| 1. | Q. |
Can I run CHARM®-2 wafers through a plasma etcher without seriously damaging them? |
| A. |
Yes, if you keep the etching cycle short. CHARM®-2 sensors respond very rapidly, so you do not need to expose CHARM®-2 wafers to the complete etching cycle in order to test the etching process for wafer charging problems. Since only a very short exposure to the live plasma is needed, there will be at most only very minor wear to the wafer. The wafer will still yield valid wafer-charging test results and can be reused a number of times. For more information, please contact WCM.
|
| 2. | Q. |
Which plasma etching processes tend to cause wafer charging problems? |
| A. |
Poly, metal, and oxide etching can all cause charging problems.
|
| 3. | Q. |
Does increasing RF power in plasma etching make the charging problem worse? |
| A. |
It can, but experimental evidence supports the theory that plasma nonuniformity, not RF power, is the
main factor causing wafer charging in plasma etch processes.
|
| 4. | Q. |
Does high DC bias in plasma etching cause wafer charging problems? |
| A. |
Not necessarily. Wafer charging depends on the electrical potential developed between the wafer surface and the substrate -- whereas, in plasma etching, most of the so-called "DC bias" is dropped across the plasma sheath (not the wafer).
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| 5. | Q. |
Are downstream strippers less prone to cause wafer charging than conventional dry resist
strippers? |
| A. |
We can not generalize. In our experience, downstream strippers seem to produce
very little wafer charging -- however, with the right process conditions, conventional strippers
can also be operated with safe levels of wafer charging.
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| 6. | Q. |
Does via etching cause much wafer charging? |
| A. |
In some cases, yes. For more information, see the following references:
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| 7. | Q. |
Does metal etching cause much wafer charging? |
| A. |
In some cases, yes. For more information, see the following reference:
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Wafer Charging Monitors, Inc.