Polishing composition

Abstract

A polishing composition containing a silica, an acid, a surfactant, and water, wherein (a) the acid has solubility in water at 25° C. of 1 g or more per 100 g of an aqueous saturated solution; (b) the surfactant is a sulfonic acid represented by the formula (1) or (2), or a salt thereof; and (c) the polishing composition has a pH of a specified range; and a polishing process of a substrate using the polishing composition are provided. The polishing composition is suitably used, for example in polishing a substrate for disk recording media such as magnetic disks, optical disks and opto-magnetic disks.

1 . A polishing composition comprising a silica, an acid, a surfactant, and water, wherein: 
 (a) the acid has solubility in water at 25° C. of 1 g or more per 100 g of an aqueous saturated solution;    (b) the surfactant is a sulfonic acid represented by the following formula (1):      R—(O) n —X—SO 3 H  (1)    wherein R is a hydrocarbon group having 3 to 20 carbon atoms, wherein a part or all of the hydrogen atoms may be substituted with fluorine atoms; X is a residue resulting from removing two hydrogen atoms from an aromatic ring of an aromatic hydrocarbon; and n is 0 or 1;    or a salt thereof; and    (c) the polishing composition has a pH of from 0 to 4.    
   
   
       2 . A polishing composition comprising a silica, an acid, a surfactant, and water, wherein: 
 (a′) the acid has solubility in water at 25° C. of 1 g or more per 100 g of an aqueous saturated solution;    (b′) the surfactant is a sulfonic acid represented by the following formula (2):      R′—O—(AO) n —SO 3 H  (2)    wherein R′ is a hydrocarbon group having 3 to 20 carbon atoms; AO is an oxyalkylene group having 2 to 4 carbon atoms; and n, which is an average number of moles of alkylene oxide added, is from 1 to 6;    or a salt thereof; and    (c′) the polishing composition has a pH of from 0 to 3.    
   
   
       3 . The polishing composition according to  claim 1  wherein R in the formula (1) is an alkyl group having 6 to 20 carbon atoms or a perfluorinated hydrocarbon group having 6 to 20 carbon atoms.  
   
   
       4 . The polishing composition according to  claim 1 , wherein X in the formula (1) is a phenylene group.  
   
   
       5 . The polishing composition according to  claim 2 , wherein R′ in the formula (2) is an alkyl group having 6 to 20 carbon atoms.  
   
   
       6 . The polishing composition according to  claim 1 , wherein the surfactant is contained in an amount of from 0.005 to 2% by weight of the polishing composition.  
   
   
       7 . The polishing composition according to  claim 2 , wherein the surfactant is contained in an amount of from 0.005 to 2% by weight of the polishing composition.  
   
   
       8 . The polishing composition according to  claim 1 , further comprising an oxidizing agent.  
   
   
       9 . The polishing composition according to  claim 2 , further comprising an oxidizing agent.  
   
   
       10 . A polishing process of a substrate, comprising the steps of feeding the polishing composition as defined in any one of  claims 1  to  9  at a flow rate of 0.05 mL/minute or more per 1 cm 2  of a substrate to be polished, and polishing the substrate at a polishing pressure of from 5 to 50 kPa.  
   
   
       11 . A method for manufacturing a substrate, comprising the steps of feeding the polishing composition as defined in any one of  claims 1  to  9  at a flow rate of 0.05 mL/minute or more per 1 cm of a substrate to be polished, and polishing the substrate at a polishing pressure of from 5 to 50 kPa.  
   
   
       12 . The method according to  claim 11 , wherein the substrate is a hard disk substrate.  
   
   
       13 . A method of reducing roll-off of a substrate, comprising the step of polishing a substrate to be polished with the polishing composition as defined in any one of  claims 1  to  9 .