This paper describes an instrument and method for high-resolution characterization of lens components and assemblies for DUV retardance performance at various stages of manufacture. The instrument is a bespoke rotating analyzer Stokes polarimeter designed for DUV wavelengths (e.g. 193 nm, 213 nm, 266 nm, etc.). Using a laser source, the polarimeter delivers a small diameter beam with a characterized polarization state to the optical lens element or objective assembly at the “as-used” design angles of incidence (AOI) to characterize the retardance through the lens or objective at an arbitrary location. The polarization characteristics are usually described by the retardance at specific locations on a component or sub-assembly that can be used to characterize components during development and manufacturing or optimize performance of an assembly.
Speckle degrades the contrast of the fringe patterns in laser interferometers that measure rough objects. In this paper, we
describe a speckle reduction system that can be used with high speed cameras to increase the frame rates of the interferometer and creates less vibration in the system.
Problem definition: Transfer maximum monochromatic flux from a 1-mm-square Lambertian source in air to an equal-étendue nonimmersed
target. The target surface is rectangular with a 16:9 aspect ratio. The surface area of the target must be at least 4 mm2.
The target is defined such that only rays incident on the target surface at angles of θmax or less, relative to the surface
normal, are considered to be within the phase space of the target, where the value of θmax is determined by the equal-étendue
The beam shaping by illuminators of microlithographic optical systems is a key technological contributor to the advancement of mass production of integrated circuits. The following examines both the requirements and the design of these illumination systems. The importance of partial coherence, off-axis illumination, polarization, telecentricity and uniformity for the lithographic process are discussed. The design sections cover the systems from source to reticle, including the use of diffusers, axicons, kaleidoscopes and fly's eyes arrays.
Microlithographic objectives have been developed for deep ultraviolet and vacuum ultraviolet wavelengths used for printing and inspection applications related to microlithographic processes. Refractive and catadioptric design solutions using fused silica, calcium fluoride and other crystals are discussed. Several reflective and catadioptric design forms having central obscurations will be compared to refractive forms. Design complexity, performance and limitations are compared.
A ray tracing method of simulating interferometers from source to detector using standard optical design software is presented. The advantages, disadvantages and limitations of the method are discussed. The method is applied to the analysis of a phase measuring interferometer designed to test the form of cylindrical mechanical parts and the predicted performance is compared with experimental results.
Building successive generations of state-of-the-art wide field, sub-micron microlithographic lens systems dictates ever-tightening material tolerances that challenge glass manufacturers. This paper discusses the optical material needs for microlithographic lens systems and Tropel's in-house material qualification program. Material qualification is divided into three successive stages: (1) fluorescence testing to qualitatively analyze color center characteristics of the material; (2) homogeneity testing to determine the relative volumetric variations in index; and (3) absolute index testing at multiple wavelengths to determine the material's dispersion characteristics.
Annular illumination has been studied as a method for improving depth of focus (DOF) in microlithographic systems. A 2X increase in DOF for 0.25 micrometers dense line/space features has been demonstrated using a deep-UV exposure tool with annular illumination. The same increase in DOF for 0.35 micrometers dense line/space patterns has been demonstrated using an i- line exposure tool employing annular illumination. No improvement in isolated features has been found. Annular illumination exhibits no degradation in isolated feature DOF, but the critical dimension (CD) split between dense and isolated features is affected when using annular illumination. Prototype i-line and deep-UV annular illumination systems have been built and tested which minimize the reduction in intensity and loss of uniformity control when using annular illumination. We have employed the use of conical optics as a high efficiency method of producing ring-shaped illumination in an i-line illumination system. The deep-UV prototype system uses a pre-uniformizer device to convert the collimated excimer laser light into a flat-top pupil fill which is then centrally obscured to produce annular illumination.