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Method for generating ultra-thin metal transitional films using wet-chemical coupling

IP.com Disclosure Number: IPCOM000132121D
Publication Date: 2005-Dec-01
Document File: 6 page(s) / 26K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for generating ultra-thin metal transitional films using wet-chemical coupling. Benefits include improved functionality, improved performance, improved reliability, and improved cost effectiveness.

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Method for generating ultra-thin metal transitional films using wet-chemical coupling

Disclosed is a method for generating ultra-thin metal transitional films using wet-chemical coupling. Benefits include improved functionality, improved performance, improved reliability, and improved cost effectiveness.

Background

              The conventional solution for generating ultra-thin metal transitional films deposits barrier materials using a plasma vapor deposition (PVD) process in dual-damascene interconnects. Because PVD is a line-of-sight process, a natural overhang of the barrier (and PVD seed) develops. As device dimensions shrink, the overhang inhabits a higher proportion of the trench/via volume, making Cu-fill processes more difficult (see Figure 1).

              Conventionally, materials are typically bound to the substrate surface by secondary and weaker forces, including static electricity and Van der Waals molecular attraction. As a result, several reliability issues can occur, including the following:

•             Thin transition metal film deposition via physical or chemical methods

•             Heterogeneous film adhesion

•             Minimum thickness metal transitional (Mt) films

•             Low resistivity (extreme thin film)

•             Plating uniformity (nonconformal trench/overhang/step coverage associated with a chemical vapor deposition (CVD) or plasma vapor deposition (PVD) metal seed (such as Cu), wetting, or barrier-film deposition

•             Agglomeration (disallowed by covalent coupling to substrate and cross-linking)

•             Seed-film coverage or passivation of SiO2 or carbon-doped oxide (CDO)

•             Nucleation promotion for barrier and seed materials

              To mitigate the issues, the conventional solution includes the following techniques:

•             Deposition of a PVD Ta(N) barrier followed by in-place PVD Cu seed deposition

•             Cu that employs halides and/or polymers that lead to impurities and increased resistance

•             Industrially adopted film deposition techniques, such as PVD and CVD that are often nonconformal

•             Atomic layer deposition (ALD) film-deposition techniques, which typically generate impure and high resistance films with slow growth

•             Direct plating of Cu on highly resistive barriers, such as TaN or TiNSi, or etching native metal oxide, such as Ta2O5, using an acidic solution prior to Cu plating

•             Use of an activation chemistry, such as palladium attached to a polymer self-assembled monolayer, to chemically catalyze the resistive barrier surface and enable electroless Cu plating followed by a bulk electroplating fill

      Highly resistive barriers typically result in poor within-wafer uniformity and Cu coverage while the presence of metal oxides results in poor Cu/barrier adhesion.

              The conventional CVD, PVD, ALD, and electrochemical techniques control the deposition of material by surface roughness and/or diffusion...