Method of fabricating polysilicon electromigration sensor which can detect and monitor electromigration in composite metal lines on integrated circuit structures

A method of fabricating an electromigration sensor structure comprising:

• providing a semiconductor substrate;
• forming a first insulating layer of silicon oxide over said semiconductor substrate;
• depositing a layer of intrinsic polysilicon over said first insulating layer;
• depositing a first layer of photoresist over said polysilicon layer;
• patterning said first layer of photoresist to form a photoresist stripe;
• implanting dopant atoms into the polysilicon adjacent to said photoresist stripe;
• stripping said first photoresist layer;
• depositing a second layer of photoresist over said polysilicon layer;
• patterning said second layer of photoresist to form a wider stripe of photoresist which straddles the position of the first photoresist stripe such that the second photoresist stripe covers a portion of the ion implanted polysilicon on each side of the intrinsic section defined by said first photoresist layer;
• etching said polysilicon layer utilizing an anisotropic etching technique with end point detect capability thereby forming a polysilicon stripe having an intrinsic center section and heavily doped side sections;
• stripping said second photoresist layer;
• depositing a second insulating layer over said semiconductor substrate;
• depositing a third photoresist layer over said second insulating layer;
• patterning said third photoresist layer to expose said second insulating layer over said heavily doped side sections;
• etching said second insulating layer with an anisotropic etching technique with end point detect capability to expose said heavily doped side sections of said polysilicon stripe;
• stripping said third photoresist layer;
• depositing a metallization layer over the surface of said semiconductor substrate;
• depositing a fourth layer of photoresist over said metallization layer and patterning said photoresist to expose 1) connections from the heavily doped edges of the polysilicon stripe to probe contact pads and 2) a metal stripe over the intrinsic section of the polysilicon stripe with connections from each end of said metal stripe to probe contact pads;
• etching said metallization layer in the areas exposed by said fourth layer of photoresist using an anisotropic etching technique with end point detect capability;
• and
• stripping said fourth photoresist layer.