US 8,027,185 B2Granted

Techniques for electrically characterizing tunnel junction film stacks with little or no processing

AssigneesInternational Business Machines Corporation, Infineon Technologies North America Corp.

InventorsDaniel Christopher Worledge, Philip Louis Trouilloud, David William Abraham, Joerg Dietrich Schmid

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Abstract

Probes are electrically connected to a surface of a tunnel junction film stack comprising a free layer, a tunnel barrier, and a pinned layer. Resistances are determined for a variety of probe spacings and for a number of magnetizations of one of the layers of the stack. The probe spacings are a distance from a length scale, which is related to the Resistance-Area (RA) product of the tunnel junction film stack. Spacings from as small as possible to about 40 times the length scale are used. Beneficially, the smallest spacing between probes used during a resistance measurement is under 100 microns. A measured in-plane MagnetoResistance (MR) curve is determined from the “high” and “low” resistances that occur at the two magnetizations of this layer. The RA product, resistances per square of the free and pinned layers, and perpendicular MR are determined through curve fitting.

Claims5

Dependent claims

A method for determining variables that characterize a tunnel junction film stack, comprising:

estimating a plurality of variables defining theoretical data in order to fit the theoretical data to a plurality of measured data, the measured data comprising measured resistances determined from measuring resistances at a plurality of spacings of probes electrically coupled to a surface of a tunnel junction film stack;
and
adjusting the plurality of variables until the theoretical data fit the measured data within a predetermined error, wherein the theoretical and measured data are fit by using at least the following formula:
R
=
R
F
||
R
P
2
⁢
⁢
π
⁢
{
R
F
R
P
⁡
[
K
0
⁡
(
a
λ
)
+
K
0
⁡
(
d
λ
)
-
K
0
⁡
(
b
λ
)
-
K
0
⁡
(
c
λ
)
]
+
ln
⁡
[
bc
ad
]
}
,
where a corresponds to spacing between an I+ probe and an V+ probe, b corresponds to spacing between the I+ probe and a V− probe, c corresponds to spacing between the V+ probe and an I− probe, d corresponds to spacing between the V− probe and the I− probe, RF is a resistance per square of a free layer in the tunnel junction film stack, RP is a resistance per square of a pinned layer in the tunnel junction film stack, RF∥RP=RFRP/(RF+RP), R is a resistance, λ is a length scale, and K0 is a modified Bessel function of the second kind of order zero, wherein one or more of the estimating step or the adjusting step are performed by one or more hardware devices.

61 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/539,068Filed 11 Aug 2009 · division
Priority: 16 Sep 2002
Published: US 2010/0023287 A128 Jan 2010
Granted: 27 Sep 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G01R 33/093
Magnetoresistive devices: using multilayer structures, e.g. giant magnetoresistance sensors
G01R 33/098
Magnetoresistive devices: comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
B82Y 25/00
Nanomagnetism
G01R 31/2648
Testing of individual semiconductor devices: characterising semiconductor materials

Family

Application10/244,766Parent of this division · filed 16 Sep 2002
Application11/119,665Parent of this division · filed 2 May 2005
US 6,927,569 B2Parent of this division · filed 9 Aug 2005
US 2010/0023287 A1Pre-grant publication · published 28 Jan 2010
US 7,622,735 B2Parent of this division
US 2004/0051522 A1Published application
US 2009/0261820 A1Published application
US 8,027,185 B2This patent

From the US filing history. Foreign family members aren’t listed.