My feeling is that what you got is a result of the way you did it.
To try answering you doubt, I need to make sure one thing:after etching, is the
SiO2 layer still there? If not, I will have a possible explanation.
Depends on your temperature and KOH concentration, the selectivity of Si to SiO2
varies considerably.At higher temperature, there's a chance that SiO2 gets
etched away as fast as that of Si. The surface of SiO2 thus etched is rougher.
And the surface roughness variation will be reflected when you etch down
further to expose Si surface. The local valleys and hillocks function as lock
"masks". Therefore, your Si surface will "image" the surface roughness got on
the SiO2 surface. And for Si(100) and Si(110) roughness difference, that might
be because the etch rate difference of KOH between them. Thus one is more
apparent in surface roughness than the other while both of them suffer the same
problem.
Etching Si with SiO2 as a mask layer by using KOH is sometimes messy. Unless you
have specific reasons to use KOH, I suggest you adopt other chemicals other than
KOH.
At 2002-01-03, You Wrote
------------------------------
>Hi All
>
>I would like to clarify my question and problem that I
>encountered.
>
>I used Si (100) and Si(110) wafers using thermal oxide
>as etch mask. I etched those wafers in KOH solution. I
>am interested in the bottom surface (not side walls)
>of patterned wafers etched in KOH.
>
>What I found is that by naked eyes the bottom surface
>of (110) wafers is much rougher than (100) wafers. I
>am pretty sure that that roughness is not from powder
>deposited on surface but from its surface.
>I am wondering if anyone found the same thing that I
>noticed. If so, can anyone give explanation of that?
>
>Thanks.
>
>Onnop
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-------------------------------
Regards,
John Duke
