JP2005118939A - Etching method, vibrator, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method by which a structure in a desired shape can be precisely formed and etching friendly to the environment can be realized during etching, for example, by reducing an amount of substances scattering from a substrate, a vibrator manufactured by using the etching method, and electronic equipment provided with such a vibrator. <P>SOLUTION: The etching method is employed for working a first layer 103 into a prescribed shape by etching. The etching method has a process for forming a mask 11 provided with a mask 111 for patterning in a shape corresponding to the prescribed shape and a mask 112 for a dummy, which is separated from the mask 111 and arranged so as to make the width of a gap 110 at each part in an etching region almost equal, in an etching region of the first layer 102, a process for patterning the first layer 103 on the side opposite to a second layer 103 with first etching by using the mask 11, and a process for removing a dummy part 9 subjected to the patterning corresponding to the mask 112 for a dummy of the first layer 103. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an etching method, a vibrator, and an electronic device.

A vibrator that mechanically vibrates in synchronization with the frequency of a certain vibration current is applied to a band-pass filter, a reference clock, a vibration sensor, and the like for communication equipment such as a mobile phone.
As such a vibrator, a method for forming a structure for generating vibration (a structure having a floating part and an anchor part) on a silicon substrate by a micromachining technique using a semiconductor manufacturing process has been proposed. (See Patent Document 1).

The method described in Patent Document 1 will be briefly described with reference to FIG.
First, as shown in FIG. 12A, a substrate 90 in which a silicon oxide layer (sacrificial layer) 92 and a silicon layer 93 are laminated on a silicon substrate 91 is prepared.
Next, as shown in FIG. 12B, a mask pattern 94 is formed on the silicon layer 93.

Next, as shown in FIG. 12C, the silicon layer 93 is etched and patterned into a desired shape using the mask pattern 94 as a mask.
Next, as shown in FIG. 12D, the silicon oxide layer 92 corresponding to the portion to be the floating portion is removed by using a sacrificial layer etching technique. At this time, since the area of the anchor portion in plan view is larger than that of the floating portion, the silicon oxide layer 92 corresponding to the portion to be the anchor portion remains without being removed.

However, when the silicon layer 93 is etched using the mask pattern 94, if the width of the gap 941 formed in the mask pattern 94 is different, the silicon layer 93 is etched quickly in a region where the width of the gap 941 is wide. Occurs.
For this reason, when time elapses until the silicon layer 93 is sufficiently etched in a region where the interval 941 is narrow, overetching of the silicon layer 93 (with respect to the thickness direction) occurs in the region where the interval 941 is wide. There is a problem that etching in the vertical direction occurs.
When such over-etching occurs, the desired characteristics cannot be obtained in the vibrator.

JP 11-190635 A (paragraph number 0021)

  An object of the present invention is to provide an etching method capable of accurately forming a structure having a desired shape and reducing the amount of a substance scattered from a substrate, for example, and performing environmentally friendly etching. An object of the present invention is to provide a vibrator manufactured using the electronic device and an electronic device including the vibrator.

Such an object is achieved by the present invention described below.
The etching method of the present invention includes a first layer etched by the first etching, a second layer adjacent to the first layer and not substantially etched by the first etching, and the second layer Etching to process the first layer into a structure having a predetermined shape by applying the first etching to a substrate having a base material provided on the opposite side of the first layer to the first layer A method,
A pattern mask having a shape corresponding to the structure body is formed in an etching region of the first layer opposite to the second layer, and a gap in each part in the etching region is separated from the pattern mask. A first step of forming a mask comprising a dummy mask arranged to be substantially equal in width;
A second step of patterning the first layer by applying the first etching to the first layer using the mask;
And a third step of removing the patterned dummy portion corresponding to the dummy mask of the first layer.
Thereby, the structure of a desired shape can be formed precisely.

In the etching method of the present invention, in the third step, the dummy portion is formed by performing the second etching that allows the second layer to be etched without substantially etching the first layer. It is preferably removed when the layer is removed.
Thereby, the dummy part can be easily and reliably removed.
In the etching method according to the present invention, the structure includes a first portion having a shape such as a combination of a plurality of strips, and an area (maximum) of the strips constituting the first portion in plan view. A second portion having a large area,
When the second layer is removed by the second etching, the second layer immediately below the second portion remains due to a difference in area between the first portion and the second portion. Thus, it is preferable that the structure is fixed to the base material and the first portion is lifted from the base material.
Thereby, fixation to the base material of a structure can be performed easily and reliably.

In the etching method of the present invention, it is preferable that the dummy mask has a strip shape.
By making the dummy mask into a strip shape, the width of the gap formed in the mask can be easily adjusted.
In the etching method of the present invention, it is preferable that the width of the band-shaped dummy mask is substantially equal to the width (average) of the portion corresponding to the band-shaped body of the pattern mask.
Thereby, when removing a 2nd layer by 2nd etching, a dummy part can be reliably made to detach | leave from a base material.

In the etching method of the present invention, the second etching is preferably wet etching.
By using wet etching as the second etching, the second layer can be etched isotropically. For this reason, the second layer immediately below the first layer patterned corresponding to the mask can also be efficiently removed.

In the etching method of the present invention, it is preferable that the first etching is dry etching.
By using dry etching (particularly reactive ion etching) as the first etching, etching with high anisotropy can be performed on the first layer, and patterning of the first layer is performed with high dimensional accuracy. be able to.

In the etching method of the present invention, the thickness (average) of the first layer is preferably 0.2 to 100 μm.
Thereby, it is possible to more reliably prevent or suppress the occurrence of overetching in each part of the first layer, and it is possible to prevent the etching rate from being extremely lowered.

The etching method of the present invention preferably includes a step of removing the mask prior to the third step.
By removing the mask prior to the second etching step, when wet etching is used in the second etching step, contamination of the etching solution due to dissolution of the mask material (resist material or metal material) is prevented. Or it can be suppressed.

In the etching method of the present invention, the substrate includes the second layer mainly made of SiO ₂ and the first layer mainly made of Si on the base material mainly made of Si. It is preferable that the SOI substrate is laminated in this order.
By using an SOI substrate as the substrate, a substrate having a relatively thick first layer can be manufactured.

The vibrator of the present invention is manufactured using the etching method of the present invention.
Thereby, a highly reliable vibrator is obtained.
In the vibrator of the present invention, a microresonator is preferable.
The present invention can be applied to various types of vibrators, and is particularly suitable for application to a microresonator.
An electronic apparatus according to the present invention includes the vibrator according to the present invention.
As a result, a highly reliable electronic device can be obtained.

Hereinafter, an etching method, a vibrator, and an electronic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
Below, the case where the vibrator of the present invention is applied to a microresonator will be described as an example.

<Configuration of micro-resonator>
FIG. 1 is a plan view showing an embodiment in which the vibrator of the present invention is applied to a microresonator, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a microresonator shown in FIG. It is a schematic diagram which shows the moving direction of the movable electrode provided. In the following description, the upper side in FIG. 2 is referred to as “upper” and the lower side is referred to as “lower”.

The microresonator 1 shown in FIGS. 1 and 2 includes a base 2, a pair of fixed electrodes 31, 32 fixed to the base 2, and a movable part 4 provided to be able to vibrate between the fixed electrodes 31, 32. And have.
The movable part 4 includes movable electrodes 41 and 42 that face the fixed electrodes 31 and 32, and fixed parts 45 and 46 that are fixed to the base 2 via support parts 51 and 52 (see FIGS. 1 and 2). It has beam parts 43 and 44 which connect each movable electrode 41 and 42 and each fixed part (island part) 45 and 46. As shown in FIG.

Each of the movable electrodes 41 and 42 has a comb shape in which a plurality of 411 and 421 are provided.
On the other hand, the fixed electrodes 31 and 32 have electrode fingers 311 and 321 and fixed portions 312 and 322, respectively, provided side by side.
And each fixing | fixed part 312,322 is being fixed to the base 2 via the support parts 53 and 54 (refer FIG. 1), respectively.

The fixed electrode 31 and the movable electrode 41 are arranged so that the electrode fingers 311 and the electrode fingers 411 are alternately positioned, that is, are engaged with each other. Further, the fixed electrode 32 and the movable electrode 42 are disposed in the same manner as the fixed electrode 31 and the movable electrode 41.
In the microresonator 1, by adjusting the width, interval, thickness, and the like of these electrode fingers 311, 321 and 411, 421, characteristics such as a resonance frequency can be set as desired.

In the present embodiment, among the parts constituting the movable part 4, the movable electrodes 41 and 42 and the beam parts 43 and 44, and among the parts constituting the fixed electrodes 31 and 32, the electrode fingers 311, Each of the first portions 321 forms a shape that is a combination of a plurality of strips. These portions are in a state of floating from the base 2, that is, in a state of being separated by a predetermined distance (the thickness of the second layer 102 described later).
On the other hand, among the respective parts constituting the movable part 4, each fixed part 45, 46, and among the respective parts constituting each fixed electrode 31, 32, each fixed part 312, 322, respectively, in plan view, A second portion having a larger area than the area (maximum) of the band-shaped body constituting the first portion is formed. These parts are fixed to the base 2.

In such a microresonator 1, when a voltage is applied between the fixed electrode 31 and the movable electrode 41, an electrostatic attractive force is generated between the electrodes 31, 41 as shown in FIG. It moves so as to approach the electrode 31.
On the other hand, when the application of the voltage between the fixed electrode 31 and the movable electrode 41 is stopped and the voltage is applied between the fixed electrode 32 and the movable electrode 42, an electrostatic attractive force is generated between the electrodes 32 and 42. The movable electrode 42 moves toward the fixed electrode 32.
Thus, by alternately applying a voltage between the fixed electrode 31 and the movable electrode 41 and between the fixed electrode 32 and the movable electrode 42, the movable electrodes 41 and 42 reciprocate at a constant frequency. To do. This frequency (vibration frequency) is determined by the restoring force with respect to the displacement determined by the total mass of the movable electrodes 41 and 42 and the spring constants of the beam portions 43 and 44.

<Manufacturing method of microresonator>
Next, the case where the etching method of the present invention is applied to the method of manufacturing the microresonator shown in FIGS. 1 and 2 will be described as an example.
4 to 8 are diagrams for explaining a method of manufacturing the microresonator shown in FIGS. 1 and 2, respectively. 6A to 8A is a cross-sectional view taken along the line BB in FIG. 5, and FIG. 6B to FIG. 8B is a cross-sectional view taken along the line CC in FIG.

In the following description, the upper side in FIGS. 4 and 6 to 8 is referred to as “upper”, and the lower side is referred to as “lower”.
The method for manufacturing the microresonator 1 includes [1] a mask forming step, [2] a first etching step, [3] a mask removing step, and [4] a second etching step. Hereinafter, each process will be described sequentially.

[1] Mask formation process (first process)
First, as shown in FIG. 4, the second layer 102 that is not substantially etched by the first etching described later and the first layer 103 that is etched by the first etching are formed on the substrate 101. A substrate 10 having a three-layer structure, which is laminated in order, is prepared.
Among the layers constituting the substrate 10, the first layer 103 is the movable portion 4 and the fixed electrodes 31 and 32 of the microresonator 1 described above, and the second layer 102 is the support portions 51, 52, and 53. , 54, and the base material 101 is a part that becomes the base 2.
Examples of the substrate 10 include various combinations of the layers 101, 102, and 103. In particular, a second layer mainly composed of SiO ₂ on a base material 101 mainly composed of Si, An SOI substrate in which a first layer (active layer) 103 mainly composed of Si is laminated in this order is preferable.

By using an SOI substrate as the substrate 10, a substrate having a relatively thick first layer 103 can be manufactured. For this reason, since the thickness of each electrode finger 311, 321, 411, 421 to be formed can be increased, the sectional area of each electrode finger 311, 321, 411, 421 (in a direction perpendicular to the longitudinal direction) Can be increased. Thereby, in the microresonator 1, the electrostatic capacity can be increased, and as a result, the amount of displacement of the movable portion 4 with respect to the applied voltage can be increased.
Moreover, since the thickness of each electrode finger 311, 321, 411, 421 can be set large, the width | variety can be made small, ensuring the required cross-sectional area. Thereby, each fixed electrode 31, 32, 41, 42 can be reduced in size, and thus the entire microresonator 1 can be reduced in size.

The thickness (average) of the first layer 103 is not particularly limited, but is preferably about 0.2 to 100 μm, and more preferably about 20 to 60 μm. If the thickness of the first layer 103 is too thin, depending on the constituent material of the first layer 103, it may be difficult for the microresonator 1 to sufficiently increase the amount of displacement of the movable portion 4 with respect to the applied voltage. On the other hand, even if the thickness of the first layer 103 is increased beyond the upper limit, not only an increase in the effect cannot be expected, but it becomes difficult to perform the etching deeply and vertically.
Hereinafter, the formation of the movable portion 4 will be described as an example.

  Next, a mask 11 is formed in the etching region on the first layer 103 (on the side opposite to the second layer 102) of the substrate 10 by using, for example, a photolithography method.

Here, in the etching method of the present invention, as shown in FIG. 5, as a mask 11, a pattern mask 111 having a shape corresponding to the movable portion (structure) 4 is formed, and a strip-shaped dummy mask 112 is formed. To do.
The dummy mask 112 is separated from the pattern mask 111 and is disposed so that the widths of the gaps 110 formed in the mask 11 are substantially equal at each part in the etching region. Accordingly, overetching can be prevented or suppressed in each part of the first layer 103 when the first etching is performed on the first layer 103 (see later).

  The dummy mask 112 may have any shape. However, as in the present embodiment, the movable electrodes 41 and 42 and the beam portions 43 and 44 are formed as a combination of strips. In this case, it is preferable to use a belt shape. Thereby, the width of the gap 110 formed in the mask 11 can be easily adjusted. As a result, the difference in the etching rate in each part of the first layer 103 due to the first etching can be reduced more reliably.

The width of the gap 110 (W _{1 in} FIG. 5) is preferably about 0.5 to 3 μm. However, in the case of the illustrated configuration, for example, between the electrode finger 311 (321) and the electrode finger 411 (421) The width may be the same as the width of the interval. As a result, the effect can be further improved, and the etching rate of the first layer 103 by the first etching can be prevented from being extremely lowered.

Further, when the dummy mask 112 has a strip shape, the width is preferably set to be substantially equal to the width (average) of the portion corresponding to the strip of the pattern mask 111. Thereby, when removing the 2nd layer 102 by 2nd etching, each dummy part 9 can be reliably made to detach | leave from the base material 101 (refer later).
The mask 11 may be a mask (metal mask) made of a metal material such as Al, for example, instead of a mask (resist mask) made of a resist material.

[2] First etching step (second step)
Next, first etching is performed on the first layer 103 using the formed mask 11. As a result, the first layer 103 is patterned into a shape corresponding to the pattern mask 111 and the dummy mask 112.
Note that the second layer 102 is not substantially etched by the first etching, and functions as a stop layer that prevents the invasion during the first etching.

For the first etching, for example, reactive ion etching, plasma etching, beam etching, dry etching such as optically assisted etching, wet etching, etc. can be used alone or in combination of two or more. It is preferable to use dry etching, particularly reactive ion etching.
By using dry etching (particularly reactive ion etching) as the first etching, highly anisotropic etching can be performed on the first layer 103, and patterning of the first layer 103 can be performed with dimensional accuracy. Can be done well.

  At this time, in the etching method of the present invention, the dummy mask 112 is formed, and the width of the gap 110 formed in the mask 11 is substantially equal in each part of the etching region. For this reason, the etching of the first layer 103 by the first etching proceeds at approximately the same speed (etching rate) in each part of the etching region, and the second layer 102 is exposed at approximately the same time.

  Accordingly, overetching (etching in the surface direction near the interface with the second layer 102) can be prevented or suppressed in each part of the first layer 103. As a result, as shown in FIG. 7, the first layer 103 is processed into a precise shape corresponding to the pattern mask 111 and the dummy mask 112 and having side surfaces substantially parallel to the thickness direction.

By this step [2], the first layer 103 is patterned (processed), and the movable portion 4, the fixed electrodes 31, 32, and the plurality of dummy portions 9 are formed.
In addition, each dummy part 9 is removed from the base material 101 in the following process [4].
Here, in the conventional etching method, these dummy portions 9 are also removed by etching. In this case, for example, when dry etching is used for the etching, the material scattered by the etching of the dummy portion 9 is discharged into the environment.
On the other hand, in the etching method of the present invention, since the dummy part 9 is not etched, the amount of the material scattered from the substrate 10 with the etching of the dummy part 9 can be suppressed. Thereby, by using the etching method of the present invention, environmentally friendly etching is possible.

[3] Mask Removal Step Next, the mask 11 (pattern mask 111 and dummy mask 112) is removed. Prior to the second etching step, the mask 11 is removed, and in the step [4] described later, when wet etching is used, contamination of the etching solution due to dissolution of the mask material (resist material or metal material). Can be prevented or suppressed.
As a method for removing the mask 11, for example, when the mask 11 is made of a resist material, a resist remover, and when the mask 11 is made of a metal material, a metal remover such as a phosphoric acid solution is used. Etc. can be used.

[4] Second etching step (third step)
Next, the second layer 102 is subjected to a second etching in which the first layer 103 is not substantially etched and the second layer 102 can be etched. Thereby, a part of the second layer 102 is removed.
For the second etching, for example, one or more of reactive ion etching, plasma etching, beam etching, dry etching such as light-assisted etching, wet etching, and the like can be used. It is preferable to use wet etching.
By using wet etching as the second etching, the second layer 102 can be isotropically etched. Therefore, the second layer 102 immediately below the first layer 103 processed and remaining in the step [3] can also be efficiently removed.

As an etchant used for this wet etching, for example, hydrofluoric acid or the like can be given.
When the substrate 10 is immersed in such an etching solution, first, the second layer 102 that is not covered by the remaining first layer 103 (the movable portion 4, the fixed electrodes 31, 32, and the dummy portions 9) Etching starts from the top surface and proceeds isotropically.

Next, the second layer 102 immediately below the movable portion 4, the fixed electrodes 31 and 32, and the dummy portions 9 is also gradually removed by etching from the exposed side surfaces.
Then, by removing the second layer 102, a gap is formed between the base material 101 and the first layer 103.
Here, each of the fixed portions 45 and 46 is set to have an area larger than the area (maximum) of the belt-shaped body constituting each of the movable electrodes 41 and 42 and each of the beam portions 43 and 44 in plan view. For this reason, at the time when the second layer 102 directly under the portions other than the fixed portions 45 and 46 (the movable electrodes 41 and 42 and the beam portions 43 and 44) is almost completely removed due to the difference in area. In this state, a part of the second layer 102 immediately below the fixing portions 45 and 46 remains.

When the second etching is completed at this time (state), the remaining second layer 102 becomes the support portions 51 and 52, and the movable portion 4 is connected to each fixed portion via the support portions 51 and 52. In 45 and 46, it fixes to the base material 101 (base part 2), respectively. On the other hand, the other part of the movable part 4 is in a state of floating from the base material 101.
At this time, since each dummy part 9 is separated from the movable part 4 and each fixed electrode 31 and 32, when the second layer 102 immediately below the dummy part 9 is removed, the dummy part 9 is detached from the base material 101. (Removed).

In the present embodiment, as described above, in the mask 11, the dummy mask 112 has a strip shape, and the width thereof is set to be approximately equal to the width (average) of the portion corresponding to the strip body of the pattern mask 111. Has been. For this reason, the movable electrodes 41 and 42 and the beam portions 43 and 44 and the dummy portions 9 are substantially in the same state (condition).
As a result, the second layer 102 is removed almost simultaneously except under the fixing portions 45 and 46, so that each dummy portion 9 can be reliably detached from the base material 101.

As described above, when the second layer 102 is removed by the second etching, each dummy portion 9 is removed, whereby the manufacturing process of the microresonator 1 can be simplified. It should be noted that other methods may be used to remove each dummy portion 9.
The microresonator 1 is manufactured through the above steps.
Since the microresonator 1 manufactured in this way is precisely formed so that the cross-sectional shape of the movable portion 4 becomes a target shape, a resonance frequency that exactly matches the target resonance frequency can be obtained.

In the microresonator 1, the dimensions, shapes, etc. of each part can be arbitrarily changed. Here, for example, in the case where a part of the movable portion 4 is set to have a relatively large area in plan view, in the first etching step, the portion has a shape having a plurality of holes (for example, a lattice shape or the like). It is preferable to perform patterning. Thereby, in the second etching step, the second layer 102 immediately below the portion can be reliably removed.
The microresonator 1 as described above can be applied to various electronic devices, and the obtained electronic device is highly reliable.

Next, such an electronic device (an electronic device including the vibrator of the present invention) will be described in detail based on the embodiment shown in FIGS.
FIG. 9 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which the electronic apparatus of the present invention is applied.

In this figure, a personal computer 1100 includes a main body 1104 having a keyboard 1102 and a display unit 1106. The display unit 1106 is supported by the main body 1104 via a hinge structure so as to be rotatable. Yes.
Such a personal computer 1100 includes, for example, a reference clock, a clock for clocking, a microresonator 1 that functions as an oscillation circuit of a wireless device, a filter, and an antenna 1101.

FIG. 10 is a perspective view showing a configuration of a mobile phone (including PHS) to which the electronic apparatus of the invention is applied.
In this figure, a cellular phone 1200 includes an antenna 1201, a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and a display unit is disposed between the operation buttons 1202 and the earpiece 1204.
Such a cellular phone 1200 incorporates, for example, a microresonator 1 that functions as a carrier wave, an oscillation circuit for detection, a filter, a clock for a microcomputer, a clock for timekeeping, and the like.

FIG. 11 is a perspective view showing the configuration of a digital still camera to which the electronic apparatus of the present invention is applied. In this figure, connection with an external device is also simply shown.
Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an imaging device such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to display based on an imaging signal from the CCD. The display unit is a finder that displays an object as an electronic image. Function.
A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side (the back side in the drawing) of the case 1302.
When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory 1308.

In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation.
Such a digital still camera 1300 incorporates, for example, a microresonator 1 that functions as a clock for a microcomputer, a clock for timing, and the like.

  In addition to the personal computer (mobile personal computer) in FIG. 9, the mobile phone in FIG. 10, and the digital still camera in FIG. 11, the electronic apparatus of the present invention includes, for example, an ink jet discharge device (for example, an ink jet printer), Laptop personal computers, TVs, video cameras, video tape recorders, car navigation systems, pagers, electronic notebooks (including those with communication functions), electronic dictionaries, calculators, electronic game machines, word processors, workstations, videophones, crime prevention TV monitor, electronic binoculars, POS terminal, medical equipment (eg, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments (eg, Vehicle, aircraft, ship instrumentation), Flight Schumi It can be applied to a chromatography data, and the like.

The etching method, vibrator, and electronic device of the present invention have been described above, but the present invention is not limited to these.
For example, the vibrator of the present invention is not limited to the application to a microresonator, and can be applied to, for example, a sensor (pressure, acceleration, angular velocity, posture) for MEMS application.
The etching method of the present invention is not limited to the application to the manufacture of the vibrator as described above, and can be applied to the formation of structures having various shapes.
Moreover, in the etching method of this invention, the process of arbitrary objectives can also be added as needed.

Next, specific examples of the present invention will be described.
1. Production of microresonator (Example)
First, an SOI substrate in which a SiO ₂ layer (second layer) and a Si layer (first layer) were laminated on a Si base material (base material) was prepared.
The thicknesses (average) of the Si base material, the SiO ₂ layer, and the Si layer were 525 μm, 4 μm, and 60 μm, respectively.
Next, a resist material was applied onto the Si layer of the SOI substrate, and a mask (pattern mask and dummy mask) as shown in FIG. 5 was formed by photolithography.
The width of the dummy mask was set to be equal to the width (average) of the portion corresponding to the strip of the pattern mask. The width of the gap in each part of the mask was 3 μm.
Next, reactive dry etching was performed on the Si layer using the SiO ₂ layer as a stopper. The conditions for reactive dry etching were SF ₆ : 20 sccm, O ₂ : 10 sccm, pressure: 200 mtorr, and Rfpower: 190 W.
Next, the mask was removed using a resist stripping solution.
Next, wet etching was performed on the SiO ₂ layer using hydrofluoric acid as an etchant.
Thus, a microresonator as shown in FIGS. 1 and 2 was manufactured.
(Comparative example)
A microresonator was manufactured in the same manner as in the previous example except that a mask without the dummy mask was used.

2. Evaluation Each of the microresonators manufactured in the examples and comparative examples was driven by a known oscillation circuit, and the resonance frequency was measured based on the state of displacement of the vibrator and the change in the current value flowing during resonance.
Moreover, the beam part of each micro resonator was cut | disconnected, respectively, the cross-sectional shape was observed, and the dimension of the upper side and lower side of the cross-sectional shape was measured.
The results are shown in Table 1.

As shown in Table 1, in the microresonator manufactured in the example, the cross-sectional shape of the beam portion has a substantially rectangular parallelepiped shape, and the upper side and the lower side have substantially the same dimensions. Further, the resonance frequency was also substantially equal to the design value (32.768 Hz).
In contrast, in the microresonator manufactured in the comparative example, the cross-sectional shape of the beam portion has a trapezoidal shape, and the upper side is longer than the lower side. Further, the resonance frequency was also greatly deviated from the design value.
From the above results, when patterning the Si layer by dry etching using a mask, the Si layer can be patterned in a precise shape by setting the widths of the gaps formed in the mask to be equal. all right.

It is a top view which shows embodiment at the time of applying the vibrator | oscillator of this invention to a microresonator. It is the sectional view on the AA line in FIG. It is a schematic diagram which shows the moving direction of the movable electrode with which the microresonator shown in FIG. 1 is provided. It is a figure (longitudinal sectional view) for demonstrating the manufacturing method of the microresonator shown in FIG. It is a figure (plan view) for demonstrating the manufacturing method of the microresonator shown in FIG. 1 and FIG. It is a figure (longitudinal sectional view) for demonstrating the manufacturing method of the microresonator shown in FIG. It is a figure (longitudinal sectional view) for demonstrating the manufacturing method of the microresonator shown in FIG. 1 and FIG. It is a figure (longitudinal sectional view) for demonstrating the manufacturing method of the microresonator shown in FIG. It is an electronic device (notebook type personal computer) of the present invention. It is the electronic device (cellular phone) of the present invention. It is an electronic apparatus (digital still camera) of the present invention. It is a figure (longitudinal sectional view) for explaining a manufacturing process of a conventional vibrator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Micro-resonator 2 ... Base 31, 32 ... Fixed electrode 311, 321 ... Electrode finger 312, 322 ... Fixed part 4 ... Movable part 41, 42 ... Movable electrode 411, 421 ... Electrode finger 43 , 44 ...... Beams 45, 46 ...... Fixed parts 51, 52, 53, 54 ...... Supports 9 ...... Dummy parts 10 ...... Substrate 101 ...... Base material 102 ...... Second layer 103 ...... First 11 ... Mask 110 ... Gaps 111 ... Pattern mask 112 ... Dummy mask 90 ... Substrate 91 ... Silicon substrate 92 ... Silicon oxide layer 93 ... Silicon layer 94 ... Mask pattern 941 ... ... Gap 1100 ... Personal computer 1101 ... Antenna 1102 ... Keyboard 1104 ... Main body 1106 ... Display unit 1200 ... Mobile phone 1201 ... Antenna 1202 ... Operation button 1204 ... Earpiece 1206 ... Mouthpiece 1300 ... Digital still camera 1302 ... Case (body) 1304 ... Light receiving unit 1306 ... Shutter button 1308 ... Memory 1312 Video signal output terminal 1314 Input / output terminal for data communication 1430 Television monitor 1440 Personal computer

Claims (13)

A first layer etched by a first etch; a second layer adjacent to the first layer and not substantially etched by the first etch; and the first layer of the second layer An etching method for processing the first layer into a structure having a predetermined shape by performing the first etching on a substrate having a base provided on the opposite side of the layer,
A pattern mask having a shape corresponding to the structure body is formed in an etching region of the first layer opposite to the second layer, and a gap in each part in the etching region is separated from the pattern mask. A first step of forming a mask comprising a dummy mask arranged to be substantially equal in width;
A second step of patterning the first layer by applying the first etching to the first layer using the mask;
And a third step of removing the patterned dummy portion corresponding to the dummy mask of the first layer.   In the third step, the dummy portion is formed when the second layer is removed by the second etching in which the first layer is not substantially etched and the second layer can be etched. The etching method according to claim 1, wherein the etching method is removed. The structure includes a first portion having a shape such as a combination of a plurality of strip-shaped bodies, and a second portion having a larger area than the area (maximum) of the strip-shaped bodies constituting the first portion in plan view. And
When the second layer is removed by the second etching, the second layer immediately below the second portion remains due to a difference in area between the first portion and the second portion. The etching method according to claim 2, wherein the structure is fixed to the base material, and the first portion is lifted from the base material.   The etching method according to claim 3, wherein the dummy mask has a strip shape.   5. The etching method according to claim 4, wherein a width of the band-shaped dummy mask is substantially equal to a width (average) of a portion corresponding to the band-shaped body of the pattern mask.   6. The etching method according to claim 2, wherein the second etching is wet etching.   The etching method according to claim 1, wherein the first etching is dry etching.   The etching method according to claim 1, wherein a thickness (average) of the first layer is 0.2 to 100 μm.   The etching method according to claim 1, further comprising a step of removing the mask prior to the third step. The substrate is formed by laminating the second layer mainly made of SiO ₂ and the first layer mainly made of Si in this order on the base material mainly made of Si. The etching method according to claim 1, wherein the etching method is an SOI substrate.   A vibrator manufactured using the etching method according to claim 1.   The vibrator according to claim 11, wherein the vibrator is a microresonator.   An electronic apparatus comprising the vibrator according to claim 11.

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