JP2004040399A - Etching method, and etched product formed by the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method to form an outer shape and a groove of an object to be formed such as a quartz substrate that reduces the number of etching times applied to the object to be formed. <P>SOLUTION: In the case of forming a tuning fork quartz wafer 1A provided with grooves 11c, 12c in the middle of a principal face by applying etching processing to the quartz substrate 2, only a Cr film 31 exists in parts corresponding to the grooves 11c, 12c, and two layers of the Cr film 31 and an Au film 32 exist at parts being other regions than the part corresponding to the grooves 11c, 12c and a part to be the tuning fork quartz wafer. After start of 'outer shape etching operation' and the Cr film 31 existing in a form of a single layer is molten and removed, a 'groove etching operation' and the 'groove etching operation' are processed in parallel. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an etching method for etching a formed object such as a quartz substrate into a predetermined shape and an etched product such as a quartz wafer formed by the method. In particular, the present invention relates to measures for simplifying an etching molding process.
[0002]
[Prior art]
2. Description of the Related Art A tuning-fork type crystal resonator that can be easily reduced in size has been known as one type of piezoelectric vibration device. As disclosed in Japanese Patent Application Laid-Open No. H10-294631, for example, a vibrator of this type has a predetermined electrode formed on the surface thereof using a photolithography technique on a quartz wafer formed into a tuning fork shape by etching. A tuning-fork type quartz vibrating piece formed is provided.
[0003]
Japanese Patent Application Laid-Open No. 2002-76806 discloses a configuration in which a groove is formed in the center of the front and back (main surface) of each leg of a tuning-fork type quartz vibrating reed. When the grooves are formed on the front and back surfaces of the legs as described above, vibration loss of the legs is suppressed even when the vibrating piece is downsized, and the CI value (crystal impedance) can be suppressed to be low, which is effective. This type of tuning-fork type crystal resonator is particularly suitable for being mounted on precision equipment such as a timepiece.
[0004]
Hereinafter, the steps disclosed in the above publication as a method of forming a tuning-fork type quartz wafer having grooves on the front and back surfaces of the legs will be described.
[0005]
First, as shown in FIG. 3A, a substrate a which is a quartz plate (quartz Z plate) is processed into a plate shape. At this time, the front and back surfaces of the quartz substrate a are mirror-finished by polishing.
[0006]
Next, a Cr (chromium) film b1 is vapor-deposited on the front and back surfaces of the quartz substrate a, and an Au (gold) film b2 is further vapor-deposited on the front surface by a sputtering device (not shown) (see FIG. 3B). Then, photoresist layers c, c are formed on the surfaces of the metal films b1, b2 thus formed, as shown in FIG.
[0007]
Next, a photoresist layer c, c is formed on the vibrating piece forming region d that matches the shape (tuning fork shape) of the tuning fork type quartz wafer to be manufactured, and on the frame portions e, e, which are the outer edges of the quartz substrate a. The photoresist layer c is partially removed so as to remain, and outer shape patterning is performed. FIG. 3D shows this state in cross section, and FIG. 4A shows a perspective view in this state. In this state, as shown in FIG. 4A, the photoresist layers c, c are formed so that a predetermined shape of the tuning-fork type quartz wafer emerges.
[0008]
Thereafter, as shown in FIG. 3E, the metal films b1 and b2 in the portion where the photoresist layer c is not formed in FIG. 3D are removed by using an Au etching solution and a Cr etching solution. Therefore, as shown in FIG. 4B, the quartz substrate a is exposed at the portion where the metal films b1 and b2 have been removed.
[0009]
Next, as shown in FIG. 3F, the photoresist layer c remaining in FIG. 3E is entirely removed.
[0010]
Thereafter, as shown in FIG. 3G, a photoresist layer f is formed on the entire front and back surfaces of the quartz substrate a.
[0011]
Then, as shown in FIG. 3H, a part of the photoresist layer f is removed. Specifically, in addition to removing the photoresist layer f in a portion other than the resonator element forming region d and the frame portion e, the photoresist layer f in a portion corresponding to the groove portion g (see FIG. 3L) is also removed. The groove to be removed is patterned.
[0012]
Next, as shown in FIG. 3I, outer shape etching is performed using a quartz etchant. That is, the outer shape etching is performed while leaving only the resonator element forming region d and the frame portion e.
[0013]
Subsequently, as shown in FIG. 3 (j), each of the metal films b1 and b2 corresponding to the groove g formed in the leg of the tuning-fork type quartz wafer is removed with an Au etching solution and a Cr etching solution.
[0014]
Then, as shown in FIG. 3 (k), the quartz substrate a is etched to a predetermined depth with a quartz etchant to form grooves g, g,... . Thereafter, by removing the photoresist layer f and the respective metal films b1 and b2, a tuning-fork type quartz wafer h having legs with a substantially H-shaped cross section as shown in FIG. .
[0015]
Predetermined electrodes are formed on the upper and lower surfaces of the vibrating region of the tuning-fork type crystal wafer h thus manufactured to form a tuning-fork type crystal vibrating piece, and the tuning-fork type crystal vibrating piece is mounted in a package. This completes the tuning fork type crystal resonator.
[0016]
[Problems to be solved by the invention]
By the way, in the forming method disclosed in the above-mentioned publication, first, an outer shape etching step of removing a region outside the outer edge of the tuning-fork type quartz wafer h to be formed by etching (see FIG. 3 (i)). After the step (g), a groove etching step (step (k) in FIG. 3) for forming a groove g on the main surface of the leg is performed. That is, the outer shape forming and the groove forming of the quartz wafer h are performed in different steps.
[0017]
For this reason, there is a problem that the number of processing steps is increased and the processing operation is complicated and the processing time is lengthened. In addition, since the etching with the crystal etching solution is performed in each of the outer shape etching step and the groove portion etching step, it is necessary to perform at least two times of crystal etching, which may cause defects such as surface roughness of the crystal wafer surface. There was sex.
[0018]
In the above description, the outer shape of the tuning-fork type crystal wafer and the processing of the groove have been described. It is preferable to complete the final product.
[0019]
The present invention has been made in view of such a point, and an object of the present invention is to reduce the number of etching times for a molded object with respect to an etching method for molding the outer shape and a groove portion of the molded object such as a quartz substrate. The goal is to reduce it.
[0020]
[Means for Solving the Problems]
-Summary of the invention-
In order to achieve the above object, the present invention is to form both the outer shape and the groove portion in a single etching process by making the outer shape etching operation and the groove portion etching operation on a molded object such as a quartz substrate parallel. I have. In this case, the amount of etching required for outer shape etching and the amount of etching required for groove etching are different from each other. That is, the etching amount for forming the groove is smaller than the etching amount for forming the outer shape. Therefore, an etching delay film is previously provided on the surface of the groove forming region so that the start of the groove etching operation is delayed from the start of the external shape etching operation.
[0021]
-Solution-
Specifically, in order to form an etching molded product having a predetermined external shape and a groove by etching the molded product, the molded product is formed on the molded product more than the outer edge of the etched molded product to be molded. It is assumed that an etching method for performing an “outline etching operation” for removing an outer region by etching and a “groove etching operation” for recessing a groove forming region on a workpiece by etching. For this etching method, first, an etching delay film is previously provided only on the surface of the groove forming region. By performing the etching process on the molded object in this state, after the “outline etching operation” is started, the etching delay film is melted together with the outline etching, and after the etching delay film is melted and removed, the “groove etching” is performed. Operation ”is started. In this case, the etching delay film may be formed so that the “outline etching operation” is performed in parallel with the “groove etching operation” at the start of the “groove etching operation”, or the “groove etching operation” is started. At times, it may be formed such that the “outline etching operation” has already been completed.
[0022]
The following is a specific technique for keeping the etching delay film on the surface of the groove forming region. First, a coating layer in which a material having a high etching rate (a material which is easily melted by an etchant) is used as a lower layer and a material having a low etching rate (a material which is not easily melted) is used as an upper layer is formed by etching a molded article to be formed. It is formed in a region inside the outer edge. Then, an etching process is performed on the object using the lower layer exposed by removing only the upper layer in the groove forming region as an etching delay film.
[0023]
Further, as another method, as the material of the etching delay film, the etching rate is higher than the material of the film formed in the region inside the outer edge of the etching molded product to be molded and in the region other than the groove molding region. It is also advocated to adopt the one with high.
[0024]
According to these specific items, at the time when the etching process on the molded object is started, immediately in the region where the etching delay film is not present on the molded object, that is, in the region outside the outer edge of the etched molded product to be molded, Etching is started (start of the outline etching operation). On the other hand, in the region where the etching delay film is present on the molded object, that is, only in the groove forming region, the melting of the etching delayed film is started, and the etching of the molded object in this portion is still started. Not done.
[0025]
This state continues for a predetermined time, and after the etching delay film existing in the groove forming region is completely melted and removed, etching of the object is started also in the groove forming region (groove etching operation). The start of the). That is, the groove etching operation is performed in parallel with the outer shape etching operation. In some cases, the outline etching operation has already been completed at the start of the groove etching operation. Then, when the amount of etching in the groove forming region reaches a predetermined amount, the etching process ends.
[0026]
Thereby, in the groove forming region, a groove having a predetermined depth is formed, and in a region outside the outer edge of the etched molded product in which the etching has been started prior to the groove etching operation, a sufficient amount is provided. The etching amount is obtained, and the outer shape of the etching molded product is obtained in a desired shape.
[0027]
When two kinds of materials having different etching rates are used as described above, for example, Cr is used as a material having a high etching rate, and Au is used as a material having a low etching rate. In other words, when the above-mentioned two coat layers are used, the region inside the outer edge of the etched molded product to be molded (the portion to be an etched molded product) has a two-layer structure of Cr and Au, and the groove is formed. The region has a single-layer structure of only Cr. As a result, the etching is not performed in the two-layer structure portion, and in the one-layer structure portion, a predetermined amount (by the depth of the groove) is etched by the groove etching operation after the melting of Cr. Materials usable here are not limited to these.
[0028]
As a molded article formed by the above-mentioned etching method, a tuning fork type quartz wafer is specifically mentioned. In this case, the groove is formed at the center of the main surface.
[0029]
When the grooves are formed on the main surface of the tuning fork type quartz wafer in this way, even if the tuning fork type quartz vibrating piece manufactured using this tuning fork type quartz wafer is miniaturized, the vibration loss of the legs is suppressed, and CI This is effective because the value can be kept low.
[0030]
Further, an etching molded product molded by any one of the above-mentioned solving means is also included in the technical idea of the present invention.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention will be described with respect to a case where the present invention is applied to a forming method of a tuning fork type quartz crystal wafer constituting a tuning fork type crystal resonator by etching.
[0032]
-Description of the tuning fork type crystal unit-
Before describing the method of forming a tuning fork type quartz wafer by etching, first, the configuration of the tuning fork type quartz resonator will be described.
[0033]
FIG. 1A is a diagram showing a tuning-fork type crystal vibrating piece 1 provided in the tuning-fork type crystal resonator according to the present embodiment. FIG. 1B is a cross-sectional view taken along the line BB in FIG. 1A.
[0034]
The tuning-fork type crystal vibrating piece 1 includes two legs 11 and 12, and first and second excitation electrodes 13 and 14 are formed on each of the legs 11 and 12. In FIG. 1A, the portions where the excitation electrodes 13 and 14 are formed are shaded.
[0035]
The tuning-fork type quartz vibrating reed 1 has rectangular grooves 11c, 12c formed at the center of the main surfaces 11a, 12a serving as the front and back surfaces of the legs 11, 12, respectively. An etching process for processing these grooves 11c and 12c will be described later.
[0036]
When the grooves 11c, 12c are formed on the front and back surfaces of the legs 11, 12, the vibration loss of the legs 11, 12 is suppressed even if the tuning-fork type quartz vibrating piece 1 is downsized, and the CI value (crystal impedance) ) Can be effectively reduced.
[0037]
The first excitation electrode 13 is provided inside a groove 11c formed on the front and back (main surface) 11a of one leg 11 and on a side surface 12b of the other leg 12, and is connected to each other. I have. Similarly, the second excitation electrode 14 is provided inside the groove 12 c formed on the front and back (main surface) 12 a of the other leg 12 and on the side surface 11 b of the one leg 11. Have been. These excitation electrodes 13 and 14 are thin films formed by metal vapor deposition of chromium (Cr) and gold (Au), and the film thickness is set to, for example, 2000 °.
[0038]
Although not shown, the tuning-fork type quartz vibrating piece 1 is supported by a base, and a cap is attached to an outer peripheral portion of the base so as to cover the tuning fork-type quartz vibrating piece 1 to form a tuning fork-type quartz vibrator.
[0039]
-Explanation of the etching process of tuning fork type quartz wafer-
Next, a method of forming a tuning fork type quartz wafer by etching will be described with reference to FIG. FIG. 2 shows a processing state in a cross section taken along line II-II in FIG.
[0040]
First, as shown in FIG. 2A, the quartz substrate 2 is processed into a plate shape. At this time, the front and back surfaces of the quartz substrate 2 are mirror-finished by polishing.
[0041]
Next, a Cr film 31 is deposited on the front surface and the back surface of the quartz substrate 2 and an Au film 32 is deposited on the surface by a sputtering device (not shown). Then, photoresist layers 4 and 4 are formed on the metal films 31 and 32 thus formed, as shown in FIG.
[0042]
Next, as shown in FIG. 2D, a vibrating piece forming region A that matches the shape (tuning fork shape) of the tuning fork type quartz wafer to be manufactured, and a frame portion C that is an outer edge portion of the quartz substrate 2. The photoresist layer 4 is partially removed so that the photoresist layers 4 and 4 remain, respectively, and outer shape patterning is performed.
[0043]
Next, as shown in FIG. 2E, portions of the metal films 31, 32 where the photoresist layer 4 is not formed in FIG. 2D are removed with an Au etching solution and a Cr etching solution. As a result, the crystal substrate 2 is exposed at the portion where the metal films 31 and 32 have been removed.
[0044]
Thereafter, as shown in FIG. 2F, the photoresist layer 4 remaining in FIG. 2E is entirely removed.
[0045]
Thereafter, as shown in FIG. 2G, a photoresist layer 5 is formed on the entire front and back surfaces of the quartz substrate 2.
[0046]
Then, as shown in FIG. 2H, a part of the photoresist layer 5 is removed. Specifically, groove patterning for removing the photoresist layer 5 at a portion corresponding to the grooves 11c and 12c is performed.
[0047]
Next, as shown in FIG. 2I, only the portion of the Au film 32 where the photoresist layer 5 is not formed in FIG. 2H is removed with an Au etchant. As a result, only the Cr film 31 remains as a metal film in portions corresponding to the grooves 11c and 12c.
[0048]
Thereafter, as shown in FIG. 2J, the photoresist layer 5 remaining in FIG. 2I is entirely removed. Thus, only the Cr film 31 functioning as the etching delay film according to the present invention exists as a metal film in a portion corresponding to the grooves 11c and 12c, and a Cr film as a metal film in a region other than the portion corresponding to the grooves 11c and 12c. There are two layers, 31 and Au film 32.
[0049]
When Cr and Au are compared, Cr has a higher etching rate. That is, it is a material that can be easily melted by an etching solution (in the case of this embodiment, a hydrofluoric acid + ammonium fluoride solution). On the other hand, Au is a material that is hardly melted by the etchant.
[0050]
Subsequently, external shape etching is performed using a crystal etching solution. That is, the portion where the metal films 31 and 32 are not present and the crystal substrate 2 is exposed is etched. At this time, since only the Cr film 31 is present as the metal film in the portions corresponding to the grooves 11c and 12c, the Cr film 31 is also etched (melted and removed) by the quartz etchant. FIG. 2 (k) shows a state in the middle of the outer shape etching step, in which a portion of the Cr film 31 corresponding to the grooves 11c and 12c has been completely removed. At this time, the outer shape etching step has not been completed yet, and the crystal substrate 2 partially remains in a thin plate state.
[0051]
When the etching with the quartz etching solution is further advanced through this state, the etching of the quartz substrate 2 is started also in the portions corresponding to the grooves 11c and 12c from which the Cr film 31 has been completely removed. In other words, the crystal wafer outline etching step and the groove etching step are performed in parallel.
[0052]
This etching process is continued for a predetermined time, and the etching process is terminated when the etching amount of the grooves 11c and 12c reaches the predetermined amount. Thereby, as shown in FIG. 2 (l), grooves 11c and 12c are formed on both surfaces of the leg, and the leg has a substantially H-shaped cross section. In this manner, the quartz wafer 1A having a predetermined outer shape and having the groove portions 11c and 12c on the main surface is formed, and the remaining metal films 31 and 32 are removed by the Au etching solution and the Cr etching solution. A tuning-fork type quartz wafer 1A having legs with a substantially H-shaped cross section as shown in FIG. 2 (m) is completed.
[0053]
The metal films 31 and 32 remaining on the crystal wafer 1A in the state shown in FIG. 2 (l) are not removed and used as a part of a wiring pattern at the time of forming an electrode to be performed later, or a tuning fork. It may be used as a weighting electrode for partially removing (for example, milling for performing frequency adjustment) at the time of frequency adjustment of the shaped crystal resonator.
[0054]
The above-mentioned first and second excitation electrodes 13 and 14 are formed on the legs 11 and 12 of the tuning-fork type quartz wafer 1A formed in this manner to produce the tuning-fork type quartz vibrating reed 1, which is used as a base. , And a cap is attached to the outer peripheral portion of the base to produce a tuning-fork type quartz vibrator. The resonance frequency of the tuning-fork type crystal resonator manufactured in this manner includes, for example, 20 kHz, 32 kHz, 40 kHz, 60 kHz, 75 kHz, 77.5 kHz, and the like. In addition, it is possible to manufacture a tuning-fork type crystal resonator having a frequency other than these frequencies. Further, it may be manufactured as a surface mount type tuning fork type crystal resonator or the like.
[0055]
As described above, in this embodiment, the outer shape of the tuning-fork type quartz wafer 1A can be formed into a predetermined tuning-fork shape by performing the etching process on the quartz substrate 2 only once, and the grooves 11c and 12c are formed on the main surface thereof. be able to. That is, since the etching is not performed on the quartz substrate 2 a plurality of times, it is possible to avoid complication of the working operation and prolonging the working time, and also to prevent defects such as surface roughness of the surface of the quartz wafer 1A. A high-quality tuning-fork type quartz wafer 1A can be manufactured without inviting.
[0056]
-Other embodiments-
In the embodiment described above, only the Cr film 31 exists in the portion corresponding to the grooves 11c and 12c, and two layers of the Cr film 31 and the Au film 32 exist in the region other than the portion corresponding to the grooves 11c and 12c. I was The present invention is not limited to this, and a Cr film may be present in portions corresponding to the grooves 11c and 12c, and a Cr oxide film may be present in regions other than the portions corresponding to the grooves 11c and 12c. In general, a Cr oxide film is considered to have a lower etching rate (more difficult to dissolve in an etching solution) than a Cr (non-oxidized) film, and a portion corresponding to the grooves 11c and 12c is obtained by utilizing a difference between the etching rates. It is also possible to form the grooves 11c and 12c by etching only. As a method for partially oxidized to this Cr film, excimer UV irradiation, _{UV-O 3} dry cleaning, such as _{O 2} plasma is raised.
[0057]
As a method for providing a difference in etching rate between the films formed in the regions corresponding to the grooves 11c and 12c and the other regions, a film of the same material (for example, a Cr film) is used in each region. In addition, the thickness of the film formed in the latter region may be set to be larger than the thickness of the film formed in the former region.
[0058]
The embodiment described above is a case where the present invention is applied to a forming method of a tuning fork type quartz wafer by etching. The present invention is not limited to this, and can be applied to a case where a groove is formed in another quartz wafer (such as an AT-cut quartz wafer).
[0059]
Further, the present invention is not limited to a quartz crystal wafer, and can be applied to the manufacture of a piezoelectric vibrating reed using lithium niobate, lithium tantalate, or the like, and other various electronic components. Further, the present invention can be applied not only to the piezoelectric material as the molded object, but also to various materials such as glass, metal, and semiconductor.
[0060]
Further, the constituent material of the etching delay film is not limited to Cr, and various materials can be applied as long as the material has a relatively high etching rate. Further, a Ni film can be applied instead of the Au film.
[0061]
In addition, the method for forming the etching delay film is not limited to the method of the above-described embodiment, and the metal film (Au film in the case of the above-described embodiment) may be selectively removed by laser irradiation and only the predetermined region may be formed. The etching delay film may be exposed, or milling may be performed instead of laser irradiation.
[0062]
【The invention's effect】
As described above, in the present invention, an etching delay film is previously provided on the surface of the groove forming region so that the start time of the groove etching operation is delayed with respect to the start time of the outer shape etching operation, and in this state, The etching process is being performed. Thus, both the outer shape and the groove can be appropriately formed in a single etching step. As a result, the outer shape of the etched article can be formed into a predetermined shape by performing the etching step once on the article, and the groove can be formed. In other words, since a plurality of etchings are not performed on the molded object, it is possible to avoid complicated processing operations and a long processing time, and to prevent defects such as surface roughness of the etched molded product surface. A high-quality etched product can be obtained without inviting.
[Brief description of the drawings]
FIG. 1A is a diagram illustrating a tuning-fork type quartz vibrating piece according to an embodiment, and FIG. 1B is a cross-sectional view taken along line BB in FIG.
FIG. 2 is a view showing a forming process of a tuning fork type quartz wafer according to the embodiment.
FIG. 3 is a view showing a forming process of a tuning fork type quartz wafer in the prior art.
FIG. 4 is a perspective view showing a quartz substrate in the process of forming a tuning fork type quartz wafer in the prior art.
[Explanation of symbols]
1 tuning-fork type crystal vibrating piece 1A tuning-fork type crystal wafer 11c, 12c groove 2 crystal substrate (molded object)

Claims (5)

In order to form an etching molded product having a predetermined external shape and a groove by etching the molded product, a region outside the outer edge of the etched molded product to be molded is etched with respect to the molded product. An etching method for performing a “groove etching operation” to remove by the “etching operation” and a “groove etching operation” for recessing the groove forming region on the workpiece by etching.
An etching process is performed on the workpiece in a state where the etching delay film is present only on the surface of the groove forming region in advance, and after the “outline etching operation” starts, the etching delay film is melted together with the outline etching, and this etching is performed. An etching method, wherein the “groove etching operation” is started after the delay film is melted and removed. The etching method according to claim 1,
A coat layer having a material having a high etching rate as a lower layer and a material having a lower etching rate as an upper layer is formed in a region inside an outer edge of an etching molded product to be molded, and only the upper layer is formed in a groove molding region. An etching method, wherein an etching process is performed on a molded object by using a lower layer exposed by removal as an etching delay film. The etching method according to claim 1,
The material of the etching delay film is a material having a higher etching rate than a material of a film formed in a region inside the outer edge of the etching molded product to be molded and in a region other than the groove molding region. Etching method. The etching method according to claim 1, 2 or 3,
The etching molded product is a tuning fork type quartz wafer,
The etching method, wherein the groove is formed at the center of the main surface. An etching molded product formed by the etching method according to claim 1.

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