So - I searched Boron and then CVD Diamond:( Very Nukeish!)
edtn.com
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.
edtn.com
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.
Chucka |
