JPH01289301A - High frequency integrated circuit - Google Patents

Abstract

PURPOSE:To prevent the increase in the resistance loss as the characteristic impedance gets higher and the increase in the radiation loss when the characteristic impedance is decreased by constituting the circuit with a substrate, a dielectric substance having a different dielectric constant from that of the substrate and a transmission line made of a low resistivity metal or the like on the dielectric substance. CONSTITUTION:A substrate is made of GaAs and a dielectric substance 4 is made of SiO2. The dielectric constant of the SiO2 is nearly three and it is nearly 1/4 of that GaAs. While the characteristic impedance of a strip line formed on the GaAs substrate 1 is nearly 50OMEGA at 10GHz, the characteristic impedance of the strip line of the same width formed on the SiO2 is nearly 100OMEGA. Thus, the characteristic impedance is varied without varying the line width of the strip line. Then the increase in the resistance loss is suppressed when the characteristic impedance of the strip line is increased and the increase in the radiation loss is suppressed when the characteristic impedance is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high frequency integrated circuit in which a transmission line such as a strip line is formed on a semiconductor substrate such as a ceramic substrate or GaAs.

<Prior Art> Generally, high-frequency integrated circuits have transistors, resistors, strip lines connecting them, etc. integrated on the same substrate, so a circuit is required to match the impedance between these elements. One of these impedance matching circuits is a quarter wavelength transformer, which has been commonly used in the past.

Figure 3 is a circuit diagram showing a quarter-wavelength transformer, where ZL is the load, and between points AB is the characteristic impedance Zo1, line length 4.
This is a line 31 of 1/1 wavelength. Here, the input impedance seen from point A to the load side is Z in = Zo''/Z
t. For example, ZL=200Ω and ZQ=100
When Ω, Zin=50Ω, high impedance can be converted to low impedance.

Generally, the load zL and input impedance Zin are determined, and the necessary zo can be found from them.

When this quarter-wavelength transformer is constructed using a strip line, a desired characteristic impedance has conventionally been obtained by changing the line width of the strip line.

Also, when a transmission line with high characteristic impedance is required for a bias circuit or the like, the line width is made narrower for the same reason.

<Problems to be solved by the invention> However, in the conventional method, the characteristic impedance of the transmission line cannot be changed without changing the line width, so as the desired characteristic impedance increases, the line width becomes narrower. However, since the resistance loss increases, the transmission loss within the transmission line increases. For example, as a substrate,
Considering GaAsf with a thickness of 100 μm, the line width is about 75 μm at a characteristic impedance of 50Ω at 10GH2, whereas it becomes narrow to about 81 tm at a characteristic impedance of 100Ω.

Furthermore, when the line width is increased in order to reduce the characteristic impedance, there is a problem in that radiation loss increases.

The present invention has been devised in view of the above points, and an object of the present invention is to provide a novel high-frequency integrated circuit that eliminates the above-mentioned conventional problems.

Means for Solving the Problems In order to achieve the above object, the high frequency integrated circuit of the present invention includes a substrate and a substrate having a dielectric constant different from that of the substrate embedded in the removed portion obtained by removing a portion of the substrate. It is configured to include a dielectric material having a dielectric constant, and a transmission line formed of a low resistivity metal or the like on the dielectric material.

That is, the present invention removes a part of the substrate, for example, from the main surface side to the bottom surface, embeds a dielectric material having a dielectric constant different from the dielectric constant of the substrate in the removed part, and
The heights of the main surfaces of the substrate and the dielectric are approximately equal, and a transmission line having a characteristic impedance different from the characteristic impedance of the transmission line on the substrate is formed on the dielectric. are doing.

Effects> In the present invention, the substrates constituting the high frequency integrated circuit have partially different dielectric constants. When the dielectric constant of the dielectric is smaller than the above-described dielectric constant of the substrate, the characteristic impedance can be increased without narrowing the line width of the strip line. Conversely, when the permittivity of the dielectric is larger than that of the substrate, the characteristic impedance can be reduced without increasing the line width of the strip line. Therefore, it is possible to change the characteristic impedance without changing the line width. can. As a result, when the characteristic impedance is increased, there is no need to make the line width thinner, so new losses due to line resistance are not caused, and when the characteristic impedance is decreased, there is no need to make the line width thicker. Because it's good,
No new losses due to radiation are caused.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of the present invention. In FIG. 3 is a ground electrode of the strip line formed on the back surface of the substrate 1, and 4 is a dielectric constant different from that of the substrate 1. 5i02 etc. can be used as a dielectric material with t, and the cross section taken along line AA' in Fig. 1 is shown in Fig. 2.
It is embedded in the removed portion where a part of the substrate 1 is removed from the main surface side to the bottom surface, and the heights of the substrate 1 and the dielectric body 4 on the main surface side are made substantially equal.

In more detail: - By way of example, the substrate l is 10
0 Am thick Q a A S % dielectric 4 as 5iO
Use z. 5t (The dielectric constant of h is about 3, so G
It is about 1/4 of that of aAs. Therefore, the characteristic impedance of a 75 μm wide strip line formed on the QaAs substrate 1 is approximately 500 at 10 GHz, while the characteristic impedance of a strip line of the same width formed on Sigh is approximately It becomes 1000. Therefore, according to the present invention, the characteristic impedance can be changed without changing the line width of the strip line. i
In addition, the line width to obtain the same characteristic impedance is G
Since S i (h is thicker than aAs, the loss due to line resistance can be reduced as the characteristic impedance increases.

An example of the manufacturing method of embedding Si(h into a GaAs substrate in this embodiment) will be described below.

(i) First, At is vapor-deposited in areas other than the recessed portion of the 5iCh, and Au is vapor-deposited on the back surface of the GaAs substrate.

(if) Reactive Ion Etching
GaAs is etched using a (RI E ) device and a BCIa+C12+02 mixed gas.

(iii) 5i on the etched part of G aA s
02 was applied, and the remaining 5i (h was RI
Sigh is removed by etching back with E.

In addition, in the above embodiment, an example was explained in which 5i (h) was used as the dielectric material to be embedded in the substrate, but the present invention is not limited to this. In this case, the method is not limited to the example of removing the dielectric material from the main surface side of the board to the bottom surface and embedding the dielectric material, as in the above-mentioned embodiment. Needless to say, you can adjust the thickness of your body.

<Effects of the Invention> As described above, according to the present invention, when the characteristic impedance of the strip line is increased, the increase in resistance loss caused by the narrowing of the conventional line width can be suppressed, and the characteristic impedance can be reduced. At the same time, it is possible to suppress the increase in radiation loss caused by the conventional line width becoming thicker.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the high frequency integrated circuit of the present invention, FIG. 2 is a cross-sectional view taken along line AA' in FIG. 1, and FIG.
FIG. 2 is a circuit diagram of a 1/2 wavelength transformer. 1... GaAs substrate, 2... Upper layer line of strip line, 3... Ground line of strip line, 4... S
i02 layer 0

Claims (1)

[Claims] 1. It is characterized by comprising a substrate, a dielectric having a dielectric constant different from that of the substrate embedded in a removed portion obtained by removing a part of the substrate, and a transmission line formed on the dielectric. High frequency integrated circuit.