JPH06105802B2 - Magnetoelectric conversion element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetoelectric conversion element for converting a magnetic field or magnetic flux into an electric signal such as a Hall element and a magnetoresistive effect element.

"Prior Art" Conventionally, the magnetic sensitive portion of a magnetoelectric conversion element using a III-V group compound semiconductor has a semiconductor bonded to a substrate such as ferrite, a semi-insulating semiconductor substrate, and the same kind of substrate as that substrate. A semiconductor active layer is formed and a semiconductor layer is formed on an insulating substrate.

Is a magnetoresistive element made by bonding an InSb wafer on a ferrite substrate with resin, and then forming a thin layer of InSb by a polishing method.The example of is an active magnetoresistive element on a GaAs semi-insulating substrate by ion implantation. An example of the Hall element formed with a layer is a Hall element formed by forming a semiconductor layer of InAs on an alumina substrate by a vapor deposition method.

In the above, it is difficult to set the thickness of the semiconductor active layer to a predetermined value, which greatly affects the performance of the magnetoelectric conversion element, and the presence of the resin layer complicates the manufacturing process. With regard to (1), generally, a semiconductor material capable of forming a semi-insulating substrate has a large band gap and a low mobility, so that sufficient sensitivity cannot be obtained. In this case, since the substrate is amorphous or polycrystalline, it is difficult to form a good single crystal semiconductor layer thereon.

In addition, it has been known in the prior art to form a compound semiconductor thin film by vapor deposition, MBE, CVD, or the like on a substrate having excellent crystallinity of Cr-doped semi-insulating GaAs. However, in this case, the type of compound semiconductor thin film was limited to match the lattice constant. That is, a GaAs semiconductor thin film, which is the same material, is formed on a GaAs substrate, but it has been known only to form an AlAs semiconductor thin film having a difference in lattice constant from GaAs of only about 0.14%. GaAs
Even if a Hall element is made from the thin film of, its electron mobility is
It was only about 5,000 cm ² / Vsec, and a highly sensitive element could not be obtained. AlAs is an insulating material and cannot be used as a magnetoelectric conversion element.

Therefore, an object of the present invention is to form a good quality film of a III-V group compound semiconductor having a higher mobility than this on a semi-insulating single crystal substrate, and various kinds of semiconductor films can be used, Moreover, it is to provide a highly sensitive and highly reliable magnetoelectric conversion element.

[Means for Solving the Problems] According to the magnetoelectric conversion element of the present invention, on the (111) and (100) planes of a semi-insulating GaAs single crystal substrate, or on a plane having an inclination within 10 ° from the plane. In addition, the thickness is 0.1 to 10 μm, the electron concentration is in the range of 5 × 10 ^{15 to} 5 × 10 ¹⁸ cm ^-3 , and the electron mobility is at room temperature.
4,000 to 80,000 cm ² / Vsec of InxAsy (X + Y = 2) or InxAsySbz or InxGayAsz (X + Y + Z = 2) binary or ternary III-V group high mobility compound semiconductor film is formed on the semiconductor film An electrode is formed on a required portion of the.

Further, the electrode is a contact layer made of a metal that makes ohmic contact with the magnetic sensing portion (semiconductor film), an intermediate layer made of a metal having a Young's modulus twice or more that of Au, and a contact layer made of the metal. And a bonding layer made of Au formed on the intermediate layer.

By using a semi-insulating GaAs single crystal substrate and using the semiconductor thin film forming surface as the above surface, the difference in lattice constant is relatively large, but the quality of various compound semiconductor thin films of III-V group with high mobility is high. Therefore, a Hall element and a magnetoresistive element having high mobility and high sensitivity can be industrially easily manufactured. By the way, the difference in the lattice constant for GaAs is InAs
Is about 7.2%, InAs _1-y Sby is about 7.2 to 14.6%, InxGa _1-x As
(0.3 <x <1.0) is about 2.2 to 7.2%.

In addition, since the thermal expansion coefficient of GaAs and other III-V group compound semiconductors is very close to each other, the thermal stress generated during semiconductor film formation is very small. Moreover, although there is a slight amount of Ga or As autodoping from the substrate, it has almost no effect on the electrical characteristics of the semiconductor film. Further, since there is no layer of a poor heat conductor between the substrate and the semiconductor film, and GaAs itself has very good heat conduction, the reliability of the magnetoelectric conversion element in the high temperature region becomes very high.

For the above reasons, by forming another high mobility compound semiconductor film on a semi-insulating GaAs single crystal substrate, a highly sensitive and highly reliable magnetoelectric conversion element can be easily manufactured industrially. can do.

[Example] Fig. 1 shows an example of the structure of a Hall element, which is one of the magnetoelectric conversion elements of the present invention. In Figure 1, semi-insulating GaAs
On the (111) plane or (100) plane of the single crystal substrate 11 or on a plane having an inclination of 10 ° or less with respect to these planes, a semiconductor film 14 having a high electron mobility which constitutes a magnetic sensing section is formed, A wire bonding electrode 15 is formed on the semiconductor film 14. The electrode 15 is composed of a contact layer 16 connected to the semiconductor film 14, an intermediate layer 17 thereon, and a bonding layer 18 thereon. The semiconductor film 14 in the central portion between the electrodes is the magnetic sensitive portion 19. The electrode 15 is a fine wire 21 made of Au, Al, Al-Si alloy, etc.
Connected to. Substrate 1 leaving the end of the lead frame 22
The thin wires 21 and the like are embedded in a resin mold body 23.

FIG. 2 shows the state of the Hall element of FIG. 1 viewed from above.

3 and 4 show the Hall element chip as a lead frame.
This is an example in which it is directly attached to the printed wiring board without passing through 22. That is, the thin wire 21 is connected to the wiring 25 formed on the printed board 24.

The electrode structure of the magnetoelectric conversion element of the present invention requires caution. Conventionally, the electrode structure of a magnetoelectric conversion element using a III-V semiconductor is such that after forming an ohmic contact on a semiconductor film, a metal layer having good wire bonding property such as Au or Al is formed by a vapor deposition method or the like. A method is used in which thin wires such as Au and Al are connected by heating at around 400 ° C and by pressure bonding or ultrasonic waves. However, when this method is applied to the magnetoelectric conversion element of the present invention, two problems occur. First, since the coefficient of thermal expansion differs between the substrate GaAs 11 and the compound semiconductor film 14 other than GaAs formed thereon, the temperature cannot be sufficiently raised during bonding. When the temperature of the electrode part is raised to 300 to 400 ° C. as usual, thermal stress concentrates on the interface between the substrate 11 and the semiconductor film 14, resulting in a decrease in reliability or a gap between the substrate 11 and the semiconductor film 14. Flaking occurs. Secondly, since the substrate 11 and the semiconductor film 14 generally do not have sufficient adhesiveness, they are peeled off when an ultrasonic wave having high power is applied.

Therefore, an ohmic junction is formed with the semiconductor film 14, and
A soft metal contact layer 16 that suppresses thermal stress between the electrode 15 and the semiconductor film is formed, and ultrasonic waves are reflected on the contact layer 16.
An intermediate layer 17 that is harder than the bonding layer 18 that prevents external force from being applied to the semiconductor film 14 is formed, and a metal bonding layer 18 having good bonding properties is further formed thereon. In this way, highly reliable wire bonding can be performed at low temperature and weak ultrasonic power.

Au is used for the bonding layer 18, and secures a strong and highly reliable connection with the fine wire 21 such as Au, Al, or Al-Si alloy. For forming the bonding layer 18, a method used for forming electrodes of a usual semiconductor element such as an electroless plating method, an electric field plating method, a lift-off method by vapor deposition or sputtering is used. The thickness of the bonding layer 18 is not particularly limited, but is usually 0.1 to 30 μm, preferably 0.1 to 10 μm. In order to improve the reliability of bonding, it is preferable that the bonding layer 18 is thicker, but the increase in the internal stress due to the increase in the thickness of the layer lowers the adhesion at the layer interface, reduces the etching breakage, and reduces the price. By increasing, the upper limit is determined.

The intermediate layer 17 is made of a metal layer that is harder than the bonding layer 18 made of Ni, Fe, Ti, W, Cu or the like.
An electrolytic plating method, a lift-off method using vapor deposition or sputtering, or the like can be used. The effect of the intermediate layer 17 mainly consists of the following three points.

(A) A force acting in the direction perpendicular to the surface of the electrode 15 at the time of bonding is concentrated on the intermediate layer 17 to prevent the force from reaching the semiconductor film 14 or the interface between the semiconductor film 14 and the contact layer 16. To do.

(B) The load during bonding is distributed over the entire electrode 15,
Prevents the load from being concentrated only on the tip of the tool.

(C) The ultrasonic waves are reflected at the interface between the intermediate layer 17 and the bonding layer 18 to prevent the ultrasonic waves from adversely affecting the semiconductor film 14 or the interface thereof. At the same time, ultrasonic energy is concentrated on the bonding layer 18 to ensure reliable bonding with ultrasonic power of low power.

For the purpose of (a) or (b), the intermediate layer 17 is preferably a metal having a large Young's modulus and a large elastic limit as compared with the bonding layer 18 or the contact layer 16. (C)
When the effect of is emphasized, it is preferable to use a metal that makes the sound velocity in the bonding layer 18 or the contact layer 16 and the sound velocity in the intermediate layer 17 as different as possible. At this time, since the sound velocity mismatch is large, ultrasonic waves are reflected by the interface between the bonding layer 18 and the intermediate layer 17 or the interface between the contact layer 16 and the intermediate layer 17. Ni, Cu, and W are preferable examples of metals that satisfy the above conditions. Middle layer 1 above
The preferred metal for 7 has a Young's modulus more than twice that of Au, and the sound velocity is about twice that of Au. It is also preferable to use Cu as the intermediate layer 17.

The thickness of the intermediate layer 17 is not particularly limited, but is usually 0.1 to 30 μm.
m, more preferably 0.1 to 10 μm. In order to effectively exert the effect of the intermediate layer 17, the larger the layer thickness, the more preferable, but as the layer thickness increases, the internal stress increases, the adhesion at the layer interface decreases, and at the same time, the etching cutoff is poor. So there is an upper limit. If the intermediate layer 17 is made too thin, its mechanical strength becomes small, and ultrasonic waves easily pass through,
There is no point in providing the intermediate layer 17.

In order to effectively perform the ultrasonic wave reflecting action, it is preferable that the intermediate layer 17 is composed of a plurality of metal layers. By combining metals with greatly different sound velocities in adjacent layers, each time an ultrasonic wave passes through the interface, it is reflected according to the degree of mismatch of the sound velocities of the metals on both sides of the interface, and its amplitude is greatly attenuated. . An example of this structure is shown in FIG. In FIG. 5, a Ni layer 31, an Au layer 32, and a Ni layer 33 are sequentially stacked under the Au bonding layer 18, and the intermediate layer 17 is formed by these three layers 31, 32, and 33.
The ultrasonic waves are layer 18 and layer 31, layer 31 and layer 32, layer 32 and layer 33, layer 33 and layer 1.
It is reflected at a total of 4 interfaces of 6. The intermediate layer 17 may have a difference in overall characteristics of Young's modulus (hardness), elastic limit and difference in sound velocity of 50% or more with respect to the bonding layer 18.

The contact layer 16 is Cu, Au, Al, Al-Si alloy, Au-Ge alloy, A
g, Pt, or a metal that forms a good ohmic junction with the compound semiconductor film 14 such as an alloy thereof, has a coefficient of thermal expansion similar to that of the compound semiconductor film 14, and is as soft as the compound semiconductor film 14. Consists of layers. The contact layer 16 ensures good ohmic contact between the semiconductor film 14 and the electrode 15, and relaxes thermal stress between the semiconductor film 14 and the electrode 15. To form the contact layer 16, an electroless plating method, an electrolytic plating method, a lift-off method using vapor deposition or sputtering, or the like is used. The layer thickness is not particularly limited, but is usually 0.
It is 1 to 50 μm, and more preferably 0.1 to 10 μm. In order to improve the reliability of bonding, it is preferable that the contact layer 16 is thicker, but as the layer thickness increases, the internal stress increases,
There is an upper limit because the adhesion at the layer interface decreases, the etching cut-off decreases, and the price increases when a precious metal such as Ag, Au, or Pt is used.

When a semiconductor film such as InGaAs, which is difficult to form an ohmic contact, is used, the contact layer 16
Multiple, first, after forming an ohmic junction with the semiconductor film 14 in a thin layer such as Au-Ge, a softer metal than the intermediate layer 17 or a thermal expansion coefficient of the semiconductor film 14 compared to the intermediate layer 17. A metal close to that is formed thereon, and the contact layer 16 is formed of two layers. This example is shown in FIGS. 6 and 7. In FIG. 6, when the semiconductor film 14 is an InAs layer, the Au and Ge alloy layer 34 is formed on the semiconductor film 14. The Ge ratio of the alloy layer 34 is 0.1 to 10% by weight, and the layer 34 ensures the ohmic contact between the GaAs semiconductor film 14 and the electrode 15. The Cu layer 35 is formed on the Au-Ge alloy layer 34, and these 2
The contact layer 16 is formed by the layers 34 and 35. In FIG. 7, when an InAsxSb _1-x (0 × 1) film is formed as the semiconductor film 14, an Au layer 36 is formed on the semiconductor film 14.
A Cu layer 37 is formed on the Au layer 36, and the contact layer 16 is formed by these two layers 36 and 37. The contact layer 16 is formed by using a method usually used for forming electrodes of semiconductor elements, such as an electroless plating method, an electrolytic plating method, a lift-off method by vapor deposition or sputtering. The layer thickness of the contact layer 16 is not particularly specified, but is preferably 0.1 to 10 μm. The contact layer 16 is preferably as thick as possible in order to improve the reliability of bonding, but an increase in the layer thickness causes an increase in internal stress.
The upper limit is determined by a decrease in the adhesion at the layer interface, a decrease in etching cutoff, and an increase in the price when a precious metal such as Au, Ag, or Pt is used.

The semiconductor film 14 is formed by a vacuum vapor deposition method, an MBE method, a CVD method,
Any ordinary method for forming a semiconductor film such as MOCVD method and LPE method may be used. In particular, the MBE method can form a high-quality polycrystalline or single-crystal thin film, has excellent film thickness controllability, and since film formation can be performed at low temperatures, there is little autodoping from the substrate and thermal stress is also small. It is very preferable because of the above reasons.

It is preferable that the GaAs single crystal substrate used for the substrate 11 has as high resistance as possible. Resistance value is not specified, but 10 ⁴ Ω
It is preferably −cm or more. Usually HB method or LE
A substrate cut out from a Cr-doped or undoped single crystal ingot formed by the C method is used. The surface of the substrate is preferably as smooth as possible. A substrate cut out in a crystal orientation of (1,1,1), (1,0,0) or a direction inclined by 1 to 10 ° is used.

The electrode 15 of the magnetoelectric conversion element is a wiring pattern formed on a lead frame 22 or a printed circuit board by a fine wire 21 usually used for wire bonding of Au, Al, Al-Si alloy or the like.
It is electrically coupled to a conductor such as 25. When connecting to the lead frame 22, the material of the lead frame is Cu, phosphor bronze, etc.
It is possible to use the one used for the lead of a general semiconductor element.
In addition, to improve the bondability,
It is also preferable to form a thin layer of a metal such as Au or Ag having good bonding properties.

The printed board 24 used in the case of wiring on the printed board 24 may be one that is used for wiring of ordinary electronic components. It is also preferable to form a thin layer of Au, Ag or the like having good bondability on the wiring conductor.

The material of the molding resin 23 may be a resin generally used for molding an electronic element. Preferred are thermosetting resins such as epoxy resins and phenol epoxy resins. The molding method may be a method that is generally used for electronic parts, and examples thereof include casting molding, transfer molding, and solid pellets placed on an element, heated and melted, and then cured and molded.

Although the Hall element has been described above as an example of the magnetoelectric conversion element of the present invention, other elements, for example, the magnetoresistive effect element, are different from the Hall element in the electrode shape, the number of terminal electrodes, and the pattern of the magnetic sensitive portion. The electrodes are formed in exactly the same manner as the Hall element, and the basic configuration is the same.

Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples and extends to all magnetoelectric conversion elements having the basic structure described above.

Example 1 A semiconductor film 14 is formed by forming an InAs film with a thickness of 1.5 μm and an electron mobility of 15,000 cm ² / Vsec on a (1,0,0) GaAs single crystal substrate 11 whose surface is mirror-polished by the MBE method. It was Next, using a photoresist, the magnetically sensitive portion in the InAs film 14 is formed by the usual method.
A photoresist coating was formed on the surface of 19. After that, electroless plating was performed, and copper was adhered only to a required portion having a thickness of 0.3 μm. Further, in order to thicken copper, electrolytic copper plating was performed to form a contact layer 16 having a thickness of 4 μm. Next, using the above photoresist again, an intermediate layer 17 of a Ni layer having a thickness of 2 μm was formed only on the electrode portion by the electrolytic plating method. Further, a 2 μm thick Au bonding layer 18 was formed thereon by electrolytic plating. Next, using the above photoresist again, by the technique of photolinography,
Part of the surface of the GaAs substrate 11, the unnecessary InAs film 14 and the unnecessary portion of the bonding layer 18 in the Au layer are removed by etching with a hydrochloric acid solution of ferric chloride, and the magnetic sensitive portions 19 and 4 of the Hall element are removed.
Two electrode parts 15 were formed. Next, a stress-relieving silicone resin was applied on the magnetic sensing portion.

Put this wafer on a dicing cutter, 1.1 × 1.1
Cut into square mm Hall element chips. This was then glued onto the tie of leadframe 22. Next, the electrode 15 of the pellet and the lead frame 22 were joined with the Au thin wire 21 using a high-speed wire bonder. It was packaged by epoxy resin transfer molding.

"Effects of the Invention" The sensitivity of the Hall element manufactured in this way and to which the present invention is applied is as shown in Table 1.

In Table 1, is the Hall element in which the magnetic sensitive portion was formed on the semi-insulating GaAs substrate by the ion implantation method, is the InAs film formed on the quartz substrate by the MBD method, and was used for the magnetic sensitive portion. Is. The values in Table 1 are input voltage 1V, applied magnetic field 5
This is the output voltage at 00G. It can be seen that is highly sensitive.

Table 2 shows the rate of change in resistance in the thermal shock test at 260 ° C for 10 minutes. In Table 2, is a Hall element of the present invention, is a Hall element in which a magnetic sensitive portion is formed on a semi-insulating GaAs substrate by an ion implantation method, and is a Hall element having an InSb magnetic sensitive portion adhered to a substrate by a resin. Is. It can be seen that the heat resistance of the Hall element of the present invention is as excellent as that of the GaAs Hall element by the ion implantation method.

As described above, it is understood that the magnetoelectric conversion element of the present invention has an unprecedented excellent overall performance with high sensitivity and high reliability. Moreover, according to the present invention, the compound conductor film formation surface is formed of GaAs (111), (100) or a surface having an inclination of 10 ° or less with respect to GaAs. Therefore, various high mobility compound semiconductor films of III-V group are formed. Can be formed, the degree of freedom in material selection is increased, and a highly sensitive magnetoelectric conversion element can be obtained. By the way, the electron mobility of a 1 μm film of InAs is about 15,000 cm ² / Vsec, and that of GaAs is 5,000 cm ² / Vse.
significantly higher than c.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetoelectric conversion element according to the present invention, FIG. 2 is a plan view of the magnetoelectric conversion element of FIG. 1 before a mold body is attached, and FIG. 3 is another embodiment of the present invention. Fig. 4 is a plan view showing an example, Fig. 4 is a cross-sectional view of Fig. 3, Fig. 5 is a cross-sectional view showing an example of an electrode structure in the case where the intermediate layer 17 is composed of a plurality of metal layers, and Fig. 6 shows a contact layer 16 FIG. 7 is a sectional view showing an example of an electrode structure in the case of being composed of a plurality of metal layers, and FIG.
FIG. 7 is a cross-sectional view showing another example of the electrode structure when 16 is composed of a plurality of metal layers. 11: Insulating GaAs single crystal substrate, 14: Semiconductor film, 15: Electrode, 16:
Contact layer, 17: intermediate layer, 18: bonding layer, 19: magnetic sensitive part, 21: thin wire, 22: lead frame, 23: molded body.

Claims (1)

[Claims] 1. A semi-insulating GaAs single crystal substrate of (111), (1)
InxAsy (x + y =) formed by the epitaxial growth technique on the (00) plane or a plane having an inclination of 10 ° or less
2) binary, or InxAsySbz, or InxGayAsz (x
+ Y + z = 2) having a magnetism-sensing part made of a ternary III-V group compound semiconductor film and an electrode part electrically connected to the magnetism-sensing part, wherein the electrode part is the compound semiconductor film. A contact layer made of a metal that makes ohmic contact, an intermediate layer formed on the contact layer and having a Young's modulus of at least twice that of Au, and a bonding layer made of Au formed on the intermediate layer. A magnetoelectric conversion element comprising: