1.  Field of the Invention
This invention relates to a substrate processing apparatus and, more particularly, to a substrate transport with substrate holders each capable of transporting more than one substrate at the same time. 
2.  Prior Art
Mattson Technology has a system known as its ASPEN system that moves two semi-conductor wafers into and out of a process chamber at the same time.  Batch systems, single wafer systems and cluster tool systems are also known in the prior art.  U.S. Pat.  No.  4,951,601 discloses a substrate processing apparatus with multiple processing chambers and a substrate transport apparatus.  U.S. Pat.  No.  5,180,276 discloses a substrate transport apparatus with two substrate holders.  U.S. Pat.  No.  5,270,600 discloses a coaxial drive shaft assembly of a substrate transport apparatus.  U.S. Pat.  No.  4,094,722 discloses a rotatable palette that holds four wafers.  U.S. Pat.  No.  4,381,965 discloses a multi-planar electrode plasma etcher.  U.S. Pat.  No.  4,675,096 discloses a take-in-and-out chamber with side-by-side take-in and take-out positions.  Other related art include the following:
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