JPH07263230A - Miniature transformer - Google Patents

Abstract

PURPOSE:To provide a miniature transformer which can be built in as a part of an integrated circuit. CONSTITUTION:A first line of spiral electrode 3 is formed on the surface of an insulating board 1 and an insulating thin film 4 is formed on the spiral electrode 3. A second line of spiral electrode 5 is then formed between the adjacent electrodes of the first line of spiral electrode 3 on the insulating thin film 4 and the insulating board 1 while being superposed partially on the first line of spiral electrode 3. Two lines of spiral electrodes 3, 5 serve as primary and secondary coils, respectively. A magnetic core may be disposed in the center of the spiral electrodes 3, 5 or a magnetic material may be employed for the insulating board 1 in order to magnetically couple the primary and secondary coils tightly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer, and more particularly to a transformer which can be formed in a very small size by a thin film manufacturing technique and can be incorporated as a part of an integrated circuit for transmitting a high frequency signal. A suitable small transformer.

[0002]

2. Description of the Related Art Transformers are used in various fields such as electric power transmission and signal transmission after being insulated from a direct current.

[0003]

In recent years, various electronic circuits have been integrated and miniaturized. However, it is difficult to make the transformer small, so that the transformer should be included in the integrated circuit. Instead, it was installed as an external component. Therefore, the present invention was conceived for the purpose of obtaining a small-sized transformer that can be incorporated as a part of an integrated circuit.

[0004]

A first spiral electrode is formed on a surface of an insulating substrate, an insulating thin film is formed on the spiral electrode and the insulating substrate, and the first thin film is formed on the insulating thin film. The spiral electrode of the second section is formed so as to be disposed between the adjacent electrodes of the spiral electrode of, and at least a part of the spiral electrode overlaps with the spiral electrode of the first section,
The two spiral electrodes are connected to the primary coil and the secondary coil, respectively.
Next coil.

A magnetic core is arranged at the center of the spiral electrode, and a magnetic material is used as an insulating substrate to close the magnetic coupling between the primary coil and the secondary coil.

[0006]

EXAMPLE An example of the transformer of the present invention will be described in the order of manufacturing steps. As shown in the assembly diagram of FIG. 1, (1) first, an insulating substrate such as a silicon wafer, glass, or ceramic is prepared. In particular, a high-purity silicon wafer 1 having a large bulk resistance is suitable for the insulating substrate.

(2) A first silicon oxide film (Si) is formed on the surface of the silicon wafer 1 by chemical vapor deposition (CVD).
(3) After forming the O ₂ film) 2, (3) a metal capable of withstanding the following chemical vapor deposition process on the first silicon oxide film 2,
For example, a first metal film of gold, tungsten, molybdenum, tantalum, niobium, or the like is deposited, (4) a single spiral pattern of photoresist is formed on the metal film, and (5) this photoresist is formed. Is used as a mask to form the first spiral electrode 3 and then the photoresist is washed off. The first spiral electrode 3 has terminal portions 31 and 32 on the outer side and the inner side.

(6) A second silicon oxide film (SiO ₂ film) 4 is formed on the surface of the first spiral electrode 3 and the exposed first silicon oxide film 2 by the chemical vapor deposition method. After that, (7) the second silicon oxide film 4 in the portions corresponding to the outer and inner terminal portions 31, 32 of the first spiral electrode 3 is removed by photoetching to expose the openings 41, 42. Is formed, and (8) a second metal film is vapor-deposited thereon, and (9) on the metal film, between the adjacent electrodes of the first-row spiral electrode 3 already formed, A single spiral pattern of photoresist is formed, and (10) a second spiral electrode 5 arranged between adjacent electrodes of the first spiral electrode 3 using this photoresist as a mask. After forming, the photoresist is washed off. The second spiral electrode 5 has terminal portions 51 and 52 on the outer side and the inner side.

Through the series of steps described above, the first and second spiral electrodes 3 and 5 formed on the silicon wafer 1 serving as an insulating substrate respectively serve as a primary coil and a secondary coil. And form a transformer.

In this transformer, as is clear from the cross-sectional view of FIG. 2, the second spiral electrode 5 is arranged between the adjacent electrodes of the first spiral electrode 3, and both spiral electrodes are arranged. The magnetic coupling of 3, 5 can be made tight.

The small-sized transformer having such a structure can transmit a high-frequency signal with high efficiency and without distortion even with an air core.

(Other Embodiments) In the above embodiments,
Although the two spiral-shaped electrodes are the primary coil and the secondary coil, three or more spiral-shaped electrodes may be provided between adjacent electrodes to form a transformer having a plurality of multi-coil.

Further, by forming a plurality of spiral electrodes and silicon oxide films alternately in multiple layers and connecting them through through holes of the silicon oxide film, it is possible to manufacture a transformer having a large number of turns.

Disposing a magnetic material such as ferrite in the central portion of a spirally wound spiral electrode, or using a magnetic material such as ferrite instead of a silicon wafer as an insulating substrate for forming a transformer. By forming a thin film of a magnetic material on the surface of the formed transformer, the magnetic coupling between the two spiral electrodes can be made more dense.

[0015]

As is clear from the description based on the above embodiments, the small transformer of the present invention is suitable for transmitting high frequency signals and can be manufactured by a technique similar to an integrated circuit by a thin film manufacturing technique. It is also possible to obtain a small transformer that can be incorporated as part of an integrated circuit.

[Brief description of drawings]

FIG. 1 is an assembly diagram showing an embodiment of a small transformer of the present invention,

FIG. 2 is a sectional view of an embodiment of the small transformer of the present invention.

[Explanation of symbols]

 1 Insulating substrate 2, 4 Silicon oxide film 3, 5 Spiral electrode 31, 32, 51, 52 Terminal part

Claims (3)

[Claims] 1. A first-row spiral electrode is formed on a surface of an insulating substrate, an insulating thin film is formed on the spiral electrode and the insulating substrate, and the first-spiral spiral is formed on the insulating thin film. A small-sized transformer, wherein the second spiral electrode is formed so as to be disposed between the adjacent electrodes of the linear electrode, and at least a part of the spiral electrode overlaps the first spiral electrode. 2. The small transformer according to claim 1, wherein a magnetic core is arranged at the center of the spiral electrode. 3. The miniature transformer according to claim 1, wherein a magnetic material is used as the insulating substrate.