JP2017055224A - High-frequency semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency semiconductor device that facilitates fine adjustment to deviation in impedance between a microwave integrated circuit and a mounted member terminal.SOLUTION: A high-frequency semiconductor device 10 comprises: a semiconductor element 20 that includes a microwave integrated circuit; a mounted member 30 that includes a metal plate 32, an insulator frame part 34, and a first transmission line 37 having a characteristic impedance of 50 Ω; and a relay substrate 40 which is arranged between the semiconductor element and the first transmission line, and includes a second transmission line 44 having a characteristic impedance of 50 Ω, and a capacitive stub 45 arranged so as to be separated from the second transmission line and connectable at a central part of the second transmission line. A first bonding wire 60 connects between an inner end 37c of the first transmission line and a first end part 44b of the second transmission line. A second bonding wire 70 connects between a first electrode 20a of the semiconductor element and a second end part 44a of the second transmission line.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a high-frequency semiconductor device.

  As the size of the semiconductor element chip increases, it is necessary to secure a long scrub stroke in order to securely bond the chip to the package by scrubbing. For this reason, a gap between the inner end of the package signal terminal and the chip is increased. As a result, the bonding wire becomes long.

  The input / output impedance of the microwave integrated circuit mounted on the high-frequency semiconductor device is designed on the assumption of a load impedance in the vicinity of 50Ω, for example.

  When the semiconductor element chip constituting the microwave integrated circuit and the package terminal are connected by a bonding wire, the impedance at the package terminal deviates from 50Ω. The deviation in impedance from 50Ω increases as the frequency increases.

Patent No. 5439415

  At a frequency at which the inductance of the bonding wire connected to the package greatly affects, for example, 30 GHz, when a relay substrate is used to fill the gap between the inner end of the package signal terminal and the chip, the first and second bonding wires described later, In addition, the line length of the relay board is required to be accurate with respect to the design value. However, it is difficult to form the bonding wire as designed. Provided is a high-frequency semiconductor device in which fine adjustment can be easily made with respect to an impedance shift between a microwave integrated circuit and a mounting member terminal due to a bonding wire shift.

  The high-frequency semiconductor device according to the embodiment includes a semiconductor element, a mounting member, a relay substrate, a first bonding wire, and a second bonding wire. The semiconductor element has a microwave integrated circuit. The mounting member includes a metal plate to which the semiconductor element is bonded, an insulator frame that surrounds the semiconductor element and is bonded to the metal plate, and is provided on the insulator frame and has a characteristic impedance of 50Ω. A first transmission line. The relay substrate is disposed on the metal plate between the semiconductor element and the first transmission line, and is separated from the second transmission line and a second transmission line having a characteristic impedance of 50Ω. A capacitive stub disposed and connectable to a central portion of the second transmission line. The first bonding wire connects the inner end of the first transmission line and the first end of the second transmission line. The second bonding wire connects the first electrode of the semiconductor element and the second end of the second transmission line opposite to the first end.

1A is a schematic perspective view of the high-frequency semiconductor device according to the first embodiment, FIG. 1B is a schematic plan view, and FIG. 1C is a schematic cross-sectional view taken along the line AA. . FIG. 2A is an equivalent circuit diagram of the high-frequency semiconductor device according to the first embodiment, and FIG. 2B is a schematic diagram illustrating a relay substrate. FIG. 3A is a Smith diagram showing the impedance when the capacitive stub is not connected to the transmission line, and FIG. 3B illustrates the operation of the relay substrate when the capacitive stub is connected to the transmission line. Smith figure. FIG. 4A is a schematic cross-sectional view of a high-frequency semiconductor device according to a comparative example, and FIG. 4B is a schematic plan view of a relay substrate of the comparative example. FIG. 5A is a graph showing the input-side return loss of the high-frequency semiconductor device according to the comparative example, and FIG. 5B illustrates the operation of the relay substrate when the impedance of the bonding wire is as designed in the comparative example. FIG. 5C is a Smith diagram for explaining the operation of the relay substrate when the impedance of the bonding wire is smaller than the design value. It is a schematic cross section of a semiconductor device according to a second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A is a schematic perspective view of the high-frequency semiconductor device according to the first embodiment, FIG. 1B is a schematic plan view, and FIG. 1C is a schematic cross-sectional view taken along the line AA. .
The high-frequency semiconductor device 10 includes a semiconductor element 20, a mounting member 30, a relay substrate 40, a first bonding wire 60, and a second bonding wire 70.

  The chip of the semiconductor element 20 is provided with a microwave integrated circuit (MMIC). The microwave integrated circuit includes a field effect transistor including a HEMT (High Electron Mobility Transistor) and a matching circuit. The matching circuit can include a transmission line, an inductor, a capacitor, and the like.

  The semiconductor element 20 includes a substrate and a stacked body provided on the substrate. For example, if the substrate is SiC and the laminate is a gallium nitride material, a microwave to millimeter wave band MMIC amplifier can be configured.

  The mounting member 30 includes a metal plate 32 to which the semiconductor element 20 is bonded, an insulator frame 34 that surrounds the semiconductor element 20 and is bonded to the metal plate 32, and is provided on the surface of the insulator frame 34 and has a resistance of 50Ω. A first transmission line 37 having a characteristic impedance. The mounting member 30 can further include a lead 36. The lead 36 and the first transmission line 37 function as a signal terminal.

  The insulator frame 34 can be made of alumina, aluminum nitride, or the like, for example. The metal plate 32 can be CuMo, CuW, or the like. The insulator frame portion 34 and the metal plate 32 are joined using a silver solder or the like.

  The width of the lead 36 is 0.2 mm, and the width of the first transmission line 37 is 0.4 mm. Further, the thickness of the insulator frame portion 34 is set to 0.4 to 0.6 mm or the like, so that the lead can be surely joined and the impedance near 50Ω can be obtained in a wide frequency range.

  In the first embodiment, the relay substrate 40 includes a dielectric 42, a second transmission line 44 provided on the dielectric 42, and a capacitive stub 45 provided at the center of the second transmission line 44. ,including. If there is a pattern tolerance of the mounting member 30, a pattern tolerance of the relay substrate 40, a variation in the length of the bonding wire, etc., an impedance shift occurs between the mounting member 30 and the semiconductor element 20. The higher the frequency, such as 30 GHz, the greater the impedance shift. The relay substrate 40 is disposed on the metal plate 32 so as to be between the semiconductor element 20 and the first transmission line 37 in the insulator frame portion 34. In the first embodiment, by finely adjusting the capacitance of the capacitive stub 45 having a plurality of regions, the internal end (feed end) 37 c of the first transmission line 37 and the first of the semiconductor element 20 It is possible to finely adjust the impedance deviation between the electrode 20a and the electrode 20a.

  In the case where the semiconductor element 20 is a HEMT multistage amplifier, the planar size thereof becomes large, for example, 30 mm × 30 mm. In the case where the semiconductor element 20 having a large area is joined to the metal plate 32 using a solder material such as AuSb, it is preferable that the gap between the insulator frame portion 34 and the insulator frame portion 34 be kept while being scrubbed while suppressing the void.

  Further, when the semiconductor element 20 includes a SiC substrate and a gallium nitride laminated body thereon, the thickness is as thin as 50 to 100 μm. It is preferable that the thickness of the relay substrate 40 be equal to or greater than the thickness of the semiconductor element 20 and equal to or less than the thickness of the insulator frame 34 because bonding is easy. Further, it is more preferable that the thickness of the relay substrate 40 is equal to or slightly larger than the thickness of the semiconductor element 20.

  The relay substrate 40 includes a dielectric 42, a second transmission line 44 provided on the dielectric 42, and a capacitive stub 45 that can be connected to the center of the second transmission line 44.

  The relay substrate 40 can be made of an insulating material such as ceramic such as alumina or aluminum nitride, quartz, sapphire, or high resistance semiconductor. When a conductive portion is provided on the back surface of the relay substrate 40, it can be joined to the surface of the metal plate 32 with a solder material such as AuSn. The length of the relay substrate 40 along the signal propagation direction is 1 mm or less, which is a gap. The width of the relay substrate 40 can be set to 0.5 mm to 1 mm, for example. Since the relay substrate 40 does not generate heat, there may be some void at the joint interface with the metal plate 32, so that a large gap for scrubbing is not necessary.

FIG. 2A is an equivalent circuit diagram of the high-frequency semiconductor device according to the first embodiment, and FIG. 2B is a schematic diagram illustrating a relay substrate.
The first bonding wire 60 connects the end 44b of the second transmission line 44 and the internal end 37c. The end 44b of the second transmission line 44, which is the connection position, becomes the reference plane Q1. The second bonding wire 70 connects the first electrode 20 a of the semiconductor element 20 and the end portion 44 a of the second transmission line 44. An end 44a of the second transmission line 44 becomes a reference plane Q3. The connection position between the second bonding wire 70 and the first electrode 20a is the reference plane Q4.

  When a load 90 having an impedance of 50Ω is connected between the lead 36 and the ground, the load impedance viewed from the inner end 37c of the first transmission line 37 is 50Ω. When the lead 36 is an input terminal, the load 90 is a high-frequency signal source having an impedance of 50Ω.

  As shown in FIG. 2B, the relay substrate 40 can be connected to, for example, the dielectric 42, the second transmission line 44, and the central portion of the second transmission line 44 (which coincides with the reference plane Q2). A plurality of capacitive stubs 45. By connecting an appropriate number from a plurality of regions, the electrical length of the stub can be adjusted effectively.

FIG. 3A is a Smith diagram showing the impedance when the capacitive stub is not connected to the second transmission line 44, and FIG. 3B is a diagram when the capacitive stub is connected to the second transmission line 44. It is a Smith figure showing the impedance of.
The Smith diagram is normalized with a characteristic impedance Zcc of 50Ω. As shown in FIGS. 3A and 3B, the amount of phase rotation by the second transmission line 44 having the electrical length (EL1 + EL2) is fixed regardless of the length of the bonding wire.

  The sum of the phase rotation amount by the first bonding wire 60 and the half of the phase rotation amount by the second transmission line 44 (EL1) is 180 degrees, and the phase rotation amount by the second bonding wire 70 is equal to the second rotation amount. When the sum of half of the amount of phase rotation (EL2) by the transmission line 44 is 180 degrees, the load impedance z5 @ Q4 viewed from the reference plane Q4 is close to 50Ω by not connecting the capacitive stub.

  The sum of the half of the amount of phase rotation by the first bonding wire 60 and the amount of phase rotation by the second transmission line 44 is smaller than 180 degrees, and the amount of phase rotation by the second bonding wire 70 and the second transmission. When the sum of the half of the amount of phase rotation by the line 44 is smaller than 180 degrees, the load impedance z5 @ Q4 viewed from the reference plane Q4 is compensated by connecting the capacitive stub to compensate for the shortage of 180 degrees. Near 50Ω.

  In the first embodiment, by disposing the capacitive stub 45 at the same position from both ends of the second transmission line 44 by making the inductances of the first bonding wire 60 and the second bonding wire 70 equal. The load impedance z4 @ Q3 viewed from the reference plane Q3 can be determined to be a complex conjugate with the load impedance z1 @ Q1. In other words, the load impedance z5 @ Q4 as seen from the reference plane Q4 is in the vicinity of 50Ω by fine adjustment to add the impedance change by the capacitive stub 45.

  Making the inductances of the first bonding wire 60 and the second bonding wire 70 equal makes the inner ends 37 c of the first transmission line 37 and the second transmission line 44 connected to the first bonding wire 60. The distance between the first end portion and the height difference between the first electrode of the semiconductor element to which the second bonding wire 70 is connected and the second end on the opposite side of the first end portion of the second transmission line. This can be easily realized by equalizing the distance between the end portions and the height difference, and equalizing the parameters of the bonding sequence program of the automatic bonding apparatus.

FIG. 4A is a schematic cross-sectional view of a high-frequency semiconductor device according to a comparative example, and FIG. 4B is a schematic plan view of a relay substrate of the comparative example.
As illustrated in FIG. 4A, the high-frequency semiconductor device includes a semiconductor element 120, a mounting member 130, a relay substrate 140, a first bonding wire 160, and a second bonding wire 170.

  Further, as illustrated in FIG. 4B, the relay board 140 includes a dielectric 142 and a second transmission line 144 provided on the dielectric 142. In the comparative example, the relay board 140 does not have a stub whose capacity can be finely adjusted.

FIG. 5A is a graph showing the input-side return loss of the high-frequency semiconductor device according to the comparative example, and FIG. 5B is a Smith diagram for explaining the operation of the relay substrate when the impedance of the bonding wire is as designed. FIG. 5C is a Smith diagram for explaining the operation of the relay substrate when the impedance of the bonding wire is smaller than the design value.
The load impedance viewed from the reference plane Q1 by the first bonding wire 160 is z1 @ Q1. When the transmission line 144 is added, the load impedance is z2 @ Q2. Furthermore, when the impedance of the second bonding wire 170 is added, the load impedance becomes z3 @ Q3.

  In FIG. 5A, the vertical axis represents return loss (dB) and the horizontal axis represents frequency (GHz). There is a pattern tolerance in the relay substrate 140 and the mounting member 130. When variation in the length of the bonding wire is added to the pattern tolerance, the center frequency of the band changes in a millimeter wave band such as 30 GHz. For example, the return loss changes sharply with respect to the bonding wire inductance as shown in FIG. If the length of the bonding wire is changed, the impedance between the semiconductor element 120 and the signal terminal 136 of the mounting member 130 is shifted, and the frequency at which the return loss is minimized shifts from 30 GHz. Since there is no means for finely adjusting the impedance deviation, it is difficult to increase the product yield in the comparative example.

  In contrast, in the first embodiment, even if the bonding wire length changes due to the pattern tolerance of the relay substrate 40, the capacitance of the capacitive stub 45 provided in the center of the second transmission line 44 is reduced. By adjusting the impedance, the impedance can be matched between the semiconductor element 20 and the mounting member terminal.

FIG. 6 is a schematic cross-sectional view of a semiconductor device according to the second embodiment.
The semiconductor device 10 includes a semiconductor element 20, a mounting member 30, relay boards 40 and 80, a first bonding wire 60, a second bonding wire 70, a third bonding wire 62, and a fourth bonding. And a wire 72.

  The mounting member 30 includes a metal plate 32, an insulator frame portion 34 joined to the metal plate 32 so as to surround the semiconductor element 20, a first transmission line 37 provided on the insulator frame portion 34, 4 transmission lines 57. When the signal terminal is an output signal terminal, the load 92 (FIG. 2A) is, for example, a 50Ω load.

  The third bonding wire 62 connects the second electrode 20 b of the semiconductor element 20 and the end portion 84 a of the third transmission line 84.

  The fourth bonding wire 72 connects the end portion 84 b of the third transmission line 84 and the inner end 57 c of the fourth transmission line 57.

  In the second embodiment, between the first electrode 20 a of the semiconductor element 20 and the inner end 37 c of the first transmission line 37, and inside the second electrode 20 b and the fourth transmission line 57 of the semiconductor element 20. Fine adjustment of the impedance matching between the end 57c and the terminal 57c is made close to 50Ω.

  According to the first and second embodiments, there is provided a high-frequency semiconductor device capable of finely adjusting the frequency at which the semiconductor element constituting the microwave integrated circuit and the signal terminal of the mounting member are matched. This high-frequency semiconductor device can be used for, for example, a 30 GHz band satellite communication ground station.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 High frequency semiconductor device, 20 Semiconductor element (MMIC), 20a 1st electrode, 20b 2nd electrode, 30 Mounting member, 32 Metal plate, 34 Insulator frame part, 37 1st transmission line, 40 Relay board, 44 Second transmission line, 44a, 44b end, 45 capacitive stub, 60 first bonding wire, 70 second bonding wire

Claims (5)

A semiconductor element provided with a microwave integrated circuit;
A metal plate to which the semiconductor element is bonded; an insulator frame that surrounds the semiconductor element and is bonded to the metal plate; and a first transmission line that is provided on the insulator frame and has a characteristic impedance of 50Ω. And a mounting member having
A second transmission line disposed on the metal plate between the semiconductor element and the first transmission line, having a characteristic impedance of 50Ω, and disposed apart from the second transmission line. A relay board having a capacitive stub connectable to a central portion of the transmission line;
A first bonding wire connecting the inner end of the first transmission line and the first end of the second transmission line;
A second bonding wire that connects the first electrode of the semiconductor element and the second end of the second transmission line opposite to the first end;
A high-frequency semiconductor device comprising:   The high-frequency semiconductor device according to claim 1, wherein an inductance of the first bonding wire and an inductance of the second bonding wire are the same.   The high-frequency semiconductor device according to claim 1, wherein the capacitive stub includes a plurality of conductive portions.   The distance and the height difference between the inner end of the first transmission line and the first end of the second transmission line are on the side opposite to the first end of the second transmission line. The high-frequency semiconductor device according to claim 1, wherein the distance from the second end portion is equal to the height difference.   The high-frequency semiconductor device according to claim 1, wherein the microwave integrated circuit is a field effect transistor amplifier.

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