ELECTROPLATING WITH A POLYCARBOXYLATE ETHER SUPRESSOR

Abstract

The present inventin relates to a process for depositing a metal layer on a substrate by contacting the substrate with a metal plating bath comprising a metal ion source and a suppressor, and applying a current density to the substrate, where the suppressor is a polycarboxylate ether as described below. The invention further relates to a metal plating bath comprising a metal ion source and the suppressor which is a polycarboxylate ether; and to a use of the polycarboxylate ether in a metal plating bath for depositing a metal layer on a substrate.

Claims

1. A process for depositing a metal layer on a substrate by a) contacting the substrate with a metal plating bath comprising a metal ion source and a suppressor, and b) applying a current density to the substrate, wherein the suppressor is a polycarboxylate ether obtainable by polymerizing a mixture of monomers comprising (i) at least one ethylenically unsaturated monomer (I) which comprises at least one radical from carboxylic acid, carboxylic salt, carboxylic ester, carboxylic amide, carboxylic anhydride, and/or carboxylic imide; and (ii) at least one ethylenically unsaturated monomer (II) having a polyalkylene oxide radical.

2. The process according to claim 1, wherein the ethylenically unsaturated monomer (I) comprises at least one radical from carboxylic acid, carboxylic salt, and/or carboxylic amide.

3. The process according to claim 1, wherein the ethylenically unsaturated monomer (I) is represented by at least one of the following general formulae from the group (Ia), (Ib), and (Ic) ##STR00010## where R.sup.1 and R.sup.2 independently of one another are hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms, Y is H, —COOM.sub.a, —CO—O(C.sub.qH.sub.2qO).sub.r—R.sup.3, or —CO—NH—(C.sub.qH.sub.2qO).sub.r—R.sup.3, M is hydrogen, a mono- or divalent metal cation, ammonium ion, or an organic amine radical, a is ½ or 1, R.sup.3 is hydrogen, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms, q independently at each occurrence for each (C.sub.qH.sub.2qO) unit is identical or different and is 2, 3, or 4, r is 0 to 200, and Z is O or NR.sup.3, ##STR00011## where R.sup.4 and R.sup.5 independently of one another are hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms, Q is identical or different and is represented by NH, NR.sup.3, or O, where R.sup.3 possesses the definition stated above, R.sup.6 is identical or different and is represented by (C.sub.nH.sub.2n)—SO.sub.3H with n=0, 1, 2, 3, or 4, (C.sub.nH.sub.2n)—OH with n=0, 1, 2, 3, or 4; (C.sub.nH.sub.2n)—PO.sub.3H.sub.2 with n=0, 1, 2, 3, or 4, (C.sub.nH.sub.2n)—OPO.sub.3H.sub.2 with n=0, 1, 2, 3, or 4, (C.sub.6H.sub.4)—SO.sub.3H, (C.sub.6H.sub.4)—PO.sub.3H.sub.2, (C.sub.6H.sub.4)—OPO.sub.3H.sub.2, and (C.sub.nH.sub.2n)—NR.sup.8.sub.b with n=0, 1, 2, 3, or 4 and b=2 or 3, R.sup.7 is H, —COOM.sub.a, —CO—O(C.sub.qH.sub.2qO).sub.r—R.sup.3, —CO—NH—(C.sub.qH.sub.2qO).sub.r—R.sup.3, where M.sub.a, R.sup.3, q, and r possess definitions stated above, R.sup.8 is hydrogen, an aliphatic hydrocarbon radical having 1 to 10 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, or an optionally substituted aryl radical having 6 to 14 C atoms.

4. The process according to claim 1, wherein the ethylenically unsaturated monomer (II) is represented by the following general formula ##STR00012## in which p is an integer between 0 and 6, y is 0 or 1, v is an integer between 3 and 500, w independently at each occurrence for each (C.sub.wH.sub.2wO) unit is identical or different and is an integer between 2 and 18, T is oxygen or a chemical bond, where R.sup.1, R.sup.2, and R.sup.3 possess the definition stated above.

5. The process according to claim 4, where in the ethylenically unsaturated monomer (II) p is an integer between 0 and 4, v is an integer between 5 and 250, and w independently at each occurrence for each (C.sub.wH.sub.2wO) unit is identical or different and is 2 or 3.

6. The process according to claim 4, where in the ethylenically unsaturated monomer (II) the R.sup.3 is an aliphatic hydrocarbon radical having 1 to 20 C atoms.

7. The process according to claim 1, wherein the ethylenically unsaturated monomer (II) has a molecular weight of 500 to 10 000 g/mol.

8. The process according to claim 1, wherein the polycarboxylate ether has a molecular weight of 1 000 to 100 000 g/mol.

9. The process according to claim 1, wherein the fraction of the monomer (I) in the copolymer is 5 to 95 mol %.

10. The process according to claim 1, wherein the monomer (I) is a carboxylic amide.

11. The process according to claim 1, wherein the fraction of the monomer (II) in the copolymer is 1 to 89 mol %.

12. The process according to claim 1, wherein the polycarboxylate ether is present in the range from 1 to 10 000 mg/l based on the weight of the bath.

13. The process according to claim 1, wherein the metal ion source comprises a copper salt.

14. The process according to claim 1, wherein the metal plating bath comprises an accelerator which is a compound comprising one or more sulphur atom and a sulfonic/phosphonic acid or their salts.

15. A metal plating bath comprising a metal ion source and a suppressor which is a polycarboxylate ether as defined in claim 1.

16. (canceled)

17. The process according to claim 1, wherein the monomer (I) is N,N-dimethylacrylamide, N,N-dimethylmetacrylamide, N,N-diethylacryl-amide, or N,N-diethylmethacrylamide.

Description

EXAMPLES

[0143] Supressors:

[0144] PCE-1: Polycarboxylate ether based on acrylic acid and 4-hydroxybutyl vinyl ether-polyethylene glycol HBVE-PEG (mol weight of polyethylene glycol side chain 3000 g/mol), ratio acrylic acid to HBVE-PEG is 1:2.7, total mol weight Mw=36200 g/mol, Mn 3350 g/mol.

[0145] PCE-2: Polycarboxylate ether based on acrylic acid and HBVE-PEG (mol weight of polyethylene glycol side chain 1100 g/mol), charge density 1.61, total mol weight Mw=19290 g/mol.

[0146] PCE-3: Polycarboxylate ether based on N,N-dimethylacrylamide and HBVE-PEG (mol weight of polyethylene glycol side chain 3000 g/mol), weight ratio N,N-dimethylacrylamid to HBVE-PEG is 5:1, charge density 1.4 mmol/g, total mol weight Mw=39000 g/mol.

[0147] The mol weight of the polycarboxylate ether was determined by GPC (against Na-PAA standard). The charge density was determined by conductometric titration.

Example 1—Deposition Quality of the Metal Layer

[0148] An acidic copper plating bath was prepared which contained

[0149] CuSO.sub.4*5 H.sub.2O 200 g/l

[0150] H.sub.2SO.sub.4 (95%) 70 g/l

[0151] NaCl 100 mg/l

[0152] Wetting agent 80 mg/l (Plurafac® LF 1430 from BASF, alkoxylated fatty alcohol)

[0153] Accelerator 8 mg/l (SPS bis-(3-sulfopropyl)-disulfide disodium salt)

[0154] Leveler 24 mg/l (Lugalvan® IZE, BASF, product from imidazole and epichlorhydrin)

[0155] The amount of polycarboxylate ether suppressor PCE-1, PCE-2 and PCE-3 was 40 mg/l.

[0156] The suppressor candidates were tested according to initial plating performance in the Hull cell (2 A, 10 min, 30° C. on polished brass panel). The panels were evaluated visually with the following rating 1 to 10 (deposition quality, gloss and leveling: 1=not sufficient; 10=perfect) and the results are summarized in Table 1.

[0157] The areas on the panel with different current density are termed:

[0158] HCD=High current density

[0159] MCD=middle current density

[0160] LCD=Low current density

[0161] The concentrations of each ingredient are 50% lower than in standard industrial application in order to see the effect of the suppressor more clearly. The results demonstrated that the polycarboxylate ethers result in a good deposition quality.

TABLE-US-00001 TABLE 1 Deposition Appearance from area Suppressor Quality of HCD to LCD PCE-1 5-6 HCD: gloss MCD: gloss LCD: semi-gloss PCE-2 5-6 HCD: gloss MCD: gloss LCD: semi-gloss PCE-3 5-6 HCD: gloss MCD: gloss LCD: semi-gloss

Example 2—Electrochemical Stability of the Plating Bath

[0162] The application parameters for electrochemical stability evaluation were as follows: 250 ml of the readily formulated electrolyte as in Example 1 were exposed to 2 A current for 2 hours at 30° C. This stimulates the electrochemical degradation of the organic ingredients in the plating bath.

[0163] Afterwards a normal plating in the same electrolyte is performed as in Example 1 (2 A, 10 min, 30° C.). These depositions are evaluated. Afterwards all ingredients a re-dosed to the desired starting level and again a 10 min deposition is carried out. This shows if the electrolyte is still working (or not) and so the intensity of the failure from the current exposition run is only derived by degradation.

[0164] The panels were evaluated visually with the following rating 1 to 10 (1=very bad; 1032 excellent) and the results are summarized in Table 2. For comparison a commercial suppressor Pluriol E9000 (polyethylene glycol, mol mass 9000 g/mol) was used instead of the polycarboxylate ethers.

[0165] The results demonstrated that the polycarboxylate ethers improve the electrochemical stability of the plating bath.

TABLE-US-00002 TABLE 2 Electrochemical Appearance from area of HCD to Suppressor Stability Rating LCD Pluriol E9000 2 HCD: Dendrites, dark amorpous (comparative) dull MCD: Dull amourphous LCD: Dull PCE-1 5 HCD: Dendrites, dull MCD: Dull LCD: Dull PCE-2 4 HCD: Dendrites, minimal amourepous, dull MCD: Dull LCD: Dull

Example 3—Polarisation

[0166] Laser drilling of micro vias and subsequent copper filling is a standard manufacturing technique for high density interconnects. Our process for depositing a metal layer can be used in copper electroplating of micro via, where high filling performance of the micro via (typically a cavity with roughly 20 μm diameter, also called a bottom up filling) and a minimal surface thickness are desired. This was evaluated as follows:

[0167] The galvanostatic measurement was made on a Gamry potentiostat with the following parameters:

[0168] Amount: 700 ml

[0169] CuSO.sub.4×5H.sub.2O: 200 g/l

[0170] NaCl: 0,1 g/l (corresponds to 60 mg/L chloride)

[0171] H.sub.2SO.sub.4: 70 g/l

[0172] Suppressor: 80 mg/l

[0173] Accelerator Bis-(3-sulfopropyl)-disulfide disodium salt SPS: 8 mg/l

[0174] Cathode area: 5,812 cm.sup.2

[0175] Cathode material: Cu-ETP (E-Cu; 2.0060)

[0176] Anode: Platinum

[0177] Reference elektrode: Calomel

[0178] Elektrolyte movement: Air agitation

[0179] The salts of the base electrolyte were added to graduated flask and the measurement startet at a given current as given in Table 3. The potential is measured for about 500 sec until constant. The supressor was added and the resulting potential recorded. After further 200 sec the SPS was added and for further 1000 sec the potential measured. The average values of these potentials are given in Table 3a and 3b.

TABLE-US-00003 TABLE 3a Polarisation at lower current simulating the desired bottom up filling Suppressor: Pluriol E9000 Suppressor: Current (comparative) PCE-2 2.5 mA −148 mV −123 mV

[0180] The results in Table 3a showed that for the bottom up filling the absolute value of the polarisation was reduced, that means there was less slowdown of the electrons. This was desirable to achieve a high filling performance of the micro via.

TABLE-US-00004 TABLE 3b Polarisation at higher current simulating the unwanted surface electroplating Suppressor: Pluriol E9000 Suppressor: Current (comparative) PCE-2 10 mA −102 mV −110 mV

[0181] The results in Table 3b showed that for the electroplating of the surface the absolute value of the polarisation was increased, that means there was higher slowdown of the electrons. This was desirable to achieve a minimal surface thickness outside the micro via.

[0182] The combination of both results, namely a high filling performance of the micro via and a minimal surface thickness, result in an improve leveling of the interconnects.