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To: Sherman Chen who wrote (110)	8/16/1999 6:22:00 AM
From: Duker	Read Replies (1) \| Respond to of 1929

Batch v. Single Wafer: Take-aways from the meeting. It is not that Batch becomes less important below .18M ... it is that it becomes 'less good' ... Here are some of the areas where Batch has problems (as described by a NON-Engineer!): Particulate control and metallic contamination elimination. Batch systems operate with a massive (and, even more massive with 300mm) wheel that spins inside the unit, holding the wafers and passing them through the beam. With each pass, the beam also passes over the spaces of the wheel between the wafers ... thus providing an opportunity to dislodge particles from the surface of the wheel. Moreover, the wheel itself is a large mechanical thing with parts that generate friction and dust. Kinda have to see one. Mechanical stress reduction requirements. There is some evidence that, at smaller device geometries, the centrifugal force of the spinning (up to 1800RPM!) batch wheel alone causes damage to the device structure itself. High Angle Tilt. Batch can't perform High Angle Tilt implants. You can not move that big wheel +/- 60 degrees like you can do with a single wafer machine. The applications for High Angle Tilt applications are incredible. Using it on the Source/Drain Extension can help manufacturers reduce the length fo the channel (thus, increasing speed) ... L-effective of a .18M device can actually become .15M or even .13M. High Tilt can also save 2-3 process steps ... one of which is lithography (bottleneck with very expensive equipment) ... this can save an average of $25-50/wafer ... a BIG deal to the memory guys who are getting $6 per device ... There is a more fundamental physical property that I can not explain in words, but it has to do with how the wafers in a batch system are held in place on the wheel ... the wheel is (has to be) slightly concave (<4 degrees) ... this very tiny angle holds the wafers down ... but, also changes the angle at which the beam hits across the wafer ... not a big deal at .35M ... but a very big deal at .18M ... Along the same lines, there is a 'twist' of up to 30 degrees as wafers (300mm) pass across the fixed beam in a spinning batch system ... this creates a similar problem. Also, Batch systems require dummies -- wafers used to fill the empty spaces in the batch wheel. Typically, there are 13 spots for the wafers on a wheel ... but, people run batches of 10 ... so, there are three dummies put in place that are trashed after each implant. I was sort of skeptical going in. Now I am a full convert. --Duker