JP2013024762A - Mems sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a MEMS sensor which is capable of adjusting pressure in a sealed space formed by bonding a silicon substrate and an insulating substrate.SOLUTION: A MEMS sensor 1 comprises: a silicon substrate 4; a pair of insulating substrates 2 and 3 which are bonded to top and bottom surfaces 4a and 4b of the silicon substrate 4; and a sealed space 6 formed by bonding the silicon substrate 4 and the insulating substrates 2 and 3. A through hole 7 communicating with the sealed space 6 is provided on an exposed outer surface 3b of the insulating substrate 2 and 3 or the silicon substrate 4.

Description

  The present invention relates to a MEMS sensor.

  2. Description of the Related Art Conventionally, there has been known a MEMS sensor including a silicon substrate on which a weight portion and a spring portion that swingably supports the weight portion are formed, and a pair of insulating substrates bonded to both upper and lower surfaces of the silicon substrate. (For example, refer to Patent Document 1).

  In such a MEMS sensor, a silicon substrate and an insulating substrate are joined by anodic bonding, and a gap is formed between the weight portion and the insulating substrate when the silicon substrate and the insulating substrate are joined. It has become. This ensures the operability of the weight portion.

JP 2011-022018 JP

  However, in the conventional MEMS sensor, a gap formed between the weight portion and the insulating substrate is a sealed space portion surrounded by the insulating substrate. Therefore, there has been a problem that it is difficult to adjust the pressure of the sealed space portion that becomes a gap at the time of anodic bonding between the silicon substrate and the insulating substrate.

  Accordingly, an object of the present invention is to obtain a MEMS sensor capable of adjusting the pressure of a sealed space formed when a silicon substrate and an insulating substrate are bonded.

  In order to achieve the above object, the present invention is formed when a silicon substrate, a pair of insulating substrates bonded to both upper and lower surfaces of the silicon substrate, and the silicon substrate and the insulating substrate are bonded. In the MEMS sensor including the sealed space portion, a through hole communicating with the sealed space portion is provided on the exposed outer surface of the insulating substrate or the silicon substrate.

  According to the MEMS sensor of the present invention, since the through hole communicating with the sealed space portion is provided on the exposed outer surface of the insulating substrate or the silicon substrate, the pressure of the sealed space portion can be adjusted.

FIG. 1 is a plan view of the acceleration sensor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the acceleration sensor shown in FIG. 3 is a cross-sectional view taken along line AA in FIG. FIG. 4 is a plan view of the acceleration sensor according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view of the acceleration sensor shown in FIG. FIG. 6 is a cross-sectional view showing a state where the through hole of the acceleration sensor shown in FIG. 5 is sealed with a sealing material.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a capacitance type acceleration sensor will be exemplified as the MEMS sensor. Note that similar components are included in the following embodiments. Therefore, in the following, common reference numerals are given to those similar components, and redundant description is omitted.

[First Embodiment]
As shown in FIGS. 1 to 3, the acceleration sensor 1 of the present embodiment includes a silicon substrate 4 on which a semiconductor element device is formed and a pair of glass substrates (a pair of glass substrates bonded to the upper and lower surfaces 4 a and 4 b of the silicon substrate 4). Insulating substrate) 2, 3. In this embodiment, the silicon substrate 4 is bonded to the first glass substrate 2 and the second glass substrate 3 by anodic bonding.

  A gap 5 is formed in the silicon substrate 4 by a known semiconductor process. As a result, the silicon substrate 4 has a substantially rectangular frame portion 41 formed at the peripheral portion, a fixed electrode body 42, a weight portion 43 serving as a movable electrode body, and a spring portion 44 that supports the weight portion 43 in a swingable manner. Is formed.

  The gap 5 is formed so that the side wall surface of the gap 5 is perpendicular to the surface of the silicon substrate 4 by performing a vertical etching process such as reactive ion etching (RIE). Thus, the side wall surfaces of the gap 5 formed by the vertical etching process face each other substantially in parallel. As reactive ion etching, for example, ICP processing by an etching apparatus provided with inductively coupled plasma (ICP) can be used.

  The fixed electrode bodies 42 are provided at two positions on the left and right sides with the center line Y of the silicon substrate 4 as the center, and the outer portions of the plurality of comb-like fixed electrodes 42b are connected by the trunk portion 42a. That is, the plurality of comb-like fixed electrodes 42b are projected in parallel from the trunk 42a with a predetermined interval.

  The weight portion 43 is disposed between the fixed electrode bodies 42 disposed on the left and right sides, the trunk portion 43a disposed along the center line Y, and the extending direction of the comb-like fixed electrode 42b from the trunk portion 43a. A plurality of comb-like movable electrodes 43b extending in parallel are provided.

  The plurality of comb-like movable electrodes 43b are projected in parallel with a predetermined interval so as to be inserted between two adjacent comb-like fixed electrodes 42b from the trunk portion 43a. That is, the comb-shaped fixed electrodes 42b and the comb-shaped movable electrodes 43b are alternately arranged.

  The above-described spring portion 44 is connected to both ends of the trunk portion 43a, and a frame portion 41 that supports the weight portion 43 is formed on the peripheral portion of the weight portion 43 and the fixed electrode body 42 via the spring portion 44. Has been.

  Each spring portion 44 has a shape in which a single continuous linear spring 44a is bent into a plurality of stages. One end portion 44b of the linear spring 44a is provided at a substantially central portion of the linear spring 44a extending in the width direction, and is connected to the inner wall portion of the frame portion 41, respectively. Further, the other end portion 44 c of the linear spring 44 a is provided at a substantially central portion of the linear spring 44 a and is connected to the trunk portion 43 a of the weight portion 43.

  Thus, by connecting the spring portion 44 to the weight portion 43 and the frame portion 41, the spring portion 44 functions as a spring element that elastically supports the weight portion 43 with respect to the frame portion 41.

  Thereby, in this embodiment, the function as a mass element (mass) supported by the frame part 41 connected with the spring part 44 as a spring element and the spring part 44 is given with respect to the weight part 43, These spring elements And a mass element constitute a spring-mass system. Then, a change in the capacitance value between the weight portion 43 and the fixed electrode body 42 due to the displacement of the weight portion 43 as a mass element is detected, and applied to the acceleration sensor 1 based on the detected change in the capacitance value. Acceleration and angular acceleration (physical quantity) are detected.

  Specifically, the change in the capacitance value is detected by the detection units 49a and 49b including the plurality of comb-like movable electrodes 43b and the comb-like fixed electrodes 42b formed on the weight 43 and the fixed electrode body 42, respectively. Detected.

  For example, when acceleration is applied in the centerline Y direction shown in FIG. 1, the comb-like movable electrode 43b is displaced in the centerline Y direction. The capacitance values detected by the comb-like movable electrode 43b and the comb-like fixed electrode 42b of the detection unit 49a and the comb-like movable electrode 43b and the comb-like fixed electrode 42b of the detection unit 49b are detected. The acceleration in the centerline Y direction can be detected based on the capacitance value.

  Further, as shown in FIG. 2, the weight portion 43 is provided with a first conductive layer 46a electrically connected to the comb-like movable electrode 43c. Further, 46 b in FIG. 2 is a second conductive layer electrically connected to the comb-like fixed electrode 42 b of the left fixed electrode body 42, and 46 c is a comb-like fixed of the right fixed electrode body 42. This is a third conductive layer electrically connected to the electrode 42b.

  And the through hole 21 is formed in the site | part corresponding to the 1st-3rd conductive layers 46a-46c of the 1st glass substrate 2 by sandblasting etc. FIG. And the 1st-3rd conductive layers 46a-46c provided on the silicon substrate 4 are exposed to the back of each through hole 21, respectively. A series of electrically conductive thin films (not shown) electrically connected from the surface 2a of the first glass substrate 2 to the inner peripheral surface of each through hole 21 are formed, The potentials of the fixed electrode body 42 and the weight portion 43 can be detected from the thin film. Each conductive thin film is formed on the surface 2a of the first glass substrate 2 so as not to contact each other. Further, it is preferable that the surface 2a of the first glass substrate 2 is covered (molded) with a resin layer (not shown).

  Further, as shown in the cross-sectional view taken along the line AA of FIG. 1 shown in FIG. 3, gaps 47 and 31 are formed on the bonding surfaces of the silicon substrate 4, the first glass substrate 2 and the second glass substrate 3, respectively. ing. That is, gaps 47 and 31 are formed between at least the weight portion 43 of the silicon substrate 4 and the first and second glass substrates 2 and 3. The operability of the (movable electrode) 43 is ensured.

  In the present embodiment, the upper surface 4a of the silicon substrate 4 is recessed so as to include the formation region of the weight portion 43 and the spring portion 44 and the peripheral portion thereof, thereby allowing the upward displacement of the weight portion 43. 47 is formed. Further, the upper surface 3a of the second glass substrate 3 is recessed including the formation region of the weight portion 43 and the peripheral portion thereof, thereby forming a gap 31 that allows the downward displacement of the weight portion 43. .

  Then, the first glass substrate 2 and the silicon substrate 4 are anodically bonded, and the silicon substrate 4 and the second glass substrate 3 are anodically bonded, whereby the three-layer structure acceleration sensor 1 is formed. At this time, the sealed space 6 in which the gaps 47 and 31 are surrounded by the pair of glass substrates 2 and 3 by bonding the silicon substrate 4 and the second glass substrate 3 to which the first glass substrate 2 is bonded. It becomes. Thus, if the sealed space 6 is formed, it becomes difficult to adjust the pressure of the space 6, and the pressure of the sealed space 6 increases during anodic bonding.

  Therefore, in the present embodiment, a through hole 7 that communicates with the sealed space 6 is provided in the lower surface 3 b that is the outer surface of the second glass substrate 3. In addition, as long as the formation part of this through-hole 7 is the outer surface where a pair of glass substrate 2, 3 or the silicon substrate 4 exposed, it may be provided anywhere. That is, in the present embodiment, the outer surface includes the upper surface 2a and side surfaces 2c and 2d of the first glass substrate 2, the side surfaces 3c and 3d of the second glass substrate 3, and the side surfaces 4c and 4d of the silicon substrate 4. When the through holes 7 are formed in the side surfaces 2 c and 2 d of the first glass substrate 2 and the side surfaces 3 c and 3 d of the second glass substrate 3, they are bent in a substantially L shape toward the sealed space 6. An opening may be formed.

  Moreover, in this embodiment, when joining the 2nd glass substrate 3 in which such the through-hole 7 was formed to the silicon substrate 4 to which the 1st glass substrate 2 was joined, it anodic-bonds in a vacuum. I am doing so.

  With such a configuration, there is an advantage that so-called sticking in which the weight portion 43 of the silicon substrate 4 is fixed to the glass substrate 2 at the time of anodic bonding can be suppressed. That is, if anodic bonding is performed in a vacuum state, the weight portion 43 is attracted to the glass substrate 2 by a great electrostatic attraction force when a voltage is applied. The suction force can be reduced.

  On the other hand, in the configuration in which anodic bonding is performed in a vacuum, the air damping effect is lost if the internal sealed space 6 remains in a vacuum state, and air exists in the sealed space when a certain acceleration is input. There is a problem that the weight part moves excessively as compared with the sensor that performs.

  Therefore, in this embodiment, after the anodic bonding of the silicon substrate 4 and the glass substrates 2 and 3, the sealed space portion 6 is filled with air through the through holes 7 formed in the second glass substrate 3. Yes. Thereafter, as shown in FIG. 3, in this embodiment, the through hole 7 is sealed by using a packing material 8 as a sealing portion for sealing the through hole 7. Thereby, it can prevent that a liquid, a foreign material, etc. permeate from the outside at the time of use of the acceleration sensor 1. FIG. In addition, this sealing part is not limited to the packing material 8, For example, you may make it fill the through-hole 7 with a sealing material, or may cover the through-hole 7 with a sheet | seat from the outside.

  With the above configuration, according to the acceleration sensor 1 of this embodiment, the glass substrate (insulating substrate) 2, 3 or the silicon substrate 4 is exposed on the lower surface 3 b of the second glass substrate 3 as the exposed outer surface. A through hole 7 communicating with 6 is provided. Therefore, the pressure in the sealed space 6 can be adjusted. Thereby, at the time of anodic bonding of the silicon substrate 4 and the glass substrates 2 and 3, it is possible to suppress an increase in the pressure of the sealed space portion 6, and it is possible to suppress the weight portion 43 and the spring portion 44 from being damaged. There is an advantage.

  In this embodiment, the silicon substrate 4 and the glass substrates 2 and 3 are anodically bonded in a vacuum. Therefore, there is an advantage that so-called sticking in which the weight portion 43 of the silicon substrate 4 is fixed to the glass substrate 2 at the time of anodic bonding can be suppressed. On the other hand, since the through hole 7 is formed in the lower surface 3b of the second glass substrate 3, air can be introduced into the sealed space portion 6 through the through hole 7 after anodic bonding. Thereby, it can prevent that the sealed space part 6 remains in a vacuum state, and it can prevent that an air damping effect is no longer acquired.

  Furthermore, in this embodiment, since the packing material (sealing part) 8 which seals the through-hole 7 formed in the lower surface 3b of the 2nd glass substrate 3 is provided, when using the acceleration sensor 1, a liquid and a foreign material are externally used. And the like can be prevented from entering the sealed space 6.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. 4 to 6 are diagrams showing the acceleration sensor 100 according to the present embodiment. Whereas the acceleration sensor 1 shown in the first embodiment detects the acceleration by the horizontal displacement of the weight portion, the acceleration sensor 100 of the present embodiment detects the acceleration by the vertical displacement of the weight portion.

  Similar to the first embodiment, the acceleration sensor 100 of the present embodiment includes a silicon substrate 104 on which a semiconductor element device is formed and a pair of glass substrates (insulating substrates) bonded to the upper and lower surfaces 104a and 104b of the silicon substrate 104. ) 102, 103. The silicon substrate 104 is bonded to the first glass substrate 102 and the second glass substrate 103 by anodic bonding. The first glass substrate 102 is provided with a fixed electrode 121 (see FIG. 5) corresponding to the installation area of the weight portion 105 on the lower surface of the first glass substrate 102. In the present embodiment, the fixed electrode 121 is formed in a region facing the gap 107 formed in the silicon substrate 104 of the first glass substrate 102.

  The silicon substrate 104 is formed in a substantially rectangular shape, and the silicon substrate 104 is provided with a weight portion 105 that can be displaced in the thickness direction of the first glass substrate 102 (vertical direction in FIG. 5). Furthermore, in this embodiment, the weight part 105 comprises the movable electrode. The weight portion 105 is supported by a substantially frame-shaped support portion 116 disposed so as to surround the weight portion 105 via two beams 161 as spring portions 106. Each beam 161 is set to have a thickness dimension sufficiently smaller than the thicknesses of the weight part 105 and the support part 116 so as to be flexible in the thickness direction. That is, the beam 161 functions as a spring element that elastically moves and supports the weight portion 105 with respect to the support portion 116.

  Thus, in this embodiment, the weight part 105 is provided with a function as a mass element that is movably supported by the beam 161 as a spring element, and a spring-mass system is configured by the spring element and the mass element. . The acceleration and angular acceleration can be obtained from the displacement of the weight portion 105 as a mass element.

  As shown in FIG. 5, gaps 107 and 131 are formed on the bonding surfaces of the silicon substrate 104 and the first glass substrate 102 and the second glass substrate 103, respectively. In addition, the operability of the weight portion 105 is ensured. Further, the gap 107 between the fixed electrode 121 and the weight portion 105 is used as a detection gap, and the capacitance between the fixed electrode 121 and the weight portion 105 facing each other through the gap 107 is detected. Yes. In this embodiment, the gap 107 is formed by removing a part of the silicon substrate 104 by silicon anisotropic etching using an alkaline wet anisotropic etching solution (for example, KOH, TMAH, EDP aqueous solution, etc.). ing.

  Further, two slits 117 penetrating in the thickness direction of the beam 161 are formed around the weight portion 105, and the width dimension of each beam 161 is defined by these two slits 117.

  The slit 117 is formed so that the side wall surface of the slit 117 is perpendicular to the surface of the silicon substrate 104 by performing vertical etching processing such as reactive ion etching. In this way, the side walls of the slit 117 formed by the vertical etching process face each other substantially in parallel. As the reactive ion etching, for example, ICP processing using an etching apparatus equipped with inductively coupled plasma can be used.

  In this embodiment, the weight part 105, each beam 161, and the support part 116 are formed by performing a known etching process on a single crystal silicon substrate (Si substrate). The weight portion 105 constitutes a movable electrode, and acceleration and angular acceleration (physical quantity) are detected as a change in capacitance value between the movable electrode and the fixed electrode 121 according to the displacement of the weight portion 105. ing. At this time, the weight part 105 is formed in a substantially square frustum shape, and the surface 105a facing the fixed electrode 121 is substantially flat. In the present embodiment, the weight portion 105 constitutes a movable electrode. However, the movable electrode may be separately formed on the surface 105 a of the weight portion 105 facing the fixed electrode 121.

  In addition, a first conductive thin film 111 is formed on the surface 102a of the first glass substrate 102 and used as a wiring pattern for acquiring the potential of the fixed electrode 121, and a second conductive thin film (not shown). ) Is used as a wiring pattern for acquiring the potential of the weight portion 105.

  In the present embodiment, as shown in FIG. 4, the gap 107 of the first glass substrate 102 extends from a substantially frame-like portion where the weight portion 105 is formed to a part of the support portion 116. 107a. Then, the first through hole 122 is formed by sandblasting or the like in a portion corresponding to the extending portion 107a of the first glass substrate 102, and the portion that is out of the gap 107 of the first glass substrate 102 (that is, A second through hole 123 is formed in a portion of the first glass substrate 102 where the fixed electrode 121 is not formed in plan view. Then, a part of the upper surface of the silicon substrate 104 is exposed to the back of the first through hole 122 and the second through hole 123, respectively, and the first through hole 122 and the first through hole 122 are formed from the surface 102a of the first glass substrate 102. A series of first conductive thin film 111 and second conductive thin film (not shown) electrically connected over the inner peripheral surface of second through hole 123 and over surface 102a of first glass substrate 102. Thus, the potentials of the fixed electrode 121 and the weight portion 105 can be detected from the first conductive thin film 111 and the second conductive thin film (not shown). Note that the first conductive thin film 111 and the second conductive thin film (not shown) are formed so as not to contact each other.

  In FIG. 5, reference numeral 109 denotes a conductive layer that is conducted to each conductive thin film, and 110 denotes an insulating layer that insulates the conductive layer 109 from the silicon substrate 104. The conductive layer 109 corresponding to the first through hole 122 is short-circuited to the fixed electrode 121, and the conductive layer 109 corresponding to the second through hole 123 is short-circuited to the support portion 116 of the silicon substrate 104.

  By the way, in this embodiment, as described above, the gap 107 is formed in the silicon substrate 104 and the two slits 117 penetrating in the thickness direction of the silicon substrate 104 are formed, so that the weight portion 105 is formed on the support portion 116. It is supported via a book beam 161. Thereby, the weight part 105, the beam 161, and the support part 116 are integrally formed. Therefore, the potentials of the weight portion 105, the beam 161, and the support portion 116 can be regarded as almost equal potentials. Note that the surface 102a of the first glass substrate 102 is preferably covered (molded) with a resin layer (not shown).

  Here, in this embodiment, the through hole 700 communicated with the sealed space 600 formed by the gaps 107 and 131 on the side surface 104d of the silicon substrate 104 as the exposed outer surface of the glass substrate 102, 103 or the silicon substrate 104. Is provided.

  Even in this embodiment, anodic bonding is performed in vacuum when the silicon substrate 104 having such a through-hole 700 is bonded to the first glass substrate 102 and the second glass substrate 103. I am doing so. After the anodic bonding of the silicon substrate 104 and the glass substrates 102 and 103, the sealed space 600 is filled with air through the through hole 700, and then the through hole 700 is sealed as a sealing portion as shown in FIG. By filling the sealing material 800, the through hole 700 is sealed. Thereby, it is possible to prevent liquid or foreign matter from entering from the outside when the acceleration sensor 100 is used. In addition, as in the first embodiment, the through hole 700 can be sealed using a packing material. Further, the through hole 700 may be covered with a sheet from the outside.

  With the above configuration, according to the acceleration sensor 100 of the present embodiment, the glass substrate (insulating substrate) 102, 103 or the side surface 104d of the silicon substrate 104 as the exposed outer surface of the silicon substrate 104 communicates with the sealed space 600. A through-hole 700 is provided. Therefore, the pressure in the sealed space 600 can be adjusted. Thereby, at the time of anodic bonding between the silicon substrate 104 and the glass substrates 102 and 103, it is possible to suppress an increase in pressure in the sealed space portion 600, and it is possible to suppress damage to the weight portion 105, the spring portion 106 and the like. .

  Further, since the silicon substrate 104 and the glass substrates 102 and 103 are anodically bonded in a vacuum, it is possible to suppress the weight portion 105 of the silicon substrate 104 from being fixed to the glass substrate 102 during the anodic bonding. it can. On the other hand, since the through hole 700 is formed in the side surface 104d of the silicon substrate 104, air can be introduced into the sealed space portion 600 through the through hole 700 after anodic bonding. As a result, it is possible to prevent the sealed space portion 600 from remaining in a vacuum state and prevent the air damping effect from being obtained.

  Furthermore, since the sealing material (sealing part) 800 for sealing the through hole 700 formed in the side surface 104d of the silicon substrate 104 is provided, liquid, foreign matter, etc. from the outside enter the sealed space part 600 when the acceleration sensor 100 is used. Intrusion can be prevented.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above embodiment, the capacitance type acceleration sensor is exemplified as the MEMS sensor. However, the present invention is not limited to this, and the present invention can be applied to other MEMS sensors such as an angular velocity sensor and a vibration sensor. Can do.

  Further, the weight part and other detailed specifications (shape, size, layout, etc.) can be changed as appropriate.

1,100 Acceleration sensor (MEMS sensor)
2, 102 First glass substrate (insulating substrate)
3, 103 Second glass substrate (insulating substrate)
3b Lower surface (outer surface)
4, 104 Silicon substrate 4d, 104d Side surface (outer surface)
30, 105 Weight part 44, 106 Spring part 6, 600 Sealed space part 7, 700 Through hole 8 Packing material (sealing part)
800 Sealing material (sealing part)

Claims (3)

In a MEMS sensor comprising a silicon substrate, a pair of insulating substrates bonded to the upper and lower surfaces of the silicon substrate, and a sealed space formed when the silicon substrate and the insulating substrate are bonded,
A MEMS sensor, wherein a through-hole communicating with the sealed space is provided in an exposed outer surface of the insulating substrate or silicon substrate.   The MEMS sensor according to claim 1, wherein the silicon substrate and the insulating substrate are anodically bonded in a vacuum.   The MEMS sensor according to claim 1, further comprising a sealing portion that seals the through hole.

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