Characterization of ultra-shallow aluminum implants in silicon by grazing incidence and grazing emission X-ray fluorescence spectroscopy

Abstract

In this work two synchrotron radiation-based depth-sensitive X-ray fluorescence techniques, grazing incidence X-ray fluorescence (GIXRF) and grazing emission X-ray fluorescence (GEXRF), are compared and their potential for non-destructive depth-profiling applications is investigated. The depth-profiling capabilities of the two methods are illustrated for five aluminum-implanted silicon wafers all having the same implantation dose of 10 16 atoms per cm 2 but with different implantation energies ranging from 1 keV up to 50 keV. The work was motivated by the ongoing downscaling effort of the microelectronics industry and the resulting need for more sensitive methods for the impurity and dopant depth-profile control. The principles of GIXRF and GEXRF, both based on the refraction of X-rays at the sample surface to enhance the surface-to-bulk ratio of the detected fluorescence signal, are explained. The complementary experimental setups employed at the Physikalisch-Technische Bundesanstalt (PTB) for GIXRF and the University of Fribourg for GEXRF are presented in detail. In particular, for each technique it is shown how the dopant depth profile can be derived from the angular intensity dependence of the Al Ka fluorescence line. The results are compared to theoretical predictions and, for two samples, crosschecked with values obtained from secondary ion mass spectroscopy (SIMS) measurements. A good agreement between the different approaches is found proving that the GIXRF and GEXRF methods can be efficiently employed to extract the dopant depth distribution of ionimplanted samples with good accuracy and over a wide range of implantation energies.

High-energy-resolution grazing emission X-ray fluorescence applied to the characterization of thin Al films on Si

“…This quantification approach was cross-checked by means of a reference sample, a 15 keV Al-implanted Si wafer which was characterized in [48]. Usually, quantification measurements are realized by recording the XRF intensity at a single sample position and deducing the studied elemental quantity contained in the sample from the XRF intensity.…”

“…The high-resolution reflection-type von Hamos curved crystal X-ray spectrometer of the University of Fribourg [93] was installed downstream of the beamline's scanning X-ray microscope (SXM) chamber. The University of Fribourg's von Hamos spectrometer, when installed at the ESRF ID21 beamline and configured in the GEXRF geometry, has been characterized in terms of detection limits [42,43] and depth-profiling capabilities [47,48]. The main components of the spectrometer ( characterized in [94].…”

“…Other application domains are micro-and trace analyses, surface contamination control (see [38][39][40][41] for GIXRF and [42][43][44] for GEXRF among others for semiconductor applications) and depth-profiling of ion-implanted samples (see for example [45][46][47] for GIXRF and GEXRF, respectively). In the latter application a comparison of GIXRF and GEXRF for Al implantations in Si can be found in [48]. In the two former application domains the X-ray fluorescence intensity is detected at a fixed incidence or emission angle below the critical angle since the primary goal is to detect the presence of contaminants.…”

Complementary methodologies for thin film characterization in one tool – a novel instrument for 450 mm wafers

“…For example, GIXRF and XRR support each other by using the same parameters for layer thicknesses and properties, such as density and roughness. 25 The improvement of results can be shown for other analytical techniques, too.…”

Grazing angle X-ray fluorescence from periodic structures on silicon and silica surfaces

“…In particular they are very useful for trace elements' analysis [6,16], characterization of thin layers [7,17] and depth profiling [18][19][20]. The usefulness of grazing XRF techniques for nanoparticle characterization has also been demonstrated [8,[21][22][23][24][25][26].…”