JPH0471351B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetoelectric conversion element, such as a Hall element or a magnetoresistive element, that converts a magnetic field or magnetic flux into an electric signal. [Prior Art] Conventionally, a magnetoelectric transducer in which a magnetically sensitive semiconductor film made of a - group compound semiconductor is formed on a substrate having an organic insulating layer on the surface is, for example, InSb, which is commercially available for home appliances. Like a Hall element,
Although its electrical properties are excellent and it is highly sensitive, it has the problem of being difficult to mount using high-temperature processes around 260°C, such as solder reflow methods. [Problems to be Solved by the Invention] Therefore, an object of the present invention is to improve the heat resistance of a magnetically sensitive part made of a - group compound semiconductor film formed on a substrate having an organic insulating layer on the surface, and to improve solder reflow. Our goal is to provide highly reliable and highly sensitive magnetoelectric transducers that can completely withstand severe thermal shock during high-temperature mounting, using an extremely large-scale process that can be industrially mass-produced. [Means for Solving the Problems] In order to eliminate the drawbacks of the prior art as described above, the present inventors have investigated a wide range of structures of magnetoelectric transducer elements, and as a result, the present inventors have developed a semiconductor film that constitutes a magnetically sensitive part. We discovered that the heat resistance of the magnetoelectric transducer could be greatly improved by forming thin insulating layers of inorganic material on both the top and bottom surfaces of the magnetoelectric transducer, and created a highly reliable and high-performance magnetoelectric transducer. Completed the invention. That is, in the magnetoelectric conversion element of the present invention, the magnetically sensitive portion is formed on a substrate having an organic insulating layer on the surface,
The magnetically sensitive part is made of a - group compound semiconductor film with a thickness of 0.1 to 10 μm, and is characterized in that a thin insulating layer of inorganic material is formed on both sides of the magnetically sensitive part. [Example] An example of the structure of a Hall element, which is an example of the magnetoelectric conversion element of the present invention, is shown in FIGS. 1 and 2. Here, 1 is a substrate, and 2 is an organic insulating layer disposed on the substrate 1. 3 is a - group compound semiconductor film, and an insulating layer 2 is formed by forming thin inorganic insulating layers 4a and 4b on both sides of this semiconductor film 3.
Place it on top. 5 is a Hall element electrode consisting of a Cu layer 6, a Ni layer 7 and an Au layer 8;
A thin metal wire 9 is connected by wire bonding. The thin metal wire 9 is connected to a lead frame 10. 11 is an island formed on a portion of the lead frame 10 as shown in FIG.
The substrate 1 is bonded onto the island 11 with a die-bonding resin layer 12, and the whole is molded with epoxy resin or the like to form a mold case 13. 14 is a portion of the semiconductor film 3 that forms a magnetically sensitive portion. Here, all parts of the Hall element other than the electrode 5 of the Hall element are covered with a thin inorganic insulating layer 4a. Of course, the inorganic thin insulating layer 4a may be formed only on the magnetically sensitive portion 14. The magnetically sensitive part 14 referred to herein is a part that takes part in a substantial magnetoelectric conversion effect, and is only a semiconductor thin film part or a semiconductor thin film part on which auxiliary electrodes are formed to enhance the magnetoelectric conversion action. usually means. Furthermore, the Hall element is attached to the lead frame 10.
It can also be attached directly to a printed wiring board without going through it. In that case, the thin metal wire 9 is directly connected to the wiring formed on the printed wiring board. FIG. 3 shows a silicone resin layer 21 on the magnetically sensitive part 14.
is formed to protect the semiconductor film 3 from residual stress and the like. In FIG. 4, a magnetic focusing chip 31 is further placed on the silicone resin layer 21 to further increase the sensitivity of the element by magnetic amplification. In this case, it is preferable to use a soft magnetic material such as soft ferrite for the substrate 1. As described above, in the magnetoelectric transducer of the present invention, the inorganic thin insulating layer 4a is provided on both sides of the magnetically sensitive portion semiconductor film 3.
and 4b are formed, and the presence of these layers 4a and 4b greatly improves the heat resistance of the magnetoelectric transducer, making it possible to mount it by a high-temperature process such as a solder reflow method. The inorganic thin insulating layers 4a and 4b are made of Al ₂ O ₃ , SiO, SiO ₂ ,
It consists of an inorganic film such as a single or multiple thin films of Si ₃ N ₄ , AlN or a mixture thereof, and the thickness is
The thickness is 2 μm or less, preferably in the range of 500 Å to 10,000 Å. The presence of such insulating layers 4a and 4b dramatically improves the stability of the magnetoelectric transducer during high temperature processes. This is thought to be due to the fact that the thin inorganic insulating layers 4a and 4b prevent impurities from penetrating from the organic insulating layer 2 or the substrate 1, but also relieve thermal stress. By the inorganic thin insulating layers 4a and 4b,
Thermal stability in the high-temperature mounting process of magnetoelectric transducers at around 260°C has been significantly improved, and high-temperature mounting, which was impossible with conventional technology, has become possible. Furthermore, the inorganic thin insulating layers 4a and 4b may be formed from a plurality of layers. Instead of forming a thin inorganic insulating layer made only of Al ₂ O ₃ , for example, a 2000 Å thick SiO ₂ layer is formed on a 2000 Å thick Al ₂ O ₃ layer, and these two layers form an inorganic thin insulating layer on top. 4a
It is also preferable to improve the etching characteristics of such an insulating layer by configuring the insulating layer. Furthermore, the materials, compositions, layer structures, film thicknesses, etc. of both the insulating layers 4a and 4b do not necessarily have to be the same. In order to form the inorganic thin insulating layers 4a and 4b, various methods such as vapor deposition, sputtering, reactive sputtering, CVD, and molecular beam evaporation can be used. The semiconductor film 3 is preferably a high-mobility - group compound semiconductor film used as a normal magnetoelectric conversion element, such as InSb, InAs, INp, GaAs, GaSb, In _x , Sn _y ,
In _x , As _y , In _x P _y , Ga _x As _y , Ga _x Sb _y (x+y=2) In _x Sb _y Sn _z , In _x As _y P _z , In _x Ga _y Sb _z , In _x As _y Sb _z (x
+y+z=2) In _s Ga _t As _u P _v , In _s Ga _t As _u Sb _z , In _s Ga _t Sb _u P _v (s+
It is a - group binary, ternary, quaternary, etc. compound semiconductor such as t + u + v = 2), and has an electron mobility of 2000 to 80000 cm ² /V at room temperature.
sec, and the electron concentration is 5×10 ¹⁵ to 5×
A single crystal or polycrystalline thin film with a thickness of 0.1 to 10 μm within the range of 10 ¹⁸ cm ⁻³ is preferably used. Here, InSb and InAs exhibit high mobility and are therefore particularly preferably used. When forming the semiconductor film 3, LPE method,
Any conventional semiconductor film formation method such as CVD method, MOCVD method, vapor deposition method, MBE method, etc. may be used. Among these methods, the MBE method in particular yields a semiconductor film with good crystallinity and can easily form a semiconductor film with high electron mobility.Moreover, the thickness of the thin film is a factor that has a very large effect on the sensitivity of magnetoelectric conversion elements. It is particularly preferable because it has good controllability. Further, to form the semiconductor film 3, a method of thinning a polycrystalline or single-crystalline semiconductor wafer by a polishing method is also used. The organic insulating layer 2 is usually preferably used as an adhesive layer between the substrate 1 and the high-mobility semiconductor film 3, and is made of commonly used thermosetting epoxy resin, phenol epoxy resin, or TVB resin from Toshiba Ceramics. etc. are preferably used. The substrate 1 of the device of the present invention may be one used in general magnetoelectric transducers, such as a single crystal or polycrystalline ferrite substrate, a ceramic substrate such as alumina, a glass substrate, a quartz substrate, a silicon substrate, a sapphire substrate, semi-permanent or conductive
A GaAs substrate, an InP substrate, etc., a heat-resistant resin substrate, a strong substrate such as iron, permalloy, etc. are used. The electrode 5 of the Hall element is composed of three layers, for example, a Cu layer 6 as an ohmic contact layer, a Ni layer 7 as a reinforcing layer, and an Au layer 8 as a bonding layer. By forming this three-layered electrode, it is possible to form a highly reliable and strong wire bonding bond to the semiconductor thin film 3 on the organic insulating layer 2 by applying low-power ultrasonic waves and at low temperatures. become. In order to form the Au layer 8, the Ni layer 7, or the Cu layer 6, methods used for forming electrodes of ordinary semiconductor devices are used, such as electroless plating, electrolytic plating, lift-off method using vapor deposition or sputtering, etc. be able to. Although the thickness of each layer 6 to 8 is not particularly limited, it is usually 0.1 to 30 μm, preferably 0.3 to 10 μm. Further, it is also preferable that the electrode 5 of the Hall element be formed of two layers, the Cu layer 6 and the Au layer 8, with a thicker Cu layer 6. The resin for the mold 13 may be a resin used for molding general electronic components. Preferred examples include thermosetting resins, such as epoxy resins and phenol epoxy resins. The molding method may be a method used for ordinary electronic components, such as casting molding, transfer molding, placing a solid pellet on the element, heating and melting it, and then hardening and molding. I can do it. In the above, a Hall element has been explained as an example of the magnetoelectric conversion element of the present invention. The present invention can be effectively applied to all semiconductor magnetoelectric conversion elements that utilize the Hall effect or the magnetoresistive effect of semiconductors. Furthermore, semiconductor magnetoelectric conversion elements that combine these effects with other effects are also within the scope of the present invention. The present invention will be explained below using specific examples, but the present invention is not limited to these examples and can be effectively applied to all magnetoelectric transducers having the above-mentioned basic structure. . Example 1 An InAs film with a thickness of 1.2 μm, an electron mobility of 8500 cm ² /V.sec at room temperature, and an electron concentration of 3×10 ¹⁶ cm ^-3 was deposited on a mica substrate with a smooth surface using the MBE method (molecular The semiconductor film 3 was formed by a line epitaxy method. Next, a vacuum evaporation method is applied to this semiconductor film.
A thin inorganic insulating layer 4b was formed by forming a layer of Al ₂ O ₃ to a thickness of 4000 Å. Next, apply epoxy resin to the surface of this thin film to a thickness of 0.3 mm and a side of 50 mm.
An organic insulating layer 2 was formed by adhering it onto an alumina substrate 1 having a square shape. Then, the aforementioned mica was removed. Then use photoresist,
A photoresist film was formed on the surface of the magnetically sensitive part of the InAs thin film using a conventional method. Next, electroless plating was performed to deposit copper to a thickness of 0.3 μm only on the required areas. Further, in order to thicken the copper, electrolytic copper plating was performed to form a Cu layer 6 with a thickness of 2 μm. Next, using the above photoresist again, a 2 μm thick Ni layer 7 was formed only on the electrode portion by electrolytic plating. Furthermore, an Au layer 8 having a thickness of 2 μm was formed thereon by electrolytic plating.
Next, using the above photoresist again, the unnecessary InAs thin film and some unnecessary copper were removed by etching with an acidic solution of ferric chloride in hydrochloric acid using a photolithography method, and the magnetic sensitive part of the Hall element and the four Two electrode sections were formed. Next, a 2000 Å thick layer of Al ₂ O ₃ was formed thereon by vacuum evaporation to form a thin inorganic insulating layer 4a. Thereafter, unnecessary Al ₂ O ₃ on the electrode 5 of the Hall element was removed by etching with an ammonium fluoride solution using a photolithography technique. Next, this wafer was cut into rectangular Hall elements using a dicing cutter. Next, this was adhered onto the island 11 of the lead frame 10. Next, the electrode 5 of the Hall element and the lead frame 10 were bonded using a high-speed wire bonder using a thin Au wire 9, and then packaged with epoxy resin by transfer molding. The rate of change in input resistance of the Hall element manufactured in this way before and after testing under high temperature mounting conditions (5 minutes in a solder bath at 260° C.) was as shown in Table I below.

[Table] For each case, the numbers in Table 1 are
This is the average value of 100 elements. Also, the resistance measurement is 20
The test was conducted in the atmosphere at ℃, and the resistance value after the heat resistance test was measured after the test had been sufficiently cooled down. In Table 1, the semiconductor film 3 is manufactured using the conventional technique without providing the thin inorganic insulating layers 4a and 4b on both sides of the semiconductor film 3. Magnetically sensitive part semiconductor film 3
It can be seen that by sandwiching a thin Al ₂ O ₃ insulating layer, the heat resistance of the Hall element is dramatically improved. Example 2 A thin inorganic insulating layer 4b was formed in the same manner as in Example 1 on the InAs film on the same mica substrate as in Example 1. Next, an epoxy resin was applied to the surface of this thin film, and it was adhered onto a ferrite substrate 1 having a square shape with a thickness of 0.3 mm and a side of 50 mm to form an organic insulating layer 2. Then, the aforementioned mica was removed. Thereafter, in the same manner as in Example 1, the magnetically sensitive part 14 of the Hall element and the four electrode parts 5 were formed on the substrate 1. Next, in the same manner as in Example 1, a thin inorganic insulating layer 4a was formed on the wafer surface other than the electrode 5 of the Hall element. Thereafter, a ferrite chip 31 for magnetic convergence was adhered directly above the magnetically sensitive portion 14 using silicone resin. Next, this was assembled in the same manner as in Example 1. The rate of change in input resistance of the Hall element thus manufactured before and after the test under high temperature mounting conditions (in the atmosphere at 260° C. for 5 minutes) was as shown in Table 2 below.

〔Effect of the invention〕

As explained above, in the present invention, a -
We have improved the heat resistance of the magnetically sensitive part made of a group compound semiconductor film, and are manufacturing highly reliable and highly sensitive magnetoelectric transducers that can completely withstand severe thermal shock during high-temperature mounting such as solder reflow. It is possible to realize an extremely large-scale process that can be mass-produced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the magnetoelectric conversion element according to the present invention, FIG. 2 is a plan view of FIG. 1, FIG. 3 is a cross-sectional view showing another embodiment of the present invention, and FIG. FIG. 7 is a sectional view showing still another embodiment of the invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Organic insulating layer, 3...Semiconductor film,
4a, 4b...Inorganic thin insulating layer, 5...Hall element electrode, 6...Cu layer, 7...Ni layer, 8...Au layer, 9
... Wire bonded thin metal wire, 10... Lead frame, 11... Island, 12... Die bond resin layer, 13... Mold, 14... Magnetically sensitive part, 2
1...Silicone resin layer, 31...Magnetic focusing chip.

Claims (1)

[Scope of Claims] 1. A substrate having an organic insulating layer on its surface;
A magnetically sensitive part made of a - group compound semiconductor film of 0.1 to 10 μm and having alumina thin films on both sides, an ohmic contact layer formed in contact with the magnetically sensitive part, and an ohmic contact layer formed on the ohmic contact layer. A three-layer electrode comprising a metal reinforcing layer reinforcing the ohmic contact layer and a bonding layer formed on the metal reinforcing layer, and a wire bonding portion connected to the bonding layer of the three-layer electrode. A magnetoelectric conversion element characterized by: 2. forming a - group compound semiconductor thin film on a mica substrate by molecular beam epitaxy; forming a first alumina thin film on the compound semiconductor film; and forming a second alumina thin film on the first alumina thin film using an organic adhesive. a step of adhering onto a substrate; a step of removing the mica substrate; an ohmic contact layer in contact with the compound semiconductor thin film at a predetermined position of the compound semiconductor film; and a metal reinforcing layer for reinforcing the ohmic contact layer. a bonding layer on the metal reinforcing layer; forming a second alumina thin film on the entire surface of the compound semiconductor thin film other than the three-layer electrode; A method for manufacturing a magnetoelectric transducer, including the step of forming a wire bonding part in a bonding layer.