Al annealing

Baylor B Triplett baylortriplett at earthlink.net
Fri Mar 9 12:25:29 PST 2007


Beinn,
     Sorry, I responded to a response to your inquiry without reading 
your note to see the full context. To minimize roughening by 
crystallization make the film as thin as possible....or use metals that 
have high glass transition temperatures like refractory metals such as 
Ti. For instance, metals typically have a glass transition temperature 
about 1/3 of the melting point in absolute temperature (Kelvin) and will 
not often crystallize below this point. Thus Ti has a glass transition 
temperature about 1/3 x T(melting)= 1/3 x1933 K= ~644 K or 371 C. I have 
often used Ti deposited by e-beam evaporation and  found it to form  a 
brown glassy layer at substrate temperatures below 300 C and a silvery 
metallic crystalline film at 400 C.  I have assumed  (but not verified) 
that the brown film is smoother than the crystallized film. I should 
point out that sputter deposition and stress change this picture by ion 
or electron energy annealing of the film so that it crystallizes Ti at a 
lower temperatures (often much lower) and e-beam can produce some 
spitting which can damage your smoothness if you need it over a large 
area. As I remember chrome sublimes so it might also be a good candidate 
for e-beam or thermal evaporation.
      There must be people in the material science dept who know much 
more about this than I. You might try Bill Nix. I learned some of this 
subject from a feloow by the name of H. Windishman...I see on Google 
that he published a paper entitled "Microstructural Evolution during 
film growth" J. Appl. Physics (1987)  that also incorporates the effects 
of stress in ion beam sputtering. You might start there. Look also at 
his diamond films on metallic substrates.
     If you are stuck with aluminum, it's melting point is 660 C so it's 
glass transition temperature is about 1/3 x 933 K = 311 K or about 40 C. 
It crystallizes under almost all deposition conditions. The primary way 
I can conceive of making this crystallized film smoother is to make it 
much thinner.
        Baylor Triplett
     
Beinn Muir wrote:
> Dear Labmembers,
>
> I am interested in increasing the grain size and reducing the roughness of
> thermally evaporated films of Al (200-1000nm thick) deposited on Si with
> native oxide. Do any of you have experience with annealing Al films, or can
> reccommend any useful literature discussing the conditions and resulting
> morphology changes? Another possible route I could take would be to etch /
> polish the Al film to reduce roughness, but I have had limited success with
> this.
>
> I would be grateful for any information.
>
> Best regards,
> Beinn...
>
>
>
>   




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