JPH09180937A - Flat inductor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a flat inductor in which the deterioration in magnetic characteristics due to the increased coercive force is suppressed, and the yield of production and reliability are improved. SOLUTION: This inductor is composed of a first magnetic layer 2 formed on a supporting substrate 1, a first insulating layer 3 formed on the above- mentioned first magnetic layer 2, a conductor pattern 4 formed on the first insulating layer 3, a second insulating layer 7 formed on the conductor pattern 4 and a second magnetic layer 8 formed on the second insulating layer 7. A resin layer is provided at least on one surface of the supporting substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar inductor used in various electronic devices such as mobile phones and a method for manufacturing the planar inductor.

[0002]

2. Description of the Related Art Recently, various electronic devices have been reduced in size and weight. Along with this, there is an increasing demand for miniaturization of switching power supplies mounted in electronic devices.

Conventionally, magnetic elements used in this switching power supply, that is, choke coils and transformers, have various shapes such as an EΙ core and a ΡQ drum formed of ferrite, or an amorphous magnetic alloy ribbon. Although the one using a wound core has been used, in recent years, in order to meet the demand for size reduction, weight reduction, and thinning, a planar inductor using a thin film process has been developed.

The planar inductor has, for example, the structure shown in FIGS.
As shown in, the alumina ceramic substrate 1, Fe-Co-
A first magnetic layer 2 made of a BC film, a first insulator layer 3 made of an Al-N film, a spiral conductor pattern 4 or a spiral conductor pattern 6, and a second insulation made of an Al-N film. It has a structure in which a body layer 7 and a second magnetic layer 8 made of a Fe—Co—B—C film are sequentially stacked. The conductor pattern of the planar inductor is between the conductor coil 4 and 6 and the planar coil element 5 in which the spiral conductor pattern 4 or the spiral conductor pattern 6 is formed on the first insulator layer 3 by photolithography. In order to insulate the surface of the conductor pattern 4 or 6 and to smooth the surface of the conductor pattern 4 or 6, it is composed of an insulating film such as polyimide for covering the planar coil element 5.

By the way, a ceramic substrate such as alumina, which is usually used as a supporting substrate, has fine irregularities on its surface. When a magnetic layer is formed on a ceramic substrate having this irregularity, the magnetic layer also has irregularities. . Generally, the magnetic layer is used to improve the efficiency (Q
Low coercive force is required in order to secure the (value) and suppress the reduction of the inductance value, and the coercive force depends on the depth, number and shape of the irregularities on the substrate surface. Therefore,
If unevenness is present in the magnetic layer formed on the ceramic substrate, the demagnetizing field increases here, and a magnetic singular point (a place where it is difficult to magnetize) occurs. As a result, local anisotropy is generated in the magnetic layer, so that the coercive force of the planar inductor is increased and the above-mentioned magnetic characteristics are deteriorated.

Further, when a single crystal substrate of silicon or the like with few fine irregularities on the surface is used as the supporting base,
The increase in coercive force of the planar inductor and the deterioration of the magnetic characteristics are almost suppressed because the irregularities generated in the magnetic layer formed on the supporting substrate are reduced, but the single crystal substrate such as silicon is inferior during the manufacturing process. However, there is a problem in that the substrate is easily damaged and the yield is reduced in manufacturing the planar inductor.

Furthermore, when a magnetic layer is formed on a single crystal substrate of silicon or the like, a concave film stress is applied to the magnetic layer (the central portion of the magnetic layer is the most concave), so that the substrate warps, so that the magnetic layer is magnetic. During the manufacturing process after forming the body layer, problems such as transport troubles in the manufacturing equipment and mask misalignment during conductor pattern formation will occur, resulting in yields when manufacturing planar inductors and reliability of the manufactured planar inductors. There was a problem that it deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and suppresses the deterioration of the magnetic characteristics due to the increase of the coercive force of the planar inductor, and the yield in the manufacturing process of the planar inductor. It is an object of the present invention to provide a planar inductor that achieves improved reliability of the manufactured planar inductor and a method of manufacturing the planar inductor.

[0009]

A planar inductor according to the present invention includes a first magnetic layer formed on a supporting substrate, a first insulating layer formed on the first magnetic layer, and First
A planar inductor having a conductor pattern formed on an insulator layer, a second insulator layer formed on the conductor pattern, and a second magnetic layer formed on the second insulator layer, A resin layer is provided on at least one surface of the support substrate.

In the planar inductor of the present invention, since the resin layer is provided on at least one surface of the supporting substrate, even when a sintered body such as alumina is used as the supporting substrate, the resin is not formed on the uneven portion. As a result of being embedded, the surface of the support substrate is flattened and the magnetic layer becomes smooth, so that the occurrence of local anisotropy due to the unevenness of the magnetic layer is prevented, and the coercive force of the planar inductor is increased to improve the magnetic characteristics. Deterioration is suppressed.

Even when a support substrate made of silicon or the like, which has small surface irregularities but is susceptible to cracking or warping, is used as the support substrate, the resin protects the support substrate from impact due to collision and the like, and the support substrate To prevent the warp of
Cracks and the like are less likely to occur in the substrate, and misalignment in mask alignment at the time of forming the conductor pattern does not occur, so that reduction in yield due to substrate destruction is suppressed, and reliability of the planar inductor is improved.

In the planar inductor of the present invention, the "face" of the supporting substrate means a region on the supporting substrate where the magnetic layer is formed or a region facing this region.

The resin layer is at least 250-40.
It has heat resistance in the range of 0 ° C., and more preferably has heat resistance in the range of 300 to 400 ° C. As the resin having such heat resistance, polyimide-based resins represented by polyimide, polyamide-imide, aromatic polyamide, polyimidazole and the like are preferably used, but it is also possible to use, for example, epoxy-based resin, etc. The resin is appropriately determined based on the above temperature conditions and the characteristics required for the planar inductor. At this time, the resin layer has a layer thickness of 4 to 15 μm, preferably 5 μm.
It is formed to have a thickness of ˜8 μm.

As the insulator layer constituting the plane coil element, an insulating film made of silicon dioxide, alumina or tantalum or Si-N formed on a substrate made of ceramic or the like.
A system or Al-N system insulating film may be used. However,
The use of an Al-N insulating film is more preferable because it imparts high characteristics to the planar inductor. The layer thickness of the insulator layer formed on the substrate such as ceramic is usually 0.05 to 5.0 μm.
m. The conductor pattern forming the planar coil element is formed by ordinary photolithography, and its shape is a spiral shape or a zigzag shape. Here, the spiral is a concept including not only a spirally wound curve but also a shape having a plurality of non-differentiable points other than the end points, such as the conductor pattern 4 shown in FIG. Furthermore, the spelling fold is a concept indicating a shape in which the conductor pattern has an amplitude, like the conductor pattern 6 shown in FIG. That is, the conductor pattern forming the planar coil element is formed in a form having the largest occupied area on the insulator layer. The conductor pattern is usually made of copper, but aluminum or the like can also be used.

Generally, in a planar inductor, in order to smooth the surface on the magnetic material layer forming the conductor pattern, to insulate between the conductor patterns, and to smooth the surface of the planar coil element, the magnetic material layer is formed. Also, the planar coil element is often covered with a resin which is an insulator. As the resin used at this time, the above-mentioned polyimide resin or the like is preferably used.

A method of manufacturing a planar inductor according to the present invention comprises a step of forming a resin layer on at least one surface of a supporting substrate, and a first magnetic material on the supporting substrate having the resin layer formed on at least one surface thereof. Forming a layer, and the first
Forming a first insulator layer on the magnetic layer;
Forming a conductor pattern on the insulator layer; forming a second insulator layer on the conductor pattern;
And a step of forming a second magnetic layer on the insulating layer.

In the method of manufacturing a planar inductor of the present invention, the resin layer is formed on at least one surface of the support substrate, and the first magnetic layer is formed on the support substrate having the resin layer formed on at least one surface. To be done. Next, a first insulator layer is formed on the first magnetic layer, and a conductor pattern is formed on the first insulator layer. Then, the second insulating layer is formed on the conductor pattern, and the second magnetic layer is formed on the second insulating layer.

The method for forming the resin layer on at least one surface of the supporting substrate is not particularly limited, but spin coating can be usually performed. For example, when a resin layer is formed of a polyimide-based resin, usually N-methyl-2-pyrrolidone (NMP) is used as a solvent, and a varnish in which polyamic acid is dissolved is spin-coated and then heated. To form a resin layer. When the resin layers are formed on both surfaces of the supporting substrate, the resin layer is formed on one surface and then the resin layer is formed again on the other surface.

Further, the first magnetic layer on the supporting substrate on which the resin layer is formed, the first insulating layer on the first magnetic layer, the second insulating layer on the conductor pattern and the second insulating layer. The formation of the second magnetic layer on the body layer is usually performed by sputtering. The sputtering conditions are the same as the conditions for manufacturing a normal planar inductor.

In the formation of the conductor pattern on the first insulator layer formed by sputtering and the formation of the second insulator layer on the conductor pattern, the surface on the first insulator layer on which the conductor pattern is formed An insulating layer is usually formed in order to smooth the conductor pattern on which the second insulating layer is formed. This insulating layer is often formed of resin, but in this case as well, it can be formed by spin coating using the above-mentioned materials.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1 and Comparative Example 1) Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the planar inductor according to the present invention, and the sectional direction is A-- shown in FIG.
It is along B.

First, CT-415, which is a polyimide-based insulating varnish, is formed on the surface of the alumina ceramic substrate 1.
0 (Toshiba Chemical Co., Ltd.) was applied with a spin coater, and the temperature was 75 ° C. for 10 minutes, the temperature was 145 ° C. for 30 minutes, and then 350.
By baking at 60 ° C. for 60 minutes, a resin layer 9 made of polyimide having a layer thickness of 8 μm was formed. In addition, 25 ℃ and 60 ℃
The viscosities of CT-4150 are 80 P (poise) and 20 P, respectively, and N Ρ is used as the solvent.

Next, F having a layer thickness of 1.5 μm is formed on the resin layer 9.
The first magnetic layer 2 made of an e-Co-B-C film, having a layer thickness of 0.
A first insulator layer 3 made of Al—N having a thickness of 4 μm was formed by sputtering.

Subsequently, a resin layer 10 made of polyimide having a layer thickness of 8 μm is formed on the first insulator layer 3 similarly to the resin layer 9.
Was formed, and a copper conductor pattern 4 having an aspect ratio of 1: 1 was formed thereon by photolithography. In addition,
The pitch between the conductor patterns is 50 μm, and the film thickness of the conductor patterns is 50 μm. Then, a resin layer 11 made of polyimide having a layer thickness of 8 μm was formed on the planar coil element 5 in the same manner as the resin layer 9.

Finally, a layer thickness of 0.4 μm is formed on the resin layer 11.
Second insulating layer 7 made of Al—N and having a layer thickness of 1.5
A second magnetic layer 8 made of a Fe-Co-B-C film having a thickness of μm was formed by sputtering to obtain a planar inductor of the present invention (Example 1).

On the other hand, as a control, a planar inductor shown in FIG. 2 was obtained in the same manner as in Example 1 except that the resin layer 9 made of polyimide was not formed on the surface of the alumina ceramic substrate 1 (Comparative Example 1). .

When the magnetic characteristics of the planar inductors of Example 1 and Comparative Example 1 were compared and examined, the planar inductor of Example 1 had a coercive force of 10 A / m.
However, the planar inductor of Comparative Example 1 had a coercive force of 180 A / m, and the planar inductor of the present invention achieved a significant improvement in magnetic characteristics.

(Embodiment 2 and Comparative Example 2) FIG. 3 is a sectional view showing another embodiment of the planar inductor according to the present invention, the sectional direction being along the line AB shown in FIG. is there.

First, CT-4150 (Toshiba Chemical Co., Ltd.), which is a polyimide-based insulating varnish, is applied to the surface of the silicon substrate 13 with a spin coater, and the temperature is 75 ° C. for 10 minutes, 145 ° C. for 30 minutes, and then 350. By baking at 60 ° C. for 60 minutes, a resin layer 9 made of polyimide having a layer thickness of 8 μm was formed.

Next, on the back surface of the silicon substrate 13 on which the resin layer 9 is formed, the first magnetic layer 2 made of a Fe—Co—B—C film having a layer thickness of 1.5 μm and the Al having a layer thickness of 0.4 μm. The first insulator layer 3 made of —N type was formed by sputtering.

Then, a resin layer 10 made of polyimide having a layer thickness of 8 μm is formed on the first insulator layer 3 in the same manner as the resin layer 9.
Then, a copper conductor pattern 4 having an aspect ratio of 1: 1 was formed by photolithography. The pitch between the conductor patterns is 50 μm and the film thickness of the conductor patterns is 3 μm.
0 μm. Then, the resin layer 9 is formed on the planar coil element 5.
In the same manner as above, a resin layer 11 made of polyimide having a layer thickness of 8 μm was formed.

Finally, a layer thickness of 0.4 μm is formed on the resin layer 11.
Second insulating layer 7 made of Al—N and having a layer thickness of 1.5
The second magnetic layer 8 made of a Fe—Co—B—C film having a thickness of μm was formed by sputtering to obtain a planar inductor of the present invention (Example 2).

On the other hand, as a control, a planar inductor shown in FIG. 4 was obtained in the same manner as in Example 2 except that the resin layer 9 made of polyimide was not formed on the silicon substrate 13 (Comparative Example 2).

Here, when the manufacturing process of the planar inductors of Example 2 and Comparative Example 2 was traced, in the manufacturing process of the planar inductor of Example 2, the silicon substrate was compared with the manufacturing process of the planar inductor of Comparative Example 2. Is almost prevented, and the manufacturing yield of the planar inductor is improved by 30%.

Further, in the manufacturing process of the planar inductor of Example 2, as compared with the manufacturing process of the planar inductor of Comparative Example 2, the warpage of the silicon substrate after forming the first and second magnetic layers is almost prevented. Since the transfer trouble in the manufacturing apparatus and the deviation in the mask alignment at the time of forming the conductor pattern are reduced, the reliability of the planar inductor is improved.

(Embodiment 3) FIG. 5 is a sectional view showing another embodiment of the planar inductor according to the present invention, and the sectional direction is along the line A-B shown in FIG.

First, CT-4150 (Toshiba Chemical Co., Ltd.), which is a polyimide-based insulating varnish, is applied to the surface of the silicon substrate 13 by a spin coater, and the temperature is 75 ° C. for 10 minutes, the temperature is 145 ° C. for 30 minutes, and then 350. By baking at 60 ° C. for 60 minutes, a resin layer 9 made of polyimide having a layer thickness of 8 μm was formed.

Next, on the back surface of the silicon substrate 13 on which the resin layer 9 is formed, the resin layer 12 is formed in the same manner as the formation of the resin layer 9.
Was formed.

Then, on the resin layer 9, a first magnetic layer 2 made of a Fe--Co--B--C film having a layer thickness of 1.5 μm and a first insulator made of an Al--N system having a layer thickness of 0.4 μm. Layer 3 was formed by sputtering.

Subsequently, a resin layer 10 made of polyimide having a layer thickness of 8 μm is formed on the first insulator layer 3 similarly to the resin layer 9.
Then, a copper conductor pattern 4 having an aspect ratio of 1: 1 was formed by photolithography. The pitch between the conductor patterns is 50 μm and the film thickness of the conductor patterns is 3 μm.
0 μm. Then, the resin layer 9 is formed on the planar coil element 5.
In the same manner as above, a resin layer 11 made of polyimide having a layer thickness of 8 μm was formed.

Finally, a layer thickness of 0.4 μm is formed on the resin layer 11.
Second insulating layer 7 made of Al—N and having a layer thickness of 1.5
The second magnetic layer 8 made of a Fe-Co-B-C film having a thickness of μm was formed by sputtering to obtain a planar inductor of the present invention (Example 3).

Here, when the manufacturing process of the planar inductors of the third and second embodiments was traced, in the manufacturing process of the planar inductor of the third embodiment, the silicon substrate was compared with the manufacturing process of the planar inductor of the second embodiment. Was almost completely prevented from being damaged, and the manufacturing yield of the planar inductor was further improved by 60%.

Further, in the manufacturing process of the planar inductor of Example 3, as compared with the manufacturing process of the planar inductor of Comparative Example 2, the warpage of the silicon substrate after forming the first and second magnetic layers is almost prevented. Since the transfer trouble in the manufacturing apparatus and the deviation in the mask alignment at the time of forming the conductor pattern are reduced, the reliability of the planar inductor is also improved.

[0045]

As described above, according to the present invention, the resin layer formed on at least one surface of the supporting substrate smoothes the surface of the supporting substrate made of ceramics or the like to form the magnetic layer. Since the support substrate made of silicon or the like can be almost flattened and the damage and the warp can be almost prevented, the coercive force of the planar inductor is increased to improve the magnetic characteristics, and the yield and the reliability due to the damage are improved. A planar inductor and a method for manufacturing a planar inductor can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a planar inductor according to the present invention.

2 is a cross-sectional view showing a planar inductor obtained in Comparative Example 1. FIG.

FIG. 3 is a sectional view showing another embodiment of the planar inductor according to the present invention.

FIG. 4 is a cross-sectional view showing a planar inductor obtained in Comparative Example 2.

FIG. 5 is a sectional view showing another embodiment of the planar inductor according to the present invention.

FIG. 6 is a diagram showing a configuration of a general plane inductor.

FIG. 7 is a diagram showing a configuration of a general plane inductor.

[Explanation of symbols]

1 ... Alumina ceramic substrate 2 ... First magnetic layer 3 ... First insulator layer 4 ... Conductor pattern 5 ...
Planar coil element 6 ... Conductor pattern 7 ... Second insulator layer 8 ...
Second magnetic layer 9 ... Resin layer 10 ... Resin layer 11 ... Resin layer
12 ... Resin layer 13 ... Silicon substrate

Claims (8)

[Claims] 1. A first magnetic material layer formed on a support substrate, and a first insulator layer formed on the first magnetic material layer,
A conductor pattern formed on the first insulator layer; a second insulator layer formed on the conductor pattern;
A planar inductor having a second magnetic layer formed on an insulating layer, wherein a resin layer is provided on at least one surface of the support substrate. 2. The resin layer is at least 250-40.
The planar inductor according to claim 1, which has heat resistance within a range of 0 ° C. 3. The planar inductor according to claim 1, wherein the resin layer is made of a polyimide resin. 4. The planar inductor according to claim 1, wherein the conductor pattern has a spiral shape or a fold shape. 5. A step of forming a resin layer on at least one surface of a supporting substrate; a step of forming a first magnetic layer on the supporting substrate having a resin layer formed on at least one surface thereof; 1 forming a first insulator layer on the magnetic layer; forming a conductor pattern on the first insulator layer; forming a second insulator layer on the conductor pattern; And a step of forming a second magnetic layer on the second insulator layer. 6. The resin layer is at least 250-40.
The method of manufacturing a planar inductor according to claim 5, wherein the planar inductor has heat resistance within a range of 0 ° C. 7. The method of manufacturing a planar inductor according to claim 5, wherein the resin layer is made of a polyimide resin. 8. The method for manufacturing a planar inductor according to claim 5, wherein the conductor pattern has a spiral shape or a fold shape.