Hello,

that depends on the passivation cycle duration. The deposition rate is
roughly about 30 nm/min (for a CHF3/CH4 plasma, depend. on process
conditions). Dauksher et al. report a depo. rate of 120 nm/min for a C4F8
plasma (W.J. Dauksher et al., J. Microelctronic Engineering 57-58, pp
607-612 (2001) ).
The polymer at the bottom gets completely removed during the etching cycle,
while the film at the sidewall survives the etching cycle, although gets
etched/sputtered at low rate. Therefore, the film thickness at the sidewalls
accumulates during the various passivation cycles. A natural stop for the
cumulative film thickness growth at the sidewalls is the undercutting depth:
If the film is as thick as the size of the scallopes or ripples, it's no
longer shadowed by the mask, hence subject of ion bombardement resulting in
fast sputtering rate.
In general, the film thickness may be between a few 10 nm up to ~100 nm,
depending on your process conditions. The size of undercutting or of the
scallopes/ripples can be considered as an upper limit.

In the rare case that the deposition layer is thick enough (long passivation
cycle duration), you can measure by SEM'ing the cross section of a profile.

Best regards

Burkhard Volland

-----Ursprüngliche Nachricht-----
Von: Shawn Zhang 
An: [email protected] 
Datum: Montag, 31. Mai 2004 19:46
Betreff: [mems-talk] Passivation layer thickness in DRIE


>Dear Sir or Madam,
>I want to know the general passivation layer (C4F8) thickness in DRIE. Is
it several hundreds nanometer thick? Could you recommend the way to mesure
the passivation layer thickness? Thank you very much for your help.
>Regards,
>Shawn
>_______________________________________________
>[email protected] mailing list: to unsubscribe or change your list
>options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
>Hosted by the MEMS Exchange, providers of MEMS processing services.
>Visit us at http://www.memsnet.org/
>