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The structure that connects a transistor with the first layer of copper interconnects.


The contact is a tiny and distinct structure, which connects the transistor with the first layer of copper interconnects in a device. A chip can have billions of contacts.

Contacts are three-dimensional structures with a small gap, which is filled with tungsten, a conductive material. The tungsten structure, called a tungsten plug, is sandwiched between a liner material (titanium) and a barrier layer (titanium nitride). The entire structure is called a contact.

The problem is that the contacts are becoming smaller at each node, which in turn is leading to unwanted contact resistance in devices. Resistance represents the difficulty of a current passing through a conductor.

Historically, the contact doesn’t get that much attention, but the industry is beginning to worry about the resistance in the contacts, or contact resistance, in leading-edge chip designs. Until now the semiconductor industry has been able to scale the contact and its associated metallization scheme, which is based on tungsten. But at some point, there are fears that tungsten will run out of steam, prompting the industry to explore new and future metallization schemes, including those based on cobalt.

Contacts are manufactured in the back-end-of-line (BEOL) stage of manufacturing in the fab.

Fig. 2: Interconnect, contact, and transistor at various nodes. Source: Applied Materials.


Variation At 10/7nm


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