Hybrid hall effect device and method of operation

• US 5,652,445 A
• Filed: 05/06/1996
• Issued: 07/29/1997
• Est. Priority Date: 04/21/1995
• Status: Expired due to Term

• Current Assignee: Seagate Technology International (Seagate Technology Holdings Plc)
• Original Assignee: Mark B. Johnson
• Inventors: Johnson, Mark B.
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US08/643,805
• Time in Patent Office: 449 Days
• Field of Search: 257/421, 257/295, 257/422, 257/424, 257/425, 257/426, 257/427, 360/112, 360/113, 324/249, 324/251, 324/252, 365/97, 365/145, 365/170, 365/171, 365/182
• US Class Current: 257/295
• CPC Class Codes: G11B 5/378 Integrated structures
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/1659 Cell access
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 11/18 using Hall-effect devices
• CPC Class Codes: H01L 29/66984 Devices using spin polarized carriers
• CPC Class Codes: H03K 19/18 using galvano-magnetic devices, e.g. Hall-effect devices
• CPC Class Codes: H10N 52/101 Semiconductor Hall-effect devices

Abstract

A modified Hall Effect device can be used as a memory element for the nonvolatile storage of digital information. The novel device includes a ferromagnetic layer that covers a portion of a Hall plate and is electrically isolated from the Hall plate. The ferromagnetic layer on the Hall plate can be changed by an externally applied field, and permits the device to have two stable magnetization states (positive and negative) along an anisotropy axis, which can correspond to two different data values (0 or 1) when the device is used as a memory element. In another embodiment of the invention, the Hall plate is integrated with a conduction channel of a FET, and the ferromagnetic layer is incorporated in proximity to, or as part of the gate over the conducting channel. This device can be described as a "ferromagnetic gated FET." The resulting device also can be fabricated to be magnetically anisotropic so as to permit the device to have two stable magnetization states (positive and negative along the anisotropy axis) which again can correspond to two different data values (0 or 1) when the device is used as a memory element. Both of the above devices can be used as magnetic field sensors, (e.g. as a read head) or in memory arrays where they can operate as non-volatile memory. The modified Hall Plate and ferromagnetic gated FET devices can also be used a logic gate that stores the result of a boolean function. A magnetic field generated by the combined current of one or more input data signals is coupled to the device. Depending on the particular function to be implemented, the magnetization of the ferromagnetic layer can be configured to change or retain its orientation based on particular predefined combinations of input data signals.

Claims

1. An improved Hall Effect device comprising:

a conductive film layer having a top surface and capable of carrying an electrical current;

a ferromagnetic layer having a configurable magnetization orientation, and covering a first portion of the top surface, and not a second portion, such that a fringe magnetic field substantially normal to such surface can be generated by an edge portion of the ferromagnetic layer; and

wherein an electrical signal can be generated in response to the fringe magnetic field acting on the electrical current in the conductive film layer.

2. The device of claim 1, further including a first sensor coupled to a first edge of the conductive film layer, and a second sensor coupled to a second edge of the conductive film layer, opposite to the first edge, such that the electrical signal is a voltage generated substantially along an axis joining the first and second sensors.

3. The device of claim 1, wherein the conductive film layer and the ferromagnetic layer are separated by an insulating layer.

4. The device of claim 1, wherein the electrical current flows between a first bias terminal coupled to a third edge of the conductive film layer, and a second bias terminal coupled to a fourth edge of the conductive film layer, opposite to the third edge.

5. The device of claim 1, further including a write line for configuring the magnetization orientation in the ferromagnetic layer.

6. The device of claim 1, wherein the ferromagnetic layer is coupled to a magnetic field generated by magnetically recorded data, the electrical signal generated is related to a value of the data, and the device operates as a magnetic field sensor.

7. The device of claim 2, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

8. A memory device comprising:

a conductive film layer having a top surface;

a ferromagnetic layer having at least two configurable and stable magnetization orientation states corresponding to two different values of a data item stored in said device, and covering a portion of the top surface such that a fringe magnetic field having two states and configured substantially normal to the top surface can be generated by an edge portion of the ferromagnetic layer; and

wherein two different electrical signals, each corresponding to a different one of the two different data values, can be generated in response to the two fringe magnetization field states acting on an electrical current flowing in the conductive film layer.

9. The device of claim 8, further including a first sensor coupled to a first edge of the conductive film layer, and a second sensor coupled to a second edge of the conductive film layer, opposite to the first edge, such that the two different electrical signals are voltages generated substantially along an axis joining the first and second sensors.

10. The device of claim 9, wherein the two electrical signals comprise a first voltage output signal when a first value of the data item is stored in said device, and a second voltage output value when a second value of the data item is stored in said device.

11. The device of claim 10 further including a sense circuit for comparing the two electrical signals of the device with a reference value to determine the value of the data item stored in said device.

12. The device of claim 8, wherein the electrical current is a read current that flows between a first bias terminal coupled to a third edge of the conductive film layer, and a second bias terminal coupled to a fourth edge of the conductive film layer, opposite to the third edge.

13. The device of claim 8, further including a write line for configuring the two configurable magnetization orientation states in the ferromagnetic layer.

14. The device of claim 8, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

15. The device of claim 8, wherein the magnetization orientation of the ferromagnetic layer:

(i) can be set to a first state in response to a first amplitude write current and associated first write magnetic field; and

(ii) can be set to a second state in response to a second amplitude write current and associated second write magnetic field.

16. The device of claim 15, wherein the ferromagnetic layer magnetization orientation is retained in said state until a different state is set in said layer.

17. The device of claim 8, further including a plurality of said memory devices coupled together to form a memory array.

18. The device of claim 8, wherein the ferromagnetic layer is a 130 nm thin film of iron, cobalt or permalloy, the conductive film layer material is a 1 micron wide gallium arsenide plate, and the two layers are separated by an insulating layer of oxide 50 nm in thickness.

19. A logic device for implementing a logic function relating a combination of one or more input signals to an output signal comprising:

a conductive film layer having a top surface;

a ferromagnetic layer having at least two stable magnetization orientation states and covering a portion of the top surface such that a fringe magnetic field can be generated substantially normal to the top surface by an edge portion of the ferromagnetic layer; and

a write line for inductively coupling the ferromagnetic layer with a magnetic field generated by said input data signals on the wire, the input data signals having one of a first and a second current value, and

an electrical output signal generated in response to the fringe magnetic field acting on an electrical current flowing in the conductive film layer, and wherein the electrical output signal relates to said input signals and to said logic function.

20. The device of claim 19, wherein the electrical output signal has a first value when the ferromagnetic layer magnetization orientation state is altered by magnetic fields corresponding to a first combination of said input data signals related to said logic function, and the electrical ouput signal has a second value when the ferromagnetic layer magnetization state is not altered by magnetic fields corresponding to a second combination of said input data signals.

21. The device of claim 19, wherein the magnetization orientation state of the ferromagnetic layer corresponds to a result of said logic function implemented in said device, and this result is stored in said device until the magnetization orientation state is altered by a subsequent combination of input signals.

22. The device of claim 21, wherein the magnetization state of the ferromagnetic layer can be set initially based on the logical function to be implemented by said device.

23. The device of claim 22, further including a first sensor coupled to a first edge of the conductive film layer, and a second sensor coupled to a second edge of the conductive film layer, opposite to the first edge, such that the electrical signal is a voltage generated substantially along an axis joining the first and second sensors.

24. The device of claim 21 further including a sense circuit for comparing the electrical output signal of the device with a reference value to determine the result stored in said device.

25. The device of claim 19, wherein the electrical current is a read current that flows between a first bias terminal coupled to a third edge of the conductive film layer, and a second bias terminal coupled to a fourth edge of the conductive film layer, opposite to the third edge.

26. The device of claim 23, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

27. The device of claim 19, wherein the logic device implements the predetermined logical function of one of the following:

an OR gate, a NOR gate, a NOT gate, a NAND gate, or an AND gate, and wherein the predetermined logical function is based on an initial configuration of the magnetization orientation, and the amplitude of the current associated with each of the data input signals.

28. The device of claim 20, further including a plurality of said devices coupled together in an array to form a logic gate array, and wherein the input signals are output signals from one or more of said plurality of devices.

29. The device of claim 28, further including a readout circuit for reading out results of logic functions stored in the logic gate array in a predetermined sequence.

30. The device of claim 27, further including a level shifter circuit for converting the output of the logic device to an acceptable voltage logic level usable by a later stage semiconductor circuit.

31. A method of generating an electrical signal, said signal being related to a voltage potential developed along a first axis joining a first point coupled to a first edge of a conductive layer and a second point coupled to a second edge of the conductive layer, said method comprising the steps of:

generating an electrical current that flows along a second axis of a conductive film layer, the second axis being substantially perpendicular to the first axis;

generating a fringe magnetic field along an edge of a ferromagnetic layer located substantially along said first axis, such that the fringe field is coupled substantially normal to the second axis; and

wherein the electrical signal is generated in response to the fringe magnetic field acting on the electrical current.

32. The method of claim 31, wherein the fringe magnetic field is derived from an magnetization orientation state of the ferromagnetic layer, and wherein the magnetization state can be changed by inductively coupling the ferromagnetic layer with a write line generating a magnetic field.

33. The method of claim 32, wherein the magnetic field from the write line can set the magnetization orientation to one of a first stable, non-volatile state representing a first value of a binary data item, and a second stable, non-volatile state representing a second value of a binary data item;

and wherein the generated electrical signal also has two different values corresponding to the two values of the binary data item.

34. The method of claim 32, wherein the magnetic field from the write line can set the magnetization orientation to one of of two stable non-volatile states, and these states represent a boolean function result relating one or more input logic signals, and wherein the magnetization orientation stores the boolean function result and only changes in response to certain predetermined combinations of the input logic signals.

35. The method of claim 34, further including a step of reading the boolean function binary data stored in the device by measuring the electrical signal and comparing it with a reference value to determine the boolean function result stored in said device.

36. The method of claim 35, further including a step of converting the electrical signal to an acceptable voltage logic level usable by a later stage semiconductor circuit.

37. The method of claim 31, wherein the ferromagnetic layer is coupled to a magnetic field generated by magnetically recorded data and the electrical signal generated is related to a value of the data.

38. An electronic device comprising:

a field effect transistor (FET), including a source region, a drain region, a gate and a channel;

a ferromagnetic layer having a configurable magnetization orientation, and positioned relative to the gate and channel such that a fringe magnetic field directed substantially normal to the channel can be generated by an edge portion of the ferromagnetic layer; and

wherein an electrical signal related to the magnetization orientation of the ferromagnetic layer can be generated in response to the fringe magnetic field acting on an electrical current flowing between the source and drain of the FET.

39. The device of claim 38, further including a first sensor coupled to a first end of the channel, and a second sensor coupled to a second end of the channel, opposite to the first edge, such that the electrical signal is a voltage generated substantially along an axis joining the first and second sensors.

40. The device of claim 38, wherein the electrical current flows between a first bias terminal coupled to the source of the FET and a second bias terminal coupled to the drain of the FET.

41. The device of claim 38, further including a write line for configuring the magnetization orientation in the ferromagnetic layer.

42. The device of claim 38, wherein the channel and the ferromagnetic layer are separated by a first insulating layer, and the write line and gate are separated by a second insulating layer.

43. The device of claim 38, wherein the gate controls the electrical current flowing between the source and drain in response to a control signal.

44. The device of claim 38, wherein the ferromagnetic layer is coupled to a magnetic field generated by magnetically recorded data, the electrical signal generated is related to a value of the data, and the device operates as a magnetic field sensor.

45. The device of claim 39, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

46. A memory device comprising:

a field effect transistor (FET), including a source, a drain, a gate and a channel;

a ferromagnetic layer having at least two configurable and stable magnetization orientation states corresponding to two different values of a data item stored in said device, and positioned relative to the gate and channel such that a fringe magnetic field directed substantially normal to the channel can be generated by an edge portion of the ferromagnetic layer; and

wherein two different output electrical signals corresponding to the two different data values can be generated in response to the fringe magnetization field acting on an electrical current flowing in the channel.

47. The device of claim 46, further including a first sensor coupled to a first end of the channel, and a second sensor coupled to a second end of the channel, such that the two different electrical signals are voltages generated substantially along an axis joining the first and second sensors.

48. The device of claim 46, wherein the two electrical signals comprise a first voltage output signal when a first value of the data item is stored in said device, and a second voltage output value when a second value of the data item is stored in said device.

49. The device of claim 46 further including a sense circuit for comparing the two electrical signals of the device with a reference value to determine the value of the data item stored in said device.

50. The device of claim 46, wherein the electrical current is a read current that flows between a first bias terminal coupled to the source of the FET, and a second bias terminal coupled to a drain of the FET.

51. The device of claim 46, further including a write line for configuring the two configurable magnetization orientation states in the ferromagnetic layer.

52. The device of claim 51, wherein the channel and the ferromagnetic layer are separated by a first insulating layer, and the write line and gate are separated by a second insulating layer.

53. The device of claim 46, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

54. The device of claim 46, wherein the magnetization orientation of the ferromagnetic layer:

(I) can be set to a first state in response to a first amplitude write current and associated first write magnetic field; and

(ii) can be set to a second state in response to a second amplitude write current and associated second write magnetic field.

55. The device of claim 46, wherein the ferromagnetic layer magnetization orientation is retained in said state until a different state is set in said layer.

56. The device of claim 46, further including a plurality of said memory devices coupled together to form a memory array.

57. The device of claim 46, wherein the gate controls the electrical current flowing between the source and drain in response to a read signal.

58. A logic device for implementing a logic function relating a combination of one or more input signals to an output signal comprising:

a field effect transistor (FET), including a source, a drain, a gate and a channel;

a ferromagnetic layer having at least two configurable and stable magnetization orientation states corresponding to two different results of said logic function and positioned relative to the gate and channel such that a fringe magnetic field directed substantially normal to the channel can be generated by an edge portion of the ferromagnetic layer; and

a wire for inductively coupling the ferromagnetic layer with a magnetic field generated by said input data signals on the wire, the input data signals having at least a first or second current value, and

wherein two different output electrical signals corresponding to the two different results can be generated in response to the fringe magnetization field acting on an electrical current flowing in the channel.

59. The device of claim 58, wherein the electrical output signal has a first value when the ferromagnetic layer magnetization orientation state is altered by magnetic fields corresponding to a first combination of said input data signals related to said logic function, and the electrical ouput signal has a second value when the ferromagnetic layer magnetization state is not altered by magnetic fields corresponding to a second combination of said input data signals.

60. The device of claim 58, wherein the result of said logic function is stored in said device until the magnetization orientation state is altered by a subsequent combination of input signals.

61. The device of claim 58, wherein the magnetization state of the ferromagnetic layer can be set initially based on the logical function to be implemented by said device.

62. The device of claim 58, further including a first sensor coupled to a first end of the channel, and a second sensor coupled to a second end of the channel, opposite to the first channel, such that the electrical signal is a voltage generated substantially along an axis joining the first and second sensors.

63. The device of claim 60 further including a sense circuit for comparing the electrical output signal of the device with a reference value to determine the result stored in said device.

64. The device of claim 58, wherein the electrical current is a read current that flows between a first bias terminal coupled to the source of the FET, and a second bias terminal coupled to the drain of the FET.

65. The device of claim 58, wherein the ferromagnetic layer has an easy magnetization axis that is substantially parallel to the electrical current and substantially perpendicular to the axis joining the first and second sensors.

66. The device of claim 58, wherein the logic device implements the predetermined logical function of one of the following:

an OR gate, a NOR gate, a NOT gate, a NAND gate, or an AND gate, and wherein the predetermined logical function is based on an initial configuration of the magnetization orientation, and an amplitude of a current associated with each of the data input signals.

67. The device of claim 58, further including a plurality of said devices coupled together in an array to form a logic gate array, and wherein the input signals are output signals from one or more of said additional devices.

68. The device of claim 67, further including a readout circuit for reading out results of logic functions stored in the logic gate array in a predetermined sequence.

69. The device of claim 58, further including a level shifter circuit for converting the output of the logic device to an acceptable voltage logic level usable by a later stage semiconductor circuit.

70. A method of generating an electrical signal, said signal being related to a voltage potential developed along a first axis joining a first point coupled to a first edge of a FET channel and a second point coupled to a second edge of the FET channel, said method comprising the steps of:

generating an electrical current that flows from a source of said FET through said channel to a drain of said FET along a second axis that is substantially perpendicular to the first axis;

generating a fringe magnetic field along an edge of a ferromagnetic layer positioned relative to the gate and channel such that the fringe magnetic field is directed substantially normal to the channel; and

wherein the electrical signal is generated in response to the fringe magnetic field acting on the electrical current.

71. The method of claim 70, wherein the fringe magnetic field is derived from an magnetization orientation state of the ferromagnetic layer, and wherein the magnetization state can be changed by inductively coupling the ferromagnetic layer with a write line generating a magnetic field.

72. The method of claim 71, wherein the magnetic field from the write line can set the magnetization orientation to one of a first stable, non-volatile state representing a first value of a binary data item, and a second stable, non-volatile state representing a second value of a binary data item;

and wherein the generated electrical signal also has two different values corresponding to the two values of the binary data item.

73. The method of claim 70, wherein the magnetic field from the write line can set the magnetization orientation to either of two stable non-volatile states, and these states represent a boolean function result relating one or more input logic signals, and wherein the magnetization orientation stores the boolean function result and only changes in response to certain predetermined combinations of the input logic signals.

74. The method of claim 73, further including a step of reading the boolean function binary data stored in the device by measuring the electrical signal and comparing it with a reference value to determine the boolean function result stored in said device.

75. The device of claim 74, further including a step of converting the electrical signal to an acceptable voltage logic level usable by a later stage semiconductor circuit.