Part #2:
So - I searched Boron and then CVD Diamond:( Very Nukeish!)
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Top Technology Story: from EE Times
IBM's silicon cantilevers promise leap in disk storage
By Chappell Brown
SAN JOSE, Calif. — Atomic force microscope technology is being viewed as a route to ultrahigh capacity disk storage at IBM's Almaden Research Center (San Jose, Calif.). Specially planned silicon cantilevers have been designed to read and write data at a density of 50 billion bits/square inch.
The technique uses resistively heated tips to burn nanometer-sized pits in compact-disk media, which can then be read by another cantilever that registers their presence with the piezoresistive effect.
IBM researchers believe the technique has the potential to store 50 times the data held on a conventional compact disk.
The project began two years ago as an experiment to determine the feasibility of using atomic-force-microscope (AFM) tips with conventional recording media. "We showed that a heated atomic-force-microscope tip could be used to write small marks in polycarbonate and PMMA substrates, the same material used to make CDs. In fact, the first samples were simply pieces of cut-up CDs," said John Mamin, who has been developing the AFM technique.
The initial experiments were performed by Mamin and Dan Ruger, an IBM colleague. The research team has subsequently grown and has enlisted AFM experts at Stanford University. After some development of both the read and write techniques, the project has arrived at the point where a prototype disk system is up and running.
Exploratory effort
"We recently demonstrated the ability to track on the data while the disk is spinning. Clearly, though, the effort is quite exploratory, with much work remaining to be done," Mamin said.
At the heart of the technology are the micron-dimensioned atomic force probe tips. Read and write versions of the tips have been designed and tested and the group is now looking at a method for combining both functions in the same system.
Writing is achieved by passing a current through the cantilever, which is U-shaped with a sharpened tip at the bend. The tip is mounted on a section of the U that is made from resistive material. Passing a current through the cantilever heats the tip and causes the disk media to melt. After pits are formed, their presence can be detected by a second U-shaped cantilever that contains a piezoresistive material. A small deflection in the cantilever will show up as a change in the current caused by the piezoresistive effect.
The dual-tip scheme is an interim solution on the way to a single integrated read/write system. Originally, an infrared laser was focused on the tip to provide the heat source. "The setup was very analogous to optical recording in magneto-optic materials, except for the presence of the micromachined tip," Mamin said. "We have also demonstrated writing with a tapered optical fiber, similar to that used in near-field optical microscopy."
He added, "Ultimately, to make things compact and simple, we really wanted to do away with the laser and integrate the heater right onto the cantilever."
Speedy writing
The IBM group decided to tap the expertise of Stanford University researchers who have developed AFM techniques. "Ben [Benjamin Chui at Stanford] worked in particular to optimize the cantilever and heater characteristics to minimize the thermal time constant, so as to increase the writing speed," Mamin said.
The IBM group continued to work on variations of the design as well, seeking a means of integrating read and write functions without sacrificing speed. At this point, combined tips have been verified, although with mixed results. The write speed is slower than the Stanford variant but the read speed actually increased.
As micromachined elements, the cantilevers require some very refined characteristics. To read the pits at a density of 50 billion bits/square inch, the tips must have a radius smaller than 500 . The cantilevers must also have a very low stiffness in order to avoid wear, since they must contact the spinning disk to read the pits. However, they must be stiff enough to detect 10- changes in elevation in order to achieve acceptable signal-to-noise ratio during read operations.
The cantilevers are fabricated on silicon-on-insulator wafers that have a 5-micron top layer of single-crystal silicon. First a blunt tip is formed by undercutting an oxide mask. The tip is then sharpened with a low-temperature oxidation step.
Standard processes
Next, a boron implant is performed and annealed with rapid thermal annealing to create a thin piezoresistive layer. The IBM researchers found that the thickness of the implant layer was critical to performance, with the effectiveness of the piezoresistant layer going up as it gets thinner. The cantilevers are finally released from the wafer with an oxygen-plasma etch.
The technique uses standard VLSI processes and could be adapted to manufacturing, once the characteristics of the read/write tips have been refined.
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CVD Diamond at Bottom or Article, Sounds LIKE OUR Rhombic TECH, I have no clue though,
RE:
Potential seen for silicon carbide as 2-in. wafers debut
A service of Semiconductor Business News, CMP Media Inc.
Story posted at 3 p.m. EDT/noon PDT, 9/2/97
DURHAM, N.C. -- Silicon carbide supplier Cree Research Inc. today announced limited availability of SiC wafers with a diameter of 2 inches. In addition, Cree showed a 3-in. SiC wafer this week at the 1997 International Conference on SiC, III-Nitrides and Related Materials in Stockholm, Sweden.
Separately, the publication of a report covering SiC and other wide-band-gap materials was announced today by Frost & Sullivan, a Mountain View, Calif., market researcher. The report characterizes the potential effect of such materials on high-power, high-voltage device technology as "revolutionary."
Cree is now making available its 2-in. 6H n-type on-axis and 4H n-type 8 degree off-axis research-grade material in limited quantities, although for the time being, the majority of the company's wafer sales will continue to be 1.375-inch diameter material. Over time the company plans to transition all wafer sales to the new 2-in. material.
The release of a larger diameter wafer marks a key milestone in the evolution of SiC as a commercially significant semiconductor material, Cree officials said. The 2-in. wafers are more easily handled by existing automated semiconductor process equipment. "The release of two-inch wafers has been part of our development plan. These larger diameters definitely put SiC on track for the commercialization of more complex semiconductor devices such as microwave and power transistors," commented Dr. Calvin Carter, co-founder of Cree and Director of Materials Technology.
"DARPA is very pleased that Cree is now selling 2-in. SiC wafers," remarked Dr. Jane Alexander, Deputy Director of the Defense Sciences Office at the Defense Advance Research Projects Agency. DARPA has funded a portion of the company's research aimed at producing larger wafer diameters. "This is crucial for further device development," she said. "The 3-in. demonstration is especially critical for the development of SiC power semiconductor devices. The power area represents a tremendous market opportunity for SiC semiconductors and the larger diameter wafers can make these devices a reality."
The Frost & Sullivan report looks foward to upcoming power devices operating at 50 or even 100 kilovolts, which likely will be based on silicon carbide, it said. The devices will be more efficient than current components because switching losses will be reduced.
The report, "World High-Power Solid-State Device Markets" offers research on both power device and materials science markets. The research behind the report gives an indication of the market potential and the impact of power devices made with wide-band-gap materials. The report offers a synopsis and 10-year technical road map of the major very high-power devices available in 1997 as well as a wafer commercialization roadmap for silicon carbide, specific nitrides, and CVD diamond materials.
Very high-power semiconductors -- IGBTs, SCRs, GTOs and their design variations such as the MTO, GCT, and MCT, recorded over $1 billion in revenues worldwide, Frost & Sullivan calculates. Such revenues, however, will be threatened in the long term by the development of devices using wide-band-gap materials -- silicon carbide, gallium nitride, boron nitride, and CVD diamond, among others.
"Niche end-user industries, and power transmission and distribution, are increasingly demanding single-unit high-power devices which can operate at higher voltages. This is where the market opportunities for devices based on wide band gap materials come into play," said Frost & Sullivan research analyst Alyxia Do. Frost & Sullivan estimates this potential wide-band-gap market to be several hundred million dollars.
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Diamonds are used elsewhere, not Rhombic, but a VERIFICATION of DIAMOND TECH: IMHO:
Diamond Hikes Power Levels Of Resistors And Terminations
The availability of high-quality diamond substrates has led to the development of high-power resistors and terminations.
Thomas Dowling and Elliot Lewis
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DIAMOND heat sinks have long been known as tremendous heat conduits. Unfortunately, the high cost of the material has limited its application in high-frequency designs until now. With recent advances in both diamond-substrate material processing and thin-film technology, the engineers at RF Power Components, Inc. (Bohemia, NY) have been successful in developing lines of cost-effective, high-power drop-in resistors and terminations with as much as 200-W power-handling capability at 4 GHz.
These resistors and terminations are built with CVD diamond heat spreaders for high power-handling capability at high frequencies.
The new resistors and terminations (see figure) are housed in drop-in and flange-mount packages. A total of four resistors and four terminations comprise the initial product lines (Table 1). Model RFP-100-100DR, for example, is a high-power resistor with only 0.4-pF capacitance that can be used past 8 GHz. It is rated for 100-W power-handling capability. A 50-W 100-W termination, model RFP-100-50-DT, exhibits VSWRs of 1.11:1 from DC to 1.5 GHz, 1.20:1 to 4.0 GHz, and 1.30:1 to 8.0 GHz. The drop-in package measures 0.16 × 0.08 × 0.05 in. (4.06 × 2.03 × 1.27 mm).
HIGH-POWER RESISTOR
Model RFP-200-100DRVV is a flange-mount 200-W resistor with only 0.54-pF capacitance and can be used in applications past 4 GHz. As a termination with the same power-handling capability, model RFP-200-50DTVV exhibits VSWRs of 1.11:1 from DC to 2 GHz, 1.20:1 to 3 GHz, and 1.30:1 to 4 GHz. The flange-mount package measures 0.50 × 0.16 × 0.13 in. 12.7 × 4.06 × 3.30 mm).
The availability of high-power components based on diamond substrates is critical for several reasons. As more communications systems, such as personal-communications-services (PCS) networks, rely on high-power but unobtrusive cell sites and base stations, engineers are pressured to design smaller, more robust power combiners and terminations. Diamond provides better thermal resistance than beryllium oxide (BeO) substrates. Diamond substrates are nontoxic, which make them attractive in light of increasing Environmental Protection Agency (EPA) restrictions and in environmentally-sensitive areas, such as Europe, which restrict the use of BeO substrates.
Diamond is superior in its thermal characteristics to such materials as BeO and AlN, and has a lower dielectric constant than most commonly-used heat spreaders (Table 2). The use of diamond heat spreaders permits conventionally-accepted performance limits for power density, component size, and frequency to be dramatically extended, such as in the new lines of high-power resistors and terminations.
It is now practical to develop diamond-based high-power passive components in part due to advances in chemical-vapor-deposition (CVD) diamond processing, which allows the production of high-quality, large-area diamond wafers. The change can also be credited to improvements in thin-film processing, allowing strong bonds to be made between metallized films and diamond substrates in spite of the diamond's lack of an oxided ceramic phase (which normally aids adhesion).
On the material-processing side, Crystalline Materials Corp. (San Ramon, CA) has been able to develop uniform CVD diamond substrates called the CrystalCool heat spreaders. The firm offers various thicknesses in sizes that are precisely laser cut to a customer's specifications. The company has successfully reduced numerous cost drivers from optimizing deposition rates, including minimizing the cost of energy (the firm's diamond fabrication plant is located in Calgary, Alberta, Canada, in a region known for its low cost of electricity).
MAKING DIAMOND
Crystalline Materials Corp. has been able to deposit larger areas of diamond, resulting in dramatic increases in yield and capacity.
The company's efforts have resulted in a cost reduction of diamond substrates by a factor of 10 during the last three years. The CVD process yields free-standing diamond material from 0.01 to 0.04 in. (0.25 to 1.02 mm) thick in industry-standard substrate sizes. Polycrystalline CVD diamond is produced by condensing carbon atoms derived from a carbon and hydrogen gas mixture onto a substrate. The carbon source is usually methane, carbon monoxide, or acetylene. This gas mixture is activated by heating between 2000 to 5000 K by means of microwave energy, combustion, or DC plasma heating. Such high temperatures dissociate the hydrogen molecules to produce atomic hydrogen; atomic hydrogen stabilizes the diamond material during growth and suppresses the formation of graphite. The activated gas impinges on a substrate maintained in a vacuum between +700 and +1100°C.
The substrate must be prepared so that the surface promotes the nucleation of the tight tetrahedral bonds characteristic of diamond. Deposition rates can range from 1 to 100 mm/hour depending on the carbon transport mechanism. Crystalline Materials Corp. employs a proprietary DC arc-jet technique which offers the highest deposition rate available. After the diamond has grown to a specified thickness, the free-standing diamond substrate is separated easily from its growth substrate, polished, and then cut to size.
COMBINING SKILLS
Working with this materials supplier, the engineers at RF Power Components have combined their processing capabilities to the diamond substrates in order to produce resistors and terminations that are compatible with RF/microwave industry standards. In many cases, these resistors and terminations will drop into existing conventional circuits. Construction is similar to existing ceramic resistors and terminations based on thin-film technology.
As an example, a diamond-based resistor with a chip size of 0.080 × 0.155 × 0.025 in. (2.03 × 3.94 × 0.64 mm) and a resistor film size of 0.03 × 0.10 in. (0.76 × 2.54 mm) provided power dissipation of 100 W. The thermal resistance for this unit is 0.5°C/W, with operation at 100 W resulting in a flange temperature of +87°C and a resistor film temperature of +137°C (for a temperature delta of 50°C).
Designers who require compact, high-power/high-frequency resistors or terminations with low parasitic capacitances and low VSWR performance will find the devices quite useful. The resistors permit the construction of power combiners and dividers with high power-handling capability, low insertion loss, and high isolation. While the cost of the patent-pending diamond-based resistors and terminations is somewhat higher than that of BeO devices, overall manufacturing costs may be comparable. External resistor matching is virtually eliminated with the diamond-based devices, resulting in less circuit losses, less overall associated passive components, and less occupied printed-circuit-board space. P&A: stock. RF Power Components, Inc., 125 Wilbur Pl., Bohemia, NY 11716-2482; (516) 563-5050, FAX: (516) 563-4747.
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Diamonds Are Microwave Tubes' Best Friend
MIDDLESEX, UK--Alumina, beryllia, boron nitride, and aluminum nitride have long been used in various parts of microwave tubes due to their high electrical resistance and good thermal conductivity. But these materials could fall by the wayside due to the findings of a research program conducted by Thorn Microwave Devices Ltd. (TMD) and funded by the UK Defence Research Agency. TMD discovered that chemical-vapor-deposited (CVD) diamond offers many advantages over the traditional materials and has none of the disadvantages. CVD diamond offers up to ten times the thermal conductivity and one-quarter the coefficient of expansion together with high electrical resistivity compared with the traditional materials. One of the materials that CVD diamond could replace is beryllia, which features high resistance and good thermal conductivity, but is reported to be a carcinogen. TMD has established the machining, chemical and thermal processing, metallization, and brazing capabilities of CVD diamond. The next step is to build a prototype microwave tube using the new material.
Si And Ge Form New Marriage For High-Frequency Chips
HEILBRONN, GERMANY--The founding fathers of semiconductor technology materials--silicon (Si) and germanium (Ge)--are linking up in a joint process called silicon-germanium (SiGe) to be used for fabricating high-frequency chips for mobile communications applications. The new semiconductor cocktail is the brainchild of Temic Telefunken's Microelectronic group, which claims that the technology offers advantages over conventional silicon and the newer gallium-arsenide (GaAs) processes. The company says that it has developed SiGe devices whose operating speed is significantly faster than silicon. And it says that SiGe is much simpler and less expensive to implement than GaAs. These factors make it a natural for fabricating ICs for communications applications such as mobile and cordless phones. The company hopes to use the process to produce low-power, low-noise devices that will improve voice quality, run longer on a battery charge, and be less expensive than current ICs. Production of SiGe devices is scheduled for early this year using a process that is compatible with standard semiconductor processes now in use.
Save IEEE-488, Plead Instrument Manufacturers
PALO ALTO, CA--IEEE-488, the venerable communications warhorse of data transfer in test systems, could undergo major surgery if the Institute of Electrical and Electronics Engineers (IEEE) convinces enough engineers that the standard must be brought up to the capabilities of today's higher-speed systems. In the opposing camp are noted instrument makers such as Hewlett-Packard Co. and Keithley Instruments GmbH, along with ines, Inc., a maker of GPIB interface cards, and ACEA, a test-and-measurement development company in Wierden, Netherlands who argue that any changes to the standard could lead to significant implementation problems and testing uncertainty among a large population of IEEE-488 users. The revised standard, to be known as High-Speed 488 or HS-488, is to be voted on soon although the actual date for casting ballots has not been set.
Opponents of HS-488 claim that it constitutes a radical change to the form and function of IEEE-488 and could lead to disruptive errors for the installed customer base, which is worldwide. In fact, many companies rely on the consistency and operational simplicity of IEEE-488, which measures data accurately and without extensive troubleshooting of test setups. A key complaint of the opposition is that HS-488 has not been tested adequately on-site, particularly in the areas of interoperability and noise immunity, and very little documentation of this testing has appeared in the technical media.
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Chucka |
