DE2343539A1 - THIN FILM THROTTLE - Google Patents

Description

Patent attorneys

D! Pf .-! Ng.R. BEETZ sen, Dlpl.-lng.! <. LAMPRcCHT

Dr.-lng.R.BiiETZ je • Manch · »2 2, Steinsdörfctr. 10

HITACHI, LTD., Tokyo (Japan)

Thin film choke

The invention relates to the construction of thin-film chokes as components of integrated semiconductor circuits.

With the advancement of semiconductor integrated circuit technology became the unit area of active components such as transistors and diodes, and passive components such as resistors, and the unit cost of these components were significantly reduced. However, a choke (inductor) takes one on a silicon base with increasing inductance

^ 09814/0830

81- (Item 31 134) -Tp-r (8)

2343b39

larger area, and its cost also grows due to the A tendency towards increased difficulty in attaching them to integrated circuits.

For example, a choke made by depositing a conductive film with a spiral pattern on a sapphire backing is in "PROCEEDINGS OF THE IEEE ", Volume 59, No. 10 (October 1971), pages 1506 to 1510. According to this example, one can use a

2
Area of about 1 mm only achieve an inductance of 40 nH. A reactor obtained by winding a coil around an annular ferrite core is often used when a large inductance is required. However, such a reactor has not been satisfactory for use in integrated circuits because it has a large outer diameter on the order of at least 2 to 3 mm and is expensive.

The invention is therefore based on the object of a new thin-film choke specify which is of the smallest possible dimensions and has a large inductance. In addition, this thin film choke should be designed so that their inductance can be kept constant regardless of the current strength values and despite use of a ferromagnetic material shows a satisfactory frequency behavior. Finally, it is desirable that this thin film reactor is not very expensive and easy to manufacture.

The invention, with which this object is achieved, is a thin-film choke, characterized in that it consists of a current

UG98U / 0830

ORIGINAL INSPECTED

conductor and a uniaxial anisotropic ferromagnetic one surrounding it There is a film whose hard axis is perpendicular to the direction of current flow through the conductor.

Developments and alternative solutions of the invention as well as their advantages are illustrated using the exemplary embodiments illustrated in the drawing explained in more detail; show in it:

Fig. 1 is a schematic perspective view for illustration the basic principle of a thin film choke according to the invention,

FIG. 2 is a diagram of the specific permeability curve and the hysteresis curve obtained with the thin-film choke according to FIG of the invention were obtained,

Fig. 3 is a schematic perspective view of a practical Embodiment of the invention,

FIGS. 4 a to 4 d show the successive manufacturing steps the thin-film choke according to FIG. 3,

Fig. 5 ·. a schematic cross section of another embodiment the invention,

FIG. 6 is a schematic perspective view of that shown in FIG. 5 Thin film choke, and

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2 3 U 3 5 3 9

7 shows a schematic sectional view of a further exemplary embodiment the invention".

According to FIG. 1, which illustrates the basic principle of the thin-film choke according to the invention, the thin-film choke has a current conductor 1 and a uniaxial anisotropic ferromagnetic film 2 according to the invention surrounds this uniaxial anisotropic ferromagnetic film Film 2 shows the conductor 1, and its "hard axis" (axis of difficult magnetization) is perpendicular to the direction of current flow through the conductor 1. Thus, the magnetic field generated by the current flowing through the conductor 1 surrounds the conductor 1, and the direction of the Magnetization of the ferromagnetic film 2 coincides with its hard axis.

The ferromagnetic film 2 surrounding the conductor 1 can be formed by plating the conductor 1 with a binary alloy of iron and Nikkei with the designation "Permalloy" are formed, as will be explained in more detail. The uniaxial anisotropy of the ferromagnetic film 2 can be achieved by applying a strong magnetic field to the alloy during the plating process or by a tempering treatment of the plated alloy in a strong magnetic field. This is e.g. B. in "The Journal of the Institute of Electronic Communication Engineers of Japan ", Volume 51, No. 6 (June 1968), pages 723 to 732. The hard axis occurs in one to The direction of application of the strong magnetic field during the plating or tempering process is perpendicular.

4/0830

The inductance of the thin-film choke obtained in this way should now be in accordance with of the invention will be explained. First, it is assumed that in the thin film choke structure shown in Fig. La and b, the width and the Thickness of the conductor 1 and t is the thickness of the ferromagnetic film 2. If the relationship between a and t is generally a 5 ^ t, is the magnetic flux density in the ferromagnetic film 2 is substantially uniform in the direction of the thickness of the ferromagnetic film 2, when current flows through the conductor 1 in the direction indicated by the arrow χ in FIG.

Therefore, the average _{magnetic path I 1n is given} by the following equation:

l _m = 2 (a + b + 2t) ... (1)

Assuming now that 1 _{χ is} the length of the ferromagnetic film 2 in the current flow direction χ, then the reluctance Rc of the ferromagnetic film 2 surrounding the conductor 1 can be expressed by the following equation:

t, 1 ¹ ITi 2 (a + b + 2t) , *

Rc = χ - = ■ : - ... (2),

u-u t * 1 u u t 1

/ ο 'c x / o / c x

where u is the space permeability and u is the specific permeability of the ferromagnetic film 2 in the hard axis direction.

In general, there results an inductance L which occurs when a core with a reluctance Rc surrounds N conductors through which the same

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Current I flows in the same direction, by the formula

C),

where ψ is all of the magnetic flux flowing through the core. This total magnetic flux ψ is given by the following equation expressed:

The inductance L as follows from equations (3) and (4)

By dividing Rc in equation (2) by Rc in equation (5) and expresses it in terms of the MBS unit system, equation (2) is converted into the following equation:

'χ' ¹⁰ " ^{7 (H)} · ■ · ⁽⁶⁾

In Fig. 2, curve A represents the specific permeability u des ferromagnetic film 2 in the hard axis direction and curve B shows the hysteresis behavior of ferromagnetic film 2 in the same direction. From Fig. 2, it is seen that the specific permeability µ in the hard axis direction up to a point

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in the vicinity of the field strength H ^ corresponding to the saturation flux density on the hysteresis curve B is essentially constant. Therefore As can be understood from equation (6), the inductance of the thin film reactor according to the invention can be determined independently of the operating current (i.e. the current I flowing through the conductor 1) to hold constant to a point which is just before the saturation in the ferromagnetic film 2 is reached. Occupy in Fig. 2 the solid curves are actually measured values and the dashed curves are ideal values.

From Fig. 2, it is found that the hysteresis curve B in the direction of the hard axis compared with that in the direction of the easy axis Axis and which runs very straight according to the state of the art. Therefore, the hysteresis losses (or the electrical losses) are the result in a decrease in the value Q of the throttle, less than before, and less heat is generated when the throttle is operated. This is a very desirable benefit for integrated circuit components. It is also assumed that the magnetization in the hard axis direction is caused by rotation of the magnetic spin. In this way, the choke can reliably respond to changes in the magnetic field, d. H. Address changes in a high-frequency current flowing through the conductor 1 and shows good high-frequency behavior.

In an experiment carried out by the inventors, the conductor 1 was made of a binary iron-nickel alloy, namely Permalloy, plated under the conditions given in Table 1, and it

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it was confirmed that the ferromagnetic film 2 was up to one Film thickness on the order of 5 µ exhibited uniaxial anisotropy. In addition, the specific permeability was u in the direction the axis of difficult magnetization here at 1000 to 3000.

Table 1 Composition of the plating solution

Nickel sulfamate 307 g / l

Ferrous sulfate 9.5 gA

Hydroxylaniine hydrochloride 6.0 q / l

Boric acid 1.25 gA

Sodium saccharate 3.75 g / l

Citric acid 25.0

Plating solution temperature 60 ° C ί 0.5 ° C

2 current density 2.5 A / dm

Applied magnetic field 40 Oe

When annealing treatment on an electroplated permalloy film is used, the tempering is preferably carried out at 460 ° C. for 200 hours in vacuo.

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It is now assumed that the specific permeability ji _c in the hard axis direction is 2000 and a, b and t in the equation (6) are 50, 3 and 5 µ, respectively, and I _x 1 cm. Then you get

- fl

from equation (6) an inductance value L = 10 H, since in this Case N = 1. This is the inductance value of the thin film reactor according to the invention, and it is found that this thin film reactor has a sufficiently large inductance, although its dimensions are very small compared to known chokes of this type

When permalloy is formed with nickel in greater proportion than iron of the ferromagnetic film 2 is used, its saturation flux density is on the order of 0.8 to 1.2 Wb / m. Therefore The maximum magnetic flux in the permalloy film, the thickness t and length of which are 1 5 µ and 1 cm, respectively, is 4 to 6 x 10 6 Wb. On the other hand the result is the maximum value I of the

Max

ßenden current from the following, by modifying the equation (3) equation obtained:

max f _A χ / v

max L

If one sets the inductance L = 10 H, the maximum magnetic = 4-6 · 10 ~ Wb and N = 1 in equation (7),

so I agree

Max

I = 4-6 x 10 " ² (A).

Max

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This current value is perfectly acceptable for amplifiers consisting of transistors.

Fig. 3 shows an embodiment of the thin film reactor according to the invention. The thin-film choke is designated generally by 10 in FIG. 3 and initially has a base 11. On this base 11 are permalloy films 12 and 13 corresponding to the ferromagnetic Film 2 in Fig. 1 is plated and laminated, with an aluminum film 14 corresponding to the current conductor 1 in Fig. 1 between the permalloy films 12 and 13 is inserted. A pair of connector parts 14a and 14b for electrical connection to feed conductors are provided at opposite ends of the aluminum film.

The base 11 is advantageously free of all pores and has one even and smooth surface and is essentially due to the deposited thereon films 12, 13 and 14 acting etchant does not corrode. Suitable materials that meet these conditions, include soda lime glass, non-alkali metal-free glass (e.g., Corning Company 7059 glass), fused silica, Quartz single crystal, alumina single crystal (i.e., sapphire) and spinel single crystal or similar. Also a plate, which by applying a smooth glass layer to the surface of a sintered ceramic piece, such as B. obtained from aluminum oxide, beryllium oxide or magnesium oxide can be used as a base 11. In addition, a plate made of silicon or a plate made of silicon with an oxide surface layer can also be used.

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The surface of the pad 11 is expediently up to one Surface flatness finished from 1 to 2 u, for accuracy of the photo-etching described below. aside from that the surface roughness is appropriately less than 0.05 to 0.1 u,

so that the plated permalloy film 12 is magnetically uniform.

The individual successive steps for producing the thin-film choke illustrated in FIG. 3 will now be explained with reference to FIG. 4a to 4d.

According to Fig. 4a, a permalloy film 12 of about 5 microns thick deposited by electroplating on a base 11 under the conditions given in Table 1. If the pad 11 is an electrical insulating material, the permalloy film 12 can be deposited by touching the surface of the substrate 11 on which the Choke is to be produced, first of all applying a conductive metal by non-electrolytic plating or by vacuum vapor deposition, thereby depositing a conductive film about 0.05 to 0.2 µm thick on that surface, and then electroplating below Using this first conductive film as an electrode. A DC magnetic field is left during this electroplating process act from 40 to 50 Oe in a direction perpendicular to the plane of the drawing to create the uniaxial anisotropic permalloy film 12 whose hard axis is in the horizontal direction of the drawing.

It then becomes an aluminum film about 0.2-0.5 µm thick

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- 12 - 2 3 4 3 5 3

vapor-deposited onto this permalloy film 12 in a vacuum. This aluminum film it is then subjected to electrolysis in an aqueous solution of 50 g / l of chromic acid using the permalloy film 12 as an anode, thereby forming an Al O film (anodic oxidation film) 16. Then, an aluminum film serving as a conductor is made 14 evaporated from about 3 u thickness in a vacuum on the Al O film 16, and one brings on this aluminum film 14 a Photoresist film 17 to etch away the unnecessary portions of the film 16 and to be able to obtain a certain conductor shape according to FIG.

The unit shown in Fig. 4a is then immersed in an alkaline solution immersed to the unnecessary parts of the Al O film 16 and the aluminum film 14 except for those by the photoresist film 17 etched away protected parts without attacking the permalloy film 12. 4b shows the state reached after this etching process.

The photoresist film 17 is removed immediately after the etching step described above, and an Al O film 18 is formed on the exposed surface of the aluminum film 14 by electrolysis using the aluminum film 14 as an anode. completely with the thin transparent j
are covered.

transparent Al O films 16 and 18, the electrical insulators

After this insulating treatment, a conductive film (not shown) with a thickness of about 0.1 to 0.2 u is applied over the entire upper

4 098U / 08 3 0

side of the unit shown in Fig. 4c evaporated. This senior Film suitably consists of such a material as permalloy or similar alloy with high permeability in order to reduce the reluctance a ferromagnetic permalloy film to be deposited on this conductive film in the next step.

Using this conductive film as an electrode Then, the electroplating is carried out under the same conditions as when forming the permalloy film 12 for the deposition of a second permalloy film 13 on the conductive film with application carried out in a magnetic field. A photoresist film 19 is then applied to this second Perrnalloyfilm 13 to remove the unnecessary To etch away parts of the film 13 and to obtain the specific shape shown in FIG. This state is illustrated in Fig. 4d .

The unit shown in Fig. 4d is then immersed in an acidic solution, such as B. immersed a solution of ammonium persulphate to remove superfluous Portions of permalloy films 12 and 13 and the (not shown) conductive film except for the portions covered by the photoresist film 19. Then the photoresist film 19 is removed, so that a thin film reactor as shown in Fig. 3 is obtained.

Parts of the permalloy film 12 having the same shape as that of FIG Terminal parts 14a and 14b of the aluminum film 14 are left unetched and lie under these connector parts 14a and 14b. However, since the permalloy film 13 does not cover these parts of the permalloy

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films 12 is created · in between despite the current flow through the Connection parts 14a and 14b only an open magnetic circuit. This is how the inductance of the thin-film choke actually results from the overlapping parts of the upper and <§s lower permalloy film 13 or 12. The connecting parts 14a and 14b of the aluminum film 14 are on their outer surface with the electrically insulating AlO-FiI-men 16 and 18 which are transparent and about 0.1 to 1 µ thick. These connecting parts 14a and 14b can be made with leads Copper or gold can be electrically connected by ultrasonic welding.

In the embodiment described above, dio ferromagnetic permalloy films 12 and 13 deposited by electroplating. However, films made of uniaxial anisotropic, single crystal ferrite deposited on a single crystal base 11 by epitaxial growth instead of the permalloy material will. A ferromagnetic one consisting essentially of iron can also be used Material to be used. A preferred material is an alloy of aluminum and iron, e.g. B. an "Aluperm" said alloy with 12 to 16 wt .-% aluminum. There is a big difference between the vapor pressures of aluminum and iron at a certain temperature. In order to obtain a vapor deposition film of the desired composition, it is therefore expedient to to use an aluminum-iron starting alloy whose aluminum content is less than the desired ratio in the Evaporation layer corresponds. An aluminum-iron alloy film can also be used with a desired composition according to the

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Flush evaporation process ("flush evaporation") obtained in which fine particles of the alloy with the desired composition ratio intermittently in small quantities to a high one Temperature heated crucible can be dripped.

On a ferromagnetic film made of an iron-silicon alloy there is no noticeable mechanical stress here, and this alloy can therefore contain 5 to 15% by weight of silicon. As a result of the high silicon content, the conductivity is reduced with a reduction in the skin effect, and it can also be used at a high frequency achieve high permeability. The eddy current losses can also be reduced- For the above reasons, the iron-silicon alloy suitable for forming the ferromagnetic film.

In an integrated circuit, it is desirable that the "choice the shape or form of each individual component is free. Often there are particular difficulties in design and manufacture such a circuit if the connections of the components are at a large distance from one another and for a relatively long time Connection conductors are required for this. In such cases, a plurality of thin-film chokes according to FIG. 3 can be connected in series to obtain a composite choke with any desired inductance.

The exemplary embodiment already described related to the case in which N = 1 in equation (6). However, N can be used instead of 1 also = be 2. Such a thin-film choke has a chained connection

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Order of a ferromagnetic film and a plurality of layers or turns of electrical conductors. Such a thin-film choke can be manufactured using process steps similar to those which have been described with reference to FIGS. 4a to 4d, and has a similar structure to that in FIG Description of these procedural steps to avoid lengths to be disregarded.

First, a permalloy film is deposited on a base. Then a plurality of z. B. insulated 3 conductor-insulator composite layers each of a completely surrounding of an Al O film aluminum film, that is made of an electrically by an Al ₀ O ^ -FiIm conductive aluminum film is laminated on the permalloy film, and then a Another permalloy film is deposited in order to cover these aluminum-aluminum oxide composite layers and the previously deposited permalloy film, as is indicated in principle in FIG. 3. A desired pattern photoresist film is applied to cover parts of the upper permalloy film, and etching is performed to remove unnecessary parts. Finally, copper or gold leads are used to connect the laminated aluminum films in series so that these films can form a coil or the current can flow through these aluminum films in the same direction.

If a large inductance is required and both the thickness and the space requirement of the construction

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Elements are limited, one can have a plurality of units, each of which is a plurality of laminated aluminum films of the described Art comprises, manufacture and sequentially connect the aluminum films of these units in series to form a thin-film choke with any inductance.

A thin-film choke with a plurality of choke units can also be made of uniaxial anisotropic on a single base magnetic material are formed. In this case, however, it is necessary to make the distance between the units larger than in the case where a non-magnetic material is used as a base to make up the magnetic interaction between each Avoid units. Such a thin film reactor can be made using a uniaxial anisotropic ferromagnetic material to form the common base of the thin-film choke units obtain. Electrically insulated current conductors are on this common base according to the description with reference to FIG. 4a to 4d and of course attached so that they are directed perpendicular to the hard axis of the common ferromagnetic base are. This common ferromagnetic pad is used as part of the ferromagnetic film surrounding the current conductors , and a second ferromagnetic film is deposited on the conductors in the manner described with reference to Figures 4a through 4d.

When the common ferromagnetic pad is used in this way as part of the ferromagnetic film surrounding the current conductors only a, b and t in equation (2), which is the re-

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- is - 2 3 A 3 ^ 3 9

the inductance supplies, varies, and it yields there is no influence on the permeability, which has an essential connection with the effect of the invention. So can a thin film choke Easily obtained with a certain inductance. Further occurs as the adjacent thin film choke units in proportion far apart, no substantial magnetic mutual interference. The use of the common pad as part of the ferromagnetic film surrounding the current conductors is advantageous, as this increases the manufacturing steps and the number of parts can be reduced noticeably, which contributes significantly to reducing costs.

It is required the occurrence of hysteresis losses and To prevent eddy current losses in the ferromagnetic material present in the reactor when the reactor does the above Structure is operated with high-frequency current. The thin film structure of this ferromagnetic material has the desired effect Preventing these losses from occurring. The insertion of the electric insulating film between the thin films of ferromagnetic Material causes these thin films to be electrically insulated from one another and thus leads to a reduction in eddy current losses to a minimum.

The skin effect occurs in a high frequency range. The depth S the skin effect is given by the relationship

S -γ

^llf / ¹ O P '

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iNSPECTED

where g , u, f and u are the specific resistance of the ferromagnetic material and the specific permeability of the ferromagnetic material and the operating frequency and the spatial permeability of the ferromagnetic material, respectively. As a result of this skin effect, the high frequency field is concentrated in the area from the surface of the magnetic material to the skin effect depth S given by the above equation. Thus, only the skin or skin part of the ferromagnetic material is effective for the magnetic lines of force, and the ferromagnetic material parts beyond the skin effect depth S are essentially useless and only have the effect of increasing the eddy current losses of the ferromagnetic film is selected to be less than the skin effect depth or equal to the skin effect depth, so that the ferromagnetic material is used with optimum efficiency.

The hysteresis losses. corresponding area of the hysteresis loop is very significantly smaller in the hard axis direction than in the easy axis direction. When in the thin film of ferromagnetic Material uniaxial magnetic anisotropy is generated such that the axis is easier to magnetize with the direction of the current flow through the conductor corresponds, this is done by the Current induced magnetic field is applied in the direction of the hard axis of the ferromagnetic film. So can be added to the advantage of the thin film structure reduce the hysteresis losses, and this advantage is even more pronounced in the high frequency range.

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- 20 - 2 3 4 3 5 3

Assume that φ, R and I are all of the magnetic path that flows through the magnetic path formed by the ferromagnetic films Magnetic flux or the reluctance of the ferromagnetic material or the current flowing through the conductor; then it results Inductance L by the equation

L - φ / Ι,
and since φ = I / R, L can be written as

L = l / R

to express.

The inductance L is inversely proportional to the reluctance R. It turns out that the inductance L can be obtained by laminating the ferromagnetic May increase films over a plurality of layers and thereby decrease reluctance.

Further, when the reactor has a fixed dimension, the reluctance can be determined by the thickness of the laminated ferromagnetic Determine the films and the number of these films.

The conditions of vacuum evaporation or other deposition method are appropriately controlled so that the ferromagnetic films have a uniform thickness smaller than that Skin effect depth or this is the same. Therefore, the reluctance is determined by the number of laminated ferromagnetic films.

40 98U / 083 0

- 21 - 2 3 A 3 5 3

It can thus be seen that the inductance of the choke according to the invention can be set as desired by properly selecting the number of the laminated ferromagnetic films.

If a plurality of such ferromagnetic films are laminated, the coercive force of the lamination becomes considerably lower than that of the single film. This reduction in the coercive force interacts with the advantages already described for keeping the power losses low. Furthermore, the linearity of the hysteresis loop and the reduction in the coercive force lead to a shortening of the switching time due to pulse magnetization *

5 and 6 show a further embodiment of the Invention. A base 19 for receiving a throttle is expediently made of a material that is free of all pores, a has an even and smooth surface and is sufficiently mechanically strong is to be handled. Suitable materials for the base plate 19 include soda lime glass, alkali-free glass, quartz glass, Single crystal quartz and single crystal alumina.

A film 20 of ferromagnetic material such as Permalloy about 0.1 µm thick is deposited on the Pad 19 deposited, as indicated in FIG. A mask is used in the vacuum deposition of the permalloy film 20 to to obtain a desired shape of the film. During the vacuum deposition of this permalloy film 20, a direct current

098U / 0830

2 3 k ο γ J b

Apply a magnetic field of 40 to 50 Oe to give the permalloy film 20 a to impart such uniaxial magnetic anisotropy that the hard axis lies in a desired direction.

Then a film 21 of electrical insulating material, such as. B. silicon monoxide is deposited on the permalloy film 20. Form this insulating film 21 ′ is the same as that of the permalloy film 20. Then, on the first insulating film 21, a second permalloy film 22 and a second insulating film 23 are successively formed by vacuum evaporation deposited. A film 25 of conductive material, such as. B. aluminum, about 3 u thick and 50 u wide is then deposited on the insulating film 23 by vacuum evaporation. This conductive film 25 can be deposited on the entire surface of the insulating film 23, and unnecessary parts can be made of the conductive film by the photoetching technique to obtain the desired pattern. The conductive film 25 has the shape of an elongated strip according to FIG. 6, which in the throttle part has a length of the order of 3 mm.

A third film 24 of electrical insulating material, such as silicon monoxide, is then deposited on the conductive film 25 by vacuum evaporation using a mask. Form this insulating film 24 is appropriately determined by means of the mask so that the end portions of the conductive film 25 remain exposed from the insulating film 24, so that electrical connection lines can be connected to the end parts. A third permalloy film 26 is formed on the insulating film 24 deposited by vacuum evaporation and has a practically that of des

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ORIGINAL INSPECTED

Insulating film 24 same shape. A fourth insulating film 27 and a fourth permalloy film 28 are successively formed on the permalloy film 26 deposited on evaporation by vacuum.

A perspective view of the final state of the throttle thus obtained is illustrated in FIG. 6. The number of over the senior Film 25 arranged permalloy films can also be larger than 2. An inductance of IuH can be obtained when the permalloy films in the choke up to a total thickness of 5 u.

All of the permalloy films 20, 22, 26 and 28 of this choke are vacuum deposited while in the direction of the current flow a magnetic field is applied through the conductive film 25, and therefore have such a uniaxial magnetic anisotropy that the. hard axis of each permalloy film lies in the direction perpendicular to the direction of current flow through the conductive film .25. Further the hysteresis losses in the permalloy films are remarkably small because the alternating current magnetic field generated in the permalloy films induced by the high frequency current flowing through the conductive film 25 is directed toward the hard axis which is perpendicular to the easy axis.

In this embodiment, a pad was used made of electrically insulating material that is pore-free, has a flat and smooth surface and is mechanically strong enough to to withstand the necessary manipulations. However, this un-

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pad also a porous sintered ceramic body, such as. B. made of aluminum oxide, beryllium oxide or magnesium oxide, its Surface is covered with a thin layer of glass. Veiter can the base must also be an electrical conductor, the surface of which is covered with a film of electrical insulating material vapor-deposited in a vacuum, such as B. silicon monoxide is coated.

The uniaxial anisotropic ferromagnetic film can also be formed of nickel-zinc ferrite instead of the permalloy.

In the embodiment shown in FIGS the permalloy films 20, 22, 26 and 28 are completely insulated from each other by the insulating films 21, 23, 24 and 27 made of silicon monoxide. However, the peripheral zones of these permalloy films can also be made wider than those of the insulating films, around the peripheral zones the permalloy films in areas beyond the edge zones of the insulating films to connect with each other. Such a structure is shown in FIG. 7 illustrated. 7, a plurality of permalloy films 31, 33, 34 and 36 on a base 30 are made of electrical insulating material magnetically coupled or connected to one another to form a single closed magnetic path, so that the reluctance can be reduced and the inductance can be increased. A plurality of insulating films 32, 35 and 37 are interposed between these ferromagnetic films, and a conductive film 38 is embedded in the insulating film 35.

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The thin film choke according to the invention can be used in a wide scope, such as. B. use as a transformer, filter, line constant element and pulse delay line in integrated high-frequency circuits for television receivers, radios and the like.

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Claims (6)

2342539 Claims 1J thin film choke, characterized in that it consists of a current conductor (14) and a uniaxial anisotropic one surrounding it ferromagnetic film (12, 13), the hard axis of which is perpendicular to the direction of current flow through the conductor lies (Fig. 3). 2. Thin-film choke, characterized in that they are laminated from a group of at least two, electrically insulated from each other Current conductors and a group of conductors surrounding the uniaxial anisotropic ferromagnetic film, the hard axis of which is perpendicular to the direction of current flow through the conductor group lies. 3. Thin film choke according to claim 2, characterized in that a plurality of ferromagnetic films with one of the skin effect depth at the operating frequency inferior to or equal in thickness are laminated with interposition of electrically insulating films and a magnetic path surrendered around the ladder. 4. Thin-film choke, characterized in that it consists of a current conductor (z. B. 25) and a plurality of uniaxial anisotropic ferromagnetic films (e.g. 20, 22, 26, 28) with one of the skin 4098 U / 0830 23A3539 depth of effect at the operating frequency inferior or equal thickness exists whose axis of easier magnetization coincides with the direction of the current flow through the conductor (z. B. 25) and the are laminated with interposition of electrically insulating films (e.g. 21, 23, 24, 27) and a magnetic path around the conductor (e.g. 25) result (Fig. 5 and 6). 5. thin film choke according to claim 4, characterized in that the ferromagnetic films (31, 33, 34, 36) with reduction the reluctance are in mechanical contact with each other (Fig. 7). 6. Thin film choke according to claim 4, characterized in that the ferromagnetic films are arranged concentrically around the conductor are. 40981W CT830 empty soap