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Activities are reported on the following areas: project analysis and integration; technology development in silicon material, large area sheet silicon, and encapsulation; production process and equipment development; and engineering and operations, and the steps taken to integrate these efforts. Visual materials presented at the project Integration Meeting are included.
A cost effective process based on state-of-the-art technology has been developed for the production of large-area (55 sq cm and larger) solar cells. The process is capable of providing silicon and polysilicon cell efficiencies in excess of 10% at an overall cost of 12 c/watt in 1980 dollars. The process provides large throughputs and is suitable for complete automation with high yields. Various stages of the process development are discussed.
A process has been developed for the fabrication of a tantalum pentoxide waveguide Luneburg lens as the input collimator for an optical signal processing circuit on a silicon substrate, such as an integrated wavelength demultiplexer. The development of such a lens involved improvement of the deposition mask profile, reduction of surface scattering by underlaying the lens, reduction of edge scattering by using shims under the mask, and prediction and measurement of the TE-TM polarization aberration. It is shown that polarization aberration significantly affects the design of a demultiplexer system.
Polycrystaline silicon is presently routinely processed into low cost 10 cm by 10 cm solar cells. However assuming minimal handling difficulties, only minor equipment modifications and no increase in processing complexity, the fabrication of even larger geometries would be economically advantageous. This investigation addressed the feasibility of developing 10 cm by 15 cm solar cells from research through pilot line production stages. The major thrust was to minimize costing by using existing production equipment and proven techniques wherever possible. Accordingly methods were developed to section larger substrates from existing cast ingots, a simple solar cell was designed and low cost processes implemented. After numerous preliminary experiments, pilot line production of 1500 cells was completed. Of these approximately 62 percent exhibited efficiencies greater than 7.0 percent, 53 percent were greater than 8.0 percent and 15 percent were greater than 9.0 percent. Based on this study, the regular production of 10 cm by 15 cm solar cells was determined to be both feasible and cost effective using existing processing methods.
Efficient process aids production of silicon carbide/silicon nitride fibers. Fibers 10 to the sixth power times as electrically resistive as carbon fibers having similar mechanical properties; promising replacements for carbon fibers in composite materials in which high conductivity poses hazard.
Process produces extremely thin silicon solar cells - only 50 micrometers or less in thickness. Electrons and holes have less opportunity to recombine before collected at cell surfaces. Efficiency higher and because volume of silicon small, less chance of radiation damage in new cells. Initial steps carried out at normal thickness to reduce breakage and avoid extra cost of special handling. Cells then thinned mechanically and chemically. Final cell includes reflective layer on back surface. Layer bounces unabsorbed light back into bulk silicon so it absorbs and produces useful electrical output.
Improved reactor serves as last stage in system processing metallurgical-grade silicon feedstock into silicon powder of ultrahigh purity. Silane pyrolized to silicon powder and hydrogen gas via homogeneous decomposition reaction in free space. Features set of individually adjustable electrical heaters and purge flow of hydrogen to improve control of pyrolysis conditions. Power supplied to each heater set in conjunction with flow in reactor to obtain desired distribution of temperature as function of position along reactor.
The RH-3000 program is developing a rad-hard space qualified 32-bit MIPS R-3000 RISC processor under the Naval Research Lab sponsorship. In addition, under IR&D Harris is developing RHC-3000 for embedded control applications where low cost and radiation tolerance are primary concerns. The development program leverages heavily from commercial development of the MIPS R-3000. The commercial R-3000 has a large installed user base and several foundry partners are currently producing a wide variety of R-3000 derivative products. One of the MIPS derivative products, the LR33000 from LSI Logic, was used as the basis for the design of the RH-3000 chipset. The RH-3000 chipset consists of three core chips and two support chips. The core chips include the CPU, which is the R-3000 integer unit and the FPA/MD chip pair, which performs the R-3010 floating point functions. The two support whips contain all the support functions required for fault tolerance support, real-time support, memory management, timers, and other functions. The Harris development effort had first passed silicon success in June, 1992 with the first rad-hard 32-bit RH-3000 CPU chip. The CPU device is 30 kgates, has a 508 mil by 503 mil die size and is fabricated at Harris Semiconductor on the rad-hard CMOS Silicon on Sapphire (SOS) process. The CPU device successfully passed tesing against 600,000 test vectors derived directly on the LSI/MIPS test suite and has been operational as a single board computer running C code for the past year. In addition, the RH-3000 program has developed the methodology for converting commercially developed designs utilizing logic synthesis techniques based on a combination of VHDK and schematic data bases.
As an example of microsystems fabricated by the LIGA-technique (x-ray lithography, electroplating and molding), three systems are described and characterized: a triaxial acceleration sensor system, a micro-optical switch, and a microsystem for the analysis of pollutants. The fabrication technologies are reviewed with respect to the key components of the three systems: an acceleration sensor, and electrostatic actuator, and a spectrometer made by the LIGA-technique. Aa micro-pump and micro-valve made by using micromachined tools for molding and optical fiber imaging are made possible by combining LIGA and anisotropic etching of silicon in a batch process. These examples show that the combination of technologies and components is the key to complex microsystems. The design of such microsystems will be facilitated is standardized interfaces are available.
An overview of Microelectromechanical Systems (MEMS) reliability assurance and qualification activities at JPL is presented along with the a discussion of characterization of MEMS structures implemented on single crystal silicon, polycrystalline silicon, CMOS, and LIGA processes. Additionally, common failure modes and mechanisms affecting MEMS structures, including radiation effects, are discussed. Common reliability and qualification practices contained in the MEMS Reliability Assurance Guideline are also presented.
This Research Grant provides support for development of nanotechnology for x-ray astronomy instrumentation. MIT has made significant progress in several development areas. In the last year we have made considerable progress in demonstrating the high-fidelity patterning and replication of x-ray reflection gratings. We developed a process for fabricating blazed gratings in silicon with extremely smooth and sharp sawtooth profiles, and developed a nanoimprint process for replication. We also developed sophisticated new fixturing for holding thin optics during metrology without causing distortion. We developed a new image processing algorithm for our Shack-Hartmann tool that uses Zernike polynomials. This has resulted in much more accurate and repeatable measurements on thin optics.
A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs), on a pair of interdigitated electrodes (IDE) processed with a silicon-based microfabrication and micromachining technique. The IDE fingers were fabricated using photolithography and thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to nitrogen dioxide, acetone, benzene, nitrotoluene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing of carbon nanotubes in our sensor platform can be understood by intra- and inter-tube electron modulation in terms of charge transfer mechanisms. As a result of the charge transfer, the conductance of p-type or hole-richer SWNTs in air will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost. Additionally, a wireless capability of such a sensor chip can be used for networked mobile and fixed-site detection and warning systems for military bases, facilities and battlefield areas.
A RF MEMS switch comprising a crossbeam of SiC, supported by at least one leg above a substrate and above a plurality of transmission lines forming a CPW. Bias is provided by at least one layer of metal disposed on a top surface of the SiC crossbeam, such as a layer of chromium followed by a layer of gold, and extending beyond the switch to a biasing pad on the substrate. The switch utilizes stress and conductivity-controlled non-metallic thin cantilevers or bridges, thereby improving the RF characteristics and operational reliability of the switch. The switch can be fabricated with conventional silicon integrated circuit (IC) processing techniques. The design of the switch is very versatile and can be implemented in many transmission line mediums.
A process for preparing a silicon based substrate with a protective coating having improved thermal resistance at temperature up to at least 1500.degree. C., and the resulting article.
A 1,024 x 1,024-pixel array of quantum-well infrared photodetectors (QWIPs) has been built on a 1.8 x 1.8- cm GaAs chip. In tests, the array was found to perform well in detecting images at wavelengths from 8 to 9 m in operation at temperatures between 60 and 70 K. The largest-format QWIP prior array that performed successfully in tests contained 512 x 640 pixels. There is continuing development effort directed toward satisfying actual and anticipated demands to increase numbers of pixels and pixel sizes in order to increase the imaging resolution of infrared photodetector arrays. A 1,024 x 1,024-pixel and even larger formats have been achieved in the InSb and HgCdTe material systems, but photodetector arrays in these material systems are very expensive and manufactured by fewer than half a dozen large companies. In contrast, GaAs-photodetector-array technology is very mature, and photodetectors in the GaAs material system can be readily manufactured by a wide range of industrial technologists, by universities, and government laboratories. There is much similarity between processing in the GaAs industry and processing in the pervasive silicon industry. With respect to yield and cost, the performance of GaAs technology substantially exceeds that of InSb and HgCdTe technologies. In addition, GaAs detectors can be designed to respond to any portion of the wavelength range from 3 to about 16 micrometers - a feature that is very desirable for infrared imaging. GaAs QWIP arrays, like the present one, have potential for use as imaging sensors in infrared measuring instruments, infrared medical imaging systems, and infrared cameras.
Topics include: Multifunction Imaging and Spectroscopic Instrument; Position-Finding Instrument Built Around a Magnetometer; Improved Measurement of Dispersion in an Optical Fiber; Probe for Sampling of Interstitial Fluid From Bone; Neuropsychological Testing of Astronauts; Method of Calibration for a Large Cathetometer System; Four-Channel PC/104 MIL-STD-1553 Circuit Board; Improved Method of Locating Defects in Wiring Insulation; Strobe Traffic Lights Warn of Approaching Emergency Vehicles; Improved Timing Scheme for Spaceborne Precipitation Radar; Concept for Multiple-Access Free-Space Laser Communications; Variable Shadow Screens for Imaging Optical Devices; Verifying Diagnostic Software; Initial Processing of Infrared Spectral Data; Activity-Centric Approach to Distributed Programming; Controlling Distributed Planning; New Material for Surface-Enhanced Raman Spectroscopy; Treated Carbon Nanofibers for Storing Energy in Aqueous KOH; Advanced Infant Car Seat Would Increase Highway Safety; Development of Biomorphic Flyers; Second-Generation Six-Limbed Experimental Robot; Miniature Linear Actuator for Small Spacecraft; Process for Making Single-Domain Magnetite Crystals; A New Process for Fabricating Random Silicon Nanotips; Resin-Transfer-Molding of a Tool Face; Improved Phase-Mask Fabrication of Fiber Bragg Gratings; Tool for Insertion of a Fiber-Optic Terminus in a Connector; Nanofluidic Size-Exclusion Chromatograph; Lightweight, Low-CTE Tubes Made From Biaxially Oriented LCPs; Using Redundancy To Reduce Errors in Magnetometer Readings; Compact Instrument for Measuring Profile of a Light Beam; Multilayer Dielectric Transmissive Optical Phase Modulator; Second-Generation Multi-Angle Imaging Spectroradiometer; Real-Time Adaptive Color Segmentation by Neural Networks; Research and Development in Optical Communications; Tests of Multibeam Scintillation Mitigation on Laser Uplinks; and Spaceborne Infrared Atmospheric Sounder.
This paper presents an extreme environment capable Distributed Motor Controller (DMC) module suitable for operation with a distributed architecture of future spacecraft systems. This motor controller is designed to be a bus-based electronics module capable of operating a single Brushless DC motor in extreme space environments: temperature (-120 C to +85 C required, -180 C to +100 C stretch goal); radiation (>;20K required, >;100KRad stretch goal); >;360 cycles of operation. Achieving this objective will result in a scalable modular configuration for motor control with enhanced reliability that will greatly lower cost during the design, fabrication and ATLO phases of future missions. Within the heart of the DMC lies a pair of cold-capable Application Specific Integrated Circuits (ASICs) and a Field Programmable Gate Array (FPGA) that enable its miniaturization and operation in extreme environments. The ASICs are fabricated in the IBM 0.5 micron Silicon Germanium (SiGe) BiCMOS process and are comprised of Analog circuitry to provide telemetry information, sensor interface, and health and status of DMC. The FPGA contains logic to provide motor control, status monitoring and spacecraft interface. The testing and characterization of these ASICs have yielded excellent functionality in cold temperatures (-135 C). The DMC module has demonstrated successful operation of a motor at temperature.
The US team of the European led "MIcrostructure Formation in CASTing of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions" (MICAST) program recently received a third Aluminum - 7wt% silicon alloy that was processed in the microgravity environment aboard the International Space Station. The sample, designated MICAST#2-12, was directionally solidified in the Solidification with Quench Furnace (SQF) at a constant rate of 40micometers/s through an imposed temperature gradient of 31K/cm. Procedures taken to evaluate the state of the sample prior to sectioning for metallographic analysis are reviewed and rational for measuring the microstructural constituents, in particular the primary dendrite arm spacing (Lambda (sub1)), is given. The data are presented, put in context with the earlier samples, and evaluated in view of a relevant theoretical model.