This paper describes the design and analysis of a deep-UV diffractive beam shaper for converting a collimated Gaussian
beam into a collimated flattop beam. Diffractive beam shapers can be manufactured in most common materials to
provide good beam control with very low non-uniformity. Beam shapers, however, are generally very sensitive to beam
parameters and alignment. Here we examine the sensitivity of the beam shaper to alignment and tilt of the input beam,
phase surfaces, and various other fabrication errors. This device was successfully built and comparisons with laboratory
measurements show excellent agreement with simulation predictions.
As photolithographic tools are pressed to print the ever shrinking features required in today's devices, complex off-axis
illumination is taking an ever increasing role in meeting this challenge. This, in turn, is driving tighter, more stringent
requirements on the diffractive elements used in these illumination systems. Specifically, any imbalance in the poles of
an off-axis illuminator will contribute to reductions in the ultimate imaging performance of a lithographic tool and
increased complexity in tool-to-tool matching. The article will focus on improvements to the manufacturing process that
achieve substantially better pole balance. The modeling of the possible process contributors will be discussed.
Challenges resulting from the manufacturing methodology will be shared. Finally, the improvement in manufacturing
process performance will be reported by means of a pole balance capability index.
As CDs continue to shrink, lithographers are moving more towards using off-axis illumination schemes to increase their CD budget. There have been several papers over the last few years describing various custom illumination profiles designed for application specific optimization. These include various annular and quadrupole illumination schemes including weak quadrupole, CQUEST, and QuasarTM. Diffractive optics, if incorporated into the design of the illumination system, can be used to create arbitrary illumination profiles without the associated light loss, thus maintaining throughput while optimizing system performance. Diffractive optical elements used to generate efficient illumination profiles for 248 nm and 193 nm excimer laser-source scanners, have been reported and realized in fused silica. The fabrication of such elements in calcium fluoride (CaF2), for use in 157 nm wavelength lithographic projection tools has been developed and is presented in this paper. Three different categories of elements are shown: large-diagonal-cluster diffusers, medium- and small-rectangular-cluster diffusers. The diffusers were fabricated as binary phase devices, in order to determine calcium fluoride processing capabilities.
This paper describes the fundamentals of diffractive optics diffuser design, with an emphasis on common pitfalls and important design decisions. In addition, several new design and fabrication methods are presented, which overcome many of the current limitations of multi-level diffractive diffusers. These designs include an easily fabricated white-light diffuser and a uniform, high-NA diffuser design.
As CDs continue to shrink, lithographers are moving more towards using off-axis illumination schemes to increase their CD budget. There have been several papers over the last few years describing various custom illumination profiles designed for application specific optimization. These include various annular and quadrupole illumination schemes including weak quadrupole, CQUEST, and QuasarTM. Traditionally, pupil filtering is used to realize these complex illumination modes but this approach tends to introduce significant light loss. Therefore, compromises are made to lithographic performance to minimize the effect on wafer throughput. Diffractive optics, if incorporated into the design of the illumination system, can be used to create arbitrary illumination profiles without the associated light loss, thus maintaining throughput while optimizing system performance. We report on the design and fabrication of such devices for use with KrF, ArF, and potentially F2 scanners. Extension to I-line steppers is also possible.
System alignment is often the cost driver in the production of optical system. In order to both miniaturize and reduce production costs, wafer scale integration of active and passive components is required. This integration relies on a host of techniques to align and bond active and passive devices into a monolithic structure. Moreover, this initial packaging is accomplished while the optics and supporting structures are in wafer form, thereby providing parallel fabrication with resultant cost savings. This paper describes the fundamental techniques for producing IMOS from wafer scale substrates. The relative merits of each approach are discussed, along with design concerns for successful application. Two example systems are discussed, each using a different fabrication technique.
KEYWORDS: Sensors, Monte Carlo methods, Optical simulations, Transceivers, Thermal modeling, 3D modeling, Human-machine interfaces, Glasses, Systems modeling, Integrated optics
We have developed a modeling tool that integrates optical, cost, thermal, mechanical, and solder models under a common user interface. The models are connected together to allow trade-off studies between parameters existing within different models. We have applied the integrated models to a family of optical interconnect modules. In this paper we will show how the integrated models can help the users design, as well as understand tradeoffs, in optical modules.
Diffractive optical encoders have quickly established themselves in the marketplace because of their small seize, high accuracy and relaxed alignment tolerances, but current products are still composed of carefully packages, discrete optical and electro-optical components. MicroE and Digital Optics Corporation have been working together on the next generation of these encoders, which replaces all discrete and refractive elements with DOE's and more completely integrates the requisite optical and electro-optical components. In this paper we describe a monolithic source/optics/detector encoder module we have designed and prototyped for a satellite application under a NASA Phase I SBIR contract.
We are assembling a crosspoint switch system to demonstrate the free-space interconnects based on the smart-pixel-array (SPA) technology. The hybrid SPA including VCSEL arrays, microlens array, hologram array, and CMOS detector array will be described. The whole system is packaged using a custom designed optomechanics component. The design, fabrication and performance of the system are discussed.
We describe the optical design of an optoelectronic 3-D system that is being developed by the Optoelectronic Computing Systems Center at the University of Colorado to prove the utility and viability of 3-D computers that use free-space optical interconnects to achieve a high degree of global connectivity among the PEs of a fine-grained parallel computer. The features of the VCSEL array as a source of coherent emission for hologram reconstruction and the CGH design procedure are discussed. An optical design in paraxial approximation of the 3-D computer with bidirectional 8 x 8 holographic interconnects is presented. The effect of VCSEL wavelength variation on diftraction crosstalk is estimated. The aberration in optical system based on the shelf objective is calculated, and a distortion compensation procedure is proposed.
Ring-wedge detectors are known to produce a useful feature set for certain types of pattern recognition. Their major shortcoming is that they measure global features. We present an optical processor, based upon the computation of a two-dimensional wavelet transform, which overcomes this limitation. By using wavelet functions that are essentially compact in the space domain we generate an output that consists of a mosaic of spatially localized bandpass components. Consistent with the nature of wavelets, the radial (ring) frequency components, are organized into constant-Q (f0/(Delta) f) bands. The angular (wedge) frequency content is divided into a number of equal-width bands which cover the full 0 - 180 degree(s) range. The radial information is obtained by using a feedback iteration loop which scales the input image by a fixed factor for each time around the loop. By introducing a tilt in the Fourier plane of the feedback loop, we arrange for the space-domain representations of each scaled input to be spatially separated without altering the position of their Fourier transforms. In this way, all of the radial frequency bands can be extracted with a single wavelet filter. A diffraction grating is introduced into the optical path after the scaling loop to replicate the Fourier information M times. The angular information is extracted using M filters in parallel-- one for each wedge component. The filter outputs are minified consistent with Nyquist theory for their reduced bandwidths to produce an output whose space-bandwidth product is roughly the same as that of the input image. We present the design of the optical system along with some initial experimental results.
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