JP2565283B2 - Monolithic microwave integrated circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic microwave integrated circuit (MMIC) and its chip (MMIC chip), and more particularly to an MMIC having a field effect transistor (FET) whose electrode terminal is grounded by a via hole and its chip.

[0002]

2. Description of the Related Art Conventionally, a high frequency band (1
At 4 GHz or higher), the MMIC chip that forms the FET, which is an amplification element, on the surface of the semiconductor substrate is
In order to reduce the connection inductance between the ground terminal and the ground potential, the ground terminal is directly connected to the metallized conductor formed on the back surface of the semiconductor substrate by a via hole. In the MMIC chip having the via hole structure, it is necessary to make the semiconductor substrate forming the circuit element of the MMIC chip as thin as possible in order to facilitate the manufacturing process and reduce the connection inductance. Incidentally, in this type of MMIC, it is necessary to improve the electric performance by considering various design elements described later in addition to the reduction of the connection inductance.

FIG. 4 shows an MMIC using the above-mentioned conventional technique.
FIG. 3 is a cross-sectional view of a chip, which is an open patent publication (publication number: Sho 6
3-164503, publication date: July 7, 1988, title of invention: monolithic microwave integrated circuit).

This MMIC chip has microstrip conductors 51a and 51b on the surface of a semiconductor substrate 54.
Metallized conductors 53 are respectively formed on the back surface of the semiconductor substrate 54 by a metallization process, and the microstrip conductors 51a and 51b and the metallized conductor 53 that maintains the ground potential constitute a microstrip line, and these microstrip lines form a circuit element. Connect between. Further, in this MMIC chip, the FET or high frequency terminal (not shown) formed on the surface of the semiconductor substrate 54 and the back surface of the semiconductor substrate 54 at the ground potential are connected by the via hole 52 with a small floating reactance. Here, in this MMIC chip, slits 54a and 54b are provided in the portions corresponding to the microstrip conductors 51a and 51b on the back surface of the semiconductor substrate 54, respectively, and the electric field is concentrated at the end portions of these slits 54a and 54b, whereby the MMIC is formed. In the circuit design of the chip, the high impedance characteristics required for the microstrip line are realized.

[0005]

In the conventional MMIC chip and the MMIC using this MMIC chip, since it is necessary to thin the semiconductor substrate in order to form the via hole, it is necessary to increase the impedance of the microstrip line. It is necessary to reduce the width of the microstrip conductor, which causes a problem that the transmission loss of the microstrip line increases. This transmission loss is still larger than the desired value even if the impedance of the microstrip line is increased as shown in FIG.

When the microstrip conductor formed on the front surface of the semiconductor substrate has a complicated shape, the slit required for the end portion for concentrating the electric field is formed on the back surface of the semiconductor substrate. Is difficult.

Further, in the MMIC, it is desired that heat generated by the FET or the like can be efficiently radiated to the base carrier holding the MMIC chip.

[0008]

[0009]

SUMMARY OF THE INVENTION The monolithic microwave integrated circuit of the present invention comprises a heat generating device including a field effect transistor.
Low loss transmission circuit element including functional element and strip conductor
Are formed on the front surface side of the semiconductor substrate, and
Except for the position of the surface corresponding to said transmission circuit element and said position
A metallized conductor is formed in the area excluding the vicinity of
The source terminal of the effect transistor is via
Monolithic microwave connected to the metallized conductor
An integrated circuit chip and a metallized conductor are fixedly connected to hold the monolithic microwave integrated circuit chip, and one surface of a conductor that generates a ground potential of the transmission circuit element is electrically separated from the back surface of the semiconductor substrate. And a base carrier having the same.

One of the monolithic microwave integrated circuits may have a structure in which one surface of the conductor of the base carrier has a convex portion and a concave portion, and the metallized conductor is fixedly connected to the convex portion.

Another one of the monolithic microwave integrated circuits has a structure in which a space formed by the back surface and the recess is filled with a dielectric material having a dielectric constant lower than that of the semiconductor substrate. Good.

Still another one of the monolithic microwave integrated circuits is that the metallized conductor has a thickness of 3
0 μm or more, one surface of the conductor is a flat surface,
A configuration may be adopted in which a distance electrically separated from the back surface of the semiconductor substrate is held by the metallized conductor.

[0013]

The present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention (a).
Is a plan view, and (b) is a sectional view taken along the line A1-A2.

This MMIC is an amplifier for microwave signals, and is an MMIC chip 1 formed on a semiconductor substrate 18 made of gallium arsenide and a metallized conductor 16 (16a, 16b and 16c) formed on the back surface of the semiconductor substrate 18.
Is provided with a base carrier 2 for fixedly connecting to the convex portions 22 (22a, 22b and 22c) of itself by soldering gold-tin alloy (AuSn) or the like. The metallized conductor 16 is formed by a known metallization process.

In the MMIC chip 1, a FET 15 is formed on the surface of a semiconductor substrate 18 as a heating element as well as a microwave signal amplifying element. The chip 1 may include a resistor that constitutes a high frequency termination circuit or the like as a heating element. In addition, this chip 1 has the strip conductors 12 (12a, 12a) formed on the same surface of the semiconductor substrate 18.
b, 12c, 12d and 12e) and a bonding pad 11 (11a, 11b, which is a connection terminal for connecting the strip conductor 12 to an external circuit by a bonding wire or the like.
11c and 11d) and the capacitor 13 (13a, 1
3b and 13c).

The bonding pad 11a, which is an input terminal for the microwave signal, is connected to the FET through the strip conductor 12a, the capacitor 13a and the strip conductor 12b.
It is connected to 15 gate terminals G. Gate terminal G
Is also connected to the bonding pad 11c, which is a terminal for supplying a gate voltage, via the strip conductor 12b and the strip conductor 12c forming the inductor.
The drain terminal D of the FET 15 is connected to the bonding pad 11b, which is an output terminal of the amplified microwave signal, via the capacitor 13b and the strip conductor 12e. The drain terminal D is also connected to a bonding pad 11d, which is a terminal for supplying a drain voltage, via a strip conductor 12d that forms an inductor.

The metallized conductor 16b is arranged on the back surface of the semiconductor substrate 18 directly below the FET 15 and corresponds to the FET 1
The heat generated by 5 is quickly radiated to a space or the like through the metallized conductor 16b and the convex portion 21b of the base carrier 2. Further, the metallized conductors 16a and 16c are arranged on the back surface of the semiconductor substrate 18 corresponding to directly below the bonding pads 11a and 11b, and absorb the impact when connecting the bonding wires to the bonding pads 11a and 11b to reduce the semiconductor. The occurrence of damage to the substrate 18 is prevented.

The via hole 14a connects the source terminal S of the FET 15 and a metallized conductor (not shown) formed on the back surface of the semiconductor substrate 18. Also, via hole 14
b is connected to the ground side terminal of the capacitor 13c that bypasses the high frequency signal in the bonding pad 11d, and connects this ground side terminal and the metallized conductor (not shown) formed on the back surface of the semiconductor substrate 18. These via holes 14a and 14b have the same structure as the via hole 52 described with reference to FIG.

In the MMIC chip 1, the strip conductor 12 and the capacitor 13 are transmission circuit elements required to have low loss characteristics of microwave signals. In general, these transmission circuit elements are designed not only to supply a microwave signal and a bias current, but also to operate as matching elements on the gate terminal G side and the drain terminal D side of the FET 15. In the chip 1, the strip conductors 12c and 12d swirl the conductor to increase the conductor length and increase the inductance. Conductor 12
The overlapping portions of the conductors c and 12d are insulated by a silicon oxide film. The capacitor 13 is composed of two conductors insulated by a silicon nitride film. Here, on the back surface of the semiconductor substrate 18, at the corresponding positions of the strip conductor 12 and the capacitor 13 and in the vicinity thereof,
It should be noted that the metallized conductor 16 is not formed in order to have the effects described below.

As described above, the MMIC of FIG.
It includes a C chip 1 and a base carrier 2. The base carrier 2 made of a conductor has a convex portion 16 (1
6a, 16b and 16c) and a recess 22 (22a and 22b). The convex portion 21 is at a position corresponding to the metallized conductor 16 of the chip 1, and the concave portion 22 is a surface other than the convex portion 21, that is, the strip conductor 12 and the capacitor 1.
3 are formed at the corresponding positions and in the vicinity thereof. Therefore, the space portion 4 (4a and 4b) is formed between the convex portion 22 and the back surface of the semiconductor substrate 18. The strip conductor 12, the capacitor 13, the semiconductor substrate 18, the space 4, and the recess 22 are shown in FIG.
As can be clearly recognized by referring to
(In the case of gallium arsenide, it has a space portion 4 (relative permittivity = 1) whose permittivity is lower than relative permittivity = 12.8), so that a suspended strip line is formed.

In the above-mentioned suspended strip line, if the width of the strip conductor 12 is the same as when forming the microstrip line as shown in the conventional example, the characteristic impedance is higher than this microstrip line and the transmission loss is higher. It has the characteristic of being low. Therefore, this MMIC has an effect that the microwave signal can be transmitted with low loss while the FET amplifier circuit can be easily matched. In this MMIC, even if the thickness of the semiconductor substrate 18 is increased, the line including the strip conductor 12 and the capacitor 13 can be regarded as a suspended strip line as long as the space 4 is present. It is possible to reduce the chances of destruction and damage of. It should be noted that there is no problem in reducing the thickness of the semiconductor substrate 18 in the portion where the FET 15 and other heating elements are formed and replacing this portion with metal to facilitate heat radiation from these heating elements.

FIG. 2 is a sectional view of the second embodiment of the present invention.

This MMIC is the MMIC of the embodiment shown in FIG.
The space 4 is filled with the dielectric material 3 (3a and 3b) having a lower dielectric constant than that of the semiconductor substrate 18. Polyimide having a relative dielectric constant of 3.5 can be used for the dielectric 3. Also in the case of this MMIC, the strip conductor 12 and the capacitor 13 and the ground potential which the base carrier 2 presents are different from those in the case where the space between the strip conductor 12 and the capacitor 13 and the base carrier 2 (the recess 22 thereof) is completely filled. Extremely reduce the equivalent dielectric constant between. Therefore, the line including the strip conductor 12 and the capacitor 13 of this MMIC can be regarded as a pseudo suspended strip line, and has a characteristic of having high characteristic impedance and low transmission loss. Furthermore, since this MMIC completely fills the space between the semiconductor substrate 18 and the base carrier 2 with the dielectric material 3, it has further durability against breakage of the semiconductor substrate 18.

FIG. 3 is a sectional view of the third embodiment of the present invention.

MMIC chip 1A in this MMIC
Of the metallized conductor 16 (16a, 16b and 16c) in the MMIC chip 1 of the embodiment of FIG.
Metallized conductors 17 (17a, 17b) having the above conductor thickness
And 17c). Further, the base carrier 2 is changed to a base carrier 2A in which one surface of the conductor facing the MMIC chip 1 is flat. In this MMIC, since the metallized conductor 17 is thick, the metallized conductor 17 on the back surface of the semiconductor substrate 18 is
In a portion where no is formed, that is, at a position corresponding to a low loss transmission circuit element and its vicinity, a space 6 (6a and 6b) is formed between the back surface of the semiconductor substrate 18 and the base carrier 2A. Therefore, also in this MMIC, the line including the strip conductor 12 and the capacitor 13 forms a suspended strip line. This M
The MIC has an advantage that the manufacturing process can be simplified because it is not necessary to form the uneven portion on the base carrier 2A.

The fixed connection between the metallized conductor 17 on the back surface of the MMIC chip 1A and the base carrier 2A is generally performed by soldering with a gold-tin alloy which is a brazing agent. When the thickness of the metallized conductor 17 is 30 μm or more, there is no fear that the brazing agent will fill the space 6 in this soldering.

[0028]

As described above, the present invention provides a monolithic microwave integrated circuit (M) having a via hole structure.
In the MIC), the metallized conductor on the back surface of the MMIC chip is removed at the corresponding position of the low-loss transmission circuit element including the strip conductor and in the vicinity thereof, and these transmission circuit elements are constituted by the suspended strip line. There is an effect that a circuit having a low transmission loss and a high degree of design freedom can be configured without impairing the heat radiation effect from the heating element.

[Brief description of drawings]

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view taken along the line A1-A2.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a conventional monolithic microwave integrated circuit chip.

[Explanation of symbols]

1,1A Monolithic microwave integrated circuit (MMI
C) Chip 2, 2A Base carrier 3a, 3b Dielectric 4a, 4b, 6a, 6b Space 11a-11d Bonding pad 12a-12e Strip conductor 13a-13c Capacitor 14a-14b Via hole 15 Field effect transistor (FET) 16a-16c , 17a to 17c Metallized conductor 18 Semiconductor substrate 21a to 21b Convex portion 22a to 22b Recessed portion

Claims (4)

(57) [Claims] 1. A and a transmission circuit element with low losses comprising a heat generating function element and the strip conductor comprising a field effect transistor formed on the surface side of the semiconductor substrate, a position corresponding to the transmission circuit elements of the back surface of the semiconductor substrate And a monolithic microwave integrated circuit chip in which a metallized conductor is formed in a portion other than the vicinity thereof and the source terminal of the field effect transistor is connected to the metallized conductor by a via hole, and the metallized conductor is fixedly connected to the monolithic microwave integrated circuit chip. A monolithic microwave integrated circuit comprising: a base carrier that holds a monolithic microwave integrated circuit chip and has one surface of a conductor that generates a ground potential of the transmission circuit element at a distance electrically separated from a back surface of the semiconductor substrate. circuit. 2. The monolithic microwave according to claim 1 , wherein one surface of the conductor of the base carrier has a convex portion and a concave portion, and the metallized conductor is fixedly connected to the convex portion. Integrated circuit. The 3. space constituting the recess of the rear surface of the semiconductor substrate base carrier is claimed in claim 2, wherein the dielectric constant is filled with a lower dielectric than the dielectric constant of the semiconductor substrate Monolithic microwave integrated circuit. And a method according to claim 4 wherein the thickness of the metallized conductor is 30μm or more, and one side flat surface of the conductor, the distance the back surface was electrically separated from the semiconductor substrate is held by said metallized conductor 4. The monolithic microwave integrated circuit according to claim 3 .