Advanced photolithography tools use 193 nanometer wavelength light for conventional and immersion printing. The
increased energy of 193 nm (ArF) light coupled with the higher absorption cross section of most materials has lead to a
dramatic increase in the rate of haze formation as compared to previously used lithographic wavelengths (248 KrF and
365 nm i-line systems). It is well known that at this short wavelength photochemical reactions are enhanced leading to
progressive defect formation, or haze, on optical surfaces within microlithography tools. Therefore, strict contamination
control of the optics environment is needed to avoid cumulative effects. Such measures have been implemented in
lithography tools both for the optics and for the reticle during exposure. However, the patterned side of the photomask is
the most sensitive element in the litho optical path for haze growth, because it is in focus and small defects will show up
as printing defects. Moreover, the reticle life time depends both on rigorous contamination control for expose and
transport/storage conditions (both inside and outside of the lithography tool). The litho operating cost depends directly
on reticle life time. It is imperative that the industry takes the required measures to improve the airborne molecular
contamination levels both in the storage part of the photolithography tool and in devices used to transport reticles outside
of the tool to slow down reticle haze
Past studies have shown the large effects of humidity and AMC on haze growth during storage and exposure. Therefore,
significant improvements in storage and exposure environment have been implemented by many fabs to reduce the
frequency of haze failures. It has also been shown that outgassing from materials surrounding the mask can influence or
cause haze. It is clear that the reticle must be adequately protected from contamination sources throughout the life cycle
of the reticle (both inside and outside of the lithography tool). In this paper we examine improvements in the storage
conditions of reticles inside the lithography tool as well as improvements in commercial SMIF pods used in fab storage
and automated handling of reticles.
Determination of both the identity and quantity of species desorbing from photoresists during exposure at any
wavelength - 248nm, 193nm and EUV - has proved to be very challenging, adding considerable uncertainty to the
evaluation of risks posed by specific photoresists to exposure tool optics. Measurements using a variety of techniques for
gas detection and solid film analysis have been reported but analytical results have not in general been easy to compare
or even in apparent agreement, in part due to difficulties in establishing absolute calibrations. In this work we describe
two measurement methods that can be used for any exposure wavelength, and show that they provide self-consistent
quantitative outgassing data for 2 all-organic and 2 Si-containing 193 nm resists. The first method, based upon gas
collection, uses two primary chromatographic techniques. Organic products containing C, S and Si are determined by
collection of vapors emitted during exposure in a cold trap and analysis by Gas Chromatography-Flame Ionization
Detector-Pulsed Flame Photometric Detector-Mass Spectrometry (GC-FID-PFPD-MS). Inorganic products such as SO2
are identified by adsorbent bed with analysis by Gas Particle-Ion Chromatography (GP-IC). The calibration procedure
used provides reasonable accuracy without exhaustive effort. The second method analyzes the elemental concentrations
in resist films before and after exposure by secondary ion mass spectrometry technique (SIMS), which requires only
knowledge of the resist compositions to be quantitative. The extent of outgassing of C and S determined by the two
methods is in good agreement for all 4 resists, especially when taking their fundamentally different characters into
account. Overall, the gas collection techniques yielded systematically lower outgassing numbers than did SIMS, and the
origins of the spread in values, which likely bracket the true values, as well as detection limits will be discussed. The
data for Si were found to differ significantly, however, and we show that the discrepancy is due to photo-induced
reactions at the polymer surface with the gas atmosphere present above the resist during exposure. For example,
photolytic oxidation of the C-Si bonds in air causes volatile Si-containing products to be formed from an otherwise stable
polymer, showing it is important to take the gas environment during exposure into account when designing resist
polymers for low Si outgassing.
After the introduction of the ATHENATM alignment sensor, advanced applications of the sensor data are becoming increasingly important to meet the tightening overlay specifications for future technology nodes. As part of the total overlay budget, the effects of different alignment strategies on overlay performance need to be investigated. Keeping in mind that such strategies are simple and easy to use, two developments are addressed in this paper: advanced alignment recipes and advanced mark designs. An alignment recipe defines which signals from the sensor are used to calculate the aligned position. By making advanced use of the available data, wafer alignment can be made more accurate and more robust to processing effects. It is shown that the new Smooth Color Dynamic alignment recipes exhibit good overlay performance on STI, Cu dual damascene and W-CMP / Al-PVD layers. Since Smooth Color Dynamic also takes away the choice of a particular color in the alignment recipe, it is the preferred alignment recipe for all product layers. The optimum design of an alignment mark depends on the process characteristics. As the process characteristics may vary over time, the optimum mark design can change accordingly. To cover a larger process range, multiple alignment mark designs are combined in a new multi-grating mark: the Versatile Scribeline Primary Mark (VSPM). By measuring all gratings during regular production, the optimum grating of a VSPM can be selected and aligned with a Smooth Color Dynamic alignment recipe. For CMP layers a further overlay improvement can be achieved if all gratings have comparable phase depths. By combining alignment signals from different gratings in a predictive alignment recipe, wafer-to-wafer variations due to CMP effects can be reduced.
We report laser-ablation studies of highly-oriented thin films of the electron-doped infinite-layer copper-oxide compounds Sr1- xLaxCuO2. The primary synthesis variables were substrate or buffer layer material, temperature, laser fluence, target- substrate distance, and oxygen pressure. The films were characterized by x-ray diffraction, atomic force microscopy (AFM), Rutherford back-scattering (RBS), and electrical resistivity. Films were deposited on strontium titanate (001) or on buffer layers of T'-phase copper oxides, Ln2CuO4 (Ln equals Pr, Sm) on SrTiO3 (001). The in-plane lattice constants of such T'-phase materials (a equals 0.391 - 0.396 nm) could provide a structure more amenable to electron doping than strontium titanate (a equals 0.390 nm). Extremely flat buffer layers were obtained from stoichiometric targets of Sm2CuO4 and Pr2CuO4. However, ablation from stoichiometric infinite-layer targets onto buffer layers resulted in mixtures of infinite-layer and chain/ladder phases. Non-stoichiometric deposition was confirmed by RBS analysis. We thus utilized non-stoichiometric targets to obtain single-phased infinite-layer films. The x-ray rocking curves of highly-oriented epitaxial infinite-layer films exhibited full- widths at half maximum as narrow as 0.05 degrees. Infinite-layer films grown on T'-phase buffer layers exhibited lattice constants closer to those of the bulk superconductor than films grown directly on SrTiO3.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.