Conductive paste for front electrode of semiconductor device and method of manufacturing thereof

Abstract

The present invention provides a conductive paste characterized by a crystal-based corrosion binder being combined with a Pb-free glass frit and mixed with a metallic powder and an organic carrier. Methods for preparing each components of the conductive paste are disclosed including several embodiments of preparing Pb—Te—O-based crystallized corrosion binder characterized by melting temperatures in a range of 440° C. to 760° C. and substantially free of any glass softening transition upon increasing temperature. Method for preparing the conductive paste includes mixture of the components and a grinding process to ensure all particle sizes in a range of 0.1 to 5.0 microns. Method of applying the conductive paste for the formation of a front electrode of a semiconductor device is presented to illustrate the effectiveness of the crystal-based corrosion binder in transforming the conductive paste to a metallic electrode with good ohmic contact with semiconductor surface.

What is claimed is: 
     
         1 . A conductive paste material comprising:
 a metallic powder;   a glass frit made from materials substantially free from any Pb element;   a corrosion binder made from fully crystallized Pb—Te—O compounds having melting temperatures in a range of 440° C. to 760° C., and   an organic carrier,   wherein the metallic powder, the glass frit, and the corrosion binder are characterized by randomly dispersed particles in the organic carrier.   
     
     
         2 . The conductive paste material of  claim 1  wherein the corrosion binder comprises one or a combination of: PbTe 4 O 9 , PbTeO 3 .0.33H 2 O, PbTeO 3 , PbTeO 4 , PbTe 3 O 7 , PbTe 5 O 11 , Pb 2 TeO 4 , Pb 2 Te 3 O 7 , Pb 2 Te 3 O 8 , Pb 3 TeO 5 , Pb 3 TeO 6 , Pb 3 Te 2 O 8 H 2 O, Pb 4 Te 1.5 O 7 , Pb 5 TeO 7 , Pb 5 TeO 7 , Pb 6 Te 5 O 18 .5H 2 O, PbTe 4 O 9 , PbTe 2 O 5 , PbH 4 TeO 6 , PbTeCO 5 , and Pb 3 TeN 2 O 8  crystal compounds. 
     
     
         3 . The conductive paste material of  claim 1  wherein the corrosion binder comprises a plurality of crystalline particles substantially free from any glass softening transition upon increasing temperature. 
     
     
         4 . The conductive paste material of  claim 3  wherein the plurality of crystalline particles comprises particle sizes substantially in a range from 0.1 to 5.0 microns. 
     
     
         5 . The conductive paste material of  claim 1  wherein the glass frit comprises a plurality of glass particles bearing amorphous structure characterized by a glass softening transition temperature in a range of 500° C. to 650° C. 
     
     
         6 . The conductive paste material of  claim 5  wherein the plurality of glass particles comprises one or a combination of two or more materials selected from Bi—Si—B—Zn—O, Zn—B—P—Li—O, Bi—V—Ba—P—O, B—Al—Li—O, Bi—Si—O, Bi—Te—O, Bi—B—O, P—Zn—Na—O, Na—Al—B—O, B—Zn—Ba—O, and V—P—Ba—O-based glass materials. 
     
     
         7 . The conductive paste material of  claim 5  wherein the plurality of glass particles comprises sizes substantially in a range from 0.1 to 5.0 microns. 
     
     
         8 . The conductive paste material of  claim 1  wherein the glass frit and corrosion binder comprise a combined weight composition of 1 to 15 wt % based on a total weight of the conductive paste material. 
     
     
         9 . The conductive paste material of  claim 1  wherein the glass frit and the corrosion binder comprise a weight composition ratio ranging from 5:95 to 95:5 per any fixed amount of the conductive paste material. 
     
     
         10 . The conductive paste material of  claim 1  wherein the metallic powder comprises one metal material selected from silver, gold, platinum, copper, iron, nickel, zinc, titanium, cobalt, chromium, manganese, palladium, and rhodium or a metal alloy of two or more of them. 
     
     
         11 . The conductive paste material of  claim 1  wherein the metallic powder comprises a plurality of metal particles made by one metal material selected from copper, iron, nickel, zinc, titanium, cobalt, chromium, and manganese or a metal alloy of two or more of them, and at least 5% or more partially coated by a thickness of silver layer in a range of 1+2000 nm. 
     
     
         12 . The conductive paste material of  claim 1  wherein the metallic powder comprises a first plurality of silver particles mixed with a second plurality of silver-coated copper, iron, zinc, titanium, cobalt, chromium, manganese, nickel particles with a weight composition ratio between the first plurality of silver particles and the second plurality of silver-coated copper, iron, nickel, zinc, titanium, cobalt, chromium, manganese particles in a range from 5:95 to 95:5 per any fixed amount of the metallic powder. 
     
     
         13 . The conductive paste material of  claim 1  wherein the plurality of metallic powder particles comprises particle sizes substantially in a range from 0.1 to 5.0 micron.