JPH0945975A - Semiconductor magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor magnetic sensor utilizing a semiconductor magnetoresistive element in which the semiconductor resistive film and the electrode film are protected. SOLUTION: The semiconductor magnetic sensor comprises a semiconductor magnetoresistive film 2, a short circuit electrode 3, and an electrode part 4 for taking out an electric signal from the semiconductor reluctance film, all formed on the surface of a substrate 1, which are coated with a protective film 6 formed on the substrate 1 except the electrode part 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor magnetic sensor including a semiconductor magnetoresistive element used for magnetic detection or magnetic rotation detection.

[0002]

2. Description of the Related Art InSb, InSb-NiSb, InA
A semiconductor having a high carrier mobility such as s has a property that the resistance value changes when a magnetic field is applied, and a semiconductor magnetic sensor uses this property.

FIG. 5 shows the structure of a general magnetic detector using a semiconductor magnetic sensor. The magnetic detector is composed of four parts as shown in FIG. In the figure,
Reference numeral 31 is a semiconductor magnetic sensor, 32 is a portion for taking out an electric signal of the semiconductor magnetic sensor 31 (lead taking-out), 33
Is a bias magnet, and the semiconductor magnetic sensor 31 and the bias magnet 33 are arranged on the front and back of the base 36, and are housed in a metal protective case 34 that also serves as an electromagnetic shield.

This magnetic detector is a semiconductor magnetic sensor 31.
The magnetic material to be detected moves in pressure contact with the surface of the upper protective case 34. Since the protective case 34 may bend due to pressure contact, an air gap (air gap) 35 is provided between the semiconductor magnetic sensor 31 and the protective case 34, and a resistance change due to stress strain of the semiconductor magnetic sensor 31 occurs (hereinafter, piezo resistance). (Referred to as “effect”) and magnetic sensitivity reduction, and also serves as insulation between the protective case 34 and the electric signal extraction portion of the semiconductor magnetic sensor 31.

6 and 7 show the structure of a conventional semiconductor magnetic sensor. Reference numeral 21 is a substrate, 22 is a semiconductor magnetoresistive film provided on the substrate, 23 is a short-circuit electrode provided on the semiconductor magnetoresistive film 22, and 24 is an output extraction electrode provided on the semiconductor magnetoresistive film 22.

FIG. 8 shows an example of taking out leads from the semiconductor magnetic sensor. In the figure, 26 is a lead extraction terminal, 2
7 is a protective film, and the protective film 27 is a lead takeout terminal 2
6 is formed after being connected to the output extraction electrode 24.

[0007]

As described above, the protective film 27 on the semiconductor magnetoresistive film 22 and the short-circuit electrode 23 is formed after the lead take-out terminal 26 is connected. During mounting, the semiconductor magnetoresistive film 22 and the short-circuit electrode 23, especially the semiconductor magnetoresistive film 22
Is very soft and very difficult to handle. In particular, in the process of connecting the lead take-out terminal 26 to the semiconductor magnetic sensor and the assembling process as a magnetic detector, there is a risk of scratches or destruction of the element surface and the like, and caution is required in handling.

An object of the present invention is to provide a semiconductor magnetic sensor which can solve the above problems.

[0009]

A semiconductor magnetic sensor of the present invention for solving the above-mentioned problems includes a semiconductor magnetoresistive film formed on a surface of a substrate and an electrode portion for extracting an electric signal of the semiconductor magnetoresistive film. It is characterized in that it is configured to be protected by a protective film formed on the substrate while leaving only the electrode portion.

[0010]

With the above structure, the extremely soft semiconductor magnetoresistive film and the short-circuit electrode film are not damaged during the connection of the lead-out terminals to the magnetic sensor and the handling in the assembly process for forming the magnetic detector. It is possible to prevent the element from being broken.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the semiconductor magnetic sensor of the present invention. In the figure, 1 is a substrate such as Si or glass, and 2 is a semiconductor magnetoresistive film with high carrier mobility such as InSb, InSb-NiSb, InAs, etc., which is provided on the substrate 1. Reference numeral 3 is a short-circuit electrode, which is provided on the semiconductor magnetoresistive film 2. 4 is a semiconductor magnetoresistive film 2
Of the electric signal extracting electrode, and is provided on the semiconductor magnetoresistive film 2. The short-circuit electrode 3 and the electrode portion 4
May be configured as a two-layer structure of Cu / Ti, Cu / Cr, Al / Cr or the like, or may be configured as a single-layer structure of In or the like. If the short-circuit electrode 3 and the electrode portion 4 are made of the same material, the process is simplified.
Reference numeral 6 is a protective film for protecting the semiconductor magnetoresistive film 2 and the short-circuiting electrode 3, such as polyimide, SiO ₂ , SiN, etc., which is formed on the substrate 1 except the electrode portion 4. Reference numeral 7 denotes a lead terminal for taking out an electric signal from the element, which is connected to the electrode portion 4. Here, the electrode portion 4 is Cu / Ti,
When they are made of Cu / Cr, In or the like, they are connected by soldering, and when they are made of Al / Cr or the like, they are connected by heating. Since the protective film 6 is formed before the lead terminal 7 is connected to the electrode portion 4, high heat generated when the lead terminal 7 is connected to the electrode portion 4 is conducted to the protective film 6 by applying heat or pressure. It For example, when connecting with solder, polyimide is suitable because a high temperature of 300 to 350 ° C. is conducted and heat resistance is required for the protective film 6.

As a result of carrying out the element mounting step and the assembly step for forming a magnetic detector in the present embodiment, no damage to the element surface or element destruction was observed. Further, the semiconductor magnetoresistive film has a characteristic that a piezoresistive effect is generated when strain is applied on the element surface, and it is necessary to pay attention to the stress acting on the semiconductor magnetoresistive film in the protective film forming film. Therefore, it is desirable to reduce the stress generated by the protective film. Si
The protective film such as O ₂ and SiN can be adjusted in stress depending on the forming conditions and can reduce the influence on the device characteristics, and can be formed small according to the actual conditions. Polyimide protective film is Si
Although the film stress was formed to be slightly larger than that of the protective film such as O ₂ or SiN, the magnetic properties were examined, and it was confirmed that the influence was small. The protective film of SiO ₂ , SiN or the like is generally formed on the entire surface of the substrate 1 by a vacuum device, and is formed by removing the protective film on the electrode portion 4 by a photolithography and etching process. On the other hand, since the polyimide protective film is formed only by the photolithography process, it has features that the process can be simplified and the cost can be reduced. Furthermore, 5 × 10 ^-5
When a polyimide having a linear expansion coefficient of / ° C or less is used,
This is more advantageous because the stress can be formed to be equal to or less than the stress acting on the protective film such as SiO ₂ or SiN.

FIG. 3 shows a second embodiment of the semiconductor magnetic sensor of the present invention. As shown in FIG. 3, instead of forming the electrode portion 4 on the semiconductor magnetoresistive film 2 as in the case of the first embodiment, the electrode portion 4 is formed on the substrate 1 and provided on the substrate 1. It is formed on the semiconductor magnetoresistive film 2. In this embodiment, as the electrode portion 4, Cu / Ti, Cu / Cr,
A two-layer structure of Al / Cr was used, and the peel strength between the electrode portion 4 and the substrate 1 was improved by about 1.5 times. In the structure of the first embodiment, when the lead terminal 7 is connected to the electrode portion 4, the electrode portion 4 and the electrode portion 4 are brought into contact with each other due to the high heat generated by heat heating and the pressure contact.
Although the lower semiconductor magnetoresistive film 2 was diffused and stress was further applied, the strengths of the substrate 1 and the magnetoresistive film 2 were reduced,
In the second embodiment, since the electrode portion 4 is formed directly on the substrate 1, diffusion with the magnetoresistive film 2 and generation of stress are small. According to this second embodiment, the substrate 1 and the electrode portion 4 are
It is possible to further improve the reliability of connection with.

FIG. 4 shows a third embodiment of the semiconductor magnetic sensor of the present invention. As shown in FIG. 4, in the present embodiment, two electrodes such as Au / Ni and solder / Ni are formed on the first electrode layer 8 having a two-layer structure of Cu / Ti, Cu / Cr, and Al / Cr as the electrode portion 4. The second electrode layer 9 having a layered structure is formed, and
Since the electrode layer 9 is formed by electroplating, the electrode portion 4 is formed higher than the protective film 6, and the lead terminal 7
Is connected. By forming the electrode portion 4 higher than the protective film 6, the shape of the lead terminal 7 and the connection jig,
Moreover, the positional accuracy and connection of the lead terminal 7 are simplified. Further, by forming the second electrode layer 9 by electroplating, the selection range of the connection member is expanded and the reliability of connection is improved. In the bump formation, the allowable range of the material and thickness of the electrode portion 4 is narrow, and the formation conditions and management are strict, and it is difficult to secure the reliability of the connection, but as another method for forming the second electrode layer 9, Au, There is bump formation of Al or the like.

According to this embodiment, the lead frame and the T
The connection of the lead terminal 7 in the AB mounting becomes easy, and the connection strength is also improved. The protective film 6 also serves as a plating mask when the electrode layer 5 is formed by plating, and also has the features of simplifying the process and enabling inexpensive plating.

In the case of connection by the lead frame, if the second electrode layer 9 of solder / Ni is used, the connection strength is particularly good, and the second embodiment (Cu / Ti, Cu / Cr electrode portion 4) is used.
The connection strength of about 1.5 times or more was obtained. In case of connection by TAB mounting, Au / Ni, solder / Ni second
When the electrode layer 9 was used, the connection strength was particularly good, and about twice or more the connection strength was obtained as compared with the second embodiment (Cu / Ti, Cu / Cr, Al / Cr electrode portion 4).

Further, by forming the second electrode layer 9 of the present embodiment smaller than the area of the first electrode layer 8, the stress generated by the connection of the lead terminals 7 is applied to the entire area of the formation area of the electrode portion 4. Do not join. Therefore, no stress is directly applied to the connecting portion between the electrode portion 4 and the substrate 1, the reliability of the connecting strength is further enhanced, and the connecting condition and the handling of the lead can be facilitated.

In the third embodiment, it is needless to say that heat-resistant polyimide or polyimide having a coefficient of linear expansion of 5 × 10 ^-5 / ° C. or less can be used as the protective film 6.

In addition, Cu / Ti, Cu / Cr, Al / C
Cr, Ni, N on the surfaces of the short-circuit electrode 3 and the electrode portion 4 such as r
It may be coated with a material such as iCr. Although the protective film 6 is formed on the electrodes, it is difficult to form a defect-free film by entrapping dust or the like at the time of formation, and the present reliability is not affected, but some oxidation occurs. With the configuration of the electrode coating as in this example,
Oxidation of the electrode surface can be reliably prevented and high reliability can be obtained.

[0021]

As described above, according to the present invention, the semiconductor magnetoresistive film formed on the surface of the substrate and the electrode portion for extracting an electric signal of the semiconductor magnetoresistive film are left only on the electrode portion. Since it is covered with the protective film formed on the substrate, it is a very soft semiconductor magnetoresistive film or short-circuit electrode film when connecting the lead-out terminals to the magnetic sensor and handling in the assembly process to form a magnetic detector. It is possible to prevent the element from being damaged or the like without damaging the element.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a semiconductor magnetic sensor of the present invention.

FIG. 2 is a sectional view of the sensor.

FIG. 3 is a sectional view of a semiconductor magnetic sensor showing a second embodiment.

FIG. 4 is a sectional view of a semiconductor magnetic sensor showing a third embodiment.

FIG. 5 is a schematic sectional view showing a conventional magnetic detector.

FIG. 6 is a perspective view of a conventional semiconductor magnetic sensor.

FIG. 7 is a sectional view of the sensor.

FIG. 8 is a cross-sectional view showing a conventional semiconductor magnetic sensor lead lead-out structure.

[Explanation of symbols]

 1, 21 substrate 2, 22 semiconductor magnetoresistive film 3, 23 short-circuit electrode 4, 24 electrode part 5 second electrode layer 6, 27 protective film 7, 26 lead terminal 8 first electrode layer of two-layer structure 9 2 layers Second electrode layer of structure 31 Semiconductor magnetic sensor 32 Lead extraction part 33 Bias magnet 34 Protective case 35 Air gap 36 Base

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Tanigawa, 1006 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Akira Matsuura, 1006, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Satoshi Ouchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A semiconductor magnetoresistive film formed on a surface of a substrate, a short-circuit electrode and an electrode portion for extracting an electric signal formed on the semiconductor magnetoresistive film, and the above-mentioned substrate on the substrate leaving only the electrode portion. A semiconductor magnetic sensor comprising a semiconductor magnetoresistive film and a protective film formed so as to cover the short-circuit electrode. 2. The semiconductor magnetic sensor according to claim 1, wherein the electrode portion is formed on the substrate and is connected to the semiconductor magnetoresistive film. 3. The semiconductor magnetic sensor according to claim 1, wherein the protective film is made of a heat-resistant polyimide material. 4. The protective film has a linear expansion coefficient of 5 × 10 ⁻⁵ /
A polyimide material having a temperature of ℃ or less.
Alternatively, the semiconductor magnetic sensor according to the item 2. 5. The electrode portion comprises a first electrode layer connected to the semiconductor magnetoresistive film, and a second electrode layer formed on the first electrode layer.
5. The semiconductor magnetic sensor according to claim 1, wherein the semiconductor magnetic sensor is configured to have a thickness higher than a thickness of the protective film. 6. The semiconductor magnetic sensor according to claim 5, wherein the second electrode layer is formed by plating. 7. The semiconductor magnetic sensor according to claim 5, wherein the second electrode layer is formed smaller than the region of the first electrode layer. 8. The surface of the short-circuit electrode and the electrode portion is made of Cr, N
3. The semiconductor magnetic sensor according to claim 1, wherein the semiconductor magnetic sensor is coated with either i or NiCr alloy.