Bob,
Re: it would require half the lithography tools(assuming the time to expose a wafer is much less than 2x the 200mm tool).
I believe that assumption is absolutely false.
For example, any particular stepper will take more than twice as much time to process the surface of a 300mm wafer as it takes that exact same stepper to process the surface of a 200mm wafer. (if there was a stepper that could process both 200mm and 300mm wafers. To my knowledge, such a tool doesn't yet exist).
A stepper steps to each field, does the alignment, then exposes the field. A Step and Scan tool does everything that a stepper does. In addition, it scans through the field to be exposed. Regardless of whether the fab uses steppers or scanners, the same tool will take more than twice as long to process the larger wafer.
Obviously, flying to New York from San Francisco takes longer than flying from Chicago to New York(all else equal). But I'd freely admit that someone could fly from San Francisco to New York much faster than I could Walk from Albany to New York. It's completely irrelevant but true.
If one changes the "ceteris paribus" and substitutes a rocket for a biplane, the rules change.
Regards,
Ian. |
