JP2008244552A - Piezoelectric vibrator, method of manufacturing the same, and electronic apparatus - Google Patents

Abstract

A piezoelectric vibrator that can be miniaturized and has high reliability is provided.
A piezoelectric vibrator 300 according to the present invention includes a substrate 10, a first insulator layer 20 formed above the substrate 10, and a second insulator formed on the first insulator layer 20. The vibration portion forming layer 40 formed on the layer 30, the second insulator layer 30, the first opening H1 penetrating the vibration portion forming layer 40, and the vibration portion forming layer 40 in the first opening H1. Is formed in a cantilever shape, a second opening H2 that penetrates the second insulator layer 30 and is formed below the first opening H1 and the vibration unit 100, and the vibration unit 100. And the vibration part forming layer 40 has a layer made of at least one selected from oxide, nitride and oxynitride.
[Selection] Figure 3

Description

  The present invention relates to a piezoelectric vibrator, a manufacturing method thereof, and an electronic apparatus using the vibrator.

  Generally, a vibrator that oscillates with a fundamental frequency of 32 kHz is used for a clock module of a timepiece or a computer. As a conventional vibrator, there is a vibrator that vibrates a beam made of a piezoelectric material such as quartz using the piezoelectricity. Since it is difficult to reduce the size of such a vibrator, studies have been made to further reduce the size of the vibrator using a silicon MEMS (Micro Electro Mechanical System).

A vibrator using silicon MEMS can be manufactured by a precise manufacturing process of a semiconductor. For example, Japanese Unexamined Patent Application Publication No. 2006-030062 discloses a vibrator in which a silicon active layer of an SOI (Silicon On Insulator) substrate is used as a tuning fork type vibration part (cantilever beam). In this vibrator, the silicon oxide layer of the SOI substrate is removed by wet etching using hydrogen fluoride water to form a cantilever-like vibrating portion. When the vibrator is formed using an SOI substrate, the material of the cantilever of the vibrator is limited to silicon. Therefore, since the beam does not have piezoelectricity, a piezoelectric element for driving the vibration unit is further provided. If wet etching with hydrogen fluoride water is performed in a state where the piezoelectric element is formed, a further device for protecting the piezoelectric element from being etched becomes necessary.
JP 2006-030062 A

  When the member under the cantilever of the vibrator is removed by wet etching, a phenomenon called sticking occurs, which may deteriorate the yield. Sticking is a phenomenon in which the free end of a cantilever beam adheres to another member due to the surface tension of the liquid when the etchant that has entered under the structure of the cantilever beam is washed and dried. It is. When sticking occurred, it was difficult to return the vibration part to a normal cantilever state.

  On the other hand, as the shape of the vibration part, there are a tuning fork type or H type having a beam coupling part and a plurality of beam parts extending from the beam coupling part, and a unimorph type consisting of only one beam part. Among these, in particular, since the length of the unimorph type vibration part is directly related to the frequency of vibration, higher accuracy is required to form the fixed end of the cantilever.

  An object of the present invention is to provide a piezoelectric vibrator that can be downsized and highly reliable, to provide a method for manufacturing the piezoelectric vibrator that does not cause sticking, and to provide an electronic device including the piezoelectric vibrator. It is to provide.

The piezoelectric vibrator according to the present invention is
A substrate,
A first insulator layer formed above the substrate;
A second insulator layer formed on the first insulator layer;
A vibrating portion forming layer formed on the second insulator layer;
A first opening penetrating the vibration part forming layer;
A vibrating part formed by forming the vibrating part forming layer in a cantilever shape in the first opening;
A second opening formed through the second insulator layer and below the first opening and the vibrating part;
A piezoelectric element formed on the vibrating part;
Have
The vibration part forming layer has a layer made of at least one selected from oxides, nitrides, and oxynitrides.

  Such a piezoelectric vibrator has a wide range of design because the material of the vibration part can be widely selected. Therefore, the vibration part can be downsized and the strength of the vibration part can be selected, so that the reliability is high.

  In the present invention, when a specific B layer (hereinafter referred to as “B layer”) provided above a specific A layer (hereinafter referred to as “A layer”) is referred to as “B” directly on the A layer. This includes the case where the layer is provided and the case where the B layer is provided on the A layer via another layer.

In the piezoelectric vibrator according to the present invention,
In a plan view, the contour line of the second opening on the base end side of the vibration part may be inside the boundary line between the vibration part and the vibration part forming layer.

  In this way, the reliability of the vibration part can be further increased.

In the piezoelectric vibrator according to the present invention,
The second insulator layer and the vibration part forming layer may be continuous.

In the piezoelectric vibrator according to the present invention,
The vibrating unit may include a beam combining unit and a plurality of beam units extending from the beam combining unit.

  In the present invention, the base end side of the vibration part refers to the base side of the vibration part formed in a cantilever shape.

A method for manufacturing a piezoelectric vibrator according to the present invention includes:
Forming a first insulator layer on the substrate;
Forming a patterned second insulator layer on the first insulator layer;
Forming a silicon layer so as to cover the first insulator layer and the second insulator layer;
Polishing the upper surface of the silicon layer to expose the second insulator layer;
Forming a vibration part forming layer on the silicon layer and the second insulator layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The step of forming the second opening is performed by supplying an etching gas through the first opening.

A method for manufacturing a piezoelectric vibrator according to the present invention includes:
Forming a first insulator layer on the substrate;
Forming a patterned silicon layer on the first insulator layer;
Forming a second insulator layer so as to cover the first insulator layer and the silicon layer;
Polishing the upper surface of the second insulator layer to expose the silicon layer;
Forming a vibration part forming layer on the second insulator layer and the silicon layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The step of forming the second opening is performed by supplying an etching gas through the first opening.

A method for manufacturing a piezoelectric vibrator according to the present invention includes:
Forming a first insulator layer on the substrate;
Forming a patterned silicon layer on the first insulator layer;
Forming a vibration part forming layer so as to cover the first insulator layer and the silicon layer;
Flattening the upper surface of the vibration part forming layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The step of forming the second opening is performed by supplying an etching gas through the first opening.

  In this way, since the silicon layer below the vibrating portion is removed by dry etching, the piezoelectric vibrator can be manufactured without causing sticking.

In the method for manufacturing a piezoelectric vibrator according to the present invention,
The silicon layer may be formed of any one of amorphous silicon, polycrystalline silicon, and single crystal silicon.

In the method for manufacturing a piezoelectric vibrator according to the present invention,
In the dry etching, at least one of XeF ₂ , ClF ₃ , BrF ₃ , IF ₃ , and IF ₅ can be used as an etching gas.

An oscillator, which is an example of an electronic device according to the present invention,
Including an oscillation circuit,
The oscillation circuit is
An amplifier for amplifying an electrical signal;
A feedback circuit connected between the input and output of the amplifier;
Have
The feedback circuit includes any one of the piezoelectric vibrators described above.

A real time clock which is an example of an electronic apparatus according to the present invention is:
The oscillator described above,
A frequency divider that divides the clock pulse output from the oscillator;
A clock counter to which a clock pulse output from the frequency divider circuit is input;
And a control unit that rewrites and reads out the clock bit of the clock counter.

A radio clock receiver module which is an example of an electronic device according to the present invention,
A receiver for receiving radio waves;
A frequency filter that has any of the piezoelectric vibrators described above and filters a received electrical signal;
A peripheral circuit for reading a time code from the filtered electrical signal;
And the real-time clock described above.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, the following embodiment demonstrates an example of this invention.

1. Embodiment 1. Piezoelectric vibrator 300
FIG. 1 is a plan view schematically showing a piezoelectric vibrator 300 according to the present embodiment. FIG. 2 is a plan view schematically showing the relationship between the vibrating portion 100 and the first opening H1 of the piezoelectric vibrator 300 according to the present embodiment. FIG. 3 is a cross-sectional view schematically showing the piezoelectric vibrator 300 according to the present embodiment. A cross section taken along line AA in FIG. 1 corresponds to FIG.

  The piezoelectric vibrator 300 includes a substrate 10, a first insulator layer 20, a second insulator layer 30, a vibration part forming layer 40, a first opening H1, a vibration part 100, and a second opening H2. And the piezoelectric element portion 200.

  As shown in FIG. 3, the substrate 10 becomes a base of the piezoelectric vibrator 300. As the substrate 10, for example, a silicon substrate or a quartz substrate can be used. Various semiconductor circuits may be built in the substrate 10. The thickness of the substrate 10 can be 10 μm to 2 mm.

  The first insulator layer 20 is formed above the substrate 10. The first insulator layer 20 may be formed between the substrates 10 via other layers. The first insulator layer 20 functions as an etching stopper layer when forming the second opening H2 formed above. The first insulator layer 20 is made of a material other than silicon. The first insulator layer 20 can be made of, for example, silicon oxide. Moreover, when the substrate 10 is a silicon substrate, the first insulator layer 20 may be made of silicon oxide obtained on the surface by thermal oxidation or the like. The thickness of the first insulator layer 20 may be a thickness that can function as the above-described stopper layer, and may be, for example, 10 nm to 1 μm.

  The second insulator layer 30 is formed on the first insulator layer 20. The second insulator layer 30 may be formed between the first insulator layer 20 and other layers. A second opening H <b> 2 is formed in the second insulator layer 30. The portion of the second insulator layer 30 other than the second opening H2 has a function of supporting at least the vibration part forming layer 40 from below. A detailed description of the second opening H2 will be described later. The thickness of the second insulator layer 30 can be set to 100 nm to 20 μm, for example. The second insulator layer 30 is made of a material other than silicon. The first insulator layer 20 can be made of, for example, silicon oxide.

  The vibration part forming layer 40 is formed on the second insulator layer 30. In the vibration part forming layer 40, the vibration part 100 and the first opening H1 are formed (see FIGS. 1 and 2). The vibration part forming layer 40 may have a single layer structure or a multilayer structure. A part of the vibration part forming layer 40 becomes the vibration part 100. The thickness of the vibration part forming layer 40 may be 1 μm to 20 μm. The vibration part forming layer 40 includes a layer made of at least one of oxide, nitride, and oxynitride. Specifically, the vibration part forming layer 40 may include a layer of a material selected from silicon oxide, zirconium oxide, aluminum oxide, silicon nitride, silicon oxynitride, and the like depending on the target frequency and strength. it can.

  The first opening H <b> 1 penetrates the vibration part forming layer 40. The shape of the first opening H <b> 1 is complementary to the shape of the vibration unit 100. That is, as shown in FIG. 2, the first opening H1 and the vibration part 100 have a relationship in which the shape of the vibration part 100 is formed by the shape of the first opening H1. The first opening H1 is continuous with the second opening H2. Therefore, the cantilevered tip side of the vibration unit 100 can freely move.

  The vibration part 100 is composed of a part of the vibration part forming layer 40. The vibration part 100 is integrally continuous with the vibration part forming layer 40. At least a part of the vibration unit 100 mechanically vibrates. The vibration part 100 is formed in a cantilever shape by the first opening H1. In the example illustrated in FIG. 2, the shape of the vibration unit 100 is surrounded by a substantially C-shaped first opening H <b> 1 and protrudes in a peninsular shape inside. The portion of the vibration unit 100 that vibrates is closer to the distal end side of the vibration unit 100 than the boundary line L.

  The second opening H <b> 2 is provided through the second insulator layer 30. The second opening H2 is continuous with the first opening H1. The second opening H2 is formed below the first opening H1 and the vibration part 100. The lower surface of the second opening H <b> 2 is the first insulator layer 20. The second opening H2 is a space that allows the vibration unit 100 to operate. In plan view, the contour line of the second opening H2 in the vicinity of the base end of the vibration unit 100 is formed so as not to be outside the boundary line L. In particular, if the vibration unit 100 has a single beam shape called a unimorph type, the frequency of vibration strongly depends on the length. For this reason, when the contour line of the second opening H2 is outside the boundary line L, it is greatly deviated from the intended vibration frequency. The contour line of the second opening H2 other than the vicinity of the base end of the vibration unit 100 may be outside or inside the contour of the first opening H1. Here, the base end side of the vibration part 100 refers to the base side of the vibration part 100 formed in a cantilever shape.

  The piezoelectric element part 200 is formed above the vibration part 100. The position where the piezoelectric element part 200 is formed is arbitrary as long as it can induce vibration in the vibration part 100. The piezoelectric element unit 200 includes a piezoelectric element 75. The piezoelectric element unit 200 may include a plurality of piezoelectric elements 75. The piezoelectric element unit 200 has a function of vibrating the vibrating unit 100 by the operation of the piezoelectric element 75. In the example of FIGS. 1 and 3, one piezoelectric element 75 is provided in the vibration unit 100. The piezoelectric element 75 of this example is provided so as to expand and contract in the longitudinal direction of the vibration part 100, and the vibration part 100 vibrates in the normal direction of the surface of the vibration part forming layer 40. When the piezoelectric element unit 200 includes a plurality of piezoelectric elements 75, the piezoelectric element 75 is used to vibrate the vibration unit 100 and to detect a deviation or vibration frequency of the vibration unit 100. Functions can be shared with things.

The piezoelectric element 75 has a laminated structure of a lower electrode 50, a piezoelectric layer 60, and an upper electrode 70. The lower electrode 50 is formed above the vibration unit 100. The lower electrode 50 may be formed with a layer serving as a base between the vibrating portion 100 and the like. The lower electrode 50 can be made of, for example, a metal material such as platinum or a conductive oxide such as a composite oxide (LNO) of lithium and nickel, and may be a single layer or a multilayer structure. The thickness of the lower electrode 50 may be any thickness as long as a sufficiently low electric resistance value can be obtained, and can be, for example, 10 nm to 5 μm. The piezoelectric layer 60 has piezoelectricity and can be expanded and contracted when a voltage is applied by the lower electrode 50 and the upper electrode 70, and the lower vibration unit 100 can be operated. Conversely, when the piezoelectric layer 60 is expanded and contracted, it can generate a voltage between the lower electrode 50 and the upper electrode 70, and can detect the operation of the vibrating portion 100 below. The piezoelectric layer 60 is made of a piezoelectric material such as lead zirconate titanate (Pb (Zr, Ti) O ₃ : PZT) or lead zirconate titanate niobate (Pb (Zr, Ti, Nb) O ₃ : PZTN). Formed from. The expansion / contraction direction of the piezoelectric layer 60 can be appropriately selected according to the vibration direction of the beam unit 100. For example, the orientation of the crystal of the material constituting the piezoelectric layer 60 can be set according to the purpose. The thickness of the piezoelectric layer 60 can be set to 0.1 μm to 20 μm, for example. The upper electrode 70 can be made of, for example, a metal material such as platinum or a conductive oxide such as a composite oxide (LNO) of lithium and nickel, and may be a single layer or a multilayer structure. The thickness of the upper electrode 70 may be any thickness as long as a sufficiently low electric resistance value can be obtained, and can be, for example, 10 nm to 5 μm.

2. Modified Example of Piezoelectric Vibrator 300 The piezoelectric vibrator 300 can be modified as follows.

  FIG. 4 is a plan view schematically showing a modified piezoelectric vibrator 301. FIG. 5 is a cross-sectional view schematically showing a modified piezoelectric vibrator 301. FIG. 6 is a cross-sectional view schematically showing a modified piezoelectric vibrator 302. FIG. 7 is a plan view schematically showing a modification of the first opening H1 and the vibrating part 100. FIG.

  The piezoelectric vibrator 300 may be deformed like a piezoelectric vibrator 301 shown as a modification. As shown in FIGS. 4 and 5, the piezoelectric vibrator 301 has a contour line of the second opening H <b> 2 on the proximal end side of the vibration part 100 in the plan view, and the vibration part 100 and the vibration part forming layer 40 have a contour line. It is inside the boundary line L. In particular, in the case of the vibration part 100 formed of a single beam called a unimorph type, the vibration part 100 vibrates with the vicinity of the base end as a fixed end, and thus stress is repeatedly generated near the base end. This stress is concentrated in this region when the contour line of the second opening H2 and the boundary line L are close to each other. However, the stress generated in the vicinity of the base end can suppress the concentration of the vibration unit 100 near the base end if the contour line of the second opening H2 is set inside the boundary line L. That is, in the vicinity of the base end of the vibration part 100 as shown in FIG. 5, when the contour of the second opening H2 is closer to the distal end side of the vibration part 100 than the boundary line L, The boundary line L and the contour of the second opening H2 away from the boundary line L can be dispersed.

  The piezoelectric vibrator 300 may be deformed like a piezoelectric vibrator 302 shown as a modification. In the piezoelectric vibrator 302, the second insulator layer 30 and the vibration part forming layer 40 are continuous. By doing so, it is possible to further suppress peeling between the vibration part forming layer 40 and the second insulator layer 30 during the vibration operation. In addition, the structure of the vibrator is simplified, which is more desirable when downsizing.

  As shown in FIG. 7, the vibration unit 100 of the piezoelectric vibrator 300 may be modified to include a beam coupling unit 110 and a plurality of beam units 120 extending from the beam coupling unit 110. By doing in this way, it is possible to hardly generate stress in the portion of the vibration part forming layer 40 adjacent to the root of the vibration part 100 formed in a cantilever shape, that is, the base 111. In this modification, a plurality of beam portions 120 are formed so as to extend from the beam combining portion 110. For example, two beam portions 120 may be formed as in the example of FIG. 7, or four beam portions 120 may be formed so as to be a so-called H type. When the beam unit 120 is an H type, the beam combining unit 110 can be a T type. The beam part 120 is an operation part of the vibration part 100, and can vibrate in various directions according to the purpose. For example, the beam portion 120 can vibrate in the plane of the vibration portion forming layer 40, that is, in the lateral direction, or can vibrate in the direction perpendicular to the surface of the vibration portion forming layer 40, that is, in the vertical direction. In this modification, the number, the vibration direction, and the shape of the beam portion 120 can be designed so that the loss of vibration energy is as small as possible. For example, in the example of FIG. 7, the two beam parts 120 vibrate in the plane of the vibration part forming layer 40 and vibrate so that the tips of the two beam parts 120 approach and separate. That is, in the case of the tuning fork type vibration part 100 as in the example of FIG. In this way, the energy of vibration leaking out to the base 111 can be kept small, and almost no stress is generated in the base 111.

  In the piezoelectric vibrator 300, the deterioration of the vibration part 100 is further suppressed by the deformation as described above, and the reliability of the vibration part 100 can be further improved.

  The piezoelectric vibrator 300 according to this embodiment has a wide range of design because the material of the vibration unit 100 can be selected widely. Therefore, the vibration unit 100 can be reduced in size and the strength of the vibration unit 100 can be selected, so that the reliability is high. Furthermore, the piezoelectric vibrator 300 according to the present embodiment can be variously modified, thereby further improving the reliability.

3. Method for Manufacturing Piezoelectric Vibrator 300 An example of a method for manufacturing the piezoelectric vibrator 300 will be described with reference to the drawings. 8 to 13 are cross-sectional views schematically showing the manufacturing process of the piezoelectric vibrator 300 according to the present embodiment.

  The method for manufacturing the piezoelectric vibrator 300 of the present embodiment includes a step of forming the first insulator layer 20 on the substrate 10, a step of forming the second insulator layer, a step of forming the silicon layer 80, The step of exposing the second insulator layer 30, the step of forming the vibrating portion forming layer 40, the step of forming the piezoelectric element portion 200, the first opening H <b> 1, and the cantilever-shaped vibrating portion 100 and forming a second opening H2.

  First, as shown in FIG. 4, the first insulator layer 20 is formed above the substrate 10. This step can be formed on the substrate 10 by a method such as vapor deposition, sputtering, or CVD (Chemical Vapor Deposition). When a silicon substrate is used as the substrate 10, a thermal oxide film may be formed on the surface and used as the first insulator layer 20. When an SOI (Silicon On Insulator) substrate is used, the insulating layer of the SOI substrate can be used as the first insulator layer 20.

  Next, the patterned second insulator layer 30 is formed on the first insulator layer 20. In this step, a layer to be the second insulator layer 30 is entirely formed on the first insulator layer 20 by vapor deposition, sputtering, CVD, or the like, and a known photolithography technique and etching technique are used. Then, patterning can be performed. The shape of the region of the second insulator layer 30 removed by the patterning in this step becomes the shape of the second opening H2.

  Next, a silicon layer 80 is formed so as to cover the first insulator layer 20 and the second insulator layer 30. The silicon layer 80 is removed when the piezoelectric vibrator 300 is completed. The silicon layer 80 is formed as a sacrificial layer for forming the second opening H2. The silicon layer 80 is selected so that the etching rate during a specific etching is different from that of the first insulator layer 20 and the second insulator layer 30. For example, the silicon layer 80 can be formed of any of amorphous silicon, polycrystalline silicon, and single crystal silicon. As a method for forming the silicon layer 80, an evaporation method, a sputtering method, a CVD method, a SOG (Spin On Glass) method, or the like can be used. Irregularities may be formed on the upper surface of the silicon layer 80 formed by this step.

  Next, a step of polishing the upper surface of the silicon layer 80 to expose the second insulator layer 30 is performed. As a polishing method in this step, a CMP (Chemical Mechanical Polishing) method can be used. As shown in FIG. 9, the upper surfaces of the silicon layer 80 and the second insulator layer 30 ride on the same plane and are simultaneously planarized by this step. This polishing is performed until the second insulator layer 30 is exposed. However, even after the second insulator layer 30 is exposed, it can be further polished within a range where the first insulator layer 20 is not exposed.

  Next, as shown in FIG. 10, a step of forming the vibration part forming layer 40 a on the silicon layer 80 and the second insulator layer 30 is performed. As a method of forming the vibration part forming layer 40a, a method such as a vapor deposition method, a sputtering method, or a CVD method can be used. Also when the vibration part forming layer 40a has a multilayer structure, it can be formed by the method exemplified for each layer.

  Next, as shown in FIG. 11, a step of forming the piezoelectric element portion 200 on the vibration portion forming layer 40a is performed. This step is performed by first laminating the lower electrode layer 50a, the piezoelectric layer 60a, and the upper electrode layer 70a in this order above the vibration part forming layer 40a and then patterning them. The lower electrode layer 50a can be formed by vapor deposition, sputtering, CVD, plating, sol-gel, or the like. The piezoelectric layer 60a can be formed by a sol-gel method, a MOD (Metal-Organic Decomposition) method, a sputtering method, a laser ablation method, or the like. The upper electrode layer 70a can be formed by vapor deposition, sputtering, CVD, plating, sol-gel, or the like. Next, the three layers thus laminated are patterned as shown in FIG. 12 to form the piezoelectric element 75. The patterning method can be performed using a photolithography technique and an etching technique. Patterning may be performed multiple times. Thus, the piezoelectric element unit 200 including the piezoelectric element 75 is formed.

Next, as shown in FIG. 13, the process of forming the vibration part 100 while forming the 1st opening part H1 is performed. The first opening H1 can be formed using a photolithography technique and an etching technique. Etching of the first opening H1 may be performed by either dry etching or wet etching. The etchant may be anisotropic or isotropic. For example, when the vibration part forming layer 40a is formed of silicon oxide, when the first opening H1 is formed by dry etching, the etching gas is CF ₄ , SF ₆ , CHF ₃ , Cl ₂ , BCl _3. And those containing at least one selected from CHCl ₃ are preferred. This etching may be performed a plurality of times. The etching stopper layer is the silicon layer 80. However, since the silicon layer 80 under the first opening H1 is removed in the step of forming the second opening H2, the silicon layer 80 is etched to some extent. It doesn't matter. When the first opening H1 is formed in this way, the vibration unit 100 is formed at the same time. The length of the vibration region of the vibration part 100 is determined by the relative relationship between the first opening H1 and the second opening H2. In the formation of the first opening H <b> 1, a predetermined number of piezoelectric elements 75 are disposed above the vibration unit 100.

Next, a step of forming the second opening H2 as shown in FIGS. 1 and 3 is performed. The second opening H2 is formed by removing the silicon layer 80 by dry etching. An etching gas for dry etching in this step is supplied to the silicon layer 80 through the first opening H1. As the etching proceeds, the silicon layer 80 under the vibration part 100 is removed. Therefore, the etching gas used in this step is selected to perform isotropic etching so that the etching gas can be etched under the vibrating portion 100. Further, as the etching gas in this step, a gas having a larger etching action on the silicon layer 80 than other layers is selected. The etching gas in this step is preferably at least one of XeF ₂ , ClF ₃ , BrF ₃ , IF ₃ , and IF ₅ . Since the first insulator layer 20 is provided below the silicon layer 80, the first insulator layer 20 functions as an etching stopper layer. Therefore, since the second opening H1 is not deeply etched, the etching gas can be saved. The dry etching in this step is isotropic etching, but only the portion formed by the patterning step of the second insulator layer 30 is removed, so that an undercut shape is formed in the vicinity of the end of the vibration unit 100. There is nothing.

  The piezoelectric vibrator 300 is manufactured as described above. The manufacturing method of the piezoelectric vibrator 300 of this embodiment has the following characteristics.

  According to the manufacturing method of the present embodiment, since the second insulator layer 30a under the vibration part 100 is removed by dry etching, the piezoelectric vibrator 300 is manufactured without causing sticking, which is a problem in wet etching. be able to.

  Further, according to the manufacturing method of the present embodiment, the relative positions of the outlines of the first opening H1 and the second opening H2 viewed in a plane can be accurately determined by patterning. That is, since the dry etching stop position is determined in advance by the shape of the second insulator layer 30, overetching or the like does not occur, and the highly accurate and reliable piezoelectric vibration that forms the shape of the vibration region of the vibration unit 100 is achieved. The child 300 can be manufactured.

4). Modified Example of Piezoelectric Vibrator Manufacturing Method The piezoelectric vibrator manufacturing method of the present embodiment can be modified as follows.

  14 to 16 are cross-sectional views schematically showing modified examples of the manufacturing process according to the present embodiment. In the first modification, a silicon layer patterned on the first insulator layer 20 is used in place of the step of forming the second insulator layer 30 patterned on the first insulator layer 20 in the manufacturing process described above. The main difference is that 80 is formed. In the following description of the modified examples, detailed description of steps substantially the same as those described in the method for manufacturing the piezoelectric vibrator 300 is omitted.

4.1. Modification 1 of manufacturing method
FIG. 14 shows a modification in which a patterned silicon layer 80 is formed on the first insulator layer 20. In this example, after the silicon layer 80 is formed, a second insulator layer 30a to be the second insulator layer 30 is formed as shown in FIG. Then, the upper surface of the second insulator layer 30a is polished to expose the silicon layer 80, thereby forming the structure shown in FIG. Thereafter, the piezoelectric vibrators 300 and 301 are formed through the steps described above with reference to FIG.

  In the step of forming the patterned silicon layer 80 on the first insulator layer 20, the layer to be the silicon layer 80 is entirely formed on the first insulator layer 20 by a method such as vapor deposition, sputtering, or CVD. And patterning using a known photolithography technique and etching technique. The shape of the region of the silicon layer 80 formed by patterning in this step becomes the shape of the second opening H2.

  For the step of forming the second insulator layer 30a to be the second insulator layer 30, a vapor deposition method, a sputtering method, a CVD method, an SOG method, or the like can be used. This process may be repeated a plurality of times. Asperities may be formed on the upper surface of the second insulator layer 30a formed in this step.

  A CMP method can be used as a polishing method in the step of polishing the upper surface of the second insulator layer 30a to expose the silicon layer 80 and forming the structure shown in FIG. As shown in FIG. 9, the upper surfaces of the silicon layer 80 and the second insulator layer 30 ride on the same plane and are simultaneously planarized by this step. This polishing is performed until the silicon layer 80 is exposed. However, even after the silicon layer 80 is exposed, it can be further polished within a range where the first insulator layer 20 is not exposed.

4.2. Variation 2 of manufacturing method
In the second modification, instead of the step of polishing the upper surface of the second insulator layer 30a and exposing the silicon layer 80 in the manufacturing process of the first modification, the step of polishing and flattening the upper surface of the vibration part forming layer 40a. This is the main difference.

  FIG. 16 is a cross-sectional view schematically showing a structure obtained by the second modification. The modification 2 is a modification of the process after the patterned silicon layer 80 is formed on the first insulator layer 20 shown in FIG. 14 as in the process of the modification 1. In this modification, as shown in FIG. 15, a vibration part forming layer 40b to be the vibration part forming layer 40a is formed. Then, the upper surface of the vibration part forming layer 40b is polished and flattened to form the structure shown in FIG. Thereafter, the piezoelectric vibrator 302 is formed through the steps described above with reference to FIG.

  For the step of forming the vibration part forming layer 40b to be the vibration part forming layer 40a, vapor deposition, sputtering, CVD, SOG, or the like can be used. This process may be repeated a plurality of times. Asperities may be formed on the upper surface of the second insulator layer 30a formed in this step.

  A CMP method can be used as a polishing method in the step of polishing and planarizing the upper surface of the vibration part forming layer 40b. As shown in FIG. 9, the vibration part forming layer 40a having a flat upper surface is formed by this step. This polishing can be performed until the vibration part forming layer 40a has a desired thickness.

  In the modification in which the patterned silicon layer 80 is formed on the first insulator layer 20 as in the first and second modifications, the process can be simplified using an SOI (Silicon On Insulator) substrate. That is, the substrate 10, the first insulating layer 20, and the silicon layer 80 having the structure shown in FIG. 14 can be formed using an SOI substrate, a BOX (insulating) layer, and a single crystal silicon layer, respectively. In this case, it is possible to start from the step of patterning the silicon layer 80 (single crystal silicon layer).

  As described above, the embodiments of the present invention have been described in detail. However, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

5. Oscillator 500
Next, an oscillator 500 will be described as an example of the electronic apparatus according to the invention.

  FIG. 17 is a circuit diagram showing a basic configuration of an oscillator 500 having the piezoelectric vibrator 300 described above. The oscillator 500 can include this circuit (oscillation circuit). The oscillation circuit includes an amplifier 401 that amplifies an electric signal, and a feedback circuit 410 connected between the input and output of the amplifier 401. The amplifier 401 is composed of, for example, a CMOS inverter. The feedback circuit 410 includes, for example, a piezoelectric vibrator 300, a resistor 403, and two capacitors 404 and 405. A voltage E is applied to the amplifier 401 from a DC power supply. When the power supply voltage E is increased and the oscillation start voltage is reached, the current I increases rapidly and oscillation starts. When the power supply voltage E is further increased, the current I increases almost proportionally while maintaining the oscillation state.

  FIG. 18 is a plan view schematically showing the oscillator 500 according to the present embodiment, and FIG. 19 is a cross-sectional view schematically showing the oscillator 500. FIG. 19 is a sectional view taken along line XX of FIG. 17 and 19 show the piezoelectric vibrator 300 in a simplified manner for convenience.

The oscillator 500 is sealed with a sealing material 502. The IC (integrated circuit) 503 is connected to the external terminal 570 by a bonding wire 504 such as a gold wire. The external terminal 570 is electrically connected to the mounting terminal 541 via the lead frame 505 and the bonding material 506. The mounting terminal 541 is electrically connected to each electrode of the piezoelectric vibrator 300 by wiring (not shown). The piezoelectric vibrator 300 is sealed with a lid member 539, a seal member 540, and the like.

  FIG. 20 is a diagram schematically showing a manufacturing process example of the oscillator 500 according to the present embodiment.

  First, tape attachment and dicing are performed on the IC wafer. Next, the chip of the IC 503 is mounted on the lead frame 505. Next, wire bonding is performed on the IC 503 using the bonding wires 504.

  Next, the mounting terminal 541 of the piezoelectric vibrator 300 is joined to the lead frame 505 using a joining material 506 such as solder, and the piezoelectric vibrator 300 is mounted. Next, the piezoelectric vibrator 300, the IC 503, and the like are resin-sealed using a sealing material (mold material) 502. After that, characteristic inspection and marking are performed, taping, packing, and shipment.

  Although not shown, for example, an IC that is planarly adjacent to the piezoelectric vibrator 300 is formed on the substrate 10 (see FIG. 3) on which the piezoelectric vibrator 300 is formed using a semiconductor process. An oscillator according to the above can also be formed. Thereby, the package can be omitted, and a one-chip type oscillator can be formed.

6). Real time clock 600
Next, a real time clock 600 will be described as an example of the electronic apparatus according to the present invention.

  FIG. 21 is a circuit block diagram schematically showing a real-time clock 600 having the oscillator (OSC) 500 described above. The integrated circuit portion of the real-time clock 600 is integrated on a single substrate 601 and connected to a microprocessor (not shown).

  A clock pulse of high frequency (for example, 32 kHz) is output from the oscillator 500 connected to the timing connection terminals 602 and 603. The clock pulse is frequency-divided by the frequency dividing circuit 605, and a time measuring pulse of 1 Hz is input to the time counting counter 606. The clock counter 606 includes, for example, a second clock bit s, a minute clock bit m, a clock clock bit h, a day clock bit d, a daily clock bit D, a monthly clock bit M, and an annual clock bit Y. Has been. When a predetermined number of timing pulses are input to the timing counter 606, each timing bit can be incremented. Connected to the time counter 606 is a control unit 620 that rewrites and reads time bits. For example, the control unit 620 can include a command decoder 612 and shift registers 609 and 610.

  When rewriting the clock bit of the clock counter 606, first, a select signal is supplied from the microprocessor to the select input terminal 607. Next, external information composed of a data bit representing information to be rewritten, an address bit representing the address of the timekeeping bit, and an operation bit representing a write operation to the timekeeping counter 606 is input from the microprocessor to the data input terminal 608. Supply. As a result, the external information is stored in the shift registers 609 and 610 connected in series. Then, the command decoder 612 sends a write enable signal to the time counter 606 based on the operation bit and address bit stored in the shift register 610 and outputs an address signal designating the time bit. As a result, the data bits stored in the shift register 609 are written into the timekeeping bits of the timekeeping counter 606, and real-time data is rewritten.

When real-time data is read from the time counter 606, external information having an operation bit indicating a read operation is transmitted from the microprocessor. Then, the command decoder 612 sets the write enable signal to the time counter 606 to an inactive state. As a result, the inverter 613 supplies the write enable signal in the active state to the shift register 609, the shift register 609 becomes ready for reading, and the contents of the time counter 606 are read to the shift register 609. The real-time data read to the shift register 609 is transferred to the data output terminal 615 in synchronization with the clock signal applied to the clock input terminal 614, and is sent to, for example, a microprocessor register.

  For example, data such as calculation results can be stored in a random access memory (RAM) 616.

  FIG. 22 is a top perspective view schematically showing the real-time clock 600 according to the present embodiment, and FIG. 23 is a side perspective view schematically showing the real-time clock 600. FIG. 23 is a view seen in the direction of arrow XIV in FIG.

  An IC chip 651 having an oscillation circuit or the like is bonded and fixed to the island portion 653 of the lead frame 652 with a conductive adhesive or the like. Each electrode pad 654 provided on the upper surface of the IC chip 651 is electrically connected to an input / output lead terminal 656 disposed on the outer periphery of the package by a bonding wire 655. In a plan view, a vibrator housing 657 in which the piezoelectric vibrator 300 is housed is disposed next to the IC chip 651. In the vibrator housing 657, for example, the piezoelectric vibrator 300 shown in FIGS. 1 to 3 is sealed in an airtight state. The lead 658 electrically connected to each electrode of the piezoelectric vibrator 300 protrudes from the vibrator housing 657 to the outside. The lead 658 is bonded and fixed to the connection pad 659 of the lead frame 652 with a conductive adhesive or the like. The IC chip 651, the lead frame 652, and the vibrator housing 657 are integrally molded with a resin 660 and packaged.

  Although not shown, for example, an IC that is planarly adjacent to the piezoelectric vibrator 300 is formed on the base body 10 (see FIG. 3) on which the piezoelectric vibrator 300 is formed using a semiconductor process. It is also possible to form a real-time clock according to the above. As a result, the package can be omitted, and a one-chip real-time clock can be formed.

7). Radio clock receiver module 800
Next, a radio clock receiver module 800 that is an example of the electronic apparatus of the invention will be described.

  FIG. 24 is a circuit block diagram schematically showing the radio clock receiver module 800 according to the present embodiment.

  The radio clock receiver module 800 includes a receiver 801, a frequency filter 805, a peripheral circuit 810, and the above-described real time clock (RTC) 600. The frequency filter 805 includes, for example, a piezoelectric vibrator 400 (400A, 400B) similar to the piezoelectric vibrator 300 described above. The peripheral circuit 810 can include, for example, a detection / rectification circuit 806, a waveform shaping circuit 807, and a central processing unit (CPU) 808.

  The radio timepiece is a timepiece having a function of receiving a standard radio wave including time information and automatically correcting and displaying the correct time. In Japan, there are transmitting stations that transmit standard radio waves to Fukushima Prefecture (40 kHz) and Saga Prefecture (60 kHz).

A receiving unit (for example, an antenna) 801 receives a long standard wave of 40 kHz or 60 kHz. The standard radio wave is obtained by applying time modulation (AM) to a carrier wave of 40 kHz or 60 kHz and carrying time information (time code).

  The received electrical signal is amplified by the amplifier 802, and is filtered and tuned by the frequency filter 805 having the piezoelectric vibrators 400A and 400B having the same resonance frequency as the carrier frequency. From the filtered electrical signal, the peripheral circuit 810 can read the time code. Specifically, first, a filtered signal having a predetermined frequency is detected and demodulated by a detection / rectification circuit 806. Then, the time code is taken out via the waveform shaping circuit 807 and counted by the CPU 808. The CPU 808 reads information such as the current year, accumulated date, day of the week, and time, for example. The read information is reflected on the RTC 600, and accurate time information is displayed.

  Since the carrier wave is 40 kHz or 60 kHz, the piezoelectric vibrator according to the present invention is suitable for the piezoelectric vibrators 400A and 400B of the frequency filter 805.

  Although not shown, for example, an IC that is planarly adjacent to the piezoelectric vibrator 400 is formed by using a semiconductor process on the base body 10 (see FIG. 11) on which the piezoelectric vibrator 400 is formed. It is also possible to form a radio clock receiver module according to the above. As a result, the package can be omitted, and a one-chip radio timepiece receiving module can be formed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

The top view which shows typically the piezoelectric vibrator 300 concerning this invention. The top view which shows typically the 1st opening part H1 and the vibration part 100. FIG. FIG. 3 is a cross-sectional view schematically showing a piezoelectric vibrator 300 according to the present invention. The top view which shows typically the piezoelectric vibrator 301 concerning this invention. Sectional drawing which shows typically the piezoelectric vibrator 301 concerning this invention. FIG. 3 is a cross-sectional view schematically showing a piezoelectric vibrator 302 according to the present invention. The top view which shows typically the 1st opening part H1 and the vibration part 100. FIG. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the manufacturing process of the piezoelectric vibrator 300 of this invention. Sectional drawing which shows typically the modification of the manufacturing process of the piezoelectric vibrator of this invention. Sectional drawing which shows typically the modification of the manufacturing process of the piezoelectric vibrator of this invention. Sectional drawing which shows typically the modification of the manufacturing process of the piezoelectric vibrator of this invention. The circuit diagram which shows the basic composition of the oscillator 500 of this invention. The top view which shows roughly the oscillator 500 of this invention. A sectional view showing roughly oscillator 500 of the present invention. The figure which shows schematically the example of a manufacturing process of the oscillator 500 of this invention. The circuit block diagram which shows schematically the real-time clock 600 of this invention. FIG. 3 is a top perspective view schematically showing a real-time clock 600 of the present invention. FIG. 3 is a side perspective view schematically showing the real-time clock 600 of the present invention. The circuit block diagram which shows schematically the radio timepiece receiving module 800 of this invention.

Explanation of symbols

10 substrate, 20 first insulator layer, 30, 30a second insulator layer,
40, 40a vibration part forming layer, 50 lower electrode, 50a lower electrode layer,
60, 60a piezoelectric layer, 70 upper electrode, 70a upper electrode layer, 75 piezoelectric element,
80, 80a Silicon layer, 100 vibrating part, 110 beam coupling part, 111 base part,
120 beam part, 200 drive part, H1 1st opening part, H2 2nd opening part,
300, 301, 302 Piezoelectric vibrator, 400 Piezoelectric vibrator, 401 Amplifier,
403 resistor, 404, 405 capacitor, 410 feedback circuit, 500 oscillator,
502 sealing material, 503 IC, 504 bonding wire,
505 Lead frame, 506 bonding material, 539 lid member, 540 seal member,
541 mounting terminal, 570 external terminal, 600 real time clock, 601 board,
602, 603 Timekeeping connection terminal, 605 frequency divider, 606 time counter,
607 select input terminal, 608 data input terminal,
609, 610 shift register, 612 command decoder, 613 inverter,
614 clock input terminal, 615 data output terminal, 620 control unit,
651 IC chip, 652 lead frame, 653 island part,
654 electrode pad, 655 bonding wire, 656 input / output lead terminal,
657 vibrator housing, 658 lead, 659 connection pad, 660 resin,
800 radio clock receiver module, 801 receiver, 802 amplifier,
805 frequency filter, 806 detector / rectifier circuit, 807 waveform shaping circuit,
808 CPU, 810 peripheral circuit

Claims (10)

A substrate,
A first insulator layer formed above the substrate;
A second insulator layer formed on the first insulator layer;
A vibrating portion forming layer formed on the second insulator layer;
A first opening penetrating the vibration part forming layer;
A vibrating part formed by forming the vibrating part forming layer in a cantilever shape in the first opening;
A second opening formed through the second insulator layer and below the first opening and the vibrating part;
A piezoelectric element formed on the vibrating part;
Have
The vibration part forming layer is a piezoelectric vibrator having a layer made of at least one selected from oxide, nitride, and oxynitride. In claim 1,
In a plan view, the contour line of the second opening on the base end side of the vibration part is a piezoelectric vibrator that is located inside a boundary line between the vibration part and the vibration part forming layer. In claim 1 or claim 2,
A piezoelectric vibrator in which the second insulator layer and the vibration part forming layer are continuous. In either claim 1 or claim 3,
The vibration unit is a piezoelectric vibrator having a beam coupling unit and a plurality of beam units extending from the beam coupling unit. Forming a first insulator layer on the substrate;
Forming a patterned second insulator layer on the first insulator layer;
Forming a silicon layer so as to cover the first insulator layer and the second insulator layer;
Polishing the upper surface of the silicon layer to expose the second insulator layer;
Forming a vibration part forming layer on the silicon layer and the second insulator layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The method of manufacturing a piezoelectric vibrator, wherein the step of forming the second opening is performed by supplying an etching gas through the first opening. Forming a first insulator layer on the substrate;
Forming a patterned silicon layer on the first insulator layer;
Forming a second insulator layer so as to cover the first insulator layer and the silicon layer;
Polishing the upper surface of the second insulator layer to expose the silicon layer;
Forming a vibration part forming layer on the second insulator layer and the silicon layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The method of manufacturing a piezoelectric vibrator, wherein the step of forming the second opening is performed by supplying an etching gas through the first opening. Forming a first insulator layer on the substrate;
Forming a patterned silicon layer on the first insulator layer;
Forming a vibration part forming layer so as to cover the first insulator layer and the silicon layer;
Flattening the upper surface of the vibration part forming layer;
Forming a piezoelectric element part on the vibration part forming layer;
Forming a first opening that penetrates the vibrating part forming layer and forming a cantilever-like vibrating part fixed to the vibrating part forming layer;
Forming a second opening by dry etching the silicon layer;
Have
The method of manufacturing a piezoelectric vibrator, wherein the step of forming the second opening is performed by supplying an etching gas through the first opening. In any one of Claim 5 thru | or 7,
The method for manufacturing a piezoelectric vibrator, wherein the silicon layer is formed of any one of amorphous silicon, polycrystalline silicon, and single crystal silicon. In any one of Claim 5 thru | or 8,
The dry etching is a method for manufacturing a piezoelectric vibrator using, as an etching gas, at least one of XeF ₂ , ClF ₃ , BrF ₃ , IF ₃ , and IF ₅ .   An electronic apparatus having the piezoelectric vibrator according to claim 1.

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