Via structure in multi-layer substrate and manufacturing method thereof

Abstract

Disclosed is a via structure in a multi-layer substrate, comprising a first metal layer, a dielectric layer and a second metal layer. The first metal layer has an upper surface. The dielectric layer covers the first metal layer in which a via is opened to expose the upper surface. The second metal layer is formed in the via and contacts an upper surface and an inclined wall of the via. A contacting surface of the second metal layer has a top line lower than the upper edge of the inclined wall. Alternatively, the second metal layer can be formed on the dielectric layer as being a metal line simultaneously as formed in the via as being a pad. The metal line and the pad are connected electronically. The aforesaid metal second layer can be formed in the via and on the dielectric layer by a metal lift-off process.

1 . A manufacturing method of a via structure in a multi-layer substrate, comprising:
 forming a first metal layer having an upper surface;   forming a dielectric layer to cover the first metal layer;   opening a via to expose the upper surface of the first metal layer that the via has an inclined wall with an upper edge;   coating at least one photoresist layer on a surface of the dielectric layer and the upper surface of the first metal layer;   proceeding a photolithography process to the photoresist layer;   removing the photoresist layer in the via;   forming a second metal layer in the via and on the photoresist layer coated on the surface of the dielectric layer, wherein the second metal layer in the via contacts the upper surface, the inclined wall and a contacting surface of the second metal layer has a top line; and   removing the photoresist layer on the surface of the dielectric layer and the second metal layer formed on the photoresist layer.   
     
     
         2 . The manufacturing method of  claim 1 , wherein a shape and an area of the second metal layer formed in the via are defined by an upper edge of the photoresist layer coated on the surface of the dielectric layer. 
     
     
         3 . The manufacturing method of  claim 1 , an area formed by a lower edge of the inclined wall is smaller than an area formed by the upper edge. 
     
     
         4 . The manufacturing method of  claim 3 , wherein the top line of the contacting surface is higher than the lower edge of the inclined wall. 
     
     
         5 . The manufacturing method of  claim 1 , wherein the top line of the contacting surface is lower than the upper edge of the inclined wall. 
     
     
         6 . The manufacturing method of  claim 1 , an acute angle formed by the upper surface of the first metal layer and the inclined wall is smaller than 75°. 
     
     
         7 . The manufacturing method of  claim 1 , wherein an area formed by an upper edge of the photoresist layer coated on the surface of the dielectric layer is between the areas formed by an upper edge and a lower edge of the inclined wall. 
     
     
         8 . The manufacturing method of  claim 1 , further removing the photoresist layer in a predetermined position on the surface of the dielectric layer during the step of removing the photoresist layer in the via wherein the second metal layer in the via is employed as being a pad and the second metal layer formed in the predetermined position is employed as being a metal line. 
     
     
         9 . The manufacturing method of  claim 1 , wherein a material of the dielectric layer is polyimide.