Source: https://patents.google.com/patent/US7589528?oq=flatulence
Timestamp: 2018-02-20 02:23:03
Document Index: 346290678

Matched Legal Cases: ['Application No. 2001', 'Application No. 2001', 'arts 61', 'art 61', 'arts 61', 'art 61']

US7589528B2 - Magnetic sensor formed of magnetoresistance effect elements - Google Patents
Magnetic sensor formed of magnetoresistance effect elements
US7589528B2
US7589528B2 US11682841 US68284107A US7589528B2 US 7589528 B2 US7589528 B2 US 7589528B2 US 11682841 US11682841 US 11682841 US 68284107 A US68284107 A US 68284107A US 7589528 B2 US7589528 B2 US 7589528B2
US11682841
US20070182407A1 (en )
Toshiyuki Oohashi
Yukio Wakui
Kokichi Aiso
This application is a Continuation of U.S. patent application Ser. No. 10/821,913, filed Apr. 12, 2004 which in turn is a Division of U.S. patent application Ser. No. 10/052,525 filed on Jan. 23, 2002, claiming priority of Japanese Application No. 2001-281703, dated Sep. 17, 2001, and Japanese Application No. 2001-15805, dated Jan. 24, 2001, the contents of each are hereby incorporated by reference herein.
The present invention relates to a magnetic sensor using a magnetoresistance effect (magnetoresistive effect) element containing a pinned layer and a free layer, and more particularly to a magnetic sensor having two or more magnetoresistance effect elements formed on a single chip where the magnetization directions of the pinned layers of the magnetoresistance effect elements cross each other, as well as a method of producing the same
A characteristic feature of the present invention lies in a magnetic sensor including a magnetoresistance effect element that contains a pinned layer and a free layer, said magnetoresistance effect element having a resistance value that changes in accordance with a relative angle formed by (or between)the magnetization direction of the pinned layer and the magnetization direction of the free layer, said magnetic sensor being formed in such a manner that a plurality of said magnetoresistance effect elements are provided on a single chip (one and the same substrate), and the pinned layers of at least two of said plurality of magnetoresistance effect elements have magnetization directions that cross each other.
Another characteristic feature of the present invention lies in a method of producing a magnetic sensor including a magnetoresistance effect element that contains a pinned layer and a free layer, said magnetoresistance effect element having a resistance value that changes in accordance with a relative angle formed by the magnetization direction of the pinned layer and the magnetization direction of the free layer, said method including the steps of: forming a layer containing a magnetic layer that will become said pinned layer (for example, an antiferromagnetic layer and a ferromagnetic layer) in a predetermined configuration on a substrate; forming magnetic-field-applying magnetic layers for applying a magnetic field to the layer containing the magnetic layer that will become said pinned layer: magnetizing said magnetic-field-applying magnetic layers; and pinning the magnetization direction of the magnetic layer that will become said pinned layer with the residual magnetization of said magnetic-field-applying magnetic layers.
Still another characteristic feature of the present invention lies in a method of producing a magnetic sensor including a magnetoresistance effect element that contains a pinned layer and a free layer, said magnetoresistance effect element having a resistance value that changes in accordance with a relative angle formed by a magnetization direction of the pinned layer and a magnetization direction of the free layer, said method including the steps of preparing a magnet array constructed in such a manner that a plurality of permanent magnets are arranged at lattice points of a square lattice, where a polarity of a magnetic pole of each permanent magnet is different from a polarity of other magnetic poles that are adjacent thereto and spaced apart therefrom by the shortest distance; disposing a wafer in which a layer containing a magnetic layer that will at least become said pinned layer has been formed, above said magnet array; and pinning the magnetization direction of the magnetic layer that will become said pinned layer by using a magnetic field formed between one of said magnetic poles and another of said magnetic poles that is adjacent thereto and spaced apart therefrom by the shortest distance.
FIG. 1 is a conceptual plan view illustrating a magnetic sensor according to embodiment 1 and embodiment 2 of the present invention;
FIG. 3 is a cross-sectional view of the magnetic tunnel effect element (group) shown in FIG. 2 and cut with a plane along the line 1-1;
FIG. 7 is a schematic cross-sectional view of the magnetic sensor according to embodiment 1 at one stage during the production;
FIG. 20 is a graph depicting the change of the MR ratio of the other magnetic tunnel effect element (group) shown in FIG. 1 when an external magnetic field changing in magnitude in the direction (X-axis direction) perpendicular to the longitudinal direction of the element is applied to the element;
FIG. 24 is a schematic cross-sectional view of the magnetic sensor according to embodiment 2 at one stage during the production;
FIG. 32 is a schematic cross-sectional view of the magnetic sensor according to embodiment 2 at one stage during the production:
FIG. 37 is a graph depicting the change of the MR ratio of one magnetic tunnel effect element (group) according to embodiment 2 when an external magnetic field changing in magnitude in the direction (Y-axis direction in FIG. 1) perpendicular to the longitudinal direction of the element is applied to the element:
FIG. 38 is a graph depicting the change of the MR ratio of the other magnetic tunnel effect element (group) according to embodiment 2 when an external magnetic field changing in magnitude in the direction (X-axis direction in FIG. 1) perpendicular to the longitudinal direction of the element is applied to the element:
FIG. 40 is a graph depicting the magnetization curves of a pinned layer and a free layer when a magnetic field changing in magnitude within the direction perpendicular to the magnetization direction of die pinned layer is applied to a magnetic tunnel effect element group according to embodiment 1 and 2;
FIG. 43 is a schematic enlarged plan view of the first X-axis GMR element shown in FIG. 42;
FIG. 44 is a schematic cross-sectional view of the first X-axis GMR element shown in FIG. 43 and cut with a plane along the line 2-2 of FIG. 43;
FIG. 50 is a plan view of quartz glass on which a spin valve film has been formed at one stage during the production of the magnetic sensor shown in FIG. 42:
FIG. 51 is a plan view of a metal plate for preparing a magnet array to be used in the production of the magnetic sensor shown in FIG. 42;
FIG. 52 is a cross-sectional view of the metal plate and the permanent bar magnets shown in FIG. 51 and cut with a plane along the line 3-3 of FIG. 51:
Hereafter, embodiments of the magnetic sensor according to the present invention will be described with reference to the attached drawings. The magnetic sensor according to the first embodiment includes a generally square-shaped substrate 10 made of, for example, SiO.sub.2/Si, glass, or quartz, two magnetic tunnel effect elements (groups) 11, 21, a coil 30 for bias magnetic field, and a plurality of electrode pads 40 a to 40 f, as illustrated in the plan view of FIG. 1. Magnetic tunnel effect elements (groups) 11, 21 and coil 30 for bias magnetic field are connected respectively to electrode pads 40 a, 40 b, 40 c, 40 d, and 40 e, 40 f. Since magnetic tunnel effect element (group) 11 and magnetic tunnel effect element (group) 21 are identical in structure, magnetic tunnel effect element (group) 11 will be described hereafter as a representative example, and the description of magnetic tunnel effect element (group) 21 will be omitted.
Magnetic tunnel effect element (group) 11 is made of a plurality of (in this example, twenty) magnetic tunnel effect elements that are connected in series, as illustrated in the enlarged plan view of FIG. 2. Each magnetic tunnel effect element includes a plurality of lower electrodes 12 having a rectangular shape in a plan view on substrate 10, as illustrated in FIG. 3 showing a partial cross-sectional view along the 1-1 plane of FIG. 2. Lower electrodes 12 are arranged in a row and spaced apart from each other by a predetermined distance in the lateral direction. Lower electrodes 12 are made of Ta (which may be Cr or Ti), which is an electrically conductive non-magnetic metal material, and are formed to have a thickness of about 30 nm. On each lower electrode 12 is respectively laminated an antiferromagnetic film 13 made of PtMn having a thickness of about 30 nm and formed to have the same planar shape as lower electrode 12.
A pair of ferromagnetic films 14, 14 made of NiFe having a thickness of about 20 nm is laminated at an interval on each antiferromagnetic film 13. These ferromagnetic films 14, 14 have a rectangular shape in a plan view and are arranged so that the longer sides thereof oppose each other in parallel. The ferromagnetic films 14, 14 constitute a pinned layer in which the magnetization direction is pinned by the antiferromagnetic film 13. The ferromagnetic films 14, 14 are magnetized in the direction of arrows in the partially enlarged plan view of FIG. 4 (i.e. in the rightward direction). Here, the antiferromagnetic film 13 and the ferromagnetic films (pinned layers) 14, 14 constitute a fixed magnetization layer in which the magnetization direction of the ferromagnetic films 14, 14 is substantially fixed (i.e. having a fixed magnetization axis).
On each ferromagnetic film 14 is formed an insulating layer 15 having the same planar shape as the ferromagnetic film 14. This insulating layer 15 is made of Al.sub.2O.sub.3 (Al—O), which is an insulating material, and is formed to have a thickness of about 1 nm.
An interlayer insulating layer 18 for insulated separation of the plurality of lower electrodes 12 and the antiferromagnetic film 13 and for respective insulated separation of the pair of ferromagnetic films 14, the insulating layers 15, the ferromagnetic films 16, and the dummy films 17 disposed on each antiferromagnetic film 13 is formed in a region that covers the substrate 10, lower electrode 12, antiferromagnetic film 13, ferromagnetic films 14, insulating layers 15, ferromagnetic films 16, and dummy films 17. The interlayer insulating layer 18 is made of SiO.sub.2 and has a thickness of about 250 nm.
Through this interlayer insulating layer 18. a contact hole 18 a is respectively formed on each dummy film 17. Upper electrodes 19, 19 made of, for example, Al having a thickness of about 300 nm are respectively formed so as to fill in the contact hole 18 a and to electrically connect each one of the pair of dummy films 17, 17 disposed on a different lower electrode 12 (and antiferromagnetic film 13). Thus, by electrically connecting each of the ferromagnetic films 16, 16 (each of the dummy films 17, 17) and each of the antiferromagnetic films 13, 13 of a pair of adjacent magnetic tunnel junction structures alternately and successively with the lower electrode 12, antiferromagnetic film 13, and upper electrode 19, there is formed a magnetic tunnel effect element (group) 11 in which a plurality of magnetic tunnel junction structures whose pinned layers have the same magnetization direction are connected in series. Here, a protective film made of SiO and SiN (illustration omitted) is formed on the upper electrodes 19, 19.
First, as illustrated in FIG. 5, a film made of Ta constituting the lower electrode 12 is formed to a thickness of about 30 nm by sputtering on a substrate 10 (which is, at this stage, one sheet of substrate from which a plurality of magnetic sensors will be obtained by a later dicing process). Then, a film made of PtMn and a film made of NiFe for constructing the antiferromagnetic film 13 and the ferromagnetic film (pinned layer) 14 of the fixed magnetization layer are formed to have a thickness of 30 nm and 20 nm, respectively, by sputtering. In this description, the lower electrode 12, the PtMn film which will be the antiferromagnetic film 13, and the FeNi film which will be the ferromagnetic film 14 are referred to as a lower magnetic layer SJ.
Thereafter, Al is laminated for only 1 am, and this is oxidized by oxygen gas to form an Al.sub.2O.sub.3 (Al—O) film which will become the insulating layer 15. Subsequently, a film made of NiFe constituting the ferromagnetic film 16 of the free layer is formed, for example, to have a thickness of 80 nm by sputtering, and a film made of Ta constituting the dummy film 17 is formed to have a thickness of 40 nm thereon. Here, the ferromagnetic film 16 and the dummy film 17 are referred to as an upper magnetic layer UJ. Next, by ion milling or the like, the upper magnetic layer UJ is processed for separation, as illustrated in FIG. 6, and the lower magnetic layer SJ is processed for separation, as illustrated in FIG. 7. As a result, the layer having a predetermined configuration, which will be the magnetic tunnel effect elements, is formed.
Next, as illustrated in FIG. 8, a film made of SiO.sub.2 constituting the interlayer insulating layer 18 is formed by sputtering so that the thickness thereof on the elements will be 250 nm, and a film made of Cr and a film made of NiFe are formed thereon by sputtering to have a thickness of 100 nm and 50 nm, respectively, as a plating underlayer film. Next, a resist 51 is applied, as illustrated in FIG. 9. The resist 51 is patterned into a predetermined shape so as not to cover the part where the plating will be carried out later.
Next, as illustrated in FIG. 10, the wafer is plated with NiCo as a magnetic-field-applying magnetic layer. The thickness of NiCo is, for example, set to be 10 .mu.m. Then, after the resist is removed as illustrated in FIG. 11, the entire surface is subjected to milling (Ar milling) to remove WiFe formed as the plating underlayer film, as illustrated in FIG. 12.
FIG. 13 is a plan view of the wafer in this state. Here, in FIG. 13, each of the substrates that will be separated from each other by a later dicing process are denoted with the reference numeral 10 for convenience sake. Referring to FIG. 13, by the previous patterning of the resist, the magnetic-field-applying magnetic layers (NiCo) are each formed to have a generally square shape with its center located at the center of four adjacent substrates 10 which will be separated from each other later, and are disposed so as to exclude parts (its portions) located immediately above the magnetic tunnel effect elements (groups) 11, 21 in the longitudinal direction and in the lateral direction (i.e. so as to sandwich the layer, having the predetermined configuration, that will be the magnetic tunnel effect elements (groups) 11, 21 where the lower magnetic layer SJ including the magnetic layer that will be the pinned layer is formed in a plan view). In this state, a magnetic field having a strength of about 1000 (Oe) is given in the direction parallel to the diagonal line of the square that each magnetic-field-applying magnetic layer forms, so as to magnetize the magnetic-field-applying magnetic layer in the direction shown by arrow A in FIG. 13.
Then, electrode pads 40 a to 40 f illustrated in FIG. 1 are formed on the substrate 10, and the electrode pads 40 a to 40 f are respectively connected to the magnetic tunnel effect elements (groups) 11, 21 and the toil 30. Finally, a film (not illustrated) made of SiO having a thickness of 150 nm and a film (not illustrated) made of SiN having a thickness of 1000 nm are formed as a protective film (passivation film) by CVD. Thereafter, a part of the protective film is opened by milling, RIE, or etching using a resist mask to expose the electrode pads 40 a to 40 f Subsequently, the substrate is subjected to back grinding (thinning by grinding); the substrate is separated into individual magnetic sensors by dicing; and finally, the packaging is carried out.
Subsequently, as illustrated in FIG. 23, the upper magnetic layer UJ is processed for separation, and the lower magnetic layer SJ is processed for separation, as illustrated in FIG. 24. Next, as illustrated in FIG. 25, SiO.sub.2 is sputtered to form a film having a thickness of 250 nm so as to form an interlayer insulating layer 18, and successively a contact hole 18 a is formed through the interlayer insulating layer 18, as illustrated in FIG. 26. Subsequently, as illustrated in FIG. 27, Al is sputtered to form a film having a thickness of 300 nm and processed in a wiring pattern to form an upper electrode 19. Then, as illustrated in FIG. 28, a protective film 20 made of SiO and SiN is formed by CVD.
Next, as illustrated in FIG. 31, the wafer is plated with NICO as a magnetic-field-applying magnetic layer. The thickness of NiCo is, for example, set to be 10 .mu.m. Then, after the resist is removed as illustrated in FIG. 32, the entire surface is subjected to milling (Ar milling) to remove NiFe formed as the plating underlayer film, as illustrated in FIG. 33. At this stage, the wafer is in the state shown in FIG. 13. In this state, a magnetic field having a strength of about 1000 (Oe) is given in the direction parallel to the diagonal line of the square that each magnetic-field-applying magnetic layer forms, so as to magnetize the magnetic-field-applying magnetic layer in the direction shown by arrow A in FIG. 13. Thereafter, the magnetic field is removed.
To the magnetic tunnel effect element (group) 11′ thus produced and shown in FIG. 1, external magnetic fields changing in magnitude along the respective axes in the X-axis direction and in the Y-axis direction were applied, so as to measure the resistance changing ratio MR (MR ratio) at the time the magnetic fields were applied. The results are shown in FIGS. 36 and 37. As will be clear from FIGS. 36 and 37, the MR ratio of the magnetic tunnel effect element (group) 11′ changed more greatly in response to the external magnetic field changing in the X-axis direction than to the external magnetic field changing in the Y-axis direction. This has confirmed that, in the magnetic tunnel effect element (group) 11′. the magnetization direction of the pinned layer thereof is parallel to the X-axis.
Similarly, to the magnetic tunnel effect element (group) 21′ shown in FIG. 1. external magnetic fields changing in magnitude along the respective axes in the X-axis direction and in the Y-axis direction were applied, so as to measure the resistance changing ratio MR (MR ratio) at the time the magnetic fields were applied. The results are shown in FIGS. 38 and 39. As will be clear from FIGS. 38 and 39, the MR ratio of the magnetic tunnel effect element (group) 21′ changed more greatly in response to the external magnetic field changing in the Y-axis direction than to the external magnetic field changing in the X-axis direction. This has confirmed that, in the magnetic tunnel effect element (group) 21′, the magnetization direction of the pinned layer thereof is parallel to the Y-axis. In other words, it has been confirmed that, on one and the same substrate 10′, this magnetic sensor according to the second embodiment has two magnetic tunnel effect elements (magnetoresistance effect elements) having pinned layers that are pinned so that the magnetization directions thereof cross each other (i.e. are different from each other).
As described above, the magnetic sensors according to the first and second embodiments have, on one and the same substrate (on a single chip), magnetic tunnel effect elements in which the magnetization directions of the pinned layers cross each other (i.e. the magnetization directions of at least two of the pinned layers form an angle other than 0.degree. and 180.degree.). For this reason, these magnetic sensors can be used as a small magnetic sensor (for example, as a geomagnetism sensor or the like) that is requested to detect magnetic fields in different directions. Also, according to the methods of the above-described embodiments, these sensors can be easily produced.
Here, in the first embodiment, since PtMn is used in the fixed magnetization layer as a pinning layer, the magnetization direction of the pinned layer in the fixed magnetization layer must be pinned at the timing at which the wafer is initially brought to a high temperature. Therefore, in the first embodiment, the wafer is subjected to a high-temperature annealing process at a stage prior to the high-temperature process by CVD or the like that is carried out for forming the protective film. In contrast, in the second embodiment, MnRh is used as a pinning layer of the fixed magnetization layer. The MnRh film will be deteriorated in quality if another high-temperature process is carried out after the high-temperature annealing process. Therefore, in the second embodiment, the high-temperature annealing process is carried out after the high-temperature process by CVD or the like for forming the protective film is carried out.
Further, according to the above-described production methods of the first and second embodiments, one can obtain a magnetic tunnel effect element (group) that exhibits an even-function property to an external magnetic field to be detected. In other words, when a magnetic field changing in magnitude within the direction perpendicular to the magnetization direction of the pinned layer is applied to the magnetic tunnel effect element groups 11, 21, 11′, 21′, the magnetization of the pinned layer changes smoothly as illustrated by the line LP of FIG. 40. On the other hand, the free layer of these elements reacts sensitively to the direction of the aforesaid external magnetic field due to the shape anisotropy, and the magnetization of the free layer changes in a stepwise manner when the magnitude of the external magnetic field approaches the neighborhood of “0”, as illustrated by the line LF of FIG. 40. As a result of this, the relative angle formed between the magnetization direction of the pinned layer and the magnetization direction of the free layer attains the maximum value (approximately 90.degree.) when the external magnetic field is “0” and, according as the magnitude (absolute value) of the external magnetic field increases, the relative angle decreases. This can be confirmed by FIGS. 19, 20, 37, and 38.
More specifically described, this magnetic sensor 60 has a rectangular (generally square) shape having sides along the X-axis and the Y-axis that are perpendicular to each other in a plan view as illustrated in FIG. 42, and includes a single chip (same substrate) 60 a made of quartz glass having a small thickness in the Z-axis direction perpendicular to the X-axis and the Y-axis, a sum of eight GMR elements 61 to 64, 71 to 74 formed on the chip 60 a, a sum of eight pads 65 to 68, 75 to 78 formed on the chip 60 a, and a connecting line that connects the pads and the elements.
The first Y-axis GMR element 71 is formed in a neighborhood of the end of the chip 60 a in the positive direction of the Y-axis and a little to the left of a generally central part of the chip 60 a in the X-axis direction, and the pinned magnetization direction of the pinned layer is in the positive direction of the Y-axis, as illustrated by an arrow in FIG. 42. The second Y-axis GMR element 72 is formed in a neighborhood of the end of the chip 60 a in the positive direction of the Y-axis and a little to the right of a generally central part of the chip 60 a in the X-axis direction, and the pinned magnetization direction of the pinned layer is in the positive direction of the Y-axis, as illustrated by an arrow in FIG. 42. The third Y-axis GMR element 73 is formed in a neighborhood of the end of the chip 60 a in the negative direction of the Y-axis and a little to the right of a generally central part of the chip 60 a in the X-axis direction, and the pinned magnetization direction of the pinned layer is in the negative direction of the Y-axis, as illustrated by ah arrow in FIG. 42. The fourth Y-axis GMR element 74 is formed in a neighborhood of the end of the chip 60 a in the negative direction of the Y-axis and a little to the left of a generally central part of the chip 60 a in the X-axis direction, and the pinned magnetization direction of the pinned layer is in the negative direction of the Y-axis, as illustrated by an arrow in FIG. 42.
The first X-axis GMR element 61 includes a plurality of narrow band-shaped parts 61 . . . 61 a made of a spin valve film SV and having a longitudinal direction in the Y-axis direction and bias magnet films (hard ferromagnetic thin film layers) 61 b . . . 61 b made of a hard ferromagnetic material such as CoCrPt formed under the two ends of each narrow band-shaped part 61 a in the Y-axis direction and having a high magnetic coercive force and a high square ratio, as illustrated in FIG. 43 which is a plan view and in FIG. 44 which is a schematic cross-sectional view of the first X-axis GMR element 61 cut with a plane along the line 2-2 of FIG. 43. Each of the narrow band-shaped parts 61 a . . . 61 a extends in the X-axis direction on the upper surface of each bias magnet film 61 b and is bonded to an adjacent narrow band-shaped part 61 a.
The spin valve film SV of the first X-axis GMR element 61 is, as shown by the film construction in FIG. 45, composed of a free layer (free magnetization layer) F. an electrically conductive spacer layer S made of Cu having a thickness of 2.4 nm (24 .ANG.), a fixed magnetization layer P, and a cap layer C made of titanium (Ti) or tantalum (Ta) having a thickness of 2.5 nim (25 .ANG.) which are successively laminated on a chip 60 a constituting a substrate.
The free layer F is a layer whose magnetization direction changes in accordance with the direction of an external magnetic field, and is composed of a CoZrNb amorphous magnetic layer 61-1 formed immediately above the substrate 60 a and having a thickness of 8 nm (80 .ANG.). a NiFe magnetic layer 61-2 formed on the CoZrNb amorphous magnetic layer 61-1 and having a thickness of 3.3 nm (33 .ANG.), and a CoFe layer 61-3 formed on the NiFe layer 61-2 and having a thickness of about 1 to 3 nm (10 to 30 .ANG.). The CoZrNb amorphous magnetic layer 61-1 and the NiFe magnetic layer 61-2 constitute a soft ferromagnetic thin film layer. The CoFe layer 61-3 is for preventing diffusion of Ni in the NiFe layer 61-2 and Cu 61-4 in the spacer layer S. Here, the above-described bias magnet films 61 b . . . 61 b apply a bias magnetic field to the free layer F in the Y-axis direction (right and left directions shown by arrows in FIG. 43) for maintaining the uniaxial anisotropy of the free layer F.
The fixed magnetization layer P is a lamination of a CoFe magnetic layer 61-5 having a thickness of 2.2 nm (22 .ANG.) and an antiferromagnetic film 61-6 formed from a PtMn alloy containing 45 to 55 mol % of Pt and having a thickness of 24 nm (240 .ANG.). The CoFe magnetic layer 61-5 is lined with the magnetized antiferromagnetic film 61-6 in an exchange coupling manner so as to constitute a pinned layer whose magnetization direction (magnetization vector) is pinned (fixed) in the negative direction of the X-axis.
The X-axis magnetic sensor is constructed by full bridge connection of the first to fourth X-axis GMR elements 61 to 64, as shown by an equivalent circuit in FIG. 47. Here, in FIG. 47, the arrows show pinned magnetization directions of the pinned layers of the GMR elements 61 to 64. In such a construction, the pad 67 and the pad 68 are connected respectively to the positive electrode and the negative electrode of a constant power source (not illustrated) so as to give a voltage Vxin+ (5 V in this example) and a voltage Vxin− (0 V in this example). Then, the voltages of the pad 65 and the pad 66 are taken out as a voltage Vxout+ and a voltage Vxout−, and the voltage difference thereof (Vxout+−Vxout−) is taken out as a sensor output Vxout. As a result of this, the X-axis magnetic sensor shows an output voltage Vxout that changes generally in proportion to an external magnetic field that changes along the X-axis in the range from −Hc to +Hc, as shown by a solid line in FIG. 48, and shows a generally “0” output voltage to an external magnetic field that changes along the Y-axis, as shown by a broken line in FIG. 48.
Next, a method of producing the magnetic sensor 60 constructed in the aforesaid manner will be described. First, a plurality of films M. which are made of the aforesaid spin valve film SV and the aforesaid bias magnet film 61 b, and which will constitute individual GMR elements, are formed in a manner like islands on a rectangular quartz glass 60 a 1, as illustrated by the plan view of FIG. 50. The films M are formed by successive lamination to precise thicknesses using a ultra high vacuum apparatus. These films M are formed so that the films M will be located at the positions of the GMR elements 61 to 64, 71 to 74 shown in FIG. 42 when the quartz glass .alpha.al is cut along the broken line of FIG. 50 by a cutting process carried out later and separated into individual chips 60 a shown in FIG. 42. Further, alignment (positioning) marks 60 b having a rectangular shape excluding a shape of a cross are formed at the four corners of the quarts glass 60 a 1.
Next, as shown in FIG. 51 which is a plan view and in FIG. 52 which is a cross-sectional view cut with the cross section along the line 3-3 of FIG. 51, a rectangular metal plate 81 is prepared in which a plurality of square through-holes are formed in a square lattice configuration (namely, square through-holes having sides parallel to the X-axis and the Y-axis are formed to be equally spaced apart from each other along the X-axis and the Y-axis). Then, permanent bar magnets 82 . . . 82 having a rectangular parallelopiped shape and having approximately the same square cross section as the through-holes are inserted into the through-holes of the metal plate 81 so that the end surfaces of the permanent bar magnets 82 . . . 82, where the magnetic poles are formed, will be parallel to the metal plate 81. At this time, the permanent bar magnets 82 . . . 82 are arranged so that the polarity of the magnetic pole of each permanent bar magnet 82 will be different from the polarity of the magnetic pole of the other permanent bar magnets 82 adjacent thereto and space apart therefrom by the shortest distance. Here, the permanent bar magnets 82 . . . 82 to be used have a magnetic charge of the same magnitude.
Next, as shown in a plan view of FIG. 53. a plate 83 is prepared which has a thickness of about 0.5 mm and which is made of transparent quartz glass having approximately the same rectangular shape as the aforesaid metal plate 81. This plate 83 is let to have alignment (positioning) marks 83 a having a shape of a cross on the four corners for positioning in cooperation with the alignment marks 60 b of the aforesaid quarts glass 60 a 1. Further, in the central part, alignment marks 83 b are formed at positions corresponding to the outer shape of the permanent bar magnets 82 . . . 82 that are inserted into the aforesaid metal plate 81. Subsequently, as illustrated in FIG. 54, the upper-surface of the permanent bar magnets 82 . . . 82 are bonded to the lower surface of the plate 83 by means of an adhesive. At this time, the relative position of the permanent bar magnets 82 . . . 82 to the plate 83 is determined by using the alignment marks 83 b. Then, the metal plate 81 is removed from the lower side. At this stage, the permanent bar magnets 82 . . . 82 and the plate 83 form a magnet array constructed in such a manner that a plurality of permanent magnets having square end surfaces constituting the magnetic poles are disposed at lattice points of a square lattice and the polarity of the magnetic pole of each permanent magnet is different from the polarity of the magnetic pole of the other permanent magnets adjacent thereto and spaced apart therefrom by the shortest distance.
Next, as illustrated in FIG. 55, the quartz glass 60 a 1, on which the films to become the GMR elements (the layer containing the magnetic layer to become the pinned layer, that is, the layer containing the magnetic layer to become the fixed magnetization layer) are formed, is positioned so that the surface on which the films to become the GMR elements are formed will be brought into contact with the upper surface of the plate 83. The relative position of the quartz glass 60 a 1 to the plate 83 is exactly determined by bringing the cross shape of the alignment marks 83 a into respective coincidence with the part of the aforesaid alignment marks 60 b where the cross shape has been removed.
FIG. 56 is a perspective view illustrating a state in which four of the aforesaid permanent bar magnets 82 . . . 82 have been taken out. As will be clear from this figure, above the upper surface of the permanent bar magnets 82 . . . 82, magnetic fields are formed from one N-pole towards the four S-poles adjacent to the N-pole by the shortest distance, i.e. in four directions that are different from each other by 90.degree. Therefore, as illustrated by a model view of FIG. 57, in the state in which the quartz glass 60 a 1 is placed on the upper surface of the plate 83 shown in FIG. 55, magnetic fields in the positive direction of the Y-axis, in the positive direction of the X-axis, in the negative direction of the Y-axis, and in the negative direction of the X-axis are applied to the films which are placed in parallel to each side of the square end surface of one N-pole and which will become the GMR elements.
In this embodiment, by using such magnetic fields, a thermal treatment is carried out to fix the magnetization direction of the fixed magnetization layer P (the pinned layer of the fixed magnetization layer P). Namely, in the state shown in FIG. 55. the plate 83 and the quartz glass 60 a 1 are fixed to each other by a clamp CL, heated to 250.degree. C. to 280.degree. C. in vacuum, and left to stand in this state for about four hours.
Thereafter, the quartz glass 60 a 1 is taken out; the pads 65 to 68. 75 to 78 shown in FIG. 42 are formed; a wiring connecting these is formed; and finally the quartz glass 60 a 1 is cut along the broken lines shown in FIG. 50. The above process completes the production of the magnetic sensor 60 shown in FIG. 42.
Next, the result of measurement of geomagnetism using the aforesaid magnetic sensor 60 will be described. In this measurement, the azimuth theta. (measurement angle) is defined as 0.degree. when the positive direction of the Y-axis of the magnetic sensor 60 is directed to the south, as illustrated in FIG. 58. The measurement results are shown in FIG. 59. As will be clear from FIG. 59. the X-axis magnetic sensor output Sx shown by a solid line changes like a sine curve, and the Y-axis magnetic sensor output Sy shown by a broken line changes like a cosine curve. This result is exactly as expected from the characteristics shown in FIGS. 48 and 49.
In this case, the azimuth can be determined by (1) .theta.=arctan(Sx/Sy) when the X-axis magnetic sensor output Sx and the Y-axis magnetic sensor output Sy both assume positive values; (2) .theta.=180.degree.+arctan(Sx/Sy) when the Y-axis magnetic sensor output Sy assumes a negative value: and (3) .theta.=360.degree.+arctan(Sx/Sy) when the X-axis magnetic sensor output Sx assumes a negative value and the Y-axis magnetic sensor output Sy assumes a positive value. Therefore, the magnetic sensor 60 can be used, for example, as a geomagnetism (azimuth) sensor that can be mounted onto portable type electronic devices such as a portable telephone. Here, if the representation in the range from −90.degree. to 0.degree. is permitted when the azimuth is within the range from 270.degree. to 360.degree., the azimuth may be determined by .theta.=arctan(Sx/Sy) when the output Sy is positive, and by .theta.=180.degree.+arctan(Sx/Sy) when the output Sy is negative.
Here, the present invention is by no means limited to the aforesaid embodiments, and various modifications may be made within the scope of the present invention. For example, though NiCo having a large residual magnetization is adopted as a plating film in the aforesaid first and second embodiments, other materials (for example, Co) having a large residual magnetization may be adopted in place of NiCo. Further, the method of fixing the magnetization direction of the fixed magnetization layer in the first and second embodiments can be applied to other magnetoresistance effect elements having pinned layers (layers having a fixed magnetization axis) such as in the third embodiment. Furthermore, though PtMn is used as a pinning layer of the fixed magnetization layer P in the aforesaid three embodiments, FeMn, IrMn, or the like may be used in place of this PtMn.
1. A magnetic sensor which detects a magnetic field comprising:
eight magnetoresistance effect elements including a first through an eighth element, each of said elements comprising a spin valve film, the film comprising a free layer, a spacer layer and a pinned layer, said pinned layer having a pinned magnetization direction, wherein said layers are successively laminated on a substrate of a single chip, the substrate having a generally square shape which has a left side along a Y-axis, a right side along the Y-axis, a top side along an X-axis and a bottom side along the X-axis in a plan view, the X-axis and the Y-axis are perpendicular to each other, and each of the elements has a resistance value that changes in accordance with a relative angle formed by a magnetization direction of said pinned layer and a magnetization direction of said free layer;
said magnetic sensor being formed in such a manner that said magnetoresistance effect elements are provided on a single plane,
(a) said first element being formed at a position closer to the left side than the right side and below a first center line of the right side and the left side, the first center line being perpendicular to the Y-axis, and said first element, having a pinned magnetization direction of said first element's pinned layer in a direction of the X-axis;
(b) said second element being formed at a position closer to the left side than the right side and above the first center line, and said second element having a pinned magnetization direction of said second element's pinned layer in the direction of the X-axis;
(c) said third element being formed at a position closer to the right side than the left side other sides and above the first center line, and said third element having a pinned magnetization direction of said third element's pinned layer in the direction of the X-axis;
(d) said fourth element being formed at a position closer to the right side than the left side and below the first center line, and said fourth element having a pinned magnetization direction of said fourth element's pinned layer in the direction of the X-axis;
(e) said fifth element being formed at a position closer to the top side than the bottom side and left of a second center line of the top and bottom sides, the second center line being perpendicular to the X-axis, and said fifth element having a pinned magnetization direction of said fifth element's pinned layer in the direction of the Y-axis;
(f) said sixth element being formed at a position closer to the top side than the bottom side and right of the second center line, and said sixth element having a pinned magnetization direction of said sixth element's pinned layer in the direction of the Y-axis;
(g) said seventh element being formed at a position closer to the bottom side than the top side and right of the second center line, and said seventh element having a pinned magnetization direction of said seventh element's pinned layer in the direction of the Y-axis;
(h) said eighth element being formed at a position closer to the bottom side than the top side and left of the second center line, and said eighth element having a pinned magnetization direction of said eighth element's pinned layer in the direction of the Y-axis;
(i) said first to fourth elements construct an X-axis magnetic sensor for detecting a magnetic field in the direction of the X-axis by full bridge connection using a first wiring connecting the first to fourth elements; and
(j) said fifth to eighth elements construct a Y-axis magnetic sensor for detecting a magnetic field in the direction of the Y-axis by full bridge connection using a second wiring connecting the fifth to eighth elements,
(k) wherein said first wiring and said second wiring are provided on the single plane and are formed in such a manner that the said second wiring is surrounded by said first wiring.
2. A magnetic sensor which detects a magnetic field comprising:
(a) said first element being formed at a position closer to the left side than the right side and below a first center line of the left and right sides, the first center line being perpendicular to the Y-axis, and said first element, having a pinned magnetization direction of said first element's pinned layer in a direction of the X-axis;
(c) said third element being formed at a position closer to the right side than the left side and above the first center line, and said third element having a pinned magnetization direction of said third element's pinned layer in the direction of the X-axis;
(i) said first to fourth elements construct an X-axis magnetic sensor for detecting a magnetic field in the direction of the X-axis by full bridge connection using a first wiring connecting the first to fourth elements;
(j) said fifth to eighth elements construct a Y-axis magnetic sensor for detecting a magnetic field in the direction of the Y-axis by full bridge connection using a second wiring connecting the fifth to eighth elements;
(k) the pinned magnetization direction of the pinned layer of the first and the second elements are in a negative direction of the X-axis;
(l) the pinned magnetization direction of the pinned layer of the third and the fourth elements are in a positive direction of the X-axis;
(m) the pinned magnetization direction of the pinned layer of the fifth and the sixth elements are in a positive direction of the Y-axis; and
(n) the pinned magnetization direction of the pinned layer of the seventh and the eighth elements are in a negative direction of the Y-axis,
(o) wherein said first wiring and said second wiring are provided on the single plane and are formed in such a manner that the said second wiring is surrounded by said first wiring.
3. A magnetic sensor which detects a magnetic field comprising a plurality of magnetoresistance effect elements, each element comprising a spin valve film, the film comprising a free layer, a spacer layer and a pinned layer having a pinned magnetization direction, each element having a resistance value that changes in accordance with a relative angle formed by a magnetization direction of the pinned layer and a magnetization direction of the free layer, wherein,
(a) said layers of each of the magnetoresistance effect elements are successively laminated directly on a single substrate of a single chip;
(b) an X-axis group of four of a plurality of said magnetoresistance effect elements constructs an X-axis magnetic sensor for detecting a magnetic field in an X-axis direction and all of said magnetoresistance effect elements of the X-axis group have pinned magnetization directions of the pinned layers parallel to each other,
(c) a Y-axis group of four of a plurality said magnetoresistance effect elements constructs a Y-axis magnetic sensor for detecting a magnetic field in a Y-axis direction perpendicular to the X-axis direction and all of said magnetoresistance effect elements of the Y-axis group have pinned magnetization directions of the pinned layers parallel to each other;
(d) said X-axis group of magnetoresistance effect elements construct the X-axis magnetic sensor by full bridge connection using a first wiring connecting the magnetoresistance effect elements belonging to the X-axis group, and the pinned magnetization directions of the X-axis group of magnetoresistance effect elements are in the X-axis direction; and
(e) said Y-axis group of magnetoresistance effect elements construct the Y-axis magnetic sensor by full bridge connection using a second wiring connecting the magnetoresistance effect elements belonging to the Y-axis group, and the pinned magnetization directions of the Y-axis group of magnetoresistance effect elements are in the Y-axis direction,
(f) wherein said fire wiring and said second wiring are provided on a single plane and are formed in such a manner that the said second wiring is surrounded by said first wiring.
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