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 method for manufacturing a front electrode of a semiconductor device, the method comprising:
 providing a semiconductor device including an insulation surface coating;   printing a conductive paste material overlying a patterned region of the insulation surface coating, the conductive paste material comprising,
 a plurality of metal particles with a weight composition ranging from 70 to 93 wt % based on a given total weight of the conductive paste; 
 a corrosion binder made from a plurality of Pb—Te—O-based crystalline particles and a glass frit made from a plurality of glass particles free from Pb element with a combined weight composition ranging from 2 to 15 wt % based on the given total weight; 
 an organic carrier with a weight composition ranging from 5 to 25 wt % based on the given total weight, wherein the organic carrier dispersedly holds the plurality of metal particles, the plurality of Pb—Te—O-based crystalline particles, and the plurality of glass particles, all particles having sizes in a range of 0.1 to 5.0 microns; 
   subjecting at least the conductive paste material and the patterned region in contact with the insulation surface coating to a sintering process with temperatures ramped up to about 900° C. followed by a cooling back, wherein the temperature rise causes releasing of the organic carrier, melting of the corrosion binder after the releasing of the organic carrier along with softening of the glass frit, and sintering of the plurality of metal particles into a metallic bulk assisted by wetting effects from the molten corrosion binder and soften glass frit. The molten corrosion binder and softened glass frit induce an etch-removing of the insulation surface coating at the patterned region to form a direct bonding between the sintered metallic bulk with the semiconductor device.   
     
     
         2 . The method of  claim 1  wherein the corrosion binder made from a plurality of Pb—Te—O-based crystalline particles comprises one crystal compound selected from: 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  or a mixture of two or more these crystal compounds characterized by a melting temperature ranging from 440° C. to 760° C. 
     
     
         3 . The method of  claim 1  wherein the glass frit comprises one or a combination of two or more 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 characterized by a glass softening transition temperature in a range of 500° C. to 650° C. 
     
     
         4 . The method of  claim 1  wherein the corrosion binder and the glass frit comprise a weight composition ratio ranging from 5:95 to 95:5 per any fixed amount of the conductive paste material. 
     
     
         5 . The method of  claim 1  wherein the etch-removing of the insulation surface coating is accelerated as the corrosion binder is quickly melted into a liquid phase accumulated at the patterned region under the printed conductive paste material to allow substantially complete penetration of the metallic bulk through the insulation surface coating to form an electrode having a conductive contact with the semiconductor device at the patterned region. 
     
     
         6 . The method of  claim 1  wherein the plurality of metal particles 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. 
     
     
         7 . The method of  claim 1  wherein the plurality of metal particles comprises one metal material selected from copper, iron, nickel, zinc, titanium, cobalt, chromium, manganese, or a metal alloy of two or more of them, and at least partially being coated by a thickness of silver layer in a range of 10˜500 nm. 
     
     
         8 . The method of  claim 1  wherein the plurality of metal particles comprises a first plurality of silver particles mixed with a second plurality of silver-coated copper, iron, nickel, zinc, titanium, cobalt, chromium, manganese 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 plurality of metal particles. 
     
     
         9 . The method of  claim 1  wherein the plurality of metal particles comprises particle sizes substantially in a range from 0.1 to 5.0 microns.