JP2001085570A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device whose operation becomes stably by suppressing unwanted resonance. SOLUTION: This semiconductor device has a MMIC(monolithic microwave IC) chip 11, where at least one part of a transmission path is made of a coplanar line composed of a signal conductor 1a and grounding metals 2a1-2a3 and 2b1-2b3 positioned on both its sides. In this case, the grounding metal is divided into plural grounding metals 2a1-2a3 and 2b1-2b3, and moreover the divided ground metals 2a1-2a3, and 2b1-2b3 are connected with the others by conductors 5 and resistors 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device that handles high-frequency signals such as millimeter waves and microwaves.

[0002]

2. Description of the Related Art With the spread of the communication field, the frequency range to be used has been expanded, and in the communication field, there has been a movement to use an ultra-high frequency band of millimeter waves (30 GHz) or more.

Here, a conventional semiconductor device using a high-frequency signal will be described with reference to FIG. The semiconductor device of FIG. 5 is an MMIC (Monolithic Microwave Integrated
Circuit) and a mounting substrate 220 on which the MMIC chip 210 is mounted. MM
On the main surface of the IC chip 210, an active element such as a HEMT and an electric circuit (not shown) including a lumped constant circuit and a distributed constant circuit including a capacitor and a resistor are formed. A plurality of bonding pads 230 are provided around these electric circuits.

A line conductor 250 and a bonding pad 260 are provided on a mounting substrate 220 on which the MMIC chip 210 is mounted. A bonding wire is provided between the bonding pad 230 on the MMIC chip 210 and the bonding pad 260 on the mounting substrate 220. At 240, they are electrically connected. A part of the bonding pad 260 on the mounting substrate 220 is electrically connected to a ground electrode 280 formed on almost the entire back surface of the mounting substrate 220 via a through hole 270 formed in the mounting substrate 220.

[0005] The semiconductor device having the above-described structure is, for example,
A method of providing a depression corresponding to the size of the MMIC chip 210 in a part of the mounting substrate 220 and mounting the MMIC chip 210 in the depression is adopted.
0 is connected to the ground electrode 280.

Next, an example of an electric circuit formed on the main surface of the MMIC chip 210 will be described with reference to FIG. I
N is an input terminal and OUT is an output terminal. Active devices such as the HEMT 201, capacitors C1 and C2, and distributed constant lines 202a and 202b forming a matching circuit are connected between the input terminal IN and the output terminal OUT. HEMT2
01 and the distributed constant line 202a.
A bias circuit composed of a capacitor 2c and a capacitor C3 is connected, and a bias circuit composed of a distributed constant line 202d and a capacitor C4 is connected between the HEMT 201 and the distributed constant line 202a.

In the case of the MMIC having the above configuration, a coplanar line as shown in FIG. 8 is often used as a transmission line for connecting electric elements. (A) of the figure is a top view of the coplanar waveguide, and (b) and (c) of the figures are AA and B in the figure (a).
The electric field distribution is indicated by an arrow in the cross-sectional view at -B.

In FIG. 1, reference numeral 301 denotes a signal conductor forming a coplanar line, and 302a and 302b denote ground metals forming a coplanar line.
In order to make the potentials equal, they are connected by a bridge 303 across the signal conductor 301. The bridge 303 is formed so as not to contact the signal conductor 301.

The above-described coplanar line includes a signal conductor 30.
Ground metals 302a and 302b are arranged at equal intervals on both sides of 1. For this reason, the wiring structure is bilaterally symmetric and the electric field distribution is bilaterally symmetric as shown in FIG. At the bridge 303 as well, the wiring structure is symmetrical and the electric field distribution is symmetrical as shown in FIG.

When a coplanar line is used as a transmission line in an MMIC, grounding can be performed using a ground metal of the coplanar line. For this reason, when the grounding portion of the MMIC chip is grounded, there is an advantage that it is not necessary to provide a through hole for grounding on the mounting board.

[0011]

In a conventional semiconductor device in which an MMIC chip is mounted on a mounting substrate, bonding is performed between the grounding portion of the MMIC and the grounding conductor of the mounting substrate so as to make them electrically the same potential. It is connected using a wire or the like. This state will be described with reference to the sectional view of FIG.
In FIG. 7, parts corresponding to those in FIG.
A duplicate description is partially omitted.

Reference numeral 311 denotes M constituting the MMIC chip.
In the MIC substrate, the MMIC substrate 311 is arranged in a recess provided in the mounting substrate 312, for example.
The bottom surface of 11 is in contact with the ground conductor 316 provided on the back surface of the mounting board 312.

The signal conductor 301 is provided on the MMIC 311 substrate.
And the grounding metals 302a and 302b are provided. The grounding metals 302a and 302b are connected to the bonding wires 315, the pads 313 on the mounting substrate 312, and the mounting substrate 312.
Is electrically connected to a ground conductor 316 on the back surface of the mounting board 312 through a through hole 313a formed in the substrate.

In the case of the above configuration, the MMIC board 311
Are surrounded by conductors such as the ground metals 302a and 302b and the ground conductor 316, and a pseudo space is formed. Therefore, MM at the resonance frequency of the pseudo space
It couples with the transmission line in the IC and degrades the characteristics.

FIG. 7B is a top view of FIG. 7A, in which an MMIC chip using coplanar wiring is mounted on a mounting substrate 312.
The arrow Y indicates the distribution of the current flowing through the grounded metal 302a, 302b of the coplanar line when resonance occurs when mounted on the coplanar line. This current distribution is obtained when the above pseudo space is regarded as a cavity resonator surrounded by a conductor.
This is the same as the current distribution in the 101 mode.

In the case of the millimeter wave band, the size of the MMIC chip cannot be ignored with respect to the wavelength of the operating frequency. MM
When GaAs is used for the IC substrate, the relative dielectric constant is as high as about 13 and the resonance frequency decreases. Therefore, coupling occurs with the transmission line on the MMIC at the resonance frequency of the pseudo space, and M
It interferes with the operation of the electric circuit in the MIC.

FIG. 7B shows a case where the signal conductor 301 of the coplanar line is arranged on the center line of the MMIC 311. However, the coupling with the transmission line at the resonance frequency in the pseudo space occurs regardless of the position of the signal conductor.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a semiconductor device in which unnecessary resonance is suppressed and operation is stable.

[0019]

According to the present invention, there is provided a semiconductor device having an MMIC chip in which at least a part of a transmission line is formed by a coplanar line composed of a signal conductor and ground metal located on both sides of the signal conductor. The ground metal is divided into a plurality of parts, and the divided ground metals are connected by a conductor and a resistor.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. (A) of the figure is a top view when the MMIC chip is mounted by wire bonding on a mounting board,
(B) of the figure is an enlarged view enlarging a portion of a circle R surrounded by a dotted line of the (a), and (c) is a cross-sectional view along AA of the (a).

Reference numeral 12 denotes a mounting board, for example, a recess 12a is provided in the center of the mounting board 12, and the recess 12a
The MMIC chip 11 is arranged in the portion. A plurality of pads 13 are arranged on the mounting substrate 12 so as to surround the MMIC chip 11, and transmission lines 14 are provided at both left and right end portions.

A signal line 1a forming a coplanar line is provided in the lateral direction of the central part of the MMIC chip 11, and one side of the extension of the signal line 1a is provided with a ground metal 2a1 divided in the extension direction of the signal line 1a. 2a3 is provided, and the other side of the signal line 1a is also provided with ground metals 2b1 to 2b3 divided in the extension direction of the signal line 1a. Among the divided ground metals 2a1-2a3, 2b1-2b3, adjacent ones in the extension direction of the signal line 1a are connected by a bridge 5 of a conductor and a plurality of resistors 3, respectively. It should be noted that ground metals adjacent to each other across the signal line 1a, for example, 2a1 and 2b1, 2a2 and 2b2, 2
a3 and 2b3 are connected by a bridge 5 that straddles the signal line 1a.

In the above configuration, the grounding metals 2a1-2a3, 2b1-2b3 and the pads 13 on the mounting board 12 are connected by bonding wires 15.
The pad 13 is, as shown in FIG.
Is electrically connected to the ground conductor 16 on the back surface of the mounting board 12 through a through hole 13a penetrating through the through hole 13a. At this time, the MMIC chip 11
A pseudo space is formed surrounded by conductors such as the upper ground metals 2a1-2a3, 2b1-2b3 and the ground conductor 16 on the back surface of the mounting board 16.

Note that, as shown in FIG.
a between adjacent ground metals on the same side of
The bridge 5 is electrically connected between 1 and 2a2 at a position closer to the signal conductor 1a than the resistor 3 is. In this case, adjacent ground metals on the same side of the signal conductor 1a are electrically connected at a position close to the signal conductor 1a.
The transmission characteristics do not deteriorate in the coplanar line itself.

The resonance when the MMIC chip is mounted on the mounting substrate by wire bonding is three-dimensional when the divided ground metal is connected by a resistor and when the MMIC chip is directly connected without a resistor. The result of the simulation of the electromagnetic field analysis will be described with reference to FIG.

In the simulation, the size of the MMIC chip: 1.2 mm × 1.5 mm ×
0.2 mm, dielectric constant of the substrate of the MMIC chip: 12.9 This was performed under the condition that the transmission line of the MMIC chip was opened near the center.

When there is a resistor, adjacent ground metals are connected to each other at three locations by a resistor, and when there is no resistor, the resistance value of the resistor is set to 0 for comparison.

In FIG. 2, the vertical axis indicates the insertion loss (S21) (d
B), the horizontal axis represents frequency (GHz), the characteristic P has no resistance, and the characteristic Q has resistance (resistance of 20Ω). As can be seen from the figure, in the case without the resistor (P), the isolation is deteriorated at the resonance frequency (36.2 GHz). In the case with the resistance (Q), the maximum value of the isolation at the resonance frequency is reduced.

Therefore, if the divided ground metals are connected by a resistor, the current flowing through the ground metal during resonance can be attenuated by the resistor. Therefore, even if a coplanar line is used for the MMIC, deterioration of characteristics due to unnecessary resonance is prevented. Further, since the bridge connecting the divided ground metals is close to the signal conductor, even if the ground metals are connected by a resistor, deterioration of transmission characteristics is prevented.

Another embodiment of the present invention will be described with reference to FIG. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be partially omitted.

In this embodiment, the signal conductor of the coplanar line is partially branched to provide a branched signal conductor.
FIG. 3A is an enlarged top view of the branch portion, and FIG.
FIG. 2B is a cross-sectional view taken along line BB in FIG.

A part of the signal line 1a constituting the coplanar line is provided with a branch signal line 1b branched from the signal line 1a. Grounding metal 2 on one side of signal line 1a
a, and the branch signal line 1 b
a and divided ground metals 2b1 and 2b located on the other side of
It extends between b2. Divided ground metal 2b1 and 2
Between b2, a position near the signal line 1a is connected by a bridge 5, and a resistor 3 is connected to a position farther from the bridge 5. In this case, as shown in FIG. 2B, a portion where the branch signal line 1b intersects with the resistor 3 is formed in a bridge-like line 4 in which a part of the branch signal line 1b crosses over the resistor 3. .

When connecting the ground metals forming the coplanar line with a resistor, if the center between the adjacent ground metals coincides with the center of the resistor, a symmetrical structure is obtained. At this time, since no current flows through the resistor, no transmission loss occurs due to the connection of the resistor.

According to the above configuration, even if a T-branch including a resistor for preventing unnecessary resonance is provided, a transmission loss can be prevented from occurring in the T-branch itself.

Another embodiment of the present invention will be described with reference to FIG. FIG. 3A shows a circuit configuration formed on an MMIC chip, and FIG. 3B shows a circuit configuration of FIG.
The layout of the signal conductors, the ground metal, the resistors, and the like when laid out on C is shown. FIG. 3C is an enlarged view of a part of FIG.

In FIG. 3A, IN is an input terminal, OU
T is an output terminal, between the input terminal IN and the output terminal OUT,
In order from the input terminal IN side, the matching circuit 41 and the FET 4
2. The matching circuit 43, the matching circuit 44, the FET 45, and the matching circuit 46 are connected.

Each of the two FETs 42 and 45 is provided with two bias circuits each including a stub L and a capacitor C.

FIG. 4B shows a part of the circuit configuration of FIG.
For example, the signal conductor 101 constituting a coplanar line,
In addition, the ground metals 104a1, 104a2, and 104a3 that are separately arranged on one side of the signal conductor 101, the ground metals 104b1, 104b2, and 104b3 that are separately arranged on the other side of the signal conductor 101, and the adjacent ground metal FIG. 2 shows an arrangement of a resistor 105 connecting between the two, a bridge 106 not loaded with a resistor connecting between adjacent ground metals, and a stub L branched from the signal conductor 101 and crossing the resistor 105 in a bridge shape. ing.

The MMIC chip described above is formed in a rectangular shape as a whole, while, for example, the length 1 in the left-right direction in the figure is longer than the length s in the vertical direction in the figure. The portion surrounded by the rectangular dotted line S indicates the layout of the stub L portion.

FIG. 4 (c) is an enlarged view of a branch portion of the signal conductor surrounded by a circle R in FIG. 4 (b), and at least a part of a stub L constituting a bias circuit has a short side of an MMIC chip. It is laid out in parallel with s.

When the stub L is formed of a coplanar line, a resistor for attenuating unnecessary resonance can be provided in the coplanar line by mounting a resistor at a part of a bridge connecting ground metals, for example, at the center thereof. Can be provided.

In the above embodiment, the ground metal is connected by a resistor. In this case, the ground metal is connected by using a resistor piece partially formed of a resistor and partially formed of a conductor. You can also.

In the above embodiment, when the ground metal is divided, the ground metal is divided in the extending direction of the signal conductor. However, the location and direction of dividing the ground metal can be set arbitrarily. In the above embodiment, the case where the MMIC chip is mounted by wire bonding is described. However, the present invention can be applied to the case where the MMIC chip is mounted by bump.

[0044]

According to the present invention, a semiconductor device which suppresses unnecessary resonance and operates stably can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining characteristics of the present invention.

FIG. 3 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 4 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 5 is a schematic perspective view for explaining a conventional example.

FIG. 6 is a circuit configuration diagram for explaining a conventional example.

FIG. 7 is a schematic structural diagram for explaining a conventional example.

FIG. 8 is a schematic structural diagram for explaining a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 3 ... Resistor 5 ... Bridge 11 ... MMIC chip 12 ... Mounting board 13 ... Pad 13a ... Through hole 14 ... Transmission line 15 ... Bonding wire 16 ... Ground conductor on the back surface of mounting board 1a ... Signal conductor of coplanar line 2a1-2a3, 2b1 ~ 2b3 ... Coplanar line ground metal

Claims (6)

[Claims] In a semiconductor device having an MMIC chip having at least a part of a transmission line formed by a coplanar line formed of a signal conductor and ground metal located on both sides of the signal conductor, the ground metal is divided into a plurality of parts. And the divided ground metal is connected by a conductor and a resistor. 2. An MMIC chip in which at least a part of a transmission line is formed by a coplanar line composed of a signal conductor and ground metal located on both sides of the signal conductor,
A ground metal is formed on one side, and the MMI is formed on the other side.
A semiconductor device comprising: a mounting substrate on which a C chip is mounted; wherein the ground metal is divided into a plurality of parts, and the divided ground metals are connected by a conductor and a resistor. apparatus. 3. A branch conductor which branches from a signal conductor and passes between divided ground metals is provided, and between the divided ground metals, the conductor is connected at a position closer to the signal conductor than the resistor. 3. The semiconductor device according to claim 1, wherein 4. A portion provided with a branch conductor that branches from a signal conductor and passes between divided ground metals, and at a portion where the resistor that connects the divided ground metals intersects the branch conductor, 3. The semiconductor device according to claim 1, wherein the branch conductor straddles over the resistor. 5. A through hole is provided in the mounting board, and a ground metal of the coplanar line and a ground conductor of the mounting board are electrically connected to each other via a conductive layer formed in the through hole portion. 3. The semiconductor device according to 2. 6. The semiconductor device according to claim 2, wherein the ground metal of the coplanar line and the ground conductor of the mounting board are electrically connected by bumps.