JP3588952B2 - Semiconductor thin film magnetoresistive element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor thin film magnetoresistive element used for detecting rotation, displacement, and the like, and more particularly, to a configuration of an electrode material having a remarkably improved heat resistance of the element and further excellent ohmic properties.
[0002]
[Prior art]
In general, there are various types of rotation sensors including an optical type and a magnetic type. Among them, a magnetic system which is relatively insensitive to the influence of the atmosphere, such as dirt and dust, is most advantageous.
[0003]
On the other hand, in this magnetic system, there are various systems such as an electromagnetic pickup, a Hall element, and a magnetoresistive element.
[0004]
In recent years, as various types of sensor elements have been mounted along with electronic control of automobiles, rotation sensors, particularly rotation sensors using a Hall element (Hall IC), a ferromagnetic thin film magnetoresistive element, and a semiconductor magnetoresistive element as gear sensors, have been developed. Although it has been studied in various places from the point of zero speed detection, when used as a rotation sensor for an automobile, the operating temperature range of the element must satisfy −40 to 150 ° C.
[0005]
However, the Hall element, Hall IC, and ferromagnetic thin film magnetoresistive element having such temperature durability all have a small detection output of the detection element itself, and it is difficult to secure a sufficient air gap between the detection element and the Hall element. However, there is a problem that it is difficult to use as a gear sensor.
[0006]
On the other hand, a semiconductor thin-film magnetoresistive element is considered to be most suitable as a gear sensor because it originally has a large detection output and a wide air gap with the object to be detected. The operating temperature range of the InSb magnetoresistive element is about −40 to 120 ° C., and is not necessarily sufficient in terms of temperature durability as the above-described rotation sensor for automobiles.
[0007]
Many of the InSb magnetoresistive elements that are frequently used at present are of the InSb bulk single crystal flake type. This is because the detection output of this element is proportional to the electron mobility of InSb, which is the elementary material, and is therefore greatly affected by its crystallinity. On the other hand, this type of device uses a device in which a single crystal wafer is adhered onto a substrate via an adhesive layer, and then polished by non-strain polishing to a thickness of about 10 μm or more. Has a drawback of being susceptible to low to high temperature heat shock due to the difference in thermal expansion coefficient of
[0008]
On the other hand, as described in Japanese Patent Application Laid-Open No. 5-147422, a semiconductor thin film magnetoresistive element having an InSb thin film directly heteroepitaxially grown on a Si wafer substrate using this as an oriented substrate is not suitable for the above temperature endurance. It is useful in that it has excellent sensitivity and has sensitivity comparable to that of a bulk single crystal type flaked device.
[0009]
[Problems to be solved by the invention]
By using the configuration in which the InSb epitaxially grown thin film is formed directly on a Si wafer in this way, it is possible to realize a magnetically sensitive portion of a semiconductor thin film magnetoresistive element having excellent output sensitivity characteristics and temperature durability. In addition to this, it is necessary to minimize durability deterioration such as a change in characteristics due to mutual diffusion between a large number of short-circuit electrodes formed on the InSb thin film and the InSb thin film, which is a feature of this device.
[0010]
An object of the present invention is to provide a semiconductor thin film magnetoresistive element which prevents the interdiffusion between the electrode and the InSb thin film and has excellent temperature stability.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the semiconductor thin film magnetoresistive element of the present invention has, as an electrode material thereof, a layer having good ohmic properties with respect to an InSb thin film and a layer having good adhesion as a lower layer, and an upper layer as a lower layer. It has a configuration including a conductive material layer and a diffusion prevention layer as an intermediate layer.
[0012]
According to the present invention, when there are only two layers of a good conductive material such as Cu or Al as an upper layer material and Cr as a lower layer material, interdiffusion between Cu, Al and the InSb thin film in the upper layer passes through Cr. A thermal unstable factor such as generation of an intermediate compound of Cu and In and generation of an intermediate compound of Al and Sb is prevented by interposing the intermediate layers such as Ti and Ni to prevent mutual diffusion. This makes it possible to maintain a state where diffusion does not easily occur even at a high temperature of about 350 ° C.
[0013]
Accordingly, a semiconductor thin film magnetoresistive element which operates stably not only at −40 to 150 ° C. but also at a higher temperature can be realized.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, a plurality of InSb thin-film resistors are connected in series via a number of short-circuit electrodes provided on an InSb thin film formed on a substrate, and electrode terminals for external extraction are provided at both ends thereof. The semiconductor magnetoresistive element has a structure in which parts are connected, and at least the short-circuit electrode has a laminated structure of three layers of Cr, Ni, and Cu sequentially from the side in contact with the InSb thin film. With this electrode configuration, the upper layer Cu forms a solid solution with Ni, so that the diffusion is prevented in the intermediate layer Ni and does not diffuse into the lower InSb layer. Also, with respect to the InSb thin film, Ni and Sb form a solid solution due to the presence of the intermediate layer Ni, so that diffusion is prevented, and the InSb thin film does not easily diffuse into the upper Cu layer. As a result, a remarkable intermediate compound of Cu and In is generated particularly when the intermediate layer is not present, thereby avoiding a problem such as a change in the resistance value of the device.
[0015]
According to a second aspect of the present invention, as the electrode material of the semiconductor thin-film magnetoresistive element, a three-layered structure of Cr, Ti, and Cu is sequentially formed from the side in contact with the InSb layer. Due to the configuration, in the upper layer Cu, the intermediate layer Ti has a diffusion preventing effect, and Cu and Ti are not easily alloyed. In addition, due to the presence of Ti, InSb does not diffuse into the upper Cu layer and Ti and InSb do not easily alloy. Therefore, it is possible to realize an extremely thermally stable semiconductor thin film magnetoresistive element in which the resistance value of the short-circuit electrode does not change at high temperature and the resistance value of the entire element does not change.
[0016]
As described above, in the case of using the Cu layer as the upper layer material according to claims 1 and 2, the short-circuit electrode in the case of performing TAB (Tape Automated Bonding) by applying Ni / Au plating, Cu / Au plating, etc. to the external extraction electrode terminal portion. Configuration.
[0017]
According to a third aspect of the present invention, as the electrode material of the semiconductor thin-film magnetoresistive element, a three-layered structure of Cr, Ni, and Al is sequentially formed from the side in contact with the InSb layer. Due to the configuration, in the upper layer Al, the intermediate layer Ni has a diffusion preventing effect, and Al and Ni are not easily alloyed. In addition, since Ni and Sb form a solid solution due to the presence of Ni, diffusion is prevented, and InSb does not diffuse into the upper Al layer. Therefore, problems such as a change in the resistance value of the element can be avoided.
[0018]
According to a fourth aspect of the present invention, as the electrode material of the semiconductor thin-film magnetoresistive element, a three-layered structure of Cr, Ti, and Al is sequentially formed from the side in contact with the InSb layer. Due to the configuration, in the upper layer Al, the intermediate layer Ti has a diffusion preventing effect, and Al and Ti are not easily alloyed. In addition, due to the presence of Ti, InSb does not diffuse into the upper Al layer, and Ti and InSb do not easily alloy. Therefore, it is possible to realize an extremely thermally stable semiconductor thin film magnetoresistive element in which the resistance value of the short-circuit electrode does not change at high temperature and the resistance value of the entire element does not change.
[0019]
As described above, the first and second embodiments using the Al layer as the upper layer material have a short-circuit electrode configuration when wire bonding is mounted on the external extraction electrode terminal portion.
[0020]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6.
(Embodiment 1)
FIG. 1 is a sectional view illustrating a semiconductor thin film magnetoresistive element according to a first embodiment of the present invention. After an InSb thin film 2 is formed on a substrate 1 made of Si or the like and processed into an element pattern, a lower layer Cr3, an intermediate layer Ni4, and an upper layer Cu5 are sequentially formed in order of 0.1 μm, 0.1 μm, A solid film is formed by a thin film forming method such as vacuum evaporation with a thickness of 0.5 μm, a pattern is formed, and a short-circuit electrode 6 is obtained. Thereafter, a protective film 8 is formed so as to cover the entire surface of the short-circuit electrode 6 and the entire surface of the InSb resistor portion 7. The semiconductor thin film magnetoresistive element 9 is manufactured by this series of manufacturing methods.
[0021]
FIG. 2 shows a change from the initial value of the element resistance value when the semiconductor thin film magnetoresistive element 9 manufactured as described above is left at a high temperature of 350 ° C. In the figure, a curve 10 is a result of a Cr, Ni, Cu three-layer electrode configuration of the present invention, and a curve 11 is a result of a Cr, Cu two-layer electrode configuration without the intermediate layer Ni. .
[0022]
Even in the case of the Cr and Cu two-layer electrode structure, when left at about 250 ° C., there is little diffusion and sufficient reliability is obtained. Diffusion rapidly progresses with the passage of time, alloying occurs between the InSb thin film 2 and the upper layer Cu5 (a large amount of intermediate compounds of Cu and In are generated), and finally, such alloyed portions are brittle and have high tensile strength. Stress occurs and cracks occur, which significantly increases the resistance.
[0023]
On the other hand, as shown by the curve 10 in FIG. 2, in the three-layered electrode of the present invention, although the resistance value increases by about several% at the beginning (mainly due to the short-circuit electrode resistance due to the solid solution alloying of Cu and Cr in the electrode) No increase occurs after this time. Thus, it has sufficiently stable heat resistance even at a high temperature of 350 ° C.
[0024]
If the thickness of the intermediate layer Ni4 is about 0.05 μm, a sufficient diffusion preventing effect can be obtained.
[0025]
(Embodiment 2)
The configuration of the semiconductor thin film magnetoresistive element according to the second embodiment of the present invention is the same as that of FIG. 1 and will be described with reference to FIG. The difference is that only the electrode material is used, and the description of other manufacturing steps is omitted. As an electrode material, a lower layer Cr3, an intermediate layer Ti4, and an upper layer Cu5 are sequentially formed from the lower layer side in contact with the InSb thin film by a thin film forming method such as 0.1 μm, 0.1 μm, and 0.5 μm thickness vacuum deposition to form a solid pattern. Is performed to obtain the short-circuit electrode 6. Thereafter, a protective film 8 is formed as in the first embodiment. The semiconductor thin film magnetoresistive element 9 is manufactured by this series of manufacturing methods.
[0026]
FIG. 3 shows a change in the element resistance value from the initial value when the semiconductor thin film magnetoresistive element 9 manufactured as described above is left at a high temperature of 350 ° C. In the figure, the curve 12 is the result of the Cr, Ti, Cu three-layer electrode configuration of the present invention. As shown in the figure, the three-layered electrode of this embodiment has almost no initial fluctuation and has extremely stable heat resistance even at a high temperature of 350 ° C. This is because originally, it is difficult to alloy Cu and Ti, and it is also difficult to alloy Ti and InSb. Therefore, the short-circuit electrode resistance itself and, of course, the InSb resistor portion hardly deteriorate.
[0027]
If the thickness of the intermediate layer Ti4 is about 0.05 μm, a sufficient diffusion preventing effect can be obtained.
[0028]
As described above, the electrode composed of the upper layer Cu5 described in the first and second embodiments is, as shown particularly in FIG. 4, the mounting electrode section 14 formed by Ni / Au or Cu / Au plating in the external extraction electrode terminal section 13. Is formed in a bump shape, and is used when TAB mounting is performed on the mounting electrode portion 14.
[0029]
(Embodiment 3)
The configuration of the semiconductor thin film magnetoresistive element according to the third embodiment of the present invention is also the same as that shown in FIG. The difference is that only the electrode material is used, and the description of other manufacturing steps is omitted. As an electrode material, a lower layer Cr3, an intermediate layer Ni4, and an upper layer Al5 are sequentially formed from the lower layer side in contact with the InSb thin film by a thin film forming method such as 0.1 μm, 0.1 μm, and 0.5 μm thickness vacuum deposition to form a solid pattern. Is performed to obtain the short-circuit electrode 6. Thereafter, a protective film 8 is formed as in the first embodiment. The semiconductor thin film magnetoresistive element 9 is manufactured by this series of manufacturing methods.
[0030]
FIG. 5 shows a change in the element resistance value from the initial value when the semiconductor thin film magnetoresistive element 9 manufactured as described above is left at a high temperature of 350 ° C. In the figure, a curve 15 is a result of a Cr, Ni, Al three-layer electrode configuration of the present embodiment, and a curve 16 is a result of a Cr, Al two-layer electrode configuration without the intermediate layer Ni. It is. Even in the case of the Cr and Al two-layer electrode structure, when left at about 250 ° C., diffusion is small and sufficient reliability is obtained. However, when the temperature reaches 350 ° C., (accurately, about 300 ° C.) Diffusion rapidly progresses with the passage of time, the upper layer Al5 diffuses at the interface between the InSb thin film 2 and the lower layer Cr3, and an AlSb layer is formed at the interface. This AlSb layer has a larger forbidden band width than InSb2, thereby increasing the contact resistance at the interface, causing an increase in the element resistance value and deteriorating the magnetic characteristics. On the other hand, as shown by the curve 15 in FIG. 5, the three-layered electrode of the present embodiment has little initial fluctuation and has sufficiently stable heat resistance even at a high temperature of 350 ° C.
[0031]
If the thickness of the intermediate layer Ni4 is about 0.05 μm, a sufficient diffusion preventing effect can be obtained.
[0032]
(Embodiment 4)
The semiconductor thin film magnetoresistive element according to the fourth embodiment of the present invention has the same configuration as that of FIG. 1 and will be described with reference to FIG. The difference is that only the electrode material is used, and the description of other manufacturing steps is omitted. As an electrode material, a lower layer Cr3, an intermediate layer Ti4, and an upper layer Al5 are sequentially formed from the lower layer side in contact with the InSb thin film by a thin film forming method such as 0.1 μm, 0.1 μm, and 0.5 μm thick vacuum deposition to form a solid pattern. Is performed to obtain the short-circuit electrode 6. Thereafter, a protective film 8 is formed as in the first embodiment. The semiconductor thin film magnetoresistive element 9 is manufactured by this series of manufacturing methods.
[0033]
FIG. 6 shows a change in the element resistance value from the initial value when the semiconductor thin film magnetoresistive element 9 manufactured as described above is left at a high temperature of 350 ° C. In the figure, a curve 17 is a result in the case of a three-layer electrode configuration of Cr, Ti, and Al according to the present embodiment. The three-layered electrode of this embodiment has a small initial fluctuation and has a sufficiently stable heat resistance even at a high temperature of 350 ° C.
[0034]
If the thickness of the intermediate layer Ti4 is about 0.05 μm, a sufficient diffusion preventing effect can be obtained.
[0035]
The electrode composed of the upper layer Al5 described in the third and fourth embodiments is used for wire bonding mounting in the external extraction electrode terminal portion 13 of FIG.
[0036]
In the first to fourth embodiments, Cr is used as the lower layer material because the lower layer material has good ohmic properties with respect to the InSb thin film, has extremely low contact resistance, and further has good adhesion. Is not obtained when there is no lower layer Cr.
[0037]
In addition, in the pattern formation, even if the short-circuit electrode having the three-layer structure is formed by solid processing and then wet processing (etching) by a photolithography process, an electrode is formed after a desired mask pattern is first formed with a resist or the like. Needless to say, it may be formed by a lift-off method for removing the mask pattern.
[0038]
【The invention's effect】
As described above, according to the present invention, a semiconductor thin film magnetoresistive element having extremely excellent heat resistance can be formed by using at least the lower layer Cr, the intermediate layer of Ti or Ni, and the upper layer of Cu or Al for the short-circuit electrode configuration. And its industrial value is extremely high.
[Brief description of the drawings]
FIG. 1 is a structural cross-sectional view of a semiconductor thin film magnetoresistive element according to an embodiment of the present invention. FIG. 2 is a characteristic diagram for explaining heat resistance in an electrode configuration (upper layer Cu) according to an embodiment of the present invention. FIG. 3 is a characteristic diagram for explaining heat resistance in the electrode configuration (upper layer Cu) according to one embodiment of the present invention. FIG. 4 is a perspective view showing a mounting mode when the upper layer electrode is Cu. FIG. 6 is a characteristic diagram for explaining heat resistance in an electrode configuration (upper layer Al) according to another embodiment of the present invention. FIG. 6 is a graph illustrating heat resistance in an electrode configuration (upper layer Al) according to another embodiment of the present invention. Characteristic diagram for explaining
DESCRIPTION OF SYMBOLS 1 Substrate 2 InSb thin film 3 Lower electrode (Cr)
4 Intermediate layer electrode (Ni or Ti)
5 Upper electrode (Cu or Al)
6 Short-circuit electrode composed of three layers

Claims (4)

In a structure in which a large number of InSb thin-film resistors are connected in series via a large number of short-circuit electrodes provided on an InSb thin film formed on a substrate, and an extraction electrode terminal portion connected to the outside at both ends, at least the short-circuit electrode Has a laminated structure of three layers of Cr, Ni and Cu sequentially from the side in contact with the InSb thin film. In a structure in which a large number of InSb thin-film resistors are connected in series via a large number of short-circuit electrodes provided on an InSb thin film formed on a substrate, and an extraction electrode terminal portion connected to the outside at both ends, at least the short-circuit electrode Has a laminated structure of three layers of Cr, Ti, and Cu sequentially from the side in contact with the InSb thin film. In a structure in which a large number of InSb thin-film resistors are connected in series via a large number of short-circuit electrodes provided on an InSb thin film formed on a substrate, and an extraction electrode terminal portion connected to the outside at both ends, at least the short-circuit electrode Has a laminated structure of three layers of Cr, Ni and Al sequentially from the side in contact with the InSb thin film. In a structure in which a large number of InSb thin-film resistors are connected in series via a large number of short-circuit electrodes provided on an InSb thin film formed on a substrate, and an extraction electrode terminal portion connected to the outside at both ends, at least the short-circuit electrode Has a laminated structure of three layers of Cr, Ti, and Al sequentially from the side in contact with the InSb thin film.

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