Scanners in High-Volume-Manufacturing conditions will experience a large range of reticles that vary in reticle transmission and reticle diffraction characteristics. Especially under full production loads reticles will heat up due to the exposure light-load and as such experience thermo-mechanical deformations. The resulting reticle pattern distortion can be partially translated in a deteriorated overall system overlay. Due to the geometry of the reticle and exposure fields, these reticle thermal effects are in general barrel-shape distortions that can be well corrected with the available set of lens manipulators. Nevertheless node-over-node the residual overlay errors associated with thermo-mechanical reticle deformation needs further reduction since it contributes to the total onproduct overlay performance. To reduce overlay caused by reticle temperature drift, NXT1980Di includes an active cooling mechanism suppressing the reticle temperature changes during exposure significantly. Even though the reticle temperature excursions are well suppressed, residual intra-wafer overlay drift effect can still be observed. Before exposure of a wafer, reticle deformation is measured during reticle align using in-line alignment / image sensors (TIS or PARIS). This is enabled by adding alignment markers around the circumference of the image field on the reticle. The measured reticle deformations are then fed to the system control network and dynamically corrected for by making use of the available manipulators in the scanner and the projection lens. Wafer-by-wafer reticle distortion measurements are performed to accurately capture the transient dynamics present in reticle heating during normal production lots. A new version of Reticle Heating Feed-forward Control (RHC2) is introduced that uses reticle-heating-induced deformation measurements over time and exposure sequence information to calibrate reticle-deformation-predictionmodels. These models are based on thermo-mechanical models that simulate reticle deformation under various exposure conditions and are applied in-line to the exposures to reduce intra-wafer overlay drift effects.
ASML’s 300mm scanner-systems are built on the TWINSCAN (XT/NXT) platform and yield high productivity levels for dry as well as immersion litho-scanners. NXT:1980Di immersion scanners yield productivity levels as high as 275wph while maintaining the overlay accuracy. The NXT:1980Di can be equipped with a new leveling mode that results in a significant reduction of the time that is spent on measuring the wafer focus height map. In the new leveling mode the focus height map is measured employing the full width of the level sensor and thereby minimizing the number of leveling scans. In this paper we describe the implementation of the LIL-method in the TWINSCAN platform design. Here, we report on the focus / leveling performance for both test as well as customer product wafers, and present a productivity outlook on the performance gain for a selected set of exposure use-cases.
Overlay is one of the key factors which enables optical lithography extension to 1X node DRAM manufacturing. It is natural that accurate wafer alignment is a prerequisite for good device overlay. However, alignment failures or misalignments are commonly observed in a fab. There are many factors which could induce alignment problems. Low alignment signal contrast is one of the main issues. Alignment signal contrast can be degraded by opaque stack materials or by alignment mark degradation due to processes like CMP. This issue can be compounded by mark sub-segmentation from design rules in combination with double or quadruple spacer process. Alignment signal contrast can be improved by applying new material or process optimization, which sometimes lead to the addition of another process-step with higher costs. If we can amplify the signal components containing the position information and reduce other unwanted signal and background contributions then we can improve alignment performance without process change. In this paper we use ASML's new alignment sensor (as was introduced and released on the NXT:1980Di) and sample wafers with special stacks which can induce poor alignment signal to demonstrate alignment and overlay improvement.
For mass production of DRAM device, a stable and effective overlay control becomes more and more important as DRAM design rule shrinks. Existent technologies were already applied to overcome this situation. Nevertheless, we are still suffered from tight overlay margin and forced to move from lot-based to wafer-based overlay control. However, the wafer-based control method requires a huge amount of measurement resource.
In this paper, we present the insight for the wafer-based overlay correction with optimal measurement resource which is suitable for mass production. The experiment which is the wafer-based overlay correction by several statistical analyses carried out for 2X nm node DRAM. Among them, linear regression is a strong candidate for wafer-based overlay control, which improved up to 0.8 nm of maximum overlay.
Ionic Polymer-Metal Composites (IPMCs) of EAP actuators is famous for its good property of response and durability.
The performance of Ionic Polymer-Metal Composites (IPMCs) is an important issue which is affected by many factors.
There are two factors for deciding the performance of IPMC. By treating anisotropic plasma etching process to 6 models
of the IPMCs, enhanced experimental displacement and force results are obtained. Plasma patterning processes are
executed by changing the groove and the land length of 6 patterns. The purpose of the present investigation is to find out
the major factor which mainly affects the IPMC performance. Simulations using ANSYS have been executed to compare
with the experimental results about the values and the tendency of data. Experimental and simulating data of the
performances seem to have similar tendency. In the next part of the paper, we observed the other properties like
capacitance, resistance and stiffness of 6 plasma patterned IPMCs. And we observed that the stiffness is the major factor
which affects the performance of IPMCs. As we seen, our problem has been reduced to investigate about the property of
stiffness. We suggest that the stiffness is largely changed mainly because of the different thickness of Platinum stacked
of the groove and the land part which are produced by anisotropic plasma etching processes. And we understand that
anisotropic plasma patterned IPMCs of better performance can be applied to various applications.
Ionic polymer metal composites is the proposing material for applications, since it has many attractive qualities that are
durability, aquatic, miniature and light-weighted. Especially, IPMC has extraordinary advantages that are large
displacement at low driving voltage(~3V), low power consumption and simple structure. However, slow time response
prevents IPMC from various applications. Since IPMC is generally used in simply-supported configuration, which has
same characteristic with a cantilever beam, IPMC has natural frequency and it oscillates extremely at natural frequency.
We propose new open loop control method based on frequency response, which is combined with conventional DC
input. This method is experimentally tested and compared with result by conventional input.
The IPMC-EMIM actuator is an improved IPMC actuator to replace the water by stable ionic liquids (1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EtMeIM][TA])). Just as a general IPMC actuator which uses the
solvent of water has hysteresis, so do the IPMC-EMIM actuator exhibits hysteresis like other smart materials such as
piezoceramics (PZT), magnetostrictive materials, and shape memory alloys (SMA). Hysteresis can cause it to be
unstable in closed loop control. The Preisach Model has been used to model the hysteretic response arising in PZT and
SMA. Noting the similarity between IPMC-EMIM and other smart materials, we apply the Preisach model for the
hysteresis in the IPMC-EMIN actuator. This paper reviews the basic properties of the Preisach model and confirms
that the Preisach model of IPMC-EMIM actuator is possible.
DE EAP(Dielectric Elastomer ElectroActive Polymer) has advantages in its weight, ease of fabrication and low
power consumption. There are many efforts applied to various field in recent ten years. But the present modeling is not
enough to appear its characteristics because of its hysteresis. In this paper, we propose modeling of DE EAP with
Preisach Model that is used in order to model the hysteretic response arising in PZT and SMA. The modeling of DE
EAP with Presach model is verified by experiment with various DE EAP actuators.