High sensitivity magnetic built-in current sensor

• US 7,619,431 B2
• Filed: 12/20/2004
• Issued: 11/17/2009
• Est. Priority Date: 12/23/2003
• Status: Expired due to Fees

• Current Assignee: Eliposki Remote Ltd. L.L.C. (Intellectual Ventures LLC)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Boeve, Hans Marc Bert, Phan Le, Kim, Huisken, Josephus Antonius, De Jong, Franciscus Gerardus Maria, De Wilde, Johannes, Pineda De Gyvez, Jose De Jesus
• Primary Examiner(s): Hollington; Jermele M
• Application Number:
  US10/596,644
• Publication Number:
  US 20070063690A1
• Time in Patent Office: 1,793 Days
• Field of Search: None
• US Class Current: 324/750.3
• CPC Class Codes: G01R 15/20 using galvano-magnetic devices, e.g. Hall-effect devices , i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
• CPC Class Codes: G01R 31/3004 Current or voltage test
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods

Abstract

A sensor for contactlessly detecting currents, has a sensor element having a magnetic tunnel junction (MTJ), and detection circuitry, the sensor element having a resistance which varies with the magnetic field, and the detection circuitry is arranged to detect a tunnel current flowing through the tunnel junction. The sensor element may share an MTJ stack with memory elements. Also it can provide easy integration with next generation CMOS processes, including MRAM technology, be more compact, and use less power. Solutions for increasing sensitivity of the sensor, such as providing a flux concentrator, and for generating higher magnetic fields with a same current, such as forming L-shaped conductor elements, are given. The greater sensitivity enables less post processing to be used, to save power for applications such as mobile devices. Applications include current sensors, built-in current sensors, and IDDQ and IDDT testing, even for next generation CMOS processes.

Claims

1. A semiconductor device comprising:

a conductive element;

a current sensor, wherein the current sensor is a magnetic current sensing device for sensing direct, varying or alternating current flowing through the conductive element wherein the current sensing device is integrated in the semiconductor device where the current to be measured is generated and the current sensor is galvanically isolated from the conductive element, wherein the current sensing device comprises at least one TMR device.

2. A Semiconductor device according to claim 1, wherein the current sensor is suitable for measuring current with a pA resolution.

3. A semiconductor device according to claim 1, wherein the current sensing device shares an MTJ stack with an MRAM device.

4. A semiconductor device according to claim 3, wherein the MTJ stack comprises:

an electrically insulating material designed to form a magneto-resistive tunnelling barrier,

a pinned magnetic region positioned on one side of the electrically insulating material, the pinned magnetic region having a magnetic moment vector adjacent the electrically insulating material,

a nearly balanced free magnetic region positioned on an opposite side of the electrically insulating material, the free magnetic region having a magnetic moment vector adjacent the insulating material and oriented in a position parallel or anti-parallel to the magnetic moment vector of the pinned magnetic region, the free magnetic region including an artificial anti-ferromagnetic layer material including N ferromagnetic layers which are antiferromagnetically coupled, where N is an integer greater than or equal to. two.

5. A semiconductor device according to claim 1, wherein the current sensing device has a free magnetic layer which has an easy axis oriented to be substantially perpendicular to a magnetic field caused by current under measurement.

6. A semiconductor device according to claim 5, the current sensing device having an easy axis, wherein the easy axis of the free layer is caused by shape elongation.

7. A semiconductor device according to claim 1, wherein the current sensing device is subjected to an additional magnetic field that can either be direct, varying or alternating.

8. A semiconductor device according to claim 1, the current sensing device having a pinned magnetic layer with a magnetisation direction and a free magnetic layer having an easy axis, wherein the magnetisation direction of the pinned magnetic layer is oriented at an angle, with the easy axis of the free magnetic layer, preferably between 45°

and 135°

, more preferred substantially perpendicular to the easy axis of the free magnetic layer.

9. A semiconductor device according to claim 1, the semiconductor device comprising adjacent a first side of the current sensing device a first conductor for conveying a current (I_x) to be measured and adjacent a second side of the current sensing device a second conductor for conducting current (I₂), the first conductor and the second conductor crossing but not being electrically connected.

10. A semiconductor device according to claim 9, the free magnetic layer of the current sensing device having an easy axis, wherein the first conductor and the second conductor each include an angle of substantially between 30°

and 90°

with respect to the easy axis of the current sensing device.

11. A semiconductor device according to claim 9, furthermore comprising a feedback circuit for measuring MR changes on the current sensing device and for controlling current (12) in the second conductor in such a way that no MR change is observed on the current sensing device.

12. A semiconductor device according to claim 11, wherein the current feedback circuit has means for generating a feedback signal indicative of the current (I_x) to be measured and conveyed by the first conductor.

13. A semiconductor device according to claim 9, wherein at least one of the first conductor and the second conductor comprises at least one vertical conduction component and at least one horizontal conduction component, there being a corner between the vertical conduction component and the horizontal conduction component, thus forming a conductor structure which at least includes an L-shaped part of which the corner is located adjacent the current sensing device.

14. A semiconductor device according to claim 1, furthermore comprising a flux-concentrator to increase the magnetic field at the location of the current sensing device.

15. A semiconductor device according to claim 14, wherein the flux-concentrator comprises a dummy MTJ stack which is patterned around at least one vertical conduction component.

16. A semiconductor device according to claim 14, wherein the flux-concentrator is ring-shaped and comprises a gap between poles, the current sensing device being located in the gap.

17. A semiconductor device according to claim 1, wherein the sensor device is compatible with CMOS or MOS processing.

18. A semiconductor device according to claim 1, wherein the semiconductor device is an integrated circuit.

19. A semiconductor device according to claim 18, wherein the current sensor or sensors are arranged to sense quiescent currents (IDDQ) or transient currents (IDDT).

20. A method for manufacturing a semiconductor device according to claim 1, the method comprising providing an MTJ stack.

21. A method for manufacturing a semiconductor device according to claim 1, the method comprising providing an MTJ stack,

wherein providing the MTJ stack comprises depositing a free region,

wherein depositing a free region comprises depositing an artificial anti-ferromagnetic free region comprising a plurality of anti-ferromagnetically coupled ferromagnetic layers, and

the artificial anti-ferromagnetic free region having a net magnetic moment which is substantially zero, the method furthermore comprising modifying the net magnetic moment of the free region so as to make it non-zero.