Selective oxidation and simplified precleaning

Abstract

Methods for selectively oxidizing dielectric surfaces of substrate surfaces comprising dielectric surfaces and metal surfaces are discussed. Methods for cleaning substrate surfaces comprising dielectric surfaces and metal surfaces are also discussed. The disclosed methods use a plasma generated from hydrogen and oxygen to oxidize dielectric surfaces and / or clean substrate surfaces. The disclosed methods can be performed in a single step without the need to use separate, competing oxidation and reduction reactions. The disclosed methods can be performed at a constant temperature and / or within a single processing chamber.

Description

Technical Field

[0001] Various embodiments of the present disclosure generally relate to methods for selectively oxidizing and / or cleaning substrate surfaces. More specifically, various embodiments of the present disclosure relate to methods for oxidizing dielectric or semiconductor materials without substantially oxidizing metallic materials. Further embodiments of the present disclosure relate to methods for pre-cleaning a substrate surface having a dielectric surface and a metallic surface in a single chamber and / or at a single temperature.

[0002] background

[0003] Oxidation and reduction of material surfaces are important processes in the fabrication of semiconductor devices. These reactions can be used to alter film properties, passivate or activate surfaces in various deposition schemes, and / or change film composition.

[0004] Many semiconductor devices contain both metal and dielectric surfaces. Current methods for oxidizing either dielectric or semiconductor materials are not selective for metal. Unwanted oxidation of metal materials can lead to increased line, via, or contact resistance. Furthermore, treatments for reducing unwanted oxidation on metal materials typically use hydrogen-based treatments, which can damage dielectrics. Therefore, current methods for processing substrates with both metal and dielectric surfaces rely on alternating oxidation and reduction reactions to both oxidize the dielectric / semiconductor and eliminate any oxidation on the metal surface.

[0005] Therefore, there is a need for an oxidation process that is selective for dielectric and semiconductor materials over metallic materials.

[0006] Many modern semiconductor manufacturing processes can leave contaminants on the substrate surface. In addition, extended storage or transport between processing tools can expose the substrate surface to contaminants. Many substrate processing methods are highly specific to a given surface chemistry. Therefore, cleaning the substrate surface to remove contaminants before processing is an important part of most semiconductor manufacturing process flows.

[0007] Many semiconductor devices contain both metal and dielectric surfaces. Each of these surfaces may contain contaminants that need to be removed before processing. Unfortunately, the process of removing contaminants from one surface may damage or otherwise adversely modify another surface.

[0008] Current methods for cleaning substrates with both metallic and dielectric surfaces rely on alternating oxidation and reduction reactions to remove contaminants and eliminate any damage caused by the other reaction. Most cleaning processes require at least three oxidation or reduction reactions to fully clean the substrate surface. However, the oxidation and reduction reactions are typically performed at different temperatures. Therefore, the substrate must typically be heated or cooled between treatments. Furthermore, the process gases used for the oxidation and reduction reactions are often incompatible. Consequently, the substrate must typically be transferred from one processing chamber to another to perform the different treatments.

[0009] Therefore, there is a need for a cleaning process that is performed at one temperature. In addition, there is a need for a cleaning process that is performed within one processing chamber. Summary of the Invention

[0010] One or more embodiments of the present disclosure are directed to a method comprising exposing a substrate surface comprising a damaged dielectric surface and a reduced metal surface to a plasma formed from a plasma gas comprising hydrogen and oxygen to oxidize the damaged dielectric surface without substantially oxidizing the reduced metal surface.

[0011] Several additional embodiments of the present disclosure relate to a method for selectively oxidizing a dielectric surface. The method comprises the steps of exposing a substrate surface comprising a silicon nitride surface and a tungsten surface to a microwave plasma formed from a plasma gas comprising hydrogen, oxygen, and argon to selectively oxidize the silicon nitride surface without oxidizing the tungsten surface. The power of the microwave plasma is in a range of about 2500 W to about 3000 W. The argon concentration of the plasma gas is greater than or equal to about 95% by mole, and the ratio of hydrogen to oxygen is in a range of about 1:1 to about 1:10. The substrate surface is maintained at a temperature of about 400°C. The properties of the tungsten surface before and after exposure to the microwave plasma are similar. The properties are selected from one or more of reflectivity, resistivity, and sheet resistance.

[0012] Further embodiments of the present disclosure relate to a method for cleaning a substrate, comprising exposing a substrate surface having a contaminated dielectric surface and a contaminated metal surface to a plasma formed from a plasma gas comprising hydrogen and oxygen to remove the contaminants and form a clean dielectric surface and a clean metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order that the above-mentioned characteristic structures of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be obtained by reference to a number of embodiments, some of which are shown in the accompanying drawings. It should be noted, however, that the drawings illustrate only a number of typical embodiments of the present disclosure and are therefore not to be considered limiting of the scope of the present disclosure, as the disclosure may admit to many other equally effective embodiments.

[0014] Figure 1 An exemplary substrate having features according to one or more embodiments of the present disclosure is shown;

[0015] Figure 2 An exemplary substrate is shown during a two-step oxidation / reduction treatment according to methods known in the art.

[0016] Figure 3 shows an exemplary substrate during a one-step selective oxidation process according to one or more embodiments of the present disclosure; and

[0017] Figure 4 shows an exemplary substrate during a three-step cleaning process according to methods known in the art;

[0018] Figure 5 An exemplary substrate is shown during a one-step cleaning process according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0019] Before describing several exemplary embodiments of the present disclosure, it should be understood that the present disclosure is not limited to the details of construction or processing steps set forth in the following description. The present disclosure is capable of many other embodiments and can be practiced or carried out in various ways.

[0020] As used herein, "substrate" refers to any substrate or material surface formed on a substrate on which film processing is performed during a manufacturing process. For example, substrate surfaces on which processing may be performed include materials such as silicon, silicon oxide, strained silicon, silicon-on-insulator (SOI), carbon-doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, but are not limited to, semiconductor wafers.

[0021] As used in this specification and the appended claims, the term "substrate surface" refers to the surface or portion of a surface upon which a process is applied. Those skilled in the art will also understand that, unless the context clearly indicates otherwise, references to a substrate may also refer to only a portion of a substrate. Additionally, references to depositing on a substrate may refer to both a bare substrate and a substrate having one or more films or features deposited or formed thereon.

[0022] The substrate may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, electron beam cure, and / or bake the substrate surface. In addition to treatments performed directly on the surface of the substrate itself, in the present disclosure, as disclosed in more detail below, any of the disclosed processing steps may also be performed on an underlying layer formed on the substrate, and the term "substrate surface" is intended to include the underlying layer as indicated by the context. Thus, for example, where a film / layer or portion of a film / layer is already deposited on the substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0023] Some embodiments of the present disclosure relate to methods for selectively oxidizing a substrate. Some embodiments of the present disclosure relate to methods for selectively oxidizing a surface of a substrate having both a dielectric surface and a metallic surface.

[0024] Some embodiments of the present disclosure advantageously provide methods for oxidation that are selective for dielectric or semiconductor materials / surfaces over metallic materials / surfaces. In this regard, the amount of oxidation observed on the metallic surface is virtually zero.

[0025] The advantages of the present disclosure are best understood as compared to known methods. Figure 2 A method 100 known in the art is shown. The method 100 begins with a substrate 20 comprising a dielectric material 12 and a metallic material 14.

[0026] like Figure 1 As shown, in some embodiments, substrate 20 has a feature 16 (or structure) formed in substrate 20. Feature 16 can be any suitable shape and have any suitable dimensions (e.g., width, depth, aspect ratio). For example, in some embodiments, feature 16 comprises one or more of a trench or a via. In some embodiments, feature 16 has a top surface 17, sidewalls 18, and a bottom surface 19. Those skilled in the art will recognize that, although Figure 1 Two side walls 18 are shown, but the present disclosure is not limited to two side walls. For example, a circular via has one continuous side wall 18, but the cross-sectional view shown would show two side walls.

[0027] In some embodiments, top surface 17 of feature 16 comprises damaged dielectric surface 23. In some embodiments, bottom surface 19 comprises reduced metal surface 25. In some embodiments, sidewalls 18 of feature 16 comprise reduced metal surface 25 and bottom surface 19 of the feature comprises damaged dielectric surface 23.

[0028] In some embodiments, substrate 10 includes a semiconductor contact. In some embodiments, the semiconductor contact includes metal material 14. In some embodiments, the semiconductor contact includes a material to be formed within feature 16. In some embodiments, substrate 10 includes a memory hole, string, or other portion of a 3D NAND device. In some embodiments, the substrate includes a logic device.

[0029] In some embodiments, the dielectric material 12 comprises or consists essentially of one or more of silicon oxide, silicon nitride or silicon oxynitride, a carbon-based dielectric, silicon oxycarbide, silicon oxycarbonitride, aluminum oxide, or aluminum oxynitride. In this regard, a material consisting essentially of the material comprises greater than or equal to about 95%, 98%, 99%, or 99.5% of the material on an atomic basis.

[0030] The metal material 14 may comprise any suitable metal or combination of metals. In some embodiments, the metal material 14 comprises one or more of copper, tungsten, cobalt, molybdenum, ruthenium, iridium, and rhodium. In some embodiments, the metal material consists essentially of copper, tungsten, or cobalt.

[0031] Method 100 begins with a damaged substrate 20. The damaged substrate 20 comprises a dielectric material 12 having a damaged dielectric surface 23 and a metal material 14 having a reduced metal surface 25. As used herein, the term "reduced metal surface" refers to an electrochemically reduced material or a metal surface having a reduced oxidation state. In some embodiments, the reduced oxidation state of the reduced metal surface is approximately 0. In some embodiments, the reduced metal surface 25 is a metal surface devoid of any metal oxide. The reduced metal surface does not indicate a reduction in thickness or other undesirable changes in the metal material 14.

[0032] The damaged dielectric surface 23 contains a reduced oxygen concentration at the surface of the dielectric material 12. For illustrative purposes only, the damaged dielectric surface 23 is Figure 2 The middle indicator is a local star mark.

[0033] The method 100 continues with an oxidation process 120. The oxidation process 120 forms an oxidized substrate 30. The oxidized substrate 30 has a dielectric material 12 having an oxidized dielectric surface 33 and a metal material 14 having an oxidized metal surface 35. For illustrative purposes, the oxidized metal surface 35 is shown with oxygen atoms, while the dielectric material 12 within the oxidized dielectric surface 33 is shown as a clean line segment compared to the marked line segment shown before the oxidation process 120.

[0034] Oxidized dielectric surface 33 contains an increased oxygen concentration at the surface of dielectric material 12 relative to the oxygen concentration at damaged dielectric surface 23. Oxidized metal surface 35 contains additional oxygen contaminants (eg, metal oxides) relative to reduced metal surface 25.

[0035] In some embodiments, the oxidation treatment 120 comprises a plasma treatment. In some embodiments, the oxidation treatment 120 comprises exposure to an oxidizing plasma. In some embodiments, an oxygen-containing gas is used to form the oxidizing plasma. In some embodiments, the oxygen-containing gas comprises oxygen (O2). The oxidation treatment 120 is performed under an oxidizing pressure, and the substrate is maintained at an oxidation temperature and with an oxidizing bias applied to the substrate 10. Other process conditions may also be controlled as described below.

[0036] The oxidation temperature is relatively low. In some embodiments, the oxidation temperature is in the range of about 50°C to about 200°C, in the range of about 50°C to about 250°C, or in the range of about 50°C to about 150°C. In some embodiments, the oxidation temperature is about 50°C, about 75°C, about 100°C, about 125°C, or about 150°C.

[0037] The method 100 continues with a reduction process 130. The reduction process 130 forms a clean substrate 40. The clean substrate 40 has a dielectric material 12 having a clean dielectric surface 43 and a metal material 14 having a clean metal surface 45.

[0038] The cleaned dielectric surface 43 of some embodiments contains a reduced oxygen concentration at the surface of the dielectric material 12 relative to the oxygen concentration at the oxidized dielectric surface 33. For embodiments in which the oxidized dielectric surface 33 contains an excess of oxygen relative to the expected stoichiometric ratio of oxygen to other elements, the reduction treatment 130 reduces the oxygen concentration to at or about the expected stoichiometric ratio. For example, the oxygen content of an oxygen-contaminated silicon oxide surface is greater than the expected stoichiometric amount of silicon oxide. For embodiments in which the oxidized dielectric surface 33 contains oxygen at or near the expected stoichiometric ratio of oxygen to other elements, the reduction treatment 130 may have little effect on the oxidized dielectric surface 33 when forming the cleaned dielectric surface 43.

[0039] The clean metal surface 45 contains a reduced concentration of oxygen (or oxygen contamination) at the surface of the metal material 14 relative to the oxygen concentration at the oxidized metal surface 35. In some embodiments, the clean metal surface 45 contains virtually no oxygen. In short, the clean metal surface 45 can be described as a "bare" metal surface. In some embodiments, the clean metal surface 45 contains substantially no oxygen atoms. In this regard, a surface that contains "substantially no" oxygen atoms contains less than or equal to about 95%, less than or equal to about 98%, less than or equal to about 99%, or less than or equal to about 99.5% oxygen atoms at the surface of the material.

[0040] In some embodiments, the reduction treatment 130 comprises a plasma treatment. In some embodiments, the reduction treatment 130 comprises exposure to a reducing plasma. In some embodiments, the reduction treatment 130 comprises exposure to a reducing plasma formed from a hydrogen-containing gas. In some embodiments, the hydrogen-containing gas comprises hydrogen (H2).

[0041] At least some of the conditions of the oxidation treatment 120 and the reduction treatment 130 are different. The reduction temperature is higher. In some embodiments, the reduction temperature is in the range of about 250°C to about 550°C, in the range of about 300°C to about 500°C, or in the range of about 350°C to about 450°C. In some embodiments, the reduction temperature is about 350°C, about 400°C, or about 450°C.

[0042] In order to perform the reduction process 130 after the oxidation process 120, other process conditions may also need to be modified. For example, the oxidation pressure and the reduction pressure may be different, or the oxidation bias and the reduction bias may be different.

[0043] It takes a lot of time to modify the process conditions between the oxidation process 120 and the reduction process 130 in the same process chamber. For example, the chamber must be heated or cooled to an appropriate temperature and the gas source must be switched to a different process gas.

[0044] The modification of process conditions between the oxidation process 120 and the reduction process 130 can be performed by transitioning the substrate from one process chamber to another. Such transitions between process chambers can be faster than transitioning a single process chamber from the conditions used for the oxidation process 120 to the conditions used for the reduction process 130. However, the transition process requires additional time, thereby reducing overall throughput and requiring a multi-chamber processing tool.

[0045] Various embodiments of the present disclosure implement improvements to the above-described method 100. Some embodiments of the present disclosure are performed at a single process temperature. The inventors surprisingly discovered that prior art competitive oxidation and reduction processes can be performed at a single temperature with a single plasma exposure. Some embodiments of the present disclosure are performed within a single process chamber. These improvements are directly related to reduced process time and increased throughput.

[0046] Reference Figure 3 One or more embodiments of the present disclosure are directed to a method 200 for selectively oxidizing a substrate 10. The substrate 10 comprises a dielectric material 12 and a metal material 14. The surface of the substrate 10 is also referred to as the substrate surface. The dielectric material 12 has a damaged dielectric surface 23, and the metal material 14 has a reduced metal surface 25. For illustrative purposes only, the damaged dielectric surface 23 is Figure 3 As used throughout the disclosure, dielectric material 12 may also refer to semiconductor material.

[0047] Figure 3 An embodiment is depicted in which dielectric material 12 comprises a first dielectric material 12a and a second dielectric material 12b. In some embodiments, as shown, first dielectric material 12a and second dielectric material 12b are arranged in alternating layers. In some embodiments, first dielectric material 12a comprises or consists essentially of silicon oxide, while second dielectric material 12b comprises or consists essentially of silicon nitride. In some embodiments, dielectric material 12 comprises only one dielectric material.

[0048] Despite Figure 3 , a substrate 20 is shown having a specific structure and material pattern, but the illustrations shown are not limiting.

[0049] The method 200 exposes the substrate surfaces (i.e., the damaged dielectric surface 23 and the reduced metal surface 25) to a plasma at operation 210 to form a clean substrate 40 having a clean dielectric surface 43 and a clean metal surface 45. Advantageously, the method 200 is performed by a single operation rather than the two or more operations of the method 100. The single operation method 200 eliminates the need to modify the processing chamber or to transfer the substrate between multiple chambers on a cluster tool.

[0050] The plasma is formed from a plasma gas comprising hydrogen (H2) and oxygen (O2). In some embodiments, the plasma gas consists essentially of hydrogen (H2) and oxygen (O2). In this regard, the plasma gas "consists essentially of" hydrogen and oxygen has a molar concentration of greater than or equal to about 95%, greater than or equal to about 98%, greater than or equal to about 99%, or greater than or equal to about 99.5% hydrogen and oxygen, excluding any inert diluent gas(es).

[0051] In some embodiments, the plasma gas further comprises an inert diluent gas. In this regard, the inert gas does not alter the oxidation state (i.e., oxidation or reduction) of the substrate surface. In some embodiments, the diluent gas comprises or consists essentially of argon. In this regard, the diluent gas consisting essentially of argon comprises greater than or equal to about 95%, greater than or equal to about 98%, greater than or equal to about 99%, or greater than or equal to about 99.5%, based on the moles of all inert gases.

[0052] In some embodiments, the plasma gas is formed by providing hydrogen, oxygen, and an optional diluent gas at predetermined flow rates. In some embodiments, the plasma gas is formed by delivering hydrogen having a hydrogen flow rate, oxygen having an oxygen flow rate, and a diluent gas having a flow rate to the processing chamber.

[0053] In some embodiments, the hydrogen flow rate is in a range of about 0 sccm to about 30 sccm or in a range of about 0 sccm to about 15 sccm. In some embodiments, the hydrogen flow rate is less than or equal to about 30 sccm, less than or equal to about 15 sccm, or less than or equal to about 10 sccm. In some embodiments, the oxygen flow rate is in a range of about 10 sccm to about 50 sccm or in a range of about 10 sccm to about 20 sccm. In some embodiments, the oxygen flow rate is about 10 sccm, about 15 sccm, or about 30 sccm. In some embodiments, the diluent flow rate is in a range of about 3000 sccm to about 6000 sccm, about 4000 sccm to about 5000 sccm, or about 4900 sccm to about 5000 sccm. In some embodiments, the diluent flow rate is about 5000 sccm.

[0054] In some embodiments, the ratio of the oxygen flow rate to the hydrogen flow rate is in the range of about 1:2 to about 20:1, in the range of 1:1 to about 10:1, in the range of about 1:1 to about 5:1, in the range of about 5:1 to about 10:1, in the range of about 5:1 to about 15:1, or in the range of about 10:1 to about 15:1. This ratio may also be referred to as a flow rate ratio. In some embodiments, the molar ratio of hydrogen to oxygen in the plasma gas is in the range of about 1:2 to about 20:1, in the range of 1:1 to about 10:1, in the range of about 1:1 to about 5:1, in the range of about 5:1 to about 10:1, in the range of about 5:1 to about 15:1, or in the range of about 10:1 to about 15:1.

[0055] In some embodiments, the plasma is a electrically coupled plasma (CCP). The frequency of the plasma can be any suitable frequency. In some embodiments, the plasma frequency is in the range of 50 Hz to 100 MHz, or in the range of 100 kHz to 60 MHz, or in the range of 500 kHz to 40 MHz, or about 13.56 MHz.

[0056] The power of the plasma can be any suitable power. In some embodiments, the plasma power is in the range of about 100 W to about 500 W, in the range of about 100 W to about 300 W, or in the range of about 300 W to about 500 W. In some embodiments, the plasma power is about 200 W or about 400 W. In some embodiments, the plasma is a microwave plasma having a power in the range of about 2500 W to about 3000 W or in the range of about 2800 W to about 2900 W. In some embodiments, no bias power is applied to the substrate or substrate support.

[0057] The substrate surface can be exposed to the plasma for any suitable period of time. In some embodiments, the substrate surface is exposed to the plasma for a period in a range of about 15 minutes to about 30 minutes.

[0058] In some embodiments, the method 200 further includes exposing the substrate 10 to a plasma formed from hydrogen gas. In some embodiments, these plasma exposures are performed prior to exposing the substrate to the plasma described above with respect to operation 210.

[0059] The substrate surface may be maintained at a suitable processing temperature during operation 210. In some embodiments, the substrate surface is maintained at a temperature in a range of about 100°C to about 400°C. In some embodiments, the substrate surface is maintained at about 400°C.

[0060] Method 200 can be performed at any suitable pressure. In some embodiments, the pressure of the processing chamber used for method 200 is maintained at a pressure in a range of about 5 Torr to about 50 Torr.

[0061] As described above, the single plasma exposure at operation 210 is capable of oxidizing the damaged dielectric surface 23 without oxidizing the reduced metal surface 25 to form a clean dielectric surface 43 and a clean metal surface 45. However, in contrast to method 100, method 200 is performed in a single processing chamber at a single processing temperature.

[0062] Oxidizing the damaged dielectric surface 23 without oxidizing the reduced metal surface 25 can be described as selectively oxidizing the damaged dielectric surface 23. In some embodiments, selectively oxidizing the damaged dielectric surface 23 means that the properties of the reduced metal surface are similar before and after exposure to the plasma at operation 210. In some embodiments, the property is selected from one or more of reflectivity, resistivity, and sheet resistance. In this regard, if the reflectivity of the cleaned metal surface is within ±5%, then the reflectivity of the cleaned metal surface is similar to the reflectivity of the reduced metal surface. In this regard, if the resistivity of the cleaned metal surface is within ±10%, then the resistivity of the cleaned metal surface is similar to the resistivity of the reduced metal surface. In this regard, if the sheet resistance of the cleaned metal surface is within ±10%, then the sheet resistance of the cleaned metal surface is similar to the sheet resistance of the reduced metal surface.

[0063] In some embodiments, the damaged dielectric surface 23 comprises a relatively low oxygen concentration. In some embodiments, the oxygen content of the damaged dielectric surface 23 may be less than 20 atomic percent. In these embodiments, the method 200 increases the oxygen concentration to provide a clean dielectric surface 43. In some embodiments, the clean dielectric surface 43 has an oxygen content greater than or equal to about 45 atomic percent. In some embodiments, the method 200 increases the oxygen content of the damaged dielectric surface 23 to a range from about 40 atomic percent to about 50 atomic percent.

[0064] In some embodiments, method 200 further comprises selectively depositing a bulk metal layer on clean metal surface 45. In some embodiments, the bulk metal layer completely fills the feature. In some embodiments, the bulk metal layer is deposited on bottom surface 19 of the feature, growing from the bottom upward. In some embodiments, no deposition is observed on top surface 17 or sidewalls 18. In some embodiments, the bulk metal layer partially fills feature 16. In some embodiments, the bulk metal layer is coplanar with top surface 17. In some embodiments, the metal material comprises tungsten, and the bulk metal layer comprises tungsten.

[0065] As used in this disclosure, the terms "selectively depositing" a film (and the like) on one surface "over" another surface means that a first amount of the film is deposited on the first surface and a second amount of the film is deposited on the second surface, wherein the second amount of the film is less than the first amount of the film, or no film is deposited on the second surface.

[0066] The term "relative to" does not imply the physical orientation of one surface on top of another, but rather refers to the relationship of the chemical reaction to the thermodynamic or kinetic properties of one surface relative to the other. For example, selectively depositing a film on a metal surface relative to a dielectric surface means that the film is deposited on the metal surface while little or no film is deposited on the dielectric surface; or that film formation on the metal surface is thermodynamically or kinetically favored relative to film formation on the dielectric surface.

[0067] The selectivity of a deposition process can be expressed as a multiple of the growth rate. For example, if one surface grows (or deposits) 25 times faster than another surface, the process would be described as having a selectivity of 25:1. In this regard, a higher ratio indicates a more selective process. The selectivity of a deposition process can also be expressed by stating the amount of film that can be deposited on a first surface before the film is deposited on a second surface.

[0068] Some embodiments of the present disclosure relate to methods of cleaning substrates. Some embodiments of the present disclosure relate to methods for cleaning a substrate surface having both a dielectric surface and a metal surface. Some embodiments of the present disclosure relate to methods of cleaning semiconductor contacts.

[0069] Some embodiments of the present disclosure advantageously provide cleaning methods performed at a single processing temperature. Some embodiments of the present disclosure provide methods performed in a single processing chamber. In this regard, some embodiments of the present disclosure provide cleaning methods with shorter processing times and / or higher throughput.

[0070] The advantages of the present disclosure are best understood when compared to known cleaning methods. Figure 4 An exemplary method known in the art is shown. Method 400 begins with a substrate 510 comprising a dielectric material 512 and a metallic material 514 .

[0071] In some embodiments, substrate 510 has a feature 516 formed in substrate 510. Feature 516 can be any suitable shape. For example, in some embodiments, feature 516 comprises one or more of a trench or a via. In some embodiments, feature 516 has a top surface 517, sidewalls 518, and a bottom surface 519. One skilled in the art will appreciate that, although Figure 4 Two sidewalls 518 are shown, but the present disclosure is not limited to two sidewalls. For example, a circular via technically has one continuous sidewall 518, but the cross-sectional view shown would show two sidewalls.

[0072] In some embodiments, top surface 517 comprises a contaminated dielectric surface 513. In some embodiments, sidewall 518 comprises a contaminated dielectric surface 513 or a contaminated metal surface 515 (not shown). In some embodiments, bottom surface 519 comprises a contaminated metal surface 515. In some embodiments, substrate 510 comprises a semiconductor contact. In some embodiments, the semiconductor contact comprises metal material 514. In some embodiments, the semiconductor contact comprises a material to be formed within feature 516.

[0073] In some embodiments, dielectric material 512 comprises or consists essentially of one or more of silicon oxide, silicon nitride, or silicon oxynitride. In this regard, a material consisting essentially of the aforementioned materials may be greater than or equal to about 95%, 98%, 99%, or 99.5% of the aforementioned materials on an atomic basis.

[0074] The metal material 514 may comprise any suitable metal or combination of metals. In some embodiments, the metal material 514 comprises one or more of tungsten, cobalt, molybdenum, ruthenium, iridium, and rhodium. In some embodiments, the metal material consists essentially of tungsten or cobalt.

[0075] The surface of substrate 510 (also referred to as substrate surface) is contaminated. In some embodiments, the contaminated substrate surface includes a contaminated dielectric surface 513 and a contaminated metal surface 515. In some embodiments, the substrate surface is contaminated with carbon, nitrogen, oxygen, organic residues (-CH x ) or perfluorinated organic residues (-CF x ) of one or more types of pollution.

[0076] The dielectric material 512 has a contaminated dielectric surface 513, and the metal material 514 has a contaminated metal surface 515. In some embodiments, the contaminants on the contaminated dielectric surface 513 include carbon, nitrogen, organic residues (-CH x ) or perfluorinated organic residues (-CF x In some embodiments, the contaminants on the contaminated metal surface 515 include nitrogen, oxygen, organic residues (-CH x ) or perfluorinated organic residues (-CF x). In some embodiments, the contaminants on the metal surface 515 are different from the contaminants on the dielectric surface 513. In some embodiments, the contaminants on the metal surface 515 are the same as the contaminants on the dielectric surface 513. In some embodiments, the concentration per unit area of ​​the contaminants on the dielectric surface 513 is different from the concentration per unit area of ​​the contaminants on the metal surface 515. In some embodiments, the concentration per unit area of ​​the contaminants on the dielectric surface 513 is the same as the concentration per unit area of ​​the contaminants on the metal surface 515.

[0077] Method 400 begins with a first reduction process 410. First reduction process 410 forms a damaged substrate 520. Damaged substrate 520 comprises a dielectric material 512 having a damaged dielectric surface 523 and a metal material 514 having a reduced metal surface 525. As used herein, the term "reduced metal surface" refers to a metal surface having a reduced oxidation state. A reduced metal surface does not indicate a difference or change in the thickness of the metal material.

[0078] The damaged dielectric surface 523 contains a reduced concentration of contaminants. In some embodiments, the damaged dielectric surface 523 is substantially free of contaminants. In this regard, the surface of the dielectric material 512 has been cleaned. However, due to the first reduction process 410, the damaged dielectric material contains a reduced concentration of oxygen at the surface of the dielectric material 512. The reduced metal surface 525 contains a reduced concentration of contaminants present on the contaminated metal surface 515.

[0079] In some embodiments, the first reduction treatment 410 comprises a plasma cleaning process. In some embodiments, the first reduction treatment 410 comprises exposure to a hydrogen-containing plasma. In some embodiments, the first reduction treatment 110 comprises exposure to a hydrogen plasma. Those skilled in the art will recognize that "hydrogen plasma" is a plasma formed using molecular hydrogen (H2), and the hydrogen-containing plasma may include H2.

[0080] The first reduction process 410 is performed at a first pressure, wherein the substrate is maintained at a first temperature and has a first bias voltage. Other process conditions may also be controlled. The first temperature is relatively high. In some embodiments, the first temperature is in the range of about 250°C to about 550°C, in the range of about 300°C to about 500°C, or in the range of about 350°C to about 450°C. In some embodiments, the first temperature is about 350°C, about 400°C, or about 450°C.

[0081] Method 400 continues with a second process, referred to as second oxidation process 420. Those skilled in the art will recognize that the sequence numbers used herein, such as first, second, etc., merely provide a nomenclature for distinguishing individual process steps and should not be construed as limiting the method to a particular sequence or number of reactions or reactive species. Second oxidation process 420 forms oxidized substrate 530. Oxidized substrate 530 comprises dielectric material 512 having an oxidized dielectric surface 533 and metal material 514 having an oxidized metal surface 535.

[0082] The oxidized dielectric surface 533 contains an increased oxygen concentration at the surface of the dielectric material 512 relative to the oxygen concentration at the damaged dielectric surface 523. For embodiments where the contaminated metal surface contains nitrogen, the oxidized metal surface 535 contains virtually no nitrogen. In some embodiments, "virtually no nitrogen" refers to a nitrogen content of less than 10%, 9%, 8%, 7.5%, or 7% nitrogen on an atomic basis. However, relative to the reduced metal surface 525, the oxidized metal surface 535 contains additional oxygen contaminants.

[0083] In some embodiments, the second oxidation process 420 comprises a plasma treatment. In some embodiments, the second oxidation process 420 comprises exposure to an oxygen-containing plasma. In some embodiments, oxygen (O 2 ) is used to form the oxygen-containing plasma. The second oxidation process 420 is performed at a second pressure, with the substrate maintained at a second temperature and having a second bias voltage. Other process conditions may also be controlled.

[0084] At least some of the conditions of the first reduction treatment 410 and the second oxidation treatment 420 are different. For example, the second temperature is relatively low. In some embodiments, the second temperature is in the range of about 50°C to about 200°C, in the range of about 50°C to about 250°C, or in the range of about 50°C to about 150°C. In some embodiments, the second temperature is about 50°C, about 75°C, about 100°C, about 125°C, or about 150°C. In order to perform the second oxidation treatment 420 after the first reduction treatment 410, other process conditions may also need to be changed. For example, the first pressure and the second pressure may be different, or the first bias voltage and the second bias voltage may be different.

[0085] The method 400 continues with a third reduction process 430. The third reduction process 430 forms a clean substrate 540. The clean substrate 540 has a dielectric material 512 having a clean dielectric surface 543 and a metal material 514 having a clean metal surface 545.

[0086] In some embodiments, the cleaned dielectric surface 543 contains a reduced oxygen concentration at the surface of the dielectric material 512 relative to the oxygen concentration at the oxidized dielectric surface 533. For embodiments in which the oxidized dielectric surface 533 contains an excess of oxygen relative to the expected stoichiometric ratio of oxygen to other elements, the third reduction treatment 430 reduces the oxygen concentration to at or about the expected stoichiometric ratio. For example, the oxygen content of an oxygen-contaminated silicon oxide surface is greater than the stoichiometric amount of silicon oxide. For embodiments in which the oxidized dielectric surface contains oxygen at or near the stoichiometric ratio of oxygen to other elements, the third reduction treatment 430 has little effect on the oxidized dielectric surface 533 when forming the cleaned dielectric surface 543. In short, the cleaned dielectric surface 543 contains fewer contaminants than the contaminated dielectric surface 513.

[0087] The clean metal surface 545 contains a reduced concentration of oxygen at the surface of the metal material 514 relative to the concentration of oxygen at the oxidized metal surface 535. In some embodiments, the clean metal surface 545 contains virtually no oxygen. In short, the clean metal surface 545 contains fewer contaminants than the contaminated metal surface 515 and might otherwise be described as a bare metal surface.

[0088] In some embodiments, the third reduction treatment 430 comprises a plasma treatment. In some embodiments, the third reduction treatment 430 comprises exposure to a hydrogen-containing plasma. In some embodiments, the third reduction treatment 430 comprises exposure to a hydrogen plasma.

[0089] At least some of the conditions of the second oxidation treatment 420 and the third reduction treatment 430 are different. For example, the third temperature is relatively high. In some embodiments, the first temperature is in the range of about 250°C to about 550°C, in the range of about 300°C to about 500°C, or in the range of about 350°C to about 450°C. In some embodiments, the first temperature is about 350°C, about 400°C, or about 450°C.

[0090] Additional process conditions may also need to be changed in order to perform the third reduction process 430 after the second oxidation process 420. For example, the second pressure and the third pressure may be different, or the second bias voltage and the third bias voltage may be different.

[0091] In some embodiments, the process conditions for the first reduction treatment 410 and the third reduction treatment 430 are the same. In some embodiments, the process conditions for the first reduction treatment 410 and the third reduction treatment 430 are different.

[0092] Modifying the process conditions between the first reduction process 410, the second oxidation process 420, and the third reduction process 430 within the same process chamber takes a considerable amount of time. For example, the chamber must be heated or cooled to an appropriate temperature and the gas source must be switched to a different process gas.

[0093] Modification of process conditions between the first reduction treatment 410, the second oxidation treatment 420, and the third reduction treatment 430 can be performed by transitioning the substrate from one process chamber to another. Such transitions between process chambers may be faster than transitioning a single process chamber from the conditions used for the first reduction treatment 410 to the second oxidation treatment 420 and / or the second oxidation treatment 420 to the third reduction treatment 430. However, transitioning processes requires additional time, thereby reducing overall throughput and requiring a multi-chamber processing tool.

[0094] Some embodiments of the present disclosure improve upon the known processes described above. Some embodiments of the present disclosure are performed at a single process temperature. Some embodiments of the present disclosure are performed within a single process chamber. These improvements are directly related to reduced process time and increased throughput.

[0095] Reference Figure 5 One or more embodiments are directed to a method 600 for cleaning a substrate 510. The substrate 510 is as described above. The substrate 510 includes a dielectric material 512 and a metal material 514. A surface of the substrate 510 (also referred to as a substrate surface) is contaminated. Thus, the dielectric material 512 has a contaminated dielectric surface 513, and the metal material 514 has a contaminated metal surface 515. The contaminants are as described above.

[0096] Figure 5 A dielectric material 512 is depicted, comprising a first dielectric material 512a and a second dielectric material 512b. In some embodiments, as shown, the first dielectric material 512a and the second dielectric material 512b are arranged in alternating layers. In some embodiments, the first dielectric material 512a comprises or consists essentially of silicon oxide, and the second dielectric material 512b comprises or consists essentially of silicon nitride.

[0097] Method 600 exposes the substrate surface (i.e., contaminated dielectric surface 513 and contaminated metal surface 515) to a plasma at cleaning operation 610 to form a clean substrate 540 having a clean dielectric surface 543 and a clean metal surface 545. The plasma is formed from a plasma gas comprising hydrogen (H2) and oxygen (O2). In some embodiments, the plasma consists essentially of hydrogen (H2) and oxygen (O2). In some embodiments, the plasma gas further comprises an inert diluent gas. In some embodiments, the diluent gas comprises or consists essentially of argon.

[0098] In some embodiments, the plasma gas is formed by providing hydrogen, oxygen, and an optional diluent gas at predetermined flow rates. In some embodiments, the plasma gas is formed by delivering hydrogen having a hydrogen flow rate, oxygen having an oxygen flow rate, and a diluent gas having a flow rate to the processing chamber.

[0099] In some embodiments, the hydrogen flow rate is in the range of about 50 to about 750 sccm. In some embodiments, the hydrogen flow rate is about 60 sccm or about 600 sccm. In some embodiments, the oxygen flow rate is in the range of about 50 sccm to about 75 sccm. In some embodiments, the oxygen flow rate is about 60 sccm. In some embodiments, the diluent flow rate is in the range of about 2500 sccm to about 5000 sccm. In some embodiments, the diluent flow rate is about 3000 sccm.

[0100] In some embodiments, the ratio of the oxygen flow rate to the hydrogen flow rate is in the range of about 1:2 to about 20:1, in the range of 1:1 to about 10:1, in the range of about 1:1 to about 5:1, in the range of about 5:1 to about 10:1, in the range of about 5:1 to about 15:1, or in the range of about 10:1 to about 15:1. This ratio may also be referred to as a flow rate ratio. In some embodiments, the molar ratio of hydrogen to oxygen in the plasma gas is in the range of about 1:2 to about 20:1, in the range of 1:1 to about 10:1, in the range of about 1:1 to about 5:1, in the range of about 5:1 to about 10:1, in the range of about 5:1 to about 15:1, or in the range of about 10:1 to about 15:1.

[0101] In some embodiments, the plasma is a electrically coupled plasma (CCP). The frequency of the plasma can be any suitable frequency. In some embodiments, the plasma frequency is in the range of 50 Hz to 100 MHz, or in the range of 100 kHz to 60 MHz, or in the range of 500 kHz to 40 MHz, or about 13.56 MHz. The power of the plasma can be any suitable power. In some embodiments, the plasma power is in the range of about 100 W to about 500 W, in the range of about 100 W to about 300 W, or in the range of about 300 W to about 500 W. In some embodiments, the plasma power is about 200 W or about 400 W. In some embodiments, no bias power is applied to the substrate or substrate support.

[0102] In some embodiments, method 600 further includes exposing substrate 510 to a plasma formed of hydrogen and / or a plasma formed of oxygen. In some embodiments, these plasma exposures are performed prior to exposing the substrate to the plasma described above with respect to operation 610.

[0103] The substrate surface may be maintained at a suitable processing temperature during operation 610. In some embodiments, the substrate surface is maintained at the same processing temperature during operation 610 and any additional plasma exposures. In some embodiments, the substrate surface is maintained at a temperature of approximately 400°C.

[0104] The method 600 can be performed at any suitable pressure. In some embodiments, the pressure of the processing chamber of the method 600 is maintained at about 5 Torr.

[0105] As described above, the single plasma exposure at operation 610 can remove contaminants from the contaminated dielectric surface 513 and the contaminated metal surface 515 to form a clean dielectric surface 543 and a clean metal surface 545. However, in contrast to method 400, method 600 is performed in a single processing chamber at a single processing temperature.

[0106] In some embodiments, the contaminated dielectric surface 513 contains a relatively low concentration of oxygen. In some embodiments, the oxygen content of the contaminated dielectric surface 513 may be less than 20 atomic percent. In these embodiments, the method 600 increases the concentration of oxygen to provide a clean dielectric surface 543. In some embodiments, the clean dielectric surface 543 has an oxygen content greater than or equal to about 45 atomic percent.

[0107] In some embodiments, the contaminated dielectric surface 513 comprises silicon oxynitride and has a relatively low oxygen to silicon ratio. In some embodiments, the oxygen to silicon ratio of the contaminated dielectric surface 513 may be less than or equal to about 1.5. In these embodiments, the method 600 increases the oxygen to silicon ratio to provide a clean dielectric surface 543. In some embodiments, the clean dielectric surface 543 has an oxygen to silicon ratio greater than or equal to about 3.9.

[0108] As described above, in some embodiments, the contaminated metal surface 515 is contaminated with nitrogen. In some embodiments, the nitrogen content of the contaminated metal surface 515 may be greater than or equal to about 15 atomic percent. In these embodiments, the method 600 reduces the concentration of nitrogen to provide a clean metal surface 545. In some embodiments, the clean metal surface 545 has a nitrogen content of less than or equal to about 7.5 atomic percent.

[0109] The contaminated metal surface 515 has a reduced reflectivity relative to silicon compared to a surface comprising a pure metal material having (multiple) the same metal but without the contaminants. Without being bound by theory, it is believed that this reduction in reflectivity is due to oxidation or the presence of oxygen contaminants on the surface of the metal material. For example, the reflectivity of pure tungsten material relative to silicon at 190 nm is approximately 0.85, and the reflectivity of the contaminated metal surface 515 of tungsten metal material 514 is less than or equal to approximately 0.8. In some embodiments, method 600 increases the reflectivity to provide a clean metal surface 545. In some embodiments, the metal material 514 comprises tungsten, and the clean metal surface 545 has a reflectivity relative to silicon greater than or equal to approximately 0.85 at 190 nm.

[0110] Without being bound by theory, it is believed that the reduction in reflectivity of the contaminated metal surface is a result of contaminants (particularly oxygen) on the contaminated metal surface. Thus, the increase in reflectivity demonstrates the removal of oxygen contaminants from the contaminated metal surface 515.

[0111] In some embodiments, method 600 further comprises selectively depositing a bulk metal layer on cleaned metal surface 545. In some embodiments, the bulk metal layer completely fills the feature. In some embodiments, the bulk metal layer is deposited on bottom surface 519 of the feature, growing from the bottom upward. In some embodiments, no deposition is observed on top surface 517 or sidewalls 518. In some embodiments, the bulk metal layer partially fills feature 516. In some embodiments, the bulk metal layer is coplanar with top surface 517. In some embodiments, metal material 514 comprises tungsten, and the bulk metal layer comprises tungsten.

[0112] Example

[0113] Example 1 - Adding Hydrogen to Oxygen Plasma Gas

[0114] like Figure 1 A series of substrates, each having a dielectric material 12 comprising SiN and a metal material 14 comprising tungsten, were provided to a processing chamber. The substrates were maintained at 400°C, and the processing chamber was maintained at 5 Torr. The substrates were exposed to a plasma formed from a plasma gas. As shown in Table 1, the composition of the plasma gas varied between substrates. The plasma power also varied between substrates. For each substrate, the oxygen content of the SiN material and the reflectivity of the tungsten material relative to silicon at 190 nm were evaluated before and after exposure to the plasma. The oxygen content and reflectivity results are shown in Table 1.

[0115] Table 1

[0116]

[0117] Example 2 - Reducing Nitrogen Contamination on Metal Surfaces

[0118] A series of substrates similar to those described in Example 1 were prepared. The substrates were exposed to a plasma formed from a plasma gas containing varying ratios of H2 and O2. The plasma power was also varied. Table 2 shows the elemental composition of the reference substrate along with various plasma gas compositions and plasma powers.

[0119] Table 2

[0120] sample <![CDATA[H2:O2比例]]> Plasma power N％ O％ W％ 6 N / A N / A 17.1 40.6 39.7 7 1:1 200W 8.9 48.1 40.7 8 10:1 200W 14.3 36.6 46.5 9 10:1 400W 5.0 43.5 47.3

[0121] Example 3 - Co-flow with additional plasma

[0122] A series of substrates similar to those described in Example 1 were prepared. The substrates were exposed to plasma (H2O2) formed from a plasma gas containing H2 and O2 in a ratio of 10:1, as well as hydrogen plasma (H2) and / or oxygen plasma (O2). The plasma power was maintained constant at 400 W. The nitrogen content of the tungsten surface and the ratio of oxygen to silicon on the dielectric surface relative to the reflectivity of silicon on the tungsten surface are shown in Table 3.

[0123] Table 3

[0124]

[0125]

[0126] Throughout this specification, references to "one embodiment," "certain embodiments," "one or more embodiments," or "an embodiment" mean that the particular features, structures, materials, or characteristics described in connection with that embodiment are included in at least one embodiment of the present disclosure. Thus, the appearance of phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the present disclosure. Furthermore, in one or more embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner.

[0127] Although the present disclosure has been described with reference to a number of specific embodiments, it will be understood by those skilled in the art that the various embodiments described are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations may be made to the methods and apparatus of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure may include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A method comprising the steps of: exposing a substrate surface comprising a damaged dielectric surface and a reduced metal surface to a plasma formed from a plasma gas comprising hydrogen and oxygen to oxidize the damaged dielectric surface without substantially oxidizing the reduced metal surface, wherein the method increases the oxygen content of the damaged dielectric surface to a range of about 40 to about 50 atomic percent.

2. The method of claim 1, wherein the plasma gas further comprises a dilution gas.

3. The method of claim 2, wherein the dilution gas forms greater than or equal to about 95% of the plasma gas.

4. The method of claim 3 , wherein the plasma gas is formed by delivering to the processing chamber: hydrogen gas having a flow rate in a range of about 0 sccm to about 15 sccm, oxygen gas having a flow rate in a range of about 10 sccm to about 20 sccm, and a dilution gas having a flow rate in a range of about 4900 sccm to about 5000 sccm. The method of claim 2 , wherein the diluent gas comprises argon.

6. The method of claim 1, wherein the ratio of hydrogen to oxygen is in the range of about 1:1 to about 1:

10.

7. The method of claim 1, wherein the dielectric surface comprises one or more of silicon oxide, silicon nitride, or silicon oxynitride.

8. The method of claim 1, wherein the metal surface comprises one or more of tungsten or cobalt.

9. The method of claim 1, wherein the plasma is a microwave plasma having a power in the range of about 2500 W to about 3000 W.

10. The method of claim 1, wherein the substrate surface is exposed to the plasma for a period in a range of about 15 minutes to about 30 minutes.

11. The method of claim 1 , wherein the substrate surface is maintained at a temperature of about 400°C.

12. The method of claim 1, wherein a reflectivity of the metal surface after exposure to the plasma is within ±5% of a reflectivity of the metal surface before exposure to the plasma.

13. The method of claim 1, wherein the resistivity of the metal surface after exposure to the plasma is within ±10% of the resistivity of the metal surface before exposure to the plasma.

14. The method of claim 1, wherein the sheet resistance of the metal surface after exposure to the plasma is within ±10% of the sheet resistance of the metal surface before exposure to the plasma.

15. The method of claim 1, further comprising the step of exposing the substrate surface to a hydrogen plasma to form the damaged dielectric surface.

16. A method for selectively oxidizing a dielectric surface, the method comprising the steps of: exposing a substrate surface comprising a silicon nitride surface and a tungsten surface to a microwave plasma formed from a plasma gas comprising hydrogen, oxygen, and argon to selectively oxidize the silicon nitride surface without oxidizing the tungsten surface, wherein the power of the microwave plasma is in a range of about 2500 W to about 3000 W, the argon concentration of the plasma gas is greater than or equal to about 95% by mole, and the ratio of hydrogen to oxygen is in a range of about 1:1 to about 1:10, and the substrate surface is maintained at a temperature of about 400° C. wherein the properties of the tungsten surface before and after exposure to the microwave plasma are similar, the properties being selected from one or more of reflectivity, resistivity, and sheet resistance, and The method increases the oxygen content of the silicon nitride surface to greater than or equal to about 45 atomic percent.

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