JP2586434B2 - Magnetic detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic detecting device in which a thin-film ferromagnetic magnetoresistive element is formed on a substrate as magnetic detecting means.

[Conventional technology]

As a means for detecting magnetism, there has been proposed a magnetic detection device in which a thin film of a ferromagnetic magnetoresistive element containing a ferromagnetic material as a main component is formed on a substrate.

Such a magnetic detection device is configured to output a change in magnetism, for example, as a voltage change, by utilizing the fact that the resistance value of the ferromagnetic magnetoresistive element changes when it receives magnetism (magnetic field). .

[Problems to be Solved by the Invention] However, since the output signal of the magnetic detection device as described above is very small, the signal is generally amplified by another component such as an amplification IC formed in another process. Although the output is performed in such a state, it is still easily affected by noise, and a magnetic detection device having higher magnetic sensitivity is desired.

The inventors of the present application have conducted experimental studies on what is caused by the magnetic detection device itself as the cause of the noise, and as a result, when the surface roughness of the underlayer of the ferromagnetic The present invention has been made based on the finding that Hausen noise has been generated, and an object of the present invention is to provide a magnetic detection device having high magnetic sensitivity by controlling the surface roughness.

[Means for solving the problem]

In order to achieve the above object, a magnetic detection device of the present invention includes a semiconductor substrate, an insulating underlayer formed on the semiconductor substrate, and a predetermined pattern formed on the underlayer, A wiring conductor electrically connected to the semiconductor substrate through an open region of the base layer; and a wiring conductor formed on the base layer and having an end covering the wiring conductor to electrically connect to the wiring conductor. A thin-film ferromagnetic magnetoresistive element mainly composed of Ni whose resistance value changes due to a change in a magnetic field; and a resistance value of the ferromagnetic magnetoresistance element formed inside the semiconductor substrate by being electrically connected to the wiring conductor. A signal processing circuit for processing the change, and a surface roughness of an underlayer under the ferromagnetic magnetoresistive element is 120.
Å or less, wherein the inclination angle of the wiring conductor is 78 degrees or less at an electrical connection portion between the wiring conductor and the ferromagnetic magnetoresistive element.

[Action]

According to the above configuration, the magnetic domains in the ferromagnetic magnetoresistive element move continuously with a change in the magnetic field to be measured, and Barkhausen noise caused by discontinuous movement of the magnetic domains is effectively suppressed. Become like

Further, by setting the inclination angle of the wiring conductor to 78 degrees or less, the disconnection failure rate is effectively reduced. Further, the contact area at the electrical connection between the wiring conductor and the ferromagnetic magnetoresistive element increases, so that the electrical resistance at the electrical connection decreases. Also,
Since the signal processing circuit for processing the change in the resistance value of the ferromagnetic magnetoresistive element is formed inside the semiconductor substrate, a separate component is not required and the mounting area is reduced.

〔Example〕

 Hereinafter, the present invention will be described using embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, in which a signal processing circuit is integrated on the same substrate. In the figure, reference numeral 1 denotes a P-type semiconductor substrate, on which a N ⁺ -type buried layer 2, an N ^-- type epitaxy layer 3, a P ⁺ -type element isolation region 4, a P-type ^{A +} type diffusion region 5 and N ⁺ type diffusion regions 6 and 7 are formed. Here, the N ⁺ type buried layer 2, N
^The -type epitaxial layer 3, the P ⁺ -type diffusion region 5, and the N ⁺ -type diffusion regions 6, 7 constitute a vertical NPN bipolar transistor. Amplifying.

Then, the silicon oxide film 8 is coated on the main surface of the substrate processed as described above by a sputtering device. that time,
The surface roughness Ra (arithmetic average roughness) of the silicon oxide film 8 is controlled to 120 ° or less, for example, 100 ° by controlling the deposition speed. Thereafter, an opening is selectively formed in the silicon oxide film 8 by using a photolithography process in order to make electrical connection with the above-described transistor.

Then, after depositing Al on the entire surface, the wiring conductor 9 is formed by etching into a predetermined pattern. At this time, the inclination angle θ at the end face 9a of the connection portion of the wiring conductor 9 with the ferromagnetic magnetoresistive element 10 described later is formed to be less than 78 degrees, for example, 50 degrees by performing wet taper etching. The inclination angle θ is defined as the angle formed between the surface of the silicon oxide film 8 and the end face 9a as shown in FIG.

Then, Fe, C is formed on the connection portion and the silicon oxide film 8.
o, ferromagnetic thin film containing Ni as a main component, that is, Ni-F
e, a ferromagnetic magnetoresistive element 10 composed of a Ni-Co thin film having a thickness of 10
The film is deposited so as to have a thickness of 00 ° and subsequently etched to form a predetermined pattern. Then, a surface protection film 11 is formed from above, and only the conduction terminal portion is covered with the surface protection film 11.
Is etched to form an opening, and then subjected to an appropriate heat treatment to form the magnetic detection device of this embodiment.

Therefore, according to the present embodiment, since the resistance value of the ferromagnetic magnetoresistive element 10 changes according to the magnetism to be measured, the change is sent, for example, as a voltage change to a processing circuit formed on the same substrate, for example, the above-described transistor, The signal is amplified and output to the subsequent circuit.
Since separate components are not required unlike the prior art, the mounting area can be reduced, and the wiring such as bonding wires for connecting the components can be simplified.

Since the surface roughness of the underlayer of the ferromagnetic resistance element 10, that is, the silicon oxide film 8 in this embodiment is 100 °, the surface roughness and the Barkhausen noise generation shown in FIG. As shown in the characteristic diagram showing the relationship with the ratio, the Barkhausen noise generation rate can be reduced to almost 0% and the magnetic sensitivity can be increased, so that the S / N ratio can be improved. Here, the characteristics shown in FIG. 2 are obtained by forming the ferromagnetic magnetoresistive element 10 in a linear pattern as shown in FIG. 5 and applying a voltage to both ends thereof.
By applying the magnetic field H in a direction perpendicular to the direction in which the current I flows,
It was measured by detecting the resistance value of the ferromagnetic magnetoresistive element 10. In addition, the experiment used Yokogawa XY recorder: YEW,
The test was performed under the conditions of normal temperature (25 ± 2 ° C.) and I = 1 mA. The measurement result is the characteristic shown by the solid line in FIG. 6. When Barkhausen noise occurs, a noise component A deviating from the solid line appears as shown by the dotted line in FIG. This noise component A
The frequency of the presence or absence of the noise was detected, and the noise generation rate was finally obtained. In FIG. 2, the noise generation rate of 0% was defined because the XY recorder used in this experiment had a limit resolution of 0.5% or less of the maximum output pulse (100%). As can be seen from FIG. 2, the surface roughness is 12
If it is 0 ° or less, it is possible to effectively suppress the occurrence of Barkhausen noise as in the present embodiment, and the present invention does not dare to limit the lower limit of the surface roughness, but the value is not limited to the surface roughness. The processing limit value may be used.

When the surface roughness is 120 ° or more, Barkhausen noise is generated because, when the surface roughness of the underlayer is rough, the lower surface of the ferromagnetic magnetoresistive element 10 on the underlayer side has a low surface roughness. And the magnetic domain of the ferromagnetic magnetoresistive element 10 is deformed, and an internal stress is applied. As a result, the anisotropic dispersion of the ferromagnetic material increases, and the domain wall of the magnetic domain moves discontinuously with the change of the magnetic field to be measured. Is considered to be distorted. Therefore,
In order to suppress the occurrence of Barkhausen noise, it is only necessary to control the roughness of the lower surface of the ferromagnetic magnetoresistive element 10, but the roughness substantially inherits the roughness of the underlying layer as described above. Therefore, the surface roughness of the underlayer may be controlled. FIG. 2 shows the characteristics of the ferromagnetic magnetoresistive element 10 made of Ni--Fe.
Are almost the same. This means that the composition ratio of Ni-Fe is 83:17 and the composition ratio of Ni-Co is 76: 2.
4 (both ± 2% error, unit wt%), both of which have Ni as a main component with strong ferromagnetic properties,
It is also apparent from the fact that the magnetic domain structure of the film is the same.

Further, according to the present embodiment, since the inclination angle θ at the connection portion of the wiring conductor 9 with the ferromagnetic magnetoresistive element 10 is formed to be 50 degrees, the inclination angle θ in FIG. As shown in the diagram of the relationship with the disconnection failure rate of the element 10, the disconnection failure rate can be reduced to almost 0%. Here, the thin film of the ferromagnetic magnetoresistive element 10 is usually formed with a thickness of 500 to 1000 mm, and is at most about 2000 mm at most, and is a very thin film, and has a step at a connection portion with the wiring conductor 9. However, by setting the inclination angle θ of the wiring conductor 9 to 78 degrees or less as shown in FIG. 3, the disconnection failure rate can be effectively reduced. The material of the wiring conductor 9 is not limited to Al,
The same applies to Au, Cu, or the like containing impurities such as Cu or Si.

As described above, the present invention has been described using one embodiment. However, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof, for example, as described below.

The insulating layer other than the silicon oxide film 8 may be used as the underlayer according to the present invention. About this underlayer,
Silicon nitride film and glass (Corning # 7059)
, The characteristics shown in FIG. 2 hardly change. The substrate referred to in the present invention may be an insulating substrate other than a semiconductor substrate. In this case, a ferromagnetic magnetoresistive element may be formed directly on the insulating substrate.

In the above embodiment, a signal processing circuit other than an amplifier circuit may be formed on the same substrate. For example, when the magnetic detection device of the present invention is used for rotation control or the like, a Schmitt trigger circuit is used. May be formed.

In the above embodiment, the surface roughness of the silicon oxide film 8 is controlled by controlling the deposition speed, but it can also be controlled by polishing. In this case, the surface of the semiconductor substrate before the formation of the silicon oxide film 8 is polished to, for example, a surface roughness Ra of 20 to 30 °, and thereafter, the silicon oxide film 8 is formed on the surface by thermal oxidation. Then, the surface of the silicon oxide film 8 becomes
Inherited the surface roughness of semiconductor substrate to some extent, Ra = 100Å
Can be controlled to a degree.

〔The invention's effect〕

As described above, according to the present invention, since the surface roughness of the underlayer of the ferromagnetic magnetoresistive element is set to 120 ° or less,
Noise generation can be effectively suppressed, magnetic sensitivity is high, and S /
There is an effect that a magnetic detector having a large N ratio and good characteristics can be provided.

Further, by setting the inclination angle of the wiring conductor to 78 degrees or less, the disconnection failure rate of the ferromagnetic magnetoresistive element can be effectively reduced. Furthermore, the contact area at the electrical connection between the wiring conductor and the ferromagnetic magnetoresistive element increases, so that the electrical resistance at the electrical connection can be reduced. In addition, since the signal processing circuit for processing the change in the resistance value of the ferromagnetic magnetoresistive element is formed inside the semiconductor substrate, the mounting area can be reduced without requiring separate components.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between the surface roughness and the Barkhausen noise generation rate, and FIG. 3 is a diagram showing the inclination angle θ and the disconnection of the ferromagnetic magnetoresistive element. FIG. 4 is a partial cross-sectional view of FIG.
FIG. 5 is a diagram showing the measurement state of the characteristics in FIG. 2, and FIG.
The figure shows the relationship between the magnetic field strength and the resistance value. 1 ... P-type semiconductor substrate, 8 ... silicon oxide film, 9 ... wiring conductor, 10 ... ferromagnetic magnetoresistive element.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshikazu Arasa 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-59-46079 (JP, A) JP-A-62- 131589 (JP, A) JP-A-53-34484 (JP, A)

Claims (1)

(57) [Claims] A semiconductor substrate, an insulating underlayer formed on the semiconductor substrate, a semiconductor substrate formed in a predetermined pattern on the underlayer, and the semiconductor layer interposed through an open region of the underlayer. A wiring conductor electrically connected to a substrate, Ni formed on the base layer and electrically connected to the wiring conductor by covering the wiring conductor at an end thereof, and having a resistance value changed by a change in a magnetic field. A ferromagnetic magnetoresistive element having a thin film as a main component, and a signal processing circuit formed inside the semiconductor substrate in electrical connection with the wiring conductor, for processing a change in resistance value of the ferromagnetic magnetoresistive element. The surface roughness of the underlayer under the ferromagnetic magnetoresistive element is 120 °.
A magnetic detection device according to claim 1, wherein an inclination angle of said wiring conductor is 78 degrees or less at an electrical connection portion between said wiring conductor and said ferromagnetic magnetoresistive element.