Papers by Keyword: SIMS

Abstract: Ion implantation is a crucial step in the process of SiC device fabrication. Precise and predictable doping distributions are necessary for reduced cell pitches and integrated circuit development. However, straggling due to ion channeling affects this goal. Even though vertical channeling has been investigated successfully, lateral straggling remains unclear. Therefore, two-dimensional SIMS concentration distributions are used to investigate lateral straggling of Al and P implanted in 4H-SiC. Results, for both Al and P, show that there is a significant influence of the crystal orientation showing that some channels lead to a few micrometers more lateral straggling than others. High implantation doses increase the amount of amorphization, which leads to more dechanneling and, thus, less straggling. Even though elevated implantation temperatures increase lattice vibrations and thus act in favor of dechanneling, the implantation distributions show significant lateral straggling as amorphization is suppressed.

Abstract: Secondary electron imaging of SiC epi-structures is commonly used as it allows doping topography i.e. the knowledge of the spatial extension of differently doped layers. Determination of the doping level of the layers was not possible until now. The present work presents how to use this technique for 4H-SiC p-type doping determination. This is indeed, possible for specific experimental data analysis and for doping levels higher than 10¹⁷cm^-3.

Abstract: In this Chapter, we review knowledge about diffusion in quasi-crystalline alloys (quasicrystals). In Section 1 we first remind the reader of some major aspects of the quasi-crystalline state and in Section 2 we introduce phase diagrams with quasi-crystalline phases, for which detailed diffusion studies are available. We mention in Section 3 the more common experimental methods for diffusion studies. The diffusive motion of atoms in quasi-crystalline alloys can be studied by the same techniques used for crystalline metallic alloys and intermetallics – measurements of radiotracer diffusion and diffusion of stable isotopes and solute atoms by SIMS profiling. The best-studied quasi-crystalline alloys are icosahedral AlPdMn, icosahedral ZnMgRE (RE = rare earth metal), and decagonal AlNiCo. The major diffusion results for these quasicrystals are reviewed in Sections 4, 5, and 6. Section 7 is devoted to the pressure dependence of diffusion in quasicrystals and to a comparison of the activation volumes with those of crystalline metals. Positron annihilation studies are also mentioned, which together with activation volumes for diffusion strongly favour a vacancy mechanism in quasicrystals. The major results and conclusions are summarized in Section 8.

Abstract: Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n-and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 oC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO₂ surface. Close to the moving SiO₂/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For p-type 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na⁺<K⁺<Cs⁺, but the sodium mobility is substantial already at 1150 °C.

Abstract: Computer simulation of the concentration profiles evolution in SiC/Si heterostructures during growth and subsequent ion sputtering is presented. Simulation is based on a complex self-consistent approach combining kinetic and ballistic methods. Within the framework of the proposed method concentration depth profiles in SiC/Si heterostructure with pre-deposited Ge impurity are calculated and compared with experimental sputtering profiles obtained by secondary ion mass spectrometry.

Abstract: Iron (Fe) impurity concentrations in a SiC bulk crystal and source powders used for the bulk crystal growth are analyzed by means of secondary ion mass spectrometry and the validity of the obtained data are discussed. The secondary ion signal of ⁵⁶Fe is found to be affected significantly by the mass interference of ²⁸Si₂, and therefore measurements of ⁵⁴Fe instead of ⁵⁶Fe offer a better detection limit for the analysis. A high concentration of Fe is found at proximity of the SiC bulk crystal surface. Possible sources of the Fe contamination are discussed based on the depth profile data of Fe in both the bulk crystal and the source powders.

Abstract: Ion implantation and subsequent diffusion are very essential stages in today's advanced VLSI (Very Large Scale Integration) semiconductor devices processing. High precision calibration of device simulation is a key procedure to ensure simulation is accurate. For this purpose, accurate prediction of the doping profiles resulted from ion implantation and diffusion will be studied using a few models of ion implantation and diffusion. We collected data of Boron as P-type ion implantation profiles using TCAD simulation software with different ion implantation models and diffusion models then compared with Secondary Ion Mass Spectrometry (SIMS) data of ion implantation profile database as experimental data. Models plays very important role in this calibration. In this paper, calibrations have done using Monte Carlo and Taurus analytical as implantation model and pd.full, pd.fermi and pd.5stream as diffusion model. All calibration simulations were simulated using Synopsys TCAD Simulation. The experimental results shown by using Monte Carlo ion implantation model with pd.5str diffusion model is close to SIMS profile.

Abstract: In the present contribution, the trends in voluntary incorporation of aluminum in 4H-SiC homoepitaxial films are investigated. The films were grown on Si-and C-face 4H-SiC 8°off substrates by chemical vapor deposition (CVD) in a horizontal, hot wall CVD reactor. Secondary Ion Mass Spectrometry (SIMS) and capacitance-voltage (C-V) measurements were used to determine the Al incorporation in the samples. The influence of Trimethylaluminum (TMA) flow rate, growth temperature, growth pressure and C/Si ratio on the dopant incorporation was studied.

Abstract: This work is a study of the segregation of alloying elements and salts to the surface of Direct Chilled-cast (DC-cast) ingots of alloy: (i) AA5083; and (ii) AA5182. The ingots only have slightly different chemical compositions. Alloy AA5182 contains Cu, while alloy AA5083 is grain refined, contains Cr, and is lower in Si and Fe compared to AA5182. The ingot microstructures were investigated using Optical Microscopy, Scanning Electron Microscope (SEM) and Secondary Ion Mass Spectrometry (SIMS). The results showed that the surfaces contained aluminum dendrites, large intermetallic crystals (Al₆(MnFe) and Al₃(Fe,Mn)) and impurities, and small crystals between dendrite arms. Between the dendrites small salt crystals containing Na, K, Ca, Mg, F and/or Cl were found. The conclusion is that salt and minority impurities are mainly located to grain boundaries in the segregation zone.

Abstract: Diffusion of lithium, sodium and potassium in SiC has been studied by secondary ion mass spectrometry. The alkali metal diffusion sources have been introduced by ion implantation. Subsequent anneals have been carried out in vacuum or in Ar atmosphere in the temperature range 700 °C - 1500 °C for 5 min to 16 h. The bombardment-induced defects in the vicinity of the ion implanted profile are readily decorated by the implanted . In the bulk, the diffusing alkali metals are most likely trapped and detrapped at boron and/or other defects during diffusion. The diffusivity of the studied alkali metals decreases as the mass increases, Li⁺<Na⁺<K⁺, but the sodium mobility in SiC is substantial already at 1100 °C.