JP4609363B2 - Condenser microphone and manufacturing method thereof - Google Patents

Description

  The present invention relates to a condenser microphone manufactured by processing a semiconductor substrate.

  Capacitor-type microphones using a semiconductor substrate such as a silicon substrate are such that the outer periphery of a flat fixed electrode is fixed to an annular insulating layer formed on the semiconductor substrate, so that the fixed electrode is bridged inside the insulating layer. The diaphragm electrode is supported in parallel with a distance between the fixed electrode and the fixed electrode, and the change in the distance between the two electrodes when the diaphragm electrode vibrates due to sound or the like. It is detected as a change in capacitance between both electrodes.

  In this type of condenser microphone, the semiconductor substrate and the diaphragm electrode are set to the same potential, and the capacitance change between the diaphragm electrode and the fixed electrode is detected. However, the outer periphery of the fixed electrode and the semiconductor substrate are insulated from each other. Since the layers are arranged to face each other, a parasitic capacitance (stray capacitance) is generated between them, and the parasitic capacitance intervenes in parallel with the capacitance between both electrodes, which causes a decrease in sensitivity. It is considered to be.

In the capacitor-type microphone described in Non-Patent Document 1, a part of the outer peripheral portion of the fixed electrode is formed narrow, and only the narrow portion is fixed on the insulating layer, and the fixed electrode supporting portion on the insulating layer By reducing the area, the parasitic capacitance is reduced, and a large part of the fixed electrode is disposed opposite to a portion where the vibration width at the central portion of the diaphragm electrode is large.
Toshifumi Tajima, Masayoshi Esashi et al., Micromachine Sensor System Study Material, MSS-01-34, “Mechanical Characteristics of Condenser Silicon Microphone”, The Institute of Electrical Engineers of Japan

  However, parasitic capacitance still remains in the support portion on the insulating layer in the fixed electrode. In addition, since the support portion of the fixed electrode becomes narrow, the rigidity of the support portion becomes low. For this reason, the fixed electrode is easily bent by the electrostatic attractive force between both electrodes, and the so-called pull-in voltage is lowered. Arise. In order to prevent the occurrence of the pull-in state, it is necessary to reduce the applied bias voltage. Due to this limitation, there is a problem that a high-sensitivity device cannot be manufactured.

  The present invention provides a condenser microphone that can reduce parasitic capacitance and improve sensitivity, and a method of manufacturing the same.

  The capacitor-type microphone of the present invention has a flat plate shape in which a cavity is formed in a semiconductor substrate and an insulating layer formed on the semiconductor substrate so as to surround the periphery of the cavity is spanned in the inner space. A fixed microphone and a diaphragm electrode parallel to the fixed electrode at a distance from each other, and a condenser microphone for detecting a change in capacitance between the diaphragm electrode and the fixed electrode corresponding to pressure fluctuations. An air layer formed by removing a part of the insulating layer is interposed between the semiconductor substrate and an outer peripheral portion of the fixed electrode opposed to the semiconductor substrate.

  That is, since an air layer without an insulating material is interposed between the fixed electrode and the semiconductor substrate, the parasitic capacitance between the fixed electrode and the semiconductor substrate is such that the capacitance of the air layer portion is in series. Since it is equivalent to the intervening one and the capacitance of the air layer is extremely small, the overall parasitic capacitance is small.

  In the semiconductor device according to the present invention, the diaphragm electrode is supported in a suspended state at an inner end portion of a support beam extending inward from the insulating layer, and the fixed electrode is disposed at a radially outward position of the diaphragm electrode. A ring-shaped layer facing the outer periphery of the fixed electrode is provided between the semiconductor substrate and the semiconductor substrate, and the air layer is formed between the ring-shaped layer and the semiconductor substrate.

  By adopting such a configuration, a ring-shaped layer provided at an outer position of the diaphragm electrode is interposed between the fixed electrode and the semiconductor substrate, and an insulating layer portion and an air layer portion are interposed therebetween. The two can be separated. Therefore, the parasitic capacitance between the fixed electrode and the semiconductor substrate is equivalent to the capacitance of the insulating layer portion and the capacitance of the air layer portion connected in series, and the capacitance of the air layer portion is small. The overall parasitic capacitance is also reduced.

  In this case, if the diaphragm electrode and the ring-shaped layer are made of the same material, the ring-shaped layer is formed at the same time as the diaphragm electrode by a technique of sequentially laminating an insulating material layer on the semiconductor substrate and a conductive layer thereon. In addition, the ring-shaped layer can function as an etching stopper layer when the insulating material layer is wet-etched, and the air layer can be efficiently formed by the etching process.

  That is, an insulating material layer is formed in a portion corresponding to the air layer, and the ring-shaped layer is formed of a material having a lower affinity with the etching solution than the insulating material layer, and these are immersed in the etching solution. By doing so, the air layer can be formed by removing the insulating material layer to the interface with the ring-shaped layer.

The production method of the present invention is shown in order as follows.
(1) A diaphragm electrode and a ring-shaped layer surrounding the diaphragm electrode at a position outside the diaphragm electrode are formed on a semiconductor substrate flat plate with a first insulating material layer interposed therebetween, and the diaphragm electrode and the ring A second insulating material layer is laminated on the plate-like layer, and a flat plate-like fixed electrode and an inner circumference of the ring-shaped layer facing the inner circumference of the diaphragm electrode and the ring-shaped layer are formed on the second insulator layer. A laminating step for forming a support beam facing the outer periphery of the diaphragm electrode;
(2) A cavity forming step of forming a semiconductor substrate having a cavity larger than the inner diameter of the ring-shaped layer by removing a central portion of the flat plate for a semiconductor substrate to the interface with the first insulating material layer;
(3) A resist layer is formed in a ring shape so as to cover from the outer peripheral portion of the fixed electrode to the outer peripheral portion of the second insulating material layer, and these insulating material layers are partially immersed by immersing them in an etching solution. And an etching process step to be removed.
In the etching process, a gap layer is formed between the diaphragm electrode and the fixed electrode, and a connecting column for connecting the support beam and the diaphragm electrode is formed, while the diaphragm electrode is connected to the cavity portion. And an air layer is formed between the semiconductor substrate and the ring-shaped layer.

  According to the condenser microphone and the method of manufacturing the same of the present invention, the parasitic capacitance between the semiconductor substrate and the fixed electrode is reduced by interposing the air layer between the semiconductor substrate and the outer peripheral portion of the fixed electrode. As a result, the sensitivity can be improved. At that time, by providing a ring-shaped layer between the semiconductor substrate and the fixed electrode, the ring-shaped layer can function as an etching stopper layer, and no new equipment is required for air layer formation. Thus, it can be easily manufactured by an existing semiconductor process.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, this condenser microphone is provided with an annular insulating layer 3 on a block-like semiconductor substrate 2 having a cavity 1 formed in the center so as to surround the cavity 1. An outer peripheral portion of a flat fixed electrode 4 is fixed to the upper surface of the insulating layer 3, and a diaphragm electrode 6 is supported in parallel with the fixed electrode 4 through a gap layer 5. A ring-shaped layer 7 is provided at an outer position so as to be disposed between the outer peripheral portion of the fixed electrode 4 and the semiconductor substrate 2, and an air layer 8 is formed between the ring-shaped layer 7 and the semiconductor substrate 2. It is configured.

  The fixed electrode 4 is formed in a circular plate shape as a whole, and in the example of FIG. 2, in the example of FIG. 2, recesses 9 are formed at three locations spaced by 120 ° in the circumferential direction, A tongue-like support beam 11 is arranged in each recess 9 with a slight gap from the fixed electrode 4. Since the support beam 11 is disposed in the concave portion 9 of the fixed electrode 4, a slit 12 in a bent state is formed between the support beam 11 and the fixed electrode 4. The outer peripheral portion of the fixed electrode 4 excluding the support beam 11 and the outer end portion of the support beam 11 are fixed to the insulating layer 3, and the inner end portion of the support beam 11 has a radius from the insulating layer 3. It is in a state of projecting inward.

  On the other hand, three portions of the outer peripheral portion of the diaphragm electrode 6 are connected to the inner end portions of the support beams 11 via connecting columns 13 made of an insulating material. The diaphragm electrode 6 is formed in a circular shape as a whole, and is supported in a state of being suspended from the support beam 11 toward the cavity 1 by fixing the outer periphery of the support beam 11 at three locations. As shown in FIGS. 2 and 3, an arm portion 14 projecting radially outward is integrally formed on a part of the outer periphery, and a land portion 15 is formed on the projecting end portion of the arm portion 14. Yes.

  The ring-shaped layer 7 is disposed around the diaphragm electrode 6. This ring-shaped layer 7 has a notch 16 formed in part so as to avoid the arm portion 14 of the diaphragm electrode 6, and a ring 17 is formed between the diaphragm electrode 6 and the ring-shaped layer 7. .

  The fixed electrode 4, the diaphragm electrode 6, and the ring-shaped layer 7 are made of a conductive semiconductor film such as polycrystalline silicon (polysilicon), and the diaphragm electrode 6 is formed as a thin film that can be vibrated by sound waves. The fixed electrode 4 is formed with a plurality of through holes 18 through which sound waves pass evenly distributed on the center side excluding the outer peripheral portion. In this case, as shown in FIG. 1, the fixed electrode 4, the diaphragm electrode 6, and the ring-shaped layer 7 are arranged on the same axis X, and the diaphragm electrode 6 and the ring-shaped layer 7 have the same thickness. The fixed electrode 4 and the support beam 11 are also arranged on the same plane with the same thickness. Further, as shown in FIGS. 1 and 2, the outer diameter of the fixed electrode 4 is set to be larger than the outer diameter of the diaphragm electrode 6, but the ring-shaped layer 7 disposed outside the diaphragm electrode 6. It is set smaller than the outer diameter. The outer diameter of the diaphragm electrode 6 is set smaller than the inner diameter of the cavity 1 of the semiconductor substrate 2, and the inner diameter of the ring-shaped layer 7 is larger than the inner diameter of the cavity 1.

  The insulating layer 3 is annularly laminated on the outer peripheral side excluding the vicinity of the peripheral part of the cavity 1 which is the inner peripheral side of the semiconductor substrate 2, and its upper half is radially inward from the lower half. The fixed electrode 4 and the supporting beam 11 are fixed to the upper surface of the protruding inner peripheral portion, and the ring-shaped layer 7 is fixed to the lower surface. That is, the lower portion of the ring-shaped layer 7 is an air layer 8 in which no insulating material is interposed between the ring-shaped layer 7 and the semiconductor substrate 2. In addition, the air layer 8 is formed so as to extend slightly beyond the outer peripheral edge of the ring-shaped layer 7 to the upper side due to the progress of the etching process described later, so that the ring is formed near the outer peripheral edge of the ring-shaped layer 7. A tunnel portion 19 is formed in a shape. The insulating layer 3 and the connecting pillar 13 are made of, for example, silicon oxide as the same insulating material. Further, the tunnel portion 19 is not always necessary and may be omitted.

Further, as shown in FIGS. 2 to 4, an external connection input terminal 21 is formed in the insulating layer 3 in a connected state to the land portion 15 at the tip of the arm portion 14 of the diaphragm electrode 6. On the back surface, as shown in FIG. 4, a conduction portion 22 that connects the land portion 15 and the semiconductor substrate 2 is formed.
Note that these configurations are not limited to the structures described here.

Next, a manufacturing method of the condenser microphone configured as described above will be described with reference to FIG. FIG. 5 shows the transition of the cross-sectional structure at each stage of the manufacturing process, but shows the transition of the cross-section at the portion of the support beam 11 indicated by the line BB in FIG.
(1) Laminating Step First, as shown in FIG. 5A, silicon oxide (SiO 2) is formed on the surface of a substrate flat plate 31 such as single crystal silicon to be the semiconductor substrate 2 by a thin film forming technique such as CVD (Chemical Vapor Deposition). ₂ ) A first insulating material layer 32 is formed by depositing an insulating material.
Next, a conductive layer 33 made of polysilicon or the like is formed on the first insulating material layer 32 by a CVD method or the like.

Then, a resist is coated on the conductive layer 33 and exposed and developed to form a resist layer 34 that covers the portions to be the diaphragm electrode 6 and the ring-shaped layer 7 and etched by RIE (Reactive Ion Etching) or the like. Processing is performed to form the diaphragm electrode 6 and the ring-shaped layer 7 around it, and then the resist layer is removed using a resist stripping solution. In this state, as shown in FIG. 5B, the diaphragm electrode 6 and the ring-shaped layer 7 are separated through a substantially annular slit 17 therebetween.
In the arm portion 14 of the diaphragm electrode 6, a through hole is formed in the first insulating material layer 32 at a position to be the land portion 15, and the conductive layer 33 is formed so as to fill the through hole. A conduction portion 22 is formed integrally with the land portion 15.

Next, an insulating material made of silicon oxide or the like is deposited by CVD or the like so as to cover the entire diaphragm electrode 6 and the ring-shaped layer 7 to form a second insulating material layer 35.
Further, a conductive layer made of polysilicon or the like is formed on the second insulating material layer 35 by a CVD method or the like, and a resist layer is formed on the conductive layer to cover the portions to be the fixed electrode 4 and the support beam 11. Then, the fixed electrode 4 and the support beam 11 having the through holes 18 are formed by an etching process such as RIE. After the fixed electrode 4 and the support beam 11 are formed, the resist layer stacked thereon is removed, and the state shown in FIG. 5C is obtained. In this state, the fixed electrode 4 and the support beam 11 are separated via a slit 12 bent between them.
On the land portion 15 of the diaphragm electrode 6, a through hole is formed in the second insulating material layer 35, and the external connection input terminal 21 is formed by plating through the hole such as aluminum.

(2) Cavity Part Formation Step Next, as shown by a chain line in FIG. 5C, a resist layer 36 is formed on the back side of the substrate flat plate 31 leaving the central part to be the cavity part 1, and so-called deep etching ( The central portion of the substrate flat plate 31 is removed by Deep RIE until the interface with the first insulating material layer 32 is reached, and the semiconductor substrate 2 having the cavity 1 is formed as shown in FIG. . After the cavity 1 is formed, the resist layer 36 on the semiconductor substrate 2 is removed.

(3) Wet Etching Process Step Next, as shown in FIG. 5E, the outer peripheral portion of the fixed electrode 4 and the outer end of the support beam 11 except for the central portion where the through hole 18 of the fixed electrode 4 is formed. A resist layer 37 is formed in a ring shape so as to cover the portion, and the whole is immersed in an etching solution such as hydrofluoric acid to perform wet etching.
By this etching process, when the first insulating material layer 32 that contacts the etching solution in the cavity 1 of the semiconductor substrate 2 is dissolved from the central portion and the diaphragm electrode 6 is exposed, the diaphragm electrode 6 and the ring-shaped layer 7 are exposed. Etching solution enters from the ring-shaped slit 17 between them and dissolves the second insulating material layer 35 at the slit 17 portion, and on the opposite side, between the through hole 18 of the fixed electrode 4 and the support beam 11. The second insulating material layer 35 in contact with the etching solution through the slits 12 is dissolved from the through holes 18 and the slits 12. The dissolution of the insulating material layers 32 and 35 proceeds not only in the thickness direction but also in the surface direction called so-called side etching. By appropriately setting the etching time, the insulating material between the fixed electrode 4 and the diaphragm electrode 6 is removed, and a gap layer 5 is formed between the electrodes 4 and 6, and each support beam 11. A connecting column 13 is formed between the ring electrode 7 and the diaphragm electrode 6, and an air layer 8 is formed below the ring-shaped layer 7.

  In the condenser microphone configured as described above, when the diaphragm electrode 6 is vibrated by the sound pressure transmitted through the through hole 18 of the fixed electrode 4, the distance between the fixed electrode 4 and the diaphragm electrode 6 is reduced. It changes, and the change of the electrostatic capacitance between both electrodes 4 and 6 accompanying the change is detected. At this time, the parasitic capacitance between the fixed electrode 4 and the semiconductor substrate 2 is also interposed in parallel with the capacitance between the electrodes 4 and 6, and an output corresponding to the combined capacitance is obtained.

  However, since the ring-shaped layer 7 is interposed between the fixed electrode 4 and the semiconductor substrate 2, the ring-shaped layer 7 separates the fixed electrode 4 and the semiconductor substrate 2 into two parts. Accordingly, the capacitance between the semiconductor substrate 2 and the fixed electrode 4 is determined by the capacitance between the fixed electrode 4 and the ring-shaped layer 7 and the capacitance between the ring-shaped layer 7 and the semiconductor substrate 2. Equivalent to those connected in series. Among them, since the space between the ring-shaped layer 7 and the semiconductor substrate 2 is an air layer 8, the capacitance between them is extremely small, and eventually the total parasitic capacitance generated between the fixed electrode 4 and the semiconductor substrate 2. The capacity is small.

  That is, as shown in FIG. 6A, the variable capacitance between the fixed electrode 4 and the diaphragm electrode 6 is Cm, the capacitance between the outer periphery of the fixed electrode 4 and the ring-shaped layer 7 is Cs1, and the ring-shaped layer Assuming that the capacitance between the semiconductor substrate 2 and the semiconductor substrate 2 is Cs2, the total combined capacitance C of the total capacitance Cs1 and Cs2 is a variable capacitance Cm as shown in an equivalent circuit in FIG. 6B. Since they exist in parallel, they are represented by C = Cm + Cs1 * Cs2 / (Cs1 + Cs2). Among them, the capacity Cs2 of the air layer 8 is extremely smaller than the capacity Cs1 of the insulating layer 3 between the fixed electrode 4 and the ring-shaped layer 7, so that Cs1 * Cs2 / (Cs1 + Cs2) ≈Cs2. Therefore, the combined capacity is C≈Cm + Cs2, and since Cs2 is extremely small, the influence of Cs2 can be substantially ignored.

  On the other hand, in the case of a structure having no ring-shaped layer and no air layer between the outer periphery of the fixed electrode 4 and the semiconductor substrate 2 as shown in FIG. As shown in the equivalent circuit in (b), the combined capacitance C0 is C0 = Cm + Cs, and depends on the size of Cs.

For example, the thickness of the insulating layer 3 between the fixed electrode 4 and the ring-shaped layer 7 in FIG. 6A is d1, the area of the fixed electrode 4 fixed on the insulating layer 3 is S1, and the ring shape The thickness of the air layer 8 between the layer 7 and the semiconductor substrate 2 is d2, and the projected area of the ring-shaped layer 7 that overlaps the semiconductor substrate 2 is S2, and the fixed electrode 4 and the semiconductor substrate 2 in FIG. The thickness of the insulating layer 3 between and d0 is d0, and the area of the fixed electrode 4 fixed on the insulating layer 3 is S0,
d1 = (1/2) * d0,
d2 = (1/2) * d0,
If S1 = S2 = S0,
Cs1 = 2 * Cs,
Since Cs2 = 2 * (1 / 3.9) * Cs≈ (1/2) * Cs,
The combined capacitance C≈Cm + (1/2) * Cs, and the parasitic capacitance can be reduced.

  6B and 7B, reference numeral 41 denotes an impedance converter that amplifies the output from the fixed electrode 4, and reference numeral 42 denotes an output terminal. The impedance converter 41 may be formed on a semiconductor chip different from the microphone chip, or may be incorporated in a circuit board on which the microphone chip is mounted.

  This condenser microphone has a special structure in which an air layer 8 is interposed in a part of an insulating layer 3 laminated on a semiconductor substrate 2 so as to extend in the surface direction of the substrate, but a ring-shaped layer 7 is provided. Therefore, as described above, a series of processing can be performed by a normal semiconductor manufacturing process technology such as a lamination process, a dry etching process, a wet etching process, etc., and it can be easily manufactured without using special equipment. it can.

  Since the parasitic capacitance is reduced by the air layer 8, the sensitivity as a microphone can be increased, and the area of the outer periphery of the fixed electrode 4 on the insulating layer 3 can be increased. The rigidity of the electrode 4 increases, and the so-called pull-in voltage increases. For this reason, the bias voltage can be increased, and a microphone with high sensitivity can be obtained by a synergistic effect with the parasitic capacitance reduction.

  Further, since the diaphragm electrode 6 is supported by the support beam 11 in a suspended state, the parasitic capacitance between the fixed electrode 4 and the diaphragm electrode 6 is also excluded, and higher sensitivity can be achieved. In other words, if the structure in which the diaphragm electrode is supported by the insulating layer as well as the fixed electrode, parasitic capacitance is generated between the outer peripheral portions of both electrodes, which causes a decrease in sensitivity. However, the diaphragm electrode 6 is insulated. By separating from the layer 3 and being suspended by the support beam 11, the problem of parasitic capacitance with the fixed electrode 4 does not occur. There may be three or more supporting beams 11 supporting the diaphragm electrode 6 in a suspended state.

In the above-described embodiment, the ring-shaped layer 7 is made of the same material (polysilicon) as the diaphragm electrode 6. However, as long as it can function as an etching stopper layer, a hydrofluoric acid or the like may be used even if it is not a polysilicon film. Any material that has a lower affinity for the etchant than the insulating material (SiO ₂ ) that constitutes the insulating layer 3 may be used, and a nitride film or the like is also applicable. In this case, a material smaller than the dielectric constant of SiO ₂ constituting the insulating layer 3 is preferable.
In addition, although the ring-shaped layer 7 is formed on the same plane as the diaphragm electrode 6 in the above embodiment, it may be formed on a different layer.

It is a longitudinal cross-sectional view in the capacitor | condenser microphone of embodiment of this invention, and is an arrow line view which follows the BB line of FIG. It is a top view of the fixed electrode and support beam in FIG. It is a plane sectional view of the insulating layer part which follows the AA line of FIG. It is arrow sectional drawing of the external connection terminal part which follows the CC line of FIG. It is a longitudinal cross-sectional view which shows the manufacturing process of the capacitor | condenser microphone of this embodiment in order. (A) for demonstrating the electrostatic capacitance in the capacitor | condenser type | mold microphone of this embodiment is a longitudinal cross-sectional view, (b) is an equivalent circuit schematic. As a comparative example, (a) is a longitudinal sectional view, and (b) is an equivalent circuit diagram for explaining the capacitance in a condenser microphone without an air layer or the like.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cavity part, 2 ... Semiconductor substrate, 3 ... Insulating layer, 4 ... Fixed electrode, 5 ... Air gap layer, 6 ... Diaphragm electrode, 7 ... Ring-shaped layer, 8 ... Air layer, 11 ... Supporting beam, 12 ... Slit, DESCRIPTION OF SYMBOLS 13 ... Connection pillar, 14 ... Arm part, 15 ... Land part, 16 ... Notch part, 17 ... Slit, 18 ... Through-hole, 21 ... Input terminal, 22 ... Conduction part, 31 ... Flat plate for semiconductor substrates, 32 ... No. 1 insulating material layer, 33 ... conductive layer, 34 ... resist layer, 35 ... second insulating material layer, 36 ... resist layer, 37 ... resist layer.

Claims (4)

A flat plate-shaped fixed electrode in a state where a hollow portion is formed in the semiconductor substrate, an insulating layer formed on the semiconductor substrate so as to surround the periphery of the hollow portion, and spanned inside the space, and the fixed electrode And a diaphragm type microphone that supports a diaphragm electrode parallel to each other at an interval, and detects a change in capacitance between the diaphragm electrode and the fixed electrode corresponding to pressure fluctuation,
An air layer formed by removing a part of the insulating layer is interposed between the semiconductor substrate and the outer peripheral portion of the fixed electrode facing the semiconductor substrate,
The diaphragm electrode is supported in a suspended state at an inner end portion of a support beam projecting inward from the insulating layer, and between the fixed electrode and the semiconductor substrate at a radially outward position of the diaphragm electrode. A capacitor-type microphone , wherein a ring-shaped layer facing the outer peripheral portion of the fixed electrode is provided, and the air layer is formed between the ring-shaped layer and the semiconductor substrate . Condenser microphone according to claim 1, characterized by being composed of the same material as the diaphragm electrode and a ring-shaped layer. A method for producing a condenser microphone according to claim 1 or 2 ,
An insulating material layer is formed in a portion corresponding to the air layer, and the ring-shaped layer is formed of a material having a lower affinity with the etching solution than the insulating material layer, and these are immersed in the etching solution. The method for manufacturing a condenser microphone, comprising: removing the insulating material layer between the semiconductor substrate and the ring-shaped layer to form the air layer. A diaphragm electrode and a ring-shaped layer surrounding the diaphragm electrode at a position outside the diaphragm electrode are formed on a semiconductor substrate flat plate with a first insulating material layer interposed therebetween, and the diaphragm electrode and the ring-shaped layer A second insulating material layer is stacked thereon, and a diaphragm electrode and a flat plate-like fixed electrode facing the inner peripheral portion of the ring-shaped layer on the second insulating layer and the diaphragm electrode from the inner peripheral portion of the ring-shaped layer. A laminating step for forming a supporting beam facing the outer periphery;
A cavity forming step of forming a semiconductor substrate having a cavity larger than an inner diameter of the ring-shaped layer by removing a central portion of the semiconductor substrate flat plate to an interface with the first insulating material layer;
Leave a resist layer in a ring shape so as to cover them from the outer peripheral portion of the fixed electrode to the outer portion of the second insulating material layer, removing them and then immersed in an etching solution both insulating material layer partially And an etching process step
In the etching process, a gap layer is formed between the diaphragm electrode and the fixed electrode, and a connecting column for connecting the support beam and the diaphragm electrode is formed, while the diaphragm electrode is connected to the cavity portion. A method of manufacturing a condenser microphone, characterized in that an air layer is formed between the semiconductor substrate and the ring-shaped layer.

Images