Mike B wrote:
>
> Hello,
>
> I've kind of gotten myself in a bind and was wondering if anyone out there
> had an idea of how I could get myself out of it.
>
> The situation is this:  I've bonded single-side polished <100> wafers
> together with an oxide in between.  The wafers are between 500 and 538
> microns thick and the oxide is about 0.8 microns.
>
> The problem is: the company I've asked to polish down the top wafer needs
> to know how thick (within a micron) the wafers are.
>
> I would prefer not to damage the wafers.  They are annealed, btw, so
> separating and rebonding is not an option.  The ideas I've had so far
> require some damage.  A KOH etch down to the oxide with subsequent measure
> of the base area of the resulting triangular hole might be accurate
> enough. A profilometer would require cutting the wafer and the Dektak I
> have can only go 100 microns.
>
> Any ideas?  Thanks in advance.
>
> Mike
>
> Michael H. Beggans
> New Jersey Institute of Technology (NJIT)
> [email protected]
> 973-642-7738 voice
> 973-596-5794 fax
>
>
Mike,

I would also anisotropically etch some windows until it stops at the
interface. The depth can be measured with an optical microscope, by
focusing on the top and interface surfaces and measure the respective
stage travel. Usually, microscopes have a gage built in the z-axis
control, but it has play and is probably not accurate enough. To
overcome the play, only turn the wheel in one direction. Nikon sells a
device called Digimicron that can measures travel down to the micron (or
better).
--
Alexander Hoelke

graduate student

University of Cincinnati
ECE - CMSM

Phone:  (513)556-1997 / (513)556-4795
FAX:            (513)556-7326