Synthesis of chemically reactive ceria composite nanoparticles and CMP applications thereof

Abstract

The present invention provides a method of synthesizing nanosized abrasive particles and methods of using the same in chemical mechanical polishing slurry applications. The nanosized abrasive particles according to the invention are produced by hydrothermal synthesis. The crystallites of the particles include cerium atoms and atoms of metals other than cerium. In a preferred embodiment of the invention, the crystallites exhibit a cubic crystal lattice structure. The differences in electric potential between the cerium atoms and the atoms of metals other than cerium facilitate the polishing of films without the need for chemical oxidizers.

1 . A method of producing abrasive particles for use in CMP slurries comprising: 
 a. providing an aqueous reaction mixture comprising 
 i. one or more compounds that provide a source of cerium ions,  
 ii. one or more compounds that provide a source of metal ions selected from the group consisting of Be, B, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ba, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Hp, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, and combinations thereof,  
   b. contacting the aqueous reaction mixture with a base to raise the pH to above about 1.5, and,    c. subjecting the aqueous reaction mixture to hydrothermal treatment at a temperature of from about 70° C. to about 500° C. to produce the abrasive particles,    d. wherein the abrasive particles comprise crystallites having crystal lattice structures that include cerium and one or more metals other than cerium.    
     
     
         2 . The method of  claim 1  wherein the ratio of cerium ions to guest ions is about 100000:1 to about 1:100000.  
     
     
         3 . The method of  claim 1  where the compound that provides the source of cerium ions is a Ce(III) salt or a Ce(IV) salt.  
     
     
         4 . The method of  claim 1  wherein the reaction mixture is subjected to hydrothermal treatment for about 10 minutes to about 48 hours.  
     
     
         5 . The method of  claim 4  wherein the aqueous reaction mixture is contacted with the base by double jet injection.  
     
     
         6 . The method of  claim 5  wherein the compound that provides the source of guest ions is a salt of the guest ion.  
     
     
         7 . The method of  claim 6  wherein the compound that provides the source of guest ions is selected from the group consisting of Fe(NO 3 ) 3 , Cu(NO 3 ) 2 , Nd(NO 3 ) 3 , and hydrated forms thereof.  
     
     
         8 . The method of  claim 1  wherein the particles have a crystallite size of about 5 to about 100 nm.  
     
     
         9 . The method of  claim 1  wherein the particles agglomerate to form a secondary particle size of about 50 to about 500 nm.  
     
     
         10 . A method of making composite CMP ceria particles comprising: 
 a. contacting an aqueous solution of Ce(NH 4 ) 2 (NO 3 ) 6  with a second metal salt to form a reaction mixture;    b. contacting the reaction mixture with a base to raise the pH to above about 1.5; and    c. heating the reaction mixture to form the particles.    
     
     
         11 . The method of  claim 10  wherein the second reaction mixture is heated for about 10 minutes to about 48 hours at a temperature of about 70° C. to about 500° C.  
     
     
         12 . The method of  claim 10  wherein the first reaction mixture is contacted with the base by double jet injection  
     
     
         13 . The method of  claim 10  wherein the second metal salt is selected from the group consisting of nitrates, chlorides, bromides, sulfates, perchlorides, and acetates of iron, copper and neodymium in their anhydrous and hydrated forms.  
     
     
         14 . The method of  claim 10  wherein the second metal salt is selected from the group consisting of Fe(NO 3 ) 3 , Cu(NO 3 ) 2 , Nd(NO 3 ) 3 , and hydrated forms thereof.  
     
     
         15 . A method of removing a film at a desired rate in the absence of chemical oxidizers comprising: 
 a. determining the desired polishing rate of film to be removed;    b. selecting abrasive particles according to  claim 1  that provide a desired polishing rate for the film be removed; and    c. polishing the film with a CMP slurry comprising the particles selected in step b.    
     
     
         16 . The method of  claim 15  wherein the film be removed is selected from the group consisting of silver, gold, platinum, copper, palladium, nickel, cobalt, iron, ruthenium, iridium, and osmium, silicon, aluminum, germanium, tungsten, tantalum, and alloys or blends thereof.  
     
     
         17 . The method of  claim 15  wherein the film to be removed is selected from the group consisting of oxides, nitrides or silicides of boron, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, gallium, germanium, arsenic, selenium, rubidium, strontium, yttrium, zirconium, tin, antimony, cesium, nickel, cobalt and barium.  
     
     
         18 . The method of  claim 15  wherein the film to be removed is a polymer is selected from the group consisting of poly(para-xylylenes), halogenated poly(para-xylylenes), b-staged polymers, polyimides, halogenated polyimides, silsequioxanes, alkyl substituted silsequioxanes, poly-(arylene ethers) and poly-(tetrafluoroethylene).  
     
     
         19 . The method of  claim 15  wherein the CMP slurry further comprises a pH adjuster.  
     
     
         20 . A CMP slurry comprising: 
 a. water; and    b. abrasive particles according to  claim 1 .    
     
     
         21 . The CMP slurry of  claim 20  wherein the slurry is substantially free of chemical additives/oxidizers.  
     
     
         22 . The CMP slurry of  claim 20  wherein the ratio of cerium ions to guest ions is about 1000:1 to about 1:1000.  
     
     
         23 . The CMP slurry of  claim 21  wherein the guest ion is selected from the group consisting of Fe, Nd, and Cu.  
     
     
         24 . The CMP slurry of  claim 21  wherein the guest ion is selected from the group consisting of Ti, Ta and Y.  
     
     
         25 . A method of removing a portion of a substrate in a CMP operation comprising: 
 a. providing the CMP slurry of  claim 20;     b. adjusting the pH of the slurry to 3.0 to 11.0 using at least one pH adjuster;    c. contacting the slurry and the substrate to be polished; and    d. performing CMP on the substrate using said slurry.    
     
     
         26 . The method of  claim 25  wherein the difference in electronegativity of the cerium ions and the guest ions is sufficient to drive a redox reaction between the particle and the substrate when the particle contacts the substrate.