System Capabilities

Thin films comprising 2D and 3D structures need to be characterized in order to provide
accurate depth, CD and profile results. All n&k scatterometers have the capability to mea-
sure OCD structures and their thin films, whether the films are on the mesa, bottom, or
wall of the structure, and will furnish thickness and n and k spectra of any particular film.
In addition, all n&k Scatterometers will measure complex 2D and 3D OCD Structures for
a wide range of pitches, CDs, and Depths, and with no lower limit on structure size.

These tools offer measurements of compressive & tensile stress and waferless recipe generation.
They can be configured for measurements of 300mm, 200mm, 150mm wafers.

The n&k Olympian scatterometer provides measurements covering the spectral range
from 190nm to 15,000nm. The Olympian’s complete spectral range is needed:

• For complex line/space trench and hole structures with ultra-deep depths, including
  depths of 60μm or greater
• For high aspect ratio structures, such as holes in silicon, or line/space trenches with
  narrow CD
• If initial measurements using DUV-Vis-Near IR wavelength range does not reveal
  sufficient information to determine depth, CD, and profile
• For measurements of complex ultra-thick film structures (for example thick SOI)
• For measurement of Epi-Si thickness be cause silicon is transparent in the Infrared
  wavelength range (but opaque in the DUV-Vis-Near Infrared wavelength range)

The tools belonging to the OptiPrime-CD Series and LittleFoot-CD Series (DUV-Vis-NIR
scatterometer systems), are capable of measuring FinFET structures. Although there is
coupling between some parameters that need to be determined, these tools have the
sensitivity to distinguish the coupled parameters, because of their optical design that
produces a strong signal of the order of 2%-5% per 2nm change in the parameters. In
general, since changes in the reflectance at all wavelengths can be observed, the effect
of coupling is not too significant – the wide spectral range helps.

The reflectance spectrum of Epi-Si in the UV-Vis-NIR wavelength range (190nm –
1000nm) is indistinguishable from that of the Si substrate. However, the spectra of
these two materials can be distinguished in the infrared wavelength range. Thus the
tools belonging to the Olympian Series, which cover the UV-Vis-IR range from 190nm –
15,000nm, are used to determine to determine thickness and n and k spectra of Epi-Si
encompassed in a variety of film structures. Thicknesses as thin as 200nm and as thick
as 100μm have been recently measured by the n&k Olympian.

UV-Vis-NIR n&k tools, whether fully automated or manual load, will measure very thin
films less than 20Å thick and very thick films that are 50μm or more. The UV-Vis-IR
wavelength range of the n&k Olympian allows for thickness measurements of 100μm or
more.

The tools belonging to the Gemini Series, have the following capabilities for EUV Photo-
mask measurements:

Inhomogeneous films are films whose n and k values vary within the film. For example
the n and k values of the top of the film will be different that those in the middle or bottom
of the film. All n&k systems have the capability to determine if a film is inhomogeneous.
In particular, if the experimental reflectance data of a single layer film surpasses that of
bare-Si at a number of wavelengths, then that film must be inhomogeneous. Once it is
determined that a film is inhomogeneous, then the n&k tool will provide the n and k spec-
tra of that film at any point along the Z-direction within the film. Please refer to the
TF Series .

Because the unique optical design of all n&k tools, which provides optimized signal-to-
noise ratio, reflectance spectra of less than 2%, over the entire measured wavelength
range, of films on rough surfaces are measureable. This is particularly important for mea-
surements involving solar cells, which are purposely made on rough substrates in order
to absorb as much light as possible.Please refer to the TF Series .

Because the unique optical design, which provides optimized signal-to-noise ratio, all n&k
tools have the capability to measure and formulate deviations from specular reflectance
and analytically determine surface and inter-face roughness of a film stack.Please refer
to the TF Series .

n&k scatterometers, for example the OptiPrime-CD Series, LittleFoot-CD Series and
Olympian Series, are used extensively as an etch monitor for power devices. Multiple
etch steps can be monitored: Si Trench, Poly Recess, and Contact Trench. Measure-
ment structures are typically large pitch (>1μm) and deep gratings (> 1μm) in Si. Depth
measurement is most important, but CD and profile are also desired. n&k scatterometers
offer the following advantages for power device measurements:

• Fast calculation for depth measurements
• Customer has the ability to create their own recipes and libraries

• Excellent Matching with SEM, AFM
• Excellent Repeatability & Reproducibility

n&k’s high resolution scatterometers and thin film measurement systems are used ex-
tensively in the MEMS industry, due to their versatility and capabilities. For instance,
the tools belonging to the OptiPrime-CD Series and LittleFoot-CD Series measure OCD
structures and provide results for large and small pitch structures, complex 2-D and 3-D
structures, as well as ultra-thin and ultra-thick films. The Olympian Series goes beyond
the measurements provided by the Opti-Prime-CD Series to include measurements of
Epi-Si layers and high aspect ratio trenches and contact holes.

In terms of thin film MEMS applications these tools are used for SOI measurements
and complex thin film structures, such as ultra-thin multi-layer Mo/AlN/Mo/AlN/SOI, plus
MEMS Si-membrane and ink jet print head dielectric membrane.

In addition to EUV Mask measurements, the tools belonging to the Gemini Series are
used extensively for measurements of conventional masks. These tools provide simulta-
neous measurements of polarized reflectance (Rs and Rp) and polarized transmittance
(Ts and Tp) from 190nm to 1000nm of phase-shift and double patterning ArF masks. The
spot size for both the reflectance and transmittance is 50μm. The inclusion of transmit-
tance is very important in order to ensure accuracy. This is because Intensity of Ts and
Tp >> Intensity of Rs and Rp → More transmitted photons reach detector than reflected
photons and the signal-to-noise ratio is in proportion to # of detected photons.

Also, there is a direct correlation between transmittance and CD, which in turn furnishes
a fast and accurate way of measuring CDs in a production environment.

The tools belonging to the Gemini Series accurately and repeatabley measure film thick-
nesses, for example, thicknesses of all films in a typical stack such as Resist/ARC/CrOx/
CR/MoSi/Quartz-Substrate. Furthermore, height, CD and side wall of phase-shift and
double patterning ArF masks, plus the phase-shift of phase-shift masks are also mea-
sured. In addition the tools provide through-pellicle measurements. Excellent correlation
with other metrology techniques has been obtained. An automated flipper for front-side
and back-side measurements is an option with the n&k Gemini.