Hello Moshe,

Perhaps this is a simplistic view however the major difference between
BOE and 49% HF is their etch rate.

49% HF will etch much faster than 5:1 BOE which in turn will etch much
faster than 10:1 BOE. Might I suggest you have a look at the (in my
view) excellent paper, "Etch Rates for Micromachining Processing -Part
II" by Kirt Williams (Journal od Micromechanical systems Vol. 12, No. 6
December 2003).

The native oxide on silicon is only 20 A thick and 10: 1 BOE will remove
native oxide at around 20 nm/minute so I would use this BOE for around
30 seconds.

Obviously HF etching is isotropic (etches in all directions) so to
reduce the undercut of patterned features one should choose an BOE
concentration and etch time accordingly.

James



Moshe wrote:
> Is three is differences between BOE and HF solution (10-48%) for etching
native oxide layer?
>

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Dr. James Paul Grant
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