KR102659226B1 - Microphone including field effect transistor - Google Patents

Abstract

The microphone starts. The microphone includes an acoustic sensor configured to respond to sound waves and output an output current corresponding to the sound wave, a control circuit configured to process the output current of the acoustic sensor to generate an audio signal in electrical form, and output the audio signal to the outside. It includes an output interface configured to do so, and the acoustic sensor includes a field effect transistor that outputs an output current that changes depending on the sound pressure of the sound wave.

Description

Microphone including a field effect transistor {MICROPHONE INCLUDING FIELD EFFECT TRANSISTOR}

Embodiments of the present invention relate to microphones, and in particular, to microphones including a field effect transistor (FET).

A microphone is a device that converts sounds, such as speech, into electrical voice signals. There are various types of microphones on the market, and recently, microphones based on MEMS (micro electro mechanical system) have been widely used.

MEMS microphones are largely divided into piezoresistive, piezoelectric, and capacitive types. The piezoresistive method uses an element whose resistance changes depending on the applied pressure, the piezoelectric method uses an element that generates voltage according to the applied pressure, and the capacitive method uses the phenomenon of capacitance changing depending on the pressure. It's a method.

Recently, the capacitance method has been used in many mobile devices, but the manufacturing process is complicated because a capacitor structure with capacitance must be implemented.

In particular, in the case of the piezoelectric method, there are problems with the materials that can be used being limited and the signal-to-noise ratio being low. In the case of the piezoresistive method, the difficulty of the manufacturing process is not high and the signal-to-noise ratio is excellent, but in general, the micro current flowing through a high-resistance material is used. There is a problem in that an additional detection circuit (eg, a Wheatstone bridge circuit, etc.) is required to detect this minute current.

[Assignment number] UR210033

[Name of Ministry] Ministry of Strategy and Finance

[Project management (professional) organization name] Korea Institute of Industrial Technology

[Research Project Name] Research and Development Reserve Project

[Research project name] [Demand-based internal-Track1] Research on energy conversion techniques for upgrading MEMS microphones

The present invention is an invention made to solve the problems of the prior art described above, and has the purpose of providing a microphone that utilizes the piezoresistive characteristics of a field effect transistor.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A microphone according to embodiments of the present invention for achieving the above object is an acoustic sensor configured to output an output current corresponding to the sound wave in response to a sound wave, and processes the output current of the acoustic sensor to produce a voice signal in electrical form. It includes a control circuit configured to generate and an output interface configured to output a voice signal to the outside, and the acoustic sensor includes a field effect transistor that outputs an output current that changes depending on the sound pressure of the sound wave.

The microphone including a field effect transistor according to embodiments of the present invention is a piezoresistive microphone, has a simpler manufacturing process than a capacitive microphone, and has a superior signal-to-noise ratio than a piezoelectric microphone.

In addition, the microphone including a field effect transistor according to embodiments of the present invention is a piezoresistive microphone, and is easier to detect signals than a piezoresistive microphone using a conventional high-resistance material, so it has high sensitivity even without a separate detection circuit. and has the effect of having an excellent signal-to-noise ratio.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned above will be clearly understood by those skilled in the art from the description of the claims.

1 shows a microphone according to embodiments of the present invention.
Figure 2 shows an acoustic sensor according to embodiments of the present invention.
Figure 3 shows an acoustic sensor including a field effect transistor according to embodiments of the present invention.
Figure 4 is a diagram for explaining the operation of the acoustic sensor when sound waves do not exist.
Figure 5 is a diagram for explaining the operation of the acoustic sensor when sound waves exist.
Figure 6 conceptually shows a plan view of an acoustic sensor according to embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In describing this embodiment, the same names and the same symbols are used for the same components, and additional description accordingly will be omitted.

1 shows a microphone according to embodiments of the present invention. Referring to FIG. 1, the microphone 10 includes an acoustic sensor 100, a memory 200, a control circuit 300, and an output interface 400.

The acoustic sensor 100 can convert the physical energy (i.e., wave energy) of sound waves into an electrical signal. Depending on embodiments, the acoustic sensor 100 may include a field effect transistor (FET). The microphone 10 according to embodiments of the present invention can convert sound waves into electrical signals and output them by using the piezoresistance of a field effect transistor.

The memory 200 can store data necessary for the operation of the microphone 10. For example, the memory 200 may include at least one of non-volatile memory and volatile memory.

The memory 200 may store conversion information associated with the correlation between the output of the acoustic sensor 100 and the pressure caused by sound waves (i.e., sound pressure).

The control circuit 300 can control the overall operation of the microphone 100.

Depending on embodiments, the control circuit 300 may include a circuit configured to control the operation of the acoustic sensor 100. The circuit can apply a gate voltage to the field effect transistor included in the acoustic sensor 100 and adjust the size of the gate voltage.

Additionally, depending on embodiments, the control circuit 300 may include a circuit configured to generate an audio signal by processing an output signal output from the acoustic sensor 100. The circuit may generate an audio signal by amplifying and/or filtering the output signal of the acoustic sensor 100.

The output interface 400 can output a voice signal. Depending on embodiments, the output interface 400 may output a voice signal according to a wireless communication method or a wired communication method. For example, the output interface 400 may include a wireless communication integrated circuit that supports wireless communication or a wired communication port that supports wired communication.

Figure 2 shows an acoustic sensor according to embodiments of the present invention. Referring to FIG. 2, the acoustic sensor 100 may include a base substrate 110 and field effect transistors 120A and 120B.

The base substrate 110 may support the overall structure of the acoustic sensor 100. Depending on embodiments, the base substrate 110 may be a substrate containing a semiconductor material. For example, the base substrate 110 may be a semiconductor substrate containing silicon (Si).

The base substrate 110 may include a groove 111 configured to allow sound waves to enter. The groove 111 may be formed in the lower part of the base substrate 110. The thickness of the base substrate 110 at a location where the groove portion 111 is formed may be thinner than the thickness of the base substrate 110 at a location where the groove portion 111 is not formed. Accordingly, sound waves flowing into the groove 111 may apply stronger stress (or pressure) to the base substrate 110.

The field effect transistors 120A and 120B may be disposed on the base substrate 110. Depending on the embodiment, the field effect transistors 120A and 120B may be plural, and the plurality of field effect transistors 120A and 120B may be arranged to face each other with the groove 111 as the center. For example, the plurality of field effect transistors 120A and 120B may be arranged to be symmetrical to each other about the groove 111.

According to embodiments of the present invention, by using the piezoresistance of the field effect transistors (120A, 120B), the physical energy of the sound wave can be converted into electrical energy, and an electric signal corresponding to the sound wave can be output.

Figure 3 shows an acoustic sensor including a field effect transistor according to embodiments of the present invention. Referring to FIG. 3, the acoustic sensor 100 may include a base substrate 110, a field effect transistor 120, a semiconductor layer 130, and a dielectric layer 140.

The field effect transistor 120 shown in FIG. 3 representatively represents the field effect transistors 120A and 120B described with reference to FIG. 2 .

The field effect transistor 120 may be disposed on the base substrate 110. The field effect transistor 120 may generate an output signal according to the sound pressure of the sound wave flowing in through the groove 111. The output signal generated by the field effect transistor 120 may be transmitted to the control circuit 300.

The semiconductor layer 130 may be stacked on the base substrate 110. Depending on the embodiment, the semiconductor layer 130 may be composed of a p-type semiconductor, but is not limited thereto. Depending on embodiments, the semiconductor layer 130 may be a silicon substrate.

In FIG. 3, the base substrate 110 and the semiconductor layer 130 are shown separated, but depending on embodiments, the base substrate 110 and the semiconductor layer 130 may be formed integrally to form one silicon substrate. .

The dielectric layer 140 may be stacked on the semiconductor layer 130. Depending on embodiments, the dielectric layer 140 is a layer containing a dielectric and may be an oxide layer.

Depending on embodiments, the field effect transistor 120 may include a drain region 121, a source region 122, a channel region 123, a drain electrode 124, a gate electrode 125, and a source electrode 126. You can.

The drain region 121, source region 122, and channel region 123 may be formed in the semiconductor layer 130 stacked on the base substrate 110.

Depending on the embodiment, the field effect transistor 120 may be an n-type transistor, the drain region 121 and the source region 122 may be composed of an n-type semiconductor, and the base substrate 110 may be composed of a p-type semiconductor. You can.

The channel region 123 may be formed between the drain region 121 and the source region 123. As will be described later, when a gate voltage higher than the threshold voltage is applied to the gate electrode 125, current flows from the drain region 121 to the source region 123 through the channel region 123.

The amount of current flowing in the channel region 123 may be proportional to the voltage applied to the gate electrode 125, and accordingly, the channel region 123 can be understood as a resistor.

Meanwhile, the electrical characteristics of the channel region 123 may be determined by electron mobility. That is, even if the same voltage (eg, gate-source voltage) is applied, the higher the electron mobility of the channel region 123, the more current can flow.

Meanwhile, the electron mobility of the channel region 123 may vary depending on the pressure (or stress) applied to the channel region 123. That is, the channel region 123 has piezoresistive properties. The acoustic sensor 100 according to embodiments of the present invention can convert the sound pressure of a sound wave into an electrical signal using the piezoresistive characteristics of the channel region 123 of the field effect transistor 120.

Hereinafter, for convenience, this specification will assume that the resistance of the channel region 123 of the transistor 120 is inversely proportional to the stress, but embodiments of the present invention are not limited thereto.

In order to increase the sensitivity of the acoustic sensor 100, it is preferable that the channel area 123 is placed at a location where the sound pressure (i.e., stress due to the sound pressure) applied to the acoustic sensor 100 is relatively large.

Depending on embodiments, the channel region 123 may be arranged so that at least a portion of the channel region 123 overlaps the groove 111 formed in the base substrate 110 in the vertical direction. For example, the drain region 121 may be arranged not to overlap the groove 111, and the source region 122 may be arranged to overlap the groove 111.

Depending on embodiments, the channel area 123 may be arranged to overlap the boundary area 111a of the groove 111 formed in the base substrate 110. For example, the boundary area 111a of the groove 111 may be located between the drain area 121 and the source area 122.

Sound waves flowing through the groove 111 may exert the greatest stress on the boundary area 111a (eg, side boundary) of the groove 111. The field effect transistor 120 according to embodiments of the present invention is arranged so that the channel region 123 at least partially overlaps the groove 111, and stress changes due to sound waves can be well transmitted to the channel region 123. Therefore, sensitivity is excellent and signal-to-noise ratio can be high.

Drain electrode 124 may be connected to drain region 121. The drain electrode 124 may be made of a conductor such as copper, and may transmit a voltage (eg, ground voltage) transmitted from the outside to the drain region 121 .

The gate electrode 125 may be made of a conductor such as copper. A gate voltage (VG) may be applied to the gate electrode 125. The gate electrode 125 may be electrically separated from the drain region 121, source region 122, and channel region 123. For example, the gate electrode 125 may be electrically separated from the drain region 121, source region 122, and channel region 123 by the dielectric layer 140.

The source electrode 126 may be connected to the source region 122. The source electrode 126 may be made of a conductor such as copper and may transmit a voltage (eg, input voltage VD) transmitted from the outside to the source region 122 .

Additionally, the source electrode 126 may be connected to the control circuit 300. The control circuit 300 may convert the output signal (ie, current) output from the source electrode 126 to output an audio signal (ie, voltage).

Figure 4 is a diagram for explaining the operation of the acoustic sensor when sound waves do not exist. Referring to FIG. 4, a gate voltage for turning on the field effect transistor 120 is applied to the gate electrode 125. This voltage is called the turn-on level gate voltage.

When a gate voltage of the turn-on level is applied, electrons move from the source region 121 to the drain region 122, and thus, an output current flows from the drain region 122 to the source region 121. The control circuit 300 may convert the output current of the field effect transistor 120 to output the first voltage V1.

Figure 5 is a diagram for explaining the operation of the acoustic sensor when sound waves exist. Referring to FIG. 5, a gate voltage at the turn-on level is applied to the gate electrode 125.

Meanwhile, when sound is applied to the outside of the acoustic sensor 100, sound pressure according to the sound is applied to the acoustic sensor 100. Accordingly, stress acts on the acoustic sensor 100. For example, acoustic stress is applied to the semiconductor layer 130 of the acoustic sensor 100, and this stress is applied to the channel region 123.

When stress acts on the channel region 123, the resistance of the channel region 123 is reduced due to the piezoresistance of the channel region 123. For example, the electron mobility of the channel region 123 may increase in proportion to the stress. That is, when stress acts on the channel region 123, the output current of the field effect transistor 120 may increase.

The control circuit 300 may convert the output current of the field effect transistor 120 to output the second voltage V2. If the remaining conditions except for the stress acting on the acoustic sensor 100 are the same, the second voltage V2 of FIG. 5 may be greater than the first voltage V1 of FIG. 4.

That is, referring to FIGS. 4 and 5 together, when stress acts on the channel region 123, the output current of the field effect transistor 120 may increase, and as a result, the acoustic sensor 100 may respond to the field effect. Depending on the piezoresistance of the transistor 120, the sound pressure of the sound can be converted into a voice signal, which is an electrical signal, and output.

Depending on embodiments, the memory 200 may store conversion information associated with the correlation between the output current of the acoustic sensor 100 and the pressure (i.e., sound pressure) caused by sound waves, and the control circuit 300 may store the conversion information. Based on this, the output current of the field effect transistor 120 can be converted into an audio signal corresponding to sound pressure.

Meanwhile, the output current of the field effect transistor 120 may vary depending on the gate voltage (VG) applied to the gate electrode 125. According to embodiments, the control circuit 300 adjusts the size of the gate voltage (VG) according to the size of the sound input to the acoustic sensor 100, and applies the adjusted gate voltage (VG) to the field effect transistor 120. It can be output as .

According to embodiments, the control circuit 300 may increase the gate voltage (VG) as the size of the sound (i.e., the size of the output current) input to the acoustic sensor 100 is smaller. For example, if the sound level is less than the first reference level, the gate voltage (VG) may be increased by the first ratio. Conversely, depending on embodiments, the control circuit 300 may decrease the gate voltage VG as the size of the sound input to the acoustic sensor 100 (i.e., the size of the output current) increases. For example, when the size of the sound exceeds the second reference size that is larger than the first reference size, the gate voltage (VG) may be reduced by a second ratio.

By adjusting the size of the gate voltage (VG), the sensitivity or signal-to-noise ratio of the acoustic sensor 100 can be improved.

In addition, since the acoustic sensor 100 according to embodiments of the present invention uses the field effect transistor 120 as an acoustic element, various control functions can be easily implemented by adjusting the voltages applied to the field effect transistor 120. It works.

Figure 6 conceptually shows a plan view of an acoustic sensor according to embodiments of the present invention. Referring to FIG. 6, the acoustic sensor 100 may include a plurality of field effect transistors 120A, 120B, 120C, and 120D.

A plurality of field effect transistors 120A, 120B, 120C, and 120D may be disposed on the base substrate 110. Depending on the embodiment, the plurality of field effect transistors 120A, 120B, 120C, and 120D may be arranged to face each other with the groove 111 as the center. For example, a plurality of field effect transistors (120A, 120B, 120C, and 120D) may be arranged to be symmetrical to each other about the groove portion 111.

According to embodiments, the plurality of field effect transistors (120A, 120B, 120C, and 120D) include a first field effect transistor (120A) and a second field effect transistor (120B).

The first field effect transistor 120A and the second field effect transistor 120B are arranged to face each other. At this time, the drain region of the first field effect transistor 120A and the drain region of the second field effect transistor 120B may be arranged to face each other with the groove 111 as the center.

Although the embodiments have been described with limited examples and drawings as described above, various modifications and variations can be made by those skilled in the art from the above description. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

10: Multi-group teaching system
10-1~10-N: Voice processing device
200-1~200-N: Image processing device
300: Video synthesis device
CIMG: Integrated output video

Claims (10)

An acoustic sensor configured to respond to a sound wave and output an output current corresponding to the sound wave; a control circuit configured to process the output current of the acoustic sensor to generate an audio signal in electrical form; and an output interface configured to output the voice signal to the outside,
The acoustic sensor is,
It includes a field effect transistor that outputs the output current that changes depending on the sound pressure of the sound wave, and a base substrate having a groove formed to allow the sound wave to flow into it,
The field effect transistor is,
A plurality of field effect transistors are disposed on the base substrate so as to at least partially overlap the groove portion, and the plurality of field effect transistors are arranged symmetrically with respect to the groove portion of the base substrate.
microphone. delete The method of claim 1, wherein the field effect transistor is:
a semiconductor layer formed on the base substrate and including a drain region and a source region;
Comprising a gate electrode, a source electrode connected to the source region, and a drain electrode connected to the drain region,
microphone. According to paragraph 3,
The semiconductor layer includes a channel region formed between the drain region and the source region,
The mobility of electrons included in the channel region is configured to change depending on the sound pressure,
microphone. According to paragraph 4,
The correlation between the electron mobility and the negative pressure is a positive correlation,
microphone. The method of claim 4, wherein the field effect transistor is:
disposed on the base substrate such that the channel region of the field effect transistor at least partially overlaps the groove portion of the base substrate,
microphone. The method of claim 3, wherein the field effect transistor is:
Further comprising a dielectric layer disposed on the gate electrode and the semiconductor layer,
microphone. The method of claim 1, wherein the microphone is:
further comprising a memory configured to store conversion information associated with a correlation between the magnitude of the output current and the sound pressure,
The control circuit converts the output current using the conversion information to generate the audio signal corresponding to the sound pressure,
microphone. delete According to paragraph 1,
The plurality of field effect transistors include a first field effect transistor and a second field effect transistor facing each other,
The drain region of the first field effect transistor and the drain region of the second field effect transistor are arranged to face each other around the groove,
microphone.

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