JP4305728B2 - Manufacturing method of vibrating piece - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a resonator element.
[0002]
[Prior art]
Patent Document 1 describes a manufacturing method for forming grooves on both main surfaces of a resonator element and making the cross section of the resonator element an H-shaped. Specifically, a metal mask is formed on the front and back surfaces of the quartz wafer, a photoresist film is formed on the metal mask, and the photoresist film is patterned. Then, the metal mask is patterned in accordance with the pattern of the photoresist film. This pattern is designed according to the outer contour of the vibrator. Next, a photoresist film is formed on the metal mask pattern, and then the photoresist film is patterned. The pattern of the photoresist film is designed according to the groove pattern of the resonator element. Next, the quartz wafer is etched according to the pattern of the metal mask, and the outer contour of the vibrating piece is formed. Next, the metal mask is patterned in accordance with the groove pattern, and then a groove is formed in the resonator element by etching.
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-76806
[Problems to be solved by the invention]
According to this manufacturing method, the dimensional accuracy of the groove formed in the resonator element is excellent. However, the outer contour of the resonator element is different from the design pattern. Specifically, there has been a problem that the thickness of the resonator element is smaller than the design value, and the resonance frequency of the resonator element is deviated from the design value. The deviation from the design value of the resonance frequency of the resonator element may be different for each manufactured vibrator, causing a reduction in manufacturing yield.
[0004]
An object of the present invention is to provide a method capable of increasing the dimensional accuracy of the outer contour of a resonator element when manufacturing a resonator element having a recess.
[0005]
[Means for Solving the Problems]
The present invention is a method of manufacturing a resonator element in which a recess is formed,
Substrate, is provided on the substrate, a metal mask forming a first opening, and the metal mask and covers the first opening, a second photo-openings that have been formed The first member that forms the contour of the resonator element corresponding to the second opening by etching the member to be processed including the resist film while the photoresist film covers the metal mask and the first opening . Etching process,
A removal step of removing the photoresist film after the first etching step;
A second etching step of forming a recess corresponding to the first opening by etching the substrate after the removing step ; and
It has a metal mask removal process which removes a metal mask from a board | substrate after a 2nd etching process .
[0006]
By the method of the present invention , a resonator element and a vibrator having the resonator element can be manufactured .
[0007]
The present inventor, for example, examines the cause of the width of the resonator element being smaller than the design value when the contour and the recess of the resonator element are formed in two stages by the manufacturing method described in Patent Document 1, and Obtained knowledge. That is, in the first etching step, the crystal wafer is etched in accordance with the pattern of the metal mask, and the outer contour of the resonator element is formed. Next, the metal mask is patterned in accordance with the groove pattern, and then a groove is formed in the resonator element by etching (second etching step). However, when the metal mask is patterned in accordance with the groove pattern, side etching is likely to occur in the metal mask. In this case, in the etching process for forming a groove in the substrate, the outer contour of the vibrating piece is further etched, and the vibrating piece is likely to become thin.
[0008]
According to the present invention, in the first etching step, the substrate is etched from the opening of the photoresist film to form the contour of the resonator element. When the photoresist film is removed thereafter, the patterned metal mask forming the first opening is exposed. Thereafter, the substrate is etched to form a recess corresponding to the first opening.
[0009]
In other words, the photoresist film is used as a mask during the etching process for forming the contour of the resonator element, and the metal mask subjected to the patterning for groove formation is protected under the photoresist film. Therefore, the metal mask pattern for groove formation is not subjected to side etching. As a result, it is possible to improve the dimensional accuracy of the contour of the resonator element.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, more specific embodiments will be described.
1-4 is for demonstrating the process which concerns on 1st embodiment of this invention. First, a substrate 1 is prepared as shown in FIG. The substrate 1 may be a wafer. The material of the substrate 1 is not limited, but a piezoelectric single crystal is preferable. Crystal, lithium niobate single crystal, lithium tantalate single crystal, lithium niobate-lithium tantalate solid solution single crystal, lithium borate single crystal, langasite single crystal A piezoelectric single crystal made of, for example, is particularly preferable. The substrate may be either a Z plate or an X plate (Y plate), or may be an offset substrate of a Z plate or an X plate (Y plate).
[0011]
By etching the surface of the substrate 1, the work-affected layer on the surface can be removed. Next, the particles can be reduced by cleaning the substrate 1. Examples of the cleaning liquid at this time include alkaline detergents, ultrapure water, and isopropyl alcohol (EL grade).
[0012]
Next, metal films 2A and 2B are formed on the main surfaces 1a and 1b of the substrate 1, respectively. These metal films are made of a material that can function as an etching mask described later. Although such a material is not specifically limited, The following are especially preferable. There are a multilayer film in which the base is Cr and Au is laminated thereon, a multilayer film in which the base is Ti and Au is laminated thereon, tungsten and the like.
[0013]
Next, as shown in FIG. 1B, photoresist films 3A and 3B are formed and covered on the metal films 2A and 2B, respectively. Next, as shown in FIG. 1C, the photoresist films 3A and 3B are patterned to obtain patterned photoresist films 4A and 4B. The patterning of the photoresist films 3A and 3B can be performed by a normal exposure method. A contact aligner can be used during exposure.
[0014]
Next, as shown in FIG. 2A, the metal film is etched, and the patterns of the photoresist films 4A and 4B are transferred to the metal film to form patterned metal masks 5A and 5B. Next, the photoresist films 4A and 4B are removed, and the metal masks 5A and 5B having a predetermined pattern shown in FIG. 2B are exposed. Here, the metal masks 5A and 5B are formed with a first opening 6 corresponding to the groove pattern and a second opening 15 corresponding to the outer contour of the vibrator.
[0015]
Next, as illustrated in FIG. 2C, a photoresist film 7 is formed so as to cover the metal masks 5 </ b> A, 5 </ b> B, the first opening 6, and the second opening 15. Next, the photoresist film 7 is patterned to produce a member 20 to be processed as shown in FIG. In the member 20 to be processed, a patterned photoresist film 7A is formed, and a second opening 10 is formed between the photoresist films 7A. The second opening 10 corresponds to the outer contour of the resonator element. The patterns of the metal masks 5A and 5B and the first opening 6 are covered with a photoresist film 7A.
[0016]
Next, the substrate 1 is etched to form the outer contour 12 as shown in FIG. 3B (first etching step). At this time, the photoresist film 7A functions as an etching mask. Moreover, since the patterns of the metal masks 5A and 5B and the first opening 6 are covered with the photoresist film 7A, side etching of the metal masks 5A and 5B can be prevented.
[0017]
Next, the photoresist film 7A is removed, and the metal masks 5A and 5B and the first opening 6 are exposed as shown in FIG. Next, this member to be treated is etched (second etching step) to form recesses 13A and 13B as shown in FIG.
[0018]
In the present embodiment, in the first etching step (FIGS. 3A to 3B), the substrate 1 is etched from the opening 10 of the photoresist film 7A to form the outline of the resonator element. . Thereafter, when the photoresist film 7A is removed (FIG. 4A), the patterned metal masks 5A and 5B forming the first opening 6 are exposed. Thereafter, the substrate 1A is etched to form the recesses 13A and 13B corresponding to the first opening 6.
[0019]
That is, in the etching process for forming the contour of the resonator element, the photoresist film 7A is used as a mask, and the metal masks 5A and 5B subjected to patterning for groove formation are protected under the photoresist film 7A. . Therefore, the pattern of the metal masks 5A and 5B for forming a groove is not subjected to side etching. As a result, it is possible to improve the dimensional accuracy of the contour of the resonator element.
[0020]
The specific method of etching is not limited, and dry etching or wet etching may be used, but wet etching is preferable.
[0021]
Etching methods for metal masks are known per se. For example, the gold etchant is preferably an aqueous solution of iodine and potassium iodide, and the chromium etchant is preferably an aqueous solution of ceric ammonium nitrate and perchloric acid. In the case of simultaneously etching gold and chromium, an aqueous solution of ceric ammonium nitrate, perchloric acid and hydrochloric acid is preferable.
[0022]
The substrate etching method itself is known. For example, the following can be illustrated as an etchant.
There are a hydrogen fluoride solution, an ammonium hydrogen fluoride solution, a buffered hydrofluoric acid solution (a mixed solution of ammonium hydrogen fluoride and ammonium fluoride), a sodium hydroxide solution, and the like.
[0023]
In the present invention, the material of the photoresist film covering the metal mask must be durable to the substrate etchant. Examples of such materials include the following.
Novolac resin-based positive resist, main chain cleavage (collapse) -type positive resist, cyclized polyisoprene-azide compound-based negative resist, phenol resin-azide compound-based negative resist, dissolution-inhibiting electron beam positive resist, crosslinking Type electron beam negative resist.
[0024]
In a preferred embodiment, the thickness of the photoresist film 7 is 1 μm or more, more preferably 3 μm, still more preferably 8 μm or more. This embodiment will be described.
[0025]
As shown in FIGS. 3A and 3B, when the outer contour of the resonator element is formed using the photoresist film 7 as an etching mask, the photoresist film is damaged and the etchant enters the inside of the photoresist film. It was found that the groove formation is likely to be poor. Thus, the following knowledge was acquired when the cause which the photoresist film was torn was examined. That is, in the member 20 to be processed, the interface adhesion differs between the interface between the metal masks 5A and 5B and the substrate 1 and the interface between the photoresist film 7A and the substrate 1. For this reason, thermal stress is likely to occur at the boundary 30 between the metal masks 5A and 5B and the photoresist film, and cracks are likely to occur in the photoresist film due to this thermal stress. In order to prevent the occurrence of defective products when forming such grooves, it has been found that it is preferable to increase the thickness of the photoresist film as described above.
[0026]
In order to prevent such defects due to cracking of the photoresist film, a material etched in the second etching step between the substrate and the photoresist film and between the metal mask and the photoresist film. It is preferable to form a buffer layer made of Thereby, the adhesiveness between the substrate and the photoresist film and between the metal mask and the photoresist film can be made equal, and the thermal stress can be reduced.
[0027]
5 and 6 are schematic cross-sectional views for explaining this embodiment. In this embodiment, in FIG. 2B, a buffer layer made of a material etched in the second etching step is formed, and the main surfaces 1a and 1b of the substrate 1 and the metal masks 5A and 5B are covered with the buffer layer. To do. Next, a photoresist film 7 shown in FIG. 2C is formed on the buffer layer. The photoresist film 7 is patterned to obtain a member 20A to be processed shown in FIG.
[0028]
In the member 20A to be processed, a patterned photoresist film 7A is formed, and the second opening 10 is formed between the photoresist films 7A. The second opening 10 corresponds to the outer contour of the resonator element. The patterns of the metal masks 5A and 5B and the first opening 6 are covered with a buffer layer 19, and the buffer layer 19 is covered with a photoresist film 7A.
[0029]
Next, the substrate 1 is etched to form an outer contour 12 as shown in FIG. 5B (first etching step). At this time, the photoresist film 7A functions as an etching mask. Since the patterns of the metal masks 5A and 5B and the first opening 6 are covered with the photoresist film 7A, side etching of the metal masks 5A and 5B can be prevented. In addition, the adhesion between the substrate 1 and the photoresist film 7A and between the metal masks 5A and 5B and the photoresist film 7A is equalized by interposing the buffer layer 19. Therefore, thermal stress is reduced in the vicinity of the outer edge interface 30 of the metal masks 5A and 5B.
[0030]
Next, the photoresist film 7A is removed, and the buffer layer 19, the metal masks 5A and 5B, and the first opening 6 are exposed as shown in FIG. Next, this member to be treated is etched (second etching step) to form the recesses 13A and 13B as shown in FIG.
[0031]
Here, if the etching rate of the buffer layer 19 is low or the buffer layer 19 is too thick, the dimensional accuracy of the recesses 13A and 13B decreases. Therefore, the material of the buffer layer 19 is preferably a material that can be easily etched into a crystal etching solution and has a high etching rate, and the following materials are particularly preferable.
There are Cr, Ti, Al, Ni, Mo, Co and the like, and Cr is particularly preferable.
Further, the thickness of the buffer layer 19 is preferably 50 nm or less, and more preferably 10 nm or less.
[0033]
The vibrating piece of the present invention may be, for example, a vibrating piece of a tuning fork vibrator. Examples of such vibrators include vibrators for automobile direction control systems, ceramic package tuning fork vibrators, cylinder type tuning fork vibrators, tuning fork crystal oscillators, and vibrators for digital mobile phones. In addition, a camera shake correction vibrator attached to the portable information terminal can be exemplified.
[0034]
FIG. 7 is a perspective view schematically showing a vibrator 29 according to an embodiment of the present invention. The vibrator 29 includes a base 21, a pair of support pieces 22 protruding from the base 21, a pair of drive vibration pieces 23 protruding from the support pieces 22, and a pair of detection vibration pieces 26 protruding from the base 21. Yes. A wide portion or a weight portion 25 is provided at the tip of each drive vibration piece 23. A wide portion or a weight portion 28 is provided at the tip of each detection vibrating piece 26.
[0035]
Each drive vibration piece 23 is formed with an elongated recess 24, and each detection vibration piece 26 is formed with an elongated recess 27. The present invention can be applied to each drive vibration piece 23 and detection vibration piece 26.
[0036]
At the time of driving, each driving vibration piece 23 is bent and vibrated in the XY plane around the root to the support piece 22 as indicated by an arrow A. When the vibrator 29 is rotated around the Z axis in this state, each support piece 22 bends and vibrates in the XY plane as indicated by an arrow B around the root to the base 21. In response to this, each detection vibrating piece 26 bends and vibrates as indicated by an arrow C around the root to the base 21. The bending vibration of the detection vibrating piece 26 is detected, and the rotational angular velocity is calculated.
[0037]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the claims. And the structure of the said embodiment can abbreviate | omit a part, or can be changed into the other arbitrary combinations which are not mentioned above.
[0038]
【Example】
In accordance with the method described with reference to FIGS. 1 to 4, a vibrator having a form as shown in FIG. 7 was produced.
Specifically, the quartz substrate 1 having a length of 2 inches, a width of 2 inches, and a thickness of 0.1 mm was etched and washed with dilute hydrofluoric acid, and then dried by a spin dryer to clean the main surfaces 1a and 1b. Next, a chromium film having a thickness of 0.01 μm is formed on the main surfaces 1a and 1b of the clean quartz substrate 1 by using a sputtering apparatus, and an Au film having a thickness of 0.2 μm is formed on the chromium film, thereby forming a metal film. 2A and 2B were formed (FIG. 1 (a)). Next, a photoresist was applied on the Au film formation surface by a spin coater to form photoresist films 3A and 3B having a thickness of 1 μm (FIG. 1B). In order to remove the solvent component of the photoresist film, it was pre-baked at 100 ° C. for 30 minutes using an oven.
[0039]
Next, the main surfaces 1a and 1b of the quartz substrate 1 are used by using an exposure apparatus capable of high-precision alignment of the main surfaces 1a and 1b of the substrate and a photomask on which the outer shape etching pattern and the groove pattern formed on the vibrating piece are drawn. A photomask pattern was transferred onto the substrate by photolithography to form resist patterns 4A and 4B (FIG. 1C). Using this resist pattern 4A and 4B as a mask, a mixed solution of cerium ammonium nitrate, hydrochloric acid and perchloric acid was used. The metal films 2A and 2B were etched to form patterned metal masks 5A and 5B (FIG. 2A. Next, the photoresist films 4A and 4B remaining on the metal masks 5A and 5B were dissolved in acetone. (FIG. 2 (b)) A photoresist is applied onto the metal mask patterns 5A and 5B by a spin coater. Coated, to form a photoresist film 7 having a thickness of 10 [mu] m (FIG. 2 (c)). The thickness of the photoresist film 7 is 10 [mu] m.
[0040]
Next, using an exposure apparatus capable of high-precision alignment of the front and back surfaces and a photomask on which only an outer shape etching pattern is drawn, the photomask pattern is transferred to the main surfaces 1a and 1b of the quartz substrate 1 by photolithography, and a resist A pattern 7A was formed (FIG. 3A). Next, the substrate 1 was immersed in a 40% ammonium hydrogen fluoride solution heated to 70 ° C. for 10 hours, and the crystal was etched to obtain the outer shape of the vibrator (FIG. 3B). The photoresist film 7A was dissolved and removed with acetone to expose the metal masks 5A and 5B on the vibrating piece (FIG. 4A), and then the vibrator 1A was added to a 40% ammonium hydrogen fluoride solution heated to 70 ° C. Was etched for 0.5 hour, and the groove patterns 13A and 13B of the resonator element were etched to a depth of 30 μm (FIG. 4B), and then mixed with cerium ammonium nitrate, hydrochloric acid and perchloric acid The metal masks 5A and 5B remaining on the vibrator 1A were peeled and removed with a liquid to obtain a crystal vibrator 29 having a desired shape.
[0041]
Next, using a sputtering apparatus, an Au film for electrodes having a thickness of 0.2 μm was formed on the main surfaces 1 a and 1 b and the side surfaces of the crystal resonator 29 using Cr having a thickness of 0.03 μm as an underlayer. Next, using a spray resist coater, a photoresist was applied to the main surfaces 1a and 1b and the side surfaces of the vibrator 29 and further to the edge portion. Next, using an exposure apparatus capable of high-precision alignment of the front and back surfaces and a photomask on which the electrode wiring pattern is drawn, the electrode wiring pattern is transferred onto the front and back surfaces of the vibrator 29 by photolithography, An electrode pattern made of a photoresist film was formed. Next, using the photoresist electrode pattern as a mask, the electrode metals Au and Cr were immersed in a mixed solution of ceric ammonium nitrate, hydrochloric acid and perchloric acid for 30 seconds to be removed by etching to form a desired electrode pattern. A crystal resonator was obtained.
[0042]
Further, in the above embodiment, when the thickness of the photoresist film 7 was variously changed and the presence or absence of defects due to cracking of the photoresist film was confirmed, the defects were remarkably increased by setting the thickness of the photoresist film 7 to 8 μm or more. Reduced.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a method capable of increasing the dimensional accuracy of the outer contour of the resonator element when manufacturing the resonator element in which the concave portion is formed.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view schematically showing a substrate 1 on which metal films 2A and 2B are formed, and FIG. 1B is a diagram in which photoresist films 3A and 3B are formed on the metal films 2A and 2B. FIG. 4C is a cross-sectional view showing the patterned photoresist films 4A and 4B.
2A is a cross-sectional view showing a substrate 1, patterned metal masks 5A and 5B, and photoresist films 4A and 4B. FIG. 2B is a view after removing the photoresist films 4A and 4B. It is sectional drawing which shows a state, (c) is sectional drawing which shows the state which coat | covered the board | substrate 1 and metal mask 5A, 5B with the photoresist film 7. FIG.
FIG. 3A is a cross-sectional view showing a member to be processed 20 after patterning a photoresist film 7, and FIG. 3B is a view after etching the member to be processed 20 (first etching step). It is sectional drawing which shows this state.
4A is a cross-sectional view showing a state after removing a photoresist film 7A, and FIG. 4B is a cross-sectional view showing a state in which recesses 13A and 13B are formed by a second etching step. is there.
5A is a cross-sectional view showing a member 20A to be processed on which a buffer layer 19 is formed, and FIG. 5B is a state after the member 20A is subjected to an etching process (first etching step). FIG.
6A is a cross-sectional view showing a state after removing a photoresist film 7A, and FIG. 6B is a cross-sectional view showing a state in which recesses 13A and 13B are formed by a second etching step. is there.
7 is a perspective view schematically showing a vibrator 26 according to an embodiment of the present invention. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 1A Vibrator (vibration piece) 1a, 1b Main surface of substrate 1 2A, 2B Metal film 3A, 3B, 7 Photoresist film before patterning 4A, 7A Patterned photoresist film 5A, 5B Patterned metal mask 6 1st opening part 10 2nd opening part 12 Vibrating piece (outline outline) 13A, 13B Recessed part 20, 20A Processed member

Claims (5)

A method of manufacturing a resonator element in which a recess is formed,
Substrate, is provided on the substrate, a metal mask forming a first opening, and covers the this metal mask and the first opening, that has a second opening is formed The member to be processed having a photoresist film is etched in a state where the photoresist film covers the metal mask and the first opening, so that the vibration piece corresponding to the second opening is formed. A first etching step to form a contour;
A removing step of removing the photoresist film after the first etching step;
A second etching step of forming the recess corresponding to the first opening by etching the substrate after the removing step ; and
A method for manufacturing a resonator element , comprising: a metal mask removing step of removing the metal mask from the substrate after the second etching step .   The method of claim 1, wherein the photoresist film has a thickness of 1 μm or more.   A step of forming a buffer layer made of a material to be etched in the second etching step, between the substrate and the photoresist film, and between the metal mask and the photoresist film. The method according to claim 1 or 2.   The method according to any one of claims 1 to 3, wherein the metal mask and the photoresist film are formed on one main surface and the other main surface of the substrate, respectively.   The method according to claim 1, wherein the substrate is made of a piezoelectric single crystal.

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