Electrochemical reduction of surface metal oxides

Abstract

[0003] Embodiments of the present disclosure relate to methods for reducing metal oxide layers to pure metal using microwave radiation. Particular embodiments provide methods for reducing native metal oxide on metal interconnects within substrate features, including dielectric sidewalls. In some embodiments, the surrounding dielectric material is not damaged by the disclosed process.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to methods for converting surface metal oxides to pure metals. In particular, embodiments of the present disclosure relate to methods for reducing metal oxides by microwave processes. [Background technology]

[0002] When pure metal materials are exposed to air, a thin layer of metal oxide can form on the surface of the metal. This surface layer of metal oxide can interfere with the selectivity of subsequent processing steps and increase the resistance of interconnects. Therefore, a method is needed to prevent and / or clean metal oxide from the surface of metal materials.

[0003] While integrated processing equipment and wafer transport under vacuum have reduced the need to remove these metal oxide layers, current pre-cleaning methods typically require hydrogen plasma, high processing temperatures (above 300 °C), and / or high-energy argon (Ar) sputtering. However, these processes often damage adjacent dielectric materials (e.g., feature sidewalls) and can adversely affect the selectivity of many metal deposition processes (e.g., selective tungsten deposition).

[0004] Additionally, current pre-cleaning methods must be tailored and / or tailored for different metal oxide materials (e.g., WOx, MoOx, CoOx, RuOx, CuOx, etc.), each of which may require a different plasma source, a different reactive gas mixture or chemical soak, and / or different processing conditions (e.g., temperature, pressure).

[0005] Therefore, there is a need for a universal method for converting surface metal oxides to pure metals, particularly a process that can be performed at relatively low temperatures without damaging the surrounding materials. Summary of the Invention

[0006] One or more embodiments of the present disclosure relate to a method for reducing a metal oxide layer on a surface, the method comprising exposing the metal oxide layer on a metal material to microwave radiation.

[0007] A further embodiment of the present disclosure relates to a method for reducing molybdenum oxide, the method comprising exposing a substrate surface having at least one feature to microwave radiation to reduce a molybdenum oxide layer on the molybdenum metal material, the at least one feature extending a depth from the substrate surface to a bottom comprising the molybdenum oxide layer and having two sidewalls comprising a low-k dielectric.

[0008] In order that the above-mentioned features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above can be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure, which may admit of other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a microwave processing tool including a microwave source in accordance with one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of a semiconductor processing tool including a modular microwave source in accordance with one or more embodiments of the present disclosure. [Figure 3] FIG. 1 is a perspective view of a source array of a modular microwave source in accordance with one or more embodiments of the present disclosure. [Figure 4] FIG. 1 is a cross-sectional view of a processing chamber for reducing metal oxides on a surface according to one or more embodiments of the present disclosure. [Figure 5A] 1 illustrates an exemplary substrate during processing in accordance with one or more embodiments of the present disclosure. [Figure 5B] 1 illustrates an exemplary substrate during processing in accordance with one or more embodiments of the present disclosure. [Figure 5C] 1 is a cross-sectional view of an exemplary substrate according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] To facilitate understanding, wherever possible, like reference numerals will be used to refer to like elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further description.

[0011] Before describing several example embodiments of the present disclosure, it is to be understood that the present disclosure is not limited to the details of construction or process steps set forth in the following description. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0012] As used herein, the term "about" means approximately or approximately, and in the context of a stated numerical value or range, refers to a variation of no more than ±15% of the numerical value. For example, values ​​that vary by ±14%, ±10%, ±5%, ±2%, ±1%, ±0.5%, or ±0.1% meet the definition of "about."

[0013] As used herein and in the appended claims, the term "substrate" or "wafer" refers to a surface or portion of a surface upon which a process acts. Those skilled in the art will also understand that a reference to a substrate may refer to only a portion of a substrate unless the context clearly indicates otherwise. Additionally, a reference to depositing on a substrate can refer to both a bare substrate and a substrate upon which one or more films or features have been deposited or formed.

[0014] As used herein, "substrate surface" refers to any substrate or surface of a material formed on a substrate on which film processing is performed during a manufacturing process. For example, substrate surfaces on which processing can 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, 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. The substrate may be subjected to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, and / or bake the substrate surface. In addition to performing film processing directly on the surface of the substrate itself, the present disclosure also contemplates that any of the disclosed film processing steps may be performed on an underlying layer formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include the underlying layer as the context indicates. Thus, for example, if a film / layer or partial film / layer is deposited on a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0015] One or more features may be formed on the substrate surface, one or more layers may be formed, or a combination thereof may be formed. The shape of the feature may be any suitable shape, including, but not limited to, a trench, a hole, or a via (circular or polygonal). As used in this context, the term "feature" refers to any intentional surface irregularity. Suitable examples of features include, but are not limited to, a trench having a top, two sidewalls, and a bottom that extends into the substrate, and a via having one or more sidewalls that extend to a bottom in the substrate.

[0016] The term "on" indicates direct contact between elements. The term "directly above" indicates direct contact between elements with no intervening elements.

[0017] As used herein and in the appended claims, the terms "precursor," "reactant," "reactive gas," and the like are used interchangeably to refer to any gas species capable of reacting with a substrate surface.

[0018] Embodiments of the present disclosure advantageously provide methods for reducing metal oxides on surfaces at relatively low temperatures without affecting adjacent materials. Certain embodiments advantageously provide methods for reducing metal oxides using a microwave process. In some embodiments, the metal oxide layer is not exposed to a plasma.

[0019] Embodiments of the present disclosure are illustrated by figures that depict processes, substrates, and apparatus according to one or more embodiments of the present disclosure. Those skilled in the art will understand that the illustrated processes, schemas, and resulting substrates are merely exemplary of the disclosed processes, and that the disclosed processes are not limited to the applications shown.

[0020] Referring to FIG. 1 , a cross-sectional view of an exemplary processing tool 100 is shown. Processing tool 100 may be a processing tool suitable for any type of processing operation using microwaves. While the embodiments described in detail herein relate to microwave processing methods, it should be understood that additional processing methods (including plasma processing methods) may be performed with processing tool 100. Furthermore, it should be understood that the PEALD methods described herein may be performed using different processing tools.

[0021] Generally, the processing tool 100 includes a chamber 178. In a processing tool 100 used for substrate processing, the chamber 178 may be a vacuum chamber. The vacuum chamber may include a pump (not shown) for removing gases from the chamber to provide the desired vacuum. Further embodiments may include the chamber 178 including one or more gas lines 170 for supplying process gases to the chamber 178 and an exhaust line 172 for removing byproducts from the chamber 178. Although not shown, it should be understood that the processing tool may include a showerhead or other gas distribution assembly for uniformly distributing the process gases over the substrate 174.

[0022] In some embodiments, the substrate 174 may be supported on a chuck 176. For example, the chuck 176 may be any suitable chuck, such as an electrostatic chuck. The chuck may also include cooling lines and / or heaters to provide temperature control of the substrate 174 during processing.

[0023] The processing tool 100 includes one or more microwave sources 104. The microwave sources 104 may include a solid-state microwave amplifier circuit 130 and an applicator 142. In some embodiments, a voltage control circuit 110 provides an input voltage to a voltage-controlled oscillator 120 to generate microwave radiation at a desired frequency that is transmitted to the solid-state microwave amplifier circuit 130 of each microwave source 104. The microwave radiation is processed by the microwave amplifier circuit 130 before being transmitted to the applicator 142. In some embodiments, an array 140 of applicators 142 is coupled to a chamber 178, each functioning as an antenna to couple microwave radiation to a substrate 174 within the chamber 178.

[0024] 2-4, a series of diagrams illustrating a microwave processing tool 100 according to an embodiment are shown. The microwave processing tool 100 generates microwaves useful for the low temperature reduction of metal oxides.

[0025] Referring to FIG. 2, a cross-sectional view of a microwave processing tool 100 (abbreviated as processing tool 100) according to an embodiment is shown. The processing tool can emit high frequency electromagnetic radiation. As used herein, "high frequency" electromagnetic radiation includes radio frequency radiation, extremely high frequency radiation, extremely high frequency radiation, and microwave radiation. "High frequency" can refer to frequencies between 0.1 MHz and 300 GHz.

[0026] Generally, embodiments include a processing tool 100 that includes a chamber 178. In the processing tool 100, the chamber 178 may be a vacuum chamber. The vacuum chamber may include a pump (not shown) for removing gases from the chamber to provide a desired vacuum. Further embodiments may include the chamber 178 including one or more gas lines 170 for supplying process gases to the chamber 178 and an exhaust line 172 for removing byproducts from the chamber 178. Although not shown, it should be understood that gases may be injected into the chamber 178 through a source array 150 (e.g., as a showerhead) to uniformly distribute the process gases over the substrate 174.

[0027] In embodiments, the substrate 174 may be supported on a chuck 176. For example, the chuck 176 may be any suitable chuck, such as an electrostatic chuck. The chuck 176 may also include cooling lines and / or heaters to provide temperature control of the substrate 174 during processing. The modular configuration of the radio frequency emission modules described herein allows embodiments to enable the processing tool 100 to accommodate substrates 174 of any size. For example, the substrate 174 may be a semiconductor wafer (e.g., 200 mm, 300 mm, 450 mm, or larger). Alternative embodiments include substrates 174 other than semiconductor wafers. For example, embodiments may include a processing tool 100 configured to process glass substrates (e.g., for display technology).

[0028] According to an embodiment, the processing tool 100 includes a modular radio frequency radiation source 104. The modular radio frequency radiation source 104 may include an array of radio frequency radiation modules 105. In an embodiment, each radio frequency radiation module 105 may include an oscillator module 106, an amplification module 130, and an applicator 142. As shown, the applicator 142 is shown schematically as being integrated into the source array 150.

[0029] In embodiments, the oscillator module 106 and the amplification module 130 may include electrical components that are solid-state electrical components. In embodiments, each of the multiple oscillator modules 106 may be communicatively coupled to a different amplification module 130. For example, each oscillator module 106 may be electrically coupled to a single amplification module 130. In embodiments, the multiple oscillator modules 106 may generate incoherent electromagnetic radiation. Thus, the electromagnetic radiation directed into the chamber 178 does not interact in a manner that would create undesirable interference patterns.

[0030] In embodiments, each oscillator module 106 generates high frequency electromagnetic radiation that is transmitted to an amplification module 130. The electromagnetic radiation is processed by the amplification module 130 before being transmitted to an applicator 142. In embodiments, each applicator 142 emits electromagnetic radiation into a chamber 178. In some embodiments, the applicators 142 couple the electromagnetic radiation to a substrate 174 within the chamber 178.

[0031] 3 , a perspective view of a source array 150 according to an embodiment is shown. In the embodiment, the source array 150 includes a dielectric plate 160. A plurality of cavities 167 are disposed on a first surface 161 of the dielectric plate 160. The cavities 167 do not extend through to a second surface 162 of the dielectric plate 160. The source array 150 may further include a plurality of dielectric resonators 166. Each of the dielectric resonators 166 is located in a different one of the cavities 167. Each of the dielectric resonators 166 may include a hole 165 at an axis of the dielectric resonator 166.

[0032] In an embodiment, the dielectric resonators 166 may have a first width W1, and the cavities 167 may have a second width W2. The first width W1 of the dielectric resonators 166 is smaller than the second width W2 of the cavities 167. This width difference provides a gap G between the sidewalls of the dielectric resonators 166 and the sidewalls of the cavities 167. In the illustrated embodiment, each of the dielectric resonators 166 is shown as having a uniform width W1. However, it should be understood that not all of the dielectric resonators 166 in the source array 150 need have the same dimensions.

[0033] Referring to FIG. 4 , a cross-sectional view of a processing tool 100 including an assembly 190 is shown, according to an embodiment. In an embodiment, the processing tool includes a chamber 178 sealed by the assembly 190. For example, the assembly 190 can abut one or more O-rings 181 to provide a vacuum seal for the interior volume 183 of the chamber 178. In other embodiments, the assembly 190 can interface with the chamber 178. That is, the assembly 190 can be part of a lid that seals the chamber 178. In an embodiment, the processing tool 100 can include multiple processing volumes (which can be fluidly coupled to one another), each processing volume having a different assembly 190. In an embodiment, a chuck 179 or the like can support a substrate 174 (e.g., a wafer, a workpiece, etc.). The substrate 174 can be separated from the assembly 190 by a distance D. That is, the chamber 178 can be a vacuum chamber. In an embodiment, the assembly 190 includes a source array 150 and a housing 182. The source array 150 may include a dielectric plate 160 and a plurality of dielectric resonators 166 extending upwardly from the dielectric plate 160. A cavity 167 in the dielectric plate 160 may surround each of the dielectric resonators 166. The sidewalls of the cavity 167 are separated from the sidewalls of the dielectric resonators 166 by a gap G. The dielectric plate 160 and the dielectric resonators 166 of the source array 150 may be a unitary structure (as shown in FIG. 3D ), or the dielectric plate 160 and the dielectric resonators 166 may be separate components.

[0034] The housing 182 includes a ring 131 that fits into the gap G. In an embodiment, the ring 131 and the conductors 173 of the housing 182 may be of one unitary structure (as shown in FIG. 3D ), or the conductors 173 and the ring 131 may be separate components. The housing 182 may have an opening sized to receive the dielectric resonator 166. In an embodiment, the monopole antennas 188 may extend into the holes of the dielectric resonators 166. The monopole antennas 188 are each electrically coupled to a power source (e.g., the radio frequency radiation module 105).

[0035] Embodiments of the present disclosure use a microwave process. Without being bound by theory, it is believed that the microwave process described herein weakens the bonds in metal oxide materials with the aid of the oscillatory rotational motion of metal oxide dipoles at microwave frequencies. The disclosed method uses an electric field for dipole rotation and a magnetic field for eddy currents to heat the metal oxide material without affecting other substrate materials. The microwave energy can be adjusted low enough (e.g., no plasma, low temperature) to avoid significant damage to the dielectric material. Furthermore, the disclosed method is self-limiting by only affecting the metal oxide and not the metal material.

[0036] 5A and 5B, method 200 begins with a metal oxide layer 260 on a metal material 250. In operation 210, metal oxide layer 260 is exposed to microwave radiation. As used in this context, exposing a substrate to "microwave radiation" should be understood to include activating a microwave source and exposing metal oxide layer 260 to the microwave radiation generated. In some embodiments, the microwave process does not generate a reactive plasma. In other words, in some embodiments, the metal oxide layer is not exposed to a plasma.

[0037] Metallic material 250 can include any suitable metal. In some embodiments, metallic material 250 and metal oxide layer 260 include one or more of the same metal. In some embodiments, metallic material includes or consists essentially of one or more of molybdenum, tungsten, ruthenium, copper, cobalt, tantalum, or titanium.

[0038] In some embodiments, metal oxide layer 260 has a thickness in the range of about 20 Å to about 30 Å. In some embodiments, method 200 reduces the thickness of metal oxide layer 260 to a range of about 10 Å to about 30 Å, or to a range of about 20 Å to about 30 Å, or to a range of about 15 Å to about 25 Å. In some embodiments, method 200 reduces the entire metal oxide layer to pure metal.

[0039] In some embodiments, the microwave process in operation 210 includes exposing the metal oxide layer 260 to a gas flow. In some embodiments, the gas flow is continuous and the microwave exposure is continuous. In other words, in some embodiments, neither the gas flow nor the microwave source is pulsed during the microwave process.

[0040] In some embodiments, the gas stream comprises an inert gas. Without being bound by theory, it is believed that exposure to an inert gas stream can help facilitate removal of volatile reaction by-products. In some embodiments, the inert gas comprises, or consists essentially of, helium (He) or argon (Ar). In some embodiments, the inert gas comprises, or consists essentially of, a hydrocarbon (e.g., CH, C, H, C, H). In some embodiments, the inert gas comprises, or consists essentially of CO.

[0041] In some embodiments, the gas flow includes a reactant. Without being bound by theory, it is believed that exposure to the reactant gas flow can react with activated oxygen atoms from the metal oxide layer 260 to form volatile species that are more easily removed from the processing chamber. In some embodiments, the reactant includes, or consists essentially of, one or more of hydrogen gas (H) or carbon monoxide (CO).

[0042] In some embodiments, method 200 is performed at a relatively low temperature. A relatively low temperature is advantageous because it causes less damage to surrounding materials (e.g., dielectrics). In some embodiments, the metallic material is maintained at a temperature in the range of about 300°C to about 400°C. In some embodiments, the metallic material is maintained at a temperature of about 300°C or less. In some embodiments, the metallic material is maintained at a temperature in the range of about 20°C to about 50°C, or in the range of about 20°C to about 100°C.

[0043] In some embodiments, the exposure duration is controlled to reduce a predetermined depth of metal oxide layer 260. In some embodiments, the duration is in the range of about 60 seconds to about 600 seconds, in the range of about 60 seconds to about 300 seconds, or in the range of about 30 seconds to about 120 seconds.

[0044] In some embodiments, the power of the microwave array 140 is in the range of about 800W to about 8000W, or in the range of about 900W to about 5000W, or in the range of about 1000W to about 3000W.

[0045] In some embodiments, the pressure of 178 can be controlled. In some embodiments, the pressure is maintained in a range of about 1 mTorr to about 10 Torr, or in a range of about 10 mTorr to about 1 Torr, or in a range of about 10 mTorr to about 100 mTorr, or in a range of about 50 mTorr to about 75 mTorr.

[0046] 5C, in some embodiments, a metal material 250 is disposed on a bottom 218 of a substrate feature 215. The feature 215 has sidewalls 214, 216. In some embodiments, at least a portion of the sidewalls 214, 216 comprise a low-k material 270. In some embodiments, the top surface 212 of the feature comprises a high-k dielectric 280. In some embodiments, the high-k dielectric 280 comprises silicon nitride.

[0047] In some embodiments, the low-k material comprises SiOC. In some embodiments, the low-k material of the sidewalls 214, 216 is not significantly damaged by the method 200. In this regard, a dielectric is "not significantly damaged" if the carbon / silicon normalized loss is about 30% or less.

[0048] Throughout this specification, references to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of phrases such as "in one or more embodiments," "in a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment of the present disclosure. Furthermore, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0049] Although the present disclosure has been described herein with reference to particular embodiments, those skilled in the art will recognize that the described embodiments 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 can be made in the disclosed method and apparatus without departing from the spirit and scope of the present disclosure. Accordingly, the present disclosure is intended to cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. A method for reducing a surface metal oxide layer, the method comprising exposing the metal oxide layer on a metal material to microwave radiation.

2. The method of claim 1 , wherein the metallic material comprises one or more of molybdenum, tungsten, ruthenium, cobalt, copper, tantalum, or titanium.

3. The method of claim 1 , wherein the metal oxide layer is not exposed to a plasma.

4. The method of claim 1 , further comprising exposing the metal oxide layer to a gas flow while exposing the metal oxide to the microwave radiation.

5. The method of claim 4 , wherein both the gas flow and the microwave radiation are continuous.

6. The method of claim 4 wherein the gas stream comprises an inert gas.

7. The method of claim 6 , wherein the inert gas comprises helium (He).

8. The method of claim 4 wherein the gas stream comprises a reactant.

9. The method of claim 8, wherein the reactants are supplied at a flow rate ranging from about 1 sccm to about 50 sccm.

10. The reactant is hydrogen gas (H 2 9. The method of claim 8, comprising:

11. 9. The method of claim 8, wherein the reactant comprises carbon monoxide (CO).

12. The method of claim 1 , wherein the metallic material is maintained at a temperature in the range of about 300° C. to about 400° C.

13. The method of claim 1 , wherein the metallic material is maintained at a temperature of about 300° C. or less.

14. The method of claim 1, wherein the metallic material is maintained at a temperature in the range of about 20°C to about 100°C.

15. 10. The method of claim 1, wherein the exposure period ranges from about 60 seconds to about 600 seconds.

16. The method of claim 1 , wherein the metal material is disposed at a bottom of a substrate feature, the substrate feature having sidewalls comprising a low-k material.

17. 17. The method of claim 16, wherein the low-k material is not significantly damaged by the method.

18. The method of claim 1 , wherein the method reduces the thickness of the metal oxide layer to a range of about 15 Å to about 25 Å.

19. 1. A method for reducing molybdenum oxide, comprising: exposing a substrate surface having at least one feature to microwave radiation to reduce a molybdenum oxide layer on a molybdenum metal material; The method, wherein the at least one feature extends a depth from the substrate surface to a bottom comprising the molybdenum oxide layer and has two sidewalls comprising a low-k dielectric.

20. 20. The method of claim 19, wherein the low-k dielectric is not significantly damaged by the method.

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