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DESCRIPTION JPH06125038

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DESCRIPTION JPH06125038
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic integrated circuit in which an electronic element such as a transistor using III-V
compound semiconductor and an electroacoustic element such as a resonator or a filter are
integrally integrated. The present invention relates to the reduction in size, weight, and
performance of an oscillation circuit and a high frequency amplification circuit.
[0002]
2. Description of the Related Art Conventionally, in an electronic circuit using an electroacoustic
element, for example, an oscillation circuit such as an oscillator using a crystal resonator, or a
high frequency amplification circuit using a filter of crystal, oscillation is caused or amplified. It is
composed of a transistor which is an electronic element, a resonator for oscillating at a desired
frequency, a filter for taking out only a desired frequency, and electric parts such as some
capacitors and resistors. The resonator or filter used here has a predetermined value as its
vibration frequency or selection frequency, and is sealed in a container such as a metal tube so
that its performance is stable for a sufficiently long period of time. Therefore, the shape and
dimensions of the resonator and the filter become several times larger than the size of the
resonator and the filter itself, and the miniaturization is extremely important in a device such as a
car telephone and a mobile telephone where it is extremely important to be small. It is an
important issue.
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[0003]
On the other hand, a piezoelectric thin film such as ZnO or AlN is formed on a semiconductor
substrate such as Si by thin film technology such as sputtering, a resonator is formed of this
piezoelectric thin film, and a Si electronic element and an electroacoustic element are integrated.
An example of integration is known.
[0004]
As described above, in the oscillation circuit and the high frequency amplification circuit
configured by the method of individually connecting the resonator, the filter, the transistor, and
the related components accommodated in the container on the substrate, the size and weight
become large and heavy. Therefore, there has been a problem that it is not preferable in a device
such as a car phone and a mobile phone, which has small size and light weight as the most
important element.
[0005]
In the method of integrating on a semiconductor substrate such as Si by thin film formation
technology, the film that can be formed is limited to a part of materials such as ZnO and AlN, and
its characteristics are inferior to the characteristics of bulk. Also, good thin films have not been
obtained with quartz, lithium niobate, lithium tantalate, lithium borate etc. excellent in
electroacoustic properties.
[0006]
[Means for Solving the Problems] In order to solve the above problems, quartz, lithium niobate,
lithium tantalate, lithium borate, and the like having excellent electroacoustic characteristics on a
III-V compound semiconductor substrate having electronic elements such as transistors. And the
like are integrated by direct bonding.
[0007]
With the above construction, a compact, lightweight, high-performance electroacoustic
integrated circuit, in particular, an oscillation circuit or a high frequency amplification circuit can
be obtained.
[0008]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an
electroacoustic integrated circuit according to an embodiment of the present invention, in
particular, an oscillator and a high frequency amplifier circuit, and a method of manufacturing
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the same will be described with reference to the drawings.
[0009]
EXAMPLE 1 A first example of the structure of the oscillator circuit of this example is shown in
FIG.
FIG. 1 (a) is a side view of the structure of this embodiment, and FIG. 1 (b) is a perspective view
thereof.
In the figure, 1 is a GaAs substrate which is a III-V compound semiconductor, 2 is a surface
acoustic wave resonator comprising a quartz substrate which is a single crystal piezoelectric
body directly bonded onto the GaAs substrate 1 and 3 is formed on a GaAs substrate Transistor,
4 is a variable capacitance diode chip whose capacitance changes with voltage, 5 is a passive
chip component such as a capacitor, an inductor, or a resistor, 6 is an electrode of a surface
acoustic wave resonator, 7 is an electrode of a surface acoustic wave resonator And a wiring on
the GaAs substrate.
In the figure, only an example of a typical arrangement of each component is shown, and in
actuality, each component is disposed and each electrode is connected so as to be the
configuration of the voltage controlled oscillator shown in the circuit diagram of FIG.
Also, a resistor, a capacitor, a variable capacitance diode and the like can be integrally formed on
the GaAs substrate.
Moreover, it is also possible to wire by the metal thin film on a board | substrate, without using a
connection wire.
By changing the voltage applied to the variable capacitance diode, it is possible to change the
capacitance and change the oscillation frequency. The GaAs substrate 1 and the quartz substrate
2 are directly bonded. A very compact voltage controlled oscillator can be obtained by storing the
integrated components in a sealed container in this manner. With such a structure, since the
oscillation circuit unit and the resonator can be integrated as one unit, the size can be reduced
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more than in the past. With such a configuration, the volume is about 1/10 and about 1/5 in
weight as compared with the conventional case in which the surface acoustic wave resonator is
sealed in a container and attached individually.
[0010]
When bonding is performed using an adhesive such as a general resin, there is a problem that
the semiconductor process can not be performed after that from the viewpoint of heat resistance
and chemical resistance, but if the method of this embodiment is used, GaAs is used. The
substrate and the quartz substrate are directly bonded, and such problems are significantly
improved.
[0011]
Also, when bonding using an adhesive such as a resin, the parallelism of the GaAs substrate and
the quartz substrate stuck thereon becomes worse, and the dimensional accuracy of the combshaped electrode formed by photolithography on the quartz substrate becomes worse thereafter.
Become.
For example, when the resonance frequency is about 1 GHz, the electrode size has a width of
about 1 micron or less. Therefore, if the parallelism is bad, it is not possible to form a surface
acoustic wave resonator in the quasi-microwave band. However, in the method of the present
embodiment, the direct bonding is performed, and the processing accuracy of the substrate
surface can be obtained, and this accuracy can be sufficiently high. Therefore, the above
problems are solved. This effect is particularly large at high frequencies.
[0012]
In the case of using a resin adhesive, there are problems such as long-term reliability due to
mechanical distortion due to the problem of heat resistance and the large difference in thermal
expansion coefficient between organic resin and inorganic GaAs substrate or quartz substrate.
However, such a problem is also solved in this embodiment.
[0013]
Although the example of the oscillation circuit of the circuit configuration shown in FIG. 2 is
shown in this embodiment, it is obvious that the configuration of other oscillation circuits can be
integrated and integrated in the same manner.
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[0014]
In addition, since the GaAs substrate is about six times faster in electron mobility than the Si
substrate, it is easy to fabricate a high frequency transistor, which is particularly suitable for high
frequency circuits.
[0015]
Further, although an example of the surface acoustic wave element is shown as the
electroacoustic element in this embodiment, it is also possible to form a bulk type vibration
element.
[0016]
(Example 2) An application example to the high frequency amplification circuit of this example is
shown in FIG.
FIG. 3 shows a filter and an amplifier circuit directly connected, and the components are a filter, a
transistor and a capacitor.
Therefore, as in the first embodiment, various electronic elements are formed on a GaAs
substrate, and surface acoustic wave filters are formed on a quartz substrate, and they are wired
so as to be the high frequency amplification circuit shown in FIG. An integrated electroacoustic
integrated circuit is obtained.
The bonding of the GaAs substrate and the quartz substrate can be direct bonding as in the first
embodiment, and the effect is also the same as the first embodiment. .
[0017]
EXAMPLE 3 Another example of the method of manufacturing the oscillator circuit of this
example is shown.
[0018]
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First, a concave portion is provided in a predetermined portion of a GaAs substrate by etching or
the like, and a series of semiconductor process treatments including a process performed at a
heat treatment temperature or more for direct bonding, such as a diffusion process, are
performed inside thereof. Form a variable capacitance diode or the like.
The diffusion process is usually performed at high temperatures of 1000 ° C. or higher.
Next, a protective film is formed on the GaAs portion in which various electronic elements are
formed. Thereafter, the surface of the GaAs substrate and the quartz substrate to be bonded are
extremely cleaned, and the surface of the GaAs substrate is etched away with a sulfuric acidhydrogen peroxide based etchant and the quartz substrate with a hydrofluoric acid based
etchant. , The surface layer is treated to be hydrophilic. Thereafter, the surface is sufficiently
washed with pure water and uniformly superposed to easily obtain a bond. By performing heat
treatment in this state, bonding strength is enhanced. The heat treatment at a temperature of
100 to 800 ° C. further strengthens the bond. When the heat treatment temperature is high,
there is a difference in the shape, size, etc. due to the difference in thermal expansion coefficient
between the GaAs substrate and the quartz substrate, but basically, the thickness of the quartz
substrate is higher as heat treatment is performed at high temperature. If the area is made small,
the bonding strength can be improved without peeling or breakage. Next, various processes for
processing below the heat treatment temperature of bonding, such as electrode formation, are
carried out, and then or after that, electrodes are formed on the surface of the quartz substrate
by vacuum deposition, etc. Form. The electrodes are made of aluminum or gold. The heat
treatment effect of bonding strengthening is, for example, that the bonding strength is several
times as high as holding at 200 ° C. for about one hour, and a strength of several tens kg /
square cm can be obtained.
[0019]
Further, as the temperature becomes higher, As becomes easy to evaporate. In that case, it is
preferable to suppress the evaporation of As by placing a GaAs wafer on top.
[0020]
In the case of the high frequency amplification circuit, it is apparent that the manufacturing can
be performed in the same manner as in Example 3 except that a filter is used as the
electroacoustic element and the circuit configuration is slightly different.
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[0021]
In the present embodiment, an example of a surface acoustic wave element is shown as a
resonator or a filter, but the invention can be applied to an electroacoustic element using bulk
wave vibration in substantially the same manner.
In this case, it can be realized by hollowing out the semiconductor substrate under the bulk type
vibration element by etching or the like.
[0022]
Example 4 A third example of the structure of the oscillator circuit of this example is shown in
FIG.
FIG. 4 (a) is a side view of the structure of this embodiment, and FIG. 4 (b) is a perspective view
thereof. In the figure, 1 is a GaAs substrate which is a III-V compound semiconductor, and 2 ′ is
a single crystal piezoelectric lithium Niobate or lithium tantalate or lithium borate single crystal
piezoelectric substrate directly bonded onto the GaAs substrate 1 The functions and names of the
surface acoustic wave resonators and the components 3 to 7 are the same as in the first
embodiment. The figure only shows an example of the typical arrangement of each part, and in
this case, each part is configured as in the configuration of the voltage controlled oscillator
shown in the circuit diagram of FIG. It arrange | positions and each electrode is connected. Also, a
resistor, a capacitor, a variable capacitance diode and the like can be integrally formed on the
GaAs substrate. The GaAs substrate 1 and the lithium niobate or lithium tantalate or lithium
borate single crystal piezoelectric substrate 2 'are directly bonded by superposing heat treatment
after the surfaces of both substrates are subjected to a hydrophilic treatment. Thereby, the same
function and effect as those of the first embodiment can be obtained. That is, with such a
structure, since the oscillation circuit unit and the resonator can be integrated as one unit, the
size can be reduced more than in the past. With such a configuration, the volume is about 1/10
and about 1/5 in weight as compared with the conventional case in which the surface acoustic
wave resonator is sealed in a container and attached individually.
[0023]
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The effect of direct bonding is also the same as in the first embodiment. Although the example of
the oscillation circuit of the circuit configuration shown in FIG. 2 is shown in this embodiment, it
is obvious that the configuration of other oscillation circuits can be integrated and integrated in
the same manner.
[0024]
In addition, since the GaAs substrate is about six times faster in electron mobility than the Si
substrate, it is easy to fabricate a high frequency transistor, which is particularly suitable for high
frequency circuits.
[0025]
Further, as in the second embodiment, it can be applied to the high frequency amplification
circuit shown in FIG. 3 and it is apparent that the same effect can be obtained.
[0026]
(Example 5) An example of a method of manufacturing the oscillator circuit of Example 4 is
shown.
[0027]
The manufacturing process is basically the same as in Example 3.
That is, in Example 3, a lithium niobate or lithium tantalate or lithium borate single crystal
substrate is used instead of the quartz substrate, and bonding can be performed by the same
hydrophilic treatment, pure water washing, and superposition heat treatment.
The formation of various electronic circuits and wiring can be similarly performed.
The etching of the lithium niobate and lithium tantalate substrate surfaces is carried out with a
hydrofluoric acid based etchant as with quartz. In the case of lithium borate, a weak acid such as
acetic acid is used. The etching process of the GaAs substrate surface is the same as that of the
third embodiment. In addition, good direct bonding can be obtained between 100 and 800 ° C.
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as in the third embodiment.
[0028]
In the case of the high frequency amplification circuit, it is apparent that the manufacture can be
similarly performed by using a filter as the electroacoustic element and slightly changing the
circuit configuration. Also, the bulk type vibration element can be formed in the same manner as
described in the third embodiment.
[0029]
EXAMPLE 6 A fourth example of the structure of the oscillator circuit of this example is shown in
FIG. FIG. 5 (a) is a side view of the structure of this embodiment, and FIG. 5 (b) is a perspective
view thereof. In the figure, 1 'is an InP substrate which is a III-V compound semiconductor, 2 is a
surface acoustic wave resonator comprising a quartz substrate directly bonded onto the InP
substrate 1, functions and names of respective components 3 to 7 Is the same as in Example 1.
The figure only shows an example of the typical arrangement of each part, and in this case, each
part is configured as in the configuration of the voltage controlled oscillator shown in the circuit
diagram of FIG. It arrange | positions and each electrode is connected. Also, a resistor, a
capacitor, a variable capacitance diode and the like can be integrally formed on the InP substrate.
The InP substrate 1 'and the quartz substrate 2 are directly bonded by superposing heat
treatment after the surfaces of both substrates are subjected to a hydrophilic treatment. Thereby,
the same function and effect as those of the first embodiment can be obtained. That is, with such
a structure, since the oscillation circuit unit and the resonator can be integrated as one unit, the
size can be reduced more than in the past. With such a configuration, the volume is about 1/10
and about 1/5 in weight as compared with the conventional case in which the surface acoustic
wave resonator is sealed in a container and attached individually.
[0030]
The effect of direct bonding is also the same as in the first embodiment. Although the example of
the oscillation circuit of the circuit configuration shown in FIG. 2 is shown in this embodiment, it
is obvious that the configuration of other oscillation circuits can be integrated and integrated in
the same manner.
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[0031]
In addition, since the InP substrate has about twice the electron mobility as the GaAs substrate
and the electron mobility about twice as fast as the Si substrate, it is easy to make a high
frequency transistor, and is particularly suitable for a high frequency circuit.
[0032]
Further, as in the second embodiment, it can be applied to the high frequency amplification
circuit shown in FIG. 3 and it is apparent that the same effect can be obtained.
[0033]
(Example 7) An example of a method of manufacturing the oscillator circuit of Example 6 will be
shown.
[0034]
The manufacturing process is basically the same as in Example 3.
That is, in the third embodiment, an InP substrate can be used instead of a GaAs substrate, and
bonding can be performed by the same hydrophilic treatment, pure water washing, and
superposition heat treatment.
The formation of various electronic circuits and wiring can be similarly performed.
The etching process of the InP substrate surface uses a sulfuric acid-hydrogen peroxide system
etching as in the third embodiment. In addition, good direct bonding can be obtained between
100 and 800 ° C. as in the third embodiment.
[0035]
In the case of the high frequency amplification circuit, it is apparent that the manufacture can be
similarly performed by using a filter as the electroacoustic element and slightly changing the
circuit configuration.
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[0036]
(Example 8) A fifth example of the structure of the oscillation circuit of this example is shown in
FIG.
FIG. 6 (a) is a side view of the structure of this embodiment, and FIG. 6 (b) is a perspective view
thereof. In the figure, 1 ′ is an InP substrate which is a III-V compound semiconductor, and 2 ′
is a single crystal piezoelectric body directly bonded onto the InP substrate 1 ′, lithium niobate
or lithium tantalate or lithium borate single crystal piezoelectric body The functions and names
of the surface acoustic wave resonators and the components 3 to 7 made of a substrate are the
same as in the first embodiment. The figure only shows an example of the typical arrangement of
each part, and in this case, each part is configured as in the configuration of the voltage
controlled oscillator shown in the circuit diagram of FIG. It arrange | positions and each electrode
is connected. Also, a resistor, a capacitor, a variable capacitance diode and the like can be
integrally formed on the InP substrate. The InP substrate 1 'and the lithium niobate or lithium
tantalate or lithium borate single crystal piezoelectric substrate 2' are directly bonded by
superposing heat treatment after the surfaces of both substrates are subjected to a hydrophilic
treatment. Thereby, the same function and effect as those of the first embodiment can be
obtained. That is, with such a structure, since the oscillation circuit unit and the resonator can be
integrated as one unit, the size can be reduced more than in the past. With such a configuration,
the volume is about 1/10 and about 1/5 in weight as compared with the conventional case in
which the surface acoustic wave resonator is sealed in a container and attached individually.
[0037]
The effect of direct bonding is also the same as in the first embodiment. Although the example of
the oscillation circuit of the circuit configuration shown in FIG. 2 is shown in this embodiment, it
is obvious that the configuration of other oscillation circuits can be integrated and integrated in
the same manner.
[0038]
In addition, since the InP substrate has about twice as fast an electron mobility as the Si
substrate, it is easy to fabricate a high frequency transistor, which is particularly suitable for a
high frequency circuit.
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[0039]
Further, as in the second embodiment, it can be applied to the high frequency amplification
circuit shown in FIG. 3 and it is apparent that the same effect can be obtained.
[0040]
(Example 9) An example of a method of manufacturing the oscillator circuit of Example 8 is
shown.
[0041]
The manufacturing process is basically the same as in Example 3.
That is, in Example 3, using an InP substrate instead of a GaAs substrate and a lithium niobate or
lithium tantalate or lithium borate single crystal substrate instead of a quartz substrate, similar
hydrophilic treatment, pure water washing, superposition heat treatment Can be joined by
The formation of various electronic circuits and wiring can be similarly performed.
The etching of the lithium niobate and lithium tantalate substrate surfaces is treated with a
hydrofluoric acid based etchant as with quartz. In the case of lithium borate, a weak acid such as
acetic acid is used. The etching process of the InP substrate surface is the same as that of the
seventh embodiment. In addition, good direct bonding can be obtained between 100 and 800 °
C. as in the third embodiment.
[0042]
In the case of the high frequency amplification circuit, it is apparent that the manufacture can be
similarly performed by using a filter as the electroacoustic element and slightly changing the
circuit configuration.
[0043]
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EXAMPLE 10 A sixth example of the structure of the oscillator circuit of this example is shown in
FIG.
FIG. 7 (a) is a side view of the structure of this embodiment, and FIG. 7 (b) is a perspective view
thereof. In the figure, 1 ′ ′ is a GaAs substrate having an InGaAs layer which is a III-V
compound semiconductor, 2 is a surface acoustic wave resonator comprising a quartz substrate
directly bonded on a GaAs substrate 1 ′ ′ having an InGaAs layer, 3 The functions and names
of the components from 7 to 7 are the same as in the first embodiment. The figure only shows an
example of the typical arrangement of each part, and in this case, each part is configured as in
the configuration of the voltage controlled oscillator shown in the circuit diagram of FIG. It
arrange | positions and each electrode is connected. Also, a resistor, a capacitor, a variable
capacitance diode and the like can be integrally formed on a GaAs substrate having an InGaAs
layer. The GaAs substrate 1 ′ ′ having the InGaAs layer and the quartz substrate 2 are directly
bonded together by superposing heat treatment after hydrophilic treatment of the surfaces of
both substrates. Thereby, the same function and effect as those of the first embodiment can be
obtained. That is, with such a structure, since the oscillation circuit unit and the resonator can be
integrated as one unit, the size can be reduced more than in the past. With such a configuration,
the volume is about 1/10 and about 1/5 in weight as compared with the conventional case in
which the surface acoustic wave resonator is sealed in a container and attached individually.
[0044]
The effect of direct bonding is also the same as in the first embodiment. Although the example of
the oscillation circuit of the circuit configuration shown in FIG. 2 is shown in this embodiment, it
is obvious that the configuration of other oscillation circuits can be integrated and integrated in
the same manner.
[0045]
Also, since the InGaAs layer has about 3-5 times faster electron mobility than the Si substrate like
the GaAs substrate, it is easy to make a high frequency transistor, which is particularly suitable
for a high frequency circuit.
[0046]
Further, as in the second embodiment, it can be applied to the high frequency amplification
circuit shown in FIG. 3 and it is apparent that the same effect can be obtained.
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[0047]
(Example 11) An example of a method of manufacturing the oscillator circuit of Example 10 will
be shown.
[0048]
The manufacturing process is basically the same as in Example 3.
That is, in Example 3, a GaAs substrate having an InGaAs layer on the surface is used instead of
the GaAs substrate, and bonding can be performed by the same hydrophilic treatment, pure
water washing, and superposition heat treatment.
The formation of various electronic circuits and wiring can be similarly performed.
The etching process of the surface of the InGaAs layer uses a sulfuric acid-hydrogen peroxide
system etching as in the third embodiment. In addition, good direct bonding can be obtained
between 100 and 800 ° C. as in the third embodiment. Electronic elements are formed in the
InGaAs layer. If the thickness of the InGaAs layer is about 1-5 μm, various electronic devices can
be formed.
[0049]
In the case of the high frequency amplification circuit, it is apparent that the manufacture can be
similarly performed by using a filter as the electroacoustic element and slightly changing the
circuit configuration.
[0050]
Example 12 A seventh example of the structure of the oscillator circuit of this example is shown
in FIG.
FIG. 8 (a) is a side view of the structure of this embodiment, and FIG. 8 (b) is a perspective view
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thereof. In the figure, 1 ′ ′ is a GaAs substrate having an InGaAs layer which is a III-V
compound semiconductor, and 2 ′ is a lithium niobate or lithium tantalate or lithium borate
directly bonded onto the GaAs substrate 1 ′ ′ having an InGaAs layer. The functions and
names of the surface acoustic wave resonators composed of a single crystal piezoelectric
substrate and the components 3 to 7 are the same as in the first embodiment. The figure only
shows an example of the typical arrangement of each part, and in this case, each part is
configured as in the configuration of the voltage controlled oscillator shown in the circuit
diagram of FIG. It arrange | positions and each electrode is connected. Also, a resistor, a
capacitor, a variable capacitance diode and the like can be integrally formed on a GaAs substrate
having an InGaAs layer. The GaAs substrate 1 ′ ′ having the InGaAs layer and the single crystal
piezoelectric substrate 2 ′ are directly bonded together by superposing heat treatment after the
surfaces of both substrates are subjected to a hydrophilic treatment. Thereby, the same function
and effect as those of the first embodiment can be obtained. That is, with such a structure, since
the oscillation circuit unit and the resonator can be integrated as one unit, the size can be
reduced more than in the past. With such a configuration, the volume is about 1/10 and about
1/5 in weight as compared with the conventional case in which the surface acoustic wave
resonator is sealed in a container and attached individually.
[0051]
The effect of direct bonding is also the same as in the first embodiment. Although the example of
the oscillation circuit of the circuit configuration shown in FIG. 2 is shown in this embodiment, it
is obvious that the configuration of other oscillation circuits can be integrated and integrated in
the same manner.
[0052]
Also, since the InGaAs layer has about 3-5 times faster electron mobility than the Si substrate like
the GaAs substrate, it is easy to make a high frequency transistor, which is particularly suitable
for a high frequency circuit.
[0053]
Further, as in the second embodiment, it can be applied to the high frequency amplification
circuit shown in FIG. 3 and it is apparent that the same effect can be obtained.
[0054]
(Example 13) An example of a method of manufacturing the oscillator circuit of Example 12 will
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be shown.
[0055]
The manufacturing process is basically the same as in Example 3.
That is, in Example 3, a GaAs substrate having an InGaAs layer on the surface instead of a GaAs
substrate is used, and lithium niobate or lithium tantalate or lithium borate single crystal
piezoelectric substrate is used instead of a quartz substrate, similar hydrophilic treatment, pure It
can be joined by water washing and superposition heat treatment.
The formation of various electronic circuits and wiring can be similarly performed.
The etching process of the surface of the InGaAs layer uses a sulfuric acid-hydrogen peroxide
system etching as in the third embodiment. In addition, good direct bonding can be obtained
between 100 and 800 ° C. as in the third embodiment. Electronic elements are formed in the
InGaAs layer. If the thickness of the InGaAs layer is about 1-5 μm, various electronic devices can
be formed.
[0056]
In the case of the high frequency amplification circuit, it is apparent that the manufacture can be
similarly performed by using a filter as the electroacoustic element and slightly changing the
circuit configuration.
[0057]
Although this example shows GaAs, InP and InGaAs as III-V compound semiconductors, the
present invention can be widely applied to other III-V compound semiconductors having similar
chemical and electronic properties. .
[0058]
Since the present invention comprises the construction and the manufacturing method as
described above, the effects as described below are exhibited.
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[0059]
In any of the embodiments, firstly, since the electroacoustic elements such as the oscillator and
the filter and the electronic elements such as the transistor are integrated, the oscillation circuit
and the high frequency amplification circuit are greatly miniaturized and lightened. It is easy to
reduce the volume by about 1/10 and the weight by about 1⁄5, as compared to the case of using
a resonator or a filter housed in a conventional container.
[0060]
In the bonding method of this embodiment, since the III-V compound semiconductor substrate
and the quartz substrate are directly bonded, the flatness is extremely good, and submicron
photolithography necessary for setting the operating frequency becomes possible. The reliability
against heat and vibration is also greatly improved.
[0061]
In this embodiment, an example of the configuration of the oscillation circuit and the high
frequency amplification circuit of the voltage controlled oscillator is shown, but basically, the
electroacoustic element and the electronic element such as the transistor can be integrated
integrally. It is widely applicable to electroacoustic integrated circuits in general.
[0062]
In the method of this embodiment, a single crystal piezoelectric substrate of quartz, lithium
niobate, lithium tantalate, lithium borate etc. excellent in electroacoustic characteristics can be
used, and the crystal orientation can be freely selected. It is possible to obtain better performance
than the thin film type which can be made of only limited materials and which can only exhibit
performance inferior to the bulk characteristics.
[0063]
In addition, GaAs and InP, which are III-V compound semiconductors, have electron mobility
faster than Si and are more suitable for high frequency circuits.
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