JP4655919B2 - Electrostatic driving element and manufacturing method thereof, semiconductor device, filter, and communication device - Google Patents

Description

  The present invention relates to an electrostatic driving element, in particular, an electrostatic driving element having a microelectromechanical element that is electrically driven, a method for manufacturing the same, a semiconductor device including the electrostatic driving element, a filter including the electrostatic driving element, The present invention also relates to a communication device using a filter with an electrostatic drive element.

  An element having a micromechanical structure, that is, a so-called MEMS (Micro Electro Mechanical System) device is subjected to an airtight sealing process, so-called hermetic packaging, in order to ensure initial characteristics and maintain characteristics, that is, to guarantee reliability in products. .

  These micro mechanical elements are used as electronic elements such as filters, mixers, resonators, signal switchers, sensors, etc., but the configuration in which the micro drive unit that constitutes the elements is packaged in a reduced-pressure atmosphere results in deterioration of the characteristics of the elements due to charging effects. It is known to be effective in reducing the above. For example, it has been reported that it is particularly effective to configure the resonator with a high vacuum package of about 50 μTorr in order to maintain a high Q value of the vibrator (see, for example, Non-Patent Document 1).

  However, since the above-described electronic elements are required to have a high degree of precision in operation and control, it is difficult to sufficiently reduce or avoid the characteristic deterioration only by packaging the micro drive unit in a reduced pressure atmosphere. That is, when polar molecules such as water remain in the package even under a reduced pressure atmosphere, the molecules generated by the electric field near the micro-driving unit constituting the element are accompanied by the operation of the element such as voltage application. Charging effects such as alignment and electrolysis occur. At this time, for example, if charges are concentrated (charging) on a part of the surface of the vibrator, the neutral position of the vibrator is biased and the element function is impaired.

  In addition, the charging effect caused by such polar molecules also causes alteration of the micro-driving unit and the surrounding wiring material. Generally, the higher the frequency of an electrical signal, the more likely it is to propagate through the surface of the wiring. Therefore, if the surface is altered by oxidation or the like, the resistance will increase and the device characteristics will deteriorate due to a decrease in propagation characteristics. . Therefore, as long as polar molecules remain even under a reduced pressure atmosphere, the wiring material that makes up the micromechanical element is selected with priority given to the fact that the material itself is less likely to be altered than the resistance of the body itself. There was a fact that it was unavoidable.

  As a method for manufacturing a micro mechanical element, a method for selecting a sealing means when packaging in a reduced-pressure atmosphere, or a substance that easily binds or adsorbs to polar molecules is used as a so-called getter inside the package. A method of providing it has been proposed (see, for example, Patent Document 1).

Micromechanical Mixer + Filters by Ark-Chew Wong, HaoDing, and Clark T.-C.Nguyen; TechnicalDigest, IEEE International Electron Device Meeting, San Francisco, Dec. 6-9,1998, pp.471-474. Japanese Patent Laid-Open No. 2003-133552

  However, it is difficult to solve the problem caused by the above-described charging effect only by selecting the sealing means. That is, the selection of the sealing means makes it possible to select the main component of the substrate to be sealed in the package as, for example, a normally used inert gas such as argon or nitrogen, but the amount of the inert gas is within the package. It is limited by the volume of For this reason, it is not always possible to sufficiently suppress the polar molecules remaining in the gas phase, and even if the polar molecules remain in the liquid phase or the solid phase, they are vaporized over time. There remains a risk that the device characteristics will deteriorate.

  In addition, the method of fixing polar molecules with a getter provided inside the package requires a heat treatment for operating the getter, and it is also necessary to separately provide an energization system for the heat treatment. This would require more labor and cost for the production of hermetic packages where high costs exceeding their own costs are a problem.

In view of the above-described points, the present invention provides a micromechanical element that can ensure excellent initial characteristics and guarantee device reliability, that is, an electrostatic driving element, a manufacturing method thereof, a semiconductor device, and a filter. .
Moreover, this invention provides the communication apparatus provided with this electrostatic drive element.

  The electrostatic drive element according to the present invention includes an electrostatic drive type micro electromechanical element having an electrically driven beam and a capacitor having a function of storing electric charge and polar molecules sealed in the same housing. It is characterized by being made.

  In the electrostatic driving element of the present invention, a capacitor serving as a charge and polar molecule accumulator is provided adjacent to the microelectromechanical element. Even if polar molecules remain in either the phase or the solid phase, the alteration of the driving unit or the oxidation of the current-carrying unit due to the charge effect by the polar molecules can be minimized.

  The method for manufacturing an electrostatic drive element according to the present invention includes a step of forming a lower electrode of a microelectromechanical element and a lower electrode of a capacitor on a substrate, a required region including the lower electrode of the microelectromechanical element, and a capacitor A step of selectively forming a sacrificial layer on the lower electrode, a step of forming an upper electrode of a beam and a capacitor having ends fixed to the substrate on each sacrificial layer, and removing the sacrificial layer to form the lower electrode; Forming a microelectromechanical element composed of a beam, a capacitor having a function of accumulating charges and polar molecules composed of a lower electrode and an upper electrode sandwiching the space, and the microelectromechanical element and the capacitor in the same housing And a step of sealing.

  A method of manufacturing an electrostatic driving element according to the present invention includes a step of forming a lower electrode of a microelectromechanical element and an upper electrode of a capacitor on a substrate having an insulating film formed on a surface of a semiconductor substrate, and a microelectromechanical element. Forming a sacrificial layer selectively on a required region including the lower electrode, forming a beam having an end fixed to the substrate on the sacrificial layer, and removing the sacrificial layer from the lower electrode and the beam. Forming a microelectromechanical element, a semiconductor substrate serving as a lower electrode, a capacitor having a function of accumulating electric charges and polar molecules composed of an insulating film and an upper electrode, and the microelectromechanical element and the capacitor in the same casing. And a step of sealing in the body.

  In the method for manufacturing an electrostatic drive element of the present invention, the microelectromechanical element and the capacitor can be formed in the same process.

  A semiconductor device according to the present invention includes the electrostatic drive element described above.

  In the semiconductor device having the electrostatic driving element of the present invention, excellent initial characteristics and high reliability can be obtained.

  In the filter according to the present invention, a vibrator using an electrostatically driven microelectromechanical element having an electrically driven beam and a capacitor having a function of accumulating charges and polar molecules are sealed in the same housing. It is characterized by comprising an electrostatic drive element.

  In the filter of the present invention, since a capacitor serving as an accumulator of charge and polar molecules is installed in the vicinity of the vibrator, characteristic deterioration due to a charging phenomenon caused by adsorption of polar molecules such as water can be avoided.

  A communication apparatus according to the present invention is characterized in that a filter having the above-described configuration is used as a filter in a communication apparatus including a filter that limits a band of a transmission signal and / or a reception signal.

  In the communication apparatus according to the present invention, since the filter of the present invention is used as a filter, as described above, characteristic deterioration due to the charging phenomenon of the filter is avoided, and high reliability can be achieved.

  According to the electrostatic driving element according to the present invention, the capacitor serving as a charge and polar molecule accumulator is installed adjacent to the microelectromechanical element, and the deterioration of the driving unit and the oxidation of the energizing unit are minimized. The characteristic deterioration of the microelectromechanical element can be sufficiently suppressed. Therefore, excellent initial characteristics can be ensured and high reliability of the electrostatic drive element can be guaranteed.

  According to the manufacturing method of the electrostatic drive element according to the present invention, the micro electromechanical element and the capacitor can be formed in the same process, so that the manufacturing can be facilitated without increasing the cost.

According to the semiconductor device of the present invention, by having the electrostatic drive element of the present invention, a semiconductor device having excellent initial characteristics and reliability, such as a filter, a mixer, a resonator, a signal switch, a sensor, etc. A communication device can be configured.
Further, for example, it is possible to avoid charging due to polar molecules adhering to the surface of the driving unit constituting the micro electro mechanical element, and to prevent an increase in stray capacitance due to oxidation of the driving unit surface.

  According to the filter of the present invention, it is possible to suppress deterioration due to the charging phenomenon and provide a highly reliable filter.

  According to the communication device of the present invention, it is possible to suppress a deterioration factor derived from the charging phenomenon and provide a highly reliable communication device.

  An electrostatic drive element according to an embodiment of the present invention has an electrostatic drive type micro electromechanical element having a beam to be electrically driven, and an area sufficiently larger than the area of the micro electro mechanical element. A capacitor having a function of accumulating (including adsorption) polar molecules such as electric charge and water, and the micro electro mechanical element and the capacitor are sealed in the same casing.

  The capacitor provided in the electrostatic drive element is connected to means for applying a DC voltage. For example, a DC voltage is applied to a capacitor through a DC power supply circuit that applies a DC voltage to a beam of an electrostatically driven micro-electromechanical element. The capacitor accumulates charges and polar molecules as a capacitor while a DC voltage is applied through a DC power supply circuit of a micro electromechanical element.

  When viewed from the DC power supply terminal, the capacitor is electrically connected in parallel with the electrostatic drive type micro electromechanical element, and signal leakage from the AC line to the capacitor is avoided between the capacitor and the micro electro mechanical element. Means are provided.

The capacitor is formed by using the same electrode layer as the lower electrode or beam of the microelectromechanical element, and has the same surface structure as the driving portion of the microelectromechanical element.
In the capacitor, one electrode is provided with a plurality of holes sufficient to allow liquid to pass through. These holes play a role in increasing the adsorption area of polar molecules and make it possible to form a capacitor using the same process as the sacrificial layer removal of the driving part of the microelectromechanical element in manufacturing the capacitor. .

  In the method for manufacturing an electrostatic drive element according to an embodiment of the present invention, an electrostatic drive type micro electromechanical element having a beam and a capacitor are manufactured using the same film formation layer. That is, the lower electrode of the microelectromechanical element and the lower electrode of the capacitor are formed on the substrate. Next, a sacrificial layer is selectively formed on a required region including the lower electrode of the microelectromechanical element and on the lower electrode of the capacitor. Next, on each sacrificial layer, a beam whose end is fixed to the substrate and the upper electrode of the capacitor are formed, and then the sacrificial layer is removed to form a microelectromechanical element composed of the lower electrode and the beam, and a space A capacitor having a function of accumulating electric charges and polar molecules is formed by the lower electrode and the upper electrode sandwiching the electrode. Thereafter, the microelectromechanical element and the capacitor are sealed in the same casing to complete the target electrostatic driving element.

  According to another embodiment of the present invention, there is provided a method for manufacturing an electrostatic drive element, in which a capacitor manufactured simultaneously with an electrostatic drive type microelectromechanical element is provided with the same film formation layer as a substrate and a lower electrode of the microelectromechanical element. Use to form. That is, the lower electrode of the microelectromechanical element and the upper electrode of the capacitor are formed on the substrate on which the insulating film is formed on the surface of the semiconductor substrate. Next, after a sacrificial layer is selectively formed on a required region including the lower electrode of the microelectromechanical element, a beam whose end is fixed to the substrate is formed on the sacrificial layer. Next, the sacrificial layer is removed to form a microelectromechanical element composed of a lower electrode and a beam. At the same time, a capacitor having a function of accumulating electric charges and polar molecules composed of the insulating film on the substrate surface and the upper electrode is formed using the semiconductor substrate as the lower electrode. Thereafter, the microelectromechanical element and the capacitor are sealed in the same casing to complete the target electrostatic driving element.

  In order to remove the sacrificial layer on the capacitor side, it is preferable to form a plurality of holes in the upper electrode of the capacitor. In addition, a material film having good adsorptivity to polar molecules may be formed on the surface of the upper electrode of the capacitor.

A semiconductor device according to an embodiment of the present invention includes the above-described electrostatic drive element. The electrostatic drive element is configured as at least one of a filter (so-called band pass filter), a mixer, a resonator, a signal switch, and a sensor.
In addition, the semiconductor device of this embodiment can be configured as a system-in-package type device or a system-on-chip type device including the above-described electrostatic drive element.

  The filter according to the embodiment of the present invention includes a vibrator using an electrostatically driven microelectromechanical element having an electrically driven beam and a capacitor having a function of storing electric charge and polar molecules in the same housing. It is comprised from the electrostatic drive element sealed in the body.

  A communication device according to an embodiment of the present invention is configured using the above filter as a filter in a communication device including a filter that limits a band of a transmission signal and / or a reception signal.

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

  The electrostatic drive element, particularly the microelectromechanical element, which is the object of the present embodiment, is a micrometer scale or nanometer scale element.

  1A to 1C show a first embodiment according to the present invention. The electrostatic drive element 1 according to the present embodiment includes a vibrator element 12 that is an electrostatic drive type microelectromechanical element on a substrate 11 and a capacitor having a function of accumulating charges and polar molecules (such as water). 13 and the vibrator element 12 and the capacitor 13 are hermetically sealed in the same housing 10.

The vibrator element 12 is formed with an input electrode 15 and an output electrode 16 which are lower electrodes on the substrate 11, and a vibrator which vibrates by electrostatic driving facing the two electrodes 15 and 16 with a space 18 interposed therebetween, that is, A beam 17 is arranged. The input electrode 15 and the output electrode 16 function as so-called driving electrodes. The beam 17 straddles the input / output electrodes 15 and 16 in a bridge shape, and both ends thereof are integrally supported by anchor portions (support portions) 19 [19A, 19B]. The input electrode 15 is connected to a signal input line passing through the input terminal t1, the output electrode 16 is connected to a signal output line leading to the output terminal t2, and the beam 17 is supplied with a DC bias voltage (hereinafter referred to as DC bias voltage) V _DC . It is connected to a DC supply line that leads to a terminal t3.

In the transducer element 12, when an input signal (for example, a high frequency signal (RF)) is input to the input electrode 15 through the input terminal t 1, the electrostatic force generated between the beam 17 to which the DC bias voltage V _DC is applied and the input electrode 15. The beam 17 vibrates and an output signal (a high frequency signal (RF)) corresponding to the resonance frequency of the beam 17 is output from the output electrode 16 through the output terminal t2. In this example, the transducer element 12 is It is driven electrostatically and excited in the second harmonic vibration mode.

On the other hand, the capacitor 13 is formed by forming a lower electrode 21 on the substrate 11 and forming an upper electrode 23 facing the space 22 serving as a dielectric layer on the lower electrode 21. A plurality of holes 24 for removing a sacrificial layer for forming the space 22 is formed in the upper electrode 23, and a column 25 in which a part of the sacrificial layer remains between the upper electrode 23 and the lower electrode 21. The upper electrode 23 is supported. A ground potential is applied to the lower electrode 21, and a DC voltage _VDC is applied to the upper electrode 23 from a terminal t3. The capacitor 13 has an area sufficiently larger than the area of the transducer element 12.

  The lower electrodes 15 and 16 of the transducer element 12 and the lower electrode 21 of the capacitor 13 are formed in the same process, and the space 18 of the transducer element 12 is formed in the same process as the space 22 that becomes the dielectric layer of the capacitor 13. The beam 17 of the transducer element 12 and the upper electrode 23 of the capacitor 13 are formed in the same process. The transducer element 12 and the capacitor 13 are hermetically sealed by providing a hollow with the housing 10.

The DC voltage (V _DC ) feed line 20 connected to the transducer element 12 is used to prevent an AC signal, for example, a high frequency signal (RF) input to the transducer element 12 from passing to the DC power supply (V _DC ) side. A passage blocking means, for example, an element for forming an impedance mismatch is connected. In FIG. 1, a resistor Rb is connected as an element for forming an impedance mismatch.

  The substrate 11 is formed of a substrate in which an insulating film is formed on the surface of a semiconductor substrate such as a silicon substrate, or an insulating substrate. In this example, it is formed of a substrate in which an insulating film is formed on the surface of a high resistance silicon substrate. The two electrodes 15, 16 and the beam 17, which are the lower electrodes of the transducer element 12, and the upper and lower electrodes 21, 23 of the capacitor 13 are formed of a conductive layer such as a polycrystalline silicon layer, for example, a polycrystalline silicon layer in this example. Is done.

According to the electrostatic drive element 1 of the above-described first embodiment, when the vibrator element 12 is driven, water is in the gas phase, liquid phase, or solid phase inside the housing 10 (so-called package). Even in the case where polar molecules such as those remain, many polar molecules are adsorbed by the capacitor 13 having a larger area than the vibrator element adjacent to the vibrator element 12, particularly on the surface of the upper electrode 23. That is, the capacitor 13 is formed of the same film formation layer as that of the transducer element 12, and the same DC voltage _VDC as that of the beam 17 is applied to the upper electrode 23. Compared to the element 12, the area is larger and the area is larger. As a result, the adsorption of polar molecules to the transducer element 12 can be reduced to suppress charging, and the transducer element 12, particularly the beam 17 can be altered due to the charging effect of the polar molecule, Oxidation and the like can be reduced. Therefore, characteristic deterioration of the transducer element 12 can be sufficiently suppressed, initial characteristics can be secured, and the reliability of the transducer element 12 can be improved.

  In the present embodiment, the pores can be made porous by appropriately designing the size and interval of the holes 24 formed in the upper electrode 23 of the capacitor 13 according to the etching conditions of the sacrificial layer. The efficiency of physical adsorption of water molecules can be increased. In the capacitor 13, the insulating support pillar 25 inserted between the lower electrode 21 and the upper electrode 23 can be formed of a hygroscopic insulator. As the hygroscopic insulator, for example, a porous silica (SiO 2) thin film is suitable. Porous silica can also be used as a sacrificial layer in the production of the transducer element. The porous silica thin film can be formed by RF magnetron sputtering.

Here, the mechanism of moisture adsorption on the capacitor 13 will be described.
When the vibrator element is formed of the same material as the capacitor, the following moisture adsorption mechanism acts on the vibrator element as well. However, when the capacitor is sacrificed, adverse effects on the vibrator element (for example, when applied to a filter) due to moisture adsorption can be reduced.
Water (water vapor) is a polar molecule and has a dipole moment of 0.387εÅ. Water molecules in a gaseous state between the electrodes of the capacitor, particularly in the vicinity of the electrode surface, are adsorbed on the electrode surface by the electric field created by the electrode. Similarly, polar polymers are also adsorbed. (Note that εÅ is a dipole moment generated when positive and negative elementary charges are placed at a distance of 1Å.)
Further, in the case of a capacitor whose electrode is made of polycrystalline silicon, the adsorbed water molecules are electrolyzed (2H ₂ O + 2e− → H ₂ ; 2OH−). The generated hydrogen is adsorbed on the Si surface and further penetrates into the silicon. At the same time, adsorption of OH groups to the surface or oxidation of the electrode surface also occurs.

On the other hand, in the first embodiment described above, the capacitor 13 can be used as a capacitor constituting a part of a constant voltage circuit for stabilizing the DC bias voltage V _DC to the beam 17 of the transducer element 12. As shown in FIG. 4, a resistor Ra is inserted in series between the DC power supply (V _DC ) 300 of the transducer element 12 and the feed line 301 between the beams 17, and a capacitance (shunt capacitance) is connected between the feed line 301 and the ground. ) By inserting Ca and forming the DC voltage stabilizing circuit 302 by the resistance Ra and the capacitance Ca, the DC bias voltage to the beam 17 can be stabilized. The capacitor 13 of the embodiment can also be used as the capacitance Ca of the stabilization circuit 302.

In the present embodiment, since the resistor Rb for forming an impedance mismatch is connected between the signal line, and hence the beam 17 of the transducer element 12 and the DC power supply (V _DC ), Signal leakage is avoided, and for example, the filter characteristics when a filter is configured are not changed.

  2A and 2B show a second embodiment according to the present invention. In the electrostatic driving element 2 according to the present embodiment, the transducer element 12 and the capacitor 33 having a function of accumulating charges and polar molecules are formed on the substrate 11, and the transducer element 12 and the capacitor 13 are made the same. The casing 10 is configured to be hermetically sealed. The configuration of the transducer element 12 is formed in the same manner as the transducer element 12 of the first embodiment.

On the other hand, in the present embodiment, a substrate in which an insulating film 35 is formed on the surface of the silicon semiconductor substrate 34 is used as the substrate 11. As the insulating film 35, a composite insulating film in which a silicon nitride (SiN) film is stacked on a silicon oxide (SiO 2) film on the surface of the silicon substrate 34 is used. The capacitor 33 includes a silicon semiconductor substrate 34 as a lower electrode, an insulating film 35 as a dielectric film, and an upper electrode 36 formed simultaneously with the lower electrodes 15 and 16 of the vibrator element 12 thereon. Further, a hygroscopic layer 37 with good hygroscopicity is formed on the surface of the upper electrode 36. The moisture absorption layer 37 can be formed, for example, by depositing layered carbon by spin coating, CVD (chemical vapor deposition), sputtering, or the like. The layered carbon film thus formed is etched through a resist mask and processed into a capacitor shape. This carbon film is effective for polymer adsorption. The layered carbon film is cleaned as necessary. The silicon substrate 34 to the ground potential in this example, the upper electrode 36 by applying a DC bias voltage V _DC, configured as a capacitor 33. The area of the capacitor 33 is sufficiently larger than that of the vibrator element 12.
Since other configurations are the same as those in FIG. 1, the same reference numerals are given and redundant description is omitted.

Also in the electrostatic driving element 2 according to the second embodiment, since the hygroscopic layer 37 is formed on the surface of the upper electrode 36 of the capacitor 33, the vibrator element 12 is the same as in the first embodiment. Even when polar molecules remain in the gas phase, liquid phase, or solid phase in the housing 10 (so-called package), the moisture absorption layer 37 on the surface of the upper electrode 33 of the capacitor 33 is present. Polar molecules are adsorbed, and adsorption of polar molecules to the transducer element 12 can be suppressed. Therefore, the characteristic deterioration of the vibrator element 12 can be sufficiently suppressed. Therefore, initial characteristics can be secured and the reliability of the transducer element 12 can be improved.
Also in the second embodiment, the electrodes and the dielectric layer constituting the capacitor 33 except for the hygroscopic layer 37 are formed of the same film forming elements as the transducer element 12, and therefore the transducer element 12 and the capacitor 33 can be formed in the same process. In addition, the same effects as described in the first embodiment can be obtained.

  3A and 3B show a third embodiment according to the present invention. In the electrostatic driving element 3 according to the present embodiment, a vibrator 41 and a capacitor 41 having a function of accumulating charges and polar molecules are formed on a substrate 11, and the vibrator element 12 and the capacitor 41 are made the same. The casing 10 is configured to be hermetically sealed. The configuration of the transducer element 12 is the same as that of the transducer element 12 of the first embodiment.

On the other hand, in the present embodiment, the electrode 42, the space 43, and the electrode 44 are formed on the formation region of the capacitor 41 of the substrate 11 in the same process as the formation of the lower electrodes 15, 16, the space 18, and the beam 17 of the transducer element 12. A plurality of holes 45 are formed in the electrode 44, and a column 46 is formed in the space 43 due to the remaining part of the sacrificial layer. Further, a moisture absorption layer 47 made of, for example, layered carbon similar to the above is formed so as to be electrically connected to both the electrodes 42 and 44. In this example, the substrate 11 is a substrate in which an insulating film 35 is formed on the surface of a silicon substrate 34 as in FIG. The capacitor 41 is configured with the silicon substrate 34 as a lower electrode, the insulating film 35 as a dielectric film, and the electrodes 42 and 44 including the moisture absorption layer 47 as upper electrodes. The area of the capacitor 41 is sufficiently larger than the transducer element 12.
Since other configurations are the same as those in FIGS. 1 and 2, the same reference numerals are given and redundant description is omitted.

Also in the electrostatic drive element 41 according to the third embodiment, since the hygroscopic layer 47 is formed on the surface of the upper electrode of the capacitor 41, the drive of the vibrator element 12 is performed as in the first embodiment. In some cases, even if polar molecules remain in the gas phase, liquid phase, or solid phase inside the housing 10 (so-called package), the polar molecules remain in the moisture absorption layer 47 on the upper electrode surface of the capacitor 41. The adsorption of polar molecules to the vibrator element 12 can be suppressed. Therefore, characteristic deterioration of the transducer element 12 can be sufficiently suppressed, initial characteristics can be secured, and the reliability of the transducer element 12 can be improved.
Also in the third embodiment, since the electrodes and the dielectric layer constituting the capacitor 41 except for the moisture absorption layer 47 are formed of the same film forming elements as the transducer element 12, the transducer element 12 and the capacitor 41 can be formed in the same process. In addition, the same effects as described in the first embodiment can be obtained.

Next, an embodiment of a method for manufacturing an electrostatic drive element according to the present invention will be described. In the following description, a cross section taken along the line CC ′ shown in FIG. 1 is taken as an example.
5 to 9 show an embodiment of a method for manufacturing an electrostatically driven microelectromechanical element according to the present invention. First, as shown in FIG. 5A, a silicon substrate 51 is prepared, and a composite insulating film 52 of, for example, a silicon oxide thin film (HDP thin film: High Density Plasma oxide film) and a silicon nitride film is formed on the upper surface thereof to a required film thickness. Film. Thereafter, a conductive layer 91 made of, for example, a polycrystalline silicon thin film (PDAS film: Phosphorous Doped Amorphous Silicon) is formed on the composite insulating film 52 to a required film thickness. The conductive layer 91 is patterned by a dry etching method through a resist mask of a buried wiring pattern, and the conductive layer 91 is used to bypass the lower part of a wafer bonding pad to be formed in a later process and to connect to the outside. A buried pattern 92 is formed.

  Next, for example, a silicon oxide thin film 93 is grown, and the previously formed embedded wiring pattern 92 is refilled. After planarization of the wafer surface, a composite insulating film 93 of a silicon oxide thin film and a silicon nitride thin film is further grown to refill the previously formed embedded wiring pattern 92. Next, after a via hole 94 for electrical connection is formed in the composite insulating film 93, a polycrystalline silicon thin film (PDAS film) is formed on the wiring pattern 92, and a chemical mechanical polishing (CMP) method is performed. Then, a planarization process is performed to selectively expose the connection body 95 made of polycrystalline silicon in the via hole 94 on the surface.

  Subsequently, a polycrystalline silicon thin film (PDAS film) 53 is formed on the entire surface. The wiring pattern 92 and the thin film 53 are connected by vias.

  Next, as shown in FIG. 5B, a capacitor forming region 72 is formed on the polycrystalline silicon thin film 53 corresponding to the transducer element forming region 71 so as to form a base for fixing a beam serving as a lower electrode and a wiring layer. The shape of the lower electrode and the wiring is formed on the polycrystalline silicon thin film 53 corresponding to the shape of the pad. A resist mask (not shown) is formed. Through this resist mask, unnecessary portions of the polycrystalline silicon thin film 53 are selectively removed by a dry etching method, and the lower electrodes 54 and 55 and the beam fixing base (by a polycrystalline silicon thin film) in the transducer element forming region 71 ( 56 [56A, 56B] also serving as a wiring layer. Further, in the capacitor formation region 72, a lower electrode and a wiring 81 are formed of a polycrystalline silicon thin film. Further, a bonding pad 96 for wafer bonding and a signal input / output pad 97 are formed. Capacitors, vibrator beams and lower electrodes, bonding pads, signal input / output pads are formed as desired.

  Next, as shown in FIG. 6C, the lower electrodes 54 and 55 on the transducer element side and the beam fixing base 56, the lower electrode 81 on the capacitor side, the bonding pad 96, and the input / output signal pad 97 are formed on a sacrificial layer (for example, A silicon oxide thin film (HDP film) 57 is filled back, and the sacrificial layer 57 is planarized by a chemical mechanical polishing (CMP) method. The surface of 97 is exposed.

  Next, as shown in FIG. 6D, on the flattened thin film, the distance between the electrodes 54 and 55 on the transducer element side and the beam to be formed later (space between the upper and lower electrodes of the capacitor becomes a dielectric) The sacrificial layer 58 having a required thickness corresponding to the above is formed. The sacrificial layer 58 can be formed of, for example, a silicon oxide (LP-TEOS: Low Pressure Tetraethoxy Silane) thin film having a thickness of about 50 nm.

  Next, as shown in FIG. 7E, it corresponds to a space for isolating the through hole 60 [60A, 60B] connecting the beam of the transducer element finally obtained and the fixing bases 56A, 56B and the wafer bonding pad portion. The groove 98 to be formed is formed by, for example, a dry etching method.

Next, as shown in FIG. 7F, after a polycrystalline silicon thin film (PDAS film) is formed on the sacrificial layer 58 including the inside of the through hole 60 and the groove 98 until a desired film thickness is obtained, patterning is performed by, for example, dry etching. Then, a film 83 that covers the beam 62 on the transducer element side, the upper electrode 82 on the capacitor side, the wiring (not shown), and the wafer bonding pad 96 is formed. Both ends of the beam 62 are fixed to the fixed base 56 [56A, 56B] via the support portion 63 [63A, 63B].
Next, the shape of the capacitor-side upper electrode 82 (including a plurality of through holes 84) and the shape of a beam (including wiring) are selectively formed. Next, an Al-Si thin film is formed on the wiring or wafer bonding pad portion 83 as necessary, and a closed curve formed around the wiring pattern and the wafer bonding pad portion (micro electromechanical vibrator and capacitor). Form a bank).

  Next, a metal thin film 87 made of Ti / W and a metal thin film 88 made of Au are formed on the wafer bonding pad portion with required thicknesses, for example, about 50 μm and 250 μm, respectively, and lift-off is performed. A bonding metal layer is formed on a wafer bonding pad for bonding a desired lid (wafer).

  Next, as shown in FIG. 8G, the sacrificial layers 57 and 58 are removed using, for example, an etching solution containing hydrogen fluoride. Thereby, a transducer element 65 in which a space 64 of about 50 nm is formed between the lower electrodes 54 and 55 and the beam 62 is formed. Further, on the capacitor forming region side, the sacrificial layer 58 is etched through the hole 84 of the upper electrode 82, and a space 86 serving as a dielectric is formed between the upper electrode 82 and the lower electrode 81, leaving a partial support 85. The capacitor 80 is formed. Also, pads (or wirings) 97 for signal input / output are formed.

  On the other hand, as shown in FIG. 8H, for example, a silicon substrate 101 serving as a lid is prepared. This silicon substrate 101 has a plurality of grooves (corresponding to one chip in FIG. H) corresponding to the height and area of the vibrator element 65 having the beam 62 and the electrostatic drive element having the capacitor 80 produced in the previous step. Only one groove is shown) 102 is formed. Next, after a silicon oxide film 103 is formed on the entire surface of the substrate 101 by thermal oxidation, a composite insulating film 104 of a silicon oxide film and a silicon nitride film by HDP oxidation, for example, has a required thickness, for example, a thickness of about 200 nm. The film is passivated to passivate the surface. Further, a metal thin film 106 made of Ti / W for bonding and a metal thin film 107 made of Au with a thickness of, for example, about 50 μm and 250 μm, respectively, are formed on the portion remaining in the convex shape without being grooved, that is, the peripheral portion of the groove After film formation, a lift-off is performed to form a bonding metal layer, and the lid body 108 is obtained.

Next, as shown in FIG. 9, the lid 108 shown in FIG. 8H and the substrate 51 on which the transducer element 65 and the capacitor 80 shown in FIG. Then, the wafer is hermetically sealed by pressurizing at 50 kg / cm ² under the required temperature and pressure, for example, at 320 ° C.
This embodiment exemplifies a manufacturing method for forming a hermetic package at a wafer level.

  Thereafter, the bonded wafer is diced to obtain the target electrostatically driven micro-electromechanical element 110 as an individual chip (see FIG. 9).

  10 to 11, another embodiment of the method for manufacturing an electrostatic drive element according to the present invention will be described. In the figure, parts corresponding to those in the embodiment shown in FIGS.

  The manufacturing method of the electrostatic driving element according to the present embodiment is the same as the steps shown in FIGS. 5A to 7E. That is, as shown in FIG. 10A (same as the process of FIG. 7E), a composite insulating film 52, a wiring pattern 92, a composite insulating film 93, and a connection body 95 are sequentially formed on the silicon substrate 51, and further, polycrystalline. The lower electrodes 54 and 55 on the vibrator element side, the fixing bases 56A and 56B, and the wafer bonding pad 96 are formed by a silicon thin film, and the electrode 111, the sacrificial layer 57, the sacrificial layer 58, and the through hole 60 [ 60A, 60B] and the through groove 98 is formed.

Next, as shown in FIG. 10B, after a polycrystalline silicon thin film (PDAS film) is formed on the sacrificial layer 58 including the inside of the through hole 60 and the through groove 98 until a desired film thickness is obtained, for example, by a dry etching method. By patterning, the beam 62 on the transducer element side and the conductive layer 83 on the wafer bonding pad 96 are formed. Both ends of the beam 62 are fixed to the fixed base 56 [56A, 56B] via the support portion 63 [63A, 63B].
Next, an Al—Si thin film is formed on the conductive layer 83 on the wiring and bonding pad portions to form a wiring pattern and the like.

  Next, a bonding metal layer formed by laminating a metal thin film 87 made of Ti / W and a metal thin film 88 made of Au is selectively formed on the conductive layer 83 on the bonding pad portion.

Next, as shown in FIG. 11C, the sacrificial layers 57 and 58 are removed using, for example, an etching solution containing hydrogen fluoride, and face the lower electrodes 54 and 55 via the space 64 in the transducer element formation region 71. A vibrator element 64 composed of the beam 62 is formed. On the other hand, in the capacitor forming region 72, a capacitor having the silicon substrate 51 as a lower electrode, the composite insulating film 93 as a dielectric film, and the electrode 111 manufactured in the same process as the lower electrodes 54 and 55 of the vibrator element as an upper electrode. 112 is formed. In the capacitor 112, as described above, the ground potential is applied to the silicon substrate 51 and the DC bias voltage V _DC is applied to the upper electrode 111 during driving.

  If necessary, a moisture absorption layer made of, for example, layered carbon as described above is formed on the upper electrode 111 of the capacitor 112.

  Next, as shown in FIG. 11D, as in FIG. 9 described above, the lid 108 is hermetically bonded and hermetically sealed to the substrate 51 on which the transducer element 64 and the capacitor 112 are formed. Thereafter, the bonded wafer is diced to obtain the target electrostatic drive element 113 as an individual chip (see FIG. 11D).

  According to the manufacturing method of the electrostatic drive element according to the above-described embodiment, the vibrator element 65 and the capacitor 80 or 112 can be formed in the same process. Then, the electrostatic drive that can sufficiently suppress the deterioration of the transducer element and the oxidation of the current-carrying portion by the process of forming the transducer element 65 and the capacitor 80 or 112 and the process of hermetically sealing them. The element can be easily manufactured with high reliability and low cost. Accordingly, since it is possible to select whether the hermetically sealing is performed at the wafer level or the device level, the electrostatic driving element, various electrostatic driving elements including the electrostatic driving element, and these Can be provided at a low price. That is, it is possible to provide a method for manufacturing an electrostatic drive element and a semiconductor device that can be manufactured and put into practical use at a low price.

In another embodiment according to the present invention, a signal filter, a mixer, a resonator, a SiP (system in package) device module including the signal filter, a mixer, a resonator, and a SoC (system A semiconductor device such as an on-chip device module can be configured.
According to the semiconductor device of the present embodiment, since the electrostatic driving element having high reliability as described above is provided, a highly reliable semiconductor device can be provided.

  The electrostatic drive element according to the present invention can be configured as a vibrator group in which a plurality of vibrator elements are arranged in parallel. The electrostatic drive element according to the present invention can be used as a band signal filter such as a high frequency (RF) filter or an intermediate frequency (IF) filter. The present invention can provide a communication apparatus that communicates using electromagnetic waves, such as a mobile phone, a wireless LAN device, a wireless transceiver, a TV tuner, and a radio tuner, by applying the filter using the electrostatic drive element described above. .

Next, a configuration example of a communication device to which the filter of the present embodiment is applied will be described with reference to FIG.
First, the configuration of the transmission system will be described. I-channel transmission data and Q-channel transmission data are supplied to digital / analog converters (DACs) 201I and 201Q, respectively, and converted into analog signals. The converted signal of each channel is supplied to band pass filters 202I and 202Q to remove signal components other than the band of the transmission signal, and the outputs of the band pass filters 202I and 202Q are supplied to the modulator 210. Supply.

  The modulator 210 supplies the frequency signals corresponding to the transmission frequency supplied from the PLL (phase-locked loop) circuit 203 for transmission to the mixers 212I and 212Q via the buffer amplifiers 211I and 211Q for each channel. The signals are mixed and modulated, and both mixed signals are added by an adder 214 to form a single transmission signal. In this case, the signal phase of the frequency signal supplied to the mixer 212I is shifted by 90 ° by the phase shifter 213 so that the I channel signal and the Q channel signal are orthogonally modulated.

  The output of the adder 214 is supplied to the power amplifier 204 via the buffer amplifier 215 and amplified so as to have a predetermined transmission power. The signal amplified by the power amplifier 204 is supplied to the antenna 207 via the transmission / reception switch 205 and the high frequency filter 206, and is wirelessly transmitted from the antenna 207. The high frequency filter 206 is a band pass filter that removes signal components other than the frequency band transmitted and received by the communication apparatus.

  As a configuration of the reception system, a signal received by the antenna 207 is supplied to the high frequency unit 220 via the high frequency filter 206 and the transmission / reception switch 205. In the high frequency unit 220, the received signal is amplified by a low noise amplifier (LNA) 221 and then supplied to the band pass filter 222 to remove signal components other than the received frequency band, and the removed signal is buffer amplifier 223. To the mixer 224. Then, the frequency signals supplied from the channel selection PLL circuit 251 are mixed, a signal of a predetermined transmission channel is used as an intermediate frequency signal, and the intermediate frequency signal is supplied to the intermediate frequency circuit 230 via the buffer amplifier 225.

  The intermediate frequency circuit 230 supplies the supplied intermediate frequency signal to the band-pass filter 232 via the buffer amplifier 225, removes signal components other than the band of the intermediate frequency signal, and automatically removes the removed signal. The signal is supplied to an adjustment circuit (AGC circuit) 233 to obtain a signal with a substantially constant gain. The intermediate frequency signal whose gain has been adjusted by the automatic gain adjustment circuit 233 is supplied to the demodulator 240 via the buffer amplifier 234.

  The demodulator 240 supplies the supplied intermediate frequency signal to the mixers 242I and 242Q via the buffer amplifier 241, mixes the frequency signal supplied from the intermediate frequency PLL circuit 252 and receives the received I channel signal. The component and the Q channel signal component are demodulated. In this case, the I-signal mixer 242I is supplied with a frequency signal whose signal phase is shifted by 90 ° by the phase shifter 243, and the quadrature-modulated I-channel signal component and Q-channel signal component. Is demodulated.

  The demodulated I channel and Q channel signals are supplied to band pass filters 253I and 253Q via buffer amplifiers 244I and 244Q, respectively, to remove and remove signal components other than I channel and Q channel signals. The obtained signals are supplied to analog / digital converters (ADC) 254I and 254Q, sampled and converted into digital data, and I-channel received data and Q-channel received data are obtained.

  In the configuration described so far, it is possible to limit the band by applying the filter of the configuration of this example as a part or all of each band-pass filter 202I, 202Q, 206, 222, 232, 253I, 253Q. is there. In the example of FIG. 12, each filter is configured as a band pass filter. However, a low pass filter that passes only a frequency band lower than a predetermined frequency, or a frequency band that is higher than a predetermined frequency is used. It is also possible to configure as a high-pass filter that passes, and apply the filter of the configuration of this example to these filters. In the example of FIG. 12, the communication device performs wireless transmission and reception, but may be applied to a filter included in a communication device that performs transmission and reception via a wired transmission path, and only transmission processing is performed. The filter of the configuration of this example may be applied to a filter included in a communication device that performs or a communication device that performs only reception processing.

  According to the communication apparatus according to the present embodiment, by using the filter by the electrostatic drive element of the present invention as the bandpass filter, it is possible to avoid the deterioration due to the charging phenomenon in the filter, and the communication apparatus with high reliability. Can be provided.

A, B, and C It is the schematic block diagram which shows 1st Embodiment of the electrostatic drive element which concerns on this invention, its sectional drawing on the AA line, and sectional drawing on the BB line. A and B It is the schematic block diagram which shows 2nd Embodiment of the electrostatic drive element which concerns on this invention, and its sectional drawing on the AA line. A and B It is the schematic block diagram which shows 3rd Embodiment of the electrostatic drive element which concerns on this invention, and its sectional drawing on the AA line. It is explanatory drawing with which it uses for description of the constant voltage stabilization circuit applied to this invention. 1A to 1B are manufacturing process diagrams (part 1) illustrating an embodiment of a method for manufacturing an electrostatic driving element according to the present invention. C to D are manufacturing process diagrams (part 2) illustrating an embodiment of a method for manufacturing an electrostatic driving element according to the present invention. E to F are manufacturing process diagrams (part 3) illustrating an embodiment of a method for manufacturing an electrostatic driving element according to the present invention. GH is a manufacturing process figure (the 4) which shows one Embodiment of the manufacturing method of the electrostatic drive element which concerns on this invention. It is a manufacturing process figure (the 5) which shows one Embodiment of the manufacturing method of the electrostatic drive element which concerns on this invention. FIGS. 9A to 9B are manufacturing process diagrams (part 1) illustrating another embodiment of a method for manufacturing an electrostatic driving element according to the present invention. FIGS. C to D are manufacturing process diagrams (part 2) illustrating another embodiment of the method for manufacturing an electrostatic driving element according to the present invention. It is a block diagram which shows one Embodiment of the communication apparatus which concerns on this invention.

Explanation of symbols

1, 2, 3, .. Electrostatic drive element, 10 .. Lid, 11 .. Substrate, 12 .. Transducer element, 13 .. Capacitor, 15, 16 ... Lower electrode, 17 .. Beam, 21. · Lower electrode, 22 ·· Space, 23 ·· Upper electrode, 25 ·· Strut, 36 ·· Upper electrode, 37 ·· Hygroscopic layer, 51 ·· Silicon substrate, 52 ·· Insulating film, 53 ·· Polycrystalline silicon Thin film, 54, 55, lower electrode, 56 [56A, 56B], fixing base, 57, 58, sacrificial layer, 62, beam, 65, transducer element, 71, transducer element formation region, 72. Capacitor formation region, 73 .. Wafer bonding pad and I / O pad formation region, 80 .. Capacitor, 81 .. Lower electrode, 82 ... Upper electrode, 101 ... Silicon substrate, 102 ... Groove, 108 ... Lid, 110 ... electrostatic drive element

Claims (12)

An electrostatic drive type micro electromechanical element having an electrically driven beam and a capacitor having a function of accumulating electric charge and polar molecules are sealed in the same housing. Drive element. The electrostatic drive element according to claim 1, wherein the capacitor is connected to a DC power supply circuit of the micro electromechanical element to become a capacitor. The capacitor viewed from the DC power supply terminal is electrically connected in parallel with the microelectromechanical element,
The electrostatic drive element according to claim 1, wherein an AC signal passage blocking unit is provided between the capacitor and the microelectromechanical element. The electrostatic drive element according to claim 1, wherein the electrode of the capacitor is formed of the same film formation layer as the electrode or beam of the microelectromechanical element. The electrostatic drive element according to claim 1, wherein a sufficient hole is formed in one electrode of the capacitor to allow liquid to pass through. Forming a lower electrode of a microelectromechanical element and a lower electrode of a capacitor on a substrate;
Forming a sacrificial layer selectively on a required region including the lower electrode of the microelectromechanical element and on the lower electrode of the capacitor;
Forming a beam having an end fixed to the substrate and an upper electrode of the capacitor on each sacrificial layer;
Removing the sacrificial layer to form a microelectromechanical element composed of a lower electrode and a beam, a capacitor composed of a lower electrode and an upper electrode sandwiching a space, and a capacitor having a function of accumulating polar molecules;
A method of manufacturing an electrostatic drive element, comprising: sealing the micro electro mechanical element and the capacitor in the same casing. Forming a lower electrode of a microelectromechanical element and an upper electrode of a capacitor on a substrate having an insulating film formed on a surface of a semiconductor substrate;
Selectively forming a sacrificial layer on a required region including a lower electrode of the microelectromechanical element;
Forming a beam having an end fixed to the substrate on the sacrificial layer;
A microelectromechanical element composed of a lower electrode and a beam by removing the sacrificial layer, a capacitor having a function of accumulating charges and polar molecules composed of the semiconductor substrate serving as the lower electrode, the insulating film, and the upper electrode; Forming a step;
A method of manufacturing an electrostatic drive element, comprising: sealing the micro electro mechanical element and the capacitor in the same casing. A semiconductor device comprising the electrostatic drive element according to claim 1. The semiconductor device according to claim 8, wherein the electrostatic driving element is configured as at least one of a filter, a mixer, a resonator, a signal switch, and a sensor. The semiconductor device according to claim 9, wherein the semiconductor device is configured as a system-in-package type device or a system-on-chip type device including the electrostatic driving element. An electrostatic drive element in which a vibrator having an electrically driven micro electromechanical element having an electrically driven beam and a capacitor having a function of accumulating charges and polar molecules are sealed in the same housing A filter characterized by comprising. In a communication apparatus provided with a filter for limiting the bandwidth of a transmission signal and / or a reception signal,
The communication device according to claim 11, wherein the filter according to claim 11 is used as the filter.

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