Ebara Technologies of Sacramento, CA, has joined the SiLKnet Alliance in order to help develop CMP processes on Ebara's Frex tool platforms. Ebara becomes the 25th company to join the alliance, established by Dow Chemical to focus on integrating low-k materials in copper interconnects. Dow Chemical manufactures SiLK dielectric films. Alliance members have been developing CMP tools and slurries that can use low-k films like SiLK resin without damaging them.

Member firms are concentrating on CMP-related issues such as chemical compatibility, mechanical compatibility, overpolishing, underpolishing, erosion, and defectivity, Ebara says. The company specializes in vacuum and wafer process equipment, including CMP polishers and dry mechanical pumps for deposition.

Low-k will be ready

Low-k materials will be available in time to meet chipmakers' manufacturing timetables in 2003, asserts International Sematech's interconnect director. Navjot Chhabra says the consortium's engineers have worked with approximately 20 suppliers and universities to develop a material with the required dielectric constant.

"I strongly believe that we will have 2.2-k materials that manufacturers can accept—and can actually start early integration into devices with—by the end of the year," says Chhabra. Member companies are already testing some of the materials.

Engineers overcame many obstacles to reach this point, Chhabra notes. Low-k materials with dielectric constants between 2.2 and 2.7 were mentioned in the 1999 version of the International Technology Roadmap for Semiconductors, the director points out. That deadline was extended to 2007 because engineers could not find a way to make the materials compatible with other processes.

"Integration turned out to be the critical issue," Chhabra says. "How do you take a low-k material and make sure that it fits into the whole process scheme?"

The interconnect director says issues such as mechanical strength, chemical stability, and interaction with barrier materials delayed the developmental process. "It wasn't just a matter of fixing one thing. We, along with the suppliers and universities, had to fix a gamut of things to make it work."

The use of copper circuits will ultimately force a search for more-radical solutions to the electrical resistivity limits looming at the 65- and 45-nm technology nodes, Chhabra says. Two bridge technologies are insulating air gaps and three-dimensional packaging.