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Thermal alumina growth data

I am currently doing microfabrication research, and we are working on a plasma etching process that uses an Aluminum layer as the etch mask (etching SiO2). The Aluminum layer is eroding during the etch, and completion of the etch is difficult due to loss of the mask integrity. We are investigating ways of 'hardening' the mask layer. The mask layer is only about 1µm thick.

During these types of etching processes, the natural oxide that forms on the aluminum usually serves to slow the mask erosion. We were wondering about increasing the thickness of this alumina layer to increase the erosion resistance. Specifically, using thermal alumina growth in an oxygen environment. I have spent some time trying to find data showing aluminum oxide thickness vs. time at different temperatures, but haven't found anything particularly useful.

Because this is an issue related to aluminum anodization, I thought that this might reach someone with the information or a good reference for the information. I am not sure anodization would work for us, because the acids could adversely affect other materials, the potentials used might adversely affect IC electronics, and the aluminum needs to be used after processing for electrical contact. (We can work with a thin Al2O3 layer, but probably not a thick anodized layer).

Any advice or references would be greatly appreciated.

Nicholas Jankowski
University of Virginia - Charlottesville, Virginia
2002

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Nicholas,

Some time has gone by and there has been no response to your question. You are attending a college that is well known for its semiconductor fabrication research. I assume you have exhausted all of the resources at UVa? If not, you might find someone in Tom Crowe's group (in the Applied Electrophysics Lab) who would be able to help. They have been fabricating high frequency microwave semiconductor devices for decades and may have some insight into the problem you are attempting to solve. They have fabricated many unusual and innovative devices over the years.

Sometimes the answer can be found very close to home.

There are many other research groups associated with UVa. I would be very surprised if you can't find one that could give you some advice.

Ronna Erickson
Radio Astronomy, Univ. of Massachusetts - Amherst, Massachusetts
2002

Actually, I work in the Applied ElectroPhysics Lab :) Yes, I have been in touch with some people in his group. They have done some work with aluminum dioxide primarily with respect to tunnel junctions. The main problem seems to be that (and I've come across this in the literature quite a bit as well) they are dealing with extremely thin aluminum films, and native oxidation at room temperature is usually more than enough to completely oxidize the films they're working with. So, its not quite applicable to what I'm looking at.

Nicholas Jankowski
University of Virginia, Electrical Engineering - Charlottesville, Virginia
2002