JPH07230913A - Small-sized transformer - Google Patents

Abstract

PURPOSE:To obtain a small-sized transformer capable of being assembled in an integrated circuit as a part. CONSTITUTION:Two lines of spiral electrodes 32 and 35 for a first layer are formed in parallel on the surface of an insulating board 1, and on them an insulating thin film 4 having through holes 41 and 42 are formed. On this insulating thin film 4, two lines of spiral electrodes 52 and 55 for a second layer are formed in parallel. Then the spiral electrodes 32, 35, 52 and 55 for the first and second layers are connected by the use of through holes 41 and 42, and the respective sets of the two spiral electrodes are used as the primary and secondary coils of a transformer respectively.

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
The present invention relates to a small transformer which can be incorporated as a part of an integrated circuit and is suitable for transmitting high frequency signals.

[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]

[Means for Solving the Problems] First parallel two-row spiral electrodes are formed on the surface of an insulating substrate, an insulating thin film having through holes is formed thereon, and two layers are formed on the insulating thin film. The two parallel spiral-shaped electrodes of the eye are formed, and the spiral electrodes of the first and second layers are connected to each other through the through holes to make them continuous, and the two spiral-shaped electrodes are connected to the primary coil and the spiral coil, respectively. Use as a secondary coil.

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

[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 vapor-deposited, and (4) two parallel spiral patterns of photoresist are formed on the metal film. (5) This 1 using the photoresist as a mask
After forming the second row spiral electrodes 32, 35,
Rinse the photoresist. These two strips of spiral electrodes 32, 35 have terminal portions 31, 34 on the outside and terminate on the inside.
I have 33, 36.

(6) The second silicon oxide film (SiO ₂ film) 4 is formed on the surface of the spiral-shaped electrodes 32, 35 of the first layer and the exposed first silicon oxide film 2 by the chemical vapor deposition method.
After forming (7) 1st layer 2 rows spiral electrode
The second silicon oxide film 4 at the portions corresponding to the outer terminal portions 31, 34 of the portions 32, 35 and the inner end portions 33, 36 is removed by photoetching and exposed to expose the through holes 41, 42 and the opening portions 43. Forming, (8) depositing a second metal film on it, (9) forming two parallel spiral patterns of photoresist on the metal film, (10) masking this photoresist Then, after forming the second layer of two spiral electrodes 52 and 55, the photoresist is washed off. The two strip-shaped spiral electrodes 52, 55 have terminal portions 51, 54 on the outer side, and the inner ends 53, 56 have one layer through the through holes 41, 42 provided on the second silicon oxide film 4. Eye 2
Connected with the spiral electrodes 32 and 35 of the strip to make them continuous, 2
The spiral electrodes of the strip are the primary coil and the secondary coil, respectively.

Through such a series of steps, two coils 32, 35 and two coils are formed on the silicon wafer 1 serving as an insulating substrate.
A transformer consisting of 52, 55 can be formed. In this transformer, as is clear from the cross-sectional view of FIG. 2, the spiral electrodes adjacent to the first spiral electrodes 32, 52 are always the second spiral electrodes 35, 55, and both spiral electrodes are The magnetic coupling can be 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,
The two spiral electrodes are used as the primary coil and the secondary coil, but with three or more spiral electrodes,
A transformer having a plurality of multi-order coils can be constructed.

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 plurality of spirally wound spiral electrodes, 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.

[0014]

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 31, 34, 51, 54 Terminals 32, 35 52, 55 2 spiral electrode 41, 42 Through hole

Claims (3)

[Claims] 1. A plurality of parallel spiral electrodes of a first layer are formed on a surface of an insulating substrate, an insulating thin film having through holes is formed on the spiral electrode, and a second layer of the spiral electrodes is arranged in parallel on the insulating thin film. A small transformer characterized in that a plurality of spiral electrodes are formed, and the spiral electrodes of the first layer and the second layer are connected to each other through the through holes to be continuous. 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.