Papers

AVS1997 Session QS-MoM: Ion Methods

Monday, October 20, 1997 8:20 AM in Room N

Monday Morning

Start	Invited?	Item
8:20 AM		QS-MoM-1 Surface Composition and Topography of Compound Semiconductors after Sputtering. J.B. Malherbe (University of Pretoria, South Africa) Ion bombardment of compound semiconductors usually leads to a change in the surface composition and in the surface topography. This has implications for both quantitative surface analytical techniques and industrial processes which employ ion implantation. A brief review of these two processes will be presented. Special emphasis on experimental results on GaAs and InP will be given because most of the published investigations have been on these two materials. Steps how to compensate for these changes in quantitative AES/XPS using the relative sensitivity method with matrix dependent factors will be outlined.
9:20 AM		QS-MoM-4 Ion-Implanted Reference Materials for the Semiconductor Industry D.S. Simons (National Institute of Standards & Technology) This presentation will describe the development and application of two ion-implanted standard reference materials for calibrating the secondary ion response to minor and trace levels of specific dopant species in a silicon matrix by secondary ion mass spectrometry (SIMS). In SRM 2137, released in 1993, ¹⁰B has been implanted into a single crystal Si substrate that was rendered amorphous by Si ion implantation. The retained dose of ¹⁰B was certified by a neutron reaction method known as neutron depth profiling. This SRM is useful for making calibrated measurements of the implanted boron dose or of the boron concentration in silicon samples, with good reproducibility among different laboratories, as has been demonstrated in a recent ISO round robin study. A new reference material of Si implanted with ⁷⁵As, SRM 2134, will be released by NIST in 1997. In this case the retained As dose and its uniformity among 1 cm x 1 cm pieces were certified by instrumental neutron activation analysis (NAA). By eliminating the Si amorphization step and by using 200 mm rather than 76 mm diameter wafers, the development time has been greatly reduced for this new SRM. Comparison measurements of retained dose in this material by Rutherford backscattering spectrometry and x-ray fluorescence are in good agreement with the NAA-determined value.
10:20 AM		QS-MoM-7 Quantitative Analysis by Static SIMS: Exploiting All the Information in the Spectra B.D. Ratner (University of Washington) SIMS is often referred to as a surface technique with little or no potential for quantitative analysis. This presentation will argue that static SIMS is not only quantitative, but is one the most quantitative analytical tools available. There are two aspects of SIMS that form the basis for this statement: (1) SIMS spectra are highly reproducible, and (2) the spectra are exceptionally rich in information. For organics and polymers, matrix effects are often minimal and, in some situations, relatively simple correlations between a SIMS peak (or a ratio of two peaks) and sample composition are possible. This is seen with some methacrylate polymer series and with some mixed composition self-assembled monolayers. Ratios of atomic peaks to molecular peaks can, for polymers, be correlated quantitatively with sample crosslinking and other parameters related to chain mobility. Finally, multivariate statistical methods permit complex correlations using information from all the peaks in the spectra. Such correlations will be shown with C/O and C/H ratios, and with biological phenomena such as cell growth and protein adsorption.
11:20 AM		QS-MoM-10 Surface Analysis Using Slow, Highly Charged Ions like Au⁶⁹⁺ T. Schenkel, A.V. Hamza, A.V. Barnes, D.H. Schneider (Lawrence Livermore National Laboratory); D.S. Walsh, J.C. Banks, B.L. Doyle (Sandia National Laboratories) Slow (v<10⁶ m/s), highly charged ions like Xe⁴⁴⁺ and Au⁶⁹⁺ deposit tens to hundreds of keV of electronic excitation energy when they interact with surfaces. Power densities are in the order of 10¹⁵ W/cm². Strong electronic sputtering and desorption effects result in secondary ion yield increases by over two orders of magnitude as compared to yields from collisional sputtering using singly charged ions ¹. The intense local excitation has been proposed to result in a reduction of the matrix effect in secondary ion production. We have investigated the potential of highly charged ions for highly sensitive and quantitative surface analysis in TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) studies of B-SiO₂ layers on Si. Films were independently characterized using elastic recoil detection analysis. Peak boron concentrations in the percent range as determined by both methods were found to agree within an accuracy of ~10%. In our presentation we will discuss the indicated possibility to accurately profile impurities in shallow layers of materials without distortions due to surface transient effects. Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-ENG-48. ¹T. Schenkel, et al., Phys. Rev. Lett. 78 (1997) 2481
11:40 AM		QS-MoM-11 Contribution of SIMS Analysis to Characterization of GaN and Related Compounds Y. Gao, C. Huang, R. Clark-Phelps, S. Mitha (Charles Evans & Associates) The III-nitrides has recently been the subject of intense research because their promising application in bleu and ultraviolet optoelectronic devices and microwave devices. The growth of epitaxial layers, grown by MOCVD and MBE techniques, needs the close control of purity, doping, alloy composition, thickness and interface quality. Secondary ion mass spectrometry (SIMS) is a very suitable characterization technique because of its ability to depth profile with high sensitivity and good depth resolution. We describe depth profiling for the concentration of dopants (Mg, Zn and Si) and common impurities such as O, C, H and some metals incorporated during the growth and determining In and Al composition. The samples includes p-n junction GaN, AlGaN/InGaN/GaN LED, Quantum well LED and AlN/GaN photodetector. Also SIMS measurement on finished LED devices will be described for the purpose of failure analysis and reveres engineering. The wealth information so obtained has proven very useful for solving problems encountered in both research and production.