Semiconductor device and method of manufacturing the same

Abstract

Making the relative size of the surface area of a bump electrode at a portion in contact with an under electrode larger than the surface area of a base of a hole increases the contact surface area between the lower surface of the bump electrode and a polyimide layer. As a result, effect by the polyimide layer to mitigate the impact loads applied during bonding greatly increases. The impact loads applied during bonding can also be mitigated by using a material for the conductive layer that is as flexible as, or even more flexible than, the material of the bump electrode. It is therefore possible to reduce cracks in semiconductor chips or the like directly under the bump electrode more efficiently.

1 . A semiconductor device comprising; 
 a semiconductor substrate having an electrode;    a protective insulating layer which protects the electrode;    a buffer layer formed over the protective insulating layer;    a hole provided over the electrode in such a manner as to penetrate the protective insulating layer and the buffer layer;    an under electrode formed over a surface of the buffer layer, an inner surface of the hole, and a surface of the electrode;    a conductive layer of an electrically conductive material which is formed in the hole; and    a bump electrode formed on the under electrode and on the conductive layer,    wherein the electrically conductive material is a material that is more flexible than a material of the bump electrode.    
     
     
         2 . The semiconductor device defined by  claim 1 , wherein the hole and the conductive layer are formed at substantially a center of the bump electrode.  
     
     
         3 . The semiconductor device defined by  claim 1 , wherein the buffer layer is of a photosensitive polyimide.  
     
     
         4 . The semiconductor device defined by  claim 1 , wherein the bump electrode is formed of gold or a gold alloy.  
     
     
         5 . A semiconductor device comprising: 
 a semiconductor substrate having an electrode;    a protective insulating layer which protects the electrode;    a buffer layer formed over the protective insulating layer;    a hole provided over the electrode in such a manner as to penetrate the protective insulating layer and the buffer layer;    an under electrode formed over a surface of the buffer layer, an inner surface of the hole, and a surface of the electrode;    a conductive layer of an electrically conductive material which is formed in the hole; and    a bump electrode formed on the under electrode and on the conductive layer,    wherein the ratio of a surface area of the bump electrode at a portion in contact with the under electrode and the conductive layer to a surface area of a base of the hole is greater than or equal to 5 and less than or equal to 100.    
     
     
         6 . The semiconductor device defined by  claim 5 , wherein the hole and the conductive layer are formed at substantially a center of the bump electrode.  
     
     
         7 . The semiconductor device defined by  claim 5  wherein the buffer layer is of a photosensitive polyimide.  
     
     
         8 . The semiconductor device defined by  claim 5 , wherein the electrically conductive material formed in the conductive layer is formed of the same material as a material of the bump electrode.  
     
     
         9 . The semiconductor device defined by  claim 5 , wherein the electrically conductive material is a material that is more flexible than a material of the bump electrode.  
     
     
         10 . The semiconductor device defined by  claim 5 , wherein the bump electrode is formed of gold or a gold alloy.  
     
     
         11 . A semiconductor device comprising: 
 a semiconductor substrate having an electrode;    a protective insulating layer which protects the electrode;    a buffer layer formed over the protective insulating layer;    a hole provided over the electrode in such a manner as to penetrate the protective insulating layer and the buffer layer;    an under electrode formed over a surface of the buffer layer, an inner surface of the hole, and a surface of the electrode;    a conductive layer of an electrically conductive material which is formed in the hole; and    a bump electrode formed on the under electrode and on the conductive layer,    wherein the ratio of the thickness of the buffer layer with respect to the diameter of the hole is greater than or equal to 1 but less than or equal to 3.    
     
     
         12 . The semiconductor device defined by  claim 11 , wherein the hole and the conductive layer are formed at substantially a center of the bump electrode.  
     
     
         13 . The semiconductor device defined by  claim 11 , wherein the buffer layer is of a photosensitive polyimide.  
     
     
         14 . The semiconductor device defined by  claim 11 , wherein the electrically conductive material formed in the conductive layer is formed of the same material as a material of the bump electrode.  
     
     
         15 . The semiconductor device defined by  claim 11 , wherein the electrically conductive material is a material that is more flexible than a material of the bump electrode.  
     
     
         16 . The semiconductor device defined by  claim 11 , wherein the bump electrode is formed of gold or a gold alloy.  
     
     
         17 . A method of manufacturing a semiconductor device, the method comprising: 
 forming a protective insulating layer for protecting an electrode, on a semiconductor substrate having the electrode;    forming a buffer layer over the protective insulating layer;    forming a hole in the protective insulating layer and the buffer layer over the electrode;    forming an under electrode layer over the surface of the buffer layer, the inner surface of the hole, and the electrode;    forming a pattern mask which defines a region for forming a bump electrode on the under electrode layer;    continuously forming a bump electrode and a conductive layer by a plating method in a region for forming the bump electrode and in the inner surface of the hole, respectively; and    removing a part of the under electrode layer, to form an under electrode.    
     
     
         18 . A method of manufacturing a semiconductor device, the method comprising: 
 forming a protective insulating layer for protecting an electrode, on a semiconductor substrate having the electrode;    forming a photosensitive polyimide layer as a buffer layer over the protective insulating layer;    forming a hole in the photosensitive polyimide layer by photolithography;    using the photosensitive polyimide layer as a mask to remove the protective insulating layer to form a hole;    forming an under electrode layer over the surface of the buffer layer, the inner surface of the hole, and the electrode;    forming a pattern mask which defines a region for forming a bump electrode on the under electrode layer;    continuously forming a bump electrode and a conductive layer by a plating method in a region for forming the bump electrode and in the inner surface of the hole, respectively; and    removing a part of the under electrode layer, to form an under electrode.    
     
     
         19 . A method of manufacturing a semiconductor device, the method comprising: 
 forming a protective insulating layer for protecting an electrode, on a semiconductor substrate having the electrode;    forming a buffer layer over the protective insulating layer;    forming a hole in the protective insulating layer and the buffer layer over the electrode;    forming an under electrode layer over the surface of the buffer layer, the inner surface of the hole, and the electrode;    forming a conductive layer in the hole by an electrically conductive material that is more flexible than a material of a bump electrode after the formation of the under electrode layer;    forming a pattern mask which defines a region for forming a bump electrode on the under electrode layer;    forming a bump electrode over the under electrode layer and the conductive layer; and    removing a part of the under electrode layer, to form an under electrode.    
     
     
         20 . The method of manufacturing a semiconductor device as defined by  claim 19 , wherein the electrically conductive material is an electrically conductive resin.  
     
     
         21 . The method of manufacturing a semiconductor device as defined by  claim 19 , 
 wherein the buffer layer is formed of a photosensitive polyimide, and    wherein a hole is formed in the photosensitive polyimide by photolithography and also the photosensitive polyimide in which the hole has been formed is used as a pattern mask to form a hole in the protective insulating layer, during the step of forming a hole.