Method for etching metal oxide with less etching residue

Abstract

Methods for etching metal oxide films with minimal etch residue are described. The methods include etching the metal oxide film with a metal halide etchant; and exposing the etch residue to a reducing agent to remove the etch residue. Some embodiments involve etching tungsten oxide films. Some embodiments utilize tungsten halides to etch metal oxide films. Some embodiments utilize hydrogen as a reducing agent to remove the etch residue.

Description

[0001] This application is a divisional application of a Chinese patent application (PCT application number PCT / US2018 / 065379) filed on December 13, 2018, with application number 201880084984.2 and titled “Method for etching metal oxides with less etching residue”. Technical Field

[0002] The present disclosure generally relates to methods of etching oxidized metal films. In particular, the present disclosure relates to processes for etching oxidized metal films that provide less etch residue. Background Art

[0003] The semiconductor industry is rapidly developing chips with smaller and smaller transistor sizes to achieve more functions per unit area. As the size of devices continues to shrink, the gaps / spaces between devices are also shrinking, making it more difficult to physically isolate devices from each other.

[0004] Creating high-aspect ratio structures is one of the challenges in device patterning. Many structures in logic and memory benefit from high aspect ratios. Several methods for creating high-aspect ratio structures exploit the volume expansion of tungsten through oxidation to create pillars of material around which other materials can be deposited. These tungsten-containing pillars are then removed to provide high-aspect ratio structures. These structures can then be filled with metal contacts or other conductive materials.

[0005] However, removal of these tungsten-containing pillars typically leaves behind etch residues that can reduce the volume available for any subsequently provided metallization layers and can increase the resistivity of these layers.

[0006] Therefore, there is a need in the art for methods of etching metal oxides that produce less etch residue. Summary of the Invention

[0007] One or more embodiments of the present disclosure relate to a substrate processing method, comprising exposing a substrate including an oxidized metal layer to a metal halide to etch a portion of the oxidized metal layer and generate an etch residue, and exposing the substrate to a reducing agent to remove the etch residue.

[0008] Additional embodiments of the present disclosure relate to a substrate processing method, comprising: providing a substrate including an oxidized metal layer in a processing chamber having a processing volume; exposing the substrate to a metal halide to remove a portion of the oxidized metal layer and produce an etch residue; exposing the substrate to a reducing agent to remove the etch residue; and repeating the exposure of the substrate to the metal halide and the exposure of the substrate to the reducing agent until a predetermined thickness of the oxidized metal layer has been removed.

[0009] A further embodiment of the present disclosure relates to a substrate processing method, comprising: providing a substrate including a WO3 layer in a processing chamber having a processing volume; exposing the substrate to an etchant including one or more of WF6 or WCl5 to remove a portion of the WO3 layer and produce an etch residue; purging the processing volume with an inert gas; exposing the substrate to a reducing agent including H2 to remove the etch residue; purging the processing volume with an inert gas; and repeating exposing the substrate to the etchant, purging the processing volume, exposing the substrate to the reducing agent, and purging the processing volume until a predetermined thickness of the WO3 layer has been removed. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0011] The accompanying drawings illustrate processing methods according to one or more embodiments of the present disclosure.

[0012] In the accompanying drawings, similar components and / or features may have the same reference numerals. Furthermore, various components of the same type may be distinguished by following the reference numeral with a dash and a second label to distinguish the similar components. If only the first reference numeral is used in this specification, the description applies to any of the similar components having the same first reference numeral, regardless of the second reference numeral. DETAILED DESCRIPTION

[0013] 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 process steps set forth in the following description, and the present disclosure is capable of other embodiments and can be practiced or carried out in various ways.

[0014] 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, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other material (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 exposed to pretreatment processes to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, electron 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 disclosed film processing steps may 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 such underlayers as indicated by the context. Thus, for example, where a film / layer or portion of a film / layer has already been deposited onto a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0015] One or more embodiments of the present disclosure relate to a substrate processing method that etches or removes an oxidized metal layer from a substrate with less etching residue. Various embodiments of the present disclosure are described with respect to detailed processes shown in the accompanying drawings.

[0016] With reference to the accompanying drawings, one or more embodiments of the present disclosure relate to a method 100 for etching an oxidized metal layer from a substrate with reduced etch residue. In some embodiments, the method is part of a larger process for forming a high aspect ratio structure.

[0017] In some embodiments, the substrate comprises a semiconductor material such as silicon (Si), carbon (C), germanium (Ge), silicon germanium (SiGe), gallium arsenide (GaAs), InP, GaAs, InGaAs, InAIA, other semiconductor materials, or any combination thereof. In some embodiments, the substrate is a semiconductor-on-isolator (SOI) substrate, comprising a bulk lower substrate, an intermediate insulating layer, and a top single crystal layer. The top single crystal layer may comprise any of the materials listed above, such as silicon. In various embodiments, the substrate may be, for example, an organic substrate, a ceramic substrate, a glass substrate, or a semiconductor substrate. Although several examples of materials that can form a substrate are described herein, any material that can be used as a basis for passive and active electronic devices (e.g., transistors, memories, capacitors, inductors, resistors, switches, integrated circuits, amplifiers, optoelectronic devices, or any other electronic devices) on which they can be built falls within the spirit and scope of the present disclosure.

[0018] In some embodiments, method 100 begins by providing a substrate 110 including an oxidized metal layer 130. In the embodiment shown in the figures, substrate 110 includes a feature, a barrier layer 115, and an additional layer 120. The feature is lined with barrier layer 115. The surface of the substrate outside the feature includes additional layer 120. In some embodiments, the additional layer includes silicon dioxide. In some embodiments, substrate 110 may be present as shown in the figures, but for the purposes of this disclosure, barrier layer 115 and additional layer 120 are each optional.

[0019] In some embodiments, barrier layer 115 comprises titanium nitride (TiN), titanium (Ti), tantalum (Ta), tantalum nitride (TaN), or any combination thereof. In another embodiment, barrier layer 115 is an oxide, such as aluminum oxide (AlO) or titanium oxide (TiO2). In yet another embodiment, barrier layer 115 is a nitride, such as silicon nitride (SiN). In some embodiments, barrier layer 115 has a thickness of from about 0.5 nm to about 10 nm.

[0020] In some embodiments, the method further includes oxidizing the metal layer within the feature to produce an oxidized metal layer 130. In some embodiments, the additional layer 120 is formed as a result of the oxidation process used on the metal layer. Suitable metal layers include, but are not limited to, films comprising one or more of: Co, Mo, W, Ta, Ti, Ru, rhodium (Rh), Cu, Fe, Mn, V, niobium (Nb), hafnium (Hf), zirconium (Zr), yttrium (Y), Al, Sn, Cr, lanthanum (La), or any combination thereof.

[0021] The barrier layer 115, the additional layer 120, and / or the oxidized metal layer 130 may be formed by any suitable technique known to those skilled in the art. Suitable techniques include, but are not limited to, chemical vapor deposition (CVD), atomic layer deposition (ALD), plasma-enhanced CVD, plasma-enhanced ALD, and physical vapor deposition (PVD). Those skilled in the art will be familiar with various deposition processes and techniques, and further description of these processes is not included.

[0022] The oxidized metal layer may be any suitable layer composed of any suitable material. In some embodiments, the metal of the oxidized metal layer is selected from one or more of an alkali metal, an alkaline earth metal, a transition metal, a lanthanide, an actinide, and a post-transition metal. In some embodiments, the oxidized metal layer comprises tungsten (W). An oxidized metal layer refers to a metal layer in which the average oxidation state of the metal species is greater than 0. For the purposes of this disclosure, the oxidized metal layer may or may not include oxygen.

[0023] In some embodiments, the average oxidation state of the oxidized metal layer is less than the average oxidation state of the stoichiometric metal oxide. As used in this context, stoichiometric metal oxide refers to a completely oxidized metal oxide. For example, WO 3 and Al 2 O 3 are both stoichiometric metal oxides. In some embodiments, the oxidized metal layer comprises a stoichiometric metal oxide. In some embodiments, the oxidized metal layer comprises WO 3.

[0024] In some embodiments, the oxidized metal layer comprises a substoichiometric metal oxide. For the purposes of this disclosure, a substoichiometric metal oxide is an oxidized metal layer in which the ratio of metal to oxygen is greater than the ratio of metal to oxygen in a stoichiometric metal oxide of the same metal. For example, in some embodiments, the oxidized metal layer comprises a substoichiometric metal oxide WO x , wherein x is less than 3. Without limiting the metal species, in some embodiments, the oxidized metal layer comprises a substoichiometric metal oxide.

[0025] The oxidized metal layer may include elements other than oxygen. In some embodiments, the oxidized metal layer does not substantially include oxygen. As used in this context, "substantially does not include oxygen" means that the oxidized metal layer includes less than 5%, 3%, 2%, 1%, or 0.5% oxygen on an atomic basis. In some embodiments, the oxidized metal layer includes one or more of N, Si, or C. In some embodiments, the oxidized metal layer consists essentially of metal nitride. In some embodiments, the oxidized metal layer consists essentially of metal silicide.

[0026] Referring again to the figures, substrate 110 is exposed to a metal halide to etch or remove a portion of oxidized metal layer 130 and produce etch residue 140. In some embodiments, the metal halide etches or removes a portion of barrier layer 115. Without being bound by theory, the inventors have discovered that attempts to etch a metal oxide layer with a metal halide do not result in 100% removal of the metal oxide layer, but rather leave an etch residue. The inventors believe that the etch residue may be caused by incomplete removal of the oxidized metal layer or incomplete conversion of the oxidized metal layer into non-volatile species.

[0027] The metal halide may be any suitable compound consisting of at least one metal and at least one halogen. In an embodiment, the metal element of the metal halide may include one or more of titanium, hafnium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, technetium, iron, aluminum, and gallium. In some embodiments, the metal element of the metal halide has an atomic number of 22, 23, 24, 40, 41, 42, 72, 73, or 74. In one or more embodiments, the metal element includes an element of Group 4, Group 5, or Group 6 of the periodic table, or may be a transition metal. In some embodiments, the oxidized metal layer and the metal halide include the same metal substance. In some embodiments, the oxidized metal layer and the metal halide include different metal substances. In some embodiments, the metal halide includes tungsten (W).

[0028] In some embodiments, the metal halide comprises one or more of fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). In some embodiments, the metal halide comprises one or more of WF6 or WCl5. In some embodiments, the metal halide consists essentially of WF6. In some embodiments, the metal halide consists essentially of WCl5. As used in this context, "consisting essentially of..." means that the metal halide is greater than 95%, 98%, 99%, or 99.5% of the recited substance on a molar basis.

[0029] In some embodiments, little or no local plasma is used in the etching process to make the etching process more selective, precise, and isotropic. The term "plasma-free" will be used herein to describe a substrate processing region during which no or substantially no plasma power is applied to the substrate processing region. The described etchants (metal- and halogen-containing precursors) have an energetically favorable etching reaction path that enables the substrate processing region to be plasma-free during the operation of etching the metal-containing materials herein. In other words, according to one or more embodiments, the electron temperature in the substrate processing region may be less than 0.5 eV, less than 0.45 eV, less than 0.4 eV, or less than 0.35 eV. In addition, in embodiments, the metal- and halogen-containing precursors may not have been excited in any remote plasma prior to entering the substrate processing region. For example, if a remote plasma region or a separate chamber region is present and used to direct the halogen-containing precursor toward the substrate processing region, the separate chamber region or the remote plasma region may be plasma-free, as defined herein.

[0030] Referring again to the figures, substrate 110 is exposed to a reducing agent to remove etch residue. The reducing agent can be any compound capable of removing etch residue. In some embodiments, the reducing agent comprises one or more of H2, B2H6, or BCl3. In some embodiments, the reducing agent consists essentially of one of H2, B2H6, or BCl3. As used in this context, "consisting essentially of..." means that the reducing agent is greater than 95%, 98%, 99%, or 99.5% of the recited substance on a molar basis, excluding any carrier or diluent gas.

[0031] The metal halide and / or reducing agent may be exposed to the substrate in the presence of a carrier gas or diluent gas. Suitable carrier gases or diluent gases include, but are not limited to, Ar, N2, He, Ne, Kr, Xe, and mixtures thereof.

[0032] Exposing the substrate to the metal halide and the reducing agent can be referred to as a cycle. In some embodiments, the method includes multiple cycles. In other words, in some embodiments, the method further includes repeating the exposure to the metal halide and the exposure to the reducing agent. In some embodiments, the exposure to the metal halide and the exposure to the reducing agent are repeated until a predetermined thickness of the oxidized metal layer has been removed.

[0033] The conditions under which the method is performed can also be controlled. Controllable conditions include, but are not limited to, temperature, pressure, exposure time, flow rate, and purge time.

[0034] In some embodiments, the methods of the present disclosure are performed at a pressure of about 40 Torr or less, about 30 Torr or less, about 20 Torr or less, about 10 Torr or less, or about 5 Torr or less. In some embodiments, the methods of the present disclosure are performed at a pressure of about 5 Torr or greater, about 10 Torr or greater, about 15 Torr or greater, about 20 Torr or greater, or about 30 Torr or greater.

[0035] The substrate processing methods of the present disclosure may be performed at any suitable temperature. In some embodiments, the substrate is maintained at a temperature of about 475° C. or less, about 450° C. or less, about 400° C. or less, about 350° C. or less, or about 300° C. or less. In some embodiments, the substrate is maintained at a temperature of about 200° C. or greater, about 250° C. or greater, about 300° C. or greater, or about 350° C. or greater.

[0036] In some embodiments, a substrate is provided in a processing chamber having a processing volume. In some embodiments, the methods of the present disclosure include: purging the processing volume after exposing the substrate to the metal halide; and purging the processing volume after exposing the substrate to the reducing agent. The processing volume can be purged with any suitable inert gas. Examples of inert gases include, but are not limited to, those listed as carrier gases or diluent gases.

[0037] References throughout this specification to "some embodiments," "certain embodiments," "one or more embodiments," or "an embodiment" indicate that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least some embodiments of the present disclosure. Thus, phrases such as "in one or more embodiments," "in certain embodiments," "in some embodiments," or "in an embodiment" appearing 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.

[0038] Although the disclosure herein has been described with reference to specific embodiments, it should be understood that these 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 may be made to the disclosed method without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is intended to include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A substrate processing method, comprising: oxidizing a metal layer within a feature in a substrate to produce an oxidized metal layer, the feature being lined with a barrier layer having a thickness in a range of 0.5 nm to 10 nm; exposing the substrate including the oxidized metal layer to a metal halide to etch a portion of the oxidized metal layer and produce an etch residue; as well as The substrate is exposed to a reducing agent to remove the etch residue.

2. The method of claim 1, wherein the average oxidation state of the oxidized metal layer is less than the average oxidation state of the stoichiometric metal oxide.

3. The method of claim 2, wherein the oxidized metal layer comprises less than 5 atomic percent oxygen.

4. The method of claim 1, wherein the method is plasma-free.

5. The method of claim 1, wherein the oxidized metal layer and the metal halide comprise the same metal species.

6. The method of claim 1, wherein the metal layer comprises one or more of Co, Mo, W, Ta, Ti, Ru, Rh, Cu, Fe, Mn, V, Nb, Hf, Zr, Y, Al, Sn, Cr, or La. The method of claim 1 , wherein the barrier layer is a nitride. The method of claim 1 , wherein the barrier layer is an oxide.

9. The method of claim 1, wherein the barrier layer comprises one or more of AlO, TiO2, TiN, TaN, SiN, Ti, or Ta.

10. The method of claim 1, wherein the reducing agent comprises one or more of H2, B2H6 or BCl3.

11. The method of claim 1 , further comprising repeating said exposing to said metal halide and said exposing to said reducing agent.

12. The method of claim 1, wherein oxidizing the metal layer within the feature forms an additional layer on a surface of the substrate outside of the feature.

13. A substrate processing method, comprising: (A) oxidizing a metal layer within a feature of a substrate in a processing chamber having a processing volume to form an oxidized metal layer within the feature, the oxidized metal layer comprising less than 5 atomic percent oxygen; (B) exposing the substrate to a metal halide to remove a portion of the oxidized metal layer and produce an etch residue; (C) exposing the substrate to a reducing agent to remove the etching residue; as well as (D) Repeating (B) and (C) until a predetermined thickness of the oxidized metal layer has been removed.

14. The method of claim 13, further comprising: After exposing the substrate to the metal halide, purging the processing volume; and after exposing the substrate to the reducing agent, purging the processing volume.

15. The method of claim 13, wherein the oxidized metal layer has an average oxidation state less than an average oxidation state of a stoichiometric metal oxide.

16. The method of claim 13, wherein the features are lined with a barrier layer.

17. The method of claim 13, wherein the metal halide comprises one or more of WF6 or WCl5.

18. The method of claim 13, wherein the reducing agent comprises one or more of H2, B2H6, or BCl3.

19. A substrate processing method, comprising: (A) oxidizing a tungsten layer on a substrate in a processing chamber having a processing volume to form a WO3 layer; (B) exposing the substrate to an etchant to remove a portion of the WO3 layer and produce an etch residue; (C) purging the processing volume with an inert gas; (D) exposing the substrate to a reducing agent including H2 to remove the etching residue; (E) purging the processing volume with an inert gas; and (F) repeating (B) to (E) until a predetermined thickness of the WO3 layer has been removed, The method is plasma-free.

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