INDUSTRY NEWS

Finnish optoelectronics firm eyes breakthrough with spin-on material

A Finnish firm with expertise in optoelectronic waveguide technology has set its sights on one of the semiconductor industry's hottest market segments. Silecs of Espoo, Finland, has introduced a line of "nonporous" materials with dielectric constants in the range of 3.0 to 2.2. The low-porosity property puts the supplier in a position to claim a solution to the much-discussed problems of integrating the intermetallic materials in the fab IC process.

"The original technology came out of the waveguide area," says Robert Donia, vice president of business development, during a July visit to Semicon West in San Francisco. "We said, 'Let's see what we can do with that.'"

FINNISH LINE: A technician at VTT Microelectronics National Laboratories in Finland processes Silecs's ultra-low-k material.

What Silecs has done is develop "tunable" spin-on dielectric films with a total porosity of 8% to 12%. Effectively nonporous, the average pore size measures ≤1 nm. The company says the organosiloxane-based films are robust enough for use in etch, cleaning, and CMP steps.

Aside from the lack of porosity, the films "had to look like CVD materials" with "a porosity of CVD TEOS," Donia says. Instead of "blending" the components by "putting air with organo material, we build the properties we want." The technique "allows us to essentially 'tune in' different properties."

The organic-based films avoid the integration problem caused by a mismatch between the coefficient of thermal expansion (CTE) of the dielectric and interconnect metals. The films' CTE is 15–20 ppm/°C, close to that of aluminum and copper. The materials are well suited for subtractive aluminum processing because of their good planarization and gap-fill capabilities, the company claims.

FILM CLASS: This chart shows a "dense" 2.4-k dielectric film with a porosity favorable to that of CVD TEOS, Silecs says. CVD TEOS has a 7­8% porosity but a dielectric constant of 4.2, according to the start-up. SOURCE: MEASUREMENTS BY XPEQT AT IMEC

Over the past five to six months, Silecs and Cypress Semiconductor in San Jose have been developing a version of the organosiloxane films with a k value of 2.8 for SRAM production. In a cowritten white paper, Silecs says its first-generation material meets rigorous requirements for device manufacturing, including batch-to-batch reproducibility, thermal stability, mechanical properties, and planarization coverage.

According to the partners, the low-k material performs as well as standard PECVD oxide films in both via resistance and CMP. Twenty small-scale batches were made at the company's R&D facilities in Finland. The goal is to develop a next-generation film with a dielectric constant lower than 2.4 at the same film density, and Silecs hopes to bring a film to market in the first quarter of 2004.

Privately owned and founded in 2000, Silecs is backed by the investment firms of Kleiner, Perkins, Caufield & Byers and Viventures Partners. The start-up also has the backing of organizations affiliated with the Finnish government. With facilities in San Jose, Silecs also has access to a semiconductor fab at VTT Microelectronics Laboratories in Finland. In September the company, which has 25 patents pending, plans to open a second alpha site with a European partner.

Donia mentions that Silecs took note of the "strong players" and the very competitive market for dielectric materials. Not the least of the company's concerns is the nature of the challenge. "It's probably the most contentious material to be integrated into semiconductors. Ever," says the executive.