conference report technology
Mantech reflects its roots
Increasing GaAs fab throughout, streamlining carrier mobility measurements on pHEMT production wafers and suggesting new ways to improve the performance of this class of transistor featured in this year’s CS-Mantech. Richard Stevenson reports.
D
uring the middle of the last decade the GaAs- Mantech conference changed its name to
CS-Mantech to reflect the expansion of materials used by III-V chipmakers. Since then presentations at this meeting have covered a wider variety of topics, but conference proceedings are still dominated by papers about the manufacture of GaAs transistors. This year was no different, and the delegates that headed to Portland, Oregon, in mid-May, were fed a diet with a large dollop of GaAs. Here we’ll look at four of those papers: Skyworks Solutions’ account of its fab upgrade to 6-inch; RFMD’s non-destructive method for measuring mobilities and sheet charges in pHEMTs; Hitachi Cable’s study of pHEMT degradation in BiHEMTs; and the development of a high-frequency HEMT, which was led by researchers at the Indian Institute of Technology–Kharagpur.
Boosting fab throughput The first of these papers detailed the 4-inch to 6-inch conversion of Skyworks’ Newbury Park fab, which processes GaAs HBT and BiFET epiwafers into finished product. Glenn Hafer revealed that these changes led to a 61 percent increase in four-inch equivalent throughput, and a 140 percent hike in die production.
Upgrading the fab was not easy, because conversion had to take place in the existing, fully consumed cleanroom space. In addition, full production output had to be maintained throughout the process, along with no drop in the quality of service provided to every customer.
Implementing the fab upgrade involved the introduction of 27 new tools, plus conversion of another 145 from 4-inch to 6-inch, 8 of which had to be relocated. Switching to the larger wafer size also required development of 51 new 6-inch process recipes to new equipment platforms.
Conversion to the 6-inch fab kicked-off with a high-level, top-down plan that identified the critical phases in the project. A ground-level plan followed, which identified every task needed to complete the fab upgrade. This involved input from every engineer responsible for a particular tool and its process. Once this exercise was complete, it appeared that the entire project could take up to three years; the management wanted it rolled out in just two. So to hit the shorter deadline, the project plan was optimized, with more tasks performed in parallel.
To break this large project down into more manageable July 2010
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