Systems and methods for processing a silicon surface using multiple radical species

Abstract

A method for treating a silicon surface is provided, comprising using a first radical species to remove contaminants from the surface and roughen the surface; and using a second radical species to smooth the roughened surface. A reaction system for performing such a method and a silicon surface prepared using such a method are also provided.

Description

Technical Field

[0001] This disclosure generally concerns the treatment of silicon surfaces using free radical species. Prior Technology

[0002] It is desirable to remove contaminants from silicon surfaces before depositing films onto them. For example, if a silicon film is to be epitaxially grown on this surface, the presence of contaminants such as interfacial oxides (IFO) and / or interfacial carbon (IFC) can disrupt the crystal quality of the epitaxially grown film. Free radical species such as chlorine, fluorine, or hydrogen have been used to remove or reduce IFO and / or IFC. However, it is desirable to further improve the quality of the silicon surface, for example, to improve the quality of one or more films subsequently deposited onto this surface. Summary of the Invention

[0003] This overview is provided to introduce a set of concepts in a simplified form. These concepts are described in more detail in the following detailed description of the example embodiments disclosed. This overview 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.

[0004] Some examples disclosed herein provide a method for treating silicon surfaces. The method may include using a first radical species to remove contaminants from the surface and to roughen the surface. The method may also include using a second radical species to smooth the roughened surface.

[0005] In some instances, the first free radical species isotropically roughens the surface.

[0006] In some instances, the first radical species forms an exposed silicon plane at the surface. In some instances, the second radical species preferentially reacts with the exposed silicon plane to smooth the roughened surface. In some instances, the exposed silicon plane includes Si(100), Si(110), or Si(111).

[0007] In some instances, the smoothed surfaces comprise Si(100), Si(110), or Si(111) and have an orientation different from any exposed silicon planes removed using a second radical species.

[0008] In some instances, silicon is located in the same chamber during the use of the first radical species and during the use of the second radical species.

[0009] In some instances, the first radical species includes fluorine, chlorine, or hydrogen radicals. Some instances also include the generation of fluorine radicals using at least one of the following groups of precursors: nitrogen trifluoride (NF3); sulfur hexafluoride (SF6); carbon tetrafluoride (CF4); fluoroform (CHF3); octafluorocyclobutane (C4F8); chlorine trifluoride (ClF3); and fluorine (F2).

[0010] In some instances, the second radical species includes chlorine or small molecule radicals. Some instances also include the use of chlorine (Cl₂) to generate chlorine radicals.

[0011] In some instances, contamination includes interfacial oxides or interfacial carbon. In some instances, the first radical species forms covalent bonds with the interfacial oxides or interfacial carbon as well as with the silicon surface. In some instances, the first radical species essentially removes all interfacial oxides or interfacial carbon.

[0012] In some instances, the second radical species forms covalent bonds with the silicon surface.

[0013] In some instances, the smoothed surface is primarily composed of silicon with a essentially single crystallographic orientation.

[0014] Some examples disclosed herein provide a system for treating silicon surfaces. The system may include a reaction chamber configured to hold a substrate having a surface to be treated. The system may include a distal plasma unit. The system may include a first radical precursor source unit configured to provide a first radical species precursor to the distal plasma unit. The system may include a second radical precursor source unit configured to provide a second radical species precursor to the distal plasma unit. The system may include a controller. The controller may be configured to cause the distal plasma unit to generate a first radical species using the first radical species precursor. The controller may be configured to cause the first radical species to flow into the reaction chamber to remove contaminants from the surface and roughen the surface. The controller may be configured to cause the distal plasma unit to generate a second radical species using the second radical species precursor. The controller may be configured to cause the second radical species to flow into the reaction chamber to smooth the roughened surface.

[0015] In some instances, the first radical species isotropically roughens the surface. In some instances, the first radical species forms an exposed silicon plane at the surface. In some instances, the second radical species preferentially reacts with the exposed silicon plane to smooth the roughened surface. In some instances, the exposed silicon plane includes Si(100), Si(110), or Si(111).

[0016] In some instances, the smoothed surfaces comprise Si(100), Si(110), or Si(111) and have an orientation different from any exposed silicon planes removed using a second radical species.

[0017] In some instances, silicon is located within the reaction chamber during the use of the first radical species and during the use of the second radical species.

[0018] In some instances, the first free radical species include fluorine, chlorine, or hydrogen free radicals.

[0019] In some instances, the first radical species precursor is selected from the group consisting of: nitrogen trifluoride (NF 3); sulfur hexafluoride (SF 6); carbon tetrafluoride (CF 4); fluoroform (CHF 3); octafluorocyclobutane (C 4F 8); chlorine trifluoride (ClF 3); and fluorine (F 2).

[0020] In some instances, the second radical species include chlorine or small molecule radicals.

[0021] In some instances, the precursor to the second free radical species is chlorine (Cl₂).

[0022] In some instances, contamination includes interfacial oxides or interfacial carbon. In some instances, the first radical species forms covalent bonds with the interfacial oxides or interfacial carbon as well as with the silicon surface. In some instances, the first radical species essentially removes all interfacial oxides or interfacial carbon.

[0023] In some instances, the second radical species forms covalent bonds with the silicon surface.

[0024] In some instances, the smoothed surface is primarily composed of silicon with a essentially single crystallographic orientation.

[0025] Some examples disclosed herein provide examples of silicon surfaces treated with operations including using a first radical species to remove contaminants from the surface and roughen the surface, and using a second radical species to smooth the roughened surface.

[0026] To summarize the invention and the advantages it achieves over the prior art, some of the objects and advantages of the invention have been described above. It should be understood, of course, that not all of these objects or advantages can be achieved according to any particular embodiment of the invention. Therefore, by way of example, those skilled in the art will recognize that the invention may be implemented or carried out in a manner that achieves or optimizes one or more advantages as taught or suggested by this disclosure without necessarily achieving other objects or advantages as may be taught or suggested by this disclosure.

[0027] All these embodiments are intended to be included within the scope of the disclosed invention. These and other embodiments will be apparent to those skilled in the art from the following detailed description of some embodiments taken in conjunction with the accompanying drawings, and the invention is not limited to any particular embodiment disclosed. Simple Explanation of the Diagram

[0028] Although this disclosure concludes by specifically pointing out and explicitly claiming the scope of the invention as an embodiment of the invention, the advantages of the embodiments of this disclosure can be more readily determined from the description of some examples of the embodiments of this disclosure when read in conjunction with the accompanying drawings: Figures 1A-1D schematically illustrate cross-sections and operations of example structures during methods of treating silicon surfaces using multiple free radical species. Figure 2 schematically illustrates the components of an example system for treating silicon surfaces using a variety of free radical species. Figure 3 schematically illustrates components of an example system for treating a silicon surface with a variety of free radical species and then depositing a film on that surface. Figure 4 illustrates the operational flow of an example method for treating silicon surfaces using multiple free radical species. The illustrations presented in this disclosure are not intended to be actual views of any particular material, structure, or device, but are merely idealized diagrams used to describe embodiments of this disclosure. Implementation

[0029] Although some embodiments and examples are disclosed below, it should be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, as well as obvious modifications and equivalents thereof. Therefore, it is contemplated that the scope of the invention should not be limited to the specific disclosed embodiments described below.

[0030] Numerous examples are provided throughout the embodiments disclosed herein. It should be noted that the chemical formulas given for each example should not be construed as limiting, and the non-limiting examples given should not be limited to the given physical quantifications of the generated entities.

[0031] Throughout this disclosure, the terms “substantially,” “approximately,” and “about” are used to describe and account for small fluctuations, such as those due to variations in the processing. For example, they may refer to less than or equal to ±10%, such as less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%.

[0032] The term "silicon film" is intended to encompass films comprising silicon, and may optionally include one or more non-silicon components. For example, a "silicon film" may include silicon as well as dopants, and may optionally consist substantially of silicon and dopants. Dopants may include Group III elements and / or Group V elements. Non-limiting examples of dopants include phosphorus (P) and arsenic (As).

[0033] In previously known processes for removing contaminants from silicon using radical species, the radical species covalently react with the contaminants to form gaseous molecular species. While such operations were previously thought to produce clean or low-contaminant silicon surfaces, the inventors have recognized that such operations can undesirably roughen the silicon surface, and such roughness can degrade the quality of one or more films subsequently deposited thereon. For example, radical species comprise a single valence electron that reacts rapidly and isotropically with the contaminants and / or with the silicon surface, and the formation of gaseous molecular species can weaken the bonds between adjacent silicon atoms at the surface. Therefore, if the silicon surface comprises both (110) and (111) planes, the residence time of radical species on the surface will be so short that any available silicon atom can be used for the reaction, not just higher-energy sites. The reaction of radical species with lower-energy sites can generate higher-energy sites, thereby roughening the silicon surface.

[0034] As disclosed herein, silicon surfaces can be treated using a first radical species that reduces contamination, followed by a second, distinct radical species that reduces any surface roughness caused by the first radical species. The first radical species can be more reactive than the second radical species. For example, the second radical species can be less stable than the first radical species and / or generated using diatomic species such as chlorine (Cl₂(g), hydrogen (H₂(g)) or hydrofluoric acid (HF(g)). Thus, the first radical species can effectively react with and remove contamination from the silicon surface, while the second radical species can repair the damage caused to the silicon surface by the first radical species. Therefore, the first and second radical species together can generate a smoother, lower-energy surface, on which one or more films can be deposited with higher quality than those provided by removing contamination using only a single radical species.

[0035] Figures 1A-1D schematically illustrate cross-sections and operations of example structures during a method of treating a silicon surface using multiple radical species. In operation 100, illustrated in Figure 1A, a structure comprising silicon 110 and contaminants 120 disposed on a surface 111 of silicon 110 is exposed to a first radical species R1. Silicon 110 may have a thickness T1, and contaminants 120 may have a thickness T2. In some instances, depending on the technology node and application, T1 may range from about 5 nm to about 200 nm. T2 may vary, for example, depending on any upstream processing. For example, surface 111 may be impregnated with HF prior to the processing of the present invention. In some instances, T2 may range from about 1 nm to about 6 nm.

[0036] A first radical species R1 removes contaminants 120 from the surface 111 of silicon 110 and roughens the silicon surface. The first radical species R1 can react indiscriminately and isotropically with both contaminants 120 and silicon 110. Because contaminants 120 form the uppermost layer of the element, the first radical species can remove some or substantially all of the contaminants from the surface 111. However, the first radical species R1 can also roughen the surface 111 isotropically, for example, by reacting non-preferentially with sites on the surface 111, substantially independently of the relative energies of such sites. For example, contaminants may include IFO, IFC, or a combination of IFO and IFC. The first radical species R1 can form covalent bonds with IFO, IFC, and / or the silicon surface. At least some products of such reactions may be gaseous, but some products of such reactions may remain coupled to the surface 111.

[0037] Then, at operation 101, as illustrated in Figure 1B, an inert gas stream is used to remove the first radical species R1 and any gaseous reaction products. As shown in Figure 1B, after using the first radical species R1, silicon 110 may have substantially the same thickness T1 as before using the first radical species, such that the surface 111 of silicon 110 is located substantially in the same position as before using the first radical species. However, the surface 111 may be roughened due to the reaction with the first radical species R1, and the roughness may have a thickness T3 extending into silicon 110. In some instances, the thickness T3 of the roughness (e.g., root mean square roughness as measured by atomic force microscopy) is on a scale of several atomic layers, for example, from about 1 angstrom to about 10 angstroms. The surface 111 may also include non-gaseous products from the reaction with the first radical species R1.

[0038] At operation 102, as illustrated in Figure 1C, a structure comprising silicon 110 with surface roughness is exposed to a second radical species R2, which smooths the roughened surface. The second radical species R2 can also react with any non-gaseous product of the reaction with the first radical species R1. In some instances, one or more products of the reaction with the second radical species R2 can be gaseous. Alternatively or additionally, one or more products of the reaction with the second radical species R2 can form a surface termination at the silicon surface. More specifically, depending on the particular second radical species R2 used, the silicon surface can be partially terminated with a Si-halide (e.g., Si-Cl or Si-F) and / or Si-H. The inventors have recognized that such surface termination can inhibit oxide regrowth. For example, if silicon is transferred from the radical subsystem 200 to the deposition subsystem 360 in the manner described with reference to Figure 3, the silicon surface may be exposed to moisture. Terminating the Si-halides (e.g., Si-Cl or Si-F) and / or Si-H moieties on the silicon surface can inhibit the chemisorption of water and thus inhibit the reaction of such water at the silicon surface to form oxides.

[0039] Then, at operation 103, as illustrated in Figure 1D, the second radical species is removed, for example, using an inert gas stream. As shown in Figure 1D, after using the second radical species R2, the surface roughness of silicon 110 is substantially removed. Smoothing the roughened surface will remove a portion of silicon 110, such that surface 111' is lower than the original height of surface 111, and silicon 110 has a reduced thickness T4 less than T1.

[0040] In some instances, a first radical species R1 forms an exposed silicon plane at surface 111. For example, the first radical species R1 can remove such a portion from surface 111 by reacting with a portion of silicon 110 during operation 100. Depending on the composition and the crystal orientation of silicon 110, such a reaction can expose the silicon plane that forms at least a portion of the surface roughness. During operation 102, a second radical species can form covalent bonds with the silicon surface. For example, the second radical species R2 can preferentially react with the exposed silicon plane because such an exposed plane can have a higher energy and / or a larger surface area than the remainder of silicon 110. Thus, the smoothed surface 111' can consist primarily of a single crystallographic orientation (the same crystallographic orientation as silicon 110) (and in some instances can consist essentially of it) and can be substantially free of any contaminants 120, such as any IFC and / or IFO. In an example where silicon 110 is primarily (e.g., substantially) composed of silicon with a single crystallographic orientation, the smoothed surface 111' may be primarily (e.g., substantially) composed of silicon with substantially the same single crystallographic orientation. As a result of the smoothing process provided by treatment with a second radical species R2 after treatment with a first radical species R1, the number of defect site points, such as the number of stepped edges formed by unfavorable crystal planes, can be reduced. For example, depending on the application, silicon may be primarily or substantially composed of Si (100), Si (110), or Si (111), and the surface roughness may include deviations from such corresponding crystal orientations. Schematably, silicon 110 comprises or may be substantially composed of Si (100), defect sites may include Si (110) and / or Si (111) in the form of stepped edges, and the smoothed surface may be primarily (e.g., substantially) composed of Si (100), substantially free of contamination 120. In another example, silicon 110 comprises or may be substantially composed of Si (110), defect sites may comprise Si (100) and / or Si (111) in the form of stepped edges, and the smoothed surface may be primarily (e.g., substantially) composed of Si (110), substantially free of contamination 120. In another example, silicon 110 comprises or may be substantially composed of Si (111), defect sites may comprise Si (100) and / or Si (110) in the form of stepped edges, and the smoothed surface may be primarily (e.g., substantially) composed of Si (111), substantially free of contamination 120.

[0041] Any suitable first radical species R1 can be used to substantially remove contaminants 120 and roughen the surface 111 of silicon 110, and can be generated in any suitable manner. In a non-limiting example as described with reference to FIG2, the first radical species R1 can be generated using a first radical precursor and a distal plasma unit that uses the first radical precursor to generate the first radical species. In some examples, the first radical species R1 includes fluorine, hydrogen, or chlorine radicals. Fluorine radicals can be generated using at least one precursor selected from the group consisting of: nitrogen trifluoride (NF3); sulfur hexafluoride (SF6); carbon tetrafluoride (CF4); fluoroform (CHF3); octafluorocyclobutane (C4F8); chlorine trifluoride (ClF3); and fluorine (F2).

[0042] Any suitable second radical species R2 can be used to smooth the roughened surface of silicon 110, and the second radical species can be generated in any suitable manner. In a non-limiting example as described with reference to Figure 2, the second radical species R2 can be generated using a second radical precursor and a distal plasma unit that uses the second radical precursor to generate the second radical species. In some examples, the second radical species R2 comprises chlorine radicals or small molecule radicals such as HF or H2. Chlorine radicals can be generated using chlorine (Cl2). Small molecule radicals can reach the surface as is.

[0043] It should be understood that any suitable system can be used to treat the surface of silicon 110 with the first radical species R1 and the second radical species R2. In some instances, silicon 110 can be located in the same chamber during the use of the first radical species R1 and during the use of the second radical species R2. That is, silicon 110 does not have to be located in one chamber during the use of the first radical species R1 and then moved to another chamber to use the second radical species R2. Instead, operations 100, 101, 102, and 103 described with reference to Figures 1A-1D can all be performed in the same chamber as each other, thus providing a simplified operation for treating silicon surfaces.

[0044] For example, Figure 2 schematically illustrates components of an example system for treating silicon surfaces using multiple radical species. The system 200 illustrated in Figure 2 may include a reaction chamber 210; a remote plasma unit 220; a first radical species precursor source unit 230; a second radical species precursor source unit 240; an inert gas source unit 250; a series of gas lines 260A-260C connecting the first radical species precursor source unit, the second radical species precursor source unit, and the inert gas source unit to the remote plasma unit 220, respectively; a main gas line 270 connecting the remote plasma unit 220 to the reaction chamber 210; and a controller 280.

[0045] The controller 280 can be operatively connected to the first radical species precursor source unit 230, the second radical species precursor source unit 240, the inert gas source unit 250, and the remote plasma unit 220 (such electrical connections are shown in dashed lines). The controller 280 can be configured to control operations 100, 101, 102, and 103 as described with reference to Figures 1A-1D. For example, the controller 280 can be configured to cause the first radical species precursor source unit 230 to flow the first radical species precursor through gas line 260A, and to cause the inert gas source unit to flow inert gas through gas line 260C into the remote plasma unit 220. The controller 280 can also be configured to cause the remote plasma unit 220 to ignite the resulting gas mixture to form a plasma comprising the first radical species R1, and to cause the first radical species to flow through the main gas line 270 to the reaction chamber 210 to implement operation 100 as described with reference to Figure 1A. The controller 280 can also be configured to cause the inert gas source unit to flow inert gas into the remote plasma unit 220, and to cause the remote plasma unit 220 to flow inert gas through the main gas line 270 to the reaction chamber 210 without initiating plasma, so as to implement the operation 101 described with reference to FIG1B after the operation 100 is completed.

[0046] The controller 280 can also be configured to cause the second radical species precursor source unit 240 to flow the second radical species precursor through gas line 260B, and to cause the inert gas source unit to flow inert gas through gas line 260C into the distal plasma unit 220. The controller 280 can also be configured to cause the distal plasma unit 220 to initiate the resulting gas mixture to form a plasma including the second radical species R2, and to cause the second radical species to flow through the main gas line 270 to the reaction chamber 210, so that operation 102, as described with reference to FIG. 1C, can be performed after operation 101 is completed. The controller 280 can also be configured to cause the inert gas source unit to flow inert gas into the distal plasma unit 220, and to cause the distal plasma unit 220 to flow inert gas through the main gas line 270 to the reaction chamber 210 without initiating plasma, so that operation 103, as described with reference to FIG. 1D, can be performed after operation 102 is completed.

[0047] The reaction chamber 210 may include a platform 212 configured to hold silicon 210, and a flow regulator 211 configured to provide a relatively uniform gas flow to the surface of silicon during operation 100-103.

[0048] It should be understood that components of system 200 described with reference to FIG. 2 may optionally be incorporated into a larger system configured to perform one or more additional operations using the silicon surface provided in this disclosure. For example, FIG. 3 schematically illustrates components of an example system for treating a silicon surface using multiple radical species and then depositing a film on that surface. System 300 includes a radical subsystem 200 that may correspond to system 200 described with reference to FIG. 2, and a controller 380 that may correspond to controller 280 described with reference to FIG. 2 but has additional functionality to control additional subsystems. For example, system 300 may include a wafer initiation chamber 310; a robot 320; a wafer transfer chamber 330; a robot 340; a deposition subsystem 360; and a wafer completion chamber 370. Controller 380 may be operatively coupled to radical subsystem 200, robot 320, robot 340, and deposition subsystem 360 (such electrical connections are indicated by dashed lines).

[0049] The wafer start chamber 310 can be configured to receive any suitable number of silicon wafers for processing. The controller 380 can be configured to cause the robot 320 to move one or more wafers from the wafer start chamber 310 to the wafer transfer chamber 330. The controller 380 can also be configured to cause the robot 340 to move one or more wafers from the wafer transfer chamber 330 to the radical subsystem 200 for processing, as described with reference to Figures 1A-1D and 2. The controller 380 can also be configured to cause the robot 340 to move one or more wafers from the radical subsystem 200 to the deposition subsystem 360 to deposit at least one film on the processed silicon. In a non-limiting example, the deposition subsystem 360 is configured to epitaxially grow a silicon film on the processed silicon. The controller 380 can also be configured to cause the robot 340 to move one or more wafers from the deposition subsystem 360 to the wafer transfer chamber 330. The controller 380 can also be configured to cause the robot 320 to move one or more wafers from the wafer transfer chamber 330 to the wafer completion chamber 370.

[0050] It should be understood that systems 200 and 300 provide non-limiting examples of hardware and software that can be used to process silicon in the manner provided in this disclosure. For example, Figure 4 illustrates an operational flow in an example method for treating a silicon surface using multiple radical species. The method 400 illustrated in Figure 4 may include using a first radical species to remove contaminants from the surface and roughen the surface (operation 410), for example, in a manner described as described with reference to operation 100 of Figure 1A. Method 400 may also include using a second radical species to smooth the roughened surface (operation 420), for example, in a manner described as described with reference to operation 102 of Figure 1C. Other suitable operations may be performed between operations 410 and 420, and other suitable operations may be performed after operation 420, such as depositing a film on the treated surface. As provided in this disclosure, the present invention provides a silicon surface of higher quality than that obtained using only a single radical species, and therefore one or more films subsequently deposited on such surfaces may also have higher quality.

[0051] The silicon 110 used in operations 100-103 or 410-420 and in systems 200 or 300 can comprise any suitable combination of materials. For example, silicon 110 can consist essentially of a silicon wafer. Alternatively, for example, silicon 110 can comprise a film disposed on a silicon wafer. Silicon 110 and / or any other film that can be disposed on a silicon wafer can be patterned. For example, silicon 110 can comprise components of a FINFET or storage node capacitors for DRAM. It should be noted that any such patterning can have feature sizes significantly larger than, for example, the feature size of any silicon plane exposed using the first radical species R1 as described with reference to Figures 1A-1B. Such patterning can have significantly lower energies than such exposed silicon planes. Therefore, compared to any such patterning, the second radical species R2 can preferentially react with the higher-energy silicon plane.

[0052] It should be understood that controller 280 can be implemented using any suitable combination of digital electronic circuits, integrated circuits, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), central processing units (CPUs), graphics processing units (GPUs), computer hardware, firmware, software, and / or combinations thereof. For example, one or more functions of controller 280 can be implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be dedicated or general-purpose, coupled to receive data and instructions from a storage system, at least one input device, and at least one output device, and to transmit data and instructions to the storage system, at least one input device, and at least one output device. The programmable system or computing system may include a client and a server. The client and server are typically geographically separated and typically interact via a communication network. The relationship between the client and the server is generated by computer programs running on the respective computers that have a client-server relationship with each other.

[0053] These computer programs, also referred to as modules, programs, software, software applications, applications, components, or code, may include machine instructions for a programmable processor and / or may be implemented in high-level programming languages, object-oriented programming languages, functional programming languages, logic programming languages, and / or assembly / machine languages. As used in this disclosure, the terms "memory" and "computer-readable medium" refer to any computer program product, apparatus, and / or device such as disks, optical discs, solid-state storage devices, memory, and programmable logic devices (PLDs) used to provide machine instructions and / or data to a programmable data processor, including machine-readable media that receive machine instructions as computer-readable signals. The term "computer-readable signal" refers to any signal used to provide machine instructions and / or data to a programmable data processor. Computer-readable media may temporarily or non-temporarily store such machine instructions, just as temporarily or non-temporarily stored solid-state memory or magnetic disk drives or any equivalent storage medium. Computer-readable media may alternatively or otherwise store such machine instructions in a temporary manner, such as, for example, processor cache or other random access memory associated with one or more physical processor cores.

[0054] Computer components, software modules, functions, data storage, and data structures can be directly or indirectly connected to each other to allow the data flow required for their operation. It should also be noted that modules or processors include, but are not limited to, code units that perform software operations, and can be implemented, for example, as subroutine units of code, or as software functional units of code, or as objects (such as object-oriented paradigms), or as applets, or in a computer instruction code language, or as another type of computer code. Software components and / or functions can reside on a single computer or be distributed across multiple computers and / or in the cloud, as appropriate.

[0055] In a non-limiting example, the controller 280 described with reference to Figures 2-3 can be implemented using a computing device architecture. In such an architecture, a bus (not specifically shown) can act as an information highway interconnecting with other illustrated components of the hardware. The system bus may also include at least one communication port (such as a network interface) to allow communication with external devices physically connected to the computing system or available externally via a wired or wireless network. The controller 280 can be implemented using a CPU (Central Processing Unit) (e.g., one or more computer processors / data processors at a given computer or multiple computers), which can perform computational and logical operations required by a program. The controller 280 may include transient and non-transitory processor-readable storage media, such as read-only memory (ROM) and / or random access memory (RAM), that communicate with one or more processors, and may include one or more programming instructions for the operations provided in this disclosure, for example, for implementing system 300 and / or method 400. Optionally, the memory may include a magnetic disk, optical disk, recordable memory device, flash memory, or other physical storage media. To provide interaction with the user, the controller 280 may include or may be implemented on a computing device having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and an input device through which the user can provide input to the computer, such as a keyboard and / or a pointing device (e.g., a mouse or trackball) and / or a touch screen.

[0056] The exemplary embodiments described above do not limit the scope of the invention, as these embodiments are merely examples of embodiments of the invention, which are defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be included within the scope of the invention. In fact, various modifications to this disclosure, such as alternative combinations of the elements, will be apparent from the specification to those skilled in the art, in addition to those shown and described herein. Such modifications and embodiments are also intended to fall within the scope of the appended claims.

[0057] 100: Operation 101: Operation 102: Operation 103: Operation 110: Silicon 111: Surface 120: Pollution 200: System 210: Reaction Chamber 211: Flow Regulator 212: Platform 220: Remote Plasma Unit 230: First free radical species precursor source unit 240: Second radical species precursor source unit 250: Inert gas source unit 260A: Gas pipeline 260B: Gas pipeline 260C: Gas pipeline 270: Main gas pipeline 280: Controller 300: System 310: Wafer start chamber 320: Robot 330: Wafer Transfer Chamber 340: Robot 360: Sedimentation Subsystem 370: Wafer Completion Chamber 380: Controller 400: Method 410: Operation 420: Operation R1: First free radical species R2: Second free radical species T1: Thickness T2: Thickness T3: Thickness T4: Thickness

Claims

1. A method for treating the surface of silicon, the method comprising: By exposing the surface to first free radical species, contaminants are removed from the surface and the surface is roughened. The roughened surface is smoothed by exposing the surface to a second free radical species; and a silicon film is epitaxially grown on the smoothed surface, wherein roughening the surface includes exposing a plurality of silicon planes at the surface, and wherein smoothing the roughened surface includes preferentially reacting the second free radical species with the exposed silicon planes.

2. The method of claim 1, wherein roughening the surface includes isotropically roughening the surface.

3. The method of claim 1, wherein the exposed silicon planes comprise at least one of Si(100), Si(110), or Si(111).

4. The method of any one of claims 1 to 3, wherein the smoothed surface comprises Si(100), Si(110) or Si(111) and has an orientation different from any exposed silicon plane removed using the second radical species.

5. The method of any one of claims 1 to 3, wherein silicon is located in the same chamber during the use of the first radical species and during the use of the second radical species.

6. The method of any one of claims 1 to 3, wherein the first radical species comprises a fluorine radical, a chlorine radical, or a hydrogen radical.

7. The method of claim 1, wherein the first radical species comprises a fluorine radical, and the method further comprises generating the fluorine radical using at least one precursor selected from the group consisting of: nitrogen trifluoride (NF3); sulfur hexafluoride (SF6); carbon tetrafluoride (CF4); fluoroform (CHF3); octafluorocyclobutane (C4F8); chlorine trifluoride (ClF3); and fluorine (F2).

8. The method of any one of claims 1 to 3, wherein the second radical species comprises a chlorine radical or a small molecule radical.

9. The method of claim 1, wherein the second radical species comprises a chlorine radical, and the method further comprises generating the chlorine radical using chlorine (Cl2).

10. The method of any one of claims 1 to 3, wherein the contamination comprises interfacial oxides or interfacial carbon.

11. The method of claim 10, wherein using the first radical species includes forming a covalent bond between the first radical species and the interface oxide or the interface carbon on the surface.

12. The method of claim 10, wherein removing contaminants from the surface comprises substantially removing all of the interface oxides or the interface carbon.

13. The method of any one of claims 1 to 3, wherein using the second radical species comprises forming a covalent bond between the second radical species and the surface.

14. The method of any one of claims 1 to 3, wherein the smoothed surface is composed primarily of silicon having a substantially single crystallographic orientation.

15. A system for treating silicon surfaces, the system comprising: A reaction chamber configured to hold a substrate with a surface to be treated; Remote plasma unit; A first radical precursor source unit is configured to provide a first radical species precursor to the distal plasma unit; a second radical precursor source unit is configured to provide a second radical species precursor to the distal plasma unit; one or more processors execute a plurality of memory storage instructions, which, when executed, cause the system to: cause the distal plasma unit to generate a first radical species using the first radical species precursor; remove contamination from the surface and roughen the surface by allowing the first radical species to flow into the reaction chamber; cause the distal plasma unit to generate a second radical species using the second radical species precursor; smooth the roughened surface by allowing the second radical species to flow into the reaction chamber; and epitaxially grow a silicon film on the smoothed surface, wherein the first radical species is configured to form a plurality of exposed silicon planes at the surface, and wherein the second radical species is configured to preferentially react with the exposed silicon planes.

16. The system as claimed in claim 15, wherein the first radical species is configured to isotropically roughen the surface.

17. The system of claim 15, wherein the exposed silicon planes comprise at least one of Si(100), Si(110), or Si(111).

18. The system of any one of claims 15 to 17, wherein the smoothed surface comprises Si (100), Si (110) or Si (111) and has an orientation different from any exposed silicon plane removed by using the second radical species.

19. The system of any one of claims 15 to 17, wherein when the one or more processors execute the memory storage instructions, the system causes the distal plasma unit to generate the first radical species and the second radical species when silicon is located in the reaction chamber.

20. The system of any one of claims 15 to 17, wherein the first radical species comprises a fluorine radical, a chlorine radical, or a hydrogen radical.

21. The system as claimed in claim 15, wherein the first radical species precursor is selected from the group consisting of: nitrogen trifluoride (NF3); sulfur hexafluoride (SF6); carbon tetrafluoride (CF4); fluoroform (CHF3); octafluorocyclobutane (C4F8); chlorine trifluoride (ClF3); and fluorine (F2).

22. The system of any one of claims 15 to 17, wherein the second radical species comprises a chlorine radical or a small molecule radical.

23. The system as claimed in claim 15, wherein the precursor of the second free radical species is chlorine (Cl2).

24. The system of any one of claims 15 to 17, wherein the contamination comprises interfacial oxides or interfacial carbon.

25. The system of claim 24, wherein the first radical species is configured to form a covalent bond between the surface and the interface oxide or interface carbon.

26. The system of claim 24, wherein when the one or more processors execute the memory storage instructions, the system removes contaminants from the surface by substantially removing all the interface oxides or the interface carbon using the first free radical species.

27. The system of any one of claims 15 to 17, wherein the second radical species is configured to form a covalent bond with the surface.

28. The system of any one of claims 15 to 17, wherein the smoothed surface is composed primarily of silicon having a substantially single crystallographic orientation.

29. The system as claimed in claim 15 further includes a deposition subsystem, wherein when the one or more processors execute the memory storage instructions, the silicon film is epitaxially grown on the surface by means of the deposition subsystem.

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