JPH0671105B2 - Method for manufacturing magnetoelectric conversion element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetoelectric conversion element such as a Hall element or a magnetoresistive effect element, which converts a magnetic field or magnetic flux into an electric signal.

"Prior Art" Conventionally, a compound semiconductor film is epitaxially grown on a semi-insulating substrate, and an electrode is formed on a part of the compound semiconductor film, a metal thin wire is thermocompression bonded to the electrode. As described above, the thermocompression bonding has good mass productivity and can be manufactured in a small size. However, when the semiconductor film is directly formed on the substrate as described above, it is difficult to obtain a thin film having good crystallinity as the semiconductor film, and selection of the material for the semiconductor film is limited.
It was not possible to obtain a high electron mobility and high sensitivity.

On the other hand, for example, a Hall element in which a resin layer is formed on a ferrite substrate, the III-V group compound semiconductor film formed on the concave surface of mica is transferred onto the resin layer, and the semiconductor film is used as a magnetic sensitive section is used. Are known. Although this Hall element has a characteristic of extremely high sensitivity, it was difficult to make it small in size and with good mass productivity. That is, the wire bonding used in the conventional transistor technology needs to apply a relatively large load at a relatively high speed, and the electrode must be annealed at a relatively high temperature.
Even if the wire bonding is applied to the Hall element to attach a lead wire, the resin layer under the semiconductor film may be softened at a temperature during thermocompression bonding or a temperature during annealing, and a large load may be applied. The semiconductor film is destroyed because it cannot be done.

For this reason, conventionally, the lead wires of the Hall element are connected by soldering. This soldering requires a comparatively large area, there is a limit to miniaturization, mass productivity is poor compared to wire bonding, and when the lead wire of the Hall element is soldered to the circuit after manufacturing. There is a problem that the soldered portion with the electrode is melted and the connection state is deteriorated.

[Means for Solving the Problems] According to the present invention, I having a thickness of 0.1 to 10 μm is formed on the surface of mica.
A II-V group compound semiconductor thin film is formed, an oxide insulating film is deposited on the surface of the semiconductor thin film, the semiconductor thin film is adhered to the substrate with the resin through the oxide insulating film, and then the mica is removed. Remove the metal material to form a contact layer of metal material only on the required portion of the surface of the semiconductor thin film, and form an intermediate layer of metal material on the contact layer. Young's modulus of the intermediate layer is 50% or more than the intermediate layer. A bonding layer of a small metal material is formed, the semiconductor thin film is etched into a predetermined pattern, and a metal thin wire is bonded to the bonding layer by applying ultrasonic waves.

Example As shown in FIG. 1A, the first example is a semiconductor film formed by vacuum-depositing a 1 nSb thin film having a thickness of 1 μm and an electron mobility of 30,000 cm ² / Vsec on a single crystal mica substrate 11 having a smooth surface. made. Next, as shown in FIG. 1B, an Al ₂ O ₃ film 13 having a thickness of 3,000 Å was formed as an oxide insulating film on the semiconductor film 12 by a vacuum deposition method. As shown in FIG. 1C, an epoxy resin was applied to the surface of the Al ₂ O ₃ thin film 13 to form a resin layer 14, and the resin layer 14 was adhered onto a square ferrite substrate 15 having a thickness of 0.3 mm and a side of 45 mm. Next, the mica substrate
After removing 11, the photoresist was used to form a photoresist coating 16 on the surface of the magnetic sensing portion of the InSb thin film 12 by a commonly used method, as shown in FIGS. 1D and 1E.

Next, electroless plating was performed to deposit copper only on a required portion having a thickness of 0.3 μm. In addition, to thicken copper,
Electrolytic copper plating was performed to form a contact layer 17 having a thickness of 4 μm as shown in FIG. 1F. Next, using the above photoresist again (as shown in FIGS. 2A and 2B, only the electrode portion has a thickness of 2
The intermediate layer 18 of the Ni layer of μm was formed by the electrolytic plating method.
Further thereon, a bonding layer 19 of Au layer having a thickness of 2 μm was formed by electrolytic plating as shown in FIG. 2C. Next, using the above-mentioned photoresist again, the unnecessary InSb thin film 14 and a part of the unnecessary contact layer 17 are removed by etching with a ferric chloride-hydrochloric acid solution by a photolithography method. As shown in, the magnetic sensitive parts 21 and 4 of the Hall element
Two electrodes 22 were formed. Thereafter, as shown in FIG. 2F, a ferrite chip 23 for magnetic focusing was adhered directly above the magnetic sensing part with a silicone resin. Next, this wafer was subjected to a dicing cutter and cut into rectangular Hall element chips of 1.1 × 1.1 mm. This was then glued onto the die of leadframe 24. Next, the electrode 22 of the pellet and the lead frame 24 were joined with the Au thin wire 25 using a high speed wire bonder.
The epoxy resin 26 was packaged by the transfer molding method.

The defective rate at the time of wire bonding of the Hall element thus manufactured according to the present invention is as shown in Table 1.

In Table 1, the Ni layer of the intermediate layer 18 is omitted and the Cu layer which is the contact layer 17 is set to 6 μm. Shows the case where a 2 μm Au layer is directly formed on the InSb thin film. Is In
An intermediate layer 18 of Ni layer of 6 μm is put on Sb, and 2 μm on it.
Forming a bonding layer 19 of Au layer of
This is the case when the layer also serves as the contact layer 17. In each case, the element temperature during bonding is 100 ° C. The ultrasonic energy is also chosen to minimize the defect rate in each case. The number of samples is 2,000 each. The defect rate is a value per junction. Those having a tensile strength of 2 g or less between the electrode and the Au thin wire 25 were regarded as defective. Regarding the causes of the defects in each case, is that the strength of the bond between the Au wire 25 and the electrode 22 is insufficient, is the strength of the bond between the Au wire 25 and the electrode 22 is insufficient, and the semiconductor film 12 and Al ₂ O _{3 are} The peeling between the thin films 13 was almost the same. For most of the semiconductor film 12 and Al ₂ O ₃ thin film 1
It was peeling between 3 times. In most of the cases, there was peeling between the Ni layer and the semiconductor film 12. From the above results, the following two points can be seen.

When the intermediate layer 18 is provided, the defective rate is drastically reduced as compared with the case where the intermediate layer 18 is not provided.

Even if the intermediate layer 18 is provided, omitting the contact layer 17 increases the defect rate.

Further, due to a cause of failure, ultrasonic energy may be concentrated between the semiconductor film 12 and the Al ₂ O ₃ thin film 13 when the intermediate layer 18 is removed, and may be concentrated between the intermediate layer 18 and the semiconductor film 12 when the contact layer 17 is omitted. Recognize.

Second example 1.2 m thick electron mobility on mica substrate with smooth surface 10.
MBE method (molecular beam epitaxy method) with InAs film of 000 cm ² / Vsec
Formed by. Next, a 1,000 Å thin SiO ₂ film was formed on the semiconductor film by a vacuum evaporation method. This SiO ₂ thin film was bonded onto a ferrite substrate having a thickness of 0.3 mm and a square of 45 mm on each side. After this, the Hall element was assembled in exactly the same manner as in the first example. The defective rate of the Hall element thus produced at the time of wire bonding is as shown in Table 2.

In Table 2, those to which the present invention is applied, the Ni layer as the intermediate layer is peeled off, and the Cu layer as the contact layer is 6 μm.
This is the case. Shows the case where a 2 μm Au layer is formed directly on the InAs thin film. Is an intermediate layer with a 6 μm Ni layer formed on the InAs thin film and an Au layer 2 μm formed on it.
This is the case where the Ni layer also serves as the contact layer. In each case, the element temperature during bonding is 100 ° C. The ultrasonic energy is also chosen to minimize the defect rate in each case. The number of samples is 2,000 each, and the defect rate is a value per joint. In addition, if the tensile strength between the electrode and the Au thin wire was 2 g or less, it was determined to be defective. Regarding the causes of defects in each case, is that the strength of the Au wire-electrode bond is insufficient, and that of the Au wire-electrode strength is insufficient and the semiconductor film is
The peeling between the SiO ₂ thin films was almost the same. In most cases, the peeling was between the semiconductor film and the SiO ₂ thin film. In most of the cases, there was peeling between the Ni layer and the InSb film. The following two points can be seen from the above results.

When there is an intermediate layer, compared to when there is no intermediate layer,
The defective rate is drastically reduced.

Even if there is an intermediate layer, omitting the contact layer increases the defect rate.

Further, it can be seen from the cause of the defects that ultrasonic energy is concentrated between the semiconductor film and the SiO ₂ thin film when the intermediate layer is removed, and is concentrated in the intermediate layer and the semiconductor film when the contact layer is omitted.

As the bonding layer 19, Au, Au-Ge alloy, Pt, Al, Al
A metal having good wire bondability such as —Si alloy, Ag, Cu or alloys thereof is preferable. The metal used for this layer 19 may be any as long as it has a good wire bonding property,
Au is particularly preferable. This layer 19 has electrodes 22 and Au, Al, Al-Si
This ensures a strong and highly reliable connection with the thin wire 25 such as an alloy. For forming the bonding layer 19, a method used for forming electrodes of a usual semiconductor element such as an electroless plating method, an electrolytic plating method, a lift-off method by vapor deposition or sputtering is used. The layer thickness of the bonding layer 19 is not particularly limited, but is usually 0.1 to 30 μm, preferably 0.1 to 10 μm.
m is good. In order to improve the reliability of bonding, it is preferable that the bonding layer 19 is thicker, but the increase in the internal stress accompanying the increase in the layer thickness reduces the adhesion at the layer interface,
The upper limit is determined by the decrease in etching cutoff and the increase in price when a precious metal such as Ag, Au, Pt is used.

When using a metal that is easily oxidized such as Cu and Al for the bonding layer 19, a very thin layer of a metal that is hard to be oxidized such as Au and Ag is formed on the surface, and the reliability of bonding is further improved by forming a plurality of bonding layers 19. Is improved. FIG. 3A shows a sectional shape of this electrode 22. In FIG. 3A, the intermediate layer 18
Although a bonding property such as Cu or Al is good on the upper part, a bonding body layer 26 of a metal that easily rusts is formed, and a thin metal layer 27 that has good bonding property such as Au or Ag and is hard to rust is formed on the bonding body layer 26. The bonding layer 19 is formed by the bonding body layer 26 and the thin metal layer 27. When using Al for the bonding body layer 26, care must be taken in forming the thin metal layer 27. This is because Al is instantly oxidized in air. It is preferable to continuously form the bonding body layer 26 and the thin metal layer 27 in a vacuum or a reducing atmosphere.

Further, even when a metal such as Ag, Pt or the like which is hard to be oxidized is used for the bonding layer 19, if Au, which has the best bonding property, is formed very thin on the surface, the reliability is further increased. The cross-sectional structure is shown in FIG. 3B. On the intermediate layer 19, a metal layer 28 of Ag, Pt or the like other than Au, which has good bonding properties and is resistant to rust, is formed, and a thin layer 29 of Au is formed on the metal layer 28.

The intermediate layer 18 is made of a metal layer that is harder than the bonding layer 19 made of Ni, Fe, Ti, W, Cu, etc., and is formed by electroless plating.
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 18 mainly consists of the following three points.

(A) A force acting in the direction perpendicular to the surface of the electrode 22 during bonding is concentrated on the intermediate layer 18, and this force is applied to the semiconductor film.
12 or the interface between the semiconductor film 12 and the contact layer 17 is prevented.

(B) The load during bonding is distributed over the entire electrode 22,
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 18 and the bonding layer 19 to prevent the ultrasonic waves from adversely affecting the semiconductor film 12 or the interface thereof. At the same time, ultrasonic energy is concentrated on the bonding layer 19 to ensure reliable bonding with low power ultrasonic energy.

For the purpose of (a) or (b), the intermediate layer 18 is preferably a metal having a larger Young's modulus and a larger elastic limit than the bonding layer 19 or the contact layer 17. When the effect of (c) is emphasized, it is preferable to use a metal that makes the sound velocity in the bonding layer 19 or the contact layer 17 and the sound velocity in the intermediate layer 18 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 19 and the intermediate layer 18 or the interface between the contact layer 17 and the intermediate layer 18. Ni, Cu, and W are preferable examples of metals that satisfy the above conditions. It is preferable to use Au for the bonding layer 19 and the contact layer 17, but the preferable metal for the intermediate layer 18 has a Young's modulus more than twice that of Au, and the sound velocity is about twice that of Au. Become. Bonding layer
It is also preferable to use Cu as the intermediate layer 18 when 19 is Au.

The thickness of the intermediate layer 18 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 18, 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 cut becomes worse. So there is an upper limit. If the intermediate layer 18 is made too thin, its mechanical strength becomes small, and ultrasonic waves easily pass through,
There is no point in providing the intermediate layer 18.

In order to effectively perform the ultrasonic wave reflecting action, it is preferable that the intermediate layer 18 is composed of a plurality of metal layers. By combining metals with greatly different sonic velocities in adjacent layers, each time an ultrasonic wave passes through the interface, it is reflected according to the degree of mismatch in the sonic velocities of the metals on both sides of the interface, and its amplitude is greatly attenuated. . An example of this configuration is shown in FIG. 3C. In FIG. 3C, the bonding layer 19 is composed of an Au layer, and a Ni layer 31, an Au layer 32, and a Ni layer are formed under the bonding layer 19.
Layers 33 are sequentially laminated, and these three layers 31, 32 and 33 are intermediate layers.
Forming 18. Ultrasound is layer 18 and layer 31, layer 31 and layer 32, layer 32
And the layers 33 and 16 and the total of four interfaces of the layers 16 and 16 are reflected.

The intermediate layer 18 only needs to have a difference of 50% or more in the overall characteristics of Young's modulus (hardness), elastic limit, and difference in sound velocity with respect to the bonding layer 19.

The contact layer 17 is Cu, Au, Al, Al-Si alloy, Au-Ge alloy, A
It forms a good ohmic junction with a compound semiconductor such as g, Pt or an alloy thereof, has a coefficient of thermal expansion similar to that of the compound semiconductor, and is composed of a metal layer which is as soft as the compound semiconductor. The contact layer 17 secures good ohmic contact between the semiconductor film 12 and the electrode 22 and relaxes thermal stress between the semiconductor film 12 and the electrode 22. To form the contact layer 17, 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 0.1 to 50 μm, more preferably 0.1 to 10 μm. In order to improve the reliability of bonding, it is preferable that the contact layer 17 is thicker, but as the layer thickness increases, the internal stress increases, the adhesion at the layer interface decreases, and the etching cutoff decreases.
When using precious metals such as g, Au and Pt, there is an upper limit due to price increase.

When using a semiconductor that is difficult to form ohmic contacts such as GuAs, InP, or Au, Pt, Ag in the contact layer 17
If you do not want to use a large amount of expensive metal such as
After forming an ohmic contact with the intermediate layer 12, a metal softer than the intermediate layer 18 or a metal having a coefficient of thermal expansion closer to that of the semiconductor film 12 than that of the intermediate layer 18 is formed thereon to form two layers. The contact layer 17 is formed. An example of this is shown in FIGS. 3D and 3E. In FIG. 3D, when the semiconductor film 12 is a GaAs layer,
The Au—Ge alloy layer 34 is formed on the semiconductor film 12. The Ge ratio of this alloy layer 34 is 0.1 to 10% by weight.
This ensures an ohmic contact between the GaAs semiconductor film 12 and the electrode 22. A Cu layer 35 is formed on the Au-Ge alloy layer 34, and the contact layers 17 are formed by these two layers 34 and 35. In FIG. 3E, when an InAsxSb _1-x (0 ≧ x ≧ 1) film is formed as the semiconductor film 12, the Au layer 36 is formed on the semiconductor film 12, and the Cu layer 37 is formed on the Au layer 36. These two layers 36,3
The contact layer 17 is formed at 7. The contact layer 17 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 17 is not particularly specified, but is preferably 0.1 to 10 μm. In order to improve the reliability of bonding, the thicker the contact layer 17, the more preferable it is, but as the layer thickness increases, the internal stress increases, the adhesion at the layer interface decreases, the etching cut decreases, Au, When using precious metals such as Ag and Pt, the upper limit is determined by the price increase.

The contact layer 17 may be omitted when the metal used for the intermediate layer 18 forms a good ohmic contact with the semiconductor film 12 and has good adhesion with the semiconductor film 12. At this time, the metal used for the intermediate layer 18 has a coefficient of thermal expansion close to that of the semiconductor film 12 and a Young's modulus not so large as that of the semiconductor film 12, but preferably a Young's modulus larger than that of the bonding layer 19. . An example of this configuration is shown in FIG. 3F. In FIG. 3F, when InAsxSb _1-x (0 ≦ x ≦ 1) is used as the semiconductor layer 12, the intermediate layer 18 is directly formed on the semiconductor layer 12.
A Cu layer is formed, and an Au layer is formed thereon as a bonding layer 19.

The substrate 15 of the device of the present invention may be one that is used in a general magnetoelectric conversion device, and is a single crystal or sintered ferrite substrate, a ceramic substrate, a glass substrate, a silicon substrate, a sapphire substrate, a semi-insulating GaAs substrate, An InP substrate or the like, a heat-resistant resin substrate, a substrate of a ferromagnetic material such as iron or permalloy, the surface of which is subjected to an insulation treatment is used.

The insulating layer 13 on the surface of the substrate 15 is preferably an inorganic insulating layer, particularly an oxide or nitride insulating layer, or a resin insulating layer. The oxide or nitride insulating layer is usually used for insulating treatment coating on the surface of the substrate, and alumina, SiO ₂ , silicon nitride, or a mixture thereof or a multilayer insulating layer is preferably used. Moreover, the thickness of the inorganic insulating layer is usually 10 μm or less, and vapor deposition, sputtering,
It is formed by a method such as chemical vapor deposition (CVD) or molecular beam deposition. The resin layer 14 is usually preferably used as an adhesive layer between the substrate 15 and the high mobility semiconductor film 12, and a thermosetting epoxy resin, a phenol epoxy resin or the like which is usually used is used. Also, the insulator layers 13 and 14
The thickness is not particularly limited, but is preferably 60 μm or less.

The magnetic field sensitive semiconductor film 12 is preferably a high-mobility semiconductor thin film used as an ordinary magnetoelectric conversion element, such as InSb, GaAs, InS.
b, GaAs, InAs, InxSbySnz InxAsyPz, InxGaySbz (x + y +
z = 2), InsGatAsuPv (S + t + u + v = 2), etc. III
A group V binary, ternary, or quaternary intermetallic compound semiconductor having an electron mobility in the range of 2,000 to 80,000 cm ² / Vsec, and a single crystal or polycrystal thin film is used.

The electrode 22 of the magnetoelectric conversion element is electrically coupled to a conductor such as a wiring pattern formed on the lead frame 24 or the printed circuit board by a fine wire 25 normally used for wire bonding of Au, Al, Al-Si alloy or the like. . When the lead frame is connected to the lead frame 24, the material of the lead frame may be Cu, phosphor bronze, or the like that is used for the leads of ordinary semiconductor elements. Also, in order to improve the bondability, Au, A
It is also preferable to form a thin layer of a metal having good bonding property such as g.

In the case of wiring on the printed circuit board, the printed circuit board used 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 26 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.

The Hall element has been described above as an example of the magnetoelectric conversion element of the present invention, but other elements such as a magnetoresistive effect element also differ from the Hall element in the electrode shape, the number of terminal electrodes, and the magnetic sensing part pattern. However, the electrodes are formed in exactly the same manner as the Hall element, and the basic structure is the same.

[Advantages of the Invention] As described above, according to the present invention, a compound semiconductor film is formed on a mica substrate, an oxide insulating film is formed on the surface thereof, and the semiconductor film is formed of a resin layer through the insulating film. The resin layer is adhered to the substrate, the contact layer, the intermediate layer, and the bonding layer are sequentially formed on a part of the semiconductor film, and the metal wire is directly bonded on the bonding layer by applying ultrasonic waves. Even if it exists, a thin metal wire can be firmly connected, no peeling occurs between the semiconductor film and the oxide insulating film, and high sensitivity, high moisture resistance, and high reliability are obtained. To be

[Brief description of drawings]

FIG. 1 shows a process of an embodiment of the present invention, A to D and F are sectional views, E is a plan view, and FIG. 2 shows a continuation of the process of FIG.
A, C, D and F are sectional views, B and E are plan views, and FIG. 3 is an electrode.
FIG. 23 is a cross-sectional view showing a part of various modifications of 22.

Claims (1)

[Claims] 1. A mica surface having a thickness of 0.1-10 μm III-
A step of forming a group V compound semiconductor thin film, a step of depositing an oxide insulating film on the surface of the semiconductor thin film, and a resin layer for insulating the III-V compound semiconductor thin film through the oxide insulating film. Adhere to the substrate with, then,
A step of removing the mica, a step of forming a contact layer of a metal material only on a required portion of the surface of the III-V compound semiconductor thin film on the substrate, and an intermediate layer of the metal material on the contact layer. A step of forming, a step of forming a bonding layer of a metal material having a Young's modulus of 50% or more smaller than that of the intermediate layer on the intermediate layer, a step of patterning the group III-V compound semiconductor thin film by etching, an ultrasonic wave And a step of bonding a thin metal wire to the above-mentioned bonding layer by applying a voltage, and a method for manufacturing a magnetoelectric conversion element.