JP2006217207A - Vibrator and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a structure of a vibrator whose electrode intersection area can be made large while an increase in occupation area is suppressed and to obtain a structure of a vibrator whose electrode intersection area can be made large without sacrificing patterning precision nor simplicity of a manufacturing process. <P>SOLUTION: The vibrator 100 is configured to generate mechanical longitudinal vibration on a substrate 101 with an electrostatic force, and equipped with a 1st counter electrode 121 having a counter surface 121a at its periphery and a 2nd counter electrode 122 having a plurality of vibration electrodes 111 which are peripherally arranged around the 1st counter electrode and supported to extend and contract in a direction radially to contact and leave the 1st counter electrode and each have a vibration surface 111a opposite the counter surface 121a of the 1st counter electrode inside a radius direction R and another vibration surface 11b outside the radius direction R, and a counter surface 122a opposite to radially outside vibration surfaces 111b of the plurality of vibration electrodes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vibrator and a semiconductor device, and more particularly, to a vibrator structure of a type in which an electrostatic force is applied to a vibrating electrode from both sides to cause longitudinal vibration.

  In the advanced information society in recent years, performance of various electronic systems has been remarkably improved, and as a result, vibrators used in oscillation circuits, filter circuits, and the like are required to have higher frequencies. In addition, electronic devices such as communication devices are becoming more and more multifunctional, and accordingly, downsizing and multifunctional elements are required.

  On the other hand, electronic devices using MEMS (Micro Electro Mechanical System) technology are surely spreading in the market as represented by printer heads, DMD (Digital Micromirror Device), and the like. Features of the MEMS device include that it can be made much more compact than conventional elements, that batch processing can be used in the manufacturing process, and that internal loss is small. In particular, by forming an element structure on a silicon substrate, it can be integrated into the system integrally with the IC, so it has a great advantage in making the system more compact and multifunctional. .

  There are vibrators using MEMS technology that use flexural vibrations of structures formed on a substrate and those that use torsional vibrations, and can obtain a high frequency that is most suitable for higher frequencies. The vibrator uses longitudinal vibration (vibration corresponding to expansion / contraction deformation of the structure).

  As the most basic vibrator using this longitudinal vibration, there is one having the structure shown in FIG. In this vibrator, a beam-shaped vibrating electrode 1 is formed on a substrate, and a supporting beam 2 having a base fixed to a supporting and fixing portion 2 is connected to both ends of the central portion of the vibrating electrode 1 so that the vibrating electrode 1 is mounted on the substrate. And a pair of counter electrodes 4 and 5 are arranged opposite to each other on both sides in the longitudinal direction of the vibration electrode 1, and the pair of counter electrodes 4 and 5 and the gap therebetween. It is a bulk longitudinal vibration resonator (BLR) in which longitudinal vibration is generated by applying variable voltage between the vibration electrode 1 and the vibration electrode 1 to expand and contract in the longitudinal direction (Bulk Longitudinal Resonator). For example, see the following non-patent document 1).

  In addition, as shown in FIG. 7, a ring-shaped vibrator RBAR in which a vibrating electrode 7 is formed in a ring around one counter electrode 6, and another ring-shaped counter electrode 8 is arranged around the vibrating electrode 7. (Radial Bulk Annular Resonator) is also known (see, for example, Non-Patent Document 2 below).

Further, in order to improve the shortage of the electrode crossing area (electrode facing area), which is a drawback of the BLR, an improved BLR in which both ends of the vibration electrode are configured to be wide has been proposed (for example, the following non-BLR). (See Patent Document 3).
T. Mattila and 7 others “12 MHz Micromechanical Bulk Acoustic Mode Oscillator” Sensor and Actuators A; Physics Vol. 101, 1-2, September 20, 2002 Pages 1-9 (Sensor and Actuators A; Physical, Volume 101, Issues 1-2, 30 September 2002, Pages 1-9) Brian Bircumshaw and 6 others “THE RADIAL BULK ANNULAR RESONATOR: TOWARDS A 50Ω RF MEMS FILTER” Transducers 2003, 875th -879 pages (Transducers '03, Pages: 875-879) M. Koskemvouri and 6 others “Long-term stability of single-crystal silicon microresonators” Sensor and Actuators A; Physics Vol. 115, September 2004 15th pages 23-27 (Sensors and Actuators A; Physical, Volume 115, 15 September 2004, Pages: 23-27)

  The aforementioned BLR has advantages such as a simple and easy manufacturing process, or a simple longitudinal vibration that is easy to design, but on the other hand, between the vibrating electrode and the counter electrode. Since the electrode crossing area (electrode facing area) is small, there is a disadvantage that the output becomes small.

In order to increase the output of the BLR, the electrode crossing area may be increased. However, in order to increase the electrode crossing area, it is necessary to increase the width W of the vibrating electrode 1 shown in FIG. Since the widths of the electrodes 4 and 5 must also be increased, the element occupation area on the substrate increases. In order to suppress an increase in the area occupied by the element, the length L is made relatively small (in practice, the length L is constant when the frequency is maintained), and the width W is made relatively large (for example, The width W is larger than the length L, that is, W / L> 1). In this case, the width direction end is caused by the Poisson effect of the vibrating electrode 1 as shown by a two-dot chain line in FIG. The amount of deformation of the part becomes larger than that of the other part in the width direction. Accordingly, as shown in the graph of FIG. 6, the resonance frequency f _FEM (the value calculated by the finite element method in the graph) is the resonance frequency f _BLR (= (1) obtained by the one-dimensional model ignoring the width W. / 2L) · (E / ρ) ^0.5 , indicated by a broken line in the figure)). As described above, when the width W of the vibrating electrode 1 is larger than the length L, the resonance frequency is lowered due to the Poisson effect. In addition, if the width W is relatively large even in a range where the decrease in frequency is not significant, it is generally difficult for longitudinal vibration to occur. Become. This point is basically the same in the improved BLR described in Non-Patent Document 3 described above.

  On the other hand, in FIG. 7, the RBAR can take a large electrode crossing area, and the Poisson effect does not occur because the vibrating electrode 7 and its vibrating surface are formed in an annular shape. Is difficult to deform in the radial direction (becomes uniaxial strain), and it is difficult to obtain sufficient amplitude.

  Therefore, when forming the RBAR, it is necessary to reduce the facing distance (electrode spacing) between the vibrating electrode 7 and the facing electrodes 6 and 8 or to increase the applied voltage (driving voltage). However, there is a limit to increasing the applied voltage (drive voltage). Further, in order to reduce the electrode spacing of the RBAR, the patterning processing method using a normal photolithography method or the like has insufficient patterning and etching accuracy, and the electrode spacing cannot be accurately formed. A normal operation mode may not be realized due to the eccentricity of the electrode position.

  Furthermore, when a normal patterning method cannot be used due to the above-described patterning accuracy problem, it is necessary to form an electrode pattern by a two-layer process, which causes a problem that the manufacturing process becomes complicated. For example, after depositing a polysilicon film or the like, patterning is performed to form the vibrating electrode 7, and the surface of the vibrating electrode 7 is covered with a thin oxide film, and then a polysilicon film or the like is deposited again to perform patterning. There is a method in which the electrodes 6 and 8 are formed and then the oxide film is removed to realize the same electrode spacing as the thickness of the oxide film. However, in this method, it is necessary to form the pattern of the vibrating electrode 7 and the pattern of the counter electrodes 6 and 8 in separate steps, and the polysilicon film formation and patterning steps are required twice. Increases the manufacturing cost.

  Therefore, the present invention solves the above-described problems, and an object of the present invention is to realize a vibrator structure that can increase the electrode crossing area while suppressing an increase in the occupied area. Another object is to realize a structure of a vibrator that can increase the electrode crossing area without sacrificing the tolerance of patterning accuracy and the simplicity of the manufacturing process.

  In view of such circumstances, the vibrator of the present invention is a vibrator configured to generate mechanical longitudinal vibration by electrostatic force on a substrate, and includes a first counter electrode having a counter surface on the outer periphery, Arranged in a circumferential direction around the first counter electrode, each supported in a radially expandable / contractible manner with respect to the first counter electrode, and on the inner side in the radial direction of the first counter electrode A plurality of vibration electrodes having a vibration surface facing the facing surface and having another vibration surface on the radially outer side, and a facing surface facing the vibration surface on the radially outer side of the plurality of vibration electrodes. And a second counter electrode comprising: a second counter electrode.

  According to the present invention, when viewed in the radial direction, the vibration electrode is disposed between the first counter electrode and the second counter electrode, and the plurality of vibration electrodes are arranged in the circumferential direction around the first counter electrode. Therefore, it is possible to increase the electrode intersection area between the vibrating electrode and the counter electrode while suppressing the occupied area on the substrate as a whole.

  In the present invention, it is preferable that the plurality of vibrating electrodes are uniformly distributed in the circumferential direction around the first counter electrode. As a result, it becomes easy to uniformly configure the support state, pressure distribution, and the like between the plurality of vibrating electrodes, and it becomes easier to miniaturize the entire vibrator.

  In the present invention, the vibration surfaces of the plurality of vibration electrodes, the opposed surfaces of the first counter electrode and the opposed surfaces of the second electrode facing the vibration surfaces are arranged on the same virtual circle, It is preferable that they are concentric with each other. According to this, the deformation mode by the longitudinal vibration of the plurality of vibration electrodes can be configured uniformly, and the whole can be easily configured compactly, and further downsizing can be further facilitated.

  In the present invention, it is preferable that the first counter electrode has a structure integrally including the counter surface that faces all of the plurality of vibration electrodes. As a formation mode of the first counter electrode, a plurality of first counter electrodes corresponding to each of the plurality of vibration electrodes may be provided separately, but the first counter electrode is provided inside the vibration electrode or the second counter electrode. Therefore, when the plurality of first counter electrodes are dispersedly arranged in a wide range, the occupied area of the entire vibrator increases. As described above, the first counter electrode can be reduced in size by integrally providing the counter surface opposed to all the inner vibration surfaces of the plurality of vibration electrodes, and as a result, the vibrator It becomes easy to compose the whole compactly.

  In the present invention, it is preferable to include a plurality of the second counter electrodes each provided with the facing surfaces that respectively face the vibrating surfaces outside the plurality of vibrating electrodes. As a formation mode of the second counter electrode, even if the counter surface which is opposed to all of the plurality of vibration electrodes is integrally provided (for example, having an annular electrode shape surrounding the plurality of vibration electrodes). However, since the second counter electrode is disposed outside the first counter electrode and the vibration electrode, when the second counter electrode is formed integrally, the occupied area of the entire vibrator increases. On the other hand, there is a region where the vibrator structure is not formed between the second counter electrodes in the outer peripheral portion of the vibrator by separately providing the plurality of second counter electrodes corresponding to the plurality of vibration electrodes as described above. Therefore, it becomes possible to form another circuit or element in the region, or to provide wiring that passes through the region, and to significantly reduce the effective occupation area of the vibrator structure Is possible.

  In the present invention, it is preferable that the vibrating electrode is supported from both sides in the circumferential direction by a pair of support beams including a beam portion extending in the circumferential direction connected to the intermediate portion in the radial direction. According to this, since the vibration electrode is supported from both sides in the circumferential direction by connecting the pair of support beams to the radial intermediate portion of the vibration electrode from both sides in the circumferential direction, the vibration electrode is not hindered by preventing vertical vibration. Can be supported stably. In addition, the support beam has a beam portion extending in the circumferential direction, and this beam portion is connected to the middle portion in the radial direction of the vibration electrode, so that the vertical vibration in the radial direction of the vibration electrode is efficiently prevented without being disturbed. Can occur. Furthermore, since the support beam is disposed on the same plane level with respect to the vibration electrode (that is, at a lateral position on the substrate), the vibration electrode and the support beam can be formed in the same layer. It can also be simplified.

  In the present invention, it is preferable that the beam portion extending in the circumferential direction has a shape curved along the circumferential direction. According to this, since the beam portion has a shape curved along the circumferential direction, the beam portion can be prevented from projecting to the outer peripheral side. An increase in the total occupied area can be suppressed.

  In the present invention, it is preferable that a plurality of sets of beam portions extending in the circumferential direction corresponding to the plurality of vibration electrodes are arranged on the same virtual circle. Accordingly, the plurality of vibration electrodes can be supported in the same positional relationship with each other, and the support performance can be made uniform. Here, when the vibration surfaces of the plurality of vibration electrodes and the opposed surfaces facing each other from both sides in the radial direction are arranged on the same virtual circle, and these virtual circles are configured to be concentric with each other For this reason, it is desirable that the virtual circle where the plurality of sets of beam portions are arranged to be concentric.

  In the present invention, it is preferable that the vibrating electrodes adjacent in the circumferential direction are supported by the common beam portion. According to this, since the area occupied by the support beam can be reduced by sharing the beam portion between the adjacent vibration electrodes, the entire vibrator can be configured more compactly.

  In the present invention, it is preferable that all the vibrating electrodes are connected to each other via a beam portion extending in the circumferential direction. According to this, since all the vibration electrodes are connected to each other via the beam portions extending in the circumferential direction of the support beam, it is possible to operate as an integrated vibration system, and the support beam is simplified and Since it can be configured compactly, the size can be further reduced.

  In the present invention, it is preferable that the support beam is fixed on the substrate by support fixing portions arranged alternately with a predetermined number of the vibration electrodes when viewed in the circumferential direction. According to this, a predetermined number (one or a plurality) of vibration electrodes and support fixing portions for fixing the support beams are alternately arranged in the circumferential direction, thereby increasing the support balance of the entire vibrator, A stable vibration state can be obtained.

  In this invention, it is preferable that the said support beam further has a pair of beam part extended in the said radial direction which supports the beam part extended in the said circumference direction from the said radial direction both sides. According to this, it becomes easier to secure the length of the support beam compared to the case where the beam portion extending in the circumferential direction is directly fixed on the substrate, the support performance can be improved, and the beam portion extending in the radial direction is provided. As a result, the beam portion extending in the circumferential direction can be shortened, and the length of the supporting beam in the circumferential direction can be limited. Therefore, the entire vibrator can be further reduced in size.

  In this case, it is further preferable that the vibrating electrodes adjacent in the circumferential direction are supported by a common beam portion extending in the circumferential direction, and the pair of beam portions extending in the radial direction are connected to an intermediate portion of the common beam portion. .

  In the present invention, it is preferable that the base portions of the pair of radially extending beam portions are respectively fixed on the substrate. By fixing the base of the pair of beams extending in the radial direction as they are on the substrate (connecting to the support fixing portion), the region between the vibrating electrodes can be efficiently used to securely fix the support beam on the substrate. Can be done. That is, in order to fix the support beam on the substrate, a certain amount of area is required as a support fixing portion, but by securing the base portion of the beam portion extending in the radial direction to the support fixing portion, it is ensured between adjacent vibration electrodes. The space efficiency can be effectively used as the formation region of the support fixing portion, so that the space efficiency can be improved.

  In the present invention, a fluctuation voltage is applied between the first counter electrode, the second counter electrode, and the vibration electrode to cause the vibration electrode to generate the longitudinal vibration in the radial direction. It is preferable to further include an electrical connection structure for obtaining an output based on a change in electrostatic capacitance between at least one of the first counter electrode and the second counter electrode generated and the vibration electrode. This electrical connection structure includes wiring formed in the substrate (lower wiring layer), wiring formed on the substrate surface (surface wiring layer), or wiring directly connected to the vibrator structure on the substrate (bonding wire, etc.) ) And the like.

  Next, a semiconductor device of the present invention includes any one of the vibrators described above, and the substrate is a semiconductor substrate on which a semiconductor circuit is configured. According to this, since the semiconductor circuit and the vibrator can be configured integrally, it can greatly contribute to further downsizing of the electronic device. In particular, since the vibrator is conductively connected to the semiconductor circuit, it can be integrated on the circuit and the wiring structure can be integrated with the substrate, thereby further reducing the size and improving the reliability. be able to.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view (A) and a cross-sectional view (B) of a vibrator 100 according to the present embodiment. The vibrator 100 according to the present embodiment includes a vibrating electrode 111 disposed on the substrate 101, a support beam 112 that supports the vibrating electrode 111 on the substrate 101, and first and second electrodes disposed opposite to the inside and outside of the vibrating electrode 111. It has a first counter electrode 121 and a second counter electrode 122. In addition, an electrical connection structure 130 connected to the vibration electrode 111, the first counter electrode 121, and the second counter electrode 122 is also provided.

  A plurality (four in the illustrated example) of the vibrating electrodes 111 are arranged in the circumferential direction P around the first counter electrode 121. The vibrating electrode 111 has a rod (band plate) shape that is long in the radial direction R contacting and separating from the first counter electrode 121 and short in the circumferential direction P. The dimensions of the vibration electrode 111 are not particularly limited. For example, as shown in FIG. 6, the width W (the width in the circumferential direction P in the present embodiment) and the length L (the length in the radial direction R in the present embodiment). The ratio W / L is preferably in the range of 0.1 to 0.8. This is because, within this range, the resonance frequency almost coincides with that of the one-dimensional model, so that the design can be performed easily and the reproducibility of the vibration characteristics is improved. That is, the frequency of longitudinal vibration of the vibrating electrode 111 can basically be determined by the material constant and length.

  The inner end surface of the vibration electrode 111 is a vibration surface 111 a that faces the facing surface 121 a of the first counter electrode 121. The vibration surface 111a is a plane orthogonal to the longitudinal direction of the vibration electrode 111 (radial direction R in the illustrated example). The outer end surface of the vibrating electrode 111 is a vibrating surface 111 b that faces the facing surface 122 a of the second counter electrode 122. This vibration surface 111 b is also a plane orthogonal to the longitudinal direction of the vibration electrode 111. With this configuration, the vibration electrode 111 can accurately receive an electrostatic force described later in the longitudinal direction (radial direction R) on the vibration surfaces 111a and 111b, and thereby longitudinal vibration in the longitudinal direction. (Stretching vibration) is efficiently induced.

  A pair of support beams 112 are connected to the middle portion in the radial direction R of the vibration electrode 111 from both sides in the circumferential direction P. In the illustrated example, four support beams 112 are provided throughout the vibrator 100. The support beam 112 is connected to an intermediate portion (preferably an intermediate point) in the radial direction R of the vibration electrode 111 and extends in the circumferential direction P, and an intermediate portion in the circumferential direction P of the first beam portion 112a. It includes a pair of second beam portions 112b that are connected from both sides in the radial direction R to (preferably an intermediate point) and extend in the radial direction R. The base portion of the second beam portion 112 b is connected and fixed to a support fixing portion 113 fixed on the substrate 101.

  In the present embodiment, the two vibrating electrodes 111 adjacent in the circumferential direction P are supported by a common support beam 112 disposed between them. That is, in the support beam 112, both end portions in the circumferential direction P of the first beam portion 112 a are connected together to an intermediate portion in the radial direction R of the two vibrating electrodes 111 adjacent to the circumferential direction P. In other words, in the present embodiment, a predetermined number (one in the illustrated example) of the vibrating electrodes 111 and the support beams 112 are alternately arranged when viewed in the rotation direction P, and one support beam 112 is arranged in the rotation direction. A pair of vibrating electrodes 111 on both sides of P is supported together. Thereby, each vibration electrode 111 can be supported stably.

  In the present embodiment, all the vibrating electrodes 111 arranged in the circumferential direction P are connected to each other via the first beam portions 112a of the support beams 112. As a result, all the vibration electrodes 111 are connected to each other in a state of being separated from the substrate 101, and thus operate as an integrated vibration system. In addition, since the support fixing portion 113 is not directly interposed between the vibration electrodes 111, the effective length of the support beam can be secured without increasing the occupied area of the support beam, and thus the support beam 112 can be configured simply and compactly. Therefore, further downsizing becomes easier.

  The vibration surfaces 111a and 111b of the plurality of vibration electrodes 111 are arranged on the same virtual circles b and d with the vicinity of the arrangement region of the first counter electrode 121 as a center, and are also opposed to the vibration surfaces 111a and 111b. The opposing surface 121a of the electrode 121 and the opposing surface 122a of the second counter electrode 122 are also arranged on the same virtual circle a and e, respectively. These four virtual circles a, b, d, and e are all concentric with each other. Further, each part of the support beam 112 is also arranged on the same virtual circle, and the virtual circles passing through the positions of the parts are concentric with each other, and the virtual circles on the vibration surface and the opposing surface are the same. Even concentric circles. The first beam portion 112a has a curved shape along the circumferential direction P, whereby the first beam portions 112a of the plurality of support beams 112 are arranged in an annular shape, and the whole extends along one virtual circle c. It is formed to stretch. Thus, since each structure part corresponding to the plurality of vibration electrodes 111 is arranged concentrically, each part of the vibrator 100 can be efficiently arranged in the space on the substrate 101. The space efficiency of the vibrator 100 can be increased and the size can be easily reduced.

  The first counter electrode 121 is located at the center of the vibrator 100, and in the case of this embodiment, the first counter electrode 121 is configured as an integrated body having a plurality of counter surfaces 121a that oppose the vibration surfaces 111a of the plurality of vibration electrodes 111. Accordingly, the first counter electrode 121 can be easily downsized, and the entire vibrator 100 can be further downsized. However, a plurality of first counter electrodes respectively corresponding to the plurality of vibrating electrodes 111 may be provided separately. In this case, the size of each first counter electrode is reduced and the electrical connection structure to each first counter electrode is complicated, but it can be functionally configured in the same manner as in the illustrated example. Note that the facing surface 121a is a plane parallel to the vibration surface 111a.

  In the present embodiment, the plurality of second counter electrodes 122 are separately provided on the radially outer sides of the plurality of vibration electrodes 111. That is, a plurality of second counter electrodes 122 each provided with a counter surface 122a facing the vibration surface 111b of the vibration electrode 111 are separately provided. In this way, in the outer peripheral portion of the vibrator 100, the region existing between the adjacent vibrating electrodes 111 can be structured to open outward, so that various regions can be formed between the adjacent second counter electrodes 122. Such a structure, for example, various circuits, elements, or wirings can be formed. Therefore, the area occupied by the vibrator 100 can be effectively reduced. However, the second opposing electrode may be configured such that the opposing surface 122a facing the vibration surfaces 111b of all the vibrating electrodes 111 is integrally configured. For example, the second counter electrode can be formed in an annular shape so as to surround all of the plurality of vibration electrodes 111. The facing surface 122a is a plane parallel to the vibration surface 111b.

  In the vibrator 100 according to the present embodiment, the plurality of vibrating electrodes 111 are uniformly distributed as viewed in the circumferential direction P, and each part of the first counter electrode 121 and the second counter electrode 122 is also viewed in the circumferential direction P. Since they are uniformly distributed, a support balance and a drive balance are secured, and as a result, a structure with a high vibration balance is obtained. In addition, with this configuration, the space efficiency can be improved as a whole, and thus the vibrator 100 can be easily downsized.

  The electrical connection structure 130 includes a drive wiring 131 connected to the first counter electrode 121, a drive wiring 132 connected to the second counter electrode 122, and the vibration electrode 111 via the support beam 112 and the support fixing portion 113. And the detection wiring 133 connected to each other. The drive wirings 131 and 132 are connected to the drive circuit 140 and supply in-phase drive potentials (potentials that vary with time) to the first counter electrode 121 and the second counter electrode 122. The drive circuit 140 includes an AC power supply 141, a capacitor 142, a DC power supply 143, and the like. The drive signal output from the drive circuit 140 is supplied via the drive wirings 131 and 132, whereby the vibration surfaces 111 a and 111 b of the vibration electrode 111 and the opposite surfaces 121 a of the first counter electrode 121 and the second counter electrode 122. , 122a is generated between the two electrodes 122a and 122a, and longitudinal vibration (stretching vibration) in the radial direction R is induced in the vibrating electrode 111 by the time variation of the electrostatic force. The vibration system composed of the vibration electrode 111 and the support beam 112 has a predetermined resonance frequency.

  The detection wiring 133 electrically connects the vibration electrode 111 and the detection circuit 150, and changes the capacitance due to the change in the gap between the vibration surfaces 111 a and 111 b and the facing surfaces 121 a and 122 a due to the longitudinal vibration. To detect. In the detection circuit 150, the current resulting from the change in capacitance is converted into a voltage, and an output signal corresponding to the longitudinal vibration is output.

  Note that the insulating film 102 illustrated in FIG. 1B protects the drive wirings 131 and 132 and the detection wiring 133. The gaps G between the vibration surfaces 111a and 111b and the facing surfaces 112a and 122a are all the same. Further, the vibration electrode 111 and the first beam portion 112 a and the second beam portion 112 b of the support beam 112 have a gap S between the surface of the substrate 101, whereby the vibration electrode 111 is connected only to the support beam 112. It has become a state.

  The vibrator 100 of the present embodiment basically uses longitudinal vibration (stretching vibration) in the radial direction R of the vibrating electrode 111, and high frequency can be easily achieved by using the longitudinal vibration. it can. In this case, since the plurality of vibrating electrodes 111 are arranged in the circumferential direction P, the electrode crossing area (electrode facing area) between the vibrating electrode 111 and the first counter electrode 121 and the second counter electrode 122 is increased. As a result, the output signal can be increased. In this case, since a plurality of vibration electrodes 111 are arranged in an annular shape, each vibration electrode 111 basically vibrates in the same manner as the above BLR. However, since the electrode crossing area can be ensured without increasing the width W with respect to the length L, problems due to the Poisson effect can be avoided.

  In addition, the vibrator 100 according to the present embodiment is significant in that the output can be increased by securing the electrode crossing area while solving the problems occurring in the RBAR. That is, in RBAR, it is difficult to realize a one-dimensional vibration mode, and the vibrating electrode vibrates in a state close to uniaxial strain. Therefore, it is necessary to increase the electrostatic force in order to ensure the amplitude. Therefore, it is necessary to reduce the electrode gap or increase the drive signal. On the other hand, in this embodiment, since each vibration electrode 111 has the BLR structure as described above, the amplitude of the vibration electrode 111 can be easily obtained even if the electrostatic force is small. There is no need to reduce the drive signal, and there is no need to increase the drive signal.

  FIG. 2 is a plan view showing another configuration example having a plane pattern different from that of the above embodiment. In this example, the first beam portion 112a extending in the circumferential direction of the support beam 112 extends in a straight line. As a result, the support structure of each vibration electrode 111 is basically configured in the same manner as the conventional BLR. Yes. The first beam portion 112a has a shape refracted at a portion connected to the second beam portion 112b. Even when configured in this manner, it can operate basically in the same manner as in the above-described embodiment, and has substantially the same effect. In this configuration example, the portions that are not illustrated and described can be configured in the same manner as in the above embodiment.

FIG. 3 shows the shape of a vibrator obtained by analyzing the longitudinal vibration mode of this embodiment by the finite element method. The structure shown in FIG. 3A is a structure in which a pair of support beams 112 are connected from both sides to the longitudinal intermediate portion of the vibration electrode 111, and the support structure of one vibration electrode 111 of the above embodiment is simplified. It corresponds to. Assuming that the base portion of the support beam 112 (specifically, the portion corresponding to the first beam portion 112a) is a fixed end, vibration analysis of the longitudinal vibration mode in the longitudinal direction of the vibration electrode 111 was performed by a finite element method. Here, the material having the above structure is silicon, and the material constants are Young's modulus: 169 GPa, Poisson's ratio: 0.3, density: 2500 kg / m ^3, and the length of the vibrating electrode 111 (the horizontal direction in the drawing): 50 μm. The width (the vertical direction in the figure): 10 μm, the thickness: 5 μm, the length of the pair of support beams 112 (the vertical direction in the figure): 25 μm, the width (the horizontal direction in the figure): 10 μm, and the thickness: 5 μm. The resonance frequency of the longitudinal vibration at this time was 38 MHz.

  Further, the vibration analysis of the structure shown in FIG. 3B was performed by the same method as described above. In this structure, the two vibration electrodes 111 are supported in a mutually parallel posture by a pair of support beams 112 having a fixed base and a support beam 112 ′ connecting the pair of vibration electrodes 111. Here, all the material constants were set to the same values as described above, and the lengths, widths, and thicknesses of the support beams 112 and 112 ′ were all set to the same values as those shown in FIG. As a result, the resonance frequency of the longitudinal vibration was 38 MHz as described above.

  As described above, in the present embodiment, a plurality of vibrating electrodes 111 are connected to each other via the support beams 112 and 112 ′ at a certain interval, so that the number of connected vibrating electrodes 111 is one. It can be seen that the resonance frequency does not change even with two. In general, even if a plurality of vibration electrodes 111 are connected through the support beam 112, the vibration conditions are the same as when only one vibration electrode 111 is supported, and the number of connection of the vibration electrodes 111 is not affected. Therefore, the electrode crossing area can be increased by increasing the number of connected vibration electrodes via the support beam 112 without changing the vibration conditions. In particular, by connecting the plurality of vibrating electrodes 111 in the circumferential direction P, the entire vibrator can be formed compactly.

  FIG. 4 is a schematic longitudinal sectional view showing the manufacturing process of the embodiment. In the present embodiment, a semiconductor substrate such as a silicon substrate (silicon single crystal substrate) can be used as the substrate 101. In this case, an appropriate semiconductor circuit can be formed on the surface layer portion of the substrate 101. However, the substrate of the present invention is not limited to a semiconductor substrate.

  In the case where the substrate 101 is a semiconductor substrate, a semiconductor circuit can be formed on the substrate 101, whereby the vibrator 100 and the semiconductor circuit can be integrally formed. In this case, the vibrator 100 and the semiconductor circuit are not necessarily conductively connected, but the vibrator 100 and the semiconductor circuit formed on the substrate 101 are connected and are configured to operate electrically integrally. It is desirable that As the semiconductor circuit at this time, the driving circuit 140, the detection circuit 150, an oscillation circuit including the vibrator 100, or various types of electrons that operate based on a reference signal formed based on the output signal of the vibrator 100 are used. Examples of the circuit include a communication circuit. With such a configuration, particularly when an integrated circuit including the vibrator 100 is required, connection wiring between the vibrator 100 and various circuits can be formed in the substrate 101 and connected by wire bonding or the like. This is extremely effective in reducing the size and reliability of the entire circuit because it eliminates the need for external wiring and packaging.

As shown in FIG. 4A, the drive wirings 131 and 132 and the detection wiring 133 are formed on the surface of the substrate 101 by a conductor such as Al. These wirings can be formed by forming a conductive layer of Al or the like on the substrate 101 by vapor deposition or sputtering, and patterning the conductive layer by photolithography or etching. An insulating film 102 such as SiO ₂ is formed on the drive wirings 131 and 132 and the detection wiring 133 by a sputtering method, a CVD method, or the like.

  Next, as shown in FIG. 4B, contact holes 102a, 102b, and 102c are formed in the insulating film 102 by performing a patterning process such as a photolithography method and an etching method. Thereafter, a conductive layer 103 made of conductive polysilicon (polycrystalline silicon) is formed by a CVD method or the like. At this time, the conductive layer 103, the drive wirings 131 and 132, and the detection wiring 133 are conductively connected through the contact holes 102a, 102b, and 102c.

  Next, as shown in FIG. 4C, by patterning the conductive layer 103, the vibrating electrode 111, the first beam portion 112a and the second beam portion 112b (support beam 112), the support fixing portion 113, the first A first counter electrode 121 and a second counter electrode 122 are formed. Thus, the electrode gap G is provided, and the substantial vibrator structure is completed.

  Next, a surface insulating film 104 such as an acrylic resin is formed on the vibrator structure by a method such as coating. The surface insulating film 104 can be composed of one layer or two or more layers of a so-called interlayer insulating film when a wiring or other element structure is formed above the vibrator structure. Thereafter, an opening 104a is selectively formed in the insulating film 104 by a patterning process. The opening 104 a is formed in a planar region corresponding to the vibration electrode 111 and the support beam 112 in the vibrator structure.

  Finally, wet etching is performed using a hydrofluoric acid-based etching solution, and the insulating film 102 is etched through the opening 104a. The gap S is formed by this wet etching, the vibration electrode 111 and the support beam 112 are separated from the substrate 101, and the vibrator structure in which the vibration electrode 111 is supported via the support beam 112 becomes operable. .

  In the above description, the surface insulating film 104 is provided and wet etching is performed using the surface insulating film 104 as a mask. However, a mask similar to the surface insulating film 104 is formed of a resist or the like by applying a normal photolithography method or the like. Therefore, wet etching may be performed. In this case, the mask (resist) is removed after the wet etching.

  Since the present embodiment is configured based on the BLR structure, similarly to the BLR, the vibrator structure can be formed by forming only one conductive layer (polysilicon layer). Since a layer process is not required, manufacturing time can be shortened and manufacturing cost can be reduced. In addition, since the influence due to the insufficient accuracy of the electrode gap is not as great as in the RBAR, it can be formed by a normal photo process and may cause malfunction due to insufficient precision (for example, malfunction due to eccentricity of the RBAR structure). There is little nature.

  In addition, this embodiment has an advantage that the vibrator structure is simple and the design is easy because the vibrator operates with simple longitudinal vibration. That is, since the frequency can be determined by the one-dimensional model, the frequency setting becomes easy and the influence of the shape accuracy on the frequency accuracy is not so great. Therefore, the design can be easily changed and a stable vibrator with little variation can be manufactured at low cost.

  In this embodiment, an electrode crossing area can be secured by providing a plurality of vibration electrodes, and the vibrator structure can be arranged with high space efficiency by arranging the plurality of vibration electrodes in the circumferential direction. Therefore, it can be configured compactly. Therefore, it is possible to achieve both improvement in input / output characteristics and miniaturization.

  It should be noted that the vibrator and the semiconductor device of the present invention are not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention. For example, in the above embodiment, one vibrating electrode 111 and support fixing portions 113 for fixing the support beam 112 are alternately arranged in the circumferential direction P. However, the support beam 112 ′ shown in FIG. In this manner, two or more vibration electrodes 111 are connected to each other in a manner of interposing a connecting beam that is not connected to the support fixing portion 113. As a result, a predetermined number of vibration electrodes 111 and the support fixing portion 113 are equal to or more than two. It may be a structure arranged alternately in the circumferential direction P. It is clear from the vibration analysis results shown in FIG. 3 that such a structure operates without any problem.

  In the above embodiment, the resonator having the resonator structure has been described. However, this resonator can be used not only as a resonator but also when other electronic elements such as a signal filter are configured. For example, by connecting a plurality of vibrators having different vibration electrode lengths (which have different resonance frequencies), it is possible to use the vibrator as a signal filter having a frequency characteristic that is broadened to some extent. Become.

The top view (A) and longitudinal cross-sectional view (B) which show the planar structure of the vibrator | oscillator of embodiment. The top view which shows the modification of the embodiment. The top view (A) which shows the vibration analysis model of the embodiment, and the top view (B) of a modification. Process sectional drawing (A)-(D) which shows the manufacturing process of the embodiment. The top view of the conventional BLR. The graph which shows the relationship between the resonance frequency of BLR, and ratio W / L of width | variety and length. The top view (A) and longitudinal cross-sectional view (B) of conventional RBAR.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Vibrator, 101 ... Board | substrate, 102 ... Insulating film, 111 ... Vibrating electrode, 111a, 111b ... Vibrating surface, 112 ... Support beam, 112a ... 1st beam part, 112b ... 2nd beam part, 113 ... Support fixing | fixed part 121 ... 1st counter electrode, 121a ... Counter surface, 122 ... 2nd counter electrode, 122a ... Counter surface

Claims (15)

A vibrator configured to generate mechanical longitudinal vibration by electrostatic force on a substrate,
A first counter electrode having a counter surface on the outer periphery;
Arranged in a circumferential direction around the first counter electrode, each supported in a radially expandable / contractible manner with respect to the first counter electrode, and on the inner side in the radial direction of the first counter electrode A plurality of vibration electrodes including a vibration surface facing the facing surface and having another vibration surface on the radially outer side;
A second counter electrode comprising a counter surface facing the vibration surface on the radially outer side of the plurality of vibration electrodes;
A vibrator characterized by comprising:   2. The vibrator according to claim 1, wherein the plurality of vibration electrodes are uniformly distributed in the circumferential direction around the first counter electrode.   The vibrating surfaces of the plurality of vibrating electrodes, the opposed surfaces of the first opposed electrode and the opposed surfaces of the second electrode facing the vibrating surfaces are arranged on the same virtual circle, and the virtual circles are concentric with each other. The vibrator according to claim 1, wherein the vibrator is a circle.   4. The vibrator according to claim 1, wherein the first counter electrode has a structure integrally including the counter surface that faces all of the plurality of vibration electrodes. 5.   5. The apparatus according to claim 1, further comprising a plurality of the second counter electrodes each provided with the facing surface that respectively faces the vibration surfaces on the outside of the plurality of vibrating electrodes. Vibrator.   6. The vibrating electrode is supported from both sides in the circumferential direction by a pair of supporting beams including a beam portion extending in the circumferential direction connected to an intermediate portion in the radial direction. The vibrator according to any one of the above.   The vibrator according to claim 6, wherein the beam portion extending in the circumferential direction has a shape curved along the circumferential direction.   The vibrator according to claim 7, wherein a plurality of sets of beam portions extending in the circumferential direction corresponding to the plurality of vibration electrodes are arranged on the same virtual circle.   The vibrator according to claim 6, wherein the vibrating electrodes adjacent to each other in the circumferential direction are supported by the common beam portion.   10. The vibrator according to claim 6, wherein all of the plurality of vibration electrodes are connected to each other via a beam portion extending in the circumferential direction.   The said support beam is being fixed on the said board | substrate by the support fixing | fixed part alternately arrange | positioned with the predetermined number of said vibration electrodes seeing in the said circumference direction. The vibrator according to item.   The said support beam further has a beam part extended in the said radial direction which further supports the beam part extended in the said circumference direction from the said radial direction both sides, The Claim 1 characterized by the above-mentioned. Vibrator.   The vibrator according to claim 12, wherein bases of the pair of radially extending beam portions are respectively fixed on the substrate.   A variable voltage is applied between the first counter electrode, the second counter electrode, and the vibration electrode to cause the vibration electrode to generate the radial vibration in the radial direction, and the first vibration generated by the vertical vibration. The electrical connection structure for obtaining the output based on the time change of the electrostatic capacitance between at least any one of a counter electrode and the said 2nd counter electrode, and the said vibration electrode is further provided. The vibrator according to any one of 1 to 13. A semiconductor device comprising the vibrator according to claim 1, wherein the substrate is a semiconductor substrate on which a semiconductor circuit is configured.

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