Trying to calculate thickness from measured sheet resistance and looking up
the bulk resistivity in a book is prone to error.

The resistivity of thin metal films is typically higher than than of bulk
material, and varies with the deposition conditions.

For sputtered titanium, I have varied the chamber pressure from 2 to 20
mTorr and seen the resistivity rise from ~0.8 to 2.7e-6 ohm-m.

For a bulk value (from the CRC Hanbook of Chemistry and Physics), the
resistivity is 4.2e-7 ohm-m, half of the lowest value that I measured.

    --Kirt Williams

----- Original Message -----
From: "Fei Wang" 
To: "General MEMS discussion" 
Sent: Wednesday, February 18, 2009 6:38 AM
Subject: Re: [mems-talk] Ti layer measurement...


> Guys above have provided enough information. I believe stylus
> profilometers are easiest way to do the job.
>
> Just to add one more potential way to measure the metal thickness:
>
> I know someone in my lab test the sheet resistance of the metal layer,
> and then with the resistivity, you can calculate the thickness. I am
> not very sure about the accuracy.
>
> 2009/2/17, Albert Henning :
>> Just to clarify about optical means:
>>
>> Ellipsometers and reflectometers measure blanket (unpatterned) films.
>> They cannot provide useful thickness or composition information for
>> thicknesses above about 50 nm.
>>
>> Optical interferometers (Wyko, or Zygo) can be used to measure patterned
>> films, either single steps (using e.g. the already-suggest Kapton-tape
>> approach), or multiple steps/trenches (patterned lithographically, or
>> with a shadow mask).  Calibration is essential, and unless you have
>> access to a well-maintained system, with a trained operator, it will
>> take quite a bit of time to get a useful measurement.  But, the
>> technique is sound and successful, whether you're measuring a single
>> step in a field of perhaps only a few microns square, or many steps
>> simultaneously across an entire wafer.
>>
>> In my experience, stylus profilometers are faster and simpler, and just
>> as accurate, as compared to optical interferometry, if all you want is a
>> couple of measurements on a wafer.