Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Magnetic field
Patent
1993-07-30
1995-11-28
Crane, Sara W.
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Magnetic field
257427, 257751, 257765, 257775, H01L 2722
Patent
active
054710847
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a magnetoresistive element and a manufacturing method therefor.
2. Background Art
A magnetoresistive element as disclosed in Japanese Laid-open Patent Application No. 1-125882 has been conventionally used for a magnetic sensor, etc.
Generally, in a magnetic sensor using a thin film of magnetoresistive element, as shown in FIG. 25, an insulating film 4 is formed on a monocrystal silicon substrate 1 having a circuit element, aluminum wiring metal 9 is formed on the insulating film 4, and a thin film of ferromagnetic magnetoresistive element 10 formed of Ni--Fe, Ni--Co or the like is formed on the aluminum wiring metal 9. The magnetoresistive element thin film 10 is disposed on the aluminum wiring metal 9 for the following reason. If the magnetic-resistance element thin film 10 is priorly formed, a patterning of the aluminum wiring metal 9 is subsequently carried out, and thus an etching of the magnetoresistive element thin film 10 must be considered at the patterning step.
The thin film such as Ni--Fe, Ni--Co or the like is very active, so that it is liable to be oxidized and damaged. Therefore, a surface protection film 11 formed of silicon nitride which can be formed at a low temperature is formed on the magnetoresistive element thin film 10. It is formed in the following manner, for example. The monocrystal silicon substrate which is an object on which elements are laminated is inserted into a vacuum chamber, raw gas (monosilane, nitrogen, ammonia, etc.) flows into the vacuum chamber at 200.degree. to 400.degree. C., and plasma is excited with a high-frequency power source to deposit a silicon nitride film (surface protection film 11). Through this process, the surface protection film can be formed without oxidizing the magnetoresistive element thin film 10, and in addition the silicon nitride film having defects such as pinholes, can be formed as the surface protection film. The bond resistance (contact resistance) between the magnetoresistive element thin film 10 and the aluminum wiring metal 9 is ordinarily about 1.OMEGA., however, it is experimentally proved that if a silicon nitride film having excellent moisture resistant property is deposited as the surface protection film 11, the bond resistance would be varied to several tens to 1M.OMEGA. after deposition of the silicon nitride. For the magnetic sensor as shown in FIG. 25, the result of the contact resistance of Ni--Co/Al which is measured before and after a plasma silicon nitride film (P--SiN film) serving as the surface protection film 11 is formed is shown in FIG. 26. It is apparent from FIG. 26 that in comparison with the contact resistance before the plasma silicon nitride film is formed, the contact resistance after the plasma silicon nitride film is formed is increased in two or more orders. This indicates a failure in the electrical connection of Ni--Co/Al.
An object of this invention is to provide a magnetoresistive element and a manufacturing method for the magnetoresistive element in which an increase in the contact resistance between a magnetoresistive element thin film and a wiring metal due to formation of a surface protection film can be inhibited,
DISCLOSURE OF INVENTION
In order to clarify the cause of an increase in the contact resistance due to formation of the silicon nitride as described above, the variation of the contact resistance is measured in the same manner under an NH.sub.3 gas atmosphere which is one of atmosphere gases at the formation time of the plasma silicon nitride. The result is shown in FIG. 27. The contact resistance of Ni--Co/Al is varied in about two orders by exposing it to the NH.sub.3 gas atmosphere in comparison with that before exposure to the NH.sub.3 gas atmosphere, and thus proving that the increase in contact resistance after the plasma silicon nitride film is formed is mainly caused by the NH.sub.3 gas.
FIG. 28 shows an SIMS analysis result of a bond portion (contact portion) between the magnetoresistive element thin film 10 and the alu
REFERENCES:
patent: 4091406 (1978-05-01), Lewis
patent: 4945397 (1990-07-01), Schuetz
patent: 5004064 (1991-04-01), Yoshino et al.
patent: 5198884 (1993-03-01), Yano et al.
patent: 5262666 (1993-11-01), Yoshino et al.
Ao Kenichi
Eguchi Koji
Ito Ichiro
Noguchi Hiroki
Suzuki Yasutoshi
Bowers Courtney A.
Crane Sara W.
Nippondenso Co. Ltd.
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