We demonstrate high resolution reduction imaging in the soft x-ray spectral region using multilayer-coated reflective optics. In particular, a Schwarzschild objective was used at 20:1 reduction with 14 nm radiation to image line and space features from a transmission mask onto a resist-coated silicon wafer with a resolution better than 0.1 μm. The mirrors of the objective were coated with Mo/Si multilayers to provide nearly 40% reflectance at near-normal incidence for the 14 nm radiation. Our results demonstrate that multilayer coatings are capable of enhancing the reflectance of optical components at soft x-ray wavelengths without significantly degrading their imaging performance.
Although electron cyclotron resonance (ECR) plasma reactors are being used in the microelectronics industry for etching and deposition of thin films they are prone to instabilities that can wreak havoc with manufacturing processes. Plasma conditions are often unstable because of nonlinear coupling between wave propagation, power absorption, neutral density, and charge density profiles. We report on hysteresis, multiple steady states and abrupt transitions in an ECR plasma reactor that can alter the plasma properties drastically. Substrate platen floating potential and Langmuir probe measurements are used to identify several abrupt transitions and regions in the operating parameter space where the plasma can exist in either one of two different states under identical operating conditions (microwave power, pressure, flow rate, magnetic field, rf bias etc.) Depending on how the plasma is started either branch can be obtained. Abrupt transitions and hysteresis in plasma properties are observed both with and without rf bias under typical conditions used in plasma processes. Such transitions can cause drastic deviations in plasma parameters—density, current, uniformity—and may result in degraded process characteristics—uniformity, rate, selectivity, linewidth control. Statistical techniques used to design and develop processes cannot properly account for discontinuous changes in the state of the plasma and can produce brittle processes that can suddenly lead to catastrophic failure. Care must be taken to map out the regions of bistability for the purpose of avoiding them or controlling the plasma in these regions. While the mechanism responsible for the multiple steady states and abrupt transitions reported here is not well understood, it is clear that these phenomena depend critically on the neutral density.
Many experimental reports for the kinetics of crystal nucleation and growth, from an isothermal solution, point to a sigmoidal‐like behavior for the process. Here we consider three different nucleation models from the literature and show that all lead to sigmoidal or sigmoidal‐like behavior for the kinetics of nucleation. A two‐step nucleation process is known to occur within certain supersaturated protein solutions, and it is demonstrated in this report how the sigmoidal law yields kinetic information for the two‐step and homogeneous nucleation modes. We propose here that two‐step solute‐rich associates form in the solution around seed nuclei that are already present at or near the point in time when the solution is prepared. Using this hypothesis, we are able to model the time‐dependent volume of the two‐step phase per unit volume of solution and show that this compares well with reported experimental data. A kinetic model is given for the proposed process, which leads to a sigmoidal rate law. Additionally, a relation between the initial and final nuclei densities and the induction time is derived. As a result of this study, the conclusion is that two‐step activity increases with increasing initial supersaturation or increasing salt concentration.
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