JPH10178306A - Semiconductor device for high frequency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the transmission loss of a high frequency signal by electromagnetically combining a first microstrip line electrically connected with a high-frequency semiconductor element and a second microstrip line formed on the bottom face of a dielectric substrate within the dielectric substrate. SOLUTION: In the dielectric substrate, the first microstrip line is formed of a strip guiding body formed on the surface of the dielectric substrate in a cavity and a second microstrip line is formed between the strip conductive line on the bottom surface of a semiconductor and a ground layer. In this case, the strip conductive line and a slot hole are arranged to satisfy expressions I and at the time of setting lengths from just over the centers of the slot holes of the first and second microstrip lines to the tip part of each line to be ML, the long diameters of the slot holes SL, a wave length λ1 at the microstrip lines and wave length λ2 at the slot holes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device used for high frequencies in a microwave band to a millimeter wave band, and more particularly, to transmitting a signal to a semiconductor element or a circuit component by reducing the deterioration of characteristics of a high frequency signal. The present invention relates to a high-frequency semiconductor device capable of transmitting a signal having a specific frequency.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device equipped with a high-frequency circuit element for handling microwaves and millimeter waves, a high-frequency semiconductor element is housed in a semiconductor package having a dielectric substrate and a high-frequency transmission line formed on the surface of the dielectric substrate. The semiconductor device is mounted on a surface of a predetermined external electric circuit board, and is electrically connected to a high-frequency transmission line of the semiconductor device and a high-frequency transmission line formed on the external electric circuit board, and a high-frequency signal is transmitted. Input and output are performed.

In mounting such a high-frequency semiconductor device, the design and manufacture of a package structure and a transmission line capable of inputting and outputting a signal without deteriorating a high-frequency signal, and a semiconductor device mounted on an external electric circuit board with high precision. A mounting technology for mounting the device is required.

Therefore, as a semiconductor device of this type, as shown in FIG. 7A, a dielectric substrate 40 made of a dielectric material is used.
A high-frequency semiconductor element 43 is mounted in a cavity 42 formed by the lid 41 and is hermetically sealed. A high-frequency transmission line 44 such as a strip line connected to the high-frequency semiconductor element 43 passes through a wall 45. To the outside of the cavity 42, and further disposed on the bottom surface via the side surface of the substrate 40. The line formed on the bottom surface is soldered to the conductor layer formed on the surface of the external electric circuit board (not shown). In addition, a semiconductor device mounted on an external electric circuit board for inputting and outputting a high-frequency signal has been proposed in Japanese Patent Application Laid-Open No. 61-168939.

[0005] As shown in FIG. 7 (b), a signal transmission line 46 is formed on the bottom surface of the dielectric substrate 40, and the transmission line 46 and the semiconductor element 43 are connected through a through-hole conductor 47. Semiconductor devices have also been proposed. In this semiconductor device, the transmission line 46 is usually connected to a conductor layer of an external electric circuit board (not shown) by soldering or the like and mounted.

[0006]

However, FIG.
In (a), when the transmission line 44 passes through the wall 45, the signal line is converted from the microstrip line to the strip line at the wall passing portion, so that the signal line width needs to be reduced. As a result, there is a problem that reflection loss and radiation loss are apt to occur in the passing portion, so that the characteristics of the high-frequency signal are likely to deteriorate. Further, since the transmission line 44 is bent on the side surface of the substrate, when the transmission line 44 is used in a millimeter wave band,
The bending of the transmission line increases the reflection and makes it difficult to transmit and receive signals. Further, since the transmission line is formed on the side surface of the element mounting surface, the semiconductor device itself is inevitably large, and thus it is difficult to reduce the size of the circuit board. Moreover, in order to draw the transmission line 44 out of the cavity 42, at least the line passing portion of the wall 45 must be formed of a dielectric material, which complicates the structure and increases the cost of the entire semiconductor device. Had become.

Further, when the wall 45 is formed of a dielectric material having a high dielectric constant, when the width of the wall becomes equal to or more than 波長 wavelength of the pass frequency, resonance occurs in the wall pass portion, and the characteristics of the high-frequency signal deteriorate. There was a problem.

On the other hand, in FIG. 7 (b), since the signal does not pass through the wall 45 by the through-hole conductor 47, the characteristic deterioration of the signal is small, but the operating frequency of the signal to be transmitted is 1
When the frequency is 0 GHz or more, the transmission loss in the through-hole conductor 47 sharply increases, so that it is difficult to transmit a signal in a microwave band to a millimeter wave band without deterioration in characteristics.

Accordingly, the present invention provides a structure which has a small transmission loss in a high-frequency transmission line, can be surface-mounted, and allows only a signal of a specific frequency to pass, and a dimensional deviation caused in a processing step during manufacturing. On the other hand, it is an object of the present invention to provide a high-reliability high-frequency semiconductor device having a structure with little variation in transmission characteristics.

[0010]

The inventors of the present invention have studied the above object and found that a microstrip line is provided on the side of the dielectric substrate on which the high-frequency semiconductor element is mounted and on the bottom side of the dielectric substrate. Further, a ground layer having a slot hole formed in the dielectric substrate is formed, and two microstrip lines are electromagnetically coupled to each other with the ends of the lines facing each other with the slot hole interposed therebetween. It has been found that the transmission loss in the above can be reduced and the above object is achieved. In addition, in such a structure, in order to minimize the transmission loss, it is necessary to accurately align the transmission line and the slot hole, but the length from the slot hole to the end of the transmission line and the length of the slot hole are required. However, within the range of the specific conditions, it has been found that the deterioration of the transmission characteristics is small even with respect to the dimensional deviation occurring in the processing step at the time of manufacturing, and the present invention has been achieved.

That is, a high-frequency semiconductor device according to the present invention comprises a dielectric substrate, a high-frequency semiconductor element mounted on the surface of the dielectric substrate, and the high-frequency semiconductor device formed on the surface of the dielectric substrate. A first microstrip line electrically connected to the element, a second microstrip line formed on the bottom surface of the dielectric substrate, and a ground having a slot hole formed in the dielectric substrate; And the first and second microstrip lines and the slot hole are provided with the first and second microstrip lines.
ML (mm), the major axis of the slot hole is SL (mm), the wavelength of the microstrip line is λ ₁ (mm), When the wavelength in the slot hole is λ ₂ (mm),

[0012]

(Equation 1)

Or the following equation (2)

[0014]

(Equation 2)

[0015] The first microstrip line and the second microstrip line are electromagnetically coupled to each other so as to satisfy the following.

According to the present invention, the first microstrip line electrically connected to the high-frequency semiconductor element and the second microstrip line formed on the bottom surface of the dielectric substrate are formed inside the dielectric substrate. The transmission line can be coupled without passing through the side wall of the lid by electromagnetic coupling, so that the signal line is converted from the microstrip line to the strip line at the side wall passing portion, so that reflection loss and radiation loss are caused. Since high-frequency signals are not affected by transmission loss due to through-hole conductors, via-hole conductors, and the like, transmission loss of high-frequency signals can be suppressed, and signals of required frequencies can be transmitted.

Further, by arranging the lengths of the first and second microstrip lines from just above the center of the slot hole to the end thereof and the major axis of the slot hole so as to satisfy the above equation (1) or (2), When a semiconductor device is manufactured, deterioration of transmission characteristics is small even with respect to a dimensional deviation of a microstrip line generated in a processing step, and the yield in manufacturing can be improved.

[0018]

FIG. 1 shows an example of a high-frequency semiconductor device according to the present invention. According to FIG. 1, a high-frequency semiconductor device 1 includes a dielectric substrate 2 made of a dielectric material and a lid 3.
A cavity 4 is formed, and a semiconductor element 5 such as an MMIC or MIC is mounted in the cavity 4. The dielectric material constituting the dielectric substrate 2 is desirably ceramics having a dielectric constant of 20 or less, glass ceramics, ceramic metal composite materials, glass organic resin-based composite materials, and the like. Ceramics, ceramic metal composite materials, glass organic resin-based composite materials, and the like are particularly desirable in that the electromagnetic field hardly spreads into the air layer and cavity resonance in the device can be hardly generated.

According to the present invention, a strip conductor 6 for forming a microstrip line A for transmitting a signal to the semiconductor element 5 is formed on the surface of the dielectric substrate 2 in the cavity 4 of the semiconductor device. I have. On the other hand, a strip conductor path 7 forming the second microstrip line B is also formed on the bottom surface of the dielectric substrate 2.

The cover 3 is made of a material capable of preventing the electromagnetic wave from the cavity 4 from leaking to the outside.
Ceramics, ceramic metal composite materials, glass ceramics, etc. can be used, but electromagnetic wave absorbing materials such as carbon that can absorb electromagnetic waves are dispersed in these materials, or these electromagnetic wave absorbing materials are applied to the surface of the lid. You can also.

A ground layer 8 made of a conductor layer is formed over substantially the entire surface of the dielectric substrate 2, and a first microstrip line is formed by a strip conductor 6 formed on the surface of the dielectric substrate 2 in the cavity 4. A is formed. Also, the strip conductor path 7 on the bottom surface of the semiconductor device 1
A second microstrip line B is formed between the second microstrip line B and the ground layer 8.

A rectangular slot hole 9 in which no conductor layer is formed is formed in the ground layer 8, and the first microstrip line A and the second microstrip line B are connected to the respective lines A, By arranging the end portions of the strip conductor paths 6 and 7 in B at positions opposed to each other via the slot hole 9, the two microstrip lines A and B are electromagnetically coupled, and transmission of a lossless signal between the two microstrip lines A and B is performed. Is performed.

According to the present invention, at this time, the strip conductor path 6,
FIG. 2 is a plan view showing the arrangement of the slots 7 and the slot holes 9. In FIG. 2, the length from directly above the center of the slot hole of the first and second microstrip lines to the end of each line is ML, and the major axis of the slot hole is S
L, the wavelength in the microstrip line is λ
₁ (mm) and the wavelength in the slot hole is λ ₂ (m
m), the following equation 1

[0024]

(Equation 1)

Alternatively, the following equation 2

[0026]

(Equation 2)

Are arranged so as to satisfy the following. In the regions represented by the equations (1) and (2), it is possible to transmit a signal with a small transmission loss in the electromagnetic coupling. In particular, Equation 1
The main feature of the present invention is that it is possible to transmit a signal with a small transmission loss even in the region of SL / λ ₂ <１ ／. Therefore, even when the positions of the strip conductors 6 and 7 and the slot hole 9 are misaligned during stacking, the dimensions are controlled so as to be within the above-described range.
Transmission loss does not significantly decrease.

In particular,

[0029]

(Equation 3)

Or the following equation

[0031]

(Equation 4)

In the region of the strip conductor track 6,
Since the allowable area for the positional deviation between the slot conductor 7 and the slot hole 9 is the largest, it is possible to reduce the decrease in the yield due to the characteristic deterioration due to the positional deviation of the strip conductor paths 6, 7 during mass production.

FIG. 3 shows an example of a wiring structure in a cavity of the semiconductor device of FIG. 1. In the cavity 4, a semiconductor element 5 and a first microstrip line A are provided.
The power supply layer 10 for supplying electric power to the semiconductor element 5 is formed in addition to the strip conductor path 6 forming. One end of the power supply layer 10 is connected to the semiconductor element 5 and a ribbon, wire, T
They are electrically connected by AB (Tape Automated Bonding) or the like. The other end of the power supply layer 10 is led out to the bottom surface of the semiconductor device through the through-hole conductor 11, and is electrically connected to an external electric circuit board. Also,
The semiconductor element 5 can be connected without any transmission loss by being directly mounted on the strip conductor path 6 by solder, gold bump, or the like, but the connection method between the conductor path 6 and the semiconductor element 5 is as follows. The connection is not limited to this. For example, the connection may be made by gold ribbon or several wire bondings, or may be made by a conductor plate in which a conductor such as Cu is formed on a substrate of polyimide or the like.

A ground layer 12 for preventing leakage of electromagnetic waves is provided around the strip conductor path 6, the power supply layer 10 and the semiconductor element 5 in the cavity 4. A large number of through-hole conductors (not shown) are provided in the ground layer 12 to suppress variations in potential and prevent leakage of electromagnetic waves in some cases, and are electrically connected to the ground layer 8 inside the dielectric substrate 2. However, the through-hole conductor can be led out to the bottom surface of the semiconductor device and electrically connected to an external electric circuit board.

The ground layer 12 is electrically connected to the conductive lid 3 by a method such as brazing or soldering to leak electromagnetic waves from the cavity 4 to the outside or leak electromagnetic waves to the outside. Is further prevented. Further, a thermal via (not shown) may be provided on the lower surface of the semiconductor element 5 if desired, and a structure in which heat generated from the semiconductor element 5 is radiated to the lower surface of the semiconductor device may be formed.

Further, according to the semiconductor device 1 of FIG. 1 of the present invention, a part of the strip conductor path 7 formed on the bottom surface of the dielectric substrate 2 is made to function as a connection terminal, and the transmission line of the external electric circuit board is formed. Can be implemented directly for It should be noted that, in addition to the mounting method using solder, the mounting method using silver brazing or gold bumps, or the transmission method by overlapping the strip conductor path 7 and the transmission line on the circuit board without using the solder paste is used. There is a method of connecting while reducing the loss of the connection. On the other hand, since the through-hole conductor 11 led out to the bottom surface of the semiconductor device 1 has a low frequency, it is not necessary to form the through-hole conductor 11 with a special high-frequency line, and is generally formed with a conductor layer (not shown) of an external electric circuit board. The semiconductor device 1 can be firmly mounted on an external electric circuit board.

The wavelength in the microstrip line in the above equations 1 to 4 is λ ₁ and the wavelength λ ₂ in the slot hole is obtained by FEM analysis, for example, as shown in FIG.
The resonance frequency is calculated by analyzing the cross section of the line as shown in (b) and (b), and the wave number and the speed of light are used to calculate the resonance frequency.

[0038]

(Equation 5)

This is calculated based on the following. According to the line shown in FIG. 4, the microstrip line (a) has a strip conductor 14 on the surface side of the dielectric 13 and a ground layer 15 on the bottom side.
It has a structure in which a ground layer 18 having a slot line 17 is disposed inside a dielectric 16.

In order to confirm the performance of the high-frequency semiconductor device of the present invention, an alumina sintered body having a dielectric constant of 8.8 and a dielectric loss of 26.0 × 10 ^-4 (measuring frequency 60 GHz) was used as a dielectric substrate. Each conductor path and ground layer formed on the surface and inside of the substrate were formed using tungsten, and the surface was gold-plated to produce an evaluation wiring substrate 21 as shown in FIG.

FIG. 5 is a cross-sectional view showing a state where the evaluation wiring board 21 is bonded to a metal block 22 in order to measure the transmission loss. According to FIG. 5, the evaluation wiring board 21
Are electrically connected to the conversion board for measurement 23 and the ribbon 24. Therefore, the evaluation wiring board 21 includes two electromagnetic coupling parts for convenience of measurement, and the measurement conversion board 23
Are arranged so that their connection positions with the same plane. According to FIG. 5, the transmission characteristics measured include two electromagnetic coupling parts, two measurement conversion boards, two ribbons, two microstrip lines connecting the ribbon and the electromagnetic coupling part, and a microstrip connecting the electromagnetic coupling parts. This is the total of one strip line.

In the evaluation wiring board of FIG. 5, the frequency is 60 GHz, the length ML of the strip conductor paths 6 and 7 of the microstrip lines A and B from just above the center of the slot hole 9 to the end is ML = 0.28 mm, and the slot hole is Long diameter SL = 0.7
0 mm and slot hole width = 0.20 mm. At this time, the transmission characteristics at the input section were measured using a network analyzer.
Was measured by FIG. 6 shows the result.

According to the results shown in FIG. 6, under the condition that the length ML of the microstrip line is different from the dimension value at which the length ML is equivalent to １ ／ wavelength and the slot hole major axis SL is equal to the length corresponding to で wavelength, at 60 GHz. Excellent transmission characteristics with S11 of -22.1 dB and S21 of -2.95 dB were obtained.

Further, the transmission characteristics were measured by changing the length ML of the microstrip line from immediately above the center of the slot hole and the slot hole major axis SL. Use frequency is 60GHz
Tables 1 and 2 show the results. The operating frequency is 20GH
Tables 3 and 4 show the results of z. The insertion loss shown in Tables 1 to 4 is obtained by subtracting the loss other than the electromagnetic coupling portion (the loss of the conversion board for measurement and the loss of the ribbon connection portion) from the insertion loss value obtained from the measurement result based on FIG. This is a value obtained by dividing the value by 2 (that is, the insertion loss per electromagnetic coupling). Note that the wavelength λ ₁ in the microstrip line,
As for the wavelength at the slot hole λ _2, the resonance frequency was calculated from the model line based on FIG. 4 by FEM analysis and calculated using this and the wave number. As a result, when the frequency was 60 GHz, λ ₁ = 1.92 (mm), λ ₂ = 2.04 (m
m), when the frequency is 20 GHz, λ ₁ = 5.80 (m
m) and λ ₂ = 6.80 (mm).

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

According to the results of Tables 1 to 4, ML, SL
It can be seen that when the value of satisfies the above-described specific condition according to the present invention, coupling with an insertion loss of −5 dB or less is realized. Moreover, the frequency of the signal to be transmitted is 20G
It can be seen that this relationship does not change even if the frequency changes from Hz to 60 GHz.

According to Tables 1 and 2 at a frequency of 60 GHz in the region where the insertion loss is -1 dB or less, ML / λ ₁ is 0.1% under the condition of SL / λ ₂ = 0.5. Where SL / λ ₂ = 0.7
Then, the allowable width of ML / λ ₁ is 0.2, SL / λ ₂ = 0.3
It can be seen that the allowable width of ML / λ ₁ becomes as large as 0.2. According to Tables 3 and 4 in the case of a frequency of 20 GHz, under the condition of SL / λ ₂ = 0.5, the allowable width of ML / λ ₁ is 0.1, whereas SL / λ ₂ = It can be seen that the allowable range of ML / λ ₁ is 0.15 at 0.6 and the allowable range of ML / λ ₁ is 0.15 at SL / λ ₂ = 0.4.

Based on these results, the following equation 3

[0052]

(Equation 3)

Or the following equation

[0054]

(Equation 4)

In the region of, the insertion loss is -1 dB with respect to the change in the length from just above the center of the slot hole to the end of the line.
It can be seen that the following is a region where the allowable width that can be achieved is large, and is suitable for improving the manufacturing yield when manufacturing a high-frequency semiconductor device.

As a comparative example, a semiconductor device having the structure shown in FIG.
A network is formed by connecting a semiconductor device in which a microstrip line formed on a surface and a bottom surface of a dielectric material of 5.0 × 10 ^-4 (measurement frequency 60 GHz) is connected by a via-hole conductor made of a copper conductor having a diameter of 200 μm. The measurement was performed in the same manner using an analyzer, and the results are shown in FIG. From the results shown in FIG. 8, when the connection is made with the via hole conductor, the frequency is 20 GHz or more, S11: -10 dB or more, and S21: -30 dB or less. Therefore, it is impossible to transmit a high-frequency signal to the semiconductor element. I understand.

[0057]

As described in detail above, in the high-frequency semiconductor device of the present invention, the first microstrip line electrically connected to the high-frequency semiconductor element and the second microstrip line formed on the bottom surface of the dielectric substrate. Microstrip line and
By causing electromagnetic coupling in the dielectric substrate, reflection loss,
Since there is no radiation loss and there is no influence of transmission loss due to through-hole conductors, via-hole conductors, etc., transmission loss of high-frequency signals can be suppressed, and signals of required frequencies can be transmitted through.

Further, by configuring the length of the open side of the transmission line and the length of the slot in a region satisfying a predetermined condition,
Even with a dimensional deviation occurring in a processing step at the time of manufacturing, it is possible to increase the manufacturing yield with little deterioration in transmission characteristics.

Further, since the semiconductor device can be surface-mounted on the external circuit board, the size of the circuit board and the circuit device can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram for explaining a semiconductor device of the present invention.

FIG. 2 is a plan view for explaining the arrangement of strip conductor paths and slot holes of the microstrip line according to the present invention.

FIG. 3 is a diagram for explaining wiring in a cavity of the semiconductor device according to the present invention.

FIG. 4 shows (a) a wavelength λ ₁ in a microstrip line and (b) a wavelength λ ₂ in a slot hole according to the present invention.
FIG. 3 is a diagram for describing each model when is obtained by FEM analysis.

FIG. 5 is a diagram for explaining a method of measuring transmission characteristics in a semiconductor device according to the present invention.

FIG. 6 is a diagram illustrating an example of transmission characteristics of the high-frequency semiconductor device according to the present invention.

FIG. 7 is a diagram for explaining a mounting structure of a conventional high-frequency semiconductor device.

FIG. 8 is a diagram showing transmission characteristics in the semiconductor device of FIG. 7 (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency semiconductor device 2 Dielectric substrate 3 Lid 4 Cavity 5 Semiconductor element 6, 7 Strip conductor path A 1st microstrip line B 2nd microstrip line 8, 12 Ground layer 9 Slot hole 10 Power supply layer 11 Through Hall conductor

Claims (1)

[Claims] 1. A dielectric substrate, a high-frequency semiconductor element mounted on the surface of the dielectric substrate, and a second semiconductor element formed on the surface of the dielectric substrate and electrically connected to the high-frequency semiconductor element. 1 microstrip line, a second microstrip line formed on the bottom surface of the dielectric substrate, and a ground layer having a slot hole formed in the dielectric substrate. The length of the second microstrip line and the slot hole from directly above the center of the slot hole of the first and second microstrip lines to the end of each line is ML (mm);
When the major axis of the slot hole is SL (mm), the wavelength in the microstrip line is λ ₁ (mm), and the wavelength in the slot hole is λ ₂ (mm), Or, the following equation 2 Wherein the first microstrip line and the second microstrip line are electromagnetically coupled to each other.