JP2011173185A - Mems device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEMS device equipped with a movable part having high conductivity and in which the change of mechanical property is suppressed even when repeatedly operated. <P>SOLUTION: The MEMS device includes: a substrate 11; support layers 14a, 14b provided on the substrate 11; a fixed electrode 12 provided on the substrate 11; and a movable electrode 13 supported by the support layers 14a, 14b, and provided oppositely to the fixed electrode 12. The movable electrode 13 includes an electric functional layer 131 comprising a material having conductivity, and a reinforcement material layer 132 comprising a material having higher strength or a material having higher brittleness than the electric functional layer 131. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS (Micro Electro Mechanical System) device.

  In recent years, various MEMS devices have been manufactured using MEMS technology.

  The MEMS device is an important component constituting, for example, a high-frequency signal processing circuit.

  Some MEMS devices include a movable part. For example, a variable capacitor (variable capacitance element) and a switch (switching element) manufactured using the MEMS technology include a movable portion.

  Hereinafter, a variable capacitor manufactured using the MEMS technology may be simply referred to as a “variable capacitor”. The same applies to a switch manufactured using MEMS technology.

  FIG. 1 is a cross-sectional view showing an example of a conventional variable capacitor 7.

  As shown in FIG. 1A, the variable capacitor 7 includes a fixed electrode 72, a movable electrode 73, a pair of support layers 74a and 74b, and the like on a substrate 71. The movable electrode 73 is formed in a bridge shape so as to face the fixed electrode 72 through a gap, and the support layers 74a and 74b are formed to support the movable electrode 73 on both sides thereof.

  As shown in FIG. 1B, when a driving voltage is applied between the fixed electrode 72 and the movable electrode 73, an electrostatic attractive force acts between the two electrodes, so that the movable electrode 73 Pulled to the side and bent. Here, the amount of displacement of the movable electrode 73 in the vertical direction depends on the size of the movable electrode 73, the elastic coefficient, the magnitude of the drive voltage, and the like.

  FIG. 2 is a cross-sectional view showing an example of a conventional switch 8.

  As shown in FIG. 2A, the switch 8 has a fixed electrode 82, a movable electrode 83, a pair of contact layers 84a and 84b, a support layer 85, and the like on a substrate 81. The movable electrode 83 is formed in a cantilever shape so as to face the fixed electrode 82 with a gap therebetween, and the support layer 85 is formed to support the movable electrode 83 from one side thereof.

  As shown in FIG. 2B, when a driving voltage is applied between the fixed electrode 82 and the movable electrode 83, an electrostatic attractive force acts between the two electrodes, so that the movable electrode 83 Pulled to the side and bent. Here, the amount of displacement of the movable electrode 83 in the vertical direction depends on the size of the movable electrode 83, the elastic coefficient, the magnitude of the drive voltage, and the like.

  In the microactuator, it has been proposed to arrange a reinforcing structure having flexural rigidity on either the capacity variation layer or the carrier substrate layer that supports the capacity variation layer (Patent Document 1). .

  Further, in the actuator, it has been proposed that the bonding film for bonding the movable plate and the magnet includes a Si skeleton including a siloxane bond and a random atomic structure and a leaving group bonded to the Si skeleton ( Patent Document 2).

Special table 2005-517536 JP 2009-134194 A

  The MEMS device is required not to change the electrical or mechanical characteristics even if the number of operations is repeated. Therefore, in a MEMS device having a movable part, the displacement amount of the movable part is required to be constant for the same drive voltage.

  Conventionally, pure metals having a low electrical resistance such as gold (Au), aluminum (Al), or copper (Cu) have been used for the movable part with emphasis on conductivity. In addition, these pure metals are formed as a single layer with emphasis on the simplicity of the structure. These pure metals generally have a small elastic limit and fatigue strength.

  Therefore, the movable part continues to change irreversibly due to repeated operation. For example, the elastic modulus, strength, shape, etc. continue to change irreversibly. As a result, the electrical or mechanical characteristics of the MEMS device change from the initial characteristics. In other words, the deviation from the initial design value gradually increases.

  In addition, the movable part may break due to metal fatigue.

  For example, in the variable capacitor 7 as shown in FIG. 1, the movable electrode 73 may be deformed into a shape bent toward the fixed electrode 72 while repeatedly operating. In addition, the elastic modulus may be small. In that case, the relationship between the electrostatic capacity and the driving voltage is different from the initial relationship. That is, there is a problem that the characteristics of the variable capacitor 7 change. For the same reason, the switch 8 as shown in FIG. 2 has a problem that the characteristics change during repeated operation.

  The present invention has been made in view of such problems, and provides a MEMS device having a movable part that has high conductivity and that can suppress a change in mechanical properties even when repeatedly operated. For the purpose.

  The MEMS device according to the embodiment described herein is supported by a substrate, a support portion provided on the substrate, a fixed electrode provided on the substrate, and the support portion, and is opposed to the fixed electrode. The movable electrode is formed of a first layer made of a conductive material, a material having a higher strength than the first layer, or a material more brittle than the first layer. And a second layer.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the MEMS device provided with the movable part which has high electroconductivity and can suppress the change of a mechanical physical property even if it operates repeatedly.

It is sectional drawing which shows the example of the conventional variable capacitor. It is sectional drawing which shows the example of the conventional switch. It is sectional drawing which shows the example of the variable capacitor in 1st embodiment. It is a figure which shows the example of the preparation process of the variable capacitor in 1st embodiment. It is a figure which shows the example of the preparation process of the variable capacitor in 1st embodiment. It is sectional drawing which shows the example of the switch in 1st embodiment. It is sectional drawing which shows the example of the variable capacitor in 2nd embodiment. It is sectional drawing which shows the example of the switch in 2nd embodiment. It is sectional drawing which shows the example of the variable capacitor in 3rd embodiment. It is sectional drawing which shows the example of the switch in 3rd embodiment.

  In the drawings used for the description of the following embodiments, in order to make the structures of the variable capacitor and the switch easier to understand, the ratio of the dimensions of each part may be shown at a ratio different from the actual ratio.

[First embodiment]
FIG. 3 is a cross-sectional view showing an example of the variable capacitor 1 in the first embodiment. FIG. 3 (a) shows a state when the drive voltage is turned off, and FIG. 3 (b) shows the drive voltage. The state when turned ON is shown.

  As shown in FIG. 3, the variable capacitor 1 has a fixed electrode 12, a movable electrode 13, a pair of support layers 14 a and 14 b, and the like on a substrate 11.

  The fixed electrode 12 is made of a conductive material such as gold (Au), aluminum (Al), or copper (Cu), and is formed on the surface of the substrate 11.

  The movable electrode 13 is composed of two layers, ie, a lower electrical functional layer 131 and an upper reinforcing material layer 132. Ends on both sides are supported by support layers 14a and 14b so as to face the fixed electrode 12 through a gap. It is formed in a cross-linked form.

  The electrical functional layer 131 is made of a highly conductive pure metal such as gold (Au), aluminum (Al), or copper (Cu) or a material equivalent thereto.

  The thickness of the electrical functional layer 131 is determined in consideration of conductivity according to the type of circuit to which the variable capacitor 1 is applied. For example, when the variable capacitor 1 is applied to a circuit in which a direct current flows, a thickness sufficient to suppress the electric resistance to a predetermined value or less is ensured. Further, when the variable capacitor 1 is applied to a circuit through which a high frequency signal flows, the thickness is set in consideration of the frequency dependence of the skin effect in the high frequency signal. For example, a thickness equal to or greater than the skin thickness value of the skin effect is secured.

  The reinforcing material layer 132 is made of a material having higher strength than the material of the electrical functional layer 131 or a material having high brittleness, and is formed on the entire upper surface of the electrical functional layer 131. That is, the reinforcing material layer 132 is laminated on the entire upper surface of the electrical functional layer 131.

  As the material of the reinforcing material layer 132, a so-called high-strength alloy such as an aluminum alloy or a titanium alloy can be used. More specifically, a 2000-based Al—Cu—Mg-based alloy, a 7000-based Al—Zn—Mg—Cu-based alloy, an α-β-type titanium alloy, a β-type titanium alloy, or the like can be used. In general, an alloy has an effect of suppressing slippage on a crystal slip surface and reducing extensibility peculiar to a pure metal because a different metal is added to a pure metal.

  In addition, as the material of the reinforcing material layer 132, an oxide film such as silicon oxide (SiO 2) or aluminum oxide (Al 2 O 3), or a nitride film such as silicon nitride (SiN) or aluminum nitride (AlN) can be used.

  In addition, diamond-like carbon (DLC) can be used as the material of the reinforcing material layer 132. Diamond-like carbon is very useful because it has particularly high film strength and is excellent in film formability and workability.

  The material of the reinforcing material layer 132 is selected from the candidates described above in consideration of the availability as well as the compatibility in the manufacturing process in addition to the functionality as the reinforcing material.

  The thickness of the reinforcing material layer 132 is basically the same as the thickness of the electrical functional layer 131. For example, when the thickness of the electrical functional layer 131 is 1 μm, the thickness of the reinforcing material layer 132 is also 1 μm. In addition, the thickness of the reinforcing material layer 132 is determined in consideration of various conditions such as the material of the reinforcing material layer 132 and the magnitude of the electrostatic attractive force applied to the movable electrode 13.

  Thus, the electrical functional layer 131 of the movable electrode 13 is reinforced by the reinforcing material layer 132 made of a material having high strength or a material having high brittleness. Therefore, the movable electrode 13 as a whole has improved strength or brittleness as compared with the case where the movable electrode 13 is composed only of the electrical functional layer 131.

  The electric functional layer 131 of the movable electrode 13 is made of a pure metal having high conductivity or a material equivalent thereto. Therefore, the movable electrode 13 as a whole has high conductivity without impairing the conductivity in the case of being composed of only the electrical functional layer 131.

  A drive voltage for driving the variable capacitor 1 can be supplied between the fixed electrode 12 and the movable electrode 13.

  As shown in FIG. 3B, when a driving voltage is supplied between both electrodes, an electrostatic attractive force acts between both electrodes, so that the movable electrode 13 is attracted to the fixed electrode 12 side and is elastic. Bend in.

  In the movable electrode 13, since the electrical functional layer 131 is reinforced by the reinforcing material layer 132, even if it is repeatedly operated, the mechanical property does not change or is negligible.

  If the movable electrode 13 is made of only the electrical functional layer 131, that is, pure metal, the shape of the movable electrode 13 may be deformed or elastic while it is repeatedly operated due to ductility and malleability of the pure metal. The coefficient (spring coefficient) decreases or the strength decreases. That is, a change in mechanical properties occurs in the movable electrode 13.

  In the variable capacitor 1, such a change in mechanical properties of the movable electrode 13 due to repetitive operations is suppressed by the reinforcing material layer 132. As a result, the amount of vertical displacement of the movable electrode 13 when the same drive voltage is supplied is constant. Therefore, the variable capacitor 1 can be driven stably.

  Hereinafter, an outline of a manufacturing method of the variable capacitor 1 using the MEMS technology will be described.

  4 and 5 are diagrams illustrating an example of a manufacturing process of the variable capacitor 1 according to the first embodiment.

  As shown in FIG. 4A, a pure metal thin film such as an Al film is formed on the surface of the substrate 11 by sputtering or the like to form the fixed electrode 12. Further, Al plating or the like is grown to a predetermined height by electroplating or the like to form the support layers 14a and 14b.

  In FIG. 4B, a sacrificial layer 100 is formed by growing a silicon film or the like up to the height of the support layers 14a and 14b by CVD (Chemical Vapor Deposition) or the like at a location where the support layers 14a and 14b are not formed. That is, the surface is flattened by filling the sacrificial layer 100 in a portion where the support layers 14a and 14b are not formed.

  Note that the order of the step of forming the support layers 14a and 14b and the step of forming the sacrificial layer 100 may be reversed.

  In FIG. 4C, a pure metal thin film such as an Al film is formed on the upper surfaces of the support layers 14a and 14b and the sacrificial layer 100 by sputtering or the like to form the electrical functional layer 131.

  When the material of the electrical functional layer 131 is different from the material of the support layers 14a and 14b, an adhesion layer may be interposed between them. For example, when the electrical functional layer 131 made of gold (Au) is formed on the upper surface of the support layer made of aluminum (Al), a chromium (Cr) film or a titanium (Ti) film is interposed as an adhesion layer.

  In FIG. 5A, an alloy thin film such as an Al—Cu film is formed on the upper surface of the electrical functional layer 131 by sputtering or the like to form a reinforcing material layer 132.

  The formation of the electrical functional layer 131 and the formation of the reinforcing material layer 132 may be performed by a method other than sputtering, that is, various methods such as vapor deposition, electroplating, and CVD.

  In FIG. 5 (b), with respect to each layer on the substrate 11, a portion constituting the variable capacitor 1 is left and other portions are removed by resist peeling or ion milling. That is, the variable capacitor 1 is cut out.

  In FIG. 5C, the sacrificial layer 100 is removed by RIE (Reactive Ion Etching) or the like.

  Although the variable capacitor 1 can be manufactured as described above, this manufacturing method is merely an example, and various other methods are conceivable.

  FIG. 6 is a cross-sectional view showing an example of the switch 2 in the first embodiment, FIG. 6A shows a state when the drive voltage is turned OFF, and FIG. 6B shows the drive voltage turned ON. This shows the state when

  As illustrated in FIG. 6, the switch 2 includes a fixed electrode 22, a movable electrode 23, a pair of contact layers 24 a and 24 b, and a support layer 25 on a substrate 21.

  The fixed electrode 22 is made of a conductive material such as gold (Au), aluminum (Al), or copper (Cu), and is formed on the surface of the substrate 21.

  The movable electrode 23 is composed of two layers, a lower electrical functional layer 231 and an upper reinforcing material layer 232, one end of which is supported by the support layer 25, so that the movable electrode 23 faces the fixed electrode 22 through a gap. It is shaped like a cantilever.

  The form and material of the electrical functional layer 231 are the same as those of the electrical functional layer 131 of the variable capacitor 1. The form and material of the reinforcing material layer 232 are the same as those of the reinforcing material layer 132 of the variable capacitor 1.

  The contact layers 24a and 24b are made of a conductive material such as gold (Au), aluminum (Al), or copper (Cu). The contact layers 24a and 24b are respectively formed on the surface of the substrate 21 and the lower surface of the end portion of the movable electrode 23 opposite to the side supported by the support layer 25 so as to face each other.

  A driving voltage for driving the switch 2 can be supplied between the fixed electrode 22 and the movable electrode 23.

  As shown in FIG. 6B, when a driving voltage is supplied between both electrodes, an electrostatic attractive force acts between both electrodes, so that the movable electrode 23 is attracted toward the fixed electrode 22 and is elastic. Bend in. As a result, the contact layer 24a and the contact layer 24b come into contact with each other and become conductive.

  Since the electric functional layer 231 is reinforced by the reinforcing material layer 232, the movable electrode 23 does not change or hardly changes mechanical properties even if it is repeatedly operated.

  That is, also in the switch 2, for the same reason as the variable capacitor 1, the mechanical property change of the movable electrode 23 due to the repetitive operation is suppressed by the reinforcing material layer 232. As a result, the amount of vertical displacement of the movable electrode 23 when the same drive voltage is supplied is constant. Therefore, the switch 2 can be driven stably.

  The switch 2 can be manufactured by a method similar to the example of the method for manufacturing the variable capacitor 1 described above.

  In the first embodiment, the electrical functional layer 131 of the variable capacitor 1 is a lower layer of the movable electrode 13, but may be an upper layer. That is, the arrangement relationship between the electrical functional layer 131 and the reinforcing material layer 132 may be reversed. The same applies to the positional relationship between the electrical functional layer 231 and the reinforcing material layer 232 of the switch 2.

  However, in that case, in order to prevent the contact resistance of the electrical functional layer 131 with respect to the substrate 11 from increasing, it is preferable to expose at least a part of the upper electrical functional layer 131 to the substrate 11 side. . More specifically, it is preferable to form a lower reinforcing material layer 132 on both ends of the movable electrode 13 so that the central portion of the upper electrical functional layer 131 is exposed to the substrate 11 side.

[Second Embodiment]
FIG. 7 is a cross-sectional view showing an example of the variable capacitor 3 in the second embodiment. FIG. 7A shows a state when the drive voltage is turned OFF, and FIG. 7B shows the drive voltage. The state when turned ON is shown.

  Hereinafter, the variable capacitor 3 will be described focusing on the movable electrode 33 that is different from the variable capacitor 1 of the first embodiment. Other constituent elements common to the variable capacitor 1 are denoted by the same reference numerals as those used in the description of the variable capacitor 1, and description thereof is omitted.

  As shown in FIG. 7, the movable electrode 33 is composed of two layers of a lower electrical functional layer 331 and upper reinforcing material layers 332a and 332b formed at two locations in a narrower range than the electrical functional layer 331. . The movable electrode 33 is formed in a bridge shape so that both end portions thereof are supported by the support layers 14a and 14b and face the fixed electrode 12 through a gap.

  The form and material of the electrical functional layer 331 are the same as those of the electrical functional layer 131 of the variable capacitor 1.

  The reinforcing material layers 332a and 332b are made of a material having higher strength or brittleness than the material of the electrical functional layer 331, and are patterned on a part of the upper surface of the electrical functional layer 331. That is, the reinforcing material layers 332a and 332b are formed only on the upper surface in the vicinity of both end portions of the electrical functional layer 331, and are not formed on the upper surface of the central portion of the electrical functional layer 331.

  More specifically, the reinforcing material layers 332a and 332b are formed so as to cover the upper surfaces of the electrical functional layer end portions 331a and 331b supported by the support layers 14a and 14b, respectively, The portions 331a and 331b are formed so as to slightly protrude from the end boundaries 331c and 331d toward the center.

  As shown in FIG. 7B, when the movable electrode 33 is bent toward the fixed electrode 12, the portion of the electrical functional layer 331 where the reinforcing material layers 332a and 332b are formed on the upper surface is stress or the like. Is the most concentrated part. For example, shear stress, bending moment, and the like act on the end boundaries 331 c and 331 d that serve as fulcrums for the bending of the movable electrode 33.

  The thickness of the reinforcing material layers 332a and 332b is basically the same as the thickness of the electrical functional layer 331. In addition, it is determined in consideration of various conditions such as the material of the reinforcing material layers 332a and 332b and the magnitude of the electrostatic attractive force applied to the movable electrode 33.

  As described above, the end boundaries 331c and 331d, which are portions where the stress and the like are concentrated most in the electric functional layer 331 of the movable electrode 33, and the vicinity thereof are reinforcing materials made of a material having high strength or a material having high brittleness. Reinforced by layers 332a and 332b, respectively. Therefore, although the movable electrode 33 as a whole is not as large as the movable electrode 13 of the variable capacitor 1, the strength or brittleness is sufficiently improved as compared with the case where the movable electrode 33 is composed only of the electrical functional layer 331.

  In addition, unlike the movable electrode 13 of the variable capacitor 1, the movable electrode 33 is not entirely covered with the reinforcing material layers 332a and 332b, so that only the electrical functional layer 131 is present. The electrical characteristics are almost the same as in the case of comprising.

  In addition, the variable capacitor 3 has better responsiveness of operation of the movable electrode 33 and less drive voltage than the variable capacitor 1.

  That is, if the entire upper surface of the electrical functional layer 331 is covered with the reinforcing material layers 332a and 332b like the movable electrode 13 of the variable capacitor 1, compared to the case where the electrical functional layer 331 alone is formed, The weight of the movable electrode 33 is increased and the inertia when operating is increased. This deteriorates the responsiveness of the operation of the movable electrode 33. In addition, more electrostatic attraction is required to displace the movable electrode 33. This leads to an increase in driving voltage. In the variable capacitor 3, the reinforcing material layers 332 a and 332 b are formed only on both sides of the movable electrode 33 and are not formed in the central portion of the movable electrode 33. The responsiveness is not deteriorated and the driving voltage is not increased. That is, high-speed capacity switching is possible, and power is saved.

  Therefore, in the variable capacitor 3, it is possible to suppress a change in mechanical properties of the movable electrode 33 due to repeated operations while reducing the disadvantages due to reinforcement.

  The variable capacitor 3 can be manufactured by a method similar to the example of the method for manufacturing the variable capacitor 1 described above.

  FIG. 8 is a cross-sectional view showing an example of the switch 4 in the second embodiment. FIG. 8A shows a state when the drive voltage is turned off, and FIG. 8B shows that the drive voltage is turned on. This shows the state when

  Hereinafter, the switch 4 will be described focusing on the movable electrode 43 that is different from the switch 2 of the first embodiment. Other constituent elements common to the switch 2 are denoted by the same reference numerals used in the description of the switch 2, and the description thereof is omitted.

  As shown in FIG. 8, the movable electrode 43 is composed of two layers of a lower electrical functional layer 431 and an upper reinforcing material layer 432 formed in one place in a narrower range than the electrical functional layer 431. The movable electrode 43 is formed in a cantilever shape so that one end of the movable electrode 43 is supported by the support layer 25 and faces the fixed electrode 22 via a gap.

  The form and material of the electrical functional layer 431 are the same as those of the electrical functional layer 231 of the switch 2.

  The reinforcing material layer 432 is made of a material having higher strength or higher brittleness than the material of the electrical functional layer 431, and is patterned on a part of the upper surface of the electrical functional layer 431. That is, the reinforcing material layer 432 is formed only on the upper surface of one end portion of the electrical functional layer 431, and is not formed on the upper surface of the central portion and the other end portion of the electrical functional layer 431.

  More specifically, the reinforcing material layer 432 is formed so as to cover the upper surface of the electrical functional layer end portion 431a supported by the support layer 25, and the end boundary 431b of the electrical functional layer end portion 431a. It is formed to protrude slightly from the center side.

  As shown in FIG. 8B, when the movable electrode 23 bends to the fixed electrode 22 side, the portion where the reinforcing material layer 432 is formed on the upper surface of the electrical functional layer 431 has the highest stress or the like. It is the part that concentrates. For example, shear stress, bending moment, and the like act on the end boundary 431b serving as a fulcrum for bending of the movable electrode 43.

  The thickness of the reinforcing material layer 432 is basically the same as the thickness of the electrical functional layer 431. In addition, it is determined in consideration of various conditions such as the material of the reinforcing material layer 432 and the magnitude of the electrostatic attractive force applied to the movable electrode 43.

  As described above, the end boundary 431b, which is the portion where the stress or the like is concentrated most in the electrical functional layer 431 of the movable electrode 43, and the vicinity thereof are formed by the reinforcing material layer 432 made of a material having high strength or a material having high brittleness. It is reinforced. Therefore, as a whole, the movable electrode 43 is not as large as the movable electrode 23 of the switch 2, but is sufficiently improved in strength or brittleness as compared with the case where it consists only of the electrical functional layer 431.

  In addition, unlike the movable electrode 23 of the switch 2, the entire upper surface of the electrical functional layer 431 is not covered with the reinforcing material layer 432, and thus the movable electrode 43 includes only the electrical functional layer 431. The electrical characteristics are almost the same.

  Further, in the switch 4, the reinforcing material layer 432 is formed only on one side of the movable electrode 43 and is not formed in the central portion of the movable electrode 43. The drive voltage is not increased. That is, high-speed switching is possible and power is saved.

  Therefore, also in the switch 4, it is possible to suppress a change in mechanical properties of the movable electrode 43 due to repetitive operations while reducing the demerits due to reinforcement.

  The switch 4 can be manufactured by a method similar to the example of the method for manufacturing the variable capacitor 1 described above.

[Third embodiment]
FIG. 9 is a cross-sectional view showing an example of the variable capacitor 5 in the third embodiment. FIG. 9A shows a state when the drive voltage is turned OFF, and FIG. 9B shows the drive voltage. The state when turned ON is shown.

  Hereinafter, the variable capacitor 5 will be described focusing on the movable electrode 53 that is different from the variable capacitor 1 of the first embodiment. Other constituent elements common to the variable capacitor 1 are denoted by the same reference numerals as those used in the description of the variable capacitor 1, and description thereof is omitted.

  As shown in FIG. 9, the movable electrode 53 includes three layers including a lower first electrical functional layer 531, an intermediate reinforcing material layer 532, and an upper second electrical functional layer 533. The movable electrode 53 is formed in a bridge shape so that the end portions on both sides are supported by the support layers 14a and 14b and face the fixed electrode 12 through a gap.

  The form and material of the first electrical functional layer 531 are the same as those of the electrical functional layer 131 of the variable capacitor 1. The form and material of the reinforcing material layer 532 are the same as those of the reinforcing material layer 132 of the variable capacitor 1.

  The second electrical functional layer 533 is made of a highly conductive pure metal, such as gold (Au), aluminum (Al), or copper (Cu), or a material equivalent thereto. For example, the first electrical functional layer 531 Made of the same material. The second electrical functional layer 533 is formed on the entire top surface of the reinforcing material layer 532. That is, the second electrical functional layer 533 is laminated on the entire upper surface of the reinforcing material layer 532.

  The thickness of the second electrical functional layer 533 may be thinner than the thickness of the first electrical functional layer 531 as long as the above-described conductivity is taken into consideration.

  Thus, the formation of the second electrical functional layer 533 can prevent the reinforcing material layer 532 from being charged. That is, if the variable capacitor 5 is repeatedly driven when a highly dielectric material is used for the reinforcing material layer 532, electric charge remains in the reinforcing material layer 532 even when no voltage is supplied between the electrodes. Sometimes. In particular, when the variable capacitor 5 is applied to a circuit through which a high frequency signal flows, such a phenomenon is likely to occur. In that case, the relationship between the electrostatic capacity and the driving voltage is different from the initial relationship. That is, the characteristics of the variable capacitor 5 change.

  In the variable capacitor 5, since the second electrical functional layer 533 is formed, the escape route for charges is widened, and the charges are less likely to stay.

  Therefore, in the variable capacitor 5, changes in the mechanical properties of the movable electrode 53 due to repetitive operations are suppressed by the reinforcing material layer 532, and charging in the reinforcing material layer 532 is unlikely to occur.

  The variable capacitor 5 can be manufactured by a method similar to the example of the method for manufacturing the variable capacitor 1 described above.

  FIG. 10 is a cross-sectional view showing an example of the switch 6 in the third embodiment. FIG. 10 (a) shows a state when the drive voltage is turned off, and FIG. 10 (b) shows that the drive voltage is turned on. This shows the state when

  Hereinafter, the switch 6 will be described focusing on the movable electrode 63 that is different from the switch 2 of the first embodiment. Other constituent elements common to the switch 2 are denoted by the same reference numerals used in the description of the switch 2, and the description thereof is omitted.

  As shown in FIG. 10, the movable electrode 63 includes three layers of a lower first electric functional layer 631, an intermediate reinforcing material layer 632, and an upper second electric functional layer 633. The movable electrode 63 is formed in a cantilever shape so that one end of the movable electrode 63 is supported by the support layer 25 and faces the fixed electrode 22 via a gap.

  The form and material of the first electrical functional layer 631 are the same as those of the electrical functional layer 231 of the switch 2. The form and material of the reinforcing material layer 632 are the same as those of the reinforcing material layer 232 of the switch 2.

  The second electrical functional layer 633 is made of a highly conductive pure metal such as gold (Au), aluminum (Al), or copper (Cu) or a material equivalent thereto. For example, the first electrical functional layer 631 Made of the same material. The second electrical functional layer 633 is formed on the entire upper surface of the reinforcing material layer 632. That is, the second electrical functional layer 633 is laminated on the entire upper surface of the reinforcing material layer 632.

  Thus, by forming the second electrical functional layer 633, the reinforcing material layer 632 can be prevented from being charged for the same reason as the variable capacitor 5.

  Therefore, also in the switch 6, the mechanical property change of the movable electrode 63 due to the repetitive operation is suppressed by the reinforcing material layer 632, and the reinforcing material layer 632 is hardly charged.

  The switch 6 can be manufactured by a method similar to the example of the method for manufacturing the variable capacitor 1 described above.

  In the above embodiment, the structure, shape, material and the like of the whole or a part of the variable capacitors 1, 3, 5 and the switches 2, 4, 6 can be appropriately changed in accordance with the gist of the present invention. The configuration of the movable electrode described above is not limited to a variable capacitor and a switch, and can be applied to various MEMS devices having a movable portion.

1, 3, 5 Variable capacitor (MEMS device)
2, 4, 6 switch (MEMS device)
11, 21 Substrate 12, 22 Fixed electrode 13, 23, 33, 43, 53, 63 Movable electrode 14a, 14b, 25 Support layer (support part)
131, 231, 331, 431 Electrical functional layer (first layer)
132, 232, 332, 432 Reinforcement material layer (second layer)
531, 631 First electrical functional layer (first layer)
532, 632 Reinforcement material layer (second layer)
533, 633 Second electrical functional layer (third layer)

Claims (8)

A substrate,
A support provided on the substrate;
A fixed electrode provided on the substrate;
A movable electrode supported by the support portion and provided to face the fixed electrode;
The movable electrode is
A first layer made of a conductive material;
A second layer made of a material having a higher strength than the first layer or a material more brittle than the first layer,
MEMS device. The second layer is formed as an upper layer of the first layer,
The MEMS device according to claim 1. The movable electrode includes a third layer made of a conductive material,
The second layer is formed as an intermediate layer between the first layer and the third layer.
The MEMS device according to claim 1. The support portion supports the movable electrode on both sides of the movable electrode,
The second layer is formed on both sides of the movable electrode,
The MEMS device according to claim 1. The support portion supports the movable electrode from one side of the movable electrode,
The second layer is formed on one side of the movable electrode,
The MEMS device according to claim 1. A high-strength alloy is used as the material of the second layer,
The MEMS device according to claim 1. An oxide or nitride is used as the material of the second layer,
The MEMS device according to claim 1. Diamond-like carbon is used as the material of the second layer,
The MEMS device according to claim 1.

Images