@article{gu_stevie_bennett_garcia_griffis_2006, title={Back side SIMS analysis of hafnium silicate}, volume={252}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2006.02.099}, abstractNote={Abstract High-k dielectrics are under study as part of the effort to continually reduce semiconductor device dimensions and hafnium silicate (HfSixOy) is one of the most promising high-k materials. A requirement of the dielectric is that the constituent elements cannot diffuse into adjacent device regions during thermal processing. Analysis for inter-diffusion using front side SIMS of high-k dielectrics has been complicated by matrix and sputtering effects. Use of a back side analysis sample preparation procedure that was successful for copper diffusion and site specific studies produced a HfSiO specimen that has less than 250 nm silicon remaining and minimal slope over the analysis region. Magnetic Sector (CAMECA IMS-6F) SIMS analysis of this specimen with low energy O2+ bombardment does not show the matrix and sputtering effects noted in the front side data. Sufficient depth resolution was obtained to define the interface between the silicon substrate and the HfSiO layer and indicate what appears to be an interfacial layer. There is no indication of hafnium diffusion into the silicon substrate.}, number={19}, journal={APPLIED SURFACE SCIENCE}, publisher={Elsevier BV}, author={Gu, C. and Stevie, F. A. and Bennett, J. and Garcia, R. and GriffiS, D. P.}, year={2006}, month={Jul}, pages={7179–7181} }
 @article{gu_stevie_hitzman_saripalli_johnson_griffis_2006, title={SIMS quantification of matrix and impurity species in AlxGa1-xN}, volume={252}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2006.02.148}, abstractNote={The quantification in Al x Ga 1-x N with different AlN mole fraction (x) is challenging because of matrix effects and charging effects. For quantitative characterization of both matrix and impurity elements in Al x Ga 1-x N, a novel charge neutralization method was employed and calibration curves were created using an O 2 + primary beam with positive secondary ion detection and a Cs + primary beam with negative and MCs + secondary ion detection. Over the range of 0 < x < 0.58, the matrix ion intensity ratios of Al + /Ga + and AlCs + /GaCs + appear linear with the mole fraction ratio x/(1-x), and the ratio of AlN - /GaN - is linear with AlN mole fraction (x). The sputter rate decreases as AlN mole fraction increases, while the relative sensitivity factors (RSF's) of impurities have an exponential relationship with AlN mole fraction. These calibration curves allow the quantification of both matrix and impurity species in AlGaN with varying AlN mole fraction. The technique can be employed for impurity control, composition and growth rate determination, as well as structural analysis of the finished optoelectronic and electronic devices.}, number={19}, journal={APPLIED SURFACE SCIENCE}, author={Gu, C. J. and Stevie, F. A. and Hitzman, C. J. and Saripalli, Y. N. and Johnson, M. and Griffis, D. P.}, year={2006}, month={Jul}, pages={7228–7231} }
 @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} }