Accurate RBS measurement of ion implant doses in silicon

Abstract

We demonstrate very accurate ion implant dose measurements using Rutherford backscattering spectrometry (RBS) traceable to a certified reference material from IRMM, Geel and the Bundesanstalt für Materialforschung (BAM), Berlin. The measurements have an absolute accuracy of better than 1.4% and a precision of better than 1.25%. The certified standard sample is compared directly with recent absolute determinations of the energy loss of He in Si, and also with a sample calibrated against the Harwell Bi standard. We determine the dose in a series of three In implants and six As implants of various doses and energies. Some of the samples were amorphized to eliminate channelling effects. A double detector geometry was used, giving pairs of spectra with a common incident charge but where the solid angle and the electronic gain were determined for each detector channel independently. The statistical uncertainty is reduced to <1%. The non-linear pile-up background is determined carefully. The errors are determined critically. The experiments were carried out at different dates and different places, so time and space reproducibility of the results is confirmed. The IBA DataFurnace is used for analysis of the certified standard reference material and compared with a transparent manual data reduction method: the use of this code for routine data analysis at the highest accuracy is validated.

Absolute dose performance of the SWIFT single wafer ion implanter

“…The detectors were independently calibrated against a secondary standard with an implanted Bi dose of 4.64x10 15 cm -2 . The estimate accuracy of this measurements is 1.4% calibrated against the IRMM-302/BAM-2001 certified Sb implant standard [2].…”

“…In fact, we use the Si substrate signal only as an inter-sample charge normalisation signal since we calibrated for this analysis against the implanted Bi standard. Accurate values of Si stopping powers are critical for such an analysis: following Boudreault et al [2] we have used the most accurate data of Bianconi [7] for Si energy loss that have been re-analysed by Barradas [8] with a sophisticated Bayesian method. The channeling part of the spectra was not included in the fitting region of interest.…”

“…Recently, a new Sb implanted standard, calibrated by reference to the international standard of weight in Paris, has become available [1]. We have very recently [2] compared this standard both with the old "Harwell" Bi implanted standard [3] and with the recent direct measurements of Si energy loss [4]. For the present work, we have used the Bi standard as a secondary reference to validate our analysis.…”

Structural analysis of silicon co-implanted with carbon and high energy proton for the formation of the lasing G-centre

“…Depth profiles used in this work can be extracted automatically from RBS spectra using the Surrey IBA Data Furnace software, 9 the accuracy of which has been validated against a certified standard sample. 10 TEM and XTEM (cross-sectional TEM) analysis were done using Philips EM400T and CM200 electron microscopes, operated at 120 and 200 kV, respectively. Both cross-sectional and plan-view specimens of all samples were prepared using low-angle argon ion-beam thinning at 5 keV.…”

Characterisation of thin film chalcogenide PV materials using MeV ion beam analysis

“…But such thin films are not easy to profile: the [5] where the depth resolution comes from the energy loss of the probing beam (such as 1.5MeV 4 He + ) detected after elastic scattering at backward angles from the atomic nuclei of the target; films of this sort of thickness have very convenient energy loss of the primary beam, so that the depth resolution is good. Because the RBS elastic scattering cross-section is derived simply from the Coulomb potential [6], and the energy losses of light ion beams in materials are well known [7]- [9], RBS is an accurate technique suitable for standards work [10], [11]. Depth profiles can now be extracted from RBS spectra (or other related particle scattering spectra) with codes validated by an IAEA-sponsored inter-comparison exercise [12], including the DataFurnace code [13] used here.…”