This is the first high resolution measurement of the electron energy spectrum from high intensity above-threshold ionization (ponderomotive energy » ionization potential ^>hv) at intensities up to 7x 10 15 W/cm 2 . In contrast to previous work, we have used a short pulse and a large focal spot along with low gas densities to minimize the effect of ponderomotive forces and collisions. Existing models do not agree well with electron energy spectra for either linearly or circularly polarized light. The electron temperature is too hot for the implementation of 820 nm multiphoton ionized recombination type XUV laser schemes. PACS numbers: 32.80.RmWe report the first high resolution measurement of the electron energy distribution from high intensity abovethreshold ionization (ATI) at intensities up to 7xl0 15 W/cm 2 with a short pulse. In the short pulse regime [1-4] the pulse is over before the electrons have been disturbed by the ponderomotive force: The electrons are therefore characteristic of the ionization intensity and not of the excitation geometry. Previous measurements of electron spectra in the so-called "long pulse regime" were dominated by the ponderomotive acceleration of the electrons, which is their quiver response to the oscillating electromagnetic field in the intensity gradient at the laser focus [1-6]. The measurements reported here are at intensities 30 times more intense than those previously published and allow us to test models of ATI in the high intensity limit when ATI models should be most valid, viz., ponderomotive energy »ionization potentialshv. ATI electron energy spectra from both linearly and circularly polarized light were measured. While the threshold intensities for multiphoton ionization agree with models of ATI [7-9], the electron spectra from linear or circular polarization differ markedly from theory. The predicted preponderance of slow electrons from linearly polarized ATI is not observed. This result is particularly noteworthy in light of recently proposed x-ray laser schemes that use multiphoton ionization to produce high ion stages in a relatively cold electron distribution [10-12].These measurements are valuable because the ATI electron energy distributions contain minimal ponderomotive force contributions, despite the fact that the ponderomotive energy is much higher than the ionization potential of the parent atom. To achieve this, we require both a short pulse and a large focus. Our laser source is a colliding-pulse mode-locked laser [13] centered at 820 nm, amplified in a Ti-sapphire chirped-pulse amplifier [14]. It is capable of delivering 50 mJ pulses of 180 fs duration at 5 Hz. Laser pulses are focused with a 1 m lens into a vacuum chamber to a Gaussian waist of 0)0 = 35 jum. After the lens the laser beam propagates almost entirely in vacuum. The electron energy spectra are measured with a field-free time-of-flight (TOF) spectrometer with a detection cone angle of 2° (3.8 x 10 ~3 sr collection solid angle) at the focus. Electrons are accelerated at the end of the TOF ...

The 2007 International Technology Roadmap for Semiconductors (ITRS) 1 specifies Extreme Ultraviolet (EUV) lithography as one leading technology option for the 32nm half-pitch node, and significant world wide effort is being focused towards this goal. Readiness of EUV photoresists is one of the risk areas. In 2007, the ITRS modified performance targets for high-volume manufacturing EUV resists to better reflect fundamental resist materials challenges. For 32nm half-pitch patterning at EUV, a photospeed range from 5-30 mJ/cm 2 and low-frequency linewidth roughness target of 1.7nm (3σ) have been specified. Towards this goal, the joint INVENT activity (AMD, CNSE, IBM, Micron, and Qimonda) at Albany evaluated a broad range of EUV photoresists using the EUV MET at Lawrence Berkeley National Laboratories (LBNL), and the EUV interferometer at the Paul Scherrer Institut (PSI), Switzerland. Program goals targeted resist performance for 32nm and 22nm groundrule development activities, and included interim relaxation of ITRS resist performance targets. This presentation will give an updated review of the results. Progress is evident in all areas of EUV resist patterning, particularly contact/via and ultrathin resist film performance. We also describe a simplified figure-of-merit approach useful for more quantitative assessment of the strengths and weaknesses of current materials.

High sensitivity actinic detection of native defects on extreme ultraviolet lithography mask blanksThe production of defect-free mask blanks remains a key challenge for extreme ultraviolet ͑EUV͒ lithography. Integral to this effort is the development and characterization of mask inspection tools that are sensitive enough to detect critical defects with high confidence. Using a single programed-defect mask with a range of buried bump-type defects, the authors report a comparison of measurements made in four different mask inspection tools: one commercial tool using 488 nm wavelength illumination, one prototype tool that uses 266 nm illumination, and two noncommercial EUV "actinic" inspection tools. The EUV tools include a dark field imaging microscope and a scanning microscope. Their measurements show improving sensitivity with the shorter wavelength non-EUV tool, down to 33 nm spherical-equivalent-volume diameter, for defects of this type. Measurements conditions were unique to each tool, with the EUV tools operating at a much slower inspection rate. Several defects observed with EUV inspection were below the detection threshold of the non-EUV tools.

Patterning nonflat substrates with a low pressure, room temperature, imprint lithography process A novel alignment system for imprint lithography in the deep sub-hundred nanometer realm is proposed. The new system is inherently more precise than the alignment systems used in conventional projection lithography because alignment marks on an imprint mold ͑the functional equivalent of a photomask in projection lithography͒ are directly compared to alignment marks on a wafer with no intermediate optics or reference points. If the measured misalignment is so severe that all marks cannot be brought into registration simultaneously by the usual x -y translations and rotations, the mold is deliberately deformed with a system of piezoelectric actuators in such a way that its induced distortions precisely match those on the wafer and all of the alignment marks at each chip site can be pulled into registration simultaneously. Finite-element analysis indicates that using actuators to distort the mold is superior to distorting the wafer.

On the road to insertion of extreme ultraviolet (EUV) lithography into production at the 16 nm technology node and below, we are testing its integration into standard semiconductor process flows for 22 nm node devices.In this paper, we describe the patterning of two levels of a 22 nm node test chip using single-exposure EUV lithography; the other layers of the test chip were patterned using 193 nm immersion lithography. We designed a full-field EUV mask for contact and first interconnect levels using rule-based corrections to compensate for the EUV specific effects of mask shadowing and imaging system flare. The resulting mask and the 0.25-NA EUV scanner utilized for the EUV lithography steps were found to provide more than adequate patterning performance for the 22 nm node devices. The CD uniformity across the exposure field and through a lot of wafers was approximately 6.1% (3σ) and the measured overlay on a representative test chip wafer was 13.0 nm (x) and 12.2 nm (y). A trilayer resist process that provided ample process latitude and sufficient etch selectivity for pattern transfer was utilized to pattern the contact and first interconnect levels. The etch recipes provided good CD control, profiles and end-point discrimination.The patterned integration wafers have been processed through metal deposition and polish at the contact level and are now being patterned at the first interconnect level.