Improved planarization process for producing carriers with low step height

Abstract

A process to reduce step heights in planarization of thin film carriers in an encapsulation system. The improvements include using an adhesive tape having a thinner adhesive thickness and a stiffer tape for the film sealing the encapsulant on the carrier to result in a low step height surface transition between the carrier and the cured encapsulant. The composition of the encapsulant is modified to reduce the shrinkage upon curing of the encapsulant. The encapsulant may include an absorbent that absorbs the irradiation and cause the top surface to harden first compared to the bulk of the encapsulant, and/or a gas-emitting additive that creates gaseous products that expand upon irradiation to thereby reduce the shrinkage of the encapsulant upon curing. Alternatively, irradiation at very low incidence angle relative to the top surface of the encapsulant causes the top surface to harden before the bulk of the encapsulant.

1 . A method of processing a thin film surface, said thin film surface comprising at least one raised portion bordered by at least one adjacent recess, said method comprising: 
 applying an adhesive film to said raised portion;    depositioning a fluid encapsulant into said recess, said encapsulant held in said recess by said film, said encapsulant comprises an irradiation activated gas-emitting material and an irradiation absorbing material; and    irradiating and curing said encapsulant.    
   
   
       2 . The method as in  claim 1 , wherein said irradiation absorbing material is present in an effective amount to cause the surface of the encapsulant exposed to irradiation to harden before the remaining bulk of the encapsulant for reducing shrinkage of the encapsulant upon curing; wherein said gas-emitting material is present in an effective amount to form bubbles within the encapsulant for reducing shrinkage of the encapsulant during the curing thereof.  
   
   
       3 . The method as in  claim 2 , wherein said irradiation absorbing material comprises at least one of a bleachable dye, unbleachable dye and photo-initiator.  
   
   
       4 . The method as in  claim 3 , wherein said unbleachable dye comprises Curcumin.  
   
   
       5 . The method as in  claim 2 , wherein the irradiation absorbing material is added in the amount of 0.05 to 0.15% by weight.  
   
   
       6 . The method as in  claim 1 , wherein said irradiation absorbing material comprises BAMC (2,6-Bis(4-azidobenzylidene)-4-methylcyclohexanone).  
   
   
       7 . The method as in  claim 6 , wherein the BAMC is added in the amount of 0.05 to 0.15% by weight.  
   
   
       8 . The method as in  claim 1 , wherein said gas emitting material comprises at least one of organic and organometallic materials.  
   
   
       9 . The method as in  claim 8 , wherein said gas-emitting material comprises DMA (DiazoMeldrums Acid).  
   
   
       10 . The method as in  claim 9 , wherein the DMA is added in the amount of 0.05 to 0.15% by weight.  
   
   
       11 . The method as in  claim 8 , wherein said gas emitting material comprises BAMC (2,6-Bis(4-azidobenzylidene)-4-methylcyclohexanone).  
   
   
       12 . The method as in  claim 1 , wherein said adhesive film comprises a thin adhesive layer having a substantially 2 to 4 micron adhesive thickness and a stiff substrate that comprises at least one of PET (Polyethylene terephthalate), polyethylene and polyethylene copolymers.  
   
   
       13 . The method as in  claim 1 , wherein said adhesive film comprises about a 4 to 5 micron thick adhesive layer and about a 35 to 40 micron thick PET (Polyethylene terephthalate) substrate.  
   
   
       14 . The method as in  claim 1 , wherein said encapsulant is selected from the group consisting of a thiol-ene composition, an acrylic composition, an epoxy composition, and mixtures thereof.  
   
   
       15 . The method as in  claim 1 , further comprising the steps of: 
 coating said thin film surface with an etch mask;    developing said etch mask; and    etch patterning said thin film surface.    
   
   
       16 . A method as in  claim 1 , wherein said irradiating step comprises the step of irradiating at a first incidence angle relative to the surface of said encapsulant such that the surface of the encapsulant exposed to irradiation hardens before the remaining bulk of the encapsulant.  
   
   
       17 . A method of processing a thin film surface, said thin film surface comprising at least one raised portion bordered by at least one adjacent recess, said method comprising: 
 applying an adhesive film to said raised portion, said adhesive film having a stiff substrate that comprises PET (Polyethylene terephthalate);    depositing a fluid encapsulant into said recess, said encapsulant held in said recess by said film; and    irradiating and curing said encapsulant.    
   
   
       18 . A patterned thin film structure, comprising: 
 a thin film surface comprising at least one recess; and    an irradiated and cured encapsulant in the at least one recess, wherein an upper surface of the encapsulant is planar.    
   
   
       19 . A structure as recited in  claim 18 , wherein the encapsulant comprises at least one of an irradiation activated gas-emitting material and an irradiation absorbing material.  
   
   
       20 . A structure as recited in  claim 18 , wherein the thin film surface further comprises at least one raised portion.