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To: Bill Jackson who wrote (73776)	3/7/2002 10:41:17 AM
From: semiconeng	Read Replies (1) \| Respond to of 275872

Semi, With feature shrink do they make more images on the same sized mask set so it takes the same number of exposure for each step? or does the mask also get smaller so there are more step and repeat ops to fill up a wafer with images? Bill Hummm.... Realizing that I haven't worked in Litho for the last 6 years, coincidentally, I did work on one of the first "Step and Scan" Litho Steppers when that technology was revolutionary instead of Common like it is now. To be brief, the old way to shoot die patterns was to step to the die location, and shoot the entire die at once through the stationary mask, then step to the next die. The problem is, that your using the entire surface area of the lens, as you get to the outer edges of the lens (and the die), the resolution decreases. BAD for maintaining profiles. In Step/Scan, the Reticle and Wafer both move in sync across a stationary lens and light source. Step to the die, scan across the die, step to the next die. Since you are exposing only a small portion of the die at any one time, you can shoot a smaller area of the die, and only use the center portion of the lens. The tradeoff is, that Step/Scan has much lower throughput. So, just from my observations (No Time Study Data), it's my IMPRESSION, that smaller die size would result in less scanning time per die, AND an increased number of steps per wafer due to the increased number of die. Since I've seen that the tools step much faster than they scan, I would GUESS that the reduction in scanning time per die would increase the throughput, negated slightly by the increased number of steppings, overall resulting in some amount of increasd throughput. WAG of course... Or maybe actually WEG (Wild Educated Guess). :-) Semi