JPH03261202A - Microwave semiconductor device - Google Patents

Abstract

PURPOSE:To decrease the space occupied by a reactance element by varying the thickness of a semiconductor base of a reactance element formed on the way of a strip line. CONSTITUTION:The thickness of a semiconductor base 1 of a reactance element C formed on the way of a strip line is varied. That is, when the thickness of the semiconductor base 1 at a part of the strip line is varied, the characteristic impedance for the part is changed, and the part with a small characteristic impedance acts like a capacitor and the part having a large characteristic impedance acts like an inductor. Thus, it is not required to vary the width Wo of an upper conductor 3 and the space occupied by the reactance element C is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to monolithic microwave integrated circuits (MMI).
The present invention relates to a microwave semiconductor device such as C) in which a reactance element portion is formed in the middle of a strip line formed on a semiconductor substrate.

[Conventional technology]

Microwave semiconductor devices such as monolithic microwave integrated circuits are manufactured by forming strip lines such as microstrip lines and coplanar lines as transmission lines on a semiconductor substrate, and forming solid-state elements on the substrate itself where necessary and connecting them. It constitutes a predetermined high frequency circuit. Since a high frequency circuit usually requires a capacitor or an inductor as a reactance element, in the microwave semiconductor device, a reactance element portion is formed in the middle of the strip line within the shell.

Conventional microwave semiconductor devices have been configured as shown in FIGS. 4 to 7, for example.

FIG. 4 is a plan view showing the main parts of a conventional microwave semiconductor device, FIG. 5 is a view taken along the ■-V arrow in FIG. 4, FIG. The figure is a plan view showing other main parts of the microwave semiconductor device.

In this microwave semiconductor device, as shown in FIGS. 4 to 7, a microstrip line is formed on a semiconductor substrate 1 as a strip line. That is, a lower conductor 2 that is on the ground side is formed on the lower surface of the semiconductor substrate 1, and an upper conductor 3 that determines the characteristic impedance of the line is formed on the upper surface of the semiconductor substrate 1. Width W of the track section. is determined to obtain a predetermined characteristic impedance, for example, 50Ω.

A wide width W is formed in the middle of the microstrip line, that is, in a part of the upper conductor 3 in this example, as shown in FIG. and the narrow width W as shown in FIG.
A portion L is formed.

In other words, the part formed in a part of the line with a low characteristic impedance becomes a capacitor, and the part formed in a part of the line with a large characteristic impedance becomes an inductance, and if the width of the upper conductor 3 is widened, that part becomes a capacitor. As the characteristic impedance of
Based on the characteristic that when the width of the upper conductor 3 is narrowed, the characteristic impedance of that portion increases, the capacitor C as a reactance element portion is formed as a portion with the wide width Wc, and the inductor L as a reactance element portion is formed as a portion with the narrow width Wc. It is formed as a part of WL. Note that the thickness of the semiconductor substrate 1 is constant ho at any location.

Incidentally, examples of circuits using the above-mentioned capacitance and inductance are shown in FIGS. 8 to 11.

FIG. 8 is a plan view of the upper conductor 3 showing an example of a low-pass filter circuit, and FIG. 9 is an equivalent circuit diagram thereof. In these drawings, C is a capacitor, and 1 to 3 and L1 to 4 are inductors.

This type of circuit is used as an input matching circuit, an output matching circuit, etc. of an amplifier circuit using FETs.

[Problem to be solved by the invention]

However, in the conventional microwave semiconductor device shown in FIGS. 4 to 7, the thickness of the semiconductor substrate 1 is constant at any location, so the width Wc of the upper conductor 3 in the capacitor C is It has the disadvantage that it becomes noticeably wider and requires a much larger space.

That is, for example, GaAs (
The thickness of the semiconductor substrate 1 is determined by using a dielectric constant of about 12.9). When 200 μm, the characteristic impedance of the line changes as shown by the curve in FIG. Width W of upper conductor 3. is 143 μm, but in order to make the characteristic impedance of the capacitor C about half that value, the width W of the upper conductor 3 at that portion is required. It is necessary to increase the width by three times (400 μm) or more, which has the disadvantage of requiring a very large space.

For this reason, it has not been possible to effectively utilize the surface area of the semiconductor substrate 1 and achieve high integration.

This situation also applies to various other conventional microwave semiconductor devices in which a coplanar line or the like is formed as a strip line on a semiconductor substrate.

The present invention provides a microwave semiconductor device that requires only a small space to be formed in the middle of a strip line or occupied by an actance element section, can effectively utilize the surface area of a semiconductor substrate, and can achieve high integration. The purpose is to try to improve the quality of life.

[Problem to be solved by the invention]

In order to solve the above problems, the present invention provides a microwave semiconductor device in which a reactance element section is formed in the middle of a strip line formed on a semiconductor substrate, in which the thickness of the semiconductor substrate at the reactance element section is changed. The structure is as follows.

[Effect]

As described above, a portion of the strip line with a low characteristic impedance formed in a portion thereof becomes a capacitor, and a portion of the strip line with a large characteristic impedance formed in a portion of the strip line serves as an inductance.

By the way, when the thickness of the semiconductor substrate in a part of the strip line is changed, the characteristic impedance of that part changes.

Therefore, according to the present invention, unlike the prior art, the thickness of the semiconductor substrate in the reactance element section is changed, so that the space occupied by the reactance element section is small, and the surface area of the semiconductor substrate can be effectively utilized. It is possible to achieve high integration.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a plan view showing the main parts of a microwave semiconductor device according to an embodiment of the present invention, and FIG.
3 is a view taken along the line m-■ in FIG. 1.

In this microwave semiconductor device, as shown in FIGS. 1 to 3, a microstrip line is formed on a semiconductor substrate 1 as a strip line. That is, a lower conductor 2 that is on the ground side is formed on the lower surface of the semiconductor substrate 1, and an upper conductor 3 that determines the characteristic impedance of the line is formed on the upper surface of the semiconductor substrate 1, and the width of the upper conductor 3 is as follows. Constant W. It is said that Note that the thickness of the semiconductor substrate 1 at a normal portion is ho.

The thickness of the semiconductor substrate 1 in the middle of the microstrip line, that is, in this example, at a position corresponding to a part of the upper conductor 3 is reduced to hl. In other words, a part of the line with low characteristic impedance becomes capacitance.
Based on the characteristic that when the thickness of the semiconductor substrate in the line is made thinner, the characteristic impedance of that portion becomes smaller, the capacitor C serving as the reactance element portion is formed as the portion having the thinner thickness hl. Note that the portion of the semiconductor substrate 1 having a small thickness hl can be formed by, for example, removing a portion of the substrate having a thickness of .

In the microwave semiconductor device shown in FIGS. 1 to 3, the semiconductor substrate 1 is made of, for example, GaAs (relative permittivity:
Approximately 12.9) and the above thickness.

is 200 μm, the characteristic impedance of the line changes as shown by curve A in FIG.
m, the characteristic impedance of the line changes as shown by curve B in FIG. 12 as the width of the upper conductor 3 changes, so the width W of the upper conductor 3. When 143 μm, the characteristic impedance of the normal line portion (thickness: −200 μm) is 50Ω, and the characteristic impedance of the capacitor C (thickness: hl−50 μm) is about half that value.

As can be seen by comparing this with the conventional example described above, in the microwave semiconductor device shown in FIGS. 1 to 3, unlike the conventional example, the thickness of the semiconductor substrate 1 is changed, so that the same characteristics can be obtained. Nevertheless, there is no need to particularly widen the width of the upper conductor 3 in the capacitor C.
occupies less space. Therefore, the surface area of the semiconductor substrate 1 can be effectively utilized, and high integration can be achieved.

In the above description, the portion of the capacitor C has been explained as a reactance element portion, but the reactance portion depends on the thickness of the semiconductor substrate 1 as in the conventional case (see FIG. 7). The width of the upper conductor 3 may be made narrower by leaving it as is. However, the width of the upper conductor 3 is W. The thickness of the semiconductor substrate 1 may be increased without changing the structure.

In the above embodiment, only the thickness of the semiconductor substrate 1 in the capacitor C was changed and the width of the upper semiconductor 3 was not changed, but in the present invention, not only the thickness of the semiconductor substrate 1 (the upper semiconductor 3 The width of the IC mask may also be changed at the same time.In that case, the degree of freedom in layout of the pattern (IC mask) is improved and design becomes easier.

In addition, in the above-mentioned embodiment, the thickness of the semiconductor substrate 1 is measured. When changing from hl to hl, the change may be made gradual. That is, for example, when etching or the like is performed to form the hl portion, the hole may be appropriately tapered. In this case, the discontinuity caused by the abrupt change in the width of the upper conductor 3 in the conventional examples shown in FIGS. 3 to 7 is alleviated.

Further, in the above-mentioned embodiment, a microstrip line is formed as a strip line on a semiconductor substrate, but the present invention also applies to a microwave semiconductor device in which a coplanar line or the like is formed as a strip line on a semiconductor substrate. It is applicable.

〔Effect of the invention〕

According to the present invention, the space occupied by the actance element portion formed in the middle of the strip line can be reduced, the surface area of the semiconductor substrate can be effectively utilized, and high integration can be achieved. can get.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the main parts of a microwave semiconductor device according to an embodiment of the present invention, FIG. 2 is a view taken along the ■-■ arrow in FIG. 1, and FIG. 4 is a plan view showing main parts of a conventional microwave semiconductor device, FIG. 5 is a view taken along the V-■ arrow in FIG. 4, and FIG. 6 is a view taken along the Vl-Vl arrow in FIG. 4. 7 is a plan view showing other main parts of a conventional microwave semiconductor device, FIG. 8 is a plan view showing an example of a circuit configuration, FIG. 9 is an equivalent circuit diagram thereof, and FIG. 10 is a characteristic diagram. It is a characteristic diagram of impedance. 1... Semiconductor substrate, C... Capacitor (reactance element part).

Claims (1)

[Claims] A microwave semiconductor device comprising a reactance element section formed in the middle of a strip line formed on a semiconductor substrate, characterized in that the thickness of the semiconductor substrate at the reactance element section is varied.