Problem p5000etch SNF 2012-11-27 19:03:34: Ch.B OXIDE ISO etch acts strangely

earlier in the day, it etches about 500A oxide in 13 sec. When I tried it again just now (after Cesar serviced the machine--but he shouldn't have touched ch.B anyway), it's not etching at all but rather depositing a couple hundred angstroms of something (i.e. the apparent oxide thickness AFTER the etch looks higher than BEFORE the etch by about 200A). Very strange.... Also, the pressure isn't getting up to setpoint in the set-up stage (stays around 20mT); have to wait 15 sec or so in the main etch for the pressure to build up to 250mT and THEN plasma comes on.