JPH0653414A - Microwave integrated circuit - Google Patents

Abstract

PURPOSE:To obtain a microwave integrated circuit in which chip size is prevented from increasing due to occupation of wide region on a substrate by passive circuits. CONSTITUTION:Passive elements, e.g. capacitors 2 and resistor elements, requiring no fine patterning and constituting a passive circuit in a function circuit are formed on the rear surface of a semiconductor substrate 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave integrated circuit having circuit elements formed on a semiconductor substrate, and more particularly to a microwave integrated circuit having passive elements forming a passive circuit formed on the back surface side of the semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 5 is a diagram for explaining a part of the structure of a conventional microwave integrated circuit in which circuit elements are formed on a semiconductor substrate, and FIG. 5 (a) is the microwave integrated circuit. 5B is a perspective view schematically showing the structure of the substrate surface of FIG. 5, and FIG. 5B is a sectional view taken along line Vb-Vb of FIG. 5A.

In the figure, reference numeral 200 denotes a passive circuit which constitutes a microwave integrated circuit (hereinafter also referred to as microwave IC), and a resistance element 1 is provided on the surface of a semiconductor substrate 6 of the integrated circuit.
0 and the capacitor 20 are arranged close to each other. Both ends of the resistance element 10 are connected to one end sides of strip lines 1a and 1b formed on the substrate 6, respectively, and the other end side of one strip line 1b is connected via an air bridge wiring 14, It is connected to the upper electrode 7 forming the capacitor 20. Also, this capacitor 20
Is connected to the wiring 5 in the via hole formed in the via hole 4, and the wiring 5 in the via hole is connected to the ground conductor 16 formed on the back surface side of the semiconductor substrate 6. Has been done.

Although not shown here, an active circuit composed of a transistor, a diode and the like which compose the microwave IC is mounted on the surface of the semiconductor substrate 6. Further, 15 is a contact portion between the strip lines 1a and 1b and the resistance element 10, and 9 is the strip line 1
An insulating film that insulates a and 1b from the substrate 6, which also serves as a dielectric film of the capacitor 20.

Next, the operation will be described. The passive circuit 200 of the microwave IC having such a configuration has a function of grounding the terminal end of the strip line 1a in high frequency,
That is, the direct current used in the microwave integrated circuit 200 is blocked by the capacitor 20, but the high frequency current equivalent to the microwave passes through the capacitor 20 and is grounded through the via hole 4.

[0006]

By the way, in the conventional microwave IC, GaAs or the like having a high charge mobility is usually used as a substrate material, and the substrate serves as a dielectric of the high frequency transmission line. Therefore, the back surface side is polished by processing such as polishing to reduce the thickness so that a predetermined line impedance can be obtained even with a wiring having a small pattern width. Therefore, the back side of the semiconductor substrate for the microwave IC is rougher than the front side, and all the circuit elements are formed on the front surface of the semiconductor substrate.

However, among the circuit elements, the capacitor (capacitance element) 2 and the like occupy a large area on the surface of the semiconductor substrate, and the capacitor 2 and the strip line 1 are included.
In order to suppress the fluctuation of the characteristic impedance of the circuit, it is necessary to arrange them so that they do not overlap vertically, which causes a problem that the chip size of the IC or the like becomes large.

The present invention has been made in order to solve the above problems, and provides a microwave integrated circuit capable of avoiding an increase in chip size due to a passive circuit occupying a large area on a substrate. The purpose is to get.

[0009]

The inventor of the present invention has focused on the fact that a passive element does not require fine pattern processing and can be formed even on a substrate surface having a slightly rough surface. We obtained a microwave integrated circuit with passive elements mounted on the back side of the wave board.

That is, the microwave integrated circuit according to the present invention includes a passive element formed on the back surface side of a semiconductor substrate,
Formed in a via hole penetrating the semiconductor substrate,
The wiring on the front surface side of the substrate and the wiring in the via hole for connecting the passive element on the rear surface side of the substrate are provided.

According to the present invention, in the above microwave integrated circuit, a resistive element and a capacitive element are formed as the passive elements on the back side of a semiconductor substrate, and these elements are combined to form a passive circuit having a predetermined function. is there.

In the microwave integrated circuit according to the present invention, a capacitive element is formed on the back surface side of a semiconductor substrate as the passive element, and the wiring in the via hole is used as an inductive element in combination with the capacitive element to perform a passive function. It is a circuit configuration.

[0013]

According to the present invention, since the passive elements forming the passive circuit are formed on the back surface side of the semiconductor substrate, the area occupied by the passive circuit on the front surface of the semiconductor substrate can be eliminated, and as a result, the external dimensions of the substrate can be defined. The chip size can be reduced by reducing the size of the substrate surface area.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. FIG. 1 is a diagram for explaining a microwave IC according to a first embodiment of the present invention. FIG. 1 (a) is an equivalent circuit diagram of a passive circuit constituting the microwave IC, FIG. 1 (b).
Is a sectional view showing a structure on a substrate for realizing the passive circuit, and FIG. 1C is a rear view showing a rear surface structure of the substrate of the passive circuit portion.

In the figure, 101 is a passive circuit of the microwave IC of the present embodiment in which the strip line 1 is grounded via a capacitor 2. Here, the fine pattern is not required to be processed and its forming process is relatively simple. The capacitor 2 is formed on the back surface side of the semiconductor substrate 6, and GaAs having a high charge mobility is used as the substrate material. Although not shown, the active element mounted on the microwave IC is formed on the GaAs substrate 6.

The capacitor 2 is composed of a capacitor upper electrode 7 on the back surface of the semiconductor substrate 6 and a capacitor base electrode 8 formed below the capacitor upper electrode 7 with a dielectric film 9 interposed therebetween. The upper electrode 7 is connected to the strip line 1 on the surface of the substrate by the wiring 5 in the via hole formed in the via hole 4 of the substrate 6.

Next, the manufacturing method will be described. FIG. 2 is a cross-sectional view for explaining the outline of the manufacturing process of the microwave IC. First, as shown in FIG. 2 (a), a predetermined surface side of a GaAs substrate 6 whose back side is polished by polishing or the like is used. The strip line 1 is formed on the region, the via hole 4 is formed in the vicinity of the strip line 1, and the wiring 5 in the via hole is formed on the inner surface of the via hole 4 so as to reach the back surface side of the substrate. Here, the depth of the via hole 4 is set to a depth corresponding to the substrate thickness of the semiconductor substrate 6 so that the via hole wiring 5 reaches the back surface of the semiconductor substrate 6.

Next, a capacitor upper electrode 7 is formed on the back surface of the semiconductor substrate 6 so that it contacts the exposed bottom surface of the via hole wiring 5 (FIG. 2 (b)). A dielectric film 9 is deposited on the entire surface (FIG. 2 (c)).

Thereafter, a capacitor base electrode 8 is formed below the dielectric film 9 so as to face the capacitor upper electrode 7 (FIG. 2 (d)). Here, for forming the capacitor, a film forming method such as vapor deposition or CVD is used.

As described above, in this embodiment, since the capacitor 2 occupying a relatively large area on the substrate is formed on the back surface of the semiconductor substrate 6, the region occupied by the capacitor on the substrate surface is unnecessary. As a result, the size of the surface area of the substrate, which defines the outer dimensions of the substrate, can be reduced, and the size of the chip can be reduced. In the past, stripline 1
In order to prevent the characteristic variation of the circuit from occurring, it is necessary to dispose the capacitor 2 in a region other than the capacitor 2 so as not to overlap the capacitor 2. However, in this embodiment, the capacitor 2 is formed on the back surface side of the substrate. By doing so, the stripline can set its disposition region irrespective of the position of the capacitor.

Example 2. 3 is a diagram for explaining a microwave IC according to a second embodiment of the present invention.
FIG. 3A is an equivalent circuit diagram of a passive circuit forming the microwave IC, and FIG. 3B is a sectional view showing a structure on a substrate for realizing the passive circuit.

In the figure, reference numeral 102 denotes a passive circuit of the microwave IC of this embodiment. Here, the passive circuit 102 prevents oscillation of an unnecessary frequency band in the microwave IC, that is, the internal circuit of the microwave IC. The circuit configuration is such that an unnecessary frequency band signal processed by is grounded to the ground side.

That is, the passive circuit 102 includes a strip line 1 and a first line inserted between one end of the strip line 1 and the ground.
2a and a series connection body composed of a resistance element 10 on the strip line 1 side and a second capacitor 2b on the ground side, which are connected in parallel with the first capacitor 2a.

Here, the resistance element 10 is the semiconductor substrate 6
Of the diffusion layer formed in the vicinity of the via hole 4 of the semiconductor substrate 6 by ion implantation or the like on the back surface of the semiconductor substrate 6. Further, the first capacitor 2a is formed on the semiconductor substrate 6
An upper surface electrode 7a formed so that one end thereof is in contact with the via hole wiring 5 and the other end is in contact with the diffusion layer of the resistance element 10, and a dielectric layer 9 is formed below the upper surface electrode 7a. The second capacitor 2b is formed on the back surface of the semiconductor substrate 6 so that a part of the second capacitor 2b is in contact with the other end of the diffusion layer 10. It is composed of an electrode 7b and a base electrode 8b formed below the electrode 7b with a dielectric layer 9 interposed therebetween. As is clear from the equivalent circuit, the resistance element 10 is in a floating state in which it is floating in a direct current manner with respect to the ground 3, and the resistance element 10 connects between the capacitor upper electrodes 7a and 7b.

The formation of the passive circuit 102 is shown in FIG.
As shown in (a), after forming the via hole 4 and the wiring 5 in the via hole in the semiconductor substrate 6, a diffusion layer as the resistance element 10 is formed in the vicinity of the via hole of the semiconductor substrate 6, and thereafter, as shown in FIG. This is performed by forming the first and second capacitors 2a and 2b on the back surface side of the semiconductor substrate 6 as shown in FIGS.

FIG. 3 (c) shows a state in which the microwave IC chip of this embodiment having the above-mentioned structure is mounted on the package 12. The microwave IC chip is formed by the conductive paste 11 in the package 12 It is fixed on the chip mounting surface. In this mounted state, the capacitor base electrodes 8a and 8b are grounded to the conductive package 12 which also functions as the ground 3 through the conductive paste 11. By using the conductive paste 11 for mounting the microwave IC chip on such a package 12, it is possible to prevent the dielectric film 9 formed on the back surface side of the substrate 6 from being damaged.

As described above, in this embodiment, since the resistance element 10 and the capacitors 2a and 2b constituting the passive circuit 102 are formed on the back surface side of the semiconductor substrate 6, the resistance element and the capacitor occupy the same as in the above embodiments. The area on the surface of the substrate becomes unnecessary, and as a result, the area of the surface of the substrate which defines the external dimensions of the substrate can be reduced, and the chip can be miniaturized.

Example 3. 4 is a diagram for explaining a microwave IC according to a third embodiment of the present invention.
FIG. 4A is an equivalent circuit diagram of a passive circuit forming the microwave IC, and FIG. 4B is a sectional view showing a structure on a substrate for realizing the passive circuit. In the figure, 103 is a passive circuit of the microwave IC of the present embodiment, in which the passive circuit 103 has a typical low-pass filter circuit configuration.

That is, the passive circuit 103 is composed of the first and second inductors 13a and 13b and the capacitor 2 connected between one end of each inductor and the ground 3.

Here, the first and second via holes 4a and 4b are formed in the vicinity of a predetermined portion of the GaAs substrate 6,
In-via-hole wiring 5a formed in each via hole,
5b denote the first and second inductors 13a, 13a,
13b, a capacitor upper electrode 7 is formed on the back surface side of the substrate 6 so as to be in contact with the back surface exposed surfaces of the adjacent via hole wirings 5a and 5b, and a dielectric film 9 is provided on the electrode 7. To form the capacitor base electrode 8.

In this embodiment, the wiring 5 in the via hole
Since a and 5b are used as inductors and the wiring in the via hole is connected by the upper electrode 7 of the capacitor 2 formed on the back surface side of the substrate to form a filter circuit, the substrate surface area occupied by the capacitor becomes unnecessary. As a result, the external dimensions of the substrate can be reduced, and the chip can be miniaturized.

[0032]

As described above, according to the microwave integrated circuit of the present invention, since the passive elements forming the passive circuit are formed on the back surface side of the semiconductor substrate, the area occupied by the passive circuit on the front surface of the semiconductor substrate. Is unnecessary, and as a result, there is an effect that the size of the substrate surface region that defines the outer dimensions of the substrate can be reduced to reduce the chip size.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a microwave integrated circuit according to a first embodiment of the present invention, FIG. 1 (a) is an equivalent circuit diagram of a passive circuit constituting the microwave integrated circuit, and FIG. ) Is a sectional structure view of a passive circuit portion of the semiconductor substrate of the microwave IC, and FIG. 1C is a rear view showing a rear surface structure of the passive circuit portion of the semiconductor substrate.

FIG. 2 is a cross-sectional view showing a step of forming a passive circuit of the microwave integrated circuit.

FIG. 3 is a diagram for explaining a microwave integrated circuit according to a second embodiment of the present invention, FIG. 3 (a) is an equivalent circuit diagram of a passive circuit constituting the microwave integrated circuit, and FIG. ) Is a sectional structure view of a passive circuit portion of the semiconductor substrate of the microwave IC of the second embodiment, and FIG. 3C is a view showing a state in which the microwave IC of the second embodiment is mounted in a package.

FIG. 4 is a diagram for explaining a microwave integrated circuit according to a third embodiment of the present invention, FIG. 4 (a) is an equivalent circuit diagram of a passive circuit forming the microwave integrated circuit, and FIG. 8] is a sectional structural view of a passive circuit portion in the semiconductor substrate of the microwave IC of the third embodiment.

FIG. 5 is a diagram for explaining a conventional microwave integrated circuit, FIG. 5 (a) is a perspective view schematically showing a schematic configuration of a passive circuit portion of the microwave integrated circuit, and FIG. Figure 5
It is a figure which shows the structure of the Vb-Vb line cross section of (a).

[Explanation of symbols]

1 Strip Line 2, 2a, 2b Capacitor 3 Ground 4, 4a, 4b Via Hole 5, 5a, 5b Wiring in Via Hole 6 Semiconductor Substrate 7, 7a, 7b Top Electrode for Capacitor 8, 8a, 8b Base Electrode for Capacitor 9 Dielectric film 10 Resistive element 11 Conductive paste 12 Package 13, 13a, 13b Inductor 14 Air bridge wiring 15 Contact part 16 Conductor for ground 101, 102, 103 Passive circuit part of microwave IC

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01P 1/00 Z 3/08

Claims (3)

[Claims] 1. A microwave integrated circuit in which a circuit element is formed on a semiconductor substrate and wiring is provided to the circuit element, wherein a passive element formed on the back surface side of the semiconductor substrate and the semiconductor substrate are penetrated. Formed in the via hole,
A microwave integrated circuit comprising: wiring on the front surface side of the substrate and wiring in a via hole connecting the passive element on the rear surface side of the substrate. 2. The microwave integrated circuit according to claim 1, wherein a resistive element and a capacitive element are formed on the back surface side of a semiconductor substrate as the passive element, and these elements are combined to form a passive circuit having a predetermined function. A microwave integrated circuit characterized by the above. 3. The microwave integrated circuit according to claim 1, wherein a capacitive element is formed as the passive element on a back surface side of a semiconductor substrate, and the wiring in the via hole is combined with the capacitive element as an inductive element to perform a predetermined function. A microwave integrated circuit comprising a passive circuit having the same.