The theory of electromigration-induced nano- and microprocesses that terminate in failure of thin-film conductors is
given. These processes determine operational reliability of IC metallization system. The physical foundations of
degradation and lifetime of interconnects are analyzed. The various mechanisms of their deformations and failures that
are of practical importance for different types of multilevel arrangement and microstructure are studied. The full 3D
theory developed considers the electromigration failures as a set of processes occurring at the nano-, micro- and
mesoscale. We reduced the general equations in order to describe specific conducting systems, developed the methods of
their numerical modeling, and created software packages. It allows carrying out the simulation of electromigration
failures and performing the lifetime analysis for various interconnect systems that are of prime practical significance as
regards the operation of IC metallization, the modeling being over a wide range of material, geometrical, structural, and
operational parameters. Some examples of the reliability analysis and of the analysis of the most likely failure locations
in dependence on the current density, parameters of multilevel metallization, temperature, and polycrystalline grain
microstructure of interconnects are represented. We also put forward an approach to modeling the electromigration in
conductors containing impurities.
The photolithographic finite-difference time-domain (PFDTD) approach to the modeling of 3D electromagnetic fields
and photolithographic structures for projection photolithography in sub-0.2μm and nanometer ranges is developed. It is
based on adaptation and application of advanced methods of the Maxwell equations' solution to photolithography
problems. The appropriate computational methods and modeling algorithms are created and applied to specific problems.
It is shown that sometimes the PFDTD-approach could be preferred over the routine the rigorous coupled-waves analysis
(RCWA), especially for the relatively small critical dimensions and in short wavelength range. It allowed us to extent the
application domain of our own photolithography software package, and to improve quality and accuracy of topical
projection schemes' simulation.
A new model for copper chemical mechanical polishing (CMP) process in the (K3Fe(CN)6+NH4OH) slurry is developed
in the work. A distinctive peculiarity of the model is quantitative consideration of the kinetics of the passivating layer
growth and accounting of its action on the polishing rate. In accordance with the model the main stages of copper CMP
are the Cu+ ion diffusion and tunneling of copper conductivity electrons through the passivating layer towards its
interface with the slurry, as well as chemical reactions in the slurry at the passivating layer surface resulting in growth of
its thickness and formation of dissoluble compounds removed from the system. The closed set of equations of the CMP
kinetics is derived. Its solutions are obtained for the steady-state regime as to the chemical reactions in two limiting
cases when Cu+ ion diffusion through the passivating layer predominates over their electromigration or vice versa. The
estimates of the CMP rate and limiting values of passivating layer thickness for these two modes are carried out and give
reasonable results which correlate with experimental data.
In the work the influence of vacancy clusters on strength properties of solid-solid interfaces is studied on the base of the
thermodynamic approach. The conditions of cluster formation at the interface are obtained and analyzed. A model
describing the influence of vacancy clusters in the contacting materials on the surface tension coefficient γ12 of the
interface is also developed. The dependences of the contribution of nonequilibrium vacancy clusters in γ12 on a vacancy
supersaturation, cluster concentrations, the number of vacancies in clusters, and temperature are analyzed.
A traditional aerial image model has been used to demonstrate a good applicability of 13nm EUV projection lithography to printing sub-0.1mm features. To estimate the potential of a possible candidate for EUV optics--a two- mirror projection system, we investigated the issues of aerial image formation by the reflective optics with account for aberrations. We have developed a simplified method to determine the optical parameters of the ring-field system that minimize aberrations of the 3rd order and, partially, of the 5th. As a result, we have found that the uncompensated aberrations contribute to a sharply asymmetrical impulse response of the ring-field projection system, where the characteristic width of the impulse response in some directions might be two times larger than the diffraction limit.
A 3D planar pseudo-vector approach to modeling resist exposure has been implemented for optical projection lithography. The approach allows for high numeric aperture effects revealed by others in the resist latent images; comparisons made show its fine agreement with rigorous vector modeling up to NA value of 0.7. Fast Fourier transform technique has been applied to reduce mask and resist (including postbake) modeling runtime; the effects of finite accuracy approximations of the mask areas and mask periodicity have been investigated and compensated. The overall performance of the exposure model has been optimized to be 10X faster than for a similar vertical propagation model. A modified `cell' algorithm has also been used to model resist development; this resulted in more accurate resist profiles for the same latent image accuracy, providing additional runtime savings to resist profile simulations.
We present a description of a software tool and a methodology for easily creating photoresist development rate parameters in lithography simulation. The tool optimizes parameters using the Modified Simplex Method. The methodology uses the tool to provide insight into the effects of the development rate parameters and to find usable parameters quickly. The reasonings behind the methodology are discussed as well as advantages and disadvantages. Results from three different lithography simulators are shown to agree well with experimental cross-section SEM data.
The research of ways to increase the degree of integration and the functional possibilities of integrated circuits in recent years has resulted in the development of new investigations directed to the creation of new technological processes with high resolution. In the developing of submicron and nanometer technologies, physical and technical difficulties appear that are more critical in comparison with the problems of "old" classical microtechnology
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