106 and / or transfer tube gas inlet 128) and contains hydrogen-containing reactant 16. A carrier / purging gas source 112 is further connected to reaction chamber 102 (e.g., further via inlet 130 of remote plasma unit 106 and / or transfer tube gas inlet 128) and contains carrier / purging gas 18. In some instances, the halogen-containing reactant 14 includes fluorine (F), such as diatomic fluorine (F2), fluorine precursors, or anhydrous hydrogen fluoride (HF). According to some instances, the hydrogen-containing reactant 16 may include ammonia (NH3), hydrazine (N2H4), alcohols, or acids. Suitable examples of alcohols include methanol (CH3OH) and isopropanol (C3H8O). Suitable examples of acids include acetic acid (C2H4O2). The carrier / purging gas 18 may include nitrogen (N2), argon (Ar), helium (He), hydrogen (H2), krypton (Kr), or mixtures thereof.

[0035] As explained above, in some semiconductor processing systems, chemicals used to pre-clean the substrate before depositing a material layer onto the substrate can be self-limiting. For example, certain chemicals can create one or more intermediate reaction products that slow down (or terminate) the reaction (or multiple reactions), which are operable to remove silicon oxide from the substrate surface. Certain chemicals can also interact with the substrate topology (such as a patterned substrate with trenches), and because the intermediate reaction products tend to accumulate in the trenches, silicon oxide removal tends to slow down (or stop) within the trenches, which may occur before other parts of the substrate, potentially leading to uneven silicon oxide removal across the wafer. To limit (or eliminate) the effect that such intermediate reaction products may have on the removal of silicon oxide (e.g., silicon oxide 20 (shown in FIG. 5A)) from the surface of substrate 10, controller 114 has instructions to limit the formation of intermediate reaction products during silicon oxide removal from the substrate.

[0036] Controller 114 is operatively connected to semiconductor processing system 100 and includes processor 134, device interface 136, user interface 138, and memory 140. Device interface 136 connects processor 134 to one or more of reaction chamber 102, remote plasma unit 106, halogen-containing reactant source 108, hydrogen-containing reactant source 110, and / or carrier / purging gas source 112, for example, via wired or wireless connection. Processor 134 is operatively connected to user interface 138, for example, to receive user input and / or provide output to a user, and is configured to communicate with memory 140. Memory 140 includes a non-transitory machine-readable medium having a plurality of program modules 142 written thereon. The plurality of program modules 142 include instructions that, when read by processor 134, cause processor 134 to perform some operation. Among these operations is a pre-cleaning method 200 for removing silicon oxide from the surface of a substrate, for example, removing silicon oxide 20 (shown in FIG. 5A) from the surface 12 (shown in FIG. 5A) of the substrate 10.

[0037] Referring to Figures 2 and 5A to 5D, method 200 is illustrated. As shown in block 210, a substrate 10 (shown in Figure 5A) is first supported in a reaction chamber (e.g., reaction chamber 102 (shown in Figure 1)), which has silicon oxide 20 (shown in Figure 5A) on its surface 12 (shown in Figure 5A). Then, a halogen-containing reactant 14 (shown in Figure 5B) and a hydrogen-containing reactant 16 (shown in Figure 5B) are flowed into the reaction chamber, as shown in block 220, and a first pre-cleaning material 22 (shown in Figure 5B) is formed from a first portion 24 of the halogen-containing reactant 14, the hydrogen-containing reactant 16, and the silicon oxide 20, as shown in block 230. Subsequently, additional halogen-containing reactant 26 (shown in FIG. 5D) is allowed to flow into the reaction chamber without additional hydrogen-containing reactant, as shown in block 240, and a second pre-cleaning material 28 (shown in FIG. 5D), as shown in block 250, is formed from the additional halogen-containing reactant 26 and the second portion 30 of silicon oxide 20 (shown in FIG. 5A). Advantageously, allowing the additional halogen-containing reactant 26 to flow into the reaction chamber without additional hydrogen-containing reactant allows the second portion 30 of silicon oxide 20 to be removed without forming additional first pre-cleaning material. This limits the amount of first pre-cleaning material formed, limiting (or eliminating) the tendency of the first pre-cleaning material 22 to slow down (or stop) the removal of silicon oxide 20.

[0038] In some instances, blocks 220 to 250 of method 200 may be repeated one or more times, as indicated by arrow 260. As those skilled in the art will understand from this disclosure, repeating blocks 220 to 250 allows tuning the ratio of silicon oxide removed during the formation of the first pre-cleaning material 22 and the second pre-cleaning material 28, allowing tuning of the pre-cleaning method 200. For example, the amount of hydrogen-containing reactant 16 flowing with the halogen-containing reactant 14 may be adjusted according to the effect that the first pre-cleaning material 22 may have on the reaction and / or the role that additional reaction products generated with the first pre-cleaning material may play in the formation of the second pre-cleaning material 28.

[0039] Referring to Figure 3 and continuing to Figures 5A through 5D, the operation of method 200 is illustrated according to some examples. In some examples, silicon oxide 20 (shown in Figure 5A) may be etched during the formation of the first pre-cleaning material 22 (shown in Figure 5B), as shown in block 232. In such examples, the etching process used to form the first pre-cleaning material 22 removes a first portion 24 (shown in Figure 5A) of silicon oxide 20 by the reaction between the first halogen-containing reactant 14 (shown in Figure 5B) and the hydrogen-containing reactant 16 (shown in Figure 5B) and the silicon oxide 20. As shown in block 252, silicon oxide 20 may be etched during the formation of the second pre-cleaning material 28 (shown in Figure 5D). In such instances, the etching process used to form the second pre-cleaning material 28 removes the second portion 30 (shown in Figure 5A) of the silicon oxide 20 by reacting an additional halogen-containing reactant 26 (shown in Figure 5D) with the silicon oxide 20 located below the first portion 24 of the silicon oxide 20.

[0040] As shown in block 254, silicon oxide 20 can be etched at a predetermined ratio during the formation of the first pre-cleaning material 22 and the second pre-cleaning material 28. For example, the ratio of the thickness of the second silicon oxide removed during the formation of the second pre-cleaning material 28 to the thickness of the first silicon oxide removed during the formation of the first pre-cleaning material 22 can be greater than 1. In some instances, the predetermined etching ratio can be between about 2:1 and about 50:1, or between about 3:1 and about 30:1, or between about 5:1 and about 20:1. Advantageously, etching ratios within these ranges allow the use of reaction products generated during the formation of the first pre-cleaning material 22 to initiate the reaction for forming the second pre-cleaning material 28 (shown in FIG. 5D), while limiting the effect that the removal of the second portion 30 (shown in FIG. 5A) of silicon oxide 20 may have under other circumstances by the first pre-cleaning material 22. For example, as shown in block 280, water (H2O) 32 (shown in FIG. 5C) formed during the formation of the first pre-cleaning material 22 can be used to initiate the reaction between the additional halogenated reactant 26 (shown in FIG. 5D) and the second portion 30 of silicon oxide 20 (shown in FIG. 5A), which is then self-sustaining using further water (H2O) 34 (shown in FIG. 5D) generated during the reaction of the additional halogenated reactant 26 and the second portion 30 of silicon oxide 20.

[0041] As shown in bracket 270, in some instances, method 200 may include terminating the flow of hydrogen-containing reactant 16 (shown in FIG. 5B) into the reaction chamber. In some instances, the reaction chamber may subsequently be flushed, for example using the flow of carrier / flushing gas 18 (shown in FIG. 1), as shown in block 272. According to some instances, the carrier / flushing gas 18 may be flowed into the reaction chamber before additional halogen-containing reactant 26 (shown in FIG. 5D) is flowed into the reaction chamber, as shown in block 274. It is contemplated that, according to some instances, residual halogen-containing reactants residing in the reaction chamber from halogen-containing reactant 14 (shown in FIG. 5B) introduced during the formation of the first pre-cleaning material 22 (shown in FIG. 5B) may be purged from the reaction chamber, for example using carrier / flushing gas 18 and / or additional halogen-containing reactant 26, as shown in block 276. It is also envisioned that, in a further embodiment, residual hydrogen-containing reactants residing in the reaction chamber from the hydrogen-containing reactant 16 (shown in FIG. 5B) introduced during the formation of the first pre-cleaning material 22 (shown in FIG. 5B) can be removed, for example, using a carrier / purging gas 18 and / or additional halogen-containing reactant 26, as shown in block 278. As those skilled in the art will understand from this disclosure, removing residual hydrogen-containing reactants from the reaction chamber limits (or eliminates) the influence that such hydrogen-containing reactants might have on the reaction used to form the second pre-cleaning material 28 (shown in FIG. 5D) under other conditions, providing control over the pre-cleaning operation.

[0042] Referring to Figure 4, method 200 is illustrated according to an example using hydrogen fluoride (HF) and ammonia (NH3). As shown in block 210, substrate 10 (shown in Figure 5A) is supported within a reaction chamber (e.g., reaction chamber 102 (shown in Figure 1)). Halogen-containing reactant 14 (shown in Figure 5B) and hydrogen-containing reactant 16 (shown in Figure 5B) are flowed into the reaction chamber, as shown in block 220. As shown in block 222, it is contemplated that halogen-containing reactant 14 comprises hydrogen fluoride (HF). As shown in block 224, it is also contemplated that hydrogen-containing reactant 16 comprises ammonia (NH3). In some examples, halogen-containing reactant 14 and hydrogen-containing reactant 16 may consist essentially of anhydrous hydrogen fluoride (HF) and ammonia (NH3). According to some examples, halogen-containing reactant 14 and hydrogen-containing reactant 16 may consist of anhydrous hydrogen fluoride (HF) and ammonia (NH3).

[0043] As shown in block 230, the first pre-cleaning material 22 (shown in FIG. 5B) is formed from the first portion 24 (shown in FIG. 5A) of the halogen-containing reactant 14, the hydrogen-containing reactant 16, and silicon oxide 20 (shown in FIG. 5A). More specifically, anhydrous hydrogen fluoride (HF) reacts with ammonia (NH3) and the first portion 24 of silicon oxide 20 to form ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O)32 (shown in FIG. 5C), as shown in blocks 234 and 236. It is believed, without being limited to any particular theory or operating mode, that anhydrous hydrogen fluoride (HF) reacts with ammonia (NH3) to form ammonium fluoride (NH4F). Ammonium fluoride (NH4F) then removes the first part 24 of silicon oxide 20 by reacting with silicon oxide to form ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O) remaining on the surface of silicon oxide.

[0044] As those skilled in the art will understand from this disclosure, a film formed from ammonium hexafluorosilate ((NH4)2SiF6) can restrict access to the silicon oxide substrate. As the film formed from ammonium hexafluorosilate ((NH4)2SiF6) thickens, access becomes increasingly restricted, potentially slowing down (or stopping) the reaction, as explained above. To limit (or eliminate) the tendency of the film formed from ammonium hexafluorosilate ((NH4)2SiF6) to slow down (or stop) the reaction, it is conceivable to stop the flow of ammonia (NH3) to the reaction chamber. Subsequently, additional anhydrous hydrogen fluoride (HF) is flowed into the reaction chamber without additional ammonia (NH3), as shown in blocks 240 and 242, whereby water (H2O) generated during the formation of the first pre-cleaning material initiates the reaction between the additional anhydrous hydrogen fluoride (HF). In this regard, it has been envisioned that the additional hydrogen fluoride (HF) can be used in the reaction chamber in the form of surface-adsorbed water (H2O) molecules, surface water (H2O), or water (H2O) vapor.

[0045] As shown in block 250, additional anhydrous hydrogen fluoride (HF) reacts with the second portion 30 (shown in Figure 5A) of silicon oxide 20 (shown in Figure 5A) to form a second pre-cleaning material 28 (shown in Figure 5D) and additional water (H2O) 34 (shown in Figure 5D). In this respect, the water (H2O) 32 formed together with the formation of the first pre-cleaning material 22 acts to initiate the reaction between the additional anhydrous hydrogen fluoride (HF) and the second portion 30 of silicon oxide 20, forming additional silicon tetrafluoride (SiF4) and additional water (H2O) 34 as the second pre-cleaning material 28, as shown in blocks 256 and 258. In this respect, the water (H2O) 32 is operable to dissociate the hydrogen fluoride (HF) into H+ and F- cations and anions, respectively, initiating the removal of the second portion 30 of silicon oxide 20. In some instances, additional silicon tetrafluoride (SiF4) is formed in the absence of ammonia (NH3). The silicon tetrafluoride (SiF4) remains as a gas, and therefore the reaction is not slowed down (or stopped) during the reaction by further restricting access to the silicon oxide 20 located on the surface 12 of the substrate 10 and below the first pre-cleaning material 22.

[0046] In some instances, one or more of the halogen-containing reactants, hydrogen-containing reactants, and / or additional halogen-containing reactants may be activated by a plasma source. For example, one or more of anhydrous hydrogen fluoride (HF), ammonia (NH3), and / or additional anhydrous hydrogen fluoride (HF) may be activated by a distal plasma unit (e.g., distal plasma unit 106 (shown in Figure 1)) to generate one or more activated reactant species, such as charged ions, and / or neutral atoms, and / or free radicals. According to some instances, one or more of the halogen-containing reactants, hydrogen-containing reactants, and / or additional halogen-containing reactants may not be activated by a plasma source. It is also contemplated that a carrier gas may be included together with one or more of the halogen-containing reactants, hydrogen-containing reactants, and / or additional halogen-containing reactants flowing into the reaction chamber. In some instances, the carrier gas may be activated by a plasma source. According to some instances, the carrier gas may not be activated by a plasma source.

[0047] Referring to Figures 6 and 7A through 7E, a method 300 for forming a structure (e.g., an integrated circuit semiconductor device 36 (shown in Figure 7E)) is illustrated. As shown in block 310, a substrate (e.g., substrate 38 (shown in Figure 7A)) is supported in a reaction chamber, such as reaction chamber 102 (shown in Figure 1). In some embodiments, a pattern 40 (shown in Figure 7A) may be defined on the surface of substrate 38, as shown in block 312. According to some embodiments, substrate 38 may have a plurality of trenches 42 (e.g., trenches 42 (shown in Figure 7A)) defined on the surface of the substrate, as shown in block 314. In some embodiments, the plurality of trenches 42 may have a high aspect ratio. For example, the plurality of trenches 42 may each have a depth greater than its width. In some instances, high aspect ratios include depth-to-width ratios between approximately 2:1 and approximately 50:1, or between approximately 10:1 and approximately 40:1, or between approximately 25:1 and approximately 40:1.

[0048] As indicated in parentheses, once supported in the reaction chamber, the substrate 38 is pre-cleaned, for example, to remove silicon oxide 46 from the substrate 38 and at least partially disposed within the pattern 40. A pre-cleaning method 300 is envisioned for cleaning the substrate 38. In this regard, it is envisioned that halogen-containing reactant 14 (shown in FIG. 7B) and hydrogen-containing reactant 16 (shown in FIG. 7B) flow into the reaction chamber, as shown in block 320. Once in the reaction chamber, halogen-containing reactant 14 and hydrogen-containing reactant 16 react with a first portion 44 (shown in FIG. 7A) of silicon oxide 46 to form a first pre-cleaned material 48 (shown in FIG. 7B), as shown in block 330. Then, additional halogen-containing reactant 26 (shown in FIG. 7C) is flowed into the reaction chamber without additional hydrogen-containing reactant, as shown in block 340, and a second pre-cleaning material 50 is formed on the surface of substrate 38 using the additional halogen-containing reactant 26 and a second portion 52 of silicon oxide 46 (shown in FIG. 7A), as shown in block 350.

[0049] As shown in block 360, the first pre-cleaning material 48 is then removed from the surface of the substrate 38. It is envisioned that the first pre-cleaning material 48 is sublimated from the surface of the substrate, for example, by heating the substrate, as shown in FIG7D. As shown in block 370, a silicon-containing layer 54 is then epitaxially deposited onto the pre-cleaned surface of the substrate 38. In some instances, the silicon-containing layer 54 may be a silicon layer. According to some instances, the silicon-containing layer 54 may include germanium. It is also envisioned that, according to some instances, the silicon-containing layer 54 may include dopants, such as n-type or p-type dopants. The silicon-containing layer 54 may be deposited in another reaction chamber, for example, by transferring the substrate 38 from reaction chamber 102 (shown in FIG1) to another reaction chamber of the semiconductor processing system 100 (shown in FIG1) once pre-cleaned.

[0050] Prior to certain deposition operations (e.g., epitaxial deposition of silicon layers), native oxides on silicon and silicon-germanium surfaces may need to be cleaned and / or removed for use in high-quality epitaxial films. The need for cleaning can be particularly acute at technology nodes employing high aspect ratios and / or different dielectric films on patterned substrates or wafers. For example, native oxides on the bottom surface and sidewalls of deep trenches may require complete cleaning. Low-k dielectric materials can limit the use of certain types of etching processes, such as some plasma etching processes and chemicals. Cleaning chemicals may need to be highly selective for the various dielectric films located on the patterned substrate.

[0051] In some examples described herein, a catalyst is used to initiate the etching process, and subsequently, an etchant is used to perform the etching after the initiation of the etching process. According to some examples, relatively small amounts of anhydrous hydrogen fluoride (HF) and ammonia (NH3) are co-flowed into the reaction chamber (e.g., for a relatively short period of time) and a limited amount of silicon oxide to be cleaned is removed during the cleaning process. In further examples, the anhydrous hydrogen fluoride (HF) and ammonia (NH3) are then flushed from the reaction chamber, for example, using an inert gas such as argon (Ar). It is envisioned that additional anhydrous hydrogen fluoride (HF) will then be introduced into the reaction chamber, and additional silicon oxide will subsequently be removed from the substrate, for example, by removing a second, larger portion of the silicon oxide from the substrate.

[0052] Advantageously, as will be understood by way of this application, in cases where byproducts of a catalyst-initiated reaction can act to continue the reaction, self-cleaning of silicon oxide from the substrate does not require a continuous supply of catalyst. For example, in cases where surface moisture and / or water (H2O) generated by a catalyst-assisted reaction is sufficient to continue subsequent etching using additional etchant without an additional catalyst. This can be particularly advantageous where high-k dielectric materials on the substrate surface may be damaged by the catalyst or intermediate reaction media generated by the catalyst. For example, in some instances, very limited amounts of reaction byproducts (such as ammonium hexafluorosilicate (NH4)2SiF6) are generated, promoting high aspect ratio pre-cleaning by limiting the tendency of such materials to fill trenches on the substrate and, in other cases, preventing the lower portions of the trenches from being cleaned. Limiting the formation of such reaction byproducts can also improve selectivity for other films on the substrate surface, such as SiN, SiOC, and / or Al2O3 films.

[0053] While this disclosure has been provided in the context of some embodiments and examples, those skilled in the art will understand that this disclosure extends beyond the specifically described embodiments to other alternative embodiments, and / or uses of such embodiments, and obvious modifications and equivalents thereof. Furthermore, although several variations of the embodiments of this disclosure have been shown and described in detail, those skilled in the art will understand other modifications within the scope of this disclosure based on this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and styles of the embodiments can be made, and still fall within the scope of this disclosure. It should be understood that the various features and styles of the disclosed embodiments can be combined or substituted with each other to form variations of the embodiments of this disclosure. Therefore, it is intended that the scope of this disclosure should not be limited to the specific embodiments described above.

[0054] The headings provided herein (if any) are for convenience only and do not necessarily affect the scope or significance of the apparatus and methods disclosed herein.

[0055] 10: Substrate

[0056] 12: Surface

[0057] 14: Halogen-containing reactants

[0058] 16: Hydrogen-containing reactants

[0059] 18: Carrier / Purge Gas

[0060] 20: Silicon oxide

[0061] 22: First pre-cleaning material

[0062] 24: Part One

[0063] 26: Additional halogenated reactants

[0064] 28: Second pre-cleaning material

[0065] 30: Part Two

[0066] 32: Water

[0067] 34: Water

[0068] 36: Semiconductor devices

[0069] 38: Substrate

[0070] 40: Pattern

[0071] 42: Trench

[0072] 44: Part One

[0073] 46: Silicon oxide

[0074] 48: First pre-cleaning material

[0075] 50: Second pre-cleaning material

[0076] 52: Part Two

[0077] 54: Silicon-containing layer

[0078] 100: Semiconductor Processing System

[0079] 102: Reaction Chamber

[0080] 104: Transfer tube

[0081] 106: Remote Plasma Unit

[0082] 108: Halogen-containing reactant source

[0083] 110: Hydrogen-containing reactant source

[0084] 112: Carrier / Purge Gas Source

[0085] 114: Controller

[0086] 116: Base

[0087] 118: Sprayer Head

[0088] 120: Gas inlet to the reaction chamber

[0089] 122: Internal

[0090] 124: Reaction chamber end

[0091] 126: Remote plasma unit end

[0092] 128: Gas inlet of transfer tube

[0093] 130: Entrance

[0094] 132: Export

[0095] 134: Processor

[0096] 136: Device Interface

[0097] 138: User Interface

[0098] 140: Memory

[0099] 142: Program Module

[0100] 200: Method

[0101] 210: Square

[0102] 220: Square

[0103] 222: Square

[0104] 224: Square

[0105] 230: Square

[0106] 232: Square

[0107] 234: Square

[0108] 236: Square

[0109] 240: Square

[0110] 242: Square

[0111] 250: Square

[0112] 252: Square

[0113] 254: Square

[0114] 256: Square

[0115] 258: Square

[0116] 260: Arrow

[0117] 270: brackets

[0118] 272: Square

[0119] 274: Square

[0120] 276: Square

[0121] 278: Square

[0122] 280: Square

[0123] 300: Method

[0124] 310: Square

[0125] 312: Square

[0126] 314: Square

[0127] 320: Square

[0128] 330: Square

[0129] 340: Square

[0130] 350: Square

[0131] 360: Square

[0132] 370: Square

Claims

1. A method for pre-cleaning a substrate, comprising: supporting a substrate in a reaction chamber of a semiconductor processing system, the substrate having silicon oxide on its surface; flowing a halogen-containing reactant and a hydrogen-containing reactant into the reaction chamber; forming a first pre-cleaning material on the surface of the substrate from a first portion of the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide; flowing an additional halogen-containing reactant into the reaction chamber without flowing an additional hydrogen-containing reactant into the reaction chamber; and forming a second pre-cleaning material on the surface of the substrate from a second portion of the additional halogen-containing reactant and the silicon oxide.

2. The method as described in claim 1, further comprising epitaxially depositing a silicon-containing material layer onto the pre-cleaned surface of the substrate.

3. The method as claimed in claim 1, wherein the flow of the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber comprises the flow of anhydrous hydrogen fluoride (HF) together with at least one of ammonia (NH3), hydrazine (N2H4), methanol (CH3OH), isopropanol (C3H8O), or acetic acid (C2H4O2) into the reaction chamber.

4. The method as described in claim 1, wherein flowing the additional halogen-containing reactant into the reaction chamber includes flowing anhydrous hydrogen fluoride (HF) into the reaction chamber without flowing the additional hydrogen-containing reactant into the reaction chamber.

5. The method as described in claim 1, wherein forming the first pre-cleaning material comprises forming ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O) from the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate.

6. The method as claimed in claim 1, wherein forming the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide comprises forming silicon fluoride (SiF4) and water (H2O) from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate.

7. The method as described in claim 1, further comprising, after forming the second pre-cleaning material from the additional halogenated reactant and the silicon oxide on the surface of the substrate, sublimating the first pre-cleaning material from the surface of the substrate.

8. The method of claim 1, wherein the substrate comprises a patterned substrate having a plurality of recesses or grooves having a high aspect ratio between about 2:1 and about 50:

1.

9. The method as described in claim 1, wherein forming the second pre-cleaning material comprises using water (H2O) formed during the formation of the first pre-cleaning material to initiate the formation of the second pre-cleaning material.

10. The method as claimed in claim 1, further comprising, before the additional halogenated reactant flows into the reaction chamber and after the first pre-cleaning material is formed from the halogenated reactant and the hydrogen-containing reactant, flowing an inert gas into the reaction chamber.

11. The method as described in claim 1, further comprising removing residual halogenated reactants from the reaction chamber before allowing the additional halogenated reactant to flow into the reaction chamber.

12. The method as described in claim 1, further comprising removing residual hydrogen-containing reactants from the reaction chamber before allowing the additional halogen-containing reactant to flow into the reaction chamber.

13. The method of claim 1, wherein forming the first pre-cleaning material comprises etching the silicon oxide to a first depth; wherein forming the second pre-cleaning material comprises etching the silicon oxide to a second depth; and wherein a ratio of the second depth to the first depth is between about 2:1 and about 50:1, or between about 3:1 and about 30:1, or between about 5:1 and about 20:

1.

14. The method as described in claim 1, further comprising terminating the formation of the first pre-cleaning material by rinsing the reaction chamber before allowing the additional halogenated reactant to flow into the reaction chamber.

15. A method of forming a structure comprising: pre-cleaning a substrate using the method described in claim 1, wherein the substrate includes a patterned substrate having a plurality of recesses or trenches having a high aspect ratio between about 2:1 and about 50:1; subsequently, after forming the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate, sublimating the first pre-cleaning material from the surface of the substrate; and subsequently, after sublimating the first pre-cleaning material from the surface of the substrate, epitaxially depositing a silicon-containing material layer onto the surface of the substrate.

16. The method as claimed in claim 15, wherein flowing the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber includes flowing anhydrous hydrogen fluoride (HF) and ammonia (NH3) into the reaction chamber, and wherein flowing the additional halogen-containing reactant into the reaction chamber includes flowing anhydrous hydrogen fluoride (HF) into the reaction chamber without flowing the additional hydrogen-containing reactant into the reaction chamber.

17. The method of claim 15, wherein forming the first pre-cleaning material comprises forming ammonium hexafluorosilate ((NH4)2SiF6) and water (H2O) from the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate, and wherein forming the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide comprises forming silicon fluoride (SiF4) and water (H2O) from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate.

18. A semiconductor processing system comprising: a gas system configured to flow a halogen-containing reactant and a hydrogen-containing reactant into a reaction chamber; the reaction chamber connected to the gas system and configured to support a substrate having silicon oxide on its surface; and a controller operatively associated with the gas system and the reaction chamber, the controller responding to instructions recorded on a non-transitory machine-readable medium to: support the substrate in the reaction chamber, the substrate having silicon oxide on its surface; flow the halogen-containing reactant and the hydrogen-containing reactant into the reaction chamber; form a first pre-cleaning material on the surface of the substrate from a first portion of the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide; flow an additional halogen-containing reactant into the reaction chamber without an additional hydrogen-containing reactant; and form a second pre-cleaning material on the surface of the substrate from a second portion of the additional halogen-containing reactant and the silicon oxide.

19. The semiconductor processing system as claimed in claim 18, wherein the instruction further causes the controller to: allow anhydrous hydrogen fluoride (HF) and ammonia (NH3) to flow into the reaction chamber to form the first pre-cleaning material; and allow additional anhydrous hydrogen fluoride (HF) to flow into the reaction chamber without allowing additional ammonia to flow into the reaction chamber.

20. The semiconductor processing system of claim 18, wherein the instruction further causes the controller to: form ammonium hexafluorosilate ((NH4)2SiF6) as the first pre-cleaning material from the halogen-containing reactant, the hydrogen-containing reactant, and the silicon oxide on the surface of the substrate, together with water (H2O); terminate the formation of ammonium hexafluorosilate ((NH4)2SiF6) by rinsing the reaction chamber before allowing additional anhydrous hydrogen fluoride (HF) to flow into the reaction chamber; form silicon fluoride (SiF4) as the second pre-cleaning material from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate, together with water (H2O); and sublimate ammonium hexafluorosilate ((NH4)2SiF6) from the surface of the substrate after the formation of silicon fluoride (SiF4) on the surface of the substrate using the additional anhydrous hydrogen fluoride (HF) and the silicon oxide.

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