Tungsten-processing slurry with cationic surfactant
Described are chemical mechanical polishing compositions and methods of using the compositions for planarizing a surface of a substrate that contains tungsten, the compositions containing silica abrasive particles and cationic surfactant.
1. A chemical mechanical polishing composition useful for processing a tungsten-containing surface, the slurry comprising:
a liquid carrier,
silica abrasive particles dispersed in the liquid carrier, the particles having a permanent positive charge of at least 8 millivolts (mV) at a pH of from 1 to 6, and
cationic surfactant of Formula 1:
wherein
n is at least 1;
X is P + or N + ; and
each of R 1 , R 2 , R 3 , and R 4 can be independently selected from:
hydrogen,
a saturated or unsaturated cyclic group which may be substituted or unsubstituted and which may optionally include a charged group,
a linear or branched alkyl group which may be saturated or optionally include unsaturation, and which may include a saturated or unsaturated cyclic group, any of which may be substituted or include a charged group, and
a saturated or unsaturated ring structure formed from two or three of R 1 , R 2 , R 3 , and R 4 , the ring optionally being substituted, and
wherein the value of n and the Log P of the cationic surfactant meet the formula:
8( n− 1)+Log P≧ 1.
2. The composition of claim 1 wherein each of R 1 , R 2 , R 3 , and R 4 is independently a linear alkyl group having from 1 to 12 carbon atoms.
3. The composition of claim 2 wherein the cationic surfactant includes one or a combination of: tetrabutylammonium, tetrapentylammonium, tetrabutylphosphonium, tributylmethylphosphonium, tributyloctylphosphonium.
4. The composition of claim 1 wherein each of R 1 , R 2 , and R 3 is independently a linear alkyl group each having from 1 to 12 carbon atoms, and R 4 is a group that includes a cyclic alkyl or aromatic ring optionally substituted and optionally containing a heteroatom.
5. The composition of claim 4 wherein the cationic surfactant is benzyltributylammonium bromide.
6. The composition of claim 1 wherein R 1 is a straight or branched alkyl group optionally substituted or unsaturated and having from 1 to 12 carbon atoms, and wherein R 2 , R 3 , and R 4 form an aromatic ring structure that may optionally be substituted by a group that contains a saturated or aromatic ring structure.
7. The composition of claim 6 wherein the cationic surfactant includes one or a combination of: 1-dodecylpyridinium, 1-dodecylpyridinium, 1-heptyl-4(4-pyridyl)pyridinium, 1-(4-pyridyl)pyridinium, methyl viologen.
8. The composition of claim 1 wherein R 1 is hydrogen; R 2 and R 3 are each independently an alkyl group each having from 1 to 12 carbon atoms; and R 4 is a heteroatom-containing alkyl having from 4 to about 15 carbon atoms.
9. The composition of claim 8 wherein the cationic surfactant is a salt of 1,1,4,7,10,10-hexamethyltriethylenetetramine.
10. The composition of claim 1 further comprising a nitrogen-containing inhibitor compound that is not a cationic surfactant according to Formula 1.
11. The composition of claim 10 wherein the nitrogen-containing inhibitor compound includes at least one nitrogen group and at least one carboxylic acid group.
12. The composition of claim 10 wherein the nitrogen-containing inhibitor compound contains at least two nitrogen groups.
13. The composition of claim 1 further comprising a metal-containing catalyst.
14. The composition of claim 1 comprising from about 0.5 to about 4 weight percent of the silica abrasive particles.
15. The composition of claim 1 wherein 30 percent or more of the silica abrasive particles include from 3 to 10 aggregated primary particles.
16. The composition of claim 1 wherein the silica abrasive particles comprise a cationic compound incorporated into the particles, and wherein the cationic compound is a charged nitrogen-containing compound or a charged phosphorous-containing compound, in the slurry.
17. The composition of claim 1 comprising from about 0.1 to about 5,000 parts per million of the cationic surfactant.
18. A method of chemical mechanical polishing a substrate that includes a surface comprising tungsten, the method comprising:
(a) contacting the substrate with a polishing composition comprising:
a liquid carrier,
silica abrasive particles dispersed in the liquid carrier, the particles having a permanent positive charge of at least 8 millivolts (mV) at a pH of from 1 to 6, and
cationic surfactant of Formula 1:
wherein
n is at least 1;
X is P + or N + ; and
each of R 1 , R 2 , R 3 , and R 4 can be independently selected from:
hydrogen,
a saturated or unsaturated cyclic group which may be substituted or unsubstituted and which may optionally include a charged group,
a linear or branched alkyl group which may be saturated or optionally include unsaturation, and which may include a saturated or unsaturated cyclic group, any of which may be substituted or include a charged group, and
a saturated or unsaturated ring structure formed from two or three of R 1 , R 2 , R 3 , and R 4 , the ring optionally being substituted, and
wherein the value of n and the Log P of the cationic surfactant meet the formula:
8( n− 1)+Log P≧ 1;
(b) moving the polishing composition relative to the substrate; and
(c) abrading the substrate to remove a portion of the tungsten from the substrate.
19. The method of claim 18 wherein the cationic surfactant includes one or a combination of: tetrabutylammonium, tetrapentylammonium, tetrabutylphosphonium, tributylmethylphosphonium, tributyloctylphosphonium.
20. The method of claim 18 wherein each of R 1 , R 2 , and R 3 is independently a linear alkyl group each having from 1 to 12 carbon atoms, and R 4 is a group that includes a cyclic alkyl or aromatic ring optionally substituted and optionally containing a heteroatom.
21. The method of claim 20 wherein the cationic surfactant is benzyltributylammonium bromide.
22. The method of claim 18 wherein R 1 is a straight or branched alkyl group optionally substituted or unsaturated and having from 1 to 12 carbon atoms, and wherein R 2 , R 3 , and R 4 form an aromatic ring structure that may optionally be substituted by a group that contains a saturated or aromatic ring structure.
23. The method of claim 18 wherein R 1 is hydrogen; R 2 and R 3 are each independently an alkyl group each having from 1 to 12 carbon atoms; and R 4 is a heteroatom-containing alkyl having from 4 to about 15 carbon atoms.