INDUSTRY NEWS

Suppliers claim breakthroughs in dielectric materials, copper CMP, and copper metrology

Three major suppliers to the semiconductor industry announced breakthroughs in March in process areas crucial to advanced chipmaking. Two of the advances involve product introductions in the copper market segment. The other has been touted as a major development in low-k dielectric materials.

Dow Chemical claims that a major research breakthrough with its SiLK resin means chipmakers can continue to extend their processes into the sub­ 100-nm device regime. The Michigan-based company says it is the first supplier of low-k dielectric materials to offer an organic material with a dielectric constant of 2.0.

Both KLA-Tencor and Cabot Microelectronics of Aurora, IL, announced product introductions with implications for copper process technology. KLA-Tencor took the wraps off the industry's first in situ film-thickness and end-point control system for copper metal polishing, while Cabot unveiled a CMP slurry for copper processes.

Dow's Mark McClear asserts that the advance in the SiLK resin's capability will extend across the next several technology nodes. "Chipmakers are already looking to low-k materials for 100-nm device production because extendability is a decisive factor in their material choice at 130 nm," says McClear, business director of Dow Chemical's semiconductor fab materials unit. The company is making the resin available for testing during the second quarter of 2001, and Dow says it will begin production of the material later this year.

A key to the SiLK advance is the researchers' ability to lower the material's density by introducing porosity. The reduction is the only way to lower dielectric values below 2.5, according to McClear. "For integration reasons, pore size needs to be less than 20 nm for 100-nm technology, or about one-fifth the smallest printed feature."

Another key element in the breakthrough is the creation of a closed-pore system, McClear points out. Uniform distribution of the pores through the dielectric material is needed at a volume low enough to meet required mechanical properties. It's necessary to add more than 60% porosity to most CVD inorganic or spin-on films in order to bring the k value down to 2.0, he notes. "At 60% pores, these materials are difficult to integrate from a mechanical toughness standpoint."

McClear claims the new resin's mechanical properties have performed well during evaluations that included polishing of bulk films. The material showed a robustness two to three times stronger than competing materials with a comparable dielectric constant, he asserts.

In the copper area, KLA-Tencor of San Jose says the combination of optical and eddy-current technologies in its new Precice measurement system overcomes the limits imposed by optical-only in situ metrology tools. Because the system automatically compensates for variations in wafers during CMP, chipmakers will be able to improve copper interconnect processing steps, according to the tool manufacturer.

The system "dynamically adjusts for film variations to ensure proper control of the CMP process at all times," claims Pete Nunan, vice president of technology development. "This solution minimizes the yield-limiting defects such as dishing, erosion, and metal residuals that occur from over- or underpolishing wafers."

Embedded in situ sensors measure film thickness and uniformity. The Precice marks the first time that KLA-Tencor has embedded metrology capabilities in a tool. Prior to the introduction, the vendor focused on making stand-alone inspection and metrology systems.

Cabot contributed to the industry's trend toward copper processes with the introduction of iCue slurries. The line of slurries was developed for polishing both the bulk copper and barrier layer films deposited during copper interconnect processes. The vendor says all copper and barrier iCue slurries are compatible with each other, simplifying integration and allowing chipmakers to use the same platen polisher.

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