JPH0983241A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the gain and the directivity and to reduce the chip area by utilizing an antenna mirror image to increase the gain and the directivity and separating sufficiently circuit functions without causing the increase in inter-component distance associated therewith. SOLUTION: In an MMIC integrating an antenna, a 60GHz processing circuit 11 formed on a major side of a GaAs substrate 10 and consisting of an HBT, resistors and capacitive components, a line 14 formed on the major side of the substrate 10 and connecting to the processing circuit 11, a 2nd ground conductor layer 13 formed on the major side of the substrate 10 via a polyimide film 12 to form a slot antenna consisting of a reverse microstrip line with the line 14 and a 1st ground conductor layer 18 formed to a rear side of the substrate 10 are provided and the thickness of the substrate 10 is selected to be 330μm, that is 1/4 of a wavelength of an electromagnetic wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device incorporating an antenna element, and more particularly to a semiconductor device having a microwave / millimeter wave processing function.

[0002]

2. Description of the Related Art In recent years, development of ultra-high-speed devices using III-V group compound semiconductors such as GaAs and InP has progressed, and so-called M in which microwave band processing functions are integrated on a semiconductor substrate.
MIC (Monolithic Microwave Integrated Circuit)
Research and development of technology is also actively carried out. Especially 30 GHz
In the above-mentioned millimeter wave region, the radiation loss of the microstrip line or the like becomes large, so it is necessary to shorten the mutual connection between the circuit elements as much as possible. Therefore, in a millimeter wave radio device or the like, an MMIC in which an antenna is integrally integrated on a semiconductor element is required.

FIG. 6 shows a conventional MMIC integrated with an antenna.
Is shown. On the semi-insulating GaAs substrate 1, HBT (Hetero
A bipolar transistor 2 and each functional circuit 3 such as an amplifier including a resistance, a capacitance, and an inductance element are integrated, and each functional circuit 3 is connected by a microstrip line 4. The output of the amplifier is supplied to the microstrip patch antenna 6 via the matching circuit 5. A ground conductor 7 is provided on the back surface of the GaAs substrate 1.

In the above structure, the high frequency power supplied from the amplifier is the microstrip patch antenna 6.
Are stored in and radiated into free space. Normally, the thickness of the dielectric substrate that constitutes the microstrip line is set sufficiently lower than the desired wavelength. For example, in a line that transmits a frequency of 60 GHz, the GaAs substrate 1 has a thickness of 5
It is set to about 0 μm. This is about 1/28 of the wavelength of electromagnetic waves in GaAs.

In the conventional example of FIG. 6, it is possible to integrally form an antenna element and a circuit function, but there is still an unsolved problem. For example, in the example of FIG. 6, the case where there is only one patch is illustrated, but in such a case, the radiation pattern of the antenna is almost omnidirectional with respect to the half space above the ground plane, so the gain is small. . It is effective in many applications to increase the gain by giving directivity to some extent, but for this purpose, it is necessary to provide a plurality of antenna elements.

FIG. 7 shows an example in which a plurality of antenna elements 8 and 9 are provided to improve the gain by about 3 dB. But,
Since the GaAs substrate is expensive, it is necessary to make the chip area as small as possible. Considering handling a frequency of 60 GHz, the size of the microstrip patch needs to be about a half wavelength, so if the wavelength shortening rate on the GaAs substrate is 0.3, one side is 0.75 m.
A size of m is required. Furthermore, in order to form a plurality of antenna elements, an area that is an integral multiple thereof is required. This is an element that occupies most of the area of the semiconductor substrate in many applications, and therefore there is a problem that the antenna gain and the cost reduction cannot be achieved at the same time.

As another means of improving the gain of the antenna, it is possible to use a mirror image of the antenna. If the conductor layer is provided at a position separated by ¼ wavelength from the antenna, the image charge is formed at a position separated by a half wavelength, so that the antenna gain can be increased by about 3 dB and the directivity can be improved.
Considering handling the frequency of 60 GHz, GaA
The thickness of the substrate is 350 μm, which corresponds to a quarter wavelength,
Providing the ground conductor layer on the surface of the substrate increases the directivity without increasing the area of the antenna.

On the other hand, in order to avoid electrical mutual interference in the connection of the circuit functions, it is necessary to provide an element spacing and a line spacing of, for example, about 5 times that of the microstrip line substrate, and a substrate having a thickness of 350 μm is used. If yes, 60
At GHz, it becomes 1.7 mm, which rather increases the chip area.

[0009]

As described above, conventionally, in a semiconductor device having a microwave / millimeter wave processing function having an antenna element built-in, it is possible to improve gain and directivity by utilizing a mirror image of the antenna. However, if the thickness of the substrate is increased to use the mirror image, it is necessary to widen the element spacing and the line spacing in order to avoid mutual interference of circuit functions, which causes a problem of increasing the chip area.

The present invention has been made in consideration of the above circumstances. An object of the present invention is to increase gain and directivity by utilizing an antenna mirror image, and to increase the inter-element distance accordingly. An object of the present invention is to provide a semiconductor device with a built-in antenna element, which can sufficiently separate circuit functions without inviting each other and can achieve both improvement of gain and directivity and reduction of chip area.

[0011]

[Means for Solving the Problems]

(Summary) In order to solve the above problems, the present invention employs the following configuration. That is, according to the present invention, in a semiconductor device having a built-in antenna element, a circuit element including at least one semiconductor element formed on a main surface of a semi-insulating compound semiconductor substrate and an electromagnetic wave formed on the main surface of the substrate are input. Alternatively, an antenna element for outputting, a first ground conductor layer formed on the back surface of the substrate, a line formed on the main surface of the substrate and connected to the circuit element, and a line that forms a transmission line together with the line. It is characterized by comprising two ground conductor layers.

The following are preferred embodiments of the present invention. (1) The distance between the line and the second ground conductor layer is (1/1) with respect to the wavelength λ of the electromagnetic wave input or output from the antenna element.
8) λ or less, and the distance between the antenna element and the first ground conductor layer is (1/8) λ to (3/8) λ. (2) The second ground conductor layer is formed on the main surface of the substrate with an insulating layer interposed between the line and the antenna element, and the antenna element is a slot antenna including an opening of the second ground conductor layer. (3) The second ground conductor layer is formed on the main surface of the substrate on the same surface as the line, and the antenna element is formed with the line and the surface on which the second ground conductor layer is formed sandwiching an insulating layer. It must be a patch antenna. (4) A GaAs substrate was used as the semi-insulating compound semiconductor substrate. (5) HBT or HEMT (High Electron Mobility Transistor) is used as a semiconductor element formed on the main surface of the substrate. (6) Polyimide was used as the insulating layer. (Operation) In the present invention, in order to improve the gain of the microstrip antenna integrated on the substrate, the first ground conductor is formed so that the mirror image of the antenna is formed at a position separated from the antenna by an effective wavelength of about a half wavelength. A layer is provided and a second ground conductor layer is provided as a ground conductor of a transmission line used for connecting circuit functions to each other. The first ground conductor layer is formed on the back surface of the main surface of the semiconductor substrate on which the antenna element is formed.

In such a structure, the effective distance between the first ground conductor layer and the antenna element is (1/8) λ to (3/8) λ, with respect to the wavelength λ of the electromagnetic wave in the substrate. Desirably, by selecting (1/4) λ, a mirror image of the antenna occurs at a position separated by a half wavelength, so that the directivity of the antenna is increased and the gain is improved. If the thickness of the substrate is selected so that the first ground conductor layer is formed on the back surface of the semiconductor substrate, the gain can be improved without increasing the number of steps and the chip area, so that the cost can be reduced.

Further, by providing the second ground conductor layer as the ground layer of the transmission line interconnecting the circuit functions, the circuit functions can be electrically separated from each other in a short distance, and the chip area can be reduced. Therefore, the cost can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 and 2 are for explaining a schematic configuration of a semiconductor device with a built-in antenna element according to a first embodiment of the present invention. FIG. 1 is a sectional view and FIG. 2 is a perspective view. is there.

In this embodiment, Ga having a thickness of 330 μm is used.
HBT on As substrate (semi-insulating compound semiconductor substrate) 10
A processing circuit (circuit element) 11 of 60 GHz including a resistor and a capacitor is integrated, a polyimide film 12 having a thickness of 5 μm is laminated on the substrate surface, and a second ground conductor layer 13 is laminated thereon. There is. The connection between circuit elements is Ga
This is performed by a so-called reverse microstrip line (transmission line) composed of the line 14 formed on the As substrate 10 and the second ground conductor layer 13.

A slot 15 is opened at a desired position of the second ground conductor layer 13, and an inverted microstrip line extending from the processing circuit 11 is connected to the second ground conductor layer 13 at the lower portion 16 of the slot, whereby The structure is such that the electromagnetic wave 17 is radiated from the slot 15 toward the upper surface of the substrate.
The shape of the slot 15 is set so as to obtain a desired band, but when radiating 60 GHz, for example, the long side is 2 m.
A rectangle of about m is used.

A first ground conductor layer 18 is provided on the lower surface of the GaAs substrate 20. The first ground conductor layer 18 and the second ground conductor layer 13 are connected by a conductor 19 penetrating the GaAs substrate 10.

With such a structure, the second ground conductor layer 13 forming the slot antenna and the first grounding layer on the back side of the substrate are formed.
The distance from the ground conductor layer 18 is 60 Ga
Since the wavelength is ¼ of the wavelength λ of the electromagnetic wave in As, the gain and directivity can be increased due to the mirror image of the antenna. Further, since the second ground conductor layer 13 forms the microstrip line with the line 14 on the main surface of the substrate via the polyimide film 12 having a thickness of 5 μm, the circuit elements may be separated from each other by about five times as much. It is not necessary to make a large gap to prevent interference between circuit elements.

Here, when the distance between the first and second ground conductor layers is changed, the antenna image effect also changes, but the distance, that is, the thickness of the GaAs substrate is preferably in the following range. The radiated electric field strength in the direction perpendicular to the antenna main surface is shown in FIG. 3 as a function of the thickness of the GaAs substrate 10. For comparison, the electric field strength when there is no first ground conductor layer is shown by a broken line in the figure.

In the direction perpendicular to the main surface, the radiated electric fields from the dipole at the antenna position and the dipole of the opposite phase at the mirror image position are added together, and the intensity periodically changes every time the substrate thickness changes by half a wavelength. From FIG. 3, if the thickness of the GaAs substrate is larger than 1/8 wavelength and smaller than 3/8,
The electric field strength in the direction perpendicular to the main surface can be increased as compared with the case without the first ground conductor layer.

As described above, according to this embodiment, GaAs
Since the thickness of the substrate 10 is set to about 1/4 of the wavelength λ of the electromagnetic wave in GaAs and the first ground conductor layer 18 is formed on the back surface of the GaAs substrate 10, the mirror image of the antenna is separated by half a wavelength. In the position, the directivity of the antenna can be increased and the gain can be improved. Since the step for this purpose is only to set the thickness of the GaAs substrate 10 to a desired thickness, the directivity can be controlled and the gain can be improved without increasing the number of steps and the chip area, and the cost can be reduced.

Further, by providing the second ground conductor layer 13 as the ground layer of the transmission line interconnecting the circuit functions, the circuit functions can be electrically separated from each other in a short distance, and the chip area can be reduced. Therefore, the cost can be reduced. In the present embodiment, the polyimide film 12 having a thickness of 5 μm is used as the insulating layer forming the transmission line, and the element spacing can be reduced to about 25 μm without electromagnetic mutual interference, which reduces the chip area and cost. It is valid. In addition, the slot line forming the antenna is GaAs (relative permittivity = 1)
Since it is formed on polyimide having a lower dielectric constant (relative permittivity = 3) than 3), the antenna area can be made larger and the radiation efficiency in the air can be increased as compared with the case where the antenna is directly provided on GaAs. (Second Embodiment) FIGS. 4 and 5 are for explaining a schematic structure of a semiconductor device with a built-in antenna element according to a second embodiment of the present invention. FIG. 4 is a sectional view and FIG. 5 is a perspective view. .

In this embodiment, Ga having a thickness of 330 μm is used.
HBT on As substrate (semi-insulating compound semiconductor substrate) 20
A 60 GHz processing circuit (circuit element) 21 composed of a resistor and a capacitor is integrated, a second ground conductor layer 23 is laminated on the substrate surface, and a polyimide film 22 having a thickness of 5 μm is laminated thereon. There is. The connection between circuit elements is Ga
This is performed by a coplanar line (transmission line) composed of the line 24 formed on the surface of the As substrate and the second ground conductor layer 23.

The patch antenna 2 is provided on the polyimide film 22.
5 is formed, and the patch antenna 25 is connected to the center conductor (line 24) of the coplanar line. The electromagnetic wave 27 is radiated from the surface of the patch antenna 25 toward the upper surface of the substrate. The shape of the patch is
It is set so that a desired band can be obtained, but in particular, the reflection of the position of the ground conductor layer is suppressed so that it is discontinuously converted from the second ground conductor layer 23 to the later-described first ground conductor layer. To design.

Further, in the present embodiment, the patch antenna 25
However, it is also possible to omit the polyimide film 22 by directly forming the patch antenna 25 on the GaAs substrate 20.

A first ground conductor layer 28 is provided on the lower surface of the GaAs substrate 20. The first ground conductor layer 28 and the second ground conductor layer 23 are connected by a conductor 29 penetrating the GaAs substrate 20. In FIG. 5, in order to clearly show the circuit configuration on the GaAs substrate that supplies power to the antenna, the uppermost polyimide film in the circuit portion is omitted.

Even with such a configuration, the distance between the patch antenna 25 and the first ground conductor layer 28 can be set to about 1/4 wavelength of the electromagnetic wave in GaAs at 60 GHz, and the line 24 and Since the coplanar line is formed with the second ground conductor layer 23 at an extremely short interval, it is possible to prevent the mutual interference of the circuit elements without the need to greatly separate the circuit elements. Therefore, the same effect as in the first embodiment can be obtained.

The present invention is not limited to the above embodiments. In the embodiments, the case of radiating electromagnetic waves into the air has been taken as an example, but the present invention can also be applied to the configuration of a semiconductor device having a function of receiving and amplifying radio waves. Further, in the embodiment, the first ground conductor layer is placed at a position separated from the antenna main surface by about 1/4 wavelength at the effective wavelength, but this distance can be changed as appropriate within a range where a desired radiation pattern and antenna gain are obtained. Is.

The substrate is not limited to GaAs, and a semi-insulating compound semiconductor substrate suitable for forming HBT or HEMT can be used. Further, the insulating layer is not necessarily limited to polyimide, and various insulating materials can be used. However, in order to increase the radiation efficiency in the air as compared with the case where the antenna is directly provided on the semiconductor substrate, it is desirable that the dielectric constant is lower than that of the substrate. Other,
Various modifications can be made without departing from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, the first ground conductor layer for forming the antenna mirror image is provided on the back surface of the semi-insulating compound semiconductor substrate, and the transmission line is provided on the main surface side of the substrate. By providing the second ground conductor layer for formation, the gain and directivity can be increased by utilizing the antenna mirror image, and the circuit functions can be sufficiently separated from each other without causing the increase in the distance between the elements. can do. Therefore, it is possible to realize a semiconductor device with a built-in antenna element that can achieve both improvement of gain and directivity and reduction of chip area.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a semiconductor device with a built-in antenna according to a first embodiment.

FIG. 2 is a perspective view showing a schematic configuration of a semiconductor device with a built-in antenna according to the first embodiment.

FIG. 3 is a characteristic diagram showing the relationship between GaAs substrate thickness / wavelength in GaAs and electric field strength.

FIG. 4 is a sectional view showing a schematic configuration of a semiconductor device with a built-in antenna according to a second embodiment.

FIG. 5 is a perspective view showing a schematic configuration of a semiconductor device with a built-in antenna according to a second embodiment.

FIG. 6 is an antenna integrated MMI according to a first conventional example.
The figure which shows C.

FIG. 7 is an antenna integrated MMI according to a second conventional example.
The figure which shows C.

[Explanation of symbols]

 10, 20 ... GaAs substrate 11, 21 ... Processing circuit 12, 22 ... Polyimide film 13, 23 ... Second ground conductor layer 14, 24 ... Line 15 ... Slot 16 ... Slot lower part 17, 27 ... Electromagnetic wave 18, 28 ... 1. Ground conductor layer 19, 29 ... Conductor 25 ... Patch antenna

Claims (4)

[Claims] 1. A circuit element including at least one semiconductor element formed on a main surface of a semi-insulating compound semiconductor substrate, an antenna element formed on the main surface of the substrate for inputting or outputting electromagnetic waves, and the substrate. A first ground conductor layer formed on the back surface of the substrate, a line formed on the main surface of the substrate and connected to the circuit element, and a second line forming a transmission line together with the line.
2. A semiconductor device comprising the ground conductor layer of. 2. A circuit element including at least one semiconductor element formed on a main surface of a semi-insulating compound semiconductor substrate, an antenna element formed on the main surface of the substrate for inputting or outputting electromagnetic waves, and the substrate. A first ground conductor layer formed on the back surface of the substrate, a line formed on the main surface of the substrate and connected to the circuit element, and a second line forming a transmission line together with the line.
And a separation distance between the line and the second ground conductor layer is 1/8 of a wavelength λ of an electromagnetic wave input or output from the antenna element.
The semiconductor device is characterized in that the distance between the antenna element and the first ground conductor layer is 1/8 or more and 3/8 or less of the wavelength λ. 3. A slot antenna having a second ground conductor layer formed on the main surface of the substrate with an insulating layer sandwiched between the line and the antenna element, the slot element comprising an opening of the second ground conductor layer. The semiconductor device according to claim 1 or 2, wherein 4. A second ground conductor layer is formed on the same main surface of the substrate as the line, and the antenna element is different from the surface on which the line and the second ground conductor layer are formed. The semiconductor device according to claim 1 or 2, which is a patch antenna formed with an insulating layer sandwiched therebetween.