Chongfei Shen:

I have used rates in excess of 10Å/sec successfully for both Ti and
Al, so I think your rates are ok.  Please describe the dense particles
that you are seeing, or perhaps post a photo so that we can see it.
Aluminum can form hillocks, and either metal can "spit" for a number
of reasons: 1) if not cooled in the hearth properly, or 2) if the e-
beam is not being scanned on the metal sufficiently to uniformly melt
it, or 3) the melt has voids in it.  The spitting can be observed
during the deposition.  If you have access to a SEM, spits show up as
nearly spherical particles up to several microns in diameter.

Brad Cantos
brad.cantos@holage.com
http://holage.com


On Jul 29, 2009, at 4:39 PM, Chongfei Shen wrote:

> Dear all,
>
> I'm using ebeam evaporation to deposit Ti and Al. Both films have
> dense
> particles observed under microscope. The evporation rates are
> controlled to
> be 4A/s. The wafers were thoroughly cleaned.
>
> What are the reasons that forms the particles? How to solve this
> problem?
>
> Thank you very much for your suggestions.
>
> cfshen