[labnetwork] ALD TEMAHf precursor and pump oil loss

[Mac Hathaway]

Hi Elena,

We have the same tools and process here (Harvard CNS), and your pump/oil 
should be fine.

What is your base pressure (with 20 sccm of N2 flowing)?  It should be 
between 200mT and, say, 500mT.  If it is 600mT or higher, it could well 
be your pump is dying, and in need of a rebuild.  If base pressure is 
suddenly higher than previously, that is particularly suspicious.

The pump oil is probably leaking from a seal, which can be fixed with a 
rebuild.  If the pump runs low on oil, that will effect it's pumping 
ability.  Assuming your exhaust is vented (and well sealed), it is less 
likely that the oil is coming out of the exhaust, (but possible).  See 
if you can tell if the exhaust side of the pump has a lot of oil in it.

At CNS, we used to go through pumps at a rather alarming clip (less than 
6 months between rebuilds), due to the creation of oxide powders in the 
pump oil (excellent grinding slurry).  After we started putting oil mist 
traps on our pumps (as an in-line reaction surface), our pumps starting 
lasting 2 years or more between rebuilds.

What temp are you depositing your HfO2 at?  Below 240C should give more 
consistent results, as above that you start getting close to the 
decomposition temperature of the TDMAHf.  Also, if your pump rate is 
dropping (as evidenced by higher base pressure), you might find your 
wait times between pulses is no longer long enough to keep out of CVD 
mode (just a bit), which can also effect your refractive index.


Mac Hathaway

Mac Hathaway

Senior Process and Systems Engineer

Harvard Center for Nanoscale Systems

11 Oxford St.

Cambridge, MA02138

617-495-9012


On 11/21/2016 11:23 AM, Elena Cianci wrote:
>
> Good day all,
>
>
> We have a Cambridge Nanotech Savannah200, and few days ago we mounted 
> TEMAHf cylinder.
>
> The system is pumped by a rotary vane pump Pascal2021 with Fomblin 
> oil. After few processes using TEMAHf and ozone, a large oil loss has 
> been observed, with oil present in the vessel under the pump.
>
> Furthermore, HfO2 films resulted with lower refractive index than 
> expected.
>
>
> Are there incompatibility issues of precursors like TEMAHf with the 
> pump in use?
>
> or are there other issues that we should take into account to prevent 
> such problem?
>
>
> We really approeciate any suggestions you might have
>
> Elena Cianci
>
>
>
> --------------------------------------
>
> Elena Cianci, PhD
> Research associate
> CNR-IMM, Unità di Agrate Brianza
> via C. Olivetti 2
> 20864 Agrate Brianza (MB), Italy
>
>
>
>
>
>
>
>
>
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