Etching metal oxides using fluorine and metal halides

Abstract

Embodiments of this disclosure provide various methods for etching oxide materials. Some embodiments of this disclosure provide methods for selectively etching oxide materials over other materials. In some embodiments, the methods of this disclosure are performed by atomic layer etching (ALE). In some embodiments, the methods of this disclosure are performed within a processing chamber comprising a nickel chamber material.

Description

Technical Field

[0001] Embodiments of this disclosure generally relate to methods for selective atomic layer etching of metal oxides using fluorine and metal halide sources. Specifically, some embodiments of this disclosure relate to methods for selective atomic layer etching of metal oxides by fluorination and removal with metal halide. Some embodiments of this disclosure provide alternative fluorine sources for HF, which may be undesirable from a manufacturing point of view. Background Technology

[0002] As semiconductor devices continue to increase in complexity in terms of design and material composition, selective removal of materials has become critical for the continued scaling and improvement of semiconductor devices.

[0003] Selective atomic layer etching (ALE) has evolved into a precise etching method that utilizes self-limiting surface reactions. Metal oxides (MO) x Selective ALE (Alternating Range) is particularly important for many semiconductor technologies, but can be difficult to achieve due to the inherent stability of these oxide materials. One such example is the selective removal of HfO2 during recess etching in high-k metal gate structures.

[0004] Selective removal of metal oxides and nitrides is crucial for the continued miniaturization and optimization in semiconductor manufacturing. While some etching processes exist, these are not selective or rely on HF as a fluorine source. HF is toxic and presents disposal issues during manufacturing. Alternative fluorine sources for metal oxide etching that avoid these concerns are desired for the widespread adoption of etching processes.

[0005] Therefore, there is a need for novel fluorine and metal halide sources for the selective removal of metal oxides and metal nitrides. Summary of the Invention

[0006] One or more embodiments of this disclosure relate to an etching process that includes exposing a substrate surface having an oxide layer to a fluorinating agent to convert a portion of the oxide layer into a fluoride layer. The fluoride layer is then exposed to a halide etchant to remove the fluoride layer.

[0007] Further embodiments of this disclosure relate to an etching process that includes exposing a substrate surface having a hydroxide layer thereon to a fluorinating agent to form a fluoride layer. The fluoride layer is then exposed to a halide etchant to remove the fluoride layer.

[0008] Other embodiments of this disclosure relate to an etching process in which a substrate surface having an oxide layer and a second material is exposed to a fluorinating agent in a process chamber comprising a nickel chamber material to selectively convert a portion of the oxide layer into a fluoride layer. The second material comprises one or more of the following: TiN, SiN, TaN, SiO, AlO, LaO, carbon, silicon, or a combination of the above. The fluoride layer is then exposed to a halide etchant to remove the fluoride layer. Attached Figure Description

[0009] To gain a more detailed understanding of the foregoing features of this disclosure, reference can be made to some of the embodiments shown in the accompanying drawings, which provide a more detailed description of the disclosure briefly summarized above. However, it should be noted that the drawings illustrate only typical embodiments of this disclosure and should not be considered as limiting the scope of the disclosure, as other equivalent embodiments are permissible.

[0010] Figure 1 This is a flowchart of an exemplary method according to one or more embodiments of this disclosure;

[0011] Figure 2 This is a flowchart of an exemplary method according to one or more embodiments of this disclosure;

[0012] Figure 3 This is a flowchart of an exemplary method according to one or more embodiments of this disclosure; and

[0013] Figures 4A to 4E This is a cross-sectional view of an exemplary substrate during processing according to one or more embodiments of this disclosure. Detailed Implementation

[0014] Before describing several exemplary embodiments of this disclosure, it should be understood that this disclosure is not limited to the details of the construction or process steps set forth in the following description. This disclosure can have other embodiments and can be practiced or performed in various ways.

[0015] As used in this specification and the appended claims, the term "substrate" means the surface on which a process is performed or a portion thereof. Those skilled in the art will also understand that, unless the context clearly indicates otherwise, reference to substrate may also refer only to a portion of the substrate. Furthermore, references to etching from or depositing on a substrate may mean both a bare substrate and a substrate on which one or more films or features are deposited or formed.

[0016] As used herein, "substrate" means any substrate or material surface formed on a substrate on which a film treatment is performed during a manufacturing process. For example, substrate surfaces on which treatments 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, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include (but are not limited to) semiconductor wafers. Substrates may be exposed to pretreatment processes such as polishing, etching, reduction, oxidation, hydroxylation, annealing, UV curing, electron beam curing, and / or baking of the substrate surface. In addition to performing film treatments directly on the surface of the substrate itself, any film treatment steps disclosed in this disclosure 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 the underlayer as indicated by the context. Thus, for example, in cases where a film / layer or part of a film / layer has been removed from the substrate surface, the newly exposed film, layer, or exposed surface of the substrate becomes the substrate surface.

[0017] As used in this specification and the appended claims, the terms “precursor,” “reactant,” “reactive gas,” etc., are used interchangeably to refer to any gaseous substance that can react with the substrate surface.

[0018] Atomic layer etching (ALE) or cyclic etching is a variation of atomic layer deposition in which a surface layer is removed from a substrate. As used herein, ALE refers to the sequential exposure of two or more reactive compounds to etch a material layer on the surface of a substrate. The substrate or a portion thereof is separately exposed to two or more reactive compounds that are introduced into the reaction zone of a processing chamber.

[0019] In time-domain ALE processes, exposure to each reactive compound is separated by a time delay to allow each compound to adhere to and / or react on the substrate surface before being decontaminated from the processing chamber. These reactive compounds are referred to as being sequentially exposed to the substrate.

[0020] In one aspect of the time-domain ALE process, a first reactive gas (i.e., a first reactant or compound A) is pulsed into the reaction zone, followed by a first time delay. Then, a second reactant or compound B is pulsed into the reaction zone, followed by a second delay. During each time delay, a purge gas, such as argon, is introduced into the processing chamber to purge the reaction zone, or otherwise remove any residual reactive compounds or reaction byproducts from the reaction zone. Alternatively, the purge gas may flow continuously throughout the etching process, such that only the purge gas flows during the time delay between pulses of the reactive compound. Alternatively, the reactive compound is pulsed until the desired film or film thickness is removed from the substrate surface.

[0021] The ALE process, in which compound A, purge gas, compound B, and purge gas are pulsed, is called a cycle. A cycle can begin with compound A or compound B and continue in the corresponding sequence of cycles until a predetermined thickness is removed.

[0022] In the space ALE process, different portions of the substrate surface (or the material on the substrate surface) are simultaneously exposed to two or more reactive compounds, such that any given point on the substrate is substantially not simultaneously exposed to more than one reactive compound. As used in this context, and as understood by those skilled in the art, the term "substantially" means the possibility that a small portion of the substrate may be simultaneously exposed to multiple reactive gases due to diffusion, and that such simultaneous exposure is undesirable.

[0023] In one embodiment of the space ALE process, a first reactive gas and a second reactive gas are simultaneously delivered to the reaction zone but separated by an inert gas curtain and / or a vacuum curtain. The substrate moves relative to the gas delivery equipment such that any given point on the substrate is exposed to the first and second reactive gases.

[0024] Some embodiments of this disclosure relate to methods for etching or removing metal oxides from a substrate surface. Some methods of this disclosure advantageously utilize fluorinating agents other than HF.

[0025] Some methods of this disclosure advantageously provide a variety of methods that selectively remove metal oxide material over other substrate materials. As used herein, the term "selectively remove a film over another film" and similar terms mean removing a first amount from a first surface or material while removing a second amount from a second surface or material, wherein the second amount is less than the first amount, or no film is removed from the second surface. The term "over" as used herein does not imply a physical orientation of one surface on top of another, but rather a relation to the thermodynamic or kinetic nature of the chemical reaction of one surface (relative to the other).

[0026] Process selectivity is typically expressed as a multiple or ratio of etch rates between different surfaces. For example, if one surface is etched 25 times faster than another, the process would be described as having a selectivity of 25:1. In this respect, a higher ratio indicates a more selective process.

[0027] One or more embodiments of this disclosure relate to methods for removing metal oxides. In some embodiments, a substrate including an oxide surface can be treated with a fluorine source (also known as a fluorinating agent), then purged, followed by treatment with a metal halide (also known as a halide etchant), and then purged again. The cycle can be repeated to remove metal oxides of a predetermined thickness.

[0028] refer to Figures 1 to 4A Method 100 begins at operation 110, which includes exposing a substrate 600 with oxide layer 610 to a fluorinating agent to form fluoride layer 620. Method 100 continues at operation 120, where fluoride layer 620 is exposed to a halide etchant to remove fluoride layer 620. Solution 1 provides Figure 1 and Figure 4A An exemplary reaction scheme of method 100 shown.

[0029] Option 1:

[0030] Metal oxide + fluorine source → metal fluoride layer (1)

[0031] Metal fluoride layer + metal halide → volatile products (2)

[0032] In some embodiments, as shown in Embodiment 1, the oxide layer 610 comprises a metal oxide. In these embodiments, the fluoride layer 620 may be referred to as a metal fluoride layer. In some embodiments, the metal oxide comprises one or more of the following: hafnium oxide, tungsten oxide, molybdenum oxide, titanium oxide, or a combination of the above materials. In some embodiments, the metal oxide comprises hafnium oxide or is substantially composed of hafnium oxide.

[0033] As used in this regard, if, on an atomic basis, a material is greater than or equal to about 95%, 98%, 99%, or 99.5% of a so-called material, then the material is essentially composed of the material that constitutes the so-called material.

[0034] The fluorinating agent may include any suitable reactant for forming fluoride ends on at least the surface of the oxide layer. In some embodiments, the fluorinating agent includes one or more of the following: HF, NF3, plasma of the above substances, or a combination of the above substances. In some embodiments, the fluorinating agent consists essentially of HF. In some embodiments, the fluorinating agent does not substantially include HF. In some embodiments, the fluorinating agent consists essentially of NF3.

[0035] As used in this regard, if a reactant, on a molar basis, is greater than or equal to about 95%, 98%, 99%, or 99.5% of the stated species (excluding any diluent or other inert (non-reactive) species), then the reactant is substantially composed of the stated species.

[0036] As used in this context, a reactant substantially excluding a so-called species means that the so-called species constitutes less than or equal to about 5%, 2%, 1%, or 0.5% of the reactant (excluding any diluent or other inert (non-reactive) species).

[0037] In some embodiments, the fluorinating agent includes one or more of the following: organic fluorides, organic fluorine oxides, metal fluorides, or combinations thereof. In some embodiments, the organic fluoride has the general formula C0. x H y F z Where x is 1 to 16, y is 0 to 33, and z is 1 to 34. In some embodiments, the general formula of the organofluorine oxide is C0. x H y O w F z , where x is 1 to 16, y is 0 to 33, w is 1 to 8 and z is 1 to 34.

[0038] In some embodiments, the metal fluoride has the general formula MF z M is selected from one or more of molybdenum, tungsten, vanadium, niobium, titanium, or tantalum, and z is 1 to 6. In some embodiments, the metal fluoride comprises or is substantially composed of the following materials: MoF6, WF6, VF3, VF4, VF5, NbF5, TiF4, or TaF5.

[0039] In some embodiments, the fluorinating agent is co-flowed with another gas. In some embodiments, the other gas is selected from one or more of the following: O2, N2O, NH3, or H2.

[0040] After the fluoride layer is formed, the fluoride layer 620 is exposed to a halide etchant to remove the fluoride layer 620. In some embodiments, the halide etchant is referred to as a metal halide. In some embodiments, the halide etchant comprises one or more species of the general formula EX3, wherein E comprises one or more of aluminum (Al) or boron (B), and X comprises one or more of Cl, Br, or I. In some embodiments, the halide etchant comprises BCl3 or is substantially composed of BCl3.

[0041] In some embodiments, the halide etchant comprises the general formula MX y The etchant comprises one or more species, or is substantially composed of said species, wherein M includes one or more of Ti, Sn, Mo, W, or Nb, X includes one or more of Cl, Br, or I, and y is 1 to 6. In some embodiments, the halide etchant comprises substantially substantially of the general formula MX y A species or composed of said species, wherein M includes one or more of Ti, Sn, Mo, W or Nb, X includes one or more of Cl or Br, and y is 1 to 6.

[0042] In some embodiments, exposing the oxide layer to a fluorinating agent produces a fluoride layer with an average thickness of at most one monolayer. Without being bound by theory, it is believed that the surface ends of the oxide layer react with the fluorinating agent to produce fluoride ends on the surface of the oxide layer. This surface reaction is limited to the exposed surface of the oxide layer and affects only the top layer of atoms in the oxide layer. Therefore, in some embodiments, method 100 removes a thickness less than or equal to one monolayer of the oxide layer.

[0043] In some embodiments, method 100 is repeated. After removing the bulk fluoride layer, a new layer of oxide layer is exposed. Method 100 can be repeated to remove a predetermined amount or thickness of oxide layer.

[0044] Other embodiments involve various methods for removing etching residues or other contaminants from the metal oxide surface before performing the method 100 described above to etch the oxide layer. (See reference...) Figure 1 and Figure 4B For these embodiments, method 100 begins at operation 105, in which contaminants 630 are removed from the oxide layer 610 on the substrate 600. Once the contaminants 630 are removed from the surface of the oxide layer 610, method 100 continues as described above by exposing the oxide layer 610 to a fluorinating agent to form a fluoride layer 620, and by exposing the fluoride layer 620 to a halide etchant to remove the fluoride layer 620.

[0045] In some embodiments, contaminants include a carbon film or moisture on the surface of oxide layer 610. Without being bound by theory, it is believed that these residues may interfere with the fluorination and removal of oxide layer 610. In some embodiments, an etching process is performed prior to the disclosed method 100, resulting in etching residues or contaminants including moisture and / or a carbon film.

[0046] In operation 105, etching residues or contaminants 630 can be removed by exposing the substrate to a radical cleaning process. In some embodiments, the radicals of the cleaning process include one or more of H*, OH*, O*, or H2O*. In some embodiments, radicals are generated by passing a radical gas over a heated filament. In some embodiments, radicals are generated by forming a plasma from the radical gas. In some embodiments, the plasma is generated from a remote plasma source.

[0047] Option 2 provides an exemplary reaction scheme for method 100 (including operation 105).

[0048] Option 2:

[0049] Surface with moisture / carbon + plasma → metal oxide (1)

[0050] Metal oxide + fluorine source → metal fluoride layer (2)

[0051] Metal fluoride layer + metal halide → volatile products (3)

[0052] like Figure 4C As shown, in some embodiments, method 100 selectively removes the oxide layer 610 relative to other materials 640 on the exposed surface of the substrate 600. In some embodiments, the other materials may include or consist substantially of the following materials: TiN, TaN, SiN, SiO2, Al2O3, carbon-based materials, or combinations thereof.

[0053] In some embodiments, the selectivity of the removal of oxide layer 610 relative to other materials 640 is greater than or equal to about 5:1, greater than or equal to about 10:1, greater than or equal to about 15:1, greater than or equal to about 20:1, or greater than or equal to about 25:1.

[0054] In a particular embodiment, the hafnium oxide layer is etched by exposure to NF3 / H2 and BCl3. The process is selective for TiN, SiN, SiO2, Al2O3, and carbon, with a selectivity greater than or equal to about 20:1.

[0055] Additional embodiments of this disclosure relate to various methods that increase the selectivity of the method 100 described above by performing the method in a process chamber comprising a nickel chamber material. In some embodiments, the nickel chamber material is found to be part of one or more of the following: a process kit, a nozzle, a base, or a confinement ring.

[0056] As described above, a substrate 600, including an oxide layer 610, is exposed to a fluorinating agent to form a fluoride layer 620. The chamber is then cleaned. The fluoride layer is exposed to a halide etchant, and the chamber is cleaned again. This cycle can be repeated to remove the oxide layer 610 of a predetermined thickness. The fluorinating agent and halide etchant used can be any of the fluorinating agents and / or halide etchants described above.

[0057] The inventors have surprisingly discovered that, when performed in a process chamber comprising a nickel chamber material, oxide layers are selectively removed preferentially over TiN, SiN, TaN, SiO, AlO, LaO, carbon, and silicon. In some embodiments, the selectivity relative to the oxide layer of silicon is greater than or equal to about 5:1, greater than or equal to about 10:1, greater than or equal to about 15:1, greater than or equal to about 20:1, greater than or equal to about 25:1, greater than or equal to about 30:1, greater than or equal to about 35:1, greater than or equal to about 40:1, greater than or equal to about 45:1, or greater than or equal to about 50:1.

[0058] Some embodiments of this disclosure relate to various methods for removing metal oxide thicknesses greater than atomic layers within a single process cycle. References Figure 2 and Figure 4D Method 200 begins with operation 210, which includes exposing a substrate 600 of oxide layer 610 to a fluorinating agent to form a bulk fluoride layer 650 of thickness T.

[0059] The fluorinating agent used in method 200 can be any of the fluorinating agents described above for method 100. In some embodiments, to achieve a greater degree of fluorination, the fluorinating agent may further comprise H2.

[0060] In some embodiments, the thickness of the bulk fluoride layer is greater than or equal to about 5 angstroms, greater than or equal to about 10 angstroms, greater than or equal to about 15 angstroms, or greater than or equal to about 20 angstroms. In some embodiments, the thickness of the bulk fluoride layer is in the range of about 5 angstroms to about 30 angstroms, or in the range of about 7 angstroms to about 20 angstroms, or in the range of about 10 angstroms to about 15 angstroms.

[0061] Method 200 continues in operation 220, wherein the bulk fluoride layer 650 is exposed to a halide etchant to remove the bulk fluoride layer 650. The halide etchant used in method 200 can be any of the halide etchants described above for method 100. Solution 3 provides Figure 2 An exemplary reaction scheme of method 200 shown.

[0062] Option 3:

[0063] Metal oxide + fluorine source → bulk fluoride layer (1)

[0064] Bulk fluoride layer + metal halide → volatile products (2)

[0065] Some embodiments of this disclosure relate to methods for etching metal hydroxide materials rather than the oxide layers described above. References Figure 3 and Figure 4E Method 300 begins with operation 310, which exposes oxide layer 610 to oxidizing plasma to form hydroxide layer 660.

[0066] The hydroxide layer 660 can be formed by exposing the oxide layer to an oxidizing plasma. In some embodiments, the oxidizing plasma is a remote plasma. In some embodiments, the oxidizing plasma includes one or more of the following free radicals: water, peroxides, alcohols, or combinations thereof. In some embodiments, the oxidizing plasma includes OH* free radicals.

[0067] Method 300 continues at operation 320, exposing the hydroxide layer 660 to a fluorinating agent to form a fluoride layer 670. The fluorinating agent used in this method 300 can be any of the fluorinating agents described above for method 100.

[0068] Method 300 continues at operation 330, exposing the fluoride layer to a halide etchant to remove the fluoride layer 670. The halide etchant used in method 300 may be any of the halide etchants described above for method 100.

[0069] Option 4 provides Figure 3 An exemplary reaction scheme of method 300 shown.

[0070] In some embodiments, method 300 is repeated to remove oxide layer 610 and / or hydroxide layer 660 of a predetermined thickness.

[0071] Option 4:

[0072] Oxide layer + OH* group → Oxide layer (A)

[0073] Hydroxide layer + fluorine source → fluoride layer (1)

[0074] Fluoride layer + metal halide → volatile products (2)

[0075] Throughout this specification, references to "one embodiment," "some embodiments," "one or more embodiments," or "an embodiment" are intended to refer to a particular feature, structure, material, or characteristic described in connection with that embodiment and incorporated into at least one embodiment of this disclosure. Therefore, terms such as "in one or more embodiments," "in some embodiments," "in one embodiment," or "in one embodiment" appearing throughout this specification do not necessarily refer to the same embodiment of this disclosure. Furthermore, in one or more embodiments, a particular feature, structure, material, or characteristic may be combined in any suitable manner.

[0076] Although this disclosure has been described with reference to specific embodiments, those skilled in the art will understand that the described embodiments are merely illustrative of the principles and applications of this disclosure. Those skilled in the art will appreciate that various modifications and variations can be made to the methods and apparatus of this disclosure without departing from the spirit and scope of this disclosure. Therefore, this disclosure can be included within the scope of the appended claims and their equivalents.

Claims

1. An etching process, comprising: The substrate surface is exposed to a fluorinating agent to form a fluoride layer, the substrate surface having an oxide layer; as well as The fluoride layer is exposed to a halide etchant to remove it, the halide etchant comprising a compound having the general formula MX. y M includes one or more of titanium (Ti), tin (Sn), molybdenum (Mo), tungsten (W) or niobium (Nb), and X includes one or more of Cl, Br or I.

2. The etching process of claim 1, wherein the oxide layer comprises one or more of the following: hafnium, tungsten, molybdenum or titanium.

3. The etching process of claim 2, wherein the oxide layer is composed of hafnium oxide.

4. The etching process of claim 1, wherein the fluorinating agent comprises one or more of the following: HF; NF3; having the general formula C x H y F z Organofluorine compounds, wherein x is 1 to 16, y is 0 to 33, and z is 1 to 34; having the general formula C x H y O w F z Organic oxygen fluorides, wherein x is 1 to 16, y is 0 to 33, w is 1 to 8, and z is 1 to 34; metal fluorides; combinations of the above substances; or plasmas of the above substances.

5. The etching process as described in claim 1, wherein y is 1 to 6.

6. The etching process as described in claim 1, further comprising: Repeated exposure to the fluorinating agent and the halide etchant is used to remove the oxide layer of a predetermined thickness.

7. The etching process of claim 1, wherein the fluorinating agent is co-flowed with hydrogen (H2), and the fluoride layer has a thickness ranging from 10 angstroms to 15 angstroms.

8. The etching process of claim 7, wherein the fluoride layer is formed in a process chamber comprising a nickel chamber material.

9. The etching process of claim 1, further comprising: Before exposing the substrate surface to the fluorinating agent, the substrate surface is exposed to a cleaning plasma, the cleaning plasma including one or more of H*, OH*, O* or H2O*.

10. The etching process of claim 9, wherein the cleaning plasma removes carbon film and / or moisture from the substrate surface.

11. The etching process of claim 10, wherein the carbon film and / or moisture are a result of the etching process.

12. The etching process of claim 1, wherein the substrate surface has at least one other material, and the oxide layer is selectively etched in preference to the at least one other material.

13. The etching process of claim 12, wherein the at least one other material comprises one or more of the following: TiN, TaN, SiN, SiO2, Al2O3 or a carbon-based material, and wherein the oxide layer comprises one or more of the following: hafnium oxide, tungsten oxide, molybdenum oxide, titanium oxide or a combination of the above materials.

14. The etching process of claim 12, wherein the etching selectivity is greater than or equal to 10:

1.

15. An etching process, comprising: The substrate surface is exposed to a fluorinating agent to form a fluoride layer, the substrate surface having a hydroxide layer; as well as The fluoride layer is exposed to a halide etchant to remove it, the halide etchant comprising a compound having the general formula MX. y M includes one or more of titanium (Ti), tin (Sn), molybdenum (Mo), tungsten (W) or niobium (Nb), and X includes one or more of Cl, Br or I.

16. The etching process of claim 15, further comprising: The substrate surface is exposed to plasma to form the hydroxide layer, the substrate surface having an oxide layer, the plasma being formed by one or more of the following: H2O, H2O2, or alcohol.

17. The etching process of claim 16, wherein the oxide layer is composed of hafnium oxide.

18. An etching process, comprising: In a process chamber containing nickel chamber material, a substrate surface having an oxide layer and a second material is exposed to a fluorinating agent to selectively convert a portion of the oxide layer into a fluoride layer, the oxide layer comprising one or more of the following: hafnium oxide, tungsten oxide, molybdenum oxide, titanium oxide, or a combination of the above materials, and the second material comprising one or more of the following: TiN, SiN, TaN, SiO2, Al2O3, La2O3, carbon, silicon, or a combination of the above materials; as well as The fluoride layer is exposed to a halide etchant to remove it, the halide etchant comprising a compound having the general formula MX. y M includes one or more of titanium (Ti), tin (Sn), molybdenum (Mo), tungsten (W) or niobium (Nb), and X includes one or more of Cl, Br or I.

19. The etching process of claim 18, wherein the second material is composed of silicon, and the etching process has a selectivity of 20:1 or greater.

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