Search

We present a method for optimizing a free-form illuminator implemented using a diffractive optical element (DOE). The method, which co-optimizes the source and mask taking entire images of circuit clips into account, improves the common process-window and 2-D image fidelity. We compare process-windows for optimized standard and free-form DOE illuminations for arrays and random placements of contact holes at the 45 nm and 32 nm nodes. Source-mask cooptimization leads to a better-performing source compared to source-only optimization. We quantify the effect of typical DOE manufacturing defects on lithography performance in terms of NILS and common process-window.

We present advancements in the manufacture of high-performance diffractive optical elements (DOEs) used in stepper/scanner off-axis illumination systems. These advancements have been made by employing high resolution lithographic techniques, in combination with precision glass-etching capabilities. Enhanced performance of DOE designs is demonstrated, including higher efficiency with improved uniformity for multi-pole illumination at the pupil plane, while maintaining low on-axis intensity. Theoretical predictions of the performance for several classes of DOE designs will be presented and compared with experimental results. This new process capability results in improved performance of current DOE designs, and enables greater customization including control of the output spatial intensity distribution for future designs. These advancements will facilitate continuous improvements in off-axis illumination optimization required by the end user to obtain larger effective lithographic process windows.

As CDs continue to shrink, lithographers are moving towards using off-axis illumination while continuing to decrease the operating wavelength to improve their CD budget. Currently DUV lithography at 248nm and 193nm are driving the ability of the foundries and IDM’s to meet or exceed the SIA roadmap for semiconductor chip performance. In time, however, the industry will migrate to the even shorter wavelengths of 157nm and 13nm. To meet today’s needs with 248nm and 193nm requires the use of Resolution Enhancement Techniques such as Optical Proximity Correction, Phase Shift Mask, and Off Axis Illumination. The need for these techniques will be only slightly reduced as the industry migrates to 157nm in several years. Off-axis illumination (the topic of this paper) has been shown to significantly increase the lithographic process window and there have been several papers over the last few years describing various illumination profiles designed for application specific optimization. These include various annular and quadrupole illumination schemes including weak quadrupole, CQUEST, and Quasar 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 F 2 scanners.

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.

The effectiveness of utilizing spatial light modulators (SLMs), developed at Sanders, for reducing some of the critical bottlenecks inherent within the Hyperspectral Imaging (HSI) chain will be presented. Specifically, the more common classification, detection, and endmember selection algorithm used in HSI, which are suitable for optical implementation, are presented here. These algorithms were reformulated for implementation on a compact Vander- Lugt correlator based on Sanders' multi-level quantum well (MQW) spatial light modulator (SLM). Sanders devices are GaAs Fabry-Perot vertical cavity multiple quantum well (MQW) SLMs consisting of MQW optical chips flip-chip bonded to Si/CMOS driver circuitry. Details of the reformation of Pixel Purity Index, an endmember selection algorithm, to the optical correlator is presented as well as a projection of its performance based on software simulations. In addition, hardware results are presented for Spectral Angle Mapper based on a Vander-Lugt implementation using Sanders 128 X 128 binary SLMs. An opto-electronic hyperspectral workstation accelerator is proposed which is based on a Vander-Lugt correlator using Sanders' MQW-SLMs and FPGA- based compute nodes and has the capability of 6.4 Million 1D correlations per second for HSI endmember selection, classification and detection.

Graded index fiber has a limited bandwidth due to defects introduced in the fiber manufacturing process. In this paper, an alternative launch technique is presented using a diffractive element to excite specific modes in a fiber to maximize the bandwidth of graded index fiber.

Standard laser welding practices are limited by the intensity profile of the beam and spot size. The introduction of Diffractive Optical Elements (DOE) to the welding process allows for new beam shapes that are better suited to the welding process. A particular problem in laser welding is the joining of dissimilar materials. Because these materials have different material properties including different melting temperatures, it is difficult to synchronize the welding process using a single spot. Additionally, significant thermal stresses are introduced by the welding process because of the keyhole weld shape formed by a gaussian beam. By using a power splitting DOE, two spots of unequal intensity distributions may be projected onto each side of the weld joint. This paper discusses the use of DOEs in laser welding and joining of dissimilar materials. Results are presented from the testing of several candidate aerospace materials.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Silicon v-groove structures have been utilized for passive positioning of optical fiber for fiber optic and opto- electronic applications. In this paper, we will present our results of using micro-machined silicon v-groove arrays to passively align optical fiber arrays to micro rod optics. We will also demonstrate the integration of N fiber arrays bonded into the silicon v-groove with a 1xN micro lens array, which is composed of a 2 inch-phase level diffractive optics. For the assembly of 1x6 fiber array and lens array with 16 phase level diffractive optics, the experimental results indicated that total insertion loss per link is typically 1.5-2.0 dB/channel.

We review GaAs Fabry-Perot vertical cavity multiple quantum well (MQW) spatial light modulators (SLMs) developed at Sanders, a Lockheed Martin Company, and demonstrate their use in optical image correlation. These MQW SLMs are reflective- mode modulators using electrically-tunable absorption to modulate the reflected intensity. The operation of the MQW SLMs with a newly-developed Labview graphical user interface is described. A compact Vander-Lugt image correlator is described which was configured using MQW SLMs: binary 128 X 128 pixel image input with a binary filter plane. In addition, the architecture of 8-bit gray-scale MQW-SLM module developed at Sanders is discussed. The performance of the image correlator was characterized using amplitude-encoded binary phase-only filters and various test targets including test imagery supplied by US Army AMCOM, and is compared with simulations for peak-to-secondary efficiencies on these data. Finally, high-speed (250,000 frames per second) target recognition of 128 X 128 pixels binary input imagery is demonstrated.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We review GaAs Fabry-Perot vertical cavity electro-optical devices constructed at Lockheed Martin Sanders, with particular attention to spatial light modulators and discuss a number of their applications. Our manufacturing processes enable the construction of large format, highly-uniform optical modulator and smart pixel arrays integrated with silicon CMOS VLSI circuitry. These devices can be used for a wide variety of applications including: optical computing for target recognition and signal processing, optical data routing, optical interconnect systems, and optical memory storage and access.

JohnAlfredTrezzaJeffry S. Powell, Charles Garvin, Keith Kang, Richard StackSanders, A Lockheed Martin Company, 65 Spit Brook Road, NHQ6-1551, Nashua, NH 03060Vertical cavity optoelectronic modulators are the key component for future real-time electro-opticalsignal processing, computing, optical memory access, free-space optical interconnect, informationprocessing, laser printing, and data conversion systems. Here we will discuss the operation and operatingprinciples of our optical devices, the integration of these devices into large arrays, the experimentalcharacteristics of large arrays of devices, and the use of the arrays.The quantum well device arrays that we produce are comprised of "MED pixels". These are surfacenormal devices constructed (by molecular beam epitaxy) out ofthe 111-V semiconductor material system.MED pixels are so called because they:1) Modulate light: The devices can be operated in a mode in which they alter either the amplitude (onor off), the phase (0° to 360°), or the direction (either unimpeded, or altered by simple reflection).2) Emit light: The devices can be operated as resonant cavity light emitting diodes, providing outputlight that, while not coherent, is spatially collimated and spectrally confined.3) lletect light: The devices can be operated as detectors for incident light.A given pixel can perform all three of these types of operations (though one typically chooses eitherphase or amplitude modulation as one of the three properties); the type of behavior that a given MEDpixel exhibits at any one time is determined by the control signal which is applied at any given moment.When such arrays consist of close-packed pure modulating or light emitting pixels, they are referred toas 'spatial light modulator' (SLM) or 'spatial light emitter' (SLE) arrays respectively. We typicallycombine optical chips containing large (up to 1x2048 and 256 x 256) arrays of GaAs MED pixels withcustom SRAM CMOS chips. The GaAs optical and silicon driver chips are combined by placing solderbumps on the chips and then using these bumps as electrical contacts between individual optical pixelsand silicon transistor circuits. The resultant hybrid electro optical chip is then sealed, wirebonded intoan IC package, and hermetically contained. We have used this 'flip-chip' bonding technology to connectpixelated GaAs devices to silicon drivers on chips over 2 square centimeters in size, containing as manyas 307,000 pixels with pixel yields of 99.98% uncorrected and 99.998% with electrical correction. TheSRAM chips (currently 2 x 65k) can store data bits and output data optically through the optical chip.These arrays, then, are ultra-fast electrical to optical (and optical to electrical) transducers where hugeparallelism exists.Electrical data input into our 256x256 array is through a series of 256 input lines, each of which isclocked in parallel into the array. Thus, the array takes 256 clocks to load an image (our 128x128 arrayhandles 128 input lines and takes 128 clocks to load). The CMOS SRAM driver chip allows two fullframes of binary mode data can be stored at any one time. Electronic data is loaded into the CMOS's'back buffer page' while another page of memory is displayed through the optical chip. When the back

The technical approach and progress achieved under the Polymer Optical Interconnect Technology (POINT) program are described in this paper. The POINT program is a collaborative effort among GE, Honeywell, AMP, AlliedSignal, Columbia University, and University of California at San Diego (UCSD), sponsored by DARPA/ETO, to develop affordable optoelectronic packaging and interconnect technologies for board and backplane applications. Specifically, progress is reported on (a) development of a plastic VCSEL array packaging technology using batch and planar fabrication, (b) demonstration of high-density optical interconnects for board and backplane applications using polymer waveguides to a length of 50 cm at an I/O density of 250 channels per inch, (c) development of low-loss optical polymer waveguides with loss less than 0.1 dB/cm at 850 nm, and (d) development of passively alignment processes for efficient coupling between a VCSEL array and polymer waveguides. Significant progress has also been made under the POINT program at Columbia University, in applying CAD tools to simulate multi-mode-guided wave systems and, at UCSD, to assist mechanical and thermal design in optoelectronic packaging. Because of space limitations, these results will be described elsewhere in future publications.

Optical connectors utilize microlens elements for coupling light into and out of fibers. Typically, these lenses are based on sapphire ball lenses or Gradient Index lens elements.However, lenses that are on the same scale as the single-mode fiber itself have not been previously realized. This paper introduces an optical lens element that fits into the single-mode optical ferrule, without any modifications to the connector package. This approach offers substantial performance and cost benefits over other methods.Both theoretical and experimental results are presented.

GaAs asymmetric Fabry-Perot vertical cavity modulators are useful in a wide variety of applications. Vertical cavity devices have employed amplitude or phase modulation for optical switching. Amplitude modulators have been demonstrated in large format arrays. Additional uses for the pixels include directional modulation, detection, and light- emitting capability. When arrays of these deices are integrated with electronic circuits - most significantly silicon CMOS VLSI - at the pixel level, large, complex optical spatial light modulators, detectors, transceivers, computation devices, and emitters can be created for a wide variety of applications. These applications range from target recognition to SAR radar processing, to optical data routing, to optical interconnect systems, to optical memory access.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper describes the technical approach and progresses of the POINT program. This project is a collaborative effort among GE, Honeywell, AMP, AlliedSignal, Columbia University and University of California at San Diego, sponsored by DARPA/ETO to develop affordable optoelectronic packaging and interconnect technologies for board and backplane applications. In this paper, we report the development of a backplane interconnect structure using polymer waveguides to an interconnect length of 280 mm to demonstrate high density and high speed interconnect, and the related technical development efforts on: (a) a high density and high speed VCSEL array packaging technology that employs planar fabrication and batch processing for low-cost manufacturing, (b) passive alignment techniques for reducing recurrent cost in optoelectronic assembly, (c) low-cost optical polymers for board and backplane level interconnects, and (d) CAD tools for modeling multimode guided wave systems and assisting optoelectronic packaging mechanical design.

The coupling of a vertical cavity surface emitting laser (VCSEL) array into an array of multimode polymer waveguides through a 45 degree endface mirror is investigated. A coupling model for the VCSEL and waveguide interface is developed and compared with our experimental results.

The Polymer Optical Interconnect Technology (POINT) represents a major collaborative effort among GE, Honeywell, AMP, AlliedSignal, Columbia University and the University of California at San Diego (UCSD), sponsored by ARPA, in developing affordable optoelectronic module packaging and interconnect technologies for board- and backplane- level optical interconnect applications for a wide range of military and commercial applications. The POINT program takes a novel development approach by fully leveraging the existing electronic design, processing, fabrication and module packaging technologies to optoelectronic module packaging. The POINT program further incorporates several state-of-the-art optoelectronic technologies that include high-speed VCSEL for multichannel array data TM transmission; flexible optical polymers such as Polyguide or coupling of device-to-fiber using a passively alignment process; a low-loss polymer for backplane interconnect to provide a high I/O density; low-cost diffractive optical elements (DOE) for board-to-backplane interconnect; and use of molded MT array ferrule to reduce overall system size, weight, and cost. In addition to further reducing design and fabrication cycle times, computer simulation tools for optical waveguide and mechanical modeling will be advanced under the POINT program.