Fraunhofer Institute for Electronic Nano Systems ENAS
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The Fraunhofer Institute for Electronic Nano Systems ENAS is the specialist and development partner in the field of Smart Systems and their integration for various applications. Fraunhofer ENAS has specialized on the challenge of combining micro and nano sensors, actuators and electronic components with interfaces for communication and a self-sufficient energy supply to form smart systems, thus supporting the Internet of Things and the ongoing digitalization.

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On the relationship between SiF4 plasma species and sample properties in ultra low-k etching processes

The temporal behavior of the molecular etching product SiF4 in fluorocarbon-based plasmas used for the dry etching of ultra low-k (ULK) materials has been brought into connection with the polymer deposition on the surface during plasma treatment within the scope of this work. For this purpose, the density of SiF4 has been measured time-resolved using quantum cascade laser absorption spectroscopy (QCLAS). To correlate the temporal development of the SiF4 density with the ULK damage, Variable Angle Spectroscopic Ellipsometry (VASE) and X-ray photoelectron spectroscopy (XPS) were performed on the treated ULK samples. The dataset corresponds to the findings published under the title “On the relationship between SiF4 plasma species and sample properties in ultra low-k etching processes” with open access in AIP Advances 2020.

Release Date
Permanent Identifier (DOI)
Permanent Identifier (URI)
Is supplementing
Plasma Source Name
Plasma Source Application
Plasma Source Specification
Plasma Source Properties

Magnetic enhanced reactive ion etch (MERIE) chamber of a Centura 5200 cluster system (Applied Materials): radio frequency (RF) excitation at 13.56 MHz, RF power 600 W.

Plasma Source Procedure
Chamber wall temperature as well as substrate temperature is set to 288 K.
Plasma Medium Name
Plasma Medium Properties
Gas mixtures of CF4, CHF3 and Ar at constant total flow of 100 sccm and constant total pressure of 100 mTorr.
Plasma Target Name
Plasma Target Properties
Cutted pieces of 10 times 10 cm from a 300 mm wafer with 500 nm thick porous SiOCH layer (dielectric constant = 2.4) deposited on Si via PECVD.
Plasma Target Procedure
Each peace is placed on an Al wafer with 200 mm diameter to be handled in the Centura cluster system.
Plasma Diagnostics Name
Plasma Diagnostics Properties

Quantum cascade laser absorption spectroscopy (QCLAS): Q-MACS process fiber system from neoplas control, effective absorption length 5.4 m (12 passes), time resolution 1 Hz.

Variable angle spectroscopic ellipsometry (VASE): SE850 system from Sentech, incident angles 50°, 60°, and 70°, wavelength range 400-850 nm.

X-ray photoelectron spectroscopy (XPS): R3000 electron energy analyzer from VG Scienta, pass energy 200 eV, monochromatic Al-Kα radiation from a MX 650 X-ray source from VG Scienta.

Plasma Diagnostics Procedure

In situ and time-resolved determination of SiF4 concentration by QCLAS:
Enhancement of sensitivity due to a mulitpass optics (neoplas control) implemented at the chamber increasing the effective absorption length to 5.4 m by setting 12 passes. Time resolution was set to 1 Hz. The absorption of SiF4 was detected in the range between 1030.90 cm-1 and 1031.00 cm-1.

Ex situ determination of layer thicknesses and refractive Indices by VASE:
Each sample was measured at three incident angles (50°, 60°, and 70°) in the wavelength range between 400 nm and 850 nm. For the analysis, the partially etched SiOCH layer was modelled with three layers consisting of 6 parameters, i.e. refractive index and film thickness for the polymer film, for the damaged SiOCH film, and for the non-damaged SiOCH film, respectively.

Ex situ analysis of elemental composition of plasma treated surfaces by XPS:
To compensate for charging of the isolated samples, an electron flood gun was applied during the XPS measurement such that the Si 2p peak was shifted to 103.5 eV binding energy corresponding to SiO2. For the analysis of the XPS spectra, CasaXPS Version 2.3.16 Pre-rel 1.4 was applied using Scofield relative sensitivity factors in combination with a Shirley background. A numerical approximation for a Voigt profile (Lorentz 30% share) was used as a line shape model to determine the respective peaks of the deconvolution. The full width at half maximum has been limited to 1.5 − 3.0 eV for the deconvolution.

Public Access Level
Contact Name
Lang, Norbert
Contact Email

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