Polishing inhibiting layer forming additive, slurry and cmp method

Abstract

A polishing inhibiting layer forming additive for a slurry, the slurry so formed, and a method of chemical mechanical polishing are disclosed. The polishing inhibiting layer is formed through application of the slurry to the surface being polished and is removable at a critical polishing pressure. The polishing inhibiting layer allows recessed or low pattern density locations to be protected until a critical polishing pressure is exceeded based on geometric and planarity considerations, rather than slurry or polishing pad considerations. With the additive, polishing rate is non-linear relative to polishing pressure in a recessed/less pattern dense location. In one embodiment, the additive has a chemical structure: [CH 3 (CH 2 ) x N(R)]M, wherein M is selected from the group consisting of: Cl, Br and I, x equals an integer between 2 and 24, and the R includes three carbon-based functional groups, each having less than eight carbon atoms.

1 - 16 . (canceled)  
   
   
       17 . A wafer polishing slurry, comprising: 
 a plurality of polishing particles;    a solvent in which the polishing particles are suspended; and    a polishing inhibiting layer forming additive for forming a layer on a surface of a wafer in situ to inhibit a polishing rate thereof, the polishing inhibiting layer creating a polishing rate for the topography that is non-linear with polishing pressure.    
   
   
       18 . The slurry of  claim 17 , wherein the polishing inhibiting layer forming additive includes one of: an anionic surfactant and a cationic surfactant.  
   
   
       19 . The slurry of  claim 18 , wherein the cationic surfactant includes a chemical structure selected from the group consisting of: 
 a) [CH 3 (CH 2 ) x N(R)]M, wherein M is selected from the group consisting of: Cl, Br and I, x equals an integer between 2 and 24, and the R includes three carbon-based functional groups, each having less than eight carbon atoms; and    b) C p H q QN, where Q is selected from the group consisting of: Cl, Br and I, and p>8 and q>20.    
   
   
       20 . The slurry of  claim 19 , wherein the carbon-based functional groups are selected from the group consisting of: CH 3 , CH 2 OH, C 2 H 4 OH, C 2 H 5 , C 3 H 6 OH and C 3 H 7 .  
   
   
       21 . The slurry of  claim 19 , wherein the cationic surfactant includes C p H q QN, and Q is Cl, p=21, and q=38, resulting in cetylpyridinium chloride (C 21 H 38 ClN).  
   
   
       22 . The slurry of  claim 18 , wherein the cationic surfactant includes one of: 
 cetyltrimethyl ammonium bromide (CTAB), [CH 3 (CH 2 ) 15 N(CH 3 ) 3 ]Br;    cetyldimethylethyl ammonium bromide (CDB), [CH 3 (CH 2 ) 15 N(CH 3 ) 2 CH 2 OH] Br;    [CH 3 (CH 2 ) x N(CH 3 ) 3 ]Br, where x equals an integer between 2 and 24; and    [CH 3 (CH 2 ) x N(CH 3 )(C 2 H 5 )(C 3 H 7 )]Br, where x equals an integer between 2 and 24.    
   
   
       23 . The slurry of  claim 18 , wherein the anionic surfactant includes at least one of: sodium sulfate, sodium dodecyl sulfate, sodium lauryl sulfate, sodium stearate and sodium tetradecyl sulfate.  
   
   
       24 . The slurry of  claim 17 , wherein the polishing inhibiting layer is removable from the surface at a critical removal polishing pressure P crit  that is no less than approximately 2 psi and no greater than approximately 20 psi.  
   
   
       25 . The slurry of  claim 17 , wherein the slurry has a pH level between an isoelectric point of the surface and an isoelectric point of the plurality of polishing particles to cause adhesion of the layer to the surface.  
   
   
       26 . A polishing inhibiting layer forming additive for a chemical mechanical polishing slurry, the additive comprising: 
 a surfactant having a chemical structure selected from the group consisting of:    a) [CH 3 (CH 2 ) x N(R)]M, wherein M is selected from the group consisting of: Cl, Br and I, x equals an integer between 2 and 24, and the R includes three carbon-based functional groups, each having less than eight carbon atoms; and    b) C p H q QN, where Q is selected from the group consisting of: Cl, Br and I, and p>8 and q>20,    wherein the surfactant forms a polishing inhibiting layer creating a polishing rate that is non-linear with polishing pressure.    
   
   
       27 . The additive of  claim 26 , wherein the surfactant includes one of: 
 cetyltrimethyl ammonium bromide (CTAB), [CH 3 (CH 2 ) 15 N(CH 3 ) 3 ]Br and cetyldimethylethyl ammonium bromide (CDB), [CH 3 (CH 2 ) 15 N(CH 3 ) 2 CH 2 OH] Br.    
   
   
       28 . The additive of  claim 26 , wherein the polishing inhibiting layer is removable at a critical removal polishing pressure P crit  that is no less than approximately 2 psi and no greater than approximately 20 psi.  
   
   
       29 . The additive of  claim 26 , wherein the slurry has a pH level between an isoelectric point of a surface to be polished and an isoelectric point of a plurality of polishing particles therein to cause adhesion of the layer to the surface.  
   
   
       30 . The additive of  claim 26 , wherein the surfactant includes C p H q QN, and Q is Cl, p=21, and q=38, resulting in cetylpyridinium chloride (C 21 H 38 ClN).