Yakov RE: "The author suggests that one could buy an i-line stepper, then retrofit it to DUV. I was under impression that this wouldn't work??"
The author you refer to wrote this...
"I know 3 major providers of i-line steppers have stated that their new DUV systems are based on the existing i-line equipment platform such that an almost seamless production transition (operator training) could be accomplished to DUV. "
That much is true. Compatability in terms of alignment systems,
software, interface hardware etc. is being kept the same from i-line to DUV. That helps out the semi companies enormously because, from the operators perspective, the 2 pieces of equipment are identical.
However, he also wrote...
"Most of the new systems bought will be retrofittable to DUV down the road."
I have touched on this topic before. I still believe that that statement is absolutely false, at least my interpretation of what he's saying. "Upgrading" an i-line stepper to a DUV stepper is, for all practical purposes, impossible. You would first need to "upgrade" the illuminator module. That is the portion of the stepper that includes th Hg lamp or the excimer laser and the condenser optics. Operating
at a different wavelength would require total replacement of those optics. Then, the real trouble begins. From the illuminator, the
light travels through the reticle and into the projection optics.
A projection lens costs about one million dollars. Even if you ignore the cost, the difficulty of the task of replacing all these elements makes it beyond the capability of any field service engineer I've ever met. It's a high precision job that should be done by factory personell.
You can't go from 365nm light to 248nm light illumination with an upgrade. If you were to change the wavelength of illumination light by even a nanometer you would need a whole new set of optics. Unless you don't mind printing out of focus, distorted images.
That's my take on things.
James Word |
