JPS6125220Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a spiral inductor.

A so-called spiral inductor, in which a conductor film is formed in a spiral shape on a high-resistance substrate, semi-insulating substrate, or insulating substrate for integrated circuits, is used in integrated circuits in the UHF band or microwave band.

FIG. 1 is a diagram showing the shape of a conductor film of a conventional spiral inductor, and 1 is a conductor film. FIG. 2 is a sectional view of the crossover portion A-A' in FIG. 1, where 11 is a substrate, 12 is a first layer conductor, 13 is an interlayer insulating film, and 14 is a second layer conductor.

FIG. 3 is a graph showing the frequency characteristics of a spiral inductor, with the horizontal axis representing the frequency f and the vertical axis representing the inductance L. The inductance of an ideal inductor should be a constant value Le regardless of the frequency, as shown by the dotted line 22 in Figure 3, but in an actual spiral inductor, the frequency increases as shown by the solid line 21 in Figure 3. The inductance increases accordingly. Moreover, the manner in which it increases is unpredictable because it depends on various factors including the shape of the spiral inductor.

Therefore, spiral inductors can only be used in low frequency bands where the inductance exhibits a constant value. As a typical value, when the inductance is 2nH, the upper limit frequency that can be used is approximately 3GHz.

The purpose of this invention is to improve the above-mentioned drawbacks and provide a spiral inductor that can be used in higher frequency bands.

According to this idea, high-resistance substrates, semi-insulating substrates,
Alternatively, in an inductor in which a conductor film is formed in a spiral shape on an insulating substrate, a spiral inductor is obtained in which the width of the conductor line at the crossover portion is narrower than the width of the conductor line at other portions.

FIG. 4 is a diagram showing the shape of the conductor film of one embodiment of the spiral inductor according to this invention, and
1 is a conductive film. The conductor line width of the crossover portion 32 is narrower than that of the other portions.

It has been known for a long time that the reason why a spiral inductor has a frequency characteristic as shown in FIG. 3 is due to the self-resonance phenomenon of the inductor. The self-resonant frequency was considered to be the frequency at which the length of the spiral conductor of the inductor when stretched in a straight line is one quarter of a wavelength. In other words, it was considered to be a resonance phenomenon when the spiral inductor is considered as a distributed constant transmission line. However, as a result of various studies, the inventor of this application found that not only the resonance considered as a transmission line but also the resonance as a lumped element where the capacitance of the crossover part and the inductance of the inductor resonate cannot be ignored. It was made clear by That is, when the resonance frequencies of both were calculated and compared, it was found that the latter is lower and therefore has a dominant influence on the characteristics.

From the above study, it is clear that if the capacitance of the crossover portion is reduced, the self-resonant frequency will increase and the usable upper limit frequency will also increase.

According to this invention, the width of the conductor line in the crossover portion is narrower than in other portions, so when considered as a capacitor, the area of the opposing electrodes becomes smaller and the capacitance becomes smaller. Note that if only the capacitance of the crossover portion is reduced, it may be possible to reduce the width of the conductor line in other parts, but if the line width is made narrower, the loss will increase, making this impractical. This idea narrows the line width only at the crossover portion in order to minimize the increase in loss.

As described above in detail using the figures, this invention can provide a spiral inductor that can be used at high frequencies and is practically effective.

Although a rectangular spiral inductor is used in the drawings of the embodiment, it goes without saying that this invention can also be applied to a circular spiral inductor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the shape of a conductor film of a conventional spiral inductor, and 1 is a conductor film. FIG. 2 is a sectional view of the crossover portion A-A' in FIG. 1, in which 11 is a dielectric substrate, 12 is a first layer conductor, 13 is an interlayer insulating film, and 14 is a second layer conductor. FIG. 3 is a graph showing the frequency characteristics of a spiral inductor, where the horizontal axis is the frequency and the vertical axis is the inductance.The dotted line 22 represents the ideal characteristic, and the solid line 21 represents the actual characteristic. FIG. 4 is a diagram showing the shape of the conductor film of an embodiment of the spiral inductor according to this invention, and is 31
3 is a conductor film, and 32 is a crossover portion.

Claims (1)

[Scope of utility model registration request] A spiral inductor in which a conductor film is formed in a spiral shape on a high-resistance substrate, a semi-insulating substrate, or an insulating substrate, characterized in that the conductor line width at the crossover portion is narrower than the conductor line width at other portions. .