Characterization of silicon wafers through deposition of self-assembled monolayers

AFM imaging of the adsorption of self-assembled octadecylsiloxane (ODS) monolayers has been utilized for probing surface properties of silicon wafers. It has been found that both growth rate of the organic films and island size of sub-monolayer films are influenced by the doping level of the wafers as well as by the surface finishing step during wafer production. Generally, higher doping levels led to lower adsorption rates and smaller islands. Variation of the sample pretreatment used for surface finishing of similarly doped wafers led only to significant changes of the island size, but not of the surface coverage. The results presented open up a valuable perspective for characterizing the surface homogeneity of silicon wafers which is an important parameter for monitoring-wafers in semiconductor industry. Received: 26 June 2000 / Revised: 26 July 2000 / Accepted: 1 August 2000     

Machine assisted reaction optimization: A self-optimizing reactor system for continuous-flow photochemical reactions

A methodology for the synthesis of oxetanes from benzophenone and furan derivatives is presented. UV-light irradiation in batch and flow systems allowed the [2 + 2] cycloaddition reaction to proceed and a broad range of oxetanes could be synthesized in manual and automated fashion. The identification of high-yielding reaction parameters was achieved through a new self-optimizing photoreactor system.     

Influence of the Electromagnetic Forces on Momentum and Heat Transfer in a 3-Phase ac Plasma Reactor

A new 3-phase ac plasma reactor has been developed within the framework of research on hydrocarbon cracking for the production of carbon black and hydrogen. ^(1,2) One of the main characteristics of the system is related to the 3-phase, 50 Hz ac current plasma generator which induces a very particular arc motion affecting the heat and mass transfer inside the reactor. In a first step, the general flow inside the reactor in the absence of hydrocarbon injection has been studied. A simplified approach to characterize the heat and mass transfer inside the reactor is presented in this paper. The arc zone analysis is carried out simultaneously by a theoretical analysis of the electromagnetic forces and by an ultrahigh-speed cine-camera analysis. The flow in the reactor is modeled with a CFD commercial code. Results are compared with experimental temperature measurements.     

Ueber Spectralapparate

Ohne Zusammenfassung     

Bifurcations from infinity in asymmetric nonlinear oscillators

We study the existence of large-amplitude periodic or almost periodic solutions of second order differential equations with asymmetric nonlinearities, when the system is close to "nonlinear resonance". Received September 1998     

Interpretation of excitation temperature measurements in a cesium plasma

Electron densities and temperatures have been measured by using a Langmuir probe, as well as spectroscopic observations of continuum radiation and of spectral lines, in a cesium plasma. It is shown that the excitation temperatures determined from relative intensities of spectral lines do not always agree with electron temperature determinations. An interpretation of this discrepancy is proposed and discussed.     

Integrity of ultrathin gate oxides with different oxide thickness, substrate wafers and metallic contaminations

The integrity of ultrathin gate oxides was investigated as a function of polished and epitaxial wafer surfaces with various gettering sites. After intentional contamination of wafers with 1×10¹¹ atoms/cm² and 5×10¹² atoms/cm² Cu and Ni by a spin-on technique of high reproducibility, we performed 0.18-μm low-thermal-budget CMOS process runs. Thermal oxides were grown with various gate oxides in the range of 5–17 nm. After a MOS-capacitor fabrication we applied a ramped current-density test to study the gate-oxide integrity. Generally, thinner gate oxides exhibited a much more robust behavior than thicker oxides. The gate-oxide integrity was strongly influenced by different gettering sites. Although a higher Ni contamination led to a higher number of gate-oxide failures, Cu contamination exhibited a higher impact on the gate-oxide integrity than Ni. Received: 12 September 2000 / Accepted: 21 September 2000 / Published online: 22 November 2000