[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Automation the facility has been designed with a high

Info icon This preview shows pages 567–569. Sign up to view the full content.

View Full Document Right Arrow Icon
Automation The facility has been designed with a high degree of automation in mind to cope with the high throughput that can be envisaged for the years to come. Acknowledgments The realization of the facility has been possible by the dedication of Monique Navizet, the work of Paolo Mangiagalli and Giorgio Apostolo, and the skills of Guy Dumoulin. The important effort on the software aspects of automation has been supported by Emmanuel Papillon. Facility of the PTB at BESSY II Using undulator radiation at electron storage rings, very high photon fluxes of linear polarized radiation for the TXRF excitation can be achieved. The photon energy of the undulator radiation depends on the energy of the stored electrons as well as on both the strength and periodicity of the magnetic field generated by the undulator. At the 1.7 GeV electron storage ring BESSY II in Berlin, Germany, photon energies of undulator radiation range from the VUV well into the soft X-ray regime, up to about 2 keV, thus allowing for the effective inner-shell excitation of light elements. The Physikalisch-Technische Bundesanstalt (PTB), Germany’s national institute for metrology, operates a laboratory [213] at BESSY II, including a plane grating monochromator (PGM) beamline [214] for undulator radiation. Complementary to the work at SSRL and ESRF, the PTB lays emphasis on the methodological develop- ment of soft X-ray TXRF analysis, providing a means for the quantitation of low Z contaminants on silicon wafer surfaces at its PGM beamline. Ini- tial TXRF investigations were carried out in cooperation with the ATI and the semiconductor company Siltronic in order to determine the absolute LOD values of TXRF for some low Z elements [200, 215] such as C, N, Na, Mg and Al, which ranged between 0.3 pg and 1.3 pg with respect to a measuring time of 1000 s. The calculated VPD detection limits, based on the assump- tion that the sample droplets were collected from a 200 mm wafer, ranged from 2 × 10 7 atoms/cm 2 to about 10 8 atoms/cm 2 for Na, Mg, and Al, thus fulfilling current analytical requirements of the semiconductor roadmap. For the explicit purpose of the semiconductor industry, the PTB has extended its TXRF instrumentation [216] and, to date, can handle 200 and 300 mm sili- con wafers. In recent investigations employing again small droplets containing
Image of page 567

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Methodological Developments and Applications 547 the elements Na [216] and Al deposited on 200 mm Si wafers considerably improved LOD values of less than 100 fg were achieved by further optimizing the excitation conditions. Compared to the analysis of medium Z elements, such as transition met- als for which excitation energies in the 5 keV to 15 keV range are needed to induce K fluorescence, some drawbacks exist when exciting K fluorescence radiation of low Z elements below 2 keV. The measured fluorescence count rates are proportional to the fluorescence yields when the self-absorption ef- fects are negligible, which is the case when only minute amounts of a low Z element are present. Since the fluorescence yield rapidly decreases as the
Image of page 568
Image of page 569
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern