DESC:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to semiconductor devices that reproduce sound through audio playback.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Use of a PN-junction or a Schottky diode to actuate MEMS structures is not new. The technique of actuation relies on natural formation of a depletion region at a PN- junction/Schottky junction. When changing electric field is applied across this region by varying actuation voltage, it leads to a variation in the internal stresses and strains in the coupled mechanical structure, such as a cantilever beam. This results in vibration of the beam in response to the applied actuation voltage signal.
[0004] There are four widely used types of audio speakers in consumer electronic market ? electrodynamic, electrostatic, planar magnetic, and piezoelectric.
[0005] The conventional electrodynamic speakers have a voice coil attached to a diaphragm and placed in magnetic field. The electric audio signal flowing through the coil interacts with the magnetic field resulting in mechanical vibrations of the attached diaphragm producing sound.
[0006] An electrostatic loudspeaker (ESL) makes use of alternating electric field between two charged plates. A metal-coated polymer diaphragm is suspended between the two anchored plates. It vibrates in response to the alternating forces of attraction between the two plates, consequently producing sound pressure waves. ESL is huge in size and typically requires very high actuation voltage. As a result, ESL tends to be costlier than the conventional electrodynamic loudspeakers.
[0007] The planar magnetic speaker is similar to electrostatic speaker in construction. It has a diaphragm with coil going all around it which carries the electric signal. This assembly is placed between two magnets. The electromagnetic force generated moves the diaphragm to and forth generating sound. These speakers are also bulky and costly.
[0008] The piezoelectric speakers work on reverse piezoelectric effect. These speakers need a piezoelectric material in addition to substrate and electrode material. This type is usually found at MEMS scale.
[0009] There is, therefore, a requirement in the art for a means to produce or generate sound vibrations, preferably a device for producing sound vibrations that is compact, portable, and economical.

OBJECTS OF THE PRESENT DISCLOSURE
[0010] An object of the present disclosure relates in general, to semiconductor devices that reproduce sound through audio playback.
[0011] Another object of the present disclosure is to provide a device that makes the design and fabrication of electrostatic speakers incredibly simple and relatively inexpensive.
[0012] Another object of the present disclosure is to provide a device that builds an ultra-thin electrostatic speaker.
[0013] Another object of the present disclosure is to provide a device that makes the electrostatic speakers compact in size and reduces the required actuation voltage.
[0014] Another object of the present disclosure is to provide a device that reduces number of speaker parts required when compared with an electrodynamic loudspeaker, or a push-pull type electrostatic speaker.
[0015] Another object of the present disclosure is to provide a device that reduces the material processing time and cost.
[0016] Yet another object of the present disclosure provides any speaker structure made of just semiconductor flat pieces utilizing potential gradient through the material or the structure is useful to generate sound.

SUMMARY
[0017] The present disclosure relates in general, to semiconductor devices that reproduce sound through audio playback.
[0018] In an aspect, the present disclosure provides a device for sound generation, the device includes one or more plates comprising a top plate and a bottom plate of a thickness anchored to a support structure, wherein the top plate and the bottom plate are stacked in such a matter that the top plate is clamped over the bottom plate to establish a firm contact between the top plate and support structure of the bottom plate and a source adapted to supply a voltage signal across the top plate and the bottom plate, wherein, upon application of the voltage signal, an alternating potential gradient is created across the stacked plates to generate a time varying electrostatic force in the stack, and wherein the top plate is deflected due to the electrostatic force causing vibrations along a directional path at a frequency effective to produce an audible sound.
[0019] According to an embodiment, the one or more plates are made of semiconductor material selected from a group comprising silicon (Si), germanium (Ge) and any combination thereof.
[0020] According to an embodiment, the one or more plates comprise any or a combination of two flat pieces or a single piece of silicon in appropriate configurations to construct speaker structure, wherein the potential gradient across its thickness produces audible sound.
[0021] According to an embodiment, the stack is formed with any or a combination of a P-type piece placed over an N-type piece, an N-type piece placed over a P-type piece, a P-type piece placed over another P-type piece and a N-type piece placed over another N-type piece.
[0022] According to an embodiment, the one or more plates are of same shape, geometry and dissimilarly shaped, wherein each plates have different geometries, shapes, tiled surfaces and curvatures.
[0023] According to an embodiment, the one or more plates are similarly doped with same doping concentrations, or doped differently with different concentrations.
[0024] According to an embodiment, the one or more plates of silicon or any other semiconducting material stacked on top of each other without need of any dielectric or insulating layer between them.
[0025] According to an embodiment, the one or more plates provided with appropriate structural boundary conditions of any or a combination of one point fixed, four corners fixed, fixed edge, two edges fixed, three edges fixed and four edges fixed.
[0026] According to an embodiment, the vibrations generated are useful for any vibration-based applications such as resonators, particle separators, miniature feeder bowls and any combination thereof, wherein any acoustic transducer including ultrasonic transducers, made of the single silicon or any other semiconducting piece with potential gradient across its thickness are useful for applications comprising home speakers, computer speakers, cell phone speakers, headphones, earphones, hearing aid and any combination thereof.
[0027] According to an embodiment, the geometry, boundary conditions, material resistivity and actuation voltages are varied to provide sounds of different amplitude and frequency.
[0028] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0029] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0030] FIG. 1A and 1B illustrate exemplary representations of a single semiconductor and a stack of two semiconductor pieces respectively with voltage applied across it, in an accordance with an embodiment of the present disclosure.
[0031] FIGs. 2A and 2B illustrate exemplary representations of two pieces of semiconductor wafers stacked together, in accordance with an embodiment of the present disclosure.
[0032] FIG. 3 illustrates an exemplary representation of effect of higher dopant concentration or / and higher actuation voltage in the semiconductor wafers, in accordance with an embodiment of the present disclosure.
[0033] FIG. 4 illustrates an exemplary representation of a semiconductor device for reproducing sound through audio playback wherein the semiconductor device is supplied with audio signals as a varying actuating voltage, in accordance with an embodiment of the present disclosure.
[0034] FIG. 5 illustrates schematic representations of deflection of the top plate of the semiconductor device, in accordance with an embodiment of the present disclosure.
[0035] FIG. 6 illustrates schematic representations of the sound waves generated by the vibrations induced in the semiconductor device, in accordance with an embodiment of the present disclosure.
[0036] FIG. 7A illustrates exemplary views of the device stacks, in accordance with an embodiment of the present disclosure.
[0037] FIG 7B illustrates exemplary boundary conditions for the device stacks, in accordance with an embodiment of the present disclosure.
[0038] FIG. 8 illustrates a schematic representation of the proposed device and simulated deflection of the device for different resistivities and actuation voltages of the semiconductor, in accordance with an embodiment of the present disclosure.
[0039] FIG. 9 illustrates a schematic representation of the proposed device and variation in simulated sound pressure levels (SPL) of the device for different device geometries, in accordance with an embodiment of the present disclosure.
[0040] FIG. 10A illustrates an exemplary representation of geometry used in simulation model of the proposed device, in accordance with an embodiment of the present disclosure.
[0041] FIG. 10B illustrates an exemplary plot showing variation of SPL with frequency of applied voltage simulated for different sizes of silicon pieces, in accordance with an embodiment of the present disclosure.
[0042] FIG. 11 illustrates exemplary plots of variation in sound pressure levels (SPL) with different materials, in accordance with an embodiment of the present disclosure. It gives comparison between stacks of doped silicon with a dielectric (glass) – metal (Au) combination.
[0043] FIG. 12 illustrates exemplary plots of variation of SPL with different boundary conditions for the silicon plates, in accordance with an embodiment of the present disclosure.
[0044] FIGs. 13A and 13B illustrate exemplary plots of measurement of SPL obtained at a distance from the vibrating silicon piece, in accordance with an embodiment of the present disclosure.
[0045] FIG. 14 illustrates an exemplary plot of variation of SPL with variation in actuation voltages, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0046] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0047] The present disclosure relates, in general, to devices that produce sound. In particular, the present disclosure relates to a device that produces sound using only a single piece of a semiconducting material or a stack of pieces of such material.
[0048] FIGs. 1A – 1B and 2A – 2B illustrate exemplary representations of a single piece or two pieces of semiconductor wafers stacked together, in accordance with an embodiment of the present disclosure.
[0049] When a stack 100 is created with two pieces of a semiconductor (102, 104) loosely placed on one another, and opposing voltages are supplied or a voltage gradient is created across the stacked semiconductor pieces (102, 104), charge separate states are formed, which may be approximated to an equivalent electric circuit including capacitors and resistors. When an AC voltage is applied to said circuit, an alternating potential gradient is created across the equivalent capacitor, thereby generating an alternating electric field. This produces an alternating electrostatic force across the two pieces of the capacitor. With variation in applied AC voltage, variation in capacitance and consequent variation in electrostatic force produced can be observed.
[0050] In an exemplary embodiment, the semiconductor used may be any such as Silicon (Si), Germanium (Ge), etc., with P-type and / or N-type dopants, and any combination of semiconductors.
[0051] Referring to FIG. 2A, in an exemplary embodiment, an N-type semiconductor piece 102 is placed over another N-type semiconductor piece 104. On applying an AC voltage, in a first positive half of the AC voltage cycle, the N-type piece 102 is positively biased, while the supporting N-type piece 104 is negatively biased. In case of N-type silicon, the electrons are majority carriers. The majority charge carriers are pushed or pulled towards the surface depending on the charge polarity. The depletion gap is at maximum in the first positive half of the AC voltage cycle. Electrons are pulled towards positively charged silicon surface and pushed away from the negatively charged silicon surface, giving rise to a depletion region.
[0052] Referring to FIG. 2B, in a second negative half of the AC voltage cycle, polarity is reversed, and the majority carriers are pushed towards respective inner edges of two semiconductor pieces (102, 104) of the stack 100, thereby reducing the depletion gap to a minimum value.
[0053] The capacitance is inversely proportional to the gap between the majority charge carriers. The electrostatic force is directly proportional to this capacitance. Hence, on application of the AC voltage, a time varying electrostatic force is generated in the stack 100.
[0054] In another exemplary embodiment, a stack may be formed with a P-type piece placed over another P-type piece. Here, the holes form the majority charge carriers, and in the first half cycle, the charges are pushed towards inside edge of the wafer, resulting in a minimum depletion gap.
[0055] In another exemplary embodiment, a stack may be formed with a combination of a P-type piece placed over an N-type piece or an N-type piece kept over a P-type piece. A similar phenomenon as described earlier may take place in these cases.
[0056] FIG. 3 illustrates an exemplary representation of effect of higher dopant concentration or / and higher actuation voltage in the semiconductor wafers, in accordance with an embodiment of the present disclosure. Here, a stack 300 is illustrated where excessive doping of the N-type piece 302 and 304 has occurred such that actuation voltage is higher than breakdown voltage for the semiconductor pieces (302, 304). Here, the capacitor gap reduces to a point which can lead to easier breakdown, forming a short circuit, which, in turn, renders the stack 300 inoperable.
[0057] FIG. 4 illustrates an exemplary representation of a semiconductor device 400 for reproducing sound through audio playback, in accordance with an embodiment of the present disclosure. The concept of stacked pieces of a semiconductor producing an electrostatic field when supplied with an alternating voltage is adopted to provide a device 400 to produce mechanical vibrations.
[0058] Referring to FIG. 4, a cross-section of the device 400 is illustrated where a top piece of semiconductor 402 is placed over a supporting piece of semiconductor 404. In an exemplary embodiment, the pieces of semiconductor (402, 404) may be plates. In another exemplary embodiment, the pieces of semiconductor (402, 404) may be of same shape, geometry and dissimilarly shaped where each piece may have different geometries, shapes, curvatures etc.
[0059] In another exemplary embodiment, the pieces (402, 404) may be similarly doped (both N-type, or both P-type) with same doping concentrations, or the pieces (402, 404) may be doped differently with different concentrations.
[0060] In another exemplary embodiment, the top plate 402 and the supporting plate 404 may be made of the same semiconductor material or may be of different semiconductor materials.
[0061] In an embodiment, as illustrated in FIG. 4, the two plates (402, 404) may be stacked such that the top plate 402 is suspended over supporting pieces (406-1, 406-2) of the bottom plate 404. Upon application of an alternating voltage, a time varying electrostatic force is produced, the top suspended plate 402 is allowed to deflect (such as bend or flex) due to the electrostatic field, thereby generating a time varying vibration. It may be appreciated that the frequency of vibration follows the frequency of the applied AC voltage.
[0062] In an exemplary embodiment, the top plate 402 may be clamped over the bottom plate 404 to establish a firm contact between the top plate 402 and the supporting pieces (406-1, 406-2) of the bottom plate 404.
[0063] FIG. 5 illustrates schematic representations of deflection of the top plate of the proposed device, in accordance with an embodiment of the present disclosure. The application of the time varying voltage generates an equivalent electrostatic force, causing the top plate 402 to accordingly deflect to generate vibrations.
[0064] Referring to FIG. 5, the schematic 500 represents a side view of the top plate 402 suspended at two points (502-1, 502-2), which represent the two supporting pieces (406-1, 406-2) of the bottom plate 404. A non-uniform electrostatic force (fe(x)) acts on it, where the force varies across X-direction and acts in a Y-direction. In the free body diagram (FBD) illustrated, Fe is the equivalent electrostatic force; RAx, RAy, RBx and RBy are the reaction forces; and MA and MB are the bending moments acting on the top plate 402. A shear force diagram (SFD); a bending moment diagram (BMD); and a deflection profile (v(x)) for the device 400 are also illustrated.
[0065] Here, RAx represents reaction force on the supporting plate 404 at end 502-1 and RBx represents reaction force on the supporting plate 404 at end 502-2.
[0066] FIG. 6 illustrates schematic representations of vibrations produced by the device, in accordance with an embodiment of the present disclosure. The application of the time varying voltage generates an equivalent electrostatic force, causing the top plate 402 to accordingly deflect to generate vibrations. In an exemplary embodiment, when frequency of vibration is in the audible range, the configured device 400 produces audible sound.
[0067] As described earlier, when opposing voltages are supplied or a voltage gradient is created across the stacked semiconductor pieces (402, 404), charge separate states are formed, which may be approximated to an equivalent electric circuit including capacitors and resistors. When an AC voltage is applied to said circuit, an alternating potential gradient is created across the equivalent capacitor, thereby generating an alternating electric field. This produces an alternating electrostatic force across the two pieces of the capacitor. With variation in applied AC voltage, variation in capacitance and consequent variation in electrostatic force produced can be observed.
[0068] Time varying electrostatic force, which follows the time varying AC voltage applied results in vibration of the top plate 402 over the bottom plate 404, thereby generating vibrations. When the applied AC voltage is such that vibrations generated by the top plate 402 is in the audible range of frequencies, sound is produced.
[0069] In another embodiment, by varying amplitude and frequency of the alternating voltage applied, the vibration intensity and frequency of the top plate 402 of the device 400 can be controlled, wherein the amplitude of the applied AC voltage, at a given frequency, can control the vibration intensity.
[0070] In an exemplary implementation, the proposed device 400 may be used in design of speakers.
[0071] In another embodiment, the phenomenon of generation of acoustic output can also be observed in a single piece of semiconductor which is supplied with a voltage gradient. Here, the single piece behaves as both capacitor and resistor and produces an electrostatic force that results in vibration of the single piece, which generates sound.
[0072] The following section discloses exemplary embodiments of the proposed device to illustrate working of the device. The parameters disclosed are for the purposes of illustration only and may not be construed as a limitation to the operation of the device.
[0073] It may be appreciated that devices may be designed with differing parameters to suit different operational requirements, all of which are within the scope of the present disclosure.
[0074] Table-1 below provides exemplary parameter of the proposed device, using Silicon as the semiconducting material,
Parameter Description
Dopant type P and N type
P type with P type (Two-piece configuration)
N type with N type (Two-piece configuration)
P type with N type (Two-piece configuration)
Single wafer configuration: Both P and N type
Resistivity < 0.05 ohm-cm, 1-10 ohm-cm, and 10-100 ohm-cm
Circular pieces 2” diameter, 250-300 µm thick
3” diameter, 400 µm thick
4” diameter, 500 µm thick
Square and rectangular pieces Thickness 450 µm
Area:
1 x 1 cm2
1 x 3 cm2
2 x 2 cm2
2 x 3 cm2
3 x 3 cm2
4 x 4 cm2
5 x 5 cm2
8 x 8 cm2
Boundary conditions One point fixed
Four corners fixed
Fixed edge
Two edges fixed
Three edges fixed
Four edges fixed
Actuation voltages Different combinations of AC and DC voltages max tested up to 100 Vdc – 100 Vac
Metal Contact Point metal contact (probe tip) on bare silicon without any metal layer, small metal patch (2 x 2 mm2), blanket layer of metal

[0075] FIG. 7A illustrates exemplary views of the device stacks, in accordance with an embodiment of the present disclosure. Referring to FIG. 7A, one or more plates (402, 404) (also referred to as plates, herein) including the top plate 402 and the bottom plate 404 of a thickness anchored to the support structure/supporting pieces (406-1, 406-2), where the top plate and the bottom plate are stacked in such a manner that the top plate 402 is clamped over the bottom plate 404 to establish a firm contact between the top plate 404 and support structures (406-1, 406-2) of the bottom plate 404. The plates are made of semiconductor material selected from a group comprising silicon (Si), germanium (Ge) and any combination thereof. The plates can include any or a combination of two flat pieces or a single piece of silicon in appropriate configurations to construct audio speakers.
[0076] A source adapted to apply the voltage signal across the top plate 402 and the bottom plate 404, wherein, upon application of the voltage signal, an alternating potential gradient is created across the stacked plates which generates a time varying electrostatic force in the stack, and wherein the top plate is deflected due to the electrostatic force causing vibrations along a directional path at a frequency effective to produce an audible sound.
[0077] FIG 7B illustrates exemplary boundary conditions for the device stacks, in accordance with an embodiment of the present disclosure. The plates provided with appropriate structural boundary conditions of any or a combination of one point fixed, four corners fixed, fixed edge, two edges fixed, three edges fixed and four edges fixed. The plates of silicon or any other semiconducting material stacked on top of each other without need of any dielectric or insulating layer between them. The vibrations generated are useful for any vibration-based applications such as resonators, particle separators, miniature feeder bowls and any combination thereof.
[0078] FIG. 8 illustrates a schematic representation of the proposed device and simulated deflection of the device for different resistivities and actuation voltages of the semiconductor, in accordance with an embodiment of the present disclosure. The deflection values are normalized (with reference to FIG. 10) with respect to the maximum deflection value obtained for a given configuration (with reference to FIG. 7B). It may be observed that deflection varies inversely with resistivity of the silicon piece and directly with actuation voltage. Both cases hold true as long as we are away from breakdown voltage.
[0079] FIG. 9 illustrates a schematic representation of the proposed device and variation in simulated sound pressure levels (SPL) of the device for different device geometries, in accordance with an embodiment of the present disclosure. In FIG. 9, the device configuration includes a top plate with a square configuration of side S and thickness h supported on a bottom plate of thickness h. Voltage is applied across the thickness of the stack and the electrostatic field produced is over the overlapping area of the top and bottom plates. Variation in SPL is illustrated for varying values of S, keeping h constant at 450 µm and actuation voltage constant at (50 VDC – 50 VAC), and fixed corners as boundary condition. It may be observed that SPL varies directly with increase in value of S.
[0080] FIG. 10A illustrates an exemplary representation of geometry used in simulation model of the proposed device, in accordance with an embodiment of the present disclosure. Curved surfaces of the air hemisphere are set to have matched boundary condition to model the free air around the silicon piece. The top electrical contact to the silicon piece is a point contact mimicking the probe connection. Since this piece is resting on a metal chuck or another silicon piece the bottom electrical contact is a boundary (surface) contact in the model.
[0081] FIG. 10B illustrates an exemplary plot showing variation of SPL with frequency of applied voltage for different sizes of silicon pieces, in accordance with an embodiment of the present disclosure. The actuation voltage is (100 VDC – 100 VAC). Multiple parameters affect the SPL, such as, higher area produces higher SPL provided that the electrical actuation signal is kept constant. However, it may be observed that a 5 cm x 5 cm plate produces lower SPL compared to that produced by a 3 cm x 3 cm plate. This may be due to the fact that, even when the sound radiating area increases, the actuation voltage is constant in both the cases. The top electrical connection is just a point connection, and it does not scale up with the increasing area of the silicon plate.
[0082] This study is carried out for silicon assemblies with different doping levels and with different actuation voltages. For comparison, a glass diaphragm (an insulator with lower dielectric constant and higher breakdown voltage compared to silicon) with metal coating is used.
[0083] FIG. 11 illustrates exemplary plots of variation in sound pressure levels (SPL) with different materials, in accordance with an embodiment of the present disclosure. It gives comparison between stacks of doped silicon (lightly doped N-type silicon wafer with a resistivity value as 10 – 100 ohm-cm; and Si – Au: Cr/Au 30/90 nm blanket layer sputtered on silicon piece.) with a dielectric (glass) – metal (Au) combination. The geometry and structural boundary conditions retained the same in all the cases. Voltage used is as mentioned in the figures, with a sine sweep signal of frequency ranging from 1 kHz to 20 kHz.
[0084] In general, it may be observed that, for a given size of the plate used for sound generation and voltage signal applied, silicon is superior to glass. Glass is an insulating material whereas silicon is semiconducting. Further, in case of glass (or any other dielectric material), there is additional need of having a thin metal layer for electrical connection. However, in the case of silicon, direct electrical connections can be provided. By appropriately doping the semiconductor, performance of the semiconductor can also be enhanced.
[0085] In an instance, with lower voltages, higher SPL may be achieved by reducing the resistivity of silicon through doping. Reduction in resistivity leads to reduction in the internal capacitor gap which subsequently increases the electrostatic force. This further causes the plates to vibrate with higher amplitudes, producing higher SPL.
[0086] FIG. 12 illustrates exemplary plots of variation of SPL with different boundary conditions for the silicon plates, in accordance with an embodiment of the present disclosure.
[0087] FIGs. 13A and 13B illustrate exemplary plot of measurement of SPL obtained at a distance from the vibrating silicon piece, in accordance with an embodiment of the present disclosure. The measurements are carried out at a distance of 1 cm from the silicon piece.
[0088] Referring to FIG. 13A, measurement is carried out for N-Type silicon with resistivity <0.05 ohm-cm. The thickness of the piece is 400 µm (which is equal to the wafer thickness).
[0089] Referring to FIG. 13B, measurement is carried out for N-Type silicon with resistivity 10-100 ohm-cm. The actuation voltage is 100 VDC ? 100 VAC. The thickness of the piece is 400 µm (which is equal to the wafer thickness).
[0090] FIG. 14 illustrates an exemplary plot of variation of SPL with variation in actuation voltages, in accordance with an embodiment of the present disclosure. A wide range of voltages is used with a bias of 50V. it may be observed that with increase in actuation voltage, SPL increases.
[0091] Thus, the present disclosure provides a sound/acoustic signal producing device, which includes a single piece of a semiconductor or a stack of semiconductors. An alternating voltage is applied across the semiconductor thickness, which results in variation in capacitance of the stack and subsequent variation in electrostatic field generated. The proposed device has the top plate of the device suspended between two supports of the bottom plate, which allows the top plate to vibrate when the electrostatic force is generated. When the vibration frequency is in the audible range, the device produced audible sound. The geometry, boundary conditions, material resistivity and actuation voltages may be varied to provide sounds of different amplitude and frequency. Any semiconductor such as silicon, germanium, etc. may be used, along with any combinations of semiconductor material.
[0092] The embodiments of the present disclosure described above provide several advantages. The one or more of the embodiments provide the device 400 that makes the design and fabrication of electrostatic speakers incredibly simple and relatively inexpensive. The device 400 builds an ultra-thin electrostatic speaker at low cost. The present disclosure provides the device 400 that reduces the material processing time and cost. The device makes the electrostatic speakers compact in size and reduces the required actuation voltage. The device reduces number of speaker parts required when compared with an electrodynamic loudspeaker, or a push-pull type electrostatic speaker.
[0093] The present disclosure provides any speaker structure made of just semiconductor flat pieces utilizing potential gradient through the material or the structure is useful to generate sound. Any acoustic transducer including ultrasonic transducers, made on the principle described here are useful for any application including but not limited to home speakers, computer speakers, cell phone speakers, headphones, earphones, hearing aid and the likes. Any device using the vibrations generated with this principle is useful for any vibration-based applications such as resonators by altering geometry as per the resonant frequency requirements, particle separators, miniature feeder bowls and the likes.
[0094] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0095] The present disclosure provides a device that makes the design and fabrication of electrostatic speakers incredibly simple and relatively inexpensive.
[0096] The present disclosure provides a device that builds an ultra-thin electrostatic speaker at low cost.
[0097] The present disclosure provides a device that makes the electrostatic speakers compact in size and reduces the required actuation voltage.
[0098] The present disclosure provides a device that reduces number of speaker parts required when compared with an electrodynamic loudspeaker, or a push-pull type electrostatic speaker.
[0099] The present disclosure provides a device that reduces the material processing time and cost.
[0100] The present disclosure provides any speaker structure made of just semiconductor flat pieces utilizing potential gradient through the material or the structure is useful to generate sound.

,CLAIMS:1. A device (400) for sound generation, said device comprising:
one or more plates (402, 404) comprising a top plate (402) and a bottom plate (404) of a thickness anchored to a support structure (406-1, 406-2), wherein said top plate (402) and said bottom plate (404) are stacked in such a manner that the top plate is clamped over the bottom plate to establish a firm contact between the top plate and the support structure of the bottom plate; and
a source adapted to supply a voltage signal across the top plate (402) and the bottom plate (404), wherein, upon application of the voltage signal, an alternating potential gradient is created across the stacked plates to generate a time-varying electrostatic force in the stack, and wherein the top plate (402) is deflected due to the electrostatic force causing vibrations along a directional path at a frequency effective to produce an audible sound.
2. The device as claimed in claim 1, wherein the one or more plates (402, 404) are made of semiconductor material selected from a group comprising silicon (Si), germanium (Ge) and any combination thereof.
3. The device as claimed in claim 1, wherein the one or more plates (402, 404) is any or a combination of two flat pieces or a single piece of silicon in appropriate configurations to construct speaker structure, wherein the potential gradient across its thickness produces audible sound.
4. The device as claimed in claim 1, wherein the stack is formed with any or a combination of a P-type piece placed over an N-type piece, an N-type piece placed over a P-type piece, a P-type piece placed over another P-type piece and a N-type piece placed over another N-type piece.
5. The device as claimed in claim 1, wherein the one or more plates (402, 404) are of same shape, geometry and dissimilarly shaped, wherein each plates have different geometries, shapes, tiled surfaces and curvatures.
6. The device as claimed in claim 1, wherein the one or more plates (402, 404) are similarly doped with same doping concentrations, or doped differently with different concentrations.
7. The device as claimed in claim 1, wherein the one or more plates (402, 404) of silicon or any other semiconducting material stacked on top of each other without need of any separate dielectric or insulating layer between them.
8. The device as claimed in claim 1, wherein the one or more plates (402, 404) provided with appropriate structural boundary conditions of any or a combination of one point fixed, four corners fixed, fixed edge, two edges fixed, three edges fixed and four edges fixed.
9. The device as claimed in claim 1, wherein the vibrations generated is useful for resonators, particle separators, miniature feeder bowls and any combination thereof, wherein any acoustic transducer including ultrasonic transducers, made of the single silicon or any other semiconducting piece with potential gradient across its thickness are useful for home speakers, computer speakers, cell phone speakers, headphones, earphones, hearing aid and any combination thereof.
10. The device as claimed in claim 1, wherein the geometry, boundary conditions, material resistivity and actuation voltages are varied to provide sounds of different amplitude and frequency.