KR101173692B1 - Solution for the selective removal of metal from aluminum substrates - Google Patents

Abstract

The present invention relates to a solution for selectively removing a metal such as Ta or TaN from a substrate such as an aluminum containing substrate. This solution comprises an acid such as HF or buffered HF, a fluorine ion containing component such as ammonium fluoride (NH ₄ F), ethylene glycol and water. Also disclosed is a method of selectively removing metal from a substrate using this solution.

Description

SOLUTION FOR THE SELECTIVE REMOVAL OF METAL FROM ALUMINUM SUBSTRATES             

The accompanying drawings are included in and constitute a part of this specification.

1 is a schematic diagram of an exemplary embodiment of an aluminum substrate having a protective layer and some having a metal coating that must be selectively removed.

The present invention relates to a solution for selectively removing a metal such as Ta or TaN from a substrate such as an aluminum containing substrate. Also disclosed is a method of selectively removing a metal coating without substantially damaging the exposed metal of the underlying substrate.

Fabrication of semiconductor devices typically involves forming a plurality of layers including a uniform photoresist coating over the conductive metal layer. Non-limiting examples of conductive metal layers formed over the substrate as diffusion barrier layers include aluminum, titanium, tungsten, tantalum and copper, and metal-oxides, metal-bolides, metal-nitrides, metal-carbide and alloys thereof do. Such conductive metal films are typically formed as a diffusion barrier to prevent the metal of the metal layer from diffusing into the lower dielectric layer located above the substrate. For example, a barrier layer is typically formed between a silicon containing dielectric layer (eg, SiO ₂ or Si ₃ N ₄ ) and an Al or Cu metal layer.

Recently, tantalum (Ta) and tantalum nitride (TaN) have been found to be excellent substitutes for traditional Ti-based diffusion barriers for use in semiconductor processes because they are effective diffusion barriers at least in part at high temperatures of 200 ° C. . As the use of Ta in the manufacture of devices increases, a method or stripping solution for removing the Ta or TaN layer from the substrate is needed.

For example, after performing well known steps (including optional photo-etching) to obtain microcircuits, removal of metals from certain areas of the microcircuits, such as Ta or TaN layers, is typically carried out with organic stripping solutions. Was achieved by.

Chemical removal of tantalum metal from aluminum substrates is an extremely difficult method to perform. This is at least because tantalum is very resistant to most chemical attack and requires a medicament capable of giving fluorine ions to help dissolve the Ta containing layer. Recently, a method of wet processing of electronic components with a tantalum containing layer over it, using oxidants, has been attempted. For example, U.S. Patent Application No. 2002/0119245 A1 includes oxidizing agents (such as hydrogen peroxide or ozone) and fluorine ion generating agents (such as HF or buffered HF) for wet processing of electronic components. Tantalum oxidation solution is described.

One skilled in the art knows that fluorine ion generating agents such as hydrofluoric acid (HF) solutions readily attack exposed metals such as aluminum. Thus, the substrate is typically severely corroded during the process and may be damaged beyond repair.

For this reason, alternative methods to this method, such as mechanical wear, often referred to as "chemical mechanical polishing" (CMP), have been used, but the method removes tantalum but also especially when the entire substrate is not covered with Ta or TaN. Damage the substrate.

Other methods of removing Ta and TaN include sputter etching. Unlike CMP, which is most useful when the entire substrate is covered with Ta or TaN, sputter etching is generally useful for patterned etching because it can remove highly specific regions in an anisotropic manner. Because of the inherent shortcomings associated with sputtering, including the possibility that material removed by sputtering can be redeposited on an exposed surface, this technique is limited in use.

In view of the foregoing, it is necessary to remove metal from the substrate to overcome at least some of the one or more drawbacks associated with the related art. For example, some aspects of the present disclosure may relate to a chemical method for selectively removing metal from a substrate with minimal or no damage to the substrate.

One exemplary subject matter may relate to a solution for selectively removing metal from an aluminum containing substrate. The solution may comprise at least one acid (eg HF or buffered HF), at least one component comprising fluorine ions (eg NH ₄ F), ethylene glycol and water. Combinations of these components are found in amounts sufficient to remove metal (eg Ta) from the aluminum containing substrate in the final solution.

Methods of removing metal from a substrate are also disclosed. One exemplary method may be a method of selectively removing metal from a substrate comprising aluminum and at least partially covered with a metal. For example, this method uses 1-20% HF, buffered HF or a mixture thereof, 1-40% NH ₄ F, 40-95% ethylene glycol and the remaining amount of water per weight percent of the solution. Contacting the substrate with a solution comprising the same. In one embodiment, the solution further includes a surfactant to aid in the removal of metal from the substrate.

In the disclosed method, the substrate and the solution can be contacted for a time sufficient to remove metal from the substrate without substantially reacting with the underlying aluminum substrate. This example may also include forming an aluminum ethoxide layer over at least a portion of the exposed aluminum substrate.

Apart from the subject matter discussed above, the present disclosure includes many other exemplary features, such as those described below. It is to be understood that both the foregoing description and the following description are exemplary only.

As used herein, "optionally removed" (or a term derived therefrom) means removing or stripping metal from a substrate without substantially reacting with or corroding the underlying substrate. While not wishing to be bound by any theory, the highly selective removal properties associated with the disclosed solutions are in ethylene glycol present in an amount sufficient to form an ethoxide layer on at least a portion of the substrate that is not covered with metal, i.e., the exposed substrate. It is thought to be due.

In certain embodiments, ethylene glycol may be used with other components or other components may be used instead of ethylene glycol. Non-limiting examples of such components include propylene glycol, butanediol, glycerol, or any straight or branched -diol or -triol from C ₂ to C ₆ chains.

1 illustrates an example of the basic mechanism of the selective removal method described herein. In this embodiment, an organometallic layer is formed on the exposed surface of the aluminum-containing substrate to protect the substrate from HF attack during the stripping process. As shown in FIG. 1, by reacting with the exposed portion of the substrate, ethylene glycol forms a protective layer (eg, aluminum ethoxide) over the exposed portion of the substrate. This protective layer substantially protects the substrate from attack by subsequent acid treatment. For example, where the substrate comprises aluminum, ethylene glycol is present in an amount sufficient to form an aluminum ethoxide layer over at least a portion of the substrate that is not covered with metal. In one embodiment, the amount of ethylene glycol sufficient to form the ethoxide layer may be 50 to 60% per weight of the solution.

Since the metal coating does not contain a protective ethoxide layer, this metal coating may be susceptible to attack from acids such as HF. In some instances, the methods described herein can be used to modify copper, tungsten, titanium, tantalum, and metal-oxides, metal-bolides, metal-knights without substantially contacting the substrates and / or etching underlying substrates. One or more metal coatings (eg, undesirable metal coatings) such as rides, metal-carbides, alloys and mixtures thereof can be selectively removed.

As used herein, “without substantially contacting and / or not etching” means no detectable attack on the underlying substrate as determined by visual inspection of the substrate or by measuring the weight loss of the substrate. .

In one embodiment, the acid component of the solution includes fluorine ions, such as HF or buffered HF. In other embodiments, the acid may include any well known acid, such as an acid selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and mixtures thereof. Any one of these acids or any combination of these acids may be present in an amount of 1 to 20%, such as 10 to 15%, by weight of the solution.

In another embodiment, the solution includes at least one component comprising fluorine ions. Non-limiting examples of such components include ammonium fluoride (NH ₄ F), sodium fluoride, potassium fluoride, ammonium bifluoride, sodium bifluoride, ammonium fluoroborate and barium fluoride. Any one or any combination of these components may be present in an amount of 1 to 40%, such as 5 to 20%, even 5 to 15%, by weight of the solution.

으로부터의 FC 계열, 아미드 및 알킬 에톡실레이트가 포함된다.The solutions described herein may optionally include additives commonly used in stripping solutions. For example, this solution may include one or more additives selected from surfactants, corrosion inhibitors, pH adjusters, and the like. In one embodiment, these optional components may be present in amounts up to 5% by weight of the solution. Non-limiting examples of surfactants that may be optionally incorporated into the disclosed solutions include straight chain and branched primary, secondary and tertiary amines, amides, fluorocarbons and chain lengths C ₂ to C ₁₂ and Alkylethoxylates (including anionic, nonionic, cationic and amphoteric surfactants), and mixtures thereof. Examples of these surfactants can be found in US Patent Application No. 2002/0119245 A1 published August 29, 2002 and US Patent Application No. 2003/0114014 A1 published June 19, 2003 (these are Incorporated herein by reference). In one embodiment, the surfactant is octylamine (C ₈ ). Other surfactants that may be used include fluorocarbon surfactants such as 3M

FC series, amides and alkyl ethoxylates from.

Examples of corrosion inhibitors include benzotriazole and pyrocatechol.                     

Non-limiting examples of pH adjusters that can be used to maintain the pH of the solution below 7, such as below 6, even below 5 and below 4 are any such as acids selected from hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, and mixtures thereof. Suitable acids.

In one embodiment, a solution for selectively removing Ta or TaN from an aluminum-containing substrate is disclosed, wherein the solution is 1-20% HF, 1-40% NH ₄ F, 40-95 per weight of the solution. % Ethylene glycol and optionally a surfactant comprises the balance of water.

Also disclosed herein is a method for selectively removing metal from a substrate using any solution described above. For example, the method includes contacting the substrate with a solution as described above (eg, at least one component comprising fluorine ions, a solution comprising ethylene glycol and water) and the substrate Is in contact with the solution for a time sufficient to remove metal from the substrate without substantially corroding the substrate.

For example, a method of selectively removing metal from a substrate comprising aluminum and at least partially covered with metal is disclosed. In this example, the method comprises 1-20% (eg 10-15%) of HF, 1-40% (eg 10-15%) of NH ₄ F, 40-95% (by weight of the solution). Contacting the substrate with a solution comprising, for example, 50-60%) of ethylene glycol and the remaining amount of water.

According to some exemplary methods, the solution and the substrate may be contacted for a time sufficient to remove metal from the substrate without substantially reacting with the substrate, and an aluminum ethoxide layer is formed over at least a portion of the exposed substrate.

The contact time sufficient to remove the metal from the substrate will depend on a variety of factors including the thickness of the metal layer to be removed, the concentration and amount of components present (eg, acids, components containing fluoride ions, ethylene glycol and water). Can be. Other factors that can affect the contact time include the pH of the solution and the temperature at which the solution contacts the substrate. In general, the etch rate may decrease as the pH is increased. Therefore, the contact time may increase as the pH of the solution increases.

Etch rates may also be a function of solution temperature, which typically increases with increasing temperature. The method described herein can be performed using a solution heated to 120 ° C., and the maximum allowable temperature can vary depending on the selectivity of a given system. For example, in one embodiment where Ta / TaN is removed from an Al containing substrate, the solution is heated to a temperature in the range of 85 ° C to 95 ° C. In another embodiment, the solution is heated to a temperature ranging from room temperature to 85 ° C.

Any of the well known wet processing procedures can be used to carry out the method described above. For example, a metal-coated substrate may be contacted with the solution by using a batch-type procedure, such as by immersing the substrate in a bath containing the solution for a time sufficient to remove the metal. have.

Alternatively, the substrate can be contacted using a continuous procedure. In this embodiment, one or more substrates may be passed through the vessel containing the solution at a rate of removing metal.

One or both of these types of methods may consist of a single step method or a multi step method. Moreover, the method of mixing a continuous type and a batch type can also be used.

Regardless of the exact method used, the mechanism can typically be the same. For example, the processing solution may contain a sufficient amount of complexing agent to react with the substrate surface as soon as the coating is removed, ie as soon as the substrate is exposed. This organo-metal complex may be insoluble in the stripping medium, which may protect the substrate from attack but may be subsequently removed during further processing. For example, the aluminum ethoxide complex may be water soluble and may be removed by washing after removal of the coating by acid.

In one embodiment, the method includes exposing the substrate to timed immersion in a spray or wet chemical bath from a chemical spray tool until the metal is completely removed. This method can be a multi-step consisting of a stripping-irradiation-stripping-irradiation cycle until removal is complete. Continuous systems are generally rare in the semiconductor industry, but can be operated as described herein if a stripping time is set for a particular set of components.

In addition to the examples of operation, or unless otherwise indicated, it should be noted that the numbers expressing the amounts of components, reaction conditions, and the like used in the present specification and claims all bear the term "about." Accordingly, unless indicated to the contrary, the numerical variables set forth in the foregoing specification and claims are approximations that may vary depending on the desired properties to be obtained. Without wishing to at least limit the application of the principles of equivalents to the scope of the claims, each numerical variable should be considered in light of the significant figures and conventional approximations.

Those skilled in the art will appreciate that various modifications and variations can be made to the subject matter described herein. Thus, it should be understood that the invention is not limited to the discussion described in the specification. Rather, the invention is intended to cover modifications and variations.

According to the present invention, the metal coating can be selectively removed from the substrate without substantially damaging the substrate.

Claims (30)

As a solution, In weight percent of the solution, 1 to 20% HF, buffered HF or mixtures thereof; 1-10% ammonium fluoride (NH ₄ F); 50 to 60% ethylene glycol; And Solution comprising water. delete delete delete The method of claim 1, 10 to 15% HF. delete The method of claim 1, A solution comprising 1 to 5% NH ₄ F. delete delete The method of claim 1, Further comprising at least one anionic surfactant, nonionic surfactant, cationic surfactant or amphoteric surfactant. 11. The method of claim 10, The at least one surfactant has a chain length of C ₂ to the primary amine of the C _12, chain length of C ₂ to the secondary amine and the chain length of C ₂ to 3 amine of the C _12, amides of C _12, fluoro Solution selected from the group consisting of carboxycarbons and alkylethoxylates. The method of claim 1, Wherein the solution has a pH of less than 6. As a solution, In weight percent of the solution, 1 to 20% HF, buffered HF or mixtures thereof; 1-5% NH ₄ F; 50 to 60% ethylene glycol; Surfactants; And A solution comprising the remaining amount of water. Contacting the aluminum-containing substrate with a solution to selectively remove a metal containing coating from the aluminum-containing substrate, The solution is, by weight of the solution, 1 to 20% HF, buffered HF or mixtures thereof; 1-10% ammonium fluoride (NH ₄ F); 50 to 60% ethylene glycol; And Contains water, And the substrate is in contact with the solution for a time sufficient to remove the coating from the substrate without substrate corrosion. 15. The method of claim 14, The metal-containing coating is copper, tungsten, titanium, tantalum, and a metal selected from the group consisting of metal-oxides, metal-borides, metal-nitrides, metal-carbides, alloys and mixtures thereof Comprising a metal compound. 16. The method of claim 15, And the metal containing coating comprises a material selected from the group consisting of metal tantalum and tantalum nitride. 15. The method of claim 14, And the substrate comprises a material selected from the group consisting of elemental aluminum, aluminum nitride, aluminum boride, and mixtures thereof. delete delete delete delete 15. The method of claim 14, The ethylene glycol forms an aluminum ethoxide layer on at least a portion of the substrate that is not covered with the coating. delete 15. The method of claim 14, The solution further comprises at least one anionic surfactant, nonionic surfactant, cationic surfactant or amphoteric surfactant. 25. The method of claim 24, The at least one surfactant has a chain length of C ₂ to the primary amine of the C _12, chain length of C ₂ to the secondary amine and the chain length of C ₂ to 3 amine of the C _12, amides of C _12, fluoro Selected from the group consisting of carboxycarbons and alkylethoxylates. 15. The method of claim 14, Wherein the solution has a pH of less than 6. 15. The method of claim 14, The solution is heated to a temperature of up to 120 ° C. 28. The method of claim 27, The solution is heated to a temperature in the range of 85 ° C to 95 ° C. 28. The method of claim 27, The solution is heated to a temperature range from room temperature to 85 ° C. A method for selectively removing, from a substrate, a metal containing coating comprising a material selected from the group consisting of metals Ta and TaN, the substrate comprising aluminum and at least partially covered by the coating, Contacting the substrate with a solution; And Forming an aluminum ethoxide layer on the exposed portion of the substrate / RTI > The solution is weight percent of the solution, 1-20% HF, 1-10% NH ₄ F; 50 to 60% ethylene glycol; And Remaining water Wherein the substrate is in contact with the solution for a time sufficient to remove the coating from the substrate without corrosion of the substrate, wherein the solution is in the range of 85-95 ° C. prior to or during contact with the solution. And selectively remove the coating from the substrate, which is heated to a temperature of.

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