@article{pivovarov_stevie_griffis_2004, title={Improved charge neutralization method for depth profiling of bulk insulators using O-2(+) primary beam on a magnetic sector SIMS instrument}, volume={231}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2004.03.070}, abstractNote={Use of electrons for charge neutralization during positive secondary ion SIMS analysis of insulators has typically been achieved using coincident primary ion and electron beams. The normal incidence electron gun on CAMECA magnetic sector SIMS instruments can effectively eliminate sample charging during analysis of thin insulating films if the electron energy is sufficient to penetrate the film. However, positive secondary ion SIMS bulk insulator analysis using this instrument can be difficult, especially if high sputtering rates are required. A neutralization method has been developed utilizing electron beam impact of a region adjacent to the sputtered area. Prior to analysis, the surface of the sample is coated with gold which provides a conductive surface layer and which has a high secondary and backscattered electron yield. Results have been obtained showing excellent neutralization for a variety of bulk insulators including glass, silica, alumina, and lithium niobate. Sputtering rates exceeding 2 nm/s have been achieved in bulk silica. The technique should be applicable to minerals and possibly for other materials in cases where the analyzed area cannot be directly irradiated with an electron beam.}, journal={APPLIED SURFACE SCIENCE}, author={Pivovarov, AL and Stevie, FA and Griffis, DP}, year={2004}, month={Jun}, pages={786–790} }
 @article{kachan_hunter_kouzminov_pivovarov_gu_stevie_griffis_2004, title={O-2(+) versus Cs+ for high depth resolution depth profiling of III-V nitride-based semiconductor devices}, volume={231}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2004.03.211}, abstractNote={Abstract Optimum depth resolution with adequate sensitivity for the elements of interest is required to obtain the information desired from SIMS analysis of multilayer nitride III–V structures. For many of the species of interest, particularly the p-type dopants, O2+ bombardment at low energy is often used. Use of Cs+ bombardment and detection of the cesium attachment secondary ions (CsM+ where M is the element of interest) may provide several advantages over O2+ analysis. Using similar low primary ion impact energy analysis conditions for O2+ and Cs+ on CAMECA IMS-6f and IMS-4f instruments, the depth resolution obtained for positive secondary ions is compared.}, journal={APPLIED SURFACE SCIENCE}, author={Kachan, M and Hunter, J and Kouzminov, D and Pivovarov, A and Gu, J and Stevie, F and Griffis, D}, year={2004}, month={Jun}, pages={684–687} }
 @article{gu_pivovarov_garcia_stevie_griffis_moran_kulig_richards_2004, title={Secondary ion mass spectrometry backside analysis of barrier layers for copper diffusion}, volume={22}, ISSN={["1071-1023"]}, DOI={10.1116/1.1617278}, abstractNote={Secondary ion mass spectrometry (SIMS) backside analyses have been performed on a Cu/TaN/Ta/SiO2/Si structure to determine barrier effectiveness for Cu diffusion. Sample backside access to the barrier layers was obtained by removal of the Si substrate using a polishing method that maintains parallelism between the sample surface and the polished back side by monitoring changes in facets at the four corners of the specimen. Determination of the Si thickness remaining during the polishing process was improved through the use of optical interference measurements using a narrow band pass optical filter. Samples having slopes with respect to the original surface less than 6 nm over 60 μm have been obtained. A difference in polishing rate between SiO2 and Si was exploited to obtain this parallelism. For SIMS analyses, the presence of a SiO2 layer required electron gun charge neutralization for the O2+ 0.5 keV impact energy analysis. SIMS analyses show the ability to distinguish all layers and to monitor copper through the barrier material. With the high depth resolution conditions used, SIMS analyses were able to provide detailed elemental distribution information such as the presence of nitrogen at specific interfaces.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Gu, C and Pivovarov, A and Garcia, R and Stevie, F and Griffis, D and Moran, J and Kulig, L and Richards, JF}, year={2004}, pages={350–354} }
 @article{gu_garcia_pivovarov_stevie_griffis_2004, title={Site-specific SIMS backside analysis}, volume={231}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2004.03.140}, abstractNote={For maximum SIMS depth resolution for any layer in a sample, the depth profile should begin only as far from the layer as necessary to establish a constant implant concentration of the primary ion beam species. Depth resolution and detection limit can be severely degraded if it is necessary to sputter through an over layer having non uniform sputtering properties or containing a high level of the impurity of interest prior to reaching the layer of interest. A SIMS backside analysis method based on mechanical polishing is extended to allow site-specific SIMS backside depth profile analysis. Optical microscopy employing a red filter was used to allow direct viewing of the site to be depth profiled both during polishing and in situ during SIMS analysis. Depth profile analyses were performed on 100μm×100 μm device test structures. Sample charging resulting from insulator layers present in these device test structures was alleviated using a modified sample mounting technique. Backside SIMS depth profile analysis using an O2+ primary ion beam having an impact energy of 1.25 keV was used to determine if boron had penetrated a thin SiO2 layer.}, journal={APPLIED SURFACE SCIENCE}, publisher={Elsevier BV}, author={Gu, C and Garcia, R and Pivovarov, A and Stevie, F and Griffis, D}, year={2004}, month={Jun}, pages={663–667} }
 @article{pivovarov_gu_stevie_griffis_2004, title={Utilization of electron impact ionization of gaseous and sputtered species in the secondary ion acceleration region of a magnetic sector SIMS instrument}, volume={231}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2004.03.069}, abstractNote={Negative secondary ion insulator analysis using a normal incidence electron gun (NEG) on CAMECA magnetic sector SIMS instruments can be difficult due to an inability to adequately determine the electron beam impact region during NEG alignment. The electron impact energy is too low to utilize phosphor cathodoluminescent materials that can be used for NEG alignment for positive secondary ion analyses. Detection of electron beam desorbed H− is often used for NEG alignment, but the presence of H on the surface is not always uniform and it is transient, making it difficult to determine whether variations in the H− secondary ion intensity are due to non-uniformity of the electron beam or of the H on the sample. To overcome this difficulty, a new technique has been developed that takes advantage of sputtering of the sample surface by positive ions created by electron impact ionization in the spectrometer secondary ion acceleration region between the sample and the immersion lens of the mass spectrometer. The formation of the ions occurs by interaction of residual gas species in the spectrometer secondary ion acceleration region with the NEG electron beam. This method is used to align the NEG for negative secondary ion charge neutralization.}, journal={APPLIED SURFACE SCIENCE}, author={Pivovarov, A and Gu, C and Stevie, F and Griffis, D}, year={2004}, month={Jun}, pages={781–785} }
 @article{pivovarov_stevie_griffis_guryanov_2003, title={Optimization of secondary ion mass spectrometry detection limit for N in SiC}, volume={21}, ISSN={["0734-2101"]}, DOI={10.1116/1.1595108}, abstractNote={Controlled changes in the Cs+ primary ion beam density and analytical expressions describing the sources (bulk concentration, memory effect, and adsorption of N from the residual vacuum) of secondary ion mass spectrometry analyte secondary ion intensities were used to determine the contributions to the N secondary ion intensity obtained during the analysis of trace levels of N in bulk SiC. This methodology allows the determination of N concentrations that can be substantially less than the apparent N secondary ion background intensity. It was shown that for the Cameca IMS-6F instrumental conditions used, memory effect is the main contributor to the N background signal. Taking into consideration the Cs+ beam diameter, the raster size, the diameter of the ion-extracted area, and the impurity secondary ion intensity, an optimized combination of primary ion beam current and raster size was determined that resulted in the best detection limit for N in bulk SiC. This detection limit for N in bulk SiC (∼6×1014 atoms/cm3) was obtained for a primary ion current of 100 nA, a raster size of 45 μm×45 μm, and a secondary ion extraction area diameter of 30 μm.}, number={5}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Pivovarov, AL and Stevie, FA and Griffis, DP and Guryanov, GM}, year={2003}, pages={1649–1654} }