JP2000261214A - High frequency integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a high frequency integrated circuit for microwave and millimetric wave bands. SOLUTION: First to third layers of BCB thin films 106 are laminated as a dielectric thin film on a silicon substrate 109 by spin coating and firing. Four metallic layers are provided on the silicon substrate 109 and BCB thin films 106. The fourth metallic layer 105c is used to constitute a matching circuit and a transmission line, and the third metallic layer 105b and the fourth metallic layer 105c constitute a parallel plane plate type capacity 103 having BCB thin films as an insulating material. An active element 101 is mounted on the fourth metallic layer 105c by flip chip mounting using a bump 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency integrated circuit, and more particularly to a high-frequency integrated circuit used for a radio communication device of a microwave or millimeter wave band radio system.

[0002]

2. Description of the Related Art Conventionally, as a high frequency integrated circuit, 199
The one described in 6th year IEEE MTT-S Microwave Symposium Digest pp. 1209-1213 is known.

FIG. 11 is a sectional view showing the structure of a conventional high frequency integrated circuit. In this high frequency integrated circuit, a MESFET as an active element is formed on a gallium arsenide substrate 901.
902, a parallel plate type capacitor 903 and a resistor 904, which are passive elements, are formed by a semiconductor process. Also, four polyimide layers 90 are formed on the active element and the passive element.
5 are stacked. A ground layer and other wiring layers are formed between the polyimide layers 905 and on the polyimide layer 905. The layers formed on and between the polyimide layers are connected by via holes 906.

[0004]

In a high-frequency integrated circuit having such a configuration, the influence of a floating component becomes large at a high frequency, particularly at a microwave and a millimeter wave band.
Lumped constants cannot be used. For this reason, the low-pass filter used for the bias circuit needs to be configured by combining a plurality of quarter-wavelength lines, and has a larger shape than a matching circuit or the like. Therefore, there is a problem that the high-frequency integrated circuit having the low-pass filter having such a structure is increased in size.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a high-frequency integrated circuit that can be reduced in size.

[0006]

The gist of the present invention is such that BCB thin films having different thicknesses are laminated in multiple layers on a substrate having a high dielectric constant, and active elements are mounted by flip chips. . Thereby, a small and inexpensive high-frequency integrated circuit can be configured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-frequency integrated circuit according to a first aspect of the present invention comprises a substrate having a first dielectric constant, a high-frequency blocking low-pass filter circuit formed on the substrate,
A dielectric layer formed on the substrate, having a second dielectric constant lower than the first dielectric constant, and including at least three layers; a ground layer provided between the dielectric layers; The configuration includes a wiring layer formed on the uppermost layer of the dielectric layer, and an active element mounted on the wiring layer.

According to this structure, the effective dielectric constant of the substrate is higher than other metal wiring layers. For this reason, the quarter wavelength line can be formed short, and the high-frequency integrated circuit can be improved in performance and downsized.

A high-frequency integrated circuit according to a second aspect of the present invention includes a substrate having a first dielectric constant, a matching circuit and a high-frequency transmission line formed on the substrate, and a high-frequency transmission line formed on the substrate. A dielectric layer having a second dielectric constant lower than the first dielectric constant and having at least three layers, a ground layer provided between the dielectric layers, and a top layer of the dielectric layer; A configuration including the formed wiring layer and an active element mounted on the wiring layer is adopted.

According to this configuration, by providing the matching circuit on the silicon substrate having a high dielectric constant, the circuit can be made compact. Further, according to this structure, the ground layer provided above the matching circuit can be used as a shield plate, so that there is little influence of external unnecessary radio waves, stable characteristics, small size, low cost, and high frequency. An integrated circuit can be realized.

A high frequency integrated circuit according to a third aspect of the present invention is the high frequency integrated circuit according to the first or second aspect, wherein the dielectric layer is made of benzocyclobutene.

In a high frequency integrated circuit according to a fourth aspect of the present invention, in any one of the first to third aspects, the thickness of the dielectric layer near the substrate is greater than the thickness of the dielectric layer far from the substrate. Also adopts a thick configuration.

A high-frequency integrated circuit according to a fifth aspect of the present invention, in any one of the first to fourth aspects, adopts a structure having a region from which the dielectric layer is removed immediately below the active element.

According to this configuration, a change in the characteristics of the dielectric material on which the active element is formed can be reduced, and a high-frequency integrated circuit having excellent characteristics can be realized without deteriorating the characteristics of the active element.

A high-frequency integrated circuit according to a sixth aspect of the present invention, in any one of the first to fifth aspects, adopts a configuration having a region in which the ground layer is partially removed.

According to this configuration, by removing the ground layer below the active element, the parasitic capacitance between the active element and the ground layer can be reduced, and the characteristics of the active element do not deteriorate. A high-frequency integrated circuit with excellent characteristics can be realized. Further, by removing the ground layer below the parallel plate type capacitor, the parasitic capacitance between the capacitor and the ground layer can be reduced to reduce the loss, and a high frequency integrated circuit having excellent characteristics can be realized.

A high-frequency integrated circuit according to a seventh aspect of the present invention, in any one of the first to sixth aspects, has a configuration in which the active element is mounted in a region from which the dielectric layer has been removed.

According to this configuration, a small and thin high-frequency integrated circuit can be realized by mounting the active element in the area of the removed portion immediately below the active element.

According to an eighth aspect of the present invention, there is provided a high-frequency integrated circuit according to any one of the first to seventh aspects, further comprising an insulator layer formed between the substrate and the dielectric layer. Take.

According to this configuration, the line loss can be suppressed even if a low resistivity, for example, a silicon substrate is used, and a high frequency integrated circuit having excellent characteristics can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a sectional view showing a high-frequency integrated circuit according to Embodiment 1 of the present invention. FIG. 2 is a plan view showing the high-frequency integrated circuit according to Embodiment 1 of the present invention. This high-frequency integrated circuit includes HE
MT (High Electron Transfer Transistor) and MMIC are integrated.

In the high frequency integrated circuit of the present invention, first to third BCB (benzocyclobutene) thin films 106a to 106c are formed on a silicon substrate 109 as dielectric thin films.
Are laminated.

Silicon substrate 109 and BCB thin film 106
On top, four metal layers are provided, the first BCB
The metal layer formed on the thin film 106a is used as the ground layer 107, and the metal layer 105 formed on the silicon substrate 109 and the second and third BCB thin films 106b and 106c is used as a strip conductor. A low-pass filter and a bias circuit are mainly configured using the first metal layer 105a, and a matching circuit and a transmission line are configured using the third metal layer 105c.
b and the third metal layer 105c to form a third BCB thin film 106.
Parallel plate type capacitor (capacitor) 103 where c is an insulator
Is configured.

The third metal layer 105c formed on the third BCB thin film 106c has bumps 10 as conductive members.
An active element 101 such as a MESFET having the number 4 is mounted. That is, the active element 101 is electrically connected to the third metal layer 105c with the bump 104 provided on the electrode formed on the back surface thereof being positioned. The space between the active element 101 including the bump 104 and the third metal layer 105c is filled with a sealing material 102.

The high-frequency integrated circuit having the above configuration is manufactured as follows. That is, first, the first metal layer 105a is formed on the silicon substrate 109 and patterned by a photolithography process. Then
A first BCB thin film 106a is formed on the silicon substrate by spin coating.

Next, by etching, a region corresponding to the first metal layer 105a of the first BCB thin film 106a is formed.
Then, a hole for the via hole 108 is formed. The hole is filled with a conductive material to electrically connect the first metal layer 105a to the conductive material in the hole.

Next, a ground layer 107 is formed on the first BCB thin film 106a and is patterned by a photolithography process. Next, a second BCB thin film 106b is formed on the first BCB thin film 106a by spin coating.

Next, a hole for the via hole 108 is formed by etching on the second BCB thin film 106b where the ground layer 107 is not formed. The holes are filled with a conductive material to electrically connect the conductive materials in the holes of each BCB thin film.

Next, a second metal layer 105b is formed on the second BCB thin film 106b and patterned by a photolithography process. Then, this second B
A third BCB thin film 106c is formed on the CB thin film 106b by spin coating.

Next, by etching, a region corresponding to the first metal layer 105a of the second BCB thin film 106a is formed.
Then, a hole for the via hole 108 is formed. The hole is filled with a conductive material to electrically connect the second metal layer 105b and the conductive material in the hole of the third BCB thin film 106c.

Next, a third metal layer 105c is formed on the third BCB thin film 106c, and is patterned by a photolithography process. At this time, the conductive material in the via hole 108 is electrically connected to the third metal layer 105c.

Next, an active element having an electrode on the back surface is mounted on the third metal layer 105c via the bump 104 so that the third metal layer 105c and the electrode are electrically connected. That is, the active element 101 is mounted on the third metal layer 105c by flip chip mounting. Then, a sealing material 102 is filled between the third metal layer 105c and the active element 101.

The three BCB thin films 106a to 106b
The thickness c can be adjusted by changing the number of rotations of the spin coat. Here, the first BCB thin film 106a and the second BCB thin film 106b have a thickness of about 10 μm.
m, and the thickness of the third BCB thin film 106c is about 5 μm. That is, a low-pass filter that requires high performance is sandwiched between relatively thick BCB thin films, and a parallel plate capacitor that requires small size is sandwiched between relatively thin BCB thin films. As described above, the thickness of the BCB thin film is controlled according to the characteristics required for the element to be formed. Thereby, an appropriate circuit structure can be obtained according to the characteristics of the element.

Each of the metal layers 105a to 105c is electrically connected by a conductive material filled in the via hole 108 as appropriate.

FIG. 2 shows a specific example of such a high-frequency integrated circuit.
This will be described with reference to FIG. This circuit consists of HEMT 111 and MM
A low-noise, high-gain IC in which the IC 112 is integrated;
The first stage HEMT 111 realizes low noise characteristics, and the second stage MMIC 112 realizes high gain characteristics.

The high-frequency signal input from the input terminal 114 is supplied to the flip-chip mounted H
Amplified by a low-noise amplifier constituted by the EMT 111 and a matching circuit 116 constituted by using the third metal layer 105c, the MM for low-noise and high-gain amplification at the subsequent stage is used.
The signal is amplified by the IC 112 and output from the output terminal 115.

A bias to the HEMT 111 and the MMIC 112 is applied via a bias circuit 118 formed on the first metal layer 105a. The capacitance required for the bias circuit 118 and the DC cut is built in the circuit by the parallel plate type capacitors 103 and 113 configured using the second and third metal layers 105b and 105c.

At high frequencies, especially in the microwave and millimeter wave bands, lumped constants cannot be used because the influence of floating components increases. For this reason, the low-pass filter used for the bias circuit needs to be configured by combining a plurality of quarter-wavelength lines, and has a larger shape than a matching circuit or the like. Therefore, there is a problem that the high-frequency integrated circuit having the low-pass filter having such a structure is increased in size.

By employing the structure according to the present embodiment, the microstrip line formed on the first metal layer 105a has an effective dielectric constant of another metal wiring due to the effect of the silicon substrate 109 having a high dielectric constant. Higher than the layer. The 波長 wavelength line refers to a line having an electrical length of 90 degrees, and the physical length of this line is determined by (physical length when the dielectric constant is 1) / (√effective dielectric constant). Therefore, the higher the effective permittivity, the shorter the physical length of the quarter wavelength line can be realized. For this reason, high performance and miniaturization of the high frequency integrated circuit can be achieved.

Further, the parallel plate type capacitor 103 can be formed by using the same dielectric material (the same material as the insulating material for the wiring) in the same process as the process for forming the other dielectric layers, thereby simplifying the process. It is possible. In this parallel plate type capacitor, the third BCB thin film 106c
By setting the thickness of the layer to 5 μm or less, the capacitance value can be increased.

In the above embodiment, the BCB
Although the case where the thin film 106 is composed of three layers is described, the same effect as described above can be obtained even if the BCB thin film (dielectric layer) is further laminated in four or more layers.

In the above embodiment, the case where a BCB thin film is used as the dielectric layer has been described. However, as the dielectric layer, another dielectric material such as polyimide or a dielectric material having a higher dielectric constant than BCB is used. The present invention can be similarly implemented by using a material having a ratio.

In the above embodiment, the case where a silicon substrate is used as the dielectric substrate has been described. However, as the dielectric substrate, a ceramic substrate, a ceramic multilayer substrate, a quartz substrate, a GaAs substrate, and especially a resistor substrate may be used. The present invention can be similarly implemented by using a high-resistance silicon substrate having a high rate.

(Embodiment 2) FIG. 3 is a sectional view showing a high frequency integrated circuit according to Embodiment 2 of the present invention. FIG.
1 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, and therefore the difference between them will be described. In the following embodiment, the manufacturing method is the same as that of the first embodiment, and the description is omitted.

In the high frequency integrated circuit shown in FIG.
The difference from the high frequency integrated circuit shown in FIG. 1 is that a metal layer is formed as a ground layer 207 on the second BCB thin film 106b. The metal layer 205c formed on the third BCB thin film 106c is provided with a low-pass filter circuit for blocking high frequencies and a bias circuit, and the metal layer 205a formed on the silicon substrate 109 and the first BCB The first BCB thin film 10 with the metal layer 205b formed on the thin film 106a.
A parallel plate type capacitor 103 using 6a as an insulator is provided.
A matching circuit and a line for transmitting a high frequency are provided on the metal layer 205a.

With such a structure, that is, by providing a matching circuit on a silicon substrate having a high dielectric constant, the circuit can be miniaturized. This is because matching circuits having the same phase characteristic can be made smaller on a substrate having a high dielectric constant. Further, according to this structure, the ground layer provided above the matching circuit can be used as a shield plate, so that there is little influence of external unnecessary radio waves, stable characteristics, small size, low cost, and high frequency. An integrated circuit can be realized.

(Embodiment 3) FIG. 4 is a sectional view showing a high-frequency integrated circuit according to Embodiment 3 of the present invention. FIG. 5 is a plan view showing a high-frequency integrated circuit according to Embodiment 3 of the present invention. Since the high-frequency integrated circuits shown in FIGS. 4 and 5 have the same basic structure as the high-frequency integrated circuits shown in FIGS. 1 and 2, differences between the two will be described.

In the high frequency integrated circuit shown in FIG. 4, the ground layers 107 and 119 immediately below the active element 101 are removed.
A ground layer removing unit 310 is provided.

With such a structure, that is, by providing the ground layer removing portion 310 immediately below the active element 101, the parasitic capacitance between the active element 101 and the ground layer 107 can be reduced. A high frequency integrated circuit having excellent characteristics can be realized without deteriorating device characteristics.

(Embodiment 4) FIG. 6 is a sectional view showing a high-frequency integrated circuit according to Embodiment 4 of the present invention. FIG.
1 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, and therefore the difference between them will be described.

In the high-frequency integrated circuit shown in FIG. 4, a ground layer removing portion 409 is provided by removing the ground layer 107 immediately below the parallel plate type capacitor.

By adopting such a structure, that is, by providing the ground layer removing portion 409 immediately below the parallel plate type capacitor, the parasitic capacitance between the capacitor and the ground layer can be reduced to reduce the loss. A high frequency integrated circuit having excellent characteristics can be realized.

(Fifth Embodiment) FIG. 7 is a sectional view showing a high-frequency integrated circuit according to a fifth embodiment of the present invention. FIG.
1 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, and therefore the difference between them will be described.

In the high frequency integrated circuit shown in FIG. 7, the BCB thin film 106 and the ground layer 107 just below the active element 101 are provided.
And a removing unit 510 is provided.

By adopting such a structure, that is, by providing the removing portion 510 immediately below the active element 101, a change in the characteristics of the dielectric material on which the active element is formed can be reduced, and A high frequency integrated circuit having excellent characteristics can be realized without deteriorating characteristics.

(Embodiment 6) FIG. 8 is a sectional view showing a high-frequency integrated circuit according to Embodiment 6 of the present invention. FIG.
1 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, and therefore the difference between them will be described.

In the high-frequency integrated circuit shown in FIG. 8, the second BCB thin film 106b, the third BCB thin film 106c, and the ground layer 107 immediately below the active element 101 are removed, and a removing section 610 is provided. The active element 101 is flip-chip mounted in the region.

By adopting such a structure, that is, by mounting the active element 101 in a region of the removal portion 610 immediately below the active element 101 by flip-chip mounting, a small and thin high-frequency integrated circuit can be realized.

In this embodiment, the second B
Although the case where the removed portion 610 is formed by removing the CB thin film 106b, the third BCB thin film 106c, and the ground layer 107 has been described, even if the removed portion is formed by removing only the BCB thin film 106, Third BCB thin film 10
6a to 106c, the ground layer 107 may be removed to form a removed portion, and the present invention can be similarly implemented.

(Embodiment 7) FIG. 9 is a sectional view showing a high-frequency integrated circuit according to Embodiment 7 of the present invention. FIG.
1 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, and therefore the difference between them will be described.

In the high frequency integrated circuit shown in FIG. 9, an SiO ₂ thin film 710 is laminated on a silicon substrate 109 as an insulator thin film.

With such a structure,
First, the SiO.sub. _TwoLaminate thin film 710
By using a silicon substrate with low resistivity,
Line loss can be suppressed, resulting in excellent characteristics
A frequency integrated circuit can be realized.

In this embodiment, the case where the SiO ₂ thin film 710 is used as the insulator thin film has been described, but other insulator thin films, for example, silicon nitride (Si)
N) can be similarly implemented.

A bipolar transistor or a field-effect transistor may be formed on a silicon substrate to form a circuit for processing a low-frequency signal.

(Eighth Embodiment) FIG. 10 is a sectional view showing a high-frequency integrated circuit according to an eighth embodiment of the present invention. Since the high-frequency integrated circuit shown in FIG. 10 has the same basic structure as the high-frequency integrated circuit shown in FIG. 1, the difference between them will be described.

In the high frequency integrated circuit shown in FIG.
Instead of a silicon substrate, a capacitor 804, a thin film resistor 80
2 and an inductor 805 are formed, and a ceramic multilayer substrate 809 in which a first metal layer and an inductance 805 are connected by a via hole 807 is used.

By adopting such a structure, that is, by incorporating a capacitance, a resistor, and an inductor, the number of components mounted on the circuit can be reduced, and a small-sized and inexpensive high-frequency integrated circuit can be realized.

The present invention is not limited to the first to eighth embodiments, but can be implemented with various modifications. Also,
Embodiments 1 to 8 above can be implemented in appropriate combinations.

The high-frequency integrated circuit of the present invention can be applied to a base station device, a communication terminal device, and a wireless measurement device used in a wireless communication system.

[0071]

As described above, according to the present invention, BCB thin films having different thicknesses are stacked in multiple layers on a silicon substrate, and the active elements are mounted by flip chips.
An advantageous effect that a small-sized and inexpensive high-frequency integrated circuit can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a high-frequency integrated circuit according to a first embodiment of the present invention;

FIG. 2 is a plan view showing the high-frequency integrated circuit according to the first embodiment.

FIG. 3 is a sectional view showing a high-frequency integrated circuit according to a second embodiment of the present invention;

FIG. 4 is a sectional view showing a high-frequency integrated circuit according to a third embodiment of the present invention;

FIG. 5 is a plan view showing the high-frequency integrated circuit according to the third embodiment.

FIG. 6 is a sectional view showing a high-frequency integrated circuit according to a fourth embodiment of the present invention;

FIG. 7 is a sectional view showing a high-frequency integrated circuit according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing a high-frequency integrated circuit according to a sixth embodiment of the present invention;

FIG. 9 is a sectional view showing a high-frequency integrated circuit according to a seventh embodiment of the present invention;

FIG. 10 is a sectional view showing a high-frequency integrated circuit according to an eighth embodiment of the present invention;

FIG. 11 is a sectional view showing a conventional high-frequency integrated circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101,801 Active element 102 Sealant 103 Parallel plate type capacitor 104 Bump 105,205 Metal layer 106 BCB thin film 107,119,207 Ground layer 108 Via hole 109 Silicon substrate 111 HEMT 112 MMIC 113 Parallel plate type capacitor 114 Input terminal 115 output terminal 116 matching circuit 117 bias terminal 118 bias circuit 310,409 ground layer removal portion 510, 610 removing unit 710 SiO ₂ thin film 802 thin film resistor 804 capacitor 805 inductor 809 ceramic multilayer substrate

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hiroshi Ogura F-term (reference) in Matsushita Communication Industrial Co., Ltd. 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa 5F044 KK04 KK05 KK09 KK13 KK23 QQ01 RR18 5J014 CA05 CA41 CA55

Claims (8)

[Claims] 1. A substrate having a first dielectric constant, a high-frequency blocking low-pass filter circuit formed on the substrate, and a low-pass filter circuit formed on the substrate and having a lower dielectric constant than the first dielectric constant. A dielectric layer having a dielectric constant of 2 and comprising at least three layers, a ground layer provided between the dielectric layers, a wiring layer formed on the uppermost layer of the dielectric layer, and the wiring An active element mounted on the layer. 2. A substrate having a first dielectric constant, a matching circuit and a high-frequency transmission line formed on the substrate, and a second dielectric formed on the substrate and having a lower dielectric constant than the first dielectric constant. A dielectric layer having a refractive index and comprising at least three layers;
A high-frequency integrated circuit comprising: a ground layer provided between the dielectric layers; a wiring layer formed on an uppermost layer of the dielectric layer; and an active element mounted on the wiring layer. circuit. 3. The device according to claim 1, wherein the dielectric layer is made of benzocyclobutene.
A high-frequency integrated circuit according to claim 1. 4. The high-frequency integrated circuit according to claim 1, wherein a thickness of the dielectric layer close to the substrate is larger than a thickness of the dielectric layer far from the substrate. 5. The high-frequency integrated circuit according to claim 1, further comprising a region immediately below said active element, from which said dielectric layer is removed. 6. The high-frequency integrated circuit according to claim 1, further comprising a region in which the ground layer is partially removed. 7. The high-frequency integrated circuit according to claim 1, wherein the active element is mounted in a region where the dielectric layer has been removed. 8. The high-frequency integrated circuit according to claim 1, further comprising an insulator layer formed between said substrate and said dielectric layer.