International Business Machines Corporation

Hans Helmut Zappe

Robert Fontana

Timothy C Reiley

Long-Sheng Fan

Tomotake Furuhata

Archibald C Munce, Jr

Charles J Kircher

Long-Shen Fan

A microfabricated wobble motor with a positioning arm attached to the wobble motor rotor acts as a fine positioner with bidirectional movement. The primary application is a rotary actuator for the read/write head in a very small magnetic recording disk drive. An integrated head-arm assembly is attached at one end to the rotor of the wobble motor. The other end of the head-arm assembly has a head carrier that is maintained in contact with the disk. Head position error information is read from the disk and used to provide control signals to each of the stator elements. The stator elements are sequentially addressed by applying a voltage from a driver circuit. This causes the rotor to be electrostatically attracted to the activated stators, so that the rotor is movable bidirectionally. The read/write head can thus be moved bidirectionally to any of the data tracks on the disk and maintained on a desired data track for reading or writing data. The fine positioner also includes a digital control system where each of the stator elements is represented by an address, and the movement of the rotor is controlled by incrementing or decrementing the stator address in an address register.

Wobble motor microactuator for fine positioning and disk drive

A motor based on the wobble motor provides pure rotary motion and can be used as a spindle motor for very small disk drives. The primary components of the motor are fabricated using thin film processes. The rotor has inner and outer rings that are interconnected by flexible members, such as semicircularly-shaped spring elements, with the rings and flexible members being formed of the same material. The rotor resides within the wobble motor stator elements that are circumferentially spaced on a substrate. The inner rotor ring is supported by a bearing structure that may be a ball bearing assembly or a pin bearing comprising a post and a restraining cap. The outer rotor ring functions as the wobble motor rotor and rolls around the inside of the stator as the stator elements are sequentially electrostatically activated. The flexible members act as a transmission to convert the wobble motion of the outer rotor ring to pure rotary motion of the inner rotor ring. The motor can function as a disk drive spindle motor by attachment of a data recording disk to the inner rotor ring and use of appropriate control circuitry to drive the motor at constant speed. The disk drive actuator may be attached to the same substrate that supports the stator elements. The stator elements, the rotor, and the bearing assembly may all be fabricated on a suitable substrate using thin film processes, without the necessity of assembly of separate components.

Microfabricated rotary motion wobble motor and disk drive incorporating

In the fabrication of a free-standing miniaturized structure in a range of about 10 to 20 .mu.m thick, a method based on a sacrificial system includes the steps of selecting a substrate material, depositing on the substrate material a sacrificial layer of material and patterning the sacrificial layer to define a shape. A photoresist layer of material is deposited on the sacrificial layer and patterned by contrast-enhanced photolithography to form a photoresist mold. Upon the mold there is plated a metallic layer of material. The electroplated structure conforms to the resist profile and can have a thickness many times that of conventional polysilicon microstructures. The photoresist mold and the sacrificial layer are thereafter dissolved using etchants to form a free standing metallic structure in a range of about 10 to 20 .mu.m thick, with vertical to lateral aspect ratios of 9:1 to 10:1 or more.

Micro-miniature structures and method of fabrication thereof

Josephson interferometers contain inductive, capacitive and resistive components, and, as a result, such devices are subject to the presence of relatively high amplitude resonances similar to those found in in-line gases. Interferometer structures exhibit the same resonant behavior as long tunnel junctions, except that there exist only as many discrete resonance voltages as meshes in the interferometer device. Hence, a two-junction interferometer has one resonance as compared to two resonances in a three-junction device. In the I-V characteristic of a Josephson tunneling device such as an interferometer, such resonances appear as current steps which must be taken into account in the design of Josephson switching circuits primarily to avoid the situation where the load line of an external load intersects a resonance peak. Where the load line and the resonance peak intersect, because such an intersection is stable, the device is prevented from switching to the full voltage desired. Such resonances can be effectively suppressed in interferometers by providing a resistance which is in parallel with the main inductance of the interferometer. In a two-junction interferometer, the resistance is effectively connected between the base electrode metallizations which are utilized to form one of the electrodes of each of the pair of electrodes required for each interferometer junction. To the extent that more than two junctions are utilized, the resonance suppressing resistor is connected between pairs of junctions and across the main inductances which interconnect the junctions. The structure of a two-junction interferometer with its resonance-suppressing resistor, R.sub.RS, is shown as well as the schematics of a multiple junction interoferometer which clearly indicates how such structures may be fabricated.

Josephson interferometer structure which suppresses resonances

An electronically alterable logic circuit is disclosed which provides different logical outputs which are a function of control signals applied to the circuit. More specifically, a non-latching Josephson junction circuit is provided which is capable of providing true and complementary outputs at a pair of output terminals when at least one pair of a plurality of pairs of fixed biases are applied to a plurality of serially arranged Josephson junction devices. The Josephson devices are arranged so that a true output can be obtained from an output circuit which shunts a pair of Josephson devices while the complement of the true output can be obtained at an output circuit which shunts an appropriately biased Josephson junction which is disposed in series with the above mentioned pair of Josephson junctions. The complementary output is achieved by utilizing a portion of the output circuit which shunts the pair of Josephson junctions as a control line for the single Josephson junction in series with the pair of Josephson junctions. The current through the control line portion, when present, opposes a bias current setting up a situation such that when current flows in the output representative of a true output, no current flows in the output representative of a complementary signal and vice versa. In addition to achieving true and complementary outputs which can be characterized as AND, NAND, OR and NOR outputs, it has been recognized that these same outputs can be attained at the complementary output by simply applying binary combinations of biases to the two bias lines associated with the logic circuit.

Electronically alterable non-latching Josephson AND, OR, NAND, NOR logic

A fabrication method for integrated circuits is disclosed wherein a structure is formed on one side of a supporting substrate which provides a ground plane with 'X' wiring on one side and 'Y' wiring on the other side thereof. The method includes a number of alternative initial planarization steps which permits the resulting device to be substantially planar, thereby allowing it to be used as a substrate for preparation of high density integrated circuits. A first planarization step includes the deposition of a niobium thin film on a doped silicon substrate; the delineation of the desired niobium 'X' wiring pattern using well-known photolithographic and etching techniques, leaving the photoresist in place to protect the niobium; the anodization of exposed silicon substrate portions to form silicon dioxide surrounding the niobium to a higher level than the niobium; and the removal of the photoresist.

Process for fabricating above and below ground plane wiring on one side

A Josephson logic network which includes high and low transmission line impedance sections in the feeder line enables multiple logic devices to be connected in series to the same feeder line with minimum crosstalk between the logic devices. Also, the arrangement of the high and low impedance sections results in resetting of a switched Josephson logic device without the need for altering the d.c. current supplied to the feeder line.

Low-crosstalk-automatic resetting scheme for Josephson junction logic

Josephson tunneling devices are used as parametrons in circuits for logic and memory. Parametron circuits are used as input devices to conventional pulsed Josephson tunneling device circuitry, and as output devices from pulsed Josephson tunneling device circuitry. Therefore, transfers from phase information to pulse information and from pulse information to phase information are obtained. Interconnection between superconducting circuit chips is achieved using Josephson tunneling parametrons and Josephson tunneling detectors. Another interconnection scheme uses capacitive coupling between superconducting circuit chips without physical interconnections therebetween, and employs Josephson tunneling devices on separate chips for the receiving and sending circuitry.

Phase-to-pulse conversion circuits incorporating Josephson devices and

A quantum interference Josephson junction logic device is disclosed which comprises three or more junctions connected in parallel which are capable of carrying Josephson current and includes means integral with at least one of the junctions for carrying a larger maximum Josephson current than the remaining junctions. This integral means includes means for carrying a maximum Josephson current which is twice as large as the maximum Josephson current in the remaining junctions. While the spacing between the lobes of the threshold curve (I.sub.m vs. I.sub.c) is increased over that of a two junction interferometer by adding another junction resulting in an increased operating region in which logic circuits switch to the voltage state, good current gains with large lobe separation could not be achieved by the mere addition of junctions. Current gain with large lobe separation is obtained if the two outer junctions having a zero field threshold current, I.sub.o, are connected via an inductance, L, to the center junction with a maximum Josephson current, 2I.sub.o. The gain is maximized if the gate current, I.sub.g, is fed into the device through inductances, L.sub.p, having a value of inductance approximately equal to 3L in the center of inductances L which are disposed between pairs of junctions forming a symmetrical dual feed. Increased gain and operating range can be achieved using the symmetrical dual feed and interferometer arrangements where the maximum Josephson current in all the junctions thereof is the same.

Quantum interference Josephson logic devices

An information storage device which stores a single flux quantum without bias is disclosed. The device includes a single Josephson tunneling device made from two superconductive materials spaced apart by an insulator wherein a Josephson current density profile J.sub.1 (x) defined by ##EQU1## IS CHARACTERIZED SUCH THAT THE PROFILE HAS A LARGER MAGNITUDE AT THE BOUNDARY PORTIONS OF SAID DEVICE THAN AT THE CENTER. The current density profile is controlled by adjusting either the oxide thicknesses, the work function of the superconductors or by changing the shape of the junction from its usual rectangular cross-section. A sensing arrangement for the above described storage devices is also disclosed. By controlling the damping of the above described structures, the gain characteristics and the vortex characteristics are adjusted to permit coincident selection of a single device. The overall reduction in the magnitude of the Josephson current density profile provides a higher junction resistance with a consequent decrease in damping. This increase in resistance across the tunneling junction unexpectedly extends the switching characteristic from the envelope boundary of all vortex modes to the extent that the application of the same coincident currents permits the unambiguous reading of both positive and zero or negative vortices. Each device during sensing acts as its own sense detector and is capable of switching to the voltage state if a flux quantum is stored. A bit-organized memory array utilizing the devices disclosed is also shown.

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Granite Springs, NY, United States of America

Hans Helmut Zappe