COMPOSITION AND PROCESS FOR SELECTIVELY ETCHING A LAYER COMPRISING AN ALUMINIUM COMPOUND IN THE PRESENCE OF LAYERS OF LOW-K MATERIALS, COPPER AND/OR COBALT

Abstract

A composition for selectively etching a layer including an aluminum compound in the presence of a layer of a low-k material and/or a layer including copper and/or cobalt, and a corresponding process, are described. Further described is a process for the manufacture of a semiconductor device, including the step of selectively etching at least one layer including an aluminum compound in the presence of a layer of a low-k material and/or a layer including copper and/or cobalt by contacting the at least one layer including an aluminum compound with the described composition.

Claims

1. A composition for selectively etching a layer comprising an aluminum compound in the presence of a layer of a low k material and/or a layer comprising copper and/or cobalt, the composition comprising: (A) at least one solubilizer, selected from the group consisting of a compound of formula I: ##STR00005## wherein R.sup.1 is at least one selected from the group consisting of hydrogen and C(O)R.sup.2 wherein R.sup.2 is selected from the group consisting of hydrogen and alkyl having 1, 2, 3 or 4 carbon atoms; a compound of formula II: ##STR00006## wherein R.sup.3 is alkyl having 1, 2, 3 or 4 carbon atoms; trimethylamine-N-oxide, triethylamine-N-oxide, triethanolamine-N-oxide, pyridine-N-oxide, N-ethylpyrrolidine-N-oxide, and mixtures thereof; (B) an etchant comprising fluoride anions; (C) at least one corrosion inhibitor, selected from the group consisting of benzotriazole which is unsubstituted or substituted once or twice independently by C.sub.1-4-alkyl, amino-C.sub.1-4-alkyl, phenyl, thiophenyl, halogen, hydroxy, nitro and/or thiol; ethylene urea, ethylene thiourea, 1,2,4-triazole, 5-aminotetrazole, 5-amino-1,3,4-thiadiazol-2-thiol, 3-amino-1H-1,2,4 triazole, 3,5-diamino-1,2,4-triazole, tolyltriazole, 3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole, 1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole, 3-mercapto-1,2,4-triazole, 3-isopropyl-1,2,4-triazole, naphthotriazole, 1H-tetrazole-5-acetic acid, 1-phenyl-2-tetrazoline-5-thione, 4-methyl-2-phenylimidazole, 2-mercaptothiazoline, 2,4-diamino-6-methyl-1,3,5-triazine, thiazole, imidazole, benzimidazole, triazine, methyltetrazole, 1,3-dimethyl-2-imidaz-olidinone, 1,5-pentamethylenetetrazole, 1-phenyl-5-mercaptotetrazole, 2H-imidaz-ole-2-thione, 4-methyl-4H-1,2,4-triazole-3-thiol, 5-amino-1,3,4-thiadiazole-2-thiol, benzothiazole, tritolyl phosphate, indazole, adenine, cytosine, guanine, thymine, 2,2-azanediyldiacetic acid, propanethiol, citric acid, ascorbic acid, thiourea, 1,1,3,3-tetramethylurea, urea, uric acid, glycine, dodecylphosphonic acid, oxalic acid, malonic acid, succinic acid, nitrilotriacetic acid, and mixtures thereof; (D) at least one chelating agent selected from the group consisting of histidine, 1,2-cyclohexylenedinitrilotetraacetic acid, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, acetylacetonate, 2,2-azanediyldiacetic acid, ethylenediaminetetraacetic acid, etidronic acid, methanesulfonic acid, acetylacetone, 1,1,1-trifluoro-2,4-pentanedione, 1,4-benzoquinone, 8-hydroxyquinoline, salicylidene aniline; tetrachloro-1,4-benzo-quinone, 2-(2-hydroxyphenyl)-benzoxazol, 2-(2-hydroxyphenyl)-benzothiazole, hydroxyquinoline sulfonic acid, sulfosalicylic acid, salicylic acid, pyridine, 2-ethylpyridine, 2-methoxypyridine, 3-methoxypyridine, 2-picoline, dimethylpyridine, piperidine, piperazine, triethylamine, triethanolamine, ethylamine, methylamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diglycol amine, monoethanolamine, methyldiethanolamine, pyrrole, isoxazole, bipyridine, pyrimidine, pyrazine, pyridazine, quinoline, isoquinoline, indole, 1-methylimidazole, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidinedithiocarbamate, dimethyl malonate, methyl acetoacetate, N-methyl acetoacetamide, tetramethylammonium thiobenzoate, 2,2,6,6-tetramethyl-3,5-heptanedione, tetramethylthiuram disulfide, lactic acid, ammonium lactate, formic acid, propionic acid, gamma-butyrolactone, and mixtures thereof; and (G) water.

2. The composition according to claim 1, wherein the at least one solubilizer (A) is selected from the group consisting of a compound of formula I; and a compound of formula II; the etchant (B) is at least one selected from the group consisting of ammonium fluoride, ammonium bifluoride, triethanolammonium fluoride, diglycolammonium fluoride, methyldiethanolammonium fluoride, tetramethylammonium fluoride, triethylamine trihydrofluoride, hydrogen fluoride, fluoroboric acid, tetrafluoroboric acid, ammonium tetrafluoroborate, fluoroacetic acid, ammonium fluoroacetate, trifluoroacetic acid, fluorosilicic acid, ammonium fluorosilicate, tetrabutylammonium tetrafluoroborate, and mixtures thereof, and/or the at least one corrosion inhibitor (C) is selected from the group consisting of benzotriazole which is unsubstituted or substituted once or twice independently by C.sub.1-4-alkyl, amino-C.sub.1-4-alkyl, phenyl, thiophenyl, halogen, hydroxy, nitro and/or thiol; succinic acid; and mixtures thereof.

3. The composition according to claim 1, wherein the at least one chelating agent (D) is selected from the group consisting of histidine, 1,2-cyclohexylenedinitrilotetraacetic acid, and mixtures thereof, and/or the composition comprises as further component: (E) a surfactant.

4. The composition according to claim 1, wherein a pH of the composition is in the range of from 3.5 to 8, and/or the composition comprises as further component: (F) a buffering system which is suitable to buffer a pH of the composition in the range of from 3.5 to 8.

5. The composition according to claim 1, comprising (A) at least one solubilizer selected from the group consisting of a compound of formula I, and a compound of formula II; (B) at least one etchant, selected from the group consisting of ammonium fluoride, ammonium bifluoride, triethanolammonium fluoride, diglycolammonium fluoride, methyldiethanolammonium fluoride, tetramethylammonium fluoride, triethylamine trihydrofluoride, hydrogen fluoride, fluoroboric acid, tetrafluoroboric acid, ammonium tetrafluoroborate, fluoroacetic acid, ammonium fluoroacetate, trifluoroacetic acid, fluorosilicic acid, ammonium fluorosilicate, tetrabutylammonium tetrafluoroborate, and mixtures thereof; (C) at least one corrosion inhibitor, selected from the group consisting of benzotriazole which is unsubstituted or substituted once or twice independently by C.sub.1-4-alkyl, amino-C.sub.1-4-alkyl, phenyl, thiophenyl, halogen, hydroxy, nitro and/or thiol, succinic acid, and mixtures thereof, (D) at least one chelating agent selected from the group consisting of histidine, 1,2-cyclohexylenedinitrilotetraacetic acid, and mixtures thereof, and (G) water, wherein a pH of the composition is in the range of from 3.5 to 8.

6. The composition according to claim 1, the composition comprising: (A) at least one solubilizer, selected from the group consisting of 4-methylmorpholine-4-oxide, trimethylamine-N-oxide, triethylamine-N-oxide, triethanolamine-N-oxide, pyridine-N-oxide, N-ethylmorpholine-N-oxide, N-ethylpyrrolidine-N-oxide, and mixtures thereof; (B) an etchant comprising fluoride anions; (C) at least one corrosion inhibitor, selected from the group consisting of benzotriazole, 6-methyl-benzotriazole, 5-methyl-benzotriazole, ethylene urea, ethylene thiourea, 1,2,4-triazole, 5-aminotetrazole, 1-hydroxybenzotriazole, 5-amino-1,3,4-thiadiazol-2-thiol, 3-amino-1H-1,2,4 triazole, 3,5-diamino-1,2,4-triazole, tolyltriazole, 5-phenyl-benzotriazole, 5-nitro-benzotriazole, 3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole, 2-(5-amino-pentyl)-benzotriazole, 1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole, 3-mercapto-1,2,4-triazole, 3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole, halobenzotriazoles, naphthotriazole, 1H-tetrazole-5-acetic acid, 2-mercaptobenzothiazole, 1-phenyl-2-tetrazoline-5-thione, 2-mercaptobenzimidazole, 4-methyl-2-phenylimidazole, 2-mercaptothiazoline, 2,4-diamino-6-methyl-1,3,5-triazine, thiazole, imidazole, benzimidazole, triazine, methyltetrazole, 1,3-dimethyl-2-imidazolidinone, 1,5-pentamethylenetetrazole, 1-phenyl-5-mercaptotetrazole, 2H-imidazole-2-thione, 4-methyl-4H-1,2,4-triazole-3-thiol, 5-amino-1,3,4-thiadiazole-2-thiol, benzo-thiazole, tritolyl phosphate, indazole, adenine, cytosine, guanine, thymine, 2,2-azanediyldiacetic acid, propanethiol, citric acid, ascorbic acid, thiourea, 1,1,3,3-tetramethylurea, urea, uric acid, glycine, dodecylphosphonic acid, oxalic acid, malonic acid, succinic acid, nitrilotriacetic acid, and mixtures thereof; (D) at least one chelating agent selected from the group consisting of 1,2-cyclohexylenedinitrilotetraacetic acid, 1,1,1,5,5,5-hexafluoro-2,4-pentane-dione, acetylacetonate, 2,2-azanediyldiacetic acid, ethylenediaminetetraacetic acid, etidronic acid, methanesulfonic acid, acetylacetone, 1,1,1-trifluoro-2,4-pentanedione, 1,4-benzoquinone, 8-hydroxyquinoline, salicylidene aniline; tetrachloro-1,4-benzoquinone, 2-(2-hydroxyphenyl)-benzoxazol, 2-(2-hydroxyphenyl)-benzothiazole, hydroxyquinoline sulfonic acid, sulfosalicylic acid, salicylic acid, pyridine, 2-ethylpyridine, 2-methoxypyridine, 3-methoxypyridine, 2-picoline, dimethylpyridine, piperidine, piperazine, triethylamine, triethanolamine, ethylamine, methylamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diglycol amine, monoethanolamine, methyldiethanolamine, pyrrole, isoxazole, bipyridine, pyrimidine, pyrazine, pyridazine, quinoline, isoquinoline, indole, 1-methylimidazole, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidinedithiocarbamate, dimethyl malonate, methyl acetoacetate, N-methyl acetoacetamide, tetramethylammonium thiobenzoate, 2,2,6,6-tetramethyl-3,5-heptanedione, tetramethylthiuram disulfide, lactic acid, ammonium lactate, formic acid, propionic acid, gamma-butyrolactone, and mixtures thereof; (E) at least one surfactant; (F) a buffering system which is suitable to buffer a pH of the composition in the range of from 6 to 8, and (G) water, wherein the pH of the composition is in the range of from 6 to 8.

7. The composition according to claim 3, wherein the total amount of the at least one solubilizer (A) present is in the range of from 0.01 to 20 wt. % based on the total weight of the composition.

8. The composition according to claim 5, wherein the total amount of the at least one etchant (B) present is in the range of from 0.001 to 1 wt. % based on the total weight of the composition.

9. The composition according to claim 1, wherein the total amount of the at least one corrosion inhibitor (C) present is in the range of from 0.01 to 4 wt.-% based on the total weight of the composition.

10. A method comprising: contacting the composition according to claim 1 with a substrate, wherein the method is suitable for selectively etching a layer comprising an aluminum compound in the presence of a layer of a low-k material and/or a layer comprising copper and/or cobalt; for selectively removing from a substrate a layer comprising an aluminum compound in the presence of a layer of a low-k material and/or a layer comprising copper and/or cobalt, and/or for selectively removing from the surface of a semiconductor substrate a layer comprising an aluminum compound in the presence of a layer of a low-k material and/or a layer comprising copper and/or cobalt.

11. The method according to claim 10, wherein the method comprises a two-step-process of removing (i) a metal hard mask, and (ii) an etch-stop layer of an aluminum compound deposited on a layer comprising copper and/or a layer comprising cobalt.

12. A process for manufacturing a semiconductor device, the process comprising: selectively etching at least one layer comprising or consisting of an aluminum compound in the presence of a layer of a low-k material and/or a layer comprising copper and/or cobalt, by contacting the at least one layer of an aluminum compound at least once with the composition according to claim 1.

13. The process according to claim 12, wherein the at least one layer comprising or consisting of an aluminum compound is a top layer and the layer comprising copper and/or cobalt is a lower layer covered by the top layer, with or without at least one further layer being present in between the top layer and the lower layer.

14. The process according to claim 12, the process comprising a two-step cleaning process, the process comprising removing in a first step a metal hard mask, before selectively etching in a separate second step the at least one layer comprising or consisting of an aluminum compound.

15. The process according to claim 12, wherein the at least one layer comprising or consisting of an aluminum compound before etching has a maximum thickness of 30 nm or below.

16. The process according to claim 12, wherein the etching is conducted in the presence of a layer of a low k material and a layer comprising copper and/or cobalt.

17. The composition according to claim 1, wherein the component (B) is ammonium fluoride.

18. The composition according to claim 1, wherein the chelating agent (D) is L-histidine.

19. The composition according to claim 1, wherein the at least one corrosion inhibitor (C) is benzotriazole which is unsubstituted or substituted once or twice independently by C.sub.1-4 alkyl and/or halogen.

20. The composition according to claim 1, wherein the total amount of the at least one solubilizer (A) present is in the range of from 2 to 15 wt. %, based on the total weight of the composition.

Description

EXAMPLES

[0308] The following examples are meant to further explain the invention without limiting its scope.

Example 1: Preparation of Compositions According to the Invention (First Preferred Variant) and of Comparative Compositions (not According to the Invention)

[0309] The following preferred compositions according to the first preferred variant of the invention (marked as I, i.e. compositions I1 to I8) were prepared by mixing the components (A) to (G) or (A) to (H), as applicable. Details are given below in table 1a. Further compositions according to the invention (marked as I, i.e. compositions I9 to I13) were prepared by mixing the components (A) to (G) or (A) to (H), as applicable. Details are given below in table 1b. In addition, comparative compositions (not according to the invention, marked as C, i.e. compositions C1 to C2) were also prepared in a similar manner, as shown in more detail in table 1c below. For adjusting the pH of the different compositions, a total amount of an acidic buffer component (acetic acid as a 96% w/w solution in water where an acetate buffer was used) was added to the composition, followed by a suitable amount of the corresponding basic (alkaline) buffer component (ammonia as a 29 wt.-% solution in water where an acetate buffer was used) until the desired pH of the composition was reached.

TABLE-US-00001 TABLE 1a Preferred test compositions according to the invention (first preferred variant) Composition [wt. %] Component Constituent I1 I2 I3 I4 I5 I6 I7 I8 (A) 4-MM-4-O 5.0 5.0 2.5 5.0 5.0 5.0 5.0 5.0 (B) NH.sub.4F 0.06 0.03 0.06 0.06 0.06 0.06 0.06 0.06 (C) 6-Me-BTA 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.25 (C) BTA 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.25 (D) CDTA 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 (E) PNAAS 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.004 (F) Acetic acid 0.5 0.5 0.3 0.3 0.7 0.6 0.6 0.6 (F) Ammonia 0.2 0.2 0.2 0.2 0.3 0.2 0.2 0.2 (G) Water 93.12 93.15 90.92 88.32 87.82 88.02 93.02 93.536 (H) Sulfolane 0 0 5.0 5.0 5.0 5.0 0 0 pH: 7.4 7.4 7.3 7.3 7.1 6.4 6.4 7.0

TABLE-US-00002 TABLE 1b Further test compositions according to the invention (first preferred variant) Com- Composition [wt. %] ponent Constituent I9 I10 I11 I12 I13 (A) 4-MM-4-O 5.0 5.0 7.5 7.5 7.5 (B) NH.sub.4F 0.06 0.06 0.06 0.06 0.06 (C) 6-Me-BTA 0.5 0.5 0.5 0.5 0.6 (C) BTA 0.5 0.5 0.5 0.5 0.6 (D) CDTA 0.1 0.1 0.1 0.1 0.1 (E) PNAAS 0.02 0.02 0.02 0 0 (F) Acetic acid 0.75 0.75 0.5 0.5 0.5 (F) Ammonia 0.3 0.3 0.2 0.2 0.22 (G) Water 87.77 92.77 83.12 83.14 82.92 (H) Sulfalane 5.0 0 0 0 0 BDG 0 0 7.5 7.5 7.5 pH: 6.3 6.3 7.4 7.4 7.4

TABLE-US-00003 TABLE 1c Comparative test compositions Com- Composition po- [wt.-%] nent Constituent C1 C2 (A) 4-MM-4-O 7.5 7.5 (B) NH.sub.4F 0.06 0.06 (C) 6-Me-BTA 0 0 (C) BTA 0 0 (D) CDTA 0.1 0.1 (E) PNAAS 0.02 0 (F) Acetic acid 0.5 0.5 (F) Ammonia* 0.2 0.22 (G) Water 84.1 84.12 (H) Sulfolane 0 0 BDG 7.5 7.5 pH: 8.2 8.2 BDG: butyl diglycol (diethyleneglycol butyl ether) All wt.-% of constituents in tables 1a, 1b and 1c are calculated as pure, undiluted compounds.

Example 2: Determination of Aluminum Oxide (AlOx) and Corner Etch Results of Test Compositions (First Preferred Variant)

[0310] Si wafers or wafer pieces (collectively referred to as test wafers in the following) with the appropriate types of outer layers were obtained from commercial sources. The test wafers were pre-treated as applicable: Cu was immersed into an oxalic acid solution for 20-30 s and then rinsed with water and dried. AlOx-coated surfaces were not pre-treated. The copper and AlO.sub.x-layers on the test wafers had a thickness of 100 ? in each case.

[0311] Aluminum oxide (AlO.sub.x)-coated surfaces were used as a representative model for layers of (comprising or consisting of) an aluminium compound (as defined above).

[0312] The test compositions (as defined in tables 1a, 1b and 1c) were prepared and the test wafers (see above) were contacted with the test compositions in a glass beaker, at a temperature of 60? C. and for a reaction time period of 1 min in the case of AlO.sub.x surfaces and for a reaction time period of from 5 min to 10 min in the case of Cu surfaces, and then withdrawn from the test compositions, rinsed with water or isopropanol and dried with nitrogen gas.

[0313] The thicknesses of the copper and aluminium oxide layers on the test wafers were determined before and after contact with the test compositions by X-ray fluorescence analysis. Experiments were repeated at least three times to ensure reproducibility.

[0314] The difference of the measured value of the thickness of a copper or an AlO.sub.x layer, respectively, before its contact with a test composition, minus the measured value of the thickness of the same copper or aluminium oxide layer, respectively, after its contact with the test composition was determined in each case as the total etch loss and the total etch loss so determined was divided by the process time to yield the etch rate. The results are shown in table 2 below as etch rate of a layer after contact with a test composition in ?/min (each given value in table 2 representing the average of at least three experiments).

TABLE-US-00004 TABLE 2 Aluminium oxide and copper etch results of the test compositions (first preferred variant) Etch rates per layer [?/min] Composition Cu AlO.sub.x I1 0.1 96 I2 0 50 I3 0.1 55 I4 0.1 53 I5 0.1 79.1 I6 0.1 88 I7 0.1 >100 I9 0.1 >100 I10 0.1 >100 I11 5 >100 I12 7.4 >100 I13 6 >100 C1 >50 25 C2 >50 22

[0315] Etch rate values of >100 in table 2 for AlO.sub.xlayers on a Si wafer have the meaning that the entire AlO.sub.x-layer was removed within the applicable reaction time period of one minute or before said applicable reaction time period of one minute had passed, with the effect that an exact etch rate could not be measured in these cases (such cases also being referred to as cases of over-etching hereinafter).

[0316] From the test results received, the following observations can be made:

[0317] The preferred test compositions according to the first preferred variant of the invention listed in table 1a (I1, I2, I3, I4, I5, I6 and I7) all show a high etch rate selectivity for etching of AlO.sub.x vs Cu layers (see results in table 2). Occurrence of over-etching (i.e. values of >100% etching) of the AlO.sub.x-layer first disappears (in the time period applied) in compositions with pH value of 6.4 (or higher; see compositions I6 and I7). Compositions which have a pH of 6.4 (or higher, up to a pH of 7.5) are therefore regarded as preferred test compositions according to the invention.

[0318] Over-etching results demonstrate that deviations from optimal pH or composition can lead to an unfavourable increase in etch rates and hence in a loss of etch rate selectivity. A mere reduction of etch times in order to optimize etch results is not preferred as this can lead to more inaccuracy in etch time due to practical limitations. For example, the etch time of 1 min as selected for etching the AlO.sub.x-layers in the present examples is an industrially relevant time period. For practical reasons, the etch rate achieved with a certain composition is relevant, not only the total etch loss.

[0319] In the pH range most preferred in practice (pH 6.8 to 7.5), compositions according to the first preferred variant of the invention which comprise an organic solvent have a stronger tendency to show incomplete etching results, with a sharp decline between pH values 7.1 and 7.3 (see compositions I4 and I5). In contrast, composition I1 which does not comprise organic solvents shows a high but controlled etch rate for the Cu layer (but no over-etching) in the preferred pH range, and a high etch rate selectivity. Compositions according to the first preferred variant of the invention which do not comprise organic solvents (see e.g. compositions I1 and I2) are therefore preferred.

[0320] Test compositions according to the first preferred variant of the invention listed in table 1b show a good (see compositions I19, I110 containing no organic solvent or a preferred organic solvent) or satisfactory (see compositions I11, I12 and I13, all containing butyl diglycol as a less preferred organic solvent) etch rate selectivity for etching of AlO.sub.x vs Cu layers. All test compositions listed in table 1b showed over-etching under the reaction conditions applied.

[0321] Comparative compositions listed in table 1c (C1, C2) did not show a satisfactory etch rate selectivity for etching of AlO.sub.x vs Cu layers, i.e. significant unfavourable etching of the Cu layer was observed in each case (see table 2 above).

Example 3: Preparation of Compositions According to the Invention (Second Preferred Variant) and of Comparative Compositions (not According to the Invention)

[0322] The following compositions according to the second preferred variant of the invention (compositions I20, I21 and I22) were prepared by mixing the components (A) to (D) and (G). Details are given below in table 3. In addition, comparative compositions (not according to the invention, compositions C20 and C21) were also prepared in a similar manner, as shown in more detail in table 4 below.

TABLE-US-00005 TABLE 3 Test compositions according to the invention (second preferred variant) Compo- Composition [wt.-%] nent Constituent I20 I21 I22 (A) NFM 10.0 5.0 5.0 (B) NH.sub.4F 0.03 0.03 0.03 (C) 5-Me-BTA 0.75 0.5 0.8 (C) 5-Cl-BTA 0.15 0 0 (C) BTA 0 0.5 0.8 (C) Succinic acid 0.12 0.1 0.1 (D) L-histidine 0.1 0.1 0.1 (G) Water 88.85 93.77 93.17 pH: 4.7 4.7 4.7

TABLE-US-00006 TABLE 4 Comparative test compositions Compo- Composition [wt.-%] nent Constituent C20 C21 (A) NFM 0 0 (B) NH.sub.4F 0.03 0.03 (C) 5-Me-BTA 0.5 0.5 (C) 5-Cl-BTA 0.1 0 (C) BTA 0 0.5 (C) Succinic acid 0.09 0.09 (D) L-histidine 0.1 0.1 (G) Water 99.28 98.88 (H) DMSO 5.0 5.0 pH: 4.7 4.7 DMSO: dimethyl sulfoxide All wt.-% of constituents in tables 3 and 4 are calculated as pure, undiluted compounds.

Example 4: Determination of Aluminium Oxide (AlOx) and Cobalt Etch Results of Test Compositions (Second Preferred Variant)

[0323] Si wafers or wafer pieces (collectively referred to as test wafers in the following) with the appropriate types of outer layers (Co; AlO.sub.x; plasma-deposited tetraethyl orthosilicate (TEOS)) were obtained from commercial sources. The test wafers were pre-treated as applicable: Co was immersed into an oxalic acid solution for 20-30 s and then rinsed with water and dried. AlO.sub.x-coated surfaces were not pre-treated.

[0324] Aluminium oxide (AlO.sub.x)-coated surfaces were used as a representative model for layers of (comprising or consisting of) an aluminium compound (as defined above).

[0325] The test compositions (as defined in tables 3 and 4) were prepared and the test wafers (see above) were contacted with the test compositions in a glass beaker, at a temperature of 40? C. and for a reaction time period of 1 min in the case of cobalt-coated surfaces, at a temperature of 35? C. and for a reaction time period of 15 s in the case of aluminium oxide-coated surfaces and at a temperature of 35? C. and for a reaction time period of 10 min in the case of TEOS surfaces. The test wafers were then withdrawn from the test compositions, rinsed with water or isopropanol and dried with nitrogen gas.

[0326] The thicknesses of the cobalt, TEOS and aluminium oxide layers on the test wafers were determined before and after contact with the test compositions by X-ray fluorescence analysis. Experiments were repeated at least three times to ensure reproducibility.

[0327] The difference of the measured value of the thickness of a cobalt, TEOS or AlOx layer, respectively, before its contact with a test composition, minus the measured value of the thickness of the same cobalt, TEOS or AlOx layer, respectively, after its contact with the test composition was determined in each case as the total etch loss and the total etch loss so determined was divided by the process time to yield the etch rate. The results are shown in table 5 below as etch rate of a layer after contact with a test composition in ?/min (each given value in table 5 representing the average of at least three experiments).

TABLE-US-00007 TABLE 5 Cobalt, TEOS and aluminium oxide etch results of the test compositions (second preferred variant) Etch rates per layer [?/min] Composition Co AlO.sub.x TEOS I20 2.6 6.0 <1 I21 6.1 no data no data I22 2.5 no data no data C20 2.0 6.0 <1 C21 5.4 no data no data

[0328] From the test results shown in table 5, the following observations can be made:

[0329] Composition I20 according to the invention shows a satisfactory etch rate selectivity for etching of AlO.sub.x vs Co and TEOS layers.

[0330] Compositions I22 according to the invention and C20 (comparative composition not according to the invention) show similar satisfactory results regarding etch rate selectivity for etching of AlO.sub.x vs Co layers (but see results of example 5, below).

Example 5: Stability of Test Compositions (Second Preferred Variant) Against Precipitation

[0331] The test composition I20 according to the invention and the comparative test composition C20 were cooled to 5? C. for 72 h. Immediately after the cooling period, both compositions were visually inspected for stability of the solution (i.e. precipitated material).

[0332] It was found that composition I20 according to the invention had remained clear after the cooling period, indicating stability of the solution even at lowered temperatures, while comparative composition C20 showed precipitation of materials, indicating insufficient stability of the solution at temperatures below room temperature.

[0333] From these observations it can be concluded that compositions comprising a solubilizer according to the present invention (in composition I20: N-formylmorpholine) show enhanced stability of solution against precipitation in comparison with compositions comprising no or other solubilizers than the ones according to the present invention (in comparative composition C20: DMSO).

[0334] As is known in the field, compositions for etching one or more materials for use in the manufacture of a semiconductor device must remain stable under the conditions of manufacture and not, e.g., form precipitates which can interfere with or corrupt said manufacture process or its products. Therefore, compositions for etching one or more materials for use in the manufacture of a semiconductor device which form precipitates under the conditions of such manufacture process are not acceptable for industrial use.