Step and flash imprint lithography: materials and process development

textStep and flash imprint lithography (SFIL) is a high resolution, low cost patterning technique developed at The University of Texas at Austin. Envisioned as an alternative to conventional photolithographic techniques currently used to pattern semiconductor substrates, SFIL utilizes photocurable monomers in a micromolding process to replicate features etched into a transparent template. The elimination of expensive projection optics and sources required for photolithography offers tremendous potential cost savings. This dissertation presents an overview of the SFIL process and provides a description of each process step. Particular attention is paid to development of SFIL compatible etch processes as well as to the effects of polymerization induced densification on feature profile. Modeling of polymerization induced feature shrinkage and simulation of line profiles during etch processing are also presented.Chemical Engineerin

Materials and processes for advanced lithography applications

textStep and Flash Imprint Lithography (S-FIL) is a high resolution, next-generation lithography technique that uses an ambient temperature and low pressure process to replicate high resolution images in a UV-curable liquid material. Application of the S-FIL process in conjunction with multi-level imprint templates and new imprint materials enables one S-FIL step to reproduce the same structures that require two photolithography steps, thereby greatly reducing the number of patterning steps required for the copper, dual damascene process used to fabricate interconnect wirings in modern integrated circuits. Two approaches were explored for the implementation of S-FIL in the dual damascene process: sacrificial imprint materials and imprintable dielectric materials. Sacrificial imprint materials function as a pattern recording medium during S-FIL and a three-dimensional etch mask during the dielectric substrate etch, enabling the simultaneous patterning of both the via and metal structures in the dielectric substrate. Development of sacrificial imprint materials and the associated imprint and etch processes are described. Application of S-FIL and the sacrificial imprint material in a commercial copper dual damascene process successfully produced functional copper interconnect structures, demonstrating the feasibility of integrating multi-level S-FIL in the copper dual damascene process. Imprintable dielectric materials are designed to combine the multi-level patterning capability of S-FIL with novel dielectric precursor materials, enabling the simultaneous deposition and patterning of the interlayer dielectric material. Several candidate imprintable dielectric materials were evaluated: sol-gel, polyhedral oligomeric silsesquioxane (POSS) epoxide, POSS acrylate, POSS azide, and POSS thiol. POSS thiol shows the most promise as functional imprintable dielectric material, although additional work in the POSS thiol formulation and viscous dispense process are needed to produce functional interconnect structures. Integration of S-FIL with imprintable dielectric materials would enable further streamlining of the dual damascene fabrication process. The fabrication of electronic devices on flexible substrates represents an opportunity for the development of macroelectronics such as flexible displays and large area devices. Traditional optical lithography encounters alignment and overlay limitations when applied on flexible substrates. A thermally activated, dual-tone photoresist system and its associated etch process were developed to enable the simultaneous patterning of two device layers on a flexible substrate.Chemical Engineerin

Unified modeling language description of the object-oriented multi-scale adaptive finite element method for step-and-flash imprint lithography simulations

In the first part of the paper we present the multi-scale simulation of the Step-and-Flash Imprint Lithography (SFIL), a modern patterning process. The simulation utilizes the hp adaptive Finite Element Method (hp-FEM) coupled with Molecular Statics (MS) model. Thus, we consider the multi-scale problem, with molecular statics applied in the areas of the mesh where the highest accuracy is required, and the continuous linear elasticity with thermal expansion coefficient applied in the remaining part of the domain. The degrees of freedom from macro-scale element's nodes located on the macro-scale side of the interface have been identified with particles from nano-scale elements located on the nano-scale side of the interface. In the second part of the paper we present Unified Modeling Language (UML) description of the resulting multi-scale application (hp-FEM coupled with MS). We investigated classical, procedural codes from the point of view of the object-oriented (O-O) programming paradigm. The discovered hierarchical structure of classes and algorithms makes the UML project as independent on the spatial dimension of the problem as possible. The O-O UML project was defined at an abstract level, independent on the programming language used

Methods for fabricating patterned features utilizing imprint lithography

One embodiment of the present invention is a method for generating patterned features on a substrate that includes: (a) forming a first layer on at least a portion of a surface of the substrate, the first layer comprising at least one layer of a first material, which one layer abuts the surface of the substrate; (b) forming a second layer of a second material on at least a portion of the first layer, which second layer is imprinted with the patterned features; (c) removing at least portions of the second layer to extend the patterned features to the first layer; and (d) removing at least portions of the first layer to extend the patterned features to the substrate; wherein the first layer and the second layer may be exposed to an etching process that undercuts the patterned features, and the first material may be lifted-off.Board of Regents, University of Texas Syste

Compositions for dark-field polymerization and method of using the same for imprint lithography processes

A composition is provided and a method of using the same to form a pattern on a substrate using imprint lithography employing dark-field polymerization is disclosed. The composition includes a polymerizable bisvinylether and an initiator that produces an acid in response to radiation.Board of Regents, University of Texas Syste

Simulation of UV nanoimprint lithography on rigid and flexible substrates

Nanoimprint lithography (NIL) is a low cost, high throughput process used to replicate sub-20 nm feature from a patterned template to a rigid or flexible substrate. Various configurations for NIL are analyzed and classified based on type of template and substrate. The steps involved in pattern transfer using roller template based NIL are identified and models to study these steps are proposed. Important process parameters such as maximum web speed possible, required UV intensity, minimum droplet size and pitch and required force on the roller are calculated. The advantages, disadvantages and optimal process window for the different configurations are identified. Droplet spreading is simulated in NIL with rigid substrates in order to study the effect of droplet size, droplet placement error, gas diffusion and template pattern on throughput and defectivity. Square arrangement is found to be the optimum arrangement for achieving minimum throughput. Large droplet-free regions on the substrate edge and error in droplet placement error have significant impact on the throughput. A fluid flow model with average flow permeability is presented to account for flow in the template patterns. Optimum droplet dispensing for multi-patterned templates is achieved by distributing droplet volume according to local filling requirements. Non-fill defects in NIL are classified into pocket, edge and channel defects. A model to predict the size of non-fill defects based on imprint time and droplet size is presented. Defect characterization is presented for various pattern-types. A model is presented to determine the time required for the encapsulated gas to diffuse into the resist. The coupled fluid-structure interaction in NIL with flexible substrate is studied by simulating the web deformation as the droplet spreads on the substrate. It is found that the flexible substrate can be modeled as a membrane due to the lack of rigidity. RLT variation reduces as the number of droplets or the web tension increases. For the magnitude of RLT variation, thinner residual layers require higher web tension. The position of the template on the substrate is important and template positioned at the corner of the substrate is found to provide the least RLT variation.Chemical Engineerin

CONVERGENCE OF ITERATIVE SOLVERS FOR NON-LINEAR STEP-AND-FLASH IMPRINT LITHOGRAPHY SIMULATIONS

The paper presents the analysis of the iterative solvers utilized to solve the non-linear problemof Step-and-Flash Imprint Lithography (SFIL) a modern patterning process. The simulationsconsists in solving molecular statics problem for the polymer network, with quadratic potentials.The model distinguishes the strong interparticle interactions between particles forminga polymer network, and weak interactions between remaining particles. It also allows for largedeformations, which all together implies the non-linear model. To illustrate the convergenceof the iterative solvers, we present snapshots of the deformation of the sample being subjectto the iterative solution. We claim that the animation is an interesting way of illustratingthe convergence of the iterative solvers

Materials for imprint lithography

The present invention is directed to a material for use in imprint lithography that features a composition having a viscosity associated therewith and including a surfactant, a polymerizable component, and an initiator responsive to a stimuli to vary the viscosity in response thereto, with the composition, in a liquid state, having the viscosity being lower than about 100 centipoises, a vapor pressure of less than about 20 Torr, and in a solid cured state a tensile modulus of greater than about 100 MPa, a break stress of greater than about 3 MPa and an elongation at break of greater than about 2%.Board of Regents, University of Texas Syste

Evolutionary Multi-Agent Computing in Inverse Problems

The paper tackles the application of evolutionary multi-agent computing to solving inverse problems. High costs of fitness function call become a major difficulty when approachingthese problems with population-based heuristics, however evolutionary agent-based systems (EMAS)turn out to reduce the fitness function calls, which makes them a  possible weapon of choicefor them. The paper recalls the basics of EMAS and describes the considered problem (Step and Flash Imprint Lithography),later showing convincing results, that EMAS turns out to be more effective than classical evolutionary algorithm