METHOD OF MAKING AN INTEGRATED CIRCUIT INCLUDING ELECTRODEPOSITION OF ALUMINIUM

- INFINEON TECHNOLOGIES AG

A method of making an integrated circuit including composition of matter for electrodepositing of aluminium is disclosed. One embodiment includes a bath having a solution of selected aluminium salts in a substantially anhydrous organic solvent, to uses of certain aluminium salts for electrodepositing and to processes for electrodepositing aluminium.

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Description
BACKGROUND

The invention relates to a method of making an integrated circuit including composition of matter for electrodepositing of aluminium, to uses of certain aluminium salts for electrodepositing and to processes for electrodepositing aluminium.

Aluminium is a metal of high technical value based on its superior attributes. Especially coatings of aluminium are used in a lot of high-tech technologies.

Aluminium may not be electrodeposited from aqueous solutions. The electrodepositing baths/solutions used successful up to now for the electrodepositing of aluminium do fall under one of the following three groups:

AlX3 (especially with X being Cl, or Br)

ALH3 (especially LiAlH4 and AlCl3 in ether)

AlR3 (especially with R being ethyl or isobutyl)

As examples of the processes for electrodepositing the following will be mentioned:

The most common process used today is using baths for electrodepositing of organoaluminium electrolytes. The electrolytes used are aluminiumtrialkyls in connection with alkali halogenides dissolved in aromats. The SIGAL™-process (Siemens-Galvanisch Aluminium) is using a complex of general formula


KF.2AlR3(1:2 complex)

in which different aluminium alkyls and mixtures of alkyls are employed with the (1:2 complex) being superior to the (1:1 complex).

Electrodepositing of aluminium was also achieved from AlCl3 and LiCl in DMSO (dimethylsulfoxide) or from aluminiumtrifluoroacetate (Al(TFA)3) in methanol achieving 30% effectiveness.

Even though the aluminium coatings achieved with the aluminium organyl compounds used commonly in the state of the art are of high quality, executing and supervising the related processes on the other hand is generally quite complicated and never is without risks. The following points do contribute to the overall problem:

Aluminium organyl compounds are extremely sensitive to humidity, being decomposed already by traces of water. Decomposition is then accompanied by an intense hydrolysis leading to the formation of hazardous hydrogen.

The sources of aluminium used are self-igniting in air.

Aluminium organyl compounds are incompatible with a number of other chemicals like oxidants or alcohols.

Thus these processes according to the state of the art have to be conducted with the utmost of care and strict surveillance under an atmosphere of a protective gas.

All of these facts and disadvantages clearly indicate a strong need for improvement in the technical field of electrodepositing of aluminium.

For these and other reasons, there is a need for the present invention.

SUMMARY

One embodiment provides a method of making an integrated circuit including a composition of matter for electrodepositing aluminium, including a bath having a solution of selected aluminium salts in a substantially anhydrous organic solvent. In one embodiment, the salts are halogenated aluminium alcoholates. An additional embodiment includes the use of selected aluminium salts for electrodepositing. Halogenated aluminium alcoholates are used. According to a third embodiment, a process for electrodepositing aluminium from a bath having a solution of selected aluminium salts in a substantially anhydrous organic solvent is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles of the invention. Other embodiments of the present invention and many of the intended advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

FIG. 1 illustrates a scanning electron microscopic picture with the total view of electrodeposited aluminium on brass as in the 1st experiment. Different areas (dark and bright) can be seen likely due to the organization of the bath/cell with a stirrer on top and the electrode on the bottom. The dark area compared to the bright area is having a thicker layer, but is also more brittle and showing more cracks. The layer in the bright area is thinner, more bright and more homogeneous. So it is clear that by chosing the right conditions different forms of layers can be achieved.

FIG. 2 illustrates a scanning electron microscopic picture of electrodeposited aluminium on Brass, limited to the dark area described above (FIG. 1).

FIG. 3 illustrates a scanning electron microscopic picture of electrodeposited aluminium on Brass, limited to the bright area described above (FIG. 1).

FIG. 4 illustrates a scanning electron microscopic picture electrodeposited aluminium on Brass, limited to the bright area described above (FIG. 1). In addition an EDX (an energy dispersion x-ray) of the bright area is shown. With this the elements of a certain sample can be determined by exciting the atoms by x-ray and measuring the energy of the excited particles. This EDX shows the purity and quality of the layer, with fluorine coming from the alcoholate.

FIG. 5 illustrates a scanning electron microscopic picture with the total view of electrodeposited aluminium on platinum as in the 2nd experiment. In addition an EDX (an energy dispersion x-ray) is shown. With this the elements of a certain sample can be determined by exciting the atoms by x-ray and measuring the energy of the excited particles. This EDX shows the purity and quality of the layer, with fluorine coming from the alcoholate.

 DETAILED DESCRIPTION

In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

One or more embodiments provide a method of making an integrated circuit, a semiconductor or wafer, including a composition of matter for electrodeposition of aluminium. According to one embodiment, a composition of matter for electrodepositing of aluminium is provided including a bath having a solution of an aluminium salt selected from

halogenated aluminium alcoholate; or

aluminium salts with an anion with strongly electron-withdrawing groups;

in a substantially anhydrous organic solvent.

The composition of matter as well as the other embodiments described below show the big advantage of providing a new way of electrodepositing aluminium from a bath without having to revert back to the necessary strict surveillance and care—including the hermetically sealed cells for electrolysis—of the processes in the state of the art. Still the aluminium salts selected in the different embodiments of this invention are sensitive to humidity, but they are neither prone to self-ignition in air nor do they show any toxicity or incompatibility to other chemicals like oxidants. Accordingly the processes may be executed with standard electrodepositing equipment under an atmosphere of a protective gas, without the necessity of utmost surveillance.

“Substantially anhydrous organic solvent” is as defined herein an organic solvent with a water content of equal to or less than 1% determined by the standard Karl-Fischer-Titration. It is further understood that the substantially anhydrous organic solvent can also be a mixture of different substantially anhydrous organic solvents.

“Bath” is defined herein as a composition of a container and a fluid comprised in the container in which aluminium is present. By applying an electrical current by using a cathode and an anode to the fluid the aluminium is electrodeposited from the bath thus aluminium-plating a chosen surface.

“Alcoholate” is a salt between the aluminium and an alcohol, preferably a homologous alcohol, preferably a halogenated alcohol. Examples include methanolate, ethanolate, propanolate or butanolate, here especially their halogenated derivatives.

An “Electron withdrawing group” or EWG draws electrons away from a reaction center. Examples include pentahalogenated benzoate, substituted sulfonate anions or halogenated carboxylic acid anions.

Preferably the aluminium salt is dissolved in the substantially anhydrous organic solvent in a concentration of between 0.05 and 5 mol/kg of solvent or also preferably in an amount greater than or equal to 0.1 mol/kg of solvent.

In one embodiment of the composition of matter according to the invention the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

In another embodiment of the composition of matter the alcoholate anion of the halogenated aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

In another embodiment of the composition of matter in the compound according to general formulas Ia to Ig more than half of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

In another embodiment of the composition of matter in the compound according to general formulas Ia to Ig R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl;

or

R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

In another embodiment of the composition of matter in the composition the alcoholate anion of the halogenated aluminium alcoholate is a compound according to general formula Ib.

In another embodiment of the composition of matter in the compound according to formula Ib R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl;

preferably are F or Cl;

more preferably are either all F or all Cl;

or

R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen;

preferably R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen;

more preferably R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

In another embodiment of the composition of matter the anion with the strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5COO−, or C6Cl5COO−;

substituted sulfonate anions, preferably from sulfonate anions of any of general structure II

wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or

halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId

wherein R31R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, preferably at least half of R31, R32, R33R34, R35R36, and R37 being halogen.

“Alkyl” herein is defined as an univalent radical consisting of carbon and hydrogen atoms arranged in a optionally branched chain. Thus, “alkyl” is understood as meaning a saturated, linear or branched chain of hydrocarbons, which can be unsubstituted or mono- or polysubstituted. In these, C1-4alkyl represents C1-, C2-, C3- or C4-alkyl, so methyl, ethyl, propyl or butyl, if substituted also CHF2, CF3 or CH2OH etc.

The term “substituted” in the context of this invention is understood as meaning replacement of at least one hydrogen radical by F, Cl, Br, I, NH2, SH or OH, “polysubstituted” (more than once substituted) being understood as meaning that the replacement takes effect both on different or on the same atoms several times with the same or different substituents, for example three times on the same C atom, as in the case of CF3, or at different places, as in the case of e.g., —CH(OH)—CH2—CH2—CHCl2. “Optionally at least monosubstituted” means either “monosubstituted”, “polysubstituted” or—if the option is not fulfilled—“unsubstituted”.

In another embodiment of the composition of matter in the anion according to general structure (II) or (IIIa) to (IIId)

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or

R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32R33R34R35, R36 and R37 being For Cl.

In another embodiment of the composition of matter the organic solvent is selected from aprotic organic solvents or from organic solvents not forming a complex with the aluminum salts described above or from organic solvents having a donator power of between 30 and 10, preferably of between 25 and 12, or from solvents in which the aluminium salts described above may be dissolved.

It is understood that the organic solvents preferably used may—but do not have to—also show combinations of the attributes set out above. For reasons of stability of the aluminium salts in the solvent especially aprotic solvents (not donating hydrogen bonds) are preferred. In one embodiment, it is preferred if the organic solvent is not forming a complex with the aluminium salts described above. This is partly predictable by the donator power but—due to the complicated nature of the solvent salt interactions—may not always be predictable by this characteristic. Nevertheless, this can easily be determined by someone skilled in the art using simple experiments. This is also true for determining solvents in which the aluminium salts may be dissolved. These are preferred solvents and especially those in which the aluminium salts may be completely dissolved in higher concentrations e.g., 5 mol/kg or—more preferably—2.5 mol/kg or 1 mol/kg. Donator power is a characteristic of a solvent well defined in literature (Gutmann V., The Donor-Acceptor Approach to Molecular Interactions, Plenum Press, New York, 1978).

In another embodiment of the composition of matter the organic solvent is selected from aprotic organic solvents, or from solvents in which the aluminium salts may be dissolved, preferably from aprotic organic solvents in which the aluminium salts may be dissolved.

In another embodiment of the composition of matter the substantially anhydrous organic solvent is provided in form of a mixture of different substantially anhydrous organic solvents. This is a mixed-solvents-approach.

In another embodiment of the composition of matter the organic solvent has a water content of less than 1% preferably of equal to or less than 0.5%, more preferably of equal to or less than 0.25%, most preferably of equal to or less than 0.15%. This may be determined using the standard Karl-Fischer-Titration.

In a further embodiment of the composition of matter the organic solvent is selected from

Acetonitril, Tetrahydrofuran (THF), tert.butyl-methyl ether;

or carbonates, preferably selected from dimethyl carbonate, or propylene glycol carbonate (4-Methyl-1,3-dioxolan-2-on);

or carboxylic acid esters; preferably selected from ethyl acetate.

In a further embodiment of the composition of matter the aluminium salt is present in the bath in an amount greater than or equal to 0.1 mol/kg solvent or in a concentration of between 0.05 and 5 mol/kg of solvent.

In another embodiment of the composition of matter the bath is additionally having at least one further electrolyte, preferably a nonaqueous electrolyte, more preferably a phosphate, alkyl-sulfonate, borate, antimonite or arsenate; most preferably the electrolyte is selected from hexafluorophosphates, tris(pentafluoroethyl)trifluorphosphate, methanesulfonates, trifluoromethanesulfonates, tetrafluoroborates, bis[oxalato(2-)]borate, bis[silicylato(2-)]borate, bis[1,2-benzenediolato(2-)-0,0′]borate, hexafluoroanitmonate, or hexafluoroarsenate; or is selected from hexafluorophosphates, or tetrafluoroborates.

An “electrolyte” as defined here is a substance containing a free ion that behaves as an electrical conductor medium. Examples include especially salts, and include nonaqueous electrolytes, preferably those also known in the techical field of dry batteries or dry cell batteries. Examples are phosphates, alkyl-sulfonates, borates, antimonites or arsenates.

Another embodiment of the composition of matter is additionally having an anode and cathode; preferably a soluble aluminium anode.

“Anode” and “cathode” are both electrodes through which electric current flows into a polarised electrical device, like a solution having electrolytes, like aluminium salts.

In another embodiment of the composition of matter the anode and the cathode are arranged at least partly inside the solution comprised within the bath, preferably while no physical barrier or membrane is blocking the flow of the substantially anhydrous organic solvent between the cathode and anode.

This embodiment is specifically drawn to an undivided arrangement of the cell/bath in the composition of matter according to the invention.

In another embodiment, the composition does also comprise a means for excluding oxygen or humidity or both from the bath, preferably from the surface of the bath or of the solution comprised within the bath; preferably in the form of a sealing, or lid covering the surface of the bath or solution comprised within the bath or a means for introducing a protective gas to the surface of the bath or solution comprised within the bath; or combinations thereof.

“Lid” and “sealing” refers to different means for closing the area having the bath, or more precisely the surface of the solvent comprised in the bath of the composition of matter according to the invention against incursion of gases or e.g., humidity. Especially this is to be understood as preferably providing a closed system. On the other hand another commonly used approach to exclude incursion of oxygen, or humidity is the use of protective gases occupying the space above the surface of a reaction mixture, e.g., the solution comprised in the bath. Means for introducing a protective gas include e.g., different valves or orifices through which the protective gas may be applied etc., with the protecting gas then preferably being confined to the space above the solution by e.g., a lid or a sealing, which would then also serve to further exclude incursion of gases or humidity.

Another embodiment is the use of an aluminium salt selected from

halogenated aluminium alcoholate; or

aluminium salts with an anion with strongly electron-withdrawing groups;

for electrodepositing aluminium.

In an embodiment of the use the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

In another embodiment of the use the alcoholate anion of the halogenated aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

In another embodiment of the use in the compound according to any of general formulas (Ia) to (Ig) more than half of R1, R2, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

In another embodiment of the use in the compound according to any of general formulas (Ia) to (Ig)

R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl;

or

R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

In another embodiment of the use the alcoholate anion of the aluminium alcoholate is a compound according to general formula Ib.

In another embodiment of the use according to the invention in the compound according to general formula (Ib)

R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl;

or

R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen, preferably R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen, more preferably R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

In another embodiment of the use the anion with strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5COO−, or C6Cl5COO−;

substituted sulfonate anions, preferably from sulfonate anions of any of general structure II

wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or

halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId

wherein R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, preferably at least half of R31, R32, R33, R34R35, R36, and R37 being halogen.

In another embodiment of the use in the compounds according to general formula (II) or (IIIa) to (IIId)

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or

R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32R33R34R35R36 dR37 beingFor Cl.

In another embodiment of the use the aluminium is electrodeposited on a conductive surface, preferably a conductive surface selected from metals, alloys of metals and conductive polymers.

A “conductive surface” in the sense of this invention is the surface of an item which surface is able to conduct an electric current. Examples include i.a. the metal-coated surface of a wafer (see below).

In another embodiment of the use the aluminium is electrodeposited on a conductive surface, preferably a conductive surface selected from metals, alloys of metals and conductive polymers, more preferably on a metal surface of a conductive metal, preferably a metal being selected from

Ag, Au, Cr, Cu, Fe, Ge, Ir, Mn, Mo, Nb, Ni, Pd, Pt, Si, Ta, Ti, V, W, Zn or In, Pb, Sb and Sn;

more preferably from

Ag, Au, Cr, Cu, Fe, Ge, Ir, Mn, Mo, Nb, Ni, Pd, Pt, Si, Ta, Ti, V, W, or Zn;

or from alloys of these metals.

In another embodiment of the use the aluminium is electrodeposited for the purpose of creating a new package material, for pattern plating or for replacing sputtering on or creating of a conductive surface, or for anticorrosive protection or for layering—optionally with other metals.

“Sputtering” as defined herein is a process whereby atoms in a solid target material are ejected into the gas phase due to bombardment of the material by energetic ions. It is commonly used for thin film deposition like e.g., the sputtering of a wafer (see below) with metal to create a conductive surface.

Another embodiment provides a process for electrodepositing of aluminium from a bath, wherein by using an electrode/cathode and an anode being arranged at least partly inside the bath an electric current is applied to the bath having a solution of an aluminium salt with an anion selected from

halogenated aluminium alcoholate; or

aluminium salts with an anion with strongly electron-withdrawing groups

in a substantially anhydrous organic solvent.

In a further embodiment of the process the electric current is applied in a continuous way of a direct current as a DC-Process or in varying strengths as pulses as a pulse-plating.

In another embodiment of the process the anode is a soluble aluminium anode.

In another embodiment of the process no physical barrier or membrane is blocking the flow of the organic solvent between the cathode and anode.

This embodiment is specifically drawn to an undivided arrangement of the cell/bath in the process according to the invention.

In another embodiment of the process oxygen or humidity or both are excluded from the surface of the bath; preferably by using a sealing, or lid covering the surface of the bath or of the solution comprised within the bath or a means for introducing a protective gas to the surface of the bath or of the solution comprised within the bath; or combinations thereof.

In another embodiment of the process the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

In another embodiment of the process the alcoholate anion of the aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

In another embodiment of the process in the compound according to general formula (Ia) to (Ig) more than half of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

In another embodiment of the process in the compound according to general formula (Ia) to (Ig)

R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl;

or

R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

In another embodiment of the process the alcoholate anion of the halogenated aluminium alcoholate is a compound according to general formula Ib.

In another embodiment of the process in the compound according to general formula (Ib)

R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl;

or

R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen, preferably R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen, more preferably R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

In another embodiment of the process the anion with strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5COO−, or C6Cl5COO−;

substituted sulfonate anions, preferably from sulfonate anions of any of general structure II

wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or

halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId

wherein R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, or preferably at least half of R31, R32, R33, R34R35, R36, and R37 being halogen.

In another embodiment of the process in the compound according to general formula (II) or general formula (IIIa) to (IIId)

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or

R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32, R33, R34, R35, R36 and R37 being F or Cl.

In another embodiment of the process the organic solvent is selected from aprotic organic solvents or from organic solvents not forming a complex with Cr (II) or Cr (III) or its respective salts or from organic solvents having a donator power of between 30 and 10, preferably of between 25 and 12, or from solvents in which the aluminium salts may be dissolved.

In another embodiment of the process the organic solvent is selected from aprotic organic solvents, or from solvents in which the aluminium salts may be dissolved, preferably from aprotic organic solvents in which the aluminium salts may be dissolved.

In another embodiment of the process the substantially anhydrous organic solvent is provided in form of a mixture of different substantially anhydrous organic solvents. This is a mixed-solvents-approach.

In another embodiment of the process the organic solvent has a water content of less than 1%, preferably of equal to or less than 0.5%, more preferably of equal to or less than 0.25%, most preferably of equal to or less than 0.15%.

In another embodiment of the process the organic solvent is selected from

Acetonitril, Tetrahydrofuran (THF), tert.butyl-methyl ether;

or carbonates, preferably selected from dimethyl carbonate, or propylene glycol carbonate (4-Methyl-1,3-dioxolan-2-on);

or carboxylic acid esters; preferably selected from ethyl acetate.

In another embodiment of the process the bath is additionally having at least one further electrolyte, preferably a nonaqueous electrolyte, more preferable a phosphate, alkyl-sulfonate, borate, antimonite or arsenate; most preferably is selected from hexafluorophosphates, tris(pentafluoroethyl)trifluorphosphate, methanesulfonates, trifluoromethanesulfonates, tetrafluoroborates, bis[oxalato(2-)]borate, bis[silicylato(2-)]borate, bis[1,2-benzenediolato(2-)-0,0′ ]borate, hexafluoroanitmonate, or hexafluoroarsenate; or is selected from hexafluorophosphates, or tetrafluoroborates.

One or more embodiments may be used for various uses of high practical value. These include making an integrated circuit, a semiconductor device and electrodepositing of aluminium on a wafer. A wafer is a thin slice of a preferably semiconductive material, such as e.g., a silicon crystal, used in microelectronics, upon which e.g., microcircuits may be constructed by various means.

The use of aluminium can be a full alternative to the use of copper. It is likely that the electrodepositing of aluminium may be more cost-effective than sputtering. Electrodepositing aluminium according to one embodiment might leads to thicker layers of aluminium. Currently these thicker layers are achieved by a substitution process in which first Cu ECD is produced. The invention—especially its cheaper aluminium layer—might be a more cost effective alternative here.

Aluminium alloys might be produced through targeted layering e.g., Cu, Ge. Even sandwich structures with different layers could be producible (e.g., Cu 100 nm/Al 5 μm/Cu 100 nm/Al 10 μm). Alloys of aluminium would show improved conductivity or electron migration. Even pattern plating could be possible and thus a structuring of thick aluminium layers.

As comparison using sputtering the economical and technical limit for the layers of aluminium is 5 μm.

In general aluminium shows the following advantages over copper:

Less stress leading to lower wafer-bow

Aluminium is bondcompatible with Alu w/b, Au w(b, and Cu w/b according to the state of the art,

Aluminium is self-passivating and does not tend to the problematic oxidation.

In addition the electrodeposited aluminium achieved through the embodiments of this invention may also be used in the production of new packaging material, in which packaging is done using metal bands instead of wire. Here the use of thicker aluminium may be advantageous. It would be

easy to structure,

would show thick and cost-effective layers,

and would be self-passivating.

In addition the electrodeposited aluminium resulting from one or more embodiments may also be used for refining by plating or as a corrosion protective. The conductive surfaces or preferred metals have already been described above.

EXPERIMENTAL PART

1st experiment: A bath with a solution of 0.3 mol/kg Al(OCH2CF3)3 in substantially anhydrous acetonitrile was prepared and subjected to an electronic current with a current densityj of −0.2 to −0.8 mA/cm2 by using an anode and a cathode at 50° C. The aluminium was electrodeposited on brass. The results can be seen in FIGS. 1 to 4.

2nd experiment: A bath with a solution of 0.3 mol/kg Al(OCH2CF3)3 in substantially anhydrous acetonitrile was prepared and subjected to an electronic current with a current density j of −0.2 to −0.5 mA/cm2 by using an anode and a cathode at 50° C. The aluminium was electrodeposited on platinum. The result can be seen in FIG. 5.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.

Claims

1. A composition of matter for electrodepositing of aluminium comprising a bath comprising a solution of an aluminium salt selected from

halogenated aluminium alcoholate; or
aluminium salts with an anion with strongly electron-withdrawing groups; in a substantially anhydrous organic solvent.

2. The composition of claim 1, wherein the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

3. The composition of claim 1, wherein the alcoholate anion of the halogenated aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

4. The composition of claim 3, wherein more than half of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

5. The composition of claim 3, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

6. The composition of claim 3, wherein the alcoholate anion of the halogenated aluminium alcoholate is a compound according to general formula Ib.

7. The composition of claim 6, wherein R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen, preferably wherein R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen, more preferably wherein R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

8. The composition of claim 1, wherein the anion with the strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5 COO—, or C6C15 COO—;
substituted sulfonate anions, preferably from sulfonate anions of any of general structure II
wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or
halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId
wherein R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, preferably at least half of R31, R32, R33, R34, R35, R36, and R37 being halogen.

9. The composition of claim 8, wherein

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or
R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32, R33, R34, R35, R36, and R37 being F or Cl.

10. The composition of claim 1, wherein the organic solvent is selected from aprotic organic solvents or from organic solvents not forming a complex with the aluminum salts of claims 1 to 9 or from organic solvents having a donator power of between 30 and 10, preferably of between 25 and 12, or from solvents in which the aluminium salts of claim 1 to 9 may be dissolved.

11. The composition of claim 1, wherein the organic solvent has a water content of less than 1%, preferably of equal to or less than 0.5%, more preferably of equal to or less than 0.25%, most preferably of equal to or less than 0.15%.

12. The composition of claim 1, wherein the organic solvent is selected from

Acetonitril, Tetrahydrofuran (THF), tert.butyl-methyl ether;
or carbonates, preferably selected from dimethyl carbonate, or propylene glycol carbonate (4-Methyl-1,3-dioxolan-2-on);
or carboxylic acid esters; preferably selected from ethyl acetate.

13. The composition of claim 1, wherein the aluminium salt is present in the bath in an amount greater than or equal to 0.1 mol/kg of solvent or in a concentration of between 0.05 and 5 mol/kg of solvent.

14. The composition of claim 1, wherein the bath is additionally comprising at least one further electrolyte, preferably a nonaqueous electrolyte, more preferable a phosphate, alkyl-sulfonate, borate, antimonite or arsenate; most preferably is selected from hexafluorophosphates, tris(pentafluoroethyl)trifluorphosphate, methanesulfonates, trifluoromethanesulfonates, tetrafluoroborates, bis[oxalato(2-)]borate, bis[silicylato(2-)]borate, bis[1,2-benzenediolato(2-)-0,0′]borate, hexafluoroanitmonate, or hexafluoroarsenate; or is selected from hexafluorophosphates, or tetrafluoroborates.

15. The composition of claim 1, additionally comprising an anode and cathode; preferably a soluble aluminium anode.

16. The composition of claim 1, wherein the composition does also comprise a means for excluding oxygen or humidity or both from the bath, preferably from the surface of the bath or of the solution comprised within the bath; preferably in the form of a sealing, or lid covering the surface of the bath or of the solution comprised within the bath or a means for introducing a protective gas to the surface of the bath or of the solution comprised within the bath; or combinations thereof.

17. Use of an aluminium salt selected from

halogenated aluminium alcoholate; or
aluminium salts with an anion with strongly electron-withdrawing groups; for electrodepositing aluminium.

18. Use of claim 17, wherein the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

19. Use of claim 17, wherein the alcoholate anion of the halogenated aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

20. Use of claim 19, wherein more than half of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

21. Use of claim 19, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

22. Use of claim 19, wherein the alcoholate anion of the aluminium alcoholate is a compound according to general formula Ib.

23. Use of claim 22, wherein R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen, preferably wherein R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen, more preferably wherein R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

24. Use of claim 17, wherein the anion with strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5 COO—, or C6Cl5 COO—;
substituted sulfonate anions, preferably from sulfonate anions of any of general structure II
wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or
halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId
wherein R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, preferably at least half of R31, R32, R33, R34, R35, R36, and R37 being halogen.

25. Use of claim 24, wherein

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or
R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32, R33, R34, R35, R36, and R37 being F or Cl.

26. Use according to claim 17, characterized in that the aluminium is electrodeposited on a conductive surface, preferably a conductive surface selected from metals, alloys of metals and conductive polymers more preferably on a metal surface of a conductive metal, preferably a metal being selected from more preferably from

Ag, Au, Cr, Cu, Fe, Ge, Ir, Mn, Mo, Nb, Ni, Pd, Pt, Si, Ta, Ti, V, W, Zn or In, Pb, Sb and Sn;
Ag, Au, Cr, Cu, Fe, Ge, Ir, Mn, Mo, Nb, Ni, Pd, Pt, Si, Ta, Ti, V, W, or Zn; or from alloys of these metals.

27. Use according to claim 17, characterized in that the aluminium is electrodeposited for the purpose of creating a new package material, for pattern plating or for replacing sputtering on or creating of a conductive surface, or for anticorrosive protection or for layering—optionally with other metals.

28. A process for electrodepositing of aluminium from a bath, wherein by using an electrode and an anode being arranged at least partly inside the bath an electric current is applied to the bath comprising a solution of an aluminium salt with an anion selected from

halogenated aluminium alcoholate; or
aluminium salts with an anion with strongly electron-withdrawing groups in a substantially anhydrous organic solvent.

29. The process of claim 28, wherein the anode is a soluble aluminium anode.

30. The process of claim 28, wherein no physical barrier or membrane is blocking the flow of the organic solvent between the cathode and anode.

31. The process of claim 28, wherein oxygen or humidity or both are excluded from the surface of the bath; preferably by using a sealing, or lid covering the surface of the bath or of the solution comprised within the bath or a means for introducing a protective gas to the surface of the bath or of the solution comprised within the bath; or combinations thereof.

32. The process of claim 28, wherein the alcoholate anion of the aluminium alcoholate is selected from halogenated methanolate, halogenated ethanolate, halogenated isopropanolate, halogenated n-propanolate, halogenated iso-butanolate, halogentated n-butanolate; or halogenated tert. butanolate.

33. The process of claim 28, wherein the alcoholate anion of the aluminium alcoholate is a compound according to any of general formulas Ia, Ib, Ic, Id, Ie, If or Ig

wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, or halogen, with at last one of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 being halogen.

34. The process of claim 33, wherein more than half of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 in any given anion are halogen.

35. The process of claim 33, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from hydrogen, F or Cl, while R10, R11, and R12 are hydrogen, preferably wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently from one another selected from F or Cl, while R10, R11, and R12 are hydrogen, more preferably
wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 are either all F or all Cl, while R10, R11, and R12 are hydrogen.

36. The process of claim 33, wherein the alcoholate anion of the halogenated aluminium alcoholate is a compound according to general formula Ib.

37. The process of claim 36, wherein R1, R2, R3, R11 and R12 are independently from one another selected from hydrogen, F or Cl, preferably are F or Cl, more preferably are either all F or all Cl; or

wherein R1, R2, and R3 are independently from one another selected from hydrogen, F or Cl, while R11, and R12 are hydrogen, preferably wherein R1, R2, and R3 are independently from one another selected from F or Cl, while R11, and R12 are hydrogen, more preferably wherein R1, R2, and R3 are either all F or all Cl, while R11, and R12 are hydrogen.

38. The process of claim 28, wherein the anion with strongly electron withdrawing groups is selected from

penta-halogenated benzoate, preferably from C6F5 COO—, or C6C15 COO—;
substituted sulfonate anions, preferably from sulfonate anions of any of general structure II
wherein R21 is selected from optionally at least mono substituted C1-4Alkyl, or toluoyl (p-toluene); or
halogenated carboxylic acid anions, preferably of general structures IIIa, IIIb, IIIc, or IIId
wherein R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, or halogen, with at last one, or preferably at least half of R31, R32, R33, R34, R35, R36, and R37 being halogen.

39. The process of claim 38, wherein

R21 is selected from optionally at least mono substituted CH3, CF3, CCl3, or toluoyl (p-toluene); or
R31, R32, R33, R34, R35, R36, and R37 are independently from one another selected from hydrogen, F or Cl, with at last half of R31, R32, R33, R34, R35, R36, and R37 being F or Cl.

40. The process of claim 28, wherein the organic solvent is selected from aprotic organic solvents or from organic solvents not forming a complex with Cr (II) or Cr (III) or its respective salts or from organic solvents having a donator power of between 30 and 10, preferably of between 25 and 12, or from solvents in which the aluminium salts may be dissolved.

41. The process of claim 28, wherein the organic solvent has a water content of less than 1%, preferably of equal to or less than 0.5%, more preferably of equal to or less than 0.25%, most preferably of equal to or less than 0.15%.

42. The process of claim 28, wherein the organic solvent is selected from

Acetonitril, Tetrahydrofuran (THF), tert.butyl-methyl ether;
or carbonates, preferably selected from dimethyl carbonate, or propylene glycol carbonate (4-Methyl-1,3-dioxolan-2-on);
or carboxylic acid esters; preferably selected from ethyl acetate.

43. The process of claim 28, wherein the bath is additionally comprising at least one further electrolyte, preferably a nonaqueous electrolyte, more preferable a phosphate, alkyl-sulfonate, borate, antimonite or arsenate; most preferably is selected from hexafluorophosphates, tris(pentafluoroethyl)trifluorphosphate, methanesulfonates, trifluoromethanesulfonates, tetrafluoroborates, bis[oxalato(2-)]borate, bis[silicylato(2-)]borate, bis[1,2-benzenediolato(2-)-0,0′ ]borate, hexafluoroanitmonate, or hexafluoroarsenate; or is selected from hexafluorophosphates, or tetrafluoroborates.

44. An integrated circuit comprising:

a composition of matter for electrodepositing of aluminium comprising a bath comprising a solution of an aluminium salt selected from
halogenated aluminium alcoholate; or
aluminium salts with an anion with strongly electron-withdrawing groups; in a substantially anhydrous organic solvent.

45. A process for making an integrated circuit comprising:

electrodepositing of aluminium from a bath, wherein by using an electrode and an anode being arranged at least partly inside the bath an electric current is applied to the bath comprising a solution of an aluminium salt with an anion selected from
halogenated aluminium alcoholate; or
aluminium salts with an anion with strongly electron-withdrawing groups in a substantially anhydrous organic solvent.
Patent History
Publication number: 20080257744
Type: Application
Filed: Apr 19, 2007
Publication Date: Oct 23, 2008
Applicant: INFINEON TECHNOLOGIES AG (Muenchen)
Inventors: Johannes Lodermeyer (Kinding), Edmund Riedl (Gebelkofen), Werner Robl (Regensburg)
Application Number: 11/737,530
Classifications
Current U.S. Class: Depositing Predominantly Alloy Coating (205/238)
International Classification: C25D 3/56 (20060101);