Specific Process Knowledge/Characterization/Optical characterization

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Comparison of the methods

For comparison of the methods for measuring optical constants and film thickness, see here: Film thickness and optical constants of optical transparent films

Ellipsometer RC2, Ellipsometer M2000XI (VASE) and Ellipsometer M-2000V

This section is written by Berit Herstrøm @ DTU Nanolab

Ellipsometer RC2: positioned in cleanroom A-1, Photo: DTU Nanolab internal

Ellipsometer VASE: positioned in cleanroom C-1, Photo: DTU Nanolab internal

The ellipsometer RC2 from J.A. Woollam Co., Inc is the newest of our ellipsometers. It performs slightly better then the M2000 and can measure the full Müller matrix. For most users the differences are very small. The ellipsometer VASE is actually a M2000XI-210 ellipsometer from J.A. Woollam Co., Inc.. We call it VASE (Variable Angle Spectroscopic Ellipsometry) because it can do spectroscopic ellipsometry at variable angles.
The ellipsometer M2000V is an in-situ ellipsometer from J.A. Wollam Co., Inc. This dedicated for being used on the Sputter System Lesker instrument or the ALD2 for in-situ measurements. When it is not on any system it is positioned next to the ALD2.

Ellipsometry is a very sensitive characterization technique which can be used to determine thin film layer thicknesses and/or optical constants. It sends in polarized light on the surface at different angles and measures the change in polarization state of the reflected light.

It is especially good for thin films in the thickness range of a few nanometers to a few microns. The layer should be transparent to light in the usable wavelength range for the thickness to be determined. Large roughness (>40nm) and features within the field of view can cause the measurement to fail.

Ellipsometry is an indirect measurement so a model has to be fit to the data in order to obtain the film thickness and optical constants. To learn more about ellipsometry you can take a look at the tutorial provided by the J. A. Woollam Co.

Access to use the CompleteEASE software can be found using Remote Desktop connection to: DTU-8CC0321MFL (you can only log on when you have the user competences in LabManager) or log on to https://remote.dtu.dk. There should be a connection via Citrix to DTU-8CC0321MFL. You will be prompted for user/password.

The user manuals, quality control procedure and results and contact information can be found in LabManager:

LabManager page for Ellipsometer RC2
LabManager page for Ellipsometer VASE
LabManager page for Ellipsometer M-2000V

More details

• Before training:
  • First go through the Woollam short tutorial: tutorial
  • Second watch our training video: Training Video
  • To get more understanding - short intro from Quantum Design - Europe: [1] - optional
• Examples of advanced use of the ellipsometer

A rough overview of the performance of the Ellipsometers

Equipment		Ellipsometer RC2	Ellipsometer VASE (M2000XI)	Ellipsometer M-2000V
Purpose		Measure thinfilm thicknesses and optical constants for single and multilayer optical transparent thinfilms. Measure opticals constants for bulk material. Measure thinfilm thicknesses and optical constants at elevated temperature <300C	Measure thinfilm thicknesses and optical constants for single and multilayer optical transparent thinfilms. Measure opticals constants for bulk material	Measure growth rate of depositions done in the Sputter System Lesker. Measure thinfilm thicknesses and optical constants for single and multilayer optical transparent thinfilms.
Performance	Films that can be examined	Any film that is transparent to the light in the given wavelength range e.g.: Silicon Oxide Silicon nitride PolySilicon Resists Polymers Very thin layers of metals	Any film that is transparent to the light in the given wavelength range e.g.: Silicon Oxide Silicon nitride PolySilicon Resists Polymers Very thin layers of metals and many more	Any film that is transparent to the light in the given wavelength range e.g.: Silicon Oxide Silicon nitride PolySilicon Resists Polymers Very thin layers of metals and many more
	Film thickness range	~20Å to a few micrometers (depending of the material)	~20Å to a few micrometers (depending of the material)	~20Å to a few micrometer (depending of the material)
Process parameter range	Wavelength range	210nm-1690nm	210nm-1690nm	370nm-1000nm
	Incident angle range	45-90 degrees	45-90 degrees	One fixed angle - about 70 degrees
	Beam size	3mm (spot size on sample depends on the angle)	2mm (spot size on sample depends on the angle)	5mm (spot size on the sample depends on the angle)
	Mapping facility	Can make wafer maps on up to 150mm wafers	Can make wafer maps on up to 150mm wafers	No mapping facility
Accessories	Focusing optics	Focus lenses can be applied, reduces the beam diameter to 120µm	Focus lenses can be applied, reduces the beam diameter to 125µm	No focusing lenses
	Transmission stage	Extra stage for transmission measurements	Extra stage for transmission measurements	Base for ex-situ measurements, transmission data can be done by holding the sample up against the detector
	Heating stage	Heating stage for measurements at temperatures up to 300C	None	None
Substrates	Batch size	One sample at a time smaller than 150mm (ask if you have anything larger)	One sample at a time smaller than 150mm (ask if you have anything larger)	One sample at a time, any sample size that goes in the Sputter System Lesker
	Allowed materials	Any material that does not leave residuals on the stage and that does not evaporate	Any material that does not leave residuals on the stage and that does not evaporate	Any material that may go into the ALD2 (when mounted on that system)

Filmtek 4000

Unless otherwise stated, all content in this section was done by Berit Herstrøm, DTU Nanolab

FilmTek 4000: positioned in cleanroom D-1, Photo: DTU Nanolab internal

FilmTek 4000 is a computerized film thickness measurement and material characterization system. This system combines fiber-optic spectrophotometry with advanced material modeling software to provide an affordable and reliable tool for the simultaneous measurement of film thickness, index of refraction, and extinction coefficient

Normal incidence and polarized 70 degree reflection data is collected and used to calculate thickness and index of refraction of the measured film using SCI’s patented Differential Power Spectral Density (DPSD) technique. Absolute reflection data is obtained by comparing sample data to the measured reflection of a known reference sample, typically a silicon wafer with a thermally grown thin oxide (~63 nm) film.

The spectrophotometer scans the sample over a predefined range of wavelengths. The software generates a reflection spectrum based on a previously stored reference scan, and then performs a regression on the unknown parameters to fit the simulated reflection and power spectral density to the observed values. The resulting thin film parameters along with the measured and modeled spectra are then displayed for the user to examine.

The user manual, quality control procedure and results, technical information and contact information can be found in LabManager:

FilmTek in LabManager

An overview of the performance of the FilmTek

Purpose	Film thickness measurements and optical characterization of optically transparent thin films	Measurement of (multi layer) film thickness (only one unknown layer) Optical constants Surface roughness
Performance	Thin film materials that can be measured	Any film that is transparent to the light in the given wavelength range ex: Silicon Oxide Silicon nitride PolySilicon Photoresists SU8 Other polymers Very thin layers of metals (<20 nm) and many more
	Film thickness range	<100 Å to 250 µm (depending of the material)
Process parameter range	Wavelength range	400-1000 nm
Substrates	Batch size	One sample at a time - all sample larger than 5x5 mm2sizes up to 6"
	Substrate material allowed	In principle all materials Only pure silicon, silicon oxides, silicon nitrides and quartz may be in direct contact with the surface of the stage. If you have metals, III-V materials or polymers on the back side of the substrate the please mount your sample on a silicon carrier wafer.