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Ultra-thin diffusion barrier formation

IP.com Disclosure Number: IPCOM000240433D
Publication Date: 2015-Jan-29
Document File: 4 page(s) / 45K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is structure for a barrier layer and a formation that enables the perfect diffusion barrier with the minimum occupation of the space leading the low line resistance, high reliability, small dimensioned Cu interconnect. The structure has only Cobalt Nitrogen (CoN) layer, which works both as the diffusion barrier and the wetting layer.

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Ultra-thin diffusion barrier formation

As the device dimension shrinks, the interconnect also shrinks, causing a high line resistance (R) problem which delays the circuit operation speed. The line width shrinkage is the major reason for the line R increase. Copper (Cu) interconnects require the diffusion barrier layer, which prevents the Cu from diffusing out to dielectrics and prevents oxygen from intruding into Cu from the dielectric area. Cu diffusion into dielectrics causes the line-to-line leakage and malfunction of the circuits. Oxygen diffusion into Cu causes oxidation of Cu, resulting in the electromigration reliability problem. Since the Cu line width has decreased, the volume of Cu becomes smaller.

The common approach to maximize the volume of Cu is to reduce the thickness of the diffusion barrier layer. However, thinner diffusion barriers are apt to have defects from which Cu and Oxygen (O2) diffuse and cause reliability and circuit malfunction problems. In addition, thinner barrier layers are not likely to work properly as diffusion barriers because of oxidation with such barrier materials.

Another problem in fine dimensioned Cu interconnects is the increasing difficulty in filling the trench via gaps with Cu. Such small dimensions of trench/via in the damascene structures can be filled using a wetting layer such as Ruthenium (Ru) and Cobalt (Co). On such wetting layers, Cu atoms can conformally stick, which makes it possible for plating or Physical Vapor Deposits (PVD) of Cu to fill the gap on top of the wetting layers. However, since the Cu volume needs to be maximized to minimize the line resistance, such an extra layer further increases the line resistance by occupying the space with the wetting layer itself.

The solution is a novel structure for the barrier layer and a formation that enables the perfect diffusion barrier with the minimum occupation of the space leading the low line resistance, high reliability, small-dimensioned Cu interconnect. The structure has only Cobalt Nitrogen (CoN) layer, which works...