Depth profile characterization of ultra shallow junction implants

Abstract

A need for analysis techniques, complementary to secondary ion mass spectrometry (SIMS), for depth profiling dopants in silicon for ultra shallow junction (USJ) applications in CMOS technologies has recently emerged following the difficulties SIMS is facing there. Grazing incidence X-ray fluorescence (GIXRF) analysis in the soft X-ray range is a high-potential tool for this purpose. It provides excellent conditions for the excitation of the B-K and the As-L(iii,ii) shells. The X-ray standing wave (XSW) field associated with GIXRF on flat samples is used here as a tunable sensor to obtain information about the implantation profile because the in-depth changes of the XSW intensity are dependent on the angle of incidence. This technique is very sensitive to near-surface layers and is therefore well suited for the analysis of USJ distributions. Si wafers implanted with either arsenic or boron at different fluences and implantation energies were used to compare SIMS with synchrotron radiation-induced GIXRF analysis. GIXRF measurements were carried out at the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II using monochromatized undulator radiation of well-known radiant power and spectral purity. The use of an absolutely calibrated energy-dispersive detector for the acquisition of the B-Kalpha and As-Lalpha fluorescence radiation enabled the absolute determination of the total retained dose. The concentration profile was obtained by ab initio calculation and comparison with the angular measurements of the X-ray fluorescence.

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

“…This method does not rely on any calibration samples or subsequent etching of the sample and is described in detail in ref. 13.…”

“…The routine, described in detail in ref. 13, uses an incidentangle dependent convolution of the IMD 34 calculation of the XSW field, a mathematical model of the depth profile as well as a correction term for the absorption of the excited fluorescence radiation. All relevant geometrical and experimental parameters, i.e., the solid angle of detection or the incident photon flux, are included to gain quantitative information about the depth profile.…”

A new generation of x-ray spectrometry UHV instruments at the SR facilities BESSY II, ELETTRA and SOLEIL

“…PTB addresses this challenge by XRS techniques where all instrumental and experimental parameters are determined with a known contribution to the uncertainty budget of the analytical results. The functionality of nano-scaled materials is driven by optimized spatial elemental and chemical distributions involving layered structures 2 , interfacial passivation 3 , and elemental depth profiles 4 , or 3D nanostructures 5 calling for adapted analytical sensitivity and information depth as can be provided by XRS, even in a reference-free quantification 6 mode, e.g. without using any calibration samples 7 , but using wellknown excitation radiation and calibrated X-ray detectors.…”

Depth profiling of dopants implanted in Si using the synchrotron radiation based high‐resolution grazing emission technique

“…Alternatively, an XRF based depth profiling approach can also be realized with grazing incidence XRF (GIXRF) [6] or by combining GIXRF and SIMS approaches. [7] GIXRF and GEXRF are physically equivalent in the sense that the refraction effect takes place on the same interface but from different incidence directions and for different X-ray energies (photon beam energy or fluorescence energy).…”