JPH0562010U - Spiral inductor - Google Patents

Abstract

(57) [Abstract] [Purpose] To increase the resonance frequency by connecting the upper and lower spiral inductors to each other and dividing the capacitance that directly enters between the input and output. In a spiral inductor, a plurality of lower layer spiral wirings 22, 26, 30 formed separately on an insulating substrate, an insulator 20 formed on the spiral wiring, and a through hole 23 formed in the insulator. , 25,
27, 29, 31 are formed, and a plurality of upper-layer spiral wirings 24, 28 separated from each other and connected in a two-layer structure by drawing a spiral in the same direction as the spiral wirings 22, 26, 30 through the through holes. 32, and the spiral wirings 22, 26, 30 of the lower layer and the spiral wirings 24, 2 of the upper layer in a spiral wiring portion not having a two-layer structure by the through holes 23, 25, 27, 29, 31.
The connection with 8, 32 is made.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the structure of a spiral inductor used in the high frequency band.

[0002]

[Prior Art]

 Conventionally, as a technique in such a field, for example, a literature name; “Miniature Multi Layer Spiral Inductor For GaAs MMICs”, Ga As IC Symposium 1989 pp. 303-306, “Miniature Multilayer Spiral Inductors Fors MMIC. W. Gene, G.M. J. Green, R.M. G. Arnold, J.M. A. Jenkins and R.M. H. Jansen, (GaAs IC symposium, 1989, pp 303-306).

Conventionally, this type of element has been used as an inductance of a matching circuit or as a choke coil of a bias circuit for the purpose of blocking an AC component of a current. FIG. 4 is a top view of a conventional spiral inductor. A large inductance is often used in a circuit used at a frequency of 1 GHz or less. In FIG. 4, single-winding wirings 2a, 2b, 2c are sequentially formed on the insulator 1 from the outer side to the inner side, and the connecting portions of the single-winding wirings 2a, 2b, 2c are connected via the insulator 1. The connection wiring 4 is used for connection at the contact hole 3.

In order to increase the inductance in the structure of FIG. 4, a method of increasing the number of turns by making the wiring of the inductor denser is adopted. However, in order to obtain a large inductance, it is necessary to widen the element area, which causes a problem of increasing the area of the integrated circuit. An improved version of this is shown in FIG. That is, the spiral inductor has a two-layer structure of an upper layer spiral wiring 12 and a lower layer spiral wiring 13 with an insulator 11 such as SiO ₂ or Si ₃ N ₄ sandwiched therebetween to increase the inductance. That is, the spiral wiring 12 is formed in the clockwise direction, and the spiral wiring 13 formed in the counterclockwise direction at the central portion of the spiral wiring 12 is connected by the contact hole 12b. Therefore, the circuit current or signal passes from the input terminal 12a in the upper layer to the center from the outside through the spiral wiring 12 (inductor), passes through the contact hole 12c, and is connected to the center of the spiral wiring 13 in the lower layer (inductor). Then, it comes out while drawing a spiral from the center to the outer output terminal 12c. At this time, mutual inductance occurs in the part where the wiring of the upper and lower inductors overlap, and this adds to the inductance of each spiral inductor, resulting in a larger inductance.

[0005]

[Problems to be solved by the device]

 However, in the structure of the inductor shown in FIG. 5 described above, when a current or a signal is input to the inductor in the upper layer, a current or a signal is output to the wiring of the inductor below the inductor. Capacity is added in parallel. FIG. 6 is an equivalent circuit of the structure of the inductor.

As is clear from this figure, this capacitance corresponds to the capacitance between the wirings of the inductor, and the capacitance increases as the element area of the inductor increases. Moreover, if the overlapping portions of the wirings of the inductors in the upper and lower layers are increased to increase the mutual inductance, the capacitance also increases accordingly. Assuming that the maximum frequency at which this element can be used as an inductor is the resonance frequency ω _res , the relational expression between the capacitance C of the inductor and the inductance L is ω _res = 1 / √LC.

Therefore, the capacitance C increases as the inductance increases, so that the resonance frequency decreases. In order to eliminate the disadvantage that the resonance frequency is reduced due to the capacitance that directly enters between the input and output described above, the spiral inductors in the upper and lower layers are connected to each other to reduce the capacitance that directly enters between the input and output. It is an object of the present invention to provide a spiral inductor that can increase the resonance frequency by dividing it into small pieces.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a spiral inductor in which a plurality of lower-layer spiral wirings formed on an insulating substrate are separated from each other, an insulator formed on the spiral wirings, and A through hole is formed in the insulator, and a plurality of spiral wirings in the upper layer, which are separated from each other and are connected in a two-layer structure by drawing a spiral in the same direction as the spiral wiring through the sulfol, are provided. The spiral wiring portion not having a two-layer structure connects the lower layer spiral wiring and the upper layer spiral wiring.

[0009]

[Action]

 According to the present invention, as described above, the spiral inductors in the upper and lower layers are patterned so as to be partially separated, and the inductors in the upper and lower layers are connected by the contact hole by the spiral wiring portion not having the two-layer structure. By doing so, a large capacity between the input and output can be reduced.

Moreover, since the spiral inductors in the upper and lower layers have the same spiral direction, it is possible to obtain an appropriate value for the inductance and to increase the resonance frequency. Thus, it is possible to obtain an inductor that can be used at a higher frequency than the conventional spiral inductor.

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a top view of a spiral inductor showing an embodiment of the present invention. In the figure, 21 is a lower layer input terminal, 22 is a lower layer first spiral wire, 23, 25, 27, 29, 31 are contact holes, 24 is an upper layer first spiral wire, and 26 is a lower layer second wire. Spiral wiring, 28 is an upper-layer second spiral wiring, 30 is a lower-layer third spiral wiring, and 32 is an upper-layer third spiral wiring.

To explain the flow of current or signal, the current or signal enters from the input terminal 21 of the lower layer, passes through the first spiral wiring 22 of the lower layer and the contact hole portion 23, and then passes through the first layer of the upper layer. Connect to the spiral wiring 24. The first spiral wiring 24 in the upper layer is connected to the second spiral wiring 26 in the lower layer via the contact hole portion 25. By repeating this, a current or a signal is output from the output terminal 41.

FIG. 2 is a cross-sectional view of a spiral inductor manufacturing process showing an embodiment of the present invention. First, as shown in FIG. 2A, a lower first spiral wiring 22 and a lower second spiral wiring which serve as inductors are formed on an electrically insulated substrate (for example, a GaAs semi-insulating substrate) 50. 26, the lower third spiral wiring 30 is patterned to form an inductor lower layer pattern.

As shown in FIG. 2B, an insulator (for example, SiO ₂ film, Si ₃ N ₄ film) 20 is coated thereon so as to cover the entire wiring. Next, as shown in FIG. 2 (c), in the required parts of the inductor lower layer pattern, here, the lower layer first spiral wiring 22, the lower layer second spiral wiring 26, and the lower layer third spiral wiring 30 are formed. Contact holes 23, 27 and 31 are formed in a part of the film so as to be connected to the upper spiral wiring.

Next, as shown in FIG. 2D, the first spiral wiring 24 in the upper layer and the first spiral wiring 24 in the upper layer are connected so as to be connected to the spiral wiring in the lower layer through the contact holes 23, 27, 31. The second spiral wiring 28 and the upper third spiral wiring 32 are formed. These can be easily manufactured by using the conventional semiconductor device technology.

FIG. 3 is an equivalent circuit diagram of the spiral inductor of the present invention. Here, the inductance L'means a value obtained by adding the inductance of each of the upper and lower layers and mutual inductance. The capacitance C'means the capacitance between the wirings in the upper and lower layers which are overlapped with each other. Compared with the equivalent circuit of the conventional spiral inductor shown in FIG. 6, the resonance frequency can be made larger than that of the conventional one because there is no capacitance C ₁ connected only between the input and the output. Moreover, because of the two-layer structure, the inductance per element area can be increased.

Further, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0018]

[Effect of the device]

 As described in detail above, according to the invention, the following effects can be achieved. (1) Since the spiral wiring can be formed in two layers, the inductance per area of the device can be increased. Therefore, a large inductor can be obtained with a small area.

(2) Since the directions of the currents or signals flowing in the wirings are the same, mutual inductance between the wirings works and the overall inductance can be increased. (3) Since the inductors in the upper layer and the inductors in the lower layer are connected to each other, there is no capacitance directly connected between the input and the output, so that the resonance frequency can be increased. This makes it possible to obtain an inductor that can be used at high frequencies.

[Brief description of drawings]

FIG. 1 is a top view of a spiral inductor showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a spiral inductor manufacturing process showing an embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of the spiral inductor of the present invention.

FIG. 4 is a top view of a conventional spiral inductor.

FIG. 5 is a plan view of another conventional spiral inductor.

6 is an equivalent circuit diagram of the spiral inductor of FIG.

[Explanation of symbols]

 20 Insulator 21 Input Terminal of Lower Layer 22 First Spiral Wiring of Lower Layer 23, 25, 27, 29, 31 Contact Hole 24 First Spiral Wiring of Upper Layer 26 Second Spiral Wiring of Lower Layer 28 Second Spiral of Upper Layer Wiring 30 Third spiral wiring in the lower layer 32 Third spiral wiring in the upper layer 50 Substrate

Claims (1)

[Scope of utility model registration request] 1. A plurality of lower layer spiral wirings formed on an insulating substrate so as to be separated from each other, (b) an insulator formed on the spiral wirings, and (c) through holes formed in the insulators. And a plurality of upper-layer spiral wirings separated from each other and connected in a two-layer structure by drawing a spiral in the same direction as the spiral wirings through the through-holes, and (d) the through-holes form a two-layer structure. A spiral inductor, characterized in that the spiral wiring of the lower layer and the spiral wiring of the upper layer are connected by a spiral wiring portion which is not provided.