[labnetwork] foreline and exhaust line maintenance

[Bob Hamilton]

Iulian,

The UC Berkeley Microlab's biggest concern has been soaking 
the silicon nitride forelines in water, overnight. If left 
open to air they will corrode. In water this does not happen 
to the same degree. The ammonium chloride resides swell and 
become easy to remove after a 12-24 hour soak. There is 
likely some trapped DCS in these films which water helps 
mitigate. One can see some bubbles emanating from the 
coating when first immersed so this should be done in an 
exhausted enclosure. In the past, we have made long troughs 
by buying PVC piping, putting on end-caps on and slicing it 
in half, longitudinally on a band saw; however, our current 
forelines do not exceed a few feet in length.

Poly generates red powder which we assume is silicon and 
phosphorus compounds. Scratching this material generates 
some sparks, even after long exposure to air; however, I 
have not seen it be a particular problem. It wipes off 
easily with towels. One gets a whiff of Eau D'phosphine 
doing this work. We can set off our hand-held hydride 
detector, above its 1 ppm threshold when sampling forelines 
so you may want a respirator for the short time it takes to 
move these parts. A rubber glove over each end serves well.

I would not dispose of any LTO residues in a trash container 
unless it is fire-proof. I prefer to wet the towels to 
assure they are reacted and not flammable.

The LTO exhaust deposition seems to have no particulary 
issues except some residual PH3 odor.

UC Berkeley does not use TEOS in lpcvd so I do not have 
experience with this material.

Bob Hamilton


On 9/15/2010 5:52 AM, Iulian Codreanu wrote:
> Good Morning.
>
> I understand that the foreline and pump exhaust line on
> tools using particular precursors (e.g. silane) need to be
> made of short (4-5 ft) sections so that they can be immersed
> in a liquid bath to neutralize the exhaust byproducts that
> accumulate over time.
>
> If you do something similar in your fab could you please
> share your experience with us?
>
> Thank you very much.
>
> Iulian

-- 
Robert Hamilton
UC Berkeley Marvell Nanolab
Equipment Manager
Rm 520 Sutardja Dia Hall
Berkeley, CA 94720-1764
bob at eecs.berkeley.edu (preferred)
510-642-2716
510-642-2916 (Fax)
510-325-7557 (Personal Cell)