Contact chain for testing and its relevantly debugging method

Abstract

The present invention provides a structure of a contact chain comprising a substrate of a first conductive type, a dielectric layer on the substrate, a plurality of contact structures and two probe pads. The contact structures are connected in series and have two ends. Each contact structure comprises a contact hole in the dielectric layer and conductive material in the contact hole, for electrically contacting with a first doped layer of a second conductive type. The first doped region is formed on the substrate. Two probe pads are coupled to the two ends, respectively. The contact chain further comprises a means for selectively coupling the first doped layer to the substrate. When the first doped layer is not coupled to the substrate, the total resistance of the contact chain can be measured through the two probe pads. During FIB failure analysis, the first doped layer can be forced to couple to the substrate, such that the PN junction between the first doped layer and the substrate will not interfere with the analytic process.

What is claimed is:  
     
         1 . A structure of a contact chain, comprising: 
 a substrate of a first conductive type;    a dielectric layer on the substrate;    a plurality of contact structures connected in series and having two ends, each contact structure comprising a contact hole in the dielectric layer and conductive material in the contact hole, and serving to electrically contact with a first doped layer of a second conductive type, wherein the first doped region is formed on the substrate;    two probe pads coupled to the two ends, respectively; and means for selectively coupling the first doped layer to the substrate;    wherein, when the substrate is not coupled to the first doped layer, a total contact resistance is measured by probing the probe pads.    
     
     
         2 . The structure of the contact chain as claimed in  claim 1 , wherein means for selectively coupling the first doped layer to the substrate comprising: 
 a second doped layer of the second conductive type, formed on the substrate and coupled to the substrate; and    a control gate, formed on a surface of the substrate between the first doped layer and the second doped layer to control electric connection between the first doped layer and the second doped layer.    
     
     
         3 . The structure of the contact chain as claimed in  claim 2 , wherein the second doped layer is coupled to the substrate through conductive material in a substrate contact hole and a third doped layer of the first conductive type, portion of the substrate contact hole being located on the second, doped layer and portion of the substrate contact hole being located on the third doped layer.  
     
     
         4 . The structure of the contact chain as claimed in  claim 2 , wherein the control gate is coupled to a gate pad to be controlled by an external voltage.  
     
     
         5 . The structure of the contact chain as claimed in  claim 2 , wherein the control gate is coupled to a gate pad via at least one gate contact hole.  
     
     
         6 . The structure of the contact chain as claimed in  claim 1 , further has a connection net to respectively couple the two ends to the two probe pads, the connection net having at least two metal strips formed by the same metal layer.  
     
     
         7 . The structure of the contact chain as claimed in  claim 1 , wherein the first conductive type is N type and the second conductive type is P type.  
     
     
         8 . The structure of the contact chain as claimed in  claim 1 , wherein the first conductive type is P type and the second conductive type is N type.