Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
1998-01-26
2001-02-06
Strecker, Gerard (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S207210, C338S03200R, C428S900000
Reexamination Certificate
active
06184680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field sensor which is provided with a magnetic field detecting element for detecting an external magnetic field change and, in particular, to a magnetic field sensor for detecting rotation and position.
2. Description of the Prior Art
(1) A magnetoresistance effect element is an element for measuring a magnetic field intensity by using a phenomenon (magnetoresistance effect, i.e., MR effect) in which an electric resistance of a ferromagnetic metal changes with an external magnetic field change. For a single-layer magnetic film, a heretofore known anisotropic magnetoresistance effect has been used. Recently, as disclosed in, for example, publications of patent application laid-open Nos. Hei 5-259530 and 7-77531, another element is developed by using a giant magnetoresistance effect (hereinafter referred to as the GMR effect) of a magnetic film with a multilayered structure.
Also, as introduced in National Technical Report, Vol. 42, No. 4, pp. 465-472, a VTR capstan motor rotation detecting sensor uses a NiFeCo/Cu multilayered film as a GMR effect element. By detecting a magnetic field change from a multipolar magnetic rotor, the magnetic field sensor, as a result, detects a rotational speed in a non-contact manner. Therefore, in this magnetic field sensor, it is very important to minimize a distance (gap) of the magnetoresistance effect film as a detecting portion from the magnetic rotor. For this, the technical report discloses a structure in which inside through holes formed in an alumina substrate AgPd are used to print an electrode draw portion on a rear face of a substrate. Also, in a magnetic field sensor using Hall element which is introduced in National Technical Report, Vol. 42, No. 4, pp. 480-488, to realize a surface mounting thickness of 200 &mgr;m or less, TAB (tape automatic bonding) mounting is performed on a substrate with a magnetic field detecting element formed thereon, to draw an electrode by using a CU foil lead. However, in such a conventional method, process is complicated, thereby increasing cost.
Also, in Japanese Applied Magnetics Journal, 1992, Vol. 16, pp. 643-648 it is described that in a conventional magnetic field detecting element constituted of a magnetic thin film deposited on a hard substrate since a magnetic property of the magnetic film changes with a magnetic elasticity effect produced by an unavoidable stress from the substrate or a protective film, various attempts are necessary when the change is considered. Especially, a thermal stress is an important factor which influences the magnetic property. By sufficiently considering a film-forming temperature and an operation temperature, the magnetic element needs to be designed. Further, the magnetic property of magnetoresistance effect film often needs to be finely optimized in accordance with various product specifications. As a result, products are diversified, thereby complicating a process control.
(2) As aforementioned, National Technical Report, Vol. 42, No. 4, page 465 introduces the VTR capstan motor rotation detecting sensor which uses the NiFeCo/Cu multilayered film as the GMR effect element.
Also, as a prior-art magnetic field detecting element, the publication of patent application laid-open No. Hei 7-77531 discloses a magnetic position detecting element and a rotation detecting element,in which a magneto-sensitive pattern using a GMR effect is disposed at a magnetic-field pitch &lgr;/2 or &lgr;/4 of a detected body.
As another prior-art magnetic field detecting element, a publication of patent application laid-open No. Hei 1-297508 discloses a magnetic sensor in which four magneto-sensitive patterns are disposed to have a constant relationship with a magnetic-field pitch of a detected body.
Plural magneto-sensitive patterns are disposed so as to have a predetermined relationship with the magnetic-field pitch of the detected body. A differential magnetic field detecting element constituted in this manner is heretofore known broadly.
However, for example, as shown in
FIG. 25
, a magnetic field detecting element
100
, which is heretofore proposed as aforementioned, is constituted of two thin-film patterns (magneto-sensitive pattern portions)
111
and
115
for detecting a magnetic field. These films are formed on a substantially flat common substrate (e.g., wafer substrate)
110
with a predetermined distance D therebetween which is determined by considering a magnetic-field pitch of a detected body. Numeral
120
denotes electrode pads for applying a current.
According to the prior-art constitution, however, for the purpose of making multiple magnetic field detecting elements
100
, when plural magnetic field detecting elements
100
are formed altogether on the wafer substrate having a constant area, the number of magnetic field detecting elements
100
which can be deposited on the wafer substrate cannot be increased.
Also, when there are plural types of magnetic-field pitches of the detected body, the magneto-sensitive patterns need to be disposed and formed with different intervals formed thereamong in accordance with the magnetic-field pitches. To form the patterns on the magnetic field detecting element
100
, masks and the like must be prepared beforehand in accordance with the magnetic-field pitches. Therefore, various types of masks and the like are necessary for each of the multiple detected bodies.
Also, the conventional magnetic field detecting element
100
has the following operational problem. To depict the problem,
FIG. 24
shows an operation example of the conventional magnetic field detecting element
100
. The magnetic field detecting element
100
is dispose spaced from the teeth of soft magnetic body rotary gear
160
as illustrated in FIG.
24
. On the magnetic field detecting element
100
a permanent magnet
170
is disposed. A magnetic flux from the permanent magnet
170
changes with a positional relationship with the rotary gear
160
. The condition of the change is detected by the magneto-sensitive pattern portions
111
and
115
which are formed with the predetermined interval D therebetween. In this case, the direction of a variation in magnetic-field pitch is, i.e. the smaller pattern line widths Pw of the magneto-sensitive pattern portions
111
and
115
in an x-direction in which the rotary gear
160
rotates are, the better. This is because a differential operation is preferable at a point where a difference in magnetic field to be detected is the largest. However, in the conventional magnetic field detecting element
100
, as shown in the drawing, since the pattern line is folded plural times, an actual magnetic field detecting region is distributed in the x-direction. Therefore, if the magnetic-field pitch of the detected body is narrow, the magnetic field to be originally detected cannot be detected in some case.
(3) As aforementioned, the magnetic field sensor is a device for converting an external magnetic field change into an electric signal, and is constituted by patterning a ferromagnetic body and a semiconductor thin film to form an element which converts the external magnetic field change as a voltage change into the electric signal when a current is applied to the thin-film pattern. For example, the magnetoresistance effect film measures a magnetic field intensity using a phenomenon (MR effect) in which the electric resistance of a ferromagnetic metal changes with the external magnetic field. For the single-layer magnetic film, a heretofore known anisotropic magnetoresistance effect of the ferromagnetic metal film has been used. Recently, however, the GMR effect element constituted of the multilayered film structure has been reported. For example, as introduced in National Technical Report, Vol. 42, No. 4, page 465, the VTR capstan motor rotation detecting sensor uses a NiFeCo/Cu multilayered film as the GMR effect element. Also, in National Technical Report, Vol. 42, No. 4, page 84 disclosed is a semiconductor magnetic field detecti
Sato Yuichi
Shinoura Osamu
Suzuki Hideyuki
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Strecker Gerard
TDK Corporation
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