This paper presents a novel mask corner rounding (MCR) modeling approach based on Synopsys' Integrated Mask and
Optics (IMO) modeling framework. The point spread functions of single, double, and elliptical Gaussians are applied to
the IMO mask kernels to simulate MCR effects. The simulation results on two dimensional patterns indicate that the
aerial image intensity variation is proportional to the MCR induced effective area variations for single type corners. The
relationship may be reversed when multiple types of corners exist, where the corners close to the maximum intensity
region have a greater influence than others. The CD variations due to MCR can be estimated by the effective area
variation ratio and the image slope around the threshold. The good fitting results on line-end patterns indicate that the
ΔCD is the quadratic function of the Gaussian standard deviations. OPC modeling on 28nm-node contacts shows that
MCR has significant impact on model fitting results and process window controls. By considering the real mask
geometry effects and allowing in-line calibration of model parameters, the IMO simulation framework significantly
improves the OPC model accuracy, and maintains the calibration speed at a good level.
Topographic mask effects can no longer be ignored at technology nodes of 45 nm, 32 nm and beyond. As
feature sizes become comparable to the mask topographic dimensions and the exposure wavelength, the popular
thin mask model breaks down, because the mask transmission no longer follows the layout. A reliable mask
transmission function has to be derived from Maxwell equations. Unfortunately, rigorous solutions of Maxwell
equations are only manageable for limited field sizes, but impractical for full-chip optical proximity corrections
(OPC) due to the prohibitive runtime. Approximation algorithms are in demand to achieve a balance between
acceptable computation time and tolerable errors.
In this paper, a fast algorithm is proposed and demonstrated to model topographic mask effects for OPC
applications. The ProGen Topographic Mask (POTOMAC) model synthesizes the mask transmission functions
out of small-sized Maxwell solutions from a finite-difference-in-time-domain (FDTD) engine, an industry leading
rigorous simulator of topographic mask effect from SOLID-E. The integral framework presents a seamless solution
to the end user. Preliminary results indicate the overhead introduced by POTOMAC is contained within the same order of magnitude in comparison to the thin mask approach.
Liberal use of assist features of both tones is an important component of the 45nm lithography strategy for many
layers. These features are often sized at λ/4 on the mask or smaller. Under these conditions, formerly successful
approximations of the mask near field using boundary layer methods or domain decomposition methods break
down. Rigorous simulations of the mask near field must include a three-dimensional (3D) Maxwell's equation
analysis, but these computations are cost-prohibitive for full-chip OPC, RET, and lithographic compliance
The purpose of this paper is to describe a simple and computationally efficient method that can improve model
fidelity for 45nm assist features of either tone, while still retaining computational simplicity. While the model
lacks the generality of a rigorous solution of Maxwell' sequations, it can be well-anchored to the real physics by
calibrating its performance to a lithographic TCAD mask simulator. The approach provides a balanced tradeo.
between speed and accuracy that makes it a superior approach to boundary layer and domain decomposition
methods, while retaining the capability to realistically be deployed on a full-chip lithography simulation.
Recently artificial inhomogeneous broadening was proposed to expand the bandwidth of slow light. The point is to independently slow down all harmonic components of the input pulse via inhomogeneous broadening. An input pulse or sequence of pulses can be split into independent spectral channels by a dispersive element such as a prism or grating. These sub-pulses are then slowed by bandwidth-matched slow-light array elements, and then recombined with another dispersive element to produce the output pulse. The proof of principle experiment was done with a photorefractive crystal Ce:BaTiO3 where the crystal function as both dispersive elements and slow lights devices.
Associative memories that recognize a pattern based on partial input have numerous applications such as homeland security. Optical implementations of associative memories, for example using computer-generated holograms, have the inherent parallelism as an advantage over software realizations. The nonlinear thresholding operation is a key step in the optical associative memories. A major source error in these memories is the thresholding uncertainties caused by fluctuation, for example in the input illumination or varying degrees of partial obscuration. Here, we show a proof-of-principle demonstration of a new scheme to suppress such errors using real time thresholding and a modified Hopfield associative memory model.
A critical limitation of slow light schemes is the limited time-bandwidth product. Recently we showed that this limitation can be overcome by making use of inhomogeneities. Here we analyze the effects of crosstalk noise that can be induced by these inhomogeneities in certain situations, and how to minimize such noise. The proof of principle experiment was done using three-wave mixing in a photorefractive crystal Ce:BaTiO3 where Bragg selection is used to provide the inhomogeneity.
Enhancement and suppression of spontaneous emission is vital to both quantum optics research and optoelectronics industry. Surface plasmon has been known to feature such characteristics. Waveguide-coupled-atom systems are studied for this goal. The enhancement is proportional to a field focusing factor and inverse to the group velocity along the waveguide. Comparison is made to the Purcell factor. A numerical example shows a promising structure with a grating-coupled plasmonic waveguide, projecting an emission enhancement by 51 times in spite of heat dissipation.
For many applications of slow or stopped light, the delay-time-bandwidth product is a fundamental issue. However, existing slow light demonstrations do not give a satisfactory delay-time bandwidth product, especially in room temperature solids. Here we demonstrate that the use of artificial inhomogeneous broadening has the potential to solve this problem by simultaneously slow down all the frequency components of the input pulse. The proof of principle experiment was done using three-wave mixing in a photorefractive crystal Ce:BaTiO3 where Bragg selection is used to provide the inhomogeneity.
Lately, active research has been conducted in slowing down light
pulses to the order of tens of meters per second or below. An
interesting application would be an optical buffer for all optical
routers, where solid state devices operating under room
temperature are desired. In this paper, we investigate the
possibility of such a device with a Ce:BaTiO3 crystal. Group
velocity as slow as 2 mm/s is obtained in the two-wave coupling
experiment. By modulating the angular-multiplexed pump beams in
the experiment, we also demonstrate the modulation of the output
waveform, which could be used to address the problem of pulse
broadening that so far limits the application of room temperature