difficult to get much accuracy at his level
(roughness, vibrations).
The Zygo has ~ 1 nm precison but will only work on
metals or semiconductors. For dielectrics, it is
easily confused by the multiple reflections. The Zygo
uses "white light" interference centered at about
600nm. Some metals or semiconductors are
semi-transparent at this wave length. If the material
is not optically opaque on both side of the step
measured, a systematic, thickness dependent, error can
result. If you need to measure a thin metal or a
dielectric step, overcoat the step with a (smooth)
metal thick enough to be opaque at 600 nm.
AFM is also possible but is even more trouble (in my
opinion).
jimkruger
--- Ying Chen <mihuhou@stanford.edu> wrote:
> Hi, labmembers,
>
> I am trying to measure step heights (40~50nm) on a
> partly etched sample. Can
> anyone tell me whether the alphastep could measure
> such small steps?
>
> Thanks!
>
> Ying
>
>
>
>
> ----- Original Message -----
> From: "Jim McVittie" <mcvittie@cis.Stanford.EDU>
> To: <mihuhou@stanford.edu>
> Sent: Thursday, February 28, 2008 9:29 AM
> Subject: Re: Gold substrate in Rudolph.
>
>
> > Ying,
> >
> > 6328A is not a great place to do measurements on
> Au since it has a
> > transition in this its optical properities in this
> region. The Wollam will
> > give better results since you can change the
> wavelength. The following
> > results are from http://www.luxpop.com/.
Jim
> >
> > First set of refs:
> > At a wavelength of 6328 nm (0.196 eV), the index
> of refraction of gold is
> > n = 5.21, k = 43.82.
> >
> > Note that for thin films the index can vary
> depending on deposition
> > parameters.
> >
> > References:
> > [1] L. G. Shulz, "The optical constants of silver,
> gold, copper and
> > aluminum. 1) the absorption coefficient k and 2)
> the index of refraction
> > n," J. Opt. Soc. Am. , Vol. 44, No. 5, pp. 357-362
> and 362-368,
> > [2] M. A. Ordal, L. L. Long, R. J. Bell, S. E.
> Bell, R. W. Alexander, Jr.,
> > and C. A. Ward, "Optical properties of the metals
> Al, Co, Cu, Au, Fe, Pb,
> > Ni, Pd, Pt, Ag, Ti, and W in the infrared and far
> infrared," Appl. Opt. ,
> > Vol. 22, No. 7, 1 April 1983, pp. 1099-1119
> (Molutevich et al).
> >
> > Second set of refs:
> > At a wavelength of 6328 nm (0.196 eV), the index
> of refraction of gold is
> > n = 5.635, k = 38.1493.
> >
> > Note that for thin films the index can vary
> greatly depending on
> > deposition parameters.
> > References:
> > [1] E. D. Palik, "Handbook of Optical Constants of
> Solids, " Academic
> > Press.
> >
> >
> > On Wed, 27 Feb 2008 mihuhou@stanford.edu wrote:
> >
> >> Hi, Jim,
> >>
> >> Can you check up the gold optical information and
> show me how to use
> >> it with Rudolph? I am available tomorrow
> afternoon.
> >>
> >> Thanks a lot!
> >> Ying
> >>
> >
> > --
> >
>
--------------------------------------------------------------
> > Jim McVittie, Ph.D. Senior Research Scientist
> > Allen Center for Integrated Systems Electrical
> Engineering
> > Stanford University
> jmcvittie@stanford.edu
> > Rm. 336, 330 Serra Mall Fax: (650) 723-4659
> > Stanford, CA 94305-4075 Tel: (650) 725-3640
> >
> >
>
>
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