JP2013034156A - Mems vibrator, oscillator and manufacturing method of mems vibrator - Google Patents

Abstract

A MEMS resonator having high reliability and easy management of frequency characteristics is provided.
A MEMS vibrator is disposed with a gap between the substrate, a first electrode disposed above the substrate, and the first electrode, and the thickness direction of the substrate is And a second electrode 30 having a beam portion 32 that can be vibrated by an electrostatic force and a support portion 34 that supports the beam portion 32, and the side surface 22 of the first electrode 20 is formed on the upper surface 21 of the first electrode 20. A first surface 22a connected; and a second surface 22b connected to the first surface 22a and the upper surface 11 of the substrate 10. The first surface 22a is inclined with respect to the upper surface 11 of the substrate 10, The angle of the first surface 22a with respect to the upper surface 11 of the substrate 10 is a first angle α, and the angle of the second surface 22b with respect to the upper surface 11 of the substrate 10 is a second angle β that is larger than the first angle α.
[Selection] Figure 2

Description

  The present invention relates to a MEMS vibrator, an oscillator, and a method for manufacturing the MEMS vibrator.

  2. Description of the Related Art In recent years, attention has been focused on MEMS vibrators manufactured using MEMS (Micro Electro Mechanical System) technology. The MEMS vibrator is used for an oscillator, for example, and requires high reliability. Patent Document 1 discloses a technique for preventing the occurrence of a sidewall-like etching residue in the manufacturing process as a technique for improving the reliability of the MEMS vibrator. Specifically, in Patent Document 1, in a MEMS vibrator including a fixed electrode and a movable electrode having a beam that vibrates due to an electrostatic force, the side surface portion of the fixed electrode is inclined to the substrate. This prevents the occurrence of sidewall-like etching residue.

JP 2007-160495 A

  Here, the frequency characteristic of the MEMS vibrator depends on the length of the beam of the movable electrode (the length of the beam that is substantially movable by the electrostatic force). Therefore, measuring the length of the beam of the movable electrode is important in managing the frequency characteristics of the MEMS vibrator. As a method of measuring the length of the beam of the movable electrode, there is a method of observing the beam of the movable electrode in a plane (observing from the upper surface side of the substrate) using SEM (Scanning Electron Microscope) or the like. According to the method of observing the beam of the movable electrode in a plane, the length of the beam can be easily measured without destroying the MEMS vibrator.

  However, when the side surface portion of the fixed electrode is inclined as in the MEMS vibrator described in Patent Document 1, the beam of the movable electrode is also inclined along the side surface portion. Therefore, in planar observation using the SEM, In some cases, the boundary of the beam (the boundary between the beam and the support part that supports the beam) cannot be clearly observed. Therefore, in the MEMS vibrator described in Patent Document 1, there is a case where it is impossible to use a method of observing the beam of the movable electrode in a plane, and there is a problem that it is difficult to manage frequency characteristics.

  One of the objects according to some aspects of the present invention is to provide a MEMS resonator having high reliability and easy management of frequency characteristics, and a method of manufacturing the same. Another object of some aspects of the present invention is to provide an oscillator having the MEMS vibrator.

The MEMS vibrator according to the present invention includes:
A substrate,
A first electrode disposed above the substrate;
A second electrode having a beam portion that is arranged with a gap between the first electrode and that can vibrate by an electrostatic force in the thickness direction of the substrate; and a support portion that supports the beam portion;
Including
The side surface of the first electrode is
A first surface connected to an upper surface of the first electrode;
A second surface connected to the first surface and the top surface of the substrate;
Have
The first surface is inclined with respect to the upper surface of the substrate;
The angle of the first surface with respect to the upper surface of the substrate is a first angle;
The angle of the second surface with respect to the upper surface of the substrate is a second angle larger than the first angle.

  According to such a MEMS vibrator, since the first surface constituting the side surface of the first electrode is inclined with respect to the upper surface of the substrate, it is possible to prevent the occurrence of a sidewall-like etching residue. Therefore, reliability can be improved. Furthermore, since the side surface of the first electrode has the first surface and the second surface, the first corner can be formed on the side surface of the first electrode. By forming the first corner portion on the side surface of the first electrode, the second corner portion can be easily formed on the upper surface of the second electrode. Since the second corner corresponds to the boundary of the beam portion, the length of the beam portion contributing to the frequency characteristics of the MEMS vibrator can be measured by, for example, planar observation using an SEM. Therefore, the frequency characteristics can be easily managed.

  In the description of the present invention, the word “upper” is, for example, “forms another specific thing (hereinafter referred to as“ B ”) above a specific thing (hereinafter referred to as“ A ”)”. The word “above” is used to include the case where B is formed directly on A and the case where B is formed on A via another object. .

In the MEMS vibrator according to the present invention,
A first corner formed by the first surface and the second surface is formed on a side surface of the first electrode,
A second corner portion to which the shape of the first corner portion is transferred may be formed on the upper surface of the second electrode.

  According to such a MEMS vibrator, the second corner portion is formed on the upper surface of the second electrode, whereby the length of the beam portion can be measured by planar observation using, for example, an SEM. Therefore, the frequency characteristics can be easily managed.

In the MEMS vibrator according to the present invention,
The first angle may be not less than 5 ° and not more than 45 °.

  According to such a MEMS vibrator, it is possible to prevent the occurrence of a sidewall-like etching residue and improve the reliability.

In the MEMS vibrator according to the present invention,
The second angle may be not less than 80 ° and not more than 90 °.

  According to such a MEMS vibrator, the second corner transferred to the upper surface of the second electrode can be clearly observed by planar observation using, for example, SEM. Therefore, the length of the beam part contributing to the frequency characteristics of the MEMS vibrator can be easily measured, and the frequency characteristics can be easily managed.

The oscillator according to the present invention is
A MEMS resonator according to the present invention;
A circuit unit electrically connected to the first electrode and the second electrode of the MEMS vibrator;
including.

  According to such an oscillator, reliability can be enhanced and management of frequency characteristics can be facilitated.

A method for manufacturing a MEMS vibrator according to the present invention includes:
Forming a first semiconductor layer over the substrate;
Patterning the first semiconductor layer to form a first electrode;
Forming a coating layer covering the first electrode;
Forming a second semiconductor layer above the covering layer;
The second semiconductor layer is patterned and disposed with a gap between the first electrode and the beam portion that can vibrate by electrostatic force in the thickness direction of the substrate, and supports the beam portion Forming a second electrode having a support;
Removing the coating layer;
Including
In the step of forming the first electrode,
Forming a side surface of the first electrode to have a first surface connected to an upper surface of the first electrode and a second surface connected to the first surface and the upper surface of the substrate;
The first surface is inclined with respect to the upper surface of the substrate;
The angle of the first surface with respect to the upper surface of the substrate is a first angle;
The angle of the second surface with respect to the upper surface of the substrate is a second angle larger than the first angle.

  According to such a method of manufacturing a MEMS vibrator, the first surface of the first electrode is formed so as to be inclined with respect to the upper surface of the substrate. Thereby, in the step of patterning the second semiconductor layer, it is possible to prevent a sidewall-like etching residue from occurring. Therefore, reliability can be improved. Further, in the step of forming the first electrode, the side surface of the first electrode is formed to have a first surface and a second surface. Thereby, a 1st corner | angular part can be formed in the side surface of a 1st electrode. By forming the first corner, the second corner can be easily formed on the upper surface of the second electrode in the step of forming the second semiconductor layer. Therefore, the length of the beam part that contributes to the frequency characteristics of the MEMS vibrator can be measured, for example, by planar observation using an SEM. Therefore, the frequency characteristics can be easily managed.

In the manufacturing method of the MEMS vibrator according to the present invention,
The step of forming the first electrode includes:
Forming a mask layer above the first semiconductor layer;
Dry etching the first semiconductor layer using the mask layer as a mask;
Including
The step of dry etching the first semiconductor layer may be performed using a gas containing chlorine, sulfur hexafluoride, hydrogen bromide, and oxygen.

  According to such a method of manufacturing a MEMS vibrator, for example, the side surface of the first electrode having the first surface and the second surface is formed without forming a mask layer a plurality of times or switching a gas used for etching. It can be formed easily.

In the manufacturing method of the MEMS vibrator according to the present invention,
The step of forming the first electrode includes:
A first dry etching step of dry-etching the first semiconductor layer using a first gas to form the first surface;
A second dry etching step of dry-etching the first semiconductor layer using a second gas different from the first gas to form the second surface;
You may have.

  According to such a method for manufacturing a MEMS vibrator, the side surface of the first electrode having the first surface and the second surface can be formed with one mask layer.

In the manufacturing method of the MEMS vibrator according to the present invention,
The step of forming the first electrode includes:
Implanting impurities into the first semiconductor layer such that the impurity concentration on the upper surface side of the first semiconductor layer is higher than the impurity concentration on the lower surface side of the first semiconductor layer;
Forming a mask layer above the first semiconductor layer;
Dry etching the first semiconductor layer using the mask layer as a mask;
You may have.

  According to such a method of manufacturing a MEMS vibrator, reliability can be improved and frequency characteristics can be easily managed.

FIG. 3 is a plan view schematically showing the MEMS vibrator according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing the MEMS vibrator according to the first embodiment. FIG. 3 is an enlarged cross-sectional view illustrating a part of the first electrode of the MEMS vibrator according to the first embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on 1st Embodiment. Sectional drawing which shows typically the mode after forming the 2nd semiconductor layer in the manufacturing process of the MEMS vibrator | oscillator which concerns on 1st Embodiment. Sectional drawing which shows typically a mode after forming a 2nd semiconductor layer in the case where the side surface of a 1st electrode is a surface perpendicular | vertical with respect to the upper surface of a board | substrate. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 1st modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 1st modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 2nd modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 2nd modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 3rd modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 3rd modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 3rd modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 4th modification of 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the MEMS vibrator which concerns on the 4th modification of 1st Embodiment. The top view which shows typically the MEMS vibrator | oscillator concerning 2nd Embodiment. Sectional drawing which shows typically the MEMS vibrator | oscillator concerning 2nd Embodiment. Sectional drawing which shows typically the MEMS vibrator | oscillator concerning 3rd Embodiment. Sectional drawing which expands and shows a part of 1st electrode of the MEMS vibrator | oscillator concerning 3rd Embodiment. A circuit diagram showing an oscillator concerning a 4th embodiment. The circuit diagram which shows the oscillator which concerns on the modification of 4th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. 1. First embodiment 1.1. First, a MEMS vibrator according to a first embodiment will be described with reference to the drawings. FIG. 1 is a plan view schematically showing the MEMS vibrator 100 according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the MEMS vibrator 100. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is an enlarged cross-sectional view showing a part of the first electrode 20 of the MEMS vibrator 100. In FIG. 3, the second electrode 30 is not shown for convenience.

  As illustrated in FIGS. 1 to 3, the MEMS vibrator 100 includes a substrate 10, a first electrode 20, and a second electrode 30.

  The substrate 10 can include a support substrate 12, a first foundation layer 14, and a second foundation layer 16.

  As the support substrate 12, for example, a semiconductor substrate such as a silicon substrate can be used. As the support substrate 12, various substrates such as a ceramic substrate, a glass substrate, a sapphire substrate, and a synthetic resin substrate may be used.

  The first foundation layer 14 is formed on the support substrate 12. For example, a trench insulating layer, a LOCOS (local oxidation of silicon) insulating layer, or a semi-recessed LOCOS insulating layer can be used as the first base layer 14. The material of the first insulating layer 20 is, for example, silicon oxide. The first underlayer 14 can electrically isolate the MEMS vibrator 100 and other elements (not shown) formed on the support substrate 12.

  The second underlayer 16 is formed on the first underlayer 14. An example of the material of the second underlayer 16 is silicon nitride. The second underlayer 16 can function as an etching stopper layer in a release process described later.

  The first electrode 20 is disposed on the substrate 10. The planar shape of the first electrode 20 is, for example, a rectangle as shown in FIG. The first electrode 20 has four side surfaces corresponding to the four sides of the rectangle. In addition, the planar shape of the 1st electrode 20 is not specifically limited, For example, polygons other than a rectangle may be sufficient.

  As shown in FIGS. 2 and 3, the side surface 22 of the first electrode 20 has a first surface 22a and a second surface 22b.

  The first surface 22a is connected to the upper surface 21 and the second surface 22b of the first electrode 20. The first surface 22 a is a surface located on the upper side (upper surface 21 side) of the side surfaces 22 of the first electrode 20. The first surface 22 a is inclined with respect to the upper surface 11 of the substrate 10. The angle α of the first surface 22a with respect to the upper surface 11 of the substrate 10 is, for example, not less than 5 ° and not more than 45 °. The angle α of the first surface 22a is desirably 25 °. The angle α of the first surface 22 a can be said to be the inclination angle of the first surface 22 a with respect to the upper surface 11 of the substrate 10.

  The second surface 22 b is connected to the first surface 22 a and the upper surface 11 of the substrate 10. The second surface 22 b is a surface located on the lower side (substrate 10 side) of the side surface 22 of the first electrode 20. The angle β of the second surface 22b with respect to the upper surface 11 of the substrate 10 is, for example, not less than 80 ° and not more than 90 °. That is, the angle α of the first surface 22 a with respect to the upper surface 11 of the substrate 10 is larger than the angle β of the second surface 22 b with respect to the upper surface 11 of the substrate 10. The angle β of the second surface 22b is desirably 90 °. That is, the second surface 22 b is desirably a surface perpendicular to the upper surface 11 of the substrate 10. The angle β of the second surface 22b is an angle formed by the second surface 22b and the upper surface 11 of the substrate 10.

  Since the angle α of the first surface 22a and the angle β of the second surface 22b are different in size, the first corner portion formed by the first surface 22a and the second surface 22b is formed on the side surface 22 of the first electrode 20. 25a is formed. Since the second electrode 30 is formed along the upper surface 11 of the substrate 10, the side surface 22 and the upper surface 21 of the first electrode 20, the upper surface of the second electrode 30 has the first corner portion 25 a of the first electrode 20. The shape is transferred to form the second corner portion 35a. Therefore, the second corner portion 35 a of the second electrode 30 reflects the shape of the first corner portion 25 a of the first electrode 20.

  The angle of the upper surface 21 of the first electrode 20 with respect to the upper surface 11 of the substrate 10 (0 ° in the illustrated example) and the angle α of the first surface 22a are different in size. Therefore, the first electrode 20 has a third corner 25b formed by the upper surface 21 and the first surface 22a. Therefore, the shape of the third corner portion 25b of the first electrode 20 is transferred to the second electrode 30 to form the fourth corner portion 35b. Therefore, the fourth corner portion 35 b of the second electrode 30 reflects the shape of the third corner portion 25 b of the first electrode 20.

  As shown in FIG. 3, the height of the first corner 25a (the distance between the upper surface 11 of the substrate 10 and the first corner 25a) L1 is, for example, the film thickness of the first electrode 20 (the upper surface of the substrate 10). 11 and the upper surface 21 of the first electrode 20 is equal to or less than ½ of L2. The height L1 of the first corner 25a is preferably about 1/3 of the film thickness L2 of the first electrode 20. When the film thickness of the first electrode 20 is 300 nm, the height L1 of the first corner portion 25a is, for example, not less than 10 nm and not more than 150 nm.

  The second electrode 30 includes a beam portion 32 disposed with a gap between the second electrode 30 and a support portion (fixed portion) 34 that supports the beam portion 32. In the illustrated example, the second electrode 30 is formed in a cantilever shape. When a voltage is applied between the electrodes 20 and 30, the beam portion 32 can vibrate in the thickness direction of the substrate 10 due to an electrostatic force generated between the electrodes 20 and 30.

  In the illustrated example, two second electrodes 30 are provided for one first electrode 20. The two second electrodes 30 may have different natural frequencies or the same natural frequency. In addition, the number of the 2nd electrodes 30 with respect to one 1st electrode 20 is not specifically limited.

  The beam portion 32 extends from the support portion 34. The beam portion 32 is disposed to face the first electrode 20. The thickness of the beam portion 32 (the size in the thickness direction of the substrate 10) is, for example, constant. The beam portion 32 includes a first portion 32 a provided along the upper surface 21 of the first electrode 20 and a second portion 32 b provided along the first surface 22 a of the first electrode 20.

  The first portion 32 a extends from the second portion 32 b along the upper surface 21 of the first electrode 20. There is a gap between the first portion 32 a and the first electrode 20. The first portion 32 a has an inner surface 33 a that faces the upper surface 21 of the first electrode 20.

  The second portion 32 b extends from the support portion 34 along the first surface 22 a of the first electrode 20. There is a gap between the second portion 32 b and the first electrode 20. The second portion 32b connects the support portion 34 and the first portion 32a. The second portion 32 b has an inner surface 33 b that faces the first surface 22 a of the first electrode 20.

  The support portion 34 is disposed on the substrate 10. The support part 34 supports the beam part 32. For example, the support portion 34 is fixed on the substrate 10. The support portion 34 has an inner surface 33 c that faces the second surface 22 b of the first electrode 20.

  Note that the MEMS vibrator 100 may include a covering structure that hermetically seals the first electrode 20 and the second electrode 30 in a reduced pressure state. Thereby, the air resistance at the time of vibration of the beam part 32 can be reduced.

  The material of the first electrode 20 and the second electrode 30 is, for example, polycrystalline silicon provided with conductivity by doping a predetermined impurity.

  The MEMS vibrator 100 has the following features, for example.

  In the MEMS vibrator 100, the first surface 22 a constituting the side surface 22 of the first electrode 20 is inclined with respect to the upper surface 11 of the substrate 10. As a result, the occurrence of sidewall-like etching residue can be prevented. Therefore, reliability can be improved. The reason for this will be described later.

  Further, in the MEMS vibrator 100, the angle of the first surface 22a with respect to the upper surface 11 of the substrate 10 is the first angle, and the angle of the second surface 22b with respect to the upper surface 11 of the substrate 10 is a second larger than the first angle. Is an angle. As a result, the first corner portion 25 a formed by the first surface 22 a and the second surface 22 b is formed on the side surface 22 of the first electrode 20. By forming the first corner portion 25 a in the first electrode 20, the corner portion (second corner portion 35 a) can be easily formed on the upper surface of the second electrode 30.

  The second corner portion 35a formed on the upper surface of the second electrode 30 has an edge effect (when viewed from the upper surface 11 side of the substrate 10) when observed in a plane with an SEM or the like (in the SEM observation, a projection or a step on the sample surface). If there is a shape-like structure, the tip and edge portions of the protrusions can be clearly confirmed by the phenomenon of brightening with a certain width). Therefore, the distance L32 between the second corner portion 35a and the tip portion of the beam portion 32 can be measured by plane observation using SEM or the like. Here, the second corner portion 35a corresponds to the boundary between the beam portion 32 and the support portion 34, and the distance L32 corresponds to the length of the beam portion of the MEMS vibrator that contributes to the frequency characteristics of the MEMS vibrator. Yes. Therefore, according to the MEMS vibrator 100, the frequency characteristics can be easily managed.

  In the MEMS vibrator 100, the angle α of the first surface 22a with respect to the upper surface 11 of the substrate 10 can be 5 ° or more and 45 ° or less. As a result, as will be described later, it is possible to prevent the occurrence of a sidewall-like etching residue and improve the reliability.

  In the MEMS vibrator 100, the angle β of the second surface 22b with respect to the upper surface 11 of the substrate 10 can be, for example, not less than 80 ° and not more than 90 °. Thereby, the length (distance L32 between the 2nd corner | angular part 35a and the front-end | tip part of the beam part 32) of the beam part 32 can be measured easily. For example, when the angle β of the second surface 22b is smaller than 80 °, the difference (angle difference) between the angle α of the first surface and the angle β of the second surface is small, and the side surface of the first electrode Becomes smooth. Therefore, it becomes difficult to form the second corner. Even if the second corner is formed, the edge effect is hardly obtained. In the MEMS vibrator 100, since the angle β of the second surface 22b is not less than 80 ° and not more than 90 °, such a problem does not occur, and the second corner portion 35a is clearly clarified by planar observation using an SEM or the like. Can be confirmed. Therefore, according to the MEMS vibrator 100, the length of the beam portion 32 (the distance L32 between the second corner portion 35a and the tip portion of the beam portion 32) can be easily measured.

1.2. Manufacturing Method of MEMS Vibrator According to First Embodiment Next, a manufacturing method of the MEMS vibrator according to the first embodiment will be described with reference to the drawings. 4 to 9 are cross-sectional views schematically showing manufacturing steps of the MEMS vibrator 100 according to the first embodiment.

  As shown in FIG. 4, the first base layer 14 and the second base layer 16 are formed in this order on the support substrate 12 to obtain the substrate 10. The first underlayer 14 is formed by, for example, a LOCOS method. The second underlayer 16 is formed by, for example, a CVD (Chemical Vapor Deposition) method or a sputtering method.

  Next, the first semiconductor layer 2 is formed on the substrate 10. The first semiconductor layer 2 is formed by, for example, a CVD method or a sputtering method. The material of the first semiconductor layer 2 is, for example, polycrystalline silicon (polysilicon).

  Next, impurities are implanted into the first semiconductor layer 2. Thereby, conductivity can be imparted to the first semiconductor layer 2. Examples of the implanted impurity include phosphorus (P) and boron (B). Further, heat treatment for activating the impurities may be performed.

  As shown in FIGS. 5 and 6, the first semiconductor layer 2 is patterned to form the first electrode 20.

  First, as shown in FIG. 5, a mask layer M is formed on the first semiconductor layer 2. As the mask layer M, a known resist or the like can be used. The mask layer M is formed, for example, by applying a resist by spin coating, spraying, etc., and then exposing and developing.

  Next, as shown in FIG. 6, the first semiconductor layer 2 is dry-etched using the mask layer M as a mask. In the dry etching, for example, a gas mixed with a gas used for etching non-doped (impurity-implanted) polysilicon and a gas used for etching doped (impurity-implanted) polysilicon is mixed. Is done using.

  Here, the gas used for etching non-doped polysilicon (hereinafter also referred to as “gas for non-doped polysilicon”) is a gas for vertically etching non-doped polysilicon in dry etching. That is, the non-doped polysilicon gas is a gas that is set so that side etching is smaller than that of the non-doped silicon. Therefore, when the non-doped polysilicon gas is used, the side etching becomes larger for the doped polysilicon.

  A gas used for etching doped polysilicon (hereinafter also referred to as “gas for doped polysilicon”) is a gas for vertically etching doped polysilicon in dry etching. That is, the doped polysilicon gas is a gas set so that side etching is smaller than that of the doped silicon. Therefore, when the doped polysilicon gas is used, the side etching becomes larger for the non-doped polysilicon.

The non-doped polysilicon gas is, for example, a mixed gas of chlorine (Cl ₂ ) and sulfur hexafluoride (SF ₆ ). The doped polysilicon gas is, for example, a mixed gas of chlorine (Cl ₂ ), hydrogen bromide (HBr), and oxygen (O ₂ ). Therefore, the gas for etching the first semiconductor layer 2 is a gas containing, for example, chlorine, sulfur hexafluoride, hydrogen bromide, and oxygen.

  By etching the first semiconductor layer 2 using this gas, side etching proceeds near the boundary between the mask layer M and the first semiconductor layer 2 as shown in FIG. And an inclined surface appears. Further, in the vicinity of the boundary between the substrate 10 and the first semiconductor layer 2, a surface that is perpendicular to the upper surface 11 of the substrate 10 or an angle close to perpendicular (80 ° to 90 °) appears. Thereby, the side surface 22 having the first surface 22a and the second surface 22b is formed.

  The conditions for dry etching the first semiconductor layer 2 are, for example, a pressure in the chamber of 10 to 20 mTorr and a high frequency power (RF-POWER) of about 200 to 300 W. Further, the angle α of the first surface 22a and the angle β of the second surface 22b can be controlled, for example, by adjusting the ratio of the etching gas and the etching time.

  Through the above steps, the first electrode 20 can be formed.

  As shown in FIG. 7, a covering layer (sacrificial layer) 4 that covers the first electrode 20 is formed. The covering layer 4 is, for example, a silicon oxide layer. The covering layer 4 is formed, for example, by thermally oxidizing the first electrode 20. The distance between the first electrode 20 and the second electrode 30 is determined by the thickness of the covering layer 4.

  As shown in FIG. 8, the second semiconductor layer 6 is formed on the coating layer 4. In the illustrated example, the second semiconductor layer 6 is formed on the covering layer 4 and the substrate 10 (on the upper surface 11). Specifically, the second semiconductor layer 6 is formed along the upper surface 11 of the substrate 10, the first surface 22 a, the second surface 22 b, and the upper surface 11 of the first electrode 20 with the coating layer 4 interposed therebetween. The second semiconductor layer 6 is formed by, for example, a CVD method or a sputtering method. The material of the second semiconductor layer 6 is, for example, polycrystalline silicon.

  By forming the second semiconductor layer 6 on the covering layer 4, the shape of the first corner portion 25 a is transferred to the upper surface of the second semiconductor layer 6, and the second corner portion 35 a is formed. The shape of the triangular part 25b is transferred to form the fourth angular part 35b.

  Next, impurities are implanted into the second semiconductor layer 6. Thereby, conductivity can be imparted to the second semiconductor layer 6. Examples of the implanted impurity include phosphorus (P) and boron (B). Further, heat treatment for activating impurity activation may be performed.

  As shown in FIG. 9, the second semiconductor layer 6 is patterned to form a second electrode 30 having a beam portion 32 and a support portion 34. The patterning of the second semiconductor layer 6 is performed by, for example, a photolithography technique and an etching technique. Since the first surface 22a of the first electrode 20 is inclined with respect to the upper surface 11 of the substrate 10, it is possible to prevent a sidewall-like etching residue from occurring. Details will be described later.

  As shown in FIG. 2, the coating layer 4 is removed (release process). The removal of the coating layer 4 is performed by wet etching using, for example, hydrofluoric acid or buffered hydrofluoric acid (mixed liquid of hydrofluoric acid and ammonium fluoride). At this time, the second underlayer 16 can function as an etching stopper layer.

  Through the above steps, the MEMS vibrator 100 can be manufactured.

  The method for manufacturing the MEMS vibrator 100 according to the first embodiment has the following features, for example.

  According to the method for manufacturing the MEMS vibrator 100, the first surface 22 a of the first electrode 20 is formed so as to be inclined with respect to the upper surface 11 of the substrate 10. Thereby, in the step of patterning the second semiconductor layer 6, it is possible to prevent a sidewall-like etching residue from occurring around the first electrode 20 (excluding a region overlapping the second electrode 30). Therefore, reliability can be improved. The reason will be described below.

  FIG. 10 is a cross-sectional view schematically showing a state after the second semiconductor layer 6 is formed in the manufacturing method according to the present embodiment. FIG. 11 is a comparative example schematically showing a state after the second semiconductor layer 6 is formed when the side surface 22 of the first electrode 20 is a surface perpendicular to the upper surface 11 of the substrate 10. It is sectional drawing. 10 and 11 are cross-sectional views of a region where the first electrode 20 and the second electrode 30 do not overlap after the second semiconductor layer 6 is patterned. For example, it corresponds to the cross section taken along line XX shown in FIG.

  As shown in FIG. 11, when the side surface 22 of the first electrode 20 is a surface perpendicular to the upper surface 11 of the substrate 10, the film thickness T <b> 1 of the second semiconductor layer 6 formed in the vicinity of the side surface 22 is It is larger than the film thickness T2 of the second semiconductor layer 6 formed on the other region and the coating layer 4 above. Therefore, by patterning the second semiconductor layer 6 by dry etching, a sidewall-like etching residue 7 is generated in the vicinity of the side surface 22 of the first electrode 20. The etching residue 7 is separated from the substrate 10 and adheres to the electrodes 20 and 30 and the like, thereby causing a short circuit between the electrodes 20 and 30 and a change in vibration characteristics of the beam portion 32. May decrease.

  On the other hand, in the MEMS vibrator 100, as shown in FIG. 10, the first surface 22 a constituting the side surface 22 of the first electrode 20 is inclined with respect to the upper surface 11 of the substrate 10. Compared to the example, the film thickness T of the second semiconductor layer 6 can be made uniform. Therefore, it is possible to prevent etching residue from occurring in the step of patterning the second semiconductor layer 6.

  In the method of manufacturing the MEMS vibrator 100, in the step of forming the first electrode 20, the side surface 22 of the first electrode 20 is formed to have the first surface 22a and the second surface 22b. Thereby, the first corner portion 25 a can be formed on the side surface 22 of the first electrode 20. By forming the first corner portion 25 a, the second corner portion 35 a can be easily formed on the upper surface of the second electrode 30 in the step of forming the second semiconductor layer 6. Therefore, the distance L32 (see FIGS. 1 and 2) between the second corner portion 35a and the tip of the beam portion 32 can be measured by, for example, planar observation using an SEM, and the frequency characteristics can be easily managed. can do.

  According to the method for manufacturing the MEMS vibrator 100, the step of dry etching the first semiconductor layer 2 is performed using a gas containing chlorine, sulfur hexafluoride, hydrogen bromide, and oxygen. By performing dry etching using such a gas, for example, the first layer having the first surface 22a and the second surface 22b can be formed without forming the mask layer twice or switching the gas used for the etching. The side surface 22 of the electrode 20 can be easily formed.

  According to the method for manufacturing the MEMS vibrator 100, as shown in FIG. 6, in the step of patterning the first semiconductor layer 2, the second surface 22 b is formed on the side surface 22 of the first electrode 20. The width WM and the width W20 of the first electrode 20 can be made the same size. Thereby, in the process of patterning the first semiconductor layer 2, the accuracy of the width W20 of the first electrode 20 can be increased. The width W20 of the first electrode 20 is a distance between the second surfaces 22b facing in opposite directions. Since the width W20 of the first electrode 20 affects the frequency characteristics of the MEMS vibrator, according to the manufacturing method of the MEMS vibrator 100, it is possible to manufacture a MEMS vibrator with little variation in frequency characteristics.

  Here, in the step of patterning the first semiconductor layer 2, when the side surface of the first electrode is an inclined surface, the width of the first electrode also varies when the etching amount varies. According to the manufacturing method of the MEMS vibrator 100, when the etching amount varies, the height L1 (see FIG. 3) of the first corner portion 25a varies, but the width W20 of the first electrode 20 cannot be varied. . Therefore, according to the method for manufacturing the MEMS vibrator 100, the accuracy of the width W20 of the first electrode 20 can be increased.

1.3. Modified Example of Manufacturing Method of MEMS Vibrator According to First Embodiment Next, a modified example of the manufacturing method of the MEMS vibrator according to the first embodiment will be described with reference to the drawings. Hereinafter, differences from the manufacturing process of the MEMS vibrator 100 according to the first embodiment shown in FIGS. 4 to 9 described above will be described, and description of similar points will be omitted.

  (1) First, a first modification will be described. 12 and 13 are cross-sectional views schematically showing the manufacturing process of the MEMS vibrator 100 according to the first modification.

  In the method of manufacturing the MEMS vibrator 100 according to the first embodiment described above, the step of forming the first electrode 20 is performed by dry etching the first semiconductor layer 2 using the first gas, as shown in FIG. First dry etching process for forming the first surface 22a, and as shown in FIG. 13, the first semiconductor layer 2 is dry etched using a second gas different from the first gas, and the second surface 22b is formed. And a second dry etching step to be formed.

  In the step of forming the first electrode 20 according to this modification, first, as shown in FIG. 12, the first semiconductor layer 2 is dry-etched using the first gas to form the first surface 22a ( First dry etching step). The first gas is, for example, the aforementioned non-doped polysilicon gas. Specifically, the first gas is, for example, a mixed gas of chlorine and sulfur hexafluoride. Since the first semiconductor layer 2 is doped polysilicon, side etching proceeds by using the first gas. As a result, as shown in FIG. 12, a first surface 22 a that is inclined with respect to the upper surface 11 of the substrate 10 is formed in the first semiconductor layer 2.

  Next, as shown in FIG. 13, the first semiconductor layer 2 is dry-etched using the second gas to form the second surface 22b (second dry etching step). The second gas is, for example, the above-described doped polysilicon gas. Specifically, the second gas is, for example, a mixed gas of chlorine, hydrogen bromide, and oxygen. Since the first semiconductor layer 2 is doped polysilicon, by using the second gas, the first semiconductor layer 2 has a second surface perpendicular to the upper surface 11 of the substrate 10 as shown in FIG. 22b is formed.

  Through the above steps, the first electrode 20 can be formed.

  According to this modification, the side surface 22 of the first electrode 20 having the first surface 22a and the second surface 22b can be formed with one mask layer M by switching the gas used for dry etching.

  According to this modification, reliability can be improved and frequency characteristics can be easily managed, as in the method of manufacturing the MEMS vibrator according to the first embodiment described above.

  (2) Next, a second modification will be described. 14 and 15 are cross-sectional views schematically showing manufacturing steps of the MEMS vibrator 100 according to the second modification.

  In the method of manufacturing the MEMS vibrator 100 according to the first embodiment described above, the step of forming the first electrode 20 is performed by changing the impurity concentration on the upper surface side of the first semiconductor layer 2 and the impurity concentration on the lower surface side of the first semiconductor layer 2. The step of implanting impurities into the first semiconductor layer 2 so as to be higher than the concentration, the step of forming the mask layer M above the first semiconductor layer 2, and the first semiconductor layer 2 using the mask layer M as a mask And a step of dry etching. In this modification, the step of implanting impurities into the first semiconductor layer 2 shown in the method for manufacturing the MEMS vibrator according to the first embodiment described above is not performed.

  In the step of forming the first electrode 20 according to this modification, first, as shown in FIG. 14, the impurity concentration on the upper surface side of the first semiconductor layer 2 is made higher than the impurity concentration on the lower surface side of the first semiconductor layer 2. Impurities are implanted into the first semiconductor layer 2 so as to be. As a result, a region 2 a having a high impurity concentration is formed on the upper surface side of the first semiconductor layer 2, and a region 2 b having a lower impurity concentration than the region 2 a is formed on the lower surface side of the second semiconductor layer 2.

  Next, as shown in FIG. 15, a mask layer M is formed on the first semiconductor layer 2. The mask layer M is formed, for example, by applying a resist by a spin coater or spraying, and then exposing and developing.

  Next, the first semiconductor layer 2 is dry etched using the mask layer M as a mask. The first semiconductor layer 2 is performed using, for example, a non-doped polysilicon gas. As a result, in the region 2 a on the upper surface side of the first semiconductor layer 2, side etching proceeds and a first surface 22 a that is inclined with respect to the upper surface 11 of the substrate 10 is formed. In the region 2 b on the lower surface side of the first semiconductor layer 2, a second surface 22 b perpendicular to the upper surface 11 of the substrate 10 is formed.

  Through the above steps, the first electrode 20 can be formed.

  According to this modification, by implanting impurities into the first semiconductor layer 2 so that the impurity concentration on the upper surface side of the first semiconductor layer 2 is higher than the impurity concentration on the lower surface side of the first semiconductor layer 2, For example, the side surface 22 of the first electrode 20 having the first surface 22a and the second surface 22b can be easily formed without forming the mask layer twice or switching the gas used for etching. .

  According to this modification, reliability can be improved and frequency characteristics can be easily managed, as in the method of manufacturing the MEMS vibrator according to the first embodiment described above.

  (3) Next, a third modification will be described. 16 to 18 are cross-sectional views schematically showing manufacturing steps of the MEMS vibrator 100 according to the third modification.

  In the method for manufacturing the MEMS vibrator 100 according to the first embodiment described above, the step of forming the first electrode 20 includes the step of forming the silicon oxide layer 8 above the first semiconductor layer 2 and the step of forming the silicon oxide layer 8. A step of forming a mask layer M above the silicon oxide layer, a step of etching the silicon oxide layer 8 using the mask layer M as a mask so that the width W8 of the silicon oxide layer 8 is smaller than the width WM of the mask layer M, And etching the first semiconductor layer 2 using the mask layer M and the silicon oxide layer 8 as a mask.

  In the step of forming the first electrode 20 according to this modification, first, the silicon oxide layer 8 is formed on the first semiconductor layer 2 as shown in FIG. The film formation is performed by, for example, a CVD method or a sputtering method.

  Next, a mask layer M is formed on the silicon oxide layer 8. The mask layer M is formed, for example, by applying a resist by a spin coater or spraying, and then exposing and developing.

  Next, as shown in FIG. 17, etching is performed using the mask layer M as a mask so that the width W8 of the silicon oxide layer 8 is smaller than the width WM of the mask layer M. By etching the silicon oxide layer 8 so that side etching proceeds, the width W8 of the silicon oxide layer 8 can be made smaller than the width WM of the mask layer M. Thereby, the silicon oxide layer 8 is positioned inside the mask layer M in a plan view, and a gap can be provided between the mask layer M and the first semiconductor layer 2.

  Next, as shown in FIG. 18, the first semiconductor layer 2 is etched using the mask layer M and the silicon oxide layer 8 as a mask. Etching of the first semiconductor layer 2 is performed by dry etching, for example. As a result, gas is positively supplied to the gap between the mask layer M and the first semiconductor layer 2, and the first semiconductor layer 2 is etched from the region adjacent to the gap (microloading effect). Therefore, as shown in FIG. 18, the first surface 22a and the second surface 22b are formed. The second surface 22b may be formed, for example, by performing dry etching with increased anisotropy after forming the first surface 22a.

  Through the above steps, the first electrode 20 can be formed.

  According to this modification, reliability can be improved and frequency characteristics can be easily managed, as in the method of manufacturing the MEMS vibrator according to the first embodiment described above.

  Here, an example in which the silicon oxide layer 8 is used as a mask has been described. However, the present invention is not limited to the silicon oxide layer, and layers of other materials may be used.

  (4) Next, a fourth modification will be described. 19 and 20 are cross-sectional views schematically showing the manufacturing process of the MEMS vibrator 100 according to the fourth modification.

  In the manufacturing method of the MEMS vibrator 100 described above, the step of forming the first electrode 20 includes the step of forming the first mask layer M1 above the first semiconductor layer 2 and the first mask layer M1 as a mask. A step of patterning the first semiconductor layer 2 to form the first surface 22a, a step of forming the second mask layer M2 on the first semiconductor layer 2 on which the first surface 22a is formed, and a second mask layer M2 As a mask, there may be a step of patterning the first semiconductor layer 2 on which the first surface 22a is formed to form the second surface 22b.

  In the step of forming the first electrode 20 according to this modification, first, as shown in FIG. 19, a first mask layer M <b> 1 is formed on the first semiconductor layer 2. The first mask layer M1 is formed by, for example, applying a resist by a spin coater, spraying, etc., and then exposing and developing. The material of the first mask layer M1 is, for example, the same as that of the mask layer M described above.

  Next, the first semiconductor layer 2 is patterned using the first mask layer M1 as a mask. The patterning of the first semiconductor layer 2 is performed, for example, by dry etching using a non-doped polysilicon gas. Thereby, in the first semiconductor layer 2, side etching proceeds and a first surface 22 a inclined with respect to the upper surface 11 of the substrate 10 is formed. Thereafter, the first mask layer M1 is removed.

  Next, as shown in FIG. 20, a second mask layer M2 is formed on the first semiconductor layer 2 on which the first surface 22a is formed. The second mask layer M2 is formed, for example, by applying a resist by spin coater, spraying, etc., and then exposing and developing. The material of the second mask layer M2 is, for example, the same as that of the mask layer M described above.

  Next, the first semiconductor layer 2 is patterned using the second mask layer M2 as a mask. The patterning of the first semiconductor layer 2 is performed, for example, by dry etching using a doped polysilicon gas. Thereby, the second surface 22b perpendicular to the upper surface 11 of the substrate 10 is formed.

  Through the above steps, the first electrode 20 can be formed.

  In this modification, reliability can be improved and frequency characteristics can be easily managed, as in the method for manufacturing the MEMS vibrator according to the first embodiment described above.

2. Second Embodiment Next, a MEMS resonator according to a second embodiment will be described with reference to the drawings. FIG. 21 is a plan view schematically showing the MEMS vibrator 200 according to the second embodiment. FIG. 22 is a cross-sectional view schematically showing the MEMS vibrator 200. 22 is a cross-sectional view taken along line XXII-XXII in FIG. Hereinafter, in the MEMS vibrator 200 according to the second embodiment, members having the same functions as those of the constituent members of the MEMS vibrator 100 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the MEMS vibrator 100 according to the first embodiment described above, as shown in FIGS. 1 and 2, two second electrodes 30 are provided for one first electrode 20.

  On the other hand, in the MEMS vibrator 200, as shown in FIGS. 21 and 22, one second electrode 30 is provided for one first electrode 20.

  According to the MEMS vibrator 200 according to the second embodiment, the same operational effects as those of the MEMS vibrator 100 can be obtained.

  The manufacturing method of the MEMS vibrator 200 is the same as the manufacturing method of the MEMS vibrator 100 described above except that one second electrode 30 is provided for one first electrode 20. Omitted.

3. Third Embodiment Next, a MEMS resonator according to a third embodiment will be described with reference to the drawings. FIG. 23 is a cross-sectional view schematically showing the MEMS vibrator 300 according to the third embodiment. FIG. 24 is an enlarged cross-sectional view showing a part of the first electrode 20 of the MEMS vibrator 300. In FIG. 24, the second electrode 30 is not shown for convenience. Hereinafter, in the MEMS vibrator 300 according to the third embodiment, members having the same functions as the constituent members of the MEMS vibrator 100 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the example of the MEMS vibrator 100 described above, as shown in FIGS. 2 and 3, the first surface 22a of the first electrode 20 is a flat surface.

  On the other hand, in the MEMS vibrator 300, the first surface 22a of the first electrode 20 is a curved surface. In the illustrated example, the first surface 22a is a concave surface, but may be a convex surface. For example, in the step of etching the first semiconductor layer 2, the first surface 22 a can be a surface having an arbitrary shape by controlling the type of gas used for dry etching and other conditions.

A line connecting the third corner 25b formed by the upper surface 21 of the first electrode 20 and the first surface 22a and the first corner 25a formed by the first surface 22a and the second surface 22b is a straight line L _α . Then, if the first surface 22a is a curved surface, the angle alpha of the first surface 22a with respect to the upper surface 11 of the substrate 10, for example, an angle formed between the upper surface 11 and the straight line L _alpha of the substrate 10.

  According to the MEMS vibrator 300 according to the third embodiment, the same operational effects as those of the MEMS vibrator 100 can be obtained.

  The manufacturing method of the MEMS vibrator 300 is the same as the manufacturing method of the MEMS vibrator 100 described above, and the description thereof is omitted.

4). Fourth Embodiment Next, an oscillator according to a fourth embodiment will be described with reference to the drawings. FIG. 25 is a circuit diagram showing an oscillator 400 according to the fourth embodiment.

  As shown in FIG. 25, the oscillator 400 includes a MEMS resonator (for example, the MEMS resonator 300) according to the present invention and an inverting amplifier circuit 410.

  The MEMS vibrator 300 has a first terminal 300 a electrically connected to the first electrode 20 and a second terminal 300 b electrically connected to the second electrode 30. The first terminal 300a of the MEMS vibrator 300 is connected to the input terminal 410a of the inverting amplifier circuit 410 at least in an AC manner. The second terminal 300b of the MEMS vibrator 300 is connected to the output terminal 410b of the inverting amplifier circuit 410 at least in an AC manner.

  In the illustrated example, the inverting amplifier circuit 410 is configured by one inverter, but may be configured by combining a plurality of inverters (inverting circuits) and amplifier circuits so that a desired oscillation condition is satisfied. .

  The oscillator 400 may include a feedback resistor for the inverting amplifier circuit 410. In the example shown in FIG. 25, the input terminal and the output terminal of the inverting amplifier circuit 410 are connected via a resistor 420.

  The oscillator 400 includes a first capacitor 430 connected between the input terminal 410a of the inverting amplifier circuit 410 and a reference potential (ground potential), and between the output terminal 410b of the inverting amplifier circuit 410 and the reference potential (ground potential). And a second capacitor 432 connected to the second capacitor 432. As a result, the MEMS vibrator 100 and the capacitors 430 and 432 can form an oscillation circuit that forms a resonance circuit. The oscillator 400 outputs the oscillation signal f obtained by this oscillation circuit.

  Elements (not shown) such as transistors and capacitors constituting the oscillator 400 may be formed on the substrate 10 (see FIG. 1), for example. Thereby, the MEMS vibrator 300 and the anti-amplification circuit 410 can be formed monolithically.

  When an element such as a transistor constituting the oscillator 400 is formed on the substrate 10, the element such as a transistor constituting the oscillator 400 may be formed in the same process as the process for forming the MEMS vibrator 100 described above. Specifically, in the step of forming the covering layer 4 (see FIG. 7), a gate insulating layer of a transistor may be formed. Further, in the step of forming the second electrode 30 (see FIGS. 8 and 9), a gate electrode of a transistor may be formed. As described above, by sharing the manufacturing process of the MEMS vibrator 300 and the manufacturing process of the elements such as the transistors constituting the oscillator 400, the manufacturing process can be simplified.

  The oscillator 400 includes the MEMS vibrator 100 with high reliability and easy management of frequency characteristics. Therefore, reliability can be improved and management of frequency characteristics can be facilitated.

The oscillator 400 may further include a frequency dividing circuit 440 as illustrated in FIG. The frequency dividing circuit 440 divides the output signal _Vout of the oscillation circuit and outputs the oscillation signal f. Thereby, the oscillator 400 can obtain an output signal having a frequency lower than the frequency of the output signal _Vout , for example.

  In addition, embodiment mentioned above and a modification are examples, Comprising: It is not necessarily limited to these. For example, a plurality of embodiments and modifications can be combined as appropriate.

  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 objects 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 exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

M mask layer, M1 first mask layer, M2 second mask layer, 2 first semiconductor layer,
2a, 2b region, 4 coating layer, 6 second semiconductor layer, 7 etching residue,
8 silicon oxide layer, 10 substrate, 11 upper surface, 12 support substrate, 14 first underlayer,
16 second underlayer, 20 first electrode, 21 upper surface, 22 side surface, 22a first surface,
22b 2nd surface, 25a 1st corner, 25b 3rd corner, 30 2nd electrode, 32 beam,
32a 1st part, 32b 2nd part, 33a, 33b, 33c inner surface,
35a second corner, 35b fourth corner, 100, 200, 300 MEMS vibrator,
300a first terminal, 300b second terminal, 400 oscillator, 410 inverting amplifier circuit,
410a input terminal, 410b output terminal, 412, 414, 416 inverter,
420, 422, 424 resistor, 430 first capacitor,
432 Second capacitor, 440 frequency divider

Claims (9)

A substrate,
A first electrode disposed above the substrate;
A second electrode having a beam portion that is arranged with a gap between the first electrode and that can vibrate by an electrostatic force in the thickness direction of the substrate; and a support portion that supports the beam portion;
Including
The side surface of the first electrode is
A first surface connected to an upper surface of the first electrode;
A second surface connected to the first surface and the top surface of the substrate;
Have
The first surface is inclined with respect to the upper surface of the substrate;
The angle of the first surface with respect to the upper surface of the substrate is a first angle;
The MEMS vibrator, wherein an angle of the second surface with respect to an upper surface of the substrate is a second angle larger than the first angle. In claim 1,
A first corner formed by the first surface and the second surface is formed on a side surface of the first electrode,
A MEMS vibrator, wherein a second corner portion to which the shape of the first corner portion is transferred is formed on an upper surface of the second electrode. In claim 1 or 2,
The MEMS vibrator, wherein the first angle is not less than 5 ° and not more than 45 °. In any one of Claims 1 thru | or 3,
The MEMS vibrator, wherein the second angle is not less than 80 ° and not more than 90 °. The MEMS vibrator according to any one of claims 1 to 4,
A circuit unit electrically connected to the first electrode and the second electrode of the MEMS vibrator;
Including oscillator. Forming a first semiconductor layer over the substrate;
Patterning the first semiconductor layer to form a first electrode;
Forming a coating layer covering the first electrode;
Forming a second semiconductor layer above the covering layer;
The second semiconductor layer is patterned and disposed with a gap between the first electrode and the beam portion that can vibrate by electrostatic force in the thickness direction of the substrate, and supports the beam portion Forming a second electrode having a support;
Removing the coating layer;
Including
In the step of forming the first electrode,
Forming a side surface of the first electrode to have a first surface connected to an upper surface of the first electrode and a second surface connected to the first surface and the upper surface of the substrate;
The first surface is inclined with respect to the upper surface of the substrate;
The angle of the first surface with respect to the upper surface of the substrate is a first angle;
The method of manufacturing a MEMS vibrator, wherein an angle of the second surface with respect to an upper surface of the substrate is a second angle larger than the first angle. In claim 6,
The step of forming the first electrode includes:
Forming a mask layer above the first semiconductor layer;
Dry etching the first semiconductor layer using the mask layer as a mask;
Including
The method of manufacturing a MEMS vibrator, wherein the step of dry etching the first semiconductor layer is performed using a gas containing chlorine, sulfur hexafluoride, hydrogen bromide, and oxygen. In claim 6,
The step of forming the first electrode includes:
A first dry etching step of dry-etching the first semiconductor layer using a first gas to form the first surface;
A second dry etching step of dry-etching the first semiconductor layer using a second gas different from the first gas to form the second surface;
A method for manufacturing a MEMS vibrator, comprising: In claim 6,
The step of forming the first electrode includes:
Implanting impurities into the first semiconductor layer such that the impurity concentration on the upper surface side of the first semiconductor layer is higher than the impurity concentration on the lower surface side of the first semiconductor layer;
Forming a mask layer above the first semiconductor layer;
Dry etching the first semiconductor layer using the mask layer as a mask;
A method for manufacturing a MEMS vibrator, comprising:

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