JP6852569B2 - MEMS elements, electronics and mobiles - Google Patents

Description

The present invention relates to a MEMS element, an electronic device including a MEMS element, and a mobile body.

Conventionally, a MEMS oscillator in which a working element is formed on a silicon substrate by using MEMS technology is known. For example, in Patent Document 1 below, the working space (internal space) of a working element of a silicon substrate on which a working element is formed is also formed of a silicon substrate, and a through silicon via (TSV: Through Silicon Via) for external connection is provided. Disclosed is a method of manufacturing a MEMS transducer by joining a lid substrate provided with a silicon wafer, vacuum-sealing (vacuum-sealing), and individualizing the lid substrate.

Japanese Unexamined Patent Publication No. 2016-171393

However, in the MEMS vibrator described in Patent Document 1, in order to vacuum-seal the working space, an advanced processing method for processing the joint surface of the lid substrate provided with the through-hole electrode into a uniform surface without unevenness is used. There was a problem that it was necessary.
Further, in order to seal the silicon substrate and the lid substrate together in a vacuum atmosphere (vacuum atmosphere), there is a problem that the technical difficulty is high, the apparatus becomes large, and the manufacturing cost is high.

The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following application example or form.

[Application Example 1] The MEMS element according to the present application example is provided with an element having a movable portion and a base portion in a cavity composed of a substrate and a lid portion, and the substrate is used to drive the element. Two through electrodes connected to the element electrodes of the above, a through hole penetrating the substrate, and a sealing film for sealing the through hole are arranged, and the through hole is formed with respect to the base portion in a plan view. It is characterized in that it is arranged on the side facing the movable portion.

According to this application example, the inside of the cavity containing the element can be easily airtightly sealed by sealing the through hole communicating with the cavity composed of the substrate and the lid with a sealing film. it can. Therefore, it is possible to obtain a highly reliable MEMS element without requiring an advanced processing method. Further, since the through hole for sealing is arranged on the side facing the movable portion with respect to the base portion of the element, when sealing the through hole, the sealing film enters the cavity and the movable portion of the element is formed. It is possible to reduce the amount of adhesion to the device, and it is possible to obtain a MEMS device having stable characteristics. Further, since the through hole is provided near the base, the vibration of the movable part is alleviated by the through hole, and the vibration of the movable part can be reduced from leaking to the entire substrate, and has a high Q value. A MEMS element can be obtained.

[Application Example 2] In the MEMS element described in the above application example, the joint surface between the lid portion and the substrate has a plurality of corner portions, and the two through electrodes face each other in a plan view. Each is arranged in a part of the region in contact with the corner portion, and the through hole is arranged in a part of the region in contact with the corner portion other than the two corner portions in which the two through electrodes are arranged in a plan view. It is preferable that it is provided.

According to this application example, since the through holes are arranged in a part of the region in contact with the corners other than the two corners where the two through electrodes are arranged, that is, the through holes are arranged in the two through electrodes. Since it is arranged at a position away from the through hole, the insulation resistance value generated when the sealing film for sealing the through hole adheres to the wiring or electrode pad connected to the through electrode arranged in the cavity. Fluctuations can be reduced. Therefore, a MEMS device having stable characteristics can be obtained.

[Application Example 3] In the MEMS device described in the above application example, the through hole is composed of a first hole portion and a second hole portion, and the opening width of the second hole portion is the first hole portion. It is narrower than the opening width of the hole portion, and the communication portion between the first hole portion and the second hole portion is sealed by the sealing film disposed on the first hole portion side. Is preferable.

According to this application example, since the opening width of the second hole portion is narrower than the opening width of the first hole portion, the sealing film disposed on the first hole portion side can be used to obtain the first hole portion. The communication portion with the second hole portion is closed, and the inside of the cavity containing the element can be easily airtightly sealed.

[Application Example 4] In the MEMS element described in the above application example, it is preferable that the element is an oscillator.

According to this application example, since the element is an oscillator, the influence of disturbance can be reduced by airtightly sealing the inside of the cavity containing the oscillator, so that an oscillator having stable characteristics can be obtained. Obtainable.

[Application Example 5] The electronic device according to the present application example is characterized by including the MEMS element described in the above application example.

According to this application example, it is possible to provide a higher performance electronic device by utilizing a highly reliable MEMS element for the electronic device.

[Application Example 6] The moving body according to the present application example is characterized by including the MEMS element described in the above application example.

According to this application example, it is possible to provide a mobile body with higher performance by utilizing a MEMS element having excellent reliability for the moving body.

The schematic plan view which shows the structure of the MEMS element which concerns on 1st Embodiment. FIG. 6 is a schematic cross-sectional view taken along the line P1-P1 of FIG. The enlarged view which shows the Q1 part of FIG. 2A. The enlarged view which shows the Q2 part of FIG. 2A. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the manufacturing process of the MEMS element which concerns on this embodiment. The schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 which shows the structure of the MEMS element which concerns on 2nd Embodiment. The perspective view which shows the structure of the mobile type (or notebook type) personal computer as the electronic device which comprises the MEMS element of this invention. The perspective view which shows the structure of the mobile phone as the electronic device which comprises the MEMS element of this invention. The perspective view which shows the structure of the digital camera as the electronic device which comprises the MEMS element of this invention. The perspective view which shows the structure of the automobile as a moving body provided with the MEMS element of this invention.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. The following is an embodiment of the present invention and does not limit the present invention. In addition, in each of the following figures, in order to make the explanation easy to understand, it may be described on a scale different from the actual one.

(First Embodiment)
[MEMS element]
First, the MEMS element 1 according to the first embodiment will be described with reference to FIGS. 1, 2A, 2B, and 2C.
FIG. 1 is a schematic plan view showing the configuration of the MEMS element 1 according to the first embodiment, FIG. 2A is a schematic sectional view taken along line P1-P1 shown in FIG. 1, and FIG. 2B is Q1 of FIG. 2A. It is an enlarged view of the part, and FIG. 2C is an enlarged view of the Q2 part of FIG. 2A. Note that FIG. 1 illustrates a state in which the lid 5 is removed for convenience of explaining the internal configuration of the MEMS element 1. Further, in FIGS. 2A, 2B and 2C, the line indicating the background of the cross section is omitted.

As shown in FIGS. 1, 2A, 2B and 2C, the MEMS element 1 according to the present embodiment has a lid 5 for airtightly sealing the element 20 and an SOI (Silicon on) on which the element 20 is formed. Insulator) The substrate 10 and the like are included in the configuration. In this embodiment, the SOI substrate 10 corresponds to a substrate.
The lid portion 5 is made of single crystal silicon or the like, and has a cavity 7 that opens on the SOI substrate 10 side. The surface of the lid 5 on the side where the cavity 7 is provided is joined to the surface of the SOI substrate 10 on the side where the element 20 is formed. Further, the joint surface 3 between the lid portion 5 and the SOI substrate 10 (surface silicon layer 13) has four corner portions 3a, 3b, 3c, and 3d.

The SOI substrate 10 is a substrate in which a silicon layer 11, a BOX (Buried Oxide) layer 12, and a surface silicon layer 13 are laminated in this order. For example, the silicon layer 11 and the surface silicon layer 13 are composed of single crystal silicon, and the BOX layer 12 is composed of a _{silicon oxide layer (SiO 2 and the like).} In the present embodiment, the silicon layer 11 and the BOX layer 12 correspond to a support substrate, and the surface silicon layer 13 corresponds to an element substrate.

The element 20 made of silicon on the surface silicon layer 13, the electrode pad 50 formed on the surface silicon layer 13, and the element electrode and the electrode pad 50 for driving the element 20 are connected to the SOI substrate 10. The wiring 46 (see FIG. 2A, not shown in FIG. 1), the through electrode 59 that connects to the electrode pad 50 and pulls out the electrode on the surface opposite to the side on which the element 20 is formed, and the through electrode 59. It is composed of an electrode through hole 52 composed of a first through hole 54 and a second through hole 55 for forming, a cavity 7 of the lid portion 5, and a cavity 8 formed in the SOI substrate 10. A through hole 60 composed of a first hole 62 and a second hole 64 for airtightly sealing the internal space to be formed, and the cavities 7 and 8 are air-sealed by closing the second hole 64. A sealing film 56a for stopping is provided.

The element 20 has a base portion 21 supported by the BOX layer 12 and a movable portion 22 separated from surrounding silicon other than the base portion 21 by a groove 13a on the region from which the BOX layer 12 has been removed. The element 20 illustrated in this embodiment has three movable parts 22. The silicon layer 11 and the BOX layer 12 at positions facing the movable portion 22 are provided with cavities 8 forming an internal space. Therefore, the element 20 having the movable portion 22 and the base portion 21 is provided in the cavities 7 and 8 composed of the SOI substrate 10 and the lid portion 5.
Further, on the surface of the element 20 on the lid 5 side, an element adjustment layer 30 which is a silicon oxide film arranged in a predetermined region of the element 20 and a piezoelectric drive unit 40 which covers at least a part of the element adjustment layer 30. And are provided.

The element adjusting layer 30 is provided to correct the temperature characteristic of the resonance frequency of the movable portion 22. Silicon has a resonance frequency that decreases as the temperature rises, while silicon oxide film has a resonance frequency that rises as the temperature rises. Therefore, by disposing the element adjustment layer 30 which is a silicon oxide film on the silicon element 20, the temperature characteristic of the resonance frequency of the composite composed of the movable portion 22 of the element 20 and the element adjustment layer 30 is flattened. Can be approached to.

The piezoelectric drive unit 40 includes a polysilicon film 41, a first electrode 42, a piezoelectric layer 43, and a second electrode 44. In this embodiment, the first electrode 42 and the second electrode 44 correspond to element electrodes.
The polysilicon film 41 is made of polysilicon that is not doped with impurities, and may be made of amorphous silicon, for example. In the present embodiment, the polysilicon film 41 is provided so as to cover the element adjusting layer 30 arranged on the element 20. By having the element adjusting layer 30 between the polysilicon film 41 and the element 20 in this way, the polysilicon film 41 protects the element adjusting layer 30 from the etching of the silicon oxide film around the piezoelectric drive unit 40. be able to.

The first electrode 42 and the second electrode 44 are arranged so as to sandwich the piezoelectric layer 43. In the example shown in this embodiment, three sets of the first electrode 42, the piezoelectric layer 43, and the second electrode 44 are arranged corresponding to the three movable portions 22.

The wiring 46 is electrically connected to the first electrode 42 and the second electrode 44 so as to vibrate the adjacent movable portions 22 in opposite phases. Further, the plurality of wires are electrically connected to the electrode pads 50, and by applying a voltage from the outside via the through electrodes 59 between the two electrode pads 50, the adjacent movable portions 22 vibrate in opposite phases. Can be made to.

When a voltage is applied between the first electrode 42 and the second electrode 44 via the two electrode pads 50, the piezoelectric layer 43 expands and contracts, causing the movable portion 22 to vibrate. The vibration direction of the movable portion 22 is a direction that intersects the plan view, and when the central movable portion 22 is displaced in the lid portion 5 direction in the three movable portions 22, the movable portions 22 at both ends are formed by the silicon layer 11. When the central movable portion 22 is displaced in the direction of the silicon layer 11, the movable portions 22 at both ends are displaced in the lid portion 5 direction. Therefore, the element 20 illustrated in this embodiment is an oscillator in which adjacent movable portions 22 vibrate in opposite phases. The vibration is greatly excited at the inherent resonance frequency and the impedance is minimized. As a result, by connecting the MEMS element 1 to the oscillation circuit, it oscillates at an oscillation frequency mainly determined by the resonance frequency of the movable portion 22.

As materials constituting these, for example, the piezoelectric layer 43 is made of aluminum nitride (AlN) or the like, and the first electrode 42 and the second electrode 44 are made of titanium nitride (TiN) or the like. , The wiring 46 and the electrode pad 50 are made of aluminum (Al), copper (Cu), or the like.

The through electrode 59 is arranged in the through hole 52 for the electrode, and is configured by laminating the electrode layer 56 and the electrode layer 58. As shown in FIG. 1, the two through electrodes 59 are a part of a region of the cavity 7 of the lid portion 5 in a plan view, each of which is in contact with two corner portions 3a and 3c facing each other with the element 20 interposed therebetween. That is, one through electrode 59 is arranged in a region closer to the corner 3a than the element 20, and the other through electrode 59 is arranged in a region closer to the corner 3c than the element 20.
The electrode through holes 52 in which the through electrodes 59 are arranged are formed in the silicon layer 11 corresponding to the support substrate, the first through holes 54 arranged in the BOX layer 12, and the surface silicon layer 13 corresponding to the element substrate. It is composed of a second through hole 55 arranged, and the first through hole 54 and the second through hole 55 communicate with each other.

The electrode pad 50 is arranged at a position overlapping the through electrode 59 in a plan view, and at the position overlapping with the through electrode 59, the through electrode 59 arranged in the through hole 52 for the electrode and the wiring 46 are interposed. It is arranged so as to be electrically connected, and at a position where it does not overlap with the through electrode 59, it is arranged on the surface silicon layer 13 via the element adjusting layer 30, the polysilicon film 41, and the wiring 46. Therefore, the electrode pad 50 and the through electrode 59 are electrically connected, and the first electrode 42 and the second electrode 44, which are element electrodes, are on the side opposite to the side on which the element 20 of the SOI substrate 10 is formed. Can be pulled out to the surface of.

The material constituting the through electrode 59 is made of titanium (Ti), tungsten (W), copper (Cu), or the like, and the electrode layer 56 is a sputtered layer formed by a sputtering method, and the electrode layer 58. Is a plating layer formed by a plating method, and a plating layer (electrode layer 58) is laminated on a sputtering layer (electrode layer 56).

As shown in FIG. 1, the through hole 60 is formed in a corner portion 3b other than the two corner portions 3a and 3c in which the two through electrodes 59 are arranged in the region of the cavity 7 of the lid portion 5 in a plan view. It is arranged in a part of the contact area. That is, it is arranged in a region closer to the corner portion 3b than the element 20 on the side of the base portion 21 facing the side where the movable portion 22 is provided. Further, the through holes 60 are the first hole 62 arranged in the silicon layer 11 and the BOX layer 12 corresponding to the support substrate, and the second hole arranged in the surface silicon layer 13 corresponding to the element substrate. It is composed of a portion 64, and the first hole portion 62 and the second hole portion 64 communicate with each other.

A plurality of the second hole portions 64 are arranged at positions where the opening width W2 is narrower than the opening width W1 of the first hole portion 62 and overlaps with the first hole portion 62. In the present embodiment, since the shape of the second hole 64 is rectangular, the one having the shorter opening width is defined as the opening width W2. Further, the communication portion 66 (see FIG. 2C) between the first hole portion 62 and the second hole portion 64 is made of the same metal as the sealing film 56a, that is, the electrode layer 56 forming a part of the through electrode 59. The layer is arranged, and the internal space composed of the cavity 7 of the lid portion 5 and the cavity 8 formed in the SOI substrate 10 is airtightly sealed.
In the first hole 62, an electrode layer 56 (sealing film 56a) made of a sputter layer is arranged, and an electrode layer 58 made of a plating layer laminated on the electrode layer 56 is arranged. In the present embodiment, two second hole portions 64 are arranged, but the present invention is not limited to this, and any one or more may be provided.

As described above, according to the MEMS element 1 according to the present embodiment, the through hole 60 communicating with the cavities 7 and 8 composed of the SOI substrate 10 and the lid portion 5 is sealed with the sealing film 56a. As a result, the inside of the cavities 7 and 8 containing the element 20 can be easily airtightly sealed. Therefore, the MEMS element 1 having excellent reliability can be obtained without requiring an advanced processing method. Further, since the through hole 60 for sealing is arranged on the side facing the movable portion 22 with respect to the base 21 of the element 20, when the through hole 60 is sealed, the sealing film 56a is formed in the cavity 7. , 8 can be reduced from adhering to the movable portion 22 of the element 20, and the MEMS element 1 having stable characteristics can be obtained. Further, since the through hole 60 is arranged near the base portion 21, the vibration of the movable portion 22 is alleviated by the through hole 60, and the vibration of the movable portion 22 can be reduced from leaking to the entire SOI substrate 10. It is possible to obtain a MEMS element 1 having a high Q value.

Further, since the through hole 60 is arranged close to the corner 3b other than the two corners 3a and 3c where the two through electrodes 59 are close to each other, that is, the through hole 60 is separated from the two through electrodes 59. Since it is arranged at a vertical position, the sealing film 56a for sealing the through hole 60 adheres to the wiring 46 and the electrode pad 50 connected to the through electrodes 59 arranged in the cavities 7 and 8. It is possible to reduce the fluctuation of the insulation resistance value caused by this. Therefore, the MEMS element 1 having stable characteristics can be obtained.

Further, since the opening width W2 of the second hole portion 64 is narrower than the opening width W1 of the first hole portion 62, the first hole portion is provided by the sealing film 56a arranged on the first hole portion 62 side. The communication portion 66 between the 62 and the second hole portion 64 is closed, and the inside of the cavities 7 and 8 containing the element 20 can be easily airtightly sealed.

Further, since the element 20 is an oscillator, the influence of disturbance can be reduced by airtightly sealing the insides of the cavities 7 and 8 containing the oscillator, so that an oscillator having stable characteristics can be obtained. be able to.

[Production method]
Next, the manufacturing process of the MEMS element 1 according to the present embodiment will be described with reference to FIGS. 3A to 3Q.
3A to 3Q are schematic cross-sectional views corresponding to the positions of lines P1-P1 of FIG. 1 showing the manufacturing process of the MEMS element 1 according to the present embodiment. The line indicating the background of the cross section is omitted.

First, as a preparatory step, a lid portion 5 having an SOI substrate 10 and a cavity 7 in which a silicon layer 11, a BOX layer 12, and a surface silicon layer 13 are laminated in this order is prepared (see FIG. 2A). The SOI substrate 10 may be manufactured by forming the BOX layer 12 on the silicon layer 11 and forming the surface silicon layer 13 on the BOX layer 12.

In the first step, as shown in FIG. 3A, a trench in the surface silicon layer 13 of the SOI substrate 10 that separates the region serving as the movable portion 22 of the element 20 from the surrounding silicon other than the region serving as the base 21 of the element 20. 13b and the second hole 64 are formed. At that time, the slit 13c may be formed in the region separated from the movable portion 22 of the element 20 by the trench 13b of the surface silicon layer 13 of the SOI substrate 10. Thereby, in the wide region of the groove 13a (see FIG. 1), it is possible to facilitate the release etching of the silicon around the movable portion 22 which is performed later.

The trench 13b and the second hole 64 are formed by applying a resist 14 on the surface silicon layer 13, forming a mask pattern by a photolithography method, and etching the surface silicon layer 13 using the resist 14 as a mask. As shown in FIG. 3A, a trench 13b and a second hole portion 64 are formed in the surface silicon layer 13 to separate the region serving as the movable portion 22 of the element 20 from the surrounding silicon other than the region serving as the base portion 21 of the element 20. To do. A silicon oxide film is formed by thermally oxidizing the surface of the surface silicon layer 13 of the SOI substrate 10, a mask made of the silicon oxide film is formed by a photolithography method, and the surface silicon layer 13 is etched to form a trench. 13b and the second hole 64 may be formed.

In the second step, as shown in FIG. 3B, the element adjusting layer 30 which is a silicon oxide film is formed on the upper surface of the surface silicon layer 13, the side wall in the trench 13b, and the side wall in the second hole 64. For example, by thermally oxidizing the surface silicon layer 13 of the SOI substrate 10, a thermal oxide film (silicon oxide film) is formed on the upper surface of the surface silicon layer 13, the side wall in the trench 13b, and the side wall in the second hole 64. It is formed. The thickness of the thermal oxide film is, for example, about 0.3 μm to 1.2 μm, and may be adjusted according to desired temperature characteristics. This thermal oxide film serves as a protective wall that protects the movable portion 22 and the piezoelectric drive portion 40 from the release etching of silicon around the movable portion 22 that is performed later.

Next, a silicon oxide film that fills the trench 13b of the surface silicon layer 13 and the second hole 64 is formed by a CVD (chemical vapor deposition) method. At that time, even if "su" is generated in the silicon oxide film in the trench 13b and the second hole 64, there is no problem because the thermal oxide film is strong. Further, since the trench 13b and the second hole 64 of the surface silicon layer 13 formed by the processing are filled with the silicon oxide film to make the surface substantially flat, the adverse effect due to the step on the subsequent photolithography process is eliminated. can do.

Therefore, the thermal oxide film formed by thermally oxidizing the surface silicon layer 13 and the silicon oxide film formed by the CVD method form the element adjusting layer 30 shown in FIG. 2A. In the second step, the element adjusting layer 30 may be formed only of the thermal oxide film depending on the degree of flatness. Alternatively, a silicon oxide film may be formed by a thermal CVD method without forming a thermal oxide film, or further, a silicon oxide film may be formed by a two-step CVD method of a thermal CVD method and a plasma CVD method. You may.

In the third step, a resist is applied on the element adjusting layer 30, and a mask pattern that protects a predetermined region such as the element 20 including the second hole portion 64 and the movable portion 22 is formed by a photolithography method. By etching the element adjusting layer 30 with the resist as a mask, a trench reaching the surface silicon layer 13 is formed. After that, as shown in FIG. 3C, a polysilicon film 41 covering the upper surface of the element adjusting layer 30 and the side wall of the trench is formed by the CVD method.

In the fourth step, a resist is applied onto the polysilicon film 41, a mask pattern is formed by a photolithography method, and the polysilicon film 41 is etched using the resist as a mask. As a result, as shown in FIG. 3D, the polysilicon film 41 is formed in the region including the side surface of the element adjusting layer 30 formed in the predetermined region of the element 20 including the movable portion 22.

The polysilicon film 41 covers the element adjusting layer 30 with the element 20, and the thickness of the polysilicon film 41 is, for example, about 0.2 μm. Since the polysilicon film 41 has good embedding property by the CVD method, the wall of the polysilicon film 41 that protects the element adjusting layer 30 from the release etching of the silicon oxide film around the movable portion 22 and the piezoelectric drive portion 40 that is performed later. Can be formed with a small thickness.

In the fifth step, as shown in FIG. 3E, the first electrode 42, the piezoelectric layer 43, and the second electrode 44 are placed in this order on the polysilicon film 41 formed in the predetermined region of the element 20. It is formed by the photolithography method. The polysilicon films 41 to 2nd electrodes 44 form a piezoelectric drive unit 40. Further, when forming the first electrode 42 and the second electrode 44, the wiring 46 for connecting the first electrode 42 and the electrode pad 50 and the second electrode 44 and the electrode pad 50 are connected. Wiring 46 for the purpose is also formed at the same time.

In the sixth step, the silicon oxide film 33 is formed by the CVD method on the SOI substrate 10 on which the piezoelectric driving unit 40 is formed. After that, as shown in FIG. 3F, a mask pattern in which the position where the electrode pad 50 is formed is opened is formed by a photolithography method, and aluminum (Al) or copper (Cu) or the like is formed by a sputtering method using the silicon oxide film 33 as a mask. A film is formed at a position where the electrode pad 50 is formed, and the electrode pad 50 is formed.

In the seventh step, as shown in FIG. 3G, the silicon oxide film 34 is formed on the SOI substrate 10 on which the electrode pad 50 and the silicon oxide film 33 are formed by the CVD method. Then, a resist is applied onto the silicon oxide film 34, a mask pattern is formed by a photolithography method, and the silicon oxide film 34 is etched using the resist as a mask. As a result, as shown in FIG. 3G, a silicon oxide film 34 in which a predetermined region corresponding to the trench 13b reaching the surface silicon layer 13 opens is formed.

In the eighth step, as shown in FIG. 3H, a resist 16 is applied onto the silicon oxide film 34, a mask pattern is formed by a photolithography method, and the resist 16 is used as a mask to form a silicon oxide film 34 corresponding to the trench 13b. , The element adjustment layer 30 and the BOX layer 12 are etched in this order. As a result, the depth reaches the silicon layer 11 in a shape that surrounds the movable portion 22 while leaving the silicon oxide film 34 and the element adjusting layer 30 that protect the movable portion 22, the piezoelectric drive portion 40, and the electrode pad 50. Form an opening.

In the ninth step, as shown in FIG. 3I, after the resist 16 is peeled off, the silicon around the movable portion 22 is removed through the openings of the silicon oxide film 34, the element adjusting layer 30, the surface silicon layer 13 and the BOX layer 12. Etch (release etching). At that time, a part of the silicon of the silicon layer 11 is etched to form the cavity 8 in the silicon layer 11 below the movable portion 22. In the ninth step, wet etching is performed, and as the etching solution, for example, TMAH (tetramethylammonium hydroxide) is used.

In the tenth step, as shown in FIG. 3J, the movable portion 22, the piezoelectric drive portion 40, the electrode pad 50, the silicon oxide film 34 around the second hole portion 64, the element adjusting layer 30, and the BOX layer 12 are etched. Be done (release etching). As a result, the element adjusting layer 30 remains on the movable portion 22. In the tenth step, wet etching is performed, and as the etching solution, for example, BHF (buffered hydrofluoric acid) is used. After that, the surface of the SOI substrate 10 having the cavity 7 of the lid 5 is arranged on the surface (upper surface of the surface silicon layer 13) on which the element 20 is formed, and the surface is joined. As the joining method, direct joining performed by activating the joining surface 3, a method using a joining member such as low melting point glass, an anode joining, or the like may be used.

In the eleventh step, as shown in FIG. 3K, the first through hole 54 and the first hole portion 62 are formed in the silicon layer 11 and the BOX layer 12 of the SOI substrate 10. The first through hole 54 and the first hole portion 62 are formed by forming the mask layer 36 for etching and then etching the silicon layer 11 of the SOI substrate 10 by a photolithography method. A resist film is used as the mask layer 36, but a silicon oxide film obtained by thermally oxidizing the surface of the silicon layer 11 may also be used.

In the twelfth step, as shown in FIG. 3L, the film resist 18 is attached onto the mask layer 36, a pattern for opening the first through hole 54 is formed by a photolithography method, and the surface silicon layer 13 is etched. , A second through hole 55 is formed.

In the thirteenth step, as shown in FIG. 3M, after removing the film resist 18 and the mask layer 36, the element adjusting layer 30 exposed in the second through hole 55 and the second hole portion 64 is etched.

In the 14th step, as shown in FIG. 3N, the surface of the silicon layer 11 and the first through hole 54, the second through hole 55, the first hole 62 and the second hole 64 are subjected to the CVD method. A silicon oxide film 32 is formed on the inner side wall. Then, the silicon oxide film 32 formed on the polysilicon film 41 of the second through hole 55 and the second hole 64 is removed by anisotropic dry etching such as reactive ion etching (RIE).

In the fifteenth step, as shown in FIG. 3O, the polysilicon film 41 exposed in the second through hole 55 and the second hole portion 64 is formed in a vacuum (decompression) atmosphere in a pretreatment chamber such as a sputtering apparatus. Etching is performed to create through holes in the polysilicon film 41 on the second through hole 55 and the second hole portion 64. After that, the internal space composed of the cavities 7 and 8 is set to the same pressure as the pretreatment chamber, and a metal layer such as titanium (Ti), tungsten (W), or copper (Cu) that becomes the electrode layer 56 by continuous treatment is applied. Sputter.

By this step, an electrode layer 56 that is a part of the through electrode 59 connected to the first electrode 42 and the second electrode 44 can be formed on the surface opposite to the side on which the element 20 is formed. .. Further, in this step, the electrode layer 56 acts as a sealing film 56a to close the second hole 64, so that the internal space formed by the cavities 7 and 8 in which the element 20 is formed is created in a vacuum atmosphere. It can be sealed in a reduced pressure atmosphere). Therefore, the step of forming the electrode layer 56 to be a part of the through electrode 59 in the first through hole 54 and the second through hole 55 and the second hole portion 64 are closed by using the electrode layer 56 as the sealing film 56a. The step of airtightly sealing the internal space can be performed at the same time.

In the 16th step, as shown in FIG. 3P, a metal layer equivalent to the metal layer used for the electrode layer 56 is laminated on the surface of the electrode layer 56 which is a part of the through electrode 59 by a plating method or the like, and the through electrode 59 is formed. The electrode layer 58 to be a part of the above is created. By completely closing the first through hole 54, the second through hole 55, and the first hole 62, the conductivity and mechanical strength are improved, and the reliability is improved. It can be said that the electrode layer 56 is a sputter layer and the electrode layer 58 is a plating layer.

In the 17th step, as shown in FIG. 3Q, the surface of the SOI substrate 10 opposite to the surface to which the lid 5 is joined is flattened by a polishing device or the like, so that the MEMS element has excellent reliability. 1 is completed.

(Second Embodiment)
[MEMS element]
Next, the MEMS element 1a according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a schematic cross-sectional view corresponding to the position of the P1-P1 line of FIG. 1 showing the configuration of the MEMS element 1a according to the second embodiment. The differences from the above-described embodiments will be mainly described, and the same reference numerals are given to the same configurations, and the description thereof will be omitted for the same matters.

Compared with the MEMS element 1 according to the first embodiment, the MEMS element 1a according to the second embodiment has a first through hole 54a forming a through hole 52a for an electrode and a first hole portion forming a through hole 60a. The structure is different from that of 62a.
In the MEMS element 1a of the present embodiment, as shown in FIG. 4, the first through hole 54a and the first hole 62a arranged in the silicon layer 11 and the BOX layer 12 are the silicon layer 11 and the BOX layer 12. It has a tapered portion that extends toward a surface facing the surface that supports the surface silicon layer 13. In the present embodiment, the tapered portion is provided on the silicon layer 11 and the BOX layer 12, but the silicon layer 11 alone may be used. Further, it may be provided from the middle of the silicon layer 11.

As described above, according to the MEMS element 1a according to the present embodiment, since the first through hole 54a has a tapered portion extending toward the surface facing the surface silicon layer 13, the electrode pad 50 and the electrode pad 50 are used. The electrode layer 56 can be easily arranged on the wiring 46 to be connected. Further, since the first hole portion 62a has a similar tapered portion, the electrode layer 56 serving as the sealing film 56a that closes the second hole portion 64 can be reached and sealed easily.

[Electronics]
Next, an electronic device to which the MEMS elements 1 and 1a according to the embodiment of the present invention are applied will be described with reference to FIGS. 5, 6 and 7. In the following, a configuration to which the MEMS element 1 is applied will be described as an example.

FIG. 5 is a perspective view showing an outline of the configuration of a mobile (or notebook) personal computer as an electronic device including the MEMS element 1 according to the present embodiment. In this figure, the personal computer 1100 is composed of a main body 1104 having a keyboard 1102 and a display unit 1106 having a display 1000, and the display unit 1106 rotates with respect to the main body 1104 via a hinge structure. It is supported as much as possible. Such a personal computer 1100 has a built-in MEMS element 1 that functions as a reference clock or the like.

FIG. 6 is a perspective view showing an outline of the configuration of a mobile phone (including a PHS (Personal Handyhone System) and a smartphone) as an electronic device including the MEMS element 1 according to the embodiment of the present invention. In this figure, the mobile phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and a display 1000 is arranged between the operation button 1202 and the earpiece 1204. Such a mobile phone 1200 has a built-in MEMS element 1 that functions as a reference clock or the like.

FIG. 7 is a perspective view showing an outline of the configuration of a digital steel camera as an electronic device including the MEMS element 1 according to the embodiment of the present invention. It should be noted that this figure also briefly shows the connection with an external device. The digital still camera 1300 generates an image pickup signal (image signal) by photoelectrically converting an optical image of a subject by an image pickup device such as a CCD (Charge Coupled Device).
A display 1000 is provided on the back surface of the case (body) 1302 of the digital still camera 1300, and is configured to display based on an image pickup signal by a CCD. The display 1000 serves as a finder for displaying a subject as an electronic image. Function. Further, on the front side (back side in the drawing) of the case 1302, a light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided.
When the photographer confirms the subject image displayed on the display 1000 and presses the shutter button 1306, the image pickup signal of the CCD at that time is transferred and stored in the memory 1308. Further, in the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. Then, as shown in the figure, a television monitor 1330 is connected to the video signal output terminal 1312, and a personal computer 1340 is connected to the input / output terminal 1314 for data communication, respectively, as needed. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1330 and the personal computer 1340 by a predetermined operation. Such a digital still camera 1300 has a built-in MEMS element 1 that functions as a reference clock or the like.

As described above, by utilizing the highly reliable MEMS element 1 for the electronic device, it is possible to provide a higher performance electronic device.

In addition to the personal computer 1100 (mobile personal computer) of FIG. 5, the mobile phone 1200 of FIG. 6, and the digital still camera 1300 of FIG. 7, the MEMS element 1 according to the embodiment of the present invention is, for example, an inkjet. Ejection device (for example, inkjet printer), laptop personal computer, TV, video camera, car navigation device, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game equipment, workstation, videophone , Security TV monitors, electronic binoculars, POS (Point of Sale) terminals, medical equipment (for example, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic devices, electronic endoscopes), fish finder, various types It can be applied to electronic devices such as measuring devices, instruments (for example, instruments for vehicles, aircraft, and ships), flight simulators, and the like.

[Mobile]
Next, a moving body to which the MEMS elements 1 and 1a according to the embodiment of the present invention are applied will be described with reference to FIG. In the following, a configuration to which the MEMS element 1 is applied will be described as an example.
FIG. 8 is a perspective view schematically showing an automobile 1400 as an example of the moving body of the present invention.
The MEMS element 1 is mounted on the automobile 1400. The MEMS element 1 includes a keyless entry, an immobilizer, a navigation system, an air conditioner, an antilock braking system (ABS), an airbag, a tire pressure monitoring system (TPMS), an engine control, a hybrid vehicle, and electricity. It can be widely applied to electronic control units (ECUs: Electronic Control Units) 1410 such as automobile battery monitors and vehicle body attitude control systems.

As described above, by utilizing the highly reliable MEMS element 1 for the moving body, it is possible to provide a moving body having higher performance.

The MEMS elements 1, 1a, electronic devices (1100, 1200, 1300), and mobile body (1400) of the present invention have been described above based on the illustrated embodiments, but the present invention is limited thereto. Instead, the configuration of each part can be replaced with any configuration having the same function. Further, any other constituents may be added to the present invention. In addition, each of the above-described embodiments may be combined as appropriate.

Further, in the above-described embodiment, the element 20 is arranged so that the base portion 21 and the movable portion 22 extend along the direction of one diagonal line of the rectangular SOI substrate 10, but this has been described. Not limited to. As another example of arrangement, the element 20 may be arranged so that the base portion 21 and the movable portion 22 extend along the outer edge of the rectangular SOI substrate 10.

Further, in the above description, as an example of the MEMS element, the MEMS element 1, 1a including the element 20 as a functional element including the base portion 21 and the movable portion 22 has been described, but the present invention is not limited to this. Other MEMS elements having the above-mentioned sealing structure include an acceleration sensor element having an acceleration detection function as a functional element, an angular velocity sensor element having an angular velocity detection function, and a pressure having a pressure detection function. It may be a MEMS element including a sensor element, a weight sensor element having a weight detection function, a composite sensor in which these functional elements are combined, and the like. Further, the MEMS element may be an oscillator, an oscillator, a frequency filter or the like provided with a vibrating element as a functional element.

1,1a ... MEMS element, 3 ... junction surface, 3a, 3b, 3c, 3d ... corner, 5 ... lid, 7,8 ... cavity, 10 ... SOI substrate, 11 ... silicon layer, 12 ... BOX layer, 13 ... Surface silicon layer, 13a ... Groove, 13b ... Trench, 13c ... Slit, 14, 16 ... Resist, 18 ... Film resist, 20 ... Element, 21 ... Base, 22 ... Movable part, 30 ... Element adjustment layer, 32, 33, 34 ... silicon oxide film, 36 ... mask layer, 40 ... piezoelectric drive unit, 41 ... polysilicon film, 42 ... first electrode, 43 ... piezoelectric layer, 44 ... second electrode, 46 ... wiring, 50 ... Electrode pad, 52 ... Through hole for electrode, 54, 54a ... First through hole, 55 ... Second through hole, 56, 58 ... Electrode layer, 59 ... Through electrode, 60 ... Through hole, 62, 62a ... 1st hole, 64 ... 2nd hole, 66 ... Communication, 1000 ... Display, 1100 ... Personal computer, 1102 ... Keyboard, 1104 ... Main body, 1106 ... Display unit, 1200 ... Mobile phone, 1202 ... Operation Button, 1204 ... Earpiece, 1206 ... Mouthpiece, 1300 ... Digital steel camera, 1302 ... Case, 1304 ... Light receiving unit, 1306 ... Shutter button, 1308 ... Memory, 1312 ... Video signal output terminal, 1314 ... Input / output terminal, 1330 ... TV monitor, 1340 ... Personal computer, 1400 ... Automobile, 1410 ... Electronic control unit, W1, W2 ... Opening width.

Claims (6)

An element having a movable part and a base part is provided in a cavity composed of a substrate and a lid part.
On the substrate
Two through electrodes connected to the element electrodes for driving the element,
A through hole penetrating the substrate and
A sealing film for sealing the through hole is provided.
A MEMS element characterized in that the through hole is arranged on a side facing the movable portion with respect to the base portion in a plan view. The joint surface between the lid portion and the substrate has a plurality of corner portions.
The two through electrodes are respectively arranged in a part of a region in contact with the two corners facing each other in a plan view.
The first aspect of the present invention, wherein the through hole is arranged in a part of a region in contact with the corner portion other than the two corner portions where the two through electrodes are arranged in a plan view. MEMS element. The through hole is composed of a first hole portion and a second hole portion.
The opening width of the second hole is narrower than the opening width of the first hole.
2. The second aspect of the present invention is characterized in that the communication portion between the first hole portion and the second hole portion is sealed by the sealing film disposed on the first hole portion side. The MEMS element described. The MEMS device according to any one of claims 1 to 3, wherein the device is an oscillator. An electronic device comprising the MEMS element according to any one of claims 1 to 4. A mobile body including the MEMS element according to any one of claims 1 to 4.

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