WO2006025211A1 - Electret capacitor microphone - Google Patents

Abstract

An electret capacitor microphone comprising a semiconductor substrate (101) having a membrane region (113) removed to leave the peripheral part, a diaphragm (112) formed on the semiconductor substrate (101) to cover the membrane region (113), an air gap (109) provided above the diaphragm (112) to overlap the membrane region (113), and an upper electrode (118) provided above the air gap (109). The diaphragm (112) in the membrane region (113) is provided with a lower electrode (104). Respective patterns of the lower electrode (104), the diaphragm (112) and the air gap (109) have an outline defined by a straight line and a curve.

Description

 Specification

 Electret condenser microphone

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to an electret condenser microphone having a vibrating electrode and a fixed electrode, and more particularly to an electret condenser microphone formed using MEMS (Micro Electro Mechanical Systems) technology.

 Background art

 Conventionally, an electret condenser applied to an element such as a condenser microphone. One microphone is an electret film that is a dielectric having permanent electric polarization between a fixed electrode and a movable electrode constituting a parallel plate condenser. And an air gap (cavity) layer.

 In recent years, in order to reduce the thickness of the air gap layer and reduce variations in the thickness, a structure and a manufacturing method of the air gap layer using a microfabrication technique have been proposed. As a specific example, for example, as shown in Patent Document 1, a technique for forming a recess by removing a part of a Si substrate by wet etching using potassium hydroxide hydroxide is proposed. Also

As shown in Patent Document 2, a technique for suppressing variation in polyimide film thickness by providing a silicon nitride film as a flat film on the surface of polyimide serving as a spacer has been proposed.

 Patent Document 1: Japanese Patent Laid-Open No. 2002-345088

 Patent Document 2: Japanese Patent Laid-Open No. 2002-315097

 Disclosure of the invention

 Problems to be solved by the invention

 However, in recent years, in order to realize further downsizing and higher performance of equipment, it is hoped that an electret condenser microphone with smaller size and higher performance, and with excellent productivity and reliability will be realized. It is rare.

[0005] That is, an object of the present invention is to provide an electret condenser microphone that is small and has high performance, and is excellent in productivity and reliability. Means for solving the problem

 [0006] In order to solve the above problems, a first electret condenser microphone mouthphone according to the present invention includes a semiconductor substrate having a region removed so as to leave a peripheral portion, and the semiconductor substrate so as to cover the region. A vibration film formed thereon, an air gap provided on the vibration film so as to overlap the region, an upper electrode provided on the air gap, and a sound hole region provided on the upper electrode The lower electrode is formed on the vibrating membrane in the region, and the patterns of the lower electrode, the vibrating membrane, and the air gap have a contour that also has a straight line and a curved force.

 [0007] A second electret condenser microphone according to the present invention includes a semiconductor substrate having a region removed so as to leave a peripheral portion, a vibration film formed on the semiconductor substrate so as to cover the region, An air gap provided on the vibrating membrane so as to overlap the region, and an upper electrode provided on the air gap, wherein a lower electrode is formed on the vibrating membrane in the region, Each pattern of the electrode, the vibrating membrane, and the air gap is a square with corners formed into arcs.

 The invention's effect

 [0008] According to the present invention, it is possible to realize an electret condenser microphone that is small in size and high in performance and excellent in productivity and reliability. Furthermore, various application devices equipped with the electret condenser microphone of the present invention can be widely supplied to society.

 Brief Description of Drawings

 FIG. 1 (a) and (b) are configuration diagrams of an ECM unit according to an embodiment of the present invention, and FIG. 1 (a) is a plan view of the ECM unit. (b) is a cross-sectional view of the ECM unit.

 FIG. 2 is a circuit block diagram of an ECM unit according to an embodiment of the present invention.

 FIG. 3 is a cross-sectional view of an electret condenser microphone according to one embodiment of the present invention.

FIG. 4 is a plan view showing a configuration of a vibrating membrane in an electret condenser microphone according to an embodiment of the present invention. FIG. 5 is a plan view showing the formation positions of the air gap and the anchor tick hole in the electret condenser microphone according to one embodiment of the present invention.

Explanation of symbols

 18 Electret condenser microphone

 19 SMD

 20 FET

 21 Printed circuit board

 22 cases

 23 Internal circuit

 24 output terminals

 25 Output terminal

 26 External terminal

 27 External terminal

 28 terminals

 29 terminals

 30 terminals

 101 Semiconductor substrate

 102 Silicon oxide film

 103 Silicon nitride film

 104 Bottom electrode

 105 Silicon oxide film

 106 Silicon nitride film

 107 Leakhole

 108 Silicon oxide film

 109 Air gap

 110 Fixed membrane

111 Acoustic Hall 112 Vibration membrane

 113 Membrane area

 114 Silicon nitride film

 115 Lead wiring

 116 opening

 117 opening

 118 conductive film

 119 Silicon nitride film

 120 Corner

 121 Corner

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, as an application example of the electret condenser microphone of the present invention, an electret condenser microphone unit (hereinafter referred to as an ECM unit! /) Will be described with reference to the drawings.

 FIGS. 1 (a) and (b) are configuration diagrams of the ECM unit of the present embodiment, FIG. 1 (a) is a plan view of the ECM unit, and FIG. 1 (b) is the ECM unit. FIG.

 [0013] As shown in Figs. 1 (a) and (b), the ECM unit of the present embodiment has an electret condenser microphone 18, an SMD (surface mount component) 19 such as a condenser, and an FET (electric field) on a printed circuit board 21. It is configured by mounting an effect type transistor) unit 20. Although not shown in FIG. 1 (a), as shown in FIG. 1 (b), the printed circuit board 21 mounted with the electret condenser microphone 18, SMD 19 and FET 20 is protected by a case 22. It has been.

 FIG. 2 is a circuit block diagram of the ECM unit of the present embodiment.

As shown in FIG. 2, the internal circuit 23 of the ECM unit of the present embodiment includes an electret condenser microphone 18, an SMD 19, and an FET 20 which are electret condenser microphones of the present invention described later. In addition, signals are output from the output terminal 24 and the output terminal 25 of the internal circuit 23 to the external terminal 26 and the external terminal 27. During actual operation, for example, a voltage of about 2 V is supplied from the terminal 28 connected to the external terminal 26 via a resistor. When a signal having a pressure is input, a signal having an AC voltage of, for example, several tens of mV is output to the terminal 29 connected to the external terminal 26 via a capacitor. Each of the external terminal 27 and the terminal 30 connected thereto is connected to the output terminal 25 which is a GND terminal in the internal circuit 23.

 Hereinafter, the electret condenser microphone of the present invention will be described. FIG. 3 is a sectional view of the electret condenser microphone of the present invention.

 As shown in FIG. 3, the electret condenser microphone of the present invention covers a membrane region 113 on a semiconductor substrate 101 having a region removed so as to leave a peripheral portion (hereinafter referred to as a membrane region 113). And a fixed film 110 having an air gap 109 interposed between the vibrating film 112 and an electrode, and a parallel plate type capacitor structure. Here, the lower electrode 104 is provided on the vibration film 112 in the membrane region 113. The fixed film 110 includes a conductive film (upper electrode) 118.

 Specifically, a silicon oxide film 102 is formed on a semiconductor substrate 101 on which the electret condenser microphone of the present invention is mounted, and the semiconductor substrate 101 and the silicon oxide film 102 are respectively formed. The membrane region 113 is formed by partially removing so that the peripheral portion of the film remains. Here, the membrane region 113 is a region in which the semiconductor substrate 101 is partially removed so as to leave its peripheral portion in order to allow the vibrating membrane 1 12 to vibrate under pressure from an external force. .

 A silicon nitride film 103 is formed on the silicon oxide film 102 so as to cover the membrane region 113. On the silicon nitride film 103, a lower electrode 104 and a lead wiring 115 made of the same conductive film are formed. The lower electrode 104 is formed on the silicon nitride film 103 covering the membrane region 113, and the lead-out wiring 115 is formed on the silicon nitride film 103 outside the membrane region 113 so as to be connected to the lower electrode 104. Yes.

A silicon oxide film 105 and a silicon nitride film 106 are sequentially formed on each of the silicon nitride film 103, the lower electrode 104, and the lead wiring 115. Here, the vibration film 112 is constituted by the silicon nitride film 103, the lower electrode 104 made of a conductive film, the silicon oxide film 105, and the silicon nitride film 106 located in the membrane region 113. Also vibration A plurality of leak holes 107 connected to the air gap 109 are formed in the film 112. The silicon nitride film 103 and the silicon nitride film 106 are formed so as to cover the entire surface of the lower electrode 104 and the silicon oxide film 105 including the inner wall surface of the leak hole 107. Further, the silicon oxide film 105 is an electret film that stores electric charges.

 Furthermore, as shown in FIG. 3, above the vibration film 112, that is, above the silicon nitride film 106, the conductive film 118 covered with the lower silicon nitride film 114 and the upper silicon nitride film 119, respectively. A fixed membrane 110 is provided. Here, an air gap 109 is formed between the vibrating membrane 112 and the fixed membrane 110 in the membrane region 113 (including the vicinity thereof). On the other hand, a silicon oxide film 108 is formed between the silicon nitride film 106 or the silicon oxide film 102 and the fixed film 110 in the outer area of the membrane area 113 (excluding the area near the membrane area 113). Yes. That is, the air gap 109 is formed on the region including at least the entire membrane region 113, and the fixed film 110 is supported by the silicon oxide film 108 above the vibration film 112. The air gap 109 is formed by partially removing the silicon oxide film 108 formed on the semiconductor substrate 101 including the membrane region 113.

 In addition, the fixed film 110 above the air gap 109, that is, the conductive film (upper electrode) 118 covered with each of the silicon nitride films 114 and 119, has a plurality of acoustic holes connected to the air gap 109 ( (Sound hole region) 111 is formed. An opening 116 is provided in the fixed film 110 including the silicon nitride film 114 and the silicon oxide film 108 so that the lead-out wiring 115 is partially exposed. The lower electrode 104 is electrically connected to the gate of the FET 20 shown in FIG. The silicon nitride film 119 constituting the fixed film 110 is provided with an opening 117 and the conductive film 118 constituting the fixed film 110 is exposed through the opening 117, and the exposed portion is It is electrically connected to GND pin 25 in Fig. 2.

Hereinafter, the configuration of the vibrating membrane 112 will be described in detail with reference to FIG. FIG. 4 is a plan view showing a configuration of the vibration film 112 (a laminated structure of the silicon nitride film 103, the lower electrode 104, the silicon oxide film 105, and the silicon nitride film 106). As shown in FIG. 4, a lower electrode 104 is formed inside the membrane region 113. In the cross-sectional view of FIG. The force showing the lead wiring 115 for the pole 104 to be electrically connected to the outside. In FIG. The silicon nitride film 103, the silicon oxide film 105, and the silicon nitride film 106 are each formed so as to be larger than the membrane region 113 and cover the membrane region 113. Further, the silicon nitride film 103 and the silicon nitride film 106 are formed so as to extend further outside the silicon oxide film 105 so as to cover the silicon oxide film 105. The leak hole 107 is formed so as to penetrate the lower electrode 104 and the silicon oxide film 105 in the vibration film 112. The inner wall surface of the leak hole 107 is covered with a silicon nitride film 103 and a silicon nitride film 106.

 As a feature of the present embodiment, as shown in FIG. 4, corner portions in respective patterns of the silicon nitride film 103, the lower electrode 104, the silicon oxide film 105, and the silicon nitride film 106 constituting the vibration film 112 are provided. 120 has a round shape with no sharp corners. The shape of the corner 120 is preferably a circular arc for the reason described below. That is, in the capacitor structure in which the lower electrode 104 in the vibration film 112 and the upper electrode (conductive film 118) in the fixed film 110 are electrodes, respectively, the silicon nitride film 103, the lower electrode 104, and the silicon oxide film 105 The silicon nitride film 106 preferably has the shape of the membrane region 113, that is, a square. However, when the corner portion 120 of each film is sharp, due to the stress concentration in each film, cracks are easily generated in the film during the production, or film peeling tends to be induced after completion. On the other hand, as in the present embodiment, the film stress can be dispersed and relaxed by making the corner portion 120 of each component of the vibrating membrane 112 into a round shape without a sharp corner. It is possible to reduce defects that occur during manufacturing or after completion. Accordingly, it is possible to realize an electret condenser microphone that is small in size and high in performance and excellent in productivity and reliability.

Next, referring to FIG. 5, each of the air gap 109 and the region in the fixed film 110 where the coarse stick hole 111 is formed will be described in detail. FIG. 5 is a plan view showing the positions where the air gap 109 and the anchor tick hole 111 are formed. In FIG. 5, only the silicon nitride film 114 is shown as the fixed film 110 for simplicity. As shown in FIG. 5, the air gap 109 is provided in a region overlapping the acoustic hole 111. Air gap 109 is larger than membrane area 113 And formed outside the membrane region 113.

 As a feature of the present embodiment, as shown in FIG. 5, the corner portion 121 of the air gap 109 has a round shape with no sharp corners, like the corner portion 120 of the vibrating membrane 112 shown in FIG. is doing. The shape of the corner portion 121 is preferably an arc for the same reason as the corner portion 120 of the vibration film 112. The reason is as follows. In the capacitor structure in which the lower electrode 104 in the vibration film 112 and the upper electrode (conductive film 118) in the fixed film 110 are provided so as to sandwich the air gap 109, the shape of the air gap 109 is The shape of the membrane region 113, that is, a square is preferable. If the corner 121 of the air gap 109 is sharp, the stress concentration at the part where the corner 121 is in contact with the fixed film 110 and at the part where the corner part i 21 is in contact with the vibration film 112 is reduced. As a result, cracks are likely to occur in the film during manufacturing, or film peeling is likely to be induced after completion. On the other hand, the film stress can be relieved by making the corner portion 121 of the air gap 109 round with no sharp corners as in this embodiment, so that it occurs at the time of manufacturing or after completion. Defects can be reduced. Therefore, it is possible to realize an electret condenser microphone that is small in size and high in performance and excellent in productivity and reliability.

 Hereinafter, the operation of the electret condenser microphone of the present invention will be described. In the electret condenser microphone of the present invention shown in FIG. 3, when the vibrating membrane 112 receives an upward force through the acoustic suction hole 111 and the air gap 109, the vibrating membrane 112 mechanically vibrates up and down according to the sound pressure. . The electret condenser microphone of the present invention has a parallel plate type capacitor structure in which the lower electrode 104 in the vibration film 112 and the conductive film 118 in the fixed film 110 are electrodes. Therefore, when the vibrating membrane 112 vibrates, the interelectrode distance between the lower electrode 104 and the conductive film 118 changes, thereby changing the capacitance (C) of the capacitor. Here, since the charge (Q) stored in the capacitor is constant, when the capacitance (C) of the capacitor changes, the voltage (V) between the lower electrode 104 and the fixed film 110 (conductive film 118) changes. Change occurs. This is because it is necessary to physically satisfy the condition of the following formula (1).

[0028] Q = CV · · · (1) Further, when the voltage (V) between the lower electrode 104 and the fixed film 110 (conductive film 118) changes, the lower electrode 104 is electrically connected to the gate of the FET 20 in FIG. The gate potential changes. As described above, the gate potential of the FET 20 changes due to the vibration of the vibrating membrane 112, and the change in the gate potential of the FET 20 is output as a voltage change to the external output terminal 29 in FIG.

 In the present embodiment, polysilicon, gold, refractory metal, aluminum, an aluminum-containing alloy, or the like doped with impurities may be used as the conductive material constituting the lower electrode 104.

 Industrial applicability

[0030] The present invention relates to an electret condenser microphone having a vibrating electrode and a fixed electrode, and particularly when applied to an electret condenser microphone formed using MEMS technology, it is small and has high performance and excellent productivity and reliability. The electret condenser microphone can be realized and is very useful.

Claims

The scope of the claims  [1] a semiconductor substrate having a region removed so as to leave a peripheral portion;  A vibration film formed on the semiconductor substrate so as to cover the region;  An air gap provided on the vibrating membrane so as to overlap the region;  An upper electrode provided on the air gap;  A sound hole region provided in the upper electrode,  A lower electrode is formed on the vibrating membrane in the region;  Each of the patterns of the lower electrode, the vibrating membrane, and the air gap has an outline of a straight line and a curved force.  [2] a semiconductor substrate having a region removed so as to leave a peripheral portion;  A vibration film formed on the semiconductor substrate so as to cover the region;  An air gap provided on the vibrating membrane so as to overlap the region;  An upper electrode provided on the air gap,  A lower electrode is formed on the vibrating membrane in the region;  Each pattern of the lower electrode, the vibrating membrane, and the air gap is a square whose corner is a circular arc.