Method and slurry for tuning low-k versus copper removal rates during chemical mechanical polishing
A composition and associated method for the chemical mechanical planarization (CMP) of metal substrates on semiconductor wafers are described. The composition contains a nonionic fluorocarbon surfactant and a per-type oxidizer (e.g., hydrogen peroxide). The composition and associated method are effective in controlling removal rates of low-k films during copper CMP and provide for tune-ability in removal rates of low-k films in relation to removal rates of copper, tantalum, and oxide films.
1 . A method of chemical mechanical planarization comprising: movably contacting a substrate having a surface which comprises copper, a low-k dielectric material, and a barrier material with a polishing pad and a polishing composition disposed between the polishing pad and the surface, said polishing composition comprising between 0.5% and 9% of a per-type oxidizer and between 10 ppm and 4000 ppm of a non-ionic fluorosurfactant, wherein the non-ionic fluorosurfactant reduces the removal rate of the low-k material compared to the removal rate of the low-k material during polishing with an otherwise identical slurry but not having a non-ionic fluorosurfactant.
2 . The method of claim 1 wherein the pH of the polishing composition is greater than about 8, and wherein the polishing composition further comprises 1% to 10% by weight of colloidal silica abrasive and between 50 and 400 ppm of a corrosion inhibitor.
3 . The method of claim 1 wherein the pH of the polishing composition is between about 9 and about 12, wherein the per-type oxidizer is a peroxide, and the low-k material is a carbon-doped oxide, the concentration of the non-ionic fluorosurfactant is greater than about 250 ppm, and the removal rate of the carbon-doped oxide is between 50 A/min and 350 A/min.
4 . The method of claim 3 wherein the polishing composition further comprises colloidal silica abrasive that is substantially free of soluble polymeric silicates.
5 . The method of claim 3 wherein the polishing composition further comprises an aromatic sulfonic acid oxidizer compound in an amount between about 0.2% to 3%.
6 . The method of claim 6 wherein the aromatic sulfonic acid oxidizer is benzesulfonic acid present in an amount between 0.5% and 1.5% by weight.
7 . The method of claim 1 wherein the polishing composition further comprises an anionic phosphate fluorosurfactant in an amount between 10 ppm and 3000 ppm, the per-type oxidizer is a peroxide, the low-k material is a carbon-doped oxide, the concentration of the non-ionic fluorosurfactant is greater than about 250 ppm, and the removal rate of the carbon-doped oxide is between 50 A/min and 450 A/min when measured at 2 psi polishing pressure.
8 . The method of claim 1 wherein the low-k material is a carbon-doped oxide having a dielectric constant below about 2.4, the per-type oxidizer is a peroxide, the concentration of the non-ionic fluorosurfactant is greater than about 250 ppm, and the non-ionic fluorosurfactant is a block copolymer comprising a block of polyoxypropylene and a block of polyoxyethylene.
9 . The method of claim 1 wherein the non-ionic fluorosurfactant is present in the polishing composition in an amount which does not significantly affect the removal rates of copper, silica, and the barrier layer material.
10 . The method of claim 1 wherein the non-ionic fluorosurfactant has the following structure:
(R f )(R 1 O) x R b
where: R f =X(CX 2 ) y , where X is F or any combination of H and F provided that at least a portion of the X atoms in the surfactant are F, and where y is between 1 to about 9; R 1 O is independently CH 2 CH 2 O—, CH 2 CH 2 CH 2 O—, or C a H 2a O—, where the number of carbon atoms “a” is between 3 and 8, or any combination of the above, and where x=1 to about 25; and R b is H or a straight, branched, or ringed alkane, alkene, alkyne, alcohol, or fatty acid having between 1 and about 18 carbon atoms.
11 . The method of claim 10 wherein at least three quarters of the X atoms in the R f segment are F; the average y in the R f segment is between 3 and 6; and (R 1 O) x comprises block of CH 2 CH 2 O— segments where x is at least 4.
12 . The method of claim 11 wherein the average x is between about 5 to 20.
13 . The method of claim 1 wherein the substrate surface comprises silica, and the polishing composition comprises colloidal silica, benzenesulfonic acid, between 250 ppm and 2000 ppm of the non-ionic fluorinated surfactant; hydrogen peroxide, wherein the removal rate of copper is between 50 and 150 A/min, the removal rate of silica is between 150 and 250 A/min, the removal rate of tantalum is 200 to 400 A/min, and the removal rate of carbon-doped low-k material is between about 200 and 400 A/min, where each removal rate is measured at 2 psi polishing pressure.
14 . A method of chemical mechanical planarization comprising: movably contacting a substrate having a surface which comprises copper, a low-k dielectric material, and a barrier material with a polishing pad and a polishing composition disposed between the polishing pad and the surface, said polishing composition comprising between 0.5% and 9% of a per-type oxidizer and between 10 ppm and 4000 ppm of an anionic phosphate fluorosurfactant and has a pH between 9 and 12, wherein the anionic phosphate fluorosurfactant tunes the removal rate of the low-k material.
15 . The method of claim 14 wherein the polishing composition further comprises colloidal silica abrasive and a corrosion inhibitor, wherein the per-type oxidizer is a peroxide, the low-k material is a carbon-doped oxide, the concentration of the anionic phosphate fluorosurfactant is greater than about 250 ppm, and the removal rate of the carbon-doped oxide is between 50 A/min and 450 A/min.
16 . The method of claim 15 where the polishing composition further comprises benzenesulfonic acid and a non-ionic fluorosurfactant.
17 . The method of claim 16 wherein the polishing composition further comprises colloidal silica abrasive that is substantially free of soluble polymeric silicates.
18 . A polishing slurry for chemical mechanical polishing of substrates comprising both copper and a low-k material, the polishing composition comprising water, between 0.5% and 9% by weight of a peroxide, and between 10 ppm and 4000 ppm of a non-ionic fluorosurfactant, between 1% to 10% by weight of colloidal silica abrasive, and has a pH greater than about 8.
19 . The polishing slurry of claim 18 further comprising a polyvinylpyridine-N-oxide polymer or between 0.2% and 3% by weight of an aromatic sulfonic acid compound, which increases the removal rate of Ta.
20 . The polishing slurry of claim 18 comprising between 0.2% and 3% by weight of benzenesulfonic acid, and further comprising between 50 and 400 ppm of a corrosion inhibitor.