Fransisca Sudargho

Survivable network design under optimal and heuristic interdiction scenarios

We examine the problem of building or fortifying a network to defend against enemy attacks in various scenarios. In particular, we examine the case in which an enemy can destroy any portion of any arc that a designer constructs on the network, subject to some interdiction budget. This problem takes the form of a three-level, two-player game, in which the designer acts first to construct a network and transmit an initial set of flows through the network. The enemy acts next to destroy a set of constructed arcs in the designer’s network, and the designer acts last to transmit a final set of flows in the network. Most studies of this nature assume that the enemy will act optimally; however, in real-world scenarios one cannot necessarily assume rationality on the part of the enemy. Hence, we prescribe optimal network design algorithms for three different profiles of enemy action: an enemy destroying arcs based on capacities, based on initial flows, or acting optimally to minimize our maximum profits obtained from transmitting flows.

Investigating Effect of Conditioner Aggressiveness on Removal Rate during Interlayer Dielectric Chemical Mechanical Planarization through Confocal Microscopy and Dual Emission Ultraviolet-Enhanced Fluorescence Imaging

The effect of conditioner aggressiveness is investigated in interlayer dielectric polishing on three types of pad. A method using confocal microscopy is used to analyze the effect of conditioner aggressiveness on pad–wafer contact. Results show that a more aggressive conditioner produces a higher interlayer dielectric polishing rate while at the same time a pad surface with fewer contacting summits and less contact area. It is found that the ratio of the contacting summit density to the contact area fraction is more important than either parameter measured separately since the ratio determines the mean real contact pressure. Modeling results based on contact area measurements agree well with experimental results. Moreover, it is found that a more aggressive disc also generates a thicker slurry film at the pad–wafer interface. This is in agreement with our general findings regarding pad asperity height distribution obtained using confocal microscopy.

Effect of cerium oxide particle sizes in oxide chemical mechanical planarization

This study explored the effect of different cerium oxide abrasive particle sizes in chemical mechanical planarization of 200 mm blanket plasma-enhanced tetraethylorthosilicate wafers. All polishing experiments were done with a polisher and tribometer capable of measuring shear force and down force in real-time. Coefficient of friction and removal rate were found to correlate well with the slurry median particle size distribution. Removal rate modeling based on particle size was explored to support the interpretation of the experimental results.

Tribological, Thermal, and Wear Characteristics of Poly(phenylene sulfide) and Polyetheretherketone Retaining Rings in Interlayer Dielectric CMP

Retaining rings made of poly(phenylene sulfide) (PPS) and polyetheretherketone (PEEK) with two different slot designs were subjected to a 4 h wear test. During the chemical mechanical planarization (CMP) process, the PPS retaining ring induced a higher coefficient of friction (COF) by ∼0.1 than the PEEK retaining rings. In addition, the PPS retaining ring exhibited a higher wear rate than the PEEK retaining rings by ∼28%. Although the retaining ring slot design did not significantly affect the COF and wear rate, retaining rings with sharp slot edges resulted in higher pad surface abruptness.

Effect of Various Cleaning Solutions and Brush Scrubber Kinematics on the Frictional Attributes of Post Copper CMP Cleaning Process

Brush scrubbing has been widely used in post chemical mechanical planarization (CMP) applications to remove contaminations, such as slurry residues and particles, from the wafer surface. During brush scrubbing, particle removal results from direct contact between a soft poly vinyl alcohol (PVA) brush and the wafer surface in which the brush asperities engulf the particles while the rotating motion of the brush, as well as the cleaning fluid at the surface, dislodge and carry the particles away from the wafer. The cleaning performance of brush scrubbing depends heavily on the choice of the cleaning solution and brush scrubber kinematics. In this work, the effect of various cleaning solutions and brush scrubber kinematics on the frictional attributes of post copper CMP cleaning process was investigated.