US3480740A - Sound transducer - Google Patents

Sound transducer Download PDF

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Publication number
US3480740A
US3480740A US396859A US3480740DA US3480740A US 3480740 A US3480740 A US 3480740A US 396859 A US396859 A US 396859A US 3480740D A US3480740D A US 3480740DA US 3480740 A US3480740 A US 3480740A
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Prior art keywords
layer
stylus
emitter
transducer
semiconductive
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Expired - Lifetime
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US396859A
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English (en)
Inventor
Tadashi Matsumoto
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Sony Corp
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Sony Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H04R23/006—Transducers other than those covered by groups H04R9/00 - H04R21/00 using solid state devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor

Definitions

  • Still another object of the instant invention is to provide a semiconductor transducer having high sensitivity.
  • Still another object of the present invention is to provide an electromechanical transducer which is extremely compact in size and light in Weight.
  • Yet another object of the instant invention is to provide an electromechanical transducer which employs a planar-type diode or transistor.
  • FIGURE l-A is a schematic and diagrammatic view of an electromechanical transducer employing a usual planar type diode
  • FIGURE 1-B is a curve illustrating the relationship of current to voltage of the transducer shown in FIGURE l-A;
  • FIGURE 2-A is a schematic and diagrammatic view illustrating an electromechanical transducer employing a usual planar-type transistor
  • FIGURE 2-B is a curve illustrating the relationship between collector current and collector voltage of the transducer shown in FIGURE 2-A;
  • FIGURE 3 is a graph illustrating the novel realizations of the present invention.
  • FIGURE 4 is a diagrammatic sectional side view of an electromechanical transducer according to the present invention.
  • FIGURE 5 is a top view of the transducer illustrated in FIGURE 4.
  • FIGURE 6 is a sectional view of a microphone in accordance with the present invention.
  • FIGURE 1A there is illustrated a planar-type diode of the prior art with an n-type semiconductive layer 2 formed in a p-type semiconductive wafer 1.
  • a stylus 3 is deposited on the surface of the n-type semiconductive layer 2 of the diode for applying point contact pressure thereto.
  • a p-n junction 4 of the diode is defined between the p-type semiconductive wafer 1 and the n-type semiconductive layer 2.
  • a solid line curve designated with the reference numeral 5 of FIGURE l-B illustrates the voltage versus current characteristic of the diode of FIGURE 1-A.
  • the voltage versus current characteristic of the diode varies from the curve 5 to a dotted line curve designated with the reference numeral 6. That is, the current increases with an increase in the pressure P at a particular operating point.
  • Such action is considered to be caused by the p-n junction 4 becoming more ohmic or non-rectifying at that portion where the pressure P is applied.
  • the same eifect can be expected in a planar-type transistor as illustrated by the prior art structure shown in FIGURE 2-A.
  • the planar-type transistor includes a collector 7, a base 8, and an emitter 9.
  • the base is illustrated as being an n-type semiconductive layer
  • the collector 7 is illustrated as a p-type semiconductive wafer
  • the emitter 9 is illustrated as a p-type semiconductive layer.
  • the base 8 is formed on the collector 7 and the emitter 9 is formed on the base 8.
  • a p-n junction 4' is defined between the base 8 and the emitter 9 and the stylus 3 is disposed on the emitter for applying a pressure P to the p-n junction.
  • the collector voltage V versus the collector current I characteristic varies as indicated by a curve 5 in FIGURE 2-B.
  • the collector voltage versus collector current characteristic is altered as indicated by the dotted line curve designated with the reference numeral 6'.
  • This condition is considered to be caused by the fact that some portion of the p-n junction 4' becomes an ohmic junction and the current amplification degree a of the transistor decreases.
  • the devices illustrated may be employed as electromechanical transducer elements such, for example, as microphones.
  • FIGURE 3 illustrates the relationship between changes in collector current AI and the thickness of the emitter 9 designated a.
  • the curve illustrated and the values applied thereto resulted from experiments using a transistor of emitter configuration such as shown in FIGURE 2-A under the conditions that an initial current of 9.6 milliamperes and a constant current of 0.25 milliampere flowed respectively to the collector 7 and base 8 when a weight of 1 gram was applied to the surface of the emitter 9 by the stylus 3.
  • the collector current variation AI is less than 0.01 milliamperes when the thickness a of the emitter 9 is more than 2 microns.
  • the conversion gain can be appreciably increased by making the thickness a of the emitter 9 as thin as possible, such as, for example, 0.5 micron or less.
  • an electrode or lead wire is required in the emitter layer and when the thickness at of the emitter is small, the p-n junction between the emitter and base is easily destroyed by thermo-compression bonding for attaching a lead wire or electrode to the emitter.
  • Such conditions cause great difficulty when it is desired to obtain a semiconductive transducer element of high sensitivity.
  • the present invention is intended to remove such difficulty as experienced in the prior art when it is desired to bond the lead wire or electrode by thermo-compression to the emitter electrode.
  • the present invention is intended to remove such difficulties experienced in the prior art to provide a highly satisfactory electromechanical transducer.
  • the normal thickness of semiconductive layer is provided at a peripheral or annular portion of the emitter.
  • a central portion of the emitter semiconductive layer within the peripheral portion, however, is made substantially thinner and the stylus 3 is contacted thereto for applying pressures to the device.
  • FIGURE 4 The preferred embodiment of the present invention is illustrated in FIGURE 4, wherein the collector 7 is as that shown in FIGURE 2A.
  • the structure of the emitter 9 is such that the thickness of a peripheral or annular portion 9a is made relatively large, for example, 1 to microns, sufficient for attaching an electrode 19 or a lead wire thereto and a central portion 9b being contiguous to the peripheral portion 9a is formed as thin ts possible, for example, 0.1 micron.
  • the stylus 3 is contacted with the surface of the central portion 91) for applying pressures thereto in response to mechanical vibrations.
  • a preferred exemplification of a method for forming such novel configurations is as follows. Firstly, an oxide coating is formed on the surface of the base layer 8 and a thickness of the oxide coating corresponding to the desired thickness of the peripheral portion 9a is removed and a material such as, for example, aluminum, is diffused into the thus exposed limited surface area forming a relatively thick p-type layer. Then, a thickness of the oxide coating corresponding to the desired thickness of the central portion 915 is removed and a shallow p-type layer is formed therein.
  • the emitter electrode 19 can be attached to the relatively thick peripheral portion 9a, and there is no possibility that the p-n junction will be destroyed by thermo-compression bonding when attaching the electrode or lead wire thereto.
  • the relatively thin p-type layer 9b for the emitter is of sufiicient area to allow the stylus 3 to be readily contacted therewith. Although the stylus may shift from its initial position due to shock and the like, it is unlikely that it will become disengaged from the central portion 9a due to the relatively large area that can be provided.
  • FIGURE 5 is a top view of the transducer shown in FIGURE 4 and illustrates the emitter electrode 19 and the base electrode 20 as being annular or ring-shaped.
  • FIGURE. 6 illustrates one preferred embodiment of a microphone employing the novel transducer of the present invention.
  • the housing of the microphone is defined by a base 10, a frame 11 supported on the base 10, and a diaphragm 12 supported on the frame.
  • a pressure transmitting stylus 13 is fixedly mounted at one end thereof to the center of the diaphragm 12.
  • the pointed end of the stylus 13 engages a semiconductive transducer 14 such as that illustrated in FIGURE 4.
  • a header member 15 disposed on the base 10 supports the semiconductive element 14 and an upright support 16 thereon.
  • a rod 21, which may have resilient characteristics, is secured to a mid-point of the stylus 13 and is supported between the upright support 16 and a screw 17.
  • Adjustment of the initial pressure to be applied to the stylus 13 is accomplished by positioning of the screw 17 which is threadedly engaged with the rod 21. It can be appreciated that rotation of the screw 17 in either one of two directions will pre-set the initial pressure applied to the stylus 13 through the rod 21.
  • a plurality of lead pins 18 extend through the base 10 to the electrodes or terminals of the semiconductive element 14.
  • vibrations applied to the diaphragm 12 transmit pressures to the p-n junction of the semiconductive element 14 through the stylus 13.
  • current flowing through the serniconductive element 14 is accordingly controlled and mechanical vibrations of the diaphragm 12 are translated into electrical variations or vibrations and appear in the lead pins 18.
  • the teachings of the present invention can similarly be applied to the diode structure illustrated in FIGURE 1-A and a highly sensitive transducer element can be obtained.
  • the present exemplified microphone can similarly employ a diode transducer constructed in accordance with the present invention. It is to be understood that the present invention, although exemplified with particular semiconductive layers, can be applied to n-p-n type semiconductor and, accordingly, substitution of the semi conductive layers with one another is encompassed by the present invention.
  • An electromechanical transducer comprising a first layer of semiconductor material of a first type and having a central portion and a peripheral portion with the central portion having a thickness of approximately 0.1 micron and the peripheral portion being substantially thicker than said central portion, a second layer of semiconductor material of a second type disposed on said first layer of semiconductor material and conf-ormably shaped to the central and peripheral portions thereof, a stylus in engagement with said central portion of said first layer of semiconductor material, and a pair of electrodes with one of said electrodes attached to the peripheral portion of said first layer of semiconductor material and the other of said electrodes secured to said second layer of semiconductor material.
  • An electromechanical transducer comprising a first layer of semiconductor material of a first type and having a substantially circular central portion Which is relatively thinner than a peripheral portion thereof, a second layer of semiconductor material of a second type disposed on said first layer and conformably shaped thereto, a stylus in engagement with the circular central portion of said first layer, and a pair of electrodes with one of said electrodes attached to the peripheral portion of said first layer and the other of said electrodes secured to said second layer of semiconductor material.
  • An electromechanical transducer comprising a first layer of semiconductor material having a central recessed portion in one surface thereof and said central recessed portion having a thickness of approximately 0.1 micron, a second layer of semiconductor material disposed on said first layer and conformably shaped thereto to enclose all but another surface thereof opposite said one surface, a stylus disposed on the other surface of said first layer opposite said central recessed portion thereof, and a pair of electrodes with one of said electrodes disposed on said second layer of semiconductor material and the other of said electrodes disposed on the other surface adjacent the peripheral edge of said first layer.
  • An electromechanical transducer comprising a housing, a pressure sensitive semiconductor device mounted within said housing and including a first layer of semiconductor material formed with a thin center portion and a thicker outer portion, a second layer of semiconductor material in intimate contact with said first layer of semiconductor material and insulatingly supported by said housing, a pair of leads with one of said leads connected to the thicker outer portion of the first layer and a second lead connected to the second layer, a support connected to said housing, a rod attached to said support, a stylus connected to said rod to support it with one end of said stylus in engagement with the first layer of said semiconductor material at the thin portion thereof, a diaphragm supported by said housing and the other end of said stylus connected to said diaphragm.
  • An electromechanical transducer comprising means for adjusting said rod relative to the housing to vary the pressure of said stylus on said semiconductor.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Pressure Sensors (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
US396859A 1963-09-19 1964-09-16 Sound transducer Expired - Lifetime US3480740A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5017963 1963-09-19

Publications (1)

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US3480740A true US3480740A (en) 1969-11-25

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US396859A Expired - Lifetime US3480740A (en) 1963-09-19 1964-09-16 Sound transducer

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DE (1) DE1280326B (it)
GB (1) GB1051550A (it)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5520388B1 (it) * 1970-08-12 1980-06-02

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2632062A (en) * 1949-06-15 1953-03-17 Bell Telephone Labor Inc Semiconductor transducer
US3119947A (en) * 1961-02-20 1964-01-28 Clevite Corp Semiconductive electron emissive device
US3241931A (en) * 1963-03-01 1966-03-22 Rca Corp Semiconductor devices
US3295085A (en) * 1963-09-03 1966-12-27 Raytheon Co Semiconductor strain transducer device
US3312790A (en) * 1963-05-23 1967-04-04 Bell Telephone Labor Inc Stress-responsive semiconductor transducers
US3403307A (en) * 1962-03-30 1968-09-24 Raytheon Co Strain sensitive barrier junction semiconductor device

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE490715A (it) * 1948-08-19
FR1295244A (fr) * 1960-07-18 1962-06-01 Western Electric Co Dispositifs semiconducteurs
DE1231033B (de) * 1963-09-13 1966-12-22 Siemens Ag Druckempfindliches Halbleiterbauelement mit drei Zonen abwechselnd entgegengesetztenLeitungstyps und einem Stempel auf einer Zone

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2632062A (en) * 1949-06-15 1953-03-17 Bell Telephone Labor Inc Semiconductor transducer
US3119947A (en) * 1961-02-20 1964-01-28 Clevite Corp Semiconductive electron emissive device
US3403307A (en) * 1962-03-30 1968-09-24 Raytheon Co Strain sensitive barrier junction semiconductor device
US3241931A (en) * 1963-03-01 1966-03-22 Rca Corp Semiconductor devices
US3312790A (en) * 1963-05-23 1967-04-04 Bell Telephone Labor Inc Stress-responsive semiconductor transducers
US3295085A (en) * 1963-09-03 1966-12-27 Raytheon Co Semiconductor strain transducer device

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GB1051550A (it)
DE1280326B (de) 1968-10-17

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