[en] Exfoliation of SiC by hydrogen implantation and subsequent annealing forms the basis for a thin-film separation process which, when combined with hydrophilic wafer bonding, can be exploited to produce silicon-carbide-on-insulator, SiCOI. SiC thin films produced by this process exhibit unacceptably high resistivity because defects generated by the impact neutralize electrical carriers. Separation occurs because of chemical interaction of hydrogen with dangling bonds within microvoids created by the impact, and physical stresses due to gas-pressure effects during post-implant anneal. Experimental results show that exfoliation of SiC is dependent upon the concentration of implanted hydrogen, but the damage generated by the implant approaches a point when exfoliation is, in fact, retarded. This is attributed to excessive damage at the projected range of the implant which inhibits physical processes of implant-induced cleaving. Damage is controlled independently of hydrogen dosage by elevating the temperature of the SiC during implant in order to promote dynamic annealing. The resulting decrease in damage is thought to promote growth of micro-cracks which form a continuous cleave. Channeled H⁺ implantation enhances the cleaving process while simultaneously minimizing residual damage within the separated film. It is shown that high-temperature irradiation and channeling each reduces the hydrogen fluence required to affect separation of a thin film and results in a lower concentration of defects. This increases the potential for producing SiCOI which is sufficiently free of defects and, thus, more easily electrically activated

[en] We have recently described modifications to the program CONTIN for the solution of Fredholm integral equations with convoluted kernels of the type that occur in the analysis of positron annihilation lifetime data. In this article, modifications to the program to correct for source terms in the sample and reference decay curves and for shifts in the position of the zero-time channel of the sample and reference data are described. Unwanted source components, expressed as a discrete sum of exponentials, may be removed from both the sample and reference data by modification of the sample data alone, without the need for direct knowledge of the instrument resolution function. Shifts in the position of the zero-time channel of up to half the channel width of the multichannel analyzer can be corrected. Analyses of computer-simulated test data indicate that the quality of the reconstructed annihilation rate probability density functions is improved by employing a refernce material with a short lifetime and indicate that reference materials which generate free positrons by quenching positronium formation (i.e. strong oxidizing agents) have lifetimes that are too long (400-450 ps) to provide reliable estimates of the lifetime parameters for the shortlived components with the methods described here. Well-annealed single crystals of metals with lifetimes less than 200 ps, such as molybdenum (123 ps) and aluminium (166 ps) do not introduce significant errors in estimates of the lifetime parameters and are to be preferred as reference materials. The performance of our modified version of CONTIN is illustrated by application to positron annihilation in polytetrafluoroethylene. (orig.)

[en] Spectroscopic ellipsometry, scanning electron microscopy, and transmission electron microscopy are all invaluable routine characterization techniques to determine the thickness of silicon nitrides during manufacturing of compound semiconductor devices. We describe in detail the accuracy and convenience of each technique. In addition to thickness, nitride composition is another process parameter that needs to be controlled in manufacturing. Therefore, we also discuss using UV Raman spectroscopy, Rutherford backscattering spectroscopy, and spectroscopic ellipsometry to measure composition. Finally, we discuss the correlation between electrical parameters (capacitance and breakdown voltage) and the stoichiometry of the silicon nitride used as a dielectric in a metal-insulator-metal capacitor

[en] The performance of the program CONTIN, modified to solve Fredholm integral equations with convoluted kernels of the type that occur in the deconvolution and analysis of positron annihilation lifetime data, is investigated with computer-simulated test data. The method avoids direct determination of the instrument resolution function by employing the decay curve of a reference material with a well-known single lifetime. CONTIN employs a constrained, regularized least-squares analysis to calculate a continuous annihilation-rate probability density function (pdf) which is the most parsimonious solution that is consistent with the experimental data and prior knowledge. The performance of the algorithm for extracting positron annihilation lifetime information was evaluated by using several measures of the information content of the data described by Schrader and Usmar. The quality of the CONTIN reconstruction of the annihilation-rate pdf is strongly dependent on the information content of the data and is greatly improved as the total number of counts in the data set is increased. Nevertheless, the method provides excellent estimates of the intensities and mean lifetimes of peaks in the annihilation-rate pdf, even when the total counts in the data set are relatively low (10⁵-10⁶). The sensitivity of the algorithm to systematic errors in the data, including errors in the instrument resolution function, shifts in the position of the zero-time channel of the sample and reference data and contamination of the reference decay by additional lifetime components was also evaluated. Errors in the FWHM of the instrument resolution function and shifts in the zero time channel as small as 1/10 to 1/5 of the channel width of the instrument generate additional spurious peaks in the annihilation-rate pdf and introduce errors in the lifetime parameters of the short-lived components. (orig.)

[en] The reliability of a least squares analysis of positron annihilation lifetime data represented as a sum of convoluted exponentials is investigated with computer-simulated test data. The method of analysis, which is available as a computer program called 'SPLMOD' [R.H. Vogel, Technical Report EMBL-DA08, European Molecular Biology Laboratory, Heiselberg, FRG, (1986)], avoids direct determination of the instrument resolution function by employing the decay curve of a reference material with a well-known single lifetime. The performance of the algorithm for extracting positron annihilation lifetime information was evaluated by using several measures of the information content of the decay curve described recently by Schrader and Usmar [in: Positron Annihilation Studies of Fluids, ed. S. Sharma (World Scientific, Singapore, 1988)]. The sensitivity of the algorithm to systematic errors including errors in the resolution function, shifts in the zero time channel and contamination of the reference decay curves by additional lifetime components was evaluated. The method provides excellent estimates of lifetime parameters when the reference decay curve accurately reflects the resolution function of the sample data. However, the algorithm is extremely sensitive to errors in the instrument resolution function. (orig.)

[en] A Varian IA-200 isothermal annealer has been used to anneal ion implantation damage and electrically activate dopants in As and B implanted silicon with minimal redistribution of the impurity. The anneal occurs in vacuum using infrared radiation from a resistively heated sheet of graphite. Good quality anneals of ₁₁B implanted samples have been obtained with minimal boron diffusion. Arsenic implanted wafers have also be annealed with excellent results except for a substantial loss of As which occurs unless the wafer has an SiO² cap. The anneal quality of (100) wafers was independent of dose, however, the anneal quality of the (111) wafers improved with increasing As dose

[en] H⁺ implantation of SiC is the basis for a thin-film transfer process, which when combined with oxidation and hydrophilic wafer bonding, can be exploited to produce silicon carbide-on-insulator material useful as a wide-band-gap semiconductor. This thin-film transfer process has been successfully applied to Si to produce a commercial silicon-on-insulator material. The efficacy of hydrogen to produce thin-film separation was studied by investigation of H⁺-induced exfoliation in implanted SiC. Results showed that the onset and degree of exfoliation of SiC depends initially upon the concentration of implanted H⁺. However, the dose dependence of exfoliation exhibits a rather marked retrograde behavior. The degree of exfoliation eventually starts to decrease with increasing ion dose until exfoliation is completely suppressed. This behavior is attributed to a competition between the positive effects of hydrogen on exfoliation and the negative effects of ion-induced damage. Experiments were done to isolate the effects of the hydrogen - silicon chemistry from that of implant damage. Damage is reduced independently of H⁺ dosage by elevating the temperature of the SiC during implant in order to promote dynamic annealing. This will be shown to have a dramatic effect upon exfoliation. The hot implant lowers the H⁺ fluence required to affect thin-film separation, making the process more efficient, and producing SiC material with fewer defects. copyright 1999 American Institute of Physics

[en] Single crystal Si wafers and polycrystalline Si films on Si₃N₄ have been implanted with large doses (1 x 10¹⁵/cm²--4 x 10¹⁶/cm²) of P or As and laser annealed with either a cw or pulsed laser. The samples were then subjected to thermal anneals between 450 and 900 ⁰C to determine the thermally stable dopant concentration for each sample. Sheet resistance and Hall measurements have been used to measure the electrical properties in each case. SIMS, RBS, and TEM have been used to measure atomic profiles, As substitutionality and residual defects after laser and thermal annealing. In each case the maximum electrically active dopant concentration achieved by laser annealing decreased after a 700--800 ⁰C thermal anneal

[en] Heavy Ion Backscattering Spectrometry (HIBS) is a new IBA tool for measuring extremely low levels of surface contamination on very pure substrates, such as Si wafers used in the manufacture of integrated circuits. HIBS derives its high sensitivity through the use of moderately low energy (∼ 100 keV) heavy ions (e.g., C¹²) to boost the RBS cross-section to levels approaching 1,000 barns, and by using specially designed time-of-flight detectors which have been optimized to provide a large scattering solid angle with minimal kinematic broadening. A HIBS User Facility has been created which provides US industry, national laboratories, and universities with a place for conducting ultra-trace level surface contamination studies. A review of the HIBS technique is given and examples of using the facility to calibrate Total-Reflection X-ray Fluorescence Spectroscopy (TXRF) instruments and develop wafer cleaning processes are discussed

[en] Sputtered Ba_1-xSr_xTiO₃ (BST) and SrTiO₃ (STO) films and capacitors made with these dielectrics have been characterized with respect to physical and electrical properties. Specific capacitance values included a high of 96fF/μm² for BST films deposited of 600 degree C and a high of 26fF/μm² for STO films deposited at 400 degree C. Leakage current densities at 3.3 V for the most part varied from mid 10^-8 to mid 10^-6A/cm². All of the dielectrics are polycrystalline, although the lowest temperature STO films have a nearly amorphous layer which impacts their capacitance. Grain size increases with deposition temperature, which correlates to higher dielectric constants. The lattice parameter of the BST films is larger than that of bulk samples. Capacitance, leakage, breakdown, and lifetime results are reported. copyright 1997 American Institute of Physics