Method of manufacturing inkjet printhead using crosslinked polymer

Abstract

Provided is a method of manufacturing an inkjet printhead. The method includes: preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater; applying a negative photoresist composition to the substrate having thereon the heater and the electrode and patterning the same to form a passage forming layer that surrounds an ink passage; patterning the substrate having thereon the passage forming layer by photolithography at least twice to form a sacrificial layer having a planarized upper surface in a space surrounded by the passage forming layer; applying the negative photoresist composition to the passage forming layer and the sacrificial layer and patterning the same to form a nozzle layer having a nozzle; etching the substrate from the rear surface thereof to be perforated to form an ink supply hole; and removing the sacrificial layer, wherein the negative photoresist composition includes a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone. The sacrificial layer may be planarized using a chemical mechanical polishing process. Therefore, an upper surface of the sacrificial layer can be planarized, and thus, it is possible to easily control a shape and dimension of an ink passage, thereby improving uniformity of the ink passage.

1 . A method of manufacturing an inkjet printhead, the method comprising: 
 preparing a substrate having thereon a heater for heating ink and an electrode for supplying current to the heater;    coating a negative photoresist composition on the substrate having thereon the heater and the electrode and patterning the negative photoresist composition using a photolithography process to form a passage forming layer that defines an ink passage;    forming a sacrificial layer on the substrate having thereon the passage forming layer so as to cover the passage forming layer;    planarizing upper surfaces of the passage forming layer and the sacrificial layer using a polishing process;    coating a negative photoresist composition on the passage forming layer and the sacrificial layer and patterning the negative photoresist composition using a photolithography process to form a nozzle layer having a nozzle;    forming an ink feed hole in the substrate; and    removing the sacrificial layer,    wherein the negative photoresist composition comprises a prepolymer that has a glycidyl ether functional group or a ring-opened glycidyl ether functional group on monomer repeating units thereof and a phenolic novolak resin-based backbone, a bisphenol A-based backbone, or an alicyclic-based backbone.    
   
   
       2 . The method of  claim 1 , wherein the polishing process is a chemical mechanical polishing (CMP) process.  
   
   
       3 . The method of  claim 1 , wherein the formation of the passage forming layer comprises: 
 forming a first photoresist layer by coating the negative photoresist composition on the entire surface of the substrate;    exposing the first photoresist layer using a first photomask having an ink passage pattern; and    forming the passage forming layer by developing the first photoresist layer to remove an unexposed portion of the first photoresist layer.    
   
   
       4 . The method of  claim 1 , wherein the sacrificial layer comprises a positive photoresist or a non-photosensitive soluble polymer.  
   
   
       5 . The method of  claim 4 , wherein the positive photoresist is an imide-based positive photoresist.  
   
   
       6 . The method of  claim 4 , wherein the non-photosensitive soluble polymer is at least one selected from the group consisting of a phenolic resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acrylic resin, a polyamide resin, an urea resin, a melamine resin, and a silicone resin.  
   
   
       7 . The method of  claim 1 , wherein in the formation of the sacrificial layer, the sacrificial layer is formed to be higher than the passage forming layer.  
   
   
       8 . The method of  claim 1 , wherein in the formation of the sacrificial layer, the sacrificial layer is formed using a spin coating process.  
   
   
       9 . The method of  claim 1 , wherein in the planariziation, the upper surfaces of the passage forming layer and the sacrificial layer are planarized by polishing the upper surfaces of the passage forming layer and the sacrificial layer using the polishing process to reach a desired height of the ink passage.  
   
   
       10 . The method of  claim 1 , wherein the formation of the nozzle layer comprises: 
 forming a second photoresist layer by coating the negative photoresist composition on the passage forming layer and the sacrificial layer;    exposing the second photoresist layer using a second photomask having a nozzle pattern; and    forming the nozzle layer having the nozzle by developing the second photoresist layer to remove an unexposed portion of the second photoresist layer.    
   
   
       11 . The method of  claim 1 , wherein the formation of the ink feed hole comprises: 
 coating a photoresist on a rear surface of the substrate;    forming an etch mask for forming the ink feed hole by patterning the photoresist; and    etching a rear surface portion of the substrate exposed through the etch mask to form the ink feed hole.    
   
   
       12 . The method of  claim 11 , wherein the rear surface of the substrate is etched by a dry etching process using plasma.  
   
   
       13 . The method of  claim 11 , wherein the rear surface of the substrate is etched by a wet etching process using tetramethylammonium hydroxide (TMAH) or KOH as an etchant.  
   
   
       14 . The method of  claim 1 , wherein the negative photoresist composition further comprises a cationic photoinitiator and a solvent.  
   
   
       15 . The method of  claim 1 , wherein the prepolymer is prepared from a backbone monomer unit selected from the group consisting of phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic-based compound, and mixtures thereof.  
   
   
       16 . The method of  claim 1 , wherein the prepolymer comprises at least one represented by Formulae 1 through 7 below:  
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       wherein m is an integer ranging from 1 to 25, and n is an integer ranging from 1 to 20.  
     
   
   
       17 . The method of  claim 1 , wherein the prepolymer comprises addition products of 1-2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol.  
   
   
       18 . The method of  claim 1 , wherein the prepolymer of the negative photoresist composition is crosslinked by exposure to radiation of actinic ray.  
   
   
       19 . The method of  claim 14 , wherein the cationic photoinitiator is a sulfonium salt or an iodonium salt.  
   
   
       20 . The method of  claim 14 , wherein the solvent is at least one selected from the group consisting of  -butyrolactone, propylene glycol methyl ether acetate (PGMEA), tetrahydrofuran (THF), methyl ethyl ketone, methy isobutyl ketone, cyclopentanone, and mixtures thereof.  
   
   
       21 . An inkjet printhead manufactured according to the method of any one of claims  1  through  20 .