Lanthanide oxide dissolution from glass surface

Abstract

A method and product for computer disk drives. Glass substrates are provided having low content of residual polishing particles on the surfaces thereof. An exemplary method includes reduction of residual polishing particle content by immersion of the glass substrate in an acid bath containing nitric acid, hydrogen peroxide and an organic acid having a carboxylic acid group.

What is claimed is:  
     
         1 . A method for manufacturing a disk, comprising the steps of: 
 polishing a glass substrate with a slurry comprising lanthanide oxide particles; and    cleaning the polished glass substrate having lanthanide oxide particles thereon to remove said lanthanide oxide particles, said cleaning step leaving no more than about 1.52×10 −4  ng/mm 2  of each type of lanthanide oxide on said glass substrate.    
     
     
         2 . The method of  claim 1 , wherein said cleaning step comprises immersing the substrate in an acid bath comprising nitric acid, hydrogen peroxide and an organic acid having a carboxylic acid group.  
     
     
         3 . A glass substrate having a polished surface comprising less than about 1.52×10 −4  ng/mm 2  each of oxide particles of lanthanide series elements selected from the group consisting of: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.  
     
     
         4 . The glass substrate of  claim 3 , wherein the glass is aluminosilicate glass.  
     
     
         5 . The glass substrate of  claim 3  produced by the method of: 
 polishing the surface of the glass substrate with a slurry to an atomically smooth finish, the slurry comprising at least one oxide of a lanthanide series element;  
 immersing the polished glass substrate having residual lanthanide oxide particles thereon in an acid bath comprising at least about 1N nitric acid, at least about 0.15N hydrogen peroxide and at least about 0.0067M tartaric acid; and  
 thereafter immersing the polished glass substrate in a basic bath of potassium hydroxide having a pH of between about 11.5 and about 13, wherein the step of immersion in the acid bath substantially dissolves the residual lanthanide oxide particles from the polished glass substrate into the acid bath thereby reducing the content of the lanthanide oxide particles present on the polished surface.  
 
     
     
         6 . A glass substrate having a polished surface comprising less than about 1.52×10 −4  ng/mm 2  each of oxide particles of lanthanide series elements selected from the group consisting of: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, said substrate produced by the method of: 
 (a) polishing a glass substrate with a slurry comprising oxide particles of lanthanide series elements;  
 (b) ultrasonically cleaning the polished glass substrate;  
 (c) mechanically scrubbing the polished glass substrate with soap and a pad;  
 (d) immersing the polished glass substrate in an acid bath comprising nitric acid, hydrogen peroxide and an organic acid having a carboxylic acid group;  
 (e) scrubbing the polished glass substrate with polyvinyl alcohol pads and potassium hydroxide; and  
 (f) immersing the polished glass substrate in a basic bath of potassium hydroxide, wherein the step of immersion in the acid bath substantially dissolves the lanthanide series oxide particles from the polished glass substrate into the acid bath thereby reducing the content of the lanthanide series oxide particles present on the polished surface.  
 
     
     
         7 . A glass substrate having a polished surface comprising less than about 1.52×10 −4  ng/mm 2  each of oxide particles of lanthanide series elements selected from the group consisting of: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, said substrate produced by the method of: 
 (a) polishing a glass substrate with a slurry comprising oxide particles of lanthanide series elements;  
 (b) ultrasonically cleaning the polished glass substrate;  
 (c) mechanically scrubbing the polished glass substrate with soap and a pad;  
 (d) immersing the polished glass substrate in an acid bath comprising nitric acid, hydrogen peroxide and an organic acid having a carboxylic acid group;  
 (e) scrubbing the polished glass substrate with polyvinyl alcohol pads and potassium hydroxide;  
 (f) immersing the polished glass substrate in a basic bath of potassium hydroxide;  
 (g) subjecting the polished glass substrate to chemical strengthening;  
 (h) immersing the polished glass substrate in an etching bath of a surfactant and an acid selected from the group consisting of organic acids and sulfuric acid;  
 (i) repeating step (e); and  
 (j) repeating step (f), wherein the step of immersion in the acid bath substantially dissolves the lanthanide series oxide particles from the polished glass substrate into the acid bath thereby reducing the content of the lanthanide series oxide particles present on the polished surface.  
 
     
     
         8 . A disk drive product comprising a glass substrate having a polished surface comprising less than about 1.52×10 −4  ng/mm 2  each of oxide particles of lanthanide series elements selected from the group consisting of: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.  
     
     
         9 . The disk drive product of  claim 8 , wherein the glass substrate is aluminosilicate glass.