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CHEMICAL MECHANICAL POLISHING

17.10 WAFER PROCESSING

as a carrier. Carriers for these systems are, in general, back referencing. A classic rotational CMP
tool is the IPEC (Integrated Process Equipment Corporation)-Westech 372. This single-head system
consisted of a single carrier on a gantry, a 22- to 26-in polishing pad, and a wand holding a 75- to
100-mm diameter TBW Inc. type pad conditioning disk. These tools also look much like first CMP
systems, first offered by Struassbaugh Inc. For basic low-volume CMP work, these tools are quite
effective. They are all “wet in, wet out” (WIWO) in configuration and process a single wafer at a
time. Loading and unloading of wafers is completed with a water jet and track system, and the wafers
remain submerged in the unload station. For basic WCMP and Oxide CMP, these reliable tools work
well and can typically be found in the used equipment market or in R&D labs.

17.5.2 Multihead Rotational CMP Systems
As productivity and defectivity requirements increased, multihead rotational CMP tools were born.
This classification of tools has a wide variety of variants. In general, multihead rotational CMP sys-
tems are developed for high throughput production applications.
High productivity multihead CMP systems can achieve productivities of greater than 40 wafers
per hour (ILD or WCMP). The benchmark multihead, twin platen CMP tool is the Speedfam-IPEC
Auriga system. Evolving from the Speedfam Inc. CMP-V platform, the Auriga is a five-head CMP
tool that uses one main 32 in diameter platen and a secondary smaller platen for post-CMP buffing.
The pad conditioner is a large diamond ring or brush that conditions the pad in between each five-
wafer run. At full bore, the Auriga can process more than forty 200 mm wafers per hour (1 min pol-
ish at 3000 Å/min) in a production environment. Each head is individually controlled to allow for
better process control. Initially a WIWO system, the Auriga evolved into the Auriga C, being the first
multihead tool to offer an integrated wafer cleaning system. The Auriga was the throughput king for
many years, and was mimicked by the three-head Straussbagh Symphony platform. Other two-and
three-head CMP tools, like those offered by Ibarra hit the market later using up the three polishing
platens to increase process flexibility.

17.5.3 Multiplaten CMP Systems
The lack of process flexibility, for example, polishing a lot of 22 wafers versus 25, limited the Auriga
and Symphony platforms to simple high-volume CMP processes. Though fast, the Auriga also had
reliability problems and could not be extended to multistep, multichemistry CMP processes like Cu
CMP. This weakness of multihead single-platen tools allowed multiplaten rotational systems, like
those offered by Peter Wolters, Ibarra of Japan, and Applied Materials Inc., to capture the CMP
equipment market. The best example of a multiplaten CMP carousel tool is the Applied Materials,
Inc. Mirra CMP system (see Fig. 17.4). Initially a WIWO system, the Mirra quickly evolved into a
DIDO system. Using three polishing platens, the Mirra can polish up the three wafers simultaneously

FIGURE 17.4 Applied Materials Mirra CMP tool.
(Courtesy of Applied Materials, Inc.)

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