The Si surface yield as a calibration standard for RBS

Surface & Interface Analysis

Wendler

et al. 2002

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.

Section: Is the Rbs Of Ion Implant Doses In Si 479supporting

confidence: 68%

Accurate RBS measurement of ion implant doses in silicon

Boudreault

Surface & Interface Analysis

Wendler

et al. 2002

“…For accurate work, amorphisation of crystalline samples is essential to eliminate channelling effects 23 .…”

Section: Channelling Effectsmentioning

confidence: 99%

High accuracy traceable Rutherford backscattering spectrometry of ion implanted samples

Colaux

2014

Anal. Methods

There are few techniques capable of the non-destructive and model-free measurement at 1% absolute accuracy of quantity of material in thin films without the use of sample-matched standards. We demonstrate that Rutherford backscattering spectrometry can achieve this robustly, reliably and conveniently. Using 1.5 MeV He + , a 150 keV ion implant into silicon with a nominal fluence of 5 × 10 15 As/cm² has been independently measured repeatedly over a period of 2 years with a mean total combined standard uncertainty of 0.9 ± 0.3% relative to an internal standard given by the silicon stopping power (a coverage factor k=1 is used for all uncertainties given). The stopping power factor of this beam in silicon is determined absolutely with a mean total combined standard uncertainty of 0.8 ± 0.1%, traceable to the 0.6% uncertainty of the Sb-implanted certified reference material (CRM) from IRMM, Geel. The uncertainty budget highlights the need for the accurate determination of the electronic gain of the detection system and the scattering angle, parameters conventionally regarded as trivial. This level of accuracy is equally applicable to much lower fluences since it is not dominated by any one effect; but it cannot be reached without good control of all of these effects. This analytical method is extensible to non-Rutherford scattering. The stopping power factor of 4.0 MeV lithium in silicon is also determined at 1.0% absolute accuracy traceable to the Sb-implanted CRM. This work used SRIM2003 stopping powers which are therefore demonstrated correct at 0.8% for 1.5 MeV He in Si and 1% for 4 MeV Li in Si.

“…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.…”

Section: Resultsmentioning

confidence: 99%

“…The electronics calibration was done independently for the two detectors at a precision of about 0.5% using a Au/Ni/SiO 2 /Si sample and the procedure in Jeynes et al [7].…”

Section: Methodsmentioning

confidence: 99%

Absolute dose performance of the SWIFT single wafer ion implanter

Claudio

Boudreault

Ion Implantation Technology. 2002. Proceedings of the 14th International Conference On

et al. 2002

Abstract-The characteristics of a new high performance implanter ("SWIFT") manufactured by Applied Materials include high accuracy implantation angle control, minimal energy spread [and uniformity and repeatability of dose [<0.5%] at various beam incident angles up to 60 degrees from normal. The latter is achieved using beam current monitoring equipment designed to measure absolute dose. It should be mentioned that although repeatability is much more important than absolute accuracy in implanter dosimetry, absolute accuracy is very convenient, making cross-machine comparisons, the establishment of new processes and day to day validation of different processes much easier. Four silicon wafers implanted by SWIFT at about 5*10 15 As/cm 2 were analysed by Rutherford backscattering spectrometry in order to characterise the absolute dosimetry of this implanter with an accuracy of 1.6% traceable to the international standard of weight in Paris. Repeatability and internal consistency of the RBS could be demonstrated at the 1% level consistent with the expected statistical and other errors. We could also find no significant error in the implanter dosimetry I INTRODUCTIONIn modern Integrated Circuits, the uniformity of the dose implanted is a critical parameter because a variation in dose can lead to unwanted variations in the device yield, performance and reliability. Applied Materials has manufactured a new implanter ("SWIFT") capable of a great uniformity and repeatability in the dose implanted. We report here absolute measurements of dose accuracy.SWIFT is designed as a medium current single wafer implanter capable of high energies (up to 1700keV).Accurate measurement of film thickness by Rutherford backscattering (RBS) utilises the fact that the scattering crosssections are given accurately by analytical functions. However, absolute interpretation of RBS spectra implies an accurate knowledge of both deposited charge and detector solid angle. All the samples were provided by Applied Materialsand implanted on SWIFT ion implanter. A. SWIFT Dosimetry InstrumentationIn the SWIFT implanter the ion beam is magnetically scanned in the horizontal axis, and the wafer is mechanically scanned vertically with a high precision variable speed mechanism. The behaviour of the beam charge is given by the transmission characteristics of the beam path through the implanter and is effectively an instrumental constant. The scan speed function is then chosen (in software) to give a constant dose rate as a function of position.The wafer can be tilted at arbitrary angles (up to 60), but the scan is isocentric, that is, the wafer is moved in its plane. This means that the position of the implantation does not change in space, which is essential to maintaining uniformity. The magnetic scan is large enough to pass the beam over a fixed Faraday cup, which monitors the beam charge deposited on every pass. The vertical (mechanical) scan speed is adjusted at the end of each half scan.The fixed Faraday cup is magnetically suppressed. Calculations of...