KR101758017B1 - Piezo mems microphone and thereof manufacturing method - Google Patents

Abstract

The present invention relates to a piezoelectric MEMS microphone and a method of manufacturing the same. A diaphragm formed at an upper portion thereof and having at least one venthole at a central portion thereof; A ring-shaped lower electrode formed around the diaphragm edge; A ring-shaped piezoelectric element formed on the lower electrode; And an upper electrode formed on the piezoelectric element.
According to the present invention as described above, unlike the prior art, a piezoelectric element is arranged around the periphery of a diaphragm to improve a signal-to-noise ratio (SNR), to facilitate manufacture and reduce the unit cost, and to improve the signal- A MEMS microphone and a method of manufacturing the same are provided.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a piezoelectric MEMS microphone,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MEMS microphone and a method of manufacturing the same. More particularly, the present invention relates to a piezoelectric MEMS microphone having improved signal-to-noise ratio (SNR) and a method of manufacturing the same.

A microphone is a device that converts an acoustic signal into an electric signal, and is used in an acoustic device, a communication device, a medical device, or the like. As the various devices with built-in microphones become smaller in size, miniaturization of microphones is required. In response to these demands, the development of MEMS microphones is being actively pursued.

MEMS microphones have become very popular for their performance and production efficiency because they can be miniaturized and can be separated into separate production processes. MEMS microphones are fabricated using surface mount technology (SMT) and semiconductor processing technology using electromechanical systems (MEMS) technology. Surface mount technology (hereinafter referred to as 'SMT') refers to a technique of contacting the leads of electronic components included in a substrate and a MEMS microphone. By mounting the electronic parts such as the transducer and the semiconductor chip on the substrate through the SMT process, the manufacturing of the MEMS microphones can be simplified and miniaturized.

Korean Patent No. 10-1496192 discloses a MEMS microphone having a piezoelectric diaphragm, and FIG. 1 shows a structure of a MEMS microphone having a conventional piezoelectric diaphragm.

As shown in Fig. 1, the prior art patent discloses a cover which is combined with a substrate to form an inner space; A transducer coupled to an upper portion of the substrate and disposed in the inner space, the transducer converting external sound introduced through the acoustic passage hole into an electric signal; And a semiconductor chip coupled to an upper portion of the substrate and electrically connected to the transducer for amplifying an electric signal so as to convert the converted electric signal into an analog or digital electric signal, (Piezoelectric element), and a vent hole is formed in the piezoelectric diaphragm.

However, in the related art, a MEMS microphone element for forming a vent hole in a piezoelectric element is formed. Since the diaphragm itself is formed of a piezoelectric element, the conversion efficiency of converting the vibration generated by the negative pressure into an electrical signal is lowered, There is a problem that the signal-to-noise ratio (SNR) falls due to the placement of the vent hole.

Korean Registered Patent No. 10-1496192 (Registered Date: February 17, 2015) Korean Patent Laid-Open Publication No. 10-2011-0025697 (public date: March 10, 2011)

The present invention provides a piezoelectric MEMS microphone and a method of manufacturing the same.

First, the present invention provides a piezo-MEMS microphone capable of improving a signal-to-noise ratio (SNR) by disposing a piezoelectric element around the periphery of a diaphragm, and a method of manufacturing the same.

Second, the present invention is to provide a method of manufacturing a piezo-MEMS microphone in which a manufacturing method is easy, a unit price can be reduced, and a signal-to-noise ratio (SNR) and performance are improved.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus and method for controlling the same.

A first aspect of the present invention to solve the above-described problems is a piezoelectric MEMS microphone comprising: a substrate having an acoustic chamber formed at a lower center thereof; A diaphragm formed at an upper portion thereof and having at least one venthole at a central portion thereof; A ring-shaped lower electrode formed around the diaphragm edge; A ring-shaped piezoelectric element formed on the lower electrode; And an upper electrode formed on the piezoelectric element.

It is preferable to further include an insulating layer formed between the substrate and the diaphragm, and the vent hole may be formed to be open in an upward direction and disposed symmetrically with respect to a center.

Preferably, the diaphragm is at least one of a nitride film, an oxide film, and a polysilicon film including silicon (Si), and the piezoelectric element and the lower electrode are formed in the same ring shape as the center, Is preferably equal to or larger than the ring-shaped diameter of the lower electrode, and the acoustic chamber is preferably structured such that its diameter increases toward the lower side.

According to a second aspect of the present invention, there is provided a method of manufacturing a piezo-MEMS microphone, comprising the steps of: (a) laminating an insulating film, a diaphragm, a lower electrode film, a piezoelectric film and an upper electrode film on a substrate in this order; (b) sequentially removing the circular film having a predetermined diameter at the same center of the upper electrode film, the piezoelectric film and the lower electrode film, respectively; (c) forming at least one vent hole in the center of the diaphragm corresponding to the position where the circular film is removed; And (d) forming an acoustic chamber by etching a part of the insulation film from a lower surface of the center of the substrate so that the vent hole is included.

The step (b) may include: removing a circular film having a first diameter at a center of the upper electrode film and opening the circular film; Removing the same center circular film having a second diameter smaller than the first diameter in the piezoelectric film, and opening the same; And removing the same central circular membrane having a third diameter smaller than the second diameter in the lower electrode film.

Preferably, the diaphragm is formed of at least one of a nitride film, an oxide film, and a polysilicon film including silicon (Si), and the step (d) It is preferable to form a vent hole which is a through-hole at at least one position symmetrical in the center.

The piezoelectric MEMS microphone and the method of manufacturing the same according to the present invention have the following effects.

The present invention relates to a piezoelectric MEMS microphone having an improved signal-to-noise ratio (SNR) by reducing a noise signal by forming a piezoelectric element or a piezo element in a ring shape around a diaphragm and forming a plurality of ventholes in the center of the diaphragm And a method for producing the same.

Secondly, according to the present invention, a piezoelectric element is arranged on the outer rim of a diaphragm to allow the diaphragm to vibrate elastically, and the diaphragm is most likely to be subjected to tensile stress or stress at the periphery of the rim to increase sensitivity of a piezoelectric element that converts vibration or pressure to an electrical signal And a method of manufacturing the same.

Third, according to the present invention, a plurality of vent holes are formed in the central portion of the diaphragm, thereby allowing the air in the acoustic chamber and the outside of the lower space to pass therethrough and to increase the flexibility of vibration, A MEMS microphone and a manufacturing room thereof.

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

FIG. 1 is a view showing a structure of a conventional MEMS microphone having a piezoelectric diaphragm.
2 is a plan view and a front view showing a structure of a piezo-MEMS microphone according to an embodiment of the present invention.
3 is a schematic diagram of a sound pressure structure of a piezoelectric element applied to a piezo-MEMS microphone according to an embodiment of the present invention.
4 is a schematic view showing a process of a method of manufacturing a piezo-MEMS microphone according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto.

Means that a particular feature, region, integer, step, operation, element and / or component is specified and that other specific features, regions, integers, steps, operations, elements, components, and / It does not exclude the existence or addition of a group.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

2 is a plan view and a front view showing a structure of a piezo-MEMS microphone according to an embodiment of the present invention.

As shown in FIG. 2, the piezoelectric MEMS microphone according to the embodiment of the present invention includes a substrate 100 having an acoustic chamber formed at a lower center thereof; A diaphragm 120 having at least one venthole 125 formed at the center thereof; A ring-shaped lower electrode 130 formed around an edge of the diaphragm 120; A ring-shaped piezoelectric element 140 formed on the lower electrode 130; And an upper electrode 150 formed on the piezoelectric element 140.

As described above, in the embodiment of the present invention, the piezoelectric element 140 or the piezoelectric element is formed in a ring shape around the diaphragm 120, unlike the conventional piezo or piezoelectric MEMS microphone, A plurality of ventholes 125 are formed at the center of the piezoelectric element 140 to reduce a noise signal generated by a force applied to the central portion of the piezoelectric element 140 and a vent hole 125 formed in the piezoelectric element 140 To-noise ratio (SNR) performance of the MEMS microphone can be improved.

1, an insulating layer 110 is formed on a substrate 100 having an acoustic chamber formed at a lower center thereof, and a vent hole 125 (not shown) is formed in a central portion of the insulating layer 110, ) Is formed on the upper surface of the diaphragm 120. A ring-shaped lower electrode 130 surrounding the diaphragm 120 is formed and a ring-shaped piezoelectric element 140 is stacked on the lower electrode 130. Then, Shaped upper electrode 150 is formed.

The lower electrode 130 and the upper electrode 150 may be formed of a metal such as Mo, Al, Ti, Au, Cu, Pt, or TiN, It is preferable to use a high-quality material, and it is preferable that the thickness has a thickness of several tens nm to several micrometers.

The acoustic chamber formed under the substrate 100 is a space through which air for sound vibration is communicated and may be a cylindrical shape or may be a hollow having various hollows such as an elliptical column or a polygonal column, Is widened. This is because there is a structural advantage to more widely accommodate the sound coming down the substrate 100.

It is preferable that the lower electrode 130, the upper electrode 150 and the piezoelectric element 140 have a ring shape because the propagation direction of the sound wave is symmetrical in the sound source so that the sensing sensitivity can be increased, So that it can be easily connected electrically. It is also possible to arrange the piezoelectric element 140 laminated on the lower electrode 130 in a ring shape so that the piezoelectric element 140 is arranged on the outer rim of the diaphragm 120 to make the diaphragm 120 more elastic It is possible to increase the sensitivity of the piezoelectric element 140 that converts vibration or pressure to an electrical signal because it is most likely to be subjected to tensile force or stress on the outer rim of the piezoelectric element.

Here, the diaphragm 120 is a driving device for sensing and driving a sound source (sound pressure), and the diaphragm 120 is driven by a sound source. The diaphragm 120 is preferably formed to have a thickness of several hundreds of angstroms to several micrometers, and the material is at least one of a nitride film, an oxide film, and a polysilicon film including silicon (Si). This is because it is easier to fabricate and has higher flexibility and elasticity than a metal diaphragm 120, which is generally used, thereby increasing the sensitivity of the microphone and providing excellent durability.

At least one vent hole 125 is preferably formed in the central portion of the diaphragm 120 as a through hole. Generally, the piezoelectric or piezoelectric type MEMS microphone does not require the vent hole 125 because there is no sacrificial layer. However, since there is no back volume when the vent hole 125 is not formed, There was a falling problem.

In the embodiment of the present invention, instead of forming the vent hole 125 in the piezoelectric element 140 or the piezoelectric element, a plurality of vent holes 125 may be formed in the central portion of the diaphragm 120, So that the air between the acoustic chamber and the outside of the lower space is allowed to pass therethrough and the flexibility of the vibration is increased to improve the conversion sensitivity of the electrical signal by the vibration.

In the absence of the vent hole 125, the flow of sound is less likely to occur, so that the sensitivity is lowered in the low frequency range (20 to 50 Hz). In order to improve the low frequency characteristics, At least one vent hole 125 is formed in the central region of the bottom plate 120.

Also, as shown in FIG. 2, the vent hole 125 formed in the diaphragm 120, which is applied in the embodiment of the present invention, is preferably disposed at a symmetrical position with respect to the center. This is to increase the sensitivity by uniformly vibrating against the negative pressure and to reduce the noise generated by the uneven air flow.

In addition, the structure of the vent hole 125 can have a structure of upper light-narrowing narrowly formed at the upper part and narrower at the lower part. The upper and lower portions of the vent hole 125 can have a narrow bottom light structure, And may be formed to have a structure that makes air flow more comfortable by making it wider than the body. (Not shown)

2, it is preferable to form an oxide film or a nitride film as the insulating film 110 between the diaphragm 120 and the substrate 100. [ This is to prevent the insulation of the silicon substrate 100 and the leakage current of the diaphragm 120. Here, the oxide film may be made of SiO _x , the nitride film may be made of SiN _x , the oxide film may be formed on the substrate 100, and a nitride film may be formed again.

3 is a schematic diagram of a sound pressure structure of a piezoelectric element 140 applied to a piezo-MEMS microphone according to an embodiment of the present invention. As shown in FIG. 3 (b), the piezoelectric MEMS microphone according to the embodiment of the present invention illustrates a structure in which the diaphragm is in surface contact with the diaphragm 120 in the form of a ring at the periphery of the diaphragm.

3 (a), in the case of the disk-shaped piezoelectric element 140 located above the conventional acoustic chamber, when the vibrating plate 120 vibrates up and down due to the negative pressure, Is the edge portion, and the least stressed or tensioned portion is the central portion. Therefore, in the disk-shaped piezoelectric element 140, the voltage due to vibration is smallest at the center, and this portion acts as a noise component, so that the overall signal-to-noise ratio (SNR) performance deteriorates.

In the embodiment of the present invention, as shown in FIG. 3 (b), a disc-shaped diaphragm 120 made of silicon or polysilicon having good elasticity and durability is formed on the acoustic chamber, By forming the ring-shaped piezoelectric element 140 around the rim of the diaphragm 120, it is possible to obtain an effect of improving the overall signal-to-noise ratio (SNR) by taking only a high voltage signal.

By adopting a structure in which the diaphragm 120 and the ring-shaped piezoelectric element 140 are laminated so that the vibrating and electrical signal converting part can be effectively performed, the vibration resilience and durability can be enhanced and the noise can be reduced, It is possible to provide a piezo-MEMS microphone structure having excellent performance.

4 is a schematic view showing a process of a method of manufacturing a piezo-MEMS microphone according to another embodiment of the present invention. 4, a method of manufacturing a piezoelectric MEMS microphone according to an embodiment of the present invention includes the steps of: (a) forming an insulating film 110, a diaphragm 120, a lower electrode 130 film, a piezoelectric element 140) and the upper electrode (150) in this order; (b) sequentially removing a circular film having a predetermined diameter at the same center of the film of the upper electrode 150, the piezoelectric film 140, and the lower electrode 130, respectively; (c) forming at least one vent hole 125 in the center of the vibration plate 120 corresponding to the position where the circular film is removed; And (d) forming an acoustic chamber by etching a part of the insulating film 110 from the lower center of the substrate 100 to include the vent hole 125.

4, the insulating film 110, the vibration plate 120, the lower electrode 130 film, the piezoelectric element 140 film, and the upper electrode 150 are sequentially stacked on the silicon substrate 100, In the step (a), the lower electrode 130 and the upper electrode 150 are preferably formed by sputtering, LPCVD, or PECVD, and the deposition is preferably several hundreds of angstroms . The lamination of the diaphragm 120 made of silicon (Si) or polysilicon (Poly Si) can be easily laminated through LPCVD or PECVD.

In the step (b), the step of sequentially removing the circular film having the predetermined diameter at the same center of the film of the upper electrode 150, the piezoelectric film 140, and the lower electrode 130, respectively, Refers to a step of removing a circular film having a predetermined diameter by patterning or etching in order to form a ring-shaped film having an open center.

That is, in the step (b), the circular film having a certain first diameter at the center of the film of the upper electrode 150 is removed by etching or the like to be opened, and a second diameter smaller than the first diameter And removing the same center circular film having a third diameter smaller than the second diameter in the lower electrode 130 film to open the upper portion of the vent hole 125 .

Each of the circular membranes to be removed is preferably increased in the upward direction. This is to improve the performance of a microphone that smoothes the flow of external air to form vibrations due to negative pressure and converts the vibrations into electrical signals. to be.

In step (c), the vent hole 125 formed in the diaphragm 120 is formed by etching a plurality of through holes symmetrically with respect to the center point, and the upper part of the vent hole 125 is opened. In step (d), a part of the lower surface of the substrate 100 is etched to form an acoustic chamber.
4, it is preferable that the piezoelectric element and the lower electrode formed through the above-described manufacturing method have the same ring-shaped center, and the ring-shaped diameter of the piezoelectric element is equal to or larger than the ring-shaped diameter of the lower electrode.

A ring-shaped piezoelectric element 140 is formed around the rim of the diaphragm 120 and the upper part of the diaphragm 120 and the acoustic chamber beneath the diaphragm 120 are formed by the manufacturing method according to the embodiment of the present invention. The ventilation hole 125 allows the air to flow smoothly, thereby enhancing the elasticity of the diaphragm 120 to increase the sensitivity and improve the signal-to-noise ratio (SNR), thereby making it easy to manufacture a piezo- ≪ / RTI >

The embodiments and the accompanying drawings described in the present specification are merely illustrative of some of the technical ideas included in the present invention. Accordingly, the embodiments disclosed herein are for the purpose of describing rather than limiting the technical spirit of the present invention, and it is apparent that the scope of the technical idea of the present invention is not limited by these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: substrate 110: insulating film
120: diaphragm 125: vent hole
130: lower electrode 140: piezoelectric element
150: upper electrode

Claims (10)

A substrate having an acoustic chamber formed at a lower center thereof;
A diaphragm having at least one venthole formed at the central portion thereof and at least one of a nitride film including silicon (Si), an oxide film and a polysilicon (Poly Si) ;
A ring-shaped lower electrode formed around the diaphragm edge;
A ring-shaped piezoelectric element formed on the lower electrode; And
And an upper electrode formed on the piezoelectric element,
Wherein the piezoelectric element and the lower electrode are ring-shaped with the same center, and the ring-shaped diameter of the piezoelectric element is greater than or equal to the ring-shaped diameter of the lower electrode. The method according to claim 1,
And an insulating layer formed between the substrate and the vibration plate. The method according to claim 1,
Wherein the vent holes are opened upward and symmetrically disposed at the center. delete delete The method according to claim 1,
Wherein the acoustic chamber has a structure in which the diameter of the acoustic chamber is increased toward the lower side. (a) stacking an insulating film, a diaphragm, a lower electrode film, a piezoelectric film and an upper electrode film on the substrate in this order;
(b) sequentially removing the circular film having a predetermined diameter at the same center of the upper electrode film, the piezoelectric film and the lower electrode film, respectively;
(c) forming at least one vent hole in the center of the diaphragm corresponding to the position where the circular film is removed; And
(d) forming an acoustic chamber by partially etching the insulating film to a lower surface of the center of the substrate so that the vent hole is included,
Wherein the diaphragm is made of at least one of a nitride film including silicon (Si), an oxide film, and a polysilicon (Poly Si)
Wherein the piezoelectric element and the lower electrode to be formed have the same ring-shaped center, and the ring-shaped diameter of the piezoelectric element is equal to or larger than the ring-shaped diameter of the lower electrode. The method of claim 7,
The step (b)
Removing a circular membrane having a first diameter at the center of the upper electrode film and opening the circular membrane;
Removing the same center circular film having a second diameter smaller than the first diameter in the piezoelectric film, and opening the same; And
And removing the circular film of the same center having the third diameter smaller than the second diameter from the lower electrode film to open the same. delete The method of claim 7,
The step (d)
And forming a vent hole as a through hole at at least one position symmetrical to the center of the opened diaphragm with the circular film removed.

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