David Shykind

The hole shrink problem: Theoretical studies of directed self-assembly in cylindrical confinement

We use self-consistent field theory (SCFT) to study the self-assembly of cylinder-forming diblock copolymers confined in a cylindrical prepattern. This situation arises in contact holes -the hole shrink problem- where the goal is to produce a cylindrical hole with reduced dimensions relative to a guiding prepattern. In this study, we focus on systems with a critical dimension (CD) ranging from 50nm to 100nm and which consequently lead to the formation of a single cylinder in the middle of the hole. We found that different morphologies arise from the self-assembly process and are strongly governed by the prepattern dimensions, wetting conditions as well as the polymer molecular weight. We also considered blends of diblock copolymers and homopolymers and determined optimal blending configurations that not only favor the formation of the desired cylindrical morphology but also extend the processing window relative to the pure diblock case.

Field-theoretic simulations of directed self-assembly in cylindrical confinement: placement and rectification aspects

We have investigated the directed self-assembly (DSA) of cylinder-forming block copolymers inside cylindrical guiding templates. To complement and corroborate our experimental study, we use field-theoretic simulations to examine the fluctuations-induced variations in the size and position of the cylindrical microdomain that forms in the middle of the guiding hole. Our study goes beyond the usual mean-field approximation and self-consistent field theory simulations (SCFT) and incorporates the effects of thermal fluctuations in the description of the self-assembly process using complex Langevin (CL) dynamics. In both our experimental and modeling efforts, we focus on minor-block-attractive sidewalls and bottom substrates and neutral top surfaces and explore the properties of the formed cylinders, including fluctuations in the center position and the size of the domain, for various prepattern conditions. Our results indicate robust critical dimensions (CD) of the DSA cylinders relative to the incoming CD, with a sigma CD < 0.9nm. Likewise, we find that the DSA cylinders are accurately registered in the center of the guiding hole, with deviations in the hole-inhole distance on the order of ≈ 0.7-1nm, translating to errors in the hole-to-hole distance of ≈ 1-1.5nm.

Self-consistent field theory of directed self-assembly in laterally confined lamellae-forming diblock copolymers

We use Self-Consistent Field Theory (SCFT) to study the directed self-assembly of laterally confined diblock copolymers. In this study, we focus on systems where the self-assembled lamellae are oriented parallel to the selective sidewalls of the channel. While well-ordered, perfect lamellae are observed both experimentally and numerically, undesirable defective structures also emerge. We therefore investigate the energetics of two isolated defects, dislocations and disclinations, for various chain lengths and channel dimensions and establish conditions that favor the formation of defects. We also determine the energy barrier and the transition path between the defective and perfect state using the string method.

Double-exposure materials for pitch division with 193nm lithography: requirements, results

We present the results of both theoretical and experimental investigations of materials for application either as a reversible Contrast Enhancement Layer (rCEL) or a Two-Stage PAG. The purpose of these materials is to enable Litho- Litho-Etch (LLE) patterning for Pitch Division (PD) at the 16nm logic node (2013 Manufacturing). For the rCEL, we find from modeling using an E-M solver that such a material must posses a bleaching capability equivalent to a Dill A parameter of greater than 100. This is at least a factor of ten greater than that achieved so far at 193nm by any usable organic material we have tested. In the case of the Two-Stage PAG, analytical and lithographic modeling yields a usable material process window, in terms of reversibility and two-photon vs. one-photon acid production rates (branching ratio). One class of materials, based on the cycloadduct of a tethered pair of anthracenes, has shown promise under testing at 193nm in acetonitrile. Sufficient reversibility without acid production, enabled by near-UV exposure, has been achieved. Acid production as a function of dose shows a clear quadratic component, consistent with a branching ratio greater than 1. The experimental data also supports a acid contrast value of approximately 0.05 that could in principle be obtained with this molecule under a pitch division double-exposure scenario.

Non-Ideal Frequency Dependent Loss In Realistic PCB Transmission Lines

Digital signaling frequencies are approaching the GHz range for a variety of CPU, memory and peripheral interconnect schemes. The portions of timing budgets allocated to chip-to-chip interfaces are becoming concomitantly smaller, making accurate high-frequency characterization of physical layer components critical to robust HVM designs. At GHz frequencies the primary contributor to the physical layer timing budget is inter-symbol interference (ISI), which is a strong function of transmission line loss. This loss is dependent on the physical properties of the package and/or board materials, which exhibit batch-to-batch and vendor-to-vendor variation. Understanding these variations is imperative to close modeling gaps and enable predictable system designs. This document describes a simple, sparameter based measurement method for extracting RLGC parameters and presents results showing the impact of copper roughness and dielectric loss as functions of frequency for a variety of common PCB materials.

Effects of thermal fluctuations on directed self-assembly in cylindrical confinement

Abstract. We investigate the directed self-assembly (DSA) of cylinder-forming block copolymers inside cylindrical guiding templates. To complement and corroborate our experimental investigations, we use field-theoretic simulations to examine the fluctuation-induced variations in the size and position of the cylindrical microdomain that forms in the middle of the guiding hole. Our study goes beyond the usual mean-field approximation and self-consistent field theory simulations (SCFT) and incorporates the effects of thermal fluctuations in the description of the self-assembly process using complex Langevin (CL) dynamics. In addition to CL simulations, we present an efficient SCFT-based approach that can inform about the positional error of the formed cylinders. In this new scheme, an external chemical-potential field is applied to displace the inner cylinder away from its centered, lowest energy configuration. In both our experimental and modeling efforts, we focus on two wall-wetting conditions: (1) minor-block-attractive sidewalls and bottom substrates and neutral top surfaces and (2) neutral sidewalls, substrates, and top surfaces. For both cases, we explore the properties of the formed cylinders, including fluctuations in the center position and the size of the domain, for various prepattern conditions. Our results indicate robust critical dimensions (CDs) of the DSA cylinders relative to the prepattern CD, with a standard deviation <0.9  nm. Likewise, we find that the DSA cylinders are accurately registered in the center of the guiding hole, with deviations in the hole-in-hole distance on the order of ∼0.7 to 1.4 nm, translating to errors in the hole-to-hole distance of ∼1 to 2 nm.

Reaction kinetics of non-reciprocal photo-base generator (NRPBG)patterning

We present a simple reaction rate analysis of lithographic patterning using the Non-Reciprocal Photo Base Generation (NRPBG) scheme of Bristol (Bristol, et. al., to be published in Proceedings of the SPIE - The International Society for Optical Engineering, 2010, presentation 7639-4). Multistep reaction kinetics simulations demonstrate that the NRPBG scheme produces clear pitch division upon 193 nm double-exposure, over a range of photochemical reaction rate constants.