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We describe a variety of technologies for patterning transmissive and reflective soft x-ray projection lithography masks containing features as small as 0.1 μm. The transmission masks fabricated for use at 13 nm are of one type, a Ge-absorbing layer patterned on a boron-doped Si membrane. Reflective masks were patterned by various methods that included absorbing layers formed on top of multilayer reflectors, multilayer-reflector-coating removal by reactive ion etching, and ion damage of multilayer regions by ion implantation. For the first time, we believe, a process for absorber repair that does not significantly damage the reflectance of the multilayer coating on the reflection mask is demonstrated.

A laboratory extreme ultraviolet lithography tool (EUVL) has been assembled atSandia National Laboratories [1]. Its major components include a Schwarzschildcamera with 0.1 jim resolution integrated with a laser plasma source (LPS) and amagnetically levitated stage. Other subsystems are a grazing-incidence optical system to maintain focus, and a through-the-lens Moire alignment system for overlay. This exposure tool is being used to study integration issues for EUVL.Experiments have been performed to characterize the alignment system's performance. The measured sensitivity of the alignment system is 15 nm 3. 1. INTRODUCTION A laboratory extreme ultraviolet lithography tool (EUVL) has been assembled atSandia National Laboratories' . Its major components include a Schwarzschild camera with 0.1 jim resolution integrated with a laser plasma source (LPS) and a magnetically levitated stage. Other subsystems include a grazing-incidence opticalsystem to maintain focus and an alignment system for overlay. This exposure toolis being used to study integration issues for EUVL. In order to demonstrate thesuccessful integration of the system, microelectronic devices and circuits will befabricated with at least one lithography step performed with EUVL.In this paper, we will describe in detail the EUVL tool and its capabilities. We willalso report results from recent experiments performed to characterize theperformance of the visible through-the-lens (TTL) Moire alignment system.

We have studied two mark geometries for possible use in a projection e-beam lithography system using SCALPEL (scattering with angular limitation in projection electron lithography). These are V-grooves and vertically etched geometries, pedestals or trenches. We report results of measurements of backscattered electron (BSE) contrast form topographic marks of varying size and as a function of energy up to 100 kV. The marks were fabricated on silicon wafers. The measurements were taken both in a scanning electron microscope and in an experimental SCALPEL machine operating in focused probe mode. The V-grooves ranged from 1.0 to 30 micrometers wide. The vertical etched features ranged from 2 to 30 micrometers wide and 0.6 and 50 micrometers depth. The results depended not only on the feature width and depth, but also on whether the features were isolated or in line and space patterns. Using a BSE ratio of 1.05 as a criterion for acceptable contrast from an alignment mark, V-grooves and vertical etched features had acceptable contrast with exception of the smallest and shallowest features for both geometries.

The multi-component, positive acting, chemically amplified deep-UV ((lambda) equals 248 nm) resist ARCH, has been evaluated for use in proximity x-ray and electron-beam lithography. Characterization of the x-ray lithographic response of ARCH resist using a pulsed laser point source ((lambda) equals 1.4 nm) proximity print stepper resulted in a process producing sub-0.20 micrometers features at a dose of 22 mJ/cm2. A time delay study was conducted in the helium environment of the x-ray exposure tool and the results indicate that a > 30 min delay period after exposure produced no change in the resist image profile. Electron- beam exposures using a JEOL JBX 5D-II tool operating at 50 KeV delineated patterns below 0.10 micrometers on silicon. The measured exposure sensitivity was in the range of 8-16 (mu) C/cm2. Time delay experiments performed in the vacuum environment of the e-beam exposure tool over a 15 hr. time period resulted in no line size variation. These results suggest that ARCH resist represents a common material platform for the various advanced lithography programs currently under investigation for fabrication of circuits having

This paper reports results from a study of defect printability for extreme ultraviolet lithographic masks (EUVL). Imaging experiments were preformed with an EUVL mask containing programmed defects. The mask contained defects of different sizes and locations with respect to the absorber patterns. Since an EUVL mask consists of absorber layer patterned above a multilayer-coated substrate, both substrate defects, located below the reflective coating, and absorber defects, located above the reflective coating, were included on the programmed defect mask. The absorber layer was patterned using a process previously described by Tennant et al. Imaging was performed using a 10X Schwarzschild camera operating at 13.4 nm with a numerical aperture of 0.08, corresponding to a Rayleigh resolution of 0.1 micrometers . This system has an effective exposure field of 0.4 mm diameter. Both positive-tone and negative-tone resists were used. Measurements of the defect-induced linewidth variations on the printed resist lines were performed with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results show that substrate defects are more printable compared to defects of the same sizes located above the reflective coating. In addition, defects located in the center of a clear region in lines-and- space pattern are more printable compared to those located nearer to the absorber lines.

The development of a laboratory EUV lithography tool based on a laser plasma source, a 10x Schwarzschild camera, and a magnetically levitated wafer stage is presented. Interferometric measurements of the camera aberrations are incorporated into physical-optics simulations to estimate the EUV imaging performance of the camera. Experimental results demonstrate the successful matching of five multilayer reflecting surfaces, coated to specification for a wide range of figure and incidence angle requirements. High-resolution, 10x-reduction images of a reflection mask are shown.

Transition metal suicides are receiving an increasing amount of attention as materials for VLSI interconnects because of their low resistivities and ease of integration with silicon. A recently invented technique, mesotaxy, allows the production of buried single-crystal suicide layers in silicon.Buried suicide layers made by implantation into (100) Si wafers can be patterned by restricting the implant with an oxide mask, giving great flexibility in the types of features that can be produced. We have fabricated simple microstructures to investigate the formation and properties of mesotaxial CoSi2. Wires of constant dose but varying widths exhibit a transition in morphology from {111} faceted wires to largely (100) faceted layers. After annealing for prolonged periods, the finer wires show the effects of coarsening. We have also observed the movement of a significant amount of Co from the oxide implant mask into the substrate during these anneals. The wires show greatly improved thermal stability compared to polycrystalline suicides formed by deposition.1

A new approach to dose modification proximity effect correction (PEC) has been proposed that accounts for both short range and long range scatter in advanced direct-write electron beam lithography systems. This scheme can be applied to device writing and to optical mask making where critical dimension (CD) control is of increasing importance. This technique is unique because detailed knowledge of the short range scatter dose distribution is unnecessary; by correcting only for long range scatter, both short and long range compensation is obtained. The new approach is based on the fact that if the characteristic distance of short range scatter is about one third or less of the smallest feature, and if each feature is at least five addressable pixels in the beam writer, then the feature can be printed at its coded dimension if the resist clearing or threshold dose is at the midpoint of the dose profile. Si wafers coated with a positive tone e-beam resist were exposed to a test pattern using no PEC, conventio...

The effective backscatter coefficient η is a quantity that must be known with precision so that the proximity effect can be adequately compensated to minimize feature size variations in electron beam lithography. A unique technique to measure η that does not require the precise form of the backscatter dose distribution was employed. This method simply compares the resist response near the center of printed features that are much smaller and much larger than the characteristic range of the long range scatter. This technique was already employed to estimate the backscatter coefficient on Si at 100 keV beam energies. We have extended this measurement to determine η at lower beam energies. Results show that η on Si is 0.38, 0.50, 0.55, and 0.46 for 100, 50, 40, and 20 keV beam energies, respectively. Monte Carlo simulations indicate a trend of decreasing η with increasing beam energy, consistent with the experimental results except at 20 keV.

Resistance fluctations in submicrometer narrow Si inversion layers are studied over a wide range of temperatures and electron concentrations. Thermally activated switching on and off of discrete resistance increments is observed, caused by the capture and emission of individual electrons at strategically located scatterers (interface traps). The traps have a broad distribution of activation energies, as assumed in accounting for $\frac{1}{f}$ noise in larger devices.