JPS60124851A - Microwave integrated circuit device - Google Patents

Abstract

PURPOSE:To form a passive circuit element having a circuit parameter within a wide range by forming a transmission line section in a strip conductor constituting a circuit element and the transmission line to the upper section of a section where there is no conductor film. CONSTITUTION:With a monolithic microwave integrated circuit 15, metallic films (conductor films) 17a, 17b as grounding conductors are shaped on a semi-insulating semiconductor substrate 16 at a regular interval, an insulating film (a dielectric film) 19 is formed, and a strip conductor 20 constituting a circuit element and a transmission line is shaped so that the transmission line section is positioned at the upper section of a slot 18. The variance range of characteristics impedance by the adjustment of the width of the slot 18 is very large, and inductance and capacitance having a circuit parameter within a wide range can be formed even when each circuit element is shaped by the strip conductor 20 by a distributed parameter circuit.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a microwave integrated circuit device for use in the microwave band, forming an integrated circuit on an insulating or semi-insulating semiconductor substrate.

[Technical background of the invention]

As is well known, in microwave integrated circuits, active elements and passive elements are fabricated on insulating or semi-insulating semiconductor substrates from hybrid microwave integrated circuits for the purpose of equalizing characteristics and downsizing. Monolithic microwave integrated circuit (hereinafter abbreviated as MMIC) formed to form an electronic circuit
is being transitioned to.

FIG. 1 shows the basic structure of a conventional MMIC.

That is, the reference numeral 11 in the figure is a QaAs (f lium arsenide) semi-insulating semiconductor substrate, and on the upper surface of this semiconductor substrate 11 are circuit elements such as an FET 12 which is an active layer, and strip conductors 13 which constitute a transmission line. A string line 14, which serves as a ground conductor, is formed on the lower surface.

Here, in the MMIC having the above structure,
There are two methods for constructing a microwave circuit: a method using a lumped constant circuit and a method using a distributed constant circuit.

First, the lumped constant circuit is formed on the semiconductor device No. 1 by using a conductor film and an insulating film as a circuit mother circuit having desired characteristics. For example, as shown in FIG. 2(a), the circuit elements of this lumped constant circuit include a conductor film A and a spiral circuit/? A conductive film A i as shown in Fig. 2 (bl)
, A s as a comb-shaped circuit/mother main with predetermined gaps, and an overlay capacitor with an insulating thin film B formed between conductor films A4 and A as shown in FIG. 2(c). and shita, etc. Such a lumped constant circuit element has the advantage that it can be formed sufficiently small compared to the wavelength.

On the other hand, the distributed constant circuit is configured to form an inductance or a capacitance t+sequence by changing the characteristic impedance and electrical length of the transmission line made of the strip conductor 13. That is, to explain an example with reference to FIG. 3, the LC circuit as shown in FIG. 3(a) can be constructed as shown in FIG. 3(b). That is, by partially narrowing the width of the strip conductor 130, the line 13a has a high "·ν characteristic impedance.
By forming an inductance L a = L c with ~13c and widening the width of the strip conductor 13, it is possible to form lines 13d, 13e"t' capacitance cd, Ce having a low characteristic impedance. In this case, The series inductance consisting of the above inductance L a " Lc
Let C be the parallel capacitance, and the characteristic impedance zO and the transmission line length! It is known that the series reactance X and parallel susceptance B when configured as follows are approximated by the following equations.

(However, λ is the line wavelength) ・・・・・・・・・・・・・・・
...(1) [Problems with the background art] However, the conventional MMIC configured as described above
However, it has the following drawbacks.

First of all, when forming the lumped constant circuit element mentioned above, it is difficult to make a circuit element having a large circuit and 4 parameters. (p
p) Degree is the limit.

Further, although the overlay capacitor can have a large capacitance value, a reliable process technique is required to form an insulating thin film between the conductor films.

Next, when forming the above-mentioned distributed constant circuit element, as is clear from equation (1), in order to obtain a wide range of inductance and capacitance, the characteristic impedance of the transmission line must be varied over a wide range. For example, GaA
In a microstrip line formed on a semi-insulating semiconductor substrate, the characteristic impedance Zo with respect to the ratio of the width W of the strip conductor to the substrate thickness H has a characteristic as shown in FIG. In other words, in areas where the width W of the strip conductor is extremely large, such as 1 [13 or more], MMI, which is called a circuit hut,
C The circuit becomes so large that it goes against the original purpose.

Further, in a region where the conductor width W is extremely small, such as 10 [μ doors] or less, conductor loss increases and propagation loss increases, making it unusable.

Therefore, the appropriate substrate thickness H (for example, 10
0 to 400 [μm]), the achievable W/H is 0
, 1 to 2.0, and the characteristic impedance zO of the line is limited to about 20 to 120 [Ω].

Here, the propagation loss per wavelength with respect to the substrate thickness H will be explained by showing the calculated values assumed for the GaA insulating semiconductor substrate in FIG. 5 (substrate specific resistance ρ=IX10[:Ω・[For].

When the substrate relative dielectric constant gr=12.5). That is, %i
The propagation loss for an impedance of 50 [Ω] is 0.21 for a thickness of
Not only does it increase rapidly when the substrate is thinner than 1:fl), but the thin GaA-substrate is easily broken and difficult to handle. On the other hand, if a thick substrate is used, the line width of the microstrip line with the desired characteristic impedance becomes wide, making it unsuitable for forming fine circuits.

Therefore, the thickness H of the substrate forming the distributed constant circuit element
The allowable range of the characteristic impedance Zo of the microstrip line formed on the substrate is quite narrow.

As mentioned above, with conventional MMICs, it is difficult to form passive circuits with a wide range of circuit f parameters, whether using lumped constant circuits or distributed constant circuits. .

[Purpose of the invention]

This invention was made to improve the above-mentioned problems, and it can be applied to a wide range of circuits/? It is an object of the present invention to provide an extremely good microwave integrated circuit device that can form a passive circuit element included in a ramometer.

[Summary of the invention]

That is, the microwave integrated circuit device according to the present invention has the following features:
An insulating or semi-insulating semiconductor substrate, a conductor film formed on a part of this semiconductor substrate and serving as a ground conductor, a dielectric film formed on this conductor film and the semiconductor substrate, and a dielectric film formed on this dielectric film. a strip conductor that is formed on the semiconductor substrate and constitutes a circuit element and a transmission line, and a transmission line portion of the strip conductor is located above a portion where the conductor film is not formed, where a dielectric film is directly formed on the semiconductor substrate. It is characterized by the following.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 6 to 9.

FIG. 6 shows the basic structure of a monolithic microwave integrated circuit (MMIC) Js according to the present invention.

That is, in this MMIC 7s, a plurality of (two in the figure) metal films (conductor films) 1ya are provided on the semi-insulating semiconductor substrate 16 to serve as ground conductors.

17b are formed at predetermined intervals. Then, on the metal films 17a, Ilb and the metal film absent portion (slot) 18 on the semiconductor substrate 16,
An insulating film (dielectric film) 19 is formed, and a strip conductor 20 is further formed on this insulating film 19. The IJ tube conductor 20 constitutes a circuit element and a power transmission line, and in particular, the power transmission line portion of this strip conductor 20 is formed above the slot 18.

Such MMICJs are generally used by being placed in a container 21 made of a grounded conductor, as shown in FIG.
In this case, the metal film 17&, l'lb of the above MMICJ s
are the grounding conductor of the container 21 and the conducting wires 22&, 22, respectively.
Connected at b.

In other words, the MMIo 15 configured as described above is capable of connecting the strip conductor 2 regardless of the thickness of the semi-insulating semiconductor substrate 16.
By adjusting the respective widths of the slot 0 and the slot 18, a transmission line having a characteristic impedance ranging from several ohms to several hundred ohms can be formed. That is,
When the slot 18 is not formed, the characteristic impedance of the transmission line is the lowest, and if the width of the slot 18 is made sufficiently large, the transmission line is constituted by the ground conductor of the container 21 and the strip conductor 20 of the MMIC 15, thereby increasing the characteristic impedance. It is.

In this way, the range in which the characteristic impedance can be varied by adjusting the width of the slot 18 is extremely wide compared to the range in which the characteristic impedance can be varied in conventional microstrip lines or cosolena lines. Even when each circuit element is formed using the strip conductor 20, inductance and capacitance having a wide range of circuit characteristics can be formed.

Further, as shown in FIG. 8, the MMICJ s has a strip conductor 20 on the insulation film 19 above the metal film 17&
If the capacitor electrode 22 is formed by extending the metal film, it becomes possible to easily create a capacitance having a large capacitance value between the capacitor electrode 22 and the metal film 17a via the insulating film 19. Furthermore, the metal film 1
Strip conductor 2 formed on the insulating film 19 above 7&
When the open stub 23 is configured with 0, the characteristic impedance of the line can be made extremely low, and a distributed constant type parallel capacitance having a large capacitance value can be created.

By the way, in a microwave integrated circuit, it is necessary to connect a desired circuit pattern constituting the microwave circuit to a ground conductor. In this case, in a conventional microwave integrated circuit,
By forming a peer hole that penetrates a semi-insulating semiconductor substrate,
Since the circuits and turns formed on the board were connected to the ground conductor formed on the back of the board, parasitic inductance occurred at the connection part, and holes were formed by etching, especially in the case of thick boards. Therefore, there were problems such as the diameter of the pier hole becoming large. However, in the MMIC 7s configured as described above, as shown in FIG. 9, a through hole (or pier hole) is formed by etching a small diameter hole in the insulating film 19 and forming a metal film on the inner surface.
By providing the strip conductor 24, it becomes possible to easily connect the strip conductor 20 formed with the desired circuit arm turn to the metal film 171L which becomes the ground conductor. Furthermore, since the insulating film 19 is sufficiently thinner than the semi-insulating semiconductor substrate 16, problems like those of the prior art are unlikely to occur.

Therefore, the MMIC 15 configured as described above not only can form a transmission line having a wide range of characteristic impedances regardless of the thickness of the semiconductor substrate 16, but also can form circuit elements in lumped constant circuits and distributed constant circuits. It is possible to have large circuit parameters when forming a circuit) 4? The ground conductor can be easily and precisely connected to the ground conductor.

Although the above embodiments have been described using a semi-insulating semiconductor substrate, the same implementation is possible even when an insulating semiconductor substrate is used.

〔Effect of the invention〕

As described above, according to the present invention, an extremely good microwave integrated circuit can be provided, in which passive circuit elements having a wide range of circuit parameters can be easily formed, and furthermore, the circuit pattern and the ground conductor can be easily connected. equipment can be provided.

2

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic structure of a conventional microwave integrated circuit device, FIG. L
) and (b) are a circuit diagram and a plan view to explain the number of turns of each circuit element of a distributed constant circuit, respectively, and Figure 4 is a characteristic showing the characteristic impedance characteristics with respect to the line width and basic thickness of a microstrip line. 5 is a characteristic diagram for explaining propagation loss with respect to substrate thickness of a microstrip line, FIG. 6 is a basic configuration diagram showing an embodiment of a microwave integrated circuit device according to the present invention, and FIGS. 9th
Each figure is a configuration diagram showing an example of use of the above embodiment. 11.16... Semi-insulating semiconductor substrate, 12... FE
T, IJ... Strip conductor, 14... String line, 15... Monolithic microwave integrated circuit (M
MIC), zy...Metal film, 18...Slot, 1
9... Insulating film, 2o... Strip conductor, 21...
- Container, 22... Cano 4-side electrode, 23... Open stub, 24... Through hole. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 (a) (b) (C) Figure 3 Figure 6 Leap 0.04 0. + 0.2 0.40.6to 2.0
4. OW/H Fig. 5 8 Closed

Claims (1)

[Claims] An insulating or semi-insulating semiconductor substrate, a conductor film formed on a part of this semiconductor substrate and serving as a ground conductor, a dielectric film formed on this conductor film and the semiconductor substrate, and a dielectric film formed on this dielectric film. a strip conductor that is formed to constitute a circuit element and a transmission line, such that a transmission line portion of the strip conductor is located above a portion where the conductor film is absent where a dielectric film is directly formed on the semiconductor substrate. A microwave integrated circuit device characterized by: