JP2016007681A - Mems element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MEMS element of which a capacity of a buck chamber can be increased without an additional manufacturing process.SOLUTION: In an MEMS element, a buck chamber 11, in which a substrate is so removed that a movable electrode 3 is exposed on the substrate side, is formed, an electrode support part 14 comprising the substrate on which the movable electrode 3, a spacer 4 and a stationery electrode are laminated is formed outside the first buck chamber, and further, a second buck chamber 12 in which the substrate is removed is formed outside the electrode support part. Communication parts are so formed on the first buck chamber 11 and the second buck chamber 12 that respective spaces are communicated with each other. The first buck chamber 11 and the second buck chamber 12 can be formed similarly to a general buck chamber.

Description

  The present invention relates to a MEMS element, and more particularly to a pressure detection type MEMS element used as a microphone, various sensors, switches, and the like, and a method for manufacturing the same.

  Conventionally, in a micro electro mechanical systems (MEMS) device using a semiconductor process, a fixed electrode, a sacrificial layer (insulating film), and a movable electrode are formed on a semiconductor substrate, and then a part of the sacrificial layer is removed to form a spacer. An air gap (hollow) structure is formed between the fixed electrode fixed via the movable electrode and the movable electrode.

  For example, in a condenser microphone that is a MEMS element, a fixed electrode having a plurality of through-holes that allow sound pressure to pass through and a movable electrode that vibrates in response to sound pressure are arranged facing each other, and vibrates in response to sound pressure. The displacement of the movable electrode is detected as a change in capacitance between the electrodes.

  Generally, in order to increase the sensitivity of a condenser microphone, it is necessary to increase the displacement of the movable electrode by sound pressure. Therefore, a method of softening the spring of the movable electrode and a method of increasing the volume of the back chamber are employed.

  FIG. 10 is an explanatory diagram of a conventional MEMS device in which the volume of the back chamber is increased. As shown in FIG. 10, a movable electrode 3 is formed on a silicon substrate 1 with a thermal oxide film 2 interposed. A fixed electrode 5 and a nitride film 6 are formed on the movable electrode 3 via a spacer 4, and a through hole 7 is formed in the fixed electrode 5.

  In the MEMS element shown in FIG. 10, the volume of the back chamber is increased by removing the silicon substrate 1 stepwise (Patent Document 1). Further, the volume of the back chamber can be further increased by increasing the number of stages.

  By the way, when forming such a step-like back chamber, it is necessary to repeat the formation of the etching mask and the etching process a plurality of times. A specific manufacturing process is shown in FIG. First, after forming the thermal oxide film 2, the movable electrode 3, the fixed electrode 5, etc. on the surface side of the silicon substrate 1, the first mask film 9 a used when etching the silicon substrate 1 on the back side of the silicon substrate 1. And a second mask film 9b. The first mask film 9a and the second mask film 9b are a combination of films that can be selectively removed. Specifically, the first mask film 9a is a metal film, and the second mask film 9b is a photoresist. Next, using the second mask film 9b as an etching mask, the exposed surface of the silicon substrate 1 is anisotropically etched by the RIE method. As a result, a first recess 10a is formed as shown in FIG.

  The second mask film 9b is selectively removed to expose the first mask film 9a. The first mask film 9a is patterned so as to open at a position recessed from the second mask film 9a, and a part of the back surface side of the silicon substrate 1 remaining without being etched is exposed ( FIG. 11b).

  Thereafter, using the first mask film 9a as an etching mask, the exposed surface of the silicon substrate 1 is anisotropically etched by RIE to expose the thermal oxide film 2. As a result, as shown in FIG. 11C, a first recess 10a and a second recess 10b are formed, and a stepped back chamber is formed. Here, when a back chamber having a larger number of stages is formed, the formation of the etching mask and the etching are repeated.

  Thereafter, a part of the spacer film 4a is removed from the through hole 7, whereby the MEMS element shown in FIG. 10 can be formed.

JP 2008-17395 A

  By the way, the conventionally proposed method has a problem that it is necessary to repeat the formation and etching of the etching mask when forming the back chamber, and the manufacturing process becomes long. In order to solve such a problem, an object of the present invention is to provide a MEMS device capable of increasing the volume of a back chamber without an additional manufacturing process.

  In order to achieve the above object, the invention according to claim 1 of the present application is such that the movable electrode is exposed in a MEMS element in which a fixed electrode and a movable electrode are arranged opposite to each other with a spacer interposed on a substrate having a back chamber. A first back chamber part from which the substrate has been removed, an electrode support part that partitions the first back chamber part and supports the fixed electrode and the movable electrode via the spacer, and the electrode support part A second back chamber part from which the substrate has been removed so as to partition, and a communication part in which the first back chamber part and the second back chamber part are continuous. .

  The invention according to claim 2 of the present application is the MEMS device according to claim 1, further comprising a space from which the spacer is removed on the second back chamber portion, the space being continuous with the second back chamber portion. It is characterized by that.

  According to a third aspect of the present invention, there is provided a method for manufacturing a MEMS device in which a fixed electrode and a movable electrode are arranged opposite to each other with a spacer interposed therebetween on a substrate having a back chamber, and a first insulating film is formed on the substrate. A step of forming a movable electrode on the first insulating film, a step of forming a second insulating film constituting the spacer on the movable electrode, and on the second insulating film In addition, a step of forming a fixed electrode, a step of forming a through hole in the fixed electrode, a first back chamber portion for removing a part of the substrate and exposing the movable electrode, and the spacer Forming a second back chamber section that partitions an electrode support section that supports the fixed electrode and the movable electrode, and a communication section that connects the first back chamber section and the second back chamber section; , Some from the hole of the second insulating film is removed by etching, characterized in that it comprises a step of forming a spacer of the second insulating film on the electrode support.

  According to a fourth aspect of the present invention, in the method of manufacturing a MEMS element according to the third aspect, when the spacer is formed, the second insulating film on the second back chamber is removed by etching, and the removal is performed. The method includes a step of continuing the formed space and the second back chamber portion.

  The MEMS element of the present invention has a structure in which the first back chamber portion, the second back chamber portion, and the communication portion can be formed only by forming an etching mask once and etching, and an additional manufacturing process. Without this, the volume of the back chamber can be increased.

  In addition, the MEMS element of the present invention can set the movable area of the movable electrode to an arbitrary size by the electrode support portion, and can appropriately set the size of the second back chamber portion so that the volume of the back chamber can be increased. There is also an advantage that can be enlarged in a desired size.

  Furthermore, the spacer is removed from the second back chamber portion of the MEMS element of the present invention, and the volume communicating with the back chamber is increased, so that the sensitivity of the MEMS element is improved.

It is a top view of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is explanatory drawing of the back chamber part of the MEMS element of this invention. It is a figure explaining the manufacturing process of the MEMS element of this invention. It is explanatory drawing of the back chamber part of the MEMS element of this invention. It is explanatory drawing of the conventional MEMS element. It is a figure explaining the manufacturing process of the back chamber of the conventional MEMS element.

  In the MEMS element of the present invention, the first back chamber part from which the substrate is removed is formed so that the movable electrode is exposed to the substrate side, and the movable electrode, the spacer, and the fixed electrode are laminated on the outer side of the substrate. And the second back chamber part from which the substrate is removed is formed on the outer side of the electrode support part, and the first back chamber part and the second back chamber part are continuous with each other. A communication part is formed in the. The communication portion is formed by removing the substrate. The first back chamber portion and the second back chamber portion according to the present invention have side walls formed substantially vertically, and can be formed in the same manner as a general back chamber.

  Furthermore, the MEMS element of the present invention can have a structure in which the spacer disposed on the second back chamber portion is removed. Examples of the present invention will be described in detail below.

  The embodiment of the present invention will be described in detail by taking a condenser microphone as an example. FIG. 1 is a plan view of the MEMS element of this embodiment, and cross-sectional views of the AA plane are shown in FIGS. 2 to 6 and FIG. In FIG. 1, the silicon substrate in a region surrounded by a dotted line is removed, and the first back chamber portion 11, the second back chamber portion 12, the first back chamber portion 11 and the second back chamber portion 12 are continuously connected. A communicating portion 13 is formed. Between the first back chamber portion 11 and the second back chamber portion 12, an electrode support portion 14 in which the silicon substrate remains is formed.

  Hereinafter, it demonstrates according to a manufacturing process. First, a thermal oxide film 2 (corresponding to a first insulating film) having a thickness of about 0.5 μm is formed on a silicon substrate 1 having a (100) plane crystal orientation. Further, a conductive polysilicon film having a thickness of 0.5 μm is laminated and formed on the thermal oxide film 2 on the surface side by a CVD (Chemical Vapor Deposition) method. Next, patterning is performed by a normal photolithographic method to form the movable electrode 3 serving as a movable portion (FIG. 2). A slit may be formed in the movable electrode 13 for stress relaxation.

  On the movable electrode 3, a spacer film 4a (corresponding to a second insulating film) made of a USG (Undoped Silicate Glass) film having a thickness of about 3 μm is laminated (FIG. 3). The spacer film 4a is partially removed to form an air gap, and the remaining portion becomes a spacer.

  A polysilicon film having a thickness of 0.1 μm is formed on the spacer film 4a, and predetermined patterning is performed to form the fixed electrode 5 (FIG. 4). A wiring portion 15 shown in FIG. 1 is formed on the movable electrode 3 and the fixed electrode 5.

  After removing the spacer film 4a on the scribe line, a nitride film 6 is laminated on the entire surface. The nitride film 6 is integrated with the fixed electrode 5 (corresponding to the fixed electrode). The nitride film 6 and a part of the fixed electrode 5 are removed, and a through hole 7 is formed to expose the surface of the spacer film 4a. The through-hole 7 functions as a sound hole for transmitting sound to the movable electrode 3, and the size, number, and arrangement of the diameter are set so as to obtain desired characteristics (FIG. 5).

  Thereafter, in order to form a back chamber, the silicon substrate 1 is etched using an RIE apparatus. The back chamber of the present invention has a structure in which a first back chamber portion 11 that opens the movable electrode 3 and a second back chamber portion 12 on the outside thereof, and the silicon substrate 1 that becomes the electrode support portion 14 remains therebetween. (FIG. 6). FIG. 7 shows a plan view of the silicon substrate 1 on which the first back chamber portion 11 and the second back chamber portion 12 are formed. As shown in FIG. 7, between the first back chamber portion 11 and the second back chamber portion 12, the silicon substrate that becomes the electrode support portion 14 is left, and the movable electrode is supported. Further, a part of the electrode support portion 14 is removed and the communication portion 13 is formed so that the first back chamber portion 11 and the second back chamber portion 12 are continuous.

  Thereafter, in order to form a hollow structure between the movable electrode 3 and the fixed electrode 5, a part of the spacer film 4a is removed by etching to form the spacer 4 (FIG. 8).

  The capacitor microphone, which is a MEMS element formed in this way, detects the displacement between the fixed electrode 5 and the movable electrode 3 as a change in capacitance between the electrodes by the vibration of the movable electrode 3 caused by the sound pressure that has passed through the through hole 7. become. Here, in the present invention, in addition to the first back chamber portion 11 corresponding to the conventional back chamber, a continuous second back chamber portion 12 is formed, and the volume of the back chamber can be increased. A sensitive MEMS element can be formed.

  Further, in the present invention, when a part of the spacer film 4a is etched, the spacer film 4a on the second back chamber portion 12 is also etched away, and a space 16 continuous with the second back chamber portion 12 is formed. The Since this space 16 is also continuous through the first back chamber part 11, the second back chamber part 12 and the communication part 13, it constitutes a part of the back chamber and contributes to the improvement of the sensitivity of the MEMS element. become.

  The shape of the back chamber can be variously changed as shown in FIG. 9 in addition to the structure shown in FIG. In addition, in the right figure of FIG. 9, 17 is a stopper provided in order to prevent the movable electrode 3 from being greatly deformed and damaged.

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to the said Example. For example, in the above embodiment, the communication unit 13 has been described in the case where the silicon substrate 1 is entirely removed by etching, but it is not necessary to completely remove the silicon substrate 1. When the silicon substrate is etched into the structure shown in FIG. 7, even if the etching mask is the structure shown in FIG. 7, if the deep etching corresponding to the thickness of the silicon substrate is performed, the communicating portion 13 is formed. May not be completely removed by etching, and the silicon substrate 1 may remain slightly. In this case, the communication part is constituted by a region where the silicon substrate is removed by etching, and the electrode support part is a silicon substrate remaining in a circular shape. With such a structure, the movable electrode and the fixed electrode are also firmly fixed to the electrode support portion via the spacer even in the communication portion, and there is an advantage that the strength of the movable electrode and the fixed electrode can be maintained.

1: silicon substrate, 2: thermal oxide film, 3: movable electrode, 4: spacer, 4a: spacer film, 5: fixed electrode, 6: nitride film, 7: through-hole, 8: back chamber, 9a: first Mask film, 9b: second mask film, 10a: first recess, 10b: second recess, 11: first back chamber section, 12: second back chamber section, 13: communication section, 14: Electrode support, 15: wiring, 16: space, 17: stopper

Claims (4)

In a MEMS element in which a fixed electrode and a movable electrode are arranged to face each other with a spacer on a substrate provided with a back chamber.
A first back chamber part from which the substrate is removed so that the movable electrode is exposed, and an electrode support that partitions the first back chamber part and supports the fixed electrode and the movable electrode via the spacer And a second back chamber part from which the substrate has been removed so as to partition the electrode support part, and a communication part in which the first back chamber part and the second back chamber part are continued. A MEMS element characterized by comprising: The MEMS device according to claim 1, wherein
A MEMS device comprising a space from which the spacer is removed on the second back chamber portion, the space being continuous with the second back chamber portion. In a method of manufacturing a MEMS element in which a fixed electrode and a movable electrode are arranged to face each other with a spacer interposed therebetween on a substrate provided with a back chamber.
Forming a first insulating film on the substrate;
Forming a movable electrode on the first insulating film;
Forming a second insulating film constituting the spacer on the movable electrode;
Forming a fixed electrode on the second insulating film;
Forming a through hole in the fixed electrode;
A first back chamber part for removing a part of the substrate and exposing the movable electrode; a second back chamber part for partitioning an electrode support part for supporting the fixed electrode and the movable electrode through the spacer; Forming a communication part that connects the first back chamber part and the second back chamber part;
And a step of etching away a part of the second insulating film from the through-hole and forming a spacer made of the second insulating film on the electrode support portion. .   4. The method of manufacturing a MEMS device according to claim 3, wherein when the spacer is formed, the second insulating film on the second back chamber is removed by etching, and the removed space and the second back are removed. A method of manufacturing a MEMS device, comprising a step of making a chamber portion continuous.

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