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A method for an ALD barrier using a diffusion-blocking boundary layer

IP.com Disclosure Number: IPCOM000131679D
Publication Date: 2005-Nov-14
Document File: 4 page(s) / 62K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an atomic-layer deposition (ALD) barrier using a diffusion-blocking boundary layer. Benefits include improved functionality and improved performance.

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A method for an ALD barrier using a diffusion-blocking boundary layer

Disclosed is a method for an atomic-layer deposition (ALD) barrier using a diffusion-blocking boundary layer. Benefits include improved functionality and improved performance.

Background

              Ultra-thin barriers are not thick enough to prevent Cu diffusion from one metal layer through a via to an underlying or overlying metal layer during electromigration (EM) stress. As a result, Cu atoms are transported in the direction of current flow. Cu atoms are depleted in a narrow line upstream and accumulated in a wider line downstream. One solution to this problem is the physical vapor deposition (PVD) of a flash layer after ALD barrier deposition. This metal layer functions as a blocking boundary in the via bottom. However, the layer is also deposited on the trench bottom, resulting in an increase in line resistance. The additional resistance is expected to become increasingly noticeable as line widths are shrunk in successive technology generations (see Figure 1).

              Conventionally, the diffusion problem is not solved for ALD barriers. The deposition of a flash layer during barrier/seed deposition leaves as much or more of the flash material on the trench bottom as in the via, increasing line resistance.

General description

              The disclosed method deposits a thin metal film layer to block EM to enable the integration of an ultra-thin Cu diffusion barrier, such as an ALD barrier. The metal film is deposited after a via clean process step.

 

              The key elements of the disclosed method include:

•             Use of a highly directional thin-film deposition method, such as advanced PVD, or a selectively deposited thin film after via clean

•             Deposition of an ultra-thin barrier layer after trench patterning

•             Use of a blocking boundary for Cu diffusion during subsequent EM stress

•             Deposition after via clean of a material that is resistant to oxidation from wet cleans (such as a noble metal or a carbided/nitrided material)

•             Removal during a preclean step before barrier deposition of the part of the deposited thin film that may be damaged (such as partially oxidized)

•             Sputter deposition of a material in the wafer field as a stopping layer for Cu chemical/mechanical planarization (CMP) when an ultra-thin barrier is used

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing an ALD barrier using  diffusion-blocking boundary layer

•             Improved functionality due to providing a Cu CMP stopping layer when an ultra-thin ALD or a chemical vapor deposition (CVD) barrier is used
•             Improved performance due to preventing Cu migration from one metal layer during EM stress

•             Improved performance due to preventing increased line resistance because of ALD barrier layer deposition

•             Improved performance...