henry@utzoo.uucp (Henry Spencer) (10/29/89)
In article <261500011@S41.Prime.COM> CIS@S41.Prime.COM writes: >It would be interesting to see the follow-up paper on how the fab process was >improved for 64K RAMs. I got mail from a friend about this; I probably shouldn't identify him since I haven't checked with him on it. His comment was that the paper's main mistake was to assume that full-wafer mask-in-contact-with-chip technology was the limits of optical processing. In fact, the way most chip companies solved the problem was to go to wafer steppers (as I understand it, these are projection rather than contact systems, and expose only part of the wafer at a time), which bypassed the limitations of the full-wafer contact process. This *did* take time and money, so he wasn't entirely wrong in predicting some delay. As it turned out, eventually a full-wafer projection system showed up which was just barely good enough for 64K RAMs, so everybody switched to using that and put their steppers to work on more advanced projects. Most companies also did redesign the memory cell, shooting down another assumption in the paper. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu