Paul:
        PSG etch rate in 10:1 HF is depended on how PSG being deposited and any
post deposition densify anneal was carried out. Undensified PSG can have
etch rate 5-10 times higher than that of thermal SiO2. Densified PSG (850C
and up for 30 minutes in O2) has etch rate 1.5-2 times higher usually.
        But any rate is not even near what your 15 seconds. For 1.8um, at least
1-2
minutes is needed to strip all in 10:1 HF for undensified PSG.

Hong Wu

-----Original Message-----
From: mems-talk-bounces+hwu=semicoa.com@memsnet.org
[mailto:mems-talk-bounces+hwu=semicoa.com@memsnet.org]On Behalf Of Paul
Vescovo
Sent: 2004Äê3ÔÂ19ÈÕ 3:11
To: mems-talk@memsnet.org
Subject: [mems-talk] PSG etch rate in HF:H2O


Dear all,

There is a critical flaw on devices I worked out recently.
A possible explanation for it is the complete etching of 1.8um of PSG (6%P)
during a RCA (15s in HF(49%):H2O 1:10 at 20°C).

Is this hypothesis sensible ?

Thank you,


paul


Paul VESCOVO
Laboratoire de Mécanique Appliquée R. Chaléat
24 rue de l'Epitaphe
25000 Besançon
FRANCE
tél : 03 81 66 60 16
fax : 03 81 66 67 00


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