Browse Prior Art Database

Diffusion Barriers for Cu

IP.com Disclosure Number: IPCOM000061686D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Hu, CK: AUTHOR [+2]

Abstract

Ta, TiN and Si3N4 are found to be good diffusion barriers to Cu without degradation of its resistance. Combinations of one or two of these materials can be deposited to encase Cu lines using processes compatible with VLSI processing. Cu is a material of high potential for VLSI metallizations due to its better conductivity, better electromigration resistance, and smaller power consumption than Al. As the device dimensions are continually scaling down, the switching speed in the chip is mainly limited by the RC time delay which is associated with interconnections. For these reasons, the use of Cu metallizations in VLSI becomes more important than before. Cu is a fast diffuser into SiO2 and Si. In order to prevent Cu contamination of the devices, both insulator and metal dif fusion barriers for Cu must be found.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 74% of the total text.

Page 1 of 2

Diffusion Barriers for Cu

Ta, TiN and Si3N4 are found to be good diffusion barriers to Cu without degradation of its resistance. Combinations of one or two of these materials can be deposited to encase Cu lines using processes compatible with VLSI processing. Cu is a material of high potential for VLSI metallizations due to its better conductivity, better electromigration resistance, and smaller power consumption than Al. As the device dimensions are continually scaling down, the switching speed in the chip is mainly limited by the RC time delay which is associated with interconnections. For these reasons, the use of Cu metallizations in VLSI becomes more important than before. Cu is a fast diffuser into SiO2 and Si. In order to prevent Cu contamination of the devices, both insulator and metal dif fusion barriers for Cu must be found. Proposed here are Si3N4 as an insulator diffusion barrier, and Ta and TiN as metal diffusion barriers. TiN is well known as a good diffusion barrier to Cu. Experimental results have also shown that TiN is indeed a good barrier to Cu. In addition to that, Ta is found to be an excellent barrier for Cu. The figure shows a Rutherford backscattering profile (RBS)) of Cu/Ta on oxidized silicon wafer annealing at up to 750OEC. A layer of Ta (300~) can prevent Cu diffusion in Ta at 750OEC for at least 2.5 hours. The out diffusion of Ta through Cu was found to have an activation energy of 1.1 eV. The Ta concentration in Cu grains was undetec...