Open structure polishing pad and methods for limiting pore depth

Abstract

An improved polishing pad, starting from a traditional sintered pad core or similar, is designed with a feature that controls the pore depth of the polishing pad. The pad interstitials are impregnated with a chosen material. This material is then liberated from the surface of the pad, by a variety of methods, leaving the remaining void space to form the desired surface texture for polishing. The invention allows for the bulk properties of the pad to remain more solid-like with a higher modules for improved planarization. At the same time a surface porosity depth is limited to both create an ideal surface texture and to allow for the polishing pad surface to remain clean and free of polishing by products and debris that tend to build-up with in the depths of a traditional sintered pad. This invention yields a polishing pad that is better suited for applications such as semiconductor wafer polishing, and the like.

1 . A polishing pad comprising a mixture of at least two material types where, 
 a) a first material participates of a contiguous collection of polymeric like particles to form the body of polymeric like structure, and    b) a second material acts to fill some portion of the void spaces between the polymeric like particles.    
     
     
         2 . A polishing pad comprising a mixture of at least two material types where, 
 a. a first material participates of a contiguous collection of polymeric like particles to form the body of polymeric like structure, and    b. a second material acts to fill some portion of the void spaces created, and    c. some portion of the second material type is liberated from the surface of the said polishing pad resulting in the creation of surface texture.    
     
     
         3 . A polishing pad in accordance with claims  1  or  2  wherein said methods of material liberation include: contacting the said polishing pads with a fluid, which acts to dissolve the said portion of the said second material, either as the sole method of material liberation or combined with any number of other means of surface material liberation.  
     
     
         4 . A polishing pad in accordance to  claim 3  where the said fluid is water in either an acidic, neutral or basic pH range and said second material is comprised of a host of soluble materials which includes but is not limited to, 
 a. polymeric materials including Polyacrylic acid, Polyethylene oxide,  
 b. inorganic materials including CaO, CaCO 3 , Ca(NO 3 ) 3 , KCO 3 , Zr(SO 4 ) 2 ,  
 c. salts or crystals including sugars and dried acids and,  
 d. physical and molecular level combinations of the above either as the sole method of material liberation or combined with any number of other means of surface material liberation.  
 
     
     
         5 . A polishing pad in accordance with  claim 1  or  2  wherein said methods of material liberation include, contracting the said polishing pad with a substance which chemically reacts with the said second material and forms reaction byproducts which become liberated from the surface of the said polishing pad, either as the sole method of material liberation or combined with any number of other means of surface material liberation.  
     
     
         6 . A polishing pad in accordance with  claim 1  or  2  wherein said methods of material liberation include, exposing the said polishing pad with a environment which lends the second material to undergo a phase transformation which results in a volatile or otherwise mobile condition which facilitates the liberation of the said second material, either as the sole method of material liberation or combined with any number of other means of surface material liberation.  
     
     
         7 . A polishing pad in accordance with claims  1  or  2  wherein said methods of material liberation include: exposing the said polishing pad with a environment which lends the second material to substantially higher rate of physical wear when compared to the said polymer like particle material  11 , either as the sole method of material liberation or combined with any number of other means of surface material liberation.  
     
     
         8 . A polishing pad in accordance with  claim 1  wherein said methods of material liberation include: exposing the said polishing pad with a environment which lends he said second material to undergo a phase transformation which results in a volatile or otherwise mobile condition which facilitates the liberation of the said second material, either as the sole method of material operation or combined with any other number of means of surface material liberation.  
     
     
         9 . A polishing pad in accordance with claims  1  or  2  wherein said methods of material liberation includes but is not limited to exposing the said polishing pad to an environment which induces the said second material to physically wear at a substantially higher rate when compared to the remainder of the polishing pad, creating surface topography, either as the sole method of material liberation or combined with any other number of means of surface material liberation.  
     
     
         10 . A polishing pad in accordance with claims  1  or  2  wherein said methods of material liberation includes but is not limited to exposing the said polishing pad to temperatures, pressures, shear rates, abrasion or surfaced agitation where the said second phase undergoes a deformation, decomposition, reaction, or increased mobility of said second material when compared to he remainder of the polishing pad material, creating surface topography, either as the sole method of material liberation or combined with any other number of means of surface material liberation.  
     
     
         11 . A polishing pad in accordance with claims  1  or  2  wherein said methods of material liberation includes but is not limited to exposing the said polishing pad to an applied surface energy flux including but not limited to light, acoustic or sonic energy, vibrations or thermal energy resulting in either surface degradation, decomposition, reaction, dissolution, increase mobility, combination or other means of surface liberation of said second material when compared to the remainder of the polishing pad, creating surface topography, either as the sole method of material liberation or combined with any other number of means of surface material liberation.  
     
     
         12 . A polishing pad in accordance to claims  1  or  2  where the recess  13  of the said second material is greater than 1 microns and less than 10,000 microns.  
     
     
         13 . A polishing pad in accordance to claims  1  or  2  where the recess  13  of the said second material is greater than 50 microns and less than 500 microns.  
     
     
         14 . A polishing pad in accordance to claims  1  or  2  where the said pore depth or said surface texture of the said polishing pad is controlled by the depth that the said second material has been liberated from the said polishing pad surface.  
     
     
         15 . A polishing pad in accordance to  claim 1  or  2  where the said polymeric like particle material  11  has a hydrophilic surface, at least after pad conditioning or creation of surface texture and is composed of a density of greater than 0.5 g/cm3, a critical surface tension of greater than 33.5 milliNewtons/m, a tensile modulus of 0.02 to 5 gigapascals, a ratio of tensile modulus at 30 C. to tensile modulus at 60 C. of 1.0 to 2.5, a shore-D hardness of 25 to 90, a yield stress of 300-600 psi, a tensile strength of 1000 to 15000 psi, an elongation to break less than or equal to 500%.  
     
     
         16 . A polishing pad in accordance with claims  1  or  2  where the liberated material either provides: gas bubbles for wafer release and cleaning, lubricants for reduced friction, active polishing ingredients, self cleaning or pores, secondary reactions to eliminate undesired polishing by-products, or buffering properties.  
     
     
         17 . A polishing pad where multiple layers of the polishing pad materials are positioned one or the other and assembled together with a connecting material used to fill spaces between these pad layers.  
     
     
         18 . A polishing pad in accordance with claims  1  or  2  and  claim 17  where the polishing pad materials are the said first material and the said connecting materials are the said second material.  
     
     
         19 . A polishing pad in accordance with  claim 17  or  18  where the said multiple layers can be exposed with the use of an extensive liberation process, by any of a number of means, to allow for the expose of an underlying layer below the surface layer, with the benefit of removing this top layer to expose the lower layer in a manner where fresh pad surfaces can be exposed for polishing use in a repeating fashion, dictated by the number of remaining pad layers and the polishing application.  
     
     
         20 . A polishing pad in accordance with  claim 19  where the said pad contact polishing surface can be removed to expose a lower level as a fresh polishing surface without removing the pad from the polisher to facilitate application needs typically addresses by changing the polishing pad, including but not limited to raised defects levels due to paid degradation and contamination, process changes between incompatible processes, and undesired thickness profiles induced into the top surface pad wear.