PSG deposition problems.

[Harshal Surangalikar]

hello all,

i wanted to know if anyone has had a problem with
deposition in the Tylanbpsg furnace lately. i have
been  using PSG400 recipe to put down a 2 um layer.
but yesterday as i was trying to put down the layer in
two parts (for better uniformity), the furnace failed
the leak check on every occassion and i had to re-run
the process. also the process pressure was unusually
high (~610)and that has affected the dep rate. 

i wanted to know if anybody has had similar problems
and the dep rates that they observed. i observed dep
rates of 180 A/min  for both 8% and 4% PSG (which is
odd), down from ~240 A/min i have measured earlier for
8% PSG.

also, after the release etch/removal of the PSG layers
lately, i am seeing a dirty carbon/soot residue at the
site of PSG layer. as i am trying to understand why
this layer is seen, i wanted to know if anybody is
having similar "contamination" issues with regards to
etch chemicals used, or a bad furnace run where
hydrocarbon contamination could have caused a
contaminated PSG layer to be deposited. contamination
can also be caused while cleaning and wafer handling
on my part, but as i try to eliminate the possible
reasons, i would like to check if similar observations
have been made.

thank you and any and all inputs will be very helpful.

best,
harshal.