Page 40 - Semiconductor Manufacturing Handbook

Geng(SMH)_CH04.qxd 04/04/2005 19:36 Page 4.3

COPPER, LOW-k DIELECTRICS, AND THEIR RELIABILITY

COPPER, LOW-κ DIELECTRICS, AND THEIR RELIABILITY 4.3

Resistivity (µΩ-cm)
8

6 5.6 5.5

4
2.7
2.4
2 1.6 1.7

0
Al Ag Au Cu Mo W
FIGURE 4.2 Resistivity of different metallizations.

Here one can see the higher diffusivity of copper compared to aluminum. It is also susceptible to
corrosion. Hence interconnects have to be encapsulated by diffusion barriers on the base and side
walls along with capping layers on top. Different materials have been researched as potential diffusion
barriers for copper metallization. 4,7,8,9 Typically refractory metal alloys have proven to be good barriers
against copper diffusion. Materials like Ta/TaN, TiN, TiSiN, and TiW can be used for this purpose.
Certain qualities are desired of a good liner material. Besides being a diffusion barrier, it should have

Elch slop
(silicon nitride)

(a)

Via Line
Insulator
Via
(b) (c)

Barrier

Seed layer

(d) Plated metal (e)
FIGURE 4.3 Process steps for the fabrication of a via and line level by the
dual-damascene approach. 2

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.