The extension of optical lithography to 2Xnm and beyond is often challenged by overlay control. With reduced overlay
measurement error budget in the sub-nm range, conventional Total Measurement Uncertainty (TMU) data is no longer
sufficient. Also there is no sufficient criterion in overlay accuracy. In recent years, numerous authors have reported new
method of the accuracy of the overlay metrology: Through focus and through color. Still quantifying uncertainty in
overlay measurement is most difficult work in overlay metrology. According to the ITRS roadmap, total overlay budget
is getting tighter than former device node as a design rule shrink on each device node. Conventionally, the total overlay
budget is defined as the square root of square sum of the following contributions: the scanner overlay performance,
wafer process, metrology and mask registration. All components have been supplying sufficiently performance tool to
each device nodes, delivering new scanner, new metrology tools, and new mask e-beam writers. Especially the scanner
overlay performance was drastically decreased from 9nm in 8x node to 2.5nm in 3x node. The scanner overlay seems to
reach the limitation the overlay performance after 3x nod. The importance of the wafer process overlay as a contribution
of total wafer overlay became more important. In fact, the wafer process overlay was decreased by 3nm between DRAM
8x node and DRAM 3x node. We develop an analytical algorithm for overlay accuracy. And a concept of nondestructive
method is proposed in this paper. For on product layer we discovered the layer has overlay inaccuracy. Also
we use find out source of the overlay error though the new technique.
In this paper, authors suggest an analytical algorithm for overlay accuracy. And a concept of non-destructive method is
proposed in this paper. For on product layers, we discovered it has overlay inaccuracy. Also we use find out source of
the overlay error though the new technique. Furthermore total overlay error data is decomposed into two parts: the
systematic error and the random error. And we tried to show both error components characteristic, systematic error has a
good correlation with residual error by scanner condition, whereas, random error has a good correlation with residual
error as going process steps. Furthermore, we demonstrate the practical using case with proposed method that shows the
working of the high order method through systematic error. Our results show that to characterize an overlay data that is
suitable for use in advanced technology nodes requires much more than just evaluating the conventional metrology
metrics of TIS and TMU.
In recent semiconductor manufacturing, hardmask is unavoidable requirement to further transfer the patterning from
thin photoresist to underlayer. While several types of hardmask materials have been investigated, amorphous carbon has
been attractive for good etching resistance and high-aspect-ratio resolution. However, it has fatal problem with lowering
overlay controllability due to its high extinction coefficient (k). Thus, the correlation of alignment and overlay
performance with varying hardmask materials is required to meet a tight overlay budget of 2x nm node and beyond. In
this paper, we have investigated the effects of the hardmask materials with respect to the optical properties on the
performance of overlay applicable to 2x nm memory devices.
The electromechanical performance of interpenetrating polymer networks (IPN) in which one elastomer network is
under high tension balanced by compression of the second network, were investigated. Uniaxial stress relaxation
analysis confirmed significant decrease in viscoelasticity in comparison with 3M VHB films, the primary component
network in the IPN films. In dynamic mechanical analysis, the IPN composite showed a higher mechanical efficiency,
suggesting delayed relaxation of the acrylic chains in the presence of IPN formation. This improvement was found to be
dependant on the contents of poly(TMPTMA). Actuation performance without mechanical prestrain showed that these
IPN electroelastomers had demonstrated high elastic strain energy density (3.5 MJ/m<sup>3</sup>) and a high electromechanical
coupling factor (93.7%). These enhanced electromechanical performances indicate that IPN electroelastomer should be
suitable for diverse applications.
The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times around a spring core in
order to form a multilayer actuator system with unidirectional actuation. The freestanding rolled configuration enables
the use of the DE film for muscle like linear actuators with a broad application potential. The stress state of the pre-strained
acrylic film in the rolled configuration and the required stiff core can cause several serious problems concerning
lifetime, size and efficiency of the actuator.
In order to obtain an acceptable specific actuator performance and lifetime the pre-stretching stress has to be essentially
reduced or even eliminated. This can be achieved by the interpenetrating polymer network (IPN) process newly
developed at the UCLA. Thereby a trifunctional methacrylate monomers is introduced into the highly pre-strained
acrylic films and subsequently curing the monomers to form an interpenetrating elastomeric network. The as obtained
interpenetrating polymer network (IPN) can effectively support the pre-strain of the acrylic film and consequently
eliminate the need for external pre-strain-supporting structures.
In this study a new rolled actuator design is presented based on the IPN post treated VHB material. Due to the stress free
state of the wrapped film no spring core is necessary. As a result a significantly longer lifetime and better specific
volume efficiency of the actuator has been achieved at lower unidirectional elongation when activated.
Introductorily, the specific problems on conventional rolled actuators are discussed and the aims for core free rolled
actuators are specified. Then some structural design parameters are addressed in order to achieve a slight shape and
reliable working principle. In the main part of the study the manufacturing process of the actuators and some
measurement results and experiences are discussed in detail.
Dielectric elastomer actuators which consist of an electrode/dielectric elastomer/electrode sandwich structure show
greater than 100% electromechanical strain performance when high electrical field is applied. The strain in the dielectric
elastomer film occurs due to attraction of opposite charges across the dielectric film and repulsion of similar charges on
each compliant electrode. Structural defects present in these elastomers such as gel particles, uneven thickness, and stress
concentration may cause dielectric breakdown, leading to premature failure during continuous or repeated actuations.
Dielectric breakdown consequently reduces production yield and device lifetime. Carbon nanotubes (CNTs) have been
introduced as compliant electrodes for dielectric elastomers. Higher than 100% electromechanical strain was obtained
with ultrathin CNT electrodes due to the high aspect ratio and the high electrical conductivity of the nanotubes. These
ultrathin CNT electrodes also exhibit fault-tolerance in dielectric elastomers through the local degradation of CNTs
during dielectric breakdown. The degraded areas electrically isolate the defects, while keeping the rest of the elastomer
active. The "self-clearing" electrodes significantly increase the lifetime of the dielectric elastomers, making the dielectric
elasomer actuator much more reliable.
Polyaniline nanofibers (Pani nanofibers) have exhibited high performance and fault tolerant properties for dielectric
elastomer actuator devices. Electrodes comprised of uniformly sprayed Pani nanofibers in thicknesses 0.7 μm, 1.1 μm,
1.3 μm, and 1.5 μm have shown the following high strains: 65% in area for 0.7 μm electrodes at 3 kV, 97% in area for
1.1 μm thick electrodes at 3.5 kV, 84% in area for 1.1 μm thick electrodes at 3 kV, and 114.% in area for 1.5 μm thick
electrodes at 3.5 kV. Optimal performance was achieved with actuators with electrodes 1.1 μm thick, which
demonstrated self-healing properties at 3 kV. These actuators displayed a preserved strain of 91% after the clearing and
sustained a 93% area strain for 10 minutes at 3 kV. Devices with 1.1 μm thick electrodes were also able to perform 700
actuation cycles over a total duration of 75 minutes with a pulsed half-sinusoidal voltage of 3 kV. Mechanical
compliance tests performed on a film with a 1.1 μm thick Pani nanofiber electrode reveals that the electrode material
does not significantly alter the mechanical properties of the film. The estimated Young's modulus was found to be 32
MPa for the film with the electrode and 31 MPa for the film itself.
Dielectric elastomer actuators exert strain due to an applied electric field. With advantageous properties such as high efficiency and their light weight, these actuators are attractive for a variety of applications ranging from biomimetic robots, medical prosthetics to conventional pumps and valves. The performance and reliability however, are limited by dielectric breakdown which occurs primarily from localized defects inherently present in the polymer film during actuation. These defects lead to electric arcing, causing a short circuit that shuts down the entire actuator and can lead to actuator failure at fields significantly lower than the intrinsic strength of the material. This limitation is particularly a problem in actuators using large-area films. Our recent studies have shown that the gap between the strength of the intrinsic material and the strength of large-area actuators can be reduced by electrically isolating defects in the dielectric film. As a result, the performance and reliability of dielectric elastomers actuators can be substantially improved.
Interpenetrating polymer networks (IPN) in which one elastomer network is under high tension balanced by
compression of the second network have been shown to exhibit electrically-induced strain up to 300% and promise a
number of polymer actuators with substantially enhanced performance and stability. This paper describes the
mechanical and thermal properties of the IPN electroelastomer films. The quasi-linear viscoelastic model and Yeoh
strain energy potential are used to characterize the viscoelastic response and stress-strain behavior of the IPN films in
comparison with 3M VHB films, primary component network in the IPN films. Material parameters were determined
from uniaxial stress relaxation experiments. An analysis of the results confirms that the IPN composites have reduced
viscoelasticity and fast stress-strain response due to preserved prestrain. Differential scanning calorimetry showed two
glass transition temperatures that are slightly shifted from the two component networks, respectively. The two networks
in the IPN are considered to be independent of each other. The thermal property is also studied with termogravimetric
This paper describes new electroelastomer films that exhibit high actuation performance at zero to minimal mechanical prestrain. Prestrain is generally required for electroelastomers, also known as dielectric elastomers, such as the VHB 4910 acrylic elastomer, to obtain high electromechanical strain and high elastic energy density. However, the prestrain can cause several serious problems, including the use of a prestrain-supporting structure, a large performance gap between the active materials and packaged actuators, instability at interfaces between the elastomer and prestrain-supporting structure, and stress relaxation. We have introduced a polymerizable and closslinkable liquid additive into highly prestrained acrylic films and subsequently cured the additive to form the second elastomeric network. In the as-obtained Interpenetrating Polymer Networks (IPN), the additive network can effectively support the prestrain of the acrylic films and consequently eliminate the external prestrain- supporting structure. The IPN composite films without external prestrain exhibit electrically-induced strains up to 233% in area, comparable to the VHB 4910 films under high prestrain.