Multi-step pre-cleaning for selective metal gap fill

Abstract

Methods for pre-cleaning a substrate having metal and dielectric surfaces are described. The substrate is exposed to a strong reducing agent to remove contaminants from the metal surface and to damage the dielectric surface. The substrate is then exposed to an oxidizing treatment to repair the damage to the dielectric surface and to oxidize the metal surface. The substrate is then exposed to a weak reducing agent to reduce the metal oxide to a pure metal surface without substantially affecting the dielectric surface. Processing tools and computer readable media for implementing the methods are also described.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to methods for filling gaps in semiconductors. In particular, embodiments of the present disclosure relate to methods for pre-cleaning substrates to improve metal deposition selectivity. BACKGROUND

[0002] Interconnect metallization is widely used in logic and memory devices. Liner, followed by bulk deposition of CVD / PVD films, is commonly used for via / trench gap fill applications. However, as feature size is reduced, via / trench structures become smaller and the volume ratio of liner increases, making it difficult to achieve defect-free and low-resistivity metal gap fill.

[0003] Selective deposition processes take advantage of incubation differences on one surface material versus another during deposition. This incubation delay can be utilized to achieve bottom-up gap fill without the need for seams / voids and liners. However, there are several challenges that have hindered the widespread adoption of this technology. One of the most serious issues comes from impurities on the via bottom and dielectric surface that reduce the selectivity of selective metal growth on the metal surface versus the dielectric field. Current processes employ a single gas pre-clean (e.g., H2plasma or Ar plasma) to clean the surface contaminants (e.g., oxygen, carbon, fluorine, chlorine) from the surface of the metal bottom to shorten the incubation time. However, Ar plasma is very prone to sputtering, which can cause loss of selectivity on the sidewalls of the feature (trench or via). Hydrogen (H2) plasma can be used to remove fluorine, chlorine, and oxygen contaminants from the metal surface, but is not efficient enough to remove carbon contaminants. More aggressive hydrogen / argon (H2 / Ar) plasma can cause defects and ultimately loss of selectivity on the field surface.

[0004] In general, effectively cleaning the metal surface while still maintaining no or minimal growth on the field is the main challenge that prevents widespread use. With a single step pre-clean process, the selectivity window is not robust enough to accommodate a wider range of applications. For example, different surface structures with different etch residues or contaminants can require different pre-clean processes to achieve selective growth.

[0005] Additionally, current selective metal deposition processes typically have a very narrow selectivity window between loss of selectivity (field damage) and via bottom cleaning efficiency. This narrow window limits the process to only one or two applications.

[0006] Accordingly, there is a continuing need in the art for improved methods and apparatus for pre-cleaning a substrate surface for selective deposition. SUMMARY

[0007] One or more embodiments of the present disclosure relate to a method of pre-cleaning a substrate. A substrate comprising a surface structure having a metal bottom with a surface contaminant and a dielectric sidewall and field is exposed to a strong reducing agent to remove oxides and / or nitrides from the pure metal bottom and create surface defects in the sidewall and / or field of the dielectric. The substrate is exposed to an oxidizing agent to repair the surface defects in the sidewall and / or field of the dielectric and oxidize the metal bottom of the structure to form a metal oxide bottom of the structure. The substrate is exposed to a weak reducing agent to reduce the metal oxide bottom to a metal bottom without substantially damaging the dielectric.

[0008] Further embodiments of the present disclosure relate to a processing tool comprising a central transfer station comprising a robot configured to move a substrate between processing chambers. A first processing chamber is connected to the central transfer station and is configured to perform a strong reducing process to remove a surface contaminant from a metal surface and create defects in a dielectric sidewall. A second processing chamber is connected to the central transfer station and is configured to perform an oxidizing process to repair the defects in the dielectric sidewall and oxidize the metal surface to form a metal oxide. A third processing chamber is connected to the central transfer station and is configured to perform a weak reducing process to reduce the metal oxide to a pure metal without substantially damaging the dielectric. At least one controller is connected to the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber. The at least one controller has one or more configurations selected from the group consisting of: a configuration to move the substrate between the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber; a configuration to perform the strong reducing process in the first processing chamber; a configuration to perform the oxidizing process in the second processing chamber; and a configuration to perform the weak reducing process in the third processing chamber.

[0009] Further embodiments of the present disclosure relate to a non-transitory computer readable medium comprising instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: move a substrate between a central transfer station, a first processing chamber, a second processing chamber, and a third processing chamber; perform a strong reducing process in the first processing chamber; perform an oxidizing process in the second processing chamber; and perform a weak reducing process in the third processing chamber. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure can admit to other equally effective embodiments.

[0011] Figure 1A schematic of a substrate structure is shown in accordance with one or more embodiments of the present disclosure.

[0012] Figure 2 A flowchart of a method is shown in accordance with one or more embodiments of the present disclosure.

[0013] Figures 3A to 3D A schematic of a substrate is shown during a method of Figure 2

[0014] Figures 4A to 4D A schematic of a substrate is shown during a method of Figure 2

[0015] Figure 5 A schematic of a processing tool for use with one or more embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0016] Before several exemplary embodiments of the present disclosure are described, it is to 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 other embodiments and of being practiced or being carried out in various ways.

[0017] As used in this specification and the appended claims, the term "substrate" refers to a surface or portion of a surface upon which processing is performed. Those skilled in the art will further appreciate that reference to a substrate can also refer to only those surfaces of the substrate that are exposed during a process unless otherwise specifically stated or otherwise clear from the context of the specific matter at hand. In addition, reference to depositing on a substrate can mean both a bare substrate and a substrate having one or more films or features deposited or formed thereon.

[0018] As used herein, "substrate" refers to any substrate or material surface formed on the substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, 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, without limitation, semiconductor wafers. Substrates can be exposed to pre-treatment processes to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure, and / or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed can also be performed on an underlayer formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include this underlayer as the context dictates. Thus, for example, where a film / layer or partial film / layer has been deposited on the substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface. ​​

[0019] One or more embodiments of the present disclosure advantageously provide a method for selective deposition that can be directed to potentially more applications. Some embodiments advantageously provide a method for pre-cleaning substrates for a wider range of structure types and selective windows. Some embodiments advantageously provide a series of processing steps to effectively clean metal (e.g., tungsten, cobalt) surface contaminants while maintaining a sidewall / top field dielectric selectivity.

[0020] Some embodiments of the present disclosure method are used for selective metal deposition processing in a contact or via bottom that requires a clean surface to start with minimal incubation. In some embodiments, metal oxide / metal nitride / metal carbide, etc. contaminants that can hinder the selective deposition process and cause significant incubation delays are removed. Some embodiments can effectively clean metal contaminants while maintaining a contact / via structure that is preferred for selective processing.

[0021] One or more embodiments of the present disclosure use a series of processing steps that have different purposes for different contaminants using oxidation and reduction reactions. Some embodiments use two hydrogen reduction processes with an oxidation in between. Some embodiments advantageously provide a method that can effectively clean metal contaminants (e.g., metal oxide, metal nitride) using two hydrogen reduction steps and one oxidation step in between. Some embodiments advantageously maintain a dielectric selectivity for downstream selective deposition processing. For example, some embodiments prevent metal deposition on a dielectric sidewall / field of a substrate.

[0022] Some embodiments of the present disclosure provide a relatively low temperature oxidation process. Some embodiments oxidize at a temperature low enough to be used on different metal surfaces (e.g., tungsten, cobalt).

[0023] In exemplary, non-limiting embodiments, the cleaning process sequence includes: (1) exposure to a hydrogen inductively coupled plasma (ICP) plasma at 400-450 °C. In some embodiments, this step involves a high density hydrogen plasma to reduce the primary metal contaminants, i.e., to reduce metal oxides and metal nitrides to pure metals. It is expected that most metal compounds will be reduced by this step, and only a small fraction of contaminants will be left for further disposal; (2) a low temperature (-15-180 °C) oxidation treatment, which can convert the remaining metal nitrides to oxides, which can be reduced to pure metals in the next step, and / or oxidize the sidewall and top field dielectric materials (oxides and nitrides) that were damaged during the initial strong hydrogen plasma treatment. In some embodiments, the oxidation treatment repairs the dielectric surface by strong oxidation, thereby maintaining high selectivity for selective metal deposition. One advantage of this treatment is that the low temperature treatment will not cause excessive oxidation of some metals like cobalt (Co), and thus, the oxidized metals can be later reduced to pure metals; and (3) a second hydrogen plasma treatment (e.g., at 400-450 °C) of a capacitively coupled plasma (CCP) treatment, which, in some embodiments, reduces the metal oxides to pure metals. The treatment of some embodiments is performed at a pressure range of about 5-20 Torr. In some embodiments, the relatively low plasma density of the CCP gently accomplishes the metal reduction without significant impact on the dielectric. After the second reduction treatment, the contact / via bottom of some embodiments is pure metal, ready for selective deposition treatment, and the sidewall / top field dielectric remains selectively inert to selective deposition, thereby maintaining bottom-up growth throughout the structure.

[0024] A single-step pre-clean cannot meet the requirements of some selective metal deposition. Some embodiments combine an effective cleaning (corrosive H2or Ar plasma), which can easily cause damage to the dielectric field and loss of selectivity. Therefore, embodiments of the present disclosure provide a multi-step pre-cleaning approach, which can widen the selectivity window to make the selective metal technology a more robust process.

[0025] Figure 1 A contact structure used in accordance with one or more embodiments of the present disclosure is shown. Figure 1The substrate 100 shown includes a structure 130 defined by a first material 102 and a second material 104. In the illustrated embodiment, the structure 130 is a through-hole or trench. The structure is defined on a bottom 132 by the first material 102 and on a side 134 by a second material 104 different from the first material 102. In some embodiments, the first material 102 comprises a metal 110 forming a metallic bottom 115 of the structure. The metal 110 can be any suitable metal, including (but not limited to) tungsten (W), cobalt (Co), and / or copper (Cu). In some embodiments, the first material 102 and the bottom 132 of the structure 130 comprise nonmetals. Suitable nonmetals include, but are not limited to, metal nitrides (e.g., titanium nitride (TiN)), metal silicides (e.g., titanium silicide (TiSi)), or silicon (Si). As used in this specification and the accompanying claims, unless otherwise specified by subscripts, chemical formulas represent elemental identity and are not intended to imply any particular stoichiometry. For example, titanium nitride (TiN) films can have any suitable combination of titanium and nitrogen atoms, and are not limited to a single relationship.

[0026] In some embodiments, the second material 104 comprises a dielectric 120. The sidewalls 134 of the structure 130 are formed by the sidewalls 122 of the dielectric 120. The top surface 106 of the second material 104 is also referred to as a field. In some embodiments, the second material 104 comprises a dielectric 120 having sidewalls 122 and a field 124. The dielectric 120 may be any suitable material, including (but not limited to) silicon oxide (SiO), silicon dioxide (SiO2), silicon nitride (SiN), silicon oxynitride (SiON), aluminum nitride (AlN), aluminum oxide (AlO), or high-k dielectric materials. In some embodiments, the second material 104 comprises a hard mask material (e.g., carbon (C)).

[0027] Figure 2 Method 200 according to one or more embodiments of this disclosure is shown. Figures 3A to 3D A method 200 for pre-cleaning a substrate 100 prior to selective deposition is shown. Figure 3A A surface structure 130 is shown having a metallic surface 115 with surface contaminants 116. A dielectric sidewall 122 defines the structure 130. In some embodiments, one or more of the dielectric sidewalls 122 or fields 124 have contaminants 125 thereon. In some embodiments, the contaminants comprise one or more of oxygen, nitrogen, carbon, or halogens (e.g., fluorine, chlorine, bromine, or iodine). In some embodiments, the contaminants comprise organic compounds.

[0028] Figures 4A to 4D Another embodiment of this disclosure is shown. Figure 4A In the middle, the structure 130 formed in the substrate 300 is...Figure 3A The structure shown in FIG. 1 is more complex and includes more than one metal 110, 110'. Those skilled in the art will recognize that, Figures 3A to 3D and Figures 4A to 4D are merely representative of possible configurations and the present disclosure is not limited to the structures shown.

[0029] Each of the metals 110, 110' has a surface of the metal surface 115, 115' that forms the structure 130, such that the structure 130 has multiple bottoms at different locations within the structure 130. Figure 4A Embodiments of the structure 130 include a gate 140 under the metal 110. The gate 140 is not exposed to the structure 130 and is not affected by the cleaning method 200. The sidewall 134 of the structure shown is made of several layers of material. Alternating layers of the first dielectric 120a and the second dielectric 120b form the sidewall 134. The metal bottom shown has a contaminant 116, while the bottom 115' has a contaminant 116'.

[0030] The method 200 includes a strong cleaning treatment 210, a curing treatment 220, and an oxide reduction 230 treatment. The method 200 proceeds to the strong cleaning treatment 210 to remove the contaminant 116 from the metal surface 115. In some embodiments, the strong cleaning treatment 210 removes the contaminant 125 from the sidewall 122 and / or the field 124 of the dielectric 120.

[0031] The strong cleaning treatment 210 of some embodiments results in Figure 3B The substrate 100 shown in FIG. 1. The bottom surface 115 of the metal 110 is cleaned of contaminants. In Figure 4B In FIG. 1, the strong cleaning reduces the contaminant 116 on the bottom surface 115 of the metal 110, leaving some species of the contaminant 117 on the surface 115 that are, for example, not as easily reduced. In Figure 4B In embodiments of the structure 130, similar to Figure 3B The contaminant 116' on the metal surface 115' is removed, as shown.

[0032] The strong cleaning treatment 210 of some embodiments includes exposing the substrate 100 to a strong reducing agent. Figure 3B The substrate 100 is shown after exposure to the strong reducing agent. The strong reducing agent removes oxides and / or nitrides from the metal surface 115 and creates surface defects 127 in / on the sidewall 122 and / or the field 124 of the dielectric 120. The surface defects 127 of some embodiments include hydrogen dangling bonds. Figure 4B The substrate 300 is shown after exposure to the strong reducing agent to form surface defects 127 in / on the sidewall 122a, 122b and / or the field 124a, 124b of the dielectric 122a, 122b.

[0033] During the cleaning process, damage occurs to the sidewalls and / or field of the dielectric. In some embodiments, the strong cleaning process 210 results in hydrogen (H) dangling bonds on the surface of the dielectric. The hydrogen dangling bonds of some embodiments reduce the selectivity of the deposition process. In other words, the hydrogen dangling bonds of some embodiments provide nucleation sites (nurseries) resulting in a loss of selectivity.

[0034] In some embodiments, the "strong cleaning" process includes exposure to a plasma. In some embodiments, the plasma includes one or more of hydrogen (H2) or argon (Ar). In some embodiments, the plasma includes a mixture of hydrogen and argon (H2 / Ar) to clean contaminants on the metal surface 115 to form a pure metal surface or a metal surface with a reduced concentration of contaminants. In some embodiments, the plasma includes a mixture of hydrogen and argon to clean contaminants on the metal surface 115 to form a metal surface with a modified concentration of contaminants. Figure 3B Embodiments shown in FIG. 1 produce a pure metal surface 115, while Figure 4B Embodiments of FIG. 1 produce a metal surface 115, 115' with a reduced concentration or modified contaminants 117.

[0035] In some embodiments, the strong cleaning process 210 includes a hydrogen (H2) plasma. In some embodiments, the hydrogen plasma is an inductively coupled plasma (ICP). In some embodiments, the hydrogen plasma is a high density, high energy plasma. In some embodiments, the high energy plasma has a power greater than or equal to 400 Watts (W). In some embodiments, the high energy plasma has a power greater than or equal to 450 W, 500 W, 550 W, 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, 950 W, or 1000 W. In some embodiments, the high density plasma has an ion density greater than or equal to 10 19 ions / m 2 In some embodiments, the high density plasma has an ion density greater than or equal to 2 x 10 19 ions / m 2 , 3 x 10 19 ions / m 2 , 4 x 10 19 ions / m 2 , 5 x 10 19 ions / m 2 , 6 x 10 19 ions / m 2 , 7 x 10 19 ions / m 2 , 8 x 10 19 ions / m 2 , 9 x 10 19 ions / m 2 , 1 x 10 20 ions / m2 2 x 10 20 ions / m 2 3 x 10 20 ions / m 2 4 x 10 20 ions / m 2 or 5 x 10 20 ions / m 2 .

[0036] In one or more embodiments, the pressure of the hydrogen plasma is in a range from 1 mTorr to 50 mTorr, or in a range from 2 mTorr to 40 mTorr, or in a range from 3 mTorr to 30 mTorr, or in a range from 4 mTorr to 20 mTorr, or in a range from 5 mTorr to 10 mTorr.

[0037] In one or more embodiments, the substrate is maintained at a temperature in a range from 200 °C to 500 °C during exposure to the hydrogen plasma. In some embodiments, the substrate is maintained at a temperature in a range from 250 °C to 450 °C, or in a range from 300 °C to 400 °C during exposure to the hydrogen plasma.

[0038] In some embodiments, a bias is applied to the substrate during the hydrogen plasma. Those skilled in the art will appreciate that a bias is an electromagnetic field that directs ions toward or away from the source of the bias. In some embodiments, the bias applied to the substrate during the hydrogen plasma is in a range from 30 W to 300 W. In some embodiments, the bias is in a range from 50 W to 280 W, or in a range from 75 W to 260 W, or in a range from 100 W to 250 W.

[0039] As a result of the strong clean 210 causing damage to the dielectric, a "cure" process is performed. After the strong clean 210, the method 200 proceeds to a defect cure process 220 to repair damage caused to the dielectric.

[0040] The defect cure process 220 of some embodiments includes exposing the substrate to a reactant that removes the damage. In some embodiments, the reactant also oxidizes the metal bottom of the structure. In some embodiments, the defect cure process 220 includes exposing the substrate to an oxygen (O2) plasma. In some embodiments, the oxygen plasma cures hydrogen dangling bonds caused by the strong clean process and oxidizes one or more of the metal and / or the dielectric surface.

[0041] Referring to Figure 3B and Figure 3CIn some embodiments shown, the substrate 100 is exposed to an oxidant to repair surface defects 127 in the sidewalls 122 and / or fields 124 of the dielectric. Additionally, the defect curing treatment 220 of the illustrated embodiment oxidizes the metal surface 115 of the structure 130 to form a metal oxide bottom 111 of the structure 130. The bottom of the structure 130 now has a metal oxide bottom 119.

[0042] Similarly, in Figure 4B and Figure 4C During the defect curing process 220, from Figure 4B Start to Figure 4C The substrate 300 is exposed to an oxidant, resulting in the curing of defect 127 and the formation of a metal oxide base or oxidized contaminant on the metal substrate. Figure 4C In the middle, the contaminants on the bottom of the surface of the lower metal 110 are residues 113 that were not initially reduced in the strong cleaning treatment 210 or were not completely oxidized in the defect curing treatment 220. In some embodiments, the residues 113 are chemically altered by one or more of the treatments 210, 220 to make removal possible in subsequent treatments.

[0043] In some embodiments, the defect curing process 220 includes exposing the substrate to an oxidant. In some embodiments, the oxidant comprises oxygen plasma. In some embodiments, the oxidant is substantially composed of oxygen. When used in this way, the term "substantially composed of oxygen" means that the oxide species in the plasma are greater than or equal to about 95%, 98%, 99%, or 99.5% oxygen (O2 or its ions or radicals). Inert gases, diluent gases, and / or carrier gases are not considered unless the gaseous substance also acts as an oxidant for the present material.

[0044] In some embodiments, the oxygen plasma is an inductively coupled plasma. In some embodiments, the oxygen plasma is a capacitively coupled plasma. In some embodiments, the oxygen (O2) plasma is a high-density, low-energy plasma. In some embodiments, the low-energy oxygen plasma has a power of less than or equal to 200 watts (W). In some embodiments, the low-energy oxygen plasma has a power of less than or equal to 175 W, 150 W, 125 W, 100 W, 75 W, 50 W, or 25 W. In some embodiments, the high-density oxygen plasma has a power of greater than or equal to 10 W. 19 ions / m 2 ion density.

[0045] In some embodiments, the substrate is maintained at a temperature ranging from -15°C to 180°C during exposure to oxygen plasma. In some embodiments, the substrate is maintained at a temperature ranging from -10°C to 180°C, or from -5°C to 170°C, or from 0°C to 165°C, or from 5°C to 160°C, or from 10°C to 155°C, or from 20°C to 150°C, or from 25°C to 125°C, or from approximately 30°C to 100°C during exposure to oxygen plasma.

[0046] In some embodiments, the pressure of the oxygen plasma is in the range of 1 mTorr to 200 mTorr. In some embodiments, the pressure of the oxygen plasma is in the range of 2 mTorr to 150 mTorr, or in the range of 3 mTorr to 100 mTorr, or in the range of 5 mTorr to 50 mTorr.

[0047] Some embodiments of this disclosure do not include a strong cleaning treatment 210, such that method 200 is initiated at curing treatment 220 or exposure to oxidizing plasma.

[0048] During the intense cleaning process 210 and the defect curing process 220, in some embodiments, O2 plasma expands the treatment window by curing defects and impurities on the dielectric surface, thus allowing for more effective cleaning of the substrate using a more aggressive H2 plasma while maintaining minimal or no growth on the dielectric surface. Experiments show that a single H2 plasma treatment (CCP or ICP) causes varying degrees of selectivity loss in the dielectric field. Using a two-step pre-cleaning approach (O2 plasma + H2 plasma) in some embodiments, no selectivity loss was observed, and the deposited vias maintained good growth after cleaning. In some embodiments of the two-step pre-cleaning, the method ends after combining O2 / H2 plasma.

[0049] Those skilled in the art will recognize that oxygen plasma can effectively reduce the concentration of carbon (C) and / or fluorine (F) impurities on metal and dielectric surfaces. Additionally, the inventors have found that curing dielectric surfaces reduces impurities and results in more uniform surface termination. In some embodiments, oxygen plasma is used to produce a clean metal surface and a “cured” oxide / dielectric surface. In some embodiments, oxidation results in the metal surface 115 being oxidized to a metal oxide bottom 119. A subsequent oxide reduction treatment 230 using a suitable reducing agent (e.g., H2 plasma) can reduce the metal oxide bottom 111 to pure metal 110 and further clean other residues 113 on the metal surface 115 (see [link to relevant documentation]). Figure 4C ).

[0050] In some embodiments of the method 200, an oxide reduction process 230 is performed after the defect solidification process 220. In the oxide reduction process 230 of some embodiments, the substrate is exposed to a process that reduces metal oxides to metal or removes residue 113 formed on the metal surface. In some embodiments, a hydrogen (H2) thermal anneal is used to reduce metal oxides to a metal surface without any damage or any significant damage to the dielectric. The H2 thermal bake is a mild reduction process that can effectively reduce metal oxides to metal without creating dangling bonds in the dielectric.

[0051] In some embodiments, the oxide reduction process 230 includes exposing the substrate to a mild reducing agent to reduce the metal oxide bottom 119 to the metal 115 bottom without substantially damaging the dielectric 120, as shown in FIG. 1C. Figures 3C to 3D In some embodiments, the oxide reduction process 230 includes exposing the substrate to a mild reducing agent to remove residue 113 on the metal surface 115 without damaging the dielectric 120, as shown in FIG. 1C. Figures 4C to 4D

[0052] In some embodiments, the oxide reduction process 230 includes a mild reducing agent. In some embodiments, the mild reducing agent includes a hydrogen (H2) plasma. In some embodiments, the hydrogen plasma includes a capacitively coupled plasma (CCP).

[0053] In some embodiments, the hydrogen plasma has a pressure in a range from 1 Torr to 100 Torr. In some embodiments, the hydrogen plasma has a pressure in a range from 2 Torr to 80 Torr, or in a range from 3 Torr to 60 Torr, or in a range from 4 Torr to 40 Torr, or in a range from 5 Torr to 30 Torr.

[0054] In some embodiments, the plasma of the oxide reduction process 230 is a low density, low energy plasma. In some embodiments, the low energy plasma has a power less than or equal to 200 Watts (W). In some embodiments, the low energy plasma has a power less than or equal to 175 W, 150 W, 125 W, 100 W, 75 W, 50 W, or 25 W. In some embodiments, the low density plasma has an ion density less than or equal to 10 19 ions / m 2 In some embodiments, the low density plasma has an ion density less than or equal to 8 x 10 18 ions / m 2 or 6 x 10 18 ions / m 2 or 4 x 10 18 ions / m 2 ​or 2 x 10 18 ions / m 2 or 1 x 10 18 ions / m 2 .

[0055] In some embodiments, the substrate is maintained at a temperature in a range from 300 °C to 550 °C during the oxide reduction treatment 230. In some embodiments, the substrate is maintained at a temperature in a range from 350 °C to 500 °C, or in a range from 400 °C to 450 °C during exposure to the weak reducing agent during the oxide reduction treatment 230.

[0056] Some embodiments of the method include or consist essentially of three treatments: a strong clean, and a defect cure and an oxide reduction treatment (also referred to as a weak clean). As used in this manner, a method "consists essentially of refers to the absence of intervening treatments that affect the chemical composition of the dielectric surface, dangling bonds, metal surface, metal oxide surface, contaminants, or residues. In one or more embodiments, the strong clean treatment 210 includes inductively coupled plasma at 450 °C, the defect cure treatment 220 includes inductively coupled plasma at -15 °C, and the oxide reduction treatment 230 includes capacitively coupled plasma at 450 °C. In one or more embodiments, the strong clean treatment 210 includes inductively coupled plasma at 450 °C, the defect cure treatment 220 includes inductively coupled plasma at 120 °C, and the oxide reduction treatment 230 includes capacitively coupled plasma at 450 °C.

[0057] In some embodiments, the integrated multi-step pre-clean method as shown in Figure 2 is effective to clean residues and to enhance selectivity of subsequent deposition treatments. In some embodiments, an oxygen plasma is used to mitigate selectivity loss issues by cleaning impurities / dangling bonds and terminating metal and / or dielectric surfaces to a uniform oxide. In some embodiments of this kind, one or more of an alcohol, water, or ozone treatment is used to widen the selectivity window. In some embodiments, the method includes or consists essentially of an H2 / Ar plasma, an oxygen plasma, and a tungsten hexafluoride soak. In some embodiments of this kind, the tungsten hexafluoride soak improves the state of a particular metal bottom (e.g., tungsten). In some embodiments, the WF6is exposed to the substrate at a pressure in a range from 30 Torr to 300 Torr. In some embodiments, the substrate is maintained at a temperature in a range from 300 °C to 600 °C during exposure to the WF6.

[0058] Various hardware arrangements can be used to implement the method 200. In some embodiments, one or two chambers can be applied for surface cleaning to achieve multiple treatments. Chambers can be used for O2 / Ar H2 plasma treatment using different gas species. In some embodiments, H2 and O2 treatment are performed in one chamber with a designated gas panel design, and low pressure is maintained to avoid additional water formation. In some embodiments, H2 bake (anneal) is performed in the same chamber as the H2 plasma or in a tungsten CVD chamber.

[0059] One or more embodiments of the present disclosure provide more robust solutions to target more selective deposition applications. Different structures have different selectivity under different metal / oxide surface conditions. Certain applications will not have a selectivity window for selective W if only H or Ar plasma is used.

[0060] Referring Figure 5 Further embodiments of the present disclosure relate to a processing system 900 to perform the methods described herein. Figure 5 A system 900 that can be used to process a substrate according to one or more embodiments of the present disclosure is shown. The system 900 can be referred to as a cluster tool. The system 900 includes a central transfer station 910 having a robot 912 therein. The robot 912 is shown as a single-armed robot; however, those skilled in the art will recognize that other robot 912 configurations are within the scope of the present disclosure. The robot 912 is configured to move one or more substrates between chambers connected to the central transfer station 910.

[0061] At least one pre-clean / buffer chamber 920 is connected to the central transfer station 910. The pre-clean / buffer chamber 920 can include one or more of a heater, a radical source, or a plasma source. The pre-clean / buffer chamber 920 can be used as a holding area for a single semiconductor substrate or a wafer cassette for processing. The pre-clean / buffer chamber 920 can perform a pre-clean process, or can pre-heat a substrate for processing, or can simply act as a staging area for processing. In some embodiments, there are two pre-clean / buffer chambers 920 connected to the central transfer station 910. In some embodiments, the pre-clean chamber is used for one or more of the processes of the method 200.

[0062] In Figure 5 In the illustrated embodiment, the pre-clean chamber 920 can be used as a chamber between the factory interface 905 and the central transfer station 910. The factory interface 905 can include one or more robots 906 to move substrates from a cassette to the pre-clean / buffer chamber 920. The robot 912 can then move the substrates from the pre-clean / buffer chamber 920 to other chambers within the system 900.

[0063] The first processing chamber 930 can be connected to the central transfer station 910. In some embodiments, the first processing chamber 930 is configured to perform one or more of the strong clean process 210, the defect solidification process 220, or the oxide reduction process 230. The first processing chamber 930 is in fluid communication with one or more reactive gas sources to provide one or more reactive gas flows to the first processing chamber 930 depending on its configuration. The substrate can be moved into and out of the processing chamber 930 by the robot 912 through the isolation valve 914.

[0064] The processing chamber 940 can also be connected to the central transfer station 910. In some embodiments, the processing chamber 940 is configured to perform one or more of the strong clean process 210, the defect solidification process 220, or the oxide reduction process 230, and is in fluid communication with one or more reactive gas sources to provide a reactive gas flow to the processing chamber 940 to perform the subject processes. The substrate can be moved into and out of the processing chamber 940 by the robot 912 through the isolation valve 914.

[0065] The processing chamber 945 can also be connected to the central transfer station 910. In some embodiments, the processing chamber 945 is configured to perform one or more of the strong clean process 210, the defect solidification process 220, or the oxide reduction process 230. In some embodiments, the processing chamber 945 is configured to perform the same processes as the processing chamber 930 or the processing chamber 940. This arrangement can be useful when the processes occurring in the processing chamber 940 take longer than the processes in the processing chamber 930.

[0066] In some embodiments, the processing chamber 960 is connected to the central transfer station 910 and is configured to perform one or more of the strong clean process 210, the defect solidification process 220, or the oxide reduction process 230. The processing chamber 960 can be configured to perform the same or different processes as any of the other processing chambers.

[0067] In some embodiments, each of the processing chambers 930, 940, 945, and 960 is configured to perform a different portion of the processing method. For example, in some embodiments, the processing chamber 930 is configured to perform the strong clean process 210, the processing chamber 940 is configured to perform the defect solidification process 220, and the processing chamber 945 is configured to perform the oxide removal process 230. Those skilled in the art will recognize that the number and arrangement of the various processing chambers on the tool can vary, and that Figure 5 The illustrated embodiments represent only a few of the possible configurations.

[0068] At least one controller 950 is coupled to the central transfer station 910, the pre-clean / buffer chamber 920, one or more of the process chambers 930, 940, 945, or 960. In some embodiments, there is more than one controller 950 connected to each chamber or work station, and a master control processor is coupled to each individual processor to control the system 900. The controller 950 can be any form of a general- purpose computer processor, microcontroller, microprocessor, etc., that can be used in an industrial setting to control various chambers and sub-processors.

[0069] The at least one controller 950 can have a processor 952, memory 954 coupled to the processor 952, input / output devices 956 coupled to the processor 952, and support circuits 958 to facilitate communication with different electronic components. The memory 954 can include one or more of a transient memory (e.g., a random access memory) and a non-transient memory (e.g., a storage device).

[0070] The memory 954 (or computer readable medium) of the processor can be one or more readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk or any other form of digital storage, local or remote. The memory 954 can retain an instruction set that is operable by the processor 952 to control the parameters and components of the system 900. The support circuits 958 are coupled to the processor 952 to facilitate the processor in a conventional manner. These circuits can include cache, power supplies, clock circuits, input / output circuitry, subsystems, and the like.

[0071] The processes are typically stored as software routines in the memory and are executed by the processor when executed to cause the process chamber to perform processes of the present disclosure. The software routines can also be stored and / or executed by a second processor (not shown) that is located remotely from the hardware being controlled the processor. Some or all of the methods of the present disclosure can also be performed in hardware. As such, the processes can be implemented in software and can be executed using a computer system, in hardware as, e.g., an application specific integrated circuit or other type of hardware implementation, or as combinations of software and hardware. When executed by the processor, the software routines transform the general purpose computer into a specific purpose computer (controller) that controls the operation of the chamber to perform processes.

[0072] In some embodiments, the controller 950 has one or more configurations to perform individual processes or sub-processes to perform the method. The controller 950 can be connected to and configured to operate intermediate components to perform the functions of the method. For example, the controller 950 can be connected to and configured to control one or more of gas valves, actuators, motors, slit valves, vacuum controls, etc.

[0073] The controller 950 of some embodiments has one or more configurations selected from: a configuration to move a substrate on a robot between a plurality of processing chambers and metrology stations; a configuration to load and / or unload a substrate from the system; a configuration to move a substrate between a central transfer station, a first processing chamber, a second processing chamber, and a third processing chamber; a configuration to perform a strong reduction process in the first processing chamber; a configuration to perform an oxidation process in the second processing chamber; and a configuration to perform a weak reduction process in the third processing chamber. The locations of the various processing chambers are not limited to Figure 5 The embodiments shown, as will be well understood by those skilled in the art.

[0074] One or more embodiments of the present disclosure relate to a processing tool including a central transfer station including a robot configured to move a substrate between processing chambers. A first processing chamber is connected to the central transfer station and is configured to perform a strong reduction process to remove surface contaminants from a metal surface and create defects in a dielectric sidewall. A second processing chamber is connected to the central transfer station and is configured to perform an oxidation process to repair the defects in the dielectric sidewall and oxidize the metal surface to form a metal oxide. A third processing chamber is connected to the central transfer station and is configured to perform a weak reduction process to reduce the metal oxide to pure metal without substantially damaging the dielectric. At least one controller is connected to the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber. The at least one controller has one or more configurations selected from: a configuration to move a substrate between the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber; a configuration to perform a strong reduction process in the first processing chamber; a configuration to perform an oxidation process in the second processing chamber; and a configuration to perform a weak reduction process in the third processing chamber.

[0075] Throughout this specification, references have been made to "one embodiment," "some embodiments," "one or more embodiments," or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Therefore, the appearances of such phrases in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments.

[0076] While the disclosure has been described with reference to particular embodiments, it will be understood by those skilled in the art that various modifications and changes in the described embodiments can be made without departing from the spirit and scope of the disclosure. It will be appreciated that the disclosure can be practiced in a variety of ways, and that the disclosure can be implemented using any suitable electronic devices, data processing systems, and / or computer programs known now or in the future. Accordingly, the disclosure is not intended to be limited to the described embodiments, but rather is to be accorded with the widest scope consistent with the principles and features disclosed herein.

Claims

1. A method of pre-cleaning a substrate, the method comprising the steps of: exposing the substrate comprising a surface structure having a metal base containing surface contaminants and a dielectric sidewall and a dielectric field to a strong reducing agent to remove oxides and / or nitrides from the metal base and to create surface defects in the dielectric sidewall and / or the dielectric field; exposing the substrate to an oxidizing agent to repair the surface defects in the dielectric sidewall and / or the dielectric field and to oxidize the metal base of the surface structure to form a metal oxide base of the surface structure; and exposing the substrate to a weak reducing agent to reduce the metal oxide base to a pure metal base without substantially damaging the dielectric sidewall and / or the dielectric field.

2. The method of claim 1, wherein the strong reducing agent comprises a hydrogen plasma.

3. The method of claim 2, wherein the hydrogen plasma is an inductively coupled plasma.

4. The method of claim 2, wherein the hydrogen plasma is a high density, high energy plasma.

5. The method of claim 2, wherein the hydrogen plasma has a pressure in the range of 5 mTorr to 10 mTorr.

6. The method of claim 2, wherein the substrate is maintained at a temperature in the range of 200 °C to 500 °C during the hydrogen plasma.

7. The method of claim 2, wherein a bias in the range of 30 W to 300 W is applied to the substrate during the hydrogen plasma.

8. The method of claim 1, wherein the oxidizing agent comprises an oxygen plasma.

9. The method of claim 8, wherein the substrate is maintained at a temperature in the range of -15 °C to 180 °C during exposure to the oxygen plasma.

10. The method of claim 8, wherein the oxygen plasma is a capacitively coupled plasma (CCP) or an inductively coupled plasma (ICP).

11. The method of claim 10, wherein the oxygen plasma is a high density, low energy plasma.

12. The method of claim 10, wherein the oxygen plasma has a pressure in the range of 5 mTorr to 50 mTorr.

13. The method of claim 1, wherein the weak reducing agent comprises a hydrogen plasma.

14. The method of claim 13, wherein the hydrogen plasma comprises a capacitively coupled plasma (CCP).

15. The method of claim 14, wherein the hydrogen plasma is at a pressure in the range of 5 Torr to 30 Torr.

16. The method of claim 14, wherein the hydrogen plasma is a low density, low energy plasma.

17. The method of claim 14, wherein the substrate is maintained at a temperature in the range of 400 °C to 450 °C during exposure to the weak reducing agent. ​ 18. The method of claim 1, wherein the dielectric sidewall and / or the dielectric field comprise one or more of silicon nitride (SiN), silicon oxide (SiO), silicon oxynitride (SiON), or a high-k dielectric, and the metal bottom comprises one or more of tungsten (W) or cobalt (Co).

19. A processing tool for pre-cleaning a substrate, comprising: a central transfer station including a robot configured to move a substrate between processing chambers; a first processing chamber connected to the central transfer station and configured to perform a strong reduction process that exposes the substrate including a surface structure having a metal bottom with surface contaminants and a dielectric sidewall and a dielectric field to a strong reducing agent to remove oxides and / or nitrides from the metal bottom and to create surface defects in the dielectric sidewall and / or the dielectric field; a second processing chamber connected to the central transfer station and configured to perform an oxidation process that exposes the substrate to an oxidizing agent to repair the surface defects in the dielectric sidewall and / or the dielectric field and to oxidize the metal bottom of the surface structure to form a metal oxide bottom of the surface structure; a third processing chamber connected to the central transfer station and configured to perform a weak reduction process that exposes the substrate to a weak reducing agent to reduce the metal oxide bottom to a pure metal bottom without substantially damaging the dielectric sidewall and / or the dielectric field; and at least one controller connected to the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber, the at least one controller having one or more configurations selected from the group consisting of a configuration to move a substrate between the central transfer station, the first processing chamber, the second processing chamber, and the third processing chamber; a configuration to perform the strong reduction process in the first processing chamber; a configuration to perform the oxidation process in the second processing chamber; and a configuration to perform the weak reduction process in the third processing chamber.

20. A non-transitory computer readable medium comprising a plurality of instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the following operations: move a substrate between a central transfer station, a first processing chamber, a second processing chamber, and a third processing chamber; and perform the method of pre-cleaning a substrate of claim 1, wherein the strong reduction process is performed in the first processing chamber; the oxidation process is performed in the second processing chamber; and the weak reduction process is performed in the third processing chamber. ​ ​

Images