Etching solution composition and method

Abstract

A composition and method for selectively etching titanium nitride, cobalt, or combinations thereof. The composition and method generally leave molybdenum and other materials unaffected by the process. The process can achieve high etching rates and can provide uniformly patterned upper and lower layers with a concave shape.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor manufacturing. Specifically, the present disclosure relates to an etching solution composition and method for etching a titanium nitride film.

[0002] Priority The present disclosure claims priority based on U.S. Provisional Patent Application No. 63 / 346,748, filed on May 27, 2022. The priority document is incorporated herein by reference.

Background Art

[0003] A photoresist mask can be used to pattern materials such as semiconductors or dielectrics. For example, a photoresist mask can be used in a dual damascene process to form interconnects in the back-end metallization of microelectronic devices. The dual damascene process may require forming a photoresist mask on a low-k dielectric layer that covers a metal conductor layer such as a copper layer. The low-k dielectric layer can be etched according to the photoresist mask to form trenches that expose the metal conductor layer. Trenches, generally known as dual damascene structures, are typically defined using two lithography steps. Then, after the photoresist mask is removed from the low-k dielectric layer, a conductive material is deposited in the trenches to form interconnects.

Summary of the Invention

[0004] In some embodiments, a metal mask is used to provide better profile control of the trenches. The metal hard mask can be made of titanium or titanium nitride and is removed by a wet etching process after the formation of the trenches in a dual damascene structure. In some embodiments, the wet etching process uses a removal chemical that effectively removes the metal hard mask and / or photoresist etching residues without affecting the underlying metal conductor layer and low-k dielectric material, or other materials on the microelectronic device. Some embodiments of the etching solution composition can be utilized in a wet etching process to selectively remove substances such as titanium nitride while being compatible with the metal conductor layer (e.g., molybdenum, AlO x , SiO x , or polysilicon).

[0005] In some embodiments, the composition includes an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor including an N-heteroatom-containing aromatic compound.

[0006] In some embodiments of the present composition, the first corrosion inhibitor prevents the chemical reaction of a first material including Cr, Mo, W, or any combination thereof.

[0007] In some embodiments of the present composition, the second corrosion inhibitor prevents the chemical reaction of a second material.

[0008] In some embodiments of the present composition, the first corrosion inhibitor includes 5-methylbenzotriazole.

[0009] In some embodiments of the present composition, the second corrosion inhibitor includes polyvinylpyrrolidone.

[0010] In some embodiments of the present composition, the first corrosion inhibitor includes 4-(3-phenylpropyl)pyridine.

[0011] In some embodiments of the composition, the second corrosion inhibitor comprises polyvinylpyrrolidone.

[0012] In some embodiments, the etching method uses the composition described herein and the method comprises removing TiN at a TiN removal rate of at least 5.0 nm / min. In some embodiments of the method, the TiN removal rate is at least 10 nm / min.

[0013] In some embodiments, the method further comprises removing Co at a Co removal rate of at least 20 nm / min. In some embodiments of the method, the Co removal rate is at least 25 nm / min.

[0014] In some embodiments of the method, the removal rate of the first material is less than 1.8 nm / min due to the protection by the first corrosion inhibitor. In some embodiments of the method, the first material is Cr, Mo, W, or any combination thereof.

[0015] In some embodiments of the method, the removal rate of the second material is less than 0.5 nm / min due to the protection by the second corrosion inhibitor.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Among the disclosed benefits and improvements, other objects and advantages of the present disclosure will become apparent from the following description. Although detailed embodiments of the present disclosure are disclosed herein, it should be understood that the embodiments of the present disclosure are merely exemplary of the present disclosure which can be implemented in various forms. Further, each of the examples given with respect to the various embodiments of the present disclosure is intended to be illustrative and not limiting.

[0017] Throughout this specification and the claims, the following terms have the meanings explicitly associated with them in this specification, unless the context clearly indicates otherwise. As used herein, the phrases "in one embodiment," "in an embodiment," and "in some embodiments" do not necessarily refer to the same embodiment, but may do so. Further, the phrases "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to different embodiments, but may do so. All embodiments of the present disclosure are intended to be combinable without departing from the scope or spirit of the present disclosure.

[0018] As used herein, the term "microelectronic device" corresponds to semiconductor substrates, flat panel displays, phase change memory devices, solar panels, and other products including microelectromechanical systems (MEMS) manufactured for use in solar cell devices, photovoltaic power, and microelectronics, integrated circuits, energy harvesting, or computer chip applications. The terms "microelectronic device," "microelectronic substrate," and "microelectronic device structure" are not meant to be limiting and are understood to include any substrate or structure that will ultimately become a microelectronic device or microelectronic assembly. A microelectronic device can be patterned, blanketed, or made into a control device and / or a test device.

[0019] As used herein, the terms "titanium nitride" and "TiN" x " correspond to pure titanium nitride as well as impure titanium nitride with various stoichiometries and oxygen contents (i.e., TiO x N y ).

[0020] As used herein, "about" is intended to correspond to plus or minus 0.5% of the recited value.

[0021] As used herein, the term "low-k dielectric material" corresponds to any material used as a dielectric material in a layered microelectronic device, and the dielectric constant is less than about 3.5. In certain embodiments, the low-k dielectric material is a silicon-containing organic polymer, a silicon-containing hybrid organic / inorganic material, an organosilicate glass (OSG), TEOS, a fluorinated silicate glass (FSG), silicon dioxide, aluminum oxide (AlO x ), zirconium oxide (ZrO x ), and low-polarity materials such as carbon-doped oxide (CDO) glass. It should also be recognized that the low-k dielectric material can have various densities and various porosities.

[0022] As used herein, the term "metal conductor layer" includes copper, tungsten, cobalt, molybdenum, aluminum, ruthenium, alloys containing them, or combinations thereof.

[0023] As used herein, "fluoride" species corresponds to ionic fluorides (F - ) or species having covalently bonded fluorine. It should be understood that the fluoride species may be included as a fluoride species or generated in situ.

[0024] The compositions of the present invention can be embodied in a wide variety of specific formulations, as described in more detail below.

[0025] In all such compositions, the specific components of the composition are discussed in terms of weight percent ranges that include a zero lower limit, and such components may or may not be present in various specific embodiments of the composition, and it will be understood that in examples where such components are present, they may be present at a low concentration of 0.0001 weight percent based on the total weight of the composition in which the component is utilized.

[0026] In some embodiments, the present disclosure relates to compositions and processes for creating recesses within microelectronic device structures, such as 3D NAND flash memory devices. Some embodiments of the process can be characterized as including a dry or wet etching process, and a process in which a titanium nitride (TiN) layer is selectively etched such that overall some other materials are left unaffected by the process and any aluminum oxide, silicon dioxide, and polysilicon can also be left present. In some embodiments, the process can have an improved etching rate and can provide upper and lower layers with uniform concave patterns. In some embodiments, the composition is highly stable; for example, the bath life is longer than 24 hours and the storage life is longer than 6 months.

[0027] According to some embodiments, exemplary materials include a TiN layer and a cobalt (Co) layer, and the TiN layer and Co layer are selectively removed such that overall some other materials are left unaffected by the process of chemical etching by the exemplary composition.

[0028] Some examples of some other materials include, but are not necessarily limited to, a first material, a second material, silicon-based materials, etc. According to some embodiments, examples of the first material include molybdenum (Mo) or a Mo-containing alloy. According to some embodiments, examples of the first material are Cr, Mo, W, a Cr-containing alloy, a Mo-containing alloy, a W-containing alloy, or any combination thereof, or include them. According to some embodiments, examples of silicon-based materials include silicon (Si), SiO x , silicon oxide, SiN x , silicon nitride (Si x N y ), polysilicon, or a combination thereof.

[0029] In some embodiments, an exemplary composition includes an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor. The first corrosion inhibitor prevents a chemical reaction between the oxidizing agent and / or the etching solution and the first material. According to some embodiments, the composition selectively etches TiN and Co, but does not etch (i.e., chemically react with) the first material (e.g., Mo), and the chemical reaction does not result in or form an oxide (e.g., MoO x ) of the first material. According to some embodiments, the composition selectively etches TiN and Co, but the first corrosion inhibitor in the composition does not etch (i.e., chemically react with) the first material (e.g., Mo). Thus, even when the composition is used, an oxide (e.g., MoO x ) of the first material is neither formed nor generated.

[0030] In some embodiments, the first corrosion inhibitor includes 5-methylbenzotriazole, benzotriazole, or a combination thereof.

[0031] In some embodiments, the first corrosion inhibitor is 5-methylbenzotriazole.

[0032] In some embodiments, the first corrosion inhibitor is benzotriazole.

[0033] Some embodiments of the present composition further include one or more pH adjusters and a solvent (i.e., a solvent solution). In some embodiments, the composition includes a solvent that is a water-miscible solvent. Some embodiments of the present composition include water (e.g., deionized water, etc.). In some embodiments, the composition includes a water-miscible solvent and water (e.g., deionized water, etc.). In some embodiments of the present composition, the etching solution is one or more TiN etching agents. In some embodiments of the present composition, the etching solution is or includes a TiN etching agent and a Co etching agent. In some embodiments of the present composition, the etching solution is or includes one or more TiN·Co etching agents.

[0034] Furthermore, for example, according to some embodiments, the material includes a TiN layer disposed above the Co layer. The Co layer is disposed above a Mo layer (an example of a first material). The Mo layer is disposed above Si x N y material.

[0035] For example, according to some embodiments, the material includes a TiN layer disposed above the Co layer. The Co layer is disposed above a Mo layer (an example of a first material). The Mo layer is disposed above SiO x material.

[0036] For example, according to some embodiments, the material includes a TiN layer disposed above the Co layer. The Co layer is disposed above a Mo layer (an example of a first material). The Mo layer is disposed above the Si material.

[0037] In some embodiments, the composition has a TiN etching rate of 5 nm / min or more (at 60 °C).

[0038] In some embodiments, the composition has a Co etching rate of 20 nm / min or more (at 60 °C).

[0039] In some embodiments, the composition has a TiN etching rate of 5 nm / min or more and a Co etching rate of 20 nm / min or more (at 60 °C).

[0040] Exemplary materials include a titanium nitride (TiN) layer and a cobalt (Co) layer, and the TiN layer and the Co layer are selectively removed so that some other materials as a whole are present without being affected by the chemical etching process with the exemplary composition.

[0041] Some examples of some other materials include, but are not necessarily limited to, a first material, a second material, a silicon-based material, etc.

[0042] In some embodiments, the second material includes one or more of transition metals.

[0043] In some embodiments, an exemplary composition includes an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor. The first corrosion inhibitor prevents a chemical reaction between the oxidizing agent and / or the etching solution and a first material. The second corrosion inhibitor includes an N-heteroatom-containing aromatic compound and prevents a chemical reaction between the oxidizing agent and / or the etching solution and a second material.

[0044] For example, according to some embodiments, the material includes a TiN layer disposed above a Co layer. The Co layer is disposed above a second material. The second material is Si x N y disposed above the material.

[0045] For example, according to some embodiments, the material includes a TiN layer disposed above a Co layer. The Co layer is disposed above a second material. The second material is SiO x disposed above the material.

[0046] For example, according to some embodiments, the material includes a TiN layer disposed above a Co layer. The Co layer is disposed above a second material. The second material is disposed above a Si material.

[0047] In some embodiments, at 60 °C, the composition has a very high TiN etching selectivity. In some embodiments, the composition has a TiN etching rate of 5 nm / min or more and a Co etching rate of 20 nm / min or more, and the composition is compatible with Mo, Si x N y , and SiO x . In some embodiments, the composition does not etch Mo, Si x N y , and SiO x . In some embodiments, the composition does not react with Mo, Si x N y , and SiO x .

[0048] In some embodiments, at 60 °C, the composition has a TiN etching rate of 5 nm / min or more and a Co etching rate of 20 nm / min or more, and the composition is compatible with Mo, Si x N y , and SiO x , or any combination thereof. In some embodiments, the composition does not etch Mo, Si x N y , and SiO x , or any combination thereof. In some embodiments, the composition does not react with Mo, Si x N y , and SiO x , or any combination thereof.

[0049] In some embodiments, a portion of the material includes an exemplary material and another exemplary material, each of these materials including a titanium nitride (TiN) layer and a cobalt (Co) layer. The TiN layer and the Co layer are to be selectively removed, leaving the entirety of some other material present without being affected by the process of chemical etching with the exemplary composition.

[0050] Some examples of some other materials include, but are not necessarily limited to, a first material, a second material, a silicon-based material, and the like.

[0051] According to some embodiments, an example of the first material includes molybdenum (Mo) or a Mo-containing alloy. According to some embodiments, the example of the first material is Cr, Mo, W, a Cr-containing alloy, a Mo-containing alloy, a W-containing alloy, or any combination thereof, or includes them.

[0052] According to some embodiments, examples of the silicon-based material include silicon (Si), SiO x , silicon oxide, SiN x , silicon nitride (Si x N y ), polysilicon, or a combination thereof.

[0053] In some embodiments, an exemplary composition includes an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor. The first corrosion inhibitor prevents a chemical reaction between the oxidizing agent and / or the etching solution and a first material.

[0054] In some embodiments, an exemplary composition includes an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor. The first corrosion inhibitor prevents a chemical reaction between the oxidizing agent and / or the etching solution and a first material. The second corrosion inhibitor includes an N-heteroatom-containing aromatic compound and prevents a chemical reaction between the oxidizing agent and / or the etching solution and a second material. The composition is compatible with or does not react with the silicon-based material. That is, according to some embodiments, the composition reacts with TiN and Co at a much faster rate than the silicon-based material is removed so that TiN and Co are removed much faster than the silicon-based material, or the composition reacts with TiN and Co but does not substantially react with the silicon-based material, and thus TiN and Co are removed but the silicon-based material is not substantially removed, or the composition reacts with TiN and Co but does not react with the silicon-based material, and thus TiN and Co are removed but the silicon-based material is not removed.

[0055] In some embodiments, the composition is a TiN·Co etching solution composition including an oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor, the first corrosion inhibitor includes 5-methylbenzotriazole and 4-(3-phenylpropyl)pyridine, and the second corrosion inhibitor includes polyvinylpyrrolidone. In some embodiments, the composition further includes a pH adjuster and deionized water.

[0056] In some embodiments of the composition, the chemical reaction does not cause or form MoO x either.

[0057] According to some embodiments, the contemplated etchant may include a fluoride source such as HF, ammonium fluoride, tetrafluoroboric acid, hexafluorosilicic acid, other compounds containing B--F or Si--F bonds, tetrabutylammonium tetrafluoroborate (TBA-BF4), tetraalkylammonium fluoride (NR1R2R3R4F), tetraalkylammonium hydroxide (NR1R2R3R4OH), and other strong bases, where R1, R2, R3, and R4 may be the same as or different from each other and are selected from hydrogen, linear or branched C1-C6 alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), C1-C6 alkoxy groups (e.g., hydroxyethyl, hydroxypropyl), substituted or unsubstituted aryl groups (e.g., benzyl), weak bases, or combinations thereof. In one embodiment, the fluoride source includes HF, tetrafluoroboric acid, hexafluorosilicic acid, H2ZrF6, H2TiF6, HPF6, ammonium fluoride, tetramethylammonium fluoride, tetramethylammonium hydroxide, ammonium hexafluorosilicate, ammonium hexafluorotitanate, or a combination of ammonium fluoride and tetramethylammonium fluoride. In another embodiment, the etchant includes HF, hexafluorosilicic acid, or tetrafluoroboric acid. In yet another embodiment, the etchant is HF.

[0058] According to some embodiments, TiN x Ti in the film 3+An oxidizing agent included for etching or oxidizing. Oxidizing agents contemplated herein include hydrogen peroxide (H2O2), FeCl3, FeF3, Fe(NO3)3, Sr(NO3)2, CoF3, MnF3, Oxone® (2KHSO5·KHSO4·K2SO4 - CAS number 70693-62-8), periodic acid, iodic acid, t-butyl hydroperoxide, vanadium(V) oxide, vanadium(IV, V) oxide, ammonium vanadate, ammonium polyatomic salts (e.g., ammonium peroxomonosulfate, ammonium chlorite (NH4ClO2), ammonium chlorate (NH4ClO3), ammonium iodate (NH4IO3), ammonium nitrate (NH4NO3), ammonium perborate (NH4BO3), ammonium perchlorate (NH4ClO4), ammonium periodate (NH4IO4), ammonium persulfate ((NH4)2S2O8), ammonium hypochlorite (NH4ClO)), ammonium tungstate ((NH4) 10H2(W2O7)), sodium polyatomic salts (e.g., sodium persulfate (Na2S2O8), sodium hypochlorite (NaClO), sodium perborate), potassium polyatomic salts (e.g., potassium iodate (KIO3), potassium permanganate (KMnO4), potassium persulfate, nitric acid (HNO3), potassium persulfate (K2S2O8), potassium hypochlorite (KClO)), tetramethylammonium polyatomic salts (e.g., tetramethylammonium chlorite ((N(CH3)4)ClO2), tetramethylammonium chlorate ((N(CH3)4)ClO3), tetramethylammonium iodate ((N(CH3)4)IO3), tetramethylammonium perborate ((N(CH3)4)BO3), tetramethylammonium perchlorate ((N(CH3)4)ClO4), tetramethylammonium periodate ((N(CH3)4)IO4), tetramethylammonium persulfate ((N(CH3)4)S2O8)), tetrabutylammonium polyatomic salts (e.g., tetrabutylammonium peroxomonosulfate), peroxomonosulfuric acid, ferric nitrate (Fe(NO3)3), urea hydrogen peroxide ((CO(NH2)2)H2O2), peracetic acid (CH3(CO)OOH), 1,4-benzoquinone, toluquinone, dimethyl-1,4-benzoquinone, chloranil, alloxan, or combinations thereof, but not limited thereto. The oxidizing agent, when it is a salt, can be hydrated or anhydrous. The oxidizing agent can be introduced into the composition by the manufacturer before introducing the composition onto the device wafer or, alternatively, onto the device wafer, i.e., in situ. In one embodiment, the oxidizing agent comprises periodic acid.

[0059] The pH of the present composition can be adjusted using any suitable compound capable of adjusting the pH of the present composition. The pH adjuster is desirably water-soluble and compatible with the other components of the composition. Typically, the composition has a pH of about -1 to 5, or 0 to 4, or 2 to 4 at the time of use. Non-limiting examples of pH adjusters include mineral acids and organic acids including methanesulfonic acid, ethanesulfonic acid, phosphoric acid, sulfuric acid, hydrogen chloride, and the like.

[0060] In some embodiments, the solvent can include water, at least one water-miscible organic solvent, or a combination thereof, and the at least one water-miscible organic solvent is of the formula R 1 R 2 R 3 selected from the group consisting of compounds of C(OH), wherein R 1 , R 2 , and R 3 are independent of each other and are hydrogen, C2-C 30 alkyl, C2-C 30 alkene, cycloalkyl, C2-C 30It is selected from the group consisting of alkoxy and combinations thereof. For example, at least one solvent is water, methanol, ethanol, isopropanol, butanol, and higher alcohols, tetrahydrofurfuryl alcohol (THFA), 3-chloro-1,2-propanediol, 3-chloro-1-propanethiol, 1-chloro-2-propanol, 2-chloro-1-propanol, 3-chloro-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-iodo-1-propanol, 4-chloro-1-butanol, 2-chloroethanol), dichloromethane, chloroform, acetic acid, propionic acid, trifluoroacetic acid, tetrahydrofuran (THF), N-methylpyrrolidinone (NMP), cyclohexylpyrrolidinone, N-octylpyrrolidinone, N-phenylpyrrolidinone, methyldiethanolamine, methyl formate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylene sulfone (sulfolane), diethyl ether, phenoxy-2-propanol (PPh), propiophenone, ethyl lactate, ethyl acetate, ethyl benzoate, acetonitrile, acetone, ethylene glycol, propylene glycol (PG), 1,3-propanediol, 1,4-propanediol, dioxane, butyryl lactone, butylene carbonate, ethylene carbonate, propylene carbonate, dipropylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether (i.e., butyl carbitol), triethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether (DPGME), tripropylene glycol methyl ether (TPGME), dipropylene glycol dimethyl ether, dipropylene glycol ethyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether (DPGPE), tripropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether acetate, tetraethylene glycol dimethyl ether (TEGDE), dibasic ester, glycerin carbonate, N-formylmorpholine, triethyl phosphate, or a combination thereof, and can include at least one species selected from the group consisting of. In one embodiment, the at least one solvent includes water, such as deionized water. In one embodiment, the water-miscible solvent is selected from ethylene glycol and propylene glycol.,

[0061] Non-limiting and exemplary compositions are described below.

[0062] Composition Example TIFF2025519118000001.tif47170

[0063] When using the above composition example (etching at 60 °C), a TiN etching rate exceeding 10 nm / min was achieved. By using the same composition example, a Co etching rate of 28.9 nm / min or more was also obtained. Furthermore, an Mo etching rate of less than 1.8 nm / min could be achieved. Under some circumstances, an Mo etching rate of less than 1.5 nm / min could be achieved. Under some conditions, an Mo etching rate of less than 0.7 nm was achieved. An SiN x etching rate of less than 0.1 nm / min was also achievable.

Claims

1. An oxidizing agent, an etching solution, a first corrosion inhibitor, and a second corrosion inhibitor are included, and the second corrosion inhibitor includes an N - heteroatom - containing aromatic compound, a composition.

2. The composition according to claim 1, wherein the first corrosion inhibitor prevents a chemical reaction of a first material including Cr, Mo, W, or any combination thereof.

3. The composition according to claim 1 or 2, wherein the second corrosion inhibitor prevents a chemical reaction of a second material.

4. The composition according to claim 1, wherein the first corrosion inhibitor includes 5 - methylbenzotriazole.

5. The composition according to claim 4, wherein the second corrosion inhibitor includes polyvinylpyrrolidone.

6. The composition according to claim 4, wherein the first corrosion inhibitor includes 4 - (3 - phenylpropyl)pyridine.

7. The composition according to claim 6, wherein the second corrosion inhibitor includes polyvinylpyrrolidone.

8. The composition according to claim 1, wherein the first corrosion inhibitor includes 4 - (3 - phenylpropyl)pyridine.

9. The composition according to claim 8, wherein the second corrosion inhibitor includes polyvinylpyrrolidone.

10. The composition according to claim 1, wherein the second corrosion inhibitor includes polyvinylpyrrolidone.

11. A method of etching using the composition according to any one of claims 1 to 8, the method including removing TiN at a TiN removal rate of at least 5.0 nm / min.

12. Further including removing Co at a Co removal rate of at least 20 nm / min The method according to claim 11.

13. The method according to claim 12, wherein the TiN removal rate is at least 10 nm / min.

14. The method according to claim 13, wherein the Co removal rate is at least 25 nm / min.

15. The method according to claim 14, wherein the removal rate of the first material is less than 1.8 nm / min by the protection of the first corrosion inhibitor.

16. The method according to claim 15, wherein the first material is Cr, Mo, W, or any combination thereof.

17. The method according to claim 16, wherein the removal rate of the second material is less than 0.5 nm / min by the protection of the second corrosion inhibitor.

18. The method according to claim 17, wherein the second material is any one or more of Group 9 transition metals.

19. The method according to claim 14, wherein the removal rate of the second material is less than 0.5 nm / min due to the protection by the second corrosion inhibitor. **Claim 20** The method according to claim 19, wherein the second material is one or more of Group 9 transition metals.

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