JP2752638B2 - Magnetoelectric conversion element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-electric conversion element, and more particularly to a magneto-electric conversion element in which a ferromagnetic material is buried on the back surface of a substrate to provide a magnetic field focusing effect and high sensitivity. It is.

[Conventional technology]

Conventionally, in a GaAs Hall element or the like, a configuration example as shown in FIGS. 5 and 6 has been adopted in order to increase the sensitivity of the Hall element.

In FIG. 5, the substrate 1 on which the Hall element 3 is formed is shown.
A ferromagnetic material 2 such as ferrite is bonded to the lower portion of the lead frame 6A using an adhesive 7, and the ferromagnetic material 2 is bonded to the lead frame 6A using the adhesive 7. On the other hand, the bonding wires 8 from the input / output electrodes 4 on the Hall element 3
Extends and is joined to the lead frames 6A and 6B. Such an entire device is sealed with an epoxy resin 9.

In FIG. 6, an epoxy resin containing a ferromagnetic material such as ferrite is applied to a lower portion of the substrate 1 on which the Hall element 3 is formed to form a ferromagnetic layer 10. The ferromagnetic layer 10 and the lead frame 6A are joined via an adhesive 7.

On the other hand, a bonding wire 8 extends from the electrode 4 on the Hall element 3 and is connected to the lead frames 6A and 6B.
The entire element thus formed is sealed with the epoxy resin 9.

[Problems to be Solved by the Invention] However, in the configuration examples shown in FIGS. 5 and 6, the distance between the magnetically sensitive portion of the Hall element 3 and the ferromagnetic layer 10 is limited to the thickness of the substrate 1 (200 μm- (500 μm).

As a result, there is a problem that the sensitivity and the thickness of the Hall element 3 cannot be reduced. Further, the Hall element 3
The height between the upper electrode 4 and the surfaces of the lead frames 6A and 6B becomes extremely high, which causes a problem of lowering the yield and reliability of bonding at the time of wire bonding, and is also a problem in mass production technology. .

Therefore, an object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a magnetoelectric conversion element which is highly sensitive, thin, has a high yield, and is highly reliable.

[Means for Solving the Problems] In order to achieve such an object, a magnetoelectric conversion element according to the present invention includes a substrate made of a III-V compound semiconductor,
A magnetic sensing portion formed on the surface of the substrate, a concave portion provided on the back surface of the substrate at a position corresponding to the magnetic sensitive portion, a ferromagnetic material embedded in the concave portion, and a machine for the substrate. A reinforcing layer formed only on the back surface of the substrate to cover the entire back surface thereof, a lead frame on which the substrate is adhered via the reinforcing layer, and the lead frame. Except for the electrical external connection of the substrate,
And a resin sealing portion covering the entirety of the magnetic sensing portion, the reinforcing layer, and the lead frame.

[Operation] According to the present invention, since the ferromagnetic material such as ferrite is buried immediately below the magnetically sensitive portion inside the substrate or sandwiched by the ferromagnetic layer of the Hall element, high sensitivity can be achieved by the magnetic field focusing effect. This can be realized and the element can be made thinner. When the back surface is processed into a concave shape using a substrate made of a very brittle single crystal material, such as a III-V compound semiconductor such as GaAs, because the entire back surface of the substrate including the recess is covered with the reinforcing layer. Substrate cracking and dicing
Occurrence of cracks in the element pellets in the die bonding step can be avoided, and the yield can be significantly improved.

Further, according to the present invention, since the size and depth of the hole of the concave portion can be appropriately set by embedding a ferromagnetic material which brings about a magnetic field focusing effect, the degree of freedom in element and sensitivity design can be increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The magnetoelectric conversion element of the present invention is generally a Hall element having a magnetically sensitive part formed by an ion implantation method, a Hall element having a magnetically sensitive part formed by an epitaxial growth method, a Hall element having a magnetically sensitive part formed by a vapor deposition method, and a magnetoresistive effect element. However, in this embodiment, a Hall element will be described as an example.

1 (A) and 1 (B) are a plan view and a sectional view, respectively, showing an embodiment of the present invention.

In FIG. 1, a Hall element 3 is formed on the surface of a substrate 1, and an electrode 4 is formed on the Hall element 3. The back surface of the substrate 1 immediately below the magnetic sensing portion of the Hall element is processed into a concave shape (see FIG. 1 (B)). Substrate 1 is GaA
Materials such as ceramics, glass, and resin may be used as well as s, InP, and Si. A ferromagnetic material 2 having a high magnetic permeability is embedded in a concave portion on the back surface of the substrate 1. Here, the ferromagnetic material 2 generally has a low residual magnetic flux density.
Anything may be used, but ferrite and permalloy are particularly preferred. The shape of the high-permeability ferromagnetic material 2 embedded in the concave portion of the substrate 1 is preferably a prism or a column.

Further, it is preferable that the ferromagnetic material is powdered in advance in the structure as shown in the cross-sectional view of FIG.

Regarding the position of the concave portion, it is preferable that the center of the magneto-sensitive portion of the Hall element 3 coincides with the center of the concave portion. The shape of the concave portion may be a hole, a groove, or the like. It is desirable that the size of the magnetic sensing part of the Hall element 3 having a large concave portion is good and that the concave portion be as deep as possible for high sensitivity. However, depending on the use conditions, it is preferable to have an appropriate depth to obtain a desired sensitivity. .

A reinforcing layer 5 is provided on the back surface of the substrate 1 in which the ferromagnetic material is embedded. The reinforcing layer 5 is bonded to the lead frame 6A via an adhesive 7.

The reinforcing layer 5 covering the entire back surface of the substrate 1 having the concave portion may be used as long as it can be used to reinforce the substrate 1.
Materials include epoxy resin, heat-resistant resin adhesive,
Polyimide or glass is preferred. The thickness of the reinforcing layer 5 may be any thickness required to maintain its strength,
It is usually preferable that the thickness be 10 μm or more, but 20 μm to 10
More preferably, it is in the range of 0 μm. This reinforcing layer 5
By mixing a ferromagnetic material into the Hall element 3, the sensitivity of the Hall element 3 can be further increased.

Further, as shown in FIG. 3, a buried layer of the concave portion and a reinforcing layer for reinforcing the substrate 1 may be integrally formed using a resin or glass mixed with a ferromagnetic material.

Further, as shown in FIG. 4, a ferromagnetic layer 11 made of silicon resin or the like mixed with a powder of a ferromagnetic material is formed on the upper surface of the magneto-sensitive part in order to increase the sensitivity of the Hall element 3. By forming a ferromagnetic layer 10 made of an epoxy resin mixed with a ferromagnetic material powder on the back of
May be sandwiched between upper and lower ferromagnetic layers.

Next, a prototype example corresponding to the configuration example shown in FIGS. 1 and 4 is shown below.

Prototype Example 1 50mm in diameter and 300μm in thickness with the structure shown in Fig.1.
130+ keV Si ⁺ on a non-doped GaAs semi-insulating substrate 1
After ion implantation under the condition of 4 × 10 ¹² cm ⁻² , annealing is performed, and then the Hall element 3 is formed by mesa etching.
(A width of 120 μm) was formed.

Subsequently, a number of Hall elements 3 were formed by forming the input / output ohmic electrodes 4 in a layered structure of Au / Ni / Au-Ge.

Using a photoresist as a mask, a concave portion having a hole diameter of 120 μm and a depth of 200 μm was formed on the back surface of the GaAs substrate 1 on which the Hall element 3 was formed at a position corresponding to the magnetically sensitive portion of the Hall element 3. Next, Mn-Zn-based soft ferrite 2 previously formed into a cylindrical shape was embedded in the concave portion, and an epoxy resin was applied to the entire back surface of the substrate 1 so as to have a thickness of about 50 μm. The epoxy resin was cured at 200 ° C. for 3 hours to form an epoxy resin layer as the reinforcing layer 5.

Thereafter, dicing was performed to cut the element of the present invention into individual pellets.

Then, the pellet is die-bonded to the lead frame 6A, and the lead frames 6A, 6B and the electrode 4 are wire-bonded, and then sealed with an epoxy resin 9 by a transfer molding method as shown in FIG. A device was created.

Apply the output voltage of the prototype device and the conventional device to the applied voltage 3.
Table 1 shows the results measured under the conditions of V and an applied magnetic field of 500G.

As shown in Table 1, the output voltage of the device of this prototype is 1.6 times larger than that of the device of the prior art.

Furthermore, the results obtained by calculating the defect rate of the element of the prototype and the defect rate of the element of the conventional example for each of 1000 elements are shown in FIG.
It is shown in the table.

As is clear from Table 2, the failure rate of this prototype is much lower than that of the conventional example, indicating that the yield is very good. The reason for this is that in the case of the device of this prototype,
This is because the presence of the reinforcing layer eliminates substrate cracking in the dicing and die bonding steps. In the case where an embedded structure was provided on the back surface of the substrate and no reinforcing layer was provided, no element could be produced due to substrate cracking.

Prototype Examples 2 to 3 As shown in FIG. 4, an undoped GaAs substrate 1 having a thickness of 300 μm and having a Hall element 3 formed on the surface thereof was subjected to ion implantation and electrode formation steps in the same manner as in Prototype Example 1. On the back surface, a dry etching method using a photoresist as a mask has a hole diameter of 120 μm, the same as
A 00 μm concave portion was formed at a position corresponding to the magneto-sensitive portion of the Hall element formed on the surface of the substrate. Next, an epoxy resin mixed with ferrite powder (average particle size of 3 to 4 μm) is injected into the concave portion, and the entire back surface of the substrate 1 is coated with the epoxy resin, and the epoxy resin is cured at 200 ° C. for 3 hours. Then, the ferromagnetic layer 10 as a buried layer of the concave portion and the reinforcing layer having a thickness of about 50 μm were integrally formed at the same time.

Thereafter, dicing was performed to cut the Hall elements into individual pellets. Thus, an element pellet having the structure shown in FIG. 3 was prepared.

Next, the pellet is die-bonded to the lead frame 6A, and the electrode 4 and the lead frames 6A and 6B are wire-bonded, and then the ferromagnetic layer 11 made of silicon resin mixed with ferrite powder is used as the magnetically sensitive portion. (See FIG. 4) and cured at 150 ° C. for 8 hours to produce a sandwich structure in which the Hall element 3 was sandwiched between upper and lower ferromagnetic layers.

Subsequently, the device was sealed with an epoxy resin 9 by a transfer molding method, thereby producing an element of the present invention shown in FIG. 4 (Trial Production Example 2).

Table 3 shows the results of measuring the output voltage of the device of the prototype example 2 and the output voltage of the device of the conventional example under the conditions of an applied voltage of 3 V and an applied magnetic field of 500 G. In the same table, as Trial Production Example 3, an element having a structure shown in FIG. 3 was prepared by trialling a silicon resin alone which was dropped on the surface of the magnetic sensing portion of the Hall element and cured, and its output voltage was measured.

As shown in Table 3, the output voltage of the device of this prototype example was 3.4 times that of the device of the conventional example. Prototype example 3
As a result, an output voltage 1.5 times that of the conventional example was obtained.

Further, the improvement of the yield in the dicing and die bonding steps due to the presence of the reinforcing layer was the same as that of the prototype 1 in both the prototype and the comparative example.

[Effects of the Invention] As described above, according to the present invention, since a ferromagnetic material such as ferrite is buried immediately below a magnetically sensitive portion inside a substrate or sandwiched by a ferromagnetic layer of a Hall element, a magnetic field , The sensitivity can be increased and the element can be made thinner. Since the entire back surface of the substrate including the concave portion is covered with the reinforcing layer, usually, a III-V
It is possible to avoid the occurrence of substrate cracking, dicing, and element pellet cracking in the die bonding process that occur when the back surface is processed into a concave shape using a substrate made of a very brittle single crystal material such as a group III compound semiconductor. And yield can be greatly improved.

Furthermore, according to the present invention, since the size and depth of the hole of the concave portion can be appropriately set by embedding a ferromagnetic material that brings about a magnetic field focusing effect, the degree of freedom in the sensitivity design of the element can be increased.

Furthermore, since the height from the lead frame surface to the electrode surface is reduced, the adjustment of the wire loop at the time of wire bonding is facilitated, the yield of wire bonding is greatly improved, and the reliability of the element is improved.

[Brief description of the drawings]

1 (A) and 1 (B) are a plan view and a cross-sectional view, respectively, of the device of the present invention. FIGS. 2 to 4 are cross-sectional views of the device of the present invention. It is sectional drawing of the conventional element. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Ferromagnetic material, 3 ... Hall element, 4 ... Electrode, 5 ... Reinforcement layer, 6A, 6B ... Lead frame, 7 ... Adhesive, 8 ... Bonding wire, 9 ... Epoxy resin, 10,1
1 ... ferromagnetic layer.

Claims (1)

(57) [Claims] A substrate made of a group III-V compound semiconductor; a magnetically sensitive portion formed on a surface of the substrate; a concave portion provided on a back surface of the substrate at a position corresponding to the magnetically sensitive portion; A material having ferromagnetism embedded in the concave portion, a reinforcing layer formed over the entire back surface only on the back surface of the substrate to reinforce the mechanical strength of the substrate, and A lead frame on which the substrate is adhered, and a resin sealing portion covering the entirety of the substrate, the magneto-sensitive portion, the reinforcing layer, and the lead frame except for an electrical external connection portion of the lead frame. A magnetoelectric conversion element, comprising: