Papers by Keyword: ToF-SIMS

Abstract: For precise investigation of distribution for impurity or composition at SiO₂/SiC interface, dual-beam Time-of-flight Secondary ion mass spectrometry (TOF-SIMS) with low energy sputtering beam was available. In addition to the experimental profiles, simulation using MRI model, in which Mixing, Roughness and Information depth were employed as parameters, enabled to acquire a more authentic distribution at the SiO₂/SiC interface. Slight discrepancy on depth profiles between samples with different surface roughness was duplicated on the convoluted profiles in the simulation. Moreover, reconstructed profile of nitrogen indicated a real distribution with less impact of mixing and roughness, although that may contain uncertainty due to incompletion in the simulation model or variation of the distribution owing to detection species in the experiment. From the result of carbon profiles of both experimental and convoluted profiles, the relative discrepancy on the carbon distribution between samples was clarified, which suggested the possibility that a carbon thin layer at the SiO₂/SiC interface would be found in the future.

Abstract: The recently developed bombardment induced ion transport (BIIT) technique is reviewed. BIIT is based on shining an energy-selected alkali ion beam at the surface of a sample of interest. Attachment of these ions leads to the build-up of a surface potential and a surface particle density. This in turn generates the corresponding gradients which induce ion transport towards a single metal electrode connected to the backside of the sample where it is detected as a neutralization current. Two different versions of BIIT are presented, i.) the native ion BIIT and ii.) the foreign ion BIIT. The former is demonstrated to provide access to absolute ionic conductivities and activation energies, the latter leads to the generation of electrodiffusion profiles. Theoretical modelling of these concentration profiles by means of the Nernst-Planck-Poisson theory allows to deduce the concentration dependence of diffusion coefficients.

Abstract: The effectiveness of a FOUP (Front Opening Unified Pod) conditioning test bench was tested with respect to the reduction of outgassing materials from FOUP materials and cleanroom compatibility. The equipment uses vacuum and heat to reduce volatile organic compounds from construction material and wafers. Five different analysis methods were used to asses the performance of the equipment with respect to organic, ionic and metal contamination. The experiments showed that the use of heat and vacuum has a positive effect on the organic contamination from FOUPs, and that the equipment is suitable for semiconductor applications in cleanroom environments.

Abstract: Reference samples were produced for development, benchmarking and comparison of analytical techniques based on mass spectroscopy as TD-GCMS and TOF-SIMS and x-ray analysis as TXRF-NEXAFS. Organic contaminants representing plasticizers, disinfectants and flame retardants were chosen. The contaminants were selected with respect to reliable detection using the above analytical techniques. The stability of the reference samples produced with dethylphtalate, triclosane, and tetrabrombisphenol A on silicon stripes or wafers with a diameter of 200 mm was found to be approx. 10 days. The comparison of the techniques showed that the mass spectroscopy methods allowed reliable qualification of organic surface contamination. TD-GCMS quantifies and identifies the volatile organic compounds whereas TXRF quantifies the carbon contamination, especially the non-volatile, on sample surfaces.

Abstract: Tungsten importance in semiconductor manufacturing is renewed more and more due to its usage not only as metallization for plugs, but also in metal gates architectures. As the scaling down of the devices is becoming aggressive, the metal interfaces become more critical. Hence, a deeper understanding of the evolution of the W surface after wet cleaning processes is becoming increasingly more important.

Abstract: Ti-rich Mg1ЎxTi1+xO3 samples were synthesized by solid-state reaction. Sampleswere characterized by room temperature x-ray powder di®raction, scanning electron microscopyand energy dispersive spectroscopy of x-rays. Hexagonal lattice parameters a and c increasedwith increasing Ti content. Time-of-Flight-Secondary-Ion-Mass-Spectroscopy (ToF-SIMS, de-tection limit 10Ў6) measurements revealed that no magnetic impurities were present. Sampleswith x = 0:10; 0:12 and 0:32 showed ferromagnetic hysteresis loops. The result demonstratesthat excess Ti at the Mg-O cation layer controls the magnetic properties. This is a technologicaladvantage especially for thin Їlm applications.

Abstract: The formation of plasma-polymerized materials made from organic molecules is a technologically attractive way to obtain films with unique properties for life science applications. Surface properties like bio-compatibility, wettability, etc., can be adjusted by tailoring the chemical functionalization. It is well known that after deposition these films undergo post-plasma reactions, especially when they are exposed to ambient atmosphere. Most often, in applications these films are not used immediately after their deposition – they are usually stored for a certain time. Therefore there is a need for a development of analytical procedures enabling studies of ageing phenomena of plasma chemically deposited films. With the help of these studies a better understanding of basic post-plasma reaction phenomena as well as relevant empiric information for practical applications can be obtained. However, a detailed chemical characterization of plasma chemically deposited films is a great challenge for the analysts because of the co-existence of a number of different chemical species. We investigated r.f. plasma-polymerized organic films by using photoelectron spectroscopy for chemical analysis (ESCA), spectroscopy of the near edge X-ray absorption fine structures (NEXAFS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Ethylene, styrene, allyl alcohol and allyl amine were used as monomers. A dedicated plasma preparation chamber was designed and added to the main analysis chamber of the respective spectrometer. This approach offers the possibility to study plasma-polymerized films in situ and, subsequently, the influence of post-plasma reactions. The important effect of air exposure of the film, in terms of plasma technology denominated as “ageing”, can be studied subsequentially step by step by this unique approach.

Abstract: The concentration of nitrogen and phosphorous in SiC bulk material and epitaxial layers was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The advantage of TOF-SIMS of acquiring a complete mass spectrum in a single run was used to identify the most sensitive atomic ion or ionic cluster for the selected element to be monitored. For the investigation of N with its intrinsic low ionization yield the use of a Cs containing cluster ion is necessary. Selection of a CNCs2 + cluster allows to reach a detection limit of about cN,min » 5×1016 cm-3. In the case of P the elemental ion was used. However, the adjacent mass of 30SiH influences the P peak as well as its background and has to be suppressed. This can be achieved by limiting the residual gas re-adsorption during the measurement resulting in a detection limit of about cP,min » 5×1015 cm-3. These measurement parameters were used to investigate a single crystal SiC bulk sample grown by the modified Lely method with intentional P doping and an N doped epitaxial SiC layer sample.