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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
voice input / output device for converting voice into an electrical signal or converting an
electrical signal into voice, and more particularly, to an invention of a voice input / output device
integrated on a semiconductor substrate. .
2. Description of the Related Art Conventionally, voice input and output devices are devices
independent of each other, the former being called a microphone and the latter being a speaker.
Microphones include electrodynamic microphones used for karaoke microphones and the like,
and electrostatic microphones used for cassette tape recorders and the like, and speakers are
usually electrodynamic (dynamic). is there.
Conventional voice input / output devices rarely share the same parts because the structures of
the input device and the output device are largely different from each other, and drive these
devices. The degree of integration in the case of simultaneously integrating the electric circuits of
is as low as 10 K or less.
Therefore, since the present voice input / output device is constructed by combining and
mounting individual components, it is expensive in terms of manufacturing cost.
In addition, although the electrodynamic microphone can be manufactured at low cost, its
miniaturization is difficult due to its structure, and its use is restricted due to the use of a magnet.
On the other hand, although the electrostatic microphone can be miniaturized, its application is
limited because it requires a DC power supply.
In addition, since the speaker needs a cone etc., the size can not but be increased, and at the
same time it is susceptible to the influence of the magnetic field at the same time as the magnetic
force is exerted on other devices to use the magnet. is there.
Although the conventional microphone can withstand a large input of about 100 W, its
impedance is as low as several Ω cm, and there is also a problem of consuming a large amount
of power.
SUMMARY OF THE INVENTION It is an object of the present invention to solve the abovementioned problems and to provide a voice input / output device which has a simple structure,
high integration, small size and low power consumption.
SUMMARY OF THE INVENTION In the present invention, both input and output are performed
using the above thin film by using a thin thin film formed on a semiconductor substrate without
dripping as a vibrator. At the same time, it is possible to integrate an electric circuit and other
peripheral circuits for driving a thin film on the same substrate.
That is, according to the present invention, one electrode is formed on the outer side of the
vibratable thin film formed in at least a part of the opening on the semiconductor substrate, and
the other substrate is disposed opposite to the semiconductor substrate via the support. The
other of the electrodes is formed on the inner surface of the voice input / output device.
The voice input / output device of the present invention uses a well-known microfabrication
technology, so it can be easily manufactured even if it is miniaturized, and can be manufactured
In addition, the reduction in size reduces the power consumed at the input and output, enables
battery operation, and improves portability.
Furthermore, since the voice input / output device of the present invention does not utilize
magnetic force, its application is not limited.
EXAMPLES The present invention will be described in more detail by way of the following
examples, which should not be construed as limiting the invention thereto.
Embodiment 1 FIG. 1 shows a cross-sectional view of an embodiment of a voice input / output
device according to the present invention.
In the present embodiment, a thin film 12 made of a Si oxide film having a thickness of 3 μm is
formed on the Si semiconductor substrate 11 and vibrates in response to the vibration of the
sound wave incident from the opening 16.
An opposing substrate 13 made of glass is provided above the semiconductor substrate 11 with a
support 15 having a thickness of 10 μm.
First, the voice input mechanism will be described.
When the thin film 12 vibrates due to the incident sound wave, the distance between the
electrode 17 provided on the outer surface of the thin film 12 and the electrode 14 provided on
the inner surface of the counter substrate 13 changes, and as a result, the capacitance between
the electrodes changes Let
Therefore, if the electrodes 14 and 17 are connected to a capacitance detection circuit (not
shown) provided on the semiconductor substrate 11, the vibration of the thin film 12 is detected
as a capacitance change.
Next, the audio output mechanism will be described.
An electric signal generation circuit (not shown), for example, a sine wave generation circuit of
about 10 to 10000 Hz is provided on the semiconductor substrate 11, and a voltage is applied
between the electrodes 14 and 17. Approach and move away.
That is, the thin film 12 vibrates to generate an acoustic wave.
According to this embodiment, the electrostatic voice input / output device that can be used for
both the microphone and the speaker can be easily integrated on the semiconductor substrate.
In addition, a driver circuit of the input / output device and other electric circuits can be
simultaneously integrated on the same substrate.
In the present embodiment, the opening 16 can be formed with high productivity, stability, and
low cost by anisotropic etching of Si, which is a known technique.
In addition, devices having a size of 100 μm square or less can be manufactured.
Further, as the thin film 12, any film other than the Si oxide film may be used as long as it has no
pinhole and is strong. For example, Si nitride film, Si oxynitride film, PSG film, BPSG film, other
multi-layer stack Membranes can be used. As a method of forming the thin film 12, formation by
thermal oxidation, thermal nitridation and various vapor deposition methods of the
semiconductor Si can be considered. The film thickness of the thin film 12 is preferably 0.1 to
1000 μm, preferably 1 to 100 μm.
Since the voice input / output device of this embodiment is of an electrostatic type, there is no
direct current flowing between the electrodes 14 and 17, and only the power required to
rearrange the charges present on both electrodes is consumed. Therefore, the power
consumption is small. Further, by configuring the circuit for driving the present embodiment with
a small power consumption, for example, a CMOS inverter circuit or the like, it is possible to
minimize the power consumption of the system of the entire device.
Embodiment 2 Next, a second embodiment of the present invention is shown in FIG. FIG. 2 shows
an embodiment in which the through hole 18 is provided in the counter substrate 13 in the
present invention. When there is no through hole 18 (FIG. 1), a closed space is formed between
the thin film 12 and the electrode 17 by both substrates and the support material. Therefore,
when the thin film 12 vibrates, a pressure change occurs in the closed space (the inner chamber
19 in FIG. 1), and the pressure change attenuates the vibration of the thin film 12 and the sound
reproducibility is lowered.
When the through hole 18 is provided in the counter substrate 13, air can be moved into and out
of the inner chamber through the through hole 18, thereby preventing pressure change in the
inner chamber 19 and improving sound reproducibility. In the present embodiment, the number
of through holes 18 is not particularly limited, and a necessary number of through holes may be
formed at necessary places.
Further, contrary to the above embodiment, for a special application utilizing the pressure
change of the inner chamber 19, the through hole 18 is not provided, and a specific gas is
enclosed in the inner chamber 19 at an arbitrary pressure to be used as a pressure. It can also
enhance the effect.
[Third Embodiment] FIG. 3 shows a third embodiment of the present invention.
In the present embodiment, the concave portion 20 is formed in a region facing the thin film 12
of the counter substrate 13.
In the present invention, a uniform gap can be realized as the support 15 by using, for example, a
sealing technique used for a liquid crystal display device. However, in this technology, since the
gap amount is as small as about 10 μm, the vibration amplitude of the thin film can be increased
to about 500 μm by forming the recess 20 as in this embodiment. Furthermore, providing the
recess 20 is also advantageous for preventing the thin film 12 from being broken.
[Embodiment 4] Next, a configuration which is preferably used to enhance the effect of the voice
input / output device of the present invention will be described.
In the present invention, it is desirable that the stress of the thin film is a tensile of 10 8 dyne /
cm 2 or more, preferably 10 8 to 10 10 dyne / cm 2 so that the thin film does not sag.
The residual stress of the thin film changes depending on the true stress, formation temperature,
thermal expansion coefficient, annealing conditions, etc. of the material constituting the thin film,
so by changing these conditions, preferably about 10 8 to 3 × 10 9 dyne / cm 2 It can be
adjusted to be weakly tensile. In the case where the stress is a strong tensile property of 10 10
dyne / cm 2 or more, breakage of the film may occur, which is not preferable.
In the present invention, when the residual stress of the thin film is as high as 10 9 dyne / cm 2
or more, the rigidity of the thin film becomes high, and the resonance frequency shifts to the
higher side. Therefore, although not suitable for bass processing, it is possible to obtain an input
/ output device excellent in high-pitched sound characteristics.
In addition, by simultaneously mounting a plurality of input / output devices using a plurality of
thin films of different sizes, thicknesses, materials, and residual stresses, faithful reproducibility
can be obtained for the entire frequency range.
As described above, when the residual stress of the thin film is increased, the stress acting on the
electrode on the thin film naturally also increases.
In the present invention, the material of the electrode may be Al widely used in semiconductor
processes, Au which is rich in malleability and is easy to deposit, etc., but the tensile strength of
Al is not very high and it is used for high stress film Not suitable. An electrode structure formed
in a mesh shape is suitable for such a high stress film, and for example, in addition to the
honeycomb structure shown in FIG. 4, a triangular lattice, a square lattice, etc. may be mentioned.
In the mesh-like electrode structure, excessive bending exists in the shape of the electrode with
respect to the longitudinal and lateral directions of the thin film, and that portion becomes a
margin for deformation, and the breaking strength is improved. In addition, the mesh-like
electrode structure has an advantage that the capacitance value between the upper and lower
electrodes can be adjusted.
Fifth Embodiment FIG. 5 shows a fifth embodiment of the present invention. This embodiment is
an example in which the voice input / output device of the present invention is simultaneously
mounted with a liquid crystal display (LCD) which is one of display devices.
As the LCD in the present embodiment, for example, the LCD described in Japanese Patent LaidOpen No. 5-273591 is used. Thus, the liquid crystal display 25 in which the openings 16 and 16
'are formed in the same semiconductor substrate 11 and the liquid crystal 23 is sealed with the
sealing material 27, the voice input / output device 24 and the drive circuit 26 of the present
invention are the same substrate. The AV system can be easily configured by accumulating on
According to this embodiment, the AV system which has conventionally been several cm in size
can be formed on a single chip of several mm in size, and its power consumption can be
remarkably reduced.
According to the present invention, a compact, low-power-consumption audio input / output
device can be provided at low cost, and a compact AV system is realized by combining the
present invention with another display device .
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