Thanks for all your suggestions. My way of telling how much materials have
been removed is by measuring the sheet rho on the Si. Remember that I have a
diffusion at the surface? I am suspecting that at the very top Si surface
there are lotta lattice damage by phosphorus precipitates etc so that is why
I try to remove a small amount of material at the top surface.

I have tried very diluted CP etch (HNA=1:10:9) but it always leaves a
white-ish cloud Si surface. I don't understand why.
For the room temperature KOH, I leave it in there for 5 minutes but it
doesn't seem to etch anything. I will do more trials on this. the KOH seems
pretty promising.

Dave

On Dec 27, 2007 1:28 AM, Kvel Bergtatt  wrote:

> >From my experience, KOH and any other primary amine etching of Si don't
> go
> hand in hand with uniformity. Try a quaternary amine: TMAH is great for
> high
> etch rates; the more concentrated (>25%) and smoother the resulting
> surface
> and the lower the ER. Alcohols can be mixed to reduce the ER even lower.
>
>
>
> On Dec 21, 2007 8:15 AM, Andrea Mazzolari  wrote:
>
> > Etch rate of HNA depends strongly on HNA composition.
> >
> > With the right mixings you can obtain very low etch rate.
> >
> > See Chemical Etching of Silicon, B. Schwart and H. Robbin, J.
> EIectrochem.
> > Soc, Vol. 123, No. 12.
> >
> > on line you can find also other articles from the same authors.
> >
> > In any case, in my opinion the best solution is to use KOH at room
> > temperature (it will works on 110 or 100 wafers, not 111)